Foam centrifuge

Abstract

A foam centrifuge for separating a foam into a foam concentrate and a gas portion, comprising a pot-shaped housing (1) with a rotatably drivable impeller (2) accommodated in the housing (1), which impeller has a plurality of radial vanes (21) arranged on a hub (20) and circulating in an annular pumping section (13) of the housing (1), wherein the housing (1) has a foam inlet (10) at one axial end (15) and an exhaust air opening (11) for the gas portion at the opposite axial end (16), as well as a concentrate outlet (12) leading tangentially out of the pumping section (13), wherein the housing (1) has a cylindrical rotary chamber (17) extending from the foam inlet (10) and adjoining the pumping section (13),which has an enlarged cross-section compared to the impeller chamber (17) and is cylindrical, and the vanes (21) each comprise a working surface (210) circulating in the impeller chamber (17) and a pumping surface (211) adjoining the working surface (210) and circulating in the pumping section (13), wherein the pumping surface (211) is arranged radially further outward than the working surface (210) on the impeller (2), wherein the vanes (21) are not connected to one another at their radially outward end.

Description

[0001] The invention relates to a foam centrifuge for separating a foam into a foam concentrate and a gas portion, comprising a pot-shaped housing with an impeller accommodated in the housing and rotatably drivable, which has a plurality of radial vanes arranged on a hub, which rotate in an annular pumping section of the housing, wherein the housing has a foam inlet at one axial end and an exhaust air opening for the gas portion at the opposite axial end, as well as a concentrate outlet leading tangentially out of the pumping section.

[0002] Foam centrifuges of the type mentioned above are widely known and are used, for example, in fermentation processes, such as vinegar or beer production, since these processes generate large quantities of foam. Using the foam centrifuge, the foam is freed as completely as possible from its gas component, which is then discharged via the exhaust vent. A predominantly liquid foam concentrate component remains. This component is discharged separately from the gas component via the concentrate outlet and can be returned, for example, to a reactor or fermenter from which the foam was originally taken, or disposed of separately.

[0003] A common design of a foam centrifuge, disclosed, for example, in EP 1 660 207 B1, has an impeller whose radial vanes merge at their radially outer end into a circulating cylinder and are connected via this cylinder, which in turn rotates in the enclosing housing. Immediately in front of each individual vane, passage openings distributed around the circumference are arranged in the circulating cylinder through which the foam passes, separating into a liquid and a gas portion. By means of pump vanes arranged on the outer circumference of the circulating cylinder, the foam concentrate that has passed through the passage openings is discharged from a spiral-shaped pump section of the housing. The design is therefore comparatively complex. Furthermore, with such a design, the desired defoaming can only be achieved up to a certain limit, which appears to be in need of improvement.

[0004] The object of the invention is to propose a foam centrifuge of the type mentioned above which has a simpler structure but also enables a particularly reliable and powerful separation of a foam into a foam concentrate and a gas component largely independent of the foam consistency.

[0005] To achieve the stated object, the invention proposes the design of a foam centrifuge according to the features of patent claim 1.

[0006] Advantageous embodiments and further developments of the invention are the subject of the dependent claims.

[0007] The inventive proposal provides that the housing, starting from the foam inlet, has a cylindrical impeller chamber and, adjoining the impeller chamber, the pumping section, which has a larger cross-section than the impeller chamber and is also cylindrical. According to the invention, the blades of the impeller each comprise a working surface circulating in the impeller chamber and a pumping surface adjoining the working surface and circulating in the pumping section. The pumping surface is arranged radially further outward than the working surface on the impeller, corresponding to the enlarged cross-section of the pumping section.

[0008] The design according to the invention therefore dispenses with the circulating cylinder present in the prior art, thereby significantly reducing manufacturing costs. In the design according to the invention, the vanes are connected to the hub at their radially inward end or are integrally formed therewith, but are not connected to one another at their radially outward end, but rather rotate freely within the housing, i.e. the respective working surface in the impeller chamber and the respective pumping surface in the pumping section of the housing. Since both the pumping section and the impeller chamber of the housing are cylindrical, a rotationally symmetrical design of the housing results, which facilitates its manufacture.

[0009] When the impeller within the housing of the foam centrifuge according to the invention is set in rotation by a suitable rotary drive, for example a drive motor, the foam entering the housing via the foam inlet is captured in the impeller chamber by the rotating working surfaces of the impellers and, as a result of the prevailing centrifugal force, runs over the rotating impellers towards the inner surface of the impeller chamber. The foam is subjected to considerable acceleration and shear forces, whereby a portion of the gas volumes enclosed in the foam is already released. Upon reaching the radially outer end of the impellers, the gas bubbles contained in the foam are subjected to strong shear forces in the gap between the rotating impeller ends and the inner surface of the impeller chamber, so that the remaining gas bubbles open.The liquid foam concentrate, which thus accumulates on the inner surface of the rotary chamber and whose gas volume has been reduced, gradually rises along the inner surface of the rotary chamber towards the pumping section, with further gas volume being released by the rotating working surfaces. As soon as the foam concentrate reaches the pumping section, it enters the enlarged cross-section of the housing and is captured by the quasi-rotating pump impellers, whereby the remaining gas volume in the foam concentrate is further reduced and the foam concentrate is pumped tangentially by the rotating pump impellers into the concentrate outlet leading out of the housing and discharged. The gas portion released from the foam, however, is discharged separately via the exhaust air opening at the axial end of the housing opposite the foam inlet.

[0010] According to one proposal of the invention, the cross-section of the housing is stepped in the transition area between the impeller chamber and the pumping section, and the working surface and the pumping surface of the vanes are each arranged with a stepped offset relative to the hub. This design enables particularly effective separation of the gas component from the foam.

[0011] According to a further proposal of the invention, a deflection disk is inserted into the housing at the end of the vanes facing the exhaust air opening. This deflection disk covers the vanes towards the axial end of the housing containing the exhaust air opening and has a central cylindrical section that borders the pumping surfaces of the vanes on the radial inside and encloses the hub under load, forming an annular passage for the released gas portion. Such a deflection disk is easy to manufacture and, together with the pumping section of the housing, defines and delimits a concentric pump chamber in which the pumping surfaces of the vanes rotate, thus ensuring a particularly high pumping performance for discharging the foam concentrate into the concentrate outlet.

[0012] According to a further proposal of the invention, the axial end of the housing, which has the exhaust air opening, is closed by a detachably attached cover in which the exhaust air opening is formed. Such a detachably attachable cover facilitates the installation of the impeller inside the housing.

[0013] According to a proposal of the invention, the cover can be releasably attached to the housing by means of clamps with a seal in between.

[0014] Further details and embodiments of the invention are explained below with reference to the drawings illustrating an exemplary embodiment. They show: Fig. 1 a section through a foam centrifuge according to the invention, Fig. 2 in perspective view the foam centrifuge according to Fig. 1 with the lid removed.

[0015] From the Fig. 1 shows a foam centrifuge for separating a foam into a foam concentrate portion and a gas portion, as can be used, for example, in biotechnology and pharmaceutical technology.

[0016] The foam centrifuge comprises a pot-shaped housing 1 which is rotationally symmetrical to the central longitudinal axis M and which, at its lower axial end 15, has a foam inlet 10 in the form of a bore running concentrically to the central longitudinal axis M, which bore transitions into a cylindrical impeller chamber 17 of the housing 1 via a conically widening transition section (not further designated). At the end of the cylindrical impeller chamber 17 facing away from the axial end 15, a further section of the housing 1 is a pump section 13 which, compared to the cylindrical impeller chamber 17, has a stepped, widened cross-section and is also cylindrical. The other axial end 16 of the housing 1, opposite the axial end 15, is closed by a cover 5 which is releasably fixed to the housing 1 by means of clamps 6 with the interposition of seals 7.The cover 5 has a nozzle-like exhaust air opening 11 through which the interior of the housing 1 communicates with the environment. The foam inlet 10 is also nozzle-like.

[0017] Concentrically in the housing 1 is an impeller 2 which, as shown in the Fig. 2 can be set in rotation by a drive motor (not shown) in or against the direction of rotation R. The impeller extends axially symmetrically along the central longitudinal axis M, so that its axis of rotation coincides with the central longitudinal axis M. The impeller 2 is accommodated within the housing 1 with a longitudinal section designed as a hub 20 and with a further longitudinal section led out of the housing via a corresponding through-bore in the cover 5, so that the drive motor can act on this led out end.

[0018] In the illustrated embodiment, the hub 20 accommodated in the housing 1 carries a total of four diametrically opposed and equidistant vanes 21, which extend radially outward from the hub 20. Their radially inward end is attached to the hub 20, for example, welded or integrally formed, and their radially outward end protrudes freely from the hub 20. In particular, they are not connected to one another at the radially outward ends. The vanes 21 are connected to one another only at the radially inward end via the hub 20.

[0019] Corresponding to the stepped cross-sectional ratios between the impeller chamber 17 and the pumping section 13 of the housing 1, each vane 21 has a working surface 210 arranged within the impeller chamber 17 and a pumping surface 211 integrally adjoining the working surface 210 and arranged in the pumping section 13, which are arranged with a correspondingly stepped offset with respect to the hub 20 and the central longitudinal axis M in accordance with the stepped widening of the cross section of the housing in the transition from the impeller chamber 17 to the pumping section 13. Accordingly, only the working surfaces 210 of the vanes 21 are connected to the hub 20, whereas the pumping surface 211 adjoining the working surface 210 with an offset is spaced from the hub 20.As a result, a constant gap with a stepped cross-section runs between the working surface 210 and the inner surface of the impeller chamber 17 of the housing 1 and between the pumping surface 211 and the inner surface of the pumping section 13 of the housing 1, which gap enables the rotation of the hub 20 with the radially projecting vanes 21 within the housing 1 and correspondingly the rotation of the vanes 21 with the working surface 210 and the pumping surface 211 in the impeller chamber 17 or pumping section 13 of the housing 1.

[0020] In the area of ​​the axial end 16, between the axial end of the pumping section 13 and the cover 5, a deflection disk 3 is inserted into a corresponding stepped shoulder, which covers the pumping surfaces 211 of the vanes 21 towards the axial end 16 of the housing and, together with the pumping section 13 of the housing, defines a concentric pumping chamber 130 in which the pumping surfaces 211 of the vanes 2 rotate. At the radially inwardly directed end, the deflection disk 3 comprises a central cylindrical section 30, which radially inwardly adjoins the pumping surfaces 211 of the vanes and encloses the hub 20, leaving an annular passage space 31. The deflection disk 3 is shown in the illustration according to Fig. 2 as well as the cover 5 are removed from the housing 1.

[0021] Finally, the illustration according to Fig. 1 and Fig. 2 also has a pipe socket 120 leading tangentially out of the pump section 13 or the pump chamber 130, which forms a concentrate outlet 12.

[0022] The functionality of these from the Fig. 1 and Fig.2 is as follows: a foam volume to be separated enters the housing 1 via the foam inlet 10, for example from an upstream fermenter, and reaches the circulation area of ​​the blades 21 rotating in the housing 1. The incoming foam is initially captured by the working surfaces 210 in the rotary chamber 17, whereby gas bubbles are already mechanically opened and the liquid portion of the foam is forced radially outwards along the working surfaces 210 due to the prevailing centrifugal force until it reaches the inner surface of the rotary chamber 17. There, the foam is subjected to a strong shear force due to the passing outer blade ends, which leads to the opening of the gas bubbles contained therein.As the foam concentrate thus formed progressively accumulates on the inner surface of the impeller chamber 17, it gradually rises along the inner surface of the impeller chamber 17 and passes through the transition region into the pumping section 13 with an enlarged cross-section, where it is captured and further conveyed by the rotating pumping surfaces 211 of the vanes 21, with further release of the gaseous components in the foam concentrate and correspondingly further concentration.The foam concentrate, which accumulates on the inner surface of the pump section 13 and is predominantly liquid and largely separated from gaseous components, is conveyed in the pump chamber 130 formed together with the deflection disk 3 by the pumping surfaces 211 of the vanes 21 in the direction of circulation R and is finally pumped tangentially out of the housing 1 into the concentrate outlet 12, from where the foam concentrate separated from the gas component can, for example, be discharged and disposed of or returned to the reactor or fermenter upstream of the foam inlet 10.

[0023] The gas components released within the housing by the action of the vanes 21, however, flow along the surface of the hub 20 in the annular passage 31 between the central cylindrical section 30 of the deflection disc 3 and the hub 20 into the cover 5 and from there out of the housing 1 in the region of the axial end 16 via the exhaust air opening 11. From the exhaust air opening 11, the gas components can be fed, for example, to a downstream sterile filter (not shown).

[0024] The removable cover 5 allows the parts, which are otherwise easy to manufacture, namely the impeller 2 and the deflection disc 3, to be easily fastened in the housing and, if necessary, removed for inspection purposes.

[0025] With the foam centrifuge described above, foams can be separated into a foam concentrate and a gas component in a simple manner and with high performance.

Claims

[1] Foam centrifuge for separating a foam into a foam concentrate and a gas portion, comprising a pot-shaped housing (1) with an impeller (2) accommodated in the housing (1) and rotatably drivable, which impeller has a plurality of radial vanes (21) arranged on a hub (20) and circulating in an annular pumping section (13) of the housing (1), wherein the housing (1) has a foam inlet (10) at one axial end (15) and an exhaust air opening (11) for the gas portion at the opposite axial end (16) as well as a concentrate outlet (12) leading tangentially out of the pumping section (13), wherein the housing (1) has a cylindrical rotary chamber (17) starting from the foam inlet (10) and adjoining the pumping section (13),which has an enlarged cross-section compared to the impeller chamber (17) and is cylindrical, and the vanes (21) each comprise a working surface (210) circulating in the impeller chamber (17) and a pumping surface (211) adjoining the working surface (210) and circulating in the pumping section (13), wherein the pumping surface (211) is arranged radially further outward than the working surface (210) on the impeller (2), wherein the vanes (21) are not connected to one another at their radially outward end. [2] Foam centrifuge according to claim 1, characterized by that the cross-section of the housing (1) is widened in steps in the transition area between the rotary chamber (17) and the pumping section (13) and the working surface (210) and the pumping surface (211) of the vanes (21) are arranged accordingly with a step-like offset in relation to the hub (20). [3] Foam centrifuge according to one of claims 1 or 2, characterized bythat at the end of the vanes (21) facing the exhaust air opening (11), a deflection disc (3) is inserted into the housing (1), which deflection disc covers the vanes (21) towards the axial end (16) of the housing (1) having the exhaust air opening (11) and has a central cylinder section (30) which borders on the pumping surfaces (211) of the vanes radially on the inside and encloses the hub (20) while leaving an annular passage space (31). [4] Foam centrifuge according to claim 3, characterized by that the pumping section (13) of the housing (1) and the deflection disc (3) delimit a concentric pumping chamber (130) in which the pumping surfaces (211) of the vanes (2) rotate. [5] Foam centrifuge according to one of claims 1 to 4, characterized by that the axial end (16) of the housing (1) is closed by a detachably fastened cover (5) in which the exhaust air opening (11) is formed. [6] Foam centrifuge according to claim 5, characterized bythat the cover (5) is detachably fastened to the housing (1) by means of clamps (6) with a seal (7) interposed.

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