Measuring CO2 and N2O Mass Transfer into GAP-1 CO2-Capture Solvents at Varied Water Loadings

This paper investigates the CO2 and N2O absorption behavior in the water-lean gamma amino propyl (GAP)-1/TEG solvent system using a wetted-wall contactor. Testing was performed on a blend of GAP-1 aminosilicone in triethylene glycol at varied water loadings in the solvent. Measurements were made with CO2 and N2O at representative lean (0.04 mol CO2/mol alkalinity), middle (0.13 mol CO2/mol alkalinity), and rich (0.46 mol CO2/mol alkalinity) solvent loadings at 0, 5, 10, and 15 wt % water loadings at 40, 60, and 80 degrees C and N2O at (0.08-0.09 mol CO2/mol alkalinity) at 5 wt % water at 40, 60, and 80 degrees C. CO2 flux was found to be nonlinear with respect to log mean pressure driving force (LMPD). Liquid film mass transfer coefficients (k'(g)) were calculated by subtracting the gas film resistance (determined from a correlation from literature) from the overall mass transfer measurement. The resulting k'g values for CO2 and N2O in GAP1/TEG mixtures were found to be higher than that of 5 M aqueous monoethanolamine under comparable driving force albeit at higher solvent viscosities. The k'(g) values for CO2 were also found to decrease with increasing solvent water content and increase with a decrease in temperature. These observations indicate that mass transfer of CO2 in GAP-1/TEG is linked to the physical solubility of CO2, which is higher in organic solvents compared to water. This paper expands on the understanding of the unique mass transfer behavior and kinetics of CO2 capture in water-lean solvents.