Optimal design and control of pressure swing adsorption process for N2/CH4 separation

Abstract

Pressure swing adsorption (PSA) is a very versatile, albeit complex gas separation and purification technology. Due to its complexity and periodic operation, calculation of the optimal PSA system that simultaneously obtains process design and control decision variables is a complicated task. This work presents detailed design and control optimization study of a two-bed, six-step PSA system aimed at heavy component CH4 upgrading. The key optimization objective is to enhance product CH4 recovery while achieving a closed loop product CH4 purity of 75% for separating 68%N2/32%CH4 feed under external disturbances. Traditional sequential and simultaneously design and control approach are employed and compared based on this purpose. The benefits of simultaneous methodology over conventional sequential approach are successfully demonstrated by closed-loop performance results and simulation profiles. The simultaneously design and control methodology has succeeded in synthesizing the optimal PSA cycle which can generate CH4 recovery as high as 97.30%.