2018-02-06
PSA oxygen technology is one of the air separating technology for oxygen booming in recent ten years. Compared with traditional cryogenic technology, PSA oxygen technology is known for its low investment, low consumption, low operation-maintenance fee, mild process conditions, simple process flow, high automation, high operation flexibility, short construction duration, and safe performance. Up to now, PSA oxygen technology can replace cryogenic in many circumstances, and the PSA oxygen technology is more economic than cryogenic in running.
The main components of air are nitrogen and oxygen, so oxygen can be generated through a selective adsorbent which can separate oxygen from nitrogen in a suitable operation condition. In a pressurized condition, when air flows through adsorption beds with zeolites, nitrogen will be largely adsorbed, while little oxygen will be adsorbed, thus oxygen get enriched. When adsorbent is close to saturation, air will be stopped feeding into the bed, and will get desorbed after pressure get released, in which adsorbent get recycled. Two adsorption beds work in turns to get continual oxygen.
We can know from the principles above that PSA oxygen technology must contain two steps: one is adsorption (high pressure in relative) and the other is desorption (low pressure in relative), and such two steps repeat in turns. So, if there is only one adsorption bed, the oxygen is generated discontinuously. In order to get oxygen continuously, two adsorption beds are set in the process. Additionally, from the point of consumption and stability, some other assisted steps are also included into the process, such as equalization and purge.
According to desorption pressure, there are two specific PSA oxygen technology:
PSA Process: Pressurized adsorption (0.2~0.6MPa) and ordinary pressure desorption. This technology has a simple process and low investment, but low recovery rate and high consumption, so it is best for small plant (＜200Nm3/h).
VPSA Process. Adsorption under ordinary pressure or a little higher than ordinary pressure(0-50KPa), and vacuum desorption(-50~-80Kpa). Compared with PSA process, VPSA technology has a complex process and high investment, but high recovery rate and low consumption, so it is best for large plant (500Nm3/h~20000Nm3/h).
For the actual separation process, some other microelements in air should be taken into consideration. Carbon dioxide and water are stronger than nitrogen and oxygen to be adsorbed, so some other suitable adsorbents (or the oxygen generation adsorbent itself) should be added into the adsorption beds to attract carbon dioxide and water.
Through constant technological innovation and staff’s hard working, Beijing Peking University Pioneer Technology has made great achievements in gas industry. Pioneer has gained approval and respect from users and competitors for its typical characteristics and advantages, such as high efficient adsorbent, adsorption vessel making, PSA process, project experiences, engineering services and so on.
