A new disruptive technology

According to George Shields, Chair of the Ontario Mining Association’s Energy Committee and an energy manager with DeBeers Canada, ventilation and air compression are highly energy-intensive processes in deep mining. “Anything that can reduce the costs associated with these processes would be a significant benefit to the industry,” said Shields.

A mining engineer himself, Millar knew he was onto a potential game-changer when he visited the historic site at Cobalt three years ago. After extensive research following that visit, he decided the timing was right to build a demonstration project and test his prototype.

“Taylor’s system was incredibly energy efficient and durable,” said Millar. “If hydraulic air compression was used in mining and other sectors at the rate that mechanical air compression is currently, I believe it would result in energy savings of approximately 13 per cent.”

Hydraulic air compression is also a much more cost-effective investment, says Millar, because mechanical compressors typically have to be replaced within 10 years. “Hydraulic compressors can last for decades because there are no moving parts. On the basis of lower costs alone, hydraulic air compression definitely counts as a disruptive technology.” 

The same, but different

In mining, compressed air is used primarily for drilling – drilling holes that lodge explosives that blast away bedrock, or for opening up chutes so that underground water can be channelled off or pumped out.

There are critical differences between Taylor’s century-old system and the new one. For one, the Ragged Chutes plant was built near a dam on the Montreal River, which propelled water mixed with air 107 metres down using a run-of-river system.

In contrast, there is no on-site river for Millar’s project. Instead, a circulation pump drives water up a short distance to a header tank and compresses the air as it falls downward. The pressure of the air produced depends on the depth of the shaft. The compressed air and water are separated in a cylinder at the shaft bottom so that the air is drawn out through a pipe and sent for service. The water re-ascends to the surface pumps, which closes the loop, and the whole process begins again. See process diagram.

The challenges of thermodynamics

In addition to different conditions above ground, Millar and his team are tackling specific thermodynamic challenges underground with which Taylor didn’t have to contend.

At just 20 metres down, the Big Nickel mine only mimics the construction conditions in deep mining today, where the deepest site in Canada is about four kilometres underground. At this depth, pressure and air temperatures are high.

“The greater the depth, and higher the pressure, the more the gas dissolves in the water, and by-passes the separator. We addressed that challenge by adding a salt to the water, resulting in more bubbles.”

Temperature is another key challenge in mines. “The earth’s core is incredibly hot because it’s comprised of molten iron and nickel. The deeper you go, the hotter it gets,” said Millar. “In our project, as the air is compressed by the circulating water, it is also cooled by the water. We can expand the air at the bottom so it cools even further, reaching temperatures as low as -60 degrees Celsius or even lower. This frigid air could be redirected through the mine’s existing ventilation system to decrease the amount of electricity being used for conventional mine air conditioning.”

More to this than meets the eye

The verification process for Millar’s new project continues until the end of 2017. But already, Millar’s team is looking at complementary potential applications. Air conditioning and carbon capture are two examples of what might come next.

According to Shields, the air compression part is a no-brainer. “Hydraulic air compression makes perfect sense and would help make mining operations more energy efficient and, ultimately, more competitive. I suspect the energy savings might actually come in higher than Millar’s conservative estimate.”

Like the rest of us, he’ll wait to see the final results. In the meantime, he thinks using the system to capture carbon -- and selling the offsets -- sounds like another ground-breaking idea.

Sometimes what's old is new again. And sometimes what's new makes what's old even better.

Older but better is exactly what Dean Millar is banking on. His company, Electrale Innovation Ltd., has updated, and is currently testing, a century-old hydraulic air compression system to address the modern-day needs of companies in the mining sector.

Pioneered in the 1900s by Canadian engineer Charles Havelock Taylor, hydraulic air compression was used at 13 mines around the world, including the unit at Ragged Chutes that served the silver mines in and around the town of Cobalt in northeastern Ontario. By the 1970s, run-of-river air compression was replaced with mechanized air compression systems.

Professor Millar is MIRARCO Research Chair in Energy and Mining in the Bharti School of Engineering at Laurentian University in Sudbury, Ontario. In an abandoned shaft located at Sudbury’s Big Nickel Mine, he is overseeing a demonstration project to test the performance of his version of Taylor’s system. The ultimate goal is to commercialize the system, making it available for widespread use in industries such as natural gas and deep mining, as well as the steel industry.

“We see this project as an opportunity for Ontario to demonstrate technology leadership that will deliver significant energy savings for deep-mining customers,” said Terry Young, the IESO’s vice president, Policy, Engagement and Innovation.

Bottom photo: From left to right: Dominic Giroux (Laurentian University), Mayor Brian Bigger (City of Greater Sudbury), Julie Moskalyk (Science Director, Science North), Bora Ugurgel (Ultra Deep Mine Network), Hon. Glenn Thibeault (MPP for Sudbury and Ontario Energy Minister), Declan Doyle (IESO), Guy Labine (CEO, Science North) and Dean Millar (MIRARCO, Laurentian University & Electrale)