**DERA GHAZI KHAN CEMENT INDUSTRY**

(Nishat Group Of Industries)

INTERNSHIP REPORT

Submitted By :

Muhammad Hamza RaheelSp07-Bec-025

Submiited To:

Sr. Manager Production DG CEMENT

Mr. Mohammad Shafique

*DEPARTMENT OF CHEMICAL ENGINEERING*

**COMSATS INSTITUTE OF INFORMATION TECHNOLOGY**

( LAHORE)

CEMENT

Cement can be defined as any substance which can join or unite two or more pieces of some other substance together to form a unit mass.

Introduction

D.G Cements is a project of NISHAT GROUP OF INDUSTRIES . It is the one of largest cement manufacturing plant in Pakistan having record production in Asia .

It is established in 1978.

Site of D.G cement plant lies near to Dera Ghazi Khan city about 40 K.m away .

The site have many Geographical advantages . This area is rich in basic raw materials required for cement production . Only small amount of Iron is taken from other areas .

The site also facilitates its employe and ensure their safety, also meeting their basic needs .

The environmental conditions of the site are also very suitable for processes .

For continuous and smooth operations of the plant uninterrupted power supply is very crucial.

The plant have its own production of electricity using furnace oil . Recentally Heat Recovery plant is installed which also contribute to the production of electricity with the help of Japanese company KAWASAKI.

DG CEMENT lies in the centr of three provinces.PUNJAB,SINDH AND KHBER PAKHTHUN KHAN.

DG CEMENT meet the WORLDS BANK ENVIRONMENTAL STANDARDS.

The first and only cement company have both ISO 14001 & ISO-9002 certification.

The installed generation capacity is 23.84 MW.

UNITS

There are two Units working simultaneously .

UNIT 1FUJI ( Installed by japan in 1984)Production capacity = 2700 tons/day

UNIT 2FLS ( installed by Denmark in 1997)Production capacity = 4000 tons/day

Raw Materials

Limestone ( 70% - 75%)

It is the basic raw material for cement.

Clay /Shale (15%-20%)

Shale is the 2nd major raw material used for the cement production.

Iron Ore (2 %)

Iron ore as the name indicates is the iron rich material containing

substantial amount of silica together with certain amount of alumina

and calcium carbonate.

Silica Sand (1 %)

Silica sand is also used in cement making process especially when the

shale/clay is deficient in silica contents.

Gypsum (4% - 5%) Gypsum is used as an additive with clinker. Its contains sulphate, calcium carbonate, alumina, etc. as impurities.

Water

Gypsum is added with clinker as corrective additives for producing cement .

Gypsum is used to increase the settling time of cement.

MANUFACTURING PROCESSES OF CEMENTS

There are two manufacturing processes of cements.

1. DRY PROCESS2. WET PROCESS

CHOICE OF DRY OR WET PROCESSIt depends upon the following factors

I. Physical condition of raw material.II. Local climate condition of the factory.

III. Price of fuel.

DRY PROCESS

This process needs excessive grinding and it is suitable for harder material . Grinding is difficult as compared to wet process.

WET PROCESS

In the wet process grinding is done in the presence of water. Wet process is free from dust. Grinding is easier. Composition of cement can be easily controlled.

IN PAKISTAN MOST OF THE FACTORIES USE WET PROCESS. DG CEMENT ALSO USE DRY PROCESS

Type Of Cement Products In D.G Cements

Plant have following two types of cement production

OPC ( Ordinary Portland Cement )

SRC ( Sulphate Resisting Cement )

OPC (Odinary Portland Cement)

It is defined a material obtained by pulverizing and calcining the calcareous (lime) and argillaceous (clay) materials.

SRC (SULPHATE RESISTING CEMENT)

For SRC limestone and clay similarly are used as basic raw materials where as iron ore and silica are added as corrective additives . It is used in High

Moisture areas to resist salts such as sulphates ( e.g Dam Construction )

Manufacrturing

Te manufacturing of cement involves the followimg major steps ;

Grinding and mixing of raw mixture. Burning of mixture to give Clinker. Grinding the clinker along with Gypsum

Section in D.G.Cement plant

Quarry Area Utility and Water Treatment Raw Mill Area Coal Mill Area Kiln Area Cement Mill Area

Packing Plant Quality Control

Quarry Area

First of all we visited Quarry Area of D.G.Cement Plant.

There is a massive quantity of basic raw materials necessarily required for cement production (limestone and clay) available in KOH-E-SULEMAN lies near to industry.

Most impotant is that each deposit is nearly available to each other. Each material is crushed in transported to industry through long Belt Conveyors.

These belts travel a distance of about 7 to 7.5 Km to transport raw materials .

Interlocking

These Belts are specially designed based on interlocking system. The belts throughout the plant are interlocked. Interlocking is actually helpfull when any belt or instrument is damaged due to any reason ,all the previuous system of these belts along with instrument are locked(switched off) .

MAJOR STEPS IN QUARRY AREA

Quaryy area involves following major steps.

Limestone Crusher Clay Crusher Mining Section(Drilling/Blasting)

Auto Section

Limestone

Limestone is a available as hard rock of mountains . Blasting is done to break it from mountains . Blasting is done by drilling holes of about 100mm in dia and 60ft depth using drilling machienes. The holes are drilled by consulting mining engineers . Different explosive materials (Bombs) are placed in these holes . Bombs are blasted to break hard rocks. Blasting is dangerous phenomena so high quality precautions are used during this process.

Explosive in most cases ANFO is preferred due to its low price. It can be filled in the bore holes as bulk material or pre-packed in cartridges.

Finally after blasting material is sent to Hammer crushers with the help of loader or dumpers.

In hammer crusher the particle are broken by sets of swing hammers pinned to a rotor disc.

This crushed material iis sent to industry through belts .

Clay (Shale)

Blasting is not required for clay because it is soft material.

Produced shale is dumped into the feed hopper and fed to the roller crusher by the apron feeder .

The speed of the feeder is controlled by the load cell on the roller motor.

After crushing it is sent to industry through belts.

Gypsum

It is also soft material and requires in small quantity.

It is transported to industry through trucks.

Raw Mill Area

The materials came form quarry is stored separately in their respective storages.The storage system consist of stacker and reclaimer.It is a two piled system in which one is staked and other is reclaims.Pile of every material is made with the help of stacker .Reclaimer is used to transport limestone to belts which fed into the hoppers. Side Scrappers are used for clay transport to hoppers.Similarly silica sand and iron ore are transport to hopper with similar method. The material stored in separate hopper which is feed to Raw Mill Unit 1 and 2 by dosimate feeder.Load cell are use to weight the feed.After weighing all th 4 raw materials are combining them on a single belt before entering into raw mill.Basic Working Principal for Unit 1 and 2 of Raw Mill is same .

MAGNETI SEPARATOR

MAGNETIC SEPARATOR is erected on the common belt on which all the raw materials are combined to separate magnetic objects.

METAL DETECTORS

METAL DETECTORS is built for the metals which are not attracted by magnetic separator to save raw mill.

PNEUMATIC OPERATED GATE

Whenever a metallic piece is detected the PNEUMATIC OPERATED GATE will be operated for the discharge of metal piece.It is also called as CHANGE OVER GATE.

Working

Milling is basic purpose of Raw Mill . After entering to raw mil the feed material drops on to the

rotary grinding table. Due to the rotation of the table, the material is driven towards

the edge of the grinding table and forced under the rollers and ground.

The rollers are thrust down against the grinding table by gravity and hydraulic pressure.

The grinding table is driven by the main motor. Unit 1 contain three vertical rollers and unit 2 contain four

vertical rollers . The feed which is not properly crushed is recycled usind small

BUCKET ELEVATOR to DYNAMIC SEPARATOR & again into the mill.

The mill is equipped with a VIBRATION SENSOR which stops the mill automatically if too strong vibrations are measured.

A number of oil pumps secure lubrication and cooling of the gear unit and bearings of the grinding table and rollers.

Temperature is important parameter used for milling which is maintained by hot gasses coming from kiln .

Induced draft(I.D) Fan is used to suck hot gasses from kiln to mill & separator.

It is constant speed fan & stabalize the operatinal stability. These to ensure sufficient and constant gas flow through the

mill.

Nozzles are installed for water injection in front of the rollers and on the grinding table to control the temperature.

Raw meal ground to a fineness of 15% residue on the 90 micron sieve

The temperature of the supplied hot gas must be sufficient to provide the necessary drying of the raw material when they leaving the mill.

The mill fan take the gas stream out of the mill / separator carries the fine fraction, the product, the raw meal.

The raw meal is collected by cyclones due to gravity.

The raw meal produced is transported to the CF silo through buckets elevator and air slides from cyclones.

When the mill is stopped, the collected kiln dust can be directed either to the kiln feed system or to the CF silo.

COAL MILL AREA

There is a separate storage for coal.

Stacker is used to make the pile.

Reclaimer is used to transport it to the coal hoppers through belts.

From there it enters to coal mill and it is crushed there.

Temperature is required for crushing & it is obtain from hot gases which is obtained from kiln through I.D.FANS.

Coal which is not properly crushed is came out of the mill.and from there is again put to the pile.

From the coal mill,crushed coal is entered into bag filter where hot air is separated from the coal.

The powdered coal is then sent to pneumatic conveyoy through rotary valve.

With the help of conveyor,the coal is send to raw coal silo.

Load cells are placed to weigh the coal,when it is trasfered to calciner and kiln for coal firing.

Kiln Area

Then I visited Kiln Area .

Material that is stored in CF SILO act as a kiln feed.

The aim is to produce a homogeneous raw meal quality in order to facilities the kiln operation.

Stable kiln operation is the basis for good clinker quality and consequently good cement quality.

The kiln feed is extracted from the homogenizing silo & transported to the inlet of preheater through air slides and bucket elevator.

The pre-heater is operating as a counter current heat exchanger with the raw meal passing downwards through the pre-heater stages by gravity, and the gas moving upwards drawn by the ID-fan.

Having passed 4 or 5 pre-heater stages – depending on to which unit the feed is directed.

From the preheaters Kiln feed is send to calciner for coal firing.

In the calciner vessel approximately 55-60% of the coal is burnt as a fuel.

The raw meal will be calcined to a degree of about 90-95%.

The calciner can be operated at high temperature of more than 1000°C, which increases the combustion rate.

The combustion gas used in the calciner is a mixture of hot atmospheric air and the kiln gases from the proper rotary kiln.

From this last pre-heater stage the material slides to the rotary kiln inlet.

Due to the inclination and rotation of the kiln, the raw meal is transported downstream through the kiln.

The raw meal is gradually heated and fully calcined by the heat supplied to the kiln by the firing installation at the outlet end of the kiln.

KILNZONES IN KILN

There are four zones in kiln listed below

Initiall Zone ( 350-850 degree celcius) Transition Zone (1400 degree celcius) Burning Zone (1800 degree celcius) Cooling Zone (150 degree celcius)

The length of kiln is 67.5 m & its diameter is 4.3 m & it is inclined to 4 degree.

It rotation is up to 4 rpm.

The capacity of kiln is 4000 ton/day.

KILN LINING The temperatures in the kiln system are so high that most of the system is protected by means of a lining consisting of bricks and concrete.

Calciner is placed before the kiln and it is very helpful in increasing the rpm of kiln because most of the feed is heated due tocalciner.

Cooling shell fans are used to maintain the temperature of the metal surface.

Major components of Portland Cement Clinker

Tricalcium silicate 3CaO Si02( Alite, C3S) Diacalcium silicate 2CaO Si02(Belite ,C2S) Tricalcium Aluminate 3CaO Al2O3 (C3A) Tetra Calcium Aluminiferrite 4CaO Al2O3 Fe2O3 (C4AF)

Major steps in clinkering

Decarbonation of calite( Calcinations )CaCO3 CaO+CO2 (Highly endothermic)

Rapid Neutralization of free lime (Exothermic)3CaO + Al2O3 C3A

2CaO + Fe2O3 C2F2CaO + SiO2 C2S(belite)

Formation of Alit (Slow Reaction)CaO+ C2S C3S(alite)

(>1200*C)

Cooling (Cooler )

When fed enter the cooler its temperature decreased to 150 degree celcius.

Clinkerization – clinker formation – takes place when he raw meal passes through the burning zone of the kiln to the cooler.

Cooler have 2 chambers.

To ensure effective cooling at the cooler inlet, it may as previously stated be necessary to start the first fans of the cooler.

The cooler has horizontal grates consisting of movable and fixed rows of grate shoes.

Cooling fan are used to cool the feed by using air.

Afterr clinker formation,the clinker is moved towards the roller press for pre crushing after leaving the coolers.

From the roller press, clinkers are entered to the CLINKER YARD through apron feeder.

CLINKER YARD are the storage of clinkers.

Clinker size should be 32-50 mm.

GAS CONDITIONING TOWER

Whenever the kiln is in normal operation,the mill is also in operation , part of the gases is used for drying purposes in mill.

The remaining gases are used for in the gas conditioning tower, so this gas, and the gas from the mill is conditioned to a temperature which is acceptable to the ESP-filter, where the gas mixture is dedusted.

The entire exhaust gas flow passes through the conditioning tower, where the gases are cooled down to 150 °C, before they are dedusted in the filter installation

ELECTROSTATIC PRECIPITATOR (ESP)

The gases after cooled down from gas conditioning tower are entered to electrostatic precipitator for dedusting.

The ESP has electrodes which have a charge on it & the gases containing dust have charged by the electrodes & positive electrode captured the dust.

It is stick with the electrode and by continuous hammering in ESP the dust is collected and sent to CF SILO.

The hot gases from the electrostatic seperator is send to heat recovery plant for power generation.

Cement Mill

There are three cement mills . Unit 1 use cement mill 1 and Unit 2 use cement mill 2 and three.Material taken from clinker yard transported to hopper by the system of interlocking belts . There is also a conveyer for gypsum from where gypsum is pre crusher & stored to fed hopper.The fixed proportion of clinker and gypsum in the ratio 95 clinkers and 5 of gypsum respectively. The mixture of clinker and gypsum is fed via two weigh feeders & combine on one belt conveyor.At the end of the conveyor belt, just before the elevator, a metal detector and a magnetic separator is installed.If metal or a magnetic item is detected, then the changeover gate is used to remove them.

The elevator take the material to the feed bin which is placed above the roller press.

ROLLER PRESS

The feed bin is opened, and the mixture is flowing by gravity through the vertical the roller press. . The flow is controlled by adjustment of the speed of rollers of the roller pressThe crushed material leaves the roller press and these flakes are divided into two streams.The material extracted by the feeder from the overflow box is weighed and transported to the cement mill. The feed bin is opened, and the mixture is flowing by gravity through the vertical the roller press. . The flow is controlled by adjustment of the speed of rollers of the roller pressThe crushed material leaves the roller press and these flakes are divided into two streams.The material extracted by the feeder from the overflow box is weighed and transported to the cement mill.

The rollers are pressed together by the hydraulic system. The material passing through the roller gap is compressed / crushed, and the particle size is considerably reduced. Most of the material leaving the roller press is pressed into compressed flakes.The material send to the mill is controlled by the mill capacity.

BALL MILL

This ball mill has two compartment s.Compartment 1 has length of 3.30 meters .It is containing an equilibrium grinding media charge of 66.4 – 72.4 tons of steel balls .The size is vayring from 50-75 mm.

The partition between the first and second compartment is done with the help of diaphragm.Compartment 2 has an effective length of 8.91 meters .It is containing a grinding media charge of 194.8 -212.5 tons of steel .The sizi is varying from 20-30 mm.The ball mill fan, which ventilates the ball mill, draws the dedusting air from the mill to the bag filter dedusting this airflowThe water injection equipment is installed in both the inlet and the outlet end of the ball mill. Water vapours developed when the cement is cooled by water injection are removed from the mill by this air flow.The water injection ensure that the cement leave the ball mill has a temperature of 115-120 degree C.The material leaving the cement mill is transported by an inclined air slide, n elevator and another air slide to the inlet of the separator.

In this separator the material is dispersed and the fines are separated from the course.

The course material is returned via a weighing unit to the ball mill inlet for further grinding in the ball mill. The fines passing the separator is collected in the large bag filter, from where the collected material is transported to the cement silos.

Cement silos

At this point , cleaned air is recycled and circulating in a closed system as it is necessary foe separation.

The excess air containing some very fine dust is escaping via the chimney.

The material than send to cement silos.

Packing Unit:

After visiting the cement mill we went to packing unit where .

There are four packers in the packing unit.

Cement comes from silos through air slide to the bucket elevator throws the cement to screen then after screening it cement bin and then to rotary packer where it is weighed and packed in 50 Kg bags.

Each packer has two conveyer belts. Bags come through the belts conveyer to the loading trucks etc.

Two different products are:

1. DG brand and elephant brand ordinary port land cement.2. DG brand sulphate resistance cement.

WATER TREATMENT PLANT

Industry takes the water from the canal which is very closed to the industries.

Then took the water from there & pumped the water to the storage tanks with the help of centrifugal pumps.

Water is stored in thestorage tanks.

Water filtration is done before using in the process.The impure water can cause scaling and corrosion.

Water is send to softening tank to remove the hardness.

Softening Tank:

The raw water is pumped from the storage in to the softening thanks where it softened.

During regeneration, brine is led into the softening tank. During regeneration of one softening tank the other tanks can

operate. For regeneration 72 kgs of salt (98% NaCL) is used.

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

Cooling towers:

The 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.

Than water is send to the procees.After using water in a process water again come to the water treatment plan for softening and cooling.

Softened water is used at:

1. Compressor (To cool the compressor hot air)2. Raw mill (To control the temperature of mill)3. Cement mill (To control the temperature of bearing)4. Kiln bearing

Quality Controll

In the quality control, chemists are worked and they maintain the quality of the feed by examined them in hourly basis by taking samples.

Sampling of raw materialSample of raw mixture(in raw mill)Control the raw mixture through(Raw mill)Sample from CF SILO/BLENDING SILO(Intermediate storage)Sampling of kiln feedFinal processingSampling from clinkeThey take the samples of all the materials from different unit and analyse it by using QCXs(Quality Control by X-Ray analysis) technique.It is a machine and software is installed in the machine according to the standard composition.Unlss the quality control not pass the finished cement product it cannot be loaded onto the truck.

Followin parameters are under consideration for raw

mixture composition

Lime saturation factor (LSF)

CaO x 100

=

2.8xSiO2 + 1.18xAl2O3 + 0.65xFe2O3

Silica Modulus (SM)

SiO2

=

Al2O3 + Fe2O3

Alumina Modulus (AM)

Al2O3

=

Fe2O3

Hydraulic Modulus (HM)

CaO

=

SiO2 + Al2O3 + Fe2O3

FORMULAE FOR CLINKER

Tricalcium Silicate (C3S)

= (4.071xCaO – 7.60xSiO2 – 1.430xFe2O3 – 6.718xAl2O3 / LOIFAC.

Dicalcium Silicate (C2S)

= (2.867x–SiO2) / (LOIFAC – 0.7544xC3S)

Trcalcium Aluminate (C3A)

= (2.65xAl2O3 - 1.692xFe2O3)

Tetracalcium Aluminoferrite (C4AF)

= 3.04x Fe2O3 / LOIFAC

Liquid Phase

= (3.00xAl2O3) + (2.25xFe2O3) + MgO + K2O + Na2O + SO3

But if AM < 0.64, then

Tricalcium Silicate (C3S)

= (4.071xCaO – 7.60xSiO2 – 2.859xFe2O3 – 6.718xAl2O3 / LOIFAC.

C4AF + C2F

= (2.100xAl2O3 + 1.702xFe2O3) / LOIFAC.

ANALYSIS TECHNIQUES AND QC EQUIPMENT

In QC laboratories, generally dry as well as wet testing is done to control the

product at different stages.

a) X-ray Analyzer (XRF Spectrometer) is the main and most important

equipment used in the cement industry. On XRF, usually powder samples

are analyzed to determine different elements in the various materials.

Powder press or fused bead is prepared as per prescribed procedure and

then analyzed on the XRF.

b) Blaine apparatus is usually used for the cement fineness (specific

surface). A known weight of cement sample is taken in a cell and its time

flow is measured. Then the Blaine is calculated with reference to some

standard sample of known Blaine.

c) The residue (particle size) is determined on different micro sieves. A

known quantity of sample is taken on the sieve and the sieve is placed in

the apparatus under vacuum. The passing particles are sucked with

vacuum cleaner.

d) Liter weight is determined by passing the clinker from 10 mm sieve and

retaining on 5 mm sieve. This sample is taken in one-liter vessel and

weighed.

e) Free Lime of clinker is determined by solvent extraction method with

Monoethylene Glycol at a specific temperature for specific time and then

titrating against Hydrochloric Acid solution. This hydrochloric acid has

already been used for the titration of standard lime to calculate the factor.

f) Moisture and Loss on ignition are determined by keeping the material at

certain temperature for a specific time in oven or furnace.

g) Compressive strength of cement is determined by preparing cement-sand

moulds, placing the moulds in water and then breaking the moulds on

compressive strength machine.

CEMENT LOADING (DISPATCH)

Cement being loaded to customer from the packing plant is actually the

same that had come out of the cement mill but even then the material being

dispatched is also analyzed with respect to Blaine and chemical analysis.

However, sampling frequency is reduced for dispatched cement. Generally,

two samples of loading cement are collected in a shift if there is continuous

dispatch.

PHYSICAL TESTING OF CEMENT

The quality of cement is evaluated by carrying out following tests under

standard conditions.

Short Time Strength of cement (03 Days)

Long Time Strength of cement (28 Days)

Initial Setting Time

Final Setting Time

Cement Expansion

Water Consistency

FORMULAE FOR CEMENT

Lime saturation factor (LSF)

(CaO x 100) – (0.70 x SO3)

2.8xSiO2 + 1.18xAl2O3 + 0.65xFe2O3

Silica Modulus (SM)

SiO2

Al2O3 + Fe2O3

Alumina Modulus (AM)

Al2O3

Fe2O3

LOIFAC

= 1.0 – 0.01xLOI

Tricalcium Silicate (C3S)

= (4.071xCaO – 7.60xSiO2 – 1.43xFe2O3 – 6.718xAl2O3 – 2.852xSO3) / LOIFAC.

Dicalcium Silicate (C2S)

= (2.867x–SiO2) / (LOIFAC – 0.7544xC3S)

Trcalcium Aluminate (C3A)

= (2.65xAl2O3 - 1.692xFe2O3)

Tetracalcium Aluminoferrite (C4AF)

= 3.04x Fe2O3 / LOIFAC

But if AM < 0.64, then

Tricalcium Silicate (C3S)

= (4.071xCaO – 7.60xSiO2 – 2.859xFe2O3 – 6.718xAl2O3 – 2.852xSO3) / LOIFAC.

C4AF + C2F

= (2.100xAl2O3 + 1.702xFe2O3) / LOIFAC.

CEMENT STANDARDS

There are different cement standards that are followed during the cement

manufacturing process and the product cement must always comply with the said

standard. Generally following standards are being followed in cement industry.

Pakistan Standard (PS 232-1983 R) / British Standard (BS 12-1978)

This standard is applied to ordinary Portland cement and has following

specifications.

ITEM MINIMUM LIMIT MAXIMUM LIMIT

LSF 0.66 1.02

L.O.I. Nil 3.00%

I.R. Nil 1.50%

MgO Nil 4.00%

SO3 Nil 3.00

3-days strength 2200 PSI (15 N/mm2) Nil

28-days strength 5500 PSI (34.5 N/mm2) Nil

Initial S.T. 45 minutes Nil

Final S.T. Nil 10 Hours.

Expansion Nil 10 mm

Blaine 2250 cm2/g. Nil

Pakistan Standard (PS 612-1989 R)

This standard is applied to sulphate resistance cement and has following

specifications.

ITEM MINIMUM LIMIT MAXIMUM LIMIT

LSF 0.66 1.02

L.O.I. Nil 3.00%

I.R. Nil 2.00%

MgO Nil 4.00%

SO3 Nil 2.50%

3-days strength 20 N/mm2 Nil

28-days strength 39 N/mm2 Nil

Initial S.T. 45 minutes Nil

Final S.T. Nil 10 Hours.

Expansion Nil 10 mm

Blaine 2500 cm2/g. Nil

C3A Nil 3.50%

FACTORS AFFECTING THE CEMENT QUALITY

Generally all the materials and ratios affect the cement quality. But there are

some factors that, in particular, affect the quality of cement. Some of those

factors are already mentioned in the standard limits. Following are the major

items / factors that can make the cement quality below standard limits:

Sulphurtrioxide (SO3)

SO3 is one of the important factors that affect the cement quality with

reference to setting time. Therefore, gypsum is added to the clinker to

maintain the required initial and final setting time. If SO3 in cement is greater

than limit, setting time will be increased and vice versa.

Lime Saturation Factor (LSF)

LSF is also an important factor in cement quality. Greater LSF increases the

cement strength. But up to certain limit, there is no increase in cement

strength. On the other hand, more LSF requires more fuel to form the clinker.

Therefore, usually LSF is kept from 90 to 98 to get a good quality cement at

reasonable cost.

Free Lime

As discussed in the clinker manufacturing stage, free lime is an important

factor to verify the burning factor of clinker. If free lime is more than 1.5%, it

shows that clinker is not burnt properly. The cement of this un-burnt clinker

will give high expansion when applied. Therefore, it is tried at best to

minimize the free lime in clinker.

Chlorides

Chlorides also affect the cement quality. But there is no way to reduce the

chloride at any stage if it is in abundance in the raw materials. Usually cracks

are developed on the applied cement if chlorides percentage is high in the

cement.

Blaine (Specific Surface)

Fineness of cement is also a major factor that plays a key role in the cement

quality. High Blaine cement gives high cement strength as compared to low

Blaine cement. Like LSF, very high Blaine (> 3500) has uncountable affect on

cement strength, therefore, Blaine is always kept below this. More Blaine will

require more power consumption in cement mill.

Loss on Ignition (LOI)

If LOI in cement is on higher side, cement will set soon and ultimately its

strength will be lost. Reducing the cement mill outlet temperature can

control LOI.

Magnesium Oxide (MgO)

MgO is also a factor that affects the cement quality.

Special Feature Of DG Cement

Limestone and shale raised in mines through controlled blasting , ripping and dosing .

Conveying of limestone from mines to the limestone stacker through entirely covered single over long belt conveyer .

Separate closed conveying system for additives

All silos are equipped with closed mechanical or pneumatic conveying system .

All the transfer points and loading or unloading have provided with Back Filter

Conclusion

Working and training in D.G cement is very helpful to us . people and all staff members cooperated and treated us very well

In the end we will like to thanks the management for giving us the chance to visit and study operation of D.G cement plant . We students of COMSATS would also like to thanx all the senior members and engineers for giving us a lot of knowledge out of their experiences .

**THE END**