Research On Processes Of Removing Carbon Dioxide From Mixture Gases By Pressure Swing Adsorption

The technology of pressure swing adsorption (PSA) had been industrialized in removing carbon dioxide for its simple process, less energy consumption and no pollution. But it still had a problem of low adsorbent selectivity and rate of product recovery. So the key point of removing carbon dioxide by PSA lied in the development and selection of high quality adsorbent and the design for suitable process flow.The purpose of this paper was to remove carbon dioxide from synthesis gas of synthetic ammonia industry by the way of PSA. Based on measuring the static and dynamic adsorption performances of carbon dioxide on indigenous usual decarbonization adsorbents(active carbon and silicon gel). The adsorbent of high capacity and selectivity for carbon dioxide was selected and the pressure swing step researched and model calculated. Ultimately, the industrial process of decarbonization was designed using the research of this paper.Adsorption isotherms of carbon dioxide and nitrogen were measured. The equilibrium data measured were fitted by Langumuir adsorption equilibrium model. The adsorption performance of carbon dioxide in mixture gas containing hitrogen or nitrogen on three adsorbents was studied. Then the comparison of adsorption character among three adsorbents was made. The adsorption selectivity for carbon dioxide in binary gas on AC and SG1 adsorbents were measured. The effects of pressure and flow rate had also been studied. The reason of different adsorbed amount of carbon dioxide on two silicon gel adsorbents was analyzed after comparing the diversity between inner structure in two adsorbents.The rate of product recovery was greatly related to the pressure swing process. So the steps of cocurrent blow down and countercurrent blow down on two adsorbents of AC and SG1 were measured. The effect of pressure on carbon dioxide concentration in off-gas during two decompression steps under condition of different use ratio of adsorbent bed was studied. The cause of diversity in two type of decompression step on two adsorbents were compared and discussed. The research work above was fit for the design of separating mixture gas containing carbon dioxide by PSA.Based on the experimental data ,an appropriate adsorption equilibrium model wasestablished. The model was used for researching the steps of adsorption and cocurrent blow down when the feed gas contained carbon dioxide and nitrogen ,or carbon dioxide and hitrogen. The calculation results by the model were coincident with experimental data. The circumstances inside the adsorbent bed which could not be measured by experiment were researched by adsorption equilibrium model. The calculation with model gave a tool for industrializing the adsorbents.According to the datas dynamic adsorption model and the technical requirement, the flow path of removing carbon dioxide from pyrolysis gas produced from methonal by PSA was designed to calculate the size of adsorber and admission space of adsorbents and to determine the reasonable operation chart. The results from factory showed that the purity of product was above 99.99% and the rate of recovery was above 92%. The economic effectiveness was remarkable.