Seawater electrolysis hydrogen production system and control method therefor

Abstract

The present invention relates to a seawater electrolysis hydrogen production system and a control method therefor. The seawater electrolysis hydrogen production system comprises: an electrolytic cell (16), an oxygen-liquid separator (1), a hydrogen-liquid separator (6), a seawater heat exchanger (28), a seawater condenser (32), an alkaline-solution heat exchanger (12), a demineralized low-salinity water storage tank (40), a salt-precipitation storage tank (45), an alkali tank (20) and a water tank (18). The seawater electrolysis hydrogen production system of the present invention can effectively use waste heat generated during electrolysis to remove easily deposited ions from seawater, and reduce the concentration of monovalent ions in the seawater so that the seawater can be used as feed water for water electrolysis hydrogen production; moreover, the content of salt accumulated in the hydrogen production system is reduced by means of evaporating a solvent to precipitate salt, so as to address the adverse effect of ions in the seawater on the performance of the seawater electrolysis hydrogen production system.

Description

Electrolysis seawater hydrogen production system and control method thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of electrolysis seawater hydrogen production, in particular to an electrolysis water hydrogen production system and a control method thereof, which is particularly suitable for an electrolysis water hydrogen production system using seawater as the electrolysis raw material. BACKGROUND

[0002] With the increasing demand for clean energy worldwide, electrolysis seawater hydrogen production technology as a sustainable and pollution-free energy production means has important significance for increasing the application range of electrolysis water hydrogen production, reducing the water cost of electrolysis water hydrogen production, increasing the offshore energy utilization rate, and achieving the double carbon goal. However, the complex chemical composition of seawater brings many challenges to the industrial application of electrolysis water hydrogen production technology.

[0003] Specifically, seawater contains a large amount of easily deposited ions, such as Ca 2+ , Mg 2+ , etc. During the electrolysis process, these ions are prone to deposit on the electrode surface of the electrolysis cell, forming non-conductive deposits, which not only reduces the conductivity of the electrode, but also increases the resistance of the electrode, thereby reducing the efficiency of the electrode and affecting the efficiency and yield of electrolysis hydrogen production.

[0004] At the same time, monovalent ions such as Cl - in seawater will gradually accumulate in the hydrogen production system during the electrolysis process. When the ion concentration reaches saturation, salt crystals will be formed and precipitated, which may block the pipelines of the hydrogen production system, and in severe cases, may even cause equipment shutdown or damage, posing a great hidden danger to the safe operation of the hydrogen production system.

[0005] In view of the problems of deposition of easily deposited ions in seawater on the electrode surface and accumulation of monovalent ion concentration in the hydrogen production system, there is an urgent need for an electrolysis water hydrogen production system and a control method thereof that can remove easily deposited ions in seawater and reduce monovalent ion concentration. In order to solve the above problems, the commonly used method is to filter and remove the ions in seawater through multiple reverse osmosis membranes and EDI technology (continuous electrolysis desalination technology) before the seawater enters the electrolysis water hydrogen production system. However, this method requires additional energy to maintain high pressure, and the reverse osmosis membrane assembly needs to be replaced frequently, resulting in high energy consumption, frequent maintenance, and wide occupation area, which is not conducive to the large-scale use of offshore conditions. In addition, the waste heat generated by the electrolysis cell during the electrolysis process is often ignored and cannot be effectively recycled, resulting in waste of energy.

[0006] Therefore, developing an electrolytic seawater hydrogen production system capable of utilizing the waste heat generated by the electrolytic cell, maintaining high pressure without additional energy, less maintenance, and small footprint, and a control method thereof, has important significance for improving the economic and environmental benefits of the electrolytic water hydrogen production technology and promoting the industrial application of the electrolytic water hydrogen production technology.

[0007] To solve the above problems, the present application is proposed. SUMMARY

[0008] The present application aims at solving the problems of the prior art, and provides an electrolytic seawater hydrogen production system capable of recycling the waste heat of the electrolytic cell, maintaining high pressure without additional energy, less maintenance, and small footprint, and a control method thereof, to solve the adverse effects of ions in seawater on the performance of the electrolytic seawater hydrogen production system. The electrolytic seawater hydrogen production system can effectively utilize the waste heat generated during the electrolysis process to remove the easily precipitated ions in seawater and reduce the concentration of monovalent ions in seawater, so that the seawater can be used as raw material water for electrolytic hydrogen production. At the same time, the salt content accumulated in the hydrogen production system is reduced by using evaporation of the solvent to precipitate salt, to solve the adverse effects of ions in seawater on the performance of the electrolytic seawater hydrogen production system.

[0009] The present application provides an electrolytic seawater hydrogen production system and a control method thereof, which mainly comprises an oxygen-liquid separator, a hydrogen-liquid separator, an alkali liquid circulating pump, an alkali liquid heat exchanger, an electrolytic cell, a water tank, an alkali tank, an alkali supplement pump, a seawater heat exchanger, a seawater condenser, a vacuum pump, a water pump, a low-salt water tank for removing hardness, a salt precipitation tank, and a back-alkali pump. The alkali supplement pump supplements alkali liquid into the hydrogen production system, the electrolytic cell produces oxygen and hydrogen and heats the alkali liquid, the seawater heat exchanger uses hot alkali liquid to evaporate seawater to generate steam, the seawater condenser uses cooling water to condense seawater steam to generate low-salt water for removing hardness as electrolytic raw material, and the salt precipitation tank heats and evaporates high-salt-concentration alkali liquid in the hydrogen production system to precipitate salt crystals and reduce the salt content in the hydrogen production system. Through the technical scheme provided by the present application, the electrolytic seawater waste heat can be recycled, the hardness of seawater can be reduced, and the seawater can be used as electrolytic raw material. At the same time, the salt content gradually accumulated in the electrolytic seawater hydrogen production system can be removed.

[0010] Specifically, the present application is implemented by the following technical scheme:

[0011] The present application provides an electrolytic seawater hydrogen production system, which comprises an electrolytic cell 16, an oxygen-liquid separator 1, a hydrogen-liquid separator 6, a seawater heat exchanger 28, a seawater condenser 32, an alkali liquid heat exchanger 12, a low-salt water tank for removing hardness 40, a salt precipitation tank 45, an alkali tank 20, and a water tank 18.

[0012] The alkali tank 20 is in communication with the oxygen-liquid separator 1 and the hydrogen-liquid separator 6 through a first alkali liquid supplement pipe 23, and the first alkali liquid supplement pipe 23 is provided with an alkali supplement pump 24.

[0013] The electrolytic tank 16 is communicated with the hydrogen liquid separator 6 through the hydrogen liquid circulation pipe 5, and the hydrogen liquid separator 6 is provided with a hydrogen discharge pipe 7; the electrolytic tank 16 is communicated with the oxygen liquid separator 1 through the oxygen liquid circulation pipe 3, and the oxygen liquid separator 1 is provided with an oxygen discharge pipe 2; the hydrogen liquid separator 6 and the oxygen liquid separator 1 are communicated with the seawater heat exchanger 28 through the first alkali liquid circulation pipe 8 and the second alkali liquid circulation pipe 10, and the second alkali liquid circulation pipe 10 is provided with an alkali liquid circulation pump 9;

[0014] The seawater heat exchanger 28 is communicated with the seawater condenser 32 through the steam intercommunication pipe 31, and the seawater condenser 32 is connected with a first cooling water circulation pipe 33; the seawater condenser 32 is communicated with the hard-removing low-salt water storage tank 40;

[0015] The seawater heat exchanger 28 is communicated with the alkali liquid heat exchanger 12 through the third alkali liquid circulation pipe 11, and the alkali liquid heat exchanger 12 is connected with the second cooling water circulation pipe 52; the alkali liquid heat exchanger 12 is communicated with the electrolytic tank 16 through the fourth alkali liquid circulation pipe 14 and the fifth alkali liquid circulation pipe 15;

[0016] The hard-removing low-salt water storage tank 40 is communicated with the water tank 18 through a water pumping pipe 39;

[0017] The salt precipitation storage tank 45 is communicated with the fifth alkali liquid circulation pipe 15 through a first alkali returning pipe 44, and is communicated with the alkali tank 20 through a second alkali returning pipe 57; the salt precipitation storage tank 45 is connected with a salt discharge pipe 47, and is communicated with a vacuum pump 35 through a vacuum pipe 51, and the vacuum pipe 51 is provided with a twelfth ball valve 50.

[0018] Preferably, the first alkali liquid supplement pipe 23 is provided with a third ball valve 21 and an alkali liquid supplement pipe ball valve 25, and the fifth alkali liquid circulation pipe 15 is provided with a fourth ball valve 22.

[0019] Preferably, the seawater heat exchanger 28 is connected with a seawater supplement pipe 26 and a concentrated seawater blowdown pipe 30, the seawater supplement pipe 26 is provided with a fifth ball valve 27, and the concentrated seawater blowdown pipe 30 is provided with a fourteenth ball valve 29.

[0020] Preferably, the hard-removing low-salt water storage tank 40 is provided with a first liquid level meter 41.

[0021] Preferably, the water pumping pipe 39 is provided with a second ball valve 19, an eighth ball valve 37 and a water pumping pump 38.

[0022] Preferably, the salt discharge pipe 47 is provided with a tenth ball valve 46.

[0023] The first back-alkali pipeline 44 is provided with the fifteenth ball valve 43, and the second back-alkali pipeline 57 is provided with the thirteenth ball valve 55 and a back-alkali pump 56.

[0024] The salt precipitation storage tank 45 is provided with a second liquid level meter 48.

[0025] Preferably, the seawater condenser 32 is in communication with the vacuum pump 35, and a sixth ball valve 34 is arranged between the seawater condenser 32 and the vacuum pump 35, so that the pressure in the seawater heat exchanger 28 and the seawater condenser 32 is reduced through the sixth ball valve 34 and the vacuum pump 35, thereby reducing the boiling point of seawater, so that seawater can be evaporated and condensed at a lower temperature.

[0026] Preferably, the water tank 18 is in communication with the first alkali solution supplement pipeline 23 through a first ball valve 17, and when the liquid level in the oxygen gas-liquid separator 1 and the hydrogen gas-liquid separator 6 decreases, the first ball valve 17 is opened, and the alkali solution supplement pump 24 and the alkali solution supplement pipeline ball valve 25 are opened to supplement the water in the water tank 18 to the electrolytic seawater hydrogen production system.

[0027] The electrolytic seawater hydrogen production system further comprises:

[0028] A nitrogen filling pipeline 4 is connected to an external nitrogen source and the oxygen gas-liquid separator 1 and the hydrogen gas-liquid separator 6, and is a pipeline for supplementing nitrogen from the outside to the hydrogen production system;

[0029] A ninth ball valve 42 is arranged to connect the seawater condenser 32 and the soft low-salt water storage tank 40.

[0030] A seventh ball valve 36 is arranged to connect external air and the soft low-salt water storage tank 40, and when the water in the soft low-salt water storage tank 40 needs to be discharged into the water tank 18 for storage, the ninth ball valve 42 needs to be closed and the seventh ball valve 36 needs to be opened, so that the soft low-salt water storage tank 40 reaches normal pressure.

[0031] A fifteenth ball valve 43 is arranged in the first back-alkali pipeline 44, and is used to control the connection and disconnection between the salt precipitation storage tank 45 and the fifth alkali solution circulation pipeline 15 in the hydrogen production system.

[0032] An eleventh ball valve 49 is arranged to connect external air and the salt precipitation storage tank 45, and when the alkali solution in the salt precipitation storage tank 45 needs to return to the alkali tank 20, the twelfth ball valve 50 needs to be closed to disconnect the salt precipitation storage tank 45 from the vacuum environment, and then the eleventh ball valve 49 needs to be opened to connect external air, so that the salt precipitation storage tank 45 reaches normal pressure.

[0033] A second cooling water circulation pipeline 52, which is connected to an external cooling water source and the caustic soda heat exchanger 12;

[0034] A pneumatic regulating valve 53, which is located on the second cooling water circulation pipeline 52;

[0035] A temperature transmitter 54, which is located on the fourth caustic soda circulation pipeline 14;

[0036] An interlock 13, which is connected to the pneumatic regulating valve 53 and the temperature transmitter 54, and controls the pneumatic regulating valve 53 to increase the flow of cooling water in the second cooling water circulation pipeline 52 when the temperature in the temperature transmitter 54 exceeds a set value, so as to increase the heat exchange amount and reduce the caustic soda temperature of the hydrogen production system.

[0037] The second aspect of the present application provides a control method of the electrolytic seawater hydrogen production system according to the first aspect of the present application, which comprises:

[0038] The caustic soda in the caustic soda tank 20 is pumped by the caustic soda supplement pump 24 to the oxygen gas-liquid separator 1 and the hydrogen gas-liquid separator 6 through the first caustic soda supplement pipeline 23 until the target liquid level,

[0039] The caustic soda circulation pump 9 is opened, the electrolytic cell 16 is powered on to start electrolysis, the hydrogen gas generated by the electrolysis of water and the high-temperature mixed fluid of caustic soda enter the hydrogen gas-liquid separator 6 through the hydrogen gas-liquid circulation pipeline 5 to perform gas-liquid separation, the separated hydrogen gas is discharged through the hydrogen gas discharge pipeline 7, and the separated high-temperature caustic soda enters the caustic soda circulation pump 9 through the first caustic soda circulation pipeline 8 to enter the next caustic soda circulation;

[0040] The oxygen gas generated by the electrolysis of water in the electrolytic cell 16 and the high-temperature mixed fluid of caustic soda enter the oxygen gas-liquid separator 1 through the oxygen gas-liquid circulation pipeline 3 to perform gas-liquid separation, the separated oxygen gas is discharged through the oxygen gas discharge pipeline 2, and the separated high-temperature caustic soda enters the caustic soda circulation pump 9 through the first caustic soda circulation pipeline 8 to enter the next caustic soda circulation;

[0041] The high-temperature caustic soda enters the seawater heat exchanger 28 through the second caustic soda circulation pipeline 10 to heat and evaporate the seawater, the generated seawater vapor enters the seawater condenser 32 through the vapor intercommunication pipeline 31 to exchange heat with the cooling water in the first cooling water circulation pipeline 33, and the condensed water is generated, at this time, the condensed water has a reduced ion concentration and monovalent ion concentration compared with the original seawater, and can be used as the electrolytic raw material water of the electrolytic seawater hydrogen production system;

[0042] The condensed water enters the low-hardness and low-salinity water storage tank 40 through natural overflow for standby use;

[0043] The high-temperature caustic solution after heat exchange in the seawater heat exchanger 28 enters the caustic solution heat exchanger 12 through the third caustic solution circulation pipe 11 to exchange heat with the cooling water in the second cooling water circulation pipe 52, and then returns to the electrolytic cell 16 through the fourth caustic solution circulation pipe 14 and the fifth caustic solution circulation pipe 15 to carry out a new round of electrolytic water hydrogen production process.

[0044] Preferably, before the seawater heat exchanger 28 and the seawater condenser 32 work, the twelfth ball valve 50, the eighth ball valve 37, the seventh ball valve 36, the fourteenth ball valve 29, and the fifth ball valve 27 are closed, and the sixth ball valve 34 and the vacuum pump 35 are opened, so that the air pressure in the seawater heat exchanger 28 and the seawater condenser 32 is reduced, thereby reducing the boiling point of seawater, so that seawater can be evaporated and condensed at a lower temperature.

[0045] Preferably, the fifth ball valve 27 is opened, and the seawater heat exchanger 28 is supplemented with raw seawater through the seawater supplement pipe 26. After the seawater supplement is completed, the fifth ball valve 27 is closed to maintain the vacuum state in the seawater heat exchanger 28. When the raw seawater stored in the seawater heat exchanger 28 is consumed to a target liquid level, the fourteenth ball valve 29 is opened, and the concentrated seawater after evaporation is discharged through the concentrated seawater blowdown pipe 30. Then, the fourteenth ball valve 29 is closed to maintain the vacuum state in the seawater heat exchanger 28.

[0046] Preferably, the water storage in the softening and low-salinity water storage tank 40 is observed through the first liquid level meter 41. When the softening and low-salinity water storage tank 40 is full, the ninth ball valve 42 is closed to isolate the softening and low-salinity water storage tank 40 from the vacuum environment in the seawater heat exchanger 28 and the seawater condenser 32. Then, the seventh ball valve 36 is opened to restore the softening and low-salinity water storage tank 40 to normal pressure. Then, the eighth ball valve 37 and the water pump 38 and the second ball valve 19 are opened, and the water stored in the softening and low-salinity water storage tank 40 is pumped into the water tank 18 through the water pumping pipe 39 as standby electrolytic raw water for the electrolytic seawater hydrogen production system.

[0047] Preferably, as the electrolytic cell 16 consumes water in the electrolytic seawater hydrogen production system, when the liquid level in the oxygen and liquid separator 1 and the hydrogen and liquid separator 6 decreases, the first ball valve 17, the caustic solution supplement pump 24, and the caustic solution supplement pipe ball valve 25 are opened to supplement the water stored in the water tank 18 into the electrolytic seawater hydrogen production system. After the supplement is completed, the first ball valve 17, the caustic solution supplement pump 24, and the caustic solution supplement pipe ball valve 25 are closed.

[0048] Preferably, the salt precipitation tank 45 is provided with a heating function, the fourth ball valve 22 and the fifteenth ball valve 43 are normally closed valves, when the accumulated salt concentration in the electrolytic seawater hydrogen production system approaches saturation, the fifteenth ball valve 43 is opened, and after the high-salt-concentration lye enters the salt precipitation tank 45, the fifteenth ball valve 43 is closed; the eleventh ball valve 49 and the tenth ball valve 46 are closed, the twelfth ball valve 50 and the vacuum pump 35 are opened, so that the salt precipitation tank 45 is in a vacuum state, the heating function of the salt precipitation tank 45 is started, and the high-salt-concentration lye is evaporated and salted, and after the liquid level in the salt precipitation tank 45 is observed to be reduced to the target liquid level by the second liquid level meter 48, the twelfth ball valve 50 and the vacuum pump 35 are closed, the eleventh ball valve 49 is opened to restore the salt precipitation tank 45 to normal pressure, and then the tenth ball valve 46 is opened to discharge salt crystals through the salt discharge pipe 47, and at the same time, the thirteenth ball valve 55 and the lye return pump 56 are opened to pump the remaining lye into the lye tank 20 through the second lye return pipeline 57 for standby use.

[0049] Compared with the prior art, the present application has the following beneficial effects:

[0050] 1、The present application uses vacuum to reduce the boiling point of seawater, uses the seawater evaporator 28 to evaporate seawater to generate steam, and uses the seawater condenser 32 to generate seawater condensate, so as to remove hardness and reduce salt in the original seawater, and the electrolytic raw water is used as the electrolytic water for the hydrogen production system, and the waste heat generated in the electrolysis process is used to reduce the easily deposited ions in the electrolytic raw water.

[0051] 2、The present application uses vacuum to reduce the boiling point of high-salt-concentration lye, and uses the salt precipitation tank 45 to evaporate high-salt-concentration lye to precipitate salt, so as to avoid the problem that the salt crystals block the pipelines of the hydrogen production system, and even cause the equipment to stop or be damaged in severe cases. BRIEF DESCRIPTION OF DRAWINGS

[0052] Fig. 1 is a process flow diagram of the electrolytic seawater hydrogen production system of the present application.

[0053] Names of reference numerals in the description of the drawings: 1. Oxygen liquid separator, 2. Oxygen discharge pipe, 3. Oxygen liquid circulation pipe, 4. Nitrogen charging pipe, 5. Hydrogen liquid circulation pipe, 6. Hydrogen liquid separator, 7. Hydrogen discharge pipe, 8. First caustic circulation pipe, 9. Caustic circulation pump, 10. Second caustic circulation pipe, 11. Third caustic circulation pipe, 12. Caustic heat exchanger, 13. Interlock, 14. Fourth caustic circulation pipe, 15. Fifth caustic circulation pipe, 16. Electrolyzer, 17. First ball valve, 18. Water tank, 19. Second ball valve, 20. Caustic tank, 21. Third ball valve, 22. Fourth ball valve, 23. First caustic makeup pipe, 24. Caustic makeup pump, 25. Second caustic makeup pipe, 26. Seawater makeup pipe, 27. Fifth ball valve, 28. Seawater heat exchanger, 29. Fourteenth ball valve, 30. Concentrated seawater blowdown pipe, 31. Steam crossover pipe, 32. Seawater condenser, 33. First cooling water circulation line, 34. Sixth ball valve, 35. Vacuum pump, 36. Seventh ball valve, 37. Eighth ball valve, 38. Water draw pump, 39. Water draw line, 40. Deionized low-salinity water storage tank, 41. First level gauge, 42. Ninth ball valve, 43. Fifteenth ball valve, 44. First caustic return line, 45. Salt crystallization storage tank, 46. Tenth ball valve, 47. Salt discharge pipe, 48. Second level gauge, 49. Eleventh ball valve, 50. Twelfth ball valve, 51. Vacuum pipe, 52. Second cooling water circulation line, 53. Pneumatic control valve, 54. Temperature transmitter, 55. Thirteenth ball valve, 56. Caustic return pump, 57. Second caustic return line. DETAILED DESCRIPTION

[0054] The present application will be further described with reference to the following examples.

[0055] Those skilled in the art will appreciate that the following examples are intended to be illustrative only and should not be viewed as limiting the scope of the present application. Unless otherwise indicated, in the examples, technical or conditions not specified are performed according to the techniques or conditions described in the literature or according to the product manual. Unless otherwise indicated, in the examples, the materials or apparatuses not specified are all conventional products that can be purchased.

[0056] Those skilled in the art will appreciate that, as used herein, singular forms "a", "an" and "the" include plural references unless the context clearly dictates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It will be understood that when an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements can be present. In addition, as used herein the term "connected" can include wirelessly connected.

[0057] In the description of the application, unless otherwise specified, the meaning of "a plurality of" is two or more. The orientation or state relationship indicated by the terms "inner", "upper", "lower" and the like is based on the orientation or state relationship shown in the drawings, and is only for the convenience of describing the application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the application.

[0058] In the description of the application, it should be noted that, unless otherwise specified and limited, the terms "mounting", "connection", "provided with" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, or electrical connection; it can be direct connection, or indirect connection through intermediate medium. For those skilled in the art, the specific meaning of the above terms in the application should be understood according to the specific circumstances.

[0059] Those skilled in the art can understand that, unless otherwise defined, all terms including technical terms and scientific terms used herein have the same meaning as that generally understood by those skilled in the art to which the application belongs. It should also be understood that terms such as those defined in general dictionaries should be understood as having meanings consistent with those in the prior art, and should not be interpreted in an idealized or overly formal sense unless otherwise defined.

[0060] Embodiment

[0061] As shown in FIG. 1, the electrolysis seawater hydrogen production system of the embodiment comprises an electrolytic cell 16, an oxygen liquid separator 1, a hydrogen liquid separator 6, a seawater heat exchanger 28, a seawater condenser 32, an alkali heat exchanger 12, a low-salt water tank 40 for removing hardness, a salt precipitation tank 45, an alkali tank 20, and a water tank 18.

[0062] The alkali tank 20 is in communication with the oxygen liquid separator 1 and the hydrogen liquid separator 6 respectively through a first alkali supplement pipe 23, and the first alkali supplement pipe 23 is provided with an alkali supplement pump 24.

[0063] The electrolytic cell 16 is in communication with the hydrogen liquid separator 6 through a hydrogen liquid circulation pipe 5, and the hydrogen liquid separator 6 is provided with a hydrogen discharge pipe 7. The electrolytic cell 16 is in communication with the oxygen liquid separator 1 through an oxygen liquid circulation pipe 3, and the oxygen liquid separator 1 is provided with an oxygen discharge pipe 2. The hydrogen liquid separator 6 and the oxygen liquid separator 1 are in communication with the seawater heat exchanger 28 through a first alkali circulation pipe 8 and a second alkali circulation pipe 10, and the second alkali circulation pipe 10 is provided with an alkali circulation pump 9.

[0064] The seawater heat exchanger 28 is communicated with the seawater condenser 32 through a steam intercommunication pipe 31, and the seawater condenser 32 is connected with a first cooling water circulation pipe 33, and the seawater condenser 32 is communicated with the softening low-salt water storage tank 40;

[0065] The seawater heat exchanger 28 is communicated with the lye heat exchanger 12 through a third lye circulation pipe 11, and the lye heat exchanger 12 is connected with the second cooling water circulation pipe 52, and the lye heat exchanger 12 is communicated with the electrolytic cell 16 through a fourth lye circulation pipe 14 and a fifth lye circulation pipe 15;

[0066] The softening low-salt water storage tank 40 is communicated with the water tank 18 through a water pumping pipe 39;

[0067] The salt precipitation storage tank 45 is communicated with the fifth lye circulation pipe 15 through a first lye returning pipe 44, and communicated with the lye tank 20 through a second lye returning pipe 57, and connected with a salt discharging pipe 47, and communicated with a vacuum pump 35 through a vacuum pipe 51, and the vacuum pipe 51 is provided with a twelfth ball valve 50.

[0068] The first lye supplement pipe 23 is provided with a third ball valve 21 and a lye supplement pipe ball valve 25, and the fifth lye circulation pipe 15 is provided with a fourth ball valve 22.

[0069] The seawater heat exchanger 28 is connected with a seawater supplement pipe 26 and a concentrated seawater blowdown pipe 30, and the seawater supplement pipe 26 is provided with a fifth ball valve 27, and the concentrated seawater blowdown pipe 30 is provided with a fourteenth ball valve 29.

[0070] The softening low-salt water storage tank 40 is provided with a first liquid level meter 41.

[0071] The water pumping pipe 39 is provided with a second ball valve 19, an eighth ball valve 37 and a water pumping pump 38.

[0072] The salt discharging pipe 47 is provided with a tenth ball valve 46.

[0073] The first lye returning pipe 44 is provided with the fifteenth ball valve 43, and the second lye returning pipe 57 is provided with a thirteenth ball valve 55 and a lye returning pump 56.

[0074] The salt precipitation storage tank 45 is provided with a second liquid level meter 48.

[0075] The seawater condenser 32 is communicated with the vacuum pump 35, and provided with a sixth ball valve 34 therebetween, and the seawater heat exchanger 28 and the seawater condenser 32 are lowered in pressure through the sixth ball valve 34 and the vacuum pump 35, so as to lower the boiling point of seawater, and make the seawater evaporate and condense at a lower temperature.

[0076] The water tank 18 is communicated with the first lye supplement pipe 23 through the first ball valve 17. When the liquid level in the oxygen liquid separator 1 and the hydrogen liquid separator 6 decreases, the first ball valve 17 is opened, the lye supplement pump 24 and the lye supplement pipe ball valve 25 are opened, and the water in the water tank 18 is supplemented to the electrolytic seawater hydrogen production system.

[0077] The electrolytic seawater hydrogen production system further comprises:

[0078] The nitrogen filling pipe 4 is connected with an external nitrogen source and the oxygen liquid separator 1 and the hydrogen liquid separator 6, and is a pipeline for supplementing nitrogen to the hydrogen production system from the outside.

[0079] The ninth ball valve 42 is connected between the seawater condenser 32 and the softening low-salt water storage tank 40.

[0080] The seventh ball valve 36 is connected between the external air and the softening low-salt water storage tank 40. When the water in the softening low-salt water storage tank 40 needs to be discharged into the water tank 18 for storage, the ninth ball valve 42 needs to be closed and the seventh ball valve 36 needs to be opened, so that the softening low-salt water storage tank 40 reaches normal pressure.

[0081] The fifteenth ball valve 43 is located in the first lye return pipe 44 and is used to control the connection and disconnection between the salt precipitation storage tank 45 and the fifth lye circulation pipe 15 in the hydrogen production system.

[0082] The eleventh ball valve 49 is connected between the external air and the salt precipitation storage tank 45. When the lye in the salt precipitation storage tank 45 needs to return to the lye tank 20, the twelfth ball valve 50 needs to be closed to disconnect the salt precipitation storage tank 45 from the vacuum environment, and then the eleventh ball valve 49 needs to be opened to connect the external air, so that the salt precipitation storage tank 45 reaches normal pressure.

[0083] The second cooling water circulation pipeline 52 is connected between an external cooling water source and the lye heat exchanger 12.

[0084] The pneumatic regulating valve 53 is located in the second cooling water circulation pipeline 52.

[0085] The temperature transmitter 54 is located in the fourth lye circulation pipe 14.

[0086] An interlock 13 is connected to the pneumatic regulating valve 53 and the temperature transmitter 54, when the temperature in the temperature transmitter 54 exceeds a set value, the interlock 13 controls the pneumatic regulating valve 53 to increase the flow of cooling water in the second cooling water circulating pipeline 52, so as to increase the heat exchange amount and reduce the temperature of the caustic solution in the hydrogen production system.

[0087] The control method of the electrolytic seawater hydrogen production system comprises the following steps:

[0088] The caustic solution in the caustic tank 20 is pumped by the caustic solution supplementing pump 24 to the oxygen gas-liquid separator 1 and the hydrogen gas-liquid separator 6 through the first caustic solution supplementing pipeline 23 until the target liquid level,

[0089] The caustic solution circulating pump 9 is opened, the electrolytic cell 16 is powered on to start electrolysis, the hydrogen gas generated by the electrolysis of water and the high-temperature mixed fluid of caustic solution enter the hydrogen gas-liquid separator 6 through the hydrogen gas-liquid circulating pipeline 5 to carry out gas-liquid separation, the separated hydrogen gas is discharged through the hydrogen gas discharge pipeline 7, and the separated high-temperature caustic solution enters the caustic solution circulating pump 9 through the first caustic solution circulating pipeline 8 to enter the next caustic solution circulation;

[0090] The oxygen gas generated by the electrolysis of water in the electrolytic cell 16 and the high-temperature mixed fluid of caustic solution enter the oxygen gas-liquid separator 1 through the oxygen gas-liquid circulating pipeline 3 to carry out gas-liquid separation, the separated oxygen gas is discharged through the oxygen gas discharge pipeline 2, and the separated high-temperature caustic solution enters the caustic solution circulating pump 9 through the first caustic solution circulating pipeline 8 to enter the next caustic solution circulation;

[0091] The high-temperature caustic solution enters the seawater heat exchanger 28 through the second caustic solution circulating pipeline 10 to heat and evaporate seawater, the generated seawater vapor enters the seawater condenser 32 through the vapor intercommunication pipeline 31 to exchange heat with the cooling water in the first cooling water circulating pipeline 33 to generate condensed water, at this time, the condensed water is easy to deposit ions and has reduced monovalent ion concentration compared with the original seawater, and serves as the electrolysis raw material water of the electrolytic seawater hydrogen production system.

[0092] The condensed water enters the low-hardness and low-salinity water storage tank 40 through natural overflow for standby use;

[0093] The high-temperature caustic solution after heat exchange through the seawater heat exchanger 28 enters the caustic solution heat exchanger 12 through the third caustic solution circulating pipeline 11 to exchange heat with the cooling water in the second cooling water circulating pipeline 52, and then returns to the electrolytic cell 16 through the fourth caustic solution circulating pipeline 14 and the fifth caustic solution circulating pipeline 15 to carry out a new round of electrolysis water hydrogen production process.

[0094] Before the seawater heat exchanger 28 and the seawater condenser 32 work, the twelfth ball valve 50, the eighth ball valve 37, the seventh ball valve 36, the fourteenth ball valve 29 and the fifth ball valve 27 are closed, and the sixth ball valve 34 and the vacuum pump 35 are opened, so that the air pressure in the seawater heat exchanger 28 and the seawater condenser 32 is reduced, thereby reducing the boiling point of seawater, so that seawater can be evaporated and condensed at a lower temperature.

[0095] The fifth ball valve 27 is opened, and the seawater heat exchanger 28 is supplemented with raw seawater through the seawater supplementing pipe 26. After the seawater supplementing is completed, the fifth ball valve 27 is closed to maintain the vacuum state in the seawater heat exchanger 28. When the raw seawater stored in the seawater heat exchanger 28 is consumed to a target liquid level, the fourteenth ball valve 29 is opened, and the concentrated seawater after evaporation is discharged through the concentrated seawater blowdown pipe 30. Then, the fourteenth ball valve 29 is closed to maintain the vacuum state in the seawater heat exchanger 28.

[0096] The water storage in the softening and low-salinity water storage tank 40 is observed through the first liquid level meter 41. When the softening and low-salinity water storage tank 40 is full, the ninth ball valve 42 is closed, and the softening and low-salinity water storage tank 40 is isolated from the vacuum environment in the seawater heat exchanger 28 and the seawater condenser 32. Then, the seventh ball valve 36 is opened, so that the softening and low-salinity water storage tank 40 returns to normal pressure. Then, the eighth ball valve 37 and the water pumping pump 38 and the second ball valve 19 are opened, and the water stored in the softening and low-salinity water storage tank 40 is pumped into the water tank 18 through the water pumping pipeline 39 as standby electrolysis raw water for the electrolytic seawater hydrogen production system.

[0097] With the consumption of water in the electrolytic seawater hydrogen production system by the electrolytic cell 16, when the liquid level in the oxygen gas-liquid separator 1 and the hydrogen gas-liquid separator 6 decreases, the first ball valve 17, the alkali supplementing pump 24 and the alkali supplementing pipe ball valve 25 are opened to supplement the water stored in the water tank 18 into the electrolytic seawater hydrogen production system. After the supplementing is completed, the first ball valve 17, the alkali supplementing pump 24 and the alkali supplementing pipe ball valve 25 are closed.

[0098] The salt precipitation tank 45 is provided with a heating function, the fourth ball valve 22 and the fifteenth ball valve 43 are normally closed valves, when the accumulated salt concentration in the electrolytic seawater hydrogen production system approaches saturation, the fifteenth ball valve 43 is opened, the high-salt-concentration lye enters the salt precipitation tank 45, and then the fifteenth ball valve 43 is closed; the eleventh ball valve 49 and the tenth ball valve 46 are closed, the twelfth ball valve 50 and the vacuum pump 35 are opened, the salt precipitation tank 45 is in a vacuum state, the heating function of the salt precipitation tank 45 is started, the high-salt-concentration lye is evaporated and salt is precipitated, when the liquid level in the salt precipitation tank 45 is observed to be reduced to a target liquid level by the second liquid level meter 48, the twelfth ball valve 50 and the vacuum pump 35 are closed, the eleventh ball valve 49 is opened, the salt precipitation tank 45 returns to normal pressure, then the tenth ball valve 46 is opened, the salt crystals are discharged through the salt discharge pipe 47, and at the same time, the thirteenth ball valve 55 and the lye return pump 56 are opened, the remaining lye is pumped into the lye tank 20 through the second lye return pipeline 57 for standby use.

Claims

1. A system for producing hydrogen by electrolysis of seawater, characterized in that it comprises: It includes: Electrolytic tank (16), oxygen liquid separator (1), hydrogen liquid separator (6), seawater heat exchanger (28), seawater condenser (32), lye heat exchanger (12), low salt water tank (40), salt tank (45), lye tank (20), water tank (18); The lye tank (20) is communicated with the oxygen liquid separator (1) and the hydrogen liquid separator (6) respectively through the first lye supplement pipe (23), and the first lye supplement pipe (23) is provided with a lye supplement pump (24); The electrolytic tank (16) is communicated with the hydrogen liquid separator (6) through the hydrogen liquid circulation pipe (5), and the hydrogen liquid separator (6) is provided with a hydrogen discharge pipe (7); The electrolytic tank (16) is communicated with the oxygen liquid separator (1) through the oxygen liquid circulation pipe (3), and the oxygen liquid separator (1) is provided with an oxygen discharge pipe (2); The hydrogen liquid separator (6) and the oxygen liquid separator (1) are communicated with the seawater heat exchanger (28) through the first lye circulation pipe (8) and the second lye circulation pipe (10), and the second lye circulation pipe (10) is provided with a lye circulation pump (9); The seawater heat exchanger (28) is communicated with the seawater condenser (32) through the steam intercommunication pipe (31), and the seawater condenser (32) is connected with the first cooling water circulation pipe (33); The seawater condenser (32) is communicated with the low salt water tank (40); The seawater heat exchanger (28) is communicated with the lye heat exchanger (12) through the third lye circulation pipe (11), and the lye heat exchanger (12) is connected with the second cooling water circulation pipe (52); The lye heat exchanger (12) is communicated with the electrolytic tank (16) through the fourth lye circulation pipe (14) and the fifth lye circulation pipe (15); The low salt water tank (40) is communicated with the water tank (18) through the water pumping pipe (39); The salt tank (45) is communicated with the fifth lye circulation pipe (15) through the first lye return pipe (44), and is communicated with the lye tank (20) through the second lye return pipe (57); The salt tank (45) is connected with a salt discharge pipe (47), and is communicated with a vacuum pump (35) through a vacuum pipe (51); The vacuum pipe (51) is provided with a twelfth ball valve (50).

2. The hydrogen production system of claim 1, wherein, The first lye supplement pipe (23) is provided with a third ball valve (21) and a lye supplement pipe ball valve (25), and the fifth lye circulation pipe (15) is provided with a fourth ball valve (22). The seawater heat exchanger (28) is connected with a seawater supplement pipe (26) and a concentrated seawater blowdown pipe (30); The seawater supplement pipe (26) is provided with a fifth ball valve (27), and the concentrated seawater blowdown pipe (30) is provided with a fourteenth ball valve (29); The low salt water tank (40) is provided with a first liquid level meter (41); The water pumping pipe (39) is provided with a second ball valve (19), an eighth ball valve (37) and a water pumping pump (38); The salt discharge pipe (47) is provided with a tenth ball valve (46); The first back-alkali pipeline (44) is provided with the fifteenth ball valve (43), and the second back-alkali pipeline (57) is provided with a thirteenth ball valve (55) and a back-alkali pump (56); The salt precipitation tank (45) is provided with a second liquid level meter (48).

3. The hydrogen production system of claim 1, wherein, The seawater condenser (32) is communicated with the vacuum pump (35), and a sixth ball valve (34) is arranged between the seawater condenser (32) and the vacuum pump (35); the sixth ball valve (34) and the vacuum pump (35) are used to reduce the air pressure in the seawater heat exchanger (28) and the seawater condenser (32), so as to reduce the boiling point of seawater, so that seawater can be evaporated and condensed at a lower temperature.

4. The hydrogen production system of claim 1, wherein, The water tank (18) is communicated with the first alkali solution supplement pipe (23) through a first ball valve (17); when the liquid level in the oxygen liquid separator (1) and the hydrogen liquid separator (6) decreases, the first ball valve (17) is opened, and the alkali supplement pump (24) and the alkali solution supplement pipe ball valve (25) are used to supplement the stored water in the water tank (18) into the electrolytic seawater hydrogen production system.

5. The hydrogen production system of claim 1, wherein, The electrolytic seawater hydrogen production system further comprises: A nitrogen filling pipe (4) is connected with an external nitrogen source and the oxygen liquid separator (1) and the hydrogen liquid separator (6), and is a pipeline for supplementing nitrogen into the hydrogen production system from the outside; A ninth ball valve (42) is arranged to communicate the seawater condenser (32) and the low-salt water tank (40); A seventh ball valve (36) is arranged to communicate external air and the low-salt water tank (40); when the water in the low-salt water tank (40) needs to be discharged into the water tank (18) for storage, the ninth ball valve (42) needs to be closed first, and the seventh ball valve (36) needs to be opened, so that the low-salt water tank (40) is brought to normal pressure; A fifteenth ball valve (43) is arranged on the first back-alkali pipeline (44) to control the communication and disconnection between the salt precipitation tank (45) and the fifth alkali solution circulation pipe (15) in the hydrogen production system; An eleventh ball valve (49) is arranged to communicate external air and the salt precipitation tank (45); when the alkali solution in the salt precipitation tank (45) needs to return to the alkali tank (20), the twelfth ball valve (50) needs to be closed to disconnect the salt precipitation tank (45) from the vacuum environment, and then the eleventh ball valve (49) is opened to communicate external air, so that the salt precipitation tank (45) is brought to normal pressure; A second cooling water circulation pipeline (52) is connected with an external cooling water source and the alkali solution heat exchanger (12); A pneumatic regulating valve (53) is arranged on the second cooling water circulation pipeline (52); A temperature transmitter (54) is arranged on the fourth alkali solution circulation pipe (14); Interlock (13) is connected with the pneumatic regulating valve (53) and the temperature transmitter (54), when the temperature in the temperature transmitter (54) exceeds the set value, the interlock (13) controls the pneumatic regulating valve (53) to increase the flow of cooling water in the second cooling water circulating pipeline (52), so as to increase the heat exchange amount and reduce the caustic soda temperature of the hydrogen production system.

6. A control method of the hydrogen production system by electrolysis of seawater as claimed in any one of claims 1 to 5, characterized by, It comprises: The caustic soda in the caustic soda tank (20) is pumped by the caustic soda supplement pump (24) to the oxygen gas-liquid separator (1) and the hydrogen gas-liquid separator (6) through the first caustic soda supplement pipeline (23) until the target liquid level, Open the caustic soda circulating pump (9), power on the electrolytic cell (16) to start electrolysis, the hydrogen gas generated by the electrolysis of water and the high-temperature mixed fluid of caustic soda enter the hydrogen gas-liquid separator (6) through the hydrogen gas-liquid circulating pipe (5) for gas-liquid separation, the separated hydrogen gas is discharged through the hydrogen gas discharge pipe (7), and the separated high-temperature caustic soda enters the caustic soda circulating pump (9) through the first caustic soda circulating pipe (8) for next caustic soda circulation; The oxygen gas generated by the electrolysis of water and the high-temperature mixed fluid of caustic soda enter the oxygen gas-liquid separator (1) through the oxygen gas-liquid circulating pipe (3) for gas-liquid separation, the separated oxygen gas is discharged through the oxygen gas discharge pipe (2), and the separated high-temperature caustic soda enters the caustic soda circulating pump (9) through the first caustic soda circulating pipe (8) for next caustic soda circulation; The high-temperature caustic soda enters the seawater heat exchanger (28) through the second caustic soda circulating pipe (10) to heat and evaporate the seawater, the generated seawater vapor enters the seawater condenser (32) through the vapor intercommunication pipe (31) to exchange heat with the cooling water in the first cooling water circulating pipeline (33), and generate condensed water, at this time, the condensed water is easy to deposit ions and monovalent ions, and the concentration of the condensed water is reduced, so as to be used as the electrolysis raw water of the electrolytic seawater hydrogen production system; The condensed water enters the low-salt water storage tank (40) through natural overflow for standby; The high-temperature caustic soda after heat exchange through the seawater heat exchanger (28) enters the caustic soda heat exchanger (12) through the third caustic soda circulating pipe (11) to exchange heat with the cooling water in the second cooling water circulating pipeline (52), and then returns to the electrolytic cell (16) through the fourth caustic soda circulating pipe (14) and the fifth caustic soda circulating pipe (15) for a new round of electrolytic water hydrogen production process.

7. The control method according to claim 6, wherein before the seawater heat exchanger (28) and the seawater condenser (32) are operated, the twelfth ball valve (50), the eighth ball valve (37), the seventh ball valve (36), the fourteenth ball valve (29) and the fifth ball valve (27) are closed, the sixth ball valve (34) and the vacuum pump (35) are opened, so that the pressure in the seawater heat exchanger (28) and the seawater condenser (32) is reduced, thereby reducing the boiling point of seawater, so that seawater can be evaporated and condensed at a lower temperature; the fifth ball valve (27) is opened, and the seawater heat exchanger (28) is supplemented with raw seawater through the seawater supplementing pipe (26); after the supplementing of seawater is completed, the fifth ball valve (27) is closed, so as to maintain the vacuum state in the seawater heat exchanger (28); when the raw seawater stored in the seawater heat exchanger (28) is consumed to a target liquid level, the fourteenth ball valve (29) is opened, and the concentrated seawater after evaporation is discharged through the concentrated seawater blowdown pipe (30), and then the fourteenth ball valve (29) is closed, so as to maintain the vacuum state in the seawater heat exchanger (28).

8. The control method according to claim 6, wherein the water storage in the softening and low-salinity water tank (40) is observed through the first liquid level meter (41); when the softening and low-salinity water tank (40) is full, the ninth ball valve (42) is closed, the softening and low-salinity water tank (40) is isolated from the vacuum environment in the seawater heat exchanger (28) and the seawater condenser (32), the seventh ball valve (36) is opened, the softening and low-salinity water tank (40) is returned to normal pressure, the eighth ball valve (37) and the water pumping pump (38) and the second ball valve (19) are opened, and the water stored in the softening and low-salinity water tank (40) is pumped into the water tank (18) through the water pumping pipeline (39) as standby electrolysis raw water of the electrolytic seawater hydrogen production system.

9. The control method according to claim 6, wherein as the electrolytic cell (16) consumes water in the electrolytic seawater hydrogen production system, when the liquid level in the oxygen liquid separator (1) and the hydrogen liquid separator (6) decreases, the first ball valve (17), the alkali supplementing pump (24) and the alkali supplementing pipe ball valve (25) are opened, and the water stored in the water tank (18) is supplemented into the electrolytic seawater hydrogen production system; after the supplementing is completed, the first ball valve (17), the alkali supplementing pump (24) and the alkali supplementing pipe ball valve (25) are closed.

10. The control method according to claim 6, characterized in that the salt precipitation tank (45) is provided with a heating function, the fourth ball valve (22) and the fifteenth ball valve (43) are normally closed valves, when the accumulated salt concentration in the electrolytic seawater hydrogen production system approaches saturation, the fifteenth ball valve (43) is opened, high-salt-concentration lye enters the salt precipitation tank (45), and then the fifteenth ball valve (43) is closed; the eleventh ball valve (49) and the tenth ball valve (46) are closed, the twelfth ball valve (50) and the vacuum pump (35) are opened, the salt precipitation tank (45) is in a vacuum state, the heating function of the salt precipitation tank (45) is started, high-salt-concentration lye is evaporated and salt is precipitated, after the liquid level in the salt precipitation tank (45) is observed to decrease to a target liquid level by the second liquid level gauge (48), the twelfth ball valve (50) and the vacuum pump (35) are closed, the eleventh ball valve (49) is opened to restore the salt precipitation tank (45) to normal pressure, then the tenth ball valve (46) is opened, salt crystals are discharged through the salt discharge pipe (47), and at the same time, the thirteenth ball valve (55) and the lye return pump (56) are opened, the remaining lye is pumped into the lye tank (20) through the second lye return pipeline (57) for standby use.

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