Metallurgical characteristics of Samarco Mineraçãos product portfolio and their influences on Western European blast furnace operations

Abstract

Western European Blast Furnaces have been increasing the participation of pellets in their burden in substitution of sinter and lump ores through time. The hot metal production process as a whole is therefore becoming more subject to the quality characteristics of this ferrous agglomerate. This study provides a comprehensive evaluation of the metallurgical characteristics of three low-slag pellets from Samarco Mineraçãos blast furnace portfolio which differ significantly in binary basicity (CaO/SiO2). As to assess the influence of these pellets in the behavior of a blast furnaces granular zone, low temperature disintegration, reducibility and swelling tests were carried out. As to understand the behavior of the subject pellets in the cohesive zone of a blast furnace, reduction under load tests and rounds of softening and melting tests with individual pellet types and their combination with a typical Western European sinter were made in partnership with Studiengesellschaft Für Eisenerzaufbereitung (SGA). Pellets and sinter samples have been produced in pilot plants of Samarco Mineração and SGA, respectively. Metallurgical results point at low degradation during reduction for all pellet types and relative higher reducibility of pellets, especially the fluxed types when compared to sinter. Different swelling, softening, melting and dripping temperatures of pellets are closely associated to their reduction degree, slag content, basicity and microstructural characteristics. The microstructures of oxide pellets with different basicities significantly change in relation to grain sizes, coalescence and recrystallization levels. When mixtures of pellets and typical Western European Sinter are subject to the REAS methodology, a strong interaction between the agglomerate types is noticed, promoting changes in the overall softening, melting and dripping behavior of the bulk.