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Hydrometallurgical reprocessing of Peruvian pyrometallurgical slags
Caplan, Michael
Caplan, Michael
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2023
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Slag samples were obtained from 3 Peruvian smelting operations with the goal of determining what economic constituents are present in the slags. Once identified, one slag was selected for the purpose of developing a processing methodology in order to recover the identified economic constituents. The slags were obtained from the Ilo copper smelter, the Funsur tin smelter, and the La Oroya metallurgical complex. It was determined that copper is a viable potential target present in the Ilo slag at approximately 0.84%. Magnesium at 1.39% and titanium at 1.24% were identified as potential targets present in the Funsur slag. The La Oroya slag contained copper at approximately 0.5%, lead at approximately 2.4%, and zinc at approximately 7% as potential targets. Additionally, silver and gold were present in amounts that could be considered secondary targets in La Oroya slag, less than 3 mg/kg for gold, and approximately 45 mg/kg for silver . The La Oroya slag was selected for further work, and a process to recover the copper, lead, and zinc was developed. The process first leaches the slag via sulfuric acid. The copper and zinc report to the leachate, and the lead to the residue. The leachate is neutralized, and zinc dust is added in order to remove copper and iron through cementation. The leach residue is subjected to WHIMS in order to generate a lead bearing concentrate and a waste stream. The cemented solids are fed into the copper converting furnaces to recover the copper via the standard La Oroya process. The remaining solution after cementation is sent to the standard zinc La Oroya circuit for zinc recovery via electrowinning. The lead bearing concentrate is fed into the lead sinter plant for lead recovery via the standard La Oroya lead circuit. Additionally, silver and gold follow the lead in the developed process. Because of this, they end up in the lead anode slimes where they are then recovered through the standard gold and silver circuits. Two versions of the process were proposed, one with hydrogen peroxide and one without. An economic analysis showed that the one using hydrogen peroxide would not be profitable, and that the one without had a positive NPV of over $65,000,000 at a discount rate of 17%, and an IRR of over 120%. Additionally, MetSIM computer process models were developed of both versions of the proposed process and integrated into digital process models of historical (old) La Oroya operations and newly developed (new) La Oroya operations. The models were used to determine how the proposed recycle streams would behave in the existing circuits and ensure that the overall process is technically viable.
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