Methane production equipment

Abstract

Nutrients are supplied to methanogenic bacteria supported on a carrier using a simple configuration. [Solution] The methane production apparatus 10A includes a methane fermentation tank 12 which 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 which is separated from the methane fermentation liquid and communicates with the gas phase section 12R and has a carrier that supports methane-producing bacteria; a hydrogen supply section 16 which supplies hydrogen to the methanation section 20; a circulation path 34 which has one end connected to the gas phase section 12B and the other end connected to the liquid phase section 12L and returns biogas sent from the methane fermentation tank 12 to the methane fermentation tank; a pump 39 provided in the circulation path 34 which sends methane fermentation liquid from the liquid phase section 12L to the gas phase section 12R via the circulation path 34; and a control unit 40 which operates the pump 39 when supplying nutrients to the methanation section 20.

Description

Technical Field

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

Background Art

[0002] In recent years, the development of biomethanation technology that converts carbon dioxide in biogas into methane by microorganisms has been underway. For example, in Patent Document 1, 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] A methane production apparatus according to the first embodiment 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 having a carrier for supporting methane-producing bacteria, separated from the methane fermentation liquid and in communication with the gas phase section; a hydrogen supply section for supplying hydrogen to the methanation section; a circulation path having one end connected to the gas phase section and the other end connected to the liquid phase section, for returning biogas discharged from the methane fermentation tank to the methane fermentation tank; a fermentation liquid discharge section provided in the circulation path for discharging the methane fermentation liquid from the liquid phase section to the gas phase section via the circulation path; and a control section for operating the fermentation liquid discharge section when supplying nutrients to the methanation section.

[0007] The methane production apparatus of the first embodiment includes a circulation path, one end of which is connected to the gas phase of a methane fermentation tank and the other end of which is connected to the liquid phase. When nutrients are supplied to the methanation section, the control unit operates the fermentation liquid delivery unit to deliver the methane fermentation liquid from the liquid phase to the gas phase via the circulation path. This makes it possible to pump up the methane fermentation liquid via the circulation path and supply the methane fermentation liquid containing nutrient-rich organic matter to the methanation section, which is in communication with the gas phase, without providing a separate route.

[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 unit in the gas phase, the methane fermentation liquid pumped up to the gas phase can be supplied to the methanation unit.

[0010] In the third embodiment of the methane production apparatus, the methanation unit is provided in the circulation path.

[0011] In this way, by providing a methanation section in the circulation path, the methane fermentation liquid flowing through the circulation path can be supplied to the methanation section.

[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. [Figure 3] This is a flowchart of the nutrient supply processing program. [Figure 4] This is a schematic diagram showing the configuration of a methane production apparatus according to a modified example of this embodiment. [Figure 5] This figure illustrates the opening and closing control and flow path of a three-way valve in another modified example of this embodiment. [Figure 6] This is a schematic diagram showing the configuration of a methane production apparatus according to another modification of 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 nutrient supply unit 24, and a control unit 40.

[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 nutrient supply section 24 stores the organic matter nutrients to be supplied to the methane fermentation tank 12. The nutrients here are nutrients and nourishment for maintaining the activity of methanogenic bacteria. One of the lower side walls of the methane fermentation tank 12 is provided with a nutrient supply port 12A. The organic matter nutrients are supplied from the nutrient supply section 24 to the methane fermentation tank 12 through the nutrient supply passage 36 and the nutrient supply port 12A.

[0018] On the other side of the lower side wall of the methane fermentation tank 12, a discharge port 12B for discharging the treated water is provided, and the treated water is discharged from the discharge port 12B to the outside of the methane fermentation tank 12 through the liquid discharge passage 38. A discharge on-off valve 38A is provided in the liquid discharge passage 38. The discharge on-off valve 38A is connected to a control section 40 described later.

[0019] In the methane fermentation tank 12, under the methanogenic 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 section 20 is provided in the biogas space 12R. The methanation section 20 includes a housing communicated with the biogas space 12R, and a carrier 22 is housed inside the housing. The carrier 22 has fine voids and methanogenic bacteria are attached thereto. As the carrier 22, a fiber material derived from a polymer material, activated carbon, zeolite, or the like can be used. As the methanogenic bacteria to be attached (supported) to the carrier 22, Methanobacterium, Methanobrevibacter, etc. are suitable.

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

[0022] 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.

[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 circulation port 12D are provided. A biogas outlet 30 is connected to the biogas outlet 12C. The biogas in the biogas space 12R undergoes methane conversion in the methanation section 20, resulting in a high methane concentration. The biogas, containing unreacted hydrogen, is then sent from the biogas outlet 12C to the biogas outlet 30. The biogas outlet 30 is connected to a gas holder 14, where the methane-containing biogas is stored.

[0025] A shower section 35 is provided at the circulation port 12D, and one end of the circulation path 34 is connected to it. The other end of the circulation path 34 is connected to the area below the liquid level of the methane fermentation liquid in the methane fermentation tank 12. The portion of the methane fermentation liquid stored in the methane fermentation tank 12 is designated as the liquid phase section 12L. A pump 39 is provided in the circulation path 34. The pump 39 is connected to the control unit 40.

[0026] Pump 39 diverts a portion of the biogas sent from the biogas space 12R to the biogas discharge path 30 to the circulation path 34 and returns it to the methane fermentation tank 12. By driving in the reverse direction, it also pumps up methane fermentate from the methane fermentation tank 12 and supplies it to the methanation section 20 of the methane fermentation tank 12 from the shower section 35. For pump 39, the direction from the circulation path 34 toward the liquid phase section 12L of the methane fermentation tank 12 is designated as the forward direction D1, and the direction from the circulation path 34 toward the shower section 35 of the methane fermentation tank 12 is designated as the reverse direction D2. Normally, pump 39 is driven to flow biogas in the forward direction D1, and when supplying nutrients as described later, it is driven to flow methane fermentate in the reverse direction D2.

[0027] As shown in Figure 2, the control unit 40 is connected to the supply valve 36A and the discharge valve 38A. 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.

[0028] 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.

[0029] 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.

[0030] In this embodiment, a nutrient supply processing program and the like are stored as part of the control program. Furthermore, data such as the nutrient supply time T1 is stored as data used in this processing. The nutrient supply time T1 is set to an appropriate time for supplying nutrients to the methanogenic bacteria supported on the carrier 22.

[0031] In the methane production apparatus 10A, the nutrient supply 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 nutrient supply processing program is executed at predetermined intervals will be described.

[0032] First, in step S10, the system waits until the timing for nutrient supply arrives. When the timing for nutrient supply arrives, in step S12, the pump 39 is driven in the reverse direction D2. As a result, the methane fermentation liquid in the methane fermentation tank 12 is pumped up through the circulation path 34 to the circulation port 12D at the top of the methane fermentation tank 12 and supplied from the shower section 35 to the carrier in the methanation section 20.

[0033] In step S14, the system waits until the nutrient supply time T1 has elapsed, and the supply of methane fermentate continues. After the nutrient supply time T1 has elapsed, in step S16, the pump 39 is switched to the forward direction D1. This stops the supply of methane fermentate from the shower section 35 to the methanation section 20, and biogas is supplied from the biogas space 12R to the liquid phase section 12L via the circulation path 34.

[0034] In step S18, it is determined whether the operation has ended. If the determination is positive, the nutrient supply processing program is terminated. If the determination is negative, the process returns to step S10 and the above process is repeated.

[0035] 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.

[0036] Furthermore, in 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 gas holder 14 can be increased.

[0037] Furthermore, in the methane production apparatus 10A of this embodiment, the methane fermentation liquid, which contains nutrient-rich organic matter, can be easily supplied to the methanation section 20, which is connected to the biogas space 12R, by pumping up the methane fermentation liquid using the circulation path 34.

[0038] 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.

[0039] Furthermore, in this embodiment, since biogas containing unreacted hydrogen from the circulation path 34 is returned to the methane fermentate in the methane fermentation tank 12, the methane fermentate is stirred, and the methane reaction in the methane fermentate can be promoted.

[0040] In this embodiment, nutrients are supplied to the methanation unit 20 by switching the rotation direction of the pump 39. However, it is also possible to supply nutrients to the methanation unit 20 by switching a valve while the pump 39 is driven in a constant direction. In this case, as an example, as shown in Figure 4, a parallel first circulation path 34A and a second circulation path 34B are provided for the circulation path 34, and the pump 39 is provided in a connecting path 34C that connects the first circulation path 34A and the second circulation path 34B at their intermediate points. A three-way valve V1 is provided at the connection point between the second circulation path 34B and the connecting path 34C, and a three-way valve V2 is provided at the connection point between the first circulation path 34A and the connecting path 34C.

[0041] Under normal conditions, the three-way valves V1 and V2 are switched so that the pathway is from the shower section 35 to the three-way valve V1 to the pump 39 to the three-way valve V2 to the liquid phase section 12L of the methane fermentation tank 12 (see Figure 5(A)). When supplying nutrients, the three-way valves V1 and V2 are switched so that the pathway is from the liquid phase section 12L of the methane fermentation tank 12 to the three-way valve V1 to the pump 39 to the three-way valve V2 to the shower section 35 (see Figure 5(B)).

[0042] Furthermore, in this embodiment, the methanation unit 20 is provided in the biogas space 12R within the methane fermentation tank 12, but as shown in Figure 6, the methane production apparatus 10B may also be configured in which the methanation unit 20 is provided in the circulation path 34. In this case, a carrier 22 carrying methane-producing bacteria is housed in a sealed enclosure and connected to the circulation path 34. By providing the methanation unit 20 in the circulation path 34 in this way, the methane fermentation tank 12 can be made smaller compared to the case in which it is provided within the methane fermentation tank 12. [Explanation of Symbols]

[0043] 10A Methane Production System 10B Methane production equipment 12 methane fermentation tanks 12L liquid phase part 12R Biogas Space (Gas Phase) 20 Metanation Section 22 carriers 34 Circulation path 39 Pump (fermentation liquid discharge section) 40 Control Unit

Claims

[Claim 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 aforementioned methanation unit, One end is connected to the gas phase section, and the other end is connected to the liquid phase section, forming a circulation path that returns the biogas discharged from the methane fermentation tank to the methane fermentation tank, A fermentation liquid delivery unit is provided in the circulation path and delivers the methane fermentation liquid from the liquid phase to the gas phase via the circulation path, A control unit that operates the fermentation liquid delivery unit when supplying nutrients to the methanation unit, Equipped with, The methanation unit is provided in the circulation path, Methane production equipment.

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