Assessment of char property on tar catalytic reforming in a fluidized bed reactor for adopting a two-stage gasification process

To well understand the effect of char property on tar catalytic reforming and support the development of two stage gasification technology for the clean fuel gas production, the roles of pore structure and metal oxide in tar removal behavior were examined and compared on a fluidized bed two-stage reactor. The results show that although both of micro pore and meso pore had a remarkable influence on tar removal efficiency, fuel gas component and distilling fractions in tar, perhaps micro pore played a much more important role. Moreover, the tar removal efficiency did not have a good proportional relationship with the specific surface area of char. For the spent char, the activation treatment in steam was very beneficial to renew the catalytic reforming on tar by increasing the surface area of micro pore and maintain its high gasification activity. Compared to the demineralized char, the char samples that loaded metal oxide by impregnation approach largely promoted the tar removal efficiency, following the rank of Na2O > Fe2O3 > CaO > MgO. For Na2O, it not only had the best catalytic activity on tar, but also greatly promoted the generations of light tar and effective fuel gas, such as H-2 and CO. Finally, considering the different effect of pore structure and metal oxide on tar catalytic reforming, a brief mechanism of tar catalytic reforming by char was proposed.