Mining - Verderflex - #1

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Pumping challenges in the mining process Mining Mining is a tough, uncompromising process and the mining industry is equally demanding being driven by the goals of mine profitability, plant efficiency, cost minimisation and yield maximisation. �¡ Ores have varying mineral contents and recovery systems must accommodate such variations. Pumps must consistently vary their dosing rates to optimise chemical usage and maintain plant throughput. Peristaltic pumps have a linear flow-speed characteristic and excellent repeatability, an ideal complement to plant SCADA systems. �¡ Process reagents, such as cyanides and acids are often highly corrosive but as the chemically resistive hose is the only part in contact with the pumped product then there are no working parts exposed to the chemical. �¡ Many process chemicals, including Powder Activated Carbon (PAC), are highly abrasive, creating continual wear problems for progressing cavity pumps leading to ongoing high stator replacement costs and frequent maintenance downtime. �¡ pH moderating chemicals, such as lime, are usually too abrasive for diaphragm pumps, causing them to persistently clog up, resulting in continual downtime and maintenance requirements. Verderflex peristaltic pumps have an exceptional record dosing lime into process and waste, many being used for bulk dosing to remediate post-mining waste and effluents. �¡ Reagents may be mixed at the mine or the processing plant leading to less than perfectly dissolved solutions but such solids in the liquid stream are not a problem for a Verderflex peristaltic pump - mine operators can use pumping solutions that allow for mining realities. �¡ The seal-free design of the Verderflex peristaltic pump eliminates leaks and the consequent risk of workplace or environmental contamination. �¡ For aggressive activator solutions including Copper Sulphate, pumps can optionally be fully Nickel plated to maximise corrosion resistance and prolong the pump’s operational life. �¡ Flocculants and coagulants can be highly shear sensitive products, where excessive shearing noticeably affects plant performance. Verderflex peristaltic pumps have a gentle pumping action which result in a low shear rate. Mining industry studies have shown that Verderflex hose pumps maintain flocculent particle size. The same studies showed that progressive cavity pumps reduced particle sizes by approximately 50 to 75%, reducing flocculation performance thereby increasing chemical usage to maintain throughputs or requiring longer flocculation times. Dosing Process Reagents, Coagulants and Flocculants Thickener Underflow �¡ Mining slurries often have sub-micron solid contents in excess of 80% by weight and have slurry specific gravities (SGs) in excess of 2.0 - Usually these slurries are also highly abrasive. A Verderflex peristaltic pump is ideal for slurries of this type. �¡ In addition to their abrasion resistant slurry pumping performance, hose pumps can be reversed to clear thickener blockages if necessary. �¡ Peristaltic pumps have a smooth liquid passage, there is no opportunity for the product to settle as the peristaltic action keeps the product in suspension. �¡ The Verderflex VF125, with a 125mm or 5” internal diameter hose, is the world’s largest high pressure hose pump with single pump slurry flow rates in excess of 60m3/hour. This allows larger high SG thickeners to be designed, maximising process plant yields. Benefits of using a Verderflex® Peristaltic Pump to pump slurries �¡ Traditional low cost solutions such as centrifugal pumps can suffer from severe impeller wear requiring frequent replacement. This brings consequent downtime and high maintenance costs which are often measured in days - A False Economy! �¡ Attempts to increase maintenance intervals, with such traditional solutions often use expensive wear-resistant alloys, often installing the more costly parts once the pump is in service. �¡ A Verderflex hose pump, is by definition, rubber-lined and does not suffer abrasive wear – the lifetime of it’s only service part, the hose, is primarily related to pump speed. �¡ Alternative solutions using rotary lobe pumps rely on consistent close tolerances between the rotor and casing to maintain performance and similarly, require extensive maintenance. At a South African mine, gold is recovered using the heap leaching process - abandoned spoil heaps or tailings are treated with cyanide to separate out the residual gold. Typically, these early 1900s workings still contain around 2% gold and the heap leaching process recovers over 99% of the residual gold. Three VF25 pumps are used to dose the treatment chemical, cyanide, throughout the recovery process. Firstly, cyanide is dosed onto the spoil heap to dissolve the residual gold, leaching it from the sand and then the initial leachate is treated again with cyanide to increase the reclamation percentage. The Verderflex range is particularly useful for this application because of its sealless pump design (preventing liquid spills), the ability to pump solids (allowing for imperfect reagent mixing), dosing consistency and a hose which is chemically resistant to hazardous treatment compounds. Dosing heap leaching reagents A mine in the Peruvian Andes has to dose sodium chromate, sodium cyanide, copper sulphate and xanthate. They have installed five Verderflex pumps (two VF25s, one VF15 and two VF10s) because of their excellent repeatablity and accurate dosing as well as their ability to handle corrosive media. Reagent Dosing Plant must - �¡ Perform as expected �¡ Have a low cost of ownership �¡ Be reliable, be easy to maintain and not require specialist maintenance skills �¡ Be able to survive the rigours of the mining environment �¡ Be resistant to operator induced problems Mining pumps should - �¡ Deliver repeatable quantities of products into the process, stabilising process variables �¡ Have high levels of plant availability �¡ Resist abrasive wear �¡ Withstand normal pumped product or process variations �¡ Be controllable via plant control systems �¡ Be easy to maintain yet require infrequent attention �¡ Not affect overall levels of plant performance