Reaction sequences in the formation of silico-ferrites of calcium and aluminum in iron ore sinter

Scarlett, Nicola V. Y.; Pownceby, Mark I.; Madsen, Ian C.; Christensen, A. Nørlund

doi:10.1007/s11663-004-0087-4

Cited by 139 publications

(119 citation statements)

References 13 publications

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“…A large number of investigations 2,3,[18][19][20][21][22][23][24][25] have aimed to determine the formation mechanisms of complex Ca-rich ferrite phases. Increased understanding of the mechanisms has the potential to improve the efficiency of the sintering process by a) being able to predict the optimal sintering conditions (temperature, pO2) to produce high quality product based on the chemical and physical composition of the iron ore fines, and b) being able predict the chemical and physical modifications of a particular iron ore fines mixture required to produce high quality product.…”

Section: Introductionmentioning

confidence: 99%

“…Increasing Al2O3 concentration also increased the stability range of SFCA before it melted to form a Fe3O4 + melt phase assemblage. The formation of CFA during heating had not been described in a previous in situ XRD investigation of reaction sequences in the formation of SFCA phases, which was performed under vacuum in the range 298-1 533 K by Scarlett et al 23,24) Eqs. (3) and (4) Based on the absence of Fe3O4 in the study of Scarlett et al 23,24) it was inferred by Webster et al 25) that the oxygen partial pressure was somewhere in the range 0.21 -5 × 10 -3 atm, and it was speculated that pO2 may affect the formation of CFA.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Oxygen Partial Pressure on the Formation Mechanisms of Complex Ca-rich Ferrites

et al. 2013

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The formation mechanisms of the complex Ca-rich ferrite iron ore sinter bonding phases SFCA and SFCA-I, during heating of a synthetic sinter mixture in the range 298-1 623 K and at pO2 = 0.21, 5 × 10 -3 and 1 × 10 -4 atm, were determined using in situ X-ray diffraction. SFCA and, in particular, SFCA-I are desirable bonding phases in iron ore sinter, and improved understanding of the effect of parameters such as pO2 on their formation may lead to improved ability to maximise their formation in industrial sintering processes. SFCA-I and SFCA were both observed to form at pO2 = 0.21 and 5 × 10 -3 atm, with the formation of SFCA-I preceding SFCA formation in each case, but via distinctly different mechanisms at each pO2. No SFCA-I was observed at pO2 = 1 × 10 -4 atm; instead, a Ca-rich phase designated CFAlSi, formed at 1 420 K. By 1 456 K, CFAlSi had decomposed to form melt and a small amount of SFCA. Such a low pO2 during heating of industrial sinter mixtures is, therefore, undesirable, since it would not result in the formation of an abundance of SFCA and SFCA-I bonding phases. In addition, CFA phase, which was determined by Webster et al. (Metall. Mater. Trans. B, 43(2012), 1344) to be a key precursor phase in the formation of SFCA at pO2 = 5 × 10 -3 atm, was also observed to form at pO2 = 0.21 and 1 × 10 -4 atm, with the amount decreasing with increasing pO2.KEY WORDS: iron ore sinter; complex Ca-rich ferrite sinter bonding phases; SFCA and SFCA-I; in situ X-ray diffraction; oxygen partial pressure; phase formation mechanisms; synchrotron X-ray diffraction.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of Oxygen Partial Pressure on the Formation Mechanisms of Complex Ca-rich Ferrites

et al. 2013

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“…Parâmetros de microestrutura como fases de sustentação da matriz, morfologia das ferritas (aciculares ou colunares), composição química das ferritas, porosidade (total, forma e tamanho), distribuição de elementos químicos na microestrutura (como Al, Ca, Mg e Mn), foram investigados para tipos diferentes de minérios [5][6][7].…”

Section: Análise Microestrutural Em Pastilhas Prensadas Com Diferenteunclassified

Análise Microestrutural Em Pastilhas Prensadas Com Diferentes Tipos De Minérios De Ferro

Domingues¹,

Brandão²

2016

TMM

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ResumoA produção de aglomerados de minério de ferro envolve a adição de materiais como calcário e cal para a formação de escória, que assume função importante na microestrutura do aglomerado envolvendo e sustentando as partículas de minério de ferro. Dessa forma, realizou-se um estudo comparativo das microestruturas formadas a partir de três minérios com características diferentes: hematítico, goethítico e magnetítico. Os minérios foram misturados à cal para obtenção de basicidade binária de 1,5% para todas as amostras. Em seguida, foram prensados e as pastilhas foram submetidas a aquecimento em forno irradiante que atingiu cerca de 1280 °C. As amostras foram então analisadas por microscopia de luz refletida com analisador de imagens e microscopia eletrônica de varredura. Foram observadas diferenças na quantidade de hematita, magnetita, silicatos e ferritas. A porosidade na pastilha hematítica foi menor, enquanto a pastilha magnetítica apresentou os maiores valores de porosidade total. A sustentação da matriz é feita por fases diferentes em cada caso e a composição química das ferritas mostra uma complexa variação composicional. Palavras-chave: Microestrutura; SFCA; Aglomerados; Mineralogia; Minério de ferro. MICROSTRUCTURAL ANALYSIS OF PRESSED SAMPLES WITH DIFFERENT TYPES OF IRON ORES (HEMATITIC, MAGNETITIC AND GOETHITIC) AbstractThe production of iron ore agglomerates involves the addition of materials such as limestone and burnt lime to form slag, which plays an important role in the microstructure involving and sustaining the iron ore particles. Thus, a comparative study of microstructures formed from three ores with different characteristics: hematitic, magnetitic and goethitic, was carried out. The ores were mixed with burnt lime to obtain binary basicity of 1.5% for all samples. Then they were pressed and the samples were subjected to burnt in a rapid heat oven that has reached about 1280 °C. Then the samples were extensively analyzed by reflected light microscopy with digital images analyzer and scanning electron microscopy. Differences were observed in the amount of hematite, magnetite, silicates and ferrites. Porosity in the hematitic sample was lower, while the magnetitic sample had the highest total porosity values. The support matrix is made up by different phases in each case and the chemical composition of ferrites shows a complex compositional variation. Keywords: Microstructure; SFCA; Iron ore agglomerates; Mineralogy; Iron ore. INTRODUÇÃOÉ comum em sinterização o conhecimento de que a formação de fase líquida promove a resistência do aglomerado. Entretanto, excesso de fases líquidas (principalmente SFCA e calcioferritas) podem comprometer sua qualidade química. O que as sinterizações e pelotizações ao redor do mundo fazem, é tentar ajustar a qualidade química dos aglomerados por meio das qualidades dos insumos acrescentados nas misturas.Entretanto, nem sempre com a composição química considerada ideal obtêm-se resultados físicos e desempenho satisfatórios em altos-fornos. Relata-se que a microe...

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“…A partir de la hematita, la wustita se reduce de forma homogénea y rápida, aunque alguna wustita se encuentra rodeada de metal. A partir de la magnetita, la reducción es La reductibilidad de SFCA se puede relacionar con su morfología, su porosidad y si está recubierto de vidrio [43][44][45] . El ferrito acicular (<10 µm) formado a baja temperatura (<1.300 °C), es más reductible, mientras que el ferrito columnar (>10 µm) formado a alta temperatura (>1.300 °C, posiblemente recubierto de vidrio) es menos reductible.…”

Section: íNdice De Reductibilidadunclassified

Racionalización de mezclas de minerales de hierro para la obtención de sinterizados de calidad optima

Cores¹,

Ferreira²,

Muñiz³

2009

Rev. metal.

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ResumenSe utilizaron diversos minerales de hierro, fundentes y coque para preparar cuatro mezclas minerales con distintas proporciones de estos minerales. Con cada mezcla se fabricó una serie de sinterizados en planta piloto. Se caracteriza cada uno de los sinterizados mediante análisis químico y granulométrico, ensayo de la degradación del sinterizado durante la reducción en el horno alto (ensayo RDI), ensayo de la resistencia en frío (ensayo Tumbler), ensayo de reductibilidad; determinación de las temperaturas de reblandecimiento y fusión y determinación de la estructura del sinterizado por microscopia electrónica. Se establecen las condiciones de las mezclas y los parámetros de operación para la obtención de sinterizados de calidad óptima. Palabras claveSinterización; Mezclas minerales; Minerales de hierro; Horno alto. Rationalisation of iron ore mixtures for obtaining optimum quality sinters AbstractVarious iron ores, fluxes and coke, were used to prepare four ore mixtures with different proportions of these minerals. With each mixtures a series of sinters were produced in the pilot plant. Each one of the sinters was characterised by: chemical and granulometric analysis; degradation test on the sinter during reduction in the blast furnace, (RDI test); cold resistance test, (Tumbler Test); reducibility test; determining of softening and melting temperatures; and the determination of the structure of the sinter by electron microscopy. T he conditions of the mixtures and the operational parameters for obtaining the optimum quality of the sinters were established. KeywordsSintering; Ore mixtures; Iron ores; Blast furnace. INTRODUCCIÓNEl proceso de sinterización se utiliza para aglomerar una mezcla de minerales de hierro, fundentes y coque, de tamaño de partícula inferior a 8 mm, de tal forma que el sinterizado producido, con tamaño tamizado entre 12 y 35 mm, una vez cargado en el hormo alto, puede soportar las presiones y temperaturas del horno.En el proceso de sinterización, la mezcla de mineral se somete, previamente, a una granulación que consiste en homogenizar la mezcla en un tambor giratorio, con la adición de un 6-8 % de agua, durante unos minutos.Los gránulos formados se cargan sobre la parilla de la banda de sinterización, en donde la temperatura de los gránulos se eleva entre 1.250 y 1.350 °C para producir la fusión parcial y producir material semifundido, el cual, durante el enfriamiento posterior, cristaliza en varias fases minerales de distinta composición química y morfológica, principalmente, hematita, magnetita, ferritos y ganga formada en sus mayor parte por silicatos cálcicos [1][2][3] . La energía del proceso la suministra la combustión del coque. Los factores que afectan a la sinterización y a la calidad del sinterizado producido son, entre otros: a) el tamaño y composición de los gránulos; b) el tamaño, composición y propiedades relativas de los componentes de la alimentación (minerales de hierro, fundentes y coque); c) la composición mineralógica

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Reaction sequences in the formation of silico-ferrites of calcium and aluminum in iron ore sinter

Cited by 139 publications

References 13 publications

Effect of Oxygen Partial Pressure on the Formation Mechanisms of Complex Ca-rich Ferrites

Effect of Oxygen Partial Pressure on the Formation Mechanisms of Complex Ca-rich Ferrites

Análise Microestrutural Em Pastilhas Prensadas Com Diferentes Tipos De Minérios De Ferro

Racionalización de mezclas de minerales de hierro para la obtención de sinterizados de calidad optima

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