Effects of Preoxidation of Titania-Ferrous Ore on the Ore Structure and Reduction Behavior

Park, Eungyeul; Ostrovski, Oleg

doi:10.2355/isijinternational.44.74

Cited by 77 publications

(58 citation statements)

References 8 publications

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“…Previous studies show that coal-based direct reduction followed by magnetic separation is the most effective method to achieve titanium and iron separation from TTM ore. [8][9][10][11][12][13][14][15] The process involves the following steps: First, TTM ore of the proper size, coal, and additives are mixed together. Second, the mixture is placed in a crucible and roasted at a high temperature.…”

Section: Introductionmentioning

confidence: 99%

Effect of Na2SO4 on the Embedding Direct Reduction of Beach Titanomagnetite and the Separation of Titanium and Iron by Magnetic Separation

et al. 2015

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A novel process for separating iron and titanium from Indonesian beach titanomagnetite (TTM) concentrates is proposed. This process involves several steps, including mixing the TTM concentrate and additive, pressing the mixture into pellets, embedding direct reduction of the pellets, and magnetic separation. Given that coal and additives are the main factors influencing the coal-based direct reduction of beach TTM, this study employed embedding reduction, where pellets are embedded under the coal to be reduced, and Na 2 SO 4 was used as an additive. The best result was obtained when the Na 2 SO 4 dosage was 4%, and the direct reduction iron powder (DRI powder) with an iron grade of 94.45%, iron recovery of 85.18%, and TiO 2 content of 0.44% were obtained. Titanium concentrate assay yielded 40.43% TiO 2 containing main titanium minerals of ilmenite and ferrous pseudobrookite. The results showed that a suitable Na 2 SO 4 addition (4-6%), DRI powder and titanium concentrate presented better iron recovery and TiO 2 grade as compared without addition, while this advantage disappeared as Na 2 SO 4 addition increased ( > 6%). The characteristics of roasted pellets were analyzed through X-ray diffraction, scanning electron microscopy, and energy dispersive spectrometry. Results showed that FeS and nepheline are formed by addition of Na 2 SO 4 , thereby benefiting the migration and growth of metallic iron particles in the redox system and separation of titanium and iron. While a suitable dosage of Na 2 SO 4 could promote porosity and induce a reducing atmosphere, but more liquid phase formed by an excessive Na 2 SO 4 was unfavorable and caused expansion of the pellets.

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Section: Introductionmentioning

confidence: 99%

Effect of Na2SO4 on the Embedding Direct Reduction of Beach Titanomagnetite and the Separation of Titanium and Iron by Magnetic Separation

et al. 2015

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“…They found that pre-oxidation accelerated the reduction process by destroying the crystal lattice of the VTM and causing the formation of pores in the particles. Similarly, Park 10) concluded that pre-oxidation of the iron sand increased its reducibility because of the structural transformation of spinel cubic TTM to rhombohedral TTH. However, different conclusion was obtained by Liu,11) the main phases of the VTM oxidized at 900°C for 6 min were Fe 9 TiO 15 and Fe 2 O 3 .…”

Section: Relationship Between the Phases Structure Mgo Migration Anmentioning

confidence: 99%

Relationship between the Phases, Structure, MgO Migration and the Reduction Performance of the Pre-oxidized Vanadium-titanium Magnetite Ore in a Fluidized Bed

Pan

Zhang

et al. 2017

ISIJ International

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This paper contrastively investigated the reduction behavior of raw and oxidized vanadium titanium magnetite ore (RVTM and OVTM) in a bubbling fluidized bed at 800°C under 75%N 2 -25%H 2 , and systematically revealed the relationship between the structure, phases change, MgO migration behavior and the reduction performance. Microstructure observations suggest that oxidization conditions greatly affect structural evolution, phase transformation of Fe-Ti oxides, and migration of MgO in OVTM. The reduction results indicated that the average metallization degree enhanced by 8-10% as the OVTM ore had high oxidization degree. When the RVTM ore was treated at 800°C, the reduction rate increased with the increase of oxidization degree, no significant difference was observed among these oxidized samples due to their similar internal and surface structure. However, the reduction rate of OVTM at 950°C depended on the oxidization time. The reduction rate of OVTM oxidized at 950°C for 2 h was faster than the one for 1 h, which was attributed to the better exsolution of MgO and the formation of bigger pores, even though both samples were fully oxidized and Fe 2 TiO 5 formed in the oxidization process.

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“…The basis for the experiments rest on reported investigations of many alternative routes for the production of TiN from ilmenite (FeO · TiO 2 ). [36][37][38][39][40][41][42][43] The production of grain refiners directly from ilmenite ore eliminates the need of mixing of different powders; it is economically attractive and can easily be scaled up to industrial scale in a DRI-type of installation.…”

Section: Development Of New Ces-based Grain Refinersmentioning

confidence: 99%

Progress in the Development and Use of Grain Refiner Based on Cerium Sulfide or Titanium Compound for Carbon Steel

et al. 2009

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A fine-grained microstructure yields the optimum combination of strength and toughness of steel. Moreover refinement of the as-cast structure can reduce the tendency for hot-cracking during forging and rolling. This paper describes how small inclusions can be used to control the microstructure of steels. These small inclusions (dispersoids) are oxides, sulfides, nitrides and carbides which are in the 1 mm size range and capable of promoting grain refinement during solidification by a process of epitaxial nucleation or in the solid state through intragranular nucleation of ferrite. Such particles are sufficiently small to be harmless from a toughness point of view, but at the same time large enough to act as potent nucleation sites during phase transformation. The dispersoids can either be created by balanced additions of strong oxide and sulfide forming elements to an impure steel melt or be added directly into the liquid steel through a specially designed master alloy containing the nucleating particles. In both cases it is possible to manipulate the steel microstructure in a positive direction, but the latter method, involving the use of a master alloy, has probably a wider industrial application.KEY WORDS: steels; solidification structure; oxides, sulfides; inclusions; nucleation.Therefore, and for the sake on inclusion size control, a number of special "grain refiner alloys" for steels is now under development. First Generation Grain Refiner AlloysIn order to utilize the inclusions for grain refinement purposes, it is essential to have control over their size distribution. An average size of about 1 mm is desirable. This is a compromise between two conflicting requirements. On the one hand, a submicron particle size implies that the dispersoids start to lose their potency because a curved interface increases the associated energy barrier against nucleation. On the other hand, if the particle size is significantly larger than 1 mm the dispersoids may become detrimental to toughness. At the same time the particle number density drops rapidly, which makes grain nucleation at such sites less likely. 1)So far, the new steel developments have been hampered by the fact that the nucleating dispersoids used to control the microstructure evolution must be created within the system as a result of deoxidation or desulfurization reactions. The problem is the uncontrolled coarsening of the inclusions, with subsequent loss of toughness. Elkem has developed 23) a Ce containing ferroalloy that can be added as a cored wire at a late stage during steelmaking reducing the time for coarsening. The advantages of using such a ferroalloy to add Ce contra the addition of pure Ce metal are 1) a higher Ce yield and 2) no oxidation of such a ferroalloy in air. This is a so-called first generation grain refiner. Application of the First Generation Grain Refinerto Austenitic Steels Grain refinement of highly alloyed austenitic steels is important because these steels maintain their solidification microstructure during cooling due to the ...

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Effects of Preoxidation of Titania-Ferrous Ore on the Ore Structure and Reduction Behavior

Cited by 77 publications

References 8 publications

Effect of Na<sub>2</sub>SO<sub>4</sub> on the Embedding Direct Reduction of Beach Titanomagnetite and the Separation of Titanium and Iron by Magnetic Separation

Effect of Na<sub>2</sub>SO<sub>4</sub> on the Embedding Direct Reduction of Beach Titanomagnetite and the Separation of Titanium and Iron by Magnetic Separation

Relationship between the Phases, Structure, MgO Migration and the Reduction Performance of the Pre-oxidized Vanadium-titanium Magnetite Ore in a Fluidized Bed

Progress in the Development and Use of Grain Refiner Based on Cerium Sulfide or Titanium Compound for Carbon Steel

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