WO2017092931A1

WO2017092931A1 - Device for the production of a fibrous web

Info

Publication number: WO2017092931A1
Application number: PCT/EP2016/075619
Authority: WO
Inventors: Thomas RÜHL; Andreas Ziegelwanger; Marc HARMS
Original assignee: Voith Patent Gmbh
Priority date: 2015-11-30
Filing date: 2016-10-25
Publication date: 2017-06-08
Also published as: CN108291367A; EP3384082A1; DE102015223662A1

Abstract

A device for producing a fibrous web, in particular a web of packaging paper, comprises a headbox, a screen section for dewatering a fibrous suspension introduced via the headbox and forming a fibrous web from the fibrous suspension, a press section for further dewatering the fibrous web, and a drying section for drying the fibrous web. The screen section comprises a single-layer former, and the press section comprises at least one press nip, in particular at least one shoe press nip, which is extended in the direction of travel of the web. Furthermore, the drying section is formed at least in part by steel cylinders and is designed for drying screen wire tensions ≥ 4 kN/m, in particular ≥ 5 kN/m.

Description

Device for producing a fibrous web

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 of the pulp suspension, a press section for further dewatering of the fibrous web and a dryer section for Drying of 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 the middle layer between two liner layers, ie the two layers used on the inside and outside of the corrugated cardboard or cardboard. 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 in the dryer section steel cylinders are used to the dryer fabrics are performed with partially increased wire tension and whose wire section has a Mehrlagenformer. The invention has for its object to provide a suitable in particular for the production of packaging papers device of the type mentioned, which in particular has a smaller overall length with a minimization of investment and operating costs, whereby the required machine hall length is reduced.

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 wrapping 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 of the fibrous web. In this case, the wire section comprises a single-layer former and the press section comprises at least one press nip extended in the direction of travel of the web, in particular at least one nip. In addition, the dryer section is at least partially designed with steel cylinders and designed for Trockensiebspannungen> 4 kN / m, in particular> 5 kN / m.

On account of this training, packaging papers in particular can be produced more economically, that is to say with lower investment and operating costs. The various sections of the device or paper machine are not only more efficient, the device or paper machine is also more compact overall and in particular shorter, so that the required machine hall length can be kept correspondingly lower. With the at least one in running direction extended press nip results due to the higher line load a correspondingly higher dry content after the press section. The fact that the dryer section is at least partially designed with steel cylinders and that it is designed for higher dryer fabric tensions improves the heat transfer to the fibrous web and increases the efficiency of the drying process, which can further reduce the length of the dryer section. 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.

The wire section may in particular comprise a gap former. 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.

According to an expedient practical embodiment of the device according to the invention, the wire section comprises a hybrid former with a pre-dewatering zone and an adjoining twin-wire section.

It is particularly advantageous if the wire section comprises a former, in particular inguinal gap former, with an at least substantially horizontal dewatering section. 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. It can thus be used, for example, a relatively short horizontal Leistengapformer.

According to a further expedient embodiment of the device according to the invention, the press section comprises two extended in the web running direction Press nips, in particular two shoe press nips. In this case, the press section may in particular comprise a double shoe press or tandem NipcoFlex press. A tandem NipcoFlex press is characterized in particular by a relatively high line load, whereby a high dry content is achieved after the press section.

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 of particular advantage if the polyurethane covering of the opposite roller 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.

Preferably, an impermeable lower conveyor belt is guided by the second 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 headbox may be designed for separate feeding of the pulp suspension with at least two layers. However, in particular, such an embodiment of the device according to the invention is conceivable in which the head box is designed for separate feeding of the pulp suspension with at least three layers.

It is particularly advantageous if the headbox is provided with at least one protruding from the headbox separating blade. A protruding separating blade in particular allows a good delamination and thus good masking qualities, i. a reduced show through of the uncoloured opposite side of the testliner.

The fibrous web is preferably guided supported up to the first drying cylinder of the drying section, which results in a good web guide and the risk of web breaks is reduced to a minimum. To further increase the drying performance, the dryer section may be equipped with high-performance dryers such as in particular impingement hoods or the like. The 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, preferably at least one high-performance dryer is arranged in the initial region of a pre-drying section of the dryer section. With additional high-performance dryers in the initial region of the pre-dryer section, the total length of the device or paper machine can be further shortened. In addition, the strength of the end product is thereby increased, for example, when starch introduced between the individual layers binds earlier.

The machine concept according to the invention is tailored to the optimum specific investment costs. Among other things, account is taken of the fact that the raw material potential, in particular for the production of packaging papers, may contain a high proportion, partially or up to 100%, of recycled pulp. 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 defines 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. Since Asia represents a major growth market for packaging paper, the raw material used there and available economically must be taken into account. A suitable speed range for the operation of the device is between 1 100 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, the production of two-layer products such as test liners with a single-layer former concept using a two-layer headbox is particularly advantageous. In this case, a protruding separating blade allows good delamination and thus good masking qualities, ie a reduced show through of the uncoloured opposite side of the testliner. It has been found that due to the moderate speed in combination with lighter weight per unit area, the use of a roll blade gap former is no longer required and 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 hybrid formers, the conceptually slightly longer longitudinal orientation in sheet formation is favorable in order to be able to exploit the maximum speed potential. The impaired strength properties in the transverse direction can be compensated by additives such as starch or special or higher-value fiber material. In this case, strength-increasing additives such as starch can be added to the raw material. The addition takes place either before the headbox, in the headbox, in the material jet or in the former section in the form of starch spraying pipes. 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 pressing momentum and thus with 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 here and can be exposed to 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. In addition, this can in particular also be combined with a higher drying wire tension. The higher wire tension causes another Increase of the heat transfer. In this case, the device is advantageously operated so that this drying wire tension is in the range of 4 to 8 kN / m, in particular 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 on the basis of exemplary embodiments with reference to the drawing; in this show:

1 is a schematic representation of an exemplary embodiment of an apparatus according to the invention for producing a fibrous web, in particular for producing a packaging paper web,

2 is an enlarged view of the press section of the apparatus of FIG. 1, a schematic partial view of a running with two layers and provided with a protruding separating blade headbox,

a schematic partial view of a running with three layers and provided with a protruding separating blade headbox,

5 is a schematic representation of the flow of a 3-

Layer headbox and

a schematic partial view of the dryer section of an exemplary embodiment of a device according to the invention with provided in the dryer section impingement hoods.

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

The device 10 comprises a headbox 12, a wire section 14 for dewatering a introduced over the headbox 12 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 of the fibrous web. The drying section 18 may be arranged downstream of a roller 20 for rolling up the dried fibrous web.

In this case, the wire section 14 comprises a single-layer former and the press section 16 at least one extended in the web running direction L press nip 22, in particular at least one Schuhpressnip. The drying section 18 is at least partially designed with steel cylinders and designed for dry-wire tension> 4 kN / m, in particular> 5 kN / m. In this case, the wire section 14 may in particular comprise a gap former.

In the illustration according to FIG. 1, the device 10 comprises, for example, a hybrid former with a pre-dehydration zone 26 and a double-sieve part 24 adjoining it.

The wire section may for example comprise a former, in particular also a strip gap former, with an at least substantially horizontal dewatering section.

In the present case, for example, the press section 16 comprises two press nips extended in the web running direction L, for example two shoe press nips. In this case, the press section 16 can be designed in particular as a double shoe press or tandem NipcoFlex press.

In the present case, the press section comprises only the two extended in the web running direction L press nips or only the two shoe press nips or only the double shoe press. A respective shoe press nip may in particular be 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 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 .

The second or last press nip 22 of the press section, viewed in the web running direction L, can guide an impermeable lower conveyor belt 28.

The headbox 12 can be designed for separate feeding of the fibrous web, for example, with at least two layers (see Fig. 3) and in particular also with three layers (see Fig. 4). In this case, the headbox 12 may also be provided in each case with at least one of the headbox nozzle 30 protruding separating blade 32. The separating blade 40 ends within the headbox nozzle 30.

The fibrous web can be guided supported up to the first drying cylinder 34 of the drying section 18, which results in a good web run.

The drying section 18 can be equipped with high-performance dryers 36, in particular impingement-flow hoods or the like (cf., in particular, FIG. In this case, at least one such high-performance dryer 36 can be arranged in particular in the initial region of a pre-drying section of the drying section 18, as a result of which the overall length of the device 10 is further shortened. Fig. 2 shows the press section 16 of the device 10 of FIG. 1 in an enlarged view. Corresponding parts are assigned the same reference numerals.

Fig. 3 shows a schematic partial view of a running with two layers headbox 12, while the headbox 12 shown in Fig. 4 is performed with three layers. The headbox 12 is in each case provided with a projecting from the headbox nozzle 30 separating blade 32.

5 shows a schematic representation of the flow of a 3-layer headbox 12.

6 shows, in a diagrammatic partial representation, the drying section 18 of an exemplary embodiment of a device according to the invention with high-performance driers 36, for example in the form of impingement hoods, which can be arranged in particular at the beginning of a pre-drying section of the drying section 18.

In the various figures, like reference numerals are assigned to corresponding parts.

The device according to the invention is particularly suitable for the production of packaging papers. With this device, not only the investment and operating costs are minimized. The device or paper machine can also be made shorter overall, so that the required machine hall length can be kept correspondingly low.

The high-performance dryers 36 may be arranged, for example, on stabilizing rollers 38 at the beginning of a single-row pre-drying section.

LIST OF REFERENCES

10 device

12 headbox

14 wire section

16 press section

18 drying section

20 scooters

22 extended press nip, shoe nip 24 double strainer part

26 pre-dewatering zone

28 conveyor belt

30 headbox nozzle

32 separating lamella

34 drying cylinders

36 high-performance dryers

38 stabilizing rollers

40 Trennlamelle L Web running direction

Claims

claims

1. A device (10) for producing a fibrous web, in particular a packaging paper web, with a headbox (12), a wire section (14) for dewatering 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 wire section (14) having a single-layer former and the press section (16) at least one press nip (22) extended in the web running direction (L). , in particular at least one shoe press nip, and wherein the dryer section (18) is at least partially designed with steel cylinders and designed for dry-wire tensions> 4 kN / m, in particular> 5 kN / m.

2. Apparatus according to claim 1,

in that the wire section (14) comprises a gap former.

3. Apparatus according to claim 1 or 2,

Thereby, the wire section (14) comprises a hybrid former having a pre-dewatering zone (26) and a twin-wire section (24) adjoining it.

4. Device according to at least one of the preceding claims, characterized in that the wire section (14) comprises a former, in particular inguinal gap former, with an at least substantially horizontal dewatering section.

5. Device according to at least one of the preceding claims,

characterized in that the press section (16) comprises two press nips (22), in particular two shoe press nips, which are elongated in the web running direction (L).

6. Device according to at least one of the preceding claims,

This means that the press section (16) comprises only the two press nips (22) which are elongated in the web running direction (L) or only the two shoe press nips or only the double shoe press.

7. Device according to at least one of the preceding claims,

Thereby, a respective shoe press nip is formed between a shoe press roll and a counter roll provided with a polyurethane cover.

8. Apparatus according to claim 7,

Thereby, the polyurethane covering of the backing roll of a respective shoe press has an open area in the range between 10 and 40%.

9. Apparatus according to claim 7 or 8,

characterized in that 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 .

10. Device according to at least one of the preceding claims, characterized in that an opaque lower conveyor belt (28) is guided by the in the web running direction (L) considered second press nip (22) of the press section (16).

Device according to at least one of the preceding claims, characterized in that the headbox (12) is designed for separate feeding of the pulp suspension with at least two layers.

Device according to at least one of the preceding claims, characterized in that the headbox (12) is designed for separate feeding of the pulp suspension with three layers.

Device according to at least one of the preceding claims, characterized in that the head box (12) is provided with at least one separating lamella projecting from the headbox nozzle (30) thereof.

Device according to at least one of the preceding claims, characterized in that the drying section (18) is equipped with high-performance dryers (36), in particular impingement-flow hoods or the like.

Device according to claim 14,

Thereby, at least one high-performance dryer (36) is arranged in the initial region of a pre-drying section of the dryer section (18).