BY May this year and only 12 weeks into commercial production the Moranbah North longwall operation in central Queensland had already produced its first one million tonnes of coal. It was another important landmark for Shell Coal Australia subsidiary Moranbah North Coal (Management) which brought the mine into production five months ahead of schedule and under budget.
In fact, Moranbah North has performed so well during its first months of operation that production had to be scaled back to match output with predicted sales.
According to management, this was largely a function of a flat market. Placing new coal into the market — particularly into the conservative steelmaking industry, often nervous about changing brands — had proven difficult. Despite this, about 80% of Moranbah North’s 1999 production has been sold by contract to Asia and Europe and Shell’s marketing division is understood to be reasonably well advanced with the extended process of having Moranbah North coal tested and approved by potential Asian steel manufacturers.
When output targets for Moranbah North were first conceived some 3-4 years ago, it was thought the mine could produce about 2mtpa. As annual tonnage at both Australian and American mines steadily rose, so too did expectations of Moranbah North. Officially, the operation is capable of easily producing more than 4mtpa as evidenced by its hitting 2mt in July — on target for budgeted production of 4mt for calendar 1999. But Moranbah North’s performance to date suggests a benchmark considerably above 4mt.
The original plan for the longwall was a gradual ramp up from 60,000t a week to 120,000t/week by late 1999, according to Steve Newson, the mine’s technical services manager. “In the first week we did 60,000t, then 63,000t, then 75,000t, then 103,000t in the fourth week. By the sixth week we had done 131,000t. We had greatly exceeded all our expectations,” Newson said.
“This was a greenfield mine, a brand new longwall, and the first time we’d operated at this mine with a workforce that was about 80% green in terms of longwall mining. At that point we had to put the brakes on and come down in our mining rate because our sales and our deliveries were matched around the original forecasts.”
At present coal is only produced on night shift while the day shift is dedicated to maintenance. As this is perhaps not the ideal way to work the longwall, management has opted to cut coal at slightly below the 4.5m extraction height, leaving coal in the roof for added stability. Though it is undoubtedly frustrating to run the mine at half throttle, it has given management the opportunity to pay careful attention to ironing out operational challenges, as well as proving what the mine is capable of.
Before mining began some 30km of underground entry, mains and gateroad development had to be completed but because production began five months early, development was never significantly ahead of the longwall. Moranbah has a float of around eight weeks in advance of the longwall which has the advantage of keeping capital investment in check.
“Gateroad development for us is about a $12 million investment. That’s money you’re laying down and putting into drivage,” Newson said. “If you develop two panels in advance you’ve invested $24 million which is giving you no direct return. When you work with fairly tight float times, like us, you’ve got no slack there. Every dollar is important to us.”
Development rates have steadily improved from an average of 160m/week in 1997 to about 300m/week this year. Newson said there was still room for improvement and that management was aiming for 500m/week.
“Development of LW102 is our priority drivage where we have one development crew. We have another system set up in LW103 doing maingate driveage. If there is any unplanned stoppage in LW102 we put the crew onto LW103 because our aim is to cut development coal on every shift.”
Moranbah North probably won’t be breaking any production records this
year, but next year could be another story.