Grinding & Classification Circuits

Grinding & Classification Circuits

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Large carbonate scales on vibrating screens (4 replies)

H
Helen
7 years ago
Helen 7 years ago

Hello all... I found out the scales forming are that of carbonate due to the lime and hardness of the process water. A little confusion i have is how can very large scales of carbonate form on a highly agitating component? the vibrating screen agitates as it screens.. I thought the slurry/water should be washed of in the course of screening due to the agitation. how can scales precipitate to such a large extent on the metallic support beams of the vibrating/agitating screen?

M
Mike Rockandel
7 years ago
Mike Rockandel 7 years ago
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Helen

Same problem as when you wash your car with hard water. White Ca/Mg scale everywhere. It is due to the wet and dry cycles. Agitation makes little difference. You might consider flushing the screen every few hours with a low hardness water. That will slow but not stop the accretions. 

http://www.rockandel.com/

F
Siddiquf
7 years ago
Siddiquf 7 years ago
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Asking the right question is often half the answer. It appears that crystal nucleation occurs at many sheltered points and the force of crystal growth is sufficient to overcome vibrations and fluid flow, as long as abundant dissolved carbonates are available. How about bleeding some process water, softening it and then remixing it to bring down the overall hardness and calcium content of process water on an ongoing basis?

P
Philip Stewart
7 years ago
Philip Stewart 7 years ago
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I had this problem many years ago.  The scale proved to be the aragonite form of calcium carbonate.  One solution which worked was to use polyurethane screen where the "wires" are capable of flexing in addition to the surface itself being more inimical to the scale.  The disadvantage of this is that the open area of such screens is very much less than normal screens but maybe not than the wedge wire you are using.  The reason for the ready formation when you have hard water is that the high exposure of the surface to air is ideal for the absorption of carbon dioxide which reacts with the calcium.  One point to note is that the water is softened by this calcium removal.  If you can arrange to segregate this water and use the recycled water as the principal source of process water then the problem will be alleviated.

H
Helen
7 years ago
Helen 7 years ago
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Thanks for the information!

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