Method for recovering process heat, plant for stretching, and apparatus for producing and stretching a plastic film

Abstract

The invention relates to a method for recovering process heat from the waste heat of a plant (300) for stretching plastic films (F). It is characterized in that the waste heat generated in the stretching process is at least partially recovered by means of a heat pump (500). A plant (300) for stretching a plastic film, which film moves during stretching through successive plant sections in the direction of movement (B) of the plastic film (F), comprises for this purpose at least one exhaust air duct, wherein an exhaust air stream (600) in the at least one exhaust air duct is in direct or indirect operative connection, via a heat pump (500), with a heat transfer medium to be heated which circulates in a heating circuit (400) for providing process heat.

Description

[0001] PA23015W0

[0002] November 7, 2025

[0003] 1

[0004] Method for recovering process heat, system for stretching and equipment for producing and stretching a plastic film

[0005] The invention relates to a method for recovering process heat from the waste heat of a plastic film stretching system. The invention also relates to a plastic film stretching system which, during the stretching process, moves at least once through successive system components in the direction of movement of the plastic film, with at least one exhaust air duct. Furthermore, the invention relates to a device for producing and stretching a plastic film, comprising a production unit for the plastic film and a stretching system.

[0006] In principle, it is known to use the high energy required for stretching plastic films as optimally as possible and to release as little of this energy as possible unused back into the environment in the form of heat energy.

[0007] EP 3 650 199 B1 describes a film stretching plant in which exhaust air from the first treatment zones of the plant is recirculated to other treatment zones. This exhaust air contains a significant amount of thermal energy. However, it is fed directly to the first treatment zones, which can lead to an accumulation of oligomers in these zones. This impairs the quality of the plastic films.

[0008] From EP 2 576 188 B1, a device for drawing a film from synthetic material is known, in which energy recovered from the exhaust air of the system by means of a water cycle is supplied to a heating area. This allows at least some of the waste heat to be recovered.

[0009] For further general information on the state of the art, reference can also be made to EP 3 260 271 A1. This describes a manufacturing process for a microporous PA23015W0 07.11.2025

[0010] 2

[0011] Plastic film. It is generally described that a chiller can be used to cool the casting roller. Furthermore, JP 08025459 A describes a chiller process that runs automatically within the casting roller to cool the surface area relevant for cooling the plastic film.

[0012] The object of the present invention is to provide an energy-optimized method for recovering process heat, as well as a suitable system and an application for it.

[0013] According to the invention, this problem is solved by the method with the features in claim 1. Advantageous embodiments and further developments of the method are described in the dependent claims. Furthermore, a system with the features in claim 13 solves the problem. Advantageous embodiments and further developments of this system are also described in the dependent claims. Finally, a device for producing and stretching a plastic film with such a system also solves the problem.

[0014] The inventive method provides for the recovery of process heat from waste heat via a heat pump. A system for stretching plastic films according to the inventive method is understood to be a system in which the plastic films are stretched longitudinally and / or transversely. Typical for such systems are temperatures of 70 to 140°C during the stretching of the plastic film, as well as correspondingly higher temperatures during the so-called thermosetting, a processing step that concludes the stretching process and in which the properties created by the longitudinal and / or transverse stretching are fixed, so that the plastic film retains these properties even after cooling. Waste heat generated in such a stretching process can therefore be used to recover at least some of it via a heat pump.Recovery within the meaning of the invention refers to the use of PA23015W0 07.11.2025.

[0015] The recovered heat should be understood as process heat, meaning it should not be used for other purposes, such as building heating or similar. In principle, the use of other waste heat sources would also be conceivable. For example, hot air, gas, and / or liquid flows could be used, which are generated as waste heat from manufacturing and / or processing, or as combustion waste heat.

[0016] The use of a heat pump transfers heat from the medium containing waste heat, such as exhaust air from the stretching process. Unlike the prior art mentioned earlier, the medium itself is not recycled; only the thermal energy it contains is returned. Therefore, an accumulation of oligomers, which can impair the quality of the plastic films, does not occur.

[0017] The method according to the invention is particularly suitable when the waste heat is generated at a relatively high temperature level, such as in an exhaust air stream from the area of ​​the aforementioned thermal fixation process. A particularly advantageous embodiment of the method according to the invention—without being limited to this application—provides that heat is first extracted from the waste heat stream via a heat exchanger before the cooled waste heat stream is fed to the heat recovery system via the heat pump. The already cooled waste heat stream benefits the operating principle of the heat pump. It can utilize this waste heat stream, which is at a temperature level of, for example, approximately 90 to 170°C, to raise its temperature for the renewed provision of process heat.

[0018] According to a particularly advantageous embodiment, a high-temperature heat pump can be used as the heat pump itself. Such a high-temperature heat pump, as defined by the invention, is a heat pump known per se, which delivers thermal energy at a temperature level above 100°C in a single-stage or preferably two-stage heat pump process. Such high-temperature heat pumps are known in the prior art (PA23015W0 07.11.2025).

[0019] 4 for example in the form of the AGO Calora from the company AGO GmbH Energie + Anlagen, Kulmbach, which received the Bavarian Energy Prize 2022 for this heat pump.

[0020] According to a highly advantageous embodiment of the inventive method, the process heat can be supplied via a heating circuit with a heat transfer medium. Common heat transfer media used in industry are typically thermal oils or, where possible, water-based heat transfer media, which are far more environmentally friendly and do not exhibit the problematic toxicity and flammability of thermal oils, for example. Accordingly, a highly advantageous embodiment provides for the use of water or a water-based medium as the heat transfer medium.

[0021] This heat transfer medium of the heating circuit now releases process heat to corresponding process heat consumers within the system for stretching the plastic film. After releasing the process heat, according to a particularly advantageous embodiment of the inventive method, the cooled heat transfer medium of the heating circuit can first be heated by the heat pump and then passed through the heat exchanger. The waste heat flow and the heat transfer medium thus flow in counterflow, so that the waste heat flow first passes through the heat exchanger and then, after cooling, heats the evaporator of the heat pump directly or via an intermediate circuit. The cooled heat transfer medium of the heating circuit, on the other hand, is first heated or preheated in the heat pump and then further heated in the heat exchanger.

[0022] A particularly advantageous embodiment of the method according to the invention provides that the process heat consumers are traversed by the heat transfer medium in series. The individual process heat consumers, i.e., corresponding heat exchangers, heat transfer fluids, or heated rollers in a longitudinal stretching area or a preheating zone thereof, can thus be traversed in series one after the other. The process medium is thereby only... PA23015W0 07.11.2025

[0023] The heat transfer medium is cooled by a few degrees at each process heat consumer and can thus flow through a large number of process heat consumers in series, providing heat to each individual process heat consumer with a continuous, but only a few degrees / Kelvin, temperature drop. It flows to the individual process heat consumers in the opposite direction to the movement of the plastic film in the system. Despite the small temperature drop in the individual consumers, the heat transfer medium is cooled sufficiently in this counterflow series connection to achieve a large overall temperature difference, enabling economical operation of the heat pump.

[0024] After the heat transfer medium has flowed through the heat exchanger following the heat pump, it can be reheated if necessary, for example via a boiler with preferably electric heating, although heating via other energy carriers such as oil, gas or coal is also conceivable directly or indirectly.

[0025] Preferably, as already indicated by way of example, exhaust air can be used as a source of waste heat. According to an advantageous embodiment, this exhaust air stream can be taken from an area of ​​the system where the temperature is much higher than in the drawing areas. For example, the temperature in the drawing area can be between 90 and 150°C, depending on the part of the system. The exhaust air stream can, for example, and this is provided for in a very advantageous embodiment of the method according to the invention, originate from an area used for heat fixing, where temperatures typically exceed 200°C, and often exceed 225°C. The exhaust air stream from this area is ideally suited for reheating the heat transfer medium in the heat exchanger and for subsequent energy recovery in the heat pump, particularly the high-temperature heat pump.

[0026] Preferably, a film made of polyester or polyamide can be processed as the plastic film using the inventive method. In particular, such as PA23015W0

[0027] November 7, 2025

[0028] 6

[0029] Films made of polyester or polyamide, especially compared to films made of polypropylene, require a temperature for heat setting that is significantly higher than the maximum temperature in the stretching area of ​​the system. This large temperature difference is advantageous for the process according to the invention, as it allows a large amount of heat to be recovered from the exhaust air of the area used for heat setting.

[0030] The inventive system for stretching plastic film, in which the plastic film moves through successive system components in the direction of movement of the plastic film during the stretching process, now includes at least one exhaust air duct. According to the invention, it is provided that an exhaust air stream in the at least one exhaust air duct is directly or indirectly connected via a heat pump to a heat transfer medium of a heating circuit to provide process heat. The system is thus designed to be suitable for use with the inventive method, in that an exhaust air stream in an exhaust air duct serves as a heat source and a heat pump transfers this heat directly or indirectly to a heat transfer medium to provide process heat.

[0031] Similar to the method according to the invention, a particularly advantageous embodiment of the system according to the invention provides that the heat transfer medium flows through a heat exchanger located in the exhaust air duct upstream of the heat pump, in the direction of flow of the exhaust air stream. The exhaust air stream, which here simultaneously represents the waste heat stream, first releases energy in a heat exchanger before the cooled exhaust air or waste heat stream flows into the heat pump. Preferably, in a favorable embodiment of the system according to the invention, an inlet heat exchanger for the heat pump is arranged in the exhaust air duct downstream of the heat exchanger, which provides the heat of vaporization for the heat pump directly or indirectly via an intermediate circuit. PA23015W0

[0032] November 7, 2025

[0033] 7

[0034] The heat pump itself, similar to the method already described, can be designed as a high-temperature heat pump according to a very advantageous further development. It can then, in one or more stages (two stages being particularly preferred), provide a heat flow for the heat pump at a temperature level increased by, for example, up to approximately 50 K, from the residual heat contained in the remaining waste heat stream after the heat exchanger.

[0035] An advantageous embodiment of the system according to the invention can further provide that it has at least one system section for preheating the plastic film and, adjoining this in the direction of movement of the plastic film, at least one system section for longitudinally and / or transversely stretching the plastic film, wherein, adjoining this in the direction of movement of the plastic film, a system section for heat fixing is connected. The at least one exhaust air duct is arranged in this system section for heat fixing, so that at least partially, or preferably exclusively, exhaust air from the area of ​​heat fixing is used as waste heat for the heat pump. As mentioned, the system itself can have a system section for longitudinally and / or transversely stretching the plastic film.It is therefore conceivable to design a system exclusively with a longitudinal section, which could then be equipped with an optional integrated thermal fixation system or an alternative heat source. However, it is also possible to provide a system exclusively with a transverse section, or a system in which a transverse section is connected to a longitudinal section. In principle, so-called simultaneous stretching systems are also known from the prior art, which can perform both longitudinal and transverse stretching in a single system component. All of these can be part of the system according to the invention.

[0036] The process heat consumers in the individual plant components are arranged in series with respect to the flow direction of the heat transfer medium in the heating circuit and are subjected to series flow, as already explained in the description of the design of the method according to the invention. PA23015W0 07.11.2025

[0037] 8

[0038] The invention can further comprise a device for producing and stretching a plastic film, wherein the device for stretching the plastic film is designed according to one of the embodiments just described and is operated using the method according to the invention. Upstream of these parts of the device for stretching the plastic film, in the direction of travel of the plastic film, a production unit for the plastic film can then be located in a manner known per se, which has at least one casting roller cooled by a cooling medium, wherein a heat pump is provided which uses the cooling medium as a heat source. Such a heat pump or chiller on the casting roller can then be used to recover heat at a lower temperature level and also utilize the heat generated during the cooling of the casting roller via this heat pump.Typically, the temperature level is much lower than the temperature level required for process heat, making this particularly suitable for heating and / or air conditioning applications, for example for a machine hall, for administration buildings, for warehouses or the like.

[0039] Further advantageous embodiments of the inventive method, the system according to the invention, and the device for producing and processing a plastic film with such a system will also become apparent from the exemplary embodiment, which is described in more detail below with reference to the figure.

[0040] The only accompanying figure 1 shows a schematic representation of a device for producing and stretching a plastic film in a possible embodiment according to the invention.

[0041] Figure 1 shows a schematic view of a device 100 for producing and stretching a plastic film F. In Figure 1, the plastic film F moves from left to right through the device 100, as indicated by the arrow labeled B, which shows the direction of movement of the plastic film F. PA23015W0 07.11.2025

[0042] 9

[0043] The first part of this apparatus 100, shown on the left, forms a production unit 200 for the plastic film F. Such a production unit 200 is known in principle from the prior art. It comprises at least one casting roller 201, onto whose surface the plastic material for the formation of the plastic film F is poured or applied by extruder. The casting roller 201 is cooled so that the plastic material on the casting roller 201 hardens to form the plastic film F, from which it can be removed as a film web. A chiller or heat pump 202 is provided to cool the casting roller 201 of the production unit 200. This is shown schematically in Figure 1. The heat generated in its area can then be dissipated as usable heat. It can, for example, be supplied to a building heating system designated 203.

[0044] The core of facility 100 is now the system 300 for stretching the plastic film F produced in production unit 200. This system 300 comprises several system components, which are subsequently described from left to right, i.e., following the direction of movement B of the plastic film F.

[0045] The first part of the system is a longitudinal stretching section 310. This includes a preheating zone 311 for the plastic film F, followed by a longitudinal stretching section 312. Within this section, the plastic film F is stretched in the direction of movement B, which is why the longitudinal stretching section 310 is also referred to as MDO (Material Direction Orientation). Thus, in the longitudinal stretching section 310, the plastic film F is preheated and stretched in the direction of movement B. Typically, the plastic film F is then cooled at the end of the longitudinal stretching section.

[0046] The plastic film F is then transferred to a transverse stretcher 320. Within this stretcher, it first moves through a heating zone 321 and then, in the direction of movement B of the plastic film F, enters a transverse stretching area 322. In this transverse stretching area 322, the material of the plastic film F is stretched or taut perpendicular to the direction of movement B of the plastic film F, which is why the transverse stretcher 320 is also referred to by the abbreviation TDO (Transversal Direction PA23015W0 07.11.2025).

[0047] 10

[0048] Orientation). As can be seen schematically in Figure 1, the film web of the plastic film F then has a greater width.

[0049] After the transverse stretching section 322, it enters a section 323 for heat fixing, in order to fix (at least largely) the geometric and mechanical properties achieved through longitudinal and transverse stretching of the plastic film F by applying a corresponding temperature. This section, also simply referred to as heat fixing 323, is typically implemented as part of the transverse stretching section 320. However, it could just as well form its own separate system component.

[0050] In the preferred example of a polyester plastic film F, where similar temperatures also apply to polyamide, the plastic film F has a temperature in the range of 40 to 70°C upon entering the system 300 and a temperature of 90 to 125°C within the longitudinal section 310 during stretching. Upon exiting the longitudinal section 310, the plastic film F has a temperature between 30 and 50°C due to a final cooling zone within the longitudinal section 310. Upon entering the heating zone 321 of the transverse section 320, the typical temperature is also in these ranges or slightly below. At the beginning of the transverse stretching section 322, temperatures of approximately 90 to 130°C are typical, and upon exiting the transverse stretching section 322, i.e., in the direction of movement B of the plastic film F before heat fixing 323, temperatures of approximately 100 to a maximum of 140°C are typical.In the area of ​​thermal fixing 323, temperatures on the order of more than 220°C prevail, at least in the above-mentioned example of polyester film.

[0051] The provision of the process heat required for stretching the plastic film F will now be explained using heating circuit 400 of system 300 as an example. For clarity, this heating circuit 400 is described starting from the point designated "0" here, in the direction of flow of its heat transfer medium. It comprises the individual process heat consumers 1 to 19, which are each represented here as heat exchangers in the area of ​​the corresponding system components 311, 312, 321, and PA23015W0.

[0052] November 7, 2025

[0053] 1 1

[0054] Figure 322 shows the starting temperature of the heat transfer medium, in particular water, in the heating circuit 400. In the example mentioned, for the stretching of a polyester plastic film, the starting temperature is 150°C. The heat transfer medium then flows in series through the individual process heat consumers 1 to 5 of the transverse stretching area 322 and the process heat consumers 6 to 8 of the heating zone 321 of the transverse stretching area 320, in the order of their numbering. The flow is realized here in series through the individual process heat consumers 1 to 8, whereby – as indicated by the dotted lines – individual process heat consumers 1 to 19 could, in principle, be bypassed via bypass lines and valve devices (not shown).In the example described here, with a starting temperature of 150°C at starting point 0, the temperature decreases accordingly in each of the process heat consumers 1 to 8. This results in a temperature of approximately 125 to 130°C after process heat consumer 8, i.e., in the transition zone of the heat transfer medium from the heating zone 321 of the transverse section 320 to the longitudinal section 310. Subsequently, the process heat consumers 9 to 19 of the longitudinal section 312 and the preheating zone 311 for the longitudinal section 310 are traversed. Here, too, energy is released in each of the individual process heat consumers 9 to 19, so that the heat transfer medium of the heating circuit 400 flowing out of process heat consumer 19 has a residual temperature of approximately 110 to 120°C.

[0055] The heat transfer medium is circulated in the heating circuit 400 via one or more conveying devices not explicitly shown here. After leaving the process heat consumer 19, its residual temperature, which as mentioned is in the range of 110 to 120°C, enters the area of ​​a high-temperature heat pump 500. There, it is heated in a heat exchanger 401 to an output temperature of approximately 135 to 140°C. The heat transfer medium then flows through a heat exchanger 402 of the heating circuit 400, where it is heated again, ideally to a temperature of 145 to 150°C. Should the temperature of 150°C at the starting point PA23015W0

[0056] November 7, 2025

[0057] 12

[0058] If the target temperature of 0 is not reached, a heating device 403 provides the option of reheating, thus reliably guaranteeing a temperature of 150°C before the first process heat consumer 1, independent of the heat transferred in the heat exchanger 402 and supplied by the high-temperature heat pump 500. The heating device 403 can also be used to heat the heat transfer medium when the system 300 is started up at the beginning of the process and there is not yet a sufficient amount of waste heat available to generate the process heat.

[0059] The waste heat source used to generate the process heat, or at least a large part of it, is exhaust air from the thermosetting unit 323. An exhaust air stream 600 from the thermosetting unit 323, which simultaneously forms the waste heat stream 600, is shown with a dashed line in Figure 1. This exhaust air stream 600 is extracted from the area of ​​the thermosetting unit 323 by an air conveying device (not shown here), such as a blower. It enters the heat exchanger 402 at a temperature of approximately 220°C in the aforementioned example of stretching a polyester plastic film F, transfers heat to the heat transfer medium, and, as previously explained, heats it from approximately 135–140°C to 145–150°C. Afterwards, the exhaust air stream 600 has a residual temperature of approximately 170°C. It then flows into an inlet heat exchanger 501 of the high-temperature heat pump 500 and releases heat there again.The exhaust air is then cooled to approximately 90 to 110°C and, after optional filtration, can be released into the environment designated here as 601. Of course, it could also be used for other low-temperature applications, such as building heating or similar.

[0060] The high-temperature heat pump 500, which is known per se, can preferably be designed as a two-stage unit. Heat output can be transferred from the inlet heat exchanger 501 directly or via an intermediate circuit to an evaporator of the first stage. A condenser of this first stage then forms the evaporator of the second stage, whose condenser is PA23015W0.

[0061] November 7, 2025

[0062] 13

[0063] The heat output is then transferred directly or indirectly to the heat transfer medium of the heating circuit 400 via the heat exchanger 401. Further illustration of this otherwise known operating principle has been omitted from Figure 1. Only the inlet heat exchanger 501 and the heat transfer medium 401 are shown as examples within the high-temperature heat pump 500. As mentioned above, the high-temperature heat pump 500 could be an AGO Calora from AGO GmbH Energie + Anlagen, Kulmbach, or a model with a comparable function.

[0064] From an energy perspective, in the example described here, the evaporator of the first stage has an inlet temperature of 80 to 100°C. This temperature can be transferred, for example, from the inlet heat exchanger 501 to the evaporator of the first stage via the intermediate circuit mentioned above. This means that in heat exchanger 501, the exhaust air stream 600 is cooled from approximately 170°C to about 90°C, thereby heating water in the intermediate circuit from, for example, 60°C to 80 to 100°C. The water circulated in the intermediate circuit then heats the evaporator of the first stage. An intermediate heat exchanger serves as the condenser of the first stage and the evaporator of the second stage, transferring the energy at a higher temperature level to the second stage of the high-temperature heat pump 500. This provides an output temperature of approximately 135 to 140°C at the condenser of the second stage, which is formed by the heat exchanger 401.This heats the heat transfer medium from approximately 120°C to approximately 135 to 140°C.

[0065] Operating the system 300 with the described heat recovery is particularly economically worthwhile when electricity prices approach those of thermal energy from gas, oil, or coal at a high price level, as the system 300 offers the particular advantage that the heat pump 500 can utilize several times the amount of heat energy from the waste heat as electrical energy. In this case, the system 300 can be operated exclusively with electricity. However, combined operation is also possible, so that, for example, the PA23015W0 area can be heated using either electricity or heat.

[0066] November 7, 2025

[0067] 14

[0068] Thermal fixation 323 and the heating device 403 can be used to reheat thermal energy from gas, oil or coal.

[0069] PA23015W0 07.11.2025

[0070] 15

[0071] Reference symbol list

[0072] 100 Equipment for the production and stretching of plastic films

[0073] 200 production units

[0074] 201 Casting roller

[0075] 202 Refrigeration machine or heat pump

[0076] 203 Building heating

[0077] 300 plant

[0078] 310 Longitudinal section (MDO)

[0079] 311 Preheating zone

[0080] 312 Longitudinal stretch area

[0081] 320 Crossbar (TDO)

[0082] 321 Heating zone

[0083] 322 Crossbar area

[0084] 323 (area of) thermal fixation

[0085] 400 heating circuit

[0086] 401 Heat exchangers

[0087] 402 Heat exchangers

[0088] 403 Heating system

[0089] 500 (high-temperature) heat pump

[0090] 501 Inlet heat exchanger

[0091] 600 exhaust air flow or waste heat flow

[0092] 601 surroundings

[0093] F Plastic film

[0094] B Direction of movement

[0095] 0 Starting point

[0096] I to 19 process heat consumers

Claims

PA23015W0 November 7, 2025 1 Patent claims 1. Method for recovering process heat from the waste heat of a plant (300) for stretching plastic films (F), characterized in that the waste heat generated in the stretching process is recovered at least partially via a heat pump (500).

2. Method according to claim 1, characterized in that heat is first extracted from the waste heat flow (600) via a heat exchanger (402) before the waste heat flow (600) thus cooled is supplied to the heat recovery via the heat pump (500).

3. Method according to one of the preceding claims, characterized in that a high-temperature heat pump (500) is used as the heat pump.

4. Method according to claim 1, 2 or 3, characterized in that the process heat is provided via a heating circuit (400) with a heat transfer medium.

5. Method according to claim 4, characterized in that water or a water-based medium is used as the heat transfer medium.

6. Method according to claim 4 or 5, characterized in that the heat transfer medium of the heating circuit (400), which has cooled down after releasing the process heat, is first heated via the heat pump (500) and then passed through the heat exchanger (402).

7. Method according to claim 4, 5 or 6, characterized in that the process heat consumers (1 ,... 19) are connected in series to the heat transfer medium PA23015W0 November 7, 2025 2 are flowed through.

8. Method according to one of claims 4 to 7, characterized in that the heat transfer medium is reheated in the flow direction after the heat exchanger (402) if required.

9. Method according to one of the preceding claims, characterized in that exhaust air is used as a source for the waste heat.

10. Method according to claim 9, characterized in that the exhaust air stream (600) used as a source is taken from an area (323) of the system (300) in which a much higher temperature prevails than in the stretching areas (312, 322).

11. Method according to claim 9 or 10, characterized in that exhaust air from an area (323) used for thermosetting is used as a source for the waste heat.

12. Method according to one of the preceding claims, characterized in that the plastic film (F) is a film made of polyester or polyamide.

13. Plant (300) for stretching a plastic film (F), which moves during the stretching through successive plant parts in the direction of movement (B) of the plastic film (F), with at least one exhaust air line, characterized in that an exhaust air stream (600) in the at least one exhaust air line is directly or indirectly in operative connection with a heat transfer medium to be heated of a heating circuit (400) via a heat pump (500) for the provision of process heat.

14. System (300) according to claim 13, characterized in that the heat transfer medium in the flow direction after the heat pump (500) has a PA23015W0 November 7, 2025 3 heat exchanger (402) arranged in the exhaust air duct in the direction of flow of the exhaust air stream (600) in front of the heat pump (500).

15. System (300) according to claim 14, characterized in that an inlet heat exchanger (501) of the heat pump (500) is arranged in the exhaust air duct in the flow direction of the exhaust air stream (600) after the heat exchanger (402), which directly or indirectly provides the heat of vaporization for the heat pump (500).

16. System (300) according to claim 13, 14 or 15, characterized in that the heat pump (500) is designed as a high-temperature heat pump (500).

17. System (300) according to claim 16, characterized in that the high-temperature heat pump (500) is designed in multiple stages.

18. System (300) according to one of claims 13 to 17, characterized by at least one system part for preheating the plastic film (F) and, adjoining this in the direction of movement (B) of the plastic film (F), at least one system part for longitudinal and / or transverse stretching of the plastic film (F), wherein, in the direction of movement (B) of the plastic film (F), a system part is adjoining this which serves for thermal fixing, and wherein at least one exhaust air line branches off from the system part for thermal fixing (323).

19. Plant (300) according to one of claims 13 to 18, characterized in that the process heat consumers (1 ,... 19) in the plant parts are arranged in series with respect to the flow direction of the heat transfer medium in the heating circuit (400) and are flowed through.

20. Device (100) for the production and stretching of a plastic film (F) comprising a production unit (200) for the plastic film (F), which includes at least one casting roller (201) cooled by a cooling medium and a heat pump .2025 4 (202) features the cooling medium as a heat source for the heat pump (202) serves, characterized by a system (300) adjoining the production unit (200) in the direction of movement (B) of the plastic film (F) for stretching the produced plastic film (F), according to one of claims 13 to 19.

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