Seawater direct electrolysis hydrogen production system
By using a seawater pretreatment device, manganese oxide coated anode plates, and a multi-stage circulating electrolysis method, the problems of ion corrosion and chlorine generation in seawater were solved, enabling efficient and economical direct electrolysis of seawater to produce hydrogen, reducing electrolysis costs and improving electrolysis efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-07-20
- Publication Date
- 2026-04-17
AI Technical Summary
In existing technologies, seawater hydrogen production equipment cannot directly utilize seawater electrolysis to produce hydrogen because the complex ions in seawater cause electrode corrosion and chlorine gas is generated during the electrolysis process, increasing costs and environmental risks.
The system employs a seawater pretreatment device, an electrolyzer, and a gas-liquid separation device. It uses manganese oxide-coated anode plates and a multi-stage circulating electrolysis method. Through the staggered arrangement of bipolar plates and the design of a three-stage electrolysis chamber, it achieves direct electrolysis of seawater to produce hydrogen. Furthermore, it reduces chlorine generation and improves electrolysis efficiency by migrating ions through an electric field.
This technology enables direct seawater electrolysis to produce hydrogen, reducing electrolysis costs, decreasing chlorine generation, and improving electrolysis and production efficiency, while also addressing freshwater resource pressures and environmental issues.
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Figure CN121874789A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of seawater hydrogen production, specifically a direct seawater electrolysis hydrogen production system. Background Technology
[0002] In conventional alkaline water electrolysis (ALK) and proton exchange membrane electrolysis (PEM) hydrogen production technologies, the raw material water is ultrapure water or deionized water. This type of water falls under the category of freshwater and is obtained through a series of purification processes. The overall purification investment and operating costs are relatively high. Furthermore, current hydrogen production through water electrolysis mainly utilizes green power sources such as wind and solar power in the northwest region. On the other hand, considering that freshwater resources account for only 2.8% of global water resources, of which 2.1% is undevelopable glacial water, usable freshwater for humans accounts for only 0.2% of global water resources. More than 97% of the water resources on Earth are saline, and seawater resources are quite abundant.
[0003] The presence of complex ions in seawater can corrode the electrodes of electrolytic hydrogen production equipment, making it unsuitable for direct electrolysis (e.g., seawater containing high concentrations of Cl). - During the electrolysis process, chlorine gas is released at the anode, leading to anode corrosion. Generally, seawater needs to be purified to obtain deionized water before electrolyzing it to produce hydrogen. However, this not only increases the investment and operating costs of seawater purification, but also means that the concentrated brine produced after desalination is not allowed to be discharged into the sea by current environmental regulations, causing secondary pollution. Therefore, using seawater to directly electrolyze hydrogen can alleviate the pressure on water sources.
[0004] This case arose in order to resolve the aforementioned issues. Summary of the Invention
[0005] (a) Technical problems to be solved
[0006] The present invention aims to overcome the existing technology and solve the problems mentioned in the background art.
[0007] (II) Technical Solution
[0008] To achieve the above objectives, the present invention provides the following technical solution: a seawater direct electrolysis hydrogen production system, comprising a seawater pretreatment device, an electrolyzer, and a gas-liquid separation device. The seawater pretreatment device pretreatments the seawater and then connects to the electrolyzer. The electrolyte flows through the outlet of the electrolyzer to the gas-liquid separation device. The electrolyzer contains multiple bipolar plates arranged alternately, with their ends supported by brackets inside the electrolyzer. Seawater enters from the bottom of the electrolyzer, passes through the bipolar plates sequentially upwards for electrolysis, and is then output from the top. The outlet of the gas-liquid separation device is connected to a multi-stage circulation device to ensure that the seawater remains within a dischargeable pH range while electrolyzing hydrogen.
[0009] As a preferred embodiment, the bipolar plate further comprises one cathode plate and one anode plate as a unit, and uses 10-50 units.
[0010] The anode plate has a manganese oxide surface coating. The coating process is as follows:
[0011] The anode plate uses a metal plate as the substrate, and a manganese oxide sintering coating is formed on the surface of the substrate, including the following process steps:
[0012] Step 1: Sandblast the substrate surface with diamond abrasive with a particle size of 3-5 μm.
[0013] Step 2: Passivate the surface of the sandblasted substrate using a passivation solution;
[0014] Step 3, Primary Processing: After the substrate undergoes surface passivation treatment, a manganese salt solution is sprayed onto it to form a surface coating, which is then sintered at a temperature of 400-450℃.
[0015] Step 4, Secondary treatment: Perform a second spraying of manganese oxide solution and sinter it at a temperature of 550-600℃.
[0016] Step 5, three-stage treatment: The ultrasonic sprayer is used to spray a nano-sized manganese oxide solution to form a suspended particulate solution, and "laser irradiation" is performed simultaneously until a catalyst coating with a single-sided thickness of 0.5 mm and honeycomb-like pores is formed. This makes the chloride ions have lower selectivity on the surface of the anode plate, almost generating oxygen and making it difficult to form chlorine gas.
[0017] Based on production experience, the concentration and thickness of the coating used have little impact on the function of the final anode plate surface coating.
[0018] As a preferred embodiment, the multi-stage circulation device further includes a two-stage three-chamber electrolysis chamber and a three-stage three-chamber electrolysis chamber connected in series. Bipolar membranes are provided on both sides of the two three-chamber electrolysis chambers. Seawater is injected into the outer side of the bipolar membrane in the two-stage three-chamber electrolysis chamber, and seawater or pure water is injected into the outer side of the bipolar membrane in the three-stage three-chamber electrolysis chamber.
[0019] As a preferred embodiment, the seawater pretreatment device further comprises a coarse filter and a fine filter arranged sequentially in the direction of seawater inflow into the system, wherein the fine filter is equipped with a small head pump to pump seawater in.
[0020] An application process for a direct seawater electrolysis hydrogen production system includes the following steps:
[0021] S1. Filtration step: After being filtered by a coarse filter and a fine filter, the pretreated seawater is pumped into the electrolysis cell by a small head pump.
[0022] S2, First-stage electrolysis: After seawater enters the electrolytic cell, it flows through the bipolar plates arranged in an alternating pattern to be buffered, and is fully electrolyzed in the direction of flow. The electrolyzed oxygen and hydrogen are mixed gases, which are then separated by the gas separation membrane in the gas-liquid separation device.
[0023] S3, Secondary Electrolysis: The electrolyzed seawater is introduced into a secondary three-chamber electrolysis chamber. In the middle of the three-chamber electrolysis chamber, the seawater after the primary electrolysis is introduced. By setting the voltage to 2-2.6V, high-valence ions migrate and are discharged through the bipolar membranes on both sides. The middle gradually desalinates to form fresh water, while anions (mainly chloride and bromide ions) and cations (mainly calcium and magnesium ions) accumulate on both sides, and the alkalinity and acidity gradually increase. Next, seawater is introduced into the outer side of the bipolar membranes. After mutual neutralization on both sides, it is discharged with the seawater (mainly removing chloride, bromide, calcium, and magnesium ions from the seawater). The seawater after the secondary electrolysis is introduced into the tertiary three-chamber electrolysis chamber after gas separation.
[0024] S4. Three-stage electrolysis: Seawater after two-stage electrolysis is introduced into the middle part of the three-chamber electrolysis chamber. By setting the voltage to 1.8-1.9V, low-valence ions migrate to the outside of the bipolar membrane. Then, seawater or pure water is introduced into the outside of the bipolar membrane, and by-products are collected at the same time.
[0025] Furthermore, the flow rate of seawater in the three-chamber electrolysis chamber is 0.1-10 m / min.
[0026] (III) Beneficial Effects
[0027] By adopting the above technical solution, the seawater direct electrolysis hydrogen production system provided by the present invention has the following advantages compared with the prior art:
[0028] 1. The anode plate uses a metal plate as the substrate, and a manganese oxide sintering coating is formed on the surface of the substrate. The corresponding coating application process is designed to form a honeycomb-like pore on the surface of the anode plate, so that chloride ions have lower selectivity on the surface of the anode plate, and almost generate oxygen, making it difficult to form chlorine gas.
[0029] 2. The electrolyzer is equipped with multiple bipolar plates, which are arranged in an interlaced manner to form an extended path. Seawater enters from the bottom of the electrolyzer and passes through the bipolar plates one by one for full electrolysis. Considering the impact of the number of bipolar plate units on production efficiency and the mechanical strength required for its design, it is set to 10-50 units, which ensures full electrolysis for hydrogen production while saving the overall cost of seawater electrolysis.
[0030] 3. The three-stage electrolysis method is used to directly produce hydrogen from seawater. Ions in the seawater migrate out of the system through the electric field, so that the electrolyzed seawater is within the discharge range. At the same time, the by-products formed in the three-stage reaction can be collected, which improves production efficiency and achieves economic benefits. Attached Figure Description
[0031] Figure 1 This is a schematic diagram of the present invention;
[0032] Figure 2 This is a schematic diagram illustrating the application of the two-stage three-chamber electrolysis chamber of the present invention;
[0033] Figure 3 This is a schematic diagram illustrating the application of the three-stage, three-chamber electrolysis chamber of the present invention.
[0034] In the diagram, 1 is the coarse filter; 2 is the fine filter; 3 is the electrolytic cell; 4 is the support; 5 is the bipolar plate; 6 is the gas-liquid separator; 7 is the two-stage three-chamber electrolysis chamber; 8 is the three-stage three-chamber electrolysis chamber; and 9 is the bi-stage membrane. Detailed Implementation
[0035] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments are described below, with reference to the appendix. Figure 1-3 The present invention will be further described in detail below.
[0036] See appendix Figure 1 As shown, in the seawater direct electrolysis hydrogen production system, the seawater input first passes through a coarse filter 1 to filter impurities, and then through a fine filter 2 equipped with a small-head pump. The particulate impurities in the coarsely filtered seawater are then screened and pumped into the electrolyzer 3. A platform is provided at sea level, and is designed with a gas-liquid separator 6 for receiving the products of the electrolyzer 3, a purification device, a power supply, and other equipment.
[0037] The bipolar plates 5 inside the electrolytic cell 3 are arranged in an interlaced pattern, and their ends are supported inside the cell by brackets 4 (the bipolar plates 5 are inserted into the brackets 4). Example of prototype dimensions for the electrolytic cell 3: The length of the cylindrical reactor is 1.5m, the length of the bipolar plates 5 is 90cm, and the radial diameter of the reactor can be 60cm, 90cm, etc., depending on the selection.
[0038] Generally, the cathode and anode plates are considered as one unit, with no more than 100 units. This is because each unit has a voltage distribution of approximately 1.8V. If there are more than 100 units, the seawater electrolysis will generate huge resistance, which will greatly reduce the electrical efficiency.
[0039] This scheme uses 10-50 units (this range is controllable and is based on the engineering experience of the parties involved in this scheme), and the design process is as follows.
[0040] Generally, if the size of bipolar plates with more than 50 units is too small, the resistance will be too high after stacking, and the electrolysis efficiency will decrease (the approximate power consumption range is as follows: the general industry level is 4.5 kWh / Nm). 3 With approximately 50 units or more, the power consumption is roughly 5.5 kWh / Nm³. 3 When the electrolysis efficiency drops to around 80% or even higher (loss is converted into thermal efficiency, without electrolysis reaction), the hydrogen production decreases, while the chlorine content tends to increase.
[0041] If designed with fewer than 10 units, the area required to prepare the electrode plates is large, while the thickness of the bipolar plate 5 is relatively thin (generally only about 2 mm). The large size will cause it to sag and deform easily, resulting in insufficient mechanical strength.
[0042] The oxygen and hydrogen produced by electrolysis in the electrolytic cell 3 are a mixed gas, and are separated by a gas separation membrane in the gas-liquid separation device. The seawater after electrolysis is introduced into the subsequent circulation after gas-liquid separation.
[0043] The anode plate has a manganese oxide coating. Hydrogen is produced at the cathode, while oxygen and a trace amount of chlorine are produced at the anode. Under normal circumstances, the ratio of chlorine to hydrogen and oxygen is 4:6. After spraying the manganese oxide coating onto the anode plate, the chlorine content in the hydrogen can be reduced to approximately 15-20%. This design further reduces chlorine production through anode plate design (based on production experience, the chlorine content in the hydrogen can be controlled to below 1%). The specific design is as follows.
[0044] The anode plate manufacturing process involves using a metal plate as the substrate and forming a manganese oxide sintering coating on the substrate surface, including the following process steps:
[0045] Step 1: Sandblast the substrate surface with diamond abrasive with a particle size of 3-5 μm.
[0046] Step 2: Passivate the surface of the sandblasted substrate using a passivation solution;
[0047] Step 3, Primary Processing: After the substrate undergoes surface passivation treatment, a 3%-30% manganese salt solution (manganese salt solution includes manganese sulfate, manganese chloride, manganese nitrate, etc.) is sprayed onto the substrate to form a surface coating, which is then sintered. The thickness after sintering is 0.1-0.3 mm, and the sintering temperature is 400-450℃.
[0048] Step 4, Secondary treatment: A second spraying of a manganese salt solution with a mass concentration of 10%-20% is performed, followed by sintering. The thickness after sintering is 0.01-0.1 mm, and the sintering temperature is 550-600℃.
[0049] Step 5, three-stage treatment: The ultrasonic sprayer is used to spray nano-sized manganese oxide solution, forming a suspended particulate solution, and simultaneously "laser irradiation" is performed until honeycomb-like pores are formed on the surface, so that chloride ions have lower selectivity on the surface of the anode plate, almost generating oxygen and making it difficult to form chlorine gas.
[0050] It should be noted that the formed manganese oxide is mainly MnO2 with a content of more than 70%, and the remainder is MnO, Mn2O3, etc. Secondly, the sintering temperature in step 3 is controlled at 400-450℃. The resulting manganese oxide coating has a lower density than manganese oxide sintered at 550-600℃, which is more conducive to the adhesion of the internal structural layer. Furthermore, the outermost manganese oxide coating in step 5 also has a higher density.
[0051] The gas-liquid separator 6 is equipped with a gas outlet (with a built-in gas separation membrane to separate hydrogen and oxygen) and a liquid outlet. A valve at the outlet allows the liquid to be circulated back to the three-chamber electrolysis chamber for the next electrolysis cycle. After each cycle, the liquid's pH value increases. The number of electrolysis cycles can be set according to requirements (generally 2-3 cycles to reach a pH of around 9), with 2 stages, 3 stages, ..., 6 stages. Typically, after 2 stages of circulation, the liquid's pH value is approximately 9, and after 3 stages, the liquid's pH value is approximately 11.
[0052] like Figure 2 As shown, this is a two-stage, three-chamber electrolysis chamber 7. Bipolar membranes (currently available conventional products) are installed on both sides of the chamber to divide it into three chambers. Seawater from the first-stage electrolysis is introduced into the middle section. The voltage is set to 2-2.6V to achieve the migration and precipitation of high-valence ions, primarily high-valence Ca. 2 +, Mg 2 Divalent ions (+) are released first and then gradually desalinated to form fresh water. Anions and cations accumulate on both sides, causing both alkalinity and acidity to gradually increase. Therefore, neutralization is required before discharge (the pH of seawater is generally between 6 and 9). In addition, seawater is injected into the outer side of the bipolar membrane to discharge the ionic solution in the three-chamber electrolysis chamber.
[0053] The flow rate of seawater in the three-chamber electrolysis chamber is approximately 0.3-1 m / min, which allows ions to partially migrate.
[0054] like Figure 3 As shown, this is a three-stage, three-chamber electrolysis chamber 8. Bipolar membranes are installed on both sides of the chamber to divide it into three chambers, with seawater from the second stage of electrolysis flowing into the middle section. Furthermore, the voltage within the three-stage, three-chamber electrolysis chamber is set to 1.8-1.9V, at which point most of the ions migrate and precipitate as Na+. + K + These monovalent ions can be used to prepare solutions of KOH, NaOH, and ClO. -Hypochlorous acid water, 80 ppm, etc., can be collected as the main reaction byproducts.
[0055] Ions in the seawater migrate out of the system through an electric field, ensuring that the electrolyzed seawater is within a dischargeable range, while saving the overall cost of seawater electrolysis while achieving full electrolysis for hydrogen production.
[0056] This scheme utilizes a three-stage electrolysis method to directly produce hydrogen from seawater. The temperature range of each electrolyzer is between 60-80℃, although the temperature may vary depending on the operating conditions. The hydrogen production ratio in the first-stage electrolysis, the recycled second-stage electrolysis, and the third-stage electrolysis is approximately 7:2:1.
[0057] The technological outlook of this solution is as follows: Currently, offshore wind energy utilization mainly involves generating electricity near the coastline and transporting it via submarine cables. As the number of coastal wind power installations gradually increases, offshore wind energy utilization faces challenges due to the high investment required for laying distributed long-distance submarine cables. This invention solves the problem of direct and efficient hydrogen production in offshore areas, which can be coupled with our company's unique hydrogen storage technology (a patent application will be filed for this technology later). This will fully utilize offshore wind energy resources, solve problems such as freshwater consumption, and the technology of producing hydrogen through seawater electrolysis is also receiving increasing attention.
[0058] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A seawater direct electrolysis hydrogen production system, comprising a seawater pretreatment device, an electrolyzer, and a gas-liquid separation device, wherein the seawater pretreatment device pretreatments the seawater and then connects to the electrolyzer, and the electrolyte flows through the outlet of the electrolyzer to the gas-liquid separation device, characterized in that: The electrolytic cell is equipped with multiple bipolar plates, which are arranged alternately on the top and bottom, and the ends are supported inside the electrolytic cell by brackets. Seawater is introduced from the bottom of the electrolytic cell, passes through the bipolar plates in sequence for electrolysis, and is then output from the top. The outlet of the gas-liquid separation device is connected to a multi-stage circulation device to keep the seawater within the dischargeable pH range while electrolyzing hydrogen.
2. The seawater direct electrolysis hydrogen production system according to claim 1, characterized in that: The bipolar plate consists of one cathode plate and one anode plate as a unit, and 10-50 units are used.
3. The seawater direct electrolysis hydrogen production system according to claim 2, characterized in that: The anode plate has a manganese oxide surface coating.
4. The seawater direct electrolysis hydrogen production system according to claim 1, characterized in that: The multi-stage circulation device includes a two-stage three-chamber electrolysis chamber and a three-stage three-chamber electrolysis chamber connected in series. Bipolar membranes are provided on both sides of the two three-chamber electrolysis chambers. Seawater is injected into the outer side of the bipolar membrane in the two-stage three-chamber electrolysis chamber, and seawater or pure water is injected into the outer side of the bipolar membrane in the three-stage three-chamber electrolysis chamber.
5. The seawater direct electrolysis hydrogen production system according to claim 1, characterized in that: The seawater pretreatment device consists of a coarse filter and a fine filter arranged sequentially in the direction of seawater inflow into the system. The fine filter is equipped with a small head pump to pump seawater in.
6. The application process of a seawater direct electrolysis hydrogen production system according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Filtration step: After being filtered by a coarse filter and a fine filter, the pretreated seawater is pumped into the electrolysis cell by a small head pump. S2, First-stage electrolysis: After seawater enters the electrolytic cell, it flows through the bipolar plates arranged in an alternating pattern to be buffered, and is fully electrolyzed in the direction of flow. The electrolyzed oxygen and hydrogen are mixed gases, which are then separated by the gas separation membrane in the gas-liquid separation device. S3, Secondary Electrolysis: The seawater after electrolysis is introduced into the secondary three-chamber electrolysis chamber. The seawater after primary electrolysis is introduced into the middle part of the three-chamber electrolysis chamber. Ions migrate through the bipolar membranes on both sides. The middle part is gradually desalinated to form fresh water, while the two sides accumulate anions and high-valence cations respectively. The alkalinity and acidity gradually increase. Then, seawater is introduced into the outer side of the bipolar membrane. After mutual neutralization, the two sides are discharged with the seawater. The seawater after secondary electrolysis is introduced into the tertiary three-chamber electrolysis chamber after gas separation. S4. Three-stage electrolysis: Seawater after two-stage electrolysis is introduced into the middle part of the three-chamber electrolysis chamber. By setting the voltage, low-valence ions migrate to the outside of the bipolar membrane. Then, seawater or pure water is introduced into the outside of the bipolar membrane. By collecting the by-products while collecting the gas during electrolysis.
7. The application process of the seawater direct electrolysis hydrogen production system according to claim 6, characterized in that: The flow rate of seawater in the three-chamber electrolysis chamber is 0.1-10 m / min.
8. The application process of the seawater direct electrolysis hydrogen production system according to claim 6, characterized in that: In step S3, the voltage in the secondary three-chamber electrolysis chamber is set to 2-2.6V, allowing high-valence cations to diffuse, migrate, and be eliminated. In step S4, the voltage in the tertiary three-chamber electrolysis chamber is set to 1.8-1.9V, allowing low-valence ions to migrate out of the anion and cation chambers to form by-products for collection.
9. A process for manufacturing the anode plate in an electrolyzer of a seawater direct electrolysis hydrogen production system, characterized in that: The anode plate uses a metal plate as the substrate, and a manganese oxide sintering coating is formed on the surface of the substrate, including the following process steps: Step 1: Sandblast the substrate surface with diamond abrasive with a particle size of 3-5 μm. Step 2: Passivate the surface of the sandblasted substrate using a passivation solution; Step 3, Primary Processing: After the substrate undergoes surface passivation treatment, a manganese salt solution is sprayed onto it to form a surface coating, which is then sintered. Step 4, Secondary Treatment: Perform a second spraying of manganese oxide solution and sintering; Step 5, three-stage treatment: The catalyst coating is applied using an ultrasonic sprayer with a nano-sized manganese oxide solution to form a suspended particulate solution, while simultaneously subjected to "laser irradiation" until a catalyst coating with a single-sided thickness of 0.5 mm and honeycomb-like pores is formed.
10. The process for manufacturing the anode plate in the electrolyzer of a seawater direct electrolysis hydrogen production system according to claim 9, characterized in that: In step 3, the mass concentration of the manganese salt solution in the primary treatment is 3%-30%, the sintering temperature is 400-450℃, and the thickness after sintering is 0.1-0.3mm; in step 4, the mass concentration of the manganese salt solution in the secondary treatment is 10%-20%, the sintering temperature is 550-600℃, and the thickness after sintering is 0.01-0.1mm.