Note: Descriptions are shown in the official language in which they were submitted.
~002835
, . ,
The present invention relates to a method of separating a
substance from a liquid by binding the substance to a particu-
late material. By a particulate material is meant in this
connection any suitable material in a finely divided form, thus
5 comprising not only solids but also particles of a more or less
liquid material, for instance gel particles. The particles may
be porous or impervious to liquid. Preferably, they are
~ chemically stable, and in certain applications of the invention
: they have to be inert to the liquid, with which they are to come
10 into contact, and/or to the substance or substances which t,hey
are to separate from the liquid. Even if the particles may have
any suitable form they are preferably spherical and substan-
tially of the same size.
., .
15 Separation by means of so called liquid chromatography tradi-
tionally means that a liquid, from which a substance is to be
separated, is caused to pass through a treatment chamber filled
with a lot of small particles retained closely packed together
in the treatment chamber between two perforated end walls. The
~ 20 liquid thus has to flow through the interspaces between the
J, immobilized particles, the substance to be separated being
retained by means of the particles by adsorption at their
8urfaces or in some other way.
25 A problem in connection with this separation technique is that
the flow resistance for the liquid is very large in the inter-
spaces between the particles. The smaller the particles are, the
larger this flow resistance will be. The liquid thus has to be
highly pre6surized to be able to pass through the interspaçes
~ 30 between the particles. The problem is accentuated by the fact
3 that the particles preferably are made as small as possible,
since a certain volume of packet particles exposes a larger
total particle surface to a through-flowing liquid the smaller
~ the particles.
.
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--` Z~)02835
For ~hese reasons it ls difflcult to provide for acceptable
costs a separation plant having a large separation capacity,
and the described separation technique, therefore, is mainly
utillzed in a small scale, e.g. for analysing purposes or for
the separation of very small amounts of very expensive
substances.
As an alternative to the above described separation technique it
has been suggested that a liquid, from which a substance is to
be separated, be supplied to the lower part of a treat-
ment chamber containing a bed of particles, which are free~to
move relative to each other, and then be caused to flow through
the bed of particles from below , upwardly in a way such that
the particles are maintained in a fluidized or suspended state
within the treatment chamber.
A fluidizing technique of this kint would require a smaller
overpressure of the supplied liquid than the previously
described separation technique. However, the capacity of a
separation plant in this case woult instead be limited by the
I fact that the flow velocity of the liquid through the bed of
¦ particles could not be too large. This flow velocity must not
¦ be larger than that required to retain the particles in the
bed by gravity and not b~ elltrained by th~ ~pwaraly flow~ing
liquid and thereb~ carried out of the treatment chamber.
One further technique suggested to bind a certain
subtance in a liquid to particles resides in keeping the
particles suspended in the liquid by agitation for some time
ant then - after the particles have attracted the said substance
in the liquid - separating the particles from the liquid by
gravity separation or centrifugal force separation. A disadvan-
tage of this technique is that it will take a relatively long
time to create the required contact between the particles and
~ 35 all parts of the liquid for the separation of the substance
i therein-
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The present invention provides a new
method of sep&rating a substance from liquid by blnding the
substance to small partLcles, which method makes it possible
to obtain a substantially larger separation capaclty than the
5 above described methods and, thus, can be used in a much larger
scale than these methods. The invention also
enables the use of substantially smaller pa~ticles than could
be used ln the prior art.
10 These results are obtained according to the invention by
keeping a body of liquid having a predetermined density in
rotation together with small particles having a density lower
than that of the liquid, and by bringing liquid, from which said
3 substance is to be separated, into contact with the particles in
15 a way s~ch that the particles are maintained suspended in the
rotating liquid.
,:
The invention consequently resides in keeping particles lighter
than a liquid in a suspended state in a rotating liquid body,
20 while the liquid, from which a substance is to be separated,
is caused to flow past the suspendet particles.
'~ If desired, the partlcles may be kept suspended in the whole of~, the rotatlng llquld body. Preferably, however, the partlcles are
25 kept suspended only in a layer of the liquid body, the liquid to
~ be freed from said substance being caused to flow through the
q suspensi~n layer. The main part of the liquid should flow bet-
ween the suspended particles in a directi,Qn from the rotational
;j axis of the rotatlng liquld body outwardly towards the radially~ 30 outermost part of the liquid body.
.. . .
~ Slnce the particles are lighter than the llquld, the particles
; suspendet in the liquid will try,due to the centrifugel force,to
;~ move radially inwards, the force influencing the particles in
~ 35 this direction being larger the furtherfrom the rotational axis
:~;, ,. ; , . -
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the particles are situated. Therefore, the supply of liquld from
which said substance ls to be separated may be made very large
without any risk that the particles should leave the treatment
chamber together with radially outwardly flowing liquid. The
force to which the particles are sub~ected by the flow of the
supplied liquid is independent of the distance between the
; particles and the rotational axis.
If the particle size would vary somewhat in the suspension
layer, this does not matter very much, since extremely small
particles which are easily entrained by the supplied liquid will
still be retained in the vicinity of the other particles as a
consequence of the radially outwardly increasing centrifugal
force. By the same mechanism a particle is immediately returned
ratially inwardly, if it has been influenced by occasional
forces and been transferred too far out from the rotational
axis.
The liquid body kept in rotation may have any desired shape.
If it has a shape such that the through-flow ~ection for the
supplied liquid increases radially outwardly, the balanclng
effect on the suspended particles will be even larger, since
the force acting on the particles and caused by the flow of the
liquid in this case decreases with increasing distance from
the rotational axis of the liquid body, whereas the centrifugal
force, acting in the opposite direction, increases.
An increasing through-flow section for the supplied liquid may
be desirable, particularly in the radially outer part of the-
suspension layer, for safe retainment of the particles therein.In the main part of the suspension layer it may be desirable,
however, to have instead a radially outwardly decreasing
through-flow section for the supplied liquid. Thereby, namely,
it may be accomplished if desired a substantially uniform
distribution of the particles in the suspension layer along the
.~ . . - . , .
2002835
flov path ofthe llquld thercthrough If the partlcle~ h~ve -
cert~n ~lze dl~trlbutlon, tbld haJ to bs conrldered ln
connectlon wlth the p1~ning of tbe flo~ path of the liquid
throu~h the 4u~pen~10n l~yer or e~tabllRhIn2 ~ de~lrea
dl-trlbutlo~ o~ the partlcle~ ther~ln
ould be ob~lou~, ~ny deslr~d di~tance botween the psrticl--
in the ~u8pe~100 layer ~J b- cco~pll~hed b~ ~ ~ult~bl~ cholcc
of centrlfug~l force ~ehlD 8~t llquld flow through the ~u~p~n-
~lon lAyer ~hl~ tlst~nce mAy ~ou bc chnng~d by controlllng ofthe cenerlfu~al ~orce ~nt/or the llqult flo~ durlng the co~r~o
of the ~cpArntlon procs~-
If tesired, lt 18 po~s~ble by uoln~ p8rtlcle~ of dlfferent ~l~es
to obtcln dlfferent (oep8rste or overl-pplng) l-~er~ of ~urpen-
ted psrtlc1-~ ln the rotatlng llquld body. ~ could be 8~ful
ln conne~tlon wlth b~tch-~ise u~e of partlcla~ durlng a ~cp-r-
~
i tlng operselon 1~ order to ll~lt the r-dl-l ~ove~ent of tb~
particlo~ wlthln the ~uspenslon l-yer of the rot~tlng llquld
boty
Atv~nt~$oou-ly, o con~8ntloo-1 c-ntrli'~g~ p r-tor bal~ only
ln~lgnlflc-ntl~ ~odl~l~d -~ bc ~ed for eh~ p~rfor~ln~ of the
cthod ~ccordln~ to th~ ln~entloo~ both oald llquld ~nd tbe
p rtlcles belng kept ln rot-t~oo 1~ the i~or~ of ~ ub~t~ntlelly
~nnul~r body
Th~ lo~entlon ~ay be u~ed lo coonoctlo~ wlth ubst~ntl~
ep-r-tion proce~e~ of ~ klnd ln ~hlch coo~ntlon-l liqu~d
cbrc~tography could co~e ~nto qu-rtloa Furth-r~ore, the
lnventlon ~ke~ lt po~lble by ee-~ of th~ ~epar-tLon technlqu-
her~ ln qu&~tlon to re~olve - y cp-r-tlon problemJ ~hlch at
pre-enc cannot b~ recol~ed ln ~ econo~Lcall~ ccept-ble vCg
Thu~, the ln~ntlon nake- lt por~ble ~n an lndu~trlal ~c-l~ to
~parate ~ery ~all ~ount~ of ~clu~blQ or hA~mful ~ub~tance~
.~
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fr~ l~r~e ~ount~ of hesvlly t~lut-t ~olut~on- ~or IQ~t~nc~,
th- lnvent~on ~y b- u-ed for ~xtr~ctln~ v-l~ blc net~ uch
s p ld nd ~llvor, fro~ ~olutlon~, or ~or ostr-ctSng proteln-,
polypoptlde~ or a~lno~cld- fro~ blotechnlcal proce-- llquld~.
Al~o c-rbohy~rate~ snd llplde~ ccn be extracted. Furtber-ore,
the qu-l~ty of cort-ln trln~r, uch 4 be~r or ~lne, ~ay be
l~proved by re~oval of cert~ ubat-nce~. Another o~
th-t wa~te ~ater nay be purlfl~t fro~ uod-Rlrod ~ub-t~nce~, ~uch
a~ heavy ~etal~, phenole- or cy-nldo, befor~ lt 1~ du~ped 1~ ehe
n-ture
:.
The cholce of ~Aterl~l foe the p-rtlc~-~ to ~e u~ed ~c~ to b~
c~de wlth reg-rd to tho llqu~d ~ro~ ~hlch a ~ub~tance ~hould be
~ep~rat~d and to ~ald ~ub-tanc~. Slnc- ~Ang proces~ llquld- h-vo
15 a tens~ey of about 1,0 g/c 3. p~rticloc h-vl~ d-n~ley low-lr
than 1,0 g/c~3 often have to bn ¢h4~0n. Then, dlffer-nt ~l~dr
of pla~tlc ~terl~ y co C icto que~tlon. rOr ln~tcnce pol~-
- ethene or polypropene ~sy be u~ed A~ a b sic o terl-l ln tho
partlclc~. ~o~Qver, ~at-rl-l ha-vler th-n 1,0 g/c~3 ~y b-
20 u~e,ll, if partlcl~ of l~uch -terl-l re e~pJInte,a by ~e-n- of
pre~iou-ly known t-chn1qu~, c~h th~t they wlll conteln a Sac ol
on- ~lnt or Aaother P~rtlcl-c of thl- ~lnd bc~g de7~clt~ e-
lo~ ~ 0~04 s/c~3 ra A-~ll-bl~ on thc u-rktt.
25 I7~ th- a~o- u~nn-r ~ n-r~lly bno~n In connectlon ~lth
con~cAtlo?~al llqult chro~to~raph~ tho p FtlCl~ to bc u-ed for
th~ m~thod cccordln~ eo th- Inv ntlo~ aors-ll~ h-vc to S~
pr-p ect cuCh th t they ca~ attr-ct or b~nd a cubstc~c- to bc
~e?p r-tod froo llquld. In on~ v~ or ~noth-r - of c~vcral
30 ~no~n ~ay- - t~c p~rtlcle- r- glv~n ?~ ctl~e ~urÇ-c~ ~bleh
` for ln-t-nce chc~lc-lly or ph~lccll~ olnd -~d ~bc~ancc
i to ehe p-rtlclec, ~hen llquld ~at~ l~to cont~ct there~lth, ~or
? ln~t-ncc, lt 1- po--lbl- to ~1~ th- p~rtlcl~ urf-ce- c-rt d n`? chJrRln~, ~0 th-t th-~ c n tt~ ct nd blnd p~rtlcul-tc ~ub-t-n-35 c~ h~ln~ thc oppo-lta ch rslns ~lon e~chc~ge technlqu-). E~e
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2002835
6 a
~ell known pr~ncl~loo ~or oo cnll~t fflnl q -chrooatoaraph~,
hydrofob~c lnter~ctlon, tc , ~Ay b~ uuod ln connectlon wlth
the pre~ont lnventlon~
It 1~ o po~lble to uoe p~rtlcl~- hevlng the blllty of
ab-orblng a ~ub~t-nce ln llq~ld. In euch c~eo~ the aubst-nce
penetr~tes lnto th- p rtlclo body ln quo~tlon, ~her- lt 1
reta~ned~
AA ln connectlon wlth conventlonal llq~ld chro~ tography lt 1-
often de~lred that the p-rtlcl~e u~ed at the oepar-tloD ~ethod
; ccordlng to the inventlon can b re~od ~oy tl~eo ~orreepon-
tlng technlqueo ~a~ be ~eot ao ln connection vlth convent~onnl
~i llquld chro~tography ~or ~r-olD~ ~hc p~rtlelec froo oubot-ncee
lS h-vlng bcon bound to the partlcl~- durlng ooparatlon proce~.
She p rtlcle ~lze ~hould b- a- 04~11 ae po~lble but ha- to be
d-ptod to the cho-en co~bln~tlon of tho accoopll-hed contrl-
~o~al forc- nd tho ~gnltude of the ISqlsd ~lo~ ln the ccntrl-
_..
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20~Z835
fugal field ln question. Preferably, particles in the magnitudeof 0,1 - 10 ~m are used.
The invention is described in the followlng wity reference to
the accompanying drawing. In the drawing fig 1 shows schemati-
cally a so called open centrifuge rotor of a ki ~ that can be
used upon application of the invention. Fig 2 6hows a pa~ of
; the centrifuge rotor in fig 1 somewhat modified. Fig 3/shows a
so called closed centrifuge rotor that alternatively can be used
upon application of the invention.
Fig 1 shows a part of a centrifuge rotor comprising a rotor
body 1 supported by a vertical drive shaft 2. The rotor body 1
defines a separation chamber 3, in which a stack of conven-
tional frusto-conical separation discs 4 18 arranged coaxially
with the rotor. The stack of separation discs 4, which have ,~
axially aligned 80 called tistributing holes 5, rests upon a ~-
conical bottom plate 6. This plate has corresponding holes 7
aligned with the tistributing holes 5. The bottom plate 6 forms
~ 20 together with the lower part of the rotor body 1 a chamber 8
¦ which communicates with the separation chamber 3 through the
hole~ 7 in the bottom plate 6. A channel 9 extending axially
through the drive shaft 2 opens into the cha~ber 8.
;~ 25 A conical partitlon 10 delimiting together with the upper part
of the rotor body 1 a number of channels ll rests upon the stack
of separation discs 4. The channels 11 extend from a radially
outer part of the separatlon chamber 3 towards the centre of
the rotor and open in a first outlet chamber 12 formed by the
radially inner parts of the rotor body 1 and the partition 10,
respectively.
Radially inside the first outlet chamber 12 the radially inner
part of the partition 10 forms a second outlet chamber 13. The
separation chamber 3 communicates through an overflow outlet 14
; with said second outlet chamber 13.
$
. ~ . . ~ . .
~002835
Both of the outlet chambers 12 and 13 are formed as radially
inwardly open annular groves, and lnto these groves there extend
stationary outlet members 15 and 16, respectively, which nay
have the form of conventional 80 called paring discs. Both of
the outlet members are supported by a stationary inlet pipe 17
extendlng from the outside of the rotor into a central inlet
chamber 18 in the rotor, formed radially inside the frusto-
conical separation discs 4. The part of the inlet pipe 17 that
is situated in the inlet chamber 18 is perforated, 80 that a
liquid supplied through the inlet pipe may be sprayed radially
outwardly and be distributed along the axial extension of the
inlet chamber.
At the radially outermost part of the separation chamber 3 the
rotor body 1 has a number of outlet openings 19 evenly distri-
buted around the rotor axis. In a manner known per se these
outlet openings may be arranged to be opened and closed during
operation of the rotor.
During operation the above described centrifuge rotor will
contain both llquid and very small particles having a density
less than that of the liquid. The liquid will form a rotating
body filllng the largest part of the separation chamber 3
comprlslng the spaces between the 8eparatlon discs 4 and part
of the central inlet chamber 18, and the particles will be
su8pended ln a cyllndrlcal sleeve formed layer 20 of the liquid
body sltuated close8t to the rotor axls. The layer 20 extends
radlally inwardly to the level of the overflow outlet 14, where-
by llquld supplled to the rotor through the lnlet plpe 17 wlll
be sprayet agalnst the lnslde of the layer 20. The layer 20 may
be dlvided in separate sectors by means of radially and axlally
extending entrainment wings (not shown) supported radlally
lnside the separatlon dlscs 4 by the bottom plate 6 and the
partltlon 10.
: ~ . - . . ..
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' ', ',''' ' , ' - ` ` ' ' -
- 200283~;
~he centrifuge rotor in fig 1 is intended to operate in the
following manner.
Liquid from which a certain substance is to be separated is
supplied through the inlet pipe 17 and is sprayed towards the
inside of the rotating sleeve formed liquid layer 20 containing
particles. By this liquid supply the particles will be main-
tained in a suspended state in the rotating liquid body. The
larger the liquid supply through the inlet pipe 17 is made, the
larger distance will be obtained between the particles in the
liquid body.
During the passage of the supplied liquid through the layer 20
it is brought into effective contact with the particle surfaces
which are prepared in a known manner to attract the substance to
be separated from the liquid. When the liquid has passed through
the layer 20 and been freed from all or part of said ~ubstance,
it flows further on radially outwardly through the spaces
between the separation discs 4 to the radially outer part of the
separation chamber 3. From there the liquid flows through the
channels 11 radially inwartly to the outlet chamber 12, from
where lt i8 removed by means of the stationary outlet member 15.
During the separating operation described above new particles
may be supplied to the rotor and used particles may be removed
from the rotor either continuously or intermittently. New
particles can be supplied through the channel 9 in the drive
shaft 2 and, through the chamber 8 and the distributing holes 5,
be pumped into the spaces between the separation discs 4.
Supplied new particles will thus move countercurrently relative
to the liquid flowing radially outwardly in the rotor. Hereby, a
corresponding s~ount of particles having separated the above
mentioned substance from the supplied liquid is displaced out of
the inlet chamber 18 through the overflow outlet 14 to the
outlet chamber 13. By means of the stationary outlet member 16
the particles are removed from the outlet chamber 13.
,: ~ ;` - . . ' !. ~'
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2002835
Accordlng to an alternative way of intermittently displacing
particles out of the separatlon chamber 3 the outflow of llquld
through the 6tatlonary outlet member 15 may be lnterrupted
temporarily, while new liquid contlnuously is supplied through
S the lnlet plpe 17. Then, the liquld ~urfaces ln both the outlet
chamber 12 and the separatlon chamber 3 (or the lnlet cha~ber
18) wlll move radlally lnwardly.
New partlcles are preferably supplied to the centrifuge rotor
suspended in a llquid of a suitable kind, for instance a part
of the liquid having left the centrifuge rotor after having been
freed from the above said substance. In a known manner particles
having been used ln the descrlbed separatlng operation, l.e.
having been discharged from the centrifuge rotor through the
outlet chamber 13, may be reconditioned and be used anew. Upon
need the particle suspenslon supplied to the rotor through the
channel 9 may be more tiluted, i.e. contain less particles per
unit of volume of the particle suspension, than the particle
suspension discharged from the rotor by means of the outlet
member 16. The composition of the discharged particle suspension
is determined by the particle density that is used in the layer
20 of partlcles fluidized ln liquid.
By use of conical separation discs 4 of the described kind
particles havlng for its ob~ect to attract the said substance in
the supplied llquid may be effectlvely prevented from belng
entrained by liquit too far on lts way radially outwartly in the
rotor. However, it may be sultable to dimension the separation
dlscs in a way such that a large part of the particle suspension
is formed radlally inside the separation discs in order to avoid
that the particle suspension will become too dense.
It has been assumed above that the centrifuge rotor has a
separate inlet for new particles. Alternatively, new particles
may be supplied to the centrifuge rotor through its ordinary
. ` . -''' " ' ' . - ' . .
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. . -.
20~)2~335
11
inlet for the said liquid, i.e. they may be mixed with the
liquid before it ls supplied to the centrifuge rotor. Fig 2
shows an embodiment of a centrifuge rotor arranged for supply
of new particles in this way.
Fig 2 shows a perforated inlet pipe 17a supporting an outlet
member 16a. The outlet member extends radially outwards in an
outlet chamber 13a, which through a number of holes 21 in a
partition 22 communicates with the separation chamber of the
rotor. The holes 21 are placed at a level radially outsite the
free liquid surface formed in the inlet chamber lôa by the
liquid body rotating therein.
In the ratially innermost layer of the liquid body, which layer
ls designated 20a in fig 2, the particles are maintainet in a
suspentet state by supply of liquit through the perforatet inlet
pipe 17a. As can be seen, the partition 22 extends radially
inwartly to a level insite the layer 20a, so that the particle
suspension cannot flow into the outlet chamber 13a any other way
than through the holes 21. These are situated at the level of
the ratially outer part of the layer 20a.
In the embodiment shown in fig 2 the centrifuge rotor has
frusto-conical separation tiscs 4a, which at their radially
2S innermost edges support annular members 23 extending substan-
tially horlzontally. The members 23 have a ratially outwartly
increasing thickness, whereby the interspaces between them
converge ratially outwartly. This is a design of the members 23
enabling that a substantially unchanget or even tecreasing
throughflow section may be provided for liquid flowing radially
outwardly through the layer 20a of the particle suspension.
The members 23 have holes 24 axially aligned with each other and
with the holes 21, whereby particles having separated a certain
substance from the passing liquit may leave the layer 20a at the
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20QZ835
12
actual radial level and flow out lnto the outlet chamber 13a.
Thereln, if desired, a free liquid surface may be maintained
by means of the outlet member 16a radlally outside the free
llquid surface ln the inlet chamber 18a. It ls presumed that
the holes 21 form a throttle for the flow of suspension out lnto
the outlet chamber 13a.
In an embodlment of the centrlfuge rotor according to fig 2 new
particles preferably are supplled to the layer 20a together with
the liquid supplied through the lnlet plpe 17a. Thls enables the
new particles at the beginning to be kept su6pended in the
radially innermost part of the layer 20a and - as they gradually
separate said 6ubstance from the llquld and thereby in certaln
appllcations of the lnventlon get heavier - to move rsdlally
outwardly and finally leave the layer 20a through the holes 24
and 21.
Fig 3 shows an alternatlve embodiment of a centrifuge rotor by
means of which the method according to the invention may be
performed. Parts of the centrlfuge rotor in fig 3 corresponding
to parts of the centrifuge rotor in fig 1 have the same refe-
rence numerals as the latter with the adtition of a letter b.
The centrlfuge rotor in flg 3 has an inlet pipe 25 for liquit
from which a substance is to be separated, extending into the
rotor through the channel 9b in the drive shaft 2b. The inlet
pipe 25, that i8 rotatable together with the rotor, is per-
forated along its extension in the inlet chamber 18b.
The rotor body lb supports at it~ upper part a pipe 26 and a
pumping wheel 27 connected with the pipe. The pipe 26 and the
pumplng wheel 27 are surrounded ~ealingly by a statlonary
pumplng house 28 having an outlet conduit 29. The interior of
the pipe 26 communlcates with the channels 11b ln the rotor and
with the interior of the pumping wheel 27, whereby the latter is
.,,.~.. . , . - . ,
:. ~: ' ' . '
-
- ' .
.
200~83s
arranged to pump llquid from the separation chamber 3b through
the channels 11b out into the pumping housing 28 and further
through the outlet conduit 29.
In a similar manner the conical partition lOb at its upper part
ls connected with a plpe 30, which extends coaxially through the
pipe 26, and supports a pumping wheel ~1. The upper part of the
pipe 30 and the pumping wheel 31 are surrounded sealingly by a
stationary pumping housing 32 having an outlet conduit 33. The
interior of the pipe 30 communicates with the inlet chamber 18b
and with the interior of the pumping wheel 31, whereby the
latter is arranged to pump particle suspension from the inlet
chamber 18b out into the pumping housing 32 and further through
the outlet conduit 33.
A centrifuge rotor according to fig 3 operates in substantially
the same manner as a centrifuge rotor according to fig 1. The
only difference is that the whole inlet chamber 18b is filled
with particle suspension during operation and that the separa-
ting operation within the rotor may be perfored at a super-
atmospheric pressure and without the liquid and particles coming
into contact with the atmosphere surrounding the rotor.
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