Comminution '23: Summary of the technical presentations

Comminution '23 was MEI's 13th International Comminution Conference, and the first face-to-face comminution event since Comminution '18 post-Covid.

The conference was held at the Vineyard Hotel, Cape Town from April 17th-20th. Following is a summary of the presentations made in the technical sessions over the four days.  The draft papers associated with the presentations are available online. The drafts have not been refereed, but all the presenters have been invited to submit their final papers for peer-review to a virtual special issue of Minerals Engineering.

Table Mountain from the Vineyard Conference Centre

Monday April 17th

Jon Wills opened the conference this morning, welcoming our 215 delegates from 25 countries and thanking our sponsors for their support and patience over the time of the pandemic.

The conference got off to a great start with a keynote lecture, Taking ownership of our future: the case for cooperative research and technology development in the mining industry from Malcolm Powell, one of the world's most well known comminution specialists. He has applied fundamental comminution research to design and process improvement on over 60 mines worldwide during 30 years at Mintek, University of Cape Town, and the JKMRC. He developed the comminution group at UCT into a world renowned leader in the field, now headed by our conference consultant Prof. Aubrey Mainza. Prof. Powell collaborates extensively, with close compatriots on 5 continents and he is the founder of the Global Comminution Collaborative, whose members are represented this week at the conference.

Malcolm Powell (right) with Leon Lorenzen of Mintrex, Australia

Breakage and energy was the theme of the nine papers that followed Malcolm's keynote in the morning session. Grant Ballantyne showed how comminution can be described by combining fractal dimension of fracture surfaces and "Size Specific Energy." It was good to see Grant, who was awarded the MEI Young Person's Award in 2017 when he was with JKMRC. He is now Director of Technical Solutions at Ausenco, Australia.

Grant Ballantyne (right) with Daniel Lay, of JKMRC, Australia

It is always a privilege to have CSIRO's Paul Cleary at the comminution conferences. Paul, ranked #1 of the 600 elite scientists in the field of Mining & Metallurgy in the recent Stanford University listing of the Top 2% of Scientists in the world, is recognised as one of the great pioneers of the Discrete Element Method (DEM) and he has developed world class DEM capabilities for predicting the flow of granular materials in industrial processes. He is also a leading developer of the Smoothed Particle Hydrodynamics (SPH) method for industrial fluid dynamics and presented an SPH model for prediction of fracture of realistic complex structured elastic brittle rocks.

Paul Cleary (right) with Holger Lieberwirth of TU Bergakademie Freiberg, Germany

A breakage model for DEM was the subject of the paper by Michael Denzel, a research assistant at the University of Leoben, Austria, and this was followed by two papers on the  Geopyörä breakage test, a state-of-the-art rock breakage characterisation technology.

MEI's Amanda with Michael Denzel

Marcos de Paiva Bueno, the CEO of Geopyörä Oy, Finland, presented the first paper, on assessing the accuracy and precision of energy and force measurements using the Geopyörä breakage test. Marcos has carried out extensive comminution circuit surveys as well as pilot plant campaigns both in Australia and internationally. Working as a senior process engineer for Ausenco, he was involved in technical and engineering studies related to most key mining commodities. More recently, as a senior researcher and lecturer at the University of Oulu, Finland, he developed the Geopyora breakage test with financial support from Business Finland, together with fellow senior researcher and lecturer, Gabriel Barrios, co-author of the next paper showing how Geopyörä can be used to measure particle strengths and fracture energy distributions. This was presented by Marcelo Tavares of Universidade Federal do Rio de Janeiro, Brazil.

Marcelo and Marcos at the Geopyörä booth

Sami Makni is a researcher at Corem in Canada, and he described the development of a mini-drop tester at Corem for particles from 12.5 mm to 3.35 mm. The objective of the mini-drop tester was to provide the results of the mini-drop in a simulator using a DEM model to predict ball mill grinding product size distribution. 

Shujaat Ali is currently completing his PhD at the JKMRC, Australia with a particular focus on the development of a novel ore characterisation method to quantify practical minimum comminution energy requirements and as he was unable to attend the conference, Malcolm Powell presented on his behalf a comparison of different ore breakage characterisation methods to measure practical minimum comminution energy, relative to a novel test developed at the JKMRC, the Precision Rolls Crusher. 

Tulio Campos, of Universidade Federal do Rio de Janeiro, Brazil, presented work investigating single-particle breakage behaviour of a polymetallic ore under slow compression when stressing particles individually up to a single-layer full of particles. 

Tulio Campos with Magnus Evertsson of Chalmers University, Sweden

There has rarely been any mine plan for a SAG milling operation that captures both the variation in mill throughput, and the related value of metals produced for the life of mine. Since it is now possible to accurately measure ore hardness using standard drill cores, it is also possible to krig the associated geometallurgical data into the mine plan and forecast the metal production and mill throughputs together. Unfortunately John Starkey, of Starkey & Associates, Canada, was unable to travel to Cape Town and Xinyi Tian, of the University of Alberta, gave the presentation "Ore Hardness Testing and Geo-metallurgy Management" on his behalf.

Xinyi Tian with Hamid Manouchehri of Northland Oretech, Sweden 

We are all missing John and his wife Donna this year. John's company has sponsored MEI's comminution conferences for a number of years. He is the inventor of SAGDesign technology, and commercialized the test in 2004, the same year the technology was patented by Outotec. In 2018 his company bought the Patent and in 2020, patented the Mini Pilot SAG mill which can run pilot SAG grinding and beneficiation tests using commercial drill core from any deposit for feed. I have no doubt that we will see them both at Comminution '25.

A break for lunch

The first paper after lunch, presented by Nubia Bottosso, a research engineer in iron or processing at ArcelorMittal Global Research, France, investigated the influence of mineralogy on energy consumption at Mont-Wright's concentrator, where grinding energy fluctuations affect productivity, in this Canada's largest supplier of iron ore to the global steel market.

Nubia Bottosso with Louis Steyn of Metso Outotec

There then followed six papers on modelling and simulation. Yousef Mohammadi joined Molycop Global, Australia in 2020 as Leader Data Analytics to manage digital transformation and developed the Molycop Digital Engine for mineral processing circuit analysis and plant-wide optimisation, which was the subject of his presentation.

Edward Mavungu of Anglo American presented a method for development of industrial scale ball mill model parameters from laboratory milling tests that can be used for optimisation of the ball mill performance and estimation of performance under different operating conditions.

Edward Mavungu with Sherry Bremner of UCT

Indresan Govender is at the University of KwaZulu-Natal (UKZN) as Professor of Particle Technology and Mineral Processing and he is also Group Executive: Mineral Processing & Characterisation at Mintek, South Africa. Indresan maintains an active research relationship with UCT and UKZN through his concurrent appointments as honorary Professor, and he presented a new granular flow model of rotating drum flows.

Brazilian company Rocky DEM is sponsoring an MEI comminution conference for the first time, and Vinicius Daroz, an applications specialist at Ansys do Brasil, Brazil, showed how the Rocky DEM high-fidelity and fully coupled SPH-DEM solver has been used to solve the complex flow structure within grinding mills, focusing on the development and validation of both small-scale and large-scale SAG mills using this new solver.

Smooth Particle Hydrodynamics to model the slurry and DEM to capture charge behaviour have been used at Mintek, South Africa, after tracking the motion of slurry and charge particles by nuclear imaging measurements. Taswald Moodley, a senior researcher at Mintek showed how the optimised simulation parameters were employed to find the operating conditions that maximise performance.

The final paper of the day was presented by this morning's keynote speaker, Malcolm Powell, Emeritus Professor at the University of Queensland and Director of Liner Design Services, Australia. He argued that rocks do not instantaneously transport along a tumbling grinding mill and are consequently not perfectly mixed, but this is not captured in mill modelling, a lack of understanding of the transport phenomenon and the difficulty of modelling realistic transport in a complex tumbling system, contributing to this. Visual evidence of segregation in mills and lag time of mill response to changes in feed support incorporating transport in dynamic models to underpin dynamic simulation for design and for model-based control. Results from preliminary model development indicate the incorporation of size-dependent transport substantially changes the fitted rates and modelling outcomes. This points towards the value of incorporating transport to improve the accuracy of mill design for ranges of ore competence from AG to high ball load SAG mills.

It has been a long and intense first day, so it was good to relax in the Vineyard Gardens for the first of our evening sundowners (more on Day 1).

Afternoon speakers Taswald Moodley (2nd left) and Vinicius Daroz (3rd left) with
Ann-Christin Bottcher, of Netzch Trockenmahltechnik, Germany and
Michael Denzel, of University of Leoben, Austria

Tuesday April 18th

Following on from yesterday's afternoon session, modelling and simulation was the subject of three papers in the morning session, software for conference sponsor Rocky DEM again being highlighted in the first paper, presented by Carlos Les, a senior consultant with Element Digital Engineering, UK. 

Carlos explained that DEM is a technology that can simulate the space- and time-dependent comminution behaviour. However, as the product particles and their collision count grow exponentially through the milling process, memory and computing requirements very rapidly become unmanageable. This means the use of DEM for practical full-sized comminution devices is currently limited to those with no particle breakage. To overcome this limitation, a reduced-order semi-analytical mathematical model has been developed which can estimate the machine output product size distribution and wear rates from the machine operational parameters. The model combines physics-based breakage and wear models with impact data generated from non-braking DEM simulations computed using Rocky software. Carlos described the model architecture and validation using a multi-shaft compact vertical mill as a case study.

Carlos Les with Simon Bailey of Keramos and Alex Wang of King's Beads

Christoph Thon is a research associate at the Institute of Particle Technology at the Technical University of Braunschweig, Germany. He discussed the application and development of artificial intelligence techniques in the context of process engineering, specifically comminution, in close concert to experimental investigation and computer simulations such as CFD or DEM.

Christoph Thon with Michael Prenner of University of Leoben, Austria
and Michael Mairhofer of Cemtec, Austria

Paul Cleary was then back on the podium to present a complete particle scale model for the prediction of SAG mill performance, based on a coupled DEM+SPH model which can be used to predict the motion of solid charge and of the slurry phase

Dean David, of Wood, Australia, then showed how Loesche’s Vertical Roller Mill (VRM) has achieved superior pilot plant comminution outcomes on WA's Grange Resources hard Southdown magnetite ore  compared to a conventional AG, magnetic separation and ball milling pilot circuit. VRMs utilise hydrostatic breakage to emulate HPGR power efficiency and can also achieve selective liberation. 

With Dean David (2nd right), Aubrey Mainza (centre), of UCT
and Carsten Gerold and Christian Schmitz, of Loesche, Germany

Following these papers, the rest of the morning highlighted control and instrumentation, beginning with a paper from Andrew Bauristhene, a Process Engineer with conference sponsor Magotteaux International, Belgium. He introduced MagoSense, and innovative real-time mill monitor, which has resulted from a close development between Magotteaux and KIMA Process Control. The MagoSense can be used to investigate the effects of many parameters on the milling process as well as to assist with controlling the mill filling level.

Some of the Magotteaux delegates

Rajiv Chandramohan leads the global operational optimisation group at Ausenco, Canada, providing debottlenecking and operational optimisation services. His paper presented steps to set up an effective control system, from the base layer control to advanced tuning, ensuring a comminution circuit’s operational stability is met for highly variable feed.

Rajiv Chandramohan with Nick Wilshaw of gsl

Joe Felix is a familiar face at many MEI Conferences; since 2010 he has concentrated on business development, growing the CiDRA brand across Sub-Sahara Africa region via his own company, Felix Projects, which currently is the sole agent for CiDRA Minerals Processing Inc. He explained the shift in perspective for new technology implementation, using real examples from commissioning of CiDRA's CYCLONEtrac™ Particle Size Tracking (PST) system at Freeport McMoRan's Cerro Verde’s C2 Concentrator in Peru and the benefits they witnessed. This concentrator witnessed improved Net Metal Production, among other benefits by using PST, which provides real-time, online, and direct particle size measurement at the individual hydrocyclone level.

Joe Felix with his son Travis, of CiDRA,
with Tako De Jong, of Tata Steel, Netherlands

Hydrocyclones formed the basis of the next two papers. Lin Yang, a PhD candidate at the University of Adelaide presented the development of a real-time particle size distribution and P80 monitor. The measuring of these two parameters is challenging due to feed and operational conditions continually changing but are crucial in assessing comminution performance. The study provided a unique method based on solids impact mechanics. An adjustable physical-threshold in-stream probe was designed for measuring particle size distribution and P80 online. The force and vibration signal on the probe due to particle impact are sensed and the link between the impact vibration signal, particle size distribution and P80 can then be modelled.

Lin was a co-author of the next paper, presented by  Lei Chen, who has more than 30 years of experience in developing cutting-edge mechatronics systems for multi-disciplinary applications including mining. He is chief investigator for both the PRIF Mining Consortium – “Unlocking Complex Resources” and ARC Training Centre for Integrated Operations for Complex Resources. Ultrafine solids online detection and corresponding particle-size-distribution (PSD) analysis at hydrocyclones, being essential to energy-efficient comminution, has been challenging due to operation condition variation with time and between individual hydrocyclones, and has been costly given the large number of hydrocyclones to be monitored. An attempt towards a cost-effective solution was proposed in previous work by the authors, presented at Sustainable Minerals ’22, which however, was subjected to accuracy loss caused by operation condition shifts with increased presence of coarse particles. The current study, focused on improving PSD approximation in the ultrafine size regime under operation variability. Featuring sensor fusion with both force and acceleration measurements, the new approach allows ultrafine particles detection in real time, with wide-spectrum capability to handle coarse-particle contamination, delivering enhanced robustness and accuracy in PSD approximation. 

Lei Chen (left) and Li Yang (right), with University of Adelaide colleague Zeqi Li

In August 2021 Kevin Brooks formed APC Smart to mentor and train upcoming advanced process control engineers and provide profit improvement programs and project implementation in APC. In July 2019, he was appointed visiting and later an honorary adjunct professor at the University of the Witwatersrand. He was president of the South African Council for Automation and Control in 2013 and 2014, and hosted the very successful IFAC World Congress in Cape Town.  With the increase in available data and the stricter control requirements for grinding circuits, the development of data-driven models brings an opportunity to enhance the capability and efficiency of model-based control for a grinding circuit. Kevin presented a data-driven model that was developed based on historical data from an operating plant. The advantages of this approach are that there is no need to disturb the process during step testing, and that modeling is based on long term operation where asset degradation and ore variability are considered.

In many hard-rock mine sites, comminution constitutes over 50% of the total energy consumption, so every effort is being made to to reduce this, preconcentration before the crushing stage having progressed rapidly over recent years, mainly due to the advances in sensor-based sorting, but other innovative methods are under developments.

Daniel Lay is a postdoctoral fellow at the University of Queensland, working on high voltage pulses and their application to the mineral industry. High voltage pulse enabled preconcentration has the potential to provide large energy savings  but although the concept is well established in the laboratory it is yet to be demonstrated at the throughputs needed for industry. Daniel described a novel electrode design which has been patented which may scale up the concept from laboratory to continuous operations.

Last year it was reported (posting of 18 July 2022) that a team from Canada was awarded a US$3.9 million grant to further develop CanMicro, which combines microwave-assisted comminution and multi-sensor ore sorting technology to selectively break particles and sort waste from desired minerals, reducing crushing and grinding requirements. The University of Alberta and Sepro Mineral Systems are major players in this team, and Xinyi Tian discussed her work on the commercialisation of the technology with the team at Sepro.

Steinert is one of the major suppliers of sensor-based sorting machines, and Priscila Esteves is head of the laboratory for the Steinert Latinoamericana Test Center in Brazil. She described a comprehensive study on a polymetallic ore, with the aim of generating a better understanding of how pre-concentration impacts the grinding circuit of the Aripuanã Project, located in Brazil.

Priscila Esteves with Ergin Sarp Zencirci, of Esan, Turkey

Elpidius Muleba, a comminution senior metallurgist at First Quantum Minerals' Kansanshi Mine in Zambia, then described the impact of scalping coarse material from the crushing circuit on throughput at Kansanshi's copper oxide circuit.

Elpidius Muleba (3rd left) relaxing with delegates in the Vineyard gardens

Crushing was the subject of the four presentations after the coffee break.

Magnus Evertsson is a professor at the department for Industrial and Materials Science at Chalmers University of Technology, Sweden, and represents Chalmers on the Global Comminution Collaborative. He described a model used to simulate particle fracture and showed how the fatigue lifespan and liner wear of cone crushers depend on the feeding conditions.

Magnus Evertsson with Quentin De Jager, of Crush Force, South Africa

Prof Evertsson's colleague, Kanishk Bhadani, is a senior researcher at Chalmers and is currently the project manager in an Horizon Europe project Rotate where the focus is to develop a process and environmental platform. He looked at the design of experiments in evaluating crusher circuit performance.

Kanishk Bhadani delivers his presentation

Mark Drechsler is a Director of CBRM Mining Services, Australia, that is patenting and commercialising its Gyratory Rolls Crusher (GRC or GRolls) innovative technology for the global markets. The GRC technology has been developed to reduce energy and water consumption, providing dry and wet crushing from ~20mm to 20 micron fractions without media, replacing up to two stages of size reduction.  The GRC is a compression based particle size reduction device, designed to generate fine and ultra-fine products from coarse feeds, by simultaneously applying pulsed compression and shear forces to a packed particle bed.  The breakage mechanisms initiated by these forces include impact breakage, inter-particle compression, induced tensile failure and particle shear forces generated by a gyrating roll. Mark discussed the commercialisation pathway of the GRC technology, from “proof of concept" to laboratory scale Alpha prototype and upscaled Beta prototype for a pilot plant.  

In the final paper of the day Holger Lieberwirth, Director of the TU Bergakademie Freiberg, Germany, looked at new insights into double roll crushing (DRC) which he said belonged to the older comminution principles. It is known for high throughputs of sometimes sticky materials such as oil-sands. but its applicability for ore and hard rock processing has been underestimated in recent decades. Holger showed that recent research on DRCs has shown that they are suitable for these applications as they are a robust and reliable group of comminution machines.

It has been another long day, so it was good to relax at Cape Town's Gold Restaurant in the evening for the informal conference dinner (more on Day 2).

The Global Comminution Collaborative at the Gold Restaurant

Wednesday April 19th

A slightly later start today, to allow for last night's dinner!  The morning got off to a good start with a keynote lecture from MEI's comminution consultant, Aubrey Mainza, Professor and Head of the Chemical Engineering Department at the University of Cape Town, and a member of the Global Comminution Collaborative. In his keynote he asked what is driving the growing trend of using high steel load in SAG mills?

Aubrey's keynote was followed by two papers on innovative comminution machines. Titus Nghipulile is a senior engineer at Mintek, South Africa, and he is also researching for PhD at the University of the Witwatersrand. He described the use of DEM to study breakage and transportation of particles in a new comminution device, the rotary offset crusher, which is under development with a promising performance potential.

Steve Wilson, Chief Technical Officer at Canada Mining Innovation Council's subsidiary ReThinkMilling, then introduced a new, high efficiency grinding machine, the Conjugate Anvil Hammer Mill,  a patented technology that translates Klaus Schoenert's comminution energy efficiency principles of unconfined, thin particle bed, compressive breakage into commercial, production-scale devices in multiple size ranges.

Steve Wilson (right)with Lawrence Nordell
of Comminution & Transportation Tech, USA

The benefits of compressed bed technology are now well known with the introduction of high compression grinding mills for dry comminution circuits and three papers on HPGR followed the break.

Adrian Thamm is a Sales Engineer for HPGR, at Köppern Aufbereitungstechnik in Freiberg, Germany. He reviewed fundamental research in the field of edge effect in HPGR and its physical basis and limits. Wide machines effects, side activation systems like flanges and additional rollers, as well as gap related grinding efficiencies were presented. 

To flange, or not to flange rollers was the subject of the next paper, by Ralph van Rijswick, Chief Engineer at Weir Minerals, The Netherlands. He reported on an extensive test programme on HPGR's which showed that flanges can have both positive as well as negative effects. Furthermore, the impact appears to be very dependent on the aspect ratio of the rolls. 

SAG mills are designed to run with up to 95% mill availability. This can only be achieved if unscheduled downtime due to any mill liner/bolting failures is eliminated and the time span between liner replacements (scheduled maintenance and downtime) is maximised. Amit Saxena, Technical Director with conference sponsor ME Elecmetal Inc, USA, showed how SAG mill liner survivability and wear life can be quantified.

Amit Saxena (3rd left)with the ME Elecmetal team

Taking us up to the lunch break Matt Hazell, the product lead at Bradken Resource, Canada, showed that stable and reliable SAG mill operation is critical to ensure the overall productivity of the comminution circuit. The ability to predict the current mill charge level and to derive associated shell trajectories based on the charge level are essential for reducing its variability and improve overall throughput. He described a suite of digital tools that has been developed by Bradken to address the SAG mill operational challenges.

Matt Hazell (centre) with Ben Docherty of Bradken Australia
and Tarisha Naidoo of Bradken South Africa

Unbalanced vibrations, which occur every cycle whenever there is a broken liner, could be detected and applied to monitor AG/SAG mills liner health conditions, according to Zeqi Li, a Phd Candidate at the University of Adelaide. He described Magotteaux-sponsored research to measure the operating angular positions of the liners in a laboratory-scale SAG mill and the relationship to unbalance vibrations during every cycle under varying mill operating loads and speeds.

Boaz Friedland is Technical Director at Energy and Densification Systems, South Africa and he introduced the EDS Multishaft Mill, a compact vertical mill which utilises high-speed impacts to break down particles with large reduction ratios, low energy consumption and improved liberation. Anglo American, together with EDS, designed a single pass pilot plant with the EDS mill at the centre, which was then installed at Anglo’s Amandelbult mine near Thabazimbi, South Africa. The unit was set up to process the mine’s UG2 run-of-mine ore, although waste ore was also later processed through the mill. Boaz showed that results from the project have been very positive.

The well-known trade-off, when aiming to increasing ball mill throughput, between capacity benefits from increasing circuit recirculating load, versus diminishing classification efficiency, was explored by Jun Heo, of Weir Minerals, Australia,  using digital tools and simulation to evaluate ball mill circuit recirculating load and performance.

Jun Heo with Xinyi (Wendy) Tian, of Sepro, Canada

Yogesh Reja is a simulation engineer at Derrick Corporation, India, focusing on operational improvements in mineral processing circuits through improvements in classification. He described a methodology to predict improvements in capacity of closed grinding circuits considering both classification efficiency and recirculation load for real-world grinding circuit capacity predictions.

Yogesh Reja (centre) with Jean Makola of Derrick South Africa
and Robert Winterfield of Derrick, USA

Michael Mairhofer is Technical Manager at Cemtec Cement & Mining Technology, Austria, and he showed, from results at a new gold ore processing plant in Siberia, that a modern mechanical drive solution for power rates up to 28MW is a good alternative to gearless design.

With Michael Mairhofer (centre) and
Craig Naude of Solo Resources, South Africa

Hydrocyclones play an essential role in the performance of comminution flowsheets. The classification performance of the hydrocyclones drive the efficiency of the balance between throughput and grind size. Therefore, optimising closed-circuit grinding circuits requires stabilizing the hydrocyclone operation and balancing the operational constraints for variable ore and feed characteristics. In his second presentation at the conference, Rajiv Chandramohan of Ausenco, Canada, detailed several optimization case-studies, highlighting the importance of process control strategies to achieve circuit throughput and grind size targets.

The final paper of the day was presented by Sam Palaniandy, the Global Product Manager (TowerMill) at Nippon Eirich Co. Ltd. based in Brisbane, Australia. He showed that over-grinding is a major issue when dealing with soft ore such as the high-grade iron ore deposits in Asia with a Bond Ball Mill Work Index of 6–8 kWh/t. These ores require grinding to prepare pellet feed and the main challenge is to achieve a narrow particle size distribution and ore variability is another challenge as the plant will be purchasing ores from various mines. A flexible grinding circuit with multi-stage classifications and TowerMill was designed for this duty and Sam discussed ore characterization, grinding test work, circuit design, modelling, simulations, and total cost of ownership calculation of the grinding circuit.

Sam Palaniandy with Edwin Joon Yean of Orica, Australia

And so another very productive day ended, with a late afternoon sundowner (more on Day 3).

Thursday April 20th

The final day of the conference began with a keynote lecture from Arno Kwade, Head of the Institute For Particle Technology, TU Braunschweig, Germany and Vice-President of the Global Comminution Collaborative. He showed how the wet stirred media milling process can be predicted and optimized regarding energy efficiency, mill and media wear as well as product particle size distribution. However, recently dry operation of stirred media mills has come into focus for the minerals industry in order to improve efficiency compared to tumbling ball mills and to avoid the use of water and eventually expensive drying processes. 

Arno Kwade with Ann-Christin Bottcher, of Netzch Trockenmahltechnik, Germany

Prof. Kwade was a co-author of the next presentation by Maximillian Tobaben, a research associate at TU Braunschweig, who discussed the fine grinding of pyrometallurgically produced battery slags for dissolving and recovery of lithium. The fine grinding of the slag generates a high specific surface area and a significantly reduced crystal size, which increases the solubility of the lithium-containing slag phases.

Sandile Nkwanyana has been working as a researcher in the comminution group at Mintek since 2021. He completed his PhD study at the University of KwaZulu-Natal in 2021, under the supervision of Professor Brian Loveday and Indresan Govender, his co-authors for his presentation which showed that throughput expansions in excess of 15% can be achieved by employing composite media in ball-mills in a typical SAG/Ball mill circuit, if the charge level in the ball-mills can be increased.

Adolph Mwale, a Process Optimisation Specialist at Metso Outotec, South Africa presented a summary of the optimization path followed by Minera Sabinas, Mexico, as well as the results obtained from the operation after commissioning the tertiary grinding circuit. A comprehensive summary of results was presented to benchmark the previous circuit configuration and its performance in terms of comminution circuit energy efficiency, flotation recovery, reagent adjustment for circuit fine-tuning purposes and the path forward for continuous process improvement. 

Jesse Ting is currently working for Metso Outotec as a Product Manager of Grinding Plant Unit within the Concentrator Plant product group. His role focuses on developing the most sustainable grinding process and plant solution for reduction in cost, time, and risk. He showed how Metso Outotec is leading a sustainable change with its integrated grinding circuit units.

Jesse Ting and Adolph Mwale with Bjorn Nielsen of Metso Outotec Australia

Edwin Joon Yean Koh, a specialist in process modelling and machine learning at Orica, South Africa, then described how value at a Platinum Group Metals Concentrator was maximised by the development of an integrated comminution and flotation Flowsheet.

Edwin Koh by his poster presentation

Conference sponsor Russell Mineral Equipment has a big team of 12 delegates at the conference. Following the morning break there were two presentations from RME. Samuel McQuade presented a case study of mechanical liner manipulation vs manual liner manipulation. Mill relining can be a dangerous and difficult task. Workers are often required to complete manual handling activities in dark, hot, confined spaces, and on uneven surfaces and John focused on a safer relining solution for mills with liner weights of up to 400 kg. 

In the second presentation Stephen Gwynn provided an update on best practice in plant design for relining.  Examples provided guidance to owners and designers to elevate the relining practices within the industry.

Stephen Gwynn and Samuel McQuade

Continuing the theme of liners, Abhishek Sinha, of Tega Industries, India, highlighted that it has always been a big challenge to design an efficient lining system for large diameter SAG/AG and ball mills in the mining industry. The conventional steel lining has been in use for several decades and mill operators continue to be challenged in handling effectively the ever growing need of mill throughput resulting in higher impacts from bigger ball sizes, along with the need to design bigger and larger liners to reduce the installation/ reline time. These challenges, together with the safety of workers during installation has always been a key concern and Abhishek showed how the Tega composite design lining system- Dyna Prime is addressing these concerns.

Abhishek Sinha (left) with Tega colleagues

Chris Greet, the Manager Mineral Processing Research at Magotteaux, Australia is a familiar face not only at MEI's comminution conferences, but also at the flotation series. He showed how  the development of fine grinding technologies like the IsaMill, HIG mill and the SMD, which are all eminently capable of achieving product sizes as fine as 4 microns, have regrind mill discharge pulp chemistry which is invariably unsuitable for the subsequent flotation stage. He provided a number of examples demonstrating how fine grinding effects the product pulp chemistry and influences subsequent flotation behaviour.  Fine grinding generally produces discharge pulps that have reducing Eh value, very low dissolved oxygen contents and high oxygen demands and methods of improving the pulp chemistry prior to flotation were explored.

Chris Greet with Wenhua Liu of Grintec Magotteaux Ceramic Technology, China

Divine Ssebunnya is a PhD candidate within the Centre for Minerals Research in the Department of Chemical Engineering at the University of Cape Town. Her research focuses on the development of models of comminution devices using methods such as DEM and SPH and she described the modelling of particulate and fluid flow in laboratory scale stirred media detritors.

Divine's fellow UCT student Wilco Sievers then described a DEM numerical modelling approach to simulating size segregation of media in a stirred mill and the effects on grind characteristics.

Wilco Sievers with Divine Ssebunnya

Stirred milling was the theme of the final session after the lunch break, beginning with a presentation from Bjorn Nielsen, the Vice-President of Stirred Mills and HPGR at Metso Outotec, Australia. He showed that, as  different design stirred grinding mills have different grinding and breakage characteristics and will perform differently for each duty, machine specific test work is required in order to accurately determine specific energy requirements for each stirred mill type in each grinding duty. 

Bjorn Nielsen (right) with Jesse Ting and Arno Kwade

Studies of the dynamics of grinding media within a shearing environment such as an IsaMill require indirect methods of observation due to the opaque nature of the system and high shear forces any internal probes are subjected to. For this reason, Positron Emission Particle Tracking, a non-invasive particle tracking technique, has been extensively utilised to study the grinding media dynamics in tumbling mills and IsaMills. Sherry Bremner, of the University of Cape Town, compared the dynamics of grinding media in a 3 disc horizontally stirred mill as it is derived from PEPT experiments, as well as DEM simulations.

Sherry Bremner with Paul Cleary

Andres Paz, Sales Manager at Swiss Tower Mills Minerals, Switzerland, discussed recent developments in coarse grinding using Vertical Stirred Mills, which have become a recognized solution for secondary, regrind and fine grinding applications in the mining industry due to their energy efficiency, small footprint and cost savings. This technology has further potential as the number of comminution circuits where the vertical stirred mills are paired with other energy efficient size reduction devices, such as HPGRs or crushers, is growing.

Matthew Toll is a research metallurgist at the ultrafine grinding metallurical laboratory of conference sponsor Keramos in Australia. He discussed how in general recirculating loads are typically associated with comminution mills operated in closed circuit with classification stages. However, some stirred mill comminution circuits, particularly IsaMills, are often operated with an “internal recirculating load” whereby the mill product is separated by a positional valve and partially recirculated to the feed sump to maintain the stability of volumetric feed rate to the regrind circuit/IsaMill. He showed that the occurrence of high internal recirculating loads can significantly hinder IsaMill efficiency and a number of methods for control of IsaMill recirculating load were discussed and evaluated across different ore types. 

Glencore's IsaMill™ has established a reputation of being the leader in the fine grinding market over the last 25 years and Hans De Waal, Principal Metallurgist with Glencore Technology, South Africa looked at open and closed stirred mill circuit design. As future ore body grades decline, the industry will naturally shift to treat harder finely disseminated ores. This is going to drive the liberation requirements finer and increase the corresponding specific energy demands higher. Ultimately this is going to put greater emphasis on how to manage heat (e.g. closed circuit) within the stirred milling process whilst keeping the ability to maintain the sharp product size distribution that the IsaMill™ is known for.

Hans De Waal (2nd right) at the Glencore booth

Alex Wang, Technical Director of King's Beads, China, discussed collaborative research with the University of British Columbia investigating the impact of media density and bead size on stirred mill energy performance. Selecting media with physical properties best suited for a given grinding duty could improve the grinding energy performance as well as the quality of ground product. 

Alex Wang (3rd right) with the King's Beads team

Charlie Ingham is the Grinding Media Sales and Services Manager for Australia and SE Asia with Keramos, and like the previous speaker, Matthew Toll,  is based at the ultrafine grinding metallurgical laboratory in Australia. He explained how ceramic grinding media continues to be a large operational expenditure for mine sites operating stirred media mills, and selecting a suitable media product is crucial to reducing this expense. Laboratory and pilot testing can be used to inform the decision as to the most optimal media product and size selection from the perspective of wear, process and cost performance. However, the effectiveness and reliability of such laboratory and/or pilot studies are significantly influenced by test work practices and as such can be subject to debate. Charlie analysed the effect of laboratory test methodologies on the results of media product wear performance testing in differing stirred media laboratory milling technologies.

There are major changes taking place at Keramos, and Simon Bailey, Head of Grinding Media and Metallurgy, who is based in Falmouth, Cornwall, outlined the imminent launch of the new comminution sector of Keramos, Global Met Tech (posting of 6th April 2023).

Charlie Ingham (left), Matthew Toll (2nd right) and Simon Bailey (right), of Keramos,
with Chris Martin of RSG Inc, USA

And so we came to the end of one of our most successful and enjoyable comminution conferences (more on Day 4). But not quite- Prof Aubrey Mainza is a prominent member of the Global Comminution Collaborative (GCC) whose members have played a major part in this conference. After summarising the four days, Aubrey, on behalf of the GCC, presented prizes of 500 Euros each to the two students who were judged to have made the best overall student presentations at the conference, Tulio Campos, of Universidade Federal do Rio de Janeiro, Brazil and Maximilian Tobaben, of Technische Universitat Braunschweig, Germany.

Tulio Campos and Maximilian Tobaben with GCC members Luis Marcelo Tavares and Arno Kwade

MEI's Amanda then closed the conference by thanking once again our sponsors, exhibitors, presenters, delegates and the excellent staff of the Vineyard Hotel, and inviting everyone to return in two years time for Comminution '25, which will be held from March 31st to April 3rd. Such is the interest in this event that nine companies have already signed up as sponsors.

Here's to Comminution '25

We would greatly appreciate your views on the conference via comments to this posting.  There are also many comments on Twitter and on LinkedIn.

All the photos on the blog postings, and more, are in a Comminution '23 Album.

Please feel free to download photos for your personal use. If you would like to use any photos on a company website, please acknowledge the source (MEI Blog).

#Comminution23   @barrywills