Effects of Temperature and Oxygen Potential on Removal of Sulfur from Desulfurization Slag

Abstract

The effects of temperature (1373–1673 K) and oxygen potential on removal of sulfur from hot metal desulfurization slag were investigated in laboratory-scale experiments. Both CaS and CaSO₄ exist as sulfur compounds in hot metal desulfurization slag. CaS can be removed under the condition of higher oxygen potential, whereas CaSO₄ can be removed at a lower oxygen potential. Thus, in order to remove both CaS and CaSO₄ from desulfurization slag, it is important to control the temperature and oxygen potential to the optimum values. In this study, a higher sulfur removal ratio exceeding 90% was obtained under the conditions of a temperature range of 1473–1673 K and oxygen potential range of 10⁻³−10⁻⁸ atm. These results were in good agreement with thermodynamic calculations.

In order to confirm the possibility of reusing desulfurization slag as flux after sulfur removal, hot metal desulfurization experiments were carried out with a 70 kg-scale laboratory furnace. At the same CaO amount in the desulfurization flux, [S] content at 900 seconds after flux addition was approximately equal to that when using virgin flux. The effect of SiO₂ contamination due to slag recycling on the desulfurization rate constant K was also estimated.

From these experimental results, it may be suggested that removal of sulfur from desulfurization slag is an effective approach for constructing a slag recycling system.