Modeling and simulation of size reduction of fuels in circulating fluidized bed combustor by considering attrition and fragmentation

Abstract

A Circulating Fluidized Bed Combustor (CFBC) is a high efficient combustor. It can handle various types of solid fuels such as coal, biomass or mixed fuels. Coal and biomass has been used as fuels to generate heat for a boiler in many industries. The particle size distribution (PSD) of the solid inventory in a CFBC affects the hydrodynamic and heat transfer leading to the changes of combustion efficiency and gas emission. The understanding of the particle comminution is useful for PSD prediction. The experiments of coal and bagasse comminution was studied in the 2.5 cm ID, and 160 cm height of the CFBC. The PSD resulted from the devolatilization and combustion processes were obtained. The ASPEN PLUS program was used to simulate the PSD of fuel particles by adding the fragmented particle models resulted from the experiment. The simulation result showed that by adding these models the prediction is better than those with only the shrinking particle model. Moreover, for the industrial-scale CFBC simulation, gas emission models were included to calculate the kinetic rates of NO[subscript 1] N[subscript2]O and the conversion of SO[subscript2] to predict the gas emission to the environment.