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Effect of magnesium on sintering of hematite
2009 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Magnesium compounds are added to iron ore pellets to improve the performance (flow, slag properties and desulphurization) in the blast furnace. The magnesium compounds may also affect processes before the blast furnace, for instance the sintering of iron ore green pellets. However, the effect of magnesium compounds on sintering of green pellets is not fully understood. This Master Thesis work was therefore devoted to a careful study of the effect of magnesium compounds on sintering of hematite. Thin films of hematite nano crystals (86 nm) with mono modal size distribution were therefore prepared by spin coating on alumina supports. Such films are ideal for studies of grain growth by XRD and SEM. Both pure hematite films and films containing hematite and a magnesium compound were prepared. These films were sintered with different holding times from 0-16 hours at 855ºC. The results showed that a new phase of magnetite/magnesioferrite, initially comprised of small crystals (< 90 nm) formed in the presence of magnesium. obviously, some of the hematite nano crystals were converted to even smaller crystals of magnetite/magnesioferrite when the sample was heated to the sintering temperature. after some time of sintering, all crystals grew, independent of phase. however, the hematite crystals grew more rapidly in the presence of the small crystals of the magnetite/magnesioferrite phase, i.e. in the presence of magnesium, as compared to in a pure hematite system. this more rapid growth of hematite crystals is probably an effect of better mass transport in the presence of the magnetite/magnesioferrite. it is known from literature that the diffusion of fe2+ and fe3+ ions is faster in magnetite than in hematite, which may be one reason for better mass transport in the system containing magnesium. in addition, the system with magnesium will contain more and smaller crystals and the size distribution of crystals will be broader, which also should improve mass transport. this should have implications on a number of metallurgical processes and for instance sintered pellet strength. to the best of our knowledge, this is the first time this important effect of magnesium on sintering of hematite has been observed experimentally.

Place, publisher, year, edition, pages
2009.
Keywords [en]
Physics Chemistry Maths
Keywords [sv]
Fysik, Kemi, Matematik
Identifiers
URN: urn:nbn:se:ltu:diva-44932ISRN: LTU-EX--09/164--SELocal ID: 2acadfe4-bf4e-42d4-af16-f011196d5c5cOAI: oai:DiVA.org:ltu-44932DiVA, id: diva2:1018211
Subject / course
Student thesis, at least 30 credits
Educational program
Chemical Engineering, master's level
Examiners
Note
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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CiteExportLink to record
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Citation style
  • apa
  • harvard1
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  • vancouver
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  • Other locale
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Output format
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