Reduction in cyanide purchased for gold recovery is not wishful thinking. GreenGold Technology tells Australian Mining about the technology that could revolutionise gold process plants.
GreenGold Technology is not afraid to tackle the negativity surrounding cyanide in gold processing plants head-on.
Cyanide is still considered the best lixiviant for gold, and alternative processes have their problems, according to GreenGold chief executive Malcolm Roy Paterson.
With over one million tonnes of cyanide consumed each year in thousands of gold mines around the world, the gold plant effluent is sometimes discharged without adequate detoxification.
This action is mainly due to the high cost of conventional detox processes. Any significant failure or leakage from the storage facility compounds the negativity associated with cyanide usage.
In response, GreenGold has commercialised a resin-based technology that can reduce the overall cost and use of cyanide in gold projects by 50 per cent, producing a thoroughly decontaminated tailings stream from the process plant.
“Back in the 1990s, we were developing a variant of ReCYN technology for gold recovery, but we had mixed success with that,” Paterson tells Australian Mining.
“We moved away from gold to focus on detoxification and cyanide recovery, which is now being successfully implemented. However, clients are saying, ‘Can we do all three together?’ ‘Can we go back and add in the gold recovery?’
“The addition of gold recovery was always intended to be part of ReCYN technology, but that was to be a later stage of development. It was not a simple move to include the gold component while maintaining the ability to detox.”
However, the idea was pushed by mining companies upon realising the shortcomings of their carbon processes, according to Paterson. Also, the quality of activated carbon appears to be deteriorating and negatively impacting gold recovery.
The result has been an innovative solution called ReCYN III.
ReCYN technology is now comprised of three options: ReCYN I for active (free) cyanide recovery, ReCYN II when detox is included to recover cyanide complexes such as copper, and ReCYN III when gold recovery is added.
All three aspects have been tested through laboratory, piloting and commercial application, but this is the first time the technology has been integrated into a single process plant.
For greenfields projects, the ReCYN III concept becomes very attractive as an alternative to a carbon circuit, which requires a more complex counter-current adsorption circuit with interstage screens and pumps, thermal regeneration and separate detox.
We believe this development is exciting as the new technology will have a big impact on the gold industry and fundamentally change the way process plants are built and operated, including lower capital and operating costs.
There are many other benefits of using ReCYN technology.
“The lower cost of recycled cyanide allows plants to economically operate at higher cyanide levels in the leach, thereby improving gold and silver recoveries,” Paterson says.
Combined with the ability to recover dissolved base metals and other cyanide complexes, the process simultaneously detoxifies the tailings stream.
Recovered base metals, especially at high concentrations, can provide a significant income stream.
The ReCYN process can solve the problem of nuisance levels of cyanide soluble copper, allowing for treatment of ores previously considered uneconomical.
“Tailings dams are no longer considered toxic due to cyanide and dissolved metals, and public perception of environmentally-damaging gold projects changes 180 degrees: it ceases to be an issue,” Paterson says.
ReCYN III is designed to not only provide a compliant standard of discharge, but also to beat those discharge levels.
In addition to two commercial operations in Indonesia, ReCYN III is being implemented in one brownfields project in the United States, and is designed into a greenfields project in Australia, both at commercial scale.
GreenGold is working at different stages on 30 different projects around the world that are considering applying its ReCYN technology, with the early adopters “very keen” to implement it.
The projects are spread over 10 countries, including Siberia, Alaska, Africa and South America, and several applications in Australia. GreenGold has assigned its metallurgical experts to conduct the test work on-site to execute a project-specific solution.
“We believe this development is exciting as the new technology will have a big impact on the gold industry and fundamentally change the way process plants are built and operated, including lower capital and operating costs,” Paterson says.
GreenGold employs over 60 people engaged in the development and implementation of the ReCYN technology. A full range of disciplines tackle all aspects of the technology, from research and development, studies, design and project implementation.
“There’s nobody else in the world that’s dedicating such a big workforce to focus on one aspect of gold recovery technology,” Paterson concludes.
This article also appears in the October edition of Australian Mining.