MEASURING THE EFFECT OF CONCENTRATE MINERALOGY ON FLASH FURNACE SMELTING USING DROP TOWER TESTING AND A NOVEL OPTICAL PROBE
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The selection of furnace operating parameters during the flash smelting of copper is based on the elemental composition of a blend and does not account for mineralogy, which may impact on the process. Thus, it is important to study the impact of blend mineralogy on flash combustion processes. This thesis investigates the impact of pure minerals, chalcopyrite and pyrite, on the flash combustion behaviour of three mineralogically distinct but chemically similar copper concentrates through experimental test work. In tandem, proof of concept testing of a novel fibre optic probe for monitoring flash combustion reactions was done. A drop tower reactor was used to study the effect of O2/S stoichiometry on flash combustion processes under 21 different test conditions. Tests were conducted at 950oC with O2/S stoichiometries in the range of 0.8 to 4.0, and a solids feed rate of 3 grams per minute. The results suggest that concentrates with low pyrite mineralization require a higher O2/S stoichiometry to be desulphurized to the target matte composition, and that the O2/S stoichiometry impacts the fraction of dust in the products, the flame temperature as well as the flame brightness. In this work, the impact of mineralogy on flash combustion processes is studied using different monitoring techniques to gain real-time information about the process. Ultimately this information may then be used to optimize the blending process and to adjust the operation of a flash furnace in real time. Monitoring of combustion reactions was done using emission spectroscopy, where the spectra were acquired through a custom-built fibre optic probe. The two-wavelength method was used to measure the temperature of combusting particles and the integrated intensity was used to measure the flame brightness. This information was found to be useful for identifying feed distribution problems, which are also experienced in commercial scale furnaces. There were no atomic or molecular Cu, Fe, S nor O emission lines or bands in the emission spectrum; however, alkali metal emissions from Na, K and Li were observed. The lack of Cu, Fe, S and O emissions is attributed to the low flame temperatures, which were between 900 and 1500oC. Testing of the sensor in a commercial scale furnace is recommended and is expected to expand the application range of the probe.
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