Carbon Dioxide Reforming of Tar During Biomass Gasification

Abstract

The energy demand increase and the necessity to contain CO2 emissions lead to a growing interest on renewable and CO2 free energy sources. Gasification has been identified as a key technology to enhancethe environmental tolerability of low quality fuels such as biomass. The principal problem related with the use of biomass in gasification processes is the high quantity of tar released during the pyrolysis step of this fuel. Tar can account up to 50% of the total volatiles and contains a great part of the biomass energy. For this reason it is necessary to recover the tar and to transform it in combustible lighter gas species such as methane, carbon monoxide and hydrogen by means of catalytic processes. Another important issue is to lower the carbon dioxide content of the produced gas in order to increase its calorific value. The dry reforming represents an interesting solution. In this work the dry reforming of tar in a two stages bench scale reactor is proposed. In the proposed dry reforming process the tar reacts with the carbon dioxide released during the biomass pyrolysis to form carbon monoxide and hydrogen. It is thus possible to recover the tar energy converting it into CO and H2 and to lower the syngas dilution using the CO2 as a reagent. The dry reforming is a catalytic process and one of the major issues is the deactivation of the catalysts due to carbon deposition. The solution of this problem is very important in the case of tar dry reforming because of its high C/H ratio, which intensifies this phenomenon. Nickel has been extensively studied for the dry reforming but it is known that it suffers from carbon deposition. In this work Ce-promoted bimetallic Ni-Co catalysts with two different supports were tested.