FI117565B - Procedure in connection with an outlet box in a paper machine or equivalent to regulate the surface fold profile - Google Patents

Description

117565

The present invention relates to a method for adjusting the basis weight of a web on a paper machine or similar headbox. The invention relates to a method for adjusting the basis weight of a web on a papermachine or similar headbox.

The basis weight profile of the web to be manufactured on a paper machine or the like must be constant over the entire width of the web. Due to shrinkage of the drying machine 15 in the drying section of the paper machine, particularly at the edges of the web, the paper pulp suspension must be diluted at the periphery of the web than in the central regions. In practice, this is accomplished by a dilution headbox having, for example, valves at 60 mm intervals through which dilution water is supplied. Valve adjustment is done automatically based on the measurement of the basis weight profile.

'Ϊ: 20 • · *: *. · Because the basis weight profile errors are mainly caused by stable local • · · * ... * errors, the basis weight profile correction can also be achieved by manual valve adjustment. Problems with manual adjustment are changes in the machine, such as species changes and retention changes.

25 These changes have traditionally been compensated by manual dilution headboxes • · · ;; adjust by adjusting the entire dilution valve profile to match the new changed «·.

• · * "situation. Due to the large number of dilution valves, such adjustment is * * '· *. * Laborious and slow.

1 '1 30 In order to improve the situation, a new kind of control philosophy and

III

where the once-adjusted dilution valve profile is no longer altered 2 117565, but in the event of a change, the performance of the dilution profile is adjusted by adjusting only the pressure level at the inlet side of the dilution valves, for example by adjusting the rpm of the dilution pump.

5 As retention drops, the dilution power drops, changing the basis weight profile without knocking. Instead of correcting the situation by opening additional peripheral valves, the flow rate of the edge valves is increased by increasing the pressure level at the inlet side of all dilution valves, for example by increasing the dilution pump revolutions, thereby correcting the basis weight profile of the paper web.

10

The proposed adjustment significantly reduces the need for adjustment of the dilution valves and reduces the threshold for switching from automatic valve profiling to manual.

It is also possible to use retention measurement to assist in the adjustment. In the invention, it has been realized that retentiomuutokset can be compensated first manual dilution of 15 / after the flow control valve without touching the valves so that the modified valve inlet pressure level of, for example, by adjusting the pump speed. Instead of adjusting the pump speed, it is also possible to use a constant-speed pump and adjust the valve on its pressure side. I, Olen, ί woman, for example, that the pressure level is adjusted, for example, in the dilution water manifold, across the width of the manifold and thus at the inlet side of the dilution valves Vj, V2 ... The retention lowering pressure is increased and the retention pressure lowered at the inlet side of the manually adjustable dilution valves V1, V2 ..., preferably the dilution water distribution. 1 in log J2. Thus, according to the invention, the dilution valves V1, V2, V3 ...

«• · · · · · · * 'inlet pressure level is adjusted produced web basis weight profile variable appropriate, 25. 5 • · ♦ • · · ♦ 1 · ··· • · * · 1 A paper machine or the like refers to paper-board, tissue-paper and wall-paper machines.

«·« • · ♦ · ♦ ·· j .... . . . · 1: 30 The paper machine can be equipped with retention measuring devicesq blocked to detect · «· retention changes after the first adjustment of the dilution valves. Based on this retention change 3 117565, the pressure level adjustment at the inlet side of the valves V1, V2 .. can be performed automatically. Thus, in the method of the invention, based on retention changes, flow through all valves is controlled simultaneously without interfering with manual valve control.

5 The term retention describes how much dry matter from the headbox remains on the wire. For example, 60% retention means that 60% of the dry matter remains on the wire.

65% retention means that 65% of the dry matter remains on the wire. When running tap water as a dilution water, this means, for example, that at 65% retention, the tap water and further the dilution water comprise less dry matter than the tap water and the dilution water at 60% retention.

The process according to the invention is characterized by what is stated in the claims.

15

The invention will now be described with reference to certain preferred embodiments of the invention shown in the accompanying drawings, but which are not intended to be limited thereto.

The headbox of the invention is illustrated in Fig. 1A with manually adjustable dilution valves V 1, V 2, V 3 ... V 1, and rotational speed! adjustable pump.

Figure 1B shows another embodiment of the control having a pressure regulating valve 25.

Figure 2A shows in the top graph the valve opening (dilution vent * · *. *. * Brick) in the vertical coordinate system and in the horizontal coordinate system the paper machine's • • * * width position.

: * · *: 30 * · • «* 1 • · • · • · a 4 117565

The middle graph in Figure 2A shows the dilution achieved by opening the top graph. The vertical coordinate system has a dilution and the horizontal coordinate system has a headbox width position.

The bottom graph of Figure 2A shows the basis weight achieved by the valve opening of Figure 2A over a machine width of 60% retention. The vertical coordinate system shows the basis weight of the web and the horizontal coordinates the machine width.

Fig. 2B is a top graph showing the coefficient of t 10 of the incorrect basis weight of Fig. 2A. The top graph shows the valve opening in the vertical coordinate system and in the horizontal coordinate system the machine latitude corresponding to that opening.

The middle graph represents the dilution at machine width in the vertical coordinate system, and the lowest graph shows the result, i.e., a uniform basis weight of the web over the entire machine width.

15

In Figure 3A, a retention change of 65% has occurred. Further, the valve opening is the same as the dilution shown in the graph of Figure 2B and in the middle graph, respectively. However, due to the change in retention, the dilution power has changed from ϊ.ϊ *: and the basis weight profile of the web has changed to an unfavorable, not constant, machine width.

* * · “Ή.

Figure 3B shows a correction of 65% retention in accordance with the invention. The top graph shows a machine width venttiiliaukeamaa • * · «· ·· *. * Occurred through all the valves in the flow rate is reduced by dropping the valve 25 bricks inlet pressure levels at the same time. Figure 3B in the top graph # · · '||| * in particular, the valve opening profile is unchanged. In the middle of Figure 3B described • · * · "* vaajassa shown koijatulla valves Vi, V2, .. inlet pressure level occurring s • · ·. ·. * Va dilution and resulted in the lowest graph in Figure 3B • · ·> corrected valves V , V2 .. inlet pressure level reached steady-adjusted * · * ♦ '; 30 basis weight across machine width. The web weight per machine width is now constant.

• · · · * * * * * 5 117565

Figure 4 illustrates a retention-based dilution control correction. The retention is calculated and, based on the retention calculation, the dilution pump Pj, which is connected to a line connected to the water jet in J2, is adjusted. If there is a change in the retention (%), the pump speed is adjusted.

Figure IA shows a dilution headbox 100 as an illustrative representation.

From the manifold support J 1, the mass is led through the pulley 11 to the intermediate chamber E and further through the piping of the turbulence generator 12 to the lip cone K and further to the forming wire Hi. As shown in Figure 1, the dilution water pumped by the pump Pi is led to the dilution water manifold J2 and further to the ducts a1, a2, a3 .. and the headbox piping 11 at different widths of the dirt, 1d2 ... 11a2i, 11a22 .. The channels a1, a2, a3 ... comprise manually adjustable dilution valves V1, V2 .. By adjusting the inlet of dilution water 15 derived from the dilution water distribution brackets J2 to the pulley mi, the basis weight of the paper web is adjusted at each width. To the dilution water manifold J2, tap water is supplied from the wire section 200 through channel b. Channel b comprises a tap water well 300 from which tap water is led to a dilution water manifold J2.

The apparatus may comprise an apparatus for adjusting the basis weight profile at the dry end of the papermaking machine for measuring the basis weight profile of the web. If, in the basis weight profile? · 1 • · · * ... 1, a deviation from the width of the web is observed after dilution, the manual adjustment of the valves Vj, V2 .. is adjusted by the basis weight of the web • 1 ** · 1 tab. This will change the initial open profile of the dilution valve opening # 25. It has been found that changes in retention in tap water and further in dilution water 0 • i · cause the need to change the opening profile of dilution valves V1, V2 ...

* · • 1 to regain the basis weight profile.

• 1 • · t f 1 · # 1 1 '; 1 * 1.

According to the invention, if the basis weight profile changes due to retention changes, the pump Pi is used to adjust the pressure of the dilution water before the dilution valves V1, V2 .. and again to obtain a linear basis weight profile.

6 117565

If the retention decreases, the pressure of the dilution water at the inlet side of all dilution valves V1, V2 ... is increased, and if the retention increases, the pressure level at the inlet side of all dilution valves V1, V2 ... is preferably lowered at the dilution water distributor J2. In this application and the invention, it has been realized that after the above-mentioned first adjustment, the dilution valves V1, V2 ... do not need to be adjusted separately anymore, but the basis weight control of the web is performed by adjusting the flow through all dilution valves V1, V2 .. , V2 .. the pressure of the dilution water prevailing on the inlet side of the dilution water manifold J2 and thus further adjusts the pump Pj. The pump Pi is preferably 10 speed controlled pumps and can be used to control the flow through the dilution valves V1, V2 .. by controlling the dilution water pressure at the inlet side of the dilution valves V1, V2 .. in the dilution water distributor support J2.

Figure IB illustrates another embodiment of the invention in which pump P10 is not adjustable at rpm but wherein the pressure in the dilution water manifold J2 is controlled by adjusting valve 13 in the dilution water inlet line b to the dilution water manifold J2. The valve 13 is preferably a throttle valve-r1. Preferably, the dilution water is tap water derived from the wire section 200. Fig. 2A and 2B show a retention adjustment of 60%. Figure 2A top · «· · ... ·! the graph shows a dilution valves Vi, V2, V3 .. venttiiliaukeamaa pystykoor-: vaakakoordinaatistossa coordinate system and the width of the paper machine is shown in therapeutic «· * · ..1 side (HP) and the drive side (KP) route. Initially, as shown in Figure 2A, the valve opening is constant over the entire machine width. Correspondingly, the dilution is averaged • · 1 · ** “1 on the machine width. But in the lower graph, the brochure 1 · · · · “1 is quite uneven in its web width. The lower graph shows the measured basis weight profile of the web in the vertical coordinate system at each of the web points. The basis weight profile is measured on the dried web before 1.1 to 30 rolls.

• «· * · * · • · ♦ 7 117565

Figure 2B shows the adjustment at this 60% retention. The orifice of the dilution valves V1, V2 .. is adjusted to obtain a dilution profile as desired in the web width direction and shown in the lower graph, resulting in a straight basis weight profile over the entire web width. The basis weight is thus 5 constant over the web width.

Figure 3A shows the change in retention during the run of a paper machine. retention; The thio in the representation of Fig. 3A is 65%. The opening of the dilution valves V1, V2 .. is still the same as the dilution shown in the previous control and in the middle 10 respectively. However, due to the change in retention, as shown in the lower figure, the basis weight profile of the web changes from straight to edges.

'- • Ί

Figure 3B shows an adjustment according to the invention. According to the invention, the flow through all the dilution valves V1, V2 .. is regulated without changing the openings of the dilution valves V1, V2 .. by adjusting the pressure level at the inlet side of the valves, for example by adjusting the rotational speed of the pump Pi. The pump Pi is used to direct dilution water to the dilution water manifold J2 at the inlet side of the dilution valves Vi, V2 ί, ί.ϊ ... As shown in Figure 3B, the aforementioned pressure level control has been performed

IM

V * 20 and as shown in the middle graph, dilution is reduced by pressure reduction.

· * I

: V by applying to the inlet side of the dilution valves Vi, V2 .. and thereby reducing the rotation speed of the pump Pi, resulting in a linear basis weight profile in the lower graph of the machine width. Thus, a constant net weight of the web width is achieved • · · • · * ··. *.

25 '· «· ·' '*' · * Figure 4 shows a tracking based on rction calculation. If changes occur in the retention • 4 4 * “, based on the retention calculation, the pump Pj revolutions • *. adjusting the flow and thus adjusting the flow profile of the dilution valves V |, V2 ..

* «· * ...: to obtain a direct basis weight profile from the web width.

30 When adjusting the pressure in the dilution water at the inlet side of the dilution valves Vi, V2 .. • ♦ ·! T i: however, the settings of the dilution valves Vi, V2 .. are maintained unchanged.

8 117565

Measure the consistency of the main mass line f with the measuring device S1 and the consistency of the tap water discharged from the wire through the channel b with the measuring device S2. The metric data is passed through lines no and e ^ to calculator 100, via which line e3 is driven to pump Pi to adjust its rotational speed depending on calculated retention 5 or to valve 13 in FIG (IB) to adjust its throttle / opening to control dilution water pressure level with dilution valves Vi, V2.

1 ° i * * f · »· · -i

• M

• • • »• • • * • • • • • • • • • • • • • • • • • • • • • • * • • • • • • • • • • • • • • •

»M

• f • · ia * ··; 'i t •' • · * • · ·

* · J

• »* * M» • · · • ♦ · * · • «« · »· * t

IM

: 1

Claims (6)

A method in connection with an inlet carriage (100) in a paper machine or the equivalent for controlling the surface weight profile of the web, in which method the pulp (mi) is led from a pulp distribution stock (J) to a pipe system (11) in the inlet carriage and further, to a lip cone (K) and out onto a fuming wire (Hi) and in which method dilution water is conducted to different width sites of the inlet carriage from a distribution log (J2) for dilution water to control the surface weight profile of the web, and that channels exist (ai , a2, a3 ".) in conjunction with the pipe system (11) and that the channels (ai, a2, a3 ...) comprise dilution valves (V |, V2, V3 ...) with which the supply of dilution water can is regulated to the desired at each width of the inlet carriage, characterized in that in the process, dilution water used is the wastewater discharged from the wire portion (200) and the retention in the wire portion is observed and if there is a change in the retention the pressure of the dilution stock (J2) for dilution water on the basis of the change in question, whereby the pressure of the dilution water (J2) for the dilution water is reduced if the retention water is diluted in the distribution stock (J2). flag. • · · i · «* · · • · ·: 20 2. A method according to claim 1, characterized in that the pressure of the dilution water in the distribution water (J2) for the dilution water is regulated by regulating the pressure of the dilution water by regulating the speed of a pump. ♦ f • · * (PO- · ♦ · • »• · ··· 25 Method according to the preceding claim, characterized in that in the process the speed of the pump (Pi) is controlled in a position where the pump is located in a • T * channel (b) through which the dilution water is led. to the distribution block (J2) for ## # · *. *. dilution water. • · · • · • · ♦ ·· j * \: 30 Method according to the preceding claim, characterized in that in the method the pressure of the dilution water in the distribution stock (L) for the dilution water is controlled by regulating a valve (13) located in the line (b). ) for supplying dilution water to the dilution stock (J2) for dilution water. Method according to the preceding claim, characterized in that such a valve (13) is used as a throttle valve and is located on the pressure side of a pump (Pio) which causes the dilution water to flow in the line (b). ) for the supply of dilution water. Method according to any of the preceding claims, characterized in that dilution valves (Vi, V2. ··) which are manually adjustable valves are used in the process. • '<· • · · * · · • · · • · · * * * * ♦ · ·; ♦ · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ··· · · • «··· · * · • · • * * • · *» • · * 1 2 · * «· • · * · • · · t *] •« 2