Home > Encyclopedia

Density Separation of Aggregate

Much aggregate is won from alluvial deposits laid down by rivers or glaciers. It is possible, although uncommon, that these deposits contain dense minerals of value e.g. ironstone, magnetite, chromite and even precious metals and diamonds--the 'placer deposits'. More usually, the objective is to reject weak porous rock types of typically low density such as chalk and lignite from the gravel. Two density separation processes that treat the relevant range of particle sizes (200-0.Smm) have been  applied: jigging and dense medium separation.

Diagram of a jig

Jigging has widespread application to iron ores and coal processing. The mineral particles are transported by water along a trough which is provided with a perforated base often fabricated from screening media . Repeated vertical pulsations of water cause the mineral particles to stratify according to density almost independently of particle size. The upper layer of low density porous mineral or lower layer of denser valuable mineral may be removed as appropriate. This process has been applied to beneficiate sand and gravels.

Dense medium separation employs a fluid of density intermediate between those of the two minerals it is required to separate. It is sometimes referred to as 'float-sink' separation. In place of a true liquid a suspension of a finely powdered dense substance, the 'media', is employed. In the popular processes a magnetic substance is used to permit its ready recovery from water used to wash the 'float' and 'sink' products. For suspension densities less than 2700 kg/m 3 the natural mineral magnetite (Fe304) is used owing to its low cost. Such suspensions will usually be adequate to remove weak, porous rocks as the float product from siliceous and carbonate aggregates. In order to remove ironstones as the 'sink' product a suspension of higher density containing powdered ferrosilicon alloy (FeSi) is necessary. The use of dense media or heavy media separation (HMS) upon aggregates was first reported in Canada in the 1950s during the period of extensive infrastructure construction and has since been applied in the USA, U K and Denmark. DMS has also been applied in Northamptonshire for the recovery of dense ironstone from gravel.

>>Previous: Washing and scrubbing of sand & gravel in Aggregate Plant

>>Next: Shape sorting of aggregate

Get Support & Quotation

Please fill in the form below(* are required). We will get in touch with you ASAP!

Concrete Plant Concrete Mixer Crusher Other

Solution

  • Aggregate Production,River Pebble or Cobblestone Sand Manufacturing LineRiver Pebble or Cobblestone Sand Manufacturing Line

    The manufactured sand made of river pebble materials has a wide applications in cement concrete, asphalt concrete and various soil cement (stabilized soil) materials and other road, tunnel, bridge and culvert engineering projects....

  • Concrete Aggregates Processing Plant,Sand and Gravel Processing PlantSand and Gravel Processing Plant

    A cone crusher is depicted as most suitable to crush very coarse rejects into the desirable size range of concrete aggregates. A ZS vertical shaft impactor may be used to increase the yield of sand....

  • The Aggregates Production Line for Highway Construction,Stone and Aggregate CrushingThe Aggregates Production Line for Highway Construction

    In the production line, Camelway technical staffs mainly configure the vibrating feeder, jaw crusher, hydraulic cone crusher, circular vibrating screen, vertical shaft impact crusher(sand making machine), belt conveyor, etc....

  • Concrete Mixing Plant for Concrete BlocksConcrete Mixing Plant for Concrete Blocks

    The production of concrete blocks on block machines has become one of the most popular industrial prefabrication methods in the construction sector worldwide. T...

  • Andesite Manufactured Sand Production LineAndesite Manufactured Sand Production Line

    The Andesite Manufactured Sand Production Line designed by Camelway Machinery has the advantages of reasonable configuration, high automation degree, low operation cost, high crushing ratio, low energy consumption, high productivity and simple maintenance...

Contact Us

Tel: 008637165861518

Fax: 008637165861528

E-mail:info@camelway.com

Mobile: 008618838109566

WhatsApp: 008618838109566

Skype: Camelway1983