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Steam Power Plant

Steam Power Plant. Content. Arrangement Efficiency Advantages Disadvantages Comparison with diesel engine powered vessels Basic glossary Main elements of a steam power plant A uxiliaries. The Arrangement.

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Steam Power Plant

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  1. Steam Power Plant

  2. Content Arrangement Efficiency Advantages Disadvantages Comparison with diesel engine powered vessels Basic glossary Main elements of a steam power plant Auxiliaries

  3. TheArrangement • mechanical power is produced by a heat engine that transforms thermal energy (from combustion of fuel) into rotational energy • heat (generated in the furnace) is transmitted to the boiler where water, forced into the boiler by the feed pump, is converted into steam

  4. TheArrangement • steam drives turbine blades shaft

  5. Efficiency • the efficiency of a steam turbine is limited by the maximum temperature of the steam produced and is not directly a function of the fuel used (for the same steam conditions, coal, nuclear and gas power plants all have the same theoretical efficiency)

  6. Advantagesof SPP • Low noise • Low weight • Little or no vibration • Relatively easy and simple plant maintaining and handling • Cargo (any suitable form of energy can be used to make steam)can be used as bunker fuel - on board LNG and LPG carriers

  7. Disadvantagesof SPP • Higher specific fuel consumption (HOWEVER: Reheating) • Less efficient than reciprocating engines (at idle speeds)

  8. Comparisonwith diesel enginepoweredvessels Diesel engines Steam propulsion less efficient than reciprocating engines (at idle speeds) higher specific fuel consumption cargo can be used as bunker fuel - on board LNG and LPG carriers relatively easy and simple plant maintaining and handling low noise little or no vibration low weight • most efficient prime mover • lower fuel consumption • less bunker space • more expensive to build and maintain • more noise and vibration • heavier

  9. Basicglossary • Operating pressure • Boiler efficiency • Steaming hours • Heating surface • Generating surface • Superheated steam

  10. Basicglossary • Operating pressure – the pressure at which the boiler is operated in service • Boiler efficiency -the ratio between the thermal energy actually absorbed by water and the thermal energy available in fuel (80 – 90 %)

  11. Basicglossary • Steaming hours -the time during which the boiler generates steam • Heating surface -the total surface of all parts exposed to combustion gases (tubes, superheater, economiser)

  12. Basicglossary • Generating surface - a part of the surface in which water is heated and steam is generated (drum) • Superheated steam = saturated steam + more heat at constant pressure –> dry steam (to avoid damage to turbine blades)

  13. MainElementsof SPP • FURNACE • BOILER • SUPERHEATER • TURBINE • CONDENSER

  14. Furnace • a chamber in which heat is produced – combustion of fuel & generation of hot gases • burners – break fuel into fine particles to ensure efficient combustion

  15. Boiler • steam generator – saturated & superheated steam • steam drum - a reservoir of water/steam at the top end of the water tubes, it acts as a separator for the steam/water mixture (difference in densities) • water circulation – natural or forced

  16. Boiler

  17. Boiler • watertube boiler • firetube boiler

  18. Firetubeboiler • hot gases pass through the tubes, feed water surrounds them

  19. Watertubeboiler • steam and water circulate through small diameter tubes and drum, gases of combustion pass around them • more commonly used, lighter, occupies less space and has increased efficiency (higher pressure and temperature)

  20. Watertubeboiler

  21. Superheater • consists of headers and superheater tubes • converts saturated steam into dry steam

  22. Turbine • steam is admitted to the turbine • heat energy is converted into mechanical energy – useful work • high pressure turbine • low pressure turbine

  23. Condenser heat exchanger • tubes sea water • steam water (condensate) • vacuum is created due to steam / condensate volume difference • vacuum is maintained by constant cool water circulation through the tubes

  24. Condenser

  25. Auxiliaries • CONDENSATE – COLLECTING TANK (HOTWELL) • MAIN CONDENSATE PUMP • AIR EJECTOR • DEAERATING FEED TANK • MAKE UP TANK (EMERGENCY FEED TANK) • FEED PUMP • ECONOMISER

  26. MainCondensatePump • condensate – collecting tank (hotwell) • Main Condensate Pump • to pump water from the hotwell through the main air ejector to the deaerating feed tank

  27. Air Ejector • no moving parts • jet pump • Bernoulli’s principle • to remove air and gases from the condensate

  28. DeaeratingFeed Tank • to remove air from the system • to heat the condensate • to be used as storage tank for heated feed water

  29. DeaeratingFeed Tank Form: cylindrical tank in three sections First section (the lowest) – storage space = beginning of the feed phase Middle section: atomizing valve assembly to release entrapped air from the water Upper section: preheater compartment

  30. MakeUp Tank • losses in cycle • when the feed water level in the deaerating tank drops to a minimum, make-up feed water enters the system

  31. Feedpump • pump that forces feed water into the boiler

  32. Economiser • to improve the efficiency of the steam plant by using thermal energy, i.e. preheating the feedwater before it passes into the boiler • water is heated under pressure to remove dissolved air and vapour to minimize internal boiler corrosion

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