The kinetics of combustion of pulverized semi-anthracite in the temperature range 1400–2200°K

The rates of combustion of four size-graded fractions of semi-anthracite (78, 49, 22, and 6 μm) have been measured in the temperature range 1400–2200°K and at oxygen partial pressures of 0.1 and 0.2 atm. The rates were usually much less than the limiting rate of oxygen diffusion to the particles. For the 78-, 49-, and 22-μm fractions the chemical reaction rate coefficients [g/(cm2 sec atm. O2], calculated from the measured rates corrected for external diffusion resistance, were independent of particle size, and of burn off up to 99% burn off. The particles burned with decreasing size and density. The temperature coefficient of the reaction corresponded to an apparent activation energy of about 20 keal/mole. These factors indicate that the reaction rate is limited by the combined effects of pore diffusion and chemical reaction on the pore walls. The chemical reaction rate coefficients were independent of oxygen partial pressure at 0.1 and 0.2 atm. The absolute values of the rates and other results agree well with those of previous workers for anthracites and semi-anthracites. The values of the chemical rate coefficient for the 6-μm fraction were lower than for the larger fractions, such behaviour indicating that this fraction burned with little restriction by pore diffusion. The results are compared with other workers' data for the combustion rates of anthracites and semi-anthracites.