Study on the importance of bed shape in combined DEM-CFD simulation of fixed-bed Biomass gasifiers

Abstract

The extensive utilization of fossil fuels is limited by the environmental problems related to carbon dioxide and other greenhouse gas emissions. As a result, the generation of energy and heat from biomass has become increasingly economically and ecologically important in recent decades. In existing numerical studies, the effect of slope form on airflow within the biomass gasifier was not systematically investigated. To explore the potential impact of the real shape of a fuel bed on local gasification conditions, a small-scale updraft fixed-bed gasifier was modeled in this study with a default lateral feeding position and air supply from below. The discrete element method (DEM) was combined with computational fluid dynamics (CFD) by using two open-source software: LIGGGHTS® and OpenFOAM®. The particle models of two biomasses (olive stone and almond shells) were calibrated and used to investigate qualitatively and quantitatively the airflow patterns, including the resulting uneven pressure and temperature distribution at/over the slope surface. Besides, the effects of operating parameters of the feeding system on slope form were highlighted. Therefore, the real fuel heap shape should be taken into consideration for future simulation studies on side-fed, fixed bed gasifiers. • Material models for DEM simulation are calibrated and validated. • The influences of heap shape and inlet air velocity are explored comprehensively. • Quantitative discussion on the rates of temperature and pressure change. • Suggests that different screw feeding speeds can realize dynamic combustion optimization. • Limitations of a particular DEM-CFD co-simulation model are addressed.