GOLD PROCESSING
determined in real time from continuous measurement of conveyed flows .
One example is a 1 Moz / y-plus gold operation in North America which increased ore throughput by 3 % within a month of installing a moisture analyser as moisture factors used previously to comply with dry tonnage processing limits were too conservative .
“ Moisture content can also be used to indicate the proportion of clay in plant feed and to control dust suppression systems ,” Kurth and Dr Balzan said .
In terms of fragmentation , volume and mass flow , Scantech ’ s SizeScan ( developed by COREM ) measures particle size distribution , volume and belt speed using 3D infrared camera technology and advanced algorithms to overcome segmentation software limitations on images from 2D cameras . It has also been successfully configured for foreign object detection .
“ It is used for oversize detection and fragmentation analysis and particularly effective in dusty and humid environments where other systems have not worked ,” Kurth and Dr Balzan said , adding that dedicated lighting is not required .
SizeScan has also been shown to measure volume very accurately , as well as belt speed , allowing mass flow to be determined to within 1 % of a nucleonic weigh scale , according to Scantech . As the system requires only a single calibration on installation , it has major benefits over belt scales and their need for ongoing calibration .
Kurth and Dr Balzan explained : “ The above technologies provide results in real time directly to the plant control system and all analysis data is owned by the client , with no accessibility issues . Data can be accessed on remote devices in real time .”
Measuring and managing conveyed flows at full throughput rates has proven very effective and measurement solutions that are customised to the quality of data required for optimal process control have generated major benefits , according to the company .
“ The application of high-quality representative measurement systems provides a new level of feed quality data visibility to all levels of the organisation at very low cost and for significant benefit ,” Kurth and Dr Balzan said . “ Most analysers integrate seamlessly with plant control systems ensuring data is easily accessed on site or remotely in real time . The availability of highquality measurement data enables operations to respond decisively and efficiently to unexpected variations in quality and automate process responses where needed .”
They concluded : “ Gold mining companies now have a new capability available to help with representative grade measurement in conveyed plant feed . Elemental measurement , combined with moisture and fragmentation data , can provide new levels of plant control through improved ore management , early waste rejection , process improvements through reduced consumption of resources such as energy , water and reagents , and reduced fine tailings generation .
“ Higher and more consistent feed grades result in higher metal recoveries and increased product for the same throughput capacity , generating major increases in revenue and reductions in costs .”
At the same time , more precise measurements enable tighter process control and improved outcomes , typically providing additional value amounting to many millions of dollars per year , Kurth and Dr Balzan said . Many resources companies are also adopting these technologies in various applications to not only improve sustainability , but also demonstrate responsible resource and environmental management to their stakeholders .
Enviro developments
Canada-based EnviroGold Global Ltd is , meanwhile , one company advocating for more environmentally friendly gold processing routes that avoid the use of cyanide . The company has recently filed a patent applications for a proprietary electrochemical process designed to achieve advanced metal recoveries from refractory ores with reduced capital expenditure compared with industrystandard solutions .
EnviroGold uses a range of mineral processing technologies as well as its own proprietary Electrochemical Separation Technologies to improve the oxidation of the refractory components from suitable fine ores and tailings . Through a combination of these technologies , EnviroGold ’ s metal recovery process induces changes in the metal-bearing material to solubilise metals from the surrounding ore matrix , it said .
Dr Mark Thorpe , EnviroGold Global ’ s CEO , said the new patent application increases the value of its intellectual property portfolio , while expanding the company ’ s opportunities to remediate legacy tailings dumps .
“ The residual metals contained in tailings are commonly encapsulated in refractory ores and it is estimated that the value of precious metals currently locked up in tailings storage facilities and old mine sites exceeds $ 1 trillion , increasing by $ 20 billion per annum ,” he said .
Commenting on the patent filing , EnviroGold Global ’ s Chief Technology Officer , Brock Hill , said : “ Refractory ores resist conventional metal extraction due to an impervious mineral matrix surrounding super-fine metal particles . The
complex processes required to significantly improve extraction from these ores can drive substantial increases in a project ’ s capital expenditure and operating expenditure , often rendering otherwise attractive resource recovery opportunities uneconomic . EnviroGold Global ’ s patent-pending process is designed with advanced electrochemical technology to induce changes in the metal-bearing matrix and achieve superior metal recovery rates .”
This process , in conjunction with other proprietary solutions developed for the removal of environmental contaminants , including cyanide , allows EnviroGold to provide a compelling value proposition for mine site owners while reclaiming and recharging natural resources , ultimately positioning the company to actively increase its significant tailings reprocessing pipeline , it said .
One project set to benefit from EnviroGold ’ s technology is the Buchans River Delta Reclamation Project .
The project includes approximately 1,225 ha of mining claims located in the Canadian Province of Newfoundland and Labrador .
The Buchans tailings were produced during decades of mining operations within the Buchans Mining District , which was home to one of the world ’ s largest volcanogenic massive sulphide deposits . From 1928 to 1984 , American Smelting and Refining Company Inc mined approximately 16 Mt from five deposits with an average mill head grade of 14.51 % Zn , 7.56 % Pb , 1.33 % Cu , 126 g / t Ag and 1.37 g / t Au . From the start of the operation to about 1965 , tailings from the operations were deposited into the Buchans River and flowed down the creek contributing to the Buchans River Delta .
Consistent with the company ’ s strategy of reclaiming valuable and strategic commodities while remediating legacy and other environmental hazards , EnviroGold anticipates commissioning recovery and clean-up operations at Buchans in 2022 . The company expects the reclamation technology and systems to be deployed will be designed with the capacity to process up to 1,000 t / d of the reclaimed tailings .
EnviroGold says it has one major project under contract , three major projects subject to MoUs , is negotiating commercial terms on two additional major projects and is conducting advanced analysis on three qualified major project opportunities .
“ The company expects to leverage its rapid analysis capabilities , its innovative profit share business model , and its scalable , modular approach to project development to acquire and develop nine major projects by 2025 with seven of the nine projects in commercial metal production by this time ,” it added . IM
34 International Mining | NOVEMBER / DECEMBER 2021