Report on Birla CementT

8/2/2019 Report on Birla CementT

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Report

On

Industrial Training

(18th

May To 19th

June, 2009)

At

Grasim Aditya Birla Cement, Kotputli

SubmittedBy

Vanshaj Kaul

In

Partial fulfillment of

Award of B. Tech. degree

In

Electronics Instrumentation and Control Engineering

Of

Rajasthan Technical University, Kota

(Department of Electronics Instrumentation and Control

Engineering)

GLOBAL INSTITUTE OF TECHNOLOGY,

JAIPUR

(Accredited with A Grade by NAAC-UGC)


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CONTENTS

1. Introduction1.1Overview of plant1.2Goals and Vision1.3Process of cement production1.4Types of cement

2 Field instruments

2.1 Temperature transmitters

2.2 Pressure transmitters

2.3 Level transmitters

2.4 Weigh feeders

2.5 Gas analyzer

2.6 X-ray analyzer

3. ESP

4. Drives

4.1 AC drives (VFD)


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INTRODUCTION

The family of Birla hails from a small but beautiful town of Pilani in Rajasthan. This s

place from where the illustrious and magnificent history of the Birla Industrial House

began. The Birla Industrial House rests on the strong foundations built on the vision,

dedication, commitment and hard work of our beloved and visionary leader late Shri

Ghanshyam Das Birla.

Shri Aditya Vikram Birla-

Shri Aditya Birla was one of the most progressive industrialists who moved much

ahead of his time. He was the chairman of many major industries and was also a

Director of several government bodies such as the Reserve Bank of India, India Fund,

Air India, Infrastructure Leasing and Financial Services, ICICI and was a member of

the Asian Institute of Management, Asian Convertible and Income Fund, FICCI and

Board of Trade. Leading Indian Management bodies and business publications had

conferred upon him several awards such as `Businessman of the year` award,

`Businessman Leadership` award, `Management Man of the year` award and the

`Rashtra Bhusan` award. He was also posthumously awarded the first `JRD TataAward for Corporate Leadership`.

Shri Kumar Mangalam Birla-

Shri kumar mangalam Birla was groomed to take over the mantle of the Group by his

father Shri Aditya Birla. He has been giving new thrust to Marketing strategy

,expansion ,Core competence ,Benchmarking ,HRD etc ,so as to make the group a

truly Indian Multinational with global vision. The Aditya Birla Group has three clear

strength

1) Continuous investment in new technologies2) Motivated and decentralized management3) Strict accounting and monitoring system


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1.1) PLANT OVERVIEW

Grasim Cement is one of the largest cement plants in India of Grasim Aditya Birla

Group, situated nearMohanpura village, Kotputli, Rajasthan. It is one of the major

suppliers of various grades of cement in the north of India. It has very high production

to fulfill the demands of the market as it is one of the best & well known cement, used

by the people. To accomplish the production, VC-I (accompanied by new

technologies) with the latest technology used for the cement production. VC-I was

established in the year 2005, with the production of 8000 TPD, VC-II was established

in the year 2007 producing the same 8000 TPD. The main technology supplier for line

1 & 2 is M/s KHD Humboldt Wedge Germany and for line 3 it is M/s Krupp Polybius

Germany.

It is also the winner of many quality awards such as TPM (Total Productive

Maintenance), ISO etc. & is working well to upgrade its certificates day by day. All

the employees have been made responsible to take care of all these awards & to

maintain the quality of the production as required by the certifying authorities.

1.2)GOALS AND VISION

Goals by 2010-2012:-

1) To achieve 10,000 TPD production in the year 2010-2011.2) Achieve the lowest power consumption and fuel consumption among the

ABG group units as well as in the cluster by 2011-2012.

3) Produce quality as per the group norms from the day one.4) Highest fly ash consumption among the group units by 2011-2012.5) Produce cement at the lowest cost in the cluster as well as group units.6) Plant highest number of trees approx-15,000 per annum.7) Lowest dust emission per ton of cement in India.8) The highest OHS score among all the group units.


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Goals by 2015:

1) Exploit full potential of the plant i.e. 12,000 TPD by the year 2013.2) Achieve global benchmark in terms of environmental norms.3) Productivity and energy efficiency by 2015.

Vision:

1) To be the most carbon efficient.2) Lowest fuel consumption.3) Lowest power consumption.4) Higher conversion ratio.5) Use of the alternate fuels.6) Low SOx and NOx emission.7) Waste heat recovery.8) Dense deep rooted plantation.9) Use of renewable energy resources.

Special features:

1) Entire process is fully computerized, leaving no scope for human errors.All the control systems are Windows based.

2) Cement and other raw material are checked as per our quality plan.3) All the raw materials are stacked in separate bins and are stored under

cover so that aggregates are not exposed to direct sunlight and

environment pollution.

4) Cement, Fly ash, Slag etc. are stored in separate silos for better control onrecipe.

5) Handling of fly ash and slag are done from closed bunkers to silos directly.6) Separate weigh-batchers are provided for each ingredient like cement,

water, admixtures and aggregates. The weighing is done on sophisticated

electronic weigh batchers. Precise weighing of all materials is done

through electronic load cells made up of special alloys.


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7) Homogeneous mixing of concrete is ensured by use of special high-efficiency mixers like pan-type or turbo-twin shaft mixers.

8) A fully equipped onsite plant laboratory is available at each plant.9) A Sprinkler system is installed to ensure temperature control of aggregates

in hot weather.

10)In line with Groups focus towards environment and eco-friendliness allsilos are installed with bag filters and level indicators to avoid any kind of

pollution.

11)Processes are in place for effective and periodic maintenance andcalibration of all critical components.

12)Laser sensor and moisture control are used for a stringent qualityassurance.

13)Well trained and experienced engineers are available at every plant to takecare of the quality of concrete.

The Aditya Birla Groups (ABG) products and the services offer distinctive customer

solution worldwide. The group has operation in 25 countries-


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Globally the Aditya Birla group is:

1) A metal powerhouse, among the worlds most cost-efficient aluminum,and copper producers. Hindalco from its fold is a fortune 500 company. It

is also the largest Aluminum rolling company and one of the 3 biggest

producers of Aluminum in Asia with the location copper smelter.

2) The 11th largest cement producer globally and 2nd largest in India.3) Among the most energy efficient fertilizer plant.4) The 4th largest producers of the carbon black.5) The 4th largest producers of the insulators.6) Among the worlds top 15 BPO companies and among Indias top 4


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1.3) PROCESS FOR CEMENT PRODUCTION:

Cement is basically produced by two processes: - Dry & Wet. In Birla Cement dry

process is used for cement production as it is less power consuming & easy to

manufacture. The basic raw material used for cement production is the Limestone.

Birla Cement has its own mines for acquiring limestone.The basic process for the

cement production is being described here under:-

Mines:

The process of mining which is used here to extract Limestone from the Earth is Open

cast mining. The process of mining includes three things:

Prospecting: It is the process of finding potential at place from where very useful &

bulk quantity of limestone can be extracted.

Drilling: After providing with a better place for mining, the process of drilling takes

place, in which the place is drilled with the drilling machines, for inserting the

dynamites.

Blasting: After drilling holes, this place is blasted by blasting materials inserted insidethe drilled part to break the huge rocks into pieces.

These pieces of rocks are brought near to the crusher & are further processed.

Crusher:

The crusher crushes these collected rocks into fine pieces of 50 mm size. It just breaks

down the huge rocks into compatible sizes with Impact / hammer mechanisms.

Pre-homogenization of raw material:

In this process this crushed material is arranged in the form of piles with the help of

stacker, to make it available for picking it up for further processing. Here definite pile

size is fixed. Laterite [Iron ore] is also mixed in this process. This piled material is

then reclaimed by the Reclaimer. The function of Reclaimer is just to reclaim the

definite amount of material from the pile & provide it to conveyor belt, which

conveys this picked up material to the raw-mill. Reclaimer ensures equal distribution

of material over conveyor belt. Before conveying the material to raw-mill, the


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magnetic separation process takes place to remove all the magnetic material

accompanying the raw material.

Raw-Mill section:

In Raw-mill section, this conveyed material is transferred into hopper which feeds and

regulated amount of material to the mill. This feeding is carried out with TFG (Triple

Feed Gate), which is a hydraulic gate used to avoid overfeeding of material in mill.

Raw-Mill consists of large rollers, which is used to grind this crushed material into

fine powder. This fine powder is collected & is stored in Raw-mill silos, which is

called Raw-Meal for Kiln.

Preheater section:

In this the Raw-Meal stored in raw mill silo is first preheated before feeding it to Kiln

section. For heating this material here, mainly pulverized Coal / Pet coke is used

which is procured from various places. This imported coal / pet coke is first crushed

in crusher, then grinded to fine powder in vertical coal mill & then this powdered coal

is stocked in coal mill silos.

A proper amount of coal powder is sucked from coal mill silos & then fired through

burners for preheating the raw meal at Pre-calciner and Kiln.

Preheating is necessary to raise the temperature of raw meal and to utilize waste heat

for further calcinations of kiln feed.

Kiln section:

A Kiln is a big rotating cylinder about 55 to 60m long, 3.8 to 4.2m in diameter. Here

the continuous heating of this preheated material takes place at around 1200-1450oC.

The Kiln cylinder is tilted to an angle of 3-4 degrees and is rotating at about 3 to

5.5rpm to make the material flow in one direction only.

Cooler section:

In this section, hot clinker coming out from kiln is fed. This hot clinker is cooled from

air stream produced by various cooler fans. This cooled clinker is stacked in clinker

stock piles. The clinker is then fed to cement mill for further processing.


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Cement mill:

Before feeding to cement mill, the clinker is further mixed with definite amount of

Gypsum, which determines setting time for cement. This mixed material is then fed to

cement mill, where this mixed material is further grounded in fine powder, forming

cement.This cement thus produced is stocked in huge silos equipped with packing

plant at the bottom from where the cement bags are filled, weighed & packed & hence

supplied to the market through various transporters.

To accomplish this long process for definite amount of mixing & process control for

controlling various processes of the plant, as it is operated fully automatically, that is,

no manual operation is needed, for which an upgraded & better control system is

needed. And for making the control system functional & to take care of various

electronic measuring systems, where the field electronics have its necessity. The plant

is equipped with PLCs (Programmable Logic Controls) controlling the whole

processes of the plant from a single office namely CCR (Central Control Room) with

PCs controlling the operation of each machine in the plant all around 24 hours driving

each & every electrical machines with definite supplies & frequency for

accomplishing cement manufacturing.

1.4) TYPES OF CEMENT:

There are many types of cement in the market to suit every need. Some of them which

are included in the revised ISO: 456-2000 is as follows:

1) Ordinary Portland Cement 33, 43, 53 grades (OPC), 53-S (Sleeper Cement)2) Portland Pozzolana Cement (PPC),3) Portland Slag Cement (PSC)4) Sulphate Resisting Portland Cement (SRC)5) Low Heat Portland Cement

Even though only Ordinary Portland Cement is graded according to strength, the other

cements too have to gain a particular strength. 33, 43 and 53 grade in OPC indicates

the compressive strength of cement after 28 days when tested as per IS: 4031-1988,

eg, 33 Grade means that 28 days of compressive strength is not less than 33 N/mm2


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(MPa) . Similarly for 43 grade and 53 grade the 28 days compressive strength should

not be less than 43 and 53 MPa respectively. 43 and 53 grade are also being

introduced in PPC and PSC shortly by the Bureau of Indian Standards (BIS)

PORTLAND POZZOLANA CEMENT

PPC is manufactured by inter grinding OPC clinker with 15-35% of pozzolanic

material. Pozzolanas are essentially siliceous or aluminous material, which in itself

possesses no cementitious properties, which will be in finely divided form and in the

presence of moisture react with calcium hydroxide, liberated in the hydration process,

at ordinary temperature, to form compounds possessing cementitious properties. The

pozzolanic materials generally used are fly ash or calcined clay. PPC produces less

heat of hydration and offers greater resistance to attack of aggressive environment

gives long-term strength and enhances the durability of structures.

PORTLAND SLAG CEMENT

PSC is obtained by mixing blast furnace slag, cement clinker and gypsum and

grinding them together to get intimately mixed cement. The quantity of slag varies

from 30-70%. The gain of strength of PSC is somewhat slower than OPC. Both PPC

and PSC will give more strength than that of OPC at the end of 12 months. PPC and

PSC can be used in all situations where OPC is used, but are preferred in mass

construction where lower heat of hydration is advantageous or in marine situations

and structures near seacoast or in general for any structure where extra durability is

desire.

2) FIELD INSTRUMENTS

The various field instruments that are being used here for measuring various

parameters for the chemical reactions, taking place & to notice any malfunctioning of

the systems are:

2.1) Temperature Measurement:

The various instruments used here for the measurement of temperature are:

1) Thermocouple2) Resistance temperature detector (RTD)


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3) Radiation pyrometersThermocouples:

A thermocouple has two junctions. The measuring or hot junction, which is subjected

to the temperature being measured & the reference or cold junction where the free

ends of the thermocouples are connected to the measuring instrument. Since, the

instrument measures the mV generated by the temperature difference between the

measuring & reference junction. It is important that the reference junction be

maintained at a constant temperature or that the measuring instrument be

automatically & accurately. Compensated for temperature changes at this junction. It

is a two terminal device.

Working Principle:

The thermocouple depends upon the principles known as the SEEBECK EFFECT.

Seebeck found that an electric current flows in a continuous ckt. of two metals if the

junctions are at different temperature. Thermocouple converts temperature to

millivolts. The millivolt signal goes to temperature transmitter at site and transmitter

converts the millivolts signal to 4-20 mA, for this 24 V excitation comes from

MP panel. 4 - 20 mA signal goes to MP panel from transmitter & MP panel

converts 4 - 20 mA to temperature and this temperature is displayed on monitor at

CCR.

The thermocouples can be classified into various types according to their chemical

composition. Three of them can be given as,

1. K-type (chromal, allumal) (1200 & more degree Celsius)

2. J-type (iron, constantan) (up to 650 degree Celsius)

3. R-type (rubidium, platinum) (1800 & more degree Celsius)

Resistance Temperature Detector (RTD):

RTDs, basically works on the principle that the value of resistance changes with the

change in temperature. It is a three terminal device. Two of its terminals are

connected to the two ends of the platinum bulb, & the third terminal to one of its end

of the bulb to nullify the effects due to the resistance of the transmission wires. The

temperature dependency of the resister can be shown as,


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Rt = R0(1+ T)

For positive temperature coefficients of Platinum. The resistance thermometers can be

made up of mainly three materials namely, platinum, nickel, copper, where each one

is used according to its application.

Pt- 2000-500

0C

Ni- 1300-150

0C

Cu- 00-120

0C

Here, RTDs are used to measure a temperature up to 600-6500C as it can measure

with complete accuracy & precision up to this temperature range. So, these are

equipped around the motors, drives, lubricating systems, etc.

2.2) Pressure Measurement:

The model Rosemount 1151 ALPHALINE series of pressure transmitters brings true

precision to the measurement of flow, level, gauge & absolute pressure, vacuum &

specific gravity. Direct electronic sensing with the completely sealed delta-cell

capacitance sensing element allows significant improvement & stability in pressure

measurement. Installation, calibration and commissioning are simplified by compact

design, integral junction box and local span

and zero adjustment.

Construction:

The isolating diaphragms and fill fluids on the

high & low sides transmit the process pressure

to the oil fill fluid. The fluid in turn transmits

the process pressure to a sensing diaphragm in

the center of delta-cell sensor. The sensing

diaphragm functions as a stretched spring

element that deflects in response to differential

pressure across it.

Working Principle:


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In AP transmitters, a reference pressure is maintained on the low side. The

displacement of the sensing diaphragm is proportional to the pressure. Capacitor

plates on both sides detect the position of the sensing diaphragm. The differential

capacitance between the sensing diaphragm & the capacitor plates is converted

electronically to an appropriate current, voltage or digital HART(Highway

addressable remote transducer) o/p signal.

Features:

1) Superior Performance: 0.1% accuracy, 15:1 range ability.2) Smart, analog or low power electronics.3)

Compact, rugged construction resistant to vibration.

4) Differential pressure from 30 in H2O to 1000 psig.5) Gage pressure from 30 in H2O to 6000 psig.6) Absolute pressure from 150 in H2O to 1000 psig.

2.3) Level controllers:

Capacitance type level controller:

This level controller consists of two units:

1) The CONTROLLER wall mounted at a particular location.2) The PROBE HEAD with electrode mounted from the top of the tank or bin or

silo. It is designed to provide on-off control or as an alarm sensor at two

points, low & high. It is usable for level control of granular solids, powders &

liquids -conductive and non-conductive.

Working principle:

This unit operates in conjunction with a single probe unit which converts capacitance

sensed by the probe to current and (the container) i.e. the capacitance which is formed

between the probe and the container, when the probe is gradually covered or

uncovered by the material in the container. The probe unit feeds a dc signal

proportional to material level, to the controller unit. The probe head houses transducer

disc type T-910 (P).


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The controller unit contains, regulated dc supply & control ckt on one PCB, two set

level control adjustments- one for low level and one for high level, and respective

control relays.

The two relays are having one set of change over contact each. Appropriate relay

operates when the level in the container reaches the point at which the high or low

level control is set. The relays are wired for fail safe operation, i.e. low level drops out

above level (high). These control adjustments are provided on front panel, accessible

via the hinged front door of the controller.

Installation:

Installation of the LC-112 is simple. The probe unit is mounted vertically on the

container with its 1" BSP connection (standard) and the controller mounted on a

convenient surface. The location of the probe should be as away as possible from

entry or exit material.

The distance between the probe and the controller can be 1000 meters, maximum.

Cable to connect probe to controller can be standard 3 cores, aluminum conductor 1.5

mm2

up to 300 meters. The relay change over contacts is brought out on the terminal

strip and can be used to controls pumps, valves, solenoids etc. The length of the probe

is such that at least 100mm. Of the probe should always be covered by material when

it is at the lowest level.

Application:

Capacitance type level controller finds almost universal application in any processing

plant or storage depot. The performance of this instrument is not affected by

properties of material such as conductivity corrosiveness or by process parameter

such as temperature, pressure. The NIVOLARM ALC is used for detecting mini/max.

level of the material in containers.

Probe:The probe is the active element of the system that goes with in the container &

comes in contact with the material of which level is to be detected. The probe used for

level detection can be partly or fully insulated either of rod type or flexible rope with

an attached to its lower end.


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Pre-amplifier:-The pre- amplifier consists of an oscillator & detections ckt. That

converts the capacitance change into DC signals for transmission to NIVOLARM.

The ckt. Is mounted on a glass epoxy board. The board is encased in plastic housing

& housing is filled with synthetic potting resin.

Admittance Level Limit Switch:

SAPCON admittance level limit switch utilizing specially designed immuno coat

probe offers a reliable solution to level detection problem. Immuno coat probe

comprises of two concentrically constructed electrodes that are insulated from each

other & ground.

The inner most electrode is the measuring electrode, the next is the shield & the outer

most is ground. The measuring electrodes & shield are connected to a radio frequency

source, so that they have identical w/f but are isolated from each other.

RF currents does not flow b/w the shield & mounting (GND), which being out of the

measuring ckt. does not affect indication. The only path left for the current to flow

through is the admittance path via the material to the vessel wall (GND). This being

the only path of interest, the system gives a reliable indication of level. This method

gives satisfactory solutions into environment such as where:

1). Conductive or non-conductive materials coats the probe.

2). There is bridging of material coats the probe.

3). Materials particles with Es change & varying temperature float in the vicinity of

the probe.

Operatingprinciples:-The sensitive portion of the probe & container wall (or GND

element) forms a means of measure the admittance of the system with & without the

inverting meters, when all the parameters that effects the admittance valve are kept

constant then its values change only due to the different material level. This change

after amplifier is used to operate is by the o/p contacts of which used for signaling &

control measurement system comprises of the following:

1).Probe of special constructions immune coat system.

2).Electronic inserts ICA-3000.

3).Evaluation unit type levtester-SLA SERIES.


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The probe is of a special construction with two concentrically positioned electrodes

that are isolated from each other & GND. It is provided with suitable mounting

arrangement of the screwed flange type. The electronic insert can either be directly

mounted on probe or remotely installed in a separate housing. The electronic insert

comprises of an RT oscillator, detector & coat immunizing circuitry all enclosed in a

plastic housing & potted with epoxy resin built in terminals on electronic insert

facilitate inter connection.

The electronic insert converts admittance variation into a dc current, which is

transmitted via the 3- core connecting cable to the evaluation unit. A low voltage dc

supply is provided for the operation of the insert by the evaluation unit. The

evaluation unit consists of step down transformer, rectifier, and Voltage regulator, I to

V Converter, Amplifier, Fail safe ckt, and Relay & Led indication. Initial admittance

of the installed system can be tuned out by setting the range selection switch to

appropriate position.

Metal Detecting Devices:

The metal detecting devices type (sq & sqta) are designed to be used on conveyor

systems as they are employed in various industries, wherever metal pieces in the

conveyed material may damage sensitive machinery, metal detecting devices will

prevent expensive repairs & production breakdowns.

Function: - A high frequency alternating voltage is fed from the amplifier to a coil in

the probe via a 75cms coaxial cable. This generates an electromagnetic field. If a

metal piece comes into this field, induction current will generated that will drain

power from the oscillators.

If depending on the selected sensitivity an unwanted metal piece in the conveyed

material is identified by the electronics in the amplifier, the output relay will switch to

its other state for about 0.5 seconds.

The output relay has two potential free NC/NO contacts that are wired to the terminal

strip. These contacts can be used to stop the conveyor belt, or to activate an ejection

device.

2.4) Weight Indicators / Feeders:

The reaction which is taking place inside, for cement production should be controlled,

in order to produce a good quality of cement & in order to achieve this, the feeding &


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mixing of material should be proper. This constant feeding (say) is achieved by using

weigh feeders. The principle behind the weigh feeder is that if we maintain a constant

amount of material to flow into the processing machines then the above requirement

can be fulfilled. A definite amount of material is maintained over the conveyor belts

by analyzing the tones per hour (TPH) over the conveyor belts again & again &

increasing or decreasing the material feed over it, for constant feed.

For above control the tones per meter are measured using two instruments, namely,

Load cells & taco generators.

Load cells are placed at the bottom of the conveyor belts. The load over it produces a

pressure over it. Load cells probably functions on the principle that the value of

resistance changes with the pressure over it producing a change in the voltage value

across it. This change of value indicates the tones per meter of the belt. The taco

generator connecter at the rolling end of the conveyor belt rollers gives the speed of

the rotating belt in meters per hour. These two values when multiplied using the

software gives the value in tones per hour indicating the amount of feed per unit time.

Thus by analyzing this value the operator in the CCR can analyze it & can increase or

decrease the amount of feed into the machines by adjusting the feed into these

conveying belts

2.5) Gas Analyzers:


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Gas analyzers are mainly used to measure the amount of different gases inside the

heating machines, such that for a definite reaction definite amount of gas should be

evolved & to reduce the harmful gases evolved during the reactions.

The amount of gas evolved can be measured by using gas analyzers. There are mainly

two types of gases that should be maintained in this plant for completing the required

reactions in it, these are oxygen & carbon mono oxides. There amount is measured by

using gas analyzers. The gas analyzers work on the principle that different gases

absorb different amount of heat radiations. As such the change in the properties of the

gas in accordance with the heat absorbed gives the amount of gas.

For measuring the gas amount an infrared source is used. This infrared radiation is

passed on to a mirror which absorbs this radiation & allows it to pass through two

different paths. One path having inert gas tank, which has the property that it does not

alter the properties of the radiation. While the other path having the gas inlet. The gas

evolved during the reaction is given as a inlet at this point.

CO measurement:

The CO gas when comes into this tank absorbs a definite amount of radiation, thus

changing the amount of heat flow through the second path. By measuring the amount

of this difference in the heat flow one may be able to guess the amount of CO

evolved.

O2 measurement:

The O2 gas when comes into the tank at the path second have some change in its

paramagnetic properties, by noticing this particular amount of change one may guess

the amount of O2 gas used.

2.6) X-Ray Analyzer:

Principle of X-ray

analyser:

An X-RAY tube irradiates

the specimen with high


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intensity primary X-ray radiation. The elements present in the specimen are excited

and emit their own characteristic X-ray radiation. The wavelength or energy of which

serves to uniquely identify the elements. The intensities of these radiation represent a

measure of the concentration of the element present in the sample. A maximum of 28

monochromators are arranged radially arround the specimen. Each monochromators

consists of an analyzer crystal, a detector, an inlet slit & an outlet slit. Each is

optimized for the characteristic radiation of a specific element.

Analyzer crystals: PET, Ge, Graphite, AdP, InSb, KAP, RbAP, TIAP, PbSt. For each

element, the crystal used in the monochromators is specially bent because the mean

radius of curvature is different for each wavelength. The radiation emerging from the

outlet slit falls on a detector, in which each X-ray quantum produces an electrical

pulse.

Spectrometer:

Spectrometer chamber: The monochromators & the detectors are housed in the

spectrometer chamber. The sample is introduced into the spectrometer chamber from

below and is irradiated by the X-ray tube located in the center.

The spectrometer chamber is evacuable and consists of a trough and a removable

cover with counter weights. The spectrometer chamber can be opened easily &

quickly; the X-ray tube, sample changer & monochromators are not disturbed by this

action.

X-raytube : A type AGRh-65 oil insulated X-ray tube with Rh or Pd anode is used in

the MRS 400. The protective housing is firmly connected to the tube. The front

window permits a circular arrangement of the monochromators around the specimen.

In this tube, the cathode is at ground potential & the anode (Rh or Pd ) at high

potential. Therefore anode needs its own closed cooling circuit, filled with deionized

water, which is cooled through a heat exchanger to the water fed in from outside.

Sample changer: The pneumatically operated sample changer is located at the

bottom of the spectrometer trough. It consists of a rotatable sample plate, a swivel

bracket and a sample changer.


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Monochromator: MRS 400 can be fitted with up to 28 permanently set

monochromators. Each monochromator contains an analyzer crystal specific to an

element and is adjusted in such a manner that the Bragg condition or a fluorescence

line of the element to be measured is fulfilled.

Detectors: Flow counter tubes and scintillation counters are used as detectors. They

detect particular element of interest and produces pulses accordingly. Flow counter

tube covers the wavelength range from 0.15 to 0.18mm.

Counter tube gas : The flow Counter tubes are generally operated using a

commercial counter tube gas mixture consisting of 90% argon & 10% methane. Gas

mixture only absorb the short wave background radiation to a small extent while

absorbing the long wave radiation adequately.

Pressure controller: Flow Counter tubes are sensitive to pressure fluctuations in the

atmosphere. The pressure controller ensures that the spent counter tube gas flows into

a constant pressure rather than into the variac atmospheric pressure.

Temperature control unit: Any instability in the temperature in the spectro -meter

undesirably affects the measuring accuracy, especially due to changes in the lattice

constant of the analyzer crystals. The MRS 400 therefore equipped with a temp.

Control unit which maintain the temp. in the spectrometer cabinet within 24 C+,- 0.5

C. It comprises a cooling unit, two heat exchangers, a heating element & a ventilator.

Vacuum unit: Since the fluorescent radiation of the light element is absorbed to a

great extent in air, the spectrometer is equipped with a vacuum unit.

Vacuum unit produces vacuum to avoid the absorption of the radiation. The vacuum

control unit permits automatic operation from the start to the completion of the

measurement.

Electronic measuring cabinet:

High voltage generator: The high voltage generator supply the high voltage required

for operating the detectors. Several detectors (same type) can be connected to one

high voltage generator, but in doing so high voltage distributors must be connected in


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between. If flow Counter tubes & scintillation counters are used at the same time,

separate high voltage generator is required.

High voltage distributors:

The high voltage for each detector is set separately on the high voltage distributors.

Different distributors are used for flow counter tubes & scintillation counters.

Compact channels: The pulses of the detectors are processed & counted in this

channel. The compact channels consist of a linear amplifier, a discriminator, a pulse

counter & a gate which can be used to interrogate the result of the count. Signals from

the detectors are fed into compact channels in which three modules are combined. For

each detector & thus for each element, there is one compact channel.

1) Linear amplifier for incoming pulses.2) Discriminator for filtering the pulses according to pulse amplitude.3) Scaler4) Pulse counter5) Rate meter converts the pulse rate to a proportional D.C. voltage which can be

read from an indicating instrument.

Control & evaluation unit:

The control and evaluation unit consists of a process computer and a floppy disk with

two mechanisms.

The computer controls the measurement accepts the measured values and calculates

the concentrations of the elements using an evaluation program. The computer also

monitors important equipment functions.

Control commands, acknowledgment signals and measurement results are input and

output via a terminal with line printer or screen.

X-Ray generating unit:

The X - ray generator generates the high voltage and the heating current for the X-ray

tube. It consists of the control module, a.c. voltage adjuster, high voltage unit, ion

exchanger and cooling unit.The oil insulated and water cooled high voltage unit


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contains the high voltage transformer and a rectifier. The a.c. voltage adjuster controls

the primary voltage of the high voltage transformer.The anode of the X-ray tube is

supplied with the high voltage and must therefore be cooled by deionized water. This

is supplied by a sealed unit containing an ion exchanger and a cooling unit.The X-ray

generator contains a current limiter which protects the X-ray tube from being

overloaded. The onset of limitation depends on the high voltage set.The flow and

temp. of the inner cooling water circuit are also monitored. The flow in the outer

cooling water circuit is monitored by a dynamic flow detector.

3)Electrostatic Precipitator [ESP]

Introduction:

Bag houses and Precipitators are used for effective dust collection. Both are quite

efficient. Although they collect dust in a vastly different manner. The primary

difference between them is that Precipitators have a constant pressure drop and

variable performance, while Bag houses have a variable pressure drop and

constant performance.

Advantages :

1). Versatility: - Effective performance.

2). Efficiency: - Sustained high efficiency collection (often greater than 99.9%) on

particles of all sizes, sub micron included.

3).Power consumption: - 20 to 60 kW per 100,000 cubic feet of gas.

4). Pressure loss:-Resistance negligible, rarely more than 0.4" water column. Fan

power costis therefore low.

Electrostatic precipitation process consists of three fundamental steps:

a). Charging of particulate

b). Collection of particulate

c). Removal of the collected material

There are basically two types of Precipitators: Wet & Dr


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Working Principle:

Electrostatic precipitator is an apparatus which cleans process gases by using

electrical forces to remove solid particles carried in the gas stream. The dirty gases are

passed through an intense electrical field set up between electrodes of opposite

polarity. The discharge electrodes -so called because of the corona discharge which

results from the application of high voltage-impart a negative charge to the particles.

These particles are then attracted to the collector electrodes which are positive with

respect to the discharge electrodes and in practice are connected to ground through the

structure or through ground cables.

The particles build up into a layer on the grounded collecting electrodes until a

rapping force is applied to the electrodes to dislodge and break up the layer into

agglomerated sheets which are heavy enough to fall into the hopper without being re-

entrained.

Precipitator Components:

Housing / Shell:

Exterior sheet metal/stiffened casing, penthouse or insulator

Compartments, support columns and beams, hoppers.

Treatment zone :

Perforation plates, wires/ discharge electrodes, collecting plates/

Electrodes.

Structural components:

Lower discharge electrodes frames, upper discharge electrodes frames,

Plate support system.

High voltage electrical supply system :

Circuit breaker, magnetic contactor, meters, automatic voltage controls,

SCRs, current limiting reactors, Xmer

/rectifier sets.

Other important component:

Rappers and vibrators, rapper controls, purge air system, insulators.


26/33

Electrical system and components:

A steady DC voltage obtained from a filtered power supply was not suitable for use in

precipitator due to an unsatisfactory spark response. In modern precipitators power

supplies deliver an unfiltered or pulsating output. The pulsating DC output is fed into

the precipitator field, which, in effect, forms a capacitor (two conductors separated by

insulating material). The cause of Sparks & arcsis a momentaryfield breakdown and,

in effect, cause the gas to become a conductor rather than an insulator.

POWER SUPPLY COMPONENTS:

1). Silicon-Controlled Rectifier: - SCRs are used to control the AC power to the

transformer/rectifier. They are solid-state semiconductors devices that act like a

switch with a "gate" that allows them to be turned on electrically. Because an SCR

conducts in only one direction, two SCRs are connected in an inverse-parallel

configuration to provide control on both the positive & negative half cycle. Each SCR

conducts alternately, one on the positive half cycle, the other on the negative half-

cycle. The automatic voltage control (typically microprocessor- based) determines

which SCR is switched on & at what time in that half-cycle.

An SCR which is switched on remains on until the current flowing through it decays

below what is called the "holding current," usually at or near the end of the half-cycle.

The point at which SCR is fired, is measured in degrees from the beginning of

the half-cycle and is called the firing angle

Each half-cycle is chopped at the point in that cycle where an SCR is switched (fired)

into a conductive state.

2). Current Limiting Reactor: - The Current limiting reactor (CLR) reshapes the

wave form to something more like a sine wave. Properly shaped wave forms are

essential to electrical efficiency. The current limiting reactor (CLR) is an inductor of

fixed value used in series with the transformer/rectifier.

The CLR's main function is to limit the current flow during sparking. If a spark

occurs while an SCR is conducting, the spark continues until the SCR stops

conducting near the end of the half-cycle. During this time, the T/R set effectively has


27/33

a short on its secondary due to the spark, and this is reflected into the primary. A

properly designed T/R set has some built-in circuit impedance, but it is not enough to

significantly limit the current during sparking.

Since the SCR is fully turned on and the T/R set presents a low impedance due to the

spark, the only circuit element remaining to control current flow is the CLR.

Therefore, it isimportant that the CLR have the right inductance value to control

spark currents. Another function of the CLR is to shape the voltage & current wave

forms. For optimum electrical & collecting efficiencies, the wave shape of the voltage

& current presented at the T/R set must be a sine wave. The CLR is needed to filter

restore the wave form to some approximation of a sine wave.

If average power can be increased without increasing the peak voltage, so spark rates

dont rise in case of variable inductance CLR.

3). Main disconnect breaker (SFU):- This is a circuit breaker that provides a

lockable disconnect & over-current protection from the main line supply to the control

cabinet.

4). Magnetic contactor (K1):- The magnetic contactor is usually located in the

individual control cabinet and provides overload protections for the

Transformer/Rectifier. It is magnetically actuated from the start & stop button.

5). Transformer/Rectifier set: - A Transformer/Rectifier (T/R) set is a combination

step-up transformer & full-wave rectifier. The transformer raises the incoming 480 V

AC to between 45 to 75 KV DC averages. The rectifier converts the alternating

current (AC) output from the secondary of the Xmer

to full-wave rectified DC. A

typically T/R set used in a precipitator application is filled with oil for cooling &

insulation.

RMSprimary voltage : 415 V AC

RMS primary current : 240 Amp.

Average secondary voltage : 45 KV DC

Average secondary current : 1500 mA

Transformer turns ratio :1:135


28/33

6). Automatic voltage control :- The automatic voltage control (AVC) controls the

operation of the SCR stack. It also measures the primary & secondary voltage &

currents levels. The AVC s main function is to provide the triggering pulses which

fire the SCRs, putting them into a state of conduction. It determines the point in the

electrical half-cycle where the SCR is fired , thus achieving power control.

7). Meters :- Meters are also included in the control circuitry and monitor the

vibration in the electrical power input.

Primary voltmeter:- This meter measures the input voltage coming into the

transformer in AC volts. The input voltage ranges from 0 to 480 volts AC. The

meter is located across the primary winding of the transformer.

Primary ammeter :- This meter measures the primary current flow in the

transformer in amperes. The primary ammeter is located off a current transformer in

the primary power circuit. The primary voltage & current readings give the power

input to the transformer/rectifier.

Secondary voltmeter :- This meter measures in DC volts the operating voltage

delivered to the discharge electrodes. This meter is located between the input side of

the rectifier & the discharge electrodes.

Secondary ammeter :- This meter measures the current supplied to the discharge

electrodes in milliamperes. The secondary ammeter is located between the rectifier

output & the automatic control module. The combination of the secondary voltage &

current readings gives the power input to the discharge electrodes.

Spark meter :This meter measures the numbers of sparks per minute in a

precipitator field.

Spark: - A short, self-extinguishing discharge from the high voltage system to the

grounded system. Sparks effectively cause the gas stream to act as a conductor.


29/33

The Precipitation Process :- The complete precipitation process consists of five

basis steps.

1). Gas distribution into the treatment zone

2). Particle charging/corona discharge (gas conduction)

3). Deposition of the dust on to the collector plates.

4). Accumulation of the dust.

5). Removal of the collected material.

Electrical Efficiency & Power Transfer:- A precipitators Electrical Efficiency is

assumed when opacity reading are good ; if the ESP is efficient, it is collecting dust

and the opacity level will be low.

Primary form factor :- Primary form factor is a measures of how closely the shape

of the current in the primary of the T/R set approaches an ideal sine wave.

Primary form factor = RMS Pri. Current / Average Pri. Current

For an ideal sine wave, the value of form factor is 1.11. Precipitators power supplies

operating at the maximum nameplate rating of the T/R set are normally designed to

operate at a form factor of 1.2

Precipitator Efficiency: - Deutsch- Anderson equation is used to determine the ESP

collection efficiency under ideal conditions.

e-/Q)Where: - =collection efficiency of the precipitator.

A = the effective collecting plate area of the precipitator, m2

Q = gas flow rate through the precipitator, m3/s

e = base of natural logarithm = 2.718

= migration velocity, cm/s

Specific Collection Area:- The Specific Collection Area is calculated by dividing the

surface area of collecting electrodes in the precipitator by the gas volume flowing the

precipitator. Therefore, the total number plates (size) and the total gas volume have a

direct effect on Precipitator Efficiency.


30/33

SCA= Total collection surface (m2)/1000 m

3/hr

4)VARIABLE FREQUENCY DIGITAL AC DRIVE (VFD):

Generally, in the process requirement where ac motor is installed is controlled by

damper/vanes to restrict the flow of current. In this case motor energy gets lost as

motor is running on full speed. To overcome this, variable speed drives replaces the

conventional dampers/vanes to save the energy loss.

4.1 )AC motor control:

DC Drives are extensively used in the industry for variable speed applications for a

long time but recently AC drives are being introduced gradually due to the fact that

cage type induction motors have several advantages over dc motors. They relate to

improved ruggedness, low cost & size, higher efficiency & reliability, & less required

maintenance due to the absence of commutator & brushes.

There are various methods for controlling the speed of an induction motor viz.:

1. Stator-Voltage Control2. Variable-Voltage, Variable-frequency Control3. Variable-Current, Variable-frequency control4. Slip Power RegulationStator-Voltage Control System: Stator-Voltage Control System is relatively simple.

The stator voltage is controlled with the help of thyristors connected anti-parallely in

three phases of the incoming line & controlling the instant of firing of SCR's. Usually

motors with a higher slip are used in this system & the torque reduced with the

reduction of stator voltage. The loss of the machine is also high.

Variable-Voltage-Variable-frequency system: The Variable-Voltage-Variable-

frequency system has greater flexibility of control. This system comprises voltage-fed

inverters. Two types of inverters, the square wave & pulse-width-modulated types are

popular. In this system three phase ac supply is converted into a variable dc supply

with the help of phase control rectifiers. The variable dc voltage is impressed at the

input of force-commutated bridge inverter which produces a variable voltage, variable


31/33

frequency output to control the speed of an ac motor. The voltage-feed-inverter

produces a square-wave voltage at the machine input. The line to line voltage

waveform is a six-stepped wave. In this system the speed of the motor can be varied

by varying the inverter frequency & the voltage-to-frequency ratio should be

maintained constant to ensure the constancy of the air-gap flux. The voltage-fed

inverter system is suitable for medium-power applications & multi motor drives.

Now a days instead of Thyristors, Insulated Gate Bi-polar Transistor (IGBT) are used

in VVF system due to their High switching ability and low switching loss.

Current-fed Inverter: In Current-fed Inverter the supply line voltage is converted to

a variable ac voltage by SCR's & a large choke is connected at the output of the

rectifier to make it a current source. This is fed to a three-phase inverter circuit which

produces a six-step current wave.

Slip Power Regulation system: In Slip Power Regulation system the slip power of

the rotor is rectified by a three-phase controlled bridge-rectifier and fed back to the ac

line through a line-commutated inverter. This system operates only in the

synchronous speed range.

Various closed loop control:

1) Voltage fed inverter control2) Pulse width modulation control (PWM)3) Current fed inverter control4) Vector method control

Voltage fed inverter control:

The open loop control of the motor in the variable-frequency variable-voltage mode is

quite satisfactory for long term steady-state operation. For fast dynamic response,

closed-loop control is essential. In a closed-loop system it is easy to achieve the

optimum operating conditions of voltage & frequency. So that the motor speed can be

controlled with high torque, power factor & efficiency and both the constant-torque &

constant-horse power mode can be used. In the closed loop system the reference

signal determines the operating frequency or speed of the motor. The arrangement


32/33

makes the use of feedback from the taco generator & current transformers to achieve

the desired speed of the motor. The speed loop error signal controls the inverter

frequency & also generates a voltage signal through an amplifier to control the firing

angle of SCR converter.

PWM Control:

In PWM control scheme the DC link voltage is obtained by uncontrolled bridge

rectifier & the output voltage & frequency are controlled in the inverter itself. The

sinusoidal PWM is most widely used. In this system the carrier is synchronized to

reduce the harmonic content. The fundamental output voltage is controlled by the

variation of modulation index. A micro processor-based control also provides

facilities for jog control, smooth starting & reversing & braking.

Current fed control:

In the voltage-fed inverter speed control, the motor input voltage & frequency are

altered keeping v/f constant. In the current-fed inverter control system, the slip of the

motor is regulated for both speed & torque control. With this control the motor can

operates at its optimum torque/ampere rating point, while the fast response, wide

speed range, torque limit & regeneration are maintained. Since, inverter is supplied

from a constant current source and the current waveform is square, the motor voltage

determined by the response of the motor & load.

SPEED CONTROL METHODS OF INDUCTION MOTORS:

The rotor speed of a three-phase slip-ring motor can be controlled either by varying

the frequency of the supply keeping the voltage to frequency ratio constant or by

controlling the power flow in the rotor control circuit.

The rotor control circuit power flow can be controlled by:

1) By inserting an adjustable external resistance in the rotor circuit2) By varying the stator supply voltage3) By inserting a voltage of slip-freq. in the rotor circuit4) By recovery of the slip-power


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The speed control of an induction motor by variation of supply frequency maintaining

the air gap-flux constant is the superior to other methods of speed control. In this

method the control is continuous & precise and the speed range is wide. To avoid

core-saturation, the air gap flux must be maintain constant by keeping the input E l / fl

constant under all conditions of operations, provided the stator leakage reactance is

small.

Now-a-days to control speed of AC motors variable frequency digital ac drives are

extensively used. These drives acquire control using inverter panels which facilitates

easy & reliable operation in controlling speed of AC motors.

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