The 2012 technical report describes proposed heap leaching and carbon adsorption-desorption-recovery processing for the Kirazlı and Ağı Dağı gold projects, with design capacities of 15,000 and 30,000 tonnes per day respectively.
Report context
The July 31, 2012 NI 43-101 technical report for the Kirazlı and Ağı Dağı Gold Project presents preliminary designs for ore processing and heap leach facilities at both sites. The processing sections describe the proposed recovery methods, equipment, and facility designs. Heap leach facility evaluations and preliminary designs were completed by the Reno, Nevada office of Golder Associates Inc. The report states that studies for this section were considered adequate and conducted following generally accepted engineering practices, suitable to support the NI 43-101.
Processing route
Crushing and agglomeration
Run-of-mine ore will be delivered by haul trucks from the open pit to the primary crusher. Ore will be direct-dumped or reclaimed by front-end loader into a dump hopper above an apron feeder. A stationary grizzly will prevent oversized ore from entering the crushing circuit, and a rock breaker will break up oversize material. The apron feeder will regulate feed at nominally 833 dry t/h for Kirazlı and 1,666 dry t/h for Ağı Dağı. Grizzly oversize will discharge into a jaw crusher with a 100 mm discharge setting. Crusher discharge and grizzly undersize will be collected on the primary crushing discharge conveyor and delivered to the coarse ore stockpile.
The coarse ore stockpile will be conical. Two reclaim apron feeders at Kirazlı and four at Ağı Dağı will reclaim ore onto the reclaim conveyor.
Secondary crushing will be an open circuit arrangement. Kirazlı will have a single secondary crusher and screen, while Ağı Dağı will have two of each. The secondary screen will be a 3-deck banana type vibrating screen with apertures of 60 mm and 30 mm on decks 1 and 2 respectively. Oversize will discharge to a vibrating pan feeder followed by a standard head cone crusher with a closed side setting of 30 mm. Undersize and crusher discharge will be collected on the agglomerator feed conveyor, delivering secondary crushed ore at P80 26 mm to the agglomerator.
Cement will be added to the conveyor at an average rate of 2.5 kg per tonne of ore before the agglomeration drum. Kirazlı will have one agglomeration drum and Ağı Dağı two. Barren solution will be added at the agglomerator to bring ore moisture to 7.5%. The agglomerator will discharge onto a conveyor to the heap feed conveyor. The agglomerator and subsequent conveyor belts will be located over lined areas at the heap leach pad.
Heap stacking
Heaps will be constructed using a conveyor stacking system including a heap feed conveyor, up to three high-horsepower and up to 20 standard grasshopper portable transfer conveyors at Kirazlı (15 at Ağı Dağı), a horizontal feed conveyor, a 43 m mobile bridge conveyor on a dozer crawler carriage, and a 30 m radial stacking conveyor with powered luffing, slewing, and a 7 m telescoping stinger. Ore will be placed in 10 m lifts using the radial stacker, with heaps constructed retreating up the slope of the pad.
Heap leach facilities
The leach pads will be a multiple-lift, single-use type designed for 90 days of ore leaching. Ore will be leached using a dilute sodium cyanide solution applied by drip emitters and sprinklers at a nominal application rate of 10 L/h/m². Solution will percolate through the ore and collect on a geomembrane liner at the base of the heaps. Drainage pipes above the liner will deliver solution to pregnant solution ponds. A submersible trash pump will pump pregnant solution to the adsorption facility. Antiscalant will be added to the suction side of the pregnant solution pump.
The Kirazlı heap leach facility will be constructed in two phases to accommodate 26 million tonnes of processed ore. The Ağı Dağı heap leach facility will be constructed in three phases to accommodate 70 million tonnes. Both facilities will require fills during construction for gravity solution control, storm water diversion, and geotechnical stability. Mine waste will be used for fills.
Both facilities will have a composite base liner consisting of 0.5 m of compacted low permeability soil, a 2.0-mm thick HDPE geomembrane, and a 0.7-m thick drainage layer of crushed ore or mine waste. The maximum heap height is planned at 70 meters, potentially increased to 100 meters based on additional percolation and geotechnical testing. Slope stability analyses completed for static and earthquake loading conditions indicated stable slopes under North American standards. Solution will be collected above the HDPE geomembrane and delivered to the pregnant pond using a gravity drainage pipe system within the 0.7-m drainage layer.
Pregnant and event ponds have been sized to contain normal operating volume, heap drain down during a 24-hour outage, precipitation from a 100-year, 24-hour storm event, and seasonal accumulation under average climate conditions. Ponds will be double-lined with 0.5 m of compacted low permeability soil, a 1.5-mm HDPE secondary geomembrane, an HDPE geonet leak detection layer, and a 2.0-mm HDPE primary geomembrane.
Event ponds are included for storm events, extended power failures, and pump or pipeline failures. Kirazlı will have one event pond and Ağı Dağı two. Overflow from pregnant solution ponds and barren solution tanks will flow to event ponds. Submersible trash pumps will transfer solution to the barren solution tank.
Adsorption
The adsorption facility at Kirazlı will consist of one train of five up-flow, open-top, carbon steel columns, and two trains at Ağı Dağı. Pregnant solution will be pumped at a nominal flow rate of 777 m³/h at Kirazlı and 1,599 m³/h at Ağı Dağı. A magnetic flow meter and wire sampler will provide continuous sampling. Carbon will be moved counter-currently from column 5 to column 1, with stripped and regenerated carbon pumped into column 5. Screw centrifugal pumps will transfer carbon.
Barren solution from the last carbon column will be sampled, then discharged to a carbon safety screen to recover fugitive carbon, with the discharge pumped to the barren solution tank.
Recovery plant
Each recovery plant will include a pressure strip system with two 5.0 t elution columns, heat exchangers, solution heater, storage tanks, and electrolytic cells, capable of processing 10 t of carbon per 24-hour day. The plant will also include two 5.0 t acid wash circuits, an electric fired mercury retort, a tilting crucible-type diesel-fired smelting furnace of 430 kg red brass capacity, a carbon regeneration system with a 400 kg/h horizontal rotary kiln, a carbon handling circuit, a mixing system, plate and frame heat exchangers, and a 6,500,000 Btu/h diesel-fired solution heater.
After loaded carbon is transferred to an elution column, barren caustic-cyanide strip solution will be pumped through heat recovery exchangers and the solution heater, introduced at 135°C and approximately 450 kPa. Gold-laden strip solution will be cooled to approximately 80°C and flow through two electrowinning cells where gold will be deposited onto stainless steel punched plate cathodes. Barren strip solution will be recycled until stripping is completed.
Several times per week, cathodes will be removed to a wash box where gold precipitates will be washed using high pressure water sprays, filtered in a filter press, retorted, dried, and smelted. The filter cake will consist primarily of gold and silver with some copper and mercury.
Acid wash facilities include two 5.0 t acid wash vessels, two acid mix tanks of 5.0 m³ capacity, a positive-displacement acid resistant metering pump, and two recirculation pumps of 21.0 m³/h capacity. Stripped carbon will be acid washed to remove scale and inorganic contaminants. Hydrochloric acid will be metered to maintain a pH of 1.0 to 2.0. After acid washing, carbon will be pumped to the carbon regeneration circuit or to the fifth carbon column.
Carbon regeneration will include a vibrating dewatering screen, an 8.0 t kiln feed hopper, a diesel-fired rotary kiln reactivation furnace with a capacity of 400 kg of carbon per hour, and an 8.0 t quench tank. Carbon will be thermally reactivated at approximately 750°C, then quenched to enhance adsorption capabilities. Quenched carbon will be pumped to a dewatering screen to remove fines smaller than 24 mesh.
Smelting and refining
Smelting will take place approximately 4 to 8 times per week. Retort boats with filtered precipitates will be placed in the retort furnace for drying and mercury removal. Dried metal deposits and fluxes of borax, fluorspar, soda ash, and niter will be added to the crucible. After heating, the furnace will be tilted to pour molten contents. Slag will flow to a granulation launder where fast-flowing water will cool and granulate it. The granulated slag slurry will be pumped to a slag holding tank.
Molten doré will be poured into a cascade of seven molds, sized for 20 kg of silver or 36 kg of gold. The doré will be sampled, cleaned, weighed, and prepared for shipment. A hood will collect furnace fumes, which will pass through a baghouse with an induced draft fan designed to remove over 99.5% of particulates.
Key reported parameters
| Parameter | Kirazlı | Ağı Dağı | Basis |
|---|---|---|---|
| Plant capacity | 15,000 t/d | 30,000 t/d | Proposed design |
| Primary crusher feed rate | 833 dry t/h | 1,666 dry t/h | Proposed design |
| Secondary crushed product | P80 26 mm | P80 26 mm | Proposed design |
| Cement addition rate | 2.5 kg/t ore | 2.5 kg/t ore | Proposed design |
| Ore moisture after agglomeration | 7.5% | 7.5% | Proposed design |
| Heap lift height | 10 m | 10 m | Proposed design |
| Maximum heap height | 70 m (100 m potential) | 70 m (100 m potential) | Proposed design |
| Leach cycle | 90 days | 90 days | Proposed design |
| Solution application rate | 10 L/h/m² | 10 L/h/m² | Proposed design |
| Pregnant solution flow | 777 m³/h | 1,599 m³/h | Proposed design |
| Elution columns | 2 × 5.0 t | 2 × 5.0 t | Proposed design |
| Carbon processing capacity | 10 t/24 h | 10 t/24 h | Proposed design |
| Carbon regeneration kiln | 400 kg/h | 400 kg/h | Proposed design |
| Strip temperature | 135°C | 135°C | Proposed design |
| Strip pressure | ~450 kPa | ~450 kPa | Proposed design |
| Acid wash pH range | 1.0–2.0 | 1.0–2.0 | Proposed design |
| Carbon regeneration temperature | ~750°C | ~750°C | Proposed design |
| Smelting furnace capacity | 430 kg red brass | 430 kg red brass | Proposed design |
| Leach pad capacity | 26 Mt in 2 phases | 70 Mt in 3 phases | Proposed design |
| Heap leach facility liner | 0.5 m soil + 1.5 mm HDPE + geonet + 2.0 mm HDPE | Same | Proposed design |
| Heap slope | 3H:1V | 3H:1V | Proposed design |
| Acid wash vessels | 2 × 5.0 t | 2 × 5.0 t | Proposed design |
Technical qualifications
The processing studies were completed following generally accepted engineering practices and were considered adequate to support the NI 43-101. Preliminary designs for ore processing facilities were provided by Kappes, Cassiday & Associates of Reno, Nevada. Heap leach facility evaluations and preliminary designs were completed by Golder Associates Inc of Reno, Nevada.
The heap leach facilities are intended to operate as zero discharge systems with provisions for severe storms and temporary power or pump losses. The heap leach facility designs meet or exceed North American standards for containment, piping systems, and ponds. The report states that challenges including spring management, relatively steep topography, and potential for strong earthquake events have been overcome through sound engineering practices at the current level of review. The maximum heap height could be increased to 100 meters based on positive results of additional percolation and geotechnical testing. Slope stability analyses were completed for static and design earthquake loading conditions.
The report notes that the event ponds are not sized to provide long-term storage of solutions. Heavy rain or snow melt events will result in solution being diverted to these ponds.
Source: Kirazlı and Ağı Dağı Gold Project , 2012 Technical Report, July 31, 2012, Section 17 Recovery Methods.
