High-voltage Discharge Plasma Research Articles

Study on the Drying Characteristics and Physicochemical Properties of Alfalfa under High-Voltage Discharge Plasma

High-voltage discharge plasma drying (HVDPD) is a non-thermal and efficient drying technique. In this study, we compared the drying characteristics and physicochemical properties of alfalfa dried via HVDPD, hot-air drying (HAD), and natural air-drying (AD) and analyzed the experimental results using infrared spectroscopy, scanning electron microscopy, colorimetry, and other detection techniques. The results showed that HVDPD had a higher drying rate than AD and saved more energy than HAD. Alfalfa dried via HVDPD had the most intact internal structure, the highest rehydration ratio (RR), the best color quality, and the best nutrient retention, resulting in the highest relative quality and feeding value. Therefore, HVDPD is an excellent drying technique for alfalfa, providing a new and effective way to improve the storage, transportation, and drying quality of alfalfa.

Flow characteristic investigation of localized arc filament plasma assisted turbulent jet and Bunsen flame

Localized arc filament plasma actuators (LAFPAs) have shown the capability to alter the entrainment of freestream air into a jet. This paper presents an investigation into the effects of LAFPAs on the air jet and methane/air premixed Bunsen flames at different Reynolds numbers. The flow disturbance covering the laminar to turbulent transient conditions was generated by a high voltage plasma discharge system of LAFPAs. The high speed Z-type Schlieren technique was applied to visualize the instantaneous flow and flame structures, and an optical flow algorithm was used to estimate the velocity distribution and further analyze the turbulent effect induced by the plasma. The results illustrate that, in the presence of LAFPA operation, the turbulence jet was accelerated and the jet mixing enhanced. Meanwhile, with the help of LAFPAs, the global consumption burning velocity increased significantly by the area enhancement via plasma–flame interaction. The flame front response to the flow disturbance consists of more surface stretch and flame separation. Furthermore, turbulence spectra analysis of the images reveals a considerable increase in turbulent fluctuations in both cold flow and reacting flow.

Ultra-hydrophilic Diamond-like Carbon Coating on an Inner Surface of a Small-diameter Long Tube with an Amino Group by AC High-voltage Plasma Discharge

Ultra-hydrophilic Diamond-like Carbon Coating on an Inner Surface of a Small-diameter Long Tube with an Amino Group by AC High-voltage Plasma Discharge

Enhancement and Mechanism of Rhodamine B Decomposition in Cavitation-Assisted Plasma Treatment Combined with Fenton Reactions

In our previous study, a novel method combining underwater high-voltage plasma discharge with acoustic cavitation (ACAP) was developed and implemented using rhodamine B (RhB) as a model organic pollutant. Results revealed that injecting argon gas into the ACAP reactor positively influences RhB decomposition efficiency, but there is still further potential for improvement. The aim of this study was therefore to further improve the efficiency of the ACAP process through Fenton reactions. Two options for ferrous ion supply were considered: the addition of FeCl2 or the dissolution of iron from ACAP reactor steel parts into the RhB-containing solution. The results revealed that the degradation efficiency is increased by 20% due to the Fenton reactions when the concentration of ferrous ions reaches an optimal value. Lower pH was found to be desirable for the effect of Fenton reactions. Based on measurements using high performance liquid chromatography, a plausible mechanism of RhB degradation by the ACAP process assisted by Fenton reactions is additionally proposed and discussed.

Analysis of the discharge plasma impedance of copper vapor laser

In the pursuit to analyze the impedance of copper vapor lasers (CVLs) in different conditions, a novel approach has been proposed in this paper. The underdamped behavior of the voltage waveform across the CVL is leveraged to compute the impedance of high-voltage discharge plasma in the laser. This methodology provides an accurate idea of the discharge plasma resistance and inductance as it is calculated on the basis of experimental voltage waveforms obtained from the laser system. The laser head inductance remains almost fixed and equivalent to ∼0.47 µH whereas the laser resistance changes between 34 Ω and 11 Ω depending on the discharge condition and its constituents. A critical evaluation of CVL impedance is done in all experimentally possible conditions, and a methodology has been proposed to maintain the CVL impedance, which results in the power stability of the laser in oscillator–amplifier configuration. The laser impedance variation w.r.t. time, pressure, operating voltage and electrode pin configuration has been investigated. The impact of the localized electric field at the electrode on the laser resistance has also been emphasized in this paper. A good concurrence exists between the calculated laser impedance and its experimental behavior.

Synthesis of titanium dioxide nanoparticle by means of discharge plasma over an aqueous solution under high-pressure gas environment

In this study, the utilization of an electric field generated by the high voltage discharge plasma over a liquid water surface containing glycine compound to synthesize titanium dioxide (TiO2) nanoparticles was demonstrated. The experiments were conducted in a batch-type system with applied voltages ranging from 18.6 − 23.4 kV under various pressurized gases at room temperature. The results indicated that the applied voltages, applied pulse numbers, and pulsed repetition rates had a significant influence on the decomposition reaction of glycine compounds and titanium rod electrode erosion. The ultraviolet − visible (UV − vis) spectra showed that titanium dioxide nanoparticles could be observed in each solution product, and most of them were brookite-type structures. According to the HRTEM images, TiC was also produced as a nanoparticle product. Based on the experimental results, this process is applicable and could result in advanced metal-based nanoparticle synthesis technology.

Pulsed Discharge Plasma in High-Pressure Environment for Water Pollutant Degradation and Nanoparticle Synthesis

The application of high-voltage discharge plasma for water pollutant decomposition and the synthesis of nanoparticles under a high-pressure argon gas environment (~4 MPa) was demonstrated. The experiments were carried out in a batch-type system at room temperature with a pulsed DC power supply (15.4 to 18.6 kV) as a discharge plasma source. The results showed that the electrode materials, the pulsed repetition rates, the applied number of pulses, and the applied voltages had a significant effect on the degradation reactions of organic compounds. Furthermore, carbon solid materials from glycine decomposition were generated during the high-voltage discharge plasma treatment under high-pressure conditions, while Raman spectra and the HRTEM images indicated that titanium dioxide with a brookite structure and titanium carbide nanoparticles were also formed under these conditions. It was concluded that this process is applicable in practice and may lead to advanced organic compound decomposition and metal-based nanoparticle synthesis technologies.

Advanced oxidation treatments of olive mill wastewater

New and innovative advanced oxidative processes for wastewater treatments are currently in the focus of scientific research and development for possible industrial implantation. The main aim of this study was to investigate the effect of cold plasma treatment, high intensity ultrasound and UV radiation with the addition of additives: H2O2, TiO2, FeCl3 x 6H2O on degradation and removal of complex organic compounds from olive mill wastewater (OMWW). Olive mill wastewater represents a potential ecological problem when it is raw disposed into the environment, because of its high organic load. OMWW samples (with and without additives) were treated by high-voltage plasma discharge at frequencies 60 Hz and 120 Hz in combination with pumped gases (nitrogen, air and oxygen) for 30 minutes, by UV radiation for 30 minutes and 10 minutes by high intensity ultrasound. Physico-chemical parameters of quality, chemical oxygen demand (COD), and total dissolved carbon (TOC) were determined. The results have shown the efficacy of plasma treatment in degradation of organic compounds as well as degradation and reduction of polyphenolic compounds. Reduction of colour and total dissolved carbon occurred in all treated samples, mostly with the addition of FeCl3 x 6H2O. Treatment with UV radiation and ultrasound proved to be the most efficient resulting in the 50% reduction of organic compounds after a 10-minute treatment.

Acoustic cavitation assisted plasma for wastewater treatment: Degradation of Rhodamine B in aqueous solution

A novel wastewater treatment process, acoustic cavitation assisted plasma (ACAP) is proposed in this study aiming at expanding the treatable range of water pollutants due to a synergetic effect of ultrasound irradiation and high voltage plasma discharge. In this process, the role of acoustic cavitation is not only to provide generation of chemically active OH radicals, as for example in conventional ultrasonic wastewater treatment techniques, but also to ensure conditions for stable plasma generation in wastewater and, thus, to extend the treatable range of water pollutants. Rhodamine B (RhB) was used as a model pollutant in experiments examining effects of ultrasound amplitude, RhB initial concentration, output voltage, solution pH and electrical conductivity on the RhB degradation efficiency. The results revealed that the ultrasound-assisted plasma generation requires lower output voltages and allows to increase the acceptable range of electrical conductivity of treatable solutions up to 1000 μS/cm, that is about 24 times higher than in the case of conventional plasma discharge treatment. The alkaline and acid medium were found to be favorable for higher degradation efficiency. Additional measurements and results of recent investigations concerning underwater plasma showed that microbubbles presented in cavitation zone could serve as “bridges” making the pulse discharge propagation between the electrodes easier than in the conventional case. Besides, acoustic cavitation assists a faster transition of plasma discharge from ineffective streamer type to more effective spark type that further contributes to the improvement of the treatment performance.

Kinetics of plasma assisted pyrolysis and oxidation of ethylene. Part 1: Plasma flow reactor experiments

Pyrolysis and oxidation kinetics of ethylene were studied with and without a high-voltage plasma discharge at atmospheric pressure from 420K to 1250K. Experiments were performed in a nearly isothermal flow reactor using mixtures diluted in either argon, helium, or nitrogen to minimize the temperature changes from chemical reactions. At the end of the isothermal reaction zone, the gas temperature was rapidly lowered to quench the reaction. Gas composition was then determined using inline non-dispersive infrared analysis and sample extraction, where samples are stored in a multi-position valve for subsequent analysis with gas chromatography. Experiments were performed by fixing the flow rate or residence time in the reactor, and varying the temperature to achieve a reactivity map. The discharge region occupied approximately 11% of the total length of the isothermal reaction zone and could be placed anywhere along the length of the reactor. The discharge was found to enhance both the pyrolysis and oxidation reactions from 420K to the self-ignition temperature of the fuel. Ethylene pyrolysis was enhanced nearly as much as oxidation below 750K. For plasma-assisted pyrolysis, the results suggest that ethylene dissociation by electron-impact and collisional quenching with electronically excited states of argon, resulted in the direct formation of acetylene and the growth of larger hydrocarbons. During plasma-assisted oxidation, dissociation, and excitation of oxygen led to further fuel consumption, and enhanced the low temperature oxidative chemistry. Above 750K, thermal reactions began to couple to the plasma driven reactions providing further oxidation. At the highest temperatures, the radical production by thermal reactions became competitive and the effectiveness of the plasma discharge decreased.

Some Properties of Elastomeric Compositions with High-disperse Carbon Additives

The influence of a carbon nanomaterial obtained in a high-voltage discharge plasma on the endurance of elastomer compositions has been investigated. Complex tests of elastomeric compositions with highly dispersed carbon additives allowed us to confirm the model of nonlinear elastic deformation of macromolecules and adhesion between the elastomer and the nanoparticles. The results of these investigations agree with those obtained in determining the Mooney viscosity and relaxation, the parameters of the vulcanization kinetics of rubber mix, conventional tensile strength, and relative breaking elongation of highly filled rubbers based on butadiene-nitrile caoutchoucs. To verify the assumed mechanism underlying the action of a carbon nanomaterial on elastomer compositions, the parameters of their vulcanizing network have been determined using the method of equilibrium swelling.

Characteristics of plasma sterilizer using microwave torch plasma with AC high-voltage discharge plasma

Microwave plasma sterilization has recently been attracting attention for medical applications. However, it is difficult to perform low-temperature sterilization in short time periods. Increasing the output power shortens the time required for sterilization but causes the temperature to increase. To overcome this issue, we have developed a hybrid plasma system that combines a microwave torch plasma and a high-voltage mesh plasma, which allows radicals to be produced at low temperatures. Using this system, successful sterilization was shown to be possible in a period of 45 min at a temperature of 41 °C.

Low-temperature plasma preparation and application of carbon black nanoparticles

Abstract A new route is presented for the production of carbon black (CB) in which the propane is cracked into CB and hydrogen using electric energy from a low-current, high-voltage plasma discharge. The spherical CB produced by this process possessed a narrow size distribution, an average diameter of 50 nm and a high oil absorption number (OAN) of 136 mL/100 g. The prepared CB nanoparticles were first hydroxymethylated with a formaldehyde solution and subsequently oxidized using concentrated nitric acid to introduce hydroxyl and carboxyl acid groups onto the CB surface. These hydrophilic groups were beneficial for breaking up the large CB particles into smaller particles, and they significantly improved the dispersity of the CB nanoparticles in aqueous media. The modified CB was then coated by polyvinylpyrrolidone (PVP), in which the carbonyl oxygens acted as proton acceptors to form hydrogen bonds with the carboxyl acid groups. Finally, the PVP-coated CB was dispersed in an aqueous solution and was formulated into a pigmented ink-jet ink. The physical and printing properties of the prepared ink were demonstrated to be comparable with the commercial ink.

Oxidation of S(IV) in Seawater by Pulsed High Voltage Discharge Plasma with TiO2/Ti Electrode as Catalyst

Oxidation of S(IV) to S(VI) in the effluent of a flue gas desulfurization(FGD) system is very critical for industrial applications of seawater FGD. This paper reports a pulsed corona discharge oxidation process combined with a TiO2 photocatalyst to convert S(IV) to S(VI) in artificial seawater. Experimental results show that the oxidation of S(IV) in artificial seawater is enhanced in the pulsed discharge plasma process through the application of TiO2 coating electrodes. The oxidation rate of S(IV) using Ti metal as a ground electrode is about 2.0×10−4 mol · L−1 · min−1, the oxidation rate using TiO2/Ti electrode prepared by annealing at 500°C in air is 4.5×10−4 mol · L−1 · min−1, an increase with a factor 2.25. The annealing temperature for preparing TiO2/Ti electrode has a strong effect on the oxidation of S(IV) in artificial seawater. The results of in-situ emission spectroscopic analysis show that chemically active species (i.e. hydroxyl radicals and oxygen radicals) are produced in the pulsed discharge plasma process. Compared with the traditional air oxidation process and the sole plasma-induced oxidation process, the combined application of TiO2 photocatalysts and a pulsed high-voltage electrical discharge process is useful in enhancing the energy and conversion efficiency of S(IV) for the seawater FGD system.

Pulsed Discharge Plasma over a Water Surface Induces Decoloration of Dyes

It was well known that plasma can be defined as a partially ionized gas composed of ions, electrons and neutral species. Recently, plasma-water interaction has attracted growing interest as it may provide experimental chemists with a quite unique reaction medium. In this work, decoloration of dyes in water as a reaction media and the effects of various parameters with pulsed high-voltage discharge plasma are studied. Such as plasma applied under hydrothermal conditions generates high-energy electrons, ions, and radicals, which in turn may generate new reaction fields, leading to effective organic compounds oxidation for both homogeneous and heterogeneous reactions. Here, we utilize pulse discharge plasma over water surface to study the decoloration of Orange G, Orange II, Congo Red, and Naphthol Blue Black. They were directly fed as starting materials without additives. The experiments were conducted under argon atmospheric at 313 K using a batch type reactor. The products were directly analyzed by UV-Vis (ultra violet-visible) spectrophotometer V-550. The decoloration rate increased with increasing peak pulse voltage and pulse numbers, presumably due to the increased electric field energy. Based on these results, the present system may be promising.

Multipass Millimeter/Submillimeter Spectrometer to Probe Dissociative Reaction Dynamics

We present here the instrument design and first experimental results from a multipass millimeter/submillimeter spectrometer designed to probe dissociative reaction dynamics. This work focuses on benchmarking the instrument performance through detection of the CH3O and H2CO products from methanol dissociation induced by a high-voltage plasma discharge. Multiple rotational lines from CH3O and H2CO were observed when this plasma discharge was applied to a sample of methanol vapor seeded in an argon supersonic expansion. The rotational temperature of the dissociation products and their abundance with respect to methanol were determined using a Boltzmann analysis. The minimum detectable absorption coefficient for this instrument was determined to be αmin ≤ 5 × 10(-9) cm(-1). We discuss these results in the context of future applications of this instrument to the study of photodissociation branching ratios for small organic molecules that are important in complex interstellar chemistry.

Improvement of the service properties of elastomer compositions by introduction of carbon nanomaterials

The influence of a carbon nanomaterial obtained in a high-voltage discharge plasma on the endurance of elastomer compositions has been investigated for the first time. The results of these investigations agree with those obtained in determining the parameters of the vulcanization kinetics, conventional tensile strength, relative breaking elongation, and resistance to thermal aging and swelling in liquid hydrocarbon media of highly filled rubbers based on butadiene-nitrile caoutchoucs. To verify the assumed mechanism underlying the action of a carbon nanomaterial on elastomer compositions, the parameters of their vulcanizing network have been determined using the method of equilibrium swelling. It is shown that the introduction of a carbon nanomaterial into polar caoutchouc-based rubber allows one to substantially improve its service characteristics and endurance.

Pyrrole conversion induced pulse discharge plasma over a water surface under high-pressure argon

Electric field generated by pulsed high-voltage discharge plasma over water surface has been performed under high-pressure argon environments to oligomerize pyrrole compound. In this preliminary study, oligomerization of pyrrole in water as a reaction media and the effects of various parameters with pulsed high-voltage arc discharge plasma are studied. Such as plasma applied under hydrothermal conditions generates high-energy electrons, ions, and radicals, which in turn may generate new reaction fields, leading to effective organic compounds oxidation for both homogeneous and heterogeneous reactions. Here, we utilize pulse discharge plasma over water surface to study the removal characteristics for pyrrole into more valuable higher amines group which has been fascinating for both the industry and the scientific community. The experiments were conducted at 313K and 1–2MPa using a batch type reactor. Intermediate compounds from the conversion of pyrrole in the aqueous products were identified by UV–vis (ultra violet–visible) spectrophotometer and quantified using high performance liquid chromatography (HPLC). The maximum pyrrole conversion was 24.40% with a discharge plasma pressure of 2MPa with 10,000×. It was found that pyrrole conversion can be raised considerably by increasing reaction pressure and discharge plasma amount.

Detonation of supersonic propane-air mixture by high-voltage plasma discharge

The detonation combustion of a supersonic flow of propane-air mixture, initiated by a pulsed discharge of a magnetoplasma compressor, is obtained in experiment. A backward wave of supersonic combustion propagating with a velocity of 450 m/s against the flow is observed.

Pulsed high-voltage discharge plasma for degradation of phenol in aqueous solution

Abstract Pulsed high-voltage discharge is shown in the present investigation to be effective of phenol degradation in the aqueous solution in an isothermal batch reactor with continuous gas bubbling. Removal of phenol and effects of various parameters on the removal efficiency in the aqueous solution with pulsed high-voltage corona discharge plasma are studied. It is found that phenol degradation can be raised considerably by increasing the peak voltage of the pulsed discharge and the repetition rate of pulse, or by increasing pH of the aqueous solution. Presence of a buffer such as sodium carbonate and/or a hydroxide radical scavenger such as n -butanol in the aqueous solution decreases the removal efficiency of phenol. It is also found that decreasing the diameter of discharge electrode and electric conductivity of the aqueous solution can increase the degradation efficiency. The addition of gas, especially oxygen through the hollow needle electrode, and of FeSO 4 to the aqueous solution of phenol is found to significantly enhance phenol degradation. The intermediates formed in the phenol degradation process are pyrocatechol, hydroquinone, resorcinol, 1,4-benzoquinone, and some other unidentified products. The maximum phenol degradation percentage is 62.7% when its residence time is 180 min, and the TOC of aqueous solution decreases by 83.8% after having been discharged for 420 min. The phenol degradation with pulsed high-voltage discharge in aqueous solution shows a first-order kinetics: C=C 0 e −kt .