Alkali reductive roasting of ilmenite ore

This study describes how potassium salts representative of those in bio ash affect the reactivity of the oxygen carrier ilmenite under moist and dry conditions. Ilmenite is a bench-mark oxygen carrier for chemical-looping combustion, a technique that can separate CO 2 from flue gases with minimal energy penalty. Different potassium salts were mixed with ilmenite to a concentration of 4 wt % potassium. The salts used were K 2 CO 3 , K 2 SO 4 , KCl, and KH 2 PO 4 . Experiments were performed at 850 °C under alternately oxidizing and reducing conditions in a dry atmosphere or in the presence of steam. Analyses of the oxygen carrier regarding changes in reactivity, structure, and composition followed the exposures. This study showed that salts such as K 2 CO 3 , K 2 SO 4 , and KCl increase the reactivity of the ilmenite. For the samples mixed with KCl, most of the salt was evaporated. KH 2 PO 4 decomposed into KPO 3 , forming layers around the ilmenite particles that lead to agglomeration. Additionally, the KPO 3 layer was more or less nonpermeable for CO and decreased the reactivity toward H 2 significantly in both dry and wet conditions. This decreased reactivity indicates that the concentration of phosphorus in biofuel may have a significant effect on oxygen carrier degradation. It was also observed that the presence of steam changed the chemistry drastically for the nonphosphorus-containing salts. Alkali salts may react with steam, forming volatile KOH that evaporates partly. KOH may also form K-titanates by reaction with the oxygen carrier, leading to segregation of iron and titanium phases in the ilmenite.

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“…Similar to previous studies with other iron-based oxygen carriers and ilmenite, potassium increases the reaction rate of the reduction. 23 , 37 …”

Section: Resultsmentioning

confidence: 99%

Understanding the Interaction of Potassium Salts with an Ilmenite Oxygen Carrier Under Dry and Wet Conditions

et al. 2020

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“…The molar ratio of Na 2 CO 3 /titanium dioxide for the roasting of ilmenite (42.00% TiO 2 ) recommended by El-Tawil et.al. was 0.5 [40] . Mass ratio of the additive Na 2 CO 3 was proved to be a key factor for the reaction rates during the roasting process.…”

Section: Introductionmentioning

confidence: 89%

Synthesis of rutile TiO2 powder by microwave-enhanced roasting followed by hydrochloric acid leaching

Kang

Gao

Zhang

et al. 2020

Advanced Powder Technology

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“…Also, Guo et al 21 found that a small amount of borax could enhance the reduction of Panzhihua ilmenite by affecting mineral phase transformation, microstructures, melting point, and Mg distribution. Alkali roasting of the ilmenite process, which is a pre-treatment of the hydrometallurgical process for obtaining high titanium yields, has been studied by several groups [22][23][24][25] . Sodium and potassium carbonates are more efficient for iron removal than lithium carbonate 23 .…”

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confidence: 99%

Improving the production efficiency of high-titania slag in Ti extraction process: fluxing effect on formation of pseudobrookite

Kim

Heo

Park

et al. 2020

Sci Rep

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We investigated the carbothermic reduction process of ilmenite ore at 1873 K with flux addition. Without flux, the pseudobrookite phase with a high melting temperature was precipitated during ilmenite smelting. This could be the main reason for decreased reduction of iron in ilmenite. To accelerate reduction of ilmenite, two factors were considered. One is increasing the reduction driving force during smelting. Activity of FeO is the major factor to control reduction in driving force. The other factor is delay in formation of the pseudobrookite phase, a high-melting point precipitation phase. In this system, MgO in ilmenite could be used to form pseudobrookite. To control these factors, in this study, flux agent (i.e., Na 2 o or Sio 2 ) addition was considered. The thermochemical simulation program, factSage TM 7.0 was used to calculate the viscosity of slag and the activity of components as fluxing agents were added. High-temperature experiments using an induction furnace were also conducted to confirm the computational results. To determine the composition of final products, i.e., titanium slag, X-ray fluorescence analysis was executed. As a result of Fe and Ti behaviours in slag, SiO 2 addition showed no significant difference from the slag without flux. However, Fe reduction in ilmenite, i.e. tio 2 -enrichment, was more accelerated when Na 2 O was added. X-ray diffraction, scanning electron microscopic and transmission electron microscopic analyses results also showed that even 1 wt% Na 2 o addition significantly influenced the titanium slag production compared to no flux addition.As titanium has good physical and chemical properties, e.g. excellent strength, corrosion resistance, fatigue resistance, fracture toughness, and high-temperature characteristics, its demand steadily increases 1-5 . The major raw material for titanium extraction is rutile (~95% TiO 2 ), which quickly is being depleted. Therefore, ilmenite (FeTiO 3 , 30-65% TiO 2 ) as a substitutional resource is in the spotlight. There are previous studies about the ilmenite smelting process in conjunction with pre-oxidation treatment, which improves the reactivity of ilmenite 6-13 . After the pre-oxidation treatment, the ilmenite ore is sent to direct leaching or high temperature reduction stages according to the consecutive processes [14][15][16][17][18] .Our group originally investigated the effect of temperature on FeO reduction, i.e., TiO 2 -upgrading, from ilmenite ore from 1723 to 1923 K 13 . Unlike the expectation that the Ti-yield would be greater with higher temperatures, the slag composition in the actual experiment was not significantly changed. One of the reasons is precipitation of pseudobrookite (ps-BR), which is one of the most stable phases with M 3 O 5 stoichiometry. In the position of M, the divalent cations (mainly Fe 2+ , minor Ti 2+ and/or Mg 2+ ) and the trivalent cations (primarily Ti 3+ ) are in balance of valence. Thus, it is normally expressed as [Fe,Ti,Mg] x Ti y O 5 (x + y = 3) formula. Because the melting point of ps-B...

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Alkali reductive roasting of ilmenite ore

Cited by 8 publications

References 5 publications

Understanding the Interaction of Potassium Salts with an Ilmenite Oxygen Carrier Under Dry and Wet Conditions

Understanding the Interaction of Potassium Salts with an Ilmenite Oxygen Carrier Under Dry and Wet Conditions

Synthesis of rutile TiO2 powder by microwave-enhanced roasting followed by hydrochloric acid leaching

Improving the production efficiency of high-titania slag in Ti extraction process: fluxing effect on formation of pseudobrookite

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