Blast Furnace Pellet Textures during Reduction and Correlation to Strength

Research area:
Raw materials for future iron- and steelmaking
Leimalm, U, Forsmo, S, Dahlstedt, A, Sundqvist Ökvist, L, Björkman, B, Blast Furnace Pellet Textures during Reduction and Correlation to Strength,  ISIJ Int, 50, 2010, 1396-1405.

The blast furnace is the most common means of producing hot metal. As the amounts of reductionagents increases, which influence in-furnace conditions such as ascending gas properties, temperature profilesand the ore-to-coke ratio, new demands are put on the iron-bearing material in terms of both reducibilityand mechanical strength. To investigate the possibilities to use the Pellet Multi Press (PMP) equipmentfor compression strength measurements of reduced pellets and to gain a deeper understanding of the correlationbetween pellet texture and strength, an initial study of pellets taken from the LKAB ExperimentalBlast Furnace (EBF) was conducted. Furthermore, the pellet pieces generated after compression tests werecharacterized using light optical microscopy. In order to correlate the texture of pellet pieces to the pellettexture prior to breakage, a characterization of the chronological pellet texture development during reductionin the EBF was performed. The original pellet texture remained in the beginning of reduction and differencesreceded through the EBF shaft as wustite and Femet was formed. Occurrence of Femet in the pellettexture increased the compression strength, while less reduced and less sintered textures showed the reverseeffect. So far, the results from compression strength tests indicate that disintegration of pellets takesplace at a reaction front, at the transition between different texture types of iron oxide or at the location of avisible surface crack.