GB1307220A - Fluidised bed combustion apparatus - Google Patents

Abstract

1307220 Fluidized bed combustion apparatus FOSTER WHEELER JOHN BROWN BOILERS Ltd 5 June 1970 [12 June 1969] 29940/69 Heading F4B A coal burning fluidized ash bed 12 used in a steam generator, is provided with one or more variable level offtakes 32 whereby the bed height and so the heat release to immersed steam generator tubes 22 and at least partially immersed superheating and/or reheating tubes 25, may be adjusted in dependence on the load. Combustion air from passage 20 fluidizes the bed, the combustion products passing over convection heated superheater 26 and economizer 28 to a cyclone separator (not shown), the cleaned gases being expanded, in the case of a pressurized system, in a gas turbine which drives a compressor to pressurize the combustion air. The superheat and/or reheat steam temeratures, or the immersed tubes/convection heated tubes heat pickup ratio may be controlled by varying the height of the bed. Preferably one or more of the finned tube walls 14, defining the limits of the bed, slope upwardly and outwardly so that the sensitivity of the system to changes in bed height is increased at low bed heights which correspond to low steam loads. To form the or each offtake, a tube 34 is 'bent out of the plane of tube wall 14 to form an opening which is covered by a casing 37, 40 including front and rear slots 38, 46. A spring loaded adjustable sliding plate 42 is mounted within the casing, an outlet nozzle 44 of plate 42 which extends through rear slot 46, determining the level of the outflow opening. The air in passage 20 the pressure of which is higher than that in the bed, passes in part into the bed through slots 46, 38, so keeping the sliding plate 42 clear of ash or coal particles.