Atico Mining's 2024 technical report for the El Roble mine in Chocó, Colombia, describes an established crushing, SAG milling and flotation plant. A flash cell has been moved to the SAG circuit, and a gas-fired concentrate dryer and a tailings dewatering plant have been added.
The El Roble Mine Updated Mineral Resource and Mineral Reserve Estimates report, El Carmen de Atrato, Chocó Department, Colombia, was prepared for Atico Mining Corporation by independent qualified persons. It has an effective date of March 12, 2024 and a report date of June 12, 2024. The plant has a rated nominal capacity of 850 t/d. It crushes and grinds ore to about 80% passing 200 mesh and floats a copper-gold concentrate, which is trucked to the Pacific port of Buenaventura. From January to December 2023, recovery averaged 91.67% for copper and 59.74% for gold, with concentrate grades of 18.41% Cu and 9.67 g/t Au. Mercury is the only penalty element known occasionally to exceed limits. Reagents and dosages have stayed the same for several years.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Report effective date | March 12, 2024 | Not applicable | For Atico Mining Corporation |
| Rated capacity | 850 t/d | Not applicable | Nominal |
| 2023 recovery | Cu 91.67, Au 59.74 | % | January to December 2023 |
| 2023 concentrate grade | 18.41% Cu, 9.67 g/t Au | Not applicable | Contract range 18 to 24% Cu |
| Coarse ore bins | Two of 640 t | Not applicable | 7 x 14 inch grids |
| Crusher | 24 x 36 inch jaw | Not applicable | Bypass chute for fines |
| SAG mill | 18 ft x 6 ft | Not applicable | Closed with D10 cyclones; hammer pebble crusher |
| Grind size | P80 about 120 µm | Not applicable | Cyclone overflow to flotation |
| Flash flotation | SK-240 cell on SAG discharge | Not applicable | Liberated coarse mineral |
| Regrind | 5 ft x 5 ft Otsuka ball mill, 75 hp | Not applicable | Cleaner circuit |
| Concentrate | 30 ft thickener, 8-disc vacuum filter, rotary dryer | Not applicable | About 10% moisture after drying |
| Tailings | Vertical thickener and ceramic disc filter | Not applicable | Dry stack disposal |
| Reagents | Lime 0.723, AP 3477 0.087, AP 318A 0.051 | kg/dmt | Plus Z-6 and MIBC |
Overview
Ore is fed from two coarse ore bins by apron feeders to a jaw crusher, then through a 30 t hopper to the SAG mill. The SAG mill runs in closed circuit with cyclones and a hammer crusher for pebbles. An SK-240 flash cell on the SAG discharge takes liberated coarse mineral. Cyclone overflow is conditioned and floated in OK-20 and OK-24 cells, then OK-8 and OK-14 cells, with Denver DR-100 and Sub-A 24 cleaner banks. Middlings are reground in a small ball mill closed with D-6 cyclones. Concentrate is thickened, vacuum filtered, dried and stored in a shed before trucking. Tailings are thickened and either impounded or filtered for dry stacking.
Key Process Stages
Crushing. Two apron feeders draw from the coarse ore bins onto a 30-inch conveyor that bypasses fines around the jaw crusher. An electronic belt scale records SAG mill feed.
Grinding. The SAG mill discharge grate has 19 by 50 mm openings, followed by a 12 mm trommel. Trommel oversize is crushed to minus 3/8 inch in a hammer crusher and returned. Cyclone underflow returns to the SAG mill.
Flotation and regrind. Conditioned pulp from a 10 by 10 ft conditioner is pumped to the rougher cells. Concentrate from the DR-100 cells and the underflow from the first and second coarse cleaning are cycloned. The cyclone underflow is reground in the Otsuka mill with 1-inch forged balls. The concentrate from the Sub-A 24 second cleaners goes to the concentrate conditioner.
Concentrate handling. A 30 by 10 ft rake thickener feeds a six-foot, eight-disc vacuum filter, which leaves 11 to 13% moisture. A gas-fired rotary dryer brings the cake to about 10%. Sealed, covered trucks haul it to storage at Buenaventura.
Tailings and water. Tailings are thickened in a 5 by 10 m conical vertical thickener, and the overflow is recycled to milling and flotation. A dewatering plant takes the thickened tailings at more than 70% solids and filters them on ceramic discs for dry-stack disposal. This reduces the need for wet storage. A turbidity sensor sends clean filtrate to the process water tank and diverts cloudy filtrate to an effluent tank with an alarm. Decanted water from the tailings impoundment is released to the Atrato River at pH 7.48 to 8.45.
Additional Interesting Data and Summary
Smelter treatment charges are USD 88 per dry tonne. Payables are copper content minus 1.1%, and 95% of contained gold and silver. The sales contract requires 18 to 24% Cu, 4 to 20 g/t Au and 30 to 60 g/t Ag in the concentrate.
In summary, the 2024 El Roble report covers a small, long-running SAG and flotation copper-gold plant at 850 t/d. Recent changes are a relocated flash cell, a concentrate dryer and ceramic disc filtration of tailings for dry stacking.
Key Processes
- Jaw crushing and SAG milling with pebble crushing
- Flash flotation on SAG discharge
- Rougher, scavenger and cleaner flotation with middlings regrind
- Concentrate thickening, vacuum disc filtration and rotary drying
- Tailings thickening, ceramic disc filtration and dry stacking
Source: El Roble Mine Updated Mineral Resource and Mineral Reserve Estimates, El Carmen de Atrato, Chocó Department, Colombia, prepared for Atico Mining Corporation, effective date March 12, 2024.
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.
El Roble Mine — 2023 Technical Report
The El Roble Mine process plant uses conventional crushing, grinding, and flotation to produce a copper-gold concentrate, with a nominal throughput of 850 tonnes per day.
The El Roble Mine process plant is a conventional facility that extracts copper and gold from feed material through a series of sub-processes: crushing, grinding, flotation, concentrate thickening and filtering, and tailings disposal. The plant has a rated nominal throughput capacity of 850 tonnes per day. Before flotation, the ore is ground to 80 per cent passing 200 mesh. Process tailings are deposited in an impoundment facility along the banks of the Atrato River, downstream of the plant, with decanted process waste water released into the river at a pH between 7.48 and 8.45. Over the 12 months from January 2023 to December 2023, average process recovery was 91.67 per cent for copper and 59.74 per cent for gold. The only penalty metal known to the Qualified Person responsible for this portion of the Technical Report that occasionally exceeds maximum limits is mercury. Smelter charges are currently US$88 per dry metric tonne. The concentrate sales contract specifies payables of copper content minus 1.1 per cent, 95 per cent of contained gold, and 95 per cent of contained silver. Contract specifications require copper concentrate grades between 18 and 24 per cent Cu, gold grades between 4 and 20 grams per tonne, and silver grades between 30 and 60 grams per tonne.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Nominal throughput | 850 | tonnes per day | Rated capacity of existing process plant |
| Grinding fineness | 80 | per cent passing 200 mesh | Before flotation |
| Copper recovery (Jan-Dec 2023) | 91.67 | per cent | 12-month average |
| Gold recovery (Jan-Dec 2023) | 59.74 | per cent | 12-month average |
| Smelter charge | 88 | US$ per dry metric tonne | Current |
| Copper payable | 98.9 | per cent | Copper content minus 1.1 per cent |
| Gold payable | 95 | per cent | Of contained gold |
| Silver payable | 95 | per cent | Of contained silver |
| Concentrate filter moisture | 11 to 13 | per cent water | After filtration |
| Target concentrate moisture | Around 10 | per cent | After rotary dryer |
| Tailings feed solids | Greater than 70 | per cent | To dewatering plant |
| Waste water pH | 7.48 to 8.45 | Not applicable | Released to Atrato River |
| Electrical supply | 13,200 | kVA | Three-phase, nominal voltage |
| Recirculated water consumption | 1.30 | m³/dmt | Per dry metric tonne |
Overview
The El Roble process plant is designed to treat copper-gold ore using crushing, grinding, and flotation. The plant uses a SAG mill and ball mill circuit followed by multiple flotation stages. Concentrate is thickened, filtered, dried, and stored on site before shipment by highway truck to the Pacific Coast port of Buenaventura. The flowsheet is considered suitable for the ore type, providing reasonable recoveries of copper and gold. Electrical energy is supplied from the national grid.
Key Process Stages
The crushing circuit comprises a series of bins, feeders, and conveyors. Coarse ore is fed via two coarse ore bins, each with 640 tons effective capacity, through apron feeders onto a conveyor belt system. A jaw crusher with a 24-inch by 36-inch opening is incorporated in the crushing stage. A conveyor feeds a 30-ton storage hopper, and subsequent conveyors feed the SAG mill. An electronic scale on the final conveyor records tonnage entering the SAG mill.
Grinding is performed by a SAG mill with dimensions of 18 feet diameter by 6 feet (200-ML-001), operating in closed circuit. The SAG mill discharge grate has openings of 19 mm by 50 mm, and the trommel screen mesh has 12 mm openings. Classification is completed by a nest of cyclones. Cyclone underflow reports to an Otsuka 5-foot by 5-foot ball mill for further grinding, while cyclone overflow reports to the flotation circuit.
The flotation circuit is a multi-stage arrangement of cells of various styles and sizes. The circuit begins with an OK-20-style flotation cell fed by cyclone overflow. The OK-30-style cell overflow reports to the concentrate thickener, while underflow reports to a bank of two OK-8-style flotation cells. The flotation overflow from these cells reports to the concentrate thickener, and the underflow reports to eight Denver 100-style flotation cells. Cell overflow feeds the final cleaner cells, with cleaner overflow reporting to the concentrate thickener and underflow to the tailings thickener. A flash cell (SK-240) is part of the circuit, with overflow transported by gravity to a 10-foot by 10-foot pulp conditioner and underflow returned to the SAG mill. The circuit also includes a bank of four OK-8 cells and an OK-14 flotation cell, with underflow transported to the concentrate conditioner. Sub-A 24 cells perform second fine cleaning, operating in a closed circuit. Concentrate from the second fine and coarse cleaning is sent to the concentrate conditioner.
Concentrate thickening and filtering remove water from the concentrate. Thickened material reports to a concentrate filter. The filtered material has a moisture content between 11 and 13 per cent water. A rotary dryer tank, operating with a gas burner, reduces moisture to around 10 per cent. Filtered and dried material is conveyed to a concentrate storage shed for secure storage before shipment.
Tailings are processed through a five-meter by ten-meter vertical thickener with a conical base. The thickener overflow is recycled to the ball mill and flotation circuits, while underflow reports to a pump box for pumping to the tailings impoundment. A tailings dewatering plant receives tailings pulps with solids content greater than 70 per cent from the vertical thickener. This plant produces a filtered cake for dry stack tailings disposal, reducing the need for a wet tailings storage facility. The filtered material passes through ceramic discs within the filter drum and is discharged into filter tanks. A filtration skid, comprising a filtration pump, turbidity sensor, and automatic valves, regulates filtration levels and monitors water quality in the process water tank, detecting issues such as broken or detached hoses or ceramic membranes.
Electrical energy is supplied as three-phase power from the national grid at a nominal voltage of 13,200 kVA. The high voltage line is split at the property boundary, with feeds to the process plant, mine, and smaller sub-stations across the property. Recorded electrical energy consumption for the period January to December 2023 includes 371,922 kW for SAG milling, 283,123 kW for flotation, 51,697 kW for tailings, 74,499 kW for filtration, and 86,218 kW for the filtrate dehydration plant.
Process water data from a mass balance at 815 dry metric tonnes throughput indicates total water consumption of 1,780.78 m³ per day, 44.52 m³ per hour, and a water consumption ratio of 2.16 m³ per dry metric tonne. Total water used in the plant, considering 60 per cent water reused from all processes, is 1,068.47 m³ per day, 30,172.15 m³ per month, and 362,065.80 m³ per year. Recirculated water consumption is 1.30 m³ per dry metric tonne.
Additional Interesting Data and Summary
Historical operating data from January to December 2023 provides insight into plant performance, including average copper recovery of 91.67 per cent and gold recovery of 59.74 per cent. The plant's tailings dewatering system enables dry stack disposal, significantly reducing reliance on wet storage capacity. The reported mass balance table provides a detailed breakdown of the processing parameters, highlighting water consumption and recirculation rates.
Key Processes
- Crushing using jaw crusher and conveyor system
- Grinding in SAG mill and ball mill circuit
- Flotation using multiple cell types
- Concentrate thickening, filtering, and drying
- Tailings dewatering for dry stack disposal
Source: El Roble Mine , 2023 Technical Report, 2023.
Note on the report: The report describes the flotation circuit as starting with an OK-20 cell in one passage and with an SK-240 flash cell in another.
Project website: El Roble Mine, 2023 Technical Report
