Stretching unit and film production system

Abstract

The invention relates to a stretching unit and a film production system. The invention relates to a stretching unit, in particular a transverse direction orientator and / or a synchronous stretching unit, for stretching a film, said stretching unit comprising an oven (26) and a heat recovery system (28). The heat recovery system (28) comprises: a heat exchanger (34) having an exhaust air conduit (46) for exhaust air from the oven (26), a supply air conduit (44) for supply air supplied to the oven (26), a plurality of heat conductors (48) and a plurality of heat collectors (50); and a condensate collector (52). The exhaust air duct (46) is open towards the condensate collector (52), the heat collectors (50) are located in the exhaust air duct (46), a gap (68) exists between adjacent heat collectors (50), the heat conductor (48) is thermally connected to the heat collectors (50), and the gap (68) is open towards the condensate collector (52). Furthermore, a film production system (10) is shown.

Description

Technical Field

[0001] The present invention relates to a stretching unit and a film production system. Background Art

[0002] Film production systems are known and generally comprise at least one stretching unit.

[0003] The production of plastic film in such systems is very energy-intensive due to the high temperatures required in the ovens of the stretching units.

[0004] At the same time, fresh air must be continuously fed into the oven, and exhaust air must be extracted to reduce contamination within the oven. This contamination occurs, among other things, as various substances (primarily hydrocarbons) escape from the film as it passes through the oven. Since the incoming fresh air must be heated to oven temperature, this air exchange is associated with a high heating energy requirement.

[0005] It is known to provide membrane production systems with heat exchangers for heat recovery. However, in such systems, substances contained in the oven air condense on the heat exchanger during cooling and settle on the exhaust air side of the heat exchanger surface, which poses a problem. This reduces the efficiency of the heat exchanger and necessitates laborious cleaning of the heat exchanger. Summary of the Invention

[0006] It is therefore an object of the present invention to provide a stretching unit and a film production system which are particularly energy-efficient and at the same time have low maintenance costs.

[0007] This object is achieved by a stretching unit for stretching a film, in particular a transverse direction orienter and / or a simultaneous stretching unit, comprising an oven and a heat recovery system. The heat recovery system comprises a condensate collector and a heat exchanger having an exhaust air duct for exhaust air from the oven, a supply air duct for supply air to the oven, a plurality of heat conductors, and a plurality of heat collectors.

[0008] The supply air duct and the exhaust air duct are fluidly separated from each other by a partition, and a thermal conductor extends from the exhaust air duct through the partition into the supply air duct, wherein the exhaust air duct faces the condensation collector. The heat collectors are located in the exhaust air duct, wherein a gap exists between adjacent heat collectors, and the thermal conductors are thermally connected to the heat collectors, wherein the gap opens toward the condensation collector.

[0009] The heat collector achieves a higher degree of efficiency in the heat exchanger. At the same time, the condensate that settles is reliably transported away via the condensate collector, as the gap is open to the condensate collector. As a result, a high degree of efficiency is always maintained, without the need for cleaning and, therefore, maintenance.

[0010] For example, each heat collector is thermally connected to at least one or more or all heat conductors.

[0011] The supply air, in particular fresh air, comes from the environment of the stretching unit.

[0012] In an embodiment, a plurality of radiators are provided in the supply air duct, said radiators being designed identically to the heat collectors.

[0013] In an embodiment, the exhaust air duct defines a flow path for an air flow of the exhaust air, wherein the condensation collector is located outside the flow path. In this way, condensation is avoided from being carried away from the heat exchanger by the air flow.

[0014] In order to further improve the removal of condensate from the gap, a condensate collector can be arranged at least partially below the exhaust air duct, in particular below the flow path.

[0015] In the context of the present disclosure, the term "below" is understood to be relative to the assembly location of the provided heat recovery system. In particular, "below" refers to vertically directly below without additional horizontal offset.

[0016] In an embodiment, the exhaust air duct comprises a condensation outlet opening, which is part of the condensation collector, in particular wherein the exhaust air duct comprises a base and the at least one condensation outlet opening is arranged in the base. In this way, collected condensation can be reliably removed from the exhaust air duct.

[0017] For example, the base can be designed horizontally or as a channel.

[0018] In an embodiment, the condensation collector comprises a tray, in particular, wherein the tray can be removed from the condensation collector for emptying. As a result, the condensation can be collected reliably and in particular can be disposed of simply.

[0019] In order to further reduce maintenance, the heat recovery system may comprise a condensate drain, and the condensate collector may be fluidically connected to the condensate drain, in particular via a siphon.

[0020] In order to further improve the efficiency of the heat exchanger, the heat collector may be designed in a plate shape, and the heat conductor may extend through the heat collector.

[0021] For example, each heat conductor extends through at least one, a plurality of or all heat collectors, in particular vertically.

[0022] In an embodiment, the collectors run parallel to each other and / or parallel to the partitions in order to reduce flow resistance.

[0023] In order to reliably drain away any condensation at the collector, the heating conductor can run horizontally or be arranged at an angle of between 0° and 10° to the horizontal, in particular wherein the section of the heating conductor in the exhaust air duct is lower than the section in the supply air duct.

[0024] For example, the angle is 4°.

[0025] In an embodiment, the gap includes a direction of air flow and a direction of condensate flow, wherein the direction of the air flow and the direction of the condensate flow run parallel to each other, in particular, wherein the direction of the air flow and the direction of the condensate flow run vertically or are oriented at an angle of between 0° and 10° to the vertical. In this way, the removal of condensate from the gap is supported by the air flow.

[0026] The direction of the condensate flow is, for example, the direction in which the condensate formed at the heat collector can flow unhindered, apart from the heat conductor. The direction of the condensate flow is particularly downward.

[0027] The heat conductors can extend perpendicularly to the direction of the air flow and / or the direction of the condensate flow in the region of the heat collector.

[0028] In an embodiment, the gap includes a direction of the air flow and a direction of the condensate flow, wherein the direction of the air flow and the direction of the condensate flow run perpendicular to each other, in particular, wherein the direction of the air flow runs horizontally and / or the direction of the condensate flow runs vertically or is oriented at an angle of between 0° and 10° to the vertical. This further reduces the amount of condensate transported to the environment by the air flow.

[0029] To further increase the efficiency, the heat conductor may be a heat transfer device, in particular a heat pipe.

[0030] In an embodiment, the oven comprises a supply air inlet fluidly connected to the supply air duct of the heat exchanger and / or the oven comprises an exhaust air outlet fluidly connected to the exhaust air duct of the heat exchanger, so that a direct and efficient connection of the heat recovery system to the oven is achieved.

[0031] For example, a fluid connection occurs via a pipe.

[0032] In order to perform temperature control on the supply air, the heat recovery system may include a heating register.For example, the heating register may be fluidly arranged between the supply air duct of the heat exchanger and the supply air inlet of the oven.

[0033] The supply air blower is for example located between the supply air duct of the heat exchanger and / or the heating regulator and the supply air inlet of the oven.The exhaust air blower is for example located downstream of the exhaust air duct of the heat exchanger.

[0034] This object is also achieved by a film production system comprising at least one stretching unit as described above and one further stretching unit, extrusion unit, casting roll system, draw roll unit and / or winder unit.

[0035] The features and advantages described for the stretching unit also apply to the film production system, and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Other features and advantages of the present invention are found in the following description and in the accompanying drawings to which reference is made. In the drawings:

[0037] Figure 1 A film production system according to an embodiment of the present invention is shown in a schematic perspective view, the film production system comprising at least a stretching unit according to an embodiment of the present invention,

[0038] Figure 2 Shown according to Figure 1 A scaled-up representation of the heat recovery system of a stretching unit,

[0039] Figure 3 and Figure 4 Shown according to Figure 2 A schematic cross-sectional view of a heat exchanger of a heat recovery system,

[0040] Figure 5 shows a perspective view of a heat exchanger of a stretching unit according to a second embodiment of the invention,

[0041] Figure 6 A cross-sectional view showing a heat exchanger of a heat recovery system of a stretching unit according to a third embodiment of the present invention. DETAILED DESCRIPTION

[0042] exist Figure 1 In FIG, a membrane production system 10 is shown very schematically, comprising several different units and devices.

[0043] In the example shown, the film production system 10 includes an extrusion unit 12 , a cast roll system 14 , at least one stretching unit 15 such as a machine direction orienter 16 (MDO) or a transverse direction orienter 18 (TDO), a draw roll unit 20 , and a winder unit 22 .

[0044] The films produced are, for example, biaxially oriented films, such as polypropylene films (BOPP), PP capacitor films (BOPP-C), polyethylene terephthalate films (BOPET), polyamide films (BOPA), polyethylene films (BOPE), polylactic acid films (BOPLA).

[0045] To produce the plastic film, the film is formed on a cooling roller of a casting roll system 14 by an extrusion unit 12. To this end, the extrusion unit 12 generates a melt from a starting product (eg granular material), which is applied to the cooling roller and thus forms the film.

[0046] The film is transferred from the casting roll system 14 to a machine direction orienter 16. In the machine direction orienter 16, the film is stretched in the machine direction in order to obtain a stretched film.

[0047] In the machine direction orienter 6, the film travels over a plurality of rollers that are heated in order to heat the film to the desired temperature at which the film can be stretched.

[0048] Between at least two of the rolls present in the machine direction orienter 16 , stretching is performed in the machine direction, that is, in the drawing direction, so that the film becomes a stretched film.

[0049] The obtained film is transferred by the machine direction orienter 16 to the transverse direction orienter 18 and stretched in the transverse direction in the transverse direction orienter 18 .

[0050] Along the draw direction of the film production system 10, the transverse direction orienter 18 has an oven that includes different zones for processing the film.

[0051] The film is heated in a first zone, also referred to as a preheating zone. In a subsequent second zone ("stretching zone"), the film is stretched in the transverse direction so that at the end of the second zone, the film is wider and thinner than at the beginning.

[0052] After stretching is complete, the film then passes through a third and further zone (referred to as a "heat treatment zone," "another heating zone," and / or "annealing zone") where, for example, relaxation of the film can occur at elevated temperatures.

[0053] Subsequently, the film passes through another zone (“cooling zone”), whereby the film is cooled in the final zone.

[0054] The other area is called the neutral area and is used to separate the areas. The neutral area is, for example, an empty space without any ventilation.

[0055] The area of ​​the transverse direction director 18 can also be divided differently and / or designed differently in its length. For example, a smaller or shorter neutral area can be provided, or the neutral area can be additionally arranged at other locations. Variations of the remaining areas can also be envisioned.

[0056] After the transverse direction orienter 18 , the now biaxially stretched film runs through a draw roll unit 20 and is wound by a winder unit 22 .

[0057] It is also conceivable to design the film production system 10 in another way, for example, comprising a synchronous stretching unit 19 with an oven 26 as an alternative or in addition to the machine direction orienter 16 and / or the transverse direction orienter 18 .

[0058] Within the scope of the present invention, a stretching unit 15 is now outlined, which can be a transverse direction orienter or a simultaneous stretching unit, or also a combination of these.

[0059] The stretching unit 15 , and more particularly its oven 26 , continuously requires a supply of air during operation, in particular fresh air, in order to be able to extract contaminated exhaust air in return.

[0060] In order to be able to utilize the waste heat from the exhaust air, the stretching unit 15 comprises a heat recovery system 28 .

[0061] exist Figure 2 In FIG. 1 , one of the heat recovery systems 28 is enlarged, but the stretching unit 15 may also include several of the heat recovery systems.

[0062] It can be seen that the oven 26 includes a supply air inlet 30 and an exhaust air outlet 32 ​​, both of which are fluidly connected to the heat recovery system 28 .

[0063] The heat recovery system 28 includes a heat exchanger 34 , a supply air blower 36 , an exhaust air blower 38 , a heating regulator 40 , ducting 42 , and a condensate collector 52 .

[0064] The heat exchanger 34 has a supply air duct 44 and an exhaust air duct 46 which are fluidically separated from one another and are each fluidically connected via a pipe 44 to the supply air inlet 30 or the exhaust air outlet 32 ​​of the oven 26 , respectively.

[0065] The supply air duct 44 of the heat exchanger 34 opens upstream with respect to the supply air flow towards the environment of the oven 26 and the heat recovery system 28. Optionally, an air filter is provided on this side.

[0066] Downstream, the supply air duct 44 of the heat exchanger 34 is fluidly connected to the heating regulator 40 and the supply air blower 36, which are arranged between the supply air duct 44 and the supply air inlet 30. For example, the supply air blower 36 is arranged downstream of the heating regulator 40 such that the heating regulator 40 is located between the heat exchanger 34 and the supply air blower 36.

[0067] The exhaust air blower 38 may be located downstream of the exhaust air conduit 46 of the heat exchanger 34 relative to the exhaust air flow such that the heat exchanger 34 is fluidly located between the exhaust air blower 38 and the exhaust air outlet 32 ​​of the oven 26 .

[0068] It is also conceivable that the exhaust air blower 38 is located between the exhaust air outlet 32 ​​and the heat exchanger 34 .

[0069] exist Figure 3 and Figure 4 In FIG, a heat exchanger 34 of the heat recovery system 28 is shown simplified in a longitudinal view and in a section, each orthogonal to the flow direction.

[0070] In addition to the supply air duct 44 and the exhaust air duct 46 , the heat exchanger 34 includes a plurality of heat conductors 48 , a plurality of heat collectors 50 and partitions 54 .

[0071] For the sake of clarity, only a few heat conductors 48 and a few heat collectors 50 are shown in the figures in order to explain the basic principle. It is conceivable that significantly more heat conductors 48 and / or heat collectors 50 are provided.

[0072] exist Figure 3 and Figure 4 In FIG. 3 , the heat exchanger 34 is shown in the provided assembly position so that the part shown lying below with respect to gravity is also arranged below in the drawing.

[0073] In the heat exchanger 34, the supply air duct 44 and the exhaust air duct 46 are directly adjacent to each other. The supply air duct 44 is fluidly separated from the exhaust air duct 46 by a partition 54.

[0074] The exhaust air duct 46 defines an air flow S for exhaust air. A The air flow S of the exhaust air in the exhaust air duct 46 A The direction of the supply air and the air flow S of the supply air in the supply air duct 44 ZIt is conceivable that the air flow S of the exhaust air in the exhaust air duct 46 is antiparallel to each other. A The direction of the supply air and the air flow S of the supply air in the supply air duct 44 Z directions parallel to each other.

[0075] In the first embodiment, the air flow S of the exhaust air in the exhaust air duct 46 is A The direction and air flow S of the supply air duct 44 Z Move horizontally in the direction of .

[0076] The condensation collector 52 is located below the exhaust air duct 46, and the exhaust air duct 46 is open toward the condensation collector 52. The condensation collector 52 is located outside the flow path, in particular, below the flow path.

[0077] The condensate collector 52 can be realized at least partially, in particular completely, by a condensate outflow opening 56 provided in a base 58 of the exhaust air duct 46. The base 58 can be designed as a channel here.

[0078] In this respect, below particularly means that at least a portion of the condensation collector 52 or the entire condensation collector 52 is located directly below at least a portion of the exhaust air duct 46 or the entire exhaust air duct 46 , ie following the force of gravity.

[0079] The condensate collector 52 further comprises a tray 60, which is located, for example, below the condensate outflow opening 56. To drain the tray 60, the heat recovery system 28 may comprise a condensate drain 62, such as Figure 3 The condensate drain 62 is connected to the condensate collector 52 by a siphon 64, for example. Figure 3 The middle fluid is connected to the tray 60.

[0080] The heat conductor 48 is designed as a heat transfer device, for example, in particular as a heat pipe.

[0081] The heat conductors 48 are each located partially in the supply air duct 44 and partially in the exhaust air duct 46. Thus, they extend from the exhaust air duct 46 through the partition 54 into the supply air duct 44. A and S Z direction, the heat pipe 48 runs vertically.

[0082] The heat conductor 48 can run along the horizontal direction H or as Figure 3The diagram shows an angle α of 0° to 10° with respect to the horizontal direction H. For example, the angle is 4°. The heat conductors 48 rise toward the supply air duct 44 , so that the section of each heat conductor 48 located in the exhaust air duct 46 is lower than the section of the same heat conductor 48 located in the supply air duct 44 .

[0083] The heat collectors 50 are located in the exhaust air duct 46 and are designed in the form of plates in the illustrated embodiment. They are arranged parallel to each other and run, for example, parallel to the partition 54.

[0084] The heat collector 50 is along the air flow S A and extends along the vertical direction V or at an angle β with the vertical direction V between 0° and 10°.

[0085] The heat collectors 50 extend perpendicularly to the heat conductors 46, wherein they are thermally connected to one, a plurality of or all heat conductors 48. One, a plurality of or all heat conductors extend, for example, through one of the heat conductors 50 and are thermally connected to it.

[0086] Similarly, each of the thermal conductors 48 is thermally connected to one, more than one, or all of the thermal conductors 50 .

[0087] In the same manner as the heat collector 50, a plurality of radiators 66 are provided in the supply air duct 44, wherein for the sake of clarity, the heat sinks 66 are shown in FIG. Figure 3 Only one of the heat sinks 66 is shown in FIG.

[0088] The heat collectors 50 are parallel to one another, so that in each case a gap 68 is formed between two adjacent heat collectors 50. The gap 68 therefore runs in the same direction as the heat collectors 50.

[0089] Due to the arrangement of the collector, the gap 68 is along the air flow S A Therefore, the air flow S A The direction can also be assigned to the gap 68, exhausting the air along the air flow S A direction into the gap 68.

[0090] Similarly, the gap 68 opens toward the condensation collector 52 , ie downwardly.

[0091] The gap 68 includes the direction of the condensate flow F, which describes the direction in which the condensate emerging from the exhaust air flows over the heat collector 50. The direction of the condensate flow F runs, for example, downward and has a predominantly downward component, ie in the direction of gravity.

[0092] The gap 68 also extends along the vertical direction V or at an angle β to the vertical direction V, just like the heat collector 50. Figure 3In the example shown in FIG. 4 , the heat conductor 46 extends perpendicularly to the direction of the condensate flow F.

[0093] In accordance with Figure 3 In the example, the direction of the condensate flow F is perpendicular to the air flow S A Go in the direction of .

[0094] During operation of the film production system 10 and the stretching unit 15 , and thus the heat recovery system 28 , warm air is conveyed from the oven 26 through the exhaust air duct 46 by the exhaust air blower 38 .

[0095] This exhaust air contains, for example, hydrocarbons which condense rapidly upon cooling.

[0096] The warm exhaust air thus follows the air flow S A The exhaust air flows in the direction of 48 through the exhaust air duct 46 of the heat exchanger 34 and there contacts the heat collector 50 and the heat conductor 48. Subsequently, the exhaust air is conveyed through the exhaust air blower 38 into the environment of the stretching unit 15.

[0097] In the exhaust air duct 46 , the exhaust air transfers heat to the heat conductor 48 and the heat collector 50 , which has a lower temperature than the exhaust air.

[0098] This dissipated heat is conveyed through the heat collector 50 and then via the heat conductor 48 into the supply air duct 44 .

[0099] Supply air, in particular, a fresh air flow, delivered by the supply air blower 36 passes through the supply air duct 44 .

[0100] In the supply air duct 44, the supply air is heated by contact with the heat conductor 48 and the heat sink 66, which are at a higher temperature than the supply air. The supply air then passes through the heating regulator 40 and is heated to the required oven temperature before entering the oven 26 through the supply air inlet 30.

[0101] In the exhaust air duct 46, as described, the exhaust air is cooled at the heat collector 50. Hydrocarbons found in the air condense due to this cooling and form condensation on the heat collector 50 and the heat conductor 48.

[0102] Due to the arrangement of the heat collector 50 and the gap 68 , the condensate can flow downwards, ie in the direction of the condensate flow F, without obstruction except across the heat conductor 48 .

[0103] Once the condensate reaches the lower end of the heat collector 50, it may drain or flow away from the heat collector 52 and be collected by the condensate collector 52. The condensate may then be disposed of through the condensate drain 62.

[0104] In this way, it is ensured that no condensate remains in the exhaust air duct 46 and in particular in the gap 68, which could otherwise become blocked. In this way, a very high degree of efficiency of the heat exchanger 34 is ensured without requiring complex maintenance work.

[0105] The heat recovery system 28 is therefore extremely efficient and at the same time low-maintenance.

[0106] exist Figure 5 and Figure 6 , further embodiments of the heat recovery system 28 and thus the stretching unit 15 and the film production system 10 are shown. These correspond substantially to the first embodiment, so that only the differences are described hereinafter and identical and functionally equivalent components are denoted by the same reference numerals.

[0107] Figure 5 A perspective view of a portion of a second embodiment of a heat exchanger 34 is shown.

[0108] In this embodiment, the tray 60 of the condensation collector 52 can be removed, ie removed from below the exhaust air duct 46. In this way, the tray 60 can be easily emptied without the need to provide a dedicated condensation drain 62.

[0109] exist Figure 5 In FIG. 4 , the condensate outflow opening 56 can be clearly seen in the base 58 of the exhaust air duct 46 .

[0110] For example, the condensate outflow opening 56 is provided on the downstream edge of the base 58 so that the air flow S A Condensate draining off on the base is conveyed to the condensate outflow opening 56 .

[0111] exist Figure 6 , a third embodiment of a heat recovery system 28 is shown.

[0112] In this embodiment, the air flow S of the exhaust air or supply air A 、S Z The direction of the heat transfer element is not horizontal, but vertically toward the heat collector 50 and the heat conductor 48.

[0113] Below the heat collector 50 and the heat conductor 48, the exhaust air duct 46 runs horizontally and / or deviates from the heat exchanger 34, so that the flow path changes direction (by Figure 6 Indicated by the arrows in the figure).

[0114] The condensate collector 52 is located below the point where the flow path performs a change of direction.

[0115] The condensation collector can be designed according to the description of the above embodiment.

[0116] The arrangement of the heat collector 50 and the heat conductor 48 in the supply air duct 44 corresponds to that of the first embodiment, so that the gap 68 remains open toward the condensation collector 52 .

[0117] In this embodiment, the air flow S A The direction of the condensate flow F now runs parallel to each other in the area of ​​the collector 50.

[0118] Air flow S A The direction of the condensate flow F runs along the vertical direction V or forms an angle β between 0° and 10° with the vertical direction V as shown in the figure.

[0119] Because the air flow S A The direction of the condensate flow F and the direction of the condensate flow F run in a parallel manner, so the removal of condensate from the gap 68 is improved in this embodiment.

[0120] The different features of the various embodiments can be combined with one another, in particular the use of the removable tray 60 , the condensation drain 62 and / or the location of the condensation outflow opening 56 in the base 58 .

Claims

1. A stretching unit for stretching a film, in particular a transverse direction orienter and / or a synchronous stretching unit, said stretching unit comprising an oven (26) and a heat recovery system (28), in, The heat recovery system (28) comprises a condensate collector (52) and a heat exchanger (34) having an exhaust air duct (46) for exhaust air from the oven (26), a supply air duct (44) for supply air to the oven (26), a plurality of heat conductors (48) and a plurality of heat collectors (50), wherein the supply air duct (44) and the exhaust air duct (46) are fluidically separated from each other by a partition (54), and the heat conductor (48) extends from the exhaust air duct (46) through the partition (54) into the supply air duct (44), wherein the exhaust air duct (46) opens toward the condensate collector (52), and The heat collectors (50) are located in the exhaust air duct (46), wherein gaps (68) exist between adjacent heat collectors (50), and the heat conductors (48) are thermally connected to the heat collectors (50), wherein the gaps (68) are open toward the condensation collector (52).

2. The stretching unit according to claim 1, characterized in that The exhaust air duct (46) defines an air flow (S A ) of the flow path, wherein the condensate collector (52) is located outside the flow path.

3. The stretching unit according to claim 1 or 2, characterized in that The condensate collector (52) is located at least partially below the exhaust air duct (46), in particular below the flow path.

4. The stretching unit according to claim 1, wherein The exhaust air duct (46) comprises a condensate outlet opening (56), which is part of the condensate collector (52), in particular, wherein the exhaust air duct (46) comprises a base (58) and the at least one condensate outlet opening (56) is arranged in the base (58).

5. The stretching unit according to claim 1, wherein The condensation collector (52) comprises a tray (60), in particular, wherein the tray (60) is removable from the condensation collector (52) for emptying.

6. Stretching unit according to any one of the preceding claims, characterized in that The heat recovery system (28) comprises a condensate drain (62), and the condensate collector (52) is fluidically connected to the condensate drain (62), in particular via a siphon (64).

7. Stretching unit according to any one of the preceding claims, characterized in that The heat collector (50) is plate-shaped, and the heat conductor (48) extends through the heat collector (50).

8. Stretching unit according to any one of the preceding claims, characterized in that The heat collectors (50) run parallel to each other and / or parallel to the partitions (54).

9. Stretching unit according to any one of the preceding claims, characterized in that The heating conductor (48) runs horizontally and / or is arranged at an angle (α) between 0° and 10° to the horizontal (H), in particular, wherein a section of the heating conductor (48) in the exhaust air duct (46) is lower than a section in the supply air duct (44).

10. The stretching unit according to claim 1, wherein The gap (68) includes an air flow (S A ) direction and the direction of the condensate flow (F), wherein the air flow (S A ) and the direction of the condensate flow (F) are parallel to each other, in particular, wherein the air flow (S A ) and the direction of the condensate flow (F) are vertical or arranged at an angle (β) between 0° and 10° to the vertical direction (V).

11. The stretching unit according to any one of claims 1 to 9, characterized in that The gap (68) includes an air flow (S A ) direction and the direction of the condensate flow (F), wherein the air flow (S A ) and the direction of the condensate flow (F) are perpendicular to each other, in particular, wherein the air flow (S A ) is horizontally directed and / or the condensate flow (F) is vertically directed or arranged at an angle (β) between 0° and 10° to the vertical direction (V).

12. Stretching unit according to any one of the preceding claims, characterized in that The heat conductor (48) is a heat transfer device, in particular a heat pipe.

13. Stretching unit according to any one of the preceding claims, characterized in that The oven (26) comprises a supply air inlet (30) which is fluidically connected to the supply air duct (44) of the heat exchanger (34), and / or the oven (26) comprises an exhaust air outlet (32) which is fluidically connected to the exhaust air duct (46) of the heat exchanger (34).

14. Stretching unit according to any one of the preceding claims, characterized in that The heat recovery system (28) comprises a heating regulator (40), in particular wherein the heating regulator fluid is arranged between the supply air duct (44) of the heat exchanger (34) and the supply air inlet (30) of the oven (26).

15. A film production system comprising at least one stretching unit (15) according to any one of the preceding claims and further stretching units (15), extrusion units (12), cast rolling systems (14), draw roll units (20) and / or winder units (22).

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