Froth pumping stays some of the complex engineering challenges in mineral processing. Here, Weir Minerals provides advice for dealing with the key challenges in this operation, the method to maximise pump availability and minimise upkeep in operators’ flotation circuits.
To counteract declining ore grades, more and more mine operators are investing in strategies to increase 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 gear, it can end result in the loss of useful minerals and earnings.
Froth pumping remains some of the advanced engineering challenges in mineral processing. This is basically due to the truth that air administration issues in the hopper, sump and pump itself can generally result in inefficient pumping, increased upkeep and even misplaced product.
“We’ve began to notice a pattern amongst our clients who are having bother with their froth pumps,” said Les Harvey, regional product manager for Slurry Pumps at Weir Minerals. “By using more flocculants and other chemicals designed to improve mineral restoration, they’re exacerbating existing issues in circuit design and lowering the returns they’re looking for.”
Close เพรสเชอร์เกจคือ of the froth’s make-up and bodily qualities is commonly wanted to resolve issues. Ensuring operators’ froth dealing with tools 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 in 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 motion of slurry by way of the pump.
In addition to reducing the pump’s efficiency, the air build-up in the pump will reduce its circulate and enhance the slurry degree in the suction hopper. The increased slurry degree may push the pocket of air by way of the pump, causing surging and extreme vibration which may harm the pump bearings, impeller and shaft. “The finest approach to manage air in a froth pump is to put cash into a froth pump with a continuous air removing system (CARS), which we now have 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 through a vent pipe. “It’s additionally necessary to position the pump’s discharge pipe on the top of the pump, or at a 45° angle as this can give air trapped on the prime of the casing a method to escape the pump.”
Solving problems “A persistent downside we see is when hoppers designed to fulfill the calls for of slurry pumping are utilized in a froth pumping utility. Slurry hoppers require turbulence to forestall 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 continuous circular movement, the place solids and liquids are despatched to the surface of the sump for additional transport whereas air centrifuges into the centre where it might be removed. This ‘whirlpool’ movement can be encouraged by introducing the slurry from the top of the tank at a tangential angle. Conical designs, somewhat than these with a flat or rounded floor, further 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 in course of the pump. This design allows escaped air to separate and journey again up the pipe where it could escape from the sump, rather than building up into blockages.
“The shorter your consumption pipe, the tougher it is for blockages to build up. However, along with a upkeep spool and isolation valve, it’s a good suggestion to leave enough area for a water injection port, which is useful for flushing out any solids construct up,” said Harvey.
“To make maintenance simpler, a dump valve may be included on the suction aspect of the pump, between the pump and the isolation valve. This will enable users to empty 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, where air forms tight bubbles round minerals and is troublesome to separate. Froth being extra tenacious than was accounted for is a frequent cause of blockages as air cannot successfully be eliminated.
“Two things are occurring out there at present. On one hand, mine operators are grinding the product much finer than earlier than to liberate extra from the waste rock. They’re additionally using flocculants that produce much smaller bubbles which lock up the air much more than brittle froths,” said Harvey. “We’re working along with customers to find methods to handle these extra tenacious froths, by looking at their circuit design and coping with areas where the air might accumulate and block the system, paying specific attention to their pumps, pipes and sumps.
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