Numerical Simulation Of Gas-solid Flow Characteristics Of A New Chemical Looping Combustion Device

According to the analysis of observation data,the trend of global warming continues,controlling and reducing CO₂ emissions from power plants is an important starting point for reducing emissions in China.Some scholars have proposed a new type of carbon dioxide capture technology-Chemical Looping Combustion（CLC）technology.The research by many scholars has confirmed that this method has high combustion efficiency and good carbon dioxide capture effect.Aiming at the problems of direct Chemical Looping Combustion of coal,this paper proposes a new type of Chemical Looping Combustion device.The device is characterized by gasification of solid fuel and reduction of oxygen carriers in two-stages with one device.In order to understand the operating characteristics of this device in depth,this paper uses the CPFD calculation method to perform cold state numerical simulations on the air reactor（AR）and the fuel reactor（FR）.First,the pressure drop in the height direction of the AR reaction zone tends to be uniform as the wind speed increases,while the riser pressure drop increases as the wind speed increases.The AR reaction zone shows a typical distribution of particles that are higher and more sparse in the height direction.When stable,the bed layer shows a clear ring core structure in the radial direction.When the wind speed is high,the particle concentration at the center of the lower part starts to change from the upper concentration to the lower dilution.By comparing the particle velocity distribution on different height sections at different wind speeds,the particle velocity is moderate at a wind speed of 3.5m/s.At this time,the particle concentration distribution at different heights is more uniform,which is suitable for reaction and the side wall heat transfer.As the initial bed material of AR increases,both the material flow rate at the outlet and the pressure drop in the riser section can increase steadily,but the increase of the pressure drop in the AR reaction zone increases first and then decreases.By comparing the wear conditions of different AR exit structures,the wear degree is minimized when the right-angle flat-end elbow structure is selected.Increasing the wind speed and the amount of bed material will increase the degree of wear.In the experiment,the quality of a single particle,the operating time,and the design of the plan should also be considered.Through numerical simulation of FR,it is found that FR has good symmetry and stability during operation.During stable operation,the pressure change is mainly concentrated in the lower part of the chamber where the particle concentration is large,as well as in the return valve and the riser.The fluidized wind will accelerate through the air distribution plate as the dynamic fluidized particles.The air velocity at the inlet of the cyclone separator is large,which provides power for particle separation.The air velocity inside the inclined pipe is also large,and the flow direction is single,and no backflow occurs,which is beneficial to the separation and transportation of particles.The particle velocity in the chamber is low,which is consistent with the typical bubbling state,and the flow direction of the particles in the riser and the return valve is consistent,and the material transfer is smooth,and there is no air flow back.Through the study of the bottom air of the return valve,it is pointed out that the loose air should be kept small,and the return flow rate should be mainly controlled by adjusting the return air.When the FR fluidized wind increases,the pressure in the heating chamber increases.At this time,the loose wind should be reduced and the return air should be increased.When the feed flow rate changes,the principle to be followed is to ensure that the material in the riser should be moderate.It is preferred to use loose air to adjust the material in the riser,and finally adjust the return air to obtain a suitable return flow rate.