Froth pumping remains one of the complex engineering challenges in mineral processing. Here, Weir Minerals presents advice for dealing with the important thing challenges in this operation, tips on how to maximise pump availability and minimise maintenance in operators’ flotation circuits.
To counteract declining ore grades, increasingly more mine operators are investing in strategies to extend the minerals reclaimed from froth pumping. However, when these strategies are deployed with out making allowances for the design of the mine’s froth pumping tools, it can end result in the lack of priceless minerals and earnings.
Froth pumping remains one of the most complicated engineering challenges in mineral processing. This is essentially as a end result of the reality that air administration issues within the hopper, sump and pump itself can typically result in inefficient pumping, increased maintenance and even lost product.
“We’ve began to notice a pattern amongst our clients who’re having hassle with their froth pumps,” stated Les Harvey, regional product supervisor for Slurry Pumps at Weir Minerals. “By using extra flocculants and other chemical substances designed to enhance mineral recovery, they’re exacerbating current problems in circuit design and decreasing the returns they’re in search of.”
Close examination of the froth’s makeup and bodily qualities is often wanted to resolve points. Ensuring operators’ froth dealing with gear adheres to finest design practices is a crucial first step in resolving issues.
Maintaining strain The key challenge in froth pumping is dealing 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 via the pump.
In addition to reducing the pump’s efficiency, the air build-up in the pump will reduce its flow and increase the slurry degree within the suction hopper. The elevated slurry stage might push the pocket of air by way of the pump, inflicting surging and excessive vibration which can harm the pump bearings, impeller and shaft. “The best way to manage air in a froth pump is to spend cash on a froth pump with a continuous air removing system (CARS), which we’ve 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 back via a vent gap in the impeller. From the chamber, a flow inducer removes the air from the pump by way of a vent pipe. “It’s also essential to place the pump’s discharge pipe on the high of the pump, or at a 45° angle as it will give air trapped on the top of the casing a method to escape the pump.”
Solving problems “A persistent downside we see is when hoppers designed to satisfy the calls for of slurry pumping are utilized in a froth pumping application. Slurry hoppers require turbulence to prevent the mineral content material from settling, whereas turbulence in a froth pump prevents the air from escaping and results in blockages,” mentioned Harvey.
Tanks designed for froth pumping promote continuous circular movement, the place solids and liquids are sent to the outside of the sump for further transport whereas air centrifuges into the centre the place it can be eliminated. This ‘whirlpool’ movement could be inspired by introducing the slurry from the top of the tank at a tangential angle. Conical designs, quite than these with a flat or rounded floor, additional enhance the circulate of minerals and froth into the pump.
Smooth sailing To forestall blockages, the intake pipe which links the tank to the pump ought to have a big diameter and slope downwards in course of the pump. This design permits escaped air to separate and travel back up the pipe the place it could escape from the sump, quite than build up into blockages.
“The shorter your consumption pipe, the harder it is for blockages to build up. However, in addition to a maintenance spool and isolation valve, it’s a good idea to go away enough house for a water injection port, which is helpful for flushing out any solids construct up,” said Harvey.
“To make maintenance simpler, 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 often categorised as either brittle, with large air bubbles that break simply, or tenacious, where air varieties tight bubbles round minerals and is troublesome to separate. Froth being extra tenacious than was accounted for is a frequent cause of blockages as air can’t successfully be eliminated.
“Two things are happening available in the market at present. 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 much smaller bubbles which lock up the air a lot more than brittle froths,” said Harvey. “ เกจวัดแก๊ส ’re working together with customers to search out ways to handle these extra tenacious froths, by taking a glance at their circuit design and coping with areas the place the air might accumulate and block the system, paying specific attention to their pumps, pipes and sumps.
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