During KR desulfurization process

the variation of[S] in hot metal and(S)in desulfurization slag is studied  accordingly

by sampling in the 200t hot metal ladle at Tangsteel new plant. It shows that

during the 10 minutes of KR stirring process

the sulfur in hot metal decrease from initial 0.038% to 0.002%

and the sulfur in desulfurization slag is increasing from initial0.028% to3.28%. while the desulfurization rate keeps decreasing from 68% to33%. So the limiting link of KR desulfurizing happens at the last 7 to 10 minutes

which not clear in many studies at present. In order to improve the desulfurizing efficiency for the last few minutes

step-changing stirring speed is adopted and applied for the practical industry experiments

the stirring speed decrease from 90- 110r/min to45-90 r/min

and then the amount of desulfurizer can be reduced from 8- 10 kg/tto4.0-6.5 kg/t without increasing stirring time. So

this kind of KR desulfurization model of step-changing stirring speed and immerge depth of impeller has a potential application value for practical industry production.