Microwave plasma gasification of oil palm biochar

Abstract

Conventional pressurized gasification operates at higher pressure than atmospheric pressure and requires heat up time during startup. In this study, microwave plasma gasification was used to compensate this problem. The objectives of this paper is to investigate the CO2 microwave gasification of EFB and OPS biochar, and optimizing the char reaction rate through the addition of activated carbon as the microwave absorber. A microwave plasma gasification test rig was designed to produce syngas from oil palm biochar. From the study, it was found that EFB char performed better than OPS char as gasification fuel due to its high porosity and surface area that increased the char reactivity towards CO2. The temperature increment promoted by the addition of MW absorber using activated carbon (AC) has increased the CO composition. The optimum condition for microwave plasma char gasification of EFB was 3 lpm with 25 wt% AC that produced syngas with 1.23 vol% CH4, 20.88 vol% CO2, 43.83 vol% CO, 34.06 vol% H2 and 9.40 MJ/kg gas CV. For OPS is at 2 lpm with 1.12 vol% CH4, 35.11 vol% CO2, 35.42 vol% CO, 28.35 vol% H2 and 7.32 MJ/kg gas CV. As EFB char has larger BET surface areas and larger pores than OPS char, the ability to react with the gasifying gas is better than the OPS. Thus, resulting in higher carbon conversion. The best gasification efficiency was 72.34% at 3 lpm, 10% AC for EFB biochar plasma gasification with 12% unreacted carbon. For OPS biochar plasma gasification, the best gasification efficiency was 69.09% at 2 lpm, 10% AC with 18% unreacted carbon.