Effect of Al2O3 and MgO on Flow Characerstics of Blast Furnace Slag

Abstract

The flow characteristics of the blast furnace slag determine size, shape and location of the cohesive zone in the furnace. The cohesive zone acts as a gas distributor and its location lower down the furnace reduces the high temperature zone in the furnace, which moves the alkali circulation loop to lower levels. Also, a cohesive zone lower down the furnace would result in less Si pick up in the hot metal. In the present work, softening and melting behavior of four component CaO-SiO2-MgO-Al2O3 quaternary system of high alumina blast furnace synthetic slags having Al2O3 25-30%, MgO 4-12% and C/S ratio 0.9-1.4% were investigated. Flow behavior of synthetic slags is systematically measured using a Leitz high temperature microscope in accordance with German standard 51730. The results indicated that the increase in Al2O3 content increases both softening and liquidus temperatures with decrease in flow temperature. It is observed that the softening, liquidus and flow temperatures increase with an increase in C/S ratio.Increase in MgO content decreases both softening and liquidus temperatures intern increases flow temperature. Under the range of compositions examined a high Al2O3 (30%) and high C/S ratio (1.4%) coupled with low MgO (4%) content is beneficial for the blast furnace process as it ensures the formation of a Short Slag.