A Consecutive Reaction Model and Kinetics of Cr203 Reduction from Slag by Carbon Dissolved in Molten Iron

Simukanga, Stephen (1990) A Consecutive Reaction Model and Kinetics of Cr203 Reduction from Slag by Carbon Dissolved in Molten Iron. PhD thesis, University of Zambia.

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Abstract

A first-order, consecutive, two-stage reaction model for the reduction of Cr203 from slag was developed. The model was applied to the results obtained by studying the effect of various parameters on the rate of reduction of Cr203 from a CaO-Si02-A1203 slag, by carbon dissolved in molten iron, at temperatures 1400-1550 oC. The parameters studied were: varying the furnace atmosphere; Cr20 3 concentration in slag; metal chromium content; the experimental temperature; slag and metal volume; the presence of the surface-active elements, S or Se and adding FeO and CaF2 to the slag. The progress of the reactions was monitored by taking slag samples at predetermined time intervals, and analysing them for the relevant species. The results showed that the reduction of Cr203 from slag takes place primarily at the slag/metal interface, and follows a first-order, consecutive, reversible, two-stage reaction scheme in which (Cr2 +) is the intermediary product. The rate of (Cr 3+) reduction remained the same in an argon or carbon monoxide "atmosphere whilst an argon atmosphere increased the rate of (Cr2 +) reduction by a factor of about 1.4, compared to a carbon monoxide atmosphere. The rate of reduction of the chromium species increased with increase in temperature andactivation energies obtained were 54.16, 27.15 and 81.33 3+ 2+,kcal/mol for (Cr ), (Cr) and Cr 203 reductlon. Addition of S or Se to the system markedly increased the rates of reduction of all the chromium species, with an attendant increase in the FeO content of the slag. Metal emulsification, which is a consequence of reduced surface-tension of the metal, is thought to be responsible for the increase in rate of Cr2 0 3 reduction. Addition of FeO to slag decreased the reduction rates of all the chromium species whilst CaF2 addition increased the rate of reduction of the chromium species. The reduction in slag viscosity due to caF2 addition is thought to be responsible for the increased rates of reduction.

Item Type:	Thesis (PhD)
Subjects:	T Technology > TN Mining engineering. Metallurgy
Divisions:	Africana
Depositing User:	Geoffrey Obatsa
Date Deposited:	31 Jan 2019 09:44
Last Modified:	31 Jan 2019 09:44
URI:	http://thesisbank.jhia.ac.ke/id/eprint/8944

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