Rheology and the resource industries

The world's resource industries, which include minerals, coal, and the sand mining of oil, are the world's largest producers of waste. Much of this waste is produced as a fine particle suspension which is pumped to a storage area generally at a low concentration where it behaves like a Newtonian fluid. Simply by removing water from the suspension and reusing and recycling water represents a step towards a more sustainable practice in this industry. As the concentration of such a suspension is increased as a result of dewatering, the materials exhibit non-Newtonian behaviour, characterised by shear thinning, a yield stress, and in some instances, by thixotropic behaviour. Such high concentration, non-ideal (dirty) suspensions in the resource industries has meant that new rheological methods and techniques were needed for both shear and compression rheology to measure and interpret the basic flow properties. Also, some older empirical techniques needed to be modified and interpreted in a more fundamental way so that the results could be used in design. The paper reviews these techniques and illustrates how the industry itself has motivated their development. Understanding and exploiting this rheology has resulted in dramatic improvement in the waste disposal strategy for some industries, but many have failed to embrace the available technology. Why? Is regulation the answer? Probably not. The paper concludes that a greater positive change in the waste management practice will occur in the future, motivated by a number of factors, including public perception and perhaps even by common sense accounting.The paper is an overview of thirty years of work with the resource industries on environmental waste minimisation. Aspects have been published in the Proceedings of Paste and Thickened Tailings Conferences held annually since 1999.1