Froth pumping remains one of the advanced engineering challenges in mineral processing. Here, Weir Minerals offers advice for coping with the key challenges on this operation, the method to maximise pump availability and minimise maintenance in operators’ flotation circuits.
To counteract declining ore grades, increasingly mine operators are investing in methods 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 lead to the lack of useful minerals and profits.
Froth pumping stays some of the complex engineering challenges in mineral processing. This is essentially because of the truth that air management issues within the hopper, sump and pump itself can generally lead to inefficient pumping, increased maintenance and even misplaced product.
“We’ve started to notice a sample amongst our clients who are having bother with their froth pumps,” stated Les Harvey, regional product supervisor for Slurry Pumps at Weir Minerals. “By using more flocculants and different chemicals designed to improve mineral restoration, they’re exacerbating present problems in circuit design and reducing the returns they’re in search of.”
Close examination of the froth’s make-up and bodily qualities is often wanted to resolve issues. Ensuring operators’ froth dealing with tools adheres to finest design practices is a crucial first step in resolving problems.
Maintaining stress The key problem in froth pumping is coping with air within the pump itself, as it tends to naturally centrifuge into the impeller’s eye, where it builds up into an “air lock” which impedes the movement of slurry by way of the pump.
In addition to decreasing the pump’s efficiency, the air build-up in the pump will scale back its circulate and enhance the slurry stage within the suction hopper. The elevated slurry stage could push the pocket of air by way of the pump, causing surging and excessive vibration which might injury 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 permits air to move from the pump’s impeller eye to an air collection chamber within the again via a vent hole within the impeller. From the chamber, a move inducer removes the air from the pump through 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 this will give air trapped at the high of the casing a method to escape the pump.”
Solving problems “A persistent drawback we see is when hoppers designed to meet the demands of slurry pumping are utilized in a froth pumping application. Slurry hoppers require turbulence to stop 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 further transport while air centrifuges into the centre where it can be eliminated. This ‘whirlpool’ movement can be inspired by introducing the slurry from the highest of the tank at a tangential angle. Conical designs, rather than those with a flat or rounded floor, additional improve the circulate of minerals and froth into the pump.
Smooth sailing To prevent blockages, the consumption pipe which links the tank to the pump ought to have a big diameter and slope downwards towards the pump. เกจ์อาร์กอนsumo permits escaped air to separate and travel again up the pipe the place it can escape from the sump, somewhat than building up into blockages.
“The shorter your intake pipe, the harder it is for blockages to construct up. However, along with a maintenance spool and isolation valve, it’s a good suggestion to leave sufficient space for a water injection port, which is helpful for flushing out any solids build up,” mentioned Harvey.
“To make maintenance simpler, a dump valve could be included on the suction side 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 simply, or tenacious, where air types tight bubbles round minerals and is difficult to separate. Froth being more tenacious than was accounted for is a frequent explanation for blockages as air can not effectively be removed.
“Two issues are occurring out there right now. On one hand, mine operators are grinding the product much finer than before to liberate extra from the waste rock. They’re also using flocculants that produce a lot smaller bubbles which lock up the air much more than brittle froths,” said Harvey. “We’re working along with clients to search out methods to manage these more tenacious froths, by taking a look at their circuit design and dealing with areas the place the air could accumulate and block the system, paying particular attention to their pumps, pipes and sumps.
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