Anders Sellgren

Operating points for pipelines carrying concentrated heterogeneous slurries

Early studies of slurry pipeline systems were based on moderate volumetric concentrations of solids (say up to 18%), for which the excess pressure gradient caused by solids is proportional to concentration. Much larger concentrations now coming into common use show more complicated behaviour. An algebraic analysis is developed to determine desirable operating points and associated energy consumption for settling slurries. This deals initially with the simple proportional behaviour, and then is extended to other cases. Comparison is made to recent experiments using highly concentrated settling slurries with various particle gradings. It is found that near-uniform gradings tend to have high frictional losses, while very broad gradings can give rise to energy-efficient transport at high concentrations.

Effects of Non-Newtonian Mineral Suspensions on the Performance of Centrifugal Pumps

Abstract Experimental results were obtained with various industrial suspensions with densities of 1100 to 1600 kg/m3 using a 0.15 by 0.1m four-vane centrifugal slurry pump with an impeller diameter of 0.63 m operating at 650-850rpm. The non-Newtonian behaviour for a fixated scrubber sludge and a red mud product was characterised in pipeline loops with diameters of 0.075-0.2 m. The lowering of the pump water head and efficiency at the best efficiency flow rate region was at a maximum about 10 and 20%, respectively. With the scrubber sludge, a sharp reduction in head occurred at flow rates below 40% of the best efficiency value, resulting in an unstable head curve. This result is used to demonstrate the risk of unstable operation if a Newtonian correction procedure with a high viscosity is applied giving very large reductions in efficiency and a shift of the best efficiency point to smaller flow rates.

Slurry pipeline friction losses for coarse and high density industrial products

Abstract Experimental results showed energy-efficient pseudohomogeneous-like flow behaviour when a mixture of coarse (20–200 mm) granite rock in tar sand tailings ( − 1 mm) in mass proportions 1:9 was transported at a total volumetric solids concentration of 31% in a 0.44 m i.d. (D) pipeline loop. Similar results were obtained with an industrially comminuted copper ore ( − 100 mm; mass median particle size 0.75 mm) when pumped in a 0.2 m i.d. pipe at a concentration of 39%. The partially-stratified friction loss model proposed by K.C. Wilson, G.R. Addie and R. Clift, Slurry Transport Using Centrifugal Pumps, Elsevier, Oxford 1992 predicted well the observed losses of an iron ore (relative solids density 4.1, mass median particle size 0.42 mm) at a concentration of 23% (D = 0.1 m). With a slightly heavier and coarser iron ore the model tended to underestimate losses at concentrations of 14–29%. The favourable friction loss performance in some results may demonstrate how broad particle size distributions and high concentrations may cause reduced pipe wall friction without influence of true theological mechanisms. An alternative way of characterizing experimental data in terms of excess pressure gradient versus the ratio of mean velocity to hindered settling velocity is introduced. The flow conditions discussed here correspond to velocities that clearly exceed those for which there are risks of deposition at the bottom of the pipe.

Design, selection, sizing and control considerations for cyclone feed slurry pumps

Abstract Cyclone feed centrifugal slurry pumps in semi-autogenous grinding (SAG) mill and other cyclone feed circuits see coarse size slurries at high concentrations that can result in high wear if the pump is not designed, selected, sized and operated correctly. The high proportion of static head of the normal cyclone feed circuits usually results in a relatively flat system curve which in conjunction with the typically flat slurry pump curve results in large changes in operating flow with small changes in system head. When this is combined with the normal (or abnormal) fluctuations in the output from the mill upstream of the pumps, any shortcomings in the pump control system and/or matching of the pump means large fluctuations in flow and increased wear. This difficulty could be corrected by continuous variations in speed. A means of control by which the speed is changed in an appropriate way is suggested here. In this case then the pump-input power, the known water performance of the pump and the system flow, can be used to calculate an effective pump discharge pressure. By comparison with a calculated system head, the pump speed can be regulated such that the pressures are equal and the system stable for any practical variation of incoming flow or specific gravity.

Cost-effective pumping of coarse mineral products using fine sands

Abstract Coarse mineral particles with sizes of up to 200 mm can be pumped energy-effectively together with sands (

Wear and the Total Cost of Ownership of Slurry Pumps

When slurry pumps are considered for procurement for a solids transport requirement, decisions have often been made on initial price rather than the total cost of ownership (TCO). Depending on the type of solids to be transported, the design (and selection) of the pumps and the way they are operated; the wear, part replacement, and downtime can be a significant portion of the overall operating cost. Wear lives are here estimated with recently developed numerical simulation procedures for pump impeller and suction liner wear together with an established wear modeling schema for shells. White iron material is considered and the resulting modeled wear does not include any uncertainty related to the inherent stochastic nature of wear. It is shown in an example how shell, impeller and suction wear life and relative costs are related to different pump size and rotary speed designs. The results form a basis to find the best compromise between pump wear, power and capital cost in an overall TCO-perspective including the users practice and maintenance strategy.Copyright