FERMENTER FOR PRODUCING A PSEUDOPLASTIC MEDIUM

Abstract

Fermenter for producing a shear-thinning medium comprising a tank volume and a stirring arrangement having an improved distribution capacity or a more uniform shear stress.

Claims

1.-16. (canceled)

17. A fermenter for producing a shear-thinning medium, comprising: a tank volume (70) and a stirring arrangement having a first stirring element (10) having at least one stirring blade (11), a second stirring element (20) having at least one stirring blade (21), and a rotation axis (60), wherein the first stirring element (10) and the second stirring element (20) are fixed on the rotation axis (60) such that they rotate with the rotation axis and are spaced axially, wherein the rotation axis (60) when used as intended is aligned substantially parallel with respect to the direction of the earth gravitation field, and wherein the tank volume (70) has in the region of the stirring elements (10, 20) substantially the shape of a circular cylinder (75) and the rotation axis (60) is situated substantially on the central axis of the circular cylinder (75), wherein the stirring blades (11, 12) of the first stirring element (10) and the stirring blades (21, 22) of the second stirring element (20) extend up to at least 0.8 times the distance between central axis of the circular cylinder (75) and a wall (71) of the circular cylinder, giving a ratio (d/D) of stirring-element diameter (d) to inner diameter (D) of the tank of at least 0.8, further comprising an active temperature-adjustable surface (80) for heating and/or cooling, wherein the flow profile (7) is guided along the temperature-adjustable surface, and wherein the temperature-adjustable surface (80) is formed as circumferential pipe sections (85) which are, with respect to the rotation axis (60), arranged in groups (88) in the axial direction, wherein one group extends between two stirring elements (10, 20) lying immediately one above another.

18. The fermenter according to claim 17, wherein the first stirring element (10) has, in addition to the first stirring blade (11), a second stirring blade (12), wherein the first stirring blade and the second stirring blade, with respect to the rotation axis (60), extend orthogonally away from the rotation axis on opposing sides of the rotation axis.

19. The fermenter according to claim 17, wherein the first stirring element (10) and the second stirring element (20) have a congruent number of at least two stirring blades (11, 12; 21, 22), wherein the stirring blades (11, 12) of the first stirring element are arranged offset in relation to the stirring blades (21, 22) of the second stirring element.

20. The fermenter according to claim 17, wherein the stirring blades (11, 12; 21, 22) of the first and the second stirring element (10, 20) are arranged offset to one another by a quarter circle.

21. The fermenter according to claim 17, wherein stirring surfaces (13, 14) of the first stirring blade (11) and of the second stirring blade (12) are, at least in the region of the outer ends of the stirring blades, inclined with respect to the perpendicular substantially around the extension direction of the corresponding stirring blade.

22. The fermenter according to claim 21, wherein the stirring surfaces (13, 14) of the first stirring blade (11) and of the second stirring blade (12) are inclined with respect to the perpendicular between 30 and 60.

23. The fermenter according to claim 21, wherein the stirring surfaces (13, 14) of the first stirring blade (11) and of the second stirring blade (12) are inclined with respect to the perpendicular between 40 and 50.

24. The fermenter according to claim 21, wherein the stirring surfaces (13, 14) of the first stirring blade (11) and of the second stirring blade (12) are inclined with respect to the perpendicular is 45+/2.

25. The fermenter according to claim 17, wherein the tank volume (70) has in the region of the stirring elements (10, 20, 30, 40, 50) substantially the shape of a circular cylinder (75), wherein inwardly protruding baffles (76) are provided in the circular cylinder, wherein the baffles extend further inward than the stirring blades (11, 12, 21, 22) extend outward in the direction of the wall (71) of the tank volume (70).

26. The fermenter according to claim 25, wherein the baffles keep the pipe sections (85) spaced away from a wall (71) of the tank volume, wherein the pipe sections are arranged further inward in the tank volume (70) than the stirring blades (11, 12, 21, 22) extend outward in the direction of the wall (71) of the tank volume (70).

27. The fermenter according to claim 25, wherein at least one pipe section (85) and at least three pipe sections (85) are arranged in the radial direction and in the axial direction, respectively, in a cross-sectional plane of a baffle (76).

28. The fermenter according to claim 17, wherein the stirring arrangement additionally has a third stirring element (30), a fourth stirring element (40) and a fifth stirring element (50) which are arranged on the rotation axis (60) such that they are spaced apart from one another, wherein each of the stirring elements (30, 50) has two stirring blades (31, 32; 51, 52) which are offset by a quarter circle with respect to the stirring blades (21, 22; 41, 42) of a neighboring stirring element (20, 40) on the rotation axis (60).

29. The fermenter according to claim 28, wherein four groups (88) of pipe sections (85) are provided among the five stirring elements, wherein, in each case, one group (88) of pipe sections (85) is arranged between two stirring elements (10, 20; 20, 30; 30, 40; 40, 50) lying immediately one above another.

30. The fermenter according to claim 17, further comprising a gas supply device (90), the mouth (91) of which is arranged below the at least two stirring elements (10, 20, 30, 40, 50).

31. A method for producing a polysaccharide comprising using the fermenter according to claim 17.

32. The method according to claim 31, wherein the polysaccharide in solution exhibits pseudoplastic behavior, wherein the viscosity behavior of a produced fermentation broth is described by the Ostwald de Waele power law within a shear rate range of from 1 to 150 s.sup.1, wherein the fermentation broth produced by the method achieves in the course of the process shear-rate-dependent minimum viscosity values which are characterized by a consistency factor of K=11.98 Pas.sup.2 and a flow index of n=0.1.

33. The method according to claim 31, wherein the polysaccharide is an extracellular, viscosity-increasing polysaccharide.

34. The method according to claim 31, wherein the polysaccharide is a glucan.

35. The method according to claim 31, wherein the polysaccharide is an -glucan, a -glucan or a xanthan gum.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Exemplary embodiments are described below with reference to the following drawings.

[0057] FIG. 1 shows a sectional view through a fermenter according to one exemplary embodiment of the invention.

[0058] FIG. 2 shows one detail from a stirring arrangement according to one exemplary embodiment of the invention.

[0059] FIG. 1 shows a fermenter according to one exemplary embodiment of the invention for producing a shear-thinning medium. In this connection, the fermenter 1 has a tank volume 70, which is defined by a wall of the tank volume 71. Situated in the tank volume 70 is a stirring arrangement having multiple stirring elements 10, 20, 30, 40, 50, which are each fixed on a rotation axis 60 and can rotate together with the rotation axis 60, driven via a motor M, around the rotation axis 60. The stirring elements in the embodiment shown in FIG. 1 each have two stirring blades, a first stirring blade 11 and a second stirring blade 12 for the first stirring element 10, and also analogously for the second, third, fourth and fifth stirring element 20, 30, 40, 50 a respectively first stirring blade 21, 31, 41, 51 and a second stirring blade 22, 32, 42, 52. The two stirring blades of a stirring element extend from the central axis or the rotation axis 60 in the direction of the wall 71 of the tank volume 70. In the embodiment shown in FIG. 1, each stirring element has two stirring blades which have substantially a constant inclination over the extension direction. Each stirring blade 11, 12 has a correspondingly inclined surface 13, 14, by means of which the shear-thinning medium is, upon a rotation of the rotation axis 60, substantially conveyed in an axial direction, i.e., with a component parallel to the rotation axis. In this connection, during the conveyance of the shear-thinning medium, said medium can be pushed either upward or downward by the inclined surfaces 13, 14, depending on in which direction the rotation axis 60 with the stirring elements 10 to 50 fixed thereto rotates. For example, in this connection, a flow direction 7 which may be vortex-like ensues, wherein this flow has an axial component which is stronger than a radial component. The vortex or the vortex-like flow is depicted in a simplified manner by arrows with the flow direction 7. However, in reality, the flow profile will be substantially more complex, especially since there is a differing exertion of force on the medium to be stirred 9, the shear-thinning medium, owing to the differing path speed according to the distance from the rotation axis 60. In the arrangement shown in FIG. 1, the vortexes 8 substantially form such that there is an axial circulation of the medium to be stirred 9, meaning that the regions between the stirring elements 10 to 50 are also subjected to a movement and are circulated such that they also reach the shearing region of the stirring blades of the stirring elements. In the embodiment shown in FIG. 1, each stirring element has two stirrer blades which are each arranged offset in relation to the stirrer blades of a stirring element arranged immediately adjacently, For instance, the stirring blades of the lowest stirring element 10, of the middle stirring element 30 and of the top stirring element 50 extend laterally in the image plane, whereas the stirring blades of the intermediate stirring elements 20 and 40 extend forward from the image plane or backward into the image plane.

[0060] The stirring blades of the stirring elements, as shown in FIG. 1, have an inclination which is substantially constant over the extension direction, in this case with the angle , which specifies the inclination with respect to the perpendicular, i.e., the extension direction of the rotation axis 60. It should be understood that the inclination of the stirring blades can change over the extension length of the stirring blades from the rotation axis 60 up to the blade tip, meaning that it is possible to take into account the differing path speed of the stirring elements according to the distance from the rotation axis 60. In particular, the inclination of the surfaces with respect to the direction of the rotation axis 60 can be greater in the region close to the axis than in the region far from the axis. In this connection, it should be understood that, in the case of a greater inclination, the axial propulsion component is lower than in the case of a smaller inclination.

[0061] In the embodiment shown in FIG. 1, the filling level in the tank volume 70 is situated just below the uppermost stirring element, meaning that the stirring element 50 in FIG. 1 is arranged above the medium to be stirred 9. Below the lowest stirring element 10, there is provided a gas supply device, the mouth of which is below the lowest stirring element 10. In this connection, the mouths 91 can be below the coverage circle of the two stirring blades 11, 12 of the first stirring element 10. When gas is introduced by means of the gas supply device 90 into the medium to be stirred 9, the volume of the medium to be stirred increases by the introduced gas bubbles. Consequently, the fill level in the tank volume rises, meaning that the fill level in this case can rise to above the uppermost stirring element 50, meaning that the uppermost stirring element 50 contributes to the stirring process. Depending on in which direction the rotation axis 60 with the stirring elements 10 to 50 fixed thereto rotates, the rise of the gas bubbles in the medium to be stirred 9 is promoted, specifically when the stirrer blades press upward the medium to be stirred 9 because of the inclined surfaces of the stirring blades, or slowed down, when the stirring blades move the medium downward when the rotation axis 60 rotates in the opposite direction and the stirring surfaces push downward the gas bubbles in the medium to be stirred 9.

[0062] The stirring blades 11, 21, 31, 41, 51; 12, 22, 32, 42, 52 extend from the rotation axis 60 to just before the wall 71 of the tank volume 70. The diameter of the stirring elements, which is to be understood in the context of the invention to mean the diameter of the scan circle of the particular stirring element, is approximately as large as the diameter of the tank volume 70 in the region of a circle-cylinder-based cross-sectional section of the tank volume 75.

[0063] The diameter ratio between the diameter of the stirring elements d to the diameter of the tank volume D is, for example, 0.9. It should be understood that the diameter ratio d/D can be selected as large as possible, meaning that a stirring movement of the stirring elements 10 to 50, said movement taking place up into the edge region of the tank volume, brings about at these points a shear stress on the shear-thinning medium, meaning that a good mixing of the medium to be stirred 9 is achieved there. The diameter ratio d/D can, for example, be up to 0.99, provided it is ensured that the radially outer ends 15 of the stirring blades do not collide with the wall 71 of the tank volume.

[0064] To support the fermentation process in the fermenter 1, it is possible to provide temperature-adjustable surfaces 80 which can adjust the temperature of the tank volume 70 or the medium to be stirred 9 situated therein. Said temperature-adjustable surfaces can, for example, be arranged in the form of outer cooling coils on the outside of the tank volume 70. Alternatively or additionally, it is also possible to arrange within the tank volume 70 temperature-adjustable surfaces which are, for example, then situated between the stirring elements. The temperature-adjustable surfaces provided in the tank volume 70 can, for example, be circumferential pipe sections 85 which can, for example, be arranged in the form of spiral pipes in the tank volume 70. In this connection, the circumferential pipe sections can be provided both spirally and circularly, it being possible to provide the spiral arrangement for a sequential flow-through. However, it is also possible to provide circular pipe sections which are either subjected to a flow-through in parallel, or which can be subjected to a flow-through in a sequential manner through an appropriate bend at right angles and a connection between a pipe section and an overlying pipe section through the bend at right angles. In the embodiment shown in FIG. 1, there are provided between the stirring elements groups 88 of circumferential pipe sections, which generally consist of two pipe sections lying next to one another in the radial direction, and five pipe sections arranged below/above one another. Such a group 88 of pipe sections can be subjected to a flow-through of a temperature-adjusting agent, either a cooling agent or a heating agent, in a sequential manner through an appropriate spiral guide. Owing to the design of the stirring blades and the resulting, preferably axial, flow of the medium to be stirred 9 within the tank volume, an overflow on the temperature-adjustable surfaces 80 or on the groups 88 of circumferential pipe sections 85 is achieved, meaning that it is possible in this region to achieve a temperature adjustment of the medium to be stirred 9. The fermentation process can be controlled by means of the temperature adjustment.

[0065] To prevent the rotation of the stirring elements 10 to 50 from moving the medium to be stirred in one entire rotating movement, meaning that the medium to be stirred substantially no longer moves with respect to the stirring elements, it is possible to provide baffles 76 in the tank volume 70. Said baffles can, for example, be paddles or plates which extend inwardly from the wall 71 of the tank volume 70, for example in the direction of the rotation axis. It should be understood that the baffles 76 can also extend into the tank volume 70 in a vertically and/or horizontally inclined manner and need not necessarily point toward the rotation axis 60. The baffles can be immediately fixed to the wall 71 of the tank volume 70 or else protrude into the tank volume 70 through spacers. In this connection, the baffles overlap radially with the stirring blades of the stirring elements, meaning that there is a radial overlap of baffles 76 and stirring blades 11, 21, 31, 41, 51, etc. In this way, a rotation movement of the medium to be stirred 9 is interrupted, or disrupted, and the relative movement of the stirring blades with respect to the medium to be stirred 9 is thus ensured. Consequently, it is possible to maintain by means of the stirring elements a shear stress on the medium to be stirred 9, the result being that the medium to be stirred is diluted and better flowable at this point.

[0066] In this connection, the baffles 76 can also serve as holding structures for the temperature-adjustable surfaces. In particular, the baffles can serve as holding structures for the groups of circumferential pipe sections and position them. In this connection, both the baffles 76 and the groups 88 of pipe sections 85 can extend at any distance into the space between the stirring elements, so long as they do not restrict or impede the rotation of the stirring elements around the rotation axis 60.

[0067] FIG. 2 shows a detail from a stirring arrangement which is constructed from the rotation axis 60 and a first stirring element 10 and a second stirring element 20. It should be understood that further stirring elements above and below the first or second stirring element are not ruled out here. In this connection, each of the two stirring elements 10, 20 has a first stirring blade 11 or 21 and a second stirring blade 12 or 22. In the arrangement shown in FIG. 2, the stirring blades are inclined by about 45 with respect to the extension direction of the rotation axis 60. As a result, the surfaces 13 and 14 and 23 and 24 are inclined and can, depending on the rotation direction, speed up in either an upward or downward direction the medium to be stirred 9. Owing to the applied shear forces, the shear-thinning medium becomes thinner and thus more flowable, meaning that mixing is improved. In this connection, the outer ends 15 and 25 extend to just before the wall 71 of the tank volume 70, which, however, is not shown in FIG. 2.

[0068] In FIG. 2, although the two stirring elements 10, 20 each have two stirring blades extending away on opposing sides, the stirring elements 10, 20 can also have three, four or more stirring blades. In this connection, said stirring blades can be distributed evenly along the circumference, meaning that a substantially symmetrical stirring element is provided.

[0069] In FIG. 2, the stirring blades of the first stirring element 11, 12 are arranged offset with respect to the stirring blades of the second stirring element 21, 22. FIG. 2 depicts, in particular, an offset by a quarter circle. However, it should be understood that the offset can also vary in size, meaning that, for example, in the case of three existing stirring elements on the rotation axis, the offset of neighboring stirring elements can be 60 in each case, meaning that a continued offset from stirring element to stirring element is a further 60 in each case.

[0070] Especially if more than two stirring blades are provided in the case of one stirring element or multiple stirring elements, the stirring blades can also be arranged above one another, i.e., without an offset in the case of neighboring stirring elements.

[0071] It should be noted that the present invention can be used in particular also for shear-thinning media which can serve for the extraction of petroleum, for example xanthan gum, glucans, more particularly - and -glucans.

LIST OF REFERENCE SIGNS

[0072] 1 Fermenter; stirrer for shear-thinning media for a fermentation process [0073] 7 Flow direction [0074] 8 Vortex [0075] 9 Medium to be stirred [0076] 10 First stirring element [0077] 11 First stirring blade of the first stirring element [0078] 12 Second stirring blade of the first stirring element [0079] 13 Inclined surface of the first stirring blade of the first stirring element [0080] 14 Inclined surface of the second stirring blade of the first stirring element [0081] 15 Radially outer end of the stirring blades of the first stirring element [0082] 20 Second stirring element [0083] 21 First stirring blade of the second stirring element [0084] 22 Second stirring blade of the second stirring element [0085] 23 Inclined surface of the first stirring blade of the second stirring element [0086] 24 Inclined surface of the second stirring blade of the second stirring element [0087] 25 Radially outer end of the stirring blades of the second stirring element [0088] 30 Third stirring element [0089] 31 First stirring blade of the third stirring element [0090] 32 Second stirring blade of the third stirring element [0091] 40 Fourth stirring element [0092] 41 First stirring blade of the fourth stirring element [0093] 42 Second stirring blade of the fourth stirring element [0094] 50 Fifth stirring element [0095] 51 First stirring blade of the fifth stirring element [0096] 52 Second stirring blade of the fifth stirring element [0097] 60 Rotation axis of the stirring arrangement [0098] 70 Tank volume [0099] 71 Wall of the tank volume [0100] 75 Section of the tank which has the shape of a circular cylinder [0101] 76 Baffles; holding structure for circumferential pipe sections [0102] 80 Temperature-adjustable surface for heating and/or cooling [0103] 85 Circumferential pipe sections [0104] 88 Group of circumferential pipe sections [0105] 90 Gas/oxygen supply [0106] 91 Mouth of the gas/oxygen supply [0107] (alpha) Inclination angle of the stirring blades with respect to the perpendicular [0108] d Outer diameter of the stirring elements [0109] D Inner diameter of the tank volume in the region 75