Browsing by Author "Parkkali, Mika"
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- Plant concepts - Impurity management in copper smelting
Kemian tekniikan korkeakoulu | Master's thesis(2016-08-23) Parkkali, MikaCopper smelting will confront challenges in impurity control in the future as copper ores and concentrates are becoming dirtier and poorer in copper. Many reserves are unused at present because impurity levels are too high for current pyrometallurgical processes. Most of the world’s copper, approximately 80 percent, is produced by smelting. However, smelting processes have shortcomings in the removal of certain impurities and this may lead to severe risks and disadvantages without adaptation and better impurity management. The most problematic impurities in smelting processes are considered to be arsenic, antimony and bismuth. These impurities are passed into copper matte, slag, off-gases and flue dusts. A significant proportion goes to flue dusts and slag, which are often recycled back to the furnace. This results in a slow increase in increased concentration and enrichment in the process, where they eventually end up in the copper anode. These impurities are difficult to remove from anodes, since when copper is dissolved from the anode in electrorefining processes, the impurities also dissolve into the electrolyte. Both dissolved and insoluble impurities cause challenges for electrorefining operations, since some dissolved impurities may also transfer to the cathode unless they are removed continuously. Correspondingly, some of the unwanted insoluble slimes form floatable slimes, which may be accidentally transported onto the surface of the cathode and therefore cause poor quality. The simplest way to avoid this problem is to remove the dusts or slags from the process; however, due to the high concentrations of copper this is not be economically feasible. Additionally, flue dusts and slags are considered hazardous for the environment and organisms due to their instability and solubility in surface and ground waters. Therefore, new treatment pro-cesses are needed so that most of the copper can be recovered. This work studies the feasibility of utilizing hydrometallurgical processes in copper smelting operations. The study focuses on dust leaching, which is a good alternative route for reducing these impurities to sustainable levels. It was concluded that the most beneficial route is flue dust treatment. This was chosen be-cause the dust flows are significantly smaller than slag streams, resulting in lower investment and operating costs. The study focused on leaching tests for Flash smelting furnace (FSF) and Pierce-Smith converter (PSC) electrostatic precipitator dusts. Water leaching proved to be effective only for FSF dusts and PSC dusts did not give a good leaching yield. Chloride leach-ing resulted in the best leaching yields of approx. 85 % (FSF) and 94 % (PSC). On the basis of these results, this study suggests two-stage leaching for FSF dusts and one-stage leaching for PSC dusts, followed by sulphide precipitation and neutralization. The process presented resulted in 87 % (FSF and PSC) and 95 % (PSC) copper recovery, depending on whether both dusts were utilized. Arsenic and antimony extraction were 80-90 % and bismuth extraction was lower, at approx. 60 % in both cases. Unfortunately, the impact on the whole smelting circuit could not be assessed. Annual operational costs for the dust treatment were estimated to be 6.2 M€ (FSF+PSC) and 2.7 M€ (PSC). - Prosessiteollisuudessa käytettävät venttiilit ja niiden vikadiagnostiikka
Kemiantekniikan korkeakoulu | Bachelor's thesis(2014-04-30) Parkkali, Mika