A review of cleaning technologies for biomass-derived syngas

Biomass gasification is a promising thermochemical conversion technology with substantial potential for sustainable global energy development. It can replace various fuels and chemicals derived from fossil fuels, producing a gas composed of CO, H2, and CH4 as targeted compounds and CO2, H2O, and N2 as adulterating compounds. However, the gas also contains impurities like tars, particulate matter, nitrogen and sulfur compounds, hydrogen halides, and trace metals, posing challenges for its use. Efficient gas purification is essential before application in internal combustion engines, gas turbines, or chemical processes. This paper provides a comprehensive survey of gas purification technologies arising from biomass gasification. Two main categories are explored: wet purification systems, notably using wet scrubbers, and dry purification systems, which are more appealing due to avoiding gas cooling and associated energy losses. Traditional particulate removal devices and modern catalysts for tar, acid gases, and trace metal elimination are examined in the dry purification category. Furthermore, this work describes alternative gasification concepts such as integrated gasification, supercritical-water gasification, and, chemical loop gasification, also addressing carbon capture technologies for syngas conversion. Finally, advances in syngas cleaning methods are revised and commercially available purification systems are presented and discussed, offering insights into current outcomes in this field.