Gas Separation and Purification
PSA / Membrane / Catalytic Gas Purifier
The gas separation and purification train is a 40 kg multi-stage unit that refines partially-separated volatile streams into high-purity gases, delivering 99.999% hydrogen and 99.99% oxygen at a throughput of 10 kg per day. Operating on 300 W of electrical power, the system integrates pressure-swing adsorption, selective membranes, and catalytic converters across three-stage cascades. While the lunar ambient vacuum provides a natural low-pressure desorption sink that simplifies vacuum pumping requirements during five-minute adsorption cycles, severe lunar thermal swings strictly constrain adsorbent bed material selection across wide operating temperature regimes.
Multi-stage gas purification train using pressure-swing adsorption (PSA), polymer membranes, and catalytic conversion that refines the partially-separated streams from the cold trap into pure single-species products meeting downstream-use specifications.
Purpose
Convert coarsely-separated volatile mixtures into the high-purity streams needed by RFC electrolyzer (99.999% H2), oxygen consumers (99.99% O2 from VOL-HEAT carbothermal residual), and life-support gases (>99.9% N2) for storage and use.
Context
Receives partially-separated streams from L3-ISR-VOL-TRAP cryotraps; outputs purified species to L3-ISR-VOL-STORE for high-pressure storage and direct piping to L3-ESS-FC-H2TK and L1-WMS as needed.
Principles
- ▸Pressure-swing adsorption (PSA): differential adsorbent affinity for different gases allows cycling between high/low pressure to purify
- ▸Polymer membranes: selective permeation for H2 (palladium), O2 (perfluorinated), CO2 (cellulose acetate) — continuous operation
- ▸Catalytic converters: oxidize trace contaminants (CO → CO2 over Pt, methane → CO2+H2O over Pd)
- ▸Multi-stage cascade to incrementally improve purity (each stage 95% rejection → cumulative >99.99%)
- ▸Equilibrium-based separation: PSA + membrane combined for high single-pass yield
- ▸Gas chromatograph at outlet verifies purity in real time
Typical implementations
- ▸ISS Air Revitalization System (ARS) PSA for CO2 removal
- ▸Industrial hydrogen recovery from petrochemical streams (PSA)
- ▸Polymer membrane hydrogen separators (Air Products PRISM, Linde)
- ▸Catalytic CO oxidation in life-support systems (Apollo, ISS heritage)
- ▸ESA MELiSSA closed-loop gas separation R&D
- ▸NASA Sabatier reactor downstream gas purifier
Lunar considerations
- ▸Vacuum environment provides natural low-pressure 'desorption' end for PSA — simplifies vacuum pump requirements
- ▸Wide operating temperature range for adsorbents — selection limited by lunar thermal swings
- ▸Long-life adsorbent beds with periodic regeneration (heat or pressure)
- ▸Compact membrane modules suitable for robotic replacement via L1-MNT
- ▸Recovered O2 augments L1-WMS life-support reserves (currently empty in unmanned Ark but capacity provisioned)
Specifications
Functional
| primary function | Refine coarse-separated streams to high-purity single species |
| inputs | Partially-separated gas streams from L3-ISR-VOL-TRAP, Pressurization power from L1-PDM (compressor for PSA), Heat for desorption cycle from L1-TCS |
| outputs | Pure H2 (>99.999%) to L3-ESS-FC-H2TK, Pure O2 (>99.99%) to L3-ESS-FC-O2TK / L1-WMS, Pure N2 (>99.9%) to L3-ISR-VOL-STORE / L1-WMS, Pure He / He-3 (>99.9%) to L3-ISR-VOL-STORE, Trace-component telemetry (GC outlet analysis) |
| h2 output purity percent | 99.999 |
| o2 output purity percent | 99.99 |
| n2 output purity percent | 99.9 |
| he output purity percent | 99.9 |
| throughput kg per day | 10 |
| stages per species | 3 |
| psa cycle time min | 5 |
| membrane module replaceable | True |
Physical
| mass kg | 40 |
| dimensions | Distributed train 1.0 × 0.5 × 0.5 m |
| materials | 316L stainless tubing and vessels, Zeolite 13X / activated carbon adsorbent beds, Pd-Ag alloy membrane (H2 separation), Cellulose acetate / perfluorinated polymer membranes, Pt/Pd on alumina catalyst pellets, Bellows-sealed valves for cycle control |
| operating temperature c | -40, 200 |
| vacuum compatibility | True |
Operational
| power consumption w | 300 |
| thermal range c | -40, 200 |
| lifetime years | 15 |
| mtbf hours | 80000 |
| adsorbent replacement interval years | 7 |
Interfaces
Provides
- Pure H2 for fuel cell reactant inventory
- Pure O2 for fuel cell + life-support
- Pure N2/He/He-3 to dedicated storage
- GC outlet purity verification
Requires
- Partially-separated species streams
- Compressor + valves (~300 W)
- Heat for desorption cycle
Cite this entry
Lunar Ark Codex. "Gas Separation and Purification" (L3-ISR-VOL-SEP). Retrieved 10 September 2026, from https://lunarark.com/entry/L3-ISR-VOL-SEP
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.