Method for operating a filter device and filter device

Abstract

The invention relates to a method of operating a filter device (10) for a polymer melt to be filtered, the filter device comprising at least one first large-area filter (15a) having a plurality of filter elements (14a) in a first filter chamber (12a) and a first drain (18a) for the filtered polymer melt from the first filter chamber (12a). The polymer melt to be filtered is fed under pressure through the filter device (10). According to the invention, during basic operation, the polymer melt to be filtered is fed to the first large-area filter (15a) in a filtering direction (16) and filtering is carried out continuously through the first large-area filter (15a). During a backwash operation, the at least one filter element (14a) is backwashed free of foreign bodies by reversing the flow direction of the filtered polymer melt and passing it through the filter element (14a).

Description

[Technical field]

[0001] The present invention relates to a method for operating a filter device as defined in the preamble of claim 1 and to a filter device performing said method as defined in claim 15. [Background technology]

[0002] Especially in the production of thermoplastics, it is common to filter the polymer melt to remove foreign matter from it. Large area filters are generally used for this purpose, which comprise a filter chamber in which a number of filter cartridges (usually 37 to 169) are arranged. The large number of filter cartridges ensures a large filter surface. In this process, the material to be filtered flows through the filter cartridges from the outside to the inside. The polymer melt to be filtered is filtered through the side walls of the filter cartridges. The side walls usually have a filtering precision of 3 μm to 40 μm.

[0003] It is common to use so-called duplex filter units. This type of duplex filter unit has two identical filter means. Each filter means comprises a cylindrical filter chamber in which a large-area filter is respectively attached. The filter chambers and the large-area filters attached therein are preferably aligned vertically, through which the material to be filtered flows from bottom to top. The large-area filter is a filter comprising several filter cartridges arranged on a distributor. The filter cartridges and the distributor divide the filter chamber into an inlet zone and an outlet zone. The polymer melt is fed to the filter cartridges via the inlet to the filter chamber. The feed of the polymer melt is controlled via inlet valves arranged at the respective inlets to the filter chamber. The side walls of the filter cartridges constitute the filter parts. More specifically, the side walls can be circumferentially corrugated or formed in any shape so as to increase the filter surface.

[0004] The filter surface used is e.g. 45 m 2 ~255m 2 where is the sum of the sidewall surfaces of all the filter cartridges. The filtered polymer melt exits through the sidewall downstream of the distributor to the drain zone of the filter chamber and to the drain from the filter chamber. The polymer melt is fed to the filter device via a pump. Instead of filter cartridges, stacked disc filters can also be used.

[0005] Both filter means of the dual filter device are always operated alternately, so that if one filter chamber with a contaminated large-area filter becomes contaminated, it is possible to switch to the other filter chamber with the other clean large-area filter, which ensures continuous operation at all times.

[0006] To switch from one filter means to the other, the valves in the inlet and drain are switched accordingly. The valve in the inlet to the filter chamber containing the contaminated large-area filter is closed, and the drain valve in the drain from the filter chamber containing the contaminated large-area filter is also closed. At the same time, the inlet valve to the other filter chamber containing the clean large-area filter is opened, and the drain valve in the drain from the filter chamber containing the clean large-area filter is also opened. The polymer melt in the filter chamber containing the contaminated large-area filter is discharged via the drain valve in the inlet. Then, the entire filter chamber containing the contaminated large-area filter is removed from the filter device, or the filter chamber is opened and the distributor with the filter cartridge is removed and taken away for cleaning. Depending on the type of polymer, pyrolysis processes, chemical solutions, ultrasonic baths, high-pressure cleaners are used for cleaning, which remove plastic and filtered foreign matter from the side walls of the filter cartridge.

[0007] However, the disadvantage of the prior art method of operating the filter installation is that due to the unused parallel filter units of the duplex filter installation, the total filter surface is always twice as large as that used in the basic operating mode of the duplex filter installation. This results in very high investment costs and tied up capital. Also, cleaning is very labor-intensive and time-consuming, especially if the filter installation has to be transported to a specialist company for cleaning. Also, the cleaning process required so far is disadvantageous from an environmental point of view. Summary of the Invention

[0008] The object of the present invention is therefore to further develop a method for operating a filter device of the type defined in the preamble of claim 1 in such a way that the aforementioned drawbacks are avoided while the efficiency of the filter device is increased and continuous operation is nevertheless ensured.

[0009] This object is achieved for the method for operating a filter device by a combination of the features of claim 1 and the features of its preamble and for the filter device by the features of claim 15.

[0010] The dependent claims relate to advantageous further embodiments of the invention.

[0011] The invention is based on the insight that continuous backwashing of the individual filter cartridges, on the one hand, makes it possible to clean them and, on the other hand, allows further operation through the other filter cartridges: this is a simple way of improving the efficiency of the filter device.

[0012] In one aspect of the invention, a method for operating a filter device for a polymer melt to be filtered is provided, in which at least one first large-area filter with a plurality of filter elements is provided in a first filter chamber. The filter device has a first drain for the filtered polymer melt from the first filter chamber. The polymer melt to be filtered is passed under pressure through the filter device. According to the invention, in the basic operating mode, the polymer melt to be filtered is fed to the first large-area filter in a filtering direction, and filtering is carried out continuously through the first large-area filter. In the backwash operating mode, at least one filter element is backwashed free of foreign bodies by reversing the flow direction of the filtered polymer melt and passing it through the filter element. This facilitates cleaning without removing the individual filter elements. Backwashing one or several filter elements results in an extremely high cleaning efficiency and makes it possible to generate the pressure required for backwashing on the polymer melt with only minor additional measures. Using the backwash operating mode increases the filter life to an extent that would otherwise only be possible with the use of a larger filter surface without backwashing. This means that a filter apparatus using a backwash mode of operation can also be smaller in size compared to a filter apparatus having the same specific throughput but without a backwash operation.

[0013] For example, for a filter device, there may be two different operating modes: on the one hand, a backwash operating mode is performed also during the basic operating mode, which allows permanent filtration of the polymer melt, and on the other hand, a backwash operating mode is performed when the basic operating mode is not performed and vice versa.

[0014] It is preferred to backwash only one filter element at a time in the backwash mode, as this achieves the best cleaning effect, however, it is also possible to backwash several filter elements at once, depending on the number of filter elements and the pressure available for the polymer melt.

[0015] The backwash operating mode is initiated when both large area filters reach a predetermined degree of contamination, i.e. when it becomes necessary to use the backwash operating mode to clean the first large area filter. For this purpose, there may be various predetermined parameters for the large area filters, which are related to the degree of contamination of this large area filter and / or its filter elements.

[0016] In particular, immediately after backwashing of said at least one or more filter elements, said at least one or more other filter elements are backwashed.

[0017] In one embodiment of the invention, the switching from the at least one filter element to another or from the plurality of filter elements to another is performed as a function of the pressure upstream of the one or more backwashed filter elements, the volume of filtered melt passed during backwashing, and / or time, respectively. For example, 1.0, preferably 1.5, preferably 2 times the volume of the filter chamber can be used to backwash all filter elements of one large area filter. However, the aim is to backwash with as little melt as possible on the one hand and to clean the filter elements on the other hand.

[0018] The polymer melt discharged during backwashing can be discharged through a backwashing device that can be connected as needed to the filter element or elements being backwashed, which provides several design advantages, as will be shown below.

[0019] Preferably, in the backwash mode of operation, the filtered polymer melt flows intermittently and at intervals through one or more filter elements, which improves the cleaning effect in the backwash mode of operation.

[0020] The backwash operating mode in the large-area filter can be terminated when all filter elements of the large-area filter have been backwashed, however, it is also conceivable to carry out a permanent backwash operation in parallel with the basic operation.

[0021] In one embodiment of the present invention, at least one second large-area filter having a second filter chamber is provided. In particular, this filter has a valve at the second inlet to the second filter chamber to control the polymer melt to be filtered. Furthermore, a second drain is provided for the filtered polymer melt from the second filter chamber. The first and second inlets are connected to a common inlet, and the first and second drains are connected to a common drain. In the basic operating mode, the polymer melt to be filtered is fed simultaneously to both the first and second large-area filters in the filtering direction, and parallel filtering is performed successively through the first and second large-area filters. This increases the possibilities for further optimization.

[0022] For example, backwashing is performed only in one of the two large area filters, so that the other large area filter does not perform the backwashing operation mode, which is the basic operation mode, which ensures continuous filtration of a minimum amount of polymer melt at all times.

[0023] For the same reason, the additional polymer melt to be filtered is not supplied to the large-area filter undergoing backwashing, but only to the other large-area filter, so that one large-area filter is in the basic operating mode while the backwashing mode is only effective in the other large-area filter.

[0024] In one embodiment of the present invention, after one large-area filter is cleaned by the backwash operation mode, the backwash operation mode is started on the other large-area filter. Therefore, backwashing of one large-area filter always requires backwashing of the other large-area filter. This makes it possible to carry out the necessary basic cleaning of the filter device at regular intervals without essentially interrupting the operation of the filter device.

[0025] Another aspect of the invention relates to a filter device for carrying out the above-described method, the filter device comprising a first filter chamber in which a first large area filter having a plurality of filter elements is disposed, a first inlet having a first inlet valve to the first filter chamber, and a first drain from the first filter chamber.

[0026] The invention provides for a backwashing device that can be connected as required to the inlet side of the filter element or to the inlet sides of several filter elements, via which the filtered and backwashed polymer melt can be discharged from the filter chamber in a backwash operating mode. This is a simple way to backwash individual filter elements or a small number of filter elements, for example of a large area filter, while the other filter elements are still in the basic operating mode.

[0027] In one embodiment of the invention, the backwashing device is designed to be rotatable relative to the large-area filter and / or the large-area filter is designed to be rotatable relative to the backwashing device, the rotational movement being used to establish fluid communication between the backwashing device and the individual filter elements so that the individual filter elements can be backwashed.

[0028] The backwash device may be finger-shaped and may have at least one inlet port associated with one filter element.

[0029] Preferably, the backwashing device can be fluidly connected to the inlet side of the filter element or to multiple inlet sides of multiple filter elements via an inlet port, or to multiple inlet sides of multiple filter elements via multiple inlet ports, which provides an optimal coupling of the backwashing device with the filter element to be backwashed.

[0030] To facilitate termination of the backwash mode of operation, a large area filter having a filter element on an inlet side to the filter element and associated backwash device can have a closed rest area in which the backwash device is located when the backwash mode is not active, and one or more inlet ports are closed when the backwash device is in the rest area.

[0031] Additionally or alternatively, the area on the inlet side between the filter elements arranged at a distance from one another in the direction of movement of the large-area filter and / or the backwashing device can be of closed design, with the movement of the backwashing device relative to the large-area filter into this closed area resulting in the inlet port being closed or the inlet port of the backwashing device being closed.

[0032] In an advantageous further development of the invention, the backwashing device is designed and controllable in such a way that when the next filter element or elements to be backwashed are connected to the backwashing device, the connection between the just backwashed filter element and the backwashing device is disconnected, which ensures that only a certain filter element is backwashed at a time and that the next filter element is backwashed only after the already backwashed filter element has been opened again for basic operation.

[0033] Preferably, the backwash device and the large area filter each interact with a rotary actuator. Alternatively, either the backwash device or the large area filter can interact with the rotary actuator. The rotary actuator initiates the connection of the inlet port to the filter element or the fluid connection of the inlet port to the filter element.

[0034] To increase the available control options and make them more flexible, the backwashing device has a stop valve that can be used to close or open a discharge opening through which the backwashed polymer melt can be discharged. Additionally or alternatively, the backwashing device can also interact with a pump, which is used to discharge the polymer melt that is sent during backwashing through the backwashing device. The pump can be useful to create the necessary pressure differential so that the filtered polymer melt flows through one or more filter elements for backwashing.

[0035] In one embodiment of the present invention, pressure sensors are provided to measure the pressure in the polymer melt, in particular the pressure upstream and downstream of the filter chamber and / or upstream and downstream of a large area filter in the filter chamber.

[0036] In particular, a second filter chamber is provided in which a second large area filter having a plurality of filter elements is disposed, a second inlet having a second inlet valve to the second filter chamber, and a second drain from the second filter chamber.

[0037] Preferably, the filter element is constituted by a filter cartridge through which in the basic operating mode the polymer melt to be filtered flows in particular from inside to outside, which makes it easy to carry out backwashing, i.e. from outside to inside.

[0038] To reduce the manufacturing costs of the dual design filter apparatus, all of the filter chambers, large area filters, inlet valves, drain valves and / or backwash devices are each identical in design.

[0039] In particular, to ensure pressure for backwashing in filter units of dual design, a melt pump or a throttle, in particular an adjustable and / or connectable throttle, is arranged in the common drain or in the first and second drains. A throttle or melt pump can also be arranged in the drain of a filter unit of simple design, i.e. not designed as a dual unit. To ensure backwashing, sufficient pressure against the atmosphere is necessary. Since the pump in the backwashing unit, i.e. the suction pump, is limited by its NPSH value, arranging the throttle or melt pump in the drain is a useful alternative or supplement.

[0040] In an advantageous further development of the invention, the inlet valves and / or the drain valves and / or the stop valves and / or the rotary actuators are adapted to be hydraulic and / or electrically operated. A control device is provided which controls the inlet valves, the drain valves, the stop valves, the rotary actuators, the melt pump, the throttle and / or the backwash device to set the basic operating mode and the backwash operating mode, respectively.

[0041] Further advantages, features and possible applications of the present invention will become apparent from the following description with reference to illustrated embodiments.

[0042] These terms and associated reference numbers are used throughout the specification, claims and drawings as set forth in the following list of reference numbers. [Brief description of the drawings]

[0043] [Figure 1] FIG. 1 is a schematic diagram of a filter device that is composed of a filter chamber having a plurality of filter elements and a drain pump attached to the side of the filter chamber. [Diagram 2] FIG. 2 is a schematic diagram of a filter device consisting of two filter chambers having a plurality of filter elements. [Diagram 3]FIG. 3 is a top view of a drainage arrangement having multiple inlet ports. [Figure 4] FIG. 4 is a schematic diagram of a filter device comprised of a filter chamber having a plurality of filter elements. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] 1 shows a filter device 10 for polymer melt to be filtered, comprising a first filter chamber 12a in which a stationary first large-area filter 15a is arranged. The first large-area filter 15a is provided with a number of filter cartridges 14a and a distribution disk part 14c. Furthermore, the first filter chamber 12a has a drain pipe 18, an inlet pipe 20 and a drain device 21a.

[0045] The filter cartridges 14a are arranged in a star shape on the distribution disc portion 14c. Also, there are many more filter cartridges arranged next to each other than shown in Fig. 1. Fig. 1 is only a schematic diagram / representation of an embodiment. A total of 37 to 169 filter cartridges 14c may be provided. The large number of filter cartridges 14c allows for a large filter surface, i.e. 45 m 2 More than 255m 2 The following filter surface is ensured:

[0046] The drain device 21a is provided with a first rotary actuator 30a and a first drain disk part 44a connected to the rotary actuator 30a. The first drain disk part 44a is in close contact with the distribution disk part 14c. The first drain disk part 44a has a radially extending backwash pipe 48a which runs in a finger-like manner from the inner inlet port 42a through two further inlet ports 42a radially outward to the outer periphery of the first drain disk part 44a and opens into the annular pipe 17. Adjacent to it is the first drain pipe 24a. The first drain valve 26a is attached to the first drain pipe 24a and the drain pump 22 is attached downstream thereof.

[0047] The upper part 42a of the first drain disk part 44a is in close contact with the lower part of the distribution disk part 14c of the first large area filter 15a, so that the polymer melt cannot penetrate between the drain disk part 44a and the distribution disk part 14c. In addition to the inlet port 42a for the backwash pipe 48a, a first through-hole part 42c is provided in the first drain disk part 44a, which connects the inlet pipe 20 to the individual supply ports 46a of the filter cartridges 14a. All filter cartridges 14a are arranged so that these supply ports 46a are connected to either the inlet port 42a or the through-hole part 42c of the drain device 21 in the backwash mode. When all supply ports 46a are connected to the through-hole part 42c, all filter cartridges 14a are in the basic operating mode.

[0048] The pressure sensors 13a and 13b are connected to a control device (not shown here) and are arranged in the lower and upper zones of the first filter chamber 12a. A circumferential annular pipe 17 connected to the inlet port of the first drain valve 26a is provided in the circumferential direction of the drain disk portion 44a in a region radial to the rotation axis 32 of the first large area filter 15a. A backwash pipe 48a of the drain disk portion 44a is connected to the first drain pipe 24a via the drain valve 26a.

[0049] In the basic operation mode, the polymer melt to be filtered flows in the filtering direction 16 shown in FIG. 1 and enters through the inlet pipe 20 attached to the lower region of the first filter chamber 12a. The polymer melt to be filtered flows through the through-hole 42c of the first drain disk part 42a, which is partially opened in the lower region of the filter chamber 12a (as shown in the right region of the first filter chamber 12a with respect to the filtering direction 16 in FIG. 1), through the through-hole 42c provided in the drain disk part 44a, and through the supply port 46a of the distribution disk part 14c into the filter cartridge 14a. The polymer melt to be filtered flows through the filtering process from inside to outside through the side wall part 28 of the filter cartridge 14a of the first large area filter 15a, enters the upper part of the first filter chamber 12a, and then flows into the drain pipe 18 with the adjustable throttle valve 34. The side wall part 28 of the filter cartridge 14c generally has a filtering precision of 3 μm or more and 20 μm or less.

[0050] In the backwash operating mode, which can be operated in parallel with the basic operating mode, as shown in FIG. 1, the filtered polymer melt from the upper region of the first filter chamber 12a is pushed from the outside to the inside through the side wall 28 of the filter cartridge 14a by a controllable pressure gradient. The pressure gradient is generated, inter alia, by the drain pump 22 in conjunction with the adjustable throttle valve 34. The filtered polymer melt flowing against the filtering direction 16 in the basic operating mode removes foreign bodies from the side wall 28 of the filter cartridge 14a. The backwashed polymer melt from the first filter cartridge 14a flows through the first backwash pipe 48a in the first drain disc part 44a into the annular pipe 17 and through the opened first drain valve 26a into the first drain pipe 24a. In FIG. 1, the backwash operating mode is shown in the left region of the first filter chamber 12a with respect to the filtering direction 16.

[0051] The pressure gradient required for backwashing can be generated by the pressure generated by the filtered polymer melt fed through the first filter cartridge 14a and the negative pressure generated by the drain pump 22. Another advantageous embodiment of the invention has an adjustable throttle (not shown) in the drain pipe 24a instead of the drain pump 22 shown in Figure 1. The pressure gradient can be monitored by pressure sensors 13a and 13b in the lower and upper regions of the first filter chamber 12a and a control device (not shown).

[0052] The drain pump 22, the adjustable throttle 34, the first drain valve, the rotary actuator 30a and the pressure sensor 13b are all connected to the controller.

[0053] By appropriately controlling the drain pump 22 in the backwash operating mode, the backwashed polymer melt can be moved intermittently, thereby allowing intermittent and spaced cleaning of the filter cartridge 14a to be performed and thus improved.

[0054] The control device switches between the star-shaped rows of filter cartridges 14a to be backwashed as a function of the pressure measured by the two pressure sensors 13a and 13b, the volume of backwashed polymer melt through the first drain pipe 24a, or a predefined time. For this purpose, the control device rotates the drain disk part 44a by means of the first rotary actuator 30a in the direction of rotation 31, i.e. in this case counterclockwise. In this process, the position of the first drain disk part 44a relative to the distribution disk part 14c of the first large area filter 15a, i.e. the position of the inlet port 42a provided in the first drain disk part 44a relative to the position of the supply port 46a in the distribution disk part 14c for the filter cartridge 14a, changes in the direction of rotation 31. This allows switching between a completely backwashed first filter cartridge 14a and a first filter cartridge 14a that still needs backwashing.

[0055] A row of supply ports 46a is provided at equal angular intervals in the circumferential direction on the distribution disk part 14c. A filter cartridge 14a is associated with each supply port 46a. In addition, there is an area that does not have any supply ports 46a and where no filter cartridge 14a is arranged, which serves as a rest area for the drainage device 21a. By positioning the drainage device 21a in this rest area of ​​the distribution disk part 14c of the first large area filter 15a, which does not have any supply ports 46a, all the supply ports 46a are operated in the basic operating mode.

[0056] The specific operating mode and design of the rotatable first drain disk portion 44a will become apparent from the following description.

[0057] In an alternative embodiment of the invention, the rotary actuator 30a may be connected to a rotatable first large area filter 15a, where the first drain disk portion 44a is located in a fixed position in the filter chamber 12a.

[0058] Other embodiments of the present invention (not shown) have a different number of filter cartridges 14a and a corresponding different number of through-holes 42c and inlet ports 42a in the first drain disk portion 44a, allowing the backwash mode of operation to be applied to one or more filter cartridges in the first large area filter 14, depending on the design of the drain disk portion 44a and the large area filter 46a.

[0059] Compared to the filter device 10 of Fig. 1, the filter device 10 of Fig. 2 comprises, as a further embodiment of the invention, a further second filter chamber 12b, which is identical in structure to the first filter chamber 12a, and for this reason, all the individual components will not be described again individually below, but will simply be referred to below as "second" components instead of "first" components and will be provided with the reference "b" instead of the reference "a".

[0060] The drain devices 21a and 21b in the two filter chambers 12a and 12b are connected to these rotary actuators 30a and 30b, respectively. Instead of the drain disk 44a shown in the embodiment of FIG. 1, a finger-shaped first drain outlet 54a is provided in the first filter chamber 12a, and a second drain outlet 54b is provided in the second filter chamber 12b. The drain outlets 54a, 54b are provided with backwash openings 56a, 56b that extend from the radially inner supply ports 46a, 46b to the radially outer supply ports 46a, 46b. The backwash openings 56a, 56b are connected to the backwash pipes 48a, 48b in the drain outlets 54a, 54b. The drain devices 21a and 21b are fixed. In contrast, the large-area filters 15a and 15b are rotatable and comprise a plurality of filter cartridges 14a and 14b. The filter cartridges 14a, 14b are connected to associated distributor disc sections 14c and 14d. Supply ports 46a and 46b are located in the distributor disc sections 14c, 14d.

[0061] The first filter chamber 12a has a first inlet pipe 20a in its lower region, and the second filter chamber has a second inlet pipe 20b. The two inlet pipes 20a and 20b are supplied with the polymer melt to be filtered from a common inlet pipe 20 via a common inlet valve 36. Furthermore, the first filter chamber 12a is connected in its upper region to a first drain pipe 18a, and the second filter chamber is connected to a second drain pipe 18b.

[0062] The two drain pipes 18a and 18b are connected to the common drain pipe 18 via a common drain valve 38. A first return pipe 52a having a first return valve 40a is arranged branching off from the first drain pipe 18a, and a second return pipe 52b having a second return valve 44b is arranged branching off from the second drain pipe 18b. The two return pipes 52a and 52b required for backwashing are connected to each other, and in the backwashing operation mode, the filtered polymer melt is supplied from the common drain pipe 18 via the backwashing pump 50.

[0063] In comparison with FIG. 1, FIG. 2 shows rotary actuators 30a and 30b arranged above the two filter chambers 12a and 12b as a further embodiment of the invention.

[0064] In the basic operating mode, the two inlet pipes 20a, 20b for the filter chambers 12a, 12b are fed with the polymer melt to be filtered from the common inlet pipe 20 through the common inlet valve 36. The polymer melt to be filtered flows through the inlet pipes 20a, 20b into the lower regions of the filter chambers 12a, 12b. From the lower regions of the filter chambers 12a and 12b, the polymer melt to be filtered is fed into the filter cartridges 14a and 14b through the feed ports 46a and 46b of the two large area filters 15a and 15b. The polymer melt to be filtered is filtered through the side wall 28 and flows as filtered polymer melt into the upper regions of the filter chambers 12a and 12b. The filtered polymer melt is fed through the drain valve 38 into the common drain pipe 18 through the first drain pipe 18a and the second drain pipe 18b. In FIG. 2, the basic mode of operation is shown with the first filter chamber 12a to the right and the second filter chamber 12b to the left.

[0065] The first rotary actuator 30a and first drain valve 26a of the first filter chamber 12a may be adjusted independently of the second rotary actuator 30b and second drain valve 26b of the second filter chamber 12b, and vice versa.

[0066] The backwash mode of operation can be caused by a pressure gradient in the region of the filter cartridges 14a and / or 14b created by the backwash pump 50 shown in FIG. 2. More specifically, the backwash pump 50 pumps the filtered polymer melt from the common drain pipe 18 through the return pipes 52a and / or 52b into the upper region of the filter chambers. The backwash mode can be initiated in the filter chambers 12a and 12b for the respective filter cartridges 14a and 14b by opening the return valves 40a and 40b in the respective return pipes 52a and 52b. From the upper region of the filter chambers 12a and 12b, the filtered polymer melt is guided by the side walls 28 through a pressure gradient into the filter cartridges 14a and 14b connected with the respective drain outlets 54a and 54b. From inside the filter cartridges 14a, 14b, the filtered polymer melt flows through the feed ports 46a, 46b of the two large area filters 15a, 15b, through backwash openings 56a, 56b in some areas, and into the drain outlets 54a, 54b. The filtered polymer melt is fed through backwash pipes 48a, 48b through adjustable drain valves 26a, 26b into the drain pipes 24a, 24b.

[0067] When the backwash mode of operation is active for one of the filter chambers 12a and 12b, further inflow of polymer melt to be filtered into the filter chamber 12a or 12b in the backwash mode of operation is prevented by closing the inlet line 20a or 20b by the common inlet valve 36. In this case, the drain valve 38 is also closed on one side for the filter chamber 12a or the one currently in the backwash mode of operation. In this method of operation, only one filter chamber 12a, 12b is in the backwash mode, while the other filter chamber 12a, 12b is in the basic mode.

[0068] In Fig. 3, a schematic top view of the first drain device 12a from Fig. 2 is shown with a drain outlet 54a with backwash openings 56a and backwash pipes 48a and a first large-area filter 15a with a supply port 46a arranged in the distribution disk part 14c. The first drain outlet 54a, which is shown in fluid connection with the first large-area filter 15a, is finger-shaped in the area to the left of the rotation axis 32. Further supply ports 46a of the first large-area filter 15a, which are not fluidly connected with the drain outlet 54a and can be used for the basic operating mode, are shown offset by 90° in the direction of rotation. Further supply ports 46a (not shown) are arranged at equal angular intervals in the circumferential direction in the distribution disk part 14c. In addition, there are areas that do not have any supply ports 46a and where no filter cartridges are arranged, which serve as rest areas for the drain outlet 54a. By positioning the drain outlet 54a in this rest area of ​​the distribution disc portion 14c of the first large area filter 15a which does not have any supply ports 46a, all supply ports 46a are operated in the basic mode.

[0069] 3, a rotation of the first rotary actuator 30a through an angle of rotation corresponding to the angle of the row of rotationally adjacent filter cartridges 14a can be used to effect a switch from an already backwashed filter cartridge 14a to a filter cartridge 14a that still needs to be backwashed, and twice the angle of rotation is required to pass through the rest area.

[0070] FIG. 4 is a schematic diagram of the first filter chamber 12a of FIG. 1 without the drain pump 22 attached to the first drain line 24a and without the throttle valve 34 attached to the drain line 18.

[0071] All valves shown in Figures 1, 2 and 4 can be electrically and / or hydraulically adjusted independently of one another by a control device (not shown), so that the basic and backwash operating modes can be operated in parallel not only in the individual filter chambers 12a and 12b but also between the individual filter chambers 12a, 12b.

[0072] Thus, the method illustrated in Figures 1-4 allows for a parallel backwash operating mode of filter cartridges 14a, 14b in filter chambers 12a, 12b, as well as a backwash operating mode in only one filter chamber 12a, 12b and a basic operating mode in the other filter chamber 12a, 12b, using a corresponding filter device 10 according to the present invention.

[0073] According to the invention, the backwash operating mode is initiated whenever the large-area filters 15a, 15b reach a certain degree of contamination, i.e. when the large-area filters 15a, 15b need to be cleaned, and the backwash operating mode in the large-area filters 15a, 15b is terminated again when all the filter cartridges 14a, 14b have been backwashed.

[0074] The embodiment of Fig. 2 allows both filter chambers 12a, 12b to carry out the basic operating mode. If the backwash operating mode is possible in one filter chamber 12a, 12b, the filter cartridges 14a, 14b in this one filter chamber 12a, 12b can be backwashed in one operation mode as described, with the filter cartridge 14a, 14b not in backwash operation being in basic operation. For this purpose, in the backwash operating mode, the inlet valve 36 in the partial connection of the filter chambers 12a, 12b is closed on one side. For this embodiment, a throttle valve (not shown) is provided in the drain pipe 18.

[0075] Alternatively, the filter cartridges 14a, 14b of one filter chamber 12a, 12b can be backwashed sequentially without the other filter cartridges 14a, 14b of this filter chamber 12a, 12b being in the basic operation mode, while all filter cartridges 14a, 14b of the other filter chamber 12a, 12b are in the basic operation mode. In this way, when one filter chamber 12a, 12b is completely backwashed, the filter cartridges 14a, 14b of the other filter chamber 12a, 12b are backwashed immediately thereafter. Then, all filter cartridges 14a, 14b of the filter chambers 12a, 12b that have been backwashed are in the basic operation mode. In this way, only one filter chamber 12a, 12b is used for backwashing, while the filter cartridges 14a, 14b of the other filter chamber 12a, 12b are in the basic operation mode. When the filter cartridge 14a, 14b in the other filter chamber 12a, 12b has also been cleaned, all filter cartridges 14a, 14b in the two filter chambers 12a, 12b are in the basic operating mode.

[0076] The present invention is characterized by the possibility of operating the backwash operation mode and the basic operation mode simultaneously. This ensures that a minimum amount of filtered polymer melt is always discharged from the filter device 10 and that continuous operation is guaranteed. The use of backwash significantly extends the deadline for costly removal of the filter cartridges 14a, 14b for cleaning. Moreover, this method also extends the life of the filter device 10.

[0077] The backwash pump 50 is preferably operated continuously to prevent breakage of the polymer melt in the return lines 52a, 52b. The return valves 40a, 40b are open for this purpose. [Explanation of symbols]

[0078] 10 Filter device 12a First filter chamber 12b Second filter chamber 13a Lower pressure sensor 13b Upper pressure sensor 14a: Filter cartridge of first large area filter 15a 14b Filter cartridge of second large area filter 15b 14c Distribution disk portion of first large area filter 15a 14d Distribution disk portion of second large area filter 15b 15a 1st large area filter 15b Second large area filter 16 Filtration direction 17 Circular pipe 18 Drain pipe 18a First drain pipe 18b Second drain pipe 20 Inflow pipe 20a 1st inflow pipe 20b 2nd inflow pipe 21a First drain device 21b Second drain device 22 Drain pump 24a First drain pipe 24b Second drain pipe 26a First drain valve 26b Second drain valve 28 Side wall 30a First rotary actuator 30b Second rotary actuator 31 Rotation direction 32 Rotation axis 34 Throttle valve 36 Inlet valve 38 Drain valve 40a First return valve 40b Second return valve 42a Inlet port of first drain device 21a 42b inlet port of second drain device 21b 42c: Through-hole portion of first drain device 21a 44a First drain disc part 46a: supply port of first large area filter 15a 46b Supply port of second large area filter 15b 48a 1st backwash pipe 48b 2nd backwash pipe 50 Backwash Pump 52a First return pipe 52b Second return pipe 54a First drain outlet 54b Second drain outlet 56a Backwash opening of first drain outlet 54a 56b Backwash opening of second drain outlet 54b

Claims

1. A method of operating a filter apparatus (10) for filtering a polymer melt, comprising the steps of: at least one first large area filter (15a) having a plurality of filter elements (14a) in a first filter chamber (12a); a first drain pipe (18a) for filtered polymer melt from the first filter chamber (12a); The polymer melt to be filtered is passed under pressure through said filter device (10), During a basic operating mode, the polymer melt to be filtered is fed to the first large-area filter (15a) in a filtering direction (16), and filtering is carried out continuously through the first large-area filter (15a), During a backwash mode of operation, at least one filter element (14a) is backwashed free of foreign matter by reversing the flow direction of the filtered polymer melt and passing it through said filter element (14a).

2. 10. The method of claim 1 , The method according to claim 1, wherein the basic operating mode is also active during the backwash operating mode.

3. 10. The method of claim 1 , The method, wherein the backwash mode of operation is performed when the base mode of operation is not performed, and vice versa.

4. 10. The method of claim 1 , A method according to claim 1, wherein a plurality of filter elements (14a) are backwashed simultaneously in said backwash mode of operation.

5. 10. The method of claim 1 , The method is characterized in that the backwash operation is initiated when the large-area filter (15a) reaches a predetermined degree of contamination, i.e. when the large-area filter (15a) needs to be cleaned by a backwash operation mode.

6. 10. The method of claim 1 , In particular, the method is characterized in that immediately after the backwashing of the at least one filter element (14a) or the backwashing of the plurality of filter elements (14a), at least one other filter element (14a) or a plurality of other filter elements (14a) is backwashed.

7. 7. The method of claim 6, wherein the switching from the at least one filter element (14a) to another filter element (14a) or from the plurality of filter elements (14a) to another filter element (14a) occurs as a function of pressure upstream of the backwashed filter element or elements (14a), a volume of filtered melt passed during backwashing, and / or time.

8. 10. The method of claim 1 , 4. A method according to claim 3, wherein the polymer melt discharged during backwashing is discharged through a backwashing device (21a) which can be connected as required to said one or more filter elements (14a) to be backwashed.

9. 10. The method of claim 1 , The method according to claim 1, wherein in said backwash mode of operation, filtered polymer melt flows intermittently and at intervals through said one or more filter elements (14a).

10. 10. The method of claim 1 , The method according to claim 1, wherein the backwashing operation in the large area filter (15a) is terminated when all of the filter elements (14) of the large area filter (15a) have been backwashed.

11. 10. The method of claim 1 , At least one second large area filter (15b) is provided having a second filter chamber (12b), a second inlet pipe (20b) to said second filter chamber (12b) for controlling the polymer melt to be filtered, and a second drain pipe (18b) for the filtered polymer melt from said second filter chamber (12b); the first inlet pipe (20a) and the second inlet pipe (20b) are connected to a common inlet pipe (20), and the first drain pipe (18a) and the second drain pipe (18b) are connected to a common drain pipe (18); The method according to claim 1, wherein in said basic operating mode, the polymer melt to be filtered is fed simultaneously to both the first large-area filter (15a) and the second large-area filter (15b) in the filtration direction (16), and parallel filtration is carried out successively via the first and second large-area filters (15a, 15b).

12. 12. The method of claim 11, The method according to claim 1, wherein the backwash operating mode is performed in only one of the two large area filters (15a, 15b).

13. 12. The method of claim 11, The method is characterized in that additional polymer melt to be filtered is not supplied to the large-area filter (15a, 15b) in which the backwash operation is performed, but is supplied only to the other large-area filter (15a, 15b), thereby causing the one large-area filter (15a, 15b) to be in the basic operation mode and the backwash operation mode to be effective only in the other large-area filter (15a, 15b).

14. 12. The method of claim 11, A method according to claim 1, characterized in that after cleaning the first large area filter (15a, 15b) by a backwash operating mode, the backwash operating mode is started on the second large area filter (15a, 15b).

15. A filter device (10) for carrying out the method according to any one of claims 1 to 14, comprising: a first filter chamber (12a) in which a first large area filter (15a) having a plurality of filter elements (14a) is disposed; a first inlet pipe (20a) to the first filter chamber (12a); a first drain pipe (18a) from the first filter chamber (12a); 1. A filter arrangement comprising: a backwashing device (21a) connectable, as required, to the inlet side of one filter element (14a) or to the inlet sides of a number of filter elements (14a), via which, during a backwashing operating mode, the filtered and backwashed polymer melt can be discharged from said filter chamber (12a).

16. 16. The filter device according to claim 15, A filter device, characterized in that the backwash device (21a) is designed to be rotatable relative to the large-area filter (15a).

17. 16. The filter device according to claim 15, A filter device, characterized in that the large-area filter (15a) is designed to be rotatable relative to the backwash device (21a).

18. 16. The filter device according to claim 15, The backwash device (21a) is finger-shaped and has at least one inlet port (42a) associated with the filter element (14a).

19. 16. The filter device according to claim 15, The backwash device (21a) can be fluidly connected to the inlet side of the filter element (14a) or to multiple inlet sides of multiple filter elements (14a) via the inlet port (42a), or to multiple inlet sides of multiple filter elements (14a) via multiple inlet ports (42a).

20. 20. The filter device according to claim 18, the large area filter (15a) having the filter element (14a) has an associated closed rest area on the inlet side to the filter element (14a) and to the backwash device (21a); The rest area is arranged when the backwash device (21a) is not in backwash operation, in which case the inlet port (42a) or a number of the inlet ports (42a) are closed and / or the supply-side area between the filter elements (14a) arranged at a distance from each other in the movement direction of the large-area filter (15a) and / or the backwash device (21a) is designed to be closed, whereby the inlet port (42a) or a number of the inlet ports (42a) of the backwash device (21) are closed during the relative movement of the backwash device (21a) with respect to the large-area filter (15a) from one backwash process to the next backwash process.

21. 16. The filter device according to claim 15, The backwashing device (21a) is designed and controllable such that when the next filter element (14a) or multiple filter elements (14a) to be backwashed are connected to the backwashing device (21a), the connection between the filter element (14a) that has just been backwashed and the backwashing device (21a) is released.

22. 16. The filter device according to claim 15, The backwash device (21a) and the large-area filter (15a) each interact with a rotary actuator (30a), or either the backwash device (21a) or the large-area filter (15a) interacts with a rotary actuator (30a).

23. 16. The filter device according to claim 15, The backwashing device (21a) includes a stop valve (26a) that can be used to close or open a drain port (48a) through which the backwashed polymer melt can be discharged, and / or interacts with a pump (22) that is used to discharge the polymer melt that is pumped during backwashing through the backwashing device (21a).

24. 16. The filter device according to claim 15, A filter device, characterized in that the backwash device (21a) includes an adjustable and / or connectable throttle (34).

25. 16. The filter device according to claim 15, 1. A filter device, characterized in that pressure sensors (13a, 13b) are provided for measuring the pressure occurring in the polymer melt, in particular the pressure upstream and downstream of said filter chamber (12a) and / or upstream and downstream of said large area filter (15a) in said filter chamber (12a).

26. 16. The filter device according to claim 15, a second filter chamber (12b) in which a second large area filter (15b) having a plurality of filter elements (14b) is disposed; A filter arrangement comprising a second inlet pipe (20b) to the second filter chamber (12b) and a second drain pipe (18b) from the second filter chamber (12b).

27. 16. The filter device according to claim 15, A filter device, characterized in that the filter elements (14a, 14b) are constituted by filter cartridges through which the polymer melt to be filtered flows in particular from inside to outside during said basic operating mode.

28. 16. The filter device according to claim 15, A filter device characterized in that all of the filter chambers (12a, 12b), the large area filters (15a, 15b), the drain pipes (40a, 40b) and / or the drain valves (21a, 21b) have the same structure.

29. 16. The filter device according to claim 15, A filter device characterized in that a melt pump (68) is arranged in a common drain pipe (18) or in the left and right drain pipes (18a, 18b).

30. 16. The filter device according to claim 15, 1. A filter device, characterized in that a throttle, in particular an adjustable and / or connectable throttle, is arranged in a common drain pipe (18) or in said first and second drain pipes (18a, 18b).

31. 16. The filter device according to claim 15, the valves (26a, 26b, 34, 36, 38, 40a, 40b) and / or the rotary actuators (30a, 30b) are of hydraulic and / or electric design, The filter device is characterized in that a control device is provided that controls the valves (26a, 26b, 34, 36, 38, 40a, 40b), the rotary actuators (30a, 30b), the melt pump (50), the throttle (34), and / or the backwash device (21a, 21b) to set the basic operation mode and the backwash operation mode, respectively.

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