1990-07-01

Characterization of Metal Oxide Absorbents for Regenerative Carbon Dioxide and Water Vapor Removal for Advanced Portable Life Support Systems 901431

In several previous studies, metal-oxide-based absorbents have been investigated as a regenerative means of removal of carbon dioxide (CO2) from recycled breathing gas in an astronaut portable life support system (PLSS). In most cases, the significant effect of water vapor on the successful absorption of CO2 was noted.
Under an ongoing NASA-funded program, parametric studies have been conducted to characterize the performance of a silver-oxide-based absorbent, developed by Allied-Signal researchers, in terms of its ability to remove both gaseous CO2 and water vapor. This phenomenon is highly desirable and could lead to a much simplified PLSS. These studies included an investigation of the effects of preconditioning the absorbent, the effects of cooling the absorbent bed, and the impact of various levels of inlet CO2 and water vapor partial pressures.
Results of these studies, presented in this paper, indicate that by cooling the absorbent bed during use, significant amounts of both CO2 and water vapor can be removed. Bed cooling was necessary to compensate for the exothermic nature of the gas/solid reactions. The bed operating temperature was shown to have a significant effect on water vapor removal performance. In addition, the method of absorbent preconditioning was shown to have an impact on initial water vapor uptake, so that the outlet dewpoint could be maintained above a lower limit. The behavior of the absorbent under various inlet conditions was also shown to have characteristics which are advantageous for a PLSS application.

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