Study of the simultaneous desulphurization and dephosphorization processes of hot metal with CaO and Ba)-based slags containing MnO.

Author(s)

Edmundo Burgos Cruz

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Escola Politécnica (EP/BC)
• Defense date: 1997-03-06

Examining board members

Jose Deodoro Trani Capocchi; Rupen Adamian; Eduardo Camargo de Oliveira Pinto; Cyro Takano; Antônio Cezar Faria Vilela

• Advisor: Jose Deodoro Trani Capocchi

Abstract

It has been evaluated the technical feasibility of the simultaneous desulphurization and dephosphorization processo f hot metal using BaO-BaF2 slags. In this way, the degrees of removal of sulphur and phosphorus achieved using a BaO saturated slag have been compared to the results obtained when the pre-treatment of hot metal was carried out with a typical CaO-CaF2-SiO2 slag, saturated in CaO and 3CaO.SiO2. It hás been verified the effect of the basicity of the slag, its is MnO content, the initial contents of silicon, sulphur and phosphorus of the hot metal on the degree of removal of sulphur and phosphorus ando n the mechanism and rate of the transfer reactions of such elements. The heats were carried out in graphite crucibles, under CO atmosphere, at 1573 K (1300°C). The crucible was positioned in a induction heated reactor provided with facilities for taking samples of metal and slag phases at regular intervals and measuring the volume of the gases released. The achieved results allow to conclude that the removal of surphur and phosphorus is technically feasible when the hot metal is treated with a BaO-BaF2 BaO satured slag, considering that, the degree of removal of sulphur and phosphorus was up to 95% whereas it was about 45% when a CaO Bering slag was used. It hás been noticed also that the use of BaO-BaF2 slags bearing MnO allowed the transfer of up 86% of the manganese present in the slag to the metal phase, which is near the thermodynamic equilibrium condition. These slags have also avoided the undesirable oxidation of the carbon in the metal phase and even have promoted the reduction of CO. The degree of desulphurization and simultaneous dephosphorization and the rate of the reactions have been improved by the increase of the basicity of the slags and by the addition of MnO the them. The same effect was observed when lower silicon contents and higher sulphur and phosphorus in the hot metal wereused. It hás been noticed that the desulphurization reactions and the transfer of manganese to the metal phase were accompained by the equivalent oxidation of phosphorus, silicon and iron of the metal phase and by the generation or consumption of CO. These facts allow to conclude that the simultaneous desulphurization and dephosphorization reactions of the hot metal is coherent with a mechanism of coupled reduction/oxidation reactions by which the reduction reactions such as desulphurization and manganese recovery would induce the similtaneous oxidation reactions of phosphorus, silicon, iron and carbono f the metal phase. (AU)