Comprehensive Evaluation of Electrochemical Hydrogen Separator as Hydrogen Recovery Solution for Plasma Pyrolysis Assembly

The previously tested State-of-the-Art (SOA) air revitalization architecture onboard the International Space Station recovers approximately 50% of the oxygen (O2) from metabolic carbon dioxide (CO2) via the Sabatier process. Maximum O2 recovery is required to reduce resupply mass for long-duration manned missions. O2 recovery is constrained by the limited availability of reactant hydrogen (H2) from water (H2O) electrolysis, and Sabatier-produced methane (CH4) is vented as a waste product resulting in a continuous loss of reactant H2. The Plasma Pyrolysis Assembly (PPA) has the potential to substantially increase O2 recovery by post-processing the Sabatier-produced methane to recover H2. The PPA decomposes CH4 into predominately H2 and acetylene (C2H2). A separation system is needed to purify the H2 from the PPA stream before it is recycled back to the Sabatier reactor. Two sub-scale electrochemical H2 separation systems, developed by Skyre, Incorporated, were delivered to NASA for evaluation. Complimentary of the previous submittal, ICES-2023-260, this paper reports a summation of Phase I and Phase II testing and evaluation of the C2H2 removal systems as well as lessons learned.