Use of Biomass Hydrothermal Conversion Char as the Ni Catalyst Support in Benzene and Gasification Tar Removal

摘要

One of the major issues in biomass gasification is removal of tars from syngas. Catalytic reforming of tars is considered the most promising in large-scale applications because of its fast reaction rate and reliability. In this study, a new Ni/char catalyst was prepared and used for woodchip gasification tar removal and reforming in a downdraft gasifier. Benzene was used as the model tar to optimize catalytic reaction conditions. Three parameters were investigated: reaction temperature (700°C to 900°C), gas residence time (0.1 to 1.2 s), and catalyst loadings (5% to 20% weight of char support). On the basis of the benzene test, a reaction temperature of 800°C, catalyst loading of 15 wt%, and residence time of 0.3 s were chosen as optimum reaction conditions. Testing these parameters in a downdraft biomass gasifier showed that the Ni/char catalyst removed more than 99% of tars and significantly increased the concentrations of combustible compounds in the syngas. From their initial levels before the catalytic reforming to their final levels after the catalytic reforming, H ₂ and CO in the syngas increased from 20.43% to 51.90% and from 14.20% to 18.36%, respectively. Performance of the new catalyst in terms of tar removal rate and syngas reforming was similar to that of Ni/ ? -Al ₂ O ₃ catalysts