Oxygen removal with composite membrane contactors to prevent amine solvent degradation in post-combustion CO2 capture: A comprehensive parametric study

Absorption with aqueous amine solvents is a well-established technology for acid gas removal and will continue to be a readily available option for post-combustion CO2 capture. Its main drawback is the solvent degradation under process conditions, due to oxygen captured from the flue gases. Dissolved O-2 oxidizes amines, forming various degradation products, including heat-stable salts (HSS), which intensify corrosion and reduce the sorption capacity of the solvent. This paper investigates direct removal of dissolved O-2 from amine solvents in gas-liquid membrane contactors. Novel composite membranes have been developed for this process. They consist of a highly permeable polymer blend, made from poly [1-(trimethylsilyl)-1-propyne] (PTMSP) and polyvinyltrimethylsilane (PVTMS), which is deposited as a thin protective layer on porous polysulfone hollow fibers and tubular ceramic supports. For the first time, a comprehensive study has been carried out on the efficiency of dissolved O-2 removal vs. contactor and process parameters (membrane support type; amine solvent type; solvent CO2 loading; driving force generation mode; solvent velocity; temperature). The deoxygenation performance of the contactors has been demonstrated in the O-2 removal process from the amine solvent under the conditions encountered in an absorber sump during the CO2 capture process (30 % aqueous monoethanolamine solvent with CO2 loading of 0.5 mol/mol at 60 degrees C). In this case, the O-2 removal efficiency of up to 46 % in an hour has been achieved for developed contactors, which reduces the estimated rate of HSS formation by similar to 2 times compared to non-deoxygenated solvents. The size of the membrane was calculated to remove 90 % of the dissolved oxygen in a hypothetical post-combustion CO2 capture plant with a solvent flow rate of 120 m(3)/h, amounting to similar to 1460 m(2) for ceramic-based membranes.