Study on the Equilibrium of Slag and Hot Metal at Tapping with Respect to Sulfur

The blast furnace slag and hot metal are collected from the industrial trials. The collected slag and hot metal samples are re-melted in a graphite crucible and stirred to investigate the sulfur partition at different stirring times. The experimental oxygen potential is well controlled to simulate the blast furnace conditions. The results show evidently that sulfur is transferred from hot metal to slag, which lead to an increase in the sulfur partition from its initial value (t = 0 min) of 26-33 at 1743 K, and from 23 to 37 at 1773 K after 30 min of slag-metal reaction. The results strongly indicate non-equilibrium between slag and hot metal at tapping. The sulfide capacities of the slag with typical composition of the slag at tapping are determined. On the basis of the sulfide capacity data, the theoretical sulfur partition is evaluated. The theoretically calculated partition further supports the finding obtained in the stirring experiments. This finding would suggest the possibility of improvement to increase the usage of blast furnace slag in desulfurization.