Dryer for drying a coated fibrous material web

Abstract

The invention relates to a dryer (10) for drying a coated fibrous material web (FB), wherein the dryer (10) comprises three air chambers (22, 24, 26) which are designed to blow out air onto a passing fibrous material web (FB), wherein two of the air chambers (22, 24) are substantially rectangular and are arranged back-to-back next to one another, and wherein the third air chamber (26) is a deflection air chamber which faces side walls of the first and second air chambers (24, 26) with a straight rear wall and which has a curved, preferably semi-circularly curved, outer surface, wherein the dryer (10) is designed to provide a first rectilinear drying section (12) for the fibrous material web (FB) in a first vertical portion, a curved drying section (14) for the fibrous material web (FB) in a deflection portion and a second rectilinear drying section (16) for the fibrous material web (FB) in a second vertical portion, wherein the dryer (10) further comprises a first deflection roller (18) for the fibrous material web (FB), said first deflection roller being arranged at the beginning of the first rectilinear drying section (12), and a second deflection roller (20) for the fibrous material web (FB), said second deflection roller being arranged at the end of the second rectilinear drying section (16), wherein the dryer (10) further comprises at least one support roller (32, 34), which is designed to support the side of the fibrous material web (FB) facing away from the air chambers (22, 24, 26).

Description

[0001] Dryer for drying a Fibrous web

[0002] The invention relates to a dryer for drying a coated fibrous web, wherein the dryer comprises three air chambers which are designed to blow air onto a passing fibrous web, wherein two of the air chambers are substantially rectangular and arranged back to back next to one another, and wherein the third air chamber is a deflection air chamber which faces side walls of the first and second air chambers with a straight rear wall and which has a curved, preferably semicircularly curved, outer surface, wherein the dryer is designed to provide a first rectilinear drying section for the fibrous web in a first vertical section, a curved drying section for the fibrous web in a deflection section, and a second rectilinear drying section for the fibrous web in a second vertical section,and wherein the dryer further comprises a first deflection roller for the fibrous web, which is arranged at the beginning of the first rectilinear drying section, and a second deflection roller for the fibrous web, which is arranged at the end of the second rectilinear drying section.

[0003] Such a dryer is already known from the document EP 3 848 503 A1, to whose disclosure reference is hereby made with regard to the structure and functioning of the dryer.

[0004] After a coating has been applied to one side of a fibrous web, such as a paper web, the coating must be dried in a dryer. Since the coating is usually still moist and sticky before it is dried, it is necessary to guide the coated side of the fibrous web to and through the dryer with as little contact as possible. Hot air dryers, i.e. dryers that blow hot air onto the coated side of the fibrous web, have proven particularly effective in practice for this application. Depending on the machine speed, as well as the quantity and composition of the coating, the drying distance required until the coating is dry enough that the coated side of the fibrous web can be easily contacted again can be relatively long.To save installation space, dryers of the type described above are advantageous, namely dryers in which the total drying section is divided into three sections: a straight and essentially vertical first drying section, a curved drying section for deflecting the fibrous web, and a straight and essentially vertical second drying section. This allows the length of the dryer, i.e. its extension in the horizontal plane, to be kept to a minimum.

[0005] As the fibrous web passes through the various drying sections, hot air is blown from air chambers onto the coated side of the fibrous web. Typically, at least some of this air is sucked out again through the air chambers so that the moisture extracted from the coating can be removed. For efficient dryer operation, it is important that the fibrous web is guided as close as possible to the dryer's blower nozzles, while at the same time ensuring that the coated side of the fibrous web does not touch the dryer. In other words, a well-adjusted and stable web path for the fibrous web is important. In particular, it is important to prevent the fibrous web from accidentally lifting off the dryer and / or the hot air blown onto the fibrous web from pushing it too far away from the blower nozzles.

[0006] The aforementioned document EP 3 848 503 A1 solves this problem by blowing air from a plurality of additional blow boxes onto the side of the fibrous web facing away from the coated side while the fibrous web passes through at least the first and second drying sections of the dryer. In other words, the fibrous web is blown by air on both sides, allowing it to run stably in the gap created between the blow boxes.

[0007] The disadvantage of this solution, however, is that the air technology for the additional blow boxes reduces the overall efficiency of the dryer. Generating the required amount of blow air is cost-intensive. In addition, the air blown out of the additional blow boxes leads to crossflows across the web, which can cause the fibrous web to flutter and lead to undesirable wrinkling of the fibrous web to be dried. It is therefore an object of the present invention to solve the aforementioned problems, in particular to provide a dryer for drying a coated fibrous web that not only allows a compact design and reliable web guidance, but can also be operated very efficiently. Furthermore, the risk of wrinkling in the fibrous web to be dried is to be reduced and stable web travel is to be guaranteed.

[0008] This object is achieved by the features of the independent claims. The dependent claims relate to advantageous developments of the invention. In particular, the object is achieved according to the invention in a generic dryer of the type mentioned above in that the dryer additionally comprises at least one support roller designed to support the side of the fibrous web facing away from the air chambers.

[0009] In contrast to the previously described prior art dryer, according to the invention, the stabilization of the web path of the fibrous web past the air chambers of the dryer is not achieved by blow boxes, but by support rollers. Since the side of the fibrous web not containing the coating to be dried is insensitive to contact with components such as rollers, support rollers can be used without any problems to stabilize the web. Even if this solution may seem simple in retrospect, it is to the credit of the inventors that they recognized that the problem of increased energy consumption and the risk of wrinkling caused by the blown air from the additional blow boxes in the prior art can be easily solved by providing support rollers. The support rollers support the fibrous web and prevent it from lifting off the dryer due to the hot air blown from the air chambers.

[0010] A preferred embodiment of the invention provides that the dryer comprises at least two, preferably exactly two, support rollers which are designed to support the side of the fibrous web facing away from the air chambers, wherein a first support roller is assigned to the first linear drying section and a second support roller is assigned to the second linear drying section. The inventors have recognized that to ensure stable web travel, the number of support rollers used can be kept relatively low, which keeps the design effort low. The assignment of a first support roller to the first drying section and a second support roller to the second drying section means that the first and second support rollers are arranged such that they prevent the fibrous web from lifting off the dryer in the region of the first drying section and in the region of the second drying section, respectively.For this purpose, the fibrous web is guided in the area of ​​the corresponding drying section between the corresponding air chamber and the support roller during normal operation.

[0011] As a further development of this concept, it is proposed that the first support roller be arranged in the region of the end of the first linear drying section and / or that the second support roller be arranged in the region of the beginning of the second drying section. The terms "beginning" and "end" of a drying section, within the meaning of the present invention, are to be understood with reference to the running direction of the fibrous web during normal operation of the dryer. In this context, the term "region" refers to a section of the drying section at its beginning or end, which constitutes a maximum of 20% of the total length of the drying section in question.

[0012] It can be provided that at least one support roller is mounted on a support structure that is structurally firmly connected to the dryer. For example, the support roller can be mounted on two arms that extend from the corresponding air chamber on the guide and drive sides. The arms can be directly or indirectly attached to the corresponding air chamber or form a structural unit with it.

[0013] Preferably, the at least one support roller is mounted in such a way that a distance between it and the air chamber facing it can be variably adjusted. In this way, optimal web travel on the dryer can be adapted to other, possibly variable parameters, such as the grammage of the coated fibrous web, the quantity and / or composition of the coating, and the machine speed. Furthermore, a targeted adjustment of the support roller distance can ensure a defined heat transfer from the blast air to the fibrous web. For the same reason, it is alternatively or additionally proposed that the at least one support roller be mounted in such a way that its position along the drying section to which this support roller is assigned can be variably adjusted. In other words, it is advantageous if the support roller is also variably adjustable in the direction of the web travel of the fibrous web, at least within certain limits.

[0014] As already explained above, the use of support rollers allows the dryer to be free of blow boxes, which are designed to blow air onto the side of the fibrous web facing away from the air chambers. This saves energy for this additional blow air compared to the prior art design of such a dryer. It also allows unwanted crossflows on the fibrous web to be avoided or at least reduced.

[0015] A further aspect of the present invention relates to a machine for producing and / or finishing a fibrous web, comprising a coating device for coating the fibrous web, as well as a dryer according to the present invention downstream of the coating device. Here, too, the term "downstream" refers to the running direction of the fibrous web to be coated and dried during normal operation of the machine.

[0016] It is preferred if the coating application device is designed to provide the fibrous web with a coating on one side, wherein the dryer is designed and arranged such that the coated side of the fibrous web is guided past the three air chambers of the dryer without contact and faces the three air chambers of the dryer. If the fibrous web is to be coated on both sides, two coating application devices can be used one behind the other, each with downstream dryers according to the invention, wherein each coating application device coats a different side of the fibrous web. Further features and advantages of the invention will become apparent from the following description of a preferred embodiment with reference to the drawing. A preferred embodiment is described in more detail below with reference to a single figure.Figure 1 shows schematically a dryer according to the invention for drying a coated fibrous web with two support rollers.

[0017] The dryer 10 comprises three drying sections for the coated fibrous web FB to be dried, namely a first straight drying section 12, a curved drying section 14, and a second straight drying section 16. During normal operation of the dryer 10, the fibrous web FB is first deflected by a first deflection roller 18 from a substantially horizontal upward direction of movement into a substantially vertical direction of movement. The first deflection roller is located at the beginning of the first straight drying section 12. At the end of the first straight drying section 12, the fibrous web is deflected by 180° in the curved drying section 14 before being guided substantially vertically downward in the second straight drying section 16. At the end of the second straight drying section 16, the fibrous web FB is deflected in a substantially horizontal direction via a second deflection roller 20.

[0018] The dryer 10 further comprises three air chambers which are designed to blow air onto the passing fibrous web FB. The first air chamber 22 is essentially rectangular. It is assigned to the first drying section 12, i.e. it comprises a row of air nozzles (not shown here) for blowing hot air onto the passing fibrous web FB. A second air chamber 24 is also essentially rectangular. It is assigned to the second drying section 16, i.e. it comprises a row of air nozzles (not shown here) for blowing hot air onto the passing fibrous web FB. The first air chamber 22 and the second air chamber 24 are arranged back to back, wherein “back” means the side or wall of the air chamber 22 or air chamber 24 which faces away from the side or wall with the air nozzles of the respective air chamber 22, 24.The third air chamber 26 is a deflection air chamber, which also blows hot air onto the passing fibrous web FB via a plurality of nozzles (not shown) in order to dry it and simultaneously deflect it without contact. Its outer surface with the air nozzles has a substantially semicircular shape. Each of the three air chambers 22, 24, 26 has at least one, preferably exactly one, air inlet 28 and at least one, preferably exactly one, air outlet 30. The air inlets 28 and air outlets 30 are only indicated schematically in Figure 1. Hot air is supplied to the three air chambers 22, 24, 26 through the air inlets 28 in order to blow it onto the passing fibrous web FB via the air nozzles, whereas air laden with moisture from the coating of the fibrous web to be dried is sucked out through the air outlets.

[0019] According to the invention, the dryer 10 further comprises at least one support roller 32, 34, which is designed to support the side of the fibrous web FB facing away from the air chambers 22, 24. Specifically, the dryer 10 comprises a first support roller 32, which is connected to the first air chamber 22 in the region of the end of the first rectilinear drying section 12 via a first support structure 36. Furthermore, the dryer 10 comprises a second support roller 34, which is connected to the second air chamber 24 in the region of the beginning of the second rectilinear drying section 16 via a second support structure 38. In this exemplary embodiment, the first support structure 36 and the second support structure 38 each comprise a driver-side boom and a drive-side boom, on which the respective support roller 32, 34 is mounted.Preferably, the support rollers 32, 34 are mounted in such a way that the distance between the support roller 32, 34 and the respective air chamber 22, 24 assigned to it and / or that their position along the drying section 12, 16 assigned to this support roller 32, 34 can be variably adjusted. In other words, the position of the support rollers 32, 34 can be adjusted horizontally and / or vertically in Figure 1. In this way, the travel of the coated fibrous web FB can be adjusted and stabilized for an optimal course.During normal operation of the dryer 10, the coated fibrous web FB is guided between the first air chamber 22 and the first support roller 32, wherein the first support roller 32 supports the uncoated side of the fibrous web FB and thus prevents the hot air blown from the first air chamber 22 onto the coated side of the fibrous web FB from causing the fibrous web FB to lift off the dryer 10. In this context, "lifting" means that a preset distance between the nozzles of the first air chamber 22 and the fibrous web FB is disadvantageously increased.Likewise, during normal operation of the dryer 10, the coated fibrous web FB is guided between the second air chamber 24 and the second support roller 34, wherein the second support roller 34 supports the uncoated side of the fibrous web FB and thus prevents the hot air blown from the second air chamber 24 onto the coated side of the fibrous web FB from causing the fibrous web FB to lift off the dryer 10.

[0020] List of reference symbols

[0021] 10 dryers

[0022] 12 first straight drying section

[0023] 14 curved drying section

[0024] 16 second straight drying section

[0025] 18 first deflection roller

[0026] 20 second deflection roller

[0027] 22 first air chamber

[0028] 24 second air chamber

[0029] 26 third air chamber

[0030] 28 Air intake

[0031] 30 Air outlet

[0032] 32 first support roller

[0033] 34 second support roller

[0034] 36 first supporting structure

[0035] 38 second supporting structure

[0036] FB Fibre web

Claims

1. A dryer (10) for drying a coated fibrous web (FB), wherein the dryer (10) comprises three air chambers (22, 24, 26) which are designed to blow air onto a passing fibrous web (FB), wherein two of the air chambers (22, 24) are substantially rectangular and arranged back to back next to one another, and wherein the third air chamber (26) is a deflection air chamber which faces side walls of the first and second air chambers (24, 26) with a straight rear wall and which has a curved, preferably semicircularly curved, outer surface, wherein the dryer (10) is designed to have a first rectilinear drying section (12) for the fibrous web (FB) in a first vertical section, a curved drying section (14) for the fibrous web (FB) in a deflection section and a second rectilinear drying section (16) for the fibrous web (FB) in a second vertical section,wherein the dryer (10) further comprises a first deflection roller (18) for the fibrous web (FB), which is arranged at the beginning of the first rectilinear drying section (12), and a second deflection roller (20) for the fibrous web (FB), which is arranged at the end of the second rectilinear drying section (16), characterized in that the dryer (10) further comprises at least one support roller (32, 34) which is designed to support the side of the fibrous web (FB) facing away from the air chambers (22, 24, 26).

2. Dryer (10) according to claim 1, characterized in that the dryer (10) comprises at least two, preferably exactly two, support rollers (32, 34) which are designed to support the side of the fibrous web (FB) which faces away from the air chambers (22, 24, 26), wherein a first support roller (32, 34) is assigned to the first rectilinear drying section (12) and a second support roller (34) is assigned to the second rectilinear drying section (16).

3. Dryer (10) according to claim 2, characterized in that the first support roller (32) is arranged in the region of the end of the first rectilinear drying section (12) and / or the second support roller (34) is arranged in the region of the beginning of the second drying section (16).

4. Dryer (10) according to one of the preceding claims, characterized in that the at least one support roller (32) is mounted on a support structure (36, 38) which is structurally fixed to the dryer (10).

5. Dryer (10) according to one of the preceding claims, characterized in that the at least one support roller (32, 34) is mounted in such a way that a distance between it and the air chamber (22, 24) facing it can be variably adjusted.

6. Dryer (10) according to one of the preceding claims, characterized in that the at least one support roller (32, 34) is mounted in such a way that its position along the drying section (12, 16) assigned to this support roller (32, 34) can be variably adjusted.

7. Dryer (10) according to one of the preceding claims, characterized in that the dryer (10) is free of blow boxes which are designed to blow air onto the side of the fibrous web (FB) which is remote from the air chambers (22, 24, 26).

8. Machine for producing and / or finishing a fibrous web (FB), comprising a coating device for coating the fibrous web (FB), and a dryer (10) according to one of the preceding claims, arranged downstream of the coating device.

9. Machine according to claim 8, characterized in that the coating application device is designed to provide the fibrous web (FB) with a coating on one side, wherein the dryer (10) is designed and arranged such that the coated side of the fibrous web (FB) is guided past the three air chambers (22, 24, 26) of the dryer (10) without contact and is facing the three air chambers (22, 24, 26) of the dryer (10).

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