An optimised prefeasibility study (OPFS) for the Kasiya rutile/graphite project, in Malawi, completed with oversight from a technical committee appointed by Sovereign Metals and Rio Tinto, has reconfirmed the project as a “leading global supplier of strategic critical minerals outside of China”, Sovereign reports.

The OPFS was undertaken following a strategic investment by Rio Tinto Mining and Exploration in 2023, which resulted in the establishment of a joint technical committee to advance the development of the project.

The OPFS estimates a net present value of $2.3-billion, compared with the $2.4-billion estimated in the initial PFS.

The project is expected to deliver earnings before interest, taxes, depreciation and amortisation (Ebitda) of $409-million a year, and capital expenditure to first production of $665-million.

The company expects the project to generate $16.4-billion in total revenue and an operating cost to export product through the Nacala port of $432/t.

“The level of accuracy and confidence in the economic and technical fundamentals of Kasiya have taken a massive step forward.

“The successful completion of large-scale field trials, in particular for dry mining, the high degree of technical rigour by our enhanced owner’s team, and Rio Tinto’s technical support have all contributed to confirming Kasiya’s potential to become a long-life, low-cost, secure source of two genuine critical and globally strategic minerals,” says Sovereign CEO and MD Frank Eagar.

The OPFS proposes a large-scale, long-life operation to deliver substantial volumes of natural rutile and graphite, while generating significant returns.

The company notes that the OPFS optimises seven key areas compared with the 2023 PFS.

The 2023 PFS proposed a 25-year initial life-of-mine (LoM) based on a hydraulic mining process where slurry material would be screened and pumped overland to a processing plants.

Based on findings from the mining trials undertaken as part of the pilot mining and land rehabilitation, the OPFS proposes a large-scale openpit dry mining operation using draglines and trucking of material to the processing plants.

Sovereign says the change in mining method has not changed the initial mine life of 25 years.

The 2023 PFS envisaged mining would take place on a contractor basis.

During the OPFS, Sovereign undertook a trade-off analysis between operating options, including a fully owner-operated mine with draglines and trucks bought by the owner; an owner-operated mine with draglines and trucks leased by the owner; and mining contractor operation using excavators and trucks.

Owing to the preference for draglines and maintaining flexibility, an owner-operated mine with leased equipment is selected as the preferred operating model.

Dry mining Kasiya means the material received at the plant is not pre-wet and pre-scrubbed.

Therefore, the OPFS proposes a process plant front end consisting of two scrubbers and two oversize screens per 12-million-ton plant. No further changes are proposed to the processing plant flowsheet.

Per the 2023 PFS, mining would begin in the southern area of the Kasiya deposit, ramping up to 12-million tonnes a year and then scaling up to 24-million tonnes a year in year five by building a second plant module in the same area, reaching nameplate capacity by the end of the year.

In year ten of production, another new 12-million-tonne-a-year plant module would be built and commissioned in the northern area of Kasiya, supported by the relocation to the north of one of the southern plants to maintain a steady state of 24-million tonnes a year.

However, Sovereign says the OPFS has determined the most efficient plant locations to be an initial 12-million-tonne-a-year South Kasiya plant, followed by the construction of another 12-million-tonne-a-year North Kasiya plant in year five of production, negating any relocation requirements in later years.

The company says the OPFS maintains the run-of-mine (RoM) schedule with operations beginning with 12-million tonnes a year of throughput during the first four years of production – Stage 1 – and expanding to 24-million tonnes a year in year five, with full capacity reached by the end of year five – Stage 2.

Moreover, Sovereign notes that, per the 2023 PFS, a conventional process would be used to produce rutile and graphite concentrate with tailings in separate sand and fines streams being pumped to a conventional tailings storage facilities (TSF).

The company explains that mined out pit areas would be backfilled as part of a rehabilitation process.

The OPFS proposes maximising backfilling of pits as undertaken during the pilot phase and the introduction of mud farming on the TSF to accelerate dewatering. This approach has reduced tailings volumes in the TSF by 44% from 187-million cubic metres to 105-million cubic metres.

Mud farming is a technique used by Rio Tinto at operations such as its 100%-owned Weipa bauxite operations in Queensland, Australia, which has been in production since 1963 and produced 35.1-million tonnes of bauxite in 2023.

Regarding water management, Sovereign says the 2023 PFS proposed that the primary water supply for the Kasiya mining complex would be created by building a dam and collecting run-off water from the greater catchment area.

Following the introduction of dry mining and mud farming, the size of the water dam proposed in the PFS has been significantly reduced, with less process water required and more process water recovered.

The OPFS mining trials and material deposition tests indicated a water demand of 10.2-million cubic metres a year, almost a 40% decrease in water requirement from the PFS.

The company says the effect on the raw water dam wall could be a reduction in volume from 790 000 m³ to 570 000 m³ and a reduction in dam wall height from 20 m to 17 m.

Further, Sovereign notes that the 2023 PFS envisaged a hybrid hydro-generated grid power plus solar power system solution.

The company points out that grid reliability in Malawi has improved since completion of the PFS and is expected to further improve considerably with the commissioning of the country’s first high-voltage (HV) transmission interconnector to Mozambique in the second quarter of this year.

This will provide the project with sufficient power and, therefore, the OPFS proposes to connect the project’s power system to the hydro-sourced grid network only.

This mitigates any risks associated with commissioning a new solar power project and reduces the overall power tariff by eliminating the need for an independent power producer as per the 2023 PFS.

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Over the 25-year LoM, Sovereign says Kasiya is set to produce an average of 222 000 t/y of natural rutile and 233 000 t/y of natural flake graphite.

At steady state throughput of 24-million tonnes of ore a year, the project is anticipated to produce about 246 000 t/y of natural rutile and 265 000 t/y of natural graphite, positioning Sovereign as potentially the world’s largest producer of natural rutile and natural flake graphite.

Further, Sovereign notes that the depletion of rutile reserves at Lenoil Company Limited’s Area 1 mine in the coming two to three years and the recent cessation of mining activities at Energy Fuels’ Kwale operations, in Kenya, means that Sovereign could potentially become the world’s only primary natural rutile producer of scale.

The incremental cost of producing a tonne of graphite from Kasiya under the OPFS is $241/t.

“Based on public disclosures by listed graphite companies that have undertaken project studies up to a PFS or later, an incremental graphite cost of production of $241/t would make Sovereign the world’s lowest-cost graphite producer outside of China,” says Sovereign.

The rutile/graphite-rich mineralisation will be extracted from surface and trucked to the process plant front end to scrub and screen RoM before it enters a wet concentration plant where a low-energy requirement, chemical-free process using gravity spirals produces a heavy mineral concentrate (HMC).

The HMC is transferred to the dry mineral separation plant, where premium quality rutile is produced using electrostatic and magnetic separation technology.

Sovereign says the high-quality Kasiya rutile product will be amenable for use in high-end titanium products including aerospace and defence applications.

Graphite-rich concentrate is collected from the gravity spirals and processed in a separate graphite flotation plant, producing a high purity, high crystallinity and high-value coarse flake graphite product.

“Kasiya’s graphite has been confirmed to produce outstanding anode materials suitable for battery production as well as demonstrating suitability for traditional industrial uses such as the production of refractory materials,” the company says.

“The project has excellent surrounding infrastructure including sealed roads, a high-quality rail line connecting to the deep-water port of Nacala on the Indian Ocean and hydro-sourced grid power.”

For the duration of the operation, Sovereign says Kasiya’s highly-sought-after rutile and graphite products will be railed directly from a purpose-built rail dry port at the mine site eastward via the Nacala Logistics Corridor to the Port of Nacala.

The southern Port of Beira, connecting Kasiya through the recently refurbished Sena Rail Line, offers a secondary export route.