Froth pumping remains some of the complex engineering challenges in mineral processing. Here, Weir Minerals provides advice for dealing with the key challenges in this operation, the way to maximise pump availability and minimise upkeep in operators’ flotation circuits.
To counteract declining ore grades, more and more mine operators are investing in techniques to extend the minerals reclaimed from froth pumping. However, when these techniques are deployed without making allowances for the design of the mine’s froth pumping tools, it can lead to the loss of valuable minerals and income.
Froth pumping stays some of the complex engineering challenges in mineral processing. This is basically because of the reality that air management points in the hopper, sump and pump itself can sometimes result in inefficient pumping, increased upkeep and even lost product.
“We’ve began to notice a pattern amongst our clients who’re having trouble with their froth pumps,” said Les Harvey, regional product supervisor for Slurry Pumps at Weir Minerals. “By using extra flocculants and different chemical compounds designed to enhance mineral recovery, they’re exacerbating existing issues in circuit design and reducing the returns they’re looking for.”
Close examination of the froth’s makeup and physical qualities is often needed to resolve issues. Ensuring operators’ froth dealing with equipment adheres to greatest design practices is an important first step in resolving problems.
Maintaining strain The key challenge in froth pumping is coping with air in the pump itself, as it tends to naturally centrifuge into the impeller’s eye, the place it builds up into an “air lock” which impedes the movement of slurry by way of the pump.
In addition to reducing the pump’s efficiency, the air build-up in the pump will scale back its flow and enhance the slurry level in the suction hopper. The increased slurry degree could push the pocket of air via the pump, inflicting surging and extreme vibration which may injury the pump bearings, impeller and shaft. “The greatest method to manage air in a froth pump is to invest in a froth pump with a steady air removal system (CARS), which we now have in our Warman AHF, MF and LF pumps,” says Harvey.
This system permits air to move from the pump’s impeller eye to an air collection chamber within the again by way of a vent gap in the impeller. From the chamber, a circulate inducer removes the air from the pump through a vent pipe. “It’s additionally important to position the pump’s discharge pipe on the top of the pump, or at a 45° angle as this can give air trapped on the top of the casing a method to escape the pump.”
Solving issues “A persistent downside we see is when hoppers designed to fulfill the calls for of slurry pumping are utilized in a froth pumping utility. Slurry hoppers require turbulence to prevent the mineral content material from settling, while turbulence in a froth pump prevents the air from escaping and results in blockages,” said Harvey.
pressure gauge ด้าน ดูด designed for froth pumping promote continuous circular motion, the place solids and liquids are despatched to the skin of the sump for further transport whereas air centrifuges into the centre the place it might be eliminated. This ‘whirlpool’ movement can be inspired by introducing the slurry from the top of the tank at a tangential angle. Conical designs, somewhat than those with a flat or rounded ground, additional enhance the circulate of minerals and froth into the pump.
Smooth crusing To forestall blockages, the intake pipe which hyperlinks the tank to the pump should have a large diameter and slope downwards in course of the pump. This design permits escaped air to separate and journey again up the pipe the place it can escape from the sump, quite than building up into blockages.
“The shorter your intake pipe, the harder it is for blockages to construct up. However, in addition to a upkeep spool and isolation valve, it’s a good suggestion to leave enough space for a water injection port, which is useful for flushing out any solids build up,” said Harvey.
“To make maintenance easier, a dump valve can be included on the suction aspect of the pump, between the pump and the isolation valve. This will permit users to drain slurry from the pump and the discharge pipe system when stopping the pump for maintenance.”
Tenacious froths Froths are sometimes classified as either brittle, with massive air bubbles that break easily, or tenacious, where air varieties tight bubbles around minerals and is tough to separate. Froth being extra tenacious than was accounted for is a frequent cause of blockages as air cannot effectively be eliminated.
“Two things are occurring in the market today. On one hand, mine operators are grinding the product much finer than earlier than to liberate extra from the waste rock. They’re additionally utilizing flocculants that produce a lot smaller bubbles which lock up the air a lot more than brittle froths,” mentioned Harvey. “We’re working together with customers to seek out methods to handle these extra tenacious froths, by taking a look at their circuit design and coping with areas where the air may accumulate and block the system, paying particular consideration to their pumps, pipes and sumps.
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