(17c) Steam Reforming of Tar with Co/mgo Catalyst in Biomass Gasification Process

Biomass gasification is a promising technology for producing a fuel gas which is useful for power generation systems. During biomass gasification process, tar formation often causes some problems such as pipeline plugging. Thus, proper tar treatment is necessary. So far, Ni-based catalysts have been intensively studied for the catalytic tar removal. However, the deactivation of Ni-based catalysts takes place because of coke deposition and sintering of Ni metal particles. To overcome these problems, we have developed Co/MgO solid solution state catalyst for tar removal. The performance of Co/MgO catalysts for steam reforming of tar derived from biomass gasification in a bubbling fluidized bed gasifier of 22 mm in i.d. and 500 mm in height was investigated. These experiments were carried out by two different methods: treatment inside the gasifier with catalyst as a fluidizing medium (primary method) and hot gas cleaning in a fixed bed reactor after the fluidized bed gasifier (secondary method). Using catalysts ( Co loading of 0-36 wt% ) in primary method, 12 wt% Co/MgO catalyst was found to exhibit the best performance ( carbon-base total tar conv. 16% ) at 873 K. The results of characterizations (TPR, TPO, XRD, CO adsorption, methane pulse chemisorption, BET surface area determination, etc.) showed surface area and adsorptive capacity of tar among Co metal, Co₃O₄ and CoO-MgO caused difference of performance among catalysts with different Co loadings. The reaction mechanism of steam reforming of tar with Co/MgO catalyst was elucidated by these results. The performance using catalysts in secondary method was also measured. Comparing the results of primary method with these of secondary method, we also propose an effective process of steam reforming of tar using Co/MgO catalyst.