Optimization and analysis of pressure swing adsorption process for oxygen production from air under uncertainty

Abstract

Pressure swing adsorption (PSA) units are widely used for atmospheric air separation and oxygen concentration. However, the efficiency of such installations is reduced due to accidental changes in the characteristics of the atmospheric air to be separated. The article formulates and solves the problem of optimizing the regimes of operation of PSA units with zeolite adsorbent 13X, according to the criterion of oxygen recovery rate in the conditions of interval uncertainty of composition, temperature and pressure of atmospheric air. The optimization problem also takes into account the fulfillment of the requirements on purity of oxygen, productivity of the unit and resource saving of granulated adsorbent from granule abrasion. It is proposed to provide adsorbent saving by limiting the speed of incoming flow in the frontal layer of the adsorbent by means of "soft" stepwise change of the degree of opening of control inlet and outlet valves of the unit. The problem (including the search for time change programs for the degree of opening of control valves) was solved with the use of the developed mathematical model of cyclic heat- and mass exchange processes of adsorption-desorption in a PSA unit and a heuristic iterative algorithm. The comparative analysis of the results of the optimization problem solution, with and without taking into account the constraint on the gas flow velocity in the frontal layer of the adsorbent, is carried out. The influence of the specified requirements for the performance of the PSA unit and the purity of oxygen on the degree of its recovery has been studied.