Complete analytical model for the combustion of a single porous char particle incorporated in an AFBC system model

The model deals with heterogeneous reaction rates which are of general order with respect to carbon and oxygen, effective pore diffusion which varies with solid conversion and external gas film transport. Batch-wise experiments, performed in a 100-mm diameter fluidized bed with different sized char particles, show a good agreement between measured burn-out times and model results. The single particle model has been incorporated in a system model of a coal fired atmospheric fluidized bed combustion (AFBC). In the AFBC system model all the major processes involving the combustion of the coal are taken into account: fluid hydrodynamics of the bed, devolatilization and fragmentation of the coal, combustion of the volatiles, combustion of the char, attrition and elutriation, homogeneous gas phase reactions, nitrogen oxide formation and reduction, sulfur capture, heat transfer, freeboard reactions, supply of secondary air and recycling of ash.