Flotation '13 Conference Diary

Flotation '13 was held at the Vineyard Hotel, Cape Town, from November 18th to 21st, and, as always, comprised two discrete 2-day symposia on Fundamentals and Applications. The flotation series of conferences is now established as the major meeting place for researchers, operators and manufacturers from around the world, and we thank all our sponsors for their corporate support.

This conference diary only scratches the surface of the technical aspects of the conference, and I invite all delegates to submit their own views. A feature of the Vineyard conferences is the satellite 'overflow' room, where one can view and listen to the presentations while working on laptops and iPads, thus not distracting the speakers, and I managed to catch a few of the presentations in this way.

The main conference room....

....and the satellite room

All the papers in the technical sessions, and most of the poster papers are available on flash drive from MEI Online, and selected papers from the event will be published next year in a special flotation issue of Minerals Engineering.

Monday November 18th

After a weekend of torrential rain and storms, the sun finally shone on Table Mountain today, and the 6th MEI conference on flotation got underway, with opening remarks from myself and Fundamentals consultant Prof. Dee Bradshaw (see posting of November 18th).

Over the next 4 days 257 delegates from 28 countries will attend the two symposia on Fundamentals and Applications, and it was good to see so many new faces in the audience today, as well as many familiar ones.

With Kari Heiskanen and Dee Bradshaw

Dee introduced our first keynote speaker Prof. Kari Heiskanen of Aalto University, Finland.  Kari discussed why, after a century of research, we are still struggling to fully understand flotation. There are several reasons for this. The combination of two discrete phases in a turbulent continuum has proven to be full of challenges. Phenomenological models, embodied in the first order rate model and all derivatives thereof have, in Prof. Heiskanen's view, come to the limits of their usefulness. We can and should use them to solve many practical issues where work can be based on laboratory experiments, but they will not give us any further understanding of the underlying physico-chemical phenomena involved. This understanding is needed, if we wish to develop new generations of effective flotation cells and processes.

An interesting morning session consisted of nine papers, from Australia, Chile, Poland, Sweden, South Africa and UK. The session was broken by a long coffee break, giving delegates the opportunity to view the poster displays and the exhibition booths.

There are many companies represented who have exhibited at previous events in the series, but there were a few companies for whom this is their first involvement with an MEI Conference. eDart is one of these companies, and is a producer of slurry control valves, specifically for flotation. The company is currently expanding globally as a service to suppliers such as conference sponsors FLSmidth, Outotec, Tenova Delkor and Metso.

At the eDart exhibit

Another company new to us is ACIS/REXA a USA company providing electrical/hydraulic control valve actuators for complex control. Currently their biggest installation is being commissioned at Pilansberg Platinum flotation plant in South Africa.

At the ACIS/REXA booth

The exhibition can be viewed on this YouTube video.

Kevin Galvin (left) at the FLSmidth booth

Researchers at the University of Newcastle, Australia, have previously developed a fine particle gravity separator known as the Reflux Classifier. This separator consists of a fluidized bed, with a system of parallel inclined channels mounted above. The technology is now deployed around the world in a range of fine coal and mineral processing applications.  Dr. Kevin Galvin, the inventor of the Reflux Classifier, presented an interesting paper in the morning session, showing how flotation can, in part, be thought of as a gravity separation process, in which rising air bubbles segregate from the liquid. He and his co-workers have therefore applied their recent advances in gravity separation to the field of flotation, in turn inverting the Reflux Classifier, to produce the Reflux Flotation Cell.

Positron emission particle tracking (PEPT) is becoming increasingly important as a tool for flotation research as it reveals the behaviour of particles directly inside laboratory scale flotation vessels. In the past 5 years since its initial application to flotation, analytical techniques have greatly improved to ensure a high level of confidence in the tracer behaviour. Dr. Katie Cole, of Imperial College, UK, showed how these techniques have been used to directly compare the effect of tracer hydrophobicity in a laboratory flotation system under controlled conditions and air recovery.

After an excellent lunch, there were eight further papers on flotation physics and chemistry, from Belgium, Brazil, Canada, Germany, Indonesia, Japan, South Africa and UK.

Due to scarcity of fresh water and stringent regulations on the quality of discharged water, more and more flotation plants have to use groundwater, sea water and recycle water with a high concentration of electrolytes. Despite a number of studies that have been conducted to investigate the effect of saline water on mineral flotation, effective ways to solve many problems encountered in mineral flotation plants using saline water are not currently available. Bo Wang of the University of Queensland, presented a review of published articles addressing the effect of saline water on the interfacial phenomena taking place in the flotation process, such as surface wettability, bubble-particle collision and attachment, mineral particle interactions and frothing. The review provided an overall picture of current status of studies in this area and showed directions of future researches addressing different problems associated with using saline water in mineral flotation.

Process water hardness is known to have a marked influence on the sulphidisation and flotation of base metals oxide ores. David Bastin, of the University of Liege, Belgium, highlighted the mechanisms through which calcium and magnesium ions interact with the pulp during the activating sulphidisation step and the subsequent xanthate flotation of malachite.

An intensive first day of papers ended with the first 'happy hour' where delegates relaxed and discussed the day's events over drinks in the beautiful Vineyard Gardens.

Tuesday 19th November

The final day of the Fundamentals Symposium, dawned bright and sunny with an especially stunning view of Table Mountain from the conference centre.

It has not been surprising that Fundamentals has been dominated by academic papers, but today papers from non-academics formed a fair portion of the 16 papers presented.

Nilce Alves in discussion with Jan Cilliers

Nilce Alves of Eriez Flotation Division, Brazil showed how, since the early years of flotation, proper modeling and simulation has been a challenge. The interaction and interdependence among dozens of variables, associated to different levels of relevance of these parameters for distinct minerals have been a source of numerous models and approaches, fundamental or empirical, that can be more or less accurate, more or less practically used, more or less applicable to different ores, more or less expandable beyond the limits of the original study. She presented an evaluation of a flexible approach in the use of the Compartment Model and some other models to address the main transport phenomena in flotation.

Chris Greet of Magotteaux, Australia, is a familiar figure at MEI's flotation and comminution conferences, and he questioned the value of collecting quality liberation-by-size and mineral class data to assist in defining the form by which valuable species appear in the tailing and gangue minerals report into concentrates. This has long been recognised as world's best practice.  Such studies are paramount in understanding how a flotation circuit is operating.  Unfortunately, in many instances such an approach is deemed time consuming, expensive and yields quantitative data way too late to be effective in an operating plant. Realising that an understanding of the mineralogy of a system is intrinsic to resolving metallurgical problems in their concentrator, some operators have resorted to conducting virtual sizing to extract liberation data on a sized basis from unsized samples.  Such a practice is pursued to minimise the cost.  But, how reliable is the data generated?  Does this methodology actually produce sound liberation-by-size and mineral class information that can be used to solve metallurgical problems? Chris showed unequivocally that completing a liberation study using virtual sizing via QEMSCAN is patently wrong.

Chris Greet (right) with delegates at the Magotteaux booth

The interaction between comminution and flotation has been studied by workers at the University of Queensland, and Xumeng Chen of the JKMRC discussed this with regard to stirred mills, which are widely used for regrinding, and are more energy efficient than tumbling mills. These two types of mills present different particle breakage mechanisms during regrinding. Impact and attrition are the primary grinding mechanisms in tumbling mills, while attrition is the sole breakage mechanism in stirred mills. In this study, the effect of regrinding by the two types of mills on surface chemistry and subsequent mineral flotation was studied, and pyrite was taken as an example. It was found that regrinding breakage mechanisms not only produced different particle size distribution, but also changed the pulp and surface chemistry differently, which significantly influenced the subsequent pyrite flotation and activation. This study demonstrates that the selection of regrinding mills should not only depend on the grinding energy efficiency but also the pulp and surface chemistry they produced for effective mineral flotation and separation.

It is good to see workers realising that flotation performance is influenced by comminution, and in this respect also good to see grinding media companies such as Magotteaux sponsoring this event as well as Comminution '14. Keramos is a small dynamic company sponsoring  a flotation event for the first time. They provide ceramic grinding media as well as ceramic liners for pumps, valves, cyclones etc. The company has been involved with previous comminution conferences, and is sponsoring and exhibiting at Comminution '14.

After a long day at the conference we travelled around the Mountain into the city, for the conference dinner at Moyos on the Waterfront. This was our first time at this venue, but we found it slightly disappointing compared with previous venues.

Wednesday November 20th

Jon opened the Applications symposium this morning, and MEI consultant Prof. J.-P. Franzidis set the scene for the next couple of days. He drew on Dee Bradshaw's introduction on Monday, where she said that understanding follows practice.  There have been excellent presentations over the past two days on the work that's been done to understand particle bubble-collisions, and reagent adsorption onto surfaces, and the effect of saline water on flotation: but even as our understanding improves, the industry presses on with bigger flotation cells, new designs of flotation cells, new reagents and new ways of controlling the cells and the circuits in which they are placed.

In the next two days we will hear about the application of flotation to copper, lead, zinc, gold, silver, nickel, PGMs, potash, iron ore, in places as far apart as China, Zambia, Peru, Finland, Australia, Brazil, Cote D'Ivoire, the USA, Iran and South Africa.

Flotation is a mature technology: so while there are some advances in terms of doing new things, there's a lot of effort going into doing things better ­-  better flowsheet development, better instrumentation and measurement, better control.  Flotation is being applied to new ores, and every deposit is new with new challenges. ­ as well as to retreat waste dumps, extract value from discards, and remove toxic elements from the environment. 

Jon with J-P Franzidis and Dariusz Lelinski

Prof. Franzidis then introduced the keynote lecture, given by Dr. Dariusz Lelinski, of FLSmidth, USA. This was an excellent presentation, showing how the global mining sector has faced dramatic changes over the last five years. The growth of emerging countries, especially China, initiated a global boom in metals and energy prices. High prices attract investments; companies have spent millions of dollars to open new mines, expand old ones and upgrade equipment to increase production. Increased production from multiple sources often exceeds the demand. As a result, an extended period of high commodity prices has been followed by falling industrial demand for raw material, a decrease of all commodity prices and constraints on access to capital. In response, capital expenditures have been scaled back and non-core assets are being disposed.  There is a shift from maximizing value by increasing production volumes to maximizing returns from existing operations by improved productivity and efficiencies.

The main question asked by all involved parties is when the market will pick up, as commodity prices rise and the cyclic nature of the mining industry is again proven true. It is believed that the global economy will continue expanding at a moderate pace, pushing demand for metals and energy up to new highs. Unfortunately, it looks as if we have currently more mining capacity than we need. The world will have to grow into the capacity we have. At that point, prices can head up again. How long that will take depends on the specific materials being mined. The longer the time lag to increase production and the more capital- intensive the sector, the longer it will take before prices recover. All flotation equipment suppliers, including FLSmidth, are looking for breakthrough technology, and manufacturing larger machines is the approach taken by all these suppliers, as was discussed in a later paper this morning by Dariusz. In addition there are many new machines on the market, currently for specific applications only, but there is no clear winner as yet.

This keynote led nicely into the morning's technical session which dealt with new flotation cells, coarse particle flotation and fluidized bed flotation.

Dee Bradshaw presented a paper on behalf of Metso authors who were unable to attend. She discussed how if the particle size that can be effectively recovered in a flotation cell could be increased, the product size from grinding could be significantly coarsened, resulting in a more eco-efficient flowsheet.  The Metso work shows that coarse particle recovery is extremely sensitive to froth phase effects, with recovery optimal at shallow froth depth and when turbulence at the pulp-froth interface is minimised.

Homie Thanasekaran of Eriez Flotation Division, USA then discussed how traditional conventional flotation machines are effective for fine particle size classes; however, limitations due to particle buoyancy and bubble-particle detachment restrict their effectiveness when floating coarse particles. As a result, flotation circuits are generally configured to maximize the recovery of particles finer than 150-200 micron. In fact, grinding circuits expend significant energy reducing a feed stock to a particle in the size range suitable for flotation. Fortunately, a novel flotation device has been developed, the HydroFloat Separator, that overcomes these limitations by carrying out flotation in a dense, fluidized-bed medium allowing for the selective recovery of coarser particles (>0.250 mm). Over the last 15 years, this technology has been successfully applied to industrial minerals with several full-scale units installed to recover particles up to and exceeding 3 mm diameter within the industrial mineral sector. More recently, sulphide-based laboratory test work has shown that this novel device is also capable of recovering metalliferous values at a coarse grind size. Benefits of this approach, such as improved recovery, low energy consumption and reduced reagent addition were reviewed.

Papers on new ways of developing flotation flowsheets, flotation modelling and comparing laboratory batch flotation tests and mini pilot plant testing concluded an excellent opening session.

The afternoon session began with papers on new flotation collectors and frothers.

Mike Peart of Cytec discussed recent advances in the application of AERO® 7260HFP as greener alternative to NaSH/Nokes in Cu-Mo separation, and the development and introduction of a new selective collector for copper sulphide ore at FQML, Kansanshi Mine. Jeff Aston of Huntsman Performance Products showed how  the efficiency of copper and copper gold circuits can be improved with POLYFROTH® W22 frother.

Virtually all the leading chemical manufacturers are at the conference, either sponsoring, exhibiting, presenting papers, or just attending, and it is good to see Chinese company Shenyang Florrea Chemicals exhibiting, and their representative Yang Zhiyong winning the lucky draw and a copy of Froth Flotation, a century of innovation (M.C. Fuerstenau et al) from chemical company and sponsor Clariant.

Yang Zhiyong (right) at the Shenyang Florrea Chemicals booth

A very interesting day concluded with papers on flash flotation for gold recovery, improving plant performance by optimizing the air flow rate and froth depth in PGM flotation, and methods of removing arsenic-bearing minerals from copper concentrates, after which we enjoyed another relaxing 'happy hour' in the hotel grounds.

Thursday November 21st

Jim Finch and Osvaldo Bascur

This morning featured control, focusing on level control and froth imaging, and other on-line measures of flotation cell performance such as bank profiling. The session included a paper on improving flotation grade recovery using operational data at Southern Peru Copper, presented by Osvaldo Bascur of OSIsoft LLC, USA. Osvaldo is this year's recipient of the SME's prestigious Antoine Gaudin Memorial Award, and is one of two Gaudin Award winners at the conference, the other being Jim Finch of McGill University, Canada. Unfortunately, due to personal circumstances, the 2011 award recipient Graeme Jameson, had to withdraw from Flotation '13.

With Xuming Wang

Today's papers also contained presentations on the effect of mineralogy on flotation, and some site-specific papers reporting successes in the flotation of a variety of minerals. The last paper of the conference dealt with potash flotation practice for carnallite resources in the Qinghai Province, China, and deserves a special mention, as the presenter Dr. Xuming Wang was seriously injured only 5 months ago in a car accident in Tibet, where his co-author, Prof. Jan Miller, also of the University of Utah, was also injured and is still recovering. It was great to see you looking so well at the conference, Xuming, and to hear that Jan continues to improve. We hope to see you both at Flotation '15.

There have been some excellent presentations at the conference, highlighting that flotation continues to develop to keep pace with the increasing complexity of modern ore-bodies. The number of young people presenting work has been encouraging, and recognising this, one of our sponsors, Outotec, invited all student presenters to submit their papers for consideration for the Outotec Young Talent Award.

Jussi Vaarno and Mehdi Safari

In presenting this award, Jussi Vaarno of Outotec said that all the papers submitted were of high standard, but based on the company's core value of sustainable use of the Earth's material resources, one paper stood out as having potential to make an impact in the near future for energy savings and recovery of valuables for all flotation applications. The award was thus made to Mehdi Safari for his paper The effect of energy input on flotation kinetics of sulfide minerals in an oscillating grid flotation cell. This is the second time that he has received such an award, having been the recipient at the University of Cape Town's student conference in August.

In closing the conference, consultants Dee Bradshaw and J.-P. Franzidis stressed the important role that these events now have in bringing together flotation people from around the globe every two years. It is a unique conference, neither an academic nor an operators' event, but an ideal blend of the two. Prof Franzidis remarked how impressed he had been with the networking which has taken place over the past four days, during the long lunch and coffee breaks, and particularly in the successful new innovation of the 'happy hours'.
Amanda then closed the conference, inviting all to convene again in two years time for Flotation '15, before we all adjourned once more to the hotel gardens for the final happy hour (see YouTube video)!