Effects of Basicity and Al2O3 Content on the Chemistry of Phases in Iron Ore Sinter Containing ZnO (original) (raw)
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In situ X-ray diffraction analysis of iron ore sinter phases
Journal of applied …, 2004
Owing to the depletion of world lump iron ore stocks, pre-treated agglomerates of ®ne ores are making up a growing proportion of blast-furnace feedstock ($80%). These agglomerations, or`sinters', are generally composed of iron oxides, ferrites (most of which are silicoferrites of calcium and aluminium, SFCAs), glasses and dicalcium silicates (C2S). SFCA is the most important bonding phase in iron ore sinter, and its composition, structural type and texture greatly affect its physical properties. Despite its prevalence and importance, the mechanism of SFCA formation is not fully understood. In situ powder X-ray diffraction investigations have been conducted into the formation of SFCA, allowing the study of the mechanism of its formation and the observation of intermediate phases with respect to time and temperature. Studies have been carried out to investigate the effects of changing the substitution levels of aluminium for iron. The use of the Rietveld method for phase quanti®cation gives an indication of the order and comparative rates of phase formation throughout the experiments.
A Short Review of the Effect of Iron Ore Selection on Mineral Phases of Iron Ore Sinter
Minerals, 2021
The sintering process is a thermal agglomeration process, and it is accompanied by chemical reactions. In this process, a mixture of iron ore fines, flux, and coal particles is heated to about 1300 °C–1480 °C in a sinter bed. The strength and reducibility properties of iron ore sinter are obtained by liquid phase sintering. The silico-ferrite of calcium and aluminum (SFCA) is the main bonding phase found in modern iron ore sinters. Since the physicochemical and crystallographic properties of the SFCA are affected by the chemical composition and mineral phases of iron ores, a crystallographic understanding of iron ores and sintered ore is important to enhance the quality of iron ore sinter. Scrap and by-products from steel mills are expected to be used in the iron ore sintering process as recyclable resources, and in such a case, the crystallographic properties of iron ore sinter will be affected using these materials. The objective of this paper is to present a short review on resea...
Mineralogical Investigations on the Phase Formation of Iron Ore Sinter
2019
Iron ore sinters are considered as multi-phase materials, with a heterogeneous microstructure. The amounts of the different phases mainly hematite, magnetite and a dicalcium silicate are contributing factors to a number of important on the sinter quality. The behavior of phase formation during the sintering process has a significant of effect on the chemical composition of sinter and controlling microstructure and concentration of silicoferrites of calcium and aluminum (SFCA). The mineralogical distribution of different phases determines the microstructure of the sinter which imparts the quality of the sinter. In this study, the microstructure of the sinter has been examined by considering the chemical composition, the mineralogy, the morphology and the spatial arrangement of the various mineral phases formed during sintering. The chemical composition in the process of sintering (especially CaO, Al2O3, Fe2O3, SiO2 etc.) were made optimum control and all parameters that can effect on...
2010
The structure of iron ore sinter is not uniform. It consists of pores (of varying sizes) and a complex aggregate of phases, each with different properties. It is the combination of these pores and phases, and the interaction between them that determines the sinter properties, but also makes the prediction of sinter properties so difficult1,2. Various studies are reported in the literature in which correlations are drawn between raw material composition (such as phosphorous, silica, alumina and magnesia contents, sinter basicity, melt fluidity, Al2O3/SiO2 ratio, TiO2 contents), porosity, maximum sintering temperature, as well as the structure and properties of iron sinter3–12. Alternative raw materials that can be used in the sinter mixture have also been tested, and their impact on sinter quality evaluated13,14. Despite all the research done, the correlation between the chemical composition and mineralogy of iron sinter and its properties and behaviour are still not clearly understo...
ISIJ International
Silico-ferrite of calcium and aluminum (SFCA) is the primary bonding phase of iron ore sinter, the world's most popular artificial feed material for ironmaking. However, fundamental questions about its crystal structure and the atomic occupancy at each site remain unanswered. To date, the quantitative phase analysis (QPA) of SFCA has mostly been conducted using two-dimensional information and only provided information regarding phase fractions. In contrast, Rietveld analysis uses bulk data and provides lattice information in addition to phase fraction information. This study investigates the effects of basicity and Al 2 O 3 concentration on the crystal structure and atomic site occupancy of SFCA through Rietveld analysis of the X-ray diffraction patterns. Raman spectroscopy and micro-Vickers hardness tests are used to verify the analytical results. Changes in the chemical composition affect the atomic occupancies at sites Si1 (Si-Al), Ca2 (Ca-Fe), Ca3 (Ca-Fe), Fe4 (Fe-Al), Fe5 (Fe-Al), and Fe7 (Fe-Al). With increasing basicity or Al 2 O 3 content, the microhardness increases linearly, which can be attributed to the modification of atomic site occupancies. The crystalline structure obtained in this study is essential for developing a thermodynamic model of SFCA that can be used to predict its phase stability. This information can then be used to design a novel high-performance iron ore sinter.
Archives of Metallurgy and Materials
Zinc is present in electric arc furnace dust (EAFD) mainly in two basic minerals, namely as franklinite ZnFe 2 O 4 and/or zincite ZnO. While zincite is relatively reactive and easily treatable, franklinite is considerably refractory, which causes problems during EAFD processing. In this work EAFD containing 18.53% Zn was leached in water solution of ammonium carbonate. This leaching solution selectively leaches zincite, while franklinite is refractory and stable against leaching in this case. The temperature dependence of zinc leaching from EAFD was studied and the activation energy E A was determined by two methods: 1.) classically based on zinc chemical analyses from the leaching solution and 2.) by using of X-Ray diffraction qualitative phase analyses of leaching residues. The determined values of activation energies 37.41 and 38.55 kJmol-1 match perfectly, which show the excellent possibility of using X-Ray diffraction toward the study of leaching kinetics at properly chosen experimental conditions. The important result is the determination of the amount zincite and franklinite in EAFD, which is not possible by using of classical chemical methods.
Review on the Phase Equilibria in Iron Ore Sinters
ISIJ International, 2020
Sintering process is a commonly used pre-treatment process for iron containing burden materials with an aim to produce porous, agglomerated sinter material with suitable properties to be charged into the blast furnace. During the sintering process the material undergoes a series of reactions, during which the conditions vary considerably. These changes in temperature and state of oxidation cause changes in the mineralogical composition of the material and although the sintering process does not completely reach the chemical equilibrium, it is important to understand the phase equilibria of the sinter system in order to analyse and control the effect of various factors on the sintering process. The purpose of this paper is to give a review on the research related to phase equilibria in iron ore sinters. The main components of the sinter are FeO, Fe 2 O 3 , SiO 2 , CaO, Al 2 O 3 and MgO and by studying the phase equilibria of this system, the behaviour of sinters can be evaluated. Based on the experimental data, oxide databases have been created to provide thermochemical data of all the necessary compounds within this system. Concerning the solutions, more research is required related to SFCA phases. These databases are commercially available with thermochemistry software and can be used to compute phase diagrams illustrating the effect of different factors on the phase equilibria within the FeO-Fe 2 O 3-SiO 2-CaO-Al 2 O 3-MgO system. Phase diagrams provide a useful tool to study the behaviour of the material in both sintering process itself as well as in the following reduction processes such as the blast furnace.
JOM, 2020
Analogue sinter tablets were produced at temperatures between 1250°C and 1320°C, with a range of hold times and cooling rates. Platy silico-ferrite of calcium and aluminum (SFCA) morphology was identified in samples produced at 1250°C using reflected light microscopy; however, quantitative x-ray diffraction (XRD) identified the presence of the SFCA phase, with no SFCA-I detected. This proves that the platy SFCA morphology common in analysis by reflected light microscopy cannot be attributed to the SFCA-I mineral without further analysis. Micro-XRD and electron probe micro-analysis (EPMA) were carried out on an area of platy SFCA confirming this result. The sinter analogue tablets were reduced in a 30% CO, 70% N 2 gas mixture at 900°C in a tube furnace thermo-gravimetric analyzer. The degree of reduction of the tablets in this study was found to be controlled by the porosity of the samples, rather than by the morphology or mineralogy of the bonding phase.