Conversion of coal tar to soot during coal pyrolysis in a post-flame environment

Abstract

Coal pyrolysis experiments were performed in the postflame region of a CH 4 /H 2 /air flat-flame burner operating under fuel-rich conditions, where the temperature and gas compositions were similar to those in the near-burner region of a large-scale coal-fired furnace. Volatiles released from the coal particles formed a cloud of soot particles at high temperatures in the absence of oxygen. The soot particles in the cloud were collected at different residence times using a water-cooled, nitrogen-quenched suction probe. Test variables included the reaction temperature and coal type. Soot yields in terms of weight percentage of dry ash-free coal were measured based on bulk soot collection experiments. The measured soot yields were related to coal rank, reaction temperature, and residence time. Size changes of soot particles due to soot agglomeration were also observed. The information obtained about coal-derived soot is useful in predictions of radiative heat transfer and pollutant formations in the near-burner region of pulverized coal-fired furnaces.