Effect of liquid viscosity on the performance of a non-porous membrane contactor for CO2 capture

The effect of liquid viscosity on the performance of a non-porous membrane contactor is important to study for a proper solvent selection and process design. In this work, the overall mass transfer coefficient for MEA- and NaOH-based solutions was studied using a string of discs contactor in the temperature range 28-64 degrees C and a thin composite membrane contactor at 40 degrees C. Also, viscosity, density and N2O solubility of the aqueous solutions were measured in the temperature range 30-70 degrees C. The solvent viscosity of MEA and NaOH solutions was artificially adjusted from 0.5 to 54.7 mPa s by addition of sugar and/or glycerol. The overall mass transfer coefficient was found to decrease with increasing amount of viscosifier and the decrease seemed to be independent of the solvent system. In the membrane contactor, the decrease in the overall mass transfer coefficient was attributed to the decreasing CO2 solubility and CO2 diffusion coefficient, but as these properties alone were not able to describe the experimental values, the reason was attributed also to the establishment of an additional resistance at the membrane/liquid interface.