The Nasedkino gold-copper project proposes a processing route combining gravity concentration, flotation, and cyanidation to produce gold doré and a gold-rich copper sulphide concentrate.
Report context
This technical report, dated October 2012, presents the processing flowsheet developed for the Nasedkino deposit by TOMS-Engineering, based on metallurgical testwork carried out by TOMS Institute from 2011 to 2012. The plant design capacity is set at 1.4 Mtpa. The report incorporates findings from earlier studies conducted between 2006 and 2010, including pilot plant tests, laboratory investigations, and geological-technological mapping. No metallurgical studies had been undertaken on material from the Uryum deposits other than from the Zhelanny area. SRK considers that the metallurgical tests for the principal deposits have been extensively evaluated in sufficient detail, especially since 2010, to permit classification of Mineral Reserves.
Processing route
Mineralisation and mineralogy
The mineralisation is of a gold-copper-quartz type. The most valuable components are gold (sample grade 1.52-3.12 g/t), copper (0.079-0.258%), and silver (3.52-5.48 g/t). Copper is contained in sulphides and could be easily extracted into sulphide concentrate. The majority of gold-bearing ore is native with a purity of 770-970. Grain size is no higher than 0.75 mm and the share of free gold is 48.4-67.7%. Mineralisation from Zhelanny is easily cyanidable with recoveries of 79.3-95.4%. The majority of the remaining gold is associated with sulphides and is resistant to leaching with cyanide.
The rocks are presented by sub-skarns, skarnoids, skarns, and metasomatites of quartz-feldspar composition with different ratios of minerals. In terms of chemical composition, the mass fraction is 46-55.7% for quartz. All samples have high iron content: 7-70.8%. Sulphur content varies from 1 to 4.25% within the mineralised zones. Arsenic exists with an average of 0.045%, up to 0.132-0.155% in some samples.
Proposed flowsheet
The proposed processing flowsheet integrates gravity concentration to recover coarse gold, flotation to recover copper concentrate with gold, and cyanide leaching of fine gold in the flotation tailings. The specific process steps are:
- Crushing and grinding
- Centrifugal concentrators to produce a gravity concentrate, with gravity tailings sent to the flotation circuit and gravity concentrate sent to the CIP plant
- Flotation to produce a gold-rich copper sulphide concentrate
- Cyanide leach of the tailings involving CIP
After crushing the mill feed to 80% passing 150 mm, the product is conveyed to a coarse ore stockpile located near the processing plant. From the stockpile, material is fed into a semi-autogenous grinding (SAG) circuit where it is ground to 80% passing 1 mm. The SAG mill operates in a closed circuit with a screen, with oversized material fed into a cone crusher. The product feeds a ball mill, also operating in a closed circuit with hydrocyclones, to produce 80% passing 63 μm.
The product from the hydrocyclones is fed to bulk flotation cells. The primary concentrate and middlings are further ground to 80% passing 17 μm with mills operating in a closed circuit with hydrocyclones. There are three stages of cleaning the reground primary concentrate, with tailings from the second and third stages returned for further regrinding.
The tailings of the sulphide flotation are reground to 80% passing 32 μm and are fed into the cyanidation and CIP process. The tailings are dewatered, treated with hypochlorite and ferric sulphate solutions to remove remaining cyanide, and then discharged into the pond. The carbon, loaded with gold, is fed into the desorption circuit. After electrolysis, drying and smelting, the ingots of doré gold are shipped to a refinery.
After the third recleaning, the copper and gold-bearing concentrate is thickened and dewatered using filters. The concentrate is packed into 1 t bags, loaded onto trucks for transport to Pen'kovaya station siding 23 km from the plant, and shipped to the smelter.
Physical and mechanical testing
The choice of crusher was based on studies carried out using the SAGDesign Consulting Group technique at TOMS Institute in 2012, in cooperation with Starkey & Associates Inc. Results indicated that the specific hardness (ratio of semi-autogenous mill power (WSAG) to Bond Work Index (BWi)) is in the range of 0.51-0.96, which is suitable for semi-autogenous grinding. For design development, the following parameters were used: WSAG = 12.19 kWh/t and BWi = 17.28 kWh/t.
Water balance
Overall water consumption at the plant is forecast to be 668 m³/h (excluding domestic needs) or 3.6 m³/t milled. Of this, 257 m³/h (1.4 m³/t) will be sourced from thickeners and 37 m³/h (0.2 m³/t) will be fresh water. Fresh water is used to prepare reagent solutions and for other technological processes requiring clean water, such as hydraulic compaction of pumps and sorbent washing. SRK considers that there is potential to reduce costs by pre-thickening cyanide-bearing tailings and recirculating the solution, thereby reducing the quantity of reagents needed to destroy remaining cyanide in the tailings.
Tailings management facility
No detailed designs have been prepared for the tailings management facility. SRK estimated costs based on comparable projects. Given that the tailings are fine, SRK assumed the tailings dam would be constructed using either mine waste or rock quarried from near the facility. Given the chemicals in the tailings solution, SRK assumed the facility is lined. Diversion channels around the perimeter reduce the quantity of water to be treated. Pipelines for returning decanted water are to be designed to cope with cold weather during winter. The process plant tailings will be disposed in one of the adjacent valleys. The tailings dam will be constructed using pit waste and local construction materials. The face of the tailings dam will be lined.
Process plant operation
The process plant will have round-the-clock working hours for 365 days per year. Operation will use two 12-hour shifts, with crews spending one month on site and one month off-site.
Key reported parameters
| Indicator | Units | Value | Basis |
|---|---|---|---|
| Annual throughput | Mtpa | 1.4 | Proposed design |
| Daily throughput | t/day | 3,836 | Proposed design |
| Hourly throughput | t/hour | 177.6 | Proposed design |
| Availability of crushers | % | 70 | Proposed design |
| Availability of processing units | % | 90 | Proposed design |
| Mill feed density | t/m³ | 2.94 | Testwork |
| Bond Work Index | kWh/t | 14-15 | Testwork |
| SAGDesign WSAG | kWh/t | 12.19 | Testwork |
| SAGDesign BWi | kWh/t | 17.28 | Testwork |
| Copper concentrate yield | % | 0.47 | Proposed design |
| Copper recovery to concentrate | % | 70.5 | Proposed design |
| Gold recovery to copper concentrate | % | 24.5 | Proposed design |
| Gold recovery to doré | % | 62.4 | Proposed design |
| Overall gold recovery | % | 88.9 | Proposed design |
| Water consumption (overall) | m³/h | 668 | Proposed design |
| Fresh water consumption | m³/h | 37 | Proposed design |
Technical qualifications
No metallurgical studies have been undertaken on material from the Uryum deposits other than from Zhelanny. There is no information regarding sample locations for the 2008 studies by OJSC LICIMS. No detailed designs have been prepared for the tailings management facility, and SRK estimated costs based on comparable projects rather than site-specific designs. The consumption data for materials and chemical reagents was sourced from results of laboratory tests and from similar operations, not from full-scale plant data. Historical operating data from pilot plant tests in 2007 involved a sample weight of 117 tonnes from the Pridolinny body.
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Source: Nasedkino , 2012 Technical Report, SRK Consulting, October 2012, Sections 1.15 and 17.
