Modular hydrogen liquefaction system

Abstract

The application discloses a modular hydrogen liquefaction system, comprising: one or more parallelly arranged liquefaction modules, a hydrogen inlet of the liquefaction module being connected with a hydrogen source, and a product outlet of the liquefaction module being connected with one or more parallelly arranged liquid hydrogen storage tanks; each of the liquefaction modules is an integrated structure capable of hydrogen cooling, liquefaction, primary and secondary hydrogen conversion and independent start and stop. The application realizes hydrogen liquefaction by connecting a large number of refrigeration units in series and in parallel to form modules at different levels, can effectively utilize the benefit of large-scale production of standard refrigeration units, and reduces equipment cost. By controlling the number of different level modules and refrigeration units to be started, the application can also realize large-range liquid hydrogen production capacity adjustment. In addition, by using a regenerative refrigerator as a standard refrigeration unit, rapid cooling and instant shutdown can be realized, so that the system has the advantages of rapid start and stop. The above advantages make the application particularly suitable for matching with renewable energy to produce green liquid hydrogen.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of low-temperature engineering equipment, and particularly relates to a modular hydrogen liquefaction system. BACKGROUND

[0002] In recent years, in order to help achieve carbon peak and carbon neutral, deeply promote the revolution of energy production and consumption, and build a clean, low-carbon, safe and efficient social system, hydrogen energy is one of the long-term solutions to current energy problems and the realization of the "double carbon" strategic goal. Hydrogen energy is a secondary energy source that is abundant in source, green and low-carbon, and widely used, and is also an important chemical raw material with huge scale. Hydrogen produced by renewable energy such as wind energy and solar energy is also called "green hydrogen", which is the main source of hydrogen energy in the future, and can be used in transportation, civil use and power production and energy storage fields, and is also expected to be used on a large scale in the chemical industry, such as replacing coke as a reducing agent, etc.

[0003] In order to realize the reasonable price of hydrogen at the terminal and make it economical, so as to realize large-scale market promotion, how to safely and effectively store and transport is a key technical challenge. High-pressure normal-temperature hydrogen storage is the most widely used and most mature hydrogen storage technology at present, but its storage and transportation density is low, and the cost of the whole industry chain is high. According to the current development trend of technology, it is judged that it cannot adapt to large-scale production, and it is also difficult to realize economy. The hydrogen storage technology based on materials, including physical adsorption, chemical adsorption and organic synthesis, is still at a low level of technical maturity, and does not have the possibility of large-scale economic effect, and also has the problems of high energy consumption of the whole industry chain, high cost of equipment and materials, complex system, product purity, etc., so it also does not have the possibility of large-scale application. The storage and transportation mode of low-temperature liquefied hydrogen benefits from the increasing maturity of cryogenic, adiabatic and vacuum technologies, higher storage density and lower operating pressure, which reduces the energy consumption and space cost of unit mass transportation, and is expected to become an effective way for long-distance transportation and large-scale storage of hydrogen, and is the only technical route that can realize the economic terminal hydrogen sales price.

[0004] Producing hydrogen and liquefying it by using renewable energy such as wind energy and solar energy is an important mode of future green hydrogen production. However, the volatility of renewable energy power generation puts special requirements on the downstream matching green hydrogen production system (water electrolysis and hydrogen liquefaction system):

[0005] 1. Adjustable production capacity and fast start-stop: If the green liquid hydrogen production system is continuously and stably produced, it must be equipped with a sufficient storage system to power it during the low valley of electricity, or directly use the electricity from the power grid during the low valley of electricity. However, the former requires a high-cost (currently still higher than the green hydrogen production system with the same installed capacity), large-area storage system, which greatly increases the fixed asset investment and increases the cost of hydrogen. The latter, the electricity price of the power grid is much higher than the off-grid price, causing the operating cost to increase sharply, and the entire system still causes a large fluctuation impact on the power grid, which cannot be eliminated by hydrogen production to mitigate the impact of renewable energy fluctuation on the power grid. Therefore, the green hydrogen production system (including water electrolysis and hydrogen liquefaction system) needs to have the function of adjustable production capacity and fast start-stop, to select the appropriate production capacity or start-stop strategy to match the fluctuating renewable energy system, and realize the full off-grid production mode.

[0006] 2. Lower fixed asset investment: The green liquid hydrogen production system with adjustable production capacity and fast start-stop function matches the renewable energy, and the equipment utilization rate is also correspondingly reduced, so that the fixed asset investment of the green liquid hydrogen production system increases in the cost composition of hydrogen, becoming the most important factor affecting the cost of hydrogen. Therefore, lower fixed asset investment of the green liquid hydrogen production system is a necessary condition for the green hydrogen production mode to have market competitiveness.

[0007] Hydrogen liquefaction is the most critical link in the green hydrogen industry chain, with complex technical process, high energy consumption ratio, and high investment cost. Over the past few decades, many researchers have been studying how to improve the efficiency of hydrogen liquefaction. Improving the efficiency of hydrogen liquefaction can effectively reduce the operating cost of hydrogen liquefaction equipment, and also indirectly reduce the equipment investment cost. According to the working medium and thermodynamic cycle used by the main refrigeration system, the existing commercial liquefaction devices are generally the Brayton cycle refrigeration using helium as the working medium and the improved Claude cycle refrigeration using hydrogen as the working medium. The former is generally used for medium-sized liquefaction systems with a production capacity of less than 5 tons / day, and the latter is generally used for large-scale liquefaction systems with a production capacity of more than 5 tons / day.

[0008] The traditional hydrogen liquefaction system generally comprises a precooling system, a main refrigeration system, a liquefaction system and a low-temperature heat exchanger group. The precooling system generally adopts a relatively mature process to realize refrigeration at about 70-120K, and provides precooling for the main refrigeration system and the liquefaction system. The main refrigeration system is provided with a compressor and an expander, and exchanges heat with hydrogen in the liquefaction system through the low-temperature heat exchanger group, so as to refrigerate the hydrogen and finally form liquid hydrogen products. Among them, the compressor is used for compressing the refrigerant to high pressure, and provides high-pressure working medium for the circulating pipeline of the main refrigeration system, and the expander is used for expanding the high-pressure working medium to refrigerate, and provides cold energy for the liquefaction system. In the low-temperature heat exchanger group, a plurality of primary and secondary hydrogen reactors (either isothermal continuous reactors or adiabatic step reactors) are provided to catalyze the hydrogen into equilibrium hydrogen at the temperature of the current heat exchanger. The raw hydrogen provided by the hydrogen source successively passes through the primary and secondary hydrogen reactors in the multi-stage heat exchanger, and finally enters the liquid hydrogen storage tank in the form of liquid and flows out from the product outlet.

[0009] The traditional hydrogen liquefaction technology obviously cannot meet the two conditions required for off-grid renewable energy green liquid hydrogen production:

[0010] The traditional hydrogen liquefaction technology adopts large compressors, turbine expanders and heat exchangers, and the flow is small during the cooling process. The turbine expander deviates far from the normal working condition, the circulating flow is small, and the corresponding refrigeration capacity is also small, so it needs a long time (usually 6-18 hours) to start (cooling) and stop. In order to protect the moving equipment such as compressor, expander, etc., the start-stop process is very complex. By using variable frequency compressor or selecting several of the parallel connected compressors to stop, the production capacity of the hydrogen liquefaction system can be adjusted to a certain extent, but the adjustment range is limited, and the unit energy efficiency decreases obviously.

[0011] The core components of the traditional hydrogen liquefaction device, such as compressor, heat exchanger, turbine expander, etc., are all large-scale customized components with small quantity, and the supply cycle and price are high. As a typical chemical engineering project, the equipment and engineering need to be designed, and the project needs a long project engineering cycle (24-36 months) from contract negotiation, scheme design, engineering construction to final commissioning and operation. Non-standard products and customized engineering also inevitably result in high fixed asset investment. SUMMARY

[0012] The present application is based on the demand of off-grid renewable energy green liquid hydrogen production mode, and proposes a modular hydrogen liquefaction system with adjustable production capacity, fast start-stop function, low fixed asset investment of equipment and fast production. To this end, the present application adopts the following technical solutions:

[0013] A modular hydrogen liquefaction system, comprising: one or more parallelly arranged liquefaction modules, a hydrogen gas inlet of the liquefaction module being connected with a hydrogen gas source, and a product outlet of the liquefaction module being connected with one or more parallelly arranged liquid hydrogen storage tanks; each of the liquefaction modules being an integrated structure capable of independently starting and stopping, and having functions of hydrogen gas cooling, liquefaction and primary and secondary hydrogen conversion.

[0014] The hydrogen gas source and the liquid hydrogen storage tank can be separately arranged or can be components of the present application. When being components of the present application, the modular hydrogen liquefaction system of the present application comprises the hydrogen gas source, the liquefaction module and the liquid hydrogen storage tank, which are sequentially connected through pipelines, room temperature hydrogen gas from the hydrogen gas source is cooled, liquefied and subjected to primary and secondary hydrogen reaction through the liquefaction module, and then flows into the liquid hydrogen storage tank for storage.

[0015] The liquefaction system of the present application comprises one or more (the number is k, k≥1) parallelly arranged liquefaction modules. The liquefaction module is a standardized skid-mounted device, adopts standard container outer dimensions and interfaces, and each module can independently operate to cool, liquefy and complete primary and secondary hydrogen reaction on a certain flow of hydrogen gas. The liquid hydrogen product outlets of the parallelly arranged liquefaction modules are connected through pipelines to form a total pipeline, and are connected with the liquid hydrogen storage tank. Such design has the following advantages:

[0016] 1. Parallel arrangement of multiple modules realizes larger hydrogen liquefaction capacity;

[0017] 2. Independent operation of one or several modules can realize large-scale adjustment of capacity without affecting system energy efficiency;

[0018] 3. Users can flexibly and conveniently realize expansion or reduction of system capacity, thereby reducing investment risk;

[0019] 4. Standardized modules are conducive to mass production, and greatly reduce equipment cost;

[0020] 5. The complexity of system installation is reduced, and engineering cost and period are reduced;

[0021] 6. The skid-mounted module is convenient for storage, transportation, hoisting and arrangement.

[0022] As a preferred, the liquefaction module comprises:

[0023] a precooling unit for precooling and cooling hydrogen gas;

[0024] a low-temperature liquefaction conversion unit for liquefying and converting primary and secondary hydrogen of the precooled hydrogen gas;

[0025] an expansion unit for decompressing the hydrogen after low-temperature liquefaction conversion, and the outlet of the expansion unit is connected with the liquid hydrogen storage tank as a product outlet;

[0026] A compression unit that provides refrigeration compression work to the cryogenic liquefaction conversion unit.

[0027] The compression unit is connected to the standard refrigeration unit in the cryogenic liquefaction conversion unit via pipelines.

[0028] Preferably, the precooling unit includes:

[0029] Precooling heat exchanger;

[0030] Pre-cooling cold source that provides cold source to pre-cooling heat exchanger;

[0031] The purifier and the precooling stage neutral hydrogen reactor are connected in sequence to the hydrogen flow channel of the precooling heat exchanger.

[0032] The precooling heat exchanger includes a hydrogen flow channel and a precooling working fluid flow channel; the precooling cold source provides precooling cooling capacity to the hydrogen through the precooling working fluid. The flow channel of the precooling-stage secondary hydrogen reactor is filled with a secondary hydrogen catalyst. In actual connection, the hydrogen source interface, the hydrogen flow channel of the precooling heat exchanger, the purifier, and the precooling-stage secondary hydrogen reactor are connected by pipelines; the precooling cold source is connected to the cold end inlet of the precooling working fluid flow channel of the precooling heat exchanger through a pipeline, and the precooling working fluid flows through the precooling working fluid flow channel of the precooling heat exchanger, providing cooling capacity to the hydrogen flowing through the hydrogen flow channel of the precooling-stage heat exchanger, the purifier, and the precooling-stage secondary hydrogen reactor. In actual operation, the pressure from the hydrogen source is p. supply The room-temperature hydrogen gas first enters and is pre-cooled to the pre-cooling temperature T by a pre-cooling heat exchanger. preC The hydrogen is then purified to remove gaseous and solid impurities from the raw hydrogen, preventing blockages in subsequent processes and ensuring the purity of the liquid hydrogen product. The pre-cooled and purified raw hydrogen then enters a pre-cooling stage neutral and secondary hydrogen reactor, where a neutral and secondary hydrogen reaction occurs with the aid of a neutral and secondary hydrogen catalyst, bringing the secondary hydrogen content in the hydrogen close to the pre-cooling temperature T. preC The ratio of secondary hydrogen to equilibrium hydrogen is adjusted, and the hydrogen temperature is restored to the pre-cooling temperature T. preC .

[0033] Preferably, the purifier is a low-temperature purification adsorbent. The purifier can be a single low-temperature purification adsorbent or two or more low-temperature purification adsorbents connected in parallel. More preferably, the purifier includes two low-temperature purification adsorbents that are switched via valves and alternately connected to the pipeline. The two low-temperature purification adsorbents connected in parallel form a typical temperature-switching adsorption device. When one low-temperature purification adsorbent is connected to the pipeline, the other low-temperature purification adsorbent is purged and heated by clean inert gas to achieve regeneration, thereby improving the working efficiency of the hydrogen low-temperature purifier.

[0034] The pre-cooling stage primary-secondary hydrogen reactor and the corresponding pre-cooling heat exchanger can adopt an integrated structure or an independent structure. The former is an isothermal continuous reactor, which essentially fills the catalyst in the flow channel of the low-temperature heat exchanger, and the reactor is the heat exchanger, that is, the hydrogen catalytic reaction is completed while the inflow hydrogen is cooled; the latter is an adiabatic step reactor, which essentially fills the catalyst in a separate adiabatic container, and the hydrogen is first cooled by the corresponding low-temperature heat exchanger and then enters the reactor for catalytic reaction, and the temperature rises, and then the hydrogen is cooled again by the subsequent low-temperature heat exchanger; the isothermal continuous reactor is more efficient and more compact than the adiabatic step reactor; the adiabatic step reactor is simple to manufacture, and both structures can be applied to the technical scheme of the present application.

[0035] According to different conditions of the site where the hydrogen liquefaction system is located, the pre-cooling source can be an open low-temperature frozen liquid pre-cooling system or a closed low-temperature refrigeration pre-cooling system. The open low-temperature frozen liquid pre-cooling system uses liquid nitrogen or liquefied natural gas as the cold source working medium, and the former is particularly suitable for the case where stable and inexpensive liquid nitrogen can be obtained on site, such as the presence of an air separation device near the site to provide stable and inexpensive liquid nitrogen resources; the latter is particularly suitable for liquefied natural gas ports and other places where liquefied natural gas vaporization cold energy needs to be recovered. The closed low-temperature refrigeration pre-cooling system is a turbo Brayton cycle refrigeration system, a self-recovery mixed working medium cycle refrigeration system, or a regenerative refrigeration system, which is suitable for scenarios where the electricity price is cheap or it is not easy to obtain low-temperature liquids such as liquid nitrogen and liquefied natural gas on site.

[0036] As a specific preferred scheme, the pre-cooling source is provided by a pre-cooling cycle system as follows:

[0037] A turbo compressor for compressing the pre-cooling working medium to high pressure;

[0038] A drive motor for driving the turbo compressor to work;

[0039] A water cooler for cooling the high-pressure gas output by the turbo compressor;

[0040] A low-temperature turbo expander for expanding and refrigerating the working medium output by the pre-cooling working medium inflow channel of the pre-cooling heat exchanger;

[0041] The pre-cooling heat exchanger is provided with a hydrogen flow channel, a pre-cooling working medium inflow channel, and a pre-cooling working medium return flow channel; the inlet of the pre-cooling working medium inflow channel is connected to the outlet of the water cooler, the outlet of the pre-cooling working medium inflow channel is connected to the inlet of the low-temperature turbo expander, the inlet of the pre-cooling working medium return flow channel is connected to the outlet of the low-temperature turbo expander, and the outlet of the pre-cooling working medium return flow channel is connected to the inlet of the turbo compressor.

[0042] As a further preferred, the turbo compressor recovers the expansion work generated by the low-temperature turbo expander through a connecting shaft connected between the turbo compressor and the low-temperature turbo expander.

[0043] As a preferred, the liquefaction module further comprises a vacuum insulated cold box and an insulated radiation shield. The insulated radiation shield, the pre-cooling unit (low temperature part), the expansion unit and the low temperature part of the low temperature liquefaction conversion unit (including the cold finger of the standard refrigeration unit and the para-ortho hydrogen reactor) are installed in the vacuum insulated cold box, the inside of which is evacuated to reduce the convective and conductive heat leakage from the environment. The expansion unit and the lowest temperature part of the low temperature liquefaction conversion unit are arranged in the insulated radiation shield. The insulated radiation shield is made of a thin shell of metal with good thermal conductivity, the surface of which is polished to have a high reflectivity, and is connected to the pre-cooling cold source by thermal connection, and the pre-cooled working fluid is cooled to the pre-cooling temperature T preC The insulated radiation shield surrounds the expansion unit and the lowest temperature (cold head) part of the low temperature cooling sub-module, further reducing the radiation heat transfer from room temperature to the above-mentioned components.

[0044] As a preferred, the insulated radiation shield is thermally connected to the pre-cooling unit.

[0045] As a preferred, the liquid hydrogen transfer pipeline connecting the liquefaction module and the liquid hydrogen storage tank is a double-layer vacuum insulated pipeline.

[0046] As a preferred, the low temperature liquefaction conversion unit is composed of one or more (the number is m, m≥1) low temperature liquefaction groups, and when multiple low temperature liquefaction groups are used, the multiple low temperature liquefaction groups are connected in parallel. The raw hydrogen gas from the pre-cooling unit is divided into m paths and connected to each low temperature liquefaction group respectively. The low temperature liquefaction group comprises one or more (the number is n, n≥1) low temperature cooling sub-modules connected in series, and each low temperature cooling sub-module comprises a standard refrigeration unit and a para-ortho hydrogen reactor, the para-ortho hydrogen reactor is installed at the cold end of the standard refrigeration unit and comprises a refrigeration working fluid flow channel and a hydrogen gas flow channel. The refrigeration working fluid of the standard refrigeration unit directly flows in the refrigeration working fluid flow channel of the para-ortho hydrogen reactor to provide the cooling capacity required for hydrogen cooling and para-ortho hydrogen reaction; the hydrogen gas flow channel of the para-ortho hydrogen reactor is arranged with para-ortho hydrogen catalyst for catalyzing the para-ortho hydrogen reaction.

[0047] As a further preferred, for each low temperature liquefaction group, the hydrogen gas flow channels of the para-ortho hydrogen reactors are sequentially connected in series according to the hydrogen gas flow direction, and the cold head temperature of the standard refrigeration unit or the temperature of the para-ortho hydrogen reactor decreases sequentially.

[0048] Further, in the present application, the low temperature liquefaction conversion unit comprises one or more (the number is m, m≥1) low temperature liquefaction groups, and when multiple low temperature liquefaction groups are used, the multiple low temperature liquefaction groups are connected in parallel. The raw hydrogen gas from the pre-cooling unit is divided into m paths and connected to each low temperature liquefaction group respectively. The low temperature liquefaction group comprises one or more (the number is n, n≥1) low temperature cooling sub-modules connected in series, and each low temperature cooling sub-module comprises a standard refrigeration unit and a para-ortho hydrogen reactor, the para-ortho hydrogen reactor is installed at the cold end of the standard refrigeration unit and comprises a refrigeration working fluid flow channel and a hydrogen gas flow channel. The refrigeration working fluid of the standard refrigeration unit directly flows in the refrigeration working fluid flow channel of the para-ortho hydrogen reactor to provide the cooling capacity required for hydrogen cooling and para-ortho hydrogen reaction; the hydrogen gas flow channel of the para-ortho hydrogen reactor is arranged with para-ortho hydrogen catalyst for catalyzing the para-ortho hydrogen reaction.

[0049] The hydrogen flow inlet and outlet of the para-para hydrogen reactor of the plurality of (n) low-temperature cooling sub-modules are connected in series, and the n standard refrigeration units operate at sequentially decreasing temperatures T c,1 >T c,2 >…>T c,n-1 >T c,n In actual operation, the hydrogen gas from the pre-cooling unit has a temperature of T preC , and the para-hydrogen content is close to the pre-cooling temperature T preC The low-temperature hydrogen gas with an equilibrium para-hydrogen ratio of the hydrogen gas is sequentially passed through the n para-para hydrogen reactors connected in series in each low-temperature liquefaction group, the hydrogen gas is gradually cooled in the hydrogen flow channel of the n para-para hydrogen reactors, and the gradual para-para hydrogen reaction is realized with the help of the para-para hydrogen catalyst, so that the temperature of the hydrogen gas before throttling reaches T preExp , the pressure is p preExp , and the para-hydrogen content is more than 95%. The above design has the following advantages:

[0050] 1. A large number of standardized low-temperature cooling sub-modules are used, which is conducive to mass production and installation, and can greatly reduce equipment costs;

[0051] 2. One or several of the parallel low-temperature liquefaction groups can be independently operated to realize a large range of capacity regulation without affecting the system energy efficiency;

[0052] 3. The series connection of the plurality of low-temperature cooling sub-modules can reduce the heat exchange temperature difference between the refrigeration working medium and the hydrogen gas in each para-para hydrogen reactor, and improve the system energy efficiency;

[0053] 4. The design of the para-para hydrogen reactor makes the heat exchange path between the refrigeration working medium and the hydrogen gas as short as possible (only one heat exchange partition wall), reduces the heat exchange temperature difference, and improves the system energy efficiency;

[0054] 5. The independent standard refrigeration unit improves the stability of the system, and even if an individual refrigeration unit fails, it will only affect the liquefaction capacity, and will not cause the entire system to shut down;

[0055] 6. The independent standard refrigeration unit can be individually maintained and replaced, improving the convenience of maintenance and reducing operating costs.

[0056] As a preferred embodiment, in order to improve the heat exchange efficiency in the para-para hydrogen reactor, the working medium flow channel and the hydrogen flow channel of the para-para hydrogen reactor are provided with heat exchange enhancement structures such as fins; the inlet and outlet of the hydrogen flow channel are provided with filter elements with appropriate pore sizes to prevent para-para hydrogen catalyst particles from entering the pipeline system; and the para-para hydrogen catalyst in the hydrogen flow channel of the para-para hydrogen reactor has a plurality of different arrangement forms:

[0057] 1. The para-para hydrogen catalyst completely fills the flow channel: the advantages are simple filling process, sufficient catalyst, and complete reaction;

[0058] 2. Primary and secondary hydrogen catalysts do not completely fill the flow channel: the advantages are that the filling process is simple, the hydrogen flow causes the catalyst particles to be lifted in the flow channel, and the hydrogen can achieve full contact and heat exchange, which is conducive to full reaction;

[0059] 3. Primary and secondary hydrogen catalysts are filled in sections, and a filter with a suitable pore size is used before and after each section of catalyst to fix it, reducing the pollution of micro-particles generated by catalyst particle abrasion and fragmentation;

[0060] 4. Primary and secondary hydrogen catalysts are fixed to the surface of the flow channel and the surface of the heat exchange structure with an adhesive: the advantages are small flow resistance and sufficient heat exchange.

[0061] As a preferred embodiment, the standard refrigeration unit is a regenerative refrigerator, which can be a Gifford-McMahon refrigerator, a Stirling refrigerator, a Solvay refrigerator, a GM-type pulse tube refrigerator, or a Stirling-type pulse tube refrigerator. The advantages of using a regenerative refrigerator are:

[0062] 1. Regenerative refrigerators have relatively high refrigeration efficiency between the liquid nitrogen temperature range and the liquid hydrogen temperature range;

[0063] 2. The core components of regenerative refrigerators are simple in structure, have low manufacturing process requirements, and do not require particularly expensive materials, so they are particularly suitable for mass production, thereby significantly reducing the cost of each standard refrigeration unit;

[0064] 3. Regenerative refrigerators have considerable reliability, with maintenance-free operating lives of more than 2 years for Gifford-McMahon refrigerators, Solvay refrigerators, and GM-type pulse tube refrigerators, and more than 5 years for Stirling refrigerators and Stirling-type pulse tube refrigerators;

[0065] 4. Regenerative refrigerators generally use piston-type expansion mechanisms, so they still have a large exhaust volume during the cooling process, and the refrigeration capacity is also considerable, making them naturally have the characteristics of rapid cooling and making it easier to achieve rapid start and stop of the system.

[0066] The expansion unit can be one, and the hydrogen pipelines from the m parallel low-temperature liquefaction groups are connected to the inlet of the expansion unit, and the outlet of the expansion unit is connected to the outlet of the liquid hydrogen product; this design of providing one common expansion unit for the m parallel low-temperature liquefaction groups has the advantage of low cost;

[0067] As a preferred, the expansion units are m, each of the expansion unit inlets is connected with the hydrogen pipeline from the m parallel low-temperature liquefaction groups respectively, and the pipelines of all the expansion unit outlets are connected with the liquid hydrogen product outlet after being converged.

[0068] The expansion unit is a capillary, a throttle valve or an expander. As a preferred, the expansion unit is an adjustable throttle valve with a cutoff function.

[0069] As a specific preferred, the expansion unit is a plurality of throttle valves arranged in parallel, each of which is connected with a plurality of low-temperature liquefaction groups of the corresponding low-temperature liquefaction conversion unit.

[0070] As a preferred, the product outlet of the liquefaction module is connected with a plurality (the number is j, j≥2) of parallel liquid hydrogen storage tanks. The liquid hydrogen product pipeline from the liquefaction system is divided into j pipelines, which are respectively connected with the liquid hydrogen storage tanks through low-temperature valves. The liquid hydrogen produced by the liquefaction module is sequentially stored in the liquid hydrogen storage tanks, and the full liquid hydrogen storage tank can transfer the liquid hydrogen therein to a liquid hydrogen tank truck / ship for further transportation to a liquid hydrogen terminal customer. By adopting such a design, the liquid hydrogen storage tank being transferred can be disconnected from the liquefaction system by closing the low-temperature valve, and the liquid hydrogen produced by the liquefaction system can still be stored in other liquid hydrogen storage tanks, ensuring the continuity of liquid hydrogen production and storage.

[0071] As a further preferred, the liquid hydrogen storage tank is a tank container, and the full liquid hydrogen tank container can be transported to a liquid hydrogen terminal customer by a container trailer / ship, and the removed tank container is replaced by a new empty tank container connected to the liquefaction module. By using standardized tank containers, the process of transferring liquid hydrogen from a fixed liquid hydrogen storage tank to a liquid hydrogen tank truck / ship is cancelled, and the flashing loss of the process is reduced. For large-scale applications, a large number of standardized tank containers combined with a container trailer / ship have a cost advantage over a semi-customized fixed storage tank combined with a liquid hydrogen tank truck / ship.

[0072] When the liquid hydrogen storage tank is transferred, the tank container is replaced, or stored for a long time, part of the liquid hydrogen will vaporize, causing the pressure of the liquid hydrogen storage tank to rise, and eventually causing the safety relief system to act, resulting in the waste of hydrogen discharge. In order to re-liquefy the flashed hydrogen in the liquid hydrogen storage tank, as a preferred, a flashed vapor return pipeline is connected to one or more liquefaction modules from the top of the liquid hydrogen storage tank. That is, the top of the liquid hydrogen storage tank is provided with a flashed vapor return pipeline, and the hydrogen pipeline in one or more liquefaction modules is connected to the flashed vapor return pipeline.

[0073] As an optimization, in the liquefaction module, the flash vapor return line is connected to a cryogenic compressor, and then to the piping between the last two (the last two in the hydrogen flow direction) cryogenic cooling submodules in one or more cryogenic liquefaction groups. The flash hydrogen is compressed to high pressure by the cryogenic compressor, then merges with the incoming feedstock hydrogen and enters the last cryogenic cooling submodule to be cooled and liquefied.

[0074] Alternatively, as another optimization, in the liquefaction module, the flash vapor return line is connected to the low-pressure inlet of an ejector. The high-pressure inlet of the ejector is connected to the feed hydrogen line from the secondary hydrogen reactor in the penultimate (last) cryogenic cooling submodule of one or more cryogenic liquefaction groups. The ejector outlet is connected to the secondary hydrogen reactor in the last cryogenic cooling submodule of the cryogenic liquefaction group. The ejector uses a high-flow, high-pressure feed hydrogen stream as the main stream, pumping in a small-flow, low-pressure flash hydrogen stream. The two hydrogen streams mix in the ejector and then enter the last cryogenic cooling submodule to be cooled and liquefied. Compared to cryogenic compressors, the ejector has no moving parts, resulting in lower cost and higher reliability.

[0075] The compression unit is a compressor group composed of multiple compressors, each of which provides refrigeration compression work to the cryogenic liquefaction conversion unit.

[0076] Preferably, the compressor unit comprises m*n independent compression units, each of which is individually connected to a standard refrigeration unit. This technical solution allows for easy start-up and shutdown of each standard refrigeration unit, and the smaller compression units facilitate large-scale mass production, reducing costs.

[0077] Preferably, the cold end of the standard refrigeration unit is provided with a hydrogen pipeline and a cold working fluid pipeline, and the hydrogen pipeline is partially or entirely filled with a neutral hydrogen catalyst, which simultaneously constitutes the neutral hydrogen reactor.

[0078] Compared with existing technologies, the advantages of this invention are as follows: By using a large number of standardized refrigeration units produced in series and parallel to form modules at different levels, hydrogen liquefaction can be achieved, effectively utilizing the benefits of large-scale production of standardized refrigeration units and significantly reducing equipment costs. By controlling the number of different levels of modules and refrigeration units activated, this invention can also achieve large-scale adjustment of liquid hydrogen production capacity. Furthermore, using a regenerative refrigerator as the standard refrigeration unit allows for rapid cooling and immediate shutdown, giving the system the advantage of rapid start-up and shutdown. These advantages make this invention particularly suitable for producing green liquid hydrogen in conjunction with renewable energy sources. Attached Figure Description

[0079] Figure 1Schematic diagram of a first embodiment of the modular hydrogen liquefaction system of the present application.

[0080] Figure 2 Schematic diagram of a first embodiment of the liquefaction system in the modular hydrogen liquefaction system of the present application.

[0081] Figure 3 Schematic diagram of a second embodiment of the liquefaction system in the modular hydrogen liquefaction system of the present application.

[0082] Figure 4 Schematic diagram of a second embodiment of the modular hydrogen liquefaction system of the present application.

[0083] Figure 5 Schematic diagram of a first embodiment of the liquefaction system in the second embodiment of the modular hydrogen liquefaction system of the present application.

[0084] Figure 6 Schematic diagram of a second embodiment of the liquefaction system in the second embodiment of the modular hydrogen liquefaction system of the present application.

[0085] Correspondence between the reference signs and the component names is as follows:

[0086] 1. Hydrogen gas source; 2. Liquefaction system; 2.1. ~ 2.k. Liquefaction module; 3. Liquid hydrogen storage tank; 3.1 ~ 3.j. Liquid hydrogen storage tank;

[0087] 21. Pre-cooling unit; 22. Cryogenic liquefaction unit cryogenic liquefaction group; 22.1. ~ 22.m. Cryogenic liquefaction group; 23. Expansion unit; 24. Liquid hydrogen product outlet; 25. Compression unit; 26. Vacuum adiabatic cold box; 27. Adiabatic radiation screen; 28. Flash vapor return gas pipeline; 31. Cryogenic valve; 32. Return gas control valve; 211 Pre-cooling cold source; 212. Pre-cooling heat exchanger; 212a / b. Primary / secondary pre-cooling heat exchanger; 213. Purifier; 213a / b. Cryogenic purification adsorber; 214. Pre-cooling stage normal parahydrogen reactor; 215. Adiabatic radiation screen cooling heat exchanger; 221. Cryogenic cooling sub-module; 222. Standard refrigeration unit; 223. Normal parahydrogen reactor; 231. Throttle valve; 251. Compressor unit; 252. High-pressure gas supply pipeline; 253. Low-pressure return gas pipeline. DETAILED DESCRIPTION

[0088] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the embodiments of the present application are further described in detail below with reference to the drawings of the embodiments of the present application. However, the described embodiments are part of the embodiments of the present application, not all. Based on the embodiments of the present application, other embodiments of the present application within the scope of the present application can be obtained by non-creative labor of those skilled in the art.

[0089] Case 1:

[0090] As shown in the figure, the modular hydrogen liquefaction system comprises a hydrogen gas source 1, a liquefaction system 2 and a liquid hydrogen storage tank group 3. The hydrogen gas source 1, the liquefaction system 2 and the liquid hydrogen storage tank group 3 are connected in sequence through pipelines. Figure 1

[0091] The liquefaction system 2 comprises one or more (k≥1) parallel liquefaction modules (2.1-2.k). The liquefaction modules 2.1-2.k are standardized skid-mounted devices, i.e., the components with pre-cooling, liquefaction and conversion functions, intermediate pipelines, control valves, etc. are integrated into one whole, the standard container outer dimensions are adopted, and each module can independently operate to cool, liquefy and complete the normal para-hydrogen reaction of a certain flow of hydrogen. The liquid hydrogen storage tank group 3 comprises two or more (j≥2) parallel liquid hydrogen storage tanks 3.1-3.j; the liquid hydrogen storage tanks 3.1-3.j are tank containers.

[0092] The liquid hydrogen product outlets 24 of the respective liquefaction modules 2.1-2.k in the liquefaction system 2 are gathered into one liquid hydrogen product pipeline through pipelines, and then divided into j pipelines, which are respectively connected to the respective liquid hydrogen storage tanks 3.1-3.j. The pipelines between the liquefaction system 2 and the liquid hydrogen storage tanks 3.1-3.j are double-layer vacuum-insulated low-temperature liquid hydrogen pipelines.

[0093] The working principle of realizing hydrogen liquefaction by using the embodiment is as follows:

[0094] The raw hydrogen gas from the hydrogen gas source 1 has a normal temperature T amb (263-313K) and a pressure p supply (10-26bar), and a para-hydrogen content of about 25%. The raw hydrogen gas is divided into k paths and respectively enters the respective liquefaction modules 2.1-2.k in the liquefaction system 2, is cooled, liquefied and completes the normal para-hydrogen reaction, and flows into the liquid hydrogen storage tanks 3.1-3.j for storage. The product liquid hydrogen flowing out of the liquefaction modules 2.1-2.k has a pressure p store (1-6bar), a temperature T product , and a para-hydrogen content ≥95%. The product liquid hydrogen is a supercooled liquid, i.e., the product liquid hydrogen temperature is less than the hydrogen gas saturation temperature (T product <T sat (p store )) under its pressure. By controlling the opening and closing of the low-temperature valve 31, the product liquid hydrogen fills the respective liquid hydrogen storage tanks 3.1-3.j in sequence. The tank container filled with liquid hydrogen is transferred by the container car to the liquid hydrogen terminal customer, and the tank container being transported is replaced by a new empty tank and connected to the liquefaction system.

[0095] ​The liquid hydrogen production capacity of the entire modular hydrogen liquefaction system can be adjusted within a wide range by starting different numbers of liquefaction modules. Since each liquefaction module is an independently operating unit, the overall energy efficiency of the system will not change significantly due to the adjustment of production capacity.

[0096] Implementation Case 2:

[0097] like Figure 2 As shown, the liquefaction module in the modular hydrogen liquefaction system includes a precooling unit 21, a cryogenic liquefaction conversion unit 22, an expansion unit 23, a liquid hydrogen product outlet 24, and a compression unit 25. The precooling unit 21 includes a precooling cold source 211, a precooling heat exchanger 212, a purifier 213, and a precooling-stage secondary hydrogen reactor 214. The precooling-stage secondary hydrogen reactor 214 is filled with a secondary hydrogen catalyst. The precooling heat exchanger 212 is provided with a hydrogen flow channel for hydrogen gas and a precooling working fluid flow channel. The cryogenic liquefaction conversion unit 22 consists of one or more (m≥1) parallel independent cryogenic liquefaction groups 22.1 to 22.m. Each cryogenic liquefaction group includes one or more (n≥1) series independent cryogenic cooling submodules 221. The cryogenic cooling submodule 221 includes a standard refrigeration unit 222 and a secondary hydrogen reactor 223. The secondary hydrogen reactor 223 includes a refrigerant flow channel and a hydrogen flow channel, and the hydrogen flow channel is provided with a secondary hydrogen catalyst.

[0098] Hydrogen source 1, hydrogen flow channel of precooling heat exchanger 212, purifier 213, and precooling stage intermediate hydrogen reactor 214 are connected sequentially via pipelines or directly sealed together via interfaces; the precooling cold source is connected to the cold end inlet of the precooling working fluid flow channel of the precooling heat exchanger via pipelines, and the precooling working fluid flows through the precooling working fluid flow channel of the precooling heat exchanger to provide cooling for the hydrogen flowing through the hydrogen flow channel of the precooling stage heat exchanger, the purifier, and the precooling stage intermediate hydrogen reactor; the outlet pipeline of the precooling stage intermediate hydrogen reactor 214 is divided into m lines, which are connected in parallel to m cryogenic liquefaction groups 22.1~22.m; each cryogenic In the liquefaction unit, n intermediate hydrogen reactors 223 are connected in series via pipelines; each intermediate hydrogen reactor 223 is connected to the cold end of a standard refrigeration unit 222, and the refrigerant in the standard refrigeration unit 222 flows through the refrigerant channel of the intermediate hydrogen reactor 223 to provide cooling; the outlet pipelines of m parallel cryogenic liquefaction units are connected to an expansion unit 23, and the outlet of the expansion unit 23 is connected to a liquid hydrogen product outlet 24; the compression unit 25 is connected to m*n standard refrigeration units 222 via a gas supply pipeline to drive the standard refrigeration units 222 to provide cryogenic refrigeration.

[0099] The working principle of hydrogen liquefaction in this embodiment is as follows:

[0100] The raw material hydrogen gas comes from hydrogen source 1 and is at room temperature T. amb (263~313K), pressure is psupply (10-26 bar) and the content of para-hydrogen is about 25%, the hydrogen stream first enters the hydrogen flow channel of the pre-cooling heat exchanger 212 and is pre-cooled to a pre-cooling temperature T preC . Depending on the different forms of the pre-cooling source and the pre-cooling working medium, the pre-cooling temperature is between 60 and 150 K. The pre-cooled hydrogen then enters the purifier 213 to remove residual impurity gases such as water, CO2, N2, and solid particles, and then enters the pre-cooling stage para-hydrogen reactor 214 to complete the para-hydrogen reaction with the help of the para-hydrogen catalyst in the reactor and is re-cooled to the pre-cooling temperature T preC . The amount of catalyst in the pre-cooling stage para-hydrogen reactor 214 should be sufficient to ensure that the hydrogen leaving the pre-cooling unit 21 is as close to the equilibrium hydrogen as possible (i.e., the content of para-hydrogen is as close to the equilibrium para-hydrogen content at the pre-cooling temperature T preC as possible). The hydrogen leaving the pre-cooling unit 21 is divided into m paths and enters the m low-temperature liquefaction groups 22.1-22.m in parallel. In the low-temperature liquefaction conversion unit 22, the n standard refrigeration units 222 in each low-temperature liquefaction group work at successively decreasing temperatures T c,1 > T c,2 >... > T c,n-1 > T c,n , and the hydrogen successively passes through the n para-hydrogen reactors 223 in series; each para-hydrogen reactor 223 is connected to the cold end of a standard refrigeration unit 222, and the cold energy generated by the standard refrigeration unit 222 is transferred to the hydrogen flowing in the hydrogen flow channel through the flow of the refrigeration working medium in the refrigeration working medium flow channel of the para-hydrogen reactor 223; the hydrogen is gradually cooled in the hydrogen flow channel of the n para-hydrogen reactors, and the gradual para-hydrogen reaction is realized with the help of the para-hydrogen catalyst, reaching the throttling temperature T preExp , the content of para-hydrogen is more than 95%, and the pressure is p preExp (p preExp =p supply -Δp, where Δp is the pressure drop along the way of the hydrogen through the pre-cooling unit 21 and the low-temperature liquefaction conversion unit 22); at this time, the hydrogen is in a supercooled state.

[0101] The hydrogen cooled to a supercooled state by the low-temperature liquefaction conversion unit 22 enters the expansion unit 23, and depending on the different choices of the expansion unit, the pressure of the hydrogen in the expansion unit 23 can be reduced to p product , which can experience isentropic expansion, isenthalpic expansion, or a variable process between the two, and the temperature of the hydrogen can decrease (close to isentropic expansion) or increase (close to isenthalpic expansion). The temperature of the hydrogen leaving the expansion unit 23 is T product , which is still a supercooled liquid with a certain degree of supercooling, which can ensure that the liquid hydrogen remains in a liquid state during transportation to the liquid hydrogen storage tanks 3.1-3.j; after expansion, the supercooled liquid hydrogen product is finally transported to the downstream pipeline and stored in the liquid hydrogen storage tank through the liquid hydrogen product outlet.

[0102] The standard refrigeration unit 222 contained in the low-temperature liquefaction conversion unit 22 in the modular hydrogen liquefaction system is a regenerative refrigerator, specifically a Gifford-McMahon refrigerator, a Stirling refrigerator, a Solvay refrigerator, a GM pulse tube refrigerator, or a Stirling pulse tube refrigerator. The compression unit 25 is connected to all the standard refrigeration units 222 through gas supply lines, for driving the regenerative refrigerator to work, providing cold energy for the para-ortho hydrogen reactor 223, and realizing the cooling and para-ortho hydrogen reaction of hydrogen.

[0103] The integrated compressor set or multiple independent compressors that can be used by 25 each have independent compression functions, and can also be a large single compressor. Preferably, the integrated compressor set or multiple independent compressors, so that it can be controlled conveniently, and ensure the overall energy efficiency. In particular, when it is necessary to shut down one or more low-temperature liquefaction groups, the integrated compressor set is used, and the corresponding compressor set can be shut down, without affecting the energy efficiency of the entire compression unit.

[0104] Embodiment 3:

[0105] As shown in Figure 3 , a more detailed schematic of the liquefaction system 2 in the modular hydrogen liquefaction system, in which a precooling cold source 211 adopts a turbine Brayton cycle refrigeration system, a standard refrigeration unit 222 adopts a Gifford-McMahon refrigerator, a compression unit 25 adopts multiple independent compressor units, an expansion unit 23 adopts multiple parallel throttle control valves as expansion elements, and a vacuum adiabatic cold box 26 and an adiabatic radiation screen 27 are used as system adiabatic. The difference from embodiment 2 is that:

[0106] The precooling heat exchanger 212 is a two-stage precooling structure in series, including a first-stage precooling heat exchanger 212a and a second-stage precooling heat exchanger 212b. The low-temperature adsorption purifier 213 is composed of two parallel low-temperature adsorption purifiers 213a and 213b.

[0107] Meanwhile, in the embodiment, the precooling system 21 adopts a nitrogen turbine Brayton refrigeration cycle as a precooling cold source 211, which includes a driving motor 2111, a turbine compressor 2112, a water cooler 2113, a low-temperature turbine expander 2114, a connecting shaft 2115, and an adiabatic radiation screen cooling heat exchanger 215. The above components are connected in the following order: the high-pressure outlet of the turbine compressor 2112, the water cooler 2113, the precooling working medium inflow channel inlet of the hot end of the first-stage precooling heat exchanger 212a, the precooling working medium inflow channel outlet of the cold end of the first-stage precooling heat exchanger 212a, the precooling working medium inflow channel inlet of the hot end of the second-stage precooling heat exchanger 212b, the precooling working medium inflow channel outlet of the cold end of the second-stage precooling heat exchanger 212b, the inlet of the low-temperature turbine expander 2114, the outlet of the low-temperature turbine expander 2114, the adiabatic radiation screen cooling heat exchanger 215, the precooling working medium return flow channel inlet of the cold end of the second-stage precooling heat exchanger 212b, the precooling working medium return flow channel outlet of the hot end of the second-stage precooling heat exchanger 212b, the precooling working medium return flow channel inlet of the cold end of the first-stage precooling heat exchanger 212a, the precooling working medium return flow channel outlet of the hot end of the first-stage precooling heat exchanger 212a, and the low-pressure inlet of the turbine compressor 2112, sequentially connected to form a loop. The turbine compressor 2112 and the low-temperature turbine expander 2114 are mechanically coupled through the connecting shaft 2115, and the driving motor 2111 is arranged on the connecting shaft 2115.

[0108] In the embodiment, the working principle of the precooling cold source 211 of the turbine Brayton refrigeration system is as follows: the precooling working medium is compressed to high pressure by the turbine compressor 2112, and the compression heat generated by compression is taken away by the water cooler 2113 to reduce the temperature to about room temperature. After compression and cooling, the precooling working medium enters the first-stage precooling heat exchanger 212a and the second-stage precooling heat exchanger 212b in sequence, and is cooled to about 100-120 K by the return cold working medium. Subsequently, the precooling working medium enters the low-temperature turbine expander 2114 for expansion refrigeration. According to the working medium and the pressure after expansion, the temperature of the precooling working medium can finally be reduced to about 80-100 K. The low-temperature and low-pressure precooling working medium returns to the adiabatic radiation screen cooling heat exchanger 215, the second-stage precooling heat exchanger 212b, and the first-stage precooling heat exchanger 212a in sequence to precool the inflow high-pressure working medium and the raw hydrogen gas, and is finally returned to the low-pressure inlet of the turbine compressor 2112 after being warmed to about room temperature and leaving the first-stage precooling heat exchanger 212a. The driving motor 2111 provides main driving force to drive the turbine compressor 2112, and the expansion work of the low-temperature turbine expander 2114 is recovered through the connecting shaft 2115 to provide auxiliary driving force for the turbine compressor 2112.

[0109] The pre-cooling process of hydrogen is described in more detail in this embodiment. The hydrogen source 1 is connected to the hydrogen flow inlet of the hot end of the first-stage pre-cooling heat exchanger 212a. The raw hydrogen flows through the hydrogen flow channels of the first-stage pre-cooling heat exchanger 212a and the second-stage pre-cooling heat exchanger 212b in sequence, and then is connected to the parallel low-temperature adsorption purifiers 213a and 213b. The low-temperature adsorption purifiers 213a and 213b form a typical temperature swing adsorption device. The two adsorbers are switched by valves and are connected to the pipeline alternately. The adsorber not connected to the pipeline is purged and heated by clean inert gas to realize regeneration. The parallel low-temperature adsorption purifiers 213a and 213b are connected to the inlet of the hot end of the second-stage pre-cooling heat exchanger 212b through the pipeline, and then enter the pre-cooling primary and secondary hydrogen reactor 214 in the second-stage pre-cooling heat exchanger 212b. In this embodiment, the pre-cooling primary and secondary hydrogen reactor 214 is an isothermal reactor coupled in the second-stage pre-cooling heat exchanger 212b. The catalyst particles are filled in the heat exchange channel of the heat exchanger to realize the primary and secondary hydrogen catalytic reaction while heat exchanging. This isothermal reactor has high reaction efficiency and low irreversible loss. After the raw hydrogen leaves the pre-cooling primary and secondary hydrogen reactor 214, it is connected to the inlet of the first primary and secondary hydrogen reactor 223 of each low-temperature liquefaction group 22.1-22.m in parallel.

[0110] In this embodiment, the cold end of the standard refrigeration unit 222 of the Gifford-McMahon refrigerator is connected to the primary and secondary hydrogen reactor 223. When the Gifford-McMahon refrigerator operates, the refrigeration working medium expands at the cold end and alternately flows through the refrigeration working medium flow channel in the primary and secondary hydrogen reactor 223, providing cooling and the required cold energy for the primary and secondary hydrogen reaction of the hydrogen flowing through the hydrogen flow channel of the primary and secondary hydrogen reactor 223. After passing through each primary and secondary hydrogen reactor 223, the hydrogen is gradually cooled and the primary and secondary hydrogen reaction is completed. After passing through n series-connected primary and secondary hydrogen reactors 223, the hydrogen reaches the temperature T preExp , the content of secondary hydrogen reaches more than 95%, and the pressure is p preExp (p preExp =p supply -Δp, where Δp is the pressure drop along the way of the hydrogen through the pre-cooling unit 21 and the low-temperature liquefaction conversion unit 22); at this time, the hydrogen is in a supercooled state.

[0111] In this embodiment, the compression unit 25 is composed of m*n independent compression units 251. Each compression unit 251 is connected to each Gifford-McMahon refrigerator of each standard refrigeration unit 222 through a high-pressure gas supply pipe 252 and a low-pressure gas return pipe 253 to drive the Gifford-McMahon refrigerator to work. The independent compression unit 251 can be mass-produced, thereby reducing the cost of the compression unit. In addition, the independent compression unit 251 can be started and stopped independently, so that the system can be adjusted in a wider range of working conditions, and the reliability is higher.

[0112] The expansion unit 23 is described in more detail in this embodiment: the expansion unit 23 includes m independent adjustable throttling valves 231 with a cutoff function. The hydrogen gas from the last para-ortho hydrogen reactor 223 of the m parallel low-temperature liquefaction groups 22.1-22.m is connected to the m independent throttling valves 231, respectively. The m routes of hydrogen gas are isenthalpically throttled and expanded in the m throttling valves 231, and the pressure is reduced from p preExp to T product , and the temperature is slightly increased from T preExp to T product . The throttled hydrogen gas is still a liquid with a certain degree of subcooling, and the m routes of throttled hydrogen gas are combined into one route and connected to the liquid hydrogen product interface 24.

[0113] In order to reduce the heat leakage from the environment to the low-temperature part of the system, a vacuum insulated cold box 26 and an insulated radiation screen 27 are used as the system insulation in this embodiment. The insulated radiation screen 27, the pre-cooling unit 21, the expansion unit 23, and the low-temperature part of the low-temperature cooling sub-module (including the cold finger of the standard refrigeration unit and the para-ortho hydrogen reactor) are installed in the vacuum insulated cold box 26. The interior of the vacuum insulated cold box 26 is evacuated to reduce convective and conductive heat leakage from the environment. The insulated radiation screen 27 is made of a thin metal shell with good thermal conductivity, and the surface is polished to have a high reflectivity. The insulated radiation screen is connected to the insulated radiation screen cooling heat exchanger 215 through thermal connection and is cooled to the pre-cooling temperature T preC . The insulated radiation screen surrounds the expansion unit and the lowest temperature part of the low-temperature cooling sub-module, further reducing the radiation heat leakage from room temperature to the above-mentioned components.

[0114] Embodiment 4:

[0115] As Figure 4As shown in Fig. 3, a modular hydrogen liquefaction system with a flash gas return line to recover the flash gas and re-liquefy it. When the liquid hydrogen storage tanks are being filled, replaced or stored for a long time, some of the liquid hydrogen will vaporize, causing the pressure of the liquid hydrogen storage tanks to rise, and eventually triggering the safety relief system to release the hydrogen gas, which is a waste. In this embodiment, the flash gas from the liquid hydrogen storage tanks is recovered by a flash gas return line and re-liquefied in one of the liquefaction modules (any one of the liquefaction modules 2.1 to 2.k) in the liquefaction system 2. In this embodiment, it is different from the embodiment 2 in that it further includes a flash gas return line 28 and a return control valve 32. The flash gas return line is connected to the top of each liquid hydrogen storage tank, and then the flash gas return lines from the liquid hydrogen storage tanks are connected to one of the liquefaction modules in the liquefaction system 2 through a return control valve 32.

[0116] As shown in Fig. 3, a modular hydrogen liquefaction system with a flash gas return line to recover the flash gas and re-liquefy it. When the liquid hydrogen storage tanks are being filled, replaced or stored for a long time, some of the liquid hydrogen will vaporize, causing the pressure of the liquid hydrogen storage tanks to rise, and eventually triggering the safety relief system to release the hydrogen gas, which is a waste. In this embodiment, the flash gas from the liquid hydrogen storage tanks is recovered by a flash gas return line and re-liquefied in one of the liquefaction modules (any one of the liquefaction modules 2.1 to 2.k) in the liquefaction system 2. In this embodiment, it is different from the embodiment 2 in that it further includes a flash gas return line 28 and a return control valve 32. The flash gas return line is connected to the top of each liquid hydrogen storage tank, and then the flash gas return lines from the liquid hydrogen storage tanks are connected to one of the liquefaction modules in the liquefaction system 2 through a return control valve 32. reV,high,set When the pressure of the liquid hydrogen storage tank is higher than the set value p reV,low,set , the cryogenic valve 31 is closed, the return control valve 32 is opened, and the flash gas in the liquid hydrogen storage tank is returned to the liquefaction module 2.1 through the flash gas return line 28. The flash gas returned to the liquefaction module 2.1 is re-liquefied, and the working principle will be described in detail in embodiments 5 and 6. When the flash gas continuously flows out of the liquid hydrogen storage tank, the pressure in the tank gradually decreases, and when the pressure is less than the set value p reV,low,set , the cryogenic valve 31 is opened, the return control valve 32 is closed, and the liquid hydrogen storage tank stops returning the gas and continues to receive the liquid hydrogen product from the liquefaction system 2.

[0117] Embodiment 5:

[0118] As shown in Fig. 3, a modular hydrogen liquefaction system with a flash gas return line to recover the flash gas and re-liquefy it. When the liquid hydrogen storage tanks are being filled, replaced or stored for a long time, some of the liquid hydrogen will vaporize, causing the pressure of the liquid hydrogen storage tanks to rise, and eventually triggering the safety relief system to release the hydrogen gas, which is a waste. In this embodiment, the flash gas from the liquid hydrogen storage tanks is recovered by a flash gas return line and re-liquefied in one of the liquefaction modules (any one of the liquefaction modules 2.1 to 2.k) in the liquefaction system 2. In this embodiment, it is different from the embodiment 2 in that it further includes a flash gas return line 28 and a return control valve 32. The flash gas return line is connected to the top of each liquid hydrogen storage tank, and then the flash gas return lines from the liquid hydrogen storage tanks are connected to one of the liquefaction modules in the liquefaction system 2 through a return control valve 32. Figure 5 As shown in Fig. 3, a modular hydrogen liquefaction system with a flash gas return line to recover the flash gas and re-liquefy it. When the liquid hydrogen storage tanks are being filled, replaced or stored for a long time, some of the liquid hydrogen will vaporize, causing the pressure of the liquid hydrogen storage tanks to rise, and eventually triggering the safety relief system to release the hydrogen gas, which is a waste. In this embodiment, the flash gas from the liquid hydrogen storage tanks is recovered by a flash gas return line and re-liquefied in one of the liquefaction modules (any one of the liquefaction modules 2.1 to 2.k) in the liquefaction system 2. In this embodiment, it is different from the embodiment 2 in that it further includes a flash gas return line 28 and a return control valve 32. The flash gas return line is connected to the top of each liquid hydrogen storage tank, and then the flash gas return lines from the liquid hydrogen storage tanks are connected to one of the liquefaction modules in the liquefaction system 2 through a return control valve 32.

[0119] Implementation Case 6:

[0120] like Figure 6 The diagram illustrates a detailed alternative technical solution for liquefaction system 2 in a modular hydrogen liquefaction system that utilizes a return gas pipeline to recover flash hydrogen for reliquefaction. Unlike embodiment 5, this embodiment uses a cryogenic compressor 292 instead of the ejector 291. The flash gas return gas pipeline 28 is connected to the low-pressure inlet of the cryogenic compressor 292, and the high-pressure outlet of the cryogenic compressor 292 is connected to the hydrogen flow outlet of the secondary hydrogen reactor 223 in the penultimate cryogenic cooling submodule 221 (1.n-1) of the cryogenic liquefaction group 22.1. The raw material hydrogen and the compressed flash hydrogen merge and enter the hydrogen flow channel of the secondary hydrogen reactor 223 in the last cryogenic cooling submodule 221 (1.n) of the cryogenic liquefaction group 22.1, where they are cooled and liquefied.

Claims

1. A modular hydrogen liquefaction system, characterized by, The application relates to a hydrogen liquefying system. The hydrogen liquefying system comprises a plurality of parallelly arranged hydrogen liquefying modules, a hydrogen inlet of the hydrogen liquefying module is connected with a hydrogen source, and a product outlet of the hydrogen liquefying module is connected with a plurality of parallelly arranged liquid hydrogen storage tanks; each of the hydrogen liquefying modules is an integrated structure which can independently start and stop and has the functions of hydrogen cooling, liquefying and completing primary-secundary hydrogen conversion. The hydrogen liquefying module comprises: a precooling unit for precooling and cooling hydrogen; the precooling unit comprises a precooling heat exchanger, a precooling cold source for providing a cold source for the precooling heat exchanger, a purifier and a precooling primary-secundary hydrogen reactor which are sequentially connected with a hydrogen flow channel of the precooling heat exchanger; a low-temperature liquefying and converting unit for low-temperature liquefying and converting hydrogen after precooling; an expansion unit for decompressing hydrogen after low-temperature liquefying and converting, wherein an outlet of the expansion unit is connected with the liquid hydrogen storage tank; a compression unit for providing refrigeration compression work for the low-temperature liquefying and converting unit; the compression unit is an integrated compressor set or a plurality of independent compressors; the low-temperature liquefying and converting unit is composed of a plurality of parallelly arranged low-temperature liquefying groups, each of the low-temperature liquefying groups is composed of a plurality of serially arranged low-temperature cooling sub-modules, and each of the low-temperature cooling sub-modules comprises a standard refrigeration unit and a primary-secundary hydrogen reactor which is connected with a cold end of the standard refrigeration unit; the standard refrigeration unit is provided with a hydrogen pipeline and a cold working medium pipeline in the cold end, a part or all of the hydrogen pipeline is provided with a primary-secundary hydrogen catalyst, and the part or all of the hydrogen pipeline simultaneously constitutes the primary-secundary hydrogen reactor; a refrigeration working medium of the standard refrigeration unit directly flows in a refrigeration working medium flow channel of the primary-secundary hydrogen reactor, and provides cold energy required by hydrogen cooling and primary-secundary hydrogen reaction; the primary-secundary hydrogen reactor is provided with a primary-secundary hydrogen catalyst in a hydrogen flow channel, and is used for catalyzing primary-secundary hydrogen reaction; and the standard refrigeration unit is a regenerative refrigerator; for each low-temperature liquefying group, the hydrogen flow channel of the primary-secundary hydrogen reactor is sequentially connected in series according to the hydrogen flow direction, and the cold head temperature of the standard refrigeration unit or the temperature of the primary-secundary hydrogen reactor is sequentially reduced.

2. The modular hydrogen liquefaction system of claim 1, wherein, the precooling cold source is provided by a precooling circulation system: a turbine compressor for compressing precooling working medium to high pressure; a driving motor for driving the turbine compressor to work; a water cooler for cooling high-pressure gas output by the turbine compressor; a low-temperature turbine expander for expanding and refrigerating working medium output by a precooling working medium inflow flow channel of the precooling heat exchanger; the precooling heat exchanger is provided with a hydrogen flow channel, a precooling working medium inflow flow channel and a precooling working medium return flow channel; the inlet of the precooling working medium inflow flow channel is connected with the outlet of the water cooler, the outlet of the precooling working medium inflow flow channel is connected with the inlet of the low-temperature turbine expander, the inlet of the precooling working medium return flow channel is connected with the outlet of the low-temperature turbine expander, and the outlet of the precooling working medium return flow channel is connected with the inlet of the turbine compressor.

3. The modular hydrogen liquefaction system of claim 2, wherein, the turbine compressor recovers expansion work generated by the low-temperature turbine expander through a connecting shaft connected between the turbine compressor and the low-temperature turbine expander.

4. The modular hydrogen liquefaction system of claim 1, wherein, The liquefaction module further comprises a vacuum adiabatic cold box and an adiabatic radiation screen, which is in thermal connection with the pre-cooling unit; the expansion unit and the lowest temperature part of the low-temperature liquefaction conversion unit are arranged in the adiabatic radiation screen; the adiabatic radiation screen, the low-temperature part of the pre-cooling unit and the low-temperature part of the low-temperature liquefaction conversion unit are arranged in the vacuum adiabatic cold box.

5. The modular hydrogen liquefaction system of claim 1, wherein, The regenerative refrigerator is a Gifford-McMahon refrigerator, a Stirling refrigerator, a Solvay refrigerator, a GM-type pulse tube refrigerator or a Stirling-type pulse tube refrigerator.

6. The modular hydrogen liquefaction system of claim 1, wherein, The liquid hydrogen storage tank is a tank container.

7. The modular hydrogen liquefaction system of claim 1, wherein, The liquid hydrogen storage tank is provided with a flash vapor return pipe at the top, which is connected with the hydrogen pipeline in one or more of the liquefaction modules.

8. The modular hydrogen liquefaction system of claim 1, wherein, The liquid hydrogen storage tank is provided with a flash vapor return pipe at the top, which is connected with the hydrogen pipeline in one or more of the liquefaction modules. Further comprising a low-temperature compressor, the inlet of which is connected with the flash vapor return pipe, and the outlet of which is connected with the pipeline between the last first and second low-temperature cooling sub-modules in one or several low-temperature liquefaction groups. Or further comprising an ejector, the low-pressure inlet of which is connected with the flash vapor return pipe, the high-pressure inlet of which is connected with the outlet pipeline of the second last low-temperature cooling sub-module in one or several low-temperature liquefaction groups, and the outlet of which is connected with the inlet pipeline of the last first low-temperature cooling sub-module in the corresponding low-temperature liquefaction group.

9. The modular hydrogen liquefaction system of claim 1, wherein, The compression unit is a compressor set composed of multiple compressors, which respectively provide refrigeration compression work for the low-temperature liquefaction conversion unit.

10. The modular hydrogen liquefaction system of claim 1, wherein, The expansion unit is multiple throttling valves arranged in parallel, each of which is connected with the outlet of the corresponding low-temperature liquefaction group.

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