PrefaceThis report is about the learning outcomes of internship in D.G. Cement factory (D.G.K.C.C) covering details of its environment, process, operations and other technical information. Its been very benefiting and rewarding for me as I got a lot of practical experience and it provided me an excellent opportunity to let me have exposure to all industrial equipment and particularly to my concerned Chemical equipment and systems. After completing this practical training, I am supposed to write a report which will exhibit what I learnt from this practical training and how much I have been able to gain knowledge from the trained man power of this factory.

The essence of this report will be to describe the working philosophy of the system which is being employed in the factory and not the sheer working of all the equipment as this is a report which is meant for only to tell the concerned people what I used to do during our stay at the factory. I am also working on a working manual for our convenience in future which will more or less be describing the functioning of chemical and chemical equipment and processes. However, I will explain briefly the some processes where it will be deemed fit. I will try to cover all aspects with brevity using required block and flow diagrams and tables because we all know that one picture or block diagram is worth one million words.

May God bless us with HIS countless divine favors and help us making Pakistan one of the economic giant of the world and an impregnable state. (Ameen)

Acknowledgment

I have learned that success is to be measured not so much by the position that one has reached in life as by the obstacles which he has had to overcome while trying to succeed.

Booker T. WashingtonI like to thank our Gracious Allah Almighty, Who helped me to overcome all the obstacles that came my way during the completion of my report. During my Internship, I received encouragement, support and practical help from my teachers. It is a pleasure to acknowledge their efforts and to show my gratitude.

I am greatly in debt to Shafiq Sahab(Production Manger) for giving me remarkable suggestions, encouragement and moral support throughout the internship. I am also thankful to my entire beloved teachers who provided me valuable literature which help me a lot in completing my internship. May Allah bless all of my well-wishers with great pleasures and long life!

LIST OF TABLES

TUTable 1: Chemical analysis of water ...........................................................................23TUTable 2: Chemical composition of limestone...............................................................25

TUTable 3: Chemical composition of clay................................................................26TU Table 4: Chemical composition. of silica sand..27TU Table 5: Chemical Compositon of iron ore....................................................................28TU Table 6: Parameters for opc & src.................................................................................30TU Table 7: Kiln Calculations..............................................................................................38TU Table 8: Chemical reaction of kiln ..................................................................................41

Table.9: Composition Of Clinker.41

TUTable.1: Ist chamber in grinder .................................................................................... 24T Table 10: 2nd chamber in grinder ......................................................................................24Table of CONTENTS

PREFACE ...........................................................................................................1ACKNOWLEDGEMENT...................................................................................2LIST OF TABLES ..........................................................................................31. Introduction ....52. History of Cement ..53. Cement Industry in Pakistan..64. D.G Khan Cement Factory 74.1 Types of Cement Produced84.2 Different Section In D.G.K.C.C...94.3. Quarry.9 4.3.1 Mining..10 4.3.2 Mechanical...11 4.3.3 Transportation..144.4. Utility. ....15 4.4.1 Raw Water Filter..16 4.4.2 Water....174.5. Piling and Milling.....18 4.5.1 Piling....18 4.5.2 Milling..19 4.5.3 Raw Material Transportation22 4.5.4 Preparation of Raw Material.....23 4.5.5 Raw Mill244.6. Coal Mill...274.7. Cyclone Preheating..284.8. Rotary Kiln...30 4.8.1 Process...32 4.8.2 Quality of Clinker354.9 Cement Mill.36 4.9.1 Gypsum37 4.9.2 Grinding37 4.9.3 Operation of Cement Mill.40 4.9.4 Packing Section........404.10. Quality Control........41 4.10.1 Raw Mix Proportion.........41 5. Source of Pollution ......42 6. Special Features of D.G Cement.....42 7. Conclusion.43 8. Recommendations........439. Bibliography.431. Introduction

Cement is 'a substance applied to the surface of solid bodies to make them cohere firmly' or, more specifically, 'a powdered substance which, made plastic with water, is used in a soft and pasty state (which hardens on drying) to bind together bricks, stones, etc in building' (SOED). Portland cement is a calcined material comprising lime and silicates which is mixed with sand and stone and, upon hydration, forms a plastic material which sets and hardens to a rock-like material concrete. Confusion between cement and concrete is endemic among the uninitiated.

Limestone (calcium carbonate) and other materials containing appropriate proportions of calcium, silicon, aluminium, and iron oxides are crushed and milled to a fine flour-like raw meal. This is heated in a kiln, firstly to dissociate calcium carbonate to calcium oxide with the evolution of carbon dioxide, and then to react calcium oxide with the other components to form calcium silicates and aluminates which partially fuse at material burning temperatures up to 1450C. The reaction products leave the kiln as a black nodular material, clinker. The clinker is finally interground with a small proportion of gypsum (to control the rate of hydration) yielding a fine product which is cement.

2. History of Cement

One of the most popular early quick drying cements was known as Roman Cement. It was developed in the 1780s by a man named James Parker, and was manufactured by burning a specific type of clay deposit known as septaria, a substance which contains both clay and chalk, and grinding the post firing material down into a very fine powder. When combined with sand this cement made for a very quick setting mortar which could dry in just 15 minutes.

The next major development in cement technology was a strong type of hydraulic cement. Hydraulic cement is a type of cement that needs to be mixed with water in order for it to set, and

Portland cement, a hydraulic cement which is still in popular use today was invented by Joseph Aspdin who patented the product in 1824, however it was his son, William Aspdin who developed the strength and durability of Portland cement by adding a compound called alite to it, which is still used to strengthen cement today.

William had a difficult time at first convincing people of the usefulness of his product, as it contained much more lime than the original Portland cement, and so needed to be fired at much higher temperatures. Also, due to its hardness, the resulting clinker developed during the firing process caused problems during grinding because it would wear down the millstones much more quickly than other types of cement.

Portland cement is now the most popularly used type of cement in the world, although since the 19th century, many different types of cement have been developed for use in different kinds of applications. A few of these cements include expansive cements, which do not shrink during drying like typical hydraulic cements, colored cements, for decorative uses, and masonry cements, which have been developed for used solely in masonry applications and which are not suitable for use in concrete.Portland cement is the most common type of cement in general use around the world, because it is a basic ingredient of concrete, mortar, stucco and most non-specialty grout. It is a fine powder produced by grinding Portland cement clinker (more than 90%), a limited amount of calcium sulfate which controls the set time, and up to 5% minor constituents (as allowed by various standards).As defined by the European Standard EN197.1, "Portland cement clinker is a hydraulic material which shall consist of at least two-thirds by mass of calcium silicates (3CaO.SiO2 and 2CaO.SiO2), the remainder consisting of aluminum- and iron-containing clinker phases and other compounds. The ratio of CaO to SiO2 shall not be less than 2.0. The magnesium content (MgO) shall not exceed 5.0% by mass.

Portland cement clinker is made by heating, in a kiln, a homogeneous mixture of raw materials to a sintering temperature, which is about 1450 C for modern cements. The aluminum oxide and iron oxide are present as a flux and contribute little to the strength. For special cements, such as Low Heat (LH) and Sulfate Resistant (SR) types, it is necessary to limit the amount of tricalcium aluminates (3CaO.Al2O3) formed. The major raw material for the clinker-making is usually limestone (CaCO3) mixed with a second material containing clay as source of alumino-silicate. Normally, an impure limestone which contains clay or SiO2 is used. The CaCO3 content of these limestones can be as low as 80%. Second raw materials (materials in the raw mix other than limestone) depend on the purity of the limestone. Some of the second raw materials used are: clay, shale, sand, iron ore, bauxite, fly ash and slag.

3. Cement Industry in PakistanThe cement industry in Pakistan has come a long way since independence when the country has less than half million tons per annum production capacity. By now it has exceeded 10 million tons per annum as a result of establishment of 25 manufacturing facilities and expansion by the existing units. Pakistans cement market is divided in to two distinct regions, north and south. The northern region comprises of Punjab, NWFP, Azad Kashmir and upper part of Baluchistan. Whereas, the southern region comprises of entire province of Sindh and lower part of Baluchistan.

Traditionally, the southern region has always been surplus in cement production but with the establishment of more plants in the northern parts of the country the region has become almost self-sufficient in supply of cement.

The cement industry in Pakistan faces two serious threats: closure of units based on wet process and poor cash flow rendering the units in capable of debt servicing due to increasing cost of electricity, furnace oil etc. With the increasing cost of furnace oil the increase in electricity tariff has also become inevitable.

Pakistan has remained a net importer of cement but due to privatization of units under state control and subsequent expansion programs by the new owners supported by financial aid has pushed the industry to a point where the country is bound to reach an oversupply situation. However, the recent increased in energy cost provides opportunity for the efficient unit based on dry process to sustain the situation for a relatively longer period. It would also be possible because the expansion by the existing units and establishment of new units are being delayed.

4. D.G Khan Cement Factory

D.G Khan Cement is situated at 39 kilometers northwest in Mouza Sattai Khofli form D.G KHAN City in adjoining plane surface of eastern limb of Zinda Pir Anticline in the foot hills of Suleiman Range. On its right Indus River is almost 25 kilometers away. The population is thin mainly comprises of Khosa Baluch Tribe. The access to D.G cement is by metal road while air links are D.G Khan and Multan air ports. The climate is hot and dry with lower precipitation. The seasonal hill torrents with flushing water pose threat to the industry however it is managed amicably by the administration. D.G Cement is the modern plant having well equipped manufacturing unit in Pakistan producing different types of cement with a production of 2.1 million tones per annum. D.G Cement Company is divided into five operational departments,

1. Administration

2. Works

3. Production

4. Quality Control

5. Sales and Marketing

4.1 Types of Cement Produced

D. G. Cement Company produces two types of cement viz.

1. Ordinary Port Land Cement (OPC)

2. Sulfate Resistant Cement (SRC)

Normally OPC is used in building construction while SRC is used where water logging and salinity is major problem.

SRC (sulfate resistant cement)

It contains quantity of silica sand and iron ore. It is very effective in the regions where the water level in the soil is not very low and there are various salts in the soil, such as in Karachi side. It is also used in construction of the basement of building to resist the water absorbent into the building. It contains 4.5% silica sand and 7-8% iron ore.

Total Plant Capacity = 7000m/tons 292 M.Ton. Per hour

Raw materials

Lime stone 75 To 80% Clay 20 To 25% Iron ore 02% Silica sand 01% Gypsum 04 TO 05% (Increase the settling time of cement)4.2 Different section in DG cements industry

Quarry Utility Section Raw Mill Coal Mill Kiln Area Cement Area Packing Plant Quality Plant 4.3 Quarry

It means to excavate the material over the surface. There is a huge quantity (with high purity) of raw material available near the D G Cement company. Limestone, shale and gypsum deposits are very near to each other in the quarry area. It is located 12Km away from the factory. It has three sections.

Mining section.

Mechanical section.

Auto Maintenance.

The area which is being used for mining is 200 acres

Raw materials

Lime stone 75 to 80% Clay 20 to 25% Iron ore 02% Silica sand 01% Gypsum 04 to 05% (Increase the settling time of cement)Lime StoneTotal leased area for lime stone5057acres

Area surveyed for future1000 acres

Deposits surveyed area125.8 million ton

These deposits are sufficient for about126 years

Argillaceous Clay

Leased area4159.57 acres

Area surveyed755 acres

Deposit in surveyed area32.8 Million Ton

Deposits sufficient for142 years

Gypsum

Leased area2247.9 acres

Area surveyed750 acres

Deposit in surveyed area2 Million Ton

Deposits sufficient for142 years

Silica Sand

Leased area997.18 acres

Area surveyed100 acres

Deposits sufficient for10 years

4.3.1 Mining sectionExtraction of raw materialLime stone is extracted by blasting. First of all drilling is done by the help of drilling machine and screw type compressors. The hole size is 3 in dia and the depth of this hole depends upon the deference between bed and floor. These holes are then filled with explosive.

Two types of explosive are used.

1. High explosiveEmulite is used as high explosive (from Wah Nobel)2. Low explosiveAmmonium Nitrate NH4 NO3 (ANFO) is used as low explosives.

Holes are filled is such a way that bottom area contain high explosive and mid area contain low explosive and remaining part contain powder obtain during drilling. The ratio of high explosive to low is 1:4. The number of holes depends upon the length. The material obtain after blasting contains large lumps with small amount of fine and little amount of intermediate particles. The material is then transport to the lime stone crusher and with help excavator, loader and dumpers.

Initially Gypsum was extracted from the nearby quarry and transported to the factory locally on yearly contract basis where it is crushed by the Gypsum crusher. 4.3.2Mechanical SectionLime stone crusher

Lime stone crusher capacity

=800 TPH

Feed size

=1.8 meter

Product size

=40 mm

Types of crushers

Normally crushers are categorized into two

1. Primary crushers

2. Secondary crushers

Primary Crushers 1. Jaw crushers

2. Gyratory crushers

3. Crushing rolls Secondary Crushers

1. Hammer crushers

2. Impact crushers

Mechanism of grinding

When a material is subjected to a sudden impact it will yield a few relatively large particles and a number of fine particles with a few particles of intermediate size. If a blow of energy is increased then the large particles will be rather of smaller size. Whereas the number of fines particles will be appreciably increased but there size will not be much altered. It appears that size of the fine particles is closely connected with the internal structure of the material and the size of the large particles is much more closely connected with the process by which size reduction is affected.

Size wise categorization of the crushers

CoarseIntermediateFine

Jaw CrushersCrushing RollsRoller Mill

Gyratory CrushersHammer MillTube Mill

Disc CrusherBall Mill

In the cement manufacture, the feed size for kiln falls in the range of the fine particles. So mostly intermediate crushers are installed i.e. crushing rolls and hummer mill. Hammer mill is used both for brittle and fibrous materials. It is more suitable for hard materials that are in the range of rock salt to fluorspar on the Mohr scale. Crushing rolls are suitable for relatively solids. Jaw crushers are used mostly for coarse crushing and low capacity.

Considering the above factors it is better for limestone hammer mill is used and for shale crushing, crushing rolls are used.

Limestone crusher

There is a storage hopper that has a storage capacity of 400 tons i.e. it can hold material of approximately of 9 dumpers. Form the storage hopper, the material is transferred to the hammer mill through apron feeder. Apron feeder consists of 75 plates that are being moved on the rollers. Apron feeder is supported by the bottom plates because when material drops from the dumper, it suddenly exerts pressure on the epron feeder plates. Each epron feeder is 3.2 meter long. Epron feeder is moved by two motors of 27KW each at the gate of epron feeder there are chains. If the material drops from the epron feeder there is a chain scraper that lifts up the dropped material and drops it to the mill. Material drops epron feeder onto the rolls. These rolls are moved by a motor. There are two rolls that move in the same direction. These are driven in the same direction through a chain. These rolls do not take part in the crushing at all. These functions are just to feed the material to the hammer mill. Fine material may drop in the gap between the two rolls. Gap between the two rolls is approximately 40 mm which is adjustable. Rolls drop the material to the hammer mill. There are six shafts. In the hammer mill there are 17 discs. At these discs hammer are arranged against each set of bushes following the formula; Hammer = n+2 Where, n denotes the number of bushes in a set. Bushes give a certain kind of gap for the fine material to flow to the bottom. There are 72 hammers and 38 bushes. Hammer mill is operated by a motor of 1250KW. Hammer mill is a high speed crushing mill in which impact force is the major source of crushing. It depends primarily on the centrifugal force. A chain at the gate from where feed is coming does not allow the material to bounce back. There are fixed plates around the periphery of the cylindrical mill. Some crushing, especially of the large particles is done by these fixed plates. The large particles continue to strike against this plate until it splits up. Some time lamp size particles may not break up then due to the continuous impact, it may damage the couplings of the shaft.

We can change the capacity of the crusher by two ways1. By moving the fixed plate.

2. By changing the motor rpm.

As once the fixed plate is fixed during the operation. It cannot be changed or moved again and again so product capacity can be increased by varying the motor rpm only. As hammer mill produces a large amount of fines so it is necessary that a positive lubrication is employed to the bearings in order to prevent bearings from dust. There is a hydraulic system that can move the fixed plate. That also saves the motor when a large size particle comes in the mill. At bottom of the mill there are bars through which material drops.

Shale Crusher

Type: Roll CrusherSuitable for wet and sticky raw materials.

Daily production = 3000 tons

Rated capacity = 350 tons/hr

Feed size = 500mm < 1m

Dia of rolls = 120cm

RPM of rolls = 42

Avg Product size = 40mm

OperationThere is a storage hopper for shale of a capacity of approximately of 250 tons. At the top of the storage hopper there are bars that allow the definite size material to flow to the Crusher roll feeder. Feed from the hopper is fed to rolls through the apron feeder that is being moved by a motor of 22KW. If some material drops then it is picked up by the chain scraper and dropped to rolls. It is also driven by a motor. There are two rolls both move in opposite direction. One roller is in adjustable bearing while the other one is in fixed bearings. Gap between the two rolls is approximately 40mm. Both the rollers are grooved to give a certain kind of grip to the incoming material. When material comes in between the rolls it is crushed by the compression force. Rollers are driven by a motor of 250KW.From the crushing roller material drops onto the belt conveyor system.4.3.3Transportation Of Crushed MaterialLime and Shale are separately transported from Zero Point to Pile Area via two km long belts. The material being crushed is then transported to the piles by the help of two long belt conveyors. One long belt conveyer (L.B.C) is for lime stone and the other is for shale

Belt is troughed with the help of side roller which increase the capacity of belt and safety. So that material doesnt drop side wise during the transportation. L.B.C is for shale. Slotted weight is hanged to maintain tension in the belt. Dust separators are installed turning points to avoid environmental pollution. Dust is sucked by the bags in the filter then air pressure (purging) the material is drop on the belt and ultra fines are passed into the atmosphere.

L.B.C Capacity

=1000 TPH

Speed of L.B.C

=

80m/min

4.4 Utility SectionWater is coming from the canal flowing near the DGKCC through the pipe lines (4 inch size).Three types of pump are being used in water treatment section.

1. SLUDGE PUMPS

To remove the sand or other settling material.

2. FIRE FIGHTING PUMP

Used to extinguish fire.

3. BOOSTER PUMP

Used to circulate the industrial water.

Zeolite method is being used for softening of water so as to prevent the pipeline from corrosion and scaling.

QULITY OF THE TREATED WATER

After softening the treated water has a hardness of less than 10 ppm.

The filtered water has no particles large tan 0.1 mm.

The treated water resists scaling and corrosion.

The filter plant has a capacity of 50 m3/h4.4.1 Raw water filter

From the raw water tank the water is pumped into the filters where the impurities are filtered off. After the water return to the water softener and the cooling tank. The water is pumped into the top of the filters, and is pressed down through the filter sand, during this process the impurities are detained in the filtering material. In the bottom of the filter there is a supporting layer for the filtering material, and the nozzles through which the filtered water passes, before it is led back to him cooling tanks. When the pressure drops through, the filter has been increased approx.1.5m WG, the filter has to be backwashed with water from the water cooling tank. The backwashing of the filters is carried out manually with the backwash pump and the purpose is to remove the detained impurities from the filter. Normal backwashing of the filters is carried out approx. once per week depending on the amount of impurities admitted to the plant. Softening tank

The raw water is pumped from the raw water tank into the softening tanks where it softened.

During regeneration brine is led into the softening tank.

During regeneration of one softening tank the other tanks can operate.

The softening tank 2 items, each with a capacity of 10m3/hr and a softening capacity of 180 m3/regeneration.

For each regeneration 72 kg of salt (98% Nacl) is used.

The regeneration of the softening tanks is completed automatically, controlled by a water meter.

The automatic valves are electrically driven Valves.

Brine tank

The brine tank which is made of plastic is manually filled with Nacl (salt). From the automatic valve the quantity of water necessary for the regeneration with brine is led into the salt tank, and an ejector pumps the brine from the salt tank into the ion exchanger tank.Cooling TowerThe hot water is pumped from the hot sump to the cooling tower. In the cooling tower the water is sprayed, and blower blow air on the water. The water is cooled evaporation. From the cooling tower the water runs to the tank for cooling water.

Figure : Cooling Tower4.4.2 WATER

The chemical analysis of water available at site is as follows.

Chemical analysis

Table.1 Chemical analysisConductivity 9micro mhos/cm)

Total hardness, ppm as cao3

Calcium hardness, ppm as caco3

Magnesium hardness, ppm as caco3

P-alkalinity

M-alkalinity

Chlorides, ppm as cl

Dissolved salts (ppm)

Turbidity (jtu/litre)

PH

Max 430

190

105

85

0.0

200

95

280

2

8.1

SOFTENED WSTER IS USED AT

Compressors (To cool the compressed hot air)

Raw mill (to Control the temperature of mill)

Cement mill (to control the temperature of bearing)

Kiln bearings. (To control the temperature )

COMPRESSOR

Five screw type compressor are running having 7 bar pressure. Compressed air is being used at cement mill, pack house, kiln, and air slide. OWER: Seven rotary blowers are working which shift the material from cf silo to kiln.

4.5 Piling and Milling

Figure : Pile Area

There are two stackers one for limestone and the other for shale for piling and two re-claimers one for limestone and the other for shale to drag these materials on belts for their transportation to hoppers of the raw mill. Stackers are logically programmed to pile lime and shale in a fixed No of layers in order to have uniform composition of material. Had this technique not been employed here there would not have been uniformity in the material contents resulting in non standard product. At the Re-claimer there is a big harrow, covering the whole one side, which is used to brush the pile and as a result material from all layers is collected at screw belt and then transported to hoppers through conveyer belt. For level measurement in the hoppers there are ultrasonic sensors which are controlled by PLC.There are two piles for lime stone and two piles for shale.

Capacity of lime stone pile = 2 x 40000 Tons

Capacity of shale piles

= 2 x 11000 Tons

All the operations of L.B.C, crusher, motors are controlled from control room (CCR).

4.5.2 Milling

Raw Material

Limestone

Limestone is a very common sedimentary rock of biochemical origin. It is composed mostly of the mineral calcite (CaCO3). Sometimes it is almost pure calcite, but most limestones are filled with lots of other minerals and sand and they are called dirty limestones.

The limestone used in D.G.K. Cement is pure with following chemical composition. Bulk content of limestone used is 75 to 80%.

Table : Chemical Composition

Sr No.MinimumMaximum

SiO21.635.77

Al2O30.261.41

Fe2O30120.87

CaO47.8652.96

MgO0.670.86

K2O0.030.68

Na2O0.010.08

SO3-0.012.23

Cl0.000.01

Shale (argillaceous clay viz fuller earth)

Shale is a very common sedimentary rock, and often preserves fossils and sometimes even fossil tracks. It is a clastic rock composed of silts, clays or muds that have been compacted into distinct layers. Shales may be easily split along these layers. The shale used in D.G Cement is pure with following chemical composition. Bulk content of shale used is 20 to 25Table: Chemical Composition

Sr NoMinimumMaximum

SiO247.2957.04

Al2O312.2315.85

Fe2O35.737.09

CaO2.768.46

MgO2.954.43

K2O2.042.49

Na2O0.661.02

SO30.090.30

Cl0.000.03

Silica Sand

It is an industrial term for a sand or an easily disaggregated sandstone that has very high percentage of silica (quartz, SiO2). It is a source of silicon and a raw material of glass and other industrial products. In D.G.K Cement silica is used in preparing Alite (C3S, 3CaO.SiO2) and Belite (C2S, 2CaO.SiO2) which are cements prime constituents. Bulk content of silica sand used is 01%

Table: Chemical Composition

Sr NoMinimumMaximum

SiO274.9799.88

Al2O3-0.2010.10

Fe2O30.094.76

CaO0.228.81

MgO-0.071.14

K2O0.251.36

Na2O30.010.19

SO30.202.69

Cl0.000.00

Iron OreFerruginous rock containing one or more distinct natural chemical compounds from which metallic iron may be profitably extracted. The chief ores of iron consist mainly of the oxides, hematite (Fe2O3), magnetite (Fe3O4). In D.G.K Cement addition of iron ore (Fe2O3) is used for formation of C3S. C4AF which makes the cement more resistant to seawater and results in a somewhat slower reaction which evolves less heat. Bulk content of iron ore used is 02%.

Table. Chemical Composition

Sr NoMinimumMaximum

SiO232.0354.93

Al2O34.357.00

Fe2O322.1637.47

CaO2.179.95

MgO2.384.77

K2O0.923.24

Na2O30.000.00

SO30.030.31

Cl0.000.00

4.5.3 Raw Material Transportation

Limestone Transportation

Limestone from the stockpiles is loaded on the belt conveyor through the Bridge type Reclaimer (i.e. on the bridge is mounted a racking device whose sweeping movement cause the material to the belt conveyor). From the belt conveyor the limestone falls in the limestone bin. At the exit of the bin, a decimate feeder is working to control the amount of limestone falling on the belt conveyor. From the limestone belt conveyor, the material falls on the main feed belt conveyor (i.e. raw mill feed). The capacity of Reclaimer is 600tons/hour.

Clay Transportation

Clay from the stockpile is loaded on the belt conveyor through the side scraper. From the belt conveyor, clay falls in the clay bin. At the exit of the bin, a decimate feeder is working to control the amount of clay falling on the main feed belt conveyor (i.e. raw mill feed belt conveyor). The capacity of side scraper is 250tons/hour.

Silica sand & Iron Ore Transportation

Silica sand after crushing is transported through the belt conveyor and falls in the silica sand bin. When silica sand bin fills completely about its capacity then supply of silica sand is stopped and then crushed iron ore is transported through the same belt conveyor and falls in the iron ore bin. When the bin completely fills about its capacity then supply of iron ore is stopped. The material that is exiting

from iron ore and silica sand bins is controlled through the decimate feeders. Silica sand and iron ore falls on the same belt conveyor and then falls on the main feed belt conveyor (i.e. raw mill feed belt conveyor).

4.5.4 Preparation of Raw Materials The object of processing the raw materials is to ensure that raw-feed entering the kiln is of constant composition and in a thoroughly comminuted blended state. Failure to do this result in cement with variable composition and unpredictable properties. For example, if the composition of raw-feed varied widely, making performance difficult to predict with certainty. The optimum burning temperature of the mix mill also varies with composition. In addition if the particle size were

too large, complete chemical combination might not occur during the time the material is in the kiln and would result in cement of inferior performance.

The sequence of operation for the processing of raw materials may vary considerably from plant to plant, depending upon the raw materials, equipment and plant design. D.G.K.C.C is manufacturing cement by using the dry process. In the dry process care must be taken to ensure the adequate mixing and blending to avoid excessive loss of fines. Closed circuit grinding with classifying equipment is commonly used to avoid over grinding and control of dust.

Production Of Raw Mix (In Raw Mill)

Raw Mix is obtained by grinding different raw materials in the raw mill. For raw mix production, the proportions of raw materials are calculated as per chemical composition of raw materials. Raw mix proportioning is done keeping in view the following ratios.

CaO 100

Lime Saturation Factor =

2.8 SiO2+1.18Al2O3+0.65Fe2O3 SiO2Silica Modulus (SM) =

Al2O3 + Fe2O3 Al2O3

Alumina Modulus (AM) =

Fe2O3 CaOHydraulic Modulus (HM) = SiO2 + Al2O3 + Fe2O3

Table Following parameters are used to produce good quality Ordinary Portland and Sulphate Resistance cement

RatiosOP CementOP Cement

(Dark)SR Cement

LSF90-9690-9690-96

SM2.3-2.52.3-2.52.3-2.5

AM2.10-2.301.30-1.700.60-90

4.5.5 Raw Mill

The raw mill that has been use in D.G.K.C.C is verticle roller mill whose brand name is Atox mill and it is manufactured and installed by FLSmidth that is a famous company of Denmark.

Construction

Pressure on the roller = 104 bars

Roller weight

= 32 Tons

Product size = 90 pm

RPM of grinding table = 24 - 27

Power consumption pt of Cement = 35.7 KWHThe raw mill (i.e. vertical roller mill) that is in use in D.G.K.C.C consist of three grinding rollers, a rotating table, main motor, air separator, sealing fan, mill fan, gear lubrication system, roller lubrication system, three hydraulic units and three nitrogen gas cylinders (one N2 cylinder from each unit is in use while other two are standby) along with each roller.

Working

Raw mill feed enters the raw mill through the rotary valve shoot; through rotary valve the quality of feed is controlled from CCR. A magnetic separator and a metal detecting system is working on the raw mill feed belt. Material from the shoot falls on the grinding table that rotates with speed of 24-27 rpm. When the table rotates, the material is comminuted by a combination of compressive and shearing forces caused by the weight of rollers because the roller moves up and down through the hydraulic pressure. The pressure on each roller is 104 bars. Hot gases passes through openings in a ring surrounded the table. The ground material is transported by the gas steam into the four cyclones with the help of air separator and mill fan. The fine fraction goes with the gas whereas some coarse fraction is returned to the table for further grinding while other coarse fraction through the openings in a ring surrounded the tables transported to the bucket elevator through a vibrator which takes the coarse fraction from bottom to top and drops on raw mill feed belt. Water in constantly sprinkled during the grinding of raw meal due to the following reasons.

To lower the gas volume.

To maintain the temperatureControl of Raw Mix (Through Raw Mill)

The chemical composition of raw materials usually varies in different phases and trenches (quarry site).It is not possible to keep the raw materials proportions always constant. Therefore, raw mix sample is analyzed on hourly bases to control the quality of raw mix. Raw mix of desired quality is controlled through Quality Control X-Ray Analyzer (QCX).Desired quality parameter, i.e. LSF is fed in the QCX system, which control the LSF near the set value. If, due to some variation in raw material composition, LSF of raw mix is below the set point, QCX system will adjust the raw material feeders in such a way that next 04 hours production will fall near to set point along with the compensation of deviated production.

Air SepartorBefore entering the cyclone air is separated from the material by Air Separation.Air Slide

The material from 2 Cyclones drop in 1 air slide is used to transport material. It has canvas in which air flows and is also at an angled there fore moves the material to destination. Material from G.C.T by the help of screw conveyor also drops in the air slide. Then this air slide drops the material into the air lift. Air lift gives a pressure of 7 bars (with help of 7 compressors) this pressure transport the material to the C.F silo has a capacity = 15000 ton.

Oil Hydraulic Unit For Roller

Hydraulic unit pump is there to increase roller pressure.

Circulating Oil Supply For Roller

This oil unit is to lubricate the roller bearings.

Lubricating Oil Unit For Gear Reducer

This lubricating unit serves the lubrication of rotating table upon which four heavy rollers rotate. One roller weight is 30 ton.

The ground material extracts by an exhaust fan and is sent to four cyclone separators. Here in cyclone separator the grinded material is separated from the hot flue gases. In these cones, the gases plus material from a cyclone, the material is settle down due gravity and the hot flue gases comes from top of the cones.

Dust Collection

During the transportation the points where the material changes belt, feeding points or discharge points, there are installed dust collection to avoid Air Pollution.E.P (ELECTROSTATIC PRECIPTATOR)

Fine Material from Raw mill collects by E.P then by heavy vibration this material dropped by screw conveyor to Air Slide then to C.F silo.

AIR BLASTING

It is used to separate the material from the impeller of ID fan which is collected due to moisture.4.6 Coal MillThe coal mill that has been use in D.G.K.C.C is vertical roller mill whose brand name is Atox mill and it is manufactured and installed by FLSmidth that is a famous company of Denmark. Coal mill is used to reduced the size of crushed coal into the powder from this pulverized coal is then supplied to the kiln as a fuel. The coal mill (vertical roller mill) that is in use in D.G.K.C.C consist of three grinding rollers, a rotating table, main motor, air separator, sealing fan, mill fan, gear lubrication system, roller lubrication system, three hydraulic units and three nitrogen gas cylinders (one N2 cylinder from each unit is in use while other two are standby) along with each roller. SHAPE \* MERGEFORMAT

4.7 Cyclone Preheating

The substantial energy is achieved by reusing the exit gases from the kiln to protect the kiln feed, evaporate moisture present there in and to partly calcine it. In this process, dry kiln feed passes through the pre-heater, a series of five cyclones and riser pipes where it is separated and pre-heated several times. A common characteristic of all the five cyclones is that there is an intensive heat exchange between the kiln exhaust gases and kiln feed. This heat transfer is very efficient and rapid as each particle is in contact with the gas stream over its entire surface area

Figure: Cyclone PreheatingIn-Line Calciner

Pre-calciner is equipped in line with five cyclones. In the pre-calciner about 80-90% calcinations of raw meal takes place. Raw meal is fed into the system and progresses through successive heat exchange cycles in the riser ducts and subsequent separation in the cyclones of suspension pre-heater system. However from the stage preceding the last stage cyclone, it is discharged in the pre-calciner. The calcined material is passed on to the last riser duct where it is discharged into the rotary kiln. Calciner is fired with 60% of pulverized coal and 40% in the kiln.

Figure : In-Line Calciner

4.8 Rotary Kiln

The heart of the cement making process is the kiln, which heats the raw meal to a temperature of 1450 C. the kiln is the worlds largest piece of moving industrial equipment.

Figure: Inner Shell

Figure : Kiln Bricks

Main Parts of Kiln

Weighing system of the rotary kiln

Rotary Kiln

Prehearter Suspention.

Calciner

Cooler

Clinker Yard

Table :Construction and CalculationsMaterial of constructionMedium Carbon Street

Length67m long

Internal Dia4.35m

Inclination4% of the length =2.29

Fuel usedSub Bituminous Coal or furnace Oil

Inside Temp of Kiln1200 1400 oC

Preheater out let temp RPM300 oC

Kiln RPM3 rpm

Kiln feed217 Ton/hr

Inner lining of calcinerLow Alumina

Inner lining of kilnMed { Low alumina bricks ( low temp zone) Magnesia syinel fire bricks (High Temp Zone )

Coal feed 5.8T/hr

Powder Consumption / Tons of Cement15.5KWhr

Pressure of Air Lift7 bars

Table: Chemical Composition Of Kiln Feed

Sr NoMinimumMaximum

SiO213.6814.23

Al2O33.523.64

Fe2O32.112.23

CaO41.6942.00

MgO1.431.53

K2O0.510.54

Na2O0.290.36

SO30.100.12

Cl0.0020.004

4.8.1 ProcessWith the help of airlift and screw conveyor the material is transported to air lift then to the cyclone by air pressure.

Preheater

Cyclones act as perheater material is heated in each cyclones and drop to the rent cyclone. The temp in each cyclone is different varying from 200 900 C0. Cyclones do dehydration and ad calculation.

Calciner

Cyclone act as a calciner in which the temp is 866 C0 900 C0 following reaction takes places.

CaCO3

CaO + CO2

Lime stone is converted into lime and CO2 gas.

Burning zone

The material is fed to kiln where temp is 1200 C0 1400 C0 this temp zone is called Burning Zone. In this zone lime and clay under goes chemical reaction (fusion) yielding Ca silicates Ca aluminates as a product.

2CaO + SiO2 Ca2.SiO4 (Di Calcium silicates C2S)

3CaO + SiO2

Ca3.SiO5 (tri Calcium silicates C3S)

3CaO + Al2O3

Ca3.Al2O6 (Tri Calcium silicates C2A)

4CaO + Al2O3 + Fe2O3Ca4.Al2.Fe2O10 (Tetra Calcium Alumino Ferrite C4AF)

Working

The kiln feed rate is 217 tons/hour 80-90% calcined raw material is fed at uniform rate into the upper end of the rotary kiln. The material undergoes chemical changes in succession as this pass downward to the disc charge end by the combination of rotation and inclination of the kiln. The kiln shell rests on three supported provided with the three rollers. The spacing of the support along the kiln tub will depend upon the arrangement of the tyres (riding rings) on which kiln rotates. The kiln is maintained in position by thrust rollers. It is rotated by girth gear driven by an electric motor.

In preheater tower, the raw meal from Blending silo passes down through a series 4 of cyclones. At the same time, exhaust gases from the kiln pass up the tower, gradually heating the raw meal before it enters the kiln. After the preheated cyclones raw meal now enters into the huge rotating (4.7 rpm) furnace called KILN a horizontally slopped steel cylinder, internally lined with different firebricks, depending on the zone of the kiln. Initially, these raw materials give off water Vapor (dehydration) and then give off CO2 (Calcinations). Finally, in the hottest end of the Kiln, the final chemical reactions occur and the material falls out of the kiln into a cooler, where it is quenched. In this system, the Dehydration step occurs in the preheater cyclones that offer much better heat exchange efficiencies than the chain section of an old kiln. A precalciner may also be present; it allows a good portion of the calcinations before the kiln. Since smaller material can travel through a kiln which has a smaller volume of hot gases flowing through it. In both designs, the gas and material flow is a smaller volume of hot gases flowing through it. In both designs, the gas and material flow is Opposite and exit flue gas temperatures from the process is generally quite low, 280 to 350c. The intense heat triggers chemical and physical change. Expressed at its simplest, the series of chemical reactions converts the Calcium and silicon oxides into calcium silicates, Cements primary constituents. At the lower end Of the kiln, the raw materials emerge as a new substance: red-hot rounded shape particles called Clinker grayish black pellets. Kiln Shell Corrosion

Causes

Excess sulphur in the kiln system.

High burning zone temperature.

Reducing atmosphere temperature.

Removal of basic bricks at very little residual thickness.

Use of high permeability.

Basic bricks.

Table :Chemical reactions that take place in a rotary kilnSr.noApprox.Temp C0Sequence of reaction

1100Evaporation of free water of kiln feed.

2500 and aboveWater of hydration and hydroxyl water begins to be slowly driven off

3600-700Dissociation of magnesium carbonate

4900 and aboveDissociation of calcium carbonate

Above this temperature, combination b\w lime,silica, alumina and iron compound start.

5800-900Formation of C2S

61095-1200Formation of C3A and C4AF

71250-1280

Commencement of liquid formation, depending upon the raw mix

81280-1450Formation of C3S.B\w 1370-1450C0, free lime completely disappears. Formation of clinker compounds stands complete.

Clinker is discharged at the lower end where the pulverized coal is injected and quickly cooled by coolers. Duration of passage of the material through a rotary kiln is 45-50 minutes4.8.2 Quality of Clinker

Clinker is the black, glistering and hard nodules. It emerges from the kiln at a temperature 1300C0. The quantity of free lime in the clinker is kept less then at 20%. Free lime refers to the lime left over after the formation the calcium silicates and calcium aluminates. Analysis of clinker for free lime content, though it gives a good indication of how well, the clinker had been burnt. In D.G.K.C.C, determination of free lime in clinker is carried out through wet analysis.

Table: Chemical Composition

Sr NoMinimumMaximum

SiO220.1020.83

Al2O35.115.33

Fe2O33.373.64

CaO65.1466.16

MgO2.142.34

K2O0.760.85

Na2O0.310.41

SO30.701.00

Cl0.0010.001

Cooling of ClinkerClinker from Kiln have very high temp (1300-1400 C0).Then it is air quenched by cold secondary air as it leaves the kiln and enters the cooler. This type of cooler in use is Grate Cooler. Air is injected through the underside from a series of ten fans. The air used to cool the clinker becomes highly heated and is used as secondary air in the kiln. so it is cooled in hot air duct remove hot gases removes hot gases and return them to the Kiln. Cooler out clinkers temperature is 50-70 C0. For dust collection from clinker, an EP is also installed just after the cooler.Hammer Crusher

At the end of Cooler there is hammer crusher, which crushed the large lamps of clinker. The clinker is then transferred to the clinker yard with the help apron chain conveyor.Capacity of clinker yard =40,000 tons.

4.9 Cement MillCement mill (bail mil) is used for fine grinding (90 m) and is a sub type of tumbling mill or revolving mill.

Material of construction = Medium Carbons Steel

Length of Mill

=

13.5 m

Dia of Mill

=

4.8 m

4.9.1 Gypsum

It is widely distributed rock consisting of hydrous calcium sulphate CaSO4.2H2O. It forms thick, extensive beds interstratified with limestone and shale. It is soft. It is used as a soil amendment and in making plaster of Paris. In cement it is used as retarder in. The gypsum used in D.G Cement is pure with following chemical composition. Bulk content of gypsum used is 04 to 05%.

Gypsum TransportationGypsum is crushed on the plant side by using the hammer crusher. Some of the salient features of the gypsum crusher are given below. The capacity of crusher is 100tons/hour

Crushing is achieved by impact and attrition

This type of crusher is suitable for brittle material

No of hammers is 48 and each hammer is of 19kg

Feed size is 500mm

Product size is less then 95%

From the gypsum crusher, gypsum is transported to the gypsum bin through the belt conveyor at the cement mill.

Clinker TransportationFrom the clinker yard, the clinker is transported to the clinker bin through the belt conveyor at the cement mill. 4.9.2 GrindingGypsum and clinker through bins enters into cement mill with the ratio clinker = 95% and gypsum = 5% in the cement mill. Cement mill employs impact (Ist zone) and attrition (2nd zone) for grinding.

GRINDING MEDIA

Metallic balls are used as a grinding media.

The mill has two Chambers.

Table : First Chamber (Impact Zone)Length of first chamber3.25 m

Weight of grinding media23% of 90 mm Dia + 32% of 80 mm Dia + 21% of 70 mm dia + 24 mm ov 60 mm dia.

Impact zone diaphragm 2 mm

Table: Second Chamber (Attrition Zone)

Length of 2nd chamber 80m

Weight % of grinding media20% of 25mm dia + 40% of 20 mm dia + 40% of 15 mm dia.

Diaphragm 8mm

Totol weight of balls32 tons

Material of Construction of ballsHigh Chrome Steel

RPM of cement mill14.78 rpm

Critical Speed70%

Capacity of Mill190 t/hr

Wear and Tear of media47 gm/ton

Power Consumption per ton of cement38 kw

4.9.3 Operation of Cement Mill

In the cement mill, a horizontally mounted cylindrical shell partially filled with grinding media, balls is rotated about its longitudinal centerline. The material to ground is fed into the shell through one end where it comes into contact with the tumbling media. Grinding is affected through the repeated impact of the media on the material. As it is ground, the material moves through the length of the mill and is discharged from the end opposite the one it entered.

There is an overhead air separator to which the ground from the cement is carried through the air slide. Air separator separates the fine material plus air from the coarse particles. The fine material is sent to the two cement silos (capacity: 10,000 ton each) through a fluxo pump having a capacity of 2000 Lit cement with a pressure of about 7 bar from the bottom of the air separator the course material is carried back and fed into the cement mill for further grinding.

Some quantity (250ml/hr) of glycerin is sprinkled as a grinding aid upon the clinker before entering into the cement mill so that the material may not stick upon the balls.

Some water is also sprayed in the CEMENT MILL to lower the temperature that is increased due to friction between balls and material and walls of the mill.

Temperature of the mill should be less than 120 0C, otherwise at high temperature the gypsum in the cement will anhydrate and it will lose its property (to increase the setting time).

The cooling water also controls bearing temperature of the mill.

The particle size of cement expressed in term of surface area, so the cement blain add DGKCC is 2800 blain i.e. 2800 cm2/gm surface area.

Roller pressIs used to reduce the size of material after being crushed (gypsum) and hammered (clinker) into powder form. The material after pressing goes to cement mill. After grinding the fine material are sucked transported to the Fluxo pump then to cement silo. The coarse particles are then separated and transported to mechanical separator. It separated the large particles and fed it to mill and fine one to the filter. Filter separate the fine particles having arrangement of bags and purging system, the fine one goes to the cement silo with the help of screw belt conveyor, and pressure system.Factors Affecting the Cement Quality:

Sulphur tri oxide (SO3)

Lime Saturation Factor (LSF)

Free Lime

Chlorides

Blaine (specific surface)

Loss On Ignition (LOI)

Magnesium Oxide (MgO)

4.9.4 Packing Section

The cement from silos transferred to the cement bin with the help of Air lifts. There installed a mechanically vibrated screen (10mm) mesh size to avoid any metal piece or any thing else below each cyclone. The cement is packed into bags having capacity of a 50 kg per bag. Four rotary packers used for packing. The capacity of each rotary packer is 2000tons/hour. The packing system is fully computerized and works on the Programmable Login control (PLC) system. After packing bags are transferred to vehicles by the help of belt conveyor.

Packing bags are made up of = paper polypropylene

Power consumption per ton of cement = 2.25 KWH

4.10 Quality Control

The quality department control quality. Especially in the production of cement, quality control is required at every stage Quarry to Packing. At D.G.K.C.C Quality control system is fully computerized Raw material from Quarry are analyzed and then upon the basis of these composition feed rate of raw material is given. Samples from the raw mill clinker and cement mill sent to the X-ray analyzer which calibrates the samples with the standard samples. The samples are fed in the form of press to the X-ray analyzer.

4.10.1 Raw Mix Proportioning And AnalysisThe X-ray analyzer determines the composition of the limestone and shale because the quality and operation of the cement depends upon the composition of the raw material. For the production of cement it is necessary to have, or make, raw material mixtures whose chemical composition is within certain limits. The continuous production of high quality cement is possible only if the raw mix possesses optimum composition and further more if variation in this composition remains within the narrowest possible range. The quality control department is controlling main three parameters in the cement manufacturing.

1. LSF (Lime saturation factor)

2. SM (silica modulus)

3. AM (alumina modulus)

For OPC AM is 1.61.8 but for SRC, AM =