Air Plasma Torch Research Articles

Atmospheric Pressure Portable Catalytic Thermal Plasma System for Fast Synthesis of Aqueous NO3 and NO2 Fertilizer from Air and Water

AbstractMeaningful deployment of plasma water-based nitrogen fixation in agricultural application is hindered primarily due to its poor synthesis rate in compact systems. The study reports a directly deployable thermal plasma based portable catalytic compact system, offering typical synthesis rate as high as 1035 mg/min for nitrate and 635 mg/min for nitrite directly from naturally abundant atmospheric air and water. Developed technology is clean, sustainable, easily decentralizable, and completely free from fossil fuels and harmful intermediates like ammonia. The system avoids safety hazards and costs related to the requirements of continuous energy resources, pressurized environment for synthesis, regulated storage, refrigeration need, transportation of raw materials and distribution of fertilizer, as may be required by other competing technologies. Described system, consisting of air plasma torch, reaction chamber, water injection manifold and catalytic bed creates a unique nascent reactive plasma environment at ambient pressure that auto activates the catalyst in the field of thermal plasma for highly efficient fixation of nitrogen. Presented results indicate that use of combination catalysts with mechanically enhanced surface area allows drastic enhancement in the nitrogen fixation. Possible reaction chemistries, results of trials with different catalysts, time evolution of concentration, auto-conversion from nitrite to nitrate in aqueous media, time stability of concentration of the synthesized nitrate and observed remarkable effectiveness in the actual field trials are presented. Achieved synthesis rates are compared with those reported in literature in the area of thermal and non-thermal plasma.

Long-term ablation behavior of Al4SiC4-YB4 modified Cf/ZrB2-SiC composites at 2600 °C

Long-term ablation behavior of Al4SiC4-YB4 modified Cf/ZrB2-SiC composites was characterized by air plasma torch at 2600 °C for 300 s. The phase composition and the microstructure evolution of the composites were investigated. The addition of YB4 promotes the formation of nano t-Zr0.92Y0.08O1.96 crystals, decreasing the phase transition stress in the oxide layer and reducing the volatilization of the glassy phase. However, the addition of Al4SiC4 reduces the melting point of Zr-based oxides and the viscosity of the oxide layer. Therefore, the air plasma torch blows the oxide layer away, leading to the increase of linear recession rate.

Long-term ablation mechanisms of the YB4-Al2O3-Si3N4 modified Cf/HfC-SiC composites at 2600 ℃

In this work, the long-term and repeated ablation properties of the YB4-Al2O3-Si3N4 modified Cf/HfC-SiC composites were characterized by air plasma torch at 2600 ℃ for 300 s, twice. Both the structural stability and the viscosity of the oxide layer affected the ablation resistance of the composites. The structural stability of oxide layer was improved by forming nano c-HfO2 grains and the high-viscosity Al-Si-Y-O glassy phase, which increased the ablation resistance of the composites. However, the oxidation of Si3N4 resulted in the formation of NO, NO2 and excessive SiO2 glassy phase, which both leaded to a porous structure and reduced the viscosity of the oxides layer. Hence, the ablation resistance of the composites was reduced with addition of the Si3N4.

Thermal plasma processing of high temperature insulation wools

High temperature insulation wool (HTIW) wastes, generated in large volume as a part of demolition and construction processes, are difficult to recycle and pose significant hazards to health and environment. Alkaline earth silicate wools (AESW) and alumino silicate wools (ASW) are the two major types. Typical constituents include silica and oxides of Ca, Al and Mg etc. in varying ratios, giving rise to their specific colours and inherited thermo-physical properties. Successful mitigation and reuse of such wools have not been explored enough. Possibly for the first time, the study makes an extensive investigation on air plasma mitigation of four most commonly used HTIW, namely, fresh rock wool, waste rock wool, waste stone wool and waste ceramic wool. This is a single step dry process. Use of freely available ambient air to generate plasma, extremely high enthalpy, presence of nascent atomic and ionic species and extremely high temperature make the process fast, efficient, economic and unique one to convert such wastes into valorised product. While the thermal field delivered by an air plasma torch has been derived from magneto-hydrodynamic simulation, the study makes a direct in-situ investigation of the evolution of thermal field in the melting zone using two colour pyrometer, and characterises the vitreous solidified end product using X-diffraction, Scanning Electron Microscopy, Energy Dispersive X-ray Analysis, Energy Dispersive X-ray Fluorescence Spectroscopy and Neutron Activation Analysis. Possible valorisation and use of the end product have been discussed in light of their observed elemental composition.

Novel low temperature derived Wf/W–ZrC–Cu composites by reactive infiltration with enhanced mechanical and thermal physical properties

Wf/W–ZrC–Cu composites with densities over 95% have been prepared by infiltrating Zr–Cu binary molten alloys into porous Wf/W + WC preforms at 1200−1400 °C. The hybrid strengthening of in-situ formed ZrC particles, and the addition of continuous Wf have made the composites improved flexure strength and fracture toughness of 612 MPa and 10.41 MPa m1/2, respectively. The residual Cu provided a moderate interface between Wf and W–ZrC matrix, which was beneficial to improved fracture energy of 2–3·103 J m−2 and thermal conductivity of over 80 W (m K)−1. The Wf impeded cracks and new surfaces to the ultra-high temperature air plasma torch. The composites thus possess superior thermal shock resistance, and the linear and mass ablation rates reduced to 0.40 mm s−1 and 0.0112 g s−1, respectively. This study provides a novel approach for the fabrication of refractory fiber reinforced refractory metal/carbide based composites with excellent comprehensive properties at relatively low temperatures.

Modeling and Performance Analysis of Municipal Solid Waste Treatment in Plasma Torch Reactor

Thermal plasma has emerged as a technology with tremendous promise for municipal wastes that should be disposed of sustainably. A numerical simulation of a symmetric turbulent plasma jet from a thermal air plasma torch was developed using COMSOL Multiphysics®5.4 engineering simulation software. The velocities, temperature, arc root motion, and joule heating of the plasma jet were examined under the impact of the gas mass flow rate and current. Moreover, the electrical power required for the municipal solid waste (MSW) processing was estimated. The enthalpy and the effectiveness of the plasma torch were analyzed and discussed. Subsequently an investigation was conducted into the gasification characteristics of MSW using air and steam gases. The torch’s power and efficiency could be enhanced with a higher mass flow rate and temperature. Three operating modes were identified from the current–arc flow combination. Among the plasma gas considered, the air gas plasma torch guarantees an acceptable thermal efficiency and a low anode erosion rate. Plasma gasification produces cleaner syngas with higher efficiency (84%) than the conventional process due to the elevated temperature used during the process that breaks down all the char, dioxins, and tars.

Effect of TaC Content on Microstructure and Properties of W-TaC Composites

Transition metal carbide reinforcement can improve the performance of pure W. W-(10-50) vol% TaC composites were prepared by spark plasma sintering at 2100 °C. The effect of TaC content on the microstructure, mechanical properties, and thermal conductivity of the composites was studied. The ablation resistance of the W-TaC composites was evaluated under an air plasma torch. The addition of TaC into the W matrix enhanced the densification of W-TaC composites, the density of W-40 vol% TaC composite exceeded 93%. TaC particles inhibited the growth of W grains during sintering. Reactive diffusion occurred between W and TaC, forming the solid solutions of (W,Ta)ss and (Ta,W)Css. W and TaC react to form the W2C phase at a TaC content of 50 vol%. The Vickers hardness of the composite increases from 3.06 GPa for WTA1 to 10.43 GPa for WTA5. The flexural strength reached 528 MPa in the W-40 vol% TaC composite. The thermal conductivity of W-20 vol% TaC composite was 51.2 ± 0.2 W·m-1·K-1 at 750 °C. The addition of TaC improved the ablation resistance of W-TaC composites. The mass ablation rate of W-30 vol% TaC composite was 0.0678 g·s-1. The ablation products were mainly W oxides and complex oxides of W-Ta-O.

Sustainable Development Solutions for the Medical Waste Problem Using Thermal Plasmas

Waste-to-energy (WTE) conversion is a vital process in the Middle East, especially in the Kingdom of Saudi Arabia (KSA), which is considered sustainable development for the environmental strategic project. Previous publications dealt with the environmentally friendly plasma treatment of wastes such as municipal waste, scrap tire waste, plastic waste, and grey water, using thermal plasmas produced by the cornerstone part of plasma reactors, namely the air plasma torch. In the present paper, with a view to energy recovery from medical waste, the thermodynamic properties of air plasma torches with a flow rate of air ranging from 10 mg/s to 30 mg/s and plasma jet temperatures ranging from 1500 °C to 5000 °C were investigated; these include power loss, enthalpy, plasma flux, and torch efficiency variation with plasma input power and air flow rate. The measured electrothermal efficiency of the plasma torch is in the range of 42% to 80% and increases with the increasing input power and gas flow rate. In Makkah, the number of beds in the hospitals is 10,500; the average annual weight of the medical waste in the hospitals is 2835 × 103 t, with an extracted amount of pyrolysis oil equivalent to 2268 × 103 t and an equivalent energy of 90 × 109 M J. In the proposed plasma treatment project, the amount of diesel oil after the distillation process will reach up to 1928 × 103 t, with an estimated sale profit of the electricity reaching up to 21 × 106 MW·h. The sale profit of pyrolysis oil in 2022 reaches up to USD 34.44 million, and the sale profit of electricity extracted by using the diesel oil in 2022 reaches up to USD 1020 million for households and USD 1445 million for factories.

Long-term and cyclic ablation behavior of La2O3 modified Cf/ZrB2-SiC composites at 2500 ℃

In this work, long-term and cyclic ablation behavior of the La2O3 modified Cf/ZrB2-SiC composites were studied by air plasma torch at 2500 ℃. It is indicated that a micron-sized ZrO2-La2O3-SiO2 liquid phase layer forms on the ablation surface at 2500 ℃, which reduces the evaporation of SiO2 and decreases the mass recession rates of the composites. However, the ZrO2-La2O3-SiO2 liquid phase layer exhibits poor structure stability. In addition, the La2O3 weakens the pinning effect of bulk ZrO2. Consequently, the oxide layer with low viscosity tends to sputter out due to the mechanical scouring by plasma flame. Therefore, the linear recession rates of the composites are increased during cyclic ablation with the increase of the La2O3 content.

Determining Electron Density of Atmospheric Microwave Air Plasma Torch by Microwave Power Measurement

Determining Electron Density of Atmospheric Microwave Air Plasma Torch by Microwave Power Measurement

The oxidation resistance of the heterophase ZrSi2-MoSi2-ZrB2 powders – Derived coatings

In this work, we investigate the oxidation resistance of the coatings manufactured by reactive impregnation of Cf/C-SiC composites with a melt derived from layers of ZrSi2-MoSi2-ZrB2 powder composition synthesized by SHS and alternating layers of SHS powders and elemental Si. Oxidation resistance tests were conducted in static conditions at 1650 °C in air and under an air plasma torch at 2200 °C. The performance of the coatings in these conditions is defined by the emergence and evolution of the heterogeneous oxide films based on zirconia-modified borosilicate glass. The protective oxide layers effectively inhibit the oxygen influx and further oxidation of the substrate. The increase of temperature above 1750−1800 °C resulted in evaporation of the glass phase from the surface and formation of porous thermally insulating ZrO2-based layer with Mo/MoO2, Mo3Si, and Mo5Si3 inclusions. The gradient of temperature across the coatings’ thickness allows for a partial retainment of the glassy phase in the coatings’ lower layers due to the decrease of partial pressures of boron and silicon suboxides, resulting in an additional degree of protection against oxygen diffusion. The specimens were characterized in terms of the temperature and time boundaries of their performance, mass loss kinetics, catalytic activity, and spectral emissivity of the coatings. The limiting factors of the coatings’ performance are outlined.

Environmental and Economic Aspects of the Plasma Treatment of Scrap Tires to Produce Syngas and Synthetic Fuels in Saudi Arabia

Kingdom of Saudi Arabia (KSA) has been chosen for thermal plasma treatment using a plasma torch attached to plasma reactor, with flow rate of air 10–30 mg/s and mean temperature of the plasma jet at the torch exhaust nozzle 7000–19 000 K; the air plasma torch parameters are easily tunable to produce a suitable plasma jet for the treatment of scrap tires. The calculated cold gas efficiency of the proposed plasma treatment system for scrap tires feedstocks is 82.72%. The average weight of scrap tires in KSA is 218 500 t per year. After plasma treatment, the heat energy per ton produced annually from scrap tires in KSA is 475.4 TJ. The 16 t of synthetic syngas is enough to produce 50 013 MJ/day converted into electricity 13 972.6 kWh/day, and the 80 t of slag is enough for different industrial products. The total annual gross profit for all the products (pyrolysis oils, synthetic syngas, and slag) is $28.19 million, while the gross annual cost is $9.202 million with a cash recovery period of 1.36 years, neglecting the income tax.

Erratum to “Imaging Diagnostics and Gas Temperature Measurements of Atmospheric-Microwave-Induced Air Plasma Torch” [Jun 20 2153-2162

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Imaging Diagnostics and Gas Temperature Measurements of Atmospheric-Microwave- Induced Air Plasma Torch

In this article, the core of an atmospheric-microwave-induced air plasma torch is resolved and measured by adjusting the exposure time of a high-speed camera. Gas temperature measurements of the microwave plasma core are achieved by molecular emission spectrometry of the ${A}^{2}{\Sigma }^{+}\to {X}^{2}{\Pi }_{r}$ electronic system of OH radicals. How the geometric features and gas temperature of the plasma core are related to the magnetron power and gas flow rate is explored, and the radial temperature distribution of the microwave plasma is measured. In these experiments, the magnetron power is 1033–2023 W and the gas flow rate is 10–20 L/min. The results show that microwave plasma has two parts, namely, its core and outer shell. The core radius increases approximately linearly with the magnetron power, whereas it does not change substantially with the gas flow rate. Gas temperature can be used to distinguish the core from the outer shell because the former can reach 8000 K, while the latter cools down from 5500 K. Moreover, the core temperature changes with neither the magnetron power nor the gas flow rate. Finally, a method to control the radial distribution of gas temperature of microwave plasma torch is presented.

Application of Supersonic Air Plasma Torch for Metallic Nickel-Based Alloys Spraying

This paper presents the preliminary results of the supersonic air plasma torch development for powder materials spraying. The pilot experiments on measurement the particles velocity of the disperse phase of high-temperature heterogeneous flow showed that the use of supersonic regime of the thermal plasma flow enabled more than a 1.5 increase in the average velocity of the sprayed particles. We also compare the properties of nickel-based coatings sprayed at subsonic and supersonic modes.

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.

Lithium intercalation and conduction in Fe-containing tantalum oxide films synthesized with an atmospheric pressure plasma jet

Lithium ionic intercalation and conduction performance of tantalum oxides films improved by adding with iron oxides using an atmospheric pressure plasma jet (APPJ) is investigated. Precursors [tantalum ethoxide, Ta(OC2H5)5]2] and ferrocene [Fe(C5H5)2] vapors are carried by argon gas, mixed by oxygen gas and injected into air plasma torch for rapid synthesis of organo-tantalum-iron oxides (TaFexOyCz) films onto the polished stainless steel substrate at a short exposed-duration of 35 s. The APPJ-synthesized TaFexOyCz films possess the prominent Li+ ionic intercalation performance for 200 cycles of reversible Li+ ionic intercalation and deintercalation in a 1 mol/L LiClO4-propylene carbonate electrolyte by switching measurements with a potential sweep from − 1.25 to 1.25 V at a scan rate of 40 mV/s. After 200 cycles of reversible Li+ ionic intercalation and deintercalation, the Li+ ions intercalated and deintercalated charges are respectively increased from 2.41 and 1.91mC/cm2 for TaOyCz film to 5.69 and 5.23 mC/cm2 for TaFexOyCz film. The Li+ ionic conduction performance of TaOyCz film is highly enhanced from 5.76 × 10−11 to 1070 × 10−11 S/cm for TaFexOyCz film, while proven by electrochemical impedance spectroscopy in the devices of polyethylene terephthalate (PET)/indium tin oxide (ITO)/NiOx/TaOyCz/NiOx/ITO and PET/ITO/NiOx/TaFexOyCz/NiOx/ITO.

Decreasing of the concentration quenching of fluorescent dye in a solution by introducing it to nanoparticles of silicon dioxide

The article presents the results of experimental studies of a double-chamber linear circuit DC electric arc plasmatron in experimental and industrial conditions. The electric arc plasmatron of the VORTEX-200 linear circuit with a rated power of 200 kW is designed for plasma ignition of a pulverized-coal torch, its stabilization and oil-free ignition of pulverized-coal boilers of thermal power plants.The linear circuit plasmatron contains two water-cooled casings isolated from each other, one of which has a hollow cylindrical electrode - a cathode having swirlers of the plasma-forming gas at both ends, and the other has an output electrode - an anode-diffuser having a channel with a cylindrical segment at one end and the exit nozzle in the form of a diffuser at the other end.The power of the plasmatron, depending on the process parameters, can vary from 80 to 230 kW. The plasmatron has a stable powerful air plasma torch. Tests of such plasmatrons showed their high reliability and possibility of their operation in difficult conditions of thermal power plants (high level of dust and humidity, high temperatures near the boilers). Measured volt-ampere characteristics of the plasmatron enabled us to determine the region of stable arc combustion from 350 to 475 A. Parameters of the plasmatron operation at its nominal power of 200 kW and the flow rate of the plasma-forming gas of 1000 l/min are attained at currents not exceeding 450 A. The use of mechanical ignition of the plasmatron with a needle from a refractory material, instead of breakdown the inter electrode gap by an oscillator, increased the reliability of its operation.The device for axial scanning of binding of the cathode spot of the arc, which allows us to increase the surface of cathode erosion many times,was developed. The use of azimuthal and axial scanning of the cathode spot of the arc of the plasma torch makes it possible to increase the service life of the cathode up to 200 hours with a service life of the massive anode exceeding 500 hours.

Modelling of heating of plasma-chemical reactor in Comsol Multiphysics.

For the thermophysical calculation of the reactor, a mathematical model was developed in Comsol Multiphysics, describing physical processes in the plasma-chemical reactor at a stationary mode. To simplify the calculation at this stage, it was carried out for an air plasma torch. The model includes two processes: fluid dynamic and heat transfer ones. As a result of the mathematical modelling the following parameters were obtained: temperature distribution in the reactor at steady state, average mass temperature in the reaction volume, velocity field and others.

Numerical simulation of DC air plasma torch modes and plasma jet instability for thermal spraying technology

The article is dedicated to nonstationary simulation of DC air plasma torch. The mathematical model for the analysis of plasma jet instability is developed. The proposed 2D axisymmetric model demonstrates the physical processes taking place inside and in the outer region of the plasma torch. The influence of the power source parameters and anode geometry on voltage and plasma jet fluctuation is described. Simplified mathematical model is developed in order to assess the effect of the flow behavior on heat transfer processes. The developed model can be used for the design of plasma torches and their operation modes. The results of mathematical model verification are based on experimental studies.