Mineral Processing Flowsheets
In mineral processing plant,A
general flowsheet involving almost all the unit operations pertinent to mineral
processing is shown in Figure 1. The others refer specifically to beach sands, lead zinc mining plant, molybdenum, and the
rare earths .
Processing of silica sands
provides a good example of the response of minerals to magnetic and
electrostatic fields. A generalized flowsheet for separating the mineral
constituents of beach sands is shown in Figure 2 . It will be seen that the
separation is essentially based on the differences in the magnetic properties
and in the electrical conductivity of the various minerals present in the beach
sands. The behaviour of some typical beach sand minerals, as for instance
magnetite, ilmenite, garnet, monazite, rutile, zircon, and quartz, in respect of their responses towards magnetic and
electrostatic separators. A reference is also drawn to Figure 3 which
exclusively shows flotation playing
the centrally important role in lead–zinc
concentration.
A schematic
flowsheet for molybdenum recovery from porphyry coppers is shown in Figure 4.
Here the important role is played by flotation. The first stage involves
collective flotation of copper and molybdenum. The floated product is upgraded
through two or three cleaning flotations. Finally, molybdenum is recovered by
depressing copper values. In order to depress a mineral, some kind of oxidation
should be implied on its surface, or residual flotation reagents are completely
destroyed. The removal of residual flotation reagents can be accomplished
either by heat (steam treatment or roasting), or by chemical means (oxidizing
reagents). Molybdenum remains essentially inert to these treatments, unlike
copper minerals. The rougher flotation which follows thermal/chemical oxidation
step yields molyconcentrate and depresses copper values to join as tails.
The current
rare earths resources are the base minerals, monazite, xenotime, and bastnasite.
The processing flowsheet of the mineral-bearing beach sand in Thailand is shown
in Figure 5 (A). The flowsheet for processing bastnasite mined from Mountain
Pass in California is shown in Figure 5 (B), and that proposed for
concentrating rare earths in the beneficiation plant of Baotou in China is
shown in Figure 5 (C). It is seen that flotation prominently figures in the two
flowsheets Figure 5 (B) and (C).
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