Froth pumping remains one of the complex engineering challenges in mineral processing. Here, Weir Minerals offers advice for coping with the key challenges in 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 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 lead to the lack of valuable minerals and profits.
Froth pumping remains one of the most complicated engineering challenges in mineral processing. This is essentially due to the reality that air administration points in the hopper, sump and pump itself can sometimes result in inefficient pumping, elevated maintenance and even lost product.
“We’ve began to notice a sample among our clients who are having trouble with their froth pumps,” stated Les Harvey, regional product supervisor for Slurry Pumps at Weir Minerals. “By utilizing extra flocculants and different 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 bodily qualities is commonly needed to resolve issues. Ensuring operators’ froth dealing with tools adheres to best design practices is a vital first step in resolving issues.
Maintaining pressure The key problem in froth pumping is dealing with air in 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 decreasing the pump’s effectivity, the air build-up in the pump will cut back its move and enhance the slurry level within the suction hopper. The elevated slurry level may push the pocket of air via the pump, inflicting surging and extreme vibration which might harm the pump bearings, impeller and shaft. “The best method to manage air in a froth pump is to spend money on 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 maneuver from the pump’s impeller eye to an air assortment chamber within the back via a vent gap in the impeller. From the chamber, a flow inducer removes the air from the pump via 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 prime 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 utility. Slurry hoppers require turbulence to prevent the mineral content from settling, whereas turbulence in a froth pump prevents the air from escaping and leads to blockages,” said Harvey.
Tanks designed for froth pumping promote continuous round motion, where solids and liquids are sent to the outside of the sump for additional transport while air centrifuges into the centre where it can be eliminated. This ‘whirlpool’ motion can 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 ground, further enhance the circulate of minerals and froth into the pump.
Smooth crusing To prevent blockages, the intake pipe which hyperlinks the tank to the pump should have a large diameter and slope downwards towards the pump. This design allows escaped air to separate and journey back up the pipe the place it could escape from the sump, somewhat than increase into blockages.
“The shorter your intake pipe, the tougher it is for blockages to construct up. However, along with a maintenance spool and isolation valve, it’s a good idea to go away enough space for a water injection port, which is useful for flushing out any solids build up,” said Harvey.
“To make upkeep easier, a dump valve could be included on the suction facet 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 upkeep.”
Tenacious froths Froths are often categorised as either brittle, with massive air bubbles that break simply, or tenacious, where air types tight bubbles around minerals and is difficult to separate. Froth being extra tenacious than was accounted for is a frequent explanation for blockages as air can not effectively be removed.
“Two issues are taking place available within the market today. On pressure gauge octa , mine operators are grinding the product much finer than earlier than to liberate extra from the waste rock. They’re additionally utilizing flocculants that produce much smaller bubbles which lock up the air a lot more than brittle froths,” said Harvey. “We’re working along with prospects to search out ways to handle these more tenacious froths, by looking at their circuit design and coping with areas where the air may accumulate and block the system, paying specific attention to their pumps, pipes and sumps.
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