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
