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CIP tanks not flowing (16 replies)
I checked the sanded material. It reports 60-65%<75um. But it is of a a huge quantity. It settles easily. It can only be transfered through compressed air to the former tank during carbon transfer. Now we are trying to lower the tank and lower the slurry denisty so as to flow easily, but not that much good. Is there any other means of taking it out.
Shut the tank down and bring in some vacuum trucks and vacuum it out. Alternatively shovels and buckets. Sorry, but once you get large material in the only solution is to dig it out.
Unfortunately, with the "modern" tendency to run cyclones at a high density feed this is what happens.
An operation I did some work with about 10 years ago was running their cyclones at 50% solids and where getting up to 75 mm solids in their tanks like you.
Saved on capital, but required digging out about every 6 months.
Just reducing density will cause even more settling in your tanks. Just like a thickener works better if you dilute its feed.
I found the best way to "un-sand" anything is to increase the density of a finer slurry. This is temporary, for maybe a 12-hour shift. You would do this by reducing your tonnage (20 to 30%) to improve the grind but also thicken your system by cutting water where you can. Yes, your cyclone efficiency will be reduced but the lower tonnage will secure the finer grain. The result is the fine and thick stream will carry away the coarse sand from your tanks.
No need to shut down production.
If you normally operate with a 40% density leach circuit, I will try 50 or 55% (if you can... if it runs) for that shift.
The above suggestions are good. Some others are;
- replace the airlance with a submersible pump that can be moved to the areas where the coarse material has settled. Sand blasting a hole in the tank is a REAL issue.
- Check that the tank agitator is designed for the PSD that is entering the tank. The agitator MUST create full suspension, therefore no settling.
- Check that the tank screens are the correct size for the PSD entering the tank.
Thanks all for your help. Now the system is getting better and stable. Once we start the ball mill at a lower tonnage and finer material, then tanks are getting unsanded, which eases all the problems. The agitators wont alone mix the slurry, needs sufficent air as per the design. But now looks fine. Thankyou again for your beautiful ideas.
Old ideas can still be useful https://www.911metallurgist.com/agitation-leaching-tanks/
Just a further comment on tank agitators;
Tank agitators should be designed to fully suspend the slurry in the tank by themselves and also to re-suspend settled solids after a power supply cut of say, 4 hours.
Using compressed air to assist the agitators is not a good option as it is expensive and will abrade the activated carbon in your adsorption tanks.
The best option (assuming you have the correctly sized motors and gearboxes) is to replace the agitator blades which is not expensive. You may even get improved recovery due to the better suspension which can result in less tanks dead spots and bypassing.
I have an associate here in Perth who can investigate new agitator blades if you wish.
My contact is email@example.com
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I work at a CIP Gold processing plant. Currently the CIP tank has a problem with the slurry flow. There are 9 tanks, 2 leaching and 7 adsorption. Slurry from some tanks donot flow to the next tank, like from tank#7 to tank#8. Besides the difference in density, what other factors could there be that stops the flow. The screen valves and the pipes are all fine.