Variations of PSA technology[edit]
Double Stage PSA[edit]
(DS-PSA, sometimes referred to as Dual Step PSA). With this variation of PSA developed for use in Laboratory Nitrogen Generators generation of nitrogen gas is divided into two steps: in the first step, the compressed air is forced to pass through a carbon molecular sieve to produce nitrogen at a purity of approximately 98%; in the second step this nitrogen is forced to pass into a second carbon molecular sieve and the nitrogen gas reaches a final purity up to 99.999%. The purge gas from the second step is recycled and partially used as feed gas in the first step.
In addition, the purge process is supported by active evacuation for better performance in the next cycle. The goals of both of these changes is to improve efficiency over a conventional PSA process.
The DS-PSA is also applied to up levels oxygen concentration in this case a zeolite aluminum silica based adsorb Nitrogen in the first stage focusing Oxygen 95%, and in the second stage the molecular sieve carbon-based adsorbs the residual nitrogen in a reverse cycle, concentrating to 99% oxygen.
Rapid PSA[edit]
Rapid pressure swing adsorption or RPSA is frequently used in portable oxygen concentrators. It allows a significant reduction in the size of the adsorbent bed when high purity is not essential and feed gas can be discarded.[6] It works by quickly cycling the pressure while alternately venting opposite ends of the column at the same rate. This means that unadsorbed gases progress along the column much faster and are vented at the distal end, while adsorbed gases do not get the chance to progress and are vented at the proximal end.[7]