Method for operating a fermentation device, and fermentation device
Patent Information
- Application Number
- EP2022765440
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2022-08-10
- Publication Date
- 2025-06-18
AI Technical Summary
Fermentation devices face complexity and energy inefficiency due to the need for external recycling and preconditioning of substrates, which can lead to ammonia toxicity and mixing issues, especially in plug flow fermenters, requiring a simpler and more energy-efficient operation method.
Driving at least one stirring device in a direction opposite to its usual rotation allows for internal substrate return and mixing within the container, eliminating the need for external recycling and preconditioning, while adjusting stirring device speed and operation intervals to reduce energy consumption and manage viscosity and dry matter content.
This approach simplifies the fermentation device structure, reduces ammonia toxicity risk, and achieves efficient substrate conversion with lower energy consumption by eliminating external material return and preconditioning, ensuring effective mixing and transport without additional equipment.
Smart Images
Figure 1.1
Abstract
Description
[0001] Method for operating a fermentation device and fermentation device
[0002] The invention relates to a method for operating a fermentation device of the type specified in the preamble of claim 1 and to a fermentation device of the type specified in the preamble of claim 11.
[0003] EP 1 987 129 B1 discloses a fermentation device and a method for operating a fermentation device. The fermentation device comprises an elongated container having an inlet opening on a first end face and at least one outlet opening on a second, opposite end face. Stirring devices are arranged in the container to move and mix the substrate in the container.
[0004] In such fermentation facilities, the substrate's properties must be kept within specified limits to ensure its miscibility and transportability in the vessel. These limits particularly affect the viscosity of the digestate, which is often defined by the dry matter content. A minimum water content for the digestate can also be specified to enable good biochemical degradation and metabolism of the organic dry matter in the reactor. To ensure these desired substrate properties, it is common practice in the state of the art to externally recirculate liquid phases from the digestate dewatering and mix them with the substrate freshly fed into the vessel. Alternatively or additionally, the substrate fed into the vessel can be preconditioned.For this purpose, for example, an external forced mixer can be used to mix with previously treated material, or the newly added, fresh substrate can be mixed or added into a larger, external circuit flowing around the tank. This recirculation and / or preconditioning of substrate is technically and energetically complex. High nitrogen contents in the substrate increase the risk of ammonia toxicity, which is relevant for anaerobic degradation, because the recirculated material streams have already been fermented and can therefore contain high levels of dissolved nitrogen or ammonium nitrogen. This is particularly relevant for plug-flow fermenters, in which the organic substrate is continuously degraded along the flow direction in the tank.
[0005] The invention is based on the object of providing a method for operating a fermentation device that enables a simple design of the fermentation device. A further object of the invention is to provide a fermentation device with a simple design.
[0006] This object is achieved with respect to the method by a method having the features of claim 1. With respect to the fermentation device, the object is achieved by a fermentation device having the features of claim 11.
[0007] It has surprisingly been found that external recirculation can be dispensed with if at least one stirring device is driven at least temporarily in a second direction of rotation. The second direction of rotation is a direction of rotation that is opposite to the usual direction of rotation of the stirring device. In the first, usual direction of rotation, the at least one stirrer blade moves on the bottom of the container in the direction from the first end face to the second end face of the container. In particular, sediments in the substrate are moved from the first end face to the second end face of the container, i.e. from the introduction opening in the direction of the discharge opening. Driving at least one stirring device at least temporarily in an opposite second direction of rotation brings about better mixing and partial return transport of substrate within the container.The external recirculation known in the prior art is therefore replaced according to the invention by a partial recirculation within the tank, which can be achieved simply by driving at least one stirring device in the opposite direction of rotation. It has been shown that the at least temporarily opposite drive of the at least one stirring device has no negative impact on the other tasks of the stirring device, such as mixing, destruction of floating cover, sediment transport, and substrate transport in the tank. Only fresh substrate that has not yet been treated in the fermentation device is fed in via the at least one introduction opening. Accordingly, there is no recirculation of already treated material or parts of the already treated material, for example liquid phases from the digestate dewatering.There is also no preconditioning of the substrate fed into the tank. The appropriate adjustment of the viscosity or dry matter content of the fermentation material in the tank, as well as the minimum water content, is achieved solely by appropriately adjusting the stirring devices, which are driven at least temporarily in the second direction of rotation. The dry matter content of the substrate fed into the tank is advantageously less than 45 wt.%, in particular 30 wt.% to 45 wt.%. The fermentation device is advantageously a fermentation device for continuous dry fermentation.
[0008] It has been shown that high viscosities and possible mixing problems can occur, particularly in the feed area of the vessel, i.e., near the feed opening. To avoid this, at least the stirring device adjacent to the feed opening is driven in the first direction of rotation during substrate introduction. Substrate introduced into the vessel can therefore be transported quickly and mixed with partially converted substrate already present in the vessel. By omitting external recirculation of treated material, which may contain high levels of dissolved nitrogen or ammonium nitrogen, excessive loading at the first end of the plug-flow fermenter, in the feed area of the fermentation device, is specifically counteracted. This significantly reduces the risk of ammonia toxicity associated with higher loads.In order to support the removal of treated material, it is provided that during the removal of treated material at least the stirring device adjoining the at least one discharge opening is driven in the first direction of rotation.
[0009] For energy-efficient operation of the fermentation facility, it is advantageous to shut down all agitators at least temporarily. It has been shown that good substrate conversion can be achieved even if all agitators are temporarily shut down. Preferably, each time interval in which a stirring device is rotating is followed by a time interval in which this stirring device is shut down. This can also significantly reduce the energy consumption of the fermentation facility.
[0010] The rotational speed of the stirring devices is advantageously set as a function of a predetermined nominal speed via a frequency converter. This makes it easy to set an advantageous speed adapted to the substrate. The rotational speed is set in particular in the range from 80% to 100% of the nominal speed, with the nominal speed being in particular 0.5 rpm to 2 rpm. The nominal speed is particularly advantageously about 1 rpm. Preferably, the substrate is not introduced continuously. The substrate is preferably introduced in successive time periods, with the introduction time or the amount of substrate being predetermined in each time period. The introduction time can preferably be about 10% to 60% of the time period d. The time period d can, for example, be 0.5 h to 2 h, preferably 0.75 h to 1.5 h. Preferably, the time period d is about 1 h.
[0011] A simple structure of the fermentation device results when 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. The movement due to loading and unloading as well as by the stirring devices, which simultaneously cause the substrate to be thoroughly mixed, corresponds to the operation of the fermentation device as a plug-flow fermenter. Additional devices for transporting substrate or sediment, for example, additional transport devices at the bottom of the tank, can be omitted, resulting in a simple structure of the fermentation device.
[0012] For a fermentation facility, it is provided that for the return of substrate within the container, at least one stirring device is drivable at least temporarily in a second direction of rotation opposite to the first direction of rotation, and that no device is provided for the return of treated material outside the container. The fact that the return of the substrate takes place within the container and no device is provided for the return of treated material outside the container during normal operation simplifies the structure of the fermentation facility considerably. Normal operation is any operation except for commissioning and troubleshooting. During commissioning or troubleshooting, it can be provided that treated material in the container is returned.A drive of the at least one stirring device in a second direction of rotation opposite to the first direction of rotation can be implemented very easily, so that a fermentation device according to the invention has a simple structure.
[0013] Preferably, no device is provided for preconditioning the supplied substrate or for upstream mixing of fresh substrate with treated material.
[0014] In order to ensure simple transport of the substrate in the fermentation device exclusively by loading and unloading and via the stirring devices, it is advantageously provided that each stirrer blade has a maximum radial extent to the central axis of the stirring device and the center distance of the central axis of at least two stirring devices following one another in the direction of the longitudinal axis of the container is less than or equal to the sum of the maximum radial extents of the two stirring devices. Due to this overlap of the stirring device in the direction of the longitudinal axis, sediment can be piled up between the stirrers by one stirrer blade and removed by the stirrer blade following in the longitudinal direction of the container on the opposite side of the resulting dune and transported to the next dune. This simple transport of sediment at the bottom of the container is possible without additional devices.
[0015] Embodiments of the invention are explained below with reference to the drawings. They show:
[0016] Fig. 1 is a sectional view of a fermentation device,
[0017] Fig. la is a schematic representation of an alternative arrangement of adjacent stirring devices,
[0018] Fig. 2 shows a schematic cross-section through the container of the fermentation device from Fig. 1,
[0019] Fig. 3 and 4 exemplary diagrams for the drive of the stirring devices in the first or second direction of rotation over time.
[0020] 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.
[0021] 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, and 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 the substrate in the container 3 are advantageously not provided.
[0022] 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 perpendicular to the longitudinal axis 23. At least one stirrer blade 22 extends outwards 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 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 center axes 21 of two consecutive stirring devices 11 to 16 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 center axes 21 of the stirrer shafts 20 of the second stirring device 12 and the third stirring device 13. In the exemplary embodiment, all center axes 21 of adjacent stirring devices 11 to 16 have the same axial distance a.
[0023] 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.
[0024] 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.
[0025] An alternative arrangement of two adjacent stirring devices is shown schematically in Fig. 1a for the stirring devices 11 and 12. In this exemplary embodiment, the axial distance a is equal to the sum of the maximum radial extents r of the stirrer blades 22 of adjacent stirring devices 11 to 16. Even with this arrangement, the sediments can still be transported in the manner described above. 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 directed such that the stirrer blades 22 move on the container bottom 6 from the first end face 9 in the direction of the second end face 10.On the container ceiling 7, the agitator 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 agitator 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 agitator device 11 in the first direction of rotation 18, substrate fed in via the feed opening 4 is transported quickly. This prevents overloading of the fermentation device 1 in the feeding area. During normal operation, the substrate is fed directly via the feed opening 4, without any conditioning of the substrate prior to the fermentation device 1 or mixing with already treated material.
[0026] The fermentation device 1 shown in Fig. 1 has no external recirculation. Treated material that was discharged from the container 3 via the discharge opening 5 is therefore not returned to the inlet opening or to a preconditioning device or a forced mixer to be mixed with the fresh substrate, but is completely discharged. 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. The direction of rotation 19 is shown in Fig. 1 for the second stirring device 12.
[0027] 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.
[0028] 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.
[0029] 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 introduction opening 4. In the first time interval t1, treated material can be withdrawn from the discharge opening 5 via the discharge 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 stirring devices of one group are driven, the stirring devices of the other group are advantageously stationary. Overall, this results in a comparatively short operating time for each stirring device 11 to 16, which can significantly reduce the energy requirement of the fermentation device 1. The first time interval t1, during which the stirring devices 12, 14, and 16 are driven in the first direction of rotation 18, is preferably greater than or equal to the second time interval t2, during which the stirring devices 12, 14, and 16 are driven in the opposite direction of rotation 19. As Fig. 1 shows, successive stirring devices are assigned to different groups.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] 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.
[0040] 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% by weight, in particular 30% by weight to 45% by weight. 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.
[0041] The substrate fed to the fermentation device 1 advantageously has a dry matter content of at least 20 wt.%.
[0042] 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, landscape management, 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 rotationally driven stirring devices (11, 12, 13, 14, 15, 16), wherein at least one stirring device (11, 12, 13, 14, 15, 16) is driven at least temporarily in a first direction of rotation (18), in which the at least one stirrer blade (22) on the bottom of the container (3) moves in the direction from the first end face (9) to the second end face (10) of the container (3), and wherein at least one stirring device (11, 12, 13, 14, 15, 16) is driven at least temporarily in a second direction of rotation (19) opposite to the first direction of rotation (18), Discharging treated material via the at least one discharge opening (5), and Extraction of biogas via at least one outlet opening (8), characterized in that, during normal operation, only fresh substrate which has not yet been treated in the fermentation device (1) is fed in via the at least one introduction opening (4).
2. Method according to claim 1, 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).
3. Method according to claim 1 or 2, 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).
4. Method according to one of claims 1 to 3, characterized in that at least temporarily all stirring devices (11, 12, 13, 14, 15, 16) of the fermentation device (1) are at a standstill.
5. Method according to one of claims 1 to 4, characterized in that each time interval (ti, t2) in which a stirring device (11, 12, 13, 14, 15, 16) is driven in rotation is followed by a time interval (ts) in which this stirring device (11, 12, 13, 14, 15, 16) is at a standstill.
6. Method according to one of claims 1 to 5, characterized in that the rotational speed of the stirring devices (11, 12, 13, 14, 15, 16) is adjusted via a frequency converter as a function of a predetermined nominal speed, in particular in the range from 80% to 100% of the nominal speed, the nominal speed being in particular 0.5 rpm to 2 rpm, in particular approximately 1 rpm.
7. Method according to one of claims 1 to 6, 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).
8. Method according to one of claims 1 to 7, characterized in that the introduction time (e) is 10% to 60% of the time period (d).
9. Method according to one of claims 1 to 8, characterized in that the time period (d) is 0.5 h to 2 h, preferably about 1 h.
10. The method according to any one of claims 1 to 9, 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).
11. Fermentation device with 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) for introducing substrate containing organic material, at least one discharge opening (5) on a second, opposite end face (10) of the container (3) for removing treated material and at least one discharge opening (8) for removing 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 is arranged around 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 outwardly projecting stirrer blade (22) fixed to the stirrer shaft (20), wherein at least one stirring device (11, 12, 13, 14, 15, 16) can be driven in rotation in a first direction of rotation (18), in which the at least one stirrer blade (22) moves 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), characterized in that for the return of substrate within the container (3) at least one stirring device (11, 12, 13, 14, 15, 16) can be driven at least temporarily in a second direction of rotation (19) opposite to the first direction of rotation (18) and that no device for the return of treated material outside the container (3) is intended for normal operation.
12. Fermentation device according to claim 11, characterized in that no device is provided for preconditioning the supplied substrate or for upstream mixing of fresh substrate with treated material.
13. Fermentation device according to claim 11 or 12, characterized in that each stirrer blade (22) has a maximum radial extent (r) to the central axis (21) of the stirring device (11, 12, 13, 14, 15, 16), wherein the axial distance (a) of the central axis (21) of at least two stirring devices (11, 12, 13, 14, 15, 16) following one another 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 stirring devices (11, 12, 13, 14, 15, 16).