Type Of Plasma Torch Research Articles

Unique Aspects of Thermal Plasma Torches and Reactor Design for Process Applications

Novel features of arc plasma devices with thermionic and thermo-chemical cathodes and development of associated thermal plasma process reactors are investigated from device design and application point of view. Different types of plasma torches and open arcs, their fundamental differences in architecture, jet behavior, operational constraints, and evolution of interesting electromagnetic forces inside them have been probed. Investigation of instabilities in arcs through direct real-time imaging of arc path using fast photography and impact of powder loading on such instabilities are presented. Development of low power air plasma torches delivering large volume high-temperature plasma jet with long penetration depth has been investigated together with an estimation of hazardous NOx, produced from such devices during operation. Interesting attributes of various types of thermal plasma reactors including plasma spray chemical vapor deposition (CVD) reactors for thick and dense coating, reactors for generation of H-OH plasma, radio frequency (RF) thermal plasma reactors for the synthesis of nanostructures, and air plasma gasifier reactors for environment-friendly mitigation of municipal solid waste (MSW) and electronic wastes have been presented. Coke bed air plasma gasifiers are specially investigated for their important technological aspects. Experimental results are presented with simulation supports for enhanced understanding, wherever necessary.

Plasma Disposal in Problems of Ecology (Review)

The current state and issues of plasma disposal are discussed. Various types of plasma torches used for disposal, the technological schemes of existing plasma systems, a plasma torch with an expanding output electrode, equipment characteristics, diagnostic methods for the design of an effective low-temperature plasma generator, and the studying of the effects of a high-enthalpy plasma jet generated by a direct-current plasma torch on a solid target material are described. The results obtained via high-speed imaging, micropyrometry, laser profilometry, spectroscopy, and stereoscopy methods are presented. The data on spatial and temporal changes of the temperature field on the sample surface, the dynamics of material loss, and changes in the parameters (temperature and electron density, temperature of heavy particles) of the plasma-jet incident on the sample are analyzed. The collected theoretical and experimental results and engineering solutions can be used to design various low-temperature plasma generators with a power of up to 1 MW and higher.

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.

Numerical Modelling of Wood Gasification in Thermal Plasma Reactor

Biomass gasification for synthesis gas production represents a promising source of energy based on plasma treatment of renewable fuel resources. Gasification/pyrolysis of crushed wood as a model substance of biomass has been experimentally carried out in the plasma-chemical reactor equipped with gas–water stabilized torch which offer advantage of low plasma mass-flow, high enthalpy and temperature making it possible to attain an optimal conversion ratio with respect to synthesis gas production in comparison with other types of plasma torches. To investigate this process of gasification in detail with possible impact on performance, a numerical model has been created using ANSYS FLUENT program package. The aim of the work presented is to create a parametric study of biomass gasification based on various diameters of wooden particles. Results for molar fractions of CO for three different particles diameters obtained by the modeling (0.55, 0.52 and 0.48) at the exit are relatively good approximation to the corresponding experimental value (0.60). The numerical results reveal that the efficiency of gasification and syngas production slightly decreases with increasing diameter of the particles. Computed temperature inhomogeneities in the volume of the reactor are strongest for the largest particle diameter and decrease with decreasing size of the particles.

Effects of Anode Arc Root Fluctuation on Coating Quality During Plasma Spraying

To obtain a coating of high quality, a new type of plasma torch was designed and constructed to increase the stability of the plasma arc and reduce the air entrainment into the plasma jet. The torch, called bi-anode torch, generates an elongated arc with comparatively high arc voltage and low arc fluctuation. Spraying experiments were carried out to compare the quality of coatings deposited by a conventional torch and a bi-anode torch. Alumina coatings and tungsten carbide coatings were prepared to appraise the heating of the sprayed particles in the plasma jets and the entrainment of the surrounding air into the plasma jets, respectively. The results show that anode arc root fluctuation has only a small effect on the melting rate of alumina particles. On the other hand, reduced air entrainment into the plasma jet of the bi-anode torch will drastically reduce the decarbonization of tungsten carbide coatings.

Pyrolysis/gasification of biomass for synthetic fuel production using a hybrid gas–water stabilized plasma torch

An experimental plasma-chemical reactor equipped with a novel hybrid gas–water stabilized torch is available at IPP Prague for the innovative and environmentally friendly plasma treatment of waste streams with a view to their sustainable energetic and chemical valorization and to a reduction of the emission of greenhouse gases. Gasification/pyrolysis of biomass was experimentally studied using crushed wood as a model substance. The experimental results demonstrate homogeneous heating of the reactor volume and proper mixing of plasma with treated material in spite of the low plasma mass flow rate and constricted plasma jet. The conditions within the reactor ensure complete destruction of the tested substance. The economical viability, environmental performance and safety of biofuels/hydrogen produced from syngas resulting from the plasma-thermochemical gasification of a very broad range of second generation biomass feedstock will be investigated. The performance of several types of plasma torches and of possible combinations of torches will be compared. The final biofuels will be tested in the existing Internal Combustion Engine (ICE) test stands.

Properties of Hybrid Water/Gas DC Arc Plasma Torch

A new type of plasma torch with combined stabilization of electric arc by water vortex and gas flow was investigated. This hybrid water/gas stabilization offers the possibility of adjusting plasma jet parameters within a wide range from high-enthalpy low-density plasmas typical for liquid stabilized torches to lower enthalpy higher density plasmas generated in gas stabilized torches. The torch was operated at an arc power from 22 to 130 kW with an exit centerline plasma velocity from 2 to 6.5 km/s and a plasma temperature from 14 000 K to 22 000 K. Moreover, gas flow in the cathode part protects a cathode tip and thus a consumable carbon cathode used in water torches could be replaced by a fixed tungsten cathode. The characteristics of the electric arc with combined gas/water stabilization were measured and the effect of gas properties and flow rate on plasma properties and gas-dynamic flow characteristics of the plasma jet were studied for argon, and mixtures of argon with hydrogen and nitrogen

Experimental studies on the unsteadiness of atmospheric pressure plasma jet

Spectroscopic diagnostic technique has been employed to investigate the characteristics of the unsteadiness of dc plasma spraying jets for two types of plasma torches. The continuous transient signal of the arc voltages and the spectral line intensities of the jets have been obtained, and their frequency characteristics have been studied by means of fast Fourier transform method. Three factors to jet fluctuation have been represented and distinguished from each other. Digital high-speed photography technique has also been introduced to investigate the fluctuation of plasma jet. Snapshots of the jet and the spectrum analysis result of arc voltage and spectral line intensity have indicated that the effect of the power supply occupies dominant proportion on the jet fluctuation for the argon plasma jet. The influence of gas flow rate on the arc restrike characteristics has been studied. Distributions of the jet temperature and number densities of nitrogen atom in the argon plasma jet region have been obtained with the distributions of line intensities of argon and nitrogen atom.

The industrial application of plasma technology for the production of fumed Silica

The industrial application of plasma chemistry is restricted for the time being to the use of a plasma torch as an efficient heat source for the production of existing chemicals. The techno-economic requirements for products suitable for plasma processing are outlined. There are only very few such processes at or near industrialization, such as the Tafa process for ZrO 2, the Noranda MoS 2 process and the Lonza process for fumed silica. Various types of plasma torches are evaluated according to such criteria as investment cost, efficiency, availability in industrial size, suitability for continuous operation and scale-up etc. The liquid-stabilized torch used in this work is described. The Lonza process for surface-active silica is based on the reduction of sand to silicon monoxide gas in a specially designed reactor, fired by a 200 kW alcohol-stabilized plasma torch. By direct oxidation of the SiO gas in a quench system it is possible to produce a surface-active product. At present the process has reached pilot plant scale and is being optimized. In comparison with the conventional process, based on the gas phase hydrolysis of silicon tetrachloride, the use of cheaper raw materials and the elimination of hydrogen chloride from the process lead to a cheaper process without ecological problems.