Choosing metallurgical samplers or static cutters for process control in slurry: when or why to avoid the increment delimitation error

Abstract

Despite “sample collecting”, with the objective of evaluating the quality of a material lot, being a very ancient activity, and many books and papers being published with the purpose of “educating” the sampling community, we can say that the Theory of Sampling - TOS (developed by Pierre Gy) is the one that gave the best approach of the potential, and most common, errors of this activity. The focus of TOS in the early days was primarily dry particulate material, maybe because it presents bigger challenges in terms of heterogeneity, but there are other areas that have discovered the use of this precious tool to solve the same issues on many other kinds of materials, but it is still not universally adopted. For instance, there is a belief that liquids are completely homogenous, as if every liquid have the same behaviour as water, but it is not true, especially when we talk about mixed materials, not soluble between them, and with different densities. For instance, ore slurries (pulp), is a suspension formed by pulverized ore, flotation reagents and process water. This slurry may seem a homogenous substance, looking from the top of a flotation cell or discharging in a thickener, but, any fluid, flowing in a pipe develops a specific profile of speed which is dependent of the rheology and of the pipe wall friction, etc. Other important variables to consider in the make-up of mineral suspension include the concentration gradients through the flow profile and specific gravity of the particles. This work evaluates the types of slurry samplers or static cutters to answer the question:“Which equipment do I really need?” The answer to this question will help the project owner make the correct decision for plant sampling – including longer term viability.