Effect of porous silica on the removal of tar components generated from waste biomass during catalytic reforming

Thermal gasification of waste biomass requires a method of tar removal from gasified gases, since the tar produced is at risk of obstruction of the piping of the gasification processes and failure of the subsequent power generation processes. Using laboratory-scale fluidized bed gasifier and catalytic reformers, the characteristics of tar removal was investigated. A commercial Ni-based catalyst and several kinds of porous silica with different surface areas were applied to the reforming reaction. Moreover, the feasibility of regeneration by air oxidation of both the catalyst and the porous silica was evaluated. In gasification and reforming experiments using woody waste, application of porous silica led to lower levels of highly polymerized polycyclic aromatic hydrocarbons (PAHs). The greater the specific surface area of the porous silica, the lower the concentration of PAHs. Carbon deposited on the surface of the porous silica and the mass of the carbon deposit reached a maximum at a surface area of 195 m²/g. When both the catalyst and the porous silica regeneration by air oxidation was performed, hydrogen concentration was found to level off from the third reforming operation and the amount of total tar did not increase after the second reforming operation. Our results showed that the catalyst and the porous silica is likely to have good reforming activity even repeatedly regeneration condition.