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During pulsed corona discharges, both negative and positive ions react with moisture to generated cluster ions. These cluster ions are considered to be useful for cleaning hazardous materials such as hazardous pollutants and allergen. In this paper, for such type of ions generation devices, numerical simulation is carried out on the cluster ions formation. The behavior of streamer evolution and cluster formations are simulated well, and it is clarified that the clustering progresses toward H 3 O+(H 2 O) 4 and $\mathbf{O}_{2}^{-}(\mathbf{H}_{2}\mathbf{O})_{4}$ when the chemical species of $\mathrm{H}_{3}\mathrm{O}^{+}(\mathrm{H}_{2}\mathrm{O})_{n}$ and $\mathrm{O}_{2}^{-}(\mathrm{H}_{2}\mathrm{O})_{n}\ (n=0-5)$ are considered. Ions number densities obtained in the experiment are smaller than the calculated ones because some differences between the numerical model and experiment exit and the ions may be lost near in the path of the chamber.

The aim of the present article is to study the feasibility of continuous dielectric barrier discharge (DBD) treatment of granular plastic materials in view of improving their triboelectric charging ability, and assessing the effectiveness of associating plasma treatment with the triboelectrostatic separation process. The effects of the following DBD parameters were studied: the amplitude and the frequency of the applied high voltage, the thickness of the dielectric barrier, the distance between the electrodes of the reactor as well as the speed of the conveyor that was used for the transfer of the granular materials though the nonthermal plasma zone. The study was carried out on millimeter-sized polyethylene particles. It was found that the charge of DBD-treated particles increases with the applied high voltage and decreases with the speed of the conveyor. Both the distance between the electrodes and the thickness of the dielectric barrier have a remarkable effect on the charge acquired after DBD treatment. Within the experimental domain of this study, the frequency of the high voltage does not significantly affect the efficiency of the tribocharging process. Under optimal operating conditions given by the first series of experiments, two distinct triboelectrical series were established, one for treated particles and the other for untreated particles, using eight types of granular plastics [acrylonitrile butadiene styrene, polyethylene (PE), polypropylene, polyvinyl chloride, crystalline polycarbonate, polystyrene (PS), high impact polystyrene, and crystalline polystyrene], Finally, an electrostatic separation experiment was carried out on a plasma-treated PE–PS mixture using a roll type electrostatic separator. The results were then compared with those obtained for an untreated mixture. It was found that plasma treatment improved by about 40% the purity and recovery of the sorted products.

An effective NO x -reduction aftertreatment system for a marine diesel engine that employs combined nonthermal plasma (NTP) and adsorption is investigated. The system can also treat particulate matter (PM) that employs a diesel particulate filter (DPF) and its regeneration by NTP-induced ozone. The effect of the combined reduction of accumulated PM and NO x is studied. The marine diesel engine of interest provides an output power of 1 MW at 100% of the engine load. The NO x reduction is composed of repeated adsorption and desorption flow processes using NTP combined with NO x adsorbents. With a view toward practical use, experiments on a higher number of cycles are carried out. The amount of adsorbents is 105 kg, which is greater than that in the authors’ previous study. As a result, NO x reduction efficiency by NTP is higher than in the previous study and is greater at higher amounts of adsorbents owing to higher NO x desorption. Furthermore, DPF regeneration with plasma-induced O3 injection is achieved simultaneously. This aftertreatment system demonstrates an excellent energy efficiency of 114 g(NO2)/kWh. The present aftertreatment can generate a synergistic effect of PM and NO x reduction.

The collection and incineration mechanisms in the particulate matter (PM) aftertreatment technique proposed by the author were investigated. An experiment for actual exhaust gas was performed by sampling 10 NL/min of exhaust gas from the flue gas from a stationary diesel engine generator. The reactor for PM aftertreatment comprised a glass tube with surrounding corona needles that projected negative charges. Various combinations of voltages applied to each of the corona needles and the surface electrodes were compared. The results enhanced the hypothesis that negatively charged PM is attracted by the dielectric surface that is positively charged by positive ions supplied by the electrode on the glass surface. Subsequently, conditions for carbon incineration by nonthermal plasma were investigated using a simulated dielectric barrier discharge electrode and carbon black particles applied to the surface. It was found that the gap length over which the carbon-adhered area and the surface electrode face each other is the key factor for the rate of incineration.

Toluene decomposition is performed using an adsorbent and a nonthermal plasma (NTP) induced radical flow system that consists of a surface discharge and circulation flow. The liquid toluene is vaporized in the circulation channel connected to a blower and the surface discharge plasma reactor in series, and the toluene gas is adsorbed by the adsorbent. In order to accelerate the oxidative decomposition of the adsorbed toluene, two techniques are tested. In the first technique, concentrated ozone injection is utilized and the adsorbed toluene is decomposed using the NTP flow. This occurs after introducing the concentrated ozone in advance, through the bypass channel connected in parallel with the adsorbent. In the other technique, toluene decomposition occurs under the reduced pressure of the adsorbent chamber during the decomposition process, because accelerated toluene decomposition on the surface of the adsorbent is expected. This reduced pressure is in the range of −3 to −7 kPa and is achieved by regulating the ball valve located upstream of the adsorbent chamber. When the concentrated ozone is introduced into the circulation channel, the adsorbent temperature increases drastically and the conversion ratio of toluene to $\text{CO}_{x}$ (CO and CO2) increases by a factor of 2.0 in comparison with that without the concentrated ozone injection. In addition, the energy efficiency of the conversion increases by a factor of 1.9, even when the energy required for the concentrated ozone is included. However, there was no noticeable effect of the reduced pressure on the toluene decomposition under experimental conditions.

Atmospheric pressure plasma graft polymerization-treated fluorocarbon plastics are bonded with a metal, to evaluate adhesiveness. In this research, the atmospheric nonthermal plasma graft polymerization technique is used in treating the surface of polytetrafluoroethylene (PTFE) in a dry process, capable of reducing environmental loading. The treated PTFE is joined with the stainless steel plate to perform a peeling test. We examine the peeling strength and the best condition for practical application using peeling strength as an optimization variable. A concrete numerical target is 2 N/mm, which is the standard adhesive strength applicable for industry uses. To conduct the graft polymerization, we use a monomer such as acrylic acid (CH2 = CHCOOH) and target material such as PTFE. Peeling strength is maximized (averaged value of 1.56 N/mm, largest value of 2.0 N/mm) when the temperature of the acrylic acid is 60 °C and the Ar main flow rate is 40 L/min. Influence of plasma torch cover on peeling strength and entrained flow near the torch are investigated to realize the stronger adhesion, and better shape of the cover is determined. Furthermore, by analyzing X-ray photoelectron spectroscopy and scanning electron microscope images, we evaluate the atmospheric pressure plasma graft polymerization process from a different perspective and search for optimal operating conditions of the processing method.

Plasma sterilization technologies have been the subject of several studies and remarkable developments over the last few years. Ozone (O3) is an effective sterilizer, and its range of applications has extended to include water purification. Ozone is typically generated from oxygen (O2) in nonthermal plasma (NTP). However, this process requires the use of an additional gas cylinder or supply device for O2, thereby entailing increased costs of operation and energy consumption. Air can be used as an alternative to O2 as a source gas for O 3 production. However, this leads to the generation of nitrogen oxide (NOx), an air pollutant, during plasma discharge. Hence, it is vital to develop a method for O3 generation that addresses the challenges of energy costs and emission of air pollutants. This study, therefore, proposes an energy-efficient NTP sterilization system. The system is based on electrolysis of water to produce O2 and hydrogen (H2 ). The O2 produced is used to generate O3 for sterilization, and H2 is used in fuel cells to generate electric power. The present study details the characteristics of energy consumption and efficiency in O3 production and elucidates the proposed NTP sterilization system. Reduction in energy consumption for O3 production is achieved with a power recovery rate of more than 11.1% in the present high-efficiency water sterilization system.

We present a highly efficient carbon dioxide (CO2) reduction treatment technique using an adsorbent and nonthermal plasma flow at the laboratory scale. The plasma reactor consists of twelve surface discharge elements, which are energized by a 10-kHz bipolar pulsed high-voltage power supply. As an adsorbent, the molecular sieve zeolite 13X is used, and it is placed downstream of the plasma reactor. In the physical adsorption process, approximately 10% CO2 gas with flow rate 10 L/min is prepared by 99.5% CO2/N2 cylinder and a nitrogen cylinder. It is then introduced into the flow channel, and CO2 is adsorbed by the adsorbent. After the adsorption process, the circulation flow channel is set and the N2 plasma flow is generated with a blower. Consequently, CO2 adsorbed by the adsorbent is desorbed with higher concentration (currently ∼20%) and reduced to CO with high efficiency. The generated CO can be reused as a fuel. We evaluate the experimental results by calculating the conversion efficiency of CO2 to CO and the energy efficiency of the plasma. When the number of repetitions of experiments is 5, a maximum CO concentration of 5% and a maximum CO2 concentration of 20% are reached. The energy efficiency associated with the conversion of desorbed CO2 to CO reaches 14% with the plasma power of 300 W. Discussions are carried out by comparing the value with those obtained in other studies on the plasma reduction of CO2.

Nitrous oxide (N2O) is commonly used as an anesthetic gas in hospitals. It is a greenhouse gas and should therefore be removed to limit pollution. As nonthermal plasma has low electron density, it has been considered effective for the treatment of low concentrations of gas. Moreover, N2O is extremely stable in the troposphere, and is therefore difficult to decompose. In this study, a system to remove high concentrations of N2 O using nonthermal plasma along with an adsorbent was investigated. A surface discharge plasma reactor was employed to decompose N2O gas. This gas simulated the waste gas from the anesthetic equipment used in operating theatres. Because of its high concentration, the decomposition of N2O afforded the mononitrogen oxides, nitric oxide, and nitrogen dioxide (NOx = NO + NO2), respectively. The generated NOx was adsorbed by the adsorbent. As a result, an N2O decomposition efficiency of 66% was achieved with air-based 12.8% N2O at a flow rate of 1.1 L/min and a plasma reactor input power of 375 W. Furthermore, 0.4% NO and 1.0% NO2 were generated during N 2O decomposition. Both gases were removed by the adsorbent. It was confirmed by the previous studies that the adsorbed NOx was decomposed by N2 plasma. It was demonstrated that the removal of high concentration of N2O could be accomplished by using a system that combines nonthermal plasma with an adsorbent. In practice, much higher volumes of N2O can be removed, without NOx formation, in a setup that involves a series of plasma reactors with recirculation, followed by an NOx reduction system with N2 plasma.

A pilot-scale simultaneous removal of ${\text{NO}}_{x}$ and ${\text{SO}}_{x}$ , as a nonthermal plasma and chemical hybrid process (PCHP), is carried out on combustion exhaust gas in a glass manufacturing system. The PCHP is implemented in an actual semi-dry-type exhaust gas treatment system. The exhaust gas (12 700 m3N/h) is produced by the combustion of fossil fuels and contains both ${\text{NO}}_{x}$ (160 ppm) and ${\text{SO}}_{x}$ (150 ppm). In PCHP, ${\text{NO}}$ is oxidized to water-soluble ${\text{NO}}_{{2}}$ through a plasma process using ozone. ${\text{Na}}_{{2}}{\text{SO}}_{{3}}$ is then produced as a byproduct in a desulfurizing process using a solution of NaOH. The generated ${\text{NO}}_{{2}}$ is then reduced to ${\text{N}}_{{2}}$ and ${\text{Na}}_{{2}}{\text{SO}}_{{4}}$ using an ${\text{Na}}_{{2}}{\text{SO}}_{{3}}$ solution, followed by the dried ${\text{Na}}_{{2}}{\text{SO}}_{{4}}$ particles being removed in a semi-dry reactor by a dry-type electrostatic precipitator. Our findings show the molar ratio of ${\text{NO}}$ to the injected ozone to be more than 0.75. ${\text{NO}}$ and ${\text{SO}}_{x}$ removal efficiencies of 28% and 63% are obtained. Further, the paper discusses de- ${\text{NO}}_{x}$ by the use of a bag filter (BF) for the injection of the ${\text{NaHCO}}_{{3}}$ at the BF inlet. Due to the effect of ozone and ${\text{NaHCO}}_{{3}}$ , ${\text{NO}}_{x}$ removal efficiency is increased by up to 45%. Our results show that higher de- ${\text{NO}}_{x}$ and de- ${\text{SO}}_{x}$ efficiencies are obtained by maintaining a local exhaust gas temperature of less than 150 °C. Through this experiment, it is confirmed that this simultaneous treatment of ${\text{NO}}_{x}$ and ${\text{SO}}_{x}$ using semi-dry-type PCHP is highly effective and promising for exhaust gas treatment in glass manufacturing.

A nonthermal plasma reactor (NTPR) using two 2.45-GHz microwave (MW) generators for the abatement of nitrogen oxides ( ${\text {NO}}_{\text {x}}$ ) and sulfur ( ${\text {SO}}_{\text {x}}$ ) contained in the exhaust gas of a 200-kW marine diesel engine was built and tested. Numerical analysis based on a nonthermal plasma kinetics model for the abatement of ${\text {NO}}_{\text{x}}$ and ${\text{SO}}_{\text{x}}$ from marine diesel engine exhaust gas was performed. A generic kinetic model that implements electron collisions and plasma chemistry has been developed for applications involving low-temperature (50–100 K) nonthermal plasma. Abatement efficiencies of ${\text {NO}}_{\text{x}}$ and ${\text {SO}}_{\text{x}}$ were investigated for a range of mean electron energies, which directly impact on the rate constants of electron collisions. The simulation was conducted using the expected composition of exhaust gas from a typical two-stroke, slow-speed marine diesel engine. The simulation results predict that mean electron energy of 0.25–3.2 eV gives abatement efficiency of 99% for ${\text {NO}}_{\text{x}}$ and ${\text {SO}}_{\text{x}}$ . The minimum residence time required was found to be 80 ns for the mean electron energy of 1 eV. Multimode cavity was designed using COMSOL multiphysics. The NTPR performance in terms of ${\text {NO}}_{\text{x}}$ and ${\text {SO}}_{\text{x}}$ removal was experimentally tested using the exhaust from a 2-kW lab scale, two-stroke diesel engine. The experimental results also show that the complete removal of NO is possible with the MW plasma (yellow color) generated. However, it was found that generating required MW plasma is a challenging task and requires further investigation.

In this paper, organic electroluminescence fluoropolymer film devices, i.e., organic light-emitting diodes (OLEDs) comprising polychlorotrifluoroethylene (PCTFE) films treated by an atmospheric-pressure nonthermal plasma (NTP) graft-polymerization process, are investigated. PCTFE films can provide a long lifetime for OLEDs because of their excellent gas barrier properties; however, they are difficult to laminate, owing to low adhesiveness. The surfaces of PCTFE films are treated by an atmospheric-pressure NTP-graft-polymerization process to improve their adhesiveness, and then, indium tin oxide and a luminous layer are deposited on the treated PCTFE films. As a result, OLEDs comprising PCTFE films are successfully demonstrated.

Due to the fact that it is difficult to fulfill the recent stringent regulations governing marine diesel engine emission by means of combustion improvement alone, an effective aftertreatment technology is required to achieve the efficient simultaneous removal of $\hbox{NO}_{\rm x} $ and particulate matter (PM) . In the present study, we designed and investigated an effective aftertreatment system that employs a combination of ozone injection and nonthermal plasma (NTP) reduction for a marine diesel engine. The proposed technology offers the advantage of not requiring precious-metal catalysts and harmful heavy-metal catalysts as well as urea solution. In this aftertreatment system, PM in the exhaust gas is first captured by a ceramic diesel particulate filter. Subsequently, the deposited PM is oxidized and removed by NTP-induced ozone injection. After the PM treatment, $\hbox{NO}_{\rm x} $ in the exhaust gas is treated by adsorption followed by NTP-combined desorption and reduction processes. These processes are repeated periodically, and total emission control is achieved. Since the deposited PM and the desorbed $\hbox{NO}_{\rm x} $ are treated at a high-concentration state by ozone and oxygen-lean NTP, a higher performance for total marine diesel emission control is recorded. The maximum efficiencies of $\hbox{NO}_{\rm x} $ and PM reduction were 94% and 95%, respectively.

Plasma application for environment improvement is desirable. In order to improve the efficiency of toxic gas decomposition by plasma, it is worthwhile to clarify the behavior of radicals in nonthermal plasma. Although previous studies have revealed the behavior of radical densities and temperatures in atmospheric discharge, they are not yet connected to apprehension or simulation of practical toxic gas decomposition by atmospheric plasma. In this study, the coaxial dielectric barrier discharge cylinder reactor is prepared, where the radical behavior and the toxic gas decomposition efficiency can be measured altogether. The density of OH radical is directly measured by laser-induced fluorescence, and trichloroethylene (TCE) decomposition efficiency is also investigated in the same reactor. TCE decomposition efficiency is suppressed as background humidity increases. On another front, OH density measurement in ac barrier discharge indicates that OH density is about 2-4 ×1011 cm-3 in time and spatial average and saturated with increasing humidity. From the saturation pattern, the initial OH density is estimated to be about the order of 1014 cm-3 in streamer site. In addition, TCE addition in background reduces OH density, which indicates that OH reacts with TCE. The reason for the suppression of decomposition efficiency with increasing humidity is estimated as a consequence of O radical reduction by water-originated particles.

GaN is widely studied and developed as a material for new application in power electronic devices or as an emitter of various colors of light. GaN is usually formed by nitriding GaAs and grown on the sapphire substrate with a high dislocation density. For this dislocation, microchannel epitaxy or regrowth of GaN is required to reduce dislocations. Recently, plasma treatment has been used for interface treatment, regrowing of GaN crystal, and nitridation process of GaAs. GaN surface was treated by atmospheric-pressure microplasma using Ar and N2 as process gases and powered by ac and pulsed-power supplies. Microplasma is atmospheric-pressure nonthermal plasma and a type of dielectric barrier discharge which has a small discharge gap and requires relatively low discharge voltage of only about 1 kV. Modifications of the surface were observed after the treatment, and they depend on the gas process, treatment time, and power supply. The surface was analyzed before and after the treatment using X-ray photoelectron spectroscopy analysis and atomic force microscopy.

The decomposition of bromomethane (CH3Br), which is an ozone-depleting substance, is carried out using a pulsed dielectric barrier discharge. To accomplish this, a plasma reactor comprising a stainless discharge wire electrode and a quartz cylinder wrapped with a copper mesh as the ground electrode is employed. This reactor is energized by a pulsed high-voltage power supply using an insulated-gate bipolar transistor. The effects of humidity, flow rate, and initial CH3Br concentration on CH3 Br decomposition are investigated. The relative humidity is found to slightly affect the CH3Br decomposition. Additionally, the CH3Br decomposition efficiency is found to decrease with increasing gas flow rate; however, the amount of decomposed CH3Br increases with gas flow rate. More than 95% CH3Br decomposition efficiency is achieved at a gas flow rate of 1 L/min and initial CH3Br concentrations of 1000, 5000, and 10 000 ppm. Gas chromatography/mass spectroscopy analysis shows that approximately 95% of the decomposed CH3Br is converted to HBr, which can be easily removed using an alkaline scrubber. The energy efficiency of the CH3Br decomposition increases with the initial concentration at the same specific energy. In addition, the specific energy decreases when the energy efficiency is maintained by increasing the gas flow rate.

Among various NOx reduction technologies, selective catalytic reduction (SCR) methods have been studied for cleaning of diesel engine exhaust. Urea SCR system, in which ammonia is used as reducing agent is thought to be one of the most promising methods. However, further improvement of the performance is required at low temperatures for example below 400 K. The purpose of this study is to enhance ammonia generation from urea at low temperatures. In this study, a dielectric barrier discharge (DBD) plasma reactor in which dielectric pellets and urea powder were packed was investigated experimentally. The reactor was fed with humid gas and driven by pulsed high voltage at 400 K or lower. The effect of the pellet material, gas humidity, and gas flow rate on ammonia generation was experimentally examined. Application of discharge plasma enhanced the ammonia generation significantly at low temperatures in which ammonia generation was negligible without plasma. Material of the catalyst pellets packed in the reactor significantly affected the ammonia generation. Air plasma showed nearly the same ammonia generation as that of nitrogen plasma. These results suggest that our method can provide a compact and low temperature on-board ammonia production system.

Atmospheric-pressure nonequilibrium nonthermal plasma hybrid exhaust gas aftertreatment systems that do not utilize precious metal catalysts, harmful ammonia, etc., have been developed by the authors. Two types of new environmental protection systems (a dry system and a wet system), which enable the production of ultralow , particulate matter and emissions as well as reduced fuel consumption and low cost, are investigated for diesel engines, marine engines, and combustion boiler applications. This paper reports the principles of the dry system and some recent experimental results of laboratory tests. The reduction comprises three flow processes: 1) adsorption, 2) heating, and 3) cooling processes. The heating process corresponds to the regeneration process. These processes are repeated in the following order: 1), 2), and 3). This dry system demonstrates excellent energy efficiencies that meet the most recent Japanese national regulations regarding automobile diesel engine exhaust gas. In this study, approximately 60% of the of the exhaust (: 240 325 ppm, , N: standard state) can be treated for 35 h. An improved system energy efficiency of 143 , which is the highest yet, is achieved for reduction.

Stringent NOx and volatile organic compound (VOC) flue gas regulation are set force for various industrial emission sources. The conventional emission control technologies such as selective catalytic reduction for NOx treatment and incineration and catalysts for VOC treatment have limitations in terms of operating conditions, costs, and performance. A novel, economical, and cost-effective device is mandated to meet the regulations. A new approach consists of flue gas adsorption, desorption (concentration and adsorbent regeneration), followed by nonthermal plasma decomposition. This concept was applied for NOx, various VOCs, and other hazardous air pollutant treatment. More than 90% of NOx and VOC reduction was achieved using a series of surface discharge units. The energy efficiencies of 3.35 g( NO2)/kWh for NOx and 34.2 g/kWh for toluene were achieved using concentration technique, followed by surface discharge plasma reactor. These hybrid processes make the flue gas volume order of magnitude small, resulting in the reduction of the energy yield, reactor size, power supply, and total system costs.

A toluene oxidation system is developed using an adsorbent and a nonthermal plasma (NTP) flow that consists of a surface discharge and a circulation flow. The liquid toluene is vaporized in the circulation line connected with a blower, the adsorbent, and the surface discharge plasma reactor in series, and the toluene gas is adsorbed by the adsorbent. Hydrophobic zeolite pellets are used as the adsorbent. After the toluene adsorption, ozone generated by the surface discharge is supplied to the adsorbent, and adsorbed toluene is oxidized on the surface of the adsorbent. Because the gas is circulated during toluene oxidation, ozone is used to oxidize toluene effectively and without waste. As a result, adsorbed toluene is efficiently converted to COx (CO + CO2) using the NTP flow; 88% and 43% conversion ratios of toluene to COx are achieved when 1 and 6 mL of toluene are oxidized for 90 and 150 min, respectively. In addition, CO2 selectivity of more than 89% is obtained when 1 and 6 mL of toluene are oxidized. The conversion rate of toluene to COx and the energy efficiency of the toluene-to-COx conversion increase with the amount of adsorbed toluene.

The fundamental characteristics of flue gas cleaning for NOx using a wet-type plasma reactor are evaluated, with attention being laid on concentrations of nitrate and ammonium ions in the liquid. The wet-type plasma reactor of the wire-cylinder configuration driven by a square-wave high voltage was used. A thin liquid film was maintained on the inner wall of the reactor. In this reactor, a discharge plasma oxidizes NO to NO2, and NO2 is dissolved into the liquid as NO3-. Continuous absorption of nitrogen oxides induces saturation and acidification of the liquid, therefore inhibiting further absorption. The effect of the addition of ammonium ions (NH4+) into the liquid film on the enhancement of NOx removal has been experimentally confirmed. In that case, the addition of NH4+ was effective for NO oxidation, as well as NOx absorption into the liquid, resulting in the increase of NO2- and NO3- concentrations in the liquid. With the presence of Fe2+ ions in the liquid exposed to the discharge plasma, a reduction of NO3- to NH4+ takes place. The reduction of nitrate ions to ammonia raises the solution pH and ensures continuous NOx absorption. These results suggest the possibility of the continuous operation of the wet-type plasma reactor for NOx removal without excess acidification of the absorbing water. The process that is responsible for the reduction of nitrate ions into ammonium ions is of an electrochemical nature.

A simultaneous reduction of particulate matter (PM) and NOx emitted from diesel engines has been realized by means of a barrier-type packed-bed nonthermal plasma (NTP) application driven by a pulse high-voltage power supply under oxygen-lean conditions. BaTiO3 particles having a large dielectric constant ( ~ 10 000) are used as packed pellets, and carbon PM is loaded among the pellets. NOx is reduced by N radicals, and PM is incinerated by oxygen radicals induced either by NOx or by ozone (O3) reduction under elevated local temperatures among the pellets. From the photographs of the pellets, it can be confirmed that the carbon PM or soot is removed under the condition of lean oxygen, resulting in the simultaneous removal of the PM and NOx. An optimal value for the mass of the loaded PM exists, and when the loaded PM mass is greater than a threshold value, the effect of the NTP induced by the partial discharge is too weak to simultaneously reduce the PM and NOx. Under the optimized plasma condition, the experiment yields energy efficiencies of 2.2 g/kWh for the PM incineration and 4.3 g(NO2)/kWh for the NOx reduction in the experiment.

NOx removal from the flue gas of a smoke tube boiler using an ozonizer for NO oxidation and a Na2SO3 aqueous solution scrubber (diameter: 0.6 m; height: 3.7 m) was investigated. In this paper, in order to determine the correlation NOx removal performance, the height of the packing material layer in the scrubber was varied from 2.1 to 0 m. The performance tests were carried out using both a compressed natural gas (CNG) and a heavy oil. The flue gas flow rates were in the range of 455-1440 Nm3/h under CNG firing and 675-1330 Nm3/h under heavy oil firing, and the boiler NOx emission concentrations were approximately 40 and 100 ppm, respectively. A total packing height of 0.75 m resulted in NOx removal efficiencies of 70% and 60% for CNG and heavy oil, respectively. Moreover, the Na2SO3 consumption rate at 0.75 m was 10%-20% less than that at 1.2 m, although the NOx removal efficiency was nearly the same. The correlation between the NOx removal performance and the gas retention time in the scrubber was obtained, providing the design information of the scrubber for industrial applications.

A surface modification technique that improves the adhesion of fluorocarbon polymer films such as polytetrafluoroethylene (PTFE), perfluoroalkoxy fluoroplastics, and polychlorotrifluoroethylene is developed using argon at atmospheric pressure and acrylic acid vapor nonthermal plasma. The results of the T-type peeling test show that the peeling strength of the treated PTFE film is approximately 70 times greater than that of the untreated film. From X-ray photoelectron spectroscopy and scanning electron microscope analyses, it is confirmed that chemical bonds with F atoms decrease greatly on the surface and that a hydrophilic layer is formed due to the plasma graft polymerization process. Using the present surface treatment apparatus, it is possible to bond A4-sized sheets of PTFE and metals without losing the excellent physical properties of PTFE.

A study of the induced flow pattern, in quiescent air, by the trielectrode plasma curtain (TPC) discharge is presented and analyzed in terms of the electrical characteristics of the discharge. The TPC discharge is based on the combination of a dielectric barrier discharge (DBD) with a corona discharge (CD) in a three-electrode system, and basically, it consists of the “stretching” of a pure DBD by the action of a negative CD generated between the active electrode of the dielectric barrier and a remote third electrode. It was found that the observed flow pattern is mainly controlled by the forces exerted at the vicinities of both exposed electrodes, where the electric field is very high. On the other hand, the net force produced at the interelectrode gap seems to be very small in spite of the large current flowing there, a fact that can be attributed to the relatively low value of the electric field at the streamer channel.

Inactivation of microorganisms, such as Escherichia coli, by exposure to a microplasma is experimentally investigated. A microplasma is an atmospheric-pressure nonthermal plasma. Microplasmas, which generate high-intensity electric fields, can be formed using relatively low discharge voltages (0.7-1.1 kV) across small discharge gaps (0-100 ?m). The key benefits of the practical application of exposure to a microplasma are as follows: 1) the low discharge voltage and 2) the simple apparatus because a vacuum enclosure is not required. Hence, the apparatus for generating a microplasma could be relatively small and inexpensive and could be integrated into a portable device. The ozone generated by a microplasma at a low power level was measured, although the specific power density of the microplasma was larger than that of large-scale conventional plasmas. The emission spectra of the microplasma discharge in N2 was measured: 1) to confirm the UV light emission and 2) to identify the active chemical species generated by the microplasma discharge. The emission spectra was also measured with the presence of water droplets. The UV light from the microplasma discharge showed excited nitrogen molecules and OH radicals. In this paper, two cultures of bacteria, i.e., gram-negative Escherichia coli HB101 and gram-positive Bacillus subtilis JCB 20036 were the target microorganisms to be inactivated. In the experiments reported here, the number of bacteria decreased after microplasma treatment. The inactivation rate increases as the discharge voltage increases. Escherichia coli is completely inactivated when air is used as carrier gas at a plasma discharge voltage of 1.05 kV. Using nitrogen as carrier gas, the highest inactivation rate is 77% at a discharge voltage of 1.15 kV. In addition, Bacillus subtilis is inactivated with a rate of 97% at 1.07 kV with air as carrier gas. Using nitrogen as carrier gas and a discharge voltage of 1 kV results in an inactivation rate of 70% of bacteria. The inactivation of microorganisms by microplasma may be due to several factors either individually or in combination of the following: 1) the excited molecules and ions; 2) ozone; 3) high electrical fields; and 4) UV light. The effect of active species such as OH radicals may also be important since all the bacteria were carried within a small water droplet in between the electrodes.