Centrifugal separator, in particular bacteria-removing separator, and method for sterilizing milk

Abstract

The invention relates to a centrifugal separator (1) which is designed in particular as a bacteria-removing separator for sterilizing milk and which is provided for separating a flowable product P to be processed into a solid phase S and into a first lighter liquid phase L1 and a second heavier liquid phase L2 in a centrifugal field, having at least the following: a rotatable centrifugal drum (2) with a vertical rotational axis D, a distributor (5) which is arranged in the centrifugal drum (2) for feeding a product from a product feed tube (6) into the separating chamber (7), wherein the product P is conducted into the separating chamber (7) in the distributor (5) during operation, and the distributor (5) additionally has first openings (16) so that a first part of the product P fed by the distributor is conducted from the distributor channels (8) into the disc pack, preferably into rising channels (17) of the separating disc pack (15). The separating chamber (7) has a radially outer solids collecting chamber (18), discontinuously closable solids discharge openings (21) for discharging the solid phase S, and a first liquid discharge (22) for discharging the lighter liquid phase (L1) and a second liquid discharge (25) for discharging the heavier liquid phase (L2). In addition to the first openings (16), one or more second openings (28) are formed in the distributor (5) which introduce a second part of the product P outwardly into the centrifugal drum.

Description

Centrifugal separator, in particular a sterilization separator, and method for sterilizing milk The present invention relates to a centrifugal separator, in particular a sterilization separator, according to the preamble of claim 1 and a method for sterilizing milk. Centrifugal separators are used for a wide variety of separation and / or clarification tasks, such as the purification of milk. These centrifugal separators are also called purification separators. The classic application of a purification separator is the clarification of milk – which forms the lighter liquid phase – from bacteria and spores – the so-called microbial flora – which form the heavy liquid phase. This heavy liquid phase can also contain contaminants such as udder cells. Purification can involve a continuous flow of milk into the centrifuge drum, followed by continuous centrifugal separation and clarification of the milk fed into the centrifuge drum.In this process, the milk is separated into a solid phase containing germs and spores, a first lighter liquid phase consisting of degerminated milk, and a second heavier liquid phase. The second heavier liquid phase is formed from a free-flowing concentrate containing, among other ingredients, germs and proteins. However, a separation into cream and skimmed milk does not, or essentially does not, occur during this degermination process. Such a germ removal separator is known from the generic DE 38 02 305 C1. It comprises a rotating centrifugal drum in which a separating disc assembly is arranged. The milk to be germ removed is fed through a stationary inlet pipe into a distributor of the centrifugal separator, which rotates with the centrifugal drum during operation, where it is accelerated in the distribution channels to the speed of the centrifugal drum. Openings in the distribution channels allow the milk to flow into the rising channels of the separating disc assembly. A sludge of bacteria and germs is separated from the milk as a solid phase in the centrifugal field and collected in a solids collection chamber radially outer to the centrifugal drum, from which the solids are intermittently discharged through solids discharge openings.The clarified milk flows through the separating disc assembly into the radial center of the centrifuge drum, from where it is directed into a gripper chamber, from which it is removed by a first centripetal pump. A still-flowing protein and germ concentrate, containing, among other things, germs and proteins, collects in a radial area or space between the separating disc assembly and the separated germs (= solid phase). through channels above a separating plate and above the stack of separating plates, is pumped out of the separation chamber by another centripetal pump. This free-flowing concentrate is recirculated into the inlet. This ensures that even "lighter" bacteria and spores are reliably separated during a subsequent separation run. Effective disinfection is achieved when the centrifugal separator's drum provides the largest possible clarification surface area for the clarification process, appropriate for the respective inflow rate. The clarification surface load should be at least 0.1 l / h per m 2 (Inlet capacity / equivalent treatment area). If the feed rate is selected to be lower or, in other words, if the clarification area is too large, this can lead to excessive separation of protein from the milk. If the milk protein content (milk protein content) in the heavier liquid phase (concentrate) is too high, this phase can even thicken in the solids collection chamber of the centrifuge drum, so that it can no longer be discharged from the centrifuge drum via a separating plate as a still-flowing liquid phase. This also hinders the separation of bacteria in the solids collection chamber, as the solid protein layer that builds up prevents flow into the solids collection chamber of the centrifugal separator. The incoming cow's milk typically has a protein content of approximately 3.5 wt / vol% (see e.g. EP 1 768 493 B1,

[0030] ). The effect of thickening the heavier liquid phase, described above, appears particularly problematic, with the resulting disadvantages. Based on the prior art, the object of the invention is therefore to reduce this effect. This object is achieved by the subject matter of claim 1. A centrifugal separator is created, which is designed in particular as a germ removal separator for the germ removal of milk, and is intended to separate a flowable product to be processed into a solid phase (sludge with germs) and into a first liquid phase and a second liquid phase in a centrifugal field, and which has at least the following: a rotatable centrifugal drum with a vertical axis of rotation, a separating plate package formed in a separation space of the centrifugal drum, a distributor arranged in the centrifugal drum for supplying the product from a product inlet pipe into the separation space, wherein in the distributor the product is guided into the separation space during operation (note: in this way the product is distributed in distribution channels of the distributor on Centrifugal drum speed accelerated), wherein the distributor further comprises first openings, so that a first part of the product P fed through the distributor is guided from the distribution channels into the plate pack, preferably into rising channels of the separating plate pack, wherein the separating chamber has a radially outer solids collection chamber, and discontinuously closable solids discharge openings for discharging the solid phase S as well as a first liquid discharge for discharging the lighter liquid phase and a second liquid discharge for discharging the heavier liquid phase. It is also provided that, in addition to the first openings, one or more second openings are formed in the distributor, which introduce a second part of the product P outwards into the centrifugal drum. This dilutes the heavier liquid phase in the separation chamber, thus easily preventing clogging of flow paths in the drum. The heavier liquid phase, when used to sterilize milk, is a still-flowing concentrate that contains a higher proportion of proteins and bacteria than the product, in this case, milk. It can optionally be advantageously provided that the first openings and / or the second openings are provided in a distributor base and that these are at least partially provided with replaceable sleeves. In this way, the cross-section of the respective openings can be easily changed and adapted to the respective product properties by inserting sleeves with a respective optimized passage cross-section. It can then further be particularly preferably provided that a first part of the discharged second heavier liquid phase can be recirculated into the centrifugal drum and a second part of the second liquid phase can be discharged. The invention also provides a method for the sterilization of milk with a sterilization separator according to one of claims 1 to 8, which is characterized by the following steps: i) providing the sterilization separator, ii) rotating the centrifuge drum, iii) continuously centrifugally separating milk fed into the centrifuge drum in the centrifuge drum, wherein the milk is separated into a solid phase S, which consists in particular of germs and spores, and into a first lighter liquid phase L1 of sterilized milk and into a second heavier liquid phase L2, wherein the second liquid phase consists of a flowable protein and germ concentrate is formed, which contains, among other things, germs and proteins, and iv) recirculating a first part of the second liquid phase into the centrifuge drum and discharging a second part of the second liquid phase from the germ removal separator, wherein when the milk to be processed is fed in, a first part of this is led through first openings in the distributor into the separating plate package and wherein a further part of the milk to be processed is led through the one or more second openings into an area radially outside the separating plate package. With this process, the heavier liquid phase is also diluted in the separation chamber, preventing clogging of flow paths in the drum. The separated portion of the concentrate can be further processed, for example, it can be used for protein-enriched milk drinks, yogurt—if necessary after a germ-reducing heat treatment such as sterilization and subsequent cooling—or similar products. Further advantageous embodiments of the invention can be found in the remaining subclaims. The invention is described in more detail below with reference to the drawing. It shows: Figure 1: a schematic sectional view of a centrifugal separator according to the invention; Figure 2: an enlarged section of Fig. 1 Figure 3: a schematic sectional view of a prior art centrifugal separator. The following description of the figures describes an exemplary embodiment. Individual features of this exemplary embodiment can also be combined with exemplary embodiments not shown and are also suitable as advantageous embodiments of the subject matter described in one or more of the main and subclaims. The terms used below, such as “top”, “bottom”, “right”, “left”, “horizontal” or “vertical” refer to the representation in the respective figure. First, the prior art centrifugal separator is described in Fig. 3. The centrifugal separator 1 in Fig. 3 is preferably designed as a self-emptying centrifugal separator, in particular as a disinfection separator. The centrifugal separator 1 has a centrifugal drum 2 that rotates during operation. The centrifugal drum 2 can have a vertical axis of rotation D. The centrifugal drum 2 is shown schematically here and can be designed as single- and / or double-conical (bottom and / or top, and especially inside). It is arranged on a drive spindle 11, to which it is rotationally fixedly coupled. This drive spindle can be rotated during operation by a drive motor (not shown here) and accelerated to an operating speed in order to generate a centrifugal acceleration of several thousand g in the drum. The centrifugal drum 2 is preferably designed for continuous operation, i.e., for continuous, non-batch centrifugal processing of a flowable suspension—here, preferably milk to be sterilized. The centrifugal separator is preferably designed—as shown here—as a sterilization separator, intended to separate, in the centrifugal field, a product P to be processed—here, raw milk—into a solid phase S—here, bacteria and germs—and two liquid phases of different weights, L1—here, a lighter liquid phase from clarified milk—and L2—here, a flowable, heavier concentrate phase with a high protein content. The centrifugal drum 2 can have a centrifugal drum upper part 3 and a centrifugal drum lower part 4. These centrifugal drum parts 3, 4 can be connected to each other in various ways, for example with a locking ring (also not shown here). A product inlet pipe 6 extends into the centrifugal drum 2. Furthermore, a distributor 5, which is rotationally fixedly coupled to the centrifugal drum, is formed in the centrifugal drum 2 for supplying the product from the product inlet pipe 6 into a separation chamber 7. In the distributor 5, the product P is transferred into the rotating system. The product P is accelerated in distribution channels 8 to the speed of the centrifugal drum. The distribution channels 8 can be formed in a distributor base 9. The product inlet pipe 6 is led from above through a hood 10 which is stationary during operation of the centrifugal separator 1 or from the end of the centrifugal drum 2 opposite a drive spindle 11 into the latter. The hood 10 can be arranged on a machine frame (not shown here) and supported thereon. The hood 10 can be divided into an upper conical hood section 12 and a lower conical hood section 13. The lower hood section 13 also forms a solids trap 14. The actual centrifugal separation of the product P into the various phases takes place in the separation chamber 7. The separation chamber 7 has a separation means - preferably a separation plate assembly 15 made of separation plates. First openings 16 are formed in the distribution channels 8 on the upper side of the distributor base. In a preferred embodiment, these openings can extend in the axial direction. It is essential that a first portion of the supplied product P flowing through the distributor - in particular, but not necessarily, milk to be sterilized - is introduced into the plate assembly through the first openings 16. In the illustrated embodiment, this first portion can be introduced into axially extending riser channels 17 of the separation plate assembly 15, which can be formed from aligned bores in the separation plates. The separation chamber 7 has a solids collection chamber 18 radially outside the separation plate package 15, in which the solid phase S separated from the suspension or the flowable product P collects during the separation and / or clarification process. A discharge system 19 is used to drain the solid phase S from the solid collection chamber 18 of the centrifugal drum 2. This system can be fluid-operated, as shown here. The fluid-operated discharge system 19 can have a piston valve 20 for opening and closing a plurality of solid discharge openings 21, which can be circumferentially distributed in the region of the largest diameter of the centrifugal drum 2. The discharge system 19 can further comprise a control fluid system associated with the piston valve 20 for controlling its opening and closing movements. The centrifugal separator 1 then has a first liquid discharge 22, through which the lighter liquid phase L1—that is, the sterilized or clarified milk, which flows through the separating disc pack 15 into the center of the centrifugal drum 2—can be discharged from the centrifugal drum 2. The first liquid discharge 22 can, for example, be designed as a so-called paring disc, which operates as a centripetal pump. The first Liquid discharge 22 can alternatively also be realized in another way, e.g. by a hermetically designed liquid discharge. In a radial space 23 between the separating disc assembly 15 and the solid phase S, a concentrate phase accumulates as a second, heavier liquid phase L2, which is guided through channels 24 above the separating disc assembly 15 through a second liquid discharge 25 from the centrifugal drum 2. The second liquid discharge 25 is also designed as a paring disc. The second liquid discharge 25 can also be implemented in another way, e.g., by a hermetically sealed liquid discharge. A first portion of the discharged concentrate is recirculated through a first line 26 into the product inlet pipe 6. This ensures that even "lighter" bacteria and spores are more reliably separated during a subsequent separation run. A second portion of the protein-enriched concentrate can be discharged via a second line 27 and, if necessary, further processed. During centrifugal clarification of milk, the protein content in the concentrate may increase (protein is separated by centrifugal force), which may lead to the thickening of the concentrate described in the introduction, which in turn may hinder the separation of bacteria and spores. In order to counteract this effect, unlike in Fig. 3, according to the embodiment of Figs. 1 and 2 (which is only modified in this respect), a special design of the distributor foot 9 of the centrifugal separator 1 is provided to prevent the thickening of the concentrate due to an excessively high protein content. This is achieved by providing, in addition to the first openings 16 in the distributor base 9, which guide the product P—i.e., the milk—into the rising channels 17, second openings 28 are also provided on an outer circumference of the distributor base 9, which guide a portion of the product, in particular the milk to be clarified, toward the solids collection chamber 18 (see Fig. 1 and Fig. 2). According to a preferred embodiment, these second openings 28 can be oriented such that the remaining portion of the product, in particular the milk to be clarified, flows essentially radially into the separation chamber. As a result, the protein-enriched heavier liquid phase L2 - i.e. the concentrate - is diluted in the solids collection chamber 18 and thus blocking of the solids collection chamber 18 and / or the channels above the separation plate stack is avoided. In order to be able to carry out a targeted distribution of the volume flows of the product to be clarified - i.e. the milk to be clarified - into the rising channels 17 on the one hand and the solids collection chamber 18 on the other, an optional further development can provide the first openings 16 and / or the second openings 28 of the distributor base 9 with replaceable sleeves 29 with a respective flow cross-section. These are then inserted into the openings and secured there. For example, they can be clamped there or secured via a type of thread or the like. To change the sleeves, it can also be provided that the distributor base is separable, so that, for example, a lower part can be removed so that the sleeves 29 can be replaced. In order to change the total passage cross-sections of the first and / or second openings, it is not necessary to provide all openings with sleeves, although this is also conceivable. The passage cross-section of the first and / or the second openings through which the supplied product flows into the separation chamber can thus be made variable by providing interchangeable sleeves 29 with differently sized passage openings 16, 30 or passage cross-sections. By a suitable selection of the passage cross-section of the passage openings 16, 30 of the sleeves 29, the distribution of the milk flow from the distributor 5 into the rising channels 17 or in the direction of the solids collection chamber 18 can be carried out individually and in a manner advantageous for the process. The respective optimal passage cross sections of the passage openings 16, 30 of the sleeves 29 to the riser channels 17 or in the direction of the solids collection chamber 18 can be determined, for example, by tests. It should also be noted that the centrifugal separator is assigned an electronic control unit for controlling and regulating the centrifugal processing, with which, for example, the speed of a drive motor not shown here can be regulated and with which, for example, actuators not shown here can be controlled. List of reference symbols 1 centrifugal separator 2 centrifugal drum 3 Drum top 4 Drum base 5 distributors 6 Product inlet pipe 7 Separation room 8 distribution channel 9 Distributor foot 10 hood 11 Drive spindle 12 Hood part 13 Hood part 14 solids traps 15 Separator disc package 16 first opening 17 Riser channel 18 Solids collection chamber 19 Emptying system 20 piston valves 21 Solids outlet opening 22 first liquid discharge 23 Room 24 channel 25 second liquid discharge 26 first line 27 second line 28 second opening 29 sleeve 30 passage opening D axis of rotation L1 liquid phase L2 liquid phase S solid P Product

Claims

Claims 1 . Centrifugal separator (1), which is designed in particular as a sterilization separator for sterilizing milk, and is intended to separate a flowable product P to be processed into a solid phase S and a first lighter liquid phase L1 and a second heavier liquid phase L2 in a centrifugal field, and which has at least the following: a) a rotatable centrifugal drum (2) with a vertical axis of rotation D, b) a separating plate stack (15) formed in a separation chamber (7) of the centrifugal drum (2), c) a distributor (5) arranged in the centrifugal drum (2) for supplying product from a product feed pipe (6) into the separation chamber (7), wherein in the distributor (5) the product P is guided into the separation chamber (7) during operation, d) wherein the distributor (5) further has first openings (16) so that a first part of the product P supplied through the distributor is guided from the distribution channels (8) into the plate stack,preferably in rising channels (17) of the separating plate package (15), wherein the separating chamber (7) has a radially outer solids collection chamber (18), e) discontinuously closable solids discharge openings (21) for discharging the solid phase S as well as a first liquid discharge (22) for discharging the lighter liquid phase (L1) and a second liquid discharge (25) for discharging the heavier liquid phase (L2), characterized in that f) in addition to the first openings (16) in the distributor (5), one or more second openings (28) are formed, which introduce a second part of the product P outwards into the centrifugal drum.

2. Centrifugal separator (1) according to claim 1, characterized in that the first openings (16) and / or the second openings (28) are formed in a distributor base (9).

3. Centrifugal separator (1) according to claim 1 or 2, characterized in that all or some of the first openings (16) and / or the second openings (28) of the distributor base (9) are provided with replaceable sleeves (29) which have passage openings (30) with a passage cross-section.

4. Centrifugal separator (1) according to claim 3, characterized in that the distributor foot (9) is divided into an upper part and a lower part, such that the exchange of the sleeves is possible.

5. Centrifugal separator (1) according to claim 3 or 4, characterized in that the first part of the product P supplied through the distributor is guided from the distribution channels (8) into rising channels (17) of the separating plate package (15).

6. Centrifugal separator (1) according to one of the preceding claims, characterized in that the second liquid phase L2 is passed from the separation chamber (7) to the second liquid discharge via a separating plate.

7. Centrifugal separator (1) according to one of the preceding claims, characterized in that a first part of the second, heavier liquid phase L2 discharged from the centrifugal drum (2) can be recirculated into the centrifugal drum (2) and a second part of the second liquid phase L2 can be discharged from the entire centrifugal separator via a second line (27).

8. Centrifugal separator (1) according to one of the preceding claims, characterized in that the second liquid phase L2 is a concentrate with an increased protein content compared to the product P.

9. A method for the sterilization of milk with a sterilization separator according to one of claims 1 to 8, characterized by the following steps: i) providing the sterilization separator, ii) accelerating the centrifuge drum to an operating speed iii) continuous centrifugal separation of milk fed into the centrifuge drum (2) in the centrifuge drum (2), wherein the milk is separated into a solid phase S, which consists in particular of germs and spores, and into a first lighter liquid phase L1 of sterilized milk and into a second heavier liquid phase L2, wherein the second liquid phase is formed from a flowable protein and germ concentrate, which contains, among other things, germs and proteins, and iv) recirculating a first part of the second liquid phase into the centrifuge drum (2) and discharging a second part of the second liquid phase from the sterilization separator, wherein during the supply of the processed milk, a first part of which is passed through first openings (16) in the distributor (5) into the separating plate package (15) and a further part of the milk to be processed is passed through the one or more second openings (28) into an area radially outside the separating plate package (15).

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