Biomass treatment device

Abstract

To provide a biomass treatment device that can increase methane concentration in biogas, thus allowing for diverse applications of biogas.SOLUTION: A wet-type biomass treatment device 1A ferments biomass to produce biogas and is provided with: a fermentation tank 2 for storing the fermented liquid of the biomass; and a gas supply section 5 that supplies hydrogen-containing gas to the fermented liquid. Preferably, a recycling device 7 is provided that filters the fermented liquid to discharge the filtrate, while returning the filtered residue to the fermentation tank 2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a wet-type biomass treatment apparatus that ferments biomass to produce biogas. [Background technology]

[0002] Anaerobic fermentation of organic resources (biomass) derived from living organisms ultimately produces combustible biogas, whose main components are methane and carbon dioxide. The use of biogas has attracted attention from the perspectives of preventing environmental pollution and regenerating energy.

[0003] Anaerobic fermentation of biomass is roughly divided into two stages of biochemical reactions: a solubilization process by hydrolytic bacteria and acid-producing bacteria, and a methane fermentation process by methanogens. Polymeric organic compounds such as proteins, carbohydrates, and fats are first broken down into smaller molecules by hydrolytic bacteria and other bacteria into higher fatty acids, amino acids, and sugars. Next, these small organic compounds are broken down by acid-producing bacteria into hydrogen, CO2, and organic acids (acetic acid, butyric acid, propionic acid, pyruvic acid, formic acid, lactic acid, succinic acid, etc.), and finally, methane is produced by methanogens in the methane fermentation process.

[0004] As a biomass treatment device that produces biogas containing methane and the like by anaerobic fermentation as described above, a device equipped with a single-tank fermenter that performs a solubilization step and a methane fermentation step is known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2012-183481 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the biomass treatment device of Patent Document 1, the biogas contains CO2, which is inevitably produced by the decomposition of low-molecular-weight organic matter by acid-producing bacteria, and therefore the methane concentration in the generated biogas is low at approximately 50 to 60%, and there was a problem that the biogas could only be used for limited purposes.

[0007] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a biomass treatment device that can increase the methane concentration in biogas, thereby enabling the biogas to be used for various purposes. [Means for solving the problem]

[0008] The characteristic configuration of the biomass treatment device according to the present invention for solving the above problems is as follows: A wet biomass treatment device that ferments biomass to produce biogas, A fermenter for storing a fermentation liquid obtained by fermenting the biomass; A gas supply unit for supplying a hydrogen-containing gas to the fermentation liquid; The purpose of this study is to provide

[0009] In the biomass treatment device of this configuration, methane is finally produced from acetic acid, hydrogen and CO2 by the methanogens. The former reaction of producing methane using acetic acid as a substrate is an acetic acid decomposition methane production reaction, which is caused by acetic acid decomposition methanogens. On the other hand, the latter reaction of producing methane using hydrogen and CO2 as substrates is a CO2 reduction methane production reaction, which is caused by hydrogen-utilizing methanogens. According to the biomass treatment device of this configuration, the gas supply unit supplies hydrogen-containing gas to the fermentation liquid in the fermentation tank, so that hydrogen derived from the hydrogen-containing gas supplied by the gas supply unit is contained in the fermentation liquid in addition to hydrogen produced by the decomposition of low-molecular organic matter by the acid-producing bacteria. Then, methane is produced by the CO2 reduction methane production reaction by the hydrogen-utilizing methanogens using the hydrogen derived from the hydrogen-containing gas and the CO2 inevitably produced by the decomposition of low-molecular organic matter by the acid-producing bacteria as substrates. In this way, the methane concentration in the biogas can be increased by reducing CO2 with hydrogen, and the biogas can be used for various purposes.

[0010] In the biomass treatment device according to the present invention, The fermenter has an acid fermentation zone and a methane fermentation zone, The gas supply unit preferably supplies the hydrogen-containing gas to the methane fermentation zone.

[0011] According to the biomass treatment device of this configuration, the fermenter has an acid fermentation zone and a methane fermentation zone. In the acid fermentation zone, an acid production reaction is carried out by acid-producing bacteria to decompose organic matter into lower organic acids such as butyric acid, propionic acid, and acetic acid. On the other hand, in the methane fermentation zone, a methane production reaction is carried out by methanogens to produce methane from acetic acid, hydrogen, and CO2. However, when hydrogen-containing gas from the gas supply unit is supplied to the acid fermentation zone in the fermenter, in addition to hydrogen produced as a by-product in the acid production reaction carried out in the acid fermentation zone, hydrogen derived from the hydrogen-containing gas supplied by the gas supply unit accumulates, and the hydrogen partial pressure increases. As a result, the acetic acid production reaction does not proceed due to product inhibition, and the methane production rate may be slowed down. Therefore, according to the biomass treatment device of this configuration, the hydrogen-containing gas from the gas supply unit is supplied to the methane fermentation zone in the fermenter. This makes it possible to avoid product inhibition in the acid fermentation zone. As a result, in the methane fermentation zone, methane is produced by the acetic acid decomposition methanogenesis reaction using acetic acid as a substrate, and methane is also produced by the CO2 reduction methanogenesis reaction using hydrogen and CO2 as substrates, thereby improving the efficiency of methane production.

[0012] In the biomass treatment device according to the present invention, It is preferable that a partition plate is provided to separate the acid fermentation zone from the methane fermentation zone.

[0013] In the biomass treatment device of this configuration, the partition plate prevents hydrogen from migrating to the acid fermentation zone, originating from the hydrogen-containing gas supplied to the methane fermentation zone. This reliably prevents product inhibition in the acid fermentation zone.

[0014] In the biomass treatment device according to the present invention, It is preferable that the height position of the partition plate in the fermenter is adjustable.

[0015] According to the biomass treatment apparatus of this configuration, the ratio of the acid production reaction in the acid fermentation zone and the methane production reaction in the methane fermentation zone can be easily adjusted by adjusting the height position of the partition plate in the fermenter.

[0016] In the biomass treatment device according to the present invention, The fermenter has an outer tank portion and an inner tank portion which are radially divided, It is preferable that the gas supply unit supplies the hydrogen-containing gas to the outer tank portion or the inner tank portion.

[0017] According to the biomass treatment device of this configuration, the hydrogen-containing gas supplied to the outer tank part or the inner tank part rises in the fermentation liquid as bubbles. The hydrogen-containing gas bubbles rising in the fermentation liquid cause a flow of the fermentation liquid rising in the outer tank part or the inner tank part, and accordingly, a flow of the fermentation liquid descending in the inner tank part or the outer tank part occurs, and a circulation flow occurs between the outer tank part and the inner tank part. While an acid production reaction is carried out in the outer tank part or the inner tank part, a methane production reaction is carried out in the inner tank part or the outer tank part, and the acid production reaction and the methane production reaction are carried out separately, but the acid production reaction and the methane production reaction are carried out in conjunction with each other under the condition that a certain amount of fermentation liquid moves between the outer tank part and the inner tank part due to the circulation flow between the outer tank part and the inner tank part. Therefore, the methane production efficiency can be further improved.

[0018] In the biomass treatment device according to the present invention, It is preferable that a circulation circuit is provided for returning and circulating at least a portion of the generated biogas to the gas supply section.

[0019] According to the biomass processing device of this configuration, at least a portion of the generated biogas is returned to the gas supply section and circulated, whereby the CO2 remaining in the biogas is converted to methane, thereby making it possible to further increase the methane concentration in the biogas.

[0020] In the biomass treatment device according to the present invention, It is preferable to provide a recycling device for filtering the fermentation liquid, discharging the filtrate, and returning the filtered matter to the fermenter.

[0021] According to the biomass treatment device of this configuration, the filtrate (digestive liquid) discharged after filtering the fermentation liquid can be effectively used, for example, as liquid fertilizer. The filtered liquid, which contains a large amount of methane bacteria, is returned to the fermentation tank and reused. This allows the methane bacteria to be maintained at a high concentration in the fermentation tank, allowing fermentation to be carried out efficiently. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic diagram showing a schematic configuration of a biomass treatment apparatus according to a first embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing a schematic configuration of a biomass treatment apparatus according to the second embodiment. [Diagram 3] FIG. 3 is a schematic diagram showing a schematic configuration of a biomass treatment apparatus according to the third embodiment. [Figure 4] FIG. 4 is a schematic diagram showing a schematic configuration of a biomass treatment apparatus according to the fourth embodiment. [Diagram 5] FIG. 5 is a schematic diagram showing a schematic configuration of a biomass treatment apparatus according to the fifth embodiment. [Figure 6] FIG. 6 is a schematic diagram showing a schematic configuration of a biomass treatment apparatus according to the sixth embodiment. [Figure 7] FIG. 7 is a schematic diagram showing a schematic configuration of a biomass treatment apparatus according to the seventh embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, the present invention will be described with reference to the drawings. In this specification, biomass refers to organic resources derived from living organisms. Examples of biomass include organic waste, resource crops, or waste thereof. Examples of organic waste include food waste, feces, sludge, food processing residues, livestock waste, waste oil, animal fats and oils, agricultural crop residues, or organic wastewater in the food industry, paper industry, or livestock industry. Examples of sludge include sewage treatment sludge, human waste treatment sludge, septic tank sludge, and treatment sludge of industrial wastewater generated from food factories and the like. Examples of resource crops include potatoes, sugar beets, rapeseed, sunflowers, wheat, chlorella, water hyacinth, corn, sugarcane, or waste generated in the treatment process thereof. In addition, in this specification, biogas refers to gas generated by fermentation (anaerobic fermentation) of biomass. Examples of components of biogas include hydrogen gas, methane gas, and carbon dioxide gas. In the following embodiments, a wet-type biomass treatment device that ferments organic waste to generate biogas will be described as an example. However, the present invention is not intended to be limited to the embodiments described below or the configurations shown in the drawings.

[0024] First Embodiment <Overall composition> Fig. 1 is a schematic diagram showing a schematic configuration of a biomass processing device 1A of a first embodiment. As shown in Fig. 1, the biomass processing device 1A is a wet fermentation device that includes a fermenter 2, a biomass supply unit 3, an agitator 4, a gas supply unit 5, a biogas recovery unit 6, and a recycling device 7 of an arbitrary configuration, adjusts the solid concentration in the fermenter 2 to about 10% by weight or less, and ferments (methane fermentation) the biomass by a mesophilic fermentation method or a high-temperature fermentation method to generate biogas.

[0025] <Fermentation tank> The fermenter 2 has a cylindrical body 10 with an axis (not shown) oriented in the vertical direction, and is a vertical single tank with the upper and lower sides of the body 10 closed. The fermenter 2 is configured to store a fermentation liquid FL obtained by methane fermentation of biomass, and to fill the space above the liquid level of the fermentation liquid FL with biogas BG.

[0026] <Biomass Supply Division> The biomass supply unit 3 includes a pressure-feed unit 11 and a biomass supply pipe 12. Although detailed explanation using drawings is omitted, the pressure-feed unit 11 includes a pressure-feed pump that pressure-feeds the organic waste, a control valve that controls the pressure-feed amount and pressure, and the like. The biomass supply pipe 12 connects the lower part of the fermenter 2 (the part where the fermentation liquid FL is stored) to the pressure-feed unit 11. In the stage preceding the biomass supply unit 3, the organic waste as the raw material is subjected to treatment such as homogenization of the raw material by removing foreign matter and adjustment to a moisture content suitable for methane fermentation in a pretreatment facility not shown. The organic waste that has been subjected to such pretreatment is supplied to the lower part of the fermenter 2 by the biomass supply unit 3.

[0027] <Stirring device> The agitator 4 is disposed for the purpose of homogenizing the fermentation liquid FL in the fermenter 2 and removing scum that occurs on the surface of the fermentation substrate. Examples of the agitator 4 include mechanical agitation types, gas agitation types, and circulation agitation types, and are not particularly limited, but in this example, a mechanical agitation type is used.

[0028] The mechanical stirring type stirrer 4 used in this example is configured to include a rotating shaft 15 extending in the vertical direction so as to penetrate the top of the fermenter 2 at the center of the top and be disposed within the tank, a drive unit 16 connected to the upper end side of the rotating shaft 15 so as to be capable of transmitting rotational power, and a lower rotor 17 disposed at the bottom of the fermenter 2 and fixed to the lower end side of the rotating shaft 15. In the stirrer 4, the rotational power from the drive unit 16 is transmitted to the lower rotor 17 via the rotating shaft 15 to rotate the lower rotor 17, thereby stirring the fermentation liquid FL in the bottom of the fermenter 2.

[0029] <Gas supply section> The gas supply unit 5 supplies a hydrogen-containing gas to the fermentation liquid FL in the fermenter 2. The hydrogen-containing gas means a gas containing at least 10% hydrogen by volume relative to the total hydrogen-containing gas. The hydrogen gas content in the hydrogen-containing gas is preferably 80% or more, more preferably 90% or more, and most preferably 95% or more. There is no particular upper limit to the hydrogen gas content in the hydrogen-containing gas, and it may be 100%.

[0030] The gas supply unit 5 includes a gas supply source 21 and a gas supply pipe 22. Although detailed description using drawings is omitted, the gas supply source 21 includes a hydrogen storage unit that stores hydrogen gas under high pressure, a pressure reducing valve that reduces the pressure of the high pressure hydrogen gas from the hydrogen storage unit, and the like. The hydrogen used here may be, for example, hydrogen obtained by electrolyzing water using electricity generated by renewable energy such as solar, wind, or geothermal energy, or surplus hydrogen from a nearby petrochemical plant, etc. In the gas supply pipe 22, the upstream end of the gas flow is connected to the gas supply source 21, and the downstream end of the gas flow is arranged so that a hydrogen-containing gas can be blown into the fermentation liquid FL in the fermenter 2.

[0031] <Biogas Recovery Section> The biogas recovery section 6 includes a gas discharge pipe 25 and a gas extraction section 26. In the gas discharge pipe 25, an upstream end of the gas flow is connected to the fermenter 2 so that the biogas BG can be discharged outside the tank, and a downstream end of the gas flow is connected to a gas holder 27. The gas extraction section 26 is interposed in the middle of the gas discharge pipe 25. Then, the biogas BG extracted by the gas extraction section 26 from the inside of the fermenter 2 through the gas discharge pipe 25 is temporarily stored in the gas holder 27 and then effectively utilized. A gas purification device may be connected to the downstream side of the gas flow of the gas holder 27. Examples of the gas purification device include a device that removes hydrogen sulfide from the biogas BG and a device that further reduces CO2 from the biogas BG by pressure swing adsorption (PSA).

[0032] <Reuse equipment> The recycling device 7 includes a reflux pipe 31, a pressure pump 32, and a solid-liquid separator 33. The reflux pipe 31 is disposed in such a manner that it connects an outlet 34 provided near the liquid level of the fermentation liquid FL stored in the fermenter 2 with an inlet 35 provided at the bottom of the fermenter 2. The pressure pump 32 is disposed at a position close to the outlet 34 in the reflux pipe 31. The solid-liquid separator 33 is disposed in the reflux pipe 31 so as to be located between the pressure pump 32 and the inlet 35. In the solid-liquid separator 33, for example, a filtration membrane such as a microfiltration membrane (MF membrane) or an ultrafiltration membrane (UF membrane) can be used, and the shape of the membrane can be, for example, a flat membrane or a hollow fiber membrane. In the recycling device 7, the pressure pump 32 is operated to send the fermentation liquid (methane fermentation digestion liquid) FL remaining after the biogas BG is taken out from the top of the fermenter 2 to the solid-liquid separator 33. The solid-liquid separation device 33 filters the methane fermentation digestion liquid fed from the pressure pump 32, and separates it into a filtrate and a filtrate residue. The filtrate residue is returned to the lower part of the fermenter 2 through the reflux pipe 31 and reused. Meanwhile, the filtrate (filtered digestion liquid) is discharged through a filtrate discharge pipe 36 connected to a filtrate discharge port of the solid-liquid separation device 33. The discharged filtered digestion liquid is collected in a digestion liquid recovery section 37 and is effectively used, for example, as liquid fertilizer. In this embodiment, an example is shown in which a device that separates solid and liquid using a filtration membrane such as an MF membrane or a UF membrane is used as the solid-liquid separation device 33, but the present invention is not limited thereto, and devices such as a rotating drum, a drum screen, a belt press, a screw press, a belt concentrator, a flotation separator, and a sedimentation separator can also be used.

[0033] In the biomass treatment apparatus 1A configured as described above, organic waste is supplied to the lower part of the fermenter 2 by the biomass supply unit 3. Furthermore, a hydrogen-containing gas is blown into the fermentation liquid FL in the fermenter 2 from the gas supply unit 5. Furthermore, the fermentation liquid FL is stirred by the stirring device 4 to homogenize the fermentation liquid FL.

[0034] In the fermenter 2, a two-stage biochemical reaction takes place using organic waste as a substrate: a solubilization process by hydrolytic bacteria and acid-producing bacteria, and a methane fermentation process by methanogens. That is, high molecular weight organic compounds such as proteins, carbohydrates, and fats are first broken down into lower molecular weight compounds by hydrolytic bacteria and the like, resulting in higher fatty acids, amino acids, and sugars. Next, these low molecular weight organic compounds are broken down by acid-producing bacteria into hydrogen, CO2, and organic acids (acetic acid, butyric acid, propionic acid, pyruvic acid, formic acid, lactic acid, succinic acid, etc.), and finally, methane is produced by methanogens in the methane fermentation process.

[0035] The reaction that produces methane using acetic acid as a substrate is called acetic acid decomposition methanogenesis, and this reaction is carried out by acetic acid decomposition methanogens. On the other hand, the reaction that produces methane using hydrogen and CO2 as substrates is called CO2 reduction methanogenesis, and this reaction is carried out by hydrogen-utilizing methanogens.

[0036] In the biomass treatment device 1A of the first embodiment, the hydrogen-containing gas is supplied to the fermentation liquid FL in the fermenter 2 by the gas supply unit 5, so that the fermentation liquid FL contains hydrogen derived from the hydrogen-containing gas supplied by the gas supply unit 5, in addition to the hydrogen generated by the decomposition of low-molecular-weight organic matter by the acid-producing bacteria. Then, methane is generated by a CO2 reduction methane generation reaction by the hydrogen-utilizing methanogens using the hydrogen derived from the hydrogen-containing gas and CO2, which is inevitably generated by the decomposition of low-molecular-weight organic matter by the acid-producing bacteria, as substrates. In this way, the methane concentration in the biogas BG can be increased by reducing CO2 with hydrogen. The biogas BG generated by methane fermentation accumulates above the liquid level of the fermentation liquid FL stored in the fermenter 2, and is collected by the biogas collection unit 6 for effective use.

[0037] The fermentation liquid (methane fermentation digestion liquid) FL remaining after the biogas BG is removed from the top of the fermenter 2 is sent to a solid-liquid separator 33 by a pressure pump 32 and separated into a filtrate and a filtrate cake. The filtrate cake is returned to the fermenter 2. The filtrate cake contains a large amount of methane bacteria, and is reused by returning it to the fermenter 2, thereby maintaining a high concentration of methane bacteria and allowing fermentation to proceed efficiently. Meanwhile, the filtrate (filtered digestion liquid) is collected in a digestion liquid collection section 37 and is effectively utilized, for example, as liquid fertilizer.

[0038] Second Embodiment 2 is a schematic diagram showing a schematic configuration of a biomass processing device 1B of the second embodiment. In the second embodiment, the same or similar parts as those in the first embodiment are denoted by the same reference numerals in the figure, and detailed description thereof is omitted. In the following, the description will be centered on parts unique to the second embodiment.

[0039] In the biomass treatment apparatus 1B of the second embodiment, the fermenter 2 has an acid fermentation zone 41 and a methane fermentation zone 42. That is, the portion of the fermenter 2 in which the fermentation liquid FL is accommodated is divided into a lower region and an upper region, with the lower region being the acid fermentation zone 41 and the upper region being the methane fermentation zone 42. In the acid fermentation zone 41, an acid production reaction is carried out by acid-producing bacteria to decompose organic matter into lower organic acids such as butyric acid, propionic acid, and acetic acid. Meanwhile, in the methane fermentation zone 42, a methane production reaction is carried out by methanogens to produce methane from acetic acid, hydrogen, and CO2.

[0040] Furthermore, in the biomass processing apparatus 1B, the gas supply unit 5 supplies a hydrogen-containing gas to the methane fermentation zone 42. That is, in the gas supply unit 5, the downstream end of the gas flow of the gas supply pipe 22 is disposed at the boundary position between the acid fermentation zone 41 and the methane fermentation zone 42, and bubbles of the hydrogen-containing gas blown into the boundary position rise in the methane fermentation zone 42. In this way, the hydrogen-containing gas is supplied to the methane fermentation zone 42.

[0041] Furthermore, in the biomass processing apparatus 1B, the stirring device 4 further includes an upper-stage rotor 18 fixed to the rotating shaft 15 so as to be able to stir the fermentation liquid in the methane fermentation zone 42. In the biomass processing apparatus 1B, bubbles of the hydrogen-containing gas blown into the boundary position between the acid fermentation zone 41 and the methane fermentation zone 42 rise in the methane fermentation zone 42 and are uniformly dispersed throughout the methane fermentation zone 42 by the stirring action of the upper-stage rotor 18.

[0042] However, if the hydrogen-containing gas from the gas supply unit 5 is supplied to the acid fermentation zone 41, in addition to the hydrogen produced as a by-product in the acid production reaction in the acid fermentation zone 41, hydrogen derived from the hydrogen-containing gas supplied by the gas supply unit 5 will accumulate and the hydrogen partial pressure will increase. As a result, the acetic acid production reaction will not proceed due to product inhibition, and ultimately the methane production rate may slow down.

[0043] Therefore, in the biomass treatment device 1B, the hydrogen-containing gas from the gas supply unit 5 is supplied to the methane fermentation zone 42, rather than to the acid fermentation zone 41. This makes it possible to avoid product inhibition in the acid fermentation zone 41, and in the methane fermentation zone 42, methane is produced by an acetic acid decomposition methanogenesis reaction using acetic acid as a substrate, and methane is produced by a CO2 reduction methanogenesis reaction using hydrogen and CO2 as substrates. Therefore, the methane production efficiency can be improved compared to the biomass treatment device 1A of the first embodiment.

[0044] Third Embodiment 3 is a schematic diagram showing a schematic configuration of a biomass processing device 1C according to a third embodiment. In the third embodiment, the same or similar parts as those in the previous embodiments are denoted by the same reference numerals in the drawings, and detailed descriptions thereof are omitted. In the following, the description will focus on parts unique to the third embodiment (the same applies to the following fourth to seventh embodiments).

[0045] The biomass treatment apparatus 1C of the third embodiment further includes a partition plate 43 disposed at the boundary between the acid fermentation zone 41 and the methane fermentation zone 42 so as to separate the zones, but otherwise has the same configuration as the biomass treatment apparatus 1B of the second embodiment. The partition plate 43 is fixed to the rotating shaft 15, or fixed to the fermenter 2 via a support member such as a stay. A predetermined gap S is provided between the outer periphery of the partition plate 43 and the inner circumferential surface of the body 10. This allows the fermentation liquid FL in the acid fermentation zone 41 to move through the gap S to the methane fermentation zone 42 as organic waste is supplied to the acid fermentation zone 41 by the biomass supply unit 3.

[0046] It goes without saying that the biomass processing apparatus 1C of the third embodiment can provide the same effects as the biomass processing apparatus 1B of the second embodiment. Furthermore, according to the biomass processing apparatus 1C of the third embodiment, the partition plate 43 prevents the hydrogen derived from the hydrogen-containing gas supplied to the methane fermentation zone 42 from moving to the acid fermentation zone 41, so that it is possible to reliably prevent a state in which product inhibition occurs in the acid fermentation zone 41 due to an increase in hydrogen partial pressure.

[0047] Fourth Embodiment FIG. 4 is a schematic diagram showing a schematic configuration of a biomass processing apparatus 1D of the fourth embodiment. In the biomass processing apparatus 1D of the fourth embodiment, a partition plate 43 is arranged to be movable in the vertical direction along the rotating shaft 15, and a lifting mechanism 45 for lifting and lowering the partition plate 43 is arranged, and the height position of the partition plate 43 relative to the fermentation tank 2 can be adjusted by the lifting mechanism 45. The other configurations are the same as those of the biomass processing apparatus 1C of the third embodiment. In addition, in the stirring device 4, it is preferable to configure the upper rotor 18 to move in the vertical direction along the rotating shaft 15 so as to be linked to the lifting and lowering operation of the partition plate 43 by the lifting mechanism 45. In addition, in the gas supply unit 5, it is preferable to configure the height position of the downstream end of the gas flow of the gas supply pipe 22 to be variable, and to move the blowing position (addition position) of the hydrogen-containing gas so as to be linked to the lifting and lowering operation of the partition plate 43 by the lifting mechanism 45.

[0048] It goes without saying that the biomass processing apparatus 1D of the fourth embodiment can provide the same effects as the biomass processing apparatus 1C of the third embodiment. Furthermore, according to the biomass processing apparatus 1D of the fourth embodiment, the ratio of the acid production reaction in the acid fermentation zone 41 and the methane production reaction in the methane fermentation zone 42 can be easily adjusted by adjusting the height position of the partition plate 43 in the fermenter 2.

[0049] Fifth Embodiment 5 is a schematic diagram showing a schematic configuration of a biomass processing apparatus 1E of the fifth embodiment. In the biomass processing apparatus 1E of the fifth embodiment, a return pipe 51 arranged in a form branching from a portion of the gas exhaust pipe 25 between the gas extraction section 26 and the gas holder 27 is connected to a gas supply pipe 22. A circulation circuit 50 is formed by the fermenter 2, the gas exhaust pipe 25, the return pipe 51, and the gas supply pipe 22. The rest of the configuration is the same as that of the biomass processing apparatus 1A of the first embodiment.

[0050] According to the biomass processing device 1E of the fifth embodiment, it goes without saying that the same action and effect as the biomass processing device 1A of the first embodiment can be obtained. Furthermore, in the biomass processing device 1E of the fifth embodiment, at least a part of the biogas BG extracted by the gas extraction unit 26 through the gas exhaust pipe 25 from the inside of the fermenter 2 is returned to the gas supply pipe 22 of the gas supply unit 5 through the return pipe 51 and circulated by the circulation circuit 50. As a result, CO2 remaining in the biogas BG is converted to methane, so that the methane concentration in the biogas BG can be further increased.

[0051] Sixth Embodiment FIG. 6 is a schematic diagram showing a schematic configuration of a biomass processing apparatus 1F of the sixth embodiment. In the biomass processing apparatus 1F of the sixth embodiment, a dividing tube 60 is disposed inside the fermenter 2. The dividing tube 60 is made of a cylindrical member with an axis (not shown) oriented in the vertical direction so as to coincide with the axis of the body 10, and is disposed at a predetermined interval from the inner circumferential surface of the body 10 and disposed so as to float above the bottom of the fermenter 2, and is fixed to the body 10 via a support member such as a stay (not shown). By disposing the dividing tube 60 in the fermenter 2 in this manner, the inside of the fermenter 2 is divided in the radial direction. That is, an outer tank section 61 is formed between the inner circumferential surface of the body 10 and the outer circumferential surface of the dividing tube 60. Meanwhile, an inner tank section 62 located on the inner side of the outer tank section 61 is formed inside the dividing tube 60. In this way, the fermenter 2 has an outer tank section 61 and an inner tank section 62 that are divided in the radial direction.

[0052] In the biomass processing apparatus 1F of the sixth embodiment, a gas supply pipe 22 is disposed so as to extend between the bottom of the fermenter 2 and the inner tank portion 62. A plurality of gas outlet holes are formed in the gas supply pipe 22 so that the hydrogen-containing gas can be blown throughout the fermentation liquid FL between the bottom of the fermenter 2 and the inner tank portion 62, and the hydrogen-containing gas bubbles rise throughout the inner tank portion 62. As a result, the blown hydrogen-containing gas bubbles are uniformly diffused throughout the inner tank portion 62, and the hydrogen-containing gas can be supplied throughout the inner tank portion 62 even without providing the agitator 4 provided in the biomass processing apparatus 1A of the first embodiment.

[0053] In the biomass treatment device 1F, an acid production reaction is carried out in the outer tank section 61 by acid-producing bacteria to decompose organic matter into lower organic acids such as butyric acid, propionic acid, and acetic acid. Meanwhile, in the inner tank section 62, a methane production reaction is carried out by methanogenic bacteria to produce methane from acetic acid, hydrogen, and CO2.

[0054] Incidentally, when the hydrogen-containing gas from the gas supply unit 5 is supplied to the outer tank section 61, in addition to the hydrogen produced as a by-product in the acid production reaction taking place in the outer tank section 61, hydrogen derived from the hydrogen-containing gas supplied by the gas supply unit 5 accumulates, causing an increase in hydrogen partial pressure. As a result, the acetic acid production reaction may not proceed due to product inhibition, and ultimately the methane production rate may slow down.

[0055] Therefore, in the biomass treatment device 1F, the hydrogen-containing gas from the gas supply unit 5 is supplied to the inner tank unit 62, not to the outer tank unit 61. This makes it possible to avoid product inhibition in the outer tank unit 61, and in the inner tank unit 62, methane is produced by an acetic acid decomposition methanogenesis reaction using acetic acid as a substrate, and methane is also produced by a CO2 reduction methanogenesis reaction using hydrogen and CO2 as substrates.

[0056] In the biomass processing apparatus 1F, the hydrogen-containing gas supplied to the inner tank section 62 rises in the fermentation liquid FL as bubbles. The hydrogen-containing gas bubbles rising in the fermentation liquid FL cause a flow of the fermentation liquid FL rising in the inner tank section 62. As a result, a flow of the fermentation liquid FL descending in the outer tank section 61 occurs, and a circulating flow is generated between the outer tank section 61 and the inner tank section 62.

[0057] In the biomass treatment device 1F of the sixth embodiment, an acid production reaction is carried out in the outer tank section 61, and a methane production reaction is carried out in the inner tank section 62. Basically, the acid production reaction and the methane production reaction are carried out separately, but the acid production reaction and the methane production reaction are carried out in conjunction with each other under the condition that a certain amount of fermentation liquor FL moves between the outer tank section 61 and the inner tank section 62 due to a circulation flow between the outer tank section 61 and the inner tank section 62. Therefore, the methane production efficiency can be further improved.

[0058] The downstream end of the gas flow of the gas supply pipe 22 may be disposed so that the hydrogen-containing gas is blown into the fermentation liquid FL between the bottom of the fermenter 2 and the outer tank section 61, and the hydrogen-containing gas is supplied to the outer tank section 61 by causing bubbles of the hydrogen-containing gas to rise in the outer tank section 61. In this case, an acid production reaction takes place in the inner tank section 62, and a methane production reaction takes place in the outer tank section 61.

[0059] Seventh Embodiment 7 is a schematic diagram showing a schematic configuration of a biomass processing apparatus 1G of the seventh embodiment. In the biomass processing apparatus 1G of the seventh embodiment, a return pipe 71 arranged in a form branching from a portion of the gas exhaust pipe 25 between the gas extraction section 26 and the gas holder 27 is connected to a gas supply pipe 22. A circulation circuit 70 is formed by the fermenter 2, the gas exhaust pipe 25, the return pipe 71, and the gas supply pipe 22. The rest of the configuration is the same as that of the biomass processing apparatus 1F of the sixth embodiment.

[0060] According to the biomass processing device 1G of the seventh embodiment, it goes without saying that the same action and effect as the biomass processing device 1F of the sixth embodiment can be obtained. Furthermore, in the biomass processing device 1G of the seventh embodiment, at least a part of the biogas BG extracted by the gas extraction unit 26 through the gas exhaust pipe 25 from inside the fermenter 2 is returned to the gas supply pipe 22 of the gas supply unit 5 through the return pipe 71 and circulated by the circulation circuit 70. As a result, CO2 remaining in the biogas BG is converted to methane, so that the methane concentration in the biogas BG can be further increased.

[0061] The above describes the biomass processing device of the present invention based on several embodiments, but the present invention is not limited to the configurations described in the above embodiments, and the configuration can be appropriately changed within the scope of the spirit of the present invention, such as by appropriately combining the configurations described in each embodiment. [Industrial Applicability]

[0062] The biomass treatment apparatus of the present invention can be used, for example, for producing fuels such as city gas and gas engines. [Explanation of symbols]

[0063] 1A~1G Biomass processing equipment 2 Fermentation tank 5 Gas supply section 7 Reuse equipment 41 Acid Fermentation Zone 42 Methane fermentation zone 43 Partition 50 circulation circuit 61 Outer tank part 62 Inner tank part 70 Circulation circuit

Claims

1. A wet biomass treatment device that ferments biomass to produce biogas, A fermenter for storing a fermentation liquid obtained by fermenting the biomass; A gas supply unit for supplying a hydrogen-containing gas to the fermentation liquid; A biomass treatment device comprising:

2. The fermenter has an acid fermentation zone and a methane fermentation zone, The biomass treatment apparatus according to claim 1 , wherein the gas supply unit supplies the hydrogen-containing gas to the methane fermentation zone.

3. 3. The biomass treatment apparatus according to claim 2, further comprising a partition plate for separating the acid fermentation zone from the methane fermentation zone.

4. 4. The biomass treatment apparatus according to claim 3, wherein the height position of the partition plate in the fermenter is adjustable.

5. The fermenter has an outer tank portion and an inner tank portion which are radially divided, The biomass treatment apparatus according to claim 1 , wherein the gas supply unit supplies the hydrogen-containing gas to the outer tank unit or the inner tank unit.

6. The biomass treatment device according to any one of claims 1 to 5, further comprising a circulation circuit for returning and circulating at least a portion of the generated biogas to the gas supply section.

7. The biomass treatment apparatus according to any one of claims 1 to 5, further comprising a recycling device for filtering the fermentation liquid, discharging the filtrate, and returning the filtered matter to the fermenter.

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