Hydrogen production system for coupling alkaline water electrolysis with proton exchange membrane water electrolysis

Abstract

The hydrogen production system comprises an ALK system, a PEM system, a membrane distillation system, a cooling water circulation system and a pure water system, wherein the ALK system and the PEM system are used for producing hydrogen by taking new energy as a power supply; cooling water of the cooling water circulation system is used for refrigerating the ALK alkali liquor heat exchanger, and the cooling water subjected to heat exchange enters the membrane distillation system; a PEM electrolytic bath liquid outlet of the PEM system is connected with a high-temperature feed liquid side of the membrane distillation system; a pure water inlet of the PEM electrolytic bath and a pure water inlet of the ALK system hydrogen / oxygen separator are connected with a low-temperature feed liquid side of the membrane distillation system; according to the scheme, the ALK system and the PEM system are combined with the membrane distillation system to prepare the pure water, and the prepared pure water is recycled into the ALK system and the PEM system to serve as raw material pure water for electrolytic hydrogen production, so that waste of waste heat of the original ALK system and the original PEM system and use of the pure water are reduced, and meanwhile, the hydrogen production scale is increased on the basis of matching with the volatility of new energy.

Description

Technical Field

[0001] The present invention relates to a hydrogen production system integrating alkaline water electrolysis and proton exchange membrane water electrolysis, and belongs to the technical field of water electrolysis for hydrogen production. Background Art

[0002] During the operation of an alkaline water electrolysis system, heat is continuously generated. If the heat accumulates continuously, it is easy to cause the destruction of the electrodes and membrane materials of the alkaline electrolyzer due to excessive temperature, which will further lead to the reduction of electrolysis performance, and seriously cause hydrogen-oxygen mixing and explosion. To solve this problem, currently commercial alkaline water electrolysis systems mostly use a large amount of fresh water to cool the high-temperature alkaline solution after electrolysis, so as to ensure the operation of the system within the normal temperature range. However, this method will cause a large amount of waste of cooling water and affect the economy. The temperature of this part of cooling water after heat exchange is generally about 60-70 °C. If this part of water and heat can be reasonably utilized, the economy of the system will be greatly improved.

[0003] Both the alkaline water electrolysis (ALK) system and the proton exchange membrane water electrolysis (PEM) system consume a large amount of electric energy during operation. Using commercial power has low economy. Currently, they are mainly matched with renewable energy such as wind and light for water electrolysis to produce hydrogen. The ALK system has a large single-unit hydrogen production capacity, which can reach 1000 Nm 3 / H 2 per hour, but the system cannot well match the volatility of renewable energy such as wind and light; the PEM system can be started and stopped at any time and can well match the volatility of renewable energy such as wind and light, but the single-unit hydrogen production capacity of the PEM system is small, generally less than 400 Nm 3 / H 2 per hour, which cannot well meet the production requirements. If there is a method to combine the two, the requirements of both output and stability can be achieved simultaneously.

[0004] Both ALK and PEM need to electrolyze pure water to produce hydrogen. Therefore, both usually need to be equipped with a pure water system, which will further increase the cost of hydrogen production. Membrane distillation is a membrane technology that uses a hydrophobic microporous membrane to separate aqueous solutions containing non-volatile solutes, and can effectively extract pure water from various water qualities (seawater, brackish water, fresh water, etc.). However, it usually requires heating the solution to be separated on the feed side, resulting in high energy consumption.

[0005] For example, Chinese Patent Publication No. CN114044562A discloses an integrated system of an electrolysis device and a water treatment and desalination system, which uses the abundant waste heat of the electrolysis device to provide fresh water for the environment of renewable energy devices through the water treatment system, and can also provide the water vapor and pure water required for electrolysis for similar high-temperature and low-temperature electrolysis systems.

[0006] However, the existing technologies do not consider the problem of large fluctuations in new energy. Summary of the Invention

[0007] The purpose of the present invention is to provide a hydrogen production system that couples alkaline water electrolysis with proton exchange membrane water electrolysis, so as to solve the problems raised in the above-mentioned background technology.

[0008] The technical solution of the present invention is as follows:

[0009] A hydrogen production system that couples alkaline water electrolysis with proton exchange membrane water electrolysis includes an ALK system and a PEM system that use new energy as a power source for hydrogen production, and also includes a membrane distillation system, a cooling water circulation system, and a pure water system;

[0010] The cooling water of the cooling water circulation system is used to cool the ALK alkaline liquid heat exchanger in the ALK system, and the cooled cooling water enters the high-temperature feed liquid side of the membrane distillation system;

[0011] The liquid outlet of the PEM electrolyzer of the PEM system is connected to the high-temperature feed liquid side of the membrane distillation system;

[0012] The output end of the pure water system is connected to the low-temperature feed liquid side of the membrane distillation system;

[0013] The pure water inlets of the PEM electrolyzer of the PEM system, the pure water inlet of the oxygen separator of the ALK system, and the pure water inlet of the hydrogen separator of the ALK system are all connected to the low-temperature feed liquid side of the membrane distillation system.

[0014] Preferably, the new energy is any one of wind power, photovoltaic power, and hydropower.

[0015] Preferably, the membrane distillation system is a direct contact membrane distillation system, and the separation membrane material used is any one of polytetrafluoroethylene, polypropylene, polyethylene, and polyvinylidene fluoride.

[0016] Preferably, the high-temperature alkaline liquid in the ALK system enters the alkaline liquid heat exchanger after being separated by the oxygen separator and / or hydrogen separator of the ALK system, and after heat exchange, it passes through a filter and returns to the ALK electrolyzer through an alkaline liquid circulation pump.

[0017] Preferably, the low-temperature feed liquid side of the membrane distillation system is also connected to the liquid outlets of the oxygen separator and hydrogen separator of the PEM system.

[0018] Preferably, the hydrogen production scale ratio of the ALK system and the PEM system is 3:1 to 1:1.

[0019] Preferably, the high-temperature feed liquid side of the membrane distillation system is also connected to the cooling water circulation system to form a cycle.

[0020] Preferably, corresponding valves are installed at the pure water inlets of the PEM electrolyzer of the PEM system, the pure water inlet of the oxygen separator of the ALK system, and the pure water inlet of the hydrogen separator of the ALK system to achieve pure water supplementation.

[0021] A method for a hydrogen production system integrating alkaline water electrolysis and proton exchange membrane water electrolysis includes the following steps:

[0022] When new energy fluctuates greatly, only the PEM system is operated to ensure good responsiveness and a certain hydrogen production scale. After the new energy becomes relatively stable, the ALK system is started to increase the hydrogen production scale and make full use of waste heat.

[0023] Preferably, the pure water system prepares a part of pure water in advance before starting the hydrogen production system as the low-temperature feed liquid of the membrane distillation system.

[0024] The present invention has the following beneficial effects:

[0025] Normally, the high-temperature feed liquid side of the membrane distillation system needs to be heated by an external heat source. In this solution, the low-grade cooling wastewater (≥60°C) of the ALK system and the PEM system is used in combination with the membrane distillation system to produce pure water, and the produced pure water is recycled to the ALK and PEM systems as raw material pure water for electrolytic hydrogen production. This not only reduces the external heat source but also reduces the waste of the original waste heat of the ALK system and the PEM system and the use of pure water. At the same time, the hydrogen production scale is increased on the basis of matching the volatility of new energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic structural diagram of the present invention.

[0027] The reference numerals in the drawings are represented as:

[0028] 1, 4, 8, 16, 20, 22 are valves; 2 is the oxygen separator of the ALK system; 3 is the hydrogen separator of the ALK system; 5, 12, 19 are water pumps; 6 is the cooling water circulation system; 7 is the membrane distillation system; 9 is the PEM electrolyzer; 10 is the oxygen separator of the PEM system; 11 is the hydrogen separator of the PEM system; 13 is the alkaline electrolyzer; 14 is the lye circulation pump; 15 is the lye filling tank; 17 is the lye heat exchanger; 18 is the lye filter; 21 is the pure water system. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0030] Embodiment: As Figure 1 shown:

[0031] It includes an ALK system, a PEM system, a membrane distillation system 7, a cooling water circulation system 6, and a pure water system 21.

[0032] In the ALK system, the high-temperature lye enters the lye heat exchanger 17 after being separated by the ALK system oxygen separator 2 and the ALK system hydrogen separator 3, and after heat exchange, it passes through the lye filter 18 and re-enters the alkaline electrolyzer 13 through the lye circulation pump 14.

[0033] The low-temperature cooling water in the cooling water circulation system 6 enters the lye heat exchanger 17 as a refrigerant through the water pump 5 to cool down the high-temperature lye in the lye heat exchanger 17. The cooled cooling water enters the high-temperature feed liquid side of the membrane distillation system 7 as a high-temperature feed liquid, and after membrane distillation in the membrane distillation system 7, it returns to the cooling water circulation system 6.

[0034] The pure water system 21 pre-produces a certain amount of pure water as the low-temperature feed liquid before starting up. After the hydrogen production system starts up, the low-temperature feed liquid enters the low-temperature feed liquid side of the membrane distillation system 7 through the valve 20 and the water pump 19. After continuously supplementing pure water in the membrane distillation system 7, it enters the pure water inlets of the ALK system oxygen separator 2, the ALK system hydrogen separator 3, and the PEM electrolyzer 9 through the valves 1, 4, and 8, serving as the pure water source for the ALK and PEM systems.

[0035] The high-temperature pure water at the outlet of the cooling water circulation system 6 enters the high-temperature feed liquid side of the membrane distillation system 7 as a high-temperature feed liquid, and after membrane distillation in the membrane distillation system 7, it returns to the cooling water circulation system 6; the high-temperature pure water generated by the PEM electrolyzer 9 in the PEM system enters the high-temperature feed liquid side of the membrane distillation system 7 through the water pump 12; the low-temperature pure water separated by the PEM system oxygen separator 10 and the PEM system hydrogen separator 11 in the PEM system enters the low-temperature feed liquid side of the membrane distillation system 7 as a low-temperature feed liquid through the valve 22 and the water pump 19 to continuously supplement the low-temperature feed liquid for the membrane distillation system 7.

[0036] The hydrogen production scale of the PEM system is 100 - 400 Nm 3 / H 2 Per hour, the hydrogen production scale of the ALK system is 300 - 1200 Nm 3 / H 2 Per hour, the ratio of the ALK hydrogen production scale to the PEM hydrogen production scale is 3:1 - 1:1; when the new energy fluctuates greatly, only the PEM system operates to ensure good responsiveness and a certain hydrogen production scale. After the new energy is relatively stable, the ALK system is started to increase the hydrogen production scale and make full use of waste heat.

[0037] The new energy includes wind power, photovoltaic power, hydropower, etc.

[0038] The membrane distillation system 7 is a direct contact membrane distillation system, and the separation membrane material used is one of polytetrafluoroethylene, polypropylene, polyethylene, and polyvinylidene fluoride.

[0039] The ALK system and the PEM system share a set of pure water system 21, cooling water circulation system 6, and new energy.

[0040] The cooling water circulation system 6 includes a cooling tower. The cooling water can be recycled, and the cooling water is supplemented according to the actual consumption.

[0041] The pure water system 21 only produces a part of pure water in advance before the hydrogen production system is started as the low-temperature feed liquid of the membrane distillation system 7. After the system is started, it operates intermittently according to the actual pure water usage situation and does not work all the time.

[0042] After the high-temperature feed liquid and the low-temperature feed liquid perform water molecule transfer in the membrane distillation system 7, the low-temperature feed liquid enters the oxygen separator 2 of the ALK system, the hydrogen separator 3 of the ALK system, and the pure water inlet of the PEM electrolyzer 9 in the form of pure water through valves, and is used as raw material pure water for electrolytic hydrogen production; the high-temperature feed liquid enters the cooling water circulation system 6, and after cooling, it re-enters the lye heat exchanger 17 for heat exchange.

[0043] The lye filling tank 15 completes the lye configuration and enters the alkaline electrolyzer 13 through the valve 16 and the lye circulation pump 14. The alkaline electrolyzer 13 electrolyzes the lye. The generated hydrogen and part of the lye enter the hydrogen separator 3 of the ALK system for separation. The separated hydrogen enters the post-treatment system for re-separation, purification, and collection; the generated oxygen and part of the lye enter the oxygen separator 2 of the ALK system for separation. The separated oxygen is simply cooled and then discharged; the high-temperature lye separated in the oxygen separator 2 of the ALK system and the hydrogen separator 3 of the ALK system enters the lye heat exchanger 17 for cooling. After cooling to a suitable temperature, it enters the lye filter 18 for filtration. The filtered lye enters the alkaline electrolyzer 13 again through the lye circulation pump 14 for electrolytic hydrogen production.

[0044] The lye heat exchanger 17 cools the high-temperature lye. The temperature of the cooling water after heat exchange generally exceeds 60 °C and enters the membrane distillation system 7 in the form of high-temperature feed liquid. At the same time, the high-temperature pure water generated by the PEM electrolyzer 9 also enters the membrane distillation system 7 as high-temperature feed liquid through the water pump 12.

[0045] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied to other related technical fields, shall be included in the patent protection scope of the present invention by the same token.

Claims

1. A hydrogen production system of alkaline water electrolysis coupled with proton exchange membrane water electrolysis, characterized in that: It includes an ALK system and a PEM system for producing hydrogen using renewable energy as a power source, and also includes a membrane distillation system (7), a cooling water circulation system (6) and a pure water system (21); The cooling water of the cooling water circulation system (6) is used to cool the ALK alkali solution heat exchanger (17) in the ALK system, and the cooling water after heat exchange enters the high-temperature liquid side of the membrane distillation system (7); The liquid outlet of the PEM electrolyzer (9) of the PEM system is connected to the high-temperature liquid side of the membrane distillation system (7); The output end of the pure water system (21) is connected to the low-temperature feed liquid side of the membrane distillation system (7); The pure water inlet of the PEM electrolyzer (9) of the PEM system, the pure water inlet of the ALK system oxygen separator (2), and the pure water inlet of the ALK system hydrogen separator (3) are all connected to the low-temperature feed liquid side of the membrane distillation system (7).

2. The hydrogen production system of alkaline water electrolysis coupled with proton exchange membrane water electrolysis according to claim 1, characterized in that: The new energy source is any one of wind power, photovoltaic power and hydropower.

3. The hydrogen production system of alkaline water electrolysis coupled with proton exchange membrane water electrolysis according to claim 1, characterized in that: The membrane distillation system (7) is a direct contact membrane distillation system, and the separation membrane material used is any one of polytetrafluoroethylene, polypropylene, polyethylene, and polyvinylidene fluoride.

4. The hydrogen production system of alkaline water electrolysis coupled with proton exchange membrane water electrolysis according to claim 1, characterized in that: The high-temperature alkali liquid in the ALK system is separated by the ALK system oxygen separator (2) and / or the ALK system hydrogen separator (3) and enters the alkali liquid heat exchanger (17). After heat exchange, it passes through the filter (18) and flows back to the ALK electrolyzer through the alkali liquid circulation pump (14).

5. The hydrogen production system of alkaline water electrolysis coupled with proton exchange membrane water electrolysis according to claim 1, characterized in that: The low-temperature feed liquid side of the membrane distillation system (7) is also connected to the liquid outlets of the PEM system oxygen separator (10) and the PEM system hydrogen separator (11).

6. The hydrogen production system of alkaline water electrolysis coupled with proton exchange membrane water electrolysis according to claim 1, characterized in that: The hydrogen production scale ratio of the ALK system and the PEM system is 3:1 to 1:

1.

7. The hydrogen production system of alkaline water electrolysis coupled with proton exchange membrane water electrolysis according to claim 1, characterized in that: The high-temperature liquid side of the membrane distillation system (7) is also connected to the cooling water circulation system (6) to form a circulation.

8. The hydrogen production system of alkaline water electrolysis coupled with proton exchange membrane water electrolysis according to claim 1, characterized in that: The pure water inlet of the PEM electrolyzer (9) of the PEM system, the pure water inlet of the oxygen separator (2) of the ALK system, and the pure water inlet of the hydrogen separator (3) of the ALK system are all installed with corresponding valves to achieve pure water replenishment.

9. A method for producing hydrogen using an alkaline water electrolysis coupled with proton exchange membrane water electrolysis system as claimed in any one of claims 1 to 8, characterized in that: The following steps are involved: When new energy fluctuates greatly, only the PEM system is operated to ensure good responsiveness and a certain scale of hydrogen production. After the new energy is relatively stable, the ALK system is started to increase the scale of hydrogen production and make full use of waste heat.

10. The method of a hydrogen production system of alkaline water electrolysis coupled with proton exchange membrane water electrolysis as claimed in claim 9, characterized in that: The pure water system (21) produces a portion of pure water in advance before the hydrogen production system is started up as low-temperature feed liquid for the membrane distillation system (7).

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