Non-equilibrium Molecular Dynamics Simulation Of Gas Separation Through Carbon Membranes

Carbon membrane is one type of membranes, which has good separation ability and selectivity in gas purification and separation, has a broad application prospects. Although many researches have been carried out in laboratory, there's still a long distance for industrial application. Besides the factors of membrane material and preparation, imperfection of gas separation mechanisms theoretical research is also an important reason. Therefore, to investigate these aspects is of significant value.The dual control-volume Grand-Canonical Molecular Dynamics(DCV-GCMD) simulation method is used to simulate pure gas of CO₂., CH₄N,N₂ and H₂ transport process, and a binary gas mixture of CO₂ and CH4 are investigated through a carbon membrane. In order to eliminate the effect of temperature and energy on gas kinetics, it is necessary to initialize the system first. The results showed that after 3000 steps, system energy and temperature tend to stabilize. Then experiments are carried out for pure gas under different conditions, such as membrane pore size, system temperature and pressure drop. Membrane resistance is concentrated in membrane entrance, and pore size tends to decrease adsorption of gas components;High temperature affects both the dissusion and adsoption, causing flux decrease. On the other hand, increasing temperature also causes the molecules to move and diffuse much faster, hence resulting in the tendency of the fluxes to increase. At last, taking CO₂ and CH₄ for example, parameters of L-J potential function are optimized, and the problem of the pressure in the low side of membrane is soved. The effect of the various factors, including the pore size, temperature, feed composition, and the molecular models and their parameters, on the transport, adsorption, and separation of the gases on CO2 and CH₄ was investigated in detail.Based on previous work, the transport and separation efficiency is researched.The weak point of the former simulating methods is made up. This simulating method can represent the the charaters of membrane transport and separation.Besides, this method plays an important role in the further research of carbon membrane.