Molo Graphite Project — 2024 Technical Report Update

This report update describes the process design basis for a proposed graphite concentrator at the Molo Graphite Project in Madagascar, including crushing, milling, flotation, chemical upgrading, and product handling.

Report context

This technical report update is dated 22 March 2024 and relates to the Molo Graphite Project, located at Fotadrevo, Province of Toliara, Madagascar. The report documents a preliminary economic assessment level design for processing graphite mineralized material and is prepared in accordance with NI 43-101 requirements.

Processing route

Overview

The proposed processing circuit will consist of three-stage crushing, followed by primary milling and a flotation separation circuit. The process has been designed assuming an expected recovery of 89% and an average head grade of 8.5% carbon, delivering an estimated 84,000 tonnes per annum of graphite concentrate at the designed throughput tonnage of 1.16 Mt per annum. Varying graphite head grades could lead to reduced recoveries or less graphite product for the same feed tonnage into the plant.

Design criteria and basis

The process design is based on an annual production capacity of 1,160,000 tonnes of material feed at a nominal head grade of 8.5% carbon. Test work was performed during the course of the study, and the results form the basis of the process design criteria. Design information sources were coded in the report as follows: A (assumed, based on current information), B (previously reported), C (as instructed or determined by the client), D1 (selected based on test work results), D2 (selected based on design experience), D3 (calculated based on other inputs), D4 (selected based on OEM recommendations), and E (information not available).

Key design parameters for mineralized material include a solids density of 2.4 t/m³, a broken bulk density of 1.5 to 2 t/m³, and a graphite head grade of 8.5% carbon. The estimated plant feed rate is 1,160 ktpa, with an estimated plant recovery of 89%. The estimated final concentrate grade is 88% carbon at 5% mass pull, without chemical treatment. The estimated final concentrate production is 84 ktpa.

The plant design operating schedule specifies that ROM mineralized material will be delivered at 1,160 ktpa over 7 days per week, 2 shifts per day, and 10 hours per shift. The crusher schedule is 7 days per week, 3 shifts per day, at 8 hours per shift, with an assumed utilisation of 67%, giving 5,869 operating hours per annum. The crushed material rate is calculated at 197.6 t/h. The milling schedule is 365 days per annum at 24 hours per day, with an assumed utilisation of 92.0%, giving 8,060 operating hours per annum. The circuit feed rate is 144 t/h dry.

Concentrate production design parameters include a filter feed rate of 7.19 t/h dry, a filter running time of 18 hours per day, and a filter availability of 75%. Drying plant availability is assumed at 92%. The dryer is specified as a T1500 EBR Torbed type with a size of 8 t/h. Cake moisture after drying is specified at 1% w/w. Product classifier sizes are listed as -75 µm, -150 to +75 µm, -300 to +150 µm, and +300 µm.

Crushing and sizing

The three-stage crushing circuit is designed to operate at 67% availability, equating to a feed capacity of approximately 200 tonnes per hour. ROM material will be delivered to a ROM feed bin feeding the crushing and screening section of the plant. A single tramp screen will remove any oversize material. Material will be crushed to a product size of P80 of 10 mm via the three-stage crushing process, incorporating a single primary screen after the second crushing stage. It is currently envisaged that the primary crusher will be a jaw or impact crusher, while the secondary and tertiary crushers will be cone crushers or mineral sizers. A further screening section is to be developed on the basis that large graphite flake will be screened out as a salable product ahead of the milling and flotation stages.

Primary milling

A single-stage primary milling circuit has been employed, operating in closed circuit with classifying cyclones. The primary ball mill would be approximately 4.3 metres in diameter with an effective grinding length of 6.2 metres. The motor installed power would be approximately 3,000 kW. The comminution circuit capacity will accommodate the full tonnage of 1.16 Mt per annum. The overflow from the cyclone cluster will feed the primary rougher flotation circuit of the plant.

Secondary milling

A single-stage secondary milling circuit will consist primarily of a stirred media detritor for the regrind of the primary cleaner tail. The mill will operate in open circuit with a dewatering cyclone cluster. The underflow from this cluster will feed the secondary mill, while the overflow will discharge to the secondary mill discharge sump. The secondary milling circuit product will feed the secondary cleaner section of the flotation plant. Due to the lower mass pull to the cleaner circuit, the milling circuit is expected to be relatively small, with an installed power of 90 kW.

Tertiary milling

A single-stage tertiary milling circuit will also consist of a stirred media detritor for the regrind of the secondary cleaner circuit tail. The mill will operate in open circuit with a dewatering cyclone cluster. The underflow from this cluster will feed the tertiary mill, while the overflow will discharge to the tertiary mill discharge sump. The tertiary milling circuit product will feed the tertiary cleaner section of the flotation plant. Installed power to the mill will be limited to 90 kW.

Rougher flotation

The rougher feed, consisting of the primary mill cyclone overflow, is gravitated to a transfer tank or conditioner ahead of a bank of box-type flotation cells in series. Rougher concentrate recovered will be pumped to the primary cleaner flotation circuit, while the rougher tail is to be pumped directly to the tailings storage facility via a rougher tail transfer sump and multi-stage pumps. The rougher flotation circuit has been designed to accommodate the full plant throughput capacity of 1.16 Mt per annum at an average head grade of 8.5% carbon.

Primary cleaner flotation

The primary cleaner feed, consisting of the rougher flotation concentrate together with the tail from the primary re-cleaner cell, is pumped directly to a bank of box-type flotation cells in series. Primary cleaner concentrate will be pumped to the primary re-cleaner cell. The primary cleaner tail will be pumped to the secondary mill dewatering cyclone cluster. Concentrate from the primary re-cleaner cell will be pumped directly to a concentrate thickener for final product handling.

Secondary cleaner flotation

Secondary cleaner feed, consisting of the secondary mill discharge, is pumped from a surge tank to a bank of box-type flotation cells in series. The secondary cleaner concentrate will be pumped to the tertiary cleaner flotation circuit. The secondary cleaner tails will be pumped to the tertiary milling circuit surge tank for regrind and polishing.

Tertiary cleaner flotation

The tertiary cleaner feed, consisting of the combined streams of the secondary cleaner flotation concentrate together with the tertiary mill discharge, is pumped directly to a bank of box-type flotation cells in series. The tertiary cleaner concentrate will be pumped to the tertiary re-cleaner float cell. The tertiary cleaner tail will be pumped to the rougher tail transfer sump together with the rougher tail to be transferred to the tailings storage facility. Concentrate from the tertiary re-cleaner cell will be pumped directly to the concentrate thickener for final product handling.

Concentrate thickening

The flotation circuit was designed to produce approximately 84,000 tonnes of concentrate per annum at the average head grade of 8.5% carbon. The final concentrate produced from the flotation circuit is transferred to a high-rate thickener ahead of the filtration and drying process. The thickened concentrate slurry is pumped into one of two existing stock tanks. Overflow from the concentrate thickener is clarified, and overflow from the clarifier is gravitated to the process water tank, while the underflow from the clarifier is pumped to the stock tanks. Concentrate slurry is periodically pumped from the stock tanks to a plate and frame filter for dewatering.

Concentrate chemical upgrading

Preliminary test work indicated that two methods could be used to enhance the grade of the graphite concentrate: a hydrofluoric acid leach, or alternatively a caustic hydration and hydrochloric acid dehydration process. Due to the hazardous nature of the hydrofluoric acid leach, the hydration and dehydration process was adopted. Concentrate from the concentrate thickener is transferred to an agitated leach tank where caustic soda will be introduced. A 24-hour leach residence time will be applicable, after which the concentrate will be transferred to a second agitated tank where hydrochloric acid is introduced. The concentrate is leached in acid for a further period of 24 hours. The leached concentrate is finally transferred to a third neutralisation tank. The neutralized pulp is filtered ahead of the drying and sizing plant.

The concentrate grade expected to be achieved in the flotation process is approximately 88% carbon. Utilizing a chemical treatment process, the concentrate purity could be increased to 99% carbon, resulting in battery-grade carbon. The chemical treatment plant can be isolated from the rest of the circuit without any major changes, allowing for the opportunity to bring the plant online at a later stage to defer capital costs.

Concentrate filtration and drying

Final concentrate will be periodically pumped from the stock tanks to a plate and frame type filter press, where the pulp is dewatered to acceptable moisture levels ahead of the drier. The filter cake so produced will be transferred to a drying circuit where the remaining moisture and entrapped volatiles will be driven off.

Concentrate despatch

A vendor-supplied bagging plant will be utilised. The final concentrate will be weighed and bagged into 1-tonne bulk bags. A batch reserve of 20 bags will be made up, equivalent to the full load requirement of a sea freight container, with each bulk bag in the reserve being spear sampled to form a final composite sample. The composite sample will be analysed for graphite content and moisture together with any gangue mineralization pertinent to the final product specification requirements. The bulk bags are finally sealed and covered with an ultraviolet-resistant plastic cover and placed on a wooden pallet ready for storage ahead of despatch. The graphite concentrate will be despatched on a daily basis and transferred to the warehouse in Soalara ahead of sea freighting.

Tailing disposal

The rougher tail, or final tail, from the flotation circuit will be transferred directly to the tailings storage facility at the normal flotation operating density. The rougher tail transfer tank will be equipped with two pump trains of three pumps in series per train. The two pump trains, one operational and one standby, will utilise a common discharge line. A dedicated gland service water system will be installed to service the pumps. The tailings pipeline will be HDPE above ground with knife gate valves on the discharges, and the return water line will also be HDPE.

The final flotation tail will be pumped to the tailings storage facility via three pumps installed in series. No thickening of the flotation tail will be required, and the pulp will be pumped at the nominal flotation operating density. The slimes dam will be operated employing a conventional day wall system and floating penstock to recover clarified water. The water so recovered will be pumped directly back to the plant to the process water tank via the floating penstock, eliminating the use of a return water reservoir. The TSF will be located within a kilometre radius of the process plant. The TSF has been sized by a specialist consultant, and it is proposed that the TSF will be an unlined facility constructed using waste material from the open pit mining operations. The initial TSF footprint with the capacity to accommodate 2 years of operations is proposed to be constructed in order to reduce upfront capital costs. The initial TSF will have a wall height of 10 m and a footprint of 28.8 hectares.

Services

Instrument-quality air is produced from a compressed air installation at the plant, consisting of two compressors and associated dryers and receivers. Blower air will be generated from positive displacement blowers to service the flotation cells.

The water circuit will be configured to minimise raw water usage. Raw water will only be used for reagent make-up, potable water, and process top-up water. In addition to raw water supply to a raw water dam, a facility to supply raw water directly to the process water dam will be provided. Supply sources are designated as follows: reagent make-up water will be unfiltered raw water supply; gland service water will be raw water supply; spray water will be supplied from process water; potable water will be supplied from the dedicated raw water supply, filtered and treated. Potable-quality water will be for human consumption only. Process-quality water will be used for services required within the confines of the plant, such as spray water usage and hosing. Fire water, reagent make-up, and mill bearing cooling water will be raw-water quality. Unfiltered process water will be used for mill circuit dilution.

Reagents

Dispersant make-up is fully automated and will be supplied in bulk bags. Dry powder is stored in a hopper, with storage in excess of 24 hours. A hydration time of 4 hours is allowed during reagent mixing. Dosage of the reagent will be done from a dedicated ring main system using flow control valves and flow meters at each addition point.

Illuminating paraffin or diesel will be used as the collector. The collector will be delivered in 1 m³ plastic tanks. These tanks will be mounted on a concrete slab on ground level as close as possible to the required dosing point. Small, adjustable dosing pumps will be installed directly on the dosing tanks, pumping directly to the dosing point.

Powder flocculant will be supplied in 25 kg bags and diluted as required with an automated make-up plant. Dry hopper storage in excess of 24 hours has been allowed. Dosage is from variable speed pumps, duty and standby, to the concentrate thickener.

DOW200 will be used as the activator. The activator will be delivered in 1 m³ plastic tanks similar to the collector. These tanks will be mounted on a concrete slab on ground level as close as possible to the required dosing point. Small, adjustable dosing pumps will be installed directly on the dosing tanks, pumping directly to the dosing point.

Energy, water and process materials consumption

The plant energy requirements have been calculated using the mechanical equipment list and applying a utilisation percentage to each processing unit. The plant installed power is 7.3 MW, with the primary milling plant constituting 41% of the installed power. The operational power demand is anticipated to be 4.9 MW. Power will be generated using diesel power generators.

The major water source was identified through the surface hydrology study conducted. Water will be supplied from a catchment dam situated 17 km from the processing plant and will supply the plant with raw water. Raw water from the dam is to be clarified and purified for human consumption and village requirements. Raw water make-up requirements will be 206 m³/h, of which process water requirements will make up 125 m³/h.

Most reagents will be consumed in relatively low quantities, with depressant being the only exception. Consumption of grinding media would need to be determined based on further comminution test work. The grinding media would need to be imported, as would most of the other process consumables. For the purpose of the study, the grinding media consumption is based on vendor information and estimates and assumptions used in relevant milling simulations.

Key reported parameters

Technical qualifications

This report presents a preliminary economic assessment level design. Several limitations apply to the information presented.

The process design for crushing, milling, and flotation is based on test work performed during the course of the study; however, the flowsheet development and design will follow once confirmatory test work has been concluded and specific equipment sizes have been established. The report notes that the flowsheet for the large-flake recovery circuit is to be developed following confirmatory test work.

Consumption of grinding media would need to be determined based on further comminution test work. For the purpose of the study, grinding media consumption is based on vendor information and estimates and assumptions used in relevant milling simulations.

Several design criteria are based on assumptions rather than test work or detailed engineering. These include the ROM delivery schedule, crusher schedule, milling schedule, filter availability, and drying plant availability.

The chemical treatment section notes that preliminary test work indicated two possible methods for upgrading the graphite concentrate, with the caustic hydration and hydrochloric acid dehydration process being adopted. The report states that utilizing chemical treatment, the concentrate purity could be increased to 99% carbon, resulting in battery-grade carbon.

The report also notes that the further screening section for large graphite flake removal is to be developed, and that the specific equipment sizes for the large-flake recovery circuit have not yet been established.

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Source: Molo Graphite Project, Fotadrevo, Province of Toliara, Madagascar, PEA Technical Report Update, NI 43-101, 22 March 2024, Section 17, Recovery Methods.