Optimal design of dual-reflux pressure swing adsorption units via equilibrium theory

An optimal design strategy for dual-reflux pressure swing adsorption units targeted at achieving the separation of binary gas mixtures into two pure components (complete separation) is presented. Based on the equilibrium theory, detailed study of a specific configuration (feed to high pressure bed and pressure swing using heavy gas) reveals that feed location along the adsorption column, capacity ratio of the purge step (ratio between amount of feed to be processed and amount of adsorbent) and light recycle ratio (ratio of pure light reflux to feed rate) are the three most relevant design parameters. With respect to previous literature, two major achievements can be mentioned: (i) the development of an expression to evaluate optimum feed location and (ii) the identification of an operating region inside which complete separation at cyclic steady-state conditions can be established. In the plane defined by the two quantities feed position-capacity ratio of the purge step, such region has triangular shape and optimal conditions correspond to a vertex.