INFLUENCE OF OPERATING PARAMETERS AND WALL GEOMETRY ON HEAT TRANSFER AND TEMPERATURE DISTRIBUTION IN A 12 MWth CFB BOILER
A shielded thermocouple probe and a heat flux meter were used to measure heat transfer coefficients and temperature distributions at five different elevations in the combustion chamber of a 12 MWth circulating fluidized bed (CFB) boiler. The focus of this work was to investigate the effect of the wall geometry, membrane tube wall and refractory wall, and some operating parameters on the temperature distribution as well as on the bed-to-wall heat transfer coefficient. The fuel was bituminous coal and the bed material was silica sand of mean diameter 270 µm with a particle density of 2600 kg/m3. The bed temperature was varying in the range of 800 to 900 ° C, superficial gas velocity was 3 to 6 m/s and the suspension density varied from 6 to 70 kg/m3.