Heaps

Several melting points can be simultaneously determined the substances must of course be placed in separate minute heaps in the constant temperature area on the surface of the apparatus. 

W. R. Seeker, W. S. Lanier, and M. P. Heap, Municipal Waste Combustion Study Combustion Control of MSW Combustors to Minimi Emissions of Trace Organics, EER Corporation, Irvine, Calif., 1987. 

The original process of heating coal in rounded heaps, the hearth process, remained the principal method of coke production for over a century, although an improved oven in the form of a beehive was developed in the Durham-Newcastie area of England in about 1759 (2,26,28). These processes lacked the capabiHty to collect the volatile products, both Hquids and gases. It was not until the mid-nineteenth century, with the introduction of indirectiy heated slot ovens, that it became possible to collect the Hquid and gaseous products for further use. 

R. A. Cross andJ. D. Pickett-Heaps,/. Cell Biol 63, 84 (1974). 

Fig. 2. SQM s heap leaching of caUche tailings for iodine recovery from diluted iodate solutions.

Diluted iodate solution is obtained by hydrothermal vat leaching of caUche ore during nitrate recovery. Concentrated iodide solutions are obtained by heap leaching of old waste dumps (tailings) and low grade nitrate caUche, such as blasted overburden, left over by former nitrate producers. 

Modem heap leaching practice has also made possible the treatment of extremely lean (ca 1 g/1) gold ores, which had been considered uneconomic... 

Table 1 gives the average metal content of the earth s cmst, ore deposits, and concentrates. With the exceptions of the recovery of magnesium from seawater and alkaU metals from brines, and the solution mining and dump or heap leaching of some copper, gold, and uranium (see Uranium and uranium compounds), most ores are processed through mills. Concentrates are the raw materials for the extraction of primary metals. 

Percolation In addition to being applied to ores and rock in place and by the simple technique of heap leaching (usually on verv large scale see Wadsworth, loc. cit.) percolation is carried out in batcJi tanks and in continuous or dump extractors (usually on smaller scale). 

Operation Cascading and cataracting are the terms applied to the motion of grinding media. The former applies to the rolling of baUs or pebbles from top to bottom of the heap, and the latter refers to the throwing of the baUs through the air to the toe of the heap. 

Bulk surface discharge In rapid heaping of highly insulated bulk material, particularly when coarse material (diameter > 1 mm) is present MIE<1I (silo diameter 3 m)... 

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