Effect of Metal Vapours on the Radiation Properties of Thermal Plasmas

Gleizes, Alain; Cressault, Yann

doi:10.1007/s11090-016-9761-y

Cited by 15 publications

(14 citation statements)

References 46 publications

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“…Comparing with other melts, the chromium temperature is close to the values of other melts (around 6500 K and above) between 13:48:00 and 13:49:10, whereas the iron temperature is lower than in the other melts. Lower plasma temperature has been linked to a higher amount of metal vapors in the plasma, [ 24 ] which could mean that there has been a high evaporation rate from the slag or steel between 13:41:30 and 13:42:55. In contrast, the lack of calcium temperatures and the high difference in chromium and iron temperatures between 13:47:40 and 13:49:10 is a sign that the optical emissions are affected by the changes in the furnace atmosphere or self‐absorption.…”

Section: Resultsmentioning

confidence: 99%

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Optical Emission Spectroscopy as an Online Analysis Method in Industrial Electric Arc Furnaces

Pauna

Aula

Seehausen³

et al. 2020

steel research int.

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Electricity-based steelmaking with electric arc furnaces (EAFs) has been increasing during the past decades, currently amounting to around a third of the global steel production. [1] Reasons for this, to name a few, are lower carbon dioxide emissions and better energy efficiency compared with the traditional ore-based steelmaking. [1,2] Furthermore, favoring the recycled metal as the raw material over the ore-based steelmaking has a key role in sustainable resource and energy use. [3] Due to these reasons, electricity-based steelmaking can be expected to increase even more in the future. Recycled metal is one of the main raw materials for an EAF. One of the downsides of the recycled metal is its highly varying composition and particle size. Thus, the composition of the slag that accumulates on top of the molten steel is unique for every batch. The slag is quantitatively a major byproduct in the steelmaking but the varying composition causes problems for the final slag product. [4] A common way to determine the slag composition is to make an offline X-ray fluorescence (XRF) analysis, which requires careful sample preparation [5] causing a time delay between the slag sampling and obtaining the XRF results. [6] Therefore, the results of the XRF slag composition analysis have limited use during the melting process in practice. In contrast, online evaluation of the slag composition would allow the furnace operator to decide how much and which additive materials, such as lime or ferrosilicon, should be added before the end of the melt. Also, the timing of these additions could be adjusted to optimal instances. By getting the information of the slag composition in advance, the operator would be able to plan the use of additive materials from the resource use and efficiency point of view. Due to the demand for sophisticated modeling of the EAF processes and experimental validation of the methods, the fundamental EAF research has increased over the years. Especially, the online measurements and modeling have gained a lot of attention from the steel industry because online data analysis would contribute to more efficient resource use, real-time modification of the steel composition, and anticipation of abnormal and even hazardous phenomena in the furnace. From the melting point of view, Logar et al. [7] developed a computational model that can be used online due to low computational demand to estimate the heat transfer coefficient in the EAF. Fathi et al. [8] presented a computational model to estimate the arc energy distribution to conductive, convective, and radiative heat transfer processes with low enough computation times for online applicability. Li et al. [9] have proposed a model that combines offline and online aspects of the EAF process to adjust the electrode regulation system to optimum practice. Khoshkhoo et al. [10] introduced a model for efficient power control of EAFs that uses

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Section: Resultsmentioning

confidence: 99%

“…Metal vapors in the plasma also increase the radiative heat transfer, emissivity, and conductivity of the plasma column. [24,26] The OES plasma analysis results for 30 high alloyed steel grade melts are shown in Table 2. The total number of high alloyed melts during the measurement campaign was 43.…”

Section: High Alloyed Steel Grade Plasma Analysismentioning

confidence: 99%

Optical Emission Spectroscopy as an Online Analysis Method in Industrial Electric Arc Furnaces

Pauna

Aula

Seehausen³

et al. 2020

steel research int.

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“…This challenge is evidenced by the determination of absorption coefficients. State-of-the art computations use millions of wavelength intervals [28], as exemplified by the work on microwave discharges of air, CO 2 , and CO 2 -H 2 mixtures by Kassir et al [42], and on plasmas containing metal vapors by Gleizes and Cressault [37]. Moreover, Planck's emission law is not valid for a system in NLTE, and radiative emission is function of the local thermodynamic state.…”

Section: Radiative Nonequilibriummentioning

confidence: 99%

Nonequilibrium Phenomena in (Quasi-)thermal Plasma Flows

Trelles

2019

Plasma Chem Plasma Process

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Thermal plasmas are utilized in diverse applications that require high power densities or throughputs, such as metal cutting, welding, spraying, metallurgy, and materials synthesis. Thermal plasma applications involve interactions between the highly energetic plasma and working gas streams, confining devices, or processing materials. Whereas thermal plasma implies a state of equilibrium (i.e. Local Thermodynamic Equilibrium, LTE), due to the above interactions, thermal plasma flows depict nonequilibrium phenomena of two types: kinetic and dissipative. Kinetic nonequilibrium manifests microscopically and is caused by localized imbalances between particles and fields interactions. Its occurrence is evidenced, for example, as deviations from thermal equilibrium between heavy-species and electrons or from mass-action laws. In contrast, dissipative nonequilibrium reveals macroscopically and is produced by external driving forces that incite distributed responses, such as the growth of instabilities, the occurrence of self-organization, or the establishment of turbulence. Although kinetic nonequilibrium has been increasingly incorporated in thermal plasma flow models (e.g. finite-rate chemistry, two-temperature models), it is the great advances in numerical computing that is enabling the exploration of dissipative nonequilibrium (e.g. pattern formation, small-scale turbulent features). Both types of nonequilibrium are reviewed, including their estimation and incidence, within the context of computational models and their relevance to thermal plasma sources and processes.

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“…Thus, the mole fraction gradients caused by ionization of Ar as well as by thermal diffusion could lead to an increase of non-ionized and light He in the center (high-temperature) region of the plasma jet. the injection of powder, the vapor species from evaporated feedstock power has an influence on general plasma properties such as a cooling effect [42]. Therefore, with the injection of feedstock into the plasma, T exc (A) of Ar at different powder feeding rates were calculated based on the measured I(y=0 mm) without Abel inversion by the Boltzmann plot method.…”

Section: Concentration Profiles Of Ar and Hementioning

confidence: 99%

Excitation Temperature and Constituent Concentration Profiles of the Plasma Jet Under Plasma Spray-PVD Conditions

Mauer

Vaßen

2017

Plasma Chem Plasma Process

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Plasma spray-physical vapor deposition (PS-PVD) is a promising technology to produce columnar structured thermal barrier coatings with excellent cyclic lifetime. The characteristics of plasma jets generated by standard plasma gases in the PS-PVD process, argon and helium, have been studied by optical emission spectroscopy. Abel inversion was introduced to reconstruct the spatial characteristics. In the central area of the plasma jet, the ionization of argon was found to be one of the reasons for low emission of atomic argon. Another reason could be the demixing so that helium prevails around the central axis of the plasma jet. The excitation temperature of argon was calculated by the Boltzmann plot method. Its values decreased from the center to the edge of the plasma jet. Applying the same method, a spurious high excitation temperature of helium was obtained, which could be caused by the strong deviation from local thermal equilibrium of helium. The addition of hydrogen into plasma gases leads to a lower excitation temperature, however a higher substrate temperature due to the high thermal conductivity induced by the dissociation of hydrogen. A loading effect is exerted by the feedstock powder on the plasma jet, which was found to reduce the average excitation temperature considerably by more than 700 K in the Ar/He jet.

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Effect of Metal Vapours on the Radiation Properties of Thermal Plasmas

Cited by 15 publications

References 46 publications

Optical Emission Spectroscopy as an Online Analysis Method in Industrial Electric Arc Furnaces

Optical Emission Spectroscopy as an Online Analysis Method in Industrial Electric Arc Furnaces

Nonequilibrium Phenomena in (Quasi-)thermal Plasma Flows

Excitation Temperature and Constituent Concentration Profiles of the Plasma Jet Under Plasma Spray-PVD Conditions

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