Global Event Wrap - AusIMM MillOps Outcomes

AusIMM’s Mill Operators Conference 2021 (MillOps) took place in Brisbane from 23rd-25th June, and was a great success!

This year’s MillOps was a hybrid event, with over 600 attendees joining either in-person from Brisbane or online. Over the three days of the conference, the program featured 40 technical sessions, three keynote speakers and a trade show with over 50 exhibitors.

Stephen Durkin, CEO at AusIMM, said: “A super successful week in Brisbane with 570 delegates attending our MillOps conference in person and another 60 delegates online. Super proud of the way everyone has worked together to deliver such an outstanding event in such a challenging environment - with no international delegates and a committee; delivery team and attendees from across the country challenged by interstate borders closures.”

CEEC is a long-time collaborator with the MillOps conference organizers and the AusIMM, and CEEC’s CEO and Directors were in attendance. CEO Alison Keogh delivered a global announcement about CEEC’s 10-year anniversary and the launch of CEEC’s new webinar and video series, which you can read more about here.

Conference highlights

CEEC Director and past Chair Joe Pease attended the conference and noted: “One obvious highlight was how enthusiastically people took the chance to meet face to face again. Of course, not everyone could, but there was a strong online contingent too. The atmosphere and interaction from the physical attendees may have improved the experience for virtual attendees – in every session there was a healthy mix of questions from the floor and from online, leading to active discussion and invariably the time ran out while the discussion was still in full flow.”

He added that this atmosphere was also helped by the consistent high quality of papers and presentations. The conference also used a single session format, which has several advantages.

“Everyone can go to every session, and it means that only the best quality papers are accepted,” said Pease. “The short presentation time of 15 minutes forces speakers to focus on the key messages, not to present the paper. This allows time for, and prompts, engaging discussion sessions.

“These features allowed the conference to achieve its real purpose – high quality, energetic interchange and discussion of ideas to improve efficiency of minerals production. There were simply no weak points in the technical content or discussion – from grinding, comminution, gold recovery, coarse sorting, gravity separation, process control, plant design, testwork design and minerals education.”

The conference program had an excellent line up of practical case studies and latest advances across gold, copper, nickel, tin, iron ore and other commodities. CEEC Director Greg Lane gave the keynote presentation on Day 1, on the topic ‘Operations, Engineering & Development – Metallurgists’ Worlds Apart?’.

His presentation provided guidance on different work environments for metallurgists and process engineers and covered operations, design and research and development. He also discussed how advanced technologies such as automation will cover bulk ore sorting, coarser particle flotation and more efficient comminution machines.

Selected papers – Dr Grant Ballantyne’s suggestions

CEEC medal 2020 winner for technical research Dr Grant Ballantyne was also at the conference and attended many of the presentations. He kindly provided his insights into some of the best papers presented at the conference that align with CEEC’s mission to accelerate the implementation of eco-efficient comminution practices.

Ballantyne highlighted that Professor Malcolm Powell from the University of Queensland’s Sustainable Minerals Institute (SMI) won the joint award for the best paper for the conference as he presented the endemic issue of overloaded ball mills in SAG mill/ball mill/crusher (SABC) circuits.

“The paper discussed the major reasons for overloaded ball mills: high feed rates, fine grind targets, coarse feed (especially topsize), competent feed and poor classification; and presented potential solutions,” said Ballantyne. “Practical methods for diagnosing overloaded ball mills were presented, including size specific energy (SSE) and overall equipment effectiveness (OEE). By addressing some of these concerns the mill power can be increased by 3-9% in addition to a 5% increase in efficiency, i.e. the mills could do an extra 8-12% more work.”

Newcrest Mining’s Rob Edmunds presented the upgrades that have been made to the grinding circuit at Ridgeway (part of Newcrest’s Cadia operations in New South Wales) following the upgrade of the pre-crushing circuit from secondary to tertiary crushing.

“The SAG and ball mill motors were upgraded as well as significant alterations to the SAG mill internals,” said Ballantyne. “All these changes allowed an increase in capacity from 5Mt/y when operating as an AG milling circuit to 7Mt/y operating as a tertiary pre-crushed SAG circuit even as the ore hardness increased.”

Another presentation that received a lot of interest from the audience was Ben Wraith from the Bluestone Mines Tasmania JV talking about the operation of the ore sorting plant at the Renison tin mine in Tasmania. The presentation showed that the sorting plant regularly operates at 25% mass rejection and 97% tin recovery.

“Renison have found that at higher rejection rates they achieve lower recovery in the sorter, but higher overall recovery because the mill recovery increases as the feed grade increases,” said Ballantyne. “Renison presented the breakdown of their operating costs and found that 50% of the costs are associated with maintenance.”

Newcrest Mining’s Emily Jaques presented the challenges and successes from the commissioning of the coarse ore flotation circuit at the company’s Cadia Valley operations, where the company successfully installed the Eriez HydroFloat Separator for coarse particle mineral concentration. This paper was the other joint winner of best paper at the conference.

The grind size at Cadia increased from 150µm to 220µm, with a corresponding increase in throughput, without impacting recovery. The fines devoid streams were highly abrasive and required upgrades to the wear materials. The Eriez HydroFloat separator recovered particles coarser than 425µm with very low surface exposure; however, with the HydroFloat concentrate reporting to the cleaner circuit, a finer regrind size should be targeted.

Gold Fields Australia’s Reg Radford presented the commissioning of the Gruyere gold project in Western Australia. “Interestingly, the project economics showed that the operating cost benefit for a high-pressure grinding rolls (HPGR) circuit was not great enough to warrant the increased capex, so an SABC circuit was built,” said Ballantyne.

“However, the site is close to Tropicana and has similar ore characteristics, so a direct comparison may be possible when they start treating primary ore. Wear rates were excessive with pebble crusher lasting only 6-8 days. This led to a discussion about the abrasion index test as their average Ai was 0.49.”

Takeaways, thank yous and proceedings

Pease noticed that everyone he spoke to at MillOps was energized by different ideas that related to their operation. He concluded: “CEECs objectives are to communicate, collaborate and celebrate – well, this is exactly what the conference did. I hope that in some way we can help keep some of that dialogue going now that people are back in their day jobs.”

CEEC would like to thank Joe Pease and Grant Ballantyne for their valuable input on the MillOps conference.

CEEC also wishes to acknowledge the hard work of the AusIMM events team, the authors and presenters, and the committee whose hard work made this conference such a success despite the significant pandemic challenges, with particular thanks to Conference Chairs Katie Barns (Mineralis) and David Seaman (Newcrest) and their committee: Rob Coleman (Core Resources), Diana Drinkwater (Mineralis), Stuart Emergy (Solvay), Aidan Giblett (Newmont), Bianca Newcombe (Optifroth) and Andrew Newell (RPM). Thanks to sponsors and exhibitors, who generously supported the event and functions and provided excellent displays and engaging, informative discussion.

All registered delegates can watch the MillOps conference proceedings here, or you can purchase the full proceedings from the AusIMM digital library here. Meantime, CEEC continues to build its resource library and has selected and uploaded a number of excellent 2021 MillOps paper abstracts to our website here:

Winning and mentioned papers:

Other notable papers:

The next MillOps conference will be in 2024.