SUFCO, United States of America
SUFCO – the name derives from the former owner, Southern Utah Fuel Co – is located 50km north east of Salina, Utah, and 200km south of Salt Lake City. It is operated by Canyon Fuel Co, previously owned 65% by Arch Coal and 35% by Japanese interests, but which since mid-2004 has been wholly owned by Arch.
SUFCO has been in production since 1941, initially as a room-and-pillar coal mine and more recently as a high-performance longwall operation. Production in 2005 was 6.8Mt, in line with previous years. The mine, the largest coal producer in Utah, exports steam coal through the port of Los Angeles to customers in Japan. It employs 252 people.
GEOLOGY AND RESERVES
The mine is located in the Wasatch Plateau coalfield, producing coal from the Upper Hiawatha seam hosted in the cretaceous-age Blackhawk formation. Ranging from 2.1m to 6.1m thick, the seam averages 4.1m, is generally flat-lying and is covered by an average 335m of overburden that can reach 700m in the rugged overlying topography.
Remaining longwall reserves are limited in the mine's existing leases, with the last seven panels containing an estimated 41.0Mt of recoverable coal. Arch’s acquisition of full ownership of Canyon Fuel Co. has expanded the operation’s resource base to some 145Mt within the district, with mineable reserves standing at 52Mt at the end of 2005.
The current working areas are some 16km from the mine entrance in East Spring Canyon. Longwall mining was first used at SUFCO in 1985 with the current face equipment installed in 1998. A minimum seam thickness of 2.6m is mined. Panel 18 was the first 'super-panel' to be developed, with a 283m face length and a panel length of 4.3km. The panel mined during late 2000 (panel 22) had a length of 5.7km and contained 6.9Mt of coal. Equipment moves between panels, which are scheduled to take 8–12 days, occur once a year on average and involve moving nearly 5,200t of machinery distances of up to 6km underground.
The current longwall face is equipped with a Joy 7LS-3 shearer matched with Joy face support shields and a Deutsche Bergbau Technik (DBT) armoured face conveyor and stage loader. The specified maximum face output is 4,540t/h, and longwall production is controlled to 2,300t/h, giving a typical daily output of 22,700t. Run-of-mine coal off the face is crushed to –50 mm using an MMD 500 pick-type sizer before entering the belt conveyor network.
The shearer, which has a total installed power of 1,110kW, cuts a 1.07m-wide strip of coal off the face on each pass, moving at between 8 and 12m/m along the face line. The face production rate is constrained to 2,300t/h by the main conveyor system, which has a capacity of 2,700t/h, and on which coal from development headings is also carried.
As in many longwall operations, gateroad development is a significant hindrance to faster production. SUFCO uses a three-entry gateroad system, mined by Joy 12CM12 continuous miners feeding Joy 10SC32C, 18t-capacity shuttle cars. A Joy four-head roofbolter is also used to install gateroad support.
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SUFCO occupies a very tight site in rugged topography with no immediate access to rail services. The mine has around 27,000t in storage capacity – little more than a day's output – of which only half is live storage. All the coal produced has to be trucked a distance of over 130km to one of two Union Pacific rail terminals, using contractors' vehicles. Each truck consists of a tractor unit and two trailers, and has a capacity of 38t. Two trucks can be loaded simultaneously, at a rate of one minute per truck.
System optimisation enabled SUFCO to meet its production target of 5.4Mt for 2000, and to better its 2001 target of 5.9Mt by around 500,000t. An annual output of up to 7.2Mt/y should be achievable with further capital investment.
Typical coal quality parameters are:
- Moisture – 10%
- Ash – 8.5%
- Sulphur – 0.35%
- Heating value – 26.5MJ/kg