Optimizationof Blended Amines for CO2Absorptionin a Hollow-Fiber Membrane Contactor.

To understand and optimize CO2absorption in binaryamine systems, we experimentally and theoretically investigated CO2absorption using typical amines and blended amines in a polypropylenehollow-fiber membrane contactor. The amines studied were monoethanolamine(MEA), diethanolamine (DEA), and N-methyldiethanolamine(MDEA), and their aqueous blends of MEA/MDEA, DEA/2-amino-2-methyl-1-propanol(AMP), and MDEA/piperazine (PZ). The predicted results, includingoverall mass transfer coefficients and CO2removal ratio,agreed very well with those determined experimentally. For singleamines, the optimal concentration was around 30 wt % for MEA and 20wt % for DEA. MDEA concentration had little effect on the overallmass transfer coefficient. We optimized the formulation of blendedamines using theoretical analysis. The optimal compositions in MEA/MDEA,DEA/AMP, and MDEA/PZ systems were respectively 30 wt % MEA, with MDEAin proportions from 0.1 to 0.3; 15 wt % DEA, with AMP in proportionsfrom 0.5 to 0.8; and 20 wt % MDEA, with PZ in a proportion of 0.3.To further understand the CO2membrane absorption process,we also analyzed individual mass transfer resistances as a functionof additive concentration in blended amines and the effects of liquidvelocity on the overall mass transfer coefficient. This shows thatCO2absorption is controlled by the liquid side for DEA/AMPblends and by combined liquid–gas phases for MEA/MDEA blends.For MDEA/PZ blends, control of CO2absorption is characterizedby a gradual transition from liquid side controlled to liquid–gascombined controlled as the concentration of PZ increases. [ABSTRACT FROM AUTHOR]