Advanced Plasma Pyrolysis Assembly (PPA) Reactor and Process Development

Abstract

Design and development of a second generation Plasma Pyrolysis Assembly (PPA) reactor is currently underway as part of NASA's Atmosphere Revitalization Resource Recovery effort. By recovering up to 75% of the hydrogen currently lost as methane in the Sabatier reactor effluent, the PPA helps to minimize life support resupply costs for extended duration missions. To date, second generation PPA development has demonstrated significant technology advancements over the first generation device by doubling the methane processing rate while, at the same time, more than halving the required power. One development area of particular interest to NASA system engineers is fouling of the PPA reactor with carbonaceous products. As a mitigation plan, NASA MSFC has explored the feasibility of using an oxidative plasma based upon metabolic CO 2 to regenerate the reactor window and gas inlet ports. The results and implications of this testing are addressed along with the advanced PPA reactor development.

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

“…A cleaning cycle was previously examined using a CO 2 plasma. 4 This type of chemical cleaning would likely be useful after several hours of operation. However, based on the images in Figure 11, a more intensive, possibly mechanical method would be required if several days were required between cleanings.…”

“…The PPA hardware used in this effort has been described previously and will not be discussed here. 4 However, testing methods for the 2 nd Generation PPA are described below.…”

“…Previous testing of a CRA ground development unit, called the Sabatier Development Unit (SDU) showed no affect of CH 4 on Sabatier performance when introduced at up to 15 mol% of the H 2 feed stream. 4 Acetylene and the other hydrocarbons leaving the PPA have the potential to further decompose when recycled to the CRA. This would cause fouling of the Sabatier catalyst thereby dramatically reducing the anticipated lifetime of the CRA reactor.…”

Evaluation of Iron-Based Metal-Organic Framework Activation Temperature in Acetylene Adsorption

“…[1][2] The OGA operates via an electrolysis to separate water into oxygen and hydrogen. 3 This hydrogen is then utilized to the CO2 in the carbon dioxide reduction assembly (CRA) through the Sabatier reaction, wherein CO2 is reacted with H2 over a ruthenium-alumina catalyst, 4 producing methane and water. [5][6][7] The methane produced via this process is typically vented, 8 which unfortuantely, results in a loss of about half of the hydrogen atoms utilized in the Sabatier reaction 4 and thus limiting the total oxygen recovery.…”

“…3 This hydrogen is then utilized to the CO2 in the carbon dioxide reduction assembly (CRA) through the Sabatier reaction, wherein CO2 is reacted with H2 over a ruthenium-alumina catalyst, 4 producing methane and water. [5][6][7] The methane produced via this process is typically vented, 8 which unfortuantely, results in a loss of about half of the hydrogen atoms utilized in the Sabatier reaction 4 and thus limiting the total oxygen recovery. One potential method that is being studied to improve the overall oxygen recovery is through the use of the plasma pyrolysis assembly (PPA) to convert methane to acetylene and hydrogen, recovery about 75% of the hydrogen from the methane.…”