Characteristics of low temperature biomass gasification and syngas release behavior using hot slag

Abstract

This study proposes an emerging method to prepare syngas using integrated low temperature biomass gasification combined with heat recovery from hot slag. A series of non-isothermal and isothermal gasification experiments were performed in the temperature range of 250–500 °C to determine the effect of the presence of slag on gasification. The results showed that the addition of slag remarkably increased the production of syngas in the temperature range of 425–500 °C and during the gasification at 450 °C, with a mass ratio of wheat straw to slag of 1 : 1, syngas with 0.149 L CO, 0.036 L H₂ and 0.069 L CH₄ can be produced per gram of wheat straw. The kinetic mechanism of biomass gasification changed from an Avrami–Erofeev model to a three-dimensional diffusion model with the addition of slag. Although the presence of slag altered the mechanism of gasification, it did not lower the degree of gasification, and therefore the waste heat from the hot slag can be used to produce syngas. Therefore, an industrial prototype plant composed of multiple systems was proposed, through which an energy saving equivalent to 19.1 million tons of standard coal and an emission reduction of 69.9 million tons of CO₂ emission would be achieved in China.