It is now possible to use measurement devices based on impedance tomography to create real time 3D images from inside the pipelines and tanks used by the processing industries. One significant application for this technology, spearheaded by the Finnish company Numcore Oy, is concentration plants in the mining industry.

With Numcore measurement devices, the size and quantity of air bubbles and the solid matter content of the froth bed can be monitored by means of electric conductivity distribution. Real time characteristics are a key functionality in this technology; in other words, the system continuously provides the operator with factual data on what is happening in the flotation cells, for example the location of minerals and the bottom surface of the froth bed.

The technology opens up entirely new possibilities to control flotation processes, an important component in the concentration process of minerals. In simplified terms, the principle of flotation is to blow bubbles of air into a mixture of ore, water and chemicals, whereby the mineral particles cling onto the bubbles. Mineral carrying froth is generated as the bubbles rise up to the surface and are collected from there.

Mr Jukka Hakola VP of Sales and Marketing at Numcore said that "Problems emerge if the froth cannot carry the load of mineral particles or the process otherwise becomes disturbed. The froth bed then disappears, and restarting the process wastes valuable time."

He added that "If the solid matter content and bubble size in the froth bed changes, and solid matter starts to gather under the froth, this can cause the froth to become rigid or to collapse. When this situation can be predicted, the problem can be solved by changing the operating parameters."

Mr Hakola said that "Because it has not been possible to look inside tanks, controlling a mineral concentration process has largely been based on experience derived know how. Now that operators can look inside the process, it is possible for them to maintain an optimal mix all the time."

According to Mr Hakola, measuring as such does not create added value, rather the results should be used to control the operation. Therefore Numcore has, in close co operation with a few key customers, developed measurement technology to better serve every day work.

Numcore measurement technology is currently in test use at Inmet Pyhäsalmi Mine Oy's copper and zinc mine at Pyhäsalmi, among others.