Mass transfer effects in coal combustion

Abstract

The kinetics of combustion of pulverized coal depends both on the intrinsic reactivity of the coal and on mass and heat transfer effects. Measurements of diffusion coefficients at high temperatures has been carried out for two chars obtained from pulverized coal using a nonisobaric chromatographic technique. Due to low mass transfer resistance at higher temperature, experimental values of diffusion coefficients could be measured only up to 500 K. Extrapolation of the results to combustion temperatures ( ca 1500 K) showed that pore diffusion and the intrinsic reactivity of the coal controlled the overall rate of combustion for the samples chosen. The importance of micropores and micropore enlargement during combustion was established, as was the necessity and the means to decouple intrinsic reactivity and mass transfer in studies of coal combustion.