Finnish sensors promise better flotation control

According to Numcore Oy, 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.

 

“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,” said Jukka Hakola, Numcore’s vice president of sales and marketing.

 

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.

 

“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,” said Hakola.

 

Real-time characteristics are part of the technology. According to Numcore, 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.

 

“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,” said Hakola.

 

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

 

 

The company’s close partners include Outotec, a global supplier of mineral processing and metallurgical plants, and especially in the initial phase, the Geological Survey of Finland’s Outokumpu Mineral Processing Laboratory.

 

“At the moment, our sensors are in use at two concentration plants, where we have been able to see in practice which parameters need to be controlled and how we can really numerically prove the benefits that can be achieved for the customer. Our goal is to intervene in any upcoming problems at such an early stage that the process can go on without disturbances.

 

Numcore measurement technology is currently in test use at Inmet Pyhsalmi Mine Oy’s copper and zinc mine at Pyhsalmi, among others. According to Seppo Lhteenmki, processing mill manager, the system has provided accurate information on the condition of the froth bed, and the technology has functioned well.

 

“We have tested the device for a few months, and it has provided clear benefits for those operators who have received operator training for it and actively monitored the data provided by the system. The device appears to be so useful, in fact, that we are seriously considering buying it after the test period,” he said.

 

Depending on the diameter of the pipeline or tank, Numcore measurement devices are realised either as a flow-through sensor or as a probe-type sensor for installation inside large pipelines or tanks.

 

By supplying a weak alternating current to the electrodes of the sensor, it is possible to measure conductivity differences between the phases, for example for liquids, inside pipelines and tanks, as different substances show different conductivity values. The actual image is created by means of inverse calculation, however, and this is where Numcore believes its core know-how lies.

 

“Our CoreApus flow-through sensor lends itself for analysing material flows inside pipelines of less than one metre in diameter. Because processing tanks are generally larger than this, we have developed the probe-type CoreHydra sensor which can analyse a larger area of the tank. With several sensors, one can even analyse a large tank or cell,” said Hakola.

 

Both sensor types can accurately measure interfaces between liquids and solids, but CoreApus is also applicable for imaging rapidly flowing liquids for example in pulp and paper mills.

 

“The biggest difference compared to previous systems is that now you can analyse why and how something is happening in the process, and how you can prevent an event if necessary. We focused on making the system easy to use to enable real-time and on-site corrective measures rather than relying on, say, laboratory samples,” said Hakola.

 

Numcore Oy develops measurement devices providing 3D imaging based on impedance tomography and the calculations and result reporting necessary for them. The company’s products can be used for solving problems and boosting efficiency in paper, mining, chemical and food industry processes.

 

Further applications include analysing various mixed substances and verifying separation processes. The data provided by the sensors enables real-time modelling and ensures complete mixing. This helps to reduce the mixing time and thus reduces energy and chemical consumption.

 

Jukka Hakola, Numcore vice president sales and marketing, said that the company has two CoreHydra probes in mineral processing sites in Western Australia.

 

In terms of local representation, Urpo Launonen from UJL Pty Ltd in Melbourne is representing Numcore in Australia and New Zealand.UJL has equipment available for customer trials and rents.