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Flash converting of chalcocite concentrate : a study of the flame

University of British Columbia

The “flame” resulting from the flash converting of Inco chalcocite (or “MK”) copper concentrate has been studied, with the primary objective of reducing or eliminating the dust production asso ciated with this process. Experimental trials with MK concentrate were performed in the UBC flash smelting pilot plant in which the response of the flash flame (as determined by solids and gas compositions) was examined as a function of process variables. In addition, solids and gas samples were recovered from the flash flame in the Inco Port Colbome pilot plant. These experiments indicated that the rate of dust production in the UBC pilot plant was significantly lower than that in the Inco Port Colbome pilot plant, and that the oxygen-to-concentrate ratio plays an important role in the observed dust generation rate. A mathematical model of an individual MK concentrate particle has shown that dust production is consistent with particle fragmentation initiated by the boiling of copper within the particle. Particle size, oxygen concentration and temperature were found to affect the ability of an MK concentrate particle to fragment by this mechanism. Incorporating this particle combustion study, a mathematical model of the chalcocite flash flame was developed. This model utilized the boundary-layer form of the gas-phase conservation equations (modified to deal with recirculation and incorporating the effects of particles on the gas) to describe the combustion phenomena occurring within the chalcocite flash converting flame. The mathematical model was verified first by non-reacting studies from the literature and then by comparison with experimental data taken from the UBC flash furnace. The mathematical model was then extended to describe the behaviour of the Port Colborne pilot plant. The mathematical model has shown that the production of dust within the chalcocite flash flame occurs due to the dissimilar spreading rates of the concentrate particles and the injected oxygen. Two regions within the flame were identified as leading to dust generation : a ‘near-edge” region of high local oxygen-to-concentrate ratio, and a ‘near-centre” region with high radial oxygen transport. The “near-edge” region has been suggested as being responsible for the dust produced by the UBC pilot plant, while the “near-centre” region is responsible for the dust produced in the Port Colborne pilot plant. The occurrence of these two regions could be eliminated by improved burner design.

Thesis/Dissertation

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2008-12-19

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http://hdl.handle.net/2429/3218

Materials Engineering

University of British Columbia

UBCV

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