Froth pumping remains some of the advanced engineering challenges in mineral processing. Here, Weir Minerals provides advice for coping with the important thing challenges in this operation, how to maximise pump availability and minimise upkeep in operators’ flotation circuits.
To counteract declining ore grades, increasingly more mine operators are investing in methods to increase the minerals reclaimed from froth pumping. However, when these methods are deployed with out making allowances for the design of the mine’s froth pumping equipment, it can lead to the loss of useful minerals and income.
Froth pumping stays one of the most complicated engineering challenges in mineral processing. This is essentially as a outcome of the fact that air administration points in the hopper, sump and pump itself can generally lead to inefficient pumping, elevated upkeep and even misplaced product.
“We’ve started to note a sample among our clients who’re having trouble with their froth pumps,” stated Les Harvey, regional product supervisor for Slurry Pumps at Weir Minerals. “By using เกจวัดแรง and different chemicals designed to enhance mineral recovery, they’re exacerbating present problems in circuit design and decreasing the returns they’re looking for.”
Close examination of the froth’s makeup and physical qualities is commonly wanted to resolve issues. Ensuring operators’ froth dealing with equipment adheres to finest design practices is a vital first step in resolving issues.
Maintaining stress 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 decreasing the pump’s efficiency, the air build-up in the pump will cut back its flow and enhance the slurry level within the suction hopper. The increased slurry level could push the pocket of air through the pump, causing surging and excessive vibration which might harm the pump bearings, impeller and shaft. “The best method to handle air in a froth pump is to spend cash on a froth pump with a steady air elimination system (CARS), which we’ve in our Warman AHF, MF and LF pumps,” says Harvey.
This system allows air to move from the pump’s impeller eye to an air collection chamber within the back by way of a vent gap within the impeller. From the chamber, a circulate inducer removes the air from the pump through a vent pipe. “It’s also essential to position the pump’s discharge pipe on the prime of the pump, or at a 45° angle as this can give air trapped at the prime of the casing a approach to escape the pump.”
Solving problems “A persistent problem we see is when hoppers designed to satisfy the calls for of slurry pumping are used in a froth pumping software. 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,” mentioned Harvey.
Tanks designed for froth pumping promote steady circular motion, where solids and liquids are sent to the surface of the sump for additional transport while air centrifuges into the centre the place it can be removed. This ‘whirlpool’ motion may be encouraged 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, further enhance the move of minerals and froth into the pump.
Smooth sailing To stop blockages, the intake pipe which hyperlinks the tank to the pump should have a large diameter and slope downwards in direction of the pump. This design allows escaped air to separate and travel again up the pipe where it could escape from the sump, somewhat than increase into blockages.
“The shorter your intake pipe, the tougher it is for blockages to construct up. However, along with a upkeep spool and isolation valve, it’s a good idea to leave enough area for a water injection port, which is useful for flushing out any solids build up,” mentioned Harvey.
“To make upkeep easier, a dump valve can be included on the suction facet of the pump, between the pump and the isolation valve. This will allow users to drain slurry from the pump and the discharge pipe system when stopping the pump for maintenance.”
Tenacious froths Froths are often categorized as either brittle, with giant air bubbles that break easily, or tenacious, where air types tight bubbles around minerals and is troublesome to separate. Froth being more tenacious than was accounted for is a frequent reason for blockages as air cannot effectively be removed.
“Two things are happening out there today. 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 much more than brittle froths,” stated Harvey. “We’re working together with clients to find methods to manage these more tenacious froths, by looking at their circuit design and coping with areas the place the air might accumulate and block the system, paying explicit consideration to their pumps, pipes and sumps.
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