JP7213484B2 - Methane fermentation tank, methane fermentation system and methane fermentation treatment method - Google Patents

Description

The present invention relates to a methane fermentation tank, a methane fermentation system, and a methane fermentation treatment method.

A methane fermentation treatment method is known in which organic waste is converted into methane gas by biological treatment of anaerobic microorganisms under anaerobic conditions. For example, Patent Literature 1 describes an example of a methane fermentation system that decomposes organic matter with anaerobic microorganisms and performs methane fermentation to generate methane gas.

Further, Patent Literatures 2 and 3 describe an example of a waste treatment system in which microbubbles are brought into contact with organic residue in order to solubilize the organic residue remaining after methane fermentation treatment.

Japanese Patent No. 5870343 JP 2017-121603 A JP 2018-130656 A

By the way, conventionally, the temperature of the methane fermentation tank is raised to activate anaerobic microorganisms, the retention time of the fermentation tank is lengthened, and the organic waste is pulverized in advance, acid fermentation, hydrolysis, subcritical treatment, etc. By applying this pretreatment, the decomposition of organic waste was accelerated. However, the above methods have limitations in promoting the decomposition of organic waste.

The present invention has been made in view of the above, and an object of the present invention is to provide a methane fermentation tank, a methane fermentation system, and a methane fermentation treatment method that can promote the decomposition of organic waste.

In order to solve the above-described problems and achieve the object, one aspect of the present disclosure provides a fermentation unit that performs methane fermentation of organic waste with a culture solution containing anaerobic microorganisms, and water containing bubbles with a diameter of 1 μm or less. and a water supply unit for supplying the fermentation unit.

In addition, in the aspect of the above-described methane fermentation tank of the present disclosure, the organic waste preferably contains persistent organic matter.

In addition, in the above aspect of the methane fermentation tank of the present disclosure, the bubbles having a diameter of 1 μm or less preferably contain at least one of air, carbon dioxide, hydrogen, oxygen and nitrogen.

In addition, in the above aspect of the methane fermentation tank of the present disclosure, the concentration of water bubbles containing bubbles with a diameter of 1 μm or less is preferably 6×10 ⁷ particles/ml or more and 5×10 ⁹ particles/ml or less.

Another aspect of the present disclosure is a methane fermentation system that includes the methane fermentation tank described above and a water preparation device that prepares water containing air bubbles with a diameter of 1 μm or less to be supplied to the fermentation section.

In addition, in the above aspect of the methane fermentation system of the present disclosure, it is preferable to have a control device that adjusts the amount of water containing air bubbles with a diameter of 1 μm or less supplied by the water supply unit.

In addition, in the above aspect of the methane fermentation system of the present disclosure, the first detection device that detects at least one of the hydrogen sulfide concentration, the carbon dioxide concentration, and the methane concentration in the methane fermentation tank, and the second detection device that detects the pH The water supply unit includes a first supply unit that supplies water containing bubbles of at least one of carbon dioxide, hydrogen, oxygen, and nitrogen with a diameter of 1 μm or less, and water containing air bubbles with a diameter of 1 μm or less. and a second supply unit for supplying, wherein the control device includes at least one of hydrogen sulfide concentration, carbon dioxide concentration, and methane concentration detected by the first detection device, and at least one of pH detected by the second detection device. It is preferable to adjust the supply amount of water containing air bubbles having a diameter of 1 μm or less from the first supply unit and the supply amount of water containing air bubbles having a diameter of 1 μm or less from the second supply unit.

In the above aspect of the methane fermentation system of the present disclosure, the control device includes an estimation unit that estimates the concentration of bubbles having a diameter of 1 μm or less in the culture solution of the fermentation unit, and a bubble diameter of 1 μm or less based on the concentration estimated by the estimation unit. and a controller that adjusts the supply amount of water containing air bubbles.

In the above aspect of the methane fermentation system of the present disclosure, the control unit controls the concentration of air bubbles having a diameter of 1 μm or less in the culture solution of the fermentation unit to be 2×10 ⁷ particles/ml or more and 2×10 ⁸ particles/ml or less. It is preferable to adjust the supply amount of water containing air bubbles having a diameter of 1 μm or less.

In addition, in the above aspect of the methane fermentation system of the present disclosure, it is preferable to include a desulfurization device that removes sulfur oxides from the biogas generated from the methane fermentation tank to obtain purified biogas.

In addition, in the above aspect of the methane fermentation system of the present disclosure, the bubbles having a diameter of 1 μm or less preferably contain carbon dioxide discharged by combustion of the purified biogas.

In addition, in the above aspect of the methane fermentation system of the present disclosure, water containing air bubbles with a diameter of 1 μm or less is supplied, and a slurry tank is provided for slurrying the organic waste before being put into the methane fermentation tank. is preferred.

In addition, in the above aspect of the methane fermentation system of the present disclosure, digestive juice treatment is performed by solid-liquid separating the digestive juice generated from the methane fermentation tank and supplying the liquid obtained by the solid-liquid separation of the digestive juice to the slurry tank. A device is preferably provided.

In addition, in the above aspect of the methane fermentation system of the present disclosure, water containing bubbles with a diameter of 1 μm or less is supplied, and a pre-fermentation tank is provided for hydrolyzing organic waste before being put into the methane fermentation tank. is preferred.

In addition, in the above aspect of the methane fermentation system of the present disclosure, the digestive juice generated from the methane fermentation tank is subjected to solid-liquid separation, and the liquid obtained by the solid-liquid separation of the digestive juice is supplied to the pre-fermentation tank. A processor is preferably provided.

In addition, in the above aspect of the methane fermentation system of the present disclosure, the water containing bubbles with a diameter of 1 μm or less preferably contains liquid obtained by solid-liquid separation of digestive fluid.

Another aspect of the present disclosure is a methane fermentation treatment method for methane fermentation of organic waste using a culture solution containing anaerobic microorganisms, wherein water containing bubbles with a diameter of 1 μm or less is treated as organic waste during methane fermentation. It is a methane fermentation treatment method that supplies to.

ADVANTAGE OF THE INVENTION According to this invention, it is effective in the ability to promote decomposition|disassembly of organic waste.

FIG. 1 is a schematic diagram showing a methane fermentation tank and a methane fermentation system of this embodiment. FIG. 2 is a flow chart showing the process of methane fermentation. 3 is a flowchart of a methane fermentation method using the methane fermentation system shown in FIG. 1. FIG. FIG. 4 is a graph showing the amount of methane produced in a batch test. FIG. 5 is a graph showing the final decomposition rate of persistent organic matter in a batch test. FIG. 6 is a graph showing the amount of methane produced from organic waste containing persistent organic matter in a batch test. FIG. 7 is a schematic diagram showing the methane fermentation system of the first modified example. FIG. 8 is a schematic diagram showing a methane fermentation system of a second modified example. FIG. 9 is a schematic diagram showing a methane fermentation system of a third modified example. FIG. 10 is a schematic diagram showing a methane fermentation system of a fourth modified example. FIG. 11 is a schematic diagram showing a methane fermentation system of the fifth modified example. FIG. 12 is a schematic diagram showing a methane fermentation system of the sixth modification.

EMBODIMENT OF THE INVENTION Below, embodiment of the methane fermentation tank which concerns on this invention, and a methane fermentation system is described in detail based on drawing. It should be noted that the present invention is not limited to the description of the following embodiments. In addition, components in the following embodiments include components that can be easily replaced by those skilled in the art, or components that are substantially the same. Furthermore, the components described below can be combined as appropriate.

(embodiment)
FIG. 1 is a schematic diagram showing a methane fermentation tank and a methane fermentation system of this embodiment. The methane fermentation system 1 of the present embodiment uses anaerobic microorganisms that act under anaerobic conditions to decompose organic waste and generate biogas containing methane (CH ₄ ) and carbon dioxide (CO ₂ ). It is a system that performs fermentation. This organic waste is, for example, organic sludge, waste oil, waste acid, waste alkali, or animal and plant residue. The biogas generated by the methane fermentation system 1 is used as energy after being purified.

The methane fermentation system 1 shown in FIG. 1 includes a sorting pulverizer 10, a slurry tank 20, a methane fermentation tank 100, a control device 150, an ultra-fine bubble water production device 200, a digestive fluid treatment device 40, and a desulfurization device. 50 and a gas holder 60 . In FIG. 1, "ultra-fine bubble" is abbreviated as "UFB" (the same applies to subsequent drawings).

The sorting pulverizer 10 is pretreatment equipment for smoothly performing methane fermentation. The sorting pulverizer 10 separates the input waste into organic waste and substances unsuitable for fermentation, and excludes unsuitable fermentation. Materials unsuitable for fermentation include, for example, metals, minerals, plastics, papers, and batteries containing substances that pollute the environment. The sorting pulverizer 10 coarsely pulverizes the organic waste into a paste. The sorting pulverizer 10 is connected to the slurry tank 20 through a pipe 11 . The roughly crushed organic waste is supplied to the slurry tank 20 through the pipe 11 .

The slurry tank 20 is a pretreatment facility for smooth methane fermentation. The slurry tank 20 pulverizes the organic waste supplied from the separate pulverizer 10 into slurry. In the slurry tank 20, diluent water is added and stirred until the slurried organic waste reaches a predetermined concentration, and the concentration is appropriately adjusted. Organic waste adjusted to a predetermined concentration is supplied to the methane fermentation tank 100 through the pipe 21 . It is preferable that the organic waste is supplied from the slurry tank 20 to the methane fermentation tank 100 by a predetermined amount.

The methane fermentation tank 100 decomposes the organic waste supplied from the slurry tank 20 and performs methane fermentation to generate biogas. The methane fermentation tank 100 is, for example, box-shaped or cylindrical. The methane fermenter 100 is a hermetically sealed structure. The inside of the methane fermentation tank 100 is kept in anoxic condition (anaerobic condition). The methane fermentation tank 100 has a fermentation section 110 and an ultra-fine bubble water supply section 120 .

Fermentation unit 110 contains a culture solution containing a group of microorganisms. Microbial communities include anaerobic microorganisms that operate under anaerobic conditions. Anaerobic microorganisms include methanogens. Methanogens are archaebacteria that synthesize methane under anaerobic conditions, and are responsible for the methane gas formation steps described later (first methane gas formation step S14 and second methane gas formation step S16 in FIG. 2). The fermentation unit 110 decomposes the organic waste supplied from the slurry tank 20 with anaerobic microorganisms to generate biogas containing methane and carbon dioxide. The inside of the methane fermentation tank 100 is preferably maintained under conditions such as temperature and pH in an environment in which methane bacteria can be favorably propagated.

In this embodiment, the methane fermenter 100 has a first detection device 160 and a second detection device 170 . The first detection device 160 is provided in the gas phase section above the fermentation section 110 . The first detection device 160 detects at least one of hydrogen sulfide concentration, carbon dioxide concentration, and methane concentration generated by methane fermentation. A second detection device 170 is provided in the fermentation section 110 . The second detection device 170 detects pH. Furthermore, the methane fermentation tank 100 may be provided with a thermometer. By measuring at least one of the hydrogen sulfide concentration, the carbon dioxide concentration, and the methane concentration with the first detection device 160, it is possible to detect the state of the methane fermentation reaction in the fermentation section 110. FIG. By measuring the pH with the second detection device 170 , it is possible to detect the state of the methane fermentation reaction in the fermentation section 110 . Furthermore, by measuring the temperature of the fermentation section 110 with a thermometer, it is possible to detect the state of the methane fermentation reaction in the fermentation section 110 . These detection results are sent to the control device 150, which will be described later. Although the first detection device 160 and the second detection device 170 are provided in this embodiment, only one of them may be provided. The arrangement of the first detection device 160 and the second detection device 170 is not limited to this embodiment.

A gas phase part above the fermentation part 110 is communicated with a pipe 51 connected to the desulfurization device 50 . Biogas generated by methane fermentation in fermentation unit 110 is supplied to desulfurization device 50 through pipe 51 . A pipe 41 that communicates with the digestive fluid processing device 40 is connected to the lower portion of the fermentation section 110 . Digestive juice, which is a fermentation residue after methane fermentation in fermentation unit 110 , is supplied to digestive juice processing device 40 through pipe 41 .

The principle of methane fermentation will be described with reference to FIG. FIG. 2 is a flow chart showing the process of methane fermentation. In methane fermentation, the steps from decomposition of organic waste to generation of biogas containing methane mainly include a hydrolysis step S10, an acid generation step S12, a first methane gas formation step S14, and a second methane gas formation step. It is roughly divided into S16 and S16. In the hydrolysis step S10, a decomposition reaction occurs in which the solute in the aqueous solution reacts with water molecules. In the acid generation step S12, the first methane gas formation step S14, and the second methane gas formation step S16, anaerobic microorganisms such as methane bacteria act to cause reactions. Here, the organic waste is macromolecular organic matter such as proteins, carbohydrates (polysaccharides), lipids, fibers, and fibrous substances.

First, in the hydrolysis step S10, high-molecular-weight organic substances are decomposed into low-molecular-weight organic substances. The decomposed low-molecular-weight organic substances are amino acids, sugars (monosaccharides), long-chain fatty acids, and the like. Proteins are broken down into amino acids. Carbohydrates are broken down into sugars. Lipids are broken down into sugars and long-chain fatty acids. Fibers, fibrous substances, etc. are decomposed into sugars.

Next, in the acid generation step S12, the hydrolyzed low-molecular substance is decomposed into acetic acid (CO ₃ COOH), carbon dioxide, hydrogen (H ₂ ), and the like. Amino acids are decomposed into ammonia (NH ₃ ) and short-chain fatty acids such as acetic acid, butyric acid (CH ₃ (CH ₂ ) ₂ COOH) and propionic acid (CH ₃ CH ₂ COOH). Sugars are decomposed into pyruvic acid (CH ₃ COCOOH) and the like to produce hydrogen, carbon dioxide, acetic acid and other intermediate products. This intermediate product is decomposed into acetic acid, hydrogen, and the like. Long-chain fatty acids are decomposed into acetic acid and the like.

Finally, in the first methane gas formation step S14 and the second methane gas formation step S16, methane bacteria produce methane, carbon dioxide, water, and the like. In the first methane gas formation step S14, acetic acid is decomposed into methane and carbon dioxide. In the second methane gas formation step S16, methane is produced from hydrogen and carbon dioxide.

In the above description, it is assumed that the methane fermentation is performed only inside the methane fermentation tank 100 . Here, the organic waste supplied to the methane fermentation tank 100 is slurried in the slurry tank 20 shown in FIG. In other words, the organic waste supplied to the methane fermentation tank 100 is high-molecular-weight organic matter in a hydrated state. Part of the hydrolysis step S10 is also performed inside the slurry tank 20 when the organic waste contains in advance aerobic microorganisms or enzymes that can serve as catalysts for the hydrolysis step S10. Furthermore, if the organic waste contains in advance anaerobic microorganisms or enzymes that can serve as catalysts for the acid generation step S12, part of the acid generation step S12 is also performed inside the slurry tank 20.

The ultra-fine bubbled water supply section 120 shown in FIG. 1 supplies ultra-fine bubbled water (UFB water) from the ultra-fine bubbled water production device 200 (UFB water production device) to the fermentation section 110 of the methane fermentation tank 100 . The ultra-fine bubble water supply unit 120 has a pipe 121 that connects the methane fermentation tank 100 and the ultra-fine bubble water production device 200 and a valve 122 that opens and closes the pipe 121 . Ultra-fine bubble water is an aqueous solution containing bubbles with a diameter of 1 μm or less, that is, an aqueous solution containing so-called ultra-fine bubbles. Ultra-fine bubbles are bubbles with a diameter of 1 μm or less, preferably 1 nm or more and 1 μm or less, more preferably 30 nm or more and 400 nm or less.

Addition of the ultra-fine bubble water to the methane fermenter 100 improves the mobility of substances inside the methane fermenter 100 . The adherence of the ultra-fine bubbles to the organic waste makes it easier for the microorganisms existing in the fermentation section 110 of the methane fermentation tank 100 to come into contact with the ultra-fine bubbles. Since ultra-fine bubbles contain oxygen, contact with ultra-fine bubbles is stressful for anaerobic microorganisms. In addition, the ultra-fine bubbles increase the concentration of reactive oxygen species (ROS) in the liquid. Reactive oxygen species include hydroxyl radicals, superoxide anion radicals, hydroperoxyl radicals, hydrogen peroxide, singlet oxygen, and the like. When the concentration of reactive oxygen species around and in a microorganism increases to a level that is not fatal to the microorganism, the primary metabolism and secondary metabolism of the microorganism are activated and the secondary metabolism products increase. The products may also contain enzymes that contribute to the decomposition of persistent substances. Further, when the ultra-fine bubbles come into contact with the microorganisms, at least one element of potassium, zinc, iron, and manganese contained in the methane fermentation tank 100 is easily absorbed by the microorganisms, increasing the concentration of the elements contained in the microorganisms. , microorganisms are activated. As a result, the initial fermentation rate of organic waste is improved, decomposition is promoted, and the amount of methane generated is increased.

It is difficult to use water containing bubbles (microbubbles) with a diameter of several micrometers or more and several hundred micrometers or less as the culture solution used for methane fermentation. This is because water containing microbubbles has a high oxygen solubility, and the culture solution in the methane fermentation tank becomes an environment in which anaerobic microorganisms cannot easily grow. On the other hand, since ultra-fine bubble water has a very small volume and a low oxygen content, anaerobic microorganisms can grow in ultra-fine bubble water. Also, ultra-fine bubbles have a longer lifetime than microbubbles. Therefore, in the methane fermentation system 1 of the present embodiment, energy consumption can be reduced by generating only the necessary amount of ultra-fine bubble water and adding it to the methane fermentation tank 100 .

In addition, when the organic waste contains a persistent substance, the residue from which the methane fermentation reaction did not proceed tends to remain. For this reason, conventionally, the methane fermentation reaction of the persistent substances has been promoted by increasing the pressure of the reaction system, raising the temperature, or the like. However, by using ultra-fine bubble water as in this embodiment, the initial fermentation rate of organic waste containing persistent organic matter is improved, the decomposition is promoted, and the amount of methane generated is increased. It is possible to reduce the amount of residuals.

The controller 150 adjusts the amount of ultra-fine bubble water supplied to the methane fermentation tank 100 by the ultra-fine bubble water supply unit 120 . The control device 150 has an estimation unit 151 and a control unit 152 . The estimation unit 151 estimates the concentration of ultra-fine bubbles in the culture solution of the fermentation unit 110 . For example, the estimating unit 151 is based on the amount of ultra-fine bubble water supplied to the methane fermentation tank 100, the amount of culture fluid in the fermentation unit 110, and the time elapsed since the ultra-fine bubble water was supplied to the methane fermentation tank 100. , to estimate the concentration of ultrafine bubbles in the culture. The control unit 152 can adjust the supply amount of ultra-fine bubble water based on the concentration estimated by the estimation unit 151 . The control unit 152 can adjust the amount of ultra-fine bubble water supplied to the methane fermentation tank 100 by the ultra-fine bubble water supply unit 120 by opening and closing the valve 122 .

The controller 150 electrically connects to the first detector 160 and the second detector 170 . The control device 150 causes the first detection device 160 to measure at least one of the hydrogen sulfide concentration, the carbon dioxide concentration, and the methane concentration generated by the methane fermentation, and acquires the measurement result. The control device 150 causes the second detection device to measure the pH and obtains the measurement result. Furthermore, if the methane fermentation tank 100 has a thermometer, the control device 150 is electrically connected to the thermometer to obtain the temperature of the fermentation section 110 . The control device 150 detects the state of the methane fermentation reaction based on the measurement results of the first detection device 160, the second detection device 170, and the thermometer. The control device 150 can control the amount of ultra-fine bubble water supplied from the ultra-fine bubble water production device 200 to the methane fermentation tank 100 in accordance with the state of the methane fermentation reaction.

The ultra-fine bubble water is added to the methane fermentation tank 100 when the organic waste is supplied from the slurry tank 20 to the methane fermentation tank 100, or when the organic waste is supplied from the slurry tank 20 to the methane fermentation tank 100. preferably after As a result, the ultra-fine bubbles adhere to the organic waste before the concentration of the ultra-fine bubbles decreases. The ultra-fine bubble water added to the methane fermenter 100 is preferably 10 vol % or more of the volume of the culture solution in the fermentation section 110 of the methane fermenter 100 . It is preferable that the concentration of ultra-fine bubbles in the culture solution of fermentation section 110 is 2×10 ⁷ particles/ml or more and 2×10 ⁸ particles/ml or less. The concentration of ultra-fine bubbles is the number of ultra-fine bubbles present in water per unit volume. The concentration of ultra-fine bubbles being 2×10 ⁷ particles/ml means that 2×10 ⁷ ultra-fine bubbles are present in 1 ml of ultra-fine bubble water. The concentration of ultra-fine bubbles can be measured with a nanoparticle analysis system "NanoSight" manufactured by Malvern Panalytical, a nanoparticle size distribution analyzer "SALD-7500nano" manufactured by Shimadzu Corporation, and the like.

The ultra-fine bubbled water production device 200 produces ultra-fine bubbled water supplied from the ultra-fine bubbled water supply section 120 to the fermentation section 110 of the methane fermentation tank 100 . The ultra-fine bubble water production device 200 has an ultra-fine bubble generator 201 (UFB water generator), an ultra-fine bubble water tank 202 (UFB water tank), a gas source G, and a water source W.

The gas source G supplies gas for forming ultra-fine bubbles to the ultra-fine bubble generator 201 . This gas is not particularly limited. Gases are, for example, air, carbon dioxide, hydrogen, oxygen, nitrogen (N ₂ ), and the like.

The water source W supplies the ultra-fine bubbled water tank 202 with a liquid that forms ultra-fine bubbled water. This liquid is, for example, tap water, well water, rain water, river water, digestive fluid, treated waste water, or the like.

The ultra-fine bubble concentration of the ultra-fine bubble water is preferably 6×10 ⁷ particles/ml or more and 5×10 ⁹ particles/ml or less. For example, ultra-fine bubbled water having a suitable concentration is produced by operating the ultra-fine bubbled water production device 200 for 30 minutes with respect to 1.5 L of liquid. A method for producing ultra-fine bubble water is not particularly limited. For example, as a method for producing ultra-fine bubble water, a pump or stirrer is used to create a fluid flow, gas is introduced into the fluid flow, and the gas is passed through devices and equipment such as static mixers, ejectors, and venturis. There is a method in which fine bubbles are generated by atomizing the internal gas by allowing the contained fluid to pass through at high speed. There is also a method in which a fluid is put in a container and the gas passed through various devices such as a static mixer, an ejector and a venturi is discharged into the fluid. The former includes the swirling flow method, static mixer method, ejector method, venturi method, pressurized dissolution method, and cavitation method. There are a rotation method, an ultrasonic method, a pulse magnetic field application method, and the like. The ultra-fine bubble water produced by the ultra-fine bubble water production device 200 is stored in the ultra-fine bubble water tank 202 and supplied to the fermentation section 110 of the methane fermentation tank 100 through the pipe 121 . In this embodiment, the ultra-fine bubble water is supplied only to the methane fermentation tank 100, but it may be supplied to the slurry tank 20 as well.

A digestive juice processing apparatus 40 shown in FIG. 1 is an apparatus for processing digestive juice, which is a fermentation residue after methane fermentation is performed in the fermentation section 110 of the methane fermentation tank 100 . The digestive fluid treatment device 40 has, for example, a biological treatment tank, a solid-liquid separator, a waste water treatment device, a dehydration device, a drying device, and the like. The digestive juice processing device 40 performs solid-liquid separation to separate the digestive juice into solid and liquid. The separated solids can be, for example, composted and returned to agricultural land or the like. The separated liquid is returned to the slurry tank 20 as it is or after being subjected to waste water treatment. In addition, the ultra-fine bubble water of the present embodiment may be added to the liquid returned to the slurry tank 20 .

The desulfurization device 50 introduces biogas generated by methane fermentation in the fermentation section 110 of the methane fermentation tank 100 through a pipe 51 . The desulfurizer 50 removes sulfur oxides (SO _x ) from the biogas to obtain purified biogas. The purified biogas is supplied to the gas holder 60 through the pipe 61 .

The gas holder 60 temporarily stores the purified biogas. The purified biogas is sent to power generation facility 70 . The power generation equipment 70 is, for example, a boiler, a generator, or the like. The power generation equipment 70 burns the purified biogas to generate energy such as electric power, and emits carbon dioxide. In addition, it is also possible to use the purified biogas as it is as a fuel. Further, by providing a gas flow meter between the gas holder 60 and the power generation equipment 70, the flow rate of the gas supplied to the power generation equipment 70 can be controlled.

A methane fermentation method by the methane fermentation system 1 will be described with reference to FIG. 3 is a flowchart of a methane fermentation method using the methane fermentation system shown in FIG. 1. FIG.

First, when waste is put into the sorting pulverizer 10, the sorting pulverizer 10 separates the waste into organic waste and fermentation-unsuitable waste (step S20). Excluded fermentation unsuitables are appropriately disposed of in any manner. The sorting pulverizer 10 coarsely pulverizes the organic waste sorted in step S20 into a paste (step S22).

The pasted organic waste is supplied to the slurry tank 20 . The slurry tank 20 pulverizes the organic waste into slurry (step S24). In the slurry tank 20, diluent water is added and stirred until the slurried organic waste reaches a predetermined concentration, and the concentration is appropriately adjusted.

When the organic waste adjusted to a predetermined concentration is supplied to the fermentation section 110 of the methane fermentation tank 100, the ultra-fine bubble water supply section 120 adds ultra-fine bubble water to the fermentation section 110 (step S26). . The supply amount of the ultra-fine bubble water to be added is adjusted by opening and closing the valve 122 by the controller 150 . The ultra-fine bubbles of the ultra-fine bubble water adhere to the organic waste and microorganisms and activate the microorganisms existing in the fermentation section 110 . Also, by attaching to the hydrolase, the activity of the hydrolase is enhanced.

Organic waste in the fermentation unit 110 is decomposed by methane fermentation to generate biogas (step S28). As described above, the organic waste supplied to the fermentation unit 110 is decomposed by the hydrolysis step S10, the acid generation step S12, the first methane gas formation step S14 and the second methane gas formation step S16, produce gas.

The biogas produced in step S28 is introduced into the desulfurization device 50 from the gas phase section above the fermentation section 110 . The desulfurizer 50 removes sulfur oxides from the biogas to obtain purified biogas (step S30). The purified biogas is temporarily stored in the gas holder 60 and then delivered to the power generation facility 70 .

4 to 6, the effect of promoting methane fermentation by adding ultra-fine bubble water will be described. FIG. 4 is a graph showing the amount of methane produced in a batch test. FIG. 5 is a graph showing the final decomposition rate of persistent organic matter in a batch test. FIG. 6 is a graph showing the amount of methane produced from organic waste containing persistent organic matter in a batch test.

FIG. 4 shows the amount of organic matter (g) (VS: Volatole Solids) contained in the sludge when methane fermentation is performed on 20 g of sludge as organic waste by assuming the bottle filled with the culture solution as the methane fermentation tank 100. The amount of methane produced (ml) is shown. 1 g of sludge contains 0.378 g of total solids (TS) and 0.15 g of organic matter. Water or ultra-fine bubble water is added to the sludge. As a comparative example, when water other than ultra-fine bubble water is added to sludge, the added water is distilled water (DW: Distilled Water) or tap water (TW: Tap Water). The gas forming the ultra-fine bubbled water to be added is air, carbon dioxide, hydrogen or nitrogen. In FIG. 4, the ultra-fine bubbled water containing air is indicated as "Air-UFBW", the ultra-fine bubbled water containing carbon dioxide is indicated as "CO ₂ -UFBW", and the ultra-fine bubbled water containing hydrogen is indicated. "H ₂ -UFBW" is described, and ultra-fine bubbled water containing nitrogen is described as "N ₂ -UFBW".

As shown in FIG. 4, the amount of methane produced increases when ultra-fine bubbled water is added compared to when ultra-fine bubbled water is not added. In other words, when ultra-fine bubble water is added, the decomposition speed and amount of organic waste are improved.

Table 1 shows enzyme activity units (EU: Enzyme Units) per gram of organic matter (VS) contained in sludge when sludge is subjected to methane fermentation. The enzymes measured were four hydrolases: Alkaline phosphatase, Acid phosphatase, α-glycosidase, and Protease. Distilled water or ultra-fine bubble water containing 20 vol % nitrogen is added to the sludge. In Table 1, ultra-fine bubble water containing nitrogen is described as "N ₂ -UFBW". All data in Table 1 are also presented as the mean±standard deviation of triplicate tests.

As shown in Table 1, when ultra-fine bubble water containing 20 vol% nitrogen is added to the methane fermentation of sludge, the activities of the four hydrolases are about 14 to 17 compared to when distilled water is added. %improves. In other words, the addition of the nitrogen-containing ultra-fine bubble water increases the speed and throughput of the hydrolysis step S10 performed in the methane fermentation tank 100 or the pre-fermentation tank 30 (see the third modified example below).

FIG. 5 shows a bottle filled with a culture solution as a methane fermentation tank 100, and when methane fermentation is performed on a difficult-to-decompose organic substance containing lignin as an organic waste, the amount of lignin before decomposition is decomposed in an equilibrium state. The percentage (%) of the amount of lignin added is shown. FIG. 6 shows the total organic carbon (TOC: It shows the amount of methane produced (ml) per Total Organic Carbon. 5 and 6, the components of the organic waste containing persistent organic matter are 90% acetic acid and 10% lignin. Water or ultra-fine bubble water is added to organic waste containing persistent organic matter. As a comparative example, when water other than ultra-fine bubble water is added to organic waste containing persistent organic matter, the water to be added is distilled water. The gas forming the ultra-fine bubbled water to be added is carbon dioxide or nitrogen. 5 and 6, ultra-fine bubbled water containing carbon dioxide is indicated as "CO ₂ -UFBW", and ultra-fine bubbled water containing nitrogen is indicated as "N ₂ -UFBW".

As shown in FIG. 5, when ultra-fine bubble water is added, the final decomposition amount of persistent organic matter increases compared to when distilled water is added. As shown in FIG. 6, the addition of ultra-fine bubble water increases the total methane production at equilibrium compared to the addition of distilled water. It also improves the initial methane production rate and production. That is, the initial fermentation rate of the persistent organic matter is improved, and the initial decomposition rate, the initial decomposition amount and the total decomposition amount are promoted.

As described above, the methane fermentation tank 100 of the present embodiment includes the fermentation unit 110 that performs methane fermentation of organic waste with a culture solution containing anaerobic microorganisms, and ultra-fine bubbles that are bubbles with a diameter of 1 μm or less. and an ultra-fine bubble water supply unit 120 that supplies ultra-fine bubble water to the fermentation unit 110 .

As a result, the ultra-fine bubble water is added to the methane fermentation tank 100, so that the mobility of substances inside the methane fermentation tank 100 is improved. The adherence of the ultra-fine bubbles to the organic waste activates the secondary metabolism of the microorganisms existing in the fermentation section 110 of the methane fermentation tank 100 . According to the methane fermenter 100 as described above, the activation of the microorganisms and the hydrolase can improve the initial fermentation rate of the organic waste and accelerate the decomposition thereof. Accelerating the decomposition of organic waste can improve the rate and amount of biogas production. In addition, the microorganisms existing in the fermentation section 110 are stabilized at an early stage.

In the methane fermentation tank 100, the organic waste contains persistent organic matter.

According to such a methane fermenter 100, the activation of the microorganism group and the hydrolase can improve the initial fermentation rate of the organic waste containing the persistent organic matter and accelerate the decomposition. By accelerating the decomposition of organic waste containing persistent organic matter, the rate and amount of biogas production can be improved. In addition, the microorganisms existing in the fermentation section 110 are stabilized at an early stage.

Ultra-fine bubbles in the methane fermentation tank 100 preferably contain at least one of air, carbon dioxide, hydrogen, oxygen and nitrogen.

According to such a methane fermentation tank 100, decomposition of organic waste can be favorably promoted. This can promote the production of biogas.

The concentration of ultra-fine bubbles in the methane fermentation tank 100 is preferably 6×10 ⁷ particles/ml or more and 5×10 ⁹ particles/ml or less.

According to such a methane fermentation tank 100, decomposition of organic waste can be favorably promoted. This can promote the production of biogas.

The methane fermentation system 1 of the present embodiment also has a methane fermentation tank 100 and an ultra-fine bubble water production device 200 that produces ultra-fine bubble water to be supplied to the fermentation section 110 .

According to such a methane fermentation system 1, since ultra-fine bubble water is added to the methane fermentation tank 100, the mobility of substances inside the methane fermentation tank 100 is improved. The adherence of the ultra-fine bubbles to the organic waste activates the primary and secondary metabolisms of microorganisms existing in the fermentation section 110 of the methane fermentation tank 100 . The methane fermentation system 1 can improve the initial fermentation rate of organic waste containing persistent organic matter and promote decomposition by activating the microorganisms and the hydrolase. The methane fermentation system 1 can improve the rate and amount of biogas produced by promoting the decomposition of organic waste. In addition, the microorganisms existing in the fermentation section 110 are stabilized early and for a long period of time.

The methane fermentation system 1 preferably has a controller 150 that adjusts the amount of ultra-fine bubbled water supplied by the ultra-fine bubbled water supply unit 120 .

According to such a methane fermentation system 1, the concentration of ultra-fine bubbles in the fermentation section 110 of the methane fermentation tank 100 can be adjusted. As a result, the methane fermentation system 1 can favorably promote the decomposition of organic waste and promote the production of biogas.

In the methane fermentation system 1, the control device 150 adjusts the supply amount of the ultra-fine bubble water based on the estimation unit 151 that estimates the concentration of the ultra-fine bubbles in the culture solution of the fermentation unit 110 and the concentration estimated by the estimation unit 151. It is preferable to have a control unit 152 that performs

According to such a methane fermentation system 1, the concentration of ultra-fine bubbles in the fermentation section 110 of the methane fermentation tank 100 can be adjusted appropriately. As a result, the methane fermentation system 1 can favorably promote the decomposition of organic waste and promote the production of biogas.

In the methane fermentation system 1, the control unit 152 supplies ultra-fine bubble water so that the concentration of ultra-fine bubbles in the culture solution in the fermentation unit 110 is 2×10 ⁷ particles/ml or more and 2×10 ⁸ particles/ml or less. It is preferred to adjust the amount.

According to such a methane fermentation system 1, decomposition of organic waste can be favorably promoted. This can promote the production of biogas.

The methane fermentation system 1 preferably includes a desulfurization device 50 that removes sulfur oxides from the biogas generated from the methane fermentation tank 100 to produce purified biogas.

According to such a methane fermentation system 1, biogas can be suitably used as energy by removing sulfur oxides that cause air pollution, offensive odors, and the like.

The methane fermentation system 1 is preferably provided with a slurry tank 20 to which ultra-fine bubbled water is supplied and which slurries the organic waste before being put into the methane fermentation tank 100 .

According to such a methane fermentation system 1, organic waste can be diluted to a concentration suitable for methane fermentation. Thereby, it is possible to smoothly perform methane fermentation in the fermentation section 110 of the methane fermentation tank 100 .

The methane fermentation system 1 may include a digestive juice processing device 40 that solid-liquid separates the digestive juice generated from the methane fermentation tank 100 and supplies the liquid obtained by the solid-liquid separation of the digestive juice to the slurry tank 20. preferable.

According to such a methane fermentation system 1, the liquid obtained by the solid-liquid separation of the digestive fluid can be used as the dilution water for diluting the organic waste in the slurry tank 20. Thereby, the amount of water used in the methane fermentation system 1 can be saved.

Further, the methane fermentation treatment method of the present embodiment is a methane fermentation treatment method for methane fermentation of organic waste with a culture solution containing anaerobic microorganisms, and ultra-fine bubbles, which are bubbles with a diameter of 1 μm or less during methane fermentation, are produced. to supply the organic waste with ultra-fine bubble water containing

According to such a methane fermentation treatment method, the ultra-fine bubble water is added to the organic waste, so the mobility of substances in the culture solution is improved. The adherence of the ultra-fine bubbles to the organic waste and the hydrolytic enzyme activates the primary and secondary metabolism of the microorganisms in the culture solution. By activating the microorganisms, the initial fermentation rate of the organic waste containing the persistent organic matter can be improved, and the decomposition can be accelerated. Furthermore, the adhesion of the ultra-fine bubble water to the hydrolase activates the hydrolase, thereby increasing the initial fermentation rate of the organic waste containing the persistent organic matter and accelerating the decomposition. Accelerating the decomposition of organic waste can improve the rate and amount of biogas production. In addition, the microbial community in the culture is stabilized early and for a long period of time.

(First modification)
FIG. 7 is a schematic diagram showing the methane fermentation system of the first modified example. The methane fermentation system 2 shown in FIG. 7 includes a separate pulverizer 10, a slurry tank 20, a methane fermentation tank 100, a control device 150, a first ultra-fine bubble water production device 210, and a second ultra-fine bubble water production device. A device 220 , a digestive liquid processing device 40 , a desulfurization device 50 and a gas holder 60 are provided. The methane fermentation system 2 includes a first ultra-fine bubble water production device 210 and a second ultra-fine bubble water production device 220 instead of the ultra-fine bubble water production device 200 in the configuration of the methane fermentation system 1. It is different in that it has

The first ultra-fine bubbled water production device 210 produces ultra-fine bubbled water containing at least one ultra-fine bubble of carbon dioxide, hydrogen, oxygen, and nitrogen. Here, an example containing carbon dioxide as ultra-fine bubbles will be described. Therefore, it is indicated as CO ₂ -UFB water. The first ultra-fine bubble water production device 210 has a first ultra-fine bubble generator 211, a first ultra-fine bubble water tank 212, a gas source G1, and a water source W1. The gas source G1 supplies carbon dioxide for forming ultra-fine bubbles to the first ultra-fine bubble generator 211 . The water source W1 supplies the first ultra-fine bubbled water tank 212 with a liquid that forms ultra-fine bubbled water. This liquid is, for example, tap water, well water, rain water, river water, digestive fluid, treated waste water, or the like. Also, the liquid may contain at least one of potassium, calcium and magnesium. By including potassium or calcium in the liquid, the concentration of sodium contained in fermentation section 110 can be reduced.

The second ultra-fine bubble water producing device 220 produces ultra-fine bubble water (Air-UFB water) containing ultra-fine bubbles of air. The second ultra-fine bubble water production device 220 has a second ultra-fine bubble generator 221, a second ultra-fine bubble water tank 222, a gas source G2, and a water source W2. The gas source G2 supplies air for forming ultra-fine bubbles to the second ultra-fine bubble generator 221 . The water source W2 supplies the second ultra-fine bubble water tank 222 with a liquid that forms ultra-fine bubble water. This liquid is, for example, tap water, well water, rain water, river water, digestive fluid, treated waste water, or the like. Also, the liquid may contain at least one of potassium, calcium and magnesium. By including potassium or calcium in the liquid, the concentration of sodium contained in fermentation section 110 can be reduced. Note that the water source W2 may contain a metal different from that of the water source W1. For example, water source W1 may contain potassium and water source W2 may contain magnesium.

The ultra-fine bubble water supply section 120 of the methane fermentation tank 100 has a first supply section 130 and a second supply section 140 . The first supply unit 130 supplies ultra-fine bubble water containing ultra-fine bubbles of carbon dioxide from the first ultra-fine bubble water production device 210 to the fermentation unit 110 of the methane fermentation tank 100 . The first supply unit 130 has a pipe 131 that connects the methane fermentation tank 100 and the first ultra-fine bubble water production device 210 and a valve 132 that opens and closes the pipe 131 . The second supply unit 140 supplies ultra-fine bubble water containing ultra-fine bubbles of air from the second ultra-fine bubble water production device 220 to the fermentation unit 110 of the methane fermentation tank 100 . The second supply unit 140 has a pipe 141 that connects the methane fermentation tank 100 and the second ultra-fine bubble water production device 220 and a valve 142 that opens and closes the pipe 141 .

The methane fermentation tank 100 of the methane fermentation system 2 has a first detection device 160 and a second detection device 170, like the methane fermentation tank 100 of the methane fermentation system 1 shown in FIG. The control device 150 causes the first detection device 160 to measure at least one of the hydrogen sulfide concentration, the carbon dioxide concentration, and the methane concentration in the methane fermentation tank 100, and acquires the measurement result. The control device 150 causes the second detection device 170 to measure the pH and acquires the measurement result. The control unit 152 of the control device 150 determines the second 1 The amount of ultra-fine bubble water supplied to the methane fermentation tank 100 by the supply unit 130 is adjusted. The control unit 152 can adjust the amount of ultra-fine bubble water supplied to the methane fermentation tank 100 by the first supply unit 130 by opening and closing the valve 132 . The control unit 152 of the control device 150 determines the second 2 The amount of ultra-fine bubble water supplied to the methane fermentation tank 100 by the supply unit 140 is adjusted. The control unit 152 can adjust the amount of ultra-fine bubble water supplied to the methane fermentation tank 100 by the second supply unit 140 by opening and closing the valve 142 . In this way, the control device 150 can detect the second The amount of ultra-fine bubbled water supplied from the first supply unit 130 and the second supply unit 140 is adjusted.

As described above, the methane fermentation system 2 of the first modification includes the first detection device 160 that detects at least one of the hydrogen sulfide concentration, the carbon dioxide concentration, and the methane concentration of the methane fermentation tank 100, and the pH. and the ultra-fine bubble water supply unit 120 supplies ultra-fine bubble water containing at least one ultra-fine bubble of carbon dioxide, hydrogen, oxygen, and nitrogen. 130, and a second supply unit 140 that supplies ultra-fine bubbled water containing ultra-fine air bubbles, and the control device 150 detects the hydrogen sulfide concentration, the methane concentration, and the carbon dioxide concentration detected by the first detection device 160. Based on at least one of the concentration and at least one of the pH detected by the second detection device 170, the amount of ultra-fine bubble water supplied by the first supply unit 130 and the supply of ultra-fine bubble water by the second supply unit 140 Adjust the amount and

According to such a methane fermentation system 2, the ratio of gases forming ultra-fine bubbles and the concentration of ultra-fine bubbles in the methane fermentation tank 100 can be adjusted. As a result, the methane fermentation system 1 can favorably promote the decomposition of organic waste and promote the production of biogas.

(Second modification)
FIG. 8 is a schematic diagram showing a methane fermentation system of a second modified example. The methane fermentation system 3 shown in FIG. 8 includes a separate pulverizer 10, a slurry tank 20, a methane fermentation tank 100, a control device 150, an ultra-fine bubble water production device 200, a catalyst storage device 230, and a catalyst supply unit. 180, a digestive fluid processing device 40, a desulfurization device 50, and a gas holder 60. The methane fermentation system 3 differs from the configuration of the methane fermentation system 1 in that it has a catalyst storage device 230 .

The catalyst storage device 230 stores short-chain fatty acids that act as catalysts for methane fermentation. The catalyst storage device 230 has a catalyst tank 232 and a catalyst source C. The catalyst source C supplies the catalyst tank 232 with short-chain fatty acids that act as a catalyst for methane fermentation. The short-chain fatty acids are, for example, acetic acid, butyric acid, propionic acid and the like. The catalyst supply unit 180 has a pipe 181 that connects the methane fermentation tank 100 and the catalyst storage device 230 and a valve 182 that opens and closes the pipe 181 .

Control device 150 adjusts the amount of short-chain fatty acids supplied to methane fermentation tank 100 by catalyst supply unit 180 . The control unit 152 can adjust the amount of short-chain fatty acids supplied to the methane fermentation tank 100 by the catalyst supply unit 180 by opening and closing the valve 182 . The control device 150 may add short-chain fatty acids to the fermentation section 110 of the methane fermentation tank 100 together with the ultra-fine bubble water. The control device 150 may control the supply amount of short-chain fatty acids by the time during which methane fermentation is performed. The control device 150 determines the supply amount of short-chain fatty acids based on the hydrogen sulfide concentration, methane concentration, carbon dioxide concentration and pH detected by the first detection device 160 and the second detection device 170 provided in the methane fermentation tank 100. can be controlled by Short-chain fatty acids can activate microorganisms in fermentation section 110 . Therefore, when the organic waste contains persistent organic matter, it is possible to accelerate the decomposition reaction of the persistent organic matter, which is preferable.

(Third modification)
FIG. 9 is a schematic diagram showing a methane fermentation system of a third modified example. The methane fermentation system 4 shown in FIG. 9 includes a separate pulverizer 10, a slurry tank 20, a pre-fermentation tank 30, a methane fermentation tank 100, a control device 150, an ultra-fine bubble water production device 200, and a digestive fluid treatment. A device 40 , a desulfurization device 50 and a gas holder 60 are provided. The methane fermentation system 4 differs from the configuration of the methane fermentation system 1 in that it has a pre-fermentation tank 30 between the slurry tank 20 and the methane fermentation tank 100 . The pre-fermentation tank 30 is connected to the slurry tank 20 via a pipe 21 . The pre-fermentation tank 30 is connected to the methane fermentation tank 100 via a pipe 31 .

The pre-fermentation tank 30 is a pre-treatment facility for smooth methane fermentation. The pre-fermentation tank 30 performs the hydrolysis step S10 shown in FIG. The pre-fermentation tank 30 hydrolyzes the organic waste supplied from the slurry tank 20 through the pipe 21 . In the pre-fermentation tank 30, high-molecular-weight organic substances are decomposed into low-molecular-weight organic substances. Decomposed low-molecular-weight organic substances such as amino acids, sugars (monosaccharides) and long-chain fatty acids are supplied to the methane fermentation tank 100 through the pipe 31 . It is preferable that the organic waste is supplied from the slurry tank 20 to the pre-fermentation tank 30 by a predetermined amount. It is preferable that the organic waste is supplied from the pre-fermenter 30 to the methane fermenter 100 in predetermined amounts.

In the methane fermentation tank 100, the acid generation step S12, the first methane gas formation step S14, and the second methane gas formation step S16 shown in FIG. 2 are performed. The fermentation section 110 of the methane fermenter 100 decomposes the low-molecular-weight organic matter supplied from the pre-fermenter 30 into acetic acid, hydrogen and carbon dioxide. Fermentation unit 110 decomposes acetic acid into methane and carbon dioxide to produce hydrogen and carbon dioxide into methane and water (H ₂ O).

Biogas generated by methane fermentation in fermentation unit 110 is supplied to desulfurization device 50 through pipe 51 . The desulfurization device 50 removes sulfur oxides from the biogas to obtain purified biogas. The purified biogas is temporarily stored in the gas holder 60 and then delivered to the power generation facility 70 .

Digestive juice, which is a fermentation residue after methane fermentation in fermentation unit 110 , is supplied to digestive juice processing device 40 through pipe 41 . The digestive juice processing device 40 performs solid-liquid separation to separate the digestive juice into solid and liquid. The separated liquid is returned to the slurry tank 20 and the pre-fermentation tank 30 as it is or after being subjected to waste water treatment. In addition, the ultra-fine bubble water of the present embodiment may be added to the liquid returned to the slurry tank 20 and the pre-fermentation tank 30 .

In the above description, the acid-producing step S12 is performed only inside the methane fermentation tank 100, but the organic waste contains in advance anaerobic microorganisms or enzymes that can serve as catalysts for the acid-producing step S12. If so, part of the acid generation step S12 also takes place inside the pre-fermenter 30 .

As described above, in the methane fermentation system 4 of the third modification, the pre-fermentation tank 30 is supplied with ultra-fine bubble water and hydrolyzes the organic waste before being put into the methane fermentation tank 100. Prepare.

According to such a methane fermentation system 4, the inside of the pre-fermentation tank 30 is maintained in the optimum environment for the hydrolysis step S10, and the inside of the methane fermentation tank 100 is maintained in the acid generation step S12 and the methane gas formation step (first methane gas The optimum environment can be maintained for the forming step S14 and the second methane gas forming step S16). Here, the hydrolysis step S10 is an aerobic reaction, and the acid generation step S12, the first methane gas formation step S14 and the second methane gas formation step S16 are anaerobic reactions. That is, in the methane fermentation system 4, for example, the inside of the pre-fermentation tank 30 can be an oxygen atmosphere, and the inside of the methane fermentation tank 100 can be a carbon dioxide atmosphere, a hydrogen atmosphere, an oxygen atmosphere, or a nitrogen atmosphere. Since the optimum environment in each process is different, by providing the pre-fermentation tank 30, it is possible to maintain the optimum environment in each process, suitably promote the decomposition of organic waste, and biogas can promote the generation of

The methane fermentation system 4 includes a digestive juice processing device 40 that solid-liquid separates the digestive juice generated from the methane fermentation tank 100 and supplies the liquid obtained by the solid-liquid separation of the digestive juice to the pre-fermentation tank 30. is preferred.

According to the methane fermentation system 4 as described above, the liquid obtained by solid-liquid separation of the digestive juice can be used as the water for hydrolyzing the organic waste in the pre-fermentation tank 30 . Thereby, the amount of water used in the methane fermentation system 1 can be saved.

(Fourth modification)
FIG. 10 is a schematic diagram showing a methane fermentation system of a fourth modified example. The methane fermentation system 5 shown in FIG. 10 includes a fractionating pulverizer 10, a slurry tank 20, a methane fermentation tank 100, a control device 150, an ultra-fine bubble water producing device 200, a digestive fluid processing device 40, and a desulfurization device. 50 and a gas holder 60 . The methane fermentation system 5 differs from the configuration of the methane fermentation system 1 in that the gas source G of the ultra-fine bubble water production device 200 introduces gas for forming ultra-fine bubbles from the power generation equipment 70 . The gas source G introduces carbon dioxide discharged by combustion of the purified biogas in the power generation facility 70 .

As explained above, in the methane fermentation system 5 of the fourth modified example, the ultra-fine bubbles contain carbon dioxide discharged by combustion of the post-purification biogas.

According to such a methane fermentation system 5, carbon dioxide emitted by combustion of purified biogas can be recovered and reused before it is emitted to the atmosphere. This can contribute to global warming countermeasures.

(Fifth modification)
FIG. 11 is a schematic diagram showing a methane fermentation system of the fifth modified example. The methane fermentation system 6 shown in FIG. 11 includes a separating pulverizer 10, a slurry tank 20, a methane fermentation tank 100, a control device 150, an ultra-fine bubble water producing device 200, a digestive fluid processing device 40, and a desulfurization device. 50 and a gas holder 60 . The methane fermentation system 6 differs from the configuration of the methane fermentation system 1 in that the water source W of the ultra-fine bubble water production device 200 introduces the liquid for forming the ultra-fine bubble water from the digestive fluid processing device 40 . The water source W introduces the liquid separated from the digestive juice by solid-liquid separation in the digestive juice treatment apparatus 40 or the liquid after wastewater treatment.

As explained above, in the methane fermentation system 6 of the fifth modified example, the ultra-fine bubble water contains liquid obtained by solid-liquid separation of digestive juice.

According to such a methane fermentation system 6, it is possible to reuse the digestive juice, which is the fermentation residue after performing methane fermentation in the fermentation section 110 of the methane fermentation tank 100.

(Sixth modification)
FIG. 12 is a schematic diagram showing a methane fermentation system of the sixth modification. The methane fermentation system 7 shown in FIG. 12 includes a fractionating pulverizer 10, a slurry tank 20, a methane fermentation tank 100, a control device 150, an ultra-fine bubble water producing device 200, a digestive fluid processing device 40, and a desulfurization device. 50 , a gas holder 60 and a heating device 80 . The methane fermentation system 7 differs from the configuration of the methane fermentation system 1 in that a heating device 80 in which hot water heated by waste heat generated by the power generation equipment 70 is circulated is provided around the methane fermentation tank 100. differ in

According to such a methane fermentation system 7, it is possible to heat the fermentation section 110 of the methane fermentation tank 100 appropriately. By using the heating device 80 to set the temperature of the fermentation unit 110 to a temperature capable of promoting the fermentation reaction, the fermentation reaction can be promoted. The temperature that can promote the fermentation reaction is, for example, 30°C or higher and 70°C or lower, preferably 40°C or higher and 60°C or lower. Moreover, the fermentation reaction of the fermentation section 110 can be promoted without increasing the energy amount of the entire system.

Each configuration described in the embodiment may be combined with other configurations in each embodiment without departing from the scope of the invention. Moreover, each of these configurations may be combined with configurations in other embodiments that are different from each embodiment within the scope of the invention. Also, various modifications may be made without departing from the scope of the invention.

Reference Signs List 1, 2, 3, 4, 5, 6, 7 Methane fermentation system 10 Separating pulverizer 11 Piping 20 Slurry tank 21 Piping 30 Pre-fermentation tank 31 Piping 40 Digestive liquid treatment device 41 Piping 50 Desulfurization device 51 Piping 60 Gas holder 61 Piping 70 Power generation equipment 80 heating device 100 methane fermentation tank 110 fermentation unit 120 ultra-fine bubble water supply unit 121 pipe 122 valve 130 first supply unit 131 pipe 132 valve 140 second supply unit 141 pipe 142 valve 150 control device 151 estimation unit 152 control unit 160 first detection device 170 second detection device 180 catalyst supply unit 181 pipe 182 valve 200 ultra-fine bubble water production device 201 ultra-fine bubble generation device 202 ultra-fine bubble water tank 210 first ultra-fine bubble water production device 211 first ultra Fine bubble generator 212 First ultra-fine bubble water tank 220 Second ultra-fine bubble water preparation device 221 Second ultra-fine bubble generator 222 Second ultra-fine bubble water tank 230 Catalyst storage device 232 Catalyst tank G, G1, G2 Gas Source W, W1, W2 Water source C Catalyst source S10 Hydrolysis step S12 Acid generation step S14 First methane gas formation step S16 Second methane gas formation step S20, S22, S24, S26, S28, S30 Step

Claims (16)

a fermentation unit that performs methane fermentation of organic waste using a culture solution containing anaerobic microorganisms;
a first supply unit that supplies first water containing at least one bubble of carbon dioxide, hydrogen, oxygen and nitrogen with a diameter of 1 μm or less to the fermentation unit;
a second supply unit that supplies second water containing air bubbles with a diameter of 1 μm or less to the fermentation unit;
with
In the first supply unit, the supply amount of the first water can be adjusted,
In the second supply unit, the supply amount of the second water is adjustable,
methane fermenter. The methane fermenter according to claim 1, wherein the organic waste contains persistent organic matter. The methane fermentation tank according to claim 1 or 2, wherein the first water and the second water have a bubble concentration of 6 x ¹⁰⁷ particles/ml or more and ⁵ x 109 particles/ml or less. A methane fermenter according to any one of claims 1 to 3;
a first water preparation device for preparing the first water to be supplied to the fermentation section via the first supply section;
a second water preparation device that prepares the second water to be supplied to the fermentation section via the second supply section;
A methane fermentation system with 5. The methane fermentation system according to claim 4, further comprising a control device that adjusts the amount of supply of the first water by the first supply unit and the amount of supply of the second water by the second supply unit. At least one of a first detection device that detects at least one of hydrogen sulfide concentration, carbon dioxide concentration, and methane concentration in the methane fermentation tank, and a second detection device that detects pH,
The control device detects, based on at least one of hydrogen sulfide concentration, carbon dioxide concentration and methane concentration detected by the first detection device, and at least one of pH detected by the second detection device, the first supply unit 6. The methane fermentation system according to claim 5, wherein the amount of supply of the first water by and the amount of supply of the second water by the second supply unit are adjusted. The control device includes an estimation unit that estimates the concentration of bubbles having a diameter of 1 μm or less in the culture solution in the fermentation unit, and supplies the first water and the second water based on the concentration estimated by the estimation unit. 7. The methane fermentation system according to claim 5 or 6, further comprising a controller that adjusts the amount. The ^{controller controls} the first water and the first 8. The methane fermentation system according to claim 7, wherein the supply amount of water in 2 is adjusted. 9. The methane fermentation system according to any one of claims 4 to 8, comprising a desulfurization device that removes sulfur oxides from the biogas generated from the methane fermentation tank to obtain purified biogas. The methane fermentation system according to claim 9, wherein the first water bubbles supplied by the first supply unit contain carbon dioxide discharged by combustion of the purified biogas. Organic waste to which at least one of the first water supply and the second water supply is supplied from at least one of the first supply unit and the second supply unit, and before being put into the methane fermentation tank 11. The methane fermentation system according to any one of claims 4 to 10, comprising a slurry tank for slurrying. 12. The methane fermentation according to claim 11, further comprising a digestive juice processing device that solid-liquid separates the digestive juice generated from the methane fermentation tank and supplies the liquid obtained by the solid-liquid separation of the digestive juice to the slurry tank. system. Organic waste to which at least one of the first water supply and the second water supply is supplied from at least one of the first supply unit and the second supply unit, and before being put into the methane fermentation tank 13. The methane fermentation system according to any one of claims 4 to 12, comprising a pre-fermenter that hydrolyzes the . 14. The methane according to claim 13, further comprising a digestive juice processing apparatus that solid-liquid separates the digestive juice generated from the methane fermentation tank and supplies the liquid obtained by the solid-liquid separation of the digestive juice to the pre-fermenter. fermentation system. At least one of the first water and the second water supplied by at least one of the first supply unit and the second supply unit contains the liquid obtained by solid-liquid separation of the digestive juice. 15. The methane fermentation system according to Item 12 or 14. A methane fermentation treatment method for methane fermentation of organic waste with a culture solution containing anaerobic microorganisms,
During the methane fermentation, a first water containing at least one gas bubble of carbon dioxide, hydrogen, oxygen and nitrogen with a diameter of 1 μm or less and a second water containing air bubbles with a diameter of 1 μm or less to the organic waste. supply things ,
The supply amount of the first water is adjustable,
the amount of supply of the second water is adjustable;
Methane fermentation treatment method.

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