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Monday, 19 January 2015

Fluidized Bed Boiler

Fluidized Bed Boiler Points : Fluidized Bed Boiler, Definition Fluidized bed combustion is modern development and large numbers of boilers are impending by this arrangement. At this time a bed of inert, refractory sand form material is forced to get fluidized through the air passing through it. Air use for fluidization is heated before being sent into bed. Auxiliary fuel which is commonly gas gets burnt over or in bed so as to reason bed temperature to go up to on 650C. While proper temperature level is attained then coal is fed on it or into it for being blistered. Burning of auxiliary fuel is stopped at moment as burning of coal become self sustainable.

Supply of coal and air are governed through the demand on boiler. Maximum bed hotness usually reaches up to 950°C as these temperature controls avoid ashes formation and emission of unwanted salts. For maintain temperature of bed arrangement is prepared for cooling of bed with water tubes and too by supplying excess air for cooling. At times low temperature flue gases leaving boiler are re-circulated for bed cooling. Fluidized bed combustion offers benefit of by any kind of fuel that is solid, liquid or gaseous fuel. As well in this kind of combustion the use of dolomite or lime stone as bed material helps in retain sulphur in fuel. The ashes creation and emission of undesired substances is too avoid as combustion can be controlled equal to 950°C. Due to large amount of equally combustible and fireproof material present on bed there occurs the problems of corrosion in bed tubes and surroundings and too large burden on bed and so on. Fluidized bed combustion is use in equally fire tube and water tube boilers but water tube boiler offers benefit of greater flexibility in devise of furnace shape and allow for greater freeboard in which entrained particles can fall back into bed. Air velocity is usually partial to 2.5 m/s as past this the option of incomplete combustion increases.

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