Important acid ferrous burden properties in the cohesive zone of a blast furnace

Abstract

The high-temperature behaviour of reducing ferrous materials is quantified using a laboratory softening and melting test. Using a combination of standard, non-standard and quenched tests supported by optical image analysis this work has highlighted some important differences in behaviour between lump, pellets and sinter as well as between the lump ores and the pellets. One lump ore is denser than the other and there is also a denser pellet. In both cases, the denser ore/pellet is also higher in silica content. Densification of the ferrous bed leads to reduced bed permeability. Studies indicate that densification can happen through two mechanisms. Results show that material density and silica content are two key factors causing increased bed densification. Material density influences reduction efficiency and wustite levels while silica influences the level of fayalite formed. Fayalite is formed by reactions between wustite and silica. Results also show that the behaviour of fluxed sinter is superior to ore and acid pellets because lime preferentially reacts with silica to form dicalcium silicate, a high melting temperature compound. Studies using mixtures of fluxed sinter and lump ore indicate that blast furnace burdens can easily accommodate 20% ore.