EP0414125B1 - Apparatus for drying a liquid coating applied onto a moving substrate - Google Patents

Description

The invention relates to a device for drying a liquid layer applied to a moving carrier material, which contains vaporizable solvent components and solid components, by means of a heated drying gas or heated drying air, in which a gas or air supply system is arranged below and above a moving carrier material Carrier material floating freely along a path on a support pad generated by the lower gas or air supply system through the drying zone.

Such a device is known for example from US-A-3 599 301.

Different drying processes and drying devices are used for drying large, web-shaped goods on which layers of liquid are applied. Typical drying goods are, for example, metal or plastic belts, on which liquid layers are applied, which usually consist of evaporable solution components that are removed from the liquid film during the drying process, and non-evaporable components that remain on the carrier material after drying.

From US-A-3,559,301 drying devices with lower and upper air supply system are known, each of which has nozzles that cannot ensure an air supply while avoiding layer blows. When air emerges from these nozzles A turbulent and not a laminar air flow generally occurs, so that an air supply to the liquid layer to be dried is not ensured while avoiding layer blows.

US Pat. No. 3,577,653 describes a drying device which has a slightly curved course of the drying tunnel in which a belt to be dried is carried and guided against its underside by compressed air. The curved passage of the belt prevents the belt from migrating sideways, so that it can be held in its central position opposite the drying tunnel. The air flowing upwards over the belt edges ensures the central position of the belt. The drying air sweeps away in the running direction and above the belt. Since two air flows perpendicular to each other meet along the belt edges, turbulence occurs in this area, which can lead to layer blows.

GB-A-847 548 describes a drying device in which a heat exchanger chamber is closed off from a heat exchanger wall made of porous material, such as sintered metal or a metal-ceramic compound, in the direction of the band to be dried. The strip runs a short distance over the heat exchanger wall, which is heated by a coil loaded with steam. Hot air is blown into the heat exchanger chamber, which flows through the pores of the heat exchanger wall and forms an air film next to the belt, on which the moving belt hovers. There is a high, even heat transfer to the belt, with the exception of along the belt edges.

The coating gives the surfaces of the carrier materials special properties which are only present in the form after the drying process, as are desired for later use. An example of this is the coating of metal strips with light-sensitive layers, which are assembled into printing plates. The coating of metal strips or plastic films with substances in the form of a solvent-containing wet film, hereinafter referred to as the liquid film, and its subsequent drying thus represent a process that requires special systems to ensure the desired product quality of the layers. The process step of film drying is essential as the final process measure of the coating.

When drying liquid films on carrier materials, it is customary to allow a heated gas, in particular air, to flow over the surface of the carrier materials to remove the solvent components from the film layer. The heated gas stream is brought into direct contact with the liquid film, which is applied in a uniform layer distribution on the carrier material, which passes through a drying device. In order to ensure a streak-free and mottled, dried film surface, ie to ensure an even distribution of the remaining components, the drying systems are equipped with devices which are intended to achieve a favorable or uniform distribution of the air flow over the liquid film. The aim is to achieve uniform drying across the entire width of the coated web. Furthermore, known drying systems have devices for minimizing disturbances in the air movements which, in part due to turbulent flow movements, have a disadvantageous effect on the film surface and lead to signs of mottling there.

According to US Pat. No. 3,012,335, a common design of such a drying device consists of a gas space supplied with drying gas, which is arranged over a certain length above the coating web, by means of a multiplicity of slits, nozzles, holes or even porous solids over the immediate gas space to supply the liquid film to be dried with drying gas as evenly as possible. The continuously coated belt or coated plates on a rotating conveyor belt are continuously passed through the drying device with the release of solvent vapor to the dryer air. The supplied dryer air can be constantly renewed in the open circuit or the air enriched with solvent can be completely removed. A circulating air process with partially renewed or discharged dryer air can also be used.

Difficulties in removing the dryer air from the drying room are often that in the case of longitudinal nozzles or longitudinal slots arranged transversely to the belt running direction, due to the pressure drop in the case of a lateral outflow, there is a reduction in the nozzle outlet speed in the middle of the nozzle fields of slot nozzle dryers and thus also the heat and Mass transfer across the belt running direction is affected. The consequence of this is overdrying of the edges, which leads to undesired structuring of the dried films in many coating processes.

In the journal "Chemie-Ingenieur-Technik", 42. Volume 14, Volume 14 (1970), pp. 927 to 929, Volume 43, Volume 8 (1971), pp. 516 to 519 and Volume 45, Volume 5 (1973), pp. 290 to 294, therefore, suggestions for optimization become constructive Design of nozzle fields in slot nozzle dryers, which should ensure a constant heat and mass transfer over the entire range of a dryer. In order to optimize slot nozzle dryers, mass transfer measurements in impingement flow from slot nozzle fields with different nozzle areas are empirically correlated in a wide range of external factors. The relationship found is used to determine optimal nozzle geometries with regard to the fan output per m² of goods area. It is shown that a constant heat and mass transfer over the web width is achieved in that the nozzle slots have a continuously increasing slot width from the web edge to the center.

When drying large-area webs, high uniformity of heat and mass transfer across the web width must often be required in order to avoid local overdrying and the associated reduction in quality. In these cases, slot nozzle fields are preferably used, in which the slots are arranged transversely to the running direction of the web. The edge overdrying observed in the slot nozzle dryers with outflow in the slot direction can be attributed to the distribution of the exit velocity along the slots. In order to avoid this overdrying of the edges, it follows, among other things, for nozzle dryers that the outflow area should be 3.5 times as much as possible of the nozzle exit area in order to obtain uniform drying over the width of the web.

It is state of the art today to carry out a surface treatment in suspension dryers for foil or metal strips with the aid of an air nozzle system without contact (magazine "gas warm international", Volume 24 (1975), No. 12, pp. 527 to 531). The dryer air enriched with solvent is sucked off directly in the nozzle fields in order to eliminate the undesired transverse flow. This results in so-called nozzle dryers or impact jet dryers, in which the stagnation point-like flow of individual nozzles is disadvantageous, which tends to flow-physical instabilities in both laminar and turbulent flow forms, which inevitably lead to irreversible drying structures, especially in the case of low-viscosity liquid films.

According to PCT application WO82 / 03450, the dryer air is led from a vestibule via suitable inlet openings and flow deflectors into a calm space in order to avoid stagnation-point-like flows in the initial area of the dryer apparatus, from where a part of the dryer air passes via a device arranged in close proximity to the liquid film porous filter element on the web to be dried. The mode of operation of such drying is based on the fact that there is between the porous protective shield and the drying liquid film forms a calmed, but highly enriched, weak air flow, which is constantly renewed by exchange with the residual air transversely flowing over the porous medium and thus, due to the relatively short overall length, a predrying of the liquid film with reduced tendency to mottling is achieved .

This type of drying is characterized by predominant diffusion of the solvent vapor / air mixture through the porous protective shield, which means that if there is almost no convective removal within the space between the belt and the protective shield, complete drying of the liquid film is only possible with very large dryer lengths or with the addition of subordinate auxiliary dryers.

The object of the invention is to further develop a device according to the preamble of claim 1 so that a solvent of a liquid layer on a moving carrier material evaporates so quickly and sufficiently in a first drying step that the liquid layer is insensitive to blowing in a subsequent drying step.

This object is achieved by a device for drying a liquid layer applied to a moving carrier material according to the preamble of claim 1 in such a way that an application device applies a liquid layer to the carrier material that the upper gas or air supply system into sections for supplied gas and Exhaust gas or the supply and exhaust air is divided, that each section consists of two filter plates made of porous material between which there is a gap, and that the upper gas or air supply system has a larger working width than the lower gas or Has air supply system.

In a further development of the device, the lower gas or air supply system has slots for the gas or air supply and return channels for gas or air removal arranged transversely to the direction of travel of the carrier material and alternate the slots and the return channels to each other in order to provide the gas or the air coming from the left and right of one Back suction channel arranged slots emerges, to be discharged between the carrier material and the top of the gas or air supply system into the return suction channel.

The further embodiment of the device according to the invention results from the features of claims 3 to 10.

Fig. 1

schematisch einen Längsschnitt einer ersten Ausführungsform der Vorrichtung nach der Erfindung, mit waagerechter Trägermaterialbahn,

Fig. 2

schematisch einen Längsschnitt einer zweiten Ausführungsform der Vorrichtung, ähnlich der ersten Ausführungsform, jedoch mit gekrümmt verlaufender Trägermaterialbahn,

Fig. 3

einen Querschnitt durch die erste Ausführungsform nach Figur 1, entlang der Linie I-I,

Fig. 4

schematisch einen Längsschnitt durch das untere Gas- bzw. Luftzufuhrsystem einer dritten Ausführungsform der Vorrichtung nach der Erfindung,

Fig. 5

einen Längsschnitt durch das untere Gas- bzw. Luftzufuhrsystem einer vierten Ausführungsform der Vorrichtung, mit gekrümmter anstelle waagerechter Bahnführung des Trägermaterials,

Fig. 6

schematisch einen Längsschnitt durch das untere Gas- bzw. Luftzufuhrsystem einer fünften Ausführungsform der Vorrichtung nach der Erfindung,

Fig. 7

schematisch einen Längsschnitt durch das untere Gas- bzw. Luftzufuhrsystem einer sechsten Ausführungsform der Vorrichtung, ähnlich der Figur 6, mit gekrümmter anstelle waagerechter Trägermaterialbahn, und

Fig. 8

den Zusammenhang zwischen dem Bandzug Z auf die Trägermaterialbahn und dem Auflagedruck P der Trägermaterialbahn auf das Gas- bzw. Lufttragepolster bzw. den Zusammenhang zwischen der Laufgeschwindigkeit der Trägermaterialbahn und dem Auflagedruck P.

The invention is described in more detail below with reference to exemplary embodiments illustrated in the drawings. Show it:

Fig. 1

schematically shows a longitudinal section of a first embodiment of the device according to the invention, with a horizontal carrier material web,

Fig. 2

schematically a longitudinal section of a second embodiment of the device, similar to the first embodiment, but with a curved web of carrier material,

Fig. 3

2 shows a cross section through the first embodiment according to FIG. 1, along the line II,

Fig. 4

schematically shows a longitudinal section through the lower gas or air supply system of a third Embodiment of the device according to the invention,

Fig. 5

2 shows a longitudinal section through the lower gas or air supply system of a fourth embodiment of the device, with curved instead of horizontal web guidance of the carrier material,

Fig. 6

schematically shows a longitudinal section through the lower gas or air supply system of a fifth embodiment of the device according to the invention,

Fig. 7

schematically shows a longitudinal section through the lower gas or air supply system of a sixth embodiment of the device, similar to Figure 6, with curved instead of horizontal carrier material web, and

Fig. 8

the relationship between the strip tension Z on the carrier material web and the contact pressure P of the carrier material web on the gas or air-bearing cushion or the relationship between the running speed of the carrier material web and the contact pressure P.

In Figure 1, a longitudinal section of a first embodiment of a device 1 according to the invention is shown schematically. A carrier material 2 is guided around a roller 13 and runs horizontally through the Device 1 up to a further roller 13, around which the carrier material 2 is deflected from the horizontal position into a vertical position. In the area of the first roller 13 there is an application device 5, for example a slot die, through which a liquid layer 3 is applied to the carrier material 2. The liquid layer 3 contains vaporizable solvent components and solid components which are sensitive to light, for example. The invention is described with reference to a device in which a liquid layer is dried, the solid components of which are light- or photosensitive masses, which are continuously applied and dried on a metal belt. However, the invention is in no way limited to light-sensitive layers, but rather can also be used for drying other liquid layers which are sensitive to blowing by air or gas flows. Furthermore, instead of metal strips, foil, paper strips or the like can also form the carrier material.

The application device 5 is arranged, for example, in the 9 o'clock position near the first roller 13. The carrier material 2 with the liquid layer 3 located thereon is guided through the device 1 along a horizontally running carrier material web 24. An air or gas supply system 11 or 12 is located below and above the carrier material web 24. The lower gas or air supply system 11 has a smaller width than the upper gas or air supply system 12 on. If only the air discharge and air supply systems are mentioned, these terms also include gas discharge and gas supply systems, for example for inert gases. Both air supply systems are each housed in unspecified housings. The carrier material 2 is guided in a free-floating manner through a drying zone 21 of the device 1 along the carrier material web 24 by means of an air support cushion which is generated by the lower air supply system 11. For this purpose, the lower air supply system 11 has slots 14 which are arranged transversely to the running direction of the carrier material 2 and through which supply air 8 flows against the underside of the carrier material 2. This supply air 8 of the lower air supply system 11 is generally hot air. In addition to the slots 14, there are return suction channels 15 in the upper side of the air supply system 11, through which the exhaust air 16 is extracted. The slots 14 and the suction channels 15 are arranged alternately, so that the supply air 8 from the slots 14 located on the left and right of a suction channel 15 between the underside of the carrier material 2 and the top of the air supply system 11 along the underside of the carrier material in the direction of the associated suckback channel 15 streams. This results in the back of the coated carrier material 2 being heated with hot air, through which the necessary drying energy is supplied, which leads to rapid evaporation of the majority of the solvent components. That on the top of the carrier material web 24 or the top of the coated Carrier material 2 resulting solvent vapors are removed by the upper air supply system 12. This is divided into sections 7 for the supply air 9 and the exhaust air 6, which is the return air enriched with vapors of the solvent components. Each section 7 consists of two filter plates 4 made of a material provided with pores, a gap 22 being left open between these two filter plates 4. The supply air 9 is directed onto the coated carrier material 2 by guide plates 23 and is returned as exhaust air or return air 6 via the surface of the carrier material web 24. The baffles 23 are slightly curved inwards on the underside of the sections 7 and are arranged in pairs, terminating with the side edges of the filter plates 4 of a section 7. The baffles are arranged vertically above the filter plates 4. The device 1 works on the principle of the rear heating of the coated carrier material 2 with hot air and layer-side removal of the vapors of the solvent components with a layer-gentle air flow on the top of the carrier material 2. The drying is complete when sufficient solvent components have evaporated, so that on the Carrier material 2 remaining solid components form a layer that has become largely insensitive to blowing by gas or air currents in a subsequent drying. Of course, another gas, such as nitrogen, can be used for drying instead of air.

According to the desired drying speed, any number of sections 7 are provided in the upper air supply system 12, via which supply air is supplied and exhaust air flows out. The incoming and outgoing air flowing through the porous materials of the filter plates 4 is laminar and uniform, the difference in speed between the coated carrier material 2 and the supply air 9 from the application device 5 to the end of the predrying zone 21 being less than 0.25 m / sec. This ensures that there is no layer blowing of the liquid layer 3. The return flow or exhaust air 6 enriched with the vapors of the solvent components is fed through the upper air supply system 12, for example, to a condenser for the solvent component vapors, not shown, in which the vapors condense to the liquid solvent components and either reprocessed or, after appropriate treatment, in environmentally friendly products for the landfill can be split.

Since the working width of the upper air supply system 12 is always larger than the working width of the lower air supply system 11 and thus also larger than the largest carrier material width, an undisturbed air movement over the coated carrier material 2 is obtained. The special design of the lower air supply system 11 with the slots 14 and the return suction channels 15 ensures that the coated carrier material 2 runs smoothly and without vibrations along the carrier material web 24.

In the second embodiment of the device 1, shown schematically in FIG. 2, the carrier material web 25 runs in an arc with a slight curvature. The air supply systems 11 and 12 are also curved and arranged at a distance from the curved substrate web 25. All other structural units of this second embodiment largely correspond to the components of the first embodiment and are therefore not described again.

The cross-sectional illustration shown in FIG. 3 along the line I-I of FIG. 1 shows that the two air supply systems 11 and 12 are designed to be open to one another and are only separated from one another by a partition 27 with an opening 26 and the coated carrier material 2 above the opening 26. The supply air 8 of the lower air supply system 11 is prevented by the carrier material 2 coated with the liquid layer 3 and by side cover plates 10 from flowing directly into the upper air zone 19. The small amounts of air that flow laterally and at the edges of the carrier material 2 and the cover plates 10 as excess air 20 from an under air zone 28 into the upper air zone 19 are removed by the exhaust air or return air 6 of the upper air supply system 12. Conversely, excess air from the upper air supply system is removed from the exhaust air from the lower air supply system.

The lower air supply systems of a third and fourth embodiment shown in Figures 4 and 5 of the device according to the invention differ only in that in the third embodiment the carrier material 2 is guided along a flat horizontal carrier material web 24 and in the fourth embodiment the carrier material web 25 and also the lower air supply system 11 are slightly curved. Both in the third and in the fourth embodiment, the air supply system 11 comprises a number of cylindrical bodies 17 which are arranged at a distance from one another in the transverse direction to the carrier material web 24 or 25. The supply air 8 can flow in and the exhaust air 16 can flow out through the gaps between the cylindrical bodies 17. In the fourth embodiment according to FIG. 5, the cylindrical bodies 17 are arranged at a distance from one another along an arc which has the same curvature as the carrier material web 25. The cylindrical bodies 17 are heated by the inflowing, hot supply air 8, as a result of which an air supply system 11 of this type is distinguished by a particularly good and uniform heating of the carrier material 2.

FIG. 6 shows a lower air supply system 11 of a fifth embodiment of the device, which comprises air inlet plates 18 made of porous material. The carrier material web 24 is flat and horizontal, and the air supply system 11 is also designed horizontally. The supply air 8 of the air supply system 11 exits through the porous material of the flat air inflow plates 18 in the direction of the underside of the carrier material 2 and flows out as exhaust air 16 in return suction channels 15, which between the plates 18 and on the outer edges of the plates. The return suction channels 15 are arranged between the inflow zones transversely to the running direction of the carrier material web 24. The sixth embodiment of the lower air supply system 11 according to FIG. 7 differs from FIG. 6 only in that the air supply system and also the carrier material web 25 are slightly curved. The air supply system 11 accordingly has curved air inflow plates 29, which have the same curvature as the carrier material web 25. The air inflow plates 29 are arranged at a distance from one another, and the exhaust air 16 flows out through suction channels 15, which are arranged between the plates 29 and on the outer edges of the plates.

The upper air supply systems 12 belonging to the lower air supply systems 11 according to FIGS. 4 to 7 are similar to the upper air supply system 12 according to FIGS. 1 and 2 and are therefore not shown again. The lower air supply systems 11 described here work with an air support cushion without mechanical support elements for the underside of the carrier material band. With horizontal web guidance, the air flow conditions above and below the carrier material web must be precisely coordinated in order to achieve a smooth and vibration-free belt run. The curved or curved web guide of the carrier material band shows better web stabilization than the horizontal web guide and leads to vibration-free and smooth running of the carrier material band without great effort.

mit der Auflagekraft P (N/m²) des Bandes auf dem Luftpolster, dem gedachten Durchmesser D (m) der gekrümmten Trägermaterialbahn, dem Bandzug Z = B x S x K, mit der Bahnbreite B (m), der Bahndicke S (m) und dem spezifischen Bandzug K (N/mm²), üblicherweise ≈ 10 N/mm², unter Vernachlässigung des Gewichtes des Trägermaterialbandes.FIG. 8 shows the graphical relationship between the contact force P of the belt on the air cushion, the belt tension Z and the air speed v of the supply air, which flows against the underside of the carrier material band with a slightly curved carrier material web. The following applies to the force balance of a belt on a slightly curved guideway with air cushion: $$\text{P =}\frac{\text{2 x Z}}{\text{DB}}$$

with the contact force P (N / m²) of the tape on the air cushion, the imaginary diameter D (m) of the curved carrier material web, the tape tension Z = B x S x K, with the web width B (m), the web thickness S (m) and the specific band tension K (N / mm²), usually ≈ 10 N / mm², neglecting the weight of the carrier material band.

mit der Luftgeschwindigkeit v (m/s) und der Dichte der Luft ρ (kg/m³). Die Abströmgeschwindigkeit der rückseitigen Abluft 16 bestimmt zusammen mit der Lufttemperatur die Schnelligkeit der Banderwärmung bzw. die Schnelligkeit der Verdampfung der Lösungsmittelkomponenten der Flüssigkeitsschicht. Ist beispielsweise die Auflagekraft des Trägermaterialbandes gleich P1, so ergibt sich aus dem Diagramm der Figur 8 die zugehörige Mindestabströmgeschwindigkeit v1 der Abluft 16 des unteren Luftzufuhrsystems 12. Aus der Beziehung für die Auflagekraft P ergibt sich, daß diese von der Bandbreite B unabhängig ist und nur von der Banddicke S, dem spezifischen Bandzug K und dem Durchmesser D der gekrümmten Trägermaterialbahn 25 abhängt. Für unterschiedlich dicke Schichtträgerbänder, die mit annähernd gleichem spezifischen Bandzug K entlang der Trägermaterialbahn 25 geführt werden, ergibt sich eine Proportionalität zwischen der Auflagekraft P, dem Bandzug Z, der Banddicke S und dem Quadrat der Luftgeschwindigkeit v², wobei diese Größen annähernd proportional der notwendigen Trocknungszeit sind. Mit anderen Worten bedeutet dies, daß die Trocknungszeiten im wesentlichen von der Banddicke S abhängen.The support air cushion of the supply air of the lower air supply system must counteract the contact pressure P of the carrier material band with at least the same force in order to avoid contact between the carrier material band and the upper side of the lower air supply system. The carrier air flows under the carrier material band into the return suction channels, as described above. This is done with the air velocity v corresponding to the pneumatic pressure of the air cushion, for which the Bernoulli equation applies: $$\text{v =}\sqrt{\frac{\text{2nd}}{\text{ρ}}\text{xp}}$$

with the air velocity v (m / s) and the density of the air ρ (kg / m³). The outflow velocity of the rear exhaust air 16, together with the air temperature, determines the rapidity of the band heating or the rapidity of the evaporation of the solvent components of the liquid layer. If, for example, the contact force of the carrier material strip is equal to P1, the diagram in FIG. 8 shows the associated minimum outflow velocity v1 of the exhaust air 16 of the lower air supply system 12. From the relationship for the contact force P it follows that this is independent of the bandwidth B and only depends on the strip thickness S, the specific strip tension K and the diameter D of the curved carrier material web 25. For layers of different thicknesses, which are guided along the carrier material web 25 with approximately the same specific band tension K, there is a proportionality between the contact force P, the band tension Z, the band thickness S and the square of the air velocity v 2, these sizes being approximately proportional to the necessary drying time are. In other words, this means that the drying times depend essentially on the strip thickness S.

Figure 8 shows a linear relationship between the tape tension Z and the contact force P, with the parameters D₁ and D₂ equal to the diameters of differently curved carrier layer webs 25. With the same contact force P₁, with increasing diameter D₁> D₂, the belt tension Z₁ greater than Z₂ must be selected. In other words, this means that the greater the curvature or the smaller D, the more stable the tape guide with a small contact force or low air speed v.

With conventional coatings with liquid resist, more than two thirds of the drying energy is generally required for heating the aluminum strip, for example 0.3 mm thick, and only the rest of the drying energy is available for the evaporation of the solvent components. The advantage of the invention is that the back heating of the aluminum strip or the backing material strip means that far more drying energy is applied for the evaporation of the solvent components than in the conventional drying devices.

With most liquid resist coatings, insensitivity to blowing is only guaranteed when approx. 70% of the solvent components have already evaporated from the liquid resist layer.

If the exhaust air velocity v1 and the strip thickness S are known, the required drying energy can be roughly calculated.

The carrier material can also be supported in all devices, i.e. not be free-floating, be guided.

Claims (10)

1. An apparatus for drying, by means of a heated drying gas or of heated drying air, a liquid film (3) applied to a moved substrate material (2) and containing vaporizable solvent components and solid components, where a gas or air supply system (11, 12) is arranged both underneath and above the moved substrate, and where the substrate (2) moves through the drying zone (21) while being freely suspended along a path on a carrying cushion produced by the lower gas or air supply system (11), characterized in that the liquid film (3) is applied to the substrate material by an applying device (5), that the upper gas or air supply system (12) is sub-divided into sections (7) for fed-in gas and exhaust gas or for the supply air and exhaust air, that each section (7) comprises two filter plates (4) of a material provided with pores, between which plates there is a gap (22), and in that the upper gas or air supply system (12) has a greater working width than the lower gas or air supply system (11).
2. The apparatus as claimed in claim 1, wherein the lower gas or air supply system (11) has slots (14) arranged transversely to the running direction of the substrate (2) for the gas or air supply and return channels (15) for the gas or air removal and wherein the slots (14) and the return channels (15) alternate, in order to carry away the gas or the air which leaves the slots arranged to the left and right of a return channel between the substrate (2) and the upper side of the gas or air supply system (11) into the return channel.
3. The apparatus as claimed in claim 1, wherein, in the upper gas or air supply system (12), the gas or the supply air (9) is diverted by baffles (23) onto the substrate (2) and returned over the substrate web as return air (6) or gas, and wherein the baffles (23) are arranged in pairs on the underside, terminating with the side edges of the filter plates (4) of a section (7).
4. The apparatus as claimed in claim 1, wherein the gas or air supply system (11, 12) are level and are arranged at a distance from the level, horizontal substrate web (24).
5. The appratus as claimed in claim 1, wherein the gas or air supply systems (11, 12) are arranged in a curved form, at a distance from the correspondingly curved substrate web (25).
6. The apparatus as claimed in claim 1, wherein the two gas or air supply systems (11, 12) are designed to be open, one opposite the other, and wherein, underneath the substrate web (24; 25) cover plates (10) are arranged at the sides of an opening (26) of a dividing wall (27), between the lower air or lower gas zone (16) and the upper air or upper gas zone (19).
7. The apparatus as claimed in claim 4, wherein the lower, level gas or air supply system (11) comprises a number of cylindrical bodies (17), which are arranged in transverse direction to the substrate web (24), spaced apart from one another and wherein the gas or the supply air (8) flows in and the exhaust gas or the exhaust air (16) flows away between the cylindrical bodies (17).
8. The apparatus as claimed in claim 5, wherein, in the lower, curved gas or air supply system (11), a number of cylindrical bodies (17), spaced apart from one another, are arranged along an arc which has the same curvature as the substrate web (25), and wherein the inflowing gases or the supply air (8) flow in and the outflowing gases or the exhaust air (16) flow away through between the cylindrical bodies (17).
9. The apparatus as claimed in claim 4, wherein the lower, level gas or air supply system (11) comprises gas or air inflow plates (18) of porous material, through which the gas or the supply air (8) flows in, wherein the gas or air inflow plates are arranged level and at a distance from each other and wherein the exhaust gas or the exhaust air (16) flows away in return channels (15) through between the plates as well as past the outer edges of the plates.
10. The apparatus as claimed in claim 5, wherein the lower, curved gas or air supply system (11) has curved gas or air inflow plates (29), the curvature of which is the same as that of the substrate web (25), wherein the gas or air inflow plates (29) are arranged at a distance from each other and wherein the exhaust gas or the exhaust air (16) flows away in return channels (15) through between the plates as well as past the outer edges of the plates.

Images