EP1428930A1 - Method and headbox for inducing shear and turbulence in a fibrous suspension - Google Patents

Abstract

A papermaking assembly has a head-box (1) surrendering a fiber suspension (3) through (S) a feed passage (4) vortex generator (5) to jets (6, 6.1, 6.2). The jets esp. generate a sheer flow (R1, R2) pattern through angles alpha (() and beta ((). Also claimed is a commensurate head-box assembly for the manufacture of paper or carton in which the jets are directed at different angles to each other. Further claimed is that the process operates efficiently at a fiber density of 1-3%, combining low costs with good paper machine runnability. The suspension moves at a speed of ( 1 m/s in the vicinity of the first jets, ( 3 m/s in the vicinity of the second jets, and ( 1-20 m/s in the vicinity of the third jets.

Description

The invention relates to a method for generating shear flows and Turbulence intensities in a through a headbox of a paper or board machine guided fiber suspension, the headbox at least one the system supplying the fiber suspension, optionally at least one Area for turbulence generation and one downstream in the direction of flow Has headbox nozzle.

Furthermore, the invention relates to a headbox according to the preamble of the claim 3 for performing the method according to the invention.

Such a headbox is described, for example, in the applicant's German published application DE 199 05 716 A1 (PA10845 DE). It is provided that a central part is provided with connections for at least two partial flows and that these partial flows are appropriately merged in order to generate turbulence in a material flow that forms, in particular in front of and / or in the initial region of an outlet channel. As a result, turbulence is generated in the nozzle chamber by mixing at least one second jet (partial stream) into a main jet. This defines momentum exchange processes of turbulence balls of different provenance, intensity and size, which then result in a relatively good intermixing of the partial flows. In the headbox described, the size of the turbulence bales is sufficiently large for the mixing in of the partial streams, although it is also determined to a certain extent by the size of the mixing chamber itself.
However, the long wavelength of turbulence is not very useful for the formation of a fibrous web, in particular a paper or cardboard web. Rather, the smallest possible wavelength of the turbulence is required with sufficiently large shear flows in the fiber suspension.

The invention has for its object a method and a headbox of the type mentioned at the beginning in such a way that sufficient Shear flows and turbulence intensities at low mixing or wavelengths are generated so that the headbox even at stock densities between 1% and 3% in a cost-effective and reliable manner at a high Runnability of the paper or board machine can be operated.

This object is achieved in that the shear flows and the turbulence intensities in the fiber suspension are generated by at least one, preferably two strong and preferably opposite direction changes with corresponding angles in the area of the headbox nozzle.
Due to the at least one, preferably multiple and preferably opposing deflection of the fiber suspension, intensive shear forces and turbulence intensities are generated even at low mixing or wavelengths, which tear the fiber flakes and thereby markedly improve the formation already mentioned.

A preferred embodiment of the method according to the invention provides that the shear currents and the turbulence intensities due to two strong and preferably opposite direction changes in three in the flow direction the fiber suspension successive nozzle sections with corresponding Nozzle heights, nozzle lengths and nozzle shapes are generated. Thereby are as compact and space-saving as possible Headbox produces the best possible shear flows and turbulence intensities.

A suitable headbox for carrying out the method according to the invention is characterized in that the headbox nozzle has at least one, preferably two strong and preferably opposite changes in direction with corresponding angles along the flow direction of the fiber suspension.
As already described, intensive shear forces and turbulence intensities are generated by the at least one, preferably multiple, and preferably opposite, deflection of the fiber suspension, which tear the fiber flakes and thereby markedly improve the formation.

A preferred design of the headbox according to the invention provides that the headbox nozzle due to its two strong and preferably counter rotating Changes in direction in three in the flow direction of the fiber suspension successive nozzle sections with corresponding nozzle heights, Nozzle lengths and nozzle shapes is formed. As a result, at one compact and space-saving design of the headbox the best possible Shear flows and turbulence intensities are generated.

The two angles each take a value in the range from 10 ° to 89 °, preferably in the range from 25 ° to 85 °, because in these areas an ideal generation is guaranteed by shear currents.

• der in Strömungsrichtung der Faserstoffsuspension erste Düsenabschnitt weist eine Düsenhöhe im Bereich von 5 mm bis 200 mm, eine Düsenlänge im Bereich von 50 mm bis 800 mm und eine vorwiegend konvergente und/oder parallele Düsenform auf;
• der in Strömungsrichtung der Faserstoffsuspension zweite und auf den ersten Düsenabschnitt folgende Düsenabschnitt weist eine Düsenhöhe im Bereich von 5 mm bis 100 mm, eine Düsenlänge im Bereich von 50 mm bis 500 mm und eine vorwiegend konvergente und/oder parallele Düsenform auf; und
• der in Strömungsrichtung der Faserstoffsuspension dritte und auf den zweiten Düsenabschnitt folgende Düsenabschnitt weist eine Düsenhöhe im Bereich von 3 mm bis 50 mm, eine Düsenlänge im Bereich von 50 mm bis 800 mm und eine vorwiegend konvergente und/oder parallele und/oder divergente Düsenform auf.

Auch diese Ausgestaltungen gewährleisten eine kompakte und raumsparende Bauweise des Stoffauflaufs bei Erzeugung bestmöglicher Scherströmungen und Turbulenzintensitäten.With regard to the configuration of the nozzle sections, the following properties are provided according to the invention:

• the first nozzle section in the flow direction of the fiber suspension has a nozzle height in the range from 5 mm to 200 mm, a nozzle length in the range from 50 mm to 800 mm and a predominantly convergent and / or parallel nozzle shape;
• the nozzle section in the flow direction of the fibrous suspension and following the first nozzle section has a nozzle height in the range from 5 mm to 100 mm, a nozzle length in the range from 50 mm to 500 mm and a predominantly convergent and / or parallel nozzle shape; and
• The third nozzle section following the second nozzle section in the flow direction of the fibrous suspension has a nozzle height in the range from 3 mm to 50 mm, a nozzle length in the range from 50 mm to 800 mm and a predominantly convergent and / or parallel and / or divergent nozzle shape.

These configurations also ensure a compact and space-saving construction of the headbox while generating the best possible shear flows and turbulence intensities.

As part of generating the greatest possible shear flows and sufficient Turbulence intensities according to the invention provide that the fiber suspension a flow velocity in the region of the first nozzle section of ≥ 1 m / s, a flow velocity in the area of the second nozzle section of ≥ 3 m / s and a flow velocity in the area of the third nozzle section in the range of 1 m / s to 20 m / s.

Furthermore, immediately after a strong change in direction, in Flow direction of the fibrous suspension seen, at least one preferably web-wide air feed device provided. Such an air feed primarily serves to increase the volume of the flow through the headbox nozzle Mixture, again during the volume increase Shear currents and turbulence intensities appear.

In a further embodiment according to the invention it is provided that the headbox is designed as a two-layer headbox, the third and last Nozzle section the headbox nozzle through the lower nozzle wall of one Headbox nozzle and formed by the upper nozzle wall of the other headbox nozzle is. The headbox nozzle is preferably in the third and last nozzle section a separating element is arranged, the preferably metallic Separating element in the flow direction of the fibrous suspension is preferred lamella extending beyond the headbox nozzle can.

A turbulent flow condition in the nozzle sections at high To be able to maintain material densities is the headbox nozzle in the direction of flow the fiber suspension with at least one flow obstacle. Preferably, headbox nozzle with a variety of flow obstacles provided, which are preferably offset and arranged alternately are.

Furthermore, the headbox nozzle is at least one-sided in the area of its outlet side with an aperture to limit the fiber suspension before it leaves the Atmosphere. The orifice is preferably opposite to the direction of flow the fiber suspension directed.

For the purpose of maintaining a very good formation due to shear currents and turbulence intensities, the fibrous suspension has a consistency ≥ 1%, preferably ≥ 1.5%. Such a consistency has for example the fiber suspension for the production of plasterboard, corrugating Medium (CM) and cardboard box inserts.

In a further embodiment, the headbox can also be equipped with a sectioned stock density control (Dilution water technology, "Module-Jet"). With this design of the headbox, the possibility is created that Throughput, consistency and thus basis weight and fiber orientation to be able to regulate in sections.

In addition, the headbox according to the invention can flow in the direction of flow Fibrous suspension a gap former, a hybrid former or a Fourdrinier former, in principle, therefore, each former concept must be subordinated.

Further features and advantages of the invention result from the the following description of preferred exemplary embodiments under Reference to the drawing.

Figuren 1 und 2:

zwei verschiedene Ausführungsformen des erfindungsgemäßen Stoffauflaufs in schematisierten Ansichten;

Figur 3:

eine schematisierte Ausführungsformen des erfindungsgemäßen Stoffauflaufs;

Figur 4:

ein schematisches Intensität-Größe-Diagramm; und

Figur 5:

eine weitere Ausführungsform des erfindungsgemäßen Stoffauflaufs in schematisierter Ansicht.

Show it

Figures 1 and 2:

two different embodiments of the headbox according to the invention in schematic views;

Figure 3:

a schematic embodiments of the headbox according to the invention;

Figure 4:

a schematic intensity-size diagram; and

Figure 5:

a further embodiment of the headbox according to the invention in a schematic view.

FIG. 1 shows a schematic side view of a headbox 1 of a paper or cardboard machine for producing a fibrous web 2, in particular Paper or cardboard web, from at least one fiber suspension 3, with at least a system 4 feeding the fiber suspension 3, if necessary with at least one area for generating turbulence 5 and with one in the flow direction (S) (arrow) of the fiber suspension 3 following headbox nozzle 6, the two width walls extending across the machine width (Lower nozzle wall 7, upper nozzle wall 8) comprises and from which the fiber suspension 3 exits via a nozzle gap 9 as a fiber suspension jet 10. The system 4 supplying the fiber suspension 3 can, for example, as in Figure 1 shown, a cross distribution pipe or alternatively or additionally a round distributor and the area for generating turbulence can in particular be a Pipe grid and / or a turbulence generator, these assemblies not explicitly shown, but are known to the expert.

It is now provided that the headbox nozzle 6 along the flow direction S (arrow) of the fiber suspension 3 has at least one, according to the embodiment in FIG. 1, two strong and preferably opposite changes in direction R ₁ , R ₂ (arrows) with corresponding angles α, β. Due to these two strong and opposite changes in direction R ₁ , R ₂ (arrows), the headbox nozzle 6 is in three flow sections S (arrow) of the fiber suspension 3 successive nozzle sections I, II, III with corresponding nozzle heights H _I , H _II , H _III , Nozzle lengths L _I , L _II , L _III and nozzle shapes are formed. The two angles α, β each assume a value in the range from 10 ° to 89 °, preferably in the range from 25 ° to 85 °, the two angles α, β taking on the same value in the embodiment according to FIG. 1, such as 45 °. If the two angles α, β are different, the inlet and outlet directions of the headbox nozzle 6 are not parallel, that is to say they form an angle with one another. The spaces 11 , 12 which form between the nozzle sections I, II, III and further elements of the headbox 1 can be filled, partially filled or unfilled. In the embodiment according to FIG. 1, for example, the space 11 that forms between the two nozzle sections I, II and the turbulence generator 5 is filled, while the space 12 that forms between the two nozzle sections II, III is empty.

The first nozzle section I in the flow direction S (arrow) of the fibrous suspension 3 has a nozzle height H _I in the range from 5 mm to 200 mm, a nozzle length L _I in the range from 50 mm to 800 mm and a predominantly convergent and / or parallel nozzle shape, whereas in the flow direction S (arrow) of the fibrous suspension 3 and second nozzle section II following the first nozzle section I, a nozzle height H _II in the range from 5 mm to 100 mm, a nozzle length L _II in the range from 50 mm to 500 mm and a predominantly convergent one and / or has a parallel nozzle shape. And finally, in the flow direction S (arrow) of the fibrous suspension 3 and third and following the second nozzle section II, nozzle section III has a nozzle height H _III in the range from 3 mm to 50 mm, a nozzle length L _III in the range from 50 mm to 800 mm and one predominantly convergent and / or parallel and / or divergent nozzle shape. The aforementioned configurations of the nozzle sections can be combined with one another as desired.

Furthermore, the fibrous suspension 3 has a flow velocity v _I (arrow) of ≥ 1 m / s in the region of the first nozzle section I, a flow velocity v _II (arrow) of ≥ 3 m / s in the region of the second nozzle section II and in the region of the third nozzle section III a flow velocity v _III (arrow) in the range from 1 m / s to 20 m / s.

Immediately after the second strong change in direction R ₂ , seen in the flow direction S (arrow) of the fibrous suspension 3, at least one preferably web-wide air feed device 13 is provided. This air sectioning device 13, which can preferably be operated in sections, can be designed, for example, as a blowing tube 14 with corresponding blowing nozzles 15 projecting into the nozzle section III and can be acted upon by a central air supply device which is well known to the person skilled in the art and is therefore not explicitly shown.

The headbox nozzle 6 is at least in the region of its outlet side 6A provided on one side with an orifice 16, which is preferably counter to the flow direction S (arrow) of the fiber suspension 3 is directed. This aperture 16 can of course be adjustable, preferably sectionally adjustable his.

The fibrous stock suspension 3 passed through the headbox 1 has a stock density ρ of ≥ 1%, preferably ≥ 1.5%. This makes this headbox suitable 1 in particular for the production of cardboard webs, and preferably of plasterboard, CM (Corrugating Medium) and folding box inlays.

In a further embodiment, the headbox 1 can also be sectioned Material density control (dilution water technology), as for example from the German patent application DE 40 19 593 A1 (PA04598 DE) of the applicant is known to be provided. The disclosure content of this writing will hereby made the subject of the present description.

In addition, the headbox 1 is in the flow direction S (arrow) of the fiber suspension 3 a gap former, a hybrid former (possibly FIG. 1) or a Four-wire former (possibly Figure 1) arranged downstream. In principle, the invention Headbox 1 should be subordinate to each former concept.

FIG. 2 also shows a schematic side view of a headbox 1 a paper or board machine for producing a fibrous web 2, in particular Paper or cardboard web, from at least one fiber suspension 3, this headbox 1 is designed as a two-layer headbox 1.1. Such one Two-layer headbox 1.1 with all of its operating modes and parameters belongs to the known state of the art, with which not on the same is further discussed. It will also refer to the description of the Figure 1 referenced.

The third and last nozzle section III of the headbox nozzle 6 is through the lower one Nozzle wall 7.1 of a headbox 6.1 and through the upper nozzle wall 8.1 of the other headbox nozzle 6.2 formed. It is in the third and last nozzle section III of the headbox nozzle 6.1, 6.2 a known separating element 17 arranged. This preferably metallic separating element 17 is in the direction of flow S (arrow) of the fibrous suspension 3 preferably over downstream of the headbox nozzle 6 extending lamella 18 of a known type.

FIG. 3 shows a schematic embodiment of the headbox 1 according to the invention with different angles α, β, the fibrous stock suspension 3 flowing through the headbox nozzle 6 along its flow direction S (arrow) having two strong and opposite changes in direction R ₁ , R ₂ (arrows) with respective angles experiences α, β of preferably 45 °.

FIG. 4 shows a schematic intensity-size diagram of a headbox. The size G, for example the nozzle length L or the nozzle height H, is plotted on the abscissa and the intensity (u ² / l) on the ordinate. The intensity-size parameter of a conventional headbox, as set out, for example, in the applicant's already published German patent application DE 199 05 716 A1 (PB10845 DE), is shown by a dashed line, whereas the parameter of the inventive headbox is shown by a solid line , It can be clearly seen that the mentioned parameter of the headbox according to the invention has a far more positive course, that is to say that shear flows and turbulence intensities are improved and generated more effectively.

FIG. 5 shows a further embodiment of the headbox 1 according to the invention in a schematic view, reference being generally made to the description of FIG.
However, the two angles α, β of the headbox in FIG. 5 are different, so that the inlet and outlet directions of the headbox nozzle 6 are not parallel. In other words, this means that the inlet and outlet directions form an angle that is not explicitly shown.
Furthermore, the headbox nozzle 6 in the flow direction S (arrow) of the fiber suspension 3 is provided with at least one flow obstacle 19, wherein the area provided with flow obstacles 19 can include all three nozzle sections I, II, III. The stock nozzle 6 in FIG. 5 is provided with a large number of flow obstacles 19, which are preferably offset and arranged alternately. In addition, the flow obstacles can have different contours (areas, contours, angles, etc.) and be designed in a certain way, such as an increase in area in the direction of flow and the like.

The headbox 1, 1.1 according to the invention is outstandingly suitable also to carry out the method according to the invention, that is to say to generate it of shear flows and of turbulence intensities in the through the headbox guided fiber suspension.

In summary, it should be noted that the invention is both a method as well as a headbox of the type mentioned is created, which adequate shear flows and turbulence intensities at low Generate mix or wavelengths so that the headbox even at stock densities between 1% and 3% in a cost-effective and reliable manner a high runnability of the paper or board machine can be operated.

LIST OF REFERENCE NUMBERS

1

headbox

1.1

Two-layer headbox

2

Fibrous web

3, 3.1, 3.2

Fibrous suspension

4

Feeding system

5

generating turbulence

6, 6.1, 6.2

headbox

6A

outlet side

7, 7.1

Lower nozzle wall (width wall)

8, 8.1

Upper nozzle wall (width wall)

9

die gap

10

Fibrous suspension beam

11 , 12

room

13

Air supply device

14

blowpipe

15

blow nozzle

16

cover

17

separating element

18

lamella

19

flow obstruction

G

size

H _I , H _II , H _III

nozzle height

I, II, III

nozzle section

L _I , L _II , L _III

nozzle length

R ₁ , R ₂

Change of direction (arrow)

S

Flow direction (arrow)

u ² / l

intensity

v _I , v _II , v _III

Flow velocity (arrow)

α, β

angle

ρ

consistency

Claims (20)

Method for generating shear flows and turbulence intensities in a fiber suspension (3) passed through a headbox (1) of a paper or board machine, the headbox (1) comprising at least one system (4) feeding the fiber suspension (3), optionally at least one area for turbulence generation (5) and a headbox nozzle (6, 6.1, 6.2) following the fiber suspension (3) in the direction of flow (S) (arrow),
characterized in that the shear flows and the turbulence intensities in the fiber suspension (3) by at least one, preferably two strong and preferably opposite direction changes (R ₁ , R ₂ ) (arrow) with corresponding angles (α, β) in the area of the headbox nozzle (6 , 6.1, 6.2) are generated. Method according to claim 1,
characterized in that the shear flows and the turbulence intensities due to two strong and preferably opposing changes in direction (R ₁ , R ₂ ) (arrow) in three successive nozzle sections (I, II, III.) of the fiber suspension (3) ) with appropriate nozzle heights (H _I , H _II , H _III ), nozzle lengths (L _I , L _II , L _III ) and nozzle shapes. Headbox (1) of a paper or cardboard machine for producing a fibrous web (2), in particular paper or cardboard web, from at least one fibrous suspension (3) with at least one system (4) feeding the fibrous suspension (3), optionally with at least one area for turbulence generation (5) and with a headbox nozzle (6) following in the flow direction (S) (arrow) of the fiber suspension (3), which comprises two width walls (lower nozzle wall (7), upper nozzle wall (8)) extending across the machine width and from which the fibrous suspension (3) exits via a nozzle gap (9) as a fibrous suspension jet (10), in particular for carrying out the method according to one of the preceding claims,
characterized in that the headbox nozzle (6) along the flow direction (S) (arrow) of the fiber suspension (3) at least one, preferably two strong and preferably opposite changes in direction (R ₁ , R ₂ ) (arrow) with corresponding angles (α, β ) having. Headbox (1) according to claim 2,
characterized in that the headbox nozzle (6) due to its two strong and preferably opposite changes in direction (R ₁ , R ₂ ) (arrow) in three flow sections (S) (arrow) of the fiber suspension (3) successive nozzle sections (I, II, III) with appropriate nozzle heights (H _I , H _II , H _III ), nozzle lengths (L _I , L _II , L _III ) and nozzle shapes. Headbox (1) according to claim 3 or 4,
characterized in that the two angles (α, β) each assume a value in the range from 10 ° to 89 °, preferably in the range from 25 ° to 85 °. Headbox (1) according to claim 3, 4 or 5,
characterized in that the first nozzle section (I) in the flow direction (S) (arrow) of the fiber suspension (3) has a nozzle height (H _I ) in the range from 5 mm to 200 mm, a nozzle length (L _I ) in the range from 50 mm to 800 mm and has a predominantly convergent and / or parallel nozzle shape. Headbox (1) according to one of claims 3 to 6,
characterized in that the second nozzle section (II) in the flow direction (S) (arrow) of the fiber suspension (3) and following the first nozzle section (I) has a nozzle height (H _II ) in the range from 5 mm to 100 mm, a nozzle length ( L _II ) in the range from 50 mm to 500 mm and has a predominantly convergent and / or parallel nozzle shape. Headbox (1) according to one of claims 3 to 7,
characterized in that the third nozzle section (III) in the flow direction (S) (arrow) of the fiber suspension (3) and following the second nozzle section (II) has a nozzle height (H _III ) in the range from 3 mm to 50 mm, a nozzle length ( L _III ) in the range from 50 mm to 800 mm and has a predominantly convergent and / or parallel and / or divergent nozzle shape. Headbox (1) according to one of claims 3 to 8,
characterized in that the pulp suspension (3) in the region of the first nozzle portion (I) a flow velocity (v _I) (arrow) of ≥ 1 m / s, in the area of the second nozzle portion (II) (v _II) a flow velocity (arrow) of ≥ 3 m / s and in the area of the third nozzle section (III) has a flow velocity (v _III ) (arrow) in the range of 1 m / s to 20 m / s. Headbox (1) according to one of claims 3 to 9,
characterized in that at least one preferably web-wide air feed device (13) is provided, preferably immediately after a strong change in direction, seen in the flow direction (S) (arrow) of the fiber suspension (3). Headbox (1) according to one of claims 3 to 10,
characterized in that the headbox (1) is designed as a two-layer headbox (1.1), the headbox nozzle (6, 6.1, 6.2) through the lower nozzle wall (7.1) of the one headbox nozzle (6.1, in the third and last nozzle section (III) 6.2) and is formed by the upper nozzle wall (8.1) of the other headbox nozzle (6.1, 6.2). Headbox (1) according to claim 11,
characterized in that a separating element (17) is arranged in the third and last nozzle section (III) of the headbox nozzle (6.1, 6.2). Headbox (1) according to claim 12,
characterized in that the preferably metallic separating element (17) in the flow direction (S) (arrow) of the fiber suspension (3.1, 3.2) is followed by a lamella (18) which preferably extends beyond the headbox nozzle (6.1, 6.2). Headbox (1) according to one of claims 3 to 13,
characterized in that the headbox nozzle (6, 6.1, 6.2) in the flow direction (S) (arrow) of the fiber suspension (3, 3.1, 3.2) is provided with at least one flow obstacle (19). Headbox (1) according to claim 14,
characterized in that the headbox nozzle (6, 6.1, 6.2) is provided with a plurality of flow obstacles (19) which are preferably offset and arranged alternately. Headbox (1) according to one of claims 3 to 15,
characterized in that the headbox nozzle (6, 6.1, 6.2) in the region of its outlet side (6A) is provided on at least one side with an orifice (16). Headbox (1) according to claim 16,
characterized in that the diaphragm (16) is directed against the flow direction (S) (arrow) of the fiber suspension (3). Headbox (1) according to one of claims 3 to 17,
characterized in that the fiber suspension (3, 3.1, 3.2) has a consistency (p) of ≥ 1%, preferably ≥ 1.5%. Headbox (1) according to one of claims 3 to 18,
characterized in that the headbox (1, 1.1) is provided with at least one sectioned density control ("module jet"). Headbox (1) according to one of claims 3 to 19,
characterized in that the headbox (1, 1.1) in the direction of flow (S) (arrow) of the fiber suspension (3) is followed by a gap former, a hybrid former or a wire former.

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