Note: Descriptions are shown in the official language in which they were submitted.
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SEPARATING DEVICE, SEPARATION UNIT FOR SUCH A SEPARATING
DEVICE, AND SEPARATING METHOD
FIELD OF THE INVENTION
This invention relates to a separating device for
separating particles from a fluid containing the particles, such
as a liquid or a gas, the density of the particles being greater
than that of the fluid. The invention also relates to a
separation unit for use in such a separating device. The
invention furthermore relates to a method for separating
particles from a fluid containing the particles, in which the
separating device according to the invention is utilized.
DISCUSSION OF THE PRIOR ART
Separating devices of this nature, which are used, for
example, for removing small fibres and dissolved proteins from
starch suspensions, are generally known in the form of cyclones.
The cyclones have a feed for feeding the fluid which contains
the particles to be separated in a defined concentration, an
underflow discharge for discharging fluid containing a
(considerably) higher concentration of particles, and an
overflow discharge for discharging fluid containing a
(considerably) lower concentration of particles. This action of
the cyclone is achieved without moving parts through the flow
effects of the fluid in the cyclone brought about by its
specific internal shape.
To increase the capacity of the said separating
devices, cyclones are often connected in parallel to form a so-
called multicyclone, in which the cyclones are usually
accommodated in the form of one or more sets in a common
housing.
To further increase the capacity, it is necessary to
use more housings, which can be connected to one another by
means of pipes for feeding and discharging the various flows of
fluid.
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This constitutes a drawback, since a solution of this
nature is relatively expensive and inflexible. To at least
partially overcome this drawback, cyclone housings have been
developed in which sets containing cyclones extending in the
radial direction are stacked on top of one another and are
accommodated in a common housing. In this way, it is possible
for a large number of cyclones to be placed in a single housing,
and the desired capacity can be achieved by selecting a suitable
number of sets and adapting the dimensions of the housing
accordingly.
However, this construction has the drawback that, owing
to the radial positioning of the cyclones, the accessibility of
the components thereof during assembly, maintenance and cleaning
is poor, in particular since overflow parts ("vortex finders"),
which comprise the overflow discharges, have to be secured one
by one in the cyclones (during assembly) or removed one by one
from the cyclones (during dismantling).
The feed and discharge of flows of fluid to the
individual cyclones or sets run via internal distribution ducts
which are provided in the housing, making the housing relatively
large. Moreover, the distribution ducts are difficult to clean.
Another drawback of the known multicyclones is their
limited pressure resistance (maximum 6-10 bar) owing to the
internal design, with the result that the capacity and/or the
separating efficiency, which depend on the pressure, are also
limited.
SUMMARY OF THE INVENTION
The object of the invention is to eliminate the
drawbacks of the prior art or at least to considerably reduce
these drawbacks and to provide a separating device which is easy
to assemble, dismantle and maintain, can be operated at high
pressure, is of limited dimensions and the capacity of which can
be selected according to requirements without having to
reconfigure internal distribution ducts.
To achieve these and other objects, the invention
firstly provides a separation unit for separating particles from
a fluid containing the particles, which separation unit
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comprises: a number of elongate cyclones which are arranged
parallel to and next to one another and are each provided with a
feed, an overflow discharge and an underflow discharge; a first
chamber, into which the overflow discharges of the cyclones open
out; a second chamber, in which the cyclones are arranged, which
second chamber contains the feeds of the cyclones; and a third
chamber, into which the underflow discharges of the cyclones
open out, the first, second and third chambers being stacked as
seen in the longitudinal direction of the cyclones. A separating
device comprises a number of separation units of this nature,
the separation units preferably being stacked as seen in the
longitudinal direction of the cyclones. The stacking of the
first, second and third chambers in each separation unit and the
stacking of the separation units in the separating device may be
in the vertical or horizontal direction or in another direction.
By designing the separating device in modular form with
stacked separation units, it is possible to achieve a desired
capacity of the separating device simply and expediently, by
stacking a suitable number of separation units. The feeds,
overflow discharges and underflow discharges of the various
separation units are connected to one another outside the
separating device by means of a feed connection duct, overflow
discharge connection duct and underflow discharge connection
duct, respectively, the feeds, overflow discharges and underflow
discharges of the various separation units preferably being
arranged substantially in a line in order to achieve a
connection duct which is as short as possible.
The stacking of the separation units in general, and of
the chambers of the separation units in particular, leads to a
very efficient utilization of the material of the construction.
It is thus possible, within a separation unit, for a wall of the
first chamber also to serve as a wall of the adjoining second
chamber, and an opposite wall of the second chamber can also
serve as a wall of the third chamber. Between different
separation units, it is possible for a wall of a first chamber
of a first separation unit also to serve as a wall of an
adjoining third chamber of an adjoining second separation unit.
To enable a specific separation unit to be cleaned
while the other separation units remain in operation, in a
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preferred embodiment of the separating device according to the
invention a valve is incorporated between the feed, the overflow
discharge or the underflow discharge of each separation unit, on
the one hand, and the feed connection duct, the overflow
discharge connection duct or the underflow discharge connection
duct, respectively, on the other hand. By closing the valves of
one or more separation units, it is possible for these units to
be cleaned/flushed by means of a cleaning agent which can be
guided through the separation unit via separate cleaning feeds
and discharges. The other separation units remain connected as
normal to the various connection ducts and may therefore remain
in operation as normal, while the closed valves ensure that
there is no risk of cleaning agent entering the fluid which is
to be or has been treated. Making use of this cleaning
principle, it is possible to incorporate a certain excess
capacity in the separating device by including at least one more
separation unit than is absolutely necessary, and this excess
capacity can be used for CIP ("Cleaning In Place") of the
separating device by successively cleaning the various
separation units of the separating device.
If the separation units are stacked in the vertical
direction, the capacity of the separating device can easily be
increased by placing new separation units on top of or beneath
the existing units. In principle, this does not take up any
extra floor space.
The separation units and their chambers are preferably
of cylindrical design, resulting in a particularly pressure-
resistant construction.
Although the above text has always referred to one
feed, one overflow discharge and one underflow discharge per
separation unit, a separation unit may also comprise more than
one feed, overflow discharge or underflow discharge, for example
in order to achieve optimum distribution of the fluid in the
chambers which are connected to the feeds and discharges. Each
feed, overflow discharge and underflow discharge may be provided
with a valve, as explained above.
The claims and advantages will be more readily
appreciated as the same becomes better understood by reference
to the following detailed description and considered in
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connection with the accompanying drawings in which like
reference symbols designate like parts.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a side view, partially in cross section,
of a device according to the invention;
FIG. 2 shows a plan view of the device shown in FIG. 1,
in the direction of arrow II;
FIG. 3 shows a diagrammatic cross section, on an
enlarged scale, through a cyclone and the flows of liquid inside
it;
FIG. 4 shows a plan view, on an enlarged scale, of a
wall between a feed chamber and an overflow chamber;
FIG. 5 shows a cross section on line V-V through the
wall shown in FIG. 4;
FIG. 6 shows part of a cross section, on an enlarged
scale, through a variant of the separating device according to
the invention;
FIG. 7 shows a partially diagrammatic cross section, on
a smaller scale, through a variant of the separating device
according to the invention, for the purpose of illustrating
hydraulic retaining of the separation units;
FIG. 8 shows a plan view of a cascade circuit of
separating devices according to the invention;
FIG. 9 shows a front view of the cascade circuit shown
in FIG. 8; and
FIG. 10 shows a side view, in the direction of arrow X,
of the cascade circuit shown in FIG. 8.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIGS. 1, 2 and 3 show a separating device with dish-
shaped cyclone supports 4, which each support a large number
(set) of cyclones 7, only one of which is shown in FIG. 1, for
the sake of simplicity. Each cyclone 7 has a vortex finder 14,
which is mounted on a plate 2. The cyclones 7 are thus situated
substantially in a second chamber 20, of which the cyclone
support 4 and the plate 2 form part, and in which a feed of each
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cyclone 7 is located. An overflow 40 of each cyclone 7 opens
out, via the vortex finder 14, into a first chamber 21. An
underflow 41 of each cyclone 7 opens out into a third
chamber 22. Where a first chamber 21 adjoins a third chamber 22,
these chambers 21, 22 are substantially formed by a chamber
element 3. The second chamber 20 is provided with a feed
pipe 30, which is connected to a common feed connection duct 11,
through which a fluid containing particles which are to be
separated therefrom can be fed. The first chamber 21 is provided
with an overflow discharge pipe 32, which is connected to a
common overflow discharge connection duct 12 through which
cleaned fluid can be discharged. The third chamber 22 is
provided with an underflow discharge pipe 34, which is connected
to a common underflow discharge connection duct 13, through
which substantially separated particles can be discharged.
In the separating device, there is a stack of (as seen
from the top to the bottom in FIG. 1) five separation units,
which each comprise a first chamber 21, a second chamber 20 and
a third chamber 22. The cyclones 7 are positioned with their
longitudinal directions parallel to the longitudinal axis of the
device. The fluids which enter the first chambers 21 and third
chambers 22 are immediately discharged laterally to the
respective common connection ducts 12 and 13.
The various chambers are formed by substantially
annular or partially cylindrical elements which are stacked on
top of one another with seals 43, in the form of O-rings,
between them. The number of elements which can be stacked is
virtually unlimited, since each chamber has its own connection
lines and there is no common housing constituting a limitation.
In order for the forces of pressure differences between
the chambers to be absorbed, pressure rings 6 are positioned in
the first and third chambers 21 and 22. The elements which are
situated between a base element 1 and a cover element 5 are
clamped together by means of clamping bolts 10. At their bottom
ends, the clamping bolts 10 are connected to the base element 1
in such a manner that they can pivot in the radial direction.
The top ends of the clamping bolts 10 are secured, by means of
nuts 44, in open slots formed by lugs 45 of the cover element.
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When the separating device is dismantled, the nuts 44
are unscrewed, after which the clamping bolts 10 can be pivoted
outwards in the radial direction, out of the slots. Then, the
cover element 5, the plates 2 located beneath it, the cyclone
supports 4 and the chamber elements 3 can be removed.
During dismantling, the vortex finders 14 are removed
as a single unit together with the plate 2, so that all the
associated cyclones 7 are accessible for inspection purposes.
Cleaning is also easy, since each chamber 21, 22 can be emptied
completely due to the absence of dead spaces. Considerably more
(axially positioned) cyclones can be incorporated in the
chambers 20 per unit volume than with the known radial
positioning of cyclones. The stacked, in particular cylindrical
construction is able to withstand higher feed pressures (for
example 20 bar) than designs which have been customary hitherto,
which is of benefit to operation for some products: the
separating device has a higher capacity and/or an improved
separating efficiency for the same dimensions.
As a result of valves or shut-off members being
positioned in the feed pipes 30 and discharge pipes 32, 34 (for
example diagrammatically depicted shut-off valves 31a in the
feed pipes 30, shut-off valves 31b in the discharge pipes 32,
and shut-off valves 31c in the discharge pipes 34), it is
possible for the first chamber 21, the second chamber 20, the
third chamber 22 and the set of cyclones 7 of each separation
unit to be cleaned separately, with the result that it is no
longer necessary for the entire separating device to be shut
down for cleaning purposes.
The vertical arrangement of the various chambers 20, 21
and 22 which is described above and shown in the drawing is not
essential; an inclined or horizontal arrangement is also
possible. Also, a first chamber 21 of a first separation unit
does not have to adjoin a third chamber 22 of another separation
unit, but rather the stacking of chambers may also be selected
in such a manner that a first chamber 21 or a third chamber 22
of a separation unit adjoins a first chamber 21 or third
chamber 22, respectively, of another separation unit.
FIGS. 4 and 5 show the plate 2 in more detail. The
plate 2 is provided with a central hole for the attachment of a
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lifting eyelet or the like, around which a pattern of 287
holes 48 is arranged, into which the same number of cyclones are
placed. A slot 49 centres the associated pressure ring 6.
FIG. 6 shows details of a second chamber 20,
cyclones 7a and a feed pipe 30a. The cyclones 7a comprise a
vortex finder 14a and a cyclone body 14b. At one end, the
cyclone body 14b is provided with an annular rim 14c, in which a
complementary part of the vortex finder 14a is held. The cyclone
body 14b substantially tapers and is also provided with a
collar 14d. Fluid containing particles to be separated can be
pressed out of the chamber 20 into the cyclones 7a via a feed
opening 14e. The cyclones 7a are enclosed between the plate 2
and the cyclone support 4 using seals 50. Fluid containing
particles to be separated is fed to the chamber 20 from the feed
pipe 30a. At the end remote from the chamber 20, the feed pipe
is circular, and at the end facing towards the chamber 20 this
pipe is substantially oval or elliptical, the longitudinal axis
of the oval or ellipse extending in the circumferential
direction of the chamber 20.
FIG. 7 shows a separating device according to the
invention with cyclones 7a, plates 2, cyclone supports 4, a
chamber element 3, a cover element 5 with lugs 45, a base
element 1, pressure rings 6, feed pipes 30 and overflow
discharge pipes 32 and underflow discharge pipes 34, which in
some instances are not shown.
The separation units formed by the abovementioned
components are clamped together by a preferably double-acting
piston-cylinder unit 60 which, by means of a hand pump 61 or a
generator unit, can move a plate 62 in the directions of double
arrow 63, in order to vary the distance between the locations
indicated by an "x". Pull rods 65, which can pivot about
pins 64, are attached to the plate 62. At their ends which are
remote from the plate 62, the pull rods 65 are each provided
with a plug 66 which is supported on the lugs 45 of the cover
element 5.
FIG. 7 shows two different solutions for opening and
closing the separating device in a controlled manner by pivoting
the pull rods 65 radially outwards about the pins 64.
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On the right-hand side of the figure, the pull rod 65
is guided through a radial slot in a collar of the base element
1 and the pull rod 65 is driven in the radial direction towards
the separating device by a compression spring 67 arranged in the
slot. On the pull rod 65 there is a bevelled projection 68a,
while opposite this projection, on the side wall of the base
element 1, there is a complementary bevelled projection 68b. As
a result of the piston-cylinder unit 60 being retracted, the
plate 62 moves towards the base element 1 and the
projections 68a and 68b come into contact with one another, the
pull rod 65 being pivoted radially outwards counter to the force
exerted by the compression spring 67; the separating device can
be opened. When the plate 62 is moved in the opposite direction
with respect to the base element 1, the compression spring 67
pushes the pull rod 65 radially back inwards - as far as the
projections 68a and 68b permit - until the plug 66 comes into
contact with the cover element 5; the separating device is
closed. Thus, a mechanical control of the movement of the pull
rod is provided.
On the left-hand side of FIG. 7, the pull rod 65 is
provided with a projection 69 having a pin 70 which is situated
in a slot 71 in a guide block 72. As a result of the piston-
cylinder unit 60 being retracted, the plate 62 moves towards the
base element 1 and the pin 70 moves upwards in the slot 71.
Since the slot 71 is directed away from the separating device at
an angle, the pull rod 65 is pivoted away outwards during this
movement in the radial direction; the separating device can be
opened. When the plate 62 is moved in the opposite direction
with respect to the base element 1, the fact that the pin 70 is
guided in the slot 71 ensures that the pull rod 65 is moved
radially inwards until the plug 66 comes into contact with the
cover element 5; the separating device is closed. This provides
an alternative means of mechanically controlling the movement of
the pull rod.
FIGS. 8, 9, and 10 show a cascade circuit of separating
devices 81, 82, 83 and 84 according to the invention, which each
comprise a feed connection duct 81a, 82a, 83a and 84a, an
underflow discharge connection duct 81b, 82b, 83b and 84b,
respectively, an overflow discharge connection duct 81c, 82c,
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83c and 84c, respectively, and a pump unit 81d, 82d, 83d and
84d, respectively. The cascade circuit of separating devices may
also, for example at the location where the separating device 83
is located, comprise a plurality of separating devices of the
same type which are connected to one another in a cascade
arrangement in a similar manner.
From a tank (not shown in more detail), a pipe 97 feeds
contaminated fluid to the pump unit 81d. The feed connection
duct 81a is connected to the pump unit 81d by way of a pipe 85.
The underflow discharge connection duct 81b is connected to the
pump unit 82d by way of a pipe 86. The overflow discharge
connection duct 81c discharges overflow fluid containing a low
concentration of particles. The feed connection duct 82a is
connected to the pump unit 82d via a pipe 87. The underflow
discharge connection duct 82b is connected to the pump unit 83d
via a pipe 88. The overflow discharge connection duct 82c is
connected to the pump unit 81d via a pipe 98 or feeds overflow
fluid to the pipe 97 via a tank (not shown in more detail). The
feed connection duct 83a is connected to the pump unit 83d via a
pipe 89. The underflow discharge connection duct 83b is
connected to the pump unit 84d via a pipe 90. The overflow
discharge connection duct 83c is connected to the pump unit 82d
via a pipe 91. The feed connection duct 84a is connected to the
pump unit 84d via a pipe 92. The overflow discharge connection
duct 84c is connected to the pump unit 83d via a pipe 93.
Furthermore a pipe for feeding washing water is connected to the
pump unit 84d. The separating devices 81-84 are supported by a
frame 95, which is only diagrammatically depicted.
The cascade circuit of separating devices 81-84
operates as follows. A fluid containing particles is fed to the
separating device 81 by the pump unit 81d via the pipe 85
leading to the feed connection duct 81a. From the separating
device 81, underflow fluid with a high concentration of
particles is fed to the pump unit 82d via the underflow
discharge connection duct 81b and the pipe 86. Overflow fluid
with a low concentration of particles is also fed to the pump
unit 82d from the separating device 83 via the overflow
discharge connection duct 83c and the pipe 91. The mixture of
the underflow fluid from the separating device 81 and the
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overflow fluid from the separating device 83 is fed to the
separating device 82 by the pump unit 82d via the pipe 87 and
the feed connection duct 82a. In a similar way, the pump
unit 83d receives both underflow fluid from the separating
device 82 via the underflow discharge connection duct 82b and
the pipe 88 and overflow fluid from the separating device 84 via
the overflow discharge connection duct 84c and the pipe 93. The
pump unit 83d feeds the two fluids to the separating device 83
via the pipe 89 and the feed connection duct 83a. The pump
unit 84d receives both underflow fluid from the separating
device 83 via the underflow discharge connection duct 83b and
the pipe 90 and washing water via the pipe 94, which flows are
fed to the separating device 84 by the pump unit 84d via the
pipe 92 and the feed connection duct 84a. Finally, underflow
fluid which has passed through all stages of the cascade circuit
and in which there is therefore a very high concentration of
particles comes out of the underflow discharge connection
duct 84b.
While the invention has been described and illustrated
in its preferred embodiments, it should be understood that
departures may be made therefrom within the scope of the
invention, which is not limited to the details disclosed herein.
