The Mana processing plant is designed with a nominal capacity of 4,000 mtpd, with reported expansions achieving up to 7,200 tpd in bedrock feed and 8,000 tpd in a saprolite/bedrock blend, underpinned by crushing, SAG and pebble crushing, and secondary ball milling stages.
Report context
The Mana Property technical report, dated 2012, presents a reserve and resource update for the project in Burkina Faso. The following processing description shows the plant configuration as of the report date, based on information provided by Sylvain Duchesne, P.Eng., General Manager of Construction and Engineering. All stated capacities and equipment details are drawn solely from this 2012 document.
Processing route
Introduction and overall flowsheet
Gold at Mana is recovered through a metallurgical plant with a nominal capacity of 4,000 mtpd. The report states the plant underwent various expansion stages, reaching throughput up to 7,200 tpd in bedrock and 8,000 tpd in a blend of saprolite and bedrock. The document notes that, to date, current plant capacity always exceeded expectations. The processing route comprises primary crushing, SAG milling with pebble crushing and screening, and secondary ball milling, followed by a CIL circuit.
Crushing and stockpiling
Run-of-mine (ROM) ore is loaded by a WA600 front-end loader onto a static grizzly screen to handle slabby material. A rock breaker reduces oversize material remaining on the static screen, which measures 625 mm by 665 mm. Fine material drops into a 150-tonne capacity ROM bin. Ore is extracted from the bin by a primary apron feeder (1,524 mm by 7,000 mm) and fed to a vibrating scalper (1,500 mm by 4,000 mm) to further separate fines. Coarse material from the scalper feeds directly into a 36-inch by 48-inch (950 mm by 1,250 mm) single-toggle jaw crusher.
The jaw crusher produces a product with a P80 of 100 mm at a rate of 400–500 wtph, allowing for a 17-hour-per-day crushing operation. This schedule permits regular daily maintenance of the crushing plant. The jaw crusher handles ROM ore with a maximum lump size of F100 of 665 mm. Fines from the scalper discharge directly onto a conveyor belt. Primary crushed material is transferred onto a 48-inch conveyor belt, where a scale maintains constant throughput. A magnet at the head pulley removes trash steel.
Ore is then transferred onto a mobile stacker conveyor, which stockpiles around 25,000 to 30,000 tonnes of crushed ore. Stockpiled ore is withdrawn by two apron feeders in parallel (4,500 mm by 900 mm each), each handling about 200 tph of crushed ore, and drops onto the mill feed conveyor. Ore is weighed again to maintain steady throughput into the grinding circuit. Hydrated lime is added from a dry lime system onto the mill feed conveyor belt for CIL circuit pH control, maintained at pH 10.5.
Grinding and classification
The grinding circuit comprises a semi-autogenous grinding (SAG) mill in closed circuit with a vibrating screen and a pebble crusher. The SAG mill is a 7.92-meter-diameter by 2.74-meter Allis Chalmers unit equipped with a 2,387 kW variable-speed motor and operates with 10–15% ball charges depending on ore hardness. Variable-speed control provides flexibility for processing various ore types.
Discharge from the SAG is split between fine and coarse material. Coarse material (greater than 15 mm) is crushed in closed circuit by a pebble crusher (HP200) and returned to the SAG for further grinding. Fine material (less than 15 mm) is pumped to a vibrating screen (2.1 meters by 5.2 meters). The screen uses 9.5/3.2 mm slotted aperture panels. Oversize material returns to the SAG mill, while undersize material reports to the secondary ball mills discharge pump box. The report cites a circulating load for the SAG of around 50–60% (fine plus coarse) and a product size P80 of around 1,200–3,500 μm, depending on throughput.
Secondary grinding is performed by two open-discharge ball mills. One is a 5.3-meter-diameter by 7.0-meter Outotec mill equipped with a 3,500 kW variable-speed motor, controlled through a liquid resistance starter and heat exchanger system. The original report text is cut off mid-sentence, and no further details on the second ball mill are provided in the available evidence.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Nominal plant capacity | 4,000 mtpd | Design |
| Throughput, bedrock | Up to 7,200 tpd | Historical operating data |
| Throughput, saprolite/bedrock blend | Up to 8,000 tpd | Historical operating data |
| Jaw crusher product size (P80) | 100 mm | Design |
| Jaw crusher feed rate | 400–500 wtph | Design |
| Crushing operation schedule | 17 hours per day | Design |
| ROM bin capacity | 150 tonnes | Design |
| Static grizzly openings | 625 mm x 665 mm | Design |
| Scalper size | 1,500 mm x 4,000 mm | Design |
| Jaw crusher type | 36" x 48" (950 x 1,250 mm) single toggle | Design |
| ROM maximum lump size (F100) | 665 mm | Design |
| Stockpile capacity | 25,000–30,000 tonnes | Design |
| Apron feeders under stockpile | 2 units, 4,500 mm x 900 mm, each ~200 tph | Design |
| SAG mill diameter | 7.92 m | Design |
| SAG mill length | 2.74 m | Design |
| SAG motor power | 2,387 kW | Design |
| SAG ball charge | 10–15% | Design/operating |
| Pebble crusher | HP200 | Design |
| Vibrating screen size | 2.1 m x 5.2 m | Design |
| Screen apertures | 9.5/3.2 mm slotted | Design |
| SAG circulating load | 50–60% | Operating data |
| SAG product size (P80) | 1,200–3,500 μm | Operating data |
| Secondary ball mill (Outotec) dimensions | 5.3 m diameter x 7.0 m | Design |
| Secondary ball mill motor power | 3,500 kW | Design |
| CIL pH setpoint | 10.5 | Design/operating |
Project website: https://manaproperty.in/
Technical qualifications
The 2012 report provides a description of the plant as of its date, but several limitations must be noted. The report does not include any recovery or metallurgical performance data, such as gold recovery rates or plant availability figures. It does not present a mass balance, water balance, or detailed process design criteria beyond the equipment sizes and throughputs listed. The description is provided by a company general manager, but the report does not specify any testwork that generated the stated capacities; the figures for 7,200 tpd and 8,000 tpd are presented as achieved operating rates rather than results of a formal testwork program. The original report text ends mid-sentence in the secondary grinding section, so any details on the second ball mill, leach circuit, tailings, or ancillary systems are not available from the supplied evidence.
Source: “Mana Property , 2012 Technical Report,” Advanced Technical Report, Mana Property, Burkina Faso, Reserve and Resource Update, page 132, Section 17- Recovery Methods.
