EP2531646A1 - Caisse de tête et unité de formation de feuille comprenant une caisse de tête - Google Patents

Caisse de tête et unité de formation de feuille comprenant une caisse de tête

Info

Publication number
EP2531646A1
EP2531646A1 EP11702209A EP11702209A EP2531646A1 EP 2531646 A1 EP2531646 A1 EP 2531646A1 EP 11702209 A EP11702209 A EP 11702209A EP 11702209 A EP11702209 A EP 11702209A EP 2531646 A1 EP2531646 A1 EP 2531646A1
Authority
EP
European Patent Office
Prior art keywords
turbulence
nozzle
headbox
cross
flow
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP11702209A
Other languages
German (de)
English (en)
Inventor
Hans Loser
Markus Haeussler
Wolfgang Ruf
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Voith Patent GmbH
Original Assignee
Voith Patent GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Voith Patent GmbH filed Critical Voith Patent GmbH
Publication of EP2531646A1 publication Critical patent/EP2531646A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F1/00—Wet end of machines for making continuous webs of paper
    • D21F1/02—Head boxes of Fourdrinier machines
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F1/00—Wet end of machines for making continuous webs of paper
    • D21F1/02—Head boxes of Fourdrinier machines
    • D21F1/026—Details of the turbulence section

Definitions

  • the invention relates to a headbox for use in a machine for producing fibrous webs, in particular paper, board or tissue webs of at least one pulp suspension, with at least one feeding device feeding at least one pulp suspension, a nozzle having an outlet slit for dispensing the pulp suspension a free jet and a turbulence generating device directly upstream in the direction of flow of the nozzle, in which the at least one pulp suspension can be passed through a plurality of turbulence-generating channels in partial flows, wherein at least one region forming a fluidization region is provided within the individual turbulence-generating channel.
  • the invention further relates to a sheet forming unit for machines for producing fibrous webs, in particular paper, board or tissue webs, comprising a headbox and a forming unit downstream therefrom.
  • a pulp suspension decisively determines the quality of a fibrous web present as a result of the production process. It can be observed when using fibrous suspensions with higher consistency a deteriorating, writable by the macroscopic and microscopic distribution of fibers and fillers formation.
  • fibrous suspensions with fabric densities in the range of 0.8 to 1, 0 percent are currently introduced with the known headboxes in a downstream forming unit.
  • the aim is to provide over the entire width of the headbox floc-free as possible pulp suspension jet at the exit slit of the headbox.
  • a variety of means, in particular turbulence generating and hydraulic units are used, which usually have a plurality of channels for better fluidization.
  • turbulence generating and hydraulic units which usually have a plurality of channels for better fluidization.
  • These can be designed in various ways and are characterized in the simplest case by step-like cross-sectional changes of the flow cross-section.
  • the adjoining nozzles generally have a length between 600 to 700 mm in order to obtain a sufficient jet stability.
  • the resulting from the lattice wake flow can be sufficiently attenuated within the nozzle over this length.
  • the residence time for the pulp suspension inside the nozzle becomes greater than the reflocculation time, so that renewed flocculation occurs.
  • flocculation of the fibrous stock suspension after the last fluidization in the headbox has to be avoided as far as possible. This requires correspondingly short-built units. The problem of flocculation and its effect on the quality of the resulting fibrous web is described in detail in the document EP 1 31 3 912 B1.
  • a headbox is proposed with a modification of the turbulence generating device through which within the turbulence generating device only once in a stage fluidization in each turbulence generating channel is made, whereby an acceleration of the flow and short residence time of Faserstoffsuspen- sion is achieved in the headbox.
  • the degree of fluidization can then be maintained by the special design of the fins within the nozzle.
  • stepwise changes in the cross-sectional areas and lengths of the individual portions of the flow channels of the turbulence generation device which form the fluidization region are proposed, which result in an overall length of the turbulence generation device in a prescribed range.
  • a plurality of measures which are characterized by a modification of the nozzle or of the turbulence generating device, are also previously known.
  • Document DE 101 06 684 A1 discloses an embodiment of a headbox having a fin end specifically designed to avoid flow instabilities within the nozzle and thus vibrational excitation, which has a slope on the side directed towards the nozzle wall and is provided with a structure on the side away therefrom ,
  • the publication WO 2008/077585 A1 discloses the promotion of the formation of symmetrical properties in the Z direction via symmetrically formed material run-up nozzles and the design and dimensioning of these.
  • DE 297 13 433 U1 discloses an embodiment of a headbox with a nozzle formed from machine-bordering boundary surfaces, in which at least one of the boundary faces is defined by at least three sections with different convergence angles is characterized.
  • Document DE 102 34 550 A1 discloses an embodiment of a head box in a sheet forming system, in which the nozzle is characterized by a length greater than 400 mm, wherein the length of the upstream turbulence generator preferably also lies in this range.
  • the known measures are not sufficient to suppress or reduce the reflocculation at higher densities of the pulp suspension, for example, of more than 1, 0 percent, in particular of more than 1, 2 percent, to the desired extent.
  • the invention is therefore based on the object, a headbox of the type mentioned for use in machines for the production of fibrous webs, especially paper, cardboard or tissue webs, develop such that the d-mentioned disadvantages are avoided and the reflocculation of the pulp suspension after the last fluidizing area is reduced or prevented. It is particularly important to reduce the residence time of the pulp suspension in the headbox, in particular the turbulence generating device and the nozzle with constant beam quality.
  • the solution according to the invention is characterized by the features of independent claims 1 and 9. Advantageous embodiments are described in the dependent claims.
  • a headbox for use in a machine for producing fibrous webs, in particular paper, board or tissue webs from at least one pulp suspension with at least one, the at least one pulp suspension supplying feeder, a nozzle having an outlet gap for delivering the pulp suspension in a free jet and a turbulence generating device directly upstream of the nozzle in which the at least one fibrous suspension can be passed through a plurality of turbulence-generating channels in partial flows, wherein within the individual turbulence-generating channel at least one area forming a fluidizing area is provided, the turbulence generating device is designed such that the volume which can flow through the last fluidizing area within the individual turbulence-generating channel until it exits the turbulence generating device as a function of the open area of the individual turbulence-generating channel at the outlet from the turbulence generating device is:
  • V F flowed through volume of the turbulence generating device after the last Fluidleiters Committee;
  • k1 constant, with 1 ⁇ k1 ⁇ 10, preferably 3 ⁇ k1 ⁇ 7;
  • a fluidization region is understood to mean a region in which there is a homogeneous distribution of the constituents containing the pulp suspension, such as, for example, fibers and fillers.
  • the action can be carried out actively by controllable elements with respect to their effect, such as static mixing devices or passively by the geometric design of the flow path and the consequent generation of turbulence on the pulp suspension with dissolution of accumulations, in particular flakes.
  • the region can be locally limited on a line in the cross-machine direction or can be designed to extend in the direction of flow in the direction of flow.
  • the inventive solution provides by the inventive tuning of the volume flow through a turbulence generating channel and exit cross-section of this the advantage of providing a small existing volume to be flowed to the fluidization to reduce the reflocculation and on the other hand simultaneously the possibility of optimal Filling the outlet cross section of the individual turbulence generating channel at the outlet of the turbulence generating device.
  • the geometric configuration of the volume which can be flowed through in a single turbulence-generating channel after the last fluidization region can be varied, in particular the shape of the volume with respect to the flow guide can be chosen as desired.
  • the volume which can be flowed through according to the last fluidization region within the individual turbulence-generating channel in the throughflow direction until at the exit from the turbulence generation device has at least one flow cross-section constant flow cross-section.
  • the volume which can flow through the last fluidization region within the individual turbulence-generating channel in the throughflow direction has at least one volume region with a flow cross-section which increases or decreases steadily in the direction of flow until it leaves the turbulence-generating device.
  • embodiments according to the first or second advantageous variant can be combined with one another or else embodiments according to the first and second advantageous variants with one another.
  • further aspects can be taken into account and it can also be the length of the volume flowed through can be varied.
  • the last fluidization region viewed in the flow direction can be locally strongly limited or else formed extending over a partial region of the turbulence-generating channel in the direction of flow.
  • the pressure loss may be passive, in the simplest case as a function of the geometry and / or dimensioning of the flow path in the individual turbulence generating channel or actively by providing additional means and / or possibilities for energy input into the Pulp suspension can be generated within the turbulence generating channel.
  • the energy input while generating a pressure loss can be realized in various ways.
  • the last fluidization region before entry into the nozzle is formed by a local, step-like change in the cross-sectional area of the individual turbulence-generating channel in the direction of flow.
  • the cross-sectional area of the channel can be described by a geometric shape and dimension.
  • the step change offers the advantage of easily generating higher pressure changes in a highly localized region within the flow path, producing very high turbulence to break up flocs, thereby improving overall fluidization.
  • the thus set high fiber mobility is then maintained by the short residence time due to the low volume according to the invention until it leaves the nozzle.
  • the last fluidization region before entry into the nozzle can be formed by a continuous change in the cross-sectional area of the individual turbulence-generating channel in the direction of flow.
  • the size of the change in the cross-sectional area in the case of a step-like or continuous change from the minimum cross-sectional area to the maximum cross-sectional area, which can be described as the difference between the hydraulic diameters characterizing the cross-sectional areas, is suitably selected to produce the required minimum pressure change.
  • the pressure change may additionally or alternatively be caused by at least one static mixing device to be provided in the fluidization region or at least one means for introducing energy to produce the desired pressure loss in the fiber suspension.
  • the nozzle is embodied such that its length as a function of the size of the share area of the cross-sectional area of the nozzle assigned to a single turbulence-generating channel and describing a dividing surface at the inlet the nozzle is:
  • the length of the nozzle is characterized by the distance between the exit from the upstream turbulence generating device and the exit slit of the nozzle and is measured perpendicular to the exit surface from the turbulence generating device.
  • the solution according to the invention specifically uses the relationship between the hydraulic division and the cross-section in the nozzle, wherein the formation of the length of the nozzle according to the functional relationship of the invention has the advantage of a short residence time of the pulp suspension in the nozzle while maintaining the beam quality at the exit from the exit slit offers.
  • the determination is based either on the dimensions at the nozzle and the structure of the turbulence generating device or the turbulence generating device alone.
  • the size of the individual dividing surface is determined according to a first particularly advantageous embodiment by the quotient of the cross-sectional area of the nozzle, in particular the size of the cross-sectional area at the inlet to the nozzle and the number of individual turbulence-generating channels in the turbulence generating device directly upstream of the nozzle. This definition is almost free from the influence of tolerances.
  • the size of the individual division surface is determined by the geometry of the cross-sectional area of the individual, comprising a turbulence generating channel or forming hydraulic unit at the exit from the turbulence generating device.
  • a hydraulic unit is understood to mean the unit having a single turbulence-generating channel alone or as part of an overall unit. This comprises the channel and at least one wall forming or enclosing it.
  • the individual turbulence-generating channel of the turbulence-generating device is designed such that the ratio of the flow cross-section of the channel at the outlet from the turbulence-generating device and its associated division surface of the cross-sectional area of the nozzle at the inlet to the nozzle in the range from 0.5 to 0 inclusive , 95, preferably ranging from 0.75 to 0.95, more preferably ranging from 0.75 to 0.9, respectively.
  • Such inventively embodied headbox is preferably in a sheet forming unit for machines for producing fibrous webs, in particular paper, board or tissue webs, further comprising a downstream forming unit, in which the pulp suspension from the exit slit of the headbox on a fabric under definition Auf Economicsline in a free jet on or is introduced, get used.
  • the execution of the headbox is carried out such that the residence time of the pulp suspension in the nozzle and in the turbulence generating device is kept as low as possible.
  • the forming unit may be embodied as a hybrid former, gap former, comprising two screen belts or a wire screen forming an inlet gap for the pulp suspension, comprising a screen belt, on the surface of which the pulp suspension is applied by means of the head box.
  • FIG. 1 shows, on the basis of a diagram, the relationship between the size of the consistency of the pulp suspension used and the formation
  • FIG. 2 illustrates, on the basis of a section of an axial section of a sheet forming unit of a machine for producing a material web, a headbox according to the invention
  • FIG 3a shows in detail a section of a headbox according to the invention according to Figure 2;
  • FIG. 3b shows a view A-A according to FIG. 3a.
  • FIGS. 4a to 4d show possible geometric configurations of the volumes which can be flowed through after the last fluidizing region in a turbulence-generating channel.
  • FIG. 1 illustrates the influence of the pulp density SD of a pulp suspension FS on the formation on the basis of a diagram.
  • the diagram illustrates in detail the formation of the flake structure FL in the free jet resulting from the exit of the pulp suspension FS from a nozzle of a headbox with respect to the dimension of the flakes FL forming as a function of the consistency SD.
  • This shows the relationship between high consistency SD and an uneven and coarse-grained formation with regard to the arrangement of the fibers and fillers due to increased flocculation (arrow FL +), ie the tendency for larger flocs FL to emerge in the free jet emerging from the exit slit of a headbox a pulp suspension FS in conventional known headboxes.
  • FIG. 1 illustrates only the basic relationship between the consistency of a fibrous suspension FS and the tendency of the flock to tilt.
  • FIG. 2 illustrates a schematic highly simplified representation of a section of an inventively designed headbox 1 for use in machines for producing webs, especially machines for the production of fibrous webs in the form of paper, cardboard or Tissuebah- nen with inventive length L of the nozzle 4 to reduce the reflo- tion, ie back flocculation within the pulp suspension FS before or at the exit from the headbox.
  • the headbox 1 is a forming unit 2, which is here only exemplified by a stringing, upstream, and forms with this a sheet forming unit 3.
  • the function of the headbox 1 consists in the machine width deployment of at least one Faserstoffsus- pension FS in the forming unit 2, what about at least one nozzle 4 takes place.
  • a coordinate system is applied to the illustrated section of the exemplary sheet forming unit 3.
  • the X-direction describes the longitudinal direction of the machine and is also referred to as machine direction MD. This coincides with the passage direction of the fibrous web.
  • the Y-direction describes the direction transverse to the direction of passage of the fibrous web F, in particular the width direction of the machine, and is therefore also referred to as the cross-machine direction CD, while the Z direction corresponds to the height direction.
  • the flow direction coincides in the headbox 1 with the machine direction MD.
  • other arrangements are also conceivable, in particular with an inclination relative to the machine direction MD.
  • the headbox 1 comprises a feed device 5, via which the at least one pulp suspension FS can be distributed over the entire width of the headbox 1.
  • this comprises in the machine transverse direction CD extending, a distribution channel forming element, in particular a distributor tube, which is tapered in the machine direction CD in the flow direction.
  • the pulp suspension FS passes from the feed device 5 to the nozzle 4 via at least one turbulence-generating device 6.
  • only one turbulence-generating device 6 is shown directly upstream of the nozzle 4 in the flow direction.
  • embodiments of headboxes 1 with a plurality of turbulence-generating devices are also conceivable be passed through the interposition of mixers and / or mixing chambers.
  • the nozzle 4 connects to form a nozzle chamber 8, which is suitable to substantially accelerate the flow of the pulp suspension FS during operation and the pulp suspension FS through an exit gap 1 1 to the forming unit 2 for producing a Material web.
  • the exit slit 1 1 is limited here by way of example of an aperture 9 and the nozzle walls 10.1, 10.2.
  • the fibrous suspension FS is divided according to a predefined division and distributed in sub-streams out.
  • the turbulence generating device 6 comprises a multiplicity of turbulence-generating channels 7, x extending in the direction of flow and with at least one direction component in the machine direction MD, which are either machine-width-shaped or parallel to each other in the cross-machine direction CD in rows Rx with x> 1 and in the vertical direction is called perpendicular to one the flow direction and the CD direction CD writable plane are arranged in columns SPy with y> 1 parallel to each other.
  • the first index after the reference numeral describes the arrangement of the individual channel in the respective row Rx, while the second index reproduces the arrangement in the respective column SPy perpendicular to the cross-machine direction CD.
  • channel does not describe a specific, firmly defined structural design and is functionally understood as a flow passage, which can be formed by individual components or through openings integrated into or integrated into a solid body In the simplest case, this comprises a perforated plate which describes the turbulence-generating channels 7.xy and has passage openings and / or a tube bundle forming the individual turbulence-generating channels 7.xy.
  • the individual turbulence-generating channel 7.xy is a flow channel to which means for generating turbulences are assigned or integrated in.
  • an energy input into the partial stream guided in the respective channel takes place with the formation of This region is also referred to as fluidization region 12, wherein at least one such fluidization region 12, in which a pressure change is generated in the individual partial flow of the pulp suspension FS conducted in the latter, is provided within a turbulence-generating channel 7.xy.
  • This can be due to the geometric design of the individual turbulence-generating channel 7.xy, in particular a local change in the cross-sectional area described in the flow direction and / or the arrangement of additional devices for introducing an additional energy input into the individual, in the respective turbulence-generating channel 7.xy Guided partial flow can be achieved.
  • the headbox 1 is designed and executed such that the residence time of the pulp suspension FS, in particular of the individual partial flows in the turbulence generating device 6 or, preferably, and the Nozzle 4 while maintaining a sufficient quality of the emerging from the exit slit 1 1 of the nozzle 4 of the headbox free jet is reduced.
  • the flow-through volume VF is formed by a portion of the turbulence-generating channel 7.xy, which extends from the fluidization region 12 to the outlet 6A from the turbulence generating device 6.
  • the volume VF should be as small as possible in order to ensure the least possible reflocculation.
  • the flow volume VF for the subregion of the individual turbulence-generating channel is 7.xy
  • V F flowed through volume of the turbulence generating device after the last Fluidleiters Committee;
  • k1 constant, with 1 ⁇ k1 ⁇ 10, preferably 3 ⁇ k1 ⁇ 7;
  • the headbox 1 according to the invention is designed and executed such that the residence time of the pulp suspension FS in the nozzle 4 is also reduced while maintaining a sufficient quality of the free jet emerging from the outlet gap 11.
  • the length L of the nozzle 4 is determined as a function of the hydraulic division of the lattice tracking flow in the nozzle 4. Specifically, the length L of the nozzle 4 is set as a function of a division area B T. The smaller the dividing area B T , the shorter the length L of the nozzle 4. The length L of the nozzle 4 corresponds to the extent or the distance between the outlet 6A from the turbulence generating device 6 to the outlet gap 11.
  • the length L of the nozzle 4 is measured in the flow direction, that is perpendicular to the outlet cross section from the turbulence generating device 6.
  • the division surface B T corresponds to the areal proportion of the cross-sectional area of the nozzle 4 at the nozzle start or nozzle inlet 4 E assigned to a hydraulic unit E H.
  • a single turbulence-generating channel 7.xy alone or as part of a total unit having or containing unit is referred to as a hydraulic unit E H.
  • This comprises the channel and at least one wall forming or enclosing it.
  • the division area B T can therefore be determined from the quotient of the cross-sectional area at the nozzle start or inlet 4 E and the number N of the individual flow cross-sections, that is, the number N of the individual turbulence-generating channels 7.xy.
  • FIGS. 3a and 3b show the nozzle 4 and the turbulence generating device 6 which precedes it directly in the direction of flow.
  • FIG. 3a shows the nozzle 4 and the turbulence generating device 6 which precedes it directly in the direction of flow.
  • turbulence-generating channels 7.1 1 to 7.31 are shown here in three rows with the fluidization regions 12.1 1 to 12.31.
  • FIG. 3b shows, by way of example, in a view AA according to FIG. 3a, a view of the outlet 6A from the turbulence generating device 6 with individual turbulence-generating channels extending in the machine transverse direction CD, for example in four rows R1 to R4 and the gaps SPy, here SP1 to SPn 7.1 1 to 7.4n, wherein the individual turbulence-generating channels 7.1 1 to 7.1 n, 7.21 to 7.2n, 7.31 to 7.3n and 7.41 to 7.4n within a single row R1 to R4 each preferably parallel to each other in machine transverse direction CD with preferably the are arranged the same pitch and the arrangement of the rows R1 to R4 perpendicular to the machine transverse direction CD and to the flow direction also preferably takes place parallel to each other.
  • the nozzle start cross-sectional area which can be acted on by a single turbulence-generating channel 7.1 1 to 7.xy is referred to as a division area BT.
  • the individual hydraulic unit EH is reproduced here by way of example in the form of the unit having the individual turbulence-generating channel 7.1 1.
  • the proportion of the total cross section at the entrance 4E into the nozzle 4 assigned to the individual turbulence-generating channel 7.1 1 results from the quotient of the cross-sectional area Q4E at the nozzle start or entry 4E into the nozzle 4 and the number N of the turbulence-generating channels 7.xy.
  • the cross-sectional area Q 4 E at the nozzle beginning 4 E is determined as a function of the extension of the nozzle 4 in the cross-machine direction CD, that is from the width AB and the height h D , which coincide with the width and the height of the turbulence generating device 6 at the outlet 6A that is
  • the portion of the total cross-section at the entrance 4E into the nozzle 4 as a division surface B T assigned to the turbulence-generating channel 7.1 1 can also be shown in the illustrated embodiment with completely adjacent walls of the hydraulic units E H with a rectangular cross-section through the product of the dimensions of the hydraulic Unit E H , in particular the side lengths t1 and t2 are determined.
  • the division area B T corresponds to the area of the individual hydraulic unit E H , that is to say the cross-sectional area of the turbulence-generating channel at the exit from the turbulence-generating device 6 and the surface area resulting from the wall thickness d, ie the sum of the open and closed areas of one hydraulic unit E H.
  • the lateral lengths t1 and t2 correspond to the lengths of a lattice mesh of one of the individual turbulence-generating channel 7.xy assigned to the outlet 6A from the turbulence generating device 6 theoretical grid.
  • the residence time in the nozzle 4 is further influenced by the change in the flow velocity of the individual partial flow when passing from the individual turbulence-generating channel 7.xy into the nozzle 4. If possible, this change should be kept as small as possible.
  • the turbulence generating device 6 is designed and arranged in such a way that the cross-sectional area B T o of the dividing surface B T of the cross-sectional area of the nozzle 4 at the nozzle beginning, which is open at the inlet 4E, is designed and dimensioned in such a way that Occurrence ratio B T o to B T > 0.5, preferably> 0.75.
  • the exit ratio is denoted by z, resulting from
  • B TO corresponds to the open cross-sectional area of the respective turbulence-generating channel 7.xy at the outlet 6A from the turbulence generating device 6 and thus describes the flow cross-section of the respective turbulence generating channel at the exit 6A.
  • FIGS. 4a to 4d illustrate, by way of example, different embodiments, whereby at the same time various possibilities of forming the fluidization region 12 for a hydraulic unit EH having a turbulence-generating channel 7.xy are reproduced using the example of a turbulence tube.
  • 4a illustrates the subdivision into at least two partial regions, a first partial region 18 and a second partial region 13 describing the volume VF which can be flowed through. This region is characterized by a constant flow cross section in the direction of flow until the outlet cross section at the outlet 6A of the turbulence generation device 6 is reached.
  • the fluidization region 12 is locally limited in the flow direction by a step-like cross-sectional change 1 7, in particular enlargement between the first and second portions 18 and 13 formed.
  • FIG. 4b illustrates by way of example a further embodiment of a hydraulic unit EH having a turbulence-generating channel 7.xy, in which region of the plurality of flow volumes VF describing the flow-through volume is formed by sections of different cross-sectional designs.
  • the area describing the volume VF which can flow is characterized here by way of example by three subregions 13.1, 13.2 and 14, wherein the subregions 13.1 and 13.2 are formed in the flow direction with constant but differently sized flow cross sections, ie forming an intermediate region Subregion 14 are interconnected.
  • the portion 14 is characterized by a continuous change in cross section in the flow direction, which is formed as a cross-sectional increase.
  • FIG. 1b illustrates by way of example a further embodiment of a hydraulic unit EH having a turbulence-generating channel 7.xy, in which region of the plurality of flow volumes VF describing the flow-through volume is formed by sections of different cross-sectional designs.
  • the area describing the volume VF which can flow
  • the fluidization region 12 is designed to extend over a partial region of the hydraulic unit EH in the direction of flow, wherein the formation as a function of the geometry and / or dimensioning of the flow path in the individual turbulence-generating channel 7.xy, here the partial region 16 with reduced cross-section compared to the adjacent Areas.
  • FIG. 4 d shows an embodiment according to FIG. 4 b with formation of the fluidization region 12 by at least one static mixing device 19 to be provided in the fluidization region or at least one means for introducing energy to produce the desired pressure loss in the fibrous suspension.
  • the individual hydraulic units E H of the turbulence generating device 6 are designed as outlet pipes with a square cross section.
  • the side lengths t1 and t2 are 25 mm.
  • the wall thickness d is 1 mm.
  • the division area B T results from
  • This length range allows a sufficiently short residence time while maintaining a sufficiently high beam quality.
  • headboxes 1 which are formed with or without lamellae.
  • Decisive here is the choice of the length L of the nozzle 4 as a function of the division area B T , which corresponds to the proportion of a single hydraulic unit at the nozzle start cross-section and are determined as the quotient of the nozzle initial cross-section Q E and the number N of the individual hydraulic units E H can.
  • Such a designed headbox 1 can be further modified in any manner.
  • These can be headboxes which are equipped with lamellae and / or are characterized with the dilution water technology, that is to say at least one metering device for metering in at least one further fluid into the pulp suspension.
  • the headbox 1 according to the invention can also be used in combination with arbitrarily designed forming units 2, in particular wire, hybrid former and twin-wire former.

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Abstract

La présente invention concerne une caisse de tête (1) comprenant au moins un dispositif d'amenée (5) qui amène au moins une suspension de matière fibreuse (FS), une buse (4) présentant un espace de sortie (11) et servant à émettre la suspension de matière fibreuse (FS) sous la forme d'un jet libre (F), et un dispositif de production de turbulences (6) disposé directement en amont de la buse (4) dans la direction de circulation et dans lequel la ou les suspensions de matière fibreuse (FS) est ou sont acheminées(s) sous la forme de flux partiels par une pluralité de canaux de production de turbulences (7, 7.xy, 7.11 -7.4n) lors du fonctionnement de la caisse de tête (1), au moins une zone formant une zone de fluidisation (12, 12.11 -12.31) se trouvant à l'intérieur du canal de production de turbulences (7, 7.xy, 7.11 - 7.4n) individuel. La caisse de tête (1) selon l'invention se caractérise en ce que le dispositif de production de turbulences (6) est conçu de sorte que le volume (VF) qui peut être parcouru après la dernière zone de fluidisation (12, 12.11 -12.31) dans la direction d'écoulement, à l'intérieur d'un canal de production de turbulences (7, 7.xy, 7.11 -7.4n) individuel jusqu'à la sortie (6A) du dispositif de production de turbulences (6) en fonction de la surface de section transversale ouverte (BTo) du canal de production de turbulences (7, 7.xy, 7.11 -7.4n) individuel à la sortie (6A) du dispositif de production de turbulences (6), vaut: formule (I). Dans cette formule, VF est le volume parcouru du dispositif de production de turbulences (6) après la dernière zone de fluidisation (12, 12.11 -12.31), k1 est une constante telle que 1 ≤ k1 ≤ 10, de préférence 3 ≤ k1 ≤ 7, et B TO représente la surface de section transversale ouverte du canal de production de turbulences (7, 7.xy, 7.11 -7.4n) à la sortie (6A) du dispositif de production de turbulences (6).
EP11702209A 2010-02-05 2011-02-04 Caisse de tête et unité de formation de feuille comprenant une caisse de tête Withdrawn EP2531646A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102010001613A DE102010001613A1 (de) 2010-02-05 2010-02-05 Stoffauflauf und Blattbildungseinheit mit einem Stoffauflauf
PCT/EP2011/051624 WO2011095574A1 (fr) 2010-02-05 2011-02-04 Caisse de tête et unité de formation de feuille comprenant une caisse de tête

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EP2531646A1 true EP2531646A1 (fr) 2012-12-12

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EP11702209A Withdrawn EP2531646A1 (fr) 2010-02-05 2011-02-04 Caisse de tête et unité de formation de feuille comprenant une caisse de tête

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CN102822417B (zh) 2015-02-18
DE102010001613A1 (de) 2011-08-11
CN102822417A (zh) 2012-12-12
WO2011095574A1 (fr) 2011-08-11

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