Finnish mining and battery chemical company Keliber, in which diversified miner Sibanye-Stillwater owns a significant interest, has completed a four-phase pilot-scale test programme and verified the behaviour of the ore from the company's largest deposit, Rapasaari, at all stages of the production process.

The Rapasaari deposit is located 2 km southeast of Keliber’s Syväjärvi deposit.

A similar pilot-scale test programme has previously been carried out using ore from Syväjärvi, the mine where quarrying will start first.

In the last phase of the test programme, battery-grade lithium hydroxide monohydrate was produced from spodumene concentrate that had been treated in a high-temperature conversion in a rotary kiln.

The hydrometallurgical technology, developed by Metso Outotec together with Keliber, includes soda pressure leaching and other process parts.

The pilot trial was conducted at Metso’s demonstration plant, in Pori. The continuous pilot trial lasted 400 hours and a lithium recovery rate of more than 88% was achieved.

Keliber says this is a better result than what was estimated in the company’s definitive feasibility study published in March.

“We are very pleased with the test programme’s progress and with the results achieved in the pilot trials. We have now verified that we can produce battery-grade lithium hydroxide from not only the Syväjärvi ore but also by using ore from our largest deposit in Rapasaari,” states Keliber Lithium Chemical Plant site manager Sami Heikkinen.

Sibanye acquired a 30.29% initial interest in Keliber for €40-million in February 2021.

It intends to raise its shareholding in Keliber to 80%. The companies announced last week that they had negotiated a financing arrangement that would result in Sibanye investing €250-million in two stages to acquire an 80% stake.

Firstly, Sibanye will exercise its right to achieve a 50% plus one share shareholding in Keliber for €146-million. Sibanye will then make a voluntary offer to Keliber minority shareholders to acquire a further €104-million worth of Keliber shares.

The investment by Sibanye will be used by Keliber to advance its lithium project to the construction phase.