How to calculate the product purity of PSA oxygen generator

As a customized product, the two most important parameters of PSA oxygen generator are purity and flow rate. Purity indicates the purity of finished oxygen, which can be 0 or 100%.

But in fact, in the field of PSA air separation, it is very difficult to achieve 100% pure oxygen, and there are more or less impurities in the finished oxygen. So when we mention 99.5% pure oxygen, what do we mean by 99.5%? Is it the volume of oxygen or the weight of oxygen?

Generally speaking, there are three ways to indicate the proportion of a certain substance in a gaseous mixture, namely mass fraction, volume fraction and mole fraction. The so-called mass fraction is the ratio of the mass of a certain component gas in the mixed gas to the total mass of the mixed gas. The volume fraction is the ratio of the volume of a certain component gas to the total volume of the mixed gas. The mole fraction is the ratio of the number of moles of oxygen in the gas component to the number of moles of the total mixed gas.

The product purity of the PSA oxygen generator is calculated based on the volume fraction; in other words, 99.5% pure finished oxygen means that the volume of pure oxygen accounts for 99.5% of the total volume of the mixed gas.

Note that the gas volume here refers to the proportion of oxygen in the total volume of the mixed gas in a uniform mixed gas at the same temperature and in the same space.