Weir’s solution for froth challenges

Froth pumping remains one of the most complicated engineering challenges in mineral processing. Here, Weir Minerals provides recommendation for dealing with the important thing challenges on this operation, how to maximise pump availability and minimise upkeep in operators’ flotation circuits.
To counteract declining ore grades, increasingly mine operators are investing in techniques to extend 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 some of the complicated engineering challenges in mineral processing. This is essentially due to the truth that air administration points in the hopper, sump and pump itself can generally lead to inefficient pumping, increased maintenance and even misplaced product.
“We’ve started to note a sample among our prospects who are having trouble with their froth pumps,” said Les Harvey, regional product supervisor for Slurry Pumps at Weir Minerals. “By using more flocculants and other chemicals designed to improve mineral restoration, they’re exacerbating present issues in circuit design and lowering the returns they’re on the lookout for.”

Close examination of the froth’s makeup and physical qualities is usually needed to resolve issues. Ensuring operators’ froth handling equipment adheres to finest design practices is a vital first step in resolving problems.
Maintaining strain The key challenge in froth pumping is dealing with air within the pump itself, because 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 through the pump.
In addition to lowering the pump’s effectivity, the air build-up in the pump will cut back its circulate and improve the slurry degree 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 greatest method to handle air in a froth pump is to put money into a froth pump with a continuous 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 assortment chamber within the again via a vent hole within the impeller. From the chamber, a circulate inducer removes the air from the pump by way of a vent pipe. “It’s also diaphragm seal to place the pump’s discharge pipe at the top of the pump, or at a 45° angle as this can give air trapped on the high of the casing a method to escape the pump.”

Solving issues “A persistent problem we see is when hoppers designed to satisfy the demands of slurry pumping are utilized in a froth pumping software. Slurry hoppers require turbulence to stop the mineral content from settling, while turbulence in a froth pump prevents the air from escaping and leads to blockages,” said Harvey.
Tanks designed for froth pumping promote steady circular motion, the place solids and liquids are sent to the surface of the sump for additional transport while air centrifuges into the centre where it might be removed. This ‘whirlpool’ motion could be encouraged by introducing the slurry from the top of the tank at a tangential angle. Conical designs, rather than those with a flat or rounded flooring, further enhance the circulate of minerals and froth into the pump.
Smooth sailing To stop blockages, the consumption pipe which hyperlinks the tank to the pump ought to have a large diameter and slope downwards in the path of the pump. This design permits escaped air to separate and journey again up the pipe the place it could possibly escape from the sump, quite than building up 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 suggestion to go away enough house for a water injection port, which is beneficial for flushing out any solids build up,” said Harvey.
“To make maintenance easier, a dump valve may be included on the suction side of the pump, between the pump and the isolation valve. This will allow customers to empty slurry from the pump and the discharge pipe system when stopping the pump for maintenance.”

Tenacious froths Froths are often categorised as both brittle, with massive air bubbles that break simply, or tenacious, where air types tight bubbles around minerals and is difficult to separate. Froth being more tenacious than was accounted for is a frequent reason for blockages as air cannot successfully be eliminated.
“Two things are taking place in the market at present. On one hand, mine operators are grinding the product a lot finer than before to liberate extra from the waste rock. They’re additionally using flocculants that produce much smaller bubbles which lock up the air a lot more than brittle froths,” mentioned Harvey. “We’re working along with prospects to find ways to manage these extra tenacious froths, by looking at their circuit design and dealing with areas where the air could accumulate and block the system, paying specific attention to their pumps, pipes and sumps.

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