March/April 2013

Reinventing the mill

Industry examines how to adapt to the future at CMP 2013

By Dinah Zeldin

Denis Cimon at the Canadian Malartic mine | Courtesy of Osisko

Alternative comminution technologies, improved process control, and applied geometallurgy were central to discussions at the 45th Annual Canadian Mineral Processors Conference. The event, held from January 22 to 24 at the Westin Hotel in Ottawa, featured 34 presentations and attracted over 650 attendees.

With more variable and lower grade ores feeding processing facilities, today’s plants must not only grind minerals finer than ever – to particles 74 microns and less – but must also optimize plants to process a range of grades and mineral compositions. This was the catalyst for dialogue at the conference’s round table discussion, “Regrinding below 100 microns. What we know. What we don’t know. What we need to know,” moderated by Donald Leroux, principal consultant for Triple Point Technology.

Liberating valuable minerals from finely disseminated ore bodies requires rocks to be pulverized into ultrafine sizes, according to Leroux. This means grinding technology must adapt. “Generally speaking, ball mills are efficient for down to about 74 microns but rapidly lose efficiency when grinding to finer sizes,” he explains. “There are alternative technologies like the tower mill, the ISA mill and the stirred mill, available on the market, that make better use of energy, but there are still challenges.” Among the challenges is maintaining separability of valuable minerals, as particle sizes are reduced.

The panel discussion, which drew over 200 attendees, featured six participants: Mike Larson, senior metallurgist at Xstrata Technology; David Rahal, product manager of fine grinding at FLSmidth; Louis Steyn, product manager of grinding, Outotec; Michel Brissette, account executive at SGS-Lakefield; Jan Nesset, consultant at Nessetech; and Peter Radziszewski, expert on grinding at Metso. According to Leroux, the audience was engaged, focusing questions on how to select and operate appropriate equipment, as well as on how to make ball mills grind finer.

Philip Thwaites of Xstrata Process Support addressed the importance of automated process control in his plenary presentation, “Manual Control, Process Automation – Or Operational Performance Excellence? What Is The Difference?” He made the case that automating systems is essential for boosting plant efficiency and for reducing operating costs.

The technical program also included a session on geometallurgy for the first time ever. Erin Legault, the 2013 conference chair, explained that the inclusion was well-warranted. “The field is of increasing concern to processors be­cause the protocol can help establish how lower grade or difficult ores can be processed most efficiently,” he says.

Student attendees – 32 of which were sponsored by CMP – also contributed to the discussion. In his CMP Essay Competition, winning presenter Syed Saad Ali of McGill University demonstrated how the surface energy of particles is related to their response to flotation.

The conference was also an opportunity to showcase some of the ­hard-working people in the processing world. Denis Cimon, vice-president of technical services at Osisko, was recognized as Mineral Processor of the Year. Cimon was manager of the Canadian Malartic operation before becoming a key member of Osisko’s head office in Montreal. He was honoured for surmounting both technical and social challenges to make each project he has touched a success.

“As manager at Malartic, I had to prove the project was technically and socially feasible,” he explains. “It was difficult from a processing standpoint because we were dealing with a type of rock that is very resistant to breakage, so the wear rate on equipment was very high. On top of that, it is a huge open-pit mine very close to a community, so getting social licence to go ahead was a challenge.”

This year’s event also featured five short courses that attracted 150 participants. “We went from three to five courses because we wanted to offer more variety,” says Leroux, a past-chair of CMP. Topics included grinding, chemistry, process control and metal accounting.

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