Decomposition of volatile organic compounds in a positive column glow discharge plasma

Conference · Thu Dec 31 04:00:00 EST 1998

OSTI ID:346906

Ding, W X; Ma, C Y ^[1]; McCorkle, D L; Pinnaduwage, L A ^[1]

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1. Oak Ridge National Lab., TN (United States)

Plasma processing has been used for remediation of dilute mixtures of volatile organic compounds (VOCs) in air. Energy efficiency is the main concern of these plasma technologies because large volume emissions have been treated. The destruction mechanisms of VOCs in plasmas greatly affect the economics of the process. The authors are exploring a novel plasma chemical scheme which is based on a extremely large dissociative electron attachment cross section. In this scheme highly-excited states of VOCs are excited by long-lived rare gas metastable states. Measurements were performed in a positive column glow discharge tube with a gas flow-through configuration. The methylene chloride (CH{sub 2}Cl{sub 2}) and benzene (C{sub 6}H{sub 6}) were diluted in rare gases helium, neon and argon respectively to around 400 ppm. Gas mixture passed through the discharge region and was partly collected in a sampling loop for subsequent gas chromatographic (GC) analysis. Discharge parameters were current 0--15 mA, discharge voltage 200--700 V, and gas pressure 2--22 torr. The percentage of remaining of VOCs decreased exponentially with increase of energy density (Power/Flow) delivered to the plasma. Destruction efficiency was almost proportional to gas pressure below 15 torr and saturated for higher pressure. Destruction efficiency is best for argon mixtures, and worst for helium mixtures. These observations are consistent with the proposed mechanism. Molecules could be excited by abundant metastable atoms produced by the discharge. The increase of pressure (below 16 torr) in a positive column discharge reduces the electron temperature. Destruction efficiency is better for low electron temperature. This implies that electron attachment process is important.

• Sponsoring Organization: National Science Foundation, Washington, DC (United States); USDOE, Washington, DC (United States)
• DOE Contract Number: AC05-96OR22464
• OSTI ID: 346906
• Report Number(s): CONF-980601--
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
54 ENVIRONMENTAL SCIENCES
AIR POLLUTION CONTROL
BENZENE
DECOMPOSITION
DISSOCIATION
ELECTRON ATTACHMENT
ENERGY EFFICIENCY
GLOW DISCHARGES
METHYLENE CHLORIDE
ORGANIC COMPOUNDS
PLASMA PRODUCTION
VOLATILE MATTER