Method of operating a fermentation device
Patent Information
- Application Number
- EP2022765439
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2022-08-10
- Publication Date
- 2025-06-18
Smart Images
Figure 1.1
Abstract
Description
[0001] Method for operating a fermentation facility
[0002] The invention relates to a method for operating a fermentation device of the type specified in the preamble of claim 1.
[0003] EP 1 987 129 B1 discloses a method for operating a fermentation device comprising an elongated container and several stirring devices arranged within the container. The stirring devices serve both to move and mix the substrate in the container and to transport sediment at the bottom of the container.
[0004] The invention is based on the object of specifying a method for operating a fermentation device with which an energy-saving operation of the fermentation device is possible.
[0005] This object is achieved by a method having the features of claim 1.
[0006] It is intended that the agitator devices in at least two groups are driven by the drive device. Each group of agitators comprises at least one agitator. To enable energy-saving operation, it is intended that the agitator devices of a first group are driven in at least a first time interval and the agitator devices of a second group are idle during the first time interval. Accordingly, not all agitator devices of the fermentation device are driven simultaneously during the first time interval. This can significantly reduce the energy required to operate the agitator devices. It has been shown that, surprisingly, there are no negative effects on sediment transport or the destruction of the floating cover while the agitator devices of the second group are idle during the first time interval.The maintenance of a plug flow characteristic in the container and the vertical mixing, especially the degassing of the substrate, are not negatively affected.
[0007] Advantageously, not all agitators are driven for at least 50%, in particular for at least 80%, of the operating time of the fermentation facility. Particularly preferably, not all agitators are driven simultaneously at any time. This can significantly reduce energy consumption compared to operation in which all agitators are driven simultaneously.
[0008] Preferably, the stirring devices of the first group are driven in at least one second time interval in a second direction of rotation opposite to the first direction of rotation, and the stirring devices of the second group are stationary during the second time interval. By driving the stirring devices of the first group in the second direction of rotation, a return transport of substrate within the container is achieved. Preferably, the time intervals are designed such that an external return of treated material and a device for preconditioning the substrate or a device for upstream mixing of fresh substrate with treated material can be completely dispensed with during normal operation. Normal operation is any operation except for commissioning and troubleshooting. During commissioning or troubleshooting, it can be provided to return treated material to the container.It has also been shown that driving the agitators of the first group in the second direction of rotation can surprisingly positively influence vertical mixing and degassing of the substrate. The plug flow characteristics in the tank can also be maintained or even improved. A negative impact on sediment transport and scum destruction is not observed even when driving the agitators of the first group in the second direction of rotation. In particular, the first time interval is greater than or equal to the second time interval. By ensuring that the first time interval is at least as long as the second time interval, sufficient sediment transport at the bottom of the tank can be ensured.
[0009] A preferred arrangement is achieved when the stirring devices are driven such that stirring devices of a group do not follow one another in the direction of the longitudinal axis. The first direction of rotation is preferably oriented such that the stirring blades move along the bottom of the container in the direction from the first end face to the second end face of the container.
[0010] To ensure that the substrate fed into the container is thoroughly mixed, at least the stirring device adjacent to the feed opening is driven in the first direction of rotation during the introduction of substrate. Proper removal of the treated material can be easily ensured if, during the removal of treated material, at least the stirring device adjacent to the at least one discharge opening is driven in the first direction of rotation.
[0011] The energy requirement of the fermentation device can be further reduced in a simple manner by stopping all stirring devices of the first group and the second group, in particular all stirring devices of the fermentation device, in a third time interval.
[0012] Each group of stirring devices comprises at least one stirring device. Accordingly, at least one stirring device is stationary during the first time interval and, in particular, also during the second time interval. Preferably, each group comprises two to six stirring devices. Preferably, for each time interval in which the stirring devices of a group are driven in rotation, there is a time interval in which the stirring devices of this group are stationary. The time interval over which the stirring devices of a group are driven advantageously corresponds to an integer multiple of half a revolution of the stirring devices. This provides a simple way of ensuring that the stirring devices, when stationary, are in a defined position in which they cannot collide with neighboring stirring devices. The integer multiple is preferably from 2 to 10.However, other time intervals for driving the agitators may also be advantageous. The time interval during which the agitators of a group are at rest advantageously corresponds to half a revolution or an integer multiple of half revolutions of the agitators. It is preferred that the integer multiple be from 2 to 10.
[0013] The rotational speed of the stirring devices is advantageously adjusted via a frequency converter depending on a predetermined nominal speed. The speed is preferably set in the range of 80% to 100% of the nominal speed. The nominal speed is advantageously 0.5 rpm to 2 rpm, in particular approximately 1 rpm. However, other speeds and / or other speed controls may also be advantageous.
[0014] For the introduction of substrate, it is advantageously provided that the substrate is introduced in successive time periods. The introduction time or the amount of substrate is advantageously predetermined for each time period. Preferably, the substrate is not introduced continuously. The introduction time of the substrate is preferably 10% to 60% of the time period. The time period can be, for example, 0.5 h to 2 h, preferably 0.75 h to 1.5 h, particularly preferably approximately 1 h.
[0015] Advantageously, the substrate in the fermentation device is moved exclusively by loading and unloading and via the stirring devices from the at least one inlet opening to the at least one outlet opening. Additional devices for transporting substrate, in particular substrate sediments, are advantageously not provided. This results in a simple structure of the fermentation device.
[0016] The fermentation device is preferably a plug flow fermenter.
[0017] In order to ensure good transport, in particular of sediments at the bottom of the container, it is advantageous that each agitator blade has a maximum extension to the central axis of the agitator device, wherein the axial distance of the central axis of at least two agitators arranged one after the other in the direction of the longitudinal axis of the container is preferably less than or equal to the sum of the maximum radial extensions of the two agitators. The areas covered by the agitator blades of agitators arranged one after the other in the direction of the longitudinal axis of the container overlap. The sediments are transported in the manner of shifting dunes. At the bottom of the container, a leading agitator blade piles up a dune, which is then removed by the following agitator blade on the side of the dune facing the discharge opening. In this way, sediment transport at the bottom of the container can be achieved in a simple manner without additional devices.
[0018] Embodiments of the invention are explained below with reference to the drawings. They show:
[0019] Fig. 1 is a sectional view of a fermentation device,
[0020] Fig. 1a is a schematic representation of an alternative arrangement of adjacent stirring devices, Fig. 2 is a schematic cross-section through the container of the fermentation device from Fig. 1,
[0021] Fig. 3 and 4 exemplary diagrams for the drive of the stirring devices in the first or second direction of rotation over time.
[0022] Fig. 1 shows a schematic longitudinal section of a fermentation device 1. The fermentation device comprises a container 3 which has a first end face 9 and a second end face 10. The container 3 has a longitudinal axis 23 which extends through the first end face 9 and the second end face 10. The container 3 is arranged horizontally and the longitudinal axis 23 runs horizontally in the exemplary embodiment. The container 3 has an introduction opening 4 for substrate on the first end face 9 and a discharge opening 5 for treated material on the second end face 10. In the exemplary embodiment, an exhaust opening 8 for biogas is provided on an upper container ceiling 7 of the container 3. Several introduction openings 4, discharge openings 5 and / or exhaust openings 8 can also be provided. Preferably, introduction openings 4 are provided only on the first end face 9 and discharge openings for treated material are provided exclusively on the second end face 10.Alternatively, additional insertion openings 4 may be provided between the end faces 9 and 10. The lower side of the container 3 forms a container bottom 6. Preferably, the container bottom 6 and the container top 7 are flat and aligned parallel to each other, as shown in Fig. 2.
[0023] The fermentation device 1 is designed as a so-called plug-flow fermenter. In such a plug-flow fermenter, the substrate moves horizontally in the container 3. The substrate is transported by loading and unloading as well as by stirring devices 11, 12, 13, 14, 15, 16, the design of which will be explained in more detail below with reference to the first stirring device 11. The other stirring devices 12 to 16 can be designed accordingly. Further devices for moving substrate in the container 3 are advantageously not provided. The first stirring device 11 comprises a stirrer shaft 20, which can be driven to rotate about a central axis 21. The central axis 21 is arranged transversely, preferably perpendicularly, to the longitudinal axis 23. At least one stirrer blade 22 extends outward from the stirrer shaft 20. In the exemplary embodiment, at least two stirrer blades 22 are provided, running on opposite sides of the stirrer shaft 20.The stirrer blades 22 have a maximum radial extent r relative to the central axis 21 of the associated stirring device. In the exemplary embodiment, the maximum radial extents r are the same for all stirrer blades 22 of all stirring devices 11 to 16. However, different maximum radial extents r for stirrer blades 22 of one stirring device 11 to 16 or for stirrer blades 22 of different stirring devices 11 to 16 can also be advantageous. The central axes 21 of two stirring devices 11 to 16 arranged one after the other in the direction of the longitudinal axis 23 of the container 3 have an axial distance a. Fig. 1 shows an example of the axial distance a between the central axes 21 of the stirrer shafts 20 of the second stirring device 12 and the third stirring device 13. In the exemplary embodiment, all central axes 21 of adjacent stirring devices 11 to 16 have the same axial distance a.
[0024] In the exemplary embodiment, the axial distance a is smaller than the sum of the maximum radial extents r of the agitator blades 22 of adjacent agitator devices 11 to 16. Because the axial distance a is smaller than the sum of the maximum radial extents r of the respective adjacent agitator devices 11 to 16, adjacent agitator devices 11 to 16 form an overlap region 24, which is shown in Fig. 1 for the second agitator device 12 and the third agitator device 13. The overlap region 24 is swept over by both a stirrer blade 22 of the agitator device 12 and a stirrer blade 22 of the agitator device 13.
[0025] During operation, an approximately dune-shaped sediment mound 25 collects on the tank bottom 6 below the overlap region 24. The second agitator 12 piles up the sediment at the sediment mound 25. On the side of the sediment mound 25 closer to the front face 10, sediment is entrained by the downstream third agitator 13 and transported toward the discharge opening 5. Preferably, corresponding overlap regions 24 are provided between all adjacent agitators 11 to 16. Due to the overlap of adjacent agitators 11 to 16, an additional device for transporting sediment can advantageously be dispensed with.
[0026] An alternative arrangement of two adjacent stirring devices is shown schematically in Fig. 1a for the stirring devices 11 and 12. In this embodiment, the axial distance a is equal to the sum of the maximum radial extensions r of the stirring blades 22 of adjacent stirring devices 11 to 16. Even with this arrangement, the sediments can still be transported in the manner described above.
[0027] During operation of the fermentation device 1, substrate containing organic material is fed into the container 3 via the introduction opening 4. During the introduction of substrate, the first stirring device 11 adjoining the first end face 9 rotates in a first direction of rotation 18. The direction of rotation 18 is such that the stirrer blades 22 move on the container bottom 6 from the first end face 9 towards the second end face 10. On the container ceiling 7, the stirrer blades 22 move in the opposite direction, i.e. from the second end face 10 towards the first end face 9. In the exemplary embodiment, the central axes 21 of the stirrer shafts 20 are aligned horizontally and perpendicular to the longitudinal axis 23. All central axes 21 run parallel to one another. By driving the first stirring device 11 in the first direction of rotation 18, substrate fed in via the introduction opening 4 is transported quickly further.This prevents overloading of the fermentation device 1 in the feeding area. During normal operation, the substrate is fed directly through the feed opening 4, without the substrate being conditioned prior to the fermentation device 1 or mixed with previously treated material. The fermentation device 1 shown in Fig. 1 has no external return line. Treated material that has been discharged from the container 3 via the discharge opening 5 is therefore not returned to the feed opening or to a preconditioning device or a forced mixer to be mixed with the fresh substrate, but is completely removed. The treated substrate is returned within the container 3 itself. To enable this return, provision is made for at least one of the stirring devices 11 to 16 to be temporarily driven in a second direction of rotation 19, opposite to the first direction of rotation 18.The direction of rotation 19 is shown in Fig. 1 for the second stirring device 12.
[0028] The drive of the stirring devices 11 to 16 in the first rotational direction 18 and the second rotational direction 19 is described in more detail below. The sixth stirring device 16, adjacent to the discharge opening 5 and the second end face 10, is preferably driven in the first rotational direction 18 during the removal of treated material from the container 3, so that the stirring blades 22 move adjacent to the container bottom 6 in the direction of the second end face 10, thereby promoting the sediment transport on the container bottom 6 to the discharge opening 5.
[0029] Fig. 2 shows a schematic section through the first stirring device 11. The other stirring devices 12 to 16 are preferably of identical design. In the exemplary embodiment, a drive device 17, for example a drive motor with or without a gear unit, is provided for each stirring device 11 to 16. It can also be provided that one drive device 17 drives several of the stirring devices 11 to 16 or all of the stirring devices 11 to 16 via suitable transmission devices such as belt drives or the like. The fermentation device 1 comprises a control device 27 which appropriately controls the at least one drive device 17. It is provided that none of the drive devices 17 runs continuously, but that the drive devices 17 are only in operation intermittently. This allows the energy requirement of the fermentation device 1 to be reduced in a simple manner.The drive device 17 comprises a frequency converter 28, via which the speed of the stirrer shaft 20 can be easily adjusted.
[0030] As Fig. 2 also shows, in the exemplary embodiment, four agitator blades 22 are arranged on a common agitator shaft 20. The agitator blades 22 are each formed by two outwardly projecting arms 29, which carry a horizontally extending agitator bar 26 at their radially outer end. The agitator bar 26 extends across the entire width b of each agitator blade 22. Another design of the agitator blades 22 may also be advantageous.
[0031] As shown in Fig. 2, opposing agitator blades 22 are arranged offset from one another in the direction of the central axis 21. Each agitator blade 22 therefore moves in its own disc-shaped region around the central axis 21. With reference to the sectional view shown in Fig. 2, the agitator blades 22 of a stirring device 11 to 16 do not overlap. Agitator blades 22 following one another in the direction of the central axis 21 are advantageously arranged on opposite sides of the central axis 21.
[0032] The stirring devices 11 to 16 are advantageously driven in at least two groups. Each group of stirring devices 11 to 16 preferably comprises at least one, preferably at least two, stirring devices 11 to 16. Figures 3 and 4 show two possible ways of controlling the stirring devices 11 to 16, in which the stirring devices are divided into two groups. In the exemplary embodiment, a first group comprises the stirring devices 12, 14, and 16, and a second group comprises the stirring devices 11, 13, and 15.
[0033] In a first time interval ti, in the timing sequence of the drive of the stirring devices 11 to 16 shown in Fig. 3, the stirring devices 12, 14 and 16 are driven in the first direction of rotation 18. In a later second time interval t2, the stirring devices 12, 14 and 16, which form the first group, are driven in the second, opposite direction of rotation 19. Between the first time interval ti and the second time interval t2 there is a third time interval t3, during which the stirring devices 12, 14 and 16 of the first group are at a standstill. The stirring devices 11, 13 and 15 of the second group are at a standstill during the first time interval ti, the second time interval t2 and the third time interval t3. The second time interval t2 is followed by a further third time interval t3, during which all stirring devices 11 to 16 of both groups are at a standstill again.In a fourth time interval U following this, the stirring devices 11, 13, and 15 of the first group are driven in the first direction of rotation 18. In this fourth time interval U, substrate can be fed into the container 1 via the inlet opening 4. In the first time interval t1, treated material can be withdrawn from the outlet opening 5 via the outlet opening 5. The fourth time interval U is again followed by a third time interval t3, during which all stirring devices 11 to 16 are stationary. In the subsequent fifth time interval ts, the stirring devices 11, 13, and 15 of the second group are driven in a second direction of rotation 19.
[0034] In an alternative process sequence, the supply of substrate and the removal of treated material are independent of which of the groups of stirring devices 11 to 16 is driven or stationary. For example, a supply of substrate can take place in each time interval t1, t2, U, ts over a specific period of time. Advantageously, the first stirring device 11 is driven independently of the other stirring devices 13 and 15 of the group in the first direction of rotation 18 while the substrate is being supplied. Correspondingly, the sixth stirring device 16 is advantageously driven independently of the other stirring devices 12 and 14 of the group in the first direction of rotation 18 while treated material is being removed.
[0035] Fig. 4 shows an alternative drive for the stirring devices 11 to 16. Initially, the stirring devices 12, 14 and 16 of the first group are driven in the first direction of rotation 18, specifically in the first time interval t1. This is followed by a third time interval t3, during which all stirring devices 11 to 16 are stationary. In a subsequent fourth time interval U, the stirring devices 11, 13 and 15 of the second group are driven in the first direction of rotation 18. This is followed by a third time interval t3, during which none of the stirring devices 11 to 16 are driven. Subsequently, in a second time interval t2, the stirring devices 12, 14 and 16 of the first group are driven in the second direction of rotation 19. After the subsequent third time interval t3, at which all stirring devices 11 to 16 are at a standstill, the stirring devices 11, 13, and 15 of the second group are driven in the second direction of rotation 19 in the fifth time interval ts.While the agitators of one group are operating, the agitators of the other group are advantageously idle. Overall, this results in a comparatively short operating time for each agitator 11 to 16, which can significantly reduce the energy consumption of the fermentation device 1.
[0036] The first time interval t1, during which the stirring devices 12, 14, and 16 are driven in the first rotational direction 18, is preferably greater than or equal to the second time interval t2, during which the stirring devices 12, 14, 16 are driven in the opposite rotational direction 19. As shown in Fig. 1, successive stirring devices are assigned to different groups.
[0037] The time intervals ti, t2, U and ts, at which the stirring devices of a group are driven, advantageously correspond to integer multiples of half-revolutions of the stirring devices 11 to 16. The integer multiples are advantageously from 2 to 10. The third time interval t3, during which the stirring devices 11 to 16 of both groups are stationary, also preferably corresponds to half a revolution or an integer multiple of half-revolutions of the stirring devices 11 to 16. The integer multiple is advantageously from 2 to 6. The rotational speed of the stirring devices 11 to 16 can advantageously be adjusted depending on the introduced substrate. The frequency converter 27 shown in Fig. 2 is used for this purpose. The speed is advantageously set in the range from 80% to 100% of the nominal speed. The nominal speed is preferably 0.5 rpm to 2 rpm, particularly preferably about 1 rpm.The stirrer blades 22 therefore move comparatively slowly through the substrate in container 3.
[0038] The substrate is advantageously fed in quasi-continuously via the feed opening 4 (Fig. 1) in successive time periods d. The feed advantageously takes place once in each time period d. The feed duration e or the amount of substrate per time period d is advantageously predetermined. Fig. 3 shows an example of a time period d which includes the drive of each stirring device 11 to 16 in each direction of rotation exactly once. The substrate is fed in over a feed duration e which is 10% to 60% of the time period d. In the exemplary embodiment, the feed duration e corresponds to the fourth time interval U in which the first stirring device 11 is driven in the first direction of rotation 18. The time period d is advantageously 0.5 h to 2 h, in particular 0.75 h to 1.5 h, preferably approximately 1 h. The stirring devices 11 to 16 move the substrate in the container 3 and mix the substrate.A different choice of the time period d and the introduction duration e can also be advantageous. The time period d is preferably significantly longer than the time intervals t1 to t2. The time intervals t2, t2, t3 and t4, during which the stirring devices of a group are driven, are advantageously an integer multiple of half a revolution of the stirring devices 11 to 16. The integer multiple is preferably from 2 to 10. The time intervals t1 to t4, during which the stirring devices of a group are stationary, are advantageously an integer multiple of half a revolution of the stirring devices 11 to 16. The integer multiple is preferably from 2 to 10. The rotational speed of the stirring devices 11 to 16 is advantageously 80% to 100% of a nominal speed. The nominal speed is advantageously 0.5 rpm. to 2 rpm, preferably 1 rpm. The time period d is advantageously significantly longer than the time intervals ti to ts.
[0039] It can be provided that the time intervals ti to ts are of equal length. Time intervals ti to ts of different lengths can also be advantageous. Advantageously, time intervals t4 and ts, during which the stirring devices of a group are driven in the second direction of rotation 19, are not longer than the time intervals ti and t2, during which the stirring devices of a group are driven in the first direction of rotation 18.
[0040] By appropriately selecting the time intervals ti to ts and appropriately dividing the stirring devices 11 to 16 into groups of at least one, preferably two to six, stirring devices, and by at least temporarily driving at least one stirring device 11 to 16 in the second direction of rotation 19, the substrate can be recirculated within the container 3. External recirculation of treated material and preconditioning are not required during normal operation. This enables a fermentation device 1 with a simple structure and low energy consumption during operation. The stirring devices 11 to 16 effect the vertical mixing of the substrate, the destruction and distribution of the floating cover, and the transport of sediment from the substrate. The supply of substrate to the container 4 is quasi-continuous.The stirring devices 11 to 16 are in intermittent operation and are only controlled according to the program stored in the control device 27 for driving the stirring devices 11 to 16. The stirring devices 11 to 16 are advantageously only operated for short periods of time. The first stirring device 11 and the last stirring device 16 can be driven additionally and independently of the other stirring devices in the respective group during the introduction of substrate and the removal of treated material, thus allowing longer operating times than the other stirring devices.
[0041] By at least temporarily moving at least one stirring device in the second direction of rotation 19, it is possible to recirculate the substrate within the container 3 and mix it with the supplied material in the container 3. This makes it possible to set the desired dry matter content, particularly in the first stirring device 11, as well as to achieve a desired dilution to reduce the viscosity. The dry matter content of the substrate fed into the container 2 is advantageously less than 45 wt.%, in particular 30 wt.% to 45 wt.%. The fermentation device 1 is advantageously a fermentation device for continuous dry fermentation. The at least temporary drive of at least one stirring device 11 to 16 in the second direction of rotation 19 enables the plug flow characteristic in the container 3 to be maintained and vertical mixing and degassing of the substrate.The sediment transport at the bottom of tank 6 and the destruction of the floating covers in tank 3 remain guaranteed.
[0042] The substrate fed to the fermentation device 1 advantageously has a dry matter content of at least 20 wt.%.
[0043] The substrate fed to the fermentation facility 1 comprises, in particular, various domestic or commercial organic wastes, such as separately collected biowaste, organic-enriched fine fractions from mixed household waste, green waste, or separately collected food waste from households or restaurants. Alternatively or additionally, the substrate fed to the fermentation facility 1 comprises wastes with seasonally or constantly changing properties or compositions and / or with larger proportions of contaminants, such as non-fermentable hard or inert materials such as stones, glass, ceramics, sand, or the like.The substrate fed to the fermentation device 1 includes in particular higher viscosity, structurally rich or fibrous substrates from agriculture, landscaping, trade and industry, such as straw, grass, silage or other cellulose-containing material streams, for example from the paper industry, and / or dewatered sewage sludge.
Claims
Claims Method for operating a fermentation device, wherein the fermentation device (1) comprises an elongated container (3), wherein the container (3) has at least one introduction opening (4) on a first end face (9) of the container (3), at least one discharge opening (5) on a second, opposite end face (10) of the container (3) and at least one discharge opening (8) for biogas, wherein the fermentation device (1) has several stirring devices (11, 12, 13, 14, 15, 16) and at least one drive device (17) for the stirring devices (11, 12, 13, 14, 15, 16), wherein each stirring device (11, 12, 13, 14, 15, 16) has at least one stirrer shaft (20) arranged transversely to a longitudinal axis (23) of the container (3), which stirrer shaft can rotate about a central axis (21) of the Stirrer shaft (20) can be driven in rotation by a drive device (17), wherein the stirring device (11, 12, 13, 14, 15, 16) has at least one fixed to the stirrer shaft (20),outwardly projecting agitator blades (22), the method comprising the following steps: Introducing substrate containing organic material via at least one introduction opening (4), Moving and mixing the substrate in the container (3) by means of the rotating stirring devices (11, 12, 13, 14, 15, 16), Discharging treated material via the at least one discharge opening (5), and Extraction of biogas via the at least one discharge opening (8), characterized in that the stirring devices (11, 12, 13, 14, 15, 16) are driven in at least two groups by the drive device (17), wherein each group comprises at least one stirring device (11, 12, 13, 14, 15, 16), wherein the stirring devices (11, 13, 15) of a first group are driven in at least a first time interval (ti) and wherein the stirring devices (12, 14, 16) of a second group are stationary in the first time interval (ti). Method according to claim 1, characterized in that the stirring devices (11, 13, 15) of the first group are driven in at least one second time interval (t2) in a second direction of rotation (19) opposite to the first direction of rotation (18), and in that the stirring devices (12, 14, 16) of the second group are stationary in the second time interval (t2). Method according to claim 2, characterized in that the first time interval (t1) is greater than or equal to the second time interval (t2). Method according to one of claims 1 to 3, characterized in that the stirring devices (11, 12, 13, 14, 15, 16) are driven such that stirring devices (11, 12, 13, 14, 15, 16) of a group do not follow one another in the direction of the longitudinal axis (23).Method according to one of claims 1 to 4, characterized in that when driven in the first direction of rotation (18), the stirrer blades (22) move on the bottom of the container (3) in the direction from the first end face (9) to the second end face (10) of the container (3). Method according to one of claims 1 to 5, characterized in that during the introduction of the substrate, at least the stirring device (11) adjoining the introduction opening (4) is driven in the first direction of rotation (18). Method according to one of claims 1 to 6, characterized in that during the removal of treated material. at least the stirring device (16) adjoining the at least one discharge opening (5) is driven in the first direction of rotation (18).
8. Method according to one of claims 1 to 7, characterized in that in a third time interval (t?) all stirring devices (11, 12, 13, 14, 15, 16) of the first group (11, 13, 15) and the second group (12, 14, 16), in particular all stirring devices (11, 12, 13, 14, 15, 16) of the fermentation device (1), are at a standstill.
9. Method according to one of claims 1 to 8, characterized in that each group comprises 2 to 6 stirring devices (11, 12, 13, 14, 15, 16).
10. Method according to one of claims 1 to 9, characterized in that each time interval (ti, t2) in which the stirring devices (11, 12, 13, 14, 15, 16) of a group are driven in rotation is followed by a time interval (ts) in which the stirring devices (11, 12, 13, 14, 15, 16) of the group are stationary.
11. Method according to one of claims 1 to 10, characterized in that the substrate is introduced in successive time periods (d), wherein the introduction time (e) or the amount of substrate is predetermined for each time period (d).
12. Method according to one of claims 1 to 11, characterized in that the introduction time (e) is 10% to 60% of the time period (d).
13. The method according to any one of claims 1 to 12, characterized in that the time period (d) is 0.5 h to 2 h, preferably about 1 h.
14. The method according to any one of claims 1 to 13, characterized in that the substrate in the fermentation device (1) is moved exclusively by loading and unloading and via the stirring devices (11, 12, 13, 14, 15, 16) from the at least one introduction opening (4) to the at least one discharge opening (5).
15. The method according to any one of claims 1 to 14, characterized in that each agitator blade (22) has a maximum radial extent (r) relative to the central axis (21) of the agitator device (11, 12, 13, 14, 15, 16), wherein the axial distance (a) of the central axis (21) of at least two agitator devices (11, 12, 13, 14, 15, 16) arranged one after the other in the direction of the longitudinal axis (23) of the container (3) is less than or equal to the sum of the maximum radial extents (r) of the two agitator devices (11, 12, 13, 14, 15, 16).