METHOD AND FILTER PRESS FOR THE PRODUCTION OF PELLETS FROM A PARTICLE-LOADED LIQUID AND PLANT FOR THE PRODUCTION OF PELLETS

Description

[0001] The invention relates to a method for producing pellets in a filter press according to claim 1, a filter press for producing pellets according to the preamble of claim 9, and a plant for producing pellets according to claim 14.

[0002] In addition to belt filters and drum filters, chamber filter presses are also used to separate particles from liquids. A chamber filter press is a cake filtration process that concentrates the medium to be filtered into a retentate with a solids content of approximately 40% to 60%. This process is discontinuous, however. First, the medium to be filtered is fed into the chamber filter press for a specific period of time, or until a certain filtration rate is achieved, to form the retentate. Then, the chamber filter press is opened to dissolve the retentate. To dissolve the retentate, the individual filter plates of the chamber filter press must be laboriously emptied and cleaned to be ready for the next pressing cycle.Furthermore, it was found that while such a chamber filter press initially exhibits high filtration efficiency at the start of the process and can thus remove a large number of particles from the medium being filtered, this filtration efficiency drops to zero very quickly because an impermeable, no longer drainable layer forms on the filter fabric. This can then, for example, be the starting point for opening and emptying the chamber filter press.

[0003] Furthermore, it is known that in cake filtration using filter presses, high filter pressure is associated with high filtration capacity. However, this is only true for a short time, because at higher filter pressures a highly compacted layer quickly forms on the filter fabric of the filter press, which then becomes impermeable. In extreme cases, this means that a high filtration capacity can be achieved for a short initial period, but shortly thereafter no further filtration is possible due to the formation of a thin, impermeable layer. This layer is so densely compressed that no permeate can pass through it. Thus, it may be the case that only a low overall filtration capacity can be achieved because the filter press becomes impermeable after only a short time. The filter press must then be opened and the filter fabric cleaned.

[0004] For example, US patent 5,618,423 discloses a rotary filter screen device in which foreign matter can be removed from a medium to be filtered by means of a drum in continuous operation. While this rotary filter screen device allows for continuous operation without the need to stop the process for cleaning the filter screens, the particles are only removed from the system by means of a residue removal rod. In particular, further processing of the retentate, for example for the production of pellets, is not possible.

[0005] EP 1 495 788 A1 discloses a filter device in the form of a chamber filter with a lid module and a bottom module and chambers with a filter medium arranged between them, wherein the filter device comprises a suspension inlet, a suspension outlet and a filtrate outlet and wherein a gas can be introduced into the interior of the filter device via a gas inlet line.

[0006] CN 112 516 633 A1 discloses a pneumatically operated filter press comprising a main support, a pressure plate and a press plate arranged on the main support, wherein the press plate is connected to a hydraulic drive device, wherein a group of chamber filter plates and / or membrane filter plates is arranged between the pressure plate and the press plate and wherein the chamber filter plates comprise a core plate and a filter cloth.

[0007] The object of the present invention is to provide a method and a filter press as well as a plant for the production of pellets, by means of which pellets can be produced in an economical manner.

[0008] A further object of the present invention is to provide a method and a filter press for the production of pellets, which allows production in a continuous operation and in particular in a compact device.

[0009] This and other problems are solved by a method for producing pellets according to claim 1 and a filter press according to claim 11 and a plant according to claim 16.

[0010] Advantageous embodiments of the method are found in claims 2 to 8, and advantageous embodiments of the filter press are set out in claims 10 to 13. An advantageous embodiment of the system is set out in claim 15.

[0011] The method according to the invention is particularly designed to be carried out using a filter press according to the invention or a preferred embodiment thereof. The filter press according to the invention is particularly designed to carry out a method according to the invention or a preferred embodiment thereof.

[0012] A solution to the problems is given by a method for producing pellets in a filter press from a particle-laden liquid, comprising the following steps: A) Introducing the particle-laden liquid into a filter chamber via a feed line; B) Applying a pre-pressure to the filter chamber, causing a retentate from the particle-laden liquid to be retained by a filter fabric in the filter chamber and a permeate to be directed to a drain; C) Releasing the pre-pressure on the filter chamber and backflushing at least part of the permeate from the drain into the filter chamber; D) Repeating steps A) to C) until a filter cake is obtained from the retentate in the filter chamber; E) Pressing the filter cake into a pellet by applying a main pressure to the filter chamber and removing the pellet from the filter chamber.

[0013] By backflushing a portion of the permeate into the filter chamber, the retentate, and especially the retentate particles, are detached from the filter fabric, allowing it to drain again. The retentate particles break off from the filter fabric during backflushing, restoring its drainage capacity, and remain in the filter chamber. In process step D), the particle concentration in the retentate is increased in each cycle, enabling the formation of a filter cake, which is then pressed into pellets. After pellet removal, the filter press is immediately ready for use again, as there is no need for laborious cleaning of the filter fabric; the pellet is simply ejected. This allows for continuous operation of the filter press.

[0014] A particle-laden liquid is a medium that contains solids in the form of particles. This could be, for example, beer or liquid manure that needs to be filtered.

[0015] The pellet is removed from the filter chamber, in particular by ejecting the pellet from the filter chamber, especially into a collection container or similar.

[0016] The filter fabric is preferably a stainless steel mesh with a mesh size in the micrometer range. The choice of filter fabric depends in particular on the particle-laden liquid, the size and / or size distribution of the particles in the particle-laden liquid, and the specific application of the filter press.

[0017] A pellet is a cylindrical object with a diameter of up to 10 cm, preferably around 6 cm. The diameter can be larger if required. The height or width of the pressed pellet is between 0.5 cm and 1.5 cm, preferably around 1 cm. The size and shape of the pellet are primarily determined by the size of the filter chamber. The pellet can also be a plate or a plate-shaped object. Overall, the pellet is very manageable and easy to transport.

[0018] Preferably, the particle-laden liquid is introduced slowly into the filter chamber, particularly at a low filter pressure, so that the filter fabric remains permeable for a longer period during the introduction of the particle-laden liquid. This slow introduction and correspondingly low filter pressure prevent the rapid formation of a thin, impermeable layer on the filter fabric. Thus, the slow introduction at a low filter pressure, for example over one minute, allows for the removal of more particles from the particle-laden liquid and a faster increase in the particle concentration in the retentate within the filter chamber.

[0019] Preferably, the supply of particle-laden liquid is interrupted in process step C) and resumed after backflushing.

[0020] A preferred embodiment is characterized in that the particle-laden liquid has a particle content of at least 10%, preferably at least 12%, and particularly preferably at least 15%. In particular, the particle content in the particle-laden liquid was increased upstream of the filter press by means of an oscillating membrane filter pump, such as that known from DE 10 2016 003 335 A1. An increased particle content in the particle-laden liquid accelerates the filter cake production process in the filter chamber, thereby enabling the production of more pellets in a given time interval.

[0021] Preferably, process steps A) to C) are carried out in their sequence at least 10 times, preferably at least 20 times, and particularly preferably at least 30 times. By repeating the process several times, the particle content in the retentate is increased from repetition to repetition, so that an increasingly thick filter cake builds up over time.

[0022] Preferably, the introduction of particle-laden liquid and backwashing of permeate is repeated every minute. Alternatively, or preferably additionally, the repetitions of the steps of introducing particle-laden liquid and backwashing of permeate can also be performed more quickly, for example after 10 seconds or 30 seconds. In particular, the interval can depend on the drainage capacity of the filter fabric and vary from cycle to cycle.

[0023] A preferred embodiment is characterized by the fact that the permeate backwashing is carried out in pulses. Preferably, this pulsed backwashing is achieved by applying compressed air, in particular a compressed air pulse, to the discharge. The pulsed backwashing detaches the retentate from the filter fabric, making it permeable to the permeate again for the next process or cycle. This can be done particularly easily and effectively using compressed air. In particular, a high pressure and thus a strong pulse can be generated quickly.

[0024] In a preferred embodiment, the drain is closed off by means of a valve before backwashing, preferably with compressed air being blown into the drain between the filter chamber and the valve. The valve allows the amount of permeate in the drain between the filter chamber and the valve to be limited, preventing an excessive amount of permeate from being backwashed into the filter chamber. Furthermore, the valve ensures that the backwash pulse is directed precisely into the filter chamber and through the filter fabric, rather than being dissipated in the drain.

[0025] Preferably, the particle-laden liquid is introduced into the filter chamber via at least two inlets, the inlets preferably being arranged opposite each other. The two inlets allow the particle-laden liquid to be introduced homogeneously and in large quantities into the filter chamber, particularly at a low filter pressure. This increases the throughput.

[0026] Alternatively, or preferably additionally, the permeate is discharged from the filter chamber via at least two outlets, preferably arranged opposite each other. The increased number of outlets allows the permeate to flow more quickly from the filter chamber into the discharge, thus accelerating the process.

[0027] A preferred embodiment is characterized by a filter cake having a thickness of at least 10 mm, preferably at least 20 mm, and most preferably at least 30 mm. Only when the filter cake has a thickness of at least 10 mm can corresponding pellets be pressed. Applying the main pressure further compresses the filter cake, resulting, for example, in a pellet with a thickness or height of approximately 1 cm from a filter cake with a thickness or height of 30 mm. If the desired thickness of the filter cake or pellet is not achieved, process steps A) to C) are repeated until the filter cake or pellet has the desired thickness.

[0028] Alternatively, or preferably additionally, the thickness of the filter cake is measured or determined, in particular by measuring the back pressure when the filter chamber is pressurized. The thickness of the filter cake can be measured directly by measuring the distance across the width of the filter chamber. However, the thickness of the filter cake is primarily determined by measuring the back pressure when the filter chamber is pressurized. The thicker the filter cake, the greater the back pressure, thus enabling a corresponding thickness determination.

[0029] Preferably, the residual moisture content of the pellet after pressing in process step E) is less than or equal to 25%. This ensures a low residual moisture content of the pellet during further processing. If the desired residual moisture content is not achieved, process steps A) to C) may need to be repeated once or several times. Alternatively, or preferably additionally, the main pressure can also be increased.

[0030] A preferred embodiment is characterized in that, before the pellet is removed from the filter chamber, the filter chamber is pressurized with compressed air, preferably via the supply line, for a duration of at least 10 seconds, preferably at least 20 seconds, and most preferably at least 30 seconds. Preferably, the supply line for the particle-laden liquid is shut off by means of a valve. In particular, the pressurization with compressed air is carried out from the supply line so that excess permeate is discharged into the drain. Pressurizing the filter chamber with compressed air before the pellet is removed dries the produced pellet.

[0031] Preferably, the filter chamber is pressurized with the pre-pressure and main pressure by means of a pressurizing device in the form of at least one pressure cylinder, preferably by at least two pressure cylinders, which are preferably arranged opposite each other. In particular, the at least one pressure cylinder is a pneumatic or hydraulic pressure cylinder. This allows the pre-pressure and the main pressure to build up uniformly and, especially when using hydraulic pressure cylinders, to generate higher pressures in the filter chamber and maintain them for a certain period of time.

[0032] The main pressure, the pre-pressure, the thickness of the filter cake and / or pellet, the flow rate and / or the filter pressure of the particle-laden liquid and / or the permeate are preferably determined by means of sensors. This allows for a constant overview of the current status of the process and / or the filter press.

[0033] The process is preferably controlled or regulated by a control device. Preferably, the process can be automated by means of the control device. In particular, this is an intelligent control device that, for example, repeats the number of repetitions of process steps A) to C) until a certain thickness of the filter cake is reached. The number of cycles of process steps A) to C) can vary from filter cake to filter cake or for a pellet depending on the particle content in the particle-laden liquid, the volume flow rate of the particle-laden liquid, the drainage capacity of the filter fabric, or other factors.

[0034] Preferably, to remove the pellet from the filter chamber, the pressure of at least one, or preferably at least two, closing cylinders, which are preferably arranged opposite each other, is released. The at least one closing cylinder enables simple and safe removal of the pellet.

[0035] Preferably, the filter chamber is sealed by exerting pressure from the at least one closing cylinder against the environment. Preferably, the at least one closing cylinder is a hydraulic or pneumatic closing cylinder.

[0036] Another solution to this problem and further problems is given by a filter press for producing pellets from a particle-laden liquid, comprising a filter chamber, at least one inlet for supplying the particle-laden liquid to the filter chamber, and at least one outlet for draining permeate from the filter chamber. The filter chamber includes a filter fabric arranged upstream of the outlet, and a press for pressurizing the filter chamber. Crucially, the outlet contains a device for backflushing permeate into the filter chamber or is functionally connected to it.

[0037] The backwashing device directs permeate from the drain into the filter chamber and dissolves retentate particles adhering to the filter fabric, thus enabling it to drain again.

[0038] Preferably, the filter press includes a control device designed to introduce particle-laden liquid back into the filter chamber after permeate backwashing. This allows the process of introduction and backwashing to be repeated multiple times, gradually increasing the particle content in the retentate within the filter chamber.

[0039] Preferably, the backwashing device is designed to introduce a backwash pulse. The backwash pulse allows the retentate particles to be detached from the filter fabric particularly effectively.

[0040] A preferred embodiment is characterized by the fact that the backflushing device is formed by a compressed air connection through which the drain can be pressurized with compressed air. Compressed air allows, in particular, a short and, above all, strong backflushing pulse to be generated. Furthermore, the compressed air allows high pressure to be quickly applied to the permeate and is readily available.

[0041] Alternatively or preferably additionally, the backwashing device includes a valve for shutting off the drain, with the compressed air connection preferably located between the filter chamber and the valve. The drain shut-off valve ensures that, firstly, a small but sufficient quantity of permeate is available for backwashing and, secondly, that the backwashing process takes place through the filter fabric and into the filter chamber. In particular, the shut-off valve prevents the backwash pulse from dissipating in the drain.

[0042] Preferably, the pressing device is formed by at least one pressure cylinder. In a preferred embodiment, the pressing device is formed by at least two pressure cylinders, which are preferably arranged on opposite sides of the filter chamber.

[0043] According to a preferred embodiment, the at least one pressure cylinder is a pneumatic and / or hydraulic pressure cylinder. These allow a particularly high pressure to be exerted on the retentate, the filter cake and / or the pellet, in particular a high main pressure.

[0044] Preferably, the filter chamber has at least two inlets for introducing the particle-laden liquid. This allows the particle-laden liquid to be fed into the filter chamber more evenly and quickly. Preferably, the particle-laden liquid is introduced at a low filter pressure.

[0045] Alternatively, or preferably additionally, the filter chamber has at least two outlets for draining the permeate. This allows the permeate to be drained from the filter chamber more quickly.

[0046] Preferably, the supply line has a connection for compressed air through which it can be pressurized with compressed air. The compressed air connection in the supply line further includes, in particular, a valve, preferably a controllable or adjustable valve. This allows the supply of compressed air to be controlled or regulated accordingly.

[0047] Preferably, a valve for shutting off the supply of particle-laden liquid is arranged in at least one of the supply lines for the liquid containing particles. This allows the supply of particle-laden liquid to the filter chamber to be interrupted as needed, for example, when pressing the filter cake into a pellet.

[0048] Another solution to this problem, as well as to other problems, is provided by a pellet production plant comprising at least two, preferably at least five, particularly preferably at least ten, and most preferably at least twenty filter presses as described above, and in particular a preferred embodiment thereof. The pellet throughput per unit of time can be increased by means of such a plant. In particular, such a plant is scalable within a certain range and can also be subsequently expanded by adding further filter presses as described above.

[0049] Preferably, the system for each pair of filter presses comprises a double module, preferably two double modules, of an oscillating membrane filter pump, which supplies the filter presses with a particle-laden liquid. The membrane filter pump is designed in particular according to DE 10 2016 003 335 A1.

[0050] Further advantages and features of the present invention will become apparent from the following description of an exemplary embodiment with reference to the figures. The figures show: Figure 1 shows a schematic sectional view of a filter press according to the invention; and Figures 2a) to 2e) show different states of the filter press during the process for producing pellets.

[0051] In the following, identical or equivalent parts are designated with the same reference numerals.

[0052] In Figure 1Figure 1 shows a filter press 1 according to the invention for producing pellets 16. The filter press 1 is in a closed state, in which the filter chamber 3 of the filter press 1 is closed and sealed against the environment. For this purpose, the closing cylinders 2, which are arranged opposite each other on the side of the filter chamber 3, exert a corresponding pressure. To open the filter press 1 and, in particular, the filter chamber 3 to eject a pellet 16, the pressure of the closing cylinders 2, which are designed as pneumatic cylinders in this case, is released.

[0053] Filter chamber 3 has a cylindrical cross-section with a diameter of approximately 6 cm. The diameter of filter chamber 3 extends in Figure 1 from a bottom to a top of filter chamber 3.

[0054] A particle-laden liquid 10 is introduced into the filter chamber 3 via two inlets 6, which are arranged symmetrically to the filter chamber 3. The particle-laden liquid 10 is introduced into the filter chamber 3 via two inlets. A connection 12 for compressed air is also arranged in the inlet 6, which is separated from the inlet 6 by a valve 13. The connection 12 is designed such that it is connected to both inlets 6 via a connection.

[0055] To introduce particle-laden liquid 10 into the filter chamber 3, the valves 9 in the supply line 6 are opened. The particle-laden liquid 10 flows into the filter chamber 3 via the inlets at a predetermined flow rate or a specific volumetric flow rate. The particle-laden liquid 10 flows into the filter chamber 3 particularly slowly and at a low filter pressure. The particle content in the particle-laden liquid 10 is particularly in the range of 8% to 15%, in this case approximately 10%. The particle-laden liquid 10 originates, in particular, from an oscillating membrane filter pump, such as that known, for example, from DE 10 2016 003 335 A1.

[0056] Particles from the particle-laden liquid 10 are retained in the filter chamber 3 by means of a filter fabric 8, which in this case is a stainless steel mesh with a mesh size of approximately 10 µm, to form a retentate 7. A permeate 11, which is essentially formed from a liquid, is passed through the filter fabric 8 and discharged from the filter chamber 3 into the outlets 5 via two outlets.

[0057] To form the retentate 7 in the filter chamber 3, a pre-pressure is applied to the medium in the filter chamber 3 by means of pressure cylinders 4, which are arranged on both sides of the filter chamber 3. This results in a stronger separation of particles from the particle-laden liquid 10, and the permeate 11 is directed to the drain 5. The pressure cylinders 4 are designed as pneumatic pressure cylinders. Simultaneously, the valves 9 are closed so that no further particle-laden liquid 10 enters the filter chamber 3.

[0058] The drain 5 also has a connection 14 for compressed air. The compressed air is separated from the drain 5 by a valve 15. After a certain time or if only a small outflow of permeate 11 is detected in the drain 5, the supply of particle-laden liquid 10 via the supply lines 6 is interrupted by closing the valves 9. The pre-charge pressure of the pressure cylinders 4 is also released, and the valves 18 in the drain 5 are closed. Subsequently, the valve 15 is opened, and the permeate 11 located in the drain 5 between filter chamber 3 and valves 18 is flushed back into the filter chamber 3 by means of a compressed air pulse. This pulsed backflushing of the permeate 11 detaches the retentate 7 particles from the filter fabric 8, thereby restoring its permeability.After the compressed air pulse, valve 15 is closed again and valves 18 are opened, and particle-laden liquid 10 is again directed into filter chamber 3 via the supply lines 6.

[0059] By introducing particle-laden liquid 10 and backflushing permeate 11, the retentate 7 in the filter chamber 3 is enriched, so that it has a higher particle content after each cycle. The process is repeated until a suitable filter cake of retentate 7 has formed in the filter chamber 3. When a pre-pressure is applied, the filter cake should have a thickness of approximately 30 mm.

[0060] The filter cake is then subjected to a main pressure to further increase the particle content and to press a corresponding pellet 16 with a residual moisture content of less than 25%. The main pressure is greater than the pre-pressure.

[0061] After the pellet 16 has been produced, it is dried in the filter chamber 3. For this purpose, the valve 13 of the compressed air connection 12 in the supply line 6 is opened and compressed air is blown into the filter chamber 3 for approximately 30 seconds. This forces further liquid out of the pellet 16 and feeds it as permeate 11 to the outlet 5.

[0062] After drying, the compressed air supply to the inlet 6 is stopped and the pressure in the closing cylinders 2 and the pressure cylinders 4 is released, so that the pellet 16 is ejected from the filter chamber 3. The filter chamber 3 is then resealed from the environment by pressurizing the closing cylinders 2, and the process for producing another pellet 16 is resumed.

[0063] In the Figures 2a) to 2e Individual phases of the process are listed separately below. Figure 2aFigure 1 shows process step A), in which the particle-laden liquid 10 is fed into the filter chamber 3. The particles of the particle-laden liquid 10 are retained on the filter fabric 8 in the filter chamber 3, while the permeate 11 is fed into the outlet 5.

[0064] In Figure 2b Figure 1 shows process step B), in which a pre-pressure is exerted on the retentate 7 in the filter chamber 3 by means of the pressure cylinders 4, so that further liquid in the form of permeate 11 is supplied to the drain 5 and the particle content in the retentate 7 is increased. For this purpose, the supply of particle-laden liquid 10 via the supply line 6 into the filter chamber 3 is interrupted by means of the valves 9.

[0065] After applying a pre-pressure to the retentate 7 by means of the pressure cylinders 4, the pre-pressure is released and in a process step C) a backwash pulse is initiated via the drain 5, as described in Figure 2c ) is shown. This causes the permeate 11 in the drain to be flushed back into the filter chamber, thereby dislodging the retentate 7 particles adhering to the filter fabric 8. The filter fabric 8 is then permeable and capable of drainage again.

[0066] The procedural steps, as described in the Figures 2a) to 2c ) are shown and repeated as described above until a corresponding filter cake of retentate 7 has formed in filter chamber 3. This filter cake is then subjected to a main pressure as described in Figure 2d ) is shown, whereby the filter cake is pressed into a pellet 16 whose residual moisture is less than 25%.

[0067] Finally, the pellet 16 is ejected from the filter chamber 3, releasing both the main pressure of the pressure cylinders 4 and the pressure of the closing cylinders 2, as shown in Figure 2e) shown. After the pellet 16 is ejected from the filter chamber, it is closed again and the process for producing another pellet 16 begins again. Reference symbol list

[0068] 1 Filter press 2 Closing cylinder 3 Filter chamber 4 Pressure cylinder 5 Discharge 6 Inlet 7 Retentate 8 Filter fabric 9 Valve 10 Particle-laden liquid 11 Permeate 12 Connection 13 Valve 14 Connection 15 Valve 16 Pellet 17 18 Valve

Claims

1. Method for producing pellets (16) in a filter press (1) from a particle-laden liquid (10), comprising the following steps: A) introducing the particle-laden liquid (10) into a filter chamber (3) via a feed line (6), B) applying a preliminary pressure to the filter chamber (3), whereby a retentate (7) from the particle-laden liquid (10) is retained on a filter fabric (8) in the filter chamber (3) and a permeate (11) is fed to a discharge line (5), C) releasing the preliminary pressure on the filter chamber (3) and back-flushing at least a part of the permeate (11) from the discharge line (5) into the filter chamber (3), D) repeating steps A) to C) until a filter cake is obtained from the retentate (7) in the filter chamber (3), E) pressing the filter cake to form a pellet (16) by applying a main pressure to the filter chamber (3) and removing the pellet (16) from the filter chamber (3).

2. Method according to claim 1, characterized in that the particle-laden liquid (10) has a particle content of at least 10%, preferably of at least 12%, more preferably of at least 15%, in particular in that the particle content in the particle-laden liquid (10) upstream of the filter press (1) has been increased by means of an oscillating membrane filter pump.

3. Method according to any one of the preceding claims, characterized in that the method steps A) to C) are performed in their order at least 10 times, preferably at least 20 times, more preferably at least 30 times.

4. Method according to any one of the preceding claims, characterized in that back-flushing of permeate (11) takes place in a pulsed manner, preferably by applying compressed air to the discharge line (5), in particular with a pulse of compressed air and / or in that the discharge line (5) is shut off by means of a valve (18) before back-flushing, wherein the compressed air is preferably blown into the discharge line (5) between the filter chamber (3) and the valve (18).

5. Method according to any one of the preceding claims, characterized in that the particle-laden liquid (10) is introduced into the filter chamber (3) via at least two inlets, wherein the inlets are preferably arranged opposite one another, and / or in that the permeate (11) is discharged from the filter chamber (3) via at least two outlets, wherein the outlets are preferably arranged opposite one another.

6. Method according to any one of the preceding claims, characterized in that the filter cake has at least a thickness of 10 mm, preferably a thickness of at least 20 mm, more preferably a thickness of at least 30 mm and / or in that the thickness of the filter cake is measured or determined, in particular via a counter-pressure when a preliminary pressure is applied to the filter chamber (3), and / or in that a residual moisture content of the pellet (16) after pressing in method step E) is less than or equal to 25%.

7. Method according to any one of the preceding claims, characterized in that before the pellet (16) is removed from the filter chamber (3), compressed air is applied to the filter chamber (3), in particular via the feed line (6), in particular for a duration of at least 10 seconds, preferably of at least 20 seconds, more preferably of at least 30 seconds.

8. Method according to any one of the preceding claims, characterized in that applying the preliminary pressure and main pressure to the filter chamber (3) takes place by means of a pressing device in the form of at least one pressure cylinder (4), in particular by means of a pneumatic or hydraulic pressure cylinder (4), wherein application preferably takes place by means of its pressing device in the form of at least two pressure cylinders (4), which are preferably arranged opposite one another.

9. Filter press (1) for producing pellets (16) from a particle-laden liquid (10), in particular for implementing a method according to any one of claims 1 to 8, with a filter chamber (3), with at least one feed line (6) for feeding a particle-laden liquid (10) into the filter chamber (3), with at least one discharge line (5) for discharging a permeate (11) from the filter chamber (3), wherein the filter chamber (3) comprises a filter fabric (8), which is arranged upstream of the discharge line (5), and with a pressing device for applying pressure to the filter chamber (3), characterized in that an apparatus for back-flushing permeate (11) into the filter chamber (3) is arranged in the discharge line (5) or is operatively connected to the discharge line (5).

10. Filter press (1) according to claim 9, characterized in that the device for back-flushing is formed by a connection (14) for compressed air, via which compressed air can be applied to the discharge line (5) and / or in that the apparatus for back-flushing comprises a valve (18) for shutting off the discharge line (5), wherein the connection (14) for compressed air is preferably arranged between the filter chamber (3) and the valve (18).

11. Filter press (1) according to any one of claims 9 or 10, characterized in that the pressing device is formed by at least one pressure cylinder (4), preferably by two pressure cylinders (4), which are arranged on opposite sides of the filter chamber (3).

12. Filter press (1) according to claim 11, characterized in that the pressure cylinder (4) is a pneumatic and / or hydraulic pressure cylinder (4).

13. Filter press (1) according to any one of claims 9 to 12, characterized in that the filter chamber (3) has at least two inlets for introducing the particle-laden liquid (10) and / or at least two outlets for discharging the permeate (11).

14. System for producing pellets (16), comprising at least two, preferably at least five, more preferably at least ten, most preferably at least twenty filter presses (1) according to any one of claims 9 bis 13.

15. System according to claim 14, characterized in that, in each case, the system for two filter presses (1) comprises a double module, preferably two double modules of an oscillating membrane filter pump, which supplies the filter presses (1) with a particle-laden liquid (10).