Numerical simulations on the effect of potassium on the biomass fast pyrolysis in fluidized bed reactor

Abstract

In this study, the effect of potassium on the cellulose fast pyrolysis in a fluidized bed reactor has been studied using Computational Fluid Dynamics (CFD). A multiphase pyrolysis model of cellulose has been implemented by integrating the hydrodynamics of the fluidized bed with an adjusted cellulose pyrolysis mechanism that accounts for the effect of potassium. The model has been validated with the reported experimental data. The simulation results show that potassium concentration and reactor temperature have a significant effect on the yield and component of cellulose pyrolysis products. The product yields fluctuate is caused by the unstable flow in the fluidized bed. The result shows that the increased potassium concentration in the cellulose causes a significant increase of the gas and char yields and reduction in the bio-oil. Also, the dramatic composition variations in bio-oil and gas were observed due to the inhibition of fragmentation, and the depolymerization reaction of activated cellulose, and the catalysis of the depolymerization reaction of cellulose. It is also found that the increase in reactor temperature greatly enhances the endothermic pyrolysis reaction, which leads to the significant changes in the yield and composition of cellulose pyrolysis products.