The Huguenot Coal Project technical report outlines a processing design based on a 4.0 Mt/y run-of-mine (ROM) coal feed and a 2.7 Mt/y clean coal product, with a focus on mechanical dewatering to achieve a 7.5% product moisture target.
The Huguenot Coal Project, located in the Liard Mining Division of British Columbia, Canada, is a surface mining operation currently at the Preliminary Economic Assessment (PEA) stage. The technical report details the recovery methods for the proposed Coal Handling and Preparation Plant (CHPP), which is designed to process approximately 4.0 Mt/y of ROM coal. A central design criterion is to achieve a product total moisture content of 7.5% or less; this target necessitates a focus on mechanical dewatering methods over traditional thermal drying, which carries high capital and operating costs as well as environmental constraints. The processing facility is intended to be robust for harsh winter conditions and flexible enough to handle a wide variety of feed characteristics, based on the preliminary washability testing and analyses of the Huguenot resources.
The processing flow is divided into two main components: the Coal Handling Plant (CHP) and the Coal Preparation Plant (CPP). The CHP receives ROM material from surface workings at a stockpile, where it undergoes primary crushing followed by a rotary breaker. The rotary breaker controls the raw coal top-size, typically to 50 mm, while rejecting oversize dilution rock. This equipment choice is routine in the Canadian Rocky Mountain coal fields due to the differential strengths of the coal, which is weak and friable, versus the dilution rock, which is strong. The CPP then uses a combination of heavy media cyclones, Reflux™ classifiers, and froth flotation columns to remove ash from the coal.
The fine coal circuit processes material in the 1.4 mm x 0.25 mm size range using Reflux™ classifiers, while the ultrafine circuit handles material below 0.25 mm through froth flotation columns. The rejects and tailings from these circuits are managed through a combination of screening, thickening, and filtration before disposal.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Plant throughput | 4.0 | Mt/y ROM | Target annual feed |
| Product output | 2.7 | Mt/y clean coal | Approximate |
| Operating schedule | 7,000 | h/y | |
| Mechanical availability | 92 | % | Equivalent to 6,440 coal-on hours |
| CPP feed capacity | 650 | t/h | As-received basis |
| Product total moisture | 7.5 | % | Maximum target, as-received basis |
| Average yield | 73 | % | For surface mined coal |
| Product ash | 9 | % | As-received basis, approximate |
| Coarse coal surface moisture | 3.5 | % | After centrifuge dewatering |
| Fine coal size range | 1.4 x 0.25 | mm | Reflux™ classifier feed |
| Ultrafine size range | 0.25 x 0 | mm | Froth flotation feed |
| Top-size control | 50 | mm | Via rotary breaker |
| Desliming aperture | 1.4 | mm | Wedge wire |
Overview
The Huguenot Coal Project is a proposed surface mining operation with a CHPP designed to process 4.0 Mt/y of ROM coal. The plant is based on an industry standard design for the PEA, incorporating recent coal processing industry developments for capital cost estimation. The key design driver is achieving a product moisture of 7.5% or less through mechanical dewatering, avoiding thermal drying. The processing facility is intended to operate on a 7,000 h/y schedule with a mechanical availability of 92% or better, yielding a nominal feed capacity around 650 t/h. The design emphasizes robustness for harsh winter conditions and flexibility for varying feed characteristics. Product coal from the plant is assumed to be loaded into highway-compatible tractor-trailers and hauled to the existing Peace River Coal unit train loading facility near Tumbler Ridge, BC, with no significant ground storage at the CHPP.
Key Process Stages
The ROM coal from surface workings is transported to a stockpile near the CHP. It passes through a truck dump hopper with a stilling shed, followed by primary crushing and a rotary breaker. The rotary breaker controls the top-size to typically 50 mm and rejects oversize dilution rock. After the CHP, the sized raw coal enters the CPP via the raw coal desliming screen. This large multi-slope deslime screen removes the minus 1.4 mm raw coal ahead of the coarse coal processing circuit. The fine raw coal passing through the bottom deck is pumped to the fine coal circuit, while the top decks overflow to the heavy media cyclone circuit.
In the coarse and small coal circuit, the 50 mm x 1.4 mm raw coal is mixed with a finely ground magnetite and water medium and pumped into a large diameter heavy medium cyclone. The clean coal and medium from the cyclone overflow discharge to a drain and rinse screen. The clean coals feed size-specific centrifuges to dewater the coarse and small coals to about 3.5% surface moisture. The coarse reject from the cyclone underflow is screened in a similar manner.
The fine coal circuit processes coal in the 1.4 mm x 0.25 mm size range. The fine raw coal sump collects the minus 1.4 mm material from the desliming screen underflow. The raw fines are pulped to approximately 11% solids to create a coal-water slurry for size-based classifying in cyclones. The classifying cyclones separate the fine raw coal into 1.4 mm x 0.25 mm and 0.25 mm x 0 streams. The sized fines are pumped to Reflux™ classifiers, where the product concentrate typically feeds sieve bends ahead of final dewatering screenbowl centrifuges. Fine rejects are withdrawn in a controlled manner and flow to high frequency vibrating screens before disposal via the rejects conveyor.
The ultrafine circuit processes material below 0.25 mm. Ultrafine particles are pump-fed to froth flotation columns, where hydrophobic clean coal particles adhere to air bubbles and float, while high ash particles are carried in the tailings stream. The clean ultrafine coal particles are collected. The tailings from the froth flotation circuits are collected in a large diameter thickener. The thickened underflow is then filtered to allow the material to be comingled with coarser reject streams. This comingled material is conveyed to a truck loading bin for transport to a planned disposal area.
Additional Interesting Data and Summary
The premium-product coal industry is shifting away from inefficient thermal dryers due to high capital and operating costs as well as environmental constraints. The alternative being adopted is hyperbaric filtration, which consists of vacuum disc filters housed inside a high-pressure vessel. Testing of Canadian metallurgical coals has shown the ability to utilize hyperbaric dewatering of ultrafines to about 8.5% surface moisture when steam-assist is used to augment the hyperbaric disc filter operation. The process design accounts for the fact that products from the heavy media and reflux classifier circuits are dry enough to be conveyed without additional dewatering. The target of producing about 7.5% moisture at the mine allows for moisture increases due to rainfall prevalent in the west coast climate of Canada. The plant generates high ash waste material, called refuse or rejects, where the tailings from froth flotation circuits are thickened and filtered.
Key Processes
- Primary crushing and rotary breaking
- Desliming and size classification
- Heavy media cyclone separation
- Reflux™ classifier fine coal separation
- Froth flotation column ultrafine separation
- Centrifugal and hyperbaric filtration dewatering
- Thickening and filtration of tailings
Source: Huguenot Coal Project , Technical Report, TBD.
Project website: Huguenot Coal Project, Technical Report
