The East Kemptville Project is planned as a simple, cost-effective tin recovery operation processing stockpiled material at 806,000 t/y, with gravity concentration at the core of the flowsheet.
The East Kemptville Project, with a planned processing rate of 806,000 t/y (100 t/h) of stockpiled material, is designed around a straightforward flowsheet focused entirely on tin recovery. The metallurgical process described in the technical report is based on testwork detailed in Section 13.0, incorporating data from the SGS UK and Met-Solve metallurgical test programs alongside historical information from previous operations. The original East Kemptville flowsheet, which included conventional crushing, two-stage grinding, bulk sulphide flotation followed by differential copper/zinc flotation, and gravity recovery for tin, was determined to be uneconomic at current metal prices. Consequently, the project developed a simpler process centered on producing a single tin concentrate, aiming to construct a plant with as few unit operations as possible.
The primary design consideration has been to produce a suitably sized milled product from a single stage grinding system while preventing over-grinding of the plant feed. This approach is intended to avoid the production of very fine cassiterite grains, which would be difficult to recover. The design achieves this by incorporating a gravity recovery circuit within the grinding and classification circuit and by using classifying screens instead of cyclones. Plant feed scheduling introduces higher grade mineralization from the Baby Zone Pit after Year 1 and from the Main Zone Pits starting in Year 3. Feed material will be processed at a rate of 100 t/h from the stockpiled material, with a target primary grind P80 of 80 microns. Plant availability is assumed at 91.3%, equating to 8,000 operating hours per year.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Feed throughput | 806,000 | t/y | Based on stockpiled material |
| Feed rate | 100 | t/h | Concentrator feed |
| ROM feed rate | 200 | t/h | To vibrating grizzly feeder |
| Target primary grind P80 | 80 | microns | Single stage grinding |
| Tin concentrate grade | 55 | % Sn | Target grade |
| Tin recovery to concentrate | 60 | % | Approximate |
| Plant availability | 91.3 | % | 8,000 h/y operating time |
| Course screen opening | 50 | mm | Vibrating grizzly feeder |
| Coarse classification screen | 0.5 | mm | Removes +0.5 mm material |
| Final tin concentrate moisture | 10 | % | Approximately |
| Sulphur target in final tailings | 0.05 | % | Less than |
| Shaking tables | 4 | – | Operating in parallel |
Overview
The process plant at East Kemptville is designed as a conventional tin recovery operation consisting of several processes. Run-of-mine material is fed at a rate of 200 t/h to a vibrating grizzly feeder with 50 mm openings by a front-end loader. Material larger than 400 mm is retained ahead of this feeder by a static grizzly screen and broken with a hydraulic rock breaker. The flowsheet includes crushing, single stage ball mill grinding with classifying screens, gravity concentration using high-speed centrifugal concentrators and shaking tables, and concentrate cleaning that combines magnetic separation with flotation to remove iron, copper, and zinc sulphides.
The process water system is designed to recycle water from the tailings treatment facility to minimize fresh water consumption. Raw water obtained from the existing supply is piped to a new storage tank and used for gland service water, reagent make-up water, and final concentrate filter wash water. Potable water from existing facilities serves only ablution and human consumption needs. Process water is used for comminution duties including mill dilution and screen sprays, gravity concentrator circuit flush water, shaking table wash water, and sulphide flotation circuit launder sprays.
Key Process Stages
The comminution circuit begins with a single stage grinding system using a ball mill. The ball mill discharge is pumped to a coarse classification screen where +0.5 mm material is removed and recycled to the mill. The gravity recovery circuit is incorporated within the grinding and classification circuit to recover cassiterite immediately after liberation, minimizing over-grinding. High-speed centrifugal concentrators provide the preliminary tin recovery, with the gravity concentrate directed to a cleaning circuit.
The gravity concentrate cleaning circuit comprises a low intensity magnetic separation unit and a small flotation circuit to remove entrained sulphides. Flotation reagents include potassium amyl xanthate as collector and methyl isobutyl carbinol as frother. Lime for pH control and copper sulphate as activator may be added if required, although testwork indicated these will probably not be necessary. Flotation rougher concentrate is pumped to a small cleaner circuit to recover entrained tin, with the final sulphide concentrate combined with the magnetics stream and pumped to the tailings facility.
The tin table circuit uses a dewatering cyclone followed by four shaking tables operating in parallel. The dewatering cyclone thickens the slurry to approximately 40% solids before the four-way distributor feeds the shaking tables. Final concentrates from the four tables are combined in a holding tank before being pumped to filters for final dewatering. The dewatered tin concentrate filter cake, containing approximately 10% moisture, is collected in one tonne super-sacs, containerized, and shipped to potential customers.
The bulk sulphide flotation circuit is scheduled for installation at the end of Year 5 to reduce the sulphur content of the gravity tailings to below the targeted 0.05% sulphur in final tailings. The circuit is designed to maximize sulphide removal. Tailings after sulphide removal are filtered, with the cake transported by truck to the tailings facility where it is used for capping as part of the tailings facility remediation process. The sulphide concentrate is deposited under water inside one of the abandoned or mined out pits.
Tailings management has two distinct treatment sections. Gravity circuit tailings are initially pumped to the existing tailings facility and distributed below the current water line. Once the existing facility is filled, material is deposited inside one of the existing mined out pits. The sulphide and magnetics concentrate from the tin concentrate cleaning circuits has a separate holding tank and is pumped to the existing tailings facility to a single, sub-aqueous location. Once the tailings facility is fully capped, the large flotation circuit for bulk sulphide removal will no longer be used.
Additional Interesting Data and Summary
The processing plant will have a small compressor to generate both plant air and clean or instrument air, which is filtered and dried. Mass flow systems and sampler facilities are installed on several process streams. Weightometers are located on the jaw crusher product conveyor and crushed material to the ball mill. Manual sampling of feed is provided, along with an automatic sampler on the mill circuit product and an automatic sampler plus flowmeter and densitometer on final plant tailings. The feed to the sulphide removal circuit has access for manual sampling. Eight-hour composites are sent to the laboratory for analysis.
The simplified flowsheet for East Kemptville represents a strategic departure from the original more complex design that included differential copper and zinc flotation. The current approach prioritizes tin recovery while accepting that a small portion of copper, zinc, iron, and indium will be collected into a sulphide concentrate and disposed of in the tailings facility unless a buyer is found. This design philosophy aligns with the stated objective of constructing a simple plant focused purely on the recovery of a saleable tin concentrate.
Key Processes
- Single stage ball mill grinding with classifying screens to prevent cassiterite over-grinding
- Gravity recovery circuit using high-speed centrifugal concentrators within the grinding and classification circuit
- Shaking table circuit with four tables operating in parallel for final tin concentration
- Low intensity magnetic separation and flotation for sulphide removal from gravity concentrate
- Bulk sulphide flotation circuit for tailings treatment, installed in Year 5
- Tailings filtration and capping for the existing tailings facility remediation
Source: East Kemptville Project , Technical Report, report date not stated. Project website: [Project name](URL)
Project website: East Kemptville Project, Technical Report
