Reclaiming of degraded MEA solutions by electrodialysis: Results of ED pilot campaign at post-combustion CO2 capture pilot plant

Abstract

A study of the behavior of heat stable salts (HSS) during electrodialysis (ED) reclaiming of monoethanolamine solvent (30wt.% MEA) is reported in detail. Degraded lean MEA samples with a loading of approx. 0.2mol/mol were taken from the solvent loop of post-combustion capture (PCC) pilot plant after 400, 535 and 972h of operation at real conditions. The specially designed conventional pilot ED unit equipped with cation-exchanged membranes and anion-exchanged membranes was used. Before and after ED reclaiming, all streams were analyzed for specific solvent components. A quite uniform removal of all analyzed HSS anions (except for nitrate ions) during the ED treatment prevents accumulation of any specific undesirable compound in the solvent loop. Visual inspection of the ion-exchange membranes revealed the deposition on the membrane surface having reddish-brown color. It was experimentally confirmed that such deposition did not noticeable affect on membrane performance in ED process. Furthermore, it was demonstrated on the laboratory level that selected membranes possess a good long-term stability after being contacted with fresh and degraded MEA for approx. 2 years.