Role of liquid and solid particles in solid-liquid mixed fluxes on sulfur removal from molten iron under centrifugal stirring by an impeller

Process for removal of S from molten iron alloy is successfully established process in these days, e.g. Kanbara Reactor (KR) process. However, its operating mechanism needs to be understood in a more clear manner. A series of laboratory-scale experiments using lime–fluorspar flux, which is a solid particle-liquid mixture at the reaction temperature, were carried out in order to find out effects of composition, total mass, the liquid fraction (fL), order of injection of the flux, and centrifugal stirring on the reaction performance. Theoretical calculations for the phase diagram of the flux system, flux-molten iron reaction equilibria, and the reaction rate considering flux detachment/aggregation in case of the centrifugal stirring were carried out. It was concluded that (1) major S-absorbing phase should be the liquid phase in the flux, (2) increasing the fL enhances the reaction performance when the molten iron was desulfurized without the stirring, (3) the centrifugal mechanical stirring enhances the reaction rate, but it was not effective when fL is high, (4) the centrifugal mechanical stirring for solid particle-liquid mixed flux significantly affects the interfacial reaction area: enlarging the area by the detachment of the flux and contracting the area by aggregation. The fL, therefore, influences not only the volume of the S-absorbing part of the flux, but also the degree of detachment/aggregation, which depends on the physico-chemical properties of the flux. Optimum fL may be determined by the physico-chemical properties and degree of the stirring. An index for assessing DeS performance was used to reveal the role of fL and the mechanical stirring. It shows that the mechanical stirring could enhance the DeS performance without the unnecessary increase of liquid fraction of the flux, by adding fluorspar in the present case.