Optimization and analysis of a VPSA process for N2/CH4 separation

• A VPSA process applied to recover CH4 from the mixture of 70% N2/30% CH4.
• Improving the CH4 recovery while reducing the specific power consumption.
• The sub-models established for each unit with the sensitivity analysis models.
• The r-SQP method used to optimize the decision parameters.
• A large improvement in the performance of the VPSA process.

A vacuum pressure swing adsorption (VPSA) process that uses activated carbon as an adsorbent to recover CH4 from a gas mixture (70% N2/30% CH4) is investigated through dynamic optimization and sensitivity analysis. The purpose of the research described in this paper is to improve the recovery of CH4 and reduce the specific power consumption by optimizing the decision parameters using the r-SQP method with given constraints. The sub-models for each unit in the pressure swing adsorption (PSA) process were established with sensitivity analysis models, unlike the general model, which is established around the adsorption bed for this separation. The integrated model is closer to a realistic PSA process, which makes the results of the simulation and optimization more convincing. Under optimal conditions, the purity of CH4 reaches 80% in the product gas, the recovery of CH4 is 97%, and the specific power consumption is 0.186 kW h/N m3. Analysis of the sensitivity data provides significant insight into the effects of the operating parameters for the process.