Dominion Diamond's 2016 technical report for the Ekati diamond mine in the Northwest Territories lists the changes made since the plant started up in 1998. It also covers a fines DMS circuit under construction and the handling of clay-rich Jay ore.
The Ekati Diamond Mine, Northwest Territories, Canada, NI 43-101 Technical Report was filed by Dominion Diamond Corporation in September 2016, with an effective date of July 31, 2016. The plant's original design capacity was 9,000 dmt/d. Its nameplate was 3,000,000 dmt a year at 85% utilization (7,446 h a year, 442 t/h). Efficiency improvements have raised the current capacity and budgeted rate to 10,800 dmt/d, at an overall equipment efficiency (OEE) of 83.4% in FY 2017. Further work is aimed at 12,000 dmt/d together with the Jay project. A fire in the process plant on June 23, 2016 temporarily stopped kimberlite processing. The damage was limited, and repairs were expected to finish by late September.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Report effective date | July 31, 2016 | Not applicable | Dominion Diamond Corporation |
| Original design | 9,000 dmt/d (3.0 Mt/a) | Not applicable | 85% utilization, 442 t/h |
| Current capacity | 10,800 dmt/d | Not applicable | OEE 83.4% (FY 2017) |
| Target | 12,000 dmt/d | Not applicable | With the Jay project |
| Primary crushing | MMD 1300 sizer, MMD 1000 standby | Not applicable | To about -300 mm |
| Secondary crushing | Wet cone crusher | Not applicable | To -75 mm |
| Tertiary crushing | HPGR | Not applicable | -75 +1.0 mm and recirculated -28 +10 mm |
| DMS | Two parallel modules | Not applicable | -28 +1.0 mm feed |
| Recovery | WHIMS, wet X-ray, dry single-particle X-ray, grease tables | Not applicable | Hand sorting in Yellowknife |
| Fines DMS | 120 dmt/h, -1.2 +0.65 mm | Not applicable | Commissioning early 2017 |
| Power | About 31 MW (seven 4.4 MW diesel generators) | Not applicable | Four 0.75 MW standby units |
Overview
Ore is crushed in mineral sizers and a wet cone crusher, then in HPGRs to liberate locked diamonds without damaging them. It is wet scrubbed, screened and de-gritted, and the -28 +1.0 mm fraction goes to two dense media separation (DMS) modules. DMS floats of -28 +10 mm return to the HPGR for re-crushing, and -10 +1.0 mm tailings are trucked to a coarse tailings dump. DMS concentrate is treated in the recovery plant by sizing, wet and dry high-intensity magnetic separation, X-ray sorting and grease tables. Diamond concentrate is weighed, packaged and sent to the Yellowknife sorting and valuation facility. Slimes below 0.5 mm are thickened with coagulant and flocculant and pumped to fine tailings containment.
Key Process Stages
Crushing. Ore is fed by truck or front-end loader to the MMD 1300 sizer, which replaced the original gyratory crusher. The MMD 1000 supports OEE when the main sizer is down. A wider, more powerful CV18 conveyor moves ore from the cold reclaim building into the warm plant, reducing spillage and chute blockages.
HPGR and re-crush. Re-crushing DMS floats through the HPGR became standard practice again in 2015, with correct pressure, gap and roll speed controls. It had earlier been stopped to raise throughput, and an on-demand option was restored in November 2014.
Scrubbing, de-gritting and DMS. De-grit screens were reduced from 1.6 to 1.0 mm to simplify operation and maximize diamond recovery. The DMS re-concentration circuit was shut down to make the DMS more stable and raise module availability.
Recovery. The recovery plant runs 24/7. Its magnetic separation and wet X-ray capacity were increased, attrition milling was removed, and the X-ray units and grease tables were upgraded. Recovery tailings above 1 mm return to the HPGR, and those below 1 mm go to primary scrubbing.
Fines DMS. The small diamonds recovery plant was demolished in Q4 FY16. In its place, a 120 dmt/h fines DMS treats -1.2 +0.65 mm material from the desanding screen. Its concentrate goes over grease tables and then caustic fusion and acid treatment on site. It is designed so that any downtime does not affect the main plant's OEE.
Water and tailings. Process water comes from the site reclaim system, with a 1,800 m³ raw water tank that keeps about 700 m³ for firefighting. Two more thickeners were installed.
Additional Interesting Data and Summary
Lynx ore was to start in 2017 (FY18) after a four-day production trial. Sable ore is to be blended with other feeds as reserves deplete. The plant will be optimized for Jay-only feed. Jay ore contains sticky, competent clays, and a study of clay handling at the receiving area was scheduled for 2017. Hard granite and metasediment wall rock can upset processing and is limited to 5% of the feed.
In summary, the 2016 Ekati report describes a mature diamond plant that has gained about 20% over its design rate. It uses mineral sizers, HPGR re-crush, twin DMS modules and X-ray recovery, and is adding a fines DMS ahead of the move to Jay ore.
Key Processes
- Mineral sizer and wet cone crushing
- HPGR tertiary crushing and re-crush of DMS floats
- Wet scrubbing, screening and de-gritting
- Dense media separation
- Magnetic separation, wet and dry X-ray sorting and grease tables
- Fines DMS with caustic fusion and acid treatment
- Slimes thickening and coarse tailings trucking
Source: Ekati Diamond Mine, Northwest Territories, Canada, NI 43-101 Technical Report, Dominion Diamond Corporation, effective date July 31, 2016.
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.
Ekati Mine — 2015 Technical Report
This technical report describes the process flowsheet, plant design, and ore-specific processing considerations for the Ekati Mine kimberlite processing facility in the Northwest Territories, Canada.
Report context
This NI 43-101 technical report for the Archon Minerals Limited Buffer Zone Joint Venture, Ekati Mine, Northwest Territories, Canada, is dated March 2015. The report documents the recovery methods employed at the Ekati process plant, which has been in operation since commissioning at the end of 1998 and reached full production in 1999. The plant was originally designed by Fluor Daniel Wright Signet in 1995.
Processing route
Primary Crushing
The plant flowsheet begins with primary crushing, where run-of-mine ore is fed to a dump pocket by truck or front-end loader and crushed using a primary MMD1300 mineral sizer. A second MMD1000 mineral sizer operates in parallel to meet target throughput. Run-of-mine ore is reduced to approximately -300 mm by primary crushing.
Stockpile and Secondary Crushing
A stockpile serves as a buffer between the plant and crushing operations. Secondary crushing uses a cone crusher to reduce primary crusher product to -75 mm.
Tertiary Crushing
High pressure grinding rolls liberate locked diamonds from the ore undamaged and in the critical feed size range of -75 +1.2 mm.
Scrubbing and De-gritting
Crushed ore undergoes primary and secondary wet scrubbing and screening to produce clean, suitably sized material for further size reduction (-75 +1.2 mm) and concentration by heavy media separation (-25 +1.2 mm). Primary and secondary de-gritting separates unwanted fines (-1.2 mm) from the ore.
Heavy Media Separation
Two heavy media separation modules separate washed and sized feed (-25 +1.2 mm) on the basis of density into diamond-bearing concentrate and a processed kimberlite stream. The processed kimberlite stream is discarded to the processed kimberlite stockpile area, while the diamond-bearing concentrate reports to the recovery plant.
Re-crush Loop
An optional re-crush loop allows -28+8 mm heavy media separation floats to be re-crushed with the high pressure grinding roll to further liberate locked diamonds. Automated diverter gates for on-the-fly toggling of the re-crush loop were added in 2014. The re-crush option is used when there is sufficient capacity in the high pressure grinding roll and heavy media separation circuits.
Diamond Recovery
Diamonds are extracted from heavy media separation concentrates using a combination of sizing screens, wet high intensity magnetic separation, wet X-ray sorting, drying, dry single particle X-ray sorting, grease tables, and hand sorting. Plus 1 mm recovery plant rejects are recycled to the high pressure grinding roll, while -1 mm recovery plant rejects are routed to the primary scrubbing circuit.
Product Handling
Daily drops from X-ray and grease table streams are collected and brought to the weighing room. Visual sorting is performed on +6 mm X-ray concentrate to remove non-diamond material. Every two to three days, concentrate from each stream is collected into parcels, weighed, sealed in labeled bags, and twice weekly shipped to the Sorting Valuation Facility in Yellowknife.
At the Sorting Valuation Facility, parcels are re-weighed and received into the diamond management tracking system database. The -6 mm X-ray concentrate and grease table concentrate are visually sorted using high intensity magnetic separation to aid in separating non-magnetic diamonds from magnetic and paramagnetic non-diamond material. Diamonds from X-ray streams are batched, sieved, and weighed by size fraction, while diamonds from grease table streams are batched, sieved, and weighed separately.
Fines and Coarse Rejects Disposal
The -0.5 mm slimes fraction is thickened and pumped to the Long Lake Containment Facility area. The grits fraction (-1.2 +0.5 mm) is combined with the heavy media separation processed kimberlite (-25+1.2 mm or -8+1.2 mm with re-crush loop enabled) and conveyed to a stockpile before being loaded and trucked to a coarse processed kimberlite facility.
Energy and Water
Approximately 31 MW of primary power generating capacity is available from seven 4.4 MW Caterpillar diesel generator sets. The site typically operates five generating units in winter and four in summer, with an additional four 0.75 MW auxiliary units as standby capacity. Process water is sourced from the site water reclaim system, with raw water tank capacity of 475,000 gallons, of which approximately 185,000 gallons is reserved for firefighting emergencies. Chemicals including coagulant, flocculant, and salt are used to settle material in thickeners prior to discharge.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Plant design capacity | 15,500 t/d | Design specification |
| Current/budgeted throughput | 12,320 dmt per operating day (without planned maintenance) | Operating data |
| Primary power generating capacity | 31 MW | Design specification |
| Generators | Seven 4.4 MW Caterpillar diesel generator sets; four 0.75 MW auxiliary units | Design specification |
| Raw water tank capacity | 475,000 gallons | Design specification |
| Firefighting reserve | 185,000 gallons | Design specification |
| Pigeon plant feed period | 2015 through 2019 | Proposed mine plan |
| Pigeon maximum throughput (100% feed) | 12,000 dmt/day (at 1.2 mm screen) | Testwork |
| Pigeon recovery (bulk sample test) | 95.6% | Testwork |
| Jay ore processing start | 2020 | Proposed mine plan |
| Pigeon heavy mineral concentrate | 3% compared to 1.3% normal blended feed | Testwork |
| Misery processing period | 2001 to 2007, blend 10-25% of feed | Historical operating data |
Project website: https://cabinradio.ca/247508/news/yellowknife/nwt-firm-hopes-to-rapidly-turn-newly-acquired-deposit-into-mine/
Technical qualifications
The report contains the following specific qualifications regarding recovery methods. There are 17 years of production history allowing reasonable assessment of plant performance in a production setting. No data or assumptions in the Mineral Reserves mine plan are significantly different from previous plant operating experience, previous production throughputs and recoveries, or the Ekati Project background history.
The current process facilities are appropriate to the kimberlite types that will be mined from various domains outlined in the Mineral Resource and Mineral Reserve block models. The flowsheet, equipment, and infrastructure are appropriate to support the mine plans.
As there are a number of kimberlite sources being treated, the plant will produce variations in recovery due to changes in kimberlite type and domains being processed. These variations are expected to trend to the forecast recovery value for quarterly or longer reporting periods.
Granite, clay, and tramp metal content of material sent to the plant requires monitoring, and a blending strategy is typically used. Material from the Pigeon open pit will need monitoring to ensure limited impact from sediments, fines, and heavy mineral content on the plant.
Processing of the Jay kimberlite will require minor modifications to the process plant. Due to expected high clay content in the upper portion of the Jay kimberlite pipe, combined with limited blending options available during initial processing stages for Jay, plant upgrades are being considered to better handle the sticky material and expected reduction in overall process utilization.
Reagent consumptions and process conditions are based on both test work and production data. The operating costs associated with these factors in the Mineral Reserves mine plan is considered appropriate given the nature of the kimberlites to be processed. There are sufficient processed kimberlite storage options available to support the mine plans.
On-going operation of the process plant, together with additional data collected from a small bulk sample plant, has resulted in mitigation of most processing issues. The residual list of key issues that are monitored includes risks from treatment variables such as clay behaviour and material sources yet to be sampled and characterised in detail.
A sample plant located next to the process plant building is used to regularly check diamond recovery and grade control.
Source: Archon Minerals Limited Buffer Zone Joint Venture, Ekati Mine, Northwest Territories, Canada, NI 43-101 Technical Report, March 2015, Section 17 Recovery Methods.
