Process Simulation Development of Coal Combustion in a Circulating Fluidized Bed Combustor Based on Aspen Plus

Abstract

A process simulation model has been developed to simulate and predict the condition of three kinds of coal combustion in a 30 kW circulating fluidized bed combustor based on Aspen Plus with considering gas−solid hydrodynamics via Aspen Plus in-line FORTRAN codes and combustion reaction kinetics via some external FORTRAN subroutines simultaneously. The related mathematical models in the process simulation, such as a gas−solid hydrodynamics model in the CFB riser, equivalent pyrolysis model of coal, and combustion kinetics model of coal pyrolysis products, have been presented in detail. The profiles of voidage and gas pressure along the height of riser are discussed and preliminarily predicted by the developed model in this paper. It can be concluded from the results of the process simulation model that increasing gas superficial velocity can lead to a decrease of voidage in the dense region and lower acceleration region, and a slight increase of voidage in the upper acceleration region and completely fluidized region. Furthermore, increasing gas superficial velocity can also effectively increase the total pressure drop of the riser. Therefore, a larger inlet pressure is required when more primary air is introduced into the riser bottom.