Froth pumping stays one of the most complicated engineering challenges in mineral processing. Here, Weir Minerals offers recommendation for coping with the key challenges in this operation, the means to maximise pump availability and minimise maintenance in operators’ flotation circuits.
To counteract declining ore grades, increasingly mine operators are investing in strategies to increase the minerals reclaimed from froth pumping. However, when these techniques are deployed with out making allowances for the design of the mine’s froth pumping gear, it can lead to the lack of useful minerals and profits.
Froth pumping remains one of the most advanced engineering challenges in mineral processing. This is essentially as a outcome of the truth that air management points in the hopper, sump and pump itself can typically lead to inefficient pumping, elevated maintenance and even misplaced product.
“We’ve started to notice a pattern amongst our clients who’re having bother with their froth pumps,” stated Les Harvey, regional product manager for Slurry Pumps at Weir Minerals. “By utilizing extra flocculants and different chemical substances designed to improve mineral restoration, they’re exacerbating existing 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 needed to resolve points. Ensuring operators’ froth handling tools adheres to finest design practices is an important first step in resolving issues.
Maintaining strain The key problem in froth pumping is coping with air in 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 reducing the pump’s efficiency, the air build-up within the pump will scale back its flow and enhance the slurry level within the suction hopper. The elevated slurry degree could push the pocket of air by way of the pump, causing surging and extreme vibration which can damage the pump bearings, impeller and shaft. “The greatest method to handle air in a froth pump is to spend cash on a froth pump with a continuous air removing system (CARS), which we’ve in our Warman AHF, MF and LF pumps,” says Harvey.
This system permits air to maneuver from the pump’s impeller eye to an air assortment chamber in the back through a vent hole within the impeller. From the chamber, a flow inducer removes the air from the pump via a vent pipe. “It’s additionally important to place 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 approach to escape the pump.”
Solving xp2i “A persistent problem we see is when hoppers designed to meet the calls for of slurry pumping are used 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,” stated Harvey.
Tanks designed for froth pumping promote steady round movement, where solids and liquids are sent to the outside of the sump for additional transport whereas air centrifuges into the centre where it can be removed. This ‘whirlpool’ motion may be inspired by introducing the slurry from the highest of the tank at a tangential angle. Conical designs, quite than those with a flat or rounded floor, further enhance the flow of minerals and froth into the pump.
Smooth sailing To forestall blockages, the consumption pipe which hyperlinks the tank to the pump ought to have a big diameter and slope downwards in the course of the pump. This design permits escaped air to separate and journey back up the pipe the place it could possibly escape from the sump, quite than increase into blockages.
“The shorter your intake pipe, the more durable it’s for blockages to build up. However, along with a upkeep spool and isolation valve, it’s a good idea to go away sufficient house for a water injection port, which is beneficial for flushing out any solids construct up,” said Harvey.
“To make maintenance easier, a dump valve could be included on the suction side 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 upkeep.”
Tenacious froths Froths are often categorized as both brittle, with giant air bubbles that break simply, or tenacious, the place air types tight bubbles around minerals and is difficult to separate. Froth being extra tenacious than was accounted for is a frequent cause of blockages as air can’t effectively be removed.
“Two things are taking place in the market right now. On one hand, mine operators are grinding the product much finer than before to liberate more from the waste rock. They’re also using flocculants that produce a lot smaller bubbles which lock up the air a lot more than brittle froths,” said Harvey. “We’re working together with clients to seek out methods to handle these extra tenacious froths, by taking a glance at their circuit design and dealing with areas where the air might accumulate and block the system, paying explicit consideration to their pumps, pipes and sumps.
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