Acceleration of Decarburization in RH Vacuum Degassing Process.

Inoue, Shigeru; Furuno, Yoshikazu; Usui, Tsutomu; Miyahara, Shinobu

doi:10.2355/isijinternational.32.120

Cited by 34 publications

(21 citation statements)

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“…One of the dominant factors which influence the decarburization rate in the RH process is circulation flow rate 1) (the melt flow rate per unit time through the snorkel). It is generally accepted that the decarburization rate increases as the circulation flow rate increases.…”

Section: Introductionmentioning

confidence: 99%

Numerical Calculation of Circulation Flow Rate in the Degassing Rheinstahl-Heraeus Process.

Park

Doo

et al. 2000

ISIJ International

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The circulation flow rate of a steel melt, which is one of the important factors which determine decarburization rate of RH system, was calculated by using a 3-dimensional numerical simulation technique. A new model for evaluating the shape and volume of the plume zone, formed by Ar gas blown through multiple nozzles on the wall of the snorkel, was proposed to determine the driving force of melt circulation.Circulation flow rates were measured in the 1/10 scale water model and in a real RH system to verify the calculation results with good agreement with the calculated circulation flow rates.Because the computer program can calculate the circulation flow rates at various operating conditions and dimensions of the RH system, it may be useful in determining the optimum operating conditions and designing new RH systems.

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Section: Introductionmentioning

confidence: 99%

Numerical Calculation of Circulation Flow Rate in the Degassing Rheinstahl-Heraeus Process.

Park

Doo

et al. 2000

ISIJ International

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“…In particular, analyses of the carbon and oxygen concentration acquired during the RH operations have been made. 1,2) These studies established the decarburization model based on an assumed circulation flow rate estimated by empirical equations. Kishmoto et al 3) carried out small scale experiments and evaluated the factors that influence the decarburization rate.…”

Section: Introductionmentioning

confidence: 99%

A New Numerical Model for Predicting Carbon Concentration during RH Degassing Treatment

Park

2003

ISIJ International

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A new decarburization model for the RH system was constructed to calculate the decarburization reaction using a three-dimensional fluid dynamics program. The behavior of Ar gas and the entire fluid flow in the RH process were considered. On the basis of this fluid flow, the decarburization reaction could be calculated by establishing the decarburization reaction model, which considers thermodynamics, reaction kinetics, and the decarburization sites (Ar bubble surface, bath surface, and the CO bubble formation at inner sites). The model showed good agreement with two RH operation results. Using this numerical model, the contributions of each reaction were investigated.KEY WORDS: decarburization; reaction model; reaction site; reaction area; reaction rate.where g is the acceleration due to gravity (m/s 2 ), r l and r g are the densities of the Ar gas and the melt (kg/m 3 ), V p is the volume of the plume (m 3 ) and a is the average volume fraction of the gas. The plume volume was calculated from the plume shape, which is affected by the pressure of the vacuum vessel, nozzle number and position, gas flow rate etc.. The average volume fraction is the total volume ratio of gas in the plume realm. In addition, gas bubble expansion due to the pressure drop and heat transfer from melt during rising was calculated and this effect was considered when calculating the total buoyancy force. In the Ref. 9), the bubble expansion due to only pressure drop was considered. In this study, the numerical model was modified to consider both the thermal expansion and pressure drop, Szekely's model 11) is modified as In Eq. (2), r l is the density of the melt, R b is the radius of the bubble, T is temperature in the bubble, R b and T 0 are radius and temperature at the nozzle respectively, P V is the pressure of the vacuum vessel and H is the height of the melt. To solve Eq. (2), the temperature should be known. ) and C is the heat capacity (J/kg · K). h is the heat transfer coefficient (J/m 2 · s · K) and the value can be derived from the penetration theory with the assumption of gas phase control. Komarove et al. derived heat transfer coefficient from experiments.12) Because the analysis in the Ref. 12) was based on spherical and constant size bubble, there should be some difference in the value of h and further study should be necessary to derive more realistic h value.The buoyancy force calculated by Eq. (1) was inserted as the external force for the velocity components (u, v, w) in the three dimensional Navier-Stokes equation to calculate fluid flow. The numerical model can predict the effects of the operational conditions and shapes of the RH system on fluid flow. 13) Calculation of Decarburization ReactionIn this study, the decarburization reaction was simulated by calculating the dissolved carbon concentration during the RH process. The numerical model included mass transport of dissolved carbon and oxygen due to convection and diffusion and the reaction rate at the reaction sites. The reaction rate was calculated respectively...

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“…The effects of different parameters, such as argon flow rate, snorkels diameters, pressure in the vacuum chamber and position of the argon injection points, on the melt circulation rate have been analyzed in these investigations. The decarburization rate in the RH process has also been studied using data from plant trials (Inoue et al, 1992;Yamaguchi et al, 1992;Kishimoto et al, 1993;Takahashi et al, 1995), lab scale experiments (Inoue et al, 1992;Kishimoto et al, 1993) and water models (Inoue et al, 1992;Seshadri et al, 2006). Mathematical models have been proposed to evaluate the decarburization kinetics.…”

Section: Introductionmentioning

confidence: 99%

Mass Transfer in Steelmaking Operations

Tavares¹

2011

Mass Transfer in Multiphase Systems and Its Applications

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Acceleration of Decarburization in RH Vacuum Degassing Process.

Cited by 34 publications

References 1 publication

Numerical Calculation of Circulation Flow Rate in the Degassing Rheinstahl-Heraeus Process.

Numerical Calculation of Circulation Flow Rate in the Degassing Rheinstahl-Heraeus Process.

A New Numerical Model for Predicting Carbon Concentration during RH Degassing Treatment

Mass Transfer in Steelmaking Operations

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