Take a close look at the particle size distribution of the material being stacked. My experience with these was glass / industrial sand where the product was comparatively coarse compared to my experience with sulfide flotation, i.e., all the minus 150 mesh material was removed as waste prior to processing.

That’s a good point, the tailings are not so coarse in my flotation neither, 80% is passing 65 mesh. Although being able to fabricate the CycloStack I would certainly test it out; just more details about that rubber/urethane part is what I'm looking for.

Do you have other suggestion from your experience how to de-water the flotation tailings?

What is the size distribution of the tailings? What does plant water cycle look like? Are there constraints concerning quality of water coming back to your plant from this dewatering? There may be some good ideas from aggregate industry applications. Let me look for some of the details. It’s been a few years since worked much with this.

Application for a spiral classifier?

Comments above are very good; the PSD will tell you whether it will work or not, in my experience you will be able to stack a coarse component of the feed material +150 microns, the finer material will not dewater effectively to stack. The fishtail/vacuum system is used to control the underflow flowrate, effectively a controlled roping of the cyclone underflow but as with any roping system; coarse particles are lost to overflow. As an example a PSD of 70% - 75 micron will achieve above 15% of mass to underflow at an underflow density of 1.90. That density will not be conveyable, a density above 2.1 will be conveyable but mass split to underflow will be around 5% if you lucky. If you want, I can run it through my cyclone model and I'll let you know what you could achieve.

My experience with trying to produce stackable tailings is to use horizontal belt filters, pressure filters or centrifuges. Base metal operations tend to shy away from centrifuges but they are a standard unit op in potash, trona, coal, etc. Oilsand plants are also starting to look at them for de-watering MFT (fine tails). They have to be set up properly with the correct wear materials and they do have high horsepower requirements but they dewater exceptionally well. All in a small footprint.

At Copper Mountain and Phelps Dodge Chino we used cyclones to make dams for tailings and the overflow went to the middle of the pond. But the underflow would not be stackable and you have to watch that if the plant has an upset that tailings is informed or you end up washing away the dyke you just made. As I understand it that is what the duckbill is supposed to help prevent.

Following your note "having a very limited space around, I can't be creating a new tailing pond" - what about "in situ" stabilization-dewatering existing tailings with electro osmotic technology? It is well known that if you want to remove/suck out water from any clay-like/clayish void environment, you have to apply DC current. After sucking water/soil solution, voids are to be closed and minimize sliding of landslide mass (Irreversible process!). Electro osmosis is using also for purification of soils polluted with heavy metals (DC is driving force for metal cations and advection is driving force for organic compounds).Electro osmosis technology is very cheap ''in situ" technology - fancy that - no excavation, no processing plant, no hydro - cyclone).

I was doing "in situ sucking" phenols compounds pollution - thanks to electro osmosis it was free overflow (no pumping!) of phenols from cathode electrode (well) from weathered clayish andesite soils.

I think there is some kind of misunderstanding in your question regard of the dewatering system. The cyclone dewatering overflow won’t be by any chance, clean reusable water, even worse when the feed to the cyclones is fine.

If you in some way get that 80% solid in the underflow, you will have the problem of what to do with overflow; it will be a large amount of water with a large amount of fines particles (maybe 5% to 10% in weight). Can't reuse that water in flotation and you don't have space to put it somewhere anyway!

The best option for space savings would be a total tailings filtered stacking system (compacted filtered tailings). It will be the most expensive system in terms of process cost only, but you can reuse the water recovered (if it doesn't contain any reactive that affect flotation) because it doesn't contain too many fines (a conservative estimation would be like 500 ppm), and also reduce the tailing impoundment area impacted, the tailings dam and the costs associated with.

More alternatives are the filtration without compaction, paste thickening, high density thickening, and conventional thickening. Every one of them would reduce the amount of water going into the tailings deposit thus reducing the tailings deposited instantaneous volume.

And what about backfill, can your mine storage some of the tailings?

Cyclostack-the underflow may be qualified for stack the dam for tailings pond, but you still have to have a pond to take care the flow from the underflow. The overflow from the cyclostack will have pretty big percentage solids that are not good for recycling back to the process, still needs to be sent to the pond. It does not get the separation you want.

Filter press-you need a thickener to get a proper performance or, you need to sized big enough for low efficiency. The filtrate is qualified for recycling and filter cake is good enough for "dry" stacking using a belt conveyer.

Centrifuge-A good result for this machine is that you can get pseudo dry product, such as 1 to 3% moisture, good for product that requires drying. It may not be suitable for your process since the flotation slurry can be too fine. By the way, some fines can get into water, which you probably do not want to recycle to the process.

Belt filter or belt filter press-it can treat slurry without thickening, meaning you do not have to thicken the slurry before filter it. You may get a product with less than 12% moisture with just belt filter without press. It can achieve a stackable product from river sludge when the belt filter comes with a press function. Belt filter requires a vacuum system.

Conclusion: A belt filter is likely your choice. A filter press is also possible when it is sized big enough and you have a stock tank with enough surge capacity.

Neo Solutions is stacking tailings without the use of a belt press or filter press, -85% solids at the time of disposal. You can walk across and vegetation starts to grow after a few weeks. The capital expenditure on the presses and ancillary equipment is much higher than the operating costs of our solution.

Would you provide some details about the material being stacked, the feed percent solids and the particle size distribution?

Primarily clay and silica, feed solids are -30-35%, Rejected silica is >1mm and < 0.125mm. No data on size distribution from this example as there is no grinding and % tails varies from pit to pit and grade of silica being produced. Currently testing for implementation into two iron ore mines, however this data cannot be shared yet. The angle of repose is much better with iron tails.

The fishtail valve that you refer to is a Linatex Patented product which is used on our Cyclone separators (which use the negative pressure created by your overflow, and then siphoning the water from the solids in the underflow. We have used this system successfully for around 30 years, in dewatering silica sand, quartz, coal, gypsum, and underflow in gold, platinum and uranium plants over the years. Linatex (the company and brand names) were purchased by Weir minerals globally, but the excellent Linatex products remain.

For good solution simple advice will not work. We need to study size distribution as per Taylor series of sieves in order form 150 micron down to 10 micron. Method of stacking tailing system, layout plan. I have dealt with many such cases.

Depending particle size distribution and their settling properties, dewatering facilities may be a dewatering screen, dewatering cyclone, pressure filters or adding suitable flocculants for improving settlement. However, it’s necessary to test a sample of material for a final decision.

In addition to my comment above, the total solution if the particle size is generally small, would be to put the Separator underflow over a dewatering screen, although this is more expensive, it will be effective and you will end up with very dry material, around minus 5 % moisture. Sample is not necessary, but a complete product analysis of the size range in the flow is essential.

Can anyone advise what is supposed to do with the fines after the dewatering with cyclones or screens?

Since, the tailings come from flotation, I’m sure he has a lot of fines and any dewatering system that operate as a classification device, will leave two products, the dewatered coarse particles and the fines with a lot of water. You can't reuse that water into the flotation, because you will eventually have a fines build up, and many other problems. Also, he's running out of space, can´t put that water into the tailings deposit.

So, if such dewatering classification system is applied, the problem is not resolved. He will have to separate those fines from the water even if he doesn't need the water and you can´t discharge water with solids to environment. So, I will prefer separate the solids from the water without a prior classification.

The plant capacity (150 t/d) means that it is a little one, so buy a thickener or construct one, I’m sure it will be no more than 6m diameter, add flocculants, and a little pump for discharge, and you will reduce the water content. If you want to go further, buy a filter and feed it with the thickener discharge.

Stack it with polymer and get the water back. Polymer selection and addition would/ will be much easier if the solids can be held constant and are subjected to a large amount of energy like pumping to re stabilize the colloids and expose new surface sites. I have pictures of successful implementation.

As this is an area of my expertise (selecting an appropriate holistic dewatering solution for tailings), please allow me to put in my 2 cents worth, please consider the following example consideration before getting into too many more details.

You need to work backwards - how much space do you have? Where will the material go to from the plant? How long do you have to move material from its first location, to the second, final, etc? You do need to have data on the ranges of yours particles sizes, density, volumetric flows, water chemistry, etc.

Do some basic tests - don't just accept what equipment and chemical providers say things will do - each plant is different, and ideally, requires at least some basic pre-work to understand what outputs are gained for inputs spent; this goes for consultants, too! Know what resources you have available (Capex, Opex, people, mobile equipment, water availability, real estate, etc) will help you short-list transport and dewatering options.

These are just some very quick suggestions (I have a formal process I go through with people, but won't present here!). Adequate holistic considerations can even will help you uncover multi-faceted solutions that are better than you could have hoped for, so be prepared to be creative - but also be pre-prepared with holistic, site-specific data.

You have a tough (though not unusual or impossible) scenario, but I am sure you will work something out. Additionally, of course, if you want someone to provide a few hours formal assistance, even just as a "sounding board", then I'm happy to help.

Hello!!

I have done many experiments on dewatering / fishtail hydrocyclone.  I was using 6 inch hydrocyclone with 20 % solid by weight (silica sand specific gravity 2.6) in the inlet.  The gap between the fishtail valve to the bottom of overflow pipe used is more than 1200 mm. I have tried different inlet pressure from 6 psi to 14 psi. What I found at lower pressure I observed good results but the maximum underflow density that I found is 75 %.  I need to increase this to above 85% but I am not getting it. I have tried different combinations of pressure and solid percentage, gap between fishtail valve and overflow pipe, changing vortex finder to apex ratio. Still the maximum underflow density observed is 75 %. 

Can anyone suggest what should I do to increase the underflow density. 

What is your current Vortex and Apex diameters? Have you tried just a little bit smaller Apex from where you are now? I don't think you will get 85% without plugging. You are asking a cyclone to do the work of a rotary filter...