Comprehensive DEM-CFD model and thermal uniformity optimization for biomass catalytic pyrolysis reactor

Abstract

Dense particulate beds are commonly used in energy conversion and chemical synthesis processes, while their efficiency is limited by the complex particle flow mechanism and thermal heterogeneity. Herein, we proposed a coupled DEM-CFD model (Discrete Element Method and Computational Fluid Dynamics) to investigate the thermal conversion and pyrolysis behavior for biomass catalytic pyrolysis in both fixed bed and mechanically fluidized reactors (MFR). The key factors restricting the pyrolysis process of MFR with double-helical ribbons were investigated. The effects of rotation speed on heating rate and product yield were analyzed to elucidate the evolution of heating rate uniformity. Moreover, the biochar residuals produced by the pyrolysis were used as the internal heat source and catalysts. The results indicated that the average heating rate was enhanced with the increase of the rotational speed, while a more uneven distribution of particle heating rate was presented during the rapid pyrolysis stage. In addition, a 45 rpm rotation speed and half amount of biochar residuals in the reactor can greatly improve the thermal homogeneity as well as the system economics.