Biogas production device, biogas utilization device, biogas production method, and biogas utilization method

Abstract

To provide a biogas production device and a biogas production method, and a biogas utilization device and a biogas utilization method using the same, wherein the biogas production device and the biogas production method can stably supply a biogas with a high methane concentration to a biogas consumption device.SOLUTION: A biogas production device 1 comprises: a fermentation tank 10 that produces a biogas by anaerobic fermentation of a biomass feedstock; a biogas purification device 20 that concentrates methane in the biogas supplied from the fermentation tank 10 to produce a purified biogas; and a gas tank 30 that stores the purified biogas supplied from the biogas purification device 20, wherein at least a portion of the purified biogas removed from the gas tank 30 is returned to the fermentation tank 10 and is circulated between the fermentation tank 10 and the gas tank 30.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a biogas production device, a biogas utilization device, a biogas production method, and a biogas utilization method. [Background technology]

[0002] From the perspective of waste disposal and the effective use of resources, methane-containing biogas is being generated by methane fermentation from waste materials such as food waste from homes, cafeterias, restaurants, and hotels, livestock manure from farms and piggeries, and food waste from food factories.

[0003] When biogas is consumed in a biogas consuming device such as a generator, typically, only the amount of biogas needed for the operation of the biogas consuming device is extracted from the fermenter, refined in a refinery, and supplied to the biogas consuming device. However, with this method, the amount of biogas consumed changes constantly depending on the number of operating biogas consuming devices and the operating load, which can cause the operating state of the refinery to become unstable and the refinery to be unable to keep up with changes in the operating conditions of the biogas consuming device, resulting in variations in the methane concentration of the biogas. One known device for stabilizing the methane concentration of biogas in a biogas consuming device is one that stores biogas refined in a refinery in a gas tank (gas holder) (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-217322 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in conventional devices such as those described in Patent Document 1, there is a limit to the concentration of methane in biogas, making it difficult to stably supply biogas with a high methane concentration to a biogas consuming device.

[0006] An object of the present invention is to provide a biogas production device and a biogas production method that can stably supply biogas with a high methane concentration to a biogas consumption device, as well as a biogas utilization device and a biogas utilization method that use them. [Means for solving the problem]

[0007] As a means for solving the above problems, the biogas production apparatus (1) described in claim 1 includes a fermenter (10) that generates biogas by anaerobic fermentation of biomass raw material, a biogas refinery (20) that concentrates methane in the biogas supplied from the fermenter (10) to produce purified biogas, and a gas tank (30) that stores the purified biogas supplied from the biogas refinery (20), wherein at least a portion of the purified biogas extracted from the gas tank (30) is returned to the fermenter (10) and circulated between the fermenter (10) and the gas tank (30). According to this configuration, the biogas refinery device (20) can be operated stably regardless of the operating load of the biogas consumption device (3), and biogas with a high methane concentration can be efficiently produced and stably supplied to the biogas consumption device (3).

[0008] The biogas production apparatus (2) described in claim 2 includes a fermenter (10) that generates biogas by anaerobic fermentation of biomass raw material, a biogas refiner (20) that concentrates methane in the biogas supplied from the fermenter (10) to produce purified biogas, and a gas tank (30) that stores the purified biogas supplied from the biogas refiner (20), wherein at least a portion of the purified biogas obtained in the biogas refiner (20) is returned to the fermenter (10) and circulated between the fermenter (10) and the biogas refiner (20). According to this configuration, the biogas refinery device (20) can be operated stably regardless of the operating load of the biogas consumption device (3), and biogas with a high methane concentration can be efficiently produced and stably supplied to the biogas consumption device (3).

[0009] In the biogas production apparatus (1, 2) recited in claim 3, the biogas refinery (20) includes a separator (24) that separates carbon dioxide from the biogas supplied from the fermenter (10). This configuration makes it easier to obtain purified biogas with a high methane concentration, and also makes it easier to make the device more compact.

[0010] The biogas utilization device (100, 200) described in claim 4 includes the biogas production device (1, 2) and a biogas consumption device (3) that operates by consuming the refined biogas produced in the biogas production device (1, 2). According to this configuration, biogas with a high methane concentration can be stably supplied to the biogas consumption device (3) and utilized.

[0011] A biogas production method according to claim 5 is characterized in that biogas is produced in a fermenter (10) by anaerobic fermentation of a biomass raw material, methane in the biogas produced in the fermenter (10) is concentrated in a biogas refinery (20) to produce purified biogas, the purified biogas is stored in a gas tank (30), at least a portion of the purified biogas taken out from the gas tank (30) is returned to the fermenter (10), and the purified biogas is circulated between the fermenter (10) and the gas tank (30). According to this configuration, the biogas refinery device (20) can be operated stably regardless of the operating load of the biogas consumption device (3), and biogas with a high methane concentration can be efficiently produced and stably supplied to the biogas consumption device (3).

[0012] A method for producing biogas as set forth in claim 6 is characterized in that biogas is produced in a fermenter (10) by anaerobic fermentation of a biomass raw material, methane in the biogas produced in the fermenter (10) is concentrated in a biogas refinery (20) to produce purified biogas, the purified biogas is stored in a gas tank (30), at least a part of the purified biogas obtained in the biogas refinery (20) is returned to the fermenter (10), and the purified biogas is circulated between the fermenter (10) and the biogas refinery (20). According to this configuration, the biogas refinery device (20) can be operated stably regardless of the operating load of the biogas consumption device (3), and biogas with a high methane concentration can be efficiently produced and stably supplied to the biogas consumption device (3).

[0013] A biogas utilization method according to claim 7 includes producing purified biogas by the biogas production method, and consuming the purified biogas taken out from a gas tank (30) to operate a biogas consumption device (3). According to this configuration, biogas with a high methane concentration can be stably supplied to the biogas consumption device (3) and utilized.

[0014] In the biogas utilization method described in claim 8, the biogas consumption device (3) is operated while circulating a part of the purified biogas between the fermentation tank (10) and the gas tank (30) or between the fermentation tank (10) and the biogas purification device (20). According to this configuration, the operating conditions of the biogas refinery device (20) are not affected by the operating conditions of the biogas consumption device (3) and do not need to be changed suddenly, thereby enabling stable operation that is less affected by the amount of biogas consumed.

[0015] In the biogas utilization method described in claim 9, when the operation of the biogas consumption device (3) is stopped, all of the purified biogas is circulated between the fermentation tank (10) and the gas tank (30) or between the fermentation tank (10) and the biogas purification device (20). According to this configuration, biogas with a high methane concentration can be supplied to the biogas consumer (3) immediately after the start of operation of the biogas consumer (3). [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a biogas production apparatus and a biogas production method that can stably supply biogas with a high methane concentration to a biogas consumption apparatus, as well as a biogas utilization apparatus and a biogas utilization method that use them. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a block diagram showing an outline of a biogas utilization apparatus 100 according to one embodiment of the present invention. [Figure 2] FIG. 10 is a block diagram showing an outline of a biogas utilization apparatus 200 according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] A biogas utilization apparatus according to one embodiment of the present invention will be described below with reference to the drawings. Note that the dimensions of the drawings shown in the following description are merely examples, and the present invention is not necessarily limited to these. Appropriate changes can be made within the scope of the present invention.

[0019] [First embodiment] (Biogas utilization device) As shown in FIG. 1, the biogas utilization device 100 of this embodiment includes a biogas production device 1 and a biogas consumption device 3 that consumes the refined biogas produced in the biogas production device 1 and operates.

[0020] The biogas consumption device 3 is not particularly limited as long as it is a device that operates by consuming biogas, and can be, for example, a power generation device that uses biogas to generate electricity. Specific examples of the power generation device include an engine generator, a steam turbine generator, and a micro gas turbine generator that use biogas. The number of biogas consumers 3 connected to the biogas production apparatus 1 is not limited to one, and may be two or more.

[0021] The biogas production apparatus 1 includes a fermenter 10, a biogas refinery 20, and a gas tank 30. The biogas refinery 20 includes a dehumidifier 21, a desulfurizer 22, a compressor 23, and a separator 24.

[0022] The fermenter 10 and the dehumidifier 21 are connected by a gas flow path 41. The dehumidifier 21 and the desulfurizer 22 are connected by a gas flow path 42. The desulfurizer 22 and the compression section 23 are connected by a gas flow path 43. A check valve 51 is provided in the gas flow path 43. The compression section 23 and the separation device 24 are connected by a gas flow path 44. The separation device 24 and the gas tank 30 are connected by a gas flow path 45. The gas tank 30 and the biogas consumption device 3 are connected by a gas flow path 46. A valve 52 is provided midway along the gas flow path 46. A gas flow path 47 branches off from the position of the valve 52 in the gas flow path 46, and the end of the gas flow path 47 opposite to the gas flow path 46 is connected to the fermenter 10.

[0023] There are no particular limitations on the gas flow paths 41 to 47, and it is possible to appropriately use known piping, etc. Gas supply means such as a compressor or a vacuum pump, various valves such as an on-off valve, and measuring instruments such as a pressure gauge can be appropriately installed in the gas flow paths 41 to 47.

[0024] The fermenter 10 is a fermenter that contains biomass material and generates biogas by anaerobic fermentation (methane fermentation) of the biomass material. The biogas generated in the fermenter 10 is sent to the dehumidifier 21 through a gas flow path 41. The biomass raw material is not particularly limited, and examples thereof include liquefied waste such as food waste from homes and restaurants, livestock manure from farms and pig farms, and food waste from food factories.

[0025] The fermenter 10 may be provided with, for example, an agitation mixer that agitates the biomass material contained in the fermenter 10, a temperature maintainer that maintains the interior of the fermenter 10 at a predetermined temperature, and the like. The fermenter 10 may also be provided with a circulation flow path that extracts the biomass material from the bottom of the fermenter 10 and circulates it back to the bottom of the fermenter 10. Circulating the biomass material at any desired timing improves the efficiency of anaerobic fermentation of the biomass material.

[0026] The biogas refinery 20 is a device that concentrates methane in biogas to produce purified biogas. The biogas refinery 20 is equipped with a dehumidifier 21 and a desulfurizer 22 that pretreat the biogas before supplying it to a separator 24. Note that the biogas refinery 20 does not necessarily have to be equipped with either or both of the dehumidifier 21 and the desulfurizer 22.

[0027] The dehumidifier 21 is a device that removes moisture from the biogas. The biogas supplied from the fermenter 10 through a gas flow path 41 is dehumidified by the dehumidifier 21 and sent to the desulfurization device 22 through a gas flow path 42. The dehumidifier 21 is not particularly limited, and may be, for example, a heat exchanger that can cool the biogas and discharge the moisture as drain water.

[0028] The desulfurizer 22 is a device that removes H2S from the biogas. H2S in the biogas supplied from the dehumidifier 21 through the gas flow path 42 is removed by the desulfurizer 22, and the biogas is sent to the compression section 23 through the gas flow path 43. The desulfurization device 22 is not particularly limited and may use a desulfurization agent, and may be, for example, a device that blows biogas into water to form fine bubbles and dissolves the H2S in the biogas in the water for removal. The water used for H2S removal is not particularly limited and may be, for example, groundwater, river water, industrial wastewater, tap water, or agricultural water.

[0029] A compression unit 23 and a separation unit 24 are provided downstream of the desulfurization unit 22. The biogas sent from the desulfurization unit 22 through a gas flow path 43 is compressed in the compression unit 23 and supplied to the separation unit 24 through the gas flow path 44. The compression unit 23 is provided to compress the pretreated biogas to a pressure required for treatment in the separation unit 24.

[0030] The compression section 23 may be any compressor capable of compressing the biogas to a predetermined pressure, and a known compressor can be used. The compression section 23 may also be appropriately provided with a known temperature adjustment means (such as a cooler) capable of adjusting the temperature of the biogas supplied to the separation device 24 to a predetermined temperature. The number of compressors in the compression section 23 is not limited to one, and may be two or more. Similarly, the number of temperature adjustment means is not limited to one, and may be two or more.

[0031] The separator 24 is a device that separates carbon dioxide from the biogas and concentrates methane. The purified biogas, from which methane has been concentrated in the separator 24, is sent to the gas tank 30 through a gas flow path 45. The separated gas, which contains carbon dioxide gas separated from the biogas, is discharged through a discharge flow path 48.

[0032] The separator 24 may be any device that can separate carbon dioxide from biogas and concentrate methane, and examples thereof include a membrane separator and a device using the PSA method (pressure swing adsorption method) (hereinafter also referred to as a "PSA adsorption separator"). Of these, a membrane separator is preferred because it is easy to obtain purified biogas with a high methane concentration and is compact.

[0033] A membrane separation device is a separation device that has a separation membrane housed in a casing and utilizes the fact that components permeate the separation membrane at different speeds. The separation membrane may be a hollow fiber membrane or a flat membrane, with a hollow fiber membrane being preferred. The dimensions of the hollow fiber membrane are not particularly limited, and can be, for example, an outer diameter of 0.4 to 0.9 mm, an inner diameter of 0.2 to 0.6 mm, and a membrane thickness of 0.2 to 0.3 mm.

[0034] The material of the separation membrane is not particularly limited, and either an inorganic membrane or an organic membrane may be used. Examples of inorganic membranes include a composite membrane of a ceramic or other carrier and zeolite or the like. Examples of organic membranes include polysulfone, cellulose acetate, and polyamide, with polysulfone being preferred. Membranes made of these materials have a high membrane permeation rate for carbon dioxide and a low membrane permeation rate for methane. Therefore, gas that does not permeate the separation membrane can be recovered as purified biogas with an increased methane concentration. Membranes made of these materials also have a high membrane permeation rate for water vapor as well as carbon dioxide. Therefore, the moisture content in the purified biogas can also be reduced. However, because moisture places a load on the separation membrane, in this embodiment, the moisture content of the biogas supplied to the separator 24 is reduced in advance by the dehumidifier 21.

[0035] In a PSA adsorption separator, methane and carbon dioxide are separated by the difference in the adsorption rate between methane and carbon dioxide in the adsorbent packed in the adsorption tower. The adsorbent may be one that adsorbs carbon dioxide more easily than methane, or one that adsorbs methane more easily than carbon dioxide. The desorption of the components adsorbed by the adsorbent may be set according to the conditions during adsorption. For example, if adsorption is performed under pressurized conditions, desorption is performed by reducing the pressure, and if adsorption is performed under reduced pressure, desorption is performed by applying pressure. Depending on the adsorbent, adsorption or desorption may be performed under atmospheric pressure.

[0036] The gas tank 30 may be any known gas tank (gas holder) as long as it can store purified biogas. The purified biogas extracted from the gas tank 30 can be supplied to the biogas consumption device 3 through a gas flow path 46, and can also be returned to the fermenter 10 through a gas flow path 47 from a branch point where a valve 52 is provided. The purified biogas returned to the fermenter 10 circulates within the biogas production apparatus 1 between the fermenter 10 and the gas tank 30.

[0037] (Biogas production method) Hereinafter, an example of the method for producing biogas according to the present invention will be described, in which the biogas production apparatus 1 is used. In this embodiment, biogas is first produced by anaerobic fermentation of biomass raw materials in a fermenter 10. Biogas is produced when organic matter in the biomass is decomposed by anaerobic microorganisms. Most of the components of biogas are methane and carbon dioxide, and it also contains moisture due to the fermentation atmosphere.

[0038] The anaerobic microorganisms used in the fermenter 10 are not particularly limited. The temperature inside the fermenter 10 may be adjusted appropriately to a temperature favorable for fermentation, for example, about 35 to 60°C. Furthermore, fermentation efficiency can be improved by periodically stirring the biomass inside the fermenter 10 during fermentation. Furthermore, fermentation efficiency can be improved by withdrawing the biomass from the fermenter 10 at any time and returning it to the fermenter 10 to circulate the biomass.

[0039] The ratio of methane to carbon dioxide in the biogas produced in the fermenter 10 depends on the type of waste and the fermentation conditions, but for example, the proportion of methane is about 60% by volume, with the remaining 40% by volume being carbon dioxide.

[0040] The biogas produced in the fermenter 10 is sent to the biogas refinery 20, where the carbon dioxide is separated and the methane is concentrated to produce a refined biogas. In this example, the biogas produced in the fermenter 10 is pretreated by dehumidification using a dehumidifier 21 and desulfurization using a desulfurization device 22. The pretreated biogas is then compressed to a predetermined pressure in a compression section 23 and supplied to a separation device 24, where the carbon dioxide is separated and the methane is concentrated by membrane separation, adsorption separation, or the like.

[0041] When the separator 24 is a membrane separator, the pressure of the biogas supplied to the separator 24 is set appropriately depending on the required methane concentration of the purified biogas, etc. To obtain purified biogas containing a high concentration of methane, the pressure of the biogas supplied to the separator 24 is set higher. To increase the yield of purified biogas, the pressure of the biogas supplied to the separator 24 is set lower.

[0042] The temperature of the biogas supplied to the separator 24 can be set appropriately. When the separator 24 is a membrane separator, the temperature of the biogas supplied to the separator 24 can be, for example, 40 to 60°C, preferably 45 to 55°C, depending on the material of the separation membrane. When the separator 24 is a PSA adsorption separator, the temperature of the biogas supplied to the separator 24 can be, for example, 30 to 60°C, preferably 40 to 50°C.

[0043] The purified biogas obtained in the biogas purification device 20 is sent to and stored in the gas tank 30. In this example, at least a portion of the purified biogas taken out from the gas tank 30 is returned to the fermenter 10 and circulated between the fermenter 10 and the gas tank 30. By circulating at least a portion of the purified biogas in the biogas production device 1, the methane concentration of the purified biogas can be further increased.

[0044] (How to use biogas) An example of a method for utilizing biogas will also be described. In the biogas utilization method using the biogas utilization apparatus 100 of this embodiment, biogas is produced using the biogas production apparatus 1 as described above. Then, the purified biogas extracted from the gas tank 30 is supplied to the biogas consumption apparatus 3, and the biogas is consumed to operate the biogas consumption apparatus 3. For example, if a generator is used as the biogas consumption apparatus 3, power can be generated using the biogas produced in the biogas production apparatus 1. By storing the purified biogas in the gas tank 30, even when the biogas consumption apparatus 3 is operating under high load or when there are a large number of biogas consumption apparatuses 3, the biogas refinery apparatus 20 does not need to be operated under high load, and the refining energy can be reduced.

[0045] In the biogas utilization method of this embodiment, a portion of the purified biogas extracted from the gas tank 30 is returned to the fermenter 10 and circulated between the fermenter 10 and the gas tank 30, while the remainder of the purified biogas is sent to the biogas consumer 3, thereby operating the biogas consumer 3. For example, when the biogas consumer 3 is operated under a light load, the operating conditions of the biogas refiner 20 are not changed to a low load to match the load, and biogas at a flow rate exceeding the flow rate required to operate the biogas consumer 3 is refined, and the surplus is returned to the fermenter 10 for circulation. This increases the methane concentration of the biogas at the inlet of the biogas refiner 20, thereby further increasing the methane concentration of the biogas supplied to the biogas consumer 3. Furthermore, since there is no need to suddenly change the operating conditions of the biogas refiner 20, stable operation that is less affected by the amount of biogas consumed is possible.

[0046] When the operation of the biogas consumer 3 is stopped, all of the purified biogas can be circulated between the fermenter 10 and the gas tank 30. For example, when the operation of the biogas consumer 3 is stopped, the biogas refinery 20 is operated at a low flow rate to save energy, and all of the purified biogas is returned to and circulated in the fermenter 10. This makes it possible to supply biogas with a high methane concentration to the biogas consumer 3 immediately after the start of operation of the biogas consumer 3.

[0047] When returning the purified biogas to the fermenter 10, it is preferable to return the purified biogas to the lower part (liquid phase part) of the fermenter 10 under a slight positive pressure. This agitates the biomass material in the fermenter 10, and promotes fermentation.

[0048] [Second embodiment] (Biogas utilization device) As shown in Figure 2, a biogas utilization device 200 of this embodiment includes a biogas production device 2 and a biogas consumption device 3 that operates by consuming the refined biogas produced in the biogas production device 2. The same parts in Figure 2 as those in Figure 1 are designated by the same reference numerals, and their explanation will be omitted.

[0049] The biogas utilization apparatus 200 is similar in configuration to the biogas utilization apparatus 100 except that a biogas production apparatus 2 is provided instead of the biogas production apparatus 1. The biogas production apparatus 2 is similar to the biogas production apparatus 1, except that instead of the gas flow path 47 branching off from the gas flow path 46 connecting the gas tank 30 and the biogas consumption apparatus 3, the gas flow path 47 branching off from the gas flow path 45 connecting the separation device 24 and the gas tank 30.

[0050] In the biogas utilization device 200, at least a portion of the purified biogas obtained in the biogas refinery device 20 is returned to the fermenter 10 through the gas flow path 47 from the branching point of the gas flow path 45. The purified biogas returned to the fermenter 10 circulates within the biogas production device 1 between the fermenter 10 and the biogas refinery device 20.

[0051] (Biogas production method) In the method of producing biogas using the biogas production apparatus 2, as in the case of using the biogas production apparatus 1, biogas is produced in the fermentation tank 10, and carbon dioxide is separated from the biogas in the biogas purification apparatus 20 to obtain purified biogas. The purified biogas obtained in the biogas refinery apparatus 20 can be sent to and stored in a gas tank 30. In this example, at least a portion of the purified biogas obtained in the biogas refinery apparatus 20 is returned to the fermenter 10 and circulated between the fermenter 10 and the biogas refinery apparatus 20. By circulating at least a portion of the purified biogas in the biogas production apparatus 2, the methane concentration of the purified biogas can be further increased.

[0052] (How to use biogas) In the biogas utilization method using the biogas utilization apparatus 200 of this embodiment, biogas is produced using the biogas production apparatus 2 as described above. Then, the purified biogas extracted from the gas tank 30 is supplied to the biogas consumption apparatus 3, and the biogas is consumed to operate the biogas consumption apparatus 3. Even in the aspect using the biogas utilization apparatus 200, by storing the purified biogas in the gas tank 30, even when the biogas consumption apparatus 3 is operated under high load or when there are a large number of biogas consumption apparatuses 3, the biogas refinery apparatus 20 does not need to be operated under high load, and the refining energy can be reduced.

[0053] Furthermore, the biogas consumption device 3 can be operated by returning a portion of the purified biogas obtained in the biogas refinery device 20 to the fermenter 10 and circulating it between the fermenter 10 and the biogas refinery device 20, while sending the remainder of the purified biogas to the gas tank 30 and then from the gas tank 30 to the biogas consumption device 3. This increases the methane concentration of the biogas at the inlet of the biogas refinery device 20, just as in the case of using the biogas utilization device 100, and therefore the methane concentration of the biogas supplied to the biogas consumption device 3 can be further increased. Furthermore, since there is no need to suddenly change the operating conditions of the biogas refinery device 20, stable operation that is less affected by the amount of biogas consumed becomes possible.

[0054] When the operation of the biogas consumption apparatus 3 is stopped, all of the purified biogas can be circulated between the fermenter 10 and the biogas purification apparatus 20. As a result, similar to the case where the biogas utilization apparatus 100 is used, biogas with a high methane concentration can be supplied to the biogas consumption apparatus 3 immediately after the start of operation of the biogas consumption apparatus 3.

[0055] As described above, in the embodiment of the present invention, the biogas refinery can be operated stably regardless of the operating load of the biogas consumption device, and biogas with a high methane concentration can be efficiently produced and stably supplied to the biogas consumption device.

[0056] The embodiments of the present invention are not limited to the biogas utilization devices 100, 200, the biogas production devices 1, 2, and the biogas production and biogas utilization methods using them. For example, depending on the composition of the biogas produced in the fermenter 10, the biogas refinery device 20 may not be equipped with the desulfurization device 22. Furthermore, if the degree of compression is small and the temperature of the biogas after compression is sufficiently low, the compression section 23 may not be equipped with a cooler as a temperature adjustment means. In addition, within the scope of the present invention, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described modifications may be combined as appropriate. [Explanation of symbols]

[0057] 1, 2...Biogas production device, 3...Biogas consumption device, 10...Fermentation tank, 20...Biogas purification device, 21...Dehumidification device, 22...Desulfurization device, 23...Compression section, 24...Separation device, 30...Gas tank, 100, 200...Biogas utilization device.

Claims

1. Biogas is produced by anaerobic fermentation of biomass materials in a fermentation tank. A membrane separation device provided in the biogas purification device concentrates methane in the biogas produced in the fermenter to produce purified biogas; storing the purified biogas in a gas tank; Producing purified biogas by a biogas producing method in which at least a portion of the purified biogas taken out from the gas tank is returned to the fermenter and circulated between the fermenter and the gas tank; and and operating a biogas consuming device by consuming the purified biogas extracted from the gas tank; During operation of the biogas consumption device, the biogas purification device purifies the biogas at a flow rate exceeding the flow rate required for operation of the biogas consumption device, and circulates the surplus purified biogas between the fermenter and the gas tank to increase the methane gas concentration of the biogas supplied to the biogas consumption device; When the operation of the biogas consumption device is stopped, all of the purified biogas is circulated between the fermenter and the gas tank, thereby increasing the methane gas concentration of the biogas supplied to the biogas consumption device immediately after starting operation.

2. Biogas is produced by anaerobic fermentation of biomass materials in a fermentation tank. A membrane separation device provided in the biogas purification device concentrates methane in the biogas produced in the fermenter to produce purified biogas; storing the purified biogas in a gas tank; Producing purified biogas by a biogas production method in which at least a portion of the purified biogas obtained in the biogas refinery is returned to the fermenter and circulated between the fermenter and the biogas refinery; and and operating a biogas consuming device by consuming the purified biogas extracted from the gas tank; During operation of the biogas consumption device, the biogas refiner refines biogas at a flow rate exceeding a flow rate required for operation of the biogas consumption device, and circulates the surplus purified biogas between the fermenter and the biogas refiner to increase the methane gas concentration of the biogas supplied to the biogas consumption device; When the operation of the biogas consumption device is stopped, all of the purified biogas is circulated between the fermenter and the biogas purification device, and the methane gas concentration of the biogas supplied to the biogas consumption device immediately after starting operation is increased.

Images