Tar reduction mechanism via compression of producer gas

Tar is the main impurity derived from biomass gasification which causes environmental hazards as well as technical problems in advanced power generation applications. Removal of tar to acceptable tolerance limits for Internal Combustion (IC) engines and fuel cells is one of the major limitations and considered the main obstacle to the wide commercial power generation using biomass producer gas. If tar is not removed to the required levels, it will condense at low temperatures and result in clogging and fouling of engines. Even though physical tar removal at low temperatures has been performing effectively with the technical and economical point of view, there is still need to explore new and more efficient tar removal techniques. In this work, compression of producer gas in a compressor is introduced as a tar cleaning mechanism of biomass tar. Compressor was exposed to low tar levels in the range of 138–312 ± 31 mg Nm⁻³ after the cooling and pre-cleaning system. The results demonstrate the effectiveness of the compression process in reducing tar by 84.4± 1.2% and 83± 1.1% when compressed to 0.8 MPa_g and 0.2 MPa_g respectively at ambient temperature. The blue colour flare after the compression indicates the clean producer gas from tar and corresponds to the total tar levels around and below 30 mg Nm⁻³ with negligible particulates in the producer gas as compared to the orange flare before the compression. It was found that tar condenses inside the compressor receiver tank. A mechanism explaining the condensation of tar in the compression process is proposed.