The PSA hydrogen-unit consists of four or more adsorption towers. Each of these towers passes subsequently through the stages of pressure build up, adsorption, and regeneration. By this, a continuous supply of product gas can be achieved. The pressure build-up is carried out in one or more steps. The tower in adsorption is switched over to regeneration. During this step, hydrogen-enriched gas flows to another tower for the next adsorption step.
The remaining part of the pressure build-up is done with product gas. In the subsequent production step, the feed gas is passed through the adsorption tower and hydrogen with very high purity leaves the tower. The regeneration is also done in several steps.
After pressure equalization with the previously regenerated adsorption tower, the present adsorption tower is depressurized. This is followed by a purge step with a counter-current flow of hydrogen. In case there is a high concentration of heavy hydrocarbons in the feed gas, a pre-filter system is integrated into the PSA-process.