A liquid hydrogen underground storage system

Abstract

The application provides a liquid hydrogen underground storage system, which comprises a storage body and a water injection unit. The storage body is buried underground and comprises, from inside to outside, an inner metal sealing layer, a heat insulation layer, a support layer and a water-containing rock-soil layer. The inner metal sealing layer encapsulates liquid hydrogen, the water-containing rock-soil layer is a saturated rock-soil layer formed by water injection and located outside the support layer, and the water injection unit uniformly injects water into the water-containing rock-soil layer through an underground manifold arranged around the water-containing rock-soil layer, so that the water-containing rock-soil layer forms a closed permafrost circle during liquid hydrogen storage to reduce liquid hydrogen leakage and supports the storage body together with the support layer. The heat insulation layer prevents liquid hydrogen from being gasified, and the inner metal sealing layer and the water-containing rock-soil layer form double sealing, so that the leakage amount of the stored liquid hydrogen is effectively reduced. The underground structure is used to realize large-capacity and low-cost hydrogen storage, and can also be used for liquid nitrogen, liquefied natural gas (LNG) and other low-temperature medium storage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrogen storage, in particular to a liquid hydrogen underground storage system. BACKGROUND

[0002] Hydrogen has the characteristics of green, wide source, and large mass energy density, and is a good energy storage medium and energy carrier in the future renewable energy supply system. However, the low volumetric energy density of hydrogen results in high storage and transportation costs, and poor economic efficiency of hydrogen terminal utilization. Low-cost and safe hydrogen storage means is one of the bottlenecks restricting the large-scale development of hydrogen energy industry, so the construction of hydrogen energy storage system needs hydrogen storage technology with high energy density. The mainstream hydrogen storage technologies include high-pressure gaseous, low-temperature liquefied, and metal solid storage methods, among which the volumetric energy density of liquid hydrogen storage method is the largest, 845 times that of gaseous hydrogen, which is suitable for long-distance and large-capacity storage, and is one of the research hotspots in the field of hydrogen energy storage. However, the boiling point of liquid hydrogen is low (20K), and evaporation loss is easy to occur during storage, so the liquid hydrogen storage container needs to have excellent thermal insulation measures to reduce the vaporization of liquid hydrogen caused by system heat leakage, which leads to a very large volume of liquid hydrogen storage container, and additional configuration of auxiliary refrigeration, vacuum, monitoring and other equipment.

[0003] Currently, liquid hydrogen is mainly stored in the form of ground storage tanks. The storage tank adopts a double (multi) layer structure, and the interlayer is either vacuum insulated or filled with thermal insulation materials to reduce the heat transfer of liquid hydrogen in the tank. The pure high vacuum degree insulation layer has the advantages of simple structure, compactness, and small heat capacity, and is suitable for small-scale liquefied natural gas storage, small amount of liquid oxygen, liquid nitrogen, liquid hydrogen, and small amount of short-term liquid hydrogen storage. Since it is difficult to obtain and maintain high vacuum degree, it is rarely used in large storage tanks; multi-screen insulation is an improvement of multi-layer insulation, and has excellent insulation performance, small heat capacity, light weight, and fast heat balance, but the structure is complex and the cost is high, and it is generally suitable for small-scale liquid hydrogen and liquid nitrogen storage containers; the vacuum powder filling insulation requires a low vacuum degree, and the insulation performance is two orders of magnitude better than that of the accumulated insulation, so it is widely used in large and medium-sized low-temperature liquid storage, such as liquefied natural gas (LNG) storage, liquid oxygen, liquid nitrogen transportation equipment, and large amount of liquid hydrogen ship transportation equipment. The biggest disadvantage is that the spacing of the insulation interlayer is large, the structure is complex and heavy.

[0004] There is no report on the underground storage of liquid hydrogen. The underground storage technology of liquid hydrogen can be developed by referring to the underground storage technology of natural gas, shale gas, hydrogen, compressed air, LNG (liquefied natural gas) and LPG (liquefied petroleum gas) in rock caves or rock fissures. The underground storage has the advantages of large capacity, low cost and running cost, long service life, high safety, etc. However, the storage in natural caves or salt caves is limited by geographical conditions, and the conditions such as stratum structure, underground water distribution and seismic intensity need to be considered. In addition, the stratum temperature is generally high, and it is difficult to maintain the temperature of liquid hydrogen without heat insulation, so it is not suitable for the storage of liquid hydrogen. SUMMARY

[0005] The present application aims to solve the technical problem that liquid hydrogen cannot be stored underground in the prior art.

[0006] To solve the above technical problems, the present application provides a liquid hydrogen underground storage system, which comprises a storage body buried underground, wherein the storage body comprises an inner metal sealing layer, a heat insulation layer, a support layer and a water-containing rock-soil layer arranged in sequence from inside to outside; the inside of the inner metal sealing layer is used for packaging liquid hydrogen; the heat insulation layer is connected with the inner metal sealing layer and the support layer by an adhesive respectively, so as to insulate the liquid hydrogen in the inner metal sealing layer; the support layer is used for improving the support strength of the storage body; the water-containing rock-soil layer is a saturated rock-soil layer formed by water injection outside the support layer, so as to form a closed permafrost circle to reduce the leakage of liquid hydrogen during hydrogen storage, and the support layer and the water-containing rock-soil layer jointly support the storage body; and an injection unit comprising a ground main pipe and an underground manifold communicated with the ground main pipe, wherein the underground manifold is arranged around the circumferential side of the water-containing rock-soil layer to uniformly inject water into the water-containing rock-soil layer.

[0007] Optionally, the thickness of the heat insulation layer is calculated and determined according to the allowable value of the daily evaporation amount of the liquid hydrogen in the inner metal sealing layer.

[0008] Optionally, the support layer comprises but is not limited to one or a combination of steel reinforced concrete, prestressed concrete, modified concrete, fireproof brick and the like.

[0009] Optionally, the thickness of the support layer is determined according to the confining pressure, temperature gradient, local seismic intensity and allowable stress calculated from the physical properties of the permafrost and the support layer material of the storage body.

[0010] Optionally, the liquid hydrogen underground storage system further comprises a ground thermal barrier layer arranged on the ground area corresponding to the storage body.

[0011] Optionally, the liquid hydrogen underground storage system further comprises an injection-production pipeline unit, wherein the injection-production pipeline unit comprises an injection-production pipeline and an injection-production / vent valve group arranged on the injection-production pipeline.

[0012] Optionally, the injection-production pipeline comprises a low-position injection-production pipe and a high-position injection-production pipe, the low-position injection-production pipe is inserted into the bottom of the inner metal sealing layer cavity for liquid hydrogen injection-production, and the high-position injection-production pipe is inserted into the upper part of the inner metal sealing layer cavity for liquid hydrogen injection and gaseous hydrogen discharge.

[0013] Optionally, the low-position injection-production pipe and the high-position injection-production pipe are both provided with an injection-production / discharge valve group, the injection-production / discharge valve group comprises a valve group base and a safety valve group, a flow control valve group and an instrument valve arranged on the valve group base, the safety valve group comprises a safety relief valve, a rupture disc and a safety device shut-off valve which are sequentially connected in series on the valve group base.

[0014] Optionally, the liquid hydrogen underground storage system further comprises a hydrogen leakage monitoring unit, the hydrogen leakage monitoring unit comprises a leak detector, a gas collection hood, a gas guide pipe penetrating the gas collection hood, and a mesh gas hole screen and a rainproof cover respectively arranged at two ends of the gas guide pipe, the mesh gas hole screen is located in the gas collection hood, and the rainproof cover is located outside the gas collection hood, part of the gas guide pipe and the mesh gas hole screen and the gas collection hood are buried underground, and the other part of the gas guide pipe and the rainproof cover and the leak detector are arranged on the ground.

[0015] Optionally, the liquid hydrogen underground storage system further comprises a measurement and control unit, the measurement and control unit comprises a plurality of first temperature sensors arranged at different height positions of the peripheral rock-soil and the water-bearing rock-soil layer, a plurality of second temperature sensors arranged at different height positions in the inner metal sealing layer, and a pressure sensor installed on the injection-production / discharge valve group.

[0016] From the above technical solutions, the beneficial effects of the present application are as follows:

[0017] The application provides a liquid hydrogen underground storage system, which comprises a storage body and a water injection unit. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 Fig. 1 is a structural schematic diagram of the liquid hydrogen underground storage system provided by the application.

[0019] Figure 2 Fig. 4 is a structural schematic diagram of an injection-production / discharge valve group in the liquid hydrogen underground storage system provided by the application.

[0020] Figure 3 Fig. 5 is a structural schematic diagram of a hydrogen leakage monitoring unit in the liquid hydrogen underground storage system provided by the application.

[0021] Figure 4 Fig. 6 is a temperature distribution diagram of a simulation model of the liquid hydrogen underground storage system provided by the application.

[0022] The specific signs are explained as follows:

[0023] 10, storage body; 11, inner metal sealing layer; 12, heat insulation layer; 13, support layer; 14, water-containing rock-soil layer; 20, water injection unit; 21, ground main pipe; 22, underground manifold; 30, injection-production pipe unit; 31, low-position injection-production pipe; 32, high-position injection-discharge pipe; 33, injection-production / discharge valve group; 331, safety pressure relief valve; 332, bursting disc; 333, safety device shut-off valve; 334, flow regulating valve; 335, flow shut-off valve; 336, instrument primary sampling valve; 337, instrument secondary sampling valve; 40, hydrogen leakage monitoring unit; 41, gas collection cover; 42, gas guide pipe; 43, grid air hole screen; 44, rain cover; 50, first temperature sensor; 60, second temperature sensor; 70, ground thermal barrier layer. DETAILED DESCRIPTION

[0024] The features and advantages of the present application will become more apparent from the detailed description set forth below. It should be understood, however, that the detailed description and specific examples, while indicating certain embodiments of the present application, are given by way of illustration only, and are not by way of limitation of the present application.

[0025] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features referred to. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0026] In order to further illustrate the principles and structures of the present application, the preferred embodiments of the present application will be described in detail in conjunction with the drawings.

[0027] Please refer to Figure 1 The present application provides a liquid hydrogen underground storage system, which can be used for storing liquid nitrogen, LNG (liquefied natural gas), LPG (liquefied petroleum gas) and other low-temperature liquid media. The liquid hydrogen underground storage system comprises a storage body 10 and a water injection unit 20.

[0028] The storage body 10 is buried underground, and its shape is not limited to spherical, cylindrical, square and the like, and comprises a four-layer lining structure. Specifically, the storage body 10 is sequentially provided from the inside out with an inner metal sealing layer 11, a heat insulation layer 12, a support layer 13 and a water-containing rock-soil layer 14.

[0029] The inner metal sealing layer 11 is a closed cavity composed of corrugated plates, including but not limited to corrugated aluminum plates or 304-grade and above stainless steel plates. If 304-grade and above stainless steel plates are used, an aluminum powder is coated on the inner wall of the inner metal sealing layer 11. The liquid hydrogen is encapsulated in the inner metal sealing layer 11, and the corrugated structure of the inner metal sealing layer 11 can effectively eliminate the stress concentration caused by the temperature change of the liquid hydrogen to the inner metal sealing layer 11, and the aluminum plate or the 304-grade and above stainless steel plate with an aluminum powder coated on the inner wall can reduce the radiant heat flux between each layer of the storage body 10.

[0030] The heat insulation layer 12 is arranged between the inner metal sealing layer 11 and the support layer 13, and is used for heat insulation of the liquid hydrogen in the inner metal sealing layer 11. The heat insulation layer 12 is bonded to the inner metal sealing layer 11 and the support layer 13 by an adhesive to reduce the heat transfer caused by water entering the gap between the layers. Specifically, the heat insulation layer 12 is a certain thickness of insulation material. The insulation material is not limited to high-density polyurethane, pearl wool and other porous medium insulation materials with high thermal resistance. The thickness of the heat insulation layer 12 can be calculated and determined according to the allowable value of the daily evaporation amount of the liquid hydrogen in the inner metal sealing layer. In general, the allowable value of the daily evaporation amount of the liquid hydrogen is not more than 5% of the total mass of the liquid hydrogen. It can be understood that when the underground storage system of the present application is used to store liquid nitrogen, LNG (liquefied natural gas), LPG (liquefied petroleum gas) and other low-temperature liquid media, the thickness of the heat insulation layer 12 can also be calculated and determined according to the allowable value of the daily evaporation amount of the low-temperature liquid medium stored in the inner metal sealing layer.

[0031] The support layer 13 is arranged outside the heat insulation layer 12 and is made of high-strength material to bear the main positive pressure and shear force of the storage body 10. The support layer 13 is made of one or a combination of materials such as reinforced concrete, prestressed concrete, modified concrete, firebrick and the like. The thickness of the support layer 13 is designed according to the surrounding pressure, temperature gradient, frost heaving stress of the underground rock-soil layer and local seismic intensity level of the storage body 10, so as to balance the surrounding pressure and frost heaving stress and the potential stress damage caused by earthquakes, and ensure that the deformation of the storage body 10 is within a safe range to prevent cracking of the storage body 10 during hydrogen storage operation. It can be understood that when the size of the storage body 10 is large, the support layer 13 also includes transverse supports and longitudinal supports to improve the strength of the entire storage body 10.

[0032] The water-containing rock-soil layer 14 is formed by water injection into the rock-soil layer outside the support layer 13 to saturate the rock-soil layer outside the support layer 13. After the liquid hydrogen is injected into the inner metal sealing layer 11, the saturated rock-soil layer forms a dense ice circle containing frozen ice in the low-temperature environment, so that the rock-soil layer becomes a closed permafrost circle, which not only reduces hydrogen leakage, but also supports the storage body 10 together with the support layer 13.

[0033] In terms of leakage control, the reservoir body 10 plays a role of a first leakage barrier for the liquid hydrogen stored in the reservoir body 10 by the inner metal sealing layer 11, and plays a role of a second leakage barrier by the water-bearing rock-soil layer 14. In terms of strength of the reservoir body 10, the inner metal sealing layer 11 effectively eliminates stress concentration caused by temperature change by virtue of the corrugated structure, and the water-bearing rock-soil layer 14 supports the support layer 13. In terms of heat leakage rate control, the inner metal sealing layer 11 is made of aluminum plate or stainless steel plate with aluminum powder coated on the inner wall to reduce the radiant heat flux between the layers of the reservoir body 10, and the heat insulation layer 12 is connected to the inner metal sealing layer 11 and the support layer 13 by adhesion, further reducing the heat transfer caused by water entering the gap between the layers.

[0034] Further, due to the influence of heat leakage, the temperature in the area near the ground above the reservoir body 10 is low. In order to reduce the impact of low temperature on the upper ground vegetation, the installed equipment and the harm to the operating personnel, a ground thermal barrier layer 70 is laid on the ground in this area. The thickness of the ground thermal barrier layer 70 is determined after design calculation based on the safety of the ground equipment and the operating personnel. Generally, the thickness of the ground thermal barrier layer 70 is set to be in the temperature range of 10℃ to 25℃.

[0035] The water injection unit 20 includes a ground main pipe 21 arranged on the ground and a underground manifold 22 arranged underground and communicated with the ground main pipe 21. The underground manifold 22 is arranged around the circumferential side of the water-bearing rock-soil layer 14 to form at least one annular pipeline, so as to uniformly inject water into the water-bearing rock-soil layer 14.

[0036] The liquid hydrogen underground storage system further includes an injection-production pipeline unit 30, which includes an injection-production pipeline and an injection-production / vent valve group 33 arranged on the injection-production pipeline.

[0037] Specifically, the injection-production pipeline has a double-layer structure, and the interlayer is subjected to vacuum extraction treatment to reduce heat loss. The injection-production pipeline includes a low-position injection-production pipe 31 and a high-position injection-vent pipe 32. The low-position injection-production pipe 31 is inserted into the bottom of the inner cavity of the inner metal sealing layer 11, and is mainly used for injection and production of liquid hydrogen. The high-position injection-vent pipe 32 is inserted into the upper part of the inner cavity of the inner metal sealing layer 11, and is used for injection of liquid hydrogen and discharge of gaseous hydrogen. Further, the injection-production pipeline is provided with a fire arrester to prevent the flame front from spreading to the reservoir body 10 when an external fire occurs. Understandably, the ground part of the liquid hydrogen underground storage system can be provided with an auxiliary refrigeration system. When the pressure of the liquid hydrogen in the reservoir body 10 rises to a certain value, the gaseous hydrogen is discharged from the high-position injection-vent pipe 32, and the gaseous hydrogen is liquefied by the auxiliary refrigeration system and then injected into the reservoir body 10, but this is not a necessary part.

[0038] The low-position injection-production pipe 31 and the high-position injection-production pipe 32 are provided with an injection-production / discharge valve group 33, which is installed in an integrated ground base and includes a safety valve group, a flow control valve group, an instrument valve group and a valve assembly base.

[0039] Please refer to Figure 2 The safety valve group includes a safety relief valve 331, a bursting disc 332 and a safety device shutoff valve 333, and the safety relief valve 331 and the bursting disc 332 are connected to the valve assembly base through the safety device shutoff valve 333. The safety relief valve 331 and the bursting disc 332 constitute two-stage safety relief, which can be connected in series or in parallel, and play a safety protection role for the storage. Specifically, the start pressure (upper limit I value) of the safety relief valve 331 is higher than the upper limit of the operating pressure of the storage but lower than the detonation pressure (upper limit II value) of the bursting disc 332, and the safety relief valve 331 can be but is not limited to a spring pre-pressing type, and the pre-pressing pressure is adjusted to the I value. When the pressure of the storage abnormally rises to the upper limit I value due to gasification or other reasons, the safety relief valve 331 is automatically opened to discharge and relieve pressure, and the discharge pipe is installed in a high place with good ventilation. The bursting disc 332 is of a diaphragm type, and when the pressure of the storage continues to rise to the II value, the diaphragm is broken to relieve pressure, and the relief discharge pipe is installed in a high place with good ventilation (the upper limit values I / II are set according to the design pressure of the storage, or can refer to relevant standards such as the national standard GB / T 16918 Safety Device for Bursting Discs for Gas Cylinders, GB / T 33215 Safety Relief for Gas Cylinders, TSG 23 Technical Regulations for Gas Cylinders, etc.). The safety device shutoff valve 333 is used to separate the storage body 10 from the safety relief valve 331 and the bursting disc 332, and the safety device shutoff valve 333 is in a fully open position and is provided with a locking device. When the safety valve is needed to be repaired for maintenance or other purposes, the safety device shutoff valve 333 can be closed, and the safety device shutoff valves 333 on the low-position injection-production pipe 31 and the high-position injection-production pipe 32 cannot be closed at the same time.

[0040] The flow control valve group includes a flow regulating valve 334 and a flow shutoff valve 335, which are connected in series and connected to the valve assembly base, and the injection flow and speed are controlled through the flow regulating valve 334.

[0041] The instrument valve group includes an instrument primary sampling valve 336 and an instrument secondary sampling valve 337, which are installed on the valve assembly base and connected in series.

[0042] In the aspect of pressure safety control, the injection-production valve group 33 is arranged on the low-position injection-production pipe 31 and the high-position injection-production pipe 32, forming double pressure safety protection under different pressures. Since the internal pressure of the storage body 10 must be controlled within the allowable pressure range, the over-high or over-low (negative pressure) internal pressure of the storage body 10 is potentially dangerous. Many factors can affect the pressure of the storage body 10, such as the evaporation of liquid caused by heat entering, rapid flashing of liquid during filling, atmospheric pressure drop or incorrect operation, which can cause the internal pressure of the storage body 10 to rise. In addition, if the liquid is discharged or pumped out of the storage body at a very fast speed, a negative pressure can be formed in the storage body. The excessive evaporated gas in the storage tank is transported to the external connected equipment or system through the flow regulating valve 334, so as to maintain the stable pressure in the storage body; the safety relief valve 331 and the bursting disc 332 form double and two-stage safety control and protection for the pressure in the storage body 10. In the case of sudden increase of evaporated gas or unexpected situation that the evaporated gas cannot be consumed externally, the safety relief valve 331 is automatically opened to vent the evaporated gas, and the bursting disc 332 is broken to release pressure in the case of danger.

[0043] The safety protection device of the storage body must have sufficient discharge capacity. The discharge capacity required by the safety discharge device is calculated according to the Chemical Process Design Manual or the following formula:

[0044]

[0045] In the formula, q v - flow rate relative to air (15.5℃, 101.35kPa), m3 / h;

[0046] Φ - total heat flow, kW;

[0047] γ - gasification phase change enthalpy of the stored liquid, kJ / kg;

[0048] T - thermodynamic temperature of the gas at the inlet of the safety valve, K;

[0049] M - relative molecular mass of the gas.

[0050] Please refer to Figure 3In order to monitor the leakage of hydrogen, the liquid hydrogen underground storage system further comprises a hydrogen leakage monitoring unit 40. The hydrogen leakage monitoring unit 40 comprises a leak detector, a gas collection hood 41, a gas guide pipe 42 arranged in the gas collection hood 41, and a mesh gas hole screen 43 and a rain cover 44 arranged at two ends of the gas guide pipe 42 respectively, the mesh gas hole screen 43 is located in the gas collection hood 41, the rain cover 44 is located outside the gas collection hood 41, the gas guide pipe 42 has an underground section and an aboveground section, the underground section of the gas guide pipe 42, the gas collection hood 41 and the mesh gas hole screen 43 constitute an underground part of the hydrogen leakage monitoring unit 40, and the aboveground section of the gas guide pipe 42, the rain cover 44 and the leak detector constitute an aboveground part of the hydrogen leakage monitoring unit 40. The leaked hydrogen enters the gas guide pipe 42 through the mesh gas hole screen in the underground part, the gas collection hood 41 is used for collecting the leaked hydrogen within a certain range, and has an amplification effect. By adjusting the length of the underground part of the gas guide pipe 42, the underground part of the hydrogen leakage monitoring unit 40 can be arranged at different heights in different areas, and the storage area is effectively monitored. When the leak detector detects hydrogen, a signal is transmitted to the signal acquisition and control system to trigger an alarm or related emergency operation and disposal. The rain cover 44 is used to prevent rain, snow or foreign matter from entering the gas guide pipe 42 to cause channel blockage, and the rain cover 44 can also strengthen the diffusion of hydrogen to the air and reduce the potential risk of hydrogen explosion caused by hydrogen accumulation.

[0051] Further, the liquid hydrogen underground storage system further comprises a measurement and control unit, and the measurement and control unit comprises a first temperature sensor 50, a second temperature sensor 60 and a pressure sensor.

[0052] The first temperature sensor 50 is arranged at different heights of the peripheral rock-soil and water-bearing rock-soil layer 14, and is used for monitoring the three-dimensional temperature distribution of the peripheral rock-soil and water-bearing rock-soil layer 14, so as to understand the underground three-dimensional temperature distribution and heat conduction of the storage system.

[0053] The second temperature sensor 60 is arranged at different heights of the inner cavity of the inner metal sealing layer 11, and is used for measuring the temperature of the liquid hydrogen in the inner metal sealing layer 11, and judging the stratification of the liquid hydrogen according to the height-reversed temperature gradient. Since the liquid hydrogen filling control in the reservoir body 10 is improper or the liquid hydrogen vertical density (temperature) deviates due to heat leakage, the natural convection of the liquid hydrogen is intensified, and the gasification rate is increased. Therefore, preventing the stratification of the liquid hydrogen in the storage is an important means to ensure the safety of the liquid hydrogen storage. By arranging the temperature sensor at different heights in the inner metal sealing layer 11, whether stratification occurs is determined by measuring the temperature gradient in the vertical direction of the inner metal sealing layer 11. When the liquid layer vertical temperature gradient is greater than 0.2K / m (the value is a recommended value, and can be selected according to design requirements and safety requirements), it is considered that stratification occurs.

[0054] A pressure sensor is installed on the injection-production / valve group 33 for measuring the pressure value of the reservoir.

[0055] The signal data lines of the entire liquid hydrogen underground reservoir system are concentrated nearby and then led out to the ground by several conduits to access the PLC or DCS signal acquisition and control system for data monitoring display and control interlocking use. The control system adopts centralized control mode and can realize signal data acquisition, logical judgment, and valve and equipment operation, and has automatic control function.

[0056] The use procedure of the liquid hydrogen underground reservoir system mainly includes four steps of "replacement-precooling-liquid injection-storage". When the medium density injected in the "replacement" and "liquid injection" processes is greater than the medium density in the tank, top injection should be used; when it is less than or close to the medium density in the tank, bottom loading method should be used.

[0057] Specifically, the "replacement" step is to use inert gas as replacement gas to replace the air in the initial state in the reservoir, and the inert gas includes but is not limited to nitrogen. The replacement gas is injected into the lower part of the inner cavity of the inner metal sealing layer 11 through the low-position injection-production pipe 31, and the mixed gas is discharged through the high-position injection-discharge pipe 32 until the oxygen volume fraction in the discharged mixed gas is not less than 0.5% (or refer to the corresponding standards such as GB 50516 Hydrogen Station Technical Specification, GB 50156 Technical Standard for Gasoline and Gas Filling and Hydrogen Station, GB / T 34584 Safety Technical Specification for Hydrogen Station, etc.). Through the "replacement" step, the direct hydrogen into the inner cavity of the inner metal sealing layer 11 is avoided to mix with the original air in the cavity to produce explosion, and the safety hidden danger is reduced.

[0058] At the same time of the "replacement" process, the water injection unit 20 is used to inject water into the water-bearing rock-soil layer 14 until saturation; after the water-bearing rock-soil layer 14 is saturated, liquid nitrogen is injected into the inner cavity of the inner metal sealing layer 11 through the low-position injection-production pipe 31 to precool the reservoir system, and the gasified nitrogen is discharged through the high-position injection-discharge pipe 32. This process gradually cools the tank body 10 to the liquid nitrogen temperature, and the nearby saturated rock-soil layer gradually cools to below freezing point to form a dense ice ring, thereby completing the "precooling" step.

[0059] After the "pre-cooling" step, a period of time is allowed to elapse, and the data of each temperature measuring point is stabilized, and then the "liquid injection" step is started. Liquid hydrogen is slowly injected through the high-position injection and discharge pipe 32, and hydrogen gas is generated during the injection of liquid hydrogen, which gradually increases the pressure in the inner cavity of the inner metal sealing layer 11, and at the same time, the temperature of the storage body 10 continues to decrease to the boiling point of liquid hydrogen, and the liquid nitrogen is discharged through the low-position injection and extraction pipe 31 by relying on the action of the pressure; when the liquid hydrogen appears at the pipe opening of the low-position injection and extraction pipe 31 in the inner metal sealing layer 11, the liquid hydrogen injection channel is switched to the low-position injection and extraction pipe 31, and the hydrogen gas discharge channel is changed to the high-position injection and discharge pipe 32, and the formal injection and storage of liquid hydrogen is started, until the "storage" step of liquid hydrogen in the entire storage body 10 is completed, and the capacity of the stored liquid hydrogen is understood by monitoring the liquid level.

[0060] It should be noted that the use procedure of the entire liquid hydrogen underground storage system needs to monitor the data of each temperature measuring point and pressure measuring point, understand the changes of temperature and pressure, prevent the occurrence of sudden cooling cracking, pressure surge damage and other serious accidents, and estimate the heat leakage and evaporation of the system. In addition, in order to prevent the occurrence of liquid hydrogen stratification, that is, the vertical density (temperature) deviation of liquid hydrogen, the correct liquid filling sequence is adopted during the "injection" period, and the stratification occurs during the "storage" period. By connecting the ground part of the high-position injection and discharge pipe 32 and the low-position injection and extraction pipe through an external pump, a circulating stirring method is adopted to make the density (temperature) distribution of liquid hydrogen in the inner metal sealing layer 11 uniform.

[0061] The shutdown procedure of the liquid hydrogen underground storage system is different according to short-term shutdown and long-term shutdown or abandonment. When short-term shutdown is considered, the storage body needs to be injected with liquid nitrogen to keep cold, maintain the low-temperature state of the storage body and the frozen state of the frozen soil ice circle in the freezing and thawing process, so as to prevent the occurrence of cracks and affect the tightness of the storage system when it is used again. If the storage body needs to be used for a long time or abandoned due to special circumstances, the "replacement" step in the storage body use procedure needs to be followed, and inert gases such as nitrogen or carbon dioxide are used to evaporate and replace the residual liquid hydrogen or hydrogen gas in the storage body 10, until the hydrogen content in the mixed gas is lower than the explosion interval.

[0062] The present application takes a spherical storage body 10 with a diameter of 1 m as an example for heat transfer simulation. The specific setting data of the simulation model are as follows: a spherical storage tank with a diameter of 1 m, a thermal insulation layer of 20 cm, a concrete support layer 1310 cm, and a saturated frozen soil as the external frozen soil; the storage model is located 10 m underground, and the calculation domain is a two-dimensional space of 100 m x 60 m; the ground temperature is 293 K, and the liquid hydrogen parameters are 1.5 bar.a / 20 K. The temperature distribution is shown in Figure 4 . According to the temperature field data of Figure 4 , the temperature outside the thermal insulation layer is about 200 K, and the thermal insulation layer has good heat insulation effect. The heat flux density of the tank wall is 61.55 W / m 2 , and the equivalent heat leakage is 775 W (≈0.75% of the daily evaporation rate).

[0063] The present application provides a liquid hydrogen underground storage system, which comprises a storage body 10 and a water injection unit 20. The storage body 10 is buried underground and comprises, from inside to outside, an inner metal sealing layer 11, a heat insulation layer 12, a support layer 13 and a water-containing rock-soil layer 14. The inner metal sealing layer 11 is used for encapsulating liquid hydrogen, the heat insulation layer 12 is used for insulating the liquid hydrogen in the inner metal sealing layer 11, the support layer 13 is used for improving the support strength of the storage body 10, and the water-containing rock-soil layer 14 is a saturated rock-soil layer formed by water injection and located outside the support layer 13. The water injection unit 20 uniformly injects water into the water-containing rock-soil layer 14 through an underground manifold 22 arranged around the water-containing rock-soil layer 14, so that the water-containing rock-soil layer 14 forms a closed permafrost zone during hydrogen storage to reduce the leakage of liquid hydrogen, and the water-containing rock-soil layer 14 and the support layer 13 jointly support the storage body 10. The heat insulation layer 12 and the water-containing rock-soil layer 14 jointly insulate the liquid hydrogen from being vaporized, and the inner metal sealing layer 11 and the water-containing rock-soil layer 14 form double sealing, effectively reducing the leakage of the stored liquid hydrogen. The underground structure is used to realize large-capacity and low-cost hydrogen storage, the materials used are mostly common industrial materials, and the procurement and maintenance costs are low, which is conducive to reducing the construction and maintenance costs and the liquid hydrogen storage cost, and is conducive to realizing large-scale application and popularization.

[0064] Although the present application has been described with reference to several exemplary embodiments, it is understood that the words that have been used are words of description and illustration, rather than words of limitation. As the application can be embodied in many different forms without departing from the spirit or essential characteristics thereof, it is understood that the present embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the application should be determined, not with reference to the above description, but should be given with reference to the appended claims, and throughout the claims the use of "comprising" or "including" or "having" or "containing" or "characterized by" does not preclude the presence of elements or limits them to the specific elements stated, but can "comprise additional elements without departing from the spirit of the application stated.

Claims

1. A liquid hydrogen underground storage system, characterized by, The application relates to a liquid hydrogen storage device. The library body is buried underground and comprises an inner metal sealing layer, a heat insulation layer, a support layer and a water-containing rock-soil layer arranged in sequence from inside to outside; the inner metal sealing layer is used for packaging liquid hydrogen; the inner metal sealing layer is a closed cavity composed of a plate with a corrugated structure; the heat insulation layer is connected with the inner metal sealing layer and the support layer through an adhesive respectively, so as to insulate the liquid hydrogen in the inner metal sealing layer; the support layer is used for improving the support strength of the library body; the water-containing rock-soil layer is a saturated rock-soil layer located outside the support layer and formed by water injection, so as to form a closed permafrost circle to reduce liquid hydrogen leakage during liquid hydrogen storage, and the support layer and the support layer are used for supporting the library body together; The water injection unit comprises a ground main pipe and an underground manifold communicated with the ground main pipe, and the underground manifold is arranged around the circumferential side of the water-containing rock-soil layer to uniformly inject water into the water-containing rock-soil layer. The hydrogen leakage monitoring unit comprises a leak detector, a gas collection cover, a gas guide pipe penetrating the gas collection cover and a mesh air hole screen and a rain cover arranged at two ends of the gas guide pipe respectively; the mesh air hole screen is located in the gas collection cover, and the rain cover is located outside the gas collection cover; part of the gas guide pipe and the mesh air hole screen and the gas collection cover are buried underground, and the other part of the gas guide pipe and the rain cover and the leak detector are arranged on the ground; The injection and extraction pipeline unit comprises an injection and extraction pipeline and an injection and extraction / vent valve group arranged on the injection and extraction pipeline; the injection and extraction pipeline comprises a low-position injection and extraction pipeline and a high-position injection and extraction pipeline; the low-position injection and extraction pipeline is inserted into the bottom of the inner cavity of the inner metal sealing layer to inject and extract liquid hydrogen; the high-position injection and extraction pipeline is inserted into the upper part of the inner cavity of the inner metal sealing layer to inject liquid hydrogen and discharge gaseous hydrogen; one injection and extraction / vent valve group is arranged on the low-position injection and extraction pipeline and the high-position injection and extraction pipeline; the injection and extraction / vent valve group comprises a valve assembly base and a safety valve group, a flow control valve group and an instrument valve arranged on the valve assembly base; the safety valve group comprises a safety relief valve, a bursting disc and a safety device shut-off valve connected in sequence on the valve assembly base; The measurement and control unit comprises a plurality of first temperature sensors arranged at different height positions of the peripheral rock-soil and the water-containing rock-soil layer, a plurality of second temperature sensors arranged at different height positions in the inner metal sealing layer and a pressure sensor installed on the injection and extraction / vent valve group.

2. The liquid hydrogen underground storage system of claim 1, wherein, The thickness of the heat insulation layer is determined according to the allowable value of the daily evaporation amount of the liquid hydrogen in the inner metal sealing layer.

3. The liquid hydrogen underground storage system of claim 1, wherein, The support layer is made of one or a combination of materials such as reinforced concrete, prestressed concrete, modified concrete and refractory bricks.

4. The liquid hydrogen underground storage system of claim 3, wherein, The thickness of the support layer is determined according to the confining pressure, temperature gradient, local seismic intensity of the library body and the allowable stress calculated from the physical properties of the permafrost and the support layer material.

5. The liquid hydrogen underground storage system of claim 1, wherein, The application further comprises a ground thermal barrier layer laid on the corresponding ground area above the library body.

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