Posted: November 26, 2015
The main objective of tailings ponds remediation is to remove water so that a trafficable load-bearing surface can be produced within a reasonable time frame to allow subsequent reclamation. A tailings pond includes water, sand, clay and residual oil that remain after oil sands processing. Once in the pond, the sand quickly sinks to the bottom and the water released to the surface is recycled. However, the middle layer consisting of a mixture of clay and water, referred to as fine tailings, could take decades to settle and solidify naturally. As such, there have been many efforts to dewater the fines in as little time as possible. Efforts include – filtering, centrifuging, thermal drying, electrical treatment and freeze thaw treatment. Most of these processes are very costly and the dewatering efficiency is poor. Recently, chemical/biological treatments have been suggested, but these methods require increased robustness and efficiency.
University of Alberta inventors have developed a method to rapidly dewater the fine tailings. They use a polymeric nanofiber or a combination of different types of nanofibers made from water soluble polymers having moderate to high molecular weight to form large structures that can be rapidly and efficiently separated from the water. The initial, strong interactions of the nanofiber with several particle surfaces play a significant role in the rapid flocculation and dewatering of the fines compared to water soluble, high molecular polymers traditionally used in the industry. The performance of the nanofibers is a function of many parameters, such as, surface charge, hydrophilic/hydrophobic nature, and nanofiber thickness and length
Photo: Mature Fine Tailing (MFT) sample before (left) and after nanofiber treatment (right). The dewatering was achieved in less than 10 seconds.
- High dewatering efficiency of 60-80% has been achieved.
- The nanofibers can be made from existing polymers and are regarded as environmentally safe.
- Simple process steps make it cost effective.
- The method is robust and can deal with variability in the tailings consistency.
Technology Management Group
TEC Edmonton – University of Alberta