Slag-metal separation in the blast furnace trough

Abstract

It is important to reduce metal losses associated with the slag in the blast furnace runner. Insufficient separation gives rise to technological problems in the subsequent processing of hot metal and slag in addition to the losses themselves. By using a water-oil physical model of the blast furnace trough, the flow behavior and the separation efficiency in the trough were investigated. A series of experiments was carried out by changing the process variables such as flow rate of liquids, properties of oil (slag), and geometrical design of the trough. The results indicate that, at constant physical properties, the flow velocity in the upper stream of the trough is the predominant factor in determining the amount of metal carried over with slag. Oil (slag) viscosity was also found to be an important contributor in the separation efficiency. The mechanism for the slag entrainment into the metal phase was also investigated. The results indicate that the amount of slag (oil) entrained into metal (water) is mainly determined by the force balance between inertial force in the metal stream, the viscous force, and the gravity force in the upper stream. Because of this mechanism, the oil entrainment ratio decreased sharply with oil volume while the effect of total flow rate, water and oil, was comparatively small. In order to extend the results obtained by this modeling study to the actual system, a technique of dimensional analysis was also employed. As a result, dimensionless group correlations which can describe the separation efficiency as a function of process variables and dimensions of the trough were derived.