Lab-scale and pilot-scale two-stage gasification of biomass using active carbon for production of hydrogen-rich and low-tar producer gas

Laboratory- and pilot-scale two-stage air gasification of various types of biomass was performed to produce hydrogen-rich and low-tar gas. Typical tar removal apparatuses, such as scrubbers and electrostatic precipitators, were not employed and the only tar removal agent used was coal-based active carbon. The hydrogen content of all producer gases was remarkably high, whereas the tar content was low (maximum H2: 29 vol%; minimum tar: 0 mg/Nm3). The producer gases from the pilot-scale experiment also exhibited an exceedingly high hydrogen content and low tar content (maximum H2: 27 vol%; minimum tar: 3.3 mg/Nm3). The pilot-scale operation continued without any external heat supply via autothermal operation. A gas engine was connected to the pilot-scale gasification plant to generate electricity. The generated power ranged from 20 to 35 kWe depending on the type of biomass used. This indicated that the two-stage gasification process could be applied to decentralized power generation. To summarize, the present study provided positive experimental results of the two-stage gasification process in terms of tar reduction, hydrogen production, and power generation. Furthermore, studies on long-term operation are needed to obtain more reliable results. •Lab-scale and pilot-scale two-stage gasification was successfully conducted.•Producer gases from various types of biomass were almost free of tar.•Maximum H2 content from air biomass gasification went up to 29 vol%.•Pilot scale gasification produced a gas having 27 vol% H2 and 3.3 mg/Nm3 tar.•The maximum power production from biomass was 20–35 kW.