Froth pumping stays one of the most complicated engineering challenges in mineral processing. Here, Weir Minerals presents advice for coping with the key challenges in this operation, the means 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 methods are deployed without making allowances for the design of the mine’s froth pumping equipment, it may end up in the loss of useful minerals and profits.
Froth pumping remains one of the most advanced engineering challenges in mineral processing. This is basically due to the fact that air management issues in the hopper, sump and pump itself can typically result in inefficient pumping, elevated maintenance and even lost product.
“We’ve began to notice a pattern amongst our prospects who’re having trouble with their froth pumps,” mentioned Les Harvey, regional product supervisor for Slurry Pumps at Weir Minerals. “By using more flocculants and other chemicals designed to enhance mineral restoration, they’re exacerbating current problems in circuit design and lowering the returns they’re looking for.”
Close examination of the froth’s make-up and bodily qualities is commonly needed to resolve issues. Ensuring operators’ froth dealing with equipment adheres to best design practices is a crucial first step in resolving issues.
Maintaining stress The key problem in froth pumping is dealing with air within the pump itself, because it tends to naturally centrifuge into the impeller’s eye, where it builds up into an “air lock” which impedes the movement of slurry through the pump.
In addition to reducing the pump’s effectivity, the air build-up in the pump will scale back its move and increase the slurry degree within the suction hopper. The elevated slurry degree may push the pocket of air by way of the pump, causing surging and extreme vibration which might damage the pump bearings, impeller and shaft. “The best approach to handle air in a froth pump is to invest in a froth pump with a steady air removing system (CARS), which we 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 back via a vent hole 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 at the prime of the pump, or at a 45° angle as it will give air trapped at the top of the casing a way to escape the pump.”
Solving problems “A persistent problem we see is when hoppers designed to fulfill the demands of slurry pumping are utilized in a froth pumping application. Slurry hoppers require turbulence to forestall the mineral content from settling, while turbulence in a froth pump prevents the air from escaping and leads to blockages,” mentioned Harvey.
Tanks designed for froth pumping promote continuous round motion, the place solids and liquids are despatched to the surface of the sump for further transport while air centrifuges into the centre the place it can be eliminated. This ‘whirlpool’ motion could be inspired by introducing the slurry from the highest of the tank at a tangential angle. Conical designs, quite than those with a flat or rounded flooring, additional improve the move of minerals and froth into the pump.
Smooth sailing To forestall blockages, the intake pipe which links the tank to the pump should have a large diameter and slope downwards towards the pump. This design allows escaped air to separate and travel again up the pipe where it could possibly escape from the sump, somewhat than building up into blockages.
“The shorter your intake pipe, the more durable it is for blockages to construct up. However, in addition to a maintenance spool and isolation valve, it’s a good suggestion to leave enough area for a water injection port, which is helpful for flushing out any solids construct up,” stated Harvey.
“To make maintenance simpler, a dump valve could be included on the suction facet of the pump, between the pump and the isolation valve. This will permit customers to drain slurry from the pump and the discharge pipe system when stopping the pump for maintenance.”
Tenacious froths Froths are sometimes classified as both brittle, with large air bubbles that break easily, or tenacious, the place air forms tight bubbles round minerals and is tough to separate. Froth being extra tenacious than was accounted for is a frequent explanation for blockages as air can’t successfully be removed.
“Two things are occurring out there today. On one hand, mine operators are grinding the product a lot finer than before to liberate extra from the waste rock. ไดอะแฟรม ซีล ’re also using flocculants that produce a lot smaller bubbles which lock up the air much more than brittle froths,” mentioned Harvey. “We’re working together with prospects to search out methods to manage these extra tenacious froths, by looking at their circuit design and coping with areas where the air could accumulate and block the system, paying explicit consideration to their pumps, pipes and sumps.