Transcript of "Thermal Power Plant Basic to Knowledge"
THERMAL POWER PLANTA thermal power plant is a power plant in which the prime mover is stream. Wateris heated, turns into steam and spins a turbine which drives an electrical generator.After it passes through the turbine, the steam is condensed in a condenser andrecycled to where it was heated; this is known as a Rankine cycle.
WORKING SYSTEMCoal is conveyed (14) from an external stack and ground to a very fine powder by large metal spheres inthe pulverised fuel mill (16). There it is mixed with preheated air (24) driven by the forced draught fan(20). The hot air-fuel mixture is forced at high pressure into the boiler where it rapidly ignites. Water of ahigh purity flows vertically up the tube-lined walls of the boiler, where it turns into steam, and is passedto the boiler drum, where steam is separated from any remaining water. The steam passes through amanifold in the roof of the drum into the pendant superheater (19) where its temperature and pressureincrease rapidly to around 200 bar and 570°C, sufficient to make the tube walls glow a dull red. The steamis piped to the high pressure turbine (11), the first of a three-stage turbine process. A steam governor valve(10) allows for both manual control of the turbine and automatic set-point following. The steam isexhausted from the high pressure turbine, and reduced in both pressure and temperature, is returned tothe boiler reheater (21). The reheated steam is then passed to the intermediate pressure turbine (9), andfrom there passed directly to the low pressure turbine set (6). The exiting steam, now a little above itsboiling point, is brought into thermal contact with cold water (pumped in from the cooling tower) in thecondensor (8), where it condenses rapidly back into water, creating near vacuum-like conditions insidethe condensor chest. The condensed water is then passed by a feed pump (7) through a deaerator (12),and pre-warmed, first in a feed heater (13) powered by steam drawn from the high pressure set, and thenin the economiser (23), before being returned to the boiler drum. The cooling water from the condensoris sprayed inside a cooling tower (1), creating a highly visible plume of water vapor, before being pumpedback to the condensor (8) in cooling water cycle.The three turbine sets are sometimes coupled on the same shaft as the three-phase electrical generator(5) which generates an intermediate level voltage (typically 20-25 kV). This is stepped up by the unittransformer (4) to a voltage more suitable for transmission (typically 250-500 kV) and is sent out onto thethree-phase transmission system (3).Exhaust gas from the boiler is drawn by the induced draft fan (26) through an electrostatic precipitator(25) and is then vented through the chimney stack (27).
COAL FEEDING SYSTEMCoal is conveyed through rail wagon from out side ofplant and through conveyor system collected in hopperand ground to a very fine powder by large metal spheresin the pulverised fuel mill.Conveyor Coal HopperPulverised MillWagon Tippler
COAL FEEDING SYSTEMThen it is mixed with preheated air driven by the forced draught fan. The hot air-fuel mixture is forced at high pressure into the boiler.Air Pre-heater Forced Draft Fan
Wagon Tippler 1 &2Wagon Tippler 3 &4Sloping ConveyorTunnelTP-3Conveyor 3A/3BCHP RetainingWallOverview of Under construction BOP- Coal Feeding System
Crusher HouseTP-4TP-5Conveyor4A/4B Conveyor 5A/5BStacker ReclaimerCoal Stock YardOverview of Under construction BOP- Coal Feeding System
BOILERA boiler or steam generator is a device used tocreate steam by applying heat energy to water.The steam generator or boiler is an integral component of a steam engine whenconsidered as a prime mover; The boiler is a furnace on a side. Its walls are made ofa web of high pressure steel tubes.Pulverized coal is air-blown into the furnace from fuel nozzles at the four cornersand it rapidly burns, forming a large fireball at the center. The thermal radiation ofthe fireball heats the water that circulates through the boiler tubes near the boilerperimeter. The water circulation rate in the boiler is three to four times thethroughput and is typically driven by pumps. As the water in the boiler circulates itabsorbs heat and changes into steam at 700 °F (371 °C) and 3,200 psi . It is separatedfrom the water inside a drum at the top of the furnace.
ASH HANDLING SYSTEMAt the bottom of the furnace, there is a hopper for collection of bottom ash. Thishopper is always filled with water to quench the ash and clinkers falling down fromthe furnace. Some arrangement is included to crush the clinkers and for conveyingthe crushed clinkers and bottom ash to a storage site.
SUPER HEATERIn a power plant, after the steam is conditioned by the drying equipment inside thesteam drum, it is piped from the upper drum area into tubes inside an area of thefurnace known as the super heater, which has an elaborate set up of tubing wherethe steam vapor picks up more energy from hot flue gases outside the tubing andits temperature is now superheated above the saturation temperature. Thesuperheated steam is then piped through the main steam lines to the valves beforethe high pressure turbine.Superheated steam is steam at atemperature higher than waters boilingpoint. If saturated stream is heated atconstant pressure, it increases toward100% Dry Saturated Steam. Continuedheat input will then generate superheatedsteam. This will occur if saturated steamcontacts a surface with a highertemperature. The steam is then describedas superheated by the number of degreesit has been heated above saturationtemperature
STEAM TURBINEThe hot reheat steam is conducted to the intermediate pressure turbine where itfalls in both temperature and pressure and exits directly to the long-bladed lowpressure turbines and finally exits to the condenseA steam turbine is a mechanical devicethat extracts thermal energy frompressurized steam, and converts it intorotary motion.The steam turbine is a form of heat enginethat derives much of its improvement inthermodynamics efficiency through theuse of multiple stages in the expansion ofthe steam.
CONDENSERCondenser is a device or unit used to condense a substance from its gaseous to itsliquid state, typically by cooling it.The exiting steam from steam turbine, now a little above its boiling point, isbrought into thermal contact with cold water (pumped in from the cooling tower)in the condenser. where it condenses rapidly back into water, creating near vacuum-like conditions inside the condenser chest.Water Cooled Condenser Air Cooled Condenser
COOLING TOWERNatural Draft CoolingTowerInduced Draft Cooling TowerCooling towers are heat removal devices used to transfer process waste heat tothe atmosphere. Cooling towers either use the evaporation of water to removeprocess heat and cool the working fluid or in the case of closed circuit dry coolingtowers rely solely on air to cool the working fluid.
DE AREATORDe AreatorThe condensed water is then passed by a feed pump through a deaerater.A deaerator is a device that is widelyused for the removal of air and otherdissolved gases from the feed water tosteam-generating boiler.
ECONOMISEREconomiserPre-warmed water first enter in a feed heaterpowered by steam drawn from the highpressure set, and then in the economiserEconomizer are mechanical devices intendedto reduce energy consumption, or to performanother useful function like preheating a fluid.Economizer is a flue gas to water heat exchanger. Usually it is located below theLPSH in the boiler and above Air pre heater. Outside surface of the economizer tubesare heated by flue gases leaving the superheater and reheater which subsequentlytransfer heat to feed water flowing inside the tubes.Advantages of Economizer include1) Fuel economy: – used to save fuel and increase overall efficiency of boiler plant.2) Reducing size of boiler: – as the feed water is preheated in the economizer andenter boiler tube at elevated temperature. The heat transfer area required forevaporation reduced considerably.
Electrostatic PrecipitatorExhaust gas from the boiler is drawn by the induced draft fan through anelectrostatic precipitatorElectrostatic precipitators are mandatory installation in modern power plants tocontrol stack emission. Each boiler has electrostatic precipitators which containhigh voltage electrodes, these attract the pulverized fuel ash (PFA) from the fluegases. At regular intervals the electrodes are rapped with motor-driven hammersand the PFA falls into hoppers below.Electrostatic precipitator is a collectiondevice that removes particles from a flowinggas (such as air) using the force of an inducedelectrostatic charge. Electrostaticprecipitators are highly efficient filtrationdevices that minimally impede the flow ofgases through the device, and can easilyremove fine particulate matter such as dustand smoke from the air stream.
CHIMNEYExhaust gas from electrostatic precipitator vented through the chimney tack.A chimney is a structure for venting hotgases or smoke from a boiler, furnace orfireplace to the outside atmosphere.A chimney is a vertical structure for ventinghot flue gases or smoke from a boiler to theoutside atmosphere by means of the stackeffect. The space inside a chimney is calledaflue. The height of chimneys plays a role intheir ability to transfer flue gases using stackeffect. The dispersion of pollutants at higheraltitude helps to ease down its influence onsurroundings and reduces theirconcentrations in compliance with regulatorylimits.
BOILER MAKE-UP WATER TREATMENT PLANT & STORAGEBoiler make-up water treatment plant and storageSince there is continuous withdrawal of steam andcontinuous return of condensate to the boiler, lossesdue to blowdown and leakages have to be made up tomaintain a desired water level in the boiler steamdrum. For this, continuous make-up water is added tothe boiler water system. Impurities in the raw waterinput to the plant generally consist of calcium andmagnesium salts which impart hardness to the water.Hardness in the make-up water to the boiler will formdeposits on the tube water surfaces which will lead tooverheating and failure of the tubes. Thus, the saltshave to be removed from the water, and that is done bya water demineralising treatment plant
FUEL OIL SYSTEMAn auxiliary oil system pump is used to supply oilat the start-up of the steam turbine generator. Itsupplies the hydraulic oil system required forsteam turbines main inlet steam stop valve, thegoverning control valves, the bearing and seal oilsystems, the relevant hydraulic relays and othermechanisms.Light oil used as the fuel for igniters. Light oil is also required for warming up oilguns to start the boiler from cold conditions.
TURBO GENERATORTurbo Generator - Generator consisting of a steam turbine coupled to an electricgenerator for the production of electric power. They are usually preferred, sincethey offer much better fuel efficiency and are also more reliable, but on the otherhand they are much heavier and need more space.
GENERATOR COOLINGHydrogen gas is used for generator cooling. Sosupply of pure hydrogen is essential for generatorfilling and maintaining of hydrogen gas pressureinside the generator casing.Hydrogen PlantDirect current passes through caustic potash and DM water for hydrogen gasproduction .
OTHER STRUCTURE – AERATOR & CLARIFLOCCULATORAeration is the process of bringing water andair into close contact in order to removedissolved gases, such as carbon dioxide, and tooxidize dissolved metals such as iron. It canalso be used to remove volatile organicchemicals (VOC) in the water.As lot of water used in thermal plant for various purpose. Structure to clear it fromundesirable gases & dirt are required. Raw water generally supplied from pond arefirst pass through aerators which remove gases by mixing water with air.
OTHER STRUCTURE – AERATOR & CLARIFLOCCULATORAeration is the process of bringing waterand air into close contact in order toremove dissolved gases, such as carbondioxide, and to oxidize dissolved metalssuch as iron. It can also be used to removevolatile organic chemicals (VOC) in thewater.
Raw Water Pump HouseRaw Water ReservoirChemicalHousePipe Rack PR-32CascadeAeratorSludge PitHRSCC -1BBack WashPitHRSCC – 1ARapid Gravity SandFilter Filter Water Tank & PumpHouseOverview of Under construction BOP- Raw Water System
DM PlantDM TanksNeutralization PitDM RegenerationAreaOverview of Under construction BOP- De-mineralization System
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