Dr. David Williams is the Golder Professor of Geomechanics at the University of Queensland. Dr. Williams discusses the settling of clay-rich tailings slurries. As coal mining in Australia moves west to tap into new coal seams, companies are increasing encountering clay rich soil. Clay rich tailing slurries have poor settling and dewatering qualities.
The new mines are mostly small and they have two strategies: to avoid the clay rich materials before the coal gets treated at the plant, or to treat the results. To treat clay rich slurries, there are complex interactions occurring at the micro-scale. He describes the studies undertaken to understand the amount of settling taking place in the slurries of commercial clays and the amount of time needed to reach the optimum settling. Deionized water and salt water didn't differ that much. It was also found that metallic salts, particularly calcium chloride and magnesium chloride, improved the amount of settling in the test slurries.. The slurry mixtures of commercial clays behaved much the same as the processed tailing water from the clay-rich coal mines. Settling was not improved by higher content solids and the tests only achieved 20-25% settling. The complexity of settling means that mechanical settling alone is not a solution for these mines.
Dr. David Williams' presentation was part of the Tailings and Mine Waste Conference, Banff, Alberta, Nov. 3-6, 2013
