Evaluation of softening, shrinking and melting reduction behavior of raw materials for blast furnace

To evaluate influences on the softening and melting behavior of blast furnace raw materials, the examinations of high temperature properties in various types of raw materials for blast furnaces were executed. Shrinking behavior before reaching approximately 1 300°C is estimated by using softening viscosity taking into consideration pores of particles, and void ratio as well as liquid phase ratio of the layer. The softening viscosity of the solid phase of approximately 10¹⁰ Pa·s was obtained and the influence of the mineral species of the solid phase or temperature is small. Melting reduction sharply progresses through expanding the liquid phase deriving from FeO and gangue. And this behavior is affected with position of the reduction curve and the liquidus curve. Sinter forms a solid phase from FeO and gangue due to a rise of reduction degree according to melting reduction. This solid obstructs contact of the liquid phase including FeO with coke, which restricts the progress of melting reduction. On the other hand, with lumpy ore and pellet, melting reduction rapidly progresses without interruption, since no solid phase is formed even when FeO decreases due to melting reduction.