Pyrolysis of coal in hydrogen and helium plasmas

Abstract

The rate of formation of acetylene, the most interesting product of coal pyrolysis in hydrogen plasma, is determined by heat transfer to coal and by the kinetics of pyrolysis and homogeneous gas phase reactions. Experiments were carried out with the inert gas helium and hydrogen in order to distinguish between pyrolysis and reactions with hydrogen. The time resolution of the apparatus facilitated measurement of the increase of non-condensable reaction products. The experiments were performed with a high volatile bituminous coal (particle size 100 μm) at temperatures between 1000 °C and 2000 °C. the coal particles are rapidly heated to a temperature lower than the gas temperature, then volatiles are released, which react with highly reactive plasma species as far as these are available. When the pyrolysis of coal is finished after about 4 ms, the char is heated up to gas temperature. Coal can burst in the plasma jet to very fine particle sizes, thus enhancing the acetylene yield.