Corona Discharge Technology Research Articles

·OH Scavenger Optimized Grounding Electrode Atomization Corona Discharge Technology for Treatment of Coal Mine Acidic Wastewater

Coal mine acid drainage is a type of industrial wastewater generated in the process of coal production and utilization that has a low pH and contains a small amount of organic matter and SO42−, which is harmful to the environment. The ·OH scavenger was used to optimize the grounded electrode atomized corona discharge (GEACD) technology for the treatment of coal mine acidic wastewater. The effects of various factors on the discharge effect were investigated, and the optimal operating scheme for the subsequent test was determined as 35 mm distance between barrel electrodes, 0.6 mm diameter of wire electrodes, and a flow rate of 45 mL/min. The effects of discharge voltage, discharge time, and ·OH scavenger on COD removal rate and pH in coal mine acid drainage were also investigated. The results showed that at the optimum discharge voltage of 12 kV, discharge time of 66 min, and SO42− to ethanol concentration ratio of 1, the COD value decreased from 152.84 mg/L to 43.27 mg/L, and the pH value increased from 5.6 to 6.1.

Electrochemical generation of ozone for application in environmental remediation

This work focuses on the production, in continuous mode, of ozone using a new electrochemical cell, specially designed and manufactured with 3-D printing to produce in a very efficient way high concentrations of this powerful oxidant. The gaseous ozone produced is tested in the degradation of a synthetic waste containing methomyl. The new cell has been characterized in terms of flow distribution, mass transfer, and production of ozone, being able to reach efficiencies as high as 9.5 g/kWh, which may be even competitive with those produced with the corona discharge technology. The prototype manufactured with an electrode area of 1.5 cm2 can produce a stream containing 30 mg/h of O3. This stream can be used to degrade methomyl. However, the direct bubbling was not found to be very efficient and activation of ozone with the simultaneous irradiation of UV light or the dosing of hydrogen peroxide was needed to improve performance, showing important synergism. The efficient removal of methomyl from wastewater opens the window for the development of alternative technologies to direct anodic oxidation based on the production and dosing of gaseous oxidants such as ozone. The operation of these new technologies does not depend on the salts contained in wastewater and prevents the deterioration in the quality of the waste because it does not leave any residue after application in the treated waste.

Corona discharge actuator as an active sound absorber under normal and oblique incidence

In the majority of active sound absorbing systems, a conventional electrodynamic loudspeaker is used as a controlled source. However, particular situations may require an actuator that is more resistant to harsh environments, adjustable in shape, and lighter. In this work, a plasma-based electroacoustic actuator operating on the atmospheric corona discharge principle is used to achieve sound absorption in real-time. Two control strategies are introduced and tested for both normal in the impedance tube and grazing incidence in the flow duct. The performance of plasma-based active absorber is competitive with conventional passive technologies in terms of effective absorption bandwidth and low-frequency operation, however, it presents some inherent limitations that are discussed. The study reveals that the corona discharge technology is suitable for active noise control in ducts while offering flexibility in design, compactness, and versatility of the absorption frequency range.

A Preliminary Study for Modification of Wetting Properties on Cotton Polyester (TC) Fabric Surface Using Atmospheric Plasma Corona Discharge Technology

Textile materials generally have intrinsic properties, such as flexibility, light volume density, strength, tenacity, comfort and softness. Based on these characteristics, the textile material is generally given a special additional function, such as hydrophobic or hydrophilic properties. The addition of these special functions to the textile industry is generally using conventional wet methods that require more energy and water as well as more chemicals need and expensive price. Plasma technology is one of the dry process technologies and it can reduce the use of chemicals that can pollute the environment. This article describes the application of atmospheric plasma corona discharge technology in the textile sector, especially its use in modifying wetting properties on the surface of polyester cotton (TC) 70%. The results showed that by varying the time of plasma treatment on 70% TC cotton polyester fabric with density of weft and warp respectively 70 strands / inch and 60 strands / inch we found that there was a change in the wetting properties of the fabric with increasing hydrophilic properties of the fabric. SEM images show the example of morphology of cotton polyester fabric surfaces treated with time of exposure by plasma at one minute (60 s) at 3 kV of output voltage as the optimal exposure time and applied voltage to enhance the wetting properties.

Phage-Mediated Control of Flavobacterium psychrophilum in Aquaculture: In vivo Experiments to Compare Delivery Methods.

Phage-based approaches have gained increasing interest as sustainable alternative strategies to antibiotic treatment or as prophylactic measures against disease outbreaks in aquaculture. The potential of three methods (oral, bath, and injection) for delivering a two-component phage mixture to rainbow trout fry for controlling Flavobacterium psychrophilum infections and reduce fish mortality was investigated using bacteriophages FpV4 and FPSV-D22. For the oral administration experiment, bacteriophages were applied on feed pellets by spraying (1.6 × 108 PFU g–1) or by irreversible immobilization (8.3 × 107 PFU g–1), using the corona discharge technology (Fixed Phage Ltd.). The fish showed normal growth for every group and no mortality was observed prior to infection as well as in control groups during the infection. Constant detection of phages in the intestine (∼103 PFU mg–1) and more sporadic occurrence in kidney, spleen, and brain was observed. When fish were exposed to F. psychrophilum, no significant effect on fish survival, nor a direct impact on the number of phages in the sampled organs, were detected. Similarly, no significant increase in fish survival was detected when phages were delivered by bath (1st and 2nd bath: ∼106 PFU ml–1; 3rd bath: ∼105 PFU ml–1). However, when phages FpV4 and FPSV-D22 (1.7 × 108 PFU fish–1) were administered by intraperitoneal injection 3 days after the bacterial challenge, the final percent survival observed in the group injected with bacteriophages FpV4 and FPSV-D22 (80.0%) was significantly higher than in the control group (56.7%). The work demonstrates the delivery of phages to fish organs by oral administration, but also suggests that higher phage dosages than the tested ones may be needed on feed pellets to offer fish an adequate protection against F. psychrophilum infections.

An investigation on the sterilization of berry fruit using ozone: An option to preservation and long-term storage

Abstract In the present study, the effect of ozone treatment on the bacteria affecting fruits was investigated. The process of application of ozone for treatment was termed as OTRE technique. Ozone is a trioxygen inorganic molecule having a pungent smell and formed from the atmospheric oxygen (O2) by the action of electrical discharge. Ozone was generated adopting Ozonizer through corona discharge technology. The bacteria isolated from Kiwi fruits by microbiological technique were exposed to ozone in two approaches, firstly, the ozone discharged at various time from 10 to 60 min into the reactor vessel containing bacteria (1.5 × 108 CFU mL−1). Secondly, use of OTRE in cycle basis, where the sample was treated 30 min and 5 min break and again repeated for 10 min, which continued to the discharge of 60 min. The absorbance of all these varied intervals showed decrease in absorbance, which implies that the number of colonies were decreasing as the OTRE continued. In addition, the growth of these colonies on the nutrient agar was also confirming that the OTRE is quite effective to prevent bacteria from kiwi viz., the bacterial count was decreased from 1.5 × 108 CFU mL−1 to 2.0 × 102 CFU mL−1 in 30 min and 1.5 × 108 CFU mL−1 to 1.2 × 102 CFU mL−1 in 60 min. Thusly, OTRE technique is a rapid, better solution to preserve fruits from disease causing bacteria and enhance fruits durability against spoilage during postharvest storage.

Use of Cold Plasma To Inactivate Escherichia coli and Physicochemical Evaluation in Pumpkin Puree

This work aimed to study the pumpkin puree processing by cold plasma corona discharge as an alternative to heat treatment to reduce Escherichia coli contamination and evaluate physicochemical alterations, using argon (Ar) as the process gas. The treatment time to verify E. coli inactivation was between 2 and 20 min, while physicochemical alterations were analyzed at 5, 10, 15, and 20 min. Cold plasma corona discharge technology to inactivate E. coli proved to be promising, reaching 3.62 log cycles of reduction at 20 min of treatment. The inactivation kinectics showed a tendency of higher decrease with time. Physicochemical characteristics indicate that plasma induces a decrease of pH; however, there is an indication that process gases have an important role and react with the environment and procedure reactive species. This technology may reduce the total carotenoid content of pumpkin puree and in color, mainly the a* parameter, which showed great reduction.

Analysis of Fine Dust Removal Time Using Circular Hole Electrodes of Various Sizes by Corona Discharge

Corona discharge technology is used widely for air purification in laboratory experiments and industry. On the other hand, corona discharge technology has the disadvantage of requiring large-sized electrodes. Therefore, research is needed to reduce the size of the electrodes. In this study, circular hole aluminum electrodes and an air purifier system were designed to reduce the size of the electrodes. Several sets of power conversions were performed to generate a corona discharge. The system consisted of a half bridge inverter, step-up transformer, and Cockcroft Walton circuit. The range of input and output voltages was 30–70 V and 20–25 kV, respectively. A corona discharge was generated by the output voltage. The system could remove smoke in less time with a combination of 13 kHz and an electrode with a hole diameter of 0.2 cm than with the other combinations. The electrode hole diameter affected the removal time of species such as hydrogen carbon hydrogen oxygen (HCHO, formaldehyde), total volatile organic compounds (TVOC), and fine dust, which was confirmed by laboratory experiments. Mathematical derivation and experiments were carried out to prove the validity of the approach; the Clean Air Delivery Rate (CADR) index was 480 μm/m3.

Abatement of amoxicillin and doxycycline in binary and ternary aqueous solutions by gas-phase pulsed corona discharge oxidation

The presence of pharmaceutical compound residues in water bodies is becoming an increasingly serious problem. Various pharmaceuticals have been detected in raw municipal wastewaters, after wastewater treatment plant processes, and even in drinking water. Many common pharmaceuticals are bio-accumulating and they can have a harmful impact on aquatic and terrestrial organisms.In this work, pulsed corona discharge technology (PCD) is studied as a potential method for antibiotic compounds abatement. Two antibiotics, amoxicillin and doxycycline, were chosen as test pharmaceutical compounds. The aim of the study was to investigate the transformation kinetics of binary solutions (water – single antibiotic compound) and ternary solutions (water – two antibiotic compounds) of the compounds and to optimize operational parameters for improved oxidation performance. Ternary solutions were investigated to obtain data on transformation kinetics when two competing pharmaceutical molecules are present in the solution. The experiments showed that reactions of doxycycline oxidation are always first order reactions. Reaction of amoxicillin oxidation has second order in the case of experiments with binary solution in alkaline medium. In other cases, it has first order. The transformation products formed were identified and monitored based on liquid chromatography mass spectrometer analysis. OH-amoxicillin, amoxicillin pencilloic acid, OH-doxycycline and 2-OH-doxycycline had the largest peaks areas. All studied compounds and all transformation products can be easily oxidized by PCD. Approximately 1 kWh/m3 and 0.5 kWh/m3 delivered energy is enough for oxidation of great part of amoxicillin and doxycycline respectively. Low frequency, 50 pps, and high (pH = 12) are preferable for oxidation of both antibiotics from the energy consumption point of view.

Design and performance evaluation of a small unipolar aerosol charger system

A small unipolar aerosols charger system is designed by using corona discharge technology. The performance is evaluated and calibrated in this paper. This system has two main components, one is the corona discharge which adopt tip - arc structure, and the another is high voltage constant current control circuit based on the weak current feedback adjustable as the corona current control part, which ensure that ion concentration remain stable in the process of discharge. The experimental results show that negative corona discharge is better than the positive corona discharge in the same discharge corona current. The intrinsic charging efficiency get better with corona current increases, which can as high as 99% when the negative discharge corona current is 3 µA. However the extrinsic charging efficiency change with corona current change, it got the best performance in the corona current 1.5µA at different particle size in this paper. This small and simple design of the unipolar charger system is suitable for portable aerosol classifier based on electrical mobility techniques.

Inactivation of Bioaerosol in Indoor Air by DC Corona Discharge

A novel DC corona discharge technology was applied on inactivation of bioaerosol in indoor air. A wide range of initial concentration of microorganisms (from 35×104 CFU/m3 to 3×106 CFU/m3) was tested to show excellent germicidal properties for its high inactivation efficiency. Over 99.997% of microbe into the reactor were inactivated at t=150s, EP 2kV/cm and initial population was 3.0×106 CFU/m3. The effects of active species produced by a DC corona discharge on the inactivation of a mixture of bacteria in flowing aerosol were proved. The active radicals like OH radical which acted on microbes in the way of direct oxidation were the most significant factors influencing the microbe inactive efficiency through the assessment of heat variety, ultraviolet emission and ozones generation. The active radicals generation in the process of sterilization can be simply controlled by regulating applied voltage before ozone generated. The results indicate that use DC corona discharge technology in the future application of indoor air decontamination.

Small onset voltages in negative corona discharges using the edges of gold and aluminum foils as nano-structured electrodes

Gold and aluminum foils with nano-structured edges were investigated as electrodes for corona discharges in nitrogen and ambient air. Low onset voltages were observed due to the field enhancement near the edges of the foil. The lowest onset voltage was determined to be about 1.2 kV in ambient air and about 1.1 kV in nitrogen for a 5 mm inter-electrode spacing. This is significantly smaller than the values reported in the literature for sharp tips with similar electrode spacing. The foil-based electrode tips are extremely simple to produce, making them candidates for low-cost, low power consumption and easily available corona-discharge technology.

Optimization of discharge types and electrode structure in a cylinder discharge reactor with saw-wheel array electrodes

The application of corona discharge technology in gas purification and wastewater treatment has been received great attention in recent years. The configuration of discharge electrode and the discharge types directly affect the discharge power and the power density, and then affect the generation of active species as well as the removal efficiency of pollutants. A novel cylinder-type discharge reactor with saw-wheel-array electrodes was developed for removal of SO2/NOx from flue gas, and influence factors such as electrode structure (ratio of spacing of saw-wheel slices and discharge distance, herein defined as R) and power supply types (positive DC, negative DC, and pulse power) on discharge characteristics and the output power was discussed. The experimental results show that the current and output power of three types of discharges firstly increased with R increasing from 0.3–1.7, and then tended to a stability from 1.7–2.5; while the power density reached a maximum at the ratio of 1.7.

Study on earthed atomizing corona discharge enhancing the biodegradability of waste water from oil extraction

This paper studies the usage of earthed atomizing corona discharge to dispose waste water from oil extraction. The I - V characteristic curves of earthed atomizing positive and negative corona discharge are compared to study the influence of water flux and inter-electrode distance (which refers to the distance between line electrode and plate electrodes) on discharge characteristics, and to measure the turbidity, pH, biochemical oxygen demand (BOD 5 ), chemical oxygen demand (COD) and the variation tendency of BOD 5 /COD in the process of dealing with waste water from oil extraction by earthed atomizing corona discharge. Ultimately, the mechanism of earthed atomizing corona discharge is analyzed. Research results indicate that when using earthed atomizing corona discharge to dispose of waste water from oil extraction, as the processing time grows there is a maximum value of turbidity, the pH level increases gradually then stabilizes, COD appears to descend, and BOD 5 as well as BOD 5 /COD both have minimum values. When the processing time attains 300 min, waste water from oil extraction is suitable for biochemical treatment, foreshadowing that earthed atomizing corona discharge technology demonstrates energy conservation characteristic in improving the biodegradability of waste water from oil extraction and has a brilliant application prospect waiting ahead.

Phenol degradation kinetic property in coking wastewater with pulse corona

The degradation kinetics of phenol in coking wastewater and the effect of electrode parameters on phenol’s removal ratio in pulse corona discharge were investigated with experiments and theoretical analysis. The result showed that Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand after five days (BOD 5 ) in the wastewater increased in the initial step, and decreased later. Conductivity rose, and pH of the wastewater decreased with the increase of action time. The phenol degradation process was a one order reaction, and the rate constant ( k ) was positively related to discharge frequency and voltage. Phenol’s removal ratio and degradation rate in weak acidity were larger than those in weak alkalinity and neutral wastewater. The removal ratio reached its maximum when the electrode distance was set at 3.6 cm. This achievement is beneficial to the application of pulse corona discharge technology in coking wastewater disposal.

Degradation of the endocrine disrupting chemicals (EDCs) carbamazepine, clofibric acid, and iopromide by corona discharge over water

Common wastewater treatment plants often do not eliminate endocrine disrupting chemicals (EDCs). Aqueous solutions of three EDCs were treated with an enhanced corona discharge technology. The three EDCs were clofibric acid, a blood lipid regulator, carbamazepine, an antiepileptic drug, and iopromide, a contrast media. To simulate real conditions, EDC solutions containing landfill leachate were also used. In our setup, two barrier electrodes provided an atmospheric pressure corona discharge over a thin water film, in which the counter-electrode was submerged. Clofibric acid, carbamazepine, and iopromide were effectively removed from a single solution. After a treatment of 15 min, there were no traces of iopromide estrogen activity either as a single substance or as degradation products when using an E-Screen Assay. Continuous treatment was compared with pulsed treatment using carbamazepine solutions mixed with pretreated landfill leachate. Best degradation results were achieved with a 500 W continuous duty cycle treatment. Counter-electrodes from materials such as boron doped diamond (BDD), titanium iridium oxide, and iron were investigated for their influences on the process effectivity. Significant improvements were achieved by using an enclosed reactor, BDD electrodes, and circulating only a fresh air or argon/air mixture as cooling gas through the barrier electrodes.

NOx reduction from compression ignition engines with pulsed corona discharge

Abstract A study of pulsed corona discharge technology for NO x reduction from diesel engine exhaust is presented. The pulsed corona reactor consists of two coaxial cylinders used as electrodes of opposite polarities. The results are presented in terms of the cleanness (mass of NO x removed relative to its initial mass), and the efficiency (the energy required to theoretically dissociate 1 g of NO x , relative to the energy actually needed). Experimental results show that for a pulsed corona, the polarity of the electrodes has no significant effect on the reactor performance. Cleanness was found to be independent of the engine load. The pulsed corona reactor design considers the most efficient means of energy transfer from pulse-forming capacitor to the discharge zone. It is shown experimentally that an external electrode of smaller diameter provides better NO x reduction. For a pulsed corona reactor, the residence time that provides the best performance must be sufficient to allow all the pollutant molecules to interact with the radicals produced by the corona discharge. The residence time is calculated for the pulsed corona reactor and experimentally confirmed to be the one that results in the best cleanness and efficiency of NO x removal. The empirical relations, based on working conditions, are obtained and provide a route for reactor design.

NO x reduction from compression ignition engines with DC corona discharge—An experimental study

An experimental study of DC corona discharge technology for NO x reduction from diesel engine exhaust is presented. The DC corona reactor consists of a flat electrode against a multi-needle electrode. The results are presented in terms of the cleanness (mass of NO x removed relative to its initial mass), and the efficiency (the energy required to theoretically dissociate 1 g of NO x , relative to the energy actually needed). For both cleanness and efficiency, negative polarity (negative needles) is preferable. Cleanness was found to be independent of the engine load. The results show that the performance of a DC corona reactor depends on the reactor length L, electrode separation distance D, and needle density a. The cleanness and efficiency of the NO x decomposition were mapped, and optimal geometrical parameters for the best reactor performance have been obtained. It is concluded that for best performance, the residence time of the exhaust gas inside the reactor should be longer than 1 second ( τ > 1 s ); the electrode separation distance D must be less than 30 mm (for the electric field intensity to remain sufficiently high for dissociation reactions); and the needle separation distance a must not exceed 20 mm (to provide sufficiently dense distribution of plasma regions from each needle). The cleanness and efficiency values for the optimal geometry lay between 55% (cleanness) with 10% (efficiency), and 50% (cleanness) with 18% (efficiency), for needle separation distances a of 10 and 20 mm, respectively.

Emission of ozone and organic volatiles from a selection of laser printers and photocopiers.

To estimate the impact of office equipment on the quality of indoor air, the emission of ozone and organic volatiles was measured from one photocopier and four laser printers, three of which operated according to traditional corona discharge technology. The laser printers equipped with traditional technology emitted significant amounts of ozone and formaldehyde. Lesser amounts of other volatile aldehydes were emitted during printing. The photocopier emitted mainly ozone. In a well-ventilated office environment, the amounts encountered here for individual volatiles were within recommended maximum exposure limits for a reasonable density of printers. Because it is not known whether the concentration of irritating volatiles, such as formaldehyde, should be kept lower in an ozone rich environment or not, and because emissions in the immediate vicinity of the printers exceeded recommendations, the authors recommend that laser printers equipped with the traditional corona rods not be placed beside or immediately at the working site of office personnel. This way, ozone concentrations can be kept below recommended maximum exposure limits, provided that the ventilation rate is adequate. Further, it seems that if a reliable quantitative comparison of total organic volatiles prior to and during printing is to be made, the inertness of the sorbent toward ozone should be confirmed.

98/01634 Mercury vapor control by means of corona discharge: Helfritch, D. et al. Emerging Solutions VOC Air Toxics Control, Proc. Spec. Conf., 1996, 277–288

The work reported here describes the construction and performance of a novel corona discharge flue gas reactor designed to oxidize mercury vapor, allowing the mercuric oxide to be subsequently captured in a downstream particulate control device. A corona discharge in flue gas produces oxidizing radicals, such as OH and atomic oxygen, which can then react with elemental mercury. Optimum performance demands that the corona discharge, and hence the oxidizing radicals, be uniformly distributed within the flow volume of the reactor. When a uniform volume distribution of electrons is achieved, then uniform exposure and treatment of the gas is assured, and maximum energy efficiency can be obtained. By means of a laboratory based, pilot scale system, it is shown that the spatially distributed corona discharge produced by the corona reactor operating at low power level and short residence time yields a high level of mercury vapor oxidation. The mercuric oxide, in the form of solid particles, can then be removed by a conventional electrostatic precipitator or fabric filter. It is also shown that low temperature, high humidity conditions enhance mercury oxidation. For an application to solid waste incineration, this suggests the placement of the reactor downstream of the spray dryer andmore » upstream of the fabric filter. Economic analysis indicates that this method of mercury vapor control is very competitive with adsorption by activated carbon. For example, if mercury control regulations are promulgated for coal burning power plants, the corona discharge technology could potentially save the US utility industry and electricity consumers up to 250 million dollars per year. 10 refs., 6 figs., 2 tabs.« less