Modelling of devolatilization in circulating fluidized bed combustion

摘要

A mathematical model is developed to describe the devolatilization process in a circulating fluidized bed combustor. The model is a combination of two submodels: single particle devolatilization and fluid dynamics. The single particle modelincludes the influence of both chemical kinetics and heat transfer on the rate of devolatilization. The results show a good agreement with literature data. The fluid dynamic model describes the main characteristics of a CFB: A dense zone in the bottom,followed by a splash zone and a dilute zone with a core-annulus structure. Each zone is modelled as a number of CSTR's and the size and number of CSTR's has been estimated from tracer experiments in an 80 MW{sub}(th) CFB boiler. It was not possible toevaluate the model against experimental data, but the dependence of particle size on the degree of devolatilization in the dense bed agrees qualitative with the expected behavior. The model shows that the devolatilization mainly occurs in the dense bed.