Abstract:This paper presents an analysis of the electric field,at the contact point of zero contact angle for different curvature of the dielectric interface near the contact point. The arrangement considered here is a dielectric solid (a spheroid or an elliptic cylinder) standing on a grounded plane under a uniform external field. The electric field has been calculated by using the boundary element method for 2D and AS arrangements. The calculation results show that the contact-point electric field is intensified by e… Show more
“…However, the void between spherical packing pellets is usually not spherical and the electric field inside is more complicated. In fact, the maximum electric field near the contact point between pellets can be 10−10 4 times higher than that in a spherical void, depending on the contact angle, curvature, and dielectric constant of the packing pellets. ,,, 2 Enhancement of electric field as a function of dielectric constant of pellets. The subscript i in E x , i stands for the dielectric constant of packing pellets (ε p ).…”
Section: Characteristics Of Packed-bed Reactorsmentioning
Packed-bed plasma reactors, constructed by packing noncatalytic dielectric pellets inside nonthermal plasma reactors, have been demonstrated to effectively alleviate the major bottleneck encountered by nonthermal plasma, i.e., the energy efficiency needs to be further improved. As far as the environmental issues are concerned, packed-bed plasma reactors are mainly applied to ozone generation and gaseous pollutant removal. According to the available experimental data, for a given specific energy density, the energy efficiency for ozone generation and gaseous pollutant abatement obtained with packed-bed reactors, if compared to that of nonpacked reactors, could be 1.1-4.3 and 1.1-12 times higher, depending on the type of pollutant, the reactor geometry, and the packing pellets used. Nevertheless, it is worth noticing that the packing pellets suitable for ozone generation and pollutant removal are quite different. The influences of material, dielectric constant, size, and shape of the packing pellets on the performance for ozone generation and gaseous pollutant removal are comprehensively reviewed in this paper and guidelines for pellet selection are provided as well. For the single-stage plasma catalysis system, in which catalyst pellets are directly packed inside the plasma reactor, the physical parameters of catalyst would also have significant influence on the plasma characteristics and the performance. Therefore, the content of this review paper could provide useful information for singlestage plasma catalysis system from the viewpoint of plasma characteristics.
“…However, the void between spherical packing pellets is usually not spherical and the electric field inside is more complicated. In fact, the maximum electric field near the contact point between pellets can be 10−10 4 times higher than that in a spherical void, depending on the contact angle, curvature, and dielectric constant of the packing pellets. ,,, 2 Enhancement of electric field as a function of dielectric constant of pellets. The subscript i in E x , i stands for the dielectric constant of packing pellets (ε p ).…”
Section: Characteristics Of Packed-bed Reactorsmentioning
Packed-bed plasma reactors, constructed by packing noncatalytic dielectric pellets inside nonthermal plasma reactors, have been demonstrated to effectively alleviate the major bottleneck encountered by nonthermal plasma, i.e., the energy efficiency needs to be further improved. As far as the environmental issues are concerned, packed-bed plasma reactors are mainly applied to ozone generation and gaseous pollutant removal. According to the available experimental data, for a given specific energy density, the energy efficiency for ozone generation and gaseous pollutant abatement obtained with packed-bed reactors, if compared to that of nonpacked reactors, could be 1.1-4.3 and 1.1-12 times higher, depending on the type of pollutant, the reactor geometry, and the packing pellets used. Nevertheless, it is worth noticing that the packing pellets suitable for ozone generation and pollutant removal are quite different. The influences of material, dielectric constant, size, and shape of the packing pellets on the performance for ozone generation and gaseous pollutant removal are comprehensively reviewed in this paper and guidelines for pellet selection are provided as well. For the single-stage plasma catalysis system, in which catalyst pellets are directly packed inside the plasma reactor, the physical parameters of catalyst would also have significant influence on the plasma characteristics and the performance. Therefore, the content of this review paper could provide useful information for singlestage plasma catalysis system from the viewpoint of plasma characteristics.
“…The widths of the packing gaps located between the HV and the supporting electrodes control several parameters, including the thickness of filling, packing geometry, the shape and size of voids, angles and number of contact points between the dielectrics. These parameters are expected not only to determine the plasma properties [10,11,[37][38][39], but also the effectiveness of heat transfer [22,40,41] and consequently the overall performance of the PBPR. Figure 5 shows surface plots of ozone concentration as a function of the packing gap width (PGW), dielectric material and specific input energy using the arrangement B2 of the discharge cell.…”
Section: The Effect Of the Packing Gap Width On Ozone Generationmentioning
A packed bed plasma reactor (PBPR) was designed, characterized and optimized for ozone generation from oxygen and air. The effects of reactor arrangement, feed gas flow rate, coolant temperature, input power and dielectric material on ozone generation were investigated. The highest ozone concentration of 152 g m −3 was obtained using 2.0 mm borosilicate glass beads and a 0.06 dm 3 min −1 oxygen feed at 5 °C, whilst the highest ozone yield efficiency was 209 g kW −1 h −1 at an oxygen feed rate of 20 dm 3 min −1 . The highest ozone concentration produced from air was 15.6 g m −3 at a flow rate of 0.06 dm 3 min −1 with 2.0 mm 3 A molecular sieves beads (MS) beads as the dielectric. It was found that the effect of the dielectric on ozone generation affected significantly by the feed gas composition and flow rate. In addition, ozone production affected significantly by the number of dielectric layers in contact with the HV electrodes, thickness of packing and reactor arrangement. Different NO x by-products were formed along with ozone when the PBPR was fed with air depending on the coolant temperature and feed gas flow rate.
“…The pellets can refract the electric field, making the local electric field non-uniform and stronger than the externally applied field by a factor of 10 to 250 depending on the shape, porosity, and permittivity of the beads [8]. The local electric field strength near the contact points between the beads, and the beads and quartz tubes can be 10-10 4 times higher than that in the void between the beads, depending on the contact angle, curvature, and dielectric constant of the packing pellets [27][28][29][30]. An increase in the dielectric constant of the packing materials from 1 to 1000 can result in an increase in the electric field strength by a factor of 1-1.5.…”
CO2 can be converted to the more reactive species, CO and O, by non-thermal plasmas (NTPs) even in atmospheres containing significant quantities of O2. The conversion of CO2 was 15 -21%, when the O2 concentration was in the range 0 -20% (remainder CO2). At 20% the conversion began to decline, falling to ~10% at 50% O2. These conversions would require a few thousand K in conventional "thermal" chemistry, in the absence of a catalyst, but here they were achieved at ambient pressure and temperature. The NTP reactor used was a dielectric barrier discharge (DBD) design, packed with BaTiO3 spheres. The concentration of O2 was varied between 0 and 50% in CO2, at temperatures below 373K and atmospheric pressure, at a residence time of 4.2s. This discovery could open up new routes for direct CO2 decomposition to CO and O2, where the presence of O2 would have been assumed problematic. This "activation" of CO2 may open up a range of possible chemistries for the use and sequestration of CO2 as CO is more reactive. It may also open up opportunities for the use of CO2 as an oxidant, i.e. a source of the O radical.
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