This report describes the conventional sulphide flotation processing route at Perkoa Mine, the associated historical plant performance from 2013 to 2017, and the life-of-mine production and consumables plan.
Report context
This technical report on the Perkoa Mine, Project #2926, was prepared for Trevali Mining Corporation and is dated April 12, 2018. It provides an integrated description of the mine's processing facilities, including the current operating configuration, historical metallurgical performance, and planned production parameters over the life of mine.
Processing route
Crushing and screening
The process plant at Perkoa is a conventional sulphide flotation facility with a design capacity of 2,000 tpd. Run-of-mine ore is fed through a grizzly to a primary jaw crusher at approximately 150 tph. The crusher product is sent to a secondary cone crusher circuit operating in closed circuit with a screen splitting at 10 mm. Screen oversize (+10.0 mm) is returned to the cone crushers, while undersize (−10.0 mm) is directed to the mill feed stockpile.
Grinding and classification
From the stockpile, the ball mill (measuring 10.5 ft x 16 ft) is fed at 85 tph to 88 tph solids, depending on variations in mineral hardness. The ball mill operates in closed circuit with cyclones to produce a flotation feed with a minimum of 60% of the cyclone overflow passing 200 mesh (75 μm).
Flotation and regrinding
Flotation feed passes through a conditioner where reagents,hydrated lime, copper sulfate (CuSO₄), xanthate, and frother,are added before entering rougher tank cells. High-grade concentrate from the first three roughers is sent to final concentrate, while lower-grade concentrate from the last rougher is routed to the cleaner circuit. Rougher tailings proceed to a scavenger circuit, where concentrate from the first two scavenger cells reports to final concentrate, and concentrate from the remaining scavenger cells is sent to the regrinding circuit. Cyclone overflow from regrinding also reports to the cleaner/scavenger circuit. Concentrate from the first three cleaning cells is collected as final concentrate; cleaner/scavenger concentrate recycles to the head of the cleaning circuit, and cleaner tails combine with rougher tails to feed the scavenger circuit. Scavenger tailings report to final tailings.
Dewatering and product handling
Final concentrate is thickened and dewatered using a Larox pressure filter. Filter cake is discharged onto a drying floor, dried, stockpiled, and then loaded into trucks for dispatch to the port of Abidjan, Côte d’Ivoire, a haul distance of 1,200 km. In 2017, 178,756 wet metric tonnes (wmt) were shipped in 4,157 truck trips (about 11 trucks per day, 45 t per truck); a round trip took seven days due to border delays between Côte d’Ivoire and Burkina Faso. Trucks backhaul clinker for the local cement market.
Historical plant performance
From 2013 to 2017, the plant processed a total of 2,805 thousand tonnes of ore grading 13.1% Zn on average. Annual zinc recovery ranged from 89.3% to 96.7%. Concentrate grade varied from 50.6% Zn to 53.0% Zn, with contained zinc metal totalling 340.1 thousand tonnes over the period. Availability improved from 75.2% in 2015 to 90.2% in 2017. The concentrate was considered “clean,” with only small penalties for mercury and iron.
Life-of-mine production schedule
The life-of-mine plan (2018–2022) projects total processed tonnage of 3,329 thousand tonnes at an average of 1,903 t/d. Planned zinc head grade averages 13.1% Zn, with recovery of 93.3%. Concentrate production is planned at 764.4 thousand tonnes grading 52.8% Zn, for 405.4 thousand tonnes of contained zinc metal and 344.0 thousand tonnes of payable zinc metal.
Major consumables and energy
The report lists annual life-of-mine consumables, including grinding balls (1" and 2½"), methyl isobutyl carbinol (MIBC), copper sulphate, sodium isopropyl xanthate (SIPX), Orifloc 4014 and 1024, and hydrated lime. Energy demand is given as 18.9 kW/t for mine, 37.8 kW/t for mill, and 6.3 kW/t for surface, totalling 63.0 kW/t annually (42,450 MW/year). The report states all consumables are readily available and that the mine has ample water supply.
Key reported parameters
| Parameter | Unit | Value | Basis |
|---|---|---|---|
| Plant design capacity | tpd | 2,000 | Design |
| Current throughput | tpd | ~1,900 | Actual |
| ROM crusher feed | tph | ~150 | Actual |
| Ball mill feed | tph | 85–88 | Actual |
| Grind size (cyclone overflow) | % passing 75 μm | 60 (minimum) | Design/actual |
| Screen split size | mm | 10 | Design |
| Zinc head grade (2013–2017) | % Zn | 6.3–15.2 | Historical |
| Zinc recovery (2013–2017) | % | 89.3–96.7 | Historical |
| Concentrate grade (2013–2017) | % Zn | 50.6–53.0 | Historical |
| LOM recovery (2018–2022) | % | 93.3 | Planned |
| LOM concentrate grade | % Zn | 52.8 | Planned |
| Concentrate haul distance | km | 1,200 | Actual |
| Concentrate shipments (2017) | wmt | 178,756 | Actual |
| Truck trips (2017) | trips | 4,157 | Actual |
| Trucks per day | # | ~11 | Actual |
| Round trip duration | days | 7 | Actual |
Project website: https://miningdataonline.com/property/3024/Perkoa-Mine.aspx
Technical qualifications
The report presents historical plant performance and life-of-mine projections on stated assumptions, but several qualifications should be noted. The original lead recovery circuit is no longer in service, and its reconfiguration is described qualitatively without detailed process design data. Grind size is defined as a minimum (P₆₀ 75 μm), and actual achieved values are not given. Annual availability is only provided for 2015–2017, with no figures for 2013–2014. The life-of-mine schedule and consumables are forward-looking estimates based on planned head grades and recoveries; actual performance may vary with ore hardness, mineralogy, and reagent behaviour. The haulage description includes operational challenges such as border delays and port congestion, which affect logistics but are not quantified in cost terms. The report does not provide a detailed mass balance or metallurgical accounting for the proposed design beyond historical and planned annual figures.
Source: Perkoa Mine, Technical Report NI 43-101, Project #2926, Trevali Mining Corporation, April 12, 2018, Section 17 Recovery Methods.
