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The case for using peristaltic hose pumps when pumping slurry

Supplier: Global Pumps
01 August, 2013

Peristaltic hose pumps have many advantages over traditional, centrifugal pumps, when the process fluid being pumped is a slurry.

Centrifugal pumps lose efficiency when the specific gravity of the process fluid rises above about 1.3 (equivalent to 30 per cent solids). Therefore, to pump fluids with a higher specific gravity, they are diluted with water, to reduce the specific gravity to less than 1.3.

Peristaltic pumps are capable of pumping process fluids with specific gravity of up to 1.8 (about 80 per cent solids). So, if a mining operation processes 70 tons of ore per hour, each peristaltic hose pump that is used in place of a centrifugal slurry pump saves 1,000 million litres of water per year – because of the centrifugal pump's inability to pump high specific gravity fluids. At the same duty, a peristaltic pump uses less than 33 per cent of the water that would be required for a slurry pump.

Another benefit of the peristaltic pump over the slurry pump is power use. Using the same scenario described above, on thickener underflow duty at full flow, a slurry pump would consume roughly 45kW of power, whereas a VerderFlex VF125 would only use about 20kW, a savings of over 200MWh annually.

This is a savings of more than 50 per cent on the direct cost of electricity alone, but additional benefits can be imagined when we take into account the fact that using less power will also result in reduced power import and reduced infrastructure development to deal with the imported power. These benefits are indirect, but tangible and this could also be seen to reduce the delays and environmental opposition associated with developing this power infrastructure.

Peristaltic pumps also lead directly to a reduced environmental impact, especially where cyanide, or other toxic chemicals are used in the mineral recovery process. It is well known that cyanide has adverse affects on the environment. It destroys land around the plant, pollutes water supplies, leading to destruction of the aquatic life.

Traditionally, progressive cavity pumps are used to dose the cyanide into the process, but these have traditional seals, prone to leaking unless regularly replaced, signifying a clear risk in which the cyanide could escape into the environment. Peristaltic hose pumps, on the other hand, have a significantly reduced risk of leakage. In the case of the hose pump, the hose itself is the only part of the pump that comes into contact with the process fluid. Peristaltic hose pumps are seal-less.

Because peristaltic hose pumps can pump higher specific gravity fluids, the number of post thickening filter stages can be reduced, resulting in overall increase in plant performance due to the increased downstream efficiency of the extraction process. Higher plant efficiency results in overall reduction of plant size, resulting in a smaller mining footprint.

The pumping action of the peristaltic hose pump results in low shear stress compared to slurry pumps. This is ideal for pumping the fluids containing the cell cultures required in bio-oxidation reaction techniques. Indeed, some of these bio-techniques replace the traditional extraction of gold using cyanide, also resulting in less use of cyanide and concomitantly, improving process yields.

Another advantage of the low shear stress pumping action is that it maintains particle size, minimising the use of chemical additives to prevent flocculation. Screw pumps or progressive cavity pumps require these additives, resulting in increased reagent use and the subsequent need to proved post processing procedures to prevent reagent carryover. Use of peristaltic hose pumps means that the additives are not required and therefore are also don't need to be removed – again leading to a multitude of advantages. No reagent cost, decreased operational cost and decreased waste cost.

Lastly, the maintenance and downtime of peristaltic hose pumps are both a clear advantage for these pumps when used in place of slurry pumps. As slurries are often abrasive and sometimes acidic or caustic, the impellers used in the slurry pumps, although constructed out of resistant and expensive materials, have lifetimes that can be measured in days. In hose pumps, as previously mentioned, only the hose, made from one of several standard elastomeric compounds, comes into contact with the process fluid.

The result is that the hoses have lives which can be measured in months rather than days. Plus, the hoses can be replaced in situ, without extended downtime required to replace an impeller in a centrifugal pump.

In summary, peristaltic hose pumps use less water, less energy, take up less space resulting in reduced plant footprint, are less prone to leak dangerous chemicals into the environment, have a gentler pumping action and therefore produce less shear stress on the process fluid obviating the need for chemical additives, are more abrasion and corrosion resistant resulting in less downtime and lower maintenance costs, than centrifugal slurry pumps.

Finally, the replacement parts for hose pumps are generally less costly than the expensive impellers produced of exotic metals typically used in slurry pumps.