System for producing hydrogen by electrolyzing seawater under variable load working condition and control method thereof

Abstract

The invention discloses a system for producing hydrogen by electrolyzing seawater under a variable load working condition and a control method thereof. The system mainly comprises an electrolytic bath, a separator, a waste heat recovery device, an alkali liquor heat exchanger, a differential pressure transmitter, an alkali liquor circulating pump, a pneumatic diaphragm regulating valve, a flow meter, a temperature transmitter and a manual ball valve. Under the condition that the power supply power from the front end to the electrolytic cell fluctuates, the working power of the electrolytic cell is changed by synchronously adjusting the electrode current density, and the waste heat recovery vacuum degree, the hydrogen-oxygen separator liquid level difference, the system working pressure, the cooling water flow, the electrolyte flow and the hydrogen-oxygen small chamber pressure drop difference are dynamically adjusted; and an operation function is added into the control logic, so that a theoretical value of a control parameter is accurately calculated, and the beneficial effects of stable operation of a hydrogen production system and product gas quality are achieved when the power of the electrolytic cell fluctuates.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen production by electrolysis of seawater, and in particular to a hydrogen production system by electrolysis of seawater under variable load conditions and a control method thereof, which is particularly suitable for hydrogen production equipment in offshore wind and solar power plants in the deep sea. Background Art

[0002] With the increasing severity of the global energy crisis and the improvement of environmental awareness, offshore renewable energy (such as wind power, solar energy, etc.) as a clean and renewable energy source is receiving more and more attention. However, in the hydrogen production occasions powered by offshore renewable energy, the conventional alkaline water hydrogen production system faces many challenges, which limits its application in this field.

[0003] First of all, conventional alkaline water hydrogen production systems have extremely high requirements for electrolysis raw water, and usually require ultrapure water as the electrolysis raw material. However, the cost of treating seawater into ultrapure water is high, not only requiring a large amount of chemical agents and energy consumption, but also requiring the corresponding water treatment equipment and facilities. This not only increases the cost of hydrogen production, but the waste generated during the treatment process may also pollute the environment. In addition, the processing equipment occupies a large area and will occupy valuable offshore platform land resources, further limiting its application in hydrogen production occasions powered by offshore renewable energy.

[0004] Secondly, the power generation of offshore renewable energy has large fluctuations. This volatility requires that the hydrogen production system must have strong adaptability and flexibility so that the hydrogen production process can be adjusted in time according to changes in power generation. However, conventional alkaline water hydrogen production systems often improve the adaptability to power fluctuations by improving the performance of equipment components. Although this method can improve the stability of the system to a certain extent, it cannot fundamentally solve the problem of poor adaptability of the system to power fluctuations. At the same time, the system control logic of conventional alkaline water hydrogen production systems can usually only maintain the stable operation of the system, and cannot be dynamically adjusted according to fluctuations in load conditions, which further limits its application in hydrogen production occasions powered by offshore renewable energy.

[0005] In addition, the control loop of the conventional alkaline water hydrogen production system lacks the support of calculation formulas. This results in the system being unable to achieve precise automatic control of the selection of control parameters, and relying more on manual intervention and empirical judgment. In the hydrogen production occasions of offshore renewable power supply, due to the limitations of factors such as harsh environment and sparse personnel, this manual control method is not only inefficient, but also has safety hazards, and is not suitable for the unmanned or sparsely populated environment of hydrogen production occasions of offshore renewable power supply.

[0006] Therefore, the conventional alkaline water hydrogen production system has many shortcomings in hydrogen production occasions powered by offshore renewable energy, which limits its application in this field. In order to solve these problems, it is necessary to develop a new type of hydrogen production system and its control method to adapt to the characteristics and requirements of hydrogen production occasions powered by offshore renewable energy.

[0007] In order to solve the above problems, the present invention is proposed. Summary of the invention

[0008] The present invention is adopted.

[0009] In view of the above problems, the present invention proposes a seawater electrolysis hydrogen production system which adopts a waste heat recovery device as the source of electrolysis raw water. Based on this system, a system control method is proposed for the dynamic change of system control logic when the power of offshore renewable energy power generation fluctuates, and the relationship between the parameters of various components of the system is coordinated and considered, and a system control parameter operation function is added to the control method; so that the proposed seawater electrolysis hydrogen production system and its control method under variable load conditions can achieve the beneficial effects of low cost, low energy consumption, small footprint, adaptability to a large power fluctuation range, accurate control parameter calculation, and automatic control parameter selection.

[0010] Under the condition of offshore wind and solar power fluctuations, the system of the present invention can adapt well to its wide power variable load. By adjusting the vacuum degree of the waste heat recovery device, the liquid level difference of the gas-liquid separator, the system pressure, the cooling water flow rate, the opening of the gas-liquid two-phase pipeline valve, and the alkali liquid flow rate, the system can maintain stable operation of the system under wide power fluctuations, stabilize the purity of the product gas, and maintain stable energy consumption of the system under wide power fluctuations.

[0011] The present invention is mainly to solve the problem of stable operation of the seawater electrolysis hydrogen production system under variable load conditions and the high hydrogen content in the system's oxygen. Under low load conditions, the current density decreases, the amount of gas produced decreases, and the gas purity decreases when the pressure remains unchanged. Under high load conditions, the current density increases, the thermal power increases, and the temperature at the gas-liquid two-phase port increases. High temperature will increase the risk of organic diaphragms leaking in alkaline media, which will have an adverse effect on the overall life of the electrolyzer. The present invention maintains stable system operation and product gas purity by adjusting the vacuum degree, liquid level difference, pressure, cooling water flow, gas-liquid two-phase pipeline valve opening, and alkali solution flow of the waste heat recovery device.

[0012] The present invention discloses a system for producing hydrogen by electrolyzing seawater under variable load conditions and a control method thereof, which mainly includes an electrolyzer, a separator, a waste heat recovery device, an alkali solution heat exchanger, a differential pressure transmitter, an alkali solution circulation pump, a pneumatic diaphragm regulating valve, a flow meter, a temperature transmitter, and a manual ball valve. In the case of power fluctuations from the front end to the electrolyzer, the present invention changes the working power of the electrolyzer by synchronously adjusting the electrode current density, dynamically adjusting the waste heat recovery vacuum, the hydrogen-oxygen separator liquid level difference, the system working pressure, the cooling water flow, the electrolyte flow, the hydrogen-oxygen chamber pressure drop difference, and adding an operation function to the control logic, so as to accurately calculate the theoretical value of the control parameter, so as to achieve the beneficial effect of ensuring the stable operation of the hydrogen production system and the product gas quality when the electrolyzer power fluctuates.

[0013] To achieve the above object, the technical method adopted by the present invention is:

[0014] The first aspect of the present invention provides a system for producing hydrogen by electrolyzing seawater under variable load conditions, the system comprising: an electrolytic cell 1, a first electrolyte thermometer 2, a second electrolyte thermometer 3, an oxygen-liquid separator 4, a hydrogen-gas-liquid separator 5, an oxygen separator level gauge 6, a hydrogen separator level gauge 7, an electrolyte circulation pump 8, a waste heat recovery device 9, a waste heat recovery barometer 10, a waste heat recovery pressure regulating valve 11, an electrolyte heat exchanger 12, a third electrolyte thermometer 13, a cooling water regulating valve 14, an electrolyte flowmeter 15, an oxygen-hydrogen measuring instrument 16, a hydrogen-oxygen measuring instrument 17, a hydrogen production system pressure gauge 18, a first pneumatic diaphragm regulating valve 19, a second pneumatic diaphragm regulating valve 20, an oxygen-side manual ball valve 21, and a hydrogen-side manual ball valve 22;

[0015] The external power supply inputs a rated current and voltage to the electrolytic cell 1, so that the electrolytic cell 1 operates at a rated current density, electrolyzes the electrolyte to produce hydrogen and oxygen, and heats the electrolyte;

[0016] After electrolysis, oxygen follows the electrolyte and enters the oxygen-liquid separator 4 in the form of gas-liquid two-phase flow for gas-liquid separation. A first electrolyte thermometer 2 is provided on the pipeline between the electrolytic cell 1 and the oxygen-liquid separator 4 to detect the gas-liquid two-phase flow temperature at the oxygen-side electrolytic cell outlet, and an oxygen-side manual ball valve 21 is provided to control the opening of the oxygen-side gas-liquid two-phase to the oxygen-liquid separator 4; the oxygen separated by the oxygen-liquid separator 3 is discharged outward, and an oxygen-hydrogen measuring instrument 16 is provided on the oxygen discharge pipeline to monitor the oxygen purity, a hydrogen production system pressure gauge 18 is provided to detect the operating pressure of the hydrogen production system, and a first pneumatic diaphragm regulating valve 19 is provided to adjust the oxygen discharge speed, thereby adjusting the hydrogen production system pressure; an oxygen separator liquid level gauge 6 is provided in the oxygen-liquid separator 4 to detect the liquid level height in the oxygen separator liquid level gauge 6;

[0017] After electrolysis, hydrogen follows the electrolyte and enters the hydrogen gas-liquid separator 5 in the form of gas-liquid two-phase flow for gas-liquid separation. A second electrolyte thermometer 3 is provided on the pipeline between the electrolytic cell 1 and the hydrogen gas-liquid separator 5 to detect the gas-liquid two-phase flow temperature at the hydrogen side electrolytic cell outlet. A hydrogen side manual ball valve 22 is provided to control the opening of the hydrogen side gas-liquid two-phase to the hydrogen gas-liquid separator 5; the hydrogen separated by the hydrogen gas-liquid separator 5 is transported outward, and a hydrogen oxygen measuring instrument 17 is provided on the hydrogen outlet pipeline to monitor the purity of hydrogen, and a second pneumatic diaphragm regulating valve 20 is provided to adjust the hydrogen discharge speed, thereby adjusting the pressure difference between the oxygen liquid separator 4 and the hydrogen gas-liquid separator 5; a hydrogen separator liquid level meter 7 is provided in the hydrogen gas-liquid separator 5 to detect the liquid level height in the hydrogen gas-liquid separator 5;

[0018] The liquid level difference between the oxygen separator liquid level gauge 6 and the hydrogen separator liquid level gauge 7 reflects the pressure difference in the oxygen liquid separator 4 and the hydrogen liquid separator 5; the electrolyte separated by the hydrogen liquid separator 5 and the oxygen liquid separator 4 is mixed through the connecting pipe and pumped out by the electrolyte circulation pump 8 at a rated flow rate, and the pumped electrolyte passes through the waste heat recovery device 9 and the electrolyte heat exchanger 12 in turn and then returns to the electrolytic cell 1 for electrolysis.

[0019] Preferably, a third electrolyte thermometer 13 is provided on the connecting pipeline between the electrolyte heat exchanger 12 and the electrolytic cell 1 to detect the temperature of the cooled electrolyte, and an electrolyte flowmeter 15 is provided to detect the electrolyte flow.

[0020] Preferably, the electrolyte heat exchanger 12 is provided with cooling water inlet and outlet pipelines to cool the electrolyte, and a cooling water regulating valve 14 is provided on the cooling water inlet pipeline to regulate the cooling water flow rate.

[0021] The second aspect of the present invention provides a control method for the seawater electrolysis hydrogen production system under variable load conditions as described in the first aspect of the present invention, wherein the hot electrolyte separated by the hydrogen gas-liquid separator 5 and the oxygen liquid separator 4 enters the waste heat recovery device 9, exchanges heat with external seawater, and generates hot steam by heat exchange evaporation, which is condensed by external cooling water to generate low-concentration brine and enters the raw water tank of the seawater electrolysis hydrogen production system for standby use; the waste heat recovery device 9 generates a vacuum through an external vacuum generating device, and adjusts the evaporation temperature of the external seawater in the waste heat recovery device 9 according to the vacuum degree, thereby controlling the heat exchange power between the waste heat recovery device 9 and the hot electrolyte.

[0022] Preferably, when the external power supply to the electrolytic cell 1 changes, the heating power of the electrolytic cell 1 changes accordingly, and the vacuum degree in the waste heat recovery device 9 is controlled by interlocking the waste heat recovery pressure gauge 10 and the waste heat recovery pressure regulating valve 11 connected to the external vacuum generating device, so as to realize dynamic adjustment of the heat exchange power between the waste heat recovery device 9 and the hot electrolyte as the heating power of the electrolytic cell 1 changes, and at the same time, the external seawater inlet temperature and flow rate are controlled to be constant;

[0023] The adjustment logic is as follows:

[0024] S1, power supply changes;

[0025] S2, heating power change of electrolytic cell 1;

[0026] S3, calculate the theoretical seawater evaporation temperature required by the waste heat recovery device 9: electrolytic cell heating power - (seawater evaporation temperature - seawater inlet temperature) * seawater specific heat capacity * seawater flow + electrolyte heat exchanger heat exchange power 12;

[0027] S4, looking up a table to obtain the vacuum degree corresponding to the seawater evaporation temperature;

[0028] S5, determine: Is the waste heat recovery pressure gauge 10 equal to the vacuum corresponding to the seawater evaporation temperature? If yes, the vacuum corresponding to the seawater evaporation remains unchanged; if not, the opening of the waste heat recovery pressure regulating valve 11 changes, and then this step is determined again until the result is yes, and then proceed to the next step;

[0029] S6, reaching the target value of seawater evaporation temperature;

[0030] S7, the heat exchange power of the waste heat recovery device 9 changes and matches the heating power of the electrolytic cell 1.

[0031] Preferably, due to the possible heat exchange error of the waste heat recovery device 9, in order to ensure the stability of the heat exchange power, that is, the stability of the alkali solution control temperature at the inlet of the electrolytic cell 1 and the system target control temperature, an electrolyte heat exchanger 12 is arranged between the waste heat recovery device 9 and the electrolytic cell 1 for secondary heat exchange, and the heating power of the electrolytic cell 1 is equal to the heat exchange power of the electrolyte heat exchanger 12 plus the heat exchange power of the waste heat recovery device 9; when the external power supply to the electrolytic cell 1 changes, the heating power of the electrolytic cell 1 changes accordingly, and the average temperature of the readings of the electrolytic cell outlet thermometer is taken as the system target control temperature, that is, the sum of the readings of the first electrolyte thermometer 2 and the second electrolyte thermometer 3 divided by two, to obtain The reading of the thermometer at the inlet of the electrolytic cell, that is, the reading of the third electrolyte thermometer 13, is used as the alkali solution temperature at the inlet of the electrolytic cell. The alkali solution control temperature at the inlet of the electrolytic cell 1 is calculated by the heating power of the electrolytic cell 1 and the system target control temperature. When the alkali solution control temperature at the inlet of the electrolytic cell is higher than the reading of the thermometer at the inlet of the electrolytic cell, the opening of the cooling water regulating valve 14 is increased. When the alkali solution control temperature at the inlet of the electrolytic cell is lower than the reading of the thermometer, the opening of the cooling water regulating valve 14 is reduced, thereby realizing the dynamic adjustment of the heat exchange power between the electrolyte heat exchanger 12 and the hot electrolyte with the change of the heating power of the electrolytic cell 1. At the same time, the inlet and outlet temperatures of the external cooling water, the electrolyte flow rate and the heat exchange capacity of the waste heat recovery device 9 are controlled to be constant.

[0032] The adjustment logic is as follows:

[0033] S1, power supply changes;

[0034] S2, heating power change of electrolytic cell 1;

[0035] S3, calculate the control temperature of the alkali solution at the inlet of electrolytic cell 1: electrolytic cell heating power = waste heat recovery heat + (cooling water inlet and outlet temperature difference * cooling water specific heat capacity * cooling water flow rate = (system target control temperature - electrolytic cell inlet alkali solution temperature) * alkali solution specific heat capacity * alkali|liquid flow rate) = heating voltage * rated power / working voltage;

[0036] S4, the first electrolyte thermometer 2, the second electrolyte thermometer 3, and the third electrolyte thermometer 13 obtain temperatures;

[0037] S5, determine whether the alkaline solution control temperature at the inlet of the electrolytic cell minus the temperature of the third electrolyte thermometer 13 is greater than zero, if so, the opening of the cooling water regulating valve 14 is increased; if not, the opening of the cooling water regulating valve 14 is decreased;

[0038] S6, the heat exchange power 12 of the electrolyte heat exchanger changes and matches the heat generation power of the electrolytic cell 1.

[0039] Preferably, when the external power supply to the electrolyzer 1 decreases, the current density of the electrolyzer 1 decreases accordingly. At this time, the values ​​of the hydrogen in oxygen meter 16 and the oxygen in hydrogen meter 17 will increase accordingly. Since the value of hydrogen in oxygen changes more, the hydrogen in oxygen is used as the control point, and the first pneumatic diaphragm regulating valve 19 connected to the pressure control device is increased through interlocking control to increase the opening, thereby increasing the gas discharge rate and reducing the system pressure to reduce the trend of the increase of hydrogen in oxygen; when the external power supply to the electrolyzer 1 increases, the current density of the electrolyzer 1 increases accordingly. At this time, the values ​​of the hydrogen in oxygen meter 16 and the oxygen in hydrogen meter 17 will decrease accordingly. Since the value of hydrogen in oxygen changes more, the hydrogen in oxygen is used as the control point, and the first pneumatic diaphragm regulating valve 19 connected to the pressure control device is reduced through interlocking control to reduce the opening, thereby reducing the gas discharge rate until the system pressure is restored; to achieve dynamic regulation of pressure and product gas purity with fluctuations in the power supply of the electrolyzer 1;

[0040] The power supply reduction regulation logic is as follows:

[0041] S1, power supply decreases

[0042] S2, the current density of electrolytic cell 1 decreases

[0043] S3, the values ​​of the oxygen-hydrogen measuring instrument 16 and the hydrogen-oxygen measuring instrument 17 increase

[0044] S4, reduce the opening pressure of the first pneumatic diaphragm regulating valve 19

[0045] S5, determine whether the upward trend of the value of the oxygen hydrogen measuring instrument 16 decreases. If yes, the system pressure decreases and matches the current density of the electrolyzer 1, and the purity of the product gas is stable; if not, return to step S4 until the judgment result is yes;

[0046] The power supply increase regulation logic is as follows:

[0047] S1, power supply increases;

[0048] S2, the current density of electrolytic cell 1 increases;

[0049] S3, the values ​​of the oxygen-hydrogen measuring instrument 16 and the hydrogen-oxygen measuring instrument 17 decrease;

[0050] S4, increasing the opening pressure of the first pneumatic diaphragm regulating valve 19;

[0051] S5, determine: whether the opening pressure of the first pneumatic diaphragm regulating valve 19 is equal to the rated system pressure. If so, the system pressure rises and matches the current density of the electrolytic cell 1, and the purity of the product gas is stable; if not, return to step S4 until the judgment result is yes.

[0052] Preferably, when the external power supply to the electrolyzer 1 decreases, the current density of the electrolyzer 1 decreases accordingly. At this time, the values ​​of the hydrogen in oxygen meter 16 and the oxygen in hydrogen meter 17 will increase accordingly. Since the value of hydrogen in oxygen changes more, the hydrogen in oxygen is used as the control point, and the second pneumatic diaphragm regulating valve 20 connected to the liquid level control device is controlled through interlocking to reduce the liquid level difference response speed, so as to reduce the trend of the increase of hydrogen in oxygen; when the external power supply to the electrolyzer 1 increases, the current density of the electrolyzer 1 increases accordingly. At this time, the values ​​of the hydrogen in oxygen meter 16 and the oxygen in hydrogen meter 17 will decrease accordingly. Since the value of hydrogen in oxygen changes more, the hydrogen in oxygen is used as the control point, and the second pneumatic diaphragm regulating valve 20 connected to the liquid level control device is controlled through interlocking to increase the liquid level difference response speed until the rated response speed of the system is restored; the dynamic adjustment of the liquid level difference and the purity of the product gas with the fluctuation of the power supply of the electrolyzer 1 is realized;

[0053] The power supply reduction regulation logic is as follows:

[0054] S1, power supply decreases;

[0055] S2, the current density of electrolytic cell 1 decreases;

[0056] S3, the values ​​of the oxygen-hydrogen measuring instrument 16 and the hydrogen-oxygen measuring instrument 17 increase;

[0057] S4, reducing the response speed of the second pneumatic diaphragm regulating valve 20, if n (n>5), the system liquid level difference response speed is independent of the current density of the electrolytic cell 1; if n (n<5), proceed to the next step;

[0058] S5, determine: whether the rising trend of the value of the oxygen hydrogen measuring instrument 16 decreases, if so, the system liquid level difference response speed decreases and matches the current density of the electrolyzer 1, and the product gas purity is stable; if not, return to step S4 until the judgment result is yes.

[0059] The power supply increase regulation logic is as follows:

[0060] S1, power supply increases;

[0061] S2, the current density of electrolytic cell 1 increases;

[0062] S3, the values ​​of the oxygen-hydrogen measuring instrument 16 and the hydrogen-oxygen measuring instrument 17 decrease;

[0063] S4, increase the response speed of the second pneumatic diaphragm regulating valve 20. If n (n>5), the system liquid level difference response speed is independent of the current density of the electrolytic cell 1; if n (n<5), proceed to the next step;

[0064] S5, determine whether the response speed of the second pneumatic diaphragm regulating valve 20 is equal to the rated response speed. If yes, the system liquid level difference response speed increases and matches the current density of the electrolytic cell 1, and the product gas purity is stable; if not, return to step S4 until the judgment result is yes.

[0065] Preferably, when the external power supply to the electrolyzer 1 decreases, the current density of the electrolyzer 1 decreases accordingly. At this time, the values ​​of the oxygen-hydrogen measuring instrument 16 and the hydrogen-oxygen measuring instrument 17 will increase accordingly. By adjusting the opening of the manual ball valve 21 on the oxygen side and the manual ball valve 22 on the hydrogen side, the pressure drop difference between the hydrogen and oxygen sides is adjusted. When the rising rate of hydrogen in oxygen is greater than that of oxygen in hydrogen, the pressure drop of the oxygen pipeline is increased. When the rising trend of hydrogen in oxygen is less than that of oxygen in hydrogen, the pressure drop of the hydrogen pipeline is increased. The dynamic adjustment of the pressure drop difference between the hydrogen and oxygen sides and the purity of the product gas as the power supply of the electrolyzer 1 changes is realized, wherein increasing the pressure drop of the oxygen pipeline will cause more oxygen to penetrate into the hydrogen, thereby increasing the change rate of oxygen in hydrogen, and the same is true for increasing the pressure drop of the hydrogen pipeline.

[0066] The adjustment logic is as follows:

[0067] S1, power supply decreases;

[0068] S2, the current density of electrolytic cell 1 decreases;

[0069] S3, the values ​​of the oxygen-hydrogen measuring instrument 16 and the hydrogen-oxygen measuring instrument 17 increase;

[0070] S4, adjusting the opening of the manual ball valve 21 on the oxygen side and the manual ball valve 22 on the hydrogen side;

[0071] S5, determine whether the rising rate of hydrogen in oxygen is greater than that of oxygen in hydrogen. If yes, increase the pressure drop of the oxygen pipeline; if no, increase the pressure drop of the hydrogen pipeline;

[0072] S6, the pressure drop difference between hydrogen and oxygen changes and matches the current density of electrolyzer 1, and the purity of the product gas is stable.

[0073] Preferably, when the external power supply to the electrolytic cell 1 increases, the current density of the electrolytic cell 1 increases accordingly, and the energy consumption of the electrolytic cell 1 also increases accordingly, and then the values ​​of the first electrolyte thermometer 2 and the second electrolyte thermometer 3 increase accordingly, and the flow rate of the electrolyte circulation pump 8 is controlled and adjusted by calculating the target control flow rate of the adjustment system to reduce the temperature difference of the alkali solution at the inlet and outlet of the electrolytic cell, thereby reducing the rising trend of the energy consumption of the electrolytic cell; when the current density decreases to the rated current density, the energy consumption of the electrolytic cell is reduced, and the flow rate of the pump is restored to the rated flow rate;

[0074] The power supply increase adjustment logic is as follows:

[0075] S1, power supply increases;

[0076] S2, the current density of electrolytic cell 1 increases;

[0077] S3, energy consumption of electrolyzer 1 increases;

[0078] S4, calculate the target control flow of electrolytic cell 1: electrolytic cell heating power = waste heat recovery heat + (cooling water inlet and outlet temperature difference * cooling water specific heat capacity * cooling water flow rate = (system target control temperature - electrolytic cell inlet alkali solution temperature) * alkali solution specific heat capacity * alkali solution flow rate);

[0079] S5, the first electrolyte thermometer 2, the second electrolyte thermometer 3, and the third electrolyte thermometer 13 obtain the temperature;

[0080] S6, the alkali solution flow rate is less than the system target control flow rate;

[0081] S7, the electrolyte circulation pump 8 adjusts the alkali solution flow rate to increase;

[0082] S8, the temperature difference between the inlet and outlet of the electrolytic cell decreases;

[0083] S9, the rising trend of electrolytic cell energy consumption decreases;

[0084] The power supply reduction adjustment logic is as follows:

[0085] S1, power supply decreases;

[0086] S2, the current density of electrolytic cell 1 decreases to the rated value;

[0087] S3, energy consumption of electrolytic cell 1 is reduced;

[0088] S4, the electrolyte circulation pump 8 adjusts the alkali solution flow rate to return to the rated value.

[0089] Compared with the prior art, the present invention has the beneficial effect of adopting a control method and utilizing existing equipment to ensure stable operation of the system and quality of product gas without increasing equipment cost.

[0090] In the case of power fluctuations from the front end to the electrolyzer, the present invention changes the working power of the electrolyzer by synchronously adjusting the electrode current density, dynamically adjusts the waste heat recovery vacuum, the hydrogen-oxygen separator liquid level difference, the system working pressure, the cooling water flow, the electrolyte flow, the hydrogen-oxygen chamber pressure drop difference, and adds an operation function to the control logic to accurately calculate the theoretical value of the control parameter, thereby achieving the beneficial effect of ensuring the stable operation of the hydrogen production system and the quality of the product gas when the electrolyzer power fluctuates. BRIEF DESCRIPTION OF THE DRAWINGS

[0091] Figure 1 This is the process flow chart of the hydrogen production system by electrolyzing seawater under variable load conditions;

[0092] Figure 2-Figure 7 This is the adjustment logic diagram in the system control method of the present invention.

[0093] The names of the figure symbols in the figure description are: 1. electrolytic cell, 2. first electrolyte thermometer, 3. second electrolyte thermometer, 4. oxygen liquid separator, 5. hydrogen gas-liquid separator, 6. oxygen separator level gauge, 7. hydrogen separator level gauge, 8. electrolyte circulation pump, 9. waste heat recovery device, 10. waste heat recovery air pressure gauge, 11. waste heat recovery air pressure regulating valve, 12. electrolyte heat exchanger, 13. third electrolyte thermometer, 14. cooling water regulating valve, 15. electrolyte flow meter, 16. oxygen-hydrogen measuring instrument, 17. hydrogen-oxygen measuring instrument, 18. hydrogen production system pressure gauge, 19. first pneumatic diaphragm regulating valve, 20. second pneumatic diaphragm regulating valve, 21. manual ball valve on the oxygen side, 22. manual ball valve on the hydrogen side. DETAILED DESCRIPTION

[0094] The present invention is further described in detail below in conjunction with embodiments.

[0095] Those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the art or the product specifications are used. If the manufacturer of the materials or equipment used is not specified, they are all conventional products that can be purchased.

[0096] Those skilled in the art will appreciate that, unless expressly stated otherwise, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when we refer to an element as being "connected" to another element, it may be directly connected to the other element, or there may be intermediate elements. In addition, the "connection" used herein may include wireless connections.

[0097] In the description of the present invention, unless otherwise specified, "plurality" means two or more than two. The terms "inside", "upper", "lower", etc., indicating positions or state relationships, are based on the positions or state relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operate in a specific position, and therefore cannot be understood as limiting the present invention.

[0098] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "provided with" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention will be understood according to specific circumstances.

[0099] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0100] Example

[0101] like Figure 1As shown, the electrolysis of seawater for hydrogen production under variable load conditions in this embodiment comprises: an electrolytic cell 1, a first electrolyte thermometer 2, a second electrolyte thermometer 3, an oxygen-liquid separator 4, a hydrogen-gas-liquid separator 5, an oxygen separator level gauge 6, a hydrogen separator level gauge 7, an electrolyte circulation pump 8, a waste heat recovery device 9, a waste heat recovery barometer 10, a waste heat recovery pressure regulating valve 11, an electrolyte heat exchanger 12, a third electrolyte thermometer 13, a cooling water regulating valve 14, an electrolyte flowmeter 15, an oxygen-hydrogen measuring instrument 16, a hydrogen-oxygen measuring instrument 17, a hydrogen production system pressure gauge 18, a first pneumatic diaphragm regulating valve 19, a second pneumatic diaphragm regulating valve 20, an oxygen-side manual ball valve 21, and a hydrogen-side manual ball valve 22;

[0102] The external power supply inputs a rated current and voltage to the electrolytic cell 1, so that the electrolytic cell 1 operates at a rated current density, electrolyzes the electrolyte to produce hydrogen and oxygen, and heats the electrolyte;

[0103] After electrolysis, oxygen follows the electrolyte and enters the oxygen-liquid separator 4 in the form of gas-liquid two-phase flow for gas-liquid separation. A first electrolyte thermometer 2 is provided on the pipeline between the electrolytic cell 1 and the oxygen-liquid separator 4 to detect the gas-liquid two-phase flow temperature at the oxygen-side electrolytic cell outlet, and an oxygen-side manual ball valve 21 is provided to control the opening of the oxygen-side gas-liquid two-phase to the oxygen-liquid separator 4; the oxygen separated by the oxygen-liquid separator 3 is discharged outward, and an oxygen-hydrogen measuring instrument 16 is provided on the oxygen discharge pipeline to monitor the oxygen purity, a hydrogen production system pressure gauge 18 is provided to detect the operating pressure of the hydrogen production system, and a first pneumatic diaphragm regulating valve 19 is provided to adjust the oxygen discharge speed, thereby adjusting the hydrogen production system pressure; an oxygen separator liquid level gauge 6 is provided in the oxygen-liquid separator 4 to detect the liquid level height in the oxygen separator liquid level gauge 6;

[0104] After electrolysis, hydrogen follows the electrolyte and enters the hydrogen gas-liquid separator 5 in the form of gas-liquid two-phase flow for gas-liquid separation. A second electrolyte thermometer 3 is provided on the pipeline between the electrolytic cell 1 and the hydrogen gas-liquid separator 5 to detect the gas-liquid two-phase flow temperature at the hydrogen side electrolytic cell outlet. A hydrogen side manual ball valve 22 is provided to control the opening of the hydrogen side gas-liquid two-phase to the hydrogen gas-liquid separator 5; the hydrogen separated by the hydrogen gas-liquid separator 5 is transported outward, and a hydrogen oxygen measuring instrument 17 is provided on the hydrogen outlet pipeline to monitor the purity of hydrogen, and a second pneumatic diaphragm regulating valve 20 is provided to adjust the hydrogen discharge speed, thereby adjusting the pressure difference between the oxygen liquid separator 4 and the hydrogen gas-liquid separator 5; a hydrogen separator liquid level meter 7 is provided in the hydrogen gas-liquid separator 5 to detect the liquid level height in the hydrogen gas-liquid separator 5;

[0105] The liquid level difference between the oxygen separator liquid level gauge 6 and the hydrogen separator liquid level gauge 7 reflects the pressure difference in the oxygen liquid separator 4 and the hydrogen liquid separator 5; the electrolyte separated by the hydrogen liquid separator 5 and the oxygen liquid separator 4 is mixed through the connecting pipe and pumped out by the electrolyte circulation pump 8 at a rated flow rate, and the pumped electrolyte passes through the waste heat recovery device 9 and the electrolyte heat exchanger 12 in turn and then returns to the electrolytic cell 1 for electrolysis.

[0106] Preferably, a third electrolyte thermometer 13 is provided on the connecting pipeline between the electrolyte heat exchanger 12 and the electrolytic cell 1 to detect the temperature of the cooled electrolyte, and an electrolyte flowmeter 15 is provided to detect the flow of the electrolyte.

[0107] Preferably, the electrolyte heat exchanger 12 is provided with cooling water inlet and outlet pipelines to cool the electrolyte, and a cooling water regulating valve 14 is provided on the cooling water inlet pipeline to regulate the cooling water flow rate.

[0108] In the control method of the seawater electrolysis hydrogen production system under variable load conditions, the hot electrolyte separated by the hydrogen gas-liquid separator 5 and the oxygen liquid separator 4 enters the waste heat recovery device 9, exchanges heat with the external seawater, and generates hot steam by heat exchange evaporation, which is condensed by external cooling water to generate low-concentration brine and enters the raw water tank of the seawater electrolysis hydrogen production system for standby use; the waste heat recovery device 9 generates a vacuum through an external vacuum generating device, and adjusts the evaporation temperature of the external seawater in the waste heat recovery device 9 according to the vacuum degree, thereby controlling the heat exchange power between the waste heat recovery device 9 and the hot electrolyte.

[0109] Preferably, when the external power supply to the electrolytic cell 1 changes, the heating power of the electrolytic cell 1 changes accordingly, and the vacuum degree in the waste heat recovery device 9 is controlled by interlocking the waste heat recovery pressure gauge 10 and the waste heat recovery pressure regulating valve 11 connected to the external vacuum generating device, so as to realize dynamic adjustment of the heat exchange power between the waste heat recovery device 9 and the hot electrolyte as the heating power of the electrolytic cell 1 changes, and at the same time, the external seawater inlet temperature and flow rate are controlled to be constant;

[0110] like Figure 2 As shown, the adjustment logic is as follows:

[0111] S1, power supply changes;

[0112] S2, heating power change of electrolytic cell 1;

[0113] S3, calculate the theoretical seawater evaporation temperature required by the waste heat recovery device 9: electrolytic cell heating power - (seawater evaporation temperature - seawater inlet temperature) * seawater specific heat capacity * seawater flow + electrolyte heat exchanger heat exchange power 12;

[0114] S4, looking up a table to obtain the vacuum degree corresponding to the seawater evaporation temperature;

[0115] S5, determine: Is the waste heat recovery pressure gauge 10 equal to the vacuum corresponding to the seawater evaporation temperature? If yes, the vacuum corresponding to the seawater evaporation remains unchanged; if not, the opening of the waste heat recovery pressure regulating valve 11 changes, and then this step is determined again until the result is yes, and then proceed to the next step;

[0116] S6, reaching the target value of seawater evaporation temperature;

[0117] S7, the heat exchange power of the waste heat recovery device 9 changes and matches the heating power of the electrolytic cell 1.

[0118] Preferably, due to the possible heat exchange error of the waste heat recovery device 9, in order to ensure the stability of the heat exchange power, that is, the stability of the alkali solution control temperature at the inlet of the electrolytic cell 1 and the system target control temperature, an electrolyte heat exchanger 12 is arranged between the waste heat recovery device 9 and the electrolytic cell 1 for secondary heat exchange, and the heating power of the electrolytic cell 1 is equal to the heat exchange power of the electrolyte heat exchanger 12 plus the heat exchange power of the waste heat recovery device 9; when the external power supply to the electrolytic cell 1 changes, the heating power of the electrolytic cell 1 changes accordingly, and the average temperature of the readings of the electrolytic cell outlet thermometer is taken as the system target control temperature, that is, the sum of the readings of the first electrolyte thermometer 2 and the second electrolyte thermometer 3 divided by two, to obtain The reading of the thermometer at the inlet of the electrolytic cell, that is, the reading of the third electrolyte thermometer 13, is used as the alkali solution temperature at the inlet of the electrolytic cell. The alkali solution control temperature at the inlet of the electrolytic cell 1 is calculated by the heating power of the electrolytic cell 1 and the system target control temperature. When the alkali solution control temperature at the inlet of the electrolytic cell is higher than the reading of the thermometer at the inlet of the electrolytic cell, the opening of the cooling water regulating valve 14 is increased. When the alkali solution control temperature at the inlet of the electrolytic cell is lower than the reading of the thermometer, the opening of the cooling water regulating valve 14 is reduced, thereby realizing the dynamic adjustment of the heat exchange power between the electrolyte heat exchanger 12 and the hot electrolyte with the change of the heating power of the electrolytic cell 1. At the same time, the inlet and outlet temperatures of the external cooling water, the electrolyte flow rate and the heat exchange capacity of the waste heat recovery device 9 are controlled to be constant.

[0119] like Figure 3 As shown, the adjustment logic is as follows:

[0120] S1, power supply changes;

[0121] S2, heating power change of electrolytic cell 1;

[0122] S3, calculate the control temperature of the alkali solution at the inlet of electrolytic cell 1: electrolytic cell heating power = waste heat recovery heat + (cooling water inlet and outlet temperature difference * cooling water specific heat capacity * cooling water flow rate = (system target control temperature - electrolytic cell inlet alkali solution temperature) * alkali solution specific heat capacity * alkali|liquid flow rate) = heating voltage * rated power / working voltage;

[0123] S4, the first electrolyte thermometer 2, the second electrolyte thermometer 3, and the third electrolyte thermometer 13 obtain temperatures;

[0124] S5, determine whether the alkaline solution control temperature at the inlet of the electrolytic cell minus the temperature of the third electrolyte thermometer 13 is greater than zero, if so, the opening of the cooling water regulating valve 14 is increased; if not, the opening of the cooling water regulating valve 14 is decreased;

[0125] S6, the heat exchange power 12 of the electrolyte heat exchanger changes and matches the heat generation power of the electrolytic cell 1.

[0126] Preferably, when the external power supply to the electrolyzer 1 decreases, the current density of the electrolyzer 1 decreases accordingly. At this time, the values ​​of the hydrogen in oxygen meter 16 and the oxygen in hydrogen meter 17 will increase accordingly. Since the value of hydrogen in oxygen changes more, the hydrogen in oxygen is used as the control point, and the first pneumatic diaphragm regulating valve 19 connected to the pressure control device is increased through interlocking control to increase the opening, thereby increasing the gas discharge rate and reducing the system pressure to reduce the trend of the increase of hydrogen in oxygen; when the external power supply to the electrolyzer 1 increases, the current density of the electrolyzer 1 increases accordingly. At this time, the values ​​of the hydrogen in oxygen meter 16 and the oxygen in hydrogen meter 17 will decrease accordingly. Since the value of hydrogen in oxygen changes more, the hydrogen in oxygen is used as the control point, and the first pneumatic diaphragm regulating valve 19 connected to the pressure control device is reduced through interlocking control to reduce the opening, thereby reducing the gas discharge rate until the system pressure is restored; to achieve dynamic regulation of pressure and product gas purity with fluctuations in the power supply of the electrolyzer 1;

[0127] like Figure 4 As shown, the power supply reduction regulation logic is as follows:

[0128] S1, power supply decreases

[0129] S2, the current density of electrolytic cell 1 decreases

[0130] S3, the values ​​of the oxygen-hydrogen measuring instrument 16 and the hydrogen-oxygen measuring instrument 17 increase

[0131] S4, reducing the opening pressure of the first pneumatic diaphragm regulating valve 19

[0132] S5, determine whether the upward trend of the value of the oxygen hydrogen measuring instrument 16 decreases. If yes, the system pressure decreases and matches the current density of the electrolyzer 1, and the purity of the product gas is stable; if not, return to step S4 until the judgment result is yes;

[0133] like Figure 4 As shown, the power supply increase regulation logic is as follows:

[0134] S1, power supply increases;

[0135] S2, the current density of electrolytic cell 1 increases;

[0136] S3, the values ​​of the oxygen-hydrogen measuring instrument 16 and the hydrogen-oxygen measuring instrument 17 decrease;

[0137] S4, increasing the opening pressure of the first pneumatic diaphragm regulating valve 19;

[0138] S5, determine: whether the opening pressure of the first pneumatic diaphragm regulating valve 19 is equal to the rated system pressure. If so, the system pressure rises and matches the current density of the electrolytic cell 1, and the purity of the product gas is stable; if not, return to step S4 until the judgment result is yes.

[0139] Preferably, when the external power supply to the electrolyzer 1 decreases, the current density of the electrolyzer 1 decreases accordingly. At this time, the values ​​of the hydrogen in oxygen meter 16 and the oxygen in hydrogen meter 17 will increase accordingly. Since the value of hydrogen in oxygen changes more, the hydrogen in oxygen is used as the control point, and the second pneumatic diaphragm regulating valve 20 connected to the liquid level control device is controlled through interlocking to reduce the liquid level difference response speed, so as to reduce the trend of the increase of hydrogen in oxygen; when the external power supply to the electrolyzer 1 increases, the current density of the electrolyzer 1 increases accordingly. At this time, the values ​​of the hydrogen in oxygen meter 16 and the oxygen in hydrogen meter 17 will decrease accordingly. Since the value of hydrogen in oxygen changes more, the hydrogen in oxygen is used as the control point, and the second pneumatic diaphragm regulating valve 20 connected to the liquid level control device is controlled through interlocking to increase the liquid level difference response speed until the rated response speed of the system is restored; the dynamic adjustment of the liquid level difference and the purity of the product gas with the fluctuation of the power supply of the electrolyzer 1 is realized;

[0140] like Figure 5 As shown, the power supply reduction regulation logic is as follows:

[0141] S1, power supply decreases;

[0142] S2, the current density of electrolytic cell 1 decreases;

[0143] S3, the values ​​of the oxygen-hydrogen measuring instrument 16 and the hydrogen-oxygen measuring instrument 17 increase;

[0144] S4, reducing the response speed of the second pneumatic diaphragm regulating valve 20, if n (n>5), the system liquid level difference response speed is independent of the current density of the electrolytic cell 1; if n (n<5), proceed to the next step;

[0145] S5, determine: whether the rising trend of the value of the oxygen hydrogen measuring instrument 16 decreases, if so, the system liquid level difference response speed decreases and matches the current density of the electrolyzer 1, and the product gas purity is stable; if not, return to step S4 until the judgment result is yes.

[0146] like Figure 5 As shown, the power supply increase regulation logic is as follows:

[0147] S1, power supply increases;

[0148] S2, the current density of electrolytic cell 1 increases;

[0149] S3, the values ​​of the oxygen-hydrogen measuring instrument 16 and the hydrogen-oxygen measuring instrument 17 decrease;

[0150] S4, increase the response speed of the second pneumatic diaphragm regulating valve 20. If n (n>5), the system liquid level difference response speed is independent of the current density of the electrolytic cell 1; if n (n<5), proceed to the next step;

[0151] S5, determine whether the response speed of the second pneumatic diaphragm regulating valve 20 is equal to the rated response speed. If yes, the system liquid level difference response speed increases and matches the current density of the electrolytic cell 1, and the product gas purity is stable; if not, return to step S4 until the judgment result is yes.

[0152] Preferably, when the external power supply to the electrolyzer 1 decreases, the current density of the electrolyzer 1 decreases accordingly. At this time, the values ​​of the oxygen-hydrogen measuring instrument 16 and the hydrogen-oxygen measuring instrument 17 will increase accordingly. By adjusting the opening of the manual ball valve 21 on the oxygen side and the manual ball valve 22 on the hydrogen side, the pressure drop difference between the hydrogen and oxygen sides is adjusted. When the rising rate of hydrogen in oxygen is greater than that of oxygen in hydrogen, the pressure drop of the oxygen pipeline is increased. When the rising trend of hydrogen in oxygen is less than that of oxygen in hydrogen, the pressure drop of the hydrogen pipeline is increased. The dynamic adjustment of the pressure drop difference between the hydrogen and oxygen sides and the purity of the product gas as the power supply of the electrolyzer 1 changes is realized, wherein increasing the pressure drop of the oxygen pipeline will cause more oxygen to penetrate into the hydrogen, thereby increasing the change rate of oxygen in hydrogen, and the same is true for increasing the pressure drop of the hydrogen pipeline.

[0153] like Figure 6 As shown, the adjustment logic is as follows:

[0154] S1, power supply decreases;

[0155] S2, the current density of electrolytic cell 1 decreases;

[0156] S3, the values ​​of the oxygen-hydrogen measuring instrument 16 and the hydrogen-oxygen measuring instrument 17 increase;

[0157] S4, adjusting the opening of the manual ball valve 21 on the oxygen side and the manual ball valve 22 on the hydrogen side;

[0158] S5, determine whether the rising rate of hydrogen in oxygen is greater than that of oxygen in hydrogen. If yes, increase the pressure drop of the oxygen pipeline; if no, increase the pressure drop of the hydrogen pipeline;

[0159] S6, the pressure drop difference between hydrogen and oxygen changes and matches the current density of electrolyzer 1, and the purity of the product gas is stable.

[0160] Preferably, when the external power supply to the electrolytic cell 1 increases, the current density of the electrolytic cell 1 increases accordingly, and the energy consumption of the electrolytic cell 1 also increases accordingly, and then the values ​​of the first electrolyte thermometer 2 and the second electrolyte thermometer 3 increase accordingly, and the flow rate of the electrolyte circulation pump 8 is controlled and adjusted by calculating the target control flow rate of the adjustment system to reduce the temperature difference of the alkali solution at the inlet and outlet of the electrolytic cell, thereby reducing the rising trend of the energy consumption of the electrolytic cell; when the current density decreases to the rated current density, the energy consumption of the electrolytic cell is reduced, and the flow rate of the pump is restored to the rated flow rate;

[0161] like Figure 7 As shown, the power supply increase regulation logic is as follows:

[0162] S1, power supply increases;

[0163] S2, the current density of electrolytic cell 1 increases;

[0164] S3, energy consumption of electrolyzer 1 increases;

[0165] S4, calculate the target control flow of electrolytic cell 1: electrolytic cell heating power = waste heat recovery heat + (cooling water inlet and outlet temperature difference * cooling water specific heat capacity * cooling water flow rate = (system target control temperature - electrolytic cell inlet alkali solution temperature) * alkali solution specific heat capacity * alkali solution flow rate);

[0166] S5, the first electrolyte thermometer 2, the second electrolyte thermometer 3, and the third electrolyte thermometer 13 obtain the temperature;

[0167] S6, the alkali solution flow rate is less than the system target control flow rate;

[0168] S7, the electrolyte circulation pump 8 adjusts the alkali solution flow rate to increase;

[0169] S8, the temperature difference between the inlet and outlet of the electrolytic cell decreases;

[0170] S9, the rising trend of electrolytic cell energy consumption decreases;

[0171] like Figure 7 As shown, the power supply reduction regulation logic is as follows:

[0172] S1, power supply decreases;

[0173] S2, the current density of electrolytic cell 1 decreases to the rated value;

[0174] S3, energy consumption of electrolytic cell 1 is reduced;

[0175] S4, the electrolyte circulation pump 8 adjusts the alkali solution flow rate to return to the rated value.

Claims

1. A system for producing hydrogen by electrolyzing seawater under variable load conditions, characterized in that: The electrolysis seawater hydrogen production system comprises: an electrolytic cell (1), a first electrolyte thermometer (2), a second electrolyte thermometer (3), an oxygen liquid separator (4), a hydrogen gas-liquid separator (5), an oxygen separator level gauge (6), a hydrogen separator level gauge (7), an electrolyte circulation pump (8), a waste heat recovery device (9), a waste heat recovery barometer (10), a waste heat recovery pressure regulating valve (11), an electrolyte heat exchanger (12), a third electrolyte thermometer (13), a cooling water regulating valve (14), an electrolyte flow meter (15), an oxygen-hydrogen measuring instrument (16), a hydrogen-oxygen measuring instrument (17), a hydrogen production system pressure gauge (18), a first pneumatic diaphragm regulating valve (19), a second pneumatic diaphragm regulating valve (20), an oxygen-side manual ball valve (21), and a hydrogen-side manual ball valve (22); The external power supply inputs a rated current and voltage into the electrolytic cell (1), so that the electrolytic cell (1) operates at a rated current density, electrolyzes the electrolyte to produce hydrogen and oxygen, and heats the electrolyte; After electrolysis, oxygen follows the electrolyte and enters the oxygen-liquid separator (4) in the form of gas-liquid two-phase flow for gas-liquid separation. A first electrolyte thermometer (2) is provided on the pipeline between the electrolytic cell (1) and the oxygen-liquid separator (4) for detecting the gas-liquid two-phase flow temperature at the oxygen-side electrolytic cell outlet. A manual ball valve (21) on the oxygen side is provided to control the opening of the gas-liquid two-phase flow from the oxygen side to the oxygen-liquid separator (4). The oxygen separated by the oxygen-liquid separator (3) is discharged to the outside. A hydrogen-in-oxygen measuring instrument (16) is provided on the oxygen discharge pipeline to monitor the purity of oxygen. A hydrogen production system pressure gauge (18) is provided to detect the operating pressure of the hydrogen production system. A first pneumatic diaphragm regulating valve (19) is provided to adjust the oxygen discharge speed, thereby adjusting the pressure of the hydrogen production system. An oxygen separator liquid level gauge (6) is provided in the oxygen-liquid separator (4) to detect the liquid level height in the oxygen separator liquid level gauge (6). After electrolysis, hydrogen follows the electrolyte and enters the hydrogen gas-liquid separator (5) in the form of a gas-liquid two-phase flow for gas-liquid separation. A second electrolyte thermometer (3) is provided on the pipeline between the electrolytic cell (1) and the hydrogen gas-liquid separator (5) for detecting the gas-liquid two-phase flow temperature at the hydrogen side electrolytic cell outlet. A hydrogen side manual ball valve (22) is provided to control the opening of the hydrogen side gas-liquid two-phase to the hydrogen gas-liquid separator (5). The hydrogen separated by the hydrogen gas-liquid separator (5) is transported outward. A hydrogen oxygen measuring instrument (17) is provided on the hydrogen outlet pipeline to monitor the purity of the hydrogen. A second pneumatic diaphragm regulating valve (20) is provided to adjust the hydrogen discharge speed, thereby adjusting the pressure difference between the oxygen liquid separator (4) and the hydrogen gas-liquid separator (5). A hydrogen separator liquid level meter (7) is provided in the hydrogen gas-liquid separator (5) to detect the liquid level height in the hydrogen gas-liquid separator (5). The liquid level difference between the oxygen separator liquid level gauge (6) and the hydrogen separator liquid level gauge (7) reflects the pressure difference between the oxygen liquid separator (4) and the hydrogen liquid separator (5); the electrolyte separated by the hydrogen liquid separator (5) and the oxygen liquid separator (4) is mixed through a connecting pipe and pumped out by an electrolyte circulation pump (8) at a rated flow rate. The pumped electrolyte passes through a waste heat recovery device (9) and an electrolyte heat exchanger (12) in turn and then returns to the electrolytic cell (1) for electrolysis.

2. The system for producing hydrogen by electrolysis of seawater under variable load conditions according to claim 1, characterized in that: A third electrolyte thermometer (13) is provided on the connecting pipeline between the electrolyte heat exchanger (12) and the electrolytic cell (1) to detect the temperature of the electrolyte after cooling, and an electrolyte flowmeter (15) is provided to detect the flow rate of the electrolyte.

3. The system for producing hydrogen by electrolysis of seawater under variable load conditions according to claim 1, characterized in that: The electrolyte heat exchanger (12) is provided with cooling water inlet and outlet pipelines for cooling the electrolyte, and a cooling water regulating valve (14) is provided on the cooling water inlet pipeline for regulating the cooling water flow rate.

4. A control method for a hydrogen production system by electrolyzing seawater under variable load conditions as described in any one of claims 1 to 3, characterized in that: The hot electrolyte separated by the hydrogen gas-liquid separator (5) and the oxygen liquid separator (4) enters the waste heat recovery device (9), exchanges heat with external seawater, and generates hot steam by evaporation. The hot steam is condensed by external cooling water to generate low-concentration brine, which enters the raw water tank of the electrolytic seawater hydrogen production system for standby use. The waste heat recovery device (9) generates a vacuum through an external vacuum generating device, and adjusts the evaporation temperature of the external seawater in the waste heat recovery device (9) according to the vacuum degree, thereby controlling the heat exchange power between the waste heat recovery device (9) and the hot electrolyte.

5. The control method according to claim 4, characterized in that: When the external power supply to the electrolytic cell (1) changes, the heating power of the electrolytic cell (1) changes accordingly. The vacuum degree in the waste heat recovery device (9) is controlled by interlocking control of a waste heat recovery pressure gauge (10) and a waste heat recovery pressure regulating valve (11) connected to an external vacuum generating device, so as to achieve dynamic regulation of the heat exchange power between the waste heat recovery device (9) and the hot electrolyte as the heating power of the electrolytic cell (1) changes. At the same time, the external seawater inlet temperature and flow rate are controlled to be constant. The adjustment logic is as follows: S1, power supply changes; S2, change in heating power of electrolytic cell (1); S3, calculate the theoretical seawater evaporation temperature required by the waste heat recovery device (9): electrolytic cell heating power - (seawater evaporation temperature - seawater inlet temperature) * seawater specific heat capacity * seawater flow rate + electrolyte heat exchanger heat exchange power (12); S4, looking up a table to obtain the vacuum degree corresponding to the seawater evaporation temperature; S5, determine: Is the waste heat recovery pressure gauge (10) equal to the vacuum corresponding to the seawater evaporation temperature? If yes, the vacuum corresponding to the seawater evaporation remains unchanged; if not, the opening of the waste heat recovery pressure regulating valve (11) changes, and then this step is determined again until the result is yes, and then proceed to the next step; S6, reaching the target value of seawater evaporation temperature; S7, the heat exchange power of the waste heat recovery device (9) changes and matches the heat generation power of the electrolytic cell (1).

6. The control method according to claim 4, characterized in that: Due to the possible heat exchange error of the waste heat recovery device (9), in order to ensure the stability of the heat exchange power, that is, the stability of the alkali solution control temperature at the inlet of the electrolytic cell (1) and the system target control temperature, an electrolyte heat exchanger (12) is set between the waste heat recovery device (9) and the electrolytic cell (1) for secondary heat exchange. The heat generation power of the electrolytic cell (1) is equal to the heat exchange power of the electrolyte heat exchanger (12) plus the heat exchange power of the waste heat recovery device (9); when the external power supply to the electrolytic cell (1) changes, the heat generation power of the electrolytic cell (1) changes accordingly, and the average temperature of the readings of the electrolytic cell outlet thermometer is taken as the system target control temperature, that is, the sum of the readings of the first electrolyte thermometer (2) and the second electrolyte thermometer (3) divided by two , taking the reading of the thermometer at the inlet of the electrolytic cell, i.e., the reading of the third electrolyte thermometer (13), as the alkali solution temperature at the inlet of the electrolytic cell, the alkali solution control temperature at the inlet of the electrolytic cell (1) is calculated by the heating power of the electrolytic cell (1) and the system target control temperature, when the alkali solution control temperature at the inlet of the electrolytic cell is higher than the reading of the thermometer at the inlet of the electrolytic cell, the opening of the cooling water regulating valve (14) is increased, and when the alkali solution control temperature at the inlet of the electrolytic cell is lower than the reading of the thermometer, the opening of the cooling water regulating valve (14) is reduced, thereby realizing dynamic regulation of the heat exchange power between the electrolyte heat exchanger (12) and the hot electrolyte as the heating power of the electrolytic cell (1) changes, and at the same time, controlling the inlet and outlet temperatures of the external cooling water, the electrolyte flow rate, and the heat exchange capacity of the waste heat recovery device (9) to be constant; The adjustment logic is as follows: S1, power supply changes; S2, change in heating power of electrolytic cell (1); S3, calculate the control temperature of the alkali solution at the inlet of the electrolytic cell (1): electrolytic cell heating power = waste heat recovery heat + (cooling water inlet and outlet temperature difference * cooling water specific heat capacity * cooling water flow rate = (system target control temperature - electrolytic cell inlet alkali solution temperature) * alkali solution specific heat capacity * alkali|liquid flow rate) = heating voltage * rated power / working voltage; S4, the first electrolyte thermometer (2), the second electrolyte thermometer (3), and the third electrolyte thermometer (13) obtain temperatures; S5, determining whether the alkaline solution control temperature at the inlet of the electrolytic cell minus the temperature of the third electrolyte thermometer (13) is greater than zero, if so, the opening of the cooling water regulating valve (14) is increased; if not, the opening of the cooling water regulating valve (14) is decreased; S6, the heat exchange power (12) of the electrolyte heat exchanger changes and matches the heat generation power of the electrolytic cell (1).

7. The control method according to claim 4, characterized in that: When the external power supply to the electrolytic cell (1) decreases, the current density of the electrolytic cell (1) decreases accordingly. At this time, the values ​​of the oxygen-hydrogen measuring instrument (16) and the hydrogen-oxygen measuring instrument (17) will increase accordingly. Since the value of the oxygen-hydrogen changes more, the oxygen-hydrogen is used as the control point. The first pneumatic diaphragm regulating valve (19) connected to the pressure control device is controlled to increase the opening, thereby increasing the gas discharge rate and reducing the system pressure to reduce the trend of the increase of the oxygen-hydrogen; When the external power supply to the electrolytic cell (1) increases, the current density of the electrolytic cell (1) increases accordingly. At this time, the values ​​of the oxygen-hydrogen measuring instrument (16) and the hydrogen-oxygen measuring instrument (17) will decrease accordingly. Since the value of the oxygen-hydrogen changes more, the oxygen-hydrogen is used as the control point. The first pneumatic diaphragm regulating valve (19) connected to the pressure control device is controlled to decrease the opening, thereby reducing the gas discharge rate until the system pressure is restored; dynamic regulation of the pressure and product gas purity with the fluctuation of the power supply of the electrolytic cell (1) is achieved; The power supply reduction regulation logic is as follows: S1, power supply decreases S2, the current density of the electrolytic cell (1) decreases S3, the values ​​of the oxygen-hydrogen measuring instrument (16) and the hydrogen-oxygen measuring instrument (17) increase S4, reducing the opening pressure of the first pneumatic diaphragm regulating valve (19) S5, determine whether the upward trend of the value of the oxygen hydrogen measuring instrument (16) decreases. If yes, the system pressure decreases and matches the current density of the electrolyzer (1), and the purity of the product gas is stable; if not, return to step S4 until the judgment result is yes; The power supply increase regulation logic is as follows: S1, power supply increases; S2, the current density of the electrolytic cell (1) increases; S3, the values ​​of the oxygen-hydrogen measuring instrument (16) and the hydrogen-oxygen measuring instrument (17) decrease; S4, increasing the opening pressure of the first pneumatic diaphragm regulating valve (19); S5, determine whether the opening pressure of the first pneumatic diaphragm regulating valve (19) is equal to the rated system pressure. If so, the system pressure rises and matches the current density of the electrolytic cell (1), and the purity of the product gas is stable. If not, return to step S4 until the judgment result is yes.

8. The control method according to claim 4, characterized in that: When the external power supply to the electrolyzer (1) decreases, the current density of the electrolyzer (1) decreases accordingly. At this time, the values ​​of the hydrogen in oxygen meter (16) and the oxygen in hydrogen meter (17) will increase accordingly. Since the value of hydrogen in oxygen changes more, the hydrogen in oxygen is used as the control point. The second pneumatic diaphragm regulating valve (20) connected to the liquid level control device is controlled through interlocking to reduce the liquid level difference response speed, thereby reducing the trend of the increase of hydrogen in oxygen; when the external power supply to the electrolyzer (1) increases, the current density of the electrolyzer (1) increases accordingly. At this time, the values ​​of the hydrogen in oxygen meter (16) and the oxygen in hydrogen meter (17) will decrease accordingly. Since the value of hydrogen in oxygen changes more, the hydrogen in oxygen is used as the control point. The second pneumatic diaphragm regulating valve (20) connected to the liquid level control device is controlled through interlocking to increase the liquid level difference response speed until the rated response speed of the system is restored; the liquid level difference and the purity of the product gas are dynamically adjusted as the power supply of the electrolyzer (1) fluctuates; The power supply reduction regulation logic is as follows: S1, power supply decreases; S2, the current density of the electrolytic cell (1) decreases; S3, the values ​​of the oxygen-hydrogen measuring instrument (16) and the hydrogen-oxygen measuring instrument (17) increase; S4, reducing the response speed of the second pneumatic diaphragm regulating valve (20), if n (n>5), the system liquid level difference response speed is independent of the current density of the electrolytic cell (1); if n (n<5), proceed to the next step; S5, determine: whether the upward trend of the value of the oxygen hydrogen measuring instrument (16) decreases. If so, the system liquid level difference response speed decreases and matches the current density of the electrolytic cell (1), and the product gas purity is stable; if not, return to step S4 until the judgment result is yes. The power supply increase regulation logic is as follows: S1, power supply increases; S2, the current density of the electrolytic cell (1) increases; S3, the values ​​of the oxygen-hydrogen measuring instrument (16) and the hydrogen-oxygen measuring instrument (17) decrease; S4, increasing the response speed of the second pneumatic diaphragm regulating valve (20), if n (n>5), the system liquid level difference response speed is independent of the current density of the electrolytic cell (1); if n (n<5), proceed to the next step; S5, determine whether the response speed of the second pneumatic diaphragm regulating valve (20) is equal to the rated response speed. If so, the system liquid level difference response speed increases and matches the current density of the electrolytic cell (1), and the product gas purity is stable; if not, return to step S4 until the judgment result is yes.

9. The control method according to claim 4, characterized in that: When the external power supply to the electrolyzer (1) decreases, the current density of the electrolyzer (1) decreases accordingly. At this time, the values ​​of the oxygen-hydrogen measuring instrument (16) and the hydrogen-oxygen measuring instrument (17) will increase accordingly. By adjusting the opening of the manual ball valve (21) on the oxygen side and the manual ball valve (22) on the hydrogen side, the pressure drop difference between the hydrogen and oxygen sides is adjusted. When the rising rate of hydrogen in oxygen is greater than that of oxygen in hydrogen, the pressure drop of the oxygen pipeline is increased. When the rising trend of hydrogen in oxygen is less than that of oxygen in hydrogen, the pressure drop of the hydrogen pipeline is increased. The pressure drop difference between the hydrogen and oxygen sides and the purity of the product gas are dynamically adjusted as the power supply of the electrolyzer (1) changes. Increasing the pressure drop of the oxygen pipeline will cause more oxygen to penetrate into the hydrogen, thereby increasing the change rate of oxygen in hydrogen. The same is true for increasing the pressure drop of the hydrogen pipeline. The adjustment logic is as follows: S1, power supply decreases; S2, the current density of the electrolytic cell (1) decreases; S3, the values ​​of the oxygen-hydrogen measuring instrument (16) and the hydrogen-oxygen measuring instrument (17) increase; S4, adjusting the opening of the manual ball valve (21) on the oxygen side and the manual ball valve (22) on the hydrogen side; S5, determine whether the rising rate of hydrogen in oxygen is greater than that of oxygen in hydrogen. If yes, increase the pressure drop of the oxygen pipeline; if no, increase the pressure drop of the hydrogen pipeline; S6, the pressure drop difference between the hydrogen and oxygen sides changes and matches the current density of the electrolyzer (1), and the purity of the product gas is stable.

10. The control method according to claim 4, characterized in that: When the external power supply to the electrolytic cell (1) increases, the current density of the electrolytic cell (1) increases accordingly, and the energy consumption of the electrolytic cell (1) also increases accordingly, and then the values ​​of the first electrolyte thermometer (2) and the second electrolyte thermometer (3) increase accordingly. By calculating the target control flow of the regulation system, the flow of the electrolyte circulation pump (8) is controlled and regulated in a chain manner to reduce the temperature difference of the alkali solution at the inlet and outlet of the electrolytic cell, thereby reducing the increasing trend of the energy consumption of the electrolytic cell; when the current density decreases to the rated current density, the energy consumption of the electrolytic cell decreases, and the flow of the pump is restored to the rated flow; The power supply increase adjustment logic is as follows: S1, power supply increases; S2, the current density of the electrolytic cell (1) increases; S3, the energy consumption of the electrolytic cell (1) increases; S4, calculate the target control flow of the electrolytic cell (1): electrolytic cell heating power = waste heat recovery heat + (cooling water inlet and outlet temperature difference * cooling water specific heat capacity * cooling water flow rate = (system target control temperature - electrolytic cell inlet alkali solution temperature) * alkali solution specific heat capacity * alkali solution flow rate); S5, the first electrolyte thermometer (2), the second electrolyte thermometer (3), and the third electrolyte thermometer (13) obtain temperatures; S6, the alkali solution flow rate is less than the system target control flow rate; S7, the electrolyte circulation pump (8) adjusts the alkali solution flow rate to increase; S8, the temperature difference between the inlet and outlet of the electrolytic cell decreases; S9, the rising trend of electrolytic cell energy consumption decreases; The power supply reduction adjustment logic is as follows: S1, power supply decreases; S2, the current density of the electrolytic cell (1) decreases to a rated value; S3, the energy consumption of the electrolytic cell (1) is reduced; S4, the electrolyte circulation pump (8) adjusts the alkali solution flow rate to restore it to the rated value.

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