Methods for Improving the Electromembrane Regeneration Efficiency of Industrial Alkanolamine Absorbents

Abstract

A traditional technology for removing acid gases includes absorption by aqueous solutions of alkanolamines. Despite a high degree of gas flow purification and the high productivity of this process, there is a problem of thermo-oxidative degradation of the absorption solution. Degradation products are thermally stable and tend to accumulate within the system, resulting in significant operational problems. One of the promising approaches to the regeneration of alkanolamine absorbents is combining of membrane filtration and electrodialysis. This paper presents the first study of the effect of the pore size of a membrane used for prefiltration of an alkanolamine absorbent on the efficiency of the removal of heat-stable salts (HSS) by electrodialysis. Our findings indicate that both the initial HSS content and the effectiveness of their extraction vary depending on the alkanolamine type. Such variation is determined by the different mechanisms of a resin formation in absorbent solutions depending on the alkanolamine type. It was shown that decreasing the pore size and transition from microfiltration to nanofiltration enhances the degree of HSS extraction from 55 to 65% for classical electrodialysis and up to 87% for bipolar electrodialysis. To address the issue of fouling in ion-exchange membranes, a sequential washing with acid and alkaline solutions has been proposed. Our results indicate that this method makes it possible to restore the degree of HSS extraction from absorption solutions by 95%.