The Metallurgy and Materials Society of the Canadian Institute for Mining recently feted Barrick with the MetSoc Innovation Award for successfully developing a thiosulfate leaching circuit at its Goldstrike mine in Nevada. The new circuit uses thiosulfate, a chemical reagent, to treat double-refractory ore that cannot be treated using conventional processes.
"In an era where many companies are pulling back from supporting and developing new ideas, Barrick is to be commended on having the perseverance to carry a novel idea to fruition," says James Budac, PhD and MetSoc Awards Chair.
Developing this patented technology, which does not use cyanide, took years. The success of the project marked the first time any company in the western world has produced gold on a commercial scale using thiosulfate. The MetSoc Innovation Award supports innovation as a key pillar of the growth and development of the Canadian metallurgical industry. The award was accepted on behalf of Barrick by some of the team members who developed this technology: Peter Kondos, Senior Director of Strategic Technology Solutions, Yeonuk Choi, Director of Strategic Technology Solutions, John Langhans, Superintendent of Metallurgical Services, and Chief Metallurgists Janet Baron and Averne Flaharty-Escobar.
"It has been a fascinating journey seeing this technology through from a lab curiosity to an industrial success," Kondos says.
Thiosulfate is infamous in chemistry circles for yielding varying results if not managed exactly right. In gold mining terms, failing to get it right means that gold recovery rates can be unpredictable and thiosulfate consumption can be very high, pushing up costs. However, by trialing the process in a demonstration plant for 16 months, Barrick's team made gold recovery economically feasible.
While Barrick has long considered using thiosulfate, the newest phase of the project began in 2009 as an effort to unlock the value of Goldstrike's large stockpile of complex sulfur-carbon based ore, known as double-refractory ore. Traditionally, this ore required treatment in the mine's roaster, however, roaster capacity at Goldstrike was maxed out for years to come. Meanwhile, the mine's autoclave circuit had significant excess capacity, and was at risk of shutting down. The challenge was to develop a process that would treat double refractory ore using the autoclave circuit, therefore unlocking the value of the stockpiles.
In 2009, the site began testing the thiosulfate process in a laboratory setting. The results were promising enough to merit construction of the demonstration plant the following year. The full-scale facility began operating in 2015.
The success of the thiosulfate project will allow Goldstrike to process four million ounces of double-refractory ore that would otherwise have been processed at the end of the mine's lifecycle many years from now. It also allowed the mine to continue operating its autoclave facilities and retain the associated jobs, as these facilities are part of the new leaching circuit.
"We are extremely pleased to see Barrick's efforts in developing the thiosulfate leaching circuit recognized by MetSoc," says Kelvin Dushnisky, President of Barrick. "As we pursue best-in-class initiatives across the company and move to digitize our business, we look forward to expanding our technical knowledge and continuing to contribute to innovation in our industry."