AC Plasma Torch Research Articles

Modelling of Electric Processes in Circuits of Arc Plasma Torches Part 1. Approximations of Static Characteristics of Arc Plasma Torches

The article discusses selected structural and operational properties of DC and AC arc plasma torches. References cited in the article contain generalised analytical expressions identifying experimental current-voltage characteristics of typical arc plasma torches. Values of coefficients in formulas approximating static current-voltage characteristics depend not only on the type and the polarity of the plasma torch but also on values of criterial factors. The study discusses separately DC plasma torches and single-phase AC plasma torches.

Modeling of an AC Plasma Torch—Part II: Gasdynamic Pattern and Effect of Flow Rate

The article is the continuation of the work devoted to the numerical study of processes in the single-phase ac plasma torch operating at low current (up to 10A RMS). The main attention is paid to the analysis of the flow pattern and the behavior of gasdynamic parameters. The effects of flow acceleration and rarefaction of near axial arc core are shown. The effects of the transformation of gasdynamic structures typical for cold flow (e.g., vortex behind the back step), as well as the appearance of new structures (e.g., vortexes in the jet periphery), are demonstrated and discussed. An explanation is given for the effect of the increase of the arc voltage drop with the increase of the flow rate of supplied air, associated with the increase of the medium electric resistance. The presented results are in accordance with the experimental data on the voltage drop in a conventional ac plasma torch.

Modeling of an AC Plasma Torch—Part I: Electrical Parameters and Flow Temperature

A numerical study of airflow in a single-phase ac plasma torch is presented. The values of electrical current being considered are up to 10-A rms, and the ac frequency is 50 Hz. The electric and gas-dynamic parameters of the plasma torch are efficiently simulated using the model based on the Navier–Stokes equations for compressible medium and the reduced Maxwell equations. The difference in the behavior of parameters in the channel and jet is demonstrated and discussed. The effect of decreasing the observed maximum value of the flow temperature with decreasing the flow rate is shown. An explanation of this effect and an analysis of the gas-dynamic patterns of cold flow and flow with the ac discharge are presented in the following article of the series.

Soot Formation during the Decomposition of Chlorine-Containing Hydrocarbons with an AC Plasma Torch

The process of decomposition of organochlorine compounds by a three-phase ac plasma torch with vortex arc stabilization is studied. The plasma torch had two zones for introducing the plasma-forming media: the near-electrode and arc-burning zones. The near-electrode zone was fed with a shielding gas, and the arc-burning was fed with water vapor, methane, and vapors of organochlorine compounds. The resulting products were analyzed using mass spectrometry, XRD, scanning electron microscopy, and IR spectroscopy. In an experiment with chlorobenzene and carbon tetrachloride, in the gaseous and liquid fractions, only one chlorine-containing compound, HCl, was detected. However, in the experiment with chlorobenzene, the soot yield was 0.98 wt % of the raw material and the chlorine content in the soot was 1.61%. IR spectral data confirm the presence of the Cl–O and Cl–С bonds.

Investigation of wood ash melting by AC plasma torch

One of the methods for processing ash from waste incineration can be plasma treatment. In most cases, studies are carried out with inert gas systems. The size of the processed pieces of sintered ash is 10-50 mm. The power of the plasma torch is 75 kW at an air flow rate of 8.8 g/s. Temperature control on the ash surface is carried out using a two-beam pyrometer. The total melting time is 7 hours. The temperature of the least heated part of the melt is 1300°C. Liquid slag is cooled in a large number of cold water. Upon contact of the hot molten slag with water, glass-like pieces 2-3 mm in size are formed. The composition and properties of the slag are studied using a scanning electron microscope with an attachment for elemental analysis and an X-ray diffractometer.

Investigation of Electrode Erosion Parameters in Direct and Alternating Current Plasma Torches

This paper deals with the study of the wear resistance (erosion) of the material of electrodes in direct and alternating current plasma torches. The life time of electrodes is determined by many factors, such as the material composition of the electrode, the design of the electric arc chamber, the temperature of the electrode, the temperature in the arc attachment zone and the method of its movement, and the nature of the chemical reactions between the plasma gas and the electrode material. At the same time, the main factors that affect the erosion of the material are the magnitude of the current in the arc and the nature of attachment to the electrode (cathode or anode spot), as well as the organization of the gas flow in the spot area. AC and DC plasma torches with a power of up to 50 kW were used in these experiments. Electrodes were made of copper, stainless steel, and an iron–copper composite material. This paper presents the characteristic values and dependences of the specific erosion of plasma torches of various designs in a wide range of operating pa-rameters.

A non-stationary model of the AC plasma torch

Modelling of a single-phase two-channel AC plasma torch with a calculated power of 1.1 kW at a current value of 6 A is presented in the paper. A model of the plasma torch operation on argon at a flow rate of 0.69 g/s is considered. A 35-millisecond operation of the plasma torch has been simulated. The obtained temperature distributions and arc voltage drops allow us to evaluate the simulation results at a qualitative level.

The usage of low-voltage AC plasma torch for polystyrene gasification

The article describes the plasma-chemical process of polystyrene processing by air low voltage AC plasma torch with a power of up to 500 kW. Polystyrene is a highly toxic compound, so its processing is very important. In this case, it consists mainly of carbon and hydrogen. The thermodynamic calculation of plasma gasification of polystyrene using air plasma and steam was carried out. It is established that the maximum concentration of steam in the gasifying agent is 50%wt . In this case, the plasma enthalpy of 12 MJ/kg is sufficient for the implementation of this process.

Interaction of methane with thermal carbon dioxide plasma obtained in the AC plasma torch

The article discusses a new method for producing synthesis gas using an ac electric arc. The relationship between the electrical parameters and the energy characteristics of the process was established: with an increase in carbon dioxide concentration in the electrode zone, the hydrogen concentration increases. This leads to an increase in the plasma torch power, which can be used to adjust the chemical process.

Obtaining nano-disperse soot from orthoxylene by the high-voltage AC plasma torch

The article deals with the synthesis of fullerene-containing soot using high-voltage AC plasma torch. The plasma torch consists of three electric arc channels with three graphite rod electrodes. Orthoxylene vapors are fed into the arc zone of the plasma torch, and argon is used as a protective gas. In the plasma torch orthoxylene decomposes under the action of an electric arc. The prodused soot contains 5.4% C60 fullerene and 1.6% C70 fullerene.

Co-gasification of lignite and used car tires by H2O/air thermal plasma

The article considers a high-voltage AC plasma torch working on a mixture of water vapor and air up to 90 kW. A thermodynamic calculation of the co-gasification of used automobile tires and lignite is presented. Assessment of the operation of the plasma torch working on mixtures of H2O/air at co-gasification of lignite and used car tires shows prospect of these processes implementation.

AC Plasma Torches. Arc Initiation Systems. Design Features and Applications

This series of articles is devoted to the study of high-power AC plasma torches with different designs, purposes, and characteristics that allow the operation of a certain type of plasma generator in wide power and pressure ranges. The first part is devoted to the investigation of AC plasma torches with a specific purpose, that is, the initiation of an arc of a powerful PT. This paper describes the design features of a PT in detail, its characteristics, the parameters of the plasma stream, such as temperature, and heat content. The features of operation and various options of auxiliary plasma torch injectors that provide ignition of the main arc in the electric-discharge chamber are considered as well.

Arc initiation in plasma installations

The paper is devoted to a research of electric arc ignition devices in plasma torch of alternating and direct current. High-voltage alternating current plasma is used as one of ignition devices. Its power is 5–10 kW, the plasma-forming gas flowrate is 2–5 g/s. The plasma flow with electron concentration of 1014–1016 cm−3 sufficient for main arc ignition is set in a zone of the minimum distance between the main electrodes of a plasma torch by injector operation. The second method uses a construction series of the direct current plasma torches. They were designed to transfer ac plasma torches with rail electrodes into a class of electrical installations with a supply voltage less than 1000 V. Their current-voltage characteristics and life tests are received. The cathode erosion is about 10−6 g/C, the anode erosion is 10−7 g/C. The pulse erosion injector is developed for an arc ignition in a direct current plasma torch. The pulsed injector is supplied from the capacitive storage.

Fullerenes production by electric arc pyrolysis of methane in an AC three-phase plasma torch

The article deals with a high-voltage three-phase AC plasma torch working as a part of a plasma-chemical facility. The plasma torch consists of three electric arc channels and three rod copper electrodes. The initial breakdown occurs with high voltage (10 kV) provided by a high voltage power supply. The electric arc plasma oxygen-free pyrolysis of methane was realized on the facility. The fullerene-containing fraction was extracted from the carbonaceous material by extraction with orthoxylene. The produced carbon-black and the selected extract were analyzed by modern methods of physical and chemical analysis: scanning electron microscopy, X-ray phase analysis, IR spectroscopy.

AC plasma torch operating on a mixture of air and methane

The article considers a high-voltage AC plasma torch for air reforming of natural gas. It has two inputs of plasma-forming gases: the electrode zone (for shielding gas) and the arc zone (for the main plasma-forming gas). The voltage drop on the arc increases with increasing methane flow rate due to the formation of hydrogen and intensification of heat transfer.

Metal ferrites synthesis by AC plasma torch

The article describes the ac air plasma torch with the supply of a liquid aqueous solution of iron (III) nitrate of (mol/l). When the solution is heated, water evaporates, and the iron nitrate is converted to a solid residue (mainly iron oxide). The obtained samples were collected on a heated filter to prevent condensation of water and nitrogen dioxide. The obtained samples were investigated by the X-ray diffractometer and the scanning election microscope with an elemental analyser. The proposed plasma method can be applied to the synthesis of ferrites of various metals.

Investigation of a high voltage AC plasma torch operating on mixtures of methane and other gases

The article considers the high-voltage AC plasma torch working on a mixture of gaseous hydrocarbon (methane, propane-butane) and inert gases (argon). During the burning of the electric arc, methane is transformed into soot containing fullerenes. The composition of the soot was analyzed by optical UV-spectroscopy, IR-spectroscopy and X-ray phase analysis.

Operation of High-Voltage Plasma Torches with Rod Electrodes

The paper deals with single-phase AC plasma torches with rod electrodes made of iron-copper composite material, with air as the plasma-forming gas and an life time of ~200 h. The construction peculiarities of this type of plasma torch and its power-supply systems is described. The experimental results, in particular, the current-voltage and the voltage-flow rate characteristics of the plasma torches, as well as the typical current and voltage oscillograms, are presented.

Use of Alternating-Current Plasma Torch for Processing Potentially Hazardous Substances

The decomposition of tetrachloromethane and tetrafluoromethane by air plasma in the presence of methane has been studied using an ac plasma torch of up to 500 kW power with rail electrodes. Methane reacts with air in the partial oxidation mode to form hydrogen, which reacts with a halogen to produce the hydrogen halide.

Erosion of rod electrodes of the air AC plasma torch

Depending on the plasma-forming mixture, various types of electrode materials are used. If air, carbon dioxide and steam are used, it is optimal to use copper electrodes, since copper has a high thermal conductivity. Copper rod electrodes of an air AC plasma torch are considered. In the binding zone of the electric arc, the electrode material melts and boils, which leads to physical erosion of the electrode. Scanning electron microscopy with elemental analysis, X-ray phase analysis and IR Fourier spectroscopy were used to analyze the products of electrode erosion. The erosion products content copper, iron, nitrogen, oxygen, and other metals from the plasma torch case.