Supercritical Water Oxidation: Testing Of Aqueous Wastewater Solutions For Space Applications

Author

Caleb Anthony Riggins, Prairie View A&M University

Date of Award

5-2023

Document Type

Thesis

Degree Name

Master of Science

Degree Discipline

Mechanical Engineering

Abstract

Future extended-duration space missions will only be practicable with effective life support systems that incorporate resource reclamation technologies from bio[1]waste streams. In the case of water reclamation during these missions, Supercritical Water Oxidation (SCWO) has been proposed as an attractive technology. In SCWO processes, organic waste compounds are oxidized in water above its critical point at 374°C and 22 MPa. This work focuses on the SCWO of ersatz wastewater (EWW) streams that simulate waste streams typically observed during International Space Station (ISS) isolated crew missions. A tubular reactor was designed and built at NASA’s Glenn Research Center (NASA-GRC) to allow the oxidation of a continuous flow of ersatz waste at isobaric supercritical conditions. A description of the reactor design and the operational procedures for the heat-up, injection, and establishment of steady-state conditions are presented. The oxidizer in these tests, air (21% O2 with balanced N2) was used and “fuel” (i.e., EWW at different levels of dilution) were independently heated and pressurized as they entered the reactor in a co-flow configuration at supercritical conditions. Experiments were performed at reactor set point temperatures and pressures ranging from 550-610°C and 26-28 MPawith air flows ranging from 0.75 to 2.5 standard liters per minute (SLPM) and fuel flows ranging from 2.0 to 4.0 mL/min. Qualitative assessments of the extent of conversion (odor, foaming, turbidity) are discussed along with quantitative measurements using Raman spectroscopy and Total Organic Carbon (TOC) analysis. Additional co-fuel experiments using ethanol were conducted to increase internal bulk temperatures for conversion of the dilute EWW stream. The overall results of the EWW tests concluded that with appropriate reaction temperatures, equivalence ratios favoring excess air, and residence time of 55 seconds to 93 seconds, near 100% TOC conversion could be achieved. An additional preliminary study for less complex mixtures using urea-aqueous solutions was conducted. Preliminary results show a similar trend in the EWW results, but with challenges in maintaining sufficient bulk fluid temperatures due to reactor constraints, thus limiting complete conversion of ammonia. Preliminary on-time gas measurements taken presents great potential for future gas analysis from detections of CO2 and NO.

Committee Chair/Advisor

Yuhao Xu

Committee Member

Ziaul Huque

Committee Member

Paul O. Biney

Committee Member

Michael C. Hicks

Publisher

Prairie View A&M University

Rights

Date of Digitization

10/07/2023

Contributing Institution

John B Coleman Library

City of Publication

Prairie View

MIME Type

Application/PDF

Recommended Citation

Riggins, C. A. (2023). Supercritical Water Oxidation: Testing Of Aqueous Wastewater Solutions For Space Applications. Retrieved from https://digitalcommons.pvamu.edu/pvamu-theses/1523