Wolf minerals, page-3

From Mining Magazine Oct 14

Made in England
Carly Leonida looks at progress at Wolf Minerals’ Drakelands tungsten project, the first new mine in the UK for nearly 50 years. It has been a solid start to the year for Australian miner Wolf Minerals. Following the grant of an environmental permit for its Drakelands mine site nearPlymouth in Devon, UK, at the end of
2013, the company successfully raised the capital needed in March to break ground at the site, and the pace of work has now picked up significantly.On a visit to Drakelands, formerly known as Hemerdon, on July 4, Managing Director Russell Clark and Operations Manager Jeff Harrison talked MM through the work that has already taken place, as well as plans for the next 12 months.
History
The discovery of tungsten near Hemerdon dates back to 1867 and the site is now recognised by the British
Geological Survey as the fourth-largest tungsten resource in the world. The first significant workings took place around the time of the First and Second World Wars, although by today’s standards the operations were relatively small. “We will mine in two months what has been mined previously; it’s a completely different scale of operation,” explained Clark.

Operations ceased in 1944 due to the reinstatement of tungsten shipments from overseas. Attempts during the 1960s and early 1970s to reopen the mine failed, until US-based AMAX became involved in the late 1970s and an exploratory drilling programme got under way in 1977. In 1986, planning permission was granted by Devon County Council; however, due to a fall in the tungsten price, AMAX decided to discontinue the project and it reverted to the original landowners.

Wolf Minerals picked up the project in 2007, and in 2008 appointed SRK Consulting (Australasia) to provide a mineral resource based on existing AMAX drilling data. Scoping-level studies followed and the definitive feasibility study (DFS) was released in May 2011, at which point the planning permission that
covers mining at the site until 2021 was updated and Wolf began to seek funding to develop the mine.

Clark came on board in October 2013. “Humphrey Hale [Wolf’s previous MD] is an exploration geologist. He realised the company was at the point where it needed someone with more operational and development experience to take the project forward. What I found when I went out with analysts and brokers was that no one appeared to believe the story – a mine in England, in a pristine part of the country – they said you will never get the permit, and you’ve got to buy 15residential properties as well,” he said.
But that is just what Wolf did. The company received the environmental permit, the first of its kind in the EU, in December 2013, and bought the last property required by the planning permission shortly after.
“Gaining the permit was quite a challenge because this is the first new mine in the UK in 45 years; no one from our side or the agency had worked through one of these permits before,” Clark said. “It came through in December and we finalised the 40-year lease with our three mineral and landowners [Hemerdon, Newnham and Olver Estates], which jointly form the Hemerdon Mine Association (HMA). Along with
raising the equity needed, those were the two biggest hurdles.”

Construction
The Drakelands DFS was based on a two-stage open pit with an initial 10-year life, and a 3Mt/y concentrator with associated infrastructure. The first major project was completed in 2012 when a
600m link road was built and opened between Lee Moor Road and West Park Hill in Plympton.
Work to construct the mine, processing plant and other infrastructure started in March this year. The site has been cleared of scrub and the old concrete processing plant demolished. The 400m x 200m site
for the new concentrator has been levelled and tailings ponds created. Pouring of the concrete foundations and steel work erection is under way.

“We will mine in two months what has been mined previously; it’s a completely different scale of operation”
We aim of having the buildings weather-tight by the end of October. “The idea is to take advantage of the
summer weather, the rest of the work is inside,” said Clark. “We plan to wet-commission the plant in April-May next year, and be in production by the start of the third quarter, with first delivery of concentrate in September.”

The project is currently on schedule and Wolf has a fixed-price contract (£75 million) in place for the concentrator, so the chance of costs overrunning from this aspect is limited. The bulk of the earthworks is now largely complete, and those costs are known and within budget.“We have five months for commissioning once we take delivery of the plant, and then a further six months to take the concentrator from 50% throughput to 100%; there’s a lot of comfort factors in there,” Clark added.

Aussie engineering expert GR Engineering Services (GRES) won the tender to build the plant and has what Harrison described as “a small experienced team” on site, masterminding several British subcontractors. Clark noted: “I get asked a lot why we didn’t select a British engineering firm. The truth is, no one here has built a mine in nearly 50 years.“The knowledge and experience that GRES brings to the project, along with experts from the mine’s previous owner, who still consult for us, and local expertise within our management team help to provide our investors with reassurancenthat the project really will work.”

Harrison, who worked for nearby china clay mine operator Imerys prior to joining Wolf, noted that the setting of the mine and ready access to power and water utilities have also contributed to the economic nature of the project. “If we were in Australia, we would have had to build an air strip, our own power station and a camp before we could even start construction,” he said.

The mine will be an 800m-long x 450m-wide open pit and a 5m-high bund has been constructed around the excavation to shield residents from noise. There is still significant geotechnical work that needs to take place to determine the optimal angle of the pit walls, and the first of six holes was being drilled by Meridian Drilling during MM’s visit to provide data for consulting firm SLR’s engineers. Until this information has
been calculated, a conservative slope of 40º will be adhered to, but by steepening the pit walls there is the potential to add another 2-3 operating years to the LOM.

Operating and Processing
Wolf has a six-year contract (first year set-up, five years’ production) with British contractor Blackwells, which began to operate the mine in January , and the company will provide a new fleet of Caterpillar mobile equipment, including 16-17 Cat 775 haul trucks each with 65t capacity, presumably sourced from local dealer Finning. The equipment will be divided into two fleets initially: one to mine the ore and one to remove the waste, with the option to introduce a third fleet in year three for further waste movement. At its peak the mine will move 10Mt/y of material; of which 3Mt/y will be sent to the plant to produce 5,000t/y of 65% tungsten concentrate (which will equate to 3,500t/y after smelting) and 1,000t/y of tin concentrate.
All processing equipment for the plant has been ordered, most of which is off the shelf, from multiple suppliers including Sandvik, MDL and Holman “The process itself is not particularly challenging, it uses gravity as wolframite [the primary ore mineral, tin is also present as cassiterite] is very heavy and easy to separate with proven technology such as dense-media separation (DMS), spirals and shaking tables,” explained Clark. “Primary, secondary and tertiary crushing plus screening will take the feed down to less than 9mm, which is quite coarse in mineral-processing terms, and the waste will be floated off.” The production fleet is expected to extract around 800t/h of ore, which will be fed to the run of mine (ROM)
stockpile. This will be used to feed two Sandvik hybrid rotary crushers, each with a capacity of 500t/h, and from there ore is conveyed to a rotary scrubber trommel. Oversize from the trommel will be sent to two tertiary cone crushers working in closed circuit with the product screen, while undersize will gravitate to the scrubber screen fitted with a double deck with 9mm and 4mm aperture media. Plus-9mm material will be combined with scrubber trommel oversize and sent to the tertiary crushers; product below 9mm plus the 4mm material will be directed to the 1,500t-capacity DMS feed bin. Crushed ore will be drawn from the
DMS feed bin by two vibratory feeders, each feeding a primary DMS circuit at a rate of 150t/h. Each primary DMS circuit comprises a bank of three cyclones operating at a separating density of 2.7kg/L using ferrosilicon as the medium. Primary DMS floats will be rejected to the DMS floats bin and from there trucked to the mine waste facility (MWF). The primary DMS ‘sinks’ that will contain the bulk of the tungsten and tin will be sent to the secondary DMS circuit. The secondary DMS will operate at a density of 3.3kg/L. Secondary floats will be sent to the primary regrind ball mill, operating in closed circuit with a double-deck screen fitted with 1.7mm and 0.5mm screen decks. Plus-1.7 mm material will be sent back to the primary
regrind mill and the minus-1.7mm and 0.5mm ore sent to the scavenger DMS circuit. Scavenger DMS sinks will join the secondary DMS sink product going to the concentrate regrind mill. Minus-0.5mm
fines in the primary regrind mill screen undersize will then be pumped to the fines storage tank. Natural minus-0.5mm fines from the washing and screening circuit, plus fines from the primary mill, will be de-slimed in two stages using 500mm and 250mmcyclones. Deslime cyclone underflow will be pumped to three banks, each having 11 triple-start rougher spiral concentrators, and these will feed concentrate to
the middling and cleaner spirals. Concentrates will then be pumped to the rougher shaking table and tailings sent back to the spirals feed. Rougher table concentrate will be screened at 0.15mm; both coarse and fine concentrates are further upgraded on two stages of shaking tables and the combined concentrate pumped to the flotation conditioner. The secondary and scavenger DMS sinks will be reduced in size in the concentrate regrind ball mill, in closed circuit with a 0.45mm-aperture concentrate sizing screen. Screen oversize will return to the ball-mill feed and undersize pumped to the flotation conditioner.
The conditioner will receive concentrate from both the fines gravity circuit and the concentrate regrind mill.
Sulphide minerals including arsenopyrite will be removed by froth flotation, and non-floating minerals containing tungsten as pre-concentrate will be sent to a beltfilter. Filter cake containing roughly 10%
moisture will go to a concentrate dryer and from there to the reduction kiln. The top 30m of the orebody at
Drakelands is fairly well weathered and the plant has been designed with a high clay content feed material in mind.

“The guys we have working for us have come from the china clay industry, so they have plenty of experience mitigating problems with clay,” explained Harrison. “It’s about making sure chute angles are
right, and that you have plenty of water to wash stuff through. The crusher that was going to be put in place in the 1980s was a jaw crusher, which is no good as clay tends to pack, whereas we now have
a sizer that will feed clay through. It’s been given a lot of thought.” In Cornwall mine operator Imerys used
a similar trommel set-up with dry feed at its Melbur site. “Because we’re not competitors, Imerys very kindly let us bring some of our managers and GRES people down to the site,” said Harrison. “There’s always the potential for problems but most of us are very experienced with these types of plants.
At Drakelands we will mine softer clay-rich ore for the first couple of years, then move into harder granite.”
“There’s a reason why we have a ramp-up period included too,” pointed out Clark. “So we can learn how to deal with the material and tweak the process if necessary.”

Future opportunities
While Clark’s initial priority is to get the mine running, there seem to be multiple opportunities to increase recovery and extend the LOM. For example, the orebody is thought to extend at depth and to the south, although further investigation is yet to take place. “We will understand the orebody and the extent of mineralisation a lot better in 18 months when we have more people onsite and can use some of the
information we’re generating to expand our knowledge,” said Harrison.

Most drilling has been done to 200m (the current planned depth of excavation). However, two holes were drilled to 400m and proved that the mineralisation is still present. “As part of our current drilling campaign we may put another 3-4 holes down to that depth,” said Clark.When asked whether Wolf might consider taking Drakelands underground in the future, Clark replied: “The orebody may be suitable for block caving, bearing in mind that the grades here are good but not stellar. That has the potential to add another 10-15 years’ LOM upfront, but as Jeff said, once we have more experience with the host rock and the
orebody we will be in a better position todetermine the feasibility.” The mine will initially operate on a
24-hour basis for 5.5 days per week, closing at 6pm on Saturday and reopening at 6am on Monday. This is in accordance with the planning permission that was granted in 1986 under previous ownership, and which both Harrison and Clark acknowledge is somewhat outdated. “That’s another opportunity forus, to see if we can get permission increased to seven days a week. It would allow us to increase output by about 15% without any additional CAPEX,” explained Harrison.

Once production gets under way, Wolf expects Drakelands to add around 3.5% to global tungsten output (currently 100,000t/y). The company has two offtakers in place for 80% of the product: one in Austria, Wolfram Bergbau und Hütten, which specialises in tungsten carbide cutting tools, and US-based Global
Tungsten and Powders. Clark and Harrison’s enthusiasm for the project is certainly infectious, and it’s hard not to get excited at the prospect of mining returning to Britain. The southwest in particular has a rich mining heritage and, with companies like Wolf and the privately owned Treliver Minerals actively investigating the mineral wealth of Devon and Cornwall, as well as significant movement in Yorkshire and
Scotland, it looks like there could besomething of a renaissance.
T
hose interested in following Wolf’s progress at Drakelands can watch live streaming of construction online at
http://www.wolfminerals.com.au/hemerdon-tungsten-and-tin-project/live-stream