EP1731666A1 - Paper machine - Google Patents

Abstract

A paper mill feeds a wet web (1) with to a drying station consisting of two suction drums (4, 5), each closely co-located with a suction hood (12, 14) and an impingement air drier (6, 7). At the suction drum (4, 5) the web transfers from a first drying sieve (3) to a second drying sieve (9). The second sieve exerts greater adhesive force than the first. The second sieve has more contact points to the web than the first sieve. Each successive drying sieve (13) has more contact points than the previous sieve (9). The sieves are made of fluoridated polymer threads, each successive sieve having a greater fluoridated content than the previous sieve. The sieves have a sequential permeability of 95, 112 and 125 cfm. Also claimed is a commensurate operating process.

Description

The invention relates to an arrangement in a machine for producing a paper, cardboard, tissue or other fibrous web with at least one first suction roll in a dryer section, wherein an external or internal suction box is employed on the suction roll and this in its outer Outer surface at least partially comprises holes for sucking the fibrous web, wherein in particular the first suction roll at least one impingement dryer can be arranged opposite one another.

In the DE 70 44 366 A1 a drying roller is described for drying a material web, which serves in particular for guiding and holding a paper web applied by means of a drying gas. The drying roller has a jacket over which the material web is guided during operation of the roller while partially wrapping around the roller. In the jacket gas passage openings are present. Further, means are provided for conveying gas through the roll shell. In the interior of the roll shell, a second, gas-tight jacket is provided, which forms an annular space with the outer roll shell. The annular space is sealed gastight relative to the interior of the inner shell.

Known drying groups of a dryer section in a machine for producing a fibrous web, in particular a paper web, consist of steam-heated cylinders and wire guide rolls. The paper web transfer between two drying groups is usually carried out as a "lick-up", ie the drying wire of a subsequent drying group decreases in contact with the last drying cylinder of the previous drying group, the fibrous web. The transfer through the dryer section takes place by means of a transfer strip, which can have a width between 300 and 600 mm and secrete separately leaves. It is also known to provide a dryer section with impingement hoods in which the paper web is guided onto screens without contact with a drying cylinder. For process-technical reasons, a web-wide transfer into the area after the impingement-flow dryers is required.

It is the object of the invention to provide an arrangement in which a fibrous web is safely transferred.

According to the invention, this object is achieved in an arrangement of the type mentioned above in that the fibrous web at the periphery of the first suction roll from a first dryer fabric on a second dryer fabric can be transferred, which exerts a stronger adhesive effect on the fibrous web than the first dryer fabric.

By means of the invention, the transfer of a fibrous web, in particular a paper web, between individual dryer fabrics is assisted by the adhesive forces between the respective dryer fabric and the fibrous web being successively reinforced in the web running direction. Advantageous developments of the invention will become apparent from the dependent claims, the description and the drawings.

Advantageously, it can be provided that each drying wire following in the web running direction of the fibrous web on a preceding drying wire exerts a stronger adhesive effect on the fibrous web than the preceding drying wire.

In one embodiment of the arrangement, it is provided that the second or the following dryer fabric has a higher number of contact points with the fibrous web than the first or the preceding dryer fabric with the fibrous web.

An advantage is an embodiment in which the screen threads of the second or subsequent dryer fabric form a larger contact surface with the fibrous web than the wire filaments of the first and the preceding dryer fabric.

Advantageously, the adhesion of the second or subsequent dryer fabric to the fibrous web is greater than the adhesion of the first or preceding dryer fabric to the fibrous web.

The adhesion between the fibrous web and the dryer fabric can also be increased in the web running direction by virtue of the fact that the screen yarn of the second or subsequent dryer fabric has a smaller proportion of fluorinated polymer than the first or the preceding dryer fabric. Specifically, the screen yarn of the second or subsequent dryer fabric may have a higher Teflon content than the first or previous dryer fabric.

The surface tension may alternatively and / or in addition to the material selection be influenced by suitable chemical and / or mechanical methods such as etching or oxidation.

1. 1. Sieb: 17 bis 27mN/m
2. 2. Sieb: 27mN/m bis 37mN/m
3. 3. Sieb: mehr als 37mN/m.

For example, consecutive screens may follow
Surface tensions have:

1. 1st sieve: 17 to 27mN / m
2. 2nd sieve: 27mN / m to 37mN / m
3. 3rd sieve: more than 37mN / m.

A further advantageous embodiment for increasing the adhesion of the fibrous web to the dryer fabric is that the permeability of the second or of the subsequent dryer fabric is higher than that of the first or the preceding dryer fabric.

In particular, it can be provided in an advantageous manner that the permeability of the first drying wire is between 75 and 112 cfm and in particular 95 cfm is that the permeability of the second dryer fabric is between 95 and 125 cfm and is preferably 112 cfm and that the permeability of a third dryer fabric following the second dryer fabric is between 112 and 155 cfm and preferably 125 cfm.

The invention also relates to a method for producing a paper, board, tissue or other fibrous web having at least one suction roll in a dryer section, wherein the fibrous web along a contact section on one side with a first drying wire and on its opposite Side is in contact with a second dryer and in this case, in particular by supporting a negative pressure effect of the suction roll, is transferred from the first dryer to the second dryer fabric.

According to the invention, the method is characterized in that a stronger adhesive effect is exerted on the fibrous web by the second drying wire than by the first drying wire.

According to an advantageous development, the method is characterized in that the fibrous web is transferred from a preceding drying wire to a downstream in the web running direction drying wire and that a stronger adhesive effect is exerted on the fibrous web by the subsequent drying wire as by the previous drying wire.

In another development of the method, at least one drying wire is moistened, whereby the transfer of the fibrous web is improved. Preferably, several of the dryer fabrics are moistened, the subsequent dryer fabric each being moistened more strongly than the preceding one.

Another advantage is a method in which the entrained by the dryer fabrics boundary air layer of the respective preceding drying wire to the subsequent drying wire is reduced.

In the realization of the invention, a suction roll with several n areas over the circumference and / or width can be used, in which during the transfer process with a transfer strip, the boundary air between the transfer strip and the suction roll or between the fibrous web and one on the suction roll lying dry sieve is quickly removed, so that the fibrous web can be kept as a whole safely and over the entire width and transferred.

The invention is particularly suitable for high-speed paper machines in which safe transfer and web guidance of the fibrous web is more critical than at paper machines running at lower speeds. Before the section of impingement drying, the fibrous web is passed over process sections in which it is constantly supported, for example by a twin-wire former and then by a press section with two press points arranged one behind the other, as in a tandem Nipcoflex press.

The invention will be explained in more detail in an embodiment with reference to the drawings.

Fig.1:

einen Abschnitt einer Trockenpartie mit zwei hintereinander angeordneten Saugwalzen in Verbindung mit jeweils zwei Prallströmungstrocknern und

Fig. 2:

eine Schnittansicht durch die erste der Saugwalzen gemäß Fig. 1 und den unterhalb der ersten Saugwalze angeordneten Saugkasten.

Show it

Fig.1:

a section of a dryer section with two successively arranged suction rollers in conjunction with two impingement flow dryers and

Fig. 2:

a sectional view through the first of the suction rollers of FIG. 1 and arranged below the first suction roller suction box.

Usually, in a machine for producing a fibrous web 1, which is supported in a press section by a belt or felt 2 and is transferred from this to a first dryer wire 3, at the beginning of the dryer section two successively arranged suction rolls 4, 5 (FIG. 1) are used, to which each impingement flow dryer 6, 7 are employed.

The fibrous web 1 is discharged from the felt 2 by means of a roller 8 equipped with a suction zone, wherein the drying wire 3, resting on the roll shell of the roll 8, is additionally guided over the roll 8. The drying wire 3 is, after it has run around the roller 8 together with the fibrous web 1, then led out upwards.

From the roller 8, the fibrous web 1 is transferred to the suction roll 4, while at the same time a second dryer fabric 9 is guided from below between the fibrous web 1 and the shell of the suction roll 4 together with the fibrous web 1 to the suction roll 4, so that the fibrous web 1 in Sandwich between the drying wires 3, 9 is transferred to the outer surface of the suction roll 4. Between rollers 10, 11, the drying wire 9 is returned back down. The drying wire 9 thus wraps around a large portion of the circumference of the suction roll 4th

Further, a suction box 12 is disposed on the underside of the suction roll 4, in which the vacuum required for the suction roll 4 is generated. On the upper side of the suction roll 4, the impingement dryer 6 is arranged, which covers a region of about one third of the mantle surface of the suction roll 4 and dries the fibrous web 1.

From the suction roll 4, the fibrous web 1 is sucked onto a third drying wire 13 and toward the second suction roll 5, wherein the drying wire 13 rests on the mantle surface of the suction roll 5, while the fibrous web 1 is guided around the suction roll 5. The negative pressure of the suction roll 5 is generated in a suction box 14.

To the suction roller 5 of the impingement dryer 7 is in the lower web outlet side quadrants arranged on the lateral surface of the suction roller 5 to further dry the fibrous web 1.

Immediately adjacent to the suction roll 5, a drying cylinder 15 of a single-row dryer region follows, in which the drying of the fibrous web 1 is continued. About this, the drying wire 13 is continued.

The suction roll 4 comprises on its lateral surface at least a first region 16 (FIG. 2) which extends over the greater part of its width, and a second region 17 arranged near one of its end faces, which serves to receive the transfer strip.

Since during the transfer operation according to the width of the transfer strip only the area 17 must be evacuated, is in the suction roller 4 attached to the suction box 12 one of the division of the suction roller 4 in areas 16, 17 corresponding division into two modules 18, 19 is provided. During the transfer operation, only the module 18 is operated, i. h., Only in the region of the module 18 and thus only in the region 17 of the suction roll 1, a negative pressure is generated.

By a convertible to a desired date flap 20 or other control means is when the width of the fibrous web 2 increases to the full width, and the module 18 is switched on, so that over the entire width of the fibrous web 1, a negative pressure is generated. It is understood that instead of only two modules 18, 19 arranged next to one another, a multiplicity of modules can be arranged next to one another so that they are switched on or off depending on the width of the fibrous web 1. The transfer zone is either, as shown in Figure 2, arranged in the edge region of the suction roll 4. However, it can also be arranged in the middle of the suction roll 4.

The open, determined by the number and diameter of the holes Area in the areas 16, 17 and the suction force per unit area thereby determined may be different in each of the areas 16, 17. For example, it can be provided that the open area is greater in the area 17 provided for the transfer strip than in the area 16.

The suction roller 5 and the associated suction box 7 are divided into sections or modules in a similar manner as the suction roller 4 and the suction box 6. The dryer fabrics 3, 9, 13 have successively an increasing adhesion to the fibrous web 1, so that it can be easily transferred from a drying wire to the respective subsequent.

Claims (12)

Arrangement in a machine for producing a paper, board, tissue or other fibrous web (1) with at least one suction roll (4, 5) in a dryer section, wherein an external and / or internal suction box (12, 14) to the Suction roller (4, 5) is employed and this comprises at least partially bores for sucking the fibrous web in its outer circumferential surface, wherein the suction roll (4, 5) in particular at least one impingement flow dryer (6, 7) opposite,
characterized,
in that the fibrous web (1) on the circumference of the suction roll (4, 5) can be transferred from a first drying wire (3) to a second drying wire (9) which exerts a stronger adhesive effect on the fibrous web (1) than the first drying wire (3) , Arrangement according to claim 1,
characterized,
that each in the web running direction of the fibrous web (1) on a preceding drying wire (3, 9) subsequent drying wire (9, 13) exerts a stronger adhesive effect on the fibrous web (1) than the preceding drying wire (3, 9). Arrangement according to claim 1 or 2,
characterized,
that the second (9) or the subsequent drying wire (13) has a higher number of contact points with the fibrous web (1) than the first (3) or the preceding drying wire (9) with the fibrous web (1). Arrangement according to one of claims 1 to 3,
characterized,
in that the screen threads of the second or subsequent drying wire (9, 13) form a larger contact surface with the fibrous web (1) than the screen threads of the first and the preceding drying wires (3, 9). Arrangement according to one of claims 1 to 4,
characterized,
that the adhesion of the second (9) or the subsequent drying wire (13) is greater with the fibrous web (1) than the adhesion of the first (3) or of the preceding drying wire (9) with the fibrous web. Arrangement according to one of claims 1 to 5,
characterized,
Siebgarn that the second (9) or the subsequent drying wire (13) a minor proportion of the fluorinated polymer comprises as the first (3) or the preceding drying wire (9). Arrangement according to one of claims 1 to 6,
characterized,
that the permeability of the second (9) or of the subsequent drying wire (13) is higher than that of the first (3) or the preceding drying wire (9). Arrangement according to one of claims 1 to 7,
characterized,
that the permeability of the first drying wire (3) is between 75 and 112 cfm and in particular 95 cfm, that the permeability of the second drying wire (9) is between 95 and 125 cfm and preferably 112 cfm and that the permeability of a third, on the second drying wire (9) following the drying wire (13) is between 112 and 155 cfm and is preferably 125 cfm. Method for producing a paper, board, tissue or another A fibrous web (1) having at least one first suction roll (4, 5) in a dryer section, wherein the fibrous web (1) along a contact section (21, 22) on its one side with a first drying wire (3) and on its opposite side with a second drying wire (9) is in contact and is thereby transferred from the first drying wire (3) to the second drying wire (9),
characterized,
that is exerted by the second dryer fabric (9) has a greater adhesion to the fibrous web (1) than by the first dryer fabric (3). Method according to claim 9,
characterized,
in that the fibrous web (1) is transferred from a preceding drying wire (3, 9) to a drying wire (9, 13) following in the web running direction and that a stronger adhesive action is exerted on the fibrous web (1) by the subsequent drying wire (9, 13) as by the preceding drying wire (3, 9). Method according to claim 9 or 10,
characterized,
that the following drying wire (9, 13) is each moistened more strongly than the preceding (3, 9). Method according to one of claims 9 to 11,
characterized,
in that the boundary air layer entrained by the drying wires (3, 9, 13) is reduced by the respective preceding drying wire (3, 9) to the subsequent drying wire (9, 13).

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