Research On The Nitrogen Adsorbent And Simulation Of Energy-Saving Process For Oxygen Enrichment

In this thesis, the molecular sieve was modified by water ion-exchang processunder a higher pressure and temperature （the temperature is set, and the pressure ischanging with the temperature）. The effects of the pressure and temperature, theconcentration of LiCl solution and reaction time on the nitrogen adsorption capacityof the synthesized zeolite were studied. And the X-zeolite was synthesized with silicasol and NaAlO₂, which named ZX. The ZX-zeolite was modified by LiCl, whichnamed L4-ZX, the N₂adsorption capacity and the N₂/O₂separation factor of L4-ZXwas obviously improved. A three-bed VPSA process for oxygen enriched wasestablished by Aspen Adsim simulation software. The effects of operating factors,such as, the cycle time, pressure equalization time and the flowrate of product on theprocess performance were studied, which provided basic design parameters for theoxygen enrichment process in industrial plants.In the temperature range100℃-130℃, the Li⁺ion-exchang degree of zeoliteincreases with the temperature and pressure in the reactor, and so does the N₂adsorption capacity. The Li⁺ion-exchang degree and N₂adsorption capacity increasewith the reaction time. The effect of the concentration of LiCl solution on the Li⁺ion-exchang degree and N₂adsorption capacity of zeolite is the same as that of thereaction time. The concentration of LiCl solution is no longer the key factor effects onthe ion-exchang of zeolite when the concentration of LiCl solution increases to3mol/L, because the zeolite has arrived ion-exchange equilibrium. As a result, the bestion-exchange conditions in water ion-exchange process are obtained: exchange with a3M aqueous lithium chloride solution at130℃,0.2MPa, this exchange is carried out4times,6h for each time. Then the N₂adsorption capacity and N₂/O₂separation factorreached to1.02mmol/g and6.1respectively at ambient temperature and150KPaabsolute pressure.The X-zeolite is synthesized with silica sol and NaAlO₂, and the reaction ratio isSiO₂/Al₂O₃=2.5, Na²O/SiO₂=1.6, H₂O/Na²O=45. Then the mixture is aged at ambienttemperature for12h, afterwards, the crystallization process is carried out at100℃for3h. After reacting with LiCl solution under the conditions described above, the N₂ adsorption capacity and N₂/O₂separation factor reached to1.02mmol/g and6.3respectively at ambient temperature and150KPa absolute pressure.The VPSA process produced O₂with a purity of94.6%and a recovery of57.6%when the cyclic time is75s, the pressure equalization time4s and the product flowrate64.8L/s. In the proposed process, the energy consumption was reduced throughtwo methods:（1） Reducing the ratio of adsorption and desorption pressure. The ratiowas determined to be2.88, which is lower than that in the industry and comsume lessenergy.（2）. Feeding under atmospheric pressure. When the pressure in the bed islower than atmospheric pressure, it is energy-saving to fill the bed from the feed gasrather than from the Blower. In this VPSA process, about27%feed gas was filledautomatically of feed air.