Telfer processing operations have evolved from an initial gold leach operation through to a complex flowsheet producing both gold doré and a gold-bearing copper concentrate.
Report context
This Technical Report on the Telfer Property is dated December 31, 2011. The report describes recovery methods for the Telfer treatment plant, which was commissioned in late 2004 following a feasibility study completed in November 2002. The processing operation sources feed ore from both open pit and underground mining operations.
Processing route
Historical background
Processing operations at Telfer initially commenced in 1977 as a gold leach operation that treated the oxidized ore near the surface of the deposit. A flotation plant was added in 1991 to separately process copper ore from the deeper zones. Site operations were suspended in 2000 when the level of cyanide soluble copper in the gold ore essentially caused its processing to be uneconomic.
Current plant design
The feasibility study completed in November 2002 identified an optimum strategy for processing a combination of open pit and underground ore through a single treatment route. The rationale focused on maximizing the value obtained from both copper and gold to generate a gold-bearing copper concentrate as well as gold doré. A new treatment plant was constructed on-site and commissioned in late 2004. Two products are generated: gold doré and a gold-bearing copper concentrate.
Approximately 35% of Telfer gold production reports to the doré and the balance reports in the copper concentrate, based upon average production statistics over the past five years.
Minor amounts of oxide ore are scheduled for processing in a dump leach operation as an adjunct to the main treatment route, with the dump leach output incorporated within the overall gold doré production total.
Flowsheet description
Owing to the range of ore types with differing mineralization of both gold and copper, together with variation in ore hardness, the treatment flowsheet is relatively complex. Two parallel process trains have been incorporated through the grinding and flotation circuits. There is a general operating strategy to blend ore on the coarse ore stockpile in order to control the feed to the treatment plant in terms of ore grade and hardness.
The circuit was designed to maximize recovery of value minerals, starting with a flash flotation and gravity recovery section within the grinding circuit intended to capture the coarse free copper and gold mineralization that is liberated early in the process route. The milled product from the grinding stage passes to the copper flotation circuit where the residual copper is recovered, together with a proportion of gold associated with the copper minerals as well as a proportion of liberated gold.
Approximately 5% of the gold in the ore is locked within the pyrite mineralization which reports to the copper circuit tailings. Tailings from the copper circuit are therefore processed through the pyrite flotation circuit from which the recovered pyrite concentrate is processed through a cyanidation leach circuit for final gold extraction. The gold is extracted from the leach liquor by adsorption onto activated carbon followed by stripping and electrowinning.
Gold production history
Gold production from the overall Telfer operation for the past five years is summarized in Table 17.1 of the report. The distribution of recovered gold between the different processing sequences for the 2010-2011 year was as follows: gravity accounted for 26.6% of production, dump leach for 0.9%, pyrite for 4.4%, and copper concentrate for 68.2%.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Nominal throughput capacity | 20 Mtpa | Design |
| Actual throughput range | 17 Mtpa to 23 Mtpa | Operating data |
| Gold to doré | Approximately 35% | Average over past five years |
| Gold to copper concentrate | Balance | Average over past five years |
| Gold locked in pyrite | Approximately 5% of gold in ore | Design basis |
| Plant commissioning | Late 2004 | Actual |
| Initial operations commenced | 1977 | Historical |
| Flotation plant added | 1991 | Historical |
| Operations suspended | 2000 | Historical |
Project website: https://www.newswire.ca/news-releases/newcrest-mining-limited—newcrest-releases-telfer-and-lihir-technical-reports-514015601.html
Technical qualifications
The report notes that throughput rate generally varies between 17 Mtpa and 23 Mtpa depending upon the ore characteristics. The production statistics presented cover the six year period since plant startup. The gold production distribution figures are based upon average production statistics over the past five years. The report states that approximately 5% of gold in the ore is locked within pyrite mineralization.
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Source: Technical Report on the Telfer Property, December 31, 2011, Section 17 Recovery Methods.
