Heavy media

Potassium Chloride. The principal ore encountered in the U.S. and Canadian mines is sylvinite [12174-64-0] a mechanical mixture of KCl and NaCl. Three beneficiation methods used for producing fertilizer grades of KCl ate thermal dissolution, heavy media separation, and flotation (qv). The choice of method depends on factors such as grade and type of ore, local energy sources, amount of clay present, and local fuel and water availabiUty and costs. 

Froth Flotation. Froth flotation (qv) of potassium chloride from sylvinite ores accounts for ca 80% of the potassium chloride produced in North America and about 50% of the potassium chloride in Europe and the CIS. Fractional crystallisation and heavy-media processing account for the remaining amounts produced. Froth flotation has been described (6,16,17). 

Heavy-Media Separation. Heavy-media separation, depicted in Eigure 3, can only be used for relatively rich sylvinite ores that consist of large crystals of KCl and NaCl, such as those mined in Saskatchewan (6,20). Crystals of the two salts in the Saskatchewan deposits are 6—9 mm in diameter. Mine ore that is cmshed sufficiently to pass through 6—9-mm screens in this size range results in a mixture consisting of discrete grains of each salt. 

Media Si. Media are suppHed in several size grades and the grade used varies at each plant. The finer grades improve media stabiUty, but finer particles are more difficult to recover and the feed rate of these finer-grade slurries should be reduced by a factor of 0.5—0.75 to maintain magnetic recovery. A typical size analysis as used in various heavy-media separation plants treating coal (qv) is given in Table 4. 

Dmm diameters are typically 762, 914, or 1219 mm, all of which have been used in the various basic appHcations. In some instances, standardization of diameter is specified because of maintenance considerations. Because these separators are constmcted more mggedly and requHe repulping stages, capital costs are higher than heavy-media separators. Costs in 1995 were approximately 10,000/m of width for single-dmm modules and multiples of the single-dmm module. 

Cadmium occurs primarily as sulfide minerals ia ziac, lead—ziac, and copper—lead—ziac ores. Beneftciation of these minerals, usually by flotation (qv) or heavy-media separation, yields concentrates which are then processed for the recovery of the contained metal values. Cadmium follows the ziac with which it is so closely associated (see Zinc and zinc alloys see also Copper Lead). 

Charles, M. E. and CHARLES, R. A. Paper A12, Advances in Solid-Liquid Flow in Pipes and its Application, Zandi. 1, (ed.), Pergamon Press (1971). The use of heavy media in the pipeline transport of particulate... 

Density alone, heavy media In cyclones In cones In drums ... 

Heavy-media separation plants, 25 442 feed solids content in, 25 443-445 Heavy melting steel, 22 409 Heavy-metal additives, in PVC, 25 682 Heavy-metal alloy process, of tungsten recycling, 25 357... 

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. 

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