Argon Flow Rate Research Articles

Wall stresses in dual bottom purged steel making ladles

Dual gas purging is often done in a ladle to accelerate the refining operations in steel industries. The purged gas, mainly argon imparts momentum to the molten metal and establishes a turbulent recirculating flow in the melt, which generates shear stresses on the ladle walls. These stresses in-turn leads to the erosion of the refractory lining, which is undesirable. A three dimensional, transient, multi-phase turbulent model has been developed to predict the shear stress distribution along the wall in dual plug, bottom purged ladles. A parametric study has been performed to understand the dependence of wall stresses on various operating parameters like argon flow rate, metal bath depth, slag thickness as well as on the configuration of the gas injectors. A dimensionless correlation is proposed using regression analysis that predicts the maximum wall stress in the form of skin friction coefficient in terms of the above parameters.

Improvement of mechanical strength of hydrophobic coating on glass surfaces by an atmospheric pressure plasma jet

Non-thermal plasma is getting more popular in industrial applications, mainly treatment of material surfaces. Hydrophobic coatings often suffer mechanical instability and do not function well after abrasion/scratching. In this study, non-thermal plasma jet generated at atmospheric pressure in ambient condition was applied to the hydrophobic treatment of glass surface using two precursors. Tetramethylsilane (TMS) was used to promote hydrophobicity and (3-Aminopropyl)triethoxysilane (APTES) was used to get durable mechanical strength of the coating although it is hydrophilic in character. An alternating current (AC) high voltage (operating frequency: 11.5 kHz) was used to generate plasma jet for producing a coating layer onto the soda-lime glass sample. Water contact angle of 139° and a stable mechanical strength were achieved at an optimal TMS/APTES ratio of 4.8. The coating thickness, strength and water contact angle were varied by changing treatment time, applied voltage, and carrier gas (argon) flow rate. The coating layer were characterized by atomic-force microscopy (AFM), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), water contact angle (WCA), scratch test and UV/visible spectroscopy.

Characterization of a rotating gliding arc in argon at atmospheric pressure

The dynamics of a low-power (<40 W) rotating gliding arc in atmospheric pressure argon sustained by a homemade dual DC power supply between a conical cathode and a grounded sleeve anode and forced into motion by the combined action of a vortex gas flow (<26.3 SLPM) and axial magnetic field (~0.043–0.122 T) was studied. High-speed imaging and electrical diagnostics were used to gain an understanding of the projected arc length, position of the attachment point on the central cathode, and frequency of arc rotation. The electrical signals revealed a glow-type mode of operation, which characteristically low current and high voltage. The square root dependency of the rotating arc frequency on the applied current predicted by a simplified model considering the gas vortex drag and Lorentz forces was confirmed with measurements. Rotation frequencies in the ~100–300 Hz range with average projected arc lengths of 4–8 mm creating a large stabilized reactive volume were obtained. We further demonstrated that the Lorentz force acting on the rotating gliding arc is equivalent to the hydrodynamic drag caused by an argon flow rate of ~8 SLPM for this device configuration.

A Parametric Study on the Effects of Process Conditions on Dehydrogenation, Wall Shear and Slag Entrainment in the Vacuum Arc Degasser Using Mathematical Modelling

The effect of vacuum pressure and argon flow rate on hydrogen degassing of molten steel in a triple plug, 100 tonne vacuum arc degasser has been examined using a three phase Eulerian CFD-mass transfer coupled model. The model takes into account the interaction between the slag, steel and argon phases over a 20-minute degassing period. Increasing the argon flowrate from 13-29 Nm3hr−1 produces a 10% increase in the hydrogen removal ratio, generating a faster melt velocity and larger slag eye. This also results in the maximum shear stress on the ladle walls increasing by a factor of 2.2 and the shear stress integrated across the wall increasing by a factor of 3.75, thus contributing to enhance refractory erosion. Within the same flowrate range the volume of entrained slag also increases by a factor of 1.4, which may result in increased nitrogen/oxygen pickup. Reducing the vacuum pressure maintains a low equilibrium hydrogen concentration and allows more efficient hydrogen removal, with a 38% reduction in the removal ratio between 102−104 Pa.

In-situ growth of silicon carbide nanowire (SCNW) matrices from solid precursors

In an effort to develop highly porous silicon carbide for high temperature air filtration, an alternative approach to forming silicon carbide nanowires (SCNW) was developed by blending carbon containing materials with silicon powder and heating these precursors to 1400 °C. The mixing ratio of precursor materials and processing temperature were investigated with respect to the formation of SCNWs. Results indicate that anthracite and starchy materials can yield high purity SiC ceramics, yet these combinations did not produce SiC nanowires. SCNWs were successfully grown from a combination of guar gum and silicon powder precursors at 1400 °C, when held for 4 h with an argon flow rate of 1 L/min. The produced SiC is a high purity product with nanowire diameters of approximately 40 nm and ranging in length from about 100 nm to several micrometers in length. Iron was used to catalyze the nanowire growth through vapor-liquid-solid (VLS) mechanisms by adsorbing the silicon and carbon vapor at the iron rich tip, which then led the nanowire growth. TEM analysis revealed the growth of SCNWs followed the [1,1,2] direction. A wafer comprised of the synthesized SiC nanowire matrix has much higher hardness compared with a wafer of the porous commercially available cordierite.

Effect of magnetron sputtering parameters on adhesion properties of tungsten-rhenium thin film thermocouples

Tungsten-Rhenium (W-Re) thin films were grown on alumina ceramic substrate using the magnetron sputtering technique. The feasibility and reliability of the tungsten-rhenium thin film thermocouples application are largely dependent on the adhesion properties between the W-Re film and substrate. In order to get the good adhesion, we researched the effect of magnetron sputtering parameters on adhesion properties of tungsten-rhenium thin film thermocouples. With the help of three factors and three levels orthogonal table, nine orthogonal experiments were designed to study the influences of argon flow rate, sputtering power and vacuum degree on the performance of adhesion. The result showed that the effect of vacuum degree on adhesion properties was the largest, then come sputtering power, while the effect of the argon flow rate was the least and the optimal parameters combination was: argon flow rate 30 Sccm, sputtering power 400 W and vacuum degree 0.7 × 10−6 Torr.

Estimation of hydrogen flow rate in atmospheric Ar:H2 plasma by using artificial neural network

Atmospheric Ar:H2 plasma is an eco-friendly option for the reduction of metal oxides. For better reduction performance and safety concern, the hydrogen gas injected into the reactor should be monitored. A hydrogen flow rate estimation system is presented in this paper by using an artificial neural network (ANN) model fed with features of optical emission spectra of the plasma. ANN models are studied with two different sets of input, i.e. for the first case the inputs to the model are the three features of Hα line such as the peak intensity count, full-width half maximum and area under Hα line, while for the second case, the peak intensity count of a group of emission lines like Hα, Ar I, O I, K I, Na D lines are considered as the inputs. ANN model is developed for estimating four different sets of hydrogen flow rates 5, 8, 10 and 12 litres per minute (lpm) when the argon flow rate is constant at 10 lpm. For both the input features, the model performances are compared, and it is shown that improved estimation accuracy is observed from the second case, i.e. from peak intensity count of a group of emission lines instead of only hydrogen emission line.

Synthesis and Characterisation of Carbon Nanomaterials (CNMs) Using Polypropylene(PP) Waste as Carbon Precursor: Effect of Reactor Temperature

Fully utilisation of urban wastes such as polymer waste is considered as promising step to save the environment besides contributing to the production of Carbon Nanomaterials (CNMs) and their insight in mechanism involved. In this work, CNMs were successfully synthesised using polypropylene (PP) waste as carbon precursor via Chemical Vapour Deposition (CVD). Ferrocene was used as metal catalyst whereas argon was used as purging gas. The CVD were operated at various reactor temperatures to assess the possibility of CNMs growth at 600°C, 700°C, 800°C, 900°C, and 1000°C. The reaction time and argon flow rate were fixed at 90 minutes and 85 ml/min, respectively. The production of CNMs started at reactor temperature of 700°C and increased steadily from 0.0178 g to 0.2950 g with elevated temperature up to 1000°C. The diameter distribution of synthesised-CNMs reduced with the increased of reactor temperature. The XRD patterns revealed a sharp diffraction peak at around 26o(002) and broad diffraction peak at around 44o(111) which was proven to be Carbon Nanotubes (CNTs). Reactor temperature of 800°C considered as the best temperature to synthesis small diameter of CNMs in high quantity.

Characterization of a novel microwave plasma sheet source operated at atmospheric pressure

Typically, microwave plasma sources (MPSs) operated at atmospheric pressure deliver plasmas in the common form of flames or cylindrical columns. In contrast to that, in this paper, a novel MPS (recently patented by us) for generating a new type of plasma in the form of a plasma sheet, which is sustained within a dielectric flat cuboid box, is presented. It is waveguide based, operated at a frequency of 2.45 GHz and in argon at atmospheric pressure. The plasma sheet consists of many filaments, typical of a microwave argon plasma. The MPS is described and analyzed in terms of optical emission spectroscopy, simulation of the electric field distributions in the MPS and numerical modeling of the working gas flow. Depending on the argon flow rate and absorbed microwave power, the determined electron density and rotational temperatures of OH radicals ranged from 3.6 × 1014 to 5.6 × 1014 cm−3 and from 800–1250 K, respectively. Numerical simulations have confirmed that the dimensions of the box are chosen correctly to ensure a sufficiently homogeneous distribution of the gas flow velocity field. The calculated electromagnetic field distributions in the MPS with plasma have shown that the device is well matched to the feeding line. The relative simplicity of the presented plasma source and industrially convenient plasma shape make it attractive for practical applications in the surface treatment of various materials.

Formation of Titanium Hydride from the Reaction Between Magnesium Hydride and Titanium Tetrachloride

The reaction between magnesium hydride (MgH2) and titanium tetrachloride (TiCl4) to produce titanium hydride (TiH2) was carried out at varying temperature, time and Argon (Ar) gas flow rate. The reaction conditions were optimized for increasing the formation of TiH2 by using the statistical design of experiments (DOE). The hydriding temperature was varied from 200 to 300 °C, while the reaction time was changed from 60 to 180 minutes. The flow rate of argon gas was controlled in the range of 20 to 60 mL.min−1 to minimize TiCl4 dilution. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Elemental hydrogen analyzer. From the experiments, the highest weight change (Xw) of the sample produced at 300 °C for 180 minutes with Ar flow rate of 20 mL.min−1 was 0.19 wt.% and the degree of hydriding (Xh) of 38.49% by elemental hydrogen analysis. The DOE analysis inferred that the reaction time was the most significant factor followed by the flow rate of Ar gas and reaction temperature. The SEM/EDX analysis indicated that the product was composed of MgH2, MgCl2, TiCl2.3 and TiH2.The product contained a minor phase of TiO2 that could be due to seepage of ambient moisture into the reaction chamber.

Microstructural and Properties of P-type Nickel Oxide (NiO) Thin Films Deposited by RF Magnetron Sputtering

Nickel oxide (NiO) thin films were deposited on glass substrates using the RF magnetron sputtering technique at room temperature. The Argon and oxygen flow rates were kept constant at 10 sccm and 5 sccm respectively. The films were annealed at various temperatures (RT-300 °C) and its influence on the microstructural, optical and electrical properties were investigated. The X-ray diffraction (XRD) investigation of NiO films indicated the polycrystallinity of the films with the (111), (200) and (220) reflections corresponding to the cubic structure of NiO films. The crystallite size of NiO films was in the range ~4–14 nm. The transmittance of the films increased from 20 to 75% with increasing annealed temperature. The optical band gap of the films was 3.6–3.75 eV range for the as-deposited and annealed films. The Hall effect studies indicated the p-type conductivity of films and the film annealed at 300 °C showed higher carrier concentration (N), high conductivity (σ) and high mobility (μ) compared to other films. These NiO films can be used as a P-type semiconductor material in the devices require transparent conducting films.

Mathematical Modelling of Titanium Hydride Formation from Titanium Tetrachloride with Magnesium Hydride using Matlab

Titanium hydride (TiH2) is an important material for the synthesis of titanium metal by dehydriding reactions. The reaction to synthesize TiH2 by reacting titanium tetrachloride (TiCl4) with magnesium hydride (MgH2) was investigated so that the important factors governing the kinetics of the reaction could be determined. Experiments were carried out by varying the reaction conditions to establish the optimum level to achieve highest degree of hydriding (Xh). The combination of reaction parameters that yielded the highest degree of hydriding (38.49%) was a reaction temperature of 300°C at 180 minutes and Argon (Ar) flow rate of 20 cc/min. The reaction products were characterized using scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) to confirm the formation of TiH2. The Xh was measured by means of weight gain of the sample after the reaction with elemental hydrogen content analysis. Based on the experimental results, the reaction was simulated using Shrinking Core model (SCM) with MATLAB and the kinetic parameters were estimated by fitting the model to the experimental data. The simulated isothermal SCM model achieved an Xh of 57% at a reaction time of 180 minutes and Ar flow rate of 20 cc/min. The results of simulation inferred that the isothermal SCM showed good agreement with the experimental outcome providing a good fit to the data. In general, the Xh increased with increasing temperature, time and Ar flow rate within the investigated range of parameters.

Behavior Characteristics of Argon Bubbles on Inner Surface of Upper Tundish Nozzle during Argon Blowing Process

During continuous casting of aluminum-killed steel, clogging of tundish nozzle frequently occurs, which seriously disrupts the normal casting sequences and deteriorates strand quality. Generally, argon blowing technology in the form of a stable and continuous argon film on the inner surface of the upper nozzle is employed to prevent the upper nozzle from clogging in the production. To explore the formation mechanism and influence factors of this argon film, a water model of the upper nozzle with blowing argon with a similarity ratio of 1:1 was built. The results show that the number of bubble chains increases gradually with increasing argon flow rate and casting speed, and the argon gas curtain appears at the bottom half of the upper nozzle. For a given argon flow rate, the velocity of argon gas bubbles increased gradually with increasing casting speed, and decreased gradually with increasing distance from the upper nozzle top. For a given casting speed, the average velocity of argon gas bubbles was largest at a distance from the upper nozzle top of 6 mm with argon flow rate of 150 L/h. The results could provide theoretical and technical basis for the optimization of blowing argon parameters in order to prevent the clogging of upper nozzle and improve strand quality.

Microwave Plasma Jet in Water: Characterization and Feasibility to Wastewater Treatment

Plasma–liquid interactions have gained escalated interests over the last decade due to their potentials in many applications. The simultaneous generation of physicochemical phenomena of interest promotes itself to the top of the promising technologies for liquid processing. Here, we study the physics of a microwave plasma jet (MWPJ) submerged into water and its feasibility to wastewater treatment. We investigate the plasma and bubble dynamics using high-speed imaging. The effects of the argon flow rate, additive gas, and microwave power on the dynamics are examined highlighting the retreating behaviors of plasma channels due to the losses of electrons and power caused by nearby water surface. The addition of N2 (< 5%) to Ar flow results in an oscillatory motion of the foremost edge of the plasma channel. We characterize the submerged MWPJ using a time- and space-averaged optical emission spectroscopy. We found the dominant OH (A–X) molecular band and atomic Ar lines with pure Ar flow indicating the effective dissociation of water. Meanwhile, the addition of N2 leads to an intense emission of NH (A–X) molecular band. Finally, we assess the submerged MWPJ as a viable method for water purification based on the degradation of methylene blue (popular model compound). We find a significant improvement in the efficiency by adding 1–3% of N2 to the Ar, which should be attributed to a combined effects of NH radicals, having high redox potential, and the backward reactions of H2O2 to form OH radicals with NO and NO2.

Obtaining of non-stoichiometric titanium oxide using reactive magnetron sputtering

A mode of obtaining of non-stoichiometric titanium oxide film in magnetron system with turbomolecular pump of low performance was found. The mode provides significantly lower volumetric flow rate of argon and reactive gas comparing with known mode. Dependencies of discharge voltage and film sputtering rate on reactive gas volumetric flow were investigated. Measurements of film obtained by the mode with low oxygen volumetric flow proved deviation of composition stoichiometry.

Quantitative analysis of C, Si, Mn, Ni, Cr and Cu in low-alloy steel under ambient conditions via laser-induced breakdown spectroscopy

A diode-pumped solid-state laser (DPSSL) with a high energetic stability and long service life is applied to ablate the steel samples instead of traditional Nd:YAG laser pumped by a xenon lamp, and several factors, such as laser pulse energy, repetition rate and argon flow rate, that influence laser-induced breakdown spectroscopy (LIBS) analytical performance are investigated in detail. Under the optimal experiment conditions, the relative standard deviations for C, Si, Mn, Ni, Cr and Cu are 3.3%–8.9%, 0.9%–2.8%, 1.2%–4.1%, 1.7%–3.0%, 1.1%–3.4% and 2.5%–8.5%, respectively, with the corresponding relative errors of 1.1%–7.9%, 1.0%–6.3%, 0.4%–3.9%, 1.5%–6.3%, 1.2%–4.0% and 1.2%–6.4%. Compared with the results of the traditional spark discharge optical emission spectrometry technique, the analytical performance of LIBS is just a little inferior due to the less stable laser-induced plasma and smaller amount of ablated sample by the laser. However, the precision, detection limits and accuracy of LIBS obtained in our present work were sufficient to meet the requirements for process analysis. These technical performances of higher stability of output energy and longer service life for DPSSL, in comparison to the Q-switch laser pumped by xeon lamp, qualify it well for the real time online analysis for different industrial applications.

Experimental investigation of effects of grain size, inlet pressure and flow rate of air and argon on pressure drop through a packed bed of granular activated carbon

Considering the wide range of applications of the activated carbon in different applications, the behavior of fluid flow through a packed bed of irregular shaped activated carbon grains has significant importance. Hence, an experimental investigation is conducted on axial-horizontal flow of air and argon through 5 different packed beds of granular activated carbon (GAC) with different grain sizes. Investigations are done different flow line pressure and flow rates. Based on the previous studies, a simple correlation is proposed and results are presented in terms of dimensionless friction factor versus Reynolds number. Results are presented for different grain sizes and the correlation coefficients have been estimated with excellent curve fitting to the experimental data. Outcomes of this study could be used to design the systems in which the pressure drop through a packed bed of GAC is required.

Effect of the gas flow rate on the spatiotemporal distribution of Ar(1s5) absolute densities in a ns pulsed plasma jet impinging on a glass surface

This work presents spatial (axial-z and transversal-y) and temporal distributions of Ar(1s5) metastable absolute densities in an atmospheric pressure argon micro-plasma jet impinging on an ungrounded glass surface. Guided streamers are generated with a DBD device driven by pulsed positive high voltages of 6 kV in amplitude, ns in FWHM and 20 kHz in frequency. The argon flow rate is varied between 200 and 600 sccm. The glass plate is placed at 5 mm away from the reactor’s nozzle and perpendicular to the streamers propagation. At these conditions, a diffuse stable discharge is established after the passage of the streamers allowing the quantification of the Ar(1s5) absolute density by means of a conventional TDLAS technique coupled with emission spectroscopy and ICCD imaging. The good reproducibility of the absorption signals is demonstrated. The experiments show the strong dependence of the maximum density on the gas flow rate and the axial and transversal position. At 200 sccm, high maximum densities are obtained in a small area close to the plasma source, while with increasing flow rate this area expands towards the glass plate. In the transversal direction, density maxima are obtained in a small zone around the propagation axis of the streamers. Finally, a noticeable increase is measured on the Ar(1s5) effective lifetime close to the glass surface by varying the flow rate from 200 to 600 sccm. In overall, the effective lifetime varies between ∼25 and ∼550 ns, depending on the gas flow rate and the values of z and y coordinates. The results obtained suggest that the present system can be implemented in various applications and particularly in what concerns the detection of weakly volatile organic compounds present in trace amounts on different surfaces.

Hydrogen Degassing in a Vacuum Arc Degasser Using a Three‐Phase Eulerian Method and Discrete Population Balance Model

A three‐phase Eulerian model incorporating slag‐steel interactions to predict the rate of hydrogen removal from molten steel in a full‐scale industrial vacuum arc degasser (VAD) has been developed. The interfacial area for hydrogen transfer is calculated using a bubble population balance model. This accounts for bubble growth due to changes in hydrostatic pressure as well as coalescence and breakup. The predicted velocity field and bubble distribution are compared with experimental data in the literature. The bubble size predictions under atmospheric pressure conditions are sensitive to the initial bubble size, while under vacuum conditions they are relatively independent of the initial size. The omission of the slag layer from the model results in a 12% increase in the hydrogen removal rate. Variation in the slag eye diameter as a function of argon flowrate is simulated and compared with empirical correlations in the literature. Hydrogen measurements from a full‐scale VAD unit at Sheffield Forgemasters International Ltd. steelworks are compared to the model predictions for a series of melts of varying initial hydrogen content. Based on the initial hydrogen content of the liquid steel, the model predicts the amount of hydrogen removed to within ±20% of final experimental measurements obtained from the melt.

Effect of CrN barrier on fuel-clad chemical interaction

Abstract Chromium and chromium nitride were selected as potential barriers to prevent fuel-clad chemical interaction (FCCI) between the cladding and the fuel material. In this study, ferritic/martensitic HT-9 steel and misch metal were used to simulate the reaction between the cladding and fuel fission product, respectively. Radio frequency magnetron sputtering was used to deposit Cr and CrN films onto the cladding, and the gas flow rates of argon and nitrogen were fixed at certain values for each sample to control the deposition rate and the crystal structure of the films. The samples were heated for 24 h at 933 K through the diffusion couple test, and considerable amount of interdiffusion (max. thickness: 550 μm) occurred at the interface between HT-9 and misch metal when the argon and nitrogen were used individually. The elemental contents of misch metal were detected at the HT-9 through energy dispersive X-ray spectroscopy due to the interdiffusion. However, the specimens that were sputtered by mixed gases (Ar and N 2 ) exhibited excellent resistance to FCCI. The thickness of these CrN films were only 4 μm, but these films effectively prevented the FCCI due to their high adhesion strength (frictional force ≥1,200 μm) and dense columnar microstructures.