Regeneration principle of molecular sieve in pressure swing adsorption air separation equipment

For PSA pressure swing adsorption molecular sieve air separation equipment, molecular sieve is the core component of the system; only by continuously adsorbing and regenerating clean compressed air through molecular sieve can we continuously produce the nitrogen or oxygen we need.

Regeneration can be understood as the reverse process of adsorption; because when the molecular sieve completes a saturated adsorption, it cannot continue to adsorb gas, and its adsorption capacity needs to be "restored", which is what we call "regeneration".

Molecular sieve "regeneration" can help the molecular sieve last as long as possible and maintain good working performance. The attenuation and aging of the adsorption performance and mechanical properties of the molecular sieve after correct regeneration are very low. There are two ways to regenerate the molecular sieve;

1、 Change the temperature. It heats the molecular sieve to remove the metal ions and combined water with low electric charge and large ion radius in the molecular sieve, so that it can be restored to the cavity state; in industrial production, the preheated regeneration gas is used to heat, purge the molecular sieve, and take away the desorbed adsorbate. Generally speaking, the regeneration temperature of the molecular sieve is recommended to be 200-250 degrees. If the temperature is too high, the micropores of the molecular sieve will be permanently blocked and the molecular sieve will fail.

2、Change the relative pressure. It is generally used in the gas phase adsorption process. The basic method is to keep the adsorbent temperature unchanged and remove the adsorbate by reducing the pressure and backwashing with inert gas.

Regeneration is usually carried out in the opposite direction of adsorption. Most of the adsorbate contained at the entrance of the adsorption bed does not need to pass through the entire bed layer, which effectively reduces the contact between the molecular sieve and the hot and humid gas and increases the service life of the molecular sieve. Of course, the regeneration gas should be as dry as possible, otherwise it will affect the adsorption efficiency.

As for whether the regeneration is qualified or not, the usual way to judge is to look at the instrument. The regeneration time and temperature curve of the same tower recorded by the instrument remain normal, and the fluctuation value is stable; and the sampled product gas concentration (purity) of the same tower when it is put into adsorption again is within the qualified range, and the fluctuation range is also very small, which means that the regeneration is complete.