Thursday, 10 July 2014

Drakelands, Britain's first new metal mine in over 40 years, prepares to open

During the late 1970s I was marginally involved with work carried out at the Camborne School of Mines (CSM) pilot plant into the feasibility of opening up the historic Hemerdon tungsten mine, situated on the edge of Dartmoor National Park near Plymouth. The work was undertaken by international mining company AMAX, under the supervision of Dr. Simon Meik and Dr. Gillian Hall. Simon, who I last met 4 years ago at Precious Metals '10, is now with Dundee Precious Metals, Bulgaria, and Gillian is with FLSmidth in Cornwall.
During this period at Camborne, a shy young man named Charlie Northfield was just commencing a honours degree course in Mineral Processing Technology. He graduated in 1980 and then commenced a very colourful career, which included, apart from working in tungsten mines in Thailand and Zimbabwe, imprisonment in Gambia under 'trumped up charges' and a daring escape into Senegal across a swollen river (MEI Online 2008).
Now Charlie is Process Plant Manager at Hemerdon (now known as Drakelands Mine), owned by Australian company Wolf Minerals. The mine is scheduled to open in September next year, 32 years after the end of the AMAX study, and 71 years after the mine's last closure at the end of World War 2. The collapse of the tungsten and tin prices in the mid-80s meant that the mine never made it into production despite the favourable feasibility study.
Now the time, and prices, are right and this will be Britain's first new metal mine for more than 40 years, exploiting the world's fourth-largest deposit of tungsten, and projected to be the world's largest producer of tungsten concentrate at about 3,450 tonnes of WO3 per year, amounting to 3-4 % of global tungsten production, compared with the 80% produced by China, which has dictated supply to the rest of the world. Drakelands will provide security of supply for tungsten and valuable export revenue for the UK.
The mine contains 23.5Mt of proven reserves grading 0.15% W as wolframite and 0.03% Sn as cassiterite. Saleable tungsten concentrate, grading 62-65% WO3 will be produced, as well as around 460 tonnes of tin concentrate per year, containing 40-60% Sn.
As this region of Dartmoor has been mined for well over 100 years and the local community is here because of that, the overwhelming reaction from the local community has been supportive, as this will bring around 200 much needed jobs, ranging from geologists, engineers and mining surveyors to truck drivers, to the area.
Yesterday I travelled the 75 miles from Falmouth to meet up with Charlie, and to see how things are progressing, and I was surprised and pleased to find so many CSM graduates involved with the operation.
With CSM graduates Nick Hall (Mining 2014), Andy Bond (Geology 1984 and Mining 1988),
Barnaby Hudson (Environmental 2002), Henry Chalcraft (Mining 2009),
Charlie Northfield (Mineral Processing 1980), Simon Holland (Mining 1987) and David Howourth (Mining 1984)
Drakeslands tungsten mine
The processing plant site with the open pit in the background
The site is a hive of activity, the foundations are in place, and the equipment is on site ready for installation. It will be an interesting flowsheet, commencing with primary and secondary crushing in Sandvik hybrid toothed roll crushers, and tertiary cone crushing. Gravity concentration is the main method of beneficiation, by dense medium cyclones after crushing, and spirals and Holman-Wilfley shaking tables (MEI Online) for the finer fractions. Grinding is by ball mills in closed circuit with Derrick screens rather than hydrocyclones, to minimise overgrinding of the heavy minerals.
Drakeslands tungsten mine
Charlie Northfield at the mill site
The flowsheet also includes flotation, in Outotec cells, to remove arsenopyrite and other sulphides from the gravity concentrates, high temperature reduction of hematite to magnetite, which will then be removed by low intensity magnetic separators, and high intensity magnetic separation to separate the final wolframite from cassiterite. The magnetic separators have been supplied by Eriez Europe.
I look forward to returning in a couple of years time when the mine will be in full operation, but in the meantime Charlie is hoping to present an overview of the operation at Physical Separation '15 next June in Falmouth.

6 comments:

  1. Interesting to see an Aussie company taking their chances to develop a deposit long known to the brits.

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  2. <any would be interested to know the flowsheet and material recovery at each stage of the plant; if the information is not confidential. However, good to know of the machines selected .
    T.C.Rao

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    1. Hopefully Charlie will be presenting a paper at Physical Separation '15 next year, which will detail the flowsheet

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  3. I wonder why they are not considering using Multi Gravity Separator (MGS) in place of Shaking tables. They give much sharper separation and produce better grade of products. At least it could be used in cleaning circuit.May be the floatation cells could be done away with. In fact these were developed for the Tin mines in Cornwall by Richard Mozley Ltd.
    Arabinda Bandyopadhyay
    CDE Asia Limited, India

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  4. Ever heard of the Wise Technology incorporating the Wise Wet Gravity Concentrator and the associated Wise Particle Settling Rate Sorting Process,. Concentration from 200 mm to 0.040 mm at unit gravity with at least 0.1 and better SG differential. James Wise, ex Senior Plant Metallurgist Ardlethan Tin NL NSW Autralia, now retired consulting metallurgist .

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    Replies
    1. Unfortunately not James. Why not send us more info- where it is being used, its advantages over other methods etc.

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