The revised February 2015 preliminary economic assessment for the Halilağa copper-gold project in Turkey plans a 54 x 75 inch gyratory crusher, a 10,000 hp SAG mill, a four-stage flotation circuit and a six-tank CIL plant that makes gold doré.
Halilağa is a copper-gold porphyry deposit in northwest Turkey, near the Izmir-Çanakkale Highway. JDS Energy & Mining prepared the Revised Preliminary Economic Assessment Technical Report for Pilot Gold Inc., the joint venture partner of Teck Madencilik Sanayi Ticaret A.Ş. The report has an effective date of December 20, 2014 and a report date of February 16, 2015. The plant is designed to treat 25,000 t/d of run-of-mine (ROM) material, or 9.125 Mt/y, and to make copper concentrate, gold doré and tailings. The proposed process includes crushing and grinding of the ROM material, rougher and cleaner flotation, regrinding, cyanide leaching, cyanide detoxification, a gold room and dewatering of copper concentrate. Head grade averages 0.34% copper and 0.34 g/t gold.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Plant throughput | 25,000 | t/d | 9.125 Mt/y |
| Crusher availability | 75 | % | One gyratory crusher |
| Mill and flotation availability | 92 | % | Not applicable |
| Mill throughput | 1,132 | t/h | SAG plus ball mill |
| Bond ball mill work index | 12.2 | kWh/t | Test work |
| Primary grind | 150 | µm P80 | Cyclone overflow |
| Concentrate regrind | 20 | µm P80 | Regrind mill |
| Head grade, average / maximum | 0.34 / 0.9 | % Cu | 0.34 / 0.55 g/t Au |
| Copper flotation recovery | 88.2 | % | Concentrate grade 30.4% Cu |
| Gold recovery to concentrate | 58.4 | % | Average |
| Gold leaching recovery | 15 | % | Of feed gold |
| CIL retention time | 12 | h | Six tanks |
| Cyanide detox retention | 120 | min | Two tanks |
| Concentrate filter moisture | 12 | % w/w | Filter cake |
| Tailings to storage | 120 | Mt | 13 years, 86 Mm3 |
Overview
The Halilağa flowsheet recovers copper by flotation and gold by two routes. Gold that reports to the copper concentrate is sold in it, and gold left in the first cleaner tailings is leached in a carbon-in-leach (CIL) circuit. Flotation and cyanide destruction tailings are thickened before placement in a lined tailings storage facility. The process plant, with milling, flotation, regrind, thickening, filter presses, reagent storage, electrical rooms, an oxygen plant and a refinery, would sit in a 150 m by 50 m steel building on a plateau near the site access road.
Key Process Stages
Primary crushing and stockpile
A gyratory crusher, 1,370 x 1,900 mm (54 x 75 inch, 600 hp), takes ROM material from haul trucks through a dump pocket with two dump aprons and a hydraulic rock breaker. It makes a product of 80% passing 150 mm at 1,390 t/h and discharges to a sacrificial conveyor and a stockpile feed conveyor. A dust collection and suppression system serves the crusher and transfer points. The coarse mill feed stockpile holds one day of live storage, or 25,000 t, and two apron feeders, one standby, meter ore to the SAG mill feed conveyor.
Grinding and classification
The grinding circuit has a 30 ft diameter by 18 ft EGL SAG mill of 10,000 hp, a vibrating screen and a 22 ft by 36 ft ball mill of 10,000 hp. Lime is added to the SAG feed belt to raise slurry pH for copper flotation. SAG discharge at 70% solids passes a screen, and the pebbles go to a pile outside for manual re-entry, storage or disposal. Screen underflow joins ball mill discharge in a common pump box and goes to a 14 x 26 inch cyclone cluster. Overflow at about 32% solids and 150 µm P80 feeds flotation, and underflow at about 72% solids returns to the ball mill at a circulating load near 250%.
Rougher flotation and regrind
Slurry is conditioned in a rougher conditioner tank, with frother added to the overflow pipes. Five 300 m3 forced air tank cells in series give the roughing residence time of 24 minutes. Rougher concentrate flows by gravity to a launder and is pumped to an 18 ft by 37 ft EGL, 7,500 hp regrind ball mill, which grinds it to 20 µm P80. The report says the type of regrind mill will be settled after regrind tests.
Cleaner flotation
Reground concentrate is mixed with collector and frother and sent to the first cleaners, a bank of four 50 m3 cells with a two-cell 50 m3 scavenger bank. Second cleaners are four 20 m3 cells, and third cleaners four 10 m3 cells. Third cleaner tails go back to the second cleaners, second cleaner tails go to the first, and scavenger concentrate returns to the first cleaner feed. Cleaner scavenger tailings go to the leach thickener pump box. On-stream analysis gives online copper assays, and online particle size analysis runs on the rougher feed.
Concentrate thickening and filtration
Third cleaner concentrate goes to a high-rate thickener, with overflow returned to the process water tank. Underflow goes to a filter feed tank with about 12 hours of storage, then to a filter press. The press cuts moisture to 12% w/w. Cake falls into a bunker, and a front-end loader moves it to a covered, sheeted concentrate shed and loads it into trucks.
Gold leaching and recovery
First cleaner tailings are thickened to about 50% solids so that carbon has neutral buoyancy, and about 20% of feed gold reports to the thickener underflow. Six CIL tanks, arranged in descending steps so any one can be isolated, give 12 hours of leaching. A two-tank cyanide destruction module with a 2 hour residence time uses SO2 and copper sulphate before tailings go to storage. Loaded carbon is acid washed with hydrochloric acid, then stripped in a Zadra vessel with hot caustic at about 135 °C and 345 to 480 kPa. Gold plates onto stainless steel cathodes or falls as sludge, and a plate and frame press and an electric induction furnace turn it into doré. Carbon is regenerated in a rotary kiln at about 700 °C after every second strip.
Additional Interesting Data and Summary
The tailings storage facility (TSF) is a fully lined rock fill design. Two embankments are raised downstream to a combined crest length of 1,695 m and a maximum height of 97 m, with a 560 m starter embankment 46 m high. The facility is designed for zero discharge until closure with a dry cover. Upstream and centreline raises were rejected because of high seismicity, and a cyclone sand embankment was rejected because of the weak layer under a liner.
The project also needs about 30 MW of power, a 154 kV line and a substation, and a potable water system sized for 1,600 people. The report notes a 154 kV line owned by TEIAS crosses the pit and needs about 9 km of rerouting before mining starts.
Key Processes
- Gyratory crushing and coarse ore stockpiling
- SAG and ball milling with cyclone classification
- Rougher flotation with regrind
- Three-stage cleaner flotation
- Concentrate thickening and filter press dewatering
- Carbon-in-leach for gold in cleaner tailings
- Zadra stripping, electrowinning and carbon regeneration
- Cyanide destruction ahead of lined tailings storage
Source: Revised Preliminary Economic Assessment Technical Report, Halilağa Project, Turkey, February 16, 2015.
