Experimental Studies On The Miniature Type PSA Equipment Of Producing Oxygen From Air

This paper presents a miniature type pressure swing adsorption equipment using diskas columns with diameter 80mm and thickness 10mm,which stack together tightly. ThePSA equipment runs a Skarstrom cycle with co-current equalization for air separation.VP800 zeolite molecular sieves were used as the adsorbent and oxygen is the desiredcomponent.The experiment has two parts. In one part we carried out the experiments of Li-ionexchange in 13X zeolite molecular sieve. The dynamic breakthrough curves of N₂ and O₂on 13X zeolite with 87.5% Li-ion were measured at 25℃. The data demonstrated the 13Xzeolite with 87.5% Li-ion could not used as adsorbent for air separation. In the other part,the adsorption isotherms as well as dynamic breakthrough curves of N₂ and O₂ on 5A andVP800 zeolites at different pressures were also measured at 25℃. The separation factorof N₂/O₂ at different pressures was calculated in terms of the breakthrough curves of N₂and O₂. From the results, the VP800 zeolite was selected as the adsorbent for airseparation because of higher N2 adsorption capacity as well as better adsorptionselectivity for nitrogen than oxygen. At the same time, the breakthrough curves overVP800 zeolite at different pressures were also measured using just one-bed of theflowsheet at feed flow-rate 284.67ml/min. From the breakthrough curves we concludedthat the best pressure for PSA was about 0.4MPa. We compared the performance of thedisks placed vertically with that placed horizontally, and found better performance asachieved on the disks placed vertically. Therefore the disks were placed verticallyafterwards. Experiments were carried out to examine the factors affecting the processperformance. The first factor was the environmental temperature. It was shown that theoptimal temperature was 24℃. Then the effects of feed flow-rates, production stepduration, equalization time, purging time, re-pressurization time and purging to productratio on the performance was studied and compared at 0.4MPa. As a result, the optimaloperating factors for each step in the process of PSA were selected. In addition, the centertemperature of four-bed in one cycle was observed when the product purity and recoverydid not change at the condition of 0.4MPa. And it illustrated the temperature fluctuationin the center of beds during adsorption and de-sorption is less than 5℃. Finally thestability of the system was studied in the condition of 0.4MPa by 160 PSA cycles and itbecame stable when the number of cycle is beyond 80. Hence the feasibility of miniaturetype equipment was proven. According to the experimental results the optimal productpurity was 80.9%, the recovery was 29.29%, the productivity of each amount adsorptionwas 52.51NLO2/[hkg(adsorbent)] and the consumed energy power was 0.738 kwh/Nm3O2.