Dissolution of iron oxide containing doloma in model basic oxygen furnace slag

Abstract

The mechanism of dissolution of an iron oxide enriched doloma in a static dissolution test has been compared with those of standard doloma and dolomite in a model basic oxygen furnace (BOF) slag. Post-mortem microstructural examination reveals that iron oxide acts as an effective liquid phase sintering aid via formation of low melting C2F. The presence of a C2F bonding phase in the iron oxide impregnated doloma, on subsequent immersion in a molten BOF slag, enhances structural disintegration with the dispersion and dissolution of periclase particles and assimilation of the lime component in the slag. The dissolution mechanism takes place via initial melting of the C2F bonding phase, slag penetration through this liquid and simultaneous reaction between oxide species in the flux and in the slag driven by concentration gradients. The lime in the flux reacts with silica and iron oxide from the slag, forming primarily C2S and C2F. The MgO in the flux reacts predominantly with iron oxide in the slag to form magnesiowustite. Simultaneous formation of low melting C2F and magnesiowustite prevents the buildup of a C2S cortex on the flux that would otherwise retard the dissolution. The iron oxide enriched doloma has several significant commercial advantages over standard doloma slag additives.