Influence of process parameters on biomass gasification: A review of experimental studies in entrained flow reactors and droptube furnaces

Efficient management of renewable energy sources is crucial for sustainable economic development and reducing carbon footprint. The use of biomass agricultural residues through thermochemical conversion processes, such as gasification, offers a promising solution by producing eco-friendly fuels and chemicals. Biomass properties, type of gasifier and its operating conditions have important roles on the quality and characteristics of gasification products. Entrained flow gasifiers (EFR) and droptube furnaces (DTF) represent popular technologies that can operate at higher temperatures with various feedstock types. They are easy to scale up and commercially available. However, the released syngas may contain impurities like polycyclic aromatic hydrocarbons and soot, impacting the syngas cleaning system and equipment performance. Therefore, the understanding of biomass gasification at a laboratory scale is a preliminary step in evaluating its relevance for industrial applications, for which EFR and DTF can provide extremely useful information. The present manuscript reviews experimental works on biomass gasification in these types of reactors and discusses the effect of the operating conditions (temperature, gasifying agent, diameter, residence time and ash effect) in the current used approaches to identify the existent gaps, such as related to impurity release and handling. It was shown that the presence of ashes catalyzes the conversion of tars, inhibiting the formation of soot during biomass gasification. The retrieved information is anticipated to be useful for researchers, end users as well as energy planners.