(239b) Structured Adsorbent Pressure Temperature Swing Adsorption Cycles for Metabolic CO2 Removal from Spacecraft Cabins

NASA has a great deal of interest in the use of structured adsorbents in environmental systems for space applications for a variety of reasons. The most important reason perhaps is to minimize or even eliminate the formation of sorbent dust. Sorbent dusting most recently caused the failure of a TSA unit on board the International Space Station (ISS). The use of a Catacel structured 13X adsorbent may alleviate the dusting problem associated with the TSA unit in the carbon dioxide removal assembly (CRDA) and possibly provide even better performance characteristics.

The overall goal of this project is to design a temperature swing adsorption (TSA) process that utilizes this structured 13X adsorbent. This TSA cycle design would be perhaps a drop-in replacement for the TSA unit on board the ISS or it may be a grass root s design for future applications. This design is based on simulations being carried out with the USC dynamic adsorption process simulator (DAPS) and validated experimentally using the USC single bed apparatus in a TSA mode.

A corrugated structured sorbent consisting of a steel foil support coated with a layer of 13X is being experimentally evaluated for potential use in CDRA in lieu of traditional pelletized zeolite systems. Interest in using this type of column stems from faster kinetics that allow better bed utilization, lower pressure drop and stronger resilience against mechanic stress over pelletized systems. An 18 in long by 1.5 in diameter column containing the structured sorbent, with an effective zeolite 13X bulk density of around 150 g/L is being cycled between T_ambient (20 ^oC) and P_ambient (14.7 psia) during feed and 170 ^oC and 0.5 psia during regeneration without purge. This study is evaluating the performance in terms of CO₂ removal as a function of cycle time and other design variables. The latest results of this project will be presented.