Methane production system, power generation apparatus using methane production system, subcritical water reaction treatment apparatus used in methane production system, methane production method, and power generation method using methane production system

Abstract

The present invention makes it possible to obtain, from one or more forms of organic waste (hereinafter referred to as a subject organic waste) obtained by removing wood waste from organic waste materials encompassing animal feces, urban waste, agricultural or fishery residue, organic building waste in building materials, and organic sludge, a torrefied material having a higher energy and a higher yield than those of the subject organic waste as the feedstock, thereby producing a high-energy, high-yield organic waste biogas. The present invention is provided with a subcritical water reaction treatment apparatus, an organic waste biopellet production apparatus, and an organic waste biogasification reactor. In the subcritical water reaction treatment apparatus, part of a solidified low-molecular organic waste biomaterial derived from the subject organic waste bonds to another low-molecular organic waste biomaterial to form a torrefied organic waste biomaterial. The organic waste biopellet production apparatus produces organic waste biopellets from the torrefied organic waste biomaterial, and the organic waste biogasification reactor produces methane.

Description

Methane generation system, power generation device using methane generation system, subcritical water reaction treatment device used in methane generation system, methane generation method, and power generation method using methane generation system

[0001] The present invention relates to a methane generation system, a power generation device using the methane generation system, a subcritical water reaction treatment device used in the methane generation system, a methane generation method, and a power generation method using the methane generation system.

[0002] A method is known in which organic waste is torrefied and the resulting torrefied material is turned into organic waste pellets. The organic waste is fed into a rotary kiln at a constant rate using a constant feeder. The temperature inside the kiln during torrefaction is 200 to 300°C, and the residence time is approximately 60 minutes. The torrefied material is then stored in a drum at the exit of the rotary kiln.

[0003] "Semi-carbonization," also known as "torrefaction," is a fuel conversion technology that involves heating organic waste biomass in a low-oxygen environment at 200-300°C to decompose the organic matter into a substance with a high carbon content. Semi-carbonization is known to increase energy density and improve crushability and water resistance, and some semi-carbonization processing equipment is known to be able to perform drying and semi-carbonization in one unit, thereby increasing the semi-carbonization speed by blowing hot air directly onto the raw material.

[0004] The International Energy Agency (IEA) defines "torrefaction" as "a heat treatment carried out at 250 to 320°C in a reduced oxygen atmosphere."

[0005] The pelletizing device used is a device capable of forming powdered semi-carbide into a cylindrical shape with a diameter of about 6 mm.

[0006] Large-scale production facilities with a capacity of tens of thousands of tons are being constructed mainly in Europe and the US. In Japan, there is a large amount of organic waste resources, which makes it easy to use them on a small scale in a decentralized manner, and it can also contribute to revitalizing local areas by switching from fossil fuels to local resources.

[0007] Various types of organic waste are resources that can be used on a small scale.

[0008] When organic waste is treated with subcritical water, the polymer components are thermally decomposed into smaller molecules, and the remainder is turned into a carbonized residue.

[0009] An organic waste biogasification power generation system is known. The organic waste biogasification power generation system includes a fixed-bed gasification furnace, a cyclone, a scrubber, a cooling tower, a filter device, and a gas engine generator. The gas engine generator generates, for example, 80 kW of electricity.

[0010] Patent Document 1 describes that by holding the material for 5 to 90 minutes in a temperature range of 200 to 240°C, where hemicellulose decomposition proceeds slowly, the hemicellulose decomposition products volatilize and diffuse outside the carbonized material before charring. It also describes that the first-stage temperature is preferably 210 to 235°C and the carbonization time is preferably 15 to 60 minutes, and that the second-stage carbonization temperature is preferably 250 to 280°C and the carbonization time is 15 to 60 minutes.

[0011] Patent Document 2 describes a subcritical water treatment apparatus, and describes that a reaction vessel used in the subcritical water treatment apparatus has a double structure consisting of an outer vessel and an inner vessel housed inside the outer vessel.

[0012] Patent Document 3 describes a method for producing biomass solid fuel, which includes a step of hydrothermal carbonization of EFB (palm oil residue) at a temperature of 150 to 250°C and a pressure of 0.3 to 4.2 MPa (G).

[0013] In Non-Patent Document 1, Table 1: Classification of Biomass Gasifiers [6] lists fixed bed, fluidized bed, entrained bed, and rotary kiln gasifiers, and describes the gasification of wood chips. Non-Patent Document 1 also describes the use of high-temperature gasification temperatures, such as 700 to 1200°C.

[0014] JP 2020-45373 A Japanese Patent No. 4789595 A Japanese Patent No. 7252389 A

[0015] Journal of the Combustion Society of Japan, Vol. 49, No. 150 (2007) 228-235

[0016] Conventionally, biogasification systems have been used to produce semi-carbonized material from organic waste as a processing material and then gasify the semi-carbonized material in a biogasification furnace. However, the amount of semi-carbonized material produced from organic waste is reduced, and a large amount of semi-carbonized material with high energy consumption is not obtained compared to the amount of wood used as the raw material.

[0017] As mentioned above, there are many organic waste resources in Japan. There is a need to make effective use of organic waste that is dispersed on a small scale and to switch from fossil fuels to organic waste resources.

[0018] In view of the above, the present invention employs a newly discovered method for utilizing subcritical water reaction treatment equipment, thereby adopting a "torrefaction method" that can be defined in a different form from the conventional "torrefaction method" defined by the IEA, and aims to obtain a high amount of torrefied material with a higher energy content than the amount of organic waste used as raw material from the amount of organic waste used as raw material, thereby generating a high amount of organic waste biogas with a higher energy content.

[0019] The applicant of the present application previously filed patent applications in Japan (Japanese Patent Application Nos. 2024-57030 and 2024-57237) regarding the production of semi-carbonized material from wood waste. In the present invention, the organic waste used as the raw material for treatment includes animal droppings, municipal solid waste, agricultural or fishery product residues, organic waste from construction materials, and organic sludge. One or more organic wastes excluding wood waste (hereinafter referred to as "organic waste") are the target of subcritical water reaction treatment. This organic waste can be considered as organic waste excluding the wood waste that was the subject of the previous patent application. The present invention produces semi-carbonized material from the organic waste. The organic waste used as the raw material for treatment may be in the form of powder, or in the form of chips or pellets solidified from the powder.The present invention relates to a methane generation system that produces semi-carbonized organic waste biomaterial (hereinafter referred to as the organic waste biomaterial) by heat-treating organic waste as a processing raw material under a low-oxygen condition, produces semi-carbonized organic waste biopellets (hereinafter referred to as the organic waste biopellets) from the organic waste biomaterial, and gasifies the organic waste biopellets in a gasifier, the system comprising a subcritical water reaction treatment device, an organic waste biopellet production device, and an organic waste biogasification furnace, the subcritical water reaction treatment device having a superheated steam generator as a heat source for the subcritical water reaction treatment and semi-carbonization treatment, and the relationship between temperature X and weight loss rate Y is such that, on the XY axis coordinate, the temperature X is 220°C or less and the shoulder part of the gradual weight loss line continues to the part of the sudden weight loss, the part of the sudden weight loss on the S-shaped curve, and the part where the sudden weight loss ends and the exit part of the S-shaped curve of the gradual weight loss line The methane generation system is characterized by the following: the temperature is expressed as an S-shaped curve divided into three sections, with the shoulder temperature of the S-shaped curve having a first temperature range of 220°C or less and a second temperature range adjusted to a temperature of 130°C or less, and the organic waste biomaterial is semi-carbonized, with some solidified low-molecular-weight organic waste adhering to other low-molecular-weight organic waste, and the organic waste biomaterial retains 90% of the calorific value of the organic waste used as a raw material for treatment (hereinafter referred to as the 90% calorific value organic waste biomaterial); the wood biopellet generator generates the organic waste biopellets from the 90% calorific value organic waste biomaterial; and the organic waste biogasifier gasifies the organic waste biopellets to generate methane.Furthermore, the present invention provides a methane gas production method that produces torrefied organic waste biomaterial (hereinafter referred to as the organic waste biomaterial) by heat-treating a raw organic waste under low-oxygen conditions, produces torrefied organic waste biopellets (hereinafter referred to as the organic waste biopellets) from the organic waste biomaterial, and gasifies the organic waste biopellets in a gasifier, the method comprising: a subcritical water reaction treatment apparatus, an organic waste biopellet production apparatus, and an organic waste biogasification furnace; the subcritical water reaction treatment apparatus comprises a superheated steam generator as a heat source for the subcritical water reaction treatment and the torrefaction treatment; and the relationship between temperature X and weight loss rate Y is such that, on the XY axis coordinate, temperature X is 220°C or less and the shoulder of the gradual weight loss line continues to the part where the weight suddenly decreases, the part where the weight suddenly decreases on the S-shaped curve, and the part where the weight suddenly decreases and the end of the gradual weight decrease line are located at the end of the S-shaped curve. The temperature at the shoulder of the S-curve is a first temperature range of 220°C or less and a second temperature range of 130°C or less, and the semi-carbonized organic waste biomaterial is formed by fixing a portion of the solidified low-molecular-weight organic waste to other low-molecular-weight organic waste, and the organic waste biomaterial retains 90% of the calorific value of the raw organic waste to be treated (hereinafter referred to as the 90% calorific value organic waste biomaterial), the organic waste biopellet generator generates the organic waste biopellets from the 90% calorific value organic waste biomaterial, and the organic waste biogasifier gasifies the organic waste biopellets to produce 10 Mj / Nm. ３ The present invention also provides a power generation system using the methane generation system, a subcritical water reaction treatment device used in the methane generation system, and a power generation method using the methane generation system.

[0020] In some literature, organic waste biopellets are sometimes referred to as organic waste biomass pellets.

[0021] According to the present invention, as described above, by carrying out the subcritical water reaction treatment by hydrolysis, the input organic waste is transformed into low molecular weight organic waste, and a semi-carbonized organic waste biomaterial can be formed in which a portion of the low molecular weight organic waste solidified from the subcritical water reaction treated organic waste adheres to other low molecular weight organic waste.

[0022] When the change in the temperature X of the organic waste and the weight loss rate Y on the XY coordinate system is represented by an S-shaped curve that is divided into three sections: the shoulder of the gradual weight loss line, the section that continues into the sudden weight loss section, the sudden weight loss section of the S-shaped curve, and the section where the sudden weight loss ends and the exit of the S-shaped curve into a gradual weight loss line, a portion of the organic waste is liquefied and solidified at the temperature set at the shoulder of the S-shaped curve, and the low-molecular-weight organic waste that is the other component of the organic waste is fixed, forming organic waste biomaterial, and making it possible to semi-carbonize the low-molecular-weight organic waste biomaterial.

[0023] The semi-carbonization process is carried out at a temperature of 150 to 220°C, which is lower than the temperature range used in conventional semi-carbonization processes, and therefore semi-carbonized material that retains 90 to 95% of the heat value of the organic waste before processing can be obtained in an extremely short period of time.

[0024] Furthermore, according to the present invention, methane can be efficiently produced from the highly energy torrefied material.

[0025] Fig. 1 shows an overview of a methane generation system according to an embodiment of the present invention. Fig. 2 shows the configuration of a subcritical water reaction treatment device according to an embodiment of the present invention. Fig. 3 shows the configuration of another subcritical water reaction treatment device according to an embodiment of the present invention. Fig. 4 shows the processing temperature X and the weight change Y of the processing material as XY coordinates, and shows the processing temperature and the weight change of the processing material. Fig. 5 shows the organic waste solidified by breaking down into smaller molecules to form organic waste biomaterial, and the fixation of the solidified organic waste to other smaller organic wastes, and the semi-carbonization process on the XY coordinates. Example: Microscopic photograph taken in the case of cow dung. Example: Municipal waste (paper, wood chips, plastics, etc.). Example of a microscopic photograph taken in an example of a mixture of organic waste (plastic, food residues): Example of a microscopic photograph taken in an example of tea grounds: Example of a microscopic photograph taken in an example of coffee grounds: Example of a microscopic photograph taken in an example of tofu dregs: Example of a microscopic photograph taken in an example of rice husks: Example of a microscopic photograph taken in an example of vegetable waste: Example of a microscopic photograph taken in an example of bamboo waste: Example of a microscopic photograph taken in an example of scallop uro: Example of a microscopic photograph taken in an example of clothing waste: Example of a microscopic photograph taken in an example of organic activated sludge Diagrams explaining the optimal semi-carbonization process. Diagram showing the produced organic waste biopellets Diagram showing the process of producing organic waste biofuel bodies Explanatory diagram about the gasification process of organic waste biopellets Diagram explaining the areas used in the present invention in an XY axis coordinate diagram Diagram showing the steps of a methane production method which is an embodiment of the present invention

[0026] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0027] Fig. 1 is a diagram showing an outline of a methane generation system according to an embodiment of the present invention. The present invention relates to a methane generation system 100 that generates torrefied matter from organic waste and gasifies the torrefied matter in a gasifier. The organic waste is defined above.

[0028] In FIG. 1, the methane generation system 100 is mainly composed of a biopellet production apparatus 2 and a biogas production apparatus 3 connected to the biopellet production apparatus 2 by a transport means 8 such as a transport vehicle.

[0029] The biopellet production apparatus 2 is composed of a subcritical water reactor 5 and an organic waste biopellet production apparatus 6, and a superheated steam generator 4 is attached to the biopellet production apparatus 2. The superheated steam is delivered to the subcritical water reactor 5.

[0030] The organic waste is processed into chips of any shape, collected by any means, and then input 8 into a subcritical water reaction apparatus 5 .

[0031] The organic waste 1 is semi-carbonized by subcritical water reaction treatment using superheated steam as described below, and a semi-carbonized organic waste biomaterial is formed. The subcritical water reactor 5 can perform subcritical water reaction treatment on the input organic waste 1.

[0032] Subcritical water reactions involve the hydrolysis of high-molecular-weight organic substances into smaller molecules by confining high-temperature, high-pressure water in a pressure vessel. A subcritical water reactor (also called a subcritical treatment device or subcritical device) is used.

[0033] The organic waste biomaterial is sent to an organic waste biopellet production device 6, which produces organic waste biopellets 7. The organic waste biopellet production device 6 produces organic waste biopellets 7 using the organic waste biomaterial in accordance with a known method.

[0034] The organic waste biopellets produced may also be called torrefaction pellets.

[0035] The organic waste biopellets 7 are transported by transport means 8, for example a transport vehicle, to a silo 11 of the biogas production device 3 and stored therein.

[0036] The biogas production system 3 includes a silo 11, a superheated steam gasifier 12 (hereinafter referred to as the gasifier 12), a bag filter 13, a buffer tank 14, a gas engine 15, and a generator 17. Although not shown in the figure, a condenser and a cyclone may also be provided. A branching device 23 can be installed in the biogas conduit connecting the gasifier 12 and the bag filter 13 to branch the organic waste biogas. The branched organic waste biogas is led to a reformer 24, which constitutes a hydrogen production system. The reformer 24 uses steam to reform methane, the main component of the organic waste biogas, to produce hydrogen. That is, the reformer 24 produces hydrogen from methane through steam reforming. The hydrogen produced in the reformer 24 is liquefied and stored in a hydrogen storage device 25. The liquefied hydrogen can be used for various purposes. While the reformer 24 is used in this example, hydrogen and solid carbon may also be produced from methane using plasma pyrolysis. The method for producing hydrogen is not limited to the above-mentioned method, and other methods may be adopted. Methanol can be produced from the produced hydrogen using known means.

[0037] A superheated steam generator 16 is attached to the gasification furnace 12, and a generator 17 is connected to the gas engine 15. A belt conveyor 18 is disposed between the silo 11 and the gasification furnace 12, and a char discharge device 19 is disposed below the gasification furnace 12, through which char 20 is discharged from the gasification furnace 12 and used as fuel 21 for the superheated steam generator 16.

[0038] A hydrogen concentration detector can be disposed inside the gasification furnace 12 to constantly detect and monitor the hydrogen concentration inside the gasification furnace 12. A commercially available hydrogen concentration detector can be used.

[0039] The organic waste biopellets 7 stored in the silo 11 are transported to the gas furnace 12 and gasified with superheated steam from the superheated steam generator 16 to produce organic waste biogas. The organic waste biogas produced in this process is subjected to subcritical water reaction treatment to produce high-energy organic waste biogas with a high carbon content and mainly composed of methane, as will be described later, due to the characteristics of the organic waste biopellets produced. The gasifier 12 produces 22 even more high-energy organic waste biogas.

[0040] As will be described later, by applying an improved organic waste gas generation method to the formed organic waste biopellets, in addition to the previously mentioned high energy content, the gas furnace 12 can produce 22 even more highly energyed organic waste biogas, which is primarily composed of methane.

[0041] The electricity generated by the generator 17 is normally transmitted to a power transmission system after being adjusted in voltage, current, and frequency using a well-known power transmission device.

[0042] As described above, the methane generation system 100 shown in FIG. 1 is configured to include a first-stage component that generates organic waste biopellets through subcritical water reaction treatment using the biopellet production apparatus 2, and a second-stage component that generates methane from the highly-energized organic waste biopellets using the biogas production apparatus 3.

[0043] FIG. 2 is a diagram showing the configuration of an organic waste biopellet manufacturing apparatus according to an embodiment of the present invention.

[0044] In Fig. 2, the hydrothermal reaction treatment system includes a subcritical water reaction treatment device, and the hydrothermal reaction treatment system is composed of a treatment material input system, a subcritical water reaction device including a heat source for supplying heat, a hydrothermal reaction residue treatment system, and a control device. A general hydrothermal reaction treatment system itself has a well-known configuration.

[0045] In this embodiment of the present invention, the subcritical water reaction apparatus 5 includes a pressure vessel (also called a reactor) 101. The pressure vessel 101 is connected to a boiler 102 used as a heat source for supplying steam using an aqueous medium, and is also connected to a processing material input system, a methane recovery system, a hydrothermal reaction treatment system, and a torrefaction treatment system. A control device 105 is provided to control the temperature, pressure, and treatment time within the pressure vessel.

[0046] The pressure vessel 101 is composed of an outer cylindrical vessel (also referred to as an outer jacket) 111 and an inner cylindrical vessel (also referred to as an inner jacket) 112 arranged on the inner wall of the outer cylindrical vessel 111 with a space therebetween, and an agitator 113 is provided in the space (inner space) 106 within the inner cylindrical vessel.

[0047] The pressure vessel 101 is provided with closure lids 114 and 115 at both ends, and one of the lids 115 is provided with a drive motor 116 on its side. The drive motor 116 is connected to an agitator 113 having rotating blades.

[0048] An outer temperature sensor and an outer pressure sensor 121 are provided to measure the temperature and pressure in the space (outer space) 107 between the outer cylindrical container 111 and the inner cylindrical container 112, an inner temperature sensor and an inner pressure sensor 122 to measure the temperature and pressure in the space (inner space) 106 of the inner cylindrical container 112, and a moisture sensor 123 to measure the moisture in the space of the inner cylindrical container 112. These sensors measure the temperature and pressure in the inner space 106 and the moisture in the inner space 106 of the inner cylindrical container 112, and the respective measured values ​​are transmitted as data signals to the control device 105 via electronic circuits. These signal data are recorded in the recording means of the control device 105. The measured moisture content is used to set control data for the torrefaction treatment time.

[0049] The pressure vessel 101 is equipped with a steam discharge pipe 118 connected to the inner cylindrical vessel 112, and a discharge control valve 119 is provided on the steam discharge pipe 118. This configuration allows water vapor in the inner space to be discharged to the outside. The pressure vessel 101 is equipped with an input hopper 125 connected to the inner cylindrical vessel 112, and an outlet having an outlet pipe 126 connected to the inner cylindrical vessel 112. The outlet pipe 126 is provided with an outlet discharge control valve 120. This configuration allows the torrefied material produced by the hydrothermal reaction treatment to be recovered to the outside, i.e., to a torrefied material recovery device.

[0050] The crusher 103 receives the collected raw material to be treated (the organic waste) 131, crushes the raw material to be treated, and feeds the powdered raw material to the feed hopper 125. The feed hopper 125 is provided with a control valve, and the feeding of the raw material to be treated 131, the subsequent processing, and the temperature adjustment to be adopted are controlled by the control device 105.

[0051] The crushing operation of the crusher 103 is controlled by a control device 105 connected by an electronic circuit.

[0052] The type of raw material to be processed 131 (in Figure 1, this is the organic waste 1) is identified when it is collected. In many cases, the type of raw material to be processed is identified by the operator, who is the raw material processor. By installing a photographing means (not shown) near the input hopper 125, comparing the image with a reference image, and providing a means (not shown) for identifying the type of raw material to be processed, the type of raw material to be processed can be identified automatically. The identification data is input into the control device 105.

[0053] The boiler 102 includes a steam supply line 133 that supplies the generated steam to the pressure vessel 101. A superheated steam generator 140 is provided in the steam supply line 133, and superheats the generated steam and supplies it to the pressure vessel 101.

[0054] The steam supply line 133 branches into a branch line 134 that supplies superheated steam into the space between the outer cylindrical vessel 111 and the inner cylindrical vessel 112, and a branch line 135 that supplies superheated steam into the space inside the inner cylindrical vessel 112, and control valves 136 and 137 are installed on each branch line. The control valves 136 and 137 are connected to the control device 105, and their opening and closing are controlled and adjusted by the control device 105. The superheated steam is supplied to the space between the outer cylindrical vessel 111 and the inner cylindrical vessel 112 and / or the space inside the inner cylindrical vessel 112. By providing the superheated steam generator 140, the internal temperature, i.e., the hydrothermal reaction treatment temperature, can be increased regardless of the pressure inside the inner cylindrical vessel.

[0055] The subcritical water reaction apparatus 5 is composed of a pressure vessel equipped with an inlet for the raw material to be treated, a mechanism for making the hydrothermal reaction uniform, and an outlet for removing the semi-carbonized powder produced after the hydrothermal reaction treatment, a heat source for the hydrothermal reaction treatment and heat treatment, and a control device for controlling the hydrothermal reaction treatment and heat treatment.A slightly blackish semi-carbonized material is produced by the hydrothermal reaction treatment and heat treatment of wood material.

[0056] The pressure vessel is composed of an outer cylindrical vessel and an inner cylindrical vessel, and an inner space within the inner cylindrical vessel and an outer space between the inner cylindrical vessel and the outer cylindrical vessel are defined by the inner cylindrical vessel.

[0057] The control means sets the hydrothermal reaction temperature of the subcritical reaction zone of water under a predetermined pressure in the hydrolysis treatment zone, and the organic waste is hydrolyzed in the hydrolysis treatment zone to produce a hydrolyzed substance, i.e., semi-carbonized material as the treatment result of the organic waste.

[0058] For example, water vapor is introduced into the inner space, a hydrothermal reaction temperature in the subcritical reaction range of water is adopted, and a hydrothermal reaction zone is formed in which the hydrothermal reaction pressure is within 2.5 MPa, typically within 0.3 to 3.5 MPa, and the hydrothermal reaction time is controlled to an appropriately set time, and the organic waste is hydrolyzed to produce a semi-carbonized powder, which is a powdered hydrolysis-treated substance.

[0059] The introduction of water vapor into the inner space is stopped, and the water vapor in the inner space is discharged to the outside.

[0060] In the drying and semi-carbonization treatment area, a semi-carbonization treatment temperature obtained from the type of raw material to be treated and the calorific value multiple is set under a predetermined pressure, and a semi-carbonized powder material having a predetermined calorific value relative to the calorific value of the organic waste is produced from the hydrolysis treatment material using a semi-carbonized hydrothermal reaction treatment.

[0061] A torrefaction treatment zone is formed within the outer space, where the carbonization temperature is within the range of 150 to 220°C and the treatment time is controlled, to form torrefied pellets from the hydrolysis-treated material through a hydrothermal reaction process, typically torrefied pellets using a hydrothermal reaction process with a high calorific value. The torrefied pellets are dried, torrefied, and powdered hydrothermal reaction solids, which are torrefied. A portion of the torrefied pellets may be used for other purposes.

[0062] Organic waste with a moisture content of 35-50% and a calorific value of 3,300 kcal / kg is widely known. A lower calorific value of 3,040 kcal / kg has been reported. In this invention, wood chips with a calorific value of 3,300 kcal / kg are used as the reference wood chips when calculating the calorific value multiple. The inventors' analysis also confirmed that semi-carbonized wood chips have a calorific value of 3,300 kcal / kg.

[0063] According to experiments conducted by the inventors, it has been confirmed that the provision of a torrefaction pellet forming system makes it possible to produce torrefied wood chips that have a calorific value 1.25 times that of 3,300 kcal / kg. The carbon content of the elemental composition of wood chips, which is about 50%, increases to over 60% in the torrefied wood chips that have been hydrothermally treated, resulting in a high energy content.

[0064] A torrefaction and powder treatment region can be formed by controlling the treatment time within the torrefaction temperature range of 150 to 220°C.

[0065] When the powdery particulate semi-carbonized material is obtained, a hydrothermal reaction-based semi-carbonized pellet can be formed, which is mainly composed of the semi-carbonized material described above and is an aggregate of the powdery particulate semi-carbonized material after hydrothermal reaction semi-carbonization.

[0066] The semi-carbonized powder after the hydrothermal reaction is recovered in a semi-carbonized powder recovery device 141, and the harmful substances are rendered harmless and reduced in volume 142.

[0067] This achieves the following: - High calorific value resource: Production of semi-carbonized powder with a calorific value multiple of 1.25, preferably 1.5 or more, relative to the calorific value of wood chips. - Reduction of carbon dioxide, dioxins, and odors.

[0068] In this embodiment, a subcritical water reaction apparatus 5 is used.

[0069] The pressure vessel is composed of an outer cylindrical vessel and an inner cylindrical vessel, and the inner space within the inner cylindrical vessel and the outer space formed between the inner and outer cylindrical vessels are partitioned by the inner cylindrical vessel. A first heating means is provided in the inner space to introduce steam and directly heat the inner space, and a second heating means is provided to directly heat the outer space and indirectly heat the inner space. The first heating means makes it possible to form a hydrolysis treatment zone in the inner space where a hydrothermal reaction by hydrolysis is carried out at hydrothermal reaction pressure, and the second heating means makes it possible to form a drying / semi-carbonization treatment zone in the inner space under a predetermined pressure.

[0070] Furthermore, a system is constructed which includes a subcritical water reactor 5 using a pressure vessel with a double-pipe configuration, a hydrothermal reaction treatment and semi-carbonization powder treatment system 6, and the subcritical water reactor 5, and which uses the subcritical water reactor 5 as a heating means, i.e., a heat source such as a boiler.

[0071] FIG. 3 is a diagram showing the configuration of another subcritical water reaction apparatus according to an embodiment of the present invention.

[0072] The configuration of the subcritical water reaction apparatus 5 is substantially the same as the configuration of the subcritical water reaction apparatus shown in FIG.

[0073] 3, a heater 117 is provided in an external space 107, and a heating power supply 102A is provided in parallel with the boiler 102. The heating power supply 102A is connected to a control device 105 by an electric circuit and is controlled to be turned on and off.

[0074] The heater 117 is electrically heated by the supply of electricity from the heating power supply 102A.

[0075] 2 in that the outer space 107 is heated by a heat medium from a heater 117 instead of by steam heat. However, the same applies to the subcritical water reaction apparatus 5 in that the hydrothermal reaction produces torrefied pellets, typically dried torrefied hydrothermal pellets with a high calorific value.

[0076] Similar to the previous example, water vapor is introduced into the inner space to form a low-temperature hydrolysis treatment area controlled at a temperature within the subcritical reaction range of water and a hydrothermal reaction pressure of 3.5 MPa or less, typically 2.5 MPa or less, for an appropriately set hydrothermal reaction treatment time, whereby the wood is hydrolyzed to form a powdery hydrolyzed substance called a semi-carbonized product. However, what is different is that a low-temperature drying / semi-carbonization treatment area is formed within the outer space, where the semi-carbonization temperature is above the hydrothermal reaction temperature but not exceeding 220°C, and the treatment time is controlled, and this area is electrically heated and formed by heater 117 supplied with electricity from heating power source 102A.

[0077] FIG. 4 is a diagram showing the relationship between temperature X and weight loss rate Y on an XY coordinate system when the raw material is carbonized.

[0078] This is a diagram showing the relationship between the processing temperature X and the weight change Y of the processing material, with the XY axis coordinate representing the processing temperature X and the weight change Y of the processing material. When the organic waste, which is the processing raw material, is carbonized, it is known that the relationship between the temperature X and the weight loss rate Y is expressed as an S-shaped curve on the XY axis coordinate, which can be divided into three sections: the shoulder part of the gradual weight loss line that continues into the part of the rapid weight loss, the part of the S-shaped curve where the rapid weight loss ends and the end part of the S-shaped curve where the rapid weight loss ends and the gradual weight loss line ends.

[0079] In heat treatment (dry distillation) where the raw material is isolated from air, the weight change is known to follow a curve similar to the thermal decomposition curve (dry distillation curve) shown in Figure 4, which shows the relationship between the treatment temperature and the weight change of the organic waste material. Here, the horizontal axis represents the heating temperature, and the vertical axis represents the weight percentage of the remaining solid (carbon residue) relative to the original organic waste material. The decrease in carbon residue occurs most rapidly at around 250°C and continues slowly even above 400°C, ultimately resulting in a carbonized product with a weight of about one-third to one-quarter of the original weight. Here, the shoulder of the gradual weight loss line that continues into the rapid weight loss line is referred to as Region (1), the portion of the S-shaped curve where the weight rapidly decreases is referred to as Region (2), and the portion at the end of the S-shaped curve where the gradual weight loss line ends is referred to as Region (3).

[0080] The International Energy Agency (IEA) defines "torrefaction" as "heat treatment carried out at 250 to 320°C in a reduced oxygen atmosphere," and conventionally, semi-carbide formation was carried out at temperatures in the (2) region.

[0081] Figure 5 is a diagram illustrating the semi-carbonization process of the organic waste that has been solidified into smaller molecules that form organic waste biomaterial and the other smaller molecules to which the solidified organic waste has adhered, on the XY coordinate system.

[0082] The low-temperature semi-carbonization treatment associated with the subcritical water reaction treatment will now be described.

[0083] Low-temperature semi-carbonization is performed in the (1) region. Semi-carbonization in the (1) region is possible by performing a subcritical water reaction treatment.

[0084] In FIG. 5, in process (1), hydrolysis treatment (subcritical water reaction treatment) is carried out using superheated steam to break down the organic waste into smaller molecules.

[0085] The temperature used is the subcritical water reaction temperature, preferably 230 to 240° C., although the temperature is not limited to this.

[0086] In process (2), the wood is semi-carbonized at a low temperature.

[0087] By performing the process (1) → (2), semi-carbonization is performed at a low temperature.

[0088] First stage: Temperature treatment at 150-220°C. In order to liquefy a portion of the organic waste, the waste is heated to this temperature and maintained at this temperature. Some of the organic waste is vaporized. The liquefied portion of the organic waste is present among the other organic waste that has been reduced to low molecular weight.

[0089] Second stage: Temperature treatment at 110-130°C. By lowering the temperature to this temperature, some of the liquefied organic waste solidifies and adheres to the other low molecular weight organic waste.

[0090] These two processes result in torrefied organic waste biomaterial.

[0091] Semi-carbonized organic waste biomaterial: The main components are solidified low molecular weight organic waste and other non-solidified low molecular weight organic waste.

[0092] The process (3) involves the production of organic waste pellets.

[0093] The resulting semi-carbonized organic waste biomaterial is then used to produce organic waste pellets.

[0094] The semi-carbonization process is carried out at a temperature of 150 to 220°C, which is lower than the temperature range used in conventional semi-carbonization processes, and therefore semi-carbonized material that retains 90 to 95% of the heat value of the organic waste before processing can be obtained in an extremely short period of time.

[0095] Below, we will explain the photographs obtained when the organic waste was treated with subcritical water according to this example. Two photographs are presented for each case. The top photograph shows the state before subcritical water treatment, and the bottom photograph shows the state after treatment. Here, "treatment" refers to subcritical water treatment, in which some of the coagulated organic waste, which has been treated with subcritical water, is bound to the other organic waste, forming a slightly dark, semi-carbonized organic waste biomaterial. Figure 6 is a microscopic photograph obtained from the example: cow dung. Comparing the two photographs, it can be seen that the cow dung was treated with subcritical water treatment, and some of the coagulated organic waste was bound to the other non-coagulated organic waste, forming a semi-carbonized cow dung biomaterial. Figure 7 is a microscopic photograph obtained from the example: municipal waste (a mixture of paper, wood chips, plastic, and food waste). Comparing the two photographs reveals that the subcritical water reaction treatment breaks down the food residue into smaller molecules, with some of the smaller molecules solidifying and adhering to the remaining smaller molecules but not solidifying, forming a semi-carbonized food residue biomaterial. Figure 8 shows a microscopic photograph taken in the case of tea grounds. Comparing the two photographs reveals that the subcritical water reaction treatment breaks down the tea residue into smaller molecules, with some of the smaller molecules solidifying and adhering to the remaining smaller molecules but not solidifying, forming a semi-carbonized tea residue biomaterial. Figure 9 shows a microscopic photograph taken in the case of coffee grounds. Comparing the two photographs reveals that the subcritical water reaction treatment breaks down the coffee grounds into smaller molecules, with some of the smaller molecules solidifying and adhering to the remaining smaller molecules but not solidifying, forming a semi-carbonized coffee residue biomaterial. Figure 10 shows a microscopic photograph taken in the case of tofu grounds. By comparing the two photographs, it can be seen that the tofu dregs that were subjected to the subcritical water reaction treatment were broken down into smaller molecules, and that some of the smaller molecules solidified and adhered to the other smaller molecules that had not solidified, forming a semi-carbonized tofu dregs biomaterial.Figure 11 is a microscopic photograph taken in the case of rice husks. Comparing the two photographs, it can be seen that the rice husks were treated with subcritical water to break down into smaller molecules, with some of the broken down rice husks solidifying and adhering to the remaining broken down but not solidified rice husks, forming semi-carbonized rice husk biomaterial. Figure 12 is a microscopic photograph taken in the case of vegetable waste. Comparing the two photographs, it can be seen that the vegetable wastes were treated with subcritical water to break down into smaller molecules, with some of the broken down vegetable wastes solidifying and adhering to the remaining broken down but not solidified vegetable waste, forming semi-carbonized vegetable waste biomaterial. Figure 13 is a microscopic photograph taken in the case of bamboo waste. Comparing the two photographs, it can be seen that the bamboo waste treated with subcritical water reaction was broken down into smaller molecules, some of the broken down bamboo waste solidified, and adhered to the remaining broken down but not solidified bamboo waste, forming semi-carbonized bamboo waste biomaterial. Figure 14 is a microscopic photograph taken in the case of scallop oocytes. Comparing the two photographs, it can be seen that the scallop oocytes treated with subcritical water reaction were broken down into smaller molecules, some of the broken down fish residue solidified, and adhered to the remaining broken down but not solidified scallop oocytes, forming semi-carbonized scallop oocytes. Figure 15 is a microscopic photograph taken in the case of clothing waste. Comparing the two photographs, it can be seen that the clothing waste treated with subcritical water reaction was broken down into smaller molecules, some of the broken down clothing waste solidified, and adhered to the remaining broken down but not solidified scallop oocytes, forming semi-carbonized clothing waste. Figure 16 is a microscopic photograph taken in the case of organic activated sludge. Comparing the two photographs, it can be seen that the organic activated sludge treated with subcritical water reaction was broken down into smaller molecules, and that some of the broken down organic activated sludge coagulated, adhering to the remaining broken down but uncoagulated organic activated sludge, forming semi-carbonized tofu sludge biomaterial. Figures 6 to 16 show examples where the organic waste is a single substance, but similar microscopic photographs can also be taken for mixtures of two or more organic wastes.

[0096] As can be seen in each photograph, the organic waste is made up of solidified, low-molecular-weight organic waste and other non-solidified, low-molecular-weight organic waste that are connected together in an organized manner with no gaps.

[0097] In the case of wood biopellets, they are black overall, indicating that they have been semi-carbonized.

[0098] In this way, the micrograph shows the solidified, low-molecular-weight organic waste in question connected together with other non-solidified, low-molecular-weight organic waste in question, in an orderly state with no voids.

[0099] Therefore, according to the present invention, a semi-carbonized organic waste biomaterial is provided in which the solidified, low-molecular-weight organic waste is connected together with other non-solidified, low-molecular-weight organic waste, and is formed in an orderly manner without any voids.

[0100] FIG. 17 is a diagram illustrating the optimum semi-carbonization process.

[0101] When organic waste biomaterials that have been treated with a subcritical water reaction are torrefied, the amount of carbon (C) produced varies depending on the temperature.

[0102] FIG. 17 shows an optimum range in which a large amount of carbon C can be obtained in the temperature range of 180 to 200° C., a low temperature range in which an increased amount of carbon C can be obtained in the temperature range of 150 to 180° C., which is practical but the amount of carbon C is small, and a high temperature range in which an increased amount of carbon C can be obtained in the temperature range of 180 to 220° C., which is practical but the amount of carbon C is small.

[0103] The semi-carbonization treatment is carried out at an appropriate temperature selected within the temperature range of 150 to 220°C.

[0104] For example, 190° C. is selected to produce organic waste biomaterial with a calorific value of 5330 kcal / kg.

[0105] In the temperature range of 150 to 180°C or 180 to 220°C, it is possible to produce organic waste biomaterials with a calorific value of, for example, 4000 kcal / kg, which is greater than the 3300 kcal / kg of wood chips, although the thermal energy is less than the maximum calorific value of 5330 kcal / kg.

[0106] FIG. 18 shows the produced organic waste biopellets.

[0107] Figure 18(1) shows a single organic waste biopellet, and Figure 18(2) shows an aggregated organic waste biopellet.

[0108] Organic waste biopellets are produced from the organic waste biomaterial.

[0109] In FIG. 18(1), the produced organic waste biopellets are cylindrical with a diameter of 6 mm and made of powdered semi-carbonized material.

[0110] One of its characteristics is that the torrefied organic waste biomaterial has a high calorific value of, for example, 5,330 kcal / kg, compared to the calorific value of 3,300 kcal / kg of typical wood chips.

[0111] FIG. 19 is a diagram showing a process for producing an organic waste biofuel body.

[0112] FIG. 19(1) is a diagram showing the process of producing an organic waste biofuel body, and FIG. 19(2) is a partially enlarged view of the solid body.

[0113] The organic waste biofuel production system uses a semi-carbonized material production device that is equipped with a subcritical water reaction treatment device, and that produces semi-carbonized organic waste biomaterial from the organic waste used as a processing material, by forming semi-carbonized organic waste biomaterial in which a portion of the organic waste that has been broken down into smaller molecules is solidified and fixed to other smaller molecules of the organic waste in the subcritical water reaction treatment device. The organic waste biofuel production system uses a semi-carbonized material production device that produces solid semi-carbonized material and powder semi-carbonized material from the organic waste in the subcritical water reaction treatment device, and mixes them to produce organic waste biofuel.

[0114] Organic waste in chip form was used as the raw organic waste for treatment. Of course, powdered organic waste can be used instead of chipped organic waste. Subcritical water reaction treatment of the organic waste 1 using the subcritical water reaction treatment apparatus 5 shown in Figure 1 maintains the organic waste chip shape of the organic waste 1, reduces the external dimensions, and forms easily crushable solids 51 and powder 52.

[0115] As shown in Figure 19 (2), the solidified low-molecular-weight organic waste was connected to other non-solidified low-molecular-weight organic waste, and voids 64 due to the subcritical water hot water treatment were observed.

[0116] The powder 52 is collected 53 and the organic waste biopellets 7 are produced by the organic waste biopellet production device 6 as described above.

[0117] In manufacturing the organic waste biopellets 7, a powder formed by pulverizing a part of the solid body 51 may be mixed with the powder 52 and used.

[0118] The solid bodies 51 are aggregated 54 to form solid fuel bodies 55 .

[0119] The organic waste biopellets 7 and the solid fuel bodies 55 are mixed to form organic waste biofuel bodies 56 , which are stored in the silo 11 of the gasification furnace 12 and then fed into the gasification furnace 12 .

[0120] The subcritical water reaction treatment device is used to generate solid semi-carbonized material and powder semi-carbonized material from the organic waste, and these materials are mixed to produce organic waste biofuel. This organic waste biofuel production device uses a semi-carbonized material production device.

[0121] FIG. 20 is an explanatory diagram of the gasification process of organic waste biopellets.

[0122] In Figure 4, it is shown that the organic waste is usually expressed as an S-shaped curve on the XY coordinate system, where the temperature X and the weight loss rate Y are divided into three sections: the shoulder part of the gradual weight loss line that continues into the part where the weight suddenly decreases, the S-shaped curve where the weight suddenly decreases, and the end part of the S-shaped curve where the weight suddenly decreases and the gradual decrease line.

[0123] As mentioned above, the carbon content of the organic waste, which is about 50% of the elemental composition, increases to 60% or more in the semi-carbonized material after hydrothermal reaction treatment, resulting in high energy content.

[0124] After the processes (1) to (3) shown in Figure 5, the gasification process of the organic waste biopellets (process (4)) and the process for power generation (process (5)) are carried out. The gasification process of the organic waste biopellets is completed by processes (1) to (5). The gas produced is 10 Mj / Nm3, mainly composed of methane. ３ Typically, gases with energies of 25 Mj / Nm are produced. ３ The data obtained for each case is as follows: Case: Cow dung 33Mj / Nm ３ Example: Municipal waste (mixture of paper, wood chips, plastic, and food waste) 25-40 Mj / Nm ３ Example: Tea waste example 23Mj / Nm ３ Example: Coffee grounds 27Mj / Nm ３ Example: Tofu dregs 27Mj / Nm ３ Example: Rice husk example 26Mj / Nm ３ Example: Vegetable waste 25Mj / Nm ３ Example: Bamboo waste material 23Mj / Nm ３ Example: Scallop uro example 25Mj / Nm ３ Example: Clothing waste: 20-35Mj / Nm ３ Example: Organic activated sludge 23-27Mj / Nm ３

[0125] By forming semi-carbonized organic waste biomaterial from the shoulder area, which is mainly composed of the solidified, low-molecular-weight organic waste and other non-solidified, low-molecular-weight, integrated organic waste, it is possible to obtain semi-carbonized organic waste biomaterial that retains 90 to 95% of the heat generation value before treatment.

[0126] The temperature is adjusted to the shoulder of the S-shaped curve, and for a predetermined time and under a predetermined pressure, a portion of the organic waste is liquefied and solidified, and fixed to the other components, the low-molecular-weight organic waste, to form organic waste biomaterial, which is then semi-carbonized. Organic waste biopellets are produced from the pretreated organic waste biomaterial using an organic waste biopellet manufacturing device. The organic waste biopellets are fed into the biogasification furnace and organic waste biogasification is carried out for a predetermined time and under a predetermined pressure at a temperature set in the temperature range of 230 to 600°C, which is set at the part of the S-shaped curve where the weight suddenly decreases.

[0127] FIG. 21 is an XY coordinate diagram illustrating the temperature range employed in this embodiment.

[0128] In FIG. 13, the first and second stage processes are shown.

[0129] The first stage treatment refers to the treatment area where the torrefaction of the present invention takes place.

[0130] The second stage treatment is a gasification treatment, i.e., a gasification treatment region by superheated steam reaction. On the XY axis coordinate, region (1) is the first stage treatment, and regions (2) and (3) are the second stage treatment.

[0131] The first stage treatment consists of a temperature range of 150 to 220°C and a temperature range of 110 to 130°C, and in the first stage treatment, the torrefaction of the present invention is carried out.

[0132] In the temperature range of 150 to 220°C, a semi-carbonized organic waste biomaterial is formed in which some of the organic waste that has been broken down into smaller molecules is solidified and adheres to other smaller molecules of the organic waste.

[0133] This temperature range is also where some of the organic waste that has been broken down into smaller molecules liquefies and volatilizes, with most of it liquefied and some evaporating.

[0134] The temperature range of 110 to 130°C is the temperature range in which some of the liquefied low molecular weight organic waste solidifies and adheres to the other low molecular weight organic waste.

[0135] The treatment (2) in FIG. 5 is carried out in the temperature range of 150 to 220°C in the first stage treatment and in the temperature range of 110 to 130°C.

[0136] The treatment (4) in FIG. 12 is carried out in the temperature range of 230 to 600° C. in the second stage treatment.

[0137] As an example of conventional torrefaction, it has been proposed to perform torrefaction at a temperature of 200 to 320°C.

[0138] Although the temperature range for the torrefaction of the present invention is partly covered at 200 to 220°C, the present invention differs in that the temperature range for the torrefaction of the present invention is set after the process (1) in Fig. 5 is carried out. That is, the present invention is characterized by having a subcritical water reaction process to set the temperature range for the torrefaction of the present invention.

[0139] (2) Regarding the selection of the temperature range: A temperature range of 230 to 450°C is selected.

[0140] (3) Regarding the selection of the temperature range: A temperature range of 450 to 600°C is selected.

[0141] FIG. 22 is a diagram showing steps of a method for producing biogas from organic waste according to an embodiment of the present invention.

[0142] First stage treatment: Pretreatment using subcritical water treatment reaction: The organic waste as the raw material for treatment is fed into a subcritical water reaction treatment device. The organic waste is treated with a subcritical water reaction to reduce the molecular weight of the waste. In this way, pretreatment is carried out on the organic waste biomaterial after the subcritical water reaction treatment.

[0143] Semi-carbonization process: A part of the organic waste that has been broken down into smaller molecules is solidified and adheres to other smaller molecules of the organic waste, forming semi-carbonized organic waste biomaterial.

[0144] Through these processes, the organic waste is semi-carbonized to produce semi-carbonized organic waste biomaterial.

[0145] The organic waste biopellets are then produced.

[0146] Second stage treatment: Production of methane gas, i.e. organic waste biogas The organic waste biopellets produced in the first stage are fed into a wood biogasification furnace, where they are gasified to produce organic waste biopellets, i.e. methane gas, while the hydrogen concentration is kept low.

[0147] Gas temperature: 230 to 600°C Treatment time: Predetermined time: 15 to 60 minutes

[0148] 100...methane generation system, 1...organic waste (processing raw material), 2...biopellet manufacturing apparatus, 3...biogas production apparatus, 4...superheated steam generator, 5...subcritical water reaction apparatus, 6...organic waste biopellet manufacturing apparatus, 7...organic waste biopellets (torrefaction pellets), 8...transport means, 11...silo, 12...superheated steam gasifier (referred to as gasifier), 13...bag filter, 14...buffer tank, 15...gas engine, 16...superheated steam generator, 17...generator, 19...carbide discharge device, 20...carbide, 21...fuel, 22...methane generation, 23...branching device, 24...reforming device, 25...hydrogen storage container, 51...solid body, 52...powder, 55...solid fuel body, 56...organic waste biofuel body.

Claims

1. A methane generation system that produces semi-carbonized organic waste biomaterial (hereinafter referred to as the organic waste biomaterial) by heat-treating organic waste as raw material under low-oxygen conditions, produces semi-carbonized organic waste biopellets (hereinafter referred to as the organic waste biopellets) from the organic waste biomaterial, and gasifies the organic waste biopellets in a gasifier, comprising a subcritical water reaction treatment device, an organic waste biopellet production device, and an organic waste biogasification furnace, and the subcritical water reaction treatment device is equipped with a superheated steam generator as a heat source for the subcritical water reaction treatment and semi-carbonization treatment, and the relationship between temperature X and weight loss rate Y is as follows: on the XY axis coordinate, the part where temperature X is 220°C or less, the part that continues to the part of the shoulder of the gradual weight loss line at the part where weight suddenly decreases, the part of the S-shaped curve where weight suddenly decreases, and the part where the sudden weight decrease ends and the exit of the S-shaped curve where weight suddenly decreases. a methane generation system characterized in that the temperature is expressed as an S-shaped curve divided into three sections, with the shoulder temperature of the S-shaped curve having a first temperature range of 220°C or less and a second temperature range adjusted to a temperature of 130°C or less, and the system is a semi-carbonized organic waste biomaterial in which some solidified low-molecular-weight organic waste adheres to other low-molecular-weight organic waste, and the organic waste biomaterial retains 90% of the calorific value of the organic waste used as a processing raw material (hereinafter referred to as the 90% calorific value organic waste biomaterial); the wood biopellet generator generates the organic waste biopellets from the 90% calorific value organic waste biomaterial; and the organic waste biogasifier gasifies the organic waste biopellets to generate methane.

2. The methane generation system according to claim 1, characterized in that the temperature range of the second stage adjusted to 130°C or less is 110 to 130°C.

3. The methane generation system according to claim 2, characterized in that the temperature range of the first stage below 220°C is 150 to 220°C.

4. A methane generation system as described in claim 1, characterized in that the subcritical water reaction treatment device generates semi-carbonized solid matter and semi-carbonized powder, which are mixed together to form organic waste biopellets.

5. A power generation device using a methane generation system as described in claim 1, characterized in that the gasification furnace is equipped with a second superheated steam generator as a heat source for gasification, and methane gas is generated from the organic waste biopellets through a decomposition process using the second superheated steam, which has a higher temperature than the temperature of the first superheated steam input into the subcritical water reaction treatment device, and a gas engine connected to a generator is connected to the gasification furnace, and the generated methane gas is used to generate electricity.

6. A power generation device using the methane generation system described in claim 5, characterized in that the temperature of the superheated steam is 230 to 600°C.

7. The subcritical water reaction treatment apparatus used in the methane generation system according to claim 1, The subcritical water reaction treatment device is equipped with a superheated steam generator as a heat source for the subcritical water reaction treatment and the semi-carbonization treatment, and the relationship between temperature X and weight loss rate Y is expressed as an S-curve on the XY coordinate system, which is divided into three sections: a section where temperature X is 220°C or less and continues to the section of rapid weight loss at the shoulder of the gradual weight loss line, a section where the rapid weight loss of the S-curve continues, and a section where the rapid weight loss ends and the exit of the S-curve of the gradual weight loss line. The temperature of the shoulder of the S-curve has a first temperature range of 220°C or less and a second temperature range of 130°C or less, and forms semi-carbonized organic waste biomaterial in which some of the solidified organic waste that has been broken down into smaller molecules adheres to other small molecules of the organic waste, and the organic waste biomaterial retains 90% of the calorific value of the calorific value retained by the raw organic waste to be treated (hereinafter referred to as the 90% calorific value organic waste biomaterial).

8. A methane gas production method in which raw organic waste is heated under low-oxygen conditions to produce semi-carbonized organic waste biomaterial (hereinafter referred to as the organic waste biomaterial), semi-carbonized organic waste biopellets (hereinafter referred to as the organic waste biopellets) from the organic waste biomaterial, and the organic waste biopellets are gasified in a gasifier, the method comprising: a subcritical water reaction treatment device, an organic waste biopellet production device, and an organic waste biogasification furnace; the subcritical water reaction treatment device is equipped with a superheated steam generator as a heat source for the subcritical water reaction treatment and semi-carbonization treatment; and the relationship between temperature X and weight loss rate Y is expressed as follows on the XY axis coordinate system: a portion where temperature X is 220°C or less, which is the shoulder of the gradual weight loss line and continues to the portion where the weight suddenly decreases, the portion where the weight suddenly decreases on the S-shaped curve, and the portion where the weight suddenly decreases and the end of the S-shaped curve where the weight suddenly decreases are reached. The temperature of the shoulder of the S-curve is a first temperature range of 220°C or less and a second temperature range of 130°C or less, and the semi-carbonized organic waste biomaterial is formed by fixing a part of the solidified organic waste that has been reduced in molecular weight to the other part of the organic waste that has been reduced in molecular weight, and the organic waste biomaterial retains 90% of the calorific value of the calorific value retained by the organic waste as a raw material to be treated (hereinafter referred to as the 90% calorific value organic waste biomaterial), the organic waste biopellet generator generates the organic waste biopellets from the 90% calorific value organic waste biomaterial, and the organic waste biogasifier gasifies the organic waste biopellets to produce 10 Mj / Nm ３ A methane gas generation method characterized by generating methane gas having an energy of 1000 kJ / kg or more.

9. The methane gas production method according to claim 8, wherein the organic waste biogasification furnace has a methane gas concentration of 25 Mj / Nm ３ A methane gas generation method characterized by generating methane gas having an energy of 1000 kJ / kg or more.

10. A methane gas production method according to claim 8, characterized in that the temperature range of the first stage below 220°C is 150 to 220°C, and the temperature range of the second stage adjusted to a temperature below 130°C is 110 to 130°C.

11. A power generation method using the methane gas generation method described in claim 8, characterized in that the gasification furnace is equipped with a second superheated steam generator as a heat source for gasification, and methane gas is generated from the organic waste biopellets through a decomposition process using superheated steam using second superheated steam having a higher temperature than the temperature of the first superheated steam input into the subcritical water reaction treatment device, and power is generated using the methane gas generated by a power generator connected to a gas engine connected to the gasification furnace.

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