Mechanisms of NO Formation during SiO Combustion

Kamfjord, Nils Eivind; Tveit, Halvard; Naess, Man K; Myrhaug, Edin H.

doi:10.1002/9781118364987.ch49

Cited by 6 publications

(9 citation statements)

References 2 publications

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“…Kamfjord et al found that the time for particle growth and formation time for thermal NO formation was in the same order of magnitude, and it is hence not surprising that a correlation is found between NO x and particle size in this study. Similarly, the dust concentration was given by the amount of SiO available for combustion, which was the source for the energy needed to form thermal NO and would also facilitate particle growth and reduce SSA.…”

Section: Resultssupporting

confidence: 75%

“…A significant positive correlation for FGR rate with water content and SO 2 content in the off-gas was found, and a significant negative correlation between the SSA and the temperature of the off-gas, PM concentration, and NO x concentration in the off-gas, both with and without corrections for NO x recirculated through FGR, was also shown. Kamfjord et al 34 found that the time for particle growth and formation time for thermal NO formation was in the same order of magnitude, and it is hence not surprising that a correlation is found between NO x and particle size in this study. Similarly, the dust concentration was given by the amount of SiO available for combustion, which was the source for the energy needed to form thermal NO and would also facilitate particle growth and reduce SSA.…”

Section: ■ Results and Discussionsupporting

confidence: 74%

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Silica Fume Formation in Different Gas Atmospheres

Andersen

Einarsrud

Rasouli

et al. 2023

Ind. Eng. Chem. Res.

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Silica fume is an important byproduct from the silicon production process, with mainly concrete and refractory applications. In this work, the effect of different combustion gas atmospheres on the properties of silica fume has been investigated through small-scale experiments and a pilot-scale experiment. In the small-scale experiments, SiO gas was formed and reacted with four mixtures of nitrogen fixed at 79 vol %, oxygen, carbon dioxide, and carbon monoxide. No significant difference between the particulate matter (PM) formed was found when replacing O 2 with CO 2 using a holding temperature of 1700 °C, when measuring the specific surface area (SSA), particle size distribution, or carbon content. PM formed at a holding temperature of 1650 °C was found to have a significantly higher SSA of 32.9 m 2 /g compared to the SSA of 22.3 m 2 /g formed at 1700 °C with the same gas mixtures. Condensation products were only found when replacing O 2 with CO, where brown PM was formed through SiO reacting with SiO 2 , SiC, and Si. Using a pilot-scale setup, the combustion gas for the silicon process was altered by recirculating different ratios of flue gas back to the furnace hood. Silica fume samples were collected during several tapping cycles with varying flue gas recirculation (FGR) rates. The SSA was measured for the sampled PM and correlated to a selection of operational parameters. A significant negative correlation was found between the SSA of PM and the concentration of H 2 O and SO 2 in the off-gas, while a significant positive correlation was found between the SSA and the temperature of the off-gas, the concentration of dust in the off-gas, and the NO X generation during the process. These results indicate that the temperature and SiO concentration during combustion are more important than the CO 2 (or O 2 ) concentration in the combustion atmosphere. Using FGR to increase the CO 2 concentration in the off-gas should not change the silica fume particle size, if the H 2 O content is controlled.

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Section: Resultssupporting

confidence: 75%

Section: ■ Results and Discussionsupporting

confidence: 74%

Silica Fume Formation in Different Gas Atmospheres

Andersen

Einarsrud

Rasouli

et al. 2023

Ind. Eng. Chem. Res.

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“…This accounts for the spherical shape of the particles. Their near uniformity of size can be explained by particle growth theory [11].…”

Section: Discussionmentioning

confidence: 99%

Active Oxidation of Liquid Silicon: Experimental Investigation of Kinetics

et al. 2012

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Small scale laboratory experiments on the oxidation of liquid silicon have reproduced important features of the industrial refining of liquid silicon: active oxidation led to the formation of amorphous silica spheres as a reaction product. The boundary condition for active oxidation in terms of maximum oxygen partial pressure in the bulk gas was found to lie between 2Á10 -3 and 5Á10 -3 atm at T = 1,500°C. The active oxidation of liquid silicon had linear kinetics, and the rate was proportional to bulk oxygen partial pressure and the square root of the linear gas flow rate, consistent with viscous flow mass transfer theory. Classical theory for unconstrained flow over a flat plate led to mass transfer rates for SiO (g) which were 2-3 times slower than observed. However, computational fluid dynamic modeling to take into account the effects of reactor tube walls on flow patterns yielded satisfactory agreement with measured volatilization rates.

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“…In these high-temperatures zones, thermal NO X production is promoted (see the NO X section). 26,95 It is clear from Table IV that the major sources of PM, both inside the plant and escaping from the plant, are those which involve the liquid alloy. Tapping, refining, casting and other operations where high-temperature liquid alloy is in contact with air produces a silica fume which has many similarities to the microsilica.…”

Section: Particulate Emissionsmentioning

confidence: 99%

Airborne Emissions from Si/FeSi Production

Kero

Grådahl

Tranell

2016

JOM

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The management of airborne emissions from silicon and ferrosilicon production is, in many ways, similar to the management of airborne emissions from other metallurgical industries, but certain challenges are highly branch-specific, for example the dust types generated and the management of NO X emissions by furnace design and operation. A major difficulty in the mission to reduce emissions is that information about emission types and sources as well as abatement and measurement methods is often scarce, incomplete and scattered. The sheer diversity and complexity of the subject presents a hurdle, especially for new professionals in the field. This article focuses on the airborne emissions from Si and FeSi production, including greenhouse gases, nitrogen oxides, airborne particulate matter also known as dust, polyaromatic hydrocarbons and heavy metals. The aim is to summarize current knowledge in a state-of-the-art overview intended to introduce fresh industry engineers and academic researchers to the technological aspects relevant to the reduction of airborne emissions.

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Mechanisms of NO Formation during SiO Combustion

Cited by 6 publications

References 2 publications

Silica Fume Formation in Different Gas Atmospheres

Silica Fume Formation in Different Gas Atmospheres

Active Oxidation of Liquid Silicon: Experimental Investigation of Kinetics

Airborne Emissions from Si/FeSi Production

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