Coal Pyrolysis at Fire-Level Heat Flux

Abstract

Pyrolysis of Pittsburgh Seam coal at fire-level surface heat fluxes of 0.76 and 2.0 cal/cm2-sec was investigated by means of measurements of mass-loss rate, density, temperature and internal gas pressure of pyrolyzing coal and thermal properties of coal and coke. Local and overall heats of pyrolysis were determined from these measurements at 2.0 cal/cm²-sec. It was found that as coal pyrolyzes, a surface coke layer (580 °C <T <800°C) grows behind a low-density plastic zone (410°C <T<580°C) that propagates into the virgin coal. The plastic zone is characterized by initial endothermic decomposition of virgin coal into a metaplast of liquid and gas and subsequent exothermic polymerization of these products to form coke. Exothermic reactions also occur in the surface coke layer. The sequential pyrolysis reactions were identified with respect to various density zones in the reacting coal