Fluidized Bed Cogasification of Wood and Coal Adopting Primary Catalytic Method for Tar Abatement

The cogasification of coal and biomass represents a valid measure to overcome the limitation of the low energetic density of biomasses and problems arising from use of seasonally produced renewable fuels. The present paper reports on results of fluidized bed cogasification tests carried out with wood/coal pellets (70% wood and 30% coal by mass). With respect to the base case of an inert bed, the presence of catalyst in the bed had a beneficial effect on the concentration of stable gases (e.g., H2, CO2, CO, CH4, and light hydrocarbons) as well as on the efficiency of tar conversion. Upon gasification of wood/coal pellets, the total concentrations of combustible species (CO, H2, CH4, and C2H4) in the syngas always exceeds 45%. Compared to wood pellets, a more energetic syngas (4.5-5.1 MJ/Nm3) is produced with wood/coal pellets. The tar concentration is reduced to around 50% with sintered dolomite and Ni-alumina catalyst with respect to inert bed (quartzite). The gasification of wood/coal pellets gives rise to a substantially higher elutriation rate of fine particles with respect to wood pellets, as a consequence of the larger ash and fixed carbon content in the wood/coal pellets, as well as the lower char reactivity.