Keeping oxygen levels below a certain level prevents the possibility of an explosion underground, and several different methods of injecting inert gases, mostly using nitrogen, are used as part of this safety process.

 

North Wambo technical services manager Tim Britten told International Longwall News the decision to opt for the Floxal unit came down to cents per cubic metre for nitrogen and the flexibility the unit provided.

 

Compared to using a boiler, the Floxal unit has a lower carbon footprint and does not need staff to operate or maintain it.

 

The floxal unit also removes the mine’s need to rely on liquid nitrogen deliveries, which are sometimes affected by availability issues that can even be caused by wet weather or bush fire.

 

Britten worked with an Air Liquide Floxal unit during his time at Dartbrook and said the new unit was a standalone modular system with good technology.

 

The unit can also be used as a backup to the compressed air system, but Britten said the mine had plenty of air.

 

Air Liquide national product manager Sajimon Joseph told ILN that through its proactive management of spontaneous combustion risks, the Floxal unit costs were insignificant compared to the income loss to a longwall mine caused by a site evacuation.

 

He estimated the money lost from even half a day’s disruption to production could surpass the cost per year for installing the Floxal unit.

 

Joseph said Air Liquide was also receiving plenty of good coal industry feedback, especially for its technical support.

 

Air Liquide is also set to commission its AMSA 3000 series Floxal nitrogen generator at Peabody’s North Goonyella longwall mine this month.

 

The contract was won in April after a six-month trial at the Bowen Basin mine.

 

As part of his thesis, University of Queensland student William Hall found the Floxal unit more effectively controlled oxygen levels than competing technologies.

 

North Goonyella ventilation officer Mike Slater told ILN the Floxal unit provided more cost-competitive inertisation of goaf areas with much lower carbon emissions.

 

Air Liquide has also won a contract to supply the technology at Vale’s Carborough Downs longwall mine in Queensland.

 

Work on the installation is expected to start at the end of April.

 

Carborough Downs ventilation officer Owen Morgan said the unit offered flexibility and could also be used for balance chambers as well as inerting goaf areas.