Design and Experimental Validation of a Miniature Vacuum Pressure Swing Adsorption System for High-Efficiency Biogas Upgrading

Methane (CH4) is a high-calorific, low-carbon fuel whose widespread use is often limited by the need for efficient purification from CO2-rich biogas. Typical biogas contains about 60% CH4 and 40% CO2, making separation a critical step for energy recovery and utilization. This study presents the design and experimental evaluation of a compact, multifunctional vacuum pressure swing adsorption (VPSA) system, incorporating CH4 purification, adsorbent breakthrough testing, and automated operation. The system enables direct RS-485 communication between pressure transmitter, controllers, and human–machine interface (HMI), replacing conventional programmable logic controller (PLC) interfacing. The VPSA cycle was optimized by structuring the four-bed process into four main stages, each subdivided into six adjustable substages, allowing flexible parameter tuning via the HMI. Comparative experiments between two-bed and four-bed configurations were conducted using 5A zeolite. Under optimized conditions (2 L/min feed flow, 40 s adsorption time, and 0.3 MPa adsorption pressure), the four-bed system achieved CH4 purity above 97% and recovery above 80%. The proposed VPSA system offers a cost-effective, flexible, and high-performance solution for biogas upgrading.