A dissertation submitted to the Faculty of Engineering, University of the
Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of
Master of Science in Engineering. Johannesburg, 1998. / Experiments have been conducted at around 17000C to determine the whether
carbothermic reduction of alumina is possible at these temperatures. Total pressure
of the system was reduced to around 30 kPa and various metallic solvents such as
copper, nickel, iron and tin were used to dissolve the metallic aluminium
produced. The use of a solvent (and hence decreasing the activity of metallic
aluminium) and a lower pressure are thermodynamic requirements to increase the
extent of reduction under a given set of conditions. This enables the use of lower
temperatures than are required under atmospheric conditions.
The highest recovery of aluminium was achieved with the nickel solvent
decreasing in order from iron, copper and tin. This ranking was also in accord with
the extent of deviation from ideality in the respective binary solutions of these
solvents with aluminiur, The nickel-aluminium system displays the largest
negative deviation from ideality whereas the till, aluminium system showed a
positive deviation.
The rate and extent of the reduction was found to be highly dependent on
temperature and pressure. The pseudo first order reaction rate was found to be the
primary order for the reduction of aluminium in all the solvents used. It is also
suggested that the reduction rate was controlled primarily by chemical reaction
rate father than by transport processes. This is due to the extreme sensitivity of the
rate and extent of the reaction to temperature. / AC2017
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/22048 |
| Date | January 1998 |
| Creators | Caizergues, Derek |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | Online resource (106 leaves), application/pdf |
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