Modelling of Coal Pyrolysis and Combustion

A coal particle combustion model starting from the devolatilization to the final char combustion is presented. The most serious shortcoming of modelling the coal devolatilization by means of Arrhenius kinetics is the failure to account for the apparently asymptotic yield of volatiles that depends on the temperature. A coal devolatilization model that is based on the temperature dependent asymptotic yield of volatiles is presented. This model applies well for the usual non-isothermal coal particle pyrolysis. Three different char combustion models are compared to measurements presented in the literature. Intra-particle heat transfer during the drying and the pyrolysis stage of the combustion is considered. The spatial temperature differences during the char combustion stage are usually insignificant, but there is a significant spatial temperature distribution inside the particle during the drying and the devolatilization even the particle is small. This paper is based on three larger unpublished reports /1,2,3/ that are available on request from Domestic Fuel Laboratory.