Paste Technology / Surface Disposal
The disposal of mine tailings and other waste materials has historically constituted a large portion of the operating costs and potential liability risk of a mining or other processing facility. As environmental regulations in most countries become more stringent, these costs and the difficulties involved in obtaining permits have increased dramatically.
Historically, the most common method of disposing of waste/tailings has been accomplished by placement in an impoundment area in a low density slurry form.
This method does still have its place in some operations; however, the cost savings that can be achieved by placing the material in a semidry state can be substantial.
Furthermore, the final reclamation costs of waste disposal sites can be enormous and the liability for this final clean-up can be significant. An efficient deposition and reclamation strategy has become absolutely critical to the profitability of a mining/processing facility.
Due to the shift in environmental responsibility and the subsequent increase in costs for traditional waste placement methods, alternative placement strategies are emerging that are more cost effective for meeting the environmental and regulatory requirements.
One of these alternative methods is the placement of the waste material in a semi-dry state as either a non-segregating thickened or paste product or a filter cake.
The advantages of this placement method are:
- Smaller tailings / waste impoundment
- Less environmental impact and less clean-up
- Reduced risk of dam failure and the enormous financial compensation and repair work typically required (anything from $20 million to > $40 million, based on well publicized dam failures around the world)
- When combined with concurrent reclamation, acid generation can be minimised
- Reduced water management problems
- Little susceptibility to extremes in weather, such as large amounts of precipitation that can cause traditional impoundments to overflow into the local watershed
- No critical velocity in the pipeline transport of paste or risk of settling and plugging the line
In effect, the placement of the waste material as a paste involves ‘engineering’ the waste itself rather than engineering the containment facility. This shift in thinking has been prompted by changing environmental expectations that will likely continue to increase worldwide.
