Installation having a drying section, drying section, and method for operating an installation having a drying section

Abstract

The invention relates to an installation (2) which has a drying section (4) for drying a printed web (6) made of paper, wherein the drying section (4) has a hot air dryer (10) for the hot-air drying of the web (6), the drying section (4) has a radiation dryer (14) for the radiation drying of the web (6), the hot air dryer (10) has an air outlet (20) for discharging exhaust air (A1), the radiation dryer (14) has an air inlet (22) for supplying supply air (Z2), and the air outlet (20) is connected to the air inlet (22) via a coupling section (26) in order to conduct exhaust air (A1) at least partly as supply air (Z2) from the hot air dryer (10) to the radiation dryer (14). The invention further relates to a drying section (4) and to a method for operating an installation (2).

Description

[0001] Description

[0002] Plant with a drying section, drying section and method for operating a plant with a drying section

[0003] The invention relates to a system with a drying section for drying a printed paper web, as well as to a corresponding drying section. Furthermore, the invention relates to a method for operating such a system.

[0004] A drying section is, for example, integrated into a printing system and is used to dry a print image, which is then printed onto a web of paper upstream of the drying section using a printer in the printing system.

[0005] Reference is made to WO 2020 222 806 A1 and WO 2015 016 902 A1 .

[0006] In principle, it is desirable to operate a drying line as energy-efficiently and cost-effectively as possible.

[0007] Against this background, it is an object of the invention to provide a correspondingly improved drying section as well as a system with such a system and a method for operating the system, in particular its drying section.

[0008] The object is achieved according to the invention by a system having the features according to claim 1, by a drying section having the features according to claim 14 and by a method having the features according to claim 15. The statements regarding the system also apply analogously to the drying section and the method and vice versa. If steps of the method are stated implicitly or explicitly below, advantageous embodiments for the system and / or drying section result from the fact that it is designed to carry out one or more of these steps. For this purpose, the system and / or the drying section has in particular a suitably designed control unit. For example, a control unit of the drying section is integrated into a control unit of the system or is designed separately therefrom, or a single control unit controls both the drying section and other parts of the system.

[0009] The system has a drying section for drying a printed paper web. The web can be single-layer or multi-layer. Preferably, the system is an inkjet printing system with a printer for printing the web with a print image before drying. The printer is in particular an inkjet printer, e.g., a CMYK primer or varnish printer. The printer is arranged upstream of the drying section with respect to a conveying direction of the web. During operation, the web is therefore first printed with the printer and then dried with the drying section. Such a system is assumed below, without restriction of generality.

[0010] The drying section includes a hot air dryer for hot air drying the web. In other words, during operation, hot air is generated in the hot air dryer by supplying air to the hot air dryer and heating it with a heating element of the hot air dryer. The hot air is then directed onto the web; the hot air dryer is therefore also referred to as an "impact jet dryer." Suitably, the hot air is directed toward the web via a plurality of nozzles or through a perforated plate. The contact of the hot air with the web causes the web to be hot-air dried.

[0011] The drying section further comprises a radiation dryer for radiation drying the web. In other words, during operation, radiation, in particular thermal radiation, is generated in the radiation dryer using one or more radiation elements. The radiation dryer preferably comprises several radiation elements. The web is then irradiated with the radiation and thereby radiation-dried. The radiation dryer is preferably an infrared dryer, or IR dryer for short, which will be assumed below without restriction of generality. An infrared dryer comprises, for example, carbon filaments as radiation elements, through which a current flows, whereby the radiation elements are heated, typically to a temperature of 800°C or more, and accordingly generate thermal radiation.The radiation dryer is also characterized by the fact that it, in particular its radiation elements, are electrically operated, i.e. that electrical energy is used to dry the web.

[0012] The hot air dryer has an air outlet for discharging exhaust air. The exhaust air is, in particular, hot air that has already come into contact with the web in the hot air dryer. Accordingly, the hot air is typically moisture-laden to a certain extent. The radiation dryer has an air inlet for supplying supply air. The air outlet of the hot air dryer is connected to the air inlet of the radiation dryer via a coupling section in order to guide exhaust air from the hot air dryer, at least partially as supply air, into the radiation dryer. The coupling section is, in particular, an air duct along which the exhaust air is guided to the air inlet of the radiation dryer. During operation, the exhaust air from the hot air dryer is then fed to the radiation dryer and used there as supply air. The supply air can be used in the radiation dryer in various ways, as explained further below.More importantly, the exhaust air from the hot air dryer is not simply discarded, but is also utilized in the radiation dryer. This results in a significantly reduced exhaust air flow from the drying section as a whole, making it particularly energy-efficient and cost-effective to operate. Instead of supplying supply air to the hot air dryer and the radiation dryer separately and then discharging exhaust air accordingly (parallel connection), the exhaust air from the hot air dryer is now passed on to the radiation dryer and used there as supply air (series connection), so that correspondingly less supply air is required and less exhaust air is generated. Furthermore, the heat still present in the exhaust air is not discarded but still utilized.

[0013] As already indicated, the exhaust air from the hot air dryer can be profitably used in a radiation dryer in a variety of ways. In a first suitable embodiment, the radiation dryer is designed such that the supply air (as hot air) is directed onto the web for additional hot air drying in the radiation dryer. Analogous to the hot air dryer, the web is then additionally dried with hot air in the radiation dryer; the statements regarding the hot air dryer then also apply analogously to the radiation dryer. The radiation dryer is then, in particular, a radiation dryer with an integrated hot air function and is therefore also referred to as a combination dryer. Due to the additional hot air drying, the radiation dryer has an improved drying rate, which is 30% higher than without the hot air function. In addition, the risk of water condensation in the radiation dryer is reduced due to the now warmer supply air.

[0014] As already mentioned, the radiation dryer has at least one radiation element. In a second suitable embodiment, the radiation dryer is then designed such that the supply air flows around the radiation element (or several or all radiation elements) for cooling. This exploits the fact that the radiation element itself is typically many times warmer than the exhaust air from the hot air dryer, so that cooling of the radiation element is still possible despite the heat contained therein. For example, the hot air in the hot air dryer has a temperature of 200 °C and the exhaust air still has a temperature of 160 °C. The radiation element, on the other hand, has a temperature in the range, for example, from 800 °C to 1400 °C.

[0015] The above-mentioned first and second embodiments are expediently combined with each other, so that the supply air first serves to cool the radiation element, is thereby heated, and then flows onto the web as hot air.

[0016] To generate the hot air, the hot air dryer has, in particular, a heating element with which supply air to the hot air dryer is heated. Various designs are suitable for the heating element, particularly with regard to the form of energy used. For example, the heating element can be a steam register or be operated with a fossil fuel (e.g. gas burner) or with electrical energy (e.g. electric heating register). The latter is preferred. Accordingly, the hot air dryer is preferably an electric hot air dryer, i.e. the heating element is operated with electrical energy and the hot air is generated electrically. In combination with the radiation dryer, which is also electrically operated in principle, a fully electric drying section is then created which does not require any fossil fuels for operation and is correspondingly flexible and potentially particularly climate-friendly.Suitably, the hot air dryer has a stationary operation in which the web is dried at a constant drying capacity, and in this stationary operation, the hot air dryer is operated purely electrically. Stationary operation is particularly suitable when the web speed is also constant, as is typically the case with roll-to-roll operation of the system.

[0017] The combination of a hot air dryer with a radiation dryer (hybrid solution) presented here is also more energy-efficient and less expensive than a drying section that uses only radiation dryers for equivalent drying. While such a drying section typically requires less installation space than the hybrid solution presented here, the latter is less cost-intensive due to the hot air dryer. Due to the hot air dryer, the drying section is also gentler on the paper, especially with a web made of paper with a low grammage (< 120 g / m²). 2), and can still be used even with only a small amount of water applied. As already indicated, the hybrid solution described here can also be operated entirely electrically if required. Due to the thermal inertia of the hot-air dryer compared to the radiation dryer, non-stationary electrical operation of the hot-air dryer is not necessarily optimal due to the typically long required heat-up time. However, this can be compensated for by the additional radiation dryer, so that optimal drying of the web is achieved in fully electric operation even with dynamic changes in the web speed.

[0018] The radiation dryer is preferably arranged downstream of the hot air dryer with respect to a conveying direction of the web. During operation, the web is therefore first dried in the hot air dryer and then dried in the radiation dryer. In particular, studies have shown that with this arrangement, a higher evaporation rate is achieved in the hot air dryer than with a reversed arrangement. The radiation dryer is preferably arranged immediately downstream of the hot air dryer, i.e., no further processing, in particular drying and / or moistening of the web, takes place between these two dryers. Nevertheless, the reverse configuration, in which the radiation dryer is arranged upstream (i.e., not downstream) of the hot air dryer with respect to a conveying direction of the web, is also possible and, in principle, suitable.However, the wiring of the drying section with regard to the routing of exhaust air and supply air remains the same.

[0019] In a suitable embodiment, the drying section has a common fresh air supply, which is connected both to an air inlet of the hot air dryer and to the coupling section and thus to the air inlet of the radiation dryer. In particular, the fresh air supply is connected to the coupling section via a mixing section at a (first) branch. Both dryers can therefore be supplied from the same fresh air supply. This means that fresh air can also be supplied to the radiation dryer when required, which is then mixed in particular with the exhaust air from the hot air dryer, e.g. to suitably adjust the moisture content of the supply air. However, a sole supply of fresh air to the radiation dryer is not intended; the exhaust air from the hot air dryer is primarily used as the supply air for the radiation dryer, and fresh air is preferably only mixed in when required.

[0020] In a suitable embodiment, the drying section has a (first) fan with a suction side connected to the air outlet of the hot air dryer and a pressure side connected to the air inlet of the radiation dryer. The fan thus serves to convey the exhaust air from the hot air dryer to the radiation dryer. Accordingly, the fan is arranged in particular along the coupling section. If - as described above - a supply of fresh air to the radiation dryer is also possible, the fan is preferably arranged upstream of the (first) branch of the coupling section, with the fresh air then being supplied at this branch.

[0021] Downstream of the air outlet of the hot air dryer, a (second) branch is expediently formed to distribute the exhaust air between the air inlet of the radiation dryer and an ambient outlet of the drying section. The ambient outlet serves to discharge exhaust air (in whole or in part) from the hot air dryer to the environment as required, particularly when the exhaust air is not fully used in the radiation dryer or when the radiation dryer is deactivated. The second branch is arranged in particular along the coupling section, in particular upstream or downstream of the first branch, the latter being preferred. This results in the particular advantage that energy-saving drying using exclusively hot air is possible, especially at lower web speeds. In this case, the exhaust air from the hot air dryer is expediently discharged to the environment.At comparatively higher web speeds, the radiation dryer is conveniently connected as a booster and the exhaust air is fed to the radiation dryer accordingly.

[0022] As already described, the hot air dryer has an air inlet. In an advantageous embodiment, this air inlet is connected to the air outlet of the hot air dryer via a recirculation line, so that the hot air dryer can be operated in recirculation mode. In recirculation mode, exhaust air from the hot air dryer is then fully or partially recirculated via the recirculation line to the air inlet, in particular reheated with the heating element, and used again to dry the web. If necessary, fresh air is added. Any remaining exhaust air is guided to the radiation dryer, for example, as described, or discharged to the environment via the ambient outlet. The recirculation line connects, in particular, the coupling line to a supply line of the hot air dryer, which leads to the air inlet of the hot air dryer.

[0023] The recirculation section expediently extends from the aforementioned first branch to a (third) branch of the supply line, and the fresh air supply is also connected to this third branch. The recirculation section is then identical to the mixing section and is accordingly referred to as a recirculation and mixing section. In mixing mode, the air flow direction along the recirculation and mixing section is opposite to the air flow direction in recirculation mode, so that mixing mode and recirculation mode exclude each other. However, a separate design of the recirculation section and the mixing section is also fundamentally suitable.

[0024] The drying section, in particular, comprises one or more control elements, e.g., air dampers, to control the supply and / or distribution of supply air and / or exhaust air as described above, appropriately and depending on the operation. The radiation dryer suitably comprises a (second) fan to discharge exhaust air via an air outlet of the radiation dryer, e.g., to the environment. Optionally, the drying section comprises a further (third) fan, with which exhaust air from the hot air dryer is conveyed into the radiation dryer at a higher static pressure.

[0025] The drying section with the two dryers is particularly suitable for optimised drying of the web at different web speeds, i.e. different operating points of the system. Preferably, the hot air dryer is used primarily and the radiation dryer is only activated at certain web speeds when required. In a correspondingly suitable embodiment, the system is designed such that during operation the web is conveyed at a web speed such that this (i.e. the system) can be switched between slow operation, at a first web speed, and fast operation, at a second web speed, wherein the second web speed is greater than the first web speed. The first web speed is in particular selected from a first speed range which lies below a second speed range from which the second web speed is selected.For example, the second web speed is twice the first web speed. For example, the first web speed is 150 m / min and the second web speed is 300 m / min. The system is further designed such that the radiation dryer is deactivated in slow operation and only activated in fast operation. The radiation dryer thus serves as a booster for high web speeds. The web is therefore only radiation-dried when fast operation is activated. Slow operation is preferably also stationary operation of the system, in particular roll-to-roll operation, and the hot air dryer is then also operated in stationary operation. Despite the radiation dryer being deactivated in this case, the hot air dryer is then advantageously operated purely electrically, which is also possible due to the constant web speed.Fast operation, on the other hand, is particularly a dynamic operation in which the track speed varies, e.g. due to a speed control of the system.

[0026] The method according to the invention serves for operating a system as described above, in particular for operating a drying section as described above. In the method, exhaust air from the hot-air dryer is at least partially fed into the radiation dryer as supply air, ie, it is supplied to the radiation dryer as supply air.

[0027] In the following, exemplary embodiments of the invention are explained in more detail with reference to a drawing. In each case, the following schematically show:

[0028] Fig. 1 a drying section,

[0029] Fig. 2 shows an embodiment of the drying section from Fig. 1 in detail.

[0030] Fig. 1 shows a system 2 having a drying section 4 for drying a printed paper web 6. The system 2 shown here as an example is an inkjet printing system with a printer 8 for printing the web 6 with a print image before drying in the drying section 4. Accordingly, the printer 8 is arranged upstream of the drying section 4 with respect to a conveying direction F of the web 6. During operation, the web 6 is therefore first printed with the printer 8 and then dried with the drying section 4. An exemplary embodiment of the drying section 4 is shown in detail in Fig. 2. The drying section 4 has a hot air dryer 10 for hot air drying the web 6. During operation, hot air H1 is generated in the hot air dryer 10 by supply air Z1 being fed to the hot air dryer 10 and heated by a heating element 12 of the hot air dryer 10. The web 6 is then subjected to the hot air H1, e.g.The hot air H1 is discharged through a plurality of nozzles or through a perforated plate toward the web 6 (not shown). The contact of the hot air H1 with the web 6 causes the web to be hot-air dried.

[0031] The drying section 4 further comprises a radiation dryer 14 for radiation drying the web 6. During operation, radiation W, in this case heat radiation, is generated in the radiation dryer 14 using at least one, here several, radiation elements 16. The web 6 is then irradiated with the radiation W and thereby radiation-dried. The radiation dryer 14 shown here is an infrared dryer, which is characterized by being operated purely electrically.

[0032] In the embodiment shown here, the radiation dryer 14 is arranged downstream of the hot-air dryer 10 with respect to the conveying direction F of the web 6. During operation, the web 6 is thus first dried in the hot-air dryer 10 and then subsequently in the radiation dryer 14.

[0033] The hot air dryer 10 has an air inlet 18 for supplying supply air Z1, and an air outlet 20 for discharging exhaust air A1, which here is hot air H1 that has already come into contact with the web 6. Analogously, the radiation dryer 14 has an air inlet 22 for supplying supply air Z2, and an air outlet 24 for discharging exhaust air A2. The air outlet 20 of the hot air dryer 10 is now connected via a coupling section 26 to the air inlet 22 of the radiation dryer 14 in order to guide exhaust air A1 from the hot air dryer 10 at least partially as supply air Z2 into the radiation dryer 14. The coupling section 26 is, for example, an air duct along which the exhaust air A1 is guided to the air inlet 22 of the radiation dryer 14. During operation, the exhaust air A1 from the hot air dryer 10 is then fed to the radiation dryer 14 and used there as supply air Z2.The supply air Z2 can be used in various ways in the radiation dryer 14, as explained below. The exhaust air A1 from the hot air dryer 10 is therefore not simply discarded, but is also used in the radiation dryer 14.

[0034] In the present case, the radiation dryer 14 is designed such that the supply air Z2 is directed onto the web 6 for additional hot air drying in the radiation dryer 14. Analogous to the hot air dryer 10, the web 6 is then additionally hot air dried in the radiation dryer 14; the statements in this regard regarding the hot air dryer 10 then also apply analogously to the radiation dryer 14. The radiation dryer 14 thus has an integrated hot air function. Furthermore, the radiation dryer 14 is designed such that the supply air Z2 flows around the radiation elements 16 for cooling. This utilizes the fact that the radiation elements 16 are many times warmer than the exhaust air A1 of the hot air dryer 10. However, the hot air function and the cooling of the radiation elements 16 can also be implemented independently of one another (not shown).

[0035] The hot air dryer 10 has a heating element 12 for generating hot air H1, which heats the supply air Z1 to the hot air dryer 10. Various configurations are possible for the heating element 12; in this case, the heating element 12 is an electric heating register, and accordingly, the hot air dryer 10 is an electric hot air dryer. In combination with the also electrically operated radiation dryer 14, a fully electric drying section 4 is then realized.

[0036] The hot air dryer 10 shown here has a stationary operation in which the web 6 is dried at a constant drying performance, and in this stationary operation, the hot air dryer 10 is operated purely electrically. Stationary operation is particularly preferred when the web speed is constant, which is typically the case with roll-to-roll operation of system 2. The combination of a hot air dryer 10 with a radiation dryer 14 (hybrid solution) shown here is operated entirely electrically. Due to the thermal inertia of the hot air dryer 10 compared to the radiation dryer 14, non-stationary electrical operation of the hot air dryer 10 is not necessarily optimal due to the required warm-up time.However, this is compensated for by the additional radiation dryer 14, so that even with dynamic changes in the web speed, optimal drying of the web 6 is achieved in a fully electric operation.

[0037] The drying section 4 shown here also has a common fresh air supply 30, which is connected both to the air inlet 18 of the hot air dryer 10 and to the coupling section 26 and thus to the air inlet 22 of the radiation dryer 14. The fresh air supply 30 is also connected to the coupling section 26 at a first branch 34 via an admixing section, here a recirculation and admixing section 32. Both dryers 10, 14 are therefore supplied from the same fresh air supply 30. However, a sole supply of the radiation dryer 14 with fresh air is not provided in this case; the exhaust air A1 of the hot air dryer 10 is primarily used as supply air Z2 for the radiation dryer 14, and fresh air is only added when required.

[0038] In the embodiment shown here, the drying section 4 has a fan 36 with a suction side connected to the air outlet 20 of the hot air dryer 10 and a pressure side connected to the air inlet 22 of the radiation dryer 14. The fan 36 thus serves to convey the exhaust air A1 from the hot air dryer 10 to the radiation dryer 14. Accordingly, the fan 36 is arranged along the coupling section 26. Furthermore, the fan 36 is arranged upstream of the first branch 34, to which fresh air is supplied as needed.

[0039] Downstream of the air outlet 20 of the hot air dryer 10, a second branch 38 is formed to distribute the exhaust air A1 to the air inlet 22 of the radiant dryer 14 and an ambient outlet 40 of the drying section 4. The ambient outlet 40 serves to discharge exhaust air A1 (in whole or in part) from the hot air dryer 10 to the environment as needed, especially when the exhaust air A1 is not fully used in the radiant dryer 14 or when the latter is deactivated. The second branch 38 is arranged along the coupling section 26 downstream of the first branch 34.

[0040] In the embodiment shown here, the air inlet 18 of the hot air dryer 10 is also connected to the air outlet 20 of the hot air dryer 10 via a recirculating air section, here the recirculating air and mixing section 32, so that the hot air dryer 10 can be operated in recirculating air mode. In recirculating air mode, exhaust air A1 from the hot air dryer 10 is then fully or partially recirculated via the recirculating air section 32 to the air inlet 18, in this case even reheated with the heating element 12, and used again to dry the web 6. If necessary, fresh air is also added. Any remaining exhaust air A1 is guided, as described, for example, to the radiation dryer 14 or discharged to the environment via the ambient outlet 40. The recirculating air section 32 connects the coupling section 26 to a supply line 42 of the hot air dryer 10, which leads to the air inlet 22 of the hot air dryer 10.

[0041] In this case, the recirculation section is identical to the mixing section and is therefore referred to as the recirculation and mixing section 32. In mixing mode, the air flow direction along the recirculation and mixing section 32 is opposite to the air flow direction in recirculation mode, so that mixing mode and recirculation mode exclude each other. The recirculation and mixing section 32 extends from the first branch 34 to a third branch 44 of the supply line 42, and the fresh air supply 30 is also connected to this third branch 44. A separate design of the recirculation section and the mixing section (not shown) is also possible in principle.

[0042] The drying section further comprises one or more control elements 46, e.g., air dampers, for controlling the supply and / or distribution of supply air Z1, Z2 and / or exhaust air A1, A2 as described above, as appropriate and depending on operation. Furthermore, the radiation dryer 14 also comprises a second fan 48 for discharging exhaust air A2 from the radiation dryer 14 via its air outlet 24, e.g., to the environment.

[0043] The drying section 4 is suitable for drying the web 6 at different web speeds, i.e. different operating points of the system 2. In the present case, the hot air dryer 10 is primarily used and the radiation dryer 14 is only activated at certain web speeds when required. In one possible embodiment, the system 2 is designed such that during operation the web 6 is conveyed at a web speed such that this (i.e. the system 2) can be switched between slow operation, with a first web speed, and fast operation, with a second web speed, wherein the second web speed is greater than the first web speed. The system 2 is further designed such that the radiation dryer 14 is deactivated in slow operation and only activated in fast operation. The radiation dryer 14 thus serves as a booster for high web speeds.Web 6 is thus only radiation-dried when fast operation is activated. Slow operation here also represents stationary operation of system 2, e.g., roll-to-roll operation, and hot-air dryer 10 is also operated in stationary mode. Despite the radiation dryer 14 being deactivated, hot-air dryer 10 is then operated purely electrically, which is also possible due to the constant web speed. Fast operation, on the other hand, is dynamic operation in which the web speed varies, e.g., due to a speed control of system 2.

[0044] To carry out one or more of the steps described above, the system 2 has a control unit 50, which controls the drying section 4 and, if necessary, other parts of the system 2 accordingly. List of reference symbols

[0045] 2 Appendix

[0046] 4 T drying section

[0047] 6 tracks (made of paper)

[0048] 8 printers

[0049] 10 hot air dryers

[0050] 12 Heating element

[0051] 14 radiation dryers

[0052] 16 Radiation element

[0053] 18 Air inlet (hot air dryer)

[0054] 20 Air outlet (hot air dryer)

[0055] 22 Air inlet (radiation dryer)

[0056] 24 Air outlet (radiation dryer)

[0057] 26 coupling section

[0058] 30 Fresh air supply

[0059] 32 Recirculation and mixing section

[0060] 34 first junction

[0061] 36 first fan

[0062] 38 second junction

[0063] 40 Ambient outlet

[0064] 42 Pre-run (hot air dryer)

[0065] 44 third branch

[0066] 46 Control element

[0067] 48 second fan

[0068] 50 control unit

[0069] A1 Exhaust air (hot air dryer)

[0070] A2 Exhaust air (radiation dryer)

[0071] F Conveying direction

[0072] H1 Hot air (hot air dryer)

[0073] H2 hot air (radiation dryer)

[0074] W radiation

[0075] Z1 Supply air (hot air dryer) Z2 Supply air (radiation dryer)

Claims

Claims 1. A system (2) having a drying section (4) for drying a printed paper web (6), a. wherein the drying section (4) has a hot-air dryer (10) for hot-air drying the web (6), b. wherein the drying section (4) has a radiation dryer (14) for radiation drying the web (6), c. wherein the hot-air dryer (10) has an air outlet (20) for discharging exhaust air (A1), d. wherein the radiation dryer (14) has an air inlet (22) for supplying supply air (Z2), e. wherein the air outlet (20) is connected to the air inlet (22) via a coupling section (26) in order to guide exhaust air (A1) from the hot-air dryer (10) at least partially as supply air (Z2) into the radiation dryer (14).

2. Plant (2) according to claim 1, wherein the radiation dryer (14) is an infrared dryer.

3. Plant (2) according to claim 1 or 2, wherein the radiation dryer (14) is designed such that the supply air (Z2) is flowed onto the web (6) for additional hot air drying in the radiation dryer (14).

4. Plant (2) according to one of claims 1 to 3, wherein the radiation dryer (14) has at least one radiation element (16) and is designed such that the supply air (Z2) flows around it for cooling.

5. Plant (2) according to one of claims 1 to 4, wherein the hot air dryer (10) is an electric hot air dryer.

6. Plant (2) according to one of claims 1 to 5, wherein the hot air dryer (10) has an electric heating element (12) to generate hot air (H1) for hot air drying.

7. Plant (2) according to one of claims 1 to 6, wherein the radiation dryer (14) is arranged downstream of the hot air dryer (10) with respect to a conveying direction (F) of the web (6).

8. Plant (2) according to one of claims 1 to 7, wherein the drying section (4) has a common fresh air supply (30) which is connected both to an air inlet (18) of the hot air dryer (10) and to the coupling section (26) and thus to the air inlet (22) of the radiation dryer (14).

9. Plant (2) according to one of claims 1 to 8, wherein the drying section (4) has a fan (36) with a suction side which is connected to the air outlet (20) of the hot air dryer (10) and with a pressure side which is connected to the air inlet (22) of the radiation dryer (14).

10. System (2) according to one of claims 1 to 9, wherein a branch (38) is formed downstream of the air outlet (20) of the hot air dryer (10) in order to distribute the exhaust air (A1) to the air inlet (22) of the radiant dryer (14) and an ambient outlet (40).

11. System (2) according to one of claims 1 to 10, wherein the hot air dryer (10) has an air inlet (18) which is connected to the air outlet (20) of the hot air dryer (10) via a recirculation path (32), so that the hot air dryer (10) can be operated in a recirculation mode.

12. Plant (2) according to one of claims 1 to 11, This is an inkjet printing system.

13. Installation (2) according to one of claims 1 to 12, wherein it is designed such that a. in operation the web (6) is conveyed at a web speed, b. that it can be switched between a slow operation, with a first web speed, and a fast operation, with a second web speed, wherein the second web speed is greater than the first web speed, c. that the radiation dryer (14) is deactivated in slow operation and is only activated in fast operation.

14. Drying section (4) for a plant (2) according to one of claims 1 to 13.

15. Method for operating a system (2) according to one of claims 1 to 13, wherein exhaust air (A1) from the hot air dryer (10) is at least partially guided as supply air (Z2) into the radiation dryer (14).

Images