Biogas fermentation system and biogas fermentation method

Abstract

To provide a biogas fermentation system which comprises a fermentation tank and enables air mixed in the fermentation tank to be discharged by simple constitution, and which enables generated biogas to be efficiently recovered.SOLUTION: A biogas fermentation system 1 comprises: a fermentation tank 10 which produces biogas by fermenting charged fermentation raw materials 5; at least one expansion / contraction member 20 which is placed inside the fermentation tank 10 and whose volume changes by expanding and contracting; at least one gas piping 3 connected to the fermentation tank 10; and an introduction portion 21 which is connected to the expansion / contraction member 20 and introduces a filling medium into the expansion / contraction member 20. The expansion / contraction member 20 is expandable by introducing the filling medium through the introduction portion 21. The biogas fermentation system 1 can discharge air and residual biogas from the fermentation tank 10 by expanding expansion / contraction member 20.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a biogas fermentation system and a biogas fermentation method for recovering biogas generated in a fermenter. [Background technology]

[0002] Conventionally, biogas such as methane gas has been recovered by fermenting fermentation raw materials (biomass) introduced into a fermenter. In batch-type fermentation processes, it is necessary to introduce the fermentation raw materials into the fermenter and remove the post-fermentation residue from the fermenter after fermentation. As described above, when removing the fermentation raw materials or the post-fermentation residue from the fermenter, it is necessary to vent the residual biogas (including harmful gases such as hydrogen sulfide) remaining in the fermenter or replace it with a safe gas before the process. Therefore, when discharging used biomass from the fermenter or introducing raw biomass into the fermenter, it is common to perform a purge using carbon dioxide-containing exhaust gas and outside air to remove explosive biogas and the like from the fermenter (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-22271 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the conventional technology described in Patent Document 1 requires detecting the carbon dioxide content in the fermenter while controlling the amount of carbon dioxide introduced into the fermenter, resulting in problems such as a complex configuration and increased costs. Furthermore, in the conventional technology described in Patent Document 1, residual biogas remaining in the fermenter is combusted and discharged as exhaust gas. However, the residual biogas also contains biogas to be recovered (e.g., methane gas), and discharging it as is reduces the yield of recovered biogas. Furthermore, in the batch-type fermentation process described above, the fermenter must be opened and closed when removing used biomass from the fermenter or adding new biomass to the fermenter, and the air in the fermenter must be vented after the biomass is added to the fermenter. However, in the conventional technology described in Patent Document 1, carbon dioxide-containing exhaust gas is introduced after the biomass is added to the fermenter, which raises concerns that oxygen-containing air may be introduced into the fermenter.

[0005] Therefore, an object of the present invention is to provide a biogas fermentation system that has a simple configuration, can discharge air that has become mixed inside the fermenter, and can efficiently recover the generated biogas. [Means for solving the problem]

[0006] (1) The biogas fermentation system of the present invention, which is provided to solve the above-mentioned problems, comprises a fermentation tank that produces biogas by fermenting input fermentation raw materials, at least one expansion / contraction member that is placed inside the fermentation tank and whose volume changes by expanding and contracting, at least one gas pipe connected to the fermentation tank, and an introduction part that is connected to the expansion / contraction member and introduces a filling medium into the expansion / contraction member, and the expansion / contraction member can be expanded by introducing the filling medium through the introduction part.

[0007] The biogas fermentation system of the present invention can expand the expansion member within the fermenter by introducing a filling medium into the expansion member through the introduction section. This allows the volume of the fermenter to be reduced, allowing biogas (e.g., methane gas containing hydrogen sulfide) and air in the fermenter to be discharged to the outside of the fermenter through the gas piping. Therefore, the biogas fermentation system of the present invention has a simple configuration, allowing air mixed in the fermenter to be discharged and the generated biogas (e.g., methane gas) to be efficiently recovered. The expansion member can be made of various materials that can be expanded by the filling medium, such as elastic rubber, flexible resin, or air- and water-impermeable fiber material. The expansion member can also be made of various expandable and contractible shapes, such as a balloon or bellows-shaped member. The filling medium can be air, water, or digestive fluid used in fermentation. These filling media can be pumped into the expansion member using a pump or other device.

[0008] (2) In the biogas fermentation system of the present invention described above, the gas pipe comprises a first pipe communicating with the fermenter to discharge air from the fermenter, a second pipe communicating with the fermenter to discharge biogas produced in the fermenter, and a switching unit that switches to one state selected from a plurality of states, including a first communication state in which the first pipe is connected to the fermenter and the second pipe is not connected, and a second communication state in which the second pipe is connected to the fermenter and the first pipe is not connected, and the switching unit is configured to switch to one state selected from a plurality of states after the fermentation raw material is introduced into the fermenter and before fermentation of the fermentation raw material is started. and, prior to the start of fermentation of the fermentation raw material, switches the state to the first communication state, and switches the state to the second communication state, and the expansion / contraction member is freely expandable and contractible according to at least each of a first expansion state in which it expands in the first communication state to discharge air from within the fermentation tank, a natural contraction state in which the introduction of the filling medium is stopped in the second communication state, and a second expansion state in which it expands in the second communication state when fermentation of the fermentation raw material is completed to discharge the biogas remaining in the fermentation tank.

[0009] In the biogas fermentation system of the present invention, the gas pipe includes a first pipe, a second pipe, and a switching unit, and the switching unit can switch to one state selected from a plurality of states, including a first communication state in which the first pipe is connected to the fermenter and the second pipe is not connected, and a second communication state in which the second pipe is connected to the fermenter and the first pipe is not connected. Therefore, the biogas fermentation system of the present invention can selectively distribute and discharge the biogas (also referred to as residual biogas) and air remaining in the fermenter to the first pipe and the second pipe. Here, the first pipe and the second pipe can be in various forms that allow for switching their communication states, such as being provided independently of each other or being formed by branching the gas pipe midway to form the first pipe and the second pipe. Furthermore, the switching unit can be implemented by various valves, etc., and the first pipe can be Depending on the type of the second pipe, a single pipe or multiple pipes may be used.

[0010] Furthermore, the biogas fermentation system of the present invention can be switched to the first communication state after the fermentation raw material is charged into the fermenter but before fermentation of the fermentation raw material begins, and the expandable member can be expanded in the first communication state to switch to the first expanded state in which air is discharged from the fermenter. This allows the biogas fermentation system of the present invention to discharge air that has entered the fermenter when the fermentation raw material is charged into the fermenter by expanding the expandable member, thereby allowing the subsequent anaerobic fermentation to proceed smoothly.

[0011] Furthermore, the biogas fermentation system of the present invention can be switched to the second communication state before the fermentation of the fermentation raw material begins, thereby preventing discharged air from backflowing into the fermenter. This allows the biogas fermentation system of the present invention to efficiently perform anaerobic fermentation of the fermentation raw material. Furthermore, the biogas fermentation system of the present invention can expand or contract the expansion member depending on whether it is in a natural contraction state in which the introduction of the packing medium is stopped in the second communication state or a second expansion state in which it expands when the fermentation of the fermentation raw material ends and discharges biogas remaining in the fermenter. This allows for smooth fermentation processing without the need to attach or detach the expansion member. Furthermore, the biogas fermentation system of the present invention can discharge residual biogas from the fermenter by expanding the expansion member when the fermentation of the fermentation raw material ends. Therefore, even if the residual biogas contains harmful gases such as hydrogen sulfide, workers can be prevented from being exposed to harmful gases when removing the residual fermentation raw material.

[0012] (3) The biogas fermentation system of the present invention described above may be characterized in that the expansion / contraction member is gradually expanded from the side away from the gas pipe toward the side approaching the gas pipe.

[0013] By configuring the biogas fermentation system of the present invention as described above in (3), the biogas or air in the fermenter can be sequentially pushed toward the gas piping from the side of the fermenter that is farther away from the gas piping. This allows the biogas fermentation system of the present invention to smoothly discharge the biogas (also referred to as residual biogas) or air remaining in the fermenter, thereby reducing the amount of residual biogas or air remaining in the fermenter.

[0014] Here, the expansion / contraction member may be formed of, for example, a plurality of expansion / contraction members, which may be arranged in sequence from the side farther from the gas pipe toward the side closer to the gas pipe, and configured so that the plurality of expansion / contraction members are expanded in sequence from the side farther from the gas pipe toward the side closer to the gas pipe.

[0015] In addition to the above, the expandable / contractable member may have, for example, a plurality of compartments therein. In such a case, the plurality of compartments may be arranged in sequence from the side farther away from the gas pipe toward the side closer to the gas pipe, and may be configured to expand in sequence from the side farther away from the gas pipe toward the side closer to the gas pipe.

[0016] (4) The biogas fermentation system of the present invention described above may be characterized in that the expansion / contraction member has at least one protrusion on at least the surface facing the fermentation raw material, and the protrusion can penetrate into the fermentation raw material as the expansion / contraction member expands.

[0017] By configuring the biogas fermentation system of the present invention as described above in (4), the protrusions can penetrate into the fermentation raw material when the expansion member is expanded. This allows the biogas fermentation system of the present invention to form a passage for biogas accumulated inside the highly viscous residue fermentation raw material, allowing the biogas inside the residue fermentation raw material to be smoothly discharged. Therefore, the biogas fermentation system of the present invention can further improve the yield of biogas. Furthermore, the biogas fermentation system of the present invention can discharge air from inside the fermentation raw material when the fermentation raw material is introduced, allowing for smooth anaerobic fermentation.

[0018] (5) In the biogas fermentation system of the present invention described above, the fermenter may be provided with a lid that can be opened and closed freely for adding or discharging fermentation raw materials, and the fermentation may be carried out in a batch manner.

[0019] By configuring the biogas fermentation system of the present invention as described above in (5), it is possible to construct a system suitable for a batch system in which the fermentation raw materials are replaced sequentially.

[0020] (6) In the biogas fermentation system of the present invention described above, the fermenter may be characterized in that, when the fermentation raw material is charged, a buffer space is formed above the fermentation raw material, and the expansion / contraction member is provided on the upper interior side of the fermenter and reduces the volume of the buffer space in the expanded state.

[0021] By configuring the biogas fermentation system of the present invention as described above in (6), the expansion / contraction member is located at the upper part of the interior of the fermenter, facilitating maintenance of the expansion / contraction member and other components. Furthermore, by configuring the biogas fermentation system of the present invention as described above in (6), a buffer space is formed above the fermentation raw material, allowing biogas to be easily discharged.

[0022] (7) The biogas fermentation method of the present invention described above may be a biogas fermentation method using a biogas fermentation system, characterized in that a lid that can be opened and closed freely is provided in the fermenter tank for introducing the fermentation raw material, and the fermentation raw material introducing step of introducing the fermentation raw material into the fermenter tank, a fermenter tank closing step of closing the lid to close the fermenter tank, and an anaerobic condition creating step of introducing the filling medium into the expansion member to expand the expansion member and discharging the air in the fermenter tank through the gas piping.

[0023] By configuring the biogas fermentation method of the present invention as described above in (7), the air in the fermenter can be discharged through the gas piping in the anaerobic condition creation step. This allows the fermenter to be placed in an anaerobic state before the start of fermentation of the fermentation raw material, thereby improving the fermentation efficiency of the fermentation raw material. Furthermore, by configuring the biogas fermentation method of the present invention as described above in (7), the air in the fermenter can be discharged with a simple configuration, which is expected to reduce costs.

[0024] (8) The above-described biogas fermentation method of the present invention may be a biogas fermentation method using a biogas fermentation system, characterized in that the fermenter is provided with a lid that can be opened and closed freely for removing fermentation residue of the fermentation raw material, and after fermentation of the fermentation raw material and before removing the fermentation residue, a residual biogas discharge step is carried out in which the filling medium is introduced into the expansion / contraction member to expand the expansion / contraction member, and the biogas in the fermenter is discharged through the gas piping.

[0025] By configuring the biogas fermentation method of the present invention as described above in (8), when the fermentation residue of the fermentation raw material is removed from the fermenter, the expansion / contraction member can be expanded to discharge the biogas (also referred to as residual biogas) in the fermenter through the gas piping. This allows the residual biogas (e.g., methane gas containing hydrogen sulfide) in the fermenter to be discharged prior to removing the fermentation residue, thereby preventing workers from being exposed to residual biogas containing harmful substances when opening and closing the fermenter. Furthermore, if the biogas fermentation method of the present invention is configured so that the gas piping is connected to a gas pack or the like, the residual biogas can be recovered, which is expected to improve the biogas production yield. Furthermore, by configuring the biogas fermentation method of the present invention as described above in (8), the air in the fermenter can be discharged with a simple configuration, which is expected to reduce costs. [Effects of the Invention]

[0026] According to the present invention, it is possible to provide a biogas fermentation system that has a simple configuration, can discharge air that has become mixed inside a fermenter, and can efficiently recover generated biogas. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a schematic overall explanatory diagram of one embodiment of a biogas fermentation system of the present invention.

[0023] FIG. [Figure 2] 1A and 1B are explanatory diagrams illustrating the operation of the biogas fermentation system of the present invention, in which FIG. 1A is an explanatory diagram illustrating the state in which fermentation raw materials are introduced into a fermenter, and FIG. 1B is an explanatory diagram illustrating the state in which air is discharged from the fermenter. [Figure 3] 3 is a continuation of FIG. 2, where (a) shows the state in which the expansion / contraction member is expanded to expel air, and (b) shows the state in which biogas is being generated by fermenting the fermentation raw material. [Figure 4] 4 is a continuation of FIG. 3, where (a) shows the expansion member expanding to discharge residual biogas after fermentation is completed, and (b) shows the residual fermentation raw material being removed after fermentation is completed. [Figure 5] FIG. 1 is a schematic overall explanatory diagram of a first modified example of a biogas fermentation system according to the present invention. [Figure 6] FIG. 10 is a partially omitted schematic plan view of a second modified example of the biogas fermentation system of the present invention. [Figure 7] FIG. 10 is a partially omitted schematic plan view of a third modified example of the biogas fermentation system of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] A biogas fermentation system 1 according to one embodiment of the present invention will be described in detail below with reference to the drawings. Note that each drawing is a schematic representation for ease of understanding, and may differ from the actual shape, size, and arrangement of components. Also, note that the thickness of the material of the expansion / contraction member 20 in each drawing may differ from the actual thickness.

[0029] As shown in Fig. 1, a biogas fermentation system 1 of the present invention includes a fermenter 10, an expansion / contraction member 20, a gas pipe 3, and a control unit 50. The biogas fermentation system 1 in this embodiment will be described as an example in which fermentation is carried out batchwise and by anaerobic fermentation.

[0030] The fermenter 10 is formed, for example, in a rectangular shape when viewed from above, and has an opening 11 (see FIG. 2(a)) on the top side. The fermenter 10 is provided with a lid 12 for opening and closing the opening 11. The fermenter 10 can accommodate a fermentation raw material 5 therein. The fermenter 10 can generate biogas such as methane gas by anaerobic fermentation of the fermentation raw material 5 introduced therein. The fermenter 10 can be provided with a temperature controller such as a heater, various sensors such as a gas detector, an agitator, and the like, as appropriate.

[0031] The lid 12 can be attached to and detached from the top of the fermenter 10 so as to be freely opened and closed. The lid 12 may also be hinged so as to be freely opened and closed. A sealing member 13 is provided between the lid 12 and the expansion / contraction member 20. The lid 12 can cover and close the opening 11 of the fermenter 10. A first pipe 30 and a second pipe 35 serving as the gas pipe 3 are connected to the lid 12. The first pipe 30 and the second pipe 35 are detachably connected to the lid 12 via a connection adapter (not shown) as appropriate. An introduction portion 21 for introducing a filling medium into the expansion / contraction member 20 (described later) is inserted into the lid 12.

[0032] One end of the first piping 30 is connected to the lid 12 and communicates with the fermenter 10 via the lid 12. The other end of the first piping 30 is open to the atmosphere via a first switching unit 40 (switching unit 4) provided midway through the first piping 30. As will be described in detail later, by communicating with the fermenter 10, the first piping 30 can exhaust the air inside the fermenter 10 to the outside of the fermenter 10.

[0033] The second pipe 35 is disposed adjacent to the first pipe 30, and one end thereof is connected to the lid 12. The second pipe 35 is configured to communicate with the fermenter 10 via the lid 12. The other end of the second pipe 35 is connected to the gas pack 2 via a second switching unit 45 (switching unit 4) provided midway through the second pipe 35. As will be described in detail later, by communicating with the fermenter 10, the second pipe 35 can discharge the biogas generated inside the fermenter 10 toward the gas pack 2.

[0034] The gas pack 2 can collect the biogas produced in the fermenter 10. The gas pack 2 from which the biogas has been collected is used as fuel, etc. as appropriate. The biogas fermentation system 1 of the present invention can also be configured so that the biogas is directly supplied to a gas turbine, a gas engine, etc., instead of the gas pack 2. Furthermore, a dehumidifier, a filter for harmful gases (e.g., hydrogen sulfide), etc. may be provided between the gas pack 2 and the fermenter 10, as necessary.

[0035] The first switching unit 40 and the second switching unit 45 (collectively referred to as the switching unit 4) are each configured with a switching valve. When the first switching unit 40 is in an open state, it connects the first piping 30 to the fermenter 10, and when it is in a closed state, it disconnects the first piping 30 from the fermenter 10.

[0036] The second switching unit 45 can connect the second pipe 35 to the fermenter 10 in an open state, and can disconnect the second pipe 35 from the fermenter 10 in a closed state.

[0037] Therefore, the switching unit 4 can switch to one state selected from a plurality of states, including a first communication state in which the first pipe 30 is in communication with the fermenter 10 and the second pipe 35 is in non-communication, and a second communication state in which the second pipe 35 is in communication with the fermenter 10 and the first pipe 30 is in non-communication. Note that the switching by the switching unit 4 between the communication state and the non-communication state of the first pipe 30 and the second pipe 35 with the fermenter 10 is not limited to the above combinations, and various combinations can be employed, such as a combination in which both are in a communication state or a non-communication state.

[0038] The switching unit 4 is configured to switch the state (piping connection state) to the first communication state after the fermentation raw material 5 is charged into the fermenter 10 and before the fermentation of the fermentation raw material 5 starts. Furthermore, the switching unit 4 is configured to switch the state to the second communication state before the fermentation of the fermentation raw material 5 starts.

[0039] The expansion / contraction member 20 is formed as a balloon using, for example, elastic rubber or flexible resin. In this embodiment, the expansion / contraction member 20 is provided on the upper interior side of the fermenter 10. The expansion / contraction member 20 can be attached to the inner wall of the fermenter 10 or to the lid 12. An introduction portion 21 for introducing a filling medium is connected to the expansion / contraction member 20. The expansion / contraction member 20 can be expanded (expanded) by introducing a filling medium through the introduction portion 21, and can be contracted by discharging the filling medium. Here, air, water, digestive juice used in fermentation, etc. can be used as the filling medium.

[0040] To the introduction section 21, for example, a pump 22, a valve 23, and a filling medium storage section 24 are connected. Specifically, the pump 22 is connected to the filling medium storage section 24 via the valve 23, and the introduction section 21 is connected to the pump 22. Therefore, when the valve 23 is opened and the pump 22 is operated, the filling medium is introduced from the filling medium storage section 24 through the introduction section 21 into the expansion / contraction member 20. This causes the expansion / contraction member 20 to expand. Meanwhile, although not shown, the expansion / contraction member 20 is provided with a return flow path, and when the expansion / contraction member 20 contracts, the filling medium is recovered into the filling medium storage section 24 as the expansion / contraction member 20 naturally contracts. Note that when the expansion / contraction member 20 contracts, the pump 22 can be rotated in the reverse direction, for example, to forcibly recover the filling medium into the filling medium storage section 24.

[0041] 1, in this embodiment, the expansion / contraction member 20 is provided on the upper side inside the fermenter 10, so that when the fermentation raw material 5 is charged into the fermenter 10, a buffer space 6 is formed above the fermentation raw material 5. Therefore, when the expansion / contraction member 20 is in an expanded state (expanded state), the volume of the buffer space 6 is reduced.

[0042] Although details will be described later, the expandable / contractable member 20 can be expanded in the first communication state described above (a state in which the first pipe 30 is connected to the fermenter 10 and the second pipe 35 is not connected to the fermenter 10) to assume a first expanded state (see FIG. 2(b)) in which air is discharged from the fermenter 10. Furthermore, the expandable / contractable member 20 can be expanded in the second communication state described above (a state in which the second pipe 35 is connected to the fermenter 10 and the first pipe 30 is not connected to the fermenter 10) to assume a natural contraction state (see FIG. 3(a)) in which the introduction of the packing medium is stopped. Furthermore, the expandable / contractable member 20 can be expanded in the second communication state described above when fermentation of the fermentation raw material 5 is completed, to assume a second expanded state (see FIG. 4(a)) in which biogas remaining in the fermenter 10 is discharged. In other words, the expandable / contractable member 20 is freely expandable / contractable according to at least the first expanded state, the natural contraction state, and the second expanded state.

[0043] The control unit 50 is formed by a microcomputer or the like, and can perform various controls of the pump 22, the switching unit 4, the valve 23, etc. in the biogas fermentation system 1. The control unit 50 can perform various controls such as control of the expansion and contraction of the expansion and contraction member 20, management of the fermentation state of the fermentation raw material 5, and temperature control of the fermenter 10 (not shown).

[0044] The above is one embodiment of the biogas fermentation system 1 of the present invention. Next, the effects achieved by the biogas fermentation system 1 of the present invention will be described below.

[0045] The biogas fermentation system 1 of the present invention is provided with the following configurations (a) to (d), and thereby is able to achieve unique effects.

[0046] (a) The biogas fermentation system 1 of the present invention comprises a fermenter 10 that produces biogas by fermenting input fermentation raw materials 5, at least one expansion / contraction member 20 that is placed inside the fermenter 10 and whose volume changes by expansion and contraction, at least one gas pipe 3 connected to the fermenter 10, and an introduction section 21 that is connected to the expansion / contraction member 20 and that introduces a filling medium into the expansion / contraction member 20, and is characterized in that the expansion / contraction member 20 can be expanded by introducing the filling medium through the introduction section 21.

[0047] The biogas fermentation system 1 of the present invention can expand the expansion member 20 within the fermenter 10 by introducing a filling medium into the expansion member 20 through the introduction section 21. This allows the volume of the fermenter 10 to be reduced, allowing the biogas and air within the fermenter 10 to be discharged to the outside of the fermenter 10 through the gas piping 3. Therefore, the biogas fermentation system 1 of the present invention has a simple configuration, allowing air mixed in the fermenter 10 to be discharged and the generated biogas to be efficiently recovered. The expansion member 20 can be formed from various materials that can be expanded by the filling medium, such as elastic rubber, flexible resin, or air- and water-impermeable fiber material. The expansion member 20 can also be formed from various expandable and contractible shapes, such as a balloon or bellows-shaped member. The filling medium can be air, water, digestive fluid used in fermentation, or the like, and these filling media can be delivered to the expansion member 20 by, for example, a pump or the like.

[0048] (b) In the biogas fermentation system 1 of the present invention, the gas pipe 3 comprises a first pipe 30 that communicates with the fermenter 10 to discharge air from the fermenter 10, a second pipe 35 that communicates with the fermenter 10 to discharge biogas produced in the fermenter 10, and a switching unit 4 that switches to one state selected from a plurality of states including a first communication state in which the first pipe 30 communicates with the fermenter 10 and the second pipe 35 does not communicate with the fermenter 10, and a second communication state in which the second pipe 35 communicates with the fermenter 10 and the first pipe 30 does not communicate with the fermenter 10, and the switching unit 4 switches to one state selected from a plurality of states including a first communication state in which the first pipe 30 communicates with the fermenter 10 and the second pipe 35 does not communicate with the fermenter 10, and a second communication state in which the second pipe 35 communicates with the fermenter 10 and the first pipe 30 does not communicate with the fermenter 10, and The expansion / contraction member 20 is characterized in that it can be expanded and contracted freely according to at least each of the following states: a first expanded state in which it expands in the first communication state to discharge air from the fermentation tank 10; a natural contracted state in which the introduction of the filling medium is stopped in the second communication state; and a second expanded state in which it expands when the fermentation of the fermentation raw material 5 is completed in the second communication state to discharge the biogas remaining in the fermentation tank 10.

[0049] In the biogas fermentation system 1 of the present invention, the gas pipe 3 includes a first pipe 30, a second pipe 35, and a switching unit 4. The switching unit 4 can switch the gas pipe 3 to one state selected from a plurality of states, including a first communication state in which the first pipe 30 is connected to the fermenter 10 and the second pipe 35 is not connected, and a second communication state in which the second pipe 35 is connected to the fermenter 10 and the first pipe 30 is not connected. Therefore, the biogas fermentation system 1 of the present invention can selectively distribute and discharge the biogas (also referred to as residual biogas) and air remaining in the fermenter 10 to the first pipe 30 and the second pipe 35. Here, the first pipe 30 and the second pipe 35 can be provided in various forms that allow for switching their communication states with each other, such as being provided independently or being formed by branching the gas pipe 3 midway to form the first pipe 30 and the second pipe 35. The switching unit 4 can be implemented by various valves or the like, and a single or multiple valves can be used depending on the form of the first pipe 30 and the second pipe 35.

[0050] Furthermore, the biogas fermentation system 1 of the present invention can be switched to the first communication state after the fermentation raw material 5 is charged into the fermenter 10 and before fermentation of the fermentation raw material 5 begins, and the expansion / contraction member 20 can be expanded in the first communication state to switch to the first expanded state in which air is discharged from the fermenter 10. In this way, the biogas fermentation system 1 of the present invention can discharge air that has entered the fermenter 10 when the fermentation raw material 5 is charged into the fermenter 10 by expanding the expansion / contraction member 20, allowing the subsequent anaerobic fermentation to proceed smoothly.

[0051] Furthermore, the biogas fermentation system 1 of the present invention can be switched to the second communication state before fermentation of the fermentation raw material 5 begins, thereby preventing discharged air from backflowing and invading the fermenter 10. This allows the biogas fermentation system 1 of the present invention to efficiently perform anaerobic fermentation of the fermentation raw material 5. Furthermore, the biogas fermentation system 1 of the present invention can expand or contract the expansion / contraction member 20 in accordance with two states: a natural contraction state in which the introduction of the packing medium is stopped in the second communication state, and a second expansion state in which the expansion member 20 expands when fermentation of the fermentation raw material 5 is completed, thereby discharging biogas remaining in the fermenter 10. This allows the fermentation process to be carried out smoothly without having to attach or detach the expansion / contraction member 20. Furthermore, the biogas fermentation system 1 of the present invention can expand the expansion / contraction member 20 when fermentation of the fermentation raw material 5 is completed, thereby discharging residual biogas from the fermenter 10. Therefore, even if the residual biogas contains harmful gases such as hydrogen sulfide, workers can be prevented from being exposed to harmful gases when removing the residual fermentation raw material 5.

[0052] (c) In the biogas fermentation system 1 of the present invention described above, the fermenter 10 is characterized in that it has a lid 12 that can be opened and closed freely for adding or discharging the fermentation raw material 5, and the fermentation is carried out in a batch manner.

[0053] By configuring the biogas fermentation system 1 of the present invention as described above in (c), it is possible to construct a system suitable for a batch system in which the fermentation raw material 5 is replaced sequentially.

[0054] (d) In the biogas fermentation system 1 of the present invention described above, when the fermentation raw material 5 is charged into the fermentation tank 10, a buffer space 6 is formed above the fermentation raw material 5, and the expansion / contraction member 20 is provided on the upper side inside the fermentation tank 10 and reduces the volume of the buffer space 6 in the expanded state.

[0055] By configuring the biogas fermentation system 1 of the present invention as described above in (d), the expansion / contraction member 20 is located at the upper interior side of the fermenter 10, facilitating maintenance including the expansion / contraction member 20. Furthermore, by configuring the biogas fermentation system 1 of the present invention as described above in (d), a buffer space 6 is formed above the fermentation raw material 5, allowing biogas to be easily discharged.

[0056] The above is the configuration and effects of the biogas fermentation system 1 of the present invention. Next, the operation of the biogas fermentation system 1 and one embodiment of a biogas fermentation method will be described with reference to Figs.

[0057] As shown in Fig. 2(a), the fermentation raw material 5 is introduced into the fermenter 10 (fermentation raw material introduction step). Once the fermentation raw material 5 has been introduced into the fermenter 10, the opening 11 of the fermenter 10 is closed with the lid 12 as shown in Fig. 2(b) (fermenter closing step), and a buffer space 6 is formed above the fermentation raw material 5 inside the fermenter 10. Furthermore, once the opening 11 of the fermenter 10 is closed, the switching unit 4 switches the connection state of the gas pipe 3 to a first communication state in which the first pipe 30 is connected to the fermenter 10 and the second pipe 35 is not connected to the fermenter 10.

[0058] Furthermore, when the connection state of the gas pipe 3 is switched to the first communication state, a filling medium is introduced into the expansion / contraction member 20, causing the expansion / contraction member 20 to expand (expand). As a result, the volume of the buffer space 6 in the fermenter 10 is reduced, and the air in the buffer space 6 is discharged through the first pipe 30 (anaerobic condition creation step).

[0059] Next, as shown in FIG. 3( a), the switching unit 4 switches the connection state of the gas pipe 3 to a second connection state in which the second pipe 35 is connected to the fermenter 10 and the first pipe 30 is not connected. That is, the connection state of the gas pipe 3 is switched from the first connection state to the second connection state. Furthermore, the introduction of the filling medium into the expansion / contraction member 20 is stopped, and the expansion / contraction member 20 is placed in a natural contraction state. Furthermore, when the connection state of the gas pipe 3 is switched to the second connection state, the fermenter 10 is maintained at an appropriate temperature, and an appropriate digestive fluid or the like is added to the fermentation raw material 5, thereby starting fermentation (anaerobic fermentation) of the fermentation raw material 5. When fermentation of the fermentation raw material 5 starts, biogas (methane gas, etc.) is generated, and the generated biogas is collected in the gas pack 2 through the second pipe 35.

[0060] In the natural contraction state, as the fermentation raw material 5 expands due to fermentation (expansion due to biogas trapped inside the fermentation raw material 5, etc.), the expansion / contraction member 20 is pressed, and the filling medium inside the expansion / contraction member 20 is pushed back into the filling medium storage section 24. At this time, the pushed-back filling medium is returned to the filling medium storage section 24 through an appropriate return flow path (not shown). Note that the pump 22 (see FIG. 1) may be reversed as necessary to forcibly recover the filling medium.

[0061] As the natural contraction state progresses, as shown in Figure 3(b), the filling medium is discharged from the expansion / contraction member 20, and fermentation continues. At this time, the continuously generated biogas is collected into the gas pack 2 through the second piping 35.

[0062] When the fermentation of the fermentation raw material 5 is completed, as shown in Figure 4(a), with the gas pipe 3 in the second communication state, a filling medium is introduced into the expansion / contraction member 20, causing the expansion / contraction member 20 to expand (expand) (second expansion state). This causes the residual biogas remaining inside the fermenter 10 to be discharged (biogas discharge step). Furthermore, when the biogas discharge step is completed, the lid 12 (not shown) is opened, and the residue fermentation raw material 5 is removed from the fermenter 10.

[0063] The above is an embodiment of the operation of the biogas fermentation system 1 and the biogas fermentation method of the present invention. Next, the configuration and effects of the biogas fermentation system 1 and the biogas fermentation method of the present invention will be described below.

[0064] (e) The biogas fermentation method of the present invention is a biogas fermentation method using a biogas fermentation system 1 configured as in any one of (a) to (d) above, characterized in that a fermentation tank 10 is provided with a lid 12 that can be opened and closed freely for introducing the fermentation raw material 5, and the method carries out the following steps: a fermentation raw material introduction step in which the fermentation tank 10 is introduced with the fermentation raw material 5; a fermentation tank closing step in which the fermentation tank 10 is closed by closing the lid 12; and an anaerobic condition creation step in which the filling medium is introduced into the expansion / contraction member 20 to expand the expansion / contraction member 20 and the air in the fermentation tank 10 is discharged through the gas piping 3.

[0065] By configuring the biogas fermentation method of the present invention as described above in (e), the air inside the fermenter 10 can be discharged through the gas pipe 3 in the anaerobic condition creation step. This allows the inside of the fermenter 10 to be put into an anaerobic state before the start of fermentation of the fermentation raw material 5, thereby improving the fermentation efficiency of the fermentation raw material 5. Furthermore, by configuring the biogas fermentation method of the present invention as described above in (e), the air inside the fermenter 10 can be discharged with a simple configuration, which is expected to result in cost reduction effects.

[0066] (f) The biogas fermentation method of the present invention is a biogas fermentation method using a biogas fermentation system 1 configured as in any one of (a) to (d) above, characterized in that the fermenter 10 is provided with an openable and closable lid 12 for removing the fermentation residue of the fermentation raw material 5, and after fermentation of the fermentation raw material 5 and before removing the fermentation residue, a residual biogas discharge step is carried out in which the filling medium is introduced into the expansion / contraction member 20 to expand the expansion / contraction member 20, and the biogas in the fermenter 10 is discharged through the gas piping 3.

[0067] By configuring the biogas fermentation method of the present invention as described above in (f), when the fermentation residue of the fermentation raw material 5 is removed from the fermenter 10, the expandable member 20 can be expanded to discharge the biogas (also referred to as residual biogas) in the fermenter 10 through the gas piping 3. This allows the residual biogas (e.g., methane gas containing hydrogen sulfide) in the fermenter 10 to be discharged prior to removing the fermentation residue, thereby preventing workers from being exposed to residual biogas containing harmful substances when opening and closing the fermenter 10. Furthermore, in the biogas fermentation method of the present invention, if the gas piping 3 is configured to be connected to a gas pack 2 or the like, the residual biogas can be recovered, which is expected to improve the biogas production yield. Furthermore, by configuring the biogas fermentation method of the present invention as described above in (f), the air in the fermenter 10 can be discharged with a simple configuration, which is expected to reduce costs.

[0068] The above is the configuration and effects of the biogas fermentation method of the present invention. Next, a biogas fermentation system 100 according to a first modified example of the present invention will be described below. The biogas fermentation system 100 according to the first modified example has the same configuration as the biogas fermentation system 1 except that the expansion / contraction member 20 of the biogas fermentation system 1 described above is provided with a protrusion 110, and therefore a detailed description of the configuration of similar parts will be omitted. Also, please note that the same reference numerals are used for components similar to those of the biogas fermentation system 1.

[0069] First Variation As shown in FIG. 5, the biogas fermentation system 100 according to the first modification has at least one protrusion 110 on the surface of the expansion / contraction member 20 on the side facing the fermentation raw material 5 .

[0070] In this embodiment, the protrusion 110 is formed in a rod shape, and one end (base end) is attached to the underside of the expansion / contraction member 20 (the surface facing the fermentation raw material 5). The other end of the protrusion 110 forms a free end, and can penetrate into the fermentation raw material 5 as the expansion / contraction member 20 expands. In other words, the protrusion 110 pierces the fermentation raw material 5, thereby forming a passage for gases such as biogas that have accumulated inside the fermentation raw material 5. This allows gases such as biogas and air that have accumulated inside the fermentation raw material 5 to be smoothly discharged, even if the fermentation raw material 5 has high viscosity.

[0071] In this way, the biogas fermentation system 100 according to the first modified example can be configured as shown in (g) below, and this configuration can provide the following unique operational effects.

[0072] (g) The biogas fermentation system 100 according to the first variant of the present invention is characterized in that the expansion / contraction member 20 has at least one protrusion 110 on at least the surface facing the fermentation raw material 5, and the protrusion 110 is capable of penetrating into the fermentation raw material 5 as the expansion / contraction member 20 expands.

[0073] By configuring the biogas fermentation system 100 of the present invention as described above in (g), the protrusions 110 can penetrate into the fermentation raw material 5 when the expansion / contraction member 20 is expanded. This allows the biogas fermentation system 100 of the present invention to form a passage for biogas accumulated inside the highly viscous residue fermentation raw material 5, thereby allowing the biogas inside the residue fermentation raw material 5 to be smoothly discharged. Therefore, the biogas fermentation system 100 of the present invention can further improve the yield of biogas. Furthermore, the biogas fermentation system 100 of the present invention can discharge air from inside the fermentation raw material 5 when the fermentation raw material 5 is introduced, allowing anaerobic fermentation to be carried out smoothly.

[0074] The above is the configuration and effects of the biogas fermentation system 100 according to the first modified example of the present invention. Next, a biogas fermentation system 200 according to the second modified example of the present invention and a biogas fermentation system 300 according to the third modified example of the present invention will be described below. The biogas fermentation system 200 according to the second modified example and the biogas fermentation system 300 according to the third modified example have the same configuration as the biogas fermentation system 1 described above, except for the configuration of the expansion / contraction member 20, so a detailed description of the configuration of the similar parts will be omitted. It should also be noted that the same reference numerals are used for the same components as those in the biogas fermentation system 1.

[0075] <<Second Variation>> As shown in FIG. 6 , the biogas fermentation system 200 according to the second modification includes a plurality of expansion / contraction members 220 (two in the second modification). The plurality of expansion / contraction members 220 are arranged on the upper side of the fermenter 10, as in the above-described embodiment. One of the plurality of expansion / contraction members 220 is formed in a rectangular shape, and the other is formed in a generally L-shape. The plurality of expansion / contraction members 220 are connected to each other so as to be in communication with each other. The plurality of expansion / contraction members 220 are arranged side by side so as to expand in a diagonal direction from a corner on the side away from (away from) the gas pipe 3 (first pipe 30 and second pipe 35). The plurality of expansion / contraction members 220 are configured to expand sequentially from the side away from the gas pipe 3 toward the side approaching the gas pipe 3. That is, the plurality of expansion / contraction members 220 are configured to expand sequentially as a filling medium is introduced sequentially from the side away from the gas pipe 3 toward the side approaching the gas pipe 3. Therefore, as the multiple expansion / contraction members 220 expand sequentially, air and residual biogas are sequentially pushed out toward the gas pipe 3 from the side remote from the gas pipe 3. This allows the air and residual biogas in the fermenter 10 to be smoothly discharged through the gas pipe 3.

[0076] The above is the configuration of the biogas fermentation system 200 according to the second modified example. Next, a biogas fermentation system 300 according to a third modified example of the present invention will be described below.

[0077] <Third Variation> As shown in FIG. 7 , in a biogas fermentation system 300 according to the third modification, an expansion / contraction member 320 includes a plurality of rectangular compartments 310 (four in the third modification). The expansion / contraction member 320 is disposed on the upper side of the fermenter 10, as in the above-described embodiment. The compartments 310 are disposed so as to gradually expand in the diagonal direction of the fermenter 10 from the side farther from the gas pipe 3 toward the side closer to the gas pipe 3. The compartments 310 are also communicated with each other through openings 311. Therefore, the expansion / contraction member 320 gradually expands as the packing medium is sequentially introduced into each compartment 310 from the side farther from the gas pipe 3 toward the side closer to the gas pipe 3. As the expansion / contraction member 320 gradually expands, air and residual biogas are sequentially pushed toward the gas pipe 3 from the side farther from the gas pipe 3. This allows the air and residual biogas in the fermenter 10 to be smoothly discharged through the gas pipe 3.

[0078] The above is an embodiment of the biogas fermentation system 300 according to the third modified example of the present invention. In this way, the biogas fermentation system 200 according to the second modified example and the biogas fermentation system 300 according to the third modified example can be configured as shown in (h) below, and by adopting such a configuration, the following operational effects can be achieved.

[0079] (h) In the biogas fermentation systems 200, 300 of the present invention, the expansion / contraction members 220, 320 are characterized in that they are gradually expanded from the side away from the gas pipe 3 toward the side approaching the gas pipe 3.

[0080] By configuring the biogas fermentation systems 200, 300 of the present invention as described in (h) above, the biogas or air in the fermenter 10 can be sequentially pushed out toward the gas pipe 3 from the side of the fermenter 10 that is remote from the gas pipe 3 (the far side). This allows the biogas fermentation system 1 of the present invention to smoothly discharge the biogas (also referred to as residual biogas) or air remaining in the fermenter 10, thereby reducing the amount of residual biogas or air remaining in the fermenter 10.

[0081] Here, the expansion / contraction member 220 can be formed, for example, by a plurality of expansion / contraction members 220. In such a case, it is preferable that the plurality of expansion / contraction members 220 are arranged sequentially from the side away from the gas pipe 3 toward the side approaching the gas pipe 3, and that the plurality of expansion / contraction members 220 are configured to be expanded sequentially from the side away from the gas pipe 3 toward the side approaching the gas pipe 3.

[0082] In addition to the above, the expansion / contraction member 320 may be provided with, for example, a plurality of compartments 310 therein. In such a case, the plurality of compartments 310 may be arranged in sequence from the side farther away from the gas pipe 3 toward the side closer to the gas pipe 3, and may be configured so that the plurality of compartments 310 are expanded in sequence from the side farther away from the gas pipe 3 toward the side closer to the gas pipe 3.

[0083] The above is the configuration and effects of the biogas fermentation system 1, 100, 200, 300 and biogas fermentation method according to one embodiment of the present invention. However, the biogas fermentation system 1, 100, 200, 300 and biogas fermentation method according to the present invention are not limited to the above-described embodiment and can be modified in various ways within the scope of the present invention. For example, the biogas fermentation system 1 may be configured in various shapes and sizes as long as it is similar to the configuration described above in (a). The biogas fermentation system 1 according to the present invention may not include some or all of the configurations described above in (b) to (d), (g), and (h), or may include some or all of the configurations described above in (b) to (d), (g), and (h) in addition to other configurations. The biogas fermentation method according to the present invention may be configured as described above in (e) and (f), and various means may be used and the order of the means may be changed within the scope of the present invention.

[0084] In this embodiment, the fermenter 10 is formed in a rectangular parallelepiped shape, but this is not limiting and the fermenter 10 can be formed in various shapes and sizes. For example, the fermenter 10 may be formed in a cylindrical shape. The expansion / contraction member 20 can be made of various materials (e.g., rubber, resin, fiber, etc.) that have elasticity, resilience, flexibility, etc. The expansion / contraction member 20 can be formed of various expandable materials, such as air- and water-impermeable fiber materials. The expansion / contraction member 20 can be formed of various materials that can hold a filling medium. The expansion / contraction member 20 can be formed in various shapes that can be expanded and contracted, such as a bellows-shaped member. The expansion / contraction member 20 is not limited to a rectangular shape and can be formed in various shapes and sizes depending on the shape and size of the fermenter 10 and the fermentation raw material 5 used. The expansion / contraction member 20 may be a single member or multiple members. Furthermore, the filling medium introduced into the expansion / contraction member 20 is not limited to that in the embodiment, and various materials (gas, liquid, etc.) that can contribute to the expansion of the expansion / contraction member 20 can be used.

[0085] In this embodiment, the expansion / contraction member 20 is provided at the upper interior side of the fermenter 10, and the buffer space 6 is formed above the fermentation raw material 5 in the fermenter 10, but the present invention is not limited to this, and the expansion / contraction member 20 can be provided in various positions. For example, the expansion / contraction member 20 may be provided below, inside, or to the side of the fermentation raw material 5. The location of the expansion / contraction member 20 may be determined depending on the fermentation raw material 5, the composition of the biogas to be generated, the shape and size of the fermenter 10, etc.

[0086] In addition, in the first variant, the expansion / contraction member 20 is exemplified as having at least one protrusion 110 on at least the surface facing the fermentation raw material, but various shapes, sizes, and numbers of protrusions 110 can be used.

[0087] Furthermore, the number of gas pipes 3 can vary from a single pipe to multiple pipes, depending on the type of biogas to be discharged. In this embodiment, the gas pipes 3 are provided independently as the first pipe 30 and the second pipe 35. However, the gas pipe 3 may branch off from one or more pipes to provide one or more pipes. In such a case, the switching unit 4 may be configured to switch the connection state of each pipe. The gas pipe 3 may not only be attached to the lid 12, but also be attached to the main body of the fermenter 10. The gas pipe 3 can be attached to various positions. It is desirable that the gas pipe 3 not only be attached directly to the fermenter 10, but also be detachably attached using an appropriate adapter or the like.

[0088] Furthermore, the introduction section 21 connected to the expansion / contraction member 20 can be provided at various positions, and multiple introduction sections 21 may be provided. The introduction section 21 can have various configurations depending on the material of the filling medium, etc. Furthermore, the filling medium can be introduced into the expansion / contraction member 20 not only by using the pump 22 as in this embodiment, but also by various means capable of introducing the filling medium into the expansion / contraction member 20.

[0089] In the present embodiment, the switching unit 4 is shown to be capable of switching between a first communication state in which the first pipe 30 is connected to the fermenter 10 and the second pipe 35 is not connected to the fermenter 10, and a second communication state in which the second pipe 35 is connected to the fermenter 10 and the first pipe is not connected to the fermenter 10. However, the present invention is not limited to this configuration, and the connection state of the gas pipe 3 can be switched in various combinations. For example, both the first pipe 30 and the second pipe 35 can be connected to the fermenter 10, or both can be not connected to the fermenter 10. The switching unit 4 can be implemented using various valves and can be provided in various quantities, from one to multiple. The timing of switching between the first communication state and the second communication state by the switching unit 4 can also be varied depending on the composition of the biogas generated, the fermentation state, and other factors. In the present embodiment, the introduction of the filling medium into the expansion / contraction member 20 is stopped at the start of fermentation, resulting in a natural contraction state. However, the present invention is not limited to this configuration. For example, at the start of fermentation, the filling medium in the expansion / contraction member 20 can be forcibly discharged, or the filling medium can be reintroduced into the expansion / contraction member 20 at an appropriate timing. Also, the timing for introducing the filling medium into the expansion / contraction member 20 can be various.

[0090] In this embodiment, fermentation is performed in a batch manner, but the present invention is not limited to this and can be used for various fermentation methods that require the discharge of biogas or air from the fermenter 10. Furthermore, the biogas fermentation system 1 of the present invention is preferably used for anaerobic fermentation, but is not limited to this and can be used for various fermentation methods. Furthermore, fermentation may be performed not only by dry fermentation but also by wet fermentation.

[0091] The foregoing are various embodiments and modifications of the biogas fermentation system and biogas fermentation method according to the present invention. However, the present invention is not limited to the above-described embodiments and modifications, and it will be readily apparent to those skilled in the art that other embodiments are possible within the scope of the claims and the teachings and spirit of the present invention. [Industrial Applicability]

[0092] The biogas fermentation system and method of the present invention can be used to ferment various fermentation raw materials (biomass) and extract biogas. The biogas fermentation system and method of the present invention can be used to ferment fermentation raw materials using a fermenter. [Explanation of symbols]

[0093] 1: Biogas fermentation system 2: Gas pack 3: Gas piping 4: Switching section 5: Fermentation raw material (residue fermentation raw material) 6: Buffer space 10: Fermentation tank 12: Lid 20: Expandable member 21: Introduction 30: First piping (gas piping) 35: Second piping (gas piping) 40: First switching unit (switching unit) 45: Second switching unit (switching unit) 100: Biogas fermentation system 110:Protrusion 200: Biogas fermentation system 220: Expandable member 300: Biogas fermentation system 310: Compartment 311: Open hole 320: Expansion member

Claims

1. a fermenter that generates biogas by fermenting the input fermentation raw material; At least one expansion / contraction member that is disposed inside the fermenter and that changes in volume by expansion and contraction; at least one gas line connected to the fermenter; an introduction portion connected to the expansion / contraction member and configured to introduce a filling medium into the expansion / contraction member; Equipped with A biogas fermentation system, characterized in that the expansion / contraction member is expandable by introducing the filling medium through the introduction portion.

2. The gas pipe is a first pipe communicating with the fermenter to discharge air from the fermenter; a second pipe communicating with the fermenter to discharge the biogas produced in the fermenter; a switching unit that switches to one state selected from a plurality of states, including a first communication state in which the first pipe is in communication with the fermenter and the second pipe is not in communication with the fermenter, and a second communication state in which the second pipe is in communication with the fermenter and the first pipe is not in communication with the fermenter; Equipped with The switching unit is After the fermentation raw material is introduced into the fermenter, the state is switched to the first communication state before fermentation of the fermentation raw material is started, and the state is switched to the second communication state before fermentation of the fermentation raw material is started, The expansion and contraction member a first expansion state in which the fermenter expands in the first communication state to discharge air from the fermenter; a natural contraction state in which the introduction of the filling medium is stopped in the second communication state; a second expansion state in which the fermenter expands when the fermentation of the fermentation raw material is completed in the second communication state, thereby discharging the biogas remaining in the fermenter; 2. The biogas fermentation system according to claim 1, wherein the system is expandable and contractable according to at least each of the above conditions.

3. 3. The biogas fermentation system according to claim 1, wherein the expansion / contraction member is gradually expanded from a side farther away from the gas pipe toward a side closer to the gas pipe.

Images