Browsing by Author "Hicks, Michael"

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Supercritical Water Oxidation (SCWO) – Observations of Hydrothermal Flames in a Co-Flow Constant Pressure Reactor
(48th International Conference on Environmental Systems, 2018-07-08) Hicks, Michael; Hegde, Uday
Under supercritical temperatures and pressures, water demonstrates profound changes in transport properties, dielectric properties, thermal and caloric state variables, and solvating properties. These attributes combine to create highly efficient oxidizing environments that allow for complete conversion of a wide range of wet organic waste streams. Supercritcal Water Oxidation (SCWO) technology, recognized as “green technology” because of its ability to extract useful energy while converting environmentally challenging waste streams into benign products, is receiving renewed attention for a variety of applications. Of particular interest to NASA is the fact that SCWO is especially well suited for conversion and resource recovery from wet organic wastes. Although SCWO reactors have traditionally been designed as low temperature systems, hydrothermal flames, if properly controlled, can be used to accelerate conversion rates. Results reported in this study demonstrate the feasibility of spontaneously igniting and stabilizing hydrothermal flames in a SCWO reactor operating at constant pressure. Hydrothermal flames are observed as highly localized and luminous reaction zones occurring in supercritical water; i.e., water at conditions above its critical point (218 atm and 374 °C). A co-flow injector is used to inject fuel (inner flow), comprising an aqueous solution ranging from 10%‑vol to 50%‑vol ethanol, and air (annular flow) into a reactor filled with supercritical water at approximately 240 atm and 425 °C. Results show hydrothermal flames are auto‑ignited and quickly stabilize as either laminar or turbulent diffusion flames, depending on the injection velocities, buoyant forces and test cell conditions. Two orthogonal camera views are used; one providing a backlit shadowgraphic image of the co-flow jet and the other providing color images of the flame geometry. Depending on the fuel/air flow ratios, varying degrees of sooting are observed and are qualitatively compared using light absorption measurements from the backlit images.
Supercritical Water Oxidation for Wastewater Recovery – Status on Recent Testing of Ersatz Wastewater and a Conceptual Design for Near-Term Lunar Application
(2024 International Conference on Environmnetal Systems, 2024-07-21) Scott, Sheldon; Hicks, Michael; Hegde, Uday; Kojima, Jun; Gotti, Daniel; Padilla, Rosa E.; Xu, Yuhao
Water is a necessary resource for crewed space exploration missions and the efficient reclamation of aqueous waste streams presents the only long-term viable option for achieving a sustainable extra-terrestrial human presence. Although early Artemis missions are considering water as part of the payload manifest, it would be extremely advantageous if follow-on missions were supplied — either in total or in part — by a reclamation technology that would operate autonomously between missions. NASA Glenn Research Center (GRC) employs a Supercritical Water Oxidation (SCWO) process that has demonstrated the successful destruction of all organic hydrocarbons in a typical International Space Station (ISS) aqueous waste stream. SCWO conversion has shown reductions in Total Organic Carbon (TOC) consistently greater than 99% with reactor residence times less than 3 s and average reaction temperatures ca. 620° C. Recent effort has been directed toward developing a conceptual design based on the current tubular reactor used in the evaluation of the conversion of SCWO. This conceptual design along with the results of recent SCWO conversion experiments will be presented. Recent design enhancements to achieve shorter residence times along with "production simulation" tests will be presented. The diagnostics used in assessing the extent of the waste conversion include a total organic carbon (TOC) analysis, Raman analysis, along with measurements of pH, turbidity, and conductivity. Results obtained from the modified reactor configuration will also be compared to those of the Phase I configuration presented in earlier work.
Supercritical Water Oxidation: A Promising Wastewater Treatment Technology
(51st International Conference on Environmental Systems, 7/10/2022) Figueroa, Adrialis; Flynn, Michael; Padilla, Rosa; Gotti, Daniel; Hegde, Uday; Kojima, Jun; Hicks, Michael
Supercritical water oxidation (SCWO) is a water treatment technology that operates above the critical point of water. The main benefits of SCWO are its ability to completely oxidize organic compounds and mineralize/separate inorganic compounds from wastewater. This suggests SCWO technology can conceptually be applied as a single step water treatment system. Additionally, with proper design and operations it is capable of handling liquid waste streams with high solid loading, thus eliminating the need for extensive pretreatment of the waste stream. This paper provides a description of commercial, academic and NASA developed SCWO reactors. A trade study is presented that shows SCWO is competitive with the International Space Station (ISS) state-of-the-art water recovery systems in all categories except power. However, thermal and mechanical energy recovery approaches are discussed that could be used to reduce SCWO energy consumption to a level that is more competitive with the ISS state-of-the art.