The Pre-Feasibility Study for the Joanna gold project details a processing flowsheet that relies on the Albion Process for sulphide oxidation, rejecting other oxidation routes due to economic, metallurgical, or environmental constraints.
The 2013 technical report for the Joanna Gold Property, prepared by SGS Canada Inc., presents the findings of a Pre-Feasibility Study for processing ore from the Hosco sector. A key conclusion of the study is that conventional cyanide leaching of a flotation concentrate is not an economically viable processing option for the Hosco ore. Consequently, an evaluation was conducted comparing Conventional Pressure Oxidation (POX) and sulphide oxidation at atmospheric pressure (Albion). The development of flowsheet options incorporated design criteria and assumptions largely based on previous testwork results. The study also evaluated various third-party off-site processing options for either the whole ore or the flotation concentrate. A more thorough comparison of local (onsite contaminated tailing) versus global (transportation risk and impacts) considerations was recommended for the next stage of the study.
The final process flowsheet integrates a primary grinding and flotation circuit at the Joanna site with an Albion Process oxidation and carbon-in-pulp (CIP) circuit at the nearby Casa Berardi operation. The design uses the existing infrastructure at Casa Berardi, assuming the mine will be in operation for at least the same duration as the Joanna project. The existing carbon stripping and gold room at Casa Berardi will require a capacity increase but will be used to process the CIP product from the Hosco material. One new thickener is to be installed in the process plant for dewatering flotation tailings and concentrate, with further testwork required for final sizing and to validate flocculant consumption. Design criteria for the plant include a nominal capacity of 8,500 tonnes per day of dry, run-of-mine ore, operating 365 days per year with 93% equipment utilization. The SAG mill and ball mill were not sized from first principles; instead, used equipment with specifications close to the requirements was deemed available, and plant design was based on incorporating this equipment.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Plant Nominal Capacity | 8,500 | tpd | Dry, run-of-mine ore. |
| Crushing Product Size (P80) | 110,000 | μm | Crusher design criteria. |
| Crushing Feed Size (F80) | ≈ 600,000 | μm | Crusher design criteria. |
| SAG Mill Discharge Size (P80) | 2,000 | μm | Design particle reduction. |
| Ball Mill Feed Size (F80) | 1,000 | μm | Design particle reduction. |
| Ball Mill Discharge Size (P80) | 135 | μm | Design particle reduction, feed to flotation. |
| SAG Mill Dimensions | 8.5 m x 3.7 m (28’ x 12’) | m | Used equipment, 6,000 hp installed, variable speed. |
| Ball Mill Dimensions | 5.0 m x 9.1 m (16 ½’ x 30’) | m | Used equipment, 5,000 hp installed, fixed speed. |
| Crusher Availability | 65 | % | Design criteria. |
| Plant Utilization | 93 | % | Basis for equipment dimensioning and capacities. |
| Flotation Weight Recovery | 5.5 | % | From latest locked cycle test results. |
| Final Flotation Tailings Au Grade | 0.11 | g/t | Constant value based on design criteria. |
| Gravity Concentrate Production | 7.68 | t/d | Estimated, cleaned by three shaking tables. |
| Estimated Overall Gold Recovery | 86.8 | % | With the Albion Process. |
| Albion Process Leach Residence Time | Not stated | h | Design criteria not specified in source. |
| IsaMill Installed Power | 1,500 | kW | Recommended model M3000 based on lab test results. |
| POX Capital Cost | Not stated | Not applicable | Option not retained due to higher capital cost. |
| Nitrox Gold Recovery | >90 | % | Test result from 1987, process not retained. |
| Roasting Gold Recovery | Not stated | % | Not effective for arsenic-bearing ore. |
| Geocoat® Operating Temperature | 5 to 80 | °C | Mesophiles (5 to 65°C) or thermophilics (45-80°C), not suited for Nordic climate. |
Project website: https://www.mining.com/aurizon-increases-hosco-in-pit-measured-and-indicated-mineral-resources-by-31-at-joanna/
Overview
The Joanna Gold Property Pre-Feasibility Study details a processing strategy that was revised after test results confirmed that direct cyanide leaching of a flotation concentrate was not economically viable. The study compares different oxidation technologies and selects the Albion Process for the project. The design incorporates a combination of onsite crushing, grinding, and flotation with offsite oxidation and gold recovery at the Casa Berardi facility. The overall design criteria, equipment specifications, and metallurgical assumptions are presented, with a noted estimated overall gold recovery of 86.8% for the proposed flowsheet. The study relies on a range of data sources, including client information, testwork, calculations, mass and water balances, suppliers, literature, in-house data, BBA assumptions, and available used equipment specifications.
Key Process Stages
The processing flowsheet is divided into several key stages. An onsite crushing and grinding circuit, featuring a SAG mill and ball mill, prepares the ore for flotation. The flotation circuit produces a concentrate with a 5.5% weight recovery, with tailings containing a constant 0.11 g/t Au. The concentrate is then processed at the Casa Berardi site using the Albion Process, a sulphide oxidation method, followed by a CIP circuit for gold recovery.
Crushing and Grinding: The primary crusher is designed to produce a product with a P80 of 110,000 μm from a feed with an F80 of approximately 600,000 μm. The grinding circuit includes a SAG mill (8.5 m x 3.7 m) and a ball mill (5.0 m x 9.1 m), both being used equipment. The design criteria specify a particle reduction from an F80 of 110,000 μm to a P80 of 2,000 μm for the SAG mill and from an F80 of 1,000 μm to a P80 of 135 μm for the ball mill. SAG mill specific energy consumption was estimated from SMC and Bond Ball Mill Grindability tests.
Gravity and Flotation: A gravity concentrator is included, producing an estimated 7.68 tonnes of concentrate per day, which is cleaned using a circuit of three shaking tables. The unrecovered weight fraction from the tables reports to the flotation concentrate thickener. The design favored longer flotation residence times over a finer grind to achieve target gold recovery. Cyclones are sized to produce a flotation feed with a P80 of 135 μm, with further work required to determine the accurate separation and particle size for the gravity concentrator.
Albion Process and Gold Recovery: The flotation concentrate is treated at Casa Berardi using the Albion Process. Based on laboratory test results, Xstrata Technology recommends a model M3000 IsaMill with an installed power of 1,500 kW for this step. Following oxidation, the gold is recovered in a CIP circuit. The retention time for the adsorption circuit was determined based on literature, typically stated as 0.75 to 1.0 hour per stage with 5 to 7 stages. The existing carbon stripping and gold room at Casa Berardi will require capacity increases to process the CIP product.
Additional Interesting Data and Summary
The selection of the Albion Process was influenced by the rejection of other oxidation methods. POX was not retained due to its higher capital cost despite comparable metallurgical results. Roasting was not retained, as it is not effective for ores containing arsenic, which is the case for Joanna. The Geocoat® process was not retained due to its unsuitability for a Nordic climate and potential environmental permitting issues with leach pads. The Nitrox process, while showing an encouraging gold recovery above 90% in a 1987 test, was not retained due to its complexity and high cost. Activox® was not retained, with test results showing a poor gold recovery of 40%.
Recent testwork results were used to establish a key design assumption that the final flotation tailings gold content is a constant 0.11 g/t Au. The design for the Albion Process was based on the acidic version, and preliminary testwork results supported this assumption. A relationship between overall gold recovery and head grade was established based on the design criteria. The overall gold recovery for the process is estimated at 86.8%. Further testwork is still required to confirm the recovery value and to finalize the sizing of thickeners and flocculant consumption.
Key Processes
- Crushing and grinding to a P80 of 135 μm using used SAG and ball mills.
- Gravity concentration with a concentrate production of 7.68 t/d cleaned by three shaking tables.
- Flotation with a weight recovery of 5.5%, with tailings grade set at 0.11 g/t Au.
- Sulphide oxidation via the Albion Process, using a model M3000 IsaMill with 1,500 kW installed power.
- Gold recovery via a carbon-in-pulp (CIP) circuit at the Casa Berardi site, with 0.75 to 1.0 h retention per stage.
- Alternative oxidation processes (POX, Roasting, Geocoat®, Nitrox, Activox®) were evaluated and not retained.
Source: Joanna Gold Property , 2013 Technical Report, 2013.
Project website: Joanna Gold Property, 2013 Technical Report
