Why required?

• To minimize heat losses from the reaction chamber
• To allow thermal energy dependent conversion of chemically reactive reactants into products because metallic vessels are not suitable.

In steelmaking, the physico- chemical properties of the following phases are important:

Slag:    Mixture of acidic and basic inorganic oxides like etc.; temperature             varies in between .

Molten steel: Iron containing carbon, silicon, manganese, phosphorous, tramp elements, non metallic                       inclusions, dissolved gases like nitrogen, oxygen and hydrogen and different alloying                       elements like  etc.; temperature  

Gases:   containing solidparticles of  etc.; temperature
                        .

 The above phases are continuously and constantly in contact with each other and are in turbulent motion

.