(30b) Numerical Simulation of Downdraft Biomass Gasifier: Influence of Structure Designs Using CFD Simulation

Gasification is becoming a more and more popular process for biomass thermal conversion because of less toxic gas and more valuable gas production. However, conducting experiment usually costs a lot of time and resources. Thus numerical study approaches such as CFD (Computational Fluid Dynamics) provide efficient alternative ways for structure design to reach optimal operations.

In this work, three-dimensional CFD models were proposed to simulate flow fields, temperature profiles and gas composition distributions of downdraft biomass gasifiers. At first, one validation model was proposed according to experimental works to compare gas compositions and temperature distributions with real data. It was found that the simulated results were comparable with experimental results. After validation, gasifier structures were modified for optimal reactor designs. Parameters such as air injection positions, air injection angles were studied for better mixing of air with pyrolysed products. Changes in temperature profiles were also studied for fully utilization of the gasifier with high converting efficiency. Also, the influence of reduction-cone shapes was also studied for high quality gas production and temperature distribution. The objective of this study is to use numerical methods to provide guidance for real gasifier design and optimization.