Determinação de parâmetros cinéticos que influenciam na taxa de redução do óxido de ferro em pelotas

• Ano de defesa: 2015
• Autor(a) principal: Sandra de Castro Guerra
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: Engenharia metalúrgica; materiais e de minas; Óxidos de ferro; Metalurgia extrativa; Redução de minérios
• Link de acesso: http://hdl.handle.net/1843/BUBD-A9DJK3

The usual route of producing steel is blast furnace and oxygen steelmaking and it represents 70% of steel production in the world. Blast furnace is a thermochemical reactor for producing pig iron by reducing iron oxides. Its metallic burden is composed by lump, sinter and pellet and its quality impacts on process efficiency. Pellet, that will be studied in this project, is evaluated due its physical and metallurgical properties among which is reducibility. Reducibility is related to the velocity that pellet reduces, and can be estimated by Reduction Degree index. It impacts directly on fuel consumption of blast furnace. Coke consumption is lower when metallic burden reduction is easier. The kinetic model more accepted to describe pellet reduction is the topochemical one. According to this, reduction happens from the outer layer of the pellet particle to its core, and layers of different phases: hematite, magnetite and wustite are formed. The velocity depends on phases properties and is related to kinetic constant (k) and diffusion coefficient (D). The methodology proposed in this study combined physical and numerical simulation, to estimate kinetics k and D for pellets with different reducibilities. It were evaluated two pellets in three temperatures: 700, 800 e 900°C under reduction by carbon monoxide and hydrogen. From the results were determined Arrhenius equations for each one of the kinetic parameters. The results were sensitive to temperature variations and different product's properties. For the same pellet, higher temperature, higher were the values for k and D. Comparing both pellets, for the one with higher reduction it was obtained higher values for k. This is due the high reducibility ferrite composts and a catalyst effect of MgO on iron oxide reduction. This pellet has higher values for diffusion coefficient too because its homogeneous distribution of pores. The estimation of those parameters will help to understand in future studies what is the impact of high reducibility pellets on blast furnace process.