Method and equipment for carrying out hydrate hydrogen storage by utilizing seawater

Abstract

The invention relates to the technical field of hydrogen storage, in particular to a method and equipment for conducting hydrate hydrogen storage through seawater, and the method comprises the steps that a thermodynamic accelerant is added into a seawater raw material, and a mixed solution is obtained; according to the phase equilibrium diagram of the hydrogen hydrate and the non-hydrogen hydrate, setting target temperature and pressure which tend to generate the hydrogen hydrate; reducing the temperature of the mixed solution to a target temperature, preserving heat, injecting hydrogen into the mixed solution to a target pressure, and guiding the seawater reaction system to tend to generate a hydrogen hydrate. The invention provides a safer, economical and environment-friendly hydrogen storage mode.

Description

Technical Field

[0001] This application relates to the technical field of hydrogen storage, and particularly to a method and device for hydrogen storage in hydrates using seawater. Background Art

[0002] As a new type of solid-state hydrogen storage technology, hydrogen hydrate hydrogen storage has stronger adaptability in the marine environment due to its advantages such as lower equipment requirements, mild operating conditions, strong reversibility, and high safety. By generating hydrogen through wind power generation on an offshore platform and storing hydrogen in the form of hydrates, and finally transporting it to land by ship for downstream applications, it provides a safe, efficient, and economical new path for hydrogen storage and transportation, and promotes the realization of the integrated application of "wind power generation + hydrogen energy storage".

[0003] Hydrogen hydrate refers to a solid compound formed by hydrogen and water molecules under specific temperature and pressure conditions. However, in the marine environment, the extraction of fresh water faces many challenges, requiring additional seawater desalination equipment, offshore operation space, and high process costs. With the large-scale preparation and application of green hydrogen in the future, the consumption of fresh water resources has become an important factor restricting the development of hydrogen hydrate hydrogen storage technology. Summary of the Invention

[0004] In view of this, this application provides a method and device for hydrogen storage in hydrates using seawater, providing a safer, more economical, and environmentally friendly way to synthesize hydrogen hydrates.

[0005] In a first aspect, this application provides a method for hydrogen storage in hydrates using seawater, including: adding a thermodynamic promoter to a seawater raw material to obtain a mixed solution; setting a target temperature and a target pressure for preferentially generating the hydrogen hydrate according to the phase equilibrium diagram of the hydrogen hydrate and the non-hydrogen hydrate; reducing the mixed solution to the target temperature and keeping it warm, and injecting hydrogen into the mixed solution to the target pressure to guide the seawater reaction system to preferentially generate the hydrogen hydrate.

[0006] The hydrogen storage method provided in this application uses seawater as the reaction raw material for preparing hydrogen hydrates, without the need for a complex seawater desalination process, greatly simplifies the seawater hydrogen storage process, reduces the operation links on the offshore platform, improves the economic benefits of operation, saves the limited offshore platform operation space, makes the seawater hydrogen storage operation more convenient and feasible, and breaks through the limitation in the traditional concept that "seawater is not conducive to gas storage"; at the same time, in the seawater reaction system with the target pressure and target temperature for preferentially generating hydrogen hydrates, seawater has an inhibitory effect on the formation of non-hydrogen hydrates and a promoting effect on the formation of hydrogen hydrates, that is, it adjusts the formation ratio of hydrogen hydrates and the non-hydrogen hydrates in the reaction system and guides the formation of more hydrogen hydrates; and a thermodynamic promoter is also introduced during the synthesis process, enabling hydrogen hydrates to be formed under relatively mild conditions and reducing the reaction difficulty.

[0007] In some embodiments, setting the target temperature and target pressure for hydrogen hydrate formation according to the phase equilibrium diagram of hydrogen hydrate and non-hydrogen hydrate specifically includes: obtaining seawater samples with multiple different salt ion concentrations, respectively preparing multiple mixed solutions by mixing thermodynamic promoters with the multiple seawater samples, injecting hydrogen into the multiple mixed solutions to a preset pressure, reducing the temperature of the mixed solutions to form hydrogen hydrate, and plotting the temperature-pressure curves of the hydrogen hydrate formation process at different salt ion concentrations; raising the temperature of the mixed solutions to decompose the hydrogen hydrate, and plotting the temperature-pressure curves of the hydrogen hydrate decomposition process at different salt ion concentrations; determining the intersection points of the temperature-pressure curves in the formation process and the temperature-pressure curves in the decomposition process to obtain the phase equilibrium points of the hydrogen hydrates formed at different salt ion concentrations under the preset pressure; determining the phase equilibrium points of the hydrogen hydrates formed at different salt ion concentrations under different preset pressures; determining the phase equilibrium points of non-hydrogen hydrates formed at different salt ion concentrations under different preset pressures, plotting the phase equilibrium points of the hydrogen hydrates and the phase equilibrium points of the non-hydrogen hydrates as a phase equilibrium diagram; and determining the target temperature and target pressure for synthesizing the hydrogen hydrate according to the phase equilibrium diagram.

[0008] First, experimentally plot the phase equilibrium diagram of hydrogen hydrate and non-hydrogen hydrate formed during hydrogen storage in the seawater system, and select the target temperature and target pressure at which the seawater system tends to form hydrogen hydrate based on the thermodynamic data of the phase diagram. The process of obtaining the target temperature and target pressure is simple.

[0009] In some embodiments, the salt ion includes NaCl, and the concentration of NaCl in the seawater sample is 0 to 3.5 wt%.

[0010] The main salt component affecting the formation ratio of hydrogen hydrate in seawater is NaCl. By setting the adjustable value of the NaCl concentration in the seawater sample within the above range, more accurate test values of the target temperature and target pressure can be obtained.

[0011] In some embodiments, the seawater sample includes actual seawater in the sea area or artificially configured simulated seawater.

[0012] Artificially prepared simulated seawater can precisely control its composition and concentration, simulate the actual water quality of different sea areas, thus ensuring the wide applicability of experimental results. In addition, by using artificially prepared simulated seawater, the interference of environmental changes on experimental results can be effectively reduced, enhancing the repeatability and accuracy of the experiment; using seawater from actual sea areas can more truly reflect the hydrogen storage characteristics of hydrogen hydrate in the seawater system, providing reliable data support for the practical application of offshore wind power hydrogen production and hydrate hydrogen storage technologies.

[0013] In some embodiments, the thermodynamic promoter includes a gas promoter and a liquid promoter; wherein, the gas promoter includes at least one of methane or propane, and the liquid promoter includes at least one of 1,3-dioxolane, cyclopentane or organic salt compounds, and the organic salt compounds include at least one of tetrabutylammonium bromide or tetrabutylammonium nitrate.

[0014] Introducing a thermodynamic promoter can enable hydrogen hydrate to form under relatively mild conditions and improve the hydrogen storage efficiency.

[0015] In some embodiments, the concentration of the thermodynamic promoter in the mixed solution is 1 mol% - 5.56 mol%.

[0016] When the concentration of the thermodynamic promoter is within the above range, it can better reduce the formation pressure of hydrogen hydrate, and under relatively mild temperature and pressure conditions, achieve a better hydrogen storage capacity in the seawater system than in the pure water system.

[0017] In some embodiments, determining the phase equilibrium points of non-hydrogen hydrates formed at different salt ion concentrations under different preset pressures includes: using a high-pressure differential scanning calorimeter to determine the phase equilibrium points of non-hydrogen hydrates formed at different salt ion concentrations under different preset pressures.

[0018] In the reaction system of seawater hydrogen storage, hydrogen hydrate and non-hydrogen hydrate will be formed. Then, the phase equilibrium diagram can be obtained by plotting the phase equilibrium points of non-hydrogen hydrates and hydrogen hydrates. By analyzing the phase equilibrium diagram, appropriate target temperature and target pressure can be selected to make the reaction system tend to generate a higher proportion of hydrogen hydrate.

[0019] In some embodiments, the method for hydrogen storage in hydrates using seawater further includes: monitoring the growth morphology evolution and gas-liquid contact mode during the formation of hydrogen hydrate; according to the growth morphology evolution and gas-liquid contact mode of the hydrogen hydrate, adjusting the NaCl concentration of the mixed solution to induce the hydrogen hydrate to form a slurry-like morphology.

[0020] During the actual synthesis process, by regulating the salt ion concentration in the seawater system according to the hydrate morphology and the gas-liquid contact mode, the formation of a slurry morphology of the hydrogen hydrate can be induced, the continuous growth time of the hydrogen hydrate can be prolonged, and the hydrogen storage capacity of the hydrogen hydrate can be increased; and by regulating the salt ion concentration in the seawater system, the proportion of the seawater system that tends to generate hydrogen hydrate is further increased, and the hydrogen storage capacity of the seawater system is also further increased.

[0021] In some embodiments, the formation process and the decomposition process of the hydrogen hydrate are carried out under a water bath condition.

[0022] By using a water bath for temperature control, the reaction temperature can be better maintained during the reaction process, avoiding the influence of temperature fluctuations on the growth of hydrogen hydrate and ensuring the progress of the seawater hydrogen storage process.

[0023] In a second aspect, the present application provides a device for storing hydrogen in hydrates using seawater. The device for storing hydrogen in hydrates using seawater is used to execute the method for storing hydrogen in hydrates using seawater according to any one of the first aspects, and includes an air injection system, a hydrate formation system, and a temperature control system that are connected; wherein, the hydrate formation system is used to accommodate a mixed solution containing seawater and a thermodynamic promoter, the air injection system is used to inject hydrogen into the hydrate formation system until the hydrate formation system reaches a target pressure; the temperature control system is used to control the temperature of the hydrate formation system to a target temperature. Description of the Drawings

[0024] Figure 1 It is a system diagram of the device for storing hydrogen in hydrates using seawater provided by the present application.

[0025] Figure 2 It is a phase equilibrium diagram of hydrogen hydrate and non-hydrogen hydrate under different NaCl concentrations provided in Example 1 of the present application.

[0026] Figure 3 It is the hydrogen volume consumption under different NaCl concentrations provided in Example 2 of the present application.

[0027] Figure 4 It is the gas-liquid contact situation during the growth process of the hydrogen hydrate layer under different NaCl concentrations provided in Example 3 of the present application.

[0028] Description of the main component symbols: 1. High-pressure hydrogen cylinder; 2. Booster device; 3. Pressure gauge; 4. Hydrate reaction vessel; 5. Image collector; 7. Magnetic stirrer; 8. Magnetic stirrer; 9. Water bath; 10. Temperature control device; 11. Thermocouple; 12. Pressure sensor; 13. Data acquisition system. Detailed Embodiments

[0029] The technical solutions in the embodiments of the present application will be described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments.

[0030] With the increasing global demand for clean energy, hydrogen energy has gradually become a key secondary energy source for promoting decarbonization in fields such as transportation, industry, and construction due to its wide range of sources, clean and carbon-free nature, and high energy density. In recent years, the technology of hydrogen production from offshore wind power has developed rapidly, mainly due to its ability to produce high-quality hydrogen energy using low-quality new energy electricity. This technology can not only effectively reduce the cost of far-sea power transmission but also solve the problems of large-scale consumption of sodium in offshore wind power and long-term energy storage, and has good application prospects for popularization.

[0031] The offshore wind power hydrogen production industry can be divided into three main parts: offshore wind power generation systems, water electrolysis hydrogen production technology, and offshore hydrogen storage and transportation methods. Among them, how to store hydrogen safely and efficiently is one of the key technical bottlenecks restricting the large-scale application of offshore wind power hydrogen production technology. Currently, the offshore hydrogen storage and transportation method mainly relies on ships to transport hydrogen, and the hydrogen storage technology mainly uses high-pressure gaseous and liquid hydrogen. However, these technologies still have problems such as high energy consumption, complex equipment requirements, and safety risks of leakage and explosion. As a new type of solid hydrogen storage technology, hydrogen hydrate hydrogen storage has stronger adaptability in the offshore environment due to its low equipment requirements, mild operating conditions, strong reversibility, and high safety. By using wind power to produce hydrogen on an offshore platform and storing hydrogen in the form of hydrates, and finally transporting it to land by ship for downstream applications, it provides a safe, efficient, and economical new path for hydrogen storage and transportation, and promotes the realization of the integrated application of "wind power generation + hydrogen energy storage".

[0032] Hydrogen hydrate is a solid compound formed by hydrogen and water molecules under specific temperature and pressure conditions. However, in the offshore environment, extracting fresh water faces many challenges, requiring additional seawater desalination equipment, offshore operation space, and high process costs. With the large-scale production and application of green hydrogen in the future, the consumption of fresh water resources has become an important factor restricting the development of hydrogen hydrate hydrogen storage technology.

[0033] In view of this, the present application provides a method and device for hydrogen storage using seawater hydrates. First, the target temperature and target time for hydrogen hydrate formation are selected based on experimental phase equilibrium data, and the formation ratio of hydrogen hydrates to non-hydrogen hydrates in the reaction system is adjusted to guide the seawater reaction system to tend to generate more hydrogen hydrates. Then, the salt ion concentration during the synthesis process is regulated to extend the continuous growth time of hydrogen hydrates, and the hydrogen storage capacity of hydrogen hydrates is superior to that in a pure water system. Moreover, by regulating the salt ion concentration in the seawater system, the proportion of the seawater system tending to generate hydrogen hydrates further increases. That is, by adjusting the target temperature, target pressure, and salt ion concentration, the formation ratio of hydrogen hydrates to non-hydrogen hydrates can be adjusted to maximize the efficiency of seawater hydrogen storage.

[0034] Some embodiments of the present application will be described in detail below. Without conflict, the features in the following embodiments and examples can be combined with each other.

[0035] Step S10: Add a thermodynamic promoter to the seawater raw material to obtain a mixed solution.

[0036] The thermodynamic promoter includes a gas promoter and a liquid promoter. Among them, the gas promoter includes at least one of methane or propane, and the liquid promoter includes at least one of 1,3-dioxolane, cyclopentane, or organic salt compounds. The organic salt compounds include at least one of tetrabutylammonium bromide or tetrabutylammonium nitrate. The type of thermodynamic promoter can be selected according to actual needs and is not limited here. It can be understood that currently, the methods for improving the hydrogen storage capacity of hydrate hydrogen storage in a pure water system mainly involve adding kinetic promoters, including various hydrophobic and hydrophilic amino acids or surfactants, or optimizing the hydrate reaction container, or optimizing the reaction kettle design or adding complex hydrate pre-generation steps. However, these methods require the use of additional additives, have higher requirements for hydrogen storage equipment, and have cumbersome hydrate generation steps, adding to the cost and process of hydrate hydrogen storage. The above-mentioned thermodynamic promoter used in the present application can enable hydrogen hydrates to form under relatively mild conditions and improve the hydrogen storage efficiency without additional processing steps and with simple requirements for adding equipment.

[0037] The concentration of the thermodynamic promoter in the seawater raw material is 1 mol% - 5.56 mol%. Specifically, it can be 1 mol%, 2 mol%, 3 mol%, 4 mol%, 5 mol%, 5.6 mol%, etc., or other values within the range, and can be selected according to the characteristics of different thermodynamic promoters and is not limited here. It can be understood that when the concentration of the thermodynamic promoter is within the above range, it can better reduce the formation pressure of hydrogen hydrates and reduce the synthesis difficulty of hydrogen hydrates under relatively mild temperature and pressure conditions.

[0038] Step S10 directly utilizes the naturally abundant seawater as the raw material for hydrogen hydrate formation, avoiding the seawater desalination process and significantly reducing the process cost and resource consumption.

[0039] Step S20, according to the phase equilibrium diagram of hydrogen hydrate and non-hydrogen hydrate, sets the target temperature and target pressure that tend to generate hydrogen hydrate.

[0040] Under the target temperature and target pressure, seawater has an inhibitory effect on the formation of non-hydrogen hydrate and a promoting effect on the formation of hydrogen hydrate, that is, it adjusts the formation ratio of hydrogen hydrate and the non-hydrogen hydrate in the reaction system and guides the formation of more hydrogen hydrates.

[0041] Step S30, injects hydrogen into the mixed solution to the target pressure, reduces the mixed solution to the target temperature and keeps it warm, thereby generating hydrogen hydrate.

[0042] In step S30, according to the phase equilibrium diagram of hydrogen hydrate and non-hydrogen hydrate, setting the target temperature and target pressure that tend to generate hydrogen hydrate specifically includes step S301, step S302, step S303, step S304, step S305 and step S306. Specifically: Step S301, obtains seawater samples with multiple different salt ion concentrations, respectively configures thermodynamic promoters with multiple seawater samples into multiple mixed solutions, continuously injects hydrogen into the multiple mixed solutions to the preset pressure, reduces the temperature of the mixed solutions to generate hydrogen hydrate, and plots the temperature-pressure curves of the hydrogen hydrate formation process at different salt ion concentrations.

[0043] The salt ions of the seawater samples include NaCl, and the NaCl concentration is 0 - 3.5 wt%, optionally, the NaCl concentration can specifically be 0.1 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%, 3.0 wt% and 3.5 wt% etc., and can also be other values within the range, which can be selected according to actual needs and are not limited here. It can be understood that the main salt component affecting the synthesis ratio of hydrogen hydrate in seawater is NaCl. The adjustable value of the NaCl concentration in the seawater samples is within the above range, and more accurate test values of the target temperature and target pressure can be obtained. Optionally, the number of seawater samples is five, and the salt ion concentrations of the five seawater samples are 0, 0.1 wt%, 0.3 wt%, 1.0 wt% and 3.0 wt% respectively.

[0044] The seawater sample includes seawater from the actual sea area or artificially prepared simulated seawater. Understandably, the artificially prepared simulated seawater can precisely control its composition and concentration, simulate the actual water quality of different sea areas, thus ensuring the wide applicability of experimental results. In addition, by using artificially prepared simulated seawater, the interference of environmental changes on experimental results can be effectively reduced, and the repeatability and accuracy of the experiment can be enhanced; while using seawater from the actual sea area can more truly reflect the hydrogen storage characteristics of hydrogen hydrate in the seawater system, providing reliable data support for the practical application of offshore wind power hydrogen production and hydrate hydrogen storage technologies. The type of seawater sample used in the experiment can be selected according to actual needs, and no limitation is made here.

[0045] It should be noted that when hydrogen is not injected, the reaction system is in a state of normal pressure and normal temperature. After hydrogen is injected, the synthesis process of hydrogen hydrate is a reversible exothermic reaction. Lowering the system temperature can promote the forward progress of the reaction. The preset pressure and system temperature during the experiment can be selected according to actual needs, and no limitation is made here. Optionally, the preset pressure in the seawater system of this application can maintain a certain driving force for the synthesis process, and the system temperature is lower than the equilibrium temperature of the pure water system; further optionally, the preset pressure is 12 MPa to 12.5 MPa, and the system temperature is 270K to 275K.

[0046] It should also be noted that as the synthesis process proceeds, the consumption of hydrogen increases and the pressure in the reaction system decreases. As the decomposition process proceeds, the pressure in the reaction system returns to the initial value, that is, the preset pressure in this application refers to the initial pressure before the reaction starts.

[0047] At the same time, multiple seawater samples with different concentrations are used for the synthesis and decomposition processes of hydrogen hydrate. Then, a temperature-pressure curve of the generation process can be drawn for each concentration of seawater sample, and multiple temperature-pressure curves of the generation process can be obtained.

[0048] Step S302: Raise the temperature of the mixed solution to decompose the hydrogen hydrate, and draw the temperature-pressure curve during the decomposition process of the hydrogen hydrate at different salt ion concentrations.

[0049] The synthesis process of hydrogen hydrate is a reversible exothermic reaction. Raising the system temperature to a certain value can cause the hydrogen hydrate to decompose until it is completely consumed. A temperature-pressure curve of the decomposition process can be drawn for each concentration of seawater sample, and multiple temperature-pressure curves of the decomposition process can be obtained.

[0050] Step S303: Determine the intersection points of the temperature-pressure curve during the generation process and the temperature-pressure curve during the decomposition process to obtain the phase equilibrium points of the hydrogen hydrate generated at different salt ion concentrations under the preset pressure.

[0051] By intersecting the temperature-pressure curves corresponding to each salt ion concentration, the phase equilibrium points corresponding to each salt ion concentration under the preset pressure can be obtained. It can be understood that at the phase equilibrium point, the synthesis and decomposition reactions of hydrogen hydrate reach a dynamic equilibrium.

[0052] Step S304: Determine the phase equilibrium points of the hydrogen hydrates formed at different salt ion concentrations under different preset pressures.

[0053] The preset pressure refers to the initial pressure when hydrogen injection is completed. A certain preset pressure can promote the reaction. By changing the magnitude of the preset pressure, the phase equilibrium points of the hydrogen hydrates formed by seawater samples with different salt ion concentrations will also change. Thus, the phase equilibrium points of the hydrogen hydrates formed at different salt ion concentrations under different preset pressures can be obtained.

[0054] Step S305: Determine the phase equilibrium points of the non-hydrogen hydrates formed at different salt ion concentrations under different preset pressures, and plot the phase equilibrium points of the hydrogen hydrates and the non-hydrogen hydrates as a phase equilibrium diagram.

[0055] In the reaction system, non-hydrogen hydrates will also be formed. At this time, the phase equilibrium points of the non-hydrogen hydrates formed at different salt ion concentrations under different preset pressures can be determined by a high-pressure differential scanning calorimeter, and the phase equilibrium points of the hydrogen hydrates and the non-hydrogen hydrates are plotted as a phase equilibrium diagram.

[0056] In the reaction system of seawater hydrogen storage, hydrogen hydrates and non-hydrogen hydrates will be formed. Thus, the phase equilibrium points of the non-hydrogen hydrates and the hydrogen hydrates can be obtained and plotted as a phase equilibrium diagram. By analyzing the phase equilibrium diagram, appropriate target temperature and target pressure can be selected to make the reaction system tend to generate a higher proportion of hydrogen hydrates.

[0057] Step S306: Set the target temperature and the target pressure for synthesizing the hydrogen hydrate according to the phase equilibrium diagram.

[0058] At the target temperature and target pressure, the seawater system has an inhibitory effect on the formation of non-hydrogen hydrates and can promote the formation of hydrogen hydrates, maximizing the efficiency of seawater hydrogen storage. The target temperature and target pressure can be selected according to the phase equilibrium diagram of hydrogen hydrates and non-hydrogen hydrates and the specific parameters of the actual seawater raw materials, which are not limited here.

[0059] In some embodiments, the method for hydrogen storage in hydrates using seawater further includes step S40: Step S401: Monitor the growth morphology evolution and gas-liquid contact mode during the formation process of the hydrogen hydrate. Step S402: According to the growth morphology evolution and the gas-liquid contact mode of the hydrogen hydrate, adjust the NaCl concentration of the mixed solution to induce the hydrogen hydrate to form a slurry morphology.

[0060] In step S401, an image collector 5 is used to monitor the process, record the growth morphology evolution and the gas-liquid contact mode during the formation of the hydrogen hydrate, observe the formation of the hydrate, and timely adjust the NaCl concentration. It can be understood that by using the image collector 5 to monitor the synthesis process of the hydrate, the salt ion concentration in the seawater system can be adjusted according to the monitoring situation, the NaCl concentration of the mixed solution can be adjusted, the hydrogen hydrate is induced to form a slurry morphology, the growth of the hydrate layer at the gas-liquid interface is inhibited at the same time, the continuous growth time of the hydrogen hydrate is prolonged, the gas-liquid contact mode is optimized, and the hydrogen storage capacity of the hydrogen hydrate is more excellent than that in the pure water system; and by adjusting the salt ion concentration in the seawater system, the proportion of the seawater system tending to generate hydrogen hydrate is further increased. That is, by adjusting the target temperature, the target pressure and the salt ion concentration, the generation ratio of the hydrogen hydrate and the non-hydrogen hydrate can be adjusted to maximize the efficiency of seawater hydrogen storage.

[0061] In some embodiments, the formation process and the decomposition process of the hydrogen hydrate are carried out under the water bath condition. It can be understood that by using the water bath for temperature control, the reaction temperature can be better maintained during the reaction process, the influence of temperature fluctuation on the growth of the hydrogen hydrate can be avoided, and the seawater hydrogen storage process can be ensured.

[0062] This application also provides a device for storing hydrogen by hydrate using seawater. Please refer to Figure 1 , the device includes an air injection system, a hydrate formation system, a stirring system, a temperature control system and a data acquisition system 13. Among them, the hydrate formation system is used to store the mixed solution prepared from seawater raw materials and a thermodynamic promoter; the air injection system is used to provide hydrogen to the hydrate formation system; the stirring system is used to enhance the gas-liquid contact in the hydrate formation system; the temperature control system is used to control the system temperature; the data acquisition system 13 is used to collect the system pressure and the system temperature; the hydrate formation system includes an image sensor, and the image sensor is used to observe the morphology and the gas-liquid contact mode of the hydrogen hydrate. Specifically: The gas injection system includes a high-pressure hydrogen cylinder 1, a booster device 2 and a pressure gauge 3; the hydrate formation system includes a hydrate reaction vessel 4, a thermocouple 11 and a pressure sensor 12. A viewing window is provided at the top of the hydrate reaction vessel 4, and an image collector 5 such as a CCD camera is placed above the viewing window; the stirring system consists of a magnetic stirrer 7 and a magnetic stirrer 8, and the magnetic stirrer 7 is placed at the bottom of the hydrate reaction vessel 4; the temperature control system includes a water bath 9 and a programmable temperature control circulating water bath. The hydrate reaction vessel 4 is placed in the water bath 9, and the water bath 9 is placed on the magnetic stirrer 8. The temperature control device 10 controls the temperature of the water bath 9; the data acquisition system 13 acquires the temperature and pressure values collected by the thermocouple 11 and the pressure sensor 12.

[0063] In the actual application process, the high-pressure hydrogen cylinder 1 is connected to the booster device 2, and the pressure gauge 3 is installed on the booster device 2. The boosting value of the booster device 2 can be observed through the pressure gauge 3, and hydrogen is injected into the hydrate reaction vessel 4 through the booster device 2; the hydrate reaction vessel 4 is used to store the mixed solutions prepared by the thermodynamic promoter and seawater with different concentrations respectively. The magnetic stirrer 8 can enhance the gas-liquid contact during the hydrate formation process by controlling the rotation of the magnetic stirrer 7. The water bath 9 is connected to the programmable temperature control circulating water bath to control the temperature of the reaction vessel and maintain the temperature stable; the temperature and pressure inside the hydrate reaction vessel 4 are collected by the thermocouple 11 and the pressure sensor 12 and then reflected on the data acquisition system 13. The image collector 5 such as a CCD camera observes the evolution of the hydrate crystal morphology during the formation of hydrogen hydrate, which is convenient for the operator to timely adjust the salt ion concentration in the seawater system, induce the formation of a slurry morphology of hydrogen hydrate, simultaneously inhibit the growth of the hydrate layer at the gas-liquid interface, extend the continuous growth time of hydrogen hydrate, optimize the gas-liquid contact mode, and improve the hydrogen storage efficiency.

[0064] It can be understood that by using the above-mentioned device and going through steps S10 to S40, hydrogen hydrate with a high hydrogen storage capacity can be obtained, that is, the hydrogen storage method provided by the present application. Using seawater as a reaction raw material, without a complex seawater desalination process, greatly simplifies the seawater hydrogen storage process, reduces the operation links on the offshore platform, improves the economic benefits of operation, saves the limited offshore platform operation space, makes the seawater hydrogen storage operation more convenient and feasible, and breaks through the limitation of the traditional concept that "seawater is not conducive to gas storage"; during the hydrogen storage process, first, an experimental phase equilibrium diagram of hydrogen hydrate and non-hydrogen hydrate generated in the seawater system during hydrogen storage is drawn. Based on the thermodynamic data of the phase diagram, the target temperature and target pressure that tend to generate hydrogen hydrate are selected, and the generation ratio of hydrogen hydrate and non-hydrogen hydrate in the reaction system is adjusted to guide the seawater reaction system to tend to generate more hydrogen hydrates; and during the actual synthesis process, the salt ion concentration in the seawater system is regulated according to the hydrate morphology and gas-liquid contact mode, prolonging the continuous growth time of hydrogen hydrate, increasing the hydrogen storage capacity of hydrogen hydrate, and by regulating the salt ion concentration in the seawater system, the proportion of the seawater system that tends to generate hydrogen hydrate is further increased. That is, by adjusting the target temperature, target pressure, and salt ion concentration, the generation ratio of hydrogen hydrate and non-hydrogen hydrate can be adjusted to maximize the efficiency of seawater hydrogen storage; at the same time, a thermodynamic promoter is introduced during the synthesis process to enable hydrogen hydrate to be generated under relatively mild conditions and reduce the reaction difficulty.

[0065] The foregoing method is further described below through specific examples.

[0066] Experimental Example 1: (1) Wash and dry the hydrate reaction vessel 4, and then inject 30 ml of a mixed solution (prepared from 5.56 mol% 1,3-dioxolane and NaCl solutions with concentrations of 0, 0.1 wt%, 0.3 wt%, 1.0 wt%, and 3.0 wt% respectively, and stored in different reaction kettles), cover the lid of the hydrate reaction vessel 4, and place it statically in the water bath 9.

[0067] (2) Open the valve connecting the high-pressure hydrogen cylinder 1, and inject hydrogen through the gas injection system to 0.3 - 0.5 MPa to purge the hydrate reaction vessel 4 three times.

[0068] (3) Slowly inject hydrogen into the reaction kettle to 12.3 MPa, and turn on the magnetic stirrer 8.

[0069] (4) Then set the water bath temperature program, and reduce the temperature to 264 K at a fixed cooling rate and stabilize for 3 - 4 hours to fully generate hydrogen hydrate in the reaction kettle.

[0070] (5) Heat the temperature from 264 K to 278 K at a slow heating rate, and continuously decompose the hydrogen hydrate during this process.

[0071] (6) Through the intersection point of the pressure-temperature curves of the hydrogen hydrate formation process and the decomposition process, the phase equilibrium points of the hydrogen hydrate at different salt ion concentrations can be obtained.

[0072] (7) Through the hydrogen hydrate phase equilibrium experiment at different pressures, obtain the phase equilibrium points of non-hydrogen hydrates formed at different salt ion concentrations under multiple different preset pressures. Then, measure the phase equilibrium points of the non-hydrogen hydrates at different preset pressures and different concentrations through a high-pressure differential scanning calorimeter (DSC), and plot the phase equilibrium points of the hydrogen hydrate and the non-hydrogen hydrate as a phase equilibrium diagram.

[0073] After the above steps, the phase equilibrium diagrams of hydrogen hydrates and non-hydrogen hydrates at different NaCl concentrations can be plotted.

[0074] Experimental Example 2: 1. Wash and dry the hydrate reaction vessel 4, then inject 30 ml of the mixed solution (prepared from 5.56 mol% 1,3-dioxolane and NaCl solutions with concentrations of 0, 0.1 wt%, 0.3 wt%, 1.0 wt%, and 3.0 wt% respectively, stored in different reaction kettles), cover the lid of the hydrate reaction vessel 4, and place it statically in the water bath 9.

[0075] 2. After analyzing the phase equilibrium diagrams of the hydrogen hydrate and the non-hydrogen hydrate in Example 1, determine the generation temperature and pressure conditions of the kinetic experiment as 270.5 K and 12.3 MPa.

[0076] 3. Set the temperature of the water bath 9 to 270.5 K, wait for the temperature of the reaction kettle device to drop to the set temperature, and stabilize for 2 hours.

[0077] 3. Open the valve connecting the high-pressure hydrogen cylinder 1, and inject hydrogen through the gas injection system to 0.3 - 0.5 MPa to purge the hydrate reaction vessel 4 three times.

[0078] 4. Slowly inject hydrogen into the reaction kettle to 12.3 MPa. When the temperature stabilizes at -3°C, turn on the magnetic stirrer 8 and set the rotation speed to 600 r / min.

[0079] 5. After stirring, hydrogen hydrate is continuously generated in the following process.

[0080] 6. When the pressure drop in the reaction kettle is less than 0.01 MPa / h, the hydrate formation is basically completed.

[0081] 7. Collect the pressure and temperature data at the end of the reaction, and analyze the hydrogen consumption and the hydrogen storage capacity of the hydrogen hydrate.

[0082] Through the above steps, the hydrogen volume consumption at different NaCl concentrations can be obtained.

[0083] Example 3 1. Wash and dry the hydrate reaction vessel 4, and then inject 30 ml of the mixed solution (prepared from 5.56 mol% 1,3-dioxolane and NaCl solutions with concentrations of 0, 0.1 wt%, 0.3 wt%, 1.0 wt%, and 3.0 wt% respectively, stored in different reaction kettles), cover the lid of the hydrate reaction vessel 4, and place it statically in the water bath 9.

[0084] 2. Then set the temperature of the water bath 9 to 270.5 K, wait for the temperature of the reaction kettle device to drop to the set temperature, and stabilize for 2 hours.

[0085] 3. Open the valve connecting the high-pressure hydrogen cylinder 1, and inject hydrogen through the gas injection system to 0.3 - 0.5 MPa to purge the hydrate reaction vessel 4 three times.

[0086] 4. Slowly inject hydrogen into the reaction kettle to 12.3 MPa. When the temperature stabilizes at -3°C, turn on the magnetic stirrer 8, and set the rotation speed to 600 r / min.

[0087] 5. Turn on the CCD camera, and record the morphological evolution and gas-liquid contact mode during the continuous formation of the hydrate through the viewing window.

[0088] Through the above steps, the gas-liquid contact situation during the growth process of the hydrogen hydrate layer at different NaCl concentrations can be obtained.

[0089] Test result analysis; Please refer to Figure 2 , by comparing the phase equilibrium diagrams of hydrogen hydrates (H 2 -DIOX hydrates) and non-hydrogen hydrates (DIOX hydrates) at different NaCl concentrations, it can be found that the addition of NaCl shifts the phase diagrams of the two hydrates to the left, increases the formation pressure conditions of the two hydrates, and decreases the temperature conditions of the two hydrates, that is, NaCl has an inhibitory effect on the phase equilibrium of the two hydrates, and with the increase of NaCl concentration, the phase equilibrium inhibitory effect increases; however, it can be observed that NaCl has a smaller inhibitory effect on hydrogen hydrates and a larger inhibitory effect on non-hydrogen hydrates. From Figure 2As can be seen, when the NaCl content increases from 0 to 3.0 wt%, the phase equilibrium temperature of the non-hydrogen hydrate decreases by 5.5 K, while that of the hydrogen hydrate only decreases by 2.3 K. Therefore, by adjusting the NaCl concentration in seawater, the proportion of hydrogen hydrate formation in the seawater reaction system can be regulated. This shows that under the same temperature and pressure conditions, the higher the NaCl concentration, the higher the proportion of hydrogen hydrate formation in the system and the lower the proportion of non-hydrogen hydrates. Therefore, it is easier to obtain a high hydrogen storage capacity when preparing hydrogen hydrates from seawater compared to a pure water system.

[0090] Please refer to Figure 3 , by comparing the hydrogen consumption of hydrogen hydrates with and without NaCl, it can be found that adding NaCl can significantly increase the hydrogen storage capacity of hydrogen hydrates, and with the increase of NaCl concentration, the hydrogen storage capacity shows an increasing trend. Using seawater as a hydrogen storage raw material can maximize the efficiency of seawater hydrogen storage.

[0091] Please refer to Figure 4 , by comparing the growth morphology evolution of the hydrate layer and the gas-liquid contact mode of hydrogen hydrates (H 2 -DIOX hydrates) with and without NaCl, it can be found that when synthesizing hydrogen hydrates in a pure water system, a dense hydrate layer (4 min) will be rapidly formed at the gas-liquid contact interface of hydrogen and pure water, hindering subsequent gas-liquid contact, resulting in the stagnation of hydrogen hydrate growth, a very low hydrogen storage capacity in the pure water system, and the hydrogen hydrate showing a dense white blocky hydrate morphology. After adding NaCl, the growth time of the hydrogen hydrate layer is significantly extended to 22 min. As the NaCl concentration increases to 3.0 wt% NaCl, the growth time of the hydrogen hydrate layer is greatly extended to 140 min, and at the same time, it shows a slurry-like hydrate morphology. The hydrate grows continuously from the kettle wall to the center of the solution, resulting in continuous contact between the solution and hydrogen, optimizing the gas-liquid contact situation in the system and extending the continuous growth time of hydrogen hydrates. Therefore, a better hydrogen storage capacity is obtained compared to the pure water system.

[0092] That is, through this solution, the following effects are achieved: First, the problem of dependence on fresh water resources is solved. It can be understood that traditional hydrate hydrogen storage methods usually require the use of pure water or desalinated seawater as raw materials. This dependence on fresh water resources not only increases equipment complexity and energy consumption but also poses a huge challenge to the offshore scenario with a shortage of fresh water resources. This application directly uses naturally abundant seawater as the raw material for hydrogen hydrate formation, avoiding the seawater desalination process, greatly reducing the process cost and resource consumption, filling the technical gap in the brine system in the current research field of hydrate hydrogen storage, and expanding a new direction for the research and application of hydrate hydrogen storage technology.

[0093] Secondly, improving the hydrogen storage efficiency and optimizing the gas-liquid contact during the formation process of hydrogen hydrate. It is understandable that in the existing hydrogen storage method using hydrate, a dense hydrate layer is easily formed at the gas-liquid interface during the formation process, which hinders gas-liquid contact and results in a low hydrogen storage capacity of hydrogen hydrate formed in a pure water system. With the use of thermodynamic promoters, the requirements for high pressure or extremely low temperature conditions in traditional systems are significantly reduced, and energy consumption is decreased. Based on the regulation of ion concentration in seawater according to the target temperature and target pressure, the gas-liquid contact efficiency and mass transfer performance are significantly improved, the growth path of hydrogen hydrate is optimized, and a slurry-like morphology of hydrogen hydrate is induced, thereby prolonging the continuous growth time of hydrate and enhancing the hydrogen storage efficiency.

[0094] Meanwhile, solving the problems of technical economy and adaptability. It is understandable that in the scenario of hydrogen production from offshore wind power, the existing hydrogen storage methods require additional equipment such as high-pressure storage tanks, cryogenic equipment or seawater desalination equipment, which occupy a large amount of space, have high costs and large energy consumption. However, the present invention simplifies the equipment and operation process by directly using seawater and optimizing process conditions, significantly reducing the construction and operation costs of the hydrogen storage system, making it more suitable for the restrictive environment of offshore platforms. Compared with the existing offshore hydrogen storage and transportation technologies (gaseous hydrogen storage and liquid hydrogen storage technologies, gaseous hydrogen storage requires storing hydrogen in high-pressure containers, which is prone to leakage and explosion risks, while liquid hydrogen requires cryogenic storage, with large energy consumption and safety hazards of ultra-low temperature), hydrogen hydrate, as a solid hydrogen storage form, can stably store hydrogen under relatively mild pressure and temperature conditions, and has strong reversibility, significantly reducing the safety risks during hydrogen storage and having high safety and stability.

[0095] In addition, those of ordinary skill in the art of the present technology should recognize that the above embodiments are only used to illustrate the present application, rather than to limit the present application. As long as appropriate changes and variations made to the above embodiments fall within the scope of the substantial spirit of the present application, they are within the disclosure scope of the present application.

Claims

1. A method for storing hydrogen hydrate using seawater, characterized in that: include: adding a thermodynamic promoter to a seawater raw material to obtain a mixed solution; According to the phase equilibrium diagram of hydrogen hydrate and non-hydrogen hydrate, setting the target temperature and target pressure that tend to generate the hydrogen hydrate; The mixed solution is lowered to a target temperature and kept warm, and hydrogen is injected into the mixed solution to a target pressure, so as to guide the seawater reaction system to tend to generate hydrogen hydrates.

2. The method for storing hydrogen hydrate using seawater according to claim 1, characterized in that: According to the phase equilibrium diagram of hydrogen hydrate and non-hydrogen hydrate, setting the target temperature and target pressure that tend to generate hydrogen hydrate specifically includes: Acquire seawater samples with multiple different salt ion concentrations, configure a thermodynamic promoter and the multiple seawater samples into multiple mixed solutions, inject hydrogen into the multiple mixed solutions to a preset pressure, reduce the temperature of the mixed solutions to generate hydrogen hydrates, and draw temperature-pressure curves of the generation process of the hydrogen hydrates at different salt ion concentrations; Raising the temperature of the mixed solution to decompose the hydrogen hydrate, and drawing a temperature-pressure curve during the decomposition of the hydrogen hydrate at different salt ion concentrations; Determine the intersection of the temperature-pressure curve during the generation process and the temperature-pressure curve during the decomposition process, and obtain the phase equilibrium point of the hydrogen hydrate generated at different salt ion concentrations under the preset pressure; Determining the phase equilibrium points of the hydrogen hydrates generated at different salt ion concentrations under different preset pressures; Determine the phase equilibrium points of non-hydrogen hydrates generated at different salt ion concentrations under different preset pressures, and draw the phase equilibrium points of the hydrogen hydrates and the non-hydrogen hydrates into a phase equilibrium diagram; The target temperature and the target pressure for synthesizing the hydrogen hydrate are set according to the phase equilibrium diagram.

3. The method for storing hydrogen hydrate using seawater according to claim 2, characterized in that: The salt ions include NaCl, and the concentration of NaCl in the seawater sample is 0-3.5 wt %.

4. The method for storing hydrogen hydrate using seawater according to claim 2, characterized in that: The seawater sample includes actual seawater or artificially configured simulated seawater.

5. The method for storing hydrogen hydrate using seawater according to claim 1, characterized in that: The thermodynamic promoter includes a gas promoter and a liquid promoter; The gaseous accelerator includes at least one of methane or propane, the liquid accelerator includes at least one of 1,3-dioxolane, cyclopentane or an organic salt compound, and the organic salt compound includes at least one of tetrabutylammonium bromide or tetrabutylammonium nitrate.

6. The method for storing hydrogen hydrate using seawater according to claim 1, characterized in that: The concentration of the thermodynamic promoter in the mixed solution is 1 mol % to 5.6 mol %.

7. The method for storing hydrogen hydrate using seawater according to claim 2, characterized in that: Determining the phase equilibrium points of non-hydrogen hydrates generated by different salt ion concentrations under different preset pressures includes: A high pressure differential scanning calorimeter is used to determine the phase equilibrium points of non-hydrogen hydrates generated at different salt ion concentrations under different preset pressures.

8. The method for storing hydrogen hydrate using seawater according to claim 1, characterized in that: Also includes: monitoring the growth morphology evolution and gas-liquid contact mode during the hydrogen hydrate formation process; According to the growth morphology evolution of the hydrogen hydrate and the gas-liquid contact mode, the NaCl concentration of the mixed solution is regulated to induce the hydrogen hydrate to form a slurry morphology.

9. The method for storing hydrogen hydrate using seawater according to claim 2, characterized in that: The generation process and the decomposition process of the hydrogen hydrate are carried out under water bath conditions.

10. A device for storing hydrogen hydrate using seawater, characterized in that: The device for storing hydrogen hydrates using seawater is used to perform the method for storing hydrogen hydrates using seawater according to any one of claims 1 to 9, and comprises a gas injection system, a hydrate generation system, and a temperature control system connected thereto; Among them, the hydrate generation system is used to contain a mixed solution containing seawater and a thermodynamic promoter, the gas injection system is used to inject hydrogen into the hydrate generation system until the hydrate generation system reaches a target pressure; and the temperature control system is used to control the temperature of the hydrate generation system to a target temperature.

Images