EP2096205A1 - Method and device for removing water - Google Patents

Abstract

The apparatus (21) has a set of water weight sensors (12) arranged in a mutually offset position in a cross direction (CD). The water weight sensors are arranged in single dimensional and multi-dimensional sensor arrangement. The sensors are utilized for measuring water weight of a fibrous material (2), where the apparatus dewaters fibrous material based on a dewatering curve defined in a machine direction (14) and on measurements of water weight of the fibrous material. An independent claim is also included for a method for adjustably controlling dewatering of a fibrous material in a paper machine and a paperboard machine by a dewatering apparatus.

Description

The present invention relates to a dewatering apparatus, in particular a paper or board machine, for adjustable, in particular controllable, dewatering of a fibrous web guided as at least two fibrous webs which can be divided into adjacent zones in the cross-machine direction.

Furthermore, the present invention relates to a method for adjusting, in particular control, the dewatering of a pulp of a dewatering device, in particular a paper or board machine, wherein the pulp is guided as in at least two, arranged in the cross machine direction juxtaposed zones fibrous web.

Dewatering devices and methods for adjusting the dewatering of a fiber web guided as a fibrous web, in particular on a belt-shaped wire, are used in particular in the paper industry. Because of the continuous dewatering of the pulp in the machine direction, short MD direction, a paper or board machine can be considered essentially as a dewatering device for the pulp. As the machine direction, the direction in which the pulp is moved by the paper or board machine during the papermaking process is usually and thus also referred to in this document.

At the headbox, the consistency of the pulp in the cross machine direction (CD, cross direction), that is in the direction normal to the machine direction, usually the fibrous material usually initially preset by means of dilution water. A headbox working with dilution water is called dilution hydrogen headbox. As a result, however, in particular in the wet end of the paper or board machine, deviations in the dewatering in the cross machine direction of the fibrous web can occur from a dewatering curve predetermined in the MD direction, in particular for the entire width of the fibrous web. These deviations of the drainage usually lead to deviations of the basis weight in the cross machine direction of the oven-dry paper. Such deviations have a detrimental effect on the formation transverse profile, in particular in the cross-machine direction - one speaks briefly of the CD professional -, and are therefore undesirable.

Despite the adjustment of the consistency of the pulp by means of dilution water at the dilution water headbox, the problem frequently arises that unsatisfactory formation profiles, in particular unacceptable formation cross profiles of the paper, occur in the machine direction, but also in the cross machine direction, for example because of uneven drainage on the wire.

After application to the wire, the pulp continuously loses water due to gravity or additional vacuum extraction by means of dewatering elements, that is, the water weight of the pulp on the wire continuously decreases in the machine direction (MD). As a result, the formation of the pulp into paper, that is, the formation of sheets, allows. Also in the subsequent lots of paper or board machine, such as the press and the dryer section, the pulp or the forming paper is further dehydrated.

Of the WO 99/55959 A1 a device and a method for sheet measurement and control in paper or board machines can be seen. The document describes inter alia the measurement of CD profiles, in particular water weight profiles in the cross-machine direction of the paper or board machine with the aid of water-weight sensors. An under-the-screen water-weight sensor is described which can measure three properties of a material, particularly the pulp of a paper or board machine: the conductivity, the dielectric constant and the distance of the material to the water-weight sensor, depending on the material, one or more than one of these properties dominates. The response time of such a water weight sensor is about one millisecond.

By arranging the water weight sensors in the cross machine direction, the CD water weight profile is obtained instantaneously, whereby the MD and CD changes are determined substantially decoupled. As intervention points for the control, the raw material supply rate at the beginning of the wet end, the steam quantity regulation in the dryer section or the variation of the roll contact pressure in the press section are mentioned in the prior art. There are the possibilities of intervention in numerous, independently controllable or controllable actuators mentioned, which extend in each control range across the width of the pulp. For example, the headbox, the steam generation with numerous steam actuators, which regulate the applied to the individual zones across the sheet amount of heat, called. Similarly, in the calender section, where segmented calender rolls include a plurality of roller pressure control actuators applied to the sheet between the rolls in individual zones in the cross-machine direction. The control can automatically adjust actuators in the cross machine direction by evaluating signals from scanners. Factors for uneven cross-machine direction dewatering which as a result are responsible for fluctuations in the CD profile of the paper include the uneven supply of the pulp to the headbox, the clogging of the plastic mesh of the wire, the different mechanical tension of the wire and the unbalanced vacuum suction. A certain disadvantage is that the determination of MD and CD changes is essentially decoupled from each other.

Currently, the paper properties are measured only with point measurements or one-dimensional sensor arrays in MD or CD direction, in the wet end. Other known applications are traversing measurements or fixed, stationary measurements in the dryer section. With these known arrangements, MD and CD variations can not be unambiguously assigned.

The EP 1 624 298 A2 describes a microwave water weight sensor and a method for measuring the water weight in a forming section of a paper or board machine using microwaves.

The sensor generates a microwave field, which partially dips into the material to be measured. The field is generated by means of a microwave transmission device embedded in a ceramic foil or by means of a transmitting antenna and a receiving antenna which couple the microwave field through the material.

The dielectric constant of the material around the transmitter or in the space between the transmit and receive antennas affects the wave propagation velocity. The measurement is based either on the transit time or on the phase or the phase shift or the phase jump.

A dividing line resonator can also be used. The resonator essentially measures the wave propagation velocity in the resonating structure. The operating frequency is chosen to be significantly below the relaxation frequency of water of about 22 GHz. The preferred frequency is between 1 and 3 GHz, but other frequencies are also possible.

The sensor can measure the water weight in the forming section of the paper or board machine. In particular, the sensor before and after the Drying section can be used. It can also be used in double-band formation games.

The sensor signal is strong enough to make one-sided measurements. Furthermore, the sensor allows multi-sensor configurations to simultaneously measure the water weight at various machine cross-machine direction positions, that is, to produce a non-sequentially scanned measurement profile. Multiple sensors may be arranged to form a sensor array in the cross machine direction and / or in the machine direction. Arranged in the machine direction sensor fields can be advantageously used to determine drainage profiles.

The sensor makes use of the fact that the dielectric constant of the pulp in the forming section is mainly influenced by the water, which has a high relative dielectric constant, from about 80 at room temperature to frequencies of several GHz.

The document also describes a method of monitoring a pulp layer in a production line, wherein the pulp layer is permeated by microwaves having a frequency lower than the relaxation frequency of water, and an effect which the pulp layer has on the microwaves is measured. Such a sensor can be used for the present invention. The disclosure regarding the sensor is fully incorporated into the present invention description.

The EP 0 972 882 A1 describes a measuring system for measuring certain properties of a material web, such as in particular a fibrous web in a paper and / or board machine or a coating machine, by at least one stationary cross-profile measuring device with at least one radiation source for irradiation of the material web in several defined different Wavelength ranges and at least one sensor for measuring the intensity of a radiation influenced by the material web, and by at least one measuring and / or evaluation, wherein preferably only one of the defined different wavelength ranges of the radiation is detected by a respective sensor at a specific time.

It is possible to accurately measure the cross-section of certain properties. The measurement is also possible in relatively inaccessible places and even in areas of closed guidance in which the material web in question is supported, for example, by a roller, a belt, a sieve and / or a felt. For this purpose, by means of a sensor, for example, a radiation reflected by the material web or its lining can be detected. Additionally or alternatively, it is also possible to detect by means of a sensor a through the material band or its coating passed through radiation.

It is taught to provide at least two in the web running direction spaced from each other having stationary transverse profile measurements. In this case, advantageously at least one unit such as the press section, the dryer section, etc. of the paper and / or board or coater can be assigned at least two in the web running direction spaced from each other having stationary transverse profile measuring devices.

In terms of short rule times is in the EP 0 972 882 A1 it is recommended to arrange at least one stationary transverse profile measuring device immediately before and / or immediately after at least one actuator or actuator influencing the respective transverse profile.

The measuring system makes it possible, at least in the press section and / or dryer section of a paper and / or board machine, to provide at least one stationary transverse profile measuring device. Alternatively or additionally, it is also possible that at least in the wire section and / or at the end of a paper and / or board machine at least one such stationary transverse profile measuring device is provided.

Filtering means may be provided in order to filter out specific disturbance variables and / or the influence of at least one actuator or actuator on the respective transverse profile.

At least one stationary transverse profile measurement can be designed for the quantitative determination of the basis weight, the moisture, the thickness, certain ingredients and / or further properties of the material web.

In particular for a measurement in regions of a free web tension, a respective stationary transverse profile measurement can be provided with at least one optical radiation source. Also in the EP 0 972 882 A1 described sensors can be used advantageously in the present invention.

The paper industry has a need for methods which permit the production of paper with a formation profile that is as uniform as possible in both MD and CD directions, that is to say a flat nominal profile defined over the entire fibrous web, or on dewatering devices, in particular paper or board machines that implement such methods.

The satisfaction of this need succeeds with a drainage device according to claim 1 and with a method according to claim 11.

The dewatering device according to the invention for adaptable, in particular controllable, adjustment of dewatering of a pulp builds generically on a dewatering device, in particular a paper or board machine, in which the pulp is guided as in at least two, arranged in the cross machine direction juxtaposed zones fibrous web.

According to the invention, the dewatering of the pulp is advantageously adaptable to a dewatering curve predetermined in the machine direction by means of measurements of the water weight of the pulp by means of at least two water weight sensors preferably assigned in pairs in the cross machine direction. Advantageously, this results in an energy saving and production increase. Furthermore, this achieves an improvement of the formation of the paper, which in turn has an improved strength and printability of the paper. By means of the dewatering device according to the invention, furthermore, advantageously the number of required sensors can be kept low.

Dewatering of the pulp occurs "on the basis of" measurements of the water weight of the staggered water weight sensors as described above, that is, the sensor measurements are basically - though not exclusively - used for adjusting the drainage settings. Instead of "due" one could also say "basically". It is therefore basically a causal relationship between measurement on the one hand and adjustment or attitude on the other constituted. The causal relationship can be formed in very different ways, for example by means of classical analog control, but also by means of digital, in particular very simple comparative, control or by fuzzy logic systems or by means of artificial neural networks, etc. Also networking with a different, for example knowledge-based system, in particular with a statistical process control system, is a fundamentally conceivable and possible formation of the causal link.

The dewatering can be done in particular "according to" the measurements of the water weight of the staggered Wassergewichtsensoren. Instead of "according to specification" one could also say "the height". This is meant to express that the specific height of the measurements, ie the measurements (calibrated) value, into the adaptation or adjustment of the drainage, though not exclusively. If the adaptation takes place in accordance with the measurements, this means a causal relationship in terms of value, such as, for example, filtering, smoothing, averaging, statistical evaluation, etc., in particular microprocessor-based offsetting.

The dewatering device has at least two respective zonal adjustable, in the machine direction relative to each other staggered machine elements. This can, for example, foils, suction boxes, pressing elements in conjunction with a second mutual sieve or a headbox. Foils can be conveniently designed as foilleists. The Foil or the Foilleiste is used for drainage, for example by turbulence. Drainage elements can be arranged in particular in a wet end of the dewatering device. The dewatering performance of the dewatering elements according to the invention is zonal adjustable, in particular in accordance with the measurements of the water weight sensors. This allows the adaptation to the optimal operating point of the drainage elements. In the case of suction boxes, one could speak advantageously of a vacuum optimization of the suction boxes.

The water weight sensors and the dewatering elements are arranged alternately successively in the machine direction. Thus, the effect of the zonal drainage performance of a dewatering element can advantageously be determined at least almost in real time.

According to the invention, the drainage is zonally adjustable by means of at least one forward coupled control loop. In professional circles is also often spoken of a "feedforward" system. Considering a zonal drainage deviation which is detected by a sensor arrangement arranged between a first and a second dewatering element, the "feedforward control" can determine the zonal dewatering capacity of the (in MD direction) second drainage element advantageously adjust so that the already occurred and further transported disorder of the second dewatering element is eliminated.

The drainage can be adjusted zonally by means of at least one feedback loop.

In professional circles is also discussed by a "feedback" system. In the case of feedback, the zonal dewatering performance of the first (in the MD direction) first dewatering element can advantageously be set so that the disturbance in the sequence no longer occurs or at least only to a reduced extent. The control effort for an optionally existing feedforward control can be advantageously reduced.

The feedforward control can be considered as a cascaded or additional control which, compared to a mere feedback control, improves the quality of the pulp formation by further reducing deviations IST / SOLL. Of course, the stability of such a control cascade must be taken into account or interpreted by the person skilled in the art.

If forward and backward coupled control loops are present at the same time, wherein a particularly favorable embodiment can be seen, then a distributed control, in particular of a regulation acting in more than one direction, namely with respect to the machine direction at least in the forward and backward direction, can be used. to be spoken.

The dewatering elements are, in each case additionally or exclusively, arranged in at least one section of the dewatering device. They may conveniently be arranged in or in the region of a steam-blow box or a press or a headbox, in particular a dilution-hydrogen headbox. In addition, the Dewatering performance by an adjustable suction strength and / or an adjustable layer thickness and / or the preferably adjustable consistency of emerging from the headbox pulp and / or preferably adjustable pressurization of the pulp are influenced by opposing element and second sieve. By the adaptation or regulation of drainage elements, in particular of different types of drainage elements, in different parts of the dewatering device, it is possible to achieve a particularly exact guidance of the overall process close to the dewatering curve predetermined in the MD direction.

The drainage performance of a dewatering element is measured in a zone at a particular time by at least one water weight sensor. The measuring location of the water weight sensor in the machine direction is advantageously freely selectable. The positioning of sensors both within a batch and in different lots can thus be advantageously selected or determined according to the requirements of the overall process. It can thus be a metrological image on the entire fibrous web determine, but still only a manageable number of measuring sensors must be arranged.

At least one measuring location, as seen in the machine direction, at least two water weight sensors, which are offset relative to one another in the cross-machine direction, are advantageously present per zone. Alternatively, there may also be a sensor arrangement having more than two sensors, in particular a one-dimensional sensor arrangement oriented in the cross-machine direction, but also a multi-dimensional sensor field. In such a sensor arrangement or a sensor field, the sensors may in particular be integrally formed with each other. Through this more opulent Equipment allows the drainage advantageously measure more information-bearing than in the embodiments equipped with fewer sensors.

Measurements of at least a portion of the machine direction offset water weight sensors associated with a zone are averaged. By averaging is advantageously a smeared, you could also say a blurred, received signal. The signal is zonal averaged. You could also say that the signal gets zonal smeared or blurred. Instead of an averaging can also be spoken of a filtering or smoothing. In conjunction with the offset arrangement of the sensors, the course of the water (IST) can advantageously be calculated from the zonal averaged or filtered or smoothed signal. Subsequently, the actual course can be adapted to the desired course of the drainage curve.

Furthermore, a more accurate image of the dewatering behavior in the cross machine direction and / or in the machine direction can be determined by a suitable interpolation from measured values of the staggered water weight sensors.

The invention also relates to a method for adjusting, in particular control, the dehydration of a pulp of a dewatering device, in particular a paper or board machine. The dewatering device or the paper or board machine can be designed according to the invention as described above. The pulp is guided as in at least two, in the cross machine direction juxtaposed zones divisible fibrous web.

In the method according to the invention, the dewatering of the pulp is determined by means of measurements of the water weight of the pulp by means of at least two water weight sensors which are assigned to a zone and are preferably arranged in pairs in the cross-machine direction, offset relative to one another. in particular sensor arrangements of water weight sensors, adaptable to a predetermined in the machine direction drainage curve.

Fig. 1

eine Seitenansicht einer ersten Ausführungsform einer erfindungsgemäßen Entwässerungsvorrichtung, nämlich der Nasspartie einer Papier- oder Kartonmaschine, mit unterhalb des Langsiebs angeordneten Entwässerungselementen und Wassergewichtsensoren;

Fig. 2

eine Draufsicht auf die Faserstoffbahn mit strichlinierter Andeutung der Zonen;

Fig.3

eine Draufsicht auf die Nasspartie der ersten Ausführungsform zur deutlicheren Darstellung der erfindungsgemäßen gegenseitigen Versetzung der Wassergewichtsensoren; und

Fig. 4

eine Draufsicht auf die Nasspartie einer zweiten Ausführungsform einer erfindungsgemäßen Papier- oder Kartonmaschine; die gegenseitige Versetzung der Wassergewichtsensoren anders ausgebildet.

Further advantageous properties and embodiments of the invention will be described with reference to the drawings explained below. In these drawings shows

Fig. 1

a side view of a first embodiment of a dewatering device according to the invention, namely the wet end of a paper or board machine with arranged below the wire dewatering elements and Wassergewichtsensoren;

Fig. 2

a plan view of the fibrous web with dashed indication of the zones;

Figure 3

a plan view of the wet end of the first embodiment to more clearly illustrate the mutual displacement of the Wassergewichtsensoren invention; and

Fig. 4

a plan view of the wet end of a second embodiment of a paper or board machine according to the invention; the mutual displacement of the water weight sensors designed differently.

In the following, a first embodiment of a dewatering apparatus 1 according to the invention, which is a paper or board machine, is described. The paper or board machine 1 implements the method according to the invention.

The paper or board machine 1 has a wet end 20 with a dewatering device 21, in which a pulp 2 is applied to a wire 23 by means of a headbox 3, which is designed here as dilution hydrogen casserole. The dilution hydrogen casserole 3 has along the cross machine direction 15 of a fibrous web 5 a plurality of pulp outlet openings 4.

With the aid of dewatering elements 16, a first dewatering step of the fibrous material 2 guided in the fibrous web 5 takes place on the wire. The dewatering elements 16 are here designed as suction boxes. The embodiment shown comprises two suction boxes 16 whose drainage capacity is zonally adjustable. The paper or board machine 1 includes even more games, such as a dryer section and a press section, as well as a spool, which are not shown for clarity. These batches may also contain zonally adjustable drainage elements 16, such as segmented calender rolls ( FIG. 1 ).

In the machine direction 14 behind each dewatering element 16 and before the first in the machine direction 14 drainage element 16 Wassergewichtsensoren 12 are arranged to measure the dewatering of the pulp 2 in the form of its water weight. The machine direction 14 is in FIG. 1 indicated by an arrow. The water weight sensors 12 could also be arranged directly in the dewatering elements 16, for example integrally formed therewith.

The wire 23 is deflected fiber pulp side by means of a breast roll 22 and driven. The fibrous web 5 rests on the upper side of the wire 23 and is continuously moved away from it in the machine direction 14 and thus by the dilution hydrogen headbox 3, the fibrous material 2 being continuously dewatered via the dewatering elements 16. The drainage takes place here by gravity and additionally by vacuum suction through the suction boxes 16th

The fibrous web 5 here comprises two zones 6, 7 (FIG. FIG. 2 ). The zones 6, 7 each extend over half of the total transverse extent B of the fibrous web 5. The fibrous web 5 could also comprise more than two zones 6, 7, for example, it could comprise as many zones as in their drainage performance adjustable sections or zones are present on a suction box 16. The zones 6, 7 extend both in Machine direction 14 as well as in the cross-machine direction 15. The zones 6, 7 extend here over the entire longitudinal extent L of the fibrous web 5. However, they could also be made shorter. For example, each of the zones 6, 7 could be subdivided at least once in the machine direction 14, resulting in at least four zones. In this case, two zones arranged next to one another in the cross-machine direction would be assigned to a suction box. There could also be more, in particular significantly more than four zones, which follow each other in pairs in the machine direction 14 as well as in the cross machine direction 15 or spaced apart.

The water weight sensors 12 are arranged offset relative to each other. They are arranged offset both in the machine direction 14 and 15 in the cross machine direction. Here they are arranged on the underside of the fibrous web 5. They could also be arranged above the fibrous web 5. Water weight sensors 12 could also be present in other parts of the paper or board machine 1 than the wet end 20. They could, for example, also be present in or in the area of the press or the dryer section etc.

• mehrdimensionale Sensorenanordnung 17 von Wassergewichtsensoren 12 (Figur 3).
  Die Entwässerung des Faserstoffs 2 wird durch Messungen des Wassergewichts des Faserstoffs 2 mittels mindestens zweier einer Zone 6, 7 zugeordneten Sensoren 12 überwacht. Aufgrund der Messungen des Wassergewichts ist die Entwässerung an eine in Maschinenlaufrichtung 14 vorgegebene Entwässerungskurve 19 anpassbar. Eine Entwässerungskurve wird üblicherweise in der Einheit Gramm Wasser pro Quadratmeter (g/m² H₂O) über die gesamte Länge der Faserstoffbahn 5 angegeben. In dieser Einheit liegt auch die Entwässerungskurve 19 in Figur 3 vor, welche entlang der Faserstoffbahn 5, in Maschinenlaufrichtung auf deren linken Seite, dargestellt ist. Das Wort "aufgrund" bezeichnet hier einen Kausalzusammenhang zwischen der Messung des Wassergewichts einerseits und der Anpassung des IST-Entwässerungszustands des Faserstoffs 2 an die vorgebbare bzw. vorgegebene Entwässerungskurve 19 andererseits.

The water weight sensors 12 are preferably arranged in pairs offset relative to each other. The offset creates, particularly with more than two sensors 12 per zone, a gappy arrangement of the sensors 12. The arrangement of the sensors 12 has a periodicity. The periodicity can also be described as a pattern. The periodic arrangement forms a significant, patchy pattern both in the cross machine direction 15 and in the machine direction 14. The gappy line patterns in the cross machine direction 15 or in the machine direction 14 are arranged such that the sensors 12 are displaced in pairs in both the machine direction 14 and in the cross machine direction 15 relative to each other. The specific staggered arrangement results in leaky one-dimensional sensor arrangements 61 or - as here at least one

• multidimensional sensor arrangement 17 of water weight sensors 12 (FIG. FIG. 3 ).
  The dewatering of the pulp 2 is monitored by measurements of the water weight of the pulp 2 by means of at least two sensors 12 assigned to a zone 6, 7. Due to the measurements of the water weight, the dewatering is adaptable to a predetermined in the machine direction 14 drainage curve 19. A drainage curve is usually given in units of grams of water per square meter (g / m ² H ₂ O) over the entire length of the fibrous web 5. In this unit, the drainage curve 19 is in FIG. 3 which is shown along the fibrous web 5, in the machine direction on the left side thereof. The word "due" here denotes a causal relationship between the measurement of the water weight on the one hand and the adaptation of the actual dewatering state of the pulp 2 to the predefinable or predetermined drainage curve 19 on the other hand.

The dewatering device 1 has at least two each zonal adjustable, in the machine direction 14 relative to each other staggered drainage elements 16. The drainage elements 16 are designed here as suction boxes. The dewatering performance of the dewatering elements 16 is zonally adjustable due to the measurements of the water weight sensors 12.

The Wassergewichtsensoren 12 and the dewatering elements 16 are arranged alternately successively in the machine direction 14. As seen in the machine direction, at least one water weight sensor 12 is arranged here before the first and after the last dewatering element 16. Specifically, as seen in the machine direction 14 per location 18 in the first embodiment, five water weight sensors 12 in the cross machine direction 15 are arranged in a gappy manner offset from one another. There are three one-dimensional sensor arrays 13. These together form a multi-dimensional sensor field 17.

The drainage is zonal adjustable by means of at least one feedback loop 9 coupled back. The control circuit 9 preferably has at least one microprocessor 11.

The drainage is, preferably additionally, by means of at least one forward coupled control loop 8, here also with microprocessor 11, zonally adjustable. It could - albeit less preferred - only be present at least one forward coupled control loop 8, that is, the dewatering device 1 could also be constructed without backward coupled control loop 9. The feed and feedback loops 10 and the control circuits 8, 9 and the at least one microprocessor 11 are in FIG. 3 for the sake of clarity not shown.

This in FIG. 3 not shown inventive features are in FIG. 4 showing a second embodiment shown.

In both embodiments, the drainage elements 16 are present only in or in the region of the illustrated wet end 20. However, drainage elements 16 could also, in each case additionally or exclusively, be arranged in at least one further section of the dewatering device 1, such as in a steam blower box or in a press or in a headbox 3, in particular in a dilution hydrogen casserole.

The first embodiment has three one-dimensional transversely offset in the cross machine direction one-dimensional sensor assemblies 13, each with five Wassergewichtsensoren 12. The sensor arrangements 13 and thus their sensors 12 are also spaced apart in the machine direction 14. This results in a very regular periodicity as a pattern of the sensors 12. Another pattern or a different periodicity of the sensors 12 is realized in the second embodiment, which in FIG. 4 is shown.

In the second embodiment, the first sensor arrangement 13 in the machine direction 14 per zone 6, 7 is equipped with two sensors 12. The sensors 12 of the first sensor assemblies 13 in the machine direction 14 are arranged closer to the left edge of the fibrous web 5 as seen in the machine direction 14. One could speak of a left-sided sensor arrangement 13.

The three sensors 12 per zone 6, 7 of the second Sensorphalanx 13, that is, which is arranged between the two suction boxes 16, Englückiger than the two sensors 12 of the first sensor array 13 are arranged. The per zone 6, 7 three sensors 12 of the second Sensorphalanx 13 are centered relative to the cross-machine direction 15 in their respective zone as the two sensors 12 a zone of the first sensor assembly 13. One could briefly speak of a zonal mittig-engined second sensor assembly 13 ,

There is a third sensor arrangement 13 arranged in the machine direction 14 behind the second suction box 16. This is, insofar as it relates to the periodicity or the pattern, constructed analogously to the first sensor array 13, so in terms of the sensor spacing similarly-leaky. However, as seen in the machine direction 14, the sensors 12 of the third sensor arrangement 13 are arranged closer to the right edge of the fibrous web 5. In analogy to the first sensor arrangement 13, it would be possible to speak of a third sensor arrangement 13 designed in a right-handed manner. Here again, the sensors 12 of the different sensor arrangements 13 distributed in the machine direction 14 form a specific pattern in which the total number of sensors 12 is reduced in comparison to the first embodiment. This is particularly because the first and the third sensor arrangement 13 is rather wide-slit.

The dewatering performance of a dewatering element 16 in a zone 6, 7 is measured in both embodiments at a certain time by at least one water weight sensor 12. The measuring location 18 (see FIG. 4 ) of a water weight sensor 12 is freely selectable in the machine direction 14.

Also in both embodiments, as seen in the machine direction 14 at least one measuring point 18 at least two in the cross-machine direction 15 relative to each other staggered arranged Wassergewichtsensoren 12 per zone 6, 7 available.

Measurements of at least part of the water weight sensors 12, which are arranged offset in the machine direction 14 and assigned to a zone 6, 7, are averaged. One could also speak of a blurring or smearing. The terms filtering and smoothing also apply to this clearing procedure. The averaging produces a blurred or blurred signal. In conjunction with the offset-periodic arrangement of the sensors as a pattern, the water profile (IST) can be calculated from the averaged or filtered or smoothed signal. In a further consequence, the actual course can be adapted to the desired course of the drainage curve 19.

The adjustment, in particular the control, of the drainage takes place with the cooperation of at least one microprocessor 11. The averaging is preferably carried out with the aid of at least one microprocessor. The result of such a calculation is in the form of a water weight summation profile 24 of all sensors 12 in FIG FIG. 3 shown following the right end of the fibrous web 5. By a suitable interpolation from measured values of the staggered water weight sensors 12, a more accurate image of the dewatering behavior in the cross machine direction 15 and / or in the machine direction 14 is determined in a favorable manner.

As has now been understood by those skilled in the art, the dewatering devices 1 of the two embodiments implement the inventive method for adjusting, in particular control, the dewatering of a pulp 2, which is described as at least two, in Machine transverse direction 15 juxtaposed zones 6, 7 splittable fibrous web 5 is guided. Characteristic of the inventive method is that the dewatering of the pulp 2 due to measurements of the water weight of the pulp 2 by at least two, a zone 6, 7 associated, both in the machine direction 14 and in the cross machine direction 15, preferably in pairs, offset relative to each other arranged water weight sensors 12 is adapted to a predetermined in the machine direction 14 drainage curve 19.

Other embodiments of the method and the dewatering device according to the invention are conceivable and possible. For example, the patterns and / or the number of sensors could be designed differently. In the two embodiments shown in detail each similar water weight sensors are in use. However, depending on the water weight sensors equipped lot, it may be beneficial to combine dissimilar water weight sensors. The calculation of the measured values of dissimilar water weight sensors is conceivable and possible.

On the one hand, the total number of sensors on the basis of the specific, leaky arrangement of the sensors in a periodic pattern makes it possible to adapt the quality as well as the budget requirements. Furthermore, due to the gaps in all main directions and periodically offset sensors, the smearing in the settlement and thus an exact, because not disturbed by statistical process noise setting, in particular regulation, the drainage of the pulp allows.

LIST OF REFERENCE NUMBERS

1

dehydrator

2

fiber

3

headbox

4

Fuel outlet openings

5

Fibrous web

6

Zone

7

Zone

8th

Forward coupled control loop

9

Rückwarts coupled loop

10

Forward / feedback loop

11

microprocessor

12

Water weight sensor

13

One-dimensional sensor arrangement

14

Machine direction

15

CMD

16

dewatering element

17

Multidimensional sensor arrangement

18

Measuring location

19

drainage curve

20

wet end

21

dehydrator

22

breast roll

23

wire

24

Water weight total cross section

L

Longitudinal extent of the fibrous web

B

Transverse extension of the fibrous web

Claims (13)

Dewatering device (1), in particular a paper or board machine, for adjustable, in particular controllable, dewatering of a fibrous material (2) which can be split into at least two zones (6, 7) arranged adjacent to one another in the cross machine direction (15);
characterized,
that the dehydration of the pulp (2) by means of measurements of the water weight of the pulp (2) by means of at least two, in the cross-machine direction (15) preferably in pairs, relative to each other staggered relative arranged Wassergewichtsensoren (12), in particular one-dimensional or multidimensional sensor arrangements (13, 17) of water weight sensors (12), to a predetermined in the machine direction (14) drainage curve (19) is adaptable. Dewatering device (1) according to claim 1,
characterized,
in that the dewatering device (1) has at least two machine elements (16) which can be adjusted zonally, such as foils, suction boxes, contact elements in conjunction with a second mutual sieve (23) or a headbox (3), in particular in a wet end of the dewatering device (1) so that the drainage performance is zonally adjustable due to the measurements of the water weight sensors (12). Dewatering device (1) according to claim 1 or 2,
characterized,
that the water weight sensors (12) and the drainage elements (16) in the machine running direction (14) are alternately disposed sequentially. Dewatering device (1) according to one of the preceding claims,
characterized,
that the drainage by means of at least one forward-coupled control loop (8), in particular with a microprocessor (11), zonal is adjustable. Dewatering device (1) according to one of the preceding claims,
characterized,
that the drainage by means of at least one feedback control loop (9), in particular with microprocessor (11), zonal is adjustable. Dewatering device (1) according to one of claims 2 to 5,
characterized,
that the drainage elements (16), in particular in each case additionally or exclusively, in at least one section of the drainage device (1), as shown, arranged in a steam blower box or in a press or in a headbox (3), in particular in a dilution water headbox. Dewatering device (1) according to one of claims 2 to 6,
characterized,
that the dewatering performance by an adjustable suction strength and / or an adjustable layer thickness and / or the preferably adjustable consistency of emerging from the headbox (3) pulp (2) and / or preferably adjustable pressurization of the pulp (2) by means of opposing element and second sieve being affected. Dewatering device (1) according to one of claims 2 to 7,
characterized,
in that the dewatering power of a dewatering element (16) in a zone (6, 7) is measured by at least one water weight sensor (12) at a particular time, wherein in particular the measuring location (18) of the water weight sensor (12) in the machine direction (14) is freely selectable , Dewatering device (1) according to one of the preceding claims,
characterized,
that, seen in the machine running direction (14) at least one measurement location (18) at least two cross machine direction (15) offset relative to one another to arranged water weight sensors (12) per zone (6, 7) are present. Dewatering device (1) according to one of the preceding claims,
characterized,
in that the measurements of at least part of the water-weight sensors (12) arranged offset in the machine direction (14) and associated with a zone (6, 7) are averaged. Dewatering device (1) according to one of the preceding claims,
characterized,
in that the adjustment, in particular the regulation, of the drainage takes place with the cooperation of at least one microprocessor (11). Dewatering device (1) according to one of the preceding claims,
characterized,
that by a suitable interpolation from measured values of the staggered water weight sensors (12) a more accurate image of the Dewatering behavior in the cross-machine direction (15) and / or in the machine direction (14) is determined. Method for adjusting, in particular regulating, the dewatering of a pulp (2) of a dewatering device (1), in particular a paper or board machine, as claimed in any one of claims 1 to 12, wherein the pulp (2) is in at least two, in the cross machine direction ( 15) juxtaposed zones (6, 7) splittable fibrous web (5) is guided,
characterized,
in that the dehydration of the fibrous material (2) by means of at least two water weight sensors (12) assigned to a zone (6, 7) in the cross machine direction (15), preferably in pairs and offset relative to one another, to one in Machine running direction (14) predetermined drainage curve (19) is adjustable.

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