Wednesday, 13 December 2017

Flotation '19- first announcement

Last month's Flotation '17 was one of MEI's most successful conferences, thanks to an excellent technical programme and a fine mix of researchers, suppliers and operators.
Now we look towards 2019, and we are pleased to announce that the website for Flotation '19 is now live.
Once again we will be at Cape Town's Vineyard Hotel, and the conference has got off to a flying start with four of our regular sponsors supporting us as usual. We thank Axis House, FLSmidth, Maelgwyn Mineral Services and Magotteaux, and also our faithful media partner International Mining, who clearly are aware of the advantages that early sponsorship brings, in terms of pre-conference exposure on the blog, MEI Online, Twitter, LinkedIn, as well as via flyers distributed at major international conferences.
 If you would like to sponsor the conference, full details can be found on the website.
We have 23 exhibition booths in the area where delegates break out for coffee and lunch, and where two of the evening social events will be held.  Already 5 booths have been sold, so we advise that you reserve your preferred space as soon as possible. The poster displays are also in the same area. Jaisen Kohmuench, Managing Director of Eriez Australia was clearly impressed "From a presenter's perspective, it was a pleasure being able to provide a talk to an interested and engaged audience. From a booth exhibitor's perspective, we had a constant influx of visitors which made the long trip (and expense) over to Cape Town that much more worthwhile".
Evening sundowner in the exhibition area
The venue for the conference dinner is still being arranged, but I can promise that it will be somewhere special, and will supplement the other two evening sundowners which will be held in the Vineyard gardens, with the backdrop of Table Mountain.
 So, November 11-14, 2019 should be dates for your diaries if you have any involvement with this most crucial of processes. Regular updates will be posted on Twitter, via the hashtag #Flotation19.
 Twitter @barrywills

Monday, 11 December 2017

A new laboratory honours the memory of Prof. Peter King

One of the great names in mineral processing was Prof. Peter King, who sadly passed away eleven years ago, only three years after being awarded the IMPC’s Lifetime Achievement Award at the 2003 IMPC in Cape Town.
Peter and Ellen King at the 2003 IMPC in Cape Town
Peter was Professor of Metallurgical Engineering at the University of Utah for 17 years, and prior to that was Professor of Metallurgy at Wits University, South Africa. He made major contributions to flotation modelling and liberation analysis, was the editor of International Journal of Mineral Processing, and authored a number of state of the art books.
The School of Chemical and Metallurgical Engineering at the University of the Witwatersrand last month held a ceremony to mark the naming of the Peter King Minerals Processing Laboratory in recognition of Prof. King's contribution to the mathematical modelling of minerals processing. The ceremony was attended by industry, Peter's former students, and guests of honour, his wife, Ellen and son, Andrew.
Ellen and Andrew at the opening ceremony
Wits Professor Sehliselo Ndlovu, President of the Southern African Institute of Mining Metallurgy, said the laboratory would ensure the continuation of Prof. King’s vision, who was passionate about capacity building and world-renowned for developing useful techniques to quantify mineral liberation.
Former students described Prof. King as a great teacher who instilled confidence and a desire for continual progress, especially among the average students.
Prof. Michael Moys spoke of his experience of Peter King:
Michael Moys
It has been a personally valuable experience for me to prepare this “view of Peter King by a past student”. Peter had a determining effect on me for most of my adult life.
I first met Peter at a conference in Johannesburg in 1971. He delivered a paper dealing with Finite Dams. (It was above me; I remember very little but I remember wondering what an Infinite Dam was!). But I was impressed with his style and depth of presentation and enjoyed meeting with him after the paper. We got round to possible postgrad studies… and the rest is history!
I went to do an MSc at the Department of Chemical Engineering at the University of Natal – later called the University of KwaZulu-Natal.  Peter was my supervisor and I found myself a member of a large number of other students with the same fate. Peter was extremely busy and appointments were difficult to come by; but when I had them they were of great value. Peter was 100% with me for those interviews and these helped me though several hurdles over the next few years. In the end I had a PhD which I enjoyed and still value and which is still cited – with no small Gratitude to Peter at the end of it.
The Department was dominated at that time by 2 giants of South Africa Chemical and Metallurgical Engineering: Peter King and Ted Woodburn. They supported and competed intensely. Allow me to reminisce briefly about Ted. Ted would arrive in the morning in his Mini Minor. Those of you who knew Ted – a very large man- can imagine Ted extricating himself from the Mini! Ted's other idiosyncrasy was his habit of Management by Walking Around (MWA) chewing his tie. Ted also had a remarkable laugh which defies description and echoed through the building every now and then. Peter kept his cool!
In approximately 1974 Peter entrusted my with the delivery of a paper on his Magnum Opus (at that time) a paper on his simulator, FLOTE,  of flotation plants of arbitrary complexity. This was at an AIME conference in Dallas, Texas.  There were no questions after the delivery - I had obviously covered the topic in brilliant clarity! -but the main benefit of this trip for me was the purchase of a “Fly Anywhere” ticket which made possible visits to New Orleans, Washington, New York, Chicago and San Francisco. This was a wonderful experience for me made possible by Peter’s generosity.
A short word about MODSIM is valuable here. He worked continuously since the production of FLOTE to bring into being the generalized mineral processing simulator MODSIM. This was continuously refined and used extensively for teaching at both postgrad and undergrad level. I used it for at least 25 years at Wits and it is still being used. Early in its development it became the reference simulator for Mineral Processing used by several of his competitors. MODSIM is still the best simulator of comminution in existence.
On the way to this conference I visited Peter and Ellen and their family at UMIST for a few days while Peter  was there on Sabbatical, and was glad to deepen my friendship with the family, especially with their three children who entertained me enormously for a day or two while I recovered from a bout of flu.
In 2000 I attended the Rome IMPC. There I met Peter and Ellen and learnt about Peter’s illness. He assured us that he had it under control. I was shocked and saddened but also buoyed up by his optimism and undiminished vitality and zest for life.
In 2002 Denise and I were back in Salt Lake City and spent a day with Peter and Ellen. We had a memorable lunch and long discussions into the afternoon, some of it further discussions about MODSIM and its use in teaching.  Denise and I were still suffering from jet lag and were tempted to excuse ourselves; Peter would have none of it. He and Ellen took us on a walk through a nearby botanical garden specializing on plants typical of the SLC environs. Peter was  in good health  and stretched us to the full. After a short rest (tolerated by Peter) we went out to a memorable dinner. Peter’s vitality and enthusiasm  were  undimmed.
On 11th September 2006 we had the news that Peter had passed away. I was deeply saddened to hear of the death of a remarkable scholar and teacher who had a huge impact on my life. I have thought often of him as a colleague of tremendous energy, integrity and productivity, and as a friend who set a remarkable standard for his work and for his presence and friendship to those who were close to him.
The last word was penned by John Herbst, erstwhile Head of the Metallurgical Engineering  Department of the University of Utah:
The World Lost an outstanding scholar and human being on September 11, 2006, when Peter King died at the age of 68.

Wednesday, 6 December 2017

89th birthday greetings to Prof. Douglas Fuerstenau

Two years ago I had the enormous privilege of interviewing Prof. Doug Fuerstenau,  P. Malozemoff Professor Emeritus at the University of California, Berkeley, USA, for the MEI blog (posting of 20 July 2015). One of the all-time greats of mineral processing, Doug is 89 years old today, and we all wish him the very best as he enters his 90th year.
I am sure, however, that he and his wife of 64 years, Peggy, will want to put 2017 well behind them, as they were very much affected by the devastating fires that struck Napa and Sonoma Counties in Northern California in early October. Doug and Peggy live in a retirement village in Sonoma County and some 2000 homes were burned in Santa Rosa, but those in the Spring Lake Village where they live were spared.
The remains of Sarah and Scott's home
Doug and Peggy's daughter, Sarah, and son-in-law Scott, were not so fortunate, however, as their house in Glen Ellen, about 10 miles away, was completely incinerated, with everything in it. Doug and Peggy lost the storage building that had been constructed on Scott’s one-acre lot to store the many things that Doug had kept, related more or less to professional work.
Doug says that despite all this, they are thankful to be alive, as 44 people died in the fires. He said "one reads about disasters, but almost always the effects do not impinge on one personally.   Peg had two or three boxes with two complete sets of her very good china tableware plus antique goblets, etc. None survived.  Reprints of all my publications are ashes, including all of the original drawings of figures for theses and papers, reports, correspondence, some data files, very old books, Kodachrome slides, cameras, antique mining lamps, etc.  Whenever I think about looking  for something, I realize that it now has been burned to ashes or melted".
We wish Doug, Peggy and their family all the good fortune for 2018, and I am sure that if any of you have copies of Doug's publications and memorabilia, he would be very pleased to hear from you.

Monday, 4 December 2017

The rapidly evolving world of comminution is reflected in the Comminution '18 programme

Comminution '18 is the 11th in MEI's series of comminution conferences, and how the field has changed over the years. Prof. Alban Lynch, the first Director of Australia's JKMRC, said in 2003: "Comminution must be the key mineral processing technology during the next 50 years," and so it is without doubt. Last month at Flotation '17 in Cape Town I emphasised the crucial importance of flotation, "the world's most important technology", but flotation could not function without efficient comminution, which has had to evolve rapidly with the need to grind ores finer, and to do so with the minimum expenditure of energy. Worldwide the mining industry consumes around 2% of all electrical energy, and comminution is the major consumer, so great efforts are now made to reduce energy consumption, as well as water consumption, which is also critical.
Over 90 papers have been accepted for presentation at Comminution '18, and the provisional timetable is now available.
At the final panel discussion at Comminution '14 (posting of 5 May 2014), Prof. Tim Napier-Munn said that in terms of the future of comminution "we really have to get rid of tumbling mills". Four years on, there is no mention of rod mills in the programme- are these now finally obsolete? Ball mills would have dominated comminution conferences little over a decade ago, but they are mentioned only 5 times in the programme. SAG mills are still of major importance, but in his keynote lecture, Holger Lieberwirth, of TU Bergakademie Freiberg, Germany, will ask whether SAG mills will still be relevant in 50 years time.
The programme highlights that there are many new ideas out there,  new crusher developments, HPGRs, fine grinding devices and circuits, all offering new approaches and much hope for the future.
So, the Vineyard Hotel, in Cape Town's quiet suburb of Claremont, will be the place to be in April, not only for the fine, state-of-the-art technical programme, but for the many networking opportunities that will be available.
As always, lunches and coffee breaks will be in the exhibition and poster display area. If you are interested in exhibiting, you can view the display area here. Two of the cocktail functions, the Sunday welcoming pre-registration, and one of the afternoon 'sundowners' will be held in the exhibition area, the two other sundowners in the magnificent Vineyard gardens. The informal conference dinner will be at Lagoon Beach, with its iconic view of Table Mountain across the bay.
Vineyard scenes at Comminution '16
My report on Comminution '16 will give you some idea of what to expect. We expect more people next year, as the industry begins to pull itself out of the trough, and hopefully an increasing number of operators, which was good to see at last month's Flotation '17.
Finally, many thanks to our sponsors- we really do appreciate your support.
Current sponsors
Congratulations on a great conference [Comminution '16]. Good papers, made more powerful by a single stream which meant high attendance at each session, and good long breaks for informal discussions throughout the day, and meals in a spacious vendors area to encourage circulation. A great formula for a conference - quality over quantity, and time for discussion and networking and to keep the energy levels high. I wish all conferences could manage this balance so well."
Joe Pease, Mineralis Consulting, Chairman CEEC
More testimonials, and regular conference updates at #comminution18.
Twitter @barrywills
 
 

Saturday, 2 December 2017

Christmas is a-coming

Only a week after our last Camborne School of Mines Association event we were in Redruth today for the annual CSMA Christmas lunch.
Although fewer people than usual, it was really good to see Penda Diallo, the only current CSM staff member in attendance, who took up her duties at the School only 3 months ago. This was her second CSMA outing, and she tells me that she is really enjoying her new life in Cornwall. Below are a few photos taken at the Penventon Hotel today:
With Nick Wilshaw and Penda Diallo

Barbara with John Eyre, Steve Wilson and Nick Slade

Barbara with Phil and Joan Oliver and John Hills

Friday, 1 December 2017

TripAdvisor's Top 25 beaches in the world

TripAdvisor's list of the top 25 beaches in the world contains only one South African beach- Cape Town's Camps Bay, where Barbara and I spent 5 days last month after Flotation '17.
Camps Bay
Lists are always controversial; Camps Bay, with its backdrop of Table Mountain and the 'Twelve Apostles' is certainly lovely, but it is evident that relatively few of the TripAdvisor reviewers had visited the 'secret' places of Cornwall, which is a great pity (or maybe not!):
 
 So, what is your favourite beach in the world?

Thursday, 30 November 2017

Graeme Jameson in Germany

I have received this email from Dr. Martin Rudolph, Head of Department at Helmholtz Institute Freiberg for Resource Technology, Germany:
"... I would like to share impressions from Prof. Graeme Jameson’s visit to Dresden and Freiberg last week from Wednesday night until Friday morning. Noteworthy are his meetings with older flotation experts in Freiberg besides us from Helmholtz-Zentrum Dresden-Rossendorf showing him our recent flotation research topics at the Institute of Fluid Dynamics (Prof. Kerstin Eckert’s labs) in Dresden and the flotation labs at the Helmholtz Institute Freiberg (HIF). Below is a picture of Graeme (81) with Prof. Heinrich Schubert (91) at Schubert’s place. The other picture shows Graeme with Horst Plate, a former member of Dr. Hans Joachim Schulze’s group at the FIA in Freiberg. Graeme discussed theoretical aspects of detachment mechanisms with him after he was looking for some of his references in preparation of a review article.
Profs. Jameson and Schubert

Graeme with Horst Plate
It was great to have had him as our guests. We had him stay at a wonderful Dresden vineyard castle founded by British industrialists in the 19th century and enjoyed a great dinner at the famous Schiller Garten restaurant in Dresden. His approach to scientific and technical tasks including very philosophical mindset is a very impressing example of a personality to us. I feel very humbled to have the opportunity to learn from those people.
With that being said I also would like to thank you again for a wonderful Flotation conference in Cape Town. It would not have been possible for me with Flotation’13 and ‘15 to get to know the community that well and interact with the people, for until my PhD I have been active in an entirely different scientific community".
Thankyou for sharing this Martin. As I mentioned in my posting of 13th November, Graeme Jameson is truly inspirational; a great scientist who is also great company- the MEI team will always remember eating pizza with him a couple of weeks' ago in the Cavendish Mall close to the Vineyard Conference Centre!
Twitter @barrywills

Monday, 27 November 2017

Flotation '17 Conference Diary

Flotation '17 the 8th in MEI's series of flotation conferences, was held at the Vineyard Hotel, in the leafy Cape Town suburb of Claremont, South Africa. with its stunning view of Table Mountain.
Table Mountain from the Vineyard Conference Centre
Below is a report on the event, to which we invite comments and suggestions.

Monday November 13th
I opened the conference this morning, welcoming the first of the week's 262 delegates from 30 countries to the first of the two day symposia- Fundamentals, and thanking our sponsors for their support.  
I briefly talked (posting of 13th November) about how flotation has evolved in the 113 years since Elmore's patent in 1904. Modern computers have transformed the way we understand, simulate and optimise flotation processes, and the power of modelling was highlighted in the first session of the conference.

With Prof. Yoon
Roe-Hoan Yoon (posting of 14 August 2017) is an IMPC Lifetime Achievement Award Winner and a University Distinguished Professor at Virginia Tech, USA. He is a world-renowned expert on modelling, and his keynote lecture Developing a Flotation Model from First Principles (posting of 13 June 2016) set the scene for the complex and highly specialised papers that followed, exemplified by Nikolay Evseev, of Schlumberger Moscow Research, Russia, who spoke about the modelling of flotation processes by density functional hydrodynamics. Following this, Anna Sommer, of Helmholtz-Zentrum Dresden-Rossendorf, Germany, described a novel method for the measurement of flotation recovery by means of 4D particle tracking velocimetry.
Nikolay Evseev and Anna Sommer
Stephen Neethling
Froth behaviour has a major impact on the overall performance of flotation cells, with the froth controlling the water recovery and entrainment, as well as having a significant impact on the recovery. Froth stability, including bubble coalescence and the bursting of the bubbles at the froth surface, are the key drivers of froth performance. Even though the froth stability is hard to directly control, it is important to understand how this stability impacts froth performance parameters such as the water recovery, entrainment and froth recovery. Stephen Neethling, of Imperial College, UK, showed how a theoretical understanding of froth behaviour based on foam physics can be used to link stability to performance. Stephen is one of 6 six researchers from Jan Cilliers' excellent group at Imperial College who will be presenting papers this week.
The University of Cape Town is only a few minutes from the Vineyard Hotel, and a delegation of 14 of the flotation group is here this morning. Kirsten Corin was the first to represent the group on the podium, and she showed that, considering the importance of bubble formation and bubble-particle attachment, it is evident that the pulp phase facilitates the events for the most crucial requirements of a successful flotation operation. Water forms the bulk of the pulp phase, and as a result of water scarcities in countries like South Africa, the need to recycle process water within mining operations is increasing. Hence it is of great importance to understand the effects of water quality on the vital sub-processes within the flotation process, particularly bubble-particle attachment. Kirsten evaluated the floatability of selected sulphide minerals with reference to their propensity for attachment to bubbles under deteriorating water quality.
After such an intensive start it was good to take a break in the exhibition area, to talk to the exhibitors and view the Fundamentals posters on display.
Turkish company Ugur Seluloz Kimya A.S. was established in 2001 and is exhibiting for the second time at an MEI Conference. It has two production plants and is one of the leading developers and manufacturers of sodium carboxymethyl cellulose and polyanionic cellulose. 

Zafir Ekmekci, of Hacettepe University, Turkey,
with Belma Sonmez and Ozgur Akoglu of Ugur Seluloz Kimya
American company REXA's Linear Actuators have hydraulic stiffness and accurate dart valve positioning  required for controlling tank pulp levels and producing higher recovery rates of the desired mineral.  When installed, plants are enabled to be protected against adjacent cell slurry surges and increase process stability with improvement of dart valve position control; which in turn improves productivity due to higher launder mineral grades.   
Mark Ferra of Rexa with Francesco Bernardis of CP Kelco, Finland
Allister McBride and Ben Tordoff, of conference sponsor Zeiss, discuss automated mineralogy
with Elias Habuzwima and Cipo Mbozi of Mopani Copper Mines, Zambia
Suitably refreshed it was back to the conference with Bertil Pålsson, of Luleå University of Technology, Sweden, discussing the implications for flotation of nano-entities for surface modification of minerals, followed by Kari Heiskanen, of Aalto University, Finland, who discussed how bubble size distributions affect the physical performance of flotation. Michael Moys, of the University of the Witwatersrand, South Africa, then showed how bubble size distribution in flotation froths can be measured. This is important as most valuable products produced by flotation pass through the froth phase. Most research into flotation has however been focused on the pulp phase but the froth phase has attracted more research in recent times. The complex processes that occur in the froth phase – detachment, re-attachment, coalescence of bubbles, and competition for attachment sites, mixing and transport all combine to affect the net transfer of mineral particles into the concentrate.
Bertil Palsson, Kari Heiskanen, and Michael Moys
As Sascha Heitkam, of the Technical University Dresden, Germany, pointed out, the flowing behaviour of liquid foam and froth is rarely investigated, one reason for this being that no adequate measurement technique exists. However, industrial flotation applications could be improved by monitoring the froth flow in the process, and Sascha showed how Ultrasound Doppler Velocimetry has been used to measure the velocity distribution inside a liquid foam.
The heat of immersion is a very sensitive measure of the heat produced when a liquid, such as water, interacts with a dry mineral surface. The extent of the interaction is dependent on the polarity (or wettability) of the mineral surface. This technique has had little application in the mineral processing literature and was introduced by Jestos Taguta of the University of Cape Town, South Africa as a potentially useful tool in characterising mineral surfaces with relation to their floatability.
In the final paper of the morning Hoang Duong, of Hanoi University of Mining and Geology, Vietnam, discussed the challenges in process mineralogy and impact of hydrodynamics in the flotation study of a fine grained carbonaceous sedimentary apatite ore.

The first of the Vineyard's excellent lunches
Positron Emission Particle Tracking (PEPT) is proving to be a very important tool for analysing and rigorously interpreting experimental data of the behaviour of hydrophobic and hydrophilic particles in flotation systems. Imperial College are at the forefront of PEPT research, and in the first presentation of the afternoon Pablo Brito-Parada showed how a continuous steady-state bench scale flotation cell has been used to assess the impact of operating conditions and design parameters on flotation performance. 
Lev Filippov
Lev Filippov, of Université de Lorraine, France, then discussed methods of controlling bubble size in flotation columns, which was followed by a short break due to a "no-show" by a scheduled author from the Indian Institute of Technology.
Turbulence plays a complicated role in froth flotation: it is desirable because it helps to promote bubble-particle interactions in the pulp, and to increase the specific surface area of the air bubbles introduced into the tank, but it is undesirable because it also promotes the detachment of valuable mineral particles from bubbles, and exacerbates entrainment-inducing mixing at the pulp-froth interface. In the third paper of the day from Imperial College, Angus Morrison described an experimental program which was undertaken to optimise the performance of an easily-retrofittable froth phase insert designed to isolate the froth, and the pulp-froth interface, from the effects of pulp-phase turbulence in a laboratory-scale froth flotation tank.
During the break Amanda was chatting to Ibrahim Ayoub of Continental Engineering Services Australia & Africa, the Australian and African arm of Continental Industrie, a French based company with over 40 years experience in air displacement technology. Specialising in the engineering design, fabrication, supply, maintenance and commissioning of fluid displacement machinery and associated pipework and structures, Ibrahim told Amanda that the company was excited to be part of Flotation ’17 to showcase its multistage centrifugal blowers, and introduce its new turbo blowers, specially used for the delivery of air for flotation plants.
In the first presentation from Australia, Liza Forbes, of CSIRO Mineral Resources, showed how the type of pyrite, the most common sulphide gangue mineral in base metal sulphide ores, affects the electrochemistry of chalcopyrite/pyrite interactions. Margeth Tadie, of Stellenbosch University, South Africa, then discussed the role of redox potential in the flotation of galena, and in the final paper of the day Bent Babel, of the Helmholtz Institute Freiberg for Resource Technology, Germany, showed how mineral wettabilities on a microscale can be characterised by colloidal probe atomic force microscopy.
After a long and intensive day, with some cutting edge papers, it was good to relax in the Vineyard gardens and enjoy a glass or two of wine in the first of the conference "happy hours". We always welcome a few visitors to the happy hours, and this evening we entertained Prof. John Ralston and his wife Ann, who are holidaying in Cape Town. John was particularly pleased to meet up with his recent hosts from China's Central South University. Also welcomed were Gaynor Yorath and Prof. Sue Harrison from nearby University of Cape Town. Sue is MEI's consultant to Biohydromet '18.
 
John and Ann Ralston (centre) our welcome guests
 
John Ralston with Central South University delegates
Sue Harrison (left) another happy hour guest
Following the happy hour, delegates dispersed to various parts of Cape Town. The MEI team strolled over to the nearby Cavendish Mall for pizzas in the pleasant and entertaining company of Graeme Jameson.
More on day 1 in the posting of 13th November.

Tuesday November 14th
Not the usual view from the conference centre this morning. Capetonians have been praying for desperately needed rain, and this morning they got it, so it was a relief to be indoors for the day's sessions. 
 Many challenges still exist with the development of precise and accurate predictive models for froth flotation. Most state-of-the-art models are based on the two-compartment model, which includes entrainment; however, these models have difficulty in separating the role of froth zone recovery from collection zone recovery. As argued by Richard LaDouceur, of Montana Tech, USA, it is perhaps for this reason that modern, commercially available flotation models are still not capable of predicting some important phenomena that occur in industrial mineral flotation plants. A growing body of evidence is emerging that suggests the key to resolving these difficulties may lie in improving our understanding of the mass transfer and turbulence phenomena occurring at the interface between the dynamic collection zone and the relatively static froth zone. and Richard reviewed the evidence supporting the incorporation of the interface and proposed a model structure for a “three compartment” flotation model. 
How saline water affects the adsorption behaviour of surfactants on solid-liquid interfaces and subsequent mineral flotation is still unknown despite the widespread application of saline water in mineral flotation. Ziyong Chang, of the University of Queensland, Australia, presented a comprehensive review on the adsorption behaviours of surfactants in saline water based on research findings, guiding the application of surfactants in mineral flotation using saline water.
It is good to have the worlds largest mineral processing university, China's Central South University, represented at the conference, and Guangyi Liu discussed the new understanding of the molecular design of flotation collectors, their flotation mechanism and green manufacture which will boost their future development.
With Guangyi Liu, Chenyang Zhang and Zhiyong Gao of Central South University
This was followed by a presentation by Daniel Chipfunhu, of BASF, Australia, who described a new range of frother formulations that have been developed by BASF, the trend towards more complex and low grade ore bodies requiring increasingly specialised flotation reagent suites to deliver the required separation efficiency of the valuable mineral from the gangue, and to maximize concentrate grade and recovery. Daniel is one of 7 representatives of BASF, from offices in Australia, Germany, Russia and Turkey, and his paper was one of three to be presented in the technical sessions, a fourth being presented as a poster. BASF has a very high profile at this year's conference, sponsoring and exhibiting for the first time and presenting its new frother range and collectors for sulphide and non-sulphide flotation at the booth. The international team of flotation experts centres around Dr. Bettina Sobotka, the new head of Segment Flotation in BASF’s Mining Solutions. 
Bettina Sobotka with the BASF delegation including Daniel Chipfunhu (2nd right)
Thiosulfate ions are formed during the processing of sulfide ores. They have a detrimental effect on flotation, resulting in recovery and selectivity problems. Yasemin Öztürk, of Hacettepe University, Turkey, showed how oxidation by hydrogen peroxide was used to mitigate the negative effects of thiosulfate on the flotation performance of a Cu-Pb-Zn sulfide ore. 
Yasemin Ozturk and Hacettepe University colleagues with Bianca Newcombe and Dee Bradshaw
During the break I caught up with Joe Felix and his son Travis, representing CiDRA Minerals Processing, a regular exhibitor at MEI flotation conferences, again exhibiting its SONARtrac® wrap-around the pipeline flowmeter system which measures both flow volumes and percentage air present in the pipeline. Also on view was their latest product offering, the CYCLONEtrac™ Particle Size Tracking system (PST), which enables real time reliable particle measurement for optimization of classification circuits at the individual hydrocyclone level, helping to reduce process upsets, improve closed circuit grind and classification, and maximize mineral recovery.
Travis and Joe Felix (3rd and 4th left) in the CiDRA booth
Clariant Mining is a worlwide company, with its South African, French and Brazilian offices represented at the conference. Linda Mahlangu, of Clariant Southern Africa reviewed the potential of phosphoric acid esters for the flotation of oxidised copper minerals. Low grade oxide copper mineral flotation dates back almost 70 years. In the 1960’s the process involved 2 basic flotation methods (i) fatty acid flotation of oxide copper minerals and (ii) sulphidization of oxide copper minerals followed by flotation using sulphydryl collectors such as xanthates. Over the years the use of fatty acids to concentrate the copper oxides lost its popularity, with most operations preferring the controlled potential sulphidisation method. Linda showed how phosphoric acid esters, which have proven effective in selectively floating carbonates in the reverse flotation of phosphates, can be used as alternative collectors for oxide copper mineral flotation, particularly for carbonates such as malachite.
Linda Mahlangu with Clariant colleagues
It is good to have three representatives from Kyushu University, Japan. G.P.W. Suyantara described a study on the effect of a mixture of hydrogen peroxide and ferrous sulfate on the floatability of chalcopyrite and molybdenite. He showed how oxidation treatment using hydrogen peroxide can be improved by the addition of ferrous sulphate.
Tsuyoshi Hirajima, GPW Suyantara and Hajime Miki of Kyushu University
The employment of environmental-friendly, sustainable, and renewable chemicals in industrial processes is being demanded more and more. An interesting and promising resource is cellulose which can be treated chemically and mechanically to incorporate specific functional groups and organic components into the cellulose structure and reduce the size of fibres down to nanoscale. The modification of cellulose leads to tailored properties enabling the application of cellulose in several processes, however, the modification is expensive and time consuming. Robert Hartmann, of University of Oulu, Finland, presented a study focusing on the efficiency of hexyl amine cellulose for the flotation of quartz and the recovering of the cellulose using a simple pH treatment.
A methodology that would help to find a correlation between the structure of surfactants and performance was discussed by Magnus Svensson of Akzo Nobel Surface Chemistry AB, Sweden. The methodology includes theoretical and practical evaluation of the surface properties provided by nonionic surfactants in systems where direct flotation of apatite is involved. It has been shown that only a combination of required frothing properties and good grade/recovery can ensure stable process at a large scale flotation plant. It was found that the type and degree of branching of the alkyl chain of secondary collectors significantly contribute to the frothing properties and the ability of primary/secondary collector formulation to wet the surface of apatite.
Magnus Svensson (2nd right) at the Akzo Nobel-Danafloat booth
Yangchao Xia, of the China University of Mining and Technology, described a molecular dynamics simulation study on the promoting effect of the cationic surfactants dodecyl trimethyl ammonium bromide (DTAB) and the oil collector dodecaneon on low-rank coal flotation. It was found that dodecane cannot be adsorbed tightly onto the coal surface and the interaction energy is very low, but the addition of DTAB enhances their adsorption.
In recent years, the University of Melbourne and CSIRO have been investigating the use of temperature-responsive polymers as multi-functional reagents in flotation, featuring tuneable collector, depressant, and flocculant behaviours. These materials possess interesting thermo-switchable properties, displaying hydrophobic behaviour upon heating above the transition temperature, allowing the polymers to function as collectors. Below the transition temperature, the polymers instead exhibit hydrophilic properties, acting as depressants. Furthermore, the polymers are able to behave as selective flocculants for difficult-to-recover valuable fine particles, inducing the formation of larger aggregates more amenable to flotation, while limiting the slimes coating of valuable fines on coarse gangue particles. Liza Forbes, of CSIRO, took us to the lunch break by reviewing the advances made towards the study of these materials as thermo-switchable flotation aids.
As well as presenting two papers, Liza Forbes, is manning the CSIRO booth, with Nee San Yap, showcasing the work performed by the Fluids Engineering and Intelligent Process Measurements groups. The latest developments in process instrumentation developed by CSIRO are on display, including the iORTM , an intelligent online rheometer; Wi-SEDTM, an automatic sedimentation and separation curve instrument; and the InterFloatTM an interface detection device for multi-phase fluids. In addition to the instrumentation, CSIRO is promoting the release of their new book – Clays in the Mineral Processing Value Chain.
Amanda with Liza Forbes and Nee San Yap
Jon and Chris Greet relaxing during the lunch break
Pyrite is a gangue mineral commonly associated with valuable sulphide minerals, such as chalcopyrite, chalcocite, galena and sphalerite. The separation of pyrite from these valuable sulphide minerals by flotation is difficult due to the activation of pyrite by lead and copper ions added intentionally or dissolved from minerals. Following the lunch break, Rolf Lauten, of Pionera, Norway, showed how a type of biopolymer has been used to depress pyrite in chalcopyrite flotation, with little impact on the recovery of chalcopyrite.
Seawater flotation is becoming a reality due to the shortages of fresh water. It is well documented, however, that the use of seawater for flotation is hard on molybdenite recovery and pyrite depression at the alkaline pH where copper rougher/scavenger flotation is being carried out. These difficulties are undoubtedly due to the mono- and/or divalent cations present in seawater at high concentrations, the mechanisms of which are not fully understood. Roe-Hoan Yoon and co-workers at Viginia Tech, USA, have studied the effects of KCl and MgCl2 on bubble-particle interaction using the force apparatus for deformable surface. This new force apparatus developed at Virginia Tech is capable of measuring both the hydrodynamic and surface forces affecting the bubble-particle attachment process.
Several semi-soluble and soluble minerals are recovered by flotation. Examples of semi-soluble minerals include phosphates, fluorite, calcite, scheelite, barite and celestite, while the leading example of the flotation of soluble salts is the separation of sylvite (KCl) from halite (NaCl) in the potash industry. While the practice of flotation of these minerals is relatively well established, the mechanism of flotation is less clear. Ben Knights, of CM Solutions, South Africa, examined the mechanism of flotation of these minerals, and proposed a novel mechanism.
Claudio Schneider of CETEM, Brazil, presented the results of a campaign aimed at characterizing flotation kinetic parameters with respect to particle composition. A special type of iron ore known as Compact Itabirite was chosen for the experimental work because it consists of essentially two phases, namely quartz and hematite which in turn have very distinct densities. The results showed that the rate of flotation and, consequently the capacity of the cells or columns, is controlled by the transport of the rising particles in loaded quartz bubbles. The measured flotation rate constants do not vary with composition thus demonstrating bubble transport control.
The froth zone provides the primary means for rejecting the slimes from around the bubble-particle aggregates. While this conventional approach has generally been effective, performance can fall well short of what is possible due to froth instability, and difficulty in applying wash water to overcome gangue entrainment. Jamie Dickinson, of the University of Newcastle, Australia, described the Reflux Flotation Cell (RFC), which incorporates an inverted fluidized bed of bubbles at a volume fraction of order 0.5, offering the potential to overcome such inefficiencies. This bubbly zone exhibits far greater permeability, permitting strong counter-current washing of the bubbles, and positive bias. Coalescence is also less prevalent. He described the application of a two stage RFC system to the recovery and concentration of a copper ore, examining the influence of the gas flux on recovery, for particles up to 355 microns.
And so ended the Fundamentals Symposium, and another intensive day with relaxation this time provided at the conference dinner at Lagoon Beach, with its iconic view of Table Mountain across the bay. Despite the inclement weather, it was a very enjoyable evening with great food, wine and entertainment, and most importantly, great company.


 More on day 2 in the posting of 14th November.

Wednesday November 15th
Jon Wills opened the Applications Symposium this morning, after which we were pleased to welcome Bill Johnson, of Mineralis Consulting, Australia, making his debut at an MEI Conference, and presenting a keynote lecture on existing opportunities for increasing metallurgical and energy efficiencies in concentrators (posting of 15 August 2016).
Jon Wills and Bill Johnson
David Bulled
David Bulled, of SGS, Canada, asked the question "forecasting flotation plant results – how precise is that?" A variety of data of variable validity is frequently used by the forecaster, but precision is rarely questioned. David's presentation attempted to examine the risks in the production forecast, i.e. the sources of error and uncertainty in the data, and showed the potential precision of the outcome from one case study, involving a geometallurgical approach to characterisation of the ore to be treated by testing numerous samples and using the data to estimate flotation parameters for individual mine blocks.
Plant trials routinely involve performing various experiments ranging from testing the performance of a new reagent to assessing the potential of a different circuit configuration. Such trials are highly valuable for continuous improvement in flotation plants. However, the inevitable presence of measurement uncertainty raises concerns about risks related to decisions made upon their completion. Simon Gariepy, of Algosys, Canada, discussed how metal accounting can improve the efficiency of such plant trials.

Geometallurgy is a structured approach to integrate various aspects of the mining, mineral and processing value chain to provide relevant information for optimisation of processing efficiencies, aid production planning, and minimise environmental impact. However, according to Victor Ross, of the University of the Witwatersrand, South Africa, a conceptually robust framework of the geometallurgical landscape with respect to flotation is still lacking. He described the development of a framework that captures the interactions between key parameters that pertain to the characteristics of the ore, its resultant comminution behaviour, and ultimately its flotation efficiency. 
Paulina Vallejos
A methodology to characterize the mineral feed to the flotation process, by liberation and particle size, was proposed by Paulina Vallejos, of Federico Santa Maria Technical University, Chile. This methodology considers a modification of the classical Gaudin liberation model, incorporating a grain size distribution for the mineral in the ore deposit. Results from previous research were analyzed to test and validate the new methodology. The characterization of the mineral was successfully reproduced by liberation and particle size and the results allowed the estimation of the mineral recovery profiles along an industrial rougher flotation bank both by liberation and by particle size classes.
In what was essentially the first of a 3-part investigation, the other two papers being presented by posters, Nilce Santos, of UFMG, Brazil, showed how flotation recoveries per size liberation classes have been modeled using the particle surface area. The resulting model presented a very good adjustment for recoveries per size, and once it is directly connected to particle characteristics, the model showed in a direct way the effect of particle size and liberation on flotation.
Nilce discussing one of her posters with Rogerio Baldoino, of Vale, Brazil
and Iita Kejonen, of Outotec, Finland
Nilce's paper took us up to an extended coffee break, to allow the Applications Symposium poster authors to introduce their work, and for today's new registered delegates to talk to the exhibitors. 


Magotteaux Australia is a regular sponsor not only of the flotation series, but also the comminution series of conferences, and Chris Greet has represented the company at all these events, showing how comminution and flotation are intimately linked. He recalled that Cyril O'Connor once said that flotation is an excellent diagnostic tool to measure the effectiveness of a comminution circuit! In his presentation this morning he discussed the effect of a change in grinding medium, from forged steel to the superior wear resistance of high chrome white iron, at Oz Minerals Prominent Hill Mine, caused a marked shift in the pulp chemistry to more reducing conditions and an increase in the oxygen demand of the system. In terms of metallurgical response overall copper recovery was decreased by nominally 1.2 % as well as a drop in final copper concentrate grade.
Chris Greet (2nd right) at the Magotteaux booth
Jianyuan Liu
Following on from this theme, Jianyuan Liu, of the Beijing General Research Institute of Mining and Metallurgy, China, discussed how different milling procedures may result in different flotation responses. With co-workers from the University of Cape Town, two copper bearing ores from China were investigated in order to determine the effect of wet or dry grinding. The effect of point of addition of lime, used to promote the depression of pyrite, was also investigated. The milling was carried out in a Magotteaux Mill which allows reagent addition during milling as well as the monitoring of changes in parameters such as pH, Eh and DO. After wet milling, the ores yielded different concentrations of Cu and Fe in the pulp and also significantly different recoveries. Dry grinding also affected the behaviour of the ores differently.

Flotation recovery is a function of the size distribution and associated mineral liberation produced from comminution, which is affected by classification. Classification in comminution is traditionally performed using hydrocyclones, but multi-stack screens, which achieve a better separation efficiency, are becoming a viable classification alternative. Juan Frausto, of the JKMRC, Australia, presented the evaluation of multi-stack screens at a silver-lead-zinc mine. The installation of screens made it possible to switch between hydrocyclones or screens as the classifier in the ball milling circuit. Analysis of survey information and historical monthly composite data showed that coarse particle recovery of both lead and silver significantly improves when using screens. The potential drivers were enhanced coarse particle liberation, improved reagent coverage on coarse particle surfaces, or a decrease in pulp viscosity of the flotation feed. Juan discussed the outcomes and implications for classification design.
Bianca Newcombe
Improvement in the performance of a flash flotation cell can be achieved through optimisation of the cells flotation/classification profile via the manipulation of process operating variables such as feed rate, feed per cent solids, rotor speed and dual outlet flow. Bianca Newcombe, of OptFroth Solutions, Australia, presented the findings of changing the rotor speed on the internal hydrodynamics and valuable element (Au and Cu) performances in an industrial flash flotation cell.
Conference sponsor FLSmidth, launched its nextSTEP™ rotor/stator technology during the annual Society for Mining, Metallurgy & Exploration (SME) conference in Denver, in 2015 (MEI Online). Bartosz Dabrowski, of FLSmidth USA, described the evaluation of the nextSTEP™ installation at a South American concentrator, a test program having been carried out to evaluate the hydrodynamic and metallurgical performance of the circuit, and particularly of the new rotor/stator. FLSmidth is in the final stages of discussions with the customer to obtain permission to present all data gathered during the evaluation.
Bartosz Dabrowski (3rd left) and Dariusz Lelinski demonstrate the nextSTEP rotor/stator
The mining industry has grown and developed over the years and has adapted itself to changing economic conditions.  One of the changes has been the transition from cell-to-cell type to open flow type flotation machines. During the lunch break Pepe Wang, of Imperial College, UK was talking to the Metso team about the high aerating open flow type Metso DR flotation machine, developed specifically to meet modern requirements. The RCS flotation machine is the latest design to use the circular tank concept and combines the benefits of circular cells with the unique features of the mechanism to create the ideal conditions to maximise flotation performance for all roughing, cleaning and scavenging duties. 
Pepe Wang (right) with Metso's Paul Gallagher, Thierry Monredon and Lindy Losper
Australians Graeme Heyes and Bill Johnson relaxing during the lunch break
The afternoon session was all about flotation machines, some of which are very large indeed. When I commenced my career in the minerals industry nearly 50 years ago I could never have envisaged the size of today's machines, which have reduced overall capital and operating costs and facilitated control and instrumentation.

Dariusz Lelinski discussed the metallurgical performance of the 660 m³ SuperCell™ equipped with the nextSTEP™ rotor and stator. FLSmidth's 660 m³ SuperCell machine has been constructed and commissioned and is the largest installed and operating flotation machine in the world. Tests have proved its ability to recover particles from a wide range of sizes.
Toni Mattsson
Hot on the heels of the FLSmidth SuperCell is Outotec's forced-air TankCell® e500 flotation cell, which was installed in 2014 at Kevitsa Cu-Ni-PGE concentrator as the first cell in the Cu rougher scavenger bank. After commissioning of the 500 m3 flotation cell the metallurgical and gas dispersion performance of the cell were investigated. Toni Mattsson, of Outotec, Finland, presented detailed results of the metallurgical evaluation and compared the gas dispersion performance of the TankCell® e500 with measurements carried out in smaller size TankCell® type flotation cells.
Graeme Jameson, of the University of Newcastle, Australia, is, like our keynote speaker Prof. Yoon, a recipient of the IMPC Lifetime Achievement Award (posting of 15 September 2016). He is, of course, world renowned for his eponymous flotation cell, of which over 300 are now in operation in 25 countries. In his presentation today Graeme introduced a new froth flotation machine, known as the NovaCell. It can recover mineral particles over a wide particle size range, from the lower limit of flotation, to an upper limit which depends on the liberation characteristics of the ore. In a single device, the collection of the fines and the coarse particles takes place in separate environments. The finest particles are contacted with bubbles in a high-energy aerator, while the coarse particles are captured by bubbles in the gentle environment in a fluidised bed.
A familiar sight- Graeme Jameson with notebook and pen
Coarse particle flotation is a desirable aim, in order to reduce energy and water consumption, but work by numerous experts has shown that conventional flotation works well for a limited size range from approximately 15 to 150 microns. Particles outside this critical size range are typically lost in industrial operations due to inherent constraints associated with physical interactions that occur in the pulp and froth phases (i.e., turbulence and buoyancy constraints). To overcome these limitations, Eriez Flotation Division, USA, has developed and successfully implemented a new technology that combines fluidized-bed separation and flotation. The HydroFloatTM technology has been successfully demonstrated in sulfide applications for recovering coarse values from concentrator tailings. Other efforts have shown the positive benefit that can be derived from implementation directly in the concentrator using a split-feed approach. Jaisen Kohmuench of Eriez Magnetics, Australia, discussed the theory of operation of fluidized-bed flotation and presented data gathered from numerous lab- and pilot-scale test programs.
Jaisen Kohmuench and Richard Merwin of Eriez, with Alicia Bakalarz and Magdalena Duchnowska of Wroclaw University
Flotation performance in mechanical flotation cells is strongly influenced by hydrodynamics. This is largely driven by the action of the impeller which generates macro-turbulence thus affecting many of the sub-processes of flotation. The impeller’s ability to generate macro-turbulence may be characterized by hydrodynamic parameters such as the pumping capacity and dimensionless flow number. Thiago Souza, of Instituto Tecnológico Vale, Brazil presented an analysis of the impeller flow number in industrial Wemco mechanical flotation cells.
Small bubbles are one of the drivers of good flotation performance by improving reaction kinetics. In addition to having small bubbles it is important to have high collision and attachment efficiency as well as high froth recovery. The Jameson Cell combines these features with its small footprint, efficient froth washing and low maintenance. Cleaner circuit design is now better utilizing the features of the Jameson Cell to improve cleaner circuit performance and several examples were given by Hans de Waal, of Glencore Technology, Australia, of how the Jameson Cell can significantly improve project economics and plant simplicity. Hybrid cleaner circuits represent a significant opportunity to improve metallurgical performance, reduce plant footprint and simplify plant operation.
Francesco Bernadis
Hot batch flotation tests are often applied to reduce risks in plant trials as they combine the benefits of matching complex plant feed stream compositions with the high precision of lab scale batch flotation testwork. One of the weaknesses of hot flotation tests is the sequential nature of the testwork, where ageing of pulp samples can influence the data. When present this interference could at best generate inconclusive results, and at worst, inaccurate conclusions. To improve the reliability of test data, Francesco Bernadis described how CP Kelco of Finland has developed a novel, double batch flotation machine for conducting parallel hot flotation tests on live flotation streams.
Liberated fine valuable particles are often lost to flotation tailings streams due to their low collision efficiency with air bubbles. A variety of processing strategies are employed to overcome this, including the use of micro bubble generators, dissolved air flotation, high energy flotation cells, and agglomeration of fines. More recently, focus has shifted to high shear cavitation devices, in which the feed slurry is intimately contacted with air in a high pressure environment, typically a series of venturi aerators. The low instantaneous pressure generated in the throat section of the venturi promotes cavitation and the formation of ultrafine bubbles on particle surfaces, which is believed to aid the recovery of fines. Victor Ross, representing Mintek, South Africa, showed how a high shear cavitation device has improved the flotation of fine PGMs.
Victor Ross (2nd right) at the Mintek booth
For decades, the conventional flotation machine has been the accepted tool for processing sulfide ores. As plant capacity increases, machine size has evolved to keep pace with the required retention times. However, the excessively large size of these machines requires extreme floorspace, foundations and power to operate. Recent work conducted by Eriez has shown that high-efficiency flotation machines which are based on focused energy input can achieve similar results in less than one-quarter of the flotation time, floor space and power. Comparable performance is achieved by intense contacting in a separate chamber which provides concentrated energy input specifically for bubble/particle interaction. When compared to conventional technology, data show that this novel approach can achieve the same recovery as a mechanical cell, but in a fraction of the residence time. Jaisen Kohmuench, of Eriez Magnetics, Australia, discussed the theory of operation of the StackCellTM and presented data from various lab- and pilot-scale test programs.
In the final paper of the day Shi Shuaixing, of the Beijing General Research Institute of Mining and Metallurgy, China, described research on the influence of impeller pumping performances and gas accumulation effect on the fluid dynamics of an air forced and pulp induced flotation cell. 
Shi Shuaixing (centre) and Jianyuan Liu, of BRGIMM, with Robin Melville of Roytec Global
After an intensive 10 hour day, it was good to adjourn to relax in the exhibition and poster area for the second of our "happy hours".
Happy hour with Nick and Flee Wilshaw and Chris Magombedze
More on day 3 in the posting of 15th November.
Thursday November 16th
Froth flotation is the best available technology for the recovery of fine particles. However, as highlighted by Roe-Hoan Yoon, of Virginia Tech, USA, its effective particle size range is limited to the range of 10-100 µm, indicating problems at both ends. In search of a solution to this problem, the possibility of using oil drops rather than air bubbles to recover ultrafine particles was explored during the 1960-70s. A fundamental advantage of this approach was that oil drops in general can collect hydrophobic particles with contact angles twice as large as with air bubbles. This concept known as two-liquid flotation (or liquid-liquid extraction) showed promising results. In work carried out at Virginia Tech, the two-liquid flotation process has been modified such that a recyclable oil, e.g., pentane or heptane, is used to recover ultrafine particles. The new process known as hydrophobic hydrophilic separation (HHS) has been tested successfully for the recovery of ultrafine coal particles at both the proof-of-concept (POC) and pilot-scale continuous tests. The new separation process has a special provision to minimize the entrainment of both gangue minerals and process water, so that the product is of high grade with very low moisture. Based on the successful pilot-scale test results, the Minerals Refining Company (MRC) in Richmond, Virginia, is currently in the process of designing the first commercial plant for the recovery of ultrafine coal from the waste streams generated in existing coal preparation plants.
Along with Profs. Yoon and Jameson, Jim Finch of McGill University, Canada, is one of three holders of the SME's prestigious Antoine Gaudin Award. This morning he described how a downcomer, as employed in the Jameson Cell, was considered for producing solvent-coated bubbles for possible application in a technique referred to as “air-assisted solvent extraction”. Upon testing it was found that the bubble bed in the downcomer started to collapse upon introducing solvent, evident from decreasing air holdup, decreasing aspirated air rate, and formation of air slugs. Tests with hydrophobic solids, graphite and talc, gave increased bubble bed stability showing it is the liquid nature of the solvent that is the key factor causing the collapse. One combination, talc and MIBC, did provide stability against solvent addition. Jim discussed froth collapse/stability mechanisms and noted that the Jameson Cell is successfully employed to remove solvent droplets in SX plants.
In order to save on costs, and provide additional income, mining methods have evolved, becoming increasingly complex. Inevitably, this has in some instances brought about variability in head grades feeding into mineral processing plants. Perhaps one of the biggest challenges for a PGM concentrator with a varying head grade is being able to produce the desired PGM grade at optimum PGM recovery. Fit for purpose grade analysers are starting to play an increasingly important role in achieving this goal. The success factors of grade analysers were discussed by Karen Keet, of Blue Cube Systems, South Africa.
Karen Keet with Brian Whitehead and Jules Aupiais
Rebecca Peacock, of First Quantum's Mauritania Copper Mine (MCM), presented a case study for the implementation of the SGS MET Expert System at MCM where challenges were faced due to instabilities in the copper flotation circuit resulting in final product and recovery variations. The flotation process was manually operated with Regulatory PID controllers highly dependent on operator set-point inputs. This required the operator's constant attention which was complicated by continuous changes in ore feed grade and characteristics. A decision was taken to implement SGS’s MET Expert System with the objective of reducing operator intervention, reducing process variation, improving process stability and hence improving the grade-recovery curve and product quality.
Juha Timperi
As stressed by Juha Timperi, of Outotec, Finland, accuracy and availability are the most important properties of an on-line analyser. Real-time measurement information provided by the on-line analyser enables potential for more efficient flotation process control and thus higher concentrator recovery. However, this potential cannot be realized if accuracy or availability of the analyser system is low. Juha described the Equipment Health Indicator, which provides automatic reporting of different components of the on-line analyser system including analyser probe, multiplexer units and individual sample lines. Using this information it is possible to focus maintenance actions to problematic areas and to systematically improve overall availability of the asset.
Image-based soft-sensors are popular due to their cost-effective and non-intrusive properties. Images are high-dimensional, requiring the use of feature extractors to produce low-dimensional representations. Such feature extractors have a large impact on final soft-sensor performance. Traditional texture feature extraction methods consider limited feature types, requiring expert knowledge to select and may be sensitive to changing imaging conditions. Alternatively, deep learning may mitigate these drawbacks. A specific deep learning architecture, Convolutional Neural Networks (CNNs), described by Zander Horn, of Stellenbosch University, South Africa, lessens the curse of dimensionality inherent in fully connected networks but must be trained unlike other feature extractors. This allows features to be discovered. A platinum flotation case study provided froth images at several distinct platinum-grades. Extracted feature sets were used to train linear and non-linear soft-sensor models. CNN feature quality was compared to traditional texture feature extraction methods and found to be competitive, showing similar performance to the best traditional methods.
During the break, Jon called in at the Maelgwyn Mineral Services (MMS) booth to finalise their sponsorship of Flotation '19. MMS is a regular sponsor of MEI Conferences, and the company has recently celebrated its 20th anniversary of supplying its innovative V and G-Cell pneumatic flotation plants into the minerals processing industry. Pneumatic flotation is generally associated with flotation where the aeration of the pulp takes place outside the flotation cell. This is the main differentiating factor between pneumatic flotation and conventional tank flotation. The energy required by conventional cells to keep particles in suspension and generate bubbles is now focused solely on the production of very fine bubbles, and the suspension of particles is catered for in the surplus energy of the system. MMS claims that the Imhoflot is the most energy efficient flotation cell on the market in converting energy input into mineral collection. The external aeration is usually achieved either by utilising a simple venturi system in a pipe with down comers or in the case of Imhoflot by using specialised fine bubble generation technology.
Jon with the MMS team
Russel Schwulst of Festo, South Africa, discussing reliable level control, which is critical
in flotation cells to maximize recovery, with Andrew Lewis and Martin Rudolph
The adoption of a common approach to the scale-up, modeling, and simulation of mineral flotation circuits has been hindered by the inability to agree on a standard procedure for laboratory flotation tests, including their interpretation methods. The discord stems, in part, from the inability to estimate the recovery of mineral particles by hydraulic entrainment (Re) and the recovery of collected mineral particles across the froth zone (Rf). For lack of alternatives, most practitioners ignore entrainment (Re=0) and assume that froth recovery is 100% (Rf=1). As a consequence, differences in test scraping frequency or froth characteristics can lead to large differences in the inferred collection kinetics. Peter Amelunxen, of Aminpro, Peru, suggested resolving the problem by incorporating a phenomenological solution for Re and Rf. By considering the test water balance, incorporating hindered settling theory, and making some simple assumptions regarding pulp, interface, and froth phases, it can be shown that the entrainment recovery of any mineral can be aproximated from the particle size, shape and specific gravity. A similar approach can be used to estimate the froth recovery as a function of time.
Peter Amelunxen (centre) with Rick LaDoucer and Ewelina Kasinska-Pilut
Iita Kejonen
Flotation circuit control is typically based on regular on-line elemental analyses. In base metal applications the conventional assaying method is X-ray fluorescence (XRF), which has proven to be reliable and accurate technology. However, in large flotation plants with many sample streams to be analyzed, the measurement frequency for individual assays decreases because a centralized XRF analyzer can only measure one stream at a time. This results in unnecessary delays that reduce the control performance. However, by integrating reflectance spectroscopy measurement with the conventional XRF technology, a practically continuous assay can be obtained. Iita Kejonen, of Outotec, Finland, showed the advantages of improved analysis cycle to process performance via faster automated higher level flotation circuit control. This technology enables capturing and reacting to grade fluctuations that may have been missed with longer measurement intervals. Moreover, response time to drastic changes in flotation circuit operation is significantly reduced which results in better process performance.
The strong Outotec delegation
Froth flotation is a complex multiphase process with various disturbances that impede optimal operation and control. Robbie Brown, of Stone Three Mining, South Africa, explored how supporting information from froth sensors may be used in conjunction with plant variables to calculate individual cell metrics that prove useful in control. 
Pierre Hofmeyr, of Innovative Metallurgical Products (IMP), South Africa, reviewed recent developments which allow collected slurry samples to be transported rapidly using compressed air to a collection station in a laboratory where a number of sample preparation and analytical procedures can be carried out. These include automated filter pressing and drying, sample mounting and X-ray Diffraction (XRD) to determine mineralogy, X-ray Fluorescence Spectrometry (XRFS) on pressed powder pellets and fusion beads to determine major and minor elements and fire assay to determine Au and PGEs in all plant process streams. In particular, a new automated fire assay system called FIFA 2 has been developed which has lowered the detection limits for Precious Metals by an order of magnitude.
Jon with Arnoux van der Westhuizen and Pierre Hofmeyr of IMP
The recovery of oxide copper minerals by flotation is a longstanding challenge in the minerals industry, especially for ores not economical for direct acid leaching. Current practice involves sulfidization using NaSH or Na2S followed by flotation using traditional sulfide collectors. Controlled potential sulfidization has been shown to improve recovery of oxide Cu but is not a satisfactory solution because of health and safety issues, high consumption of NaSH, and inability to recover minerals refractory to sulfidization. Numerous collectors have been evaluated for direct flotation (i.e. without sulfidization) of oxide Cu minerals, the most researched of which is alkyl hydroxamate. While there are numerous publications dealing with the fundamentals of interaction of hydroxamates with single minerals, few publications discuss practical aspects of hydroxamates use in ore flotation, particularly with sulfidizing agents. Tarun Bhambhani, of Cytec Solvay Group, USA, presented case studies which included methods to identify combinations of sulfidizing agents and oxide collectors to maximize recovery for various types of ores.
Tarun Bhambhani (2nd left) at the Solvay booth where the new AERO® OX 100 promoter for oxide minerals recovery
and its new line of nickel collectors, AERO® NP promoters, were being highlighted 
Carbonaceous minerals in base metal sulphide ore deposits present a challenge during flotation due to the hydrophobic nature of organic carbon. Many depressants, including starches, have been trialled to depress carbonaceous minerals, but their selectivity is often limited. A carbon pre-float process where only frother is added to remove carbonaceous minerals is sometimes used prior to flotation. But this process either recovers limited organic carbon or excess sulphide minerals which display collectorless flotation when mild oxidation occurs. Brenton Fletcher, of the University of Queensland, Australia, took us up to the lunch break by showing how wheat starch polymers have been modified in terms of their molecular weights and chemical functionality to selectively depress organic carbon during chalcopyrite flotation.


Reprocessing of tailings dams is not only environmentally desirable but also increasingly economically feasible due to lower cut off grades. There is also the added benefit of no further milling being required prior to flotation. However, the effects of fine and ultrafine particles on froth stability are not yet fully understood. Isobel Mackay, of Imperial College, UK, described work using a modified AMIRA laboratory flotation column to investigate changes in dynamic froth stability with variations in particle size distribution and air flow rate. The findings provide a better understanding of the effects that air flow rate and particle size, particularly in the fine range, have on froth stability. Strategies to enhance tailings flotation through improvements in froth stability were also discussed.
The synergetic effects of nonionic reagents with carboxylic collectors was applied in the processing of the Tabuaco tungsten skarn ores in Portugal. Lev Filippov, of the Université de Lorraine, France, showed how the new reagent formulation allowed the production of a tungsten concentrate after only one cleaner stage, which can be processed by hydrometallurgy without additional use of thermal treatment or activating heavy metals salts or specific depressants.
Nickel is an important metal with total global consumption of 2 million tons per year. It is sourced from sulphide and laterite ores. Laterite ores are often complex and expensive to treat using conventional methods. While 70% of the nickel resources are contained in laterites, only 40% of the world's nickel production comes from these ores. Therefore, upgrading the nickel content in laterite ores ahead of any recovery processes is economically desirable, as discussed in a further paper from Université de Lorraine, presented by Saeed Farrokhpay. At present flotation has not been successful to recover nickel from these ores. Nickel laterite deposits are generally divided into limonite (oxide), nontronite (clay), and saprolite (silicate) zones. A systematic study was conducted on the ore samples sourced from these three categories to see the effect of different mineralogies on the flotation behaviour of laterite ores. Pre-concentration of laterite ores by flotation was found to be possible, but it is highly dependent on the ore mineralogy.  
Saeed Farrokhpay with Bill Johnson and Chris Greet
BASF representatives next presented two papers on the flotation of apatite ores. Rostislav Kamkin, of OOO BASF, Russia, described the development of a fatty acid modifier for beneficiation of the igneous apatite ores of Kovdor deposit, situated in Murmansk near the Finnish border with Russia, and Dorival Neto, of BASF, Brazil described experimental design to optimize BASF’s collector performance in apatite flotation.
To increase the sustainability and cost effectiveness of their operations, Kevitsa Mining Oy, in collaboration with academic research partners, aims to develop a holistic approach to water management in its mineral processing operation. Nora Schreithofer, of Aaolto University, Finland, described one of the first steps taken in this process, namely the monitoring and control of residual collectors. Kevitsa Mining Oy, a Cu-Ni-PGE concentrator, recycles 90-95% of its water for use in the plant. The quality of recycled water tends to deteriorate as various elements and compounds such as Ca, Na, Mg, K, SO42- and residual reagents accumulate. The accumulation shows seasonal cyclic variation that has an impact on flotation performance.
In the final presentation of the conference, Ghislain Bournival, of the University of New South Wales, Australia, discussed the analysis of water quality variation in the tailings stream of a Jameson cell operating at a coal preparation plant. Water quality data collected over two years was used for the analysis. In addition to conductivity, particle density, frother dosage and the cell operating parameters were also recorded to investigate the influence of process water composition on the flotation performance. Data analysis revealed a considerable variation in the water quality. It appears that conductivity follows seasonal patterns although a strong correlation between the rainfall and conductivity was not evident from the study.
Before presenting the two student poster awards (postings of 16th November and 20th November), MEI Consultant Jim Finch rounded off the conference with a quite superb summary of the four days. His pie-chart shows the breakdown of subject areas in the Fundamentals and Applications symposia, the former being driven by the need to understand the processes, the latter mainly by energy, water and social license.

MEI's Amanda Wills closed the conference and invited everyone to reconvene for Flotation '19 at the Vineyard again, in November 2019, after which we gathered in the late afternoon sunshine for the final farewell wine function.



 
More on Day 4 in the posting of 16th November.
At the beginning of the conference I asked two questions: how important is flotation, and are there still innovations in the process, which was patented over 110 years ago. The answer to the first question is that flotation is crucial not only to the mining industry, but to civilisation as we know it. As to the second question, this conference has shown that flotation research is vital and that the process must continually evolve to face new challenges.
The papers presented during the four days collectively provide a real state-of-the-art volume, and all the oral papers, and around 30 of the poster papers are available on USB from MEI Online. Selected papers will be published in a special issue of Minerals Engineering after peer-review. A full set of MEI high resolution photos can be found by clicking here.
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