| DENSE MEDIUM SEPARATION: COAL | METAL PLASTIC AGRICULTURE |
For the most accurate
separation on all ranks of coal, from brown coal to
anthracite, ESR International can offer two types
separators, and at times it makes sense to combine both on
the same site. The dynamic effect separator deslimes,
rinses and eliminates the bulk of the shale, while the
dense medium separator creates a two-product output that
can be blended to satisfy the requirements of multiple
markets.
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The Blackett Barrel
From 1981 to 1990, ESR
International LLC specialized in the reclamation of
abandoned coal mine sites. By redesigning and modernizing
the old Blackett barrel technology popular in the North of
England as far back as the 1890's, and by adding up to
three stages of autogenous medium cyclones to rewash the
<6 mm fines, ESR was able to sell over 35 of these
dynamic effect separators in Holland, Germany, Belgium,
France, Serbia, the United States and China.
This dynamic effect
separator is bi-directional: a stream of dense water flows
down the barrel carrying the floats over multiple flights
of scrolls welded to the interior of the drum, and sinks
are screwed up and out the barrel in the opposite direction
by means of the same set of scrolls. The Belgrade Mining
Institute conducted a study to determine the separating
efficiency or Ecart Probable (Ep) of the dynamic effect
barrel with only one stage of cyclones. They reported an Ep
of 0.07. This ranks the ESR dynamic effect separator as one
of the most precise dynamic effect separators in the world.
Two of the largest dynamic
effect drums can be mounted side by side on a single site
to handle input tonnages as high as 1,000 TPH. A coal prep
site that might conventionally cost up to $25 M dollars
could be installed with dynamic effect barrels for as
little as $ 5 M dollars, handling all ranks of coal from
sub-bituminous to anthracite. On fairly easy washabilities,
a dynamic effect barrel is all that is needed. However, on
a difficult coal, where there is a large percentage of
near-gravity material, a dense medium bath is required.
The ESR Dense
Medium Drum
In 1985, ESR transformed
this dynamic effect barrel. The angle of inclination of the
barrel was changed from 7 to 3 degrees, and a cone was
placed on the float side, raising the medium level far
above the scrolls. This eliminated the dynamic effect and
converted it into unusually long, quiescent bath. When this
happened, the concept of a bi-directional dense medium
barrel was born. Here the EP situates at an amazing 0.003.
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Closely coupled to this new
dense medium technology is the technology of a counter-flow
device called a Scrubber-rinser. The scrubber-rinser does
away with vibratory screens, and contrary to what the word
Scrubber may imply, it effects a very gentle under-water
rinsing of the coal. The scrubber-rinser uses just a
fraction of the water used by vibrating screens equipped
with multiple banks of spray nozzles, and yet achieves a
level of efficiency in rinsing 10 to 20 times greater.
ESR International can also
offer a complete water treatment package consisting of
clarifiers (six [6] and nine [9] meters in diameter) and
filter belt presses (two [2] and three [3] meters in
width). An exciting application of this dense medium
technology lies in brown coal. Many types of brown coal
separate at relatively low densities, less than 1.3. Since
classical dense medium technologies employing magnetite
would be far too expensive for this low-grade coal, the use
of sand could make an enormous difference in the economics
of cleaning brown coal.
Capacities
The following are the capacities of various ESR dense
medium drums in coal applications:
- 4-foot diameter drum = 50 TPH
- 6-foot diameter drum = 100 TPH
- 8-foot diameter drum = 175 TPH
- 10-foot diameter drum = 275 TPH
- 12-foot diameter drum = 400 TPH