WO2008138683A1

WO2008138683A1 - Cleaning method

Info

Publication number: WO2008138683A1
Application number: PCT/EP2008/054085
Authority: WO
Inventors: Susanne Berger; Holger Humberg; Alexander Wohlmuth; Roland Mayer; Daniel Gronych
Original assignee: Voith Patent Gmbh
Priority date: 2007-05-15
Filing date: 2008-04-04
Publication date: 2008-11-20
Also published as: DE102007022810A1

Abstract

The invention relates to a method for cleaning a running paper, cardboard, or other fibrous material web (6) during the production thereof in a production machine (4), the fibrous material web (6) being cleaned of loose or non-bonded, undesired particles (9) by at least one cleaning device (7) working across the width, which is to say transversely to the running direction (L) of the web (6). According to the invention, the cleaning device (7) acts on surface or web side (6a, 6b) of the fibrous material web (6) that has already been completely dried in a dryer section (3) of the production machine (4).

Description

cleaning process

The invention relates to a method for cleaning a running

Paper, board or other fibrous web during its manufacture in which the fibrous web is provided with at least one across the width, i. Clearing acting transversely to the direction of the web cleaning device is freed from loose or unbound, unwanted particles.

In the production of the fibrous web, in particular an uncoated and not highly compressed paper or board web, i. e.g. A web intended for newspaper printing and improved newsprint, which typically moves at high speed through the manufacturing machine, often removes particles from the web. These particles, in particular fiber parts, are only poorly bound to the web surface and constitute dust or impurities in the dry state of the web. These particles, in turn, later cause problems in the further processing of the fibrous web produced. Above all, if the fibrous web is to be printed later, the said particles can get on printing plates or blankets of the printing press, settle there and over a long period printing errors such as in particular so-called whitespots, i. small white unprinted stains, or so-called hickies, i. annular spots, cause.

To a large extent, these particles are vascular cells from the eucalyptus tree, which in particular through the use of waste paper as a raw material, in particular copy paper in the newspaper get printing paper. However, even the smallest adhesive constituents can occur which bring about comparable printing defects.

The mentioned printing problems occur in particular when, in the production of the paper, the relevant fibrous web for dewatering has passed through a compact 3-nip press such as, for example, a DuoCentri II or DuoCentri Nipcoflex press. In such a press, the pulp or paper web usually comes in the first nip with a felt on the bottom in contact. In the two subsequent nips, only the top of the web comes into contact with a felt while the bottom is in contact with a smooth roll. The paper is more compacted on the felt-contacting upper side than on the side facing a smooth roller. However, the corresponding compaction has a decisive influence on the binding of the vascular cells and particles to the web surface, which is due to the lower hydraulic and larger back pressure on the felted side.

There are various ways to counteract this problem from the paper-technical side. Thus, for example, a fourth press nip could be installed, in which the web underside again comes into contact with a felt. A corresponding procedure has already been proposed several times. However, such a fourth press nip entails a number of disadvantages, such as, in particular, high investment costs, in particular for retrofits, and high operating costs due to additional covering and additional equipment. There are also various chemical aids available, through which the particles mentioned can be better bound to the paper. However, even such chemical aids represent a significant cost factor for the production. From EP 0 937 178 B1 (Metso) a method for removing dust in a paper machine is known. In this method, a draft is directed to the web which separates the dust from the surface of the web. In addition, a suction effect is applied to the web to remove the dust. In addition, vortex flow is generated before the dust-separating blowing, to prevent the transport of the dust into the environment and to compensate for the suction effect.

From US 3,239,863 a web cleaner is known, which also works with directed to the web air nozzles. In this document, the application of a standing brush and also a revolving in the direction of the web round brush is disclosed.

From the magazine PuIp & Paper of November 2008, an article "Properly Configured Wob Inspection Moves Mills Towards Defect-Free Status" can be taken out, in which on pages 44 to 47, in particular in FIG. 4, a pre-calender cleaning system with adjustable dual brushes that are in direct contact with the web. In addition, suction openings for suction of the web surface are mentioned.

From DE 197 36 847 Al a device for preventing deposits of hydrophobic impurities on a fibrous web is known. This device has a take-off element, in particular a roller or endless belt or sieve with adsorption capacity. These take-off elements absorb the debris from the fibrous web, thereby cleaning the web. During the acceptance or cleaning, the fibrous web runs over drying cylinders of the last and / or penultimate drying group of the web production machine. It should also be mentioned that today's fibrous webs are often made for reasons of economy in a large width of about 10 m. Accordingly, the range of cleaning the fibrous web is correspondingly wide, which increases the expense of cleaning.

So far, newsprint is coming directly from the dryer section coming with a moisture content of about 7 to 9% wound on a large mother roll or drum and processed by this or this directly in a slitter to print rolls.

It is therefore an object of the invention to provide an effective method for cleaning a running fibrous web, in particular an uncoated web, which is to be used at a suitable location during the production of the fibrous web. In particular, the detachment of such loose and / or unbound particles from the fibrous web is to be optimized, which can cause hickies or whitespots during later printing of newsprint in the offset process. As far as particles are mentioned below, the small adhesive components mentioned in the introduction should also be included.

The object of the invention is achieved by a method according to claim 1. According to the invention, it is accordingly provided that the cleaning device acts on the fibrous web which has already been dried in a drying section of the production machine.

Here, ie, following a single or double row dryer section and even before a smooth or calendering process, the fibrous web has such a high strength that the direct action with a cleaning device no longer harms her. The final quality of the fibrous web produced is thereby higher than before. It is achieved by the method according to the invention that no particles or at least only very few particles dissolved from the fibrous web are located on the web at the end of an online or offline production process. As a result, especially the risk of printing errors, z. B. so-called hickies or whitespots in a later processing stage, ie in the printing of the web by offset printing, avoided, but at least reduced.

The cleaning method according to the invention can also be applied, as stated, in offline production methods. Here, the fibrous web is also after the drying of the web, but before the reel or only in the so-called finishing machine, i. cleaned in the calender after unwinding.

The method according to the invention can be used particularly advantageously on the side of the fibrous web which has been less compacted in the press section and / or former section or has been compacted too low in absolute terms. A high compression takes place, for example, in the press section on the side of the paper web, in the direction of which much and severely dehydrated. This is typically the side which is often in contact with a dewatering belt such as a felt in a dewatering zone such as a press nip. In these cases, it is therefore advantageous to clean the opposite side, ie the less compressed side. If the drainage as a whole is very gentle, ie both sides are less compacted, then the cleaning according to the invention can be applied on both sides. This can be advantageous, for example, for press sections with only one or two nips with an extended press zone with two felts each. It is advantageous if only the underside of the fibrous web is cleaned when it has been less compressed in the press section. This is very economical. On the other hand, the underside treatment is critical for some types of paper, which frequently causes printing errors. These printing errors can now be reduced with the underside cleaning.

In certain cases, however, it may also be expedient if the upper side of the fibrous web is also cleaned. Cleaning is thus carried out on both sides of the web. Both web pages can be cleaned both simultaneously and successively. Decisive for this is the strength and strength of the fibrous web and also the available space within the manufacturing or finishing machine.

In order to increase the cleaning effect, it may be useful if the fibrous web is moistened before cleaning. This dissolves little bound particles. The usual process of adding printing ink and dampening water to offset printing is already anticipated.

During moistening, it is also possible to add additives with the supplied water, which is closer to the process of offset printing.

The cleaning method according to the invention can be carried out, for example, with at least one brush extending over the width of the fibrous web or traversing across the web width. Conceivable in this context, a plurality of juxtaposed Single brushes, which can also be subjected to different pressure forces.

The brush or brushes may be round brushes or designed as roller brushes and should preferably rotate in opposite directions to the direction of the fibrous web. But there are also fixed brushes, such as flat brushes possible.

For cleaning, at least one scraper and / or at least one air nozzle and / or at least one suction device-the latter for discharging the brushed, scraped off or blown-off particles can be used alternately to the brushes. The air nozzles can work at high pressure and be designed as slit nozzles.

Another possibility of cleaning is that at least one roller or even an endless belt, each with an existing adhesiveness acts on the fibrous web. This can be very effective to replace the loose, unwanted particles from the fibrous web surface. The roller may therefore have a special plastic cover which acts adhesively. Likewise, this plastic material can be used for the web tapping, endless belt.

Advantageously, a cleaning device with at least one brush arrangement, at least one coating strip arrangement and / or at least one roller or belt arrangement with adhesiveness is used.

In this case, for example, a brush arrangement with at least one rotating in or against the web running circular brush can be used. Basically, for example, the use of a brush assembly with at least one stationary brush is conceivable.

Conveniently, a Streichleistenanordnung is used with at least one stationary fixed coating strip. Alternatively or additionally, a coating strip arrangement with at least one rotating roller can also be used.

If a coating strip arrangement with at least one rotating roller is used, it is advantageous if its rotational speed deviates from the web running speed, wherein the relative speed of the roller is in particular greater than 5% and preferably greater than 10% of the web running speed.

The described cleaning options can each be applied individually, but are also applicable in combination, whereby the cleaning effect increases.

It is particularly advantageous if the cleaning device acts on a fibrous web which has been compacted on one side and which has previously been guided through a section which compresses on one side, in particular a press arrangement of the production machine which compresses on one side. In this case, the fibrous web can be previously characterized in particular by a one-side compacting 3-nip compact press arrangement, preferably by a 3-nip press.

Compact press assembly be performed with a shoe press as a third press.

If the fibrous web is previously passed through a section of the production machine which compacts on one side, the cleaning device is tion preferably arranged on the side of the fibrous web at which the lower compression is present.

If the cleaning device is to act on a fibrous web having a lower compression on its underside, the cleaning device is preferably arranged on the underside of the fibrous web.

The process according to the invention can be used particularly advantageously if the waste paper (DIP) content as a fiber raw material is> 5%, in particular> 30%.

The process according to the invention is particularly suitable in the production of newsprint.

In particular, the method according to the invention can be applied to papers which are printed by offset printing.

The invention will be explained in more detail with reference to embodiments.

Show it:

Figures 1 to 4 variants of the cleaning possibilities according to the invention in a schematic representation.

In the individual figures, the same components are provided with the same reference numerals. In Figures 1 to 3, the last two drying cylinders 1 and 2, which here for example part of a single-row dryer section 3 of a web-making machine 4 are shown. Via a subsequent guide roller 5, the fibrous web 6 runs in the direction L of a cleaning device 7 to. The fibrous web 6 is an uncoated and not highly compressed (as a rule made from waste paper) paper web for newspaper printing. Such papers often have particles on their surface which are only poorly bound to the surface or poorly bound in vascular cells. These particles can cause considerable printing errors in the later printing process (newsprint printing). Therefore, a cleaning of the finished dried fibrous web 6 is performed according to the invention.

In the figures 1 to 3, a simultaneous, double-sided cleaning is shown in each case. Depending on the requirement, however, only one side of the web, that is to say, for example, top side 6a or bottom side 6b (see, for example, FIG. 3), also needs to be cleaned. For papers for newspaper printing, it is especially important to clean the underside of the web 6b.

In the figures 1 to 3, an advantageous to be used suction 8 is shown by way of example. The vertically drawn hollow arrows 8a and 8b are intended to indicate the withdrawal direction or removal direction for the unwanted particles 9 detached with the cleaning device 7.

Figure 1 shows a first variant of the cleaning of this fibrous web 6. As a cleaning device 7 here is a web-width, rotating brush roller 7.1 is provided. Instead of this brush roller or else the plurality of brushes arranged next to one another or even the web width, it is also possible for one or more adhesion rollers to be used 7.2 be provided. The Adäsionswalze has, as its name implies, a roll cover with adhesion properties. The loose particles are thus detached The adhesion roller 7.2 but itself must be freed from the adhering, ie the removed from the fibrous web 6 particles 9, which is why one of these roller / rollers 7.2 assigned / associated scraper is / are present. Such a scraper is designated 7.2.1.

FIG. 2 shows a second variant of the cleaning option, in which high-pressure air nozzles 7.3 are provided for detaching the particles 9.

FIG. 3 shows the possible use of fixed brushes 7.4 or scrapers 7.5 acting on the fibrous web 6.

FIG. 4 shows a further variant of the cleaning possibility, in which the cleaning device 7 acts on a fibrous web 6 which has been compacted on one side and which has previously been guided through a section compressed on one side, in this case a press arrangement 10 of the production machine 4 which compresses on one side.

In this case, the one-side compacting press arrangement 10 may comprise, for example, a 3-nip compact press arrangement, preferably a 3-nip compact press arrangement with a shoe press as the third press.

In the present embodiment, the 3-nip compact press assembly 10 comprises a DuoCentri press assembly in which the fibrous web 6 is removed by a first felt 12 from a traveling belt 14, e.g. Suction roller 16 and a Ge genwalze 18 formed first nip 20 is supplied. The counter-roller 18 may be, for example, a hard roller or a shoe press roller. In this case, the fibrous web is guided together with the first felt 12 and guided around the counter-roller 18 second felt 22 through the first nip 20. This first nip 20 is thus double-felted.

Subsequent to the first nip 20, the fibrous web is guided together with the first felt 12 around the suction press roll 16 and subsequently transferred to another roll or central roll 24, which together with the suction press roll 16 forms a second nip 26, through which the fibrous web 6 is passed. This second nip 26 is simply felted, wherein the upper side of the fibrous web 6 is in contact with the relevant felt 12.

Following this second nip 26, the fibrous web 6 is guided without the second felt 12 on the further roller 24 to a third nip 28 which is formed between the further roller 24 and, for example, a shoe press roll 30, around which a third felt 32 is guided , The optionally extended in the direction of web travel L third nip 28 is thus again simply felted, again in the present case the top of the fibrous web 6 comes into contact with the relevant felt 32.

In this one-sided compacting press arrangement 10, therefore, the web underside comes into contact only in the first press nip 20 with a felt, namely the first felt 22.

Subsequent to the press arrangement 10, the fibrous web 6 passes through a drying section 3, of which initially only two drying cylinders 1 with a suction deflecting roller 34 arranged therebetween are shown. Starting from a last roller, for example the last drying cylinder 1, the drying section 3, the fibrous web 6 is fed via guide rollers 5 a reel 36.

Between the last roller or the last drying cylinder 1 and this Aufrollung 36, the fibrous web 6 is acted upon by the cleaning device 7. In this case, the cleaning device 7 is arranged on the underside 6b of the fibrous web 6 having the lower compression. As can be seen from FIG. 3, the cleaning can take place, for example, in a region in which the fibrous web 6 is guided at least substantially horizontally. In this case, as already mentioned, only the web underside 6b is acted upon by the cleaning device 7.

In the case of the roller 30 forming the third nip 28 with the further or central roller 24, it may in principle be, for example, also a hard roller instead of a shoe press roller.

As already mentioned, the cleaning device 7 may comprise one or more identical or different contact or cleaning elements for removing particles from the less compressed web surface.

The cleaning is thus combined with a single-side compacting section or a single-side compacting press arrangement 10 of the web-making machine 4, that only the less densified side of the fibrous web 6 is acted upon by the cleaning device 7. Thus, for example, a combination of a 3-nip compact press is preferably conceivable with shoe press 24, 30 in the third position with a cleaning device 7, for example, at least a brush and / or a coating element and / or an adhesive roller or belt and can be arranged either after the drying section 3 before the reel 36 or on the slitter winder. The one or more contact or cleaning elements sit on the side of the paper, which undergoes a lower compression in the press assembly 10. This is the bottom of a DuozentriNipcoFlex press assembly.

LIST OF REFERENCE NUMBERS

1 drying cylinder

2 drying cylinders

3 drying section

4 web-making machine

5 guide roller

6 fibrous web

6a track top

6b track bottom

7 cleaning device

7.1 Brush roller

7.2 Adhesive roller

7.2.1 Scraper

7.3 High pressure air nozzle

7.4 fixed brush

7.5 scraper

8 suction device

8a extraction device

8b extraction device

9 particles

10 single-sided compacting press arrangement

12 first felt

14 running band

16 suction press roll

18 mating roll

20 first nip

22 second felt

24 additional roller, central roller

26 second nip third nip

Roller, shoe press roller third felt

suction turning roll

Reeling

direction

Claims

claims

Method for cleaning a moving paper, board or other fibrous web (6) when manufactured in a manufacturing machine (4), wherein the fibrous web (6) is provided with at least one across the width, i. transverse to the running direction (L) of the web (6) acting cleaning device (7) of loose or unbound, unwanted particles (9) is freed, characterized in that the cleaning device (7) on the already in a drying section (3) of the manufacturing machine (4) finished surface or web side (6a, 6b) of the fibrous web (6) acts.

2. Method according to claim 1, characterized in that the fibrous web (6) is cleaned before a smoothing process or calendering process.

3. The method according to claim 1, characterized in that the fibrous web (6) is cleaned after a smoothing process or coating process and before it is rolled up.

4. The method according to any one of claims 1 to 3, characterized in that only the underside (6b) of the fibrous web (6) is cleaned.

5. Method according to one of claims 1 to 4, characterized in that the upper side (6a) of the fibrous web is also cleaned, the cleaning of both web sides (6a, 6b) taking place simultaneously or successively.

6. Method according to one of claims 1 to 5, characterized in that the fibrous web (6) is moistened before cleaning.

7. Method according to one of claims 1 to 6, characterized in that at least one brushing roller (7.1) extending over the width of the fibrous web (6) or traversing across the web width is used for cleaning or fixed, i. non-rotating brush (7.4) is used.

8. The method according to any one of claims 1 to 6, characterized in that at least one scraper (7.5) and / or at least one air nozzle (7.3) and / or at least one suction device (8) is used for cleaning.

9. The method according to any one of claims 1 to 6, characterized in that for cleaning at least one roller (7.2) with an adhesiveness for the on the fibrous web (6) existing, unwanted loose particles (9) is used.

10. The method according to any one of the preceding claims, characterized in that a cleaning device (7) with at least one brush arrangement, at least one coating strip arrangement and / or at least one roller or belt arrangement is used with adhesiveness.

11. The method according to claim 10, characterized in that a brush arrangement is used with at least one rotating in or against the web running direction round brush.

12. The method according to claim 10 or 11, characterized in that a brush assembly is used with at least one stationary brush.

13. The method according to any one of claims 10 to 12, characterized in that a coating strip arrangement is used with at least one stationary fixed coating strip.

14. The method according to any one of claims 10 to 13, characterized in that a coating strip arrangement with at least one rotating

Roller is used.

15. The method according to claim 14, characterized in that a rotating roller is used whose rotational speed deviates from the web running speed, the relative speed of the roller being in particular greater than 5% and preferably greater than 10% of the web running speed.

16. The method according to any one of the preceding claims, characterized in that the cleaning device (7) acts on a unilaterally compressed fibrous web (6), the previously by a one-sided compaction section, in particular a one-sided compacting press arrangement (10) of the manufacturing machine (4 ) was performed.

17. The method according to claim 16, characterized in that the fibrous web (6) previously by a one-side compacting

3-nip compact press assembly, preferably by a 3-nip compact press assembly with a shoe press as a third press is performed.

18. The method according to claim 16 or 17, characterized in that the cleaning device (7) on the side of the fibrous web (6) is arranged, at which the lower compression is present.

19. The method according to any one of claims 16 to 18, characterized in that the cleaning device (7) acts on a lower compaction on its underside having fibrous web (6) and that the cleaning device (7) on the underside of the fiber web (6 ) is arranged.

20. The method according to any one of the preceding claims, characterized in that a fibrous web (6) is cleaned accordingly, in which the waste paper content as a fiber raw material> 5%

21. Method according to one of the preceding claims 10 to 20, characterized in that it is used in particular in the production of newsprint.