Settling slurries comprise a carrier fluid conveying solid particles. This type of flow has extensive applications in the mining and mineral processing industries, where the design of pumped systems must take into account the effect of solids on pipe friction loss and pump performance.

Simulating the performance of settling slurries is dependant on the solid density, concentration, particle shape and size distribution, as well as the properties of the carrier fluid. Selecting the optimum pipeline velocity is usually the most important factor in the design and operation of slurry systems. Operating with velocities too high wastes energy, while operating with velocities too low can lead to pipeline blackage.

Design methods are highly empirical and FluidFlow3 offers different calculation approaches:

    • Wilson-Addie-Sellgren-Clift (WASC)
    • Durand-Condolios-Worster
    • WASP

Carrier and solids input data

The example shows the Input Editor defined for the transportation of 1000 tonne/h of sand at a volume concentration of 30%.

FluidFlow3 will calculate the correct volumetric flowrate to acheive this requirement. We could have specified flow as total volumetric, or on a carrier basis only.

Particle size entry requirements depends on the calculation approach selected. WASC requires d50 and d85, Durand requires d50 and WASP requires a particle size distribution which the software allows.

Pump Deration

When a pump is used to transport a slurry, the prescence of the solid particles has a significant effect on the performance of the pump. As the concentration of slurry increases, the head generated by the pump decreases because of the greater friction losses that occur in the pump casing.

FluidFlow3 allows you to select the amount of derating that is applied. This value may be obtained from the pump supplier, or FluidFlow3 can estimate the deration according to Hydraulic Institude guidelines or via other text book calculation methods.

Pipeline system curve for a settling slurry

The system curve for a settling slurry is different to that of a Newtonian fluid. The friction loss curve for a nickle ore slurry is shown opposite. A minimum friction loss value is usually observed at or near the particle deposit velocity. The most economical velocity is usually at this minimum point.

The curve shown is asymptotic to the equivalent water curve at higher velocities, so essentially the slurry flow calculations are calculations of the “solids effect” of the suspended solids, i.e., the additional pressure loss due to the suspended solids over that for the same volumetric flow of the carrier alone.

Usually, because of the application of safety factors in design methods, pipelines are operated at higher flow velocities than the economic minimum. There are a series of system curves, the exact position and shape of each curve depends on the solid concentration.

Nickle ore delivery system

This example shows a pumped slurry system that has been exported to Excel. The content of the export can be fully controlled.

You can download the xls file produced by FluidFlow3 by clicking here.

Click on the tabs to display the various Excel pages. Exporting to Excel allows you to customise your reports and provides an excellent method of communicating the results of a study, to a client or colleague.