(437b) Are Ionic Liquids “Drop-In” Replacements for Conventional CO2 Capture Solvents in Packed Absorption Towers? Capital Considerations

Ionic liquids are actively being pursued as absorption solvents for CO₂ capture. Some ionic liquids have been found to have some of the largest CO₂ absorption capabilities of any known solvent.  However, the relatively slower mass transport properties of ionic liquids have been mentioned as potential challenges to their industrial implementation.  This presentation will illustrate the performance of the known and hypothetical ionic liquids for their use in absorption towers. The size and hydraulics of absorption towers using ionic liquids will be compared with conventional alcohol-amine solvents.  The interplay of the thermodynamic solubility with the mass transfer rates has large effects on the dimensions and hydraulics (capital costs) of packed absorption towers.  Our findings suggest that even ionic liquids with the highest known CO₂ capacities can yield capital costs in excess to conventional solvents due to the packed tower specifications necessary to overcome their slower mass transfer rates. Generally, improvements in the mass transport properties often yield smaller absorption towers compared to improvement in the thermodynamic CO₂ solubility.  This may indicate that other process intensification techniques may need to be considered to take advantage of some of the real thermodynamic advantages of ionic liquids.  Molecular design parameters are suggested for the improvement in ionic liquids for CO₂-capture.