Browsing by Author "Green, Robert D."
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Item Characterization of carbon particulates in the exit flow of a Plasma Pyrolysis Assembly (PPA) reactor(45th International Conference on Environmental Systems, 2015-07-12) Green, Robert D.; Meyer, Marit E.; Agui, Juan H.; Berger, Gordon M.; Vijayakumar, R.; Abney, Morgan B.; Greenwood, ZacharyThe ISS presently recovers oxygen from crew respiration via a Carbon Dioxide Reduction Assembly (CRA) that utilizes the Sabatier chemical process to reduce captured carbon dioxide to methane (CH4) and water. In order to recover more of the hydrogen from the methane and increase oxygen recovery, NASA Marshall Space Flight Center (MSFC) is investigating a technology, plasma pyrolysis, to convert the methane to acetylene. The Plasma Pyrolysis Assembly (or PPA), achieves 90% or greater conversion efficiency, but a small amount of solid carbon particulates are generated as a side product and must be filtered before the acetylene is removed and the hydrogen-rich gas stream is recycled back to the CRA. In this work, we present the experimental results of an initial characterization of the carbon particulates in the PPA exit gas stream. We also present several potential options to remove these carbon particulates via carbon traps and filters to minimize resupply mass and required downtime for regeneration.Item Development of an Inertial and Cold Trap Filter For Carbon Fines Management(51st International Conference on Environmental Systems, 7/10/2022) Agui, Juan; Green, Robert D.; Berger, GordonThe Plasma Pyrolysis Assembly (PPA) is a methane processing technology that integrates with the Sabatier Reactor Assembly (SRA) to further advance oxygen loop closure for spaceflight. A problematic reaction byproduct of the PPA is very fine carbon dust which accumulates on the walls of the reactor and migrates to downstream Environmental Control and Life Support System (ECLSS) components with the effluent flow. The reactor is regenerated periodically by generating a CO2 plasma within the reactor to clean the internal walls and microwave stub. To address the flow of carbon dust to downstream components, the PPA will require an effective carbon capture management system. While various methods have been attempted through prototype testing, the effective filtering and regenerative performance of these devices remains a challenge. A new approach is being explored which will provide large carbon dust holding capacity by flow inertial impaction and recirculation and low temperature particle quenching techniques. The technique involves a custom-designed housing to produce a strong and large recirculating pattern to remove the dust through inertial forces and confine it to a large collection cup. The collection cup is enshrouded in a cold trap to quench the PPA effluent and precipitate the remaining carbon from the reaction. The flow then passes through a single stage baffle and tube filters before exiting through the outlet at the top of the housing. A prototype of this concept was built and is being tested with simulant dust. This report will highlight the design and operation of the prototype and provide preliminary test results.Item Development of test protocols for International Space Station particulate filters(44th International Conference on Environmental Systems, 2014-07-13) Green, Robert D.; Vijayakumar, R.; Agui, Juan H.Air quality control on the International Space Station (ISS) is a vital requirement for maintaining a clean environment for the crew and the hardware. This becomes a serious challenge in pressurized space compartments since no outside air ventilation is possible, and a larger particulate load is imposed on the filtration system due to lack of gravitational settling . The ISS Environmental Control and Life Support System (ECLSS) uses a filtration system that has been in use for over 14 years and has proven to meet this challenge. The heart of this system is a traditional High- Efficiency Particulate Air (HEPA) filter configured to interface with the rest of the life support elements and provide effective cabin filtration. Over the years, the service life of these filters has been re-evaluated based on limited post-flight tests of returned filters and risk factors. On earth, a well designed and installed HEPA filter will last for several years, e.g. in industrial and research clean room applications. Test methods for evaluating these filters are being developed on the basis of established test protocols used by the industry and the military. This paper will discuss the test methods adopted and test results on prototypes of the ISS filters. The results will assist in establishing whether the service life can be extended for these filters. Results from unused filters that have been in storage will also be presented to ascertain the shelf life and performance deterioration, if any and determine if the shelf life may be extended.