Browsing by Author "Wheeler, Richard R."
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Item Hydrogen Purification in Support of Plasma Pyrolysis of Sabatier Derived Methane(45th International Conference on Environmental Systems, 2015-07-12) Holtsnider, John T.; Wheeler, Richard R.; Dewberry, Ross H.; Abney, Morgan B.; Greenwood, Zachary W.The use of microwave regenerative sorption media for purification of hydrogen has been studied. The Sabatier Assembly recovers oxygen from carbon dioxide while consuming hydrogen and producing methane and water. The Plasma Pyrolysis Assembly (PPA) is being developed to recover most of the hydrogen from the methane. Acetylene and smaller amounts of other hydrocarbons are produced as byproducts of PPA operation. The present project is directed toward purifying the hydrogen product gas using sorption media and subsequently thermally regenerating the media using microwave power. The penetrative nature of microwave heating is utilized to efficiently drive gas desorption from the physical sorbents. Microwave heating drives off captured contaminants from a sorbent bed (which is held at relative vacuum) during regeneration. A series of molecular sieves, activated carbons and high surface area forms of alumina and silica were evaluated as candidate sorbent materials. Additionally, water vapor removal with the use of silica gel was evaluated. As a result of this research, hydrogen recovery from Sabatier methane is improved, thereby further closing the air-loop. Such increases in efficiency are necessary for crewed deep space exploration missions.Item Increased Oxygen Recovery from Sabatier Systems Using Plasma Pyrolysis Technology and Metal Hydride Separation(45th International Conference on Environmental Systems, 2015-07-12) Greenwood, Zachary W.; Abney, Morgan B.; Perry, Jay L.; Miller, Lee A.; Dahl, Roger W.; Hadley, Neal M.; Wambolt, Spencer R.; Wheeler, Richard R.State-of-the-art life support carbon dioxide (CO2) reduction technology is based on the Sabatier reaction where less than 50% of the oxygen required for the crew is recovered from metabolic CO2. The reaction produces water as the primary product and methane as a byproduct. Oxygen recovery is constrained by the limited availability of reactant hydrogen. This is further exacerbated when Sabatier methane (CH4) is vented as a waste product resulting in a continuous loss of reactant hydrogen. Post-processing methane with the Plasma Pyrolysis Assembly (PPA) to recover hydrogen has the potential to dramatically increase oxygen recovery and thus drastically reduce the logistical challenges associated with oxygen resupply. The PPA decomposes methane into predominantly hydrogen and acetylene. Due to the highly unstable nature of acetylene, a separation system is necessary to purify hydrogen before it is recycled back to the Sabatier reactor. Testing and evaluation of a full-scale Third Generation PPA is reported and investigations into metal hydride hydrogen separation technology is discussed.Item Third Generation Advanced PPA Development(44th International Conference on Environmental Systems, 2014-07-13) Wheeler, Richard R.; Hadley, Neal M.; Wambolt, Spencer R.; Abney, Morgan B.A Phase 3 advanced development project has culminated in the design and fabrication of a third generation Plasma Pyrolysis Assembly (PPA), recovering up to 75% of the hydrogen currently lost as methane in Sabatier reactor effluent. By doing so, the PPA helps to minimize life support resupply costs for extended duration missions. The 3-year development effort, completed as part of NASA’s Atmosphere Revitalization Resource Recovery task, has resulted in a fully functional stand-alone 5-CM (crew member) capacity PPA prototype. This device, recently delivered to NASA-MSFC, embodies the current state of the art in microwave methane plasma pyrolysis. At 90% single pass conversion the third generation PPA shows a ten-fold increase in processing rate capability over the first generation PPA, improves microwave to chemical energy conversion efficiency by three-fold (to 22%), and maintains a low residual carbon production rate at 0.20% of carbon from converted methane. Additional third generation technology advancements include increased process autonomy, incorporation of a regenerative residual carbon trap and in-situ reactor cleaning using CO2 plasma oxidation. Future development work must focus on fully autonomous operation, increased carbon trap capacity, more complete regeneration and improved process energy efficiency.