Flow-Through and Closed-Loop Recirculating Swing Beds for Carbon Dioxide Adsorbent Evaluation Within a Rapid Cycle Amine System

Advances in Rapid Cycle Amine (RCA) technology, utilized as the carbon dioxide and humidity control method within the Extravehicular Mobility Unit (xEMU) spacesuit, require ground-level testing to facilitate system optimization, adsorbent selection, flight hardware certification, and RCA service-life viability for planned operational missions. XploSafe has developed a flow-through swing bed and a closed-loop recirculating swing bed to facilitate the required ground-level testing of these new RCA technologies. With a recent focus on regenerable materials to extend Extravehicular Activity (EVA) duration, the flow-through swing bed is capable of both in-situ positive pressure or vacuum regeneration of tested adsorbents. The swing beds facilitate comprehensive testing of both small-scale (~50－75 g) and operational-scale (~750 g) materials with a calibrated dosing source over time. Experimental parameters include CO2 injection rates of 2.128－7.980 mmHg, flow rates up to 2 L/min, relative humidity of 50% (~11.1－14.8 ˚C dew point), and 2－4 min adsorption/desorption cycles for the flow-through swing bed. The closed-loop recirculating swing bed is capable of adjustment to flow rates (1-30.6 cfm), relative humidity levels (0-95%), adsorption/desorption cycles, bed size (> 1 kg of material), vacuum regeneration, adjustable injection rates, sub-atmospheric pressure (~4.3 psia), and adjustable system volume (~2 ft3), representative of the xEMU. The closed-loop recirculating system enables sensing across two unique positions, simulating the monitoring of CO2 and ammonia concentrations in both the spacesuit and the helmet. Additionally, data logging also includes real-time pressure differential across the beds, system flow rate, internal pressure, relative humidity, and temperature. The closed-loop recirculating bed also features a heat exchanger capable of maintaining ambient, high, and low-temperature conditions. Using both the flow-through and closed-loop recirculating swing beds, several materials, including Xplo-SA9T, MMPA-sorbent, and commercial soda lime material of similar sieved particle ranges, were screened and compared at 0.5-2 minute halfcycles.