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Dissolution of MgO·Al2O3 spinel and MgO in CaO-Al2O3-MgO-SiO2 slag under forcedconvection
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. (Micro-modelling)
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In this work, the dissolution mechanism of dense MgO·Al2O3 spinel and MgO rod into molten CaO-Al2O3-MgO-SiO2 slag was investigated at 1873 K with forced convection. The dissolutionexperiments were carried out by employing a newly developed rotating cylinder method. The effect of rotation speed and reaction time on the dissolution rate was studied. The measured dissolution rates of both spinel and MgO were dependent on the rotation speed, indicating that mass transfer in the slag phase to one of the rate-limiting steps. It was also found that the dissolution rate of spinel in slag was enhanced more rapidly than that of MgO with the increasing reaction time and rotation speed. It was also found that the composition of the slag at the interface was far from equilibrium value between the slag and solid. The results implied that the chemical reaction at the solid-slag interface should be the other important step that jointly controlling the dissolution process.

Keywords [en]
Dissolution mechanism, Driving force, Slag penetration
National Category
Ceramics Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering
Identifiers
URN: urn:nbn:se:kth:diva-214597OAI: oai:DiVA.org:kth-214597DiVA, id: diva2:1141959
Projects
European Union’s Research Fund for Coal and Steel (RFCS) research program under grant agreement No RFSR-CT-2015-00005
Funder
EU, European Research Council, RFSR-CT-2015-00005
Note

QC 20170918

Available from: 2017-09-18 Created: 2017-09-18 Last updated: 2017-09-18Bibliographically approved
In thesis
1. A Study on the Reaction between MgO Based Refractories and Slag-Towards the Development of Carbon-free Lining Material
Open this publication in new window or tab >>A Study on the Reaction between MgO Based Refractories and Slag-Towards the Development of Carbon-free Lining Material
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In present thesis, the fundamental studies on the reaction between MgO based refractories and slag were undertaken for the development of a carbon-free bonding MgO lining material. Alumina was selected as a potential binder material. Due to MgO-Al2O3 chemical reaction, the developed refractory was bonded by MgO·Al2O3 spinel phase. To begin with, an investigation of the dissolution process of dense MgO and MgO·Al2O3 spinel in liquid slag was carried out. To obtain reliable information for dissolution study, a new experimental method was therefore developed. In this method, a cylinder was rotating centrally in a special designed container with a quatrefoil profile. This method also showed a good reliability in revealing the dissolution mechanism by quenching the whole reaction system. The experimental results showed that the dissolution process of MgO and spinel was controlled by both mass transfer and chemical reaction. It was found that the rapid dissolution of spinel was mainly because of its larger driving force. To improve the resistance against slag penetration, two aspects were studied to develop carbon-free MgO refractory. First, colloidal alumina was used and the effect of its addition into MgO matrix was investigated. The use of colloidal alumina was to form bonding products in the grain boundary of MgO. The results showed that the alumina addition greatly improved the resistance of MgO based refractory against slag penetration in comparison with the decarburized MgO-carbon refractory. It was found that the improvement of resistance was mainly related to the spinel-slag reaction products of CaO·Al2O3 and CaO·MgO·Al2O3 solid phases at the grain boundaries. Second, the effect of particle size distribution on the penetration resistance of MgO was investigated. The most profound improvement against the slag penetration was obtained by using a proper particle size distribution. The results highlighted the importance of considering the refractory structure. Experiments were undertaken to investigate the dissolution mechanism of different types of MgO based refractories in liquid slag. It was observed that the dissolution of spinel bonded MgO refractory was much slower than the decarburized MgO-carbon refractory. The primary dissolution in spinel bonded MgO refractory occurred at the slag-penetrated layer, and the removal of this layer by peeling off enhanced the dissolution rate rapidly.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. p. 54
Keywords
MgO refractory, lining material, carbon-free, clean steel, ladle glaze, slag penetration, dissolution mechanism
National Category
Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-214420 (URN)978-91-7729-533-4 (ISBN)
Public defence
2017-10-27, Sal F3, Lindstedtvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
European RFCS LEANSTORY project
Funder
EU, European Research Council, RFSR-CT-2015-00005
Note

QC 20170918

Available from: 2017-09-18 Created: 2017-09-13 Last updated: 2017-09-21Bibliographically approved

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