Improved hot metal desulfurization

The desulfurization of hot metal in the conventional iron and steelmaking process is widely practiced. There are two major contributors to the cost of hot metal desulfurization, the reagent, and the metallic iron losses. More than the theoretically calculated amount of desulfurizing reagent is used for industrial practices and one reason for this may be the presence of iron oxide, FeO, which may hinder the thermodynamics and kinetics of desulfurization. The FeO is from blast furnace slag that is carried over to the desulfurizing station and also from the oxidation of the metal during tapping and transporting it from the blast furnace to the steelmaking shop. Metallic iron losses, the largest contribution to the cost of desulfurization is another important aspect of hot metal desulfurization. Iron losses due to droplets entrained in the post-desulfurizing slag and from splashing during slag removal can be as high as 2.5% of the total hot metal weight.; A fundamental understanding of the thermodynamics and kinetics of the desulfurization process with the presence of FeO in the slag and the phenomena of separation of the metal droplets in the slag will aid in improving the hot metal desulfurization process. This study addresses the two economical concerns: (1) The effect of FeO on the kinetics of hot metal desulfurization, and (2) Separation of the metal from the slag. Experimental work includes high temperature kinetic experiments on 8 kg and 300 g melts and results show that in the laboratory experiments FeO in the slag does hinder desulfurization. A mathematical kinetic model is proposed for the mechanism of the kinetics of desulfurization of carbon saturated iron containing dissolved silicon with a lime based slag containing FeO. Mass transfer of sulfur and silicon in the metal and FeO and sulfur in the slag controls the kinetics of the desulfurization as well as the FeO reduction process. The model based on the laboratory experiments was expanded to include the conventional practices where desulfurization is carried out by submerged powder injection. In industrial desulfurization, sulfur removal occurs at two sites, at the rising particles that are injected, and at the interface between the accumulated top slag and the hot metal.; Water and oil modeling and high temperature x-ray fluoroscopy experiments were carried out to assess behavior of metal (water) droplets in slags (oil). Quicker metal droplet settling times is favored by slags of lower density and viscosity. Liquid metal droplets traveling through two phase slag slurries were also studied. The presence of solid slag particles in the liquid phase hindered droplet settling by forming a physical barrier to droplets being incorporated with the bulk and by increasing the bulk viscosity of the slag.