2007 Fiscal Year Final Research Report Summary
OH Radical Generation and Reaction in Water Enhanced by Gas-Liquid-Plasma Three Phase Flow
| Project/Area Number |
18360133
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
電力工学・電気機器工学
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
YASUOKA KOICHI Tokyo Institute of Technology, GRADUATE SCHOOL OF SCIENCE AND ENGINEERING, PROFESSOR (00272675)
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| Project Period (FY) |
2006 – 2007
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| Keywords | Gas-Liquid Two-Phase Flow / OH Radical / Dielectric barrier discharge / Plasma in Water / 難分解物質 |
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| Research Abstract |
Many types of pulsed electrical discharges in water have been extensively studied for environmental applications, especially for use in the decomposition of persistent materials in drinking water and wastewater treatments. In this study, the plasma-water interactions were enhanced in the mixture phase of gas, liquid and plasma phases. Two types of plasma reactors were developed and the efficient decomposition of persistent material was studied.
In reactor (A), pulsed dielectric barrier plasmas are generated in argon, neon or oxygen bubbles of gas-liquid two-phase flow. The flow classified as the Churn flow enabled to enhance the reaction between the pulsed dielectric barrier plasmas and persistent materials especially at the gas-liquid boundaries. The plasma initiated at the center of the bubbles then concentrated at the gas-liquid boundaries. 10-ppm acetic acid as a persistent material was successfully decomposed by repetitive operations up to 10 kHz. The decomposition rate and efficiency of the acetic acid were measured by evaluating the total organic carbon (TOC) concentration of the solution. In reactor (B), bubbles are formed by feeding a small amount of oxygen or argon gases through the tiny hole in the center of a dielectric spacer. The pulsed plasmas were initiated at the tiny hole then extended along the inner surface of argon or oxygen bubbles. The radical formation efficiency depends on the plasma shapes that changed from uniform one to constricted one during the duration of 150 ns. 20 plasmas were generated simultaneously using one exiting circuit and evaluated on the OH generation efficiency by changing the plasma energy densities. Time varying OH radical densities were measured by LIF method using small pulsed streamer plasmas instead. The life time and special distribution of OH revealed the optimum conditions on the surface plasmas generation for efficient production of OH radicals.
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