Energy efficiency of hydrogen sulfide decomposition in a pulsed corona discharge reactor

A novel pulsed corona wire-in-tube reactor with quartz view-ports allowed visual observation of the effect of charge voltage and gas composition on the corona distribution. The H₂S conversion and energy efficiency of H₂S decomposition in this pulsed corona discharge reactor varied at constant power (100 W) due to the selected values of the electrical parameters of pulse forming capacitance (720-2880 pF), charge voltage (11-21 kV), and pulse frequency (157-961 Hz). Low pulse forming capacitance, low charge voltage, and high pulse frequency operation produces the highest energy efficiency for H₂S conversion at constant power. H₂S conversion is more efficient in Ar-N₂ gas mixtures than in Ar or N₂. These results can be explained by corona discharge observations, the electron attachment reactions of H₂S at the streamer energies, and a proposed reaction mechanism of H₂S dissociation in the Ar-N₂ gas mixture. The energy consumption per molecule of converted H₂S in an equimolar mixture of Ar and N₂ (4.9 eV/H₂S) is the lowest that has been reported for any plasma reactor operated at non-vacuum pressures. The results reveal the potential for energy efficient H₂S decomposition in pulsed corona discharge reactors.     

Ozone Generation by Hybrid Discharge Combined with Catalysis

In this paper, combining hybrid discharge with pellet alumina catalyst is used for ozone generation. The hybrid discharge including corona discharge (CD), surface discharge (SD) and dielectric barrier discharge (DBD) may happen in the device. Factors that affect the ozone production efficiency and concentration are studied, such as energy density, power, gas flow rate, frequency, peak voltage and catalysts.     

高压脉冲放电等离子体处理工业废水实验研究

采用针-板式高压脉冲放电等离子体反应器处理工业废水.考察了脉冲电压峰值、电极间距、氧气通入量等因素对废水CODCr去除率的影响.在脉冲电压峰值为35 kV,电极间距为15 mm,氧气鼓人量为150 mL/min的实验条件下,废水被放电处理150 min,CODCr的去除率可达81.2%.研究表明,高压脉冲放电等离子体技术处理工业废水具有良好的应用前景.     

Toluene removal by a DBD-type plasma combined with metal oxides catalysts supported by nickel foam

The performance on toluene removal in a dielectric barrier discharge (DBD) type plasma system under different background gases, including N₂, Ar, N₂/Ar, and N₂/O₂ was studied at room temperature and atmospheric pressure. For comparison, another laboratory-scale plasma-catalysis system was set up and four kinds of metal oxides, i.e., copper oxide, iron oxide, cobalt oxide, and manganese oxide supported on alumina/nickel foam (NF), were used as catalysts. The reaction mechanism and dynamics analysis on toluene removal were suggested. In addition, the characterization of the catalysts was performed by BET, XRD, SEM, FT-IR, and EDS. It has been found that adding argon in the background gas could improve the toluene removal efficiency significantly in the plasma system. Combining plasma with catalyst in situ could improve the toluene removal efficiency, increase the carbon dioxide selectivity and suppress byproducts formation. In addition, manganese oxide/alumina/NF was confirmed as the most effective catalyst for toluene removal. The XRD and SEM results showed that the proportion of metal oxide increased while aluminate decreased after plasma application. The granularity of the grain on the catalyst surface became smaller and the distribution became more uniform after discharge. The results of FT-IR and EDS suggested that some organic compounds deposited on the catalysts after plasma reaction.     

Modeling of pulsed corona discharge process for the removal of nitric oxide and sulfur dioxide

A positive pulsed corona discharge process was applied to the removal of sulfur dioxide and nitric oxide from a simulated flue gas stream, and a mathematical model was proposed to describe this process theoretically. The proposed model takes into account generation of radicals by pulsed corona discharge, followed by radical utilization for the removal of the pollutants. Radicals such as O, OH, N, H, etc. may be concerned in the removal of the pollutants. Their concentrations were derived by considering direct electron impact on the dissociation of gaseous molecules (O₂, N₂, H₂O) and subsequent excitation transfer reactions of excited oxygen atoms to produce O and OH radicals. The effects of various operating parameters such as feed gas flow rate, initial concentration, oxygen content, humidity, peak voltage and pulse repetition rate on the removal were examined. So as to establish the validity of the model, the calculated results were compared with the experimental data. Although some discrepancy between the calculated and experimental results was observed at high pulse repetition rate, the proposed model was found to properly predict the experimental data on the whole.     

高压脉冲电场中活性氧化铝滴滤床对印染废水脱色的效能

研究了一种新型的用于去除液相污染物的方法———高压脉冲电场中活性氧化铝滴滤床去除有机物,并考察了其对印染废水脱色的效能。结果表明在高压脉冲电场与活性氧化铝的相互作用下和其他合适的条件下亚甲基蓝去除率可达67.68%。随着电压的增加、流速的减小、初始质量浓度的减小、pH的增加和空气的通入,亚甲基蓝的分解效率都得到了增加。在脉冲电场作用下,活性氧化铝表面产生局部放电,提高了亚甲基蓝的降解率;同时放电过程也增强了氧化铝对于亚甲基蓝的吸附,二者的相互作用促进了亚甲基蓝的降解。     

Ozone Production by an Ultra-Short Triggered Dielectric Barrier Discharge.

This work was motivated by the ozone production improvement by a dielectric barrier discharge supplied with a high voltage triggered pulsed generator. Particular attention was focused on the ozone generator cell geometry and on the type of electrical generator. A comparative parametrical analysis on two configurations of reactor was performed: an annular and a surface configuration. This study emphasizes that surface discharges coupled to ultra-short triggered high voltage generators stand out as an efficient process to produce ozone in large quantities.     

Reduction of nitrogen oxides from simulated exhaust gas by using plasma–catalytic process

Removal of nitrogen oxides (NO_x) using a nonthermal plasma reactor (dielectric-packed bed reactor) combined with monolith V₂O₅/TiO₂ catalyst was investigated. The effect of initial NO_x concentration, feed gas flow rate (space velocity), humidity, and reaction temperature on the removal of NO_x was examined. The plasma reactor used can be energized by either ac or pulse voltage. An attempt was made to utilize the electrical ignition system of an internal combustion engine as a high-voltage pulse generator for the plasma reactor. When the plasma reactor was energized by the electrical ignition system, NO was readily oxidized to NO₂. Performance was as good as with ac energization. Increasing the fraction of NO₂ in NO_x, which is the main role of the plasma reactor, largely enhanced the NO_x removal efficiency. In the plasma–catalytic reactor, the increases in initial NO_x concentration, space velocity (feed gas flow rate) and humidity lowered the NO_x removal efficiency. However, the reaction temperature in the range up to 473 K did not significantly affect the NO_x removal efficiency in the presence of plasma discharge.     

高压脉冲介质阻挡放电协同臭氧溶气降解聚丙烯酰胺模拟废水

利用高压脉冲介质阻挡放电与臭氧联用的上流式反应器,考察了高压脉冲介质阻挡放电、臭氧和二者协同处理聚丙烯酰胺的降解情况以及COD和BOD5/COD的变化趋势;另外研究了反应器内加入TiO2催化剂对处理效果的影响,并探讨了其作用机理。结果表明,停留时间为10min时,放电协同臭氧溶气对聚丙烯酰胺的降解率可达51%,比单独放电和单独臭氧分别提高了27%和4%。加入TiO2催化剂后,COD去除率达到65%,BOD5/COD提高到0.37。     

介质阻挡放电协同复合碳材料去除VOCs

挥发性有机物（VOCs）是常见的空气污染物,实验研究低温等离子体催化技术去除以甲苯为代表的VOCs。采用炭粉末、酚醛树脂和致孔有机高分子聚合物的有机溶剂混合物作为前驱物,经过炭化、水汽活化和负载锰催化剂,制备一种基于发泡金属的复合碳材料。采用扫描电子显微镜、XRD、全自动比表面积及微孔孔隙分析仪对材料进行表征。两段式介质阻挡放电反应器结合复合碳材料降解甲苯,前段介质阻挡放电初步降解甲苯,后段复合碳材料利用介质阻挡放电产生的长寿命活性物种和臭氧进一步去除甲苯。输入电压为10 kV时,甲苯去除率约99.4％,CO₂选择性达72.2%,并且有效控制了副产物臭氧。实验结果表明,复合碳材料有望应用于如臭氧和VOCs等的污染控制。     

Nitric oxide production in a multistage-compression chemical reactor

A method for producing nitric oxide(II) by binding atmospheric nitrogen in a multistage-compression chemical reactor is considered. The operation of the reactor proposed is based on the nonisentropic pulsed compression of the working gas with increasing entropy. The oxidation of atmospheric nitrogen in a cyclic reactor operating on an internal combustion engine cycle is theoretically analyzed, and it is shown that, in such a reactor with two compression strokes, the product concentration at the reactor outlet may reach 5% at a specific energy efficiency of the process of approximately 80 g NO per kilowatt-hour of energy consumed.     

双介质阻挡放电低温等离子体对模拟堆肥气体中氨气的去除

针对固体废物堆肥设施氨气污染问题,本文首次运用双介质阻挡放电低温等离子体（DDBD）技术去除模拟堆肥气体中的氨气。考察了输入功率、氨气流速、氨气初始浓度、反应器放电间隙、氧气含量等参数对氨气去除率和低温等离子体系统能量效率的影响,并分析了副产物的生成情况及其影响因子。研究结果表明,氨气去除率与输入功率和氧气含量呈正相关,与氨气流速和氨气初始浓度呈负相关。低温等离子体系统的能量效率与氨气流速、氨气初始浓度、氧气含量均正相关,但随输入功率的增加先升高后降低。研究发现,在所设定的反应条件下,4mm放电间隙反应器的能耗最低,能量效率最高。O₃和NO_x是DDBD去除氨气的反应副产物,其浓度均与氧气含量呈正相关,均呈现随输入功率的增加先升高后降低的趋势。     

The destruction of N2O in a pulsed corona discharge reactor

The removal of N₂O by a pulsed corona reactor (PCR) was investigated. Gas mixtures containing N₂O were allowed to flow in the reactor at various levels of energy input, and for different background gases, flow rates, and initial pollutant concentrations. The reactor effluent gas stream was analyzed for N₂O, NO, NO₂, by means of an FTIR spectrometer. It was found that destruction of N₂O was facilitated with argon as the background gas; the conversion dropped and power requirements increased when nitrogen was used as the background gas.Reaction mechanisms are proposed for the destruction of N₂O in dry argon and nitrogen. Application of the pseudo-steady state hypothesis permits development of expressions for the overall reaction rate in these systems. These reaction rates are integrated into a simple reactor model for the pulsed corona discharge reactor. The reactor model brings forth the coupling between reaction rates, electrical discharge parameters, and fluid flow within the reactor. Comparison with experiment is encouraging, though the needs for additional research are clearly identified.     

Pulsed electrokinetic removal of Cd and Zn from fine-grained soil

Pulsed electrokinetics studies were carried out to optimize the removal of Zn and Cd from fine-grained soils and to observe the effects of varying the pulse frequency, pulse time ratio (on/off), and DC voltage gradient. Existing forms of heavy metals in the soil matrix were determined using a sequential extraction method. The strongly bound fraction (bound to organic matter and residuals) that is difficult to remove from the soil matrix comprised 74 and 62% of the total Zn and Cd, respectively. In the electrokinetic remediation experiments, MgSO₄ was employed to increase the ionic strength of the soil for 2 weeks. Transportation of heavy metals was influenced by the frequency, pulse ratio, and the voltage gradient of the pulsed electric field. Extraction efficiency of Zn and Cd near the anode was correlated positively with the voltage gradient at a given pulse and ratio. A high pulse frequency (1,800 cycles/h) enhanced the removal efficiency of the heavy metals compared to a low pulse frequency (1,200 cycles/h) at a supplied voltage gradient of 1 V/cm. Although pulsed electrokinetics was more effective in extracting and desorbing ions near the anode than conventional electrokinetics, its ability to transport heavy metals from the anode to the cathode was relatively small. Total removals with pulsed electrokinetics were 21–31% for Zn and 18–24% for Cd. In summary, pulsed electrokinetics can enhance removal efficiency of heavy metals and is beneficial with regard to electrical energy consumption.     

DBD反应器中催化剂颗粒直径对放电功率的影响

介质阻挡放电(DBD)协同催化剂可有效脱除NOx ,在一段式DBD反应器中固体催化剂颗粒兼具有放电阻挡介质作用,可有效提高放电功率.今通过建立数学模型以及实验测试研究了在DBD反应器中填充颗粒直径对放电功率的影响规律,研究发现随填料颗粒直径增大,放电功率先增加再降低,并且随输入电压增大颗粒直径对放电功率影响更加显著.因为当填料粒径大于峰值时,在DBD反应器中随粒径增大间隙增加大,在相同条件下间隙电容小于固体颗粒电容,总电容量降低,所以放电功率随颗粒直径增大而降低.当填料粒径小于峰值时,随颗粒直径减小固体颗粒等效电容厚度变小,易被击穿,电容量降低,所以放电功率随颗粒直径减小而降低.随输入电压增大放电增强,有效面积增大,而最大有效放电面积跟填充颗粒直径有关,所以粒径对放电功率影响随输入电压增大而增强.填料颗粒直径对反应器总输入功率影响很小,因为总输入能量不仅消耗于系统放电,而且还使系统产生热量.理论模型和实验测试结果变化趋势基本一致,该结论可为DBD协同催化反应过程中选择适宜催化剂颗粒直径提供理论依据.     

高压脉冲放电等离子体技术处理有机废水试验

采用针-板式高压脉冲放电等离子体反应器处理苯酚有机废水。考察了脉冲电压峰值、电极间距、氧气鼓入量、溶液初始pH值等因素对苯酚去除率的影响。在脉冲电压峰值为35 kV,电极间距为20 mm,氧气鼓入量为150 mL/min,溶液初始pH值为10.5的试验条件下,苯酚废水放电处理60 min的去除率可达90.8%。TOC的质量浓度随处理时间的延长而下降,当放电处理300 min时,TOC的质量浓度下降了76.8%。研究表明,高压脉冲等离子体技术处理有机废水具有良好的应用前景。     

Simultaneous SO x /NO x removal in a fluidized bed reactor using natural manganese ore

In this experiment, the simultaneous removal of SO₂ and NO from flue gases was investigated through the use of natural manganese ore as a sorbent‐catalyst in a fluidized bed reactor. Selective catalytic reduction behavior was determined as a function of the sulfation degree within the temperature range from 100 °C to 500 °C. The natural manganese ore showed a high activity in the production of nitrogen and water by the reaction of nitric oxide with ammonia and oxygen up to around 200 °C. At higher temperatures, the nitric oxide removal efficiency decreased due to the oxidation of ammonia by oxygen. With the increase of sulfation degree, the temperature at which the maximum selective catalytic reduction of nitric oxide appears gradually increased, however the maximum nitric oxide removal efficiency decreased. Additionally, we investigated the removal efficiency of sulfur dioxide and nitric oxide with reaction time in a batch fluidized bed reactor within a temperature range of 350 °C to 500 °C. As the reaction temperature increased, the adsorption capacity of sulfur dioxide increased, but the nitric oxide removal efficiency decreased. © 2001 Society of Chemical Industry     

Removal of particulate matter from an air stream by a packed dielectric barrier discharge

This study elucidates the feasibility of using a packed dielectric barrier discharge approach to remove particulate matter from an air stream. The experimental results reveal that the particle removal efficiency of the packed dielectric barrier discharge system rose to 92.2% for 0.3 μm particles as the discharge voltage was increased to 20 kV at an operating frequency of 60 Hz. Only when the discharge voltage was sufficiently high to remove particulate matter did the particle removal efficiency increase with the operating frequency. The power required to adjust the discharge voltage was less than that required to adjust the operating frequency at the particular removal efficiency. Accordingly, energy can be saved in a packed dielectric barrier discharge system by adjusting the discharge voltage rather than the operating frequency to remove particulate matter from the air stream.     

脉冲气液两相放电等离子体耦合Fe改性的TiO2催化剂降解废水中的4-氯酚

为了提高酚类废水的降解效果,本文以4-氯酚为处理对象建立了多针-板式高压脉冲气液两相放电等离子体催化体系。实验制备了系列催化剂并进行了表征分析,考察了各因素对4-氯酚降解的影响,并分析了降解过程总有机碳（TOC）、中间产物及其浓度变化。结果表明,催化剂焙烧温度及投加量对降解率有很大影响;4-氯酚浓度为150mg/L时,在电极间距10mm、脉冲电压26kV、脉冲频率70Hz、曝气量4L/min条件下,添加0.05g焙烧温度为500℃的Fe-TiO₂催化剂与放电等离子体耦合降解效果最好。中间产物对苯酚、对苯醌、4-氯邻苯二酚在放电过程中浓度随着放电时间的延长先增大后减小,最后都趋于零。催化剂表征显示脉冲放电可以改变催化剂的晶形和结构,且掺杂Fe改性的Fe-TiO₂催化性能较好,能进一步提升4-氯酚的降解率。     

脉冲放电等离子体协同Mn/TiO2-分子筛、Fe/TiO2-分子筛、Cu/TiO2-分子筛催化剂降解甲醛

为进一步提高脉冲放电等离子降解甲醛的效率,增加CO₂选择性,降低O₃产生量,研究采用放电等离子体和催化剂协同技术。实验以分子筛为载体,分别制备了Mn/TiO₂-分子筛、Fe/TiO₂-分子筛和Cu/TiO₂-分子筛3种催化剂,并利用XRD、SEM、EDS、FT-IR方法对催化剂进行表征分析。进行了脉冲放电等离子体协同3种催化剂降解甲醛的研究,比较了不同催化剂协同等离子体对甲醛去除率、CO₂选择性、O₃产生量的影响。结果表明,3种催化剂与脉冲放电等离子体都存在协同作用,并能有效地提高甲醛去除率,增加CO₂选择性,降低O₃产生量。当脉冲电压为20kV、放电频率为40Hz、气体流量为0.5L/min时,Mn/TiO₂-分子筛催化剂协同效果最佳,甲醛去除率为94.4%,CO₂选择性为42.2%。催化剂表征结果显示Mn/TiO₂-分子筛的活性组分颗粒分布均匀,锐钛矿相的TiO₂和微晶状态的MnO_x的存在有效促进了甲醛的氧化分解。研究还对放电等离子体协同Mn/TiO₂-分子筛催化剂降解甲醛的机理进行了探讨。