System and method for producing a plastic film

Abstract

The invention relates to a system and a method for producing a plastic film. A system (10) for producing a plastic film has a source unit (30), a heat sink unit (32) and a heat pump (42). The source unit (30) includes an exhaust heat outlet thermally connected to a supply of the heat pump (42), and the heat sink unit (32) includes a process heat supply thermally connected to an outlet of the heat pump (42). The invention further relates to a method for operating a system (10).

Description

Technical Field

[0001] The invention relates to a system for producing plastic films and to a method for operating such a system. Technical Background

[0002] Systems for producing plastic films are known and usually comprise at least an extruder and a stretching unit.

[0003] The production of plastic film in such systems is very energy-intensive, since the various units of the system, especially the stretching unit, require process heat.

[0004] To this end, the individual units of the known systems are designed to be energy efficient and potentially include equipment for heat recovery.

[0005] It is desirable to further improve energy efficiency. Summary of the invention

[0006] It is therefore an object of the present invention to provide a system for producing plastic films and a method for operating such a system which have improved energy efficiency.

[0007] The object is achieved by a system for producing plastic films. The system comprises a source unit, a radiator unit and a heat pump, wherein the heat pump comprises a supply of heat and an outlet for useful heat. The source unit comprises a waste heat outlet thermally connected to the supply of the heat pump (42), and the radiator unit comprises a process heat supply thermally connected to the outlet of the heat pump.

[0008] The inventors have realised that an improvement in energy efficiency is possible because the exhaust heat of one unit can be used as process heat for another unit. By means of a heat pump, it is now possible to use the exhaust heat from certain units of the system and provide it as process heat to other units of the system. Thus, the energy efficiency of the system is improved.

[0009] A thermal connection within the meaning of the present disclosure takes place, for example, via a heat transfer circuit.

[0010] The system is, for example, a system for producing biaxially stretched films, such as polypropylene films (BOPP), polyethylene terephthalate films (BOPET), polyamide films (BOPA), polyethylene films (BOPE), polylactic acid films (BOPLA), capacitor films (BOPP-C) or battery separator films (BSF).

[0011] In one embodiment, the supply to the heat pump is an evaporator and / or the outlet of the heat pump is a condenser, thereby enabling an efficient thermal connection to the heat pump.

[0012] For example, the compressor is arranged downstream of the supply device and upstream of the outlet.The throttle valve may be arranged downstream of the outlet and upstream of the supply device.

[0013] In one embodiment, the system comprises a first heat transfer loop thermally connecting the source unit to the heat pump. The first heat transfer loop constitutes an efficient and low-loss thermal connection between the heat pump and the source unit.

[0014] The first heat transfer loop may comprise a pump for a heat transfer medium. The heat transfer medium may be hot oil or pressurized water.

[0015] For example, the first heat transfer circuit comprises a first heat exchanger, in particular an air heat exchanger thermally connected to the exhaust heat outlet of the source unit. Hence, no adaptation of the source unit is necessary.

[0016] To further improve the energy efficiency, the system may comprise a secondary source unit and the first heat transfer circuit may comprise a second heat exchanger, wherein the exhaust heat outlet of the secondary source unit is in particular directly thermally connected to the second heat exchanger.

[0017] For example, the second heat exchanger is arranged upstream of the first heat exchanger and / or downstream of the supply of the heat pump.

[0018] In one embodiment, the exhaust heat outlet of the source unit is an exhaust air outlet, wherein the first heat exchanger comprises a gas scrubber and a liquid heat exchanger. In this way, the heat exchanger performs a dual function.

[0019] In one embodiment, the system comprises a second heat transfer loop thermally connecting the radiator unit to the heat pump.Thereby, an efficient and low-loss thermal connection is provided between the heat pump and the radiator unit.

[0020] The second heat transfer circuit comprises in particular a pump for the heat transfer medium. The heat transfer medium may be thermal oil or pressurized water.

[0021] In one embodiment, the system comprises an additional heater in the second heat transfer loop, which is located downstream of the heat pump and upstream of the radiator unit. By means of the additional heating, the peak demand for process heat of the radiator unit can be mitigated, making it possible to install a heat pump with a lower power.

[0022] To be able to operate the additional heater independently of the heat pump, the second heat transfer circuit may comprise a bypass section with a bypass valve, wherein the bypass section opens downstream of the heat pump and upstream of the additional heater and / or originates from a point upstream of the heat pump and downstream of the radiator unit.

[0023] In one embodiment, the system comprises two heat pumps connected in parallel between the source unit and the radiator unit, in particular, wherein the heat pumps comprise different temperature performance ranges. The two heat pumps can each be designed for a narrow temperature performance range, so that they can be operated more efficiently than a single heat pump.

[0024] In particular, the source unit is thermally connected to the supply of each heat pump and the radiator unit is thermally connected to the outlet of each heat pump.

[0025] To increase the efficiency, the supply of the heat pump can be arranged in series in the first heat transfer circuit and / or the outlet of the heat pump can be arranged in series in the second heat transfer circuit.

[0026] It may be particularly efficient to arrange the outlets in the second heat transfer circuit in the reverse order to the supply devices of the first heat transfer circuit with respect to the flow of the heat transfer medium.

[0027] In one embodiment, the source unit or the secondary source unit may be a stretching unit, in particular a transverse orienter or a simultaneous stretching unit, an extrusion unit, a casting unit and / or a pulling roll unit, thereby efficiently utilizing the exhaust heat of these units.

[0028] The heat sink unit can be a stretching unit, in particular a transverse orienter or a machine direction orienter, a crystallizer, a raw material drying unit and / or a water bath of a simultaneous stretching unit, so that the exhaust heat can be used to meet the process heat requirements of these units. The heat sink can also be a preheating zone of a transverse orienter.

[0029] In particular, the exhaust heat of the extruders of the extrusion unit and / or casting unit can be obtained in the cooling water; the exhaust heat of the furnace of the stretching unit, the metering device of the extrusion unit and the take-off rollers can be utilized in the exhaust air.

[0030] The source unit is in particular a transverse orienter.

[0031] In one embodiment, the source unit comprises a device for heat recovery, wherein the exhaust heat outlet of the device for heat recovery is the exhaust heat outlet of the source unit. In this way, the exhaust heat of the source unit can be utilized particularly efficiently.

[0032] The object is also solved by a method for operating a system for producing plastic film, the system comprising a source unit, a heat sink unit and a heat pump. The method comprises:

[0033] - supplying the exhaust heat of the source unit to the heat pump, and

[0034] -Supplying useful heat from the heat pump as process heat to the radiator unit.

[0035] The features and advantages described for the system also apply to the method, and vice versa. In addition, the components of the system are designed and arranged to carry out the method.

[0036] For example, the exhaust heat of the source unit is the exhaust heat of the device used for heat recovery of the source unit, thereby further improving the efficiency.

[0037] To meet demand peaks, additional useful heat can be supplied to the radiator unit to obtain useful heat from the heat pump, which produces additional heating of the system.

[0038] In order to efficiently supply the other useful heat, the other useful heat can be generated in a second heat transfer loop of the system, which transfers the useful heat of the heat pump to the radiator unit.

[0039] To protect the heat pump, a bypass valve can be opened in a bypass section of the second heat transfer circuit that bypasses the heat pump, and a shut-off valve can be closed upstream of the heat pump if the return temperature from the radiator unit in the second heat transfer circuit exceeds the temperature in the second heat transfer circuit directly downstream of the heat pump.

[0040] Other advantages and features of the invention can be found in the following description and in the accompanying drawings with reference thereto. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A schematic perspective view shows a system for producing a plastic film according to an embodiment of the present invention.

[0042] Figure 2 The first embodiment of the present invention is shown. Figure 1 A highly schematic view of a portion of a system

[0043] Figure 3 shows a schematic flow chart of an embodiment of the method according to the present invention,

[0044] Figure 4 The second embodiment of the present invention is shown. Figure 1 A highly schematic view of a portion of a system

[0045] Figure 5 shows a schematic diagram of a gas scrubber as part of another embodiment of a system according to the invention,

[0046] Figure 6 shows a schematic diagram of a portion of a first heat transfer circuit of a system according to the invention in another embodiment,

[0047] Figure 7 The third embodiment of the present invention is shown. Figure 1 A highly schematic view of a portion of a system

[0048] Figure 8 The fourth embodiment of the present invention is shown. Figure 1 A highly schematic view of a portion of a system

[0049] Fig. 9 The fifth embodiment of the present invention is shown. Figure 1 A highly schematic view of a portion of a system

[0050] Fig.10 The sixth embodiment of the present invention is shown. Figure 1 A highly schematic view of a portion of a system

[0051] Fig.11 A highly schematic view of a part of a system according to another embodiment of the invention is shown, DETAILED DESCRIPTION

[0052] exist Figure 1 In the drawing, a system 10 for producing plastic film is shown very schematically, comprising several different units and devices.

[0053] In the example shown, the system 10 includes an extrusion unit 12 , a cast unit 14 , a machine direction orienter 16 (MDO), a transverse direction orienter 18 (TDO), a pulling roll unit 20 , a winder unit 22 , and a heat pump unit 24 .

[0054] The produced film is, for example, a biaxially stretched film such as polypropylene film (BOPP), polyethylene terephthalate film (BOPET), polyamide film (BOPA), polyethylene film (BOPE), polylactic acid film (BOPLA), capacitor film (BOPP-C), or battery separator film (BSF).

[0055] To produce the plastic film, the film is formed on a cooling roll of a casting unit 14 by an extrusion unit 12. To this end, the extrusion unit 12 generates a melt from a starting product such as a granular material, which is applied to a cooling roll and thus forms a film.

[0056] The film is transferred from the casting unit 14 to the machine direction orienter 16. In the machine direction orienter 16, the film is stretched in the machine direction to obtain a stretched film.

[0057] In the machine direction orienter 16, the film runs over a plurality of rollers that are heated to heat the film to the desired temperature so that it can be stretched.

[0058] Stretching occurs in the machine direction, ie, the pulling direction, between at least two rolls present in the machine direction orientator 16, such that the film becomes a stretched film.

[0059] The obtained stretched film is conveyed through the machine direction orienter 16 to the transverse direction orienter 18, and is stretched in the transverse direction in the transverse direction orienter.

[0060] Along the drawing direction of the system 10, the transverse direction orienter 18 has an oven 26 having different zones for processing the film.

[0061] The film is heated in a first zone (also called a preheat zone). In a subsequent second zone ("stretching zone"), the film is stretched in the transverse direction so that its width at the end of the second zone is greater than its width at the beginning of the second zone, and its thickness at the end of the second zone is less than its thickness at the beginning of the second zone.

[0062] After stretching is complete, the film then passes through a third zone and additional zones (referred to as "heat treatment zones," "additional heating zones," and / or "annealing zones") where, for example, relaxation of the film can occur at elevated temperatures. One or more of these zones can serve as a heat removal source.

[0063] Subsequently, the film passes through further zones (“cooling zones”), wherein the film is cooled in the last zone.

[0064] Another area is called a neutral area and is used to separate these areas. For example, a neutral area is an empty space without any ventilation.

[0065] The regions of the transverse orienter 18 can also be divided differently and / or designed differently in terms of their length. For example, fewer or shorter neutral regions can also be provided additionally, or the neutral region can be arranged at other points. Changes in the remaining regions can also be envisaged.

[0066] After the transverse direction orienter 18 , the now biaxially stretched film passes through a take-off roll unit 20 and is taken up by a winder unit 22 .

[0067] It is also conceivable that the system 10 is designed in another way, for example with the aid of a simultaneous stretching unit that replaces or supplements the machine direction orienter 16 and the transverse direction orienter 18.

[0068] At least the machine direction orienter 16 and the cross direction orienter 18 require process heat during operation of the system.

[0069] At the same time, exhaust heat is generated in the machine direction orienter 16 and the cross direction orienter 18, as well as in other units.

[0070] For example, one or more extruders of the extrusion unit 12 and the cooling rolls or cooling pool / water bath of the casting unit 14 generate rejection heat, in both cases in the form of heated cooling water.

[0071] For example, machine direction orienter 16 and cross direction orienter 18, as well as metering equipment of extrusion unit 12, casting unit 14, and pulling roll unit 20, generate warm exhaust air as exhaust heat.

[0072] In addition to the zones described, the transverse orienter 18 may also comprise, for example, a device for heat recovery 28. The device for heat recovery 28 is optional.

[0073] The device 28 receives both fresh air from the environment and exhaust air from the furnace 26 (e.g., the heat treatment zone and / or the cooling zone). With the help of the exhaust air from the furnace 26, the fresh air for the furnace is preheated so that part of the exhaust air heat of the furnace 26 can be directly supplied to the furnace 26 as process heat again.

[0074] The device 28 for heat recovery is known per se, and the units 12 , 14 , 16 , 18 , 20 and 22 are also known per se.

[0075] The heat pump unit 24 is only Figure 1 , and may be in thermal contact with each of the individual units 12 , 14 , 16 , 18 , 20 , and 22 to receive exhaust heat from the units 12 to 22 and / or to provide process heat to one of these units 12 to 22 .

[0076] exist Figure 2 In the diagram, it is shown very schematically that Figure 1 1. The source unit 30, the radiator unit 32 and the heat pump unit 24 can be seen.

[0077] In this embodiment, source unit 30 is transverse direction orienter 18 of system 10. Other units of system 10 may also be considered as source unit 30, for example, other stretching units, such as machine direction orienter 16 (or a simultaneous stretching unit if present), extrusion unit 12, casting unit 14 and / or pulling roll unit 20.

[0078] The source may be a certain area of ​​the source unit 30, such as an annealing zone. It is also conceivable that several areas of the source unit 30 are sources, such as an annealing zone and a preheating zone, an annealing zone and a heating zone, or an annealing zone, a preheating zone and a heating zone.

[0079] In the illustrated embodiment, the heat sink unit 32 is the machine direction orienter 16. However, it is also conceivable that the heat sink unit 32 is a crystallizer of the extrusion unit 12, a raw material drying unit of the extrusion unit 12, and / or a water bath of a simultaneous stretching unit.

[0080] The heat pump unit 24 thermally connects the source unit 30 to the heat sink unit 32 and provides process heat to the heat sink unit 32 .

[0081] In the transverse orienter 18 as the source unit 30, Figure 2 Only the furnace 26 and the device 28 for heat recovery are shown.

[0082] The exhaust heat of the device 28 for heat recovery, ie the slightly cooled exhaust air from the furnace 26 , is provided to the heat pump unit 24 as exhaust heat of the source unit 30 .

[0083] exist Figure 2 In FIG. 1 , a machine direction orientator 16 is also only shown very schematically, wherein the machine direction orientator 16 comprises an inlet 33 as a process heat supply, several rollers 34 and several mixing units 36 .

[0084] A heat transfer medium, such as hot oil or pressurized water, flows through the rollers 3, thereby controlling the temperature of these rollers.

[0085] The mixing unit 36 ​​receives both the flow of heat transfer medium to and from the rollers 34 and is configured to set the temperature (inlet temperature) of the heat transfer medium to the rollers, in particular individually for individual rollers 34 or subgroups of rollers 34 .

[0086] In the illustrated embodiment, heat pump unit 24 includes a first heat transfer loop 38 , a second heat transfer loop 40 , and a heat pump 42 .

[0087] As is known per se, the heat pump 42 comprises an evaporator 44 , a compressor 46 , a condenser 48 and a throttle valve 50 .

[0088] The evaporator 44 constitutes the supply to the heat pump 42 .

[0089] A compressor 46 is arranged downstream of the evaporator 44 , wherein a condenser 48 is arranged downstream of the compressor 46 .

[0090] The condenser 48 forms the outlet for the useful heat of the heat pump 42 .

[0091] Finally, a throttle valve 50 is arranged downstream of the condenser 48 and upstream of the evaporator 44 .

[0092] The first heat transfer loop 38 includes a first heat exchanger 52 and a pump 54. Hot oil or pressurized water may be used as the heat transfer medium.

[0093] The supply of the heat pump 42 , ie here a compressor 46 , is also arranged in the first heat transfer circuit 38 .

[0094] In the illustrated embodiment, the feed is downstream of the pump 54 such that the pump 54 is located between the first heat exchanger 52 and the feed.

[0095] The first heat exchanger 52 is formed independently of the medium carrying the exhaust heat of the source unit 30. In the example in question, this medium is air, so that the first heat exchanger 52 is designed as an air heat exchanger.

[0096] The first heat exchanger 52 receives exhaust heat from the source unit 30 and thus receives exhaust air.

[0097] The first heat transfer circuit 38 thus provides a thermal connection between the source unit 30 and the supply of the heat pump 42 , thus here the evaporator 44 .

[0098] The second heat transfer loop 40 thermally connects the outlet of the heat pump 42 to the radiator unit 32 .

[0099] The heat transfer medium of the second heat transfer loop 40 may be hot oil or pressurized water.

[0100] The second heat transfer circuit 40 comprises in the first embodiment a pump 56 , wherein the outlet of the heat pump 42 , thus the condenser 48 in the illustrated embodiment, and the radiator unit 32 are both integrated into the second heat transfer circuit 40 .

[0101] The heat transfer circuit 40 merges into the heat transfer circuit of the radiator unit 31 , for example, at the inlet 33 and supplies the mixing unit 36 ​​and optionally also the roller 34 with heat transfer medium.

[0102] During operation of the system 10, particularly in the production of plastic film, the Figure 3 The method is schematically shown in FIG.

[0103] During operation of system 10, source unit 30 generates exhaust heat. In this example, oven 25 of transverse orienter 18 generates exhaust heat in the form of exhaust air (S1).

[0104] By means of a device 28 for heat recovery, the exhaust heat is partially fed back to the furnace 26 as process heat.

[0105] The exhaust heat of the device 28, ie the now slightly cooled exhaust air from the oven 26, is the exhaust heat of the source unit 30 and has a temperature level ranging from 60°C to 140°C, for example.

[0106] In S3 , the exhaust heat of the source unit 30 is supplied to the heat pump unit 24 , more specifically, to the first heat exchanger 52 of the first heat transfer loop 38 .

[0107] The exhaust heat of the source unit 30 is now transferred to the heat transfer medium of the first heat transfer loop 38 and supplied to the supply source of the heat pump 42 (here, the evaporator 44) (S4).

[0108] Then, the exhaust heat of the source unit 30 is supplied to the heat pump 42 .

[0109] The temperature of the heat transfer medium in the first heat transfer loop 38 immediately downstream of the evaporator 44 is considered to be the supply (or feed) temperature of the heat pump 42 .

[0110] The supply temperature range of the heat pump 42 is, for example, between 55°C and 140°C.

[0111] At its useful heat outlet (ie at the condenser 48 in the illustrated embodiment), the heat pump 42 now heats the heat transfer medium of the second heat transfer circuit 40 to a temperature level that exceeds the preceding supply of the heat pump 42 ( S5 ).

[0112] For example, the temperature of the heat transfer medium in the second heat transfer circuit 40 immediately downstream of the heat pump 42 is between 90° C. and 160° C., wherein temperatures of 200° C. and higher are also conceivable.

[0113] The useful heat generated in this way is fed to the radiator unit 32 as process heat via the second heat transfer circuit 40 .

[0114] In the embodiment shown, rolls 34 of machine direction orientator 16 are heated by providing process heat.

[0115] In this way, the exhaust heat of the source unit 30 is reused very efficiently, making it possible to significantly improve the energy efficiency of the entire system 10 .

[0116] Figures 4 to 8 A further embodiment of the system according to the invention is shown and corresponds substantially to the previously discussed embodiment. Therefore, only the differences are discussed below and identical components and components having the same function have the same reference numerals.

[0117] Figure 4 Similar to Figure 2 The view of FIG. 1 shows a portion of the system 10 in a second embodiment.

[0118] Compared to the first embodiment, the system 10 now comprises an additional heater 58 .

[0119] The additional heater 58 is located in the second heat transfer loop 40 and is configured to heat the heat transfer medium of the second heat transfer loop 40. For example, it is an electric heater, such as a heating coil. It is also conceivable to use a heat exchanger as the additional heater 58.

[0120] The additional heater 58 is arranged downstream of the heat pump 42 and upstream of the radiator unit 32 .

[0121] Furthermore, in this embodiment, the second heat transfer loop 40 includes a bypass section 60 in which a bypass valve capable of closing the bypass section 60 is provided.

[0122] The bypass section branches off from the remaining section of the circuit downstream of the radiator unit 32 and upstream of the heat pump 42 , bypasses the heat pump 42 and opens again into the remaining section of the circuit downstream of the heat pump 42 and upstream of the additional heater 58 .

[0123] Furthermore, a shutoff valve 64 may be provided in the second heat transfer circuit 40 , which is arranged upstream of the heat pump 42 and downstream of the branch of the bypass section 60 .

[0124] By means of an additional heater 58 , the heat transfer medium can be heated in the second heat transfer circuit 40 in addition to or as an alternative to the heat pump 42 .

[0125] As a result, as an alternative or in addition to the heat pump 42, other useful heat can be provided to the radiator unit 32 as process heat (S7, in Figure 3 indicated by dotted lines).

[0126] If the radiator unit 32 has a particularly high demand for process heat, the additional heater 58 can be switched on, for example when starting the unit. The additional heater 58 then supplies further useful heat in addition to the useful heat provided by the heat pump 42 in order to obtain the required temperature level at the inlet 33 or at the process heat supply of the radiator unit 32.

[0127] If the temperature in the second heat transfer loop 40 just downstream of the heat pump 42 is lower than the return temperature of the second heat transfer loop 40 , ie, lower than the temperature downstream of the radiator unit 32 , operation of the heat pump 42 is impossible.

[0128] In this case, the bypass valve 62 is opened and (if this is not already closed) the shut-off valve 64 is closed, thereby bypassing the heat pump 42 (S8, at Figure 3 Indicated by dotted lines).

[0129] The overall process heat for the radiator unit 32 is then generated by the additional heater 58. This is also necessary at the start of operation of the system 10 if the source unit 30 does not provide sufficient exhaust heat.

[0130] Furthermore, since the additional heater 58 can meet the peak power output, the additional heater 58 can use a heat pump 42 with a lower heat output. As a result, the cost of the system 10 is reduced.

[0131] Figure 5 An embodiment of the heat exchanger 52 of the first heat transfer loop 38 is shown. This embodiment can be used in the remaining embodiments as the heat exchanger or one of the heat exchangers of the first heat transfer loop 38.

[0132] In this embodiment, the heat exchanger 52 includes a gas scrubber 66 and a liquid heat exchanger 68. The gas scrubber 66 and optional air filter 80 may be part of the exhaust air purification system 65.

[0133] The gas scrubber 66 comprises a flow container 70 through which the exhaust air flows; in the flow container 70 a liquid atomizer 72 and a liquid reservoir 74 are arranged. Furthermore, the flow container 70 has an exhaust air inlet 76 and an exhaust air outlet 78.

[0134] The liquid atomizer 72 is located in the flow container 70 between the exhaust air inlet 76 and the exhaust air outlet 78 .

[0135] The liquid reservoir 74 is located on a side of the exhaust air inlet 76 facing away from the liquid atomizer 72 .

[0136] This is simultaneously the underside of the flow container 70 .

[0137] The liquid reservoir 74 is connected to the inlet of the liquid heat exchanger 68 , and the liquid atomizer 72 is connected to the outflow of the liquid heat exchanger 68 .

[0138] The pump is located between the liquid reservoir 74 and the liquid heat exchanger 68 .

[0139] During operation, exhaust air from the source unit 30 flows into the flow container 70 through the exhaust air inlet 76 and flows out of the flow container 70 at the exhaust air outlet 78 .

[0140] At the same time, the liquid atomized at the liquid atomizer 72 is supplied to the flow container 70 so that the exhaust air of the source unit 30 flows through the atomized liquid. Here, impurities (especially hydrocarbons) in the exhaust air are dissolved, thereby purifying the air. At the same time, the heat of the exhaust air is transferred to the liquid.

[0141] The liquid in the liquid reservoir 74 is thereby heated and contains a portion of the exhaust air of the source unit 30 which rejects the heat.

[0142] The liquid is then pumped to the liquid heat exchanger 68 , wherein the heat contained therein is transferred to the first heat transfer loop 38 .

[0143] Additionally, the gas scrubber 66 may include an air filter 80 , such as an electrostatic precipitator, disposed in the exhaust air stream downstream of the flow vessel 70 .

[0144] In a variation, a skim tank 81 may be provided between the flow container 70 and the liquid heat exchanger 68 (at Figure 5 indicated by dotted lines).

[0145] The liquid reservoir 74 and the liquid atomizer 72 are connected to the skim tank 81, thereby forming a loop.

[0146] At the same time, the skim tank 81 is connected to the liquid heat exchanger 68 .

[0147] During operation, heated liquid from the liquid reservoir 74 is directed into the skim tank 81 such that the liquid in the skim tank 81 is heated.

[0148] The heated liquid in the skim tank 81 is then fed to the liquid heat exchanger 68 which is capable of partially removing the heat of the liquid. The cooled liquid is then fed to the skim tank 81 again.

[0149] In this alternative, the liquid reservoir 74 can be omitted. Instead, a liquid outlet can be provided on the flow container 70 .

[0150] exist Figure 6 In the drawings, another embodiment is shown which can be combined with any other described embodiments.

[0151] In this embodiment, the first heat transfer circuit 38 has a second heat exchanger 82 .

[0152] The second heat exchanger 82 is in thermal contact with the secondary source unit 84, ie the exhaust heat of the secondary source unit 84, for example as exhaust air or cooling water, directly adjoins the second heat exchanger 82. The second heat exchanger 82 is, for example, an air heat exchanger or a liquid heat exchanger.

[0153] The same units already listed for source unit 30 may also be considered as secondary source units 84 .

[0154] For example, the second heat exchanger 82 is disposed upstream of the first heat exchanger 52 .

[0155] In this way, exhaust heat from several units 30 , 74 may be absorbed by the heat pump 42 and may thus be provided to the radiator unit 32 as process heat.

[0156] The secondary source unit 84 in particular provides a smaller amount of rejection heat than the source unit 30 and therefore the arrangement of the second heat exchanger 82 upstream of the first heat exchanger 52 is particularly efficient as there is a greater temperature difference and therefore a higher degree of heat transfer.

[0157] exist Figure 7 , a fourth embodiment of a portion of system 10 is shown, which is similar to Figure 2 and4 .

[0158] In this embodiment, the heat pump unit 24 includes several heat pumps, in this example a first heat pump 42 and a second heat pump 86 .

[0159] The first heat pump 42 is designed similarly to the heat pump 42 of the previous embodiment, and is located in the heat pump unit 24 .

[0160] The second heat pump 86 is designed in the same manner as the first heat pump 42 and is arranged in parallel with the first heat pump 42 between the first heat transfer circuit 38 and the second heat transfer circuit 40 .

[0161] The supply of the heat pump 42 , here also an evaporator 44 , is arranged in the first heat transfer circuit 38 , and the outlet of the heat pump 42 , here also a condenser 48 , is arranged in the second heat transfer circuit 40 .

[0162] In the embodiment shown, the supply of the second heat pump 86 is arranged in the first heat transfer circuit 38 downstream of the supply of the first heat pump 42 , while the outlet of the second heat pump 86 is arranged in the second heat transfer circuit 40 upstream of the outlet of the first heat pump 42 .

[0163] In particular, the supply of the heat pump 42 , 86 and the outlet of the heat pump 42 , 86 are arranged in series.

[0164] The arrangement of the outlets in the second heat transfer circuit 40 is in relation to the flow of the heat transfer medium and is therefore in the opposite order to the arrangement of the supply devices in the first heat transfer circuit 38 .

[0165] For example, the temperature of the first heat transfer medium of the first heat transfer loop 38 is 85° C. at the feed of the first heat pump 42 and the remaining temperature at the feed of the second heat pump 86 is still 55° C. The two heat pumps 42 , 86 heat the heat transfer medium of the second heat transfer loop 40 to a temperature of 148° C.

[0166] By using a second heat pump 86, two heat pumps with reduced power but with a higher degree of efficiency can be used compared to a single heat pump with increased power. Since the heat pumps 42, 86 each only need to be designed for a smaller temperature performance range, a higher degree of efficiency is achieved. Although the investment cost is high, the operating costs can be lower than when a single heat pump is used.

[0167] Figure 8 The fourth embodiment shown corresponds to Figure 7 The third embodiment shown, in which the Figure 6 In the illustrated embodiment, a secondary source unit 84 brings additional heat to the first heat transfer loop 38 via a second heat exchanger 82 .

[0168] Also in this embodiment, one or both of the heat exchangers 52, 82 may be designed to be compatible with the Figure 5 The heat exchanger of the embodiment is similar.

[0169] exist Fig. 9 In the diagram, it is shown very schematically that Figure 1 A fifth embodiment of the system 10 is described. This embodiment is based on the first embodiment, wherein the remaining embodiments can also be used as a starting point.

[0170] In particular, the system 10 of the fifth embodiment has the following features: Figure 5 The exhaust air purification system 65 described in the embodiment includes as for according to Figure 5 The embodiment of the gas scrubber 66 is described with respect to the heat exchanger 52 of the first heat transfer loop 38 .

[0171] In this embodiment, the heat sink unit 32 is the transverse orienter 18 of the system 10. The transverse orienter 18 may also be the source unit 30, such that the transverse orienter 18 and the heat sink unit 32 are the same unit.

[0172] Accordingly, the transverse orienter 18 includes an inlet 33 and an air heat exchanger 88 .

[0173] The air heat exchanger 88 is located in the second heat transfer loop 40 and receives the heated heat transfer medium from the heat pump 42 .

[0174] An air heat exchanger 88 is arranged downstream of the device 28 for heat recovery of the transverse orienter 18 , but upstream of the furnace 26 .

[0175] Therefore, the air heat exchanger 88 also receives a fresh air flow preheated by the device 28 for the furnace 26 , which fresh air flow is further heated by the air heat exchanger 88 .

[0176] The fresh air heated in this way is then supplied to the furnace 26 , for example to the preheating zone.

[0177] To provide redundancy in case of failure of the heat pump 42 or to regulate the temperature level, a damper register 90 may be arranged between the device for heat recovery 28 and the furnace 26 in the flow path of the fresh air, in particular downstream of the air heat exchanger 88 .

[0178] exist Fig.10 In FIG. 6 , a sixth embodiment based on the fifth embodiment is shown.

[0179] In this sixth embodiment, no first heat transfer circuit 38 is provided, but the exhaust air of the source unit 30 , in particular the exhaust air of the device for heat recovery 28 , is led to the evaporator 44 of the heat pump 42 .

[0180] To this end, the evaporator 44 is arranged as for Figure 5 Upstream of the exhaust air purification system 65 . After passing through the gas scrubber 66 and the optional air filter 80 , the exhaust air purified by the air purification system 65 enters the evaporator 44 directly.

[0181] Therefore, the first heat transfer loop 38 can be saved.

[0182] It is contemplated that in other embodiments, exhaust air or exhaust heat present in the liquid of the source unit 30 may also be directed directly to the evaporator 44 of the heat pump 42 .

[0183] The cooled exhaust air stream after the evaporator 44 of the heat pump 42 or the heat exchanger 52 of the first heat transfer loop 38 can in each embodiment be used for cooling in the cooling area of ​​the transverse orienter 18, as low temperature heat in other processes or for heating the building.

[0184] Regardless of the embodiment, condensation may occur at the evaporator 44 or at the heat exchanger 52 of the first heat transfer circuit 38, which condensation is formed by cooling and / or expansion of the exhaust air of the source unit 30. This water may be fed to the gas scrubber, for example according to Figure 5 The gas scrubber 66 of the embodiment is provided to thereby reduce the necessary make-up amount of treated fresh water.

[0185] exist Fig.11 In FIG. 1 , a system 10 is shown that includes several source units 30, for example two transverse orienters 18 and another unit. It is also conceivable that the system 10 includes two or more than three source units 30.

[0186] The exhaust air flows of the source units 30 are combined and fed together to the evaporator 44 of the heat pump 42 or to the heat exchanger 52 of the first heat transfer loop 38 .

[0187] like Figure 5 As mentioned, here too, one or more air cleaning systems 65 can be used. For example, the air cleaning system 65 cleans the exhaust air streams that have been combined together, so that only one air cleaning system 65 is needed.

Claims

1. A system for producing a plastic film, comprising a source unit (30), a heat sink unit (32) and a heat pump (42), in, The heat pump (42) comprises a heat supply device and a useful heat outlet. wherein the source unit (30) comprises a heat discharge outlet thermally connected to a supply device of the heat pump (42), and Therein, the radiator unit (32) comprises a process heat supply thermally connected to the outlet of the heat pump (42).

2. The system according to claim 1, characterized in that The supply device of the heat pump (42) is an evaporator (44) and / or the outlet of the heat pump (42) is a condenser (48).

3. The system according to claim 1 or 2, characterized in that: The system (10) includes a first heat transfer loop (38) thermally connecting the source unit (30) to the heat pump (42).

4. The system according to claim 3, characterized in that The first heat transfer circuit (38) comprises a first heat exchanger (52), in particular an air heat exchanger or a liquid heat exchanger (68), which is thermally connected to the exhaust heat outlet of the source unit (30).

5. The system according to claim 4, characterized in that The system (10) includes a secondary source unit (84), and the first heat transfer loop (38) includes a second heat exchanger (82), wherein an exhaust heat outlet of the secondary source unit (84) is thermally connected to the second heat exchanger (82).

6. The system according to claim 4 or 5, characterized in that: The exhaust heat outlet of the source unit (30) is an exhaust air outlet, wherein the first heat exchanger (52) includes a gas scrubber (66) and a liquid heat exchanger (68).

7. A system according to any one of the preceding claims, characterised in that The system (10) includes a second heat transfer loop (40) thermally connecting the radiator unit (32) to a heat pump (42).

8. The system according to claim 7, characterized in that The system (10) includes an additional heater (58) located downstream of the heat pump (42) and upstream of the radiator unit (32) in the second heat transfer loop (40).

9. The system according to claim 8, characterized in that The second heat transfer circuit (40) comprises a bypass section (60) having a bypass valve (62), wherein the bypass section (60) is open downstream of the heat pump (42) and upstream of the additional heater (58), and / or originates from a point upstream of the heat pump (42) and downstream of the radiator unit (32).

10. System according to any one of the preceding claims, characterized in that The system (10) includes two heat pumps (42, 86) connected in parallel between a source unit (30) and a heat sink unit (32), particularly wherein the heat pumps (42, 86) include different temperature performance ranges.

11. The system according to claim 10, characterized in that The supply devices of the heat pump (42, 86) are arranged in series in the first heat transfer circuit (38) and / or wherein: The outlets of the heat pumps (42, 86) are arranged in series in the second heat transfer loop (40).

12. A system according to any one of the preceding claims, characterised in that The source unit (30) and / or the secondary source unit (84) is a stretching unit, in particular a transverse direction orienter (18) or a simultaneous stretching unit, an extrusion unit (12), a casting unit (14) and / or a pulling roll unit (20); and / or the heat sink unit (32) is a stretching unit, in particular a transverse direction orienter (18) or a machine direction orienter (16), a crystallizer, a raw material drying unit and / or a water bath of a simultaneous stretching unit.

13. A system according to any one of the preceding claims, characterised in that The source unit (30) comprises a device (28) for heat recovery, wherein the exhaust heat outlet of the device (28) for heat recovery is the exhaust heat outlet of the source unit (30).

14. A method for operating a system (10) for producing plastic film, the system comprising a source unit (30), a heat sink unit (32) and a heat pump (42), wherein: The method comprises the following steps: - supplying the exhaust heat of the source unit (30) to the heat pump (42), and - The useful heat from the heat pump (42) is supplied as process heat to the radiator unit (32).

15. The method according to claim 14, characterized in that The exhaust heat of the source unit (30) is the exhaust heat of the device (28) for heat recovery of the source unit (30).

16. The method according to claim 14 or 15, characterized in that In addition to the useful heat of the heat pump, further useful heat is supplied to the radiator unit (32), said further useful heat generating additional heating (58) of the system (10).

17. The method according to claim 16, characterized in that The other useful heat is generated in a second heat transfer loop (40) of the system (10), the second heat transfer loop (40) directing the useful heat of the heat pump (42) to the radiator unit (32), in particular, wherein a bypass valve (62) is opened in a bypass section (60) of the second heat transfer loop (40) bypassing the heat pump (42), and if the return temperature from the radiator unit (32) in the second heat transfer loop (40) exceeds the temperature in the second heat transfer loop (40) immediately downstream of the heat pump (42), a stop valve (64) is closed upstream of the heat pump (42).

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