Methane production equipment

Abstract

Nutrients are supplied to methanogenic bacteria supported on a carrier using a simple configuration. [Solution] The methane production apparatus 10 comprises a methane fermentation tank 12 having a methane fermentation liquid containing organic matter and methane-producing bacteria; a gas holder 14 provided above the methane fermentation tank 12, which stores the biogas produced in the methane fermentation tank 12 and has a top plate 14B and an arm 40 that moves up and down according to the amount of biogas stored; a methanation unit 20 attached to the arm 40, which moves between above and below the liquid surface S of the methane fermentation liquid in conjunction with the up and down movement of the top plate 14B and the arm 40 and has a carrier that supports methane-producing bacteria; and a hydrogen supply unit 16 that supplies hydrogen to the methane fermentation tank 12.

Description

Technical Field

[0001] The present invention relates to a methane production apparatus.

Background Art

[0002] In recent years, the development of biomethanation technology for converting carbon dioxide in biogas into methane by microorganisms has been underway. For example, Patent Document 1 discloses a technique in which a carrier impregnated with a fermentation liquid is arranged in a space above the fermentation liquid in a methane fermentation tank, and hydrogen is supplied to react carbon dioxide and hydrogen in the biogas generated from the fermentation liquid to produce methane. By providing such a carrier, the contact frequency between methane-producing bacteria and hydrogen / biogas is improved, the reaction of methane production proceeds, and the recovery rate increases.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, the methane-producing bacteria supported on the carrier need to be supplied with nutrients to maintain their activity. In Patent Document 1, nutrients are supplied to the methane-producing bacteria by injecting the methane fermentation liquid from the ceiling. However, in Patent Document 1, it is necessary to provide a shower and a path for nutrient supply.

[0005] The present disclosure has been made in consideration of the above facts, and an object thereof is to supply nutrients to methane-producing bacteria supported on a carrier with a simple configuration.

Means for Solving the Problems

[0006] The methane production apparatus of the first embodiment comprises a methane fermentation tank having a methane fermentation liquid containing organic matter and methane-producing bacteria; a gas holder provided above the methane fermentation tank and having a vertically moving part that stores the biogas produced in the methane fermentation tank and moves up and down according to the amount of biogas stored; a methanation unit attached to the vertically moving part and having a carrier that moves between above and below the liquid surface of the methane fermentation liquid in conjunction with the vertical movement of the vertically moving part and carries methane-producing bacteria; and a hydrogen supply unit that supplies hydrogen to the methane fermentation tank.

[0007] In the methane production apparatus of the first embodiment, a methanation unit is attached to the vertically moving part of the gas holder. The vertically moving part moves up and down according to the amount of biogas stored in the gas holder, and the methanation unit moves between above and below the liquid surface of the methane fermentation liquid in conjunction with the vertical movement of the vertically moving part. As a result, when the position of the methanation unit is below the liquid surface of the methane fermentation liquid, nutrients are supplied to the methane-producing bacteria supported on the carrier. Therefore, nutrients can be supplied to the methane-producing bacteria supported on the carrier with a simple configuration.

[0008] In the second embodiment of the methane production apparatus, the vertically moving part rises when the storage volume increases and descends when the storage volume decreases.

[0009] According to the methane production apparatus of the second embodiment, when the methane-producing bacteria lack sufficient nutrients and methane production stops, causing a decrease in the amount of biogas stored in the gas holder, the methanation section descends, allowing a carrier to be placed below the liquid surface of the methane fermentation liquid to supply nutrients from the methane fermentation liquid.

[0010] The third embodiment of the methane production apparatus is configured such that, in the first or second embodiment of the methane production apparatus, the gas holder includes an expandable portion that expands and contracts vertically in response to changes in the storage volume.

[0011] According to the third embodiment of the methane production apparatus, the expandable section expands and contracts vertically in accordance with changes in the storage volume, so the vertically movable section can be easily moved up and down using the expandable section.

[0012] The methane production apparatus of the fourth embodiment is a methane production apparatus of any one of the first to third embodiments, comprising a circulation path for returning the biogas discharged from the methane fermentation tank to the methane fermentation tank.

[0013] According to the methane production apparatus of the fourth embodiment, since biogas is returned to the methane fermentation tank in the circulation path, unreacted carbon dioxide can be brought into contact with methane-producing bacteria in the methane fermentation liquid or on the carrier, thereby promoting methane production. [Effects of the Invention]

[0014] According to this disclosure, nutrients can be supplied to methanogenic bacteria supported on a carrier using a simple configuration. [Brief explanation of the drawing]

[0015] [Figure 1] This diagram schematically shows the configuration of the methane production apparatus according to this embodiment, and depicts the state in which the methanation unit is positioned in its normal location. [Figure 2] This diagram schematically shows the configuration of the methane production apparatus according to this embodiment, and depicts the state in which the methanation unit is located at the nutrient supply position. [Figure 3] This diagram schematically shows a modified configuration of the methane production apparatus according to this embodiment, where (A) shows the state in which the methanation unit is located in the normal position, and (B) shows the state in which the methanation unit is located in the nutrient supply position. [Figure 4] This diagram schematically shows the configuration of another modified example of the methane production apparatus according to this embodiment, where (A) shows the methanation unit in its normal position and (B) shows the methanation unit in its nutrient supply position. [Modes for carrying out the invention]

[0016] Hereinafter, embodiments for implementing the present invention will be described based on the drawings.

[0017] Fig. 1 shows a schematic configuration of a methane production apparatus 10 according to this embodiment. The methane production apparatus 10 mainly includes a methane fermentation tank 12, a gas holder 14, a hydrogen supply unit 16, and a methanation unit 20.

[0018] The methane fermentation tank 12 is a container capable of storing a liquid, and a methane fermentation liquid is stored therein. The methane fermentation liquid contains organic nutrients such as sludge supplied from the outside and methane-producing bacteria that contribute to methanation. In the methane fermentation tank 12, biogas containing methane and carbon dioxide is generated by biodegradation or the like. The liquid level of the methane fermentation liquid is referred to as "liquid level S".

[0019] One of the lower side walls of the methane fermentation tank 12 is provided with a nutrient supply port 12A for supplying organic nutrients, and the organic nutrients are supplied from the nutrient supply port 12A. The other lower side wall of the methane fermentation tank 12 is provided with a discharge port 12B for discharging treated water, and the treated water is discharged from the discharge port 12B to the outside of the methane fermentation tank 12. The supply and discharge of organic nutrients are controlled so that the liquid level S of the methane fermentation liquid is maintained at a predetermined position.

[0020] In the methane fermentation tank 12, methanation is promoted by receiving hydrogen supply under the methane-producing bacteria in the methane fermentation liquid. Above the water surface of the methane fermentation liquid in the methane fermentation tank 12, a biogas space 12R for storing biogas is formed. A support plate 12C is disposed above the biogas space 12R.

[0021] A gas holder 14 is supported above the support plate 12C. The gas holder 14 has a side wall 14A and a top plate 14B that seals the upper part. The side wall 14A is in a bellows shape that is cylindrical and can expand and contract in the vertical direction, and is disposed between the top plate 14B and the support plate 12C and supported by the support plate 12C. The top plate 14B is connected to the upper part of the side wall 14A and, together with the side wall 14A, partitions the gas space 14R inside the gas holder 14.

[0022] The gas space 14R communicates with the biogas space 12R through the communication part 15. The gas holder 14 expands and contracts its side wall 14A and moves its top plate 14B up and down according to the amount of biogas stored in the gas space 14R. Specifically, in the methane fermentation liquid and the methanation part 20 described later, if the amount of biogas stored (volume) in the gas space 14R is more than a predetermined amount, the bellows of the side wall 14A extends and the top plate 14B is arranged at the upper part. This position is referred to as the "normal position P1". Also, in the methane fermentation liquid and the methanation part 20 described later, when the amount of biogas stored (volume) in the gas space 14R decreases, the bellows of the side wall 14A is folded and shrinks in the vertical direction under the weight of the top plate 14B, and the top plate 14B descends. The position of the top plate 14B when the whole of the methanation part 20 described later is immersed in the liquid surface S is referred to as the "nutrient supply position P2".

[0023] An arm 40 is attached to the outer peripheral part of the top plate 14B. The upper part of the arm 40 is connected to the top plate 14B, and the lower part is connected to the methanation part 20 described later. The arm 40 penetrates the support plate 12C and its lower part is arranged in the biogas space 12R. The arm 40 moves up and down in conjunction with the vertical movement of the top plate 14B. Note that the penetrating part of the arm 40 is processed so that the arm 40 can move up and down and the airtight state of the biogas space 12R is maintained. In the present embodiment, the top plate 14B and the arm 40 constitute the vertical movement part.

[0024] Guide members 42 are erected at both ends of the support plate 12C. The guide members 42 have grooves in the vertical direction (not shown), and the grooves are engaged with the top plate 14B to guide the vertical movement of the top plate 14B.

[0025] A methanation unit 20 is provided inside the methane fermentation tank 12. The methanation unit 20 has a housing that is in communication with the biogas space 12R, and a carrier 22 is housed inside the housing. The carrier 22 has fine voids to which methane-producing bacteria are attached. As the carrier 22, fibrous material derived from polymer materials, activated carbon, zeolite, etc., can be used. Suitable methane-producing bacteria to be attached (supported) on the carrier 22 include the genera Methanobacterium and Methanobrevibacter.

[0026] The methanation unit 20 is connected to the lower part of the arm 40 and is held in place within the methane fermentation tank 12 by the arm 40. The methanation unit 20 moves up and down in conjunction with the up and down movement of the arm 40. When the top plate 14B is in the normal position P1, the methanation unit 20 is positioned above the liquid level S. This position of the methanation unit 20 is referred to as the "normal position M1". When the top plate 14B is in the nutrient supply position P2, the methanation unit 20 is positioned below the liquid level S. This position of the methanation unit 20 is referred to as the "nutrient supply position M2".

[0027] Hydrogen is supplied from the hydrogen supply unit 16 to the methanation unit 20 via the hydrogen supply channel 17. The hydrogen supply channel 17 supplies hydrogen directly to the methanation unit 20 without merging with other channels. The hydrogen supply channel 17 is designed to follow the movement of the methanation unit 20.

[0028] In the methanation section 20, under the influence of methanogenic bacteria supported on the carrier 22, carbon dioxide and hydrogen in the biogas are converted into methane as shown in equation (1) below.

[0029] CO2 + 4H2 → CH4 + 2H2O (1)

[0030] The biogas from the biogas space 12R is converted to methane in the methanation section 20, and then sent to the gas holder 14 with a high methane concentration.

[0031] The gas holder 14 is provided with a biogas outlet 14D. A biogas discharge channel 30 is connected to the biogas outlet 14D via an internal pressure adjustment valve 44. The biogas in the gas space 14R is discharged from the biogas outlet 14D to the biogas discharge channel 30.

[0032] The biogas discharge channel 30 is branched into a recovery channel 32 and a circulation channel 34. The recovery channel 32 is connected to the second gas holder 36, and the circulation channel 34 is connected to the lower part (below the liquid level S) of the methane fermentation tank 12. Biogas containing methane is stored in the second gas holder 36. A portion of the biogas discharged to the biogas discharge channel 30 is diverted to the circulation channel 34 and returned to the methane fermentation tank 12.

[0033] Next, the operation and effects of the methane production apparatus 10 of this embodiment will be described.

[0034] In the methane fermentation tank 12, when the carrier is sufficiently nutrient-rich and normal methane fermentation is taking place, methane production progresses in the methane fermentation liquid and in the methanation section 20, resulting in a methane production amount exceeding a predetermined level. As a result, the amount of biogas stored in the gas space 14R exceeds a predetermined level, the bellows of the side wall 14A extend, the top plate 14B is positioned at its normal location P1, and the methanation section 20 is positioned at its normal location M1. In the methane fermentation tank 12, methane production is promoted not only in the methane fermentation liquid but also in the methanation section 20, thus increasing the methane recovery rate.

[0035] When the nutrients to the carrier 22 in the methanation unit 20 become insufficient, for example, at predetermined intervals, the internal pressure adjustment valve 44 is adjusted to release gas and lower the internal pressure of the gas space 14R. As a result, the bellows of the side wall 14A are folded and contracted by the weight of the top plate 14B, the top plate 14B descends, and the carrier 22 of the methanation unit 20 falls below the liquid level S and is immersed in the methane fermentation liquid. When the top plate 14B is positioned at the nutrient supply position P2, the carrier 22 of the methanation unit 20 is positioned below the liquid level S, which is the nutrient supply position M2. At this time, the concentrations of carbon dioxide and hydrogen in the methane fermentation tank 12 are high, so the hydrogen supply from the hydrogen supply unit 16 is stopped.

[0036] The carrier 22 is immersed in the methane fermentation liquid, allowing it to obtain organic nutrients. This increases the amount of methane produced. After sufficient time has elapsed for nutrient supply, the internal pressure adjustment valve 44 is adjusted to increase the internal pressure of the gas space 14R. This returns the top plate 14B to its normal position P1, and the hydrogen supply from the hydrogen supply unit 16 is restarted, allowing normal methane production to occur in the biogas space 12R in the methanation unit 20.

[0037] In the methane production apparatus 10 of this embodiment, the methanation unit 20 moves up and down according to the amount of biogas stored in the gas holder 14. When the position of the methanation unit 20 is immersed in the methane fermentation liquid, nutrients are supplied to the methane-producing bacteria supported on the carrier 22. Therefore, nutrients can be supplied to the methane-producing bacteria supported on the carrier 22 with a simple configuration.

[0038] In this embodiment, the internal pressure of the gas space 14R was raised or lowered using the internal pressure adjustment valve 44. However, the internal pressure of the gas space 14R may also be raised or lowered by adjusting the gas consumption of the gas-consuming equipment connected downstream of the biogas delivery passage 30.

[0039] Furthermore, in the methane production apparatus 10 of this embodiment, the side wall 14A of the gas holder 14 is made bellows-shaped and expandable, but other expansion / contraction means may be used. For example, the side wall 14A may be formed from an elastic material and expanded / contracted.

[0040] Alternatively, the upper part may be covered with a sheet-like membrane 54 to form a gas space 14R, and as shown in Figure 3(A), the carrier 22 may be divided into multiple parts and suspended by string-like string members 56, or as shown in Figure 4(A), the carrier 22 may be configured in a string-like form and divided into multiple parts and suspended from the membrane 54. In this case, the aggregate of carriers 22 becomes the methanation section 20. A support column 50 is erected in the center of the methane fermentation tank 12, and support wires 52 that support the membrane 54 are provided radially around the support column 50. The support wires 52 are positioned below the membrane 54 and above the liquid surface S. As shown in Figures 3(A) and 4(A), when the membrane 54 is inflated and positioned at the normal position P1, the carrier 22 is positioned at the normal position M1. Then, as shown in Figures 3(B) and 4(B), when the membrane 54 is deflated and positioned at the nutrient supply position P2, the carrier 22 is positioned at the nutrient supply position M2. If the carrier 22 is configured in a string-like shape, nutrients can be supplied to the carrier 22 above the liquid surface S by capillary action. Furthermore, the membrane 54 may be configured to bulge upwards and become convex, so that the entire top surface has a hemispherical shape. Also, the biogas delivery passage 30 may be provided on the side wall of the methane fermentation tank 12.

[0041] Furthermore, in the methane production apparatus 10 of this embodiment, since some of the biogas is returned to the methane fermentation tank 12 via the circulation path 34, the methane concentration in the biogas recovered by the second gas holder 36 can be increased.

[0042] Furthermore, although the gas holder 14 is provided on the upper part of the support plate 12C in this embodiment, the gas holder 14 may be provided anywhere in the upper part of the methane fermentation tank 12, above the liquid level S. For example, it may be provided inside the methane fermentation tank 12.

[0043] Furthermore, in this embodiment, since hydrogen from the hydrogen supply unit 16 is directly supplied to the methanation unit 20, a high concentration of hydrogen is supplied to the carrier 22 supporting the methanogenic bacteria, enabling efficient methanation.

[0044] Furthermore, in this embodiment, biogas from the circulation path 34 is returned to the methane fermentation liquid of the methane fermentation tank 12 along with unreacted hydrogen. This agitates the methane fermentation liquid, efficiently supplying biogas containing unreacted hydrogen to the methane-producing bacteria in the methane fermentation tank 12, thereby promoting the methane reaction in the methane fermentation liquid. [Explanation of Symbols]

[0045] 10 Methane production equipment 12 methane fermentation tanks 14 Gas holder 14A Side wall (extendable part) 14B Top panel (up and down movement section) 16. Hydrogen Supply Department 20 Metanation Section 22 carriers 34 Circulation path 40. Arm (up and down movement part)

Claims

1. A methane fermentation tank having a methane fermentation liquid containing organic matter and methane-producing bacteria, A gas holder is provided above the methane fermentation tank, which stores the biogas produced in the methane fermentation tank and has a vertically moving part that moves up and down according to the amount of biogas stored, A methanation unit is attached to the vertically moving unit and moves between above and below the liquid surface of the methane fermentation liquid in conjunction with the vertical movement of the vertically moving unit, and has a carrier that supports methane-producing bacteria, A hydrogen supply unit that supplies hydrogen to the methane fermentation tank, A methane production apparatus equipped with the following features.

2. The vertically moving part rises when the amount of stored material increases and lowers when the amount of stored material decreases. A methane production apparatus according to claim 1.

3. The gas holder is configured to include an expandable / contractable portion that expands and contracts vertically in response to changes in the storage volume. The methane production apparatus according to claim 1.

4. The system includes a circulation path that returns the biogas discharged from the methane fermentation tank back to the methane fermentation tank. A methane production apparatus according to any one of claims 1 to 3.

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