Leaching percolation

Percolation Leaching. Ground material coarse enough to permit circulation of a solution through a bed of particles can be leached by percolation of the solvent through the material placed ia a tank or vat. The process usually takes several days. 

Tremblay, L. Deschenes, G. Ghali, E. McMullen, J. Lanouette, M. Gold recovery from a sulfide bearing gold ore by percolation leaching with thiourea. Int. J. Miner. Process. 1996, 48, 225-244. 

Perchlorotoluene, 6 327 Perchlorylation, 12 183 Perchloryl fluoride, 18 279 Percolation leaching, 16 153 Percolation processes of filled polymers, 11 303 for wood, 26 358-359 Percolation theory, 20 345 23 63 Percolation transition, 10 16 Percutaneous transluminal coronary angioplasty (PTCA), 3 712 -per- designation, 7 609t PE resins, applications of, 20 206t. See also Polyethylene (PE)... 

The various factors that influence percolation leaching were examined by Seidel (S6). The percolation flow rate through the ore bed is very dependent on the permeability or texture of the bed. It decreases with increase in air or gas bubbles present in the bed and can be increased by increasing the temperature of the leaching solution. The size distribution of the particle, the porosity, temperature, leaching solution concentration, and percolation rates influence the mass-transfer rate. 

Lodding (Llo) described an apparatus that may find applications in continuous percolation leaching. The dewatered feed material, together with the solvent, is fed into a large insulated silo which has provisions for the continuous withdrawal of the leached material at the bottom. A w ater spray pointing at an angle of 45 is used to activate the smooth and imiform withdrawal of material, containing as much as 70% solid for a sand-size material. 

Donald (D13) presented a eomprehensive review of the theory and practice of percolation leaching as applied to a number of materials including metallic ores. The well-documented section on metallic ores includes the practices as early as the eighteenth century. Percolation leaching in tanks, heap leaching, and in-place solution mining of ores from worked out mines up to the present century are reviewed. 

Sluicing is the cheapest where water and ample disposal room are available while shoveling or mechanical excavators are used where they are not. Percolation leaching is done on ores crushed as fine as 100 mesh and as coarse as 1 inch. 

Although the overall processes have evolved for specific metals, and leachants, there are principally only two leaching techniques that provide the pregnant leach solution for metal recovery percolation leaching and agitated tank leaching. 

In agitated tank leaching systems, finely ground ore must be mixed with the lixiviant until the reaction is complete. Liquid/solid separation processes are used to recover the solution and prepare the waste for disposal in a tailing impoundment. Unlike percolation leaching operations, these operations require a large impoundment area to not only handle the solids, but also to neutralize the chemistry and pH of the solutions used to extract the metal value. 

Percolation leach particle diameter >700 pm hquid concentration 0.8 to 20% relatively fragile solid (e.g., seeds). Immersion leach particle diameter <700 pm liquid concentration <20% relatively robust solids (e.g., minerals). Combo leach high feed concentration of solute, relatively robust solid. Supercritical solvent usually CO2 for small capacity of high value products, especially for temperature sensitive foods, cosmetics, and pharmaceuticals. 

Donald, M.B. (1937) Percolation leaching in theory and practice. Transactions of the Institution of Chemical Engineers, 15, 77-104. 

Percolation leach particle diameter > 700 (xm liquid concentration 0.8 to 20 % relatively fragile solid (e.g. seeds)... 

Percolation leaching may also be regarded as a partially counter-current process. In its simple form the process involves the passing of the leaching acid down a column, or through a bed, of ore which has been ground to a suitable particle size. A suitable grid or filter medium is used as a support... 

This operation, also called solution mining, refers to the percolation leaching of minerals in place at the mine, by circulation of the solvent over and through the ore body. It is used regularly in the removal of salt from deposits below the earth s surface by solution of the salt in water which is pumped down to the deposit. It has been applied to the leaching of low-grade copper ores containing as little as 0.2 percent copper [34] and to ores as deep as 335 m (11(X) ft) below... 

C. Abbruzzese, Percolation leaching of manganese ore by aqueous sulfur dioxide, ... 

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