Model development for biomass gasification in an entrained flow gasifier using intrinsic reaction rate submodel

Intrinsic reaction rate submodel is established in this study to consider the effects of diffusion rate and kinetic rate for simulating the char reactions due to their slow reaction rates and important controlling steps. The biomass gasification model for an entrained flow gasifier is developed with the Euler-Lagrange method using ANSYS FLUENT software. Gas phase is treated as continuous phase in standard k-ε model to close governing equations whereas biomass particles are treated as discrete phase in discrete phase model (DPM) to track the movement of particles. For homogeneous phase reactions, finite rate/eddy dissipation model is applied to calculate the reaction rates. For heterogeneous phase reactions, intrinsic reaction rate model is realized by coding the user-defined functions (UDFs) to calculate char reaction rates. The results obtained from this study show that the relative errors of volumetric concentrations are mainly within the range of 1-18% and the relative errors of lower heating value, gas production, cold gas efficiency and carbon conversion efficiency are within the ranges of 1-13%, 1-8%, 1-12% and 1-11%, respectively. The CFD model developed in this study can be used to simulate biomass gasification processes for entrained flow gasifiers.