Agitating device for a digester of a biogas plant and method for manufacturing an agitating device

Abstract

Digester (1) having an agitating device (10) and an agitating device (10) and a method for manufacturing an agitating device (10), the agitating device (10) comprising multiple agitator blades (21-29) which agitator blades (11-13) comprise a plurality of blade sections (21-29) angled relative to one another. The blade sections (21-29) of the agitator blade (11-13) are angled relative to one another such that the agitator blade gradient (11-13) decreases with the distance (30) from a central rotational axis (19) increasing to configure the agitator blade in a flow-optimized three-dimensional shape.

Claims

1. An agitating device for a digester of a biogas plant having a plurality of agitator blades, each agitator blade comprising a plurality of blade sections angled relative to one another, wherein the plurality of blade sections of the agitator blade are each substantially flat and angled relative to one another along separation lines between the plurality of blade sections, and at least a pair of adjacent separation lines extend away from one another with increasing distance from a central rotational axis of the agitating device, such that the agitator blade gradient decreases with increasing distance from the central rotational axis so as to configure the agitator blade with approximately uniform advancing drive over the diameter of the agitator blade, wherein pairs of adjacent blade sections define a bending edge disposed in-between and extending substantially linearly, wherein the bending edges show a radial component transverse to a rotational axis, also an axial component parallel to the rotational axis, wherein with the radial distance of a bending edge from the rotational axis increasing, the axial component of the bending edge decreases and wherein the plurality of blade sections comprises at least five consecutive blade sections, wherein the bending lines do not intersect on the surface of the agitator blade.

2. The agitating device according to claim 1, wherein the blade sections are integrally connected with one another and wherein the blade sections are formed by bending over a flat basic body multiple times, the basic body consisting of a metallic sheet material.

3. The agitating device according to claim 1, wherein at least one angle between pairs of adjacent separation lines bending edges is larger than 1.

4. The agitating device according to claim 1, wherein the agitator blades are attached to a blade hub rotatable about a rotational axis wherein each of the agitator blades comprises a blade body and a blade base adjacent to the blade hub.

5. The agitating device according to claim 4, wherein a radially inwardly blade surface extends at an angle between 15° and 75° to the rotational axis of the blade hub.

6. The agitating device according to claim 4, wherein an agitator blade mounted to the blade hub extends in the axial direction of the rotational axis over at least ⅙ of the maximum radial extension of the agitator blade from the rotational axis.

7. The agitating device according to claim 1, wherein at least one of the blade sections shows an elevation transverse to its blade surface that is smaller than four times the material thickness of the blade section.

8. The agitating device according to claim 1, wherein the agitator blade is provided with at least six, eight or more blade sections.

9. The agitating device according to claim 1, wherein at least one blade section is edge-bent.

10. The agitating device according to claim 1, wherein a product of a distance from a central rotational axis and the local agitator blade gradient varies over the blade surface by less than the value of 4 and in particular by less than the value of 2.

11. The agitating device according to claim 1, wherein a local inclination angle in a surface location of the agitator blade relative to an axis extending through the surface location and oriented transverse to the central rotational axis decreases with the distance from the central rotational axis increasing.

12. The agitating device according to claim 1, wherein the agitator blade is attached to a mounting device.

13. The agitating device according to claim 1, wherein a plurality of two, three or more agitator blades is provided.

14. The agitating device according to claim 12, wherein the mounting devices of the agitator blades form a multi-edged axle mount overall.

15. The agitating device according to claim 12, wherein the agitator blade is attached to the mounting device by means of at least one detachable connecting device.

16. The agitating device according to claim 1, having a driving device and at least one drive shaft wherein the agitator blade is at least substantially non-rotatably connected with the drive shaft.

17. An agitating device for a digester of a biogas plant, comprising: a digester of a biogas plant having a digester wall and at least one digester interior and at least one digester roof and at least one agitating device that is disposed in the digester interior, wherein the agitating device has a plurality of agitator blades, each agitator blade comprising a plurality of blade sections angled relative to one another, wherein the plurality of blade sections of the agitator blade are each substantially flat and bent at an angle relative to one another along separation lines between the plurality of blade sections, wherein the separation lines diverge from each other with increasing distance from a central longitudinal axis, such that the agitator blade gradient decreases with increasing distance from the central rotational axis, wherein pairs of adjacent blade sections define a bending edge disposed in-between and extending substantially linearly, wherein the bending edges show in their orientation other than a radial component transverse to a rotational axis, also an axial component parallel to the rotational axis, wherein with the radial distance of a bending edge from the rotational axis increasing, the axial component of the bending edge decreases and wherein the plurality of blade sections comprises at least five consecutive blade sections, and wherein the bending lines do not intersect on the surface of the agitator blade.

18. A method for manufacturing an agitating device for a digester of a biogas plant having a plurality of agitator blades, each of the agitator blades comprising a plurality of blade sections angled relative to one another, wherein at least five consecutive blade sections of the agitator blades are each substantially flat and bent over at an angle relative to one another along separation lines between the five consecutive blade sections, wherein the separation lines diverge from each other with increasing distance from a central longitudinal axis, such that the agitator blade gradient decreases with increasing distance from a central rotational axis, and wherein pairs of adjacent blade sections define a bending edge disposed in-between and extending substantially linearly, wherein the bending edges show a radial component transverse to a rotational axis, also an axial component parallel to the rotational axis, wherein with the radial distance of a bending edge from the rotational axis increasing, the axial component of the bending edge decreases, and wherein the bending lines do not intersect on the surface of the agitator blade.

19. The method according to claim 18, wherein the agitator blade is manufactured from a two-dimensional basic body by bending over each of the blade sections.

20. The method according to claim 19, wherein the two-dimensional basic body is bent over and in particular edge-bent on a separation line between two blade sections.

21. The method according to claim 19, wherein multiple agitator blades are interconnected directly or indirectly via detachable connecting devices.

22. The method according to claim 19, wherein an angle between pairs of blade sections depends on the distance from a rotational axis.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The figures show in:

(2) FIG. 1 a schematic side view of a digester according to the invention;

(3) FIG. 2 a schematic cross section of the top end of the digester wall and an agitating unit according to the invention pulled relatively far upwardly;

(4) FIG. 3 a perspective illustration of an agitating device according to the invention;

(5) FIG. 4 a perspective exploded illustration of an agitating device according to the invention;

(6) FIG. 5 the basic body of an agitator blade of the agitating device according to the invention in a top view and side view; and

(7) FIG. 6 the agitator blade generated from the basic body of FIG. 5.

DETAILED DESCRIPTION

(8) Referring to the figures an exemplary embodiment will now be explained. FIG. 1 shows a simplistic side view of a digester 1 of a biogas plant 100. The digester 1 is preferably approximately circular in cross section and is presently provided with a circumferential digester wall 2 for example of concrete or steel. The digester roof 5 may be configured as a flat steel or concrete roof 5′, as may the floor. This digester roof 5 is formed by an in particular flexible material, extending upwardly from the wall so that a domed structure of the tank roof 5 is obtained. The inclination angle of the digester roof 5 depends on the specific conditions and may be 15° or more and in particular 30° or 45° or more. Preferably the digester roof 5 is at least partially and in particular entirely removable to render the digester interior 3 accessible.

(9) In the digester interior 3 a substrate 7 is provided when in operation.

(10) The digester roof 5 may be provided with at least one servicing opening 6 for example for servicing an agitator 10 disposed in the digester interior 3. A platform may be attached for example to the outside of the digester wall 2 for an operator to stand on.

(11) FIG. 2 shows a partial cross-section of the digester wall 2 where the agitating device 10 is visible with two of the agitator blades 11-13 provided thereat.

(12) The agitating device 10 is configured as a submersible motor agitator and it may be driven electrically or for example also hydraulically. In this exemplary embodiment the schematically illustrated agitator 10 is provided with a plurality of e.g. three agitator blades 11-13 which rotate when the agitating device is in operation, thus obtaining a thorough mixing of the substrate 7 in the digester interior 3. This allows homogenization and enhanced efficiency.

(13) The agitator 10 is retained height-adjustable at a guide unit 8 configured as a support mast or hollow profile.

(14) The agitator 10 may be traversed from the position illustrated in FIG. 2 far enough upwardly so that it abuts against the top edge of the guide unit 8. The agitating device 10 can be lowered along the guide unit 8 until the agitator blades 11 to 13 are just a short distance above the digester floor.

(15) The agitator 10 is provided pivotable together with the approximately rectangular support mast respectively with the guide unit 8 which is approximately rectangular in cross-section or has some other shape. The guide unit 8 can rotate about its longitudinal axis for pivoting the agitator 10 and for adjusting the agitating angle. This allows to align the agitator 10 in any desired direction.

(16) The guide unit 8 is attached to the inside surface of the digester wall 2 and retained thereat via support units 9. The support units 9 each comprise one or more supporting rods which extend upwardly at an angle. This allows to effectively support the guide unit 8.

(17) The fact that when in the servicing position the agitator blades 11 to 13 extend at least in part beyond the top end 38 of the digester wall 2 allows a maintenance technician standing on the platform 40 to comparatively comfortably exchange one or more of the agitator blades 11 to 13.

(18) Adjusting units 39 are provided for adjusting the height of the agitator 10 and for adjusting the pivoting angle of the agitator 10.

(19) As is schematically illustrated in FIG. 2, the agitator blades 11, 12 each comprise a plurality of blade sections. The structure of the agitator blades 11 to 13 and their architecture will now be described in detail with reference to the FIGS. 3 and 4.

(20) FIG. 3 shows a perspective illustration of the agitating device 10 which is presently equipped with three agitator blades 11, 12 and 13.

(21) Each of the agitator blades 11 to 13 is attached to a mounting device 20. The entire mounting device 20 of the three agitator blades 11 to 13 provides an axle mount 36 which serves to receive the drive shaft of the agitator. The drive shaft is fastened in the hub 41 which is pushed into, and screwed with, the axle mount 36. Thus each of the three agitator blades 11, 12, 13 is exchangeable separately. For exchanging, the screws provided as connecting devices 34 for the respective agitator blade 11 to 13 are unscrewed so that the agitator blade can be removed and exchanged.

(22) Each of the agitator blades 11 to 13 comprises a plurality 14 of blade sections 21, 22, etc. consisting of planes and flat segments.

(23) The agitating device 10 is rotatable about the central rotational axis 19. The agitator blade gradient decreases with the distance 30 from the central rotational axis 19 increasing. This allows a substantially uniform drive over the cross-sectional area of the agitating device 10.

(24) To this end the inclination angle 31 in a surface location 32 is dependent on the distance 30 from the central rotational axis relative to an axis 33 extending through the surface location 32 that is aligned transverse to the central rotational axis 19. Thus: the longer the distance 30, the smaller the inclination angle 31.

(25) The agitator blades of the agitating device 10 are attached to a blade hub 41 rotatable about a rotational axis 19. The or each of the agitator blades 11-13 comprises a blade body 43 and a blade base 44 adjacent to the blade hub 41. These blade bodies 43 extend immediately up to the blade hub 41. The radially inwardly blade surface 45 extends at an angle 46 between 15° and 75° and in particular between approximately 25° and 60° to the rotational axis 19 of the blade hub 41.

(26) At least one of the agitator blades and in particular all of the agitator blades 11-13 mounted to the blade hub 41 extend in the axial direction of the rotational axis 19 over at least ⅙ and in particular more than ⅕ of a maximum radial extension 46 of the agitator blade from the rotational axis 19.

(27) This means that on the blade base the agitator blades extend inclined relative to the blade hub 41. The blade sections of the agitator blades 11-13 are angled relative to one another such that the agitator blade gradient 11-13 decreases with the distance 30 from a central rotational axis 19 increasing so as to configure the agitator blades 11-13 in a flow-optimized three-dimensional shape.

(28) FIG. 4 shows an exploded perspective view of the agitating device 10 with the three agitator blades 11, 12 and 13. Each of the agitator blades 11 to 13 in this exemplary embodiment is welded to its mounting device 20. Other attachment options are possible and conceivable. The mounting devices 20 in turn are screwed to the hub 41 through the connecting devices 34 which in this case are screws.

(29) FIG. 5 shows the basic body 15 for an agitator blade 11 to 13 before the agitator blade is given its final shape. The agitator blades 11 to 13 are each manufactured from a flat steel plate or the like, firstly showing a flat and plane structure with a consistent wall thickness over the surface. The developed view of the agitator blade 11 to 13 is cut from a flat-lying steel plate so as to obtain a basic body 15 as it is shown in the left half of FIG. 5 in a top view.

(30) The basic body 15 can for example be cut out by means of lasering. Additional markings and indicators can be applied onto the blade surface 18 of the agitator blade by means of lasering or other devices. The individual blade sections 21 to 29 etc. are for example delineated on the basic body 15. Thus the bending lines are already applied onto the blade surface as the basic body 15 is cut. Indicators for the bending angles and the sequence of the process steps may for example be written thereon so that in manual processing, information about the type and sequence of the next process steps is available to the operator at all times.

(31) The number of blade sections 21 etc. depends on the application and requirements. The illustrated agitator blade shows a total of about 13 different blade sections wherein only the blade sections 21 to 29 are denoted with reference numerals. Each of the blade sections is configured as a stripe with the separation lines 37 between blade sections extending linearly although they may show angles 37a relative to one another. This enables a simple bending process for manufacturing the finished agitator blade. The separation line 37 concerned must be suitably placed or disposed on the bending machine or edging machine prior to bending the intended angle. After carrying out the plurality of bending actions the structure illustrated in FIG. 6 is obtained where the agitator blade extends to the front out of the plane of the drawing. Each of the blade sections 21 etc. then shows a substantially plane blade surface 18. A three-dimensional and flow-optimized structure is obtained by the plurality of the bent-over blade sections. In this way an ideal agitator blade contour is closely approximated. At the same time this manufacturing type allows cost-effective manufacturing of the agitator blades which due to the limited field of applications are produced in small or very small series and as a rule at least partially manually.

(32) The individual blade sections 21-29 show between them separation lines or bending edges 37 along which the blade sections 21-29 are bent over and/or edge-bent. In the finished agitator blades the separation lines 37 are bending edges 37 which extend substantially or entirely linearly between pairs of adjacent blade sections.

(33) The bending edges 37 show in their orientation, other than a radial component transverse to the rotational axis 19, also an axial component parallel to the rotational axis 19. With the radial distance of a bending edge 37 from the rotational axis 19 increasing, the axial component of the path of the bending edge 37 decreases.

(34) An angle between pairs of adjacent bending edges 37, e.g. the blade sections 26, 27 and 27, 28, is preferably larger than 1°. In particular all the angles between pairs of adjacent bending edges are larger than 0.5° and in particular larger than 1°. Preferred angles range between 0.5° and 3°. As illustrated in FIG. 5, adjacent bending edges preferably extend fan-like away from one another.

(35) As can be taken from the right-hand part of FIG. 5 showing a side view of the basic body 15, the basic body has a material thickness 16 of an elevation 17 which is maintained in virtually each of the blade sections 21 etc. Only the edges and bending edges of the blade sections may show a slightly larger elevation due to bending. The elevation 17 of a blade section therefore virtually always remains less than double the material thickness 16. Optionally with the exception of the bending locations.

(36) When creating the 3D contour and the developed view as it is illustrated in FIG. 5, care is taken to enable a suitable bending sequence.

(37) On the whole an agitating device or an agitator 10 is obtained and a digester equipped therewith, which show considerably reduced energy consumption since the three-dimensional contours of the agitator blades can be optimally adapted to the theoretically optimal contour. A quantity of only 4 and better 6 or 8 bends provide an effective agitating device the manufacture of which is still cost effective. Each of the agitator blades 11 to 13 of the agitating device can be exchanged separately.

(38) Although each of the blade sections 21 etc. consists of a plane metal strip having a material thickness 16, a flow-optimized and effective agitating device is provided on the whole.

(39) While a particular embodiment of the present stirrer unit for an agitating device for a digester of a biogas plant and method for manufacturing an agitating device has been described herein, it will be appreciated by those skilled in the art that changes and modifications may be made thereto without departing from the invention in its broader aspects and as set forth in the following claims.

(40) When the manufacturing process and each of the bending steps provide for employing suitable templates and brackets, manual manufacture also enables efficiency of process.

(41) TABLE-US-00001 List of reference numerals:  1 digester  2 digester wall  3 digester interior  4 horizontal  5 digester roof  6 servicing opening  7 substrate  8 guide unit  9 support unit 10 agitator, agitating device 11 agitator blade 12 agitator blade 13 agitator blade 14 plurality 15 main body 16 material thickness 17 elevation 18 blade surface 19 rotational axis 20 mounting device 21 blade section 22 blade section 23 blade section 24 blade section 25 blade section 26 blade section 27 blade section 28 blade section 29 blade section 30 distance 31 inclination angle 32 surface location 33 axis 34 connecting device 35 driving device 36 axle mount 37 separation line, bending line  37a angle 38 end 39 adjusting unit 40 platform 41 hub, blade hub 43 blade body 44 blade base 45 axial extension 46 radial extension 47 radial length 100  biogas plant