Electrolytic hydrogen production system capable of reducing lower limit of production load and control method

Abstract

The invention relates to the technical field of hydrogen production through water electrolysis, and provides an electrolytic hydrogen production system capable of reducing the lower limit of production load and a control method, the system comprises an electrolytic bath, a hydrogen separator, an oxygen separator and a pure oxygen module; a hydrogen side outlet is formed in the cathode side of the electrolytic bath, and the hydrogen separator is connected with the hydrogen side outlet; an oxygen side outlet is formed in the anode side of the electrolytic bath, and the oxygen separator is connected with the oxygen side outlet; the pure oxygen module is suitable for outputting high-purity oxygen into the oxygen separator, the high-purity oxygen is used for being mixed with initial oxygen at the oxygen side outlet, and under the condition that the hydrogen content in the initial oxygen does not meet the set condition, the hydrogen content in mixed oxygen at the outlet of the oxygen separator meets the set condition. Through the arrangement, the upper limit of the hydrogen content in the initial oxygen at the oxygen side outlet can be greatly improved, so that the lower limit of the production load of the electrolytic hydrogen production system is reduced, and the electrolytic hydrogen production system can fully adapt to wide rapid fluctuation of renewable energy treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen production by water electrolysis, and in particular to an electrolytic hydrogen production system and a control method for reducing a lower limit of a production load. Background Art

[0002] With the increasing global awareness of environmental protection and the development of renewable energy technology, clean energy such as wind power and solar energy has gradually become an important direction for the transformation of energy structure. However, due to the inherent randomness, volatility and uncertainty of renewable energy, large-scale grid connection and consumption face many challenges. In this context, hydrogen energy storage, as an emerging energy storage method for power systems, has attracted widespread attention due to its clean, efficient and flexible characteristics. The basic principle of hydrogen energy storage is to convert excess electricity into hydrogen and store it through water electrolysis, and the production of hydrogen through water electrolysis is achieved through alkaline electrolyzers.

[0003] The diaphragm is one of the key components of the alkaline electrolyzer. It has two basic functions: 1) allowing the free movement of ions in the circuit of the electrolyzer; 2) isolating the hydrogen and oxygen produced during the electrocatalytic process. At the same time, the diaphragm must also have a certain chemical stability and physical stability to meet the requirements during assembly and operation.

[0004] At present, alkaline electrolyzers widely use composite diaphragms based on polyphenylene sulfide (PPS), which is essentially a porous diaphragm. Under the dynamic operation of the electrolyzer, the pressure on both sides of the diaphragm is inconsistent, which can easily lead to imbalance and hydrogen and oxygen cross-talk on both sides of the diaphragm. In particular, hydrogen molecules with small molecular weight and extremely fast movement speed can easily penetrate the diaphragm and diffuse from the cathode to the anode oxygen, causing the hydrogen content (hydrogen in oxygen) in the oxygen at the outlet of the oxygen separator to exceed the standard, thereby triggering system alarms and interlocking shutdowns.

[0005] When the production load of the electrolyzer decreases, the amount of hydrogen diffused from the cathode to the anode remains basically unchanged, while the oxygen production at the anode decreases, so the hydrogen in the oxygen at the oxygen separator outlet increases. When the production load decreases to a certain lower limit, the hydrogen content in the oxygen at the oxygen separator outlet (hydrogen in oxygen) will exceed the safety limit (the lower explosion limit of hydrogen is 4%), bringing the risk of "tank explosion".

[0006] Therefore, the production load of alkaline electrolyzers is usually within a range. At present, the production load of mainstream electrolyzers is 50~110%, and some new electrolyzers can be expanded to 30~110% through technical optimization. Among them, the lower limit of production load (50% or 30%) is determined by the upper limit of hydrogen in oxygen at the outlet of oxygen separator, and a certain safety margin is considered (hydrogen in oxygen ≥1.5%, system alarm; ≥1.8%, system interlocking and stopping).

[0007] How to broaden the production load range of the electrolysis hydrogen production system so that it can fully adapt to the wide and rapid fluctuations in renewable energy output is an important issue that needs to be solved urgently. Summary of the invention

[0008] The present invention provides an electrolytic hydrogen production system and a control method for reducing the lower limit of production load, so as to solve the defect of a small production load range of the electrolytic hydrogen production system in the prior art, and can broaden the production load range of the electrolytic hydrogen production system to fully adapt to the wide and rapid fluctuations of renewable energy processing.

[0009] The present invention provides an electrolytic hydrogen production system for reducing the lower limit of production load, comprising: an electrolyzer, a hydrogen separator, an oxygen separator and a pure oxygen module; The cathode side of the electrolytic cell is provided with a hydrogen side outlet, and the hydrogen separator is connected to the hydrogen side outlet; the anode side of the electrolytic cell is provided with an oxygen side outlet, and the oxygen separator is connected to the oxygen side outlet; The pure oxygen module is suitable for outputting high-purity oxygen into the oxygen separator, and the high-purity oxygen is used to mix with the initial oxygen at the oxygen side outlet, so that when the hydrogen content in the initial oxygen does not meet the set conditions, the hydrogen content in the mixed oxygen at the oxygen separator gas outlet meets the set conditions.

[0010] According to an electrolytic hydrogen production system for reducing the lower limit of production load provided by the present invention, a high-purity oxygen inlet is provided on the oxygen separator, and the output end of the pure oxygen module is connected to the high-purity oxygen inlet; And / or, the oxygen separator is connected to the oxygen side outlet via a primary oxygen pipeline, and the output end of the pure oxygen module is connected to the primary oxygen pipeline.

[0011] According to an electrolytic hydrogen production system for reducing the lower limit of production load provided by the present invention, the pure oxygen module includes an oxygen purification device, a pure oxygen storage tank and a circulating compressor; The inlet of the oxygen purification device is connected to the gas outlet of the oxygen separator, and the outlet is connected to the pure oxygen storage tank; the outlet of the pure oxygen storage tank is connected to the inlet of the circulation compressor, and the outlet of the circulation compressor is used to output high-purity oxygen, forming the output end of the pure oxygen module.

[0012] According to an electrolytic hydrogen production system for reducing the lower limit of production load provided by the present invention, the compressor includes a centrifugal compressor or a positive displacement compressor.

[0013] According to an electrolytic hydrogen production system for reducing the lower limit of production load provided by the present invention, a first hydrogen content detector is connected to the oxygen side outlet, and a second hydrogen content detector is connected to the outlet of the oxygen separator.

[0014] According to the present invention, an electrolytic hydrogen production system for reducing the lower limit of production load also includes an alarm module; Determine that the hydrogen content in the initial oxygen reaches X 1 When the alarm module is controlled to alarm, it reaches X 2 When the control system stops, the X 1 <X 2 <4%; Determine that the hydrogen content in the mixed oxygen reaches X 3 When the alarm module is controlled to alarm, it reaches X 4 When the control system stops, the X 3 <X 4 .

[0015] According to an electrolytic hydrogen production system for reducing the lower limit of production load provided by the present invention, a third hydrogen content detector is connected to the outlet of the purification device; Determine that the hydrogen content in oxygen at the outlet of the purification device reaches X 5 When the alarm module is controlled to alarm, it is determined that the hydrogen content in the oxygen at the outlet of the purification device reaches X 6 When the control system stops, the X 5 <X 6 .

[0016] According to an electrolysis hydrogen production system for reducing the lower limit of production load provided by the present invention, the second hydrogen content detector is interlocked with the circulation compressor; and / or the output end of the pure oxygen module is connected to a flow regulating valve, and the second hydrogen content detector is interlocked with the flow regulating valve.

[0017] According to an electrolytic hydrogen production system for reducing the lower limit of production load provided by the present invention, n electrolytic cells are provided, and n electrolytic cells are all connected to the oxygen separator, and n≥2; The electrolyzer started first is suitable for inputting initial oxygen whose hydrogen content does not exceed the set value into the oxygen separator, so that when the electrolyzer started later is started when the hydrogen content in the initial oxygen exceeds the set value, the hydrogen content in the mixed oxygen does not exceed the set value; the electrolyzer started first constitutes the pure oxygen module.

[0018] According to the present invention, an electrolytic hydrogen production system for reducing the lower limit of production load also includes an alkali liquid cooler and an alkali liquid circulation pump; the liquid outlets of the hydrogen separator and the oxygen separator are connected to the inlet of the alkali liquid cooler, and the outlet of the alkali liquid cooler is connected to the electrolytic cell through the alkali liquid circulation pump.

[0019] According to the present invention, an electrolytic hydrogen production system for reducing the lower limit of production load also includes a hydrogen purification device, and the inlet of the hydrogen purification device is connected to the gas outlet of the hydrogen separation device.

[0020] The present invention also provides a control method for an electrolytic hydrogen production system for reducing the lower limit of production load, comprising the following steps: Obtain the hydrogen content in the initial oxygen; When it is determined that the hydrogen content in the initial oxygen does not meet the set conditions, the pure oxygen module is controlled to output high-purity oxygen into the oxygen separator so that the hydrogen content in the mixed oxygen meets the set conditions; When it is determined that the hydrogen content in the initial oxygen meets the set condition, the pure oxygen module is controlled to stop outputting high-purity oxygen into the oxygen separator.

[0021] According to a control method for an electrolytic hydrogen production system for reducing a lower limit of production load provided by the present invention, when it is determined that the hydrogen content in the initial oxygen does not meet a set condition, the pure oxygen module is controlled to output high-purity oxygen into the oxygen separator so that the hydrogen content in the mixed oxygen meets the set condition, comprising: Determining a mixing ratio of the high-purity oxygen to the initial oxygen according to the hydrogen content in the initial oxygen and the set conditions; Determining a set flow rate of high-purity oxygen according to a mixing ratio of the high-purity oxygen and the initial oxygen; The pure oxygen module is controlled to output high-purity oxygen of a set flow rate into the oxygen separator.

[0022] The present invention also provides a control method for an electrolytic hydrogen production system for reducing the lower limit of production load, comprising the following steps: when the renewable power generation system starts to produce power, starting the first electrolytic cell, gradually increasing the load to the lower limit of production load P min Then, continue to increase the load to P 1 At the P 1 <100%; According to the output of the renewable system, the nth electrolytic cell is started in sequence, and the production load of the nth electrolytic cell is increased to P n , so that the hydrogen content in the mixed oxygen formed by mixing the initial oxygen produced by the nth electrolytic cell with the initial oxygen produced by the previous n-1 electrolytic cell meets the set conditions, the P n+1 <P n <P min , where n≥2; Add the nth electrolytic cell to the system and increase the load to P 1 ; When the output of the renewable power generation device system continues to increase, the production load of n electrolyzers is increased to 100% at the same time.

[0023] The electrolytic hydrogen production system and control method for reducing the lower limit of production load provided by the present invention can output high-purity oxygen to the oxygen separator through the pure oxygen module when the hydrogen content in the initial oxygen of the electrolyzer exceeds the standard due to reduced production load, load fluctuation or other reasons. The high-purity oxygen is mixed with the pure oxygen output from the oxygen side outlet to form mixed oxygen. The high-purity oxygen can dilute the hydrogen in the initial oxygen to significantly reduce the hydrogen content in the mixed oxygen. Therefore, when the hydrogen content in the initial oxygen does not meet the set conditions, the hydrogen content in the mixed oxygen at the outlet of the oxygen separator meets the set conditions. The initial oxygen is mixed with the alkali solution before entering the oxygen separator and is in a liquid state. Therefore, it is only necessary to make the hydrogen content in the initial oxygen less than the lower explosion limit of hydrogen. In comparison, the upper limit of the hydrogen content in the initial oxygen at the oxygen side outlet can be greatly increased, thereby reducing the lower limit of the production load of the electrolytic hydrogen production system, so that it can fully adapt to the wide and rapid fluctuations in renewable energy processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 work.

[0025] Figure 1 This is one of the structural schematic diagrams of the electrolytic hydrogen production system for reducing the lower limit of production load provided in an embodiment of the present invention.

[0026] Figure 2 It is a schematic diagram of the electrolytic hydrogen production system provided by the present invention using a centrifugal compressor and a second hydrogen content detector for cascade control.

[0027] Figure 3 It is a schematic diagram of the electrolytic hydrogen production system provided by the present invention using a positive displacement compressor and a second hydrogen content detector for cascade control.

[0028] Figure 4 This is the second structural schematic diagram of the electrolytic hydrogen production system for reducing the lower limit of production load provided in an embodiment of the present invention.

[0029] Figure 5 It is a schematic diagram of the electrolytic hydrogen production system provided by the present invention using a centrifugal compressor and a second hydrogen content detector for single-loop control.

[0030] Figure 6 It is a schematic diagram of the electrolytic hydrogen production system provided by the present invention using a positive displacement compressor and a second hydrogen content detector for single-loop control.

[0031] Reference numerals: 10. Electrolyzer; 11. Hydrogen separator; 12. Oxygen separator; 13. Primary oxygen pipeline; 14. First hydrogen content detector; 15. Second hydrogen content detector; 16. Third hydrogen content detector; 17. Alkali solution cooler; 18. Alkali solution circulation pump; 19. Hydrogen purification device; 20. Oxygen purification device; 21. Pure oxygen storage tank; 22. Circulation compressor; 23. Flow control valve. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are 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 are within the scope of protection of the present invention.

[0033] In order to facilitate understanding of the electrolytic hydrogen production system and control method for reducing the lower limit of production load provided by the present invention, its application background is first introduced. Hydrogen energy storage, as an emerging power system energy storage method, has attracted widespread attention due to its clean, efficient and flexible characteristics. Its basic principle is to use water electrolysis technology to convert excess electricity into hydrogen for storage, and this process is mainly achieved through alkaline electrolyzers.

[0034] As a key component in the electrolyzer, the diaphragm is responsible for allowing ions to move and isolating the generated hydrogen and oxygen, and it needs to have chemical and physical stability. At present, alkaline electrolyzers mainly use PPS-based composite diaphragms, but this type of diaphragm is prone to hydrogen-oxygen crosstalk under dynamic operating conditions, especially when the production load is reduced, which will increase the hydrogen content in the oxygen and may exceed the safety limit, causing the system to shut down. Therefore, the production load of the electrolyzer is usually limited to a certain range, with the mainstream electrolyzer being 50~110%, and some new electrolyzers can be expanded to 30~110% through technical optimization.

[0035] How to expand the production load range of the electrolytic hydrogen production system to adapt to the wide and rapid fluctuations in renewable energy output is the current technical challenge. In view of the above problems, the present invention provides an electrolytic hydrogen production system and control method for reducing the lower limit of production load, which can broaden the production load range of the electrolytic hydrogen production system and enable it to fully adapt to the wide and rapid fluctuations in renewable energy processing.

[0036] Combine the following Figure 1-Figure 6 The present invention describes an electrolytic hydrogen production system and a control method for reducing the lower limit of production load.

[0037] Reference Figures 1 to 6A hydrogen production system by electrolysis for reducing the lower limit of production load comprises an electrolyzer 10, a hydrogen separator 11, an oxygen separator 12 and a pure oxygen module; wherein a hydrogen side outlet is provided on the cathode side of the electrolyzer 10, the hydrogen separator 11 is connected to the hydrogen side outlet, an oxygen side outlet is provided on the anode side of the electrolyzer 10, the oxygen separator 12 is connected to the oxygen side outlet; the pure oxygen module is suitable for outputting high-purity oxygen into the oxygen separator 12, the high-purity oxygen is used to mix with the initial oxygen at the oxygen side outlet, so that when the hydrogen content in the initial oxygen does not meet the set conditions, the hydrogen content in the mixed oxygen at the outlet of the oxygen separator 12 meets the set conditions.

[0038] In actual work, the electrolyzer 10 is used to electrolyze water to produce hydrogen and generate hydrogen on the cathode side and oxygen on the anode side. The mixture of hydrogen and alkali liquid enters the hydrogen separator 11 through the hydrogen side outlet. The hydrogen separator 11 can perform gas-liquid separation on hydrogen and alkali liquid. The mixture of oxygen and alkali liquid enters the oxygen separator 12 through the oxygen side outlet. The oxygen separator 12 can perform gas-liquid separation on oxygen and alkali liquid. Normally, the hydrogen content in the oxygen at the oxygen side outlet and the gas outlet of the oxygen separator 12 should be consistent.

[0039] When the hydrogen content in the initial oxygen of the electrolyzer 10 exceeds the standard due to reduced production load, load fluctuation or other reasons, high-purity oxygen can be output to the oxygen separator 12 through the pure oxygen module. The high-purity oxygen is mixed with the initial oxygen output from the oxygen side outlet to form mixed oxygen. The high-purity oxygen can dilute the hydrogen in the initial oxygen to significantly reduce the hydrogen content in the mixed oxygen. Therefore, when the hydrogen content in the initial oxygen does not meet the set conditions, the hydrogen content in the mixed oxygen at the gas outlet of the oxygen separator 12 meets the set conditions. The initial oxygen is mixed with the alkali solution in a liquid condition before entering the oxygen separator 12. Therefore, it is only necessary to make the hydrogen content in the initial oxygen less than the lower explosion limit of hydrogen. In comparison, the upper limit of the hydrogen content in the initial oxygen at the oxygen side outlet can be greatly increased, thereby reducing the lower limit of the production load of the electrolytic hydrogen production system, so that it can fully adapt to the wide and rapid fluctuations in renewable energy processing.

[0040] It should be noted that the specific structure and working principle of the electrolytic cell 10 can refer to the alkaline electrolytic cell 10 in the prior art. In the embodiment of the present invention, only its electrolysis hydrogen production function is utilized without changing the structure and principle of the electrolytic cell 10. The specific structure of the electrolytic cell 10 is not the main invention point of the present invention. Therefore, the specific structure of the electrolytic cell 10 is not described in detail in the embodiment of the present invention.

[0041] It should be noted that the specific structure and working principle of the hydrogen separator 11 and the oxygen separator 12 can refer to the hydrogen gas-liquid separator and oxygen gas-liquid separator in the prior art. The main function of the hydrogen separator 11 is to separate the hydrogen and the alkali liquid discharged from the hydrogen side outlet, and the main function of the oxygen separator 12 is to separate the oxygen and the alkali liquid discharged from the oxygen side outlet. In the embodiment of the present invention, the specific structure and working principle of the hydrogen separator 11 and the oxygen separator 12 are not changed. Therefore, the specific structure and working principle of the hydrogen separator 11 and the oxygen separator 12 are not repeated in the embodiment of the present invention.

[0042] In some optional embodiments, the pure oxygen module has a variety of optional forms according to different application scenarios.

[0043] In one embodiment of the present invention, the pure oxygen module includes an oxygen purification device 20, a pure oxygen storage tank 21 and a circulating compressor 22; wherein the inlet of the oxygen purification device 20 is connected to the gas outlet of the oxygen separator 12, and the outlet is connected to the pure oxygen storage tank 21; the outlet of the pure oxygen storage tank 21 is connected to the inlet of the circulating compressor 22, and the outlet of the circulating compressor 22 is used to output high-purity oxygen, forming the output end of the pure oxygen module.

[0044] Specifically, the oxygen purification device 20 is used to purify the oxygen discharged from the gas outlet of the oxygen separator 12, so as to obtain high-purity oxygen with a preset concentration.

[0045] It is understandable that, according to different working principles, there are multiple options for the oxygen purification device 20, such as pressure swing adsorption, membrane separation, dehydrogenation reactor, etc., which can be selected according to actual needs, and are not specifically limited in the embodiments of the present invention. In addition, the specific structure of the oxygen purification device 20 can refer to the prior art, and will not be repeated in the embodiments of the present invention.

[0046] According to different working principles, the circulating compressor 22 can be a centrifugal compressor (such as Figure 2 As shown), you can also use a positive displacement compressor (such as Figure 3 to meet different actual needs.

[0047] In actual work, the oxygen discharged from the gas outlet of the oxygen separator 12 enters the oxygen purification device 20, and is purified by the oxygen purification device 20 to obtain high-purity oxygen with a preset concentration. The pure oxygen storage tank 21 can store the high-purity oxygen. When the hydrogen content in the initial oxygen exceeds the standard, the high-purity oxygen in the pure oxygen storage tank 21 can be input into the oxygen separator 12 through the circulation compressor 22, and the high-purity oxygen is mixed with the initial oxygen so that the hydrogen content in the oxygen at the outlet of the oxygen separator 12 meets the set conditions.

[0048] In one embodiment of the present invention, referring to Figures 2 to 3, all the mixed oxygen can pass through the oxygen purification device 20, and a branch pipeline is added at the outlet of the oxygen purification device 20, so that part of the high-purity oxygen purified by the oxygen purification device 20 is stored in the pure oxygen storage tank 21, and the other part of the high-purity oxygen is used downstream (storage, bottling, filling tank trucks or direct use) or emptied. The oxygen purification device 20 and pure oxygen storage tank 21 required in this technical solution are relatively large.

[0049] In one embodiment of the present invention, referring to Figure 4 , an exhaust port can be added at the outlet of the oxygen separator 12. When the mixed oxygen that does not participate in the oxygen cycle is exhausted, it can be directly discharged through the exhaust port, and the mixed oxygen that participates in the oxygen cycle will enter the oxygen purification device 20. This can reduce the investment in the oxygen purification device 20 and the pure oxygen storage tank 21, and save energy consumption for oxygen purification. Of course, if the mixed oxygen that does not participate in the oxygen cycle has a certain downstream application, the technical solution of this embodiment cannot be adopted, because the hydrogen content in the mixed oxygen is relatively high and cannot meet the purity requirements of downstream applications.

[0050] In one embodiment of the present invention, a compressor may be provided between the oxygen purification device 20 and the pure oxygen storage tank 21 to compress high-purity oxygen and store it in the pure oxygen storage tank 21 to increase the storage capacity of the pure oxygen storage tank 21 .

[0051] According to different actual requirements, the output end of the pure oxygen module can be connected to the oxygen separator 12 in different ways.

[0052] In one embodiment of the present invention, the oxygen separator 12 is connected to the oxygen side outlet via a primary oxygen pipeline 13 , and the output end of the pure oxygen module is connected to the primary oxygen pipeline 13 .

[0053] Through the above technical solution, when the hydrogen content in the initial oxygen exceeds the standard, the pure oxygen module can pass high-purity oxygen into the oxygen separator 12 through the initial oxygen pipeline 13, and the high-purity oxygen and the initial oxygen are mixed in the oxygen separator 12 to ensure that the hydrogen content in the mixed oxygen at the outlet of the oxygen separator 12 meets the set conditions. However, since the fluid in the initial oxygen pipeline 13 is a mixture of alkali liquid and initial oxygen, it is difficult to input pure oxygen into the oxygen separator 12 through the initial oxygen pipeline 13.

[0054] Therefore, in one embodiment of the present invention, a high-purity oxygen inlet is provided on the oxygen separator 12, and the output end of the pure oxygen module is connected to the high-purity oxygen inlet. Through the above technical solution, high-purity oxygen can be directly introduced into the oxygen separator 12 through the high-purity oxygen inlet on the oxygen separator 12.

[0055] Specifically, one or more electrolyzers 10 may be provided. When more than one electrolyzer 10 is provided, the multiple electrolyzers 10 share the oxygen separator 12. When the hydrogen content in the oxygen at the gas outlet of the oxygen separator 12 exceeds the standard, pure oxygen can be input into the oxygen separator 12 through the pure oxygen module to ensure that the oxygen at the gas outlet of the oxygen separator 12 meets the set conditions.

[0056] Specifically, under set conditions, the hydrogen content in oxygen is less than 1.5%.

[0057] In order to facilitate monitoring and control, the oxygen side outlet of the electrolyzer 10 is connected to a first hydrogen content detector 14 for detecting the hydrogen content in the initial oxygen, and the outlet of the oxygen separator 12 is connected to a second hydrogen content detector 15 for detecting the hydrogen content in the mixed oxygen at the gas outlet of the oxygen separator 12.

[0058] In one embodiment of the present invention, the electrolytic hydrogen production system further includes a controller and an alarm module; the first hydrogen content detector 14, the second hydrogen content detector 15, the alarm module and the controller are electrically connected.

[0059] When the hydrogen content in oxygen reaches X 1 When the controller controls the alarm module to alarm, it reaches X 2 When the control system stops, X 1 <X 2 <4% (4% is the lower explosion limit of hydrogen). 1 and X 2 It can provide sufficient safety margin for the system to ensure safe and reliable operation of the system. 1 and X 2 The specific value of can be set according to actual needs and is not specifically limited in the embodiments of the present invention.

[0060] When the hydrogen content in the mixed oxygen reaches X 3 When the alarm module is controlled to alarm, it reaches X 4 When the control system stops, X 3 <X 4 By setting X 3 and X 4 It can ensure that the hydrogen content in the oxygen at the outlet of the oxygen separator 12 is within the safe limit, effectively avoiding the risk of tank explosion. 3 The value of X is 1.5%, 4 The value is 1.8%. When the hydrogen content in the mixed oxygen reaches 1.5%, the control alarm module alarms. When it reaches 1.8%, the control system stops.

[0061] Specifically, the hydrogen content in the mixed oxygen is calculated by the following formula: In one embodiment of the present invention, a third hydrogen content detector 16 is connected to the outlet of the purification device to determine whether the hydrogen content in the oxygen at the outlet of the purification device reaches X 5 When the control alarm module alarms, it is determined that the hydrogen content in oxygen at the outlet of the purification device reaches X 6 When the system stops, X 5 <X 6 By setting X 5 and X 6 It can ensure that the hydrogen content in high-purity oxygen does not exceed the standard. 5 and X 6 The specific value of can be set according to actual needs. In this embodiment, X 5 The value is 5×10 -4 (i.e. high purity oxygen purity <99.95%), X 6 The value is 10×10 -4 (i.e. high purity oxygen purity <99.9%).

[0062] For the convenience of control, in one embodiment of the present invention, the second hydrogen content detector 15 is interlocked with the circulating compressor 22. The flow rate of the high-purity oxygen is directly adjusted by adjusting the speed of the circulating compressor 22.

[0063] In another embodiment of the present invention, the output end of the pure oxygen module is connected to a flow regulating valve 23 , and the second hydrogen content detector 15 is interlocked with the flow regulating valve 23 for control.

[0064] Specifically, refer to Figure 2 and Figure 3 The hydrogen content in the mixed oxygen at the outlet of the oxygen separator 12 can be used as the main parameter, and the outlet flow of the circulating compressor 22 can be used as the secondary parameter to form a cascade regulation system.

[0065] However, since the cascade control system uses more instruments and the PID parameter setting is also more troublesome, Figure 5 and Figure 6 A simple regulating system for regulating the outlet flow of the pure oxygen circulating compressor 22 can also be considered, wherein the low value F of the high purity oxygen circulating flow L and low value F LL , which can be calculated by the above formula for hydrogen content in mixed oxygen and adjusted by the controller (DCS or PLC).

[0066] In practical applications, when the hydrogen content in oxygen increases due to load fluctuation or other reasons at high production load in the hydrogen production system, pure oxygen is input into the oxygen separator 12 through the pure oxygen module to reduce the hydrogen content in the mixed oxygen at the outlet of the oxygen separator 12, which will inevitably lead to an increase in the processing capacity of the oxygen separator 12. For example, when the production load is 70%, the load of the oxygen separator 12 is 70% under normal circumstances, but after inputting pure oxygen into the oxygen separator 12, the load of the oxygen separator 12 may exceed 100%. Therefore, the load P of the oxygen separator 12 needs to be expanded according to the production load. Specifically, P is any value greater than 100% load, which can be flexibly adjusted according to different design conditions, usually 120~200%. In order to maintain the liquid level balance between the hydrogen separator 11 and the oxygen separator 12, the hydrogen separator 11 needs to be expanded according to the production load.

[0067] Through the above technical solution, the oxygen discharged from the gas outlet of the oxygen separator 12 enters the oxygen purification device 20, and high-purity oxygen with a preset concentration is obtained after purification by the oxygen purification device 20. When the hydrogen content in the initial oxygen exceeds the standard, the high-purity oxygen in the pure oxygen storage tank 21 can be input into the oxygen separator 12 through the circulating compressor 22, and the high-purity oxygen is mixed with the initial oxygen, so that the hydrogen content in the oxygen at the outlet of the oxygen separator 12 meets the set conditions.

[0068] In another embodiment of the present invention, n electrolytic cells 10 are provided, and all of the n electrolytic cells 10 are connected to the oxygen separator 12, where n≥2; the electrolytic cell 10 started first is suitable for inputting initial oxygen whose hydrogen content does not exceed the set value into the oxygen separator 12, so that when the electrolytic cell 10 started later is started when the hydrogen content in the initial oxygen exceeds the set value, the hydrogen content in the mixed oxygen does not exceed the set value; the electrolytic cell 10 started first is constituted as a pure oxygen module.

[0069] Specifically, taking 4 in 1 as an example, four electrolytic cells 10 are connected to one oxygen separator 12 at the same time.

[0070] 1) When the wind and solar power station starts to produce power, first start the 1# electrolytic cell 10 and gradually increase the load to the production load lower limit P min Then, continue to increase the load to P 1 Place (P 1 <100%, the 1# electrolytic cell 10 is not increased to full load production in order to allocate part of the power to the 2# electrolytic cell 10 so that it can start up as soon as possible).

[0071] 2) When the output of the wind and solar power station continues to increase, start the 2# electrolytic cell 10. When the production load of the 2# electrolytic cell 10 increases to P 2 (P 2 <P min), as long as the hydrogen content in the mixed oxygen (initial oxygen in tank 1# + initial oxygen in tank 2#) at the outlet of oxygen separator 12 is less than 1.5%, the 2# electrolytic cell 10 can be incorporated into the system and the load can be continuously increased to P min , and then raised to P 1 ; 3) When the output of the wind and solar power station continues to increase, start the 3# electrolytic cell 10. When the production load of the 3# electrolytic cell 10 increases to P 3 (P 3 <P 2 <P min ), as long as the hydrogen content in the mixed oxygen (1# tank initial oxygen + 2# tank initial oxygen + 3# tank initial oxygen) at the outlet of the oxygen separator 12 is less than 1.5%, the 3# electrolyzer 10 can be incorporated into the system and the load can be continuously increased to P min , and then raised to P 1 ; 4) When the output of the wind and solar power station continues to increase, start the 4# electrolytic cell 10 (the last electrolytic cell 10). When the production load of the 4# electrolytic cell 10 increases to P 4 (P 4 <P 3 <P 2 <P min ), as long as the hydrogen content in the mixed oxygen (1# tank initial oxygen + 2# tank initial oxygen + 3# tank initial oxygen + 4# tank initial oxygen) at the outlet of the oxygen separator 12 is less than 1.5%, the 4# electrolyzer 10 can be incorporated into the system and the load can be continuously increased to P min , and then raised to P 1 ; 5) When the output of the wind and solar power stations continues to increase, the production load of 1#~4# electrolytic cells 10 is increased at the same time until it reaches 100% full load.

[0072] When a single tank is started normally, the production load is P 2 , P 3 , P 4 When the load is lower than the normal production load limit P min , resulting in excessive hydrogen in oxygen, and each cell cannot be incorporated into the system. For the 4-in-1 electrolytic hydrogen production system, due to the mixing of qualified oxygen from the preceding electrolytic cell 10, each subsequent cell can be safely incorporated into the system when the load is below the lower limit of normal production load, thereby shortening the overall startup time of the 4-in-1 electrolytic hydrogen production system.

[0073] Specifically, P min To determine the value, it is provided by the equipment manufacturer.

[0074] In one embodiment of the present invention, the electrolytic hydrogen production system also includes an alkali liquid cooler 17 and an alkali liquid circulation pump 18; the liquid outlets of the hydrogen separator 11 and the oxygen separator 12 are connected to the inlet of the alkali liquid cooler 17, and the outlet of the alkali liquid cooler 17 is connected to the electrolytic cell 10 through the alkali liquid circulation pump 18, thereby forming an alkali liquid circulation.

[0075] In one embodiment of the present invention, the electrolytic hydrogen production system further includes a hydrogen purification device 19, and an inlet of the hydrogen purification device 19 is connected to a gas outlet of the hydrogen separation device.

[0076] According to different working principles, there are many options for the oxygen purification device 20, such as pressure swing adsorption, catalytic deoxygenation, palladium membrane diffusion, etc. The specific one can be selected according to actual needs and is not specifically limited in the embodiment of the present invention.

[0077] It is to be understood that, without mutual contradiction, those skilled in the art may combine and combine the different embodiments or examples and the features of the different embodiments or examples described in this specification.

[0078] The control method of the electrolytic hydrogen production system for reducing the lower limit of the production load provided by the present invention is described below. The control method of the electrolytic hydrogen production system for reducing the lower limit of the production load described below and the electrolytic hydrogen production system for reducing the lower limit of the production load described above can be referenced to each other.

[0079] In one embodiment of the present invention, a control method for an electrolytic hydrogen production system for reducing the lower limit of production load is applicable to an independently arranged pure oxygen module, comprising the following steps: S1. Obtain the hydrogen content in the initial oxygen.

[0080] Specifically, before the pure oxygen module introduces pure oxygen into the oxygen separator 12, the hydrogen content in the oxygen at the oxygen side outlet and the gas outlet of the oxygen separator 12 is consistent. Therefore, the hydrogen content in the initial oxygen can be obtained by the first hydrogen content detector 14 or by the second hydrogen content detector 15.

[0081] S2. When it is determined that the hydrogen content in the initial oxygen does not meet the set condition, the pure oxygen module is controlled to output high-purity oxygen into the oxygen separator 12 so that the hydrogen content in the mixed oxygen meets the set condition.

[0082] Specifically, the inequality can be established based on the hydrogen content in the initial oxygen and the set conditions: Determine the mixing ratio of the high-purity oxygen and the primary oxygen according to the above inequality; Determine the set flow rate of high-purity oxygen according to the mixing ratio of high-purity oxygen and primary oxygen and the current flow rate of primary oxygen; The pure oxygen module is controlled to output a set flow rate of high-purity oxygen into the oxygen separator 12, so that the hydrogen content in the mixed oxygen meets the set conditions.

[0083] S3. When it is determined that the hydrogen content in the initial oxygen meets the set condition, the pure oxygen module is controlled to stop outputting high-purity oxygen into the oxygen separator 12.

[0084] As the load increases, the hydrogen content in the initial oxygen decreases. When the hydrogen content in the initial oxygen is less than 1.5%, the pure oxygen module stops outputting high-purity oxygen.

[0085] In another embodiment of the present invention, a control method for an electrolytic hydrogen production system for reducing the lower limit of production load is applicable to a case where there are multiple electrolytic cells 10, and includes the following steps: S10, when the renewable power generation system starts to produce power, the first electrolyzer 10 is started, and the load is gradually increased to the production load lower limit P min Then, continue to increase the load to P 1 P 1 <100%; S20, according to the output of the renewable system, start the nth electrolytic cell 10 in sequence, and increase the production load of the nth electrolytic cell 10 to P n , so that the hydrogen content in the mixed oxygen formed by mixing the initial oxygen produced by the nth electrolytic cell 10 with the initial oxygen produced by the previous n-1 electrolytic cell 10 meets the set conditions, P n+1 <P n <P min , where n≥2; S30, the nth electrolytic cell 10 is incorporated into the system, and the load is increased to P 1 ; S40, when the output of the renewable power generation device system continues to increase, the production load of the n electrolytic cells 10 is increased to 100% at the same time.

[0086] By means of the electrolytic hydrogen production system and control method for reducing the lower limit of production load provided by the present invention, when the hydrogen content in the initial oxygen of the electrolyzer 10 exceeds the standard due to a reduction in production load, load fluctuation or other reasons, high-purity oxygen can be output to the oxygen separator 12 through the pure oxygen module, and the high-purity oxygen is mixed with the pure oxygen output from the oxygen side outlet to form mixed oxygen. The high-purity oxygen can dilute the hydrogen in the initial oxygen to significantly reduce the hydrogen content in the mixed oxygen, so that when the hydrogen content in the initial oxygen does not meet the set conditions, the hydrogen content in the mixed oxygen at the outlet of the oxygen separator 12 meets the set conditions. The initial oxygen is mixed with the alkali solution before entering the oxygen separator 12 and is in a liquid state. Therefore, it is only necessary to make the hydrogen content in the initial oxygen less than the lower explosion limit of hydrogen. In comparison, the upper limit of the hydrogen content in the initial oxygen at the oxygen side outlet can be greatly increased, thereby reducing the lower limit of the production load of the electrolytic hydrogen production system, so that it can fully adapt to the wide and rapid fluctuations in renewable energy processing.

[0087] 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 make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrolytic hydrogen production system for reducing the lower limit of production load, characterized in that: include: An electrolyzer (10), a hydrogen separator (11), an oxygen separator (12) and a pure oxygen module; The cathode side of the electrolytic cell (10) is provided with a hydrogen side outlet, and the hydrogen separator (11) is connected to the hydrogen side outlet; the anode side of the electrolytic cell (10) is provided with an oxygen side outlet, and the oxygen separator (12) is connected to the oxygen side outlet; The pure oxygen module is suitable for outputting high-purity oxygen into the oxygen separator (12), and the high-purity oxygen is used to mix with the initial oxygen at the oxygen side outlet, so that when the hydrogen content in the initial oxygen does not meet the set conditions, the hydrogen content in the mixed oxygen at the gas outlet of the oxygen separator (12) meets the set conditions.

2. The electrolytic hydrogen production system for reducing the lower limit of production load according to claim 1, characterized in that: The oxygen separator (12) is provided with a high-purity oxygen inlet, and the output end of the pure oxygen module is connected to the high-purity oxygen inlet; And / or, the oxygen separator (12) is connected to the oxygen side outlet via a primary oxygen pipeline (13), and the output end of the pure oxygen module is connected to the primary oxygen pipeline (13).

3. The electrolytic hydrogen production system for reducing the lower limit of production load according to claim 2, characterized in that: The pure oxygen module comprises an oxygen purification device (20), a pure oxygen storage tank (21) and a circulation compressor (22); The inlet of the oxygen purification device (20) is connected to the gas outlet of the oxygen separator (12), and the outlet is connected to the pure oxygen storage tank (21); the outlet of the pure oxygen storage tank (21) is connected to the inlet of the circulation compressor (22), and the outlet of the circulation compressor (22) is used to output high-purity oxygen, forming the output end of the pure oxygen module.

4. The electrolytic hydrogen production system for reducing the lower limit of production load according to claim 2, characterized in that: The oxygen side outlet is connected to a first hydrogen content detector (14), and the oxygen separator (12) outlet is connected to a second hydrogen content detector (15).

5. The electrolytic hydrogen production system for reducing the lower limit of production load according to claim 4, characterized in that: Also includes an alarm module; When it is determined that the hydrogen content in the initial oxygen reaches X1, the alarm module is controlled to alarm, and when it reaches X2, the control system stops, and X1<X2<4%; When it is determined that the hydrogen content in the mixed oxygen reaches X3, the alarm module is controlled to alarm, and when it reaches X4, the control system stops, and X3<X4.

6. The electrolytic hydrogen production system for reducing the lower limit of production load according to claim 5, characterized in that: A third hydrogen content detector (16) is connected to the outlet of the purification device; When it is determined that the hydrogen content in oxygen at the outlet of the purification device reaches X5, the alarm module is controlled to alarm; when it is determined that the hydrogen content in oxygen at the outlet of the purification device reaches X6, the control system stops, and X5<X6.

7. The electrolytic hydrogen production system for reducing the lower limit of production load according to claim 4, characterized in that: The second hydrogen content detector (15) is interlocked with the circulating compressor (22) for control; and / or the output end of the pure oxygen module is connected to a flow regulating valve (23), and the second hydrogen content detector (15) is interlocked with the flow regulating valve (23) for control.

8. The electrolytic hydrogen production system for reducing the lower limit of production load according to claim 1, characterized in that: The electrolytic cells (10) are provided with n units, and the n electrolytic cells (10) are all connected to the oxygen separator (12), and n≥2; The electrolyzer (10) started first is suitable for inputting initial oxygen whose hydrogen content does not exceed the set value into the oxygen separator (12), so that when the electrolyzer (10) started later is started when the hydrogen content in the initial oxygen exceeds the set value, the hydrogen content in the mixed oxygen does not exceed the set value; the electrolyzer (10) started first constitutes the pure oxygen module.

9. A control method for an electrolytic hydrogen production system for reducing the lower limit of production load, characterized in that: The electrolytic hydrogen production system for reducing the lower limit of production load according to any one of claims 1 to 7 comprises the following steps: Obtain the hydrogen content in the initial oxygen; When it is determined that the hydrogen content in the initial oxygen does not meet the set condition, the pure oxygen module is controlled to output high-purity oxygen into the oxygen separator (12) so that the hydrogen content in the mixed oxygen meets the set condition; When it is determined that the hydrogen content in the initial oxygen meets the set condition, the pure oxygen module is controlled to stop outputting high-purity oxygen into the oxygen separator (12); Preferably, when it is determined that the hydrogen content in the initial oxygen does not meet the set condition, controlling the pure oxygen module to output high-purity oxygen into the oxygen separator (12) so that the hydrogen content in the mixed oxygen meets the set condition, comprises: Determining a mixing ratio of the high-purity oxygen to the initial oxygen according to the hydrogen content in the initial oxygen and the set conditions; Determining a set flow rate of high-purity oxygen according to a mixing ratio of the high-purity oxygen and the initial oxygen; The pure oxygen module is controlled to output a set flow rate of high-purity oxygen into the oxygen separator (12).

10. A control method for an electrolytic hydrogen production system for reducing the lower limit of production load, characterized in that: The electrolytic hydrogen production system for reducing the lower limit of production load as claimed in claim 9 comprises the following steps: When the renewable power generation system starts to produce power, the first electrolyzer (10) is started and the load is gradually increased to the production load lower limit P min After that, continue to lift the load to P1, where P1 is less than 100%; According to the output of the renewable system, the nth electrolytic cell (10) is started in sequence, and the production load of the nth electrolytic cell (10) is increased to P n , so that the hydrogen content in the mixed oxygen formed by mixing the initial oxygen produced by the nth electrolytic cell (10) with the initial oxygen produced by the previous n-1 electrolytic cell (10) meets the set conditions, the P n+1 <P n <P min , where n≥2; Incorporate the nth electrolytic cell (10) into the system and increase the load to P1; When the output of the renewable power generation device system continues to increase, the production load of the n electrolytic cells (10) is simultaneously increased to 100%.

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