DE102015223663A1 - DEVICE FOR PRODUCING A FIBROUS WEB - Google Patents

Abstract

An apparatus for producing a fibrous web, in particular a packaging paper web, comprises a headbox, a wire section for dewatering a introduced over the headbox pulp suspension and for forming a fibrous web from the pulp suspension, a press section for further dewatering of the fibrous web and a dryer section for drying the fibrous web. The headbox is designed with three layers and provided with a protruding over the headbox nozzle. In addition, starch introduction means are provided, via which starch can be introduced into at least one layer. The wire section comprises a single-layer gap former. The press section has at least one press nip extended in the direction of web travel, in particular at least one press nip.

Description

The invention relates to a device for producing a fibrous web, in particular a packaging paper web, with a headbox, a wire section for dewatering a introduced over the headbox pulp suspension and to form a fibrous web from the pulp suspension, a press section for further dewatering of the fibrous web and a dryer section for drying the fibrous web.

Together with paperboard, packaging papers make up the largest share of packaging materials in practice. They are universally applicable, clean and flexible. The packaging papers include all types of corrugated board, sack paper for the paper sacks, classic brown packaging paper and also the top layers of plasterboard. They usually have a high content of waste paper. Corrugated material is used in the production of corrugated cardboard as a middle layer between two liner layers, d. H. the two layers used on the inside and outside of the corrugated cardboard or cardboard used. It is usually made from 100% recycled paper. The required strengths are achieved by applying starch.

There are already known devices of the type mentioned, the wire section has a multi-layer former and are used in the dryer section steel cylinder to the dryer fabrics are performed with partially increased wire tension.

The invention has for its object to provide a suitable in particular for the production of packaging papers device of the type mentioned in particular with a minimization of investment and operating costs while ensuring the highest possible dry content, the best possible web guide and the best possible quality of the final product ensures a higher strength of the final product.

The object is achieved by a device having the features of claim 1. Preferred embodiments of the device according to the invention will become apparent from the dependent claims, the present description and the drawings.

The inventive apparatus for producing a fibrous web, in particular a packaging paper web, comprises a headbox, a wire section for dewatering a introduced over the headbox pulp suspension and to form a fibrous web from the pulp suspension, a press section for further dewatering of the fibrous web and a dryer section for drying the fibrous web. The headbox is designed with three layers and provided with a protruding over the headbox nozzle. In addition, starch introduction means are provided, via which starch can be introduced into at least one layer. The wire section comprises a single-layer gap former. The press section has at least one press nip extended in the direction of web travel, in particular at least one press nip.

Due to this design, a higher quality and in particular a higher strength of the end product are achieved with minimal investment and operating costs and ensuring a high dry content and good web guide, the device of the invention is particularly suitable for the production of packaging papers.

The three-layer or three-layer casserole can have three, in particular, superimposed suspension flow channels, via which flow streams or media are supplied to the headbox, from which the substance suspension jet emerging from the headbox is formed. A protruding separating blade allows in particular a good delamination and thus good masking qualities, d. H. z. B. a reduced show through the unstained opposite side of the testliner. In particular, the strength of the end product can be correspondingly increased by the introduction of starch. In this case, both the gap strength and the surface strength of the respective end product can be increased accordingly by a corresponding strength input. A gap former is a twin-wire former in which the pulp suspension is introduced directly between the two screens and dewatered on both sides. The use of a single-layer gap former helps to minimize investment costs. With the at least one press nip extended in the direction of travel of the web or at least one shoe press nip, a correspondingly higher dry content results after the press section due to the higher line load.

It is particularly advantageous if starch can be introduced via the starch-introducing means at least into the middle layer. In particular, the inner strength of the respective end product can be correspondingly increased with such a starch feed into the middle layer.

Thickness before the head box, in the headbox and / or at the latest in the wire section after the headbox into the pulp suspension or the fabric jet produced by the headbox can be introduced or applied to the fibrous web via the starch feed means.

Lamellae inserted into the headbox nozzle can provide uniform penetration of starch for good formation and in the event that at least part of the starch is already introduced in front of or into the headbox through the starch delivery means. If starch is at least partially introduced in front of the headbox, the starch can be introduced, for example, into a mixing vessel or the like. As already mentioned, however, the starch can at least partially also be introduced only in or after the headbox and / or at the latest in the wire section or forming section.

The headbox with three layers can, as already mentioned, be fed by three streams or media.

The gap former can in particular be designed as a strip gap former. Such a strip gap former is a gap or gap former with fixed initial drainage elements, through which the fibrous web is formed. It can thus be used, for example, a relatively compact or short Leistengapformer.

It is particularly advantageous if the gap former is designed without a suction roll, which further simplifies its structure and makes it correspondingly less expensive.

The gap former expediently comprises an at least substantially horizontal dewatering section. In such a horizontal dewatering section of the Gapformers, the drainage takes place at least substantially downwards and upwards.

The press section advantageously comprises two press nips extended in the direction of web travel, in particular two shoe press nips. In this case, the press section may in particular comprise a double shoe press or tandem Nipcoflex press.

In one of the dewatering of the fibrous web serving shoe press the pressing pressure is not built up with a rotating roller and counter-roller, but it presses a stationary shoe against a rotating counter-roller. For this to work, a flexible plastic sheath is passed around this shoe. Between shoe and plastic jacket an oil film is built up for lubrication. The water pressed out of the fibrous web is delivered to at least one circulating felt as in a conventional press. Due to the design of the shoe, the so-called press nip can be much longer than in a conventional press, whereby the residence time of the fibrous web in the press nip increases accordingly. Accordingly, the need for thermal drying is lower. Finally, the relatively soft drainage preserves the paper volume.

The press section may in particular comprise only the two press nips extended in the direction of web travel or only the two shoe press nips or only the double shoe press.

It is also particularly advantageous if a respective shoe press nip is formed between a shoe press roll and a counter roll provided with a polyurethane cover. In this case, the polyurethane cover of the backing roll of a respective shoe press preferably has an open area in the range between 10 and 40%. It is also particularly advantageous if the polyurethane cover of the backing roll of a respective shoe press has a storage volume in the range between 500 and 1500 ml / m ² . As a result, the dry content after the press section can be further increased accordingly.

An impermeable lower transfer belt is preferably passed through the second or last press nip of the press section viewed in the web running direction. With the use of such a transport or transfer belt in the lower position of the last press nip of the press, the re-wetting can be reduced, in particular with a lighter basis weight spectrum, and thus the dry content can be increased below 100 g / m ^2, in particular for lighter basis weights.

The fibrous web is preferably guided continuously supported up to the first drying cylinder of the dryer section, which results in a good web guide and the risk of web breaks is reduced to a minimum.

According to a further advantageous embodiment of the device according to the invention, the drying section is at least partially executed with steel cylinders. It is particularly advantageous if the dryer section is designed for dryer fabric tension> 5 kN / m.

Due to their material, steel cylinders have a higher heat transfer rate than cast cylinders. In particular, in combination with a higher Trockensiebspannung thus a further increase in the heat transfer can be achieved. By running the drying section for dryer fabric tension> 5 kN / m, the dryer fabrics can be passed around the cylinders with a correspondingly higher tension.

To further increase the drying performance, the dryer section can advantageously comprise at least one high-performance dryer, in particular at least one impingement-flow dryer and / or at least one infrared dryer. Both Impingement flow dryers are high-performance dryers in which the fibrous web is subjected to hot-air and / or hot-steam radiation at least on one side. In this case, for example, at least one high-performance dryer can be arranged in the initial region of a pre-drying section of the dryer section. With additional high-performance dryers in the beginning of the dryer section, the total length of the device or paper machine can be further shortened. In addition, this increases the strength of the end product, for example, after the introduced starch binds earlier.

The machine concept according to the invention is tuned to the optimum specific investment costs. The raw material potential, in particular with regard to packaging papers with a high and partial or up to 100% proportion of recycled pulp, is also taken into account. It has been shown that for packaging papers made of recycled fiber material as a raw material, the optimum operating speed also depends substantially on the strength potential of the raw material. Thus, the strength potential of the raw material specifies the speed range in which the operation can be carried out with reasonable machine efficiency. This will above all keep the demolition figures in an economically sensible framework and reduce the necessary downtime on the machine to a minimum. After Asia is a major growth market for packaging paper, the raw material used and available economically must be taken into account. A suitable speed range for the operation of the device is between 1100 and 1500 m / min. This also takes into account the trend towards lighter basis weights for testliners and corrugated grades.

With regard to the optimum machine concept for the specific boundary conditions, in particular the production of two-layer products such as testliners with a single-layer former concept using a two-layer headbox is advantageous. In this case, a protruding separating blade allows good delamination and thus good masking qualities, d. H. a reduced show through of the uncoloured opposite side of the testliner. It has been found that the use of a roll blade gap former is no longer required due to the moderate speed in combination with lighter weight per unit area and that the required production rates can be achieved even with a blade gap former with reduced dewatering or production capacity. Such a blade gap former can be embodied in particular in a horizontal construction, in order to favor the use of a clothing tensioning device by the stiffening. Compared to Hybridformern the conceptually slightly higher longitudinal orientation in the sheet formation is favorable in order to exploit the maximum speed potential can. The thus impaired strength properties in the transverse direction can by additives such. As strength or special or higher quality fiber material can be compensated. In this case, strength-enhancing additives such. B. starch can be added to the raw material. The addition takes place either before the headbox, in the headbox, in the jet or in the Formerpartie in the form of Stärkesprührohren. In the headbox or in the jet, this can be done by a multi-layer headbox.

In the further course of the device or paper machine, a press section with a high press pulse is advantageous in order, on the one hand, to enable a high dry content and, on the other hand, a high level of sheet compacting. Both favor the blade strength or wet strength and thus the runnability or runnability of the machine. For this purpose, at least one press nip is advantageously designed as a shoe press nip. Conveniently, a double shoe press can be used. Such a double shoe press has, in addition to the high pressure pulse and thus the high dry content, the further advantage of a continuously supported web guide through the press section.

An expedient variant with a lighter basis weight spectrum is the use of a transfer belt in the second lower position of the press, whereby the rewetting is reduced and thus the dry content is increased, especially for lighter basis weights below 100 g / m ² .

With regard to the moisture cross profile, a simply felted press nip is also an advantage. A good moisture cross profile at the end of the press section leads to uniform web tension ratios in the transverse direction of the machine, which in turn favors runnability or runnability in the critical exit area of the dryer section. Moisture differences and thus resulting web tension differences and tensile folds are avoided.

In the further course of the fibrous web through the dryer section, the highest possible heat flow is generally advantageous, thus increasing the efficiency of the drying and, at the same time, reducing the required length of the dryer section and thus also of the entire machine and of the machine building. It should be noted, however, that too high heat flow at the beginning of the dryer section bring a kind of sealing the web surface with it and thus be detrimental to the drying efficiency and even damage the sheet. The respective possible and sensible heat output depends on the raw material and the grammage. Especially packaging papers are not very sensitive and can be acted upon by relatively steep heating curves.

For this reason, steel cylinders with a material-related higher heat transfer can also be used with advantage as cast cylinders. This can also be combined, in particular, even with a higher drying wire tension. The higher wire tension causes a further increase in the heat transfer. The device is advantageously operated so that this Trockensiebspannung is in the range of 5 to 8 kN / m. Here are the effects on the paper, especially packaging papers, not yet quality-impairing. In addition, the usual dryer fabrics with seam can still withstand this tension. Finally, the cost leap for the dimensioning of other components such as screen tensioner, regulator and rollers is still relatively moderate and economically reasonable in relation to the benefits of the faster, more efficient drying.

In addition, intensive drying at the beginning of the pre-drying section is advantageous for the effect of the starch or other strength-increasing additives added in the constant part or wet part of the machine. This effect can be purposefully further intensified by the use of high-performance dryers, such as impingement drying hoods, at the beginning of the pre-drying section. For example, two to six hoods are economically and paper-technologically useful in order to achieve the effect of increasing the strength at moderate investment and operating costs.

The invention will be explained in more detail below with reference to exemplary embodiments with reference to the drawing; in this show:

1 a schematic representation of an exemplary embodiment of an inventive device for producing a fibrous web, in particular for producing a packaging paper web, and

2 a schematic representation of the wire section of another exemplary embodiment of a device according to the invention.

1 shows a schematic representation of an exemplary embodiment of a device according to the invention 10 for producing a fibrous web, in particular a wrapping paper web.

The device 10 includes a headbox 12 , a wire section 14 for draining one over the headbox 12 introduced pulp suspension and to form a fibrous web from the pulp suspension, a press section 16 for further dewatering of the fibrous web and a dryer section 18 for drying the fibrous web. The dryer section 18 may include a scooter 20 be downstream for rolling up the dried, finished fibrous web.

The headbox 12 is designed with three layers and provided with a projecting over the headbox separator blade. In addition, starch introduction means are provided, via which at least one layer of starch can be introduced.

The wire section comprises a single-layer gap former 22 , In this case, in the present case, for example, a roll-blade gap former with at least substantially horizontally extending rear drainage path 24 intended.

The press section 16 includes at least one in the web running direction 11 extended press nip 26 , in particular at least one shoe press nip.

The starch-introducing means may in particular be designed such that starch can be introduced at least into the middle layer.

Starch before the headbox can use the starch food 12 in the headbox 12 and / or at the latest in the wire section 14 after the headbox 12 in the pulp suspension or the headbox 12 produced fabric jet can be introduced or be applied to the fibrous web. In this case, in particular the strength of the end product is increased accordingly by the starch entry.

The headbox with three layers 12 can be fed via three streams or media.

The gapformer 22 can be embodied in particular as inguinal gap former. Such a strip gap former is a gap or gap former with fixed initial drainage elements through which the fibrous web is formed and dehydrated.

In addition, the Gapformer 22 In particular, be carried out without suction roll, whereby he receives a simpler and correspondingly cheaper construction.

The gapformer 22 may comprise an at least substantially horizontal dewatering section. The dewatering of the fibrous web takes place in such a horizontal dewatering path at least substantially upwards and downwards through the screens of the Gapformers 22 ,

The press section 16 in the present case, for example, comprises two in the web running direction L. extended press nips 26 or shoe press nips. In this case, the press section 16 In particular, a double shoe press or tandem Nipcoflex press include.

In one of the dewatering of the fibrous web serving shoe press the pressing pressure is not built up with a rotating roller and counter-roller, but it presses a stationary shoe against a rotating counter-roller. In this case, a flexible roll shell is guided around the press shoe. Between shoe and flexible roll shell an oil film is built up for lubrication. The water pressed out of the fibrous web is delivered to at least one circulating felt as in a conventional press. Due to the design of the shoe, the so-called press nip can be much longer than in a conventional press, whereby the residence time of the fibrous web in the press nip increases accordingly. Due to the high pressure pulse results after the press section a correspondingly high dry content.

As based on the 1 can be seen, includes the press section 16 in the present case, only the two extended in the web running direction L press nips 26 or only the two shoe press nips or only the double shoe press.

A respective shoe press nip 26 may be formed between a shoe press roll and a counter-roll provided with a polyurethane covering. In this case, the polyurethane cover of the backing roll of a respective shoe press may in particular have an open area in the range between 10 and 40%. In addition, the polyurethane cover of the backing roll of a respective shoe press can in particular have a storage volume in the range between 500 and 1500 ml / m ² . This allows the dry content after the press section 16 be further increased accordingly.

By viewed in the web running direction L second or last press nip 26 the press section 16 can be an impermeable lower transfer band 30 be passed. With the use of such a transport or transfer belt 30 in the lower position of the last press nip 26 In particular, the press can be rewetted with a lighter basis weight spectrum and thus the dry content can be increased below 100 g / m ^2, in particular for lighter weight per unit area.

The fibrous web can be up to the first drying cylinder 28 the dryer section 18 be guided continuously supported, which results in a safer web run and the risk of web breaks is minimized.

The dryer section 18 can be carried out at least partially with steel cylinders. In addition, the dryer section 18 be carried out for Trockensiebspannungen, in particular greater than 5 kN / m. The dryer fabrics can thus be guided around the drying cylinders or steel cylinders with a correspondingly higher tension.

By the dryer section 18 at least partially designed with steel cylinders and designed for higher Trockensiebspannungen, the heat transfer to the fibrous web are improved and increases the efficiency of drying, so that the length of the dryer section can be reduced accordingly. For example, steel cylinders have a higher heat transfer rate than cast iron due to the material. In addition, the heat transfer is further increased by the higher Trockensiebspannung.

To further increase the drying performance, the dryer section 18 be equipped with high-performance dryers such as in particular impingement flow dryers or infrared dryers. The impingement flow dryers are high-performance dryers in which the fibrous web is subjected to hot and / or superheated steam at least on one side. In particular, at least one such high-performance dryer in the initial region of a pre-drying section of the dryer section 18 be arranged, whereby the total length of the device can be further shortened. In addition, this increases the strength of the final product after the applied starch binds earlier.

2 shows a schematic representation of the wire section 14 a further exemplary embodiment of a device according to the invention 10 that differ from the according to 1 at least substantially only differs in that in the wire section 14 the forming roller 25 is missing and the entire dewatering section in the twin-wire section is guided substantially horizontally.

LIST OF REFERENCE NUMBERS

10

contraption

12

headbox

14

Wire section

16

press section

18

drying section

20

scooter

22

Gapformer

24

rear drainage route

25

forming roll

26

Pressnip, shoe press nip

28

first drying cylinder

30

lower transfer band

Claims (15)

Contraption ( 10 ) for producing a fibrous web, in particular a wrapping paper web, with a headbox ( 12 ), a wire section ( 14 ) for draining one over the headbox ( 12 ) introduced pulp suspension and to form a fibrous web from the pulp suspension, a press section ( 16 ) for further dewatering of the fibrous web and a dryer section ( 18 ) for drying the fibrous web, wherein the headbox ( 12 ) is provided with three layers and is provided with a projecting beyond the headbox separating blade, starch introduction means are provided, via which in at least one layer of starch can be introduced, the wire section ( 14 ) a single-layer gap former ( 22 ) and the press section ( 16 ) at least one in the web running direction (L) extended press nip ( 26 ), in particular at least one Schuhpressnip having. Apparatus according to claim 1, characterized in that starch can be introduced via the starch-introducing means at least into the middle layer. Device according to claim 1 or 2, characterized in that starch is deposited in front of the headbox ( 12 ), in the headbox ( 12 ) and / or at the latest in the wire section ( 14 ) after the headbox ( 12 ) in the pulp suspension or the headbox ( 12 ) can be introduced or applied to the fibrous web. Device according to at least one of the preceding claims, characterized in that the headbox running with three layers ( 12 ) is fed via three streams or media. Device according to at least one of the preceding claims, characterized in that the gap former ( 22 ) is executed as inguinal gap former. Device according to at least one of the preceding claims, characterized in that the gap former ( 22 ) is performed without suction roll. Device according to at least one of the preceding claims, characterized in that the gap former ( 22 ) comprises an at least substantially horizontal dewatering section. Device according to at least one of the preceding claims, characterized in that the press section ( 16 ) two extended in the web running direction press nips ( 26 ), in particular two shoe press nips comprises. Device according to at least one of the preceding claims, characterized in that the press section ( 16 ) only the two in the web running direction (L) extended press nips ( 26 ) or only the two shoe press nips or only the double shoe press comprises. Device according to at least one of the preceding claims, characterized in that a respective shoe press nip ( 26 ) is formed between a shoe press roll and a counter-roll provided with a polyurethane cover. Apparatus according to claim 10, characterized in that the polyurethane cover of the backing roll of a respective shoe press has an open area in the range between 10 and 40%. Apparatus according to claim 10 or 11, characterized in that the polyurethane cover of the counter roll of a respective shoe press has a storage volume in the range between 500 and 1500 ml / m ² . Device according to at least one of the preceding claims, characterized in that by the in the web running direction (L) considered second or last press nip ( 26 ) of the press section ( 16 ) an impermeable lower transfer belt ( 30 ) is passed. Device according to at least one of the preceding claims, characterized in that the drying section ( 18 ) is at least partially executed with steel cylinders. Device according to at least one of the preceding claims, characterized in that the drying section comprises at least one high-performance dryer, in particular at least one impact air dryer and / or at least one infrared dryer.

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