what is dry mill plant in mining industry?

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what is dry mill plant in mining industry?..

Answer / bhyrappa.m

Dry milling is the most desirable solution but is seldom
implemented as most known extraction processes are wet,
i.e. flotation, leaching, gravity separation and heavy
media separation. Also the cost of dry milling is
prohibitive. There are however dry milling applications
that many operations do not consider and are unaware of.

The technology of high impact dry pulverisation has been
around for more than 20 years and was originally developed
for sugar and spice milling. It involves micronising
particles from 2 mm to 2 ?m in a single autogenous
supersonic velocity mid-air collision.

Milling in mid-air requires neither mill lining nor mill
media, needing only a compressor, which accounts for 80% of
all milling costs and this makes this system suited to
remote satellite milling plants.

In addition other benefits of dry milling are in some cases
completely underestimated. Because the method of milling is
different the subsequent extraction process, such as
flotation, can have different efficiencies. For example,
carbonates won't float as easily after dry milling and this
makes zinc flotation much more efficient. Sulphates float
more readily after dry milling.

Milling using this technology normally becomes more
economical where minerals need to be ground to below 50 ?m
and finer.

In Africa, Anglo Platinum was the first company to see the
benefit of high impact fine milling. A pilot plant recently
achieved an extremely efficient size reduction from 2 mm
feed to -45 ?m and this was done at five to seven times the
design tonnage (a reduction to -10 ?m was achieved without
modification upon start-up).