REPORT OF VOCATIONAL TRAINING OF THERMAL POWER PLANT AT TITAGARH GENERATING STATION

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JISHNU PRASAD SEN GURUNANAK INST OF TECHNOLOGY ECE DEPARTMENT UNIVERSITY ROLL NO: DATE:

ABOUT CESC

Kolkata has come a long way on the wings of power. Through rapid growth and change during the world’ most eventful decades. CESC Limited ,a RPG company brought thermal power to India more than 100 years ago and supplies power to the city kolkata, serving 11 million population across it’s are of 567 sq.mtthe peak load so far handled more than 1300 mw and its’s no of consumer crossed 2.1 million. CESC have now four generating station . they are New cossipore,titagarh,southern and Budge Budge. Their capacities are 100MW,240MW,135MW,750MW . CESC is not only a generating station but also a power distribution company. It’s no of receiving stations are 6. The no of 132 KV sub station is 7. It’s distribution station is around 91. The no of transformers is above 6000. Power is distributed in industrial, domestic and commercial purposes. We all know that pollution is main obstacle in way of power generation. CESC is so much concerned about the environment that it is the India’s best environment friendly generation station.

ACKNOWLEDGEMENT In the end of such compassionately gruelling but informative training Ifelt myself much more confident and competitive. The entire creditgoes to excellent and competent personnel of your esteemedcompany. Your training and guidance showered on me by Mr. M.Choudhury (HRD), Mr. J. Roy Choudhury (generation),Mr.S.Sarkar (HRD) Mr. K. Aditya, Mr.T.Choudhury, Mr.A. Patra,Mr.B.Mitra, Mr. S.N. Nath, Mr.S.Patra, Mr. S.Dutta put me in solidrock to garner courage and expertise in facing any challenges in theyears to come.

I am thankful rather grateful for such whole hearted cooperationof not only them but also all members of TGS throughout the trainingtenure.

CONTENT

CESC LIMITEDTITAGARH Generating StationThermal Power PlantThermodynamic CycleFour Basic Cycles on Which PowerGenerating Plant OperatesCoal Handling PlantWater Treatment Plant & its OperationFan LDO PUMPBoiler & its AuxiliariesTurbine & its AuxiliariesAlternatorsExcitation SystemTransformersAsh Collection & Handling Plant

TGS is one of the oldest generating station & is the first pulverized fuel thermal station of CESC situated on B.T. road, Titagarh. It has total installed capacity of 240 MW comprising four units each rated 60 MW. Its generating voltage is 10.5 KV. The plant started commercial generation since 1983, when the first unit started operating. Subsequently the other three units started in the years 1983, 1984 & 1985. Plant Load Factor (P.L.F) of this plant is generally high (87.39) in 2006-07 & P.A.F. is 94.79 (2006-07).TGS is committed to ensuring required power supply to the CESC’s distribution network in line with the varying level of electricity demand. In TGS the generating voltage 10.5 KV is stepped up by generating transformer to 33KV. This 33 KV supply is again stepped up to 132KV in the receiving station & is sent to distribution station & stepped down to 11KV.Thereafter it is again stepped down to 6 KV, 415 V for distributing to consumers. Operation & maintenance of the plant is part of the business activity of TGS. CESC central Turbine Maintenance department (CTM) is responsible for Turbo-Alternator sets while, testing & calibration of protection metering equipments are done by company’s test department. In 2006-2007 TGS captured the 5th position all over India due to its great performance.

THERMAL POWER PLANT

A thermal power station is a power plant in which the prime mover is steam driven. Water is heated, turns into steam and spins a steam turbine which drives an electrical generator. After it passes through the turbine, the steam iscondensed in a condenser; this is known as a Rankine cycle. The greatest variation in the design of thermal power stations is due to the different fuel sources. Some prefer to use the term energy center because such facilities convert forms of heat energy into electrical energy. However, power plant is the most common term in the United States. while power station prevails in many Commonwealth countries and especially in the United Kingdom.Almost all coal, nuclear, geothermal, solar thermal electric, and waste incineration plants, as well as many natural gas power plants are thermal. Natural gas is frequently combusted in gas turbines as well as boilers. The waste heatfrom a gas turbine can be used to raise steam, in a combined cycle plant that improves overall efficiency.Such power stations are most usually constructed on a very large scale and designed for continuous operation. History -Reciprocating steam engines have been used for mechanical power sources since the 18th Century, with notable improvements being made by James Watt. The very first commercial central electrical generating stations in New York and London, in 1882, also used reciprocating steam engines. As generator sizes increased, eventually turbines took over due to higher efficiency and lower cost of construction. By the 1920s any central station larger than a few thousand kilowatts would use a turbine prime mover. Efficiency -The electric efficiency of a conventional thermal power station, considered as saleable energy produced at the plant busbars compared with the heating value of the fuel consumed, is typically 33 to 48% efficient, limited as all heat engines are by the laws of thermodynamics (See: Carnot cycle). The rest of the energy must leave theplant in the form of heat. This waste heat can be disposed of with cooling water orin cooling towers. If the waste heat is instead utilized for e.g. district heating, it iscalled cogeneration. An important class of thermal power station are associated withdesalination facilities; these are typically found in desert countries with largesupplies of natural gas and in these plants, freshwater production and electricity areequally important co-products.Since the efficiency of the plant is fundamentally limited by the ratio of the absolutetemperatures of the steam at turbine input and output, efficiency improvements require use of higher temperature, and therefore higher pressure, steam. Historically, other working fluids such as mercury have been experimentally used in a mercury vapour turbine power plant, since these can attain higher temperatures than water at

lower working pressures. However, the obvious hazards of toxicity, and poor heat transfer properties, have ruled out .mercury as a working fluid.

THERMODYNAMIC CYCLE

Rankine cycleThe Rankine cycle is a thermodynamic cycle which converts heat into work. The heat is supplied externally to a closed loop, which usually uses water as the working fluid. This cycle generates about 80% of all electric power used in America and throughout the world including virtually all solar thermal, biomass, coal and nuclear power plants. It is named after William John Macquorn Rankine, a Scottish polymath. Description Physical layout of the four main devices used in the Rankine cycle. A Rankine cycle describes a model of the operation of steam heat engines most commonly found in power generation plants. Common heat sources for power plants using the Rankine cycle are coal, natural gas, oil, and nuclear. The Rankine cycle is sometimes referred to as a practical Carnot cycle as, when an efficient turbine is used, the TS diagram will begin to resemble the Carnot cycle. The main difference is that a pump is used to pressurize liquid instead of gas. This requires about 100 times less energy than that compressing a gas in a compressor (as in the Carnot cycle). The efficiency of a Rankine cycle is usually limited by the working fluid. Without the pressure going super critical the temperature range the cycle can operate over is quite small, turbine entry temperatures are typically 565°C (the creep limit of stainless steel) and condenser temperatures are around 30°C. This gives a theoretical Carnot efficiency of around 63% compared with an actual efficiency of 42% for a modern coal-fired power

station. This low turbine entry temperature (compared with a gas turbine) is why the Rankine cycle is often used as a bottoming cycle in combined cycle gas turbine power stations.The working fluid in a Rankine cycle follows a closed loop and is re-used constantly. The water vapor often seen billowing from power stations is generated by the cooling systems (not from the closed loop Rankine power cycle) and represents the waste heat that could not be converted to useful work. Note that steam is invisible until it comes in contact with cool, saturated air, at which point it condenses and forms the white billowy clouds seen leaving cooling towers. While many substances could be used in the Rankine cycle, water is usually the fluid of choice due to its favorable properties, such as nontoxic and unreactive chemistry, abundance, and low cost, as well as its thermodynamic properties. One of the principal advantages it holds over other cycles is that during the compression stage relatively little work is required to drive the pump, due to the working fluid being in its liquid phase at this point. By condensing the fluid to liquid, the work required by the pump will only consume approximately 1% to 3% of the turbine power and so give a much higher efficiency for a real cycle. The benefit of this is lost somewhat due to the lower heat addition temperature. Gas turbines, for instance, have turbine entry temperatures approaching 1500°C. Nonetheless, the efficiencies of steam cycles and gas turbines are fairly well matched.Processes of the Rankine cycleTs diagram of a typical Rankine cycle operating between pressures of 0.06bar and 50bar .There are four processes in the Rankine cycle, each changing the state of the working fluid. These states are identified by number in the diagram to the right.Process 1-2: The working fluid is pumped from low to high pressure, as the fluid is a liquid at this stage the pump requires little input energy.Process 2-3 : The high pressure liquid enters a boiler where it is heated at constantpressure by an external heat source to become a dry saturated vapor.Process 3-4: The dry saturated vapor expands through a turbine, generating power. This decreases the temperature and pressure of the vapor, and some condensation may occur.Process 4-1: The wet vapor then enters a condenser where it is cooled at a constantpressure and temperature to become a saturated liquid. The pressure and temperature of the condenser is fixed by the temperature of the cooling coils as the fluid is undergoing a phase-change. In an ideal Rankine cycle the pump and turbine would be isentropic, i.e., the pump and turbine would generate no entropy and hence maximize the net work output. Processes 1-2 and 3-4 would be represented by vertical lines on the Ts diagram and more closely resemble that of the Carnot cycle. The Rankine cycle shown here prevents the vapor ending up in the superheat region after the expansion in the turbine , which reduces the energy removed by the condensers.Real Rankine cycle (non-ideal):

Rankine cycle with superheat

In a real Rankine cycle, the compression by the pump and the expansion in the turbine are not isentropic. In other words, these processes are non-reversible and entropy is increased during the two processes. This somewhat increases the power required by the pump and decreases the power generated by the turbine. In particular the efficiency of the steam turbine will be limited by water droplet formation. As the water condenses, water droplets hit the turbine blades at high speed causing pitting and erosion, gradually decreasing the efficiency of the turbine. The easiest way to overcome this problem is by superheating the steam. On the Ts diagram above, state 3 is above a two phase region of steam and water so after expansion the steam will be very wet. By superheating, state 3 will move to the right of the diagram and hence produce a dryer steam after expansion.

Variations of the basic Rankine cycle

The overall thermodynamic efficiency (of almost any cycle) can be increased by raising the average heat input temperature of that cycle. Increasing the temperature of the steam into the superheat region is a simple way of doing this. There are also variations of the basic Rankine cycle which are designed to raise the thermal efficiency of the cycle in this way; two of these are described below.

Rankine cycle with reheat

In this variation, two turbines work in series. The first accepts vapor from the boiler at high pressure. After the vapor has passed through the first turbine, it re-enters the boiler and is reheated before passing through a second, lower pressure turbine. Among other advantages, this prevents the vapor from condensing during its expansion which can seriously damage the turbine blades, and improves the efficiency of the cycle.

Rankine cycle with superheat

Regenerative Rankine cycle

The regenerative Rankine cycle is so named because after emerging from the condenser (possibly as a subcooled liquid) the working fluid is heated by steam tapped from the hot portion of the cycle. On the diagram shown, the fluid at 2 is mixed with the fluid at 4 (both at the same pressure) to end up with the saturated liquid at 7. The Regenerative Rankine cycle (with minor variants) is commonly used in real power stations. Another variation is where 'bleed steam' from between turbine stages is sent to feedwater heaters to preheat the water on its way from the condenser to the boiler.

Regenerative Rankine cycle

FOUR BASIC CYCLES ON WHICH A POWERGENERATING PLANT OPERATES

Any COAL FIRED Power Generating Plant operates on the following four basic cycles:

1. Coal & Ash cycle2. Air & Flue Gas cycle3. Water & Steam cycle4. Cooling Water cycle

Of all the above four mentioned cycles, the fist two i.e. COAL & ASH CYCLE & AIR & FLUE GAS CYCLE are called OPEN CYCLES.The next i.e WATER & STEAM CYCLE is a CLOSED CYCLE.The fourth and the last mentioned cycle i.e. THE COOLING WATER CYCLE occurs in the condenser.COAL ASH CYCLE

Raw coal is fed into the Coal Handling Plant (CHP) after which it is sent to the coal bunker.Then through the coal feeder the coal is fed into the pulveriser/ crusher where the coal (50mm dia.) is pulverized. After that the pulverized coal is fed through the 24(6x4) coal burners by primary air fans into the boiler furnace. After proper combustion (determined by the 3-Ts : Temperature, Time and Turbulence) ash is formed. This ash is of two types. The heavier variety is called the Bottom Ash while the lighter variety passes out as flue gas into the Economiser. From the Economiser also bottom ash is obtained. The bottom ash is obtained as clinkers which are crushed into powder form by the scrapper-clinker grinder conveyer. Then the bottom ash thus obtained is converted to slurry by water through the ash water pumps. The flue gas from the furnace is fed to the economiser and the Air Preheaters (APH).Then from the Electrostatic Precipitator (ESP) the flue gas is vent out into the atmosphere by ID fans through the chimney. The ESP collects all the suspended ash particles by high voltage discharge. The ash thus obtained is the second variety of ash and is called Fly Ash. This fly ash, as the bottom ash, is converted into slurry. The slurry (of bottom ash + fly ash) is collected in the Ash Slurry Sump. The slurry from the sump by a set of three ash slurry pumps is sent to the Ash Pond .This ash is used in several applications like cement industry, manufacture of bricks, etc.

AIR-FLUE GAS CYCLEAIR CIRCUIT:

The air requirement of the boiler is met by two forced draft fans (FD FANS). The forced draft fans supply the necessary primary and secondary air. About 80% of the total air which is the secondary air goes directly to the furnace wind box and 20% of the air goes to the mill via primary air fans. This air is known as the primary air. The air before it goes into the furnace or to the mill it is pre heated in the air pre heaters. The air pre heater installed is a tubular type heat exchanger in which the heat exchanger takes place between flue gas and air. The flue gas flows through the tubes and air flows over the tubes. The air heater serves to recovers the useful heat in the outgoing flue gas (after recovery in the economizer) and thus improves the efficiency of the boiler. At the air heater cold end the outgoing flue gas contains constituents like sulpher dioxide. If the operating temperature goes below the dew point of the vapours then the vapours get condensed and react with sulpher dioxide and sulphuric acid is former which is corrosive in nature. The possibility of cold and corrosion is more during lighting up of the boiler and at low load. To avoid this corrosion problem the flue gas bearing the air is to be maintained at a higher temperature. This is accomplished by passing the Air Pre-heater during lighting up and low load condition when flue gas temperature is low. The primary air is supplied to the five mills by the five primary air fans. The primary air is used in the mill to dry the pulverized coal and to carry it into the furnace. To ensure drying of coal a portion primary air is taken after passing through the air pre-heater. A cold air line is also connected to the hot primary air line before it enters into the mills. The temperature of the coal air mixture at the mill outlet is controlled by admitting the cold and hot primary air proportionately.

FLUE GAS CIRCUIT: The flue gases move upward in the furnace and through the rear gas pass in a downward direction to the air pre-heaters. The flue gas leaving the air preheater pass through the electrostatic precipitators and then the induced draft fan (ID FAN) sucks and forces the flue gas through the stack. The flue gas leaving the boiler furnace carries with it particles like ash, unburnt carbon etc. The quantity of these matters is small when oil is fired but it becomes quite considerable when coal is fired, particularly when high ash content coal is fired. The ESP helps in minimizing the dust concentration of flue gas thus reducing the erosion of ID FAN impellers, ducting and the atmospheric pollution.

AIR FLUE PATH

WATER & STEAM CYCLEFeed water is supplied to the boiler drum from economiser outlet header througheconomiser links and these two links at the point of entering the drum have been divided into 4 branch pipes. Altogether there are 8 downcomers from boiler drum, out of which two downcomer pipes termed as ‘short loop’ (water platen) divided into 4 branches before entering the boiler and ultimately water flows to the drum through these 4 water platen outlet headers. The front & the rear wall inlet headers feed the front and rear furnace wall tubes. The furnace side walls are fed by two side wall inlet headers. The water in the furnace sidewall, water wall platen and the extended side wall absorb heat from the furnace.The resultant mixture of water and steam is collected in the outlet headers and discharged into the steam drum through a series of

riser tubes. Steam generated in the front and the rear walls is supplied directly into the drum. In the drum separation of water and steam takes place. The boiler water mixes with the incoming water. The saturated steam is led to the roof radiant inlet header and from there to the final SH outlet header via LTSH and platen superheater stages. The steam is superheated to the designed temperature and from the superheater outlet header the steam is led to the turbine via the main steam line.

COOLING WATER CYCLE

There are NINE cooling tower fans each of voltage rating: 415 V. They are of ID fan type. All of them are controlled by MCC blocks.

COAL HANDLING PLANT

Coal is a primary fuel. Source of coal varies from thermal power plants of CESC as per design parameters of individual boiler. Much coal is supplied by ECL from Rani gaunge and Mugma fields, BCCL from Barakar and Kusunda areas and by ICML. Coal is transported through railway linkages from respective fields to generating stations. Requirement of coal at TGS is about TGS is about 3000 tones per day.There are some properties of coals which are used in TGS.# SWELLING INDEX: Some types of coal during and after release of volatile matter become soft and pasty and form agglomerates called caking coals.

# GRINDABILITY: This property is measured by grindability index.

# WEATHERABILITY: It is a measure of how coal can be stockpiled for long periods of time without crumbling to pieces.

# SULPHER CONTENT: Sulpher content in coal is combustible but the product after combustion i.e.SO2 is a major source of atmospheric pollution.

# HEATING VALUE: The coal used in TGS has4000-5000 kcal/kg of heating value.PROCESS: First the coal is coming in the station .then with the help of tripplers or bull dozer, coal from wagon or reclaim hopper is dropped to vibrating feeder through a 30mm mesh. Any large coal chunk is broken manually and then fed. The first conveyer belt starts below the ground and with an angle of 18 deg. with the ground. It comes out and discharges the coal to another conveyer belt. This also with an angle of 18 deg. makes the coal reach the crusher. But before the crusher, impurities like iron parts, which get carried so far, are separated by a magnetic separator which is oriented in cross way. The coal is then dropped to the vibrating screen. The coal chunks are already less then 20mm and go to stock. In the crusher, solid metallic, non ferrous crushing wheels are used to crush the coals to 20 mm. From the crusher, coal goes to the bunkers. From these bunkers they are dropped in ball & race mill. Here, huge solid metallic balls are used to pulverize the coal to 75 micro meters. Then the coal is fed to furnace. By primary air coal is dried from any moisture and also carries the pulverized coal to furnace. At the starting of combustion, oil is required. The volatile matter in coal starts to burn at a temp. near about 400 deg.C. This is temperature is attained by burning oil which is LDO for industrial purposes. Sometimes oil is also required to fire the furnace when the quality of coal is not up to mark or when there is high moisture content in the coal. The main function of the Coal Handling Plant (CHP) is to feed crushed coal up to the bunker. In the 4th Unit of DTPS there are 6 nos. of bunkers as well as coal mills.The CHP is divided into three zones:

ZONE 1 --- Unload uncrushed coal from wagon tippler up to UNCRUSHED COAL YARD. Equipments: WAGON TIPPLER, VIBRATOR, CONVEYER BELT.ZONE 2 --- Taking uncrushed coal from yard for crushing and send it to crushed yard. Equipments: BELT, SCREEN, CRUSHER, VIBRATOR, DISCHARGE BELT.ZONE 3 --- Taking crushed coal from yard through reclaim hopper (7, 8, 9 and 10) and send it to the bunker. Equipments: BELT, VIBRATOR, TIPPER CAR.

COMPONENTS OF DIRECT FIRING SYSTEM ARE AS FOLLOWS:1.Raw coal feeders.2. Source to supply hot primary air to the pulverizer for drying the coal.3. Pulverizer fan, also known as primary air fan arranged as a blower.4. Pulverizer arranged to operate under pressure.5. Burners.

TRANSMISSION OF COAL:(Coal yard to furnace)1. Coal is brought by rail wagons, which the Indian Railways deliver till the coal yard of TGS. From there, six to eight wagons are separated and are pulled to the Wagon Tripler where there are unloaded one by one.

2. Wagon Tripler is a device by which the wagon is tripled to unload the coal to the bunker. The Wagon Tripler consists of a moveable platform, which also acts as a Computerized Weight Bridge A single wagon is first brought to the platform. Then by a pulley and weight arrangement Powered by an electric motor, theplatform is tilted towards the bunker by 140 degree while a support from the top catches the wagon and tilts it which causes the coal to fall down to the bunker. While the unloading is done, water is sprayed on the coal to avoid spreading of coal dust.3. From the coal bunker, the different varieties of coal. May be mixed by Dozers and the coal from there is sent to the crusher.4. In the crusher, coal is broken into small pieces of sizes not exceeding 20 mm in diameter. From there by conveyor belt, the coal is taken through the chute and sent to the top of. the main building5. The coal is then dumped into an area from where it is fed into by conveyor belts to the coal trolley which gathers the coal, decides which bunker requires coal, then it rolls over to the of that bunker and pours the required amount of coal in it.6. From the bunker, the coal comes down through the Hopper to the Besta Feeder.7. The Besta Feeder controls the rate of the amount of coal to be fed tot thepulverizer.Besta Feeder is a device consisting of a conveyor belt, which transfers the coal from the hopper to the mouth of the pulverizer. The transfer rate of coal is controlled from the controlled room by monitoring the speed of the Besta feeder. This is because as the coal is grounded in the pulverizer, it becomes explosive in nature and cannot be stored.8. The coal is sent to the Pulverizer to get crushed into the size of 200 micron in diameter.The Pulverizer consists of an enclosing cylinder with a channel comprising of large Steel balls. These balls are rotated under pressure and coal is fed into this channel where due to movement of these balls, it gets grounded. This procedure is taken to achieve complete combustion of coal, better control of furnace temperature and increasing the efficiency of the boiler.9. From the Pulveriser the coal dust and air mixture is blown to the furnace by PRIMARY AIR FAN.

COAL PULVERIZATION

Coal is pulverized in order to increase it’s surface its surface exposure thus promoting rapid combustion without using large quantities of excess air. In modern power plants, lump coal, crushed to uniform size is continuously supplied to the pulverized hopper from where it is fed into the pulverized through a feeder arrangement. Combustion rate is controlled by varying the feeder speed thereby controlling the rate of coal being fed to the pulverizer. It is swept out from the mill and floated to the burner located in the furnace wall by admitting enough of the combustion air at the pulverinizer to accomplish air bone transportation. This air is called primary air as it is varied from as little as 10% to almost the entire combustion air requirements, depending upon load.

SOME SPRECIFICATION ABOUT FHP

RH1------------------------ ECL RH2------------------------- ICML, ECL RH3------------------------- ICML

CRUSHER HOUSE SPECIFICATION

The no of convert belt----------------------- 18 It’s area---------------------------------------- Wagon tippler to bunker Crusher speed--------------------------------- 750rpm Shaft per crasher------------------------------ 4 The no of hammers inside the shaft-------- 18 The no of Gates------------------------------- 19

BUNKER SPECIFICATION The no of bunker per unit-------------------- 5 The no of wagon per bunker----------------- 5 The height of bunker-------------------------- 60 Timing of to fill up a bunker----------------- 30 to 45 min Bunker division-------------------------------- 1 ECL coal Bunker 4 ICML coal Bunker Ability of supply of coal in a bunker--------- 14-15 hrs Time require for transport of coal from Wagon tippler to bunker--------- 5-6min

WATER TREATMENT PLANT & ITS OPERATION

The river water contains suspended matter with colloidal particles and some of organic and inorganic impurities which make it necessary for chemical and mechanical treatment in WT plant before being used as clarified and filtered water.

The impurities in water are of two kinds, volatile and non-volatile. Volatile impurities can be expelled from water to a very great extent by it in fine streams or droplets into the atmosphere. By this means foul gases dissolved in it are removed. By the Cascade Type, 5 Stage Aerator the iron dissolved in water also is oxidised and thus precipitates, enabling easy removal by filtration. The pH value of the water is often increased due to aeration owing to the removal of CO2 from it. Lime dosing is done to promote the coagulation efficiency. It also helps to maintain the pH value around 7.4 during coagulation. The non-volatile impurities like clay, vegetable matter, colouring matter and bacteria being minute escape through filters. Hence alum is added to sedimentation and hence, filtration. In the clariflocculator mechanical agitation is created and the mixture is allowed to fall into a trough below for integrate mixing with the chemicals used, creating violent turbulence. The flocculated water is admitted into the clarifier tank from the bottom of the flocculator tank in a continuous rotary upward movement that enhances the rate of deposition of sludge on the floor of the tank. This sludge is removed by continuous sweeping through a desludging valve. The clarified water is then collected in the gravity filter beds where they are filtered through a layer of sand and gravel by the effect of gravity. Now to clean the pores in the filter bed, backwashing is done. This process of backwashing involves flushing by compressed air and water from beneath the filter bed and simultaneous drainage of the turbid water. The filtered water thus is collected in the filtered water sump from where through colony filter pumps this water is supplied to the colony. Through plant filter pumps the clarified water is supplied to the DM plant & the Bearing Cooling Water (BCW) sump or the non-dm plant.

DEMINIRELIZED WATER PLANT

Water is required for industrial process. From the Ganges the water is taken. The water is first processed to deminarilize in DM plant. However natural water contains dissolved salts, alkaline salts such as bicarbonates & carbonates of Ca, Na& mg. there are also other dissolved impurities such as sulphates, chlorides & nitrates of Ca, Mg & Na. Silica, dissolved CO2 and metals like Fe, Mn & organic matters are also present.Ion exchange resins are porous materials that contain inert base attached to whichare free ions & can be free to move about within the resin structure. At first water is taken from Ganges is taken to main water bus and is sent to water chamber where alum is mixed. By clarifoculator system and flushing of air the alum gets mixed properly in water and all the mud, algae etc. settles down.Uper portion of the water is collected in reservoir which is divided into two sections. One portion goes for treatment & other is for cooling of machines, coal yard & other services. There are three types of pump. Clarified water pump, drinking water pump, service water pump.

Clarifloclurator

PROCESS: The clarified water is fed to pressure sand filter (PSF). There are threenumbers of PSF (A, B, C) & used to remove sand, mud etc. From PSF the water is fed to the activated carbon filter (ACF). In the ACF it absorbsany chlorine. There are 3 no.s of ACF (A, B, C) & used to remove the small particles & bacteria. From ACF the water is moved to Strong Acid Cation (SAC) which are three in no. (A, B, C). In SAC the cation exchange resin causes removal of the cation & in their place hydrogen ions are released in thesolutions.REGENERATION: While supply of exchangeable ions within the resin is exhausted, the quality of treated water from the resin deteriorates & the resin requires regeneration.SAC:RNa + HCl RH + NaCl

R2Mg + H2SO4 2RH + MgSO4

SBA:

RCl + NaOH ROH + NaClWBA:

RHCl + NaOH R + H2O + H2O

The other part of the water goes to the non-dmplant from the clarifloculator. Now from this the water is pumped out by service water pump & drinking water pump. The water from the service water pump goes to clarified water pump the water of which is used as heat absorber in case of ID,FD,PAF,generator air compressor etc. & this water is cooled by raw ganga water tapped from the condenser. The water from service water pump is also used as heat exchanger for ash water system bearing & rotary unloader bearing. Now the water from drinking watrer pump goes to bathroom etc.& the etc. part goes to the drain from the drain the water goes to the ETP1(effluent treatment plant). The water then passes through ETP2,ETP3,&ETP4 & then it goes to the circular reservoir after passing through the oil scheamer. While passing through

ETP3 chemical dodging was done. Finally the water from circular reservoir the water goes to the non-dmplant. When the water flooded in ETP then to extract this extra flooded water a tapping was done which is connected directly to the ganga & when it returns to its normal condition then again it get back to the tapping line of condenser. Again from the sump where water comesby tapping raw ganga water; the water goes to the ash water pump & by creating a slury the ashes goes to the hydrabin & then to the EADA(ash pond) from which the water goes to the ETP1 & ETP2. Now water from demineralised water tank goes to CST(condensate storage tank). From which it goes to the RFW(reserve feed water tank) by which the level of hot well is maintained. The warter from CST also goes for deareator cold filling, boiler cold filling & condensate emergency filling. Thus we can explain the full water treatment cycle in a power plant.

SOME SPECIFICATIONIn lower tower there are 9 IM PUMP used. It’s voltage-------- 415v, speed-------- 2920rpm, current---------- 31amp………There are used three type of pumps:

1. Service water pump---------------- 32. Drinking water pump--------------- 23. Clarified water pump---------------- 4

There is Oil skinning station where removes oil from the water. Outer premises of D.M plant 2 tanks are used. 1 tank is full& the other tank is empty. A rotating device is attached on top& it rotates slowly along the tanks boundary.Inner premises of D.M plant Effluent recircular systemThe no of PSF( pressure sand filter) vessel------------------------ 2The no of ACF (Activated charcoal filter) vessel------------------ 2{[A]---2kg/cm2

[B]---2.4kg/cm2 } The no of SAC (SULPHURIC acidic cation) vessel -------------------3{[A] ---off,[B]-- 0.5kg/cm2,[C]---2kg/cm2}DEGASSED WATER PUMPSPump3 ------------1kg/cm2

Pump 4------------1kg/cm2

Pump1-----------------5kg/cm2

MB air blasts: Not running-----------2, mixed bed===== 3, pressure-----6kg/cm2

Strong base anion (SBA) basin------------- 3Weak base anion (WBA) basin----------------3Each of pressure----------------------------------2kg/cm2

FAN

PRIMARY AIR FAN: It is used for pulverized system. Primary air has two functions. First one is dozing coal & transportation the coal to furnace.

No of fan per boiler 5Motor type 3 phase AC 50 HZ IMRating(KW/HP) 235/315Rated voltage 6.6 KVP.F. at full load 0.87Rated speed 1490 RPM

INDUCED DRAFT FAN: It is used only in balanced draft units to stuck the gasses out of the furnace & throw them into the stack.

No of fans per boiler 2Motor rating(KW/HP) 450/603Rated voltage 6.6 KVP.F. at full load 0.85Rated speed 740RPM

FORCED DRAFT FAN: It is used to take air from atmosphere at ambient temperature to supply essentially all the combustion air. It can either be sized to overcome all the boiler losses (pressurized system) or just put the air in furnace (balanced draft units).

FD FAN SPECIFICATIONNo of fans per boiler 2Motor rating (KW/HP) 270/362Rated voltage 6.6 KVP.F. at full load 0.85Rated speed 985 RPM

BOILER & THEIR AUXILLIARIES

Boiler is a steam raising unit of single radiant furnace type with auxiliary designated to generate 272 kg/hr. at 91.4 kg/sq. cm pressure. The unit burns pulverized coal and is equipped with oil burners. This plant is designated to operate at a 475m above sea level .the ambient temperature is 400 C with a humidity of 70%. Furnace consists of walls, tangent bare water tubes. Rear water tubes from a cavity for the pendant super heater. A boiler or steam generator is a device used creates steam by applying heat energy to water. Although the definitions are somewhat flexible, it can be said that older steam generators were commonly termed boilers and worked at low to medium pressure(1–300 psi/0.069–20.684 bar; 6.895–2,068.427 KPa), but at pressures above this it is more usual to speak of a steam generator. A boiler or steam generator is used wherever a source of steam is required. Here in T.G.S steam is generated 318ton/hour at 89.5kg/cm2 pressure and 5150c in boiler.

Steam generator (component of prime mover)

The steam generator or boiler is an integral component of a steam engine when considered as a prime mover; however it needs be treated separately, as to some extent a variety of generator types can be combined with a variety of engine units. A boiler incorporates a firebox orengine units. A boiler incorporates a firebox orfurnace in order to burn the fuel and generate heat; the heat is initially transferred to water to make steam; this produces saturated steam at ebullition temperature saturated steam which can vary according to the pressure above the boiling water. The higher the furnace temperature, the faster the steam production. The saturated steam thus produced can then either be used immediately to produce power via a turbine and alternator, or else may be further superheated to a higher temperature; this notably reduces suspended water content making a given volume of steam produce more work and creates a greater temperature gradient in order to counter tendency to condensation due to pressure and heat drop resulting from work plus contact with the cooler walls of the steam passages and cylinders and wire-drawing effect from strangulation at the regulator. Any remaining heat in the combustion gases can then either be evacuated or made to pass through an economizers, the role of which is to warm the feed water before it reaches the boiler.

DESIGN DATA:Steam pressure --------------------------------91.4 kg/sq.cm.Steam temperature ----------------------------515 deg.CFurnace volume--------------------------------- 1558 m3Drum:Length-------------------------------------------- 12.97 mPressure-------------------------------------------- 102.7 kg/cm2

Temperature---------------------------------------- 312 deg. CPulvarizer:Type --------------------------------------------------Ball & raceCapacity----------------------------------------------- 15 T/hr * 5 Nos.Speed ---------------------------------------------------49 rpmRequired power----------------------------------------- 100 KWFeeder:Type------------------------------------------------------- Drag LinkControl Device- ------------------------------------------- ThyristorTechnicial data of T.G.S drum:Length=12.93MtrWeight=56tonsO.D=1724mmDESIGN press=102.7Kg/cm2

Shell thickness=105mmDesign temp= 3120 cHead thicknes=90mm

Types of firing: a> perfect mixing of air & fuelb> for complete combustion the optimum fuel &air ratio is maintained.c> continuous and reliable ignition of fuel.d>adequate control over point of formation& accumulation of ash when coal is fuel.

Schematic diagram of typical coal-fired power plant steam generator highlighting the air preheater(APH) location .

STEAM DRUM:The steam drum is made up of high cast steel so that its thermal stress is very high. There is a safety valve in the drum, which may be explored if the temperature and the pressure of the steam are beyond to a set value.The boiler drum has the following purpose:1. It stores and supplies water to the furnace wall headers and the generating tubes.2. It as the collecting space for the steam produced.3. The separation of water and steam tube place here.4. Any necessary blow down for reduction of boiler water concentration is done fromthe drum.RISER AND DOWN COMERS:Boiler is a closed vessel in which water is converted into the steam by the application of the thermal energy. Several tubes coming out from the boiler drum and make the water wall around the furnace. Outside the water wall there is a thermal insulation such that the heat is not lost in the surroundings. Some of the tubes of the water wall known as the ‘down comer’, which carries the cold water to the furnace and some of other known as the ‘riser comer’, which take the steam in the upward direction. At the different load riser and the down comers may change their property. There is a natural circulation of water in the riser and the down comers due to different densities of the water and the steam water mixture. As the heat is supplied, the steam is generated in the risers due to this density of the steam water mixture is greater in the riser then in the down comer and the continuous flow of water takes place. Down comer connected to the ‘mud drum’, which accumulates the mud and the water. When the plant takes shut down the mud drum is allowed to clean manually.BURNERS:15 Y jet sprayers are provided for lighting up and PF flame stabilization of 15 numbers burners. There is a provision for firing both the heavy fuel oil and light diesel oil. The oil firing is done initially during the starting up and when the coal used in TGS is of poor quality, then the plant is allowed to run on oil support. In TGS light diesel oil (LDO) is used for the initiation for ignition of the pulverized coal. The LDO charged into the furnace through the oil burners. It increases the burning capacity of the pulverized coal. Heavy fuel oil passes through the pumping and heating unit to reduce the viscosity as required for firing. For LDO no heating is required. Separate oil pumps are provided for LDO. For both the type of oil, the oil pump discharge a pressure is 14 kg \ cm². Constant steam pressure 10.5 kg \ cm² is maintained for oil atomization and oil heating. P 34 gas igniters are provided for ignition.

SUPER HEATER: The super heater rises the temperature of the steam above itsSaturation point and there are two reasons for doing this:FIRST- There is a thermodynamic gain in the efficiency.

SECOND- The super heated steam has fewer tendencies to condense in the last stages of the turbine. It is composed of four sections, a platen section, pendant section, rear horizontal section and steam cooled wall and roof radiant section. The platen section is located directly above the furnace in front of the furnace arch. it is composed of 29 assemblies spaced at 457.2mm centers from across the width of the furnace. The pendant section is located in the back of the screen wall tubes. It is composed of 119 assemblies at 1114mm centers across the furnace width. The horizontal section of the superheater is located in the rear vertical gas pass above the economizer. Itis composed of 134 assemblies spaced at 102 mm centers across furnace width. The steam cooled wall section from the side front and rear walls and the roof of the vertical gas pass. The superheater works like coils on an air conditioning unit, however to a different end. The steam piping (with steam flowing through it) is directed through the flue gas path in the boiler furnace. This area typically is between 1,300–1,600 degree Celsius (2,372–2,912 °F). Some superheaters are radiant type (absorb heat by thermal radiation), others are convection type (absorb heat via a fluid i.e. gas) and some are a combination of the two. So whether by convection or radiation the extreme heat in the boiler furnace/flue gas path will also heat the superheater steam piping and the steam within as well. It is important to note that while the temperature of the steam in the superheater is raised, the pressure of the steam is not: theturbine or moving pistons offer a "continuously expanding space" and

the pressure remains the same as that of the boiler.[2]The process of superheating steam is most importantly designed to remove all droplets entrained in the steam to prevent damage to the turbine blading and/or associated piping. Superheating the steam expands the volume of steam, which allows a given quantity (by weight) of steam to generate more power. When the totality of the droplets are eliminated, the steam is said to be in a superheated state.

Water tube boiler: Another way to rapidly produce steam is to feed the water under pressure into a tube or tubes surrounded by the combustion gases. The earliest example of this was developed by Goldsworthy Gurney in the late 1820s for use in steam road carriages. This boiler was ultra-compact and light in weight and this arrangement has since become the norm for marine and stationary applications. The tubes frequently have a large number of bends and sometimes fins to maximize the surface area. This type of boiler is generally preferred in high pressure applications

since the high pressure water/steam is contained within narrow pipes which can contain the pressure with a thinner wall. It can however be susceptible to damage by vibration in surface transport appliances. In a iron sectional boiler, sometimes called a "pork chop boiler" the water is contained inside cast iron sections. These sections are mechanically assembled on site to create the finished boiler. High pressure water tube boilers generate steam rapidly at high temperatures that can be increased by lengthening the tubes.

Boiler failure:

1. overpressurisation of the boiler.

2. insufficient water in the boiler causing overheating and vessel failure.

3. pressure vessel failure of the boiler due to inadequate construction or maintenance.Fuel preparation system:

In coal-fired power stations, the raw feed coal from the coal storage area is first crushed into small pieces and then conveyed to the coal feed hoppers at the boilers. The coal is next pulverized into a very fine powder. The pulverizers may be ball mills, rotating drum grinders, or other types of grinders. Some power stations burn fuel oil rather than coal. The oil must kept warm (above its pour point) in the fuel oil storage tanks to prevent the oil from congealing and becoming unpumpable. The oil is usually heated to about 100 °C before being pumped through the furnace fuel oil spray nozzles.

Boilers in some power stations use processed natural gas as their main fuel. Other power stations may use processed natural gas as auxiliary fuel in the event that their main fuel supply (coal or oil) is interrupted. In such cases, separate gas burners are provided on the boiler furnaces.

Air path: External fans are provided to give sufficient air for combustion. The forced draft fan takes air from the atmosphere and, first warming it in the air preheater for better combustion, injects it via the air nozzles on the furnace wall.The induced draft fan assists the FD fan by drawing out combustible gases from the furnace, maintaining a slightly negative pressure in the furnace to avoid backfiring through any opening.

Auxiliary systems:

Fly ash collection: Fly ash is captured and removed from the flue gas by electrostatic precipitators or fabric bag filters (or sometimes both) located at the outlet of the furnace and before the induced draft fan. The fly ash is periodically removed from the collection hoppers below the precipitators or bag filters. Generally, the fly ash is pneumatically transported to storage silos for subsequent transport by trucks or railroad cars.

Bottom ash collection and disposal:

At the bottom of the furnace, there is a hopper for collection of bottom ash. This hopper is always filled with water to quench the ash and clinkers falling down from the furnace. Some arrangement is included to crush the clinkers and for conveying the crushed clinkers and bottom ash to a storage site.

ECONOMISER:The heat of the flue gas is utilized to heat the boiler feed water. During the start up when no feed water goes inside the boiler water could stagnate and over heat in the economizer. To avoid this economizer re circulation is provided from the boiler drum to the economizer inlet.AIR HEATER or AIR PREHEATER:The air heater is placed after the economizer in the path of the boiler flue gases andpreheats the air for combustion and further economy. There are 3 types of air pre heaters: Tubular type, rotary type and plate type.Tubular type of air heater is used in TGS. Hot air makes the combustion process more efficient making it more stable and reducing the energy loss due to incomplete combustion and unburnt carbon. The air is sucked by FD fan heated by the flue gas leaving the economizer. The preheated air is sent to coal mill as primary air where coal is pulverized. The air sucked is heated to a temp. of 240-2800C. The primary air transports the pulverized coal through three burners at TGS after drying in the mill.SPRAY ATTEMPERATOR:- In order to deliver a constant steam temperature over a range of load, a steam generating unit (Boiler) may incorporate a spray attemperator. It reduces the steam temperature by spraying controlled amount of water into the super heated steam the steam is cooled by evaporating and super heating the spray water. The spray nozzle is situated at the entrance to a restricted venture sections and introduces water into the steam. A thermal sleeve linear protects the

steam line from sudden temperature shock due to impingement of the spray droplets on the pipe walls.The spray attemperator is located in between the primary super heater outlet and thesecondary super heater inlet. Except on recommendation of the boiler manufacturer the spray water flow rate must never exceed the flow specified for maximum designed boiler rating. Excessive attemperation may cause over heating of the super heater tubes preceding the attemperator, since the steam generated by evaporation of spray water and it does not pass through the tubes. Care must also be taken not to introduce so much that the unevaporated water enters the secondary stage of the super heater.

ELECTROSTATIC PRECIPITATOR: It is a device that separates fly ash from outgoing flue gas before it discharged to the stack. There are four steps in precipitation.# Ionization of gases and charging of dust particles.# Migration of particle to the collector.# Deposition of charged particles on collecting surface.# Dislodging of particles from the collecting surface.By the electrostatic discharge the ash particles are charged due to high voltage(56KV)between two electrodes. Generally maximum amount of ash particles are collected in the form of dry ash, stored inside the SILO. Rest amount of ash(minimum) are collected in the form of bottom ash and stored under the water inside HYDROBIN.

Factors affect the dust removal by an ESP: -

a) Particle size:- 0.01μ or lessb) Particle resistivity:- 104 to 1010 ohm-cmBoth low and high resistivity beyond the stipulated value is detrimental to ESPperformances because high resitivity leads to ‘back corona’ causing re-entrainmentof deposited particle back to gas stream from the collecting electrode whereas dustparticles of low resitivity (below 108 ohm-cm) get neutralized so fast as soon as theyreach the +ve plates that particles still remain residual momentum that bouncedthem of the collecting plates and caused re-entrainment.c) Field strength, d) Corona Characteristic,e) Flue gas velocity :-1.5 to 2.5 meter /sec.,f) Area of collecting surface,g) Rapping frequency.h) Presence sulfur, carbon particles, moisture, affects the performances of the ESPi) Flue gas temperature should be within 140 to 1600 C.

SAFETY VALVE: A safety valve is a valve mechanism for the automatic release of a gas from a boiler, pressure vessel, or other system when the pressure or temperature exceeds preset limits. It is part of a bigger set named Pressure Safety Valves (PSV) or Pressure Relief Valves (PRV). The other parts of the set are named relief valves, safety relief valves, pilot operated safety relief valves, low pressure safety valves, vacuum pressure safety valves. Safety valves were first used on steam boilers during the industrial revolution. Early boilers without them were prone to accidental explosion when the operator allowed the pressure to become too high, either deliberately or through incompetence.

Boiler losses

Feedwater heater: In the case of a conventional steam-electric power plant utilizing a drum boiler, the surface condenser removes the latent heat of vaporization from the steam as it changes states from vapour to liquid. The heat content (joules or Btu) in the steam is referred to as enthalpy. The condensate pump then pumps the condensate water through a feedwater heater. The feedwater heating

equipment then raises the temperature of the water by utilizing extraction steam from various stages of the turbine. Preheating the feedwater reduces the irreversibilities involved in steam generation and therefore improves thethermodynamic efficiency of the system. This reduces plant operating costs and also helps to avoid thermal shock to the boiler metal when the feedwater is introduced back into the steam cycle.

Condenser: The surface condenser is a shell and tube heat exchanger in which cooling water is circulated through the tubes. The exhaust steam from the low pressure turbine enters the shell where it is cooled and converted to condensate (water) by flowing over the tubes as shown in the adjacent diagram. Such condensers use steam ejectors or rotary motor-driven exhausters for continuous removal of air and gases from the steam side to maintain vacuum. For best efficiency, the temperature in the condenser must be kept as low as practical in order to achieve the lowest possible pressure in the condensing steam. Since the condenser temperature can almost always be kept significantly below 100 °C where the vapor pressure of water is much less than atmospheric pressure, the condenser generally works under vacuum. Thus leaks of non-condensable air into the closed loop must be prevented. Plants operating in hot climates may have to reduce output if their source of condenser cooling water becomes warmer; unfortunately this usually coincides with periods of high electrical demand for air conditioning. The condenser generally uses either circulating cooling water from a cooling tower to reject waste heat to the atmosphere, or once-through water from a river.

Diagram of a typical water-cooled surface condenser

Deaerator:

A steam generating boiler requires that the boiler feed water should be devoid of air and other dissolved gases, particularly corrosive ones, in order to avoid corrosion of the metal. Generally, power stations use adeaerator to provide for the removal of air and other dissolved gases from the boiler feed water. A deaerator typically includes a vertical, domed deaeration section mounted on top of a horizontal cylindrical vessel which serves as the deaerated boiler feedwater storage tank. There are many different designs for a deaerator and the designs will vary from one manufacturer to another. The adjacent diagram depicts a typical conventional trayed deaerator. If operated properly, most deaerator manufacturers will guarantee that oxygen in the deaerated water will not exceed 7 ppb by weight (0.005 cm³/L).

Diagram of boiler feed water deaerator

BOILER HEAT PUMPA boiler feedwater pump is a specific type of pump used to pump feedwater into a steam boiler. The water may be freshly supplied or returning condensate produced as

a result of the condensation of the steam produced by the boiler. These pumps are normally high pressure units that take suction from a condensate return system and can be of the centrifugal pump type or positive displacement type. Feedwater pumps range in size up to many horsepower and the electric motor is usually separated from the pump body by some form of mechanical coupling. Large industrialcondensate pumps may also serve as the feedwater pump. In either case, to force the water into the boiler, the pump must generate sufficient pressure to overcome the steam pressure developed by the boiler. This is usually accomplished through the use of a centrifugal pump. Feedwater pumps sometimes run intermittently and are controlled by a float switch or other similar level-sensing device energizing the pump when it detects a lowered liquid level in the boiler. The pump then runs until the level of liquid in the boiler is substantially increased. Some pumps contain a two-stage switch. As liquid lowers to the trigger point of the first stage, the pump is activated. If the liquid continues to drop (perhaps because the pump has failed, its supply has been cut off or exhausted, or its discharge is blocked), the second stage will be triggered. This stage may switch off the boiler equipment (preventing the boiler from running dry and overheating), trigger an alarm, or both.

TURBINE SECTION Turbine is a rotating device which converts heat energy of steam into mechanical energy. It is a two cylinder machine of impulse reaction type comprising a single flow high pressure turbine and a double flow low pressure turbine. The H.P. turbine shaft and the generator are all rigidly coupled together, the assembly being located axially by a thrust bearing at the inlet end of H.P. turbine. The turbine receives high pressure steam from the boiler via two steam chests. The H.P. turbine cylinder has its steam inlets at the end adjacent to the no. one bearing block, the steam flow towards the generator. Exhaust steam passes through twin over-head pipes to the L.P. turbine inlet belt where the steam flows in both directions through the L.P. turbine where it exhausts into under slung condenser. Steam is extracted from both the H.P. & L.P. turbine at various expansion stages & fed into four feedwater heaters.

DESIGN DATA:

Economical and max. continuous rating------------------------------- 60 MWSteam pressure at emergency stop valve------------------------------- 89kg./sqr.cm.Steam temp. at emergency stop valve ------------------------------------5100CAbsolute pressure at exhaust------------------------------------------------ 0.088kg./cm2

Rotational speed---------------------------------------------------------------- 3000 rpmTripping speed-------------------------------------------------------------------- 3375r.p.m.