EP2531648A1 - 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
EP2531648A1
EP2531648A1 EP11702216A EP11702216A EP2531648A1 EP 2531648 A1 EP2531648 A1 EP 2531648A1 EP 11702216 A EP11702216 A EP 11702216A EP 11702216 A EP11702216 A EP 11702216A EP 2531648 A1 EP2531648 A1 EP 2531648A1
Authority
EP
European Patent Office
Prior art keywords
turbulence
nozzle
individual
generating
headbox
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Withdrawn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
EP11702216A
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 EP2531648A1 publication Critical patent/EP2531648A1/fr
Withdrawn legal-status Critical Current

Links

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 within the nozzle becomes greater than the reflocculation time, so that a renewed flocculation occurs.
  • flocculation of the pulp suspension after the last fluidization in the headbox has to be avoided as completely 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, which is made within the turbulence generating device only once in one stage, a fluidization in each turbulence generating channel, whereby an acceleration of the flow and short residence time of the pulp suspension 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 subregions of the flow channels of the turbulence generation device forming the fluidization region are proposed, which constitute an overall Length of the turbulence generating device in a prescribed range result.
  • 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 headbox nozzles and the design and dimensioning of these.
  • publication DE 297 13 433 U1 discloses an embodiment of a headbox with a boundary surface extending from the machine width. nozzles, in which at least one of the boundary surfaces is characterized by at least three sections with different Konvergenzwinkel.
  • 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.
  • 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 one immediately upstream in the flow direction of the nozzle
  • Turbulence generating device in which the at least one pulp suspension is feasible by a plurality of turbulence generating channels in partial flows, wherein within the individual turbulence generating channel at least one, a fluidizing area forming area is provided, the turbulence generating means is formed such that the total volume of a single turbulence generating channel
  • the dependence of the volume of this individual turbulence-producing channel, which can be traversed by the last fluidization region in the flow direction, until it leaves the turbulence-generating device is as follows:
  • V TE k2. V F
  • VTE Total volume of a single turbulence generating channel; k2 constant, with 1 ⁇ k2 ⁇ 2, preferably 1 ⁇ k2 ⁇ 1.5; and
  • V F traversed volume of turbulence generating device after the last Fluidmaschines Hoch.
  • 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 total volume of a turbulence generating channel and volume flow through a turbulence generating channel after the fluidization of the The advantage of creating very short channels that significantly reduce the segregation tendency.
  • the volume which can be flowed through according to the last fluidizing region within the individual turbulence-generating channel in the throughflow direction is also optimized until it leaves the turbulence generating device with regard to a short residence time of the individual partial flow.
  • the volume that can be flowed through is, as a function of the open area of the individual turbulence-generating channel, at the exit from the turbulence generation device
  • 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;
  • Bio open cross sectional area of the turbulence generating channel at the exit from the turbulence generating device By adjusting the volume of flow through a turbulence-generating channel and outlet cross-section, small volumes to be flowed through can be provided after the fluidization area to reduce the reflocculation and, at the same time, the outlet cross-section of the individual turbulence-generating channel can be optimally filled at the outlet from the turbulence generation device. Furthermore, the combination of measures minimizes the area of the flow restricting walls within a turbulence generating channel.
  • 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.
  • a first advantageous Variant comprises the volume which can be flowed through in the last fluidization region within the individual turbulence-generating channel in the direction of flow until it leaves the turbulence-generating device, at least one volume region with a flow cross-section which is constant in the direction of flow.
  • the volume which can be flowed through after the last fluidization region within the individual turbulence-generating channel in the throughflow direction has at least one volume region with flow area continuously increasing or decreasing in the direction of flow until it leaves the turbulence generation device.
  • embodiments according to the first or second advantageous variant can be combined with one another and / or embodiments according to the first and second advantageous variants with one another.
  • further aspects can be taken into account and it can also be varied and influenced the length of the flowable volume.
  • the last fluidization region in the flow direction can be spatially strongly limited or can be formed extending over a partial region of the turbulence-generating channel in the direction of flow.
  • the pressure loss can be generated passively, 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 devices and / or possibilities for introducing energy into the pulp suspension within the turbulence-generating channel.
  • the last fluidization region before entering the nozzle is determined by a local, step-like change in the cross-sectional area of the individual turbulence formed generating channel in the flow direction.
  • the cross-sectional area of the channel can be described by a geometric shape and dimension.
  • the step-like change offers the advantage of easily generating higher pressure changes in a highly localized area within the flow path, producing very high fouling turbulence, 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 pulp suspension.
  • the nozzle is designed such that it has a length which is assigned as a function of the size of the individual turbulence-generating channel. arranged and a dividing surface descriptive share area of the cross-sectional area of the nozzle at the inlet to 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 definition of the division surface can be made in different ways. Depending on the design, the determination is based either on the dimensions at the nozzle and the structure of the turbulence generating device or turbulence generating device alone.
  • the size of the individual division surface is, 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 on Entry into the nozzle and the number of individual turbulence-generating channels in the turbulence generator immediately upstream of the nozzle determined. 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 each, more preferably ranging from 0.75 to 0.9, respectively.
  • Such a headbox according to the invention is preferably used in a sheet forming unit for machines for producing fibrous webs, in particular paper, board or tissue webs, further comprising a subordinate forming unit, in which the pulp suspension from the exit slit of the headbox on a string under definition of a line of impact in a free jet 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 can be used as a hybrid former, gap former, comprising two screen belts forming an inlet gap for the pulp suspension or long Siebformer be executed, comprising a screen belt, on the surface of the pulp suspension is applied by means of the headbox.
  • FIG. 1 illustrates, by way of a diagram, the relationship between the size of the substance density of the used material
  • Figure 2 illustrates on the basis of a section of an axial section of a sheet forming unit of a machine for manufacturing ung a web of material 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 volume which can be flowed through after the last fluidization 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 pulp density 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 +), that is, 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. This is also dependent on the chosen pulp itself-
  • FIG. 2 shows, in a schematized and highly simplified representation, a section of a headbox 1 designed for use in machines for producing material webs, in particular machines for producing fibrous webs in the form of paper, board or tissue webs with the length L of the nozzle according to the invention 4 for reducing the reflocculation, that is, flocculation within the pulp suspension FS before or at the exit from the headbox 1.
  • the headbox 1 is a forming unit 2, which is here only indicated by a string example, precedes and forms with this a sheet forming unit 3.
  • the function of the headbox 1 consists in the machine width spreading at least one pulp suspension FS in the forming unit 2, which has at least one Nozzle 4 takes place.
  • 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 is distributed over the entire width of the headbox 1 can be.
  • this comprises an element which extends into the machine cross-section CD and forms a distribution channel, in particular a distributor tube which is designed to taper in the direction of flow in the cross-machine direction CD.
  • 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.
  • 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 outlet gap 1 1 to the forming unit 2 for the production to deliver 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 perpendicular to a describable by the flow direction and the cross-machine direction CD recordable level in columns SPy with y> 1 are arranged 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 d represents the arrangement in the respective column SPy perpendicular to the cross-machine direction CD.
  • channel does not describe a concrete, well-defined structural design and is functionally to be understood as a flow passage Components or in a solid body integrated or incorporated through holes are formed. Visible here are the individual turbulence-generating channels 7.1 1 to 7.31 of the first column SP1.
  • the turbulence generating device 6 forms a flow grid and can be designed differently.
  • 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 single turbulence generating channel 7.xy is a flow channel to which turbulence generating means are associated or integrated.
  • This region is also referred to as the 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 fibrous suspension FS guided therein, is provided within a turbulence-generating channel 7.xy.
  • the headbox 1 is designed and designed such that the residence time of the pulp suspension FS, in particular the individual partial flows in the turbulence generating device 6 or, preferably, and the nozzle 4 while maintaining a sufficient quality of emerging from the exit slit 1 1 of the nozzle 4 of the headbox Free jet is reduced.
  • the individual ne turbulence-generating channel 7.xy is carried out in such a way and designed so that its total volume VTE, which is determined from the sum of the individual volumes of individual subregions of a turbulence generating channel 7.xy, as possible, is kept low.
  • the total volume VTE of the individual turbulence generating channel 7.xy is determined as a function of the volume VF of the turbulence generating device after the fluidization region 12 according to the following relationship: k2.
  • the flowable through the individual partial flow volume or V F is chosen such that a good filling of the open cross-sectional area B T o in the form of the open area at the outlet 6a from the turbulence generating device 6 and thus at the inlet 4E in the nozzle 4 is achieved.
  • the volume V F flowed through 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 V F which characterizes the region of a turbulence-generating channel 7.xy, which extends from the region of the fluidization 12 to the outlet 6A from the turbulence generating device, should be as small as possible in order to ensure the least possible reflocculation.
  • V F kl * B.
  • 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.
  • the length L of the nozzle 4 is set as a function of a division area B T.
  • the smaller the division area B T the shorter the length L of the nozzle 4 is.
  • the length L of the nozzle 4 corresponds to the extension or the distance between the outlet 6 A from the turbulence generating device 6 to the outlet gap 1 1.
  • the length L of the nozzle 4 is measured in the flow direction, that is perpendicular to the outlet cross section of the turbulence generating device 6.
  • the division area 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 individual flow cross-sections, that is, the number N of the individual turbulence-generating channels 7.xy.
  • FIG. 3 a shows the nozzle 4 and the turbulence generating device 6 which precedes it directly in the flow direction. To illustrate, only turbulence-generating channels 7.1 1 to 7.31 are shown 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 proportion of the total cross-section at the inlet 4E in the nozzle 4 as a division surface B T associated with the turbulence-generating channel 7.1 1 can also be 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 area of a hydraulic unit E H.
  • the side lengths t1 and t2 correspond to the lengths of a lattice mesh associated with the individual turbulence-generating channel 7.xy of the turbulence generating device 6 applied to the outlet 6A 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 such that the open at the entrance 4E into the nozzle 4 cross-sectional area B T o the division surface B T of the cross-sectional area of the nozzle 4 at the nozzle start, designed and dimensioned such that the outlet 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 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 different possibilities of forming the fluidizing region 12 for a turbulence-generating element are also shown by way of example. generating 7.Y having hydraulic unit EH on the example of a turbulence tube.
  • FIG. 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 flowing through it.
  • 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 defined here locally in the flow direction by a step-like cross-sectional change 17, in particular enlargement between the first and second sub-regions 18 and 13.
  • FIG. 4b illustrates by way of example a further embodiment of a hydraulic unit EH having a turbulence-generating channel 7.xy, in which the region describing the volume VF flowing through is formed by a plurality of partial regions of very different cross-sectional embodiments.
  • the region describing the volume VF through which it flows is characterized by three subregions 13.1, 13.2 and 14, wherein the subregions 13.1 and 13.2 are constructed with constant but differently sized flow cross sections which are interconnected by an intermediate region 14 ,
  • 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. 4c illustrates the formation of the intermediate region as partial region 15 with a continuous cross-sectional reduction.
  • the fluidization region 1 2 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 a reduced cross-section compared to adjacent areas.
  • FIG. 4d shows an embodiment according to FIG. 4b 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 fiber 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
  • the length L of the nozzle 4 corresponds with between 250 mm to 500 mm inclusive. This length range allows a sufficiently short residence time while maintaining a sufficiently high beam quality.
  • V F (k1 1) 12,167 mm 3
  • V F (k1 7) 85,000 mm 3
  • the solution according to the invention applies to 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 section and can be determined as a quotient of the nozzle initial cross section Q E and the number N of the individual hydraulic units E H.
  • 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 formed forming units 2, in particular wire, hybrid former and twin-wire former.

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 volume total (VTE) d'un canal de production de turbulences (7, 7.xy, 7.11 -7.4n) individuel en fonction du volume (VF) de ce canal de production de turbulences (7, 7.xy, 7.11 -7.4n), qui peut être parcouru après la dernière zone de fluidisation (12, 12.11 -12.31 ) dans la direction de circulation, vaut jusqu'à la sortie (6A) du dispositif de production de turbulences (6) : VTE = k2•VF où VTE représente le volume total d'un canal de production de turbulences (7, 7.xy, 7.11 -7.4n) individuel, k2 est une constante telle que 1 ≤ k2 ≤ 1,5, et VF est le volume parcouru du dispositif de production de turbulences (6) après la zone de fluidisation (12, 12.11 -12.31).
EP11702216A 2010-02-05 2011-02-04 Caisse de tête et unité de formation de feuille comprenant une caisse de tête Withdrawn EP2531648A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102010001614A DE102010001614A1 (de) 2010-02-05 2010-02-05 Stoffauflauf und Blattbildungseinheit mit einem Stoffauflauf
PCT/EP2011/051641 WO2011095582A1 (fr) 2010-02-05 2011-02-04 Caisse de tête et unité de formation de feuille comprenant une caisse de tête

Publications (1)

Publication Number Publication Date
EP2531648A1 true EP2531648A1 (fr) 2012-12-12

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DE102015209389A1 (de) * 2015-05-22 2016-11-24 Voith Patent Gmbh Verfahren und Vorrichtung zur Herstellung von hochgefüllten Papieren

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WO2011095582A1 (fr) 2011-08-11
DE102010001614A1 (de) 2011-08-11
CN102782214A (zh) 2012-11-14

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