Control of volatile organic compounds by an AC energizedferroelectric pellet reactor and a pulsed corona reactor

Two laboratory-scale plasma reactors, an alternating current (AC) energized ferroelectric (high dielectric ceramic) packed bed reactor and a nanosecond pulsed corona reactor, were constructed. This study was done to develop baseline engineering data to demonstrate the feasibility of the application of plasma reactors to the destruction of various volatile organic compounds (VOCs) at PPM levels. Complete destruction was obtained for toluene. Conversions of methylene chloride at 95% and trichlorotrifluoroethane (known as CFC-113) at 67% were achieved for the plasma reactors used. The conversion was dependent on the mean electron energy in the reactor and was also related to how strongly halogen species were bonded with carbon     

Removal of volatile organic compounds in water using low-energyelectron beam

This paper presents the experimental results concerning removal of organic contaminants in water using low energy electron beam radiation. A laboratory scale apparatus for electron beam irradiation of water is described. The absorbed dose of radiation was controlled by water circulation time (1 to 10 min), accelerating voltage (100 to 170 kV), and electron beam current (0.5 to 1.2 mA) for a constant flow rate of 2 kg/min. The volume of the treated water was 1 dm³. The electron beam was generated in vacuum (p<10^-5 Pa), and electrons were injected into the water through the electron transparent window made of titanium foil with a thickness of 25 μm TCE (trichloroethylene) and chloroform dissolved in deionized water were used in the experiment. The dependency of the relative concentration c=C/C₀; where C is the weight content of compound after electron irradiation and C₀ the initial contaminant concentration, on radiation energy density and the absorbed dose are presented. Although the initial contents of the compounds were higher than those occurring in real water sources, it has been found that it is possible to decompose both of the chemicals with high efficiency (total decomposition of TCE, and up to 90% reduction of chloroform) using a relatively low accelerating voltage (<200 kV). The results have indicated that the removal of TCE and chloroform mainly depended on the absorbed dose of electron radiation     

Destruction of residual fumigant using a plasma reactor

Methyl bromide is amply used as a fumigant for soil conditioning in greenhouses, as well as for storage grain conditioning. The treatment is carried out in a confined place, and after treatment the residual gas is vented to the atmosphere. Despite this gas being very toxic, it does not result in harm to human beings because it is vented in open places. However, it is harmful to the atmosphere because its reaction with high-energy photons in the stratosphere reduces the ozone concentration. Therefore, the present investigation is concerned with the study of the feasibility for destruction of the residual fumigant. One of the nonthermal plasma techniques, a packed-bed ferroelectric reactor, was applied for destruction of mixtures of methyl bromide in nitrogen or air. The performance of the process was studied by analyzing the influence and effect of the operating variables on the process efficiency. The results obtained showed the residence time and the applied voltage as the most significant variables. When nitrogen is employed as the carrier gas destruction efficiencies as high as 80% are obtained.     

Treatment of volatile organic compounds contained in soil by pulsed intense relativistic electron beam irradiation

A volatile organic compound (VOC) contained in soil was treated by irradiation with a pulsed intense relativistic electron beam (PIREB). A treatment chamber was filled with the molded soil sample containing formaldehyde solution as a VOC, and was irradiated by a PIREB (2 MeV, 0.4 kA, 70 ns). The soil sample was a mixture of red and black clay representing the Kanto loam in Japan. The diffused formaldehyde of 64% is resolved by firing five shots of the PIREB at the initial concentration of 55 ppm. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Analysis of low-temperature surface discharge plasma products fromgaseous organic compounds

Nonequilibrium low-temperature discharge plasma decomposition products of 1000 ppm gaseous organic compounds contaminated in atmospheric pressure air, nitrogen, or oxygen, such as chlorofluorocarbon (CFC-113), organic chloride (trichloroethylene), and carbon tetrachloride, were studied for a better understanding of the decomposition mechanism of the plasma processing. A gas chromatograph-mass spectrometer was used as a main analyzing equipment. When the decomposition rate is not high (20-80%) for CFC-113, many various halogenated carbons or halogenated hydrocarbons are identified as intermediate products by the plasma processing. As the electric discharge power consumption increases, the decomposition rate of CFC-113 increases and intermediate products decrease. At the decomposition rate of more than 90%, some elemental products of hydrochloric acid, carbon dioxide, and nitrogen suboxide are recognized as final products. On the other hand, if the environmental gas is pure nitrogen without any oxygen and water vapor, the decomposition products are still intermediate with sufficient electric discharge power consumption, suggesting the existence of double decomposition mechanisms of nitrogen radicals and oxygen radicals. In the case of trichloroethylene decomposition, harmful intermediate decomposition products were observed when the decomposition rate was 20-90%     

Removal of volatile organic compounds from air streams andindustrial flue gases by non-thermal plasma technology

Gaseous pollution control technologies for acid gases (NO_x , SO_x, etc.), volatile organic compounds (VOC), greenhouse gases, ozone layer depleting substance (ODS), etc., have been commercialized based on catalysis, incineration and adsorption methods. However, non-thermal plasma techniques based on electron beams and corona discharges become significant due to advantages such as lower cost, higher removal efficiency, smaller space volume, etc. In order to commercialize this new technology, the following needs faster investigation: pollution gas removal rates, energy efficiency of removal, pressure drop of reactors, usable byproduct production rates, identification of major fundamental processes, and optimization of reactor and power supply for an integrated system. In this work, recent development of gaseous pollution control technology based on discharge plasmas is reviewed critically and the principle of processes and reactor technologies are outlined     

A study of NO removal by packed-beads discharge reactor

Recently, air pollution has become a serious problem; photochemical smog and acid rain are typical phenomena. NO_x is a serious air pollutant and a toxic gas. In spite of an attempt to reduce the amount of NO_x emitted, the density of NO_x in the atmosphere has remained on a stable level, or even become worse. Here, the authors propose a new reactor in which the gap area is filled as a single layer of glass plates and beads. They expect that surface and silent discharges are generated simultaneously in the same space. In this paper, the removal of NO_x from a dry NO/N₂ mixed gas by barrier discharge among glass beads in the reactor is experimentally investigated. The experiments are carried out for the frequency 50 Hz, with applied voltage from 0 to 20 kV_pp and a gas flow rate from 0.4 to 1.4 L/min. The results show that the NO and NO_x removal rates with glass beads are higher than those without glass beads at the same flow rate or residence time. Thus, the new reactor in which the gap area is filled with glass beads is more effective for NO_x removal     

漆包线残留挥发性有机物HS-GC-MS法测定分析

用HS-GC-MS(顶空进样气相色谱-质谱)分析法测定漆包线漆膜中挥发性有机物的残留量,适用于各种类型漆包线漆膜中残留挥发性有机物的痕量分析。本方法检出限为10-8(ω),线性范围为2.5×10-8～5×10-6(ω),加标平均回收率超过95%。     

脉冲等离子体反应器放电特性研究

脉冲放电等离子体被广泛用于气态污染物处理的研究,放电参数直接影响反应器内等离子体状态,进而影响污染物的去除效果,研究不同条件下的放电特性可为脉冲等离子体技术的应用提供参考.本文利用线板式脉冲等离子体反应器, BPFN型高压脉冲电源供电, 研究了电源电容、极板间距及介质阻挡对放电特性的影响.结果表明:增大电源电容可以有效地提高电源能量效率;增大极板间距,峰值电压VP增大,峰值电流IP减小,脉宽减小,波形更加理想;陶瓷板阻挡放电可解决间隙火花放电,使脉冲电晕放电空间分布均匀,在大范围内提高电源能量效率.     

交联聚乙烯电缆绝缘气体检测系统算法研究与设计

本文基于电化学传感器研制便携式仪器检测交联聚乙烯电力电缆绝缘挥发物中“特征气体”的浓度,并设计气腔以降低气体耗散速度。为了提高检测效率与气体浓度,采用永磁无刷微型泵提高气体流速。考虑仪器便携性,设计滑模控制器转子估计速度,无需速度传感器即可完成速度闭环控制。设计乒乓控制算法降低PWM高频信号对气体传感电路的影响,提高检测系统的信噪比。分别在实验室与测试现场对比速度开环与速度闭环情况下的检测时间与气体浓度,结果表明,相对速度开环控制,速度闭环时仪器的检测时间缩短至少10倍,检测浓度提高20%以上。     

超级电容器放电测试用电子负载

设计了一个电子负载,用于超级电容器的放电测试,工作在定电流(CC)模式.主要分两部分:恒流源部分和逻辑控制部分.恒流源部分采用CMOS集成电路驱动的MOSFET设计,应用功率MOSFET工作在恒流区时,漏极电流不随着VDS的电压而变化的恒流特性.逻辑控制部分通过数字电路实现,由计数器控制恒流源单元导通或关断.电子负载电路设计简单,受温度影响小,可以对超级电容器特性进行测试,从而了解超级电容器的性能,更好地应用超级电容器.     

Hysteresis effect of corona discharge in a narrow coaxial wire-pipedischarge tube with gas flow

An experimental investigation has been conducted to study corona discharge in a narrow tube. Narrow or capillary corona discharge (discharge tube diameter d≈1-20 mm) is used for many industrial applications such as flue gas cleaning corona-induced plasma reactors, ion sources, and electrohydrodynamic heat exchangers. In this work, corona discharge characteristics of a narrow coaxial wire-pipe discharge tube with gas flow are experimentally investigated. The results show that, unlike normal corona discharge, a hysteresis in the corona discharge current-voltage characteristic was observed for narrow tube discharges. The onset of the corona discharge was observed to be significantly dependent on the gas temperature and gas flow rates     

燃料电池用微通道反应器的研究现状

微通道反应器,是一种借助特殊微加工技术以固体基质制造的可用于进行化学反应的三维结构单元。它较常规反应器体积小一个数量级以上,安全性好,适用于汽车或移动电源;而且它可以利用现有的加油站和加气站直接进行能量补给,解决了通常难解决的燃料供给问题。重点介绍了它的结构和各个组成部分及相关的国内外研究现状。     

用电渗法测定电池碳棒的毛细管半径

利用电渗法可以测定电池碳棒毛细管半径r值.r值大的碳棒,透气性优于r值小的;r值为零的,说明碳棒毛细管已全被堵塞或不存在毛细管,没有透气性.r值是鉴定碳棒透气性的一项很有用的指标.用本方法测得的毛细管半径是宏观平均值.     

在植物基因工程中应用的高压脉冲放电基因枪

本文介绍了一种用于植物基因工程领域的外源基因导入技术和高压放电基因枪的工作原理及关键结构，采用高速摄影法获得了射弹的运动速度。当储能为500J时，测得第一放电电流峰值为19．3kV，电流上升时间为9μs。生物学试验结果表明，高压放电基因枪能有效地将外源基因导入植物细胞并得到表达。     

Atmospheric pressure of nitrogen plasmas in a ferroelectric packed bed barrier discharge reactor. Part I. Modeling

Numerical modelling of ferroelectric packed bed nonthermal plasma reactor has been conducted to predict plasma parameters in a pure nitrogen environment. Simplified time averaged one-dimensional physical model based on Poisson's equation for electric field and transport equation for electrons was developed. The mean electron energy was obtained by a swarm relationship from calculated electric field profiles and plasma neutral conditions. For chemical model, N/sup +/, N/sub 2//sup +/, N/sub 3//sup +/, N/sub 4//sup +/, N/sup */, N/sub 2//sup */ and electron were considered where N/sup */ and N/sub 2//sup */ are the total excited atoms and molecules, respectively. The results show that all the plasma parameters increase with increasing applied AC voltage and pellet dielectric constant. The numerical results also show that the dominant ion is N/sub 4//sup +/ and the metastable molecule density is much higher than radical and the electron densities at atmospheric gas pressure.     

超级电容器用有机电解液的研究

介绍了一种有机电解液体系活性碳基超级电容器的制作过程,对比研究了6种不同的有机电解液,并组装成超级电容器,测试了其电化学性能.结果表明:Et4NBF4/PC体系适合作为超级电容器的电解液;LiPF6/PC、LiPF6/EC PC体系因发生分解反应,不适宜用于超级电容器.     

发电机局部放电在线监测中的抗干扰技术

大型发电机局部放电在线监测的关键技术之一是如何掏现场的各种电磁干扰。本文对现场干扰的特性进行了分析,并提出了相应的抑制方法。最后介绍了已成功用于发电机局部放电在经监测仪中的抗干扰系统。对现场实测数据的处理结果表明这些方法是有效的。     

Simultaneous qualitative analysis of volatile and nonvolatile organic contamination on silicon wafer by online pyrolysis mass spectrometry

This paper presents a new analytical setup that aims for a qualitative analysis of both volatile and nonvolatile organic contamination simultaneously from one whole silicon wafer. The aim was to develop a screening method that can be used for the identification of the source(s) of organic contamination for quality control in the manufacturing process. The model compounds used in the analysis were a solvent (toluene), a photoresist, and a resist stripper solution. The instrumental setup consisted of a heatable chamber for sample handling and an online mass spectrometer for detection. The organic contamination could be directly desorbed from the surface of the silicon wafer (volatile organic components) or pyrolyzed/desorbed from the surface in air atmosphere at elevated temperature (nonvolatile components), and consequently detected by the mass spectrometer. The mass spectra and the ion chromatograms obtained by the mass spectrometer during the heating of the silicon wafer can be used for the identification of all organic compounds on the silicon wafer and thus, for the identification of a possible source of contamination.     

Characteristics of ozone generation by a diffuse glow discharge at atmospheric pressure using a double discharge method

In this research, a diffuse glow discharge generated by a double discharge is used to improve the efficiency of ozone generation. In this method, corona discharge occurs in the space between the cathode and the trigger electrode covered by Pyrex glass tubes, set in a groove cut on the cathode. Thus, many initial electrons are generated around the cathode. In the present research, experiments were done in air (O₂/N₂ mixture) at atmospheric pressure and the discharge repetition frequency was 1 Hz for all experiments. The maximum ozone concentration generated was about 150 ppm. The average ozone yield was about 400 g O₃/kWh, much higher than the typical yield of about 100 g O₃/kWh. The efficiency of energy transfer from energy stored in storage capacitor C₁ to the main discharge zone was about 40% to 50%. © 1999 Scripta Technica, Electr Eng Jpn, 127(2): 8–14, 1999