EP1156155A2 - Dryer section - Google Patents

Abstract

Web (14) and screen (12) pass through a guidance section (10), where the web is subjected to pressurized gas causing alternate lifting and resting against the screen, along the running direction (L) of the web. Preferred features: At least one web guidance unit is included, implemented as a suspension dryer. The screen passes through the guidance section in a straight line. A series of nozzles (16) along the path of the web, exert gas pressure on it. Nozzle beams are located on both sides of the screen. At least one compressed gas driven web guidance unit is located before the first drying cylinder. The gas is air. At least one web drying hood with an impinging blast dryer is included, employing hot air or steam. The web is passed over a larger support- or suction roller with impinging flow dryer. This precedes the first drying cylinder. The impinging flow dryer follows the pressurized gas driven web guidance system. The web leaving the first drying cylinder, or first withdrawn from a smooth heated surface, is already more than 58%-65% dry. Following the last press nip of a pressing section, at least one inventive guidance unit is included. Further alternative arrangements based on the foregoing principles are described. Gas permeability of the screen for the guidance unit exceeds 300 cfm, preferably exceeding 500 cfm. Further equipment for pressing, alternative drying arrangements, vertical rising, falling and angled guidance sections, and transfer arrangements are described. In a lower temperature guidance section, gas at 20 degrees C-150C is employed.

Description

The invention relates to a dryer section of a machine for production a material web, in particular a paper or cardboard web. It affects also a floating dryer for such a dryer section.

In the previously common multi-cylinder dryer sections, the paper web for drying over steam-heated cylinders or over steam-heated cylinders and screen suction rollers. Especially at the beginning of the Drying where the wet paper web is still not strong enough has problems with the web routing, which are due in particular to the fact that the still moist and badly ventilated sheet sticks to the smooth contact surfaces, which are absolutely necessary for adequate heat transfer. In order to be able to pull the web off the cylinders, it is sufficient Web tension necessary which can only be achieved by train, i.e. corresponding differential speeds, before or immediately after the first smooth contact surface can be generated. However, this often leads to web breaks and overstretching the web edges. Accordingly, usually ensure that drying takes place more slowly, i.e. for example at the beginning there is a lower vapor pressure, which also means that the required dryer section will be longer overall. The previously mentioned problems occur increasingly at higher web speeds on.

The aim of the invention is to provide a dryer section of the type mentioned to create with both at high machine speed the best possible drying rate at the beginning of drying as well as secure web guidance is guaranteed. In addition, a for such a dryer section suitable float dryer can be created.

This object is achieved according to the invention with regard to the dryer section the characterizing features of claim 1 solved.

Because of this training, the still relatively moist material web can no longer be removed prematurely from a smooth surface. As a result Avoiding smooth contact surfaces at the start of drying is the Danger of web breaks and overstretching of the web edges practically eliminated. In particular, they are now higher Drying rates possible, which increases the overall length of the dryer section shortened accordingly. The load on the web after the press section is minimized after the web only at higher dryness exposed to higher stripping voltages caused by tension must become. After all, there are correspondingly higher machine speeds possible.

In a preferred practical embodiment of the invention Drying section is at least one designed as a floating dryer pressurized gas-operated web guiding device is provided. So in particular such a floating dryer directly after the press section and be provided in front of the first drying cylinder. As a result of the combination a float dryer with a dryer can also reduce the web Strength (e.g. at high humidity such as before cylinder drying) be dried.

During the material web through a corresponding gas pressure distribution in particular wavy in the respective web guiding device deflected and stabilized for example in a sine wave can, the screen in the respective compressed gas-operated web guiding device usually an at least essentially straight line Course on.

The web guiding device comprises for pressurizing the Material web expediently several in a row in the direction of web travel arranged nozzles, preferably on both sides of the material web such nozzles are provided. In particular, several nozzle bars each extending in the direction of the web width be provided.

In a preferred practical embodiment of the invention The dryer section is at least one pressurized gas-operated web guiding device arranged in front of the first drying cylinder.

Air can in particular be provided as the compressed gas.

It is also advantageous if at least one with at least one dryer hood Provided baffle dryer is provided through which Hot air and / or hot steam impingement flow can be applied to the material web is. The material web is preferably at least a larger support roller in particular with an associated impingement dryer guided.

Such a baffle dryer is preferably again before arranged first drying cylinder.

Before the web of material has a smooth heated surface for the first time is withdrawn, so it can by at least one float dryer and, if necessary, pre-dried at least one impingement flow dryer. The gas or air drying expediently takes place until a sufficient dryness is reached at which the required web tension is reached can be easily applied.

In a preferred practical embodiment, the material web has when draining from the first drying cylinder or when starting for the first time Pulling off a smooth heated surface already a dry matter, which is higher than about 58 to about 65 °. As already mentioned, part of the gas or air drying also by an impingement dryer or an impingement hood.

The press section is advantageously connected to the last press nip initially at least one pressurized gas-operated web guiding device intended.

In certain cases, it is useful if the material web in the connection to the last press nip of a press section first by at least a pressurized gas powered web guiding device and in the connection attached to it via at least one, in particular larger, support roller assigned impact flow dryer is performed before the first Drying cylinder is fed.

The drying speed in the area of each, as a floating dryer executed web guiding device or a respective one Impingement dryer is advantageously over the pressure gas temperature, speed and / or humidity adjustable.

The air permeability of a respective compressed gas powered Sieve assigned to the web guiding device is preferably possible chosen high. This is the case in a preferred embodiment Air permeability of the respective sieve is greater than approximately 300 cfm and preferably greater than about 500 cfm.

It is also advantageous if the material web starts from the last press nip the press section the first drying cylinder in a closed train is fed.

In certain cases it is useful if the material web from the Press section directly to that of a pressurized gas-operated web guiding device assigned sieve is passed. The handover of the material web from the press section to that of a pressurized gas-operated guide device assigned sieve can, however, also have at least one transfer belt or the like.

The web of material can pass through the last press nip of the press section guided felt (top or bottom felt) can be removed. It is but also an acceptance directly from one of the last press nips of the press section assigned press roll conceivable.

To achieve the desired dry content, several can also be used Float dryer and / or several impingement flow dryer provided his.

A respective compressed gas-operated web guiding device can be horizontal, be arranged vertically or at an angle. In the latter case, the Material web in the inclined pressure gas operated web guiding device generally obliquely upwards or generally obliquely downwards be led below.

If several pressurized gas-operated web guiding devices are provided, so can at least part of these web guiding devices each have their own sieve.

In certain cases, it is also an advantage if at least one through several pressurized gas operated web guiding devices guided screen is provided.

To hold the web of material on the screen can before and / or after assigned pressurized gas-operated web guiding device and / or between successive web guiding devices, suction rolls, Transfer foils and / or suction boxes can be provided.

The roller following the last levitation dryer (suction roller or cylinder) can be assigned to the web transfer partially by the levitation dryer Sieve can be wrapped, or the web can be covered by a suction roller can be transferred to a subsequent dryer fabric.

For transferring the material web through a respective compressed gas-operated one The web guiding device is expediently attached to the Sieve pressed and / or sucked. This is possible, for example, that the web to be transferred in a respective pressurized gas Web guiding device only on its side facing away from the wire and in the web running direction with compressed gas and / or from the Vacuum side is applied.

In the latter case, you can choose between the ones facing away from the material web Nozzle boxes provided on the sieve side his.

The transfer through the gas or air dryer is preferably done through the air dryer. However, the transfer can also partially or entirely with transfer belt and corresponding transfer zones in suction and blow boxes. In the case of a transfer belt be sure that the rest of the web is in front of the corresponding gas or felt or sieve air dryer with an additional removal device can be driven into the pulper or cellar.

In certain cases it can also be advantageous if at least one Web guiding device is provided through which the material web with Low temperature compressed gas preferably in the range of about 20 to about 150 ° can be applied. This is particularly the use of a such pressurized gas-operated web guiding device as a pure transfer element possible.

To avoid shrinkage in the cross machine direction that is as free as possible allow and so slight differences in cross shrinkage between Reaching the edge and center can be done between the last press nip Press section and the first drying cylinder and / or within one Predrying section provided at least one floating dryer without a sieve his. This possibility exists regardless of whether there is still a Float dryer with sieve is provided or not.

The levitation dryer according to the invention is characterized in that it comprises a screen serving to support the web.

The invention, designed for example as a floating dryer Compressed gas operated levitation system (possibly in connection with at least one impingement flow dryer) can be used especially at the beginning the drying between the press and the first drying cylinder, preferably in Combination with a tandem NipcoFlex press or DuoCentri press with tape around the central roller or other press configurations, at where the web is not pulled off a smooth roller become. Use within the (pre) drying section is also conceivable, shrinking in the cross-machine direction as freely as possible allow and so slight differences in cross shrinkage to reach between edge and middle. In addition, the web guiding device even with a low gas or air temperature, for example operate in the range of about 20 to about 150 ° C. The leadership facility can be used as a pure transfer element be used.

Figur 1

eine schematische Teildarstellung einer beispielsweise als Schwebetrockner ausgeführten druckgasbetriebenen Bahnführungseinrichtung mit zugeordnetem Sieb,

Figur 2

eine schematische Darstellung einer Ausführungsform einer Trockenpartie mit zwei beispielsweise als Schwebetrockner ausgeführten druckgasbetriebenen Bahnführungseinrichtungen und einem Prallströmungstrockner, wobei durch die beiden Bahnführungseinrichtungen ein gemeinsames Sieb geführt ist, und

Figur 3

eine schematische Darstellung einer anderen Ausführungsform einer Trockenpartie mit zwei beispielsweise als Schwebetrockner ausgeführten druckgasbetriebenen Bahnführungseinrichtungen, wobei jeder dieser beiden Bahnführungseinrichtungen ein eigenes Sieb zugeordnet ist.

The invention is explained below using exemplary embodiments with reference to the drawing; in this show:

Figure 1

1 shows a schematic partial illustration of a web-guiding device operated by compressed gas and designed as a floating dryer, with an associated screen,

Figure 2

a schematic representation of an embodiment of a dryer section with, for example, a compressed gas-operated web guiding device and a baffle flow dryer, for example a suspended dryer, a common screen being passed through the two web guiding devices, and

Figure 3

a schematic representation of another embodiment of a dryer section with two pressurized gas-operated web guiding devices, for example designed as a floating dryer, each of these two web guiding devices being assigned its own screen.

Figure 1 shows a schematic partial representation of one with compressed gas, here Compressed air, operated web guiding device 10, which in particular as Floating dryer can be executed.

The web guide device 10 is used to support the web Assigned screen 12, which together with the material web 14 through the Web guide device 10 is passed. With the material web 14 can in particular be a paper or cardboard web.

In the web guiding device 10, the material web 14 is thus also Compressed air pressures that they alternate in the web running direction L from Sieve 12 is lifted up and abuts against it. Because of the air permeability has the screen 12 within the web guiding device at least essentially a straight line.

For the appropriate loading of the material web 14 includes the Web guiding device 10 several in a row in the web running direction L. arranged nozzles 16. There are 12 on both sides of the sieve and 14 nozzles 16 are provided corresponding to the material web. In the present Case are on both sides, each facing each other the width of the nozzle bar 16 is provided.

The air permeability of the screen 12 is advantageously greater than about 300 cfm, and preferably greater than about 500 cfm.

In addition, the nozzles 16 can be designed and / or controlled so that that for transferring the material web 14, the web 14 in the web guiding device 10 only on their side facing away from the screen 12 and in Compressed gas, here compressed air, is applied to the web running direction L. For Transfer of the material web 14 can also be the material web 14 from the sieve side through the sieve 12 through with negative pressure become. You can do this between those provided on the lower side of the sieve Nozzle bar 16 vacuum boxes (not shown) arranged his.

In principle, it is also possible to include the web guiding device 10 Pressurized gas, especially compressed air, low temperature in the range of preferably operate from about 20 to about 150 °. This web guiding device 10 can thus in particular also as a pure transfer element be used.

Figures 2 and 3 each show a purely schematic representation Dryer section 18 of a machine for producing a material web, at which can in particular be a paper or cardboard web.

In both embodiments of Figures 2 and 3 are two Web guiding devices 10, 10 'of the type described in FIG. 1 intended. These two web guiding devices 10, 10 'are each after the last press nip 20 of the press section 22 and before the first Drying cylinder 24 of the dryer section 18 is arranged.

In the embodiment according to FIG. 2 there is between the two web guiding devices 10, 10 'one with a dryer or impingement hood 26 provided impingement flow dryer 28 through which the material web 14 with a hot air and / or hot steam impingement flow is acted upon. The material web 14 is with a special sieve 30 assigned to impingement flow dryer 28 over a larger one with the dryer hood 26 provided support roller 32.

The drying speed in the range of a particular, for example web guiding device 10, 10 'or a floating dryer of the impingement flow dryer provided in the embodiment according to FIG. 2 28 is about the compressed air temperature, speed and / or moisture adjustable. It can in the different embodiments drying, for example, take place so that the material web 14 (cf. also FIG. 1) when the first drying cylinder 18 runs off or when pulling off a smooth, heated surface for the first time already has a dry matter content that is preferably higher than about 60 up to about 65%.

As can be seen from FIGS. 2 and 3, the material web 14 in both cases, starting from the last press nip 20 of the press section 22 fed to the first drying cylinder 18 in a closed train. there is the material web 14 each by the last press nip 20 of the Press section 22 guided bottom felt 34 removed.

In the embodiment according to FIG. 2, the two web guiding devices 10, 10 'a common sieve 12 out. The web of material 14 is in the area of a suction roller 36 from through the last Press nip 20 of the press section 22 guided bottom felt 34 removed.

The screen 12 is between the two web guiding devices 10, 10 ′ passed over a further suction roller 38. In the web running direction L behind the Web guide device 10 ', a suction roller 40 is provided, via the the sieve 12 is guided. Subsequently, the material web 14 by the screen 30 assigned to the impingement dryer 28. At the takeover point, for example, a transfer foil 44, a suction box 46 or the like can be provided. In the area of another Suction roller 48, the material web 14 from the wire 30 to a drying wire 44 passed, through which the web finally the first drying cylinder 18 is supplied.

In the embodiments shown in FIGS. 2 and 3, the material web is 14 in the first web guiding device 10 generally obliquely down and in the second web guiding device 10 'in general led diagonally upwards.

In the embodiment according to FIG. 3, only two are operated by compressed gas Web guiding devices 10, 10 'are used. A baffle dryer is not provided here. The two web guiding devices A separate sieve 12, 12 'is assigned to 10, 10'. The Transfer of the material web 14 from the lower wire 34 of the press section 22 to the screen 12 guided by the first web guiding device 10 here via a transfer belt 50. The acceptance takes place from Bottom wire 34 in the area of a suction roller 52, over which the transfer belt 50 is performed. The web transfer to the screen 12 takes place again in the area a suction roller 36 assigned to the screen 12. The transfer of the material web 14 from the screen 12 to the through the second web guiding device 10 'guided sieve 12' takes place in the area of another, the sieve Suction roller 54 assigned to 12 '. The sieve 12' also serves as a drying sieve, through which the material web 14 following the second Web guiding device 10 'via a further suction roller 56 to the first one Drying cylinder 18 is supplied.

As already mentioned, at least one of the compressed gas operated Web guiding device 10, 10 'can be designed as a floating dryer. In principle, however, it is also conceivable for at least one of these web guiding devices 10, 10 'with compressed gas or compressed air lower Operating temperature and, for example, at least predominantly as Insert transfer element.

Basically, it is also possible between the last press nip 20 Press section 22 and the first drying cylinder 18 and / or within a predrying section to provide at least one floating dryer without a sieve.

Reference list

10th

Web guiding device, floating dryer

10 '

Web guiding device, floating dryer

12th

scree

12 '

scree

14

Material web

16

Nozzles, nozzle bars

18th

Dryer section

20th

last press nip

22

Press section

24th

first drying cylinder

26

Dryer hood

28

Impingement flow dryer

30th

scree

32

Backup roller

34

felt

36

Suction roll

38

Suction roll

40

Suction roll

42

Suction roll

44

Transfer foil

46

Suction box

48

Suction roll

50

Transfer belt

52

Suction roll

54

Suction roll

56

Suction roll

L

Web direction

Claims (35)

Drying section (18) of a machine for producing a material web (14), in particular paper or cardboard web,
characterized in that at least one web guiding device (10, 10 ') is provided, through which the material web (14) is passed together with a sieve (12, 12') and in which the material web (14) can be pressurized with compressed gas such that it in the web running direction (L) is alternately lifted off the screen (12, 12 ') and bears against it. Dryer section according to claim 1,
characterized in that at least one pressurized gas-operated web guiding device (10, 10 ') is provided. Dryer section according to claim 1 or 2,
characterized in that the screen (12, 12 ') is guided in a straight line through the compressed gas-operated web guiding device (10, 10'). Dryer section according to one of the preceding claims,
characterized in that the web guiding device (10, 10 ') for pressurizing the material web (14) comprises several nozzles (16) arranged one behind the other in the web running direction (L). Dryer section according to claim 4,
characterized in that nozzles (16) are provided on both sides of the screen (12, 12 '). Dryer section according to claim 4 or 5,
characterized in that several nozzle bars (16) each extending in the direction of the web width are provided. Dryer section according to one of the preceding claims,
characterized in that at least one compressed gas-operated web guiding device (10, 10 ') is arranged in front of the first drying cylinder (18). Dryer section according to one of the preceding claims,
characterized in that air is provided as the compressed gas. Dryer section according to one of the preceding claims,
characterized in that at least one impact flow dryer (28) provided with at least one dryer hood (26) is provided, through which the material web (14) can be subjected to a hot air and / or hot steam impact flow. Dryer section according to claim 9,
characterized in that the material web (14) is guided over at least one in particular larger supporting or suction roller (32) with an associated impingement flow dryer (28). Dryer section according to claim 9 or 10,
characterized in that at least one impingement flow dryer (28) is arranged in front of the first drying cylinder (18). Dryer section according to one of the preceding claims,
characterized in that the impingement flow dryer (28) is arranged in the web running direction (L) behind at least one pressurized gas-operated web guiding device (10, 10 '). Dryer section according to one of the preceding claims,
characterized in that the material web (14) when the first drying cylinder (18) runs off or when it is first pulled off from a smooth heated surface already has a dry content which is higher than about 58 to about 65%. Dryer section according to one of the preceding claims,
characterized in that at least one pressurized gas-operated web guiding device (10, 10 ') is provided after the last press nip (20) of a press section (22). Dryer section according to one of the preceding claims,
characterized in that the material web (14) following the last press nip (20) of a press section (22) initially by at least one pressurized gas-operated web guiding device (10, 10 ') and then by at least one in particular larger support or suction roll (32 ) is guided with an associated impingement dryer (28) before it is fed to the first drying cylinder (18). Dryer section according to one of the preceding claims,
characterized in that the drying speed in the area of a respective web guiding device (10, 10 ') or a respective impingement flow dryer (28) can be regulated via the pressure gas temperature, speed and / or moisture. Dryer section according to one of the preceding claims,
characterized in that the air permeability of the screen (12, 12 ') assigned to the compressed gas-operated web guiding device (10, 10') is greater than approximately 300 cfm and preferably greater than approximately 500 cfm. Dryer section according to one of the preceding claims,
characterized in that, starting from the last press nip (20) of the press section (22) , the material web (14) is fed to the first drying cylinder (18) in a closed train. Dryer section according to one of the preceding claims,
characterized in that the material web (14) is transferred from the press section (22) directly to the screen (12) assigned to a web guide device (10, 10 ') operated by compressed gas. Dryer section according to one of claims 1 to 18,
characterized in that the transfer of the material web (14) from the press section (22) to the screen (12) associated with a pressurized gas-operated web guiding device (10, 10 ') takes place via at least one transfer belt. Dryer section according to one of the preceding claims,
characterized in that the material web (14) is removed from a felt (34) passed through the last press nip (20) of the press section (22). Dryer section according to one of the preceding claims,
characterized in that the material web (14) is removed directly from a press roll assigned to the last press nip (20) of the press section (22). Dryer section according to one of the preceding claims,
characterized in that a plurality of web guiding devices (10, 10 ') and / or a plurality of impingement flow dryers (28) are preferably each provided as a floating dryer. Dryer section according to one of the preceding claims,
characterized in that at least one horizontally arranged compressed gas-operated web guiding device (10, 10 ') is provided. Dryer section according to one of the preceding claims,
characterized in that at least one vertically arranged compressed gas-operated web guiding device (10, 10 ') is provided. Dryer section according to one of the preceding claims,
characterized in that at least one compressed gas-operated web guiding device (10, 10 ') is provided, in which the web of material is guided generally obliquely upwards. Dryer section according to one of the preceding claims,
characterized in that at least one compressed gas-operated web guiding device (10, 10 ') is provided, in which the web of material is guided generally obliquely downwards. Dryer section according to one of the preceding claims,
characterized in that several pressurized gas-operated web guiding devices are provided and that at least some of these web guiding devices (10, 10 ') are each assigned their own sieve (12, 12'). Dryer section according to one of the preceding claims,
characterized in that at least one screen (12) guided by a plurality of web guide devices (10, 10 ') operated by compressed gas is provided. Dryer section according to one of the preceding claims,
characterized in that to hold the material web (14) on the wire (12, 12 ') before and / or after the associated compressed gas-operated web guiding device (10, 10') and / or between successive web guiding devices (10, 10 ') suction rolls (36 - 40, 54, 56), transfer foils (44) and / or suction boxes (46) are provided. Dryer section according to one of the preceding claims,
characterized in that for transferring the material web (14) the web (14) can be acted upon with compressed gas in a respective compressed gas-operated web guiding device (10, 10 ') only on its side facing away from the wire (12, 12') and in the web running direction (L) and / or a vacuum can be applied from the sieve side. Dryer section according to one of the preceding claims,
characterized in that vacuum boxes are arranged between nozzle bars (16) provided on the screen side facing away from the material web (14). Dryer section according to one of the preceding claims,
characterized in that at least one web guiding device (10, 10 ') is provided, through which the material web (14) can be acted upon by compressed gas at a low temperature in the range of preferably about 20 to about 150 °. Drying section (18) of a machine for producing a material web (14), in particular paper or cardboard web, in particular according to one of the preceding claims,
characterized in that at least one floating dryer without a screen is provided between the last press nip (20) of a press section (22) and the first drying cylinder (18) and / or within a pre-drying section. Hover dryer (10, 10 '), in particular for a dryer section (18) according to one of Claims 1 to 33,
characterized in that it comprises a screen (12, 12 ') serving to support the web.

Images