Tag Archives: bioheapleaching

BacTech, GMR, Dundee Sustainable Technologies to revisit Snow Lake gold project

BacTech Environmental, GMR and Dundee Sustainable Technologies are joining together to develop a potential solution for the remediation of the gold residual stockpile in Snow Lake, Manitoba.

As part of this effort, BacTech has signed a letter of intent with GMR to license its proprietary bioleach technology.

Through this agreement, BacTech received a C$20,000 ($14,689) cash payment as an advance on the right to use the bioleach technology on the project. In addition, BacTech will earn 3% undivided equity interest in the net income of the project.

This proprietary bacterial oxidation technology liberates precious and base metals from difficult-to-treat sulphide ores and concentrates, according to BacTech. This is a safe and environmentally-friendly process that has the advantage of improving metal recovery at significantly lower capital and operating costs when compared with traditional treatment methods of smelting, roasting and pressure oxidation, the company said.

BacTech said: “GMR is relying on BacTech’s historical research conducted in 2011-12 that showed oxidation rates of 95% and gold recovery of 88.6% on material obtained from the arsenic stock pile.”

It added: “Due to a lack of iron in the stockpile the residual material could not be stabilised and was abandoned.”

Ross Orr, CEO of BacTech, said: “Our return to Snow Lake is predicated on Dundee Sustainable Technologies providing a solution to the unstable arsenic product we generated in our earlier work that killed the project. The stockpile has a deficiency in iron leading to an unstable ferric arsenate product after bioleaching. By passing this unstable material to be vitrified, the arsenic can be safely disposed. We look forward to re-engaging in the Snow Lake project.”

David LeClaire, the CEO of GMR, said: “BacTech’s historic work on the project and its proprietary bioleach technology, teamed with DST’s vitrification technology, is a promising solution to the remediation of a longstanding environmental concern of the community of Snow Lake without cost to the taxpayer.”

The project consists of a stockpile of arsenopyrite concentrate proven to contain residual gold and silver. BacTech drilled and assayed the stockpile, which is currently the responsibility of the Government of Manitoba, in 2011 and produced a NI 43-101 report.

Current measured mineral resource estimates were generated in 2012 by BacTech estimating the Snow Lake concentrate stockpile contains 264,596 t grading 9.76 g/t Au and 2.17 g/t Ag. In addition, indicated resource estimates include 9,300 t grading 9.2 g/t Au and 2.15 g/t Ag, and an inferred mineral resource came in at 28,000 t at 7 g/t Au and 2.4 g/t Ag.

Former Talvivaara nickel mine on the rebound under Terrafame

The former Talvivaara nickel mine in central Finland is back in the black and looking to new developments four years after the previous owner went bankrupt.

Operating under Terrafame, majority owned by the Finnish government through the Finnish Minerals Group, the mine is finally making good on its early promise.

On a site visit to the mine this week, part of the Finland Mine Safari programme for analysts and investors, CEO Joni Lukkaroinen talked about getting back to planned capacity of 35,000 t/y of nickel, 75,000 t/y of zinc, 1,400 t/y of cobalt and 5,000 t/y of copper.

The company hasn’t set out to change any major part of the process flowsheet to do this – it is still using a two-stage bioheapleaching process to produce a nickel-rich pregnant leach solution that is precipitated as sulphides in the plant – but it has refined the operations Talvivaara started up almost a decade ago.

On top of this, the company is looking to bolt on a hydrogen sulphide line that could see the company produce 170,000 t/y of nickel sulphate and 7,400 t/y of cobalt sulphate for the emerging electric vehicle battery market, in addition to 115,000 t/y of ammonium sulphate for fertilisers.

And, it also has a near-completed uranium plant that could potentially produce yellowcake in the medium term should it receive an environmental permit from the relevant authorities.

Talvivaara may be best known for the gypsum pond leak that occurred in late 2012 and saw nickel, uranium and other toxic metals go into the nearby environment, but even before this event led Talvivaara Sotkamo to eventual bankruptcy, it was struggling to achieve the production numbers it had previously forecast as the bioleaching process that justified mining the low-grade ore got the better of it.

Terrafame, which was formed in 2015 specifically to turn the operation around, has already surpassed the former owners’ production record and, earlier this year, started generating postive earnings.

EBITDA excluding work in progress (ore within the leaching pads) came in at a slim €1.6 million ($1.85 million) in the March quarter and more than doubled to €3.3 million in the most recent June quarter.

This is some change from the -€33.3 million and -€24.2 million the company posted in the same periods a year earlier.

Improved year-on-year metal prices have helped this recovery, but the company has also gone from producing 9,791 t and 4,787 t of zinc and nickel concentrate, respectively, in the March quarter of 2017, to a record 15,008 t of zinc and 6,421 t of nickel in the same quarter of 2018.

While these numbers are still some way off full capacity, they are significantly more than the circa-14,000 t per quarter Talvivaara produced at its peak.

There was at least one obvious change to the process Talvivaara set up when IM visited – Terrafame is now using Wirtgen surface miners to improve the material feed that is stacked and reclaimed from the leach pads and moved onto the metals plant – but the improvement in performance has been achieved through several tweaks, according to Lukkaroinen.

He told IM that the company has, among other things, put much more emphasis on improving the agglomeration of the ore, ensured the material on the leachpad is effectively aerated during both leaching stages and monitored the temperature of the exothermic process much more closely. The latter, in particular, is very important in judging success of the leaching.

This is really now starting to pay dividends during the 50 months, combined, the ore sits on the primary and secondary leach pads.

It has also given the company confidence to invest in a hydrogen sulphide plant that could see the company increase its exposure to the EV battery market.

As it stands, the company already sells around 50% of its nickel concentrate to this market, but the production of nickel and cobalt sulphates is likely to see the company retain more value for its product and provide further sales opportunities.

The fully-financed sulphide plant build will take some two years to construct, with start up, subject to regulatory approvals, planned for the second half of 2020. The company is just months away from awarding the major contracts for the construction.

The process, already proven on a commercial scale, will see nickel-cobalt sulphide from the existing production plant processed in an autoclave, before nickel cobalt and impurities are extracted. It will finally move on to a crystallisation phase where two separate sulphate products are produced.

The 170,000 t/y nickel capacity would make the company one of the biggest sulphate producers in the world.