A Practical Research Study Into The Environmental And Physical Impacts During An Underground Mine Inertisation With The GAG Jet

Rio Tinto Coal Australia, Queensland Mines Rescue Service and Simtars conducted a partial inertisation of an underground coal mine using the GAG-3A engine in February 2014.

This project monitored the environmental conditions and the flow of inert GAG gases into and around the mine during two separate inertisation events. In particular the project recorded the relative changes in mine temperatures and gas concentrations. Observations were made by a variety of remote sensing technologies and by direct measurements and observations by Mines Rescue personnel making excursions into the area being inertised.

This report documents the project's scope, methodology, observations and the outcomes.

This project proved that the GAG is a reliable and effective inertisation system. It demonstrated the critical requirement for effective sealing of GAG docking points and the effectiveness of underground Ventilation Control Devices (VCD's) in coursing the GAG product to its required location.

Given that temperatures close to the GAG inject point reached 90°C it is not envisaged that the GAG could be deployed where there is an expectation that mine personnel could be in the vicinity. Mine infrastructure and strata in zones close to the GAG docking station were detrimentally affected by the prolonged exposure to the high humidity and temperatures.

Recommendations

The following recommendations have been made as a result of the GAG trials and the review of previous inertisations:

· All underground coal mine sites should review their surface sealing arrangements particularly of the GAG docking points to identify and minimise possible leakage paths;

· QMRS should regularly audit underground coal mine site sealing arrangements to ensure that an adequate seal is achieved at the GAG docking point;

· Mines should investigate the options for injection of inert gas to understand their deployment of inertisation techniques;

· Mine sites should review their emergency procedures with regard to leaving on compressed air underground post explosion/fire due to the possible dilution of the GAG product when introduced;

· Underground coal mine sites should review their Emergency Response Plan for Inertisation and determine whether any additional points are required for tracking the spread of the GAG gas and install tube bundle sampling locations at these points.