This report details the process design, equipment selection, and operating performance of the Ada Tepe gold-silver processing facility, based on the 2023 NI 43-101 technical report update.
Report context
The Ada Tepe Mine 2023 Technical Report provides a mineral resource and mineral reserve update for the operation. The processing facility was commissioned in April 2019 and achieved nameplate production in September 2019. The process plant produces a gold-silver bearing concentrate for shipment to a smelter. This article summarises the recovery methods, design basis, and documented plant performance from the report.
Processing route
Comminution and classification
The original 2012 mining study design evaluated treatment rates of nominal 0.85 Mtpa and 1.1 Mtpa, with a flowsheet including a relatively fine primary grind at P80 of 30 µm. The final design, based on trade-off studies completed during 2012 and a process design review in April 2013, selected a single-stage SAG mill in closed circuit with cyclones producing a product at P80 of 125 µm, followed by two stirred mills operating in parallel. The SAG mill is a 6.71 m diameter by 3.96 m effective grinding length unit equipped with a 3,000 kW variable speed drive motor.
Primary crushing reduces ROM ore to a design P80 of 110 mm, with crushed ore stored in a coarse ore bin providing 24 hours live capacity. The crusher is designed to operate 12 hours per day at 80% utilisation for a throughput rate of 263 dry tph. A 3,000-tonne capacity surge silo is located between the crushing and grinding circuits. SAG mill discharge is screened via a trunnion-mounted trommel, with pebbles directed to a Sandvik CH420 cone crusher for recycle. The SAG mill operates with a ball charge envelope of 6% to 15% by volume.
Primary classification uses six 400 mm hydrocyclones (four operating). Cyclone overflow reports to a vibrating trash screen, then to a bank of twelve 250 mm hydrocyclones (nine operating). The overflow at design P80 of 30 µm feeds the rougher flotation circuit. Underflow is gravity transferred to two Metso Vertimill regrind mills (932 kW installed each) operating in parallel, with discharge recycled to the classification feed in closed circuit.
Flotation circuit
The flotation flowsheet was developed from an extensive test program and subsequent circuit modelling. During design trade-off studies, the conventional mechanically agitated tank cell design was compared with the Woodgrove Technologies Staged Flotation Reactor. Site layout restrictions and claimed advantages including reduced floor area (approximately 30% of the conventional footprint) led to selection of the SFR design.
The flotation circuit comprises the following stages:
- Rougher flotation with a conditioning tank and four SFRs in series
- Scavenger flotation with four SFRs, with concentrate recycled to the rougher circuit head and tail directed to final tailings thickening
- Concentrate regrind classification using five 150 mm hydrocyclones (two operating), with underflow to a Metso stirred media detritor regrind mill (355 kW installed) in closed circuit; overflow at design P80 of 15 µm feeds the cleaner 1 circuit
- Cleaner 1 flotation with two SFRs in series, with concentrate forming 50% of the final concentrate stream
- Cleaner scavenger flotation with five SFRs, with concentrate to the cleaner 2 circuit and tails recycled to the rougher conditioning tank
- Cleaner 2 flotation with four SFRs, with concentrate combined with cleaner 1 concentrate to form final concentrate
Tailings and concentrate handling
The 4 m diameter high-rate concentrate thickener receives combined cleaner 1 and cleaner 2 concentrates. Final concentrate is dewatered to a design moisture content of approximately 20% using an automated vertical plate pressure filter and packaged in a semi-automated bagging and weighing unit.
Final scavenger tail is transferred to a 16.5 m diameter deep cone tailings thickener fitted with an underflow shearing system. Thickened underflow at a design density of 56% solids is directed to one of two on-site integrated mine waste facilities for co-deposition with mine waste.
Reagent scheme
Several reagents are used to enhance flotation characteristics:
- Copper sulphate activator
- Potassium amyl xanthate collector
- Aero 238 promoter, to be replaced with Aero 208 or similar in 2020 due to EU restrictions
- Cytec F-549 frother
- Sodium silicate dispersant
Process control
The facility is controlled by a process control system located in a central control room with closed circuit monitoring cameras and database historian systems. Following steady state production, several optimisation initiatives have been implemented:
- On-stream gold analysis for flotation streams commissioned in Q4 2020
- Advanced process control and automation implemented phase by phase during 2020 through 2022
- A geometallurgical clay model deployed in 2022
- A digital twin model commissioned in 2022
Key reported parameters
| Parameter | Unit | Design value | Basis |
|---|---|---|---|
| Maximum annual ore throughput | tpa | 850,000 | Design |
| Design gold recovery | % | 85.0 (range 83.5–88.7) | Design, master composite |
| Design silver recovery | % | 70.0 (range 54.6–77.8) | Design, master composite |
| Primary grind size | µm P80 | 30 | Design |
| Concentrate regrind size | µm P80 | 15 | Design |
| Plant availability | % | 91.3 | Design |
| Grinding circuit throughput | tph | 105 (≈99% Upper Zone) to 90 (≈36% Wall Zone) | Design |
| Design feed grade, Upper Zone | g/t Au | 3.7 | Design |
| Design feed grade, Wall Zone | g/t Au | 6.7 | Design |
| Design concentrate grade | g/t Au | 380–440 | Design |
| Operating power consumption | kWh/t | 45.5 | Actual to date |
| Freshwater consumption | m³/t | 0.150 | Actual, expected to remain in range over LOM |
Project website: https://dpmmetals.com/
Project website: https://miningdataonline.com/property/261/Ada-Tepe-Mine.aspx
Actual annual plant performance from commissioning:
| Year | Plant utilisation (%) | Throughput (tpa) | Feed grade (g/t Au) | Recovery (% Au) | Concentrate grade (g/t Au) | Gold produced (oz) |
|---|---|---|---|---|---|---|
| 2019 | 68.9 | 400,891 | 4.90 | 85.91 | 692 | 54,253 |
| 2020 | 94.6 | 890,738 | 4.92 | 84.35 | 623 | 118,754 |
| 2021 | 96.4 | 865,587 | 5.75 | 83.16 | 570 | 133,028 |
| 2022 | 96.4 | 852,990 | 4.06 | 84.35 | 523 | 93,940 |
Ore physical characteristics differ significantly between the two ore types. The Wall Zone material is harder and more competent, with higher impact work index (16.1 versus 12.5 kWh/t), rod mill work index (22.8 versus 16.1 kWh/t), and ball mill work index (20.0 versus 17.0 kWh/t). The Wall Zone represents approximately 20% of total mined tonnes but approximately 33% of total feed gold content.
Technical qualifications
The report notes that the design criteria for LOM tonnage are as of 21 March 2014. Design recovery figures are based on master composite testwork and range from 83.5% to 88.7% for gold and 54.6% to 77.8% for silver. The grinding circuit design adopted a variable throughput range depending on the proportion of Wall Zone material in the feed, varying for every month of operation over the mine life.
Commissioning occurred in April 2019 with nameplate production achieved in September 2019. The report states that actual plant performance to date supports assumptions used in the current mineral resource and reserve estimate. Optimisation initiatives to reduce consumption rates may be offset by blending Wall Zone material, which has greater hardness, abrasiveness, and higher gold grade.
Source: NI 43-101 Technical Report, Mineral Resource and Mineral Reserve Update, Ada Tepe Mine, Section 17 Recovery Methods.
