Graphite Creek — 2017 Technical Report (PEA)

The 2017 Preliminary Economic Assessment for Graphite One's Graphite Creek project in Alaska outlines an integrated concept combining a Mineral Processing Plant at the mine site with a downstream Product Manufacturing Plant near a port, designed to produce 60,000 tpy of graphite concentrate for upgrading into spherical graphite and purified powders.

Article Body

The Graphite Creek project is planned as a vertically integrated operation. Mining and mineral processing would occur at the Graphite Creek property in Alaska, while purification and value-added processing would take place at a separate Product Manufacturing Plant situated at a developed brownfield site in proximity to a port. A key consideration behind this arrangement was minimizing the amount of material requiring transport from the mine site.

At full production capacity, open pit mining would deliver 1,018,000 tpy of graphite mineralization grading 7% Cg to the Mineral Processing Plant. There, the ore is beneficiated in close proximity to the mine through a flowsheet incorporating two stages of crushing, initial grinding, conventional cell rougher flotation, cleaner flotation, and multiple sequences of grinding and polishing with column flotation to progressively upgrade the concentrate. The plant is designed to produce 60,000 tpy of graphite concentrate grading 95% Cg.

The design shows a deliberate choice to produce a single concentrate stream for integrated downstream processing to spherical graphite. This decision was made to support the project's core strategy of producing only up-market, high-quality products. The concentrate would then be transported to the Product Manufacturing Plant, where it undergoes thermal purification followed by spheronization and coating processes to produce purified spherical graphite for lithium-ion battery applications, as well as purified sub-20 micron powders for other end-uses.

Critical Data

Overview

The 2017 Technical Report presents a PEA for an integrated graphite project. The concept involves mining graphite mineralization at Graphite Creek, processing it to a 95% Cg concentrate at a Mineral Processing Plant located near the mine, then transporting that concentrate to a coastal Product Manufacturing Plant for thermal purification and value-added processing into spherical graphite and purified powders. The project was designed to operate year-round on a 12-month schedule.

A six-month operating schedule that would have coincided with the Alaska-Washington shipping window was considered but dropped. The alternative schedule was rejected due to the higher capital expenditures and operating costs incurred from running at higher processing intensity, which negatively impacted project economics.

The Mineral Processing Plant was designed to operate 330 days per year. It uses five parallel circuits at full design capacity, with smaller-scaled equipment to provide better flexibility on production and improve graphite recovery. This modular design approach was applied across crushing, grinding, and flotation.

Transport and logistics were planned around year-round road access. Road clearance during winter months ensures year-round access to the mill for labour rotations, resupply of operations, and transport of concentrate to a storage area near the port. A contracted truck transport fleet moves concentrate from the mill and delivers fuel to the Graphite Creek Project site on the return trip.

Key Process Stages

The Mineral Processing Plant receives run-of-mine material that reports to dump hoppers positioned above grizzly feeders. Plus 500 mm material is removed at the grizzly stage. At full capacity, three crushing circuits operate in parallel. Crushed material from storage bins is conveyed to the primary grinding circuit, which consists of five rod mills operating in parallel at full capacity.

Following grinding, the ore undergoes conventional cell rougher flotation and cleaner flotation. At full plant capacity, five flotation circuits operate in parallel. Upgrading of the initial cleaner concentrate is carried out in four stages of column flotation. Successive column cleaner stages use different mills and grinding media to prepare the feed at progressively finer particle sizes. The column cleaner train upgrades material through column cleaner one, then column cleaner two, then column cleaner three at 93% C, and finally column cleaner four, which produces concentrate at a grade of 95% C at an overall recovery of 80%.

Tailings from rougher flotation, initial cleaner flotation, column one cleaner, and scavenger stages are pumped to tailings impoundment. Underflow from cleaner columns two, three, and four is directed to dewatering cells ahead of scavenger flotation for additional graphite recovery. The final concentrate overflow from cleaner column four is dewatered in plate and frame filter presses. The final product is pneumatically conveyed to bulk bag fillers where it is bagged in one-tonne super sacks.

Process water is pumped from the tailings pond and recycled as process water. Process reagents required at the Mineral Processing Plant for flotation include Flotanol and other reagents, though specific reagent names are partly stated.

The Product Manufacturing Plant receives 60,000 tpy of concentrate grading 95% Cg packaged in one-tonne super sacks and stacked in 20-foot shipping containers. All received concentrate is thermally purified using electric-powered thermal purification, which was selected over acid chemical purification to increase throughput and minimize or eliminate acid effluents. The purification furnaces are designed as high-throughput, low residence time units that achieve high-rate purification by exposing individual flakes to high temperature under turbulent fluid mixing conditions.

For spheronization, natural graphite flake with specific properties suitable for lithium-ion battery anode applications is jet milled to a specific particle size, then undergoes further shaping and classification processes to produce potato-shaped spherical graphite particles. A nitrogen plant is installed at the Product Manufacturing Plant site to produce high-purity inert gas. Petroleum pitch, a precursor source of carbon, is applied to spherical graphite size fractions recovered for lithium-ion battery end-use.

At full scale production, eleven spheronizing-coating systems are required, with ten operating at a daily throughput of 238 tpd. A nitrogen plant is installed at the site of the Products Manufacturing Plant to produce the required quantities of high purity inert gas.

All products are automatically bagged, robotically palletized, and stored in a warehouse on site.

Additional Interesting Data and Summary

Current industry standard product yields for spherical graphite from the spheronization process are 30-40%. Other size fractions suitable for non-EV lithium-ion battery end-uses increase the overall recovery. Pilot scale equipment is available from vendors, which will be necessary to define the yield and number of circuits required for the Graphite Creek concentrates. Future investigations on optimizing the spheronization process and customizing the surface coating process may alter the final number of installed units.

Electricity for the mine, plant, and support facilities will be generated by an on-site diesel power plant. The remote location of the Graphite Creek Project site and distance to established electrical infrastructure made it impractical or costly to install additional capacity at an existing plant. A six-megawatt power plant consisting of three 2-MW diesel generators operating at 80% of nominal capacity will generate the annual electricity requirement. Annual diesel fuel consumption is estimated at 9,000 m3 when production reaches full capacity. A three-month inventory of fuel is maintained at the plant site.

Annual process water requirements are estimated at 500,000 m3. Pending the results of water sampling and flow measurements on major streams and the Cobblestone River, it is assumed that process water will be drawn from on-site resources, with recovered water from the tailings pond also used.

The purified sub-20 micron powders serve varied end-use applications including lubricants, friction products, conductive polymers, specialty powder, and metallurgical additives. The minimum purity requirement for graphite feedstock for spherical graphite production is 99.95% C, which is also constrained by threshold limits on certain metallic impurities that would otherwise be problematic for EV lithium-ion batteries.

Key Processes

• Crushing: Two stages with three parallel circuits at full capacity, plus grizzly removal of plus 500 mm material
• Grinding: Initial rod milling with five parallel rod mills at full capacity
• Rougher flotation: Conventional cell flotation with five parallel circuits
• Cleaner flotation: Initial cleaner flotation followed by four stages of column flotation
• Column flotation: Progressive upgrading through four stages reaching 93% C at column three and 95% C at column four
• Dewatering: Plate and frame filter presses for final concentrate, dewatering cells for intermediate streams
• Scavenger flotation: For additional graphite recovery from cleaner underflow streams
• Tailings management: Rougher, cleaner, and scavenger tailings to impoundment with process water recycling
• Thermal purification: Electric-powered high-throughput furnaces at the Product Manufacturing Plant
• Spheronization: Jet milling, shaping, and classification to produce spherical graphite
• Coating: Application of petroleum pitch precursor for lithium-ion battery end-use
• Product handling: Automatic bagging, robotic palletizing, and warehouse storage
• Nitrogen generation: On-site nitrogen plant for inert gas requirements
• Power generation: On-site diesel plant with three 2-MW generators operating at 80% nominal capacity
• Water management: Process water draw from on-site resources with tailings pond recycling

Source: Graphite Creek , 2017 Technical Report (PEA), 2017.

Project website: Graphite Creek, 2017 Technical Report (PEA)