FI120368B - A method and arrangement for adjusting the properties of a fiber web - Google Patents

Description

Method and rigidity adjustment of fiber web properties

The invention relates to a method for adjusting the properties of a fibrous web to an optimum initial state according to the operation of the fibrous web. The invention also relates to an arrangement for adjusting the properties of the fibrous web to an optimum starting state according to the operation of the fibrous web.

In fiber web machines, such as paper machines, calendars, coating machines, and the like, the management of the fiber web is paramount to the runnability of the fiber web machine. The purpose of a fiber web machine is to produce a fiber web according to the target values 10 and, if the runnability is not sufficient, production will be zero or significantly less than intended. Equipment efficiency, for example, time efficiency or material efficiency, together with production rate, determine the tonnage or area produced. Thus, any factor that can in some way improve the runnability of a fiber web machine is of particular interest to the fiber web producer.

There are many factors involved in the runnability of a fiber web machine, but one of the overall factors is the control of the temperature, humidity and tension of the fiber web both in the direction perpendicular to the fiber web and in the transverse direction. Controlling the properties of a fiber web is important over the entire length of the fiber web, but especially in the proximity of some operation to be performed, its importance is emphasized. Such measures may include, for example, pressure and temperature modification of the web, such as calendering, application of a component to be added to the fibrous web, such as pigment coating, and reeling of the fibrous web, and the like. Typically, at these change-points, various fiber web guide rolls are used and used which, in their simplest form, can only change the direction of travel, but may also have a transverse effect on the fiber web (so-called spreader roll). strong rolls over which the tension of the fibrous web may be different. This is achieved, for example, by suitable coating of the roll or by the choice of a so-called crossing angle. Wrap-30 angle large enough. One possible means for influencing the runnability of the fibrous web is a non-contact air turning device.

In the context of this invention, the following terms are used in different directions. The machine direction (MD) of the fibrous web is called the x direction. The direction of the plane of the fiber web, the direction 2 perpendicular to the direction of travel, i.e. the cross direction (CD, cross direction) is called the y direction. The thickness direction of the fibrous web is called the z-direction.

WO 99/02773 discloses a method and apparatus for drying a coated web. Therein, the web is guided between a deflector and a counterpiece, where the direction of travel of the web can be contactlessly changed while blows that effect the direction of travel of the web dry the freshly coated web. Over the curved portion, the blowing nozzles are aligned so that opposing blows are applied to the web.

US 5 230165 discloses a non-contact pivoting device 10 arranged in connection with a drying device. Here, the direction of travel of the web is changed directly after the coating station by a turning device, after which the web is led to a blow dryer.

WO 01/75224 discloses a method and arrangement for controlling evaporation and humidity in a multi-nip calender. In it, the fibrous web passes through at least one air turning device when it comes out of the nip, in the most preferred embodiment, the publication mentions the replacement of all output rollers by an air turning device.

It is an object of the invention to provide a method and arrangement whereby the runnability of a fibrous web can be optimally controlled while the properties of the fibrous web are most suitable for the process step to be performed. One potential interest is in improving the cross-directional tension control of the fibrous web for the operation to be performed. Similarly, the pretreatment of a fiber web based on the properties of the operation to be performed to maintain the quality and efficiency potential of the actual operation is one of the objects of the invention. '

The method according to the invention is characterized in that in the downstream direction of the fiber web, before the process means performing the operation on the fiber web, a reversible fluidizing device is arranged through which the temperature and humidity of the fibrous web passing

Correspondingly, the arrangement according to the invention is characterized in that in the direction of travel of the fiber web 30 before the process means performing the operation on the fiber web, a reversible fluidizing device for the blowing direction is selectable to influence the transverse tension profile of the fibrous web (W).

Said process instrument target target value refers to a condition of a fibrous web which has been found to be well suited to the process and to produce a well-run and high-quality result taking into account various conditions. This target starting value may be empirically or statistically determined, and the deviation of the instantaneous actual value from the target actual value can be verified, for example, by means of on-line measurements.

According to a preferred embodiment, the blowing air humidity 10 of the reversible fluidizing device 3 is selected such that the moisture of the fibrous web W changes in the desired direction. According to another preferred embodiment, the blowing air temperature of the pivot fluidizing device 3 is selected such that the temperature of the fiber web W changes in the desired direction. Thus, a means for adjusting the temperature and humidity of the blowing air is connected to the reversible fluidizing device.

15 A process instrument is one that performs a subprocess that causes a change in the value or degree of processing of the fibrous web. Examples of such process means include coating stations, calenders or other means for smoothing and polishing the fiber web, intermediate rollers affecting the roll of the fiber web, fasteners and winders, and the like.

In the context of the invention, the technical implementation of the term "before" also plays a special role in this context and in the characterizing part of the claim, since the adjustment of temperature, humidity and possible y-direction tension profile only has a certain dwell time over the free fiber web and after this dwell time . For these reasons, the 25 most preferred embodiment is "immediately before or just before", but some flexibility is needed in defining the scope of the invention. For example, such flexibility may be achieved by positioning a guide roller or the like between a pivot fluidizing device and a process means. On the other hand, the term "before" should not be interpreted too broadly, that is, a conventional coating machine lay-out with a pivot fluidizing device after the coating station and a normal reeling after drying is outside the scope of the present invention. The technical efficiency of the invention depends on the implementation of this "before" term and can be considered to maintain the technical performance as follows: 35 more appropriate case-by-case, up to about 4 seconds for a reversible fluidizing device or up to about 10 meters for distance , depending on the surrounding conditions.

The process according to the invention is particularly effective in producing modifications of a relatively small absolute value, but particularly effective in runnability, to the condition of the fibrous web prior to the sub-process. In addition to improving runnability, the efficiency of said process means may be improved as the sensitivity to break resulting from runnability improvement is reduced. One factor here is the potential for the fiber web to change to become more elastic.

In the following, the invention will be described in more detail with reference to the accompanying figures, of which: Figure 1 illustrates another calender application, Figure 2 illustrates another fiber web forming application, the details of the pivoting fluidizing device.

Figure 1 shows a preferred embodiment of the invention in which the properties of the fibrous web W are prepared for the next process step. In the situation of Fig. 1, said process step is calendering in a nip N between the tees 20 and 11 and 12 of the conventional soft calender 1, in which the fiber web W is prepared in the most favorable condition. For some other reason, the fiber web W has been slightly 'over-dried' at some earlier stage of the process, which, however, is not the best starting point for calendering. According to the invention, the fibrous web W is again returned to a receptive state for calendering or similar type-25 modification by slightly wetting and, in this case, slightly cooling the surface layers of the fibrous web W. In the pivot fluidizing device 3 used by the present invention, air of a temperature and humidity is supplied to the pivoting air such that the surface layer of the fibrous web W is slightly cooled and wetted by the pivoting fluidizing device 3. Thus, when calendering begins, moisture is bound to the surface layer of the fibrous web 30 nanowatt, which, when properly positioned, improves the calendering result without causing bulk loss in the z-direction in the middle of the fibrous web. The humidity of the blowing air of the pivoting fluidizing device 3 is thus selected so that the moisture of the fibrous web W changes in the desired direction. In some cases, it is preferable that the humidity of the blowing air of the pivot fluidizing device 3 be selected such that the moisture of the fibrous web W changes in the direction of the equilibrium humidity of the fibrous web W.

5

According to a further preferred embodiment, the tension profile of the fibrous web W is adjusted by the blowing air of the pivot fluidizing device 3 to achieve the target output value of said process means 1. Thus, in this case, the pivoting fluidizing device 3 has a means for changing the blowing direction such that the blowing direction 5 is selectable for influencing the transverse tension profile of the fiber web W.

Figure 2 illustrates another preferred embodiment of the invention. Herein, fiber W is prepared by the method of the invention for a ValZone® metal belt calender. For example, in this hypothetical embodiment, the process means 1, 20 may be mounted off-line, wherein the fiber web W is previously rolled into a machine roll and then re-rolled for that process. The machine roll may have been stored for some time due to, for example, a plant maintenance outage, whereby the temperature and humidity of the fibrous web W are no longer in the most favorable condition for processing. For example, the moisture profile may have changed so that the ends of the machine reel have dried while the central portion is still wetter. In such a case, the method according to the invention and the pivot fluidizing device 3 can slightly preheat the fiber web W and rectify the moisture profile. This way, despite the downtime, the properties of the fiber web W are similar to those of the fiber web W directly imported from the continuous production run, and thus this "stagnant" batch does not have to be sold as a poor-quality product or run into pulp.

However, it should be noted that the properties of the fibrous web W affect the applicability of the method. The dense and smooth fibrous web W does not absorb moisture and heat as well as the porous and slightly coarser fibrous web. There are at least two reasons for this phenomenon. Partly this is due to the boundary layer air 25 which prevents air being applied to the fibrous web W by the inverted fluidizing device 3 from entering the fibrous web. In part, the dense and smooth surface of the fibrous web W does not provide a suitably micro-rough surface capable of serving as a receiving surface for moisture and heat transfer, although the tension profile may be reasonably well influenced. In a preferred embodiment, the residence time between the pivot fluidizing device and the process means 30 is adjustable, wherein the distance between the pivot fluidizing device and the process means is adjustable.

In the situation of Fig. 2, a fiber web W having a starting value of 25 degrees C can be preheated by a rotary fluidizing device 3 with a blowing air of 200 degrees Celsius to 65 ° C and a correction of the moisture profile of W 35 in the edge regions 94%. the dried area is brought to the same level as the 92% dry matter content of the middle region 6. Of course, the exact running parameters are highly dependent on the specific characteristics of each case, in particular the properties of the fiber web. Therefore, accurate generalizations of the main parameters of the examples, i.e. the blowing air temperature, the blowing air humidity, the blowing air speed and the blowing speed and direction, and the y-directional distribution of the above mentioned are unnecessary in this context.

The exemplary embodiment of Figure 3 relates to winding wherein fiber web W is rolled around reel roll 301 to machine roll 302. Tests have shown that fiber web W is best rewound at 50 ° C and 94% dry solids content. However, upon entering the roller 30 region, the fibrous web has a temperature of 55 ° C and a dry solids content of 94%. Hereby, according to the invention, the fibrous web is slightly cooled by a reversible fluidizing device 3, but it is hoped that the moisture will remain unchanged. The blowing air temperature is selected to be 20 ° C, humidity 60%, blowing speed 50 m / s, whereby the fiber web to be produced is cooled to that desired temperature of 50 ° C while the humidity remains constant.

Another aspect of the embodiment of Figure 3 is the Y-direction twist profile of the fibrous web. Conventionally, just before the winder 30, there is a spreader roll which ensures a suitable tension profile and non-leakage of the fibrous web before winding. With the method of the Kek-20 invention, this other aspect can be adjusted and changed if desired. By adjusting the air volumes and blowing directions of the pivoting fluidizer 3, it is possible to provide a much more sophisticated way of providing just the desired spreading and tension profile on the fibrous web prior to winding. Combining the features of this second aspect with the ability to influence the internal winding or winding properties of the winding fibrous web W provides a highly versatile tool for fine-tuning the winding process to achieve the best possible efficiency.

In the example of Fig. 4, the method of the invention is used just prior to the curtain coating type coating station 40. It has been found in experiments 30 that for the solidification of the coating material curtain 41, it would be good for the fiber web to have a temperature of 65 ° C. remains through the process. In this example case, under normal conditions, the fibrous web W would be at 47 degrees C when entering the coating station 40, so that the fibrous web is 18 ° C too cold compared to the most favorable starting state of the process means 35. Thus, according to the method, the fibrous web W is prepared to a more suitable temperature by means of a rotary fluidizing device 3, 7 air blows at 280 ° C and a blowing speed of 60 m / s, this fibrous web is warmed to an optimum initial value of 18 ° C. so it doesn't hurt here.

Figures 5 and 6 show some details of a pivoting fluidizing device 3 preferably adapted to apply the invention, said pivoting fluidizing device 3 having means for changing the blowing direction 33 so that the blowing direction can be set at an angle equal to or different from the normal, preferably offset up to 15 ° from normal. Said means for changing the direction of the blow 33 may be, for example, a pivotable guide, a flap, a pivotable nozzle, a geometrically changeable nozzle or the like, which is suitable for changing the direction of the air flow. In practice, the fibrous web has a curved surface of some shape to which a tangent plane can be set and a tangent plane further normal, relative to which the direction axis 35, i.e. the blowing direction, of the blowing nozzle 31 is preferably adjustable within some kind of "trajectory". the lateral angle in the x direction is adjustable by about ± 15 ° and in the y direction by about 0 to 60. Especially in the peripheral regions of the fibrous web, adjustability in the y direction can be close to said upper limit, i.e. preferably the deviation in the y direction is up to 60 ° 45 to provide a sufficiently effective spreading effect Fig. 5 and Fig. 6 illustrate by way of example a solution in which the blowing direction change means 33 is depicted by a pivot point 33, i.e. the blowing nozzle 31 can be directed by a ball joint type solution.

Further, Fig. 5 shows an embodiment of the inverted fluidizing device 3 in the transverse direction, i.e. the y direction, by means of the inverting fluidizing device 3 so that the direction of change α of the fiber web is at least 15 ° but not more than 180 °, most preferably 45 ° to 90 °.

6 is provided with means for changing the blowing direction 33 such that the blowing direction 35 can be set at an angle 30 which is the same or different from the normal tangent plane of the fibrous web W, preferably offset in the y direction such that is at its lowest and grows as you approach the edge of the fiber web. Of course, only a few blow nozzles 31 are illustrated in Figure 6, to illustrate this, in the actual production machine these transverse nozzles 35 are likely to have dozens depending on the width of the fibrous web being produced. Preferably, the blowing air directions 35 of the pivoting fluidizer 3 are selected 8 such that the transverse tension profile of the fibrous web W just before the process means 1, 20, 30, 40 is flat, wherein the value of transverse tension variation is less than 7%, preferably less than 4%. For example, the blowing air directions 35 of the pivoting fluidizing device 3 are selected such that the transverse tension profile of the fibrous web W is substantially straight or is tighter at the edges than center 60 or is tighter at the center 60 than at edges.

9

Reference numerals used in the figures: I process means II roll 12 roll 5 20 metal belt calender 3 roller 301 reel roll 302 machine roll 10 31 blowing nozzle 33 means for changing blowing direction, pivot point 35 of blowing nozzle winding lance 40, a change of direction 20

Claims (13)

A method for controlling the properties of a fiber web (W) to an optimum starting position for a measure to which the fiber web is subjected, characterized in that in the direction of the fiber web (W) before the process device (1, 20, 30, 40) performing The feeding web on the fiber web (W) has placed a turning web device (3), where as the web runs through it, the temperature, humidity and tension profile of the fiber web (W) in the y-direction are controlled by means of the blowing air in the web weaving device (3). shall achieve the desired output value for said process device (1.20, 30.40). 2. A method according to claim 1, characterized in that the humidity of the blowing air (3) of the web weaving device (3) is chosen so that the moisture of the fiber web (W) changes in the desired direction. 3. A method according to claim 1, characterized in that the temperature of the blowing air (3) of the web weaving device (3) is chosen so that the temperature of the fiber web (W) changes in the desired direction. 15 Method according to Claim 1, characterized in that the directions (35) for the blowing air of the twist-weave device (3) are chosen such that the transverse stress profile of the fiber web (W) is the pane just before the process device (1, 20, 30, 40), the value of the the transverse voltage variation is below 7%, preferably below 4%. 20 5. A method according to claim 1, characterized in that the directions (35) for the blowing air of the weaving device (3) are chosen such that the transverse stress profile of the fiber web (W) is substantially straight or tighter at the edges than in the middle (60) or tighter in the middle than at the edges. • · · 25 • · 6. A method according to claim 1, characterized in that, by means of the reversing device (3), the running direction of the fiber web is changed so that the change of the running direction * ··· * (a) is at least 15 °, but not more than 180 °, preferably 45 ° -90 °. . • · φ: 30 7. A method according to claim 1, characterized in that, with the twist fabric word (3), the z-directed moisture distribution of the fiber web (W) is changed by:. the humidity of the blowing air and with the delay that occurs before the process device (1,20,30,40). • · • · · • · ·: 35 8. Arrangements for regulating the properties of a fiber web to an optimum output position for a measure to which the fiber web (W) is subjected, characterized in that in the running direction of the fibrous web (1, 20, 30, 40) the method has placed a web weaving device (3) for controlling the temperature and humidity of the fiber web by means of the blowing air of the web weaving device (3) to obtain the output value of said process device (1, 20, 30, 40), further comprising the web weaving device (3 a means (33) for changing the blowing direction so that the blowing direction can be selected to influence the transverse tension profile of the fiber web (W). 5 Arrangement according to claim 8, characterized in that the reversing weave arrangement (3) is connected to a means for regulating the temperature and humidity of the blowing air. Arrangement according to claim 8, characterized in that the turning web arrangement (3) comprises a means (33) for changing the blowing direction so that the blowing direction (35) can be arranged at an angle which is the same angle or a different angle than the standard. to the tangent plane parallel to the path of the fiber web (W), preferably the deviation in the x-direction is at most 15 ° compared to the normal. Arrangement according to claim 8, characterized in that the turning web arrangement (3) comprises a means (33) for changing the blowing direction so that the blowing direction (35) can be arranged at an angle which is the same angle or a different angle than the normal to the tangent plane. in parallel with the path of the fiber web (W), the deviation in the y-direction is preferably at most 60 ° compared to the normal. 20 Arrangement according to claims 8 and 11, characterized in that the reversing device (3) comprises a means (33) for changing the blowing direction so that the blowing direction (35) can be arranged at an angle which is the same angle or other angle than the normal to the tangent plane parallel to the path of the fiber web (W), preferably • ·. ···. 25, the deviation in the y-direction is variable so that said deviation is at least at · · ·: ·. the center line (60) of the fiber web (60) and it increases towards the edge of the fiber web. · · · · · · · · Arrangement according to Claim 8, characterized in that the delay between the web weaving device (3) and the processing device (1, 20, 30, 40) is adjustable, the distance between the web weaving device and the processing device being variable. •••••••••••••••••••••••••••••••••••••