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INDEX

Sr.No TOPIC

Page No.

1 Introduction

4-6

2 Overview of cement manufacturing process3 Steps in cement manufacturing--a. Quarryingb. Raw meal preparationc. Pyroprocessingd. Cement grinding

10-12

4 Various instruments used in field

13-33

5 PLC , Preheater

34-36

6 Clinker Cooling,bag filter

37-38

7 Cement packing, storage &dispatch

39-40

8

Conclusion

41

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PORTLAND CEMENT

DEFINITION:

Cement is finely ground hydraulic binding medium for mortar and concrete,consisting substantially of compounds of CaO with SiO2, Al2o3 and ferric

oxide which have been formed by sintering or fusion. „Sintering‟ means

burning at a temperature which cause partial fusion of the material. Whenmixed with water cement hardens, both in air and under water and retainsits strength under water.ORPortland cement clinker is a hydraulic material which shall consist of atleast two-thirds by mass of calcium silicates (3CaO.SiO

2

and 2CaO.SiO

2

), the remainder consisting of aluminum- and iron-containing clinker phasesand other compounds. The ratio of CaO to SiO

2

shall not be less than 2.0.The magnesium content(MgO)shall not exceed 5.0% by mass.Portland cement is manufactured by burning a calcareous material, suchas, limestone, chalk, shells or marl and an argillaceous material such asclay, shale etc. at a high temperature of 1450-1500ºc and grinding the

resultant product called „Clinker‟ with the addition of the small quantity of

the Gypsum.The ordinary Portland cement consists of four major components i.e.

Tricalcium Silicate (C3S)

Dicalcium Silicate (C2S)

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Tricalcium Aluminate (C3A)

Tetracalcium Alumino ferrite (C4AF).

OVERVIEW OF cemENT MANUFACTURINGPROCESS

Cement manufacturing consists of raw meal grinding, blending, pre-calcining, clinker burning and cement grinding. In short, limestone andother materials containing calcium, silicon, aluminium and iron oxides arecrushed and milled into raw meal. This raw meal is blended and heated inthe preheated system to initiate dissociation of carbonate to calcium oxideand carbon dioxide.The secondary fuel is fed into the preheater to keep thetemperature sufficiently high.Then meal is fed into the rotary kiln forreaction between caclcium oxide and other elements to form calcium

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Tricalcium Aluminate (C3A)

Tetracalcium Alumino ferrite (C4AF).

OVERVIEW OF CEMENT MANUFACTURINGPROCESS

Cement manufacturing consists of raw meal grinding, blending, pre-calcining, clinker burning and cement grinding. In short, limestone andother materials containing calcium, silicon, aluminium and iron oxides arecrushed and milled into raw meal. This raw meal is blended and heated inthe preheated system to initiate dissociation of carbonate to calcium oxideand carbon dioxide.The secondary fuel is fed into the preheater to keep thetemperature sufficiently high.Then meal is fed into the rotary kiln forreaction between caclcium oxide and other elements to form calcium

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The raw materials used are lime stone, shale, iron ore and gypsum.The lime stone provided by nature and Iron-ore comes from BIHAR andRAJASTHAN. Firstly we get the 70mm size limestone with the help ofcrusher and stock it with the help of stacker through belt conveyor.In Raw mill / VRM section, limestone, shale, quartzite & Iron ore arefed in measured quantity through weigh feeders. In the mill the mixturefurther reduces the size to the desired fineness. The finer productseparated by air separator is goes to the Electro-static precipitator & thento the blending silos and coarse material is fed back into the mill Inlet. Rawmill / VRM s controlled by central control room. The set point for chemicalcomposition of the raw meal and fineness of the material is given by theLaboratory department.From raw mill the raw meal is fed to the blending and the storagesilos .In the blending part of the silo, further homogenization of raw mealtakes place so that a constant quality is maintained. In storage part the rawmeal is stored so that it may be fed at the desired rate. From there thematerial is fed to the low lift pumps (L.L.P.s) with the help of bucketelevators. Low lift pumps feed the material or raw meal to the preheatercyclone . To reduce the requirement of heavy coal injection in the kiln ,95%of the calcination occurs in the M.F.C., D.D.F. vessels and cyclones ofpreheating zone. About 60%of the coal firing is done at pre-calciner sectionitself . Raw meal which is almost calcined enters from the one end of thekiln . From the other end of the kiln the pulverised coal is fired . Variouschemical reactions occurs as the raw meal progresses from feed end to theburning zone , where intermediate phases consisting of CaO, Al

2

O

3

, Fe

2

O

3

become liquid and because of the rotation of kiln CaO and silica combinewith liquid to form nodules called clinker.At the lower end of the kiln the temperature reaches to about 1450degree centigrade . Due to such high temperature the physical and thechemical characteristics of the raw meal changes . Clinker that comes outof the kiln is at a very high temperature and has to be cooled to facilitate

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handling and grinding . Hence, the clinker is passed through the coolerwhere cooling takes place by means of fans. Hot air is used for combustioninside the kiln and calciner. In cooler circuit the ESP has also been installedto control the air pollution. With the help of the drag chains and bucketelevators the clinker is fed to the clinker silos. .

STEPS IN MANUFACTURING OF PORTLAND CEMENT

Portland cement is manufactured in four step process.STEP 1.

Quarrying

The raw material for cement manufacture is rock mixture which is about80% limestone (which is rich in CaCO3)and 20% clay or shale (source ofslica,alumina and ferrite ).These are quarried and stored separately.Thelime ind silica provide the main strength to cement,while the iron reduce thereaction temperature and gives the cement its characterstic grey colour.STEP 2.

Raw Meal Preparation

It involves mixing the extract raw material to obtaine the correct chemicalcomposition,and grinding them to achieve proper particle size to ensureoptimal fuel efficiency in the kiln and strength in final concrete product.If thedry process is used then raw material is dried by using dryers,Airseparaters before grinding.STEP.3

Pyroprocessing or Clinkering

In this raw mix is heated to produced cement clinker(which is grey incolour and in spherical nodules with diameter ranging 0.3-5cm).It involvesthree steps preheating,calcining(in which CaO is formed)and burning. Thepyroprocessing takes place in kiln department.The raw mix is provided inform of powder.In the rotary kiln temperature is ranging about 1400-1450°c.STEP.4

Cement Milling

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handling and grinding . Hence, the clinker is passed through the coolerwhere cooling takes place by means of fans. Hot air is used for combustioninside the kiln and calciner. In cooler circuit the ESP has also been installedto control the air pollution. With the help of the drag chains and bucketelevators the clinker is fed to the clinker silos. .

STEPS IN MANUFACTURING OF PORTLAND CEMENT

Portland cement is manufactured in four step process.STEP 1.

Quarrying

The raw material for cement manufacture is rock mixture which is about80% limestone (which is rich in CaCO3)and 20% clay or shale (source ofslica,alumina and ferrite ).These are quarried and stored separately.Thelime ind silica provide the main strength to cement,while the iron reduce thereaction temperature and gives the cement its characterstic grey colour.STEP 2.

Raw Meal Preparation

It involves mixing the extract raw material to obtaine the correct chemicalcomposition,and grinding them to achieve proper particle size to ensureoptimal fuel efficiency in the kiln and strength in final concrete product.If thedry process is used then raw material is dried by using dryers,Airseparaters before grinding.STEP.3

Pyroprocessing or Clinkering

In this raw mix is heated to produced cement clinker(which is grey incolour and in spherical nodules with diameter ranging 0.3-5cm).It involvesthree steps preheating,calcining(in which CaO is formed)and burning. Thepyroprocessing takes place in kiln department.The raw mix is provided inform of powder.In the rotary kiln temperature is ranging about 1400-1450°c.STEP.4

Cement Milling

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To produce the final product clinker is mixed with gypsum and otheradditive is grinded in large tube mill.First grinding breaks up the materialand second grinds into fine powder.The grinding process is controlled to obtain a powder with a broad particlesize range

,in which typically 15% by mass consists of particles below 5 μm

diameter.

QUARRYING

Quarry operation consists of drilling,blasting,loadingcrushing,hanhling,screening and storing.The raw materials are usually quarried from local rock, which in someplaces is already practically the desired composition and in other placesrequires the addition of clay and limestone,as well as iron ore, bauxite

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HAMMER CRUSHER: -

.

Description

:-

These are used for the size reduction of hard to medium hardlimestone and for raw marl crushing. Reduction ratios are as high as 1:40.Depending upon crusher feed this can be reduced to 1:60. Generally twotypes of the hammer crushers are manufactured:

Single shaft hammer crusher.

Double shaft hammer crusher.These work with the impact effect of the hammers according to theformula, P=mv²/2. Mass of hammers in hammer mill was reduced tominimum while increasing the velocity as far as possible, resulting ingreater impact force combined with reduced wear. Rim speed of thehammers is in the range of 5000 to 7000 rpm. Power demand of singlehammer crusher is between 1.3 to 2.8 HP h/t

Pre - blending: stacking and reclaiming

The blending bed consists of two equal material stockpiles which arearranged in line. These material stockpiles are used both for storing andalso for prehomogeniation of the material to be stacked. The materialstockpile of one pile can be reclaimed while the other stockpile is stacked.

Stacking of the blending bed:-

Stacking of the blending bed is carried out in the „Chevron method‟ by

means of a stacker with loop car. The stacker with loop car is moved into

its starting position in „manual mode‟ w

ith the boom raised its highestposition. The boom is lowered to its lowest position after reaching thestarting position.The stacker starts the operating process after the commands for automaticmode of stacking are given from a central control room. The stacker nowthrows off the incoming material to the yard as it travels from one end of thestockpile to the other, until a material probe which is mounted to the boom

tip sends a singal „material height reached‟. Then a command is given to

the luffing gear to lift the boom by one lifting step. This process is repeateduntil the boom, after 20 lifting steps, has reached its maximum lifting height

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and the stockpile is stacked to its maximumvolume

.

The material is reclaimed from the stockpile by the forward movementof the scraper travel gears in connection with the reversible rake car on thescraper bridge, the rakes mounted to the car on the scraper bridge, therake mountRAW MEAL PREPARATION

The raw materials are usually quarried from local rock, which in someplaces is already practically the desired composition and in other placesrequires the addition of clay and limestone,as well as iron ore, bauxite orrecycled materials. The individual raw materials are first crushed, typicallyed to the rake car and the material discharge by the scraperchain drive

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to below 50 mm. In many plants, some or all of the raw materials are thenroughly blended in a "prehomogenization pile." The raw materials are nextground together in a rawmill.Silos of individual raw materials are arrangedover the feed conveyor belt. Accurately controlled proportions of eachmaterial are delivered onto the belt by weigh-feeders. Passing into therawmill, the mixture is ground to rawmix. The fineness of rawmix isspecified in terms of the size of the largest particles, and is usuallycontrolled so that there are less than 5%-15% by mass of particles

exceeding 90 μm in diameter. It is important that the rawmix contains no

large particles in order to complete the chemical reactions in the kiln, and toensure the mix is chemically homogenous. In the case of a dry process, therawmill also dries the raw materials, usually by passing hot exhaust gasesfrom the kiln through the mill, so that the rawmix emerges as a fine powder.This is conveyed to the blending system by conveyor belt or by a pump.

RAW MILL

Activity of Raw mill department start from feeding the raw materials(Limestone, Shale, Quartzite and Iron ore) to the mills and ends at fillingthe raw meal to silos.

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RAW MILL CIRCUIT CONSISTS OF:1.Feed Hoppers(to feed lime stone &corrective materials).2.Weight Feeders(to feed material in different rates).3.Bucket Elevator(to carry raw material & product discharge from mill to airseparator).4.Air Separator(to separate out coarse and fine particles).5. A multi bag dust collector (for precipitating fine dust from mill draft)

1.

Function of Ball mill

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A

ball mill

is a type of grinder used to grind materials into extremely finepowder for use in many industries. The ball mill allows grinding of theharder limestone that are more common than chalk. A ball mill consists of ahorizontal cylinder that rotates on its axis. It holds spherical, cylindrical orrod-like grinding media of size 15

–

100 mm that may be steel or a variety ofceramic materials, and occupy 20

–

30% of the mill volume. The shell of themill is lined with steel or rubber plates. Grinding is effected by impact andattrition between the grinding media

.

The ball mills are two chamber tube mill lined with Mn steel liners,chambers are separated by intermediate diaphragms and charged withHyper steel balls. The compartments are separated by double diaphragmfor improving the retention time and transfer of material in second chamberfor further grinding. Size reduction of the mill feed is performed by motion ofthe grinding media. Rotation of the mill cylinder raises the pile of mill feedand grinding media to an optimum height, necessary for grinding operation

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A

ball mill

is a type of grinder used to grind materials into extremely finepowder for use in many industries. The ball mill allows grinding of theharder limestone that are more common than chalk. A ball mill consists of ahorizontal cylinder that rotates on its axis. It holds spherical, cylindrical orrod-like grinding media of size 15

–

100 mm that may be steel or a variety ofceramic materials, and occupy 20

–

30% of the mill volume. The shell of themill is lined with steel or rubber plates. Grinding is effected by impact andattrition between the grinding media

.

The ball mills are two chamber tube mill lined with Mn steel liners,chambers are separated by intermediate diaphragms and charged withHyper steel balls. The compartments are separated by double diaphragmfor improving the retention time and transfer of material in second chamberfor further grinding. Size reduction of the mill feed is performed by motion ofthe grinding media. Rotation of the mill cylinder raises the pile of mill feedand grinding media to an optimum height, necessary for grinding operation.

2

. TERTIARY CRUSHER (REVERSIBLE

IMPACTOR TYPE

)

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It is a impactor type crusher employing a high speed rotating disc towhich no. of hammers are fixed whose swung towards with centrifugalforce. the hammers are made up of mild steel. The material is fed at top ofthe crusher and it is thrown out centrifugally and crushed by being betweenhammers and

periphery of cylindrical casing. Since the the hammer barsare hinged, in case of any hard material does not cause damage toequipment. The bars are readily replaced when they are worn out.

Hammer crusher

3

.AIR SEPARATOR

Principle of operation

:

Action of air current of a certain velocity upon amass particle is prortional to surface presented by this particle to the aircurrent. Materials leaving the distributing plate are acted upon by variousforces. The action of force Fg &FcUpon a particle is proportional to its volume since volume is function ofdiameter cube.It is an industrial machine which sorts materials by a combination of size,shape, and density.It works by injecting the material stream to be sorted

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into a chamber which contains a column ofrising air.Inside the separation chamber, airdrag on the objects supplies an upward force which counteracts the force of gravity and liftsthe material to be sorted up into the air.

VERTICAL ROLLER MILL

With the continual increasing demand for Portland cement and constantpressure for reduced energy consumption, producers are exploring a wide

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variety of cost-saving manufacturing options. One option is vertical rollermill technology for raw material grinding.VRM-CIRCUIT FLOW DIAGRAM :

DESCRIPTION:

It has same way of working as of raw mill, but it is moreeconomical then raw mill. The raw material from hoppers goes to thevertical raw mill where material is grinded and fines are through to CF silo

and to bag house. Fines from bag house go to the blending silo and stackto vent off.

RAW MEAL HOMOGENISATION

Ground raw meal is stored in large blending silos. These silos are airactivated to promote homogenization of the raw meal, reducing chemicalvariation and promoting a stable sintering process in the rotary kiln.. Thesemay work continuously or batch-wise, in multi-stage systems, and incombination with air agitation. In modern plants, the trend is large,continuously operating silos. It follows that the silos, working as continuousblending systems, have to be full in order to have a blending effect. If thesilos are only partially full, the variations in the raw mix composition fromthe raw mill will go directly to the kiln. The efficiency of a blending systemcan be characterized by the ratio, H, between variations in composition ofthe incoming and the outgoing material. An example is the ratio betweenthe standard deviation of CaO in the raw meal before and after the kiln feedsilos.

Homogenization is the final opportunity to affect the raw meal chemistryand quality before introduction to the pyroprocessing phase.

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and to bag house. Fines from bag house go to the blending silo and stackto vent off.

VRMRAW MEAL HOMOGENISATION

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Ground raw meal is stored in large blending silos. These silos are airactivated to promote homogenization of the raw meal, reducing chemicalvariation and promoting a stable sintering process in the rotary kiln.. Thesemay work continuously or batch-wise, in multi-stage systems, and incombination with air agitation. In modern plants, the trend is large,continuously operating silos. It follows that the silos, working as continuousblending systems, have to be full in order to have a blending effect. If thesilos are only partially full, the variations in the raw mix composition fromthe raw mill will go directly to the kiln. The efficiency of a blending systemcan be characterized by the ratio, H, between variations in composition ofthe incoming and the outgoing material. An example is the ratio betweenthe standard deviation of CaO in the raw meal before and after the kiln feedsilos.

Homogenization is the final opportunity to affect the raw meal chemistryand quality before introduction to the pyroprocessing phase.

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VARIOUS TYPE OF FIELD INSTRUMENT USED IN GAGALCEMENT WORKS

TEMPRATURE MEASUREMENT

Resistance temprature measurement (RTD)

Thermocouple

Optical pyrometer

FLOW MEASUREMENT

Head type flow meter like orifice,venturi,pitot tube.

Electromegnatic flow meter

Rotameter

PRESSURE MEASUREMENT

Diaphragm, bourdon tube

LVDT type transducer

VEL MEASUREMENT

Capacitor level measurement

RF type level measurement

Ultra sonic level measurement

Vibrating folk type level measurement

Float type level switch

Bin level measurement

Radar type level measurement

WIEGHING SECTION (STRAIN GAUSES

)

Solid flow meter

Weigh feeder

Rotor scale

Multi core

Belt weigher

Weigh bridge

Poldos system

GAS ANALYZER

CO analyzer

Oxygen analyzer

NOX analyzer

TEMPERATURE MEASUREMENTResistance Temperature Detectors (RTD)

RTDs commonly use Platinum, Nickel and Copper to form the sensors. Therelation ship between the Resistance of these metals and Temperature is asshown below. Platinum is used very widely in the Industry for measuring thetemperature of moderate range between 0

–

300 Deg. C.

NickelCopperPlatinum

Resist

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Platinum RTD’s are used widely in industries because it is resistant to corrosion

and oxidation, malleable, has a very high melting point. As shown in the graphplots the relation ship between resistance and temperature is linear over a widerange of temperature from 250

–

800 deg C.Metals are basically crystalline in structure comprising metal ions and freeelectrons in equilibrium. The application of DC potential across the metallicelements results in directional flow of these electrons. During their movementthey collide with themselves and with the ions comprising the crystal lattice, thusrestricting its flow, which results in an electrical resistance. As the metal is heated,temperature rises and the mean free length between collision decreases due tothe increase in amplitude of oscillation, resulting in an increase in electricalresistance.The range of temperature over which this phenomenon is valid is decided by thetemperature coefficient of resistance, chemical inertness, and its crystal structurewhich should not undergo permanent changes within this range. In general, theresistivity of metals increases with an increase in temperature (i.e.: The Temp.coefficient is positive), where as in some semiconductors the resistance decreaseswith the increase of temperature. (i.e.: Temp. coefficient is negative). Suchvariation in the temperature can be measured with the suitable electrical circuits

like Wheatstone’s bridge or Muller’s bridge

R

esistance Temperature Detector (Four Wire)

Calendar’s interpolating equation for temperature above 0 deg C for Platinum

(PT100) sensor is as given below.Platinum resistance elements (PT100) fabricated with high purity wires orfoils are excellent for high precision temperature measurements. Coiled platinum

wire elements are used on board aircraft’s for outside air temperature

measurements.Application: Measurement of bearing temperatures and motor windingtemperatures. Apart from it RTDs are used in the Coal mill circuit and other lowtemperature applications.Problems faced: Damage to element of RTD due to vibration in bearings.

thermocouples

Thermocouples are perhaps the most widely and commonly used sensor’s for

temperature measurements of higher ranges in any industrial application. Thesensing is based on the principle that current flows in a closed circuit made up of two dissimilar metals if the junction of the two metals kept at different temperature. In each lead, the concentration of the valence electron isproportional to the temperature, and at the point of contact, the electrons diffusethrough the boundary layer between the two leads, resulting in one leadbecoming positive and the other becoming the negative. Thus the EMF generatedis proportional to the temperature difference in a predictable manner. Thisphenomenon is known as SEEBECK .

FLOW MEASUREMENTS

Electromagnetic Flow Meters

The Operation of this type of flow meters are based on the Faradays laws of electromagnetic induction principal. The law states that the relative motion of amedium flowing at right angles to a pair of electrodes and a magnetic field willdevelop an emf across the electrodes.ElectrodeBFig : Principle of electromagnetic flow meterIn this device the fluid passing through the pipe has to be conductive. Theschematic arrangement of the Electromagnetic flow meter is as shown in figure.The flow tube lies in the uniform magnetic density B

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The two electrodes are inserted in the tube, their surfaces being flushed with theinner surface of the tube and in contact with the liquids. As the conductive liquidpasses through the insulated tube with an velocity v, it may be considered as flatconductor disks passing through the magnetic field, inducing an emf e across theelectrodes. This is expressed as following equation.e = B X d X v X 10-8V Where, e is the inducedvoltage,B is the flux density in tesla,d is the distance between the two electrodes in meter,v is the average velocity in met/secV is the constant to care of Units.The main advantage of this flow meter is, it does not obstruct the flowing fluidand it do not have any moving part.

Application:

VRM internal water spray flow measurement.

Rotameters

A Rotameters consists of a vertical tube with a tapered cone in which a floatassumes a vertical position corresponding to each flow rate through the tube. Theconical tube is made of glass, stainless steel or Monel and the floats are made upof brass, stainless steel, monel or special plastics. The Rotameters are sometimesreferred as constant pressure drop, variable area or variable aperture meters.Flow

PRESSURE MEASUREMENTS:

Pressure is defined as the force acting per unit area, measured at a givenpoint or over a surface. This can be in absolute, gauge or differential units,depending on the reference taken.

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Pressure Transducers can be classified into gravitational and elastic types. Ingravitational type, the familiar Manometer is the simplest device. In elastictransducer the pressure exerts a force over the area of an elastic device. Theforce responsive member is in the form of diaphragm, capsule, bellows orBourdon tube as shown in figure.MembranePP CorrugatedStretched DiaphragmDiaphragmA Bpointer

Manometer Bourdon Gauge

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The resultant displacement or strain developed is measured with anappropriate electrical sensor. The conversion of this mechanical phenomenonto an equivalent electrical signal is achieved by a variety of linkagemechanisms. The transduction principles used are deflection measurementswith resistive, inductive, and capacitive principles or measurement of change innatural resonance frequency of a stretched member.In all transducer energy from the measurand is converted to energyproportional to the measurand. Conventional pressure transducers achieve thisby converting the pressure to a mechanical displacement.The pressure measuring transducers can be of two types. They are

Direct

and

Indirect

type of measurement.The direct types of measuring devices are, Manometer, barometers etc. TheIndirect types of devices are, based on the elastic elements which deflectsunder pressure, such as diaphragms, bellows and tubes. Instruments of thisgroup can be coupled to the mechanical to electrical transducers of suitabletype.

LOW MEASUREMENTS

Electromagnetic Flow Meters

The Operation of this type of flow meters are based on the Faradays laws of electromagnetic induction principal. The law states that the relative motion of amedium flowing at right angles to a pair of electrodes and a magnetic field willdevelop an emf across the electrodes.ElectrodeBFig : Principle of electromagnetic flow meterIn this device the fluid passing through the pipe has to be conductive. Theschematic arrangement of the Electromagnetic flow meter is as shown in figure.The flow tube lies in the uniform magnetic density B