On the Desulfurization in the Basic Oxygen Converter

Abstract

An analysis was done on the mechanism of desulfurization in the Basic Oxygen Converter, and the following results were obtained.
(1) Desulfurization as gas phase is less than 10% of total input sulfur, and is not considered to be a main process of desulfurization in the Basic Oxygen Converter. Almost all of desulfurization proceeds through slag-metal reactions.
(2) Behaviour of sulfur in metal during blowing is governed by the rate of lime slagging, and sulfur partition ratio between slag and metal ((S%)/[S%]) is generally influenced by the slag basicity.
(3) In some cases, increase in (FeO) content in slag increases (S%)/[S%] ratio, but this does not means the direct reaction between [S] and (FeO). Increase in (FeO) in slag accelerates the lime slagging rate and thus, increases the basicity and the quantity of the slag.
Therefore, it is important to accelerate the lime slagging and to operate under high basic slag during blowing for improving desulfurization of metal. However, because the remarkable desulfurization is not expected during blowing, it is nesessary to decrease the input sulfur by using pre-treated low sulfur hot metal and low sulfur fluxing materials for producing low sulfur steel.
Considering sulfur contents in metal charge, flux and desulfurizing reactions in the furnace, it is estimated that the lower limit of sulfur content of produced steel is 0.002% under operations using 15% scrap and 0.001% under the all hot metal operations.