Froth pumping stays some of the complicated engineering challenges in mineral processing. Here, Weir Minerals presents recommendation for dealing with the key challenges on this operation, the means 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 without making allowances for the design of the mine’s froth pumping gear, it can outcome in the lack of valuable minerals and earnings.
Froth pumping remains some of the advanced engineering challenges in mineral processing. This is largely as a result of the fact that air management points in the hopper, sump and pump itself can typically result in inefficient pumping, increased maintenance and even misplaced product.
“We’ve began to notice a sample among our customers who’re having trouble with their froth pumps,” said Les Harvey, regional product manager for Slurry Pumps at Weir Minerals. “By using more flocculants and different chemical compounds designed to improve mineral restoration, they’re exacerbating current issues in circuit design and lowering the returns they’re in search of.”
Close examination of the froth’s make-up and bodily qualities is usually wanted to resolve points. Ensuring operators’ froth handling equipment adheres to greatest design practices is a crucial first step in resolving issues.
Maintaining stress The key problem in froth pumping is dealing 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 motion of slurry by way of the pump.
In addition to reducing the pump’s effectivity, the air build-up in the pump will reduce its move and enhance the slurry level within the suction hopper. The increased slurry stage might push the pocket of air via the pump, inflicting surging and excessive vibration which may harm the pump bearings, impeller and shaft. “The finest way to handle air in a froth pump is to put cash into a froth pump with a continuous air removal system (CARS), which we have in our Warman AHF, MF and LF pumps,” says Harvey.
This system allows air to move from the pump’s impeller eye to an air assortment chamber in the back through a vent gap within the impeller. From the chamber, a move inducer removes the air from the pump through a vent pipe. “It’s additionally essential to place the pump’s discharge pipe at the top of the pump, or at a 45° angle as it will give air trapped at the top of the casing a way to escape the pump.”
Solving issues “A persistent downside we see is when hoppers designed to satisfy the calls for of slurry pumping are utilized in a froth pumping utility. Slurry hoppers require turbulence to forestall the mineral content 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, where solids and liquids are sent to the surface of the sump for further transport whereas air centrifuges into the centre where it might be removed. This ‘whirlpool’ motion may 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 ground, further improve the flow 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 big diameter and slope downwards in the direction of the pump. This design permits escaped air to separate and travel again up the pipe the place it can escape from the sump, somewhat than increase into blockages.
“The shorter your consumption pipe, the tougher it’s for blockages to construct up. However, along with a upkeep spool and isolation valve, it’s a good idea to leave sufficient area for a water injection port, which is helpful for flushing out any solids build up,” said Harvey.
“To make upkeep easier, a dump valve can be included on the suction facet of the pump, between the pump and the isolation valve. This will enable customers to empty slurry from the pump and the discharge pipe system when stopping the pump for upkeep.”
Tenacious froths Froths are sometimes categorised as either brittle, with massive air bubbles that break easily, or tenacious, the place air varieties tight bubbles around minerals and is difficult to separate. pressure gauge being more tenacious than was accounted for is a frequent explanation for blockages as air can not successfully be eliminated.
“Two issues are taking place in the market today. On one hand, mine operators are grinding the product a lot finer than earlier than to liberate extra from the waste rock. They’re also using flocculants that produce a lot smaller bubbles which lock up the air much more than brittle froths,” said Harvey. “We’re working along with clients to find methods to handle these extra tenacious froths, by taking a glance at their circuit design and coping with areas where the air may accumulate and block the system, paying particular consideration to their pumps, pipes and sumps.
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