Particulate Matter Characteristics of Mine Ventilation Air for Designing Methane Mitigation Technologies

Australian Standard Source sampling methods AS 4323.1-1995 and AS 4323.2-1995 have been utilised and shown to be appropriate standard methods for isokinetically sampling particles from ventilation systems of some underground mines. These standard methods provide a basis for the installation of future particle sampling requirements. The fundamental principles of these standards can also be utilised with other real time instruments to achieve greater information regarding the particle characteristics of the exhaust stream from underground mines, should this prove necessary for the operation of ventilation air methane mitigation systems. However, it should be noted that accurate particle sampling requires the velocity of the air stream to be measured. Most standard methods specify the use of Pitot tubes for this purpose, which at many mines, are unsuitable.

Provided suitable samples can be collected, it has been shown that optical microscopy, x-ray diffraction and scanning electron microscopy are appropriate analytical techniques for characterising mine ventilation air particulates.

Optical microscopy and scanning electron microscopy have the advantage of minimum sample requirements whereas x-ray diffraction analysis requires larger sample quantities, necessitating long collection times.

Optical microscopy is widely available, although more complex techniques such as polarized light microscopy and image analysis less so. Particle size and particle shape information can be obtained and limited mineral identification if polarized light microscopy is used.

Quantitative x-ray diffraction is less widely available and provides information only on the phase composition of the sample.

Techniques such as QEMSCAN^TM offer the most comprehensive characterisation of a particulate sample, providing information on size, shape, phase composition and abundance, and phase association. The downside is that there are few commercial laboratories that offer this service and the cost is significantly higher