Methane Post-Processor Development to Increase Oxygen Recovery beyond State-of-the-Art Carbon Dioxide Reduction Technology

Abstract

State-of-the-art life support carbon dioxide (CO 2 ) reduction technology, based on the Sabatier reaction, is theoretically capable of 50% recovery of oxygen from metabolic CO2. This recovery is constrained by the limited availability of reactant hydrogen. Post-processing of the methane byproduct from the Sabatier reactor results in hydrogen recycle and a subsequent increase in oxygen recovery. For this purpose, a Methane Post-Processor Assembly containing three sub-systems has been developed and tested. The assembly includes a Methane Purification Assembly (MePA) to remove residual CO2 and water vapor from the Sabatier product stream, a Plasma Pyrolysis Assembly (PPA) to partially pyrolyze methane into hydrogen and acetylene, and an Acetylene Separation Assembly (ASepA) to purify the hydrogen product for recycle. The results of partially integrated testing of these sub-systems are reported. NomenclatureASepA = Acetylene Separation Assembly CDRA = Carbon Dioxide Removal Assembly

Electrochemistry for Space Life Support

“…The water produced is fed to the water purification system and then to the OGA to produce H 6,7 To recover the H 2 from the PPA effluent, an electrochemical H 2 separator was developed by Skyre, Inc. under NASA's Small Business Innovative Research Program. As shown in Fig.…”

“…2a, electrochemical H 2 separation occurs when H 2 is electro-oxidized to protons and electrons and the protons are electro-reduced in a separate chamber. 6 At typical PPA operating temperatures of 150°C, the CO present in the outlet stream interferes with the catalytic electrodes' ability to oxidize H 2 . Mitigating this interference is possible, but the acidic polymer electrolyte typically used is not serviceable above 150°C.…”

“…Mitigating this interference is possible, but the acidic polymer electrolyte typically used is not serviceable above 150°C. 6 In 2015, Skyre developed electrolyte materials compatible with PPA operating conditions and delivered two single-cell stacks to NASA MSFC. Results from singlecell stack testing showed no detectable contaminants from the purified H 2 outlet stream, making this technology highly desirable for integration with Sabatier-based processes.…”

“…Results from singlecell stack testing showed no detectable contaminants from the purified H 2 outlet stream, making this technology highly desirable for integration with Sabatier-based processes. 6 In 2018, Skyre fabricated and delivered a fullscale, four-crewmember cell stack. The full-scale design was iterated upon, resulting in the subsequent delivery of two three-cell stack H 2 separators to MSFC for characterization and optimization testing.…”