Turning tailings into gold

NVRO Metals Limited has hit on a way to fulfil that demand without the environmental challenges involved in opening new mines. The opposite, in fact: the cleantech company’s proprietary NVRO Process™ actually cleans up environmental pollution from past mining operations.

Thanks to digital process optimization by ANDRITZ, NVRO Metals has improved both the economics and environmental performance of its tailings recovery operation.

TRASH OR TREASURE?

The organizations joining the new gold rush do so with their eyes wide open to the cost of new mining operations. If decades of institutional experience weren't evidence enough, then the 30,000 tailings storage facilities around the world, filled with toxic byproducts of traditional mining techniques, serve as stark reminders of the legacy a mine can leave behind.

But while many might see the global tailings stockpile purely as a cautionary tale, NVRO Metals saw an opportunity. Because mine tailings are not pure waste: they contain an estimated USD 3 trillion in unrecoverable precious, strategic, and critical metals.

Unrecoverable – until now.

The technology solves two problems at once, extracting these in-demand resources from stored tailings while neutralizing much of the toxicity that makes this waste a threat to the environment. When a 2023 internal study identified opportunties for further optimization, the company turned to ANDRITZ to help access it.

SIMULATION HELPS TURN POTENTIAL INTO PROFIT

The NVRO Process™ subjects mine tailings to a low-temperature hydrometallurgical process. As well as recovering precious, base and critical metals from the tailings, the process removes sulfides, reduces the potential for acid mine drainage, reduces heavy metal content, and stabilizes arsenic to prevent it leaching out into the surrounding soil. Following the process, the tailings no longer need to be stockpiled in specialized facilities; the remaining waste can be used to backfill the mine it came from, with greatly reduced risk of contaminating local groundwater.

NVRO Metals' 2023 pre-feasibility study indicated that the process could be more efficient. In theory it was possible to reduce operating costs while improving the quality of the end product: the metal concentrates.

To turn theory into practice and potential into profit, ANDRITZ built a simulation of the NVRO Process™ in IDEAS, the world's leading industrial process simulator. By creating high-fidelity virtual models of industrial processes, IDEAS makes it possible to test the effects of proposed process changes without risky and costly real-world trial and error.

Using IDEAS, ANDRITZ identified even bigger improvements than in NVRO Metals' own study. The simulation indicated it was possible to increase the concentrate grade of extracted gold by 286% more than the company had thought, and of silver by 450% more. 

MINOR MODIFICATIONS, SIGNIFICANT IMPROVEMENTS

Rather than requiring a major plant overhaul, the improvements were achieved through targeted, low-cost process modifications. The result was a more efficient operation that processes less unnecessary material, consumes fewer resources, and generates lower emissions. At the same time, NVRO Metals increased the recovery of valuable minerals and improved concentrate quality, demonstrating how smart process optimization can deliver both economic and environmental benefits.

“The ANDRITZ IDEAS simulation identified an additional USD 232 million in pre-tax, life-of-mine cash flows. This is just one example of the outstanding optimization outcomes achieved to date with only minor plant tweaks,” said Grant Freeman, Co-CEO, NVRO Metals.

The simulated process improvements were independently laboratory tested by ALS Global, to validate the results before NVRO Metals committed to full implementation.

The company then partnered with ANDRITZ and Hatch Pty Ltd to make the minor modifications needed to optimize its process.

The more critical metals the NVRO Process™ can extract from existing mine tailings, the less governments and industry need to rely on new mining operations to keep up with demand. By helping NVRO Metals optimize its process, ANDRITZ IDEAS has helped both to clean up toxic byproducts and to limit future environmental impact – all while boosting technological progress.

Steve Royan, Sales & Business Development, Automation & Digitalization at Separation, ANDRITZ, summarizes the project: “ANDRITZ's industry-leading IDEAS simulation software accelerated the optimization of the propriety NVRO Process™, helping to shape a more sustainable future for the mining and metals industry.” 

PROCESS OPTIMIZATION