Endeavour Mining's March 2016 resource and reserve update for the Tabakoto gold mine in Mali, effective December 31, 2015, describes a SAG mill added in series with the existing ball mill, three Falcon concentrators and a Gekko intensive leach reactor.
The Technical Report, Mineral Resource and Reserve Update for the Tabakoto Gold Mine, Mali, was prepared for Endeavour Mining Corporation with an effective date of December 31, 2015 and a report date of March 16, 2016. Since a plant expansion completed in 2013, the Tabakoto mill is designed for 4,000 t/d. Its flowsheet is crushing, ore stockpiling, milling and classification, gravity concentration with an in-line leach reactor (ILR), carbon-in-leach (CIL), tailings disposal, acid wash, elution, electrowinning and a gold room.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Report effective date | December 31, 2015 | Not applicable | Endeavour Mining Corporation; report date March 16, 2016 |
| Design throughput | 4,000 | t/d | After the 2013 expansion |
| Jaw crusher | 1,250 x 950 mm Sandvik | Not applicable | CSS 110 mm; up to 400 t/h |
| SAG mill | 6.1 x 8.46 m Polysius, 5 MW | Not applicable | Design 4,200 t/d |
| Ball mill | 4.75 x 7.92 m, 2.4 MW | Not applicable | Ten 15 inch Krebs cyclones |
| Grind | P80 75 | µm | Not applicable |
| Gravity share of production | About 48 | % | 72% of cyclone underflow treated |
| CIL | 11 tanks, 48 h | Not applicable | Three 2,155 m³ and eight 785 m³ tanks |
| Elution | 2 t and 3 t columns | Not applicable | 130°C, 3% caustic; about 96% efficiency |
| Carbon movement | About 3.5 | t/d | Not applicable |
| Sodium cyanide | 0.60 | kg/t | Lime about 2.0 kg/t, grinding media about 2 kg/t |
| Water source | Falémé River, 18 km | Not applicable | 100% process water recycle |
Overview
The expansion added a SAG mill in series with the existing ball mill, a second pre-leach thickener, three large CIL tanks, a second elution column and an enlarged gold room. Gravity recovery is very sensitive to feed grade and contributes about 48% of the mine's gold production. Elution contributes about 52%.
Key Process Stages
Crushing and stockpile. A front-end loader feeds run-of-mine ore through an 800 by 800 mm grizzly into a 150 t live ROM bin. A 1.8 by 6 m apron feeder feeds a 1,250 by 950 mm Sandvik single-toggle jaw crusher, designed for a 120 mm closed side setting but run at 110 mm, at up to 400 t/h. The product is stockpiled ahead of the SAG mill and reclaimed by three apron feeders under feed-rate control.
Milling. A 6.1 by 8.46 m Polysius SAG mill with a 5 MW motor, rated at 4,200 t/d, runs in closed circuit with a scalping screen at 50 to 150% circulating load. The 4.75 by 7.92 m ball mill (2.4 MW) is closed with ten 15 inch Krebs hydrocyclones, giving P80 75 µm to leach.
Gravity. About 28% of the cyclone underflow passes a scalping screen and one Falcon concentrator to a Gemini shaking table. About 44% passes the two other Falcon SB2500 concentrators to a Gekko 2000BA ILR, which has a dedicated electrowinning cell. The rest of the underflow returns to the ball mill.
Thickening. A trash screen modified for 5,000 t/d feeds two 86 t/h pre-leach thickeners in parallel. They raise the slurry from 22% to 50% solids, each feeding the leach at 118 m³/h.
CIL. Three new 2,155 m³ tanks run in series with eight 785 m³ tanks, giving 11 tanks and a 48-hour retention time. Each adsorption tank has a 4 m² Kemix MPS400P inter-stage screen and a carbon transfer pump, and plant air is injected through the agitators.
Elution and regeneration. The original 2 t stripping column was kept as a stand-alone unit, and a new 3 t column was added to handle about 3.5 t/d of carbon. The two share a boiler system of two Ansac thermic oil boilers at 300°C. Desorption runs at 130°C with 3% caustic, in two batches a day, at about 96% elution efficiency. A diesel Ansac kiln reactivates carbon at 200 kg/h and 700 to 800°C, 11 hours per batch.
Gold room. Two electrowinning cells were added for ILR solution, along with a diesel furnace, a filter for ILR concentrate and an electric calcining oven. Calcining and smelting use borax, nitre, silica and soda ash fluxes.
Tailings. Fraser Alexander runs the paddock-type tailings storage facility, in which settled, dried tailings build each new decant cell. Decant water returns to the mill through a penstock and holding pond. The facility was expanded for the larger plant, with tailings split at 2,000 t/d to each containment area.
Additional Interesting Data and Summary
Tabakoto does not recover cyanide. The report says ultraviolet light destroys about 90% of the cyanide reaching the tailings facility, and a peroxide and copper sulphate treatment facility is available. The mill recycles 100% of its process water, with evaporation losses of about 50%. Underground dewatering adds to the raw water ponds. Power comes from the mine's own diesel station of 19 Cummins alternators. The SAG mill uses 100 and 120 mm balls and the ball mill 40 and 60 mm, and carbon consumption is 50 g/t.
In summary, the expanded Tabakoto plant is a 4,000 t/d SAG-ball and CIL mill with an unusually strong gravity circuit that delivers nearly half the gold, backed by doubled elution capacity and an 11-tank, 48-hour CIL.
Key Processes
- Jaw crushing and stockpiling with apron feeder reclaim
- SAG milling with scalping screen and ball milling with cyclones to P80 75 µm
- Falcon gravity concentration with Gemini table and Gekko ILR
- Pre-leach thickening to 50% solids
- 11-tank CIL with 48-hour retention
- Acid wash, two-column caustic elution and kiln regeneration
- Electrowinning, calcining and smelting
- Paddock tailings storage with full water recycle
Source: Technical Report, Mineral Resource and Reserve Update for the Tabakoto Gold Mine, Mali, Endeavour Mining Corporation, effective date December 31, 2015.
Earlier report summaries
Earlier versions of this profile, based on older technical reports, are retained below for source traceability. Dates and figures reflect each report’s own effective date and are superseded by the current information above.
Tabakoto Mining Operations Report No. 217
Avion Gold Corporation's Tabakoto mine in Mali operates a 750,000 tonnes per year gold processing plant that was being expanded to double its feed rate by 2012.
The Tabakoto mine hosts a process plant that produces gold bullion from ore sourced from Avion Gold Corporation's deposits held by Tamico and Semico, with a nominal capacity of approximately 750,000 tonnes per year. The existing crushing and grinding circuit comprises a jaw crusher, secondary and tertiary cone crushers, and a ball mill operating in closed circuit with hydro-cyclones. The hydro-cyclone underflow is directed to a gravity circuit to recover liberated gold, with the remaining material returned to the ball mill. Concentrates from the gravity circuit are calcined and smelted for gold recovery. Historically, the plant achieved recovery rates of up to 96.5% for certain open pit ore types, and a 92% recovery for underground ore due to fine grained gold inclusions not amenable to cyanidation. A major expansion project was initiated in August 2010 to increase plant throughput from 2,000 to 4,000 tonnes per day.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Existing Plant Capacity | 750,000 | tonnes per year | Nominal throughput capacity |
| Historical Throughput (2009) | 562 | thousand tonnes | Actual milled tonnes |
| Historical Throughput (2010) | 706 | thousand tonnes | Actual milled tonnes |
| Head Grade (2009) | 2.95 | g/t Au | Actual |
| Head Grade (2010) | 4.02 | g/t Au | Actual |
| Overall Recovery (2009) | 95.5 | % | Actual |
| Overall Recovery (2010) | 96.5 | % | Actual |
| Gravity Recovery (2010) | 69.7 | % | Actual; 64.5% in 2009 |
| Recovered Ounces (2010) | 87,630 | oz | Actual; 51,290 in 2009 |
| Expanded Plant Throughput | 1,460 | thousand tonnes per year | Projection for 2013 onwards |
| Expanded Overall Recovery (2013 onwards) | 94.0 | % | Projected |
| Expanded Recovered Ounces (2013 onwards) | 200,000 | oz | Projected |
Project website: https://globalnews.ca/news/210645/avion-gold-starts-production-at-new-tabakoto-gold-mine-in-mali-west-africa/
Overview
The expansion project aimed to increase the processing plant's throughput from 2,000 to 4,000 tonnes per day. The original facility treated ore to produce gold bullion, with historical overall recovery reaching 96.5%. The expansion sought to maintain high recovery while doubling feed capacity, necessitating modifications across every stage of the plant, from crushing through to the refinery. Projected performance indicated that the plant would mill 1,460,000 tonnes in 2013 onwards, with an overall recovery of 94.0% and 200,000 recovered ounces.
Key Process Stages
Crushing and Grinding
The expansion required modifying the current crushing configuration to prepare feed for both the new and existing stockpiles. A new 5,000 kW SAG mill was installed to operate in closed circuit with the existing ball mill, allowing for a unique feature where the plant could return to the pre-expansion circuit during SAG mill maintenance, ensuring production continued at a reduced rate. The ball mill final product was specified to have a P80 of 74 microns.
Gravity Concentration
The existing tabling circuit was identified as insufficient for the increased throughput and was to be replaced by an Intense Leach Reactor (ILR). This high intensity cyanidation process runs in a batch mode to process the increased volume of gravity recoverable gold. A new gravity tower was required, complete with a new cyclone cluster, scalping magnet, scalping screen, and two Falcon gravity concentrators. Dedicated electro-winning cells were also installed to handle the ILR concentrate.
Trash Screen and Thickening
The current trash screen retained sufficient capacity for a 5,000 tpd flow rate, but required modifications. The existing thickener lacked the capacity for the 4,000 tpd rate, so a second thickener with underflow pumps was installed, which required relocating the current mill entrance and security clearance area.
CIL and Leaching
To maintain a 48 hour retention time, the CIL system was expanded with four additional tanks: three large 1,630 m³ leach tanks and one 830 m³ CIP tank. This was designed to give a total circuit residence time of 46 hours at a nominal feed rate of 186 tonnes per hour. The discharge from the third leach tank would be split to feed two trains of four tanks, effectively providing 26 hours of retention time in each train at a 2,000 tpd flow rate.
Elution and Refinery
The current elution system was not capable of handling increased production. The existing two tonne carbon stripping circuit was left as a standalone unit while a new three tonne standalone elution column was installed, with both columns sharing the existing boiler system. A larger capacity electro-winning cell was installed to accommodate higher gold loading, with the two older cells kept as redundant. The refinery furnace was replaced with a larger unit to handle increased gold flows.
Infrastructure
The power supply was increased by 6,000 kW, bringing total expanded power requirements to 10,000 kW. A new power house with a series of diesel powered generators rated at 22,000 kW was built to supply all mine site power needs.
Additional Interesting Data and Summary
The expansion project was projected to significantly increase recovered ounces from 100,000 in 2011 to 160,000 in 2012 and 200,000 in 2013 onwards. Projections were based on historical data which showed the plant processing 562,000 tonnes at a head grade of 2.95 g/t Au with 95.5% recovery in 2009, and 706,000 tonnes at 4.02 g/t Au with 96.5% recovery in 2010. The report indicates a planned expanded throughput of 1,460,000 tonnes annually with a head grade of 4.55 g/t Au for 2013 onwards. The plant was configured to maintain production during expansions and modifications, with construction and commissioning planned to avoid significant impact to ongoing operations.
Key Processes
- Crushing with jaw, secondary, and tertiary cone crushers
- Grinding with a ball mill in closed circuit with hydro-cyclones
- Gravity concentration with Falcon concentrators and tabling
- High intensity cyanidation in an Intense Leach Reactor (ILR)
- Carbon-in-leach (CIL) with six tanks in two trains
- Carbon elution with a standalone three-tonne column
- Electrowinning and refining for gold bullion production
Source: Tabakoto Mining Operations Report No. 217, 2011. Project website: Avion Gold Corporation.
Project website: Tabakoto Mining Operations Report No. 217
