Next-level tech injects value into mining

Air Liquide

Air Liquide’s Delaware innovation campus, home of its gold leaching testing platform.

Air Liquide has developed a gas injection technology called Nexelia to improve sustainability and quality of processes such as gold leaching and lithium carbonate purification.

The industrial gas supplier has grown out of France since 1902 to operate in 78 countries, employing around 64,500 people and serving more than 3.8 million customers.

With more than a century of experience in gas production technologies and applications, Air Liquide has served the Australian mining industry with mineral processing solutions for flotation and pH control, oxidative roasting, gold leaching and in-situ uranium leaching, process water treatment and nitrogen inerting systems for longwall underground mines.

The latest of these solutions is called Nexelia and it was designed in response to customers’ problems with chemical costs and sustainable processes. 

Air Liquide regional operation centre market manager Eiichi Mizutani explained the motive behind Nexelia. 

“Key objectives pursued by gold mine operators are to maximise productivity and gold recovery from increasingly complex ores, while doing so in a competitive and sustainable manner,” he told Australian Mining. 

“More than ever before, gold mine operators need reliable and cost-effective solutions to meet their performance goals while respecting their commitment to corporate social responsibility.”

Air Liquide
A flow chart of the gold leaching process using Nexelia.

Nexelia for gold leaching is an all-in-one gas solution that injects industrial-quality oxygen into the pre-oxidation and cyanide leaching circuit in the most resource efficient volumes. 

But no two ore samples are equal, and Air Liquide works with its customers to understand their material and design a system that will maximise productivity and minimise resource intensity. 

“It all starts with process expertise, interacting with our experts either on-site or in the lab,” Mizutani said. 

“By sending mineral samples to one of Air Liquide’s labs, we would design the experiment plan with different set-ups. 

“Then for every set-up we measure changes in oxygen uptake ratios, cyanide consumption and gold increase yields with our commercial-level testing.”

By reducing resource intensity and minimising chemical consumption, mining companies can improve their sustainability and costs.

But the benefits of Nexelia stretch even further, according to Mizutani. 

“In the gold mining field, the technology provides not only savings of cyanide consumption and sustainability, but it will also help to maintain or improve the gold recovery rate by verifying the mineral and adopting the oxygen transfer system for the specific application,” he said. 

In keeping with current demands for technology-driven solutions, Air Liquide has rolled out a monitoring solution for dissolved oxygen and pH levels.

The Air Liquide wireless monitoring system is designed primarily for gold and copper leaching monitoring, Mizutani said. 

“Using this system, the key data is uploaded almost real-time to the cloud, so we can check it anywhere from the smartphone or laptop,” he explained. 

“By monitoring key parameters like dissolved oxygen, it ensures efficient oxygen usage and high performance of the process in terms of gold recovery and chemical consumption.

“The benefits of such tools are operational traceability, early detection of abnormal situations, alarms, getting real data and less travel to remote locations.”

But Air Liquide wasn’t happy with just serving the gold and copper sector, adding Nexelia for lithium carbonate purification to the fray. Another all-in-one gas solution, this applies to lithium carbonates produced by acid or basic routes from either brines or mined rocks.

Mizutani explained how carbon dioxide was used in a three-step process.

“It dissolves lithium carbonate from slurry, then solid impurities are filtered out. Finally, when heated up, dissolved lithium carbonate precipitates and releases carbon dioxide,” he said. 

“The solution then captures the released carbon dioxide in this third precipitation phase and re-uses it in the initial dissolution phase.”

The result is battery-grade lithium carbonate and reduces the amount of carbon dioxide required per kilogram by three times – from 0.6kg of carbon dioxide per kilogram of lithium carbonate to 0.2kg of carbon dioxide. 

Mizutani is excited to watch the results in Australia’s growing lithium sector after the technology showed its worth in North America. 

“That was proven in Canada, but one of the strengths of our company is that Air Liquide’s efforts around the world can be replicated everywhere,” he said. “We feel that it is our mission to continue to contribute to the mining industry while grasping technological trends around the world.”  

This article also appears in the April edition of Australian Mining. 

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