The combustion of evolved volatile matter in the vicinity of a coal particle—An evaluation of the diffusion limited model

Abstract

A detailed analysis of the heat and mass transfer processes in the vicinity of a reacting coal particle, when the combustion of evolved volatiles is limited by the diffusion of reactants, is presented. Following the two competing reactions model of coal devolatilization, the predicted particle temperature, extent, and location of the combustion of volatile matter are shown to compare very well with the predictions from a complex model (in which the oxidation of volatiles is assumed to follow a global mechanism) suggesting the validity of the flame sheet approximation. The effect of the kinetic parameters of devolatilization on the model predictions is quantified in detail by comparison with the single particle combustion data reported in the literature. The effect of various physicochemical model parameters such as heat of devolatilization, particle specific heat partial, or complete combustion of volatiles on the model predictions is found to depend strongly on the kinetics of devolatilization.