The ACARP-funded project - Optimisation of Inertisation Practice - was completed earlier this year and a final report is due to be submitted to ACARP shortly.

The project aimed to improve on the strategies used for inertisation during longwall sealing operations. The plan was to achieve goaf inertisation within a few hours of sealing the panel.

The project work included a review of current inertisation practices, laboratory studies, computational fluid dynamics (CFD) simulations, tracer gas tests and field demonstration studies.

In six case studies that were reviewed, traditional inertisation methods were not effective in preventing the formation of explosive gas mixtures in three cases. In the other three cases oxygen concentration levels were above 12% for up to two days after panel sealing. Figure below shows oxygen distribution in the goaf – one day after sealing - inert gas injection through maingate seal at 0.5m3/s.

One of the project’s main findings is that just injecting inert gas through the maingate or tailgate seals does not achieve the objective of quick inertisation of longwall goafs. The figure shows that oxygen concentration in the goaf is above 12% over a wide area even after one day of inert gas injection through MG seal.

Based on the results of various simulations, an optimum inertisation strategy was developed which was demonstrated at the Newlands longwall mine in Queensland.

Project leader Dr Rao Balusu said during the field demonstration studies at Newlands the goaf atmosphere was inert by the time of closing the doors on the final seals, with oxygen concentration below 5% at all locations in the goaf.

The project has demonstrated that the new optimum inertisation strategies developed were highly successful in converting the goaf environment into an inert atmosphere within a few hours of panel sealing.

A more detailed article is due to be published in the September 2002 edition of Australia's Longwalls.