Two-stage Gasification of Untreated and Torrefied Wood

Abstract

The major methods of biomass thermal conversion are combustion in excess oxygen, gasification in reduced oxygen, and pyrolysis in the absence of oxygen. The end products of these methods are heat, gas, liquid and solid fuels. From the point of view of energy production, none of these methods can be considered optimal. Two-stage gasification of biomass proposed by JIHT RAS is pyrolysis of biomass, as the first stage, and cracking of the pyrolysis products as the second stage. This method can be considered optimal for energy production, because it allows obtaining synthesis gas consisting of hydrogen and carbon monoxide and not containing liquid or solid particles. Since no byproducts are formed, there is no need for complicated cleaning methods of the gas. In this study we investigated the effectiveness of heterogeneous cracking of pyrolysis products on the surface of charcoal in comparison with the homogeneous cracking. The effect of preliminary torrefaction of biomass on secondary cracking process and composition of the resulting synthesis gas was investigated. It is shown that the use of torrefied biomass allows obtaining a high-calorific gas even by homogeneous cracking of pyrolysis products.