An attempt to study conversion of biomass spheres in a stove using a DEM-CFD approach

摘要

The objective of this study is conversion analysis of biomass fuel in a bubbling fluidized bed with a DEM-CFD coupling model. This approach is based on classical Discrete Element Method (DEM) in which the conversion of solid fuel is also involved. In addition, the dynamics and conversion of solid particles are coupled to the gas phase via heat, mass, momentum and species transfer with employing OpenFOAM as Computational Fluid Dynamics (CFD) tool. This leads to encompass the interaction between solid and gas phases. That is, the chemical and physical processes of solid conversion pointing to heat-up, drying, pyrolysis, combustion and gasification caused by interaction with the reactive gas phase are considered with implementing homogeneous and heterogeneous reactions in both solid and gas phases. The test case is considered as a 3D cylindrical chamber including a packed bed of beechwood spherical particles with size of 6 mm. Two gas inlets as primary and secondary are involved with ambient pressure and temperature at the bottom and top of the bed where the superficial gas velocity of primary inlet is high enough to fluidize particles. The aim of fluidization is better mixing of the particles with the gas phase to increase the heat and mass transfer rate. The required energy for solid conversion comes from high wall temperature defined as 700°C. The predicted results are the consumption and formation of wood, char, tar and volatile matters of the bed during conversion process. At the end, it is shown the temperature distribution of solid-gas phases including the flame at 300s.