Study On The Selective Separation Of Oxygen Carrier And Coal Char During Coal-Fired Chemical Looping Combustion Process

Chemical looping combustion(CLC)has become an important CO₂ capture technology because of its role in separating and capturing CO₂ with low energy consumption,and has been widely concerned.When coal is used as fuel,the gasification rate of coal char is usually lower than the reduction rate of oxygen carrier,and the unconverted char is easily carried by the oxygen carrier into air reactor and then burn directly,which greatly affects CO₂ capture efficiency.In this paper,a set of coal-fired CLC cold test device coupled with a selective separation system of carbon particles and oxygen carriers was constructed.The separation system is composed of an inertial separator and a cyclone separator connected in series,which selectively separates coal char/oxygen carrier particles according to their density and particle size differences.The inertial separator separates the oxygen carrier into the air reactor for oxidation and regeneration,while the unburned coal char is separated by the cyclone separator and returned to the fuel reactor for re-reaction.The separation system plays a role in balancing the reaction rate and improving the efficiency of CO₂ capture.A cold test study was conducted on the gas-solid flow characteristics and separation characteristics of the whole field,and the separation process was studied using numerical simulation.Through the pressure monitoring system,the full-field pressure distribution of the cold state coal-fired CLC test device has been studied,and the fuel reactor fluidized number,solid circulation rate,solid inventory,and how the pressure ratio between the fuel reactor and air reactor affects pressure distribution on the two reactors were investigated.The test results showed that the device has a stable pressure difference in the whole field,and the total pressure drop along with the material circulation path was 0;the pressure gradient of the circulating fluidized bed riser along the height direction was large,under the condition of large fluidized number,solid circulation rate and operating material height,the pressure fluctuated greatly in the fuel reactor riser,and the gas-solid mixing was intense;increasing the fluidized number of loose air and the operating material height can significantly increased the solid circulation rate;the pressure drops of the downcomer and the two-stage counter-flow moving bed were relatively gentle,the particles in the air reactor showed a stable plunger flow state,and adjusting the pressure ratio between the two reactors and the fluidized number of air reactor within a certain range had little effect on the flow characteristics of the air reactor.The factors affecting the gas leakage between the reactors were studied through the gas tracing system,and it showed that the gas leakage ratio between the two reactors can be controlled within a relatively small range when P_b/P_a=1.7.As for selective separation of binary particles in a coal-fired CLC system,a selective separation test procedure and measurement method for light partile(plastic microbeads simulating coal char)and heavy particle(quartz sand simulating iron ore)were constructed on the cold state test device coupled with the separation system,and how different fuel reactor fluidized number,solid circulation rate,light particle size and concentration affect the separation efficiency of light and heavy particles were studied.The concentration of particle distribution in the separator was obtained through the pressure measurement point,and the gas-solid flow mode in the separator was initially explored.The test results show that the separation system has a better separation effect on heavy particles under different working conditions,and the separation efficiency of heavy particles is between 80-99%;for light particles,the overall separation efficiency is basically maintained above 80%,for most of light particles can be returned to the system for circulation after separation.When N_f=35.58,G_s=100.08kg/m²*s,d_a=100?m,and the mixing ratio is 5%,the selective separation efficiency of light particles?_sreaches about 60%.The CFD software is used to construct a three-dimensional numerical model of the carbon stripper in the CLC system.The Euler-Lagrange model and the discrete phase model were used to simulate the gas-solid flow state and particle separation characteristics using the operating parameters in the former test.The simulation results are verified with the test results,which proves the feasibility of the simulation.On this basis,the influence of operating parameters on the separation characteristics of light and heavy particles was investigated,and the test results were supplemented.