Simulation For CO₂ Capture By Using Membrane Gas Sepration From Flue Gas In Power Plant

Coal-fired power plant flue gas is a long-term stable concentration of carbon dioxide sources,the amount of carbon dioxide emissions account for nearly one-third of total emissions.In this paper,the process system of flue gas carbon dioxide membrane separation is designed around the flue gas characteristics of coal-fired power plant.The process flow is simulated by Aspen HYSYS and MATLAB software,and the operation parameters of the process are simulated and optimized.Based on the composition and characteristics of flue gas in coal-fired power plants,the factors affecting the performance and service life of membrane materials are studied.The properties,advantages and disadvantages of various membrane materials are summarized,and the membrane material,6FDA-TAPA polyimide film is selected.The structure of the membrane module is analyzed,and the hollow fiber membrane module is selected as the core device of the separation process.The internal flow mode of the membrane module adopts the counter-flow flow pattern.The pretreatment system of flue gas CO₂ membrane separation process is designed.The parameters of the process system are calculated by Aspen HYSYS software,the effects of various operating parameters on the dewatering effect are studied,the operation parameters of the dehydration process are optimized.The optimization results show that the working pressure of the absorption tower is 4MPa,the flue gas temperature of the absorption tower is 40℃,the amount of triethylene glycol is 0.3m3/h,and the regenerator tower reboiler temperature is set to 200℃.The flow rate of the flue gas is 50017Nm3/h,the water content is 0.09% and thetemperature is 38.75℃.The mass transfer model of hollow fiber membrane is established,and the three-stage membrane separation system is designed for the flue gas decarboni zation of coal-fired power plant.The simulation experiment of three-stage membrane system is established by MATLAB software.The operating parameters of the membrane separation process are analyzed,and the optimal design of the three-stage membrane system is completed.The final membrane area is 42000m2,the secondary membrane area is 50000m2,the tertiary membrane area is 5200m2,the primary membrane pressure is 0.7MPa,the secondary membrane pressure is 0.65 MPa,the tertiary membrane pressure is 1.5MPa,the final product gas CO₂ purity is 86.88%,CO₂ recovery rate is 77.02%,and the product gas flow rate is 6648.81m3/h.The flue gas for the actual gas composition system is compared with the CO₂-N2 system used in the previous foreign flue gas simulation.The calculation process of the mathematical model of membrane separation unit is designed by Aspen HYSYS software,and the membrane separation process of the two systems is simulated.The parameters of the three-stage membrane are calculated,the effect of gas composition on the purity and flow rate of the product gas under the actual gas conditions is analyzed.In addition,the system economy analysis is carried out for the three-stage membrane separation process under the actual gas composition.The final CO₂ capture cost is 73.2 $/ton.