The results have exceeded industry standards for battery anode materials with spheronising yields of up to 53% achieved and 99.98% TGC (total graphitic carbon) purity delivered with simple acid leaching.
Trial completed in China
A large-scale spheronising and purification trial was completed in China using 400 kilograms of sub 80 mesh concentrate from Mahenge generated during a March 2019 pilot plant run.
Using commercial-scale equipment in commercial processing and in dedicated research facilities, the trial demonstrated a yield to final product of 48% and 53% and final purity of 99.98% TGC.
These outcomes exceed Chinese Industry Benchmark yields of 35-45% and purity of 99.95% while using standard equipment and techniques.
Two key objectives
Black Rock’s CEO John de Vries said: “The best way to think of the bulk spheronising trial is that it is the equivalent of our pilot plant strategy, but in this case, done downstream.
“The fundamental objectives of the pilot plant approach remain the same and that is to improve our attractiveness to financiers and investors by demonstrating and de-risking Mahenge’s superior performance in our potential customers’ business.
“In completing this round of work, we had two key objectives. Firstly, to ensure that the flowsheet developed for the Mahenge concentrator preserves the integrity of the flake and does not impair spheronising performance.
“Secondly, to demonstrate that offtake partners can achieve industry-leading performance using our flake in their existing facilities. This underpins our price point and volumes in our pricing framework agreements.
“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.”
He said: “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.”
The 400 kilograms of concentrate was split into two equal batches with each batch processed through two alternative processes commonly used in the Chinese battery pre-cursor industry.
These trials were carried out at commercial producer Inner Mongolia Ruisheng New Material Co Ltd and research facility Wuhan University of Technology.
The objective of using both was to ensure comparability between Western and Chinese laboratory results and to understand how product would perform when scaled up in a commercial facility typical of Black Rock’s potential customer base.
Spherical Purified Graphite (SPG) produced from the trials has been sent to interested parties for further testing.
De Vries said: "Concentrate used for these trials was produced at the Chinese pilot plant where the design flowsheet intended for the Mahenge Graphite Project was demonstrated.
"The exceptional spheronising yields obtained in the trial show that the planned flowsheet does not damage our flake.
"This talks to the unique geological advantage of Mahenge graphite, and the diligence applied to design and trials to optimise and de-risk our flowsheet before construction.
"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.”
Mahenge has a JORC-compliant mineral resource estimate of 212 million tonnes at 7.8% TGC and ore reserves of 70 million tonnes at 8.5% TGC.
These reserves support a mine life of up to 350,000 tonnes of graphite annually for a reserve life of 16 years.
Black Rock is progressing financing discussions and detailed engineering with a view to beginning construction of the mine.