Metso says it is investing in the development of energy-saving comminution technology and has signed an agreement to acquire the outstanding shares of its long-term partner Swiss Tower Mills Minerals AG (STM).

Previously, Metso had a 15% minority ownership in the company. The parties have agreed not to disclose the transaction value.

Metso decided to exercise its right of first refusal following the divestment decision of STM’s other shareholders. As a result of the transaction, Metso’s ownership will increase to 100%. Metso has reported its previous 15% shareholding as a non-current financial asset.

Swiss Tower Mills Minerals, based in Baden, Switzerland, specialises in vertical grinding mill solutions. It is best known for the HIGmill™ grinding mill, which has been exclusively sold and serviced by Metso. This technology is crucial in modern grinding circuits and integral to the development of energy-efficient comminution processes, for example, in combination with Metso HRC™e high-pressure grinding rolls, Metso says. Over the years of cooperation, the use of vertical grinding mill technology has seen significant growth, and the trend is expected to continue.

Markku Teräsvasara, President, Minerals business area and Deputy CEO at Metso, said: “We are excited to have the Swiss Tower Mills Minerals team as part of Metso. For many years, we have collaborated in serving customers in the mining industry. Going forward, our customers will continue to benefit from an unrivalled comminution solutions offering, which we will develop further.”

Fritz Moser, Chairman of the Board of Swiss Tower Mills Minerals, said: “Being fully convinced that Metso is highly committed to further develop Swiss Tower Mills Minerals as the benchmark of the art of grinding, together with my private shareholder colleagues, we have decided to divest our ownership in the company. Hence, we are pleased to know that the technology we have established together with Metso for the mining industry will remain an essential part of Metso’s flowsheet capability.”

The acquisition, which is subject to the approvals of anti-trust authorities, is expected to be closed in early 2025.

In 2022, the Weir Group announced an alliance with STM in which Weir would market STM’s vertical stirred grinding mills for coarse grinding applications worldwide.

Last year, Weir announced the completion of the STM Minerals AG vertical stirred mill commissioning at the Weir Technology Hub in the Netherlands, as part of its energy-efficient comminution and classification solutions for customers.