Numerical investigation of gas thermal property in the gasification process of a spouted bed gasifier

Abstract Steam-biomass gasification in a three-dimensional lab-scale spouted bed gasifier is numerically simulated via the multiphase particle-in-cell approach. The spatial distribution of gas thermal properties (i.e., temperature, conductivity, specific heat capacity, density, and viscosity) together with the impact of operating parameters are comprehensively studied. The results show that distinct flow hydrodynamics in the three regions of the spouted bed gasifier lead to different spatial distributions of gas thermal properties. The gas thermal properties show significant transitions in the spout-annulus and fountain-annulus interfaces. Elevating the bed height decreases the gas temperature, density, and viscosity but increases the gas thermal conductivity and specific heat capacity. Among all operating parameters, the bed temperature exerts the most significant influence on the spatial distribution of gas thermal properties. Due to the existence of dead zone in the annulus region of the bed, bed height, biomass diameter, and steam to biomass ratio exert negligible influences on the gas thermal properties in the dense annulus region but noticeable impacts in the dilute fountain region. Based on the relationship between solid transportation and gas thermal property variations, the current work also provides a guideline for the optimization of spouted bed gasifiers, for example, the dead zone is recommended to be optimized by adjusting the inclination angle of the conical part to enhance the solid internal circulation and gasification performance.