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A sustainable approach to dust management
The issue of dust emission and management during stockpiling, reclaiming, transport and ship loading continues to demand the attention of the Australian Coal Industry. The Industry's output continues to expand and the number of operations in many coal districts has been increasing. To meet sustainability objectives, particularly with respect to increasing community expectations it is necessary for all sections of the Industry to be kept informed on improved methods of dust management.
The approach in the first instance involves attention to effective enclosure of dust sources from handling operations, consistent with operational and maintenance requirements. This includes attention to minimizing spillage, and appropriate spillage collection and clean-up action
To achieve the level of dust management required to allow major increases in Industry throughput with no increase in dust emission levels, the approach must also involve research into the dustiness characteristics of each individual coal type handled through the Mine to Ship transport chain.
Dustiness characteristics
An understanding of the dustiness characteristics, together with the relationship between dustiness and moisture content, allows the development of measures to reduce dust emission from coal products during handling operations. One of the key characteristics for each bulk product is the dust extinction moisture (DEM) level.
Moisture content
Maintaining the moisture content above the DEM level has been shown to be highly effective in reducing dust emission from most, if not all coal types. To ensure that the moisture level in each product doesn‟t fall below DEM during residence time at the port, it is desirable that each product arrives at the port, or has water addition on arrival, to a moisture level above DEM to allow for losses due to evaporation, seepage, etc.
Fines reduction
Should there be a lack of water resources at the mine site, or because of lack of water retention by a coal product, a reduction in fines content by application of an agglomeration additive may be an option. This option has been successfully used in the past, and current research suggests that it has a current use for some very dusty coal types.
There may be benefits to end users in terms of reduction in dust emission and more stable moisture content. A total mine to end use approach may also achieve an overall cost benefit when transport costs are considered.
Stockpile dust lift-off
Because the static surface of coal stockpiles can be subject to rapid loss of moisture leading to dust lift-off, moisture addition by stockyard spray system is the recommended. However some Australian port terminals are also using surface veneer treatment as a cost effective alternative to water spray on stockpiles under adverse climatic conditions.
Rail transport
Queensland Rail is now working with the Industry to implement use of chemical surface veneer treatment to reduce dust lift-off from coal during rail transport. Laboratory tests simulating typical operational and weather conditions, has demonstrated a very high reduction in dust emission compared with non use of surface veneer treatment. There is a potential overall cost benefit due to a potential reduction in track closure down time for ballast cleaning.
Proposed Whole of Coal Chain Dust Management Strategy
Mine Site Dust management objectives are largely influenced by the proximity of residential areas or other sensitive operations, or workplace health and safety issues. Dust emission during handling operations is most effectively controlled by having the moisture content close to the relevant DEM for each coal type.
The surface of haul roads and other trafficked areas should be regularly sprayed by mobile tanker with water or water containing dust suppressant chemical. The surface of coal stockpiles should be sprayed to replace lost surface moisture under hot windy conditions.
Rail Transport Before rail loading, try to have the moisture level for each coal type maintained at or near the DEM level, consistent with contractual requirements. Prior to commencing major travel distance to the Port, apply veneer chemical treatment to the top surface of coal in each wagon.
On Arrival at the Port Moisture monitoring equipment may be installed at rail discharge facility to measure the moisture level of each coal type on arrival. If the moisture level is found to be below the DEM level, calibrated water sprays may be used to raise the moisture to the pre-determined level, ensuring that moisture levels do not exceed contract limits, or do not exceed the level at which handling problems are encountered.
For a limited number of problem coal types where dust emission can‟t be controlled by moisture content, fines reduction by chemical agglomeration may be considered. Coal types which are free draining, have high fines content, or have large non coal content, may be in this category.
Fines reduction by chemical total treatment may be a cost effective method of dust suppression, if coal is exported with low moisture content resulting in excessive dust emission for the end user.
Stacking Appropriate coal moisture level, together with minimum discharge height, should reduce dust emission under most conditions. Some use of misting sprays may be necessary under adverse conditions.
Stockpiles under construction During periods when temperatures and wind speeds are high, the coal surface may become dry before the stacker places the next layer. Under these circumstances minimal use of the stockpile spray system should be adequate.
Static Stockpiles For fully constructed stockpiles, waiting on reclaiming and ship loading, during periods of the year when temperatures and wind speeds are low, minimal use of the stockpile spray system should be adequate.
During periods of the year when high temperatures and high wind speeds create conditions conducive to excessive dust lift-off, selectively apply chemical veneer treatment to stockpile surfaces. A reduction in stockpile spray system water usage, following veneer treatment, should be possible.
Reclaiming Appropriate coal moisture level should reduce dust emission under most conditions. Some use of misting sprays may be necessary under adverse conditions.
Ship loading Appropriate coal moisture level should reduce dust emission under most conditions.
An 
e-newsletter has also been published for this project, highlighting its significance for the industry.