Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
111 5663
Thi9 invention relates to a separator for separating particles
of different tensities, by treatment o~ suope~s;ons of the particles
in a liquid, ant concerns separation of suspensiono containing
material di~tributed over a ran8e of density and/or particle sizeq
The invention ls especially concerned with the treatment of suspended
material of very small particle size such as for example sand
tailings from mineral dressing equipmRnt which in current practice
are normally discharged to waste even though they contain valuable
metallierous componentsO For exampleg sand tailings from a typical
10 mill might range from 20 Briti~h Standard mesh to 400 mesh with small
proportions even finerO
In our UoKo Patent Specif;cat;on NoO 1,174~405to Mozley published
Dec. 17/6Q there is described a gravity separator which was developed primarily
to handle tin bearing slimes to recover residual tin which at that time
could not be recovered with existing equipment of conventional type.
Apparatus in accordance with U.K. Patent Specificatlon No.
1,1749405 has been available and extensively used for same years
and has given excellent performance ena~ling very considerable
oavingo to be mate in the tin min;ng and other industriesO The
principle of operation of the apparatus of U~Ko Patent Specification
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NoO 1~1749405 i8 that of adjustlng shear conditions in a flowing
suspension by applying a shak;ng motion of variable amplitude and
frequency in order to cause he~vier material to remain on a moving
surfaceg and form a close packed deposit or bank, whilst the finer
particles remain in suspension and advance along the surface~ The
decks are freely suspended and are moved by a vibratory shaking
action using an unbalanced~weight drive which~ although simple and
reliable~ is such tha~ the path traced out by the decks with a given
weight rotatlng at fixed radius will undesirably vary according to
the total shaken weightO In cer~ain applications9 it has also become
neces~ary to employ lower frequencies and then9 particularly when the
frequency employed approaches the natural frequency of the app~ratus,
control problems can ariseO Accord;ng to the invent;onD a separator
for particles of d;ffering densities ha~ all the following features
(a) to (e) 8
(a) Two sloplng surfaces each have a supply to the~r upper
regiOns o particle~ to be separateda in the form of a flowing
~u~pension in a liquidO
(b) The two surfaces are mounted side by-s;de with their sloping
directions parallel and are arranged to perform a repetitious
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non-discontinuous horizontal mo~ion generally orthogonal to their
slopeO
(c) The lower ends of ~he surfaces drain mto separate
collecting arrangementsO
(d) The motion is im~arted to the 6urfaces by a positive drive
causing the mot;on to follow a path independent of the weight on the
sur~aees 0
(e) The separator i~ arr~nged to follow a cycle of operations,
with the mot;on applied to ~he surfaces throughout9 in a first phase
of which one surface i~ receiving the guspension while the other
surfaee receives a~ a eomparable ra~e the suspending liquid without
particlesD followed by a ~hange in shear conditions on that other
surface to flush off the partieles still remaining on it, the sècond
phase being a reversal of roles of the surfaces~ the two phases
alternating~ the collecting arrangement~ separating different
time-intervals of particles draining into themO
ThusO in general terms~ the present invention provides a gravity
separator designed to apply an o~cillatory motion in a transverse
direction rela~ive to ~he progressive movement down a slcpe of a
ZO flawing suspension 3nd capable of operating a~ high amplitudes, eOgO
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at least I cmO and pos~ibly a~ large as 20 cm or more~ and preferably
from 4 to 18 cmD for example 5 to 15 cm~ or 6 to 12 cmO Thi8
apparatu~ comprlses ~wo sloping separa~;ng surfaces each receiving
material to be treated~ hereinafter termed "decks"~ mounted side by
side and arranged to perform a repetitious non~d;scontinuous
horizontal motion eOgO linear~ orbital or other oscillatory motion~
preferably simple harmonic motion~ in a generally transverse
direction relative to the slope of the deckO Jerky mo~io~ ~ust be
avoidedO The decks are driven by a positi~e drive which c~uses the;r
motion to follow a path ;ndependent of the we;ght of material
deposlted on ~hem fr3m the suspension being treatedO The positive
drive also avoids problems of loss of controL a~ lower frequenciesO
In the gravity separator according to the presen~ ;nvention the cycle
of operations i~ 80 organised that at any one time one of the decks
is functioning as a collect;ng ~urface on which banking of heavy
deposits i8 tak;ng pla~e~ whilst on the o~her deck prev;ously banked
material ;8 be;ng further separated and is then removed by al~eration
of the ~hear conditions thereon to cause banked material to be
resuspended in a stream of washing l;quidO Consequently~ the
apparatus enrails means for adJusting the shear rondition~ on each of
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the decks preferably by alteration of 810pe and/or by adjustment of
amplitude and/or by ad~usting frequency of oscillation; the
last-named for example by interchangeable drive belts or a gearboxO
The simplest arrangement 18 one in which the two decks share a common
subframe and thus are driven by a common drive means and shear
contitions are altered by adjustment of slopeO However, because the
two decks are operated for the most part in sequence, they may be
arranged to be driven independently thus giving more flexibility in
selecting running conditionsa eOgO amplitude and frequencyO To save
floor ~paceS there may be ln place of each deck a stack of (for
example 4 or 6) decks fixed on top of each other, each receiving its
own supply of material to be treated~ but each discharging into a
drain common to that stackO
The slope (when running as a collecting surface) is preferably
15 within the range l03 to 205, more preferably 105 to 202, most
preferably I o6 to 2 0 The frequency of oscillation i5 preferably
within the range of 008 ~o 3 ~Za more preferably 105 to 2 Hzo If the
atep of flushing (removal of banked solids) entails altering the
alopes the 810pe then may be 10 to 60a eOgO 30 to 45o
The in~ention will now be descr;bed with reference to the
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accompanging drawings~ in which
F;gure I is a plan vlew~ Figure 2 an elevation and F;gure 3 an
end elevation of one embodlment of a separator according to the
lnvention D
Figure 4 is an elevation of part of a second embodlment,
F;gure 5 i8 a perspect;ve schematic view of a third embodiment~
and
Figure 6 iB an end elevat;on of the embodiment of Figure 5, in
its rest pos;tionO
Turning ~o Figures 1 ~ 3~ the separator comprises two plane
decks A and B of wld~h 105m and of length 102m and with upturned ~ide
edgesO The deeks A and B are mounted s;de by side on support
~ub-rames 1 su~pended by vert;cal support wires 2 from a support
frsme 30 A s;ngle ~ubfrsme I common to both decks is also possibleO
1~ under certa~n operat;ng condlt;ons there appears a tendency for
the wire~ 2 to spring or ~lacken cycl;cally~ causing the decks to
bvunceD ~he wires can be augmented or replaced by floor-mounted
pneuma~;c ~tiffening rocking atruts~ Horizontal longitudinsl
restraining wires 4 also connect the sub-frames 1 to the support
rame 3 80 that the sub~frames 1~ and hence the decks, cannot move in
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the longitud;nal directionO The w;res 4 may be augmented or replaced
by transverse rails welded to the subframes 1, the rails running
between floor-mounted roller guides~ The deck~ A and B are mounted on
pivots 5 a~d are adJustable in slope by means of tilt p;stons 60
The decks are driven by a common drive comprising pusher rods 7
driven by a cranked drive shaft 8 off a motor 90
At the top end of the sloping decks D shown on the right in
Figure 3~ is mcunted a suspens;on feed dev;ce comprising a feed pipe
lO supplying a two compartment feedbox 11 leading through flexible
ducting 12 to the top end~ of the decks A and Bo
At the boet~m end of the decks, receiv;ng material flowing off
the bottom of each deckD is a drain ;n the form of a funnel 13
feed;ng through a spli~ter dev;ce 14 into appropriate channels 15 for
the further dispos;tion of concen~rate a middl;ngs and tailingsO
In typical operationD a suspen~;on of tin~bearing sand is
initially fed into one compartment of the feedbox 11 and hence to the
upper end of deck A wh;ch is osc;llated w;th appropr;ate frequency,
zmplitude ~nd slope to collect (bank) a deposit of material comprised
of the particles of a higher densityO
Suitable condit;onsa as a guide~ have been found t~ be as
~'
1~15663
follow~, subject to the f;nding that the wider the deck9 the larger
should be the amplitude ant the slower the frequencyO
Particle ~ize to be collected Frequency Amplitude Slope
finer than 300 mesh BS 1.72~z 705cm 13/4
coarser than 50 mesh BS lolOHz 14-l5cm 13/4
In general, the f m er the particles~ the higher the fequency and
the lower the amplitudeO
Perhsps IOZ of the solids feed may thus be banked until a
rea onable thickness of bank9 perhaps 005 cm - 2 cm thick, is built
up. The feed is next diverted through the second compartment of
feedbox 11 to ehe upper edge of deck B which then starts operating in
the manner just de-cr;bed for the f;rst deckO Meanwhile wash water is
~upplied to deck A (which ~ontinues at the previous frequencyg
amplitude ant slope) and the splitter 14 is set first to direct the
product of deck A to tails~ then ~hen the grade of the deck A product
approaches the feed 8rate it may be directed to middlings~ ant to
teck B (po~sibly with thickening by a cyclone)0 Wa~h water flow (and
feed flow) may be adjusted for optimum performance9 and are
pr-ferably fr~m 1 to 2 litre~ per mi~ute, for example 105l/minO The
~, 20 third phase of the cyclical operat;on is the discharge of the banked,
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washed concentrate on deck A into its drainO This i8 achieved by
operating the tilt pi~tons for deck A to increase the slope from
(say) 13/4 to 40 and adju6t;ng the flow of wash water until the
banked material i8 effectively dislodged on the deck (flushed off, in
other words) and passes through the splitter device to recoveryO
Other ways of removing the concentrate would be by greatly increasing
the frequency or amplitude or bothO A typical repeated cycle may
involve an 8 minute period tcould be say 6 to 10 minutes) throughout
which frequency and amplitude conveniently remain unchanged, as
followsO
Deck A Deck B
O - 3 ~upplied w;th feed irrigated with wash water
3 - 4 suppl;et with feed deck slope increased and
concentrate flu~hed off
4 - 7 lrrigated with wash deck restored to slight
wster slope and supplied
with feed
7 - 8 deck slope increased feed supply continues
and concentrate
flu~hed offO Deck
reatored to
slight slopeO
' ,
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Referring now to Figure 4~ the drawing ~hows one arrangement for
varying the amplitude of oscillationO The deck 20 is supported by
tilt mechanisms 21 on a sub-frame 22 which is suspended by suspension
S wires 23 from a support frame 240 Fixed to the sub-frame 22 is a
bracket 25 to which there is attachet a connecting rod 26 which
actuates the sub-frame 22 to perform a linear reciprocating motion.
The connecting rod 26 is secured at its other end to a block 27 which
is slidable along an arm 28 connected at its lswer end to a fixed
pivot 29~ At its upper end the arm 28 is hinged to a link 30 which is
connected to a crank 3to The crank 31 is dri~en by means of a
variable speed 750U motor 32 through a belt drive arrangement
indicated generally by reference numberal 330 The motor 32 is secured
to the support frame 240 Block 27 i8 movable along the arm 28 by
t5 means of a pneumatic ~ylinder and piston assembly 340 In operation
the arm 28 performs an oscillatory angular movement about the fixed
pivot 29 and therefore the throw of the connecting rod 26 and hence
the amplitude sf movement of the de~k 20 is dependent upon the
position of the block 27 on the arm 280 The above arrangement can be
duplicated for each deck and the other de~k (not shown) can therefore
~ .~
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be independently varied a~ regards amplitude and frequency of
oscillation through its own independent dr;ve systemO ~ariation of
amplitude can be achieved through operat~on of the piston and
cylinder aæsembly 34 without stopp;ng operation of the equipmentO
In;tiation of the changeovers every few minutes may be by linked
pneumatic timers which may be variable pneumatic timers which may be
variable to permit variation of the total cycle time and the
individual components o ito
Instead of single decks A and BD vertically stacked banks of
decks A and B are envisaged to provide increased throughput~ as in
Pigures 5 and 60 Each deck has its own materials eed l2l and the
clean-water feed (for wash water and al80 for flushing) i8 separately
fed through individual flexible tubes 12aO The latter feed 12a need
only be to a single point ln the upper region of each deckO The
former feed 12 i8 distributed over the width of each deck~ but that
it i~ alway~ ~u~pens~onD not alternating with clean water, gives
advantage~ in switching and in keeping issu;ng ~ets unblockedO
All the decks in a bank drain via a collecting board 40 common
to that one bank into one o two ~unnels l3a9 13b depending on the
deck slopeO
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Each feature of any one of the embod~ment~ shown may be adapted
for use in relat;on to any of the other embodimentsO
