cleaner technology brainstorming sessions
TRANSCRIPT
INFORMATION MANUAL ON POLLUTION ABATEMENT &CLEANER TECHNOLOGIES SERIES : IMPACTS/1 2/2003-04
TECIIIN'
SESSIONS
NEW DELHI, 24-25t h November 2003
Ministry of Environment & Forests Centra! Pollution Control BoardParyavaran Bhawan, Lodi Road Parivesh Bhawan, ShandaraNew Delhi -110003 Delhi - 110032
INFORMATION MANUAL ON POLLUTION ABATEMENT &CLEANER TECHNOLOGIES SERIES : IMPACTS/12/2003-04
TECIf 0^
BRAINSTORMINGSESSIONS
NEW DELHI, 24-25t" November 2003
Ministry of Environment & ForestsParyavaran Bhawan, Lodi Road, New Delhi -110003
Central Pollution Control BoardParivesh Bhawan, Shandara, Delhi - 110032
Ph. : 2230-5792, 2073, 2718, 0198, 2720, 2729Fax: 91-11-22307078-9/22301539/22304948
E-mail: [email protected] Website : www.cpcb.nic.in
2003, 250 Copies
Layout, Design & Printing Supervision : Shri R. N. Jindal and Shri P. K. MahendruPublished by Member Secretary, Central Pollution Control Board, Delhi-110 032Printed at Nitin Enterprises, 20-A, Ram Nagar, New Delhi-110055
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Dr. V. RAJAGOPALAN, PASCHAIRMAN
Central Pollution Control Board(A Govt. of India Organisation)
Ministry of Environment & ForestsPhone : 22304948 / 22307233
Cleaner Technology either targets sources of pollution or focuses on resource recovery to eliminateor significantly reduce the amount of any hazardous substance, pollutant, or contaminant releasedto the environment. The emphasis of Cleaner Technology is on process changes that can preventpollution.
Cleaner Technology calls for a thorough understanding of processes as well as evaluation of productsby way of life cycle assessment. A product's life cycle assessment takes into account all environmentalfactors in relation to a given product -" from cradle to grave" - sourcing of raw materials to disposalof wastes.
At the instance of the Ministry of Environment and Forests (MoEF), the Central Pollution ControlBoard has organized a two day Brainstorming Session to focus on issues and options. The compilationof technical papers to be presented at the Brainstorming session has been made possible due to theefforts of Dr. R.R.Khan and Dr. S.K.Aggarwal from MoEF, as well as my colleagues Shri R.N.Jindal,SEE, Shri Ajay Raghava, AEE, Ms. Sakshi Arora, JRF and Mrs. Alka Shrivastava, JRF under theable guidance of Dr. B. Sengupta, Member Secretary and Shri T.Venugopal, Director.
Every effort has been made to avoid errors or omissions in this publication. Errors, omissions ordiscrepancies noted may kindly be referred to the authors.
We hope this publication will serve as a useful ready reckner to industry, R & D organizations,consultants and Pollution Control Boards/Committees.
November 2003 V (Dr. , aja opa an)
'Parivesh Bhawan', C.B.D.-cum-Office Complex, East Arjun Nagar, Delhi-110 032Fax : (011) 22304948 / 22307078 e-mail : [email protected]
Website : http://www.cpcb.nic.in
CONTENTS
S.No. TOPICS PAGE
1 Role of Market Based Instruments in Promotion 1& Implementation of Cleaner Technologies:Case Study of Corporates in Kawas-Hazira Region— Prof. P Khanna
2 Use of Fly Ash in Burnt Clay Brick Manufacturing 9— Shri Anand Damle
3 Status Report on Vertical Shaft Brick Kilns in India 23— Col. Rakesh Johri
4 Demonstration of Env. Friendly Firing Technology 41for Brick kilns— Shri Rajinder Singh
5 Air pollution control in Cupola Furnace by 51adopting Better Operating and Metallurgical Practices— Er. M.S.Jaggi & Er. S.K. Jain
6 Primary/Secondary Production of Non-ferrous Metal 59— Shri Amitava Bandopadhyay
7 Pollution Control in Rice Shellers 71— Shri M.A.Patil
8 Waste Minimization and pollution Control -Sago Industries 87—Dr. N.G.Nair
9 Indian Electroplating Industry - 103Abatement : A Tool for Pollution Prevention— Shri Asif Nurie
10 Pollution Control in Lime kilns: Cleaner Production—Dr. C.L. Verma 107
11 Cleaner Technologies in Distilleries 115— Dr. B. Subba Rao
12 Gaining Environmental Security in Industrial sector: 125A Real Life Experience of Indian Leather Industry— Dr. T Ramaswami
13 Re-refining/Reprocessing of used oil/waste oil 147— Shri Himmat Singh
14 Dyes & Dye Intermediate Sector 167— Shri H.G. Joglekar
Disclaimer
The views expressed in this publication are those of the
respective authors. The Central Pollution Control Board and/
or Ministry of Environment & Forests do not take any
responsibility on the authenticity of the information provided
and views expressed.
ROLE OF MARKET BASED INSTRUMENTS INPROMOTION & IMPLEMENTATION OF
CLEANER TECHNOLOGIES: CASE STUDY OFCORPORATES IN KAWAS-HAZIRA REGION
by
PROF. P. KHANNA, Ph DCHAIR PROFESSOR & DIRECTOR
SIES-INDIAN INSTITUTE OF ENVIRONMENT MANAGEMENTSECTOR-V, NERL, NAVI MUMBAI - 400 706
TEL. : 022-27708362 / 27708370 FAX: 022-27708360E-mail : [email protected]
Role of Market Based Instruments in Promotion& Implementation of Cleaner TechnologiesCase Study of Corporates in Kawas-Hazira Region Prof. P Khanna*
1.0 Preamble
The instruments of state intervention and regulation are neither sufficient nor efficient in theimprovement of environmental management practices at the local, regional or national levels. ThePrinciple 16 of Rio Declaration on Environment and Development (1992) stipulates that the Nationalauthorities should endeavor to promote the internalization of environmental costs and the use ofeconomic instruments taking into account the approach that the polluter should, in principle, hearthe cost of pollution with due regard to the public interest and without distorting international tradeand investment.
There is now a growing consensus amongst developing countries that environment policy mustmove from a reactive stance, which almost inevitably means command and control regulation, to amore proactive sustainable development - based approach (economic-efficiency, environment-responsibility, and societal-relevance) to make markets work for the environment. The basic objectiveof economic instruments is thus to promote efficient use and allocation of environmental resourcesso that the socially optimum level of economic activity coincides with the private optimum. Thisobjective is also the stinunzun bonuin of Cleaner Production.
The Ministry of Environment and Forests (MoEF) identified Kawas-Hazira region in Surat districtof Gujarat for a case study on Market based Instruments with a view to examining the feasibility ofdesigning and implementing mechanisms for region-specific promotion of cleaner technologies.This writeup presents, albeit briefly, the experience and evidence gathered by the SIES-Indian Instituteof Environment Management, Navi Mumbai; and the Environment Management Division of theConfederation of Indian Industry, New Delhi on the warm acceptance of this environmentaleconomics based instrument for Regional Environment management by all stakeholders therbyprima facie leveraging conservation of non-nenewable feedstock though cleaner production, andcapturing and utilizing carbon dioxide from the manufacturing operations, both with attractiveinvestment payback periods.
The initiative of the MoEF in respect of the introduction of MBIs was intended to:
Facilitate cleaner production thereby conserving scarce natural resources, and protectingenvironmental quality
Attain environmental quality goals at least social costs
Implement Polluter - Pays Principle
Author is Chair Professor & Dir. with SIES -Lidian Institute of Environment Management, Navi Mumbai : 400 706.
Offer incentives for dynamic efficiency through resource conserving production - andpollution prevention - technologies on a continual basis.
Why Kawas -Hazira?
• All ten Corporate groups employ state-of-art manufacturing technology, albeit at the time oftheir establishment (1991-95).
. All these groups are seeking / have achieved leadership-status in their industry.
The Corporate groups deploy state-of-art tools for Innovation & Management of TechnologyChange for maximising their profits.
The Corporate groups wish to be trend-setters in proactive environmental management.
The study benefits form the findings of an earlier MoEF sponsored project (1997-2000) onCarrying Capacity based Planning in Tapi Estuary Region.
2.0 Case Study Algorithm
2.1 Prepare a generic inventory of raw materials, production processes, pollution control systems,environmental standards (concentration and mass based), and cleaner & cleanup technologyoptions for the industries in Kawas-Hazira region.
2.2 Develop two theoretical frameworks as the basis of analyses:
a) Pigouvian Function equalizing marginal costs and marginal damages; and
b) Engineering Cost Function equalizing marginal abatement costs.
2.3 Visit the industries in Kawas-Hazira region, examine production & pollution control systems,fill-in inventory tables, discuss CT options, and assess stakeholders mindset apropos feasiblehybrids of MBIs through a well-designed questionnaire.
2.4 On return, tabulate data, plug-in data in mathematical frameworks, and obtain & interpretresults.
2.5 Identify and analyse policy implications.
2.6 Repeat Steps 2.1 to 2.5, and present findings to Corporate groups and other stakeholders inKawas-Hazira region.
4
3.0 Theory of MBIs
Full internalization of pollution costs will occur when the marginal abatement cost of pollution (tothe polluter) is equal to the marginal damage cost of residual pollution (to the society) therebyyielding a socially optimum level of pollution control.
Balancing Pollution Control & Pollution Damage Costs
The optimum level of pollution to the polluter and the society is one, which equalizes the sum of thecosts of pollution control, and pollution-induced damage (point E, at which the cost is P*). Point Eis termed Pigouvian Function.
The second-best approach is to estimate cost-effective pollution allocation that equates the marginalcosts of controlling pollution across all polluting industries. This may be achieved, for example, bylevying a per-unit tax on pollution discharged in excess of stipulated standards, or per unit rebatefor emissions below the standard, or by pollution prevention tax / rebate based on stoichiometricand thermodynamic limits, or eco-efficiency tax / rebate based on feedstock usage / unit productproviding economic incentive to individual industries for cost-effective investments in pollutionprevention, so as to achieve the stipulated ambient environmental quality goals while promotinginternationally competitive manufacturing enterprises.
4.0 MBI Scenarios in K-H Region based on Pigouvian Functions
Since the Corporates in the region all meet emission and effluent standards at all times due to theusage of natural gas as feedstock, and internalization of efficient pollution prevention / controldevices in the manufacturing plants, the analyses here are based on feedstock usage/unitproduct(Eco-efficiency), and on GHG (CO) emissions.
Scenario I : Eco-efficiency Tax / Rebate based MBI
In this scenario, a charge is levied / rebate is provided on feedstock use per tonne of product produced.The purpose of this MBI is to achieve resource efficient manufacturing enterprises. As a commondenominator, natural gas usage per tonne of product is considered in generating MBIs in this scenario.The Eco-efficiency based tax / rebate scenario for an industry in Kawas-Hazira region are presentedin the following Table.
Ecoefficiency TA* (tons) TAC ** I TR*** (Rs in miijions)(1) (2) (3)Scenario (Rs in
millions)
At Current Level557.5 kg C equivalent Nil Nil -338.85 -290.44 242.04per ton of NH3producedAt Benchmark463 kg C equivalent
1,97,579.7 221.61 Nil Nil Nilper ton of NH3producedAt Situation `A'395.8 kg C equivalent
3,37,047.7 378.04 205.02 170.85 136.68per ton of NH3producedAt situation `B'278.7 kg C equivalent
5,81,116.8 651.79 563.79 469.83 375.86per ton of NH3
produced
Current situation:
Benchmark situation:
557.5 kg C equivalent per MT of NH 3 is released 463 kg C equivalent per MT of NH.Benchmark is achieved by 17 % abatement
Situation A: 29% abatement from current level 1 As per source belowSituation B: 50% abatement from current level I
(Source: Climate change 1995, IPCC, Cambridge University Press, 1996)
*TA :Total Abatement, * *TAC :Total Abatement Cost, ***TR: Total Revenue from tax
The Cleaner technology options identified for this industry are the change of catalyst (from iron toruthenium, which is twenty folds more active) in the optimization of ammonia synthesis process,
6
coupled with the removal / recovery of enerts (argon) from the process stream (thereby enhancingthe conversion to ammonia from 16.2 to 18.5 %).
Scenario II: GHG (CO 2 ) based Mills
This scenario is based on the premise of equating the cost of GHG control (on the polluter) with thecost of residual GHG (on the recipient community). In the graphical depiction of following Figurefor one industry, the Pigouvian function falls at E, with P* indicating the cost of abatement on theIndustry / cost of residual to the society.
Pigouvian function balancing Marginal Abatement Costand Marginal Damage Cost of CO2
200 o MAC
0 150 —mot MDC
100
á 50 * E — °'^
O>9.S
O 10 20 30 40 50 60 I(.) 80 90 100
100 90 80 70 60 50 40 30 20 10 0
% Abatement / Emission of Carbon dioxide
The two curves cross at 59.8% abatement of CO at point E at a price P*• At E, Marginal AbatementCost equals Marginal Damage Cost, ie societal optimum is achieved. The optimum amount of CO 2
abatement is 59.8 percent at the cost (P*) of Rs 27 Crores annually.
Annual Cost
E 59.8 %P* Rs 27 Crores
The proven technologies for GHG utilization include The Carnol Process, The Modified SolvayProcess and The Carbon dioxide Recovery system from the stack gas (with investment pay back of
7
two to three years from recovery of methanol, soda ash & ammonium chloride, and carbamate,respectively).
5.0 Epilogue
The Environment Management Instruments are intended to encourage environmentally - responsiblebehaviour on the part of the Corporates, which must necessarily and concurrently achieve economicgoals of its stakeholders (shareholders, customers, ecological resources, environmental quality,community, general public). The Market-based-Instruments provide economic incentives for cleanerproduction, with eoncommitant conservation of natural resources, thus meeting the objectives ofenvironment management agencies in maintaining desirable quality of ambient environment, andof its stakeholders in maintaining lower cost of production & lower residual pollution.
The experience in Kawas-Hazira supports the contention that the taxes and incentives based onefficiency improvements align the pollution control agencies better with the polluters than the CAC.Such an instrument also facilitates incentives for achieving the triple bottom line, viz Economic-efficiency, Environment-responsibility, and Societal-relevance entitling the Corporates to CDMand other Cleaner — Production benefits.
6.0 Acknowledgements
Thanks are due to the MoEF, particularly to the pragmatic thinker and philosopher Late Dr S CMaudgal, former Senior Advisor for conceiving this study; and to Dr R R Khan, Advisor; Dr S KAggarwal, Director; Mr Roy Paul, former Special Secretary, MoEF; and EMD Division of C11; asalso to the research students at SIES-ITEM for their contributions to this pioneering case study.
8
USE OF FLYASH IN BURNT CLAY BRICKMANUFAC TURING
byANAND DAMLE
MANAGING DIRECTOR
DAMLE CLAY STRUCTURALS (P) LTD.`ANANT', PLOT NO. 98, LANE 5, NATRAJ SOCIETY,
KARVENAGAR, PUNE 411 052 (INDIA)PHONE: 020-5446127 ; FAX : 020 — 545 3015
e-mail : [email protected] : damleclaystructurals.com
Use of Flyash in Burnt Clay Brick Manufacturing Anand Danzle *
1.0 `Industrial Ecology' — The Concept
Most of the economic activity that took place subsequent to the Industrial Revolution followed an`open-ended' approach as regards flow of materials and energy in all production processes. Theapproach involved transformation of natural resources into useful products and returning the worn-out products and wastes / by-products of the production process back to the Mother Nature. It hadno concern whatsoever for conservation of natural resources and environmental quality and hence,led us to a situation where `sustainable waste management' has become our highest priority todaywhich is often based on waste hierarchy — Reduce, Reuse, Recovery and (safe) Riddance — in thedescending order of priority.
Although the high consuming societies of the developed world need to take lion's share of theblame and responsibility for the environmental damage, we in India cannot remain to be silentobservers to the worsening ecology around. To resolve this apparent conflict between developmentand environment, hereafter, all governments, businesses and individuals will be required to movetowards a framework where development (or growth) becomes environmentally sustainable. Thisis the basis of the `industrial ecology' concept. It aims to transform the `open' system of productioninto one where material and energy flows are `closed', i.e. all wastes and by-products get reusedwithin the `system' as a result of transfers among `symbiotic' participating industries.
Use of flyash in clay-flyash brick manufacturing is one good example of industrial ecology at work.Not only does it solve the disposal problem of the generating agencies and minimizes the requirementsof primarily extracted clays and fossil fuels, but it also has many positive effects on the brickmaking process and the brick quality.
2.0 Burnt Clay Brick Manufacturing Process
Technically, burnt clay bricks fall under the category of heavy-clay products, forming a major partof the ceramic industry. Heavy-clay products are those that are mainly made from a single clay withvery little addition of other raw materials. They are principally used in structural work. Henceheavy-clay products like bricks, hollow clay blocks, roof tiles, split tiles, etc. are often called structuralclay products.
The burnt clay brick manufacturing process can be divided into six steps, namely, clay winning (i.e.excavation), raw-mix preparation, moulding, drying, firing and material handling. Clay is won (i.e.dug) either manually or by using excavators. For clay preparation, roller crushers, hammer mills,disintegrators, box feeders, rotavators, pamnills, double shaft `U' mixers, etc. are used. Mouldingis carried out using four techniques, as given further.
Author is working as Managing Director with the Dainle Clay Sruturals(P) Ltd, Pune.
11
3.0 Moulding Techniques
Technique Approx. water contentin raw-mix (%)
Soft mud moulding 25-35
Extrusion and wire cutting-Soft extrusion-Stiff extrusion
15-2020-25
Semi-Dry Pressing 5-15
Dry Pressing <5
Of these, the extrusion and wire cutting technique is most widely used all over the developed worldwhile soft mud moulding is practiced on a very limited scale. In India, hand-moulding - which is thesame as soft mud moulding - is prevalent everywhere. Dry pressing, though considered technicallyfeasible, is not a viable technique for making ordinary fired clay bricks due to the `high-volume-low-margin' nature of the business, and hence not exploited commercially in India.
Drying is done either under the sun (i.e. in the open) or under a shed. The process may be hastenedby circulating hot kiln flue or steam through bricks kept under the shed. This arrangement is calleda chamber dryer. Advanced countries now-a-days use a chamber dryer or a tunnel dryer withoutexception.
For firing, open clamp, Bull's trench kilns, Hoffman kilns, vertical shaft kilns, tunnel kilns androller kilns are the available options, which are progressively more and more fuel-efficient. Ofthese, open clamp is the crudest form of brick-burning methods practiced anywhere in the world. Itis non-continuous (or batch) in nature, while all other forms are continuous.
Handcarts, dump trucks, conveyors, forklift trolleys, setters, finger / transfer / kiln cars, etc. areused for material handling. All the said machinery / equipment / techniques are either indigenouslysourced or are being imported for the manufacture of bricks and other whiteware products.
4.0 Present Status of Indian Brick Industry :
Indian brick industry is the 2"t ß largest in the world after China. It is estimated that presently thereare at least 1,00,000 brick units scattered all over the country, each unit manufacturing between0.10 and 20 million bricks per year. Of these, about 20,000 units employ Fixed Chimney Bull'sTrench Kilns (of which 9,000 have Gravitational Settling Chambers), about 12,000 Moving ChimneyBull's Trench Kilns, about 1,000 Hoffman / High Draught / Zig-zag / Tunnel Kilns and the balance67,000 or so Open Clamps. The present demand and supply are estimated at about 170 and 140billion bricks per year, respectively. The industry consumes about 24 million tonnes of coal (apartfrom about 3 million tonnes of bio-mass) and provides employment to more than 8 million people.It is the 3 largest coal consuming industry in the country after Power and Steel.
12
99 % R&D of the units employ hand-moulding method. Since drying also is mostly done in theopen, bricks cannot be moulded and dried during rainy season and hence the industry is seasonal. Itoperates for 6 to 8 dry months of a year only, from November to June. Majority of the units employage-old clamp / scove / Scotch / Bull's trench kiln burning methods. The industry is `unorganized'and very few units have officially registered themselves as small-scale industrial units. Brick unitsare normally set up on leased-out lands near clay sources. Simple tools like pickaxes, shovels,baskets, etc.; hand carts, screens, moulds, arrangement for storage / pumping of water and workers'makeshift sheds constitute the only fixed investment of a brick unit.
Unlike developed countries, which utilize mined clay, shale, etc. for brick manufacturing, we onlyuse of surface soil for the same. It is often said that nature takes about 1 million years to make 10inches of top soil. Use of this precious surface soil for brick manufacturing, though considereddesirable by both sellers and buyers of the material, destroys it permanently. This adversely affectsthe acreage of cultivable land, the flora and fauna supported by it and the environment around.Royalty charged on brick earth under Minor Minerals Act is expected to take care of the cost ofreclamation of the affected land. However, in practice, the reclamation cost is tens of thousands oftimes more than the royalty being levied.
Use of firewood for brick burning, which leads to large scale tree felling, and the air pollutioncreated by the industry in the form of dust, smoke and odour, also attract stiff opposition fromenvironmentalists. Incidence of bonded labour, ill treatment meted out to animals engaged in pugging/ material handling, etc. evokes considerable uproar from social workers. Owing to their temporary,low technology and polluting nature, and total absence of professional management (includingquality control), brick units do not enjoy much respect in the eyes of people and consequently,bricks are not thought of as an `industrial' product by the common man. Only in South India (and ata few places in the North also), where roof tile plants are very common, similar technology is usedfor making wire-cut bricks, which command reasonable consumer respect.
5.0 Flyash :
With a present share of about 40 %, coal happens to be the world's most extensively used fossil fielfor generating power. Its worldwide `reserves to production ratio' is 4 times that for the oil and gastaken together. Economically accessible global coal reserves are expected to last at least another200 years. This clearly shows the eminent position coal is expected to enjoy during the foreseeablefuture as a power-generation fuel.
Use of coal as fuel brings in its wake its own share of problems, the most important being that offlyash generation. When pulverized bituminous or sub-bituminous coal (i.e.lignite) ground to 70%passing through 200 mesh is burnt in a boiler furnace within 900-1500 °C temperature range, non-combustible part of the coal gets converted into ash. Nearly 80 % of this ash `flies off' or getscarried away from the furnace by flue gases, which is then separated out by use of one or moreElectro Static Precipitators (ESP's) and is called `flyash'. The balance 20 % ash `agglomerates' to
13
Iarger particle sizes, ranging from 0.02 to 75 mm, and falls down to the bottom of the furnacethrough its grate as `bottom-ash'. Both these ashes are mixed with water and sent to ash pond forstorage and further disposal.
5.1 Present Flyash Production in India:
India is the 3 largest producer of coal in the world after China and U.S.A. However, Indian coalshave high ash content (35 to 55 % as compared to 8 to 10 % in developed countries like U.S.A.,Japan, Germany, France, etc.) and low calorific value. About 70 % of India's present power generationcapacity is coal-based. This situation is expected to continue at least till 2020.
Presently, India generates around 95 million tonnes of flyash per year and about 1,000 milliontonnes of flyash has already accumulated in Indian ash ponds. It is estimated that about 124,000MW of additional power generation capacity would be required by the end of the 10th Five YearPlan, i.e. the year 2007, to meet the growing indigenous demand arising out of rapid industrialization,farm mechanization and changing individual lifestyles. This will then lead to a staggering figure of175 million tonnes of flyash generated per year, which in turn would engage about 40,000 hectaresof land for construction of ash ponds.
Storage of flyash in ash ponds requires very large quantities of water (average ash : water ratio is1 : 12 ) and it involves huge capital and operating costs in setting up and running the mixing,pumping and transport facilities, respectively. It not only blocks large tracts of land permanently butalso results into serious groundwater contamination and deterioration of the surrounding eco-system.This brings to the fore the dire need of the hour to utilize as much quantity of flyash as possible andto solve its critical disposal problem.
5.2 Characterisation of Indian Flyashes :
The chemical and physical properties of flyash depend upon many parameters such as coal quality,type of coal pulverization and combustion process followed, nature of ash collection and disposaltechnique adopted, etc.
5.2.1 Chemical Composition:
Except Neyveli flyash, which is high in CaO (5.0 -16.0 %) and MgO contents (1.5 — 5.0 %) and lowin SiO content (45.0 — 59.0 %), the range of chemical composition of Indian flyashes is given inthe following Table. Corresponding data for American and German flyashes is also given forcomparative purpose.
14
Component i Indian flyash American German flyashflyash
Si02 50.0 - 65.0 40.0 - 51.0 42.0 - 56.0
Al203 16.0 -250 17.0-28.0 240-33.0
Fe2O3 55-152 ¡ 8.5 -19.0 5.4-13.0
CaO ( 1.5-2.5 i 1.2-7.0 ( 0.6 -8.3MgO 0.8-1.0 0.8-1.1 1 06 -43
Na20 Í 05 -0.9 j 0.4-1.8 1 02-13
K20 0 6 - 1.0 1.8-3.0 i 1.1-5k
SO3 05-0.8 0.3 -2.8 0.1 -19
LoI 2.0-15.0 j 1.2-18.0 0.8-5.8
From the above data it can be seen that Indian flyashes are more silicious and contain higherpercentage of unbumt carbon as compared to American / German flyashes.
5.2.2 Physical Properties :
Flyash is generally gray in colour, abrasive, acidic and refractory in nature. Its specific surface areavaries between 4,000 and 10,000 cm 2/g, which is more than cement, which has a specific surfacearea of about 3,000 to 3,500 cm2/g. Morphologically, flyash consists of 3 types of particles -irregularly shaped particles, solid spheres and cenospheres.
5.3 Flyash Applications :
Flyash is generally 'pozzolanic' in nature while bottom-flyash is generally not. Pozzolanicity of amaterial is its capacity to react with CaO or Ca(OH) in presence of water at room temperature toform solid and water-isoluble cementitious compounds. The pozzolanicity of flyash mainly stemsfrom the presence of various silicates and aluminates in amorphous form. This property is made useof in the manufacture of cured or autoclaved flyash products. When used as an admixture to plasticsoil / clay in the production of burnt clay bricks, flyash reduces the plasticity of the raw-mix(consequently reducing the drying time and shrinkage cracks), improves the texture of the productand increases the `internal burnability' of the green brick because of the presence of unburnt carbon(proportionately reducing the requirement of `external' fuel). Flyash can also be used as filler.
Some of the major applications of flyash are :
Brick manufacturing
Cement manufacturing
15
Partial replacement of cement in mortar and concrete
Roads & Embankment construction
Dyke raising
Structural fill for reclaiming low lying areas
Hydraulic structures
Stowing material for mines
Agriculture & Forestry
Other medium & high value added products (tiles, wood, paints, light weight aggregates,extraction of alumina, cenospheres, etc.)
6.0 Flayash Application in Burnt Clay Brick Manufacturing :
6.1 Geology and Characterization of Indian clays :
Stratigraphically, India can be divided into 3 broad regions — Extra Peninsula (NorthernMountainous Region), Indo-Gangetic Plain and Peninsula (Triangular Plateau Region). Ofthese, geologically, the Peninsular Region is the oldest, followed by Extra Peninsula andthen the Indo-Gangetic Plain. The mountainous soil is coarse and contains pieces of partiallyweathered rocks. The Indo-Gangetic Plain is formed by deposition of silt by Ganga and itstributaries and the soil is `alluvial' in nature. Its colour is faint yellow and it is a mixture offine sand, silt, clay and organic matter. It is considered good for brick manufacturing. ThePeninsular soils have varying colours and qualities and broadly, they are grouped under`regur' (black cotton), red or 'lateritic' soils. They are termed `difficult' for brickmanufacturing. Owing to these differences in the nature of available soils, the brick industryin the Indo-Gangetic Plain is dominated by Bull's trench kilns (wherein large-scale andcentralized production is practiced), while the Peninsula is dominated by open clamps(wherein small-scale and scattered production is practiced). The presence of brick industryin the Mountainous Region is negligible.
6.1.1 Chemical Composition :
Chemical analysis of a few soils used for manufacturing bricks in different regions of Indiavis-a-vis flyash is given on next page. From the table, it is evident that flyash is chemicallyvery similar to most soils / clays used in the manufacture of bricks.
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Component Indian North- D atia soil (near Kankia soil (near
flyash East Jhansi, M.P.) Berhampur,
Region Orissa)
SiO, 50.0-65.037.0-67.0 i 68.10 78.74
A1103 16.0-25.0I15.5-32.0 16.62 12.00
Fe,03 5.5-15.2 5.4-9.6 3.08 1.97
CaO 1 1.5 - 2.5 1 0.8-5.7 1 0.08 i 0.01
Paighat soil
(Kerala)
56.65
24.10
5.40
0.13
1.00
1.30
1.07
8.16
MgO 0.8-1.0 0.8-4.1
Na20 0.5-0.9 I 0.6-2.9
K2Q 0.6 - I
S03 0.5 - 0.8 -
Lol I 2.0-I5.05.3-17.4'
6.1.2 Physical Properties:
Source Name; A = Varanasi; B = Kankia (Orissa); C Pune; D = Palakkad (Kerala)
(a) Linear Shrinkages During Ambient Drying and Firing @ 950 0 C:
0.80
0.29
1.05
0.68
2.07
3.02
6.42
2.45
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(b) Grain Size Analysis by Sieving and Hydrometry:
Component iA IB{
IC DI I_
Coarse Gravel (%) 80 mm - 20 mm {- L I i-
Fine Gravel (%) 20 mm - 4.75 mm 101.47 1-°Coarse Sand/0 4.75 mm 2.0 mm 01.18 1.92 ^' 0.50
Medium Sand (%) 2.0 mm 0.425 mm ,08.82 29.26 DATA 13.50Fine Sand (%) 0.425 mm - 0.075 mm 104.42 122.50 1 141 35Silt (%) <0.075 mm 0.002 mm 180.00 144.75 ;NOT 54.65Clay (%) <0.002 mm ;04.00 [1.57
JAVAILABLE
(c)Atterberg Limits, Plasticity Index, Shrinkage Limit:
Component A B C DLiquid Limit (%) 26.00 26.00 34.00 40.00Plastic Limit ( %) 15.00 14.92 19.50 20.72Atterberg Plasticity Index(% )
11.00 11.08 14.50 19.28
Shrinkage Limit (%) 12.50 14.52 18.16 15.71
6.2 Manufacturing Techniques :
Burnt flyash-clay bricks can be manufactured by mixing upto 60 % of flyash with soil / clayand hand-moulding or extruding the mix. Firing can be done as usual in open clamp orvertical shaft or any continuous `annular' kiln (e.g. down-draught / fixed chimney / high-draught / Hoffman kiln). The extent of flyash utilization in the raw-mix depends upon thephysical properties of the soil / clay, viz, linear shrinkage, particle size distribution, plasticity,etc., and the quality requirements of the green as well as fired brick - which are dictated bythe market as also the moulding technique adopted. Thorough mixing of flyash with soil /clay is a must to avoid defects / breakages in green and fired bricks. Thus, (1) determiningproportion of flyash in the raw-mix and (2) ensuring its uniform mixing with soil / clay arevery critical.
For hand-moulding and sun-drying method, up to 7 % linear drying shrinkage and 10- 15 %Atterberg Plasticity Index (API) are generally desired. The same figures for soft extrusionand sun-drying method are 9 % and 15 - 20 %, respectively. These figures only provide
18
useful guidelines for designing the raw-mix in a laboratory and every mix has to be actuallytried in pilot-scale production before finalizing the manufacturing process. Box Feeders arewidely used for proportioning different raw materials. Volumetric measurement is the mostpractical method for proportioning the dry raw-mix ingredients. This is arrived at byconverting the `weight basis' raw-mix into volume basis' one using bulk densities ofindividual ingredients. For preparing a homogeneous mix of flyash and soil / clay, thefollowing methods / machinery may be used -
1. Manual mixing by `layering'
2. Rotavator
3. Pugmill
4. Panrnill / Disintegrator
5. Double-shaft `U' mixer
In the `layering' method, alternate layers of soil and flyash are laid one above the other in aheap, the height of each layer being proportional to its composition in the raw-mix. Theheap is dug vertically from top to bottom so that material in all intermediate strata gets fullymixed up in the process. Rotavator is a simple agricultural implement attached to the PTOshaft of a tractor and it is widely used by farmers for seed bed preparation, mixing of soilwith crop residue / manure, weed control and soil puddling. It is attached to PTO shaft of20-55 HP tractor by a three-point linkage. Depth can be controlled by the linkage and hydraulicsystem. Its use for raw-mix preparation - both with and without flyash - is becoming verypopular in Maharashtra. Pugmills — animal-driven as well as power-driven — are in use inWest Bengal and Uttar Pradesh since a very long time for preparing allulvial soil / silt. Thesame can be adopted for intense mixing of flyash and silt. Disintegrators are being used fordry-grinding of mix in the production of dust-pressed products in Gujarat while double-shaft `U' mixers are very common in the South for production of various extruded clayproducts. The same machinery can be used effectively for preparing flyash-clay mixture.
7.0 Government Initiatives and Incentives :
The Regulation notified by the Ministry of Environment & Forests, New Delhi (ExtraordinaryGazette Part II — Section 3 (i) dated 2 °d April 1996) has made it compulsory for all brickmanufacturers falling within 50-kilometre radius of thermal power plants to use at least 25% w/w flyash in their raw-mix. It has been amended on 27th August, 2003 by Governmentof India.
19
Apart from the technological R&D carried out by Thermal Power Plants and academic /R&D institutions, various departments and ministries of Government of India have taken anumber of initiatives for improving utilization of flyash. Since flyash utilization involvesmany disciplines like power, industry, finance, urban development, environment, scienceand technology, etc., these initiatives have to be often taken by inter-ministerial groups ormulti-disciplinary bodies. Some of the main initiatives taken so far are given below :
To encourage production and use of flyash-based products, Government of Indiahas withdrawn 8 % excise duty imposed earlier on such products. Now, no exciseduty shall be levied on manufacture of goods in which a minimum of 25 % w/wfly ash is used. Similarly, for import of equipment, machinery and capital goodsrequired for the production of flyash based products; additional customs duty hasbeen exempted.
• The National Housing Policy (1998) by the Ministry of Urban Development andsubsequent draft policy documents lay stress on promotion of low cost buildingmaterials which include flyash. Building Materials and Technology promotionCouncil (BMTPC) in 1990, under the aegis of Ministry of Urban Development,as an inter-ministerial apex organization, has been involved in coordination withvarious PWD schedules, preparation of technology profiles for various flyashbased products, providing inputs regarding technology scanning, fixing of landrent, policy review, etc.A centrally sponsored scheme National Network of BuildingCenters was launched in 1988-89 through HUDCO.
• HUDCO and NHB are extending financial support to promote industrial unitsfor production of building materials based on flyash.
The Ministry of Power (MoP) has proposed a legislative measure to curb utilizationof top soil for making bricks within a suitable distance like 50 kms from theThermal Power Plants, and providing fly ash free of charge.
• An inter-ministerial council — National Waste Management Council (NWMC)has been setup under the Ministry of Environment and Forests (MoEF) to utilizeindustrial wastes.
• A Fly Ash Mission has been constituted as the Nodal Agency under TechnologyInformation, Forecasting & Assessment Council (TIFAC) — an autonomous bodyof Department of Science & Technology - along with MoEF and MoP to work onlarge scale utilization of flyash and safe management of unutilized ashes.
20
State Governments of Orissa, Rajasthan, Andhra Pradesh, Tamil Nadu, Punjab,etc. have announced various schemes / measures to promote flyash utilisation.Government of Orissa has exempted flyash bricks and other products from salestax. A separate cell to promote use of flyash has been created in a few states.CPWD has included flyash bricks and blocks in their specifications and has decidedto construct at least one building using flyash bricks in each zone. DelhiDevelopment Authority (DDA) has included use of flyash in its tender documentfor construction of fly over bridges in Delhi.
8.0 Future Scenario :
As mentioned earlier, the industrial ecology concept — involving reuse and recycling ofwastes — holds much promise for the Indian Clay Brick Industry. It not only provides a wayto reconcile our developmental and environmental imperatives, but also throws open a hostof opportunities to develop, implement and market environmentally sustainable technologies.
Perhaps a concrete example shall explain this point better. At Kalundborg Industrial Complex,Denmark — a small coastal industrial zone 75 miles west of Copenhagen — a web of energyand material exchanges among companies has emerged over the last 20 years. The Kalundborgsystem consists of five core partners : Asnaes Power Station (a 1,500 MW coal-fired powerplant), Statoil Refinery (of 3.2 million tones / year capacity), Gyproc (a plasterboard factorymaking 14 million sq. metres of gypsum wallboard a year), Novo Nordisk (an internationalbiotechnology company with annual sales in excess of $2 billion, whose Kalundborg plantmanufacturers pharmaceuticals and industrial enzymes), and the City of Kalundborg whichsupplies residential heat and water to its 20,000 residents.
The power plant pipes residual steam to the refinery, and in exchange, receives refinery gas,which substitutes some of the coal. Excess steam is also supplied to Novo Nordisk and theCity (for heating). This replaces almost 3,500 individual oil furnaces, a major air pollutionsource. The power plant's de sulphurisation process also yields gypsum, which meets aboutone third of Gyproc's needs. Sludge from Novo Nordisk's processes is used as a fertilizer onnearby farms and surplus yeast from its insulin production is sold to farmers as pig food.
Industrial Clusters, in the form of industrial estates or industry belts, are quite common inIndia and more so in case of brick industry which exists in clusters. Therefore, planning andimplementation of `industrial recycling networks' at locations which are either near to thesource(s) of wastes (e.g. Coal-based Thermal Power Plants) or markets, appears very muchfeasible. However, to ensure the success of these industrial eco-systems, 2 pre-requisites
21
assume significance in the Indian context. First, the economic benefits of the exercise mustbe spelt out very clearly to the participating industries and second, our policy and regulatoryapproaches need drastic changes. Rather than being mere law-making, enforcing andmonitoring agencies, the Ministry of Environment and Forests (MoEF) and Central / StatePollution Control Boards need to achieve positive environmental outcomes through co-operation with the industry and by adopting incentive-based approaches.
22
STATUS REPORT ON VERTICAL SHAFT BRICKKILNS IN INDIA
by
SAMEER MAITHEL, N VASUDEVAN& Col. RAKESH JOHRI (Retd)
TERIINDIA HABITAT CENTRE, LODHI ROAD
NEW DELHI - 110 003TEL: 91-11-24682100, 24682111;FAX: 91-11-24682144, 24682145
e-mail : [email protected] site: http://www.teriin.org
Vertical Shaft Brick Kilns in India San:eer Maithel,N 17asudevan &
Col. Rakesh Johri*
Indian brick industry
India is the second largest producer of bricks after China. The estimated brick production during2000-01 was close to 140 billion bricks. The Indian brick industry is unorganised with smallproduction units clustered in rural and peni-urban areas. There are more than 100,000 brick kilnsoperating in the country. Brick making consumes about 24 million tonnes of coal and several milliontonnes of biomass fuels per year. Coal consumption by the brick industry is approximately 8% ofthe total coal consumption in the country. The share of energy in total costs of brick production is 35to 50%. Several types of brick kilns are used for firing bricks. The choice of technology dependsgenerally on factors such as scale of production, soil and fuel availability, market conditions andskills available. Table 1.1 shows brick kiln technologies used in the country.
Table 1.1 Brick kilns in India (2001)
Kiln type Typical.production capacity range Approximate(lakh bricks per year)# Number of kilns
BTK-Fixed chimney§ 30 - 100 20000
BTK-Moving chimney 20 - 80 13000
High draft/zig-zag firing 30 - 50 200
Clamps 0.5 - 10 > 60000
Vertical shaft brick kiln (VSBK) 5 - 40 27
§ About 40% of the fixed chimney BTKs are estimated to have gravity settling chamber# The brick making season in the country is generally 150-200 days in a year
The brick-producing regions in India can be categorized into two major zones based on nature ofsoil availability.
* Authors are working with the TERI, New Delhi- 110003
25
Indo-Gangetic Plains, consisting of the north and north east part of India. Good qualityalluvial soil is available for brick making in this region and large capacity BTKs are foundin this region. This region caters to about 65% of the total production.
• Peninsular and coastal India, consisting of the west, central and southern parts of Indiaaccounts for the rest 35% of total production. This region has shortage of good quality soilfor brick making. At present clamps and moving chimney BTKs are used for brick production.VSBK technology has higher potential in this region.
The brick kilns in general can be classified into (1) intermittent kilns and (2) continuous kilns(figure 1.1). An Intermittent kiln without permanent kiln structure is commonly called as clamp.Clamps are generally used when the volume of production is small. The production capacity ofclamps generally ranges from 5,000 to 5,00,000 bricks per firing. A variety of fuels such as coal,firewood, various types of agricultural residues, dung cakes, industrial wastes etc. are used in clamps.The arrangement of bricks in a clamp generally depends on the type of fuel used. Intermittent kilnshave low energy efficiencies as most of the heat in the flue gases, fired bricks and kiln structureremains unutilized.
BRICK KILNS
Intermittent Continuous
1. Clamp 1. Moving firing (annular kiln)• Hoffmann
2. Scove • Bull's trench kiln (BTK)• Zig-zag
• Habla3. Scotch • High draught
2. Moving ware4. Downdraught • Tunnel
• Vertical shaft brick kiln (VSBK)
Figure 1.1 Classification of brick kilns
Continuous kilns incorporate heat recovery features to utilise heat in fired bricks as well as heatavailable in hot flue gases. These kilns are superior to intermittent kilns in terms of energy efficiencyas well as the quality of bricks. Continuous kilns include bull's trench kilns (BTKs) with movingchimney and fixed chimney, Hoffmann kiln, high draught kilns and vertical shaft brick kiln (VSBK).Brick kilns can also be classified according to the production capacity. The Gazette Notification on"emission standards" for brick kilns classifies brick kilns into three categories:
(1) Small (production capacity less than 15000 bricks per day);
26
(2) Medium (15000 to 30000 bricks per day); and(3) Large (more than 30000 bricks per day).
Introduction to vertical shaft brick kiln (VSBK) technology
Historical development
Vertical Shaft Brick Kiln (VSBK) technology is an energy efficient technology for firing clay bricks. It isparticularly suited to the needs of brick production in developing countries - which is small scale anddecentralized type. The evolution and initial development of VSBK technology took place in rural China.The first version of VSBK in China originated from traditional updraft intermittent kiln during 1960's.During 70's, the kiln became popular in several provinces of China. In 1985, Chinese governmentcommissioned the Energy Research Institute of the Henan Academy of Sciences at Zhengzhou (Henanprovince), to study the kiln to improve the energy efficiency. Several thousand VSBKs were reported to beoperating in China in 1997. Attempts to disseminate VSBK technology outside China started in early1990's. Apart from India, the VSBK technology was demonstrated in several Asian countries suchas Nepal, Afganistan, Pakistan, Vietnam and Bangladesh.
VSBK technology in India
Under an `Action Research Project' supported by the Swiss Agency for Development andCooperation (SDC), four VSBK pilot plants were field-tested during the period 1996-99. Thelocations for the four pilot plants were selected so as to test VSBK technology under different `soil-fuel-climate-market' conditions.
Presently there are about 27 VSBKs are in operation in Madhya Pradesh, Maharashtra, Orissa,Uttar Pradesh, Karnataka and Tamil Nadu. A list of places where VSBKs have been installed under
the SDC sponsored India Brick Project (IBP) is given as table 2.1.
Table 2.1 VSBKs in India (as on January 2003)
Category MadhyaPradesh
UttarPradesh
Maharahstra Orissa/Karnataka/Tamil Nadu
Privarely owned and managed 8 2 7 1
IBP-funded - - - 3
Self-replicated and privately 2 - - 4
owned
Total 10 2 7 8
27
Technology adaptation under local conditions
Several design modifications have been incorporated under the IBP in the original Chinese VSBKdesign to improve its performance in energy, environment and product quality aspects. These include:
. Increasing cross-sectional area of shaft to increase production capacity;
Increasing the height of the shaft to improve energy efficiency;
Increasing the height and the area of the chimney and use of a single chimney per shaftinstead of two chimneys per shaft;
• Incorporation of shaft lids to reduce air pollution at the working platform;
Use of cooling chambers for controlled cooling of the unloaded bricks; and
Instrumentation (thermocouples to measure brick and flue gas temperature) for kiln operationand control.
India Brick Project (IBP)
The IBP programme is supported by the Swiss Agency For Development and Cooperation(SDC) since 1995. Promotion of VSBK and empowering of small brick producers throughsustainable methods are the twin objectives of IBP.
IBP has a partner network consisting of Tata Energy Research Institute (New Delhi),Development Alternatives (New Delhi), Gram Vikas (Orissa), Damle Clay StructuralsPvt Ltd (Pune) and Fourth Vision (Ahmedabad).
The project partners provide assistance in the construction, operation and troubleshootingof VSBKs. Training of manpower for VSBK construction and operation is also providedby the project
Further efforts are being made to reduce the cost of the kiln, simplify its operation and demonstrationin new regions. Several new VSBKs are under planning and construction stage, which will soonbecome operational. The main advantages claimed for VSBK technology are:
a) Highest energy efficiency among all types of kilns;
b) Lower emissions;
c) Small area requirement; and
d) Uniformity in the quality of the fired bricks.
28
Figure 2.1 View of some of the VSBKs in India
29
Working principle and design considerations of VSBK
3.1 Working principle
The VSBK is a vertical kiln with stationary fire and moving brick arrangement. Figure 3.1 showsthe cross-section of a two-shaft VSBK kiln. The kiln shaft has rectangular/ square cross section.The kiln operates like a counter current heat exchanger, with heat transfer taking place between theair (moving upwards) and the bricks (moving downwards). The kiln can be divided into threedistinct sections. The top section is the brick-preheating zone, the middle section is the firing &heat soaking zone and the lower section is the cooling zone for bricks. The shaft wall (inner surfaceof the kiln) is usually lined with refractory bricks and the outer kiln wall is made up of red brick.The gap between the shaft wall and outer kiln wall is filled with materials such as clay, fly ash etc.
VSBK is a natural draft kiln,requiring no electricity forsupply of combustion air. Theair required for combustionenters from the bottom of thekiln. It extracts the heat fromthe cooling bricks beforereaching the firing zone. Theflue gases leaving the firingzone exchange heat with drybricks loaded herebypreheating them. The fluegases finally enter the chimneythrough the flue duct at atemperature of 60 to 150oC.Each shaft is provided with twochimneys placed diagonallyopposite to each other. TheseLids are provided at the shafttop which direct the gases topass through chimney. A singlescrew jack system is used forunloading of the fired bricks.
High unloading temperaturescan lead to formation of
Figure 3.1 A two-shaft VSBK cooling cracks* in the fired
* Cracks formed due to sudden cooling of fired bricks. This problem has been observed is some VSBKs where theunloading temperature of bricks exceeds 200 °C.
9M
bricks. To reduce the formation of cooling cracks, cooling chambers are provided at the end of theunloading tunnel. The unloaded bricks can be kept in these chambers for controlled cooling ofbricks. These chambers are particularly useful for high vitrification temperature soils (vitrificationtemperatures > 1000°C).
3.2 Operation
Dry bricks are loaded from kiln top in batches. Each batch has four layers of bricks in a predeterminedpattern (figure 3.2). A predetermined quantity of crushed coal is also fed along with dry bricks. Thenumber of bricks per batch depends on the cross-section of the shaft. Larger the area of cross-section, higher will be number of bricks produced in a batch. However it can't be increased beyond1.25 m X 2.0 m because of screw jack limitations. Table 3.1 shows the production capacity ofbricks per shaft per day in VSBKs.
Table 3.1 Production capacity in VSBKs
Shaft size(metre X metre) Production capacity(bricks per day)
1 X 1 20001 X 1.5 30001 X 1.75 35001X2 4000
1.25 X 2 5000
Note: (1) For brick size of 230 mm X 110 mm X 70 mm; and(2) Number of unloading assumed as 11 batches per day
Unloading of fired bricks is carried out at an interval of 2-3 hours. The total time for firing brickson batch wise in VSBK varies between 20 to 40 hours. Duration of loading and unloading variesbetween 15 to 20 minutes. A trolley mounted on a screw jack is the main equipment used forunloading the bricks. The unloading of bricks creates space at the top of the shaft in which a newbatch of bricks is loaded. The procedure of unloading and loading is now described in followingsections.
The sequence of operations for unloading for at batch is shown in figure 3.3. Figure 3.3 (a) showsthe normal operating condition :
• The column of bricks in the shaft is resting on support bars (solid or hollow rectangularsteel bars).
• Empty trolley is resting on the ground.
The screw jack is in fully retracted position.
For unloading, the trolley is lifted up using the screw jack. On lifting, the wooden planks kept onthe trolley, go in the gap between the support bars and touches the bottom surface of the brick
31
Figure 3.2 Layer by Layer Brick Arrangement in a Batch
32
wCcj
Q
ZrL6J
C)
bU^e^a
setting. On further tightening of the screw, the weight of the brick column is transferred on to thetrolley and the support bars become free and are pulled out. This position is shown in figure 3.3 (b),in which:
The screw jack is in fully extended position.
The support bars have been withdrawn and the brick column in the shaft is nowresting on the trolley.
After removal of the support bars, the brick column resting on the trolley is lowered using the screwjack. The lowering is continued till the row of gaps in the brick setting are just above the top levelof the support beam. This position is shown in figure 3.3 (c). Now the support bars are inserted inthe gaps. After inserting the support bars, the lowering is continued till the support bars rests on thesupport beams and the weight of brick column is again transferred back on to the support bars.Further lowering of the trolley results in detachment of one batch of fired brick from the main brickcolumn. The batch resting on the trolley is lowered to the ground this is shown in figure 3.3 (d), inwhich:
The screw jack is in fully retracted position.
The main brick column is now resting on the support bars and the trolley with abatch of fired bricks is resting on the ground.
The completion of unloading operation creates space for loading a new batch of green bricks at thetop of the shaft. The bricks are arranged in the shaft in layers as per the arrangement shown earlierin figure 3.2. Three densely packed layers are followed by a fourth layer having gaps for supportbars. Crushed coal (particle size 0-15 mm) is weighed and spread over each layer of bricks.
The fuel added along with bricks is referred to as "external fuel". Crushed coal is generally used asexternal fuel in VSBKs. Recently, lignite, charcoal and firewood has also been successfully used asexternal fuel in VSBKs. Apart from the external fuel, generally some powdery fuel is also added insoil during soil-mix preparation stage, this fuel is referred to as "internal fuel". A number of fuelssuch as coal powder, fly ash, bagasse, rice husk etc. are used as internal fuels. The extent to whichinternal fuels can be used is dictated by soil quality and desired brick quality.
3.3 Design
VSBK is modular in construction. The most important component in VSBK design is thedetermination of the dimensions of the shaft (cross-section and height).
(i) Cross-section of the shaft
The nominal shaft cross-section is chosen based on the desired production capacity as per table 2.1.The exact shaft cross-section is calculated based on the size of dry green bricks. The internal shaftcross-section dimensions A and B (refer figure 2.2) are calculated using formulae as given on nextpage.
34
A=(L+G)XNLB= (L+G)XNw
Where,L = Length of dry green brickG = Gap between bricks (of about 10 mm) required to ensure air/
gas flow and for accommodating fuel between the bricksNL = Number of bricks accommodated along dimension A
(e.g. NL = 7 for brick arrangement shown in figure 3.2)Nw = Number of bricks accommodated along dimension
(e.g. Nw =4 for brick arrangement shown in figure 3.2)
(ii) Height of the shaft
The height of the shaft varies between 3.6 to 6,0 in (i.e, number of batches of bricks that can beaccommodated in the shaft varies between 8 to 13). The height sof the shaft depends on the strengthof dry green bricks available for brick production. The regions where good quality green bricks areavailable e.g. Jndo-Gangetic plains, shaft height of 5.5-b,0 m is used. For areas having poor drygreen brick quality e.g. Maharashtra, shaft height of 4.0-S.0 m is used. The height of the shaft iscalculated as below:
H=[(W+ 4)K4XNI+W+ 50
Where
H = Height of shaft in mmN = Number of batches in the shaftW = Width of brick mm
The thickness of the walls of the kiln is determined depending on the storage and working arearequirement at the kiln top.
3,4 Construction
The typical construction cost of single VSBK shaft ranges from Rs 2.5 to 3.5 lakh. The bill ofquantity for a 2 shaft VSBK are provided in table 3.2. The construction period of a VSBK rangesfrom 30 to 45 days. VSBK construction requires supervision from a trained construction supervisor/engineer. Special care is required during following stages of construction:
• Layout marking
Arch construction
Shaft construction particularly for the refractory brick masonry work and ensuringverticality of the shaft
• Flue gas outlet construction
35
Table 3,2 Construction materials required for a two-shaft VSBK (8000 bricks day capacity)
S.No Item material Specification Quantity
Bricks
Refractory bricks
Refractory clay
Cement
River sand
Boulder (Big stone)
I section for screw support
I section for Rail beam for support bar
Channel beam for shaft support
Support plate for screw I beam
Support plate for brick support I beam
Support plate for channel steel
Trolley guide
Angle iron for trolley track
Steel iron rod
Screw jack assembly
Trolley
Roofing material
9"4.5"'3" 40,000
9"4.5"'3" 3,100
50 kg/bag 10 bags
50 kg/bag 70 bags
400 Cu' ft/truck 4 truck
400 cu, ft/truck 4 truck
150X80, L=2520 mm 4 Nos
200X100, L=2480 mm 4 Nos
L,=2420 mm, 125X55 mm 2 8 Nos
350 mmX250 mmX8 mm 4 Nos
250 mmX250 mmX8 mm 8 Nos
280 mmX250 mmX8 mm 8 Nos
50 mmXIOO mm, L.=1100 mm 8 Nos
50 mmX50 mmX5 mm=6000 mm 4 Nos
Dia 6 mm 40 kg
lno,
2 no.
According to local requirement
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Note: The above table does not include the requirements for ramp/lifting arrangements, cooling chambers,
Performance measurements of VSBKs
4.1 Energy performance
The energy performance of brick kilns is calculated as the thermal energy consumed per kg ofbricks fired (MJ/kg brick fired). Coal is generally used as the external fuel in VSBKs and fuelssuch as coal powder, boiler ash, biomass fuels such as rice husk are added as internal fuel. Whileinternal fuels are added during moulding process, the external fuel i,e. coal is added during eachloading operation.
36
The specific energy consumption of VSBK technology was observed to be the lowest (0,74 to 1.1MJ/kg fired brick) ,fahle 4,1 shows the specific energy consumption of few V$BKa monitored byTERI.
Table 41 Specific energy consumption of other VSBKS
VSBK State Specific energy consumption(MJ/kg fired brick)
VSBK -Data Madhya PradeshVSBK -Kankia OrissaVSBK -Puns MaharashtraVSBK - Varanasi Uttar PradeshVSBK - Amravari Maharashtra
Source: TERI report
A comparison of specific energy consumption of different brick making technologies are shown infigure 4.1, which clearly shows that specific energy consumption for VSBK is much lower ascompared to other brick firing technologies.
0.841,060.850.830.78
Figure 4.1 Specific Energy Consumption of Brick Kiln Technologies
37
The heat input in a brick kiln is in the form of fuel. Different heat output components are free-moisture removal, heat for chemical reactions, flue gas loss, surface heat loss, residual heat inunloaded bricks and unburrtt carbon losses. A typical energy balance of V SBK is given in table 4.2.
Table 4.2 Heat Balance of VSBK
Component Share (%)
Heat for free moisture removal 10%Heat for chemical reactions 37%Flue gas loss 18%Surface heat loss 6%Heat loss from exposed bricks 14%Residual heat loss 8%Heat loss due to "CO" formation 3%Unaccounted losses 4%Total heat input = 0.84 MJ/kg / fired brick
Note: Data of VSBK-D4tiaSource: Action Research project on brick kilns (October 1997 to June 1999), TERI
4.2 Stack emissions
In BTKs, the SPM (suspended particulate matter) emissions generally follow a cycle, SPM emissionsare higher during fuel feeding and will be louver during non-feeding. IN VSBK, fuel is fed alongwith brick setting, which means the SPM emissions are fairly constant during entire operation ofVSBK. The SPM emissions from VSBK were found to vary between 77-250 mg/Nm3, Table 4.3shows SPM emissions from different brick kilns. As can be seen, the SPM emissions from VSBKsare much lower than the stringent standards of 750 mg/Nm3 .
Table 4.3 Typical SPM emissions from brick kilns (mg/Nm3)
Kiln Fuel feeding Non-feeding Weighted average
Fixed chimney 550 220 350High draught 850 350 550VSBK N.A. N.A. 170
N.A. - Not Applicable
Source: Draft report on "Development of emission standards and stack height regulations for thevertical shaft brick kilns (VSBK) vis-à-vis pollution control measures" submitted by TERI to CPCB.
38
Conclusions
A comparison covering both technical and economic aspects of VSBK and BTK kilns of similarcapacities for Gwalior is presented in table 5.1.
Table 5.1 Comparison of VSBK and BTK at Gwalior
S No lJataI information VSBK BTK1 System description 6-shaft VSBK with Fixed
each shaft of I m x chimney2m system
2 Production capacity 30,000 to 36,000 25,000 to(bricks per day) 40,000
3 Investments for kiln Rs 15 lakh Rs 10 lakhconstruction(materials, wages,consultancy)
4 Coal consumption 10 to 11 tonne * 14 to 18 tonne(per lakh bricks)(GCV of coal =5000 kcal/kg)
5 Quality of bricks• Class-1 80-84% 65-70%n Class-2 8-10% 20-30%• Class-3 — 3-5%• Broken bricks 8-10% 2-5%
6 • Manpower requirementsfor fiprin
24 6
• Wages per month) Rs 60,000 Rs.15,000
7 Land requirements for kiln 400 to 500 sq. m 2000 sq.mconstruction
* In practice 5-6 tonnes of coal (external fuel) and 8% by weight boiler ash (internal fuel) is used. These have beenconverted into equivalent coal for direct comparison with BTK.
The data presented in table 5.1 is region specific and pertain only to Gwalior. Very large diversity isfound across different geographical regions in terms of quality of raw material used for brick making(soil and fuel), skills, labour cost, market price of bricks and the quality of bricks produced. Hencesimilar comparative statements comparing VSBK technology with other firing technologies wouldhave to be prepared separately for different geographical regions.
The experience so far indicates that the data related to fuel consumption, manpower and arearequirement for VSBK technology show little variations across different geographical regions. Otherparameters (particularly those related with quality of fired bricks, production capacity, wages)
39
show significant variations. In an overall analysis it appears that VSBK is one of the viable optionsfor firing of bricks in decentralised small-scale production in India.
While factors such as fuel options, marginally higher costs for construction and mechanism/arrangement to lift dry brick have to be considered while opting for VSBK, the technology offersseveral positive features, which are:
1. High fuel efficiency, with average fuel savings of about 20% compared to BTKs and 50-60% compared to clamps
2. Lowest SPM emissions
3. Lower fugitive emissions and cleaner working environment
4. Consistency in fired brick quality
5. Less space requirements for kiln structure (space saving of about 60% compared to BTK)
6. Kiln structure is weather protected and hence VSBK can be operated even during rainyseason hence extending the brick firing season.
7. Provides flexibility in production. The kiln can be easily started and stabilizes within a veryshort time and hence, depending on market demands and raw material availability and theproduction can be varied.
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DEMONSTRATION OF ENVIRONMENTFRIENDLY, FIRING TECHNOLOGY
FOR BRICK KILNS
by
RAJINDER SINGHDIRECTOR
PRIYA BRICK TECHNOLOGY CONSULTANCY SERVICES LTD.J-1/160, RAJOURI GARDEN, NEW DELHI-110027
TEL: 91(011) 25163035/25150580FAX: 91(011) 25413620
email : [email protected]
Demonstration of Environment Friendly, Rajinder Singh*Firing Technology For Brick Kilns
ABSTRACT
The project envisages development of techniques to reduce environmental pollution rendered bybrick kilns, by designing, developing, installing methods to incorporate the use of Natural GasPulverized Coal firing systems, the less polluting energy sources into the brick making process.Specifically the project team will design, develop, install, commission brick kiln which will usenatural gas or pulverized coal for firing of bricks, thus reduce fuel consumption and the pollutionemitted by the firing process. The project entitles:
• Availability of continuous natural gas for use by brick industry.
• Construct a Demo Brick Kiln in the area adapted to zig-zag firing of bricks using naturalgas/pulverized coal.
• Design, procure, install and integrate-natural gas/pulverized coal related system, parts,supplies, accessories, instruments, control and safety equipments.
• Validate process and train workmen on using the technology.
• Monitoring and data collection under controlled conditions for the above kiln forenvironmental and operational parameters aspect.
• Validate and determine optimum design parameters for brick kiln and system assembly andsubsystems that can be adopted on large scale for commercial success.
• Transfer the benchmarked technology through an on-site demonstration model thusconstructed.
In India, the current method of brick firing uses coal in Bull's Trench kilns. Consequently, thesebrick kilns emit tremendous amount of pollutants in the area. Considering the environmentaldegradation caused by these brick kilns, the Hon'ble Supreme Court of India has ordered the closureof all the brick making units in the Taj trapezium.
The premise of this project is that the uses of natural gas/pulverized coal as a clean, continuouslyand readily available energy source. This will not only reducerpóllution and specific fuel consumption,but will also increase brick makers profits by the energy saved in the firing process, and the improvedquality of the finished brick.
* Author is working as Director with the Priya Brick Technology Consultancy Services Ltd., New Delhi-110027
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GOAL
To reduce environmental pollution by using natural gas/pulverized coal for firing of bricks andimplement energy efficiency techniques into the brick making process.
PROJECT HIGHLIGHTS
Provide a concrete, easily adaptable solution to address air quality problems, in India,from brick kilns.
• Address a CPCB priority - reduce ambient concentrations of air pollutants to mutuallyacceptable levels throughout the country by brick kilns.
Collaboration between premier organizations working in the sphere of brick making.
RATIONALE
The project is concerned with lessening the environmental impact that the brick making industryhas on air quality. In order to help combat the air pollution problem, the collaborators will developtechniques to reduce environmental pollution by designing methods to incorporate the use of lesspolluting energy sources i.e. natural gas/pulverized coal into the brick firing process, and to increasethe energy and process efficiency of the brick industry.
The CPCB clearly states that one of the primary objectives in the Taj trapezium is to reduce ambientconcentrations of air pollutants to mutually acceptable levels. This priority is due to the fact that airpollution in brick kilns in Taj trapezium is a primary cause of regional environmental degradation.In compliance of the hon'ble Supreme Court's order dated 12th December 2001 the CPCB andU.P.Pollution Control Board has identified 21 brick kilns operating in Taj trapezium.
Due to rapid population and industrial growth, and lack of sufficient pollution control and monitoringdevices the Taj trapezium has worst air pollution in North India. Although there is no definitivestudy on the subject, what data that have been collected, point to the brick kilns as one of the majorcauses of air pollution. This is symptomatic of all of India where, although thousands of these smallindustries provide an essential source of building materials for the growing population, they alsoemit high levels of contaminates into the air.
The brick kiln industry in the Taj trapezium is a small, labour intensive industry that supportsapproximately 2,500 dependent family members. Throughout India, regardless of the size of thecity, bricks are still produced as they have been for centuries. They are made by hand, dried in thesun, and generally fired in Bull's Trench kilns that use various types of fuels. Firing can last for upto seven months, all the time being fed by the fuel that is cheapest and most accessible. Often, dueto economic factors, that means waste fuels, such as scrap wood or wood by products, or trash. Thisuse of waste fuels pours high amounts of contaminates into the air. The basic premise of the projectremains:
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The environmental concern is to maintain a minimum standard of air quality whichassures continuing well being of all natural flora and fauna, human being and heritage.
To maintain the general air quality the issue which needs to be addressed is not howmuch pollutant per cubic meter stack emission are being emitted but how much pollutantload can be imposed on the system without upsetting the delicate balance.
• To achieve this objective we should be more concerned with the pollution load i.e thespecific emission than the height of chimney or anything else.
APPROACH
In order to lessen the environmental impact that the brick making industry has on air quality, notonly in the Taj trapezium but throughout India, there is a need change of brick kiln designs andbrick making processes to incorporate natural gas/pulverized coal as energy source instead of coaland other materials. This project is directed toward the development of use of natural gas/pulverizedcoal as source of brick firing in conventional kilns, thus reduce fuel consumption and the pollutionemitted by the firing process.
In order to reach this goal the project is focusing on:
System analysis of the manufacturing processes;
Incorporation of energy efficiency techniques into the process; and
• Use of natural gas/pulverized coal as an alternative energy supply for the firing of bricks.
This project can be a pilot project for CPCB . In which CPCB and other agencies coordinate effortsin the country; provides support to the project collaborators, make adjustments to content, scopeand presentation as necessary; and incorporates information provided regarding energy efficiency,process analysis and use of natural gas/pulverized coal.
PROJECT PROCESS ANALYSIS
The project team formed will determine the most effective methods to incorporate use of naturalgas/pulverized coal into the process of brick firing. The project shall be split into the followingcomponents:
Collect and review existing data on brick kiln design and the brick making process toincorporate natural gas/pulverized coal instead of present method for firing of bricks inthe existing kilns.
Collect additional material/data on the availability of natural gas in the region.
Design the system and perform systems analysis to determine process efficiency.
45
• Procure necessary equipments, fittings, burners, piping material, equipments, valves,control mechanism and safety devices for use of natural gas/pulverized coal.
• Install and test the natural gas firing system/pulverized fuel firing system.
• Design methods to increase efficiency and productivity.
• Present results at and revise designs if any based on results.
• Provide information to CPCB .
All steps in the brick firing using natural gas/pulverized coal process have to be analyzed towardsmaking the process design more ergonomically and work energy efficient.
NATURAL GAS FIRING
Natural gas is the cleanest fuel among the fossil fuels. In industry, gas is mainly used for processheating and firing of furnaces and kilns and developments in combustion technology have focusedon making gas burners as efficient as possible. Now microprocessor controls ensure optimumcombustion conditions and heat exchangers are used to recover waste heat. New burner designs arealso being developed. One such design is the Gyro-therm burner, developed in South Australia. Theburner improves the efficiency of combustion and reduces nitrogen oxide emissions. It can be usedin a wide range of industries and is being installed in plants in Australia and overseas.
Natural gas is primarily composed of methane, CH 4 When mixed with the proper amount of airand heated to the combustion temperature, it burns.
PRINICIPALS OF NATURAL GAS in BRICK FIRING
• The piped high pressure gas is reduced to a pressure of around 4kg/cm2 and then ignitesin the kiln via approximately placed burners.
• The quantity of the gas is metered through solenoid controlled valves which are operatedby controlling on and off time.
• Depth of the flame is controlled by suitable adjustment in the valves.
• To ensure complete combustion in preheating zone , appropriate ignition devices areincorporated.
Pulverized Coal Firing
Coal-fired boiler systems generate approximately 38% of the electric power generation worldwideand will continue to be major contributors in the future. New pulverized coal-fired systems routinelyinstalled today generate power at net thermal cycle efficiencies ranging from 34 to 37% (higherheating value) while removing up to 97% of the combined, uncontrolled air pollution emissions.
46
• The concept of burning coal that has been pulverized into a fine powder stems from thebelief that if the coal is made fine enough, it will burn almost as easily and efficiently asa gas.
• The feeding rate of coal according to the kiln demand can be controlled.
• Pieces of coal are crushed between balls or cylindrical rollers in appropriate grindingmachines.
• Air is used to blow the usable fine coal powder to be used as fuel directly in the furnaceor kiln.
• Under operating conditions, there is enough heat in the combustion zone to ignite allthe incoming fuel.
As the fineness increases (reduction in coal particle sizing), fuel balance improves.
• The finer the coal, the more the two-phase mixture (coal and air) behaves like a fluidthan a solid in suspension.
• The more homogenous mixture of air and coal results in even distribution.
NATURAL GAS FIRING VIS-A-VIS PULVERIZED COAL FIRING
Parameter ExistingTechnology
Pulverized fuel Natural gas
Product Quality Medium High Very good
Generation of SPM Very High Low Nil
Combustion efficiency Poor Good Very good
Green House gas High Moderate Low carbonemissions-high methane
Complexities oftechnology
Low Medium High
Adaptability Easy Comfortable Difficult
Capital cost Low Medium High
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Some Important considerations for Natural Gas Fired Kilns
Gas burners require large volumes of oxygen to complete combustion. Typically a natural gas burnerrequires for every 1 cubic meter of gas to be burnt, 10 cubic meters of fresh air. Fresh air for the kilnshould be available using fixed venting at a low level in the door or wall or through a powered fan.The vent size is sized by determining the MJ/Hour total burner rating. If the air is drawn fromoutside, the rate in our area is 160mm2 per MJ/Hour, therefore a typical gas kiln with 2 burners withan input of 400MJ/Hour would require fixed ventilation of at least 250 x 256 mm. If the kiln isdrawing air from the exposed air, area should be doubled.
Flueing
All gas fitting or flueing work will be undertaken by a licensed gas-fitter.
The products of combustion can contain hazardous gasses - and should be safely exhausted toatmosphere. A natural gas burner using 1 cubic meter of gas will produce 1 cubic meter of carbondioxide, 2 cubic meters of water vapor and 8 cubic meters of nitrogen. If the fresh oxygen supply isrestricted and the combustion process is incomplete carbon monoxide will result. This is a lethalgas even in small quantities. Of course, this is a common occurrence in reduction firings and theneed to be absolutely sure the gases are safely removed from the work area is vital.
The chimney (or flue) should be of the correct construction. It is possible to construct a brickchimney but is usually more economical to use a metal type with the large variety of connectionsand accessories available. A draft terminal can be fitted on top of an existing brick flue with theright adapter. A metal flue will also reach operating temperature, or a temperature to create sufficientdraw, quicker than a brick chimney. Generally it is more economical over the longer term to specifya stainless steel flue. It is not necessary with gas kilns fitted with venturi burners to have a chimneythat is excessively long. This used to be essential with oil burners or gas burners that relied on largevolumes of primary air (air required around the burner tip to complete combustion) for combustionas the chimney height determined the draw available.
The flue on modern downdraft gas kilns are generally terminated near the top of the kiln, a canopyis fitted over this, a pipe is continued through the roof and an approved terminal is connected to theoutlet. The canopy is necessary for two main reasons:
The canopy will slow down the draw from the kiln. Too much draw will make the kiln inefficientthrough pulling the heat through the stack before it has completed its task and can contribute touneven temperatures.
The air canopy pulls in helps to dilute the flue gasses, cooling them to ensure the chimney lastslonger and saving our environment.
It is important that the canopy is larger in area than the outlet from the kiln. This ensures that thereis no spillage of gasses. The canopy should also be a certain shape so that there are not sharp edges
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or steps to cause turbulence. This can induce spillage and effect the passage of gasses. It is a goodidea to buy a ready made unit from companies that have experience in gas flueing.
If the pipe is passing through a roof it is necessary to have a minimum clearance from any combustiblematerial of 600mm however this can be reduced if the material is protected with insulation. Anapproved flue cowl should be fitted to the end of the stack. This will help to ensure the wind doesnot affect the firing, birds stay out of the chimney and there is not excessive draw from the flue.
SAFETY DEVICES FOR KILNS
There are a range of safety devices available that will help alleviate some of the concerns with gasfiring:
1. High temperature cut-out
This device can be fitted to either gas or electric kilns and will ensure the kiln will shutdown at a preset maximum temperature in case the operator is not in attendance. It consistsof a temperature controller, probe and a connection to a gas solenoid on a gas kiln or awiring bridge to the contactor an electric kiln. The temperature controller can be either acheaper "blind" model that does not indicate temperature or the indicating type. Accuratedigital units can be quite inexpensive and will provide all the advantages of digital temperatureindication.
Cones and a special device called a "kiln sitter" can also be employed. The kiln sitter monitorsthe temperature and is activated when the desired cone bends, operating a switch.
2. Thermoelectric Safety Devices
The most common approved device is the thermoelectric type. This incorporates a pushbutton unit and the copper safety probe heated by the flame. These are quite reliable andsimple to operate although these can be disabled. As long as the probe is kept away from thehot burner port and the device is sensibly maintained, a long life should be expected. Themain disadvantage is that the unit takes approx. 10-15 seconds to close in the event of flameout. Although this is quite acceptable according to the gas regulations, many work placesfor the quick lockout units for increased safety and ease of use.
3. Flame Safety (Electronic Flame Safety and Ignition)
The electronic safety units utilize a gas solenoid, burner electrodes and a small control unit.These kits, that are required as standard equipment in most schools, shut down the gas inless than 1 second. They also have the added advantage of allowing the burner to be lit bysimply operating a start switch. A relay is closed to power an ignition transformer and openthe gas solenoid. The small spark will ignite the burner, the safety electrode senses theflame and allows the gas to safely stay on. The sensing electrical circuit works on the principal
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of flame rectification.
Briefly, these systems rely on the ability of a flame to conduct a current when a potential isapplied across it. The flame relay detects the DC voltage that is produced when the ion flowis larger in a single direction.
These systems have several important advantages:
• The flame failure lockout time is less than 1 second, thereby ensuring no build up ofunignited gas.
• Long life for the components as the wire used can withstand very high temperatures.
Automatic operation ensures the burner can be started remotely, by a time switch startor a temperature programmer.
As long as certain principles are applied, such as ensuring the earthing area for the current flow isfour times the area of the sense rod, these should provide trouble free service.
There are other flame sensing systems used that are generally more industrial. The most common isUV (ultra violet) sensing that uses a special globe to sense the UV radiation emitted from a flame.The components are more expensive but are preferred for larger burner units where there may behigher flame temperatures.
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AIR POLLUTION CONTROL IN CUPOLAFURNACE BY ADOPTING BETTER OPERATING
& METALLURGICAL PRACTICES
by
Er. M.S. JAGGI & Er. S.K. JAIN
PUNJAB STATE COUNCIL FOR SCIENCE & TECHNOLOGYADJ. SACRED HEART SCHOOL
SECTOR - 26, CHANDIGARH - 160 019PHONE: 0172-2793300, 2792325, 2793600
FAX: 0172-2793143e-mail : [email protected]
Air Pollution Control In Cupola FurnaceBy Adopting Better Operating &Metallurgical Practices Fr, M,S, Jaggi & Er, £K, Jain*
Foundry sector has been identified as one of the major air polluting units, specially the Cupolafurnace, Most of these units fall in the small and unorganized sector with limited capital base andinadequate technical background, About 80®/a of the units have less than 3 tonne per hour of themolten metal capacity and their total output is less than 100 MT per month? Various studies hadrevealed that emissions Containing mainly particulate matter and SO 2 from the melting section ofsuch units are on very high side, This had resulted in closure orders to 212 cupola furnaces at Agraby the Hon'ble Supreme Court of India, resulting in tremendous pressure on cupola furnaces inother states also. Hence, the need to identify cost effective air pollution control technology forcupola furnaces.
CUPOLA FURNACE
Cupola furnace is a relatively high thennal efficiency furnace in which melting of pig iron and castiron is done with the help of hard coke. About 1/3rd of the heat supplied by the coke is available tomolten metal. The furnace not only melts the metal charged into it but also alters its composition.Hard coke, pig iron and CI scrap are used as raw materials. Limestone is used as flux with thecharge materials, which improves the fluidity of molten metal. Various processes involved aremelting of charge materials, molding and core making, sand preparation, metal pouring, fettling,machining, etc, The chief source of emissions in these units is charge material melting process,which is being done in the tirnace for producing gray iron castings.
The other auxiliary iron foundry operations are intermittent. The hot metal is drawn continuouslyfor castings by ladles. During cupola operation liquid slag is formed by silicon present in the chargematerial and ash generated due to coke burning.
CHARACTERISTICS OF EMISSIONS FROM CUPOLA FURNACES
Cupolas mainly emit dust and grit in the form of particulate matter and stack gases carrying thesesolids are fairly large in volume, hot and potentially corrosive. The particulates are mostly metallicoxides, unburnt coke fines and fly ash arising out of the burning of coke. The quantity of theseparticulate emissions is a function of several factors such as size and design of cupola, size andnature of raw materials, volume and velocity of blast, temperature, etc.
Smoke from dirty scrap consisting of minute particles, is more difficult to remove but may beminimized by ensuring complete combustion of stack gases. Of the gases present in the stack, onlytwo are of importance. Carbon monoxide because of its toxic nature, must be burned to convert it to
* The Authors are working with the PSCS & T, Chandigarh- 160019
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harmless carbon dioxide. SO2 present in small quantities can cause rapid corrosion of steel work inthe presence of moisture.
The Pollution monitoring data compiled on the basis of studies conducted by various leadinginstitutions reveals that emission characteristics from an average cupola are as below :-
Mean range of particle emissions. It mainly consists of dust, grit and metallurgicalfumes, besides smoke. The dust emission varies from1000-2500 mg/ Nm3
SO2 Emissions 350-500 mg/Nm 3
Flue Gas Volume 8500 - 10600 Nm3 /hr
Temperature 550 - 650 ° C
IMPROVED OPERATION OF CUPOLA
The average metal coke ratio in cupola has been found to be 4:1 whereas in the case of efficientdivided blast cupola it could be 9:1 to 10:1. It is, therefore, important that possible improvements inconventional metallurgical practices are identified, thus minimizing the pollution load at sourceitself. Various identified and implemented inplant control measures are as under :-
1. In conventional cupola air is fed through one row of tuyeres at the height of about 2' to 3'from the base. In divided blast cupola, 2 row of tuyeres are used. This improves the operatingperformance of a cupola substantially. Further operating the cupola at constant blast ratehelps obtain significantly higher tapping temperature of the metal (than that obtained withone row of tuyeres at a similar charge coke consumption) . This helps to reduce the chargecoke consumption and hence pollution.
2. In conventional cupola, the effective height i.e. distance between the lower tuyeres andcharging door generally lies in the range of 12' to 14'. In modified cupola the effectiveheight is increased to 17'. This helps in better utilization of available heat in the moltenmetal.
3. Extension of height of stack beyond charging door helps in creating additional draught,thus, avoiding the chance of back firing in cupola furnace and minimizing the smoke instack gases by ensuring its complete combustion . Additional draught so developed helpsingress air entering the charge hole which helps burn cupola stack gases containing COspontaneously. If stack gases do not burn, they can often be made to burn by use, of an afterburner. An after burner is simply a suitably positioned gas or oil burner. Minimum fuelconsumption for small sized cupola is likely to be 18 to 32 litres/hr. of oil. With the provisionof extended stack height, the heat being emitted in the environment has also been conserved.
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4. It is important to control blast volume and blast pressure. In conventional cupola the industryhad no arrangement of measuring the volume and pressure of air blast. Generally air suppliedused to be in excess resulting in more coke consumption and lesser metal temperature. Inmodified cupola, there is provision for instrumentation so as to measure blast volume andpressure correctly.
5. Most of the cupolas are adopting manual/hand charging. In fact the use of mechanical devicefor charging cupolas not only saves labour but reduces material handling accidents also.
6. The size of the door opening is critical to air flow and volume of gas to be cleaned in anemission control system. Less amount of ingress air also helps in maintaining hightemperature. In modified cupola size of the opening is reduced, generally to 30" x 24" froma conventional size of 42" x 24".
7. The size of coke and limestone has a definite effect on the quality of casting. Generally theindustry uses coke and limestone of small size. Studies indicate an appropriate coke size of4" to 8" and comparatively big sized limestone. This enhances the quality of casting as wellas results in better combustion efficiency of coke.
8. Weighing of raw material before feeding results in an increased metal coke ratio and preventsunnecessary wastage of coke and limestone.
Adoption of improved metallurgical practices and divided cold blast cupola has helped to achievethe following: -
• Saving of more than 2.5 tonnes of coke costing Rs. 10,000/- in each heat for a 3tonne per hour cupola (40% saving ).
• Metal coke ratio enhanced from 4:1 to 8:1.
• Particulate emissions drastically reduced with less consumption of coke and otherimproved metallurgical practices.
• Higher melting temperature achieved.
• Life of refractory enhanced.
• Cupola melting capacity increased.
DETAILED DESCRIPTION OF THE RECOMMENDED AIR POLLUTION CONTROLSCHEME
Various conventional air pollution control devices can be installed to control air pollution from acupola furnace. The choice, however, rests on natural draught wet scrubber as it is simple to operate,involves less cost and achieves approx. 60-70 % particulate removal efficiency.
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This is an integral low pressure scrubbing system in the form of wet cap which is mounted on thetop of extended stack. It is a sheet metal canopy enclosing the top outlet of extended stack which isused to arrest particulates by striking and loosening velocity. Over the cone, 5% lime water slurry issprayed and while descending exhaust gases come in contact with the water curtain and particulatematter gets moistened and saturated which is collected in the settling tank, In this system, thenatural draught of hot gases is used to overcome the pressure drop. This does not require heavycapital investment and subsequent recurring cost on running the ID fan. The existing structure of acupola is suitably strengthened so as to carry/bear the load of extended shell and air pollutioncontrol device. This can be done easily by welding additional stiffeners/plate or by providing stay-wires/guys.
While designing the scrubber, following aspects are kept in mind: -
Arrester/Canopy should be large so as to pose less resistance to the passage of gas.
• It should be fitted with some distance above the charge hole so as to provide sufficientstack draught.
It should be thick enought to give the APCD a reasonable life.
However, this type of equipment does not remove fine dust, smoke or metallurgical fumes. Further,poorly designed scrubbers may catch less particulate matter and may have positive pressure atcharge hole thus resulting in the emissions of toxic gases from the charge hole. This can be overcomeby providing stack extensions of appropriate thickness (4-5 mm) over the charging hole wheretemperature may range from 400-450° C. For arresting particulate matter, an inverted deflector ofstainless steel is provided on the top of extended portion over which sufficient amount of water issprayed. The most important parameter is liquid to gas ratio. Too little water could cause overheating and warping of arrester shell and too much water may lead to water splash and losses fromarrester top. The splash can be minimized by limiting the spray nozzle water velocity (usually 3.5m/sec). This water absorbs SO2 originating from sulphur in the cupola coke, which would otherwisecorrode the mild steel. The sprayed water is collected in an underground settling tank provided withbaffle walls. Minimum settling period of 10 minutes is allowed to retain the heavy grit particles tominimize pump and pipe erosion. The grit is removed manually from the settling tank when it isdrained periodically.
PROCEDURE FOR WATER TREATMENT
As mentioned above, the scrubbed water could quickly become acidic and needs neutralizationbefore recirculation so as to avoid corrosion of mild steel and cast iron parts of the system. For thiswater pH is maintained at 7 or higher with the help of commercial soda ash. Initially 1 kg of sodaash ( previously dissolved in water) is added to the clean water in the settling tank, for every 100 kgof coke to be charged during the melting. At the end of melt, the water is tested for alkalinity and ifpH is less than 8 more soda ash is added.
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Salient features of cross current scrubbers are :-
• Initial investment on Air Pollution Control Device is Rs. 75,000/- to Rs.90,000/- whichincludes pumping machinery, piping, settling tank, trough, etc.
• No operation and maintenance cost, as in this indigenous system, extended height abovecupola compensates pressure loss.
• Efficiency around 70 - 75% achieved for APCD ( about 84 kg grit particulate matter trappedin the scrubbing system for 24 tonne casting).
• With the addition of soda ash, there are no chances of corrosion of the control equipment.
OTHER INDIRECT BENEFITS
• Better quality of casting due to better heat distribution in the cupola and also less rejectionrate.
• Less time is required to complete the daily casting.
• Waste minimization reflects and improves the image of industry in eyes of public regulatorybody.
• Improvement in working environment, reduction in workers' health problems and improvedplant appearance.
In a nutshell, it can be concluded that "Simple and improved metallurgical practices help convertwaste to profits."
DEMONSTRATION AND REPLICATION OF TECHNOLOGY
The Council demonstrated divided blast cupola and low cost scrubbing technology in December1994 in the State of Punjab. After successful commissioning, Council demonstrated cupolatechnology in the states of Bihar, J&K and Haryana with the partial assistance from Department ofScience & Technology, Government of India and Small Industries Development Bank of India.Technology stands replicated in around 150 units in the country and all the beneficiaries appreciatedthe gains experienced after implementation of the technology.
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PRIMARY/SECONDARY PRODUCTION OFNON-FERROUS METALS
by
AMITAVA BANDOPADHYAYSCIENTIST
NATIONAL METALLURGICAL LABORATORYJAMSHEDPUR — 831 007Email : [email protected]
Primary/Secondary Production of Non-ferrous Metals Anzitava Bandopadhyay*
The rise of civilisation and the development of mining and metal industries are inextricablyintertwined. The countries and regions of the world that mastered the art and science of economicexploitation of their natural resources of minerals and materials, are today the more prosperous andwealthy components of the human society.
India has a long history of non-ferrous metallurgy. However, what matters is the status of the industry,as it stands today, and the likely route of its growth in the future. Apart from other metals andmaterials, the non-ferrous metals that play a significant role in the building of the Indian economyare Aluminium, Copper, Lead and Zinc. In view of the above the present status report is restrictedto these four non-ferrous metals.
ALUMINIUM
Aluminium is the youngest major element in the entire family of metals with its widespread industrialproduction. The history of India's aluminium industry spans little over a half a century. With thesetting up of the first 3,500 tons per annum smelter in Alupuram in the early 1940's, the industrynow has an installed capacity of over 700,000 tons per annum.
The current world primary aluminium smelting capacity is around 22 million tons. The secondaryaluminium industry engaged in recycling of the metal supplies around 8.5 million tons per annumor over 33% of the total world requirement of the metal. While the world has been fully exploitingthe advantage of low recycling cost of aluminium, India has stayed behind. However, a beginninghas recently been made with the setting up of India's first large scale scrap recycling plant at theTaloja Works of M/s Indian Aluminium Company. Hopefully it will lead to development of anorganised aluminium recycling industry in India. It may be noted that with time the secondary metalindustry is bound to grow and it is necessary to provide more importance to this sector in Indiaalong with that for the primary and upstream processing industries.
The major strength of the aluminium industry in India is the vast deposits of its principal orebauxite. India has large deposits of high grade bauxite of over 3000 million tons. With the recoverablereserves placed at around 2500 million tons, it places India at fifth in terms of available bauxiteresources after Australia, Guinea, Brazil and Jamaica. It has now been proven that by utilisingstate-of-the-art process technologies and gaining access to an assured and efficient captive powersupply, India can emerge as one of the lowest cost producers of aluminium. However, the greatestscope of value addition and wealth creation lies in the development of downstream aluminiumindustry in the country. Products like extrusions, sheets, foils etc. and their end consumer productslike architectural fittings, beverage cans, automobile and other engineering components etc. are theones that will provide the necessary profit margins to financially equip the industry to achieveglobal levels of scale of economy.
* Author is working as scientist with NML, Jamshedpur - 831007
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The reasons that have held back India for utilising its full growth potential are lack of capital andavailability of indigenously developed and industrially proven technology, right from bauxite miningto alumina refining, smelting and fabrication. Since Independence, we have been preoccupied inbuilding production capacities and most of our R&D efforts have been directed towards overcomingthe glitches that appear while implanting a technology developed overseas. More efforts are neededfrom industry and scientific community to develop indigenous cleaner technologies that arecompatible with our requirements.
Industry Description and Practices
The production of aluminium begins with the mining and beneficiation of bauxite. At the mine(usually of the surface type), bauxite ore is removed to a crusher. The crushed ore is then screenedand stockpiled, ready for delivery to an alumina plant. In some cases, ore is upgraded by beneficiation(washing, size classification, and separation of liquids and solids) to remove unwanted materialssuch as clay and silica. At the alumina plant, the bauxite ore is further crushed or ground to thecorrect particle size for efficient extraction of the alumina through digestion by hot sodium hydroxideliquor. After removal of "red mud" (the insoluble part of the bauxite) and fine solids from theprocess liquor, aluminium trihydrate crystals are precipitated and calcined in rotary kilns or fluidizedbed calciners to produce alumina (Al 203 ).
Primary aluminium is produced by the electrolytic reduction of the alumina. The alumina is dissolvedin a molten bath of fluoride compounds (the electrolyte), and an electric current is passed throughthe bath, causing the alumina to dissociate to form liquid aluminium and oxygen. The oxygen reactswith carbon in the electrode to produce carbon dioxide and carbon monoxide. Molten aluminiumcollects in the bottom of the individual cells or pots and is removed under vacuum into tappingcrucibles. There are two prominent technologies for aluminium smelting: Prebake and Soderberg.This document focuses on the Pre-bake technology, with its associated reduced air emissions andenergy efficiencies.
Raw materials for secondary aluminium production are scrap, chips, and dross. Pretreatment ofscrap by shredding, sieving, magnetic separation, drying, and so on is designed to remove undesirablesubstances that affect both aluminium quality and air emissions. The prevailing process for secondaryaluminium production is smelting in rotary kilns under a salt cover. Salt slag can be processed andreutilized. Other processes (smelting in induction furnaces and hearth furnaces) need no orsubstantially less salt and are associated with lower energy demand, but they are only suitable forhigh grade scrap. Depending on the desired application, additional refining may be necessary. Fordemagging (removal of magnesium from the melt), hazardous substances such as chlorine andhexa-chloroethane are often used, which may produce dioxins and dibenzofurans. Other, lesshazardous methods, such as adding chlorine salts, are available. Because it is difficult to removealloying elements such as copper and zinc from an aluminium melt, separate collection and separatereutilization of different grades of aluminium scrap are necessary. It should be noted that secondaryaluminium production uses substantially less energy than primary production—less than 10-20gigajoules per metric ton (GJ/t) of aluminium produced, compared with 164 GJ/t for primaryproduction (mining of ore to production of aluminium metal).
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Waste Characteristics
At the bauxite production facilities, dust is emitted to the atmosphere from dryers and materialshandling equipment, through vehicular movement, and from blasting. Although the dust is nothazardous, it can be a nuisance if containment systems are not in place, especially on the dryers andhandling equipment. Other air emissions could include nitrogen oxides (NO,), sulfur dioxide (SO 2),and other products of combustion from the bauxite dryers.
Ore washing and beneficiation may yield process waste waters containing suspended solids. Runofffrom precipitation may also contain suspended solids. At the alumina plant, air emissions can includebauxite dust from handling and processing; limestone dust from limestone handling, burnt limedust from conveyors and bins, alumina dust from materials handling, red mud dust and sodium saltsfrom red mud stacks (impoundments), caustic aerosols from cooling towers, and products ofcombustion such as sulfur dioxide and nitrogen oxides from boilers, calciners, mobile equipment,and kilns. The calciners may also emit alumina dust and the kilns, burnt lime dust. Although aluminaplants do not normally discharge effluents, heavy rainfalls can result in surface runoff that exceedswhat the plant can use in the process. The excess may require treatment. The main solid waste fromthe alumina plant is red mud (as much as 2 tons of mud per ton of alumina produced), whichcontains oxides of alumina, silicon, iron, titanium, sodium, calcium, and other elements. The pH is10-12. Disposal is done in an impoundment.
Hazardous wastes from the alumina plant include spent sulfuric acid from descaling in tanks andpipes. In the aluminium smelter, air emissions include alumina dust from handling facilities; cokedust from coke handling; gaseous and particulate fluorides; sulfur and carbon dioxides and variousdusts from the electrolytic reduction cells; gaseous and particulate fluorides; sulfur dioxide; tarvapour and carbon particulates from the baking furnace; coke dust, tars, and polynuclear aromatichydrocarbons (PAHs) from the green carbon and anode-forming plant; carbon dust from the roddingroom; and fluxing emissions and carbon oxides from smelting, anode production, casting, andfinishing. The electrolytic reduction cells (pot line) are the major source of the air emissions, withthe gaseous and particulate fluorides being of prime concern. The anode effect associated withelectrolysis also results in emissions of carbon tetrafluoride (CF 4) and carbon hexafluoride (C 2F6 ),which are greenhouse gases, and are of concern because of their potential for global warming.Emissions numbers that have been reported for uncontrolled gases from smelters are 20-80 kilogramsper ton of product (kg/t) for particulates, 6-12 kg/t for hydrogen fluoride, and 6-10 kg/t for fluorideparticulates. Corresponding concentrations are 200-800 milligrams per cubic meter (mg/m 3); 60-120 mg/n 3 ; and 60-100 mg/m3 . These values are for a pre-baked technology plant built in 1983.An aluminium smelter produces 40-60 kg of mixed solid wastes per ton of product, with spentcathodes (spent pot and cell linings) being the major fraction. The linings consist of 50% refractorymaterial and 50% carbon. Over the useful life of the linings, the carbon becomes impregnated withaluminium and silicon oxides (averaging 16% of the carbon lining), fluorides (34% of the lining),and cyanide compounds (about 400 parts per million). Contaminant levels in the refractories portionof linings that have failed are generally low. Other by-products for disposal include skim, dross,fluxing slags, and road sweepings.
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Atmospheric emissions from secondary aluminium melting include hydrogen chloride and fluorinecompounds. Demagging may lead to emissions of chlorine, hexa-chloroethane, chlorinated benzenes,and dioxins and furans. Chlorinated compounds may also result from the melting of aluminiumscrap that is coated with plastic. Salt slag processing emits hydrogen and methane. Solid wastesfrom the production of secondary aluminium include particulates, pot lining refractory material,and salt slag. Particulate emissions, possibly containing heavy metals, are also associated withsecondary aluminium production.
COPPER
In the pre-world war era, copper reigned as the premier non-ferrous metal. With the take over ofconductor industry by aluminium and decline in the use of brass and bronze, the demand growth ofcopper has been virtually stagnant globally for more than a decade. Currently, the installed coppersmelting capacity in India is around 250,000 tons annually. While there has been five-fold increasein copper smelting capacity in India over the last few years, there has been no corresponding increasein indigenous production of copper concentrates. Therefore, the total increased capacity of smeltersis based on import of copper concentrates. The best route for maintaining economic viability of thecopper industry in India seems to be quick development of copper fabrication industry. In this areathere is an urgent need for indigenous development of metal working technologies.
Industry Description and Practices
Copper can be produced either pyrometallurgically or hydrometallurgically. The hydrometallurgicalroute is used only for a very limited amount of the world's copper production and is normally onlyconsidered in connection with in-situ leaching of copper ores. From an environmental point ofview, this is a questionable production route. Several different processes can be used for copperproduction. The traditional process is based on roasting, smelting in reverbatory furnaces (or electricfurnaces for more complex ores), producing matte (copper-iron sulfide), and converting matte forproduction of blister copper, which is further refined to cathode copper. This route for production ofcathode copper requires large amounts of energy per ton of copper: 30-40 million British thermalunits (Btu) per ton cathode copper. It also produces furnace gases with low sulfur dioxide (SO 2)
concentrations from which the production of sulfuric acid or other products is less efficient. Thesulfur dioxide concentration in the exhaust gas from a reverbatory furnace is about 0.5-1.5%; thatfrom an electric furnace is about 2-4%. Flash smelting techniques have, therefore, been developedthat utilize the energy released during oxidation of the sulfur in the ore. The flash techniques reducethe energy demand to about 20 million Btu/ton of cathode copper produced. The SO 2 concentrationin the off gases from flash furnaces is also higher, over 30%, and is less expensive to convert tosulfuric acid. It may be noted that the INCO process results in 80% sulfur dioxide in the off gas.Flash processes have been in use since the 1950s.
In addition to the above processes, there are a number of newer processes such as Noranda, Mitsubishi,and Contop, which replace roasting, smelting, and converting, or processes such as ISASMEL,Tand KIVCET, which replace roasting and smelting. For converting, the Pierce-Smith and Hoboken
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converters are the most common processes. The matte from the furnace is charged to converters,where the molten material is oxidized in the presence of air to remove the iron and sulfur impurities(as converter slag) and to form blister copper.
Blister copper is further refined as either fire-refined copper or anode copper (99.5% pure copper),which is used in subsequent electrolytic refining. In fire refining, molten blister copper is placed ina fire-refining furnace, a flux may be added, and air is blown through the molten mixture to removeresidual sulfur. Air blowing results in residual oxygen, which is removed by the addition of naturalgas, propane, ammonia, or wood. The fire-refined copper is cast into anodes for further refining byelectrolytic processes or is cast into shapes for sale.
In the most common hydrometallurgical process, the ore is leached with ammonia or sulfuric acidto extract the copper. These processes can operate at atmospheric pressure or as pressure leachcircuits. Copper is recovered from solution by electro-winning, a process similar to electrolyticrefining. The process is most commonly used for leaching low-grade deposits in situ or as heaps.
Recovery of copper metal and alloys from copper-bearing scrap metal And smelting residues requirespreparation of the scrap (e.g., removal of insulation) prior to feeding into the primary process.Electric arc furnaces using scrap as feed are also common.
Waste Characteristics
The principal air pollutants emitted from the processes are sulfur dioxide and particulate matters.The amount of sulfur dioxide released depends on the characteristics of the ore—complex ores maycontain lead, zinc, nickel, and other metals— and on whether facilities are in place for capturingand converting the sulfur dioxide. SO 2 emissions may range from less than 4 kg per metric ton(kg/t) of copper to 2,000 kg/t of copper. Particulate emissions can range from 0.1 kg/t of copper toas high as 20 kg/t of copper.
Fugitive emissions occur at furnace openings and from launders, casting molds, and ladles carryingmolten materials. Additional fugitive particulate emissions occur from materials handling andtransport of ores and concentrates. Some vapors, such as arsine, are produced in hydrometallurgyand various refining processes. Dioxins can be formed from plastic and other organic materialwhen scrap is melted. The principal constituents of the particulate matter are copper and iron oxides.Other copper and iron compounds, as well as sulfides, sulfates, oxides, chlorides, and fluorides ofarsenic, antimony, cadmium, lead, mercury, and zinc, may also be present. Mercury can also bepresent in metallic form, At higher temperatures, mercury and arsenic could be present in vaporform. Leaching processes will generate acid vapors, while fire-refining processes result in copperand SO 2 emissions. Emissions of arsine, hydrogen vapors, and acid mists are associated withelectrorefining.
Wastewater from primary copper production contains dissolved and suspended solids that mayinclude copper, lead, cadmium, zinc, arsenic, and mercury and residues from mold release agents
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(lime or aluminum oxides). Fluoride may also be present, and the effluent may have a low pH.Normally there is no liquid effluent from the smelter other than cooling water; wastewaters dooriginate in scrubbers (if used), wet electrostatic precipitators, cooling of copper cathodes, and soon. In the electrolytic refining process, by-products such as gold and silver are collected as slimesthat are subsequently recovered. Sources of wastewater include spent electrolytic baths, slimesrecovery, spent acid from hydrometallurgy processes, cooling water, air scrubbers, washdowns,stormwater, and sludges from wastewater treatment processes that require reuse/recovery orappropriate disposal.
The main portion of the solid waste is discarded slag from the smelter. Discard slag may contain0.5-0.7% copper and is frequently used as construction material or for sandblasting. Leachingprocesses produce residues, while effluent treatment results in sludges, which can be sent for metalsrecovery. The smelting process typically produces less than 3 tons of solid waste per ton of copperproduced.
LEAD AND ZINC
Lead is one of the oldest known metals in India and the world over. The inertness and corrosionresistance, softness and ease of working, are the principal reasons for its wide applications. Leadlends itself easily to alloying with other metals. This permits it to be rolled into sheets for thechemical industry, for corrosion resistance surfacing, roofing, damp proofing, cable sheathing,ornamental works, sound proofing, radiation shielding in nuclear and medical applications etc. Interms of tonnage, the principal application area of lead is lead acid batteries. It accounts for almost60% of its consumption worldwide. The current lead production capacity in India is of the order of90,000 tons. Around 47,000 tons of this comes from the primary sector and the balance from thesecondary sources of remelting of scrap and recycling of waste batteries. The lead industry dependheavily on imported concentrates and scrap recycling.
About 50% of zinc produced world wide is used for protective applications. The world producesand consumes nearly 7.8 million tons of zinc which ranks it fourth after iron, aluminium and copperas the most commonly used metal. The current production capacity in India is of the order of1,80,000 tons per annum in the primary sector and —50,000 tons per annum in the secondary sector.Apart from the galvanising sector, which in India accounts for —70% of total consumption, theother sectors for consumption of zinc are battery (10%), zinc alloys (10%), die-casting (5%) andchemical & miscellaneous (5%). This overwhelming dependence on galvanising application hastied the fate of zinc industry world wide with that of the steel and construction industry.
Industry Description and Practices
Lead and zinc can be produced pyrometallurgically or hydrometallurgically, depending on the typeof ore used as a charge. In the pyrometallurgical process, ore concentrate containing lead, zinc, orboth is fed, in some cases after sintering, into a primary smelter. Lead concentrations can be 50-70%, and the sulfur content of sulfidic ores is in the range of 15-20%. Zinc concentration is in the
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range of 40-60%, with sulfur content in sulfidic ores in the range of 26-34%. Ores with a mixtureof lead and zinc concentrate usually have lower respective metal concentrations. During sintering,a blast of hot air or oxygen is used to oxidize the sulfur present in the feed to sulfur dioxide (SO 2).Blast furnaces are used in conventional processes for reduction and refining of lead compounds toproduce lead. Modern direct smelting processes include QSL, Kivcet, AUSMELT, and TBRC.
Primary Lead Processing
The conventional pyrometallurgical primary lead production process consists of four steps: sintering,smelting, drossing, and refining. A feedstock made up mainly of lead concentrate is fed into asintering machine. Other raw materials may be added, including iron, silica, limestone flux, coke,soda, ash, pyrite, zinc, caustic, and particulates gathered from pollution control devices. The sinteredfeed, along with coke, is fed into a blast furnace for reducing, where the carbon also acts as a fueland smelts the lead-containing materials.
The molten lead flows to the bottom of the furnace, where four layers form: "speiss" (the lightestmaterial, basically arsenic and antimony), "matte" (copper sulfide and other metal sulfides), blastfurnace slag (primarily silicates), and lead bullion (98% by weight). All layers are then drained off.The speiss and matte are sold to copper smelters for recovery of copper and precious metals. Theblast furnace slag, which contains zinc, iron, silica, and lime, is stored in piles and is partiallyrecycled. Sulfur oxide emissions are generated in blast furnaces from small quantities of residuallead sulfide and lead sulfates in the sinter feed. Rough lead bullion from the blast furnace usuallyrequires- preliminary treatment in kettles before undergoing refining operations. During drossing,the bullion is agitated in a drossing kettle and cooled to just above its freezing point, 370°--425°C(700°-800°F). A dross composed of lead oxide, along with copper, antimony, and other elements,floats to the top and solidifies above the molten lead. The dross is removed and is fed into a drossfurnace for recovery of the non-lead mineral values. The lead bullion is refined usingpyrometallurgical methods to remove any remaining non-lead materials (e.g., gold, silver, bismuth,zinc, and metal oxides such as oxides of antimony, arsenic, tin, and copper). The lead is refined ina cast iron kettle in five stages. First, antimony, tin, and arsenic are removed. Next, gold and silverare removed by adding zinc. The lead is then refined by vacuum removal of zinc. Refining continueswith the addition of calcium and magnesium, which combine with bismuth to form an insolublecompound that is skimmed from the kettle. In the final step, caustic soda, nitrates, or both may beadded to remove any remaining traces of metal impurities. The refined lead will have a purity of99.90-99.99%. It may be mixed with other metals to form alloys, or it may be directly cast intoshapes.
Secondary Lead Processing
The secondary production of lead begins with the recovery of old scrap from worn-out, damaged, orobsolete products and with new scrap. The chief source of old scrap is lead-acid batteries; othersources include cable coverings, pipe, sheet, and other lead-bearing metals. Solder, a tin-basedalloy, may be recovered from the processing of circuit boards for use as lead charge.
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Prior to smelting, batteries are usually broken up and sorted into their constituent products. Fractionsof cleaned plastic (such as polypropylene) case are recycled into battery cases or other products.The dilute sulfuric acid is either neutralised for disposal or recycled to the local acid market. One ofthe three main smelting processes is then used to reduce the lead fractions and produce lead bullion.Most domestic battery scrap is processed in blast furnaces, rotary furnaces, or reverberatory furnaces.A reverberatory furnace is more suitable for processing fine particles and may be operated inconjunction with a blast furnace. Blast furnaces produce hard lead from charges containing siliceousslag from previous runs (about 4.5% of the charge), scrap iron (about 4.5%), limestone (about 3%),and coke (about 5.5%). The remaining 82.5% of the charge is made up of oxides, pot furnacerefining drosses, and reverberatory slag. The proportions of rerun slags, limestone, and coke varybut can run as high as 8% for slags, 10% for limestone, and 8% for coke. The processing capacity ofthe blast furnace ranges from 20 to 80 metric tons per day (tpd). Newer secondary recovery plantsuse lead paste desulfurization to reduce sulfur dioxide emissions and generation of waste sludgeduring smelting. Battery paste containing lead sulfate and lead oxide is desulfurized with soda ash,yielding market-grade sodium sulfate as a by-product. The desulfurized paste is processed in areverberatory furnace, and the lead carbonate product may then be treated in a short rotary furnace.The battery grids and posts are processed separately in a rotary smelter.
Zinc Manufacturing
In the most common hydrometallurgical process for zinc manufacturing, the ore is leached withsulfuric acid to extract the lead/zinc. These processes can operate at atmospheric pressure or aspressure leach circuits. Lead/zinc is recovered from solution by electro-winning, a process similarto electrolytic refining. The process most commonly used for low-grade deposits is heap leaching.Imperial smelting is also used for zinc ores.
Waste Characteristics
The principal air pollutants emitted from the processes are particulate matter (PM) and sulfur dioxide(SO2). Fugitive emissions occur at furnace openings and from launders, casting molds, and ladlescarrying molten materials, which release sulfur dioxide and volatile substances into the workingenvironment. Additional fugitive particulate emissions occur from materials handling and transportof ores and concentrates. Some vapors are produced in hydrometallurgy and in various refiningprocesses. The principal constituents of the particulate matter are lead/zinc and iron oxides, butoxides of metals such as arsenic, antimony, cadmium, copper, and mercury are also present, alongwith metallic sulfates. Dust from raw materials handling contains metals, mainly in sulfidic form,although chlorides, fluorides, and metals in other chemical forms maybe present. Off-gases containfine dust particles and volatile impurities such as arsenic, fluorine, and mercury. Air emissions forprocesses with few controls may be of the order of 30 kilograms lead or zinc per metric ton (kg/t) oflead or zinc produced.
The presence of metals in vapor form is dependent on temperature. Leaching processes will generateacid vapors, while refining processes result in products of incomplete combustion. Emissions of
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arsine, chlorine, and hydrogen chloride vapors and acid mists are associated with electrorepining,Wastewaters are generated by wet gas scrubbers and cooling water, Scrubber effluents may containlead/zinc, arsenic, and other metals. In the electrolytic refining process, by-products such as goldand silver are collected as slimes and are subsequently recovered, Sources of waste-water includespent electrolytic baths, slimes recovery, spent acid from hydro metallurgy processes, cooling water,air scrubbers, wash-downs, and stormwater. Pollutants include dissolved and suspended solids,metals, oil and grease.
The larger proportion of the solid waste is discarded slag from the smelter. Discard slag may contain0.5-0.7% lead/zinc and is frequently used as fill or for sandblasting. Slags with higher lead/ zinccontent—say, 15% zinc—can be sent for metals recovery. Leaching processes produce residues,while effluent treatment results in sludges that require appropriate disposal.
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POLLUTION CONTROL IN RICE SHELLERS
by
Sh. M.A. PatilDeputy Director
ENVIRONMENT MANAGEMENT GROUP
NATIONAL PRODUCTIVITY COUNCILNEW DELHI, INDIA
PHONE : 011-24611243, FAX: 011-24625013E-mail : [email protected]
Pollution Control in Rice SheltersM.A.Patil*
1.0 BACKGROUND
We eat rice every day with nonchalance, but if we spare a moment of thought we would be amazedto find about the amount of energy consumed in rice milling /shelling and the pollution caused bythe rice mills. Rice processing requires huge amount of energy and gives rise to pollution especiallydust and wastewater. However, the rice shellers do not generally appreciate that they are wastingenergy and polluting the environment. In this scenario, cleaner production studies were taken up infew rice mills/shellers to devise methods to check the wastages and improve process operations toincrease productivity and improve environmental performance.
There are mainly two types of rice produced in the mills — the raw rice and the par boiled rice.Paddy is cleaned, milled and polished to produce raw rice. The paddy when cleaned, parboiledusing steam, dried and then milled produces par boiled rice. The milling and polishing processesare same for producing raw rice and parboiled rice except for some minor variations. A schematicflow diagram detailing the Rice Milling Section is given in Figure-1. (See Next Page)
2.0 MATERIAL BALANCE AND SPECIFIC CONSUMPTIONS
The milling of paddy produces 65% rice, 22% husk, 6% bran, 3% broken rice and balance com-prises worms and wastage. The milling of paddy and polishing consumes electrical energy and sodo other material handling operations. The specific electricity consumption varies from 168 kWh/Mt of paddy to 230 kWh/Mt of paddy in the member units. The total daily electrical energy con-sumption is about 600 to 700 kWh. The polishing section consumes 60% of the energy; the shellingsection consumes 20% of the energy and the balance by material handling and others.
The par boiling of paddy consumes steam for hot water generation, open steam injection whilesoaking and for drying the soaked paddy. The paddy drier has a hot air generator where steam isused to heat air for drying and hot air is used to dry paddy. The specific steam consumption is 750kg/t of paddy. The specific electricity consumption is 261 to 291 kWh/Mt of paddy. The hot waterafter soaking is discharged as effluent. The specific effluent generation is 1000 litres/t to 1300litres/t.
The total daily electrical energy consumption of par boiled rice mill is 1200 kWh per day. The parboiling section consumes 30% energy, 30% energy is consumed during polishing process and thebalance by other areas. The total steam requirement is 1400 kgs/hr. The steam consumption forgeneration of hot water is 600 kgs/hr and in the heat exchanger is 800 kgs/hr. Soaking processconsumes 600 kgs/hr of steam. Either soaking or hot water generation process uses steam at anygiven time.
*Author is working as Deputy Director with NPC, New Delhi-1 10 003
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Paddy
Paddy Cleaner
Paddy in Tanks
Water soaking of paddy
Dryer
Cleaning [V.S.-I]
De-stoning
De-husker
Paddy Separation
be-husked Rice
Pre-sizing
Whitening
Polishing
Colour Sorting
Length Grader
Packing
4-Storage/Dispatch
Figure 1: Process Flow Diagram of Parboiling Rice Production
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3.0 WASTE/POLLUTION GENERATION AREAS
The following are the major wastes/pollution and the areas/causes for their generation in rice mills/shellers:
• Dust in the paddy unloading area. The dust accompanies paddy from the fields andgets airborne while opening of the bags and while cleaning of paddy in the mills. Itis difficult to quantify dust and the size of dust varies.
• Waste husk due to improper handling of husk from sheller cum husker.
• Improper storage of husk - a valuable resource. The raw rice millers sell husk on afixed price basis irrespective of the quantity of husk disposed. It is estimated thatabout 500 t of husk is wasted per annum. Assuming a very low price of Rs.200 pertonne, Rs. 100000 per rice mill is wasted. A 40 tonne par boiling and paddy millingplant produces about 8.8 tonne of husk per day. This should be enough to generateabout 1.5 t/hr. of steam. Due to improper storage of husk and inefficient boileroperations some of the circle members purchase rice husk. The value of rice huskprocured by the members varied from Rs. 1.0 to 2.5 lakhs per annum.
• Inefficient boiler operation generates CO and pollutes the atmosphere. Heat recoveryis also not complete. The steam quality is poor. The improper steam distributionsystem, leads to condensate wastage and it are drained off. This also delays heattransfer and increases the processing time.
• A 40 tonne par boiling plant is expected to generate about 50 kL of effluent per day.Due to improper water management, the quantity of effluent generated is about 30%higher. The effluent has a BOD of 1100 mg/I and COD of 2200 mg/l.
• One other major waste is ash from the boilers. The ash generated will be about 1.5 to2.5 tonne per day. This is just dumped in the boiler yard. The lower the boiler efficiencyhigher is the ash generation as more fuel is burnt to generate steam.
• The common form of waste for both raw rice mills and par boiled rice mill is electricityand production loss due to poor equipment maintenance. The field measurements ofelectrical systems indicated power variations upto 20% of a single equipment. Thisis only based on electrical systems. Further power is wasted due to equipmentoverloads and improper alignment The use of excess power is due to use of poorlyrewound motors, poor electrical distribution systems and poor maintenance. Use ofrewound motors, increases current drawn, heats up the motor and thus theenvironment.
• Improper equipment maintenance decreases the Mean Time Between Failures(MTBF) and due to unplanned shut downs, increases the repair time and use ofimproper spares.
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• The other wastes generated are wastage of bran, broken rice and wastes due to poorhouse keeping. Though these wastes are lesser in quantity, efforts can be made toimprove the collection of bran and keep percentage of broken rice at a lower threshold.
4.0 CLEANER PRODUCTION MEASURES
As a result of cleaner production study, several measures were identified to reduce waste/pollutionand improve the productivity of the rice mills/shellers. Some of the measures have already beenimplemented and others are being further studied.
I. Dust in the Paddy unloading area:
Significant improvements have been observed d by following measures enumerated below:
a. Proper design of the plant as has been done in the case of M/s. Tirumala SrinivasaIndustries, Nizamabad, Andhra Pradesh (A.P.). The unloading area is isolated andsufficient house keeping measures are taken up.
b. Isolation of paddy milling area : In a small plant like Sree Traders, Nizamabad theentire operation from Paddy cleaning to rice bagging takes place in a single largehall. The Paddy unloading area is isolated by providing a wall. PVC sheet coverscan be provided around the conveyors and appropriate slope near the elevator.Presently the mill is using gunny cloth for covering. This will be replaced by plasticsheets and a wall will be constructed to isolate the paddy cleaning area. The investmentis just Rs. 10,000/- but the dust levels will be reduced by 60%.
c. Constructing a separate room for paddy cleaning. M/s. Vishnu Lakshmi Rice mill,Nizamabad is planning to implement the same. The investment is Rs.60,000 for a50-sq.m area room. The room will have a properly designed exhaust fan.
d. Direct unloading of Paddy from truck to hopper: This has been implemented by M/s. Aishwarya Industries, Nizamabad. This reduces material handling activities. Theinvestment towards a truck bay and construction of appropriate slope is aboutRs.15,000/-. Additional investment is required (Rs.10,000/-) to cover the sides ofthe unloading area.
It is difficult to calculate the pay back period as there are no direct monetary gains. The hiddenbenefits are resultant better mill environment and ambience. This improves the productivity of theworker.
11. Improvements in Husk Collection and Storage system:
a. Eliminate use of gunny packing at joints and use of plastic sheet in the husk separator- negligible investment.
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b. Storage of husk on hard ground within four walls and open rooftop. The bulk densityof husk being low, large area is required for storing. However, due to totally openstorage the husk can fly off due to winds and is a significant resource loss. Theinvestment depends on the area enclosed. The investment is estimated to be Rs. 1.50lakhs for a 500 sq.m area.
C. Construction of Husk Room: This has been implemented by the units who are in theheart of Nizamabad town to avoid causing pollution in the township. Other units areplanning to implement the same. The investment is Rs. 1.00 to Rs. 1.50 lakhs.
d. The annual husk generation being about 300 tonne, even if 50 tonne of rice husk perannum is recovered the savings can be valued at Rs. 10,000/- @ Rs.200 per tonne ofhusk.
e. There has been a suggestion for briquetting rice husk using a binder. This isparticularly useful for raw rice mills that can sell husk at a higher price as transportcosts come down. This is to be further studied.
III. Other Dust Control Measures
The dust in other areas can be reduced to a great extent by proper house keeping. The source ofgeneration of dust is from the gaps in material handling equipment, shellers, feeding points of themilling machine, bran-handling blower etc. The gaps in the material transfer points can be coveredwith plastic sheets. The sheets can be lifted periodically to watch the flow of material. This is beingimplemented gradually by all the members. The investment will not exceed Rs.5000/-.
The base of elevators is left open for attending to jamming of elevators due to power break down orother mechanical reasons. It is recommended to cover these with 3mm MS plates. The investmentis Rs.6000 for all the elevators in the system. Thinner sheets should not be used as the sheet canbend when a person stands on it and can lead to accidents.
The Pneumatic conveying system of bran should be sealed properly. The rice bran yield is 2.5 tonneper day. The normal bran wastage is about 125 kg. A proper bran recovery system will save 37tonne of bran valued at Rs.35000/- per annum.
IV. Steam Generation and Distribution:
The existing boilers are improvised versions of Lancashire Boilers. The efficiency of the boilershave been established as low as 40%. The inefficiencies are due to higher flue gas temperature, highlevel of excess air, improper steam distribution etc. While measures in this area can be endless, thefollowing measures have been implemented by some of the units:
a. M/s.Venkata Ramana Paddy Processing Industries have installed a heat exchangerto preheat water. The water is preheated to 50 - 60°C. Presently the system is not
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insulated. The temperature can be increased to 70 - 75°C. The annual fuel savingsafter the system is perfectly insulated is expected to be 200 MT of husk valued atRs.40,000I-. The investment of Rs.30,000 will be paid back in less than one year.
b. The installation of modern boiler has been done in M/s. Aishwarya Industries. Theboiler has a better air distribution system, better insulation, optimum combustion byproper air fuel ratio. The exhaust gas from the boiler is not only dust laden but alsovery hot. The feed water tank has been mounted on the dust collector itself to enablepre-heating of the feed water by the flue gases. The feed water tank is further insulatedwith rice husk, which has good insulating properties. The boiler has higher efficiencyby a factor of 1.25 compared to the improvised Lancashire Boilers. Anticipatedsavings are 1000 tonne of rice husk per annum valued at Rs.2 lakhs. This unit wantedto invest on a boiler for its expansion. A conventional boiler would cost Rs.8.00lakhs with recurring maintenance costs. The labour required for handling husk andthe boiler is also reduced in the new high efficiency boiler. The total savings will beRs.2.5 lakhs. The incremental cost being Rs.5.00 lakhs, the pay back period isexpected to be just 2 years.
e. The steam distribution system has been scientifically carried out in the expansionpart of Aishwarya Industries. The steam tappings for the line, steam traps andcondensate recovery has been implemented as per good engineering practices. Thiseliminates leaks, ensures proper heat transfer.
d. The dryer uses preheated air at 70 to 80°C for drying the parboiled paddy. The moisturecontent of the paddy is reduced from 25% to 13%. This has a heat exchanger to heatair. There is a blower delivering air, which passes through the heat exchanger, andthe hot air is delivered to the drier. The heat exchanger so far used finned MS tubes.Aishwarya Industries have introduced Copper finned tubes in the heat exchanger.The additional investment is Rs.70,000/-. The drying temperature can also be reducedto 65°C. The air temperature was never monitored by the member industries. Thishas been started at Aishwarya Industries with the provision of thermometers.
e. Proper heat transfer is achieved by the quality of steam and optimum dryingtemperatures. The parboiling and drying process has been reduced to 7 hours from10 hrs and this is expected to be optimised at 5 hrs. This will ensure additionalproduction of 600 tonne per annum valued at Rs.73 lakhs.
f. The rice husk ash contains about 80% silica and balance other minerals. The quantityof ash generated can be reduced by 25 to 30% by using a more efficient boiler. Manypublished articles are available that exhort use of rice husk ash for making bricks, asfiller in road laying, using it in canals etc, but none of them have been commercialised.The disposal of rice husk ash continues to be a problem. Some of the industries havegiven it to turmeric farmers who use it as a fertiliser. About 6 to 7 tonne of rice huskash is sold at Rs.400 to Rs.600. This is possible only where turmeric is grown innearby fields. Otherwise the transport cost will be high and the concept is noteconomically viable.
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V Effluent Management:
The wastewater effluent is generated only from the par boiled rice mills. In these mills paddy issoaked in hot water in soaking tanks for about 6hrs. Later open steam is injected for 15 minutes andthe paddy is boiled. The water is then drained off as effluent. It has been observed that there is nocontrol of water quantity used for soaking. Following are the Waste Minimization measures recom-mended:
a. The soaking tanks will be marked to indicate water level and to avoid over filling. This willreduce the water consumption and consequently effluent generation will decrease. This hasbeen tried and water consumption has been reduced to 1.1 kL/tonne of paddy. This leads toa saving of 4,000 Its of water per day or 120 kL of water per month. The lesser effluentgenerated is expected to be more concentrated by about 20 to 30% higher BOD. Since theeffluent generally has a low BOD the treatability of the concentrated effluent would improve.It should be noted that there is no chemical added in the entire process.
b. There is one rice mill which is directly letting out it's effluent into the fields for irrigation.This has been done for the past few years. The farmers have infact been requesting this millowner for discharge of the effluent to his fields. Apparently, it increases agricultural yieldand this requires further study.
e. A full-fledged effluent treatment plant using anaerobic/aerobic system(s) will need aninvestment of Rs.5.00 lakhs to Rs.7.00 lakhs. Since there are more than 70 par boiled ricemills, a common effluent treatment plant can be techno economically viable.
d. The other non-conventional methods like hydroponics have to be experimented.
VI Electrical System-,
The improvements to electrical systems are common to both raw rice and par boiled. Following aresome of the measures recommended:
a. In the par boiling section the highest HP, motor is the motor used for the air blower of thedrier. The power and airflow of the blower was measured. The specific air delivery variedfrom 1400 M3/kW to 2200 M 3/kW — a variation of 20%. The power consumed being about12 kW, the annual energy wasted is 14000 kWh valued at Rs.76,000/-. The cost of an efficientblower is Rs.60, 000/-. The pay back period is less than one year. Further, it is not requiredto invest in a new blower. The alignment of the blower can be improved and the bladeprofile checked and dynamically balanced.
b. The air requirement of the system can be improved. The latest dryer installed at M/s AishwaryaIndustries uses one single blower of 30 HP as against 2 blowers of 20 HP in other mills forsimilar capacities. This will save 30000 kWh valued at Rs.1,20,000/-. This emphasizes therandomness of the equipment design and selection by the mill owners.
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c. The polisher motor is the largest motor in the milling section. The power measurements inmember units varied from 11 kW to 15 kW. Though the power difference can be due to thevariety of paddy being milled, at least 2 kW is being wasted in some mills. The analysis ofrubber roll sheller indicated a variation of 1 kW with a connected motor HP of 10.
d. The reasons for higher power consumption are:
• Use of rewound motors to be discontinued. The motors have been rewound manytimes. This was explained to the industry. They have stopped buying rewound motors
Poor Power factor at the AP Transco incomer and the Tail end. All the mills havesingle part tariff as they are under LT category. This can be improved by usingcapacitor banks. Most of the mills have capacitors, but they have broken down.
When a motor burns down, the mill owner changes it to the higher HP motor withoutgoing into the reasons of burn out. What needs to be appreciated is that the investmenton 10 HP motor will be about Rs.25,000/- . The running cost at 6000 hrs of annualoperation (typical of a rice mill) is Rs. 1,26,000/- per annum. Even saving a minimumof 1 kW the investment pays back in a year.
• These factors have been explained to the industry and their awareness on the subjecthas increased. They have gradually stopped buying rewound motors. This will save30,000 kWh valued at Rs.1,20,000/-. This investment is not accounted for as thereplacements are being done as and when a break down occurs.
The generation of broken rice in the rice mills can be reduced by using slow-speedcontinuous elevators for both paddy and rice, The investment is Rs,15,000/-. Thepower saved is 6000 kWh per annum valued at Rs.24,000/-, The additional costbenefit due to reduced broken rice is substantial and the economics is attractive(Rs.6.00 lakhs).
e) The electrical distribution systems of all the mills are poor. The fuses and switchgear ratingsbe not related to the load, cables are improperly terminated, wires are being used in fuses,no protection systems etc. This warms up the system. There are recurring failures in electricalsystems and motor burnouts are a regular feature. It is difficult to repair the electrical systemspiece meal and a total revamping is desired.
A properly designed electrical distribution system designed by the author has been implemented inAishwarya Industries for the expansion project.The feature of the system are:
System design instead of equipment design. This facilitates proper load managementof AP Transco and DG power.
Use of Miniature Circuit Breakers (MCB). This eliminates fuses. The system hasprotections fór overload, over voltage and over heating.
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• Optimum setting of protection systems. This is very important, as improper settingwill lead to system failures.
• Proper sizing and termination of cables.
This system is in operation for the last four months without any failure. The incremental cost isRs. 1.00 lakh. The average maintenance cost of the electrical system in the mills is about Rs. 70,000per annum. This cost is expected to reduce to Rs. 20,000 per annum. The pay back period is 2 years.This reduces the Mean Time between failure of the electrical system, thereby improving equipmentavailability. This increases production and therefore pay back period reduces.
VII Equipment Maintenance:
The maintenance of mechanical equipment is by unskilled labour. In the anxiety to get the machinestarted when a break down occurs, machine alignments are improper and improper spares are used.This reduces the Mean Time between failures. M/s. Sree Traders had a failure in the separator. Thismachine has many dynamic components. The alignment of the system is very important. When theequipment failed, it was decided the maintenance to be done by the equipment supplier. Though thedown time was more, as the skilled man-power and equipment had to come from Hyderabad, themachine was properly serviced. This increased the Mean Time Between Failure from 50 trucks ofrice to 150 trucks of rice. The value of additional production is more than Rs.12.00 lakhs. The costof proper maintenance is only Rs.20,000/-.
VIII Support Services;
The role of support services in waste minimization cannot be ignored. The support services are useof instruments for measurements, training of manpower, availability of skilled manpower, exchangeof information, promotion of scientific temperament etc. The WMC members proposed the follow-ing actions:
a. The WMC members realised the importance of measurements using the instruments availablewith the facilitator. They have proposed establishment of an instrument bank in the RiceMiller's Association to periodically measure power, temperature, air flow, %CO at the ricemill's. 2
b, Training and maintaining a base for skilled maintenance technicians, electricians etc. atNizamabad.
e. The Rice Miller's Association being strong, this will be used to display WMC Newsletter ofNPC and other information.
d, Scientific temperament has already been promoted by the concept of WMC.
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5.0 CONSTRAINTS OF CLEANER PRODUCTION IN RICE SHELLERS/MILLS
Apart from often repeated constraints of Small and Medium level Enterprises (SMEs) viz, singleowner to look after all activities, lack of qualified technical personnel etc, the following are themajor constraints identified:
Financing for WM options.The WMC members while appreciating the benefits of a betterboiler, electricals etc., might invest on it only when it is absolutely essential. Otherwise inorder to allocate finances for day to day requirements, the WM options may get overlooked.Financing through Performance Contracting approach is desired. While funds are availableearmarked for energy conservation by IREDA, technology upgradation by SIDBI and StateFinancial Corporations (SFCs), they may be skeptical in funding rice mills, which are eitherproprietary or partnership companies. The rice millers use bank finance for their workingcapital needs. For capital investments they source funds from their own resources.
• The case of M/s. Aishwarya Industries needs a special mention as the rice mill owner hasinvested on expansion using the guidelines of WMC meetings. Other WMC members alsowill follow suit when they opt for equipment replacements. The availability of cheaperfinance will accelerate this process.
• The need for Detailed Project Report and other documentation is another constraint in usingthe funds available with the Financial Institutions. As a single person has to look aftervarious other areas, the entrepreneur finds less time for interaction and preparation ofdocumentation.
• They are skeptical about use of Consultancy Services thinking that such services are costlyand the measures recommended involve investment(s). The benefit of use of Consultancyservices has been well reaslised during the WMC meetings. It is hoped that the memberswould seek expert help on the subject whenever required.
• Some of the rice mills are on lease with the present occupier. Therefore the occupier is notin a position to invest on capital equipment.
• The other major constraint is sustaining WM options. Though the WMC concept has increasedawareness and has made entrepreneurs conscious of the subject, it is hoped that in course oftime WM will sustain the interest of the rice miller's and that other day to day productionactivities and compulsions would not allow WM to be relegated to the background. In orderto make WM efforts stay in the forefront regular interaction between the facilitator and theWMC members is essential after completion of Stage VI of the milestone.
6.0 HIGHLIGHTS OF CLEANER PRODUCTION IN RICE SHELLERS/MILLS
Rice shellers/Mills have been benefited immensely from cleaner production studies in terms ofproductivity enhancement, resources conservation and pollution reduction. The highlights of the
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achievements are reflected in the measures adopted by the participating units as enumeratedbelow :-
The low cost measures initiated by the Rice Mills/Shcllers are;
• House keeping measures to reduce dust
• Regular monitoring of power bills to explore cost cutting measures
Optimization of water consumption resulting in reduced wastewater generation
• Better preventive maintenance of equipment
Improved control of combustion practices at the Boiler
. Improved insulation to reduce loss of heat energy
The investment-oriented measures undertaken by the rice mills/shellers are:
Installing failsafe electricals to prevent motor burnouts
. Installation of new energy efficient boiler
• Improvement in existing Boilers and husk handling equipment
• Better paddy unloading methods etc.
The key indicators for the raw and parboiled rice mills and the benefits accrued to the units isoutlined in the following Tables 1.1 & 1.2 and Table 2.1 & 2.2 respectively.
TABLE-1.1: KEY INDICATORS OF CLEANER PRODUCTION INRAW RICE MILLS/SHELLERS
S. No. Parameter Indicator
1 Specific Electricity Consumption (kWh/Qtl) 3.0 to 3.5
2 Standard Specific Electricity Consumption (kWh/Qtl) 1.6 to 1.7
3 Waste Generation Dust, waste husk2 MT/day, ricebran, brokens
4 Possible Power Generation by using husk(kW/per rice mill)
1.30
5 Possible Power Generation (MW/for 75 rice mills) 10
Note: I Qtl:100 kgs.
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TABLE-1.2: BENEFITS ACCRUED TO RAW RICE MILLS /SNELLERS
S. No. CPS Measure Months in Savings Effect RemarksOperation Achieved on Environ-
(Its./yr) ment
M/S Aishwarya Industries — Raw Rice Unit
1 Faulsafe electrical 9 3,80,000 Reduced Zero Motordistribution system Heat Burn outs
2 Direct Unloading of 9 4,30,000 Reduced Reduced LabourPaddy from Trucks dust
3 Conversation to 9 60,000 Better VoltageHT Supply
M/S Sri Vishnu Lakshmi Rice Mills
I Covering all 3 80,000 50% Reducedequipment to prevent reduction Maintenancedust ingress in pollution
2 Use of Plastic Bucket 2 50,000for Elevators
M/S Sree Traders
I Covering all 3 80,000 50% Reducedequipment to prevent reduction Maintenancedust ingress in pollution cost
2 Preventive No break 1,00,000 Reduced Longer runningmaintenance of down and dust hoursseparator since 9 increased
months production
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TABLE-2.1: KEY INDICATORS OF CLEANER PRODUCTION IN PARBOILED RICEMILLS/SHELLERS
S. No. Parameter Indicator
I Specific Electricity Consumption (kWh/Qtl) 3.5 to 4.5
2 Standard Specific Electricity Consumption 2.6 to 2.8(kWh/Qtl)
3 Specific Steam Consumption (kg/Qtl) 1.3 to 1.5
4 Standard Specific Steam Consumption 0.80 to 1.1(kg/Qtl)
5 Effluent Generation for 30 MT/day plant 40(cu.m/day)
6 Waste Generation Rice Husk Ash 2 MT/day, dust,waste husk IMT/day, rice bran,brokens
7 Possible Power Generation through Cogen 1.30(kW/par boiled u nit)
8 Possible Power Generation through Cogen 8.75(MW/for 65 par boiled units)
TABLE-2.2: BENEFITS ACCRUED TO PARBOILED RICE MILLS/SHELLERS
S. No. WM Measure Months in Savings Effect on RemarksOperation Achieved Environ-
(Rs./yr) ment
M/S Aishwarya Industries — Par Boiling Unit
1 Efficient 9 4,81,000 50%Boiler reduction
in pollution
2 Heat Recovery 9 1,10,000 Reduced Used rice huskfrom Boilers gas for insulation
temperature
3 Improved Steam 9 60.000 50 %Distribution reduced
effluent load
4 Control of Water 15 1,00,000 30% reducedfor Soaking effluent load
(Table 2.2 Contd...)
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(Table 2.2 Coil(d....)
S. No. WM Measure Months In Savings Effect on RemarksOperation Achieved Envïron-
(R.s./yr) ment
MIS Sree Venkata Ramana Paddy Processing Industries:
I WM Measure 6 2,50,000 30% reductionin pollution
2 Heat Recovery 12 60,000 Reduced System self designedfrom Boiler gas by the unit
temperature
3 Dust Extraction 8 48,000 Reduced Improved motor lifeFan Dryer dust load
4 Control of Water 15 1,30,000 30% reducedfor Soaking effluent load
5 Use of Effluent 15 Entire effluent Objection by Pollu-for Irrigation is used ion Board, but
farmers have noobjections
6 Use of Rice Husk 8 Ash is not Can be used forash as fertiliser wasted selective crops
M/S Noble Agro Industries:
1 Replacement 4 50,000 Reduced Will avoid use ofRewound motors heating rewound motors in
future
2 Control of Water 6 50,000 30%for Soaking reduced
effluent load
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WASTE MINIMIZATION AND POLLUTIONCONTROL - SAGO INDUSTRIES
by
Dr. N.G.NairDirector
INDIAN OPERATIONS RESEARCH GROUPPALAKKAD,KERALA
PHONE: 0491-2545453 FAX: 0491-2546720E-mail: [email protected]
Waste Minisation And Pollution Control -- Sago Industries D, N. G.Naïr*
1.0 - WASTE MINIMISATION
1.1 Introduction: Sago industries is of recent origin. This is an agro based industries producingstarch globules (sago) from tuber roots (tapioca). This is popular in south India and especially inTamilnadu in Salem and nearby districts. Following are the product mix.
- Sago-boiled;
- Sago roasted; and
- Sago starch
These units are under small scale sector. Major inputs are tapioca (20 tonnes/day), water (500m 3 /
day) and Electricity (1000 units/day). Out of 500m 3 of water supply nearly 300m 3 is wasted. Factoryworks 300 days an year and the crushing season is limited to 6 months (July to December) everyyear and production is round the year. Single and double shifts are operating by and large, theseowner driven industries with obsolete technology using primitive management and supervision.Wastages are high.
1.2 Strategy For Survival and Success: Globilisation has made competition very severe. In thisscenerio following two objectives stands out:
- attain and sustain competitive advantage by innovation in management; and
- ecologically sustainable development has become a non- negotiable requirement ofthe community.
1.2.1 Competitive advantage: In order to meet these objectives, every effort must be made toreduce the cost of production and improve quality of product. In this case, milk beingessentially a consumer product of community need comes under close security ofGovernment. Hence, there is no scope of increasing the prices in the market. Not beingdiffracted product, the quality remains almost same between competitors. Hence, the onlyalternative is to reduce the cost of production to achieve competitive advantage. Hence,waste minimization is the only option.
1.2.2 Ecology: Social requirement is achieved by controlling pollution. Waste minimization ,reduces the wastage which in turn reduces the chances of pollution and its control. Thus wefind, Waste Minimisation (WM) emerges, as the best option open to industries which increasesprofit and enhances competitive advantages, WM is essentially a strategy to conserveresources conscientiously through suitable innovation.
*Author is working as Director with IORG, Pallakkad, Kerala
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1.3 Waste Minimisation
1.3.1 Principles: Waste Minimisation (WM) has emerged as an attractive proposition these daysto achieve and sustain complete advantages as well as to tackle ecological deterioration ofindustries, all over the world. Beside reducing pollution it also improves process efficiencythus reducing cost of production. This step is essential for survival and success of industriesin the era of stiff competition due to globolisation. Waste Minimisation is defined as
"a new and creative way of thinking about product and process, which make them. It isachieved by continuous application of strategies to minimize the generation of waste andemission"
Waste Minimisation believes " prevention is better than cure" and hence prevents generationof waste at the source, rather than treating waste, after producing them by end of pipe (EOP)treatment. Having exhausted the source reduction opportunities, the next attempt is to recyclethe waste, after treatment, within the units.
1.3.2 Waste Minimisation Techniques: following are various techniques adopted: 1) Sourcereduction; 2) product change; and 3) recycle. These are briefly discussed.
- Source Reduction: This involves the following: 1) Good House Keeping; 2) Inputmaterial Change; 3) Better process control; 4) Equipment modification and 5)Technology change.
- Product Change: In cases, the source reduction is not good enough, one may attemptto change product so as to reduce use of harmful chemicals and cumbersomeproduction process.
- Recycling: This involves following 1) on site recovery and reuse; and 2) Creationof useful by-products.
1.3.3 The Need for Waste Minimization: Most of the firm are in SSI whose financial resourcesare limited. Hence, they are not in position to invest huge amount to set up effluent treatmentplant (ETP). As per regulating authorities, setting up ETP has become mandatory. This iscalled end of the pipe (EOP) treatment. Grudgingly, these units setup ETP on paper/ or instructure, but seldom operate them with conviction and commitment. Many of them remainunserviceable and operate only during the inspection visits of regulatory authorities. Theend result is pollution continued unabated. Since WM believes in prevention, it assistsindustrialists and motivate them. In one go we achieve two aspects, reduction in waste andpollution. Reduction in waste leads to profit. Hence the motto of WM " Waste-to-Profit" isa motivating factor. Thus industries found waste minimization an inescapable need andnecessity because of the following reasons:-
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- escapes punitive action by regulatory authorities;
- reduce raw material input and conserve the scarce resource;
- conserve water;
- conserve energy resources like electricity and fuel;
- reduce operating cost;
- protect environment; and
- create ecological consciousness among workers.
1.3.4 Potential for Waste Minimisation: Excellent potential exist for waste minimization inIndian industries, especially in small and medium scale, due to following reasons:-
1. Most of the industries are using obsolete technology and practices.
2. Many of them cannot afford to employ qualified manager to manage production andoperation, professionally.
3. Employ poor quality manpower and there is no regular method of training anddevelopment.
4. Difficult to change the `mindsets' of existing owners who prefer to follow old methodsunless a new method is demonstrated and yields profits.
5. No professional method of selection and procurement of raw material exists. Thisleads to considerable waste, since nearly 60 % cost of production is attributed tomaterials.
1.3.5 DESIRE : In the present study of waste minimization, we have followed the UNIDODemonstration in Small Industries for Reducing Waste under the guidance and direction ofNational Productivity Council(NPC), New Delhi and Ministry of Environmental and Forest,Government of India In this study, we have successful demonstrated waste minimizationoptions of short term, leading to saving of cost of the order of Rs. 35000 per day (Rs. 13lakh per year) . The major materials saved per day are water (50m 3), Fat and SNF(80kgeach) and milk (1300 liters).
1.3.6 Steps in Waste Minimisation : The following are the 6 steps in waste minimization whichwe have adopted in the study:
Step 1: Getting started by forming Waste Minimisation Circles(WMCs).
Step 2: Analysis of Process Flow Chart.
Step 3: Generating Waste Minimisation Opportunities.
Step 4: Selecting (short listing) Waste Minimisation Options.
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Step 5: Implementation of Waste Minimisation Options.
Step 6: Maintaining Waste Minimisation steps.
2.0 INDUSTRIAL PROFILE
2.1 Introduction: Sago is an agricultural based consumer product. This is very popular as afood item because of its unique character such as the following.
Fibrous;
Non fat, Carbohydrate; and
Nutritious.
End products are exported to countries like U.S.A. Malaysia, Turkey and Gulf countries in theMiddle East. Sago is produced out of Tapioca, which is the root of a seasonal plant which belongedto the Tuber crops(TRC) .These are grown in various parts of South Indian States in India. WhileTamil Nadu and Andhra pradesh have proper crops, these are grown in Kerala in an unorganizedmanner as an house hold item and serve as a very popular staple food for the poor people. Thailandis the other country next to India, where Tapioca is grown and used as an industrial, input for sagoindustries. Thailand accounts for 90% of sago exports to other countries, leaving only 10% of sagoexports share to India, Indonesia, and Philippines. Export from India picked up by 1980s on productmix such as Tapioca raw tuber, flour meals, starch and chip. Poor export performance of sago byIndia compared to Thailand is due to following reasons.
- poor technology;
- low production capacity;
- major production is consumed within the country as a popular staple food for thepoor; and
- lack of focus on sago industries by Govt. Agencies in general and Agricultural Sectorin particular.
Tuber Products from India are exported to EEC, Gulf Cooperation Councils (G.C.C)and someother Asian countries. In 1996, India exported 31,000 tonnes of various Cassava products earningRs. I4.13 crore.
2.1.2 Contribution to National/Regional Economy: Following are some of the statistics tohighlight these aspects:
A. The production capacity per unit is the order of 20,000 Tonnes per annum. Considering1000 industries, the total production volume is 20 million tonne. With an averageprice of Rs.15/per kg, the revenue earned by SAGO Industries is Rs.30,000 crores.
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B. In addition, at an average of 100-workers/labour force per unit, sago Industries provideemployment to nearly 1,00,000/-semi and unskilled workers.
C. Considering 25% starch consumes tapioca to the order of 80,000 tonnes annually.Thus accounts for 80 million tons of tapioca for all 1,000 industries, considering anaverage yield of 2.5tonne per hector, this gave opportunity to cultivate 32 millionhectares of land
D. Considering a family of 5 members per hectre of agriculture, sago Industries providethe livelyhood to 160 million small and medium scale farmers in India.
2.1.3 Geographic Location: In India Tamil Nadu occupy the first position in sago productionfollowing by Andhra Pradesh. However, 90% of major industries numbering 950 are locatedin Tamil Nadu in areas of Salem, Erode, Attur and Dharmapuri. 30 industries are establishedin Andhra Pradesh. Tamil Nadu accounts for 90% production of sago which is of the orderof 18 million tonnes per annum earning a revenue of Rs.27,000 Crore accountiong for theemployment of 90,000 industrial labour and 150 million agricultural labour.
2.2 Cluster Details:
2.2.1 Potential: Ninety percentage of cultivation of tapioca in Tamil Nadu is done at Salem andsurrounding area like Erode, Attur and Dharmapuri. There are approximately 950 sagoprocessing units in Tamil Nadu.
Cluster: In Salem city and sub-urban area, there are 13 registered major sago industries.Their details are given below:
Scale of operation: 13,000-21,000 tonnes/year.
Technology and product: Technology: Indigenous; Product mix: Sago, Starch and Fiber.
Major unit operation: Crushing, segregation,drying globuling ,polishing and packing.
Raw materials used: Water, Firewood and Electricity.
Water consumption :3 lakh litres per day.
Name and address of the units:
1. M/s Sri Venkatesh Sago Industries(P) Ltd, Salem
2. M/s Southerm Tapioca Industries(P) Ltd, Salem
3. M/s Sri Chenni Andavar sago Factory, Salem
4. M/s ARG&Co-Raja Sago Factory, Salem
5. M/s Gopal Sago and Food Products, Salem
6. M/s Sallakumar Sago Mfrs, Salem
7. M/s Chowdri Sago and Starch Factory, Salem
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8. M/s Thirumalai Sago Factory, Salem
9. M/s Sri Vinayaka Sago Factory,Salem
10. M/s KPN Sago Factory, Salem,
11. M/s Shanmuga Sago Factory, Salem
12. M/s Sridhar Sago Factory, Salem
13. M/s Sivamani Sago Factory, Salem
2.3 Special Features: Following are special problem faced by these industries.
- Raw materials are seasonal and supplies are limited.
- Market is quiet fluctuating.
- Tapioca processing be completed within 24 hours of harvesting.
- Factory works 300 days in 2 to 3 shifts a day.
- Non crushing season, factory works on sago processing at reduced scales of singleshift basis.
- Industries are heavily dependent on small farmers. Farmers cooperatinve are powerful.There is no captive suppliers. Hence, industries have lesser control on prices oftapioca.
- Supply cartel in marking is also powerful with State Govt. participation assisted bycooperative societies. SAGO SERVE is one such organization.
- This will restrict severely the capacity of firms in manipulating prices of end productsin the market.
2.4 W.M. Potential : Excellent scope exists for waste minimization in sago industries. Howeverthe extent of saving depends on the scale of operations and levels of innovative management ineach of such industries. A rough estimate of potential saving in indicated below :
S.No. Items Quantity per day Saving per year (Rs. Lakh)
1. Tapioca 1 Tonnes 4.50
2. Water 374 Tonnes 9.22
3. Starch 1250 kg 37.50
4. Chemicals 50 kg 3.00
5. FireWood 2 Tonnes 2.58
6. Electricity 215 KWH 2.58
Total 59.80 Lakh
3.0 PRODUCTION PROCESS:
3.1 Intoduction: As discussed in chapter-1, we have taken up Waste Minimisation study in SagoProduction in Dairy Industries. However, an indepth analysis of Waste Minimisation is not possibleunless we understand the production process properly. This is possible by studying the input materials,production process (equipment and technology) and the output in terms of quality and quantity ofend products. Keeping this in view, we shall discuss following aspects in this chapter:
- General Information;
- Availability of Information;
- Production Process; and
- Input and output analysis
3.2 General Information: All these units are under small-scale section (SSI). A unit crushing 20Tonnes of tapioca and producing 5 Tonnes of sago is taken up as a standard.
3.3 Availability of Information: Most of the firm working in small-scale category do not havesufficiently number of qualified managers. Hence, the employees are not in a position to explain thetechnical aspects of production process, calibration procedure and consumption of materials. Thisproblem is further compounded by the lack of maintenance of proper records. However for some ofthe medium scale industries, the position is different.
3.4 Production process: Production process consists of following steps.
- Receipt, inspection and cleaning;
- Pealing;
- Crushing;
- Filtration (Screening);
- Washing (Rasping);
- Sedimentation;
- Powdering;
- Sizing;
- Roasing/Boiling;
- Drying; and
- Polishing.
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The Processes are briefly discussed here.
A) Receipt Inspection and Cleaning: Tapioca, brought in lorries, are poured into apool of water for cleaning. Wastage is due to excess use of water and ineffectivecleaning process.
B) Pealing: The outer skin is removed by pealing by unskilled labour. Excess pealingcuts the core and wastage occurs due to this manual process.
C) Crushing: The roots are later crushed mechanically using water. Wastage of starchand water occurs here.
D) Filtration I (Screening): This is the process of separating the starch and residue.This is done by passing the pulp through. Vibrating filter platform in six stages. Lossof starch and water occurs due to leakage/over flows.
E) Washing process (Rasping): This is done by using four tanks of approximately25,000 litres capacity. Considerable wastages of water and chemicals take place inthis process.
F) Sedimentation: This is the process of separating sage starch from sago water bysedimentation. Wastage of water is the major loss in this process.
G) Powdering: In this process, the solidified starch is broken down by beating it withmotor. Loss is due to starch flying.
H) Sizing: The beaten starch is passed through conveyer and nice globules are formedthrough screens. Loss of starch is due to slippages.
I) Roasting/Boiling: In this process, the starch globules are boiled or roasted in thefurnaces. Loss of heat is due to poor insulation and starch by falling on ground.
J) Drying: At present, open air dying process is done.
K) Polishing/Packing: The loss is due to spillage of starch.
Input-Output analysis: An input/output analysis is done by working out requirement of majorinput raw materials including services like electricity, and manpower. This is given in terms ofquantity and price per day/monthlyear. Similarly, information regards to revenue earning is alsoworked out. These two information give rise to a surplus of Rs. 11,000/- lakhs per day. This estimateis made on the following assumptions.
96
Production capacity/day = 5 tonnes starch
No. of working shifts/day = 3
No. of working day/year = 300
However, these figures hold good to other factories having lesser/higher capacities by reducing/increasing input/output quantity/cost by appropriate proportionality factor. For example: a factoryproducing 50 tonnes of starch a day must multiply these figures by a factor 10 to get the revisedinput/output data.
4.0 WASTAGES - A DIAGONASTIC ANALYSIS
4.1 Introduction: In this chapter, an attempt is made to do a diagnostic analysis of wastages. Inorder to identify these causes, the waste minimization team collected relevant data from their factoriesand made independent analysis. These analysis were later discussed in the Waste MinimizationCircle meetings, where these data and analysis were subjected to scrutiny. From the team study andanalysis, consensus was reached and waste minimization opportunities were identified. These aspectsare discussed in this chapter under following broad headings:
- House keeping status;
- Input cost analysis;
- Waste stream analysis — materials and energy balance; and
- Environmental data and analysis.
4.2 House Keeping Status: We have examined the house keeping status of sago industries ingeneral and members of Waste Minimisation Circle, in particular. From the data and analysis wehave observed the following:
- Maintenance standard of the industry is not up to the mark.
- None of them follows preventive maintenance concept.
- No. continuous training of workers exists on their operations.
- Rough handling.
- Scope exists for effective supervision.
4.3 Input Cost Analysis: An attempt is made to identify the quantity and cost of materials received/consumed at each workstation in the process flow. The analysis assists the team of identify potentialareas of waste in each phase of manufacture.
97
4.4 Waste Stream Analysis: Following analysis was carried out as per details given below:
Energy Balance
Water Balance
Materials Balance
4.5 Environmental Pollution: Following issues and parameters were studied
Water Pollution — Wastewater source, flow, BOD, TSS, COD, TS
5.0 WASTE MINIMISATION OPPORTUNITIES AND OPTIONS
5.1 Introduction: We have seen sufficient data was collected under various heads in the previouschapter which was subjected to causative analysis. Based on these steps, the next logical step is todevelop waste minimization opportunities in each area of operation. These are then subjected tofeasibility analysis. These aspect are discussed in this chapter under following headings.
- summary of wastages;
- causative analysis of wastages;
- categorisation of waste minimization options — summary;
- identification and short listing of waste minimization options;
- technical feasibility analysis;
- economic feasibility analysis; and
- environment feasibility analysis;
5.2 Summary of Wastages: From the above we found that the total waste is amounted to Rs.20,260/- per day (or Rs. 61 lakh/year) for a firm processing 20 tonnes of tapioca per day and producing5 tonnes of sago. This is equivalent to a loss of Rs. 2/- per kg of sago sold. Considering the cost ofproduction of Rs. 10 per kg, we find this saving is substantial to the order of 20%, which is sufficientto attain advantage over others.
5.2 Causative•Analysis: we have identified the waste stream and quantified the wastages. It is nownecessary to subject these wastes stream to a diagnostics analysis to find out causes for such wastages,in each stage of manufacturing process.
5.3 Categorisation of Waste Minimisation Options: we have already mentioned about the sixtechnique of waste minimization. The waste stream was taken up for further study and analysis.Based on this the techniques needed to minimize the waste was categorized under following heads:
98
- house keeping;
- input material change;
- better process control;
equipment modification;
- technology change; and
- recycling.
5.5 Identification And Short Listing Of Waste Minimisation Options: A Total Of 31 Wasteminimization opportunities have been identified. These are categorized under the following threecategories;
- Options directly implementable;
Options requiring further study and analysis; and
Options which are impracticable.
A through scrutiny of WM options identified shows the following:
- Some of the options are not practicable either technologically or economically asidentified.
- Some of these options are of minor nature comes under effective maintenancemanagement, which does not require investment or further analysis.
Remaining options are short listed. These short-listed WM options are then taken up for further in depthanalysis.
5.6 Technical Feasibility Analysis: Technical Feasibility was analysed of short listed options toestablish the following:
- technical requirements like equipment and installation;
- technical impact in respect of production capacity saving of energy and inputmaterials; and
- grading.
Based on these analyses the options are ranked/graded.
5.7 Economic Feasibility Analysis: The short-listed 15 options are also subjected economicfeasibility analyses, based on the following factors:-
99
- capital investment;
- operating cost;
- saving per year;
- payback period; and
- grading.
Based on these analyses the options are ranked/graded.
5.8 Environmental analysis: The short listed WM options were also subjected to environmentalanalysis based on the following aspects:-
- reduction in water Pollution Load (BOA/COD/TS);
- reduction in the rate of flow of waste water;
- reduction in air pollution;
- reduction in solid waste; and
- graded.
Based on these analyses the options are ranked/graded.
6.0 POST IMPLEMENTATION ANALYSIS
6,1 Introduction: Proper implementation of W.M. option is essential to evaluate the effectivenessof planning premises and steps discussed in the earlier chapters. Even the best designed plan canfail, if it is not implemented properly. We discuss following topics in this chapter :
prioritation of W.M. options;
implementation schedule of W.M. options; and
post Implementation Analysis.
6.2 Overall Ranking of W.M. Option :In thé last chapter, the options are graded into three classes: Low, Medium and High under each category of technical, economical and environment. Theseoptions are not subjected overall weightage analysis. In this analysis, following rating scale is used to assigninterse weightages of different feasibilities viz technical, economical and environment.
Feasibility
Analysis
Total Score GradeLow Medium High
Technical 25 0-5 6-14 15-25Economical 50 0-10 11-29 30-50Environmental. 25 0-5 6-14 15-25Total 100 - - -
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6.3 Implementation Schedule: Based on the overall raking the implementation schedule was workedunder the following categories based on time period.
short-term (upto 3 months);
- medium tern (upto 3 to 6 months); and
- long-term (one year and above).
6.4 Post Implementation-Analysis: The identified W, M. Options are implemented and the resultswere analysed for the following purposes.
- to revise and finalise W.M. Option; and
- to quantify the results of actual saving vis-à-vis the saving envisaged in the plan.
Conclusion: Post Implementation result has finalized the W.M. Option as follows.
Short & Medium Term WM Options - 8
Long Term WM options - 7
Total - 15
Post implementation analysis enabled a saving of Rs. 13.150 per day (on short-term) which isequivalent to a saving of cost of products of Rs. 2.50 per Kg. This is substantial attain and sustaincompetitive advantage of those firn which are adopting W.M. options.
(Note : This paper has been edited. Author may be contacted for full Text, if required.)
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INDIAN ELECTROPLATING INDUSTRY -ABATEMENT A TOOL FORPOLLUTION PREVENTION
by
ASIF NURIECONSULTANT
H-4, GREEN PARK, NEW DELHI-110016TEL. : 011-26514527 E-mail : [email protected]
Indian Electroplating Industry —Abatement : A Tool For Pollution Prevention Asif Nurie*
Topics and Points
Introduction and Background
1. Type of plating with potential to pollute and discharge Hazardous chemicals
2. Chrome plating : 5 min presentation on methods, alternatives and viability
3. Cyanide Gold Plating: 5 minutes on methods, Alternatives, viability
4. Cyanide Zinc Plating : 10 minutes on Current status, Viable alternatives, Resistance tochange and Viablity of alternatives
5. Cyanide silver Plating : Current Status and Viable alternatives
Examples of the Japanese and US models, Taiwan and Thailand's initiatives,China lead in PP, 2 to 3 minutes
Governmental direction. Carrot and stick policy, 2-3 minutes
Policy making — EOP implementation, 3-4 minutes
Conclusion
Questions. 10 minutes
Closing
* Author is an independent Consultant based at New Delhi-110016
105
POLLUTION CONTROL IN LIME KILNS:CLEANER PRODUCTION
by
Dr. C. L. VERMADY. DIRECTOR & SCIENCE CORDINATOR
CENTRAL BUILDING RESEARCH INSTITUTEROORKEE — 247 667 UTTRANCHAL
PHONE: 01332-82306, 82296FAX: 01332-72543, 72272
E-mail : [email protected]
Pollution Control In Lime Kilns: Cleaner Production Dr.C.L.Verma*
PREAMBLE
Building materials are prime requirements of all civilized societies for catering to the needs ofpeople for housing and other civil construction activities. There is a world-wide consciousness andconcern for air pollution now a days. The principal constituent causing pollution of the atmosphereare emissions of various types, e.g. dusts, fumes, gases and vapours from different type of chemicalindustries, power plants, automobile engines, etc. These may also enter into air or water, and maydisturb the ecological balance of nature.
Lime has been identified to be a major building construction material and its production results inevolution of some polluting emissions pollutants from the kilns. Reduction of pollution from thelime-burning kiln has been identified as a major concern of the Indian lime industry, which hasbeen accorded low priority, and thus provided with inferior quality of fuel. This energy intensiveproduction process, being highly inefficient leads to the consumption of large quantity of fuel also.
THE INDIAN LIME INDUSTRY
Lime industry in India consists of major independent sectors namely:
(i) Cottage scale; (ii) Small / medium scale; and (iii) Captive lime units.
The cottage scale production of lime in tiny units is widely spread throughout the country. Limemanufacturing is effected by burning limestone in hackneyed types of kilns, which vary a great dealin their designs, shapes and sizes. For a traditional industry like this, the technologies differ whichalso lack scientific background. The kilns consume different fuels, many of them being localdepending upon their availability, such as, cinder, low grade steam coal, firewood, etc. The thermalefficiencies of such kilns are of low order and the utilization of fuel is not proper. Consequentlypolluting gases are likely to be generated. On account of the inherent design and operationaldrawbacks of these kilns vis-à-vis the capital cost involved, the installation of a pollution abatementdevice may not be feasible. Moreover, studies carried out earlier by the Central Building ResearchInstitute, Roorkee revealed that the in-efficient batch-operating kilns need to be abandoned in thenear future.
The small / medium scale sector of the lime industry is responsible for the major production oflime in the country at present. The capacities of these units range from 5 to 15 tonnes of lime perkiln per day. The lime manufacturing centers have the advantages of the proximity of the limestonedeposits as well as other favourably economic factors. This sector is concentrated at about 25important places in various parts of the country such as Dehra Dun (Uttranchal), Katni (M.P.),
* Author is Dy. Director & Science Coordinator with CBRI, Rorkee-244667
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Marwar Mundwa (Rajasthan), Paonta Sahib (H.P.), Gulbarga (Karnataka), etc. The limekilns usedin this sector are usually vertical shaft kilns operating semi-continuously. The fuels used in thesekilns are mostly steam coals of various grades, which contain large qualities of volatile matter aswell as ashes. The Central Building Research Institute, Roorkee and the Khadi and Village IndustriesCommission, Mumbai have been advocating the use of the mixed-feed (coal-fired) vertical limeshaft kilns. The volatile matter in the inferior grade steam coal, generally made available to the limeindustry, is as much as 25 to 30 per cent resulting in the evolution of hydrocarbon and suspendedparticulate matter from the kiln. The work on the development of an improved pollution abatementsystem from such kilns was taken up in view of their relevance in the National context.
The captive lime industry consists of lime production units which cater to the production of otherproducts in the same plant. Their use is restricted for high requirement of purity for the chemical,metallurgical and all process industries. On account of the sophistication of design and utilizationof better grade of fuel, the problem of atmospheric pollution is not significant. As the capitalinvestment on such kilns is of exorbitant magnitude, the same was considered to be outside thescope of the building lime industry.
THE MIXED-FEED LIME SHAFT KILNS
Manufacture of quick lime involves the endothermic process of calcination of limestone at elevatedtemperature exceeding 9000C under atmospheric condition by firing coal along with limestone. Themixed-feed of limestone and coal (in the ratio of 5-6 by weight) is charged into the kiln from the topand the product lime is withdrawn from its bottom. The volatile matter present in coal consists ofseveral compounds and these are devolatilized at their characteristic temperatures. The fuel movesdownward in the preheating zone from the top along with the rise in its temperature resulting indevolatilization of some of the constituents. Partial combustion of the volatile matter also takesplace after the fuel reaches the auto-ignition temperatures of the volatile matter in the burning zoneof the kiln. About 50-55 per cent of the volatile matter remains un-burnt and is emitted from the topof the kiln exhaust. The other pollutants emitted from the kiln top are carbon monoxide, sulphurdioxide, oxides of nitrogen and sulphides of hydrogen. Besides, the gaseous effluents from limekilns may contain particulate matter consisting of soot, coal ash and lime dust. Further, the solidparticles in the very fine form tend to enhance the contamination of the atmosphere during handling,processing and hydration of the material. The product quick lime, formed during its calcinationprocess in the burning zone and cooled up by the upcoming air in the cooling zone, is withdrawnfrom the bottom of the kiln through the discharge doors.
RESEARCH AND DEVELOPMENT
The Central Building Research Institute, Roorkee has been engaged in research and developmenton lime kilns for about three decades. Following the detailed survey of the manufacturing centers,systematic investigations were carried out on the masonry type of vertical mixed-feed lime kilns.The effect of the salient design and operational parameters, such as the superficial lime output rate,
110
kiln height to diameters ratio, sizes of lime stone and fuel particles, the proximate analysis of fueland the excess air fraction on the performance of the kilns have been evaluated. As a result of thiswork the technology for designing and setting up the masonry mixed-feed lime shaft kilns of improveddesign for capacities of production upto 15 tonnes of lime per day have been developed. Some ofthe salient features of these kilns are as follows: -
i. Mixed-feed steam coal fired masonry shaft with inner lining of fire bricks
ii. Uniformly induced natural draft from bottom of the kiln
iii. Continuous operation in 2/3 shifts per day
iv. Suitable for firing of dolomite as well as calcitic grades of limestones
V. Flexible for manual as well as mechanical charging
vi. Amenable to a fair degree of instrumentation and control
vii. Better productivity and product quality
viii. Upto 15 percent fuel economy over conventional kilns
The Khadi and Village Industries Commission, The National Building Organization and the LimeManufacturers Association of India are the institutions that have been actively associated with thetask of modernization of the lime industry.
EMISSIONS FROM LIME KILNS
Monitoring studies on some of the existing lime kilns, based on CBRI/ KVIC designs, were carriedout earlier at Dehra Dun (Uttranchal) and Ponta Sahib (H.P.). The average ranges of data for the 10tpd capacity kilns are as follows:-
S. No. Constituent Units Range
1. Exhaust gas flow rate Nm'/hr 2,000-2,500
2. Exhaust gas temperature °C 100-250
3. Suspended particulate matter(including tarry matter) mg/Nm3 1,000-2,000
4. Sulphur dioxides mg/Nm3 0.24-0.42
5. Nitrogen oxides mg/Nm3 2.0-6.5
6. Benzene Solubles mg/Nm3 300-1,000
7. Particle size less than 10 micron per cent 80-95
A permissible value of the Suspended Particulate Matter (SPM) of the order of 500 mg/Nm 3 wasenvisaged. The values of the other pollutants are generally less than those prescribed by the Central
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Pollution Control Board. The suspended particulate matter, comprising the kiln dust and the tarryorganic matter, was thus identified to be the major pollutant emitted from the lime kilns. The samewas required to be brought down within the tolerance levels. Hence the need to develop a suitablepollution abatement system was established.
POLLUTION CONTROL TECHNOLOGY
SPM is the major pollutant being emitted by the coal-fired lime kilns. Depending upon the size ofthe particles their weight distribution, and the quantity of the gas, one can use a separating device orcombination of devices. Design criteria of these devices are that the gas must be passed through azone in which particles come under the influence of some kind of forces (gravity, centrifugal, inertiathermal, diffusion, adhesion, cohesion and electrostatic), which cause them to be diverted from theflow direction of the stream for some time before diverting it to contact the collecting surface.
A system, incorporating a double deck packed bed scrubber cum entrainment separator was developedto control emissions of dust particles and hydrocarbon tarry matter from the lime kilns. It consistsof 2 fixed bed chambers containing limestone packing. The lower one serves as the counter-currentgas-liquid (water) scrubber. The entering liquid through spraying nozzles is distributed uniformlyover the top of the packing surface. The liquid descends through the column in the form of filmsdistributed over the packing surface and the exhaust gas from the masonry lime kiln rises throughthe voids between the packing particles. Consequently, a large amount of contact surface becomesavailable, which leads to efficient and economical mass transfer operations. The upper bed worksas demister cum entrainment separator for removal of moisture and tarry vapours from the upflowinggases. The gases after cleaning escape to the atmosphere through an induced draft fan installed atthe bottom of the stack.
THE IMPROVED POLLUTION CONTROL SYSTEM
The work an development and upgradation of the pollution control system was continued for the 10tonnes per day lime kilns. The system incorporating an improved scrubber with Packed Bed DemisterUnit has been developed to control emissions of dust particles and hydrocarbon tarry matter fromthe lime kiln. The control device consist of wet scrubbing of effluent gas in two parts. The first partis a contacting stage in which spray of water is generated and dust-laden gas moving at a moderatelyhigh velocity is led tangentially into the chamber. The resulting whirling motion produces centrifugalforces which drive the particles to the wall, where they are wetted by the fine spray of water beforethe gas enters the outlet pipe. In the second stage, the effluent stream passes through the whittletype sieve where some more water is sprayed. The deposited dust particles become heavy and tendto settle down through inertia. The cleaned wet gas is then passed through the packed bed demisterchamber which acts as an entrainment separator for the removal of the moisture and organic tarryvapors from the up flowing gases to the atmosphere through an induced draft fan installed at thebottom of the stack.
Water for the system is conveyed through a centrifugal pump. A reservoir for storage of water hasbeen provided. The water scrubbed material from the bottom of the lower chamber is collected into
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a slurry tank provided adjacent to the water tank. In order to reduce the consumption of water, theoverflowing liquid from the top of the slurry tank directly falls into the water tank for reusage.Limestone lumps packed into the demister chamber can be replaced at regular intervals of timenormally in about a week or so. These limestones are recycled into the lime kiln for calcination.
The salient technical features of the improved pollution control system are as follows:-
- Scrubber with Packed Bed Demister System
- Limestone as reusable packing material
- Suitable for particle sizes less than 10 micron
- Power failure not to affect kiln operation
- Water requirement: 4-5 kid
- Power requirement: 5 kw
ALTERNATIVE FUELS
In the context concurrence of the prevailing environmental consciousness, the paradigms of economicliberalization and globalization demand better product quality for sustainability in the competitivemarket conditions. The conservative building lime industry needs innovation and upliftment. Anurgent need has thus been felt to develop lime kiln designs based on alternative fuels, such as oil orgas. The oil may be furnace oil, and the gas may be produced from biomass or coal. The kiln systembased on appropriate oil or gas firing is envisaged to be thermally efficient and environment-friendlybesides yielding lime of enhanced quality. Experimental investigations thus need to be planned forthe development of an alternative fuel based system for lime burning.
CONCLUDING REMARKS
The Indian Building Lime Industry has been highly traditional in the past. It has started respondingto transformation in the past three decades. The prerogative of environmental awareness has madeit imperative for lime manufacturers to reduce the levels of pollutant emissions from their kilnswithin the acceptable limits. Some of the lime industries have already installed pollution controldevices as developed by the Central Building Research Institute, Roorkee and some other agencies.However, the problem is more severe in the manufacturing centers where the lime kilns havemushroomed within the boundaries of towns and cities. Thus, the need for utilizing alternativefuels, other than the low-grade steam coals, has been established. It is thus inferred and recommendedthat oil / gas-firing systems should be developed and utilized by the lime industry. Such cleanertechnologies are envisaged to reduce the Suspended Particulate Matter (SPM) levels significantly.
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CLEANER TECHNOLOGIES IN DISTILLERIES
a
1 B. ii• ' 1^PRESIDENT
INTERNATIONAL SCHOOL OF ENVIRONMENTALMANAGEMENT STUDIES
"ARUNDHATI", VISHRAM BHAG- 416415, SANGLI (DIST), MAHARASHTRA.TEL. (0233) 2301857 / 2302664 FAX.(0233) 2301857
e mail: san_eprf @ sancharnet.in
Cleaner Technologies in Distilleries. Dr. B. Subba Rao*
1.0 INTRODUCTION
"Cleaner Technologies" may be defined as to help the elimination of pollutional load into theEnvironment. In the true sense, the entire waste shall be recycled either in the process or in theenvironment without any residual matter. Besides the technology shall be such that the transformationof the pollution load from one form to another shall not be permitted.
The sophisticated and costlier technology may not be necessarily always "The Best Technology" or"Cleaner Technology" as it may lead to short cut measures to eliminate the cost of treatment andoperation. The approach of cleaner technology shall be the cost effective treatment and disposalwith minimum adverse impacts on the environment.
2.0 IDENTIFICATION OF TECHNOLOGIES
The CPCB has identified few technologies as treatment and disposal options. The merits and demeritsof these methods are presented in the light of "Cleaner Technologies".
I. Anaerobic Digestion followed by two State aeration and Dilution with Fresh Waterfor Disposal on Land for Irrigation.
II. Composting
III. Concentration, Drying and Incineration
In addition to the above technologies, the following technologies may be alsoevaluated.
IV. Controlled Land Application
V. Reverse Osmosis
VI. Conversion of Spentwash into fuel by mixing with Bagasse cillo (Pith)
I.A. Anaerobic Digestion followed by Two Stage Aeration
In Anaerobic Digestion, 90 % BOD reduction is achieved. However, there is no significant reductionof Inorganic Dissolved Solids Concentration. Thus the initial Inorganic Dissolved Solidsconcentration of 25,000-30,000 mg/l in Spentwash maybe reduced to 20,000 to 25,000 mg/l mainlydue to the reduction of Sulphates in Anaerobic Digestion treatment.
* Author is President of "International School of Environmental Management Studies", Sangli, Maharashtra
117
In Aeration, the total BOD reduction in both the stages together may be around 90 % and in fieldconditions the BOD concentration of the treated effluent is observed to be around 500-800 mg/l,which has been confirmed in the CPCB laboratory investigations as 300-500 mg/l.
At present the best operated treatment plants are giving the effluent BOD concentrations around800 mg/1 and the Total Inorganic Dissolved Solids concentration of around 20,000 -25,000 mg/1,The evaluation studies carried out by the CPCB as well as by Dr, 13. Subba Rao on a project sponsoredby CPCB for the Development of Methodology of Environmental Audit of Distillery industriesclearly indicate that the Distillery units are not able to achieve the Standards by treatment alone,The CPCB has now established the design criteria based on the experiences of the distillery units inHaryana State which are to be still validated.
In case of the Standards for discharge into Streams at a BOD concentration of 30 mg/l, it is next toimpossible to achieve these limits unless one resorts to Chemical treatment options. In this case, thechemical sludge handling problems would further aggravate the situation. Two of the industrieswho have adopted Chemical treatment in India have to abandon the trials due to dispute with thesuppliers of the technology. However, a few units in Thailand which had adopted ChemicalPrecipitation have discontinued due to Sludge Handling Problems and high recurring expenditure.
I. B. Disposal of Treated Effluents (Irrigation Practices)
The main option identified by the industries as well as by Regulatory Agencies is to dispose off theeffluent on land for irrigation. The IARI (Indian Agricultural Research Institute, New Delhi)developed a protocol and fixed the requirement of land as Nine Hectatre per KL of Spiritproduction considering the Inorganic Dissolved Solids concentration as 10,000 mg/1 in the treatedeffluent. Based on the material balance of Inorganic Dissolved Solids in biologically treatedSpentwash, the total concentration of Cations and Anions works out to be around 20,000- 25,000mg/I (i.e. K- 8,000 -10,000 mg/l, Ca- 2,000 -3,000 mg/l, Na- 2,000-3,000 mg/i, Mg- 1,500-2,000mg/l, Chlorides- 5,000-6,000 mg/l Sulphates- 300-500 mg/l)
Thus the requirement of minimum dilution water would be ten times to bring the Inorganic DissolvedSolids concentration to acceptable limits of 2100 mg/l as Irrigation Water. The land requirementwould then be Eighteen Hectare instead of Nine Hectare per KL of RS production.
Most of the distilleries do not have sufficient land and as such discharge the treated effluents intowater courses under the pretext of irrigation. Besides the farmers are reluctant to use this water dueto seepage of coloured effluent into Groundwater. It may be noted that the treated effluent wouldstill have a deep dark brown colour which is mainly due to the presence of `Caramel' in Spentwash.
Thus the Standards / Protocols prescribed on land application for irrigation can not be considered asCleaner Technology due to large requirements of Dilution Water, Land and colouration toGroundwater sources. The long term effects on soil due to the application of high salts concentrationmay also pose a limitation to the disposal of the effluents.
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LC. Disposal of Treated Effluents (Streams)
In Maharashtra, two Distilleries (M/s. Manjara SSK Ltd; & M/s. Terana SSK Ltd; Latur Dist) haveadopted anaerobic digestion followed by two stage aeration and chemical treatment. These plantsare not in operation due to techno-economic feasibility of the process as well as the sludge disposalproblems. Similarly, in Thailand also some distilleries who have adopted this type of technologyare not in operation due to the same reasons.
II. Composting
At present "Composting" process as a treatment and disposal gained the confidence of Regulatoryagencies and industries. The main limitation of this technology is the availability of cheap source offiller material such as Pressmud. It is felt that "Composting process" may be recommended fordistilleries having a capacity upto 45 kld due to the requirement of large area, availability of fillermaterial and marketing of Compost etc. The requirements of filler material for a 45 kld distillerycapacity may be calculated as below:
- Distillery capacity
45 kld
- Working days
300 days
- Spentwash generated per day 45,000 x 15 = 6,75,000 litre = 675 cum.(1 litre of RS produces 15 litre of Spentwash after anaerobic treatment)
- If Three hundred days of working ofthe distillery is considered Spentwashgenerated is
- Pressmud and Spentwash can bemixed at a ratio of
- Pressmud required shall be
675* 300 = 2,02,500 cum
1: 2.5
2,02,500 / 2.5 = 81,000 MT.
- If raw Spentwash is used for "Composting", the quantity of Spentwash generated forone litre of RS production shall be eight litres
- Quantity of Spentwash generatedper day is
45,000 x 8 = 3,60,000 litre = 360cum
- For 300 days
360 x 300 = 1,08,000 cum
- Pressmud required shall be
1,08,000/2.5 = 43,200 MT
Thus the industry has to estimate that how many days it can run the distillery based on the availabilityof filler material. Unfortunately most of the industries present very attractive ratios of pressmudand spentwash mixing in order to show the feasibility of the process.
(Note: There is a possibility to reduce spentwash quantity and subsequently filler material requirementif Reboilers / Evaporators are used. However, the requirement of filler material and time requiredfor composting are yet to be established)
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III. Concentration and Incineration
The adoption of"Concentration and Incineration" technology would lead to Zero Pollution approachand the most ideal system as cleaner Technology. Till today none of the systems which are inoperation in India could produce any positive results to evolve any useful data.
The distilleries having production capacities more than 45 kld may have to consider the adoption ofthis type of treatment as any other option may not be suitable for effective disposal of the treatedeffluents.
The performance of some of these units are given below:
A) Bang yee Khan Distillery of 2,10,000 litre/day at Bangkok, Thailand. MoEF shall evaluatethe feasibility of this technology.
B) DIEG technology for 30 kld at Krishna Shetkari S.S.K. Ltd; Rethare Bk., Karad, Satara(Dist), Maharashtra State. Vasantdada Institute, Pune. The plant is erected about six yearsback but not commissioned so far.
C) The "Concentration and Incineration" plant at Polychem Ltd; Nimbuti, Nira is not found tobe economical due to techno-economical reasons.
D) Concentration and Drying plant for digested effluent of 30 kld plant at Ugar Sugar WorksLtd; Ugar Khurd, Belgaum Dist, Karnataka State which was supplied by SSP (P) Ltd; is inworking condition but the cost-economics is not available.
E) Pengium Alcohols (P) Ltd; Goa have adopted "High Ferm GR" continuous fermentationTechnology. In this technology four effect evaporators were installed to produce fermentedmolasses solubes with 50% W/W solids concentration. It was originally planned to sellFMS as cattle feed. Since, there was no market; the FMS was stored in steel tanks andunfortunately there was a breakdown of one of these tanks and the entire FMS entered intoriver causing severe pollution. The unit is closed.
IV. Controlled land application
Spentwash can be applied directly as a fertiliser on land once in a year as that of any organicmanure. The raw spentwash or anaerobically digested spentwash can be applied at a rate of70-80kl per hectare of land once in a year only. If untreated spentwash is applied, it shall betransported through stainless steel or other type of acid resistant tankers. If digested effluents areused, mild steel tankers can be used. This practice has been followed extensively in many countries(Annexure I: Page 124).
The area required for land application can be calculated as below:
Distillery capacity- 45 kld
Digested effluent- 45x15= 675 kld
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300days working capacity- 675x300 = 2,02,500 kl
W Area required shall be 2,02,500 kl/80 = 2531.25 hectare Say 2500 Hectares
If Raw spentwash is used, the area required shall be 45x8x300/80 = 1350 Ha.
Advantages
1. Since the effluent is thoroughly mixed with soil and utilised by microflora as organic sourceand nutrients, the seepage of effluents into groundwater can be totally eliminated.
2. Since there is no dilution water required, the cost of disposal is low.
3. The soil gets enriched with nutrients and the requirement of fertilisers can be reducedconsiderably.
4. The application of 80 kl of spentwash per hectare is less than five tonnes of spentwashcompost which is usually added in one hectare of land. Thus there would not be any deleteriouseffects.
5. The application can be monitored very precisely.
6. It is very much beneficial to the industries where there is a shortage of filler material orwhere there is no filler material which is the usual case.
Disadvantages
1. Transportation cost may be high.
2. The application of spentwash as manure shall be completed before plantation and as suchthe time schedules are to be strictly adhered.
3. Since the Storage tank capacities required for spentwash may be large, the crop plantationpractices may be regrouped so that minimum storage is maintained.
Conclusions
1. The adoption of both "Composting" and "Controlled Land Application" may be idealapproach for treatment and disposal of spentwash whenever there are limitations of fillermaterials, land for disposal, etc.
2. There are few units who have already initiated the above combinations of treatment. Thedata from these units may be collected to evolve the Standards and Protocols.
3. The "Composting" and "Controlled land application" techniques may be used only fordistilleries having capacities upto 45 kld beyond which it may become unmanageable.
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V.Reverse Osmosis Technology
The Concentration of Digested effluent by Reverse Osmosis technology is being followed at LiquorsIndia Ltd; Hyderabad for a 30 kid distillery. The plant was supplied by Rochem (I) Ltd. It is possibleto reduce the quantity of the effluent by fifty percent and the water can be recycled as process waterfor fermentation. The concentrated effluent shall have to be treated either by "Composting" /"Concentration Drying and Incineration" / Controlled Land Application". The cost economics ofthis project could not be worked out as the system is not being operated on a full scale.
VI. Conversion of Spentwash as fuel by mixing with bagasse cillo and burning inconventional boilers.
Bagasse cilio (Pith) can absorb about five times of spentwash. After mixing bagasse cilio andspentwash, it may be dried to have a moisture content of fifty percent and burnt in conventionalboilers. The dried spentwash solids has a calorific value of 4090 kCal / Kg. and the pith has acalorific value of 1800 kCal /Kg. Taking into consideration 18% spentwash solids in a spentwashquantity of 240 cum for 30 kid distillery, the calorific value of solids would be 1200 x 1.12 (Sp. Gr.of Spenwash and five times spentwash quantity 1344 x 4090 x 1000 kCal and that of bagasse ciliowould be 268.80 x 1000 x 1800 (i.e. bagasse cilio requirement is 268.80 MT).Thus, the total energythat can be obtained would be 54,96,96000 + 483840000= 598080000 kcal, which is equivalent to260 MT of bagasse. The requirement of bagasse to dry spentwash to 50 % moisture would bearound 200 MT. Thus, there would be a savings of around 60 MT bagasse per day. Alternately, fluegas may be also used to dry spentwash to 50 % moisture.
The above technique appears to be one of the feasible and cleaner technologies. However, thismethod may not be economical for digested effluents as the solids content would be very low.
Conclusions
I. The treatment of distillery waste by anaerobic digestion followed by two stageaeration treatment is a feasible technology to achieve the maximum BOD reduction of 800 mg / 1.However, the inorganic dissolved solids concentration would be around 25,000 -30,000 mg/1. Thechlorides concentration would be also around 5000-6000 mg/1 and thus the dilution water requirementwould be minimum ten times. The colour would persist in the effluent and the groundwatercolouration can not be eliminated
I.B. The chemical precipitation of the secondary treated effluents to remove colour & BOD havenot been found to be cost-effective and as such are not in operation either in India or Thailandwhere such plants are in existence.
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II. A. Concentration and Incineration technology at Thailand has been working , however, thecost economics of the plant is not available. It is suggested to evaluate this technology.
B) DIEG technology developed by VSI, Pune has landed into technical problems and the plantappears to be defunct.
C) Concentreation and Incineration plant at M/s. Jubilant Organosys Ltd; Nira is abandoned
D) Concentration and Drying plant at M/S. Ugar Sugar Works Ltd; Ugar Khurd for digestedeffluent is in operation. However, the cost-economics of the unit is not available. It issuggested to evaluate this technology.
E) The fermented Molasses Solubles (FMS) technology adopted at Pengium Alcohols (P) Ltd;Goa appears to have no market for the product and also the capital and recurring expenditureappear to be very high.
III. "Composting" technology appears to be feasible only for the distilleries having a capacityless than 45 kid. This technology needs further improvements and considerable R & D efforts arerequired. A theme paper has been prepared.
IV. "Controlled Land Application" for raw and digested spentwash appears to be a promisingtechnology. Extensive field scale studies have been conducted at Brazil & Australia for the applicationof raw spentwash as manure.
V. Reverse osmosis (membrane technology) is being tried at Liquors India ltd; Hyderabad on afull scale for a distillery capacity of 30 kld. The feasibility of this technoiogy need to be evaluated.
VI. Mixing of bagasse cilio and spentwash burning in conventional boilers appears to be yetanother promising clean technology. Pilot plant studies are to be undertaken.
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RECOMMENDATIONS FOR APPLICATION OF DISTILLERYWASTE WATER IN DIFFERENT COUNTRIES
Country Recommendations Reference
Brazil
1. Vinasse @ 6000-8000 gallon / acre leads to 30 % Gloria and Margo (1976)enhancement in cane tonnage.
2. Application of Urea, 30 days after Vinasse application, Serra (1979)when ratoon tillage operation should be carried out. Silva et al. (1981)Profitable dose 100 m3 / ha Vinasse + 85 kg N / ha.
3. It is necessary to complement Vinasse with mineral Orlando et al. (1981)fertilizers for its beneficial effects on the crops.
4. Application of vinasse 35-50 m3 / ha from (molasses Silva et almust, 60-100 in 3 / ha (from mixed must) and (1978)100-150 m 3 / ha (from juice must) alongwith nitrogenimproves yield in sugarcane ratoon.
5. Application of vinasse upto 4112 m3 / ha through sprinkler Anon (1979)and hydraulic gun was better than mineral fertilization.
6. Vinasse diluted with 10 parts cane wash water and Rosetto et al (1978)condenser water could replace the use on mineralfertilizer without adverse effect on cane
7. Ratoon crops on latossol soil, treated with Anon (1979)90-150 m3 / ha Vinasse with ammonium sulphateincreased recoverable sugar per hectare.
8. Application of Distillery slops (i) @ 100 m / ha Penatti et al (1988)+ 150 kg N / ha for sandy soil (ii) @ 50 m3 / ha +150 kg N / ha for clayey soil, was found to be effective.
9. Application of slops (50 T / ha) alongwith N and P, Chang and Liincreased sugarcane yield in plant and ratoon crops. (1989)
India10. Soil supplement of Vinasse @ 35 m3 / ha +150 kg N / ha, Pande (1985)
enhances sucrose and cane yield in sandy loam soil Pande and Sinha(1988)Pande(1993)
11. Application of undiluted Vinasse to saline sodic soil, Singh et al (1980)equivalent to 20 % of the gypsum requirement, followedby leaching improves soil properties.
12. Use after aerobic and anaerobic treatments for irrigation, Srivastava et alafter dilution to 6-8 times. (1976)
13. Application of 5 to 7.5 MT / ha compost (spentwash+PMC) Jadhav eta!with adjusted dose of N, P, K before planting was beneficial (1992)
Puerto Rico14. Application of stillage on partially reclaimed saline—sodic Perez- Escolar
soil leads to an enhancement in cane tonnage upto 40% et al (1979)Trinidad
15. Stillage application a 12,000 gallons / acre on a sandy Cooper and Prasadsoil increased cane tonnage by 45%, in 1` t ratoon. (1978)
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GAINING ENVIRONMENTAL SECURITY ININDUSTRIAL SECTOR: A REAL LIFE
EXPERIENCE OF INDIAN LEATHER INDUSTRY
by
DR. T. RAMASWAMIDIRECTOR
CENTRAL LEATHER RESEARCH INSTITUTEADYAR, CHENNAI - 600 020, TAMILNADU
email : [email protected]
Gaining Environmental Security In Industrial Sector:A Real Life Experience of Indian Leather Industry Dr.T.Ramaswami*
India enjoys vast raw hides and skins base. There is a large manufacturing base for leather in theform of installed manufacturing capacities of tanneries in India. Human capital suited for the leathersector in India is vast. Total direct employment provided by this industry is to the tune of 2.5 millionwith 30% being women. India enjoys the image of a reliable supplier of finished leather. During thelast fifty years, India has switched over to the export of value added leather products as seen inFigure 1. The overall turnover of leather trade in India is about Rs 20,000 crores.
An analysis of the trends of export realisation during 1984-2001 indicates annual growth rates ofabout 6.5 % for finished leather, 5.9% for footwear upper components, 11.6% for closed footwear,15% for leather garments and 19% for leather goods. Growth rates observed in case of finishedleather and footwear upper components are not significantly high and may even be reflective ofexchange and inflationary trends. Positive growth can be recognised only in the case of leathergoods and garments. A carefully planned strategic intervention is necessary for the footwear sectorto perhaps realise its full potential. There is an attempt to integrate the development of the Indianleather sector with environmental security. Particularly after the landmark judgment of the SupremeCourt of India to close down large number of tanneries in Tamil Nadu and order relocation of theentire tanning industry into a new leather complex, environmental considerations have attainedhigh focus.
* Author is Director with CLRI, Chennai-600 020
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Stages in Leather Processing and the Relative Contributions to the Emissions of Polluting MaterialsIn leather processing, the basic strategy is to clean skin of the unwanted interfibrillary materialthrough a set of pretanning operations, preserve permanently by means of tanning and add aestheticproperties during post tanning stages. An inflow - outflow diagram for the process is presented inFigure 2. The relative contributions of pretanning, tanning and post tanning steps to the pollutionloads in tanning sector are compared in Table 1 (Next Page). It is evident that a major source ofpollution is the waste discharged into wastewaters during the pretanning operations.
Fig. 2 : An Inflow - Outflow DiagramSources of Pollution : pretanning Operations
The starting material for leather processing, in most cases, is raw hide or skin, which had beenpreserved temporarily by the addition of common salt. The common salt, when removed from theskin, constitutes a major source of pollution from tanneries. Since the dissolved sodium chloride isnot easily treated and removed from wastewaters, the discharge of tannery wastewaters into landleads to the significant addition of salinity of the soil. The transport of salt through the ground wateraffects the water bodies in the region and this has been a major environmental constraint. Costeffective solutions to the pollution problem through avoidance or end-of-pipe treatment ofwastewaters are not easily forthcoming.
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Table 1: Characteristics of tannery wastewaters
Parameter Soaking Liming! IDelin-dng Pickling Chrome ÏNeutralisationlRechromingTotal(dyeing, i(including
relimingi ! tanning fatliquor (washings)3Volume ofl6-9 m 3-5 m3 ^ 1.5-1 m3 1 30.5-1 m,l-2 m ^ 2-3 m3 T 3-6 m 3 i30-4Óm3
effluent/tonne:of hide/skinspH '7.5 10.0- 7.0-9.0 2.0-3.0 125-4040-65 3.5 4.5 X7.0-9.0
8.0 12.8
BOD 5 day at;1,100- ;5,000- 1,000-400-700 350-8001800-1100 1000-2000 1200-300020°C (Total) ¡2,500 10,000 13,000
COD (Total) ,3,000 10,000- 2,500 1000- 1000- ;2000-4500 2500-7000 :2500-8000¡6,000 ;25,000 17,000 3000 ;2500
Sulfides 1- 200-500 30-60 - - - - 30-150
(as S)
Total Solids 35,000- ;24,000- 15,000 ,35,000- 30,000- 110,000-14,000 4000-9000 ¡12,000-55,000 '48,000 12,000 ¡¡70,000 '60,000 123,00
(TS)Total 32,000- ! 18,000- 3000- 34,000- ,29,000- 19000-12,500 13600-8000 '9000-Dissolved 48,000 30,000 18000 167,000 ¡57,500 18,000Solids (TDS) ' ¡Suspended 3,000- 6000- 2000- 1,000- .1,000- 11000-1500 400-900 12000-5000Solids (SS) '7,000 ' 18,000 4000 ,3,000 2,500 ¡ t
Chlorides 15,000 4,000- h 1,000- 20,000- ;15,000- i 1500-2500 300-1000 1 6000-950030,000 ;8,000 2,000 30,000 ;25,000
(as Cl) 1
Sulfate as800- 600- 12000- 12,000- 12,500- J 1000-2000 1200-2500 ' 1600-2500SO4 1500 1200 14000 18,000 ;19,000
Chromium - - 1- - 11500- 115-30 150-300 120-200(as Total Cr) '4000
Since the intrinsic nature of pretanning operations demand that the unwanted interfibrillary materialsare removed, additions to the BOD and COD loads is unavoidable at the pretanning stage. However,through judicious choice of methods it is possible to minimise the BOD and COD loads.
At the pretanning stage, significant amount of chemicals are employed per kilogram of leatherprocessed. The removal of hair and flesh from skin is achieved by the use of lime and sulfide, whichcause problems of both solid and liquid waste management.
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Deliming agents based on weakly acidic salts like ammonium chloride and ammonium sulfatewhich could affect the N:P:K ratios of soil. Nitrogen based deliming agents are considered a longterm environmental threat.
Pickling and chrome tanning are two stages in leather processing which need close scrutiny fortheir contributions to environmental constraints. Excessive use of common salt and sulfuric acid ascarried out commonly during pickling operation leads to significant COD as well as TDS loads. Incase of vegetable tanning, there is no need for an extensive pickling. It has now been establishedthat sulfate ions in wastewaters constitute a major source of environmental problem.
Sulfate ions undergo ready reduction to sulfide under anaerobic conditions in wastewater treatmentplants as in the anaerobic lagoons, contact filter or upflow anaerobic sludge blanket reactor. Whenthe concentrations of sulfide build up to critical concentration through such reductions,biomethanation of organic materials is rendered less efficient. Further, the sulfide thus formedcontributes to the COD load significantly. Dissolved salts of sulfate contribute not only to the TDS,but also to COD and reduce the efficacies of effluent treatment plants in lowering the levels ofBOD.
Sources of Pollution: Tanning Operations
Tanning is the process where the protein is rendered more stable against biodegradation. Chrometanning is a commonly employed method for permanent preservation. In this method, spent solutionscontaining chromium salts, sodium chloride and sodium sulfate are discharged. The contributionsto TDS and chromium concentrations raise ecological concerns. Although the oxidation state ofchromium in the tanning salt is only trivalent, discharge norms do not often specify the redox states,because of the concerns of possible conversion of the trivalent state to the more toxic hexavalentform. The spent chrome tanning solutions are sources of both TDS and chromium pollution, whichneed to be addressed.
Sources of Pollution: Post Tanning Operations
In the post tanning operations, the tanning industry employs a wide range of performance chemicals,which add aesthetic properties to leather. Many of these are formulations based on proprietaryproducts. However, it is now realised that post tanning processes contribute to neutral salts, CODand heavy metal pollution. These apart, azo dyes, biocides and some heavy metal based pigmentsadd to toxic load of wastewater streams.
Since post tanning operations are associated with size reduction of the leather matrix, a significantamount of solid wastes are generated. Wet blue shavings, buffing dust and trimmings cause constraintsin solid wastes problem. Buffing dust and fine particulate matter can be air borne and emerge asource of air pollution. Solvent based finish formulations employed in leather processing increase
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the potential for atmospheric pollution. Formaldehyde used in leather finishing has been adisconcerting source of pollution. The contributions to BOD, COD and TDS loads in waste watersare significantly lower from the post tanning operations in comparison to the total discharge. However,it is necessary to carry out treatability studies on the proprietary formulations so that non-degradablesubstances may be avoided.
Volume of Wastewater
The volume of wastewaters generated varies from tannery to tannery and within the tannery frombatch to batch. The average volume of wastewater generated during leather processing is given inTable 2. It should be mentioned here that the figures in Table 2 pertain to locations where water isscarce, costly and conscious efforts are made to conserve its use (e.g. Tamil Nadu, India, Italy).However where copious volume of water is available, the tendency is to use anywhere between 60to 100 m3/t of raw material. (e.g. Kolkata, Jalandhar).
Table 2: Average Volume of Wastewater Generated in a Tannery
Process Volume of wastewater discharged in m 3 per tonne of wet saltedraw material processed
Hides
Raw to E.I. 15-22 f20-25
Raw to wet blue 18-25 J20-30
E.I. to finishing 12-18 ^12-18
(40-60 in terms of (40-60 in terms of E.I. weight)E.I . weight)
Wet blue to 10-15 10-15finishing
(20-30 in terms of (20-30 in terms of wetblue weight)wet blue weight)
Raw to finishing 30-40 135-45
Source: Regional Workshop on Cleaner Tanning Technologies (RWSCTT), UNIDO, September 1998.
Pollution Load from Leather Processing
The average pollution load in kilograms in tannery wastewater discharged while processing onetonne of raw hide/skin to finished leather is shown in Table 3.
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Table 3: Pollution load (kg) for processing one tonne of raw hide/skin
Pollution jSoaking Beamhouse Tanyard Post- Total pollution load, kgParameters ^ Process ( tanning
and wetfinishing
Biochemical 1244 __ 3 12 71
OxygenDemand(BOD5
@ 20°C) IChemical 23 94 C 10 27 154OxygenDemand(COD)Sulfides - 4 - - 4(as S Z ")Suspended 28 65 9 6 108SolidsTotal - - 5 1.5 6.5Chromium(as Cr)Total 160 85 130 44 419dissolvedsolidsChlorides 107 25
I54 6 192
(as C1") (Sulfate as ! 8 9 - 45 22 84(SO42 )
Discharge Norms for Tanneries
The Environment Protection Rules, 1986 have specified the discharge norms for effluents of tanningindustry. These norms are presented in Table 4.
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Table 4: Effluent discharge norms for tanning Industry in India
Characteristics (Tolerance limits for Industrial effluent dischargeInland Public' Land for arinc coastal areassurface sewer irrigationwater
Colour &1 Absent j - AbsentÍ^^__._.
OdourpH5.5-9.00 5.5-9,0.-._ 5.5-9.0
Suspended (5.5-9.0
-^^^100 600 200 100Solids
O das 2O C 1 30 350 100 100
COD 250 ) - - 250
TDS 2100 2100 2100^^ . -
Chlorides as Cl' f 1000 ¡ 1000 600 -Total 2 2 2 2Chromium asCr
Hexavalent Cr ^ 0.1 0.1 0.1 r 1SUlfide as S 2 2 2 5Boron as B 2 I 2
.._. 2 20
Oils &Grease 10 J 20 10 -Ammonical 50 50 - 50nitrogen (as N)TKS (as N) 100 - - I 100
Sodium percent -_
60 60Sulfate as SOS 2 1000 ;11000 J 1000
Note: Concentration in effluent not to exceed in mg/1 for parameters (except for pH and Sodium percent).
Do-Ecology Solutions for Tanning Sector
Prevention or reduction of pollution at source through in-process control measures has gainedimportance in leather industry in recent times. There is now an increasing recognition that end-of-pipe treatment in isolation is not an adequate strategy to meet the requirements of wastewaternorms and standards. The ideal approach is to target the zero or near-zero discharge of waste liquors.The progressive adoption of cleaner technologies by the tanners depends on the following factors:a) proven reduction of emission loads in terms of quantity and quality; b) quantifiable economicbenefits to tanners through quality improvement, cost reduction and material saving; and c) ease ofapplication with minimum additional investments on hardware and d) trade advantages on account
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of improved environmental positioning in global market. A variety of technology options for cleanerprocessing of leather have emerged.
Reduction of pollutants at source: Through in-process changes
Technologies for reduction of total dissolved solids: The contribution of neutral salts to tannerywastewaters originates from the salts used in short term preservation of raw hides/skins by theabattoirs and primary sources, processing inputs by tanners and those formed during processing onaccount of the pH alterations employed in leather manufacture. Desalting of raw hides/skins stockin tanneries has led to a reduction of 15% load of TDS at the solar pans. This solution is beingadopted in number of tanneries in Tamil Nadu. Enzyme assisted dehairing and use of better qualitylime in tanneries have led to significant reduction in TDS, (-15%) loads. Segregation and recycletechnologies for pickle and chrome tanning liquors offer a possibility to reduce about 10% of TDSload in composite tannery wastewaters. A close audit of neutral salt content of post tanning auxiliariesand appropriate choice of right formulations enable a net saving of about 5% of TDS load in compositetannery wastewaters. A typical improvement in TDS loads by the implementation of cleaner neutralsalt saving technologies in leather sector has been depicted in Figure 3. This is based on the averageexperience gained over 258 tanneries in Tamil Nadu over a period of six months.
Reduction of BOD and COD at source: It has been possible to reduce the emission of BOD andCOD loads per tonne of leather processed by 30-40% by the implementation of cleaner technologies.Critical technologies required to achieve such a reduction have involved the implementation ofmechanical desalting, enzyme assisted sulfide-reduced dehairing and cleaner chrome tanning. Someof these technology elements are successfully implemented in tanneries in India.
Fig. 3
Reduction of sulfide load in tannery: It has been possible to employ the commercially availableenzymes to replace 50-60% of sodium sulfide loads required for loosening hair from the hide/skin.
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A net gain of 2% increase in area of leather has been demonstrated in several cases. Such an increasein area could well compensate for increased cost of enzyme assisted dehairing technology. Reductionof sulfide concentration in tannery wastewaters by about 50% enjoys a potential opportunity to savethe cost of end-of-pipe treatment of tannery wastewater by about 8-10%.
Reduction of nitrogen salts: Various nitrogen salts free deliming methods are available and theirusage is gaining importance. One such methodology is based on the use of carbon dioxide fordeliming.
Technologies for reduction or elimination of chrome discharge in tannery wastewaters:Chromium(III) salts are extensively used as potential tanning material globally. The commerciallyavailable salts and methods lead to an uptake of about 40-70% of the material employed for tanning.Poor utilization of chromium leads to environmental problems. It is now technologically feasibleand economically viable to increase the uptake of chromium during tanning to nearly 98-99%.Chrome recovery/reuse technologies suited for various levels of investment potentials have alreadybeen implemented with high success. More than 400 such plants have been installed all over thecountry. Cleaner chrome tanning methods based on high exhaustion principle have now been evolved.Closed pickle-tan loop method affords a net saving of Rs.2000/- per ton of leather processed. Thesetechnologies offer a secure means to practically eliminate the problem of pollution due to chromiumbased tanning methods while avoiding also the discharge of neutral salts.
Reduction of pollutants: Through source audit and product alternatives
The reduction of pollutants through audit has been achieved through a) replacement of eco-constrained chemical inputs (for example: by replacing chromium with organic alternatives);b) treatability audit for retanning agents, fatliquors, dyes and finishing auxiliaries and c) computerassisted micro-process controlled systems for chemical, water addition and pH monitoring.
Control of pollution: Through end-of-pipe treatment solutions
The tanning industry in India is primarily in the small and medium enterprise (SME) sector. Thefinancial and technical capacity to select, install, commission, operate and maintain individual andunit specific effluent treatment plant is limited to a maximum of about 15% of the total number oftanning units in the country. Therefore, the need for a collective approach to the end-of-pipe treatmentof tannery wastewater through common effluent treatment plant (CETP) has been recognized. 16common effluent treatment plants have been commissioned in the country in different locations toserve about 70% of functional tanning units, with 12 of them being established in Tamil Nadu.Currently, there is no functional tannery in Tamil Nadu without a connection to pollution devicesfor end-of-pipe treatment. Of the 154 individual effluent treatment plants (ETP) and 16 CETPs inIndian leather sector, 140 ETPs and 12 CETPs are in Tamil Nadu.
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Technological solutions: Conventional tannery effluent treatment plants consist ofphysico-chemicaltreatment followed by biological treatment and further tertiary treatment to meet the standards.Significant technological advancements are being made in the end-of-pipe treatment methods toachieve higher efficiency in meeting the standards in a cost-effective manner. An improved solarevaporation system has provided for reduction in time and space required for treatment. The anaerobictreatment of tanning wastewaters in different locations in India has included the application oftechnologies based on lagoons, contact filter, Upflow Anaerobic Sludge Blanket (UASB) reactorand high rate biomethanation. The use of closed bioreactors offers a possibility to recover sulfurfrom hydrogen sulfide and energy from methane after suitable modifications. A plant with 36 millionliters per day (MLD) capacity is in operation at Kanpur.
Although anaerobic treatment of tannery wastewater is efficient to reduce the BOD and COD loadsby 50-60%, post-treatment using aeration methodologies is essential to achieve 30 and 250 ppmBOD and COD norms, respectively. Such post treatment methodologies for tannery wastewatersfrom anaerobic biodigestion have included the use of aerators with and without the aid of aerobes.Microbial methods are efficient and cost effective but require continuous operation. The new posttreatment technology named Chemo Autotrophic Activated Carbon Oxidation (CAACO) systemhas been developed and adopted for treating tannery wastewaters after anaerobic treatment andfiltration enables reduction of COD, sulfates and color. Diffused air floatation technique has beensuccessfully employed in aeration in CETPs in Chennai.
Activated carbon filters, reed bed and root zone techniques and reverse osmosis methods are beinginvestigated for providing tertiary treatment of tannery wastewater.
Protection of society: Through secure disposal of treated wastes
Whereas pollution reduction at source offers a potential to reduce costs by saving on wastes, anyend-of-pipe treatment technology should aim to contain costs within the price structure of the product.At the end-of-pipe treatment the chemical composition of treated wastes in solid and liquid formshave to meet the norms stipulated for various receiving bodies. Treated tannery wastewater is nowable to comply with BOD, COD and other related norms for discharging into surface waters, or foruse in irrigation or for dilution by domestic sewage. However, it has been found difficult to reachthe norm of 2100 ppm for total dissolved solids stipulated by some State Pollution Control Boardsunder the current status of end-of-pipe technologies controlling TDS. Similarly fleshing, althoughcontains only protein, causes nuisance due to putrefaction when disposed in the open. Chromiumcontaining sludge as well as sludge from ETP/CETP, resulting from end-of-pipe treatment needproper disposal. The nature and quantum of various solid wastes generated from the leather processingof 1 tonne of raw hides/skins is indicated in Table 5.
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Table 5: Nature and quantum of solid wastes (per ton of raw hides processed)
I Nature of Solid Waste Production (in Kg) ISalt from handshaking 80
Salt from solar pans (not realized) 220
Hair (pasting ovine) 100
Raw trimmings 40
Lime sludge (mostly bovine) 60
Fleshing 120
Wet blue trimmings (grain splits) 30
Chrome splitting (bovine) 65
Chrome shaving (mostly bovine) 95
EI shaving 40
Buffing dust (incl. shaving bovine after crust) 65
Dyed trimmings 35
Sludge (35 % dry solids basis) 360
Some of the technological options for handling of solid wastes are as follows: Trimmings of rawhides/skins and pelts and fleshings can be utilized for glue manufacture. The salt obtained frommechanical desalting and solar evaporation can be used for curing, pickling or disposed in nearbysea. Biomethanation of fleshings and solid sludge from primary and secondary treatments is aneconomically viable option for secured disposal. The hair recovered from leather processing isconventionally used for the manufacture of low priced rugs and carpets. Sludge from lime pits finduse in land filling as well as construction of low priced houses. The barks and nuts from vegetabletanning can be used as fuel for boilers and brick kilns. The shavings, trimmings and buffings ofvegetable and chrome tanned leather find usage in the manufacture of leather boards.
The sludge from the treatment plants can be advantageously used for brick manufacture, land fillingfor low-lying areas and as fertilizer if the chrome content is within the prescribed levels. A specialoxidative firing and reductive cooling based technology has been demonstrated for brick manufacturefrom chromium containing sludges. It has been demonstrated that the technology ensures safedeposition of chromium without any leaching in industrial bricks.
High rate transpiration system (HRTS) has emerged as a possible method for treating salt bearingtannery wastewaters. This is being employed to avoid the discharge of treated tannery wastewatersinto public land in Tamil Nadu. Reed bed technology for the treatment of tannery wastewaters isbeing explored.
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The treated liquid wastes from end-of-pipe treatment plants complying with the stipulated normscan be disposed to nearby water bodies without affecting the eco-balance. A technologicalintervention in terms of tertiary treatment becomes inevitable in cases where the compliance to eco-standards is difficult.
Demonstration of Do-Ecology Solutions in Leather Sector in Tamil Nadu
In the wake of the order of the Supreme Courts of India, nearly 400 tanneries in the state facedclosure. CLRI and NEERI have been able to work with the entire tanning industry in Tamil Naduand enable the sector to gain environmental security through application of technologies. Althoughfurther improvements are required, there has been a significant impact due to adoption of cleanertechnologies in the leather sector in Tamil Nadu.
A vast number of critical technologies and options have now emerged to render leather processingcleaner. Some of these technologies are presented in Figure 4.
Fig 4
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It has been demonstrated that BOD and COD loads could be brought down by 30-40%, whereas saltreduction by 25%, sulfide by 50-80% and chromium 95-99% are feasible. A set of data collected onthe minimization of BOD, COD, TDS, chloride, sulfide and chromium loads through theimplementation of cleaner production methods in a group of 258 tanneries is presented in Figure 5.It has also been demonstrated that a tannery with a production capacity of 2000 kg of hide/skin perday might potentially save Rs, 1.4 million per month by adoption of cleaner technologies. Theimplementation of such cleaner production systems has led to saving of vital economic activity inthe state of Tamil Nadu. There is now need for a National Movement on cleaner production in theIndian leather sector. A sector specific action plan for pollution prevention and control in the leatherindustry has been prepared at the behest of Ministry of Environment and Forests, Government ofIndia. The implementation of the action plan will pave the way for further drastically minimizingenvironmental risks from tanning sector to near-zero values.
Fig 5
Pollution Abatement: Situation Analysis in India
In recent years, there have been several attempts in the Indian leather industry to enhanceenvironmental preparedness. The total number of tanneries in India has been estimated to be 2091.These tanneries are categorized into tiny, small and medium enterprises. Government policy directiveson reservation of raw hides and skins processing have led to the development of a two tier systemin tanning capacities. Small tanneries manufacture wet-blue and medium sized tanneries processthese wet-blue further into finished leather. Tanning capacity of India could therefore be categorizedinto groups viz. raw-semi-finished (wet-blue/E.I.), raw-finished, semi-finished- finished.
Regional distribution of number of tanneries in different states in India has been shown in Figure 6.Major tannery clusters in India are in Tamil Nadu, West Bengal, U.P. and Punjab. Nearly 90% of the
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tanning capacity is concentrated in these four States only. Within Tamil Nadu, tanneries areconcentrated in Vellore, Trichy. Dindigul and Erode districts. In West Bengal, tanneries are mostlyin Kolkata. In case of UP, Kanpur is the major centre with some limited tanning activity in Agra. Incase of Punjab, Jalandhar is the major centre of tanning. Around Delhi, in Haryana some tanningcapacity has grown.
Fig. 6
Current Environmental Status and Issues of Indian Tannery Sector
Environmental preparedness of tanneries differs widely. The investment limits and potentials toestablish pollution control devices as well as lack of suitable human resource limit tiny and smalltanneries. In such cases, CETPs have been established by groups of tanneries. In all there are 16CETPs and 154 ETPs in India. The average consumption of water per kg of leather processed intanneries in different States has been listed in Table 6 (Next Page).
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Table 6: Water consumption in leather processing (Statewise)
State Average consumption ofwater / kg of hide (in litres)
Punjab 80-100
Tamil Nadu 22-30
Uttar Pradesh 40-50
West Bengal 50-60
Punjab: Jalandhar leather complex is the main centre of tanning. Water consumption per kilogramof hide processed in tanneries in the complex is higher than the global as well as national average.There is vast scope for implementation of waste minimization programmes. This would reduce thehydraulic load on the CETP and therefore improve its operational efficiency. Technology upgradationin tanning is essential. Spin-off will be enhanced environmental benefits. A second module ofCETP is being designed currently. Safeguards are being built in the design of second module ofCETP. Solid wastes disposal in the complex has been a problem. Solutions are now underway. Thesector may need technology and financing support for modernisation.
Tamil Nadu: Tannery sector in Tamil Nadu has developed in five major clusters viz. Chennai,Vellore, Trichy, Dindigul and Erode. Leather product sector is developed in Vellore. Tanneries inthe water starved Vellore region are facing serious public pressure. Salinity of treated tannerywastewaters poses problems in surface discharge. TNPCB norms of 2100 ppm for surface dischargeare difficult to reach in spite of best efforts. Tanneries in the region are open to either one of the hardand long term options namely relocation to near sea or pipeline conveyance of treated wastewaters.Tanneries in Trichy and Dindigul need technology modernisation in leather processing as well asimproved solutions to TDS management. A new leather complex is an appropriate direction.Tanneries in Erode, which need improvements in environmental preparedness, are best relocatedinto the new emerging industrial complex for hazardous industries. An industrial zoningprogramme is under development in Erode. It is best to take advantage of the opportunity andimplement secure technology options in the new proposed complex. Tanneries in Chennai areconnected to two functional CETPs. Since the tannery cluster is in a metro city on the shore of Bayof Bengal, dilution with domestic sewer as well as discharge of treated wastewaters into sea arefeasible options.
U.P.: Kanpur and Unnao are the main tanning centres in UP. CETPs and ETPs are established intanneries in these clusters. UASB plant at Jajmau needs attention in management and post treatmentof UASB output. Power supply has been a major problem in the operation of ETPs and CETPs. Thepublic objects to generation of power through generators. Frequent power failure and planned cuts
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limit the operational efficiency. A secure solution to this problem is essential. CETPs are beingdesigned currently for the leather complex at Unnao. An experience sharing dialogue with tanneriesin Tamil Nadu may be useful.
West Bengal : Kolkata leather complex is being built. This is a relocation programme. It is notimpossible that the relocation may require about 2-3 years at the current pace of development. Aninterim effort to implement cleaner tanning technologies in the present location would be useful.Initial efforts have already been taken through a UNDP assisted project: CETP module is beingdesigned. Efforts to indigenise the technologies for other subsequent modules are envisaged. Sincetotal of 30 mid capacity has been envisaged, it is necessary to build all safeguards at this stage withrespect to the environmental preparedness of the complex.
The environmental preparedness of tanneries in India is summarized in Table 7.
Table 7. Summary of Environmental Preparedness of Tanneries in India
TN WB UP ' Punj ab100%o working Relocation of all All functional Leather complextanneries connected tanneries with tanneries are is connected to ato devices CETPs will ensure connected to CETP. Expansion
100% connectivity CETPs/ETPs is underway30 and 250 ppm BOD Currently no In Kanpur, Capacityand COD norms treatment is in copliance to augmentation ofrealized place excepting in norms is debated. CETP is needed
some limited Chrome recovery for achievingnumber of is not ensured. normstanneries.
TDS residual Total solution Norms to be Capacity to beproblem needed achieved built
Technology Gaps in Cleaner Leather Processing
The technology gaps in cleaner production are
Reducing water demand per kilogram of hide to under 10 litres
Reducing TDS levels in leather processing to under 2100 mg/litre through in-process control
Reducing solid wastes generated to under 100 kg/ton of hides processed
Reducing chlorides and sulfate levels in wastewaters under 500 mg/lit through in processingchanges
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Technology gaps in end-of-pipe treatment are
• BOD and COD: improvements in current technologies with ease of start-up and shut downwith fluctuating power positions are required
• TSS: Retrofitting of current devices
• Sulfide removal: 100% removal needs R&D
• Chromium removal: 100% avoidance if technologically feasible, commercial decisions notso easy; <99% removal is feasible and viable
• TDS:2100 mg/L: Complete and viable technological solutions are needed
• Secure utilization mechanism for solid wastes needed
Total Dissolved Solids Options & Solutions
TDS discharge from tanneries is about 3 lakh tons per annum with 50% from salt based preservation,33% from wastewaters arising from processing technologies and 17% of salt from normal additionsduring processing. In-plant measures may help significantly. However, complying 2100 ppm normthrough in-plant control measures alone is difficult.
Likely solutions Implementation Challenges
Avoid completely use of salt in Technology extension to dispersedpreservation of hides and processing sources of R.M. is difficult
Concentrate solutions and recover Solar evaporation, membrane technologiescompletely salts and dispose safely offer scope, but salt disposal is necessary
Dilute streams and absorb onto Dilution is feasible when scope exists,biomass and develop a salt but salt remains in soil/landtolerant ecology in the vicinity unless absorbed
Return of salts to sources like Social resistance in wasteabattoirs, salt works, sea etc. disposal systems is large
Solutions to TOS Problem: Possible Approaches
• Repeat of technology plan for cleaner technologies with TDS focus and reach 7500 mg/1norm across the state
Establish a working methodology to collect the solar evaporate salts and dispose safely.
Commercial Scale Demonstration units for applications of membrane technologies completewith management of rejects, admixture with municipal wastes for dilution and a selectecology, phyto-remediation and treatment of low saline wastes in the existing locations
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Position in well engineered complexes with advanced technologies and management systemswithin carrying capacity considerations and safe disposal of treated wastes
Specific R&D Efforts for Secured Tanning
• Paradigm shifts from chemical to bio-processing of leather are an area much needed change.
• Ambient preservation of skin/hide without salt and drying/dehydration for wide spreadapplications in a decentralized production base of raw hides and skins
• Emission factors of beam house processes in leather sector need to be reduced by at least by400-500% through process alternatives.
• R&D applications are necessary to increase the uptake levels of chemicals employed inleather processing. This would call changes in both the nature of chemicals and applicationmethodologies.
• Reduction of pollution at source has become necessary for the management of Total DissolvedSolids (TDS). TDS data sheet for all post tanning chemicals employed in leather processingwould be necessary.
• Eco-benign rating of chemicals employed based on absorption and treatability is required.
• Safe disposable treated liquid and solid wastes as well as used leathers
• Reduction of chemical usage in wastewater treatment
• Waste treatment based on a) biotechnology b) electrochemical technology c) photochemicaltechnology, d) combination methods of the above three and e) plasma technology
R&D Applications of Developed Technologies
• Upflow anaerobic sludge blanket reactor has been adapted for management of liquid wastesfrom tanneries successfully. This methodology with complete sulfur recovery systems offersvast scope for saving of space, operating costs, gaining of energy from wastes and reductionof Green house emissions. R&D applications of this technology in different social contextsof India are valuable step forward.
• Wet Air Oxidation method, which enables an easy shut down and restart procedure is ofhigh value in situations where the power supply is not continuous and conventional aeratorsfail.
• Biomethanation technologies with stock preparation for various types of solid wastes forenergy recovery are gainful.
• Cost-effective technologies for removal of fecal coliform from treated wastewaters fromhigh rate biomethanation reactors need wider applications.
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Safe Handling of Treated Wastes from Tannery Effluent Treatment Plants
Disposal of treated tannery wastewaters containing TDS in excess of 2100 mg/lit has posedlegal problems in some states. Disposal of treated tannery waste waters in own lands for thecontrolled irrigation, dilution with treated domestic waste waters complete with select ecologyand marine outfall are conventionally used methods in other countries. Specific commercialscale demonstration trials are required for ensuring the safety of wider applications of thesemethods in water-starved regions of India.
• Membrane technologies for water renovation and recycle from treated saline waste waterscomplete with secure disposal of rejects need to be evaluated further for both technical andcommercial viabilities under tannery circumstances.
• Management options for treated saline waste waters including phyto remedial and controlledirrigation measures in green houses with water recovery may be a potential area for R&D.
Strategy for Management of Solid Wastes
• Technologies for gainful utilization of solid wastes from tannery sector inclusive of recoveredsalt, flesh, buffing dust, chrome shavings, chrome sludge and primary and secondary sludgesfrom common effluent treatment plants
• Securatization of solid wastes and safe disposal systems for hazardous solid wastes basedon space saving approaches.
Concluding Remarks: Some Recommended Actions
• A sector specific action plan for pollution prevention and control has been prepared for theMoEF. Speedy implementation of the action plan is required.
• Environmental preparedness of the tannery sector in Tamil Nadu has increased considerablysince 1996. It has become necessary to spread best practice systems in tanneries in otherregions as well. A Cleaner production centre at CLRI to work on a mission mode to spreadR&D applications over the next five years will be valuable.
• Many common effluent treatment plants in tannery sector have been commissioned prior to1997. They are based on technologies relevant at that time. Many of them need upgradationand modernization for saving of energy as well as improvement of efficiency through R&Dapplications. A modernization drive for CETPs is recommended.
• R&D approaches and applications for complying with Total Dissolved Solids Norm of 2100mg/l need to further supported.
• Development of cost effective technologies for solid waste management and utilisationmerit support.
• Water saving technologies with a potential to reduce water consumption to levels lowerthan 10 lit of water for kilogram, solid waste reduction methods to reduce levels to 100 kg/tonne of leather processed merit support for R&D.
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RE-REFINING / REPROCESSING OFUSED OIL / WASTE OIL
by
DR HIMMAT SINGHConsultant - Petroleum Technology
69, TEG BAHADUR ROAD — 4DALANWALA, DEHRADUN-248 001
PHONE: 0135-2672397; FAX: 0135-2671111E-mails : [email protected]
Re-Refining /Reprocessing Of used oil /Waste oilPr1HIwmui S11IMFh*
SUMMARY
The disposal of used / waste lubricants, estimated to be generated around 5.3 billion gallons annually,is both economic and environmental challenge throughout the world. Typically used oil refers toused motor oil as it is collected from oil change shops, garages and industry such as hydraulic oils,turbine oils, process oils and similar other fuels, Chemical composition wise these oils are atconsiderable variations with the virgin oil.
Used / waste oil can be recycled in variety of ways to utilize its lubrication or heat value. Re-refining is one of the preferred method of recycling of used oil. During re-refining used oil undergoesphysical and chemical treatment, remove impurities so that the resulting re-refined oil product is ofhigh quality and can be blended with additives and virgin oil to produce new lubricating oil.
Today, in the market there are two categories of process technologies which find application in usedoil re-rehnïng to yield high quality base oils meeting the environmental regulations. The 1 generationtechnological processes emerged in early 70s and have served very well till early 90s. However,they have been faced with four principal barriers namely: (1) cost, (2) complexity (3) physical plantsize and (4) availability of feedstocks. These barriers tend to be inter-related and make theirimplementation at scattered small scale waste oil recycling / reprocessing facilities practicallyimpossible. And hence they have given rise to 2nd generation (new) re-refining process technologies.New re-refining process technologies have been developed in US, Canada and other nations todeliver high quality base oil from spent lubricants at low cost. Three such technologies are:
Media and process : Lubriclear process
Tiqsons Technologies Inc ; Used lube oil re-refining
Probex Technologies : ProTerra process
All the three processes re-refine spent lubricant to high quality base stocks using smaller capacityunits based on proprietary concepts giving high base oil yield in an environmentally benign approach.This has been possible due to better understanding of compositional aspects of used / waste oil andquality requirements to meet high performance level products.
Status of used / waste oil refining in our country is yet to catch up with the world developments.Although there are two acid free processes available but quality of reprocessed base oils needs to belot more improved. We need to undertake serious R&D work on this subject to deliver high qualitybase stock at low cost based on environmentally benign approach.
* Author is working as independent Consultant-in the field of Petroleum Technology based at Dehradun.
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1.0 INTRODUCTION
The disposal of waste lubricants is both an economic and environmental challenge throughout theworld today. Based on a 1998 study by the U.S. Department of Energy, there are more than 1.3billion gallons of spent lubricating oil generated annually in the U.S. by automobile, truck andindustrial engines and machinery. About ape-third is largely not recovered. A substantial amount ofthat oil is presumed to be disposed of improperly, creating significant environmental problems. "Ofthe approximately 900 million gallons of used lubricating oil collected in the U.S.each year, onlyabout 140 million gallons are reprocessed and yield only about 70 million gallons of GF-2 qualityreprocessed lube base oil." The balance is burned as low grade burner fuel. Worldwide, an estimated5.3 billion gallons of used lubricating oils are generated annually.
In western Europe as per CONCAWE report 5 (1996), 49% of the lubricants sold every year, arecollectable and only 28% are actually collected. Although waste lubricants can be considered asignificant renewable resource, less than 10% is actually re-refined into high quality lubricant basestocks. The remainder is generally burned for fuel, incinerated, sprayed on the roads for dustsuppression, land fills etc. However, as stricter environmental regulations continue to limit theabove mentioned disposal options, environmentally benign technologies for the recovery of wastelubricants are becoming increasingly attractive.
In India, a rough estimate indicates that about 4,00,000 tonnes of used/waste automotive oil isgenerated annually, of which about 25% was being re-refined in the mid 1990s to generate basestocksboth for automotive and industrial oils.
2.0 USED / WASTE OIL - DEFINITION
Typically used oil refers to used motor oil as it is collected from oil change shops and garages andindustry such as hydraulic oils, turbine oils, process oils and similar other fluids. Used oil can alsooriginate at sea ports from ocean going vessels as well. Used oil may contain high level of lead,cadmium, arsenic and chromium and may also contain other contaminants such as chlorinatedsolvents, polychlorinated bi-phenyls (PCBs) and other carcinogens. It is a potent pollutant: when itis dumped in the open environment, into sewers or in land fills, it is capable of migrating into thesoil and under ground aquifers. It is said that one gallon of used oil can contaminate one milliongallons of water, rendering it un-potable. Marine species can be adversely affected, if exposed to oil
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concentration as low as one parts per million. Since waste oil contain various hazardous contaminants, the burning of such oil increases air pollution as toxic gases are vented to the atmosphere affectingnot just human being but plants and birds as well.
Table — 1.1 below compares some of the constituents found in the motor oil from automobile anddiesel truck crankcases to the constituents in virgin oil. The table shows the levels and types ofcontaminants that can enter motor oils through use.
Table-1.1 : Potentially harmful constituents in Used oil vs Virgin Motor Oil
Constituent Used Oil from Used Oil from Virgin lubricatingAutomobile Diesel Truck oilscrankcases Crankcases (Range in ppm)"(Range in ppm)a (Range in ppm)a
Cadmium 0.5-3.4 0.7-3 0Chromium 0.8-23 1.8-7.1 0Lead 5.5-150 2.9 - 1.9 0.3Benz(a)pyrene 25 —86 2.0 0.03 — 0.28
a: U.S. EPA 1991; b : U.S. EPA, 1984
Chemical composition wise these oils are at considerable variance with the virgin oil. According totitle 40 of US code of Federal regulations (CFR) part 279, a used oil is defined as follows "Used oilmeans any oil that has been refined from crude oil, or any synthetic oil, that has been used and as aresult of such use is contaminated by physical and chemical impurities" (US.EPA 1992C). Thisdefinition includes oils that are used as hydraulic fluids as well as oils used to lubricate automobilesand other machinery, cool engines or suspended materials in industrial processes. As per the Ministryof Environment & Forests, Govt. of India "Guidelines for Management of Hazardous Waste", "thewaste oil" and emulsions are covered under type of waste — category 10. Accordingly they need tobe managed properly because of the following four main reasons:
• To protect the environment
• To protect human health
• To protect against liability for environmental damages
• To reuse, rather than waste, a valuable resource
3.0 RECYCLING OF USED / WASTE OIL - OPTIONS
Recycling is reusing a substance or material in a beneficial way. In the past, used oil was reused fora wide range of different purposes. Unfortunately, many of the ways used oil was reused causedenvironmental problems. For example, used oil was sometimes used to kill weeds or keep dustdown on dirt roads (U.S. EPA, 1984b). As a result the used oil contaminated soils, ground waterand surface water in the area. In recognition of these problems, EPA's Used Oil Management
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Standards have banned options, such as road oiling, that cause significant risks to human health andthe environment. Used oil can be recycled in variety of ways to utilize its lubrication or heat value.The most common used oil recycling methods that are approved by the management standards are:
• Re-refining to use as a base stock for lubricating oil
• Slip-streaming to use as a base stock for other petroleum products
• Processing to burn for heat
• Direct burning for heat
The most common method of recycling used oil is to either use it as such as a fuel or reprocess itand convert into a good quality fuel oil and use. Re-refining is also the preferred method of recyclingused oil, but only a small percentage is actually re-refined, as a lot of capital is required to start-upand operate a facility to re-refine oil compare to the cost of a facility that processes oil. In addition,there is low demand for the re-refined oils due to the perception that it is lower in quality than thevirgin oil.
4.0 RE-REFINING PROCESSES / TECHNOLOGIES
Before describing different re-refining processes and their salient features in detail, it is desirable tomention the changes that the motor oil (taken as the basis of used oil) undergoes during use, turningthe same into a waste/used oil. The literature mentions the following four reasons for the changesthat occur in oils :
a. Engine heat can break down additives and other constituents in the oil. This processcan produce acids and other substances that contaminate the oil.
b. Dirt, dust, and rust can get into the crankcase and into the oil. Particles of metal dustfrom the engine also can contaminate oil directly.
C. Exhaust gases from combustion in the engine can leak through the engine's pistonrings and into the oil. This "engine blowby" contaminates the oil with gasoline andgasoline combustion products
d. Fluids, such as water, antifreeze and coolant, can leak into the oil during engineoperation.
Because of the changes that occur through use, used motor oil tends to differ from virgin motor oilin several ways. Most importantly, used motor oil has :
Much higher water and sediment levels than virgin oil
Relatively high levels of polynuclear aromatics, such as benzo(a) pyrene.
Relatively high levels of metals, such as aluminum and lead
All re-refining technologies that are in commercial use and also recently announced aim at correctingthe above changes in the used oil to restore its lubricant properties in the form of base oil for re-usein lubricant formulation. Typically all the processes involve the following general process stagesfor re-refining of used oil.
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1. Separation of larger solid impurities along with most of the water. This is normallyachieved by sedimentation.
2. Separation of volatile parts (fuel residues in engine oils, solvents and low boilingpoint lubricant components). This normally happens by atmospheric distillation.The separated light hydrocarbons can usually be used in-house for energy creation.
3. Separation of the additives and oxidized by-products. This can occur by acid refining,solvent (propane) extraction, vacuum distillation or partly also by hydrogenation.
4. Finishing process to separate any remaining additives, oxidation by-products andrefining reaction products. This normally happens by hydro-finishing, with absorbentssuch as bleaching clay or mild, selective solvent extraction (i.e. furfural)
However, each process technology has its own specific technological features to meet the stagerequirements and catalyst used in the finishing step.
Historically, one of the first regenerating processes was the sulphuric acid and clay process. However,because of continuous improvements in the properties of finished lubricants, this process has beenaffected as follows:
• increase in the percentage of acid used for regeneration
• longer processing periods
• ever lower yields of regenerated oil
• higher processing costs
• increase in the quantities of process residues which are difficult to dispose of.
For these reasons, the acid process is now obsolete for all practical purposes and is being replacedby more suitable regeneration processes. These include re-refining processes based on the followingoperations which are carried out on oil dried beforehand:
de-asphalting using solventvacuum distillationhydrotreating.
Today in the market, there are two categories of process technologies which find application in re-refining of used oil to yield product comparable in quality with the virgin oil and also meeting thecurrent environmental regulations. All the technologies can be easily categorized into two groupsnamely:
Environmentally benign 151 generation technological processesEnvironmentally benign 2°d generation (new) technological processes
4.1 Environmentally benign 1st generation technological processes
The first generation technological processes emerged in early 1970s and there after continuouslyimproved to keep pace with changing environment. All such processes are based on operations,
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which are normally practiced in an oil refinery to make virgin products but have been adopted toused oil re-refining considering the chemical nature of impurities present therein. As many as 6process technologies are wroth mentioning under this category. Although almost all of thesetechnologies or in / have been in commercial use but some of them have made strong presence inthe market, For example Snamprogetti waste Tube oil re-refining process has been operational withindustrial prototype of 50,000 T/yr at Cecean — Rome for Clipper oil Italianna. The process is basedbeside physical separation on two-stage solvent extraction and hydro finishing to improve base oilproperties. Process claimed to be ecologically safe, energy saving design and has high level offlexibility.
The revivoil process jointly developed by Axen-IFP and Italiana SPA, claims to be safe, simple andenvironmental friendly process. Spent oil is distilled in an atmospheric distillation followed bythermal deasphalting to primarily remove metals and metalloids followed by hydro finishing. Oilrecovery is the order of 75-95% depending upon the configuration of the process adopted.
The Phillips re-refining oil process (PROP) is an advanced oil re-refining two-step technology thatrestore the used oil to their original quality. The process combines unique and proprietary chemicaldemetalization with hydrotreating to produce high yields of high quality base oils. Process isapplicable to used oil feed stocks with wide variations in physical properties. Re-refined base oilproperties are comparable to virgin base oil quality, yielding viscosity index of the order of 102 to104, depending upon the used oil quality. The process claims to be compatible with the environment.Commercial PROP plants are currently in operation in Mexico and Canada.
Safety kleen process, Mohwak technology and DEA technology are the other three processes, whichare in commercial operation in U.S., Canada and Germany. Safety kleen process in early 90s had atotal operating capacity of 103 million US gallons per year in the American Tube re-refineries. Oflate this process is in conflict with some competitors. The Mo'hwak process begins with a thin filmvacuum distillation followed by the hydrogenation of distillate over a standard catalyst — with a lifeof 8-10 months. The process has been licensed for Ever green oil in USA and Canada. As per recentreports, Canadian assets of Mohwak Lubricants — the first commercial re-refinery built in 1983,that produces 500 bbl/day of re-refined oil is being acquired by Calgary base Newalta group, whichproposes to build additional lube re-refineries as well. DEA technology is the unique examplewherein distillates from vacuum thin film distillation are finally treated in a lube refinery solventextraction plant followed by hydro finishing. The base oil product claims to have lower PAH contentthan that of virgin solvent neutrals.
In general, commercially available 19 , generation used/waste lubricant re-refining technologies arebased upon conventional wiped film evaporation/distillation followed by hydrorefining and/or claytreatment. Currently, there are four principle barriers to re-refining waste/used lubricants usingthese general technologies, namely, (i) cost, (ii) complexity, (iii) physical plant size, and (iv)availability of feedstocks. These barriers tend to be interrelated. Specifically, the high capital andoperating cost and considerable complexity of these technologies require that large centralized
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processing facilities be built in an attempt to keep unit processing costs low. However, since thewaste lubricant feedstocks are generally dispersed throughout the country(ies) and other countries,the logistics and costs associated with the delivery of feedstocks to a centralized processing facilitythen becomes problematic. This "Catch 22" situation makes implementation of conventionaltechnology at scattered small scale waste oil recycling/collection facilities or other industrial sitesthroughout the US and in other countries impossible.
4.2 Environmentally benign 2nd generation (new) technological processes
In response to the above limitations / problems some new technologies have been developed in US,Canada and other nations that overcomes these barriers to deliver high quality base oils from used/waste lubricants at low cost. These processes employs proprietary concept to convert used/wasteoils into high quality lubricant basestocks. The processes offer many advantages over conventionaltechnology in terms of economy of scale and capital and operating cost. Additionally, finishedlubricant quality is comparable to that of virgin basestocks.
Three recently announced processes are described below for the details as available on the internet.The efforts to obtain detailed information from process developers are being pursued.
A literature scan under "used oil re-refining processes" indicated that at least three new re-refiningtechnologies have been announced in the recent past, which are either in commercial production orabout to reach that status. All the technologies are reported to be environmentally safe and arebased on new concepts with a view to meet the strict environmental regulations in respect of recyclingof used/waste lubricants. These are:
a. Media and Process (M&P) : Lubriclear Processb. Tiqsons Technologies Inc : Used Lube Oil Re-refiningc. Probex Technologies : ProTerra Process
Details of each of the above process are described separately.
a) M&P Lubriclear Process
Media and Process Technology, Inc. (on behalf of National Centre for Environment Research)office of R&D has developed and successfully demonstrated the Lubriclear Process to re-refinespent lubricants to high quality base stocks. Approximately 26,000 gallons of de-ashed or decolorizedlubricant basestock were produced for sale. In addition, five commercial units/systems of theLurbiclear process were sold and installed in the US and Canada for waste oil recycling. Some ofthese units have been operating satisfactorily for more than 20 months. One unit encountered somedifficulties, possibly due to the chemical pre-treatment used at this facility, which was later rectifiedand in parallel, M&P has converted its demonstration facility into a production plant.
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Salient Features
(i) Commercially Viable Products produced from the Lubriclear Process
• Four types of commercially viable recycled oil can be produced from the M&PLubriclear Process, ranging from a low ash (-0.1wt%) dark colored oil (Product I)for use in fuel applications to no ash light colored oil (Product IV) for use as arefined lubricant basestock. Ability to produce a range of products with the M&PLubriclear Process offers economic flexibility to adjust to fluctuations in marketneeds and price. All four products have been demonstrated in the production scaleof M&P's and/or their customers' facilities.
(ii) Field Demonstration and Production
Production runs conducted at the M&P demonstration facility confirmed the resultsof the previous laboratory study and above optimization results. About 14,000 gallonsof Product I were produced and sold as low grade lubricant basestock. In additionabout 12,000 gallon of Product III were produced as feedstock for the decolorizationtest. The product quality of both Product I and III in terms of ash content and heavymetal profiles was consistent with the laboratory results.
About 4,000 gallons of Product IV was produced using the full scale decolorizationprocess. The M&P full-scale facility adequately reproduced the results previouslygenerated from the laboratory. However, several process-related improvements wereneeded primarily in the area of the reactor design. A smaller scale unit, -75 gallon/day, was built based upon these recommendations. The unit delivered on-spec productand met the design capacity.
(iii) Process Economics
The process capital and operating costs, revenue projections and capital payback,and return on investment calculations were conducted based upon results obtainedin pilot and field level test programs. Case studies were examined for high and lowmarket prices fot each of the four oil products produced using the Lubriclear Process.For the production of finished re-refined lubricant from used mineral oils, operatingrevenues were estimated at $0.75MM to $1.1MM per year, depending upon the finalsale price, for a system producing 2.5MM gallons per year of re-refined oil. Capitalpayback was less than four months and estimated yearly return on the capitalinvestment was 45 to 65%.
• At an annual production rate of 5MM gallons per year, gross revenues for the finishedlubricant basestock increase from $1.1MM to $2.5MM per year yielding an increasein the yearly return on investment from 68 to 93%. The increment in the economicsis mostly due to the fact that the labor costs remain constant when the productioncapacity is increased from 2.5MM to 5MM gallons per year.
The return on investment can be higher for some of the lower value oil productsproduced using the Lubriclear Process. This anomaly occurs when the "spread"
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between virgin fuel and lubricant prices decreases. For instance, it is possible toachieve average yearly return on investments (ROI) of over 150% when fuel pricesare high. However, the market for the higher quality fuel products produced usingthe Lubriclear Process is relatively small, at least in the US, in comparison to themarket for the finished re-refined lubricant basestock. Hence, although ROI can behigher, overall revenues and profit potential is much more significant for the finishedlubricant basestock.
b) Tiqsons Technologies Inc : Used Lube Oil Re-refining
Founded in 1993, Tiqsons Technologies Inc., is a Canada base progressive company that "partnersequipment suppliers and technologies" to achieve the needed industrial technology and expertiserequired to setup plants overseas and to compete aggressively in today's global market.
The proprietary "lube oil re-refining process" is a procedure consisting of pre-treatment, water andlight hydrocarbons removal, fuel oil extraction, separation of lube oil by distillation, conversion oflube oil through hydrotreatment to base stock, followed by splitting of base stock into desired cutsusing fractionation.
Tiqsons and its partners have perfected this six-step process, as described below, over the years infully operational industrial sized plants, computer simulations, and in state of the art laboratoriesand research facilities.
Pre-Treatment
This procedure is proprietary to the process and critical for the trouble-free operation of the facility.Without this treatment, severe fouling, choking and corrosion of downstream equipment caused bythe breakdown of oil additives will occur making operation costly.
Water and Light Hydrocarbon Removal
This step involves flashing of pre-treated oil under near atmospheric conditions to remove waterand light hydrocarbons as overhead vapors. Tiqsons has considerable experience in the treatment ofhazardous and non-hazardous wastewater effluents from oil processing and other sources. Thecompany also provides technologies to treat oily water discharges from (plants and refineries) tomeet the effluent pre-treatment standards set by local authorities.
• Oil/water separation by settling or centrifugation
• Solids removal by filtration or centrifugation
• Volatiles removal by stripping
• Neutralization and pollutant conversion by chemical treatment
• Toxic organics removal by adsorption on activated carbon
157
Fuel Oil Fraction Removal
The incoming pre-treated and dewatered feedstock is distilled under moderate vacuum conditionsto extract the fuel fraction present. This fuel fraction can either be burned within the plant or sold.Separation of Lube Oil by Distillation
This step consists of separating the main lube oil components in the incoming dewatered and defueledfeedstock from the heavier hydrocarbons and heavy metal containing additives by evaporating itunder very high vacuum conditions in a wiped film evaporator. Bottoms from the evaporator leaveas an asphalt flux product. Lube oil distillate, as vapor, is condensed and sent to Hydro finishing forconversion to a neutral base stock.
Conversion of Lube by Hydro Treatment to Base Stocks
At this point, lube distillate is purified through contact with hydrogen at high pressure andtemperature. Under these conditions, removal of hetero-atoms (i.e. sulfur, nitrogen, oxygen, halogens,etc.), destruction of color bodies, and stabilization of the lube distillate yield a product meeting thespecifications of neutral base oils. Hydrotreating is the key to the production of high quality baseoils comparable to, or better than, virgin base oils.
Early operations of post treatment of the lube oil with the hydrogen process were marred by problemsof severe fouling, carbon deposition, and very short catalyst life. To remedy this situation a provenpretreatment technique developed and installed it at the plant. Upon installation drastic improvementsin performance were observed. This process solved major problems of fouling and carbon depositionbut did very little to enhance the life of the hydro treating catalyst. This translated into frequentshutdowns for catalyst change leading to low on-stream performance. Research in this area developedseveral important improvements to the re-refining process that specifically addressed improvedcatalyst life.
The facility includes two hydro finishers capable of operating at pressures high enough for white oilproduction. Tiqsons uses these hydro finishers to expand their information base and to conductresearch and development into new process improvements.
Splitting of Base Stock into Desired Cuts through Fractionation
Neutral base oil obtained by hydrofinishing is distilled under moderate vacuum conditions to produceproducts meeting the desired viscosity. A minimum of 95% of the lube content of the incomingused oil is recovered in two or three base oil product streams.
Tiqsons Technologies Inc claims to have received tremendous response and inquiries from all overthe world. The company can custom design small to large plants. Their list of clients includescountries in Middle-East, Egypt, South Africa, India, Pakistan and more.
158
c) Probex Technologies : ProTerra Process
Probex is a technology based renewable resource company that specializes in the production ofhigh quality automotive lubricating base oils and associated product from collected spent lubricatingoils. The company's patented, environmentally beneficial ProTerra Technology has demonstratedunparalleled advantages in the highly economic creation of high quality lubricating base oils capableof meeting new and evolving lubricating oils standards without creation of waste by-products. Thegoal of Probex is to become a world leader in the production of high quality lubricating base oilsand associated products from collected spent lubricants through timely commercialization of theProTerra Technology.
Technology
Since early in 1994, Probex Corporation has sought to find solutions to pressing needs facing thepetroleum industry. One of those needs is what to do with the 5.3 billion gallons of spent lubricatingoil generated by transportation vehicles and industry each year throughout the world. Probex hasworked for 5 years and invested over US $ 12 million in the development of proprietary technologyto recover the re-usable components from the spent lubricating oil. Probex Technology producesupgraded high quality lubricating base oils, a high quality light distillate and high grade asphaltfrom spent lubricating oils. The performance of ProTerra has been demonstrated to leading industryexperts in a fully instrumented pilot facility. Independent, highly reputable, third party laboratorieshave validated the quality of the products processed in the pilot plant.
Motor oils and industrial lubricating oils are made from base lube oil and a "package" of additives.The additives are tailored to enable the lubricating base oil to perform specific lubrication functions.In use, the additives are degraded or depleted but the lubricating base oil remains largely unaffected.The challenge to recovering the base oil is that the used oil fouls or gums-up most separationequipment. Until now, reprocessors have used equipment designed to resist fouling rather thanprovide effective separation. As a result, additional processing equipment and additional costs areneeded to remedy the shortcomings of the initial separation. In the end, and at best, reprocessinghas incurred high costs and only enabled restoration of the base oil components back to their originalcondition.
If it were possible to use the highly sophisticated and precise separation units engineered for chemicalprocessing, this separation could be made with great precision. Previous efforts to employ suchseparation units for used lubricating oil have been frustrated by the rapid fouling of the processequipment.
Probex has developed a proprietary technology, ProTerra, which eliminates used lubricating oil'spenchant to foul the process equipment. ProTerra recovers the original lubricating base oil containedin the used lubricating oil and enhances it beyond its original performance capabilities.
ProTerra is protected by two broad patents covering a total of 102 claims, and is also protected bypatents in Australia and New Zealand, and patents pending in other major countries throughout theworld and a number of trade secrets.
159
Probex's spent lubricating oil processing technology is a logical extension of conventional crudeoil refining techniques and equipment, employing a unique set of operating parameters togetherwith chemical additives. Their relatively straight forward technique adds a defouling stabilizer inthe fuel pretreatment stage. This virtually eliminates used lubricating oil's propensity to foul theprocess equipment. This is a tremendous advantage over conventional methods of processing usedlubricating oils.
Probex expects to provide high quality lubricating base oils meeting the standards for the newGF-3 motor oils and also expects to produce CL-4 compliant lubricating base oils for use in heavyduty diesel engines. These oils will enhance fuel economy, reduce emissions and pollution andprovide Probex customers with a valuable new source of high quality base oils.
Environmental Benefits
ProTerra process conserves natural resources by reusing oil that otherwise might be burned ordisposed of improperly. This works to reduce air, ground and water pollution and helps to reducethe amount of new crude oil that must be discovered, produced and refined. The process itself isenvironmentally friendly because there are no harmful waste streams and no waste by-products,other than water which can easily be treated for conventional disposal. Proactively, Probex is workingto support an industry that will provide proper and environmentally responsible disposal of usedlubricating oils.
The Products
ProTerra technology reprocesses used lubricating oil into three primary products :
ProLube Base Lubricating Oil: ProLube lubricating base oil is the primary product produced byProTerra process, suitable as a component for a variety of commercial automotive, heavy-dutydiesel engine and industrial applications. It is expected to account for approximately 68% of theyield from planned reprocessing facilities and has been seen as a source of a substantial portion offuture revenue.
ProPower Light Distillate Fuel Oil: ProTerra process also produces a light distillate that is usefulas a low-ash industrial fuel or refinery feed for the manufacture of gasoline. The light distillate andsecondary fuel products are expected to account for approximately 19% of the yield of the plannedreprocessing facilities.
ProBind Asphalt Flux: The final product produced by ProTerra process is ProBind asphalt flux,which will compete with other asphalt flux products. It is expected to account for approximately13% of the yield of the planned reprocessing facilities.
Probex has been working on the construction of first full scale reprocessing facility in the UnitedStates near Wellsville, Ohio with a planned capacity of 54 million gallons of used oil annually at a
160
cost of around 130 million US $. Arrangements of the supply of spent / used oil were being finalized.The plant is expected to go into operation during second half of 2003.
Current Statuso of Probex Technologies
Lube Report (Industry News from Lubes-N-Greases) by Tim Sullivan dated 31st Dec, 2002, vol. 2,issue 54 gives the latest status of Probex Technologies as follows :
Would-be used oil reprocessor Probex announced last week that it has entered ajoint ventureagreement to build a 120,000 metric-ton-per-year plant in France.
The announcement, included in a Dec. 26 filing with the U.S. Securities and Exchange Commission,puts two publicly identified projects on Probex's plate. The other is a plant in Wellsville, Ohio, thatwould process up to 183,000 metric tons of used oil per year
5.0 STATUS OF WASTE OIL RE-REFINING IN INDIA
As of now, in India there is no comprehensive and detailed policy or regulation specifically concerningwaste/used oil. In many of the small units handling oil, due to lack of awareness proper segregationor collection of waste oil does not take place. Some of the larger generators reclaim and re-use theirused oil. Many units auction their used oil to agents who buy it and sell it to various end users. Onlyfew of the industrial units send their used oil for reprocessing. Waste oil is also often use for heatgeneration purposes as well.
Re-refining of Used Oil
The used oil re-refining industry in India started in the 1960s, and at that time, the then prevalentused engine oil contained upto 90% oil that was basically untransformed from the original andcould be recovered by appropriate processes for re-use. During late 1990s (1998) there were about70-80 re-refiners in the country. Some of these have had good processing and quality control facilitiesand also registered with the Bureau of Indian Standards for quality certification. These units mostlyreprocessed the used oil using conventional acid and clay process based mostly on the followingindigenously developed reprocessing technologies:
a. Indian Institute of Petroleum (IIP) : Acid and clay
b. Regional Research Lab. (RRL) Jorhat : Clay contact-cum-distillation process
c. Balmer Lawrie Process : Thin film evaporation
d. IOC (R&D) Process : Non-acid treatment, flocculation process
e. NRDC License Process — Lube oil reclamation acid free Process
As per the available documents, total installed re-refining capacity in 1998 was of the order of170,000 MT/Yr with an average unit size of around 2500 MT/Yr. Indian re-refining industry peakedduring early 1990s touching 70,600 MT of re-refined oil in the year 1993-1994.
161
Beginning 1995-1996, the re-refining industry experienced difficulties because the units either couldnot get used oil for re-processing easily or there was not much market for the reprocessed oils, asbuyers were apprehensive regarding the quality of the reprocessed oil or they found it expensiveproposition with regard to procuring virgin oil. These factors adversely effected their smoothoperation. With the result as many as 60 small units were shut down, primarily due to non-availabilityof used oil. Another contributing reasons to this situation : the environmentally unfriendly nature ofacid-clay process — due to the generation of hazardous oily sludge which was often collected forburning in brick kilns or as fuel which caused emission of noxious gases.
It niay not be out of place to mention here, that in the case of automotive oils, the reprocessed oilwas / is often used (in our country) for packaging of spurious oil or as "duplicates" of branded oils.Such products are often sold to truck and 2 and 3 wheeler owners at cheaper rate. Use of suchimproperly re-refined oils in the automobiles could also increase the pollution load from vehicles.This is also one of the reasons which led to the present difficult state of the re-refining of used oilindustry in our country.
Improved Process Technologies
Considering the above situation and the fact that re-refining of used/waste oil is relevant to India,because it reduces the need for import of lube oil and conserve resources, there was need forappropriate technology development, along with proper systems for segregation and collection ofused oil within our country. Balmer Lawrie & Co. have worked hard and have come out with theenvironment friendly non-acid based used oil re-refining technology — the details of which arereproduced below as received from the company:
Basic Considerations
The process is based on the following basic considerations :
(a) Plant capacity
(b) Raw materials
(c) Product mix
(d) By-product
(e) Average feed compositionMoisture contentAcid value of used oilSpecific gravity
5000 Kl per annum used oil feed
Used lube oil, flocculent, clay, other chemicals.
Light fraction (fuel oil), gas oil, lube base stock.
Heavy residue
5%wt.1.5 mg KOH / gm max0.899 to 0.961
162
Saponifiable matter %wt. Max.Flash point (COC) >74°CYield (Typical) 62%
(f) Designed flow rate: Re-refining plant 8.5 KL/day
(g) Consumption & Yield Raw Material TPY Products Typical yield TPY
Used oil 5000 Re-refined oil 2462
Process description
Flocculent 75
Other chemicals 15
Clay (optional) 200
Gas oil 440
Lt fraction 90
Residual oil 1508
Spent material sludge 590
Used lubricating oils in general contain impurities such as worn out metal particles, used-up additives,water, dust etc. Contaminants during the passage of lubricant application, storage, transportation,handling makes it unsuitable for use. As a measure of conserving depleting energy resource, thisused oil needs to be properly treated to make it fit for reuse. Balmer Lawrie & Co. Ltd. has developedenvironment-friendly non-acid process for this purpose details of which follow. Typical processconditions and flow chart are shown in Figure 1.1 (Next Page).
Lube Oil Reclamation — Acid Free Process (Licensor NRDC)
Waste lube oil reclamation is an ideal technology for automotive lubricating oils, hydraulic oils,gear oils, engine oils, turbine oils, petroleum based oils containing additives, and petroleum basedoils containing synthetic oils.
Process Description
The free water is removed from the waste oil by settling. The oils is then passed through coarsefilter to remove any large solid lumps, present. Any free water present in the oil is removed bypassing through a series of special filters. The dehydration and removal of lighter ends is carried outin a thin film evaporator. The dehydrated oil thus obtained is subjected to treatment to removecarbon and other colouring matter. The treated oil is continuously filtered and distilled to get baseoil. The viscosities of the base oil can be changed by varying the temperature and vacuum.
163
Oil containing water as contaminant
Dehydratio
Lube Base Stock
Qil contaínine less particulates and water
USED OIL Sap value > 8 me KOH/e
Oil containing dirt, dust, metal, particulate, p^hydrationwater and other syn contaminants, Sapvalue <5 mg KAH/g
I Filter
Add Floccularitrlicnercrrl in wstrr
^ Add filter aid slurry
Transfer to FLOC. KETTLETemp: 100-200 CVac : 600 mm Hg
Flocculated oil
Vac distillation
Water & Ltfractions
YES
I Sludgeoil
Is colouracceptable?
NO
ClaytreJay t
Filtration
I Flocculated filter oil
Lubricating base stock
I Add treating agent I
Secondary treatment kettleTemp: 100-140°C
Vaccum : 400 mm HgWater I
Gas Oil DistillationTemp: upto 250°C
I Fuel OilVacuum : 5 x 10 1 torn
Base Oil DistillationTemp : upto 310°C
Vacuum :5 x 10 .2 torr I Lubricating Base Oil
I Residue
Figure 1.1 : Used re-refining by non-acid process (BL)
164
Comparison between Conventional Acid Treatment and High Vacuum Distillation Process
Parameter lConventional Processifigh Vac Distillation Processwith Acid Treatment
Average yield 160% Above 80%
Residue jAcid sludge difficult to Acid free, can be used for making iov;dispose off and causejgrade and greases or burnable briquettes.jpollution and corrosion
Feed containinglNot suitable Idealsynthetic oil
, id ¡Required Not required
hers/Earth._ .___ .... _Required____ ..
Required in small quantity
1 quality ¡Poor, normally only;Very good, viscosity of oil can!SAE 40 grade islselected as required.
Process (Batch Semi continuous or automaticManpower Intensive Only one skilled operator needed
automatic process
Capital cost (,Low Only 10-15% higher
Source: Hydrocarbon Asia, Oct 1977, p. 33
6.0 CONCLUSIONS
Used / Waste oil is once again regarded as a good hydrocarbon resource to recycle itslubrication or heat value, as is evident from the emergence of new environmentally safetechnologies and re-refining projects announced in Europe and North America.
• First generation environmentally safe technologies which emerged in early 70s have beencontinuously improved to keep pace with changing environment. However, there are atleast four principal barriers in their application.
Some new technologies (three) have emerged in the recent past employing proprietaryconcepts that yield high quality lubricant base stocks and claimed to be environmentallysafe.
New processes offer many advantages in terms of economy of scale, capital and operatingcost. Finished lubricant quality is comparable to that of virgin base stocks.
Status of used / waste oil refining in our country is yet to catch up with the worlddevelopments. Although there are two acid free processes available but quality of reprocessedbase oils needs to be lot more improved. We need to undertake serious R&D work on thissubject to deliver high quality base stock at low cost based on environmentally benignapproach.
165
ACKNOWLEDGEMENT
The author expresses his grateful thanks to Dr. B. SenSupta Member Secretary, Shri T. Venugopal,Director, and Shri R.N. Jindal, Sr Environmental Engineer of CPCB for asking me to prepare thisstatus paper and to Shri Suresh Kothari for his support in finalizing this paper.
Literature Consulted
1. Re-refining Schemes Compared: Norman. J, Weinstein, Hydrocarbon Processing, p 74-76, Dec 1994.
2. IFP Technology Symposium: Oil Refining & Petrochemicals Production (Chapter 8 — Re-refining for WasteLubricating Oil) 1982.
3. Proceedings Notional Seminar or Lubricants Conservation in India — 19th' Sept, 1986, PCRA, New Delhi,
4. Economics of Re-refining of Used Lubricants : David J. McKeagan et al., Lubrication Engg,, p 418-423, May1992.
5. Environmental Regulations and Technology — Managing Used Motor Oil. EPA Document : EPA/625/R-94/010, Dec 1994.
6. Hazardous Waste Management Guidelines for Waste Oil and Oil Emulsions. Report by National ProductivityCouncil, New Delhi, March 1998.
7. Draft report on "Study on Recyclinf, / Recovery of Waste / Used Oil — IIP Report No. PPAD.EL.694.98 — Aug1998.
8. RELUBOIL: Waste Lube Oil Re-refining Process — Snarnprogetti Milan Italy. Technology Brochure (ReceivedDec 2002).
9. PROP — An Innovation in Used Oil Re-refining (The Phillips Re-refined Oil Process) A report (Jan 2003)from Conoco Phillips — Bartlesville. OK. USA.
10. Revivoil : The Optimum Route to Lube Bases from Spent Oils : Process Brochure — Axens (IFP GroupTechnologies), Reuil Malmaison, France (Received Dec 2002).
11. ACS Preprints : Symposium "Worldwide Perspective on the Manufacture and Application of Lubricant BaseOils" — (San Francisco, CA, April 13-17, 1997), Vol. 42, No. 1, Feb 1997).
12. Details of BL Process Technology for Recycling of Used Oil — Document from Balmer Lawrie & Co. Ltd.,Kolkata, Jan 2003.
13. Lubricants and Lubrication (Chapter 8), Eds. TheoMang and Wilfried Dresel, Wiley, VCH, Germany, 2001,
14. Information from Internet using the following web sites which have relevant details on Used/Waste Oil Re-refining and Recycling.
• www.probex.com • www.atdr.cdc.gov
• www.tiqsons.com • www.dot.stat.tx.us
• www.ciwmb.ca.gov/usedoil 9 www.age.psu.edu
• www.ped.vianet.ca • www.dept.state.pa ,us
15. Lube Oil Reclamation — Acid Free Process (Licensor NRDC), Hydrocarbon Asia, Oct 1977, p. 33
166
DYES AND DYE INTERMEDIATES SECTOR:CLEANER TECHNOLOGICAL OPTION
by
DR. H. G. JOGLEKARSCIENTIST
NATIONAL CHEMICAL LABORATORYHOMI BABA ROAD, PUNE
email : [email protected] : 020-5893355
DYES AND DYE INTERMEDIATES INDUSTRY
Manufacturers in Organized sector = 50Manufacturers in Small scale sector = 900
Thousand TPA Dyes DyeIntermediates
Total Installed Capacity 123 300
Yearly Production 93 250
Exports
L_ ______
53 120
169
Growth of Dyes Sector
1986-87 2002-03
Capacity 47,000 TPA 123,000 TPA
Production 30,000 TPA 90,000 TPA
Exports Rs. 100 Cr. Rs. 8000 Cr.
Capacity, Production and Exports of Dyes and Dye Intermediates
Class of dyes Production
capacityStatew!se capacity TPA
Gujarat Maharashtra Punjab Rajasthan Tamil Nadu A.P W,B Bihar Orissa MPReactive dyes 35.0 31.6 2.5 0,2 0.1 0.1 0.3 0.0 0.0 0,0 0.0Acid dyes 25.0 21.9 2.6 0.5 0.0 0.0 0.0 0.0 0.0 0,0 0.0Pi gents 20.0 16.4 2.7 0.0 0,0 0.6 0.0 0.3 0.0 0.0 0.0Disperse dyes 15.0 6.8 6.1 2,1 0.0 0.0 0.0 0.0 0.0 0,0 0,0Vat d s 4.0 3.3 0.7 0.0 0.0 0.0 0,0 0,0 0.0 0,0 0.0Metal com lex 2.0 1.7 0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.01 rain dyes 2.0 0.7 1.0 0.0 0.0 0.0 0A 0.0 0.0 033 0.0Oil soluble d es 2.0 1.4 0.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0Food colours 2.0 0.8 12 0,0 0,0 0.0 0.0 0.0 0.0 0.0 0.00therd es 16.0 0.0 15.3 0.1 0.1 0.2 0.0 0.0 0.0 0.0 0.1
Total 123.0 84.9 33.0 3.0 0.3 0.8 0.3 0.3 0.0 0.3 0.1
170
Class of
Dye intermediatesProduction
capacityStatewise capacity TPA
Gujarat Maharashtra Punjab Rajasthan Tamil Nadu A.P W.B Bihar Orissa M.PViri1 sul hone 32.0 26.9 3.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.3H-acid 20.0 13.6 5.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.8Gamma acid 10.0 8.4 1.6 0.0 0.0 0.0 0.0 OA 0.0 0.0 0.0Tobias acid 5.0 5.0 OA 0.0 0.0 0.0 0.0 0.0 0.0 0,0Metanilic acid derivatives 5.0 5.0 0.0 0.0 0,0 0.0 0.0 0.0 0.0 0.0 0.0B naphthols 3.0 1.7 1.1 0.0 0.0 01 0.0 0.0 0.1 0.0 0.0Resorcinol 2.0 1.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0Derivatives of
anthra uinone2.0 2.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
J. acid 2.0 0.9 0.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2Otherintermediates 219.0 74.1 143.9 0.0 0.0 0.3 0.0 0.0 0.3 0.0 0.3
Total 300.0 138.6 158.0 0.0 0.0 0.4 0.0 0.0 0.4 0.0 2.6
All figures in thousand tonnes per anum.
Statewise Number of Dyes & Dye Intermediate Manufacturers
Name of State
Number of dyes manufacturersAcid dyes Disperse
Dyes
Food dyes Ingrain
dyes
Pigment
dyes
Reactive
dyes
Oil Soluble
dyes
Vat dyes Metal
Complex
dyes
Other dyes
1. Gujarat 119 10 2 2 60 493 13 33 26 0
2. Maharashtra 14 9 3 3 10 38 5 7 4 3443 Punjab 3 3 0 0 0 4 0 0 0 3
4 Rajasthan 0 0 0 0 0 2 0 0 0 3
5. Tamil Nadu 0 0 0 0 2 4 0 0 0 5
6. Andtra Pradesh 0 0 0 0 0 1 0 0 0 17. West Bengd
8. Orissa
0 0
0 0
0
0
0
1
1
0
0 0
0 0
0
0
0
0
1
0
9 Madhya Pradesh 0 0 0 0 0 0 0 0 0 2
Total 136 22 5 6 73 542 18 40 30 359
Name of State
Number of dye intermediate manufacturesTobias
acid
Gamma
acid
H. Acid J. Acid Naphtols Vinyl
Sulphone
Resorcinol Metanllic
acid &
derivatives
Derivatives
of
anthraquinone
Other
intermediates
1. Gujarat 8 16 17 5 20 21 2 12 8 221
2 Maharashtra 0 3 7 5 14 3 2 0 0 429
3 Tamil Nadu 0 0 0 0 1 0 0 0 0 1
4. Bihar 0 0 0 0 1 0 0 0 0 15. Madhya Pradesh 0 0 1 1 0 1 0 0 0 1
Total 8 19 25 11 36 25 4 12 8 653
171
Projected Production, Indigenous Consumption and Export of Dyes and Dye Intermediates
Sector Projection for 2005-2006
Consumption Export Production
Dyes 52 68 120
Dyeintermediates
166 153 319
Areas of Concernfor
Dyes and dye intermediates sector
1. Age-old inefficient processes
2. Obsolete machinery
3. Smaller scale of operation
4. Environmental impact
5. Competition from China
172
Gaseous emissions
sox
NOX
HCIHalogensH2SOrganic vapoursCOX
H 2OEntrained liquidsSPM
Liquid Effluents
High COD
High TDS
Colour
Heavy metals
Non biodegradable organic chemicals
173
Solid Wastes
Inorganic SaltsGypsum
Iron sludgeUsed filter aidSpent carbon
(all of the above contaminated with organic impurities)
Distillation residue
Effluent treatment sludgeAsh
Four Rs for Waste
Reduce the waste.
Reuse raw materials going in the waste.
Recover useful products from the waste.
Get Rid of the waste.
174
Raw materialsReduce
Product Recover
Byproducts Recover
Effluents ♦ Treatment ♦SafeDisposal
Reduce
Reduce
1. Increase the efficiency and thereby reduce rawmaterial inputs, resulting into reduction in waste.
How to increase efficiency :
1. Process optimization2. Input optimization3. Use of catalyst4. Process control and monitoring
Contd....
175
Reduce
2. Replace hazardous raw material wherever possible.
3. Replace inefficient present process by efficientprocess route.
4. Reduce utility consumption by energy conservationand thereby reduce emission from utility plants.
Re-use
1. Recover excess of raw materials / solvents / catalystto the maximum extent.
2. Purify recovered materials to remove hinderingimpurities.
3. Recycle.
176
Recover
1. Maximize product recovery to minimize effluentsby : * Better Extraction/
Crystallization/Filtration/Drying* Minimizing entrainment* Minimizing dust carry over.
2. Maximize byproduct recovery to minimize effluentsby: * Better Distillation
* ScrubbingExtractionFiltration.
3. Upgrade the byproducts quality.4. Recover useful products from waste.5. Find uses for the waste.
Get Rid of
1. Improve treatment to remove hazardous substances.
2. Safe disposal of treated effluentsolid waste.
177
Specific examples
Sulphonation :
1. Use SO3 in place of oleum.
2. Maximize required isomer.
3. Remove / recover So x
4. Recover H 2SO4 of desired qualityand reuse.
Nitration
* Optimize quantities of acids.
* Maximize desired isomer.
* Optimize process conditions.
* Remove / Recover NOR, SOX .
178
Hydrogenation:
1. Replace iron-acid hydrogenation by catalytichydrogenation and thereby eliminate Iron sludge,
2. Explore possibility of manufacturing pigmentsfrom iron sludge,
Halogenation :
1. Stagewise halogenation to improve efficiency.
2. Recover acids / halogens.
3. Process optimization.
179
Derivatives of anthraquinone
1. Replace mercury catalyst by safer catalysts.
Metal Complexes:
1. Ensure removal of heavy metals from liquid effluent.
2. Recover aluminium hydroxide of pharma grade.
180
Reactive dyes
1. Replace salting out process by spray dryingand eliminate liquid effluent.
Disperse dyes
1. Develop better catalysts to maximize selectivityof the process.
181
Vat dyes:
Dark Blue BO
1, Replace naphthalene by better and safer solventsuch as ethyl cellusolve as a reaction medium.
Pigments:
1. Improvement in filtration and washing.
2. Efficient dust collection system to minimize productloss to atmosphere.
182
TREATMENT OF WASTES:
Gaseous ---
1. Separation of entrained liquid from reactors.2. Separation of dust from dryers, pulverizers.3. Condensation of organic vapours.4. Adsorption of uncondensed organics.5. Scrubbing of HCI by multiple scrubbers to get
conc. HCI from ist scrubber.6. Scrubbing of lean HCI, C1 2 with alkali.7. Recovery of NaSH, Na2SO3 by scrubbing H 2S, SO2
by NaOH.8. Treatment of scrubber solution.9. Incineration of toxic gases.
TREATMENT OF WASTES:
Liquid --
1. Segregation of effluent streams and recyclingwherever possible.
2. Recovery of sodium sulphate from aqueous effluent3. Recovery / Reuse of H2SO4.4. Removal of non-biodegradable sulphonic acids by
extraction.5. Removal of heavy metals by precipitation.6. Biodegradation of biodegradable impurities.7. Removal of colour by adsorption / oxidation /
bleaching .
183
TREATMENT OF WASTES :
1. Recovery of salts such as sodium sulphite,sodium sulphate.
2. Effective washing of gypsum sludge and usein cement manufacture.
3. Recovery of mercury, naphthalene from theirsludges.
4. Manufacturing of pigment from iron sludge5. Regeneration of spent carbon.6. Incineration of organic residues.7. Secured landfilling of ash, ETP sludge.
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CLLAN TECHNOLOGY OPTIONS FOIR 11 - ACil) NIANUFAC'r RE.
184
H-acid Effluent Treatment
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1. Innovation
2. Technological support
3. Commitment to cleaner environment
185
Notes
186
WASTE MINIMIZATION IN LEATHER INDUSTRY— CASE STUDIES
By
Dr. S. RajamaniDIRECTOR GRADE SCIENTIST
DEPARTMENT OF ENVIRONMENTAL TECHNOLOGY
CENTRAL LEATHER RESEARCH INSTITUTEADYAR, CHENNAI — 600 020, INDIA
E-mail : [email protected]
Waste Minimization In Leather Industry — Case StudiesDr. S. Rajamani*
ABSTRACT
The tanning Industry is one of the oldest and fastest growing industries in South and South EastAsia. There are more than 3000 tanneries located in India with a total processing capacity of700,000 tons of hides and skins per year. The waste water discharge from these tanneries is about100,000 cubic metres per day. More than 90% tanneries are in small and medium scale sector withprocessing capacities of less than 2-3 tons of hides/skins per day. They follow traditional practices,mostly unorganised and unplanned on environmental pollutional control aspects. Hides and skinsare preserved by drying, salting, or chilling, so that raw hides and skins reach leather tanneries in anacceptable condition. The use of environmentally persistent toxics for preservation of raw hidesand skins is to be avoided. In the tanning process, hides and skins are treated to remove hair andnonstrutured proteins and fats, leaving an essentially pure collagen matrix. The hides are thenpreserved by impregnation with tanning agents. Leather production usually involves three distinctphases: preparation (in the beamhouse); tanning (in the tanyard); and finishing, including dyeingand surface treatment. A wide range of processes and chemicals, including chrome salts, is used inthe tanning and finishing processes. The tanning and finishing process generally consists of soakingand washing to remove salt, restore the moisture content of the hides, and remove any. foreignmaterial such as dirt and manure. Liming is done to open up th collagen structure by removinginterstitial material. Fleshing is done to remove excess tissue from the interior of the hide. Dehairingor dewooling is done to remove hair or wool by mecanical or chemical means. Deliming, batingand pickling are carried out to delime the skins and condition the hides to receive the tanningagents. Tanning is carried out to stabalize the hide material and impart basic properties to the hides.Retanning, dyeing, and fat-liqoring is done to impart special properties to the leather, increasepenetration of tanning solution, replenish oils in the hides, and impart colour to the leather. Finishingis done to attain final product quality.
The leather industry uses a wide variety of chemicals and auxiliaries in large quantities. The chemicalsused during the process are discharged into the environment in the form of waste from the industry.This increases cost of chemicals and the high pollutional load caused by them in the effluent treatmentplant. The leather processing industry is a water intensive industry. The quantity of water consumeddepends on the amount of leather processed and type of processes adopted. About 40 m 3 of water isused for processing of 1 ton of wet salted raw hides and skins to finished leather. The consumptionof water and chemicals can be considerably reduced in the process by adopting waste minimisationtechniques including recovery and reuse methods.
KEY NORDS : Trennerv. Neuste Mininitsation, cleaner processing methods, chrome recovery and reuse, recycling.
* Author is a Director Grade Scientist with the Dept. of Environmental Technology, The Central Leather ResearchInstitute, Adyar, Chennai — 600 020
189
1. WASTE MINIMIZATION IN RAW MATERIAL PRESENTATION
In conventional presentation practices about 50 — 80% of common salt is applied on raw hide /skinweight basis. About 4,00,000 lakh tonnes of salt is used in Indian tanneries.
1.1 Treatment of fresh or cooled hides and skins
The practice of processing raw hides and skins is feasible where organised slaughter houses exist invicinity. Whenever possible, treatment of fresh hides and skins is the best solution to reduce saltpollution. Time elapsing between slaughtering and further treatment (e.g. beamhouse processing)must not exceed a few hours. Beyond this period, it is necessary to cool the hides and skins, eitherin ice or cold air. Cold air is interesting if hides are transported over long distance. Storage below4°C yields good preservation up to three weeks. This system can be used only when the capacity ofthe slaughter house is equivalent to that of the tannery. It would be desirable to practise fleshing andtr11111111ng in the slaughter house.
1.2 Drying and Dry Salting
Shade drying of small skins is a low cost environmentally acceptable process in some climate.Controlled air-drying using heat pump or other system is suitable for any climate. Dry salting canminimise the amount of salt used for preservation of skins and hides.
-1.3 Use of Antiseptics
The use of antiseptics with low effect on the environment can help to increase storage time of freshor chilled hides and skins. Suitable preservatives include: TCMTB, Isothiazolone products, potassiumdimethyl dithiocarbamate, sodium chlorite, benzalkonium chloride, sodium fluoride and boric acid.Some of these are also appropriate for soaking, pickle and wet-blue preservation.
1.4 Mechanical and manual desalting
It is possible by using hand shaking, mechanical brushes or drum type shaker to eliminate up to 10% of the salt added to hides and skins for preservation. The salt can be reused after dissolution andremoval of solids for pickle processes. This method gives a partial answer to the salt pollutionproblem. Neither brine curing nor salt curing can be considered as cleaner technologies, even if pre-fleshing in slaughter house on green hides gives an easier valorisation to this specific waste.
2. BEAMHOUSE PROCESSING
The new drums and processors facilitate efficient draining and washing, and allow the routine useof low floats for processing, thereby resulting in significant savings in water consumption.
2.1 Soaking
Apart frone the use of less harmful antiseptics, the only cleaner technology that could be applied atthis stage is the fleshing of green hides after soaking. It yields a lower quantity, compared to lime
190
fleshings, with a neutral pH, and better conditions for transformation into proteins and fats that arenot contaminated with chemicals.
2.2 Classical unhairing-liming process
The enzyme assisted unhairing of hides and skins can be considered as a cleaner technology only ifthe amount of sodium sulphide is reduced substantially. However it is not yet possible to use lessthan I % of sodium sulphide for bovine hides. Compared to a classical "hair-dissolving" process,30 to 50 % of COD reduction, in beamhouse effluent, can result from enzymatic or another hairsaving treatment.
2.3 Hair saving unhairing-liming methods
For traditional skin production, painting and sweating may be considered the cleaner technologies.Recovery of hair before dissolution, either when it is separated during the liming, or at the end of ahair saving process, can lead to a COD reduction of 15 to 20 % for the mixed tannery effluent, anda total nitrogen decrease of 25 to 30 %. It is an advantage to filter off the loosened hair as soon aspossible and higher COD and nitrogen reduction can be obtained. This process can be considered asa cleaner technology if the hair is utilised, even as a nitrogen source.
2.4 The direct recycling of liming float
Direct recycling can be applied when there is a good control level in the tannery. Resulting advantagesare savings in sodium sulphide (up to 40 %) and in lime (up to 50 %). It could give a decrease of 30to 40 % of the COD and 35 % of the nitrogen for the mixed effluent. The quality of the leatherproduced might be affected negatively through this recycling process, unless unhairing and openingup processes are used in two steps. The quality of the scudding can be improved during the subsequentphases of leather processing. This cleaner technology is industrialised in several large bovine tanneriesfor shoe upper leather.
2.5 Splitting limed hides
Faced with the difficulties of upgrading the chromium-tanned split waste, splitting on the lime canbe considered as a cleaner technology as it saves chromium and yields waste that can be easilyrecovered for the production of gelatine.
2.6 CO 2 deliming
It is considered that up to 40 % of ammonia nitrogen is produced by the use of ammonium saltsduring the deliming process. The use of CO 2 can be considered as a cleaner technology giving goodresults on light bovine pelts (thickness lower than 3 mm). For thicker hides, it is necessary to increasefloat temperature (up to 35°C) and/or process duration and/or to add small amounts of delimingauxiliaries. Hydrogen peroxide can be used before CO 2 insertion, in order to reduce the creation ofH2S (preferably under redox control). If the pH of CO 2 deliming float is lower compared to commonprocedure, special bates can be used. Also, bates with a lower content of ammonium are available.
191
3. TANNING OPERATIONS
Chromium tanning salts are used today in 85 % of tanning processes. Only the trivalent form isused for tanning operations and this chemical cannot be replaced by another, except for specificarticles, to give the same quality of leather. If its concentration in waste exceeds a certain levelimposed by national regulations, it strongly limits any possibility of utilising, or disposing thewaste at acceptable costs.
3.1 Low salt in pickling floats
When tanning and pickling floats are separated, the recycling of pickling floats can economise upto 80 % salt and 20 to 25 % of either formic or sulphuric acid. When they are associated, the greatereconomy can be made on the sulphuric acid. For wool-on sheepskins, recycling of pickling andeventually bating floats, using long floats over 150 %, is a current practice, which gives goodresults. It is generally associated with chromium float recycling. Salt concentrations in picklingfloats can also be reduced by using non-swelling agents.
3.2 Degreasing operations
Solvent degreasing is still in use. This practice can lead to a cleaner technology when the solvent isrecovered, the extraction brines are recycled, and the natural grease is commercialised. Dischargeof solvents is unavoidable with solvent degreasing. Solvent degreasing is still in use but alternativescan be applied for the highest quality skin production.
On wool-on lambskins, it is a common practice to undertake a dry solvent extraction when crusted.The use of non-solvent methods implies the use of higher amounts of surfactants. Ethoxylated fattyalcohols should be recommended instead of the more widely used ethoxylated alkylphenols, giventhat they are more easily degraded. Nevertheless the effluents obtained by this method should equallybe treated, given that its COD level may amount as much as 200,000 ppm, due to the content ofnatural grease and surfactants (1 g/l of natural grease is about 2,900 ppm COD, and 1 g/l ethoxylatedalkylphenol is about 2,300 ppm COD). Proteolitic enzymes can assist for degreasing pigskins andthis reduces the amount of surfactant required.
3.3 Wet-white production
This process, giving the possibility to produce untanned and upgraded sheetings and shavings canbe considered as a cleaner technology when the chemicals used are not suspected of toxicity.Aluminium, titanium, zirconium are not listed as hazardous, although restricted in several countries.Modified aldehydes tanning agents can be considered as leading to a cleaner process, according tolocal regulations.
3.4 Chrome recovery and reuse
About 80% of the Indian tanneries adopt chrome-tanning process. In chrome tanning, the leathertakes only 60% of the chromium applied in the form of Basic Chromium Sulfate (BCS) and the
192
balance is discharged as a waste in the effluent. As per 1998 estimate 45,000 tonnes of chromiumsalt is used and out of this 18,000 tonnes of chromium salt are discharged into wastewater streams.These discharges cause environmental pollution, waste of chemicals and complicate effluenttreatment and sludge disposal system operations.
Chrome recovery and reuse system developed and adopted in other countries, cannot be totallyreplicated in India without modifications due to the small capacity and traditional nature of thetanning process applied, characteristics of the effluent, technical manpower capabilities in tanneries,local environmental conditions, capital investment, etc. Therefore, it has become necessary tointroduce and demonstrate an appropriate technology to recover and reuse the chromium. In principle,chrome recovery and reuse can be realised in three different ways: direct reuse, indirect reuse andseparating chromium compounds.
3.4.1 Direct reuse method
This method implies that spent liquors are reused directly as much as possible as a tanning liquorfor the next batch. Additional chromium is supplied to compensate the deficiency. The mainconstraint in adopting this method is that the salts and other impurities are accumulated due torepeated reuse and will have negative effects on the leather quality.
3.4.2 Indirect reuse method
This method implies that chromium is recovered by precipitation as hydroxide using alkali, whichis dissolved subsequently in sulphuric acid after which the solution can be used as a tanning liquor.The advantage of this method is a more efficient use of chromium and a cleaner reusable solution,which normally does not affect the leather quality.
3.4.3 Separating chromium compounds
In principle by this method recovery of chromium can be achieved by separating the chromiumcompounds from other salts in the waste liquors. In this method the chrome liquor may be cleanerthan by the direct reuse method, but this system requires rather sophisticated techniques such aselectrodialysis, membrane separation, ion exchange, etc. and has limited scope for implementationin tanneries. It was therefore considered to adopt a simple indirect chromium recovery and reusesystem using a suitable alkali. Such a system is technically and economically feasible in Indian andother South East Asian tanneries.
All types of alkalies such as sodium hydroxide, sodium carbonate, bicarbonate, lime, etc. are usefulfor chromium precipitation. Most of these alkalies are cheap. The highly reactive alkalies give avoluminous chromium sludge (i.e. more than 25% by volume), which makes it necessary to separatethe sludge from the liquor by a filter press. Some alkalies like sodium hydroxide make it necessaryto heat the liquor in order to obtain complete chromium precipitation. Using lime causes asimultaneous precipitation of chromium and calcium sulfate (plaster of Paris), which makes thereuse of the chromium difficult.
193
Two indirect reuse methods were considered: one with sodium alkalies which need the use of filterpresses and the other with magnesium oxide (MgO) which, because of its low reactivity and solubility,causes chromium to settle compactly, so that separation from the liquor is merely a question ofdecant of the supernatant. Dissolving of the sludge can be done instantly with sufficient sulphuricacid to obtain a reusable liquor. Using MgO, as alkali is considered more appropriate for small aswell as large sized tanneries because of flexibility in design, simplicity in operation and lowinvestment costs.
3.5 Direct recycling of chromium tanning floats
This method is applied in an individual tannery under strict control; it gives the possibility to stronglylimit the presence of chromium in the effluents arising from tanning. Savings can be obtained fromthe process, by a reduction of 20 % of the chromium used in a conventional tannery process, and upto 50 % for wool-on sheepskins, and substantial reduction in the amount of salt used. Excesschromium containing liquor should be precipitated and recycled.
3.6 Chromium free tanning
In most cases, chromium tanning should be considered as the best available technology. Manyalternative formulations have been proposed but the results obtained at the moment are not completelysatisfying for all type of leather. Synthetic organic tanning agents, alone or in combination with ametallic cation can be considered as a substitute for chromium, provided that environmental andworkers health regulations are complied with. Tanning with organic tanning agents can producemineral free leather, but such leathers do not have the same characteristics as chromium tannedleather.
Vegetable tanning with a dry drum process, or in vats, in closed circuit, can minimise waste andmust be included in these considerations. Due to the high pollution load and slow biodegradabilityconventional vegetable tanning cannot be considered more environmentally friendly than chrometanning and vegetable tanned leather has limited application. Recovery of vegetable tanning floatsby ultrafiltration is used in several European tanneries and the recovered tannins may be used in thetanning process. Vegetable plus aluminium tanning can produce chrome free leather.
4. POST-TANNING OPERATIONS
When the use of chromium is required for retanning operations, the same consideration should begiven as for chrome tanning. Absence of chromium during retanning, of environmentally riskydyestuffs and benzidine in dyes, of halogenated oils in fatliquors, are essential arguments in acleaner process. High level of exhaustion for syntans, dyes and fatliquors are also to be considered.In some cases, through feed dyeing with adapted dyes can be considered a cleaner technology.
5. FINISHING OPERATIONS
The use of water-based finishes is fundamental for a cleaner process. Pigments must not contain
194
any environmentally risky heavy metal or other restricted products. Water based formulations(containing low quantities of solvent) are available for spray dyeing. Finishing products have tomeet the current limits imposed by environmental and workers health regulations. The equipmentused is extensive. Roller coating or curtain coating machines are far more satisfying from theenvironmental point of view, but they cannot be used for all type of leather. For other types, sprayingunits with economisers and High Volume Low Pressure (HVLP) spray guns can reduce dischargesto the environment.
6. RECYCLING
Recycling means a second utilisation for the same purpose, reuse means an utilisation for differentpurposes and recovery incorporates an isolation step. Recovered material can then be recycled orreused.
Recycling technologies have been used for long time in both liming and vegetable tanning processand it can be said that the oldest technologies were using float recycling. Environmental concernsare a source of innovative action for recycling. If the main adapted step for recycling remainstanning operations, it is also possible to use recycling in beamhouse process. Simple recyclingtechnologies need some control to prevent any deviation in the tannery process. A laboratory withbasic analytical equipment is desirable.
6.1 Beamhouse process
To reduce the volume of saline effluents, particularly in the case when the segregated float needs tobe evaporated or specifically processed, it is possible to reuse the third soaking float for the firstsoaking operation. It requires collecting the third float before storage and reusing. This decreasesthe amount of water to be evaporated, when salinity is restricted, and reduces the presence ofbiocidesin effluent.
The unhairing-liming float can also be reused for the next process. It must be taken into accountthat the recovery rate of the liming float should not exceed 75 % in order to limit the nitrogenconcentration. Besides recycling materials (pumps, fine screening, storáge tanks), it is sometimesnecessary to warm the float before reuse and also to screen or skim it in order to eliminate undesirablefloating solids and to remove hair and grease from the surface. Without any sedimentation, anindustrial recycling process can save 35 to 40 % of sodium sulphide and 40 to 45 % of the lime(with classical process quantities of 2.5 %). Excessive quantities of lime should be avoided duringthe process. The only negative aspect of this recycling can be the lower scud elimination obtainedafter inadequate removal of salt during soaking. This can be adjusted further in the process.
6.2 Tanning process
When sheepskins process needs solvent degreasing, recycling of the residual solvent after distillationis currently operated. Furthermore, the extraction brine is also easy to reuse for saving of sodiumchloride. Recycling of pickling float has been proven to be highly satisfactory in terms of salt
195
savings and partly for acid savings. There is no great difficulty if density and acidity of the float canbe regularly controlled. Many possibilities exist for tanning floats. The most common practice is tocarefully collect the tanning residual float, to filter it, to adjust its acidity, and to reuse it as a newtanning float before adding fresh chromium salts. Depending of the basification process, the recoveredvolume needs perhaps to be adjusted.
Another possibility is to use the tanning float for a pretanning process. In this case, 60 % of theresidual chromium can be recovered. When pickling and tanning are carried out in the same float,it is also possible to collect the residual tanning float, to filter and acidify it and reuse it as a picklingfloat. Some high exhaustion chrome systems have the additional benefit of reducing chrome releasein subsequent operations.
6.3 Post-tanning process
It is much more risky to recycle post tanning floats as the influence of electrolytic conditions ismuch more important. Then it cannot be recommended any recycling technology in this step of theleather process.
7. WATER MANAGEMENT
Around 20-40 m3 of water is used for processing of 1 tonne of wet-salted raw hides and skins.Measurement and control of consumption are an important and essential point of the watermanagement. In many countries water has become a scarce commodity and the costs for theconsumption and discharge of water increases regularly. Water has to be managed properly andseveral options are available to minimise the overall consumption of water.
Reduction : The first step is the reduction of water consumption with strict measurement andcontrol of consumption. Low float processing, batch-type washing instead of rinsingand combining processes (compact recipes) are practical examples of technologies toreduce water consumption by 30% or more. Lower volume of water will result in ahigher pollutants concentration.
Recycling : Certain specific processes are suitable for recycling of floats, although in most casesinstallations for treatment are necessary. Examples are; soaking, liming, unhairing,pickling and chrome tanning liquors, which can reduce the overall water consumptionby 20-40%.
Re-use: Biologically treated effluent offers the opportunity of replacing a certain amount ofthe process floats such as, the beamhouse process floats, with treated water. Dependingon the type and efficiency of the treatment process additional operations might benecessary, such as filtration and disinfection, to meet the required water qualitystandards. Membrane systems give the possibility to reuse treated effluents providedthat most of the residual organic matter is removed previously and solution for disposalof the concentrate.
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197
CONCLUSION
Implementation of waste minimisation methods continuously reducing pollution and environmentalimpact through source reduction i.e. eliminating waste within the process rather than at the end-of-pipe treatment. Besides reducing pollution, it also improves the process efficiency, which leads toreduction in production cost. Implementation of waste minimisation helps to meet regulatorystandards.
REFERENCE
1. ILII TCS - IUE Commission Meeting Proceedings, Cape Town (South Africa), 6 March 2001.
S. Ra.jamani, Jakov Bullan, UNIDO (1996), "Technology Package - A system fór recovery and reuse of chromiumfrom spent tanning liquor using magnesium oxide and sulphuric acid" -TECHPACK/ UNIDO/RePO/1.
198
CLEAN TECHNOLOGY OPTIONS IN DYESAND DYE INTERMEDIATES INDUSTRY
By
Dr. H. G. JOGLEKARSr. SCIENTIST
NATIONAL CHEMICAL LABORATORYHOMI BABA ROAD, PUKE - 411 008
Email : [email protected]. No. : 020-5893300 extn. : 2420, Telefax : 020-5893359
Clean Technology Options in Dyes And Dye Intermediates Industry
Dr. H. G. Joglekar*
PREAMBLE
Dyes and dye intermediates industry represents the highest development of chemical technologyand forms an important link in the chain of other essential chemical industries. On one handpetrochemical industry and inorganic chemical industry act as upstream raw material supplierindustries, and on the other, textile, leather, plastic, paint, fine chemicals and pharmaceutical industriesact as the downstream consumer industries. The technology employed in dyes and dye intermediatesindustry covers almost all unit processes and unit operations of chemical synthesis. It generateslarge quantities of hazardous effluents.
Indian dyes and dye intermediates industry has exhibited substantial growth, particularly in the last15 years. In this span of 15 years, the production tonnage has increased 3 times, whereas the exportvalue in Rupees has increased 79 times. At present, export of dyes and dye intermediates is 50% ofthe total export of chemicals from India. The dyes and dye intermediates are being exported todeveloped countries also from India, as developed countries find it economical to import theseproducts from third world countries rather than manufacturing them under the environmentalregulations, which have become more and more stringent. However, enough attention was not paidby dyes and dye intermediates industry in India, towards environment. Letting out the effluentswithout sufficient treatment created disasters in areas where dyes and dye intermediates industrieswere concentrated. A number of dyes and dye intermediates manufacturing units had to be closeddown by judiciary and state pollution control boards, which were not meeting the standards. Moreoverthere is a stiff competition, in the world market, particularly from China and prices are notremunerative.
A remarkable feature of the Indian dyestuff industry is the co-existence of units in the small, mediumand large sectors, actively involved in the manufacture and export of dyes and dye-intermediates tothe far corners of the world. Presently there are about 950 units manufacturing dye and dyeintermediates in India. Of these, about 50 fall in the organized sector and the rest largely compriseof small-scale units, which cannot afford to have sophisticated effluent treatment facilities.
The need of the time for Indian manufacturers is to look for options, which will be cost effective.
2.0 AREAS OF CONCERN
Following are the main areas of concern for dyes and dye intermediates industry.
(i) Most of the processes followed by the industries for the various categories of dyestuffsand intermediates are based on the original German processes (IG, Bayer) or the ICI
* Author is working as Senior Scientist with the National Chemical Laboratory, Homi Baba Road, Pune-411008
201
processes with very little change. The processes are no more competitive.
(ii) Generally, the processes are conducted in a batch-wise manner. The processparameters such as pH and temperatures are controlled manually with manual additionof the required amount of reagents/intermediates. Process controls are not accurate.
(iii) Many of the plants are working with old and obsolete machinery. This leads toleakages and inefficiency.
(iv) The same plant is used for manufacturing different dyes. This generates substantialwash water at the time of changeover from one product to another.
(v) Manufacture of dyes and dye intermediates generates variety of solids, gaseous andliquid wastes.
Solid wastes are in the form of inorganic salts, such as sodium sulphate, sodium sulphite and gypsum;iron sludge from iron-acid hydrogenation; used filter aid and spent carbon from carbon treatment.All those wastes retain liquid with toxic organic chemicals. Solvents when recovered by distillationgenerate distillation residue which needs to be incinerated and incineration ash is generated. Liquideffluent treatment plant generates chemical and biological sludge containing inorganic salts andheavy metals.
Gaseous emissions from dyes and dye intermediates industry are SO,, NO S, HCI, HBr, HI, C1 2 , Br2 ,
H2S, CO, CO2 , water vapour and uncondensed organic vapours. Liquid droplets are carried awayby gases along with them if not properly arrested. Air coming out from pulverizers and dryers carryfine product dust.
Large volumes of liquid effluents are generated in the manufacture of dyes and dye intermediates.These liquid effluents usually have very high chemical oxygen demand, high total dissolved solidsand colour. Heavy metals and non biodegradable organic chemicals such as sulphonic acids arepresent in the liquid effluents of many dyes and dye intermediates.
3.0 STRATEGY FOR WASTE MINIMIZATIONClean technology options can be developed for the manufacture of dyes and dye intermediates andtreatment of effluents in the following manner.
3.1 Reduce
Increasing the efficiency of the process results in increase in the yield of the product. This reducesthe generation of side products and the quantity of unconverted raw materials and ultimately reducesthe waste. This can be achieved by optimization of process parameters, optimization of the inputsof raw materials and monitoring and control of process parameters. Use of catalyst increases theconversion of raw materials to desired product. Inefficient processes need to be replaced by moreefficient processes. Replacement of hazardous raw materials by non-hazardous raw materials, reducesthe hazardous materials in the waste. Energy conservation reduces the requirements of utilities suchas steam and electricity. This in turn, reduces the gases left in air while generating steam and electricity.
202
3.2 Reuse
It is necessary to recover the unconverted raw materials, solvents and catalyst to the maximumextent so as to avoid their going in the waste. Recovered raw materials are to be purified if necessaryto make them reusable in the process and are to be recycled.
3.3 Recover
Maximizing the recovery of the product reduces their loss in the waste. Similarly all the byproductsneed to be recovered to the maximum extent to minimize generation of waste. Byproducts need tobe purified to the desired quality so that they can be sold. If applications are developed for thebyproducts, they can be utilized and waste can be minimized. Possibility needs to be explored ofrecovering useful products from the waste. Recoveries can be improved by improving the respectiverecovery operation such as extraction, crystallization, filtration, drying, scrubbing and distillation.Product or byproduct loss in entrainment, carryover or spillage needs to be minimized.
3.4 Disposal
The waste generated after adopting the above three steps for its minimization, needs to be treated toremove hazardous substances or to convert them into non-hazardous substances. The treated wastemust be disposed of safely.
4.0 SPECIFIC CLEAN TECHNOLOGY OPTIONS IN UNIT PROCESSES EMPLOYEDIN DYES AND DYE INTERMEDIATES INDUSTRY
Following are the specific options for common unit processes employed in dyes and dye intermediatesmanufacture.
4.1 Sulphonation
Sulphonation is generally carried out by using oleum. Excess of oleum, consumes the water moleculegenerated in the reaction to form sulphuric acid and thereby avoids presence of water which affectsthe sulphonation. However, this process leaves large quantity of sulphuric acid at the end. This canbe avoided by use of sulphur trioxide in place of oleum. When sulphonation is carried out by usingoleum, the possibility of recovering and reusing sulphuric acid needs to be explored. Sulphuric acidis to be freed of undesired impurities before reuse. Oxides of sulphur liberated in sulphonation mayalso be recovered. Sulphonation reaction may generate a number of isomers. Maximizing the desiredisomer by process optimization will minimize generation of other isomers and generation of waste.
4.2 Nitration
Nitration uses mixture of sulphuric acid and nitric acid. The quantities of acid need to be optimizedto minimize the waste. Oxides of sulphur and nitrogen evolved maybe recovered. Process conditionsare to be optimized to get maximum yield of desired isomer.
203
4.3 Hydrogenation
Hydrogenation carried out by iron acid hydrogenation generates large quantity of iron sludge aswaste. It is contaminated with organic impurities and difficult to dispose of. Iron sludge can betotally eliminated by employing catalytic hydrogenation which is clean and efficient. Alternativelypossibility of recovering pigment from iron sludge may be explored.
4.4 Halogenation
Efficiency of halogenation can be improved by introducing halogen at a number of stages. This willreduce the quantity of unconverted halogens going out of the reactor. Unconverted halogens andacids generated in the process need to be recovered to the maximum possible extent.
4.5 Acetylation
Use of acetic anhydride for acetylation generates acetic acid which goes in the waste. Replacementof acetic anhydride by acetic acid will eliminate this waste.
4.6 Cyanation
Large excess of sodium cuprous cyanide is used for cyanation, which needs to be detoxified.Optimization of quality of sodium cuprous cyanide will reduce the load on detoxification andgeneration of waste.
4.7 Air Oxidation
Proper selection of catalyst and process optimization will improve the yield. Entrainment separatorsmay be provided on air outlet to arrest carryover of liquid droplets.
5.0 SPECIFIC CLEAN TECHNOLOGY OPTIONS FOR VARIOUS CLASSES OF DYESAND DYE INTERMEDIATES
Following are the specific options for the manufacture of various classes of dyes and dyeintermediates.
5.1 Reactive Dyes
Salting out of reactive dyes results in generation of large quantity of liquid effluent with organic andinorganic impurities. Liquid effluent can be totally eliminated by adopting spray drying. Propersequencing of unit processes such as cyanuration, diazotization, coupling and condensation canincrease the yield and purity and thereby reduce the waste.
5.2 Disperse Dyes
Better catalyst can improve the yield of disperse dyes and reduce the waste.
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5.3 Vat Dyes
Naphthalene is used as a medium in the manufacture number of vat dyes and it finds its way ingaseous and solid wastes. Replacement of naphthalene by safer solvent such as ethyl cellulosolvecan eliminate hazardous naphthalene going in the waste.
5.4 Pigments
Pigments require very large volumes of wash water. Better filtration equipment can reduce thequantity of wash water and thereby the liquid waste and improve the product purity. Carryover ofproduct dust alongwith air going out from dryers and pulverizers can be minimized by providingefficient dust collectors.
5.5 Metal Complexes
Heavy metals used for complexing, find their way in liquid effluent and need to be removed effectivelyfrom the liquid effluent.
5.6 Derivatives of Anthraquinone
Possibility needs to be explored of replacing hazardous mercury catalyst by safer catalyst such aszeolites, clays and other metal oxides.
6.0 TREATMENT OF WASTES FROM DYES AND DYE INTERMEDIATE INDUSTRY
Following are the clean approaches for the treatment and disposal of wastes from dyes and dyeintermediates industry.
6.1 Gaseous Emissions
Carryover of liquid droplets along with the gases coming out of reactors and carryover of productdust along with the air coming out from dryers and pulverizers must be arrested by using entrainmentseparators and efficient dust collectors. Uncondensed vapours going out with gases must be condensedby condensers of sufficient heat transfer area and coolents of lower temperatures such as chilledbrine. Uncondensed organic vapours may be adsorbed by suitable adsorbents.
Hydrochloric acid gas needs to be scrubbed in multiple scrubbers. The first scrubber can be operateduntil 30% hydrochloric acid solution is obtained which can be sold. The second scrubber can beoperated with fresh water to remove traces of hydrochloric acid effectively. Dilute hydrochloricacid obtained from the second scrubber can be used in the first scrubber. Complete removal ofhydrochloric acid can be ensured by alkali scrubbing in the third scrubber.
NaSH and Na2SO3 may be removed by scrubbing H 2S and SO2 vapours by caustic soda solution.Waste scrubber solutions must be sent to liquid effluent treatment plant. Toxic gases must beincinerated. Incinerator gases must be scrubbed and scrubber solution must again be sent to liquideffluent treatment plant. Possibility of recovering heat from hot gases emissions needs to be explored.
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6.2 Liquid Effluents
Different liquid streams must be segregated se that streams with least contamination can be recycledin the process and toxic streams can be detoxified. Separate treatments can be given to separatestreams as needed. Possibility of recovery of sulphuric acid from spent acid needs to be explored.Inorganic salts in liquid effluent such as sodium sulphate maybe recovered and purified so that theycan be sold.
Non-biodegradable organics such as sulphonic acids may be extracted using extractants such aslong chain tertiary amines. Possibility of recovering useful products need to be explored. Metalscan be precipitated out in liquid effluent treatment plants. Biodegradable impurities are degeneratedby biological treatment. Colour may be removed by adsorption, bleaching or oxidation. Quality oftreated effluents has to meet the standards before their disposal.
6.3 Solid Waste
Effective washing of solid wastes such as gypsum will result in maximum removal of retainedimpurities. Gypsum can be used in cement manufacture. Recovery of sodium sulphate of desiredquality can fetch good price for the same. Pigments can be manufactured from iron sludge. Possibilityof regeneration of spent carbon may be explored. Mercury and naphthalene need to be recoveredfrom their respective sludges. Distillation residues have to be incinerated. Secured land-filling oftreated solid waste, ETP sludge and ash has to be ensured.
7.0 CLEAN TECHNOLOGY OPTIONS IN H-ACID
7.1 H-Acid Manufacture
Various clean technology options in the manufacture of H-acid dye intermediate are showcased inFigure 1 (Pls see Next Page). Following are the clean technology options in H-acid manufacture.
(i) Sulphonation by sulphur trioxide, reduces sulphuric acid waste.
(ii) Direct use of sulphonated mass or spent acid for H-acid isolation eliminates generation ofgypsum sludge.
(iii) Catalytic hydrogenation eliminates generation of iron sludge.
(iv) Improved alkali fusion using solvent, improves the yield.
(v) Iron sludge generated in iron-acid reduction, can be utilized for manufacture of pigment.
7.2 Liquid Effluent Treatment
Following are the clean technology options in the treatment of liquid effluent of H-acid as showcasedin Figure-2 (Pis see Next Page).
(i) Sulphonic acid impurities in liquid effluent can be extracted by extractant. This removes thenon-biodegradable impurities from the effluent.
206
Napthalene i
ORAcids S03
Conventional IAcids Improved
Sulphonation Solvent I SulphonationNitration
tLe., Nitration
Ir
ORLime
Neutralisation &
ORNO ^ Salt
Isolation offiltration Scrubber
Nitromass
Gypsumfor sale
OR
Conventional ICatalyst CatalyticReduction H2 HydrogenationF'It t'y OR ira ion
Iron sludge J I I
fordisposal Pigments
fromIron Sludge sr OR
SaltPigment forWater
Sale Concentration Vapour
ORCaustic Conventional Solventlye 1.0. Alkali Fusion NaOH
ImprovedAlkali Fusion
ORH - Acid I HaSOIsolationusingNitromassFiltration, Drying
H - AcidIsolationFiltrationDrying
Mother liquorto ETP
OR
H - AcidIsolation
using spent acidFiltration, Drying
Mother liquorto ETP H-acid
Product
Fig. 1: Clean Technology Options For II - Acid Manufacture
acid Isolation
i Mother liquorZ, to ETP
Spent acidPurification
Concentration
207
(ii) Re-extraction gives the sulphonic acids in concentrated form from which useful intermediatesfor dyes can be recovered.
(iii) Sodium sulphate of better quality can be recovered from the effluent.
Acidicliquid effluent
Lime 1 ORAir Neutralisation
Desuldging Extraction
ETPNaOHSludge soin. •
ConcentrationNeutralisation
H O ConcentrationVap.
Na SO Na SOfor sale
Reextraction w Recycle
HO
IncinerationOr
Recovery
Incineration Biodegradation
Treated Effluent
Fig. 2 : H-acid Effluent Treatment Options
8.0 CONCLUSION
There are a number of clean technology options which need to be exploited by dyes and dyeintermediates industry in India, for better environment.
Author gratefully acknowledges the support given by the Central Pollution Control Board bysponsoring the work on status study of H-acid and identification and characterization of hazardouswaste streams and waste reduction options in dyes and dye intermediates sector.
National Chemical Laboratory has successfully developed the process of catalytic hydrogenationfor H-acid manufacture.
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CLEANER TECHNOLOGIESIN
PULP AND PAPER INDUSTRY
by
Dr. N. J. RAOPROFESSOR
INDIAN INSTITUTE OF TECHNOLOGY, ROORKEE(DEPARTMENT OF PAPER TECHNOLOGY, SAHARANPUR)
Tel. : 01322-727062; Fax : 01322-727354E-mail : [email protected]
Cleaner Technologies In Pulp And Paper IndustryProf (Dr.)N.J.Rao*
INDIAN PAPER INDUSTRY
v Start of organized sector in 1832
• Today's production over 5.26 MTPA through over 500 mills
v Many small mills are sick/closed.
• There is wide diversity in terms of size, age, raw material mix, products and technologylevel.
•• India imports 5 lakh tonnes NP, and 1-lakh tonnes of other paper. The growth of Indianindustry expected around 7 % while global growths are around 2.4%.
THE CHALLENGES
v It is an intensive industry - capital, raw material, water, energy, manpower and pollutionintensive.
• The performance of the industry is far from satisfactory. Global competition has puteven more pressures.
v Environmental performance needs quantum jump. The pressures on industry onenvironmental front are enormous.
• The recent charter on corporate responsibility on environmental protection (CREP) haslaid targets for environmental performance'in next few years. This include among otherthings - AOX limit of I kg/t, wastewater discharge of 100 m3/t, use of ODL, reductionof color, control of odor, etc.
•:• The industry will strive for E-E-E. Excellence in economy, efficiency and environment.
•:• The emphasis is on cleaner production to ensure better compliance to regulation, lowercosts and fact global challenge.
CLEANER PRODUCTION TECHNOLOGIES
v It is economically driven environmentally sound route through application of bestavailable technology.
v The three main cleaner production technologies includeSource reductionRecyclingProduct modification
* Author is working as Professor with Indian Institute of Technology, Roorkee
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v Good house keeping and process parameter optimization is first two steps to sourcereduction.
v Technology up gradation includes process control, changes in input materials, equipmentmodification and technology change.
CLEANER PRODUCTION
v It is an approach to better environmental performance, increased production efficiencywith economic benefits.
v Often in economic analysis, the true economic value of environmental benefits (ordamages), particularly intangibles are poorly reflected. Environmental economics is notwell appreciated resulting in improper economic evaluation of cleaner productiontechnology options.
v Newer technology options evaluation must include the costs (intangibles included) tofind economic benefits.
CLEANER PRODUCTION INDICATORS
• The indicators are tools for assessing the potential of a CP option.
• The indicator include:
Process technology (sets limits on performance)
➢ Process efficiency (fiber loss, yield, washing, recovery efficiency, etc.)
➢ Specific consumption of inputs (raw materials, energy, water, etc.)
➢ Degree of system closure (for water, condensate, chemicals)
➢ Degree of sustainability (ecological foot prints, green house gas emissions,rain water harvesting, biofuel / renewable fuel use, energy self sufficiency).
➢ Specific pollution load generation (COD, TS, AOX, VOC, SS, DS, Colour,odorous gases emissions, solid waste generation, etc).
Economic benefits including environmental advantages (RIO, payback)
➢ Aesthetics and good will.
KRAFT MILL
A Kraft Pulp Mill can be mainly divided into four main parts:
RAW MATERIAL HANDLING
v Chemical defibration with almost completely
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v Closed chemical and energy recovery.
v Bleaching with open water system.
• Extended wastewater treatment (with papermaking).
RAW MATERIAL PREPARATION AND HANDLING
v Use of renewable raw materials: renewable wood (plantation), agro residues and wastepaper.
•:• Proper dry debarking/chipping and use of bark and chip dust.
v Proper pith removal (dry/moist/wet depthing) and use of pith.
v Proper cleaning of agro residues (Disc Mills).
•:• There several new generation wood chippers which are energy efficient, give uniformchips with minimum fines/pins, high length/thickness ratio (like Camura, Carthagechipper)
v Great care is essential in storage and transport of raw materials, particularly agro residuesto avoid deterioration and loss.
v Good raw material/ chip cleaning is essential to control ingress of NPE (particularlySilica, K, Cl), use of recycled water (— 10 m 3/t) is recommended.
v Need to go in for good material handling systems/practices to reduce handling losses to1-2% level.
COOKING
•:• Alkali pulping (Kraft /soda) is popular.
v For wood, Kraft pulping in batch digesters with hot blow is popular. This results in highthermal energy demand, higher emissions and relatively higher chemical consumptionand lower yield.
• Better option is to go for RDH/Super batch cooking with extended delignification, betteralkali profile, better selectivity, higher yield, cold blow, lesser energy demand and noemissions (700 / 800 kg steam/ton pulp).
v Better control is essential in digester operation to ensure proper h Factor.
v Conventional batch cooking with hot blow has to adopt techniques to reduce emissions(blow heat recovery, stripping of NCG's, incineration).
• Direct steaming digesters need to be phased out. Continuous digesters need to replacethem for agro residues.
v For conventional cooking use of chemicals for better selectivity are needed (e.g.polysulphide).
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WASHING AND SCREENING
v The main purpose of washing and cleaning process is to give clean pulp with least carryover of BL and Shives using minimum dilution. The emission from this section includesdischarges from screens and black liquor if not processed.
v Washing results are influenced by type of pulp and washing equipments.
v Integrated washing and screening (closed screening with refining/recooking) is necessaryto reduce screen room discharges. Great care is essential to reduce discharges fromconventional rotary vacuum washers (leakage, spills, foam, vacuum/level, over loading,hoods).
v Non wood pulps, which are slow draining & need careful design/selection of equipmentfor reduced environmental discharges.
v In digester washing must be proper in continuous digesters to ensure lower environmentalimpacts.
v Wash plants should never be used as a buffer between cooking and bleaching department.
v New generation screen rooms (like Delta combi screens) for better separation of knotsand fines are needed. Tail screens can remove Shives. Modem concept is to use highconsistency (3-4%) pressure screens.
WASTEWATER FROM WOOD HANDLING
From wood handling Effluent volume COD kg/rn3 of Total P, g/m3
m3/m3 wood wood wood
Wet debarking & Press 0.6-2 4-6 5-7(30% dryness)
Dry debarking and press 0.1-0.5 0.2-2 4-7 (30% dryness)
v Bark effluents are toxic.
• Condensates from cooking and evaporator, Volume 8 — 10m 3/t, COD 20-30 kg/t, BOD7 — 10 kg/t.
v Foul condensates include methanol/ethanol, TRS, turpentine, ketones, phenolics, resin/fatty acids, N are high in hardwood.
v Strong condensates (1m 3/t) can be steam stripped and gases are incinerated.v Weak condensates (7-8 m3 /t), 0.5 —2 kg COD/ m3 , free of metal, can be directly used in
washing.
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SPILLS
v Spills occur from digestion plant, screen room, wash plant, evaporation plant, tanks.They must be collected.
• Leakages occur from pumps, right seals and proper maintenance can reduce this.
• Conductivity measurements and fiber content of wastewater must be benchmarked andchecked.
• Spill account for 10 kg/t of COD.
• Black liquor residues (washing losses) in unbleached pulp
➢ Press washing at last stage can reduce amount of water going with pulp from 6-10 m3/t to 2 —3 m3 /t. The values should be benchmarked as cod pulp. (Typically7 — 12 kg/t hardwood pulp).
v Bleach plant discharge
➢ This is main point of polluting discharge to wastewater.
➢ Partial closing the mill reduce the pollution load.
➢ Typical values can be decreased from 60— lOO m 3/t pulp to 20-40 m3/t with 25— 50% reduction in COD load.
➢ Entry pulp kappa number, use of oxygen delignification, wash loss, use of ECFbleaching, bleaching sequence, influence the pollution load from bleachingsection.
FOR OXYGEN DELIGNIFIED HARDWOOD KRAFT
v The entry Kappa number to bleach plant can be reduced from 18 — 20 for conventionalcook to 16 for modified cook to 10 for modified oxygen cook.
• AOX release:
➢ Use of elemental chlorine and Hypochlorite result in high AOX release (almost0.1 kg AOX/kg elemental C12 and 0.05 kg AOX/kg Hypo as a active chlorine).
➢ Chlorinated phenolics degrade very slowly and their values (Penta and Tri) shouldbe less than 1 g/t pulp.
➢ Full/ partial elimination of C1 2 and hypo by chlorine dioxide reduces AOX release.This with oxygen delignification can substantially reduce AOX levels.
➢ Enzyme prebleaching (Xylanase) can reduce bleach consumption by 10 — 20%.
➢ AOX generation in conventional cook with CEHH type sequence for HW is 5 —8 kg/t. this can be reduced to 2 kg by ECF, less than 1 kg by oxygen/ECF, lessthan 0.5 kg by modified cook / oxygen/ ECF. Use of enzymes will further reduceAOX.
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DISCHARGES FROM PULP MILLParameter Before treatment
Unbleached Bleached
After treatment
Unbleached BleachedFLOW, m /t 20-80 30-110 20-80 30-110
BOD, kg/t - - 1-20 0.2-40
COD, kg/t 31 - 105 - 7-50 4-90
AOX, kg/t - - 0-2
TSS, kg/t - - 0.2— 15 0.2 — 10
Total N, kg/t 0.2-0.4 0.3-0.5 0.1-1 0.1-0.8
Total P, kg/t 10 - 40 40-60 3 -40 5 - 90
Metals g/t (Cd,Pb, Cu Ni, Zn)
6.5 18.1 - -
Effluent After Treatment
Reduction in Aerated Lagoon Activated Sludge Process
BOD% 40-85 85-98
COD% 30-60 40-70
AOX %, 20-45 40-65
P% 0-15 40-85
N% 0 20-50
Emission :
Parameter Recovery Boiler LimekilnSO 2 kg/t(Without scrubber)(With scrubber)
I — 4 +
(0.2 -- 0.5) ++0.1 — 0.4
0.003 — 0.002*
(0.1 — 0.6) **-
H-,S <0.05 <0.03
NO y (as NO2) 0.6-1.8 0.2-0.3
SS (after ESP) 0.1 — 1.8 0.01(0.1 —0.4)'
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Parameter Recovery Boiler Limekiln
H 2S < 0.05 < 0.03
NO \ (as NO 2 ) 0.6-1.8 0.2-0.3
SS (after ESP) 0.1 -1.8 0.01 -0.1'
(0.1 -- 0.4)AA
63 - 65 BLS ** Oil firing with NCG
" 72 - 80% BLS firing A With ESP
Oil firing without NGC AA With Scrubber
CHLORINE COMPOUNDS FROM BLEACH PLANT (CO2)
Swedish Permit Limit = 0.2 kg Act.Cl /tonne pulp monthly
Average Total Emissions after Treatment (CEH)
Total Sr (kg/t) = 0.04 - 0.4
NO S (kg/t) = 0.85 - 2.6
Particulate (kg/t) = 0.25 - 3
SOLID WASTE GENERATION
v Dregs and Lime mud v Dust from boilers
v Bark and wood residues v Rejects (Sand)
• ETP Sludge (Inorganic, Fibre, Biological sludge)
•'• Ashes
Biological and chemical sludge have poor dewatering properties.
Mixed sludge has better dewatering property.
Sludge should be dewatered to 40 - 50% dryness if energy production has to bepositive.
+ Kg dry solid waste generated/t of pulp.
ETP sludge 10Wood Ash 9Other ashes 14Nip waste & Coating 5Wood waste 6
Total 44
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(Typically 20 — 60 kg organic, 30 — 60 kg inorganic for unbleached) & (30-60 kg organic & 40— 70 kg inorganic for bleached)
CHEMICALS USED FOR HARDWOOD PULP
MgSO4 0 — 2 kg/t Strength preservative in ODL
02 12-15 kg/t in ODL
NaOH 12 — 15 kg/t
EDTA/ DTPA 0-4 kg/t to remove metal ions in peroxide bleaching
TECHNIQUES FOR CLEANER PRODUCTION
• Dry debarking of wood.
• Rapid Displacement Heating (RDH) and Super batch cooking, a pretreatment with BLis done to reduce heat demand, maintain high initial sulphide concentration and decreaseEA charge. The kappa number is reduced to 14 — 16 for HW against 18 — 22 forconventional cooking. (1 kappa _ 0.15 % lignin in pulp)
• Extended delignification/ modified cooking results in less heat demand in cooking, loweremission (gaseous and wastewater) reduced bleach chemical demand, marginal increasein BLS.
v Closed screening of BSW is a reality the knots / sieve level in modern cooking is lessthan 0.5%. Countercurrent approach with washing (integrated washing and screening)can reduce organic discharges to wastewater.
•• New generation washing equipments (like DD washers, wash press, horizontal washer)is a common practice in washer. This gives high discharge consistency, reduces organiccarryover, reduces bleach chemical demand and increases BLS to recovery.
OXYGEN DELIGNIFICATION
v Oxygen delignification in one or two stages at high (25 — 30%) or medium (10 — 15%)consistency with oxygen alkali; MgSO 4 can result in nearly 40 — 45% reduction in inletkappa to bleaching.
• This results in increased evaporation load (-45 — 50 kg/t for HW).
• Major environmental advantage includes decrease in bleach chemical consumption,reduced pollution load and AOX from bleaching (ECF).
• Oxygen delignified pulp has lower pulp viscosity than conventional pulp, but there is nosignificant difference in burst factor, tear factor and breaking length.
ENZYME PREBLEACHING
• Enzyme prebleaching with or without oxygen delignification results in reduced bleachchemical demand (10 — 20%) with lower AOX loads.
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ECF BLEACHING
• The ECF bleaching sequence for Hardwood include D (E 0 )D(E)D, D(E0)D(E)D,D(E0 )DD,D(E0)DD, QOPZP.
• Chlorine and hypo are eliminated to improve environmental situation of bleach plants.Initially partially chlorine replacement (as C/D or D/C) and full Hypo replacement aretried in Indian mills to reduce AOX generation in bleach plant.
v Dioxide bleaching is carried out at 10% consistency, 60°C, for 30 minutes at pH of 3.5
• Alkaline extraction reinforced with O and P (EOP) is done around 12% consistency, 60- 70°C, for 60 minutes. Alkali, oxygen and peroxide changes are 10 — 20, 3 — 6 and 2 —4 kg/t.
v Peroxide can be applied at several positions (in extraction, for final brightness adjustment,separate delignification/ bleaching.
• These bleaching changes eliminate 2378 TCDD and 2378 TCDF formation to non-detectable limits. Chloroform generation is decreased; chlorinated organics generationlevel is decreased to 0.2 — 1.0 kg AOX/t before ETP.
• The Hexauronic acid is produced during Kraft pulping of HW contributes to higherKappa number and brightness reversion. This can be removed by acidic conditions inbleaching (pH — 2) and high temperature in bleaching or by ozone bleaching.
BLEACH PLANT CLOSURE
• Partial / full closing of bleach plant mill result in reduced wastewater discharges. Thiscan be done countercurrently with ODL and BSW.
• This will be associated with accumulation of DS affecting plant operation, besides needingpH adjustments. There could be possibility of Ca-oxalate precipitation, increased builtup lime chlorides may enhance corrosion of equipment.
• The current levels of bleach plant discharges at lower level are 25 — 40 m 3 /t which canbe reduced to 20 — 25 m3/t volume
• The COD discharge can be reduced to 10 m 3/t and 30 kg COD with better closure.
• Generally first acid stage filtrate with highest Ca is purged to contain mill operations.
SPILL COLLECTION
v Greater Inplant measures reduce discharges, Pulping liquors lost from BSW, pumps,valves, from knotters and screens, sewered evaporator boil out solutions.
• Spilled liquors should be collected at highest possible concentration and returned toappropriate locations.
• Adequate buffer tank capacity can reduce spills.
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• Monitoring conductivity and pH can detect losses.
v A single line Kraft mill can have 5 collection sumps.
• Evaporator plant should have 5 — 10% extra capacity to deal with sump liquors.
SECONDARY BIOLOGICAL TREATMENT — AEROBIC METHODS
• Aerated lagoons and ASP are most common.
v Aerated lagoons — residence 3 — 20 days (15 — 20 days preferred), low solids concentration100 — 300 mg/l mechanical aeration, needs large area, no biomass recirculation, sludgeremoval is seldom done (once in I — 10 years).
• Aerated lagoon removal efficiency is for BOD 40 — 85%, COD 30 — 60%, AOX 20 --45%, total P 6 — 15%, N — nil.
v Aerated lagoons are less common due to removal efficiency.
v ASP has 2 units, aeration basin and secondary clarifier, high concentration ofmicroorganisms, 15 — 48 hours retention time, mechanical aeration.
• Removal efficiency in ASP is for BOD 85 — 98%, COD 60 — 85%, AOX 40-65%, P 40-- 85%, N 20 — 25 %, TSS 85 -- 90%.
TERTIARY TREATMENT WITH CHEMICAL PRECIPITATION
•• Chemicals used Al — salts, ferric -- ferrous salts, lime, polyelectrolytes.
v Reduces nutrients P 80 — 90%, N 30 — 60%, COD 80 — 90 %, AOX80 - 90%.
v Colour removal is possible with Al, Fe and Lime.
INCREASING DRY SOLIDS CONTENT OF BL
• Conventional evaporation gives 65% DS.
v Super concentrator, forced circulation evaporator can give 80% DS 72 — 73% should beminimum DS levels:
v The viscosity increase of BL can be handled by higher temperature and pressure.
• Hardwood BL will be difficult to concentrate beyond 72%. Great care is needed in rawmaterial/ chip washing, cleaning evaporator bodies.
•:• One can look at desilication of BL and thermal treatment of BL.
v At high DS firing, may lead to S - compounds release from evaporator (better ESPoperation, collection and incineration) but SO X release from furnace is reduced.
v At high solids NO X release will increase.
v There is 4 — 7 % increase in boiler heat capacity.
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INSTALLATION OF SCRUBBER IN RECOVERY BOILER TO REDUCE SO 2 EMISSIONS
v Collection of weak gases for incineration in recovery boiler (NCG combustion).
• Collection and incineration of odorous (weak and strong) gases in limekiln.
v Dedicated incinerated for NCG followed by scrubbing.
v Use of over fire technique (OFA) on recovery boilers (tertiary/ quaternary air) to reduceNO formation.
• Introduction of improved washing of lime mud to reduce residual white liquor contentfrom 100 mg/dm 3 to 0— 30 mg/dm3 , increase lime mud dryness from 50— 60 % to 70 —80%, thus reduces TRS emission from kiln.
v Installation of limekiln if not present (improve silica management in mill).
v Remove DCE if present for lowering TRS emissions.
• Use ESP after limekiln to reduce dust emissions.
• Improve over all mill control through better automation.
EMERGING TECHNIQUES
v Gasification of Black Liquor
➢ Chemrec Process
➢ Integrated gasification with combined cycle (IGCC)
➢ This is available commercially
➢ Advantages include greater power with overall increased energy efficiency and loweremissions.
v Use of SNCR on recovery boiler - Selective non-catalytic reduction (SNCR) to cutdown on NOX emissions.
➢ Available commercially, 30% reduction in NO
v Removal of chelating agents by modest alkaline biological treatment or by use of kidneys.
➢ EDTA / DTPA are used as chelating agents in TCF (peroxide) bleaching, leading toincreased amounts of these materials in effluent. The difficulties are that thesematerials remobilize toxic heavy metals and are difficult to biodegrade.
➢ Normal ASP does not degrade these materials.
➢ New process of ASP under alkaline condition (pH 8-9) reduces EDTA by 50% inwastewater.
➢ Kemira-Net Floe Kidney recovers EDTA with metals.
➢ These processes are available on full scale and provide EDTA control in effluents.
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RCF PLANTS
• Specific water consumption
Process Water consumption m3/t
Uncoated folding Box board 2 — 10
Coated folding Box Board 7 — 15
Corrugating Medium & Packaging Paper 1.5 — 10
Newsprint 10 — 20
Tissue 5-100
Writing & Printing paper 7 - 20
ADDITIVES USE — PRODUCT AIDS
• Fillers — Kaolin, Clay, Talc, Lime, Gypsum, Ti0 2
• Sizing Agents — Modified starch, resins, Wax emulsion, AKD, Maleic anhydride,copolymer — may be toxic to bacteria.
• Fixing agents — Alum — mostly cationic maybe toxic to bacteria.
v Dry strength agents — modified starches — some maybe toxic when cationic.
v Wet strength agents — UF, MF, Epichlorohydrine condensate — toxic, increases AOX.
• Dyes — Azo components — some are toxic
v Optical Brightness — Diaminostilbene, cationic and disulfonic acid may be used.
v Coating Chemicals — Pigments, binders, defoaming agents, slimicides and disturbsclarification
ADDITIVES USE — Process Aids
v Retention Aids — Alum, PolyAl.chloride, polyacrylamide etc; mostly cationic.
• Deinking / bleaching chemicals — NaOH, Fatty acids, H 202 , Hydrosulphite, sodiumsilicate, tensides; hinders settling.
v Complexing agents — EDTA, DTPA; not degradable.
v Tensides — Acidic/alkaline surfactants; may cause floating sludge.
v Defoaming agents — Fatty acid, Poly-oxy-ethylene, higher alcohols; Lower 0 2 input inwastewater TP.
v Biocide / slimicide — organic bromine, S/N compounds; some contain AOX toxic.
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SOLID WASTE
•:• Rejects, different types of sludge.
v Rejects are pressed to 55- 65% solids.
• The total losses in processing range from 5 — 6 kg for testliner / fluting to 25 — 40 kggraphic/ tissue/ Dip market pulp.
• Rejects are usually incinerated.
v Sludge comes from mechanical treatment of wastewater treatment plant and fiber recoveryplant.
v Deinking sludge contains fibers, coatings, fillers, ink etc. They contain — 30% volatilesolids and metals particularly Cu and Zn. They can be incinerated.
BAT FOR WASTE PAPER PROCESSING
v Segregation of less contaminated waters from contaminated one and recycling. Thisreduces 10 — 15 m 3/t fresh water use.
PAPER MAKING
Water management and minimizing water usage for different paper grades.
• Efficient separation of cooling waters from process water used of micro screen.
v Segregate paper mill water from pulp mill water.
• Showers are biggest consumers of fresh water (50 — 60% of fresh water of 20 —30 m 3 /t).Clarified water can be used here for most cases.
v Recycling loop for part of vacuum pump sealing water.
These measures can reduce water use to 7 — 15 m 3 /t.
CONTROL OF POTENTIAL DISADVANTAGES OF CLOSING UP WATER SYSTEM
The disadvantages of closing water system include — higher concentration of DS and colloids, riskof slime production and deposition with web breaks, lower product quality in terms of brightness,strength, porosity, increased process aids consumption, risks of corrosion, risks of scaling andplugging of pipes, shower nozzles, wires and felts, problems of hygiene for tissue grade/ medicalgrade papers. Scaling of Ca compounds, slime, pitch are real problems in closed cycles.
The control include:
v Segregation / separation of water loops of each machine.
• Shower waters are treated with micro screens.
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•• Sealing waters are properly stored & recycled.
v Use of pinch technology to ensure proper quality of recycle.
v Use well washed pulp in paper machine.
• Ensure chemicals are of light quality.
•'• Monitor well.
• Understand wet end chemistry well.
INTERNAL TREATMENT OF WHITE WATER BY MEMBRANE FILTRATION ANDRECYCLING OF TREATED WATER
•• Microfiltration (below I bar pressure) membranes with 0.1 — 0.2 tm pores, where 1 —5mg/l very fine solids is acceptable after treatment.
• Ultra filtration operates at 1 — 2 bar pressure difference, remove nearly 100% residualsolids / colloids and high molecular weight organics.
• Nanofiltration (NF) or Reverse Osmosis (RO) uses 15 — 25 bar pressure (results only atpilot scale).
The selection of membrane (kidney) is the key. Membrane material sets the practical limitations onuse.
REDUCTION OF FIBER AND FILLER LOSSES
• Proper refining and screening
•• Efficient control of paper machine headbox.
•'• Proper use of retention aids.
• Proper management of broke.
The losses can be reduced from 10— 100 kg/t to 10 — 20 kg/t (1 — 2% loss).
RECOVERY AND RECYCLING OF COATING — COLOR CONTAINING EFFLUENT
• Paper mills with coating generate a hydraulic low flow wastewater (2 — 5% of totalflow) with rich pigments/adhesives.
•:• Environmentally sound coating waste stream management includes
Minimum discharge of coating kitchen colors.
Minimum grade changes.
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➢ Optimum design of coating color kitchen.
➢ Coating chemical recovery by UF method.
2 — 4% effluent concentration is increased to 30 — 35% and is recycled. Membranes have tobe carefully selected and washed once a week producing 2 — 5 m 3 effluent. Alternatively, coatingwastewaters are separately treated with clariflocculation and centrifugation. The sludge (at 30 —40% dryness) is sent to landfill.
MEASUREMENT AND AUTOMATION
To make process stable, it is. important to have good measurement and automation. Onlinemeasurement process control is essential in saveall operations, blending, refining and Wet Endmanagement. All these lead to better runnability, lesser breaks and uniform quality.
BAT FOR KRAFT PULP MILLS
v Dry debarking of wood with excellent dust extraction and sound control.
v Increased delignification before bleach plant (extended/modified cooking and ODL).
• High efficient BSW and closed cycle brown stock screening.
• ECF bleaching with low AOX (or TCF).
v Recycling some, mainly alkaline process water from bleach plant.
• Effective spill monitoring, containment and recovery system.
• Stripping and reuse of evaporator condensates.
v BL evaporation to high solids.
v Adequate capacity of BL evaporation plant and recovery boiler to cape up with additionalBL and dry solids load
v Collection and reuse of clean cooling waters.
v Adequate buffers for storage of spilled cooking/recovery liquors, foul condensates toprevent sudden peaks of loading to ETP.
v Good primary and secondary treatment of effluent (no over loading).
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THE BAT EMISSION LEVELS TO WATERBleached / unbleached Kraft pulp mills (for pulp mill alone) :
Parameters Bleached pulp Unbleached pulp
Flow m 3/adt 30-50 15-25
COD kg/adt 8-23 5-10
BOD kg/adt 0.3-1.5 0.2-0.7
TSS kg/adt 0.6-1.5 0.3-1.0
AOX kg/adt < 0.25 -
Total N kg/adt 0.1-0.25 0.1-0.2
Total P kg/adt 0.01-0.03 0.01-0.02
BAT FOR REDUCING EMISSION
• Collection incineration of malodorous gases and control of resulting SO 2 (burning inrecovery furnace/lime kiln/ dedicated separate low NO burner, SO 2 scrubbing and SO 2
recovery.
• Dilute malodorous gases from various sources are collected and incinerated (HVLC)and resulting controlled (SO 2by scrubbing).
• Efficient combustion control in recovery boiler and control Total Reduced Sulphur andCO emission.
v TRS emissions of lime kiln controlled by excess 0 2, using low S-fuel and controllingresidual soluble sodium in lime mud fed to kiln.
v Firing high solids to recovery boiler (>75%)to control SO 2 emission and using flue gasscrubber.
•:• Ensure proper mixing and distribution of air in recovery boiler to control NO R .
•:• Use of bark, gas, wood dust, low S fuel to reduce SO 2 emission from auxiliary boiler.Use SO 2 scrubber.
•:• ESP's are required to mitigate dust from recovery boiler, auxiliary boiler and lime kiln.
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BAT EMISSION LEVELS FROM RECOVERY AND AUXILIARY BOILERS
Dust kgladt SO 2 as (S) NO as NO2 TRS as (S)K /adt kgladt Kg/adt
Bleached/unbleached 0.2-0.5 0.2-0.4 1.0-1.5 0.1-0.2Kraft pulp
(for pulp mill alone)
BAT FOR SOLID WASTE MANAGEMENT.
v BAT to reduce waste is to minimize generation of solid waste and recover, recycle andreuse these materials where ever practicable.
• Incineration of organic waste should be considered as BAT.
v In order to reduce consumption of fresh steam/power, generation internally should bemaximized and internal demand for use is reduced. In energy efficient non-integratedpulp mills heat generated from BL and incineration of bark exceeds the energy requiredfor entire pulp mill/ recovery plant operation.
v Fuel oil will be needed for start up and some times in limekiln.
•• Energy efficient Kraft pulp and paper mill will consume heat and power as follows
Process heat PowerGJ/adt MWh/adt
Non integrated bleached Kraft pulp mill 10-14 0.6-0.8
Integrated beached Kraft pulpand paper mill(uncoated fine paper fine paper) 14-20 1.2-1.5
Integrated unbleached Kraft pulpand paper mill (Kraft lime) 14-17.5 1-1.3
BAT FOR RECYCLED FIBER PROCESSING
v Recycled fibers are indispensable raw materials for the industry
v The processing varies depending on grade to be produced and the quality of waste paper.
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v RCF processes are essentially of two main categories:
. Process with exclusive mechanical cleaning (no deinking) like for test liner,corrugating medium, board or carton board.
Processes with mechanical and chemical unit processes (deinking) for productslike NP, tissue, printing, and copy paper, magazine paper (SC/LWC).
BEST AVAILABLE TECHNIQUES FOR RECOVERED PAPER PROCESSING MILLSARE CONSIDERED TO BE:
v Optimal water management (water loop arrangements), water clarification bysedimentation, flotation, or filtration techniques and recycling of process water.
v Separation of less contaminated water from contaminated one and recycling of processwater.
v Environmental emissions to water and solid waste (specially deinking plants) form mainimpacts.
BAT FOR RECOVERED PAPER PROCESSING ARE:
v Separation of less contaminated water from contaminated one and recycling of processwater.
• Optimal water management, water clarification (sedimentation/flotation/filtration) andrecycling.
v Strict separation of water loops and countercurrent flow of process water.
• Generation of clarified water for deinking (flotation).
• Installation of an equalization basin and primary treatment.
v Because of higher degree of closure of water circuit, flocculation, chemical precipitationwith subsequent anaerobic and aerobic treatment of effluents is needed for non-deinkinggrades.
v For non-deinking grades, partial recycling of biologically treated water is recommended.
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FOR INTEGRATED RECOVERED PAPER MILLS AVERAGE EMISSION LEVELS WITHUSE OF BAT ARE AS UNDER:
Parameter Integrated RCF paper mill, nodeinking like test liner, cartonboard, white top liner
RCF paper millwith deinking likeNP, printing &writing
RCF basedtissue mills
FLOW, m /t <7 8 — 15 8 — 25
COD,kg/t 0.5-1.5 2-4 2-4
BOD, kg/t <0.05 — 0.15 <0.05- 0.5 <0.5 — 0.4
TSS, kg/t 0.05-0.15 0.1 - 0.3 0.1 -0.4
Total N, kg/t 0.02 — 0.05 0.05 — 0.1 0.05 — 0.25
Total P, kg/t 0.002 — 0.005 0.005 —0.01 0.005 — 0.15
AOX, kg/t < 0.5 <0.5 < 0.5
v Cooling waters and clean waters are discharged as separate streams.
• Air emissions from RCF plants are essentially those due to heat/cogeneration facility.
v Combustible solid waste should be burnt.
• Reduction of solid waste is achieved by optimizing fiber recovery, by upgrading stockpreparation, application of DAF as in line treatment of water loop to recover fibers/fillers.
ENERGY EFFICIENT RECOVERED PAPER MILLS CONSUME PROCESS HEAT ANDPOWER AS FOLLOWS:
Detail Integrated non- Integrated tissue Integrated NP plants/deinked RCF plants plants with writing & printing
Deinking Plan mills with DIP
Process heat, GJ/t 6 — 6.5 7 — 12 4— 6.5
Power, MWh/t 0.7-0.8 1.2-1.4 1-1.5
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PAPER MAKING PROCESS
• Papermaking involves use of fiber (pulp), chemical additives and energy. Environmentalissues are dominated by emissions to water.
v BAT for reducing emissions to water are:
➢ Minimize water use by increased recycling of process water and better watermanagement.
➢ Control of potential disadvantages of closing up water system.
➢ Maintaining proper white water balance with proper filtrate and broke storagesystem management.
➢ Control to reduce frequency of accidental discharge.
➢ Separate pretreatment of coating wastewater.
The water emission level from paper mills (per tonne paper) only with use of BATare mentioned below:
Parameter Uncoated fine Coated fine Tissue
FLOW, m3/t 10-15 10-15 10-25
COD, kg/t 0.15-0.25 0.15-0.25 0.15 -0.4
BOD, kg/t 0.5-2 0.5-1.5 0.4-1.5
TSS, kg/t 0.2-0.4 0.2-0.4 0.2 -0.4
Total N, kg/t <0.005 <0.005 <0.01
Total P, kg/t 0.003 — 0.01 0.003 — 0.01 0.003 — 0.001
AOX, kg/t 0.05 — 0.2 0.05 — 0.2 0.05 — 0.25
• Reduction of fibers and fibers losses, application of UF for coating wastewaters recovery(for coated grades only) efficient dewatering of sludge to high dry solids should befollowed.
v Use of energy efficient technologies is considered BAT. These include more effectivedewatering ofpaper web in press section (shoe press/ wide nip), high consistency slushing,energy efficient refining, twin wire forming, optimized vacuum systems, speed adjustabledriver for pumps and fans, high efficiency electric motors, good steam condensaterecovery, increasing size press solids, exhaust air heat recovery system, use of pinchtechnology to ensure careful process integration and reduce direct use of steam.
v Energy efficient paper mills (pulp mill) consume heat and power as follows:
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Detail Non integrateduncoated fine papers
Non integratedcoated fine papers
Non integrated tissue(based on lignin fiber)
Process heat GJ/t 7.0-7.5 7-8 5.5-7.5
Power (MWh/t) 0.6-0.7 0.7 —0.9 0.6— 1.1
AUXILIARY BOILERSv Use of bark is very little in India, this need to be promoted.• Bat includes cogeneration, use of renewable fuel source (wood waste, sludge), control
of NOX and SOR, use of ESP (or bag filters) for SS control use of fossil fuel with low S.v Emission on levels from auxiliary boilers:
DETAIL mg SOX /MJ OFFUEL INPUT
mg NOx/MJ OFFUEL INPUT
mg DUST/MJ OFFUEL INPUT
Coal 50-100 50-80 10-30AT6%0
H.F.0 50-100 50-80 10-40AT3%0
Gas <5 30-60 <5 AT3%0
Biofuels (e.g. barks) < 15 40 - 70 10 — 30 AT 6% 02
CONCLUSION
Paper industry has enormous potential for adopting cleaner technologies. Adoption of these will benot only environmentally sound but will prove economically beneficial. Their adoption will increasethe competitive edge of Indian industry with the face of globally competitive environment.
KEY WORDS: NP ODL, h Factor, RDH, ECF HW, RIO, NPE, NCG, BL, CEHH, Kappa No., BLS, ASP BSW, TCDA,TCDF EA, DD, AKD, UF, MF, Tenside
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CLEAN ENVIRONMENT THROUGHFLY ASH UTILISATION
By
VIMAL KUMARADVISER
MUKESH MATHURSCIENTIST `D'
FLY ASH UTILISATION PROGRAMME, TECHNOLOGYINFORMATION, FORECASTING & ASSESSMENT
COUNCIL (TIFAC)DEPARTMENT OF SCIENCE & TECHNOLOGY
NEW DELHI — 110 016Tel. :011-26961318,26963770 Fax : 011-26863866, 26515420
E-mail : [email protected], [email protected]
Clean Environment Through Fly Ash Utilisation4mal Kumar * & Mukesh Mathur **
ABSTRACT
Fly ash disposal & utilisation shall continue to be an important area of national concern due toIndia's dependence on coal for power generation for foreseeable future. The scenario with respectto fly ash management has undergone considerable improvement over past few years. Due toincreasing environmental concern and growing magnitude of the problem it has become imperativeto manage fly ash more efficiently. It is more important in view of the fact that `fly ash' has tremendouspotential that is yet to be exploited.
Current annual generation of fly ash in India is about 105 million tonne which is expectedto reach around 170 million tonne by 2012. As a result of the focussed thrust beingprovided by Fly Ash Mission (FAM) of Government of India alongwith many other agencies, itsutilisation has increased from 3% (in 1994, of 40 million tonne production) to about 27% (in Sept.2003, of 105 million tonne production). A lot more is required to be done including creating awarenessamong the people & user agencies.
The intrinsic worth of fly ash for various gainful applications has started getting recognition.It is being now taken as a friendly and useful resource material. Several agencies — (Govt.,private, public sector, NGOs etc.) are taking / have taken sincere steps in recent timestowards more & more utilisation of fly ash. These agencies include Department of Science& Technology, Ministry of Power, Ministry of Environment & Forests, Ministry of UrbanDevelopment, National Thermal Power Corporation, Council of Scientific & IndustrialResearch (CSIR) & other laboratories, Pollution Control Board & Pollution Control Committees,academic institutes, State Electricity Boards, industries, etc. Fly Ash Mission (FAM), the nationallevel effort, in this area since 1994, is a Technology Project in Mission Mode being implemented byTechnology Information, Forecasting and Assessment Council (TIFAC) with Department of Science& Technology (DST) as Nodal Agency.
Several areas of fly ash utilisation wherein Technology Demonstration Projects (55 numbers)have been completed or are underway in FAM include mine filling, construction of road /flyover embankments, hydraulic structures, raising of dykes, manufacture of several buildingcomponents like bricks, blocks, tiles & its use in agriculture, etc. The future poses challengeto the scientist & engineers towards sound management of fly ash. The technical know-how and its feasibility has generally been demonstrated.
* Dr. Vimal Kumar, Adviser, Fly Ash Utilisation Programme, Technology Information, Forecasting & AssessmentCouncil (TIFAC), Department of Science & Technology, New Delhi — 110 016** Mr. Mukesh Mathur, Scientist `D', Fly Ash Utilisation Programme, Technology Information, Forecasting & AssessmentCouncil (TIFAC), Department of Science & Technology, New Delhi — 110 016
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Good number of entrepreneurs, scientists and engineers have started coming forward to work in thearea of fly ash utilisation / safe disposal. R&D institutions have started groups exclusively workingon fly ash. It is slowly being taken as a friendly and useful resource material than a liability.
I. INTRODUCTION
India's 82 utility and more than 25 captive thermal power plants contribute more than 70% to thecountry's total electric power installed capacity (approx. 100,000 MW). Due to vast coal reserves(about 211 billion tonnes), coal is being used as the largest source of energy. In fact about 240million tonne of coal is being used every year to generate electricity. Indian coals though low insulpher, radio active elements and heavy metals content, yet rich in incombustible siliceous materialand other inorganic matter which comes out as ash on combustion. These particles are so intimatelymixed with the coal and have the specific gravity in the range close to that of coal, that the washingof coal is also not very successful so far. As a result of that India is producing about 105 milliontonne of ash every year. This figure is likely to go up in view of developing nature of Indian economy,which involves large no. of energy intensive infrastructure projects. It is estimated that fly ashgeneration would increase to around 170 million tonne by 2012.
Most power stations dispose ash using wet slurry system. This method is now proving a luxury interms of land and water requirements. Further, it downgrades the cementious properties of dry flyash. Generally, more than 1 acre of land is required for ash pond area per MW power capacity. Inrecent times dry fly ash collection has gained momentum. In addition, increasingly power stationsare shifting to separate collection of flyash and bottom ash with growing realisation that each kindof ash has advantageous uses.
Fly ash is finely divided residue resulting from combustion of pulverised bituminous coal or subbituminous coal (lignite) in thermal power plants. It consists of inorganic mineral constituents ofcoal and organic matter which is not fully burnt. It is generally grey in colour, alkaline and refractoryin nature and has a fineness 3000 to 6000 sq.cm . per gram and possess pozzolanic characteristics.Typical chemical composition of Indian fly ashes is as follows:
Constituent Representative percentage range (%)
Silica (Sí02) 49-67
Alumina (Al203) 16-29
Iron Oxide (Fe 20 3) 4-10
Calcium Oxide (CaO) 1-4
Magnesium Oxide (MgO) 0.2-2
Sulphur (SO 3) 0.1-2
Loss of Ignition 0.5-3.0
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The utilisation of fly ash in India was around 3 % of 40 million tonne annual generation during1994, the year of formulation of Fly Ash Mission (FAM) of Government of India. As a result ofsustained efforts of various organisations with the focussed thrust being provided by Fly Ash Mission,the utilisation has increased to about 27%. The overall potential of ash utilisation points outexponential growth in near future.
II. EARLIER EFFORTS
Prior to 1994, large number of efforts have been made to develop and commercialise technologiesfor use of fly ash. Academia, national research institutes, private R&D as well as industry havebeen doing some work in this field even prior to 1960s. It was only in 1970s that fly ash utilisationstarted getting attention. Fly ash properties were researched for vide range of applications, interalia, pozzolanic, geotechnical, metallurgy, ceramic and agriculture applications. Scientific resultswere published, laboratory trials and even a few field demonstrations were undertaken to demonstratethe beneficial applications of fly ash. However, most of the work remained confined within theacademia / research arena. A few utilisations of fly ash were made primarily in mass concrete,brick / block manufacturing and reclamation of low lying areas.
The Ministry of Environment & Forests (MoEF), Ministry of Power (MoP) and a few other agenciestook initiatives. National Waste Management Council (NWMC) and a few other groups/committeesconsisting of senior officials of various Ministries/Departments, State Governments, Research andDevelopment Institutions, Social Workers etc. were formed. Thermal Power Plants were directedto take actions to enhance ash utilisations and a few fiscal incentives such as concessional exciseduty and sales tax were declared.
A well researched comprehensive techno-market survey report was prepared by TechnologyInformation, Forecasting and Assessment Council (TIFAC) of the Department of Science &Technology, Government of India, during early 1990s for safe disposal and gainful utilisation of flyash. The report was widely distributed and discussed among concerned agencies. It highlightedthat only a meager percentage (less than 3 per cent) of ash was being utilised in the country and thebalance was being stored in ash ponds. The report brought to fore that the fly ash that is beingconsidered as a waste material, is in fact a useful material and can be put to gainful economicapplications.
III. MISSION MODE APPROACH
Appreciating the overall concern for environment and the need for safe disposal and gainful utilisationof fly ash, the Government of India commissioned Fly Ash Mission during 1994 with Departmentof Science & Technology (DST) as the Nodal Agency and Technology Information, Forecastingand Assessment Council (TIFAC) as the Implementing Agency. The focus is on TechnologyDemonstration Projects for developing confidence in fly ash technologies towards large scaleadaptation.
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The overall complexity of technology transfer, infrastructure support, inter-institutional linkages,development of market, orientation of Government policies to promote and support fly ash utilisation,are addressed. Further, as no single utilisation holds the potential to provide a solution to thismammoth task of safe disposal and gainful utilisation of fly ash, a judicious mix of a number ofapplications is evolved (considering impact time frame, investment requirement, technical andinfrastructure inputs requirements by fly ash utilisation, potential and expected returns, etc.). Anumber of disposal and utilisation technologies / applications have been simultaneouslydemonstrated. Optimum technologies are facilitated to catelatize projects on a wider! larger scale.The Fly Ash Mission has also created critical size of engineering teams for each of the application/ disposal areas to provide help for mass replication. The formulation of national standards andcode of practices / guidelines is also addressed to for wider acceptance and development on selfsustaining principle.
IV. CONCERTED THURST EFFORTS
Till early years of 1990s, the use of fly ash was very limited and primarily in (i) a few mass concreteprojects to reduce the heat of hydration; (ii) low percentage blend in small quantities of portlandpozzolana cement; and (iii) limited number of fly ash brick units, etc. Following the increasedawareness and concerted efforts of Fly Ash Mission alongwith various government and non-government agencies over about last 8 years, safe disposal & effective utilisation trends are gainingmomentum in the country. There is greater acceptance of fly ash products & applications. This is sobecause the agencies involved (research institutes, academia, thermal power station, industry, etc.)have been sensitized and are taking positive initiatives. Various agencies working in this area andthe stake-holder groups have been brought together to a common platform.Their efforts have beencatalysed & facilitated.
Use of fly ash would not only conserve the top soil / sand which otherwise would be used ingeotechnical applications, brick manufacturing, mine filling etc., and is already a scarce resource,but would also prevent creation of low lying areas and digging of river bed. By utilising fly ash wewould spare additional land also which currently is being used for dumping of ash. Further, it wouldnot only save cement, but would add to its production also (when used in manufacture of PPC),with reduction in contribution of greenhouse gases to the atmosphere.
The confidence building exercise has been taken up through 55 Technology Demonstration Projects( TDPs) spread through out the country (see enclosed map & a few site photographs). The projectshave been undertaken in the field involving user agencies, industries, technology suppliers, fly ashproducer, experts from academia / R&D under the following ten THURST AREAS.
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i. Utilisation of fly ash
• Roads & Embankments• Building components• Hydraulic Structures• Agriculture Related Studies & Applications• Underground Minefills
ii. Safe management of unutilized fly ash
• Ash Ponds & Dams• Reclamation of Ash Ponds for Human Settlement
iii. Facilitation of further work/utilisation
• Characterisation of Fly ash• Handling & Transportation• Research & Development
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Okhla Flyover
Two Km stretch of Raichur- Arsnagi road, via Yadlapur in Raichur distt. of Karnataka.The fly ash road (in unmetaled condition) has performed well for last 5 years.
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IIT-Delhi Caféteria Building using Fly Ash Bricks
Cultivation of wheat at Rihandnagar (U.P.) Cultivation of cabbage on coal ash amendedsoil at Dodhar, Rihandnagar (U.P.)
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Increased seed yield of sunflower with fly ash at 60 t/ha, at Raichur, Karnataka
Jojoba plant at Fly ash amended semi-arid soil of Jaipur, Rajasthan
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In addition, Fly Ash Mission has facilitated ash utilisation through:
Technology Commercialisation
• Identification of promising technology
Setting up of technology demonstration / confidence building projects
• Facilitate availability of fly ash
• Part financial assistance on soft terms
• Networking with potential user agencies (Govt. & private)
• Research & industrial infrastructure development
Techno- managerial Services
Mobilisation of scientific & technical manpower resource
• Site specific fly ash management plans
Information Dissemination
• Induction of fly ash in academic curriculum
Identification & encouragement for research
Participation & organisation of workshops, seminars, conferences, kisan melas
Policy Initiatives
Facilitation in preparation of standards, specifications, protocols
Facilitation for fiscal incentives & policy measures by the Govt.
Interaction with state Govts. & user agencies for improved fly ash management practices &induction of fly ash in their specifications & schedules of rates
The Fly Ash Mission has also developed synergy among other agencies working in this area such asAsh UtilisatiQn Division of National Thermal Power Corporation (NTPC), Building Materials &Technology Promotion Council (BMTPC), Housing & Urban Development Corporation (HUDCO),National Laboratories of Council for Scientific & Industrial Research (CSIR), Indian Institute of
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Technology (IITs), Indian Institute of Science (IISc.), Agricultural Universities, Central Public WorksDepartment (CPWD), State Public Works Departments , Thermal Power Stations, Industries etc.Other major partners are regulatory Ministries / Departments of Central as well as State Govts. thatinclude Ministry of Environment & Forest, Ministry of Power, Central pollution Control Board,Ministry of Urban Development, Ministry of Road Transport & Highways, Ministry of Agriculture,Ministry of Mines, Bureau of Indian Standards, etc.
V. MULTIPLIER EFFECTS
The confidence building and awareness created by Fly Ash Mission through its technologydemonstration projects, workshops, seminars as well as association and support of other agencieshas lead to a beginning towards acceptance of fly ash and its products. The facilitation in terms ofcreating awareness towards removal of mindset and other bottlenecks, availability of fly ash andup-dating / formulating standards codes, etc. have also provided meaningful support. Some of theMultiplier effects are illustrated below:
Roads & Embankments
1. Approach road embankment connecting new Nizamuddin bridge, New Delhi to Noida hasbeen constructed using fly ash.
Nizammuddin bridge approach road embankment at New Delhi(in flood zone of river Yamuna)
It is about 2 km long, 6-8 metre high road embankment in flood zone area of Yamuna river. It hasused about 1.5 lac tonne of fly ash (in lieu of soil) resulting in a saving of Rs. more than 1 crore toPWD-Delhi, about Rs. 30 lacs to DVB and protected the land that would have been degraded byexcavation 1.5 lac tonne of earth. Design was provided by CRRI, New Delhi and approved byMOST and PWD, Delhi.
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2. Fly ash road (1/2 km long) has been constructed at Budge-Budge Power Station (CESC) withtechnical consultancy from CRRI. More fly ash roads are being planned by CESC.
3. Road embankment (300m long and i to 2m high) is being taken up for construction using flyash at Ramagundam with CRRI design.
4. Hanuman Setu (a flyover) embankment, Yamuna Bazar, Delhi has been constructed using flyash.
5. Fly ash road has been constructed at NTPC, Dadri, as per design provided by CRRI, NewDelhi.
6. Use of fly ash for construction of flyover bridge embankments at Santa Vihar, Punjabi Bagh,Raja Garden, New Delhi
7. Railway embankment, 8m high & 3 km long, at Ramagundam Power Station, NTPC woulduse about 2.5 lakhs tonne fly ash (in lieu of soil).
8. Railway embankment of Delhi Metro Rail project has been constructed by use of Fly ash. Ithas used about 15 lac tonne of ash.
Building Components
9. IIT-Delhi has taken a decision that henceforth all construction at it's campus would use fly ashbricks. It would also use fly ash in concrete & mortar.
10. 2 lac bricks have already been used for construction of cafeteria and hostel buildings.Requirement of about 5 lac bricks for hostel extension is in process along with about 1000tonne of dry fly ash for use in concrete & mortar.
11. American Embassy has used around 25,000 fly ash bricks for construction at their campus.
12. TERI, New Delhi is finalizing their requirement for about 2 lac fly ash bricks for constructionat their R&D center.
13. Special protection group has agreed to use fly ash bricks for their housing construction. Orderfor supplying of 80,000 fly ash bricks has been received by BTPS.
14. NTPC has set up 2 additional fly ash bricks plants at BTPS.
15. PWD-Delhi has planned to use about 10 lacs fly ash bricks for construction of school building.
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Building constructed using fly ash bricks at Calcutta, West Bengal
Use of fly ash based cellular light weight concrete
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Ash Ponds & Dykes
16. Selection of ash disposal site for SPIC Power Company by IIT-Madras as consultancyassignment.
17. Ennore Thermal Power Plant ash dyke design review by IIT-Chennai.
Improving local soil properties using fly ash at Ennore Thermal Power Plant, Tamil Nadu.
18. Soil-Fly ash mix design for Ennore Power Plant dyke construction by IIT-Chennai.
19. Ash Pond maintenance & design for Tuticorin Power Station by IIT-Chennai.
20. Ash Dykes design for Korba Power Station (NTPC), Korba Power Station (MPSEB), SarniPower Station (NTPC), Rourkela (SAIL), Bokaro (SAIL) by IIT-Kanpur.
Agriculture
21. More and more farmers are seeking fly ash for application in their field as a result of higheryields at demonstration sites.
22. Agriculture agencies in Karnataka requesting more & more support from Raichur, AgricultureUniversity for use of fly ash in agriculture. Farmer's Melas & Goshaties are being held sixmonthly since last 1 y2 years.
23. Use of fly ash for agriculture applications has been taken by NLC; STPP Chandrapur and TPP- Bhusawal with technical support and advice from CFRI, Dhanbad.
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24. Large scale fly ash use by farmers has started around Raichur, Bakreswar (WB) and Phulpur(U.P.)
Structural Fill
25. DDA's low lying area at Shalimar Bagh, Parmeshwar park, Pitampura and Saria Kale Khanhave been reclaimed using DVB fly ashes.
26. Arrangements have been finalised with PWD, Delhi for filling up low lying land of PWD-Delhi at Sarai Kale Khan, using DVB fly ashes.
Dissemination of information and share of expertise
Information dissemination is done through workshops seminars, publications and experience sharingmeets etc. Fly Ash Mission has organized more than 10 workshops and supported equal number ofseminars / workshops.
At Vill. Yakubpur, U.P. at Raichur, Karnataka
In addition information sharing has been done with national and international agencies.
Fly Ash Mission has also provided expertise / technical support towards management / resolving ofspecific issues regarding safe management and utilisation of fly ash, directly or through its associatedagencies to about 40 agencies as paid consultancy assignments.
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Experience sharing meet of organisations engineers from various at Nizamuddin bridge, New Delhi
VI. Networking
In addition to working with a large number of project execution agencies across the country fortechnology demonstration projects, a network of 25 laboratories has beendeveloped to provide facilitation and guidance towards safe management / utilisation of fly ashes.(see map given below)
VII. Standards
With an objective of wider acceptance and intitutionalisation of demonstrated technologies, FlyAsh Mission is working very closely with Bureau of Indian Standards (BIS) for up dating theexisting standards for fly ash and its products and also to prepare standards for product / utilisationwhich do not exists as of now.
Some of the Standardisation initiatives include :
(a) Design guidelines for "Use of Fly ash in Road Embankments" have been approved and issuedby the Indian Roads Congress.
(b) Revision of IS 3812 - the standards for specification of fly ash for its use in cement / mortar /concrete & fine aggregate have been revised in view of the improvements in quality of fly ashover the years. The codes for other applications of fly ash viz, for lime pozzolana mixture
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applications, sintered applications, geotechnical application and agricultural application arealso under formulation.
(c) Updation of IS:456 - code of practice for plain and reinforced concrete has been updated withuse of fly ash.
(d) Minimum and maximum percentages df fly ash in PPC have been enhanced to 15% and 35%respectively etc.
VIII. Institutional/ Government Acknowledgement & Support
• CPWD has issued orders to all the zones to have atleast one construction using fly ash bricks/blocks etc.
• Notification has been issued by Ministry of Environment & Forests banning the use of top soilfor manufacture of bricks and construction of roads and embankments with in a radius of 100kms from a thermal power station.
• A number of states (Orissa, Tamilnadu, Karnataka) have also announced fiscal and policyincentives for fly ash based products.
• Central Government has granted excise & custom duty exemptions/ reliefs.
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IX. FLY ASH FOR LOW COST, ENERGY EFFICIENT AND ENVIRONMENT FRIENDLYHOUSING MATERIAL
A few details presented in the subsequent paragraphs illustrate the economic and environmentalimpact that fly ash can create if utilized appropriately in housing sector:
Fly Ash Bricks
Bricks are the building material required in large numbers. Manufacturing of ordinary clay bricksinvolves firing at high temperature, which is quite energy intensive. Average coal consumption forproduction of 1000 bricks is 180 kg which is equivalent to about 1250 kwh energy. As against this,the energy requirement for of flyash bricks production is low.
Flyash bricks can be manufactured in following four ways :
(i) Fly Ash-Clay burnt bricks
(ii) Fly Ash lime gypsum (Air-water cured) bricks.
(iii) Fly Ash lime gypsum (Steam cured atmospheric pressure)
(iv) Fly Ash lime (Autoclaved) bricks
Category (I) flyash bricks are manufactured by firing mixture of flyash and clay. The unburntcarbon of the flyash provides fuel for burning. Approx. 20-30% energy consumptions maybe reducedby adding 25-40% flyash. Fly ash bricks of category (II), (iii) and (iv) do not require any firing.Further, the thermal conductivity of flyash bricks is also lower than that of ordinary clay bricks.
The use of flyash bricks not only provides low cost & energy economic input to the building industrybut also reduces environmental degradation. In summary
180 billion clay bricks production / year.
• Consumes 540 million tonne of clay
• makes 65,000 acres of land barren
• consumes 30 million tonne coal equivalent fuel
• generates 26 million tonne CO2
• 10% switchover to flyash bricks would
• use 30 million tonne fly ash / year
• save coal and environment
• yield benefit of Rs.300 crore by way of reduction in brick production cost
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On quality and price
. Air -water cured bricks are of similar quality as clay bricks and 10 to 25 paise cheaper.
Steam cured bricks are of much superior quality; comparable to wire cut clay bricks and cheaperby 25 to 50 paise than wire cut bricks.
For per unit construction cost, steam cured bricks compete with regular clay brick construction dueto consumption of lower number bricks, cement mortar and faster speed of construction.
Flyash Cellular Light Weight Concrete (CLC)
Cellular light weight concrete is manufactured by a process of mixing flyash, lime or cement, sand,water and gypsum in a high speed mixer to form a thin slurry. A small amount of foaming agent isalso added and mixed to produce air bubbles in the slurry. It can be produced as blocks, cast in-situand also as pre-fabricated panels. It is an excellent insulating material and can be used for weatheringcourse, void filling, filler walls etc. Thermal conductivity of cellular light weight concrete is in therange of 0.082 - 0.555 W/m/K as compared to 2.10 W/m/K for normal concrete. It results insubstantial saving in power consumption for air-conditioning etc. Other advantages of CLC areextremely light weight, higher compressive strength, low water absorption etc. The importantphysical & engineering properties of flyash CLC are :
Physical Properties of Fly Ash Cellular Light Weight Concrete
Range of densities
400-1600 kg/m3
Compressive strength
10 to 150 kg/cm2
Shrinkage behaviour
1200 kg/m3-0.215 mm/m.Dense concrete - 0.145 mm/m.Thermal conductivity
0.082-0.555 (W/m/k)Dense concrete - 2.1 (W/m/k)Fire rating
OptimumWater absorption
Approx. 10% at a density of 1200 Kg/m 3
Substitution of cement by flyash, makes CLC about 10% cheaper.
Use as Part Replacement of Cement / Manufacture of cement
After aluminum and steel, the manufacture of portland cement is the most energy-intensive process.The manufacture of portland cement requires about 1200 Kwh of energy per tonne of the finishedproduct. Over the past decades, the cement industry has made major strides in reducing the energyconsumption. This has been achieved primarily by replacing wet production facilities with newmodern dry-processing plants. However, it has reached about the limit beyond which it is extremelydifficult to reduce further energy use in the cement production process. Obviously, the existingcement plants cannot be shutdown. This leaves only one option, and that is to limit the installationof new plants, and phasing out of the old inefficient installations. The loss in capacity due to thischange can be met by the use of flyash.
At present our cement production is approx. 110 MT/year and for manufacturing of each tonne ofcement we use approx. 1600 kg lime stone and about 300 kg other ingredient (Clay, sand, etc.).
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Enormous energy is required to burn such huge amount of material at a high temperature of 1450°Cto form the cement clinker. Besides this every one tonne of cement produced releases about 1 tonneof carbon dioxide in the atmosphere.
It has been proved that when flyash is added to cement, it improves its strength and durability.Apart from this, it will also reduce the emission of carbon dioxide, the greenhouse gas releasedduring manufacturing of cement.
The advantages of Portland Pozzolana Cement (PPC) over Ordinary Portland Cement (OPC) are asfollows:
• PPC makes concretedenser, improves workability and reduces heat of hydration
- more resistant to carbonation & sulphate attacks- resistant to corrosion- stronger in long run
durable even in aggressive environments like coastline and industrial areas
Environmental & economic impact is summarised below:
• 110 million tonne cement production /year.- consumes 180 million tonne of lime- consumes 30 million tonne of coal- produces 110 million tonne of CO2
If we judiciously accept that 25% requirement of our cement would be for normal portland cement,remaining 75% can be fulfilled by Portland Pozzolana Cement (PPC). In summary:
• Conversion of 75% production of OPC to PPC can- use 25 million tonne fly ash / year- make available additional 25 million tonne cement- year with marginal lead time and investment- Reduction in cement cost by 10-15%.
Annual Saving : Rs. 2500 crore+ Environmental benefits+ Conservation of mineral resources (lime is finite!)
Similarly, flyash has economic and environmental friendly use in (i) other building materials suchas pavement tiles, flooring & ceramic tiles, wood / ply- wood substitute, aggregates, pre-fab itemslike slabs, doors / window frames, use of flyash in ready mix concrete, high performance concrete- to be taken up for confidence building and (ii) infrastructure development activities like constructionof roads and flyover embankment, reclamation of low lying areas construction of hydraulic structures,etc.
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X. OVERALL IMPACT MADE BY MISSION MODE APPROACH
The impact made so far comes out clearly when we take a look at the scenario that prevailed in 1994(pre Fly Ash Mission) and the one which prevails now.
OVERALL IMPACT MADE
Si. Select 1994 2003No. Indicator ( Start of Mission
Project )
1. Fly ash Utilisation 1.5 million tonne /year 28 million tonne / year[3% of 45 million [27% of 105 million tonnetonne generation] generation]
2. Status of Technologies were Select technologies of highFly ash utilisation generally stuck up at volume utilisation are scaled up,
technologies laboratory scale or demonstrated and multipliernon-existent effects have started e.g. road /
flyover embankments, ash dykes,bricks / blocks, cement
manufacture / substitution,reclamation of low lying areas,
etc.3. Confidence in fly ash Was missing Has been established in
technologies demonstrated technologies, othersare in progress / planned and
standardisation done.
4. Technologies Practically there was Commercialisation or large scalecommercialisation no commercialisation use efforts have started especially
status effort or large scale for demonstrated technologies. Asuse a result more than 100 multiplier
effects have come up.
5. Linkages between labs Were practically Strong linkages have been& lab / user agencies missing established data & experience
sharing has become common andexperienced cadres formed.
6. Status of standards / Outdated & were not Exercise to update the existingprotocols (crucial for available for many standards / make new standards
sustained use) applications, has started. 60 stds updated and10 new stds prepared.
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XI. PARADIGM SHIFT
The impact and the considerable change in fly ash utilisation scenario is evident from the fact thatacceptance of fly ash products has started picking up and fly ash is now emerging as an importantresource material for the new millenium. Use of fly ash in bricks, blocks, cement, in construction ofroads and embankments and also in agriculture related areas are fast emerging.
The intrinsic worth of fly ash for various gainful applications is being understood. It is slowlybeing taken as a friendly and useful resource material than a liability. Further, good number ofentrepreneurs, scientists and engineers have started coming forwards to work in the area of fly ashutilisation / safe disposal. R&D institutions have started groups exclusively working on fly ash. Theutilisation of fly ash has increased from 12 lac tonne per year in 1994 to 180 lac tonne during 2001with significant upward momentum.
REFERENCES
1. Vimal Kumar and Chandi Nath Jha "Multifarious Applications of Fly Ash Mission Mode Approach", Fly AshMission, Proceedings of `Workshop on Utilization of Fly Ash' at University of Roorkee, April, 1998.
2. TIFAC "Techno Market Survey on Fly Ash Bricks", 1995
3. TIFAC "Techno Market Survey on Fly Ash Pre-fabrications technologies and market"
4. Vimal Kumar, B.K. Rao & Preeti Sharma "Fly Ash as Raw Material", Fly Ash Mission, proceedings of Internationalconference at CBIP, New Delhi, January, 1998.
5. Vimal Kumar, B. K. Rao & K.A. Zacharia "Fly Ash : Techno Economic Viability", Fly Ash Mission, proceedingsof International Conference at CBIP, New Delhi, January, 1998.
6. Vimal Kumar, C N Jha, P Sharma "Fly ash - A Fortune for the Construction Industry", New Delhi, 1999.
7. Vimal Kumar, P Sharma, Mukesh Mathur "Fly Ash Disposal: Mission beyond 2000 A.D.", Fly Ash Disposal andDeposition: beyond 2000 A.D. New Delhi, 1999.
8. "Fly Ash Management - Vision for the New Millennium", Second International Conference on Fly Ash Disposal& Utilisation, New Delhi, February 2000.
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CLEAN ALTERNATIVE TECHNOLOGIES FORTHE INDIAN ELECTROPLATING INDUSTRY
By
Asif Nurie
M/S ATLANTA GLOBALH-4 Green Park Main, New Delhi-110 016 (INDIA)
Ph.: 091-11-26514527; Mobile : 091-9810541297Telefax : 091-11-26569742; Email. [email protected]
Clean Alternative Technologies for the Indian Electroplating IndustryAsif Nurie*
Electroplating is carried out in India for decorative and functional purposes and touches the lives ofalmost every individual in one way or another. Plating is defined as
"The Art and science of depositing a metallic or non metallic layer of measurable thickness with orwithout the aid of electric current over a metallic or non metallic surface, with the intent ofprotection,beautification, improvement of wear resistance or simply increasing the dimensions to restore originalsizing, is what plating is all about".
Plating adds value to the component treated. The resultant waste generated is a matter of controland concern worldwide. Clean Plating - the ideal situation is defined as:
"Creating least amounts of waste while plating consistent quality to impeccable standards, makingprofits from the savings so generated; Recycling scarce resources to the maximum possible withZero Discharge as the ultimate target.. "
Viewed in the light of this definition we need to accept then the Indian Plating scenario is for awayfrom this Utopian statement. While electroplating is carried out Nationwide, 12 states have largeclusters of Plating units. An educated guess in place of exact demographical data on the statisticalimpact is shown below.
Nos.
• Large scale factories 400
• Medium scale factories 3,000
• Small scale units 7,000
• Tiny scale sector 18,000
(These figures are estimation and may be -inaccurate for lack of census and no guaranteefor accuracy is made)
There are a number of different kinds of plating carried out, and listed below are those processeswhich are carried out in India and have the maximum potential to pollute.
FUNCTIONAL AND DECORATIVE PROCESSES (ELECTROLYTIC AND NON -
ELECTROLYTIC)
CYANIDE BASED ACID BASED SYSTEMS CHROME BASEDZinc, Copper Zinc Hard ChromeSilver, Gold Nickel Decorative Chrome
Copper Chromating
* Shri Asif Nurie is an independent Consultant having office at H-4, Green Park, New Delhi-110016.Ph. : 091-11-26514527; Mobile: 091-98105 41297; Email. [email protected]
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The processes discharge pollutants that are subject to regulation and control. Listed below aremajor pollutants that cause concern due to their effect on humans and the environment.
Cyanides and Cyanates;
Chromates and chromic acid;
Metals : Nickel, Zinc, Copper, Tin, Lead;
In Chemical form : Nitrates, Sulphates, Chlorides, Fluorides, Nitrates; and
Metal Bearing Pickling wastes.
Another tangible pollutant caused by plating operations is air emission. Major examples:
• Pickling Operations
• Cleaners
• Chrome Plating
• Etching and stripping
• Cyanide Plating
- Acid Spray and mist
- Caustic alkaline spray
- Chromic acid spray and mist
- Cyanide, Alkaline and acid spray
- Cyanide spray
Air Pollution control takes the form of both abatement and eradication, the latter being end of pipe(EOP).
Abatement : Stable Fume suppressants are used to prevent fumes from plating, pickling, etchingand stripping. These make the work environment acceptable.
EOP : Hoods, ducts and scrubbers collect fumes and spray, neutralize the scrubber liquid inconformity with the Air Act, while preventing emissions from affecting the work environment andworker health.
Water Pollution and Plating : Decorative and functional chrome plating is carried out using chromicacid, the hexavalent form of chrome that is recognised internationally as a carcinogen, makinghexavalent chrome based waste a regulatory issue. Trivalent Chrome however is not a categorisedcarcinogen.
Hard Chrome plating on certain tools and implements has ben partially replaced by ion sputteringwith hard metals such as Titanium Nitride. The system has had success limited by application,usage and cost and is not very widely practiced.
Decorative Trivalent Chrome processes have found technical success in Europe, USA and Japan.There are issues of costs when fully addressed can permit imported processes to work in India.
White Bronze, a copper tin alloy, and an alloy based on Cobalt and tin, both based on cyanide havereplaced decorative chrome in limited applications on small parts due to the similarity in outwardappearance, but with limited success due to the polluting nature.
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Viable, technically feasible and cost effective replacements for Chrome Plating are yet to beestablished in India. In the absence of Cost effective Clean Alternative Technologies to Chromeplating the route to reduction and control on chrome pollutants should consist of :
• Better user education. The Act makes Pollution Control Boards/Committees responsible.
• Train Environmental officers of the PCB's/PCC's in Pollution Prevention.
• Environmental officers effect a role change- create family doctor image.
• Create confidence and mutual trust as the first step. Publicise disincentives.
• Make Legislation stricter. Make implementation of discharge norms stricter.
• Make checks and inspections transparent and open.
• Institute incentives and awards for conformity at user level.
• PCB's, Government and banks to coordinate provision of subsidized equipment forimplementation of abatement based systems and processes.
Hexavalent Chromating of zinc and aluminium has been successfully replaced by trivalent chromates,though in India the struggle is with cost issues. Technical viabilities of trivalent chromates are wellproven. It will be a matter of time before trivalent chromates replace hexavalent chromates, withlegislation playing a major role. Hexavalent chromates generate yellow iridescent film, in additionto blue bright, black and green. Trivalent chromates generate a blue bright, black and no othercolour so far. Dyes are used to colour Tri chrome films to yellow, to satisfy traditional attitudes andfixed mind-sets.
World wide, QA and QC managers have learned to accept trivalent blue bright, non yellow iridescentfilms, on the basis of their superior corrosion resistance. In fact, a yellow iridescent film is nowsuspect, as it is possible only from hexavalent solutions which are fully banned in Europe as a resultof the E.U's ELV act that restricts more than 2 grams hexavalent Chrome per car, and a completeban on chrome, hex or tri, 2007 onwards.
Chromic acid based polishes for copper and brass continue to remain in use due to convenience andtraditional mindset. The alternative is Peroxide based polishes which have yet to find a niche inIndia. The metallic sludge generated is recyclable and no hazardous material is generated.
Cyanides are categorised hazardous, dangerous and have been the subject of International concernand legislation. Cyanide usage is being gradually phased our worldwide. China is the latest country,in 2002, to lay down a two year time frame for the banning and complete elimination of cyanideusage in plating operations by 2004. This very progressive act of laying down a time frame for thecomplete elimination of cyanide usage in China has been accompanied by an intense determinedcampaign of educating users on the alternatives available, and their manner of adoption and continuedsuccessful usage. There are several types of cyanide based plating processes used in India i.e. Gold,Silver, Copper, Brass, Bronze and Zinc.
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There are several alternatives to cyanide silver plating.
• Thiosulphate based which is a sensitive process. Hence, partly viable,
• Trimetaphosphate based for magnesium base metal only,
• Iodide based which is costly and so have limited viability.
The major issues with the three listed processes were low shelf life of the additives, lack of indigenousavailability, expensive, poor brightness, poor tarnish resistance and poor adhesion. The iodide bathwas found partly acceptable for functional plating.
Patented Succinimide based solutions are available for indigenous usage. Their limitation is poortarnish resistance, low shelf life of the additives with high cost. The process produces bright andlow stress deposits that permit practical implementation and make for viablility in India for bothdecorative and functional applications.
Gold is traditionally plated from cyanide-based solutions. Successful Sulphite based Gold platingsystems have been around for the last twenty years, in India too, and are viable for both functionaland decorative application. The traditional mindset of the Indian decorative and industrial userprevents ready acceptance. Education and training are the keywords to successful implementationof Sulphite based systems in place of cyanide gold plating systems. Copper has been plated out ofcyanide-based solutions since very beginning. Proprietary Alkaline Non-Cyanide solutions havebeen patented and are a technical success. Cost issues and shelf life issues remain to be sorted out.Pyrophosphate solutions have in successful use worldwide since last forty years. Acid Sulphatesolutions are successful and in use for fifty years. It is only on zinc die-castings that alkaline cyanidebased solutions are actually required. Here too newly patented alkaline cyanide free solutions providea ready answer. But due to the absence of legislation banning cyanide this cyanide-based practicecontinues. While it is technically feasible to eliminate cyanide, legislation driven, education aidedpromotion are needed to actualize the move away from cyanide.
Brass too has traditionally been plated from cyanide solutions. There are reports of dull acid basedbaths, but no successful non-cyanide bright solution has been made possible. There are reports ofsuccessful lab based non cyanide solutions which expect to see the light of the day possibly in 2005.
ZINC PLATING. CLEAN VIABLE PROVEN ALTERNATIVES TO CYANIDE
The primary function of zinc plating is protective. Zinc plate over steel protects by sacrificialcorrosion. Zinc, the nobler of the two metals corrodes preferentially, protecting the steel. The metalzinc is plated over iron and steel accounting for 95 percent of zinc plating applications. The majorityof zinc continues to be plated out of Cyanide based electrolytes which retain their popularity due tohistorical reasons.
Would wide environmental awareness has led to the development of Clean Technologies whichmatured while opinions against cyanide usage were hardening. Increasing environmental pressure,legislation and proactive implementation played the major role in aiding the direction.
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There are four zinc Plating systems in use in India today.
• Cyanide Zinc Plating;
• Acid Zinc Plating;
• Alkaline Non-cyanide Zinc Plating; and
• Acid Sulphate based Zinc Plating.
Cyanide Zinc Plating
• Current Efficiency 45 to 75%
• User Friendly, simple to use
• Treated Sludge contains virtually indestructible Ferricyanides. Very difficult to dispose.
• Categorised Hazardous worldwide
• Proven Environmentally unfriendly
• Future outlook-Poor
Acid Zinc Plating
• Current efficiency 98 percent, plates difficult steels easily.
• Productive system for Barrel and rack plating. More expensive than cyanide zinc.
• Poor Deposit distribution characteristics of HCD. LCD, 1:5 average. Wastes zinc.
• Very corrosive to surroundings and equipment.
• Wastewater treatment is simple. The resultant sludge meets environmental norms.
• Future outlook, Short Term replacement for cyanide zinc.
• Long term will give way to Alkaline Zinc and other environmentally friendly economicalreplacements for cyanide zinc.
Alkaline Non -Cyanide Zinc Plating. (The ANC System)
• Environmentally friendly clean alternative technology.
• Simple one step wastewater treatment.
• Fully recyclable treated sludge. No dumping and Reuseable.
• User friendly. Needs only two basics-Caustic soda and zinc.
• Excellent throwing power, Excellent levelling, Uniform deposit all over.
• Deposit Distribution ratio. HCD:LCD 1:1.15
• Bright deposits, Excellent chromate receptivity.
• Requires Pretreatment, clean surfaces, regular filtration.
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• Very ductile deposits accept post Plate deformation. Can be bent without zinc flakingoff.
• Economical in actual use. Suits Asian and Indian requirements. Proven technology.
Acid Sulphate based Zinc Plating
• Popular for Continuous wire and strip plating.
• Produces dull to semi bright deposits. Used at high current densities of 50 to 100 ASF.
• Needs high temperature of 60° C to operate, Electricity cost factor.
• Poor metal distribution. Environment friendly.
• Unsuitable for rack or barrel plating.
• Will remain confined to continuous plating of wire and strip.
Of the prominent Clean alternative technologies (CAT), acid zinc plating was introduced nationallyin 1980. In 2003-2004, approximately 30-35 percent of zinc plating is carried out from acid zincsolutions. It took the Indian user a very long time to shed traditional inhibitions and outlook andtake to a different technology. The second CAT to make its mark Internationally was Alkaline NonCyanide Zinc. ANC was introduced in India at the same time. Due to incompatible technology,poor implementation technique and lack of user level interest or motivation, ANC never took rootin India.
The plus points on ANC Zinc are well known. These are:
• Environmentally friendly, economical and user friendly.
• Excellent metal distribution values of 1:1.15 HCD:LCD. Bright and well levelled.
• Excellent deposit ductility, accepts post plate deformation.
• Active deposits accept all chromate conversion coatings.
• Summer proof. Works up-to 52°C with ease.
In spite of these well-known advantages, ANC was not preferred in previous years. A look at thedevelopment of ANC system and the course of events will add to clarity. Development of earlyANC systems are:
• Generation One: Primary zincate. Powdery white deposits. 1950's
• Generation Two: Early 1957. Dull to Semi Bright deposits.
• Generation Three: 1965. Bright deposits. Unstable chemistry. Poor distribution.
• Generation Four: Bright. Latent Blistering prone unstable Chemistry. 1970's
• Generation Five: Narrow operational window. Blister prone, Poor stability. Poor depositdistribution. Chelated, making wastewater treatment difficult. 1980's
• Generation Six: Stable. New Chemistry. Bright. No defects. Environmentally acceptable.
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Negative attributes of previous ANC systems are :
• Dull, spongy and non-adherent deposits
• High stress cracking
• Poor temperature tolerance beyond 25°C
• Post plate blisters
• Poor plate distribution. HCD:LCD 1:5
• Strongly chelated bath
• Poor chromate acceptability
• Intolerance to brightener overload
• Blistering
• Narrow operating chemistry range
• Non-levelling chemistry
• Porous high carbon deposits
• Narrow operational window
- Generation 1
- Generation 2, 3, 4
- Generation 1, 2, 3, 4
- Generation 2, 3, 4, 5
- Generation 2, 3, 4
- Generation 2, 3, 4(Wastewater treatment issue)
- Generation 3, 4
- Generation 2, 3, 4, 5
- Generation 3, 4, 5
- Generation 2, 3, 4
- Generation. 1, 2, 3, 4
- Generation 3,4, 5
- Generation 2, 3, 4
New, the 6th generation ANC Process has following features:
• Alkaline Non-Cyanide Zinc evolved into a trouble free economical zinc plating technique.
• User friendly 6th generation, globally proven technology now available in India.
• Ideally designed for though Indian work conditions. Worker proof, easy to use.
• No blisters, ductile, bright, high levelling. Excellent LCD throw and distribution 1:1.15.
For the reasons cited above, ANC zinc did not gain ready acceptance in the developed countriesthat continued to use it till the 6`h generation technology came along and was accepted.
ANC Zinc (Operating window)
Bath composition range
• Zinc as metal
5.5 to 27 g/1
• Caustic soda
85 to 150 g/l
• Current density
5 to 65 ASF
• Voltage
Rack bath 3 to 5V Barrel bath: 5 to 9
• Barrel RPM
6 to 7
• Solution cooling
Optional, but recommended for economy
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• Rack plating agitation
• Preferred Temperature
• Solution Filtration
• Tanks and filter
• Anode baskets and anodes
Moving cathode or solution circulation byeductors.
24 to 34°C, Tolerance 12 to 52°C
Essential
Mild steel
Mild steel
These conditions are flexible and very tolerant to human error factors making ANC a viableproposition for the work conditions found in India. A number of users and interested opinion makershave wondered whether it is possible to "Slide Convert" a cyanide-based bath to ANC. The answerhas always been a strict "No" on account of the following long-term operational reasons.
1) The solution is usually over 4 to 15 years old, full of carbonates which slow it down.
2) The solution has never in it operational life been filtered and possible has large impuritylevelled both soluble and insoluble.
3) There are insoluble ferricyanides in solution that can affect the new operation adversely.
So while there is some money value left in the solution, due to its condition, the PCB/PCC authoritiesmay permit time for a phased change over which essentially consists of working the solutiondownwards till most of the usable Zinc and Cyanide are consumed. Then the remaining low levelsof cyanide are neutralized with bleaching powder, the remaining solution then consisting of Causticsoda is used as a soak cleaner or a pre soak. Anodic cleaning is generally never a good directionwith such a solution. In this way the entire value in the cyanide solution is consumed productivelyand existing resources are utilized productively. The used solution is not converted to ANC. It isused up and consumed fully.
Low cost of change over from Cyanide zinc plating to ANC is described inn the example below.Plating Tank, bus bars and rectifier is re used. Additional machinery and chemicals for 1200 litresplating bath are approximated below as an example.
• One Anodic cleaning tank Rs. 3,000.00
• One Plating filter Rs. 13,000.00
• 3 rinsing tanks/drums Rs. 2,000.00
• Steel anode baskets and anodes Rs. 1,600.00
• Caustic soda (150 kilos) Rs. 3,000.00
• Zinc (15 kilos) Rs. 1,200.00
Total Cost of change over Rs. 23,800.00
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FactorsPretreatmentChemistryElectricityZinc AnodePost TreatmentTotal Rs.
Acid Chloride zinc ANC333.00 333.00642.00 635.00192.00 150.00770.00 595.00139.00 139.00
2076.00 1852.00
Zinc Metal A Salt 100 ml @ Rs. 62/litre Rs. 6.20
B Salt Non Boric 240 g @ Rs. 32/kg Rs. 7.80
Boric Acid 34 g @ Rs. 60/kg Rs. 2.04
Basic Solution Cost
Brightener 1 ml @ Rs. 95.20/litre Rs. 0.12
Wetter 40 ml @ Rs. 89.60/litre Rs. 4.48
Proprietary additive Cost
TOTAL SOLUTION COST
Rs. 15.92/litre
Rs. 4.60/litre
Rs. 20.62/litre
COST COMPARISON
The economics of plating from acid Zinc solution are compared to an ANC solution.
Component: 2" and 0.75 drum closures and flanges plated in barrels. Plating standard : minimum 3microns in LCD.
PLATING COSTS (Rs. Per tonne)
B)
PRODUCTIVITY
Loads per dayQuantity per load. Kilos.No of BarrelsDaily Production outputDaily Rejection/Replating
18 2430 30
2 21.04 MT 1.44 MT0.04 MT 0.01 MT
Variance
-4.5%+ 0.36 MT
C) SUMMARY
Pl'ating Costs (Rs.) 1991.00 1901.00Output per day 1.04 MT 1.44 MTProductivity Increase - 33%
Conclusion : At less cost ANC plates 33 percent more material in the same time.
The cost of Making up 1 litre new Acid Zinc Plating Solution
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Estimated Costs of running Acid Zinc solution under production conditions (Basis 1000 squarefeet of Zinc Deposit 12.5 microns thickness)
Zinc Metal deposited 10.50 kg @ 75 per Kg Rs. 788.00
Basic Chemicals : A Salt 2.5 litre @ Rs. 62/litre Rs. 155.00
B salt 5 Kg @ Rs, 32 per kg Rs. 160.00
Acid Zinc additives. Brightener. 1.7 litre @ Rs. 95/litre Rs. 166.60
Wetter 1.7 litre @ Rs. 89.60 litre Rs. 152.32
Total cost. 12.5 microns zinc over 1000 sq. ft. zinc. Rs. 1421. 32
Total Cost of Making up 1 litre Cyanide Zinc Plating Solution
Zinc Oxide 43 g @ Rs. 122/kg Rs. 5.25
Sodium cyanide 90 g @ Rs. 100/kg Rs. 9.00
Sodium Hydroxide 35 g @ Rs. 20/kg Rs. 0.70
Basic Solution Cost Rs. 14.95
Brightener 5 ml @ Rs. 66/1 Rs. 0.33
Purifier 2 ml @ Rs. 35/1 Rs. 0.07
Proprietary additive cost. Rs. 0.40
Total Solution cost: 14.95 + 0.40 Rs. 15.35 per litre
Estimated Costs of running Cyanide zinc solution under production conditions (Basis 1000square feet of Zinc deposit 12.5 microns thickness)
Zinc Metal deposited 10.25 kg @ Rs. 75 per kg Rs. 788.00
Basic Chemicals. Sodium Cyanide. 2.2 kg @ Rs. 120/kg Rs. 264.00
Caustic soda 2 kg @ Rs. 18/kg Rs. 36.00
Zinc Oxide 0.5 kg @ Rs. 70/kg Rs. 35.00
Zinc Purifier. 1 litre @ Rs. 80/litre Rs. 80.00
Zinc Brightener 2.1 litre @ Rs. 75/litre Rs. 158.00
Total cost (12.5 microns zinc over 1000 sq. ft. area) Rs. 1361.00
Total Cost of making up a ANC Zinc plating solution.Method A : Using readymade zincate concentrate. Time required 6 hours to production.
Zincate Concentrate 250 ml @ Rs. 30/litre
Rs. 7.50
ANC additives 10 ml @ Rs. 190/litre
Rs. 1.90
Total Cost of ready to use zincate route
Rs. 9.40 for 1 litre ANC solution
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Method B : Using Dissolution of zinc anode slabs in caustic to make zincate (3-4 days toproduction.
Caustic soda flakes 130 g @ Rs. 18 per kg Rs. 2.34
Zinc slab 13 g @ Rs. 75 per kg Rs. 0.98
Zincate Cost Rs. 3.33
ANC additives 10 ml @ Rs. 200/litre Rs. 2.00
Total Cost (Zincate from anode dissolution route) Rs. 5.23 for 1 litre ANC Solution
Estimated Costs of running ANC solution under production conditions. Basis. 1000 squarefeet of Zinc Deposit 12.5 microns thick.
Zinc Metal deposited 8.3 kg @ 75 per kg Rs. 622.50 Caustic Soda Consumed.
4 kg @ Rs. l 8 per kg Rs. 72.00
ANC Additives. 3.5 litre @ Rs. 200 per litre Rs. 700.00
Total Cost of ANC system (1000 sq. Ft 12.5 micron Zn). Rs. 1395.00
Comparative statement of costs
Process Make up cost/litre (Rs.) Usage cost (12.5 micron 1000 sq ft.) (Rs.)
Acid zinc 20.62 1421.32
Cyanide Zinc 15.65 1361.00
ANC Zinc 9.40 1395.00
ANC Zinc 5.23 1320.00
The electricity cost difference in the three processes is summarized in the example. 1000 amperesare passed continuously for 8 hours a day for 26 days. Barrel or Rack.
Process Barrel Plating Rack Plating Barrel Plating Rack PlatingTotal KWH Total KWH cost Costconsumed consumed
Acid Zinc @ 10 volts @ 6 volts @ Rs. 4/KWH @ Rs. 4/KWH299 KWH 179 KWH Rs. 1196 Rs. 716.
Cyanide Zinc @ 14 Volts @ 12 volts @ Rs. 4/KWH @ Rs. 4/KWH418 KWH 359 KWH Rs. 1672 Rs. 1436
ANC Zinc @ 7 volts @ 3.5 volts @ Rs. 4/KWH @ Rs. 4/KWH209 KWH 106 KWH 836 Rs. 424
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Summary of Costs and Expenses
— The acid process solution make up cost is highest. Usage cost is highest.
— The cyanide process make up cost is lower than acid Zinc. Usage cost is less than acidZinc.
— The ANC make up cost is the lowest. Usage cost is lowest.
Electricity Cost factor is an important element.
• The most expensive system is the cyanide process.
. The second most expensive system is the acid based system.
• The least expensive system is the ANC system.
The fact that the ANC bath is a highly conductive non-corrosive electrolyte which enables currentpass with least resistance, great ease and has the least heating up factor per KAH of current passedmakes it least expensive.
Acid Zinc electrolytes are less conductive and exhibit higher resistivity than the ANC electrolyte.Acid Zinc baths heat up, leading to side effects like oiling out of the low cloud point organicadditives requiring shut down to set right the organic system imbalance, production loss and costlymaintenance additions to replace the lost organic additives.
The cyanide electrolyte also heats up similarly causing the decomposition of cyanide and the organicadditive. This leads to excess operating costs at high temperature.
TECHNICAL ADVANTAGES (Deposit Micro-structure)
I) Cyanide BathLaminar Microstructure
2) Acid Zinc BathLaminar and scattered microstructure ` /
3) ANC BathColumnar Microstructure
The effect of the Columnar microstructure produces Chromate coatings that are thicker and exhibitexcellent anchoring to the plated zinc base and effectively result in 25% superior corrosion resistanceas compared to the Laminar structures due to the lower porosity and thicker films.
Work Atmosphere and Life of Equipment
The corrosive fumes and spray from acid baths shorten the useful life of all the surrounding equipmentby 60%. A plating machine comes up for replacement within 18 to 20 months when installed in an
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acid zinc plant. The same machine is seen to last for five to six years in a ANC Zinc plant. Machineryis expensive and frequent replacement costs have to be borne by the user. The replacement cost getsadded to the cost of operation and is a consequence of the corrosive nature of Acid Zinc Electrolytes.
Sludge that is generated from effluent treatment is a burning issue. Cyanide Zinc sludge containsFerricyanides and is hazardous in nature. This sludge is not allowed to be dumped in the authorizeddumping pits as it is not certified safe for landfill use. It is necessarily stored in factories.
The sludge from ANC solutions is simply dried and zincate cake that is non hazardous, containszinc and is re-cycleable. The Zincate sludge is converted to Zinc Sulphate and used as a micro-nutrient in deficient soils of India. The Ministry of Agriculture has identified this deficiency andpromotes the zinc sulphate, route to overcome this deficiency. When the sludge is treated withhydrochloric acid it forms zinc Chloride used as a welding flux and in batteries.
Plating Solution CompositionANC
ACID ZINC
Caustic 125 g/l
Total Chloride 135 g/l
Zn as metal 12 g/1
Zn as metal 25-35 g/1
pH 11-12 pH 4-4.5
Composition of first Rinse
Caustic soda 0.3-1.0 g/1
Total C 12 1-3g/1
Zn As metal 0.05 g/l
0.5-1.0g/í
Alkali Usage for EOP treatment.
NaOH powder 7-8 kg/MT NaOH 30-45 kg/MT
ANC needs less caustic to treat and causes less sludge to handle.
ANC : Clean Alternative Technology : Benefits and advantages.
• Uniform Deposits: This property is unique to the ANC process and it is directlyresponsible for savings in electricity and Zinc metal up to 10%. More profits to theplater.
• This characteristic of very good LCD throw is directly responsible for increasingproductivity up to 33 percent. Lower overheads and higher productivity mean savings.
• The absence of Cyanide in ACF means there is no need to store the sludge after treatment.The sludge can be sold to Zinc sulphate manufacturers and recycled as a soil Nutrient.
• Environmentally friendly and proven in India since 1997.
• Less costly, user friendly, improves quality and increases productivity.
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ANC process has been proven countrywide over 180 users in the tiny, small, mediumand large scale level.
• Now legislation will motivate the move away from cyanide.
Examples of Pollution Prevention from Japan, China and Malaysia
• Japan has over 70% of platers using ANC since 12 years
• Singapore has only ANC users
• Malaysia has 50% ANC users
• China has declared a progressive cut down of Cyanide users. 90% are in the main list forshift away to ANC Zinc.
ANC future in India.
The ANC process has already seen moderate success in India. Nationally there are over 180 users ason date. It is possible to evaluate the usefulness of ANC, a cleaner preferred alternative to Cyanideand Acid Zinc plating and promote this system at national level in the role of a clean alternativetechnology.
Promotional Method
• Motivating SPCBs/PCCs should be the first thrust by the Ministry of Environment andForests and the Central Pollution Control Board. The second thrust has to come fromwithin the finishing community who will want to implement ANC over the alternativesavailable.
• Demo Units, Model Plants, small subsidies are proven examples of the carrot theGovernment has to offer to platers for long term benefit.
• Strict policy implementation will have its own long term rewards.
The China Government allows a big subsidy with frequent monitoring to bring about the awarenessaspect. Field officers run camps in industrial areas for entrepreneurs.
The TNPCB, in India has its Education wing and conduct camps to teach and motivate small andmedium scale units to conform to the law. Other state pollution control boards and pollution controlcommittees can also do it.
Progressive and proactive policies will meet the need of education and Training. Direct benefitswill be a move away from Cyanide as a raw material in plating.
• Judicious use of persuasion, training & legislation will have the desired effect.
• Over 180 users in India continue to use ANC zinc since 1997 onwards on every knownvariety of Mild steel.
• It is entirely possible to completely eliminate cyanide from the workplace.
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WHERE DO WE GO FROM HERE
(A) PROPOSALS TO REMOVE CYANIDE FROM THE PLATING WORKPLACE
1) Identify 6 to 8 cyanide plating units willing to set up CAT systems (ANC) and allow their unitto be a demonstration unit in each -industrialized State.
2) Subsidise capital aspects by the Government i.e. funding in exchange for the demo unit.
3) Pass legislation banning cyanide usage in electroplating with a time frame spelt out as doneby China.
(B) AND ACTION PLAN
4) Educate, train engineers ad scientists of SPCBs and PCCs in the subject. Allocate responsibilityto them.
5) Monitor progress at periodic intervals to ensure time frame is followed.
6) Implement a scheme of awards and tangible rewards for conformity and abatement practice.Both PCB/PCC officers and inductrialists and small platers who implement Clean Technologymust by rewarded in an appropriate manner.
Conclusion:
By imposing tangible enforceable limitations on cyanide usage in Zinc Plating, the ministry willprovide due motivation for enlightened users to move away from Cyanide usage.
In a matter of time, the motivation by the promotion of alternative technologies will have its effecton the Plating world and the cyanide usage in Zinc Plating will fall to desired targeted levels withinthe allotted time frame.
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