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Filter Presses (5 replies)
Depends. First off filter presses need a steady feed rate at a steady solids concentration, thus they need a surge system ahead of them. This is usually a thickener followed by a feed tank. Thickeners can take a fair amount of surge and then the feed tank can also even out some of the surge. If the variation is beyond the capacity of these to handle it, then yes the plant (and maybe even the mine) will have to slow down.
Also the mine engineers and geologists will be called into a meeting and heads will roll (eg fired).
Smartdog is right - thickeners and tanks can provide a good buffer, the other option is to increase throughput by raising the moisture content. Sometimes allowing an extra percent or two of moisture can raise the throughput but it depends on the filter type - you can change the cycle time on a plate and frame or speed up a drum.
My experience has been that filters are often sized poorly!
Todd Harvey - Global Resource Engineering http://www.global-resource-eng.com
I support the previous comments. It happened to me personally with a change of law of 4 to 8%Zn. The rougher concentrate was sent directly to the thickener, the thickener filled quickly and to empty it the percentage of solids of the thickener UF was lowered raising pump velocity, this in turn limited the operation of the filter because it took longer to load the filter and the entire filtering cycle It was getting slower. This is because there was no stock holding tank, but if we do accounts, even with this tank, depending on how much time was granted, it may not help. Often this problem arises from the lack of slack and freedom that is given to the filter when designing it, same as thickener and stock holding tank.
I suggest This type of jumps in the head grade, and therefore over load of concentrate occurs for a few hours or even shifts. The nerves of the staff make you despair in emptying the thickener and thereby aggravate the problem, the key is to keep the percentage of solids entering the filter as high as possible. The problem should not be constant, it is for short times, so that the filter does not overload the thickener floor can be used, but very dense, because it has low capacity, and discharge the filter with higher humidity to lower the cycle time. If this problem is constant, some heads will actually roll.
My personal experience, I would rate it between 5 and 6 out of 10. The feed-rate was like 1 USgpm and the solids concentration was 33% to 35% and we did install surge tank ahead of it, but it still used to get clogging, and never filled it up to 100% of its capacity. We always found out end 3 to 5 plates were dry as 'oven dry', no touch of liquid.
One of the solutions that we came up with was to put Y shape merger before press inlet, and then use extracted liquid, which is coming out from outlet of filter press as a circulatory liquid to dissolve the clogs and unwanted packing between plates.
Result: It kinda worked out well, did increased its filling efficiency to 75 - 80% which was earlier 40 - 50%. And one of the advantages were that the filled-up plate with material used act like more stringent filtration system helping to catch even sub-micron particles as well (The basic plates were rated for 40-50 Micron particles only!).
better to install a surge tank. you don't have to slow down the mill throughput to keep up with your filter presses. your surge tanks must keep the balance. Not only about the throughput, but when the machines fail at some point, your surge tanks will save you until you stop the feed.
To anyone with operational experience with filter presses,
If you get large throughputs of flotation concentrate to filter press (due to high head grades etc) than design or typical, how do you manage it?
Does the filter press become a bottleneck and hence the plant has to slow down to suit?