News and Publications

Find out latest news from Nordkalk

Side stream turned into a new wollastonite product

Tiina Roine (info a nordkalk.com), 9 March 2021

Nordkalk's goal is 100 per cent material efficiency, meaning that it uses all the stone it extracts, as well as all the side streams from the production processes.

Nordkalk is the only European producer of high-quality wollastonite. The rare mineral is extracted and processed in Lappeenranta in Finland, and the products are shipped to almost 30 countries around the world. The majority of the customers operate in the plastics and rubber, paint, and ceramics industries.

Wollastonite products are made of virgin carbonate stone in a flotation process, in which the mineral is separated by means of different chemicals. In the autumn of 2020, Nordkalk was able to introduce a new wollastonite product, made of an overflow from the calcite flotation process. For years, this side stream ended up in the tailings pond for flotation sand, because its utilisation was not considered possible due to the low wollastonite content. The overflow is created of stone that contains about 5 per cent wollastonite, while the normal feed stone has a 20-25 per cent share of wollastonite.

A systematic study focusing on how to recover and utilise the overflow was started in the spring of 2019. The biggest challenge was establishing the right chemical dose for the flotation process, which required several trial runs. The results were analysed by using the Design of Experiments (DOE) tool, in which data collected from random chemical dosings are analysed by means of statistical mathematics. This allows to identify how different variables interact in a multi-effect process, and gradually adjust the quality of the product to the desired level.

The product offering has been expanded by a sustainable, circular wollastonite alternative

Nordkalk's goal is 100 per cent material efficiency, meaning that it uses all the stone it extracts, as well as all the side streams from the production processes. The new wollastonite product enables the use of thousands of tonnes of mineral that were previously wasted. From customers’ point of view, the product offering has been expanded by a sustainable, circular wollastonite alternative.

Anne Foley

Leader in Northern Europe

Nordkalk is the leading limestone company in Northern Europe. We deliver essential raw materials to numerous industries, and our solutions contribute to clean air and water as well as productivity of agricultural land.