Desulfurization

1. Why Control Sulfur Content?
2. Sulfur Specifications
3. Removal of Sulfur
4. Slags for Desulfurization
5. Desulfurization Slag
6. Kinetics of Desulfurization I
7. Kinetics of Desulfurization II
8. Other Factors to Take into Account - Refractories
9. Ladle Stirring
10. Desulfurization: Self Assessment Exercise
11. Calcium Injection I
12. Calcium Injection II

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The slag carried over from the primary steelmaking furnace (BOS/EAF) is typically 45% CaO, 23% FeO, 15% SiO₂, 8% MnO, 7% MgO, 2% P₂O₅.

A basic slag is one which contains free oxygen ions, encouraged by the presence of CaO and MgO.
Acid slags are those deficient in O₂ and contain SiO₂ and P₂O₅.
The basicity (B) of slag is defined as:

A high slag basicity is required for desulfurization (see right)

Carry out the exercise upper-right in order to discover the optimum basic slag composition for desulfurization.

Reference to the CaO-Al₂O₃-SiO₂ at 5% MgO ternary diagrams at 1600 °C and 0.03% Al, with a superposition of the sulfur partition ratio (L_s) values reveals the slag compositions suitable for high degrees of desulfurization.

References

• Turkdogan, ET,  Fundamentals of Steelmaking, The Institute of Materials, 1 86125 004 5