Froth pumping stays one of the advanced engineering challenges in mineral processing. Here, Weir Minerals presents recommendation for dealing with the key challenges on this operation, tips on how to maximise pump availability and minimise maintenance in operators’ flotation circuits.
To counteract declining ore grades, increasingly mine operators are investing in methods 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 equipment, it can end result in the loss of priceless minerals and profits.
Froth pumping remains one of the most complicated engineering challenges in mineral processing. This is basically as a end result of the truth that air management issues within the hopper, sump and pump itself can typically result in inefficient pumping, increased upkeep and even lost product.
“We’ve began to notice a sample among our prospects who’re having bother with their froth pumps,” stated Les Harvey, regional product supervisor for Slurry Pumps at Weir Minerals. “By using extra flocculants and different chemical compounds designed to enhance mineral recovery, they’re exacerbating current 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 often wanted to resolve issues. Ensuring operators’ froth handling tools adheres to finest design practices is a vital first step in resolving issues.
Maintaining stress The key challenge in froth pumping is coping with air within 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 by way of the pump.
In addition to reducing the pump’s efficiency, the air build-up in the pump will scale back its flow and improve the slurry degree within the suction hopper. The increased slurry degree could push the pocket of air via the pump, causing surging and excessive vibration which can damage the pump bearings, impeller and shaft. “The greatest way to handle air in a froth pump is to put cash into a froth pump with a steady air removing system (CARS), which we now have in our Warman AHF, MF and LF pumps,” says Harvey.
This system permits air to move from the pump’s impeller eye to an air collection chamber in the back by way of a vent gap in the impeller. From the chamber, a circulate inducer removes the air from the pump through a vent pipe. “It’s also necessary to place the pump’s discharge pipe on the top of the pump, or at a 45° angle as it will give air trapped at the prime of the casing a way to escape the pump.”
Solving problems “A persistent downside we see is when hoppers designed to fulfill the calls for of slurry pumping are used in a froth pumping utility. Slurry เกจวัดแรงดันpressuregauge require turbulence to forestall the mineral content material from settling, while 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, the place solids and liquids are sent to the outside of the sump for further transport whereas air centrifuges into the centre the place it can be removed. This ‘whirlpool’ motion could be encouraged by introducing the slurry from the highest of the tank at a tangential angle. Conical designs, somewhat than those with a flat or rounded ground, additional improve the circulate 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 direction of the pump. This design permits escaped air to separate and journey again up the pipe the place it might possibly escape from the sump, quite than build up into blockages.
“The shorter your consumption pipe, the tougher it’s for blockages to build up. However, in addition to a upkeep spool and isolation valve, it’s a good idea to leave sufficient area for a water injection port, which is useful for flushing out any solids construct up,” mentioned Harvey.
“To make upkeep simpler, a dump valve could be included on the suction facet of the pump, between the pump and the isolation valve. This will permit 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 giant air bubbles that break simply, or tenacious, where air types tight bubbles around minerals and is tough to separate. Froth being more tenacious than was accounted for is a frequent reason for blockages as air cannot successfully be removed.
“Two issues are occurring out there 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 additionally utilizing flocculants that produce a lot smaller bubbles which lock up the air a lot more than brittle froths,” stated Harvey. “We’re working together with prospects to search out ways to handle these extra tenacious froths, by looking at their circuit design and coping with areas the place the air could accumulate and block the system, paying particular attention to their pumps, pipes and sumps.