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1.
The influence of polarity and rise time of the pulse voltage on the removal of particulate matter (PM) emitted from a diesel engine was investigated using a dielectric barrier discharge reactor. Four kinds of pulse voltage waveforms (positive, negative, positive–negative and negative–positive) were used. It was found that the energy efficiency for PM removal is just a function of energy injection and that there are no obvious influences on PM removal and energy efficiency within the voltage waveforms except the negative pulse voltage of a peak voltage below 8 kV. A comparison of PM removals using various kinds of pulse voltage waveforms and different types of plasma reactors is given.  相似文献   

2.
Elimination of CO in air stream using the plasma catalytic reactors was investigated. Two plasma catalytic systems were evaluated in this study, one consisting of a catalyst-bed packed in plasma zone of a dielectric barrier discharge (DBD) reactor directly (CID reactor), and the other (CAD reactor) consisting of a catalyst-bed after a DBD reactor. The examined operating parameters in this study included applied voltage, discharge power, the lengths of plasma zone and catalyst-bed, and inlet CO concentration. It was found that the glass packed DBD reactor without catalyst cannot eliminate CO in air stream effectively. When MnOx catalyst applied to DBD reactors, the removal of 1000 ppm CO can achieve to 97% by both type reactors. Under constant energy input condition, the CO removal of a CID reactor increased with the decrease of the initial CO concentration and the increase of the length of catalyst beds. In addition, the operating energy consumption of CID system was lower than that of CAD system.  相似文献   

3.
Particulate matter (PM) from diesel vehicles is harmful to humans and should be removed from the exhaust gases before its emission into the atmosphere. Plasma PM oxidation is an advanced method to be used for oxidative PM removal. Factors influencing plasma PM oxidation include gas temperature, gas composition, PM amount, the geometry of plasma reactors. The PM oxidation in atmospheric air discharges was carried out using a pulsed dielectric barrier discharge reactor at temperatures of 100, 150, and 200 °C. It was found that PM is oxidized to CO and CO2. CO2/CO concentration ratio is a function of PM amount in the discharge space. PM removal efficiency (PM amount oxidized per kWh energy injection) increased with increasing air temperature and PM amount in the discharge space. Water promotes PM oxidation, which suggested that oxygen atoms produced in the discharge space react with water to yield hydroxyl free radicals that are of more reactivity than oxygen atoms. The activation energy of plasma PM oxidation was kinetically calculated to be 15.4 kJ/mol.  相似文献   

4.
An ultraviolet (UV) coil reactor was designed and used for the online sterilization of cheese whey. Its microbial destruction efficiency was compared to that of the conventionally used UV reactor. Both reactors have the same geometry (840 ml volume and 17 mm gap size) and were tested at 11 flow rates of 5, 10, 15, 20, 25, 30, 35, 40, 50, 60, and 70 ml/min. The results obtained from this study showed that despite of its high turbidity, cheese whey could be sterilized using UV radiation if the proper reactor design and flow rate are used. The performances of the UV reactors were governed by the flow rate and the hydraulics of flow inside the reactor. The flow was laminar in both the reactors, as the Reynolds number was in the range of 1.39–20.10. The phenomenon of Dean Flow was observed in the coil reactor and the Dean number was in the range of 1.09–15.41. Dean vortices resulted in higher microbial destruction efficiency in the coil reactor in a shorter retention time. The rate of microbial destruction was found to be exponential in the conventional reactor and polynomial in the coil reactor. Increasing the flow rate from 5 ml/min to 70 ml/min decreased the microbial destruction efficiency of the conventional reactor from 99.40 to 31.58%, while the microbial destruction efficiency in the coil reactor increased from 60.77% at the flow rate of 5 ml/min to 99.98% at the flow rate of 30 ml/min and then decreased with further increases in flow rate reaching 46.2% at the flow rate of 70 ml/min. The maximum effluent temperatures in the conventional and coil reactors were 45.8 and 46.1°C, respectively. Fouling in the coil reactor was significantly less compared to the conventional reactor. The extent of fouling was influenced by flow rate and reactor’s hydraulics.  相似文献   

5.
Dielectric barrier discharge (DBD) and catalysis hybrid process was used to remove nitrogen oxides and particulate matters from diesel engine exhaust. The DBD reactor converts a part of NO into NO2, and then the exhaust gas containing the mixture of NO and NO2 enters the catalytic reactor where both NO and NO2 are reduced to N2. The effect of energy density (power input divided by gas flow rate) and reaction temperature on the removal of nitrogen oxides was investigated with a stationary diesel engine. The hybrid process was able to remove about 80% of the initial nitrogen oxides at an energy density of 25 J/L and 150°C. The removal of particulate matters did not largely depend on the electrode structure, but it was a strong function of the energy density. On the basis of 80% removal efficiency, the energy yield for nitrogen oxides was 40 eV/molecule while that for particulate matters was 83 kJ/mg. The present study suggests that this kind of hybrid process can be applied to simultaneous removal of nitrogen oxides and particulate matters from diesel engine exhausts.  相似文献   

6.
Cold atmospheric plasma is considered to be a promising approach for decontamination purposes, e.g. dyeing water decoloration. In order to better understand the complex mechanism of the plasma physics coupled with the plasma chemistry involved in the interaction of the polluted water with the discharge plasma, a novel approach was proposed to study the in situ oxidation process between the plasma and liquid phase in two dielectric barrier discharge (DBD) plasma reactors with different bottom shape (concave vs. plane), by using the planar laser induced fluorescence technique to visualize the process dynamics. Rhodamine B was employed as the tracer dye, which was gradually decomposed by the combined effect of the chemically active radicals (OH, O, H2O2, etc.) as well as the intense UV radiation in the DBD plasma process. The results showed that the DBD plasma filaments induced certain fluctuation on the Rhodamine B liquid layer, which accordingly intensified the mass transfer to a large extent thus accelerated the oxidation process. The comparison of the measured concentration fields in the two DBD plasma reactors illustrated that the DBD reactor #1 with concave bottom showed higher oxidation efficiency than the DBD reactor #2 with plane bottom. Additionally, the experiments demonstrated that the oxidation efficiency in the DBD plasma water treatment was much better than that in the reactor with pure oxidation by ozone gas, which can be further improved by injecting the additional oxygen gas bubbles into the liquid phase in the plasma reactor.  相似文献   

7.
在常压下研究了不同等离子体放电模式及反应器结构对氨分解制氢反应的影响.实验中调节反应器结构分别产生了介质阻挡放电和交流弧放电两种放电模式.通过对两种放电模式的放电图像、电压-电流波形和氨分解过程中等离子体区活性物种的发射光谱(OES)研究发现,与介质阻挡放电相比,交流弧放电为局部强放电,具有更高的电源效率和电子密度.因此,在介质阻挡放电中氨气分子大部分通过生成电子激发态物种NH3*,再与载能电子碰撞断裂N―H键进行氨分解反应;而在交流弧放电中载能电子具有更高的平均电子能量,可直接断裂氨气分子的N―H键生成NH2和NH等高活性物种,促进氨分解反应的进行.结果表明,交流弧放电的氨分解效果要明显优于介质阻挡放电.在交流弧放电模式下不同类型反应器对氨气分解转化率由高到低的顺序为:管-管管-板针-板板-板.在输入功率为30 W,气隙间距为6 mm时,管-管交流弧放电的氨气转化率达到60%左右,而板-板介质阻挡放电的氨气转化率仅为4%.  相似文献   

8.
The dependence of gliding arc gas discharge characteristics, including gas flow field, arc column motion and volatile organic compounds (VOCs) decomposition performance, on reactor configuration parameters was investigated based on numerical simulation and laboratory experimental findings. For a given supply voltage (10 kV) and a certain nozzle outlet diameter (1.5 mm), increasing the electrodes gap (1–4 mm) or decreasing vertical distance between electrode throat and nozzle outlet (25–10 mm) will increase the gas flow rate through the electrode throat, the gas velocity in the plasma region, the arc column velocity, the maximum attainable position of the arc column and the electrical power consumption, also, higher VOCs decomposition rate and lower specific energy requirement are observed according to the n-butane and toluene decomposition experiments.  相似文献   

9.
Dielectric Barrier Discharge (DBD) non-thermal plasma reactors built with three different dielectric materials for SO2 removal were studied. The discharge characteristics of the three dielectrics, namely glass, Teflon, and glass fiber-based epoxy resin, were analyzed using Lissajous figures. From the Lissajous figures, the transition charge and energy deposition for each dielectric material were determined. When both the discharge characteristics and mechanical processability were considered, glass fiber-based epoxy resin was regarded as the best dielectric barrier among the three for DBD plasma reactors. A multi-cell DBD reactor built with glass fiber-based epoxy resin was used for treating air stream containing SO2. SO2 % removal decreased with increasing initial SO2 concentration in a biphasic fashion. SO2 removal was greatly improved by adding NH3 into the air stream. Raising the relative humidity of the air stream also helped SO2 removal. A SEM (scanning electron microscope) test illustrated some changes in surface morphology of Teflon and glass fiber-based epoxy resin.  相似文献   

10.
介质阻挡放电与 CuZSM-5 结合方式对脱除 NOx 的影响   总被引:1,自引:0,他引:1  
陈刚  孙琪  石雷  牛金海  宋志民 《催化学报》2010,31(7):817-821
 研究了介质阻挡放电 (DBD) 与 CuZSM-5 结合方式, 即 DBD 和 CuZSM-5 两段分置 (两段法) 或将 CuZSM-5 放入 DBD 区 (一段法), 对脱除氮氧化物的影响. 结果表明, 在 NO/N2 或 NO/C2H4/N2 无氧体系中, DBD 与 CuZSM-5 结合产生的协同效应很小; 在 NO/O2/N2 富氧体系中, DBD 与 CuZSM-5 结合导致氮氧化物转化率下降; 而在 NO/C2H4/O2 /N2 富氧体系中, 在 250 ºC, 空速 12 000 h1, 输入放电能量密度 (Ein) 155 J/L 的条件下, 单纯催化、单纯等离子体放电、一段法和两段法时氮氧化物转化率分别为 39%, 1.5%, 79% 和 52%. 两段法产生了中等程度的协同效应, 主要是第一段等离子体放电产生新稳态物种 (如 NO2, CO 和 CO2 等) 起作用; 而一段法产生的协同效应较大, 主要是由于等离子体放电产生的新稳态物种和激发态短寿命物种 (如 N2*, NO*, CH 和 CN 等) 共同起作用.  相似文献   

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