SLAG-METAL SEPARATION IN THE BLAST-FURNACE TROUGH

It is important to reduce metal losses associated with the slag in the blast furnace runner. Insufficient separation gives rise to technolog ical problems in the subsequent processing of hot metal and slag in ad dition to the losses themselves. By using a water-oil physical model o f the blast furnace trough, the flow behavior and the separation effic iency in the trough were investigated. A series of experiments was car ried out by changing the process variables such as flow rate of liquid s, properties of oil (slag), and geometrical design of the trough. The results indicate that, at constant physical properties, the flow velo city in the upper stream of the trough is the predominant factor in de termining the amount of metal carried over with slag. Oil (slag) visco sity was also found to be an important contributor in the separation e fficiency. 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 ba lance between inertial force in the metal stream, the viscous force, a nd the gravity force in the upper stream. Because of this mechanism, t he oil entrainment ratio decreased sharply with oil volume while the e ffect of total flow rate, water and oil, was comparatively small. In o rder to extend the results obtained by this modeling study to the actu al system, a technique of dimensional analysis was also employed. As a result, dimensionless group correlations which can describe the separ ation efficiency as a function of process variables and dimensions of the trough were derived.