lecture 2-8-11-2014
TRANSCRIPT
Lecturer: Dr. Mahmoud Nasr
Sanitary Engineering Department Faculty of Engineering Alexandria University
Zero Liquid Discharge Systems
8th November, 2014
Fertilizer ZLD
Fertilizers
-Fertilizer is a material of natural or synthetic added to the
soil to supply one or more plant nutrients.
-Examples of primary plant nutrients are nitrogen or
phosphorus
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Nitrogen fertilizer
More than 80% of the fertilizers used in Egypt are made up of nitrogenous
fertilizers, particularly urea
Nitrogen fertilizer ZLD
Ammoniacal (NH3-N)
Example:
Ammonium Sulphate
(NH4)2SO4
Ammonium chloride
NH4Cl
Anhydrous ammonia
NH3
Nitrate (NO3−)
Example:
Sodium Nitrate
NaNO3
Calcium Nitrate
Ca(NO3)2
Potassium Nitrate
KNO3
(NH3-N) and (NO3−)
Example:
Ammonium Nitrate
(NH4)(NO3)
Calcium Ammonium Nitrate
CAN
Ammonium Sulphate Nitrate
ASN
Amide fertilizer
Example:
Urea
CH4N2O
Calcium
Cyanamide
CaCN2
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Nitrogen fertilizer
Ammoniacal (NH3-N) - Contain the nutrient nitrogen in the form of ammonium or ammonia. -Except rice, all crops absorb nitrogen in nitrate form. -Resistant to leaching loss, as the ammonium ions get readily absorbed on the colloidal complex of the soil.
Nitrate (NO3−)
-Contain the nitrogen in the form of NO3. -Easily lost by leaching because of the greater mobility of nitrate ions in the soil. -Continuous use of these fertilizers may reduce the soil acidity as these nitrogenous fertilizers are basic in their residual effect on soils.
(NH3-N) and (NO3−)
-Contain nitrogen in both ammonium and nitrate forms. -The nitrates are useful for rapid utilization by crops and the Ammoniacal is gradually available
Amide fertilizer -Are readily soluble in water and easily decomposable in the soil. -Urea is the most concentrated solid nitrogenous fertilizer, containing 46 % nitrogen.
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Nitrogen gas N2
Nitrogen fixation
Organic Nitrogen
Ammonification
Ammonium NH4
+
Denitrification
Nitrite & Nitrate NO2
- & NO3-
Nitrification
Nitrogen Cycle
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Fertilizer
Cattle manure Plants
NH4+ NO2
- NO3
-
NO2-
Denitrification
N2 Fixation (Protein)
Consumption
Leaching
ON
Dec
ay
Nitrogen Cycle
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Sewage
Ammonia NH3
NO2- NO3
- NO2-
N2
Industrial fixation
Denitrification Nitrification
Uptake
Uptake
Nitrogen Fertilizer ZLD system
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Influent
Digester
Effluent with Ammonia
Stripping
Clean effluent
Hot air Nitrogen rich
fertilizer product
Nitrogen fertilizer ZLD system
-Nitrogen fertilizers containing nitrogen as a base element, which is expressed by N2 %.
-Ammonia is considered the main raw material of nitrogenous fertilizers manufacturer.
Ammonia
gas
Reuse
Recycle
- Phosphatic fertilizers containing phosphorous as a base element, which is
expressed by P2O5 %.
- Phosphate rock is considered the main raw material for the production of
phosphate type fertilizers.
- Phosphate fertilizers industry is considered one of the most polluting
industries in Egypt.
- Phosphate fertilizers include single superphosphate and triple
superphosphate. The single superphosphate is a mixture of monocalcium
phosphate and gypsum (available P2O5 almost 16- 22 %), while triple-
superphosphate is composed mainly of monocalcium phosphate (available
P2O5) almost 46 %).
Phosphate fertilizer ZLD
Phosphate fertilizer
Phosphatic fertilizers containing phosphorous as a base element, which is
expressed by P2O5 %.
Phosphate rock is considered the main raw material for the production of
phosphate type fertilizers.
Phosphate fertilizer ZLD
Super phosphate Ca(H2PO4)2
- The most important phosphatic fertilizer in use.
- Contains 16 % P2O5 in available form. - A grey ash like powder with good
keeping or storage qualities. - Hardly moves in the soil and hence
they are placed in the, root zone.
Triple super phosphate - Contains 46 % P2O5. - Suitable for all crops and all soils. - In acid soils, it should be used in
conjunction with organic manure. - Applied before or at sowing or
transplanting.
Fertilizer
Cattle Plants
Phosphate fertilizer
Organic phosphate
Up
take
Inorganic phosphate
Mineralization
Consumption
Death
Leaching & surface runoff
Phosphorus Cycle
Fixed phosphate
Anaerobic Aerobic BOD
Substrate Clarifier
Anaerobic Aerobic
Sludge PAO Fertilizer
Reuse
Biological Phosphorus Removal
Recycle
PO4
PO4
Chemical Phosphorus Removal
- Phosphates are precipitated as calcium phosphate in the second stage
neutralization and clarification at pH range of 8 - 9.
- This demands a very fine, effective and reliable control of lime injection.
Pre-treatment for ZLD
WWTP
Process
Industry, Agric. Treatment
Influent
Effluent
Treated
Recycle
Reuse
Phosphate Fertilizer Manufacturing produce
1) Sulphuric acid
2) Phosphoric acid
3) Single superphosphate (SSP) and Triple superphosphate (TSP)
4) Compound Fertilizers (NPK)
1) Sulfuric Acid
- Sulfuric acid (H2SO4) is used in the phosphate fertilizer industry for the
production of phosphoric acid.
- Sulfuric acid is manufactured mainly from sulfur dioxide (SO2), produced
through the combustion of elemental sulfur.
- The exothermic oxidation of sulfur dioxide over several layers of a
suitable catalyst (e.g. vanadium pentoxide) to produce sulfur trioxide
(SO3) is the most common process in sulfuric acid manufacturing plants
- Sulfuric acid is obtained from the absorption of SO3 and water into
H2SO4 (with a concentration of at least 98 %) in absorbers installed after
multiple catalyst layers.
2) Phosphoric Acid
-Phosphoric acid (H3PO4) is primarily used in the manufacture of
phosphate salts (e.g. for fertilizers and animal feed supplements).
-Two different processes can be used in the manufacture of phosphoric
acid.
-In the first process, known as the thermal process, elemental
phosphorous is produced from phosphate rock, coke, and silica in an
electrical resistance furnace and is then oxidized and hydrated to form the
acid.
-The second type of process, known as the wet process, involves digesting
phosphate rocks with an acid (e.g. sulfuric, nitric or hydrochloric acid).
3) Phosphate Fertilizers (SSP / TSP)
-Phosphate fertilizers are produced by adding acid to ground or pulverized
phosphate rock.
-If sulfuric acid is used, single or normal, superphosphate (SSP) is
produced, with a phosphorus content of 16–21 % as phosphorous
pentoxide (P2O5).
-If phosphoric acid is used to acidulate the phosphate rock, triple
superphosphate (TSP) is produced with a phosphorus content of 43–48 %
as P2O5.
4) Compound Fertilizers (NPK)
-Compound fertilizers are a large group of products, varying based on the
particular nitrogen / phosphorus / potassium (N/P/K) ratios.
- This can be achieved by using two different routes, namely production
by the nitrophosphate route, and production by the mixed acid route.
-National Fertilizer Public Company Ltd of Thailand (NFC) installed modern
NPK fertilizer plant including a phosphoric acid manufacturing unit within
the complex.
Compound Fertilizers (NPK)
-Ammonium phosphates are produced by mixing phosphoric acid and
anhydrous ammonia in a reactor to produce a slurry. This is the mixed-
acid route for producing NPK fertilizers; potassium and other salts are
added during the process.
-Nitrophosphate fertilizer is made by digesting phosphate rock with nitric
acid. This is the nitrophosphate route leading to NPK fertilizers; as in the
mixed-acid route, potassium and other salts are added during the process.
-Nitrophosphate fertilizers are also produced by the mixed-acid process,
through digestion of the phosphate rock by a mixture of nitric and
phosphoric acids.
Environmental issues associated with phosphate fertilizer
plants include the following:
1· Air emissions
2· Wastewater
3· Hazardous materials
4· Wastes
5· Noise
1· Air emissions
A) Sulphuric Acid Production: The major polluting parameters are sulphur dioxide,
sulphur trioxide and acid mist. Emissions occur during sulphur burning, in converters and
absorption.
B) Process Emissions (Phosphoric Acid Production): (a)The wet process, where phosphate
rocks are digested with an acid (e.g. sulfuric, nitric or hydrochloric acid). (b) The thermal
process, where elemental phosphorous is produced from phosphate rock, coke, and silica
in an electrical resistance furnace and is then oxidized and hydrated to form the acid.
The main emissions are gaseous fluorides and dust. Gaseous fluorides such as silicon
tetra-fluoride (SiF4) and hydrogen fluoride (HF) can be major emissions from wet process
acid production.
The reactor in which phosphate rock is reacted with sulfuric acid is the main source of
emissions.
C) Process Emissions (Superphosphate Phosphate Fertilizer Production):
Sources of emissions at a single superphosphate (SSP) plant include rock unloading and
feeding, mixing operations (in the reactor), storage (in the curing building), and fertilizer
handling operations. The major polluting parameters are total suspended particulates,
fluorides, sulphuric acid mist, dust fall and inhaled dust.
Emissions of fluorine compounds and dust particles occur during the production of
granulated triple superphosphate (TSP). Silicon tetrafluoride (SiF4) and hydrogen
fluoride (HF) are released by the acidulation reaction and they evolve from the reactors,
granulator, and dryer.
Generally; Dust emissions may be generated during unloading, handling, grinding, and
curing of phosphate rock, in addition to granulation and crushing of superphosphates.
D) Process Emissions (Compound Fertilizer Production NPK): Air emissions from NPK
include ammonia emissions, nitrogen oxides (NOX), mainly NO and NO2, nitric acid,
fluorides, aerosol emissions, including ammonium nitrate (NH4NO3), ammonium
fluoride (NH4F), and ammonium chloride (NH4Cl).
2· Wastewater Effluent
A) Effluents (Phosphoric Acid Production): It may contain a considerable amount of
impurities, such as phosphorus and fluorine compounds, cadmium and other heavy
metals, and radionuclides.
B) Effluents - Superphosphate Fertilizer Production: Contaminants may include
filterable solids, total phosphorus, ammonia, fluorides, heavy metals (e.g. Cd, Hg, Pb),
and chemical oxygen demand (COD).
C) Effluents - Compound Fertilizer Production: Effluent from NPK facilities employing
the nitrophosphate route may contain ammonia, nitrate, fluoride and phosphate.
Ammonia is found in the effluents of the condensates of the ammonium nitrate
evaporation or the neutralization of the nitro phosphoric acid solution.
D) Process Wastewater Treatment: It includes filtration for separation of filterable
solids; flow and load equalization; sedimentation for suspended solids reduction using
clarifiers; phosphate removal using physical-chemical treatment methods; ammonia
and nitrogen removal, dewatering and disposal of residuals in designated waste
landfills.
E) Other Wastewater Streams & Water Consumption
Another contaminated stream may result from condensers, heat exchangers and gas
scrubbers. It was found that the main sources of pollution are attributed to the washing
water of the scrubbing towers.
Through evaporation and recycling, contaminant concentrations in water can reach
several grams per liter of phosphates and fluoride. Additional elemental contaminants
in pond water which originate in phosphate rock are arsenic, cadmium, uranium,
vanadium, and radium.
3· Hazardous Materials
Phosphate fertilizer manufacturing plants use, store, and distribute significant amounts of
hazardous materials (e.g. acids and ammonia).
4· Solid wastes
Phosphogypsum is the most significant by-product in wet phosphoric acid production.
Phosphogypsum contains a wide range of impurities (residual acidity, fluorine
compounds, trace elements such as mercury, lead and radioactive components). The
vanadium content of the V2O2 catalysts can be reclaimed for further use.
5· Noise
Noise is generated from large rotating machines, including compressors and turbines,
pumps, electric motors, air coolers, rotating drums, spherodizers, conveyors belts, cranes,
fired heaters, and from emergency depressurization
Service Units and Related Pollution Sources
A) Boilers: Boilers are used to produce steam for: Heat supply to the processes,
reaction (steam reforming) and CO shift converter (in ammonia production and
other processes utilizing steam). Electric power generation.
B) Water Treatment Units: Water Softening for medium hardness water, Water
softening for very high bicarbonate hardness, Water Demineralization
C) Cooling Towers: Cooling towers provide the means for recycling water and thus
minimizing its consumption.
D) Compressors: Several types of compressors are needed in the fertilizers plants,
including the ammonia, steam, gas and air compressors.
E) Laboratories: Research laboratory, Quality control laboratory, Environmental
laboratory
Service Units and Related Pollution Sources
F) Workshops and Garage
G) Storage Facilities: Acids such as sulphuric or nitric or phosphoric acids are stored in
large capacities tanks
H) Wastewater Treatment Plants
The effluent streams can be characterized as either a phosphoric acid effluent or an
ammonia effluent. The phosphoric acid effluent is high in fluoride concentration, low in
pH, high in phosphate and in suspended solids. The two-stage fluoride removal process
of lime precipitation followed by alum-polyelectrolytes flocculation and sedimentation
was found to be workable.
The other effluent type is characteristic of ammonia production and ammonia
containing products. These effluents require a pH adjustment and settling.
Example of Chemical Fertilizer Industry
1. Mangalore Chemicals & Fertilizers Limited, with a turnover Rs. 2,523.83
crores (2010–11), is the only manufacturer of chemical fertilizers in the state
of Karnataka, India.
The company deals with fertilizers like Diammonium phosphate.
The company has capacity to manufacture 3,79,500MT of Urea, 2,55,500MT of
Phosphatic fertilizers.
The Phosphatic plant was designed and engineered by Toyo Engineering
Corporation, Japan.
As an ISO 14001 certified Company, the company installed waste water
recovery facility to treat, recycle and reuse the entire quantity of sewage and
process effluents, thereby achieving zero liquid effluent discharge
Zero Discharge Technologies
These ZLD Systems can recycle more than 90 % of waste water.
Zero Discharge Technologies:
- Reverse Osmosis - Reverse osmosis & microfiltration treatment – Nanofiltration -
Ion Exchange Treatment - ZLD Water Softener
ZLD Application Areas:
Metals & Mining- Power Generation- Alumina Industry- Fertilizer production-
Textile Production- Food & Beverage factory- Dairy production- Waste
management- Oil & Gas- Environment- Hydrocarbon Processing- Pulp and Paper-
Chemical Processing- Pharmaceutical
Assignment Search for a published manuscript with a topic of Zero Liquid Discharge systems. Every student will discuss the paper within 5 min, as follows: Introduction (1 min) Materials and methods (1 min) Important results (1 min) Advantages (1 min) Disadvantages (1 min) Then, Q&A with other students for 5 min