(85b) Development of a Novel Nickel-Ceramic Filter for Hot Gas Removal of Tars and Particulates from Biomass Syngas

Gasification, the high temperature partial oxidation of carbonaceous fuels to produce syngas, is a promising route for converting biomass to energy. Syngas has many applicable uses including generation of electricity, production of specialty chemicals and fuels, and further separation for hydrogen production. Downstream syngas applications require contaminants to be below certain levels in order for the process to be effective. While particulates, responsible for equipment damage, can be separated through high temperature filtration, tar formation is the most cost-inducing problem whereby their condensation clogs downstream equipment presenting a major hurdle limiting biomass gasification commercialization. Catalytic tar reforming is a cost-effective strategy for tar abatement whereby conversion of tars into syngas improves the overall efficiency of the gasification process. By using a ceramic filter as a catalyst support, process intensification is achieved through reforming tars and filtering particulates in one unit. Nickel was chosen as a catalyst for its low cost and effectiveness towards tar reforming. The surface area of the ceramic filter (113 m²/g) makes it an ideal support for catalyst material and its high porosity (85%) leads to a low pressure drop with minimal internal mass transfer limitations. Steam reforming evaluation tests using naphthalene as a tar simulant were performed with nickel loadings of 2-40 wt% at 750°C, steam/carbon = 5, 0.05 s residence time, and inlet naphthalene concentration of 9 g/m³ to mimic typical fluidized bed gasifier outlet conditions. Peak naphthalene conversions of 80% were observed with a nickel loading of 15 wt% over 2 hours with no increase in pressure drop. PIXE analysis showed uneven dispersion of nickel on the filter using incipient wetness impregnation leading to investigations with vacuum urea impregnation method. This improved the surface area and achieved 81% naphthalene conversion with an activation energy of 123.3 kJ/mol, comparable with studied tar removal catalysts.