SIMULATION OF BIOMASS GASIFICATION USING INTRINSIC REACTION RATE SUBMODEL

As the rate controlling step during the whole biomass gasification, the char-gas heterogeneous reaction is of great significance, thus the intrinsic kinetic data can provide valuable insights into the understanding and evaluation of biomass gasification, as they are transportable for different reaction conditions. This chapter introduces the numerical simulation of biomass gasification using the intrinsic reaction rate submodel. The intrinsic rate of char heterogeneous reaction, actual chemical reaction rate occurs at the surface of the solid char particles, can be measured in certain experimental conditions where heat and mass transfer limitation are negelectable (under chemically controlled regime), and the kinetic model for char-gas reaction as well as the intrinsic kinetic data for various biomass materials are detailed. A CFD (computational fluid dynamic) model based on the intrinsic kinetics is developed for biomass entrained flow gasification, where the intrinsic reaction rate submodel takes both chemical reaction rate and physical diffusion rate into account for calculating the char-gas reaction rate. In order to understand the gasification mechanisms, the effects of operating conditions including gasification temperature, equivalence ratio, CO2/biomass mass ratio and average particle size on the gasification performances in a lab-scale entrained flow reactor are investigated through numerical simulation. The multi-objective optimization of biomass gasification based on response surface method is studied to improve the gasification performances. Main conclusions and future outlook are also briefly summarized. We firmly believe that the contents presented in this chapter demonstrate a CFD model based on intrinsic kinetics and they could be a useful way to solve the biomass gasification problems.