Synthesis Of The Oxygen Adsorbent And Simulation Of Duplex VPSA For Air Separation

In this paper，the13X molecular sieve was exchanged by Li+with the method ofwater ion-exchange process. The effects of the kind of molecular sieve，the mole ratioof Li+and Na+，the ratio of binder and sesbania，the activation temperature andactivation atmosphere on the nitrogen adsorption capacity were studied. As a result,the optimization conditions are as follows: the pressure and temperature are0.2MPaand130℃respectively, the zeolite exchange four times with the LiCl solution withthe concentration of2mol/L under the Li/Na ratio of4and each time is3h, the ratio ofbinder and sesbania are5%and2%, the activation temperature and activationatmosphere are450℃and dry air. The SEM and EDS were used to analysised thestructure morphology and the Li+exchange degree. Then the N2adsorption capacityand N2/O2separation factor of zeolite reached to0.75mmol/g and6.2respectively atambient temperature and120KPa absolute pressure.Stripping PSA and Enriching PSA only can get one light and heavy productrespectively, while Duplex PSA is a combination of Stripping PSA and EnrichingPSA which can get both light and heavy product simultaneously. The Duplex PSAconsist of light reflux at the top and heavy reflux at the bottom with intermediate feedlocation,which can both obtain light and product at the top and bottom of the bedrespectively. The Duplex PSA can be divided to four types based on the feed gaspressure and pressure resetting with light product A or heavy product B. The low andhigh pressure Duplex VPSA for air separation was simulated by Aspen Adsorptionsoftware using synthesised Li-X zeolite.A six-step cycle was used for low pressure Duplex VPSA with the feed/light reflux,pressurizing pressure equalization, heavy product pressurization, heavyreflux/adsorption, depressurizing equalization, countercurrent depressurization. Theadsorption and desorption pressure were2bar and0.57bar respectively, the purityand recovery of O2were reached98.08%and90.32%. At the same time, the purityand recovery of N2were97.57%and98.89%. The influence of different feedlocations, ways of pressure equalization and reflux ratio was studied for the purity andrecovery of O2and N2. The performance of the Duplex PSA process was comparedwith other foreign literature which showed better separation effect. Meanwhile，The effect ofdifferent feed locations and reflux ratio was also studied for the high pressure DuplexPSA which also can obtain two high purity and recovery of nitrogen and oxygen.Compared the two types of Duplex PSA processes, both of them can get light and heavy product. However，the feed flowrate of low pressure Duplex PSA was threetimes of the high pressure Duplex PSA，at the same time，the unit energy consumptionwas only1/3of high pressure Duplex PSA. In a word, the low pressure Duplex PSA canget both high purity and recovery of light and heavy product with high feed flowrateand low unit energy consumption.