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 technology 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 the Extravehicular Activity (EVA) duration, the flow-through swing bed is capable of both in-situ positive pressure and vacuum regeneration of adsorbents. The swing beds facilitate comprehensive testing of both subscale (~50–75 g) and operational-scale (>750 g) materials using a calibrated dosing source over time. Experimental parameters include CO2injection rates of 8 mmHg, flow rates up to 2 L/min, relative humidity of 50 percent (~11.1–14.8 ̊C dew point), and 2min 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 (0–95percent), adsorption/desorption swing 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 CO2and 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 half-cycles.