Ultrasonic Desorption from an Ionic Liquid Loop for Continuously Regenerable CO2 Removal from Spacecraft Cabin Atmospheres

The CO2 Environmental Removal for Extended-duration Spaceflight (CERES) student team at the University of Colorado Boulder uses ionic liquid (IL)-based concepts for regenerable CO2 removal from simulated cabin atmospheres. The process described here utilizes an ionic liquid loop to connect the absorption and desorption modules that together form a closed loop continuously regenerative system. The first module, the “absorber”, is a hollow-fiber membrane contactor used to provide a contacting surface between a CO2-laden atmosphere stream and the flowing IL. The IL absorbs CO2 from the cabin atmosphere stream. The CO2-rich IL flows into a custom flat-plate “desorber” module to extract CO2. A vacuum pump creates a negative pressure differential in the headspace of the desorber with respect to the partial pressure of absorbed CO2 (ppCO2). In combination with negative pressure, an ultrasonic transducer attached to the desorber module is used to enhance the desorption of weakly bonded CO2 from the ionic liquid. Once the CO2 is expelled from the system, the regenerated IL loops back to the absorber module for continuous CO2 removal. Through testing, data showed that the system was effectively absorbing and desorbing CO2, demonstrating the function of the system. However, a software failure of the ultrasonic system prevented the investigation of ultrasonic desorption, which will remain the focus of future work. Here, we present our system design and report the results from experiments to characterize the CO2 transport rate under varying conditions of cabin atmosphere CO2 concentration, atmosphere, and ionic liquid flow rates.