Emulsification behaviour caused by gas bubbles rising through a slag/metal interface was studied in both a thin-slice model and a three-dimensional model using low temperature oil/aqueous and oil/mercury analogues. A generalized model characterizing the transitional volume of droplets entrained in the upper phase in the emulsification process was developed. The transient volume of "metal" entrained, $ rm V sb{d}(t),$ following the start of bubbling followed the relation $ rm V sb{d}(t)=V sb{ propto}(1-e sp{-t/ tau}).$ Based on this model, the birth rate and mean residence time of droplets dispersed by rising bubbles could be quantified. Dimensional analysis was used to express the volume of lower liquid carried up into the emulsion per bubble, thereby allowing better estimates of the droplet birth rate in a practical emulsification process induced by bottom blowing. Emulsification behaviour in industrial in-bath smelting processes were interpreted with the present modelling results. / Slag foaming in "in-bath" iron smelting was modelled by injecting gas through a porous disc into a vertical cylinder containing a variety of low temperature liquids. Based on experimental evidence and theoretical arguments, difficulties with previous studies characterizing foam height as a function of fluid properties were addressed, and an alternative analysis in the form of a general relationship was developed. The fractional volume of gas holdup, $ varepsilon,$ in foaming slags containing large spherical cap bubbles could be expressed as $ rm varepsilon=U sb{g}/ lbrack U sb{g}+(0.5gd sb{b}) sp{0.5} rbrack.$ The average bubble size in the foaming slag of the AISI pilot trials on the smelting reduction of iron ores was estimated to be 10-25 cm equivalent diameter, suggesting that significant coalescence of small bubbles (such as CO) occurs in the process. / In modelling the mixing behaviour of ferroalloy additions in intensively stirred reactors, the AOD process was used to simulate slag chrome oxide reduction period by ferro-silicon additions. These phenomena were examined with the aid of a two dimensional slice model and then a three dimensional model using low temperature oil/aqueous analogues. Based on these modelling studies, it was observed that the ascending gas/liquid plume created two asymmetric mixing zones: a smaller mixing zone near the side wall fitted with tuyeres and a larger main mixing zone away from it. In "slag free" experiments, a dead zone formed at the far surface corner opposite the tuyeres. There, the particles simulating ferro-alloy additions accumulated. However, in the "slag covered" model experiments, the injected gas generated an emulsified "slag/metal" phase of lower apparent density which lead to the entrainment of the buoyant ferro-silicon alloy additions. This, in conjunction with the significantly modified flow patterns, and absence of any dead zones, allowed the particles simulating ferroalloy additions to be readily entrained within the recirculation flow. These results suggest that the mixing-in of such additions into the molten slag during the chrome oxide reduction period can be accomplished efficiently.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.42082 |
| Date | January 1997 |
| Creators | Lin, Zuohua Joseph. |
| Contributors | Guthrie, R. I. L. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Mining and Metallurgical Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001566613, proquestno: NQ30324, Theses scanned by UMI/ProQuest. |
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