Note: Descriptions are shown in the official language in which they were submitted.
DEVICE AND METHOD FOR MACERATING A MATERIAL TO BE CONVEYED
The invention relates to a method for macerating a material to be conveyed,
e.g. wood
chips, where the material to be conveyed is fed through a compression screw
conveyor
according to the invention, the compression screw conveyor receives the
material to be
conveyed in an inlet area, and a screw rotating round an axis of rotation
inside a
housing conveys the material to be conveyed to a discharge area and macerates
it at
the same time, the material to be conveyed being compressed between a plug
pipe and
the screw to form a gas-tight and liquid-tight plug and the plug forming a
seal between
the discharge area and the compression screw conveyor.
According to an embodiment of the invention, there is provided a compression
screw
conveyor to control maceration of a material to be conveyed comprising an
inlet area to
receive the material to be conveyed, a screw rotatable round an axis of
rotation in a housing
and an outlet area, where the screw is mounted rotatably inside a plug pipe in
the discharge
area, wherein the screw has a flight, at least partially, the screw being
formed as an area
without a flight, at least partially, in the area of the plug pipe, and the
screw and the plug pipe
being suitable for being moved and positioned in relation to one another,
where a calibrating
area is formed between plug pipe and screw, the calibrating area comprising
either an area
of the plug pipe with a decreasing inner diameter and an area of the screw
without a flight
and with a constant outer diameter or an area of the screw without a flight
and with a
decreasing outer diameter, or the calibrating area comprises an area of the
plug pipe with a
constant or increasing inner diameter and an area of the screw without a
flight and with an
increasing outer diameter.
Compression screw conveyors are used to dewater a material to be conveyed by
compressing it, but also to macerate a material to be conveyed. In this case,
maceration
means softening or defiberizing the material to be conveyed, where the
combination of
conveying and compressing in the compression screw conveyor results in
delamination
of the cell walls and mechanical defiberizing of the material to be conveyed,
i.e. reducing
the material to be conveyed to its fibre components and at the same creating a
correspondingly larger specific surface area of the material to be conveyed.
The
compression screw conveyor also permits a pressure seal between the
compression
screw conveyor and a device connected to the discharge area, for example a
reactor,
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Date Recue/Date Received 2023-06-21
because the material to be conveyed is formed into a gas-tight and liquid-
tight plug
between the inlet area and the discharge area. This is necessary because the
device
connected, e.g. the reactor, is filled with a gaseous or liquid fluid
containing reactants
and must be sealed off against the environment. The device connected to the
discharge
area of the compression screw conveyor can be designed as a pressure vessel,
for
example, as an atmospheric or pressurized reactor, as a digester, or
otherwise. Reactant
means, in particular, chemicals in a liquid fluid (e.g. a solvent, an aqueous
solution,
ethanol or similar mixtures), where the term "chemical" can be a catalyst, for
example, an
acid (e.g. H2SO4 or acetic acid), a lye (e.g. NaOH), or similar mixtures.
Typical uses are
found in the pulp and paper sector and also generally in processing of fibrous
pulps, e.g.
wood pulps, and there, for example, in the production of fibreboard, MDF, and
so on.
Hence, in addition to treating the material to be conveyed in a digester, an
important field
of application is impregnation of the material to be conveyed, where the
compression
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Date Recue/Date Received 2023-06-21
screw conveyor allows air and liquid to be expelled from the material to be
conveyed
and the material to be macerated, where the macerated material to be conveyed
is
carried out of the compression screw conveyor and into a reactor containing
the
reactants needed for impregnation. Hence, in addition to treating the material
to be
conveyed in a digester, an important field of application is impregnation of
the
material to be conveyed, where the compression screw conveyor allows air and
liquid
to be expelled from the material to be conveyed and the material to be
macerated,
where the macerated material to be conveyed is carried out of the compression
screw conveyor and into a reactor containing the reactants needed for
impregnation.
Another use is available in the production of bio-fuels, where bioethanol, for
example,
can be produced from biomass comprising cereal crops, maize or sugar beets.
Compression screw conveyors typically consist of a housing with a screw inside
that
is mounted rotatably round an axis of rotation, where the screw has a flight,
at least
partially, and where the material to be conveyed is compressed increasingly in
the
tapering area between the housing and the screw. At the discharge area of the
compression screw conveyor, the screw has no flight, at least partially, in
order to
form the plug. The housing can have openings in the area of the screw in order
to
allow dewatering and/or aeration by compression of the material to be
conveyed.
Conventional screw conveyors can be built with a cylindrical housing together
with a
screw with a cylindrical outer contour, where other housing shapes, e.g. with
a
conical outer contour, are also possible.
EP 2 817 449 B1 describes a system for handling a wood-free plant material,
where
compression screw conveyors for feeding chips to digesters are used and the
compression screw conveyor comprises a plug pipe with a constant inner
diameter at
the end of the compression screw conveyor. The aim of EP 2 817 449 B1 is,
among
other things, to disclose a compression screw conveyor arrangement with an
optimized pressure seal. This is achieved by the interaction of a compression
screw
conveyor and a force-feeding screw.
DE 1 101 126 B describes a process and a device for impregnating raw materials
containing pulp, where the material is compressed progressively in order to
expel air
and liquid and the material is brought into direct contact with the
impregnating liquid
when it expands. It is also noted that the material reduced to its fibre
components
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advantageously presents a larger surface area for subsequent application of
the
impregnating material.
EP 3 333 311 B1 describes a process and a device for impregnating biomass,
Improved maceration, among other things, is to be achieved by the pre-
compressed
biomass from the compression screw conveyor being fed through a force-feed
screw
because it was noted that pre-compression of the high-volume biomass
containing
hollow spaces results in increased compression of the plug. It was also noted
that it
is advantageous to specify the filling level of the reactor unit according to
the speed
at which the biomass is conveyed in order to enable homogeneous impregnation
of
the biomass.
EP 0 493 422 B1 refers to a plug screw feeder for use during maceration of
wood
chips, comprising a screw with variable speed and a force-feed screw with
variable
speed, where the speeds of the screw and the force-feed screw are used to
obtain
the desired extent of fibre displacement.
US 2007/164143 Al discloses a plug screw feeder for maceration, where the
maceration effect can be increased or adjusted by using tubular inserts.
US5320034A discloses a device and a method for improved maceration of wood
chips,
The aim of the invention is an improved means of macerating a material to be
conveyed, especially a pulp. Another aim is to enable a better and more even
effect
by the reactants on the macerated pulp. An additional aim is to enable optimum
dewatering while effecting the required maceration or to compensate for the
effects
of inhomogeneous material to be conveyed, which is fed unevenly to the
compression screw conveyor, for example, or has widely scattered material
properties. Another aim is to continue being able to adjust the maceration if
the screw
or plug pipe are worn and to minimize the power consumption of the compression
screw conveyor while maintaining the maceration requirement.
According to the invention, this is achieved by the degree of maceration of
the
material to be conveyed being controlled by relative positioning of the screw
to the
plug pipe. The plug pipe is disposed in the discharge area of the compression
screw
conveyor in the housing and has an annular structure, at least partially,
and/or a
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truncated cone structure, at least partially. The screw extends into the plug
pipe,
where the screw is mounted to rotate round an axis of rotation and has an area
with
no flight inside the plug pipe to form the plug. The plug pipe is normally
replaceable
so it can be changed easily if worn and because different geometries can be
formed
by changing the plug pipe. The area between the plug pipe and the screw can be
influenced by positioning of the screw in relation to the plug pipe. Thus, the
area
between plug pipe and screw, and especially the gap at the end of the screw
towards
the plug pipe can either be narrowed or widened. Maceration of the material to
be
conveyed is increased due to narrowing of the area or the gap and decreased by
widening of the area or the gap.
A favourable embodiment of the invention is characterised in that the screw is
moved
in axial direction along the axis of rotation inside the housing in order to
control the
degree of maceration. Here, the housing and plug pipe are stationary, and the
screw
is moved in axial direction, causing further narrowing or widening of the area
between the plug pipe and the screw, and in particular, of the gap at the end
of the
screw towards the plug pipe. The screw can be moved if the screw bearing unit
has a
movable design, where the bearing unit supports the screw shaft and is
arranged
opposite the discharge area. Here, the screw is driven by a stationary drive,
where a
coupling that can absorb the axial movement of the screw is provided between
the
bearing unit of the screw and the drive.
Another favourable embodiment of the invention is characterised in that the
plug pipe
is pushed in axial direction along the axis of rotation inside the housing in
order to
control the degree of maceration. Here, the housing and screw are stationary,
and
the plug pipe is moved in axial direction, causing narrowing or widening of
the area
between the plug pipe and the screw, and in particular, of the gap at the end
of the
screw towards the plug pipe.
An advantageous embodiment of the invention is characterised in that the
material to
be conveyed is brought from the discharge area into a reactor, the material to
be
conveyed reacts with a reactant inside the reactor, and the reaction result in
the
reactor is influenced by controlling the degree of maceration of the material
to be
conveyed. Controlling the degree of maceration of the material to be conveyed
means controlling disintegration of the material to be conveyed, and thus
controlling
disintegration of the material to be conveyed into its fibre components as
well as
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implying control of the specific surface area of the shredded material to be
conveyed,
which is extremely relevant in chemical but also absorptive and adsorptive
processes. Optimum effect by the reactants on the material to be conveyed and
thus
an optimum reaction result are only possible if maceration in the reactor is
controlled.
Here, the term reaction result covers, among other things and in relation to
the
material to be conveyed in each case, the extent of impregnation, the
penetration
with reactants, the product quality, and the yield.
An advantageous embodiment of the invention is characterised in that the
material to
be conveyed is compressed between the inlet area and the discharge area
between
the housing and the screw with a flight, at least partially, where the plug is
formed in
the discharge area between the plug pipe and an area of the screw with no
flight. In
the area of the plug pipe, the screw can partially have an area with a flight,
where the
area of the screw with no flight follows this area of the screw with a flight
in conveying
direction.
Another favourable embodiment of the invention is characterised in that the
plug
passes through a ring area in the discharge area, where the ring area is
formed by
an area of the plug pipe with a constant inner diameter and an area of the
screw with
no flight and with a constant outer diameter. The plug forms in this ring area
in
particular, where maceration of the material to be conveyed is not yet
controlled. The
plug passes advantageously through the ring area first of all to form the
sealing plug
and then through a calibrating area to adjust the maceration.
A similarly advantageous embodiment of the invention is characterised in that
the
plug passes through a calibrating area after the ring area in the discharge
area, the
calibrating area being formed either by an area of the plug pipe with an inner
diameter decreasing in conveying direction and an area of the screw with no
flight
and with a constant or decreasing outer diameter, or the calibrating area
being
formed by an area of the plug pipe with a constant or increasing inner
diameter in
conveying direction and an area of the screw with no flight and with an
increasing
outer diameter. To the extent that the calibrating area is formed by an area
of the
plug pipe with a constant inner diameter in conveying direction and an area of
the
screw with no flight and with an increasing outer diameter, an area with a
diameter
that is larger than the constant inner diameter of the plug pipe adjoins the
plug pipe.
Here, the area of the screw with no flight and with the increasing outer
diameter can
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be positioned inside the plug pipe or in the area with the diameter that is
larger than the
constant inner diameter of the plug pipe, where positioning between these
positions is,
of course, also possible. Due to relative positioning of the plug pipe and the
screw,
specific spacing is set between the plug pipe and the screw in the calibrating
area and,
in particular, a specific gap is set at the end of the screw as far as the
plug pipe. The
calibrating area can either be narrowed or widened by relative positioning of
the plug
pipe and screw. An area of the plug pipe with a decreasing inner diameter can
be
achieved with a conically shaped plug pipe, where the intended tip of the cone
points to
the discharge area. Then the area of the screw with no flight is formed
conically with a
constant diameter or with a decreasing outer diameter, the intended tip of the
cone
again pointing to the discharge area. The space between the cone surfaces
lying inside
one another and hence also maceration is controlled directly by the relative
movement
of the cone surfaces. An area of the plug pipe with an increasing inner
diameter can be
obtained with a conically shaped plug pipe, the intended tip of the cone
pointing
towards the inlet area. The area of the screw with no flight is then formed
conically with
an increasing outer diameter, the intended tip of the cone again pointing to
the inlet
area. In this way, maceration of the material to be conveyed can be increased
either by
the calibrating area narrowing or it can be reduced by the calibrating area
widening due
to axial movement of the screw.
According to another embodiment of the invention, there is provided a
compression screw
conveyor to control maceration of a material to be conveyed, e.g. wood chips,
comprising an
inlet area (3) to receive the material to be conveyed, a screw (6) rotatable
round an axis of
rotation (5) in a housing (4) and an outlet area (7), where the screw (6) is
mounted rotatably
inside a plug pipe (8) in the discharge area (7), characterised in that the
screw (6) has a
flight (9), at least partially, the screw (6) being formed as an area (10)
without a flight, at least
partially, in the area of the plug pipe (8), and the screw (6) and the plug
pipe (8) being
suitable for being moved and positioned in relation to one another, where a
calibrating area
(12) is formed between plug pipe (8) and screw (6), the calibrating area (12)
comprising
either an area (13) of the plug pipe with a decreasing inner diameter and an
area of the
screw without a flight and with a constant outer diameter or an area (14) of
the screw without
a flight and with a decreasing outer diameter, or the calibrating area (12)
comprises an area
of the plug pipe with a constant or increasing inner diameter and an area of
the screw
without a flight and with an increasing outer diameter (16).
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Date Recue/Date Received 2023-06-21
An advantageous design of the compression screw conveyor is characterised in
that the
screw can be moved in axial direction along the axis of rotation and in
relation to the
housing or in that the plug pipe can be moved in axial direction along the
axis of rotation
and in relation to the housing and the screw.
In addition, a ring area is formed advantageously between the plug pipe and
the screw,
the ring area comprising an area of the plug pipe with a constant inner
diameter and an
area of the screw with no flight and with a constant outer diameter.
The embodiment of the compression screw conveyor according to the invention is
characterised in that a calibrating area is formed between the plug pipe and
the screw,
where the calibrating area either comprises an area of the plug pipe with an
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Date Recue/Date Received 2023-06-21
inner diameter decreasing in conveying direction and an area of the screw with
no
flight and with a constant or decreasing outer diameter, or the calibrating
area
comprises an area of the plug pipe with a constant or increasing inner
diameter in
conveying direction and an area of the screw with no flight and with an
increasing
outer diameter. To the extent that the calibrating area is formed by an area
of the
plug pipe with a constant inner diameter in conveying direction and an area of
the
screw with no flight and with an increasing outer diameter, an area with a
diameter
that is larger than the constant inner diameter of the plug pipe adjoins the
plug pipe.
The decreasing or increasing area of the screw or plug pipe can be formed by
the
plug pipe or screw having a conical shape. According to these embodiments,
axial
positioning of the screw in relation to the plug pipe allows the calibrating
area to be
reduced or increased in size.
The invention will now be described using the examples in the drawings.
Figure 1 shows a compression screw conveyor for maceration according to the
state
of the art.
Figure 2 shows an embodiment of the compression screw conveyor according to
the
invention with a first, relative positioning of the screw to the plug pipe.
Figure 3 shows an embodiment of the compression screw conveyor according to
the
invention with a second, relative positioning of the screw to the plug pipe.
Figure 4 shows another embodiment of the compression screw conveyor according
to the invention.
Figure 1 shows a compression screw conveyor for maceration according to the
state
of the art. Here, the material to be conveyed is fed through the inlet area 3
to the
compression screw conveyor 2 and to a reactor 1 not shown here, where the
compression screw conveyor 2 has a housing 4, a screw 6 that can be rotated
round
an axis of rotation 5 and has a flight 9, at least partially, a discharge area
7, and a
plug pipe 8. In the area of the plug pipe 8, the screw 6 has an area 10 with
no flight.
Figures 2 and 3 show an embodiment of the compression screw conveyor according
to the invention, Fig. 2 showing a first relative positioning of the screw to
the plug
pipe and Fig. 3 a second relative positioning of the screw to the plug pipe.
Here, a
screw 6 that can be rotated round an axis of rotation 5 and has a flight 9, at
least
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partially, is mounted in a housing 4. In the discharge area 7, the screw 6 has
an
area 10 with no flight inside the plug pipe 8, the plug pipe 8 and the area 10
of the
screw with no flight forming a ring area 11 and the ring area 11 being
followed by a
calibrating area 12 in conveying direction of the material to be conveyed. In
addition,
the area of the screw with no flight is designed conically with an increasing
outer
diameter 16, the intended tip of the cone pointing towards the inlet area and
the plug
pipe 8 having a constant inner diameter in conveying direction. The
calibrating area
is formed by the area of the plug pipe with a constant inner diameter and the
area 16
of the screw with no flight and with an increasing outer diameter, an area 15
with a
diameter that is larger than the constant inner diameter of the plug pipe
adjoining the
plug pipe. In Figure 2, the area 16 of the screw with no flight and with the
increasing
outer diameter is positioned in the area 15 with the diameter that is larger
than the
constant inner diameter of the plug pipe, and in Figure 3, the area 16 of the
screw
with no flight and with the increasing outer diameter is positioned in the
plug pipe 8.
Advantageously, maceration of the material to be conveyed can be increased in
this
way either by the calibrating area 12 narrowing or it can be reduced by the
calibrating
area 12 widening due to axial movement of the screw 6. Figure 2 shows the
compression screw conveyor 2 with relative positioning of the screw 6 further
in
conveying direction of the material to be conveyed, i.e. closer to the
discharge
area 7. And conversely, Fig. 3 shows the compression screw conveyor 2 with
relative
positioning of the screw 6 in the opposite direction to the conveying
direction of the
material to be conveyed, i.e. closer to the inlet area 3. Hence, the
calibration area 12
in Fig. 3 is smaller than in Fig. 2, whereby positioning of the screw 6 in
Fig. 3 results
in the material to be conveyed being macerated more and positioning of the
screw 6
in Fig. 2 results in the material to be conveyed being macerated less.
Figure 4 shows another embodiment of the compression screw conveyor according
to the invention, the screw 6 being mounted rotatably in a housing 4 and the
screw 6
having a flight 9, at least partially. In the discharge area 7, the screw 6
has an
area 10 with no flight inside the plug pipe 8, the plug pipe 8 and the area 10
of the
screw with no flight forming a ring area 11 and the ring area 11 being
followed by a
calibrating area 12 in conveying direction of the material to be conveyed. In
addition,
the area 14 of the screw with no flight is designed conically with an outer
diameter
decreasing in conveying direction, the intended tip of the cone pointing
towards the
discharge area 7 and the plug pipe 8 having an area 13 with a decreasing inner
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diameter. Here, arrow A illustrates the option of relative positioning of the
screw 6 to
the plug pipe 8 and arrow B the option of relative positioning of the plug
pipe 8 to the
screw 6.
Thus, the present invention offers numerous advantages: an effective means of
controlling maceration of a pulp and also better and more even effect by the
reactants on the macerated pulp. Similarly, optimized dewatering performance
is
possible at the same time as controllable maceration. It is also possible to
select a
mode of operation in which a requested degree of maceration can be set, but
which
requires minimal power consumption by the compression screw conveyor. In this
way, wear on the compression screw conveyor, plug pipe, etc. can be kept to a
minimum and, conversely, a required degree of maceration can still be set when
there has been wear on the compression screw conveyor, plug pipe, etc., thus
making longer use possible because the worn components can be replaced at a
later
stage. Similarly, the impact of inhomogeneous material to be conveyed because
it is
fed unevenly to the compression screw conveyor, for example, has inherently
scattering material properties, or a changing composition, can be compensated
and
the requested degree of maceration can be set in each case. In addition, the
solution
according to the invention allows the compression screw conveyor to be started
up
quickly with low power consumption, where the degree of maceration can be
controlled or set quickly.
Reference numerals
1 Reactor
2 Compression screw conveyor
3 Inlet area
4 Housing
5 Axis of rotation
6 Screw
7 Discharge area
8 Plug pipe
9 Flight
10 Area of the screw with no flight
11 Ring area
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12 Calibrating area
13 Area of the plug pipe with a decreasing inner diameter
14 Area of the screw with no flight and a decreasing outer diameter
15 Area with a diameter that is larger than the constant inner diameter of the
plug
pipe
16 Area of the screw with no flight and an increasing outer diameter
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