Numerical Analysis Of Gas-solid Flow And Chemical Looping Combustion Characteristics Based On New Drag Model

The burning of fossil fuels produces large amounts of carbon dioxide gas,which is one of the main causes of global warming.It is urgent to develop CO₂ capture and storage technology.Chemical Looping combustion is a new flameless combustion technology,which has the advantages of CO₂ internal separation and high efficiency,and has become a key strategy for CO₂ capture at present.In this paper,based on the two-fluid model,the drag force model and the chemical reaction kinetics model are coupled,and the numerical calculation of the chemical chain reactor with Fe base as oxygen carrier and CO as gas fuel is carried out.The factors affecting the gas-solid flow and reaction characteristics in the reactor are studied,and the corresponding conclusions are drawn.According to the characteristics of different drag models,an improved drag model is constructed in a fuel reactor.Compared with the traditional resistance model,the prediction results of this model are closer to the experimental values.Using this model,the effects of particle size and inlet gas velocity on the cold fluidization of fuel reactor were simulated.The results show that the particle size decreases and the inlet velocity increases leads to the increase of fluctuation of gas pressure drop distribution curve and the increase of gas pres sure difference.The particle and gas velocities increase,and the particle velocity vector vortices and gas channels appear in the bed.When the particle concentration decreases,the bed expansion rate increases.The effects of temperature,inlet gas velocity and gas fuel partial pressure on the chemical reaction of fuel reactor were simulated.The results show that the increase of temperature and gas fuel partial pressure has a positive effect on the conversion rate of gas fuel.With the increase of gas inlet velocity,the residence time of gas in the bed becomes shorter and the bubbles in the bed increase,which leads to the decrease of gas fuel conversion rate.However,when the gas velocity increases to a certain extent,the change of gas fuel conversion rate is small.In the simulation of air reactor,EMMS/1M drag model was used to simulate the effect of particle diameter and inlet gas velocity on the cold fluidization of air reactor.The results show that the gap interval of heterogeneity index i ncreases with the decrease of particle size and the increase of inlet gas velocity,and the heterogeneity index decreases.The bed gas pressure is evenly distributed.The concentration of axial particles in the bed decreases.In the high bed,the particle axial velocity increases and the gas phase velocity increases.The effects of temperature and inlet gas velocity on the chemical reaction of air reactor were simulated.The results show that the increase of temperature has little effect on the inhomogeneity index,promotes the forward chemical reaction and increases the oxygen conversion rate,but too high temperature will lead to the failure of oxygen carrier sintering.The increase of inlet gas velocity makes the particles evenly distributed in the whole bed,and the gas-solid mixing is thorough,which promotes the chemical reaction.However,if the inlet gas velocity is too high,a large number of particles will be carried out,and the residence time in the bed is reduced,which is not conducive to the occurrence of gas-solid chemical reaction.To sum up,the new drag model is used to calculate and analyze the gas-solid flow and chemical chain combustion characteristics,and the conclusions obtained can play a certain reference role for the design and optimization of chemical chain reactor.