Pyrolysis of a western bituminous coal in a entrained flow reactor : a kinetic analysis

ABSTRACT Flash pyrolysis of a high volatile bituminous coal was studied by entraining small (94 or 133 ym) diameter particles in a pre-heated stream of nitrogen which passed through a heated stainless steel tube. Particle residence times in the tube ranged from 60 to 160 msec for temperatures of 570 to 730°C, and the particles were quickly cooled by mixing with cold nitrogen. The time-temperature history of the particles was calculated by incremental force and energy balances. The weight losses during subsequent heating were determined from the char which was collected in order to estimate the flash pyrolysis loss in the tube. A kinetic analysis of the pyrolysis data was analyzed by nonisothermal techniques since the particle time-temperature history in the tube was known. The weight loss data were successfully modeled by a set of independent parallel decomposition reactions. These data were used to calculate a distribution of activation energies for the set of first order reactions. There was a pronounced maximum in the distribution curve at an activation energy of 51 kcal/mole. An overall discrepancy of 2.4 percent in the weight loss data between the large and small particles indicates (from the kinetic analysis) that the initial coal decomposition products undergo further (secondary) reactions within the coal which reduce weight loss.