Hydrogen and nitrogen control in ladle and casting operations

Misra, Siddhartha; Fruehan, R. J.

doi:10.2172/1216251

Cited by 15 publications

(15 citation statements)

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“…Fully hydrated lime Ca(OH) 2 is taken as the main hydrogen source in the bath surface of non-open-eye region that represents the slag covered area. In this study, 250 kg lime is added in the ladle furnace before vacuum degassing and 2 wt% [26] hydrogen of the total hydrogen amount in Ca(OH) 2 is assumed as the hydrogen source entering the steel in the simulations. 6.…”

Section: Simplifications and Assumptionsmentioning

confidence: 99%

Mathematical Modeling of Nitrogen Removal from the Vacuum Tank Degasser

Miettinen

Shao

et al. 2014

steel research int.

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The removal of nitrogen from an industrial vacuum tank degasser depends on a series of operational parameters, steel composition, and contents of surface-active elements in liquid steel, e.g., oxygen and sulfur. The effect of some specific elements on nitrogen removal in the vacuum degasser has been (well) examined. Still, it is quite challenging to assess the overall effect of the whole steel composition on the process. The focus of the present work was to predict nitrogen removal from the vacuum degasser specially taking into account the multi-component effect of steel composition. An integrated computational fluid dynamics (CFD) model for simulating nitrogen (and hydrogen) removal in industrial vacuum tank degassers was therefore developed based on theories and methods that are relatively separate in the literature. In order to include the multi-component effect, the model is coupled with an in-house thermodynamics code that can be used to determine the activity coefficient of nitrogen, oxygen, or sulfur as a function of steel composition and temperature. The code was verified by comparing the calculated activity coefficients against experimental measurements from various sources. Efforts were also put into developing an on-line use concept to control the nitrogen removal. The gas plume, flow field, and evolutions of nitrogen and hydrogen during vacuum treatment were predicted and the on-line concept was demonstrated by presenting two operating diagrams. The results showed that the final nitrogen content decreases with an increase in the chemical reaction rate constant and a decrease in the initial nitrogen content. By contrary, the final nitrogen content increases with a decrease in the chemical reaction rate constant and an increase in the initial nitrogen content. Finally, the operating diagrams were validated by industrial data and observations.

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Section: Simplifications and Assumptionsmentioning

confidence: 99%

Mathematical Modeling of Nitrogen Removal from the Vacuum Tank Degasser

Miettinen

Shao

et al. 2014

steel research int.

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“…However, the overall denitrogenation rate is determined by the mass transfer of nitrogen in liquid steel and interfacial reaction. The fully hydrated lime, Ca(OH) 2 , is taken as the main hydrogen source in the bath surface of non‐open‐eye region which represents the slag covered area. In this study, 250 kg lime is added in ladle furnace before vacuum degassing and 2 wt% hydrogen of the total hydrogen amount in Ca(OH) 2 is assumed as the hydrogen source entering the steel in the simulations. The oxygen content in liquid steel is constant and is set as 6 ppm. The variations of activity coefficients due to the change in steel composition during vacuum treatment are neglected.…”

Section: Mathematical Modelingmentioning

confidence: 99%

“…The fully hydrated lime, Ca(OH) 2 , is taken as the main hydrogen source in the bath surface of non-open-eye region which represents the slag covered area. In this study, 250 kg lime is added in ladle furnace before vacuum degassing and 2 wt% [21] hydrogen of the total hydrogen amount in Ca(OH) 2 is assumed as the hydrogen source entering the steel in the simulations. 6.…”

mentioning

confidence: 99%

Modeling Study of Nitrogen Removal from the Vacuum Tank Degasser

Miettinen

Louhenkilpi

2014

steel research int.

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Low nitrogen content in liquid steel is required for most of the steelmaking companies, where vacuum degassing of liquid steel is usually carried out to remove nitrogen as well as other impurity elements during ladle treatment. This paper presents an integrated computational fluid dynamics (CFD) model for simulating the nitrogen removal in an industrial vacuum tank degasser (VTD). In the CFD model, oxygen and sulfur are considered as surface-active elements decreasing the denitrogenation rate at the gas-steel interface. An activity coefficient and a desulfurization sub-model are implemented to compute the effective activity coefficients of the related elements and the evolution of sulfur content in liquid steel during the process, respectively. The effect of various elements on denitrogenation rate in the VTD is studied with the developed model. For the used steel compositions the denitrogenation rate decreases with an increase in the content of [S] [Al]. The model is validated by comparing final nitrogen contents measured from the industrial plant with the ones predicted by the model and good agreements were found. The model has proven to be a useful and accurate tool for predicting final nitrogen content of liquid steel in the plant.

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“…This is given by the fact that diatomic gases are creating with metal an atomic solutions. When gas molecules are dissolved in the metal, they dissociate into atoms, so the number of atoms dissolved in the metal is twice than the number of initial molecules [2]. Sieverts law cannot be applied when the gas reacts chemically with the metal.…”

Section: Introductionmentioning

confidence: 99%

Identification of Factors Causing Nitridation of Crude Steel in Bof Before Tapping

Buľko¹,

Demeter²,

Kijac³

et al. 2014

Acta Metall Slovaca

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Determination of factors and measuring their impact on the amount of nitrogen in the metal is key attribute when optimizing technological and operational measures tending to minimize, respectively prevent of the final steel nitridization. Knowing the rate of influence of individual factors on the nitrogen content in the metal is crucial in dealing with prediction of the quantity for the production and processing stages of steel production in a closed production cycle. In this paper, factors determining nitrogen content in crude steel before tapping, using Cohen´s distribution table and graphical expression are presented. Influence of after-blows on nitrogen content is well known, but there are other factors which affect steel nitridization before tapping from oxygen converter.

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Hydrogen and nitrogen control in ladle and casting operations

Cited by 15 publications

References 0 publications

Mathematical Modeling of Nitrogen Removal from the Vacuum Tank Degasser

Mathematical Modeling of Nitrogen Removal from the Vacuum Tank Degasser

Modeling Study of Nitrogen Removal from the Vacuum Tank Degasser

Identification of Factors Causing Nitridation of Crude Steel in Bof Before Tapping

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