Techniques for filtering a viscous food mass

Abstract

The invention relates to techniques for filtering a viscous food mass, having the following steps: * feeding a viscous food mass under pressure, in particular under a pressure of 1 bar to 16 bar, into a filter chamber; * rotating at least one filter element, in particular a filter element in the form of a filter disc, in the filter chamber, wherein the viscous food mass is pressed, as a filtrate, through a filter grid by the pressure in a cavity of the at least one filter element, and the filter element is rotated at a rotational frequency which is suitable in particular for the viscous food mass so that residue is prevented from settling on the filter grid; * feeding the filtrate from the cavity of the at least one filter element within the filter chamber to an outlet opening; and * discharging the filtrate through the outlet opening.

Description

[0001] Techniques for filtering a viscous food mass

[0002] The present invention relates to the technical field of filtration of a viscous food mass and in particular to filter elements designed for this purpose, a filter system and a corresponding method.

[0003] When processing viscous foods, especially processed cheese, the process step of filtering the viscous food is usually a fundamental component. Automatic continuous filters for filtering processed cheese, for example, are known. They use a rotating scraper core. A filter device—typically cylindrical—is inserted into an outer cylinder, forming a gap between the filter device and the outer cylinder. The viscous food is introduced into the filter housing and pressed outward into the gap through a finely perforated filter of the filter device.To keep the filter surface of the filter device—especially in the form of a filter tube—clear, a rotating scraper core is provided inside the filter tube. Its scraper blades scrape off deposits, foreign particles, and contaminants from the (inner) filter surface of the filter tube. These foreign particles are present in the viscous food mass and must be removed.

[0004] In this state-of-the-art process for removing foreign particles, foreign particles – primarily plastic film residues – settle on the filter surface and, as the filter surface is scraped, are broken up by the sharp-edged scraper blades in such a way that smaller particles of the foreign matter enter the filtered food – also known as the filtrate. In addition, further foreign matter, particularly microplastics, are created by the abrasion of the filter scrapers on the filter surface. These can also enter the filtered food product. In addition, non-plastic foreign particles can enter the filtered food through the filter scrapers. Without regular removal of contaminants from the filters, the flow rate of the food mass would rapidly decrease, making production less efficient.

[0005] To prevent this contamination from foreign matter in the filtered food, the current technology uses so-called discontinuous filters, such as bag filters or stocking filters, since these do not employ scraper blades. However, the disadvantages of these filters are their very short downtimes and the labor required to replace the contaminated filters, which also generates additional waste.

[0006] Accordingly, the invention aims to solve at least one of the following problems. In particular, the invention aims to provide techniques that enable the viscous food mass to be filtered without contaminants, particularly microplastics, entering the filtrate. A further aim of the invention is to keep the flow of the constant food mass through the filter at as constant a level as possible.

[0007] The features of the various aspects of the invention or the various embodiments described below can be combined with one another unless this is explicitly excluded or technically mandatory.

[0008] Further advantageous features of the present invention are defined in the patent claims.

[0009] According to the invention, a filter chamber for filtering a viscous food mass, in particular processed cheese, is specified, wherein the filter chamber comprises

[0010] • an inlet opening for feeding a pressurised viscous unfiltered food mass into the filter chamber;

[0011] - The unfiltered, viscous food mass is fed into the inlet opening under "pressure," preferably at a pressure of 1 bar to 16 bar; ultimately, this pressure—as will be explained in more detail later—is primarily responsible for—i.e., the driving force—for the actual filtration process.

[0012] • at least one filter element having a filter grid which encloses a cavity of the filter element, wherein the viscous unfiltered food mass passes through the filter grid as filtrate into the cavity, wherein the cavity has at least one first opening for the outlet of the filtrate; - the filter element is, to a certain extent, sealed off from the unfiltered viscous food mass except for the filter grid; the viscous food mass can therefore only pass into the cavity through the filter grid; in this context, it can also be mentioned that the filter is also sealed off from the unfiltered viscous food mass except for the inlet opening and the outlet opening referred to below;a) wherein a plurality of filter elements are arranged in a row, in particular clamped together, and form a filter element stack, wherein the filter elements each have a central recess, wherein the recesses arranged in a row form a flow channel, wherein the filter element stack is drivable and rotatably mounted in the filter chamber, wherein the first opening is provided at the central recess so that the filtrate passes from the cavity of the filter elements into the flow channel;

[0013] - the filter elements are connected to one another, in particular clamped in parallel, in such a way that when the filter element stack is driven at a rotational frequency, the filter elements rotate in a twisted manner with the filter element stack; in one embodiment - which is also the best way to visualize the filter element stack - the filter elements are disc-shaped and have recesses with an inner radius.If such disc-shaped filter elements are arranged concentrically next to one another, a flow channel is formed along the axis by means of which the filtrate can be discharged; the outer contours of the filter element stack are then cylindrical except for individual interruptions between the filter elements; or a hollow shaft which is rotatably mounted and drivable in the filter chamber, wherein the at least one filter element is attached in a twisted manner to the hollow shaft, wherein the hollow shaft has at least one second opening passing through its outer surface, wherein the second opening is aligned with the first opening so that the filtrate passes from the cavity of the filter element into the hollow shaft;.

[0014] - in variant b) a rotation is also generated, in this case a rotation of the hollow shaft; the hollow shaft is, in particular, cylindrical in shape;

[0015] - also in the embodiment variant b), the respective filter element can have a central recess, in particular designed as an inner ring, and can thereby be placed on the hollow shaft;

[0016] • a first outlet opening on a base surface, in particular an end face, of the hollow shaft or on a base surface of the filter element stack for the filtrate to exit the filter chamber.

[0017] a) and b) are two different embodiments of the invention. In any case, these variants have in common that the filter elements can be set to a correspondingly high rotation frequency, in particular with a motor coupled to the hollow shaft or to the filter element stack, so that such high shear forces are generated that the formation of deposits on the surface of the filter grid is at least reduced, if not completely prevented. This works entirely without the use of scrapers, as in the prior art, so that microplastics in the filtrate are efficiently reduced, if not completely avoided. Furthermore, continuous filtration, i.e., a constant flow of the filtrate, is enabled because the filter grid is consistently "free" of deposits.The viscous food mass flows into the filter chamber and is pushed through the filter elements, especially the filter grid, by pressure.

[0018] Other possible viscous food masses that can be filtered according to the invention are: chocolate mass, sauces, other thick foods that have to be filtered due to their method of preparation or the presence of foreign matter.

[0019] As described below, the cavity of the filter elements can be supported by support elements extending from the outer edge of the filter element to the inner edge. The support elements provide the filter elements with the necessary stability against the pressure of the viscous food mass.

[0020] The filter chamber preferably has a closable opening, in particular with a closure cap, at the bottom of the filter chamber for discharging the residue. In one embodiment, the flap opens and closes automatically.

[0021] The unfiltered portion is called the residue. The residue consists of those components of the original liquid that cannot pass through the filter medium. Since the residue typically has a higher density than the viscous food mass or consists of solid and insoluble components that cannot penetrate the filter, the residue will automatically collect at the bottom of the filter chamber and can be easily drained through the additional opening provided there, even during operation. Another reason for the residue to collect at the bottom is the defined flow direction of the food mass to be filtered towards the bottom of the filter chamber. The opening can be operated manually, for example. It is helpful to have a window in the filter chamber, for example, so that the fill level of the residue can be estimated.In principle, it is also possible to install a pressure sensor in the filter chamber, as the pressure changes with an increasing amount of residue. Such a pressure sensor can automatically activate the cap of the additional opening when a threshold is exceeded, allowing the residue to be discharged. Optionally and / or in addition to pressure monitoring, a time-controlled discharge of the sediment can be performed at regular intervals.

[0022] Preferably, a plurality of filter elements are arranged spaced from one another along a longitudinal axis of the hollow shaft. In particular, the inner filter walls are arranged parallel to one another. The spacing between the filter elements is preferably approximately 1 cm. With this type of arrangement of the filter elements, the total filter surface is significantly increased, so that the flow rate of the filtrate can be increased. The filter elements, in particular in the form of filter discs in the form of an annular disc, can be plugged together on the hollow shaft and clamped using a central screw. In this case, it is possible to seal the contact points of the respective filter discs with O-rings. The filter elements are preferably arranged concentrically on the hollow shaft.

[0023] Preferably, the at least one filter element or the filter elements are each designed as a filter disc. In particular, the filter disc has the shape of an annular disc. The outer shape of a "round" disc is particularly efficient and hygienically advantageous for the "rotational" filtration process - also referred to as "cross-flow" filtration process. For example, the filter chamber can have a round shape, at least on the inside, which prevents the viscous food mass from getting stuck in the corners. In addition, with such a round design, a maximum filter surface can be achieved during rotational filtration. If the filter elements were square, for example, filter surface would always be lost during rotation, since such a square filter would then have its corners right up to the inner edge of the filter chamber.

[0024] The filter grid preferably forms the top and bottom and / or an outer ring of the filter element. If both the top and bottom of the filter element are designed as a filter grid, the filter surface can be doubled. If the outer ring, which connects the top and bottom at the outer circumference, is also designed as a filter grid, the filter surface is further increased. The percentage by which the filter surface is increased in this case naturally depends on the dimensions of the filter element. Using the filter disc as an example, this specifically depends on the height of the filter disc.

[0025] In one embodiment, the material from which at least the outer shell of the filter element is made and / or the material from which the filter grid is made is made of stainless steel, aluminum and / or 3D printed plastic or stainless steel. The support elements inside the filter elements can also be made of these materials or other materials. Stainless steel generally proves to be particularly hygienic. On the other hand, plastic can also be used because there is no friction that would wear away the plastic material and thereby create microplastics. The filter elements are preferably designed as a one-piece filter disc made of perforated stainless steel sheet that has been additionally polished. However, a one-piece version made of 3D printed metal and a multi-part, demountable version are also possible.The filter discs can have a so-called “layer structure”, which allows a minimal sheet thickness to be achieved and at the same time a support effect can be achieved against deflection in the event of high pressure losses.

[0026] In an advantageous embodiment, the filter mesh has a filter hole width—also referred to as pore size—of 25 pm to 800 pm. The perforation is selected so that the viscous food mass can penetrate while simultaneously trapping foreign matter.

[0027] Preferably, baffles are provided between the filter elements, wherein the baffles are non-rotatably connected to the filter chamber. In one embodiment, the baffles can be designed, in particular, as screws that can be screwed into the filter chamber at varying depths. The baffles prevent the viscous food mass from rotating due to their own inertia. Therefore, if baffles are always mounted tangentially to the filter surface between two filter elements, they can effectively prevent rotation, thus increasing the shear forces between the filter surface and the viscous food mass.

[0028] It is also possible to provide a heating module and / or thermal insulation in the area of ​​the filter chamber so that the temperature of the viscous food mass does not decrease too much and / or can be maintained at a defined value.

[0029] According to a second aspect of the invention, a filter system for filtering a viscous food mass is provided, the system comprising:

[0030] • a filter chamber as described above, wherein the hollow shaft or the filter element stack has a coupling section for the direct or indirect attachment of a drive means;

[0031] • a drive means, in particular a motor, configured to set the hollow shaft or the filter element stack in a rotational movement, in particular with a rotation frequency during filter operation of 100-1000 rpm, especially 500-600 rpm. o In particular, the rotation frequency during cleaning can be in the range of 1000-1200 rpm

[0032] The filter system according to the invention has the advantages described above in connection with the filter element.

[0033] In a further development, the filter system comprises a pressure generation module configured to press the viscous food mass into the inlet opening at up to 16 bar. In particular, a pressure of 1 bar to 3 bar can be provided for continuous operation, with the 16 bar being used specifically to increase service life.

[0034] According to a third aspect of the invention, a method for filtering a viscous food mass is provided, in particular using the filter system described above—in this sense, the filter system is configured to carry out the method. The method comprises the following steps:

[0035] • Feeding a viscous food mass under pressure, in particular under a pressure of 1 bar to 16 bar, into a filter chamber;

[0036] • Rotating at least one filter element, in particular designed as a filter disc, in the filter chamber, wherein the viscous food mass is pressed as filtrate by the pressure into a cavity of the at least one filter element through a filter grid, wherein the rotation of the filter element is carried out at a rotation frequency suitable in particular for the viscous food mass, so that a settling of residues on the filter grid is prevented;

[0037] • Feeding the filtrate from the cavity of the at least one filter element within the filter chamber to an outlet opening;

[0038] • Discharge the filtrate from the outlet opening.

[0039] The method has analogous advantages as described above in connection with the filter chamber and the filter system. In a further embodiment of the method, the rotation frequency of the at least one filter element can be increased at least temporarily if a decrease in the flow rate of the filtrate is detected. Since sliding friction coefficients are generally lower than static friction coefficients, such a temporary increase in the rotation frequency, particularly when starting up the system, can lead to contaminants on the filter surface being loosened, whereas a lower rotation frequency during ongoing operation is sufficient to prevent these contaminants from redepositing on the filter surface. The temporary increase in the rotation frequency can be 25%, in particular 50%, of the normal rotation frequency during ongoing operation.

[0040] In the following, preferred embodiments of the present invention are explained with reference to the accompanying figures:

[0041] Fig. 1: shows a perspective view of the inventive

[0042] filter system;

[0043] Fig. 2: shows a longitudinal section along a center point of the

[0044] filter chamber;

[0045] Fig. 3: shows an enlarged perspective view of the

[0046] filter elements;

[0047] Fig. 4: shows an enlarged view of the longitudinal section of the

[0048] filter chamber;

[0049] Fig. 5: shows a cross-section of the filter chamber and a top view of a filter element;

[0050] Fig. 6a-c: show three different designs of the filter element;

[0051] Numerous features of the present invention are explained in detail below using preferred embodiments. The present disclosure is not limited to the specifically mentioned feature combinations. Rather, the features mentioned here can be combined in any desired way to form embodiments of the invention, unless expressly excluded below.

[0052] Fig. 1 shows a perspective view of the filter system 100 according to the invention. The filter system 100 comprises an inlet opening 105 through which an unfiltered viscous food mass, in particular processed cheese, is fed to a filter chamber 110 under a pressure, in particular from 1 bar to 16 bar. Located inside the filter chamber are filter elements 115, which are set in rotation at a definable rotation frequency by means of a drive means 120 and - as explained in more detail below - thereby filter the unfiltered viscous food mass into a filtrate. The rotation ensures that no deposits form on the filter elements 110, thereby simultaneously enabling the most constant flow of the filtrate possible. The filtrate is discharged from the filter chamber 110 or from the filter system 100 via an outlet opening 125 and can be further processed.This functionality will now be explained in more detail in connection with the further figure descriptions.

[0053] Fig. 2 shows a longitudinal section along a center point of the filter chamber 110. A hollow shaft 130 is provided centrally in the filter chamber 110 and is rotatably mounted within the filter chamber 110. The hollow shaft 130 protrudes from the filter chamber 110 in a sealed manner and has a coupling portion 130a on the protruding part, wherein the drive means 120 at least indirectly engages the coupling portion 130a and can thereby set the hollow shaft 130 in rotation. A plurality of filter elements 130 are provided spaced apart from a longitudinal axis 130b of the hollow shaft 130. The spacing of the filter elements 115 from one another is preferably between 1 cm and 3 cm, preferably 2 cm. This spacing can depend on the type of viscous food mass and / or the type of contamination. The more viscous the food mass, the greater the spacing is selected.The spacing of the filter elements 115 can be achieved in particular by inserting so-called spacer disks 135, which is shown in an enlarged view in Figures 3 and 4. Preferably, the filter elements 130 and the spacer disks 135 are placed on the hollow shaft 130, the respective contact points being sealed with O-rings 140, and are clamped by means of a screw 145 provided along the axis of the hollow shaft 130. The screw 145 can extend at least partially into the hollow shaft 130.

[0054] The filter elements 115 are designed as filter discs 115 in this case. It is evident that this allows the space available in the filter chamber 110 to be utilized as efficiently as possible, thereby also increasing the filter surface. The filter discs 115 are, in particular, shaped like an annular disc, thus having an outer and an inner radius.

[0055] In the embodiment according to Fig. 3, the filter discs 115 each have a filter grid 150 on their top and bottom. The filter grid 150 can be made of stainless steel, for example, and has filter holes, also referred to as pores, through which the viscous food mass can pass and unwanted foreign particles that should not get into the filtrate get trapped. The filter discs 115 according to the embodiment shown in Fig. 3 have an outer ring 155 and an inner ring 160, which both determine the height of the filter disc 115 and have a supporting effect on the filter disc 115. The outer ring 155, the inner ring 160, and the filter grid 150 can be made of the same material or each of different materials. The outer ring 155, the inner ring 160, and the two filter grids 150 form a cavity 165 in the filter disc 115.The cavity 165 of the filter disc 115 can be supported by support elements 170 that extend radially inward from the outer ring 155 of the filter disc 115 to the inner ring 160 of the filter disc 115. The support elements 170 provide the filter elements with the necessary stability against the pressure of the viscous food mass. The support elements 170 can be made of stainless steel, aluminum, or plastic.

[0056] The inner ring 160 has at least one first opening 175, in particular a plurality of first openings 175 distributed over the inner ring 160, through which the filtrate, after having passed through the filter grid 150 into the cavity, can leave the filter disk 115 again. This is made possible in particular by a pressure difference, since atmospheric pressure, for example, prevails at the first opening 175. The hollow shaft 130 now has at least one second opening 180, in particular a plurality of second openings 180. The at least one filter disk 115 is attached to the hollow shaft 130 at a corresponding height such that the at least one first opening 175 is aligned with the at least one second opening 180. In particular, the filter disks 115 are attached to the hollow shaft 130 at a corresponding height such that the plurality of first openings 175 are aligned with a plurality of second openings 180.In this way, the filtrate is allowed to pass from the cavity 165 into the hollow shaft 130, which forms a flow channel 190, preferably under atmospheric pressure, so that the filtrate can flow downwards within the filter chamber 110 towards the outlet opening 125 to leave the filter chamber 110 and be further processed.

[0057] Fig. 4 also shows the flow breakers 185, designed as screws 185, which are mounted in the space between two filter discs 115 and are intended to prevent the viscous food mass from rotating, thereby increasing the shear forces between the filter discs 115 and the viscous food mass. The screws 185 can be flexibly inserted into the filter chamber 110 at different depths to break the flow more or less strongly. For example, the screw 185a is inserted deeper into the filter chamber 110.

[0058] Fig. 5 shows a cross-section of the filter chamber 110 and a top view of one of the filter discs 115. A baffle 185 can be seen, which is arranged above the filter disc 115. Also visible in this illustration are the (filter) pores 151 of the filter grid 150. The support elements 170 have a slightly curved shape in this case; this has the effect that a clockwise rotation of the filter disc promotes the product flow from the edge of the disc to the interior of the disc. Furthermore, this creates a turbulence during cleaning of the filter disc, which enables better cleaning of the shadow areas of the filter discs.

[0059] Fig. 6a-c show three different configurations of the filter disc 115. The filter discs 115 used according to the invention can have a height of approximately 1 cm. Depending on the type of viscous food mass, the filter discs can be thinner than 1 cm—for example, 0.5 cm. In general, the lower the height of the filter discs and the closer their spacing, the larger the effective filter surface, because more filter discs can be used for a defined overall length of a filter stack.

[0060] The first embodiment of the filter disc 115a shows a multi-part structure for threading the filter disc 115a onto the hollow shaft 130, wherein in particular the spacer disc 135 and the filter disc are different components that are not firmly connected to one another. In this way, it is possible to vary the height of the spacer disc 135 and to flexibly replace spacer discs 135. Not only in the embodiment of the filter disc according to 115a, but generally, the spacer discs 135 and / or the filter discs 115 themselves can be selected such that the gap between the filter discs 115 is approximately 2 cm. As already explained above, the gap between the filter discs 115 can also be selected to be smaller than 2 cm, in particular approximately 1 cm. The filter disc 115a has a plastic outer ring 155a, which has a height of 1 cm, for example.

[0061] The second embodiment of the filter disc 115b is preferable for hygienic reasons, since the spacer disc 135 is welded to the body, in particular to the inner ring 160, of the filter disc 115b and is thus manufactured as a single piece. The filter disc 115b has a plastic outer ring 155a, which has a height of, for example, 1 cm.

[0062] The third embodiment of the filter disc 115c differs from the second embodiment of the filter disc 115b in that the outer ring is designed as a filter grid outer ring 155b. This means that the outer ring 115b also forms a filter surface, thus increasing the total filter surface. In particular, the filter grid 115 of the outer ring 155b does not differ from the filter grid on the top or bottom of the filter disc 115c. Furthermore, the embodiments according to Figure 6b and Figure 6c show a disc arrangement without a central hollow shaft. In these two variants, the filter discs with the associated spacer rings 135 are arranged directly next to one another, forming a central cavity and eliminating the need for a hollow shaft.

[0063] Fig. 7a-c show a construction drawing of the filter disc 115.

[0064] Fig. 7a shows that the filter disc has a diameter 195 of approximately 139 mm, with an outer diameter 200 of the inner ring 160 being approximately 51 mm and an inner diameter 205 of the inner ring 160 being approximately 36 mm. The filter disc 115 can also have a thin edge region 210, to which the filter grid 150 adjoins toward the center of the filter disc 115.

[0065] Fig. 7b shows the filter grid 150 in a longitudinal section, so that the slightly conical shape of the filter pores can be seen, particularly in all embodiments. The filter grid can have a thickness 216 of approximately 0.5 mm to approximately 1 mm, wherein the filter pores can have a size of 200 μm on the outer surface 215 and a size of 287 μm on the inner surface 220. This conical shape has the technical effect of reducing pressure losses along the hole channel and preventing blockages. All hole edges of the pores are sharp-edged. This has the technical effect of making it more difficult for foreign particles to become trapped in the holes.

[0066] Fig. 7c illustrates the hole density 230, i.e., the distance 235 between the respective pores 151 and their respective centers. In this exemplary embodiment, this is 400 pm, resulting in an open filter area of ​​22.7%. The interaction between a desired larger filter area and the material's load-bearing capacity must be taken into account. This means that the larger the open area on the filter surface (or the more densely the holes are arranged), the less residual material remains and the more unstable the disc becomes under compressive loads.

[0067] Manufacturing tolerances for hole diameters are up to 10%. The angle of the conical shape can range from 1° to 5°. In general, the open filter area of ​​all designs can range from 5% to 35%. In particular, the open filter area increases with the thinner the filter mesh sheet.

[0068] The parameters of the filter disc 115 may vary and may be selected differently, particularly with regard to the viscous food mass and / or the corresponding foreign particles to be filtered.

[0069] The filtration according to the invention has been successfully tested on viscous foods, in particular processed cheese, with the following properties and is therefore at least suitable for these:

[0070] Depending on the fat content and product category (slicable or spreadable processed cheese, processed cheese preparation, cooked cheese), the dry matter content can vary between 20% and 65%, in particular between 30% and 60%. In a temperature range of 60-95°C, suitable foods have a viscosity of 400 mPa*s to 8000 mPa*s. For spreadable processed cheese, the viscosity values ​​range from 120 mPa*s to 400 mPa*s, for sliceable processed cheese in a range of 400 mPa*s to 8000 mPa*s. The viscosities are measured according to DIN 53018 using a rotational viscometer. The invention is therefore fundamentally suitable for viscous foods that exhibit a wide variation. In summary, viscous foods with a viscosity of 100 mPa*s to 12000 mPa*s can be filtered. The pore size - also referred to as hole width - of the filter grid ranges from 25 pm to 800 pm.An example throughput of such a viscous food mass can be specified based on viscosity, differential pressure range, filter unit (hole size), and total filter area. For a flow rate of 2.5 t / h, the following parameters apply: viscosity = 1 Pa*s, differential pressure range Δp = 1-10 bar, filter fineness (hole size) = 200 pm, and total filter area = 2600 cm². 2 .

[0071] So you can see that this is a very complex relationship that can be different for each specific combination.

[0072] Especially when the viscous food is processed cheese, for example, it has a temperature in the range of 80-85 °C. It is therefore advantageous to equip the filter system with heating elements if necessary, so that the processed cheese does not fall below a temperature of, for example, 72 °C. For this reason, it is also advantageous to install the filter system as soon as possible after the processed cheese has been heated within the production chain.

[0073] The rotation frequency of the filter discs 115 can be 350 to 800, preferably 500-600, revolutions per minute, especially with a disc diameter of approximately 150 mm. For inline cleaning of the filter system 100, these values ​​can be doubled – good results have been achieved with this method.

[0074] However, various factors play a role regarding the pressure, or rather the pressure difference between the inlet and outlet ports, such as temperature-dependent viscosity, contaminant load, installed filter area, and flow rate. The filter system should be designed for a pressure of up to 16 bar. This value is particularly important for pressure surges that occur in the system, for example, when production is interrupted and the product cools down in the filter. The expected "normal pressures" used during normal operation are between 1 and 3 bar.

[0075] The procedure is briefly summarized below:

[0076] As the viscous food mass flows against the filter surface, the relative movement between the filter and the viscous food generates a high flow velocity. This largely prevents the deposition of particles and the formation of a "dirt layer (filter cake)," so that a specific filtrate flow can be maintained at a virtually constant level at a constant pressure. The high flow velocity can also be referred to as overflow and, as previously mentioned, is generated by the rotation of the filter surface. This creates high shear forces at the interface between the filter and the filtered material, which largely prevent the deposition of foreign particles and prevent or maintain constant the formation or compaction of a filter cake.

Claims

Patent claims 1. Filter chamber for filtering a viscous food mass comprising • an inlet opening (105) for feeding a pressurised viscous unfiltered food mass into the filter chamber (110), • at least one filter element (115) having a filter grid (150) which encloses a cavity (165) of the filter element (115), wherein the viscous unfiltered food mass passes through the filter grid (150) as filtrate into the cavity (165), wherein the cavity (165) has at least one first opening (175) for the outlet of the filtrate; oa) wherein at least two filter elements (115) are arranged in a row, in particular clamped, and form a filter element stack, wherein the filter elements (115) each have a central recess, in particular an inner ring (160), wherein the recesses arranged in a row form a flow channel (190), wherein the filter element stack is drivable and rotatably mounted in the filter chamber (110), wherein the first opening (175) is provided at the central recess (160) so that the filtrate passes from the cavity (165) of the filter elements (115) into the flow channel (190),or whether) a hollow shaft (130) rotatably mounted and drivable in the filter chamber (110), wherein the at least one filter element (115) is mounted on the hollow shaft (130) in a rotationally fixed manner, wherein the hollow shaft (130) has at least one second opening (180) passing through its lateral surface, wherein the second opening (180) is aligned with the first opening (175) so that the filtrate passes from the cavity (165) of the filter element (115) into the hollow shaft;, • a first outlet opening (125) on a base surface, in particular an end face, of the hollow shaft (130) or on a base surface of the filter element stack for the filtrate to exit the filter chamber (110).

2. Filter chamber according to claim 1, comprising a further opening at the bottom of the filter chamber for discharging the residue.

3. Filter chamber according to one of claims 1-2, wherein a plurality of filter elements are arranged spaced apart from one another along a longitudinal axis of the hollow shaft.

4. Filter chamber according to one of claims 1 - 3, wherein the filter elements are designed as filter discs.

5. Filter chamber according to one of claims 1 - 4, wherein the filter grid forms the top and bottom and / or an outer ring of the filter element.

6. Filter chamber according to one of claims 1 - 5, wherein the material from which at least the outer shell of the filter element is made and / or the material from which the filter grid is made consists of stainless steel, aluminum and / or plastic.

7. Filter chamber according to one of claims 1 - 6, wherein the filter grid has a filter hole width of 25 pm to 800 pm.

8. Filter chamber according to one of claims 1 - 7, wherein flow breakers are provided between the filter elements, wherein the flow breakers are not rotatably connected to the filter chamber.

9. Filter system (100) for filtering a viscous food mass comprising: • a filter chamber (110) according to any one of claims 1-8, wherein the hollow shaft or the filter element stack has a coupling section for directly or indirectly attaching a drive means; • a drive means (120), in particular a motor (120), configured to set the hollow shaft or the filter element stack in a rotational movement, in particular with a rotational frequency of 500-600 rpm.

10. Filter system according to claim 9, comprising a pressure generating module, wherein the pressure generating module is configured to press the viscous food mass into the inlet opening at up to 16 bar.

11. A method for filtering a viscous food mass, in particular using the filter system according to one of claims 9-10, comprising the following steps: • Feeding a viscous food mass under pressure, in particular under a pressure of 1 bar to 16 bar, into a filter chamber; • Rotating at least one filter element, in particular designed as a filter disc, in the filter chamber, wherein the viscous food mass is pressed as filtrate by the pressure into a cavity of the at least one filter element through a filter grid, wherein the rotation of the filter element is carried out at a rotation frequency that is suitable, in particular for the viscous food mass, so that a settling of residues on the filter grid is prevented; • Feeding the filtrate from the cavity of the at least one filter element within the filter chamber to an outlet opening; • Discharge the filtrate from the outlet opening.

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