FAMILIARIZATION OF THERMAL POWER PLANT WITH CFBC BOILER

FAMILIARIZATION OF THERMAL POWER PLANT WITH CFBC BOILERTHERMAL POWER PLANTA thermal power plant works on the principle of RANKINE CYCLE

RANKINE CYCLEAn ideal Rankine cycle involves four processes:(1-2): Isentropic Compression in pump (2-3): Constant pressure heat addition in Boiler;(3-4): Isentropic expansion in Turbine; (4-1): Constant pressure heat rejection in CondenserAccording to the processes the power plant is divided into boundaries:Demineralization plantCoal Handling plantCirculating water and Make up water pump HouseCompressed air systemBoilerTurbineGenerator and Transmission systemElectrostatic PrecipitatorAsh Handling SystemNeed of De-mineralized waterIn power plant water is heated at high pressures and temperatures, this causes the salts in the water to form the precipitate or scales.The water in power plant has to pass through a large number of tubes whose internal diameters are small.When the non treated water is passed through them scales will be formed which obstruct the water or steam flow causing the failure of tubes.So the water is to be De-mineralized.Demineralization Plant (DM Plant)De mineralization is a process of removing undesirable minerals and converting raw water to Soft water and make suitable for Industrial purposesRAW WATERCLARIFLOCCULATORWATER RESERVOIRMULTI GRADE FILTERDM WATER TANKACTIVATED CARBON FILTERSTRONG ACID CATION EXCHANGERDEGASSERSTRONG ACID ANION EXCHANGERCOAL HANDLING PLANTNBEIL Coal Handling System is Designed for 450 TPH and consisting of two no. of streams, named as Stream A and Stream-B.Each stream is designed for 450 TPH, one is working and other is standby. Each stream consist three ground hoppers. Each ground hopper is of 70 MT in capacity. The Feed size of ROM (run of mine) Coal is -450 mm(Max.) and system product size is -6 mm for feeding to the Boiler coal bunkers

PICTORIAL REPRESENTATION OF STREAM-A COOLING AND MAKEUP WATER PUMP HOUSECooling Water pump House contains 3 Circulating Water Pumps, 2 Auxiliary Cooling Water pumps, Cooling Towers, Cooling Water Fans.Makeup water pump house contains Makeup water pump and a RCC reservoir The discharge from CW pumps goes to:CondenserLube oil coolersVacuum PumpsVapor Absorption Machine (VAM)EH oil coolers The discharge of ACW pumps go to:Generator Air CoolersEH oil coolersBoiler feed pumps for gland seal cooling and for oil coolersCondensate extraction pumps for bearing coolingAll fans and blowers in BoilerAll compressorsACsSample coolers

COMPRESSED AIR SYSTEMThe compressed air is used in various applications in power industry. For this four main air compressors (two stage double acting compressors) are installed. The discharge of this compressor is divided as service air and instrument air.In the instrumentation control valves, shut off valves, oxygen analyzer needs the compressed air which should be free from moisture and foreign particles for this purpose the discharge of main air compressor is sent to air drying unit. Air drying unit is the equipment in which the moisture from air is removed with the help of silica gel. Once this silica gel absorbs maximum moisture, it is removed by heating the silica gel with hot air.BOILERA boiler is an enclosed vessel that provides a means for combustion heat to be transferred to water until it becomes heated water or steam. The hot water or steam under pressure is then usable for transferring the heat to a process. Water is a useful and inexpensive medium for transferring heat to a process. When water at atmospheric pressure is boiled into steam its volume increases about 1,600 times, producing a force that is almost as explosive as gunpowder. This causes the boiler to be equipment that must be treated with utmost care.The various types of boilers are Fire tube boiler, Water tube boiler, Packaged boiler, Fluidized bed combustion boiler, Stoker fired boiler, Pulverized fuel boiler, Waste heat boiler and Thermic fluid heater.

FLUIDIZED BED COMBUSTIONWhen an evenly distributed air or gas is passed upward through a finely divided bed of solid particles such as sand supported on a fine mesh, the particles are undisturbed at low velocity. As air velocity is gradually increased, a stage is reached when the individual particles are suspended in the air stream the bed is called fluidized. With further increase in air velocity, there is bubble formation, vigorous turbulence, rapid mixing and formation of dense defined bed surface. The bed of solid particles exhibits the properties of a boiling liquid and assumes the appearance of a fluid bubbling fluidized bed. At higher velocities, bubbles disappear, and particles are blown out of the bed. There are three basic types of fluidized bed combustion boilers:1. Atmospheric classic Fluidized Bed Combustion System (AFBC)2. Atmospheric circulating (fast) Fluidized Bed Combustion system (CFBC)3. Pressurized Fluidized Bed Combustion System (PFBC).

CFBC BOILER

Boiler at NBEILCFBC boiler mainly comprises of the following components:Combustor, Cyclone, Seal pot / J- Seal, Bed ash Handling system,Coal feeding systemCoal BunkersDrag chain feedersCoal conveying feedersBed material bunker, Lime stone bunker, Startup burners

Boiler at NBEILThe mountings of the boiler are:Water level gauge - 2Continuous blow down - 2 and intermittent blow down - 1Safety valves 8 (2 on Steam Drum, 2 on Main Steam Header, 2 on Cold Re-heat Header, 2 on Hot Re-heat Header)Feed check valve - 1Man holes - 17The accessories of the boiler are:Air pre-heaterEconomizer 2 (High Temperature and Low Temperature Economizer)Super heatersRe-heaterBoiler feed pumps - 3The boiler contains the following circuits:Air and flue gas circuitCoal and ash circuitWater and steam circuit

TURBINEThe turbine is the equipment which converts the Steam energy into mechanical energy. NBEIL employed super high pressure intermediate reheat single axle impulse type double casing and double exhaust steam turbine from Dong Fang Power Systems, China.For the proper running of turbine system many equipment have to work. The major equipment are:CondenserVacuum PumpCondensate Extraction PumpGland Steam CoolerRegenerative systemVapor Absorption MachineBoiler feed pumpsLubrication systemElectro Hydraulic System

REHEAT AND REGENARATIVE SYSTEM IN TURBINE

GENERATOR AND TRANSMISSION SYSTEMGenerator is the device used to convert the mechanical energy into electrical energy.Cooling system:For cooling the generator the air cooling is employed. There are series of fans in parallel rows under the generator; these fans take air from surroundings which get cooled by circulating in the coolers through which ACW is circulating.220 KV Switchyard:220 KV Switchyard is conventional outdoor open air insulated. The switch yard have two main buses with One Bus Coupler switching scheme for the evacuation of power. The electric power generated at 15.75 KV level of GT is stepped up to 220 KV via Generator transformer and exported to grid at 220KV level. There are two out going lines, line-1 & line-2 connected to Budidhampadu substation which is about 61 km from power plant.ELECTROSTATIC PRECIPITATORThermal power plants are based on coal as fuel. Coal consists of some percentage of ash, Sox, and Nox gases in which flow into atmosphere should be controlled within hygiene, pollution free and comfort before the gas is released into atmosphere. For the control of dust, mainly the ash particles from combustion of coal in Boilers, Electrostatic Precipitator is often used.Electrostatic precipitator is electric equipment where a DC voltage is imparted through emitting electrodes creating an electrical field around it. The dust particle carried by the gas while passing through the field is charged to saturation and migrates towards the collecting electrode usually in the form of plate curtain where they deposit in layers. By suitable ramming dust is dislodged in to the hopper.ASH HANDLING SYSTEMThe coal burnt in the boiler contains bed ash and fly ash. There is continuous generation of bed ash and fly ash as there is continuous feeding of coal. For the fluidization to occur the bed ash should be drained continuously for this purpose four bed ash coolers and one emergency drain are installed. The fly ash collected in the electro static precipitator (ESP) hoppers should be conveyed to fly ash silo for this three ash handling compressors (single stage double acting compressors) are installed.The bed ash handling system comprises the followingBed drain pipesBed ash coolers Drag chain conveyor Bucket ElevatorSiloAsh conditioner & Rotary vane feeder.

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