Four-column Vacuum Pressure Swing Adsorption for biogas upgrading with co-production of high-purity biogenic CO2: Experimental and simulation study

In this work, a four-column Vacuum Pressure Swing Adsorption (VPSA) pilot unit was constructed and tested for biogas upgrading. The columns were packed with the carbon molecular sieve Shirasagi CT-350 (CMS) adsorbent. A 12-steps process configuration was designed to upgrade a synthetic mixture of CH 4 /CO 2 (60/40 %vol), representing biogas, to biomethane. Experiments and simulations were carried out at room temperature (298 K) with an adsorption pressure of 4 bar, using a non-isothermal dynamic Aspen Adsorption™ model to support process interpretation. The configuration performance was evaluated for two feed flowrates of 2 SL/min and 3 SL/min, two vacuum pressures of 0.1 bar and 0.2 bar, while variating the evacuation time from 55 s to 700 s. Results indicated that at lower feed flowrates, higher CH 4 purity and recovery were achieved at the cost of higher energy consumption. Additionally, longer vacuum times (corresponding to longer adsorption times) reduced the total energy consumption. The best case of the experimental campaign, at vacuum pressure of 0.2 bar and feed flowrate of 3 SL/min, achieved a raffinate stream with 95.9 % CH 4 purity and 97.9 % CH 4 recovery, while simultaneously producing an extract stream with 96.7 % CO 2 purity and 93.6 % CO 2 recovery. These results demonstrate the high efficiency and potential of CMS-based multi-column VPSA configurations for upgrading biogas to biomethane while generating a high-purity CO 2 co-product. • Four-column VPSA pilot unit designed and tested for biogas upgrading. • The designed process achieved high CH 4 purity (95.9 %) and CH 4 recovery (97.9 %). • Aspen Adsorption simulations validated against pilot-scale experiments. • The effect of vacuum pressures and time on CH 4 purity and recovery was investigated. • Simultaneous production of high-purity CO 2 as a valuable co-product.