Air as resource in mining.

Mining companies that operate deep mines have the dual challenge of making sure that people and machines have enough air to operate efficiently underground while ensuring neither gets overheated.

Dr. Stephan Hardcastle, research scientist with Natural Resources Canada's CANMET Energy Technology Centre, says it would be better for mining companies' bottom line to think of air as a resource that is sent down to areas where it is needed and not where it isn't.

"There are break-evens in terms of cost," Hardcastle adds. "In ventilation, there is a cubic relationship between quantity and cost so if you doubled your air flow, it's eight times the power and eight times the cost. If your primary ventilation is already your primary cost, it's really going to increase your cost if you increase your ventilation."

Hardcastle says there are three actual factors that influence cost for a company in delivering its air. One is the cost to run the main fans that drive the air underground. There are then secondary fans that deliver it to the various areas of the mine and there is also heating and cooling costs. These three factors, in assorted combinations, can have a significant impact on the cost for a mine and ventilation can account for as much as 40 per cent of the cost of operating a mine.

Heat can be a challenge since much of the heat comes from the rock, as well as from equipment, the compression of air going into the mine.

The answer many mine operations choose is to rely on natural cooling methods, says Hardcastle. That could include pumping down cool air in winter that cools the rock. That, in turn, stays cool through the summer months providing comfort. Another method used by one company that has voids in its underground operation, pumps in water that is frozen to create ice stopes. The cooling of the water releases latent heat which is then heats the mine during winter and the melting ice helps cool the mine during summer.

Many heat management systems operate by ventilation, but with bigger and bigger systems needed to move the air the further down one goes, that too comes under the scrutiny of a cost-management analysis and whether or not it becomes more economical to install a refrigeration system.

For years, mining companies have benefited from cheap energy costs, says Hardcastle. Events in recent months and years that have impacted on energy costs, as well as concerns about greenhouse gas emissions from energy generators are necessitating that companies rethink the use of air as a "resource" than simply as an afterthought to the main thrust of extracting ore.

"We have got quite a few mining communications companies around that are looking at providing some level of ventilation control. And there are some companies that are looking at being able to track equipment," he says. "Once you can marry those two things, you have the added potential to save dollars and possibly provide a better environment than you do now."

The use of such technology as hydrogen fuel cells and hybrid engines to reduce emissions is also an area that offers significant savings to mining companies in the future.

Production simulators currently used to assess the fiscal viability of mining projects could also be used to demonstrate the effectiveness of more controlled ventilation.

By ANDREW WAREING

Northern Ontario Business