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The Effect of Al2O3, CaO and SiO2 on the Phase Relationship in FeO-SiO2 Based Slag with 20 Mass% Vanadium
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2017 (English)In: Journal of Sustainable Metallurgy, ISSN 2199-3823, Vol. 3, no 2, 289-299 p.Article in journal (Refereed) Published
Abstract [en]

An innovative and sustainable way for production of vanadium (V) is to co-process V titanomagnetite ores with V-bearing steel slag, via reduction. V-slag produced from highly enriched Fe-V melt contains as high as 20 mass% V. The phase relationship in FeO-SiO2 based slag with V fixed at 20.4 mass% was investigated experimentally at 1673 K. The compositions covered the normal production range, viz. Al2O3 from 0 to 6 mass%, CaO from 1 to 5 mass% and SiO2 from 10 to 17 mass%. The content of MnO was fixed at 5.5 mass%. Samples quenched at 1673 K were found to be solid-liquid mixtures, either in a 2-phase region consisting of liquid and a solid spinel phase, or in 3-phase region consisting of liquid, spinel phase and silica phase. Free silica was only found in samples with a composition of 0 mass% Al2O3, 1 mass% CaO and 17 mass% SiO2. Formation of free silica was prohibited in samples with 1 mass% CaO and up to 17 mass% SiO2 by adding 5 mass% Al2O3. Addition of 4 mass% Al2O3 was also sufficient to prevent the presence of free silica in samples with 3 mass% CaO and 13.5 mass% SiO2. Most of the V was kept in the spinel phase, while the solubility of V in the liquid was generally less than 1 mass% as V2O3. Fe, Mn and Al coexisted in both liquid phase and spinel phase. On the other hand, Si and Ca only distributed in the liquid phase. The fraction of solid phase, viz. spinel was found to decrease with increasing SiO2 content.

Place, publisher, year, edition, pages
Springer, 2017. Vol. 3, no 2, 289-299 p.
Keyword [en]
Vanadium, Slag, Experimental, Phase relationship, Free silica, Spinel
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-208798DOI: 10.1007/s40831-016-0088-yISI: 000400824500010OAI: oai:DiVA.org:kth-208798DiVA: diva2:1109059
Funder
VINNOVA, 2014-06242
Note

QC 20170613

Available from: 2017-06-13 Created: 2017-06-13 Last updated: 2017-09-11Bibliographically approved
In thesis
1. A Study on Vanadium Extraction from Fe-V-P Melts Derived from Primary and Secondary Sources
Open this publication in new window or tab >>A Study on Vanadium Extraction from Fe-V-P Melts Derived from Primary and Secondary Sources
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Vanadium extraction methods were developed for iron-vanadium-phosphorus (Fe-V-P) melts derived from processing of V-bearing titanomagnetites and steel slags. Studies on phase relationships of V slags were carried out to provide important understanding of the extraction processes. Phase relationship in vanadiferous slag was investigated experimentally at 1573K, 1673K and 1773K, for the compositional range of 0-6mass% Al2O3, 1-5mass% CaO, 10-17mass% SiO2, with MnO and V2O3 fixed at 5.5mass% and 30mass%, balanced with FeO. The slags were found to be solid-liquid mixtures, of liquid, spinel and in some cases free silica. Alumina was identified as the preferred additive to prohibit precipitation of free silica. A method for V extraction to vanadiferous slag was developed based on Fe-V(2mass%)-P(0.1mass%) melts at 1677K using a semi-industrial scale BOF. Oxidation was carried out with an oxygen enriched air jet and iron ore pellets. The complete dissolution of pellets was achieved by deliberately creating good stirring conditions utilising high momentary decarburisation rates. The P distribution to the slag was low when good stirring conditions was obtained. Phase relationship in Al2O3-CaO(25-35mass%)-SiO2-VOx slag was investigated experimentally at an oxygen partial pressure of 9.37•10-11atm and 1873K. The maximum solubility of V-oxide in the slag was 9-10mass% V2O3. Two solid phases were found, a solid solution of Al2O3 in V2O3 (karelianite) and hibonite with fractionation of V into the crystal structure. V extraction experiments to Al2O3-CaO-SiO2 based slags were carried out in 150kg scale by blowing CO2 gas into the metal bath consisting mainly of 1-10mass% V and 1mass% P. At these conditions, oxidation of V was favoured over Fe. Up to 10-13mass% V2O3 could be dissolved in the slag before a viscous slag saturated in V-oxide was observed. The phosphate capacity in the slag was low and as a result this slag could at once be subjected to a final reduction step for production of ferrovanadium with 40-50mass% V.

Abstract [sv]

Metoder för att utvinna vanadin till högvärdiga vanadinslagger från metallsmältor innehållande främst järn (Fe), vanadin (V) och fosfor (P) utvecklades. Metallsmältorna framställs genom att processa primära V råvaror, såsom titanomagnetit, och sekundära råvaror av i huvudsak vanadinrik stålslagg. Fasstudier av högvärdiga vanadinslagger genomfördes som grund för utvecklingsarbetet. Experimentella fasstudier av vanadinspinellslagg med 30vikt% V2O3 och 5.5vikt% MnO genomfördes vid en temperatur av 1573K, 1673K och 1773K. Övriga komponenter i slaggen varierades inom ett intervall av 0-6vikt% Al2O3, 1-5vikt% CaO och 10-17vikt% SiO2, viktad med järnoxid. Samtliga slagger var sammansatt av både flytande- och fastfas. Den fasta fasen utgjordes främst av en vanadin- och järnrik spinellfas och i vissa fall även av fri SiO2. Genom försök i en stålkonverter i semi-industriell skala utvecklades och validerades en metod för vanadinutvinning från råjärnsmältor innehållande 2vikt% V och 0.1vikt% P, vid en temperatur av 1677K. Oxidationen utfördes med syreanrikad luft via en vattenkyld topplans och genom tillsats av hematit pellets. Omsättningen av pellets säkerhetsställdes genom god omrörning som erhölls under korta perioder med höga gasvolymer som en effekt av hög avkolningstakt. Råjärnet efter behandlingen innehöll cirka 3vikt% C och 0.1vikt% V. Producerad vanadinspinellslagg bestod av upp till 30vikt% V2O3. Fosforfördelningen till slaggen var låg under processbetingelser med god omrörning. Experimentella fasstudier av Al2O3-CaO(25-35vikt%)-SiO2-VOx slagg genomfördes vid en temperatur av 1873K och ett syrepartialtryck av 9.37·10-10atm. Den maximala lösligheten av vanadinoxid i slaggen var 9-10vikt% V2O3. Två fasta faser identifierades, V2O3 (Karelianit) med fast löslighet av Al2O3 och Hibonit med vanadinoxid inlöst i kristallstrukturen. Experimentella försök för att utvinna vanadin från en stålsmälta bestående av 1-10vikt% V och 1vikt% P till en slagg med en initial sammansättning av 7-40vikt% Al2O3, 25-35vikt% CaO och 27-64vikt% SiO2 utfördes i en skala av 150kg. Oxidation av vanadin åstadkoms genom att blåsa in CO2 gas i stålsmältan via en spolsten. Under dessa processförhållanden var oxidationen av vanadin gynnsam framför järn och fosfor. Lösligheten av vanadinoxid i slaggen var upp till 10-13vikt% V2O3. Slagg mättad med vanadinoxid var viskös som en konsekvens av utfällning av V2O3 med inlöst Al2O3. Slaggens gynnsamma vanadin och järn- samt vanadin och fosfor förhållande möjliggör att genom slutreduktion producera ferrovanadin med en vanadinhalt av 40-50vikt% och låg fosforhalt.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2017. 64 p.
Keyword
vanadium, V, V2O5, V2O3, ferrovanadium, vanadiferous, titaniferous, titanomagnetites, magnetite, spinel, slag, experimental, free, spinel, converter, LD, BOF, solubility, equilibrium, selective, oxidation, hibonite, karelianite, Al2O3, CaO, SiO2
National Category
Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-213747 (URN)978-91-7729-490-0 (ISBN)
Public defence
2017-10-26, Sal F3, Lindstedtvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
VINNOVAMistra - The Swedish Foundation for Strategic Environmental Research, 88031
Note

QC 20170912

Available from: 2017-09-12 Created: 2017-09-11 Last updated: 2017-09-18Bibliographically approved

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