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Influence and Mechanism of Al2O3 and SiO2 on Iron Ore Sintering

Author: HuLin
Tutor: FanXiaoHui
School: Central South University
Course: Iron and steel metallurgy
Keywords: Iron ore sinter Al2O3 SiO2 Reduction disintegration index Tumbler strength
CLC: TF046.4
Type: Master's thesis
Year: 2011
Downloads: 192
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Abstract


In recent years, imported iron ore with high aluminum and low silicon is widely used. As a result, sinter has higher A12O3 and lower SiO2 content, which is harmful to sinter yield and quality, as well as metallurgical properties. Therefore, better understanding of the influences of A12O3 and SiO2 on sintering process and their mechanisms are of great significance for production guidance, ore proportion optimization, and ore purchasing. And it is the key of high aluminum sintering technology and high iron low silicon sintering technology.The influences of A12O3 and SiO2 contents on sinter quality and metallurgical properties were studied by ore proportioning and reagents addition. It shows that tumbler strength and productivity are relatively stable when SiO2 content ranges from 4.0% to 4.8%, A12O3 content ranges from 1.0% to 1.8% and other compositions are fixed, but they drop dramatically when A12O3 content is more than 1.8% or SiO2 content is more than 4.8%. Sinter RDI+3.15 decreases when A12O3 content increases, and attains the minimum when SiO2 content is 5.32%.Mineral composition and microstructure of sinter with different A12O3 and SiO2 content were investigated using mineralogical identification and energy spectrum analysis. Element distributions of Al, Si and Ca, as well as their changes were revealed. The results shows that when A12O3 content of sinter is high, along with substantial increase of calcium ferrite, proportions of magnetite and silicate decrease, the main structure of calcium ferrite transfers from acicular to flake texture, crystal stock magnetite grow in quantity, almost all the increased Al goes into calcium ferrite, moreover, Ca and Si gather in calcium ferrite. When SiO2 content of sinter increases, calcium ferrite content drops obviously, acicular and flake textures reduce in different degrees, while magnetite and silicate increase significantly, crystal stock magnetite and silicate glass phase grow, Si and Ca gather in silicate.Characteristics of mineralization process and essential minerals under the conditions of different A12O3 and SiO2 contents were revealed by studies of liquid formation characteristics, properties of calcium ferrite, and crack initiation and propagation situation during reduction process. It shows that with increasing content of Al2O3 and SiO2, formation temperature of liquid phase and melting temperature range increase, the forming amount and generation rate of liquid decrease. Strengths of calcium ferrite with different structures are in the following order: acicular> columnar> granular> flake. Flake and granular calcium ferrites have higher liquid formation temperatures and narrower melting temperature ranges, while calcium ferrites with acicular and columnar textures have larger liquid amount and higher generation rate. Regeneration hematite is the main reason of crack initiation during reduction. Flake calcium ferrite, glass phase and macropore have poor resist ability of crack propagation. Acicular calcium ferrite and flake silicate have better strengths, therefore, helpful to resistance of crack propagation.When Al2O3 content is high, though substantial increase of calcium ferrite is beneficial to sinter quality, the growth of large amount of flake calcium ferrite and crystal stock magnetite is the main cause of lower strength and worse RDI. The effect of SiO2 content on sinter strength and RDI is the interaction results of content and structure changes of various minerals. The effect such as the decrease of calcium ferrite and acicular structure, the increase of glass phase and crystal stock magnetite is bad in general. But lower proportion of flake calcium ferrite under high SiO2 content condition improves RDI of sinter.

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CLC: > Industrial Technology > Metallurgical Industry > General issues > Smelting of raw materials and ore pretreatment > Ore pretreatment, sintered pellets > Sintering
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