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ArticleName Improvement of heap leaching process for the conditions of permafrost
DOI 10.17580/gzh.2017.07.11
ArticleAuthor Kovalev V. N., Sargaeva Yu. V., Kovalev N. V.

Polymetal Engineering, Saint-Petersburg, Russia:

V. N. Kovalev, Head of Laboratory, Candidate of Engineering Sciences,
Yu. V. Sargaeva, Engineer


Saint-Petersburg State Institute of Technology (Technical University), Saint-Petersburg, Russia:
N. V. Kovalev, Post-Graduate Student


Heap leaching is one of the basic methods to extract precious metals from low-grade ore as the other processing techniques appear economically unbeneficial. Under conditions of permafrost, it becomes necessary to heat leaching solutions. Thus, it is required to select values of temperature and fuel rate. Earlier Polymetal Engineering company developed mathematical model of leaching in permafrost rock mass. At Birkachan deposit in June 2014, the heap leaching production data were obtained. Later on, the comparative calculations were performed using the mathematical model of heat balance – a system of ordinary differential equations describing the change in the temperature in an ore stockpile and in the temperature of solution flow to the ore stockpile, the change in the liquid phase amount, the change in the ice quantity in the ore stockpile. According to the calculation results, the temperature of ore in an ore stockpile in the beginning of spraying considerably infl uences the leaching solution temperature and, consequently, the amount of heat to warm the solution. The mathematical model without modifi cation allowed estimating the heat consumption correct to 19–33% and the solution temperature correct to 10–29%. Improvement of the model included correction for the presence of water in the stockpile in the form of liquid and ice, determination of the relation between the internal bypass and the average temperature of wet ore and estimation of the effect of the thermal resistance of the sealing interlayer in the stockpile on the heat calculation outcome. The major corrective influence on the mathematical model is exerted by the initial conditions of ice content of ore by the beginning of spraying and the provision for the internal bypass of solution. Given the internal bypassing, the bias between the estimated heat to be introduced in the leaching solution and the heat calculated based on the full-scale data is 0.68%.

keywords Gold, heap leaching, ore stockpile, heat balance, permafrost zone, mathematical model

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