Airborne coal dust emission is minimised by movement of particles to lower in the coal mass by surface water application, and/or increase in surface air pressure

The ability of water applied to coal surfaces to minimise airborne dust emissions during transport or stockpile operations has been investigated. Surface water has been shown to move fine coal particles from the coal surface to lower in the coal mass, removed from the impact of surface air movement. The observation has been validated by laboratory tests and supported by operational field observations. Laboratory tests included vertical tube and wind tunnel apparatus, at the University of Newcastle. More accurate mass measurement of airborne dust emissions is achieved through downwind Dust Track apparatus. Test procedures simulated mine to port rail transport operations and typical mine site stockpile operations. Tests were conducted on six representative Australian coal products, three from NSW and three from Queensland. An alternative process to move fine coal particles to lower in the coal mass has also been hypothesised. This is based on earlier CFD modelling of surface air flow during rail transport. Modelling indicated that coal surface friction reduced the surface air speed by a factor of two, resulting in an increase in downward air pressure by application of the Bernoulli principle. The ability of coal mass water content to minimise airborne dust emissions has also been investigated. Water content at or above the relevant dust extinction moisture content (DEM) was observed to minimise airborne dust emissions. Regulatory compliance with Australian and Queensland air quality protection policies was determined for the tested dust minimisation options. A historical overview is provided of the development of Australian procedures for minimisation of airborne dust emissions by water and/or chemicals.