Pulsed Power Discharges in Water
<p>An Electrohydraulic Discharge Process (EHD) for the treatment of hazardous chemical wastes in water has been developed. Liquid waste in 4 L EHD reactor is directly exposed to high-energy pulsed electrical discharges between two submerged electrodes. The high-temperature (>14,000 K) plasm...
| Summary: | <p>An Electrohydraulic Discharge Process (EHD) for the treatment of hazardous chemical wastes in water has been developed. Liquid waste in 4 L EHD reactor is directly exposed to high-energy pulsed electrical discharges between two submerged electrodes. The high-temperature (>14,000 K) plasma channel created by an EHD discharge emits ultraviolet radiation, and produces an intense shock wave as it expands against the surrounding water. A simulation of the EHD process is presented along with experimental results. The simulation assumes a uniform plasma channel with a plasma that obeys the ideal gas law and the Spitzer conductivity law. The results agree with previously published data. The simulation is used to predict the total energy efficiency, energy partitioning, maximum plasma channel temperature and pressure for the Caltech Pulsed Power Facility (CPPF). The simulation shows that capacitance, initial voltage and gap length can be used to control the efficiency of the discharge.</p>
<p>The oxidative degradation of 4-chlorophenol (4-CP), 3,4-dichloroaniline (3,4-DCA), and 2,4,6 trinitrotoluene (TNT) in an EHD reactor was explored. The initial rates of degradation for the three substrates are described by a first-order rate equation, where k<sub>0</sub> is the zero-order rate constant that accounts for direct photolysis; and k<sub>1</sub> is the first-order term that accounts for oxidation in the plasma channel region. For 4-CP in the 4.0 L reactor, the values of these two rate constants are k<sub>0</sub> = 0.73 ± 0.08 µM, and k<sub>1</sub>=(9.4 ± 1.4) x 10<sup>-4</sup>. For a 200 µM 4-CP solution this corresponds to an overall intrinsic zero-order rate constant of 0.022 M s<sup>-1</sup>, and a G-value of 4.45 x 10<sup>-3</sup>.</p>
<p>Ozone increases the rate and extent of degradation of the substrates in the EHD reactor. Combined EHD/ozone treatment of a 160 µM TNT solution resulted in the complete degradation of TNT, and a 34% reduction of the total organic carbon (TOC). The intrinsic initial rate constant of TNT degradation was 0.024 M s<sup>-1</sup>. The results of these experiments demonstrate the potential application of the EHD process for the treatment of hazardous wastes.</p> |
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