Methane production equipment

Abstract

Nutrients are supplied to methanogenic bacteria supported on a carrier using a simple configuration. [Solution] The methane production apparatus 10 includes a methane fermentation tank 12 that stores methane fermentation liquid containing organic matter and methane-producing bacteria, and has a liquid phase section 12L in which the methane fermentation liquid is stored and a gas phase section 12R formed above the liquid phase section 12L; a methanation section 20 that is separated from the methane fermentation liquid and in communication with the gas phase section 12R and has a carrier for supporting methane-producing bacteria; a hydrogen supply section 16 that supplies hydrogen to the methanation section 20; a membrane filtrate processing section 50 that performs membrane filtrate treatment on the methane fermentation liquid in the methane fermentation tank 12 and separates it into a concentrated liquid containing organic matter and methane-producing bacteria and a membrane filtrate containing nutrients; and a membrane filtrate supply section that supplies the membrane filtrate filtered by the membrane filtrate processing section 50 to the methanation section 20.

Description

Technical Field

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[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 disposed in a space above the fermentation liquid in a methane fermentation tank, and by supplying hydrogen, carbon dioxide and hydrogen in the biogas generated from the fermentation liquid are reacted 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, it is necessary to supply nutrients to the methane-producing bacteria supported on the carrier in order 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 separate 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 first embodiment of the methane production apparatus includes a methane fermentation tank having a liquid phase section in which the methane fermentation liquid containing organic matter and methane-producing bacteria is stored, and a gas phase section formed above the liquid phase section; a methanation section separated from the methane fermentation liquid and in communication with the gas phase section, and having a carrier for supporting methane-producing bacteria; a hydrogen supply section for supplying hydrogen to the methanation section; and a membrane between the methane fermentation liquid of the methane fermentation tank and the methane fermentation liquid. filtration The membrane is used to perform the processing and separate the resulting concentrate containing the organic matter and the methane-producing bacteria into a membrane filtrate containing nutrients. filtration Processing unit and the film filtration The system includes a membrane filtrate supply unit that supplies the membrane filtrate filtered in the processing unit to the methanation unit.

[0007] The methane production apparatus of the first embodiment has a membrane filtrate processing unit that performs membrane filtrate treatment on the methane fermentation liquid of a methane fermentation tank, separating it into a concentrated liquid containing organic matter and methane-producing bacteria, and a membrane filtrate containing nutrients. The membrane filtrate is normally discharged to the outside, but by supplying this membrane filtrate to a carrier that supports methane-producing bacteria, nutrients can be supplied with a simple configuration.

[0008] In the second embodiment of the methane production apparatus, the methanation section is provided in the gas phase section.

[0009] In this way, by providing a methanation section in the gas phase, the membrane filtrate can be supplied to the methanation section in the gas phase.

[0010] In the third embodiment of the methane production apparatus, the methanation unit is provided in the membrane filtrate supply unit.

[0011] In this way, by providing a methanation unit in the membrane filtrate supply unit, the methane fermentation tank can be made smaller.

[0012] According to this disclosure, nutrients can be supplied to methanogenic bacteria supported on a carrier using a simple configuration. [Brief explanation of the drawing]

[0013] [Figure 1] This diagram schematically shows the configuration of the methane production apparatus according to this embodiment. [Figure 2] This is a block diagram of the control system of the methane production apparatus according to this embodiment. This diagram shows the state where the liquid level of the fermentation liquid is at a high level. [Figure 3] This is a flowchart of a membrane filtration process program. [Figure 4] This diagram schematically shows a modified configuration of the methane production apparatus according to this embodiment. [Modes for carrying out the invention]

[0014] The embodiments for carrying out the present invention will be described below with reference to the drawings.

[0015] Figure 1 shows a schematic configuration of the methane production apparatus 10A according to this embodiment. The methane production apparatus 10A mainly comprises a methane fermentation tank 12, a gas holder 14, a hydrogen supply unit 16, a methanation unit 20, a raw material input unit 24, a control unit 40, and a membrane filtration unit 50.

[0016] The methane fermentation tank 12 is a container capable of storing liquid, and it stores methane fermentation liquid. The methane fermentation liquid contains organic nutrients such as sludge supplied from an external source, and methane-producing bacteria that contribute to methane production. In the methane fermentation tank 12, biogas containing methane and carbon dioxide is produced through biodegradation and other processes.

[0017] The raw material input section 24 stores the raw materials to be supplied to the methane fermentation tank 12. The raw materials here are sludge raw materials containing organic waste, and they contain nutrients and nutrients necessary to maintain the activity of methane-producing bacteria. A raw material supply port 12A is provided on one of the lower side walls of the methane fermentation tank 12. Raw materials are supplied from the raw material supply section 24 to the methane fermentation tank 12 via the raw material supply passage 36 and the raw material supply port 12A.

[0018] On the other side of the lower side wall of the methane fermentation tank 12, there is a discharge port 12B for discharging the treated water. The treated water is sent from the discharge port 12B through the liquid discharge path 38 to the membrane filtration treatment unit 50 described later. The discharge port 12B is connected to the lower side of the liquid level of the methane fermentation liquid in the methane fermentation tank 12. The portion where the methane fermentation liquid in the methane fermentation tank 12 is stored is referred to as the liquid phase part 12L. A pump 39 is provided in the liquid discharge path 38. The pump 39 is connected to a control unit 40 described later. Incidentally, the pump 39 may be provided in the membrane filtrate delivery path 38B described later.

[0019] In the methane fermentation tank 12, under the methane-producing bacteria in the methane fermentation liquid, hydrogen supply is received and methanation is promoted.

[0020] 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 methanation unit 20 is provided in the biogas space 12R. The methanation unit 20 includes a housing communicating with the biogas space 12R, and a carrier 22 is housed inside the housing. The carrier 22 has fine voids and methane-producing bacteria are attached thereto. As the carrier 22, a fiber material derived from a polymer material, activated carbon, zeolite, etc. can be used. As the methane-producing bacteria to be attached (supported) to the carrier 22, Methanobacterium, Methanobrevibacter, etc. are suitable.

[0021] Hydrogen is supplied from the hydrogen supply unit 16 to the methanation unit 20 via the hydrogen supply path 17. The hydrogen supply path 17 directly supplies hydrogen from the hydrogen supply path 17 to the methanation unit 20 without merging with other flow paths or the like.

[0022] In the methanation unit 20, under the methane-producing bacteria supported on the carrier 22, carbon dioxide and hydrogen in the biogas are methanated as shown in the following formula (1).

[0023] CO2 + 4H2 → CH4 + 2H2O (1)

[0024] At the top of the methane fermentation tank 12, facing the biogas space 12R, a biogas outlet 12C and a filtrate supply port 12D are provided. A biogas discharge channel 30 is connected to the biogas outlet 12C. The biogas in the biogas space 12R undergoes methane conversion in the methanation section 20, increasing its methane concentration, and is then discharged from the biogas outlet 12C to the biogas discharge channel 30. The biogas discharge channel 30 is connected to a gas holder 14, where biogas containing methane is stored. Some of the biogas discharged to the biogas discharge channel 30 may be returned to the methane fermentation tank 12.

[0025] Pump 39 withdraws methane fermentate from the methane fermentation tank 12 and sends it toward the membrane filtration processing unit 50. In the membrane filtration processing unit 50, the methane fermentate withdrawn from the methane fermentation tank 12 is filtered through a membrane to separate it into a concentrated liquid containing organic matter and methane-producing bacteria, and a membrane filtrate containing nutrients for methane-producing bacteria such as trace metals. Hollow fiber membranes, flat membranes, tubular membranes, etc., can be used as filtration membranes in the membrane filtration processing unit 50. The concentrated liquid is returned to the methane fermentation tank 12 through the concentrated liquid discharge passage 38A. The membrane filtrate is discharged through the membrane filtrate discharge passage 38B and branched via a three-way valve 52 into a membrane filtrate return passage 38C and a membrane filtrate discharge passage 38D. The membrane filtrate sent to the membrane filtrate return passage 38C is returned to the methane fermentation tank 12. The membrane filtrate sent to the membrane filtrate discharge passage 38D is discharged to the outside.

[0026] In this embodiment, the membrane filtrate delivery passage 38B, the membrane filtrate return passage 38C, the three-way valve 52, and the control unit 40 correspond to the membrane filtrate supply unit.

[0027] A shower section 35 is provided at the filtrate supply port 12D of the methane fermentation tank 12, and one end of the membrane filtrate return path 38C is connected to it. The membrane filtrate from the membrane filtrate return path 38C is supplied to the methanation section 20 of the biogas space 12R via the shower section 35.

[0028] As shown in Figure 2, the control unit 40 is connected to the pump 39 and the three-way valve 52. The control unit 40 includes a CPU (Central Processing Unit) 41, a ROM (Read Only Memory) 42, a RAM (Random Access Memory) 43, an input / output interface (I / O) 44, and a storage unit 45.

[0029] The CPU 41, ROM 42, RAM 43, and I / O 44 are connected to each other via the bus 46. Each functional unit, including the memory unit 45, is connected to the I / O 44. These functional units are able to communicate with the CPU 41 via the I / O 44.

[0030] For the storage unit 45, for example, an HDD (Hard Disk Drive), SSD (Solid State Drive), or flash memory may be used. The storage unit 45 stores control programs for controlling each part of the methane production apparatus 10A, as well as various data. These control programs and data may also be stored in the ROM 42.

[0031] In this embodiment, a membrane filtration processing program and the like are stored as part of the control program. Data used in this processing, such as the membrane filtration processing time T1 and the nutrient supply time T2, are also stored. The membrane filtration processing time T1 is set to an appropriate time for filtering one methane fermentation liquid. The nutrient supply time T2 is set to an appropriate time for supplying nutrients to the methane-producing bacteria supported on the methane fermentation liquid carrier 22.

[0032] In the methane production apparatus 10A, the membrane filtration processing program shown in Figure 3 is executed at predetermined intervals, such as at user instructions. In this embodiment, as an example, an example in which the membrane filtration processing program is executed at predetermined intervals will be described.

[0033] First, in step S10, the system waits until it is time for membrane filtration of the methane fermentate in the methane fermentation tank 12. When it is time for filtration, the pump 39 is driven in step S12. Then, in step S14, the membrane filtrate return passage 38C side of the three-way valve 52 is opened, and the membrane filtrate discharge passage 38D side is closed.

[0034] As a result, the methane fermentation liquid in the methane fermentation tank 12 is sent through the liquid discharge channel 38 to the membrane filtration processing unit 50. In the membrane filtration processing unit 50, the methane fermentation liquid is filtered through a membrane and separated into a concentrated liquid containing organic matter and methane-producing bacteria, and a membrane filtrate containing nutrients.

[0035] The concentrated liquid is returned to the methane fermentation tank 12 via the concentrated liquid discharge channel 38A. The membrane filtrate is discharged from the membrane filtrate discharge channel 38B and returned to the methane fermentation tank 12 via the membrane filtrate return channel 38C through the three-way valve 52. The returned membrane filtrate is sprayed from the shower section 35 to the methanation section 20. This supplies the membrane filtrate to the methane-producing bacteria supported on the carrier 22 in the methanation section 20.

[0036] In step S16, the system waits until the nutrient supply time T2 has elapsed, and the supply of membrane filtrate to the methanogenic bacteria continues. After the nutrient supply time T1 has elapsed, in step S18, the membrane filtrate return path 38C side of the three-way valve 52 is closed, and the membrane filtrate discharge path 38D side is opened. This stops the supply of membrane filtrate to the methanogenic bacteria, and the membrane filtrate is discharged to the outside through the membrane filtrate discharge path 38D.

[0037] In step S20, the system waits until the membrane filtration processing time T1 has elapsed, and the return of the concentrated liquid separated in the membrane filtration processing unit 50 to the methane fermentation tank 12 continues. After the membrane filtration processing time T1 has elapsed, in step S22, the pump 39 is stopped, and the withdrawal of methane fermentate from the methane fermentation tank 12 is stopped.

[0038] In step S24, it is determined whether the operation has finished. If the determination is positive, the membrane filtration program is terminated. If the determination is negative, the process returns to step S10 and the above process is repeated.

[0039] In the methane production apparatus 10A of this embodiment, methane production is promoted not only in the methane fermentation liquid but also in the methanation section 20 within the methane fermentation tank 12, thereby increasing the methane recovery rate.

[0040] Furthermore, in this embodiment, nutrients in the membrane filtrate separated during the membrane filtration treatment of the methane fermentation liquid in the methane fermentation tank 12 are supplied to the methanation unit 20, so that nutrients can be supplied to the methane-producing bacteria supported on the carrier with a simple configuration.

[0041] In this embodiment, the membrane filtration process and nutrient supply to the carrier were started simultaneously, but they may be started separately. If the timing for nutrient supply arrives during the membrane filtration process, the three-way valve 52 opens the membrane filtrate return passage 38C, which was closed before the timing for nutrient supply, and closes the membrane filtrate discharge passage 38D, which was open before the timing for nutrient supply, after the timing for nutrient supply has arrived. Then, after the nutrient supply time T2 has elapsed, the membrane filtrate return passage 38C is closed and the membrane filtrate discharge passage 38D is opened.

[0042] Furthermore, in this embodiment, the methanation unit 20 is provided in the biogas space 12R inside the methane fermentation tank 12, but as shown in Figure 4, the methane production apparatus 10B may also be configured in which the methanation unit 20 is provided outside the methane fermentation tank 12. In this case, a circulation path 34 is provided that branches off from the biogas delivery path 30 and returns the biogas to the methane fermentation tank 12, and the methanation unit 20 is provided in the circulation path 34. The filtrate supplied from the membrane filtration processing unit 50 to the methanation unit 20 is then discharged to the outside through the discharge path 38E. Biogas containing CO2 can be supplied to the methanation unit 20 via the circulation path 34. In this way, by providing the methanation unit 20 in the circulation path 34, the methane fermentation tank 12 can be made smaller compared to the case where it is provided inside the methane fermentation tank 12. [Explanation of symbols]

[0043] 10A, 10B Methane Production Equipment 12 methane fermentation tanks 12L liquid phase part 12R Biogas Space (Gas Phase) 16. Hydrogen Supply Department 20 Metanation Section 22 carriers 50 Membrane filtration section 38B Membrane filtrate delivery path (membrane filtrate supply section) 38C Membrane filtrate return path (membrane filtrate supply section) 52 Three-way valve (membrane filtrate supply section) 40 Control Unit (Membrane Filtrate Supply Unit)

Claims

1. A methane fermentation tank having a liquid phase section in which the methane fermentation liquid containing organic matter and methane-producing bacteria is stored, and a gas phase section formed above the liquid phase section, A methanation section is separated from the methane fermentation liquid and communicates with the gas phase section, and has a carrier for supporting methane-producing bacteria, A hydrogen supply unit that supplies hydrogen to the methanation unit, A membrane filtration unit performs membrane filtration on the methane fermentation liquid of the methane fermentation tank, separating it into a concentrated liquid containing the organic matter and the methane-producing bacteria, and a membrane filtrate containing nutrients. A membrane filtrate supply unit that supplies the membrane filtrate filtered in the membrane filtration unit to the methanation unit, Equipped with, The methanation unit is provided in the membrane filtrate supply unit of the methane production apparatus.

2. The biogas discharged from the methane fermentation tank has a circulation path that returns it to the methane fermentation tank and merges with the membrane filtrate supply unit, and the methanation unit is provided at the junction of the membrane filtrate supply unit and the circulation path. The methane production apparatus according to claim 1.

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