In the present work, a mass balance allows us to predict operating conditions of coal-fired circulating fluidized
bed (CFB) combustor under full load operation. A mass balance model has been developed for the particle size
distribution and solids mass fluxes of three granular materials supplied and led out in the 966MWth supercritical
circulating fluidized bed boiler. This model emphasizes some important factors, such as feed rates, separator
characteristics, drainage and recirculation rates of solids and internal processes. In the simulation model the internal
processes such as the combustion process, particle shrinkage, fragmentation and attrition were taken into
account, respectively. The model can theoretically predict the PSD and mass balance at different operating loads,
ash content and points inside the supercritical CFB combustion system. The results of the simulation indicate that
they are in accordancewith the experimental data fromlarge-scale supercritical CFB boiler. The results of modeling
give an opportunity of studying the impact of changes on the solids particle size distribution (PSD) and solids
mass fluxes in operating conditions.