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Comminution '01

Hilton Hotel, Brisbane, Australia
March 21-23, 2001


This, the 3rd International Comminution Conference, was organised by Minerals Engineering International in collaboration with the Julius Kruttschnitt Mineral Research Centre, Australia and sponsored by Mintek of South Africa. The event dealt with all aspects of the commuinution of ores and coal.

The conference was held at the Hilton Hotel, situated on Queen Street Mall, in the heart of Brisbane's central shopping, entertainment and business district.



Conference Report

International comminution 'family' re-unites in Brisbane
by David Goeldner*

Run in collaboration with the Julius Kruttschnitt Mineral Research Centre, and sponsored by South Africa's Mintek,  Comminution 01  brought together a select group of the world's leading practitioners in this field to Brisbane, Australia, to present developments in comminution.

The conference featured the latest advances in fine grinding, SAG, AG and ball milling, the modelling, simulation and control of comminution circuits, Discrete Element Method and an array of new milling devices and other technology.

A total of 35 presentations over three days, a field trip to the JKMRC and a gala dinner at the conference venue's Hilton Hotel, kept delegates busy - and entertained - during their visit to Brisbane in late March.

It was fitting that the JKMRC's founding Director Professor Alban Lynch be the first speaker at Comminution 01. After a long and distinguished career as one of Australia's leading authorities on comminution and classification, Professor Lynch set the scene in the opening session on 'Comminution Fundamentals' with an historical overview of the problems encountered in fine grinding, from the nineteenth century to the present day.

Svedala's John Herbst advanced this discussion into the 21st Century with a critical review of grinding design features in such devices as SAG mills, lifters and stirred mills. He presented how 3-D simulations will allow microscale visualisations of drive design and optimisation.

On his first visit to Australia, Canadian-based SAG mill designer, John Starkey, offered some practical considerations when starting and maintaining a SAG milling operation, and in particular the energy implications for SAG milling. John presented how the SAG Power Index (SPI) had recently been applied in the field in eastern Russia.

The level of technical excellence presented at Comminution 01 was evident in George Banini's paper which wrapped up the first session. A former JKMRC PhD student and now with Rio Tinto Technical Services, George gave many in the audience an introduction to his work which had provided the minerals industry with its most comprehensive description of rock breakage to date. George's model focuses on energy absorption and how this affects particle size in rock surface and body breakage. His robust method takes into consideration the mechanisms for AG/SAG mill appearance function calculation.

During the second session a few key themes in comminution began to emerge, evident in Lawrence Nordell's joint paper with John Herbst on 3-D Discrete Element Method. Lawrence Nordell is president of USA company Conveyor Dynamics Inc who reappeared later in the conference to take another look at the use of DEM, this time looking more closely at how this approach can predict comminution performance by examining lifter wear.

Other speakers stepping up to the podium in the second session on the first day included JKMRC mathematician Stephen Gay who presented his work in the modelling of liberation using entropy and Jacek Kolacz of SINTEF and his investigations into flow fields in dynamic air classification. A presentation from Saitama University in Japan covered an index of tensile strength of brittle particles.

Post-lunch presentations on the first day were covered under the session 'modelling, simulation and control', a broad subject area in itself made even more so by the diversity of topics.

An alternate heading for this session could easily have been 'The use of computer software and the Internet in mineral processing', evident in the presentations from Mintek marketing consultant Philip Smith and JKMRC postgraduate educator Diana Drinkwater.

The post-lunch session began with CSIRO's Joan Esterle who enthusiastically presented CoalFrag, a software tool for optimising coal fragmentation from face to plant feed. Currently in beta form, the software has had significant input from JKMRC researchers Darren Thornton and Alan Cocker. While the concept was claimed during the presentation to be unique, JKMRC senior research fellow Walter Valery later pointed out that the JKMRC had taken a very similar approach with hard rock mining and processing, particularly with metals such as copper and gold.

Joan Esterle was followed by Professor Bill Whiten who presented work on research conducted by JKMRC PhD student Debbie Zhang on the problems in discrete element simulation and ways to speed it up.

Since the last MEI/JKMRC Comminution Conference held in Brisbane in 1998, it has become apparent that the technology used to create stunning presentations and convey information at incredulous speeds - most apparent in the fields of multi-media communication and the Internet - has advanced to the point where mineral processors are adopting these innovations not only to present research, but to drive and deliver benefits to industry by using the best IT and the Internet have to offer as the basis upon which new technology for the minerals industry is being created and transferred.

Epitomising this use of 'new media' in mineral processing is a joint on-line education initiative put together by the JKMRC/JKTech and The University of Queensland, with funding from the Sustainable Minerals Institute (formerly the Sir James Foots Institute of Mineral Resources) and the Minerals Council of Australia.

Diana Drinkwater explained in her presentation 'Teaching simulation and control by remote delivery methods' how the classroom lecture had disappeared under a typically 'user friendly' web-browser format, delivering a course based on the popular metallurgical simulator JKSimMet. Diana presented a case study on how the course had so far been successfully delivered to university students in Toronto, Canada via the Internet from The University of Queensland in Brisbane, Australia.

Continuing with the IT theme, the Mintek presentation began with an overview of their measurement and control division and how they have worked towards unifying a range of mineral processing control systems to run under a generic web-based platform, marketed as 'PlantStar 2000'.

Other topics wrapping up the first day of Comminution 01 included a presentation from the University of Malaysia, which gave some insights into that country's recent initiatives in fine grinding, and the development of a fine grinding model and simulation of planetary mills incorporating the use of JKSimMet. The presenter gave JKSimMet a warmly received endorsement as a fast, accurate method of simulation.

Technical sessions on the first day wrapped up with JKMRC visiting fellow Hakan Benzer's presentation on modelling cement in grinding circuits. Recently arrived in Australia from Turkey, Hakan pointed out that as cement is a major industry in his country, the ability to model it in grinding circuits has significant economic value to the cement industry. Hacettepe University has consequently conducted surveys at several cement plants in Turkey.

And so endeth Day One. Well, not quite. The technical sessions may have ended but the evening was about to begin.

After a few beers and heady discussion on the state of the cricket series between India and Australia, delegates convened to the Hilton's ballroom for the gala dinner.

The highlights of the evening were undoubtedly the after dinner speech from Tim Napier-Munn and a special presentation to conference convenor Dr Barry Wills.

After many long years quietly serving the world of minerals engineering as one of its foremost communicators, Barry received an engraved pewter mug to acknowledge his many years of service. A very warm applause supported this well deserved award.

Day Two

Depending on which table you sat at during the gala dinner, there appeared to be little evidence of hangovers and sore heads at the start of Day Two - although a few notable party goers appeared a little later in the morning around coffee time.

The day's proceedings kicked off with a morning session on 'New Technology', followed by an afternoon trip to the JKMRC to not only hear about, but also see some of the latest developments in comminution.

Clever use of animation and video to convey highly technical information to delegates again featured prominently, starting with Piero Velletri's presentation on comminution in a non-cylindrical roll crusher.

Part of Piero's work at the University of Western Australia, in collaboration with Central Queensland University, has been to change the shape of roll crushers based on improving the nip angle. A combination of animation and video was used to demonstrate how this worked on a new prototype non-cylindrical role crusher.

The morning's program progressed with Jonathon Campbell of CSIRO Minerals discussing the effect of feed size distribution on high pressure grinding rolls performance, focussing on collaborative work with Rio Tinto and Argyle Diamonds.

This was followed by another impressive video-based demonstration by Heinz-Ulrich Schaefer of German manufacturer Loesche on their recent developments with vertical roller mills, and in particular their 825 tonne per hour/ 5400kW mill recently commissioned in South Africa.

Before a much-appreciated break for coffee - for the few who were nursing sore heads after a great night out - a presentation from Synside based in The Netherlands outlined ten arduous years of development towards final success with their 'intelligent' crusher marketed as The SynchroCrusher.

The depth and breadth of new technology in comminution was evident from the wide variety of topics presented in the pre-lunch session following the coffee break.

Chaired by Alban Lynch, the session covered:

  • Eriez Magnetics work on new magnetic separation techniques to improve grinding circuits
  • JKMRC research on media stress intensity analysis for vertical stirred mills
  • MIM's success with its six new Isamill ultrafine grinding mills
  • A very interesting look at the problem of plastic waste disposal and the application of comminution by researchers at the University of Rome
  • A presentation from the University of Malaysia on the profile and aggregate shape effect of high intensity vertical shaft impact on autogenous crushing
  • And a joint presentation between SINTEF and Hicom International on fine dry comminution of calcium carbonate in a Hicom Mill with an Inprosys air classifier.

A bite to eat and then it was onto the bus and off to the Julius Kruttschnitt Mineral Research Centre at suburban Indooroopilly, a short 15 minute drive from the Brisbane CBD.

The JKMRC's research activities for the minerals industry covers a wide range of topics from blast optimisation and 'mine to mill' through to mineral image analysis. About 30 per cent of the centre's work falls into 'comminution', an area which essentially established the JKMRC as one of the world's foremost minerals research centres.

Upon arriving at the JK a party of about 30 delegates split into three groups, each being given the grand tour of the centre, including an overview of the University of Queensland's experimental mine on which the JKMRC is situated. This was followed by a tour of the recently renovated pilot plant and workshop facilities, featuring the recent installation of the pilot scale ANI-Bradken mill, then on to the Mineral Liberation Analysis Bureau to look at the much publicised JKMRC/FEI Company MLA in action. The JK tour wound up with practical demonstrations of JKTech software.

A tour highlight was, for many, an introduction by Andrew Jonkers to the JKPycnometer, a device commissioned for development by the Australian Coal Association Research Program (ACARP) in an effort to reduce the use of toxic chemicals to measure particle density. Early success with the prototype indicates it will soon replace float sink analysis in the coal industry, and has potential for use in other industries such as iron ore processing.

Day Three

The third day of Comminution 01 could best be summed up as 'heavy duty', with a searching look at the state of ball milling in the morning sessions, culminating with AG and SAG milling as the conference drew to a close.

Back from a field trip to Ireland and straight into presenter's mode was Bradken Mineral Processing's Greg Evans who started Day Three proceedings with some recent background on design engineering considerations for large ball mills using linear and non-linear design approaches.

Local Brisbane-based engineer Chris Meimaris of EAnD Australia provided a calibrated approach to the modelling of grinding facilities. Chris said his main concern was the structural performance of the mills. He focused on EAnD's work in modelling for vibration as a critical issue related to plant design, coupled with the problems experienced in building on various soil types. Much of his company's recent work has been conducted in Peru where vibration had been a major concern.

Former JKMRC PhD student and now with MIM, Yun Tai Man, wrapped up the first stanza of the day before a break for coffee with her work on ball mill scale-up modelling.

After the coffee ritual had been dispensed with and several sales of the JKMRC reference work "Mineral Comminution Circuits - Their Operation and Optimisation" were finalised, John Mosher stepped up to the podium to give an account of A R MacPherson Consultants work in Bond testing, explaining the pros and cons relating the Bond test to evaluating comminution energy. John's presentation covered early work by Fred Bond and the evolution of batch testing. Clearly John's presentation struck a chord amongst the comminution engineers present, attracting perhaps the most questions from the audience so far in the conference.

Clearly the audience had come alive - if it wasn't already - which gave CSIRO's Phil Cleary the opportunity to reinforce the DEM theme introduced earlier in the conference. Phil's half hour presentation looked at the introduction of breakage into the DEM model.

JKMRC researcher Frank Shi took this session to perhaps the deepest possible level of technical depth within the allowable time frame through relatively recent case studies on the effects of rheology on ball milling operations at Mount Isa Mines using different grinding media and cyclone sprigots.

Session co-chairman Antonio Peres from the Federal University of Minas Gerais in Brazil was clearly impressed with the morning's speakers, saying that he was glad to see ball milling feature so prominently in the first comminution conference of the new century.

Lunch and time to network, then back into the equally 'heavy duty' closing sessions on Autogenous and Semi-Autogenous milling, co-chaired by Jonathon Campbell and JKMRC Technical Director Rob Morrison.

Making a return to the podium was Bradken Mineral Processing's Greg Evans, who this time focussed on the use of hydrostatic bearing pressure to determine charge mass in AG/SAG mills, taking in recent case studies from Canada and Ireland.

Greg's paper was followed by another repeat performer in Chris Meimaris of EAnD who took a close look at the world's largest SAG mill, located about 600kms to the south of Brisbane at Cadia Hill in New South Wales. Chris pointed out that the Cadia SAG mill is not only the largest of its type in the world, but also has the world's largest gearless drive. Chris covered some of the remedial work carried out by EAnD on the drive.

With three presentations left, a 'future is now' theme re-emerged, firstly through Walter Valery's work on the development of JKSagCharge - a system to estimate charge volume and position 'online' in AG and SAG mills - and then a return by Lawrence Nordell as the penultimate speaker who reintroduced discrete element methodology.

The honour of wrapping up an intense, yet thoroughly enjoyable world class event in Comminution 01 went to the JKMRC's Randolph Pax with perhaps the most revolutionary presentation of the conference.

Randolph left delegates pondering the state of comminution research in the future with a look at a unique approach to investigate the behaviour of AG and SAG mills based on non-contact acoustic monitoring.

Chatting with delegates over a last cup of coffee after watching the curtain come down on three memorable days, Bradken Mineral Processing Sales and Marketing Manager Steve Hall echoed the sentiments of many delegates at Comminution 01 by observing that new issues - such as those raised by Randolph Pax's work with non-contact acoustic monitoring - showed there was great deal of interest in what more could be learned about SAG mill behaviour.

Steve said the maturing of DEM modelling was another issue on everyone's mind at this conference.

"DEM was looking good for comminution studies when it was first discussed here about three years ago," Steve said.

He said that with the advent of elegant new computer tools and high fidelity graphics there is now a greater potential for use of DEM in modelling mill power draw, liner wear, and SAG mill outlet configuration - which has been one of the industry's noted 'bottle necks'.

The installation of Bradken's curved mill outlet in a 40' SAG mill during April 2001 will provide some opportunity for correlation of DEM predictions, he noted.

"We've also had the opportunity through Greg Evans' two presentations to explain what Bradken Mineral Processing has been doing, particularly with the current manufacture of two 10,000 kW ball mills right here in Brisbane and the installation of robust SAG mill charge mass models at Noranda-Brunswick and Minorco-Lisheen," he said.

"This conference has provided a good mix for us because we are not only into grinding mills as capital equipment, but we're also in consumables and wear parts for both crushing and grinding operations."

Lawrence Nordell was also impressed with the conference and was also glad to be among the so-called international comminution 'family' gathered for Comminution 01:

"I learnt a lot," he said.

"Researchers have approached the understanding of comminution from many ways and there were many good ideas presented at this conference, particularly in how mill behaviour is being equated to the things we can measure, such as Walter Valery's hands-on approach to understanding how machines work."

As Tim Napier-Munn said during his after dinner speech at the end of the first day, it became clear quite early in proceedings that Comminution 01 will be regarded for some time to come as an important reference point for this most important of technologies.


* David Goeldner is Communications Coordinator with the Julius Kruttschnitt Mineral Research Centre. With a background in journalism since 1983, David has over ten years experience as a specialist technical writer. He has written on a wide variety of topics in the mineral resources, primary production and bulk handling sectors in Australia, including a continuing series of articles on business leaders and innovation in the Australian sugar industry. In Year 2000 David's articles on Australia - South Africa collaboration in mineral research attracted widespread interest in both countries. David holds a Masters degree in Science, Technology and Society. He also enjoys a good cup of coffee!

Contact details: email: d.goeldner@mailbox.uq.edu.au
Phone +61 7 3365 5848 (business), +61 7 332553667 (after hours), 0416164243 (mobile)


Publication of Papers

Minerals Engineering Journal

Papers presented at the meeting were refereed for publication in a special edition of the Minerals Engineering journal.

Volume 14 Number 10 (Special Comminution issue)

Model-based procedure for scale-up of wet, overflow ball mills. Part I: outline of the methodology
Y.T. Man (Australia)

Model-based procedure for scale-up of wet, overflow ball mills. Part II: worked example
Y.T. Man (Australia)

Model-based procedure for scale-up of wet, overflow ball mills. Part III: validation and discussion
Y.T. Man (Australia)

An index of the tensile strength of brittle particles
G. Hu, H. Otaki and M. Lin (Japan)

Step size control for efficient discrete element simulation
D. Zhang and W.J. Whiten (Australia)

Media stress intensity analysis for vertical stirred mills
A. Jankovic (Australia)

Engineering estimations of opposed jet milling efficiency
D. Eskin (Canada) and S. Voropayev (Russia)

Developments in the understanding of South African style SAG mills
M.S. Powell (South Africa), S. Morrell (Australia) and S. Latchireddi (Australia)

Industrial tumbling mill power prediction using the discrete element method
M.K. ABD El-Rahman (Eygpt), B.K. Mishra (USA), and R.K. Rajamani (USA)

LOESCHE vertical roller mills for the comminution of ores and minerals
H.U. Schaefer (Germany)

3D Particle tracking in a mill: a rigorous technique for verifying DEM predictions
I. Govender, M.S. Powell and G.N. Nurick (South Africa)

Recent advances in DEM modelling of tumbling mills
P.W. Cleary (Australia)

Conduct and precision of Bond grindability testing
J.B. Mosher and C.B. Tague (USA)

Vol. 14 Number 11

Modelling cement grinding circuits
H. Benzer, L. Ergun (Turkey), A.J. Lynch (Australia), M. Oner, A.Gunlu, I.B. Celik and N. Aydogan (Turkey)

Comminution in a non-cylindrical roll crusher
P. Velletri and D.M. Weedon (Australia)

Volume 15 Number 3 (2002)

Investigating flow conditions in dynamic air classification
J. Kolacz (Norway)

Investigation of the effects of chrome ball charge on slurry rheology and milling performance
F.N. Shi (Australia)



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