Atlas Copco Rental Australia supply Nitrogen solution to avoid gas explosions during drilling at open pit coal mine

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The Millennium Mine is an open-cut mine located 100 miles (160 kilometers) south-west of Mackay, Australia, which produces coking and low to mid-volatile pulverized coal injection (PCI) for export markets.

Coal Augering Services has been contracted to drill some 280 holes in the lower open pit seam in order to recover an extra 25 % of coal (or approximately 75,000 tons). Holes vary in depth from 35 to 75 meters and have a diameter of 2 meters.

During this operation there is a high risk of explosive gases being present so solution needed to be worked out. To prevent explosions Coal Augering services started by using a diesel driven Inert Gas Generator (IGG) where the air is burned using diesel in order to decrease the oxygen level to less than 12 % at 15 meters depth. They however rapidly converted to a Nitrogen generator from Atlas Copco Rental Australia for that purpose.

Thanks to our mobile NGM 200 nitrogen generator, delivering 96% N2 purity at 9 bar, combined to an XAVS 850 air compressor, it was possible to achieve the required inert levels at 12 meters for both 35 and 75 meter depth holes, thus avoiding all risks of explosions.

Along with that main challenge, there were several other aspects that we needed to account for.

• The temperatures within the pit (over 50 C°) combined with constant water trucks causing severe humidity. In order to solve that, an after-cooler was added to the compressor.
• The dusty environment. Hence, we organised maintenance and clean filters at all times to ensure the compressor would run optimally.
• The continuous move of the Auger of about 30 meters/hour. To address this we worked out a special trailer for the units so they could be moved in tandem with the loader.
• The very specific safety requirements in a mine were also taken care of and the units were tailored to match all.

Tim Vaughan, Atlas Copco Rental Australia - Account manager, Queensland & PNG explains: “After minor teething issues, the customer has signed a long term contract and is happily converted from inert gas generator to a safer and even more reliable Nitrogen solution.”