Training report at acc cements barmana

ACC

FOUR WEEK INDUSTRIAL TRAINING

AT ACC GAGAL CEMENT WORKS

BARMANA

PREPARED BY:- UNDER GUIDENCE OF:-

AASHISH KUMAR, MR. P.K. SINGH

MANOJ KUMAR ASSIT. MGR. INSTRUMENTATAION

MAHENDER CHAND

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SUMMER TRAINING PROJECT REPORT

ON PROCESS ASPECTS OF CEMENT

MANUFACTURING

(DIPLOMA IN INSTRUMENTATION)

SUBMITTED TO: SUBMITTED BY:

H.O.D. OF AASHISH KUMAR

INSTRUMENTATION MANOJ KUMAR

G.P.C. KANGRA MAHENDER CHAND

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ACKNOWLEDGEMENT

We express our deepest gratitude to Mr Atul Khosla (Director Plant) and Human Resource Development Center ACC Barmana for providing me the opportunity to undergo training in ACC.

I would like to thanks Mr. P.K SINGH (Assist. Manager Instrumentation) and his staff for cooperative guidance & helping me to learn a lot about different aspect of his company and under whose guidance I complete my summer training program.

I also put my special thanks to my training guide Mr.KHANNA, MR. MANI LAL, MR. BALWANT SINGH. who cared to give out an ample amount of time to me, regardless of being extremely busy in their work.

I would like to put forth my regardful thanks to all those who have and are making it a remarkable attempt in guiding me and making me learn the most during my short period of my training at ACC- GAGAL CEMENT WORKS, BARMANA.

AASHISH KUMAR

MANOJ KUMAR

MAHENDER CHAND

INDEX

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Sr.No TOPIC Page No.

1 Introduction 4-6

2 Overview of cement manufacturing process

3 Steps in cement manufacturing-- a. Quarrying b. Raw meal preparation c. Pyroprocessing d. 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

INTRODUCTION

ACC Limited, or ACC as it is popular known, is India’s largest manufacturer of cement and ready mix concrete, Formerly called “The Associated

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Cement Companies Limited”, it was established in 1936 following a historic merger of ten cement companies belonging to four business groups. ACC’s operations are spread throughout the country with 14 modern cement factories, 19 sales offices, and several area offices. The company has over 9000 employees.

Corporate OFFICE :

CEMENT HOUSE, 121, Maharshi. Karve . Road, Mumbai 4000 020

Regional office:

Eastern Region Northern Region South West Region

Kolkata. New-Delhi. Pune.

Cement Plants:

1. Bargar Cement Works Distt. Bargarh ( Orissa )

2. Chaibasa Cement Works Distt. Singhbhum ( Jharkhand )

3. Chanda Cement Works Distt. Chanderapur ( Maharashtra )

4. Damodar Cement Works Distt. Purulia ( West Bengal )

5. Gagal Cement Works Distt. Bilaspur ( Himachal Pradesh )

6. Jamul Cement Works Distt. Durg ( Chhattisgarh )

7. Kymore Cement Works Distt. Katni ( Madhya Pradesh )

8. Lakheri Cement Works Distt. Bundi ( Rajasthan )

9. Madukkarai Cement Works Distt. Coimbatore ( Tamil Nadu )

10. Sindri Cement Works Distt. Dhanbad ( Jharkhand )

11 Tikaria Cement Works Distt. Sultanpur ( Utter Pradesh )

12. Wadi Cement Works Distt. Gulbarga ( Karnataka )

GAGAL CEMENT WORKS – AN OVERVIEW :

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Gagal Cement Works a unit of the Associated Cement Companies Limited, has two unites Gagal I and Gagal II. Gagal I was set up in the year 1984 and Gagal II was set up in the year 1994. Clinker production of Gagal I is 2800 TPD and of Gagal II is 3300 TPD. The total annual capacity of the plant is around 6100 TPD. Both units are located at BARMANA in District BILASPUR of H.P..

KIND OF PRODUCT :

Ordinary Portland Cement (OPC) in different grades i.e. 33GR, 43GR, 53GR and Portland Pozzolona Cement (PPC). BIS (Bureo of Indian Standard). The company has registration to ISO 9002 & ISO 14001.

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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. When mixed with water cement hardens, both in air and under water and retains its strength under water.

OR

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 is manufactured by burning a calcareous material, such as, limestone, chalk, shells or marl and an argillaceous material such as clay, 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) Tricalcium Aluminate (C3A) Tetracalcium Alumino ferrite (C4AF).

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OVERVIEW OF CEMENT MANUFACTURING PROCESS

Cement manufacturing consists of raw meal grinding, blending, pre-calcining, clinker burning and cement grinding. In short, limestone and other materials containing calcium, silicon, aluminium and iron oxides are crushed and milled into raw meal. This raw meal is blended and heated in the preheated system to initiate dissociation of carbonate to calcium oxide and carbon dioxide.The secondary fuel is fed into the preheater to keep the temperature sufficiently high.Then meal is fed into the rotary kiln for reaction between caclcium oxide and other elements to form calcium silicates and other aluminates at temperature upto 1450 degree calcius.Primary fuel is used to keep temperature high enough in burning zone to chemical reaction takes place.

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PROCESS FLOW DIAGRAM OF CEMENT MEANUFACTURING

The raw materials used are lime stone, shale, iron ore and gypsum. The lime stone provided by nature and Iron-ore comes from BIHAR and RAJASTHAN. Firstly we get the 70mm size limestone with the help of crusher and stock it with the help of stacker through belt conveyor.

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In Raw mill / VRM section, limestone, shale, quartzite & Iron ore are fed in measured quantity through weigh feeders. In the mill the mixture further reduces the size to the desired fineness. The finer product separated by air separator is goes to the Electro-static precipitator & then to the blending silos and coarse material is fed back into the mill Inlet. Raw mill / VRM s controlled by central control room. The set point for chemical composition of the raw meal and fineness of the material is given by the Laboratory department.

From raw mill the raw meal is fed to the blending and the storage silos .In the blending part of the silo, further homogenization of raw meal takes place so that a constant quality is maintained. In storage part the raw meal is stored so that it may be fed at the desired rate. From there the material is fed to the low lift pumps (L.L.P.s) with the help of bucket elevators. Low lift pumps feed the material or raw meal to the preheater cyclone . 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 of preheating zone. About 60%of the coal firing is done at pre-calciner section itself . Raw meal which is almost calcined enters from the one end of the kiln . From the other end of the kiln the pulverised coal is fired . Various chemical reactions occurs as the raw meal progresses from feed end to the burning zone , where intermediate phases consisting of CaO, Al2O3, Fe2O3

become liquid and because of the rotation of kiln CaO and silica combine with liquid to form nodules called clinker.

At the lower end of the kiln the temperature reaches to about 1450 degree centigrade . Due to such high temperature the physical and the chemical characteristics of the raw meal changes . Clinker that comes out of the kiln is at a very high temperature and has to be cooled to facilitate handling and grinding . Hence, the clinker is passed through the cooler where cooling takes place by means of fans. Hot air is used for combustion inside the kiln and calciner. In cooler circuit the ESP has also been installed to control the air pollution. With the help of the drag chains and bucket elevators the clinker is fed to the clinker silos. .

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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 about 80% limestone (which is rich in CaCO3)and 20% clay or shale (source of slica,alumina and ferrite ).These are quarried and stored separately.The lime ind silica provide the main strength to cement,while the iron reduce the reaction 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 chemical composition,and grinding them to achieve proper particle size to ensure optimal fuel efficiency in the kiln and strength in final concrete product.If the dry process is used then raw material is dried by using dryers,Air separaters before grinding.

STEP.3 Pyroprocessing or Clinkering

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

STEP.4 Cement Milling

To produce the final product clinker is mixed with gypsum and other additive is grinded in large tube mill.First grinding breaks up the material and second grinds into fine powder. The grinding process is controlled to obtain a powder with a broad particle size range, in which typically 15% by mass consists of particles below 5 μm diameter.

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QUARRYING

Quarry operation consists of drilling,blasting,loading crushing,hanhling,screening and storing.

The raw materials are usually quarried from local rock, which in some places is already practically the desired composition and in other places requires the addition of clay and limestone, as well as iron ore, bauxite or recycled material.

BLASTING

LOADING & HAULAGE

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MINING, CRUSHING & HANDLING

Raw Material Crushing:

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HAMMER CRUSHER: - .

Description:-

These are used for the size reduction of hard to medium hard limestone 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 two types 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 the formula, P=mv²/2. Mass of hammers in hammer mill was reduced to minimum while increasing the velocity as far as possible, resulting in greater impact force combined with reduced wear. Rim speed of the hammers is in the range of 5000 to 7000 rpm. Power demand of single hammer crusher is between 1.3 to 2.8 HP h/t.

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Pre - blending: stacking and reclaiming

The blending bed consists of two equal material stockpiles which are arranged in line. These material stockpiles are used both for storing and also for prehomogeniation of the material to be stacked. The material stockpile 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’ with the boom raised its highest position. The boom is lowered to its lowest position after reaching the starting position.

The stacker starts the operating process after the commands for automatic mode of stacking are given from a central control room. The stacker now throws off the incoming material to the yard as it travels from one end of the stockpile 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 repeated until the boom, after 20 lifting steps, has reached its maximum lifting height and the stockpile is stacked to its maximum volume.

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The material is reclaimed from the stockpile by the forward movement of the scraper travel gears in connection with the reversible rake car on the scraper bridge, the rakes mounted to the car on the scraper bridge, the rake mounted to the rake car and the material discharge by the scraper chain drive.

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RAW MEAL PREPARATION

The raw materials are usually quarried from local rock, which in some places is already practically the desired composition and in other places requires the addition of clay and limestone, as well as iron ore, bauxite or recycled materials. The individual raw materials are first crushed, typically to below 50 mm. In many plants, some or all of the raw materials are then roughly blended in a "prehomogenization pile." The raw materials are next ground together in a rawmill. Silos of individual raw materials are arranged over the feed conveyor belt. Accurately controlled proportions of each material are delivered onto the belt by weigh-feeders. Passing into the rawmill, the mixture is ground to rawmix. The fineness of rawmix is specified in terms of the size of the largest particles, and is usually controlled 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 to ensure the mix is chemically homogenous. In the case of a dry process, the rawmill also dries the raw materials, usually by passing hot exhaust gases from 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 filling the raw meal to silos.

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RAW MILL – CIRCUIT FLOW DIAGRAM :

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 air separator).

4.Air Separator(to separate out coarse and fine particles). 5. A multi bag dust collector (for precipitating fine dust from mill draft)

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1. Function of Ball mill :

A ball mill is a type of grinder used to grind materials into extremely fine powder for use in many industries. The ball mill allows grinding of the harder limestone that are more common than chalk. A ball mill consists of a horizontal cylinder that rotates on its axis. It holds spherical, cylindrical or rod-like grinding media of size 15–100 mm that may be steel or a variety of ceramic materials, and occupy 20–30% of the mill volume. The shell of the mill is lined with steel or rubber plates. Grinding is effected by impact and attrition 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 with Hyper steel balls. The compartments are separated by double diaphragm for improving the retention time and transfer of material in second chamber for further grinding. Size reduction of the mill feed is performed by motion of the grinding media. Rotation of the mill cylinder raises the pile of mill feed and grinding media to an optimum height, necessary for grinding operation.

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2 . TERTIARY CRUSHER ( REVERSIBLE IMPACTOR TYPE)

It is a impactor type crusher employing a high speed rotating disc to which no. of hammers are fixed whose swung towards with centrifugal force. the hammers are made up of mild steel. The material is fed at top of the crusher and it is thrown out centrifugally and crushed by being between hammers and periphery of cylindrical casing. Since the the hammer bars are hinged, in case of any hard material does not cause damage to equipment. 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 a mass particle is prortional to surface presented by this particle to the air current. Materials leaving the distributing plate are acted upon by various forces. The action of force Fg &Fc

Upon a particle is proportional to its volume since volume is function of diameter cube.

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

Three forces acted upon particles are:

:

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VERTICAL ROLLER MILL

With the continual increasing demand for Portland cement and constant pressure for reduced energy consumption, producers are exploring a wide variety of cost-saving manufacturing options. One option is vertical roller mill technology for raw material grinding.

VRM-CIR

CUIT FLOW DIAGRAM :

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DESCRIPTION: It has same way of working as of raw mill, but it is more economical then raw mill. The raw material from hoppers goes to the vertical 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 stack to vent off.

VRM

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RAW MEAL HOMOGENISATION

Ground raw meal is stored in large blending silos. These silos are air activated to promote homogenization of the raw meal, reducing chemical variation and promoting a stable sintering process in the rotary kiln.. These may work continuously or batch-wise, in multi-stage systems, and in combination with air agitation. In modern plants, the trend is large, continuously operating silos. It follows that the silos, working as continuous blending systems, have to be full in order to have a blending effect. If the silos are only partially full, the variations in the raw mix composition from the raw mill will go directly to the kiln. The efficiency of a blending system can be characterized by the ratio, H, between variations in composition of the incoming and the outgoing material. An example is the ratio between the standard deviation of CaO in the raw meal before and after the kiln feed silos.Homogenization is the final opportunity to affect the raw meal chemistry and quality before introduction to the pyroprocessing phase.

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VARIOUS TYPE OF FIELD INSTRUMENT USED IN GAGAL CEMENT 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

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LEVEL 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

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OTHER MISCELENIOUS INSTRUMENT

Zero speed sensor and transmeter

VVVF drives (variable frequency variable speed drives)

Dc drive (10 nos ranging from 2.2 kw -1250kw)

Metal detector (10 nos)

CCTV kiln camera (4 nos)

Bag filter timer panel (100 n0s)

Electronic packer (7 nos)

Electronic ear (sound level)

Girth gear lubrication system ( nos)

Field bus control (10 nos)

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TEMPERATURE MEASUREMENT

Resistance Temperature Detectors (RTD)

RTDs commonly use Platinum, Nickel and Copper to form the sensors. The relation ship between the Resistance of these metals and Temperature is as shown below. Platinum is used very widely in the Industry for measuring the temperature of moderate range between 0–300 Deg. C.

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Nickel

Copper

Platinum

Res

i

s

t

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RTD Character i s t i cs

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 graph plots the relation ship between resistance and temperature is linear over a wide range of temperature from 250 – 800 deg C.

Metals are basically crystalline in structure comprising metal ions and free electrons in equilibrium. The application of DC potential across the metallic elements results in directional flow of these electrons. During their movement they collide with themselves and with the ions comprising the crystal lattice, thus restricting its flow, which results in an electrical resistance. As the metal is heated, temperature rises and the mean free length between collision decreases due to the increase in amplitude of oscillation, resulting in an increase in electrical resistance.

The range of temperature over which this phenomenon is valid is decided by the temperature coefficient of resistance, chemical inertness, and its crystal structure which should not undergo permanent changes within this range. In general, the resistivity of metals increases with an increase in temperature (i.e.: The Temp. coefficient is positive), where as in some semiconductors the resistance decreases with the increase of temperature. (i.e.: Temp. coefficient is negative). Such variation in the temperature can be measured with the suitable electrical circuits like Wheatstone’s bridge or Muller’s bridge.

Platinum wire

Mica

R1 R2 R3 R4

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Resistance 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 or foils 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 winding temperatures. Apart from it RTDs are used in the Coal mill circuit and other low temperature applications.

Problems faced: Damage to element of RTD due to vibration in bearings.

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Thermocouples

Thermocouples are perhaps the most widely and commonly used sensor’s for temperature measurements of higher ranges in any industrial application. The sensing 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 is proportional to the temperature, and at the point of contact, the electrons diffuse through the boundary layer between the two leads, resulting in one lead becoming positive and the other becoming the negative. Thus the EMF generated is proportional to the temperature difference in a predictable manner. This phenomenon is known as SEEBECK Effect.

Copper

Measuring Measuring

Junction Instrument

Constantan Reference Junction

Fig: Typical construction of Thermocouple Element

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North South

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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 a medium flowing at right angles to a pair of electrodes and a magnetic field will develop an emf across the electrodes.

Electrode

B

Fig : Principle of electromagnetic flow meter

In this device the fluid passing through the pipe has to be conductive. The schematic 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 the inner surface of the tube and in contact with the liquids. As the conductive liquid passes through the insulated tube with an velocity v, it may be considered as flat conductor disks passing through the magnetic field, inducing an emf e across the electrodes. This is expressed as following equation.

e = B X d X v X 10 -8 V Where, e is the induced voltage,

B is the flux density in tesla,

d is the distance between the two electrodes in meter,

v is the average velocity in met/sec

V is the constant to care of Units.

The main advantage of this flow meter is, it does not obstruct the flowing fluid and it do not have any moving part.

Application: VRM internal water spray flow measurement.

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Rotameters

A Rotameters consists of a vertical tube with a tapered cone in which a float assumes a vertical position corresponding to each flow rate through the tube. The conical tube is made of glass, stainless steel or Monel and the floats are made up of brass, stainless steel, monel or special plastics. The Rotameters are sometimes referred 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 given point 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. In gravitational type, the familiar Manometer is the simplest device. In elastic transducer the pressure exerts a force over the area of an elastic device. The force responsive member is in the form of diaphragm, capsule, bellows or Bourdon tube as shown in figure.

Membrane

P

P Corrugated

Stretched Diaphragm

Diaphragm

A B

pointer

Manometer Bourdon Gauge

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Elastic Element

Pressure

Transducer

Mechanical

to

Electrical Transducer

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The resultant displacement or strain developed is measured with an appropriate electrical sensor. The conversion of this mechanical phenomenon to an equivalent electrical signal is achieved by a variety of linkage mechanisms. The transduction principles used are deflection measurements with resistive, inductive, and capacitive principles or measurement of change in natural resonance frequency of a stretched member.

In all transducer energy from the measurand is converted to energy proportional to the measurand. Conventional pressure transducers achieve this by 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. The Indirect types of devices are, based on the elastic elements which deflects under pressure, such as diaphragms, bellows and tubes. Instruments of this group can be coupled to the mechanical to electrical transducers of suitable type.

Fluid

Energy Input

Mechanical Electrical Energy Output

Energy

Fig : Basic Principle for Pressure Transduce

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PROGRAMMABLE LOGIC CONTROLLER

CONCEPTUAL DIAGRAM OF A PLC:

The inputs to PLC come from the process connected devices or sensors such as:

Limit Switches/Inductive proximity Switch Push buttons Thermocouple Couples RTD Transmitters like 4 to 20 mA current source P to E converters

The Output from PLC are given to the devices and final control elements such as:

Lamps Indicators Relays Solenoids Motor contactors 4-20 mA signals to operate control valves

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SERIAL OR

PARALLEL I/O PROCESSOR

RACKS

PROCESS OR MACHINE TO BE CONTROLLED BY PLC

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The processor part of the PLC contains a Central Processing Unit (CPU), Program Memory, and Data Memory. The operation of the PLC starts with execution the control program stores in the program memory. This program reads the status of all input devices connected to it and stores it in input status table of the data memory. It then executes the instructions used for process or machine control and calculates output conditions as per the program logic. These output conditions are stored into the output status table of the Data Memory. The output devices connected to the I/O racks are updated as soon as the CPU calculates the outputs. This operation of PLC; called as ‘PLC Scan’; is cyclic and continues unless interrupted by an external command. The Time taken by the processor to complete one PLC Scan is called “ Scan Time “.

Apart from the processor and I/O Racks, a programming device is also required to enter the user program. The programming device is a personal computer, which is connected to the processor only while loading and testing the program.

TYPES OF PLC USED AT GAGAL CEMENT WORKS

Seimens S5 100U PLC in all Stacker Reclaimers Coal as well as Limestone Allen Bradley SLC500 PLC in Bag House of K2 and Packing House of Gagal I Tata Honeywell LCS 620 PLC in Gagal Packing House Compton Greaves PLC in Gagal II Packing House, and for air blasters.K1 and

K2.

HONEYWELL LCS 620 PLC

The Honeywell LCS 620 programmable controller is a modern state of the art PLC. The LCS (Logic Control System) Series consists of 620-12, 620-16, 620-36 and 620-35 processors.

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PREHEATER

All the three processes drying,preheating and calcinations are done in the preheater.

The key component of the gas-suspension preheater is the cyclone. A cyclone is a conical vessel into which a dust-bearing gas-stream is passed tangentially. This produces a vortex within the vessel. The gas leaves the vessel through a co-axial "vortex-finder". The solids are thrown to the outside edge of the vessel by centrifugal action, and leave through a valve in the vertex of the cone. Cyclones were originally used to clean up the dust-laden gases leaving simple dry process kilns. If, instead, the entire feed of rawmix is encouraged to pass through the cyclone, it is found that a very efficient heat exchange takes place: the gas is efficiently cooled, hence producing less waste of heat to the atmosphere, and the rawmix is efficiently heated. This efficiency is further increased if a number of cyclones are connected in series

Heat Transfer in preheater:

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Raw meal is fed to the top of the preheater and it flows down in feed pipe,while the hot gases coming from kiln flows in upward direction due to upward force applied by Id fan.As the hot gase going up through riser duct and raw meal coming down comes in intimate contact the heat transfer take place due to which hot gase transfer the heat to the raw material and heat it up in the preheater and gases cool down.

As we see in the graph between temperature and stages,temperature of exhaust gas decrease as it flows from 5th stage 1st stage and on other sides temp. of raw meal increases as it comes down from 1st to 5th stage.

Precalciner ;

ROTARY KILN

A Rotary kiln is a pyroprocessing device used to raise materials to a high temperature (calcination) in a continuous process. The rotary kiln consists of a tube made from steel plate, and lined with firebrick. The tube slopes slightly (1–4°) and slowly rotates on its axis at between 30 and 250 revolutions per hour. Rawmix is fed in at the upper end, and the rotation of the kiln causes it gradually to move downhill to the other end of the kiln.

The temperature of the burning zone is 1400-1500 0C.

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FUNCTIONAL DESCRIPTION :

The feed material enters the rotary kiln through the inlet housing. The inclination and the rotation of the kiln cause the material to move in counter-flow to the hot gases towards the outlet and from there into the cooler.

In this process the feed material passes through the following reaction zones :

1. Preheating zone (subject to kind of preheater )

2. Calcining zone (subject to the kind of preheater )

3. Clinkering zone 4. Cooling zone

The presence and the length of these zones is mainly dependent on the composition of the material to be burnt , the preheater and the downstream cooling system Diameter and the length of the rotary kiln depends upon the desired output and are considerably influenced by the chosen preheater and cooling. The quality of the refractory lining of the rotary kiln pipe is adjusted to the length of the reaction and temperature zone and is specifically determined for every individual plant.

The heat quantity required for different reaction stages is generated by the rotary kiln burner at the rotary kiln outlet. The combination air is high

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temperature secondary air coming from the cooler section. The hot gases flow through the rotary kiln and reach the inlet housing via the rotary kiln inlet. The heat is transmitted to the feed material by the contact between the hot gases and the material and by its contact with the refractory brick lining.

Successive chemical reactions take place in the kiln:

70 to 110 °C - Free water is evaporated. 400 to 600 °C - clay-like minerals are decomposed into their

constituent oxides; principally SiO2 and Al2O3. Dolomite (CaMg(CO3)2) decomposes to calcium carbonate, MgO and CO2.

.650 to 900 °C - calcium carbonate reacts with SiO2 to form belite

(Ca2SiO4). Cement clinker

CLINKER COOLING

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The reciprocating grate cooler serves for the cooling of the small sized or granulated burned material. An excellent cooling effect is achieved in that. The cold air is blown through the cooler grate and through the burned material lying on the grate.

Cooling principle:

The burned material discharged from the kiln falls through the inlet shaft of the cooler onto the entry to the grate . Due to the special design to the grate entry the material to be cooled forms a uniform bed. Over the stationary and movable grate plate rows, the burned material is transported by the forward movement of the movable grate plate rows to the end of the cooler.

The oscillating frame with the movable grate plate rows is driven on both the sides; the number of the strokes per minute is infinitely variable. The cooling air is generated by the several fans. Normally, one fan is allocated to each air chamber, thereby providing the targeted aeration to the grate and the material to be cooled.

The heated up cooling air is captured in the upper section of the cooler and is available for the further use as secondary air for the kiln or as the tertiary air.

CEMENT GRINDING

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Final processing step in the manufacture of the cement is cement grinding.It is the grinding of mixture of clinker and additives into a finished product Object is to create a particular fineness of the product to achieve some predetermined physical characteristics in the cement. When in concrete, Main ingredient used in cement is the clinker. Clinker is ground with gypsum to produce Portland cement. Grinding mill is the main component used in finish grinding system. A ball mill is horizontal cylindrical drum with two compartments having steel balls of the different diameter. as grinding media . Clinker is ground by a closed circuit grinding system where mill product is routed through the dynamic air separator and the material coarser than the required grain size is returned to the mill. Thus, separator removes the coarser and the fine particles, which are fed back to the mill.

Cement mill

Cement clinker is usually ground using a ball mill. This is essentially a large rotating drum containing grinding media - normally steel balls. As the drum rotates, the motion of the balls crushes the clinker. The drum rotates approximately once every couple of seconds.The drum is generally divided into two or three chambers, with different size grinding media.

As the clinker particles are ground down, smaller media are more efficient at reducing the particle size still further. Grinding systems are either 'open

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circuit' or 'closed circuit.' In an open circuit system, the feed rate of incoming clinker is adjusted to achieve the desired fineness of the product. In a closed circuit system, coarse particles are separated from the finer product and returned for further grinding.

BALL MILL INTERNAL

Ball mill

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Function of gypsum in cement:

DUST COLLECTORS

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1.Cyclone Separator:

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2.Bag Filter

3.Electrostatic Precipitator:

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CEMENT STORAGE,PACKAGING & DISPATCH

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Packing Plant is the place where cement is stored, packed and dispatched to various destinations.

Gagal Cement Works Packing Plant has seven cement silos.

All the packers have the truck loading facility because the cement from Gagal is transported to different destinations by road only.

The different varieties of cement handled are :

33 Grade OPC (Ordinary Portland Cement) as per IS : 269 43 Grade OPC (Ordinary Portland Cement) as per IS : 8112 PPC (Portland Pozzolana Cement) as per IS : 1489(part II) PPC (Portland Pozzolana Cement) super Separate bags Godown is

available in Gagal plant I and Gagal plant II, Where up to 40 lakhs and 80 lakhs can be stored respectively. Packing plant is close liason with cement Dispatch section and Laboratory.

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Cement packing and dispatch is done through road transported by trucks only.

Cement dispatch section receives order from RMO and accordingly they place demand of trucks to the truck unions, destinations wise. Then the trucks are placed in accordance to demand for loading of cement. The silo from which the cement is to be extracted for loading depends upon the type of cement and type of cement filled in the silos.

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Thank you

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