Proton exchange membrane water electrolysis hydrogen production coupled low-temperature seawater purification system and method

Abstract

The invention discloses a system for hydrogen production through proton exchange membrane water electrolysis coupled with low-temperature seawater purification. The system comprises a rectification transformation unit, a proton exchange membrane electrolytic bath unit, a hydrogen condensation separation unit, a hydrogen drying unit, an oxygen-liquid separation unit, a seawater filtering lightering unit, a pure water circulation unit, a unit for producing pure water from low-temperature seawater and a pure water storage unit. A heat exchanger in a traditional proton exchange membrane water electrolysis hydrogen production system is replaced with the low-temperature seawater pure water production unit, pure water of the proton exchange membrane electrolytic cell unit can be kept at the reasonable temperature, waste heat can be utilized for low-temperature seawater pure water production, the prepared pure water can serve as raw water for proton exchange membrane water electrolysis hydrogen production, and the energy consumption is reduced. In addition, pure water separated from the hydrogen condensation separation unit and the oxygen-liquid separation unit can be repeatedly utilized, so that dependence on fresh water resources can be eliminated, reliable technical support can be provided for a wide-power fluctuation offshore wind power hydrogen production scene, and green hydrogen energy economic development can be accelerated and promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolytic hydrogen production, and in particular to a system and method for coupling proton exchange membrane water electrolysis hydrogen production with low-temperature seawater purification. Background Art

[0002] With the access of a large proportion of renewable energy power, its volatility and randomness will bring huge pressure to the peak load regulation of the power grid. The integration of source, grid, load and storage will effectively solve the problems of consumption and peak load regulation. Water electrolysis to produce hydrogen is an ideal choice for realizing the adaptive regulation of the load and storage end of the integration of source, grid, load and storage. Proton exchange membrane has the advantages of low energy consumption, fast response speed, high current density, high purity of hydrogen production, and adaptability to rapidly changing renewable energy power input, and has gradually become an important technical path for renewable energy power generation and hydrogen production.

[0003] At present, my country's eastern coastal areas are areas where hydrogen energy applications are relatively concentrated. At the same time, the region has a relatively rich distribution of offshore wind power. Combining the two, that is, using offshore wind power to produce hydrogen, has great practical significance, but there are still problems such as complex seawater composition and shortage of fresh water resources. Therefore, how to effectively couple the proton exchange membrane water electrolysis hydrogen production technology with seawater purification technology to form a new method of proton exchange membrane water electrolysis hydrogen production coupled with low-temperature seawater purification, and design a new system of proton exchange membrane water electrolysis hydrogen production coupled with low-temperature seawater purification, can not only accelerate the development of the green hydrogen energy economy, but also help promote the optimization and adjustment of my country's new energy structure. Summary of the invention

[0004] According to the technical problems mentioned in the above background technology, a system and method for coupling proton exchange membrane water electrolysis to produce hydrogen and low-temperature seawater purification is provided. The present invention provides a system and method for coupling proton exchange membrane water electrolysis to produce hydrogen and low-temperature seawater purification, which is not only applicable to offshore wind power with wide power fluctuations for proton exchange membrane water electrolysis to produce hydrogen, but also can be used through a waste heat recovery and reuse system to purify low-temperature seawater using the waste heat generated in the process of proton exchange membrane water electrolysis to produce hydrogen, thereby realizing the preparation of pure water from seawater, and the prepared pure water can be used as raw material water for proton exchange membrane water electrolysis to produce hydrogen, and finally realize the self-sufficiency of raw material water for proton exchange membrane water electrolysis to produce hydrogen. Therefore, the present invention can not only adapt to offshore wind power with wide power fluctuations, but also use seawater as the input raw material for water electrolysis to produce hydrogen, getting rid of the dependence on fresh water resources, in order to provide technical support for the development of equipment based on proton exchange membrane water electrolysis to produce hydrogen coupled with low-temperature seawater purification method that realizes technical autonomy and controllability.

[0005] The technical means adopted by the present invention are as follows:

[0006] A system for hydrogen production by proton exchange membrane electrolysis coupled with low-temperature seawater purification comprises: a proton exchange membrane electrolyzer unit, a hydrogen condensation separation unit, a low-temperature seawater pure water production unit and a pure water storage unit; preheated seawater is obtained by using seawater as a cooling medium of the hydrogen condensation separation unit, and the preheated seawater enters the low-temperature seawater pure water production unit as a raw material for preparing pure water; at the same time, the hot pure water of the proton exchange membrane electrolyzer unit is transferred to the low-temperature seawater pure water production unit through the pure water circulation unit as a heat source for heating the preheated seawater; under negative pressure conditions, pure water is prepared from seawater and cached in the pure water storage unit, and the hot pure water of the proton exchange membrane electrolyzer unit is cooled and then returned to the proton exchange membrane electrolyzer unit.

[0007] Furthermore, the system also has a rectifying and transforming unit; the power input interface of the rectifying and transforming unit is connected to the offshore green electricity; the rectifying and transforming unit is connected to the power interface of the proton exchange membrane electrolyzer unit.

[0008] Furthermore, the system also has a hydrogen drying unit and an oxygen liquid separation unit; the hydrogen outlet of the hydrogen condensation separation unit is connected to the hydrogen drying unit; the hydrogen inlet of the hydrogen drying unit is connected to the outlet of the hydrogen condensation separation unit; and the hydrogen outlet of the hydrogen drying unit is connected to a hydrogen user or a storage tank.

[0009] Furthermore, the system also has a seawater filtering and transporting unit; the cooling seawater inlet of the condensation separation unit is connected to the outlet of the seawater filtering and transporting unit.

[0010] Furthermore, a pure water circulation unit; the hot pure water outlet of the proton exchange membrane electrolyzer unit is connected to the pure water circulation unit; the outlet of the pure water storage unit is respectively connected to the pure water circulation unit and the external water supply.

[0011] Furthermore, the oxygen outlet of the oxygen-liquid separation unit can be led to a safe area for emptying, or can be stored for use.

[0012] Furthermore, the inlet of the seawater filtration and transfer unit is a seawater source.

[0013] Furthermore, the pure water storage unit stores the pure water prepared by the low-temperature seawater pure water preparation unit, and also stores the pure water separated by the hydrogen condensation separation unit and the oxygen liquid separation unit.

[0014] The present invention also includes a method for producing hydrogen by proton exchange membrane water electrolysis coupled with low-temperature seawater purification, comprising the following steps:

[0015] Step 1: preheating seawater by using seawater as a cooling medium in a hydrogen condensation separation unit, and the preheated seawater enters a low-temperature seawater pure water production unit as a raw material for preparing pure water;

[0016] Step 2: The hot pure water of the proton exchange membrane electrolyzer unit is transferred to the low-temperature seawater pure water unit through the pure water circulation unit as a heat source for heating and preheating seawater;

[0017] Step 3: Under negative pressure conditions, pure water is prepared from seawater and cached in a pure water storage unit;

[0018] Step 4: After the hot pure water of the proton exchange membrane electrolyzer unit is cooled, it is returned to the proton exchange membrane electrolyzer unit.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] The present invention can not only adapt to offshore wind power with wide power fluctuations, but also use seawater as the input raw material to electrolyze water to produce hydrogen, thus getting rid of the dependence on fresh water resources, in order to provide technical support for the development of equipment based on proton exchange membrane electrolysis of water to produce hydrogen coupled with low-temperature seawater purification method with independent and controllable technology.

[0021] The present invention replaces the heat exchanger in the traditional proton exchange membrane water electrolysis hydrogen production system with a low-temperature seawater pure water production unit, which can not only maintain the pure water in the proton exchange membrane electrolyzer unit at a reasonable temperature, but also use waste heat to produce pure water from low-temperature seawater. The prepared pure water can be used as raw material water for proton exchange membrane water electrolysis hydrogen production, and achieve self-sufficiency. In addition, the pure water separated from the hydrogen condensation separation unit and the oxygen liquid separation unit can be reused, thereby getting rid of dependence on fresh water resources, and providing reliable technical support for offshore wind power hydrogen production scenarios with wide power fluctuations. It can not only accelerate the development of the green hydrogen energy economy, but also be conducive to promoting the optimization and adjustment of my country's new energy structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0023] Figure 1 This is a functional flow chart of the present invention.

[0024] Figure 2 It is a process system flow chart of an implementation case of the present invention.

[0025] In the figure: 1 is the baseline, 2 is the rectifier transformer unit, 3 is the proton exchange membrane electrolyzer unit, 4 is the hydrogen condensation separation unit, 5 is the hydrogen drying unit, 6 is the oxygen liquid separation unit, 7 is the seawater filtration and transfer unit, 8 is the pure water circulation unit, 9 is the low-temperature seawater pure water unit, 10 is the pure water storage unit, 21 is the rectifier transformer, 31 is the proton exchange membrane electrolyzer module, 32 is the liquid level transmitter, 41 is the hydrogen cooler, 42 is the liquid level transmitter, 43 is the remote control valve, 44 is the hydrogen water separator, 45 is the remote control valve, 46 is the liquid level transmitter, 51 is a hydrogen drying tower, 61 is an oxygen-water separator, 62 is a remote control valve, 63 is a liquid level transmitter, 71 is a seawater transfer pump, 72 is a multi-media filter, 73 is an activated carbon filter, 74 is a precision filter, 81 is a pure water circulation pump, 82 is a filter, 90 is a low-temperature seawater purifier, 91 is a vacuum instrument, 92 is a vacuum pump, 93 is a remote control valve, 94 is a temperature meter, 95 is a gas-liquid separator, 96 is a water quality monitor, 97 is a remote control three-way valve, 98 is a salinity meter, 99 is a remote control valve, 101 is a pure water tank, and 102 is a remote control valve. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0027] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0028] The present invention Figure 1 It is a main functional flow chart of a system for producing hydrogen by proton exchange membrane electrolysis of water coupled with low-temperature seawater purification. Baseline 1 is a system for producing hydrogen by proton exchange membrane electrolysis of water coupled with low-temperature seawater purification.

[0029] The functional realization units of the system and method for proton exchange membrane water electrolysis hydrogen production coupled with low-temperature seawater purification of the present invention include: a rectifier and transformer unit 2, a proton exchange membrane electrolyzer unit 3, a hydrogen condensation and separation unit 4, a hydrogen drying unit 5, an oxygen liquid separation unit 6, a seawater filtration and transfer unit 7, a pure water circulation unit 8, a low-temperature seawater pure water production unit 9, and a pure water storage unit 10.

[0030] Rectifier and transformer unit 2: The power input interface of the rectifier and transformer unit is connected to green electricity such as offshore wind power; the power output interface of the rectifier and transformer unit is connected to the power interface of the proton exchange membrane electrolyzer unit. It realizes the rectification function of green electricity such as offshore wind power and provides electrolysis driving force for the proton exchange membrane electrolyzer unit.

[0031] Proton exchange membrane electrolyzer unit 3: The power interface of the proton exchange membrane electrolyzer unit is connected to the power output interface of the rectifier transformer unit; the hydrogen outlet of the proton exchange membrane electrolyzer unit is connected to the hydrogen condensation separation unit; the oxygen outlet of the proton exchange membrane electrolyzer unit is connected to the oxygen liquid separation unit; the hot pure water outlet of the proton exchange membrane electrolyzer unit is connected to the pure water circulation unit; the low-temperature pure water inlet of the proton exchange membrane electrolyzer unit is connected to the low-temperature seawater pure water production unit. The pure water in the proton exchange membrane electrolyzer unit is driven by green electricity such as offshore wind power to produce hydrogen and oxygen, and the hydrogen and water vapor enter the hydrogen condensation separation unit, and the oxygen and water vapor enter the oxygen liquid separation unit.

[0032] Hydrogen condensation separation unit 4: The hydrogen inlet of the hydrogen condensation separation unit is connected to the hydrogen outlet of the proton exchange membrane electrolyzer unit; the hydrogen outlet of the hydrogen condensation separation unit is connected to the hydrogen drying unit; the cooling seawater inlet of the condensation separation unit is connected to the outlet of the seawater filtration and transfer unit; the cooling seawater outlet of the condensation separation unit is connected to the preheating seawater inlet of the low-temperature seawater pure water unit; the condensed pure water outlet of the condensation separation unit is connected to the pure water storage unit. The water vapor in the hydrogen is cooled and condensed into condensed water, the hydrogen temperature is reduced, and the cooling seawater is preheated at the same time.

[0033] Hydrogen drying unit 5: The hydrogen inlet of the hydrogen drying unit is connected to the outlet of the hydrogen condensation separation unit; the hydrogen outlet of the hydrogen drying unit is connected to the hydrogen user or storage tank. The residual weak moisture in the hydrogen is efficiently separated to ensure that the output hydrogen has a lower dew point.

[0034] Oxygen-liquid separation unit 6: The oxygen inlet of the oxygen-liquid separation unit is connected to the oxygen outlet of the proton exchange membrane electrolyzer unit; the oxygen outlet of the oxygen-liquid separation unit can be led to a safe area for emptying, or can be stored for use; the pure water outlet separated by the oxygen-liquid separation unit is connected to the pure water storage unit. The oxygen-liquid separation unit reduces the moisture content of oxygen.

[0035] Seawater filtration and transportation unit 7: The inlet of the seawater filtration and transportation unit is a seawater source; the outlet of the seawater filtration and transportation unit is a hydrogen condensation separation unit. The seawater filtration and transportation unit 7 performs preliminary filtration on the seawater and provides power for seawater transmission. The seawater is first used as a cooling medium for the hydrogen condensation separation unit.

[0036] Pure water circulation unit 8: The hot pure water inlet of the pure water circulation unit is connected to the hot pure water outlet of the proton exchange membrane electrolyzer unit; the hot pure water outlet of the pure water circulation unit is connected to the hot pure water inlet of the low-temperature seawater pure water production unit; the supplementary pure water inlet of the pure water circulation unit is connected to the pure water storage unit. The pure water circulation unit 8 provides power for pure water circulation and can supplement pure water for the proton exchange membrane electrolyzer unit.

[0037] Low-temperature seawater pure water unit 9: The hot pure water inlet of the low-temperature seawater pure water unit is connected to the hot pure water outlet of the pure water circulation unit; the low-temperature pure water outlet of the low-temperature seawater pure water unit is connected to the low-temperature pure water inlet of the proton exchange membrane electrolyzer unit; the preheated seawater inlet of the low-temperature seawater pure water unit is connected to the cooling seawater outlet of the hydrogen condensation separation unit; the prepared pure water outlet of the low-temperature seawater pure water unit is connected to the pure water storage unit. Under negative pressure, the low-temperature seawater pure water unit 9 uses the hot pure water of the proton exchange membrane electrolyzer unit to heat the seawater preheated by the hydrogen condenser separation unit, thereby preparing pure water from the low-temperature seawater; at the same time, it can cool the hot pure water from the proton exchange membrane electrolyzer unit to ensure that the proton exchange membrane electrolyzer unit is maintained at a reasonable temperature.

[0038] Pure water storage unit 10: The inlet of the pure water storage unit is connected to the pure water outlet prepared by the low-temperature seawater pure water unit, the pure water outlet of the hydrogen condensation separation unit, and the pure water outlet of the oxygen liquid separation unit; the outlet of the pure water storage unit is connected to the pure water circulation unit and the external water supply. The pure water storage unit 10 collects and stores pure water to provide raw pure water for the proton exchange membrane electrolyzer unit, and additional pure water can be supplied externally.

[0039] The present invention also includes a method for coupling proton exchange membrane water electrolysis hydrogen production with low-temperature seawater purification, which specifically includes the following steps: the rectification and transformation unit 2 supplies green electricity such as offshore wind power to the proton exchange membrane electrolyzer unit 3 after rectification and transformation, and the pure water in the proton exchange membrane electrolyzer unit 3 is decomposed into hydrogen and oxygen under the drive of green electricity; the hydrogen produced by the proton exchange membrane electrolyzer unit 3 is cooled and dehydrated by the hydrogen condensation separation unit 4, and then enters the hydrogen drying unit 5 to remove slight moisture, and then outputs high-purity and low-dew point product hydrogen; the oxygen produced by the proton exchange membrane electrolyzer unit 3 can be led to a safe area for emptying or storage after the moisture content is reduced by the oxygen liquid separation unit 6; the seawater filtration and transportation unit 7 preheats the seawater through the hydrogen condensation separation unit 4 and enters the low-temperature seawater pure water production unit 9 as a production unit. Pure water raw material; the pure water circulation unit 8 serves as the circulation power of the proton exchange membrane electrolyzer unit 3 and the low-temperature seawater pure water production unit 9, and can circulate the hot pure water in the proton exchange membrane electrolyzer unit 3 to the low-temperature seawater pure water production unit 9 as a heat source for heating and preheating seawater to prepare pure water. The hot pure water in the proton exchange membrane electrolyzer unit 3 is cooled by the low-temperature seawater pure water production unit 9 and then returned to the proton exchange membrane electrolyzer unit 3, which can maintain the pure water temperature requirement of the proton exchange membrane electrolyzer unit 3; the pure water storage unit 10 collects and stores the pure water prepared from the low-temperature seawater pure water production unit, the pure water separated by the hydrogen condensation separation unit, and the pure water separated by the oxygen liquid separation unit, and can supplement the raw pure water to the proton exchange membrane electrolyzer unit 3 through the pure water circulation unit 8, and can also supply additional pure water to the outside.

[0040] Figure 21 is a process system flow chart of an implementation case of the present invention. As can be seen from the figure, the rectifier transformer unit 2 is mainly a rectifier transformer 21, which realizes the rectification and transformation of green electricity such as offshore wind power to provide power for the proton exchange membrane electrolyzer module 31; the proton exchange membrane electrolyzer unit 3 is composed of a proton exchange membrane electrolyzer module 31 and a liquid level transmitter 32. The proton exchange membrane electrolyzer module 31 can use green electricity to produce hydrogen and oxygen. The liquid level transmitter 32 can control the opening and closing of the remote control valve 102 according to the high and low signals of the pure water level of the proton exchange membrane electrolyzer module 31, so as to realize the automatic replenishment of raw pure water; the hydrogen condensation separation unit 4 is composed of a hydrogen condenser 41, a liquid level transmitter 42, a remote control valve 43, a hydrogen-water separator 44, a remote control valve 45, and a liquid level transmitter 46. The hydrogen condenser 41 and the hydrogen-water separator 44 mainly realize the condensation and gas-liquid separation of hydrogen. The liquid level transmitter 42 sends a liquid level signal of the hydrogen condenser 41 to control the opening and closing of the remote control valve 43, and discharges the condensed pure water to the pure water tank 101. The liquid level transmitter 46 sends a liquid level signal of the hydrogen water separator 44 to control the opening and closing of the remote control valve 45, and discharges the separated pure water to the pure water tank 101. The hydrogen dryer 51 is used to remove the slight moisture in the hydrogen. The oxygen-liquid separation unit 6 is composed of an oxygen-water separator 61, a remote control valve 62, and a liquid level transmitter 63. The oxygen-water separator 61 mainly reduces the moisture content of oxygen. The liquid level transmitter 63 sends a liquid level signal of the oxygen-water separator 61 to control the opening and closing of the remote control valve 62, and discharges the separated pure water to the pure water tank 101. The seawater filtration and transfer unit 7 is composed of a seawater transfer pump 71, a multi-media filter 72, an activated carbon filter 73, and a precision filter 74, and mainly provides transmission power and filtration for seawater. The pure water circulation unit 8 is composed of a pure water circulation pump 81 and a filter 82, which mainly provide circulation power for pure water; the low-temperature seawater pure water unit 9 is composed of a low-temperature seawater purifier 90, a vacuum instrument 91, a vacuum pump 92, a remote control valve 93, a temperature meter 94, a gas-liquid separator 95, a water quality monitor 96, a remote control three-way valve 97, a salinity meter 98, and a remote control valve 99. The low-temperature seawater purifier 90 mainly realizes the purification of low-temperature seawater under a negative pressure environment. The vacuum pump 92 provides a vacuum environment for the low-temperature seawater purifier 90, and the vacuum pump 92 is controlled by a signal from the vacuum instrument 91 to maintain a stable vacuum degree. The temperature meter 94 sends a temperature signal of the cooled alkali solution to control the opening of the remote control valve 93 to control the amount of seawater. And ensure that the alkali solution after cooling is maintained within a reasonable range. The gas-liquid separator 95 is used to separate a small amount of water extracted by the vacuum pump 92 to protect the vacuum pump 92. The water quality monitor 96 is used to monitor the water quality of the prepared pure water. When the pure water is qualified, a qualified signal is sent to control the remote control three-way valve 97 to discharge the pure water to the pure water tank 101. When the pure water is unqualified, an unqualified signal is sent to control the remote control three-way valve 97 to discharge fresh water to the low-temperature seawater purifier 90; the pure water storage unit 10 is composed of a pure water tank 101 and a remote control valve 102. The pure water tank 101 is mainly used to store pure water. The remote control valve 102 is used to receive the high and low signals of the pure water level from the liquid level transmitter 32 to control the opening and closing of the remote control valve 102, so as to realize the automatic replenishment of raw pure water.

[0041] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages and disadvantages of the embodiments. In the above embodiments of the present invention, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, please refer to the relevant description of other embodiments. In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A system for hydrogen production by proton exchange membrane electrolysis coupled with low-temperature seawater purification, characterized in that: include: A proton exchange membrane electrolyzer unit (3), a hydrogen condensation separation unit (4), a low-temperature seawater pure water production unit (9) and a pure water storage unit (10); Preheated seawater is obtained by using seawater as a cooling medium of the hydrogen condensation separation unit (4), and the preheated seawater enters the low-temperature seawater pure water production unit (4) as a raw material for preparing pure water; at the same time, the hot pure water of the proton exchange membrane electrolyzer unit (3) is transferred to the low-temperature seawater pure water production unit (9) through the pure water circulation unit (4) as a heat source for heating the preheated seawater; under negative pressure conditions, pure water is prepared from seawater and cached in the pure water storage unit (10); the hot pure water of the proton exchange membrane electrolyzer unit (3) is cooled and then returned to the proton exchange membrane electrolyzer unit (3).

2. According to claim 1, a system for producing hydrogen by proton exchange membrane electrolysis coupled with low-temperature seawater purification is characterized in that: The system further comprises a rectifying and transforming unit (2); a power input interface of the rectifying and transforming unit (2) is connected to offshore green electricity; and the rectifying and transforming unit (2) is connected to a power interface of a proton exchange membrane electrolyzer unit (3).

3. The system of proton exchange membrane water electrolysis for hydrogen production coupled with low-temperature seawater purification according to claim 1, characterized in that: The system also comprises a hydrogen drying unit (5) and an oxygen liquid separation unit (6); the hydrogen outlet of the hydrogen condensation separation unit (4) is connected to the hydrogen drying unit (5); the hydrogen inlet of the hydrogen drying unit (5) is connected to the outlet of the hydrogen condensation separation unit (6); and the hydrogen outlet of the hydrogen drying unit (6) is connected to a hydrogen user or a storage tank.

4. The system of proton exchange membrane water electrolysis for hydrogen production coupled with low-temperature seawater purification according to claim 1, characterized in that: The system also has a seawater filtering and transporting unit (7); the cooling seawater inlet of the condensation separation unit (4) is connected to the outlet of the seawater filtering and transporting unit (7).

5. The system of proton exchange membrane water electrolysis for hydrogen production coupled with low-temperature seawater purification according to claim 1, characterized in that: A pure water circulation unit (8); the hot pure water outlet of the proton exchange membrane electrolyzer unit (3) is connected to the pure water circulation unit (8); and the outlet of the pure water storage unit (10) is respectively connected to the pure water circulation unit (8) and external water supply.

6. The system of proton exchange membrane water electrolysis for hydrogen production coupled with low-temperature seawater purification according to claim 3, characterized in that: The oxygen outlet of the oxygen-liquid separation unit (6) can be led to a safe area for emptying, or it can be stored for use.

7. The system of proton exchange membrane water electrolysis for hydrogen production coupled with low-temperature seawater purification according to claim 4, characterized in that: The inlet of the seawater filtering and transferring unit (7) is a seawater source.

8. The system of proton exchange membrane water electrolysis for hydrogen production coupled with low-temperature seawater purification according to claim 1, characterized in that: The pure water storage unit (10) stores pure water prepared by the low-temperature seawater pure water preparation unit, and also stores pure water separated by the hydrogen condensation separation unit (4) and the oxygen liquid separation unit (6).

9. A method for producing hydrogen by proton exchange membrane water electrolysis coupled with low-temperature seawater purification using the system described in any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1: preheating seawater by using seawater as a cooling medium in a hydrogen condensation separation unit, and the preheated seawater enters a low-temperature seawater pure water production unit as a raw material for preparing pure water; Step 2: The hot pure water of the proton exchange membrane electrolyzer unit is transferred to the low-temperature seawater pure water unit through the pure water circulation unit as a heat source for heating and preheating seawater; Step 3: Under negative pressure conditions, pure water is prepared from seawater and cached in a pure water storage unit; Step 4: After the hot pure water of the proton exchange membrane electrolyzer unit is cooled, it is returned to the proton exchange membrane electrolyzer unit.

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