Reagents for hot metal pretreatment

• Soda ash

It is effective reagent for both desulphurization and desiliconization. But disposal of soda bearing slag is a problem. Also soda ash generates dense fumes on addition to hot metal.

• Calcium carbide and Magnesium granules

Both are highly efficient desulphurizing agents and can decrease sulphur content to very low value. Calcium carbide along with lime is injected into the bath. Magnesium granules help to reduce injection time and slag volume.

• In some situations mill scale and sinter fines are used to desiliconize hot metal.

Location of hot metal pretreatment

Hot metal pretreatment can be carried out either at blast furnace runner, or in transfer ladle or in torpedo.
Pretreatment in the blast furnace runner (Figure 11.1a) has certain advantages: such as adequate mixing of the reagents due to flowing of hot metal. This practice saves time and increases ladle availability compared with when treatment is carried out in ladles.