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US 5,078,100 AGranted
Method and apparatus for burning solid or sludge-like fuels in a fluidized bed
AssigneeVereinigte Kesselwerke AG
InventorsHelmuth Huschauer, Ralf J. Heitmuller
Life of this patent
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Abstract
A stationary weakly expanded fluid bed for combustion of coal, refuse, sludge and the like has a free space above the fluid bed in which a so-called upper firing is effected with secondary air. The temperature of the secondary air is maintained above the temperature of the fluid bed to handle problems resulting from variations in fuel quality and varying loads and guarantees a stable upper firing.
Claims11
A method of burning a fuel, comprising the steps of:
- (a) forming a weakly expanded fuel-containing fluidized bed of particles predominantly having a particle size above about 0.5 mm and a suspension density substantially greater than 2 kg/m.sup.3 and ranging up to a bulk density of said particles, and having above said bed a free space into which particles with a particle size up to about 0.5 mm are entrained from said bed along with combustible volatile substances in combustion gases leaving said bed, said free space having a suspension density of 1 to 2 kg/m.sup.3 ;
- (b) preheating air feeding a portion of the preheated air to said fluidized bed as primary combustion air and burning fuel in said fluidized bed with said primary combustion air and feeding another portion of said preheated air to said free space as secondary combustion air to burn fuel particles and volatiles in said free space to form a flue gas and flyash entrained therewith;
- (c) recovering flyash from said flue gas and cooling said flyash;
- (d) recycling at least some of the recovered and cooled flyash to said fluidized bed at a controlled rate maintaining a temperature of said fluidized bed substantially constant;
- and
- (e) controlling a temperature of said secondary combustion air fed to said free space to maintain a temperature therein which is greater than said temperature of said fluidized bed.
3 more elements
An apparatus for burning a fuel, comprising:
- means for forming a weakly expanded fuel-containing fluidized bed of particles having a particle size above about 0.5 mm and a suspension density substantially greater than 2 kg/m.sup.3 and ranging up to a bulk density of said particles, and having above said bed a free space into which particles with a particle size up to about 0.5 mm are entrained from said bed along with combustible volatile substances in combustion gases leaving said bed, said free space having a suspension density of 1 to 2 kg/m.sup.3 ;
- means for preheating air feeding a portion of the preheated air to said fluidized bed as primary combustion air and burning fuel in said fluidized bed with said primary combustion air, and feeding another portion of said preheated air to said free space as secondary combustion air to burn fuel particles and volatiles in said free space to form said flue gas and flyash entrained therewith;
- means for recovering flyash from said flue gas and cooling said flyash;
- means for recycling at least some of the recovered and cooled flyash to said fluidized bed at a controlled rate maintaining a temperature of said fluidized bed substantially constant;
- and
- means for controlling a temperature of said secondary combustion air fed to said free space to maintain a temperature therein which is greater than said temperature of said fluidized bed.
3 more elements
Dependencies are inferred from the claim text.