Patent Application
20240125517
This application claims priority to DE Patent Application No. 102022126925.6 filed Oct. 14, 2022, the entire contents of which are hereby incorporated by reference.
The technology herein relates to a solar-thermal process temperature control system for a film stretching unit as well as a corresponding film stretching unit.
The manufacture of films and, in particular, the operation of film stretching units on an industrial-scale is linked to a high conversion of energy.
A starting material, typically at least a polymer, is provided in granular and/or powder form for film manufacture and is converted into a film, for example a bi-axially oriented film, in multiple process steps that typically comprise different temperature levels.
The largest energy consumers within this film manufacturing process are usually the drying of the polymer starting material (e.g. granules and/or powder), the extrusion as well as the uni-axial or bi-axial stretching. The stretching occurs, for example, by means of a machine direction orienter (also termed MDO), a transverse direction orienter (also termed TDO) or a simultaneous stretching unit, in which the film is stretched in the transverse direction and the machine direction at the same time.
In film manufacture, the starting material (granules and/or powder) is usually initially fed to one (or multiple) extruder(s). A typical extruder comprises a temperature-controlled (heatable) cylinder, in which one or two plasticising screw(s) can rotate. The object of the screw(s) is to convey the plastic granules (or the plastic powder) as well as the plastic melt formed upstream, to plasticise and homogenise the starting material via shearing (friction) as well as to generate sufficient pressure to press the plastic melt under pressure then continuously through a die opening (extrusion die). Different extrusion dies may be used depending on the type of film manufacture.
In the manufacture of blown film (blown film unit), the plastic melt is pressed via the extruder and/or die, for example, through a (temperature-controlled) tubular die. The resulting molten tube is then blown with air and cooled externally, and if applicable internally, by (defined temperature-controlled) cooling air. The cooled film tube is laid flat and then wound up.
In the manufacture of flat films (also termed flat film extrusion), the plastic melt is formed into a flat film after the extruder typically by means of a (temperature-controlled) slot die. The film formed by means of the slot die (also termed cast film) can be extruded, for example, on a chill roll and then stretched.
In principle, a film can be stretched sequentially or simultaneously. In sequential stretching, the film is initially stretched, for example, in the machine direction and then in the transverse direction. In simultaneous stretching, stretching occurs in the machine direction and the transverse direction at the same time.
The machine direction stretching (MDO step) of the plastic film typically comprises controlling the temperature of the extruded plastic web and guiding the (cast) film over (temperature-controlled) rollers. The plastic web can be stretched in the machine direction by the rollers that rotate at different speeds.
In the case of sequential stretching, the subsequent transverse direction stretching (TDO step) of the plastic film typically comprises controlling the temperature of the extruded plastic web (in an oven) and the subsequent stretching in the transverse direction. To this end, the film is typically gripped and then pulled (stretched) in its width. The bi-axially stretched film can then be wound up.
In simultaneous stretching, the extruded film is initially temperature-controlled and then fed, for example, to a simultaneous stretching unit (e.g. a simultaneous stretching oven). In the simultaneous stretching unit, the film is typically gripped and then pulled (stretched) in its width and length.
In the corresponding oven, as typically used in transverse direction stretching and simultaneous stretching, the film to be stretched is heated before the stretching process and then kept at a predefined temperature in and during the stretching process. Subsequently, the stretched film can be cooled in the oven.
In particular, a lot of thermal energy must be provided for simultaneous stretching, machine direction stretching and transverse direction stretching. Currently, different generation concepts exist for this supply (e.g. electric heating, heating via thermal oil, heat supply via gas burners, and suchlike). In the use of thermal oil, the temperature of the thermal oil is controlled via a heating system, for example, such as an oil, gas or coal boiler. That is, fossil fuels (coal, gas, oil, are still predominantly used, which results in the manufactured film having an unfavourable CO2e footprint.
Example technology herein eliminates the aforementioned disadvantages and to reduce the use of fossil fuels in film manufacture, or to even avoid their use. In particular, CO2e emissions are to be reduced.
Such features are provided by a solar-thermal process temperature control system as well as by a film stretching unit and by the application of the process temperature control system in a film stretching unit. Further aspects are described below.
In particular, example embodiments provide a solar-thermal process temperature control system for a film stretching unit. The process temperature control system comprises at least a solar heat generator, which is integrated into a heat generation circuit, wherein the heat generation circuit conveys a first heat transfer fluid.
The solar heat generator converts solar energy into usable thermal energy. In particular, said at least one solar heat generator comprises solar-thermal collectors that focus the incident radiation (e.g. concentrated solar power (CSP) systems) in order to heat the first heat transfer fluid to the maximum possible temperatures.
For example, the solar heat generator can heat the first heat transfer fluid to at least 250° C., to at least 300° C., to at least 400° C., to at least 450° C., to at least 500° C. or to at least 550° C.
Furthermore, the process temperature control system comprises at least one heat storage unit. Thermal energy can be fed to the heat storage unit via the first heat generation circuit, said thermal energy being generated by said at least one solar heat generator. The heat storage unit is thus configured to store thermal energy.
Depending on the construction, the storage medium used, the size of the heat storage unit and the thermal insulation of the heat storage unit, the heat storage unit can be used for short-term heat storage and/or long-term heat storage. A short-term heat storage unit enables the storage of an amount of heat for heating the consumer(s) independently of the sun for a few minutes to up to one hour. By means of a long-term heat storage unit, the consumer(s) can also be heated independently of the sun for several hours (for example, at least 2 hours, at least 3 hours, at least 4 hours, at least 5 hours, at least 6 hours, at least 7 hours, at least 8 hours, at least 9 hours, at least 10 hours, at least 11 hours, or at least 12 hours).
The storage medium that uses the heat storage unit can be the first heat transfer fluid (direct storage) or an intermediate-circuit heat transfer fluid (indirect storage). Similarly, other storage media may be used.
The process temperature control system comprises at least one heat consumer circuit that conveys a second heat transfer fluid. This second heat transfer fluid can differ from the first heat transfer fluid. Similarly, the same heat transfer fluid can be used for the first and the second heat transfer fluids.
The heat consumer circuit is connected to said at least one heat storage unit in order to be capable of drawing stored thermal energy.
In particular, the heat consumer circuit can comprise a supply section and a return section, wherein the consumer(s) can be integrated into the heat consumer circuit between the supply section and the return section so that the temperature of the second heat transfer fluid in the supply section is more than the temperature of the second heat transfer fluid in the return section.
Furthermore, the process temperature control system comprises at least one temperature control device. The temperature control device comprises at least one heat transfer fluid outlet for supplying the consumer(s). The heat transfer fluid outlet is thus arranged between the supply section and the return section.
Said at least one temperature control device is configured to supply the second heat transfer fluid at a defined temperature at said at least one heat transfer fluid outlet (and thus the consumer(s)) in order to supply at least one component of a film stretching unit directly or indirectly with defined temperature-controlled heat transfer fluid. Thus, the film stretching unit can be supplied with thermal energy.
The process temperature control system thus enables the supply of thermal energy to a film stretching unit, said thermal energy being generated by means of at least one solar heat generator. This enables the reduction of CO2e emissions.
The process temperature control system can furthermore comprise a first heat exchanger. This first heat exchanger can be connected between said at least one heat storage unit and the heat consumer circuit. In particular, the first heat exchanger can be controlled so that the thermal energy transferred from the heat storage unit to the heat consumer circuit can be monitored and/or controlled. For example, the inflow and/or outflow of the heat exchanger can be controlled (for example, the flow rate, the flow volume, . . . ). Thus, the temperature of the second heat transfer fluid can be controlled in the supply section of the heat consumer circuit.
The process temperature control system can furthermore comprise a second heat exchanger. This second heat exchanger can be connected between said at least one heat storage unit and the heat generation circuit. In particular, the second heat exchanger can be controlled so that the thermal energy transferred from the heat generation circuit to the heat storage unit can be monitored and/or controlled. For example, the inflow and/or outflow of the second heat exchanger can be controlled (for example, the flow rate, the flow volume, . . . ). Thus, the temperature of the storage medium can be controlled in the heat storage unit.
In particular, the heat storage unit can be integrated into an intermediate circuit which conveys an intermediate-circuit heat transfer fluid. This intermediate-circuit heat transfer fluid can differ from the first and/or the second heat transfer fluids. Similarly, it is possible that the same heat transfer fluid is used for the first heat transfer fluid and/or the second heat transfer fluid and/or the intermediate-circuit heat transfer fluid.
If different heat transfer fluids are used, the heat transfer fluids can be adapted to the respective requirements. A heat transfer fluid with a very high specific heat capacity can be used, for example, for the heat storage unit to be capable of storing as much energy as possible within a small space. In contrast, heat transfer fluids, which are less viscous and can thus be transported more easily to the heating unit(s) and/or the consumers, can be advantageous for the heat generation circuit and/or the heat consumer circuit. In addition, the boiling points of the heat transfer fluids can be adapted to the respective application temperatures.
Thus, said at least one solar heat generator can be configured to supply the first heat transfer fluid to the heat storage unit or the second heat exchanger at a temperature of at least 250° C. (or at least 300° C., or at least 400° C., or at least 450° C., or at least 500° C. or at least 550° C.). In this case, the first heat transfer fluid can be an oil or a molten salt, whose boiling point is, for example, above the aforementioned temperatures. Similarly, water can be used as the heat transfer fluid, which is evaporated under pressure in the solar heat generator.
The first heat transfer fluid, the second heat transfer fluid and/or the intermediate-circuit heat transfer fluid can be selected from one of the following heat transfer fluids:
wherein the first heat transfer fluid, the second heat transfer fluid and/or the intermediate-circuit heat transfer fluid may differ. Typically, heat transfer fluids are liquid. However, gaseous heat transfer fluids (e.g., steam or any other suitable gas) can be used, in particular in the heat generator(s).
Said at least one heat storage unit can be configured to store a heat transfer fluid at a temperature of at least 180° C., or at least 210° C. and in particular at least 240° C. For example, the heat storage unit can be configured to store temperatures ranging from 180° C. to 560° C. or from 210° C. to 500° C. or from 240° C. to 400° C. In particular, the temperature of the heat transfer fluid stored in the heat storage unit depends on the dimensions of the heat storage unit (e.g. volumes, geometric size, insulation, . . . ), the type of fluid used and the type of heat storage unit. It is understood that the temperature in the heat storage unit does not have to be distributed evenly and, in particular, different temperature regions may be present.
In particular, the heat storage unit can be a stratified storage unit. In such a stratified storage unit, the storage medium is present in layers at different temperatures, wherein the temperature decreases from top to bottom. This stratified storage unit can thus be connected to the heat consumer circuit with different temperature levels. This enables high amounts of energy to be drawn if this is required.
Said at least one solar heat generator can comprise a linear concentrating solar power generator, in particular at least one parabolic trough collector and/or at least one Fresnel collector.
In the case of parabolic trough collectors, direct solar radiation is concentrated by means of one or more parabolic dishes onto a receiver located in the focus of the parabolic dish(es).
In the case of Fresnel collectors, several primary mirrors are aligned in such a way that they reflect the direct solar radiation onto a centrally mounted receiver. To minimise the accuracy requirements of the primary mirrors, a secondary concentrator (for example a parabolic dish) can be used which focuses the solar rays reflected by the primary mirrors onto the receiver.
The receiver used in parabolic trough collectors or Fresnel collectors comprises, for example, a tube, such as steel tube, which can be surrounded by an evacuated glass tube in order to minimise heat losses. The tube conveys the first heat transfer fluid. The tube can also be coated. In this case, the coating of the tube ensures high absorption of the solar radiation together with emissivity as low as possible in order to minimise heat losses further. The attainable temperature level of the first heat transfer fluid is up to 550° C., or even higher.
Said at least one solar heat generator can be a tracking heat generator, said at least one heat generator can thus track the current position of the sun. To this end, a controller can be provided which determines the current position of the sun itself or contains relevant data. Based on the current position of the sun, actuators can be controlled that bring about the tracking of the solar heat generator(s). In particular, said at least one solar heat generator can comprise single-axis tracking.
In parabolic trough collectors, the parabolic dish(es) can be tracked uni-axially via a servo motor for single-axis tracking. By this means, a high energy yield with less constructional outlay is enabled. In Fresnel collectors, the tracking can take place via the primary mirrors that are variable in position. In particular, several primary mirrors can be grouped into groups and then tracked in groups in order to minimise the control engineering requirements.
Furthermore, the process temperature control system can comprise at least one pump. This pump/these pumps can be integrated in such a way into the process temperature control system to circulate a first heat transfer fluid, a second heat transfer fluid and/or an intermediate-circuit heat transfer fluid. By controlling the pump(s), the flow velocity of the heat transfer fluids can be controlled in the corresponding circuits. Thus, the amount of transferred thermal energy can also be controlled.
In particular, the temperature control device can be configured to mix heat transfer fluid of the supply section with colder heat transfer fluid, for example from the return section, in order to supply the second heat transfer fluid at a defined temperature to said at least one heat transfer fluid outlet. Furthermore or alternatively, the temperature control device can be configured to control at least one pump of the process temperature control system in order to control the flow velocity of the corresponding heat transfer fluid in the circuit allocated to the pump. By controlling the pump(s), the second heat transfer fluid can be supplied at a defined temperature to said at least one heat transfer fluid outlet.
To this end, at least one controllable pump can be located in the heat generation circuit and/or at least one controllable pump in the intermediate circuit and/or at least one controllable pump in the heat consumer circuit.
Furthermore, the process temperature control system can comprise at least one additional heating device. Said at least one additional heating device can be allocated to the heat consumer circuit, in particular the supply section and/or the heat storage unit. The additional heating device can compensate for fluctuations in the generation of solar heat, in particular naturally occurring fluctuations (day/night, weather, . . . ), and/or can increase the temperature level to a required temperature level.
The additional heating device can be an electric additional heating device or can be based on other energy sources, such as coal, oil, gas, pellets, chips and/or suchlike. If the additional heating device, for example, is allocated to the heat storage unit, this can be an electric heating blade, which controls the temperature of the corresponding heat transfer fluid directly.
Furthermore, the process temperature control system can comprise at least one supply manifold that is downstream said at least one consumer outlet. This supply manifold is configured to distribute the second heat transfer fluid to different consumers of a film stretching unit. Thus, different consumers, such as the extruder, machine direction orienter (MDO), transverse direction orienter (TDO) and/or suchlike, can be supplied with thermal energy.
In addition, the process temperature control system comprises at least one return collector and one distributing device. The return collector takes the returning second heat transfer fluid from at least one consumer and supplies this to the distributing device. The distributing device is configured to supply the heat transfer fluid to the heat storage unit, the first heat exchanger and/or the temperature control device. The distributing device can be static. Similarly, the distributing device can be controlled in order to control the corresponding volumetric flow rate. To this end, corresponding valves can be provided.
The object is also solved by a film stretching unit which comprises the process temperature control system described previously as well as at least one of the following components:
The film stretching unit is configured in such a way that at least one of the components is supplied with thermal energy directly or indirectly by means of the process temperature control system in order to be temperature-controlled in a defined manner. It is understood that the aforementioned components of a film stretching unit can be temperature-controlled as such and/or corresponding subassemblies of these (such as rollers, housings, housing sections and/or suchlike) can be temperature-controlled.
Thus, the film stretching unit, but in any case at least one component (or subassembly of the component) of the film stretching unit, can be supplied with solar-powered thermal energy so that fossil fuels required to date can be substituted. This results in an improvement in the CO2e emissions balance of the film manufacture.
Exemplary subassemblies of the components are temperature-controlled rollers, temperature-controlled housings, temperature-controlled housing sections and suchlike. The subassemblies can be supplied with heat transfer fluid and thermal energy directly or indirectly.
In particular, at least one of the components of the film stretching unit can be connected to the heat transfer fluid outlet in order to be supplied directly with heat transfer fluid. In the case of direct supply, the heat transfer fluid can be conveyed from the heat transfer fluid outlet directly to the corresponding component (or subassembly of it). For example, a roller guiding the film can have heat transfer fluid flowing through it and can therefore be temperature-controlled.
Exemplary rollers are the chill roll, roller(s) allocated to the machine direction orienter (such as preheating roller(s), stretch roller(s), annealing rollers(s), and/or suchlike), roller(s) of the pull-roll device and/or roller(s) of the wrapping device.
Similarly, temperature-controlled heat transfer fluid can flow directly through parts of the drying apparatus (in particular a housing part and/or a mixer, . . . ), the feed hopper, the extruder (in particular a screw and/or a cylinder, or another housing part), housing (parts) of the stretching unit(s) and/or the absorption cooling machine.
In the case of indirect supply, the heat transfer fluid is supplied to a heat exchanger allocated to the respective component (or subassembly). For example, the heat transfer fluid can be conveyed through a heat exchanger, through which a temperature-control medium (such as air) is flowed or blown in to control the temperature of a housing or housing section of a component (in particular a machine direction orienter, transverse direction orienter and/or simultaneous stretching unit). This temperature-control medium can be introduced into the housing or the housing section to be temperature-controlled.
In particular, the film stretching unit can comprise one or more nozzle boxes, by means of which air is blown into different temperature zones or housing sections of the stretching unit. Such nozzle boxes are used in particular as subassemblies of transverse direction orienters and/or simultaneous stretching units in order to control the temperature of the film there as exactly as possible. Said at least one nozzle box can be temperature-controlled by means of the heat transfer fluid provided by the process temperature control system.
The film stretching unit can furthermore comprise at least one additional heating device, wherein the additional heating device is configured to supply additional thermal energy to at least one of the components of the film stretching unit.
The additional heating device can compensate for fluctuations in the generation of solar heat, in particular naturally occurring fluctuations (day/night, weather, . . . ), and/or can increase the temperature level of the corresponding component to a required temperature level. In addition, this additional heating device enables the provision of a thermal base level by means of the process temperature control system. If higher temperatures are required at one (or more) components, the additional heating device can supply the thermal energy additionally required in order to attain and/or maintain the required temperature level.
Example embodiments also provide application of the process temperature control system described previously in a film stretching unit described previously, wherein the process temperature control system supplies at least one of the components of the film stretching unit (in particular a subassembly of it) directly or indirectly with thermal energy in order to control its temperature in a defined manner.
The attached figures show aspects of example embodiments. In particular,
In particular,
The process temperature control system 10 comprises a heat generation circuit 100. A solar heat generator 110, in particular a concentrated solar power CSP heating unit, such a parabolic trough collector, is integrated into this heat generation circuit 100. This solar heat generator 110 can convert solar radiation into usable thermal energy. The first heat transfer fluid 112 is conveyed for this purpose in the heat generation circuit 100 and heated by means of the solar heat generator 110, for example, to approx. 550° C. A pump 124, which is allocated to the heat generation circuit 100, can circulate the first heat transfer fluid 112 (for example water, steam, thermal oil, molten salt,
Furthermore, the process temperature control system 10 comprises at least one heat storage unit 210. Thermal energy for storage can be supplied to the heat storage unit 210 via the first heat generation circuit 100, said thermal energy being generated by said at least one solar heat generator 110. In the embodiment shown here, the heat storage unit 210 takes the first heat transfer fluid 112. The storage medium is therefore the first heat transfer fluid so that the thermal energy is stored directly.
Via a heat exchanger 230, a heat consumer circuit 300 conveying a second heat transport fluid 312 is connected to the heat storage unit 210. Thus, thermal energy can be drawn from the heat storage unit 210. The heat exchanger 230 can be arranged outside of the heat exchanger as shown in
The heat consumer circuit 300 comprises a supply section 320 and a return section 340, wherein the temperature of the second heat transfer fluid 312 is higher in the supply section 320 than in the return section 340. Furthermore, the heat consumer circuit 300 comprises at least one temperature control device 330. This temperature control device 330 comprises at least one heat transfer fluid outlet 350 that is connected to a supply manifold 500.
This supply manifold 500 is configured to distribute the second heat transfer fluid 312 to different consumers (components) of a film stretching unit 1 (see
To control the temperature as exactly as possible, the temperature control device 330 is configured to mix the second heat transfer fluid 312 of the supply section 320 and the second heat transfer fluid 312 of the return section 340 in such a way to provide the second heat transfer fluid 312 at a defined temperature at said at least one heat transfer fluid outlet 350.
The process temperature control system 10 from
In particular, pumps 322, 326, which convey or circulate the second heat transfer fluid 312, can be provided in the heat consumer circuit 300. Similarly, these can be controllable by means of the temperature control device 330.
Furthermore, the process temperature control system 10 comprises at least one additional heating device 324 that is integrated into the heat consumer circuit 300. Thus, additional thermal energy can be provided if this is required. Via the controllable valve 323, heat transfer fluid 312 can be conveyed to the additional heating device 324 and thus be heated additionally. The controllable valve 323 can be a proportional valve which allows the flow volume to be controlled. In particular, the valve 323 can be controlled by means of the temperature control device 330.
The heat consumer circuit 300 of the process temperature control system 10 shown in
Furthermore, the heat consumer circuit 300 comprises at least one temperature control device 330. This temperature control device 330 comprises at least one heat transfer fluid outlet 350 that is connected to a supply manifold 500.
This supply manifold 500 is configured to distribute the second heat transfer fluid 312 to different consumers (components) of a film stretching unit 1 (see
To control the temperature as exactly as possible, the temperature control device 330 is configured to mix the second heat transfer fluid 312 of the supply section 320 and the second heat transfer fluid 312 of the return section 340 in such a way to supply the second heat transfer fluid 312 at a defined temperature at said at least one heat transfer fluid outlet 350. To this end, the valves 330a, 330b and 330c are provided.
Furthermore, the process temperature control system 10 from
The valves 330a, 330b and 330c can be controllable valves that are controlled by the temperature control device 330. In particular, the valves 330a, 330b and 330c can be proportional valves which allow the flow volume to be controlled. By means of the targeted control of the valves 330a, 330b and 330c, the heat transfer fluid 312 can be mixed and supplied at a defined temperature to the heat exchanger 210 and/or the heat transfer fluid outlet 350.
In particular, a pump 321 can be provided in the heat consumer circuit 300 that conveys or circulates the second heat transfer fluid 312. Optionally, a pump 222 can also be provided between the heat storage unit 210 and the heat exchanger 230 for conveying the corresponding heat transfer fluid. These pumps 321, 222 can also be controllable by means of the temperature control device 330.
Furthermore, the process temperature control system 10 comprises at least one additional heating device 324 that is integrated into the heat consumer circuit 300. Thus, additional thermal energy can be provided if this is required. Via a controllable valve 323, heat transfer fluid 312 can be conveyed to the additional heating device 324 and thus heated additionally. The controllable valve 323 can be a proportional valve which allows the flow volume to be controlled. In particular, the valve 323 can be controlled by means of the temperature control device 330.
A pump 222 conveys heat transfer fluid from the heat storage unit 210 to the heat exchanger 230. The pump 331 is upstream of the heat exchanger 230. Furthermore, the heat consumer circuit 300 comprises multiple (for example two here) additional heating devices 324a, 324b that are connected parallel to the heat exchanger 230. In each case, a pump 332, 333 is upstream of the additional heating devices 324a, 324b.
The return collector 400 takes the returning second heat transfer fluid 312 from at least one consumer of the film stretching unit and supplies this to the pumps 331, 332, 333.
These pumps 222, 331, 332, 333 can be controlled by means of the temperature control device 330 in order to control the flow velocity of the corresponding heat transfer fluid in the circuit allocated to the pump. By means of the pump 222, the flow velocity of the heat transfer fluid allocated to the heat storage unit 210 can be controlled in the heat exchanger 230. By means of the pump 331, the flow velocity of the heat transfer fluid 312 can be controlled in the heat exchanger 230. Thus, the amount of thermal energy to be drawn from the heat storage unit 210 via the pump(s) 222 and/or 331 can be controlled.
Via the pumps 332 and 333, the flow velocity of the heat transfer fluid 312 can be controlled in the additional heating devices 324a, 324b. Thus, the amount of thermal energy transferred to the heat transfer fluid 312 can also be controlled here.
After the heat transfer fluid 312 has passed the branches of the additional heating device(s) 324a, 324b and/or the heat exchanger 230, the branches are mixed and supplied to the heat transfer fluid outlet 350 or the supply manifold 500. As already described above, the supply manifold 500 is optional and can be omitted if only one consumer is to be supplied with heat transfer fluid 312. Accordingly, the return collector 400 is also optional, for example, if the heat transfer fluid 312 is returned from only one consumer.
The energy generated by the solar heat generator 110 is initially transferred to the first heat transfer fluid 112 (in the solar heat generator 110) and then transferred to the intermediate-circuit heat transfer fluid 212 in the heat exchanger 215 for storage, in order to be stored in the heat storage unit 210 (indirect storage).
The starting material to be processed, i.e. a polymer (granules and/or powder), is initially supplied to an extruder 3 via a proportioner comprising a feed hopper 2 and is melted in the extruder 3.
By means of a nozzle unit 3a (for example a slot die) that is downstream of the extruder(s) 3, the polymer melt is applied to a chill roll 4 and cooled. The film 9 formed as a result is then stretched by means of a machine direction orienter (MDO) 5 in the machine direction, i.e. longitudinally. Materially and depending on the process, this machine direction stretching occurs at a temperature range of approx. 80° C. to approx. 140° C.
Subsequently, the film is fed into a transverse direction orienter (TDO) 6 and stretched here in the transverse direction. The stretching is described again in detail with regard to
Then, the film 9 is drawn out of the oven by means of a pull-roll device 7 (what is termed a pull roll) and subsequently wound by means of the wrapping device 8.
Similarly, the stretching does not have to occur sequentially, but may occur simultaneously. The difference between simultaneous and sequential stretching is that in simultaneous stretching the film is stretched in the machine direction (longitudinal direction) and the transverse direction at the same time. This occurs in what is termed a simultaneous stretching unit (e.g. a simultaneous stretching oven). The simultaneous stretching unit is temperature controlled and accelerates a gripped film in such a way that this film is stretched simultaneously in the machine direction and in the transverse direction. A separate machine direction orienter is therefore not required.
By means of a process temperature control system 10 described previously (see
The following example illustrates this. A solar heat generator is assumed that comprises linear Fresnel collectors. In the case of the solar heat generator amounting to 5000 m2, approx. 3,520 MWh thermal energy is yielded at a temperature level of the heat transfer fluid of approx. 250° C. for an average direct normal irradiance (DNI) of 340 W/m2. At a total annual heat requirement of approx. 15,000 MWh for the TDO and MDO devices, which currently are supplied by the fossil fuel coal, this equals 23% or 1.471 tCO2e.
As the above example demonstrates, using concentrated solar power contains significant energy savings potential in the case of heat generation for a film stretching unit.
The oven 612 has a drawing direction R that is the direction of travel of the film 9 to be stretched. The transverse direction Q of the oven 612 runs transverse to the drawing direction R as well as horizontally and the vertical direction H runs vertically.
The oven 612 has different zones along the drawing direction R for treating the film 9 to be stretched.
In the first zone 622, also termed preheating zone, the film is heated. In the following second zone 624 (“stretching zone”), the film is stretched in the transverse direction Q so that it has a larger width at the end of the second zone 624 than at the start.
After the stretching is completed, the film 9 then passes through a third zone 626 (termed “heat treatment zone”, “further heating zone” and/or “annealing zone”), in which a relaxation of the film 9 can occur at high temperatures.
Then, the film 9 passes through a fourth zone 628 and a fifth zone 630 (“cooling zone”), wherein the film is cooled in the fifth zone 630.
The fourth zone 628 is termed the neutral zone and is used to separate the third zone 626 from the fifth zone 630. The neutral zone is, for example, an empty space without ventilation.
The transport system 614 comprises, in a known manner, two transport rails 632 that are located mirror-symmetrically in respect to a central plane M of the stretching unit 6 and the oven 612 as well as extend at least in part into the oven 612.
In an entry zone 634 as well as an exit zone 636, in which the film to be stretched of the stretching unit 6 is fed and removed, the transport rails 632 run outside of the oven 612.
The film 9 is gripped in the known manner by grippers (not shown) of the transport system 614, which are guided along the transport rails 632, and transported through the oven 612 in the drawing direction R. The film runs in a film track F that is defined in the oven 612 by the transport system 614. The film track F intersects the central plane M.
In particular, the zones 634, 622, 624, 626, 628, 630 and 636 of the oven 612 can be temperature-controlled in a defined manner by means of the process temperature control system 10.
In addition, several nozzle boxes (not shown) are located in the oven 612 that convey the hot (temperature-controlled) air in the direction of the film web F. By means of the hot air, the interior of the oven and thus the film 9 is heated, cooled or kept at a predefined temperature. The air can be temperature-controlled via a suitable heat exchanger of the transverse direction orienter by means of the process temperature control system 10.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102022126925.6 | Oct 2022 | DE | national |
