In-situ elimination of biomass gasification tar based on the understanding of tar formation process: A review

Biomass tar is the bottleneck of biomass gasification, which lowers the quality of syngas, corrodes downstream equipment, and causes serious environmental pollution. Tar can typically be removed by in-situ and ex-situ approaches. Previous studies paid lots of attention on ex-situ method because it is efficient and easy to control, while the in-situ method shows obvious advantages as sustainability, low cost and low construction complexity. Although the in-situ method shows obvious advantages compared to the ex-situ method, the current in-situ method exhibits relatively crude and undeveloped, which is due to the lack of scientific guidance based on the perspective of tar formation. A successful in-situ approach relies on the in-depth understanding on tar formation, which is a research gap in biomass gasification field. In this work, a multi-faceted and comprehensive review on tar formation during biomass gasification is presented, and the current and future development of insitu tar control is discussed. It is hoped this review paper can shed a light on the tar formation process, and become a milestone for the in-situ tar controls and sustainable development of gasification technology.