Robust design of binary countercurrent adsorption separation processes

TLDR

The study examines binary mixture separation using a third‑component desorbent in a four‑section countercurrent adsorption unit. An optimal and robust design is derived from equilibrium theory with a constant‑selectivity stoichiometric model, yielding implicit constraints on flow‑rate ratios and robust‑design criteria after disturbance analysis. Explicit bounds on operating parameters are obtained, defining a parameter region based on equilibrium constants and feed composition, and the theoretical predictions are validated against experimental data from a six‑port simulated moving‑bed vapor‑phase unit.

Abstract

Abstract The separation of a binary mixture, using a third component having intermediate adsorptivity as desorbent, in a four section countercurrent adsorption separation unit is considered. A procedure for the optimal and robust design of the unit is developed in the frame of Equilibrium Theory, using a model where the adsorption equilibria are described through the constant selectivity stoichiometric model, while mass‐transfer resistances and axial mixing are neglected. By requiring that the unit achieves complete separation, it is possible to identify a set of implicit constraints on the operating parameters, that is, the flow rate ratios in the four sections of the unit. From these constraints explicit bounds on the operating parameters are obtained, thus yielding a region in the operating parameters space, which can be drawn a priori in terms of the adsorption equilibrium constants and the feed composition. This result provides a very convenient tool to determine both optimal and robust operating conditions. The latter issue is addressed by first analyzing the various possible sources of disturbances, as well as their effect on the separation performance. Next, the criteria for the robust design of the unit are discussed. Finally, these theoretical findings are compared with a set of experimental results obtained in a six port simulated moving bed adsorption separation unit operated in the vapor phase.