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| There are several methods adopted for firing solid fuels such as COAL, Palm Shell, Anthracite, chipped wood, Paddy Husks, Coconut Shell, Bagasse, etc. The fuel could be fired on Chain Stoker, Traveling Grate, Reciprocating Grate, Dumping Grate, etc. But today’s cutting edge technology is the “FLUIDIZED BED COMBUSTION”. This phenomenon of fluidized bed has been used in chemical engineering for half a century, but it has been used for combustion of solid fuel in only about three decades old. Solid particles could be moved by fast stream of air. The movement depends upon the velocity of air in the medium. If the velocity is too slow, air will percolate through the bed solids. On the other hand, if the velocity is too strong, the solids will be pneumatically transported. If the velocity of the air stream passing through the bed is gradually increased, a point is reached where individual particles are forced upwards with the rising bubbles. As the bubbles comes out of the bed and burst, these particles are returned back to the bed causing rapid mixing of particles. The surface is no longer defined and the bed in this state is called bubbling bed or ‘FLUIDIZED BED”. |
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HOW IT OPERATES: When air is passed through an inert bed of solid particles such as silica sand, the air will seek a path of least resistance and pass upward through the sand. With increase in velocity, the air starts bubbling and the particles attain a state of high turbulence. Under such condition, the bed assumed the appearance of fluid and exhibits the properties associated with fluid, hence the name ‘FLUIDIZED BED”. |
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