Heat and Mass Transfer in the Vicinity of a Devolatilizing Coal Particle

Abstract

A computer model has been developed to describe heat and mass transfer in the vicinity of a single reacting coal particle entrained in a laminar gas stream. The model describes the various processes that occur during devolatilization and combustion in the boundary layer between the particle surface and the bulk gas stream. Global reaction rates are used in the gas phase, with light and heavy volatiles represented by methane and benzene. Although the model was developed for a two-dimensional treatment. one-dimensional simulations are shown to yield meaningful results at low particle Reynolds numbers. Simulations indicate that the region of homogeneous volatiles combustion may extend for several particle diameters, implying that flame sheet approximations are not applicable during devolatilization. Parametric studies indicate that particle heating is dominated by homogeneous volatiles combustion for large particles and by heterogeneous reaction for small particles.