This technical report outlines the proposed processing route for the Strange Lake project, from mine-site beneficiation to rare earth and yttrium oxide recovery.
Report context
The 2014 Technical Report describes a preliminary economic assessment (PEA) for the Strange Lake project. The proposed processing scheme involves mine-site crushing, grinding, and flotation to produce a concentrate, which would then be transported to a separate hydrometallurgical facility for rare earth and yttrium recovery. The report presents design criteria, estimated production ranges, and metallurgical recoveries derived from testwork.
Processing route
Overview of Proposed Recovery Methods
Mineral resources for the Strange Lake project will be mined and beneficiated to recover a flotation concentrate at the Strange Lake site. The flotation concentrate will be transported by truck to the port at Edward’s Cove, where it will be loaded onto ships and transported to the processing facility at the Bécancour Industrial Park for recovery of rare earths and yttrium.
Processing at Strange Lake will comprise crushing, grinding and beneficiation by flotation. Processing at Bécancour will include acid thermal processing (acid bake) and water leaching to extract the payable elements into solution, followed by hydrometallurgical precipitation to recover the rare earth elements and yttrium into a mixed REE+Y concentrate. The REE+Y concentrate will be treated to recover individual rare earth and yttrium oxides.
Proposed Design Basis
The crushing, grinding and flotation processing facility at Strange Lake is designed to operate for 365 days per year at a design throughput of 1,346,000 t/y for the first 23 years of the mine life. The optimized mine plan has been developed to maintain a steady dysprosium content in material fed to the concentration plant at Strange Lake. This results in a variable feed tonnage to the beneficiation plant based on the grade of dysprosium. For the first 23 years of the mine operating life, the annual plant feed tonnage in the PEA mine plan varies from 886,000 t/y to 1,279,000 t/y. A plant expansion will enable the processing of up to 3,170,000 t/y of lower grade stockpiled mineralized material from year 24 onwards to the end of planned production (year 30).
The processing plant at Bécancour is designed to treat a maximum of 610,000 dry t/y of flotation concentrate. This plant will operate for 365 days per year, 24 hours per day. The design average throughput rate for the processing plant at Bécancour is 1,671 dry t/d.
Process Description Based on Testwork
The selected process plant flowsheet and design parameters are based on the testwork described in Section 13.0 of the report. Simplified block flowsheets for the proposed processing facility are shown in Figure 13.4 and Figure 13.5.
Crushing and Grinding
The crushing, milling and flotation circuits located at Strange Lake have been designed to support treatment of a maximum of 1,346,000 t/y feed in the first 23 years of the operation with further capacity expansion to process a maximum of 3,170,000 t/y in the last seven years. The crushing circuit is designed to operate for 365 days per year, 12 hours per day. The grinding, flotation and dewatering circuits are designed to operate for 365 days per year.
Flotation
Beneficiation at Strange Lake will be by flotation to produce a flotation concentrate.
Hydrometallurgical Processing
Processing at Bécancour will include acid thermal processing (acid bake) and water leaching to extract the payable elements into solution, followed by hydrometallurgical precipitation to recover the rare earth elements and yttrium into a mixed REE+Y concentrate. The REE+Y concentrate will be treated to recover individual rare earth and yttrium oxides.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Strange Lake plant design throughput (Years 1-23) | 1,346,000 t/y | Design |
| Strange Lake plant annual feed range (Years 1-23) | 886,000 to 1,279,000 t/y | PEA mine plan |
| Strange Lake plant maximum throughput (Years 24-30) | 3,170,000 t/y | Design (expansion) |
| Bécancour plant maximum concentrate treatment capacity | 610,000 dry t/y | Design |
| Bécancour plant average design throughput rate | 1,671 dry t/d | Design |
| Flotation concentrate annual production range | 521,000 to 608,000 dry t/y | Design (varies to maintain Dy2O3 output) |
| Total separated rare earth oxides annual production range | 9,021 to 13,114 t/y | Design (based on PEA mine plan and estimated recoveries) |
| Dy2O3 annual production range | 418 to 427 t/y | Design (mine plan based on constant Dy production) |
| Overall recovery from mine to separated oxide (Years 1-23) | 57% to 77% (varies by element) | Testwork estimates |
| Overall recovery from mine to separated oxide (Years 24-30) | Not provided | Not provided in source |
Project website: https://torngatmetals.com/the-project/strange-lake-mine-site/
Average project metal recoveries (from testwork described in Section 13 of the report):
| Element | Flotation Recovery Years 1-23 (%) | Flotation Recovery Years 24-30 (%) | Leach Extraction (%) | Direct Precipitation Plant Recovery (%) | Separation Plant Recovery (%) | Recovery from Mine to Separated Oxide Years 1-23 (%) |
|---|---|---|---|---|---|---|
| La | 93 | 60 | 87 | 95 | 98 | 75 |
| Ce | 92 | 59 | 89 | 94 | 98 | 76 |
| Pr | 92 | 58 | 91 | 94 | 98 | 77 |
| Nd | 91 | 56 | 91 | 94 | 98 | 77 |
| Sm | 91 | 54 | 90 | 93 | 98 | 75 |
| Eu | 90 | 51 | 89 | 93 | 98 | 73 |
| Gd | 91 | 52 | 90 | 94 | 98 | 75 |
| Tb | 90 | 52 | 88 | 93 | 98 | 72 |
| Dy | 90 | 52 | 86 | 92 | 98 | 70 |
| Ho | 90 | 51 | 84 | 92 | 98 | 68 |
| Er | 89 | 50 | 83 | 91 | 98 | 65 |
| Tm | 88 | 48 | 81 | 89 | 98 | 62 |
| Yb | 87 | 47 | 80 | 85 | 98 | 58 |
| Lu | 86 | 45 | 79 | 85 | 98 | 57 |
| Y | 90 | 51 | 86 | 94 | 98 | 71 |
Technical qualifications
This technical report is a preliminary economic assessment (PEA) and is based on proposed design criteria and estimated metallurgical recoveries derived from testwork described in Section 13.0 of the report. The average metal recoveries are estimated from the metallurgical testwork described in Section 13.0. The annual plant feed tonnage varies based on the grade of dysprosium, and the design production ranges given in Table 17.1 are based on the PEA mine plan and estimated metallurgical recoveries. Data for Table 17.1 was provided by Quest in March 2014.
Source: Strange Lake Project , 2014 Technical Report, Section 17.0 Recovery Methods, Section 17.1 Design Basis and Process Design Criteria, Section 17.2 Process Description.
