A prediction of defluidization time in biomass fired fluidized bed combustion

Two mathematical models to describe the complete defluidization time in biomass FBC were presented in this study; one was newly developed and another was a modified model. They considered the effects of the chemical properties of fuel ash and bed operating conditions such as air velocity, bed particle size and static bed height. The model formulations employed the approach of force balance, defining the viscous flow sintering and the gas bubble behaviors to evaluate the adhesive and segregated forces, respectively. The models were achieved by the statistical regression analyzes with the early laboratory scale experimental results and then verified by the pilot scale experimental results and previous published data. The regression analyzes revealed that the inorganic composition of ash in the fuel and temperature were most significant. In addition, the fluidizing velocity showed a strong effect among the observed operating variables. The model predictive results followed the lab scale data with the error range of ±22% and ±35% and provided fairly well predictability with the pilot scale and published data of previous bed agglomeration tests, carried out with several kinds of biomass fuels.