Monday, 29 September 2014

Does the choice of regrind mill and mill media affect downstream performance?

There has been much discussion recently on the relative energy efficiencies of various comminution machines, and this is as it should be, as comminution is such a high consumer of energy.
But does the type of particle breakage mechanism have an effect on subsequent processes, notably flotation? This is the subject of an interesting paper by workers from Australia's JKMRC, recently published in Minerals Engineering.
Stirred mills have been widely used for regrinding, and are acknowledged to be more energy efficient than tumbling mills, but these two types of mills present different particle breakage mechanisms during grinding. In the study, the effect of regrinding by both mills on surface properties and subsequent mineral flotation was studied, using chalcocite as the mineral example. A rod mill and a stirred mill with the same stainless steel media were used to regrind rougher flotation concentrates. Different chalcocite flotation recovery was achieved in the cleaner stage after regrinding in tumbling and stirred mills. The factors contributing to the different recovery included particle size, the amount of created fresh surfaces, surface oxidation and the redistribution of collector carried from rougher flotation.
It was determined that the predominant factor was the different distribution of collector resulting from different particle breakage mechanisms in the stirred and tumbling mills. In the tumbling mill, the impact particle breakage mechanism predominates, causing the collector to remain on the surface of newly produced particles. In the stirred mill, the attrition breakage removes collector from the surface, and decreases particle floatability. Furthermore, the type of grinding media in the stirred mill also influences the subsequent flotation, again due to the change of particle breakage mechanisms. The chalcocite flotation recovery was improved by the addition of more collector in the cleaner stage. More collector addition was required after regrinding in the stirred mill than in the rod mill to restore the flotation recovery to the same level.
The authors conclude that the selection of regrinding mills and grinding media should not only depend on the required energy efficiency, but also on the properties of the surfaces produced for subsequent flotation.
But what do you operators think? How significant do you think this effect on downstream performance might be compared with the economics of energy consumption? Has anyone else researched or observed the effects mentioned in the paper?
To me it is another good example of how comminution and flotation are inextricably linked.

Friday, 26 September 2014

Memories of Minerals Engineering '94

Twenty years ago today Minerals Engineering '94 began at the Hyatt Regency Resort, Incline Village, Lake Tahoe, Nevada. It was the 4th in the series of conferences organised by CSM Associates Ltd and Minerals Engineering journal, and was attended by 80 delegates from 23 countries, some of whom are sadly no longer with us, some who are still familiar faces at MEI Conferences, and others who have just slipped under the radar.
Lake Tahoe, USA
The nearby University of Nevada Reno collaborated with us, and the wonderful Lake Tahoe venue was suggested to us by the late Prof. Ross Smith of the Mackay School of Mines at Reno.
The mining industry was in one of its regular periods of crisis in the mid-90s, with primary mining under great pressure, notably from environmentalists. The perception that mining is a source of pollution in every form was inhibiting the development of mining in the Western world to such an extent that it had been suggested at the previous year's SME that a future ban on all mining activities in the USA, apart from coal, could be envisaged. In Europe opportunities in primary mining were mostly in the east, particularly in the old Soviet Union, where environmental legislation was not so intense.
It was felt that primary mining was unlikely to satisfy the increasing demand for minerals, and that there would be an increasing need from minerals from secondary sources, where the physical, chemical and biological techniques can be used to extract metals and minerals from polluting wastes, despoiled land, industrial and domestic waste etc. This has certainly proven to be the case, and was the reason for MEI instigating our sustainability conferences (see posting of 14th July 2014).
Hazen Research, Inc., a company with a high international profile on the environmental scene, sponsored the conference, and the first keynote lecture at the event "Minerals Engineering in the Environmental and Recycling Industries" was given by Erik Spiller, the then Vice President of Hazen Research and President of A.R. MacPherson Consultants, a joint venture of Hazen Research and Lakefield Research.
Forty seven papers were presented and selected papers were published in Vol. 8 Nos. 1/2 and Vol. 8 Nos. 4/5 of Minerals Engineering in 1995.
A few photos from Minerals Engineering '94 are shown below.
With delegates from Japan

With Ryan Jones of Knelson Concentrators

In Virginia City, Nevada

Conference dinner with Gulhan Ozbayoglu and Ted Bearman

Monday, 22 September 2014

MEC 2014- how was it for you?

Amanda's daily reports on the Minerals Engineering Conference in Poland (Monday, Tuesday, Wednesday) have really captured the friendly atmosphere of this event.  Now it is time for your say. If you attended the conference, let us have your views on the papers, organisation, highlights etc.

Rather belatedly, due to travelling back to UK, here is Amanda's report on the final day of MEC 2014:

Thursday 18th September
This morning started with a poster session which lasted an hour, followed by a return to parallel sessions; one on mineral processing and one on the physicochemical aspects of mineral processing. I'll hold my hands up and admit that I didn't attend either session as I was busy writing the blog, but Kwang-Suk You, of the Korean Institute of Geoscience and Mineral Resources, won 'outstanding presentation of the session' for his paper on “Phase transformation of coal gangue with the addition of Na2CO3 during combustion” and Radoslav Plackowski, of Poznan University of Technology, won in his session with “Transport metali przez polimerowe membrany inkluzyjne wykorzystaniu 1-decylo-1,2,4-triazolu jako przenosnika”, which roughly translates (thank you Google translate) as “Transport of metals by the use of polymeric membranes inclusion of 1- decyl- 1,2,4- triazole as a conveyor belt”.

Marcin Lutynski closes the conference
There followed the closing ceremony, with the “outstanding presentation of the session” awards for today being handed out. My apologies to the winners from Tuesday's sessions, their awards were given out at the Gala Dinner when I didn't have my notebook. Marcin Lutynski invited us to attend next year's Minerals Engineering Conference, which will commence in Krakow, Poland on September 14.

Hylke Glass and C.K. Asani
We then sat down to our last lunch together, and I chatted with C.K. Asani, of Indian Rare Earths Ltd, the sole Indian delegate. He told me that he had travelled to Poland in search of help with the commercialisation of his patent, “Electrostatic separators for heavy mineral separation”. According to C.K. It could lead to the elimination of froth flotation in the processing of heavy minerals.

Then there was nothing left to do except say our goodbyes and board the minibus back to Gwilice.

Zhihai Luo, Haldun Kurama, Emre Altun, Hylke Glass, Olof Forsen
In summary, although there were some teething problems with timings at the start, these were overcome by day 2, and were more than compensated for by the friendly atmosphere which pervaded this event. I feel like I have come away from MEC 2014 with a host of new friends as well as a new understanding and warm regard for the Silesian region of Poland. Hopefully I will be back for MEC 2015!

Minerals Engineering Special Issue on Froth Flotation

Around 100 papers were presented at Flotation '13 last November, and 30 of these have been peer-reviewed and published in Volumes 66-68, a special Froth Flotation issue of Minerals Engineering, now available for download on ScienceDirect. The special issue contains a Foreword from Guest Editor Dr. Pablo Brito-Parada of Imperial College, UK.

Flotation '15 will be held in Cape Town in November 2015 and again will provide speakers with the opportunity of presenting their work to an elite international audience, as well as having the opportunity of publishing the work in the world's leading mineral processing peer-reviewed journal.

Saturday, 20 September 2014

The Roseland Peninsula- a Cornish gem

Cornwall's Roseland Peninsula is tantalisingly close to Falmouth, being the next stage in the eastern journey along the Cornish coastal path. However to get there means crossing two rivers, the River Fal and its small tributary the Percuil River. However, if you are not deterred by this you will be rewarded with Falmouth's best day out, with some of the finest coastal scenery in the whole of the county.

Falmouth's Pendennis Headland and castle, with the Roseland Peninsula in the background
Our journey last Sunday started at the Prince of Wales Pier, less than a mile walk from Falmouth's main Gyllyngvase Beach and the MEI Conference venue, the St. Michael's Hotel. At the pier we bought return tickets for the ferry journeys to Place, and the start of an outstanding day out.

The 3 mile ferry journey to St. Mawes took us across the Carrick Roads, the name given to a section of the River Fal which forms a large waterway, created at the end of the last Ice Age when sea levels rose dramatically and created a huge natural harbour. The Carrick Roads is a classic drowned river valley and the entry to this, the world's 3rd largest natural harbour, is guarded on either side by the Tudor castles Pendennis and St. Mawes, built in the early 16th century in the time of Henry VIII to defend against expected invasions from Spain and France (see also posting of 4th April 2012).

The ferry entering St. Mawes harbour, with the castle on the left
Arriving in picturesque St. Mawes harbour, you may wish to stop for refreshment before taking the short crossing to Place on the Roseland Peninsula.

St. Mawes
The ferry arrives at Place
There are a number of walks from Place but we decided to opt for a 6-mile circular walk, graded 'moderate' due to the overall ascent of over 900 feet.

Taking the shaded footpath to Porth Farm, we followed the Percuil River eventually reaching the coast path at Towan Beach on the eastern side of the Roseland Peninsula.

St. Mawes from the Percuil River path
Towan Beach was good place to stop for lunch, sheltered from the easterly wind by the raised beach, a reminder of once higher sea levels.

Towan Beach
The footpath to Zone Point, the most southerly tip of the peninsula was almost deserted, as this is a remote area for many walkers, but the cliff scenery was magnificent, with precipitous vertical drops to the rocks 200 feet below.

Rounding Zone Point the views across the Carrick Roads to Falmouth and St. Mawes were spectacular, as was the scenery on the western side of the peninsula, particularly around St. Anthony Head and the walk through pine woods passing the beautiful Great Molunan Beach.

Great Molunan Beach

From there it was an easy return to Place, to catch the first of the ferries back to Falmouth, and the end of an outstanding day.

More Cornish Walks


Friday, 19 September 2014

September Mining Sundowners

A low turnout of only about a dozen people last night at Falmouth's Chain Locker pub, for the September Cornish Mining Sundowner. A pleasant surprise, however, was the appearance of Mike Hallewell of SGS, who I have not seen for several years, and two Metso men, Andrew Wilkinson, and Shane Sullivan, Shane making his debut at the sundowners (he is 2nd left on the photo below).

With fellow minerals engineers Andrew Wilkinson (Metso),
Mike Hallewell (SGS) and Nick Wilshaw (Grinding Solutions) 
And I am pleased that the Devon Mining Sundowner, just across the border, is beginning to take shape. Charlie Northfield of Drakelands Tungsten Mine has sent me the photo below taken at the Sundowner held at the Miners’ Arms, Hemerdon village, on 5th September. Current employees from Wolf Minerals enjoyed the company of three former AMAX Hemerdon employees. Left to right on the photo are Roger Craddock, AMAX Project Manager, Don Seymour, AMAX Accountant, Rick Taylor, Wolf Mine Planner, David Howourth, Wolf Health, Safety and Training Manager, Mrs Julie Taylor, Tony Delany, Wolf Process Plant Superintendent, Andrew Sarosi, AMAX Chief Metallurgist, Henry Chalcraft, Wolf Environmental Officer and Barnaby Hudson, Wolf Environmental Manager. The next Devon Sundowner will be held in the Miners' Arms, Hemerdon, on Friday 3rd October, starting at 5pm.

And more good news today from across the border, this one 500 miles away. The sun will not be going down on the UK just yet!