The PSA Process

The principle of the adsorption process for separating oxygen and nitrogen from ambient air is based on the difference in adsorption kinetics of nitrogen and oxygen on molecular sieves. Oxygen adsorbs more rapidly on molecular sieves than nitrogen and therefore separation is possible. The basics of the process therefore is different than other adsorption processes such as gas drying, Hydrogen purification or biogas upgrading.

The later processes are all based on the adsorption capacity of the adsorbed component on the molecular sieves while in Nitrogen / Oxygen separation the kinetics is the mayor basic for the separation. Compressed ambient air of approx. 8 bara is pre-treated in order to remove dust particles, oil and moisture to a level of 0.01 micron for dust particles and 0.003 ppm oil vapour. In order to achieve this a two or three stage filter train is required and also the feed air need to be dried to a dew point of approx. –22 deg C atmospheric

The pre-treated compressed air is entering an adsorber vessel filled with carbon molecular sieves in which oxygen is adsorbed and nitrogen comes free available at the adsorption pressure and flows into a mixing vessel (Nitrogen receiver). The optimum adsorption time is approx. 60 seconds and after those 60 seconds the pressure is equalised with the second adsorber and the second adsorber takes over the adsorption step.

The first adsorber is now regenerated by reducing the pressure in the adsorber vessel to ambient pressure and the adsorbed oxygen is now desorbing due to the pressure reduction, and after the 60 seconds the first adsorber is completely regenerated and the process starts again. Performance characteristics There are a few suppliers of molecular sieves for nitrogen production in the world and all of these supplier have their benefits for a certain application.

Depending on the ambient conditions, energy cost, capacity and purity a selection is made of the molecular sieve that fits best for the application. The performance characteristics are very difficult to show in a general way. For detailed information please send us the inquiry and we will give you a detailed proposal. All figures shown on this website are indicative figures only and will be optimised for the specific application.

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