A two-stage methane enrichment process with initial vacuum, temperature, and final vacuum swing adsorption (VTVSA) was applied to enrich simulated ventilation air methane (VAM) (<1 vol %) up to more than 25 vol % in the final product which can then be directly utilized by conventional gas engines for power generation. A prototype VAM enrichment unit was designed and constructed in accordance with relevant Australian Standards and local mine site regulations. The initial vacuum process was newly added to conventional temperature and vacuum swing adsorption (TVSA) processes to control the final product quality by regulating the vacuum pressure. The two-stage process eliminated a safety concern that methane concentrations may fall into the explosive range in the course of VAM enrichment, having <5 vol % CH4 in the first-stage product and >15 vol % CH4 in the second-stage product. Simulated ventilation air streams with 0.30, 0.60, and 0.98 vol % CH4 were enriched up to 19.28, 24.24, and 36.92 vol % CH4, respectively. Further improvement can be achievable for practical applications where continuous cyclic operations and feedings are available.