Dewatering: Thickening, Filtering, CCD, Water Treatment & Tailings Disposal

Dewatering: Thickening, Filtering, CCD, Water Treatment & Tailings Disposal 2017-04-04T06:57:46+00:00
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Paste Thickeners (9 replies and 1 comment)

Bill Fraser
2 years ago
Bill Fraser 2 years ago

Can you share any news on the proven technology Paste Thickeners and its applications?

Not all tailings can be converted to paste with thickeners, depends on the rheology. Only the filter can but at very high cost. The paste formation is still under development, specially the ions conditions of the material.

Some still don't use paste thickening as often as we would want because of constraints:

  • Talings deposition engineering is not handled by people who understand these techniques
  • Tailings deposition is a part of plant design that is often overlooked and is not studied properly
  • People is fearful when they think about implementing proven new technologies that have been tried only for a few companies.
  • People is close minded
  • People wants to save money in research. They save pennies compared to the millions they can make.
Alan Carter
2 years ago
Alan Carter 2 years ago

Rheology is not the limiting factor as it can be controlled with the choice of chemistry used on the paste thickener. Paste thickeners can run at 75% + underflows solid depending on mineral) with the underflow not having significant yield stress (Rheology) and can still be pumped using existing disposal systems with centrifugal pumps.

Rheology in paste tailings (high yield stress) usually comes from the flocculant used, most people do not understand this and still use high doses of high molecular weight sodium polyacrylamides which gives them the Rheology issues mentioned in this discussion. Chemistry has moved on and other alternatives are available which do not give these Rheology issues

Bill Fraser
2 years ago
Bill Fraser 2 years ago

We tested a tailings with 65% solids and due to the rheology we got paste , using flocculant (conventional) we did not improved the paste. The we tested 70& solids with other tailings and we did not get paste since the yield stress was lower. Regarding pumping we suggest the bredel pumps . As a rule (?) to get paste you need to have more than 80% less 20 microns material BUT not more than %5 less than 5 microns. Please comment, of course the nature of the taiings like alumina, or other content at this small size plays and important factor.

2 years ago
JohnnyD 2 years ago

Hi, I'm not sure whether you talked about the thickness of filtration cake, used ceramic filter, ceramic filter is a kind of processing equipment of mining. If yes,we must tell you the good news.
Recently, for mine production decreased obviously after several times ore absorption, our company developed a new type of membrane surface. The porosity of the new membrane can reach 55-56%, the micro-porous in-walls are smooth, and the tiny particles can pass smoothly in ore absorption process, so the jams will be reduced better. Meanwhile, after long-term use and backwash, the regeneration ability is obvious,the service life is longer,so as to achieve the maximum efficiency of plate surface, and improve the output.

David Kano
2 years ago
David Kano 2 years ago

I have only flirted with paste thickeners and agree that they are a technical risk when designing a mineral processing plant. On a uranium mine, test work was carried out on ore from drill samples ie from the resource itself. Based on this, a lot of equipment was designed using the rheological characteristics of the core samples. The plant we supplied (not a paste thickener) was over designed as the actual rheology from ROM was slightly different to that from the core samples. The tailings paste thickener was a white elephant that never worked even though the supplier set up a pilot plant and tested on actual tailings. Paste thickening had to be abandoned and a lined tailings dam had to be built. My suspicion is that the rheology changed as the mine moved into a different part of the resource.

This experience led me to be believe that there is much, much more to paste thickening than meets the eye. If you are designing a plant from scratch, you have to be brave to specify a paste thickener. Consequently, it is less risky to specify other tailings handling solutions and then, once you are in operation, test to see if a paste thickener will work. If it does, I believe that the capex is generally justified by the reduced opex cost.

Victor Bergman
2 years ago
Victor Bergman 2 years ago

I visited some copper concentrating plants using paste thickeners with more than 5000 ton per hour solid feed rate and 45% solid content. The thickeners have been developed by FLSMIDTH.

10 months ago

Which mine was this, Victor?

Tony Verdeschi
2 years ago
Tony Verdeschi 2 years ago

Paste thickeners themselves are well proven and work on a wide variety of PSDs, from red muds to mineral sands, in hundreds of installations.. There is generally a lower limit of about 20% -20 micron material in order to maintain flow characteristics, but as long as there are some fines, it can work with relatively coarse feeds. The paste thickeners themselves are considerably more expensive than an equivalent high rate, but the higher cost is due to much more robust design as paste thickeners can operate consistently in what would be upset conditions for a high rate thickener.

Almost every new project now considers paste technology for tailings disposal, and there are other excellent proven applications in processes like reactor feed, CCD, or filter feed where paste thickening can have great value as well.

Bob Mathias
2 years ago
Bob Mathias 2 years ago

I am glad to hear that FLS is making headway in promoting paste thickeners. Historical performance has made many engineers nervous of using them. If you can shed some light into this black box with respect to what is needed to spec them, I am sure you will have a captive audience. I have been involved in two projects in the past 2 years where paste thickening would have been appropriate but was dismissed as being too risky. So, some education would be a help.

Tony Verdeschi
2 years ago
Tony Verdeschi 2 years ago

Note that while they may look pretty similar, there are dramatic differences between high rate, high density, and deep cone paste thickeners, and that it's pretty easy to under-design while trying to control costs. If the customer is buying on price and doesn't adequately specify or control the design, they will probably end up with the lightest duty machine offered. And that probably won't work out well long term. The lowest cost option is likely low cost for reasons related to scope. So it's important that the supplier understands the application and has an understanding of what is needed to produce the desired rheology consistently.

The feed systems for the various styles of thickeners are essentially the same, and the diameters should be the same as well since the step of getting the solids out of the water is the same for all three styles. The next step, getting the water out of the solids, is where they differ. Higher underflow densities require more time and energy for dewatering, and as the rheology increases, the torque required to move the mud to the outlet increases. Typical paste thickeners drives have 8-10 times the torque compared with the same diameter high rate thickener. In addition, paste thickeners need to have much longer mud retention times in order to thicken to higher densities. That makes the tanks much deeper, again adding cost, but also an area where it's possible to skimp and under-design.

Bob Mathias
2 years ago
Bob Mathias 2 years ago

I guess the problem has been made worse by suppliers who have over promised and under delivered. It ends up giving the technology a bad reputation.

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