VPSA system has different stages to perform for purification of the Bio gas. Firstly, Bio gas stored in the gas holder goes through Suction process by Blower and pressurized. The pressurized Biogas passes through water Scrubber. In this process, water is used as an absorbent to remove partially H2S and ammonia.
The water is supplied from the top of the column while the raw biogas is allowed to pass from the bottom to top. Ammonia and H2S trapped in the water and CH4 with CO2 and some traces of other gases along with moisture leave at the top of the water scrubber. After water scrubbing the gas passes through Chemical Scrubber where further H2S is trapped in iron flakes.