Development of an industrial catalytic filter for tar reforming

Abstract

The wide spectrum of end-use applications makes gasification a process with greatpotential to exploit biomass as a renewable and sustainable energy source. Biomassgasification is in direct competition to conventional energy technologies, which makesconstant development and optimization of the technology inevitable in order to competeagainst the huge volume of oil and coal industries. The formation of heavy hydrocarbonsduring the gasification states a big problem of the process. Complex cleaning systemsto remove impurities from the product gas are required to fulfill criteria for followingprocess steps. In this study, a concept for a hot-gas filtration with an integrated catalyticstructure is elaborated. Merging two operations, namely filtration and catalytic reforming, enables an efficient use of process temperatures and leads to an overall increaseof the process efficiency. Two methods are developed to deposit a nickel based catalystonto a commercial low density filter. A Ni/MgAl2O4 catalyst is prepared via a sol-gelroute. One approach to generate a catalytic filter is by direct treatment of the filter bodywith the prepared sol-gel and calcination of the filter candle. A catalytic slurry is usedfor coating of the filter candle in a second method. Results show improved propertiesfor the catalytic filter that is prepared by the sol-gel method, as contact time betweenthe catalytic sites and the gaseous compounds is improved due to the distribution ofthe catalytic material over the whole cross-section of the filter. Light hydrocarbonsand methane are broken down up to 50 % during the experimental tests. Naphtaleneis converted up to 80 % at temperatures in the range of 750-800 °C. The efficiency forthe conversion of hydrocarbons is largely influenced by the temperature inside thefiltration-unit. Additives to the filter bodies for an improved mechanical stability haveno significant effect on the catalytic activity, but are critical when running tests with areal product gas, due to the formation of a filter cake. The concept of a catalytic hot-gasfiltration shows positive aspects, additional tests at temperatures exceeding 800 °C arerequired to determine the performance of the catalyst and gain further informationabout the improvement of the overall process efficiency.