Characterization of an Improved Solid Amine for a Regenerative CO ₂ Removal System

The Shuttle Orbiter humidity control and carbon dioxide removal system for extended duration missions presently uses a solid amine called HS-C. This August, on board STS-62, a new solid amine called HS-C+ will be used. HS-C+ uses the same amine and the substrate material, but a different preparation process. Forty-seven breakthrough tests have been conducted to characterize the performance of HS-C+. CO₂ partial pressure, bed temperature, and H₂O partial pressure were varied. Eleven HS-C breakthrough tests were also run to provide a direct comparison. Under all conditions tested, HS-C+ outperformed HS-C. Both materials adsorb all CO₂ and H₂O available at the start of a test when the beds are fully desorbed. As the bed becomes partially loaded, the CO₂ and H₂O adsorption rates decrease rapidly. HS-C+ continues adsorbing all CO₂ and H₂O available for a longer time. Greater surface area on HS-C+ may cause the improved performance.