Effect of torrefaction on the high temperature steam gasification of cellulose based upon the Gibbs free energy minimization

The steam gasification can convert biomass into syngas, which can be conveniently used as fuels or chemical raw materials. Cellulose, as an important component of biomass, has a significant effect on the gasification behavior. Steam gasification behaviors of raw and torrefied cellulose at high temperature were investigated using a non-stoichiometric equilibrium model. The effect of torrefaction severity on the high temperature steam gasification of cellulose was evaluated. With increasing of steam/cellulose molar ratio, the molar numbers of hydrogen and carbon dioxide increased, whereas the molar number of carbon monoxide decreased. Less than 1.0 molar ratio of steam/cellulose was recommended for raw and torrefied celluloses. The methane steam reaction for severely torrefied cellulose at low steam/cellulose molar ratio was found. The molar number of the hydrogen increased from 1.992 to 2.016 mol with the increasing of torrefaction temperature from 250 to 300 °C. The influence of steam content on the water-gas reaction was more obvious than that of reaction temperature. This study will promote the development of steam gasification of biomass for the purpose of high efficiency utilization.