Numerical Simulation Of Fluidized Bed Biomass Gasification Based On CPFD Method

Excessive consumption of fossil energy has made the ecological environment worsening and energy crisis increasingly prominent.Finding renewable energy to replace fossil energy has become a hot issue in the energy field.Biomass is a widely distributed,renewable and renewable green energy source.The application of biomass to fluidized bed gasification energy produces high calorific value synthesis gas that can be used in industrial production or combustion power generation.This technology is an efficient Thermal conversion technology.Due to the limitation of experimental scale and the complexity of experimental conditions,the numerical calculation method based on Computational Particle Fluid Dynamics（CPFD）is widely used in the research of fluidized bed biomass gasification.Predicting the distribution of gas,particles,and temperature in time and space in the reactor is conducive to exploring the gasification reaction mechanism and finding the best operating conditions.It can also optimize the design of the gasification furnace and conduct industrial scale-up research.In this paper,first,a numerical model of biomass gasification in a fluidized bed is established based on the CPFD.Discrete particles are described by the MP-PIC,and the gas phase is described by large eddy simulation.The biomass pyrolysis devolatilization,combustion reaction and gasification reaction are considered.Comparing the simulation results with the experimental data in the literature,the results show that the simulation data and the experimental data have good consistency,thus verifying the accuracy and reliability of the numerical model.Secondly,the particle distribution,temperature distribution and gas composition distribution in the bubbling fluidized bed gasification reactor were explored,and the distribution rule was revealed.At the same time,the effects of biomass properties and fluidized bed operating conditions on biomass gasification characteristics were studied.The results show that:in terms of biomass properties,the sawdust has the best gasification effect among the four biomasses,and the biomass particle size is The maximum combustible gas content is 0.6mm,and the high water content is not conducive to the biomass gasification reaction;for the fluidized bed operating conditions,the increase of the air equivalent ratio will reduce the combustible gas content,and the increase of the gasification temperature will help the gasification reaction,The initial bed height will change the value of the furnace outlet H₂/CO.Finally,the numerical model of the fluidized bed biomass gasification was expanded to an industrial-scale circulating fluidized bed gasifier,and a three-dimensional numerical simulation study of industrial-grade circulating fluidized bed biomass gasification was conducted to predict different sizes.The gas-solid flow morphology,temperature distribution and gas product distribution in the fluidized bed explored the influence of the air equivalent ratio,biomass type,and gasifier structure on the gasification characteristics,and revealed the effects of the fluidized bed gasifier.The gas-solid flow characteristics and gasification reaction characteristics provide a theoretical basis for optimizing the structure of industrial fluidized bed and finding the best operating conditions.The results show that the gasification effect is the best when the air equivalent ratio is 0.25,the heat value of the syngas using sawdust gasification is the highest,and the gasification effect of the abrupt diameter furnace structure is the best.