Tank leaching, also called vat leaching, is a hydrometallurgical method of extracting valuable material (usually metals) from ore. It involves placing ore, usually after size reduction and classification, in large tanks or vats containing a leaching solution. Often the vats are equipped with agitators to keep the solids in suspension in the vats and improve the solid to liquid contact. This is further assisted by the use of tank baffles to increase the efficiency of agitation and prevent centrifuging of slurries in circular tanks. Aside from chemical requirements two key factors influencing extraction are retention time and shear within the leach tanks. Retention time refers to the total volumetric capacity of the leach tank/s divided by the volumetric throughput of the solid/liquid slurry. Retention time is commonly measured in hours for precious metals recovery. A sequence of leach tanks is referred to as a leach "train", and retention time is measured considering the total volume of the leach train. Broadly speaking shear refers to energy transfer into the slurry from power input e.g.agitation. The degree of energy input in conjunction with the tank configuration determines kinetics affecting solid liquid contact. After vat leaching, the leached solids and pregnant solution are usually separated prior to further processing.
The method is commonly used to extract
goldand silverfrom ore.
* [http://wiki.biomine.skelleftea.se/wiki/index.php/Tank_leaching Tank leaching, BioMineWiki]
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