FI93980B - Process and arrangement for control of the head box - Google Patents

Abstract

The invention relates to a process and a system in the control of a head box. In the process a flow Q4.1, Q4.2 ... Q4.n of adjustable concentration is introduced at various points over the width of the head box. The concentration of the flow Q4.1, Q4.2 ... Q4.n is adjusted by means of a distributing valve 19a1, 19a2 ..., which includes an outlet duct 201, 20a2 ..., the end opening of which A3 can be set at L1, L2 in relation to the end opening A1.1, A1.2 ... of the flow duct 18a1, 18a2 ... of the constituent flow Q2.1, Q2.2 ... Q2.n and to the end opening A2.1, A2.2 ... of the flow duct 18a1, 18a2 of the second constituent flow Q3.1, Q3.2 .... Constituent flows Q2.1; Q3.1 are led to the outlet duct 20 according to how the outlet duct 20 is adjusted in relation to the end openings of the flow ducts of the constituent flows. The concentration of the flow Q4.1, Q4.2 ... Q4.n that is led to the outlet duct 20 is here adjusted whilst the flow quantity is kept constant during the adjustment. The flows in question Q4.1, Q4.2 ... Q4.n are led further to the required point on the width of the head box. <IMAGE>

Description

93980

Method and apparatus for headbox adjustment Förfarande och anordning vid regiering av inloppslädan 5

The invention relates to a method and a device for adjusting the headbox of a paper machine / board machine, by which the method and device according to the invention can reliably influence the basis weight profile of paper from paper / board web width and preferably also the paper / board web fiber orientation profile from paper / board web width.

10

As is already known, the lip flow of the headbox pulp suspension must be constant in the transverse direction of the paper / board machine. The transverse flow that creates the skew of the fiber orientation has to do with the quality factors of the paper to be made, such as the anisotropy of strength and elongation. The level and variation of the anisotropy in the transverse direction also affects the printing properties of the paper. In particular, a major requirement is that the major axes of the orientation distribution of the paper fiber network coincide with the directions of the major axis of the paper and that the orientation be symmetrical with respect to these axes.

20 Less mass flows at the edges of the headbox mass flow channel. This edge effect causes a very strong linear skew in the profile. The profile defects of the headbox turbulence generator generally cause a nonlinear skew inside the edge regions of the flow channels of the profile.

25 The unevenness of the basis weight profile caused by the drying shrinkage of the paper is compensated by bombarding the lip opening so that the lip opening is thicker in the middle of the pulp jet. When the paper web is dried, it shrinks less from the center of the web than from the edge areas, with shrinkage generally being about 4% in the center and about 5-6% in the edge area. Said shrinkage profile causes a change in the cross-sectional profile corresponding to the web so that, due to the shrinkage, the dry basis weight profile of the web transverse to the cross-section is changed during drying so that both edge areas of the web have a slightly higher basis weight than 2,93980. As is known, the said basis weight profile is adjusted by means of a tip strip so that the top strip of the headbox is kept more open from the central area than from the edge areas. By means of said arrangement, the pulp suspension is forced to move towards the central region of the web. This fact continues to affect the orientation of the fiber orientation. The directional distribution or orientation of the fiber network should coincide with the directions of the major axis of the paper and the orientation should be symmetrical with respect to these axes. In said tip list adjustment, the change of orientation is influenced as the mass suspension flow obtains lateral components.

10 Adjusting the headbox lip also causes a change in the transverse flows of the pulp jet, although the purpose of the adjustment is to affect only the basis weight profile, i.e. the thickness profile of the pulp suspension layer to be fed. The transverse flows thus have a direct relation to the distribution of the fiber orientation.

Equipment solutions for adjusting the fiber orientation and equipment solutions for adjusting the basis weight profile of the track are known separately from the prior art. However, in the prior art solution, adjusting the basis weight profile by means of a tip strip also inevitably affects the fiber orientation of the web.

A method is known in the art for controlling the distortion of the fiber orientation of a paper web in a paper machine headbox. In the method, fluid flows are directed to the edge cells at the headbox turbulence generator, and by adjusting the magnitude and relationship of said flows, the transverse flows of the pulp suspension are affected and thus the skew of the fiber orientation is adjusted. The flows introduced into the edge soles generate a transverse flow rate that compensates for the distortion of the fiber orientation.

Applicant's prior F1 patent application 884408 again discloses a method in a paper machine headbox for controlling the distribution of the fiber orientation of a paper web in the transverse direction of the machine 30, which method adjusts the transverse velocity component of a lip jet by orienting a turbulence generator turbulence tube.

3,93980

With the above-mentioned known methods of controlling the fiber orientation of the paper web, only linear skew profiles can generally be controlled. The known methods are suitable for controlling the fiber orientation, but when used they generally leave even a large nonlinear residual error with respect to the uniform distribution of the orientation. The known methods are well suited for the basic adjustment of orientation skew. However, the known methods are not able to control the individual errors that can occur in the orientation in the middle region of the track and which are caused, for example, by the piping errors of the turbulence generator.

A number of methods for adjusting the tip strip are also known, in which the position of the tip strip in the headbox of a paper machine is changed by measuring the basis weight profile and influencing the thickness of the pulp suspension discharged onto the wire and thereby the basis weight of the paper web. However, as described above, said control causes orientation errors, because the control restricts the flow on the other hand and thus causes lateral velocity components in the flow.

15

FI patent application No. 912230 is known from the prior art, in which the headbox is divided along its width into partitions and in which the solution in a single compartment has at least one input line for conducting a partial current. In addition, in the solution, a mixer is connected in front of the individual input line, with which the mass suspension ratio can be adjusted. However, the solution has not been able to show how the mixing ratio can be reliably adjusted without changing the flow rate. No detailed solution for implementing the adjustment has been presented.

Our application discloses a detailed method and apparatus solution by means of which the consistency of the pulp suspension can be adjusted without causing a change in the flow rate. Also shown is a solution in which the pressure level of the total flow can be adjusted; and thus the flow rate and flow rate while maintaining the agitation ratio at its controlled constant.

4,93980

The goal of the density control of the basis weight is to remove the coupling of the cross-sectional profile and the fiber orientation profile. When adjusting the cross-sectional profile of the basis weight by profiling the consistency, for example when using 0-water, the maximum amount of dilution water is 20 1 / m / s. In order for this amount of water not to cause transverse flows and to eliminate the goal of consistency control, the amount of dilution water must be compensated so that the flow rate from the turbulence generator in the transverse direction of the machine is constant. The mixed / controlled flow rate should be kept constant.

In the method and apparatus solution according to the invention, a flow with a controlled concentration is introduced into a pulp suspension stream with an average concentration of 10. This flow with a controlled concentration is obtained by combining two different sub-flows. The second partial flow is preferably an O-water flow and the second partial water flow is preferably a pulp suspension flow with an average concentration. Said partial flows are led along their own channels close to the distribution valve. The distribution valve 15 comprises a movable outlet pipe, the end of which can be brought into different positions with respect to the ends of the partial flow channels. In this way, partial flows to the outlet pipe are extracted from the partial flow channels at a certain distribution ratio. The part of the flow that does not go to the outlet pipe is returned to the circulation. The flow taken into the outlet pipe is further directed to a certain width position in the headbox of the paper machine / board machine. However, this flow is adjustable in concentration, while the flow rate remains at its predetermined constant value before the concentration adjustment. However, in the solution according to the invention it is also possible to adjust the pressure level of said flow, i.e. its flow rate. This is done by means of a throttle valve in the outlet pipe. In this way, the fiber orientation profile of the web can also be adjusted from the web width.

25

The invention will now be described with reference to some preferred embodiments of the invention shown in the figures of the accompanying drawings, to which, however, the invention is not intended to be exclusively limited.

The method according to the invention is mainly characterized by what is stated in claims 1 and 4.

Il 5 93980

Figure 1 shows a headbox of a paper machine / board machine according to the invention in a cross-sectional view.

Figure 2A illustrates axonometrically the control principle according to the invention. 5

Figure 2B shows the position of the end opening of the outlet pipe with respect to the end openings of the partial flow channels.

Figure 3A is a section I-I of Figure 1.

10

Figure 3B shows a section II-II of Figure 1.

Figure 3C shows a section III-III of Figure 1.

Figure 3D shows a section IV-IV of Figure 1.

Figure 3E shows a section V-V of Figure 1.

Figure 1 shows a cross-sectional view of a headbox 10 of a paper machine / board machine 20 according to the invention. The pulp Mj is led from the distribution chamber 11 to the distribution line 12 and through the distribution line either directly or as in the figure through the intermediate chamber E to the turbulence generator 13.

The turbulence generator 13 comprises a turbulence piping 14, the turbulence pipes 25 14aj, 14a2 ... of which open into the intermediate chamber E shown in Fig. 1 and at one end into the lip channel 15. The pulp suspension M is thus introduced into the lip channel 15! the flow Qj and in addition a concentration-controlled flow Q4 consisting of a suspension of mass Mj and water N M = Mj + N. The concentration-adjustable flows Q4 „Q42 .... Q4 n are directed to the different width points of the headbox of the paper machine / board-30 machine with the desired distribution or resolution, preferably 12ax j, 12aj <2 ... 12a1 n. Each flow Q41 ... Q4n is directed at its own width point to a mass M of an unregulated concentration coming to that width point 6 93980! to the flow Qj. Thus, by means of the flow-controlled flow Q4, the basis weight of the paper is adjusted at the desired web width point and the errors therein are corrected.

5 The flow-controlled flow Q4 is formed as follows. A dilution liquid, preferably a so-called 0-water through the flow channel 17at. A second partial flow of the mass Mj Q3 is led from the distribution chamber 11 to the flow channel 18aj. Flow channel 17a! the mouth is marked Aj. Flow channel 18a! the orifice is marked A2. On the outlet side of the above-mentioned orifices with respect to the flow direction 10, there is a distribution valve 19 comprising an outlet channel 20, i.e. an overflow pipe movable at its orifice A3 (arrows Lj,! ^) With respect to the orifices A1, A2 of the channels 17,18. The valve 19 further has a flow passage 21 back to the circulation. The discharge channel 20 comprises an actuator with which the discharge channel 20 can be moved at least at its end 20 '(arrows 1, 1). The end A3 of the discharge channel 20 is moved to the desired coverage position 15 with respect to the ends A15A2 of the channels 17 and 18. The flow Q3 u + Q2.1J · Channels 17a !, 18a!, Which depends on the relative position of the end-opening A3 of the discharge-channel and the end-openings A2, A2 of the channels, is thus introduced into the discharge duct 20. are superimposed on their end openings A3, A2 and the outlet channel 20 is adapted to be movable from the channels 17a !, 18a perpendicular to the end opening A3! in the flow directions S1, S2 of the incoming flows. Flows from 20 channels 17a !, 18a! come laminarly and immiscible with each other, so that they can be taken out of the outlet channel 20 without the currents being intermixed beforehand. Thus, the flows Q2.ij.Q3.iJ directed to the outlet channel 20 enter the outlet channel in the proportion which is the position of the end A3 of the outlet channel 20 in the channels 17a !, 18a! with respect to the mouths Aj, A2. Thus, the mixing ratio of the Q3.1J / Q2.U flows is adjusted steplessly by the mixing valve 19. However, the flow rate of the flows Q21J + Q31J remains constant in said concentration control. The outlet pipe 20 can be placed at its end A3 at a certain distance from the flow channels 17a !, 18a! from the end openings A !, A2 without any significance for the adjustment. The outlet pipe 20 comprises a curved pipe section 20a, by means of which the flows 30 Q4.1.Q4.2 · -Q4.n = Q2.U + Q3.1J! Q2.2J + Q3.2J ’* Q2.nJ + Q3.nJ to the discharge channel 20 I! 7 93980 and onwards. Through the flow channel 21, the final flow Qs.i.Qs ^ -Qs.n P ° is preferably recirculated.

By moving the end A3 of the outlet channel 20 to different positions with respect to the ends 5a, A2 of the channels 17 and 18, the flow rate of the second partial flow into the channel 20 is increased by an amount equal to the flow rate of the second flow into said channel 20 and vice versa. With the stiffening, the flow Q4 is kept at a constant pressure and at its controlled concentration value determined by the position of the end of the pipe 20. Each flow Q4.1. () 4.2- · -Q4.il is thus controlled in concentration by the above-mentioned arrangement of the pipe 20. The flow Q5 = (Q31 + Q2.1) - (Q3.1J + Q2 j) is circulated. Each flow Q4.1 provided. () 4.2---Q4.il 20 is passed through the flow channel being mixed with the rest of the pulp suspension Mj turbulenssigeneraat square-sectioned front face 13 of the manifold j 12al, 12al ... 12a12 nand further turbulence generator and a slice channel. The flow Q4.1.Q4.2 · --Q4.il adjusts the basis weight of the paper at said le-15 width station. With the flow-adjustable flow Q4.i, Q4.2 --- Q4.n, the cross-sectional profile of the basis weight of the paper is thus adjusted and thus the errors in the cross-sectional profile of the basis weight are corrected.

If it is desired to change the pressure of the flow Q4.i, Q4.2 --- Q4.n, i.e. the flow rate 20 of the flow and through it the flow rate and the fiber orientation of the web, said flow is affected. to the pressure level by adjusting the valve 25 in the outlet pipe 20.

Within the scope of the invention, an embodiment is also possible in which the mass flow from the mass distribution support is fed directly through the distribution pipes to the turbulence generator. In said 25 embodiments, there is no intermediate chamber E.

Figure 2A illustrates a device solution according to the invention. From the distribution chamber 11, a partial flow of the mass Mj Q3 j is led to the channel 18aj. From the distribution chamber 16, which comprises water N, a second partial flow Q2 j is led to the channel 17aj. The distribution valve 19 comprises 30 movable outlet ducts 20, the orifice A3 of which can be moved to different positions with respect to the overlapping orifices Aj, A2 of the flow channels 17aj and 18aj (arrows Lj,! ^).

8 93980 Thus, the end opening A3 of the discharge channel 20 is obtained in different coverage positions with respect to the end openings Aj, A2, so that by increasing the portion of the opening A3 at the discharge opening Aj, the portion of the opening A3 at the discharge opening A2 is reduced by a corresponding amount. The combined flow Q31J + Q2. Is thus extracted into the discharge channel 20. The flow channel 21 5 leads from the valve 19 5 to the discharge, for example back to the mass circulation. In this way, the concentration of the flow Q4 1 is adjusted and, however, the flow rate of said flow remains at its desired constant value regardless of the concentration control. The actuator 22 moves the outlet channel 20. The outlet channel 20 can be, for example, a flexible hose, whereby a control movement is possible.

10

Figure 2B illustrates the operating principle of the device according to the invention. A flow Q2A is introduced into the outlet duct 20 in proportion to the amount of the flow opening Δt of the outlet duct 20 at the end opening Aj of the duct 17aj. Correspondingly, the adjustment takes place with respect to the flow Q31 of the second channel 18. When the discharge channel 20 shown up by the arrow Lj is moved upwards, more of the end opening A3 of the discharge channel 20 is moved by the channel 17a! at the end opening Aj and at the same time reducing the coverage of the end opening A3 in the channel 18a! at the end of A2. In this case, the flow Q2_u from the channel 17a} to the pipe 20 is increased and the corresponding amount is reduced to the outlet channel 20 from the channel 18a! future flow Q3 jj. The mixture ratio at flow Q4 j = Q2.u + Q3 u is adjusted while the amount of flow-20 remains constant.

* ·

Fig. 3A shows a section I-I of Fig. 1. As shown in the figure, a partial flow Q2.1 'Q2.2---Q2.il is led from the distribution chamber 16 to the flow channels 17a1,17a2,17a3 ... 17an. The above-mentioned flows are led to the distribution valves 19aj, 19a2 ... 19a ,, and further to the outlet channels 25 20a1, 20a2 ... 20an and to the distribution pipes 12a!> 1.12a!> 2 ... 12a1-n. The flow channels 21a1,21a2 ... 21an conduct the flow of the part which does not go to the outlet channels 20a !, 10a2 ... back to the mass circulation.

Fig. 3B shows a section II-II from Fig. 1. As shown in the figure, the partial flows of mass Q3.i, Q3.2 --- Q3.n are led from the distribution chamber 11 to the hard 18a1,18a2 ... 18an and further to the valves 19a!, 19a2. .., in which the distribution valves • • 11 9 93980 conduct the partial flows Q3 π + Q2> 1J to the discharge channels 20a1,20a2 ... 20an and further to the manifolds 12a3 j, 12aj .2 * * · ^^ aj n in connection with the mass concentration having an average concentration .

Fig. 3C shows a section III-III of Fig. 1. As shown in the figure, the mass flow from the distribution chamber 11 is led to its distribution pipes 12a1, 12a2 ... 12an and further to the intermediate chamber E and further to the turbulence generator 13 to its turbulence pipe 14 and further to the lip channel 15.

Fig. 3D shows a section IV-IV from Fig. 1. From the discharge channels 208 ^ 2032 - .. 203 ,, the flows Q4.i, Q4.2 - * - Q4.n are led to the distribution pipes Υ2 & ΧΛ, \ 2 & ι 2 ·· '^ · & \ .α. and further to the turbulence generator 13.

Fig. 3E is a section V-V of Fig. 1. The channels 15 17aj, 18aj are located as shown in the figure; 17a2,18a2; 17a3,18a3 ... 17an, 18an overlap.

Claims (10)

A method of controlling an inlet carriage, in which a method of introducing a stream (Q4.1, Q4.2--Q4.il) with adjustable concentration to the pulp suspension at various locations of the width of the inlet carriage, characterized in that the concentration of the current (Q4.i, Q4.2 --- Q4.n) is controlled by a distribution valve (193 ^ 1932- ..), 80111 includes an outlet duct (20j, 20a2- ..), whose end aperture (A3) can be set (L ^ l ^) in relation to the end aperture (Aj j, Aj 2. ·.) Of the flow channel (18a |, 18a2 ...) of the subcurrent (Q2.itQ2.2---Q2.il) to the end aperture (A2 i, A2 2.-) of the flow channel (183 ^ 1832- ..) of the second subcurrent (Q3.itQ3.2-) »whereby subcurrent (Q2.i; Q3.i) is led to the outlet channel (20). after how the outlet channel (20) is set in relation to the end openings of the flow channels of the subcurrent streams, whereby the concentration on the stream (Q4itQ4.2 - Q4.11) 80111 * to the outlet channel (20) is controlled while the flow rate h is cashed at the control and the current (Q4.i, Q4.2 --- Q4.il) is routed to the desired location by the width of the inlet carriage. A method according to claim 1, characterized in that the part of the stream is allowed in the method; the current (Q5.itQ5.2--Q5.il)> 80111 is not directed to the outlet duct (20), flow to the outlet or back to the mass circulation via the distribution chamber (11) of the inlet carriage. 3. Method according to the preceding claim, characterized in that the pressure traveling in the outlet duct (20) is controlled by regulating the current resistance of the current with a throttle valve (25) in the outlet duct (20) and the current 25 (Q4itQ4.2--Q4.il). ) with adjustable concentration is directed to the distribution tube (12a, 128, 2 -12a> n) to the relative flow direction of the pulp stream front side of the turbulence generator (13). 4. Device for regulating an inlet carriage, in which device solution one introduces 30 streams (Q4.itQ4.2--Q4.il) of adjustable concentration to the pulp suspension at different places of the width of the inlet carriage, characterized in that to control the concentration on the auxiliary current (Q41, Q42 ... Q4n), the device comprises a distribution valve (19) comprising an outlet duct (20) or the equivalent whose end aperture (A3) can be moved relative to the end apertures (A2, A3) of the flow channels (17a, 18aj) for the sub-currents and from which one leads a Current 5 (Q4 i, Q4 2 -Q4.11) mec * adjustable concentration via the channel (20) of the distribution valve to a given location of the width of the inlet carriage to be connected to the current (Qj). average pulp concentration. Device according to the preceding claim, characterized in that the outlet ducts (20a1,20a2 ... 20an) from the distribution valves (19a1,19a2 ... 19an) are connected to the distribution pipes (12a1,12a2 ... 12an) on the front side of the turbulence generator (13). 6. Device according to claim 4 or 5, characterized in that there is a functional device (22) with which the end of the outlet channel (20) can be moved and that the end openings (AjjAA of the flow channels (Ha ^Sa ^) of the partial currents (Q2). i, Q3.i) are located on each other, the currents coming (arrows S1 (S2) laminarily unmixed from the channels (17al518a2) and a portion of said currents being plucked into the outlet tube (20a1,20a2 ... 20an) while the other the portion (Qs.i.Qs 3 -Qs.n) flows back into the mass circulation. Device according to any one of the preceding claims 4-6, characterized in that each outlet duct (20a1,20a2 ... 20an) comprises a valve (25a1,25a2 ... 25an), by means of which the pressure level of current (Q4 i, Q4 2 -Q4.n) and thus the fiber orientation of the web. Device according to any of the above claims 4-7, characterized in that the end of the outlet channel (20) comprises a curved channel portion (20a) by means of which the currents (Q3.1 j, Q2. 1 j) are evenly controlled. the outlet duct (20). 30 11 15 93980 9. Device according to any of the above claims 4-8, characterized in that for each current (Q4.i, Q4 2 ... Q4 n) there is a separate distribution valve (193 1932- 19au). partial current channels (17a1,17a2 ... 17an; 18a1,18a2 ... 18an) lead to these, whereby one can conduct a separate Current 5 (Q4.1 »Q4.2 --- Q4) to each width position of the inlet carriage. il) with adjustable concentration, whereby with said extra current, the surface weight of the web can be controlled at each width of the paper / cardboard web. 10. Device according to any one of the preceding claims 4-9, characterized in that one of the subcurrent streams (Q3.i »Q3.2 --- Q3.n) is a stream of mass one having an average concentration taken from the distribution chamber for the mass in the inlet carriage, i.e. from the distribution boom (11) and that the second partial stream (Q21, Q2 2 - .. Q2 n) ^ a water stream taken from its own distribution chamber, i.e. from the distribution boom (16), whereby the channels (1732 , 1732 ... 178,) are connected from one end to their distribution chamber (16) and correspondingly are channels 15 (18a j, 18a2 ... 18an) of the subcurrent (Q3 1, Q3.2- · -Q3 .il) connected from the other end to the pulp chamber (11) for the pulp (Mj) in the inlet tray of the paper machine. 20