FI92730B - Method and arrangement for regulating the head box - Google Patents

Abstract

The invention relates to a method and an arrangement for regulating a head box. A flow Q4.1, Q4.2 ... Q4.n of adjustable concentration is introduced into the pulp suspension at different points over the width of the head box. The concentration of the flow Q4.1, Q4.2 ... Q4.n is adjusted by a distributor valve 19a1, 19a2 ..., which comprises an outlet duct 20a1, 20a2 ... 20an, the end opening A3 of which can be adjusted (arrows L1, L2) in relation to the end opening A1.1, A1.2 ... of the flow duct 17a1, 17a2 ... of the partial flow Q2.1, Q2.2 ... Q2.n and the end opening A2.1, A2.2 ... of the flow duct 18a1, 18a2 ... of the second partial flow Q3.1, Q3.2 ... . The partial flows Q2.1; Q3.1 are led to the outlet duct 20a1, 20a2 ... 20an, according to how the outlet duct 20a1, 20a2 ... 20an is adjusted in relation to the end openings of the flow ducts for the partial flows. The concentration of that part of the flow Q2.1 + Q3.1, the flow Q4.1, Q4.2 ... Q4.n, which is not led to the outlet duct 20a1, 20a2 ... 20an is thereby also regulated, the flow quantity being kept constant during adjustment of the concentration. The said flow Q4.1, Q4.2 ... Q4.n is led off from the distributor valve 19a1, 19a2 ... and on to the required point over the width of the head box. <IMAGE>

Description

92730

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. Levels of anisotropy in the transverse-15 direction also affect 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 usually cause a nonlinear skew profile inside the edge areas of the flow channels.

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, the shrinkage is less from the center of the web: than from the edge areas, with shrinkage generally being about 4% in the middle 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 flat web transversely to the press changes during drying so that both edge areas of the web have a slightly higher basis weight than 92730 2 in the middle. 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.

li 3 92730

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

F1 patent application No. 912230 is known from the prior art, in which the headbox is divided along its width by partitions into compartments 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 and thus the flow rate and flow rate can be adjusted while the mixing ratio remains at its set constant value.

4,92730

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 moved to 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. In this case, the flow out of the distribution valve is also adjusted. This is further routed to a certain width position in the headbox of the paper machine / board machine. This outflow is thus controlled in concentration, however, the flow rate 20 remains at its predetermined constant value before the concentration control. However, in the solution according to the invention, it is also possible to adjust the pressure level of the flow Q4 discharged from the distribution valve, i.e. its flow rate. This is done by adjusting the pressure level of the outlet duct of the distribution valve, i.e. the overflow duct, either by a throttle valve fitted to the outlet duct or by adjusting the height of the overflow threshold of the overflow chamber at the end of the outlet duct.

The method and device according to the invention are mainly characterized by what is stated in claims 1 and 5.

li 5 92730

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.

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.

Figure 2B shows a second control principle for replacing the overflow threshold, in which the controller consists of a standard throttle valve.

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

15

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

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 1 shows a cross-sectional view of a headbox 10 of a paper machine / board machine 25 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 intermediate chamber E * to the turbulence generator 13.

The turbulence generator 13 comprises a turbulence piping 14, the turbulence tubes 30 of which open into the intermediate chamber E shown in Fig. 1 and at its other end into the lip channel 15. The flow Qj 6 92730 of the pulp suspension Mj is thus introduced into the lip channel 15. from the suspension M = + N. Concentration-adjustable flows 04.1.04 2____Q4n are led with the desired distribution, i.e. resolution, to different widths of the headbox of the paper machine / board machine. Each flow Q4.i --- Q4.n is led at its own 5 latitudes to the mass M of the unregulated concentration coming to that latitude. to the flow Qj. Thus, the flow-adjusted flow Q4 is used to adjust the basis weight of the paper at the desired web width and to correct any errors therein.

10 The concentration-controlled flow Q4 is formed as follows. Diluent, preferably the so-called dilution liquid, is discharged from the distribution chamber 16 as a partial flow Q9. 0-water through the flow channel 17aj. A second partial flow of the mass Mj Q3 is led from the distribution chamber 11 to the flow channel 18aj. The mouth of the flow channel 17at is marked Aj. The mouth of the flow channel 18at is marked A2. On the discharge side of the above-mentioned orifices with respect to the flow direction 15 there is a distribution valve 19 comprising an outlet duct 20, i.e. an overflow pipe movable from the orifice A3 (arrows with respect to the orifices A2, A2 of the ducts 17,18). an actuator 22 by means of which the outlet duct 20 at least its end 20 'can be moved (arrows L1, 1) so that the end A3 of the outlet duct 20 is brought into the desired coverage position with respect to the ends A1, A2 of the channels 17 and 18. The outlet duct 20 is thus the flow Q3> 1J + Q2.ij depending on the relative position of the end openings Aj, A2, the channels 17a1, 18a1 are superimposed on their end openings Aj, A9 and the outlet channel 20 is adapted to be movable perpendicular to the end openings A3! 17a2,18aj come laminarly and immiscible with each other, so that they can be picked up in the outlet duct 20 without the sub-flows mixing with each other beforehand. Thus, the flows Q2 ij, Q3.u 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 of the channels 1732,183! with respect to the mouths A2, A2. Correspondingly, the mixture ratio 30 is caused to be infinitely adjusted in the concentration flow control of said flow in the channel 21 discharged from the mixing valve 19, while maintaining a constant value of> 7 92730. The outlet pipe 20 can be placed at its end A3 at a certain distance from the end openings Aj, A2 of the flow channels 17aj, 18aj without it being relevant for the implementation of the control. The outlet pipe 20 comprises a curved pipe section 20a with which the flows Q2 ij »Q3 are smoothly conducted. jj to the discharge channel 20 and onwards. For the outlet flow Q4 j, the outlet pipe 20 acts as a mixer unit.

By moving the end A3 of the outlet channel 20 to different positions with respect to the ends A1, 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 10 into said channel 20 and vice versa. By means of the arrangement, the flow Q4 in the flow channel 21 leading away from the distribution valve 19 is kept at a constant pressure and at its adjusted concentration value determined by the position of the end of the pipe 20. The flow Q4.i5Q4.2---Q4.il is thus controlled in concentration by the above-mentioned arrangement of the pipe 20. The flow Q4 j is (Q31 + Q21) - (Q3 u + Q2.J) · The controlled flow Q41 is led through the flow channel 21 to the rest of the pulp suspension M! unmixed with the turbulence generator 12 and through it with the lip channel 15. With a concentration-adjustable flow Q4.i5Q4.2-- Q4.il, the cross-sectional profile of the paper weight is thus adjusted and thus the errors in the cross-sectional profile of the basis weight are corrected.

20 If it is desired to change the flow Q4.i5Q4.2---Q4.il The pressure, i.e. the flow rate of the flow and through it the flow rate, the pressure level of said flow is influenced by adjusting the valve in the outlet pipe 20, which may consist of overflow threshold D in the overflow chamber at the end of the pipe. is arranged in the compartment Fj, F2 ... of the overflow chamber F to which the outlet pipe 20 is led. 25 A flow is discharged from the overflow chamber, from each of its compartments or zones.

. The overflow chamber is compartmentalized across the width of the paper machine. Each compartment F1, F2 ... comprises a common air space I. In addition to the adjustable overflow threshold, a separate throttle valve 25 in the outlet pipe 20 or its extension 20 'can also be used (Fig. 2B).

30 δ 92730

Figure 2Α illustrates a device solution according to the invention. From the distribution chamber 11, the partial flow Q3 j of the mass M} is led to the channel 18aj. From the distribution chamber 16, which comprises water N, a second partial flow Q21 is led to the channel 17at. The distribution valve 19 comprises a movable outlet channel 20, the mouth opening A3 of which can be moved to different positions of the flow channels 5at 17a and 18a! with respect to the overlapping orifices Aj, A2. In this way, the end opening A3 of the outlet channel 20 is obtained in different coverage positions with respect to the end openings A1, A2, so that when increasing the proportion of the opening A3 in the outlet opening A! by a corresponding amount decreases the proportion of the opening A3 at the outlet A2 and vice versa. The combined flow Q3 jj + Q2 u is thus extracted into the discharge channel 20. From the valve 19, a flow Q4 j leads out of the flow-10 channel 21, which is the difference between the combined flows (Q31 + Q21) and (Qa jj + Q? Jj). Thus, the concentration of the flow Q41 is also adjusted and the flow rate of said flow remains at its desired constant value regardless of the concentration control. The actuator 22 moves the outlet duct 20. The outlet duct 20 is connected to a fixed duct part 20, for example by a telescopic connection C. The outlet duct 20 'is connected to the overflow chamber 23 in its compartment F2 separated from adjacent compartments F1, F3 by partitions 24a1 (24a2). 27. The overflow threshold Dj, D2 ... of each overflow L5 is adjustable in height from the actuator 26. Thus, at each width position, the pressure in the outlet duct 20 and thus the pressure Q4 j, i.e. the flow rate of flow Q4 j and thus the fiber orientation of the paper, can be adjusted. the compartments Fj, F? ... comprise a common air space I. Thus, with the flows Q4 1, Q4 9 ... Q4 n, the basis weight profile of the paper and the fiber orientation profile can be adjusted.

Figure 2B shows a solution in which the overflow threshold is replaced in the outlet channel 20 '. with the valve 25.

Figure 2C illustrates the operating principle of the device according to the invention. A flow Q2 j is introduced into the outlet duct 20 in proportion to the amount of flow of the outlet duct 30 20 at the end opening Aj of the duct 17aj. Correspondingly, the adjustment takes place with respect to the flow Q3 j of the second channel 18. When the discharge channel 20 is moved upwards as shown by the arrow Lj 9, more of the end opening A3 of the channel 20 is moved to the end opening Aj of the channel 17a] and at the same time the coverage of the end opening A3 at the end A2 of the channel 18aj is reduced. In this case, the flow Q2 u coming from the channel 17aj to the pipe 20 is increased and the flow Q3 jj coming from the channel 18at to the outlet channel 20at is reduced by a corresponding amount. The mixture ratio in flow Q4Λ is adjusted while the flow rate remains constant.

Fig. 3A shows a section I-I of Fig. 1. As shown in the figure, a partial flow Q2 j, Q2 2 --- Q2 n is led from the distribution chamber 16 to the flow channels 17a1,17a2,17a3 ... 17an. The flows mentioned above are led to the distribution valves 19aj, 19a2 ... 19a „and further to the outlet channels 2031,2032 ... 203 ,, and to the flow channel 2131,2182 - .. 2 ^ leading from the valve and further to the turbulence generator 18 to its turbulence tubes 14a], 14a2. ..14an.

Fig. 3B shows a section II-II of Fig. 1. As shown in the figure, the partial flows Q3.], Q3.2- "Q3.n to the pallets 18a], 18a2 ... 18an and further to the valves 19a], 19a2 are derived from the distribution chamber 15. ..., in which the flow valves lead to the discharge of the flows to the discharge channels 20a], 20a2 ... 20an described above and further to the flow of the flow Q4 i, Q4 2 - .. Q4.n) along the flow channels to the turbulence generator 13.

20

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

25

Fig. 3D is a section IV-IV of Fig. 1. The channels 17ai, 18ai are located as shown in the figure; 17a2,18a2; 17a3,18a3 ... 17an, 18an overlap.

Claims (13)

1. A method of controlling an inlet carriage, in which a method of introducing a current (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, Q42 --- Q4.n) is controlled by a distribution valve (19aj, 19a2 ...) which includes an outlet channel (20a1,20a2 ... 20an) whose end aperture (A3) can be set (arrows Lj, 1 ^) in relation to the end opening (Aj, Aj 2 ...) of the flow channel (173 ^ 1732- ..) of the subcurrent (Q2.i> Q2.2-Q2.n) 0011 the end opening ((A2i, A2 2) ...) of the flow channel (18a ,, 18a2 ...) of the second subcurrent (Q3.i, Q3.2 ···) * leading the subcurrent (Q? j; Q31) to the outlet channel (20a1,20a2 ... 20an), after the outlet channel (20a1,20a2 ... 20an) is set in relation to the end apertures of the flow channels for the subcurrent streams, also the concentration of that portion of the stream (Q2> 1 + Q3> 1), the stream ( Q41, Q4 2. ..Q4 n), which is not led to the outlet channel (20a1,20a2 ... 20an) is thus also regulated while the flow rate is constantly poured in the concentration control, and that the current (Q4 j, Q4 2 .. Q4). 11) is discharged from the distribution valve (19aj, 19a9 ...) and further to the desired location of the width of the inlet carriage. A method according to claim 1, characterized in that in the process the stream (Q2.iji.k3.ij) is fed to the overflow chamber (23) and via this to the outlet. 3. A method according to the preceding claim, characterized in that the pressure traveling in the outlet duct (20) and further in the flow duct (21) is controlled by controlling the throttle valve (25) in the outlet duct. Method according to any of the preceding claims, characterized in that in the process the pressure level which rises in the outlet duct (20) is regulated by controlling the height of the overflow threshold (D) of the overflow chamber (23). 30 14 92730 5. Device for regulating an inlet carriage, in which plant one introduces currents (Q4 i, Q4.2-- Q4.n) with 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 current (Q4 1, (¾ 2 - Q4.11)) In the desired manner, the device 5 comprises a distribution valve (19aj, 19a2 ... and an outlet channel (20aj, 20a2 ... 20a, j), the end opening of which (A3) or the equivalent can be moved in relation to the end openings (Aj, A2) of the flow channels (17a], 18a) of the sub-currents (Q2.i »Q3.i) and from which distribution valve (19a1, l9a2 ... 19an ) there is a flow channel (21a1,21a2 ... 21an), through which a current (Q4], Q4 2-. Q4.n) is conducted with a controlled concentration to a given location of the inlet carriage width and to be connected to the current ( Qt) with average pulp concentration. Device according to the preceding claim, characterized in that the flow channel (21a1,21a2 ... 21an) from the distribution valve (19a1,19a2 ... 19an) is connected to the turbulence tube (14aj j, 14aj 2 · n) of the turbulence generator ( 13), wherein the current (Q4], Q4 2 -.- Q4.n) can be directed unmixed to the lip channel (15), to the desired width location of the lip channel (15). Device according to Claim 5 or 6, characterized in that the end of the outlet channel (20) can be moved by a functional device (22) and that the end openings (A 1, A 2) of the flow channels (17a, 18a) of the partial currents ( Q2.i, Q3.i) are placed on each other, whereby the currents become laminar (arrows Sj, S9) unmixed from the channels (17a, 18a2) and a portion of said currents is plucked into the outlet tube (20) below that of the other portion ( Q4.1.Q4.2 ···) streams in the form of a control stream to the stream (Q,) with average pulp concentration. Apparatus according to any one of the preceding claims 5-7, characterized in that the outlet duct (20) is connected to the overflow chamber (23), which is divided into compartments over the width of the inlet carriage of the paper machine, each from one compartment (F). ,, F2 ... Fn) has an overflow (L5) to the outlet (27). Il 15 92730 Device according to any one of the preceding claims 5-8, characterized in that a functional device (26) is connected to the overflow threshold (D 1, D 2 ...), the position of each overflow threshold (D 1, ...). can be regulated and hereby the pressure level traveling in the pipe (20a1, 20a2 ... 20an) can be controlled and further in the outlet duct 5 (218,, 2182 ... 2 ^) and further in the current (Q4, Q4 2- .. Q4n) · Device according to any of the preceding claims, characterized in that the pipe (20) or its extension (20 ') comprises a throttle valve (25). Device according to any of the preceding claims 5-10, characterized in that the end of the outlet duct (20) comprises a curved duct portion (20a), by means of which the currents (Q3.ij, Q2, tj) evenly flow to the outlet duct ( 20). Device according to any of the preceding claims 5-11, characterized in that there is a separate distribution valve (19a1,19a2 ... 19an) for each Current (Q4.i »Q4.2-Q4.n) rch partial current channels (17a ,, 17a2 ... 17an; 18a1,18a2 ... 18an) lead to these, whereby each width position of the inlet carriage can lead its own Current (Q4.1, Q4? - Q4.n) with ^ adjustable concentration, whereby with the extra power you can regulate the surface weight of the web at each width of the paper / cardboard web. 20 Device according to any of the preceding claims 5-12, characterized in that one of the subcurrent streams ((33.1, (¾? -Q3.n)) is produced by a stream with a mass (M) of average concentration, taken from the distribution chamber ( 11) of the mass of the inlet carriage and that the second partial stream (Q2.i> Q2.2-Q2.n) is a water Current taken from its own distribution chamber (16), one end of the channels (17a1, 17a2 ... 17an) being connected to a distribution chamber (16) and correspondingly one end of the channels (18a, 18a2). ... 188η) for the subcurrent (Q3.1 'Q3.2-. Q3.n) connected to the distribution chamber (11) of the pulp (M,) of the inlet carriage of the paper machine. 30