Experimental study on the improved VPSA process of pressurization with raffinate for VAM upgrading

An improved pressurization step with raffinate and vacuum exhaust step were developed and experimentally studied in a three-bed vacuum pressure-swing adsorption (VPSA) system with activated carbon for ventilation air methane (VAM) upgrading. It is found that pressurization with raffinate from the effluent end can prolong the penetration time and increase the CH₄ concentration in product gas in the case of the same raffinate concentration;but the vacuum exhaust step can increase the CH₄ concentration in product gas without increasing pressure. A three-bed VPSA cycle which contains the two steps was also studied experimentally. The results show that the CH₄ concentration in product gas can increase from 0.4% to 0.654% with the CH₄ recovery of 65% when the CH₄ concentration in feed is 0.2% and the adsorption and desorption pressures are 140 kPa and 20 kPa, respectively.