Carbon Dioxide Removal by Ionic Liquid Sorbent (CDRILS) System Development

Using a liquid absorbent like an ionic liquid eliminates many of the disadvantages of solid adsorbent systems for carbon dioxide (CO2) removal from air in a deep space mission. Systems built around a liquid absorbent avoid complicated valve networks to switch between absorbing and desorbing beds, and deliver an even flow of product carbon dioxide. Ionic liquids are particularly desirable for space applications since they are non-volatile, non-odorous, and have high oxidative stability.

Significant progress has been made in the development of the CDRILS system for use in life support applications. Membrane contactors have been designed that provide high surface area without allowing escape of the liquid, and the long-term reliability of both contactors and ionic liquid has been assessed. Using measured CO2 and water capacities and mass transfer coefficients, alternative system designs have been evaluated to identify those that maximize performance while minimizing weight, volume and power consumption. Because water is strongly absorbed by most ionic liquids, water management is a key focus in designing the closed-loop system. Determination of optimized operating conditions and the optimum system design allows scale up of lab scale experiments to a full size unit capable of removing 4.16 kg/day of CO2.