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ArticleName Peculiarities in behaviour of kyanite in pseudo closed and pseudo open system Al2O3 — SiO2 — C
ArticleAuthor Grishin N. N., Belogurova O. A., Ivanova A. G., Neradovsky Yu. N., Voitehovsky Yu. L.

Russian Academy of Sciences, I. V. Tananaev Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials (ICTREMRM KSC RAS)

N. N. Grishin, Head of Refractory Materials Department, e-mail:
O. A. Belogurova, Senior Researcher
A. G. Ivanov, Technologist


Geological Institute, The Kola Science Center of Russian Academy of Sciences

Yu. N. Neradovskiy, Leading Researcher
Yu. L. Voitekhovskiy, Director


Thermodynamics of processes in pseudo closed and pseudo open systems Al2O3—SiO2—C for products of reaction 3(Al2O3·SiO2) → 3Al2O3·2SiO2 + SiO2 is observed. It is experimentally showed that this system behaves itself as the two formal independent systems: SiO2—C и Al2O3—C. On stand point of thermodynamics reaction 3Al2O3·2SiO2 + SiO2 + 9С → 3Al2O3 + 3SiС + 6СО is the most probable, moreover, SiО is transportable phase which reacts with C according to SiО + 2С = SiС + СО. In the pseudo closed system silicon carbide, of course, can be formed during the firing of pressed products in direct contact with carbon SiO2 at the interface of particles. Partial recovery silica component of kyanite which leads to the formation of silicon carbide by transfer of silicon by volume of the samples due to the partial formation of SiO and Si is yielded mullite-carbon refractories with high thermal stability. In the pseudo open system carbon does not take part in the reduction process of SiO2 because these particles do not have a contact. Task of elaborated technology is to provide the fullest removal SiO2 from kyanite and obtain the best raw material for alumina industry. In this process carbon improves conditions which provide formation of gaseous SiO from silica according to reaction of dissociation. Monoxide silicon diffuses and removes from volume of the samples in filling where it reduces and disproportionates on carbon with formation of Si, SiC, SiO2. High-alumina product (Al2O3 — 95%; Al2O3/SiO2 = 10–60) was developed on the base of conditions which provide formation and removing of gaseous SiO from volume of the samples. After chemical concentration the raw material for use in alumina industry (Al2O3 — 98%; Al2O3/SiO2 = 1230) was obtained.

keywords Kyanite, carbothermal reduction, thermodynamics analysis, high-alumina precursor, mullite-carbon refractory

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