Froth pumping remains one of the most complicated 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 upkeep in operators’ flotation circuits.
To counteract declining ore grades, increasingly more mine operators are investing in methods to increase the minerals reclaimed from froth pumping. However, when these strategies are deployed without making allowances for the design of the mine’s froth pumping gear, it can end result in the lack of useful minerals and profits.
Froth pumping stays some of the complicated engineering challenges in mineral processing. This is essentially due to the truth that air administration issues within the hopper, sump and pump itself can generally result in inefficient pumping, increased upkeep and even lost product.
“ Piece of cake ’ve started to notice a sample among our prospects who are having trouble with their froth pumps,” mentioned Les Harvey, regional product manager for Slurry Pumps at Weir Minerals. “By using more flocculants and other chemical substances designed to improve mineral recovery, they’re exacerbating current issues in circuit design and reducing the returns they’re looking for.”
Close examination of the froth’s make-up and physical qualities is usually needed to resolve issues. Ensuring operators’ froth dealing with gear adheres to finest design practices is an important first step in resolving problems.
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, where it builds up into an “air lock” which impedes the movement of slurry through the pump.
In addition to decreasing the pump’s efficiency, the air build-up within the pump will scale back its circulate and increase the slurry level in the suction hopper. The increased slurry level may push the pocket of air by way of the pump, inflicting surging and excessive vibration which may harm the pump bearings, impeller and shaft. “The best way to manage air in a froth pump is to invest in 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 assortment chamber within the again by way of a vent gap within the impeller. From the chamber, a move inducer removes the air from the pump by way of a vent pipe. “It’s also important to position the pump’s discharge pipe on the high of the pump, or at a 45° angle as this can give air trapped at the high of the casing a method to escape the pump.”
Solving issues “A persistent problem we see is when hoppers designed to meet the demands of slurry pumping are utilized in a froth pumping application. Slurry hoppers require turbulence to forestall the mineral content material 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 steady round movement, where 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’ movement 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, additional enhance the flow of minerals and froth into the pump.
Smooth crusing To prevent blockages, the consumption pipe which links the tank to the pump ought to have a big diameter and slope downwards in course of the pump. This design allows escaped air to separate and travel again up the pipe where it may possibly escape from the sump, quite than building up 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 leave sufficient area for a water injection port, which is useful for flushing out any solids build up,” said Harvey.
“To make maintenance easier, a dump valve may be included on the suction facet of the pump, between the pump and the isolation valve. This will allow customers 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 massive air bubbles that break easily, or tenacious, where air varieties tight bubbles around minerals and is difficult to separate. Froth being more tenacious than was accounted for is a frequent reason for blockages as air cannot successfully be eliminated.
“Two issues 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 additionally using flocculants that produce much smaller bubbles which lock up the air much more than brittle froths,” mentioned Harvey. “We’re working together with clients to search out methods to manage these more tenacious froths, by taking a glance at their circuit design and coping with areas where the air could accumulate and block the system, paying explicit consideration to their pumps, pipes and sumps.
Share