Experimental test on centrifugal pump handling mining slurries

Non-Newtonian fluids are involved in many industrial processes, for example in food and Oil and Gas applications. Drilling operations require massive employment of drilling fluids, such as mixtures of water and bentonite, to maintain a cooling and lubricating environment. Centrifugal pumps are usually employed instead of positive displacement pumps in these applications due to the greater flow rates that can be provided. The viscosity of a non-Newtonian fluid varies with the imposed stress and rheology, and consequently, pumping this type of fluid can lead to a considerable variation in the pump performance. Both the pump head and particularly efficiency are adversely affected, and the performance of small pumps is impaired to the greatest extent. Previous experimental works with bentonite slurries reported that detrimental effects arise at low flow rates. Since most of the manufacturers test their pumps only with water, the selection of the appropriate slurry pump may result very challenging. As a consequence, oversized pumps are commonly installed. In this work, a small centrifugal pump handling mixtures of water and bentonite was tested on an on-purpose test loop. Different solid concentrations were considered during tests. A critical analysis was conducted to relate the pump performance drops with the slurry's rheological properties.