Method for operating fermentation plant and fermentation plant

Abstract

The invention relates to a fermentation device (1) having an elongated container (3), the container (3) having at least one inlet opening (4) on a first end face (9) of the container (3), at least one outlet opening (5) on an opposite second end face (10) of the container (3), and at least one outlet opening (8) for biogas, having a plurality of stirring devices (11, 12, 13, 14, 15, 16) and at least one outlet opening (7) for the stirring devices (11, 12, 13, 14, 15, 16), 16), and a drive device (17) for a motor vehicle. Each stirring device (11, 12, 13, 14, 15, 16) has at least one stirrer shaft (20) arranged transversely to the longitudinal axis (23) of the container (3), which stirrer shaft can be driven in rotation about a central axis (21) of the stirrer shaft (20) by a drive device (17), and at least one outwardly projecting stirrer blade (22) fixed on the stirrer shaft (20). The invention relates to a method for operating a fermentation plant (1), comprising the following steps: introducing a substrate containing organic material through at least one introduction opening (4), moving and mixing the substrate in a container (3) by means of a rotationally driven stirring device (11, 12, 13, 14, 15, 16), discharging the treated material through at least one discharge opening (5), and removing biogas through at least one discharge opening (8). Only fresh substrate, which has not been treated in the fermentation plant (1), is supplied through the at least one introduction opening (4).

Description

Technical Field

[0001] The invention relates to a method for operating a fermentation plant of the type specified in the preamble of claim 1 and to a fermentation plant of the type specified in the preamble of claim 11 . Background Art

[0002] A fermentation device and a method for operating a fermentation device are known from EP 1 987 129 B1. The fermentation device comprises an elongated container having an inlet opening at a first end side and at least one outlet opening at an opposite second end side. A stirring device is arranged in the container, which moves and mixes the substrate in the container.

[0003] In such fermentation equipment, the property of substrate should be kept within preset limits, for the miscibility and conveying capacity of substrate in container. These limits are particularly related to the viscosity of fermentation, which is usually limited via dry matter content. It is also possible to preset the minimum water content for fermentation, so as to achieve good biochemical degradation and metabolism of organic dry matter in reactor. In order to ensure these desired characteristics of substrate, it is common in the prior art that the liquid phase from the fermentation dehydration is recirculated outside and mixed with the substrate freshly supplied to the container. Alternatively or additionally, the substrate supplied to the container can be pre-treated. For this reason, for example, an external forced mixer can be used to mix with the material that has been treated, or the fresh substrate of the new supply can be mixed or added to the larger external circulation flow around the container. The recycling and / or pre-treatment of this substrate are very complicated in technology and energy. In the case of high nitrogen content of substrate, the risk of ammonia toxicity related to anaerobic degradation will increase, because the recycled material flow has been fermented, and therefore may contain high content of dissolved nitrogen or ammonium nitrogen. This is particularly important for so-called plug flow fermenters, in which continuous degradation of organic substrates is carried out along the flow direction in the container. Summary of the invention

[0004] The invention is based on the object of specifying a method for operating a fermentation plant which allows a simple design of the fermentation plant. A further object of the invention is to specify a fermentation plant of simple design.

[0005] With regard to the method, this object is achieved by a method having the features of claim 1. With regard to the fermentation plant, this object is achieved by a fermentation plant having the features of claim 11 .

[0006] Surprisingly, it has been shown that if at least one stirring device is driven at least temporarily along the second direction of rotation, external recirculation can be omitted. The second direction of rotation is a direction of rotation opposite to the usual direction of rotation of the stirring device. In the usual first direction of rotation, at least one agitator blade moves at the bottom of the container along the direction from the first end side of the container to the second end side. Here, in particular, the sediment in the substrate also moves from the first end side of the container to the second end side, that is, from the introduction opening along the direction toward the discharge opening. The at least temporary driving of at least one stirring device along the opposite second direction of rotation promotes better mixing and partial return conveying of the substrate in the container. Therefore, according to the present invention, the external recirculation known in the prior art is replaced by the partial recirculation in the container, which can be realized simply by driving at least one stirring device along the opposite direction of rotation. It has been shown that the at least temporary opposite driving of at least one stirring device will not have a negative impact on other tasks of the stirring device (such as mixing, floating layer destruction and sediment conveying and substrate conveying in the container). Only the fresh substrate that has not yet been processed in the fermentation device is supplied through at least one introduction opening. Therefore, the recirculation of the treated material or the part of the treated material, such as the liquid phase from the fermentation product dehydration, will not be carried out. No pretreatment of the substrate supplied to the container is performed. Suitable adjustment of the viscosity or dry matter content and the minimum water content of the fermentation product in the container can be achieved only by suitable adjustment of the stirring device driven at least temporarily in the second rotation direction. Advantageously, the dry matter content of the substrate supplied to the container is less than 45% by weight, in particular 30% to 45% by weight. The fermentation device is advantageously a fermentation device for continuous dry fermentation.

[0007] It has been shown that, especially in the loading area of ​​the container, i.e. near the introduction opening, high viscosity and possibly mixing problems may occur. In order to avoid this situation, it is arranged to drive the stirring device connected to the introduction opening at least along the first rotation direction during the introduction of the substrate. Therefore, the substrate introduced into the container can be quickly further transported and mixed with the partially converted substrate already present in the container. By omitting the external recycling of the treated material with a high portion of dissolved nitrogen or ammonium nitrogen, the high load at the first end side of the plug flow fermenter in the loading area of ​​the fermentation device is specifically offset. The risk of ammonia toxicity associated with a higher load can be significantly reduced thus.

[0008] In order to support the removal of the processed material, it is provided that during the removal of the processed material at least a stirring device coupled to the at least one discharge opening is driven in a first rotational direction.

[0009] For energy-saving operation of the fermentation plant, advantageously all stirring devices of the fermentation plant remain stationary at least temporarily. It has been shown that, despite the temporary stationary state of all stirring devices, a good substrate conversion can still be achieved. Preferably, each time interval in which the stirring device is driven in rotation is followed by a time interval in which the stirring device remains stationary. This also significantly reduces the energy consumption of the fermentation plant.

[0010] The rotation speed of the stirring device is advantageously adjusted by a frequency converter according to a preset rated speed. Thus, the adjustment of the advantageous rotation speed matching the substrate can be realized in a simple manner. The rotation speed is particularly set in the range of 80% to 100% of the rated speed, wherein the rated speed is particularly 0.5 U / Min to 2 U / Min. Particularly advantageously, the rated speed is about 1 U / Min. Preferably, the substrate is introduced discontinuously. Preferably, the substrate is introduced in successive time periods, wherein the duration or substrate mass introduced in each time period is preset. The duration of introduction can preferably be about 10% to 60% of the time period d. The time period d can be, for example, 0.5 hours to 2 hours, preferably 0.75 hours to 1.5 hours. Preferably, the time period d is about 1 hour.

[0011] If the substrate in the fermentation device is moved only by loading and unloading and via a stirring device from the at least one inlet opening to the at least one outlet opening, a simple structure of the fermentation device results. The movements caused by the loading and unloading and by the stirring device, which also simultaneously causes mixing of the substrate, correspond to the operation of the fermentation device as a plug flow fermenter. Additional devices for conveying the substrate or sediment, for example additional conveying devices at the bottom of the container, can be omitted, resulting in a simple structure of the fermentation device.

[0012] The fermentation plant is provided so that, for the recirculation of the substrate in the container, at least one stirring device can be driven at least temporarily in a second direction of rotation opposite to the first direction of rotation, and no device for recirculation of the treated material outside the container is provided. By recirculating the substrate in the container and not providing a device for recirculating the treated material outside the container for normal operation, the structure of the fermentation plant is significantly simplified. Normal operation is any operation except for commissioning and troubleshooting. During commissioning or troubleshooting, it can be provided that the treated material in the container is recirculated. The driving of the at least one stirring device in a second direction of rotation opposite to the first direction of rotation can be achieved very easily, so that the fermentation plant according to the invention has a simple structure.

[0013] Preferably, no devices are provided for pre-treatment of the supplied substrate or for upstream mixing of fresh substrate with treated material.

[0014] In order to ensure in a simple manner that the substrate in the fermentation device is transported only by loading and unloading and by the stirring device, it is advantageously provided that each stirrer blade has a maximum radial extension relative to the central axis of the stirring device and that the axial distance of the central axes of at least two stirring devices that are consecutive in the direction of the longitudinal axis of the container is less than or equal to the sum of the maximum radial extensions of the two stirring devices. Due to this overlap of the stirring devices in the direction of the longitudinal axis, sediment can be deposited between the stirring mechanisms by one stirrer blade and removed by the stirrer blade that follows in the longitudinal direction of the container on the opposite side of the generated dune and transported to the next dune. This makes it possible to achieve sediment transport at the bottom of the container in a simple manner without the need for additional equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The embodiments of the present invention are explained below with reference to the accompanying drawings.

[0016] Figure 1 shows a cross-section through a fermentation apparatus,

[0017] Figure 1a A schematic diagram showing an alternative arrangement of adjacent stirring devices,

[0018] Figure 2 Shown through Figure 1 Schematic cross section of a vessel of a fermentation plant in

[0019] Figure 3 and Figure 4 An exemplary diagram over time of driving a stirring device in a first or second rotational direction is shown. DETAILED DESCRIPTION

[0020] Figure 1 The fermentation device 1 is schematically shown in longitudinal section. The fermentation device comprises a container 3 having a first end side 9 and a second end side 10. The container 3 has a longitudinal axis 23 extending through the first end side 9 and the second end side 10. In the present embodiment, the container 3 is arranged lying down and the longitudinal axis 23 extends horizontally. The container 3 has an introduction opening 4 for the substrate at the first end side 9 and a discharge opening 5 for the treated material at the second end side 10. In the present embodiment, a discharge opening 8 for biogas is provided at the upper container cover 7 of the container 3. A plurality of introduction openings 4, discharge openings 5 ​​and / or discharge openings 8 can also be provided. Preferably, the introduction opening 4 is only provided at the first end side 9, and the discharge opening for the treated material is only provided at the second end side 10. Alternatively, additional introduction openings 4 can be provided between the end sides 9 and 10 in addition. The lower side of the container 3 forms the container bottom 6. Preferably, the container bottom 6 and the container cover 7 are aligned flat and parallel to each other, such as Figure 2 shown.

[0021] The fermentation device 1 is designed as a so-called plug flow fermenter. In such a plug flow fermenter, the substrate is moved horizontally in the container 3. The transport of the substrate is carried out by loading and unloading and via stirring devices 11, 12, 13, 14, 15, 16, the design of which is explained in more detail below with reference to the first stirring device 11. The further stirring devices 12 to 16 can be designed accordingly. Advantageously, no further device for moving the substrate in the container 3 is provided.

[0022] The first stirring device 11 comprises an agitator 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 agitator blade 22 extends outward from the agitator shaft 20. In the present embodiment, at least two agitator blades 22 extending on opposite sides of the agitator shaft 20 are provided. The agitator blades 22 have a maximum radial extension r relative to the central axis 21 of the relevant stirring device. In this embodiment, the maximum radial extension r is the same for all agitator blades 22 of all stirring devices 11 to 16. However, different maximum radial extensions r may also be advantageous for the agitator blades 22 of the stirring devices 11 to 16 or for the agitator blades 22 of different stirring devices 11 to 16. The central 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. In Figure 1 , the axial distance a between the central axes 21 of the agitator shafts 20 of the second agitating device 12 and the third agitating device 13 is exemplarily shown. In the present embodiment, all central axes 21 of adjacent agitating devices 11 to 16 have the same axial distance a.

[0023] In the present embodiment, the axial distance a is smaller than the sum of the maximum radial extensions r of the agitator blades 22 of the adjacent agitators 11 to 16. Since the axial distance a is smaller than the sum of the maximum radial extensions r of the respectively adjacent agitator blades 11 to 16, the adjacent agitator blades 11 to 16 form an overlapping region 24, which is Figure 1 2 is shown for the second stirring device 12 and the third stirring device 13. The overlapping region 24 is swept over by the stirring blades 22 of the stirring device 12 as well as by the stirring blades 22 of the stirring device 13.

[0024] During operation, a sediment pile 25 in the shape of a sand dune is accumulated at the bottom 6 of the container below the overlap region 24. The sediment is deposited at the sediment pile 25 by the second stirring device 12. On the side of the sediment pile 25 close to the end side 10, the sediment is taken away by the subsequent third stirring device 13 and transported away in the direction of the discharge opening 5. Preferably, corresponding overlap regions 24 are provided between all adjacent stirring devices 11 to 16. Due to the overlap of adjacent stirring devices 11 to 16, additional equipment for transporting sediment can be advantageously omitted.

[0025] Figure 1a Schematically shows an alternative arrangement of two adjacent stirring devices for 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 stirrer blades 22 of the adjacent stirring devices 11 to 16. Even in this arrangement, the conveying of sediment can still be carried out in the above-mentioned manner.

[0026] During operation of the fermentation device 1, a substrate containing organic matter is supplied into the container 3 through the introduction opening 4. During the introduction of the substrate, the first stirring device 11 connected to the first end side 9 rotates in a first rotation direction 18. The rotation direction 18 is directed so that the stirrer blade 22 moves from the first end side 9 in the direction toward the second end side 10 at the container bottom 6. At the container cover 7, the stirrer blade 22 moves in the opposite direction, that is, from the second end side 10 in the direction toward the first end side 9. In this embodiment, the central axis 21 of the stirrer shaft 20 is aligned horizontally and perpendicular to the longitudinal axis 23. All central axes 21 extend parallel to each other. By driving the first stirring device 11 in the first rotation direction 18, the substrate supplied via the introduction opening 4 is further quickly conveyed. This avoids overloading of the fermentation device 1 in the loading area. Here, in normal operation, the substrate is directly supplied through the introduction opening 4 without conditioning the substrate before the fermentation device 1 or mixing with the already processed material.

[0027] Figure 1 The fermentation device 1 shown in FIG. 1 has no external recirculation. Therefore, the treated material that has been discharged from the container 3 through the discharge opening 5 is not recirculated again to the inlet opening or the pretreatment device or the forced mixer in order to be mixed with fresh substrate, but is completely discharged. The recirculation of the treated substrate takes place in the container 3 itself. In order to achieve this recirculation, it is provided that at least one of the stirring devices 11 to 16 is temporarily driven in a second rotation direction 19 opposite to the first rotation direction. Figure 1 2 shows the direction of rotation 19 for the second stirring device 12 .

[0028] The driving of the stirring devices 11 to 16 in the first rotational direction 18 and in the second rotational direction 19 will be described in more detail below. The sixth stirring device 16 adjacent to the discharge opening 5 and the second end side 10 is preferably driven in the first rotational direction 18 during the removal of the processed material from the container 3, so that the stirrer blades 22 are moved adjacent to the container bottom 6 in the direction of the second end side 10 and thus promote the transport of sediment at the container bottom 6 to the discharge opening 5.

[0029] Figure 2 A cross section through the first stirring device 11 is schematically shown. The other stirring devices 12 to 16 are preferably constructed identically. In this embodiment, a drive device 17 is provided for each stirring device 11 to 16, for example a drive motor with or without a transmission unit. It can also be provided that the drive device 17 drives a plurality of the stirring devices 11 to 16 or drives all the stirring devices 11 to 16 through an appropriate transmission device (e.g., a belt drive, etc.). The fermentation device 1 includes a control device 27, which appropriately controls at least one drive device 17. It is provided here that none of the drive devices 17 runs continuously, but the drive device 17 only runs temporarily. Thus, the energy demand of the fermentation device 1 can be reduced in a simple manner. The drive device 17 includes a frequency converter 28, by which the rotational speed of the agitator shaft 20 can be adjusted in a simple manner.

[0030] like Figure 2 As also shown, in this embodiment, four stirrer blades 22 are arranged on a common stirrer shaft 20. The stirrer blades 22 are each formed by two outwardly projecting arms 29, which carry horizontally extending stirring rods 26 at their radially outer ends. The stirring rods 26 extend over the entire width b of each stirrer blade 22. Another design of the stirrer blades 22 may also be advantageous.

[0031] like Figure 2 As shown, the oppositely disposed agitator blades 22 are arranged offset relative to each other in the direction of the central axis 21. Therefore, each agitator blade 22 moves around the central axis 21 in its own disk-shaped area. Figure 2 In the cross-sectional view shown in , the stirrer blades 22 of the stirring devices 11 to 16 do not overlap. The stirrer blades 22 that follow 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. Preferably, each group of stirring devices 11 to 16 comprises at least one, preferably at least two, stirring devices 11 to 16. Figure 3 and Figure 4Two possible types of actuation of the stirring devices 11 to 16 are shown by way of example, wherein the stirring devices are divided into two groups. In the present embodiment, the first group includes the stirring devices 12 , 14 and 16 , and the second group includes the stirring devices 11 , 13 and 15 .

[0033] In the first time interval t1, Figure 3 In the driving sequence of the stirring device 11 to 16 shown in the figure, stirring device 12,14 and 16 are driven along the first rotation direction 18. In the second time interval t2 later, the stirring device 12,14 and 16 forming the first group are driven along the opposite second rotation direction 19. There is a third time interval t3 between the first time interval t1 and the second time interval t2, and the stirring device 12,14 and 16 of the first group remain stationary in the third time interval. The stirring device 11,13 and 15 of the second group remain stationary during the first time interval t1, the second time interval t2 and the third time interval t3. The second time interval t2 is followed by another third time interval t3, and all stirring devices 11 to 16 of the two groups remain stationary again in this other third time interval. In the fourth time interval t4 following this other third time interval, the stirring device 11,13 and 15 of the first group are driven along the first rotation direction 18. In this fourth time interval t4, substrate can be supplied to the container 1 by introducing the opening 4. In the first time interval t1, the processed material can be discharged from the discharge opening 5 by the discharge opening 5. The fourth time interval t4 is again followed by the third time interval t3, during which all stirring devices 11 to 16 remain stationary. In a fifth time interval t5 following the third time interval, the stirring devices 11, 13 and 15 of the second group are driven in the second direction of rotation 19.

[0034] In an alternative process sequence, the supply of the substrate and the discharge of the processed material are independent of which group of the stirring devices 11 to 16 is driven or remains stationary. For example, the supply of the substrate can be carried out in each time interval t1, t2, t4, t5 within a certain period of time. Advantageously, during the supply of the substrate, the first stirring device 11 is driven in the first rotation direction 18 independently of the other stirring devices 13 and 15 in the group. Correspondingly, during the discharge of the processed material, the sixth stirring device 16 is advantageously driven in the first rotation direction 18 independently of the other stirring devices 12 and 14 in the group.

[0035] Figure 4An alternative drive of the stirring devices 11 to 16 is shown. First, the stirring devices 12, 14 and 16 of the first group are driven in the first rotation direction 18, more precisely in the first time interval t1. The first time interval t1 is followed by a third time interval t3, in which all stirring devices 11 to 16 remain stationary. In a fourth time interval t4 following the third time interval t3, the stirring devices 11, 13 and 15 of the second group are driven in the first rotation direction 18. The fourth time interval t4 is again followed by the third time interval t3, in which none of the stirring devices 11 to 16 is driven. Following this, in the second time interval t2, the stirring devices 12, 14 and 16 of the first group are driven in the second rotation direction 19. After the third time interval t3 following the second time interval t2, the stirring devices 11, 13 and 15 of the second group are driven in the second rotation direction 19 in a fifth time interval t5, in which all stirring devices 11 to 16 remain stationary. When one group of stirring devices is driven, the other group of stirring devices advantageously remains stationary. Overall, this results in a relatively short operating time for each stirring device 11 to 16 , as a result of which the energy requirement of the fermentation device 1 can be significantly reduced.

[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. Figure 1 As shown, successive stirring devices are assigned to different groups.

[0037] The time intervals t1, t2, t4 and t5 during which one group of stirring devices is driven advantageously correspond to an integer multiple of a half revolution of the stirring devices 11 to 16. The integer multiple is advantageously 2 to 10. The third time interval t3 during which the two groups of stirring devices 11 to 16 remain stationary preferably also corresponds to a half revolution of the stirring devices 11 to 16 or an integer multiple of a half revolution. Here, the integer multiple is advantageously 2 to 6. The rotation speed of the stirring devices 11 to 16 can advantageously be adjusted according to the substrate used. Figure 2 The frequency converter 27 shown in is used for this. The speed is advantageously set in the range of 80% to 100% of the rated speed. The rated speed is preferably 0.5 U / min to 2 U / min, particularly preferably about 1 U / min. Therefore, the stirrer blade 22 moves relatively slowly through the substrate in the container 3.

[0038] By introducing the opening 4 ( Figure 1 ) The supply of the substrate is advantageously carried out almost continuously in successive time periods d. Advantageously, the supply is carried out once in each time period d. Advantageously, it is provided that the amount of substrate introduced is of duration e or of each time period d. Figure 3In, the time period d is shown by way of example, and this time period includes the driving of each stirring device 11 to 16 just once in each rotation direction. The introduction of substrate occurs in the introduction duration e, which is 10% to 60% of the time period d. In this embodiment, the introduction duration e corresponds to the 4th time interval t4, wherein the first stirring device 11 is driven along the first rotation direction 18. The time period d is advantageously 0.5 hours to 2 hours, especially 0.75 hours to 1.5 hours, preferably about 1 hour. The stirring devices 11 to 16 move the substrate in the container 3 and mix the substrate. The different selections of the time period d and the introduction duration e may also be advantageous. Preferably, the time period d is significantly longer than the time interval t1 to t5. The time interval t1, t2, t4 and t5 that a group of stirring devices are driven are advantageously integer multiples of half a turn of the stirring devices 11 to 16. Here, the integer multiple is preferably 2 to 10. The time interval t1 to t5 that a group of stirring devices remain stationary is advantageously integer multiples of half a turn of the stirring devices 11 to 16. In this case, the integer multiple is preferably 2 to 10. The rotation speed of the stirring devices 11 to 16 is advantageously 80% to 100% of the rated speed. The rated speed is advantageously 0.5 to 2 U / Min, preferably 1 U / Min. Advantageously, the time period d is significantly longer than the time interval t1 to t5.

[0039] It can be provided that the time intervals t1 to t5 are of the same size. Time intervals t1 to t5 of different sizes may also be advantageous. Advantageously, the time intervals t4 and t5 during which a group of stirring devices is driven in the second rotation direction 19 are not greater than the time intervals t1 and t2 during which a group of stirring devices is driven in the first rotation direction 18.

[0040] By appropriately selecting the time interval t1 to t5 and appropriately dividing the stirring devices 11 to 16 into groups of at least one, preferably two to six stirring devices, and due to the at least temporary drive of at least one stirring device 11 to 16 in the second rotation direction 19, the substrate can be recycled in the container 3. In normal operation, external recycling and pretreatment of the treated material are not required. Thus, a fermentation device 1 with a simple structure and low energy demand in operation can be realized. The stirring devices 11 to 16 promote the vertical stirring of the substrate, the destruction and distribution of the floating layer, and the conveying of the sediment of the substrate. The supply of the substrate to the container 4 is almost continuous. The stirring devices 11 to 16 are in intermittent operation and are only controlled for the driving of the stirring devices 11 to 16 according to the program stored in the control device 27. The stirring devices 11 to 16 are advantageously only operated for a short time respectively. Here, during the introduction of the substrate and the removal of the treated material, the first stirring device 11 and the last stirring device 16 can be driven additionally and independently of the other stirring devices in the corresponding group, and therefore have a longer operating time than other stirring devices.

[0041] By at least temporarily moving at least one stirring device along the second rotation direction 19, the substrate can be recirculated in the container 3 and mixed with the supply material in the container 3. The setting of the desired dry substrate content, especially in the first stirring device 11, and the desired dilution for reducing the viscosity can be adjusted thereby. Advantageously, the dry substrate content of the substrate supplied to the container 2 is less than 45% by weight, in particular 30% 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 along the second rotation direction 19 enables the plug flow characteristics in the container 3 to be maintained and the substrate to be mixed and degassed vertically. The sediment transport at the container bottom 6 and the destruction of the floating layer in the container 3 remain ensured.

[0042] The substrate supplied to the fermentation device 1 advantageously has a dry substrate content of at least 20% by weight.

[0043] The substrate supplied to the fermentation device 1 includes in particular various domestic or commercial organic wastes, such as separately collected biowaste, organic-rich fractions from mixed domestic waste, green waste or separately collected food waste from households or restaurants. Alternatively or in addition, the substrate supplied to the fermentation device 1 includes wastes with seasonal or continuously changing properties or compositions and / or with a large proportion of pollutants, such as non-fermentable hard or inert materials, such as stone, glass, ceramics, sand or the like. The substrate supplied to the fermentation device 1 also includes in particular high-viscosity, structure-rich or also fibrous substrates from agriculture, landscaping, trade and industry, such as straw, grass, silage or other cellulose-containing material flows, such as from the paper industry, and / or dewatered sewage sludge.

Claims

1. A method for operating a fermentation plant, wherein the fermentation plant (1) comprises an elongated container (3), wherein the container (3) has at least one inlet opening (4) at a first end side (9) of the container (3), at least one discharge opening (5) at an opposite second end side (10) of the container (3), and at least one discharge opening (8) for biogas, wherein the fermentation plant (1) has a plurality of stirring devices (11, 12, 13, 14, 15, 16) and a plurality of stirring devices (11, 12, 13, 14, 15, 16) for the stirring devices (11, 12, 13, 14, 15, 16) 5, 16), wherein each stirring device (11, 12, 13, 14, 15, 16) has at least one stirring shaft (20) arranged transversely to the longitudinal axis (23) of the container (3), the stirring shaft being rotatable about a central axis (21) of the stirring shaft (20) by the driving device (17), wherein the stirring device (11, 12, 13, 14, 15, 16) has at least one stirring blade (22) fixed to the stirring shaft (20) and projecting outwards, wherein the method comprises the following steps: - introducing a matrix comprising an organic material through the at least one introduction opening (4), - moving and mixing the substrate in the container (3) by means of a rotationally driven stirring device (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), wherein the at least one stirring blade (22) is moved at the bottom of the container (3) in a direction from the first end side (9) to the second end side (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 the treated material through the at least one discharge opening (5), and - removing biogas through the at least one discharge opening (8), It is characterized in that during normal operation only fresh substrate which has not yet been processed in the fermentation plant (1) is supplied via the at least one inlet opening (4).

2. The method according to claim 1, It is characterized in that During the introduction of the substrate, at least the stirring device (11) coupled to the introduction opening (4) is driven in the first rotational direction (18).

3. The method according to claim 1 or 2, It is characterized in that During the removal of the processed material, at least the stirring device (16) coupled to the at least one discharge opening (5) is driven in a first rotational direction (18).

4. The method according to any one of claims 1 to 3, It is characterized in that At least temporarily, all stirring devices (11, 12, 13, 14, 15, 16) of the fermentation device (1) remain stationary.

5. The method according to any one of claims 1 to 4, It is characterized in that Each time interval (t1, t2) during which the stirring device (11, 12, 13, 14, 15, 16) is driven in rotation is followed by a time interval (t3) during which the stirring device (11, 12, 13, 14, 15, 16) remains stationary.

6. The method according to any one of claims 1 to 5, It is characterized in that The rotation speed of the stirring device (11, 12, 13, 14, 15, 16) is adjusted by a frequency converter according to a preset rated speed, in particular in the range of 80% to 100% of the rated speed, wherein the rated speed is in particular 0.5 U / Min to 2 U / Min, in particular about 1 U / Min.

7. The method according to any one of claims 1 to 6, It is characterized in that The substrate is introduced in successive time periods (d), wherein each time period (d) predetermines the introduction duration (e) or the substrate amount.

8. The method according to any one of claims 1 to 7, It is characterized in that The introduction duration (e) is 10% to 60% of the time period (d).

9. The method according to any one of claims 1 to 8, It is characterized in that The time period (d) is 0.5 hours to 2 hours, preferably about 1 hour.

10. The method according to any one of claims 1 to 9, It is characterized in that The substrate in the fermentation device (1) is moved from the at least one introduction opening (4) to the at least one discharge opening (5) only by loading and unloading and by the stirring device (11, 12, 13, 14, 15, 16).

11. A fermentation device having an elongated container (3), wherein the container (3) has at least one introduction opening (4) for introducing a substrate containing organic material at a first end side (9) of the container (3), at least one discharge opening (5) for discharging treated material at an opposite second end side (10) of the container (3), and at least one discharge opening (8) for removing biogas, wherein the fermentation device (1) has a plurality of 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) comprises at least one stirring shaft (20) arranged transversely to the longitudinal axis (23) of the container (3), the stirring shaft (20) being rotatable about a central axis (21) of the stirring shaft (20) by a drive device (17), wherein the stirring device (11, 12, 13, 14, 15, 16) comprises at least one stirring blade (22) fixed to the stirring shaft (20) and projecting outwards, wherein at least one stirring device (11, 12, 13, 14, 15, 16) is rotatable in a first direction of rotation (18), wherein at least one stirring blade (22) is movable at the bottom of the container (3) in a direction from a first end side (9) to a second end side (10) of the container (3), It is characterized in that, for the recirculation of the matrix 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 for normal operation no device is provided for recirculation of the treated material outside the container (3).

12. The fermentation device according to claim 11, It is characterized in that No equipment is provided for pre-treatment of the supplied substrate or for upstream mixing of fresh substrate with treated material.

13. The method according to claim 11 or 12, It is characterized in that Each stirrer blade (22) has a maximum radial extension (r) relative to a central axis (21) of the stirring device (11, 12, 13, 14, 15, 16), wherein an axial distance (a) between the central axis (21) and at least two consecutive stirring devices (11, 12, 13, 14, 15, 16) in the direction of the longitudinal axis (23) of the container (3) is less than or equal to the sum of the maximum radial extensions (r) of the two stirring devices (11, 12, 13, 14, 15, 16).

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