Simultaneous Capture of Mercury and CO2 in Amine-Based CO2 Absorption Process

The feasibility of using an amine-based carbon dioxide (CO2) capture unit for the simultaneous capture of mercury (Hg) and CO2 was studied by carrying out Hg absorption experiments with three different types of absorption solutions: mixtures of sodium chloride (NaCl) and sodium hypochlorite (NaOCl), monoethanolamine (MEA), and blended MEA and NaCl/NaOCl. The results show that it is not effective to use the amine-based CO2 unit for the concurrent capture of Hg and CO2 because the Hg absorption performance of aqueous solutions of MEA and blended MEA/NaCl/NaOCl is low. Mixtures of NaOCl and NaCl do not perform as a rate enhancer for Hg removal in the presence of MEA. The presence of Hg in the MEA solutions does not affect the CO2 absorption performance of MEA. To capture both Hg and CO2, a two-step capture process that employs an aqueous NaCl/NaOCl solution for Hg removal, prior to CO2 capture in the amine unit, might be an option.