Hot Metal Desulfurization Behavior with Dolomite Flux

Hot metal desulfurization behavior with dolomite flux was examined in heat treatment tests of pellets and in small-scale and commercial-scale hot metal desulfurization tests by mechanical stirring. In the heat treatment tests of pellets, the Mg gas generation ratio at 1673 K increased as the CaO/MgO ratio increased. The Mg gas generation ratio reached 90% with dolomite, which was 1.4 times higher than that with CaO + MgO at the same CaO/MgO. With calcined dolomite and Al ash, CaO efficiency for hot metal desulfurization at 1673 K was 20–30%, which was around double the results with CaO + MgO and CaO. In the desulfurization slag, sulfur was concentrated not with Mg, but Ca and Al were found in an EPMA analysis and detected as CaS by X-ray diffraction. Desulfurization with calcined dolomite and Al ash is considered to proceed by ① desulfurization by Mg(g) and fixing of MgS as CaS, and ② desulfurization by CaO with Mg de-oxidation. 200 t commercial-scale hot metal desulfurization tests with mechanical stirring were carried out. The obtained Mg efficiency for desulfurization was in the range of 15–25% with Mg consumption of 1–1.3 kg/t as MgO. These results were within the same trend as in other studies using metallic Mg and MgO with Al.