| Pressure Swing Adsorption (PSA) to product O2from air was a dynamic process involving the mass, heat and momentum transfer. It was difflcult to measure the pressure, temperature and concentration in the system because the changes were complicated. There exist many limitations based on pure experimental investigations and it was hard to obtain the inherent mechanism of the PSA. Despite its widely commercial application, it will be very necessary to strength the research.The Computational Fluid Dynamics(CFD) software FLUENT was used to solve the problems that single-phase porous media model not be able to express the mass, heat and momentum transfer between gas and adsorbent particles, the author programmed for achieving it. The single-phase porous media model was integrated to a perfect gas-solid two phase coupling model and then analysed the influences for gas and solid with each other.The inner mechanism of the PSA was of explored as well. The effects of particle diameters and ratios of Purge on performances of PSA were simulated with CFD that guided the experiments and analyzed the flow and distribution regular pattern inside the packed bed better. Involves the main content includes:According to the principle of PSA to produce O2, the mass transfer model and the equilibrium adsorption model were determined first. Based on FLUENT porous media model, the packed bed model of pressure swing adsorption to produce O2was established. With the User Defined Functions of FLUENT, comprehensive CFD software, the adsorption model and the porous media model were combined for achieving the mass and heat transfer of adsorption. By adding solid phase energy equation in the function of User-Defined Scalar, single-phase porous media model was integrated to a perfect gas-solid two phase coupling model, In order to verify the correctness of gas-solid two phase coupling model, the components adsorption isotherms and the average mole fraction of O2in outlet were contrasted in simulation and testing results, the grid-independence testing and the using of viscosity model were adopted too for the purposes.Based on the reliable model, the most typical PSA process, which consists of two beds and four steps, was simulated. The mole fraction of O2in gas phase, component concentrations in the solid phase and the temperature of two phases at the end of four steps for different cycles were analyzed. The analytic results show that, for the first cycle, the mole fraction and recovery of O2could reach72.0%and31.4%respectively, the temperature fluctuation of two phases was within10K. The mole fraction difference and the recovery of O2in this period of transition to the stability cycle were analyzed as well. The simulation result indicated that the mole fraction and recovery of O2increasing continuously, but the add speeds were reduced gradually. During about6cycles, the cycle reached steady state. For the stability cycle, the maximum for mole fraction of O2could reach99.9%and the recovery of O2stabilized around39.5%. The component concentrations in the solid phase were not associated with the mole fractions of components directly, instead of depending on the component concentrations in the gas phase.The main reason for the temperature fluctuating of two phases in the porous media was N2adsorption and desorption.Using the gas-solid two phase coupling model, the effects of the particle diameters and ratios of Purge on mole fraction and recovery of O2were studied. With the particle diameters of0.4mm,0.8mm,1.6mm,3.2mm and6.4mm when ratio of Purge was0.6, the most optimal particle diameters1.6mm was found, which the maximum for the average mole fraction and recovery of O2being, that99.7%and39.5%respectively. The ratios of Purge from0.4to0.8when particle diameter was1.6, the maximum for the recovery of O2being. |
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