An Analytical Design Model of a Vacuum Pressure Swing Adsorption Process for Biogas Upgrading

An analytical plant design model was developed to describe the quasi-stationary state of vacuum pressure swing adsorption (VPSA) process for upgrading biogas (CO₂ and CH₄) to biomethane (CH₄). A reduced VPSA cycle comprising the steps adsorption, depressurization, and evacuation was considered, using a model biogas with 50% CO₂ in 50% CH₄. The mass balance for the gas phase was formulated using a simplified advection-reaction approach and for the solid phase using the Linear Driving Force (LDF) model. The steady-state model serves as a basis for process design and optimization, allowing the determination of the required bed height as a function of the target product purity.