Hydrogen generator

Abstract

To provide a hydrogen generator capable of efficiently generating hydrogen from biomass raw materials containing cellulose. [Solution] The hydrogen generator 100 comprises a saccharification treatment device 10 for saccharifying biomass raw material with subcritical water, a first slurry preparation tank 20 for preparing a first slurry by adding water and stirring the saccharified material obtained by the saccharification treatment, a second slurry preparation tank 30 for preparing a second slurry by mixing the first slurry with hyperthermophilic bacteria and water, a fermentation reaction tank 40 for carrying out fermentation by hyperthermophilic bacteria in the second slurry, and a hydrogen gas storage tank T1 for storing hydrogen gas generated by fermentation. The saccharification treatment device and the first slurry preparation tank, the first slurry preparation tank and the second slurry preparation tank, the second slurry preparation tank and the fermentation reaction tank, and the fermentation reaction tank and the hydrogen gas storage tank are each connected via a transport path that maintains an anaerobic environment.

Description

Technical Field

[0001] The present invention relates to a hydrogen generator.

Background Art

[0002] From the viewpoint of reducing environmental load, waste generated in the manufacturing industries of paper, food, lumber, etc., and in the manufacturing or production of agriculture, forestry, etc. contains a large amount of organic substances such as fibrous cellulose, and thus is desired to be utilized as organic resources (biomass). Also, hydrogen gas has attracted attention as a clean energy alternative to fossil fuels. Producing hydrogen gas from the above-mentioned waste is promising for the realization of a decarbonized society.

[0003] As a method for producing hydrogen gas from biomass, for example, the methods disclosed in Patent Document 1 and Non-Patent Document 1 are known. These documents disclose a method for producing hydrogen by culturing Thermococcus kodakarensis, which is a hyperthermophilic bacterium, using an insoluble dietary fiber such as wood, paper, waste crops, or a culture solution containing a cellulose-based polysaccharide. In Patent Document 1, a wood material is used as a substrate, and in Non-Patent Document 1, food starch (potato) is used as a substrate.

[0004] On the other hand, when using the above-mentioned by-products or waste as biomass, it has been proposed to perform pretreatment with subcritical water from the viewpoint of energy recovery efficiency, etc. Non-Patent Document 2 discloses a method for producing glucose by hydrolyzing biomass waste such as paper sludge with subcritical water and further saccharifying the hydrolyzate with cellulase enzyme.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Non-Patent Documents

[0006] [Non-Patent Document 1] Tadayuki Imanaka, Journal of the Environmental Biotechnology Society, Vol. 9, No. 2, 65-68, 2009, "Continuous Hydrogen Production from Waste Biomass by Hyperthermophilic Bacteria" [Non-Patent Document 2] Takeshi Sako, Izumi Okajima, SciencePortal China No. 36: Resource Recycling Technology, September 15, 2009, "Development of Effective Utilization Technology for Biomass Waste Using Subcritical and Supercritical Water" [Retrieved July 8, 2024], Internet (URL: https: / / spc.jst.go.jp / hottopics / 0910recycle / r0910_sako.html) [Overview of the project] [Problems that the invention aims to solve]

[0007] From the descriptions in Patent Document 1 and Non-Patent Document 1, it is understood that when biomass containing cellulose, such as wood material, is used as a substrate, high-temperature heating is required compared to food starch, and in addition, the rate of hydrogen gas generation is low. The reason for this is thought to be the difficulty in decomposing cellulose, but the hydrogen generation rate (amount) in the technologies disclosed in Patent Document 1 and Non-Patent Document 1 is on a laboratory level and has little industrial feasibility. To address this problem, it is conceivable to perform a pretreatment to reduce the molecular weight of cellulose using subcritical water, as in the technology described in Non-Patent Document 2, but the treated material after treatment with subcritical water is difficult to use as a substrate for hyperthermophilic bacteria from the standpoint of fermentation conditions, etc., and it has been difficult to apply this pretreatment directly to stable hydrogen production.

[0008] The present invention aims to provide a hydrogen generator capable of efficiently generating hydrogen from biomass raw materials containing cellulose. [Means for solving the problem]

[0009] The present invention achieves the above objective by providing a hydrogen generator comprising: a saccharification treatment apparatus for saccharifying a cellulose-containing biomass raw material with subcritical water; a first slurry preparation tank for preparing a first slurry by adding water and stirring the saccharified product obtained by the saccharification treatment to a constant concentration; a second slurry preparation tank for preparing a second slurry by mixing the first slurry, hyperthermophilic bacteria, and water to a concentration suitable for fermentation by the hyperthermophilic bacteria in the saccharified product; a fermentation reaction tank for carrying out fermentation by the hyperthermophilic bacteria in the second slurry; and a hydrogen gas storage tank for recovering and storing the hydrogen gas generated by the fermentation, wherein the saccharification treatment apparatus and the first slurry preparation tank, the first slurry preparation tank and the second slurry preparation tank, the second slurry preparation tank and the fermentation reaction tank, and the fermentation reaction tank and the hydrogen gas storage tank are each connected via a transport path that maintains an anaerobic environment.

[0010] Furthermore, in the hydrogen generating apparatus of the present invention, it is preferable that in the first slurry preparation tank, the first slurry is prepared to be within a temperature range suitable for the growth of the hyperthermophilic bacteria and to be weakly acidic, and in the second slurry preparation tank, the second slurry is prepared to be within a temperature range suitable for the fermentation of the saccharified product by the hyperthermophilic bacteria and to be weakly acidic.

[0011] Furthermore, it is preferable that the hydrogen generator of the present invention includes a hot water storage tank for recovering steam derived from the subcritical water and storing hot water, and that the hot water storage tank and at least one of the first slurry preparation tank and the second slurry preparation tank are connected via a hot water transport path in which an anaerobic environment is maintained.

[0012] Furthermore, the hydrogen generator of the present invention preferably includes an organic acid storage tank for recovering and storing an organic acid solution containing organic acids produced by the fermentation, and the organic acid storage tank and at least one of the first slurry preparation tank and the second slurry preparation tank are connected via a transport path that maintains an anaerobic environment.

[0013] Furthermore, the hydrogen generator of the present invention preferably comprises a hot water storage tank for recovering steam derived from the subcritical water and storing hot water, and an organic acid storage tank for recovering and storing an organic acid solution containing organic acids produced by the fermentation, wherein the hot water storage tank and the organic acid storage tank are connected to a second slurry preparation tank via a transport path that maintains an anaerobic environment, and further preferably comprises a control unit that controls the amount of hot water and the organic acid solution supplied to the slurry being prepared in the second slurry preparation tank according to at least one of the concentration, temperature, and pH of the saccharified product in the slurry being prepared.

[0014] Furthermore, the hydrogen generator of the present invention is equipped with a hot water storage tank that recovers steam derived from the subcritical water and stores hot water, and the fermentation reaction tank has a double structure having an inner container and an outer container surrounding the inner container, and it is preferable that the fermentation reaction tank is kept warm within a temperature range suitable for the fermentation of the saccharified product by the hyperthermophilic bacteria by supplying hot water from the hot water storage tank between the inner container and the outer container.

[0015] Furthermore, in the hydrogen generating device of the present invention, it is preferable that the hyperthermophilic bacterium is Thermococcus kodakarensis.

[0016] Furthermore, the hydrogen generator of the present invention preferably uses Thermococcus kodakarensis KOD1 (depositary: Patent Organism Depositary Center, National Institute of Advanced Industrial Science and Technology, accession number: FERM P-15007). [Effects of the Invention]

[0017] According to the hydrogen generator of the present invention, hydrogen can be efficiently generated from biomass raw materials containing cellulose. [Brief explanation of the drawing]

[0018] [Figure 1]FIG. 1 is a schematic diagram showing a preferred embodiment of the hydrogen generation device of the present invention. [Figure 2] FIG. 2 is an explanatory diagram for explaining the flow of each step performed by the hydrogen generation device shown in FIG. 1. [Figure 3] FIG. 3 is a diagram corresponding to FIG. 2 for explaining another flow. [Figure 4] FIG. 4 is a diagram corresponding to FIG. 2 for explaining yet another flow.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, the present invention will be described based on its preferred embodiments with reference to the drawings. FIG. 1 shows a preferred embodiment of the hydrogen generation device of the present invention. The hydrogen generation device 100 of the present embodiment includes a saccharification treatment device 10 that performs saccharification treatment with subcritical water, a first slurry preparation tank 20 that prepares a first slurry using the saccharification product obtained by the saccharification treatment, a second slurry preparation tank 30 that mixes a hyperthermophilic bacterium into the first slurry to prepare a second slurry, a fermentation reaction tank 40 that performs fermentation by the hyperthermophilic bacterium in the second slurry, a gas recovery and separation device T that separates hydrogen gas from the fermentation gas generated by the fermentation, and a waste treatment device 50 that performs solid-liquid separation on the second slurry after the fermentation.

[0020] The saccharification treatment device 10 of the present embodiment saccharifies a biomass raw material containing cellulose with subcritical water (steam under high temperature and high pressure). As such a saccharification treatment device 10, for example, the subcritical water treatment device disclosed in Japanese Patent Application Laid-Open No. 2021-74651 can be used. The saccharification treatment device 10 of the present embodiment includes a treatment tank 15 that treats a biomass raw material containing cellulose with subcritical water, and a stirrer 11 in which a stirring shaft 13 is installed in the treatment tank 15. The processing tank 15 is a long, unidirectional pressure vessel with a sealed internal space and possesses heat and pressure resistance. The processing tank 15 includes a raw material introduction section 15a for introducing biomass raw materials and water, a steam introduction passage 15b for introducing high-temperature, high-pressure steam, a discharge section 15c for discharging the saccharified product obtained by the saccharification process, and a steam discharge passage 15d for reducing the pressure of the steam inside the processing tank 15 and discharging it outside the processing tank 15.

[0021] The raw material introduction section 15a and the discharge section 15c are tubular sections that communicate with the inside of the processing tank 15, and are equipped with opening and closing mechanisms B10 and B1. The raw material introduction section 15a and the discharge section 15c are opened and closed by the opening and closing mechanisms B10 and B1. These opening and closing mechanisms allow the inside of the processing tank 15 to be closed off. The discharge section 15c is connected to a first transport path C1, which is connected to a first slurry preparation tank 20. High-temperature, high-pressure steam is introduced into the treatment tank 15 from the hot water / steam supply unit 16 via the steam inlet passage 15b. The hot water / steam supply unit 16 heats water using waste heat from the plant or a heat source such as a boiler to generate hot water and high-temperature, high-pressure steam. This steam is sent to the treatment tank 15 by a high-pressure feed pump or the like (not shown). The steam discharge passage 15d is connected to the steam delivery passage F1, which is connected to the hot water storage tank 17. The steam delivery passage F1 is opened and closed by the discharge valve B11. By opening this discharge valve B11, steam from the treatment tank 15 is sent to the hot water storage tank 17, and the pressure inside the treatment tank 15 can be reduced. Alternatively, by closing the discharge valve B11 and introducing high-temperature, high-pressure steam from the hot water / steam supply unit 16, the pressure inside the treatment tank 15 can be increased.

[0022] The agitator 11 comprises a stirring shaft 13 arranged inside the processing tank 15 along the direction of the processing tank 15, a plurality of stirring blades 14 arranged along the stirring shaft 13, and a motor 12 located at one end of the stirring shaft 13. The end of the stirring shaft 13 where the motor 12 is located protrudes outside the processing tank 15. The agitator 11 can mix and stir the biomass raw material and subcritical water inside the processing tank 15 by rotating the stirring shaft 13 with the power of the motor 12.

[0023] Cellulose, the target of saccharification treatment, is a high-molecular-weight compound in which glucose units are linked by 1,4-β-glycosidic bonds. Examples of biomass raw materials containing cellulose (hereinafter also simply referred to as "biomass raw materials") include woody biomass such as wood, cotton, hemp, flax, straw, sugarcane, and corn stalks, as well as by-products such as waste paper, pulp residues removed in the papermaking process, dust, wastewater, and paper sludge (organic sludge). From the viewpoint of performing saccharification treatment more stably, it is preferable that the biomass raw material introduced into the saccharification treatment apparatus 10 is pulp-based biomass.

[0024] Biomass raw materials are introduced into the treatment tank 15 along with water via the raw material introduction section 15a. The biomass raw materials may be introduced into the treatment tank 15 after being dispersed in water to form a slurry (hereinafter also referred to as "raw material slurry"), or they may be introduced into the treatment tank 15 in a solid or semi-solid state without being dispersed in water. In the latter case, water is introduced into the treatment tank 15 before or after the introduction of the biomass raw materials.

[0025] Subcritical water used in saccharification is hot water that is below the critical point of water in terms of temperature and pressure. In this specification, subcritical water is defined as water at a temperature of 150°C to 350°C and a pressure of 1 to 8 MPa. Details of various conditions, such as the processing conditions for saccharification, slurry preparation conditions, and fermentation conditions, will be described later.

[0026] The biomass raw material introduced into the processing tank 15 undergoes saccharification treatment, thereby obtaining a saccharified product. The saccharified product is transported to the first slurry preparation tank 20 via the discharge section 15c and the first transport path C1 connected thereto. The saccharified product is a solid substance containing moisture and has a pulp-like appearance. Due to the influence of subcritical water, the temperature of the saccharified product is very high immediately after saccharification. Furthermore, the saccharified product contains low-molecular-weight polysaccharides obtained by hydrolysis of cellulose, oligosaccharides (disaccharides or more), glucose (monosaccharide), etc., as well as impurities (trace amounts of low-molecular-weight organic substances and inorganic substances, etc.).

[0027] The first slurry preparation tank 20 prepares the first slurry by adding water to the saccharified material and stirring it. The first slurry preparation tank 20 of this embodiment comprises a first sealed tank 25 and an agitator 21 provided inside the sealed tank 25. The first sealed tank 25 is capable of maintaining a closed internal space. The first sealed tank 25 has a first transport path C1 connected to its upper part and a second transport path C2 connected to its lower part. The second transport path C2 is provided with an on-off valve B2, which opens and closes the second transport path C2. The first sealed tank 25 is also connected to a hot water introduction path F4 through which hot water is introduced and an organic acid solution introduction path F5. Furthermore, a vacuum pump 26 is connected to the first sealed tank 25 via piping, which allows for reduced pressure inside the tank 25. This reduced pressure moves the saccharified material in the processing tank 15 to the discharge section 15c, and allows it to be drawn (suctioned) into the first sealed tank 25 via the first transport path C1.

[0028] The agitator 21 comprises an agitator shaft 23 that extends vertically through the top surface of the first sealed tank 25 and hangs down into the tank, and an agitator blade 22 provided at the tip of the agitator shaft 23. The agitator 21 can obtain a first slurry by mixing and stirring the saccharified material and hot water introduced into the sealed tank 25 through the rotation of the agitator shaft 23 by the power of a motor (not shown). The first slurry has a predetermined concentration of the saccharified material. The first slurry is transported to the second slurry preparation tank 30 via the second transport path C2.

[0029] The second slurry preparation tank 30 prepares the second slurry by mixing the first slurry with hyperthermophilic bacteria and water. The second slurry preparation tank 30 of this embodiment comprises a second sealed tank 35 and a stirrer 31 provided inside the sealed tank 35. The second sealed tank 35 has the same configuration as the first sealed tank 25, except that the connection configuration of each transport path and introduction path is different. The second sealed tank 35 has a second transport path C2 and a third transport path C3 connected to its lower part, and a bacterial introduction path C4 connected to its upper part. The third transport path C3 is provided with an on-off valve B3, which opens and closes the third transport path C3. The second sealed tank 35 is connected to a hot water introduction path F6 through which hot water is introduced, an organic acid solution introduction path F7, and a bacterial introduction path C4.

[0030] The agitator 31 in the second slurry preparation tank 30 has the same configuration as the agitator 21 in the first slurry preparation tank 20. The agitator 31 in the second slurry preparation tank 30 can mix and stir the first slurry, hyperthermophilic bacteria, and water introduced into the second sealed tank 35 by rotating the stirring shaft 33 with the power of a motor (not shown). In the second slurry preparation tank 30, the first slurry is mixed with water (hot water) introduced into the second slurry preparation tank 30 (second sealed tank 35) via the hot water introduction channel F6, and with hyperthermophilic bacteria introduced into the second slurry preparation tank 30 (second sealed tank 35) via the bacteria introduction channel C4 to obtain the second slurry. At this time, the concentration of the saccharified product in the second slurry is adjusted to a concentration suitable for fermentation of the saccharified product by the hyperthermophilic bacteria. In addition, the second slurry is prepared in the second slurry preparation tank 30 under light-shielding conditions. The second slurry obtained in the second slurry preparation tank 30 is transported to the fermentation reactor 40 via the third transport path C3.

[0031] The hydrogen generator 100 of this embodiment is equipped with a bacterial acclimatization tank 70 for culturing hyperthermophilic bacteria. The bacterial acclimatization tank 70 is a culture tank for hyperthermophilic bacteria and contains a slurry similar to the second slurry (hereinafter also referred to as "bacteria-containing slurry"). The culture environment in the bacterial acclimatization tank 70 (slurry temperature, pH, concentration of saccharified product, anaerobic environment, etc.) is the same as the culture environment in the fermentation reaction tank 40, and hyperthermophilic bacteria are grown and acclimatized in the bacterial acclimatization tank 70. In the bacterial acclimatization tank 70, hyperthermophilic bacteria that have been acclimatized to the second slurry are cultured in a light-shielded state. In this embodiment, the microbial acclimatization tank 70 has microbial introduction passages C4 and C5 connected to its lower part. The microbial introduction passage in this embodiment is bifurcated, with one branch passage C4 connected to the second slurry preparation tank 30 and the other branch passage C5 connected to the fermentation reaction tank 40. Both of these branch passages C4 and C5 are provided with on-off valves B4 and B5, respectively, and these on-off valves B4 and B5 open and close the branch passages C4 and C5 (microbial introduction passages). In the second slurry preparation tank 30, a solution containing hyperthermophilic bacteria cultured in the bacterial acclimatization tank 70 is introduced via the bacterial introduction pathway C4. In the fermentation reaction tank 40, the solution containing hyperthermophilic bacteria is introduced via the bacterial introduction pathway C5 for fine-tuning.

[0032] Hyperthermophilic bacteria can be any anaerobic bacteria that produce hydrogen using sugar as a substrate, without any particular restrictions. From the viewpoint of hydrogen generation efficiency, the hyperthermia introduced into the second slurry preparation tank 30 and the fermentation reaction tank 40 is preferably Thermococcus kodakarensis, and more preferably Thermococcus kodakarensis KOD1 (accession number: FERM P-15007) deposited with the Patent Organism Depositary Center of the National Institute of Advanced Industrial Science and Technology. The deposit is registered as Pyrococcus sp. KOD1 or Pyrococcus kodakarensis KOD1, but is more precisely Thermococcus kodakarensis KOD1 (see Journal of Bacteriology, Vol. 182, No. 22, Nov. 2000, pp. 6424-6433, etc.).

[0033] The fermentation reactor 40 carries out fermentation by hyperthermophilic bacteria in the second slurry. The fermentation reactor 40 of this embodiment comprises a fermentation tank 45 and a stirrer 41 provided inside the fermentation tank 45. The fermentation tank 45 has a double-walled structure consisting of an inner container 45b and an outer container 45a surrounding the inner container 45b. A heat-retaining medium such as hot water is supplied between the inner container 45b and the outer container 45a, and the inside of the inner container 45b can be heated or kept warm by this heat-retaining medium. The fermentation tank 45 can maintain a closed state of the internal space of the inner container 45b. The fermentation reactor 40 may have a microbial carrier (not shown) inside the fermentation tank 45. The microbial carrier can be any material that supports hyperthermophilic bacteria, and can be, for example, a mesh-like structure, a porous structure such as a sponge, or granular material. By providing the microbial carrier, the concentration of hyperthermophilic bacteria inside the fermentation reactor 40 can be maintained at a high level, thereby promoting the fermentation reaction. If the microbial carrier is a mesh-like structure or a porous structure, it is installed in a suspended state from the ceiling of the fermentation tank 45 (suspended type). If the microbial carrier is granular material, it is installed to flow within the fermentation tank 45. The fermentation reactor 40 has a third transport channel C3 and a discharge channel C7 for the reacted slurry (waste slurry) connected to its lower part, and a gas discharge channel C6 and a microbial introduction channel C5 (branch channel C5) connected to its upper part. When a granular microbial carrier is placed in the fermentation tank 45, a filter may be installed at the inlet of the discharge channel C7 in the fermentation reactor 40 to suppress the discharge of the microbial carrier from the fermentation tank 45.

[0034] The agitator 41 in the fermentation reactor 40 has the same configuration as the agitator 21 in the first slurry preparation tank 20. The agitator 41 in the fermentation reactor 40 can agitate the second slurry introduced into the fermentation tank 45 by rotating the agitator shaft 43 with the power of a motor (not shown). The second slurry introduced into the fermentation reactor 40 is kept warm within a temperature range suitable for the fermentation of the saccharified product by hyperthermophilic bacteria. Fermentation by hyperthermophilic bacteria proceeds in this second slurry. More specifically, the hyperthermophilic bacteria metabolize the low-molecular-weight sugars derived from the saccharified product, breaking them down into pyruvate, alanine, and organic acids (such as acetic acid), and generating fermentation gas containing hydrogen gas. The fermentation gas is sent to the gas recovery and separation device T via the gas discharge channel C6. In the fermentation reactor 40, the fermentation is carried out in a light-shielded state. The fermentation reactor 40 reacts the second slurry for a predetermined fermentation residence time while maintaining its temperature, and then discharges the reacted second slurry as waste slurry into the slurry discharge channel C7. The slurry discharge channel C7 is provided with an on-off valve B7, which opens and closes the slurry discharge channel C7.

[0035] The gas recovery and separation unit T uses a gas separation membrane to separate hydrogen gas, carbon dioxide, and organic acid gases from the fermentation gas. The gas recovery and separation apparatus T of this embodiment comprises a gas inlet passage connected to a gas outlet passage C6, a container having a plurality of gas separation sections inside, and hydrogen gas outlet passages, carbon dioxide gas outlet passages, and organic acid gas outlet passages connected to each gas separation section. The gas separation section is isolated into a gas inlet side space and a gas permeate side space by a gas separation membrane, and separates various gases such as hydrogen gas from the fermentation gas by utilizing the difference in permeation rate through the gas separation membrane. The gas recovery and separation apparatus T of this embodiment enables multi-stage gas separation by having a plurality of gas separation sections. As such a gas recovery and separation apparatus T, for example, the one disclosed in Japanese Patent Publication No. 2013-534863 can be used. The gas recovery and separation apparatus T may also be provided with a depressurization means on the permeate side of the gas separation section to provide power to pass the fermentation gas through the gas separation membrane. A known vacuum pump or the like can be used as the depressurization means. A shut-off valve B6 is provided in the gas discharge passage C6, and the gas discharge passage C6 is opened and closed by the shut-off valve B6.

[0036] The hydrogen generator 100 of this embodiment includes a hydrogen gas storage tank T1, a carbon dioxide storage tank T2, and an organic acid gas storage tank T3, all connected to a gas recovery and separation device T. The hydrogen gas storage tank T1 stores hydrogen gas separated from the fermentation gas, the carbon dioxide storage tank T2 stores carbon dioxide separated from the fermentation gas, and the organic acid gas storage tank T3 stores organic acid gas separated from the fermentation gas.

[0037] The waste treatment device 50 separates the waste slurry (second slurry after fermentation) into an organic acid solution containing organic acids such as acetic acid and a residue (solid content) containing the remains of hyperthermophilic bacteria, etc. The waste treatment apparatus 50 of this embodiment comprises known solid-liquid separation means such as a belt press, screw press, and filtration, and a residue discharge passage C8 and an organic acid solution discharge passage C9 connected to the solid-liquid separation means. The residue discharge passage C8 and the organic acid solution discharge passage C9 are each provided with on-off valves B8 and B9, respectively, and these discharge passages C8 and C9 are opened and closed by these on-off valves B8 and B9.

[0038] In this embodiment, the hydrogen generator 100 is connected to the saccharification treatment apparatus 10 and the first slurry preparation tank 20 via a first transport path C1, to the first slurry preparation tank 20 and the second slurry preparation tank 30 via a second transport path C2, to the second slurry preparation tank 30 and the fermentation reaction tank 40 via a third transport path C3, and to the fermentation reaction tank 40 and the hydrogen gas storage tank T1 via a gas discharge path C6, a gas recovery and separation apparatus T, and a hydrogen gas discharge path. Each of the first transport path C1, the second transport path C2, the third transport path C3, the gas discharge path C6, and the hydrogen gas discharge path is formed by a sealed pipeline (pipe, etc.) and is isolated from the outside air, thereby maintaining an anaerobic environment. This makes it possible to create a good anaerobic environment in the internal spaces of the first sealed tank 25 of the first slurry preparation tank 20, the second sealed tank 35 of the second slurry preparation tank 30, and the fermentation tank 45 of the fermentation reaction tank 40.

[0039] In this embodiment, the hydrogen generator 100 prepares the saccharified product obtained from the saccharification treatment in the saccharification treatment apparatus 10 into a first slurry in the first slurry preparation tank 20, prepares the first slurry into a second slurry in the second slurry preparation tank 30, and then generates hydrogen by fermenting the hyperthermophilic bacteria contained in the second slurry in the fermentation reaction tank 40. In the hydrogen generator 100, the series of processes from saccharification treatment to fermentation by hyperthermophilic bacteria can be controlled to prevent the saccharified product, the first slurry, and the second slurry from being exposed to the outside air, creating an environment suitable for the fermentation of hyperthermophilic bacteria. More specifically, other bacteria attached to the biomass raw material, and airborne bacteria that enter the treatment tank 15 when the raw material introduction section 15a is opened can be sterilized by the saccharification treatment in the saccharification treatment apparatus 10. In addition, the transport path allows the transport of the saccharified product from the treatment tank 15 to fermentation in the fermentation reaction tank 40 to be carried out in an anaerobic environment. This effectively suppresses contamination by airborne bacteria and other microorganisms, maintaining an environment suitable for hydrogen production limited to hyperthermophilic bacteria.

[0040] Furthermore, the first slurry has a regulation function to homogenize the saccharified product mixture within one batch and to ensure homogenization between batches, thereby facilitating the preparation of the second slurry in a short time. The concentration of the saccharified product in the first slurry is adjusted to a higher range than that of the second slurry. After the subcritical water treatment by the saccharification apparatus 10 reduces the pressure in the treatment tank 15 to atmospheric pressure, the temperature of the saccharified product immediately after being received into the first slurry preparation tank 20 is high, reaching a maximum of 100°C. In contrast, the hydrogen generator 100 of this embodiment prepares the first slurry from the saccharified product and then prepares the second slurry from the first slurry, thereby gradually adjusting the fermentation conditions (fermentation environment) for hyperthermophilic bacteria. This allows for the efficient preparation of the high-temperature saccharified material to a temperature range suitable for fermentation by hyperthermophilic bacteria before adding the hyperthermophilic bacteria. Furthermore, since the saccharified material can be efficiently dispersed in the slurry, the concentration of the saccharified material can be easily adjusted to a concentration suitable for fermentation by hyperthermophilic bacteria. In addition, by preparing the first slurry to a constant saccharified material concentration without fluctuations between batches, the concentration of the saccharified material in the second slurry preparation tank 30 can be stably and easily adjusted to a concentration suitable for fermentation by hyperthermophilic bacteria. Therefore, the hydrogen generator 100 of this embodiment can promote fermentation by hyperthermophilic bacteria in the second slurry, and thus has excellent hydrogen production efficiency.

[0041] From the viewpoint of better adapting the first slurry to the growth environment of hyperthermophilic bacteria, it is preferable to prepare the first slurry in the first slurry preparation tank 20 within a temperature range suitable for the growth of hyperthermophilic bacteria. Furthermore, from the viewpoint of better adapting the second slurry to the fermentation environment of hyperthermophilic bacteria, it is preferable to prepare the second slurry in the second slurry preparation tank 30 within a temperature range suitable for the fermentation of the saccharified product by hyperthermophilic bacteria. In this embodiment, the temperature of the first or second slurry is adjusted by adding hot water from the hot water storage tank 17, which will be described later, to the first or second slurry preparation tanks 20 and 30. More specifically, the hydrogen generator 100 of this embodiment includes a hot water storage tank 17 that recovers steam derived from subcritical water and stores it as hot water (see Figure 1). The hot water storage tank 17 is a tank that stores the steam that has moved from the processing tank 15 as hot water. A steam outlet passage F1, which is connected to the steam discharge passage 15d of the processing tank 15, is connected to this hot water storage tank 17. As mentioned above, an on-off valve B1 is provided in the steam outlet passage F1, and the flow path of the outlet passage F1 is opened and closed by the on-off valve B1.

[0042] The hot water storage tank 17 is connected to a hot water transport channel F2 equipped with a switching valve B20, and the hot water transport channel F2 is connected to a fermentation transport channel F3 and a preparation hot water transport channel F9 via the switching valve B20. The fermentation transport channel F3 is connected to the fermentation reactor 40, and can supply hot water from the hot water storage tank 17 via the hot water transport channel F2 between the outer container 45a and the inner container 45b of the fermentation tank 45. In other words, hot water derived from subcritical water can be used as a heat-insulating medium supplied between the inner container 45b and the outer container 45a, preventing a decrease in the amount of hydrogen generated due to a drop in temperature inside the fermentation reactor 40 due to ambient temperature or an excessive rise in fermentation temperature. This is effective from the viewpoint of energy efficiency and reduction of running costs of the hydrogen generator 100. The hot water supplied between the outer container 45a and the inner container 45b of the fermentation tank 45 is withdrawn from between the outer container 45a and the inner container 45b at the end of one batch of fermentation reactions. The withdrawn hot water may, if necessary, be supplied to the hot water / steam supply unit 16 through another transport path (not shown). Alternatively, the hot water between the outer container 45a and the inner container 45b may be circulated between the fermentation tank 45, the hot water storage tank 17, the hot water / steam supply unit 16, and the reserve hot water storage tank 18 without accumulating.

[0043] The switching valve B20 supplies hot water from the hot water transport path F2 to the fermentation transport path F3 or the hot water preparation transport path F9 by switching the flow path of the hot water. The switching between the fermentation transport path F3 and the hot water preparation transport path F9 during hot water supply is preferably controlled by detecting the timing of slurry preparation in the first slurry preparation tank 20 and the second slurry preparation tank 30, and the timing of the start of fermentation in the fermentation reaction tank 40, or by pre-scheduling these timings. A PLC (Programmable Logic Controller) or the like can be used for this control. Note that in Figure 1, the actuators and controllers of the valves provided in each transport path are not shown.

[0044] The hydrogen generator 100 of this embodiment includes a preliminary hot water storage tank 18 for storing the hot water generated in the hot water / steam supply unit 16. A preliminary hot water transport path F11 is connected to the preliminary hot water storage tank 18, and the preliminary hot water transport path F11 is connected to a switching valve B20. The switching valve B20 supplies hot water from the preliminary hot water storage tank 18 to the fermentation transport path F3 or the preparation hot water transport path F9 by switching the hot water supply path away from the hot water storage tank 17. This switching is preferably controlled by detecting the remaining amount of hot water (hot water level) in the hot water storage tank 17.

[0045] The hot water transport channel F9 for preparation branches into a first hot water transport channel F4 connected to the first slurry preparation tank 20 and a second hot water transport channel F6 connected to the second slurry preparation tank 30. Each of the first and second hot water transport channels F4 and F6 is equipped with an on / off valve, which opens and closes the flow path of each transport channel F4 and F6. In this embodiment, the hot water storage tank 17 and the second slurry preparation tank 30 are connected via a hot water transport channel F2, a preparation hot water transport channel F9, and a second hot water transport channel F6 (see Figure 1). Each of these transport channels F2, F9, and F6 is formed as a sealed pipe and is isolated from the outside air, thereby maintaining an anaerobic environment. In other words, the hot water storage tank 17 and the second slurry preparation tank 30 are connected via transport channels F2, F9, and F6, which maintain an anaerobic environment. With this configuration, hot water derived from subcritical water can be used for the preparation of the second slurry, while the internal space of the second sealed tank 35 of the second slurry preparation tank 30 can be kept in a good anaerobic environment. Although the hot water in the hot water storage tank 17 and the auxiliary hot water storage tank 18 has a low dissolved oxygen content due to heating, nitrogen gas purging or the like may be applied to the hot water before and after supply through the hot water transport channel F9 for preparation, if necessary. This makes the transport channels F9, F4, F6 and the first and second slurries a more anaerobic environment.

[0046] Similarly, the hot water storage tank 17 and the first slurry preparation tank 20 are connected via the hot water transport channel F2, the preparation hot water transport channel F9, and the first hot water transport channel F4 (see Figure 1). Each of these transport channels F2, F9, and F4 is formed as a sealed pipe and is isolated from the outside air, thereby maintaining an anaerobic environment. In other words, the hot water storage tank 17 and the first slurry preparation tank 20 are also connected via the transport channels F2, F9, and F4, which maintain an anaerobic environment. With this configuration, hot water derived from subcritical water can be used for the preparation of the first slurry, while the internal space of the first sealed tank 25 of the first slurry preparation tank 20 can be kept in a good anaerobic environment. In this embodiment, when hot water derived from subcritical water is used to prepare the first and second slurries, the supply amount of the hot water is controlled by the control unit 90.

[0047] From the viewpoint of making the first slurry more suitable for the growth environment of hyperthermophilic bacteria, it is preferable to prepare the first slurry to be weakly acidic in the first slurry preparation tank 20. Furthermore, from the viewpoint of making the second slurry more suitable for the fermentation environment of hyperthermophilic bacteria, it is preferable to prepare the second slurry to be weakly acidic in the second slurry preparation tank 30. In this embodiment, the pH of the first or second slurry is adjusted by adding the organic acid solution from the organic acid storage tank 51 to the first or second slurry preparation tanks 20 and 30. More specifically, the hydrogen generator 100 of this embodiment includes an organic acid storage tank 51 for recovering and storing an organic acid solution derived from waste slurry (reacted second slurry) (see Figure 1). This organic acid solution contains organic acids (such as acetic acid) produced by fermentation in the fermentation reactor 40. The organic acid storage tank 51 is connected to an organic acid solution discharge channel C9 having an on / off valve B9 and a prepared organic acid solution transport channel F8. The organic acid solution discharge channel C9 sends the organic acid solution discharged from the waste treatment device 50 to the organic acid storage tank 51. The organic acid solution discharge channel C9 is formed by a sealed pipeline (pipe, etc.) and is isolated from the outside air, thereby maintaining an anaerobic environment.

[0048] The organic acid solution transport path F8 for preparation branches into a first organic acid solution transport path F5 connected to a first slurry preparation tank 20 and a second organic acid solution transport path F7 connected to a second slurry preparation tank 30. Each of the first and second organic acid solution transport paths F5 and F7 is equipped with an on / off valve, which opens and closes the flow path of each transport path F5 and F7. In this embodiment, the organic acid storage tank 51 and the second slurry preparation tank 30 are connected via a transport path F8 for the prepared organic acid solution and a transport path F7 for the second acid (see Figure 1). Each of these transport paths F8 and F7 is formed by a sealed pipe and is isolated from the outside air, thereby maintaining an anaerobic environment. In other words, the organic acid storage tank 51 and the second slurry preparation tank 30 are connected via transport paths F8 and F7, which maintain an anaerobic environment. With this configuration, organic acids derived from waste slurry can be used in the preparation of the second slurry, while the internal space of the second sealed tank 35 of the second slurry preparation tank 30 can be kept in a good anaerobic environment.

[0049] Similarly, the organic acid storage tank 51 and the first slurry preparation tank 20 are connected via the organic acid solution transport path F8 and the first organic acid solution transport path F5 (see Figure 1). Each of these transport paths F8 and F5 is formed by a sealed pipe, and an anaerobic environment is maintained by being isolated from the outside air. In other words, the organic acid storage tank 51 and the first slurry preparation tank 20 are also connected via transport paths F8 and F5, which maintain an anaerobic environment. With this configuration, organic acids derived from waste slurry can be used in the preparation of the first slurry, while the internal space of the first sealed tank 25 of the first slurry preparation tank 20 can be kept in a good anaerobic environment.

[0050] As described above, the hydrogen generator 100 of this embodiment can utilize hot water derived from subcritical water and organic acid (organic acid solution) derived from waste slurry (reacted second slurry) for the preparation of the first and second slurries, respectively. Furthermore, the hydrogen generator 100 of this embodiment includes a control unit 90 that controls the supply amounts of hot water and organic acid (organic acid solution) during the preparation of the first and second slurries. The control unit 90 of this embodiment contains a hot water transport path F9 for preparation, first and second hot water transport paths F4, F6, organic acid solution transport path F8, and first and second organic acid solution transport paths F5, F7, and incorporates on-off valves for the first and second hot water transport paths F4, F6 and the first and second organic acid solution transport paths F5, F7. The control unit 90 is capable of controlling the supply amounts of hot water and organic acid (organic acid solution) by controlling the opening and closing of the on-off valves for the first and second hot water transport paths F4, F6 and the first and second organic acid solution transport paths F5, F7. Alternatively, the control unit 90 may control the supply amount of at least one of the hot water and organic acid (organic acid solution). Preferably, the opening and closing of the on / off valves in the control unit 90 is controlled by detecting the temperature and / or pH of the slurry in the first slurry preparation tank 20 and the second slurry preparation tank 30. On / off control, PID control, and the like can be appropriately employed for this control.

[0051] From the viewpoint of further promoting fermentation by hyperthermophilic bacteria, it is preferable that the temperature and pH of the second slurry are adjusted to a range suitable for fermentation of the saccharified product by hyperthermophilic bacteria. That is, it is preferable that the control unit 90 controls the amount of hot water and organic acid solution supplied to the slurry being prepared in the second slurry preparation tank 30 according to at least one of the temperature and pH of the slurry being prepared.

[0052] Furthermore, it is preferable that the temperature and pH of the first slurry are adjusted to a range suitable for the growth of hyperthermophilic bacteria. The range suitable for the growth of hyperthermophilic bacteria is slightly wider than the range suitable for fermentation by hyperthermophilic bacteria. In this embodiment, the slurry temperature is lowered to a temperature range (60°C to 80°C) suitable for the growth environment of hyperthermophilic bacteria by using the hot water in the hot water storage tank 17 and the auxiliary hot water storage tank 18. More specifically, the temperature of the first slurry can be adjusted by adjusting the amount of hot water supplied within the predetermined concentration range of the saccharified product described above. Furthermore, if the temperature is not expected to fall within the predetermined range as the lower limit of the solid concentration range approaches, water with a higher or lower temperature than the hot water supplied to the first sealed tank 25 may be supplied separately. In this case as well, water is supplied separately to the first sealed tank 25 via a transport path in which an anaerobic environment is maintained. The same applies to the second slurry preparation tank 30. However, due to the processing in the first slurry preparation tank 20 described above, the second slurry preparation tank 30 can be easily prepared by simply supplying hot water at the same temperature range as the optimal temperature range for fermentation by hyperthermophilic bacteria (approximately 80°C), resulting in a second slurry with a lower concentration of saccharified material than the first slurry and a concentration suitable for fermentation by hyperthermophilic bacteria.

[0053] Furthermore, if the pH of the slurry being prepared in the first slurry preparation tank 20 or the second slurry preparation tank 30 is higher than weakly acidic, the control unit 90 opens the on-off valves of the first organic acid solution transport path F5 and the second organic acid solution transport path F7 to introduce the organic acid solution into the second sealed tank 35, thereby lowering the pH of the slurry being prepared. Conversely, if the pH of the slurry being prepared is lower than weakly acidic, the control unit 90 closes the on-off valves of the first organic acid solution transport path F5 and the second organic acid solution transport path F7 to stop the introduction of the organic acid solution into the second sealed tank 35. In this case, the pH of the slurry being prepared can be increased by adding a reducing agent or the like.

[0054] The control unit 90 detects the concentration, temperature, and pH of the saccharified product in the slurry being prepared in the second slurry preparation tank 30 using sensors (not shown), and controls the degree to which the on / off valves in each of the transport paths F6 and F7 are opened or closed. Each sensor for detecting the concentration, temperature, and pH of the saccharified product is installed in the second sealed tank 35, and measures the concentration, temperature, and pH of the saccharified product in the slurry in the tank 35 intermittently or continuously. Known sensors can be used for each sensor. For example, a refractometer (turbidimeter) can be used as the sensor for the concentration of the saccharified product. Furthermore, by pre-measuring the total amount of saccharified product produced in one batch and its water content, the concentration of the saccharified product can be adjusted by adjusting the amount of water supplied to the first slurry preparation tank 20 and the second slurry preparation tank 30 based on this.

[0055] As described above, in this embodiment, the hydrogen generator 100 consists of a saccharification treatment device 10, a first slurry preparation tank 20, a second slurry preparation tank 30, a fermentation reaction tank 40, a gas recovery and separation device T, a waste treatment device 50, an organic acid storage tank 51, a microbial acclimatization tank 70, and a hot water storage tank 17, all of which are connected to transport paths C1-C9 and F1-F9, each equipped with an opening valve or a switching valve. These transport paths C1-C9 and F1-F9 are composed of sealed pipelines (piping, etc.). Each transport path C2-C9 and F2-F9, which serves as a flow path for each slurry such as the first or second slurry, hot water, organic acid solution, and other liquids, is equipped with a known liquid delivery means (not shown), such as a pump, which delivers the liquid.

[0056] Next, a hydrogen generation method for generating hydrogen from biomass raw materials using the hydrogen generator 100 of the above-described embodiment will be explained. The hydrogen generation method of this embodiment comprises a saccharification process in which biomass raw materials are saccharified with subcritical water, a first slurry preparation process in which a first slurry is prepared using the saccharified product, a second slurry preparation process in which the first slurry and hyperthermophilic bacteria are mixed to prepare a second slurry, and a fermentation reaction process in which fermentation by hyperthermophilic bacteria is carried out in the second slurry.

[0057] The saccharification process involves mixing biomass raw materials or a raw material slurry containing them with subcritical water in the processing tank 15 of the saccharification apparatus 10 to obtain a saccharified product. The biomass raw materials or raw material slurry are introduced into the processing tank 15 from the raw material introduction section 15a, which has its opening / closing mechanism B10 open. During the saccharification process, the opening / closing mechanisms B10 and B1 of the raw material introduction section 15a and discharge section 15c, as well as the discharge valve B11, are closed beforehand.

[0058] From the viewpoint of more efficiently bringing biomass raw materials into contact with subcritical water, or from the viewpoint of more reliably carrying out the saccharification process, it is preferable to carry out the saccharification process under the following conditions. The temperature of the subcritical water is preferably between 150°C and 320°C, and more preferably between 200°C and 300°C. The pressure of the subcritical water is preferably 1 MPa to 8 MPa, more preferably 2 MPa to 3 MPa.

[0059] From the viewpoint of more efficiently bringing biomass raw materials into contact with subcritical water, it is preferable to perform the saccharification treatment while stirring with the stirrer 11. In this embodiment, the saccharification process is batch-type. Specifically, for each batch, the saccharification process consists of one cycle of operations: cleaning the treatment tank 15 of the saccharification apparatus 10, introducing biomass raw materials into the treatment tank 15, subcritical water treatment, and removing the saccharified product from the treatment tank 15.

[0060] After the saccharification process, a semi-solid saccharified material is generated in the processing tank 15. The saccharified material is then suctioned and transported to the first sealed tank 25 via the first transport path C1 after the pressure inside the processing tank 15 has been reduced to atmospheric pressure. More specifically, the inside of the first sealed tank 25 is depressurized by a vacuum pump 26. During this depressurization, the opening / closing mechanism B1 of the discharge section 15c and the opening valve B2 of the second transport path C2 are closed. Next, when the opening / closing mechanism B1 of the discharge section 15c is opened, the saccharified material in the processing tank 15 is suctioned into the depressurized first sealed tank 25. That is, the saccharified material is transported into the first sealed tank 25 via the first transport path C1. After such transport, the opening / closing mechanism B1 of the discharge section 15c is closed.

[0061] In this embodiment, after the saccharified material is transported to the first slurry preparation tank 20, the opening / closing mechanism B1 of the discharge section 15c is closed. This allows the processing tank 15 to be cleaned while the processes from the first slurry preparation step onward are being carried out, and new biomass raw materials can be introduced into the processing tank 15 to carry out the saccharification process. That is, after removing the saccharified material from the processing tank 15 and cleaning the processing tank 15, new biomass raw materials can be introduced into the processing tank 15 to carry out the next saccharification process. As a result, even if the saccharification process is a batch process, the processes from the first slurry preparation step onward and the saccharification process can be carried out in parallel, so hydrogen can be generated efficiently. Hereinafter, the process of cleaning the treatment tank 15, introducing new biomass raw materials into the treatment tank 15, the saccharification process, and removing the saccharified product from the treatment tank 15 will also be referred to as the "saccharification cycle process." The three processes of the first slurry preparation process, the second slurry preparation process, and the fermentation reaction process will also be referred to as the "slurry usage process." When all of the first slurry in the first slurry preparation tank is put into the second slurry preparation tank, it is preferable that the time t1 required for the saccharification cycle process is less than or equal to the time t2 required for the slurry usage process (t1 ≤ t2). With this configuration, it becomes easy to carry out the fermentation reaction process continuously. For example, as shown in Figure 2, it becomes easier to match the cycle of the saccharification cycle process with the cycle of supplying the second slurry to the fermentation reaction process, and the fermentation reaction process can be carried out continuously. As a result, the waiting time can be shortened and the hydrogen generation efficiency can be improved. In this case, it is preferable to use a small-capacity saccharification treatment device 10 that requires a short processing time. Furthermore, by providing multiple of these small-capacity saccharification treatment devices 10 and connecting them to a single first slurry preparation tank 20, and operating each saccharification treatment device 10 simultaneously, it is possible to increase the amount of hydrogen generated during continuous operation.

[0062] Immediately after the saccharification process, the saccharified product is at a temperature of approximately 100°C, and the pH value may fluctuate due to the influence of components other than cellulose (chemicals and other substances) contained in the biomass raw material. In this embodiment, a first slurry preparation step is performed to approximate the growth environment (growth conditions) of hyperthermophilic bacteria. In the first slurry preparation step, the saccharified material is mixed with water and stirred in the first sealed tank 25 to prepare the first slurry. In this embodiment, hot water from the hot water storage tank 17 is added to the saccharified material via the hot water introduction channel F4 to prepare the first slurry. From the viewpoint of making it easier to adapt to the growth conditions of hyperthermophilic bacteria, it is preferable that the first slurry be adjusted to a weakly acidic pH that does not fall below 3.0. Alternatively, the pH may be adjusted to a weakly acidic pH by adding the organic acid solution from the organic acid storage tank 51 to the first slurry.

[0063] The first slurry has a higher concentration of saccharified material than the second slurry used for fermentation by hyperthermophilic bacteria. From the viewpoint of homogenizing the second slurry, it is preferable to perform the first slurry preparation step while stirring with a stirrer 21. Furthermore, it is preferable that the temperature of the first slurry be adjusted to a range of 60°C to 80°C, which is suitable for the growth of hyperthermophilic bacteria.

[0064] After the first slurry preparation step, the first slurry is transported to the second sealed tank 35 via the second transport path C2. This transport is performed by opening the opening valve B2 of the second transport path C2, and the first slurry is transported from the first sealed tank 25 to the second sealed tank 35 by a liquid transport means such as a pump. After the first slurry has been transported, the opening valve B2 of the second transport path C2 is closed. Furthermore, when the first slurry is being delivered, the opening valves B3 and B4 of the third transport path C3 and the bacterial introduction path C4 are closed in advance.

[0065] In the second slurry preparation step, the first slurry and water (hot water) are mixed in the second sealed tank 35 to adjust the concentration of the saccharified product to one suitable for fermentation by hyperthermophilic bacteria. The concentration of the saccharified product suitable for fermentation by hyperthermophilic bacteria is determined by balancing it with the amount of hyperthermophilic bacteria supplied to the second sealed tank 35. After the concentration of the saccharified product is adjusted to one suitable for fermentation by hyperthermophilic bacteria in the second slurry preparation step, a predetermined amount of hyperthermophilic bacteria-containing liquid is supplied and mixed to prepare the second slurry. At this time, the second slurry is adjusted to be weakly acidic, with a temperature within the range suitable for fermentation of the saccharified product by hyperthermophilic bacteria and a pH not below 3.0. From the viewpoint of further adapting the second slurry to the fermentation environment of hyperthermophilic bacteria, it is preferable that the temperature of the second slurry be adjusted to around the lower limit (80°C) of the temperature range suitable for fermentation of the saccharified product by hyperthermophilic bacteria, and more preferably to 75°C or higher and 85°C or lower. In this embodiment, the second slurry is prepared by adding the hot water from the hot water storage tank 17 to the first slurry via the hot water introduction channel F6, the organic acid solution from the organic acid storage tank 51 via the organic acid solution introduction channel F7, and further adding the bacteria-containing liquid from the bacteria acclimatization tank 70 to the first slurry via the bacteria introduction channel C4.

[0066] Furthermore, from the viewpoint of ensuring that the saccharified product and hyperthermophilic bacteria are evenly in contact in the second slurry, it is preferable to perform the second slurry preparation step while stirring with the stirrer 31.

[0067] After the second slurry preparation step, the second slurry is transported to the fermentation tank 45 via the third transport path C3. This transport is carried out by opening the opening valve B3 of the third transport path C3 and using a pump or other liquid delivery means to deliver the second slurry from the second sealed tank 35 to the fermentation tank 45. After the delivery of the second slurry, the opening valve B3 of the third transport path C3 is closed. When the second slurry is being supplied, the opening valves B7, B5, and B6 of the slurry discharge channel C7, bacterial introduction channel C5, and gas discharge channel C6 are closed in advance.

[0068] In the fermentation reaction process, fermentation is carried out in the fermentation reaction vessel 40 (fermentation tank 45) by hyperthermophilic bacteria in the second slurry. During this fermentation, the release valve B6 of the gas discharge passage C6 is opened, and the fermentation gas is recovered by the gas recovery and separation device T. As described above, hydrogen gas is separated from the fermentation gas by the gas recovery and separation device T, and this hydrogen gas is stored in the hydrogen gas storage tank T1. From the viewpoint of further improving hydrogen generation efficiency, it is preferable that the temperature of the second slurry in the fermentation tank 45 is the same as that of the second slurry in the second slurry preparation tank 30 from the time the second slurry is introduced into the fermentation tank 45 until the start of fermentation. In addition, in this embodiment, hot water is filled or circulated between the outer container 45a and the inner container 45b of the fermentation tank 45 to suppress the temperature drop inside the fermentation tank 45 due to ambient temperature. Furthermore, the hot water does not exceed 100°C under atmospheric pressure, and the temperature drops below 100°C due to heat dissipation in the fermentation transport path F3, so it is possible to suppress the temperature inside the fermentation tank 45 from rising excessively due to the natural fermentation heat of hyperthermophilic bacteria, and it is possible to maintain the temperature of the second slurry inside the fermentation tank 45 in the range of 80°C to 90°C. This temperature range is within the range of temperatures suitable for the fermentation of saccharified products by hyperthermophilic bacteria, and is a temperature range in which the hydrogen gas generation efficiency can be maintained at a high level during the fermentation.

[0069] From the viewpoint of further improving fermentation efficiency, it is preferable to carry out the fermentation reaction process while stirring with the agitator 41. In this embodiment, a hyperthermophilic bacterium-containing liquid is added to the second slurry in the fermentation tank 45 according to the hydrogen generation rate. For example, if the hydrogen generation rate is slower than a set value, the bacterium-containing liquid from the microbial acclimatization tank 70 is sent to the fermentation tank 45 via the bacterium introduction passage C5. Furthermore, when switching the second slurry in the fermentation reaction vessel, it is preferable to provide a hanging type or similar bacterial carrier in the fermentation tank 45 to more reliably ensure the concentration of hyperthermophilic bacteria in the second slurry in the fermentation tank 45. This makes it possible to increase the concentration of hyperthermophilic bacteria in the tank 45 when discarding the second slurry after the reaction and supplying a new second slurry to the fermentation tank 45.

[0070] After the fermentation reaction process, the opening valve B7 of the slurry discharge channel C7 is opened, and the second slurry in the fermentation tank 45 is sent to the waste treatment device 50 as waste slurry. At the time of sending, the opening valves B9 and B8 of the organic acid solution discharge channel C9 and the residue discharge channel C8 are closed beforehand. In the waste treatment device 50, the waste slurry is separated into an organic acid solution and a residue by solid-liquid separation treatment. The organic acid solution is discharged through the organic acid solution discharge channel C9, and the residue is discharged through the residue discharge channel C8. During these discharges, the opening valves B9 and B8 of the organic acid solution discharge channel C9 and the residue discharge channel C8 are opened, the organic acid solution is sent to the organic acid storage tank 51, and the residue is discarded.

[0071] From the viewpoint of rapidly and efficiently generating hydrogen continuously without leaving any unfermented saccharified material, it is preferable to perform the second slurry preparation step and the fermentation reaction step multiple times on the saccharified material obtained in a single saccharification step. In this case, the second slurry preparation step involves mixing a portion of the first slurry obtained in the first slurry preparation step with hyperthermophilic bacteria and water to prepare the second slurry. That is, the first slurry obtained in the first slurry preparation step is subjected to the second slurry preparation step in multiple stages, as shown in Figure 3. The numbers for the second slurry preparation step and the fermentation reaction step shown in Figure 3 represent the number of times the liquid is sent to the second slurry preparation tank 30 and the fermentation reaction tank 40. In the embodiment shown in Figure 3, the first slurry is transported to the second slurry preparation tank 30 in three stages, and the second slurry preparation step is performed three times. Accordingly, the fermentation reaction step is also performed three times. By dividing the first slurry and subjecting it to the second slurry preparation process, and by performing the second slurry preparation process and the fermentation reaction process multiple times, it becomes possible to continuously generate hydrogen for at least the number of times the first slurry is divided.

[0072] When the saccharified product obtained in a single saccharification process is subjected to multiple second slurry preparation and fermentation reaction processes, not only is continuous hydrogen production possible, but semi-continuous hydrogen production is also possible if the time required for each process satisfies the following relation (1). t1 = t21 + n(t22 + t23) ... (1) t1: Time required for the saccharification cycle process t21: Time required for the first slurry preparation step t22: Time required for the second slurry preparation process t23: Fermentation reaction process n: The number of times the second slurry preparation step and fermentation reaction step are performed on the saccharified product obtained in one saccharification step. For example, as shown in Figure 4, if the time t1 required for the saccharification cycle is 3.5 hours, and the time t21 required for the first slurry preparation is 0.5 hours, and the total time for the second slurry preparation (t22) and the fermentation reaction (t23) is set to 1 hour, then by dividing the first slurry into three equal parts and gradually converting them into the second slurry and performing fermentation, all fermentation reactions of the saccharified material obtained in the previous batch's saccharification cycle can be completed within the time of the next saccharification cycle, making it possible to generate hydrogen semi-continuously. Furthermore, by determining the size and specifications of the various devices and tanks constituting the hydrogen generator 100, as well as setting the concentrations of the saccharified material in the first slurry and the second slurry, it becomes possible to design a hydrogen generator as a plant.

[0073] The present invention is not limited to the embodiments described above and can be modified in various ways. For example, the system may be provided with multiple saccharification apparatuses 10, each of which may be connected to a single first slurry preparation tank 20 via a transport path that maintains an anaerobic environment. Alternatively, the system may be provided with multiple second slurry preparation tanks 30 and / or fermentation reaction tanks 40, or both, with a single first slurry preparation tank 20 connected to multiple second slurry preparation tanks 30 and / or fermentation reaction tanks 40 via a transport path that maintains an anaerobic environment. Thus, various apparatus configurations are possible via the first slurry preparation tank 20. [Explanation of symbols]

[0074] 100 Hydrogen Generator 10. Saccharification treatment device 11. Agitator 12 motors 13 Stirring shaft 14. Agitator blades 15 Processing tanks 15a Raw material introduction section 15b Steam Inlet 15c Discharge section 15d Steam discharge channel 16. Hot water / steam supply unit 17. Hot water storage tank 18. Reserve hot water storage tank 20. First slurry preparation tank 21 Agitator 22. Agitator blades 23 Stirring shaft 25. First sealed tank 26 Vacuum pump 30 Second slurry preparation tank 31. Agitator 33 Stirring shaft 35. Second sealed tank 35 Sealed Tanks 40 Fermentation reactors 41. Agitator 43 Stirring shaft 45 fermentation tanks 45a Outer container 45b Inner container 50 Waste treatment equipment 51 Organic Acid Storage Tank 70 Bacteria acclimation tank 90 Control Unit

Claims

1. A saccharification apparatus for saccharifying cellulose-containing biomass raw materials with subcritical water, A first slurry preparation tank is used to prepare a first slurry by adding water to the saccharified product obtained by the aforementioned saccharification treatment and stirring it so that the concentration of the saccharified product becomes a constant concentration. A second slurry preparation tank mixes the first slurry with hyperthermophilic bacteria and water to prepare a second slurry so that the concentration of the saccharified product is suitable for fermentation by the hyperthermophilic bacteria, A fermentation reactor in which fermentation by the hyperthermophilic bacteria in the second slurry is carried out, The system includes a hydrogen gas storage tank for recovering and storing the hydrogen gas generated by the aforementioned fermentation, A hydrogen generator in which the saccharification apparatus and the first slurry preparation tank, the first slurry preparation tank and the second slurry preparation tank, the second slurry preparation tank and the fermentation reaction tank, and the fermentation reaction tank and the hydrogen gas storage tank are each connected via a transport path that maintains an anaerobic environment.

2. In the first slurry preparation tank, the first slurry is prepared to be within a temperature range suitable for the growth of the hyperthermophilic bacteria and to be weakly acidic. The hydrogen generator according to claim 1, wherein in the second slurry preparation tank, the second slurry is prepared to be within a temperature range suitable for the fermentation of the saccharified product by the hyperthermophilic bacteria and to be weakly acidic.

3. The hydrogen generator according to claim 1 or 2, comprising a hot water storage tank for recovering steam derived from the subcritical water and storing hot water, wherein the hot water storage tank and at least one of the first slurry preparation tank and the second slurry preparation tank are connected via a hot water transport path in which an anaerobic environment is maintained.

4. The hydrogen generator according to claim 1 or 2, comprising an organic acid storage tank for recovering and storing an organic acid solution containing organic acids produced by the fermentation, wherein the organic acid storage tank and at least one of the first slurry preparation tank and the second slurry preparation tank are connected via a transport path that maintains an anaerobic environment.

5. A hot water storage tank for recovering steam derived from the subcritical water and storing hot water, The system includes an organic acid storage tank for recovering and storing the organic acid solution containing the organic acid produced by the aforementioned fermentation, The hot water storage tank and the organic acid storage tank are connected to the second slurry preparation tank via a transport path that maintains an anaerobic environment. Furthermore, the hydrogen generator according to claim 1 or 2, comprising a control unit that controls the amount of hot water and the organic acid solution supplied to the slurry being prepared in the second slurry preparation tank according to at least one of the concentration, temperature, and pH of the saccharified product in the slurry being prepared.

6. The system includes a hot water storage tank for recovering steam derived from the subcritical water and storing hot water. The fermentation reaction tank has a double-walled structure comprising an inner container and an outer container surrounding the inner container. The hydrogen generator according to claim 1 or 2, wherein the fermentation reaction tank is kept warm within a temperature range suitable for the fermentation of the saccharified product by the hyperthermophilic bacteria by supplying the hot water from the hot water storage tank between the inner container and the outer container.

7. The hydrogen generator according to claim 1 or 2, wherein the hyperthermophilic bacterium is Thermococcus kodakarensis.

8. The hydrogen generator according to claim 7, wherein Thermococcus kodakarensis is Thermococcus kodakarensis KOD1 (depository: Patent Biological Depository Center, National Institute of Advanced Industrial Science and Technology, accession number: FERM P-15007).

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