STATISTICAL PYROMETRIC SIZING OF PARTICLES IN FLUIDIZED-BED COMBUSTION

A theoretical basis is presented for the concept of statistical pyrome tric particle sizing (SPPS) in fluidised bed combustion (FBC). The the ory makes it possible to obtain the size distributions for observable particles within given temperature ranges, and thus a statistical esti mate can be made of the dependence of the temperature of a fuel partic le on its size during FBC. The SPPS method has been experimentally val idated by comparison with an independent reference method in a miniatu re fluidised bed reactor. Graphite spheres were burned one by one and measurements were taken with a two-colour fiber-optic pyrometer. Pyrom etric signals were obtained many times during each particle's combusti on and SPPS was applied to the results. The generation of CO2 was also recorded and the evolution of the particle's size with time was deter mined from the CO2 mass balance, assuming shrinking core combustion. T he average sizes determined by SPPS and also from the CO2 mass balance were in good agreement for all temperature ranges. The elevation of t he particle's temperature above that of the bed varied between 20 and about 200 degrees C. Copyright (C) 1997 by The Combustion Institute