Black Rock Mining’s Mahenge project in Tanzania continues to make industry waves with the successful production of spherical graphite that exceeds industry standards for battery anode materials during a large-scale trial in a commercial environment.
The spheronization and purification trial using 400 kilograms of concentrate, demonstrated yields of up to 53% and final purities of 99.98% total graphitic content, or “TGC”, using commercial-scale equipment at a commercial producer and dedicated Chinese research facility.
Management said these results exceed Chinese industrial benchmark yields of between 35% and 45% and purity of 99.5% TGC and replicate results achieved during laboratory testing.
Half of the concentrate was sent to commercial producer, Inner Mongolia Ruisheng New Material, who turned the material into spheres before using a regular acid bath process, which was not optimised for Mahenge material, to purify the graphite.
This achieved a yield of 53% with purities of 99.96%, which exceeds the minimum purity threshold for batteries of 99.95% TGC.
The remaining concentrate was sent to Wuhan University of Technology for reprocessing using more costly but environmentally benign thermal purification rather than the increasingly regulated acid bath purification route.
Micronized graphite was processed 17 times before target sizing was achieved, which the company said compares well to industry standards of 25 to 30 stages to produce final sizing.
The thermal purification achieved yields of 48% and purity levels of 99.98%, with Black Rock saying that the lower yield was due to loss of material during the thermal upgrading.
The results also demonstrate that the proposed Mahenge concentrator flowsheet does not damage the project’s flake graphite.
Ore run through the pilot plant previously produced a final concentrate grade of 98.7% TGC at a recovery of 95.5% in April. About 56% of the particle distribution came in above the 100 mesh size, which commands a premium price.
Chief Executive Officer John de Vries said: “Conducting a large-scale spheronising trial using industry-standard equipment allows us to assess how initial laboratory results obtained during the Pre-Feasibility Study in 2017 scale-up in the industrial context that our customers operate in.”
“For our customers to be able to replicate the best-in-class spheronising results, that are up to a 50% improvement on current yields, while able to replicate results obtained in highly controlled laboratory conditions by skilled researchers, with no modifications to their processes, is simply stunning.”
“With the completion of this technical work, we can confidently focus on completing our financing discussions and documenting the shareholder agreement with the Tanzanian Government.”
The current ore reserve for Mahenge stands at 70 million tonnes grading 8.5% total graphitic carbon for 6 million tonnes of contained graphite.
Black Rock recently addressed the potential customer demand for its graphite by including a fourth production module to its existing definitive feasibility study.
This resulted in a neat 30% increase in the post-tax, net present value to USD$1.16 billion whilst increasing the internal rate of return from 42.8% to 44.8%.
The additional fourth module is forecast to add USD$67.1million to the project’s capital cost, taking it up to USD$337.4m.
Further highlighting the demand for Mahenge graphite, the company has already agreed to pricing with four of its five Chinese offtake partners.
The pricing ranges from USD$1,117 per tonne up to USD$2,161 per tonne depending on the type of graphite flake product and neatly straddles the USD$1,301 per tonne estimate used in the definitive feasibility study.
With the successful large-scale trial production of spherical graphite in a commercial environment now in the bag, Black Rock can now turn its focus towards securing financing for this exciting project, with an additional level of confidence.
