The carbon molecular sieves can simultaneously adsorb oxygen and nitrogen in the air, and the amount of adsorption increases with the increase of pressure, and there is no obvious difference in the equilibrium adsorption between oxygen and nitrogen under the same pressure.
Therefore, it is difficult to complete the effective separation of oxygen and nitrogen by the change of pressure. If the adsorption velocity is further considered, the adsorption characteristics of oxygen and nitrogen can be effectively separated.
The diameter ratio of nitrogen oxygen molecules is small, so that the diffusion speed hundreds of times faster than nitrogen, so the carbon molecular sieve adsorption oxygen adsorption rate is also very fast, about 1 minutes to reach more than 90%; and only 5% of the nitrogen adsorption capacity, so the general adsorption are oxygen, and the rest of the body. Is nitrogen.
So, if the adsorption time control in less than 1 minutes, it can be preliminarily separated oxygen and nitrogen, that is to say, the adsorption and desorption by differential pressure to achieve, adsorption pressure increased, desorption pressure drop.
However, the difference between oxygen and nitrogen is the difference between the adsorption rate and the adsorption time. The time control is very short, and the oxygen has been fully absorbed, and the adsorption process is stopped before the nitrogen has enough time to adsorb. Therefore, pressure swing adsorption to nitrogen pressure changes, but also to control the time within 1 minutes.