1. AGH University of Science
and Technology
A New Method for Determining
Chemical Composition of Refining Slag
in the Ladle Furnace
Jan FALKUS, Tomasz KARGUL, Pawel DROZDZ AGH University of Science and Technology, Krakow, Poland Faculty of Metals Engineering & Industrial Computer Science Department of Ferrous Metallurgy

2. Contents Essential Process Parameters
Assumptions to models development
Static Model
Dynamic Model
Findings
Conclusions

3. Essential Process Parameters
Slag
Metal
Additions
weight and chemical composition of the slag getting into the ladle during tapping
oxygen activity before the refining process startup
final chemical composition
weight after tapping from the furnace
start and final temperature
start chemical composition
oxygen activity before and after the refining process
intensity and time of argon injection
chemical composition after argon injection
weight of the ladle additions put into the ladle during tapping and their chemical composition
weight of the additions put into metal at the ladle furnace post and their chemical composition

4. Assumptions to static models development
Based on thermodynamic model
The state close to the metal-slag equilibrium is being achieved at the refining final phase
The process time has no role

5. Thermodynamic model
Equilib determines the combination of ni , Pi , and Xi which minimizes the total Gibbs energy G of the system
Where:
ni : moles
Pi : gas partial pressure
Xi : mole fraction
i : activity coefficient
: standard molar Gibbs energy

6. Testing heats

7. Static model findings for metallic phase
Group I
Group II
Prognosis findings of the model calculations for the metallic phase

8. Static model findings for slag phase
Prognosis findings of the model calculations for the slag phase total for group 1 & 2.

9. Static model. Virtual experiments.
Al final content in the bath in relation to FeO in slag content
Mn final content in the bath in relation to FeO in slag content
Si final content in the bath in relation to FeO in slag content

10. Tools for computational calculations

11. Structure of Tank Model
Assumptions to the dynamic model development
tank I, M1
tank II, M2
tank III, M3
Division of the ladle volume into tanks in the process of bottom injection of argon into steel
tank I (M1) %  Mtotal
tank II (M2) % Mtotal
tank III (M3) % Mtotal
Structure of Tank Model

12. Arrangement of equations describing mass flow
The mathematical notation of the system of equations describing bath stirring. (Metal-slag interface reactions have not been taken into account in this model yet).
mi – mass of reactant in ith reactor, [Mg]
Mi – mass of ith elementary reactor, [Mg]
– flow rate of metal bath stream between i and j reactors, [Mg/min]
t – time, [min]

13. Structure of hybrid model
Mixing model
Input FactSage
Output FactSage
Thermodynamic model
meq – equilibrium mass of reactant in metal-slag region, [Mg]
The thicknesses of metal and slag layers which reach the state of mutual equilibrium depends on both the intensity of bath stirring and the calculation time interval value.

14. Dynamic model findings
Change of Al content in metal bath during ladle furnace refining

15. Conclusion
The ladle furnace is a unit, for which it is purposeful to create a static model in order to determine precisely the weight of the alloy additions.
When the thermodynamic model, that uses the market available thermodynamic data bases, is applied in calculations, it makes it possible to determine the equilibrium state in very complicated metal-slag configurations.
Complementing the static model with the dynamic one enables it to monitor the dynamics in change of metal and slag chemical compositions, and consequently to prepare better the metal bath for a continuous caster.

16. Thank You