Effects of heating rate and pressure on the pyrolysis yields of a brown coal

A Loy Yang brown coal sample was pyrolysed in a wire-mesh reactor where the extraparticle secondary reactions of the evolved volatiles were minimised. Pyrolysis experiments were carried out at pressures ranging from 100 kPa to 1000 kPa. Tar yield was found to be very sensitive to changes in heating rate, peak temperature, holding time and pressure. While tar yields decreased with increases in pressure at high heating rate, the corresponding char yields were generally much less sensitive to changes in pressure and heating rate. Increasing pressure seemed to have caused delays in the release of volatiles, leading to decreases in tar yield due to intraparticle cracking reactions.