EP1659210A1 - Headbox of a machine for manufacturing a fibrous web, in particular a paper or board web - Google Patents

Abstract

A papermaking assembly has a head box that discharges to a dilution zone (14) to a flow guidance zone (12) incorporating structures (13) that direct the fibrous suspension in the correct direction of travel. The structures also reduce vortices within the respective sector. The flow guidance zone is horizontally sub-divided into a number of passages forming an extension from the mixer chamber.

Description

The invention relates to a headbox for a machine for producing a fibrous web, in particular a paper or board web, with at least one distribution device for distributing a pulp suspension across the machine width, in the machine direction a dilution device, in particular a Siebwasserdosiereinrichtung, which arranged several transversely to the machine direction side by side Mixing chambers comprises, each of which sub-streams of different consistency can be supplied and each provide a partial mixing stream, a turbulence generator and a headbox, which is provided with a pulp suspension jet supplying exit slit, are arranged downstream.

Such a headbox is known for example from German Patent DE 40 19 593 C2. In this embodiment, the transition from the dilution device into a machine-wide intermediate chamber via the increment takes place with a speed ratio of about 50%, that is, the pulp suspension is braked by about half in their flow rate. Subsequently, the braked pulp suspension flows over a distance of about 250 to 500 mm to the turbulence generator.

Among other things, this design has the fluidic disadvantage that coarse turbulence structures develop in the fibrous suspension in the region of its flow from the dilution device to the turbulence generator, which can lead to turbulent mixing effects in and between the individual partial mixing streams.

In the context of European patent EP 0 772 711 B1 it has been disclosed to provide the installation of partitions (partitions) in the machine-width intermediate chamber in order to avoid the formation of these coarse turbulence structures. These partitions, which contact an upstream plate and are fixedly connected to the bottom wall and the top wall which define the headbox chamber, have only plane guide planes. As a result, the possible formation of turbulent mixing effects in the respective partial mixing streams is not prevented or at least inhibited.

It is therefore an object of the invention to develop a headbox of the type mentioned in such a way that possible turbulent mixing effects in the respective partial mixing streams in the region of their flow from the dilution device to the turbulence generator significantly reduced, even avoided and flow calming in the respective partial mixing streams are obtained.

This object is achieved in that after the dilution device, a straightening zone is arranged, which comprises at least at least partially arranged structures for aligning the respective partial mixing streams in the machine direction and to reduce possible rotational effects and turbulence within the respective partial mixing streams.

By providing a straightening zone, possible turbulent mixing effects in the respective partial mixing streams in the region of their flow from the dilution device to the turbulence generator are significantly reduced, indeed even completely avoided. Furthermore, a respective flow calming takes place in the individual partial mixed streams through the straightening zone. The partial mixing streams are aligned in the machine direction and possible rotation effects and turbulences within the partial mixing streams are reduced.

In a preferred embodiment, it is provided that the straightening zone has a plurality of directional channels, preferably oriented in the machine direction, with a channel pitch, a respective channel width and a respective channel length. By this sectioning of the straightening zone possible turbulent mixing effects between two adjacent partial mixing streams are avoided altogether.

In order for a fluidically optimal guidance of the pulp suspension through the headbox is possible, the number of mixing chambers of the dilution device is equal to the number of straightening channels of the straightening zone and the channel division of the straightening of the straightening zone corresponds to the chamber distribution of the mixing chambers of the dilution device. Moreover, the straightening channels of the straightening zone are preferably arranged as an extension of the mixing chambers of the dilution device.

The straightening channels of the straightening zone have, in an advantageous embodiment, a respective channel length in the range from 1 to 10 times, preferably from 2 to 5 times, the hydraulic cross section of the respective straightening channel. This causes an efficient flow calming in the individual partial mixing streams and a necessary alignment thereof in the machine direction.

Furthermore, the structures arranged in the directional channels comprise a plurality of flow-guiding elements which are aligned at least downstream in the machine direction. This outlet-side alignment of the flow guide elements contributes significantly to the desired flow orientation of the partial mixing streams. An inlet-side alignment of the flow guide in the machine direction is desirable, but not essential.

The structures arranged opposite one another in the respective guide channel preferably have a course which runs in opposite directions, and furthermore they preferably have a preferably opposite course to structures arranged upstream. These two measures have a particularly advantageous effect in terms of achieving the best possible flow calming in the partial mixing streams. In addition, the desired orientation of the partial mixing streams in the machine direction is favored.

The flow guide elements preferably have a respective element height in the range of 5 to 95%, preferably 30 to 70% of the respective clear channel width. In this case, the element heights of at least some, preferably all flow guide elements in the machine direction can increase. These element heights cause immersion of the flow guide elements in the partial mixing streams in their calming and alignment.

Furthermore, it is advantageous if the flow guide elements arranged in a guide channel are arranged at least on the two lateral wall sides of the respective guide channel. Of course, the flow guide can all be arranged on the circumference of the straightening channel.

The flow guide elements are preferably arranged offset in height relative to each other, so that there are no collisions and the respective partial mixing flow is continuously performed. Two adjacent flow guide elements can have a spacing in the range from 0.2 to 5 ×, preferably from 0.5 to 2 ×, of the respective clear channel width.

In order to ensure sufficient alignment of the partial mixing streams, the flow guide elements have a respective element length in the range from 1 to 20 ×, preferably from 2 to 10 ×, of the respective element height.

In the region of the straightening ducts, additional guiding devices can be arranged, which generate a desired pressure loss in the respective straightening duct.

The structures in a preferred embodiment in the form of baffles, vanes or the like. However, further fluidically suitable embodiments of the structures are of course possible.

Furthermore, a machine-width intermediate chamber between the straightening zone and the turbulence generator can be arranged, which receives the respective partial mixing streams. It preferably has a chamber length in the range from 1 to 10 ×, preferably from 2 to 6 ×, of the chamber distribution of the mixing chambers of the dilution device. In addition, the straightening channels of the straightening zone in this embodiment downstream of a respective expanding cross-section, so that a gradual transition is given in the machine-width intermediate chamber.

• sie weisen jeweils einen Strömungskanal auf, dessen seitliche Wandplatten zumindest bereichsweise als Strukturplatten ausgebildet sind, die eine turbulenzerzeugende gewellte Oberflächenstruktur aufweisen;
• sie weisen jeweils einen Strömungskanal mit wenigstens einer Drossel auf; und/oder
• sie weisen jeweils einen Strömungskanal mit wenigstens einem Carnotsprung auf.

Natürlich können diese Ausgestaltungen, die allesamt für optimale und prozesssichere Mischungen der Teilmischströme sorgen, auch miteinander kombiniert werden.The mixing chambers arranged in the dilution device preferably have the following constructions:

• they each have a flow channel, the lateral wall plates are at least partially formed as structural plates having a turbulence generating corrugated surface structure;
• they each have a flow channel with at least one throttle; and or
• they each have a flow channel with at least one Carnot jump on.

Of course, these configurations, all of which provide optimal and process-safe mixtures of the partial mixing streams, can also be combined with each other.

The inventive machine for producing a fibrous web, in particular paper and / or board web, is characterized in that it is provided with a head box according to the invention.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments with reference to the drawings.

Figur 1

eine schematische, teilweise geschnittene Darstellung eines Stoffauflaufs für eine Maschine zur Herstellung einer Faserstoffbahn;

Figur 2

eine teilweise Draufsicht auf die Richtzone samt angrenzender Baugruppen;

Figuren 3a, 4a und 5a

verschiedene Ansichten eines Richtkanals in Maschinenlaufrichtung; und

Figuren 3b, 4b und 5b

verschiedene Wandansichten der Richtkanäle der Figuren 3a, 4a und 5a.

Show it

FIG. 1

a schematic, partially sectioned view of a headbox for a machine for producing a fibrous web;

FIG. 2

a partial plan view of the straightening zone including adjacent assemblies;

FIGS. 3a, 4a and 5a

different views of a directional channel in the machine direction; and

Figures 3b, 4b and 5b

different wall views of the directional channels of Figures 3a, 4a and 5a.

1 shows a schematic, partially sectioned view of a headbox 1 for a machine for producing a fibrous web.

The headbox 1 has a distributor device 2 for distributing a fibrous stock suspension 3 over the machine width M (arrow), which in the machine direction L (arrow) comprises a thinning device 4 which comprises a plurality of mixing chambers 5 arranged side by side transversely to the machine direction L (arrow) Sub-streams T _S (arrow) of different consistency c _{T can be} supplied and each deliver a partial mixing flow T _MS (arrow), is arranged downstream. The distribution device 2 is in the embodiment of Figure 1 is a transverse distribution tube 6, in another embodiment, not shown, however, it may also be designed as a circular distributor.

For example, the diluter 4 may be a known white water dosing system, as provided in connection with the ModuleJet® headbox available on the market. The ModuleJet® ^- headbox is described for example in the already cited German Patent DE 40 19 593 C2. Among other things, it is important that the dilution device 4 delivers partial mixed flows T _MS (arrow) with different consistency and a certain mixing width.

The dilution device 4 are in the machine direction L (arrow) downstream of a turbulence generator 7 and a headbox 8, which is provided with a pulp suspension jet 10 supplying exit gap 9.

The turbulence generator 7 is preferably a turbulence insert with a plurality of turbulence channels, which are formed in particular by turbulence tubes.

Furthermore, a plurality of fins 11 are arranged in the headbox 8 of the headbox 1 according to FIG. The lamellae 11 are preferably preferably articulated between each row of turbulence channels and have different lamellae lengths so that they can end within the headbox nozzle 8 (FIG. 1), in the region of the outlet gap 9 or outside the headbox nozzle 8.

After the thinning device 4, a straightening zone 12 is arranged in the machine direction, the at least at least partially arranged structures 13 for aligning the respective partial mixing streams T _MS (arrow) in the machine direction L (arrow) and to reduce possible rotation effects and turbulence within the respective partial mixing streams T _MS (arrow ). The straightening zone 12 is located immediately after the diluter 4; However, in a further embodiment, it can also be arranged indirectly after the dilution device 4, for example, according to a machine-width or sectioned intermediate chamber.

Between the straightening zone 12 and the turbulence generator 8, in the embodiment of the headbox 1 according to FIG. 1, there is a machine-width intermediate chamber 14 arranged, which receives the respective partial mixing currents T _MS (arrow). This machine-wide intermediate chamber 14 is therefore only available as an option.

FIG. 2 shows a partial top view of the straightening zone 12 together with adjacent assemblies, namely several mixing chambers 5 for the supply of partial streams T _S (arrow) of different consistency c _T and a machine-wide mixing chamber 14.

The straightening zone 12 has a plurality of preferably in the machine direction L (arrow) aligned straightening channels 15 with a channel pitch T _K , a respective channel width B _K and a respective channel length L _K on.

The number of mixing chambers 5 of the dilution device 4 is equal to the number of straightening channels 15 of the straightening zone 12 and the channel pitch T _{K of} the straightening channels 15 of the straightening zone 12 corresponds to the chamber distribution T _{M of} the mixing chambers 5 of the dilution device 4. In addition, the straightening channels 15 of the straightening zone 12 arranged in extension of the mixing chambers 5 of the dilution device 4.

Each straightening channel 15 of the straightening zone 12 has a channel length L _K in the range of 1 to 10 times, preferably 2 to 5 times its hydraulic cross-section A.

The arranged in the directional channels 15 structures 13 include a plurality of flow guide elements 16, which are aligned at least on the outlet side in the machine direction L (arrow).

The machine-width intermediate chamber 14 arranged between the straightening zone 12 and the turbulence generator 7 accommodates the respective partial mixing flows T _MS (arrow). In this case, the machine-width intermediate chamber 14 has a chamber length L _Z in the range of 1 to 10 times, preferably from 2 to 6 times, the chamber pitch T _{M of} the mixing chambers 5 of the dilution device 4.

Furthermore, the straightening channels 15 of the straightening zone 12 in the presence of a machine-width intermediate chamber 14 downstream of a respective expanding cross-section Q on. The respective extension of the cross section Q preferably takes place on the last third, preferably quarter, in particular fifth of the channel length L _{K of} the directional channel 15.

FIG. 2 also shows two preferred embodiments of the mixing chambers 5 arranged in the dilution device 4. First, the mixing chambers 5 each have a flow channel 17, the lateral wall plates 18 of which are formed at least in regions as structure plates 19 having a turbulence-generating corrugated surface structure 20 or Second, mixing chambers 5 each have a flow channel 21 with at least one Carnot jump 22. As a third, but not shown embodiment, the mixing chambers 5 arranged in the dilution device 4 could each have a flow channel with at least one throttle. The former type of mixing chamber 5 is known, for example, from European Patent EP 0 708 201 B1.

Figures 3a, 4a and 5a show different views of a directional channel 15 in the machine direction L arrow), whereas Figures 3b, 4b and 5b show different wall views of the straightening channels 15 of Figures 3a, 4a and 5a.

The flow guide elements 16 shown in these figures have a respective element height H _S in the range of 5 to 95%, preferably 30 to 70% of the respective clear channel width B _K. In this case, the element heights H _{S of} at least some, preferably all, of the flow guide elements 16 in the machine direction L (arrow) increase.

Furthermore, the flow guide elements 16 arranged in the guide channel 15 are arranged at least on the two lateral wall sides 23. Of course, the flow guide elements 16 all together also on the circumference of the directional channel 15th be arranged. Also, the flow guide 16 may have different courses: they can be straight (Figures 3a and 3b), curved (Figures 4a, 4b, 5a and 5b) or combined run.

In addition, two adjacent flow guide elements 16 have a distance D in the range from 0.2 to 5 times, preferably from 0.5 to 2 times, the respective clear channel width B _K.

The arranged in a directional channel 15 Strömungsleitelemente 16 are equal in height (Figure 3a) or height offset from each other (Figures 4a and 5a) arranged. Of course, further combinations of arrangements are possible, whether in a straightening channel 15 or in a group of preferably adjacent straightening channels 15.

The flow guide elements 16 have a respective element length L _S in the range from 1 to 20 times, preferably from 2 to 10 times, the respective element height H _S. The flow guide elements 16 forming the structure 13 have the form of baffles, guide vanes or the like.

Furthermore, the structures 13 arranged opposite one another in the respective alignment channel 15 have a preferably opposing course (FIGS. 4b and 5b). In this case, the structure 13 of a wall plate 18 may have an upward course, whereas the structure 13 of the other wall plate 13 may have a downward course. The curves can be made straight or curved here.

Advantageously, the arranged in the respective straightening channel 15 structures 13 a preferably opposite course to upstream structures.

Moreover, in the region of the directional channels 15 additional guide means 24 (Figures 5a and 5b) for generating a desired pressure loss in respective straightening channel 15 is arranged. These guide devices 24 are generally in the channel space projecting elements of different geometry and size and they are at least individually arranged between two flow guide 16.

In summary, it should be noted that a headbox of the type mentioned above is created by the invention, the possible turbulent mixing effects in the respective sub-mixing flows in the region of their flow from the dilution device to the turbulence generator significantly reduced, even avoids and obtains flow calming in the respective sub-mixed streams.

LIST OF REFERENCE NUMBERS

1

headbox

2

distributor

3

Fibrous suspension

4

diluter

5

mixing chamber

6

transverse distribution

7

turbulence generator

8th

headbox

9

exit slit

10

Fibrous suspension beam

11

lamella

12

straightening zone

13

structure

14

intermediate chamber

15

directional channel

16

flow guide

17

flow channel

18

wall plate

19

structural panel

20

surface structure

21

flow channel

22

Carnot jump

23

wall side

24

guide

A

Hydraulic cross section

B _K

channel width

c _T

consistency

D

distance

H _E

element height

L

Machine direction (arrow)

L _E

element length

L _K

channel length

L _Z

chamber length

M

Machine width (arrow)

Q

cross-section

T _K

channelization

T _M

chamber division

T _MS

Partial mixed flow (arrow)

T _S

Partial flow (arrow)

Claims (23)

Headbox (1) for a machine for producing a fibrous web, in particular a paper or board web, with at least one distributor device (2) for distributing a fibrous stock suspension (3) across the machine width (M), which in the machine direction (L) comprises a dilution device ( 4), in particular a Siebwasserdosiereinrichtung comprising a plurality of transversely arranged side by side to the machine running direction (L) mixing chambers (5), each of which partial flows (T _S) of different consistency (C _T) are fed and which each supply a part of the mixing stream (T _MS), a Turbulence generator (7) and a headbox nozzle (8), which is provided with a pulp suspension jet (10) supplying the outlet gap (9) are arranged downstream,
characterized,
in that a straightening zone (12) is arranged downstream of the thinning device (4), the structures (13) arranged at least in sections for aligning the respective partial mixing streams (T _MS ) in the machine direction (L) and for reducing possible rotational effects and turbulences within the respective partial mixing streams ( T _MS ). Headbox (1) according to claim 1,
characterized,
in that the straightening zone (12) has a plurality of directional channels (15), preferably oriented in the machine direction (L), having a channel pitch (T _K ), a respective channel width (B _K ) and a respective channel length (L _K ). Headbox (1) according to claim 2,
characterized,
that the number of mixing chambers (5) of the dilution device (4) is equal to the number of straightening channels (15) of the straightening zone (12) and
that the channel spacing (T _K) (15) of the straightening zone (12) of the dilution means (4) corresponds to the target channels of the chamber pitch (T _M) of the mixing chambers (5). Headbox (1) according to claim 3,
characterized,
in that the straightening channels (15) of the straightening zone (12) are arranged as an extension of the mixing chambers (5) of the dilution device (4). Headbox (1) according to one of claims 2 to 4,
characterized,
in that the straightening channels (15) of the straightening zone (12) have a respective channel length (L _K ) in the range of 1 to 10 x, preferably 2 to 5 x, of the hydraulic cross section (A) of the respective straightening channel (15). Headbox (1) according to one of claims 2 to 5,
characterized,
that disposed in the guide channels (15) structures (13) comprise a plurality of flow guide elements (16), which are at least on the outlet side oriented in the machine running direction (L). Headbox (1) according to claim 6,
characterized,
that the oppositely disposed in the respective guide channel (15) structures (13) have a preferably oppositely directed course. Headbox (1) according to claim 6 or 7,
characterized,
that disposed in the respective guide channel (15) structures (13) have a preferably oppositely directed course to upstream structures (13). Headbox (1) according to one of claims 5 to 8,
characterized,
that the flow guide elements (16) have a respective element height (H _E) in the range of 5 to 95%, preferably from 30 to 70% of the respective clear channel width (B _K). Headbox (1) according to one of claims 5 to 9,
characterized,
that the element heights (H _E) of at least some, preferably all flow guiding elements (16) increase in the machine running direction (L). Headbox (1) according to one of claims 5 to 10,
characterized,
in that the flow guide elements (16) arranged in a guide channel (15) are arranged at least on the two lateral wall sides (23) of the respective guide channel (15). Headbox (1) according to claim 11,
characterized,
in that the flow guide elements (16) arranged in a directional channel (15) are arranged offset in height relative to one another. Headbox (1) according to one of claims 5 to 12, in particular according to claim 11 or 12,
characterized,
that two adjacent flow guiding elements (16) a distance x (D) in the range of 0.2 to 5, preferably from 0.5 to 2 x the respective clear channel width (B _K) have. Headbox (1) according to one of claims 7 to 13,
characterized,
that the flow guide elements (16) have a respective element length (L _E) in the range of 1 to 20 x, preferably from 2 to 10 x the respective element height (H _E). Headbox (1) according to one of claims 2 to 14,
characterized,
in that additional guide devices (24) are arranged in the region of the directional channels (15). Headbox (1) according to one of the preceding claims,
characterized,
that the structures (13) have the form of baffles, guide vanes or the like. Headbox (1) according to one of the preceding claims,
characterized,
that between the straightening zone (12) and the turbulence generator (7) a machine-width intermediate chamber (14) is arranged, which receives the respective partial mixing streams (T _MS ). Headbox (1) according to claim 17,
characterized,
that the machine-wide intermediate chamber (14) has a chamber length (L _Z) in the range of 1 to 10 x, preferably from 2 to 6 of the chamber pitch (T _M) x of the mixing chambers (5) of the dilution means (4). Headbox (1) according to one of the preceding claims,
characterized,
in that the straightening channels (15) of the straightening zone (12) have a respective widening cross section (Q) downstream. Headbox (1) according to one of the preceding claims,
characterized,
in that the mixing chambers (5) arranged in the dilution device (4) each have a flow channel (17) whose lateral wall plates (18) are at least partially formed as structural plates (19) which have a turbulence-generating corrugated surface structure (20). Headbox (1) according to one of the preceding claims,
characterized,
that arranged in the dilution means (4) mixing chambers (5) in each case (17) having a flow channel with at least one throttle. Headbox (1) according to one of the preceding claims,
characterized,
that arranged in the dilution means (4) mixing chambers (5) in each case (21) having a flow channel with at least one Carnot jump (22). Machine for producing a fibrous web, in particular paper and / or board web, with a headbox (1) according to one of the preceding claims.

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