Optimization of the Three-stage Biomass Gasification Characteristics in High-temperature Entrained-flow Bed

Abstract

The raw material requirements for the indirect liquefaction of biomass are strict. In particular, the ratio of H2/CO must be greater than or equal to 1. However, traditional biomass gasification has problems that include a low H2/CO ratio and low carbon conversion rates. This study proposes a three-stage gasification optimization model in which pyrolysis products are separated before being put through a second gasification step. The optimized model simulation used MATLAB software and the experiments were carried out in a biomass, high-temperature entrained-flow bed. The results demonstrate that, compared to traditional mixing gasification, three-stage gasification can effectively increase the H2 content in syngas. The H2 content can reach 42.3%, which is 4.6% higher than in traditional gasification. Additionally, this process can increase the H2/CO ratio to 1.23, which is 43% higher than the ratio 0.86 in traditional gasification. This also could provide raw materials for the indirect liquefaction of syngas. Thus, three-stage gasification can eliminate the need for intermediate steps such as steam reforming and adding external H2. Experiments indicated that the best gasification conditions were a first gasification time of 0.6s and a gasification temperature of 1100 °C, under which the H2/CO ratio reached a maximum of 1.2.