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Metallurgical and Materials Transactions B

, Volume 49, Issue 5, pp 2191–2208 | Cite as

Dynamic Model of Basic Oxygen Steelmaking Process Based on Multizone Reaction Kinetics: Modeling of Manganese Removal

  • Bapin Kumar Rout
  • Geoffrey Brooks
  • M. Akbar Rhamdhani
  • Zushu Li
  • Frank N. H. Schrama
  • Willem van der Knoop
Article
  • 196 Downloads

Abstract

In the earlier study, a dynamic model for the BOF process based on the multizone reaction kinetics has been developed. In the preceding part, the mechanism of manganese transfer in three reactive zones of the converter has been analyzed. The study predicts that temperature at the slag–metal reaction interface plays a major role in the Mn reaction kinetics. Further, mathematical treatments to simulate the transient rate parameters associated with each reaction interface have been developed. The model calculations of Mn removal rate obtained from different zones of the converter predicts that the first stage of the blow is dominated by the oxidation of Mn at the jet impact zone, albeit some additional Mn refining has been observed as a result of the oxidation of metal droplets in emulsion phase. The simulation result shows that the reversion of Mn from slag to metal primarily takes place at the metal droplet in the emulsion due to an increase in slag–metal interface temperature during the middle stage of blowing. In the final stage of the blow, the competition between simultaneous reactions in jet impact and emulsion zone controls the direction of mass flow of manganese. Further, the model prediction shows that the Mn refining in the emulsion is a strong function of droplet diameter and the residence time. Smaller sized droplets approach equilibrium quickly and thus contribute to a significant Mn conversion between slag and metal compared to the larger sized ones. The overall model prediction for Mn in the hot metal has been found to be in good agreement with two data sets obtained from different size converters reported in the literature.

Nomenclature

A

Area of the reaction interface (m2)

Cp,m

Heat capacity of bulk metal (J/kg)

Cp,s

Heat capacity of slag (J/kg)

dp

Diameter of the droplet (m)

\( \left( {\frac{{d{\text{Mn}}}}{dt}} \right)_{\text{overall}} \)

Overall manganese refining rate (kg/s)

\( \left( {\frac{{d{\text{Mn}}}}{dt}} \right)_{\text{iz}} \)

Manganese refining rate in jet impact zone (kg/s)

\( \left( {\frac{{d{\text{Mn}}}}{dt}} \right)_{\text{sm}} \)

Manganese refining rate in slag–bulk metal zone (kg/s)

\( \left( {\frac{{d{\text{Mn}}}}{dt}} \right)_{\text{em}} \)

Manganese refining rate in emulsion zone (kg/s)

JMn

Manganese reaction rate (kg/s)

H

Bath height (cm)

koverall

Overall mass transfer coefficient (m/s)

km

Mass transfer coefficient in metal phase (m/s)

\( k_{\text{m}}^{\text{drop}} \)

Mass transfer coefficient of metal droplet (m/s)

\( k_{\text{overall}}^{\text{em}} \)

Overall mass transfer coefficient in emulsion (m/s)

ks

Mass transfer coefficient in slag phase (ms−1)

kMn

Apparent equilibrium constant of Mn (-)

K

Equilibrium constant (-)

L

Bath diameter (cm)

LMn

Equilibrium manganese partition ratio (-)

[wt pct Mn]eq

Equilibrium manganese concentration (wt pct)

[wt pct Mn]i

Manganese concentration at slag metal interface (wt pct)

[wt pct Mn]m

Manganese concentration in the hot metal (wt pct)

PO2

partial pressure of oxygen inside the furnace (atm)

nn

Number of nozzles in lance tip (-)

\( N_{\text{p}}^{\text{eject,t}} \)

Number of droplets of pth class size ejects to the bath at blowing time t (-)

\( N_{\text{p}}^{\text{return,t}} \)

Number of droplets of pth class size returns to the bath at blowing time t (-)

P

Number of divisions in the droplet size spectrum (-)

Re

Reynolds number (-)

RB,T

Droplet generation rate (kg/s)

Sc

Schmidt number (-)

Sh

Sherwood number (-)

tres

Residence time of droplet in emulsion (seconds)

Tm

Temperature of the hot metal (K)

Tiz

Temperature at the impact zone (K)

Tdrop

Interface temperature at slag–metal droplet (K)

Ts

Temperature of the bulk slag (K)

T

Temperature in the emulsion medium (K)

T0

Initial temperature of the metal drop at the time of ejection (K)

u

Velocity of the droplet (m/s)

wd

Weight of metal droplet (kg)

Wb

Weight of bulk metal (kg)

\( W_{\text{Mn}}^{\text{eject,t}} \)

Mass of metal ejected into emulsion at time t (kg)

\( W_{\text{Mn}}^{\text{return,t}} \)

Mass of metal droplet returns to the bulk metal at time t (kg)

Greek Symbols

\( \rho_{\text{m}} \)

Density of the bulk metal (kg/m3)

\( \rho_{\text{s}} \)

Density of slag (kg/m3)

λm

Thermal conductivity of liquid metal (W/m K)

λs

Thermal conductivity of slag (W/m K)

ε

Stirring energy (W/t)

µ

Viscosity (Pa.s)

Subscripts and Superscripts

cav

Cavity

eq

Equilibrium

em

Emulsion

gm

Gas/metal

i

Interface

iz

Impact zone

m

Hot metal

sc

Scrap

sm

Slag/metal

Notes

Acknowledgments

The authors express their gratitude to Tata Steel for providing financial support for this study.

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Copyright information

© The Minerals, Metals & Materials Society and ASM International 2018

Authors and Affiliations

  • Bapin Kumar Rout
    • 1
  • Geoffrey Brooks
    • 1
  • M. Akbar Rhamdhani
    • 1
  • Zushu Li
    • 2
  • Frank N. H. Schrama
    • 3
  • Willem van der Knoop
    • 3
  1. 1.Faculty of Science, Engineering and TechnologySwinburne University of TechnologyHawthornAustralia
  2. 2.WMG, University of WarwickCoventryUK
  3. 3.Tata Steel, NetherlandsIJmuidenThe Netherlands

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