According to the latest Joint Coal Board statistical review, Australia’s 34 longwall mines produced 79.948 million tonnes of coal in 19992000, compared with 67.911Mt in the previous financial year. Ten mines produced slightly less coal than in the previous 12-month period, around 12 mines increased output by 17-109%, while the remainder produced similar tonnages.
The additional 12Mt (or 17%) rise in production was largely attributable to newer Queensland mines such as Newlands and Crinum, and could probably have been higher if mines such as Oaky North, Kenmare and Moranbah North had not lost months of production due to a range of technical and geological challenges. Serious geological roof control problems meant equipment could not perform at designed capacities.
When these complications occurred, in all cases, they proved to be far more difficult to negotiate than expected. In the severe cases of Oaky North and Kenmare, their longwalls had to be recovered, resulting in the subsequent lost time and production levels. The Oaky North recovery operation was unique in that the powered supports were retrieved by removing overburden with a dragline. This provided access to the roof supports.
MIM Holdings’ Oaky Creek No.1 mine achieved its best year to date, with 4.224Mt run of mine generated for the year to June 30 2000 (3.6Mt in 1998-99). And, despite being buried for six months of the fiscal year while the longwall was being retrieved, neighbouring Oaky North still managed to yield 33% more coal based on the same annual comparison.
At Moranbah North, the work to deal with a problem fault was delayed slightly by the nature and location of the fault. However, once the disturbed strata had been mined, operations were quickly back on track. And despite a range of technical problems including a broken AFC chain, coal clearance issues related to AFC power, and sandstone bands in the seam, Moranbah North produced a respectable 4.173Mt (up 81% — though this is still a long way off the 8Mt per annum forecast for the mine).
Beset with roof control problems since entering its lower seam, Kenmare’s production dropped 43%. Mine owner QCT Resources is currently the subject of a takeover offer from BHP and Mitsubishi.
Production per man shift for Australian longwall operations is now similar for the majority of mines in Australia and the USA. However, the ratio of thick seam extraction is greater in Australia, therefore the USA mines have to produce more shears per shift for the same production.
Top Australian performers included Kestrel (ex-Gordonstone), which produced 4.026Mt in its first full year of production since operations recommenced under Rio Tinto. The MIM Newlands mine was last year’s standout success, setting a new Australian record of 5.704Mt (5.276Mt longwall coal), a 62.5% increase in production from 3.5Mt in 1998-1999.
Strong performances were also recorded at Crinum, up 25%; North Goonyella, up 109%; South Bulga, up 46%; Southland, up 59%; and Metropolitan, up 94%.
* This article first appeared in the September 2000 edition of Australia's Longwalls.