On-line Modelling and Optimising Control

It was identified by operational and process personnel that a newly installed continuous aluminium billet homogenising oven could be improved in terms of its ease of operation and throughput. Initial attempts to arrive at a new operating strategy involved work sessions based on simple models of the process. Due to the interactive nature of the process, these attempts were not successful in formulating a solution. It was therefore decided to build a realistic dynamic simulator of the process for the purposes of improving understanding, and developing a new operating strategy.

Aluminium World
JH Zietsman
2006
© Aluminium World


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Lining to Ilmenite Smelting (PDF)

The UCAR® CHILL-KOTE™ freeze lining concept combines wall cooling with carbon and graphite refractories of higher thermal conductivities to “chill” the refractory lining by transferring heat from the refractory lining. Effective sidewall water cooling, together with the efficiency of the heat dissipating conductive refractories, lowers the temperature of the lining to below that of the molten process materials. This causes a layer of slag and process metal to solidify or “freeze” and form a protective “skull” which completely coats the refractory hot face. Once formed, the slag skull insulates the refractories, reducing heat loss and protect the lining from erosion, chemical attack, thermal shock, and other stresses. The result: extended life and greatly improved refractory performance.

Presented at INFACON 7
C Coetzee; PH Lamont; D Bessinger; J Rabe; JH Zietsman; J Muller
2006

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Process mechanisms in ilmenite smelting

It has previously been observed that industrial high-titania slags display a compositional invariance, remaining close to stoichiometric M3O5. The present study focuses on this invariance and the phenomena which may cause it. The invariance was studied using thermochemical calculations and a mechanism is proposed for the observed behaviour. The mechanism suggests that a combination of thermochemical equilibrium and transient slag solidification and melting results in the observed compositional invariance. The proposed mechanism provides new insights and prompts questions about other mechanisms in the smelting process.

Journal of the SAIMM
J.H. Zietsman and P.C. Pistorius
April 2005, vol. 105, no. 4, pp. 229
© SAIMM Journal

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