Hudbay Minerals has one of the lowest cost per tonne copper sulphide operations in Peru at Constancia, but it intends to continually improve the mine’s margins and environmental performance through a commitment to improvement. keep on going. This recently led him to explore the potential of ore sorting by sensor.
Hudbay’s Constancia operations include the Constancia and Pampacancha pits, an 86,000 tpd ore processing plant, a waste rock facility, a tailings management facility and other ancillary facilities that support operations.
The company increased reserves at the mine, located in the department of Cusco, by 33 Mt grading 0.48% Cu and 0.115 g/t Au last year – an increase of around 11% in copper content and 12% gold content over last year. reserves from the previous year.
With the incorporation of Pampacancha and Constancia North, annual production at Constancia is expected to average approximately 102,000 t of copper and 58,000 oz of gold from 2021 to 2028, an increase of 40% and 367%, respectively. compared to 2020 levels, which were partially impacted by a temporary eight-week mine shutdown related to a government-declared state of emergency.
Constancia now has a mine life of 16 years (until 2037), but the company believes there is much more value it can extract from this long-lived asset and has sought to incorporate the latest technologies to prove it.
In recent years it has, for example, worked with Metso Outotec to improve coarser flotation performance at Constancia using Center Launders in four e300 TankCells and installed a private LTE network to digitize and modernize its surface operations.
Peter Amelunxen, vice president of technical services at Hudbay, said Constancia’s ore sorting project – which has seen Hudbay partner with MineSense on a plan to test ShovelSense X-ray fluorescence (XRF)-based sorting technology ) from the Vancouver-based cleantech company – was one of many initiatives underway to further improve Constancia’s operational efficiency.
“The ore sorting program is separate from the recovery program at Constancia,” Amelunxen said, referring to a “potentially high return, low capital opportunity” that could boost crushed copper recovery by 2-3%.
He added: “The ore sorting program is expected to yield positive results in the mining phase of the operation and should increase mill head grade and reduce metal losses to the waste rock storage facility. .”
In April 2021, during a virtual site visit, Hudbay revealed that it was testing bulk sorting in Constancia as one of its “optimization opportunities”, along with the Amelunxen update I AM in mid-January on the progress.
Hudbay has already evaluated particle sorting at its Snow Lake, Manitoba operations — with benefits described in a “muted” desktop study given “bottlenecks and constraints,” Amelunxen said — but, at Constancia, he considered XRF sorting early on for copper-grade only pre-concentration, due to his perception that this application had the lowest potential risk and the highest probability of success.
The company has implemented a three-phase assessment process to prove this, with phase one involving a “bulk sortability study”, phase two moving to lab testing and phase three seeing trials. in the field.
The “bulk sortability study” examined the heterogeneity of downhole grades to estimate sortability versus unit volume curves, Amelunxen detailed. Laboratory testing of drill core samples to assess the effectiveness of the sensor was then carried out before economic analysis and long-term modeling was carried out.
With the concept and application of bulk sorting having passed all of these milestones, Hudbay in November began pilot testing XRF sensors on a loader. This involved fitting a ShovelSense unit to the 19 m3 bucket of a Cat 994H wheel loader, with approximately 20 small piles of “known grades” loaded onto the bucket and shipped through a feed and sample system ( photo below, credit: Engels Trejo, Technical Services Manager, Hudbay Peru). Once this process is complete, the company is now awaiting the results.
At the same time, the company moved to demonstration trials of a “production” ShovelSense sensor unit on the 27m3 bucket of a Hitachi ECX5600-6 excavator operating in one of the pits. It has been collecting raw spectral data from this unit since late November, with plans to continue receiving and analyzing sensor data through next month.
“We should have the XRF calibration finalized in February, at which time we will process the raw data collected over the three-month trial period and compare it with the short-term mine plan (i.e. grades of ore shipped),” Amelunxen said. . “Thus, by the end of February or the beginning of March, we will be able to validate or refine the economic model.”
If the results look favorable, Amelunxen is confident that renting additional sensors and installing them on the other two Hitachi ECX5600-6 excavators will not take long.
“Plans may change somewhat as the program unfolds,” he said. “For example, we can successfully sort the ore, but we feel that additional calibration is needed for sorting the waste at Pampacancha, in which case we can install production sensors on the Constancia ores while carrying out another program trial in Pampacancha.
“It all depends on the accuracy of the XRF calibration.”
Higher head grades and potentially higher copper recoveries can be the main benefits of using ore sorting technology, but Hudbay is also focused on achieving several key environmental benefits, including reducing energy and water consumption.
About the latter, Amelunxen said, “This is expected due to the processing of less ‘waste’ by eliminating unprofitable materials earlier in the process and reducing transportation and processing costs of unprofitable materials. “
Looking even further – beyond a possible commercial implementation of XRF-based ore sorting at Constancia – the company also plans to evaluate the application of other sensors.
“For our future copper development project in Arizona, we also plan to look at other sensors,” Amelunxen said, referring to the company’s Rosemont asset.
This ore sorting project is not the only project examined by the Constancia processing team, as Amelunxen has already hinted.
As part of the recovery uplift project, it is installing equipment that will allow the operation to increase the overall mass recovery of roughers, which is currently constrained by downstream pumps and the cleaning circuit.
“This will allow us to achieve an expected 2-3% increase in copper recoveries without affecting concentrate quality,” Amelunxen said.
Various initiatives are also underway under the banner “Moly Plant Improvement Projects”. This includes flowsheet optimization, pH control in cleaners, and pH reduction in bulk cleaners.
“This project has been ongoing since late 2019, and the installation of the new mechanical agitator in the cleaning cells was completed during the August 2021 scheduled maintenance shutdown and the new nitrogen plant was commissioned. in the second half,” explained Amelunxen. . “The next steps are pH control in the cleaners (with CO2), optimization of the water balance and possibly the installation of a Jameson flotation cell as a pre-rougher (the cell is already on site and not used, it will be reassigned pending the results of the pH tests).
A flotation reagent optimization study is also planned, aimed at reducing the zinc and lead contamination of the copper concentrate.
“A depressant addition system is on its way to site and is expected to be installed in February, with factory testing beginning in March,” Amelunxen said, explaining that this follows laboratory test work completed in 2021.