Chemical and Biomolecular Engineering - Theses
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ItemThe melting point and viscosity of nickel smelter slags( 1995-02)Western Mining Corporation produces nickel matte at the Kalgoorlie Nickel Smelter(KNS)from nickel sulphide concentrates within an integrated flash smelter.
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ItemFundamentals of foaming in molten slag systems( 1998)Liquid drainage between intersecting bubble films is an important step in the coalescence and rupture process of slag foams. Information such as the rate and extent of film drainage, as well as the critical thickness of slag films prior to rupture (their stability), was thus investigated. This study consisted of withdrawing single, and sets of "free" films of Na20-B203melts (up to 1273 K) and CaO-Si02-Al203 slags (up to 1723 K), using thin platinum wire frames. A gravimetric technique was developed to measure the "average" film thickness and the film draining rate prior to rupture. The results showed that the average film thicknesses of a model Na20-B203 system varied from several hundred microns initially, down to tens of microns before rupture. However, these values represented the 'net' mass of the liquid contained within the films and also the Plateau borders, i.e., they are likely to be an overestimation of the thickness of slag films. Non-uniform thicknesses within the CaO-SiO2-Al203 free films were observed using a color video camera. Using laser interferometry, localized and non-uniform thinning regions (known to occur in "mobile" films) were observed within a (CaO/SiO2) = 0.60, 15 wt% Al203 slag film at 1623 K. A thickness change of - 8.6 µm was obtained over a lifetime of around 25 seconds, resulting in a thinning rate of Δδ/Δt ~0.3 - 0.4 µm/s. A laser absorption/transmission technique was developed to measure the thickness of the slag films, and this showed that they do drain to thicknesses below 1 µm. Profiling of the thinning films near the edge and centre revealed that at the well-drained stages, the films become very thin and plane-parallel prior to rupture; the bursting velocity being in the submillisecond range (estimated by high speed cinegraphic studies). Critical thicknesses of the films were measured and ranged from 0.1 - 0.4 µm, approaching those generally encountered with typical aqueous ("soap") films. The addition of P2O2 in (CaO/SiO2) = 0.60, 15 wt% Al203, 9.6 wt% Fe203 slags at 1573 K, decreased the critical thickness and extended the lifetime of the bubble films before rupture. For instance, a free film containing 0.8 wt% P205 ruptured at a critical thickness of around 0.3 µm after a lifetime of about 39 seconds, while a slag film containing 1.3 wt% P205 ruptured at a critical thickness of 0.1 - 0.15 µm, after a lifetime of 47 seconds. (From Summary)
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ItemPhase equilibria in iron bath smelting type slags( 1997)New iron and steel making processes are usually highly intensified and therefore place stringent requirements on the refractory lining of the smelting vessels. Information on the interaction between metal, slag and refractory in these processes is very important to their developments. A drop quench experimental technique coupled with optical and microprobe analyses of quenched samples was used to determine liquidus temperatures and phases in the CaO-MgO- Al2O3-SiO2-FeOx (CaO/SiO2= 1 to 1.55, 10-20 wt% Al2O3, 0-10 wt% FeOx, 0-14 wt% MgO) system. Liquidus temperatures were determined for iron free slags over the compositional range of CaO/SiO2= 1, 0-14 wt% MgO and 20 wt% Al2O3 in air. The liquidus temperature results were in agreement with those of Osborn et al. (1954) in both the melilite and spinel phase fields. The effects of the addition of FeOx and MgO and the oxygen potential on the stability of melilite and spinel were studied. Liquidus temperatures increased in the melilite and spinel phase fields with an increase in the CaO/SiO2 ratio from 1 to 1.55 and a decrease in the oxygen potential from 10.0.68 to 10-8 atm. In the spinel phase field the addition of 1 wt% CrOx increased the liquidus temperature by up to 200°C. Addition of FeOx, in air, and a decrease in the alumina content decreased the liquidus temperature in the spinel and melilite phase fields. The liquidus temperature and phase stability data were compared with predicted data from the Cell model of Gaye and Welfringer (1984). The activities of oxides in the liquid slag were obtained from the Cell model and used to determine the liquidus. The Cell model predictions were compared to current literature data on activities in the systems of interest. Discrepancies were small (±10 °C) in slags with greater than 2.5 wt% MgO, containing 0-10 wt% FeOx and 10-20 wt% Al2O3 in air. In these cases the calculated activities of the components in the slag were used to explain the compositional dependency of liquidus temperature.(part of an abstract only)