DESENVOLVIMENTO DE METODOLOGIA PARA AVALIAÇÃO DA TENDÊNCIA À REOXIDAÇÃO DE PELOTAS DE MINÉRIO DE FERRO REDUZIDAS EM PROCESSO DE REDUÇÃO DIRETA A GÁS / DESENVOLVIMENTO DE METODOLOGIA PARA AVALIAÇÃO DA TENDÊNCIA À REOXIDAÇÃO DE PELOTAS DE MINÉRIO DE FERRO REDUZIDAS EM PROCESSO DE REDUÇÃO DIRETA A GÁS

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

26/11/2010

RESUMO

Among the alternative processes for reducing iron oxide to produce iron and steel, the most currently used is the Midrex technology. The product may be the sponge iron, also called DRI (Direct Reduced Iron), composed mainly of metallic iron and iron oxide, or HBI which is the DRI pressed in the form of briquettes. DRI has a tendency to reoxidation in air, especially in the presence of moisture. As most of the reactions involved are exothermic, heating normally occurs. This heat does not dissipate because of the low thermal conductivity of the material. Therefore, other chemical reactions tend to be thermodynamically and kinetically favored. This autocatalytic process continues until the material reaches auto-ignition. Due to this phenomenon, several accidents have occurred worldwide during handling, transporting and storage of DRI. In recent years, the industrial experience has shown that some different pellets tend to generate more reactive DRI than others. However, the standardized laboratorial tests do not distinguish the characteristics of the raw materials that will lead to a pyrophoric DRI from those which will lead to a more stable DRI. In this study tests were carried out to evaluate the influence of the process conditions on the reduction-disintegration and the reoxidation of the fines generated during the tests. Thermogravimetric (TGA/DSC) analysis and non-standardized reduction-disintegration tests were performed in order to understand the phenomena involved. Thermobalance tests were performed at CTF (Vales Ferrous Technology Center) in Nova Lima, MG, and the reductiondisintegration tests at the Pelletizing Department Laboratory in Vitoria, ES. A method capable of distinguishing Midrex direct reduction iron ore pellets which are more prone to generate reactive DRI is presented by the end of this paper.

ASSUNTO(S)

ferro esponja dri desintegração termogravimetria reoxidação reatividade - engenharia de materiais e metalurgica

ACESSO AO ARTIGO

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