Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to the processing of asbestos
ores and more particularly to a spicule classifier ana
: concentrator for separation of the fibres in an asbestos
milling plant Conventionally in such a plantO pxepared
ore is first processad in a rock line in which thP fibre is
separated from gangue by breaking it up in iberizers followed
by screening to produce fibre concentrates which are further
processed in fibre lines conventionally comprising successive
stages of dedusting, scraening and fiberiæing.
The material entering the fibre lines ~rom ~he rock
line comprises opened and unopenad fibre spicules in various
forms and degrees of sepa.ration together wi~h debris and
contaminants. The s~paration of these various components
for further pxocessing or rejection as appropriate is one
of th~ functions of the fibre lines~ Some compon2nts have
proved rather difficult to separ~te: for example~ a proport.ion
of the fibre, ~epending on the nature of the ore, will be
in the form of 'needles'0 which axe needle-like bundles of
fibres o-f generally uniform diameter. Thes~ tend to become
matted toge'her with already separated asbestos ibre~ and
thereafter are dificult to xe~uce to their component fib~es.
The presence o a signiicant proportion of such needles i.n the
final product pre~ents the reinforcing proper-ties of th~
fibres from being fully realized.
T`he object of the pre~ent invention is to provide a
spi~ule classifier and concentrator for incorpox~t~on in a
fibre line ~hich can effectively ~lassify the various components
of an asbe3t.0s fibre concen-tr~te, including ne~dles, according
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: to the further treatment required. The use of suc'n a
classiier anables the remainder o~ the fibre line to be
gxea~ly simplified~
According to the inven~ion, a m~thod of classifying
an asbestos fibre concentrate comprises entraining ~he concentrate
in air forming the concentrate so entrained into a substantially
horizontal streamline flow sufficiently prolonged to permit
stratiEication oE different components of the concentrate
under the influence of gravi~y0 in a first sta~e of separation
capturing those components which sink to the bottom o~ the
rlow, and in a second stage of separation subjeating the
remainder of the flow to at least one stage of inertial
separation in which the direction of the air 10w is changed
sufficiently rapidly for components of higher inertia to
escape from the flow and be captured~ In prac~ice the components
captured from th~ bottom of the flow in the first stage of
separation are rock, coarse spicules and platy waste, and
- the components captured in the second stage ara cruay cleans
and needles, opened asbestos fibres and dust remaining entrained.
Th~ needles a~d already opened fibres are thus separatea and
prevented from matting in later stages o~ treatment.0 which
in turn enables the needles to be satisfactorily reducea
to opened fibre3~
A preferred form of apparatus comprises a casing
defining an entry section~ a first chamber, a sç~ond cha~ber
and an exit section, the entry section being a generall~
horizontally disposed streamlined duct having an entrance
arranged to receive from a rock line an air-entrain~d flow
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of fibre concentrat~ the duct having a gradual transition
into a horiæontally oblong exi~ into the first chamber,
the exit being positioned at tha top of one sid~ wall of
the ~irst chamher so as to direct a s~reamline flow of entrained
spicules towards a weir dividing the first cha~ber from the
second chamber, the height of the weir being adjusted so
that rocX, coarse spicules and platy waste will fall sho~t
of the top of tha weirD the second chamb~r having a deflecting
membex extending downwardly from its top wall so a~ to
cons~ain entraining air entering th~ chambe.r from the
previous chamber to foll~w a sufficiently sinuous pa~h
downwardq around the deflecting member that crudy cl~ans
and needles escape the entraining air and are ca~ured by
the chamber, the second chamber having an e~it for the
entraining air in its far wall beyond the deflecting
member and into the exi~ section~
The inventiQn is describea further wi~'n referenc~
: to the accompanying drawing, in s~hich:
Figure 1 is a plan view and Figure ~ is a ~er~ical
section through apparatus in accordance wi'ch th~ ir.vention.
: The apparatus comprises an inlet pipe 1 which
will usually be round and receives fxom th~ rock lin~ of
an asbestos processing plant an air-entrained asbestos Eibre
concentrateO This fibre concentrate will typically contain
about 80% b~ weight of a.sbestos fibres and the entraining
air should have a veloci~y of about 20 metres/sec, From
the inlet pipe which should b~ straight and substantially
horizontal :Eor a distance at leas-t 8 -t.imes its d.iam~terO
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the air entrained concentrate passe~ through a transition
member in the ~orm of a streamlined duct 2 which provides a
gradual transition from the cross-~ection of the pipe to a
horizontally oblong coniguration of substantially ~he same
cross-section. The flow through the pipe into the duct is
thus rendered streamline, with the result that the less readily
entrained components of the concentrate tend to gravitate
toward~ the bottom of the flow. These components are rocX,
coarse spicules and plat~ wa~te~
~rom the duct 2, the flow i~ dischar~ed through a
horizontally oblong opening at the top o~ one side wall 7
of a ix~t chamber 3. The opposite wall o this chamber i3
formed by a weir 8 comprising a vertically adjustable top
portion 9. The top portion 9 is adjusted so that at least
th~ bulk of the streamline ~low from th~ duct 2 clears the
top edge of the weir and enters a secona chamher 4~ whilqt
the components which have gravitated to the bottom of the
~low fall short of the weir and fall to the bottom o~ the
first cham~er whence they ~re removed through an air lock 10
and returned to the rock line for furth~r proce~sing. In a
typical case and with the xate o flow already specifie~J
if the opening in the top o the wall 7 has a height o~ 15 cm~
then satisfacto.ry results will be achie~d with a chamher
which is 60 cm wi~e, a~d in w~ich ths top of the weir i3 15-25 cm
short of the top wall of the chamber.
Ths air flow passing over the top of the weir i~
deflected downwardly b~ a curved quadrant-shaped derlector
mem~er 11 in the chamber 4 whenc~ it must again turn upwardly
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to reach an exit in khe far wall 12 of the chamber 4 to
reach a further transition duct 5 through which the entraining
air reache~ an outlet pipe 6. The change in direction of thP
air flow around the de~lector member 11 causes a centrifugal
force to be applied to the entrained material which, i the
: rate of change of direction is coxrect will be sufficient
to cause crudy clean fibre and needles to escape from the
flow towards the bottom of th~ chamb~r 4 whilst leaving du~t
and already ~pened fibres still entrain~d. With the 10w
rate previou~ly cons.idered, a deflector member 11 with a
radius oE about 40 cm should provide sati factory re~ults,
The crud~ clean fibre and needles are removed through an air
.~ lock 13 ~or further treatment in a fibre line, and the air
~ stream leaving throu~h the exit pipe 6 is passed through a
cyclone to remove the opened fibres and thence ~reated for
dust removal by conven-tional techniques~
A further second chamber or chambers, including
d~flector plates and operating as previously describe~, may
be utilized if necessary, to achi~ve a greater deyree of
~0 s~paration: ho~sver, it is believed that a sin~le sacond
chamber will usually be sufficient,
It is ound that by using the separator describ2d above
as the ini~ial stage of a fibre linP in an asbes-t.os fibre
proce~s~ing plant, the nu~bsr of stages of treatment in the
f.ibre line ma-~ be greatly reduced~ and the risk of needle~
becominy matted with opened fibre~s i~ greatly reduced~
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