ALTA-2019-GPM Go For Gold final

GO FOR GOLD AND IGNORE CYANIDE SOLUBLE COPPER A NEW APPROACH TO GOLD/COPPER ORES.

By

Malcolm Roy Paterson

PT GreenGold Technology, Indonesia

Presenter and Corresponding Author

Malcolm Paterson malcolm@greengoldengineering.com

ABSTRACT

The Cyanide Soluble Copper (CNsolCu) contained in Gold/Copper ores has often been the Achilles Heel in making these particular projects economic. It has been a headache for geologists and metallurgists alike. The copper has proven to be more than just a nuisance element, but a determinant in the projects’ economic feasibility. In addition to the economic implications, simply quantifying the impact has proven to be a distraction in the assessment of what should be a gold project. The measurement of total copper in the ore is not sufficient to understand the cost impact as it is the cyanide soluble copper that is relevant. Total copper may become important if it can justify the inclusion of a flotation circuit pre or post CIL to produce a profitable copper concentrate. However, this aspect should be considered separately as the true economics can be marginal. The basis of this paper is to show that the application of a simple resin technology, the ReCYN Process, is a game changer in not only solving the cost impact of soluble copper but also in simplifying the assessment of copper/gold ores. The overall benefits are seen to extend beyond the processing costs, and to improved Reserve estimates. (1) The approach is to effectively ignore the cyanide soluble copper and focus on the gold. By incorporating the ReCYN process into the recovery flowsheet, the copper no longer becomes a cost. It can be shown that the additional cyanide consumed in dissolving copper is more than balanced by the recovery of the copper and its associated cyanide by the ReCYN process. The nett cyanide cost is then specifically related to gold recovery. As an example, the cyanide soluble copper can increase sodium cyanide consumption to over 15kg/t ore at certain times. Without the soluble copper, the cyanide consumption would be less than 1kg/t ore. This latter figure can now be used in the project economics without reference to CNsolCu, thus simplifying the Resource, Reserve and Process cost estimation. Cyanide soluble copper also causes downstream processing problems with adsorption onto carbon, impacting gold recovery and increasing detox costs. All these issues are able to be resolved since a higher cyanide level in the leach solution is now possible, due to the lower cost of cyanide recovered by the ReCYN process and the deletion of any detoxification costs.

There is expected to be an increase in the number of new gold projects that have ore associated with copper. Thus the challenge is expected to grow in importance.

This paper describes three diverse examples of the application of ReCYN Technology to problematic gold/copper ores.

Keywords: Cyanide, gold, copper, resin, detoxify, recovery, economic and environmental.

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