Pyro 2011

PYRO 2011
Slag Course
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Technical Programme
- Papers
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Southern African Pyrometallurgy 2011 International Conference

Cradle of Humankind, South Africa, 6-9 March 2011

Ken Mills

Slag Course by Ken Mills

Monday 7 March 2010
(Tentative outline. Subject to change.)

A. Introduction
Why do we need property data for slag systems?
Examples of industrial disasters because of wrong assumptions
Use in mathematical models, e.g. continuous casting of steel
Why do we need models?
Some data available but very limited. Industrial systems tend to be more complicated than those studied in the lab - require extrapolation - may lead to errors
What are the factors affecting properties?
Depends on the property and sometimes on slag system
e.g. viscosity is very dependent on slag structure, but density is not too dependent on it
How do we know a model works?
Check its prediction against measured data
Sources of measurements, e.g. Slag Atlas, other sources
Lack of data for many industrial slags.
Errors in measured data. Sources of these errors, e.g. reaction between slag and crucible, problems with method
No model prediction can be more accurate than the data you calibrate it with
Hence need for accurate measurements - problems which can occur
Some basics for modelling

B. Structure of slags and effect on properties - Structure of slags
- Descrption of SiO2 network and how Al2O3 and other oxides could be incorporated into network, including charge balancing
- Brief description of techniques used to measure structure of slags
- Parameters used to represent the structures of slags, e.g. NBO/T optical basicity
- Effect of structure on properties: (high to low) Viscosity > Electrical conductivity = thermal conductivity > thermal expansion > density > Cp
- Significance of glass transition and crystallisation

C. Property estimation
C1. Heat capacity, enthalpy
Factors affecting property - Cp - not very structure dependent - other factors involved
Measurement methods for slags and probable accuracy of values obtained with different methods
Results obtained
Modelling Cp - simple method
Different models available in literature
Limitations to methods

C2. Thermal expansion
Same format as C1

C3. Density of slags
Same format as C1

C4. Viscosity of slags
Same format as C1

C5. Surface tension
Same format as C1

C6. Thermal conductivity
Same format as C1, but also discussion of importance of radiation, conduction, and convection
Need for optical properties
Optical thickness: does experiment represent the actual industrial situation, for example, continuous casting?

C7. Possible other properties
e.g. Diffusion coefficients, ultrasonic velocities

D. Specific slag systems
Steelmaking slags and continuous casting and welding fluxes
Possible selection from:
- PGM smelting, Ferronickel, Ferrochromium, Ferromanganese

E. Example of SLAGS in Excel
How to write a simple model

Copyright © 2010, Ken Mills and Rodney Jones,, Randburg, South Africa (Last updated on 12 September 2010)