Co-Pyrolysis and Co-Gasification of Coal and Biomass in a Pressurized Fixed-Bed Reactor

Abstract

The co-processing of coal-biomass mixtures under inert and reducing atmospheres has been studied in a bench scale fixed-bed (‘hot-rod’) reactor. The aim was to look for evidence of synergistic effects during the co-gasification of coal and biomass. Total volatile release, tar and char yields from mixtures of Daw Mill coal and Silver Birch wood (alone and in mixtures of 25, 50 and 75 % by weight), have been determined as a function of temperature (850 and 1000 °C) and pressures (up to 25 bar) under He-pyrolysis and CO2-gasification conditions. The total volatile yields of mixtures have been found to match those calculated theoretically from pure coal and biomass values under all conditions attempted, thus suggesting a lack of synergy in the amount of char produced. However, char reactivity measurements in an atmospheric thermogravimetric analyser (isothermal combustion in air at 500 °C) indicate that chars of coal-biomass mixtures have higher combustion reactivities than would be expected from the reactivities of the raw fuels alone. Similarly, the tar yields from mixtures are also somewhat higher than those predicted from the individual contributions of coal and biomass.