June/July 2009

No smoke for this fire

Clean-burning incinerators are helping mine

By M. Eisner

Hackett River incinerator

One of the greatest challenges at a mining site is waste management. Everything from motor oils and packing materials to table scraps needs to be eliminated in the most cost-effective, eco-friendly manner. At remote or northerly sites, the problem becomes further exacerbated. With landfills and burn barrels becoming unacceptable, companies are increasingly searching for alternative solutions.

A proactive approach

Sabina Silver Corp.’s Hackett River silver-zinc project is located in Nunavut, approximately 480 kilometres northeast of Yellowknife. Currently in advanced exploration, the company has completed a Preliminary Economic Assessment (Wardrop, 2006) and is working towards a pre-feasibility study with AMEC.

Between 25 and 30 people live at the site from March to early October. The camp’s refuse is typical of many mining sites — general waste (food scraps, packaging, human waste, etc.), drilling waste (greases, lubricants, etc.), used hydrocarbons (motor oil, water-contaminated fuels, etc.), and wood/paper waste. While much of this is reused or recycled and flown to Yellowknife, the rest is incinerated.

Until last year, the site had an older, small-sized incinerator but Scott Burgess, Hackett River operations manager, said that following a conversation with Environment Canada, Sabina decided to purchase a bigger, newer dual- stage, forced air model.

“An Environment Canada representative in Yellowknife asked us what we were doing for garbage incineration,” Burgess recalled. “Because we were looking to replace our old incinerator, we thought we might as well get a bigger one now that would meet more stringent air quality emission standards. Basically, we wanted to be proactive in reducing our environmental footprint.” After speaking to other camps in Nunavut that had similarly sized operations, Sabina chose Eco Waste Solutions.

An interesting challenge

Choosing the right incinerator was the easy part of the equation. Getting it up to the camp and installing it was a different matter. The harsh climate and remoteness created interesting challenges that were met with creative solutions. “The installation took about two weeks,” explained Burgess. “We had one of the technicians from Eco Waste come up to help us right from the start so that we would install it correctly.”

Because of aircraft payload restrictions, the incinerator had to be disassembled for shipping and then put back together again on site. Once the parts were trucked from southern Ontario to Yellowknife, six flights were required to deliver them to an ice-strip on the lake adjacent to the camp. They were assembled on the ice, and then Great Slave Helicopters picked them up with a medium lift helicopter and brought them another three hundred metres to the camp.

“The pieces were very sizable, so a larger helicopter than we already had on site had to be brought in from Yellowknife to lift and swing them into place,” Burgess said. Often, in more accessible locations, these incinerators are housed within a rail container somewhere on site. In this case, there was no way to get a container in, so Burgess said they had to built a shed around the unit where it is now located.

A clean burn

Jean Lucas, business development director at Eco Waste Solutions, said her company has been creating clean-burning incinerators since 1994. At that time, their R&D department was looking to improve upon incineration in remote areas. They delivered their first unit to the Canadian military base at Alert — the northernmost, permanently inhabited place in the world.

“They had been using a landfill but had decided that it was an inappropriate way of dealing with waste in that climate,” recounted Lucas. “The landfill had also become an attractant to local wildlife, such as Arctic fox. An incinerator was the only solution that made sense. Since that time the Department of National Defence has completely removed the landfill and restored the land.”

Now, 15 years later, remote mining sites are planning ahead. During the construction phase of a project, there are often up to 1,000 people on site, which means waste can pile up quickly. The permafrost in northerly locations does not lend itself to the normal decomposition that typically occurs in a landfill over time and it is not safe to keep garbage around for too long, because the threat of attracting predatory animals is all too real. Additionally, landfills also represent a permanent alteration of the landscape in an ecologically sensitive area. These are some of the reasons why the industry is starting to think long-term, said Lucas.

“Mines are now saying ‘let’s just take care of waste as it’s generated; let’s get rid of it on site,” she explained. “This practice fits with the newer thinking of dealing with environmental issues during the mine life rather than waiting until the operations have closed to begin site rehabilitation. Our method of incineration is quite different from the old burn barrels, which would generate a lot of smoke.”

In addition to burning more cleanly, the new incinerators can also handle a wide range of items, including maintenance shop waste, vehicle and equipment oil, antifreezes, glycol, food waste, regular domestic garbage and sewage sludge. With the Eco Waste Solutions incinerator, the smoke from burning garbage in the first chamber goes into a secondary chamber, where high temperatures and the insertion of air hold the gases. “We use 1,000 degrees Celsius in that second chamber and retain the gases for two seconds,” explained Lucas. “By the time they go out from the stack, all the hydrocarbon bonds are broken down into water vapour and carbon dioxide. If you would look at the stack from outside, the exhaust gasses would be completely clear.”

Still working out the kinks

There have been a few minor challenges with the incinerator since it was installed at Hackett River in 2008, said Burgess, although he added that there have been no significant maintenance issues. However, with extreme winter cold conditions where temperatures regularly go as low as 40 and 50 degrees below zero, “nothing runs very well,” he acknowledged. Because of that, Eco Waste Solutions recommended taking the processor out from the electronic board to be stored in a warmer environment in Yellowknife. “We had to put it back in after taking it out, and it had to be reprogrammed,” explained Burgess. “We live and learn; next year we’ll know a bit more.”

Cleaner, fresher air

It has been almost a year since the new incinerator was installed and everyone at the camp sees a noticeable improvement in air quality. “The incinerator works well,” said Burgess, adding that the larger incinerator is used for the majority of burnable site waste, while the smaller one is used occasionally for lesser loads, primarily cardboard. “The volume of waste ash we must ship out has been noticeably reduced, and we all detect how much cleaner this unit burns; there’s no black smoke over the camp. We also see a difference in the air quality.”

The changes that accompany these higher standards are becoming more noticeable; as well, the industry continues to make bold efforts to achieve a cleaner future.

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