Gas cleaning for IC engine applications from fixed bed biomass gasification

Abstract

Gas cleaning for tar and particle removal is necessary for internal combustion (IC) engine applications of producer gas from fixed bed biomass gasifiers which are usually in the capacity range from 100 kW up to 5000 kW. In the present investigation, tar and particle collection efficiencies have been determined in a sand bed filter, a wash tower, two different fabric filters, and a rotational particle separator (RPS) in different test runs with fixed bed gasifiers. Tar adsorption on coke has been investigated in a fixed bed batch reactor. Furthermore data from literature for catalytic tar crackers, venturi scrubbers, a rotational atomizer, and a wet electrostatic precipitator (ESP) are given. Based on the presented gas cleaning efficiencies and the investment cost, an assessment of gas cleaning systems is made for IC engine applications from cocurrent gasifiers. The results show that the postulated gas quality requirements for IC engines cannot be safely achieved with state-of-the-art gas cleaning techniques and that 90% particle removal is easier to achieve than 90% tar removal. Except for the catalytic tar crackers which are considered as an option for applications above several MW and for gases with a high tar level, none of the investigated gas cleaning systems can securely meet a tar reduction exceeding 90%. Therefore one of the key issues for a successful application of biomass derived producer gas from small scale gasifiers is the tar removal, where further development is needed.