Effect of catalytic bed material on biomass steam gasification in a staged fluidized bed

The reuse of spent catalysts as bed materials offers a practical route for improving biomass gasification while reducing material cost and waste disposal. In this study, the effects of bed material on biomass steam gasification were investigated in a lab-scale two-stage gasification system. White corundum (BM A) was used as an inert reference, while a spent commercial catalyst-derived material (BM B) and calcined olivine (BM C) were evaluated as catalytic bed materials under identical operating conditions. Among the three bed materials, BM B showed the best overall performance. Relative to the case using BM A, by using BM B resulted in the increase in the H 2 yield from 23.1 to 36.4 mol/kg-biomass daf, while decreasing the CH 4 concentration from 15.0 to 7.3 vol% and reducing the tar content from 640 to 380 mg/Nm 3 , corresponding to a tar reduction of about 41%. By comparison, BM C showed only limited improvement, giving a H 2 yield of 22.6 mol/kg-biomass daf, a CH 4 concentration of 13.5 vol%, and a tar content of 579 mg/Nm 3 . GC–MS analysis showed that BM B suppressed condensable aromatic tar species more effectively than BM A and BM C. XRF and XRD analyses revealed differences in composition and phase structure between BM B and BM C, and the superior performance of BM B was consistent with the presence of catalytically active Ni-containing components inherited from the spent methane-reforming catalyst. These results demonstrate that spent commercial catalysts can be effectively reused as low-cost bed materials for enhancing hydrogen-rich gas production and suppressing tar formation in biomass steam gasification.