Practical Aspects of Transporting Pastes with Rotodynamic Slurry Pumps

Abstract

Reduced safety concerns, reduced environmental impact, faster land reclamation, reduced water consumption and corresponding efficiency improvements are some of the possible benefits of mine disposal in the form of thickened tails or paste. Transportation of these higher density slurries presents special challenges for the system designer. The corresponding yield stress and higher viscosity associated with these higher density slurries often result in slurry pipeline operation in laminar flow at an elevated pipeline pressure drop. Much research is ongoing with respect to determination of pipeline friction, as well as solids settling in laminar flow. Previous work has looked at the economic benefits and disadvantages of rotodynamic (i.e., centrifugal) versus positive displacement pumps as the motive source for high density, high yield stress tailings. This work has shown the choice is not always clear cut. Initial capital outlay versus long term operating costs, pipeline length, slurry concentration, corresponding rheology, corresponding volume flow rate and corresponding pressure drop are integral factors in the decision making process. Rotodynamic pumps have been shown to be a viable choice for lower concentration, higher volume flow rate, shorter pipeline distance, lower pressure drop services. This paper will discuss the application limits of standard slurry pumps on high yield stress slurries, revisit an often misused method of predicting corresponding pump performance de-rating, present test data on a modified “flow inducer” equipped rotodynamic pump with improved high yield stress capability, and finally discuss rotodynamic pump suction requirements in an effort to explain the observed change in pump performance.