Numerical Simulation Study On Flow-Reaction Coupling Process Of Fule/bed Multi Particle Component In Fluidized Bed

With the progress of industrialization and population growth,air pollution is also getting worse.Therefore,under the premise of ensuring economic development and industrialization continue to be promoted,it is also necessary to ensure that the damage to the environment is minimized.Recent years,the state has started to introduce relevant policies to control the pollution discharge from enterprises.Fluidized bed combustion and gasification technique have gained more and more attention recently due to their good fuel suitability,sulfide capture capability,and low NOx emissions.In this paper,numerical simulation method is used to study the fluidized bed gasification process.The traditional Euler-Euler method is used to analyze the the gasification process in bubbling fluidized bed and co-gasification process in internal circulating fluidized bed.Finally,a modern CFD-DEM method is used to simulate single-particle biomass gasification and particle swarm flow gasification reaction process.(1)Based on Euler-Euler model,a flow model,a heat transfer model and a chemical reaction model in a bubbling fluidized bed reactor are established,including biomass pyrolysis reaction,gas phase homogeneous reaction and gassolid heterogeneous reaction.The biomass gasification process in bubbling fluidized bed was simulated.The bed material motion characteristics,velocity vector distribution and gas composition distribution characteristics of bubbling fluidized bed are studied in detail.Finally,by changing the oxygen equivalent ratio,the function of the gasification product as a function of oxygen equivalent ratio is fitted.(2)Based on the Euler-Euler method,a gas-solid multiphase flow reaction model was established based on Kinetic Theory of Granular Mixture.The biomass/coal co-gasification process was simulated in an internal circulating fluidized bed.The flow characteristics and reaction characteristics are analyzed and the pulsation distribution characteristics of different particle components in the inner circulating fluidized bed and the influence of fluctuation on the chemical reaction are analyzed from the perspective of Kinetic Theory of Granular Flow.(3)Using the CFD-DEM method,the classic problem of droplet evaporation is taken as the verification object to simulate the evaporation process of droplets in open space with wet air.The statistics of different relative air humidity are taken and the droplets in different working conditions are extracted.The steadystate temperature is compared with the theoretical value to verify the reliability of the model.(4)The pyrolysis process of biomass single particle was studied mechanistically.The reaction model was based on the shrinking core model.The influence of the particle size of biomass on the reaction process was considered,which made up for the shortcomings of the Euler-Euler method in the reaction field.(5)The gasification process of biomass in a bubbling fluidized bed is completely simulated,taking into account the particle flow,collision,rotation,heat and mass transfer and chemical reaction process.The flow,heat transfer and chemical reaction coupling process of particles in the gasification reactor were simulated from the particle size scale.The mixing characteristics of the bed material and fuel particles and the distribution of gasification products were obtained.