Lola Graphite Project — 2023 Technical Report

The 2023 Technical Report describes the proposed mineral processing route for the Lola Project, including crushing, grinding, flotation, and downstream processing to produce natural flake graphite concentrate and battery anode material.

Report context

The Lola Project processing section, summarized from the 2023 DRA Technical Report, presents a proposed processing plant and a battery material plant (BMP) design. The BMP consists of spheroidization, purification, and coating plants. The report distinguishes proposed design parameters from historical operating data from plants in China and from testwork results. All throughput and recovery figures are based on design criteria unless otherwise noted.

Processing route

Mineral Processing Plant

The mineral processing plant consists of a crushing area and a concentrator where material beneficiation and concentrate dewatering, screening, and packaging takes place. The process flowsheet includes crushing, grinding, desliming (for Saprolite only), rougher flotation, polishing, and cleaner flotation. The back end of the concentrator includes tailings thickening, concentrate filtration and drying, dry screening and bagging of graphite products, and material handling. All the tailings from the concentrator will be thickened and pumped to the tailings ponds. Reclaiming water from the tailings ponds has been considered in the process design to minimize freshwater makeup to the concentrator.

The NFG concentrate will be recovered by a conventional flotation process. The plant startup will have Saprolite only feed for approximately nine months. Subsequently, blends with Fresh Rock ranging from 25% to 45% will feed the plant for the remainder of the Life of Mine. A NFG concentrate grade of 95.4% Cg is expected regardless of feed type. Processing plant equipment have all a design factor of 15% above the nominal production rate.

Over the Life of Mine, the process plant will produce NFG concentrate divided into four standard-size fractions: +48 mesh, -48+80 mesh, -80+100 mesh and -100 mesh.

Crushing and Storage

The RoM mineralized material will be deposited directly into a feed hopper using a front-end loader. From the hopper, an apron plate feeder will convey the material to the mineral sizer where it will be crushed by means of rotating toothed rolls reducing the material from a maximum of 24 inches (600 mm) to 8 inches (200 mm). The crushed material from the mineral sizer is then conveyed past a self-cleaning permanent magnet where any tramp steel will be removed. The material will discharge onto a radial stacker. During normal operation, the stacker will discharge directly into the crushed hopper. A belt feeder, located under the hopper, will feed the crushed material onto belt conveyors to feed the SAG mill in the concentrator. Another self-cleaning permanent magnet will remove any tramp steel on the first of these conveyors. When the plant is not operating and the mineral sizer is still operating, the radial stacker will feed an emergency stockpile. Crushed material can be reclaimed from the emergency stockpile by a front-end loader to feed the plant while the mineral sizer is not operating.

Grinding and Desliming

The SAG mill operates in a closed circuit with a single deck screen to remove pebbles greater than 13 mm. The pebbles are returned via two conveyors to the plant feed conveyor for further grinding by the SAG mill. There is also the option to dump pebbles in an emergency pile if required. Undersize material from the single deck screen is pumped to four multi-deck vibrating screens (three operating and one standby), also in a closed circuit with the SAG mill. The oversize material is returned by gravity to the SAG mill feed chute. The -0.8 mm screen undersize material discharges to a tank. Depending on the plant feed material, the material is directed to one of the two following: for a blended feed, the material is pumped directly to rougher flotation; or for Saprolite only, the material is pumped to desliming. There are two parallel trains of desliming, each with two stages.

Rougher Flotation

There are two parallel rougher flotation trains, each processing half of the material. The rougher flotation circuits recover graphite flakes early in the process to maintain as many of the large flakes as possible and to minimize flake degradation. To aid the flotation process, the reagents used are diesel as a collector and methyl isobutyl carbinol as a frother. The rougher flotation trains each consist of a bank of eight conventional flotation cells of 16 m³ each, which provides sufficient flotation residence time (sixteen cells total). The rougher concentrate is expected to be approximately 36% Cg grade. The rougher concentrate from each train is collected and pumped to its own polishing mill. Rougher concentrate cleaning is completed in three stages.

First Polishing Stage and First Cleaner Flotation

Rougher concentrate from each train is fed to one of two first stage polishing mills, which use ceramic media to scrub the graphite flake surfaces of the gangue minerals with a minimal size reduction. The polished rougher concentrate from each mill is combined in a tank. The rougher concentrate is re-split into two trains of first cleaner flotation cells. Each train has a bank of four conventional flotation cells (eight cells total), 10 m³ each. It is expected to upgrade the rougher concentrate up to 83% Cg. First cleaner concentrate is pumped to a high frequency multi-deck vibrating wet screen.

Further Polishing and Subsequent Cleaner Flotation

Based on the knowledge of the graphite flotation circuits and applicable test work results available to date, the split between the coarse (+100 mesh) and the fine (-100 mesh) fractions for the first cleaner flotation concentrate are expected to be about 50%/50% weight ratio. After the screening, both the screen oversize (+100 mesh) and the undersize (-100 mesh) streams will be upgraded in the parallel polishing and cleaner flotation circuits, each dedicated to the respective size fraction. For the screen undersize, the solids in the polishing mill feed will be controlled with the polishing mill dewatering cyclones installed in open cycle with the mill to obtain proper solids density during polishing. The discharge of each second stage polishing mill is fed to second cleaners of the coarse and fines cleaner circuits, respectively. Second cleaner concentrates are cleaned through the dedicated third cleaners. The third cleaner concentrate of each circuit (combined grade of 95.4% Cg) is pumped to filtration for dewatering. The tails from the second cleaners are recirculated upstream to the first cleaner flotation, and the tails from the third cleaner are recirculated upstream to the second cleaners feed. The coarse and the fines second cleaner flotation is performed in the dedicated banks of three conventional flotation cells of 2 m³ each. The third cleaner flotation for the coarse and the fines is performed in the dedicated banks of two conventional flotation cells of 2 m³ each.

Graphite Concentrate Filtering and Drying

Graphite concentrates from third cleaner flotation banks are pumped to a concentrate holding tank prior to being pumped to pressure filtration. The concentrate filtration circuit consists of three vertical plate pressure filters and produces a graphite product filter cake that contains 20% moisture. The concentrate cake is gravity discharged onto dedicated conveyors for each filter which feed a common conveyor. The material is transported to the dryer via a feed hopper and a feed screw conveyor. The filtrate from the filter presses gravitates to a filtrate tank. Concentrate is dried by means of a diesel-fired indirect rotary dryer. The dryer reduces concentrate moisture content down to 0.3%, which is required for efficient dry screening and packaging.

Graphite Dry Screening and Packaging

Four size fractions will be produced from the NFG concentrate. After the dryer, the NFG concentrate is pneumatically transported to a bulk graphite bin. From this bin, graphite is pneumatically transported to two sifter screening systems. Each sifter system consists of eight sections of 27 sizing screens each. The screened fractions discharging from the sifter systems gravitate to the four appropriate dedicated bins. Packaging of the NFG concentrate will be performed in the graphite bagging circuit. Dry screened NFG concentrate will be fed from the dedicated bins to a semi-automatic bagging system. Concentrate will be loaded into one tonne bulk bags. All bags are weighed, put on a pallet, and stretch wrapped.

Active Anode Battery Material Plant

The basis of the Preliminary Economic Assessment is a BMP that consists of an initial, reduced, Coating Plant that will produce for the first two years, approximately 5,300 t/a of coated spherical purified graphite product, whilst undergoing product qualification. Thereafter, the coating capacity will increase to produce approximately 26,400 t/a CSPG product. At full capacity, the BMP will process 45,000 t/a of -100 mesh (-150 µm) NFG concentrate from the Lola Project at a minimum feed grade of 94.6 wt.-% fixed carbon to produce approximately 26,400 t/a of battery anode CSPG at a fixed carbon content of greater than or equal to 99.95 wt.-%. During the two-year qualification period, the majority of spherical purified graphite produced will be sold as uncoated SPG. The BMP contains three main sections: the Spheroidization Plant, the Purification Plant, and the Coating Plant.

Spheroidization Plant

The Spheroidization Plant is designed to produce 27,000 t/a of spherical graphite from 45,000 t/a of NFG concentrate. Processing of the NFG to form SG takes place at the Spheroidization Plant and entails three unit operations: micronizing, spheroidization, and classification. The process begins with the micronizing of the NFG to meet the required feed particle size distribution. Following micronization the micronized graphite is ready to be spheroidized. The spheroidization process involves the mechanical shaping of the graphite flakes into smooth, rounded particles to improve their performance in battery applications. The Spheroidization Plant is structured into three stages: the first step is micronization, where the NFG is comminuted to a fine PSD. In the second stage, spheroidization begins, where the micronized graphite undergoes a process that changes it into coarse SG. The third step involves refining the material to produce a secondary SG product. Each equipment set in the BMP consists of a mill, a cyclone classifier, and a bag filter, all integrated through a closed-loop pneumatic piping system. The PEA assumes an optimized combined yield of 60 wt.-% (NFG to SG), divided into two size fractions. In addition to producing SG20 (20 µm) and SG10 (10 µm), 18,000 t/a of SG fines (less than or equal to 9 µm, approximately 95 wt.-% FC) will be generated as a by-product.

Purification Plant

The Purification Plant is designed to process 27,000 t/a of SG feed with a fixed carbon content of greater than or equal to 95.0 wt.-%, resulting in 23,970 t/a of purified SPG with a FC content of greater than or equal to 99.95 wt.-%. SG is fed to the Purification Plant for impurity removal. The proposed BMP applies graphite purification that consists of a mixed acid, which is a combination of HCl, HNO₃, and HF. The Purification Plant operates in alternating batches, processing the two SG product streams: the coarse SG and fine SG (secondary SG). Purification is split into four stages: thermally induced chemical reaction, pressure filtration, washing, and drying. In the reaction stage, the mixture is stirred and heated with the slow introduction of steam as a heating source. The temperature is controlled at 60°C for 12 hours. In the pressure filtration stage, the purified SG is dewatered by a filter press. In the washing phase, the purified SG undergoes two sequential washing stages. In the drying stage, the wet SPG is introduced to hot air generated by a gas furnace, which is blown into the dispersion drying chamber at around 100°C, drying the SPG to a moisture content below 1%.

Coating Plant

The Coating Plant is sized to treat 23,970 t/a SPG by applying pitch tar coating technology at an addition rate of 10 wt.-%. The final CSPG production of the BMP, producing FC battery grade at greater than or equal to 99.95 wt.-%, is approximately 26,400 t/a. The dry pitch tar coating method was selected for the BMP. This method involves four main steps: pitch tar size reduction, mixing, carbonization, demagnetization screening, and automatic packaging. In the pitch tar milling step, compressed air is used to mill the pitch tar into fine particles of approximately 2 to 3 µm in size. For mixing, the dried SPG and milled pitch tar are mixed in a sealed environment using vacuum feeding. Once mixing is completed, the material is pneumatically conveyed to the rotary kiln for carbonization. Nitrogen gas is used in the rotary kiln to create an inert atmosphere. Electrical heating raises the temperature gradually from 200°C to 1,200°C. The carbonization process is completed over approximately 13 hours, followed by 9 hours of cooling. After carbonization, the CSPG product is passed through a demagnetizer to remove any magnetic particles, screened, and automatically packaged into sealed one-ton bags.

Key reported parameters

Technical qualifications

All processing figures presented in the 2023 Technical Report are design criteria unless otherwise noted. Recoveries for different feeds are expected values based on testwork. The spheroidization plant, purification plant, and coating plant process design criteria for the BMP are based on Hensen's experience and operating plants in China. The 60 wt.-% yield assumption for spheroidization is based on operating data from plants in China and the Weihai Plant. Historical operating data is cited only for these Chinese reference plants.

The report states that the processing plant equipment have all a design factor of 15% above the nominal production rate. The report does not provide actual operating performance data for the Lola Project processing facilities as these are proposed designs. The moisture content of filter cake (20%) and dried concentrate (0.3%) are design targets. Water balance figures include reclaim water from tailings ponds as a design consideration.

Source: Section 17 Recovery Methods, 2023 DRA Technical Report, Lola Project.