Mill Circuits '24: a summary of the technical presentations

The inaugural Mill Circuits '24 was held at the Vineyard Hotel, Cape Town from June 13-14, 2024 and was attended by 51 delegates from 15 countries.

Following is a very brief summary of the presentations made over the two days.  This summary is intended to guide you to the extended abstracts associated with the presentations, most of which are available online as open-access. Unfortunately not all presenters responded to requests for drafts, but for those that did their names are linked directly to their papers in the online Proceedings.

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.

Thursday June 13th

Technical Session 1

Following my morning welcome and an introduction to the evolution of mill circuits from the industrial revolution to the present day, the sessions got underway with a keynote lecture from Dariusz Lelinski, of FLSmidth, USA,  "Evolution to revolution? How can innovation in flotation technology deliver sustainable productivity, now and into the future?", exploring how different flotation technologies can improve both productivity and sustainability performance. Dariusz is a regular contributor to MEI's flotation conferences and was the keynote speaker at Flotation’13. He has been working in flotation for 33 years, the first 8 years in academia, and the last 25 years for three different FLSmidth group companies (EIMCO, FFE Minerals and FLSmidth Minerals). His flotation experience covers a wide range of subjects, from basic flotation research, through CFD analysis, scale-up methodology, to industrial process and mechanical flotation machine design.

Dariusz Lelinski (centre) and the FLSmidth team with Kevin Galvin (right),
the inventor of the Reflux Flotation cell

Technical Session 1

Following the morning coffee break, Rajiv Chandramohan, of Ausenco, Canada, asked "what would a fully autonomous mineral processing circuit look like"?. Rajiv is Global Technical Director for Operations and Optimisation at Ausenco and has spearheaded the development of numerous innovative technologies tailored to the mining sector, contributing significantly to its advancement.

Rajiv Chandramohan (right) with Carsten Gerold of Loesche, Germany

Alan Varghese, of Metso Australia discussed optimisation of mill circuit pump reliability, detailing a comprehensive approach for pump selection, design and continuous improvement. Alan is currently undertaking a PhD in Digitalisation of Centrifugal Slurry Pumps at the University of Western Australia, while serving as the Product Head of Pumps Digital at Metso.

Alan Varghese (right) at registration

Martial Sorgho is the Process Manager for the Orezone Gold Corporation Bombore Gold Mine in Burkina Faso and he described the commissioning, optimisation and continuous improvement of the mill circuit.

Martial Sorgho (2nd right) and his colleague Mohamed Ilboudo with the MEI team

WEMCO flotation cell technology was first developed in the 1930s, updated in 1968 and has been the same ever since. Although this robust and impressive design has been a technology standard for many decades, the WEMCO II with improved rotor and stator configuration boosts metallurgical performance along with improved hydrodynamics and kinetics.  Riddhika Jain, regional flotation manager with FLSmidth, USA, discussed the development and performance of the energy efficient WEMCO II at pilot scale as compared with the traditional WEMCO, followed by consecutive trials at industrial scale.

Riddhika Jain with FLSmidth colleagues at the conference dinner at Groot Constantia

Technical Session 2

Following the lunch break Lev Filippov, Professor at the National Engineering School of Geology and Head of the Minerals engineering team of the GeoRessources Laboratory of the University of Lorraine, France, described the development of alternative processing circuits to recover critical metals such as Li, Nb, Ta and Sn from the Beauvoir rare metal granite in Allier, France.

In 2022 FLSmidth launched the Lithium Shake Up Study, focused on developing a spodumene concentrator flowsheet to reduce communication energy, improve recoveries and reduce water usage.  The FLS Shake Up flowsheet has a clear potential for energy reduction in the comminution circuit, reducing water use and reducing climate change impacts. The detailed outcomes of the comminution part of the study paint a hopeful picture of a more sustainable future for the metal supply chain, as described by Jaco Labuschagne, a Senior Lead Process Engineer MissionZero at FLSmidth, USA.

Jaco Labuschagne (centre) with FLSmidth colleagues

Due to the declining higher-grade hematite ore and increased demand for iron ore, magnetite-rich tailings from previously processed ore deposits are increasingly being exploited. Niyoshaka Lameck, head of the comminution group at Mintek, South Africa, explored an alternative flowsheet to that used for processing magnetite-rich ore for the recovery of magnetite from magnetite rich tailings.

Niyoshaka Lameck with Carsten Gerold and Christian Schmitz of Loesche, Germany

Another paper from Mintek brought the day's technical sessions to a close.  Taswald Moodley is a Principal Engineer within Mintek's Mineral Processing Division, and concurrently holds an honorary research fellow position at the University of Kwazulu-Natal, South Africa. He discussed the unravelling of steady state dynamics in comminution circuits through Principal Component Analysis and Pareto Fronts.

Taswald Moodley with Peer Druephake of Argo IPS, Germany

More on Day 1

Friday June 14th

Technical Session 3

Comminution was the theme of the final morning of the conference.

Victor Portnov is the CPO and founder of conference sponsor Conundrum AI, a technology company that provides a software platform for implementing, deploying, and running AI process control in the mining industry, discussed the integration and application of a new generation of process control models, combining fuzzy logic and model predictive control for improving the performance of SAG/AG mills.

The Vertical Roller Mill (VRM) is an established technology in cement and slag grinding applications. Adam McElroy, a specialist development engineer at Boliden Mineral AB described pilot and lab scale test work on three ores to demonstrate the potential for this technology to develop in the minerals processing industry.

Adam McElroy and Victor Portnov with Jenni Sweet of Mine3, South Africa

Carston Gerold of Loesche GmbH, Germany, compared the company's VRM milling with wet milling and HPGR alternatives, showing the power and water benefits of dry VRM milling on a magnetite ore.

Carsten Gerold (2nd left) at Groot Constantia

Sandile Nkwanyana

The potential benefits of composite media milling have been reported in past MEI comminution conferences. The benefits are in terms of reduction in ball consumption and improvement in the efficiency of energy utilization. Sandile Nkwanyana a Senior Process Engineer at Mintek, South Africa, discussed the practical issues that may necessitate closed circuit pilot test-work of composite media milling prior to implementation in sites.

Wound-rotor induction motors (WRIM) have long served large power applications, including SAG and ball mills, but despite the historical preference for WRIM, advancements in this technology have stagnated over recent years, said Mario Calvo, Managing Director of Electrodrives, Spain. In contrast, medium-voltage variable frequency drives (MV VFDs) have become increasingly sophisticated and cost-effective, positioning them as a competitive choice for both fixed and variable speed mills. Building upon the foundational technology of WRIM, Mario described the development of the FlexStarter LRS, a technical solution designed to bridge the gap between traditional WRIM setups and the newer MV VFDs, providing enhanced speed and torque control.

Mario Calvo (centre) at Groot Constantia

Sandile Nkwanyana was back on the podium for the final technical presentation of the conference, discussing surface abrasion, a key mechanism of size reduction of rocks in autogenous mills. He showed how rock surface abrasion tests can provide information on the suitability of the coarse rocks in the feed to allow operation of a mill at reasonable volumetric filling degrees.

More on Day 2

A final thanks to all concerned in making this a great conference, the sponsors, exhibitors, chairpersons, presenters and delegates, and last but not least the wonderful staff at the Vineyard Hotel.  We would greatly appreciate your comments on this posting.

A reminder also that the next conference in the series, with a modified title, Mineral Processing Circuits '24, will be held at the Vineyard from April 24th to 25th, 2026.

#MillCircuits24

Physical Separation '24: a summary of the technical presentations

Physical Separation '24, the 8th in the series, was held at the Vineyard Hotel, Cape Town from June 10-12, 2024 and was attended by 80 delegates from 17 countries.

Following is a very brief summary of the presentations made over the three days.  This summary is intended to guide you to the extended abstracts associated with the presentations, most of which are available online as open-access. Unfortunately not all presenters responded to requests for drafts, but for those that did their names are linked directly to their papers in the online Proceedings.

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.

Monday June 10th

Technical Session 1

Is physical separation still relevant in 2024? This was the question asked by James Agenbag, the regional sales manager for Africa and Europe for Mineral Technologies, South Africa in his opening keynote lecture. It is of critical importance he argued, as it is the most energy-efficient, chemical-free means of sorting and upgrading minerals. It will become an even more vital first-stage in future flow sheets. In addition, physical separation will also become a critical step in the recycling of batteries, cables, cell-phones and other electronics as we start to close the metal loop and start to re-use more and mine less.

James Agenbag (centre) with Mineral Technologies colleagues

Ajay Sihota, Director for Precious Metals Recovery with FLSmidth Ltd, Canada then discussed best practices in gravity circuit design and operation and the practical considerations involved in determining ore amenability, scale-up, design, operation, and maintenance of the modern gold gravity circuit. 

Ajay Sihota

The Reflux Classifier achieves powerful synergy between an upper system of inclined channels and lower fluidized bed arrangement, delivering gravity separation in a single stage of separation. With over 240 installations around the world, the technology has been used to beneficiate iron ore, mineral sands, metallurgical coal, potash, chromite, lithium, and other base metal oxides. Pedro Pinto, of ArcelorMittal, UK, evaluated the variation of fluidisation water and bed density in the performance of the Reflux Classifier on Western Africa iron ore fines.

Pedro Pinto

Kevin Galvin is the inventor of the Reflux Classifier and is Director of the ARC Centre of Excellence for Enabling Eco-Efficient Beneficiation of Minerals at the University of Newcastle, Australia. He is a recipient of numerous awards including the Ian Wark Medal, ATSE Clunies Ross Award, and Antoine Gaudin Award in mineral processing. He described the step-change improvement in gravity separation utlising the latest in a series of improvements.

Joshua Starrett is a PhD candidate, supervised by Prof. Galvin at the University of Newcastle. He discussed his work on the Reflux Classifier, aimed at maximising the performance of the particle size classification using inclined channels and the challenge of expanding the range of separation sizes beyond the previous limit of 180 microns. 

Joshua Starrett and Kevin Galvin

The GradePro is a modified version of the original Reflux Classifier technology and includes two key modifications to the original design: a reduced mixing chamber area and the use of secondary fluidisation water. These modifications allow for better stratification of particles by density and the removal of light gangue particles before they even enter the bed. Lance Christodoulou, of FLSmidth, USA showed how the the GradePro has been used to enhance the recovery of valuable minerals from low-grade ores and tailings.

Lance Christodoulou

Wynand Roux

Taking us to the lunch break, Wynand Roux, a lecturer at the University of Pretoria, South Africa, presented a study employing numerical modelling to explore the intricate hydrodynamics of a lab-scale inclined fluidised bed based on the Reflux Classifier design. 

Technical Session 2

Chris Ndoe

In the first presentation after lunch Chris Kaseba Ndoe, a PhD candidate at the University of Johannesburg described his work aimed at optimising chromite recovery from chrome plant tailings in South African Middle Group chromite seams using a Wilfley shaking table. Response surface methodology and central composite design facilitated the optimisation process.

There is a growing demand for lithium as it is primarily used in the production of batteries. Nichole Maistry, a Senior Engineer at Mintek, South Africa,described how two lithium bearing ores, namely spodumene and lepidolite, underwent gravity separation via heavy liquid separation laboratory tests to determine the amenability of each ore to upgrade by gravity processes, such as dense medium separation.

Nichole Maistry (right) with Mintek colleagues

Maria Cristina Vila

Maria Cristina Vila is Associate Professor in the Department of Mining Engineering at the Faculty of Engineering of the University of Porto, Portugal and she showed how dense media cyclone models have applied to the pre-concentration of a diamond ore from Angola.

Tebogo Mokgomola, an Engineer at Mintek, investigated the effect of conventional crushing and HPGR on the pre-concentration of South Africa's UG2 ore by DMS to ascertain if the crushing method can minimise PGM losses.  

Tebogo Mokgomola with Mintek colleagues

Tomas Machalek is a project manager with Heidelberg Materials AG, Germany and is also studying for a PhD at VSB - Technical University of Ostrava in the Czech Republic. His work involves technical support for quarries and sand & gravel pits and he described the optimisation of a suction dredger’s discharging pipeline.

Tomas Machalek (left)

More on Day 1

Tuesday June 11th

Technical Session 3

One of the most important developments in recent years as been sensor-based sorting as a pre-concentration process prior to crushing. It is a dry process so reduces overall water as well as energy consumption.

Conference sponsor Steinert is a leading player in this field, and Priscila Esteves, is the laboratory manager at Steinert Latinoamericana, Brazil, and she leads the development of Sensor-Based-Sorting applications in Latin America. She discussed the utilisation of sensor-based-sorting technology to enhance the quality of low grade iron ore.

Priscila Esteves (centre)

Jacek Kolacz, CEO of conference sponsor Comex Polska, Poland described how ore pre-concentration by sensor-based sorting is a complex process and must be optimised, especially when several sensors are applied. Therefore, a new optimisation method has been developed using an AI model to achieve efficient identification of required materials during sorting.

Jacek Kolacz (centre)

Vitor Andrade, a Process Engineer with Vale, Brazil, showed that understanding the amenability of the sensor for each type of ore is fundamental for obtaining better performance and can help calibrate the optimum threshold. He presented a performance evaluation of a particle sorting X-ray transmission sensor for different types of copper ore and their composition influence on the sensor performance.

Vitor Andrade (centre) with Vale colleagues

After the coffee break Tom Newman, a process engineer at ST Equipment & Technology LLC, USA, described the development of a dry separation system using a tribo-electrostatic belt separator, which requires no water or chemical additives. 

Athule Ngqalakwezi, a Senior Engineer at Mintek, South Africa then looked at the effects of mineralogical difference on magnetic separation of two magnetite tailings samples sourced from the northern part of South Africa.

Athule Ngqalakwezi (centre) with Mintek colleagues

Taking us to the lunch break Thiago Piacentini, Manager at Sibelco, USA discussed how high purity quartz is pivotal in advancing decarbonization through photovoltaic cells and enabling digitization via semiconductors and optical fibers. The primary reservoir for such quartz is found in North Carolina's leucogranite Appalachian deposits, rich in plagioclase, K-feldspar, mica, and heavy minerals. Existing purification methods, mainly flotation, incur high costs due to chemical reagents, mechanical complexity and extensive waste treatment. He described a study  exploring the efficacy of Pulsating Wet High Intensity Magnetic Separation in streamlining the purification processes.

Thiago Piacentini (right) with Francois Burger (Stark Resources, South Africa)

Technical Session 4

Frikkie Enslin, applications manager with Multotec Process Equipment, South Africa, focused on an important aspect relating to maximising profits in mineral processing- the lifecycle management and optimisation of the heart of many mineral processing plants, the hydrocyclone. He showed that cyclone lifecycle optimisation must move away from "one size fits all" to customised solutions.

Frikkie Enslin (centre) at the welcoming drinks function

Following on from this, Victor Portnov, the CPO and founder of conference sponsor Conundrum AI, a technology company that provides a software platform for implementing, deploying, and running AI process control in the mining industry, described the control and optimization of hydrocyclone classification performance with predictive models.

Victor Portnov with Jenni Sweet of Mine3, South Africa at Mill Circuits '24

Khuthadzo Mudzanani,a research engineer at Mintek, South Africa, presented case studies from various mining operations on how wet sieving efficiency is influenced by mineral ore physicochemical properties and operational conditions,

Khuthadzo Mudzanani (centre) with Mintek colleagues

As the original presenter could not attend, Max Richter, of the University of Cape Town, stepped in to present work laying the groundwork for a phenomenological screening model, offering a fundamental understanding of granular transport on vibrating screens.

In the final paper of the day Lesigen Moodley, of Eskom Research, South Africa described the microlithotype particle type classification and enrichment of coal maceral concentrates with the Reflux Classifier, Float-Sink and De Beers RhoVol techniques.

More on Day 2

Wednesday June 12th

Technical Session 5

Andrew Vietti, Director at Vietti Slurrytec, South Africa, introduced a model for understanding dispersive clay behaviour for tailings solid/liquid separation applications, highly dispersive clays within tailings often being the cause of poor flocculation and of poor dewatering unit process performance.

Andrew Vietti with his colleague Fredre Dunn

With high grade iron ore deposits in South Africa depleting, focus is placed on the use of low-grade ores. Tebogo Kale, of Gravitas Minerals, South Africa, described a new fine iron ore beneficiation process, The Kalahari Process, that aims to address the shortcomings of current technologies, with the Optima Classifier® at the heart of the circuit. The Optima Classifier® has proven its ability to produce a low, medium, and high-grade iron ore concentrate at economically favorable yields while also minimizing capital and operational costs. 

Tebogo Kale with his Gravitas colleague Franco van de Venter

CO2 emissions, water consumption, and tailings generation have driven the industry to develop environmentally friendly technologies. Thailli Conte, a geologist at Vale, Brazil, described a route for dry processing of iron ore which combines microwave technology for moisture reduction with the dry concentration of hematite and goethite fines in rare-earth permanent magnet concentrators.

Thailli Conte (centre) with Vale colleagues

Gravity separation, magnetic separation or flotation are often used to upgrade ilmenite-containing ores prior to smelting. The choice of minerals processing technology depends on the mineralogical properties, liberation size and associated gangue. Getrude Marape, head of Physical Separation at Mintek presented a study investigating the recovery of fine ilmenite by magnetic separation.

Gertrude Marape (centre) with Mintek colleagues

While bauxite residue (BR) is considered a waste product, it carries metals which can be recovered while minimizing the environmental impact. Kornel Tobiczyk, head engineer at Norwegian University of Science and Technology, Norway, presented a sustainable route for efficient extraction of metals from BR using hydrogen reduction followed by magnetic separation.

Kornel Tobiczyk (3rd left)

Technical Session 6

The production of chrome ore is growing, mostly as an outcome of China's rising demand. South Africa was the top exporter globally in 2021. The typical South African chrome concentration plant consists of 4 or more stages of spirals, still discarding chrome tailings with a grade of up to 20% Cr2O3. Franco van de Venter, process manager with Gravitas Minerals, South Africa, described a new chrome recovery process, ChromEx, which employs the use of the Optima Classifier®, with the aim of increasing overall chrome recovery and decreasing the tailings grade to less than 12% Cr2O3. 

Inga Sixhuta, an engineer in training at Mintek, discussed the characterization and processing of low-grade chromite ore for development of Cr mesoporous catalysts for oxidative desulphurization of dibenzothiophene.

Inga Sixhuta (2nd right) with Mintek colleagues at registration

The Beauvoir granite is a highly differentiated intrusion considered as one of the most promising hard-rock lithium deposit in Europe. It also contains interesting amount of tin in cassiterite, niobium and tantalum in colombo-tantalite and microlite. Bastien Demeusy, of the University Of Lorraine, France, described the concentration of tin, niobium and tantalum from the Beauvoir granite using a Falcon SB concentrator.

Bastien Demeusy with his co-author Lev Filippov

The conference came to an end with two papers on microwave technology from Vale, Brazil. Mariana Pereira is a Master Analyst at Vale and she described the calcination of kaolinite in a novel microwave rotating furnace. Vale's Kassia Toccolini then showed how a pilot plant study is proving that microwave technology for drying ores is becoming a green alternative, particularly in areas where clean electricity is largely available.

With Kassia Toccolini and Mariana Pereira

More on Day 3

A final thanks to all concerned in making this a great conference, the sponsors, exhibitors, chairpersons, presenters and delegates, and last but not least the wonderful staff at the Vineyard Hotel.  We would greatly appreciate your comments on this posting.

A reminder also that the next conference in the series, Physical Separation '26, will be held at the Vineyard from April 20th to 23rd, 2026.

#PhysicalSeparation24

June Cornish Mining Sundowner with the CSM class of '74

Despite a clash with the England v Denmark Euro '24 football match there was a good turnout last night at Falmouth's Chain Locker for the Cornish Mining Sundowner. It was a warm evening, very much like at the sundowner in Cape Town last week and a good opportunity to donate some of the MEI caps left over from Physical Separation '24 and Mill Circuits '24.

The numbers were swelled by the attendance of quite a few of the Camborne School of Mines graduates of 1974, who were celebrating their 50th anniversary this week, some travelling from Canada, the USA and South Africa for the reunion. There were some familiar faces but as I began my 22 years at CSM in 1974, I missed them as graduates as they were then undertaking their first jobs as mining engineers, mainly in southern Africa,

It was good to be back at the sundowner and the next one will be at the Chain Locker on Thursday 18th July from 5.30pm.

Memories of Reagents '04, Falmouth

Reagents '04 began 20 years ago yesterday at the Falmouth Beach Hotel, which was sadly destroyed by fire eight years later. Sponsored by Akzo Nobel and Cytec this first MEI reagents conference was attended by 50 delegates from 22 countries.

The Akzo Nobel booth

The Cytec booth

As with all MEI Conferences, an important part of the event was the social programme. On the first night, the formal Gala Dinner was preceded by a brisk cliff walk showing some of Falmouth's coastal scenery. On the second night delegates were taken on a tour of the historic Basset Mines, part of the heritage trail centred on the Great Flat Lode area of Camborne-Redruth, one of the world's most mined areas, mainly for copper and tin.

I am sure there are many familiar faces in the photos below, taken during the cliff walk, gala dinner and the mine tour.