Date of Award

Summer 2025

Document Type

Open Access Thesis

Department

Mechanical Engineering

First Advisor

Tanvir I. Farouk

Abstract

Supercritical water oxidation (SCWO) has been a topic of immense interest as an effective technique/tool for hazardous aqueous waste disposal. SCWO can be achieved by introducing an oxidizer (e.g., H2O2), or a hydrothermal flame as an internal source of both heat and oxidizer species in an aqueous environment at conditions above the critical point of water (P > 218 atm and T > 647 K). SCWO poses important environmental advantages for the treatment of harmful organic materials contained in waste streams. An SCWO reactor has the potential to be compact in design and therefore can be an ideal alternative to existing technology for wastewater reclamation during long-duration space flight. It is necessary to conduct scientific experiments to obtain fundamental insight into the different coupled processes under these extreme conditions of SCWO where understanding is lacking.

Two continuous flow SCWO reactors have been designed: a capillary flow reactor and a hydrothermal flame reactor. The capillary flow reactor represents a near canonical configuration and has been designed to have accurate control over pressure, temperature, and residence time of the reaction fluid to investigate chemical kinetics under SCWO conditions. This reactor has been fabricated, tested, and experimented with to evaluate its capability. Experiments were conducted for an ethanol-H2O2, H2O system at P = 230 atm and T = 800 – 850 K for different residence times to determine the reactivity of the systems. Samples of the product fluid from this reactor were collected and analyzed with a nuclear magnetic resonance (NMR) spectroscopy machine. Results from these experiments were compared to a representative model using an available chemical kinetic model in the literature. The comparison shows large variations between the measurements and predictions. The reactor can serve in collecting data for extremely high-pressure conditions and assist in developing chemical kinetic models.

The second reactor, referred to as the hydrothermal flame reactor, has been designed for the purpose of visual observation of SCWO in the presence of a flame. This compact continuous-flow reactor can operate at flow rates up to 10 ml/min. The reactor has been fabricated out of Hastelloy X to handle the extreme supercritical conditions of water. Two window ports were installed to be able to conduct visualization. Several structure and flow modeling were performed to assess the design's integrity. The reactor was tested to withstand its design pressures under non-heated conditions. It is envisioned that the reactor will be used for fundamental experiments.

Rights

© 2025, Victor Dubceac

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