Decomposition of benzene using a nonthermal plasma reactor packedwith ferroelectric pellets

The decomposition of benzene in air was carried out using a nonthermal plasma discharge reactor packed with ferroelectric materials. It was found that ferroelectric materials of 1-2 mm in diameter with a relative dielectric constant of ϵ_r>1100 decomposed benzene with greatest energy efficiency. Benzene at low concentrations (below 50 ppm) was completely decomposed to CO and CO₂ with no formation of other hydrocarbons. The ratio of CO to CO₂ produced from benzene was minimized under an atmosphere containing more than 5% O₂     

Reduction of CO2 from combustion gases by DC coronatorches

An experimental investigation has been conducted to reduce CO₂ from combustion gases by using DC corona torches. This plasma device, the corona torch, consists of two small-diameter hollow electrodes. The gas flow enters the upstream cylindrical hollow electrode and exits at a downstream cylindrical hollow electrode. Therefore, all the reactive gas passes through the active corona-induced plasma zone. High-speed gas flow near the exit of the electrode cools the electrodes; hence, the chemical reactions and the stability of discharge are enhanced. Various amounts of argon gas were added to the model combustion gas (N₂:O₂:CO₂=0.745:0.15:0.105). The results show that the CO₂ gas reduction rate increases with increasing corona current when the model gas is seeded with argon. The CO₂ gas reduction rate increases when the percentage of argon gas in the mixture increases up to 20%, and decreases when the percentage of argon gas in the mixture increases above 20%     

Effects of Temperature, Voltage Properties, and Initial Gas Composition on the Plasma Reforming of Aliphatic Hydrocarbons With $hbox{CO}_{{bf 2}}$

CO₂ reforming of methane, propane, and neopentane was investigated with a ferroelectric packed-bed and silent discharge plasma reactors in N₂ at temperature from 303 to 433 K. The conversions of the substrate hydrocarbons and CO₂, and the yields of H₂ and CO were expressed as functions of reactor energy density irrespective of voltage waveform. The positive temperature effect on the hydrocarbon conversions and the product yields can be ascribed to the promotion of secondary decomposition of the hydrocarbons induced by radicals formed in situ because reactor power consumption was not affected by reaction temperature at the same frequencies and peak-to-peak voltages. At 303 K, the reactivity of the hydrocarbon decreased in the following order: neopentane > propane > methane. At 433 K, propane and neopentane showed the same reactivities. The molar ratio of H₂ to CO was affected by hydrocarbon structure and the initial concentration ratio of CO₂ to the carbon atom in hydrocarbon, but not by reaction temperature. Better carbon balances were obtained for all the hydrocarbons at 433 K than at 303 K, suggesting higher reaction efficiencies at 433 K. Carbon balance was also affected by initial gas composition, and the carbon atoms in reacted neopentane were quantitatively recovered as CO, CO₂ and lighter hydrocarbons at 10 of [CO₂]/[neopentane].     

Reduction of NOx from natural gas combustion flue gasesby corona discharge radical injection techniques [thermal power plantemissions control]

An experimental investigation has been conducted to reduce NO_x in natural gas combustion flue gases by means of corona-discharge-activated ammonia/methane radical injection methods. Multihole-type corona radical injectors are used in the present investigation. Experiments were conducted for the simulated natural gas combustion flue gas (N₂:O₂:CO₂:NO=83.96:8:8:0.04) flow rate from 1 to 200 L/min, the activation voltage (DC or pulse) from 0 to 40 kV, and the Ar-ammonia or Ar-methane mixture gases flow rate from 0 to 200 mL/min. The results show that the NO_x reduction increases with increasing activation voltage and nonmonotonically depends on ammonia/methane stoichiometry     

微富氧燃烧技术下氨法脱碳试验研究

针对微富氧燃烧下烟气组分（CO₂体积分数约30%~40% ）,利用填料塔进行了氨法脱碳试验研究,考察了烟气CO₂浓度、氨水浓度、吸收液pH值、氨水流量、烟气温度、烟气流量等因素对CO₂脱除率的影响。试验结果表明：① 随氨水浓度、吸收液pH值、氨水流量增加以及填料增多,CO₂脱除率升高,但在pH值=10.5时出现一定波动;② 烟气温度为50 ℃时,CO₂脱除率最高;③ 当氨水中NH₃质量分数大于4%时,烟气中CO₂脱除率达90%以上,微富氧燃烧条件下,单位质量氨（1 kg NH₃）对烟气中CO₂吸收质量为0.32 kg,脱碳效率是常规燃烧条件下的2倍多,因此采用微富氧燃烧有利于缩小吸收塔和再生塔的体积、降低能耗。     

CO2体积分数对燃煤细颗粒物在水汽环境中凝结长大的影响

为研究燃煤烟气中CO₂体积分数对细颗粒物在水汽环境中凝结长大效果的影响,建立了计算模型并搭建了实验平台,分别从理论计算和实验研究两方面探讨了CO₂体积分数对细颗粒物凝结长大效果的影响。结果表明:随着CO₂体积分数升高,混合烟气的热、质扩散系数均降低,生长管内平均过饱和度增加,细颗粒物长大效果明显;管壁温度越高,随着CO₂体积分数的提高,细颗粒物粒径越大。     

Decomposition of benzene using alumina-hybrid and catalyst-hybridplasma reactors

In order to investigate the effects of alumina and metal ions in plasma discharge, plasma reactors packed with a mixture of BaTiO₃ pellets and porous Al₂O₃ pellets (alumina-hybrid reactor), and with a-mixture of BaTiO₃ pellets and metal-supported Al₂O₃ pellets (catalyst-hybrid reactor) were examined for oxidation of dilute benzene in air. It was found that the oxidative decomposition of benzene was enhanced by concentrating benzene on the Al₂O₃ pellets and the catalyst pellets. Furthermore, the selectivities to CO ₂ in the alumina-hybrid reactor and the catalyst-hybrid reactors were higher than those in the plasma reactor packed with BaTiO ₃ pellets alone. In particular, the selectivities to CO₂ in the catalyst-hybrid reactors using Ag, Co, Cu and Ni/Al₂ O₃ were higher than those from the alumina-hybrid reactor. In addition, the presence of the alumina and catalysts suppressed the formation of N₂O     

Reduction of NOx from combustion flue gases bysuperimposed barrier discharge plasma reactors

NO_x reduction from combustion flue gases by superimposed barrier discharge plasma reactors is experimentally investigated. The experiments are conducted for applied voltages from 0 to 28 kV, flue gas rates from 0.5 to 2 L/min, ammonia mixture concentrations from 0.7 to 2.65 stoichiometry, and applied voltage phase differences from 0° to 180°, where two 60-Hz AC power supplies are used. The results show the following: (1) NO_x reduction rate decreases with increasing discharge power for surface discharge operations, however, NO_x reduction rate increases with increasing discharge power for silent and superimposing discharge operating modes; (2) NO_x reduction rate increases with increasing discharge power, gas flow rate and ammonia stoichiometry under in-phase operations; (3) NO_x reduction rate for out-of-phase operations is much higher compared with in-phase operations, however, NO_x reduction rate has an optimum condition on ammonia stoichiometry, discharge power, and gas flow rate; and (4) energy efficiency of NO_x reduction increases with increasing ammonia mixture and gas flow rate and decreases with increasing discharge power     

Recovery of SF6 from N2/SF6 gasmixtures by using a polymer membrane

The investigation of gas recovery from N₂/SF₆ gas mixtures using a polymer membrane has been reported. It has been shown that the purity of recovered gas, the recovery loss, and the gas handling speed depend on various parameters such as original gas mixing ratio, gas feeding pressure, gas flow rate, and temperature of the membrane. A gas recovering system with two membrane separators connected in cascade has proved to be very efficient in attaining high purity in a recovered gas, with negligibly small recovery loss and high handling speed for practical use. Furthermore, this system could be applied for CO₂/SF₆, He/SF ₆ and even for ternary mixtures such as N₂/CO₂/SF₆ without any modification in the system, where we expect much better performance in comparison with N ₂/SF₆     

Breakdown Characteristics of N2O Gas Mixtures for Quasiuniform Electric Field under Lightning Impulse Voltage

From the viewpoint of mitigating global warming by SF₆ gas, this paper discusses breakdown (BD) characteristics of different electronegative gas mixtures with N₂O gas as SF₆ gas substitutes for quasi-uniform electric field under lightning impulse voltage applications. Experimental results revealed the positive synergism in breakdown strength of binary N₂O / CO₂ and ternary N₂O / CO₂ / O₂ gas mixtures, respectively. Furthermore, N₂ gas as a retardant gas was also mixed with the electronegative gas mixtures in order to reduce the electron energy into the effective levels of electron attachment ability by the electronegative gas mixtures. As the result, ternary N₂O / CO₂ / N₂ and quaternary N₂O / CO₂ / O₂ / N₂ gas mixtures could exhibit the significant synergistic effect in breakdown strength. The optimum mixture rate of quaternary N₂O / CO₂ / O₂ / N₂ gas mixtures was consistent with that estimated by assuming the independent contribution of component gases to the improvement of impulse BD characteristics.     

Fundamental insulation characteristic of high-pressure CO/sub 2/ gas under actual equipment conditions

SF₆ gas has been widely used in electrical power equipment such as circuit breakers and transformers due to its superior insulation and interruption characteristics. However since 1997, SF₆ gas has been designated a greenhouse gas subject to emission restrictions at COP3 (The 3rd session of the Conference Of the Parties to the United Nations Framework Convention on Climate Change) so a new insulating gas is needed as a substitute for SF₆ gas. This research considers the use of high-pressure CO₂ gas as an insulator while stressing the environment aspects. Fundamental insulation data for the insulating gas acquired supposing gas insulated switchgears (GIS) consists of; (1) insulation breakdown characteristics under clean conditions and, (2) insulation breakdown characteristics with metallic particle contamination. The parameters in this case were assumed from an actual apparatus viewpoint, to be a high gas pressure up to 2.0 MPa, an electrode size capable of determining the surface area effect, the electrode surface roughness, and metallic particle length, etc. at the base electrode of the 72 kV GIS. As a result, experiments using these parameters revealed insulation characteristics for high-pressure CO₂ gas and that negative lightning impulse decided the insulation design, as well as the present SF₆ GIS. The need for taking measures to suppress PD under AC voltage and also the need for restricting metallic foreign particles around the central conductor and insulating spacer were recognized     

Aerosol generation and decomposition of CFC-113 by theferroelectric plasma reactor

Plasma chemical decomposition, aerosol generation and product distribution of trichlorotrifluoroethylene (CFC-113 [CCl₂F-CClF₂]) were investigated using a ferroelectric plasma reactor. CFC-113 decomposition was the highest with dry hydrogen, but was not significantly affected by background gases (N ₂ and air) and humidity. Most of the aerosols produced under plasma were of a particle size less than 0.1 μm. The aerosol generation rate increased with applied voltage and concentration, but was not affected by humidity and background gases, indicating that aerosol generation is associated with plasma energy per volume (plasma power density). Aerosolization of 1000-ppm CFC-113 was approximately 10 aerosols/cm³ for air, significantly greater than N₂. The greatest quantity of reaction gas phase byproducts was for dry H₂, followed by dry N₂, wet N₂ , wet air and dry air. Reaction gas phase byproducts were minimal with aerated condition. The plasma reaction starts out by breaking the C-C bond to form radicals, which react with background gas radicals. The formation of CHClF-CClF₂ during CFC-113 decomposition indicates that the C-F bond is much stronger than the C-Cl bond and the C-Cl bond with more P atoms is stronger than that with fewer F atoms     

Numerical Investigation for CF4 Decomposition Using RF Low-Pressure Plasma

Among perfluorocompounds, is considered to be one of the most stable and difficult-to-decompose gases. We investigated the decomposition of CF₄ using the inductively coupled plasma (ICP) reactor with radio frequency (RF) power supply, which was used for semiconductor cleaning process as well as decomposition. This technology was confirmed to achieve an extremely high efficiency and more economical system in comparison with the conventional system. The purpose of this paper is to perform numerical simulation of CF₄ decomposition using RF low-pressure plasma. The experimental investigation of CF₄ the decomposition was performed to validate the computed results, and the reaction products such as CO, CO₂, and COF₂ upon the CF₄ decomposition were measured CO₂ using a analyzer and a Fourier transform infrared spectrophotometer. Then, the numerical simulations of the CF₄ decomposition using commercially available code were performed to obtain the gas temperature, electron temperature, electron number density, gas velocity, and chemical species number density distribution to cope with CF₄ the decomposition in the ICP reactor.     

富氧燃烧气氛石灰石溶解特性研究

在实验室小型试验台上研究富氧燃烧气氛下湿法脱硫用石灰石溶解特性,研究结果表明：较高的CO₂浓度对石灰石的溶解有促进作用,CO₂体积分数在80%时,石灰石的溶解速率明显增大;在相同的pH值情况下,CO₂浓度越高,石灰石的溶解速率越快。在pH=4.5时,低浓度CO₂气氛比高浓度CO₂气氛下溶解时间增加70 min,CO₂浓度对溶解速率的影响比较明显。     

光催化还原二氧化碳影响因素分析

光催化还原CO₂既是光能利用的一种有效途径,又可将煤炭、石油和天然气等化石燃料排放的CO₂作为碳源,变废为宝,极具经济价值。结合国内外光催化还原二氧化碳研究成果,从光催化还原二氧化碳机理出发,分别探讨了光源、光反应器、添加剂、光照时间、光催化剂等因素对光催化还原二氧化碳的影响;认为高效光催化剂的开发,优良光催化反应器的研制以及更深的机理探索,对该领域的研究至关重要。     

NOx removal by a pipe with nozzle-plate electrode coronadischarge system

The effects of additional gas composition on the corona discharge characteristics in a pipe with nozzle electrode system and the NOx removal characteristics for flue gases are experimentally investigated. The additional gas consists of a mixture of Na+O₂+NH₃ and a small amount of Ar or CO₂, and is introduced to the flue gas stream from the pipe electrode through the corona discharging zone at the tip of nozzles. The results show that corona discharge characteristics and modes are significantly influenced by the composition of the additional gas mixture. Both NO_x reduction rate and energy yield of NO_x removal increase with decreasing corona discharge input power. NO reduction rate and energy yield can be optimized by the type of the additional gas mixture and the flow rates     

Comparison of SF6/N2 and SF6/CO2 gas mixtures as alternatives to SF6 gas

The interest in SF₆ gas mixtures has been re-ignited in recent years by the issue of the greenhouse effect of the SF₆ gas, and most research work is now focused on a SF₆/N₂ gas mixture, which is suitable for application in electrical apparatus with slightly non-uniform fields. This paper presents a comparison of SF₆/N₂ and SF₆/CO₂ gas mixtures with a viewpoint of their possible applications to gas-insulated transformers, where both highly non-uniform field problems and partial discharges in gas/film insulation are inevitable. It is shown that in this case the dielectric strength of SF₆/CO₂ is superior to that of SF₆/N ₂ with a minor disadvantage related to the gas decomposition in SF₆/CO₂. However, this may not be a problem for the SF₆/CO₂ gas mixture to be used in gas-insulated transformers, where internal breakdown is not allowed     

Mechanisms for formation of inorganic byproducts in plasma chemicalprocessing of hazardous air pollutants

Plasma chemical behavior of hazardous air pollutants (HAPs) (Cl ₂C=CCl₂, Cl₂C=CHCl, Cl₃C-CH ₃, Cl₂CH-CH₂Cl, CH₃Cl, CH ₃Br and benzene), their molecular probes (CH₄, CH ₃-CH₃, and CH₂=CH₂), and carbon oxides (CO_x) was investigated with a ferroelectric packed-bed plasma reactor to obtain information on the formation of CO _x and N₂O. It has been shown that the oxidation of CO to CO₂ is a slow reaction in plasma, and that CO and CO ₂ mainly result from different precursors. Simultaneous achievement of complete oxidative decomposition of HAPs in plasma and recovery of CO as a chemical feedstock could be favorable. The process of N₂O formation is affected by HAP structures and oxygen concentration. In the decomposition of olefinic HAPs, such as Cl₂ C=CCl₂ and Cl₂C=CHCl, high-power short-residence-time operations are effective in suppressing N₂ O formation. In the cases of CH₃Cl and CH₃Br, low specific energy density operations could be necessary to reduce N₂O concentrations. The yields and selectivities of CO, CO₂ and N₂O change drastically by adding only 2% of oxygen to N₂, and oxygen concentration is not a good factor to control these inorganic oxides     

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.     

基于区间规划的多区域行业间碳排放权交易模型研究

碳排放权交易是为促进全球温室气体减排所采用的市场机制。在区域及行业层次的CO₂减排目标基础上,考虑交易过程不确定性特性及交易参数浮动特征,运用区间线性规划方法,建立了多区域行业间碳排放权交易模型,并应用于仿真案例研究,以期为区域及行业层次碳排放权交易管理决策提供有效的技术支持。