Methane gas generation apparatus and method

Abstract

Provided are a methane gas generation apparatus and method capable of generating high-concentration methane gas with higher efficiency than existing devices and methods, even when using microorganisms. Also provided are a methane gas generation apparatus and method capable of suppressing liquid from flowing back into a gas supply pipe even when the operation of the apparatus is stopped.　The methane gas generation apparatus for generating methane gas by supplying a hydrogen-containing gas A and a CO2-containing gas B to an anaerobic biological reaction tank T for performing microbial treatment is characterized in that a fixed bed FB filled with a carrier to which microorganisms adhere is arranged in the reaction tank T; and the flow (FL) of process gas in the reaction tank is directed from the upper side to the lower side in the vertical direction of the fixed bed.

Description

Methane gas generation apparatus and method

[0001] The present invention relates to a methane gas generation apparatus and method, and more particularly to a hydrogen-containing gas and CO2 generation apparatus. ２ This invention relates to a methane gas generation apparatus and method for producing methane gas by microbial treatment of contained gases.

[0002] In recent years, reducing and removing carbon dioxide, a major cause of global warming, has become a significant challenge. Since carbon dioxide is generated by the combustion of fossil fuels, its reduction, recovery, and reuse are required. Furthermore, biogas obtained through methane fermentation of organic wastewater, sewage sludge, organic waste, and food residues also contains carbon dioxide, making its removal necessary.

[0003] As a carbon dioxide removal and utilization technology, methanation technology, as shown in the following reaction equation (1), is already known. 4H ２ +CO ２ →CH ４ +2H ２ O・・・・・・・・・(1)

[0004] As shown in Patent Documents 1 and 2, a method for removing carbon dioxide and generating methane gas has already been disclosed that uses a catalyst and can achieve high methane production capacity under high pressure and high temperature conditions. However, such methods consume a large amount of energy, have high operating costs for the production system and equipment, and have poor durability.

[0005] In contrast, as shown in Patent Document 3, the above reaction (1) can also be carried out by the action of microorganisms. As shown in Figure 1, a liquid culture medium 10 containing microorganisms is placed inside the reaction vessel 1, and carbon dioxide and hydrogen gas are supplied as indicated by symbol C, and the liquid culture medium is supplied with air through the aeration means 2 inside the reaction vessel. In addition, a stirring blade MB is driven by a motor M to stir the suspended microorganisms and the liquid culture medium.

[0006] However, its methane production capacity is low and limited. For example, as shown in Patent Document 3, the maximum amount of methane gas generated per reactor is only about 10.8 L / L-Reactor / d (unit: amount of methane gas generated per liter in the reaction vessel per day), and the methane gas concentration in the processed gas discharged from the reaction vessel is also low, at about 55%. Microbial methanation reactions are greatly influenced by the microbial concentration, treatment conditions, especially the solubility and solubility rate of carbon dioxide and hydrogen gas in the reaction solution, and the diffusion rate to the microorganisms. For this reason, a stable and high methane production rate and the generation of high-concentration methane gas are major challenges in microbial methanation.

[0007] Patent Document 3 also proposes a method for producing methane gas using methane-producing bacteria immobilized on a carrier. For example, as shown in Figure 2, a fixed bed FB filled with a carrier to which microorganisms adhere is held in a reaction vessel T using a support net SN or the like. A discharge pipe ST is placed above the fixed bed, and a liquid containing nutrients for the microorganisms is supplied to the fixed bed. The liquid that falls from the fixed bed is stored in a liquid storage section LR located below the fixed bed. The symbol LQ indicates the liquid stored in the storage section LR. The liquid is circulated by a pump P in a circulating liquid line GL and supplied again to the fixed bed FB from the discharge pipe ST.

[0008] Carbon dioxide and hydrogen gas are supplied between the fixed bed FB and the liquid LQ stored in the liquid storage section LR, as indicated by symbol C. They are treated by microorganisms as they pass through the fixed bed FB, converted into a process gas containing methane, and discharged from the reaction vessel T as indicated by symbol E. Even in a methane gas generator using such a fixed bed, as in the case of Figure 1, the process gas contains a large amount of untreated carbon dioxide and hydrogen gas, making it a major challenge to achieve a stable, high methane production rate and the generation of high-concentration methane gas.

[0009] In Patent Document 4, the applicant disclosed a methane gas generation apparatus and method, including carbon dioxide removal, that can generate high-concentration methane gas with high efficiency even when using microorganisms. Specifically, as shown in Figure 3, hydrogen-containing gas A and CO ２In a methane gas generator that includes carbon dioxide removal, a contained gas B is supplied (symbol C) to an anaerobic biological reactor T for microbial treatment, and a treated gas E containing methane gas is discharged. The reactor T is equipped with a fixed bed FB filled with a carrier to which microorganisms adhere, and has a circulating gas line that circulates at least a portion of the treated gas E back into the reactor (symbol D). Symbol BL is a blower (gas blower), and symbol F indicates the supply of liquid containing nutrients for microorganisms. Symbol G indicates the discharge route for a portion of the liquid.

[0010] While methane gas generation devices utilizing circulating gas have achieved methane conversion rates of 90% or higher, many users have expressed a desire for methane gas generation devices and methods that can reduce the proportion of carbon dioxide remaining in the processed gas to, for example, 1% by volume or less, while also achieving a higher methane conversion rate (for example, 95% or higher).

[0011] Furthermore, as shown in Figure 3, hydrogen-containing gas A and CO are located below the fixed floor FB. ２ When supplying gas B, aeration means AD may be placed within the liquid LQ. In Figure 3, both gases A and B are introduced into the liquid, but to suppress the dissolution of carbon dioxide into the liquid, only hydrogen-containing gas A is sometimes introduced into the aeration means AD located within the liquid. Placing the aeration means AD within the liquid in this way has advantages such as promoting the dissolution of gas into the liquid and contributing to liquid agitation and misting.

[0012] However, when the methane gas generator is stopped, problems can occur, such as the liquid flowing back into the gas supply pipes A or B via the aeration means AD. Also, since the height of the reaction vessel reaches several meters, when the device is stopped, all the liquid in the reaction vessel collects in the liquid storage section LR, filling the space below the fixed floor with liquid, and causing the liquid to flow back into the carbon dioxide supply pipe.

[0013] Japanese Patent Publication No. 5562873, Japanese Patent Publication No. 6956665, Japanese Patent Publication No. 63-49999, International Publication WO2024 / 034541A1

[0014] An object of the present invention to solve is to solve the aforementioned problems and provide a methane gas production apparatus and method that can produce high-concentration methane gas with higher efficiency even when microorganisms are used. Another object of the present invention is to provide a methane gas production apparatus and method that can suppress backflow of liquid into a gas supply pipe even when the operation of the apparatus is stopped.

[0015] In order to solve the above problems, the methane gas production apparatus and method of the present invention have the following features. (1) A methane gas production apparatus that produces methane gas by supplying a hydrogen-containing gas and a CO ２ -containing gas to an anaerobic bioreactor that performs microbial treatment, wherein a fixed bed packed with a carrier to which microorganisms adhere is disposed inside the reactor, and the process gas in the reactor flows from top to bottom in the vertical direction of the fixed bed.

[0016] (2) In the methane gas production apparatus according to (1) above, the hydrogen-containing gas and the CO ２ -containing gas are provided with inflow ports at an upper portion of the fixed bed.

[0017] (3) In the methane gas production apparatus according to (1) above, a liquid supply means for supplying liquid to the fixed bed is disposed on an upper side of the fixed bed.

[0018] (4) In the methane gas production apparatus according to (3) above, the process gas is led out of the reactor from a lower side of the fixed bed, and the led-out process gas passes through a mist separator to separate liquid particles from the process gas.

[0019] (5) In the methane gas production apparatus according to (1) above, a part of the process gas discharged from the reactor or a part of the process gas in an intermediate stage of treatment in the reactor is extracted and circulated to the reactor at a position upstream of the flow of the process gas from the extraction position.

[0020] (6) In the methane gas generating apparatus described in any of (1) to (5) above, the reaction vessel is composed of a single container, and a pressure regulating device for maintaining the gas pressure inside the container within a predetermined range is provided in the piping that discharges the processed gas from the container.

[0021] (7) In the methane gas generating apparatus described in any of (1) to (5) above, the reaction tank is composed of a plurality of containers, each of which is provided with the fixed bed, and the plurality of containers are connected by gas flow paths so that the processed gas passes through them sequentially, and in at least one of the containers of the reaction tank, the processed gas flows from top to bottom in the vertical direction.

[0022] (8) The methane gas generating apparatus described in (7) above is characterized in that at least one of the plurality of containers is equipped with a pressure regulating device in the piping that discharges the processed gas from the container, for maintaining the gas pressure inside the container within a predetermined range.

[0023] (9) Hydrogen-containing gas and CO ２ In a method for producing methane gas, in which a contained gas is supplied to an anaerobic biological reactor that performs microbial treatment to produce methane gas, the reactor is characterized in that a plurality of fixed beds filled with carriers to which microorganisms adhere are arranged inside the reactor, and the flow of the treated gas inside the reactor flows from top to bottom in the vertical direction of the fixed beds.

[0024] (10) The methane gas production method described in (9) above, characterized in that a liquid is supplied to the fixed bed from above the fixed bed.

[0025] (11) The methane gas production method described in (10) above, characterized in that the processed gas is discharged from below the fixed bed to the outside of the reaction vessel and liquid particles are separated from the discharged processed gas.

[0026] (12) The methane gas production method described in (9) above, characterized in that a portion of the processed gas discharged from the reaction tank or a portion of the processed gas at an intermediate stage of the treatment in the reaction tank is extracted and circulated to the reaction tank located upstream of the flow of the processed gas from the extraction point.

[0027] (13) The methane gas production method according to any one of (9) to (12) above, wherein the reaction vessel is composed of a plurality of containers, each of which is provided with the fixed bed, the plurality of containers are connected by gas flow paths so that the process gas passes through them sequentially, and in at least one of the containers of the reaction vessel the process gas flows from top to bottom in the vertical direction.

[0028] According to the present invention, hydrogen-containing gas and CO ２ In a methane gas generator that supplies a contained gas to an anaerobic biological reactor for microbial treatment to produce methane gas, a fixed bed filled with a carrier to which microorganisms adhere is placed in the reactor, and the flow of the treatment gas in the reactor flows from top to bottom in the vertical direction of the fixed bed, so that hydrogen gas remains on the fixed bed for a longer period of time, promoting the microbial reaction. This makes it possible to provide a methane gas generator and method that can produce high-concentration methane gas with higher efficiency.

[0029] Furthermore, since the gas supply pipe is connected to the upper side of the reaction vessel, it is possible to provide a methane gas production apparatus and method that suppresses the backflow of liquid into the gas supply pipe even when the operation of the apparatus is stopped.

[0030] This is a diagram illustrating a conventional methane gas generator. This is a diagram illustrating an example of a methane gas generator using a fixed bed. This is a diagram illustrating an example of a methane gas generator according to Patent Document 3. This is a diagram showing a first embodiment of the methane gas generator according to the present invention. This is a diagram showing a second embodiment of the methane gas generator according to the present invention. This is a diagram showing a third embodiment of the methane gas generator according to the present invention. This is a diagram showing a fourth embodiment of the methane gas generator according to the present invention. This is a diagram showing a fifth embodiment of the methane gas generator according to the present invention.

[0031] The methane gas generation apparatus and method of the present invention will be described in detail below with reference to Figures 4 to 8. For the sake of simplicity, the following description will focus on the methane gas generation apparatus. As shown in Figure 4, the present invention generates a hydrogen-containing gas A and CO ２In a methane gas generator that supplies contained gas B to an anaerobic biological reactor T for microbial treatment to produce methane gas, a fixed bed FB filled with a carrier to which microorganisms adhere is placed inside the reactor T, and the flow of the treated gas (FL) inside the reactor flows from top to bottom in the vertical direction of the fixed bed.

[0032] Gas B can be supplied to the anaerobic biological reactor T for treatment, provided it contains carbon dioxide. Biogas obtained by methane fermentation of organic wastewater or organic sludge may be used as Gas B. Alternatively, carbon dioxide (exhaust gas) generated from combustion at factories or thermal power plants may be used.

[0033] Gas A, as long as it contains hydrogen gas, can be supplied to and used in the anaerobic biological reactor T. Hydrogen gas obtained by electrolysis of water using renewable energy such as solar or wind power, or surplus nighttime electricity from power plants, may be used as Gas A. Alternatively, hydrogen gas generated as a by-product from factory production processes may also be used.

[0034] CO ２ Gas B, which contains gas A, and gas A, which contains hydrogen, are supplied to the anaerobic biological reactor T, and therefore preferably do not contain oxygen. Furthermore, as shown in Figures 3 and 4, methods for supplying these gases to the reactor T include supplying a mixed gas C, which is a mixture of gas A and gas B, to the reactor, or supplying gas A and gas B separately to the reactor T.

[0035] The fixed bed FB of the anaerobic biological reactor T contains microorganisms, mainly methane-producing bacteria, that react carbon dioxide gas and hydrogen gas to convert them into methane gas. As methane-producing bacteria, bacteria derived from digested sludge can be used, and it is desirable to use hydrogen-assimilating methane-producing bacteria that can produce methane from hydrogen and carbon dioxide. Specifically, *Methanobacterium thermoautotrophicum* and *Methanobacterium formicicum* of the genus *Methanobacterium*, *Methanococcus vanielii* of the genus *Methanococcus*, or *Methanosaricina barkerii* of the genus *Methanosaricina* are suitably usable.

[0036] A carrier is used for retaining microorganisms. As the carrier, it is preferable to use a hydrophilic carrier to which hydrogen-utilizing methanogens easily adhere. To stably adhere the methanogens to the surface of the carrier, it is effective to immerse the carrier in anaerobic digested sludge in advance. Also, as the carrier, a hydrophilic carrier that is a polymer carrier not decomposed by microorganisms and allows the aforementioned hydrogen-utilizing methanogens to easily adhere is preferable. Examples of the polymer carrier include rigid carriers made of polyethylene, polyurethane, polypropylene and the like, synthetic polymers such as polyethylene glycol (PEG), polyvinyl alcohol (PVA), polyacrylamide, polycarbonate, and photocurable resin, and gel carriers using polymers such as carrageenan and sodium alginate.

[0037] Any of spherical, quadrangular, cylindrical, and tube shapes can be used as the shape of the carrier. The effective diameter is 5 to 20 mm, preferably 10 to 15 mm, which allows stable separation from a supporting mesh. The specific surface area of the carrier is 100 to 5,000 m ２ / m ３ , which is preferable.

[0038] Carriers having many fine pores on the surface, carriers that are hollow inside, carriers having countless irregularities on the surface, and carriers impregnated with powdered activated carbon allow faster adhesion and immobilization of methanogens, and can achieve high-concentration adhesion of methanogens through acclimation culture in a short period. Furthermore, since methanogens can be adhered and immobilized at high concentration on the carrier surface in the reaction tank for a long period of time, stable methane conversion performance can be obtained.

[0039] The specific gravity of the carrier is preferably around 0.9 to 1.0 so that an excessive load does not occur even when a large amount of the carrier is filled into the biological reaction tank. The height (thickness in the height direction) of the carrier layer (fixed bed) filled in the reaction tank is 1 to 10 m, preferably 3 to 5 m.

[0040] A fixed bed FB is filled with carrier material. For example, a large number of carriers are placed inside a mesh-like frame and then placed on a support net SN provided at a predetermined position in the reaction vessel. In Figure 4, there is only one fixed bed FB, but it is also possible to configure multiple fixed beds in series. The higher the carrier filling rate in the biological reaction vessel, the greater the amount of carrier per unit volume of the biological reaction vessel, and the greater the amount of microorganisms that can adhere to and be fixed to the carrier, resulting in high processing performance. On the other hand, considering the homogenization of gas flow within the biological reaction vessel and gas mixing in the gas layer, the carrier filling rate should be 60 to 80 V%, preferably 50 to 70 V%.

[0041] Anaerobic biological reactors can be rectangular or cylindrical in shape. A cylindrical shape is preferable considering the uniformity of the packing material and the flow of the supply gas. In the case of a cylindrical shape, the packing material can be packed almost uniformly, and the flow of the supply gas is uniform throughout.

[0042] A liquid containing nutrients for microorganisms is supplied to the fixed bed FB. The liquid can be continuously or intermittently supplied from the liquid storage section LR to the circulating liquid line GL by a circulating liquid pump P. Water is sprayed from the top of the fixed bed FB from a liquid supply means ST such as a spray pipe, and uniformly contacts the carrier layer packed in the fixed bed. As a result, nutrients in the liquid are supplied to the microorganisms on the carrier surface (the biofilm covering the carrier surface), allowing the activity of the microorganisms to be kept high and a stable methane production rate to be obtained. In the initial stages of the system's startup, when sufficient microorganisms have not yet adhered to the surface of the packed carrier, it is necessary to introduce seed sludge, such as sewage digested sludge containing methane-producing bacteria or digested sludge from organic waste treated with methane fermentation, into the liquid storage section LR in advance to allow methane-producing bacteria to adhere to the carrier surface.

[0043] The more seed sludge introduced into the LR liquid storage section during startup, the greater the amount of sludge adhering to the carrier surface, allowing for a shorter startup time. On the other hand, if the amount of seed sludge introduced is excessive, a large amount of sludge will accumulate not only on the carrier surface but also in the gaps between the packed carriers, causing localized blockages. This prevents the supplied hydrogen and carbon dioxide gases from flowing uniformly and making contact with the carrier surface, resulting in unstable treatment performance.

[0044] The amount of seed sludge to be added at startup needs to be determined considering the carrier packing amount, carrier shape, and packing rate, but generally, 0.5 to 5 g, preferably 0.5 to 2.5 g, of seed sludge is added per liter of carrier packing amount. The SS concentration of the liquid to which the seed sludge is added at startup should be 2,500 to 15,000 mg / L, preferably 2,500 to 10,000 mg / L. If the SS concentration (suspended solids concentration) is high, sludge may accumulate in the packed carrier layer, potentially leading to blockage of the liquid and supply gas flow paths. Therefore, if the SS concentration of the digested sludge used as seed sludge is high, it is preferable to dilute it with treated wastewater or the like.

[0045] The flow rate of the circulating liquid should preferably be set considering the volume of the packed carrier layer. Typically, the daily flow rate of the circulating liquid should be 2 to 20 times, preferably 5 to 10 times, the volume of the packed carrier. If the flow rate of the circulating liquid is too low, the contact between the microorganisms attached to the surface of the packed carrier and the liquid will not be uniform, making it impossible to stably supply the microorganisms with nutrients from the liquid. This reduces the activity of the microorganisms and prevents a stable methane production rate from being obtained. For this reason, it is important to maintain an appropriate flow rate of the circulating liquid.

[0046] This liquid contains nutrients for microorganisms (methane-producing bacteria) as shown in Table 1.

[0047]

[0048] The methane gas production apparatus and method according to the present invention are characterized in that, as shown in Figure 4, a fixed bed (FB) filled with a carrier to which microorganisms adhere is placed inside the reaction vessel (T), and the flow of the processed gas (dotted arrow FL) inside the reaction vessel flows from the top to the bottom in the vertical direction of the fixed bed. For this reason, hydrogen-containing gas and CO2 are present in the upper part of the fixed bed. ２ Inlets for the contained gases are provided. These inlets may be provided for each gas, or the two gases may be combined before being introduced into the reaction vessel and introduced into the reaction vessel through a single inlet.

[0049] Because hydrogen gas is less dense than carbon dioxide and methane gas in the treatment gas, it passes through the fixed bed FB more slowly when moved downwards (from top to bottom vertically) than when moved upwards (from bottom to top vertically) within the reaction vessel T, even with the same airflow pressure. As a result, the contact time between microorganisms and hydrogen gas is increased, and the conversion to methane gas proceeds more efficiently.

[0050] Furthermore, as shown in Figure 5, the supply pipe C that introduces gas into the reaction vessel T is installed above the reaction vessel T. Therefore, even when the operation of the apparatus is stopped, there is no problem of the liquid LQ accumulated in the liquid storage section LR flowing back into the supply pipe.

[0051] A key feature of the methane gas generation apparatus of the present invention, as shown in Figure 4, is the placement of a pressure regulating device PR in the piping at the outlet of the vessel constituting the reaction tank (piping for discharging the processed gas from the vessel) to maintain the gas pressure inside the vessel within a predetermined range.

[0052] The methane production (methanation) reaction is a chemical reaction that involves a decrease in gas volume before and after the reaction, and therefore the gas flow rate in the reaction vessel tends to decrease as the reaction progresses. For this reason, if the pressure of the incoming gas or the pressure inside the reaction vessel is unstable, temporary backflow or localized flow velocity fluctuations may occur in the gas flow path. Therefore, by installing a pressure regulating device downstream of the reaction vessel, pressure fluctuations inside the reaction vessel can be mitigated, the occurrence of backflow and flow velocity fluctuations can be suppressed, and the methane production reaction can proceed stably and efficiently.

[0053] Known technologies can be used as pressure regulating devices, and for example, configurations such as water seal structures, overflow type water seal devices, hydraulic tanks, mechanical pressure regulators, and buffer tanks can be employed.

[0054] As shown in Figure 4, the reaction vessel may consist of a single container, or as shown in Figure 7, it may consist of multiple containers. The pressure regulating device can be installed in the piping that discharges the processed gas from each container. When a combination of multiple containers is used, it is possible to install a pressure regulating device in each container or in the downstream container, but it is also possible to limit the number of containers to those where the methanation reaction proceeds most and install the pressure regulating device there.

[0055] The liquid LQ accumulated in the liquid storage section LR is collected in the circulating fluid tank HT. A pump P' may be installed between the liquid storage section LR and the circulating fluid tank HT. In tank HT, the liquid LQ is heated to approximately 60°C by a heater H. The liquid is sent to the liquid supply means ST via the circulating fluid line GL by the pump P. From the liquid supply means ST, the liquid, heated to approximately 55°C, is sprayed onto the fixed floor FB.

[0056] Furthermore, the process gas containing methane gas generated in reaction vessel T is discharged to the outside of the reaction vessel from below the fixed bed FB. Because the process gas discharge line E is located below the fixed bed, the process gas contains many liquid particles. Therefore, the mist separator SP separates the liquid particles from the process gas. The process gas from which the liquid particles have been removed is discharged as gas E'. The collected liquid is drained through drain DR. This drained liquid may be transferred to the circulating fluid tank HT as needed.

[0057] When a mist separator SP is installed, the pressure regulator can be placed upstream of the mist separator. If it is placed downstream of the mist separator, measures must be taken to prevent the processed gas from leaking from the drain DR.

[0058] Figure 6 shows an application of the technology for using circulating gas disclosed in Patent Document 4. In Figure 6, a portion D of the processed gas E discharged from the reaction vessel T is supplied to the upper side of the reaction vessel T (upstream of the fixed bed FB). For circulation, a blower (gas blower) BL can be used to force the gas to circulate. Except for the configuration related to the circulating gas in Figure 6, the configuration is the same as the methane gas generator in Figure 5.

[0059] As shown in Figure 6, utilizing circulating gas provides the following additional benefits: • It can mitigate the gas concentration gradient at the inlet. • It can apply a uniform load to the entire fixed bed. • Since the amount of treated gas decreases compared to the inlet gas due to the methane production reaction, this can be mitigated.

[0060] Next, Figures 7 and 8 illustrate an embodiment in which the reaction vessel T is composed of multiple containers (T1, T2). Each container is equipped with a fixed bed (FB1, FB2). In Figure 7, the flow of the processed gas (FL1, FL2) in both container T1 and container T2 is in the downward direction.

[0061] On the other hand, in Figure 8, the flow in container T1 is downward FL1, while the flow in container T2 is upward FL2. When the reaction vessel is composed of multiple containers, the multiple containers are connected by gas flow paths E1 so that the process gas passes through them sequentially, and in at least one container (T1 or T2) of the reaction vessel, the process gas is configured to flow vertically from top to bottom (downward direction). In Figure 8, of course, it is also possible to adjust the flow direction of the process gas in the containers so that it flows upward in container T1 and downward in container T2. By adopting a downward direction in at least one container in this way, it is possible to increase the methane gas conversion efficiency in that container. Generally, since container T1, which is upstream of container T2, generates more methane gas, it is preferable to set the flow of the process gas in container T1 to a downward direction.

[0062] In Figure 7, a portion of the processed gas E discharged from the reaction vessel or a portion of the processed gas E1 at an intermediate stage of the reaction vessel's processing is extracted and circulated (D2 or D1) to a reaction vessel upstream of the extraction point in the flow of the processed gas. Various modifications to the circulating gas line can be made by referring to Patent Document 4, for example, it is possible to circulate a portion of the processed gas E discharged from the last reaction vessel (container) T2 to the upstream side of the first reaction vessel (container) T1.

[0063] Furthermore, the liquid LQ accumulated in the liquid storage sections (LR1, LR2) of the containers (T1, T2) is collected in a circulating fluid tank HT. It is also possible to provide a valve to control the supply from the liquid storage sections to the circulating fluid tank HT. If pressurization is required for the transfer of liquid LQ, a pump may be provided in the supply piping. By collecting the liquid accumulated in each liquid storage section into a single tank, it is possible to uniformly manage the state of the nutrients contained in the liquid. The liquid LQ in tank HT is supplied to the liquid supply means ST of each container via piping (L1, L2) using a pump P.

[0064] The methane gas generator of the present invention includes NH as shown in Patent Document 4. ３ Needless to say, removal means (removal devices) and gas separation means (separation devices) can also be used in combination.

[0065] As described above, the present invention provides a methane gas generation apparatus and method that can generate high-concentration methane gas with higher efficiency than conventional methods, even when using microorganisms. Furthermore, it is possible to provide a methane gas generation apparatus and method that can suppress the backflow of liquid into the gas supply pipe even when the apparatus is stopped.

[0066] T, T1-2 Anaerobic biological reactor AD Aeration means LR, LR1-2 Liquid storage section FB, FB1-2 Fixed bed PR Pressure regulator A Gas containing hydrogen B Gas containing carbon dioxide D, D1-2 Circulating gas E, E1 Processed gas FL, FL1-2 Flow direction of processed gas

Claims

1. Hydrogen-containing gas and CO ２ A methane gas generator that supplies a contained gas to an anaerobic biological reactor for microbial treatment to produce methane gas, wherein a fixed bed filled with a carrier to which microorganisms adhere is placed in the reactor, and the flow of the treated gas in the reactor flows from top to bottom in the vertical direction of the fixed bed.

2. In the methane gas generating apparatus according to claim 1, the hydrogen-containing gas and the CO are provided above the fixed bed. ２ A methane gas generating apparatus characterized by having an inlet for the contained gas.

3. A methane gas generating apparatus according to claim 1, characterized in that a liquid supply means for supplying liquid to the fixed bed is arranged above the fixed bed.

4. A methane gas generating apparatus according to claim 3, characterized in that the processed gas is discharged from below the fixed bed to the outside of the reaction tank, the discharged processed gas passes through a mist separator, and liquid particles are separated from the processed gas.

5. A methane gas generating apparatus according to claim 1, characterized in that a portion of the processed gas discharged from the reaction tank or a portion of the processed gas at an intermediate stage of processing in the reaction tank is extracted and circulated to the reaction tank located upstream of the flow of the processed gas from the extraction point.

6. A methane gas generating apparatus according to any one of claims 1 to 5, characterized in that the reaction tank is composed of a single container, and a pressure regulating device for maintaining the gas pressure inside the container within a predetermined range is arranged in the piping for discharging the processed gas from the container.

7. A methane gas generating apparatus according to any one of claims 1 to 5, wherein the reaction tank is composed of a plurality of containers, the fixed bed is arranged in each of the containers, the plurality of containers are connected by gas flow paths so that the processed gas passes through them sequentially, and in at least one of the containers of the reaction tank, the processed gas flows from top to bottom in the vertical direction.

8. A methane gas generating apparatus according to claim 7, characterized in that at least one of the plurality of containers is provided with a pressure regulating device in the piping for discharging the processed gas from the container, for maintaining the gas pressure inside the container within a predetermined range.

9. Hydrogen-containing gases and CO ２ A method for producing methane gas, comprising supplying a contained gas to an anaerobic biological reactor that performs microbial treatment to produce methane gas, wherein a plurality of fixed beds filled with carriers to which microorganisms adhere are arranged in the reactor, and the flow of the treated gas in the reactor flows from top to bottom in the vertical direction of the fixed beds.

10. A method for producing methane gas according to claim 9, characterized in that a liquid is supplied to the fixed bed from above the fixed bed.

11. A method for producing methane gas according to claim 10, characterized in that the processed gas is discharged from below the fixed bed to the outside of the reaction vessel, and liquid particles are separated from the discharged processed gas.

12. A method for producing methane gas according to claim 9, characterized in that a portion of the processed gas discharged from the reaction tank or a portion of the processed gas at an intermediate stage of processing in the reaction tank is extracted and circulated to the reaction tank located upstream of the flow of the processed gas from the extraction point.

13. A method for producing methane gas according to any one of claims 9 to 12, wherein the reaction vessel is composed of a plurality of containers, each of the containers is provided with the fixed bed, the plurality of containers are connected by gas flow paths so that the processed gas passes through them sequentially, and in at least one of the containers of the reaction vessel, the processed gas flows from top to bottom in the vertical direction.

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