Pyrolysis of Torrefied Biomass

Pyrolysis, one of the most promising thermal conversion technologies for biomass conversion, can decompose biomass into solid bio-char, liquid bio-oil, and combustible gas to meet different energy needs. However, pyrolysis efficiency and product quality are not as good as expected when raw biomass is used owing to the properties of raw biomass (e.g., high moisture, oxygen, and alkali metal contents). Torrefaction is an emerging biomass pretreatment technology that can improve the physical and chemical properties of raw biomass, and pyrolysis efficiency and final product quality can therefore be improved by using torrefied biomass. We review several advantages of pyrolysis of torrefied biomass in terms of the conversion process and final product quality. The torrefaction process changes the pyrolysis characteristics of biomass, including the reaction process, kinetic parameters, and product distribution and properties. Torrefaction affects the ratio and chemical composition of pyrolysis products, improves the product quality and conversion process, and increases conversion efficiency during the pyrolysis process. Most torrefied biomass pyrolysis research has been conducted in laboratory-scale fixed beds at a relatively low temperature, and continuous reactors still need to be investigated and pilot-scale studies need to be performed. Catalytic pyrolysis of torrefied biomass is a promising technology to convert biomass into useful chemicals.