Note: Descriptions are shown in the official language in which they were submitted.
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APPARATUS FOR SORTING AND DEFLAKING FIBROUS SUSPENSIONS
The invention relates to an apparatus for sorting and deflaking
fibrous suspensions and, in particular, a so-called pressureless
sorter for heavily soiled fibrous suspensions such as those
resulting as rejected material from the most varied sorting
systems.
Known open sorting apparatuses, such as, for example, vibratlon
sorters often used as the final stage in a multistage sorting
system, do not generally lead to a rejected material which is
dewatered to any great extent and result, in addition, in
relatively high losses of usable fibers remaining in the
rejected material. The high costs connected with the storage of
the rejected material, above all the requirement of a high dry
content of the rejected material, often necessitate the purchase
of additional apparatus, such as piston-type presses and worm
compressors, to further dewater the re;ected material in a paper
mill .
E~nown sorting apparatuses comprising a rotor are, however,
subject to considerable wear and tear when processing heavily
soiled fibrous suspensions, insofar as an apparatus for
separating out dirt particles having a heavy specific weight is
not connected to their inlet sides. These dirt particles having
a heavy specific weight do have an extremely abrasive effect in
these apparatuses between rotor and screen.
The object underlying the invention was therefore to provide a
sorting apparatus which is also suitable for processing heavily
soiled fibrous suspensions and fulfills the requirement for a
r,e~ected material which has a high dry content and is as free of
f;ibers as possible.
A sorting apparatus, in which the fiber content of the fibrous
suspension to be processed is reduced and which is intended to
result in a rejected material having a relatively high dry
content, is known from EP-0 235 605~A2. this sorting apparatus
has a housing surrounding a rotor with a horizontal axis, the
housing having a housing portion on the inlet side with a larger
di.ameter and a housing portion on the outlet side with a smaller
diameter. In the housing portion on the inlet side the rotor
comprises a first rotor region which is designed as an impeller
having a relatively large diameter and is intended to effect
de!flaking, whereas a second rotor reglon located in the housing
portion at the outlet side is designed as a cylinder having a
cc,nsiderably smaller diameter and is surrounded by a cylindrical
screen, through which the accepted material and the majority of
the water pass in order to provide a relatively dry rejected
material. A screen plate is located on the side of the impeller
opposite the housing portion on the outlet side having a smaller
diameter and at a very slight axial distance from the impeller,
and is followed by an accepted material chamber provided with an
accepted material outlet. If this known apparatus is used for
processing fibrous suspensions recovered from mixed waste paper,
it is intended to be utilized for the last stage of the sorting
process. If it were to form the first stage of the sorting
process, the dirt particles, such as sand and metal parts,
contained in the fibrous suspension would quickly lead to wear
and tear on the impeller, the screen plate, the vanes arranged
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at the periphery of the second rotor region and the cylindrical
screen surrounding the second rotor region.
DE-26 11 886-8 of the applicant discloses an apparatus for
sorting and deflaking fibrous suspensions, which comprises a
housing surrounding a rotor arranged with its axis horizontal,
the housing having in a front housing end region an inlet for
th,e fibrous suspension to be processed, in a central region at
the bottom an accepted material outlet for the sorted fibrous
suspension and in a rear housing end region at the bottom a
rejected material outlet. The rotor has the form of a hollow,
approximately drum-shaped, rotationally symmetrical body and
comprises three regions arranged one behind the other in the
dLrection of the rotor axis, namely a first rotor region on the
inlet side, a central, second rotor region and a third rotor
rlgion on the outlet side. Web-like accelerator strips are
attached at the rotor periphery in the first and third rotor
r,eglons to accelerate the fibrous suspension in the
circumferential direction while the second rotor region is
provided at the perlphery with ribs extending in axial
direction, these ribs being designed such that they develop a
deflaking effect together with a screen cylinder encircling the
rotor at a slight radial distance. Together with this screen
cylinder, the first rotor region effects a dewatering of the
fibrous suspension while, at the same time, accepted material is
separated out. In other words, the first rotor region is a
sorting and dewatering region, the second rotor region brings
a,bout, as already mentioned, a deflaking of the fibrous
suspenslon, and in the annular space between third rotor region
and screen cylinder usable fibers are washed out of the rejected
material and sorted, for which purpose a supply of diluting
water ls directed from outside in radial direction onto the
2~ F;~U é
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screen cylinder. Behind the rotor the rejected material leaves
the apparatus housing through the rejected material outlet
already mentioned.
When a fibrous suspension recovered from mixed waste paper is
sorted and deflaked with this known apparatus, sand, metal
particles and the like result in considerable wear and tear on
the screen cylinder and on the accelerator and deflaking ribs
attached at the rotor periphery. In addition, this known
apparatus supplies an undesirably thin rejected material because
in the third rotor region the still usable fibers are washed out
of the rejected material by diluting water. The aforementioned
object cannot, therefore, be accomplished with this known
apparatus.
Proceeding on the basis of an apparatus of the generic type,
such as that disclosed in DE-26 11 886-8, i.e. an apparatus for
sorting and deflaking fibrous suspensions, comprising a housing
whlch has in a front housing end region an inlet for the fibrous
suspension to be processed, in addition an accepted material
outlet for the sorted fibrous suspension as well as a rejected
material outlet, and in which a rotor having a horizontal axis
is mounted for rotation, this rotor having a plurality of
regions disposed one after the other in the direction of the
rotor axis and being surrounded by annular chambers having
different functions, of these regions a first rotor region on
the inlet side and a last rotor region facing the rejected
material outlet arranged at a rear housing end region being
provided at their periphery with take-along elements for the
fibrous suspension, the last rotor region being surrounded by an
annular screen, and a deflaking rotor region located upstream of
the last rotor region having elevations for effecting deflaking,
wherein an additional rotor region surrounded by an
2'at~ v 'I g
annular screen is located between said first and said last rotor
regions, the object underlying the invention may be accomplished
in that the first rotor region is surrounded by an annular
housing wall, an outlet for particles of dirt having a heavy
specific weight opening into this wall from below, and that the
last rotor region is designed as a rejected material thickening
region and the additional rotor region is designed as a sorting
region. Since, in the inventive apparatus, no screen
surrounding the first rotor region has to be provided but rather
embodiments are preferred, in which the first rotor region is
surrounded by the housing wall which is closed apart from the
inlet arranged in the top for the fibrous suspension to be
processed and the opening of the outlet for heavy dirt, the dirt
particles having a heavy specific weight are, in the inventive
apparatus, centrifuged out of the f'ibrous suspension before they
can lead to wear and tear on a screen and the rotor parts
surrounded by the screen. the fibrous suspension, which is set
to rotate quickly by the rotor, catapults the heavy dirt
particles against the housing wall where they slide down along
this wall and reach the outlet for the dirt particles having a
heavy specific weight. Only then is the fibrous suspension
deflaked and sorted in the inventive apparatus. It is hereby
considered to be a particular advantage for the processes of
sorting and thickening not to occur in the same region of the
apparatus because in the sorting region, namely, the screen is
appropriately acted upon by wash water to clean the screen and
wash out usable fibers whereas in the inventive apparatus the
rejected material thickening region need not have any wash water
supply device.
In an apparatus of a different generic type for sorting and
washing out a fibrous suspension as well as thickening the
rejected material (DE-28 50 385-~), a rotor having a more or
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less horizontal axis is surrounded over its entire length by a
screen cylinder. At one end of the apparatus housing which also
has a more or less horizontal axis and is approximately
cylindrical in design, an inlet for the fibrous suspension to be
processed is provided. An outlet for the accepted material is
located outside the screen cylinder and at the other end of the
apparatus housing a reiected material outlet is provided. A
first rotor region on the inlet side is provided with
accelerator vanes for the fibrous suspension, a second rotor
region with transporting vanes conveying the fibrous suspension
in an axial direction and a third rotor region with centrifugal
vanes arranged at the rotor periphery. The first rotor region
serves to sort the fibrous suspension, the second to wash out
the fibrous suspension (by means of wash water outlet openings
provided in the rotor casing), and in the third rotor region the
rejected material is dewatered. This known apparatus is of a
different generic type since it does not relate to a deflaking
apparatus. In addition, it does not accomplish the present
object since it does not contain any means for removing dirt
particles having a heavy specific weight before the fibrous
suspension enters an annular space between a rotor and a screen.
A further apparatus of a different generic type
(DE-38 20 366-A), in which the fibrous suspension is also not
deflaked, relates to an apparatus for sorting cellular material
which has an approximately circular-cylindrical housing with a
horizontal axis and a rotor arranged concentrically to the
housing. The fibrous suspension to be processed is introduced
paraxially into the apparatus at one housing end, namely into a
chamber formed by the housing wall which is closed around its
circumference. A first rotor region designed as a toothed wheel
is located in this chamber and followed by a second,
circular-cylindrical rotor region which forms, directly behind
the toothed wheel, a narrow annular gap with a housing partition
wall, the external diameter of the gap being smaller than the
external diameter of the toothed wheel. Rib-like vanes
extending in axial direction are placed on the second rotor
region. A first area of said second rotor region on the inlet
side is surrounded by a region of the housing wall designed as a
screen so that the fibrous suspension is sorted in this region
whereas a second area of the second rotor region remote from the
apparatus inlet is surrounded by a closed area of the housing
wall into which a rejected material outlet opens from above. In
the region of the screen, a diluting water connection leads
through the screen. The toothed wheel is intended to be
designed such that undesired solid dirt particles are hit by the
toothed wheel and catapulted back in a radial direction towards
the outside as well as in the direction towards the apparatus
inlet in order to prevent the dirt particles from entering the
annular gap located behind the toothed wheel. However,
DE-38 20 366-A expressly points out that the major portlon of
the impurities occurring in the fibrous suspension passes
through the apparatus and leaves the apparatus with the re;ected
material. In addition, this known apparatus has no rejected
material thickening region. To summarize, it can be said that
it is inconceivable to process fibrous suspensions recovered
from very dirty, mixed waste paper with this known apparatus.
It is obvious that the different rotor regions need not
necessarily be formed by one and the same rotor. In addition, a
further rotor region may be located in front of the first rotor
region, e.g. one without take-along elements for the fibrous
suspension.
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the inventive apparatus is expediently designed such that al l
the rotor regions are formed by a single, drum-shaped rotor and
all the screens by a rotationally symmetrical screen basset. In
this connection it should be mentioned that DE-AS 26 11 886 of
the applicant discloses an apparatus for sorting, deflaking and
re-screening a fibrous suspension which comprises a drum-shaped
rotor arranged with its axis horizontal in a housing including a
circular-cylindrical screen. One end of the housing is provided
with an inlet for the fibrous suspension to be processed, the
other end with a rejected material outlet and, inbetween, the
housing has an accepted material outlet in the bottom and at the
top, next to the rejected material outlet, a diluting water
connection. The rotor is provided at its periphery in first and
third rotor regions adjacent the inlet and rejected material
outlet, respectively, with strip-like take-along elements for
the fibrous suspension, these elements extending parallel to the
rotor axis, and in a second rotor region arranged between the
first and third rotor regions it bears at its periphery a
gear-type collar, the teeth of which effect deflaking of the
fibrous suspension. In this known apparatus, therefore, all the
dirt particles, including those having a heavy specific weight
which cause a considerable amount of wear and tear, pass between
the rotor and the screen cylinder and the re;ected material
leaving the apparatus comprises a relatively large amount of
water as a result of the diluting water inlet in the region of
the third rotor region.
In a preferred embodiment of the inventive apparatus, a rotor
region designed as a fiber washing out region is provided
between the sorting region and the rejected material thickening
region, this washing out region being surrounded by an annular
screen and having associated with it a washing water inlet
directed against the rotor. In this region, the usable fibers
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are washed out of the deflaked fibrous suspension and pass
through the screen surrounding this rotor region as accepted
material and so the rejected material leaving the apparatus is,
for the most part, free of fibers.
Since the inventive apparatus is preferably a pressureless
sorting apparatus, it is recommended that the rotor be provided
at its periphery in the sorting region and the fiber washing out
region, respectively, with take-along elements for the fibrous
suspension which force the latter against the respective
screen. If these take-along elements are designed to have sharp
edges they also result in a deflaking effect, and in the fiber
washing out region they promote the distribution of the washing
water and the washing out of the usable fibers from the rejected
material. ' . .
The take-along elements are particularly effective when they are
designed as webs or sheets projecting in the manner of vanes
from the rotor periphery.
Since the process of deflaking or defibering undissolved
conglomerates of fibers essentially takes place between the
elevations at the rotor periphery and the edges of the screen
apertures and is attributable to an impact and shearing force on
the fiber conglomerates, the deflaking effect is essentially
dependent on the radial distance of the elevations and webs,
respectively, from the respective screen. In preferred
embodiments of the inventive apparatus, the radial distance of
the webs from the respective screen is approximately 1/2 to
approximately 5 mm and preferably 1/2 to approximately 1 mm.
Particularly advantageous embodiments are those in which the
webs are adjustable in their height relative to the rotor
periphery.
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In order to separate out the dirt particles having a heavy
specific weight with the lowest possible energy requirements -
the fibrous suspension to be processed flows into the apparatus
housing at a certain geodetic water column height, which is, in
particular 1 to 4 m WS (= water gage) -, the apparatus inlet for
the fibrous suspension to be processed is, in an advantageous
embodiment, aligned approximately tangentially and the rotor is
drivable in the direction of the inlet flow so that the inlet
flow already leads to a rotatory flow of the fibrous suspension
between rotor and housing wall. When the take-along elements of
the first rotor region and the annular space following the
latter between the sorting region and the screen surrounding
this sorting region are designed and arranged accordingly, it is
possible in accordance with the invention for dirt particles
having a heavy specific weight to essenti,ally not come into
contact with the take-along elements of the first rotor region
and for the fibrous suspension to be able to enter the specified
annular space essentially unhindered, additional features which
distinguish the inventive apparatus quite appreciably from the
known apparatus of a different generic type according to
DE-38 20 366-A.
In principle, it would be conceivable to surround the rotor
region effecting deflaking with a closed wall, which comprises,
for example, pro;ections promoting the deflaking process. In
view of the deflaking mechanism described above, preferred
embodiments of the inventive apparatus have an annular screen
surrounding the deflaking rotor region so that deflaking and
sorting can take place in the same region.
Slnce fleece-like fiber collections can form on the feed side of
the screens if no special measures are take, and these
collections hinder the sorting effect, it is recommended that
the take-along elements arranged at the rotor rotate as close as
possible to the pertinent screen. An additional measure for
preventing clogging of the screen apertures is to associate
washing water inlets with the screen of the sorting region for
cleaning the screen apertures.
The different screens can have screen apertures of the same size
and shape. It is, however, more advantageous for the screen of
the sorting region to be provided with finer screen apertures
than the screen of the fiber washiny out region so that, on the
one hand, an accepted material having as high a quality as
possible is first obtained and, on the other hand, all the
usable fibers are, as far as possible, passed through the screen
in the washing out region. Finally, when it comes to thickening
the rejected material, i.e. withdrawing only waxer thérefrom,
flner screen apertures can again be used so that, ln a preferred
embodiment, the screen of the rejected material thickening
region has finer screen apertures than the screen of the washing
out region.
The length of time the fibrous suspension to be processed
remains in the various regions of the apparatus depends on the
quantity supplied per time unit, the amounts of washing water
supplied per time unit, the inclination of the webs relative to
the rotor axis and the speed of rotation of the rotor. For this
reason it is recommended that the webs be constructed so as to
be adjustable in their inclination relative to a generatrix of
the rotor periphery. S1nce, in the first rotor region, the
centrifugal effect achieved is intended to be as great as
possible and the fibrous suspension located in this region is
displaced anyway by the fresh fibrous suspension flowing in
behind it, it is recommended that the webs in the first rotor
region extend approximately parallel to the generatrices of the
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rotor periphery whereas the webs in the rotor regions following
this first rotor region can be inclined relative to the
generatrices ox the rotor periphery such that they result in a
conveying effect in the direction towards the rear housing end.
In order to remove the rejected material, which is as dry as
possible, from the region between rotor and last screening
region, a preferred embodiment of the inventive apparatus has
the webs of the last rotor region projecting beyond its screen
rearwardly into a rejected material chamber formed by the
housing so that the rejected material is catapulted from the
rotor into this chamber.
Additional features, advantages and details of the invention
result from the attached drawings and the following description
of a particularly favourable embodiment of the invention
apparatus; in the drawings:
Figure 1 is an axial section through the apparatus;
Figure 2 is a section along line 2-2 in Figure l;
Figure 3 is a section along line 3-3 in Figure 1;
Flgure 4 is a section through part of the rotor,
namely a section at right angles to the
rotor axis, and
Figure 5 is a plan view onto part of the rotor periphery.
Figure 1 shows a housing mounted on a frame 10 and designated as
a whole as 12. This housing has an outer housing casing l and
is closed by an end wall 16 to the left according to Figure 1.
A right-hand end wall 18 has an opening 22 concentric to an axis
l t.J J ,~ L1
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20-and bears a rejected material box 24 which has at the bottom
an exit opening 26 for the rejected material.
The frame 10 also bears a drive motor 28 and a bearing body 30,
in which a rotor shaft 32 is rotatably mounted. This is
concentric to the apparatus axis 20, bears a belt pulley 34 and
is caused to rotate via this, drive belt 36 and a belt pulley 38
of the motor 28, and in a counter-clockwise direction according
to Figures 2 and 3. A hollow, circular-cylindrical rotor 40 is
attached to the rstor shaft 32. At its ends this rotor is
closed by end walls 42 and 44 and it has a casing 46, on which a
total of 4 sets of vanes 501, 502, 503 and 504 are attached,
these vanes serving to take along, i.e. accelerate in a rotatory
manner, the fibrous suspension to be processed. These sets of
vanes 501 to 504 are associated with 4 regions I, II, III, IV of
the apparatus or rather the rotor 40, namely - according to
Figure 1 from left to right - a heavy component separating
region I, a sorting and deflaking region II, a washing out
region III and a dewatering region IV. In this respect, vanes
of the set of vanes 50 of the sorting and deflaking region II
which are adjacent one another in the circumferential direction
are offset relative to one another in axial direction due to
their axial length, as is apparent from Figure l.
A tangentially oriented inlet pipe 54 for the fibrous suspension
to be processed opens into the housing 12 in the heavy component
separating region I; in accordance with the invention this inlet
pipe is arranged on top of the housing. In the region I the
rotor 40 is enclosed only by the outer housing casing 14, into
the bottom of whlch a vertically oriented outlet pipe 56 for
dirt particles having a heavy specific weight opens. This is
followed by a heavy component container 58, to which a diluting
water line 60 is connected. Valves closing the heavy component
- 14 -
container 58 at the top and bottom are designated 62 and 64, a
valve for the dilutlng water line 60 has been designated 66.
Along the regions II, III and IV the housing 12 accommodates a
circular-cylindrical screen cylinder 68, the screen apertures of
which are finer in the sorting and deflaking region II and in
the dewatering region IV than in the washing out region III. As
illustrated in Figures l and 3, washing water channels 70 are
attached to the outside of the screen cylinder 68, these
channels being supplied via a washing water conduit 74 provided
with a valve 72. The screen cylinder 68 does not have any
screen apertures beneath the washing water channels 70 extending
in the direction of the apparatus axis 20 but only spray
openings 76 at certain points, according to the invention only
rin the sorting and deflaking region II as well as~in the washing
out region III, whereas no washing water is supplied to the
dewatering region IV.
An accepted material chamber 78 limited by the screen cylinder
68 and the outer housing casing 14 is, according to Figure 1,
closed on the right by the end wall 18 and on the left by a
circular housing web 80; an accepted material outlet pipe 82
opens into the accepted material chamber 78 from below.
According to the invention, measures are taken to ensure that
the rejected material conveyed to the rejected material box 24
cannot conglomerate but leaves the rejected material box at the
bottom through its exit openings 26. For this purpose, the
vanes 504 of the rotor 40 project somewhat into the rejected
material box 24, a guiding wall 86 in the shape of a half shell
is associated with the lower region of the rotor 40 in the
rejected material box 24 and at the top, adjacent the rotor, a
baffle 88 is arranged in the rejected material box and this has
- lS -
the effect that the rejected material catapulted upwards is,
according to Figure 1, reflected towards the bottom right and
therefore falls downwards into the exit opening 26 to the right
of the guiding wall 86.
The fibrous suspension flowing into the apparatus via the inlet
pipe 54 is caught by the vanes 501 attached to the rotor in the
heavy component separating region I and catapulted against the
outer housing casing 14. The dirt particles in the fibrous
suspension having a heavy specific weight slide downwards along
the outer housing casing 14 due to the force of gravity; at the
lowest point of the housing 12 they pass into the heavy
component container 58 via the outlet pipe 56. A thickening of
the rejected material in the heavy component container 58 is
avoided by a counterwashing via the diluting water line 60.
In the heavy component separating region I the fibrous
suspension to be processed is, therefore, freed of dirt
particies having a heavy specific weight, such as metal parts
and the like, before it enters the annular space between the
rotor 40 and the screen cylinder 68.
In the sorting and deflaking region II the fibrous suspension is
caught by the vanes 502 and catapulted against the perforated
screen cylinder 68, the screen apertures of which allow the
accepted material, i.e. the fine fraction formed of usable
fibers and water, to pass whereas the dirt is retained in the
annular space between rotor and screen cylinder. The accepted
material leaves the accepted material chamber 78 via the
accepted material outlet pipe 82.
Due to the inventive design of the vanes 502 with sharp edges
fibers, i.e. fiber conglomerates, contained in the fibrous
2`~ ,7
- 16 -
suspension are broken up; a sllghtest possible distance between
the vanes 502 and the screen cylinder 68 has the same effect,
whereby an additional advantage is also obtained: The fibers
tend to form a fiber fleece on the inner inflow side of the
screen cylinder 68 and this would hinder the flow of the
accepted materlal through the screen cylinder. The fact that
the vanes 502 rotate at such a slight distance from the screen
cylinder 68 prevents the formation of such a fiber fleece or
removes any fiber fleece in the process of formation.
As is apparent from Figure 4, the effective height of the vanes
may be adjusted or precluded, e.g. by the washers 90
illustrated in Flgure 4. The same applies for the other vanes.
This can influence the intensity of the deflaking operation
effected~by the vanes 50 and which is performed between the
vane edges and the edges of the screen apertures by impact and
shearing effects.
As indicated in Figure 5, the inclination of the vanes relative
to the apparatus axis 20 or the generatrix of the rotor 40 may
be adjusted. In this way, the fibrous suspension or the dirt
can be transported more quickly or more slowly through the
annular space between rotor 40 and screen cylinder 68 to the end
of the screen cylinder to the right according to Figure 1. In
the heavy component separating region I the vanes 501 are
preferably axially arranged, i.e. without any angular pitch,
since the axial transport of the fibrous suspension in the
direct$on of the rejected material box 24 is effected by the
fibrous suspension flowing in behind.
The screen cylinder apertures are cleaned, inter alia, by the
washing water supplied via the washing water channels 70 and the
spray openings 76.
- 17 -
Since the major portion of the individual fibers suspended in
the water has passed through the screen cylinder apertures, the
rejected material in the washing out region II is supplied with
an increased amount of washing water in order to wash the usable
fibers still contained in the rejected material off the dirt and
then centrifuge them out of the annular space between rotor and
screen cylinder by means of the vanes 503. In the inventive
apparatus the washing out process is particularly intensive
since the jets of water entering the annular space between
screen cylinder 68 and rotor 40 strike the rotor casing 46, are
then reflected and thereby spray apart. In addition, the
washing and diluting water is well distributed by the rotating
vanes 503. These vanes 503 are, with respect to their angle,
mounted on the rotor in accordance with the desired holding time
in the washing out-re~ion III.~
the rejected material remaining in the annular space between
rotor 40 and screen cylinder 68 is now freed of the adherent
water in the dewatering region IV by means of centrifugation
with the aid of the vanes 504. the vanes 504 are, according to
the invention, formed of one piece over the entire length of the
dewatering region IV.
The dewatered rejected material leaves the apparatus via the
exit opening 26 of the rejected material box 24.
If the fibrous suspension or the rejected material are intended
to remain a particularly long time in a particular region,
despite the f$brous suspension flowing in behind, the vanes in
this region are negatively pitched, i.e. such that they act in
the sense of a return effect.
