Methane production equipment

Abstract

The methanation reaction is effectively carried out using methanogenic bacteria supported on a carrier. [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 biogas space 12R formed above the liquid phase section 12L; a methanation section 20 which is separated from the methane fermentation liquid and communicates with the biogas space 12R, and has a carrier 22 that supports methane-producing bacteria; and a hydrogen supply section 16 which supplies hydrogen to the methanation section 20 without mixing with other gases.

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 progressing. For example, in Patent Document 1, a carrier impregnated with a fermentation broth is disposed in a space above the fermentation broth in a methane fermentation tank, and by supplying hydrogen, carbon dioxide and hydrogen in the biogas generated from the fermentation broth 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, in Patent Document 1, hydrogen is supplied by merging a circulation path and a hydrogen supply path. However, in such a hydrogen supply path, the methanation reaction is not effectively carried out.

[0005] The present disclosure has been made in consideration of the above facts, and an object thereof is to effectively carry out a methanation reaction using methane-producing bacteria supported on a carrier.

Means for Solving the Problems

[0006] The methane production apparatus of the first embodiment includes a methane fermentation tank for storing a methane fermentation liquid containing organic matter and methane-producing bacteria, having a liquid phase section in which the methane fermentation liquid 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, having a carrier for supporting methane-producing bacteria; and a hydrogen supply section for supplying hydrogen to the methanation section without mixing with other gases.

[0007] According to the first embodiment of the methane production apparatus, hydrogen is supplied to the methanation section without mixing with other gases, so that a high concentration of hydrogen reaches the methanogenic bacteria on the carrier, activating the methanogenic bacteria and allowing the methanation reaction to carry out effectively.

[0008] It is possible.

[0009] In the second embodiment of the methane production apparatus, the methanation section is provided in the gas phase section with the carrier housed inside the outer casing, and an outlet for a hydrogen delivery passage that delivers hydrogen from the hydrogen supply section is open inside the outer casing.

[0010] According to the methane production apparatus of the second embodiment, hydrogen can be supplied directly from the hydrogen supply channel to the carrier housed inside the outer casing.

[0011] The methane production apparatus of the third embodiment includes a biogas delivery path for delivering biogas produced in the methane fermentation tank from the methane fermentation tank, and a circulation path for branching off a portion of the biogas from the biogas delivery path and returning it to the methane fermentation tank, wherein the methanation unit is provided in the circulation path.

[0012] According to the third embodiment of the methane production apparatus, since the methanation section is located in the circulation path, the methane fermentation tank can be made smaller.

[0013] According to this disclosure, nutrients can be supplied to methanogenic bacteria supported on a carrier using a simple configuration. [Brief explanation of the drawing]

[0014] [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. [Modes for carrying out the invention]

[0015] The embodiments for carrying out the present invention will be described below with reference to the drawings.

[0016] 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.

[0017] 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.

[0018] The nutrient supply unit 24 stores organic nutrients to be supplied to the methane fermentation tank 12. These nutrients are essential for maintaining the activity of the methanogenic bacteria. A nutrient supply port 12A is provided on one of the lower side walls of the methane fermentation tank 12. Organic nutrients are supplied from the nutrient supply unit 24 to the methane fermentation tank 12 via the nutrient supply passage 36 and the nutrient supply port 12A.

[0019] On the other side of the lower side wall of the methane fermentation tank 12, there is a discharge port 12B for discharging treated water. The treated water is discharged from the discharge port 12B to the outside of the methane fermentation tank 12 through the liquid discharge path 38.

[0020] In the methane fermentation tank 12, methanation is promoted by receiving hydrogen supply under methane-producing bacteria in the methane fermentation liquid.

[0021] 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 an exterior 20A communicated with the biogas space 12R, and a carrier 22 is housed in the space inside the exterior 20A. 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, or the like can be used. As the methane-producing bacteria to be attached (supported) to the carrier 22, Methanobacterium, Methanobrevibacter, etc. are suitable.

[0022] Hydrogen is supplied from the hydrogen supply section 16 to the methanation section 20 through the hydrogen supply path 17. The hydrogen supply path 17 directly supplies hydrogen from the hydrogen supply path 17 to the methanation section 20 without merging with other flow paths or the like. In the present embodiment, the discharge port 17A at the tip of the hydrogen supply path 17 is exposed in the space inside the exterior 20A. That is, the discharge port 17A opens into the exterior 20A. From the discharge port 17A, hydrogen is ejected toward the carrier 22, and is set so that the ejection flow of hydrogen reaches the carrier 22.

[0023] In the methanation section 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).

[0024] CO2 + 4H2 → CH4 + 2H2O (1)

[0025] 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.

[0026] 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.

[0027] 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.

[0028] As shown in Figure 2, the control unit 40 is connected to the pump 39. 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 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] Furthermore, in this embodiment, since biogas containing unreacted hydrogen from the circulation path 34 is returned to the methane fermentation liquid of the methane fermentation tank 12, the methane fermentation liquid is stirred, and biogas containing unreacted hydrogen is efficiently supplied to the methane-producing bacteria in the methane fermentation tank 12, thereby promoting the methane reaction in the methane fermentation liquid.

[0041] In this embodiment, the methanation unit 20 is provided in the biogas space 12R within the methane fermentation tank 12. However, as shown in Figure 4, the methane production apparatus 10B may also be configured with the methanation unit 20 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. The outlet 17A of the hydrogen supply path 17 is set so that the hydrogen jet reaches the carrier 22 in the methanation unit 20. 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 where it is provided within the methane fermentation tank 12. [Explanation of symbols]

[0042] 10A Methane Production System 10B Methane production equipment 12 methane fermentation tanks 12L liquid phase part 12R Biogas Space (Gas Phase) 16. Hydrogen Supply Department 17 Hydrogen delivery path 17A outlet 20 Metanation Section 22 carriers 34 Circulation route 40 Control Unit

Claims

1. A methane fermentation tank that stores methane fermentation liquid containing organic matter and methane-producing bacteria, and has a liquid phase section in which the methane fermentation liquid is stored, and a gas phase section formed above the liquid phase section, and produces carbon dioxide and methane, 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 without mixing it with other gases, A methane production apparatus equipped with the following features.

2. The methanation section is provided in the gas phase section with the carrier housed inside the outer casing. An outlet for a hydrogen delivery passage, which delivers hydrogen from the hydrogen supply unit, is open inside the exterior. The methane production apparatus according to claim 1.

3. A biogas discharge channel for discharging biogas produced in the methane fermentation tank from the methane fermentation tank, The system includes a circulation path that branches off a portion of the biogas from the biogas delivery path and returns it to the methane fermentation tank, The methanation unit is provided in the circulation path, A methane production apparatus according to claim 1 or claim 2.

Images