Thermal Stability of Molten Slag in Blast Furnace Hearth

The thermal stability of the molten slag plays an extremely important role in the smooth production of the blast furnace. In this paper, the effects of basicity, Al2O3 content and MgO content on the thermal stability of the slag during heat fluctuations were investigated. The effect of slag basicity and composition on slag viscosity behavior was measured by the rotating cylinder method under the condition of heat fluctuation and constant temperature. The slag temperature and solid phase precipitation under thermal fluctuations were calculated. The effect of thermal fluctuations of the slag on viscosity was clarified. The results show that the specific heat capacity of the slag first decreases and then increases as the slag basicity increases, and it increases with the rise of Al2O3 as well as MgO. The average viscosity change rate of slag under fixed heat is much more pronounced than that of at a constant temperature with the variation of slag basicity as well as Al2O3, while it is inverse for the effect of MgO. When the slag heat is reduced, the change in slag basicity has the greatest effect on the slag temperature, followed by the Al2O3 content and MgO content. It indicates that MgO helps to maintain a stable slag temperature. Therefore, appropriately increasing the basicity of the slag, controlling a lower Al2O3 content and maintaining a suitable MgO content will help to improve the thermal stability of the slag.