A method of determining thermal parameters of granular coal particles during devolatilization

Abstract

SUMMARYFluidized bed combustion offers great potential for the utilization of high-sulphur coal and low-grade coal in an environmentally acceptable manner. Utilization of fluidized bed technology, especially for the combustion of low quality lignites, enables pollutant emission control as well as efficient combustion. The most important stage during the combustion of coal particles is devolatilization, in which various factors such as heat transfer from the surroundings to the particle surface, heat conduction within the particle, the chemicals involved, the kinetics and the transport of volatile compounds within the particle play significant roles. The heat transfer coefficient, thermal diffusivity, thermal conductivity, heating coefficient and lag factor are the most significant thermal parameters in this process. In this study, a 1-D transient heat transfer analysis is carried out for a granular coal particle during devolatilization in a fluidized bed. The particle is idealized as a spherical solid body. Models are developed to determine the thermal parameters of such particles, and are verified using experimental centre temperatures of a 10mm granular coal particle subjected to devolatilization at a medium temperature of 960K. The data are taken from the literature. The results show that the thermal parameters determined here are in good agreement with experimental findings.