Hydrogen production method based on supercritical water pyrolysis

Abstract

The invention discloses a hydrogen production method based on supercritical water pyrolysis, which comprises the following steps: S1, sample preparation: cutting an organic matter to be pyrolyzed into a cylindrical sample; s2, preparing the device; putting the treated sample into a supporting sleeve, then putting the supporting sleeve into a clamping structure, sealing through a sealing structure, then connecting an injection system and an outlet metering system with the clamping structure, and setting test conditions; s3, starting a test, injecting supercritical water into the sample through an injection system to complete the test, and recording the amount of hydrogen generated by the organic matter along with the displacement of the supercritical water in the whole test process; s4, repeating the test, respectively changing the type of the catalyst and the mass ratio of the injected water to the organic matter, and repeating the test, so as to obtain the gas production rate of the hydrogen under different pyrolysis conditions. The purpose of hydrogen production can be achieved through supercritical water pyrolysis of organic matter, and meanwhile the gas production rate of hydrogen under different conditions can be researched by changing pyrolysis conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of in-situ hydrogen production from coal seams, and particularly relates to a hydrogen production method based on supercritical water pyrolysis. Background Art

[0002] Hydrogen is currently the most ideal clean energy source, with characteristics such as rich resources, wide sources, clean and pollution-free, and wide application range. It belongs to a clean fuel with high energy value and zero emissions. Currently known hydrogen production methods include hydrogen production from natural hydrocarbons (petroleum, natural gas, coal, etc.), electrolytic water hydrogen production, solar photovoltaic catalytic water hydrogen production, thermochemical composite method water hydrogen production, biomass gasification hydrogen production, microbial hydrogen production, etc. The main industrial applications are hydrogen production from natural hydrocarbons and electrolytic water hydrogen production. However, hydrogen production from natural hydrocarbons consumes traditional fossil energy and has large emissions of three wastes, while electrolytic water hydrogen production has high energy consumption and high hydrogen production cost.

[0003] As an emerging hydrogen production technology, supercritical water gasification can catalytically gasify various organic substances at low temperature in a supercritical water environment to produce hydrogen and carbon dioxide. It has the advantages of mild reaction conditions, fast reaction rate, clean reaction process, and rapid hydrogen production. At the same time, it can utilize the special physical and chemical properties of water in the supercritical state to solve the problems of pollutant and dust emissions in the process of using coal or organic waste from the source. Summary of the Invention

[0004] The present invention aims to provide a hydrogen production method based on supercritical water pyrolysis, which can achieve the purpose of hydrogen production by pyrolyzing organic substances with supercritical water, and at the same time, by changing the pyrolysis conditions, study the hydrogen production rate under different conditions.

[0005] Therefore, the technical solution adopted by the present invention is as follows: A hydrogen production method based on supercritical water pyrolysis, comprising the following steps:

[0006] S1: Specimen preparation. Cut or press the organic substance to be pyrolyzed into a cylindrical specimen, and then process it through a grinding machine to make the flatness of its end face within ±0.02 mm.

[0007] S2: Equipment preparation. Load the processed specimen into the support sleeve, and then sleeve a high-temperature ring compression sleeve outside the support sleeve. Then place the support sleeve into the clamping structure and seal it through the sealing structure. Connect both the injection system and the outlet metering system to the clamping structure. Then set the pressure value, heating temperature, and rate of the injected water in the injection system, and set the outflow pressure value in the outlet metering system. Apply axial pressure and confining pressure to the specimen according to the test requirements.

[0008] S3: Start the test. Inject a certain amount of supercritical water into the specimen through the injection system to complete the test, and at the same time record the amount of hydrogen generated by the displacement of the organic substance with supercritical water throughout the test process.

[0009] S4: Repeat the experiment, change the type of catalyst and the mass ratio of injected water to organic matter respectively, repeat the experiment, and record the amount of hydrogen gas generated by the organic matter during the whole process of supercritical fluid displacement under different conditions, so as to obtain the hydrogen gas production rate under different pyrolysis conditions.

[0010] As an optimization of the above solution, the clamping structure includes a mounting plate and a ductile sample tube. The sample tube is provided with upper and lower through holes. A pressurization system for realizing triaxial pressurization of the sample is arranged on the clamping structure; the pressurization system includes a high-temperature circumferential pressure sleeve arranged between the sample tube and the support sleeve, and an axial pressure mounting plate arranged below the mounting plate through a connecting column. The high-temperature circumferential pressure sleeve is equipped with a circumferential pressure tracking system, and an axial pressure cylinder is arranged on the axial pressure mounting plate.

[0011] Further preferably, the sealing structure includes floating plugs arranged at the upper and lower ends of the sample tube. A plurality of high-temperature gaskets and a double V-shaped combined graphite component are sequentially arranged between each floating plug and the sample tube from inside to outside. A bolt pre-tightening and pressing structure for ensuring reliable sealing of the sealing structure is arranged at the end of each floating plug. An outlet for fluid injection or an inlet communicating with the injection system is arranged inside the floating plug, and the outlet and the inlet are respectively arranged in different floating plugs.

[0012] Further preferably, the bolt pre-tightening and pressing structure includes an upper bolt pre-tightening and pressing structure and a lower bolt pre-tightening and pressing structure corresponding to the upper and lower floating plugs. The upper bolt pre-tightening and pressing structure includes a first flange sleeved on the upper end of the sample tube and a second flange sleeved on the upper end of the upper floating plug. The first flange and the second flange are connected by mounting bolts. A T-shaped upper top block is arranged at a position near the upper end of the floating plug, and the lower end of the upper top block can be inserted into the upper end of the sample tube. A lower notch for the upper top block to be inserted into is arranged at the lower end of the second flange, and an upper tightening bolt capable of pressing on the upper top block is arranged on the second flange;

[0013] The lower bolt pre-tightening and pressing structure includes a third flange sleeved on the lower end of the sample tube and a fourth flange sleeved at a position near the lower end of the lower floating plug. The third flange is arranged on the mounting plate located at its lower end. The upper end of the fourth flange is located inside the mounting plate. A T-shaped lower top block is arranged at a position near the lower end of the lower floating plug, and the upper end of the lower top block can be inserted into the lower end of the sample tube. An upper notch for the lower top block to be inserted into is arranged at the upper end of the fourth flange, and a lower tightening bolt capable of pressing on the lower top block is arranged on the fourth flange.

[0014] Further preferably, the mounting disc is arranged on the flipping assembly, the flipping assembly includes a flipping bracket, horizontal flipping shafts are arranged at both ends of the mounting disc, the other ends of the flipping shafts are rotatably arranged on flipping seats, the flipping seats are arranged on the flipping bracket, and a traveling mechanism for driving the whole flipping assembly to move and fixing the position after movement is arranged at the bottom of the flipping bracket.

[0015] Further preferably, the injection system includes a storage container for accommodating fluid, a constant pressure pump for realizing fluid flow, a heater for realizing fluid heating, and a fluid buffer tank for ensuring that the input fluid is in a supercritical state. The storage container, the constant pressure pump, the heater, and the fluid buffer tank are sequentially connected through an injection pipeline, and a monitoring structure for monitoring its pressure and temperature is arranged on the fluid buffer tank. A pressure vessel for buffering pressure fluctuations during heating is connected in parallel to the heater, and a control valve is arranged on the fluid buffer tank.

[0016] Further preferably, the outlet metering system includes a back pressure valve for outlet pressure control, a gas-liquid separator for realizing gas-liquid separation, a gas concentration meter for detecting gas concentration, and a chromatographic analyzer for analyzing gas components. The back pressure valve, the gas-liquid separator, the gas concentration meter, and the chromatographic analyzer are sequentially communicated with the outlet through a back pressure pipeline. A condenser is arranged between the outlet and the back pressure valve, and a buffer container and a back pressure pump are arranged on the back pressure valve through a pressure control pipeline.

[0017] Further preferably, the back pressure valve includes an upper cavity and a lower cavity arranged up and down, and a back pressure gasket is arranged between the upper cavity and the lower cavity. A valve core is arranged in the upper cavity, a taper ring is sleeved outside the valve core, a diaphragm located between the upper cavity and the lower cavity is arranged at the lower end of the valve core, a downward centering gasket is arranged in the lower cavity, a lower gasket is arranged between the centering gasket and the diaphragm, a control pressure chamber is arranged in the lower cavity, a drain port and a control pressure port communicated with the control pressure chamber are arranged on the lower cavity, a back pressure inlet and a back pressure outlet are arranged on the upper cavity, and the communication between the back pressure inlet and the back pressure outlet can be realized by the movement of the valve core.

[0018] The beneficial effects of the present invention: enabling water to react with organic matter in a supercritical state to generate hydrogen and carbon dioxide, thereby achieving the purpose of hydrogen production, and also being able to study the hydrogen production rate under different pyrolysis conditions by changing parameters. Description of the Drawings

[0019] Figure 1 is a schematic flow chart of the present invention.

[0020] Figure 2 is a schematic diagram of the test device in the present invention.

[0021] Figure 3 Schematic diagram of the clamping structure in the present invention.

[0022] Figure 4 Stereoscopic schematic diagram of the clamping structure in the present invention.

[0023] Figure 5 Schematic diagram of the clamping structure and the flipping assembly in the present invention.

[0024] Figure 6 Schematic diagram of the pressure vessel in the present invention.

[0025] Figure 7 Schematic diagram of the back-pressure valve in the present invention.

[0026] Reference numerals: inlet - 1, outlet - 2, sample tube - 3, mounting disc - 4, support sleeve - 5, floating plug - 6, high - temperature gasket - 7, graphite assembly - 8, provided with inlet - 9, first flange - 10, second flange - 11, upper top block - 12, upper tightening bolt - 13, third flange - 14, fourth flange - 15, lower top block - 16, high - temperature ring compression sleeve - 20, connecting column - 21, axial pressure mounting plate - 22, axial pressure cylinder - 23, cooling sleeve - 24, flipping bracket - 29, flipping shaft - 30, flipping seat - 31, traveling mechanism - 32, storage container - 33, constant - pressure pump - 34, heater - 35, fluid buffer tank - 36, pressure vessel - 37, base - 37a, cylinder body - 37b, piston - 37c, compression cap - 37d, plug - 37e, control valve - 38, back - pressure valve - 39, upper cavity - 39a and lower cavity - 39b, back - pressure washer - 39c, valve core - 39d, taper ring - 39e, diaphragm - 39f, centering washer - 39g, lower washer - 39h, back - pressure lower inlet - 39i and back - pressure lower outlet - 39j, back - pressure upper inlet - 39k, back - pressure upper outlet - 39m, gas - liquid separator - 40, gas concentration meter - 41, condenser - 42, buffer container - 43, back - pressure pump - 44, lower tightening bolt - 45. Detailed implementation manners

[0027] The present invention will be further described below through examples in conjunction with the accompanying drawings:

[0028] As Figures 1-7 shown, a hydrogen production method based on supercritical water gasification includes the following steps:

[0029] The first step, sample preparation. Cut or press the organic matter to be gasified into a cylindrical sample, and then process it through a grinding machine to make the flatness of its end face within ±0.02 mm. The organic matter can be various coal types, biomass, wastewater, and carbon in organic waste.

[0030] Step 2: Device assembly. Place the processed specimen into the support sleeve, and then sleeve a high-temperature ring compression sleeve outside the support sleeve. Next, place the support sleeve into the clamping structure and seal it through the sealing structure. Then, connect both the injection system and the outlet metering system to the clamping structure. After that, set the pressure value, heating temperature, and rate of the injected water in the injection system, and simultaneously set the outflow pressure value in the outlet metering system. Also, apply axial pressure and confining pressure to the specimen according to the test requirements.

[0031] The clamping assembly includes a mounting plate 4 and an extensible specimen tube 3, and the specimen tube 3 is arranged with upper and lower through holes. To ensure the temperature inside the specimen tube, it is preferably to set a heat preservation sleeve outside the specimen tube. Preferably, the specimen tube and the support sleeve are made of nickel-based alloy materials, specifically high-temperature aviation materials, such as imported alloy 718 or domestic material 4169. They have high temperature, high pressure, and corrosion resistance, do not deform after repeated use, still have high strength under high temperature and high pressure, and even have a tensile strength of 1500 N / mm 2 under the high temperature condition of 800 °C, and the yield strength reaches 800 N / mm 2 , and the elongation rate can reach more than 30%.

[0032] A pressurizing system for realizing the axial pressure and confining pressure pressurization of the specimen to simulate the surrounding environment of the coal body is arranged on the clamping structure. The pressurizing system includes a high-temperature ring compression sleeve 20 arranged between the specimen tube 3 and the support sleeve 5 and an axial pressure mounting plate 22 arranged below the mounting plate 4 through a connecting column 21. The high-temperature ring compression sleeve 20 is equipped with a ring pressure tracking system, and an axial pressure cylinder 23 is arranged on the axial pressure mounting plate 22. Preferably, a cooling sleeve 24 with water inlet and outlet is arranged between the axial pressure cylinder 23 and the specimen tube 3 to prevent the temperature of the specimen tube from affecting the axial pressure cylinder.

[0033] Preferably, the ring pressure tracking system includes a ring pressure tracking pump and a ring pressure tracking pipeline communicated with the high-temperature ring compression sleeve. The ring pressure tracking pump is equipped with a control panel, safety pressure relief function, etc., and can realize differential pressure tracking, automatic pressure lifting and lowering, display of pressure data, feedback system, etc. through a control terminal; it has the function of manually controlling pressure lifting and lowering.

[0034] The sealing structure includes floating plugs 6 arranged at the upper and lower ends of the specimen tube 3. Between each floating plug 6 and the specimen tube 3, multiple high-temperature gaskets 7 and double V-shaped combined graphite components 8 are sequentially arranged from inside to outside. When the internal pressure extrudes outward, the self-sealing rubber ring deforms, making its outer diameter fit more closely with the specimen tube and its inner diameter fit more closely with the high-temperature ring compression sleeve, thus realizing reliable sealing. The outlet 2 and the inlet 1 are respectively arranged in different floating plugs 6. Preferably, an additional inlet 9 is also arranged on the floating plug 6 provided with the outlet 2.

[0035] Preferably, the high-temperature gasket material is made of ultra-high temperature material imported from the United States. It has good elasticity even at 1000°C and can be used for frequent loading and unloading. It can be arbitrarily stamped into a formed sealing gasket. The double V-shaped combined graphite component is used as the sealing component, which has the characteristics of reliable sealing and convenient loading and unloading. At the same time, it blocks the boundary cross-flow between the ring pressure sleeve and the sample and eliminates the boundary effect.

[0036] To ensure the reliable sealing of the sealing structure, a bolt pre-tightening and pressing structure for ensuring the reliable sealing of the sealing structure is provided at the end of each floating plug 6. The bolt pre-tightening and pressing structure includes an upper bolt pre-tightening and pressing structure and a lower bolt pre-tightening and pressing structure arranged up and down. That is, the upper bolt pre-tightening and pressing structure is used to lock the upper floating plug, and the lower bolt pre-tightening and pressing structure is used to lock the lower floating plug.

[0037] The upper bolt pre-tightening and pressing structure includes a first flange 10 sleeved on the upper end of the sample tube 3 and a second flange 11 sleeved on the upper end of the upper floating plug 6. The first flange 10 and the second flange 11 are connected by mounting bolts. A T-shaped upper top block 12 is provided at a position near the upper end of the floating plug 6, and the lower end of the upper top block 12 can be inserted into the upper end of the sample tube 3. A lower notch for the upper top block 12 to be inserted into is provided at the lower end of the second flange 11, and an upper tightening bolt 13 that can press on the upper top block 12 is provided on the second flange 11.

[0038] The lower bolt pre-tightening and pressing structure includes a third flange 14 sleeved on the lower end of the sample tube 3 and a fourth flange 15 sleeved at a position near the lower end of the lower floating plug 6. The third flange 14 is arranged on the mounting plate 4 located at its lower end, and the upper end of the fourth flange 15 is located inside the mounting plate 4. A T-shaped lower top block 16 is provided at a position near the lower end of the lower floating plug 6, and the upper end of the lower top block 16 can be inserted into the lower end of the sample tube 3. An upper notch for the lower top block 16 to be inserted into is provided at the upper end of the fourth flange 15, and a lower tightening bolt 45 that can press on the lower top block 16 is provided on the fourth flange 15.

[0039] The sealing structure is tightened by multiple tightening bolts and top blocks to prevent the outward movement of the sealing structure when the internal pressure rises. Preferably, the screws are made of high-strength heat-resistant materials and will not produce sticking phenomenon at high temperatures.

[0040] To achieve horizontal and vertical flipping, the mounting plate 4 is arranged on the flipping assembly. The flipping assembly includes a flipping bracket 29. Horizontal rotating shafts 30 are arranged at both ends of the mounting plate 4. The other ends of the rotating shafts 30 are rotatably arranged on the flipping seats 31. The flipping seats 31 are arranged on the flipping bracket 29. A traveling mechanism 32 for driving the entire flipping assembly to move and fixing the position after movement is provided at the bottom of the flipping bracket 29.

[0041] The injection system includes a storage container 33 for containing fluid, a constant-pressure pump 34 for realizing fluid flow, a heater 35 for heating the fluid, and a fluid buffer tank 36 for ensuring that the input fluid is in a supercritical state. The storage container 33, the constant-pressure pump 34, the heater 35, and the fluid buffer tank 36 are sequentially connected through an injection pipeline. A monitoring structure for monitoring its pressure and temperature is provided on the fluid buffer tank 36. A pressure vessel 37 for buffering pressure fluctuations during heating is connected in parallel to the heater 35. A control valve 38 is provided on the fluid buffer tank. Preferably, a flowmeter and a solenoid valve are provided on the pipeline between the fluid buffer tank 36 and the inlet. When the injected supercritical water reaches a certain flow rate, the solenoid valve closes to ensure the injection volume.

[0042] As Figure 6 shown, the pressure vessel 37 is a piston-type pressure vessel, specifically including a cylinder body 37b provided on a base 37a. A piston 37c is slidably arranged in the cylinder body 37b. A gasket and a sealing ring are provided between the piston 37c and the cylinder body 37b to ensure the sealing between the piston and the cylinder body. Pressure caps 37d for closing the cylinder body 37b are provided at both the upper and lower ends of the cylinder body 37b. A plug 37e is provided on the pressure cap 37d, and a flow channel for the fluid to pass through is provided on the plug 37e. The pressure vessel is made of high-strength materials and is sealed and isolated using O-rings. In addition to the isolation function, the important function of the piston is to transmit the power of the power liquid to the working medium for work. There is no pulse phenomenon, and it can stably transmit pressure and flow, with low pressure loss. During the entire test process, it is necessary to ensure that the fluid types in the pressure vessel and the storage container are the same.

[0043] The specific structure of the heater 35 includes a heat transfer body with a main body made of cast aluminum. An electric heating tube is spirally arranged on the heat transfer body, and a heating channel for the fluid to pass through is provided. The heating channel is located outside the electric heating tube. Heat insulation materials are provided outside the heat transfer body, and the heat insulation materials are made of ceramic fiber blankets.

[0044] The outlet metering system includes a back-pressure valve 39 for controlling the outlet pressure, a gas-liquid separator 40 for realizing gas-liquid separation, a gas concentration meter 41 for detecting the gas concentration, and a chromatographic analyzer 46 for analyzing the gas components. The back-pressure valve 39, the gas-liquid separator 40, the gas concentration meter 41, and the chromatographic analyzer 46 are sequentially connected to the outlet through a back-pressure pipeline. A condenser 42 is provided between the outlet and the back-pressure valve 39. A buffer container 43 and a back-pressure pump 44 are provided on the back-pressure valve 39 through a pressure control pipeline. Through the settings of the back-pressure pump, the back-pressure valve, and the buffer container, the outlet pressure can be controlled, a static pressure difference can be established, and at the same time, the output pressure can be made stable and the metering accuracy can be improved.

[0045] As Figure 7As shown in the figure, the back pressure valve 39 includes an upper cavity 39a and a lower cavity 39b arranged vertically. A back pressure gasket 39c is provided between the upper cavity 39a and the lower cavity 39b. A valve core 39d is arranged in the upper cavity 39a. A taper ring 39e is sleeved outside the valve core 39d. A diaphragm 39f located between the upper cavity and the lower cavity is arranged at the lower end of the valve core 39d. A downward centering gasket 39g is arranged in the lower cavity 39b. A lower gasket 39h is arranged between the centering gasket 39g and the diaphragm 39f.

[0046] To control the pressure of the back pressure valve, a control pressure chamber is arranged in the lower cavity 39b, and the control pressure chamber is communicated with the diaphragm. At the same time, an exhaust port 39i and a control pressure port 39j communicated with the control pressure chamber are arranged on the lower cavity 39b. A certain amount of liquid is injected through the control pressure port to ensure that the diaphragm is subjected to the pressure on the upper side, and the control pressure port is connected to the back pressure pump.

[0047] A back pressure inlet 39k and a back pressure outlet 39m are arranged in the upper cavity 39a, and whether the back pressure inlet 39k and the back pressure outlet 39m are communicated can be realized by the movement of the valve core. The back pressure inlet 39k is connected to the outlet, and the back pressure outlet is communicated with the gas-liquid separator. As needed, after injecting a certain amount of liquid into the control pressure chamber through the control pressure port 39j, the opening pressure of the back pressure valve is set. When the pressure at the back pressure inlet 39k is greater than the set pressure, the valve core will push the diaphragm to move downward into the lower cavity, so that the back pressure inlet is communicated with the back pressure outlet, thereby realizing the passage of liquid. When the pressure is less than the set pressure, the liquid in the control pressure chamber will pass through the diaphragm and push the valve core to move upward into the upper cavity, thereby disconnecting the back pressure inlet and the back pressure outlet.

[0048] In the displacement test, when the fluid in the clamping structure is greater than the set pressure of the back pressure valve, the back pressure valve allows the fluid to flow out, so as to maintain the pressure in the clamping structure. When the fluid in the clamping structure is less than the set pressure of the back pressure valve, the back pressure valve does not allow the fluid to flow out, so as to realize the control of the outlet pressure.

[0049] The third step is to start the test. Start the test, inject a certain amount of supercritical water into the sample through the injection system to complete the test, and record the amount of hydrogen gas generated by the organic matter during the whole process of supercritical water displacement.

[0050] The fourth step is to repeat the test. Respectively change the types of catalysts and the mass ratio of injected water to organic matter, repeat the test, and record the amount of hydrogen gas generated by the organic matter during the whole process of supercritical fluid displacement under different conditions, so as to obtain the hydrogen production rate under different pyrolysis conditions. The catalyst is injected into the sample tube after being heated together with the supercritical water. Of course, the catalyst can also not be added. The catalysts mainly include alkali catalysts such as NaOH, KOH, Na2CO3, K2CO3, Ca(OH)2, KHCO3, etc.

Claims

1. A hydrogen production method based on supercritical hydrothermal pyrolysis, characterized in that: It includes the following steps: S1: Specimen preparation. Cut or press the organic matter to be pyrolyzed into a cylindrical specimen, and then process it through a grinding machine to make the flatness of its end face within ±0.02 mm; S2: Equipment preparation. Load the processed specimen into the support sleeve, and sleeved with a high-temperature ring pressing sleeve outside the support sleeve. Then install the support sleeve into the clamping structure and seal it through the sealing structure. Then connect both the injection system and the outlet metering system to the clamping structure. Then set the pressure value, heating temperature and rate of the injected water in the injection system, and at the same time set the outflow pressure value in the outlet metering system, and apply axial pressure and confining pressure to the specimen according to the test requirements; S3: Start the test. Inject a certain amount of supercritical water into the specimen through the injection system to complete the test, and at the same time record the amount of hydrogen gas generated by the organic matter during the whole process of supercritical water displacement; S4: Repeat the test. Change the types of catalysts and the mass ratio of the injected water to the organic matter respectively, repeat the test, and record the amount of hydrogen gas generated by the organic matter during the whole process of supercritical fluid displacement under different conditions, so as to obtain the hydrogen gas production rate under different pyrolysis conditions.

2. The hydrogen production method based on supercritical water gasification according to claim 1, characterized in that: The clamping structure includes a mounting plate (4) and a ductile specimen tube (3). The specimen tube (3) is arranged with upper and lower through holes. A pressurizing system for realizing axial pressure and confining pressure pressurization of the specimen is arranged on the clamping structure; the pressurizing system includes a high-temperature ring pressing sleeve (20) arranged between the specimen tube (3) and the support sleeve (5) and an axial pressure mounting plate (22) arranged below the mounting plate (4) through a connecting column (21). The high-temperature ring pressing sleeve (20) is equipped with a ring pressure tracking system, and an axial pressure cylinder (23) is arranged on the axial pressure mounting plate (22).

3. The hydrogen production method based on supercritical water gasification according to claim 2, characterized in that: The sealing structure includes floating plugs (6) arranged at the upper and lower ends of the specimen tube (3). Between each floating plug (6) and the specimen tube (3), multiple high-temperature gaskets (7) and double V-shaped combined graphite components (8) are arranged in sequence from inside to outside. A bolt pre-tightening and top-tightening structure for ensuring reliable sealing of the sealing structure is arranged at the end of each floating plug (6). An outlet (2) for fluid injection or an inlet (1) communicated with the injection system is arranged in the floating plug (6), and the outlet (2) and the inlet (1) are respectively arranged in different floating plugs (6).

4. The hydrogen production method based on supercritical hydrothermal pyrolysis according to claim 3, characterized in that: The bolt pre-tightening and top-tightening structure includes an upper bolt pre-tightening and top-tightening structure and a lower bolt pre-tightening and top-tightening structure corresponding to the upper and lower floating plugs. The upper bolt pre-tightening and top-tightening structure includes a first flange (10) sleeved on the upper end of the specimen tube (3) and a second flange (11) sleeved on the upper end of the upper floating plug (6). The first flange (10) and the second flange (11) are connected by mounting bolts. A T-shaped upper top block (12) is arranged at a position close to the upper end of the floating plug (6), and the lower end of the upper top block (12) can be inserted into the upper end of the specimen tube (3). A lower notch for the upper top block (12) to be inserted into is arranged at the lower end of the second flange (11), and an upper top-tightening bolt (13) capable of pressing on the upper top block (12) is arranged on the second flange (11); The lower bolt pre-tightening and jacking structure includes a third flange (14) sleeved on the lower end of the specimen tube (3) and a fourth flange (15) sleeved on the lower floating plug (6) near its lower end. The third flange (14) is arranged on the mounting plate (4) located at its lower end. The upper end of the fourth flange (15) is located inside the mounting plate (4). At the position near the lower end of the lower floating plug (6), a T-shaped lower jacking block (16) is arranged, and the upper end of the lower jacking block (16) can be inserted into the lower end of the specimen tube (3). An upper notch for the lower jacking block (16) to be inserted into is arranged at the upper end of the fourth flange (15). A lower jacking bolt (45) capable of jacking on the lower jacking block (16) is arranged on the fourth flange (15).

5. The hydrogen production method based on supercritical water pyrolysis according to claim 2, characterized in that: The mounting plate (4) is arranged on a flipping assembly. The flipping assembly includes a flipping bracket (29). Horizontal flipping shafts (30) are arranged at both ends of the mounting plate (4). The other ends of the flipping shafts (30) are rotatably arranged on flipping seats (31). The flipping seats (31) are arranged on the flipping bracket (29). A traveling mechanism (32) for driving the entire flipping assembly to move and fix the position after movement is arranged at the bottom of the flipping bracket (29).

6. The hydrogen production method based on supercritical water pyrolysis according to claim 1, characterized in that: The injection system includes a storage container (33) for containing fluid, a constant pressure pump (34) for realizing fluid flow, a heater (35) for realizing fluid heating, and a fluid buffer tank (36) for ensuring that the input fluid is in a supercritical state. The storage container (33), the constant pressure pump (34), the heater (35), and the fluid buffer tank (36) are sequentially connected through an injection pipeline. A monitoring structure for monitoring its pressure and temperature is arranged on the fluid buffer tank (36). A pressure vessel (37) for buffering pressure fluctuations during heating is connected in parallel to the heater (35). A control valve (38) is arranged on the fluid buffer tank.

7. The hydrogen production method based on supercritical water gasification according to claim 1, characterized in that: The outlet metering system includes a back pressure valve (39) for outlet pressure control, a gas-liquid separator (40) for realizing gas-liquid separation, a gas concentration meter (41) for gas concentration detection, and a chromatographic analyzer for analyzing gas components. The back pressure valve (39), the gas-liquid separator (40), the gas concentration meter (41), and the chromatographic analyzer are sequentially connected to the outlet through a back pressure pipeline. A condenser (42) is arranged between the outlet and the back pressure valve (39). A buffer container (43) and a back pressure pump (44) are arranged on the back pressure valve (39) through a pressure control pipeline.

8. The hydrogen production method based on supercritical water gasification according to claim 1, characterized in that: The backpressure valve (39) includes an upper cavity (39a) and a lower cavity (39b) arranged vertically, and a backpressure gasket (39c) is provided between the upper cavity (39a) and the lower cavity (39b). A valve core (39d) is arranged in the upper cavity (39a), a taper ring (39e) is sleeved outside the valve core (39d), a diaphragm (39f) located between the upper cavity and the lower cavity is arranged at the lower end of the valve core (39d), a downward-facing centering gasket (39g) is arranged in the lower cavity (39b), a lower gasket (39h) is arranged between the centering gasket (39g) and the diaphragm (39f), a control pressure chamber is arranged in the lower cavity (39b), an exhaust port (39i) and a control pressure port (39j) communicating with the control pressure chamber are arranged on the lower cavity (39b), a backpressure inlet (39k) and a backpressure outlet (39m) are arranged on the upper cavity (39a), and the communication between the backpressure inlet (39k) and the backpressure outlet (39m) can be achieved by the movement of the valve core (39d).

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