Seawater electrolysis device integrated with hollow fiber membrane

Abstract

The invention relates to an electrolysis device, in particular to a seawater electrolysis device integrated with a hollow fiber membrane. On the basis of a traditional electrolytic tank, the hollow fiber membrane is integrated and arranged in the anode chamber, chlorine and hydrogen are effectively produced, meanwhile, the problem that a cation exchange membrane is scaled in the application process of a bipolar membrane is solved, and the whole device is compact and easy to maintain and only needs a single external power supply to supply energy.

Description

Technical Field

[0001] This invention relates to an electrolysis device, specifically to a seawater electrolysis device integrating a hollow fiber membrane. Background Technology

[0002] As an abundant source of chlorides, seawater electrolysis for chlor-alkali production can be used for treating ship exhaust gas, wastewater treatment, marine biofouling treatment, and pipeline disinfection. Taking ship exhaust gas treatment as an example: the anode products of this technology have strong oxidizing properties, which can oxidize NO in ship exhaust gas; the cathode of the electrolytic cell produces a strongly alkaline solution that can neutralize SOx and NOx, thereby achieving simultaneous desulfurization and denitrification.

[0003] Existing direct seawater electrolysis methods typically use only cation exchange membranes to block anode and cathode products, thus forming an alkaline solution in the anode chamber. However, the presence of a significant amount of calcium in the seawater within the chamber is problematic. 2+ With Mg 2+ They will react with OH under alkaline conditions. - These substances combine to form Ca(OH)₂ and Mg(OH)₂ precipitates, eventually forming scale on the electrode plates and reducing electrode activity. To solve this problem, bipolar membranes were developed and are commonly used in seawater electrolysis or similar electrochemical processes. A bipolar membrane is a composite membrane consisting of a cation exchange layer and an anion exchange layer, capable of dissociating water molecules under an electric field to produce H₂. + and OH - ion.

[0004] However, bipolar membranes have the following problems in seawater electrolysis applications: (1) Scaling and fouling risks: High concentrations of Ca²⁺ in seawater + Mg² + Divalent cations are prone to form precipitates (such as Ca(OH)2, Mg(OH)2) on the surface of the cation exchange layer of the bipolar membrane, leading to membrane pore blockage, increased resistance, and thus reduced electrolysis efficiency and membrane life; (2) High cost and complex maintenance: The preparation process of bipolar membranes is complex and costly, and they need to be cleaned or replaced regularly during use, which increases operating costs and maintenance difficulty; (3) Insufficient selectivity: Bipolar membranes are not selective for specific ions (such as Cl-). - (3) The selective permeability of bipolar membranes is poor, which may lead to low chlorine yield or increased side reactions in seawater electrolysis, affecting the overall efficiency; (4) The system integration is complex: bipolar membranes usually require supporting pretreatment units (such as filtration or softening devices) to reduce impurities, which increases the system volume and complexity. Therefore, it is urgent to optimize the existing seawater electrolysis devices. Summary of the Invention

[0005] To address the aforementioned issues, the present invention proposes an integrated hollow fiber membrane seawater electrolysis device. This device integrates a hollow fiber membrane into the anode chamber of a traditional electrolysis cell, effectively producing hydrogen chlorine while avoiding the scaling problem of cation exchange membranes that occurs during the application of bipolar membranes. Moreover, the overall device is compact, easy to maintain, and requires only a single external power supply.

[0006] Specifically, the present invention provides a seawater electrolysis device with integrated hollow fiber membrane, including a shell (10), the shell (10) being divided into an anode chamber (2) and a cathode chamber (3) by a cation exchange membrane (9), a membrane module (6) with integrated hollow fiber membrane is inserted into the anode chamber (2), the hollow fiber membrane (6c) being made of anion exchange membrane, and the membrane module (6) being used to direct chloride ions in seawater through the hollow fiber membrane (6c) into the anode chamber (2) by electrodialysis.

[0007] Preferably, the anode chamber (2) is provided with an anode electrode (7) connected to the positive terminal of the power supply (1), and the cathode chamber (3) is provided with a cathode electrode (8) connected to the negative terminal of the power supply (1); and / or, the upper shell (10) where the anode chamber (2) is located is provided with a chlorine outlet (4), and the upper shell (10) where the cathode chamber (3) is located is provided with a hydrogen outlet (5).

[0008] Preferably, the number of membrane modules (6) inserted in the anode chamber (2) is one; or, the number of membrane modules (6) inserted in the anode chamber (2) is several, and the several membrane modules (6) are symmetrically distributed in the anode chamber (2).

[0009] Preferably, the membrane module (6) is provided with a plurality of hollow fiber membranes (6c) arranged in parallel bundles. The hollow fiber membranes (6c) are sealed and fixed at two ends on the seawater inlet pipe (6b) and the seawater outlet pipe (6a). One end of the seawater inlet pipe (6b) and the seawater outlet pipe (6a) is a dead end, and the other end is open as the seawater inlet and the seawater outlet, respectively. The hollow fiber membrane (6c) between the seawater inlet pipe (6b) and the seawater outlet pipe (6a) is exposed in the anode chamber (2).

[0010] Preferably, the hollow fiber membrane (6c) is made of quaternized polysulfone or modified polyvinylidene fluoride, with a pore size of 10-50 nm, and the surface of the hollow fiber membrane (6c) carries a negative charge.

[0011] Preferably, the hollow fiber membrane (6c) has a metal cation rejection rate of greater than 95%, and / or the hollow fiber membrane (6c) has a chloride ion permeability of greater than 90%.

[0012] Preferably, the hollow fiber membrane (6c) has a symmetrical or asymmetrical structure, and / or, the outer diameter of the hollow fiber membrane (6c) is 0.5-1.5 mm and the inner diameter is 0.3-1.0 mm; and / or, the number of hollow fiber membranes (6c) in a single membrane module (6) is 2-200.

[0013] Preferably, the distance between the midpoint of the hollow fiber membrane (6c) and the anode electrode (7) is 5-20 mm.

[0014] Preferably, the membrane assembly (6) is connected to the housing (10) by a sealing structure, and / or the sealing structure is encapsulated with epoxy resin or O-rings.

[0015] Preferably, the membrane assembly (6) is connected to the housing (10) by a snap-fit ​​or threaded connection.

[0016] Compared with the prior art, the present invention has the following advantages: First, this invention integrates a hollow fiber anion exchange membrane by inserting it into the anode chamber of a traditional electrolysis device. The anion exchange membrane blocks cations present in seawater and allows only chloride ions supplied to the anode electrode to pass through, thus avoiding scaling problems caused by direct contact between the cation exchange membrane and seawater, and enabling long-term stable operation.

[0017] The hollow fiber anion exchange membrane used in this invention possesses a unique hollow tubular structure that endows the membrane module with extremely high packing density and specific surface area. This structural advantage provides a much larger mass transfer interface for chloride ions than that of flat sheet membranes, thus becoming a core design feature for achieving a highly compact device. Furthermore, the membrane module constructed from the hollow fiber anion exchange membrane in this invention allows for rapid disassembly and replacement of the membrane module with the electrolysis unit.

[0018] Furthermore, the ion migration process of the anion exchange membrane in this invention is due to the effect of electrodialysis, which does not require additional pressure to be provided to the seawater to force chloride ions to separate and permeate into the chamber. The above-mentioned chloride ion migration can be achieved solely by electrolysis powered by an external power source. Attached Figure Description

[0019] Figure 1 Front view (a) and top view (b) of the seawater electrolysis device with integrated hollow fiber membrane provided for the present invention; Figure 2 The main view of the membrane module provided by the present invention includes: 1-power source; 2-anode chamber; 3-cathode chamber; 4-chlorine outlet; 5-hydrogen outlet; 6-membrane module; 6a-seawater outlet pipe; 6b-seawater inlet pipe; 6c-hollow fiber membrane; 6d-sealing; 7-anode electrode; 8-cathode electrode; 9-cation exchange membrane; and 10-shell. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0021] Example 1 like Figure 1 As shown, the seawater electrolysis device with integrated hollow fiber membrane provided in this embodiment includes a housing 10, which is divided into an anode chamber 2 and a cathode chamber 3 by a cation exchange membrane 9. A membrane module 6 with integrated hollow fiber membrane 6c is inserted into the anode chamber 2. The hollow fiber membrane 6c is made of anion exchange membrane. The membrane module 6 is used to directionally allow chloride ions in seawater to pass through the hollow fiber membrane 6c into the anode chamber 2 via electrodialysis. An anode electrode 7 connected to the positive terminal of a power supply 1 is disposed in the anode chamber 2, and a cathode electrode 8 connected to the negative terminal of a power supply 1 is disposed in the cathode chamber 3. A chlorine outlet 4 is disposed on the upper housing 10 above the anode chamber 2, and a hydrogen outlet 5 is disposed on the upper housing 10 above the cathode chamber 3. Only one membrane module 6 is inserted into the anode chamber 2; the distance between the midpoint of the hollow fiber and the anode electrode 7 is 10 mm. The membrane module 6 is connected to the housing 10 by an epoxy resin sealing structure 6d, and the membrane module 6 and the housing 10 are connected by a snap-fit ​​connection.

[0022] like Figure 2 As shown, the membrane module 6 is provided with several hollow fiber membranes 6c arranged in parallel bundles. The hollow fiber membrane 6c is sealed and fixed at two ends on the seawater inlet pipe 6b and the seawater outlet pipe 6a. One end of the seawater inlet pipe 6b and the seawater outlet pipe 6a is a dead end, and the other end is open as the seawater inlet and the seawater outlet, respectively. The hollow fiber membrane 6c between the seawater inlet pipe 6b and the seawater outlet pipe 6a is exposed in the anode chamber 2.

[0023] Example 2 Based on the seawater electrolysis apparatus provided in Example 1, this example provides a seawater electrolysis method.

[0024] System composition and operation: Power supply 1: DC power supply, voltage 7.5V, current density 25 mA / cm².

[0025] Anode chamber 2 and cathode chamber 3 are made of corrosion-resistant polypropylene and have volumes of 0.5 L and 0.5 L, respectively.

[0026] Cation exchange membrane 9: Uses Nafion® N-324 membrane to separate the anode and cathode chambers and prevent gas mixing.

[0027] Membrane Module 6: Contains 20 hollow fiber membranes (120 mm in length, 1.0 mm in outer diameter), the membrane material being a polyvinyl imidazole-polyvinylidene fluoride blend (PVDF-PVIm), Cl - 92% transmittance, Ca² + Retention rate: 99%.

[0028] Electrodes: Anode electrode 7 is a titanium plate coated with IrO2 and RuO2, and cathode electrode 8 is a pure titanium plate.

[0029] Operating procedures: Initialization: Add NaCl solution (concentration 30 g / L) to the anode and cathode electrolytic cells, and let seawater flow through the hollow fiber membrane cavity at a flow rate of 10 mL / min.

[0030] Electrolysis operation: A constant current of 2A is applied, with a current density of 25 mA / cm². Anode reaction: 2Cl₂ - → Cl2↑ + 2e - Cathode reaction: 2H₂O + 2e⁻ - → H2↑ + 2OH - .

[0031] Ion migration: Cl - The Cl- ions migrate from the hollow fiber membrane wall to the anode chamber via electrodialysis, replenishing the Cl- ions consumed by the anode. - ;Ca² + Mg² + It is blocked by the membrane and flows out with the seawater.

[0032] Gas collection: Chlorine and hydrogen are collected through chlorine outlet 4 and hydrogen outlet 5, respectively.

[0033] Performance data: Chlorine yield calculated based on charge efficiency: 88%.

[0034] Electrode stability: After 500 hours of continuous operation, the electrode voltage change is <5%, and there is no visible scaling.

[0035] Energy consumption: The electricity consumption for producing 1 kg of chlorine is 2.8 kWh, which is lower than the traditional direct seawater electrolysis method (≥3.5 kWh / kg) and also lower than the bipolar membrane electrolysis method for pre-treated seawater (≥3.5 kWh / kg).

[0036] Table 1 shows the changes in chlorine yield and charge efficiency over time, and Table 2 shows the stability data of electrode voltage. It is evident that this invention offers advantages in energy consumption, stability, and maintainability. Specifically, the device integrating the hollow fiber membrane exhibits good permeability to chloride ions and a large permeation area, resulting in energy efficiency advantages in chlorine production; scaling is fundamentally avoided, and impurity ions do not contact any reaction interface (electrode or functional membrane), demonstrating stable cell voltage and current efficiency (e.g., change <5% over 500 hours). A comparison with traditional methods and bipolar membrane electrolysis is summarized in Table 3.

[0037] Table 1. Chlorine yield and charge efficiency as a function of time. Note: Chlorine yield is calculated based on the theoretical maximum yield (cumulative over time); charge efficiency is calculated using Faraday's law and is basically consistent with the yield.

[0038] Table 2 Electrode voltage stability record Note: A constant current of 2A was used, and the anode voltage was recorded every 100 hours. The voltage change rate was based on the initial voltage, with a total change of +2.11% over 500 hours, which is far below the 5% stability threshold.

[0039] Table 3 Comparison of Three Seawater Electrolysis Technologies The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A seawater electrolysis device integrating a hollow fiber membrane, comprising a shell (10), the shell (10) being divided into an anode chamber (2) and a cathode chamber (3) by a cation exchange membrane (9), characterized in that, The anode chamber (2) is fitted with a membrane module (6) with an integrated hollow fiber membrane. The hollow fiber membrane (6c) is made of anion exchange membrane. The membrane module (6) is used to direct chloride ions in seawater through the hollow fiber membrane (6c) into the anode chamber (2) via electrodialysis.

2. The apparatus according to claim 1, characterized in that, The anode chamber (2) is provided with an anode electrode (7) connected to the positive terminal of the power supply (1), and the cathode chamber (3) is provided with a cathode electrode (8) connected to the negative terminal of the power supply (1); and / or, the upper shell (10) where the anode chamber (2) is located is provided with a chlorine outlet (4), and the upper shell (10) where the cathode chamber (3) is located is provided with a hydrogen outlet (5).

3. The apparatus according to claim 1, characterized in that, The membrane module (6) is inserted into the anode chamber (2) in a single quantity; or, the membrane module (6) is inserted into several quantities in the anode chamber (2), and the several membrane modules (6) are symmetrically distributed in the anode chamber (2).

4. The apparatus according to claim 1, characterized in that, The membrane module (6) is provided with several hollow fiber membranes (6c) arranged in parallel bundles. The hollow fiber membranes (6c) are sealed and fixed at two ends on the seawater inlet pipe (6b) and the seawater outlet pipe (6a). One end of the seawater inlet pipe (6b) and the seawater outlet pipe (6a) is a dead end, and the other end is open as the seawater inlet and the seawater outlet, respectively. The hollow fiber membrane (6c) between the seawater inlet pipe (6b) and the seawater outlet pipe (6a) is exposed in the anode chamber (2).

5. The apparatus according to claim 1, characterized in that, The hollow fiber membrane (6c) is made of quaternized polysulfone or modified polyvinylidene fluoride, with a pore size of 10-50 nm, and the surface of the hollow fiber membrane (6c) carries a negative charge.

6. The apparatus according to claim 1, characterized in that, The hollow fiber membrane (6c) has a metal cation rejection rate of greater than 95%, and / or the hollow fiber membrane (6c) has a chloride ion permeability of greater than 90%.

7. The apparatus according to claim 1, characterized in that, The hollow fiber membrane (6c) has a symmetrical or asymmetrical structure, and / or the outer diameter of the hollow fiber membrane (6c) is 0.5-1.5 mm and the inner diameter is 0.3-1.0 mm; and / or the number of hollow fiber membranes (6c) in a single membrane module (6) is 2-200.

8. The apparatus according to claim 1, characterized in that, The distance between the midpoint of the hollow fiber membrane (6c) and the anode electrode (7) is 5-20 mm.

9. The apparatus according to claim 1, characterized in that, The membrane module (6) is connected to the housing (10) by a sealing structure, and / or the sealing structure is encapsulated with epoxy resin or O-rings.

10. The apparatus according to claim 1, characterized in that, The membrane assembly (6) is connected to the housing (10) by a snap-fit ​​or threaded connection.

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