European Symposium on Comminution and Classification

The 13th European Symposium on Comminution and Classification (ESCC '13) was held from September 9th-12th at the Steigenberger Parkhotel in Braunschweig, an old German city south of Hamburg, with a long international history and the highest density of researchers in Europe. It was held immediately following a workshop of the International Comminution Research Association (ICRA) and a short course on fine grinding in stirred mills.

The historic city of Braunschweig

The conference, and its associated Proceedings, consisted of four themes, with papers arranged in parallel sessions:

• Processing of primary and secondary materials, especially minerals and ores
• Grinding, dispersing and classification of fine particles, particularly in pharmaceutical, chemical and electronic industries
• Fundamentals, modelling and simulation of particle breakage and of grinding and classification processes
• New and non-classical applications as well as new developments in milling machines and periphery equipment

Papers for all these themes, presented in 67 oral and 56 poster presentations, have been published in a hard back Proceedings by sierke Verlag (ISBN 978-3-86844-551-0). Due to its wide ranging scope  I would highly recommend this publication, which gives insights into how comminution is performed outside your own particular industry.

Monday September 9th

Chairman of ESCC '13 Prof. Arno Kwade, head of the Institute of Particle Technology, TU  Braunschweig, welcomed the 190 delegates to the conference this afternoon. This is very much an international event, with 26 countries represented, many outside Europe, with a sizeable contingent from Australia, Brazil, Canada, Egypt, India, Ireland, Israel, Korea, South Africa and USA.

A welcoming cocktail reception then followed a keynote speech from Bernd Sachweh of BASF SE, Germany, who discussed the status of online measurement methods for particle systems.

Tuesday September 10th

The day began with a keynote presentation by Norbert Stehr of STEHR empCONSULT, Germany, on the progress of industrial wet processing with agitated bead mills. Continuing research in academia and industry has been providing an increasingly deeper understanding of agitated bead milling, including the identification of key parameters in view of specific process targets.

The morning's sessions included High Pressure Grinding Mills, which in recent years have become increasingly used for hard rock applications. The benefits are relatively low energy consumption with improved wear performance. Also improved recoveries have also been reported, especially for leaching operations. ThyssenKrupp is a sponsor of ESCC, as well as of Comminution '14, and Ulrich Voss described an advanced model for HPGR comminution, implemented within the JKSimMet flowsheet simulating software.  A paper from Hacettepe University, Turkey's premier mineral processing institute considered the effect of recirculating load on HPGR performance.

Hacettepe University co-authors Deniz and Okay Altun, and Hakan Benzer

There were three papers presented in a session on Vertical Mills, with interesting work on energy based comparisons of vertical roller mills and tumbling mills, and descriptions of ore grinding practices.

After the lunch break, Comminution '14 consultant Malcolm Powell, of Australia's JKMRC presented a keynote lecture on how mechanistic modelling and multi-component process simulation are pushing the boundaries of comminution. In addressing the requirements of processing new types of ore bodies with far tighter constraints within an uncertain market, conventional circuits operated at historic efficiencies are not going to address the challenges of the industry, and Prof. Powell proposed a new approach and the tools required, the focus being on comminution circuit design.

Prof. Malcolm Powell discusses his keynote speech

Comminution machines and circuits are certainly evolving rapidly and this afternoon's session was the first of two sessions highlighting new technologies. What I particularly like about ESCC is its multi-discipline approach, bringing ideas from an apparently unrelated industry into one's own domain. Stirred mills, for instance, have been used for several decades in industries such as paints and pigments, but systematic application for hard rock minerals is relatively recent. Several factors have been influential, such as the demand for better energy efficiency in fine grinding of complex, low grade ores.

Ilesh Shah, of FLSmidth, USA, dealt with one such application, the onsite testing of a VXP2500 FLSmidth Vertical Mill (originally the Knelson-Deswick mill) for reprocessing of older mill tailings.  Chris Martin of RSG Inc., USA then discussed the operation of a dry vertical air-swept mill operated with mixed grinding media sizes, and the effect on grinding efficiency and ultimate product size compared with mono-sized media. It was found that the use of mixed media within the vertical agitated mill allows for the production of finer particle sizes when processing industrial minerals such as calcium carbonate and wollastonite in the range of 1-3 microns.

Chris Martin (right) with Neil O'Carroll of Lisheen Mines, Ireland

South African company Dakot Milling Media (DMM) last week became the 21st sponsor of Comminution '14, and Hanlie Kotze of DMM discussed the results of testwork on two laboratory stirred mills, an M4 Netzsch horizontal mill and the DMM Vertical Laboratory Mill, to assess wear behaviour. It was observed that when comparing wear results for different media, the variability of the test method, which can be substantial, needs to be taken into account.

The IsaMill is now established, rather than new technology, but the session ended with a presentation from Katie Barns of Xstrata Technology, Australia who showed how the IsaMill has developed from the stirred milling technology of Netzsch Feinmahltechnik GmbH in the 1990s.  The benefits of fine grinding in the IsaMill are now being applied at increasingly coarser grind sizes, and to a diverse range of minerals, a remarkable transition from the original small-scale applications.

It was good to see many young researchers presenting papers in this afternoon's poster presentations, including two post-grads from my old university, the University of Leeds, Sandra Chauruka and Tina Bonakdar.

Sandra Chauruka and Tina Bonakdar

A very interesting first day ended with a guided walk through this beautiful old city, culminating in an excellent dinner at the magnificent ancient city hall.

	Arno Kwade and Malcolm Powell with TU Braunschweig President Jurgen Hesselbach
With Chris Martin and Ulrich Voss	Peter Radziszewski (centre) with George Kyrtatos and Jim Bittner of Separation Technologies

Wednesday September 11th

The first two parallel sessions of the morning, Fine Grinding and Dispersing, and Crushing,  each contained three papers. Of particular note was a presentation by Hamid Manoucheri of Sandvik Mining, Sweden, who introduced the Vibrocone, a new crusher claimed to be a breakthrough in comminution technology. As crushers are more energy efficient than grinding mills, fine crushing is preferred to coarse grinding. According to the paper the Vibrocone is the next generation in crushing technology, combining the best of the conventional cone crusher mechanism with a grinding action in order to produce unprecedented amounts of finely crushed material. Particles are crushed not only between the liner surfaces in the crushing chamber but also to a high degree by each other in a high pressure inter-particle crushing action. This allows the omission  of coarse grinding, resulting in reduced water and energy consumption. I look forward to hearing more of this at Comminution '14.

There are areas of overlap between ESCC'13 and Comminution '14, and Italian company Industrie Bitossi, who supply ultrafine grinding and wear resistant products, are well aware of this, being sponsors and exhibitors at both events.

With Carlo Terreni and Giusy Baio of Industrie Bitossi

After the morning coffee break, Classification and Separation of Minerals ran in parallel with a session on Pharmaceuticals.

Collaboration between organisations and countries is always good to see, and MEI Consultant Aubrey Mainza presented a paper this morning which took collaboration to its limits, with a paper on the role of classification in comminution circuits co-authored by workers from the University of Cape Town, Anglo American Platinum, Gold Fields and Lonmin of South Africa, Chalmers University of Technology, Sweden, Hacettepe University, Turkey, Universidade Federal do Rio de Janeiro, Brazil and Australia's JKMRC. The need to reduce energy consumption and to achieve improved product quality has seen major shifts from the usual conservative approach in circuit design to more modern comminution circuits. Although comminution circuits have been advancing, classification has remained a major component of the comminution circuit design. The paper focused on the role of classification in different comminution circuits and the outcomes from four case studies carried out on plants operated with different circuit configurations showed that classification plays a key role in improving operational and energy efficiency of the circuits.

An interesting paper from Separation Technologies (ST) on the separation of fine minerals using triboelectric separation was perhaps slightly out of place at a comminution conference, and I would like to hear more of this technique at Physical Separation '15.  The ST triboelectric separator greatly expands the range of materials that can be beneficiated by electrostatic processes, which are limited in capacity due to the required contact of every particle to the drum or plate. The ST belt separator provides a means to treat fine material with an entirely dry technology, eliminating wet processing and required drying. It is suited to the separation of particles finer than 1 micron up to as coarse as 300 microns, with throughputs of up to 40 tonnes/h with energy consumption of only around 1 kWh/t.

The afternoon got underway with a keynote lecture from one of the world's leading experts on DEM, CSIRO's Paul Cleary. The DEM method is ideally suited to predicting particle flows such as rock and media in SAG and media in ball and stirred mills, while the Smooth Particle Hydrodynamics method is well suited to splashing-free surface slurry flows as found in SAG mills. He presented a series of examples of mills and crushers, demonstrating the capabilities of these computational methods and the insights that they can assist in developing.

The day concluded with papers on single particle stressing, dry grinding and classification modelling, as well as an afternoon of poster presentations. Then it was off to the 800 year old castle at Burg Warberg for a very memorable medieval banquet.  The photos below (and on the posting of September 12th, as well as the YouTube video) are testament to a good time being had by all!

Thursday September 12th

After last night's dinner, where the wine, beer and mead flowed freely, there were a few bleary eyes and sore heads this morning. The morning's sessions covered mechanochemistry, particle breakage characteristics, particle bed stressing and new technologies.

I was particularly interested in a presentation by Frank Shi of Australia's JKMRC who outlined the programme of work on electrical comminution by high voltage pulses which has led to a number of publications in Minerals Engineering over the last few years. Pre-weakening ore particles and preferential liberation of minerals at coarse sizes are the two major outcomes that may have potential benefits for the mineral industry. A novel particle pre-weakening characterisation  method by single-particle/single pulse test has been developed in collaboration with the Swiss company selFrag AG. Dr. Shi discussed the emerging challenges to bring electrical comminution to the mineral industry, including scale-up for industrial application, hybrid circuit design, maximisation of pulse-induced cracks and study of the downstream processing effects.

With the selFrag team, Klaas van der Wielen, Alexander Weh
and Eva Romeijn

Following the afternoon sessions on Granular and Natural Materials, and Grinding Tests, Arno Kwade closed the conference and also announced the award of best poster. We must not forget that there were well over 50 poster presentations at the conference and contributing to the Proceedings volume and it was pleasing that the organising committee made an award for the best of these. This was to Katharina Jacob of Friedrich-Schiller University Jena.

Katharina Jacob receives her award from poster judge Aubrey Mainza

Following the official closing there was a very well attended optional tour of the very impressive facilities of the TU Braunschweig's Institute of Particle Technology.

This has been a thoroughly worthwhile conference, and I will certainly be at the next one in Gothenburg, Sweden from September 7th-10th 2015. The chairman for ESCC '15 is Dr. Magnus Evertsson of Chalmers University of Technology, who is also a regular attendee and presenter at MEI's comminution series. We see no conflict whatsoever between the two conference series, and in fact will be working closely together to forge strong links between the two.

Arno Kwade passes on the chairmanship of ESCC to Magnus Evertsson

I have found ESCC '13 to be a revelation- there are so many fine-grinding machines in use in various industries, many of which are completely alien to me. Although the main focus of ESCC is on relatively small-scale ultrafine grinding, many of the ideas behind these machines could be carried over into specific areas of the high tonnage minerals industry, in much the same way as the Netzsch stirred mill was adapted for a specific application in the minerals industry and became the IsaMill. Hopefully specialists from ESCC '13 will bring fresh ideas to Comminution '14 and Magnus and I will work on delegates in Cape Town in April, to convince them of the benefits of attending ESCC '15.

A final thanks to Arno Kwade and his team for organising a remarkable event, memorable not only for its technical quality but also for its great social events, which consolidated existing relationships and made it easy to build new ones. I hope to see as many of you as possible in Cape Town in April, and a reminder that the deadline for Comminution '14 abstracts is the end of October.