Durand's slurry flow model attempted to find a single formula for sand‐size particles and larger, but Babcock's data showed that a single formula could not apply. A subsequent group of models is ...based on Wilson's layered force‐balance analysis of slurry flows applied to friction losses and deposition limit. Models based on variants of this analysis include those by Shook and others at the Saskatchewan Research Council (SRC). Early versions of Wilson's model relied on particle fall velocity to find friction losses, but the classical iterative method of finding fall velocity has now been replaced by a direct method. This is based on the shear Reynolds number of the particle, which can be expressed in terms of the better known Archimedes number. Thus, calculations of slurry friction and limit of deposition involve two principal parameters: the Archimedes number and the diameter ratio d/D.
Recent loop testing performed at the GIW Hydraulic Lab1,2 has provided pump performance data for two highly non‐Newtonian slurries with significantly different characteristics: a high clay content ...slurry with minimal coarse solids; and a typical, low clay content, two‐component tailings slurry. The importance of air removal in the sump and pipe loop was demonstrated using a simple, yet novel de‐aeration system. In addition to the measurement of performance losses, determination of the upper limit of “pumpability” for these slurries relative to their concentration and associated yield stress was investigated. However, once the slurry was de‐aerated, no limits could be found, other than those dictated by suction side losses (NPSHA) or excessive pipeline friction gradients, indicating that the only true limit in practice is one of system economics, i.e. pump operating and capital cost.
Experimentally measured pump head and efficiency were compared against corresponding predictions from two different models: the Walker and Goulas technique3 and the Graham et al. technique,4 with special focus given to the dependence of the losses on pump rotary speed.
A pipeline slurry friction loss model consisting of three regimes was initially proposed by Wilson then extended to four components consisting of fluid, pseudo‐homogeneous, heterogeneous, and fully ...stratified regimes. The weighting technique using up to four regime‐related components often works well for friction loss estimations based on simple input data and model parameters. This also holds for the Hydraulic Institute's pump performance derating procedure for settling slurries. The comparisons and discussion focus on coarse particle slurries and some cases where the modelling estimations for pipeline and pump performance were not particularly accurate.
In pipeline transport of slurries, it is desirable that the solid particles should be suspended by the fluid phase. Within the body of the flow, turbulent diffusion promotes suspension, but this ...mechanism is not effective near the lower boundary. Under certain conditions, near-wall fluid lift can provide the necessary support for the particles. The Kutta-Zhukovski equation is used to relate the lift force to the shape of the fluid velocity profile. Comparison with experimental findings shows that this lift may be associated with profiles of solid concentration that show a decreased concentration as the bottom of the pipe is approached. Observed reductions of pressure gradients result from this "off-the-wall" lift force. In certain instances, the slurry pressure gradient is found to be less than that for the "equivalent fluid," with favorable implications for pipeline economics.
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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.
The deflection that a lifter bar is subjected to when passing through a grinding charge was measured using an embedded strain gauge sensor. The obtained signal profile is analysed and interpreted in ...relation to charge properties such as toe and charge angle for the grinding charge. The current work has focused on the charge and slurry flow behaviour when solids content is changed and how well the sensor reflects this. Bench scale measurements with a vane type viscometer, roughly evaluated in terms of apparent viscosity is used as a character for the resistance to motion of the slurry.
The slurry flow resistance is strongly influenced by solids content and obviously by the addition of a dispersant. The strain gauge sensor reflected this change well, showing that toe and shoulder region of the charge varied in a systematic way. Results obtained also shows that change of slurry flow resistance exert an influence on grinding performance.
A multivariate statistical method, partial least squares regression, is applied to the sensor data producing a model that can predict the change in slurry flow resistance. The output from the model also shows good properties to be used as a process-monitoring tool. The predictive capability of the model is believed to be of such quality that it can be used for process control.
Vast tonnages of solid-liquid mixtures are pumped every year in dredging operations, mining and waste-disposal applications. Most of these systems are centrifugal pumps, and the resolution of ...problems encountered in slurry pumping requires both detailed scientific knowledge and judgment derived from practical experience. For many years the combination of up-to-date analysis and hands-on experimentation has been provided to interested engineers in a short course based at the GIW Hydraulic Laboratory. The lecturers in this course, who represent a broad background of international expertise, have prepared this widely-recognized text, Slurry Transport Using Centrifugal Pumps, Third Edition. This unique text is logically divided into two sections: the first part of the book concentrates on the behaviors of various sorts of slurry flow, and the second part deals with the behavior of centrifugal pumps handling slurries, and with how pumps and pipelines interact as a system. Slurry Transport Using Centrifugal Pumps, Third Edition also includes: New material on both non-Newtonian flows and slurries of granular particles. New information on pump wear, solids effect, and system operation. Updated and completely new material on pump selection and environmental aspects Worked examples and case studies that stress practical applications Slurry Transport Using Centrifugal Pumps, Third Edition, will be of interest to all engineers and technologists involved in the large-scale transportation of slurries. .
The addition of clay to sand slurries has been found to reduce the pipeline friction losses, thus lowering the pumping head and power consumption. Pump water heads and efficiencies are decreased by ...the presence of solid particles. Experimental results are presented for a centrifugal pump with an impeller diameter of 0.625 m for three narrowly graded sands with average particle sizes of 0.64, 1.27, and 2.2 mm. Reductions in head and efficiency of up to 30% were observed for sand slurries with volume concentrations of up to 35%. Head and efficiency were lowered by about one‐third for sand‐clay mixtures with sand to clay mass ratios between 4:1 and 6:1. Comparisons are made with design criteria and a mechanistic model approach based on a prediction of the relative motion of the solids and water in the volute region of the pump.
On a trouvé que l'ajout d'argile dans des boues de sable réduisait les pertes de friction dans les pipelines, diminuant ainsi la tête de pom page et la consummation d'énergie. Les têtes hydrauliques et les rendements des pompes sont réduites par la présence de particules solides. On présente des résultats expérimentaux pour une pompe centrifuge d'un diamètre de turbine de 0,625 m pour trois grades de sables rapprochés aux tailles moyennes de particules de 0,64, 1,27 et 2,2 mm. Des réductions de tête et de rendement atteignant 30% ont été observées pour des boues de sable ayant des concentrations de volume allant jusqu'à 35%. La charge et l'efficacité ont été réduites d'environ un tiers pour des mélanges sable‐argile avec des rapports massiques sable‐argile de 4:1 et 6:1. Des comparaisons sont faites avec des critères de conception et un modèle mécanistique d'après un déplacement relatif des solides et de l'eau dans le diffuseur de la pompe.
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.
