Leaching dump method

Batch Extractors. Coarse soHds are leached by percolation in fixed or moving-bed equipment. Both open and closed tanks (qv) having false bottoms are used, into which the soHds are dumped to a uniform depth and then treated with the solvent by percolation, immersion, or intermittent drainage methods. 

The introduction of leach solutions into the dump can be made by means of spraying, flooding, or by injecting into the dump through buried vertical pipes. The decision as to which method is most desirable is dependent on several variables such as climatic conditions, height of the dump, surface area of the dump, mineralogy, the size of the operation, the size of the materials, and most important, the experience of the operating personnel (C2, MlO, Rll, W18). 

Chile, production is based on the Guggenheim method, which permits ores containing under 10% nitrate to be profitably worked. Caliche is mined by open-pit operations, using draglines and power shovels, and is crushed to about 80% between 3/4 and 3/8 inches (1.9-0.95 cm). This product is leached at about 40°C wth water in a series of vats each vat has a capacity of some 10,000 tonnes of crushed ore. The underflow from each vat is heated before passing to the next since sodium nitrate has a negative heat of solution. After extraction and washing are complete, the residue is removed from the vats and transported to a waste dump. 

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