Froth pumping remains some of the advanced engineering challenges in mineral processing. Here, Weir Minerals offers advice for coping with the important thing challenges on this operation, the method to maximise pump availability and minimise maintenance in operators’ flotation circuits.
To counteract declining ore grades, increasingly more mine operators are investing in techniques to increase the minerals reclaimed from froth pumping. However, when these strategies are deployed without making allowances for the design of the mine’s froth pumping tools, it can lead to the lack of priceless minerals and profits.
Froth pumping stays one of the complicated engineering challenges in mineral processing. This is basically due to the fact that air administration points within the hopper, sump and pump itself can typically result in inefficient pumping, increased upkeep and even misplaced product.
“We’ve began to notice a sample among our customers who’re having bother with their froth pumps,” stated Les Harvey, regional product manager for Slurry Pumps at Weir Minerals. “By using more flocculants and different chemicals designed to enhance mineral recovery, they’re exacerbating existing problems in circuit design and lowering the returns they’re on the lookout for.”
Close examination of the froth’s makeup and bodily qualities is often needed to resolve issues. Ensuring operators’ froth handling gear adheres to finest design practices is a vital first step in resolving issues.
Maintaining pressure The key challenge in froth pumping is coping with air within 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 lowering the pump’s efficiency, the air build-up within the pump will cut back its circulate and increase the slurry level in the suction hopper. The elevated slurry degree might push the pocket of air by way of the pump, causing surging and excessive vibration which can injury the pump bearings, impeller and shaft. “The finest approach to handle air in a froth pump is to invest in a froth pump with a steady air removal system (CARS), which we’ve in our Warman AHF, MF and LF pumps,” says Harvey.
This system allows air to maneuver from the pump’s impeller eye to an air assortment chamber in the again via a vent hole in the impeller. From the chamber, a move inducer removes the air from the pump by way of a vent pipe. “It’s also necessary to position the pump’s discharge pipe at the prime of the pump, or at a 45° angle as this can give air trapped at the prime of the casing a method to escape the pump.”
Solving problems “A persistent downside we see is when hoppers designed to satisfy the demands of slurry pumping are used in a froth pumping software. 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,” stated Harvey.
Tanks designed for froth pumping promote continuous round motion, the place solids and liquids are despatched to the outside of the sump for additional transport while air centrifuges into the centre where 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 these with a flat or rounded flooring, further enhance the circulate of minerals and froth into the pump.
Smooth sailing To stop blockages, the intake pipe which links the tank to the pump ought to have a big diameter and slope downwards towards the pump. This design permits escaped air to separate and travel again up the pipe the place it might possibly escape from the sump, rather than build up into blockages.
“The shorter your consumption pipe, the tougher it is for blockages to construct up. However, along with a maintenance spool and isolation valve, it’s a good idea to go away sufficient area for a water injection port, which is beneficial for flushing out any solids build up,” said Harvey.
“To make upkeep simpler, a dump valve can be included on the suction facet of the pump, between the pump and the isolation valve. เครื่องมือวัดความดัน will permit customers to empty slurry from the pump and the discharge pipe system when stopping the pump for maintenance.”
Tenacious froths Froths are sometimes categorized as both brittle, with massive air bubbles that break simply, 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 reason for blockages as air can’t effectively be removed.
“Two things are taking place out there right now. On one hand, mine operators are grinding the product a lot finer than before 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 along with customers to search out ways to manage these extra tenacious froths, by taking a glance at their circuit design and dealing with areas where the air could accumulate and block the system, paying explicit consideration to their pumps, pipes and sumps.
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