Froth pumping stays one of the most complex engineering challenges in mineral processing. Here, Weir Minerals provides recommendation for coping with the key challenges on this operation, how to maximise pump availability and minimise maintenance in operators’ flotation circuits.
To counteract declining ore grades, more and more mine operators are investing in techniques to increase the minerals reclaimed from froth pumping. However, when these techniques are deployed without making allowances for the design of the mine’s froth pumping gear, it may find yourself in the lack of useful minerals and earnings.
Froth pumping stays one of the most complicated engineering challenges in mineral processing. This is largely due to the fact that air management issues in the hopper, sump and pump itself can typically lead to inefficient pumping, elevated maintenance and even lost product.
“We’ve started to note a sample amongst our prospects who’re having bother with their froth pumps,” mentioned Les Harvey, regional product supervisor for Slurry Pumps at Weir Minerals. “By utilizing extra flocculants and other chemical compounds designed to improve mineral recovery, they’re exacerbating present issues in circuit design and reducing the returns they’re in search of.”
Close examination of the froth’s make-up and physical qualities is usually needed to resolve points. Ensuring operators’ froth handling gear adheres to greatest design practices is an important first step in resolving problems.
Maintaining strain 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 by way of the pump.
In addition to lowering the pump’s efficiency, the air build-up in the pump will cut back its circulate and enhance the slurry degree within the suction hopper. The elevated slurry degree could push the pocket of air by way of the pump, inflicting surging and excessive vibration which can harm the pump bearings, impeller and shaft. “The best approach to handle 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 permits air to maneuver from the pump’s impeller eye to an air assortment chamber in the again through a vent hole in the impeller. From the chamber, a flow inducer removes the air from the pump by way of a vent pipe. “It’s also essential to place the pump’s discharge pipe at the prime of the pump, or at a 45° angle as this will give air trapped on 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 demands of slurry pumping are utilized in a froth pumping utility. Slurry hoppers require turbulence to stop the mineral content 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 circular motion, the place solids and liquids are despatched to the outside of the sump for further transport whereas air centrifuges into the centre the place 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, somewhat than these with a flat or rounded ground, additional improve the move of minerals and froth into the pump.
Smooth sailing To prevent blockages, the intake pipe which links the tank to the pump should have a large diameter and slope downwards towards the pump. This design permits escaped air to separate and journey again up the pipe the place it may possibly escape from the sump, quite than build up into blockages.
“The shorter your intake pipe, the harder it is for blockages to build up. However, along with a upkeep spool and isolation valve, it’s a good suggestion to leave sufficient area for a water injection port, which is beneficial for flushing out any solids construct up,” said Harvey.
“To make pressure gauge 0 10 bar ราคา , a dump valve can be included on the suction aspect 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 sometimes categorized as either brittle, with large air bubbles that break easily, or tenacious, the place air varieties tight bubbles round minerals and is troublesome to separate. Froth being more tenacious than was accounted for is a frequent explanation for blockages as air can not successfully be removed.
“Two things are happening in the market today. On one hand, mine operators are grinding the product much finer than earlier than to liberate more from the waste rock. They’re also utilizing flocculants that produce much smaller bubbles which lock up the air a lot more than brittle froths,” stated Harvey. “We’re working along with clients to find methods to manage these more tenacious froths, by looking at their circuit design and dealing with areas where the air may accumulate and block the system, paying particular consideration to their pumps, pipes and sumps.
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