Heavy Medium Separators

Gravity concentration, ie, the separation of ore from gangue based on the differences in specific gravities, using jigs, heavy—medium separators, or spiral concentrators for example, is appHcable for lead ores. However, the predominant beneficiation technique used in modem plants is the bubble or froth flotation (qv) process (4,5). 

Further upgrading of the potassium chloride content of the chloride salts recovered from the initial heavy-medium separation takes place in a second heavy-medium separation at a somewhat lower specific gravity than the first separation. Sodium chloride is discarded as a waste the enriched KCl fraction is sent to a flotation process where a final separation of KCl from NaCl is made. Mine-mn ore less than 1 mm that is not amenable to... 

The devices used for the gravity concentration of minerals are many in number. Typical examples include devices such as jigs, spirals, tables, and heavy medium separators. 

Heavy medium separation involves the following stages ... 

The recovery of valuable minerals and metals requires several stages of sequential processing operations. The mined ore must be crushed and ground to fine sizes prior to treatment by such bene-ficiation processes as heavy-medium separation, tabling, magnetic separation, electrostatic separation, flotation, selective flocculation, etc. Since most of these processes are carried out in aqueous media, solid-liquid separations by such operations as thickening and filtration are an integral part of the benefici-... 

In a heavy-medium separation process, coal particles whose density is higher than the medium sink while the lower-density coal particles float the separation efficiency and the through put of the separation device depend on the velocity of coal particles in a dense medium. The viscosity of a medium has little effect on the low-density coal particles or the high-density gangue particles, but becomes critical in the separation of material of a density equal to or near that of the medium hence, a low viscosity must be maintained to separate near-density material at a high rate of feed. 

TABLE 5 Properties of the Products of Heavy Medium Separation ... 

Ores containing monazite, bastnaesite or xenotime are concentrated by ore-dressing processes, heavy medium separation or flotation. After grinding, the concentrates are converted to soluble sulfates or chlorides by digestion with acids or alkalis. 

Extraction by carboxyUc acids (qv) is carried out in a neutral or weaMy acidic medium. The most widely used carboxyUc acid is RR (CH2)CCOOH, where Rplus represents seven carbon atoms. Trade names are Versatic 10 (Shell Chemicals) and Neodecanoic acid (Exxon Chemicals). CarboxyUc acids can be used either in chloride or in nitrate media and have a better selectivity for light lanthanides than for heavy lanthanide separation. 

Solids of different densities can be separated by immersing them in a fluid of intermediate density. The heavier solids sink to the bottom and the lighter float to the surface. Water suspensions of fine particles are often used as the dense liquid (heavy-medium). The technique is used extensively for the benefication (concentration) of mineral ores. 

At the end of its evolution, the star restores part of itself, containing the ashes of its past activities, to its surroundings. The sky gains in heavy elements, as earth grows richer in salts. For this reason, the medium separating stars also evolves. When the heavy element content reaches 2%, life and consciousness emerge, as we may deduce from the only known case our own. 

Feed Solids Content. A good HMS plant operation keeps the medium as free of fines as possible by effective screening of the heavy-media separation vessel feed. Reduced fines reduce viscosity problems in the medium and result in sharper separation of sink and float products. It also improves magnetic recovery on the magnetic drum separators and gives a cleaner magnetic concentrate. The use of cyclones in the HMS circuit, either as the heavy-media separation vessel or as a densifier for rinse or wash water, increases the solids content and must be evaluated in selecting the media recovery wet dmm separators for plants in which cyclones are used. 

For coarse-grained ores, physical methods employing froth flotation and/or heavy-media methods are employed to achieve separation. The heavy medium may consist of, for example, pulverized magnetite in a brine solution. The specific gravity of the medium is adjusted so that it falls between that of KC1 (1.99 g/cm3) and that of NaCl (2.17 g/cm3). 

All products from the laboratory heavy media separation were thoroughly rinsed to remove adhering medium and were air dried at 90°C. Representative samples were crushed to -10 mesh. Specific gravities were obtained with an air pycnometer and standard Fischer Assays were run. 

Sink-and-float methods. A sink-and-float method uses a liquid sorting medium, the density of which is intermediate between that of the light material and that of the heavy. Then the heavy particles settle through the medium, and the lighter ones float, and a separation is thus obtained. This method has the advantage that, in principle, the separation depends only on the difference in the densities of the two substances and is independent of the particle size. This method is also called heavy-fluid separation. 

Dense media (or heavy liquids) Fluids used in dense-medium separation of coal and gangue particles by their relative densities. The medium can be any suitable fluid, but in commercial coal preparation operations, it is usually a suspension of fine magnetite in water. 

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