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 in-situ 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.