Subject: Energy Conversion-I - PowerPoint Presentation

1. Subject: Energy Conversion-ITopic : Boilers

2. COURSE OUTCOMES: After successful completion of the course, the students should be able to Sr. No.DescriptionPO & PSO MappingCO601T1Outline the thermal power plant and explain, classify, analyze steam generators (i.e. Boilers), boiler mountings and accessories.(L1,2,4)PO1, PO6, PSO1,PSO3CO601T2Explain various draught system and evaluate performance parameters of boiler & natural draught (i.e. chimney) (L1,2,3,4,5)PO1, PO2, PO3, PSO1,PSO3CO601T3Explain the concept of fluidized bed boilers, coal handling system, ash handling system and Cogeneration. (L1,2)PO1, PO7, PSO1,PSO3CO601T4Compare impulse and reaction steam turbines, explain the concept of compounding, governing of steam turbine and nozzle and determine the throat area, exit area, exit velocity of nozzle. (L1,2,3,4)PO1, PO2, PO3, PSO1,PSO3CO601T5Explain various energy losses in steam turbine, Reheat, Regenerative cycles, and able to draw velocity diagrams of turbine blades to analyze the angles of the blades, workdone, thrust, power, efficiencies of turbine.(L1,2,3,4,5)PO1, PO2, PO3, PSO1,PSO3CO601T6Explain the different steam condensers, cooling towers and evaluate performance parameters of surface condenser. (L1,2,3,4,5)PO1, PO2, PO3, PSO1,PSO3

3. A steam boiler or steam generator is a closed vessel in which water is heated, vaporised and converted into steam at a pressure higher than the atmospheric pressure. The heat energy required for steam generation is produced by burning fuel in the furnace. Application: Industrial processes or heating purpose  INDIAN BOILER REGULATION (IBR, Act 1923): Steam boiler means any closed vessel exceeding 22.75 litres (other pressure vessel) in capacity and which is used expressively for generating steam under pressure. It includes any mountings or other fittings attached to such a vessel, which is wholly or partly under pressure when steam is shut off.

4. Classification:According to relative passage of water and hot gases (Fire)Water tube boiler: The water is inside the tubes and hot gases surrounded the tube.Operating pressure limited to 16bar Fire tube boiler:The hot gases are inside the tubes and water surrounded the tube.Can work under at high pressure as 100bar

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6. 2. According to water circulation arrangement: Natural circulation: Due to density difference of hot and cold waterForced circulation: Water pump forces the water along its path, steam generation rate is higher 3. According to position of boilers: (depending on the axis of boiler) Horizontal: More space (floor area) occupied, but easy to repair and inspect Vertical: less space (floor area) occupied, but difficult to repair and inspect Inclined  4. According to position of Furnace:Internally Fired: Furnace is located inside the boiler shellExternally Fired: Furnace is located outside the boiler shell

7. 5. According to pressure of steam generated:Low Pressure Boiler: 15-20barApplication: Process heating  b) Medium Pressure Boiler: 20-80barApplication: Power generation, combined use of power generation and process heating  c) High Pressure Boiler: more than 80barSub-critical Boiler: Less than critical pressure (221.1bar)ii. Supercritical Boiler:More than critical pressure, No evaporator, Once through boiler (the water directly flashes into steam)

8. 6. According to charge in furnace: Pulverised fuelSupercharged fuelFluidized bed combustion boilers  7. According to the use: Stationary Boiler: Power generation in thermal power plant or process heating b) Portable Boiler: temporary uses at the sites (mobile boiler), Locomotive Boiler: Railway steam engines, Marine Boiler: Ships

9. Factors affecting the selection of boilers: Steam generation rate of boiler at working pressure (maximum Steam generation rate and minimum fuel consumption)Type of fuel and its rate of burningAvailability of fuel and waterFloor space occupied by the boilerType of load steady, fluctuating, etc.Initial cost, running cost and maintenance cost 

10. Fire tube 1. Vertical tube boiler (Fire tube, vertical, portable)Two cross tubes: increases heating surface area Inclined tubes: efficient water circulationHand holes: to give access for cleaning tubesManhole: clean the interior of the boiler and exterior of the CC and chimneyFireboxChimney at top of the fire box: Waste flue gasesNatural convection water circulationConvection and radiation Heat transfer 

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12.  2. Cochran Boiler (Vertical multi-tubular (fire tube) boiler and has a number of horizontal fire tubes)Boiler is verticalMultiple horizontal fire tubeDome shaped furnace Hemispherical crown of boiler: space for steamSeamless furnace: one piece construction of furnaceFire brick lining: divert the hot gases in CC through flue tube (FT)Radiation HT- from dome to waterConvection HT- wall of the tubesSteam stop valve: to collect steam Mud hole: draining the muddy waterAntiprimming pipe

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14. 3. Lancashire Boiler (Fire tube, Low pressure, internally fired, natural circulation, stationary)-refer vedioHorizontal cylindrical shell filled with waterShell is constructed with several rings of cylindrical formShell is placed over brickworkBrick work create several channels for the flow of hot flue gasesTwo tubes (fire tubes) are also constructed with several rings of cylindrical formTwo tubes are surrounded by waterSolid fuel is entered through the fire doorFuel is burnt over the grate at the front end of each fire tube

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16. Small (arch shape) brickwork is provided at the end of the grate: to deflect the flue gases upwards and prevent the entry of the burning coal and ashes into the interior of the fire tubesThe fire tubes are slightly conical towards its rear end: to increase the velocity of the hot flue gasesHot flue gases are passed through the downward channel to the front end of the fire tubesThis gases passed to the side channel towards the rear end of the fire tube and finally escapes through the chimney

17. Dampers on the each side channel to regulate the air flow: combustion rate and steam generation rateDampers: operated using chain pulleyFeed check value: to fill water uniformly to the shellSteam stores at the upper portion of the boiler shellAnti priming pipe: separate the water from the steamSteam stop valve: recives the dry steam for various purposesManhole is provided at the top and the bottom of the shellBlow off valve: to remove the mud which is settle down also used to empty the boilerIn brick work, a flue passage (A) below the boiler shell, two flue passages (B) and (C) at the sides of the boiler are formed. The flue passages (B) and (C) are connected to a chamber and then to the chimney.

18. 4. Cornish Boiler: Same as Lancashire Boiler but has single fire tube and small in size

19. 5. Babcock and Wilcox BoilersStriaght horizontal longitudinal drum filled with waterBoiler drum is connected to series of up-take header tubes at the front end and down-take header tube at the rear endBoth header tubes are connected with series of inclined tube (15)Solid fuel gets burned over grate to produce hot flue gasesThis flue gases are then force to move upward between the water tubesBaffles plate: guide the movement of flue gses and ensure proper heating of the water tubesWater-steam

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21. This steam moves to the up-take header and collected over the water level in the boiler dumAnti-priming pipe is provided to separate the water from the steam and dry steam is then supplied to the superheater tubes: saturated steam to superheated steam: which can be taken out from the steam stop valveAsh pit: collect the ash formed by the burning of fuelChimney: smoke is allowed to escape into the atmosphereDamper installed before the chimney: to regulate the air supply into the fire boxInspection door: to inspect operationBoiler assembly is suspended on the steel girders to enable the boiler drum and water tubes to expand and contract during their operationOther mounting