Oxidation of hazardous waste in supercritical water: A comparison of modeling and experimental results for methanol destruction Page: 3 of 18
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Oxidation of Hazardous Waste in Supercritical Water: A
Comparison of Modeling and Experimental Results
for Methanol Destruction
P. Barry Butler
University of Iowa, Iowa City, IA
Nina E. Bergan
T. Tazwell Bramlette
Sandia National Laboratories, Livermore, CA
William J. Pitz
Charles K. Westbrook
Lawrence Livermore Laboratory, Livermore, CA
Recent experiments at Sandia National Laboratories conducted in conjunction with
MODEC Corporation have demonstrated successful clean-up of contaminated water in a
supercritical water reactor. These experiments targeted wastes of interest to Department of
Energy (DOE) production facilities. In this paper we present modeling and experimental
results for a surrogate waste containing 98% water, 2% methanol, and parts per million of
chlorinated hydrocarbons and laser dyes. Our initial modeling results consider only
methanol and water. Experimental data are available for inlet and outlet conditions
(composition, flow rate, and temperature), and axial temperature profiles along the outside
reactor wall. The purpose of our model is to study the chemical and physical processes
inside the reactor. We are particularly interested in the parameters that control the location
of the reaction zone. The laboratory-scale reactor operates at 25 MPa., between 300 K and
900 K; it is modeled as a plug-flow reactor with a specified temperature profile. We use
Chemkin Real-Gas to calculate mixture density, with the Peng-Robinson equation of state.
The elementary reaction set for methanol oxidation and reactions of other C) and C2
hydrocarbons is based on previous models for gas-phase kinetics. Results from our
calculations show that the methanol is 99.9% destroyed at 1/3 the total reactor length.
Although we were not able to measure composition of the fluid inside the experimental
reactor, this prediction occurs near the location of the highest reactor temperature. This
indicates that the chemical reaction is triggered by thermal effects, not kinetic rates.
Results from ideal-gas calculations show nearly identical chemical profiles inside the
reactor in dimensionless distance. However, reactor residence times are overpredicted 'jy
nearly 150% using an ideal-gas assumption. Our results indicate that this oxidation process
can be successfully modeled using gas-phase chemical mechanisms. The oxidation process
is characteristic of intermediate temperature chemistry dominated by the hydroxyl and
hydrogen peroxy radical species and the hydrogen peroxide reaction intermediate.
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Butler, P.B. (Iowa Univ., Iowa City, IA (United States)); Bergan, N.E.; Bramlette, T.T. (Sandia National Labs., Albuquerque, NM (United States)); Pitz, W.J. & Westbrook, C.K. (Lawrence Livermore National Lab., CA (United States)). Oxidation of hazardous waste in supercritical water: A comparison of modeling and experimental results for methanol destruction, article, March 17, 1991; [Livermore,] California. (https://digital.library.unt.edu/ark:/67531/metadc1093067/m1/3/: accessed March 25, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.