Boiler Parts :
Water walls
Almost all modern power boilers are equipped with water walls. In large boilers, water walls completely cover the interior surfaces of the furnace providing practically complete elimination of exposed refractory surface; Waterwalls serve as the only means of heating and evaporating the feed water supplied to the boiler from economizers. Waterwalls usually consists of tangential vertical tubes and are connected at the top and bottom to headers. These tubes receive water from the boiler drum by means of downcomers connected between drum and Waterwalls lower header (Bottom Ring Header). In a boiler approximately 50% of the heat released by combustion of fuel in the furnace is absorbed by Waterwalls. Heat so absorbed by the Waterwalls is used in evaporation of water supplied to the boiler. The evaporated steam supplied to Boiler Drum again by mean of riser tubes from top header of water wall.
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| W/W Top Header |
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| water wall of a thermal power plant |
Boiler drum:
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| Boiler Drum |
The function of steam drum is to separate the water from the steam generated in the furnace walls and to reduce the dissolved solid contents of the steam to below the prescribed limit of 1 ppm. The drum is located on the upper front of boiler.Made from high Carbon Steel with high tensile strength and its working involves temperatures around 350oC and pressures well above 150 Kg/Cm2. The separated steam is drawn out from the top section of the drum and distributed for process. Further heating of the saturated steam will make superheated steam normally used to drive a steam turbine. Saturated steam is drawn off the top of the drum and re-enters the furnace in through a superheater. The steam and water mixture enters the steam drum through riser tubes; drum internals consisting of demister separate the water droplets from the steam producing dry steam. The saturated water at the bottom of the steam drum flows down through the downcomer pipe, normally unheated, to headers and water drum. Its accessories include a safety valve, water-level indicator and level controller. Feed-water of boiler is also fed to the steam drum through a feed pipe extending inside the drum, along the length of the steam drum.
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