Kinetic investigation of the oxidation of naval excess hazardous materials in supercritical water for the design of a transpiration-wall reactor

Abstract

A series of experiments was conducted in Sandia's supercritical fluids reactor (SFR) to generate data for the design of a transpiration-wall supercritical water oxidation (SCWO) reactor. The reactor is intended for the disposal of excess hazardous material generated on naval vessels. The specific design parameters for the system require an accurate knowledge of destruction efficiency vs. time and temperature. Three candidate materials that are present in large quantity on ships were selected for testing. The experiments consisted of oxidizing these materials in Sandia's SFR at isothermal conditions over the temperature range of 400 "C -550 "C at 24.1 MPa.A small extrapolation of the results shows that these materials can be adequately destroyed (to 99.9% destruction removal efficiency, DRE, based on total organic carbon (TOC) in the effluent) in approximately 5 seconds at 600°C. The results vary smoothly and predictably with temperature such that extrapolation to higher temperatures beyond the experimental capabilities of the SFR can be made with reasonable confidence. The preliminary design of the transpiration-wall reactor has a rapid heat-up section within the reactor vessel that requires the addition of a fuel capable of quickly reacting with oxygen at temperatures below 500 "C. Several candidate alcohols and JP-5 jet fuel were evaluated in this context. The oxidation rates for the alcohols were examined using in situ Raman spectroscopy as the analytical tool. This method permitted the observation of partially oxidized intermediates and a measurement of the formation and consumption of carbon monoxide in the system. In addition, the potential utility of supplying the oxidizer line with hydrogen peroxide as an additive to enhance rapid ihitiation of the feed at unusually low temperatures was investigated. Experiments were conducted in the Supercritical Constant Volume Reactor (SCVR) using hydrogen peroxide as the initial oxidizing species. The results show that this concept as a method of enhancing low temperature reactivity appears to fail because thermal decomposition of the hydrogen peroxide is more rapid than the fuel oxidation rate at low temperatures. 3/4

Hydrothermal oxidation of Navy shipboard excess hazardous materials

“…The model presented in the report, and the investigations in [13], indicate it should be similar to that ofthe JP-5. These results are consistent with basic chemical reaction data generated and documented in refma?…”

“…All three materials are various compositions cf hydrocarbons with selected additives. The compositions are described in [13]. Also described in [13] are the results &om Phase 1 testing.…”

“…The compositions are described in [13]. Also described in [13] are the results &om Phase 1 testing. The results from Phase II testing are described in this paper.…”

Engineering kinetics for hydrothermal oxidation of hazardous organic substances

“…ble in water. Ten data points from Rice et al 1997 on TOC conversion as affected by temperature or residence time, spanning TOC conversions from 0.738 to 0.998 were used to Ž . obtain best-fit parameter values A and E for a single a first-order reaction kinetic model.…”

“…Rice et al 1997 studied SCWO of JP-5 jet fuel, Velsicol H537 hydraulic fluid, and Delo 400 motor oil at throughputs of about 30 grh. Wastes were treated individually in an isobaric and nearly isothermal tubular plug-flow reactor.…”