MechChem Africa September 2017

⎪ Pump systems, pipes, valves and seals ⎪

Verder Pumps South Africa stocks a variety of peristaltic pumps specifically designed to be used in mining. In this article, the advantages of adopting peristaltic technology for pumping mine slurries are outlined. Why pump slurries with a peristaltic pump?

F irst among the reasons for a switch to using peristaltic hose pumps is that they use lesswater. Hose pumps can circulate slurrywithSGs of 1.6 to 1.8, which corresponds to 60 to 80% solids content. The traditional centrifugal pump loses efficiency when the slurry SG reaches 1.3 (30% solids) or higher. With this limitation, slurry pumps have significantly higher process water demands. On a plant processing 75 t of ore per hour at 65% solids content, every time a hose pump replaces a process slurry pump, it saves over 1100-million litres ofwater per year, because at the same duty, the hose pump requires less than 25% of the process water required by the slurry pump. A second compelling reason to switch to peristaltic pumps is power use. On the same 75 t/h plant, with the thickener underflow duty at full flow, a Verder VF125 hose pump absorbsaround35kW,whereasaslurrypump needs over 70 kW: a saving of over 50%. This directly translates into reduced electrical requirements. Power rationing is a concern for many establishedmines. Onnewdevelopments the infrastructure costs to import power can be considerable and can also cause significant delays and generate considerablenon-mining environmental opposition. There is also a sig- nificant economic case! In the above example, the hose pump reduced annual operating power demand by over 210 MWh. Peristaltic pumps also increase downline efficiency and reduce overall plant size. Pulp density is critical to optimum plant perfor- mance and an increased solid content can reduce the number of post thickening filter stages, saving on the initial capital cost and

reducing the footprint of mineral pro- cessing operations. They also reduce the overall en- vironmental impact of a mine. Many mineral recovery processes use cya- nide-based leaching techniques, es- pecially where gold is the key mineral. Cyanide has many adverse environmental consequences, including polluting the land surroundingtheplant,contaminatingaquifers and decimating life in watercourses. A traditional dosing solution is generally adopted for leaching, usingprogressing cavity pumpswith integral seals that require regular replacement. The sealson thesepumps repre- sent a real leakage risk. Peristaltic pumps are seal-less and consequently, posemuch lower contamination risks. Peristaltic pumps also have a very gentle pumping action, which is ideal for bio-oxida- tion techniques. This gentle actionminimises damagetofragilecellculturesinbio-oxidation reaction techniques. One such requirement, theBiox (R) process, uses a live culture to free gold fromsulphide ores, reducing cyanide us- age and improving process yields. The peristaltic pump’s low shear pumping action alsomaintains particle size, minimising the use of flocculent and other process re- agents. Conventional high shear technologies such as progressive cavity or screw pumps significantly increase reagent usage increas- ing operating costs and raising post process- ing costs due to flotation reagent carryover. Similarly, residual reagent can increase the waste remediation cost or increase the envi- ronmental damage fromtailings dams or their resultant groundwater pollution. From a reliability perspective, peristaltic pumps use results in lower maintenance

Verderflex hose pumps for mines can pump slurries with higher SGs, more efficiently, safely and reliably because of the peristaltic principles they employ. costs, less downtime and minimal spares stock holding. Slurries are often acidic and/or highly abrasive.Consequentially,conventionalslurry pumps use impellers made from increas- ingly expensive and non-standard materials with service lives that are measured in days. Abrasion-resistant peristaltic pump hoses lower themaintenance costs associatedwith wear and corrosion. Longer service intervals and easy in situ servicing also reduce pump downtime. On a peristaltic pump, only the rubber hose is in contact with the pumped liquid and as the ul- timate rubber lined pump, service life is mea- sured in months, reducing pump downtime and, since the hose can easily be changed in situ , maintenancehours are similarly reduced. Corrosion-resistant hoses also eliminate the need for costly special metal impellers. To pump highly acidic slurries, hoses are made from several standard elastomers, each proven in the mining environment to withstand process chemicals and avoiding the use of expensive exotic metal impellers. Verder has been supplying pumps to the mining sector in South Africa for the past 15 years and is a brand synonymous with qual- ity and durability. By using Verder Peristaltic pumps for slurryapplications, productioncost and downtime can be significantly reduced, providingamore cost-effectiveandprofitable processing. q

September 2017 • MechChem Africa ¦ 13