OceanaGold has shifted to a new technology in its processing plant at the Haile gold mine in the United States by replacing wedge wire screens with Derrick G-Vault interstage screens.
Given a choice, blinding and pegging of screens in a processing plant is not a mine operator’s favourite event.
Unfortunately, it was a daily occurrence at the carbon-in-leach (CIL) circuit at OceanaGold’s Haile gold mine in the southern United States.
Haile’s senior metallurgist Jeremy Rozelle says on average, his team experienced 14 to 16 hours of interruptions per week because of the situation. This meant the circuit was not running at optimal performance.
“At the Haile gold mine, we were pulling screens daily – it takes roughly two hours per screen. The Haile CIL circuit has 16 total screens, two in each tank,” Rozelle tells Australian Mining.
Looking for answers to the problem, the Haile team decided to test Derrick G-Vault interstage screens for a 12-week trial.
Derrick, a world leader in fine separation technology, installed two G-Vault interstage screens to compete with the existing wedge wire screens in the first and last CIL tanks. This gave the Haile operation a unique opportunity to evaluate the screens side by side under typical operating conditions. Subsequently, G-Vault interstage screens exceeded expectations, allowing OceanaGold to shorten the 12-week trial at Haile to 6.5 weeks.
“We have two different flow rates in our CIL. We trialled a screen in different tanks to test against both flows,” Rozelle says.
“In both cases, the Derrick screens remained without issue for 6.5 weeks. At that time, they were lifted and inspected. We found no defects or issues, so Haile decided to move forward with the screens.”
The Derrick interstage screens have continued to allow Haile’s circuit to run more steadily and efficiently. The Haile team has now retrofitted all 16 CIL screens with the Derrick G-Vault.
“During one event where a tank was offline, the Derrick screen had partially sanded in. Operations turned the rotation on to test it. The screen cleared itself without the need for lifting and cleaning, saving operator time, potential maintenance time, and allowing for a faster restart of the tank. This was one of the many factors to a successful trial,” Rozelle says.
“This time-saving feature allows all parties to be focussed elsewhere, leading to a more stable performance throughout the process. Pulling and cleaning is not as complex as it is time consuming.”
The Haile operation has now transitioned from daily maintenance issues to experiencing no shutdowns or diversions at all from the CIL circuit.
The change-outs have also protected the maintenance team from being exposed to a suspended load as the screens had to be lifted for maintenance. Team members were also required to wear a face shield as high-pressure water was used to clean the old wedge wire screens when blinded.
The G-Vault screens do not need to be pulled, which provides better run times and delivers both safety and operational benefits.
“We expect that the circuit will remain in operation more frequently, allowing for smoother operation,” Rozelle says.
“We also plan to reduce the loss of carbon due to the screens not being removed as often.”
The Haile circuit is now running close to maximum throughput. The Derrick G-Vault screens have proven that they allow for even more throughput.
“This means the circuit, if capable, could process more. We anticipate a small increase in our circuit’s available throughput,” Rozelle explains.
The move to Derrick G-Vault interstage screens reflects OceanaGold’s modern-mining approach at the historic Haile gold mine.
OceanaGold’s leadership is proud to build upon Haile’s rich history as one of the first mines in the United States producing gold since 1827, with an array of technological and design improvements.
The company celebrated its first gold pour at Haile in 2017, with plans to continue producing until 2033 and beyond using modern technology such as Derrick G-Vault interstage screens.
This article appears in the September edition of Australian Mining.