INVESTIGATION ON REMOVAL PROCESS OF ENVIRONMENTAL CONTAMINANTS BY ATMOSPHERIC PRESSURE NON-THERMAL PLASMA

本研究项目于二零零零年四月至二零零三年三月期间，在英国科学院科学研究资助计划(B)的资助下进行。该项目的主要目标是开发利用常压非热等离子体从燃烧烟气中去除NOx的技术和从污染空气中去除稀挥发性有机化合物的技术。为此，还研究了等离子体对这些污染物的去除机理。在50 Hz交流高压驱动下，在圆柱形电抗器中心放置螺栓放电电极的阻挡放电电抗器是最佳的实用电抗器。等离子体工艺与催化剂的结合效果良好，提高了去除空气中挥发性有机化合物的能效。本文建立了一种激光诱导荧光（LIF）诊断脉冲等离子体的方法，该方法采用可调谐窄带KrF准分子层（248nm），对猝灭效应不敏感。观察了脉冲放电后二维OH自由基行为的时间演变。OH自由基的生成和衰变与放电方式和气体条件密切相关。本文还建立了用LIF法检测NO、NO^*和O_2的方法。对于NO检测，还利用了可调谐染料激光器226nm的二次谐波。在等离子体产生的流光区，放电产生OH或分解NO非常活跃。如果NO浓度较低，则存在一些自由基，并随着时间的推移向其他区域发展，分解其他NO。用激光吸收法在二维空间上检测臭氧的生成和衰变，其中臭氧分解（生成O自由基）。也被确认了。目前还在研究放电电流与各种自由基产生之间的关系，以期在不久的将来开发出更有效的环保技术。

This project was carried out from April, 200 to March 2003 supported by the "grant-in-Aid for Scientific Research (B) from JSPS. Main targets of that projet were developing NOx removal technology from the combustion flue gas and dilute VOCs removal technology from contaminated air by using atmospheric pressure nonthermal plasma. For that purpose, the removal mechanism of those contaminants by the plasma was also investigated. The barrier discharge reactor with a bolt discharge electrode at the center of that cylindrical reactor driven by a 50 Hz ac high voltage was found the best practical reactor. The plasma process combined with the catalyst worked well and improved the energy efficiency to remove VOCs from air. Newly a laser-induced-fluorescence (LIF) method was constructed for diagnosis of the pulse plasma using a tunable narrow band KrF excimer laer (248nm) which was very insensible for a quenching effect. Time evolution of two dimensional OH radical behavior was observed just after the pulse discharge. The OH radical generation and decay were strongly dependent on the discharge mode and gas conditions. The LIF method to detect NO, NO^* and O_2 were also developed. For NO detection, second harmonics of a tunable dye laser, 226nm, was also utilized. OH generation or NO decomposition by the discharge were very active in the streamer region made by the plasma. If the concentration of NO is low, some radical exists and progresses to other region to decompose other NO with time.Ozone generation and decay were also detected in two dimension by laser-absorption method where the ozone decomposition (generating O radical).was also identified.The correlation between the discharge current and generation of various kinds of radicals is also studied now resulting the development of more effective environmental techniques in near futre.