Model Calibration Experiments in Support of Metabolic Heat Regenerated Temperature Swing Adsorption Technology

Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed to address carbon dioxide (CO₂) and heat removal/rejection in a Mars Portable Life Support System (PLSS). The technology utilizes an adsorbent that when cooled with liquid CO₂ to near sublimation temperatures (∼195 K) removes metabolically-produced CO₂ in the ventilation loop. Once fully loaded, the adsorbent is then warmed (∼300 K) externally by the ventilation loop, rejecting the captured CO₂ to Mars ambient. Two beds are used to provide a continuous cycle of CO₂ removal/rejection as well as facilitate heat exchange out of the ventilation loop. To investigate the feasibility of the technology, a series of model calibration experiments were conducted which lead to the selection and partial characterization of an appropriate adsorbent. The Molsiv Adsorbents 13X 8×12 (also known as NaX zeolite) successfully removed CO₂ from a simulated ventilation loop at the prescribed temperature swing anticipated during PLSS operating conditions on Mars using a cryogenic fluid. Thermal conductivity of the adsorbent was also measured to eventually aid in a demonstrator design of the technology. These results provide no hurdles to the development of MTSA technology and allow its development to focus on other design challenges as listed in the conclusions section of this paper.