The reduction of fluxed and non-fluxed manganese ores by ferromanganese-silicide
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Date
2014-12-12
Authors
Channon, Walter Patrick
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Abstract
Medium- and low- carbon ferromanganese are produced by the
silicotherm ic redixction of slags containing MnO, Because of its
importance in the production of refined ferromanganese, the reaction
between a premelted Mamatwan manganese ore and various
ferromanganese «silicide reducing alloys has been studied with and
without additions of fluxing agents. This relatively low grade manganese
ore is partially self-fluxing and it is necessary to optimize the amounts
and timing of fluxing additions during the production of refined
ferromanganese to ensure both efficient electric furnace operation and
manganese extraction from the premelt. Therefore, throughout the
laboratory investigation, emphasis has been placed on the implications
for industrial practice,
Alloys containing different silicon concentrations were added to a
premelted sample of Mamatwan ore before the sample was introduced
into a molybdenum-wound resistance furnace,. The reaction was carried
out under an argon atmosphere and the parameters varied were reaction time
reaction temperature, alIoy~to*ore ratio, fluxing additions and the
silicon contents of the reducing alloy. The effect of stirring of the reacting
melt was also examined.
The highly exothermic nature of the reactions involved in this
investigation constituted a m ajor obstacle to any attempt to maintain
close control of temperature in the system. This also adversely affected
the possibilities of carrying out controlled equilibrium and kinetic studies
in this slag-m etal system*
Because of the highly exothermic reaction, temperature appeared
to have little effect on the rates of manganese transfer to the metal and
silicon transfer to the slag and an apparent equilibrium was rapidly
approached, Limits were determined for the favourable effects of fluxing
additions and manganese recoveries declined as the CaQ"to~MgO ratio
decreased for any percentage of basic flux additions, As the silicon
content of the alloy was progressively increased, the recovery of manganese
i passed through a maximum and subsequently decreased, Similar results
■were obtained with variations in the a lloy-to-ore ratio/ When aluminium
was used as a reducing agent together with silicon, substantial increases
in manganese recovery were achieved because the aluminoi >- „ , ,o
«
resection displaced the apparent equilibrium. The s.ilicor • ’»■* . . of the
resulting alloy was above the specifications for refine ' : cioo .anganese.
Stirring of the reacting melts decreased the manganese . .-tcovery and
this result conflicts with the results of a previous investigation but
may be explained by theexotherrnic nature of the silicon reduction
reaction.
The results obtained when used in conjunction with other physicochem ical
data related to this slag^metal system suggest optimum slag compositions
fo r m ore efficient manufacture of m edium- and low -carbon ferromanganese
■fom vlamatwan ore, -
Description
A Dissertation Submitted to the Faculty of Engineering, University
of the Witwatersrand, Johannesburg for the Degree of Master of
Science in Engineering.
Johannesburg, 1975