Promoted reactivity of char in co-gasification of biomass and coal: synergies in the thermochemical process

An experimental study on co-gasification of woody biomass and coal in oxyge n-containing atmosphere was carried out in a pressurized fluidized bed reac tor. The wood used was birch from a Swedish paper mill, while the coals use d were Daw Mill coal of UK origin and a bituminous coal from Poland. The op eration temperatures were 900 and 700 degrees C, and the pressure was 0.4 M Pa. The ratio of coal to wood was varied in the investigation. The study wa s focused on possible synergetic effects in the thermochemical treatment of the fuels. The char formed was examined. The tar produced in the process w as analyzed. The nitrogen compounds emitted were detected. A noticeable phe nomenon was that the mixtures of the fuels and their char formed in situ de monstrated an unexpected high reaction rate of gasification under the studi ed conditions. The yield of char diminished and consequently the production of gas increased. Further, both the formations of tar and nitrogen compoun ds also seemed affected synergetically in the co-gasification experiments o f the fuels. The yields of tar and of ammonia were lower than expected. (C) 1999 Elsevier Science Ltd. All rights reserved.