New solution proposed for sump management
Newalta demonstrates centrifuge technology
Alberta-based Newalta, a company specializing in recycling value from industrial waste, is proposing a new way to manage slimes in underground mines.
A mixture of mine water and solids, slimes are collected in sumps – essentially, large underground pits – on every level of a mine. The solids – consisting of dust particles and sand from backfill – settle to the bottom of the sump, and the clean water spills over the top into a clean side, where it is pumped to another area of the mine and then up to surface.
Over time, the solids fill up the sumps and spill over into the clean side, so at some point, the sumps have to be cleaned out.
“That’s where we’re offering a different solution,” said Newalta’s Todd Smith. “Currently, a loader is taken away from production to scoop out the solids and dump them somewhere else, or a submersible pump is used to transfer the slimes to another area where they’re dammed off and allowed to sit for six months in the hope that some of the water will eventually drain away.”
Newalta’s solution is to use a centrifuge to separate the solids from the water.
“By using centrifuge technology, you get a really dry product that you can transport and put back in with the other ore and send to the mill because there are metals in the slimes,” said Smith.
That fits in with what Newalta’s core competency of recovering value from waste, he noted.
“Instead of waiting six months to get a semi-dry material, you have an instantaneous process.”
Newalta has contracts with mining companies across Canada for work on surface, but this is the first time it has sought to apply its technology underground.
“We got a call from a mining company to look at a sump that had caked over,” recalled Smith. “There was a three-inch hardened cake on top, water in the middle and more solids underneath.”
Concrete mixed in with sand backfill had collected in the sump and hardened like rock, requiring miners to use sledgehammers and pickaxes to break it up.
There wasn’t much Newalta could do at that point, but the engagement highlighted underground sump management as a problem it could potentially solve using centrifuges to separate the solids from the water before the sumps filled up or acquired a rock-hard crust.
Using centrifuge technology should result in some savings on pump repair and maintenance, said Smith. Currently, “mines spend a lot of money on repair and maintenance and for purchasing pumps because they’re pumping material here, there and everywhere. Using centrifuges will reduce that significantly if we can continuously clean the sumps rather than waiting until they’re full.”
The metal content recovered from the solids will be assessed as part of a costbenefit analysis of Newalta’s proposed sump management solution.
“A significant number of mines are watching this to see if it works as planned,” said Smith. “Hopefully, it will become a new technology that everybody adopts.”
Newalta had a small workshop in Lively and an office in Sudbury to manage its dredging contracts for area mining companies, but recently consolidated its operations in a much larger facility in anticipation of playing a larger role in the underground mining sector.
Smith also sees other opportunities for recycling historical tailings for their metal content or for use as paste backfill.
Newalta serves a variety of industries, boasts a workforce of 2,200 people – up from 100 in 1993 – and operates out of 85 facilities across North America.
In 2012, said Smith, the company chalked up revenues of $726 million.