Hydrogen production system and hydrogen production method

Abstract

A hydrogen production system (1) is provided with at least one first permeator (10), a circulation flow path (20) and an alkaline water electrolyzer (30). The at least one first permeator (10) includes a semipermeable membrane (11) which partitions between a first chamber (12) into which water of interest is supplied and a second chamber (13) into which an alkaline aqueous solution having a higher osmotic pressure than that of the water of interest is supplied and makes water in the water of interest permeate from the first chamber (12) to the second chamber (13). The circulation flow path (20) is connected to the second chamber (13) to circulate the alkaline aqueous solution. The alkaline water electrolyzer (30) is arranged on the circulation flow path (20), and electrolyzes water in the alkaline aqueous solution supplied from the second chamber (13) to produce hydrogen.

Description

[Technical field]

[0001] The present disclosure relates to a hydrogen production system and a hydrogen production method. [Background technology]

[0002] Carbon dioxide is seen as a problematic cause of global warming, and there are active efforts around the world to curb carbon dioxide emissions. Hydrogen does not emit carbon dioxide when used, and can also be obtained by electrolyzing water using renewable energy, so it has been attracting attention as an alternative to fossil fuels.

[0003] Known methods for producing hydrogen by electrolyzing water include alkaline water electrolysis, solid polymer water electrolysis, and solid oxide water electrolysis. Among these, devices for producing hydrogen by alkaline water electrolysis have attracted attention because electrolysis devices are inexpensive. As a device for electrolyzing water by alkaline water electrolysis, the alkaline water electrolysis device described in Patent Document 1 is known. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 181662 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, the use of hydrogen as fuel has become widespread, and the demand for hydrogen is expected to increase. However, alkaline water electrolysis devices are operated in closed systems. Therefore, if seawater, brackish water, or fresh water is used directly from a water source as alkaline water for electrolysis, ionic components in the water are concentrated by electrolysis, and salts are precipitated in the alkaline water electrolysis device, which may adversely affect the electrolysis. Therefore, it is preferable to use water that is substantially free of ionic components, such as pure water, as the alkaline water used in the alkaline water electrolysis device. On the other hand, pure water can be obtained by distilling water from a water source, but when producing water for alkaline water electrolysis by such a method, it is necessary to boil the water from the water source. However, since fossil fuels are used to boil the water, there is a risk of increasing carbon dioxide emissions.

[0006] Therefore, an object of the present disclosure is to provide a hydrogen production system and a hydrogen production method that are capable of producing hydrogen with reduced carbon dioxide emissions compared to when the water required for alkaline water electrolysis is produced by a distillation method. [Means for solving the problem]

[0007] The hydrogen production system according to the present disclosure includes at least one first permeation device, a circulation flow path, and an alkaline water electrolysis device. The at least one first permeation device separates a first chamber to which the water to be treated is supplied and a second chamber to which an alkaline aqueous solution having a higher osmotic pressure than the water to be treated is supplied, and includes a semipermeable membrane that allows water in the water to be treated to permeate from the first chamber to the second chamber. The circulation flow path is connected to the second chamber, and the alkaline aqueous solution circulates through the circulation flow path. The alkaline water electrolysis device is provided in the circulation flow path, and electrolyzes the water in the alkaline aqueous solution supplied from the second chamber to generate hydrogen.

[0008] The water to be treated may be seawater or brackish water.

[0009] The alkaline water electrolysis apparatus may include an anode chamber that accommodates an anode, a cathode chamber that accommodates a cathode, and a diaphragm that separates the anode chamber from the cathode chamber.

[0010] The circulation flow path may include a flow path connected to the outlet of the second chamber, and to the inlet of the anode chamber and the inlet of the cathode chamber.

[0011] The hydrogen production system may further include an oxygen gas-liquid separator connected to the anode chamber and separating oxygen produced by electrolysis at the anode from the alkaline aqueous solution.The hydrogen production system may further include a hydrogen gas-liquid separator connected to the cathode chamber and separating hydrogen produced by electrolysis at the cathode from the alkaline aqueous solution.The alkaline aqueous solution supplied to the second chamber may include the alkaline aqueous solution separated in the oxygen gas-liquid separator and the alkaline aqueous solution separated in the hydrogen gas-liquid separator.

[0012] The hydrogen production system may further include a first tank provided in the circulation flow path upstream of the second chamber and downstream of the alkaline water electrolysis device.The hydrogen production system may further include a second tank provided in the circulation flow path downstream of the second chamber and upstream of the alkaline water electrolysis device.The salt concentration of the alkaline aqueous solution in the first tank may be higher than the salt concentration of the alkaline aqueous solution in the second tank.

[0013] The hydrogen production system may further include a heat exchanger that exchanges heat between the alkaline aqueous solution supplied to the alkaline water electrolysis device and the heat of the alkaline aqueous solution discharged from the alkaline water electrolysis device.

[0014] The at least one first permeation device may be a plurality of first permeation devices. The hydrogen production system may further include a water-to-be-treated flow path through which the water-to-be-treated flows. The water-to-be-treated flow path may include a plurality of first parallel flow paths connected to the first chambers of the plurality of first permeation devices, respectively, and arranged in parallel. The circulation flow path may include a plurality of second parallel flow paths connected to the second chambers of the plurality of first permeation devices, respectively, and arranged in parallel. A first stopper that stops the supply of the water-to-be-treated to the first chamber may be provided upstream of the first chamber in each of the plurality of first parallel flow paths. A second stopper that stops the supply of the alkaline aqueous solution to the second chamber may be provided upstream of the second chamber in each of the plurality of second parallel flow paths.

[0015] The hydrogen production system may further include a first turbine provided in the circulation flow path downstream of the second chamber and upstream of the alkaline water electrolysis device, and rotated by the alkaline aqueous solution supplied from the second chamber. The hydrogen production system may further include a first generator that generates electricity by rotation of the first turbine.

[0016] The hydrogen production system may further include a water to be treated flow path connected to the first chamber and through which the water to be treated flows. The hydrogen production system may further include a second permeation device that divides a third chamber provided downstream of the first chamber in the water to be treated flow path from a fourth chamber to which low osmotic pressure water having an osmotic pressure lower than that of the water to be treated is supplied, and that includes a semipermeable membrane that allows water in the low osmotic pressure water to permeate from the fourth chamber to the third chamber. The hydrogen production system may further include a second turbine provided in the water to be treated flow path and rotated by water passing through the third chamber. The hydrogen production system may further include a second generator that generates electricity by rotation of the second turbine.

[0017] A hydrogen production method according to the present disclosure includes a step of permeating water from a water source to be treated through a semipermeable membrane and supplying the water to an alkaline aqueous solution having a higher osmotic pressure than the water to be treated. The method includes a step of electrolyzing the water in the alkaline aqueous solution to which the water from the water source has been supplied in an alkaline water electrolysis device to obtain hydrogen. The method includes a step of supplying the alkaline aqueous solution remaining after electrolysis to the semipermeable membrane as an alkaline aqueous solution having a higher osmotic pressure than the water to be treated. Effect of the Invention

[0018] According to the present disclosure, it is possible to provide a hydrogen production system and a hydrogen production method that are capable of producing hydrogen with reduced carbon dioxide emissions compared to when the water required for alkaline water electrolysis is produced by a distillation method. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram illustrating a hydrogen production system according to one embodiment. [Diagram 2]FIG. 2 is a schematic diagram showing an example in which a heat exchanger is provided in a flow path connected to an alkaline water electrolysis apparatus. [Diagram 3] FIG. 3 is a graph showing the relationship between the osmotic pressure of an aqueous potassium hydroxide solution and seawater under specified conditions. [Figure 4] FIG. 4 is a schematic diagram showing an example of a hydrogen production system including a plurality of first permeation devices. [Diagram 5] FIG. 5 is a schematic diagram illustrating a hydrogen production system according to one embodiment. [Figure 6] FIG. 6 is a schematic diagram illustrating a hydrogen production system according to one embodiment. [Figure 7] FIG. 7 is a schematic diagram illustrating a hydrogen production system according to one embodiment. [Figure 8] FIG. 8 is a graph showing the relationship between the osmotic pressure of an aqueous potassium hydroxide solution and seawater under specified conditions. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, some exemplary embodiments will be described with reference to the drawings. Note that the dimensional ratios of the drawings are exaggerated for the convenience of explanation and may differ from the actual ratios.

[0021] As shown in FIG. 1, the hydrogen production system 1 according to this embodiment includes at least one first permeation device 10, a circulation flow path 20, and an alkaline water electrolysis device 30.

[0022] The first permeation device 10 includes a semipermeable membrane 11. The first permeation device 10 has a first chamber 12 and a second chamber 13, and the semipermeable membrane 11 separates the first chamber 12 from the second chamber 13. The water to be treated is supplied to the first chamber 12. The second chamber 13 is supplied with an alkaline aqueous solution having a higher osmotic pressure than the water to be treated. One surface of the semipermeable membrane 11 is in contact with the water to be treated in the first chamber 12, and the other surface of the semipermeable membrane 11 is in contact with the alkaline aqueous solution.

[0023] The semipermeable membrane 11 allows the water in the water to be treated to permeate from the first chamber 12 to the second chamber 13. The osmotic pressure of the alkaline aqueous solution supplied to the second chamber 13 is higher than that of the water to be treated. Therefore, by forward osmosis, in which the water to be treated is the feed solution (FS) and the alkaline aqueous solution is the draw solution (DS), the water in the water to be treated permeates the semipermeable membrane 11 and is supplied to the alkaline aqueous solution, which has a higher osmotic pressure than the water to be treated.

[0024] The water to be treated may be seawater, brackish water, or fresh water. Fresh water may be river water, lake water, industrial wastewater, or groundwater. Among these, the water to be treated is preferably seawater or brackish water, from the viewpoint of being able to supply a large amount of water.

[0025] The alkaline aqueous solution may contain an aqueous solution of an alkali metal hydroxide. The alkali metal hydroxide may contain at least one of sodium hydroxide and potassium hydroxide. The salt concentration of the alkaline aqueous solution may be 4% by mass or more, 20% by mass or more, or 25% by mass or more. The salt concentration of the alkaline aqueous solution may be 35% by mass or less, or 30% by mass or less.

[0026] The osmotic pressure of the water to be treated supplied to the first chamber 12 is lower than the osmotic pressure of the alkaline aqueous solution supplied to the second chamber 13. Therefore, the molar concentration of the salt of the water to be treated supplied to the first chamber 12 may be lower than the molar concentration of the salt of the alkaline aqueous solution supplied to the second chamber 13. The greater the difference between the osmotic pressure of the alkaline aqueous solution and the osmotic pressure of the water to be treated, the greater the driving force of the water to permeate the semipermeable membrane 11. Therefore, the osmotic pressure of the water to be treated supplied to the first chamber 12 may be lower than the osmotic pressure of seawater. The salinity of seawater is, for example, more than 3.0 mass% and 3.8 mass% or less. The salinity of brackish water is, for example, 0.05 mass% or more and 3.0 mass% or less. The salinity of fresh water is, for example, less than 0.05 mass%. Therefore, the salinity of the water to be treated supplied to the first chamber 12 may be 3.8 mass% or less, which is the salinity of seawater.

[0027] The osmotic pressure difference, which is the difference between the osmotic pressure of the water to be treated supplied to the first chamber 12 and the osmotic pressure of the alkaline aqueous solution supplied to the second chamber 13, is preferably greater than 0.5 MPa. When the osmotic pressure difference exceeds 0.5 MPa, the water in the water to be treated easily permeates from the first chamber 12 to the second chamber 13 through the semipermeable membrane 11. The osmotic pressure difference is more preferably greater than 4.0 MPa, and even more preferably greater than 7.0 MPa. The greater the osmotic pressure difference, the easier it is for water to permeate the semipermeable membrane 11, so the upper limit of the osmotic pressure is not particularly limited, but may be 20 MPa.

[0028] The semipermeable membrane 11 selectively allows water in the water to be treated to pass through. The semipermeable membrane 11 allows water in the water to be treated to pass through, but does not allow sodium ions and the like to pass through. Therefore, the semipermeable membrane 11 can suppress impurities other than water molecules from permeating from the water to be treated into the alkaline aqueous solution. The semipermeable membrane 11 may include at least one selected from the group consisting of a flat membrane, a hollow fiber membrane, and a spiral membrane. The pore size of the semipermeable membrane 11 may be large enough to allow water molecules to pass through and not allow sodium ions and the like in the water to be treated to pass through. The pore size of the semipermeable membrane 11 may be 0.5 nm or more, or may be 1 nm or more. The pore size of the semipermeable membrane 11 may be 10 nm or less, 5 nm or less, or 2 nm or less. The semipermeable membrane 11 may be a reverse osmosis membrane (RO membrane). The semipermeable membrane 11 may contain at least one selected from the group consisting of cellulose acetate, polyacrylonitrile, polysulfone, polyethersulfone, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic.

[0029] The first chamber 12 is connected to a water to be treated flow path 15. The water to be treated flow path 15 is provided so that the water to be treated flows through it. One end of the water to be treated flow path 15 is connected to a water source S. In addition, a pump 16 is provided in the water to be treated flow path 15. By driving the pump 16, the water to be treated is supplied from the water source S through the water to be treated flow path 15 to the first chamber 12. The water that has passed through the first chamber 12 may be discharged to the water source S through the water to be treated flow path 15.

[0030] The circulation flow path 20 is connected to the second chamber 13, and the alkaline aqueous solution circulates through the circulation flow path 20. An alkaline water electrolysis apparatus 30 is provided in the circulation flow path 20. The circulation flow path 20 may be provided with a first tank 21, a pump 22, a second tank 23, a pump 35, a pump 36, an oxygen gas-liquid separator 37, and a hydrogen gas-liquid separator 38.

[0031] The first tank 21 is provided in the circulation flow path 20, upstream of the second chamber 13 and downstream of the alkaline water electrolysis device 30. An alkaline aqueous solution is stored in the first tank 21. By providing the first tank 21, it is possible to adjust the amount of the alkaline aqueous solution supplied to the second chamber 13. The alkaline aqueous solution stored in the first tank 21 is supplied to the second chamber 13 by the pump 22. The alkaline aqueous solution that has passed through the second chamber 13 is sent to the second tank 23.

[0032] The second tank 23 is provided in the circulation flow path 20 downstream of the second chamber 13 and upstream of the alkaline water electrolysis device 30. The second tank 23 stores the alkaline aqueous solution that has passed through the second chamber 13. By providing the second tank 23, the amount of the alkaline aqueous solution supplied to the alkaline water electrolysis device 30 can be adjusted.

[0033] The alkaline water electrolysis device 30 electrolyzes water in the alkaline aqueous solution supplied from the second chamber 13 to produce hydrogen. The alkaline water electrolysis device 30 includes an anode chamber 31, a cathode chamber 32, and a diaphragm 33. The anode chamber 31 accommodates an anode 31a. The cathode chamber 32 accommodates a cathode 32a. The alkaline water electrolysis device 30 includes a DC power supply (not shown) electrically connected to the anode 31a and the cathode 32a, and water is electrolyzed by applying a voltage to the anode 31a and the cathode 32a.

[0034] At the anode 31a, oxygen is produced by a reaction as shown in the following reaction formula (1). 4OH - →O2+2H2O+4e - (1)

[0035] The anode 31a may contain at least one selected from the group consisting of nickel, nickel-cobalt oxide, nickel alloy, iron, cobalt oxide, and precious metal oxide. The shape and size of the anode 31a are not particularly limited, and a plate-like, rod-like, or plate-like anode may be used depending on the purpose.

[0036] At the cathode 32a, hydrogen is produced by a reaction as shown in the following reaction formula (2). 2H2O+2e - →H2+2OH - (2)

[0037] The cathode 32a may contain at least one of iron and nickel. The shape and size of the cathode 32a are not particularly limited, and may be in the shape of a plate, a rod, a plate, or the like, depending on the purpose.

[0038] The diaphragm 33 separates the anode chamber 31 from the cathode chamber 32 so that the oxygen gas generated at the anode 31a and the hydrogen gas generated at the cathode 32a do not mix. The anode 31a and the diaphragm 33 may be disposed with a space therebetween, and the cathode 32a and the diaphragm 33 may be disposed with a space therebetween. The diaphragm 33 has ion permeability and passes through the hydroxide ions generated at the cathode 32a to advance the electrolysis reaction. The diaphragm 33 may be a porous membrane. The diaphragm 33 may contain at least one selected from the group consisting of polysulfone, PTFE (polytetrafluoroethylene), asbestos, polyolefin, and anion exchange membrane (AEM). The anion exchange membrane may be a resin having a quaternary ammonium group and an imidazolium group.

[0039] The temperature inside the alkaline water electrolysis device 30 is not particularly limited, and may be 70° C. or higher and 90° C. or lower. Although the present embodiment has been described as an example in which the alkaline water electrolysis device 30 is a single-tank type, the alkaline water electrolysis device 30 may be a multi-tank type with two or more tanks.

[0040] The circulation flow path 20 may include a flow path connected to the outlet of the second chamber 13, and the inlet of the anode chamber 31 and the inlet of the cathode chamber 32. This allows the alkaline aqueous solution that has passed through the second chamber 13 to be supplied to the anode chamber 31 and the cathode chamber 32, and the structure of the diaphragm 33 can be stably maintained. The circulation flow path 20 branches downstream of the second chamber 13 and is connected to the anode chamber 31 and the cathode chamber 32. Specifically, the circulation flow path 20 includes a first flow path 20a that connects the second tank 23 and the anode chamber 31, and a second flow path 20b that connects the second tank 23 and the cathode chamber 32. A pump 35 is provided in the first flow path 20a. In addition, a pump 36 is provided in the second flow path 20b. The alkaline aqueous solution stored in the second tank 23 is supplied to the anode chamber 31 by driving the pump 35. In addition, the alkaline aqueous solution stored in the second tank 23 is supplied to the cathode chamber 32 by driving the pump 36. The alkaline aqueous solution that has passed through the second chamber 13 may be supplied to the anode chamber 31 and the cathode chamber 32 without passing through the second tank 23.

[0041] As described above, the alkaline water electrolysis device 30 can electrolyze the water in the alkaline aqueous solution to which the water to be treated is supplied, to obtain hydrogen. Distillation and membrane separation using a reverse osmosis membrane (RO membrane) are known methods for using the water in the water to be treated as water for electrolysis. However, in the distillation method, fossil fuels are used to boil the water to be treated to produce pure water. For this reason, 3 12~15kg / m 3 It is said that the amount of carbon dioxide emitted is about 10 ... 3 2.3~3.4kg / m 3 On the other hand, by supplying water for electrolysis from the first permeation device 10 as in the present embodiment, there is no need to pressurize the water for boiling and reverse osmosis, and therefore the amount of carbon dioxide emissions can be reduced.

[0042] The alkaline aqueous solution remaining after electrolysis by the alkaline water electrolysis device 30 is supplied to the semipermeable membrane 11 as an alkaline aqueous solution having a higher osmotic pressure than the water to be treated. The outlet of the anode chamber 31 may be connected to the inlet of the second chamber 13 of the first permeation device 10 via the circulation flow path 20. In addition, the outlet of the cathode chamber 32 may be connected to the inlet of the second chamber 13 via the circulation flow path 20. Then, a mixture of the alkaline aqueous solution that has passed through the anode chamber 31 and the alkaline aqueous solution that has passed through the cathode chamber 32 may be supplied to the second chamber 13 via the circulation flow path 20.

[0043] The circulation flow path 20 may include a third flow path 20c that guides the alkaline aqueous solution from the anode chamber 31 to the first tank 21, and a fourth flow path 20d that guides the alkaline aqueous solution from the cathode chamber 32 to the first tank 21. An oxygen gas-liquid separator 37 may be provided in the third flow path 20c. As a result, the alkaline aqueous solution that has passed through the anode chamber 31 is supplied to the oxygen gas-liquid separator 37 together with the oxygen gas generated at the anode 31a. In addition, a hydrogen gas-liquid separator 38 may be provided in the fourth flow path 20d. As a result, the alkaline aqueous solution that has passed through the cathode chamber 32 is supplied to the hydrogen gas-liquid separator 38 together with the hydrogen gas generated at the cathode 32a.

[0044] The oxygen gas-liquid separator 37 is connected to the anode chamber 31, and separates the oxygen generated by electrolysis in the anode 31a from the alkaline aqueous solution. The oxygen separated in the oxygen gas-liquid separator 37 may be stored in a storage tank, or may be transported by piping or the like and directly used in a factory or the like. On the other hand, the alkaline aqueous solution separated in the oxygen gas-liquid separator 37 is supplied to the first tank 21.

[0045] The hydrogen gas-liquid separator 38 is connected to the cathode chamber 32, and separates the hydrogen generated by electrolysis at the cathode 32a from the alkaline aqueous solution. The hydrogen separated in the hydrogen gas-liquid separator 38 is recovered and used as an energy source. The hydrogen separated in the hydrogen gas-liquid separator 38 may be stored in a storage tank, or may be transported by piping or the like and directly used as an energy source in a factory or the like. On the other hand, the alkaline aqueous solution separated in the hydrogen gas-liquid separator 38 is supplied to the first tank 21.

[0046] The first tank 21 stores the alkaline aqueous solution separated in the oxygen gas-liquid separator 37 and the alkaline aqueous solution separated in the hydrogen gas-liquid separator 38. The alkaline aqueous solution stored in the first tank 21 may be supplied to the second chamber 13 of the first permeation device 10. Therefore, the alkaline aqueous solution supplied to the second chamber 13 may contain the alkaline aqueous solution separated in the oxygen gas-liquid separator 37 and the alkaline aqueous solution separated in the hydrogen gas-liquid separator 38. This makes it possible to separate the oxygen and hydrogen electrolyzed in the first permeation device 10 and the alkaline aqueous solution remaining after electrolysis with high accuracy.

[0047] The alkaline aqueous solution that has passed through the second chamber 13 is diluted by the addition of water that has permeated through the semipermeable membrane 11. The alkaline aqueous solution remaining after electrolysis in the alkaline water electrolysis device 30 is concentrated because the water content has been reduced by the electrolysis of water. Therefore, the salinity of the alkaline aqueous solution in the first tank 21 is higher than the salinity of the alkaline aqueous solution in the second tank 23. Because the osmotic pressure difference between the water to be treated supplied to the first chamber 12 and the alkaline aqueous solution supplied to the second chamber 13 is large, the water in the water to be treated permeates from the first chamber 12 to the second chamber 13 via the semipermeable membrane 11.

[0048] The alkaline aqueous solution remaining after electrolysis in the alkaline water electrolysis device 30 is supplied to the semipermeable membrane 11 as an alkaline aqueous solution having a higher osmotic pressure than the water to be treated. The alkaline aqueous solution remaining after electrolysis in the alkaline water electrolysis device 30 may be supplied to the second chamber 13 without passing through the first tank 21.

[0049] 2, the hydrogen production system 1 may further include a heat exchanger 40 that exchanges heat between the alkaline aqueous solution supplied to the alkaline water electrolysis device 30 and the heat of the alkaline aqueous solution discharged from the alkaline water electrolysis device 30. The heat exchanger 40 is provided in the circulation flow path 20. The alkaline water electrolysis device 30 is operated at, for example, about 70°C to 90°C. Therefore, by exchanging the heat between the alkaline aqueous solution supplied to the alkaline water electrolysis device 30 and the heat of the alkaline aqueous solution discharged from the alkaline water electrolysis device 30, the energy efficiency of the alkaline water electrolysis device 30 can be improved.

[0050] The heat exchanger 40 may include a first heat exchanger 41 and a second heat exchanger 42. The first heat exchanger 41 exchanges heat between the alkaline aqueous solution supplied to the anode chamber 31 and the alkaline aqueous solution discharged from the anode chamber 31. The second heat exchanger 42 exchanges heat between the alkaline aqueous solution supplied to the cathode chamber 32 and the alkaline aqueous solution discharged from the cathode chamber 32. The first heat exchanger 41 may be connected to the first flow path 20a and the third flow path 20c. The second heat exchanger 42 may be connected to the second flow path 20b and the fourth flow path 20d.

[0051] On the other hand, the alkaline aqueous solution can also be supplied directly to the second chamber 13 without being cooled by the heat exchanger 40 or a cooler. Since the osmotic pressure increases as the temperature increases, when the temperature of the alkaline aqueous solution supplied to the second chamber 13 is high, the water in the water to be treated can be efficiently supplied to the alkaline aqueous solution. In addition, the alkaline aqueous solution heated in the alkaline water electrolysis device 30 can be cooled by exchanging heat between the alkaline aqueous solution and the water to be treated in the first permeation device 10.

[0052] Next, the osmotic pressure distribution of the water to be treated and the alkaline aqueous solution in the first permeation device 10 was evaluated. The water to be treated supplied to the first chamber 12 was seawater with a concentration of 3.5% by mass, and the flow rate of the seawater was set to 10 L / min. The alkaline aqueous solution supplied to the second chamber 13 was a 30% by mass KOH (potassium hydroxide) aqueous solution, and the flow rate of the aqueous solution was set to 10 L / min. The seawater passing through the first chamber 12 was supplied so as to flow in a countercurrent manner to the KOH aqueous solution passing through the second chamber 13. In the first permeation device 10, the temperature of the seawater was set to 15°C, and the temperature of the KOH aqueous solution was set to 20°C. The salt concentration of the 30% by mass KOH aqueous solution supplied to the second chamber 13, which was finally diluted in the first permeation device 10, was set to 20% by mass. The results of confirming the osmotic pressure distribution under the above conditions are shown in Table 1 and FIG. 3.

[0053] [Table 1]

[0054] In Table 1, the left column of the KOH aqueous solution indicates the inlet side (In) of the second chamber 13, and the right column of the KOH aqueous solution indicates the outlet side (Out) of the second chamber 13. That is, the salinity of the KOH aqueous solution is 30 mass% at the inlet of the second chamber 13, but is diluted by the supply of seawater to the second chamber 13, and is 20 mass% at the outlet of the second chamber 13. In addition, the flow rate of the KOH aqueous solution is 10 L / min at the inlet of the second chamber 13, but the flow rate increases by the supply of seawater to the second chamber 13, and is 15.0 L / min at the outlet of the second chamber 13. Accordingly, the osmotic pressure of the KOH aqueous solution is 13.0 MPa at the inlet of the second chamber 13, but is 8.7 MPa at the outlet of the second chamber 13.

[0055] On the other hand, the KOH aqueous solution passing through the second chamber 13 is supplied so as to flow in a countercurrent to the seawater passing through the first chamber 12. Therefore, in Table 1, the right column of seawater indicates the inlet side (In) of the first chamber 12, and the left column of seawater indicates the outlet side (Out) of the first chamber 12. That is, the salinity of the seawater is 3.5% by mass at the inlet of the first chamber 12, but is concentrated by the water in the seawater being supplied to the second chamber 13, and is 7.0% by mass at the outlet of the first chamber 12. In addition, the flow rate of the seawater is 10 L / min at the inlet of the first chamber 12, but is reduced by the water in the seawater being supplied to the second chamber 13, and is 5.0 L / min at the outlet of the first chamber 12. Accordingly, the osmotic pressure of the seawater is 1.4 MPa at the inlet of the first chamber 12, but is 2.9 MPa at the outlet of the first chamber 12.

[0056] In the membrane separation method using a reverse osmosis membrane (RO membrane), as described above, the water to be treated is pressurized at a pressure equal to or greater than the osmotic pressure, for example, 5 MPa to 7 MPa, to produce pure water. However, from the results of Table 1 and Fig. 3, according to the method of this example, the osmotic pressure difference (ΔP) between the osmotic pressure of the KOH aqueous solution and the osmotic pressure of seawater exceeded 7 MPa at all positions. In other words, according to the method of this example, it is found that by using the semipermeable membrane 11, water contained in the water to be treated can be easily supplied to the alkaline aqueous solution by forward osmosis.

[0057] As described above, according to the hydrogen production system 1 and hydrogen production method of this embodiment, it is possible to produce hydrogen with reduced carbon dioxide emissions compared to when the water required for alkaline water electrolysis is produced by a distillation method.

[0058] [Second embodiment] Next, the hydrogen production system 1 and hydrogen production method according to the second embodiment will be described with reference to Fig. 4. In the hydrogen production system 1 according to the second embodiment, at least one first permeation device 10 is a plurality of first permeation devices 10. Unless otherwise specified, other points are the same as those of the hydrogen production system 1 and hydrogen production method according to the above embodiment, and therefore description thereof will be omitted.

[0059] The hydrogen production system 1 includes a water-to-be-treated flow path 15 through which water to be treated flows, as in the above embodiment. The water-to-be-treated flow path 15 includes a plurality of first parallel flow paths 15a that are branched and arranged in parallel. Each of the plurality of first parallel flow paths 15a is provided so that the water to be treated flows through it. The plurality of first parallel flow paths 15a are connected to the first chambers 12 of the plurality of first permeation devices 10, respectively. That is, the plurality of first permeation devices 10 are arranged in parallel. Then, by driving the pump 16, the water to be treated is supplied from the water source S through the first parallel flow paths 15a to the first chambers 12 of each of the first permeation devices 10. The water to be treated that has passed through each of the first chambers 12 may be discharged to the water source S through the water-to-be-treated flow path 15.

[0060] The circulation flow path 20 includes a plurality of second parallel flow paths 20e that are branched and arranged in parallel. Each of the plurality of second parallel flow paths 20e is provided so that the alkaline aqueous solution circulates. The plurality of second parallel flow paths 20e are connected to the second chambers 13 of the plurality of first permeation devices 10, respectively. Then, by driving the pump 22, the alkaline aqueous solution is supplied from the first tank 21 to the second chambers 13 of each of the first permeation devices 10 through each of the plurality of second parallel flow paths 20e. The alkaline aqueous solution that has passed through each of the second chambers 13 may be supplied to the second tank 23, similar to the above embodiment.

[0061] A first stopper 17 that stops the supply of the water to be treated to the first chamber 12 is provided upstream of the first chamber 12 in each of the first parallel flow paths 15a. The first stopper 17 may be a valve, and the water to be treated flows in the first parallel flow path 15a by opening the valve, and the water to be treated stops in the first parallel flow path 15a by closing the valve. In addition, a second stopper 18 that stops the supply of the alkaline aqueous solution to the second chamber 13 is provided upstream of the second chamber 13 in each of the second parallel flow paths 20e. The second stopper 18 may be a valve, and the alkaline aqueous solution flows in the second parallel flow path 20e by opening the second stopper 18, and the alkaline aqueous solution stops in the second parallel flow path 20e by closing the second stopper 18.

[0062] As described above, in the hydrogen production system 1 according to the present embodiment, at least one first permeation device 10 is a plurality of first permeation devices 10. The hydrogen production system 1 further includes a water-to-be-treated flow path 15 through which the water to be treated flows. The water-to-be-treated flow path 15 is connected to the first chambers 12 of the first permeation devices 10, respectively, and includes a plurality of first parallel flow paths 15a arranged in parallel. The circulation flow path 20 is connected to the second chambers 13 of the first permeation devices 10, respectively, and includes a plurality of second parallel flow paths 20e arranged in parallel. A first stopper 17 that stops the supply of the water to be treated to the first chamber 12 is provided upstream of the first chamber 12 in each of the first parallel flow paths 15a. A second stopper 18 that stops the supply of the alkaline aqueous solution to the second chamber 13 is provided upstream of the second chamber 13 in each of the second parallel flow paths 20e.

[0063] As a result, it is possible to stop the operation of some of the first permeation devices 10 among the multiple first permeation devices 10 by closing the first stop part 17 and the second stop part 18. Therefore, since the first permeation devices 10 that are not stopped can be operated, it is possible to perform maintenance or replacement of the first permeation devices 10 as necessary without stopping the operation of the entire hydrogen production system 1.

[0064] [Third embodiment] Next, a hydrogen production system 1 and a hydrogen production method according to a third embodiment will be described with reference to Fig. 5. In addition to the above-described embodiments, the hydrogen production system 1 according to the third embodiment further includes a first turbine 45 and a first generator 46. Unless otherwise specified, other points are the same as those of the hydrogen production system 1 and the hydrogen production method according to the above-described embodiments, and therefore description thereof will be omitted.

[0065] The first turbine 45 is provided in the circulation flow path 20 downstream of the second chamber 13 and upstream of the alkaline water electrolysis device 30. Specifically, the first turbine 45 is provided in the circulation flow path 20 downstream of the second chamber 13 and upstream of the second tank 23. The alkaline aqueous solution discharged from the second chamber 13 is supplied to the first turbine 45. The first turbine 45 is rotated by the alkaline aqueous solution supplied from the second chamber 13. The first turbine 45 is mechanically connected to the first generator 46 and is provided to operate in conjunction with the first generator 46. Therefore, the first generator 46 generates electricity by the rotation of the first turbine 45. The alkaline aqueous solution that has passed through the first turbine 45 is supplied to the alkaline water electrolysis device 30.

[0066] As described above, the hydrogen production system 1 according to this embodiment further includes the first turbine 45 and the first generator 46. The first turbine 45 is provided in the circulation flow path 20 downstream of the second chamber 13 and upstream of the alkaline water electrolysis device 30, and is rotated by the alkaline aqueous solution supplied from the second chamber 13. The first generator 46 generates electricity by the rotation of the first turbine 45.

[0067] As a result, the hydrogen production system 1 can also generate electricity by concentration difference power generation. Specifically, in the first permeation device 10, water in the water to be treated permeates from the first chamber 12 to the second chamber 13. As a result, the flow rate of the alkaline aqueous solution that has passed through the second chamber 13 is greater than before passing through the second chamber 13. The alkaline aqueous solution that has passed through the second chamber 13 has a higher water pressure than before passing through the second chamber 13, and the first turbine 45 can be rotated efficiently. Therefore, the hydrogen production system 1 and the hydrogen production method according to this embodiment can produce hydrogen and generate electricity at the same time. The electric energy generated by the power generation can also be used as a power source for the alkaline water electrolysis device 30.

[0068] Although the present embodiment has been described as an example in which there is one first permeation device 10, as in the second embodiment, the hydrogen production system 1 may include multiple first permeation devices 10. In this case, the first turbine 45 may be provided downstream of the second chamber 13 and upstream of the alkaline water electrolysis device 30 in each of the multiple second parallel flow paths 20e, or the first turbine 45 may be provided in the treated water flow path 15 where the multiple second parallel flow paths 20e join together.

[0069] [Fourth embodiment] Next, a hydrogen production system 1 and a hydrogen production method according to a fourth embodiment will be described with reference to Fig. 6. In addition to the above-described embodiment, the hydrogen production system 1 according to the fourth embodiment further includes a treated water flow path 15, a second permeation device 50, a second turbine 56, and a second generator 57. Unless otherwise specified, other points are the same as those of the hydrogen production system 1 and the hydrogen production method according to the above-described embodiment, and therefore description thereof will be omitted.

[0070] The water to be treated flow path 15 is connected to the first chamber 12. The water to be treated flow path 15 is provided so that the water to be treated flows through it. Specifically, as described above, one end of the water to be treated flow path 15 is connected to the water source S, and the water to be treated pumped up from the water source S by the pump 16 flows into the water to be treated flow path 15.

[0071] The second permeation device 50 includes a semipermeable membrane 51. The second permeation device 50 has a third chamber 52 and a fourth chamber 53. The semipermeable membrane 51 separates the third chamber 52, which is provided downstream of the first chamber 12 in the water to be treated flow path 15, from a fourth chamber 53 to which low osmotic pressure water having an osmotic pressure lower than that of the water to be treated is supplied. One surface of the semipermeable membrane 51 is in contact with the water to be treated, and the other surface is in contact with the low osmotic pressure water. The semipermeable membrane 51 may be the same as the semipermeable membrane 11 described above.

[0072] Semipermeable membrane 51 allows the water in the low osmotic pressure water to permeate from fourth chamber 53 to third chamber 52. The osmotic pressure of the water to be treated supplied to third chamber 52 is higher than the osmotic pressure of the low osmotic pressure water supplied to fourth chamber 53. Therefore, the water in the low osmotic pressure permeates semipermeable membrane 51 and moves to the water to be treated in third chamber 52 due to positive osmotic pressure. As a result, the flow rate of the water that has passed through third chamber 52 is higher than before passing through third chamber 52.

[0073] The fourth chamber 53 is connected to a flow path 54. One end of the flow path 54 is connected to a river R, which is an example of a water source. A pump 55 is provided in the flow path 54. Fresh water is supplied from the river R to the fourth chamber 53 by the pump 55. The fresh water that has passed through the fourth chamber 53 may be discharged into the river R.

[0074] In this embodiment, river water is used as the low osmotic pressure water, but the low osmotic pressure water may be water with an osmotic pressure lower than that of the water to be treated supplied to the third chamber 52. For example, when the water to be treated supplied to the first chamber 12 is seawater, the low osmotic pressure water to be supplied to the fourth chamber 53 may be seawater. This is because the water in the seawater supplied to the first chamber 12 permeates the semipermeable membrane 11 and moves to the second chamber 13, and the concentration of the seawater that has passed through the first chamber 12 becomes high, so that the osmotic pressure of the concentrated seawater supplied to the third chamber 52 becomes higher than that of the seawater supplied to the fourth chamber 53. Then, due to the difference in osmotic pressure, the water in the seawater supplied to the fourth chamber 53 is supplied to the concentrated seawater supplied to the third chamber 52. For the same reason, when the water to be treated supplied to the first chamber 12 is brackish water, the low osmotic pressure water to be supplied to the fourth chamber 53 may be brackish water. That is, the low osmotic pressure water may be the same as the water to be treated, and may be seawater, brackish water, or fresh water.

[0075] The second turbine 56 is provided in the water to be treated flow path 15. The second turbine 56 is rotated by the water passing through the third chamber 52. The second turbine 56 is mechanically connected to the second generator 57 and is provided so as to operate in conjunction with the second generator 57. Therefore, the second generator 57 generates electricity by the rotation of the second turbine 56. The water that has passed through the second turbine 56 may be discharged to the water source S.

[0076] As described above, the hydrogen production system 1 according to this embodiment further includes the water flow path 15, the second permeation device 50, the second turbine 56, and the second generator 57. The water flow path 15 is connected to the first chamber 12, through which the water flows. The second permeation device 50 divides the water flow path 15 into a third chamber 52 provided downstream of the first chamber 12 and a fourth chamber 53 to which low osmotic pressure water having an osmotic pressure lower than that of the water, and includes a semipermeable membrane 51 that allows water in the low osmotic pressure water to permeate from the fourth chamber 53 to the third chamber 52. The second turbine 56 is provided in the water flow path 15 and rotates by water passing through the third chamber 52. The second generator 57 generates electricity by the rotation of the second turbine 56.

[0077] As a result, the hydrogen production system 1 can also generate electricity by concentration difference power generation. Specifically, in the second permeation device 50, the water in the low osmotic pressure water permeates from the fourth chamber 53 to the third chamber 52. As a result, the flow rate of the water passing through the third chamber 52 is greater than before passing through the third chamber 52. Since the water passing through the third chamber 52 has a higher water pressure than before passing through the third chamber 52, the second turbine 56 can be rotated efficiently. Therefore, the hydrogen production system 1 and the hydrogen production method according to this embodiment can produce hydrogen and generate electricity at the same time. The electric energy generated by the power generation can also be used as a power source for the alkaline water electrolysis device 30.

[0078] [Fifth embodiment] Next, a hydrogen production system 1 and a hydrogen production method according to a fifth embodiment will be described with reference to Fig. 7. The hydrogen production system 1 according to the fifth embodiment uses an anion exchange membrane-type alkaline water electrolysis apparatus 30. That is, an anion exchange membrane (AEM) such as a resin having a quaternary ammonium group and an imidazolium group is used as the diaphragm 33 of the alkaline water electrolysis apparatus 30. Unless otherwise specified, other points are the same as those of the hydrogen production system 1 and the hydrogen production method according to the above embodiments, and therefore description thereof will be omitted.

[0079] In the present embodiment, the circulation flow path 20 does not need to include the second flow path 20b, and the alkaline aqueous solution that has passed through the second chamber 13 does not need to be supplied to the cathode chamber 32. Therefore, all of the alkaline aqueous solution that has passed through the second chamber 13 may be supplied to the anode chamber 31. In addition, the fourth flow path 20d does not need to be connected to the first tank 21 or the second chamber 13. Although the alkaline aqueous solution may be supplied to the cathode chamber 32, from the viewpoint of lowering the salt concentration of the alkaline aqueous solution supplied to the second chamber 13, it is preferable that the moisture in the cathode chamber 32 is discharged to the outside of the circulation flow path 20.

[0080] When an anion exchange membrane is used as the diaphragm 33, the salt concentration of the alkaline aqueous solution may be as high as 35 mass %, as described above. However, when an anion exchange membrane is used as the diaphragm 33, the salt concentration of the alkaline aqueous solution may be low, for example, 4 mass % or more, or 5 mass % or more. In addition, the salt concentration of the alkaline aqueous solution may be 30 mass % or less, 20 mass % or less, or 15 mass % or less.

[0081] Next, the osmotic pressure distribution of the water to be treated and the alkaline aqueous solution in the first permeation device 10 was evaluated. The water to be treated supplied to the first chamber 12 was seawater with a concentration of 3.5% by mass, and the flow rate of the seawater was set to 30 L / min. The alkaline aqueous solution supplied to the second chamber 13 was a 15% by mass KOH (potassium hydroxide) aqueous solution, and the flow rate of the aqueous solution was set to 10 L / min. The seawater passing through the first chamber 12 was supplied so as to flow in a countercurrent manner to the KOH aqueous solution passing through the second chamber 13. In the first permeation device 10, the temperature of the seawater was set to 15°C, and the temperature of the KOH aqueous solution was set to 20°C. The salt concentration of the 15% by mass KOH aqueous solution supplied to the second chamber 13, which was finally diluted in the first permeation device 10, was set to 5% by mass. The results of confirming the osmotic pressure distribution under the above conditions are shown in Table 2 and FIG. 8.

[0082] [Table 2]

[0083] In Table 2, the left column of the KOH aqueous solution indicates the inlet side (In) of the second chamber 13, and the right column of the KOH aqueous solution indicates the outlet side (Out) of the second chamber 13. That is, the salinity of the KOH aqueous solution is 15 mass% at the inlet of the second chamber 13, but is diluted by the supply of seawater to the second chamber 13, and is 5 mass% at the outlet of the second chamber 13. In addition, the flow rate of the KOH aqueous solution is 10 L / min at the inlet of the second chamber 13, but the flow rate increases by the supply of seawater to the second chamber 13, and is 30.0 L / min at the outlet of the second chamber 13. Accordingly, the osmotic pressure of the KOH aqueous solution is 6.5 MPa at the inlet of the second chamber 13, but is 2.2 MPa at the outlet of the second chamber 13.

[0084] On the other hand, the KOH aqueous solution passing through the second chamber 13 is supplied so as to flow in a countercurrent to the seawater passing through the first chamber 12. Therefore, in Table 2, the right column of seawater indicates the inlet side (In) of the first chamber 12, and the left column of seawater indicates the outlet side (Out) of the first chamber 12. That is, the salinity of the seawater is 3.5% by mass at the inlet of the first chamber 12, but is concentrated by the water in the seawater being supplied to the second chamber 13, and is 10.5% by mass at the outlet of the first chamber 12. In addition, the flow rate of the seawater is 30.0 L / min at the inlet of the first chamber 12, but is reduced by the water in the seawater being supplied to the second chamber 13, and is 10.0 L / min at the outlet of the first chamber 12. Accordingly, the osmotic pressure of the seawater is 1.4 MPa at the inlet of the first chamber 12, but is 4.3 MPa at the outlet of the first chamber 12.

[0085] 8, according to the method of this example, the osmotic pressure difference (ΔP) between the osmotic pressure of the KOH aqueous solution and the osmotic pressure of seawater exceeded 0.5 MPa at all positions. In other words, according to the method of this example, it is found that by using the semipermeable membrane 11, water contained in the water to be treated can be easily supplied to the alkaline aqueous solution by forward osmosis.

[0086] As described above, the hydrogen production system 1 according to this embodiment includes at least one first permeation device 10, a circulation flow path 20, and an alkaline water electrolysis device 30. The at least one first permeation device 10 partitions a first chamber 12 to which the water to be treated is supplied and a second chamber 13 to which an alkaline aqueous solution having a higher osmotic pressure than the water to be treated is supplied, and includes a semipermeable membrane 11 that allows water in the water to be treated to permeate from the first chamber 12 to the second chamber 13. The circulation flow path 20 is connected to the second chamber 13, and the alkaline aqueous solution circulates through it. The alkaline water electrolysis device 30 is provided in the circulation flow path 20, and electrolyzes the water in the alkaline aqueous solution supplied from the second chamber 13 to generate hydrogen.

[0087] The hydrogen production method according to the present embodiment also includes a step of permeating water in the water to be treated through a semipermeable membrane 11 and supplying the water to be treated into an alkaline aqueous solution having a higher osmotic pressure than the water to be treated. The method also includes a step of electrolyzing the water in the alkaline aqueous solution to which the water in the water to be treated has been supplied, in an alkaline water electrolysis device 30, to obtain hydrogen. The method also includes a step of supplying the alkaline aqueous solution remaining after electrolysis to the semipermeable membrane 11 as an alkaline aqueous solution having a higher osmotic pressure than the water to be treated.

[0088] As a result, water from the water to be treated is supplied to the alkaline aqueous solution, and hydrogen can be produced by electrolyzing the water in the alkaline aqueous solution. Furthermore, by electrolyzing the water in the alkaline aqueous solution, the alkaline aqueous solution can be concentrated, and the water in the water to be treated can be efficiently recovered by the first permeation device 10. Therefore, according to the hydrogen production system 1 and hydrogen production method of this embodiment, hydrogen can be produced with reduced carbon dioxide emissions compared to when the water required for alkaline water electrolysis is produced by a distillation method.

[0089] The entire contents of Patent Application No. 2021-081018 (filing date: May 12, 2021) are incorporated herein by reference.

[0090] Although several embodiments have been described, the embodiments can be modified or modified based on the above disclosure. All components of the above embodiments and all features described in the claims may be individually extracted and combined as long as they are not mutually inconsistent.

[0091] This disclosure can contribute, for example, to the following Sustainable Development Goals (SDGs) led by the United Nations: Goal 7 "Ensure access to affordable, reliable, sustainable and modern energy for all," Goal 12 "Ensure sustainable consumption and production patterns," and Goal 13 "Take urgent action to combat climate change and its impacts." [Explanation of symbols]

[0092] 1 Hydrogen production system 10 1st infiltration device 11 Semi-permeable membrane 12 Room 1 13 Room 2 15. Treated water flow path 15a First parallel flow path 17 1st stop 18 Second stop 20 Circulation flow path 20e Second parallel flow path 21 First Tank 23 Second Tank 30 Alkaline water electrolysis equipment 31 Anode chamber 32 Cathode Chamber 33 Diaphragm 37 Oxygen gas-liquid separator 38 Hydrogen gas-liquid separator 40 Heat exchanger 45 First Turbine 46 No. 1 Generator 50 Second infiltration device 51 Semi-permeable membrane 52 Room 3 53 Room 4 56 No. 2 Turbine 57 Second Generator

Claims

1. a plurality of first permeation devices, which partition a first chamber to which the water to be treated is supplied and a second chamber to which an alkaline aqueous solution having a higher osmotic pressure than the water to be treated is supplied, and each of the first permeation devices includes a semipermeable membrane that allows water in the water to be treated to permeate from the first chamber to the second chamber; a circulation flow path connected to the second chamber and through which the alkaline aqueous solution circulates; an alkaline water electrolysis device provided in the circulation flow path and configured to electrolyze water in the alkaline aqueous solution supplied from the second chamber to generate hydrogen; a water-to-be-treated flow path through which the water to be treated flows; Equipped with The water flow path includes a plurality of first parallel flow paths that are connected to the first chambers of the first permeation devices and arranged in parallel, The circulation flow path includes a plurality of second parallel flow paths that are connected to the second chambers of the plurality of first permeation devices and arranged in parallel, A first stopper that stops the supply of the water to be treated to the first chamber is provided upstream of the first chamber in each of the first parallel flow paths, a second stopper that stops the supply of the alkaline aqueous solution to the second chamber is provided upstream of the second chamber in each of the plurality of second parallel flow paths.

2. The hydrogen production system according to claim 1 , wherein the water to be treated is seawater or brackish water.

3. 3. The hydrogen production system according to claim 1, wherein the alkaline water electrolysis device includes an anode chamber that accommodates an anode, a cathode chamber that accommodates a cathode, and a diaphragm that separates the anode chamber from the cathode chamber.

4. The hydrogen production system according to claim 3 , wherein the circulation flow passage includes a flow passage connected to an outlet of the second chamber, and an inlet of the anode chamber and an inlet of the cathode chamber.

5. an oxygen gas-liquid separator connected to the anode chamber for separating oxygen generated by electrolysis at the anode from an alkaline aqueous solution; a hydrogen gas-liquid separator connected to the cathode chamber for separating hydrogen generated by electrolysis at the cathode from an alkaline aqueous solution; Further equipped with 4. The hydrogen production system according to claim 3, wherein the alkaline aqueous solution supplied to the second chamber includes the alkaline aqueous solution separated in the oxygen gas-liquid separator and the alkaline aqueous solution separated in the hydrogen gas-liquid separator.

6. a first tank provided in the circulation flow path upstream of the second chamber and downstream of the alkaline water electrolysis device; a second tank provided in the circulation flow path downstream of the second chamber and upstream of the alkaline water electrolysis device; Further equipped with 3. The hydrogen production system according to claim 1, wherein a salinity of the alkaline aqueous solution in the first tank is higher than a salinity of the alkaline aqueous solution in the second tank.

7. 3. The hydrogen production system according to claim 1, further comprising a heat exchanger that exchanges heat between the alkaline aqueous solution supplied to the alkaline water electrolysis device and the alkaline aqueous solution discharged from the alkaline water electrolysis device.

8. At least one first permeation device that divides a first chamber into which the water to be treated is supplied and a second chamber into which an alkaline aqueous solution having a higher osmotic pressure than the water to be treated is supplied, and that includes a semipermeable membrane that allows water in the water to be treated to permeate from the first chamber to the second chamber; a circulation flow path connected to the second chamber and through which the alkaline aqueous solution circulates; an alkaline water electrolysis device provided in the circulation flow path and configured to electrolyze water in the alkaline aqueous solution supplied from the second chamber to generate hydrogen; a first turbine provided in the circulation flow path downstream of the second chamber and upstream of the alkaline water electrolysis device, the first turbine being rotated by the alkaline aqueous solution supplied from the second chamber; a first generator that generates electricity by rotation of the first turbine; A hydrogen production system comprising:

9. At least one first permeation device that divides a first chamber into which the water to be treated is supplied and a second chamber into which an alkaline aqueous solution having a higher osmotic pressure than the water to be treated is supplied, and that includes a semipermeable membrane that allows water in the water to be treated to permeate from the first chamber to the second chamber; a circulation flow path connected to the second chamber and through which the alkaline aqueous solution circulates; an alkaline water electrolysis device provided in the circulation flow path and configured to electrolyze water in the alkaline aqueous solution supplied from the second chamber to generate hydrogen; a treatment water flow path connected to the first chamber and through which the treatment water flows; a second permeation device that divides a third chamber provided downstream of the first chamber in the water flow path to be treated from a fourth chamber to which low osmotic pressure water having an osmotic pressure lower than that of the water to be treated is supplied, and includes a semipermeable membrane that allows water in the low osmotic pressure water to permeate from the fourth chamber to the third chamber; a second turbine provided in the water-to-be-treated flow path and rotated by water passing through the third chamber; a second generator that generates electricity by rotation of the second turbine; A hydrogen production system comprising:

10. A plurality of first permeation devices which partition a first chamber into which the water to be treated is supplied and a second chamber into which an alkaline aqueous solution having a higher osmotic pressure than the water to be treated is supplied, the first permeation devices including a semipermeable membrane which allows water in the water to be treated to permeate from the first chamber to the second chamber; a circulation flow path connected to the second chamber and through which the alkaline aqueous solution circulates; an alkaline water electrolysis device provided in the circulation flow path and configured to electrolyze water in the alkaline aqueous solution supplied from the second chamber to generate hydrogen; a water-to-be-treated flow path through which the water to be treated flows; A hydrogen production method using a hydrogen production system comprising: The hydrogen production method includes: A step of permeating the water in the to-be-treated water through the semipermeable membrane and supplying the water to an alkaline aqueous solution having an osmotic pressure higher than that of the to-be-treated water; a step of electrolyzing water in an alkaline aqueous solution to which the water to be treated is supplied in the alkaline water electrolysis device to obtain hydrogen; supplying the alkaline aqueous solution remaining after the electrolysis to the semipermeable membrane as an alkaline aqueous solution having an osmotic pressure higher than that of the water to be treated; Including, The water flow path includes a plurality of first parallel flow paths that are connected to the first chambers of the first permeation devices and arranged in parallel, The circulation flow path includes a plurality of second parallel flow paths that are connected to the second chambers of the plurality of first permeation devices and arranged in parallel, A first stopper that stops the supply of the water to be treated to the first chamber is provided upstream of the first chamber in each of the first parallel flow paths, A hydrogen production method, wherein a second stopper that stops the supply of the alkaline aqueous solution to the second chamber is provided upstream of the second chamber in each of the plurality of second parallel flow paths.

11. At least one first permeation device which divides a first chamber into which the water to be treated is supplied and a second chamber into which an alkaline aqueous solution having a higher osmotic pressure than the water to be treated is supplied, and which includes a semipermeable membrane through which water in the water to be treated passes from the first chamber to the second chamber; a circulation flow path connected to the second chamber and through which the alkaline aqueous solution circulates; an alkaline water electrolysis device provided in the circulation flow path and configured to electrolyze water in the alkaline aqueous solution supplied from the second chamber to generate hydrogen; a first turbine provided in the circulation flow path downstream of the second chamber and upstream of the alkaline water electrolysis device, the first turbine being rotated by the alkaline aqueous solution supplied from the second chamber; a first generator that generates electricity by rotation of the first turbine; A hydrogen production method using a hydrogen production system comprising: The hydrogen production method includes: A step of permeating the water in the to-be-treated water through the semipermeable membrane and supplying the water to an alkaline aqueous solution having an osmotic pressure higher than that of the to-be-treated water; a step of electrolyzing water in an alkaline aqueous solution to which the water to be treated is supplied in the alkaline water electrolysis device to obtain hydrogen; supplying the alkaline aqueous solution remaining after the electrolysis to the semipermeable membrane as an alkaline aqueous solution having an osmotic pressure higher than that of the water to be treated; A method for producing hydrogen comprising the steps of:

12. At least one first permeation device which divides a first chamber into which the water to be treated is supplied and a second chamber into which an alkaline aqueous solution having a higher osmotic pressure than the water to be treated is supplied, and which includes a semipermeable membrane through which water in the water to be treated passes from the first chamber to the second chamber; a circulation flow path connected to the second chamber and through which the alkaline aqueous solution circulates; an alkaline water electrolysis device provided in the circulation flow path and configured to electrolyze water in the alkaline aqueous solution supplied from the second chamber to generate hydrogen; a treatment water flow path connected to the first chamber and through which the treatment water flows; a second permeation device that divides a third chamber provided downstream of the first chamber in the water flow path to be treated from a fourth chamber to which low osmotic pressure water having an osmotic pressure lower than that of the water to be treated is supplied, and includes a semipermeable membrane that allows water in the low osmotic pressure water to permeate from the fourth chamber to the third chamber; a second turbine provided in the water-to-be-treated flow path and rotated by water passing through the third chamber; a second generator that generates electricity by rotation of the second turbine; A hydrogen production method using a hydrogen production system comprising: The hydrogen production method includes: A step of permeating the water in the to-be-treated water through the semipermeable membrane and supplying the water to an alkaline aqueous solution having an osmotic pressure higher than that of the to-be-treated water; a step of electrolyzing water in an alkaline aqueous solution to which the water to be treated is supplied in the alkaline water electrolysis device to obtain hydrogen; supplying the alkaline aqueous solution remaining after the electrolysis to the semipermeable membrane as an alkaline aqueous solution having an osmotic pressure higher than that of the water to be treated; A method for producing hydrogen comprising the steps of:

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