Evaluation of a process that uses phosphate additions to upgrade titania slag

Dyk, J. P. Van; Pistorius, Petrus Christiaan

doi:10.1007/s11663-999-0044-3

Cited by 16 publications

(5 citation statements)

References 9 publications

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“…Within the titanium industry, this feature has been used using phosphate to absorb impurities from titanium-rich slags. 45 The iron absorbed to the flux layer, see Figures 15 and 16 , was assumed to originate mostly from the iron-rich layer around the pretreated particles. This was indicated from the interphase between the original particles and the potassium and phosphorus-rich coating, where a layer of increased titanium concentration was observed.…”

Section: Resultsmentioning

confidence: 99%

“…KPO 3 is also known to act as a fluxing agent that absorbed iron and impurities such as manganese and aluminum but not titanium. Within the titanium industry, this feature has been used using phosphate to absorb impurities from titanium-rich slags . The iron absorbed to the flux layer, see Figures and , was assumed to originate mostly from the iron-rich layer around the pretreated particles.…”

Section: Resultsmentioning

confidence: 99%

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

et al. 2020

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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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Section: Resultsmentioning

confidence: 99%

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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“…As will be discussed subsequently, the trivalent titanium cations are incorporated in the pseudobrookite (M 3 O 5 ) phase, which constitutes the largest part of the solidified slag. Oxidation of the trivalent titanium forms the basis of different processes to upgrade solidified slag, such as the phosphate process [18] and the UGS process. [19] These processes rely, first, on the speed of the oxidation reaction (where particles with a mean diameter of 250 to 350 mm are fully oxidized by exposure for tens of minutes to gases containing 2 to 6 pct of oxygen at temperatures of 950 °C to 1100 °C; the iron in the slag is also oxidized to Fe 3ϩ during this treatment [19] ).…”

Section: Reactivitymentioning

confidence: 99%

Physicochemical aspects of titanium slag production and solidification

Pistorius

Coetzee²

2003

Metall Mater Trans B

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The titanium-rich slags produced by ilmenite smelting are unusual in several respects, including their low viscosity, high electrical conductivity, propensity to solidify predominantly as one phase (pseudobrookite), and reactivity (with oxidizers) in the liquid and solidified form. The low viscosity is related to the unexpectedly "basic" behavior of Ti 4ϩ ; the high conductivity is likely through an electron transfer mechanism involving the Ti 4ϩ -Ti 3ϩ pair; the oxidation behavior is caused by the presence of a significant amount of Ti 3ϩ . Possible reasons for the nearly single-phase structure of the solidified slag are considered, and it is concluded that the most likely cause is the presence of a eutectic groove close to the M 3 O 5 (pseudobrookite) composition. This conclusion was tested by examining the compositions and microstructure of slag samples from a pilot smelter. The results show that the slags do contain a small amount of rutile, in line with predictions.

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“…Rutile and ilmenite do not form an integral part of the smelting process in the slags under study from Pleystein and Griessbach. Experimental results and phase diagrams published by Van Dyk and Pistorius (1999) and Zietsman and Pistorius (2004) demonstrate that temperatures of more than 1600°C would have been necessary for the reduction of Fe-Ti oxides. Ilmenite has been incorporated into the slags from "nigrine" placers in the small rivulets and gorges draining the area around Pleystein (Dill et al 2007).…”

Section: Discussionmentioning

confidence: 95%

Pyrometallurgical relics of Pb–Cu–Fe deposits in south-eastern Germany: An exploration tool and a record of mining history

Dill

2009

Journal of Geochemical Exploration

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Evaluation of a process that uses phosphate additions to upgrade titania slag

Cited by 16 publications

References 9 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

Physicochemical aspects of titanium slag production and solidification

Pyrometallurgical relics of Pb–Cu–Fe deposits in south-eastern Germany: An exploration tool and a record of mining history

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