00/01508 Characteristics of pulverized-coal combustion in CO 2-recovery power plant applied O 2/CO 2 combustion

Abstract

Results of experiments to determine the extent of heterogeneous combustion in the rapid-devolatilization regime of fuel-rich bituminous and subbituminous coal-dust flames are reported. Major gas concentrations, gas and particle temperatures, and solids proximate and elemental compositions were measured as functions of residence time in pulverized-coal/O2/Ar flames stabilized on a flat-flame burner. Proximate fixed carbon and volatile matter measurements are corrected to account for devolatilization exceeding that predicted by ASTM proximate analysis. The corrected proximate data are used to determine the fraction of volatile matter consumed heterogeneously in situ and the fraction released to the gas phase by pyrolysis. Seven to thirty-five percent of the initial corrected volatile matter is removed heterogeneously. A mass transfer analysis is applied to predict a time dependent critical particle size such that the volatiles flux emerging from larger particles is sufficient to prevent surface oxidation. Critical particle radii as large as 39 μm are calculated. Results of the volatile matter partitioning and critical radius calculations indicate that heterogeneous combustion is more important in the leaner flames and for the subbituminous coal.