Reaction kinetics of desulphurisation of hot metal using CaO–SiO 2 –Al 2 O 3 –MgO–TiO 2 –Na 2 O slag systems

Abstract

In the CaO–SiO₂–Al₂O₃–MgO–TiO₂–Na₂O system slag, the desulphurisation kinetics of pig iron desulphurisation were studied. The results show that the sulphur content reduced with the increase of the temperature, the alkalinity, the lowest content was 0.01% and 0.04%, respectively. With the increase of the content of Na₂CO₃ and MgO, the sulphur content in hot metal reduced from 0.33% to 0.04% and 0.05%, respectively. In addition, the content of Al₂O₃ and TiO₂ has a great influence on the desulphurisation rate. The sulphur content in hot metal firstly decreases and then increases with increasing Al₂O₃ and TiO₂ addition, The activation energy was estimated to be 535.71 kJ/mol at the temperature from 1350 °C to 1450 °C. The desulphurisation slag was analysed by SEM-EDS. A thick layer of calcium sulphide was formed at the interface of slag–metal, which has a negative effect on the desulphurisation reaction. When the blast furnace slag was added Na₂CO₃ of the plant experiment, desulphurisation rate and the sulphur element in the slag increased. Compared to previous desulphurisation effect without Na₂CO₃, the desulphurisation efficiency increases from 50% to 83.3%. The desulphurisation efficiency is improved by optimising the thermodynamic conditions of KR stirring desulphurisation, which is beneficial to reduce desulphurisation flux consumption and the secondary desulphurisation ratio.