Mining operations require large amounts of water on their production process, and the recovery of this asset is a key element in its operational efficiency.
In the separation of solid and liquid, three methodologies are used: thickening, filtration and thermal drying. From 75% to 80% of the water can be recover in thickeners and about 90% with filters in later stages.
Thickening is the most widely used separation technique for liquids and solids because is relatively inexpensive and allows a high processing capacity.
Thickening is defined as the process by on the action of gravity, the solid particles suspended in a liquid are caused to settle, generating a thickened pulp in the lower part and a clarified liquid in the upper part.
In the thickening process a chemical called flocculant is used, which is a long-chain, high molecular weight organic polymer, soluble in water, that makes bridges or junctions between particles, creating a new particle of a larger size that will sediment faster, accelerating the process of solid and liquid separation.
The solid particles are deposited in the bottom of the thickener and are extracted to be finally discharged in the tailings dam. Most of the water is extracted from the top of the thickener and returned to the plant.
Some factors that influence the separation of solid and liquid are the following:
PARTICLE SIZE AND GRANULOMETRY
Generally fine particles have a lower sedimentation capacity. An increase in surface area means a lower concentration in the lower outlet of the thickener (underflow) in the discharge.
CONCENTRATION OF SOLIDS
Most thickeners are designed on the basis of the unit of area required (square meter per dry ton per day) and their size may vary as the concentration of solids in the feed increases.
Among the different types of flocculants are:
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