Hydrogen liquefaction low-temperature circulating system

Abstract

According to the hydrogen liquefaction low-temperature circulating system, hydrogen at an outlet of a hydrogen liquefaction low-temperature compressor unit is pre-cooled through a mechanical low-temperature pre-cooling cycle and subjected to ortho-secondary conversion heat exchange through a third heat exchanger, enters a second electromagnetic three-way valve and is divided into two parts, one part enters a back four-stage heat exchanger for ortho-secondary conversion heat exchange, and the other part enters a back four-stage heat exchanger for ortho-secondary conversion heat exchange; a saturated gas-liquid mixture of hydrogen generated by a hydrogen throttle valve enters a liquid hydrogen Dewar, and gas generated in the liquid hydrogen Dewar and another part of cold hydrogen entering a four-stage turbo expander for adiabatic expansion refrigeration are converged at a third electromagnetic three-way valve along a return pipe; and the hydrogen flows back to the first electromagnetic three-way valve and is converged with the hydrogen source precooled by the mechanical low-temperature precooling cycle to enter the hydrogen liquefaction low-temperature compressor unit, so that the hydrogen liquefaction cycle is completed. Hydrogen at an inlet of the hydrogen liquefaction low-temperature compressor unit is pre-cooled through the mechanical low-temperature pre-cooling circulation, and the compression work is reduced through low-temperature compression, so that the system efficiency is improved; the compressor is an oil-free gas suspension centrifugal compressor, oil removal and oil return are not needed, and the reliability of the system is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of low-temperature refrigeration, in particular to a hydrogen liquefaction low-temperature circulation system. Background Art

[0002] There are three main liquefaction cycles for liquid hydrogen production methods: throttling hydrogen liquefaction cycle, hydrogen liquefaction cycle with expander, and helium refrigeration hydrogen liquefaction cycle. Comparing the unit energy consumption of hydrogen liquefaction, the hydrogen liquefaction cycle with liquid nitrogen precooling and expander has the lowest energy consumption, the hydrogen liquefaction cycle with helium refrigeration has the middle energy consumption, and the throttling hydrogen liquefaction cycle has the highest energy consumption. Therefore, the most commonly used one is the hydrogen liquefaction cycle with liquid nitrogen precooling and expander.

[0003] In the hydrogen liquefaction cycle with liquid nitrogen pre-cooling and expansion machine, the purpose of liquid nitrogen pre-cooling is to save the cooling capacity in the hydrogen liquefaction process and improve the liquefaction coefficient of the cycle. However, room temperature compression is often used in this cycle. Hydrogen is difficult to be compressed at room temperature, and it is easy to generate higher compression heat during the room temperature compression process, causing a large compression temperature rise, consuming more compression work, and resulting in reduced system efficiency. In addition, traditional liquid nitrogen preparation utilizes gas separation technology, including compression, cooling, drying and separation. The preparation process is complicated and the liquefaction rate is low. The use of liquid nitrogen pre-cooling will reduce the economy of the circulation system.

[0004] The hydrogen liquefaction cycle with expander often uses screw compressors. In order to ensure the stable and efficient operation of the compressor, lubricating oil is required. Therefore, the system requires precise oil-gas separation technology and supporting complex oil separation, cooling and filtration equipment. If the oil removal is not precise enough, it may cause oil pollution, oil freezing and other disasters at low temperatures. Summary of the invention

[0005] The utility model aims to solve the existing problems of high energy consumption, poor economy and need for oil removal in hydrogen liquefaction, and provides a hydrogen liquefaction low-temperature circulation system which is economical, energy-saving, highly efficient and free of oil pollution.

[0006] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0007] A hydrogen liquefaction cryogenic circulation system, characterized in that it includes a hydrogen liquefaction circulation system and a mechanical cryogenic precooling circulation system; the mechanical cryogenic precooling circulation system provides precooling for the hydrogen liquefaction circulation system; the hydrogen liquefaction circulation system includes a first electromagnetic three-way valve, a hydrogen liquefaction cryogenic compressor unit, a second electromagnetic three-way valve, an expansion pipeline throttle valve, a first turbine expander, a second turbine expander, a third turbine expander, a fourth turbine expander, a third electromagnetic three-way valve, a hydrogen throttle valve, a liquid hydrogen dewar, a liquid storage tank, a gate valve, a heat exchanger, a first heat exchanger, a second heat exchanger, a third heat exchanger, a fourth turbine expander, a third electromagnetic three-way valve, a hydrogen throttle valve, a liquid hydrogen dewar, a liquid storage tank, a gate valve, a heat exchanger, a first heat exchanger, a second heat exchanger, a third heat exchanger, a fourth The fourth heat exchanger, the fifth heat exchanger, the sixth heat exchanger, the seventh heat exchanger, the third heat exchanger para-hydrogen conversion channel, the fourth heat exchanger para-hydrogen conversion channel, the fifth heat exchanger para-hydrogen conversion channel, the sixth heat exchanger para-hydrogen conversion channel, and the seventh heat exchanger para-hydrogen conversion channel, the number of the heat exchangers can be increased or decreased accordingly according to the scale of the system; the hydrogen liquefaction low-temperature compressor unit includes a first low-temperature compressor, an intermediate heat exchanger, and a second low-temperature compressor; the mechanical low-temperature pre-cooling circulation system includes a mechanical low-temperature compressor, an aftercooler, a turbine expander, a regenerator, and an electromagnetic three-way valve.

[0008] In some preferred embodiments, the outlet of the hydrogen liquefaction cryogenic compressor unit is connected to the hydrogen channel inlet of the second heat exchanger, the hydrogen channel outlet of the second heat exchanger is connected to the inlet of the third heat exchanger positive para-hydrogen conversion channel, the outlet of the third heat exchanger positive para-hydrogen conversion channel is connected to the second electromagnetic three-way valve inlet A, the second electromagnetic three-way valve outlet B is connected to the hydrogen throttle valve inlet through the fourth heat exchanger positive para-hydrogen conversion channel, the fifth heat exchanger positive para-hydrogen conversion channel, the sixth heat exchanger positive para-hydrogen conversion channel, and the seventh heat exchanger positive para-hydrogen conversion channel, the hydrogen throttle valve outlet is connected to the inlet of the liquid hydrogen Dewar, and the liquid hydrogen Dewar is connected to the liquid storage tank; the second electromagnetic three-way valve outlet C is connected to the first turbine expander inlet through the expansion pipeline throttle valve, and the first turbine The expander outlet is connected to the second turbine expander inlet through the fourth heat exchanger, the second turbine expander outlet is connected to the third turbine expander inlet through the fifth heat exchanger, the third turbine expander outlet is connected to the fourth turbine expander inlet through the sixth heat exchanger, and the fourth turbine expander outlet is connected to the third electromagnetic three-way valve inlet C; the gas generated by the liquid hydrogen Dewar is connected to the third electromagnetic three-way valve inlet B along the reflux pipeline through the seventh heat exchanger, and the third electromagnetic three-way valve outlet A is connected to the first electromagnetic three-way valve inlet B through the sixth heat exchanger, the fifth heat exchanger, the fourth heat exchanger, the third heat exchanger, and the second heat exchanger. The hydrogen source pre-cooled by the mechanical low-temperature pre-cooling circulation system entering the first electromagnetic three-way valve inlet A merges into the inlet of the hydrogen liquefaction low-temperature compressor unit.

[0009] Preferably, the hydrogen source is purified hydrogen.

[0010] In some preferred embodiments, the outlet of the mechanical low-temperature compressor is connected to the inlet of the aftercooler, the outlet of the aftercooler is connected to the inlet of the compression end of the turbine expander, the outlet of the compression end of the turbine expander is connected to the inlet of the first channel of the regenerator, the outlet of the first channel of the regenerator is connected to the inlet of the expansion end of the turbine expander, the outlet of the expansion end of the turbine expander is connected to the inlet B of the electromagnetic three-way valve, the outlet A of the electromagnetic three-way valve is connected to the inlet of the second channel of the regenerator after heat exchange with the outlet C of the electromagnetic three-way valve through the first heat exchanger and the hydrogen liquefaction low-temperature compressor unit through the second heat exchanger, and the outlet of the second channel of the regenerator is connected to the inlet of the mechanical low-temperature compressor.

[0011] In some preferred embodiments, the first electromagnetic three-way valve, the hydrogen liquefaction low-temperature compressor unit, the second electromagnetic three-way valve, the expansion pipeline throttle valve, the first turbine expander, the second turbine expander, the third turbine expander, the fourth turbine expander, the third electromagnetic three-way valve, the hydrogen throttle valve, the first heat exchanger, the second heat exchanger, the third heat exchanger, the fourth heat exchanger, the fifth heat exchanger, the sixth heat exchanger, the seventh heat exchanger, the third heat exchanger normal para-hydrogen conversion channel, the fourth heat exchanger normal para-hydrogen conversion channel, the fifth heat exchanger normal para-hydrogen conversion channel, the sixth heat exchanger normal para-hydrogen conversion channel, the seventh heat exchanger normal para-hydrogen conversion channel, the turbine expander, the regenerator, and the electromagnetic three-way valve are all arranged in a vacuum cold tank.

[0012] In some preferred embodiments, the hydrogen liquefaction cryogenic compressor unit is an oil-free gas-suspended centrifugal compressor, which is supported by gas-suspended bearings or magnetic-gas hybrid bearings. The compression is low-temperature compression. The hydrogen liquefaction cryogenic compressor unit uses 1-4 centrifugal compressors in series to achieve 1-10 stages of compression. The compressor stages are pre-cooled by a mechanical low-temperature pre-cooling cycle. The compressor inlet temperature is between 30K and 250K, and the working fluid used is hydrogen.

[0013] In some preferred embodiments, the mechanical low-temperature compressor is an oil-free air-suspended centrifugal compressor, which is supported by air-suspended bearings or magnetic hybrid bearings. The compression is room temperature compression, and the compressor inlet temperature is between 230K and 340K.

[0014] In some preferred embodiments, the working fluid used in the mechanical low-temperature pre-cooling circulation system is air, nitrogen, neon, argon, helium and other gases.

[0015] In some preferred embodiments, the third heat exchanger's normal-para hydrogen conversion channel, the fourth heat exchanger's normal-para hydrogen conversion channel, the fifth heat exchanger's normal-para hydrogen conversion channel, the sixth heat exchanger's normal-para hydrogen conversion channel and the seventh heat exchanger's normal-para hydrogen conversion channel are all filled with normal-para hydrogen catalytic converters, which can achieve continuous normal-para hydrogen conversion.

[0016] The advantages of the utility model using the above technical solution are:

[0017] (1) The utility model changes the traditional liquid nitrogen pre-cooling into mechanical low-temperature pre-cooling cycle pre-cooling, so that the two parts of hydrogen entering the hydrogen liquefaction cryogenic compressor unit are pre-cooled by the mechanical low-temperature pre-cooling cycle. The low-temperature compression reduces the compression work and effectively improves the system efficiency;

[0018] (2) The utility model adopts a mechanical low-temperature precooling cycle to precool the hydrogen liquefaction system. Compared with liquid nitrogen precooling, the working fluid used in the mechanical low-temperature precooling cycle is air, nitrogen, neon, argon and helium, which are easy to obtain, cheap and pollution-free. In addition, the regenerative cycle is adopted, the compression work and expansion work are effectively reduced, the irreversible loss is significantly reduced, and the economy of the system is greatly improved;

[0019] (3) The hydrogen liquefaction cryogenic compressor unit and the mechanical cryogenic compressor of the utility model both adopt oil-free gas suspension centrifugal compressors, which have the advantages of oil-free, high heat transfer efficiency, no friction, long service life, high speed, compact structure, simple system, stable and reliable operation, energy saving and high efficiency, etc., avoiding the problems of oil pollution and oil freezing, and reliability will be significantly improved;

[0020] (4) The hydrogen liquefaction cryogenic compressor unit described in the utility model adopts two two-stage compression type centrifugal compressors connected in series to achieve four-stage compression. A mechanical low-temperature pre-cooling cycle is performed between the two compressors to keep the hydrogen at the inlet of the second compressor in a low-temperature state. Inter-stage cooling effectively reduces the compression heat, and low-temperature compression improves the thermodynamic performance of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A flow chart of an open hydrogen liquefaction low-temperature circulation system provided in Example 1 of the utility model.

[0022] Figure 2 A flow chart of a closed hydrogen liquefaction low-temperature circulation system provided in Example 2 of the utility model.

[0023] Figure 3 This is a schematic diagram of the process flow of the hydrogen liquefaction cryogenic compressor unit provided in an embodiment of the utility model.

[0024] Figure 4 This is a schematic diagram of the process flow of the hydrogen liquefaction room temperature compressor unit.

[0025] In the above figure, it includes a hydrogen liquefaction circulation system 1, a first electromagnetic three-way valve 101, a second electromagnetic three-way valve 102, an expansion pipeline throttle valve 103, a first turbine expander 104, a second turbine expander 105, a third turbine expander 106, a fourth turbine expander 107, a third electromagnetic three-way valve 108, a hydrogen throttle valve 109, a liquid hydrogen dewar 110, a liquid storage tank 111, a gate valve 112, a heat exchanger 113, a first heat exchanger 121, a second heat exchanger 122, a third heat exchanger 123, a fourth heat exchanger 124, a fifth heat exchanger 125, a sixth heat exchanger 126, a seventh heat exchanger 127, and a third heat exchanger normal-para-hydrogen conversion channel 131, the fourth heat exchanger normal para-hydrogen conversion channel 132, the fifth heat exchanger normal para-hydrogen conversion channel 133, the sixth heat exchanger normal para-hydrogen conversion channel 134, the seventh heat exchanger normal para-hydrogen conversion channel 135; the mechanical low-temperature pre-cooling circulation system 2, the mechanical low-temperature compressor 201, the aftercooler 202, the turbine expander 203, the regenerator 204, the electromagnetic three-way valve 205; the vacuum cold tank 3; the hydrogen liquefaction low-temperature compressor unit 4, the first low-temperature compressor 401, the intermediate heat exchanger 402, the second low-temperature compressor 403; the hydrogen liquefaction normal temperature compressor unit 5, the first normal temperature compressor 501, the intermediate cooler 502, the second normal temperature compressor 503. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0027] Example 1

[0028] The utility model provides an open hydrogen liquefaction low temperature circulation system, please refer to Figure 1 , including a hydrogen liquefaction circulation system 1 and a mechanical low-temperature precooling circulation system 2, wherein the mechanical low-temperature precooling circulation system 2 provides precooling for the hydrogen liquefaction circulation system 1, and its working mode is as follows:

[0029] The outlet of the hydrogen liquefaction cryogenic compressor unit 4 is connected to the inlet of the hydrogen channel of the second heat exchanger 122, the outlet of the hydrogen channel of the second heat exchanger 122 is connected to the inlet of the third heat exchanger normal para-hydrogen conversion channel 123, the outlet of the third heat exchanger normal para-hydrogen conversion channel 123 is connected to the inlet A of the second electromagnetic three-way valve 102, the outlet B of the second electromagnetic three-way valve 102 is connected to the inlet of the hydrogen throttle valve 109 through the fourth heat exchanger normal para-hydrogen conversion channel 132, the fifth heat exchanger normal para-hydrogen conversion channel 133, the sixth heat exchanger normal para-hydrogen conversion channel 134, and the seventh heat exchanger normal para-hydrogen conversion channel 135, the outlet of the hydrogen throttle valve 109 is connected to the inlet of the liquid hydrogen Dewar 110, and the liquid hydrogen Dewar 110 is connected to the liquid storage tank 111; the outlet C of the second electromagnetic three-way valve 102 is connected to the inlet of the first turbine expander 104 through the expansion pipeline throttle valve 103, and the outlet 104 of the first turbine expander is connected to the inlet of the first turbine expander through the fourth The heat exchanger 124 is connected to the inlet of the second turbine expander 105, the outlet of the second turbine expander 105 is connected to the inlet of the third turbine expander 106 through the fifth heat exchanger 125, the outlet of the third turbine expander 106 is connected to the inlet of the fourth turbine expander 107 through the sixth heat exchanger 126, and the outlet of the fourth turbine expander 107 is connected to the inlet C of the third electromagnetic three-way valve 108; the gas generated by the liquid hydrogen dewar 110 is connected to the inlet B of the third electromagnetic three-way valve 108 along the reflux pipeline through the seventh heat exchanger 127, and the outlet A of the third electromagnetic three-way valve 108 is connected to the inlet B of the first electromagnetic three-way valve 101 through the sixth heat exchanger 126, the fifth heat exchanger 125, the fourth heat exchanger 124, the third heat exchanger 123, and the second heat exchanger 122, and merges with the hydrogen source pre-cooled by the mechanical low-temperature pre-cooling circulation system 2 entering the inlet A of the first electromagnetic three-way valve 101 to enter the inlet of the hydrogen liquefaction low-temperature compressor unit 4.

[0030] The outlet of the mechanical low-temperature compressor 201 is connected to the inlet of the aftercooler 202, the outlet of the aftercooler 202 is connected to the compression end inlet of the turbine expander 203, the compression end outlet of the turbine expander 203 is connected to the first channel inlet of the regenerator 204, the first channel outlet of the regenerator 204 is connected to the expansion end inlet of the turbine expander 203, the expansion end outlet of the turbine expander 203 is connected to the inlet B of the electromagnetic three-way valve 205, the outlet A of the electromagnetic three-way valve 205 is connected to the outlet C of the electromagnetic three-way valve 205 through the first heat exchanger 121 through the second heat exchanger 122 and the hydrogen liquefaction low-temperature compressor unit 4, and then merged to be connected to the second channel inlet of the regenerator 204, and the second channel outlet of the regenerator 204 is connected to the inlet of the mechanical low-temperature compressor 201.

[0031] Example 2

[0032] The utility model provides a closed hydrogen liquefaction low temperature circulation system, please refer to Figure 2, including a hydrogen liquefaction circulation system 1 and a mechanical low-temperature precooling circulation system 2, wherein the mechanical low-temperature precooling circulation system 2 provides precooling for the hydrogen liquefaction circulation system 1, and its working mode is as follows:

[0033] The outlet of the hydrogen liquefaction cryogenic compressor unit 4 is connected to the inlet of the hydrogen channel of the second heat exchanger 122, the outlet of the hydrogen channel of the second heat exchanger 122 is connected to the inlet of the normal-para-hydrogen conversion channel 123 of the third heat exchanger, the outlet of the normal-para-hydrogen conversion channel 123 of the third heat exchanger is connected to the inlet A of the second electromagnetic three-way valve 102, and the outlet B of the second electromagnetic three-way valve 102 is connected to the normal-para-hydrogen conversion channel 132 of the fourth heat exchanger, the normal-para-hydrogen conversion channel 133 of the fifth heat exchanger, the normal-para-hydrogen conversion channel 134 of the sixth heat exchanger, and the normal-para-hydrogen conversion channel 135 of the seventh heat exchanger. 135 is connected to the inlet of the hydrogen throttle valve 109, and the outlet of the hydrogen throttle valve 109 is connected to the inlet of the liquid hydrogen dewar 110. When the amount of liquid hydrogen stored in the liquid hydrogen dewar 110 meets the requirement, the inlet A of the first electromagnetic three-way valve 101 is closed, and the gate valve 112 is opened. The liquid hydrogen stored in the liquid hydrogen dewar 110 enters the heat exchanger 113 for cooling and heat exchange for other devices. After heat exchange, the liquid hydrogen is converted into hydrogen and enters the reflux pipeline and the gas generated by the liquid hydrogen dewar 110 passes through the seventh heat exchanger 127 along the reflux pipeline at the inlet B of the third electromagnetic three-way valve 108. The outlet C of the second electromagnetic three-way valve 102 is connected to the inlet of the first turbine expander 104 through the expansion pipeline throttle valve 103, the outlet 104 of the first turbine expander is connected to the inlet of the second turbine expander 105 through the fourth heat exchanger 124, the outlet of the second turbine expander 105 is connected to the inlet of the third turbine expander 106 through the fifth heat exchanger 125, the outlet of the third turbine expander 106 is connected to the inlet of the fourth turbine expander 107 through the sixth heat exchanger 126, and the outlet of the fourth turbine expander 107 is connected to the third electromagnetic three-way valve 102 through the expansion pipeline throttle valve 103, the outlet of the first turbine expander 104 ... and the outlet of the second turbine expander 105 is connected to the inlet of the third turbine expander 106 through the fifth heat exchanger 125. The gas generated by the liquid hydrogen dewar 110 is connected to the inlet B of the third electromagnetic three-way valve 108 through the seventh heat exchanger 127 along the reflux pipeline, and the outlet A of the third electromagnetic three-way valve 108 is connected to the inlet B of the first electromagnetic three-way valve 101 through the sixth heat exchanger 126, the fifth heat exchanger 125, the fourth heat exchanger 124, the third heat exchanger 123, and the second heat exchanger 122, and merges with the hydrogen source pre-cooled by the mechanical low-temperature pre-cooling circulation system 2 entering the inlet A of the first electromagnetic three-way valve 101 to enter the inlet of the hydrogen liquefaction low-temperature compressor unit 4.

[0034] The outlet of the mechanical cryogenic compressor 201 is connected to the inlet of the aftercooler 202, the outlet of the aftercooler 202 is connected to the inlet of the compression end of the turbine expander 203, the outlet of the compression end of the turbine expander 203 is connected to the inlet of the first channel of the regenerator 204, the outlet of the first channel of the regenerator 204 is connected to the inlet of the expansion end of the turbine expander 203, because the hydrogen liquefaction cycle adopts a closed type and no hydrogen source enters the system, the outlet A of the electromagnetic three-way valve 205 is closed, the outlet of the expansion end of the turbine expander 203 is connected to the inlet B of the electromagnetic three-way valve 205, the outlet C of the electromagnetic three-way valve 205 is connected to the second channel inlet of the regenerator 204 after heat exchange through the second heat exchanger 122 and the hydrogen liquefaction cryogenic compressor unit 4, and the second channel outlet of the regenerator 204 is connected to the inlet of the mechanical cryogenic compressor 201.

[0035] The hydrogen liquefaction cryogenic compressor unit provided by the utility model, please refer to Figure 3 , including a first low-temperature compressor 401, an intermediate heat exchanger 402, and a second low-temperature compressor 403, and its working method is as follows:

[0036] The low-temperature hydrogen at 80K or 120K enters the first low-temperature compressor 401 for two-stage compression, and then is pre-cooled by the mechanical low-temperature pre-cooling cycle in the intermediate heat exchanger 402. After that, the hydrogen is cooled to 80K or 120K again and enters the second low-temperature compressor 403 for two-stage compression; the hydrogen liquefaction low-temperature compressor unit 4 adopts two two-stage compression type centrifugal compressors connected in series to achieve four-stage compression, and intermediate cooling and mechanical low-temperature pre-cooling cycle pre-cooling are performed between the two compressors.

[0037] For comparison with the hydrogen liquefaction low temperature compressor unit provided by the present utility model, please refer to the hydrogen liquefaction room temperature compressor unit Figure 4 , including a first normal temperature compressor 501, an intercooler 502, and a second normal temperature compressor 503, and its working mode is as follows:

[0038] The normal temperature hydrogen at 300K enters the first normal temperature compressor 501 for two-stage compression, and then is cooled by the intermediate cooler 502. After that, the hydrogen is cooled to 300K again and enters the second normal temperature compressor 503 for two-stage compression. The hydrogen liquefaction normal temperature compressor unit 5 uses two two-stage compression type centrifugal compressors connected in series to achieve four-stage compression, and intermediate cooling is performed between the two compressors.

[0039] When the compressor efficiency, pressure ratio and hydrogen mass flow rate are the same, the comparison between normal temperature compression and low temperature compression is as follows: the compressor efficiency is 75%, the suction pressure of the first compressor is 1.05 bar, the pressure ratio of the first compressor is 4.37, the pressure ratio of the second compressor is 4.37, the total pressure ratio is 20, and the hydrogen mass flow rate is 0.1 kg / s.

[0040] (1) When normal temperature compression and intermediate cooling are adopted, the inlet temperature of the first compressor is 300K, and the temperature of hydrogen after intermediate cooling is 300K. The calculation results show that the power of the first compressor is 303.16kW, the power of the second compressor is 303.59kW, and the total power is 606.75kW.

[0041] (2) When low-temperature compression and intermediate cooling are adopted, the inlet temperature of the first compressor is 80K, and the temperature of hydrogen after intermediate cooling is 80K. The calculation results show that the power of the first compressor is 86.39kW, the power of the second compressor is 86.33kW, and the total power is 172.72kW.

[0042] (3) When low-temperature compression and intermediate cooling are adopted, the inlet temperature of the first compressor is 120K, and the temperature of the hydrogen after intermediate cooling is 120K. The calculation results show that the power of the first compressor is 125.91kW, the power of the second compressor is 126.29kW, and the total power is 252.2kW.

[0043] The above calculation results show that compared with the intermediate cooling measures for compression at room temperature, the compression work of 80K low-temperature compression is reduced by 71.53% compared with the compression work of 300K room temperature compression, and the compression work of 120K low-temperature compression is reduced by 58.43% compared with the compression work of 300K room temperature compression; the reduction effect is obvious.

[0044] The utility model provides a hydrogen liquefaction cryogenic circulation system, which changes the traditional liquid nitrogen precooling into a mechanical cryogenic precooling circulation precooling, so that the two parts of hydrogen entering the hydrogen liquefaction cryogenic compressor unit are precooled by the mechanical cryogenic precooling circulation, and the cryogenic compression reduces the compression work, which effectively improves the system efficiency; the mechanical cryogenic precooling circulation is used to precool the hydrogen liquefaction system, and compared with the liquid nitrogen precooling, the mechanical cryogenic precooling circulation adopts the working fluid of air, nitrogen, neon, argon and helium, which has the characteristics of being easy to obtain, cheap and pollution-free, and adopts the heat recovery circulation, so that the compression work and expansion work are effectively reduced, the irreversible loss is significantly reduced, and the system efficiency is greatly improved. Economical; Both the hydrogen liquefaction cryogenic compressor unit and the mechanical cryogenic compressor adopt oil-free gas suspension centrifugal compressor, which has the advantages of oil-free, high heat transfer efficiency, no friction, long service life, high speed, compact structure, simple system, stable and reliable operation, energy saving and high efficiency, etc., avoiding the problems of oil pollution and oil freezing, and reliability will be significantly improved; the hydrogen liquefaction cryogenic compressor unit adopts two two-stage compression type centrifugal compressors in series to achieve four-stage compression, and mechanical low-temperature pre-cooling cycle pre-cooling is carried out between the two compressors to keep the hydrogen at the inlet of the second compressor in a low temperature state. Inter-stage cooling effectively reduces the compression heat, and low-temperature compression improves the thermodynamic performance of the system.

[0045] Of course, the hydrogen liquefaction cryogenic circulation system of the utility model can also have various changes and modifications, and is not limited to the specific structure of the above-mentioned embodiment. In short, the protection scope of the utility model should include those changes or substitutions and modifications that are obvious to ordinary technicians in the field.

Claims

1. A hydrogen liquefaction low temperature circulation system, characterized in that: It includes a hydrogen liquefaction circulation system and a mechanical low-temperature pre-cooling circulation system; The mechanical low-temperature precooling circulation system provides precooling for the hydrogen liquefaction circulation system; The hydrogen liquefaction circulation system includes a first electromagnetic three-way valve, a hydrogen liquefaction cryogenic compressor unit, a second electromagnetic three-way valve, an expansion pipeline throttle valve, a first turbine expander, a second turbine expander, a third turbine expander, a fourth turbine expander, a third electromagnetic three-way valve, a hydrogen throttle valve, a liquid hydrogen dewar, a liquid storage tank, a gate valve, a heat exchanger, a first heat exchanger, a second heat exchanger, a third heat exchanger, a fourth heat exchanger, a fifth heat exchanger, a sixth heat exchanger, a seventh heat exchanger, a third heat exchanger normal-para-hydrogen conversion channel, a fourth heat exchanger normal-para-hydrogen conversion channel, a fifth heat exchanger normal-para-hydrogen conversion channel, a sixth heat exchanger normal-para-hydrogen conversion channel, and a seventh heat exchanger normal-para-hydrogen conversion channel. The number of the heat exchangers can be increased or decreased accordingly according to the scale of the system; The hydrogen liquefaction cryogenic compressor unit comprises a first cryogenic compressor, an intermediate heat exchanger, and a second cryogenic compressor; The mechanical low-temperature precooling circulation system comprises a mechanical low-temperature compressor, an aftercooler, a turbine expander, a regenerator, and an electromagnetic three-way valve.

2. The hydrogen liquefaction low-temperature circulation system according to claim 1, characterized in that: The outlet of the hydrogen liquefaction cryogenic compressor unit is connected to the inlet of the hydrogen channel of the second heat exchanger, the outlet of the hydrogen channel of the second heat exchanger is connected to the inlet of the positive-parahydrogen conversion channel of the third heat exchanger, the outlet of the positive-parahydrogen conversion channel of the third heat exchanger is connected to the inlet A of the second electromagnetic three-way valve, the outlet B of the second electromagnetic three-way valve is connected to the inlet of the hydrogen throttle valve through the positive-parahydrogen conversion channel of the fourth heat exchanger, the positive-parahydrogen conversion channel of the fifth heat exchanger, the positive-parahydrogen conversion channel of the sixth heat exchanger, and the positive-parahydrogen conversion channel of the seventh heat exchanger, the outlet of the hydrogen throttle valve is connected to the inlet of the liquid hydrogen Dewar, and the liquid hydrogen Dewar is connected to the liquid storage tank; the outlet C of the second electromagnetic three-way valve is connected to the inlet of the first turbine expander through the expansion pipeline throttle valve, and the outlet of the first turbine expander is connected to the inlet of the first turbine expander. The fourth heat exchanger is connected to the inlet of the second turbine expander, the outlet of the second turbine expander is connected to the inlet of the third turbine expander through the fifth heat exchanger, the outlet of the third turbine expander is connected to the inlet of the fourth turbine expander through the sixth heat exchanger, and the outlet of the fourth turbine expander is connected to the inlet C of the third electromagnetic three-way valve; the gas generated by the liquid hydrogen dewar is connected to the inlet B of the third electromagnetic three-way valve along the reflux pipeline through the seventh heat exchanger, and the outlet A of the third electromagnetic three-way valve is connected to the inlet B of the first electromagnetic three-way valve through the sixth heat exchanger, the fifth heat exchanger, the fourth heat exchanger, the third heat exchanger, and the second heat exchanger, and merges with the hydrogen source pre-cooled by the mechanical low-temperature pre-cooling circulation system entering the inlet A of the first electromagnetic three-way valve to enter the inlet of the hydrogen liquefaction low-temperature compressor unit.

3. The hydrogen liquefaction low temperature circulation system according to claim 1, characterized in that: The outlet of the mechanical low-temperature compressor is connected to the inlet of the aftercooler, the outlet of the aftercooler is connected to the inlet of the compression end of the turbine expander, the outlet of the compression end of the turbine expander is connected to the inlet of the first channel of the regenerator, the outlet of the first channel of the regenerator is connected to the inlet of the expansion end of the turbine expander, the outlet of the expansion end of the turbine expander is connected to the inlet B of the electromagnetic three-way valve, the outlet A of the electromagnetic three-way valve is connected to the inlet of the second channel of the regenerator after heat exchange with the outlet C of the electromagnetic three-way valve through the first heat exchanger and the hydrogen liquefaction low-temperature compressor unit through the second heat exchanger, and the outlet of the second channel of the regenerator is connected to the inlet of the mechanical low-temperature compressor.

4. The hydrogen liquefaction low temperature circulation system according to claim 1, characterized in that: The first electromagnetic three-way valve, the hydrogen liquefaction cryogenic compressor unit, the second electromagnetic three-way valve, the expansion pipeline throttle valve, the first turbine expander, the second turbine expander, the third turbine expander, the fourth turbine expander, the third electromagnetic three-way valve, the hydrogen throttle valve, the first heat exchanger, the second heat exchanger, the third heat exchanger, the fourth heat exchanger, the fifth heat exchanger, the sixth heat exchanger, the seventh heat exchanger, the third heat exchanger normal para-hydrogen conversion channel, the fourth heat exchanger normal para-hydrogen conversion channel, the fifth heat exchanger normal para-hydrogen conversion channel, the sixth heat exchanger normal para-hydrogen conversion channel, the seventh heat exchanger normal para-hydrogen conversion channel, the turbine expander, the regenerator, and the electromagnetic three-way valve are all arranged in a vacuum cold tank.

5. The hydrogen liquefaction low temperature circulation system according to claim 1, characterized in that: The hydrogen liquefaction cryogenic compressor unit is an oil-free gas-suspended centrifugal compressor, which is supported by gas-suspended bearings or magnetic-gas hybrid bearings. Its compression is low-temperature compression. The hydrogen liquefaction cryogenic compressor unit uses 1-4 centrifugal compressors in series to achieve 1-10 levels of compression. The compressor stages are pre-cooled by a mechanical low-temperature pre-cooling cycle. The compressor inlet temperature is between 30K and 250K, and the working fluid used is hydrogen.

6. The hydrogen liquefaction low temperature circulation system according to claim 1, characterized in that: The mechanical low-temperature compressor is an oil-free gas suspension centrifugal compressor, which is supported by gas suspension bearings or magnetic mixed bearings. The compression is room temperature compression, and the compressor inlet temperature is between 230K and 340K.

7. The hydrogen liquefaction low temperature circulation system according to claim 1, characterized in that: The working fluids used in the mechanical low-temperature precooling circulation system are air, nitrogen, neon, argon and helium gases.

8. The hydrogen liquefaction low temperature circulation system according to claim 1, characterized in that: The third heat exchanger normal-para hydrogen conversion channel, the fourth heat exchanger normal-para hydrogen conversion channel, the fifth heat exchanger normal-para hydrogen conversion channel, the sixth heat exchanger normal-para hydrogen conversion channel and the seventh heat exchanger normal-para hydrogen conversion channel are all filled with normal-para hydrogen catalytic converter, which can achieve continuous normal-para hydrogen conversion.

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