Wednesday, 20 August 2014

Automated Mineralogy continues to make big strides

Automated mineralogy has evolved rapidly over the past few years, with many new major players providing alternatives in a very competitive market.

A few months' ago Will Goodall and Al Cropp of MinAssist, called in at MEI. They were both involved with Intellection in the early days of QEMSCAN technology.

I was pleased to hear last week that Will's company MinAssist is the latest sponsor of Process Mineralogy '14 in November.

Al Cropp has since moved on from MinAssist, and is now with Carl Zeiss, also a Process Mineralogy '14 sponsor. Only a couple of weeks ago Zeiss launched a new automated mineralogy system for the mining industry, which is described on MEI Online. The new system will be on display at the conference, so I look forward to catching up with Al, and with Will, in Cape Town in November.

Al Cropp (seated) with the new Zeiss instrument
 

Monday, 18 August 2014

Call for Abstracts- Physical Separation '15 and Computational Modelling '15

Abstracts are now invited for two of MEI's small specialised conferences, which will run back to back in June next year. As with all MEI Conferences, papers accepted for presentation will be published on a Proceedings flash drive, available at the conference, and then authors will be invited to submit edited papers to Elsevier Science after the event for peer-review and publication in a special issue of Minerals Engineering, the world's highest ranked mineral processing journal. Both conferences are certified for Continuous Professional Development.
With its very long evenings June is a great time to be in Cornwall, so plan ahead and aim to spend some time exploring this beautiful area of the world.

 
 Computational Modelling '15 will be the 5th in this very specialised but popular series and as always the aim of the conference is to bring together both users and developers of computational modelling from academia and industry to share their knowledge and expertise (see report on the 2013 conference). This conference is aimed at the full spectrum of people involved in computational modelling in minerals processing and materials handling, from model development, validation and all the way through to application.
The specific areas include:
• Model development and computational techniques
• Modelling of minerals processing and materials handling unit operations
• Optimisation of plant and circuit operation and design
• Experimental validation including novel experimental techniques
 
Physical separation methods are ubiquitous, and there is no mining operation in the world which does not make use of the density differences between solids and liquids. Whether it be gravity concentration, classification or dewatering, the principles of separation are essentially the same and Physical Separation '15, the 3rd Physical Separation conference, will bring together researchers and operators who have common interests in:
• Gravity concentration methods - single and multi-G separators and dense medium separation
• Classification techniques - hydrocyclones, air classifiers etc.
• Solid-Liquid Separation - thickeners, clarifiers etc.
• Papers dealing with magnetic separation, and electronic sorting
• Microwave technology. There are many aspects of mineral processing where the use of microwaves has potential and papers dealing with the enhancement of physical processes by microwaves are encouraged.
The keynote lecture Reducing energy consumption in comminution by doing much less of it! will be given by Dr. Rob Morrison of JKMRC, Australia, who will discuss the potential of physical separation methods, particularly electronic sorting, within comminution circuits.
Cornwall, the “birthplace of modern mining”, is an appropriate place to hold such an event, as this was the first place in the world where physical separation methods were practiced on a large scale, and the programme will include a visit to the historic Camborne-Redruth copper and tin mining district, where ruins of 19th century ‘dressing floors’ can be explored (see also the report on the 2013 conference).


If you would like to present a paper at either of these meetings, please submit your short abstract by the end of December of this year. If your company is interested in exposure via sponsorship, details for Computational Modelling '15 can be found here, and here for Physical Separation '15.

Friday, 15 August 2014

A brief history of classification in grinding circuits

In our recent discussion, Prof. Alban Lynch expressed an opinion on the use of hydrocyclones in closed grinding circuits: "the way they are used now is an absolute nonsense, with circulating loads in some cases of well above 200%. The future is high frequency screens". This has led, unsurprisingly  to a few comments on the use of hydrocyclones and screens in milling circuits.
Prof. Lynch has been in touch this morning by email, and asks me to publish this short technical note, which he entitles Classification – the enigma in mineral processing.
An enigma is defined as a puzzling or inexplicable occurrence. The description fits the present position of wet classifiers well. We need to grind increasing amounts of low grade, harder ores to meet the demand for metals so the expenditure on mills and understanding breakage is high. Classifiers can limit circuit productivity by 10% or more yet there seems to be relatively little expenditure on ensuring that size separation in classifiers is accurate and efficient. Knowing the past is the starting point for doing better so I will briefly review the story of cyclones and size separation.
 Cyclone classifiers have been used in dry and wet grinding circuits for decades. The hydro-cyclones used in wet circuits are small, inexpensive, easy to operate, and handle changes in throughput without difficulty.  Their disadvantage is that their separation characteristics are poor and they can produce recycling loads up to 400% although the particles which require regrinding may comprise only a small fraction of this. These high loads limit the capacity of mills to grind new feed and reduce the sharpness of the split, both of which may be costly. The problem occurs in both dry and wet processes and the different approaches used in the cement and ore industries to operating centrifugal separators will be discussed.      
In cement circuits the Askham dynamic separator was used for many years from 1885. It was superior to static cyclones but the circulating load was high and to reduce it a second generation centrifugal separator was designed and built in 1960. Further reduction in the load was still needed to reduce the grinding cost further and a third generation separator was designed and built in 1985. The improvement which has occurred over three generations is shown in the table and figure below.
 

There was intermittent interest in hydro-cyclones for wet circuits from 1891 but the Dorr rake classifier became available in 1902 and this unit and the Akins spiral classifier were used for wet classification from 1900-1950. By then the post war minerals boom had started and this required higher capacity processing units. Hydro-cyclones were of interest because pumps were available which could create high velocity spiralling flows in cyclones and these flows provided a mechanism to separate the feed into coarse and fine streams. Performance of hydro-cyclones improved when Kelly Krebs designed the involute entry which reduced disturbances in the outer spiral.                                                                                                      
Since then the strategy to handle high capacities of grinding circuits has been to build nests of hydro-cyclones and larger hydro-cyclones and these have been effective in handling high flows. But only with high frequency screens does there seem to have been much emphasis on better separation. These screens have been successful in reducing circulating loads and improving the sharpness of separation in 300 tph grinding circuits at the Apatit mine in the Kola Peninsula, Russia.             
Screens are more expensive than hydro-cyclones and their capacity limits must be observed during operation. But these limits will be extended and they will be an important part of the future of wet classification.  

Wednesday, 13 August 2014

News of South-West England minerals people

Nick and Felicity (Flee) Wilshaw of Truro-based Grinding Solutions Ltd joined us for lunch today. Offering technical, marketing and investment consultancy, as well as laboratory testing facilities, to all fields of mineral processing, their company is particularly recognised throughout the industry as a leader in ultra-fine grinding. As such Grinding Solutions was a sponsor and exhibitor earlier this year at Comminution '14.

With Nick and Flee at MEI
Now they are seeking to broaden their flotation capabilities, and this week Jon's partner Dr. Kathryn Hadler, formally with Imperial College, joined the company to strengthen the expertise in this area.
Kathryn with IMPC Chairman Cyril O'Connor, Cape Town 2011
A very good friend of Nick and Flee is Charlie Northfield, Process Plant Manager at the new tungsten mine, Drakelands, in Devon. Charlie and Nick graduated from Camborne School of Mines with degrees in Mineral Processing Technology in 1980. Following on the success of the monthly Cornish Mining Sundowners in Falmouth, Charlie has initiated a Devon Sundowner, and has sent me the photo below, taken at the inaugural sundowner on 1st August, attended by Wolf Minerals employees, with guest of honour Andrew Sarosi, former Chief Metallurgist, Hemerdon Project, AMAX Exploration UK.
1st Devon Mining Sundowner. Andrew Sarosi 2nd left, Charlie Northfield 2nd right
The Sundowners are planned to be held on the first Friday of every month from 5pm at the Miner’s Arms, Hemerdon. Anyone involved in mining and related industries is welcome.

Monday, 11 August 2014

In Conversation with Alban Lynch, the first Director of the JKMRC

International Mining magazine's inaugural Hall of Fame took place this year at the SME Annual Meeting in Salt Lake City. Among the legends of the minerals industry profession who were honoured was Prof. Alban Lynch, one of the giants of comminution. This was one of many awards that he has received in his long and distinguished career. He is an Officer of the Order of Australia, and in 2010 in Brisbane received what is considered to be mineral processing's top award, the Lifetime Achievement Award of the International Mineral Processing Congress.
Alban Lynch (left) receiving the IMPC Lifetime Achievement Award
from Eric Forssberg, Brisbane 2010
I first met Alban in 1986 when he presented a keynote lecture at the NATO ASI in Falmouth. He and his wife Barbara live in Brisbane, and I phoned him recently to talk about his career and to hear his views on modern mineral processing and how he sees the future progression of our industry.
Alban Lynch was born in Queensland in 1930 and worked as an industrial chemist in the paint industry from 1947-1953, while studying part-time for a Diploma in Chemical Engineering from Sydney Technical College. After graduating in 1954 he took up a position as a metallurgist at Zinc Corporation, Broken Hill, as his fiancée Barbara was from there, and studied for a BSc and MSc as an external student at the University of New South Wales.
He spoke about Maurice Mawby who came from Broken Hill, and described him as "one of the real greats". Mawby was very much involved with the development of flotation and he ascended from metallurgist to Chief Executive and set up the great years of Conzinc Riotinto Australia, which became Rio Tinto Australia. Alban remembers him as a man with a remarkable memory who would walk around the plant at Broken Hill recognising everyone and asking about their families. It must have rubbed off on Alban, as this is exactly what T.C. Rao, who obviously had great respect and affection for him, said about him in our recent conversation. Alban remarked that he and Rao "had many an argument on a Sunday afternoon, which Rao always won!"
In 1958 Alban joined the Dept. of Mining and Metallurgical Engineering at the University of Queensland (UQ), where he would remain for most of his long career, spending the first 12 years as a Research Officer for mineral processing operations, and being awarded a PhD in the department in 1965.
His arrival at UQ was at an opportune time, as by 1960 the first mineral boom in 30 years was forming and in 1961 the Australian mineral industry, through the newly formed Australian Minerals Industry Research Association (AMIRA), established by Maurice Mawby, decided to fund jointly sponsored research to improve mining and mineral processing technology.  Mawby had set up a special projects laboratory at Broken Hill, which he staffed with 12 engineers, as he knew that technology had to change in the mining industry. In 1962 a three year AMIRA project on grinding started at UQ with a group consisting of Alban, two graduate students and two technicians. The theme of the research became the modelling and simulation of grinding circuits. Jim Foots, the General Manager at Mount Isa Mines Ltd, supported the work by permitting the circuits in its old concentrator to be experimental test sites and this was the start of the tradition of project research being plant based and of graduate students, including T.C. Rao, spending months at plants on thesis projects which had the objectives of improving local circuits and providing data to support the general programme on modelling and simulation. Funding of the project has been renewed periodically for 50 years, in what is now the P9 project, although changes have occurred in its scope and size.
By 1967 mathematical models had been developed for rod mills, ball mills and hydrocyclones and simulation of a copper circuit containing one rod mill, three ball mills and six hydrocyclones indicated a proposed rearrangement which, when made, resulted in a large increase in capacity. Similar simulation work with the rod mill, 2 ball mill, 2 rake classifier circuit at Zinc Corporation in Broken Hill had a similar result. By this time Bill Whiten had joined the group and brought much needed computing skills. During the next seven years research extended to modelling of crushers and screens at Mount Isa, autogenous mills at Tennant Creek, and banks of flotation cells at Mount Isa and Philex Corporation in the Phillipines, and to the control of grinding circuits using a PDP8/I computer provided by AMIRA. This culminated in the publication of one of Alban's most well known books, Mineral Crushing and Grinding Circuits.
Alban Lynch with AMIRA computer, early 1970s
In 1971 the research group was given strong encouragement by MIM Holdings Ltd when the company established the Julius Kruttschnitt Mineral Research Centre (JKMRC) to be its Brisbane base, with Alban Lynch its first Director, a position he held until 1989, when he handed over to Dr. Don McKee, allowing Alban to concentrate on his new role as UQ's Professor and Head of Mining & Metallurgical Engineering, a position he held until 1993. (Click here for a biography of Julius Kruttschnitt, who Alban regards as another outstanding figure in the history of Australian mining). 
By 1974 the modus operandi of the JKMRC group was well established and its research activities in modelling were extended to coal flotation in the Bowen Basin mines and crushing at the Mount Newman iron mine and the Bougainville copper mine. The establishment of the JKMRC made Alban "realise the importance of graduate students working in plants- to get anywhere in mineral processing you don't spend your time fiddling around in laboratories and the students realised that this was a great opportunity for them, and the mines were very supportive".
In 1975 the decision was made to extend modelling research to blasting because that was the first in the sequence of size reduction processes. The feasibility study was carried out with support from Mount Isa and Mount Newman and the blasting project became a large and long running AMIRA project. The research was very useful to blasting engineers but it was many years before the link between blasting and crushing and grinding was developed. Alban strongly believes that mineral processing in the future needs to be linked to mining, and he talked with enthusiasm of UQ's Gideon Chitombo, a Zimbabwean "who is a superb public speaker, and who is also wrapped up in the future of mining and has set up projects funded by many major mining companies". Gideon recognises that mining must take into account mineral processing, and he will be presenting a plenary lecture on this, hopefully followed by a forum, at the IMPC in Santiago in October.
By 1980 models of grinding and flotation circuits were well developed and another book was published Mineral and Coal Flotation Circuits, co-authored with N.W. Johnson, E.V. Manlapig and C.G. Thorne. Many short courses were given on modelling, but simulation could not be used widely because engineers did not have easy access to bureau type computers. Personal computers were becoming available so a project was established to put the models on a PC. To demonstrate the validity of the modelling work and debug the programme the engineer who wrote the software spent 6 months with the PC at plants of AMIRA sponsors in USA and 6 months with sponsors in Australia. This was the origin of JKSimMet, which he feels was so successful because "a guy called Dave Wiseman wrote it. He had a lot of experience at Mount Isa, so he knew what was needed from a simulator". Knowing Dave well, I could understand Alban's praise for him, and his ability to keep things simple, a failing of many modern models, which have become so complex and difficult to understand that they are not easily accepted by operators. I remarked that often at conferences I get the impression that academics are talking to each other, but that the people at the 'sharp end' are not truly involved.

Dave Wiseman keeping it simple for me in Seattle, 2012
It was interesting to hear that he is "very sceptical about where SAG mills have gone, I think they have taken us along the wrong track. They may be attractive in terms of high productivity, but their energy efficiency is poor, and I feel that these immense machines are going to turn into very large ball mills". 
Although he has been involved with hydrocyclones for very many years he feels that "the way they are used now is an absolute nonsense, with circulating loads in some cases of well above 200%. The future is high frequency screens". He and Hakan Dundar from Hacettepe University, Turkey, have analysed data from several large operations and "it is very clear that these screens are so much better than hydrocyclones and there will be a paper on this at the IMPC in October". It is interesting that the new tungsten mine in UK will be operating their ball mills in closed circuit with Derrick screens, rather than hydrocyclones, and we will be hearing more of this at Physical Separation '15 in Falmouth.
After 6 years as Head of Department at UQ. Alban spent a large portion of the next 15 years lecturing on modelling and setting up research programmes in other countries, notably in Malaysia, Brazil, Mexico and Turkey. The most successful was concerned with cement clinker grinding in Turkey where the research group has expanded from one graduate student in 1999 to 3 staff and 8-10 graduate students in 2009. Following the pattern developed at JKMRC the dry grinding group at Hacettepe University works closely with the cement industry and is expanding its activities into related areas.   He regards Hacettepe as being "far and away the best mineral processing University in Turkey, for exactly the same reason as why the JKMRC became so successful- the students are prepared to go out on plants and actually do the work, whereas this does not happen at the other Turkish Universities".
He also found time during this period to co-author two more books, in 2005 The History of Grinding, with Chester Rowland, and the latest in 2010, The History of Flotation with Greg Harbort and Mike Nelson.

Launch of History of Flotation at Metplant 2010, Perth,
with Mike Nelson and Greg Harbort
His latest project is a Handbook on Comminution, with the AusIMM, which he hopes will be available at Comminution '16 in Cape Town. He is also involved, with the AusIMM, in the development of a virtual museum at Broken Hill, recording the town’s mining industry and its great contributions to mineral processing technology.
Talking to Alban Lynch was a great pleasure and privilege and I hope that his interesting views on mineral processing will lead to some open debate.

Saturday, 9 August 2014

The Valleys- the Heart and Soul of Wales

Barbara and I are back in Cornwall after a few interesting days in South Wales, once one of the great coal mining areas of the world, prior to the mass closure of UK coal mines in the mid 1980s. At its peak in 1913, 57 million tons of coal were dug out of the hills by 232,000 men and boys working in 620 mines. 
Blaenavon main street
We based ourselves in Blaenavon, a World Heritage Site, and almost certainly the best preserved example of a traditional South Wales iron-making town. Although part of the town dates from the late 1780s, most of the buildings are representative of an early mid-Victorian Welsh industrial community with much of it built before 1870.
 Blaenavon lies on the very edge of the South Wales coalfield, above the valleys of Ebbw Vale and Merthyr Tydfil, where seams of coal and bands of iron ore are shallow and outcrop on a hill overlooking Abergavenny.

There were many coal mines around Blaenavon, and Big Pit was one of them. Sunk sometime between the late 1830s and 1860, by 1870 the Blaenavon Iron & Steel Coal Company was the second largest coal producer in South Wales, employing 1300 workers in its heyday. It closed in 1980 and three years later was opened as the excellent Big Pit National Coal Museum, which I cannot recommend highly enough.

Big Pit National Coal Museum

The underground tour, with guides who were former miners, is an eye-opener to life underground in a working coal mine, and the visual displays are magnificent.

 

 
Nearby is the Blaenavon Ironworks museum, equally impressive. The ironworks was built in 1788 and in 1812 the furnaces were claimed to be among the most productive in the world. The site became a highly integrated ironworking operation where the mining of coal and iron ore took place alongside the smelting and forging processes.


It was here that Sydney Gilchrist Thomas made one of the last major breakthroughs in steel making in the 19th century. In 1878 he and his cousin Percy discovered how to remove phosphorus from steel, which revolutionised steel making in Europe and America.


By one of the huge iron furnaces
Aberfan
Coal mining is a hazardous business and many lives have been lost in South Wales collieries, but no mine disaster has been so tragic as the one that occurred in the tiny village of Aberfan in October 1966, when an avalanche of colliery waste buried part of the village. Torrential rain brought the waste down onto several buildings, engulfing the Pantglas Junior School, where morning lessons had just begun. 144 people were killed, including 116 children. Today the school site is a garden of remembrance to this disaster which perversely brought the valleys worldwide attention.

Although Wales is renowned for its mining, it is also famous for its many castles, 641 of them, some built to keep the English out, others built by the Normans and Plantagenets to keep the Welsh out. We visited the 13th century castle at Caerphilly, the largest castle in Wales, and second largest in the UK after Windsor, and only 25 miles from Blaenavon. Its most dramatic feature has to be the tower that 'out leans' Pisa! 

Caerphilly Castle
Returning to Cornwall we spent a few hours in the Welsh capital, Cardiff, and visited its castle, with its 13th century Norman motte and keep.


Cardiff Castle