A method for optimizing the thickness of a gasket for an alkaline electrolyzer

Abstract

The application relates to a kind of tooling gasket thickness optimization design methods of alkaline electrolytic cell, comprising the following steps: S1: obtaining the single bolt torque of electrolytic cell, bolt pitch, bolt number, calculating the actual axial force of the electrolytic cell to be tested;According to the axial force result obtained in S1, select the pressure range of the corresponding pressure device, and perform the pressure operation on the gasket element with different thicknesses to obtain the acceptable gasket thickness range;S3: based on the acceptable gasket thickness range obtained in S2, assemble the tooling in the actual electrolytic cell, and obtain the static ohm value under different thicknesses by using electrochemical workstation, so as to obtain the best gasket thickness result.Compared with the prior art, the application comprehensively considers the electrode-diaphragm interface factor, introduces a specific analysis method, effectively promotes the development and application expansion of alkaline electrolytic water technology and brings significant economic benefits.

Description

Technical Field

[0001] The invention relates to the technical field of alkaline electrolytic cells, in particular to a thickness optimization design method for a tooling gasket of an alkaline electrolytic cell. Background Art

[0002] In the current world energy landscape dominated by fossil fuels, hydrogen energy, with its advantages such as high calorific value and zero emissions, is widely considered a strong contender for reversing the energy landscape. Among its various main production methods, water electrolysis has become a research focus in various countries due to its clean and efficient advantages. Ambient-temperature water electrolysis hydrogen production technologies are mainly divided into alkaline water electrolysis (AWE), proton exchange membrane (PEM), and anion exchange membrane (AEM) based on the type of electrolyte. Among these, alkaline water electrolysis technology is the most mature, with the lowest cost and the most economical, and is considered the primary method for large-scale water electrolysis hydrogen production applications. Its main structural feature is the "sandwich" structure of cathode + diaphragm + anode.

[0003] Among them, the degree of contact between the electrode and the diaphragm in the electrolysis chamber has a significant impact on the occurrence of the electrolysis reaction. A large number of literature and patents have studied this related problem and proposed corresponding solutions. Conventional electrolysis assembly experience believes that relatively tight assembly of the diaphragm and electrode can minimize the ohmic impedance and thus enhance the reaction current. Therefore, the smallest possible axial compression distance will be selected to maximize the diaphragm-electrode interface contact. In Chinese patent CN117926299A "A proton exchange membrane water electrolyzer and its assembly device and manufacturing method", a water electrolyzer assembly method proposed by Shanghai Jiaotong University and Shanghai Jian Hydrogen Energy uses a coil spring as a compression device to achieve axial tightening of the electrode and diaphragm assembly to maximize interface contact. In addition, some existing laboratory electrolyzers use axial pressure modules to control the maximization of interface contact. However, in actual operation, excessive compression force does not bring continuous positive gain to the reaction current, and sometimes even causes diaphragm rupture or even electrolyzer short circuit. In this regard, the team of Xiamen University's Tan Kah Kee Laboratory used microcurrent detection to observe the current transmission and material transfer effects near the contact interface of catalytic materials and other surfaces in PEM electrolyzers. They found that interface distances that are too far or too close are not conducive to the transmission of current and materials, respectively, thereby causing poor electrochemical reactions. This indirectly illustrates that during the assembly of the electrolyzer, it is necessary to adjust the contact degree between the diaphragm and the electrode by controlling a reasonable range of pressing force.

[0004] Currently, no research has identified the optimal assembly method for adjusting the compression of the electrode diaphragm in alkaline electrolyzers. The most direct way to adjust this is to control the support thickness of the polytetrafluoroethylene gasket. Therefore, it is necessary to design a reasonable test method for the gasket thickness range. Summary of the Invention

[0005] The purpose of the present application is to overcome the defects of the prior art and provide a method for optimizing the thickness of a tooling gasket of an alkaline electrolyzer, which comprehensively considers the electrode-diaphragm interface factors and introduces specific analysis methods to promote the development and application of alkaline electrolysis water technology and bring significant economic benefits.

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] The present application provides a method for optimizing the thickness of a tooling gasket of an alkaline electrolyzer, comprising the following steps:

[0008] S1: Obtain the single bolt torque, bolt pitch and bolt number of the electrolyzer, and calculate the actual axial force of the electrolyzer to be tested;

[0009] S2: According to the axial force result obtained in S1, select a pressure range of the pressing device, and perform pressing operation on the gasket-containing element with different thicknesses to obtain an acceptable gasket thickness range;

[0010] S3: Based on the acceptable gasket thickness range obtained in S2, assemble the tooling in the actual electrolyzer, and use an electrochemical workstation to obtain the static ohmic value under different thicknesses to obtain the optimal gasket thickness result.

[0011] Further, in S1, the method for calculating the actual axial force of the electrolyzer to be tested is:

[0012]

[0013] Wherein:

[0014] F axis : Actual axial force of the electrolyzer to be tested, unit N;

[0015] T: Single bolt torque, obtained according to the electrolyzer manual provided by the manufacturer or actual operation, unit N.m;

[0016] p: Bolt pitch, unit mm;

[0017] n: Number of bolts.

[0018] Further, in S2, the following specific steps are included:

[0019] Measure the thickness of the electrode and the membrane to be tested;

[0020] According to the thickness of the cathode and anode, select a polytetrafluoroethylene (PTFE) gasket with the same thickness;

[0021] Select the thickness range of the PTFE gasket for the diaphragm;

[0022] Combine the electrode, the electrode-adapted PTFE, the diaphragm, and the diaphragm-adapted PTFE;

[0023] Based on the compression during the test, the actual working thickness is determined;

[0024] Filter gasket thickness combinations to obtain information on gasket combinations that fall within the acceptable range.

[0025] Furthermore, in S2, the thickness of the electrodes and membranes to be measured includes the thickness of the cathode and anode and the thickness of the diaphragm;

[0026] In S2, in the process of adapting polytetrafluoroethylene (PTFE) gaskets of equal thickness according to the thickness of the cathode and anode: the shape of the gasket is consistent with the cross-sectional shape in the electrolytic cell and its internal flow field area can accommodate the electrodes, and the shape of the PTFE gasket for the diaphragm is required to be consistent.

[0027] Furthermore, in S2, when selecting the thickness range of the PTFE gasket for the diaphragm, the measured diaphragm thickness is used as the lower reference value of the thickness, the step size is 0.05 mm, and the setting is performed in sequence.

[0028] Furthermore, in S2, during the process of assembling the electrode, the electrode-adapted PTFE, the diaphragm, and the diaphragm-adapted PTFE, an empty electrolytic cell plate is used as a pressure piece each time to clamp the assembled parts therein and ensure that the relative positions are at the geometric center and will not slip.

[0029] Furthermore, in S2, the process of determining the actual working thickness based on the compression amount during the test includes: turning on the pressure instrument, fixing the axial pressure to the axial pressure calculated in S1, recording the relative position when the pressure head begins to contact the plate and the final stable position, obtaining the compression amount at this time, and thus determining the actual working thickness.

[0030] Furthermore, S3 specifically includes the following sub-steps:

[0031] Using the actual electrolytic cell to be tested, install the gasket-electrode-diaphragm combinations within the acceptable gasket thickness range obtained in S2 in the actual cell.

[0032] Connect the electrochemical workstation to the electrolytic cell;

[0033] Using the electrochemical impedance spectroscopy function of the electrochemical workstation, static EIS measurements were performed on gasket-electrode-diaphragm combinations of different thicknesses under open circuit conditions.

[0034] The EIS curves under different thickness combinations were compared, and the thickness result with the smallest ohmic impedance was selected and determined as the optimal gasket thickness combination.

[0035] Furthermore, in S3, during the static EIS measurement, the working electrode and the SENSE are connected to the positive electrode, and the reference electrode and the counter electrode are connected to the negative electrode.

[0036] Furthermore, in S3, the specific process of determining the optimal gasket thickness combination includes: comparing the EIS curves under different thickness combinations, focusing on the part of the curve that reflects the ohmic impedance, intercepting the intersection of the curve and the horizontal axis in the impedance diagram to obtain the ohmic value of the entire electrolytic cell under this gasket thickness, and by comparing the ohmic values ​​corresponding to each thickness combination, selecting the thickness result with the smallest ohmic impedance and determining it as the optimal gasket thickness combination.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1) This invention fully considers the critical impact of interfacial conductivity and mass transfer on the electrochemical reaction near the electrode-diaphragm interface. By designing a method for determining the optimal gasket tooling thickness, the contact environment between the electrode and the diaphragm is effectively optimized. On the one hand, precise gasket thickness selection reduces interfacial resistance, making current conduction more efficient, thereby significantly improving the intensity of the alkaline water electrolysis reaction.

[0039] 2) In the previous alkaline electrolytic cell tooling fastening process, there was a lack of clear and unified gasket thickness selection standards, resulting in a large degree of arbitrariness in the assembly process and unstable product performance. The present invention successfully unified the assembly standards and determined the optimal gasket thickness for different electrolytic cells based on scientific and rigorous axial force calculations, compression tests, and electrochemical analysis processes. This standardized process greatly improves the consistency and repeatability of alkaline electrolytic cell assembly, ensuring that each electrolytic cell achieves a similar high performance level, whether in large-scale production or in the construction of small-scale experimental devices, effectively reducing quality problems and performance fluctuations caused by assembly differences.

[0040] 3) The present invention innovatively introduces electrochemical impedance and reaction interface contact degree as core analytical means, opening up new research and development directions for the field of alkaline electrolyzer technology. This not only helps to deeply understand the complex electrochemical reaction mechanism of the electrode-diaphragm interface, but also provides a strong theoretical basis and practical guidance for the subsequent development of more advanced electrolyzer technology. Based on the present invention, researchers can further explore how to synergistically improve the performance of the electrolyzer by optimizing other related factors, such as developing new gasket materials, improving electrode structures, etc., thereby promoting the continuous innovation and expansion of the entire alkaline electrolysis water technology, playing a more important role in the new energy field and adapting to the diversified application needs of the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Schematic diagram of electrolytic cell bolt torque and its equivalent axial force;

[0042] Figure 2 The figure is a schematic diagram of the change of working thickness before and after pressure;

[0043] Figure 3 The figure is a schematic diagram of the process of the thickness optimization design method of the gasket for the alkaline electrolyzer. DETAILED DESCRIPTION

[0044] The present application will be described in detail below with reference to the accompanying drawings and specific examples. In the technical solution, if the component model, material name, connection structure, control method, algorithm and other features are not explicitly stated, they are considered as common technical features disclosed in the prior art.

[0045] Example 1

[0046] The optimal gasket thickness design method for the alkaline electrolyzer in this embodiment includes the following steps:

[0047] 1) Calculate the axial force of the electrolyzer under pressure;

[0048] 2) According to the axial force result, select the corresponding pressure range of the compression device to compress the gasket-containing element with different thicknesses to obtain the acceptable gasket thickness range;

[0049] 3) Based on the acceptable gasket thickness range result in 2), use the actual tank to perform the gasket and use the electrochemical workstation to obtain the static ohmic value under different thicknesses to obtain the optimal gasket thickness result.

[0050] In order to facilitate the simulation of the pressure level of the to-be-tested electrolyzer, the actual axial pressure size needs to be obtained to facilitate the compression test. The commonly used laboratory-scale electrolyzer usually uses multiple extended bolts as the axial fastening device, and the tank axial pressure calculation can refer to the formula:

[0051]

[0052] F axis : actual axial force of the to-be-tested electrolyzer, unit N;

[0053] T: single bolt torque, which can be obtained according to the electrolyzer manual provided by the manufacturer or the actual operation condition, unit N.m;

[0054] p: bolt pitch, unit mm;

[0055] n: number of bolts.

[0056] According to the axial force result obtained by calculation, a pressure instrument with a corresponding range is selected to perform a gasket compression test. The pressure instrument needs to meet the requirements of simultaneously providing the real-time pressure value at the pressure head and the absolute displacement. First, measure the thickness d ec , dea , d d , according to the thickness of the cathode and anode, the thickness of the polytetrafluoroethylene (PTFE) gasket (hereinafter referred to as PTFE) is adjusted, the shape of the gasket must be consistent with the cross-sectional shape of the electrolytic cell, and the internal flow field area can exactly accommodate the electrode, and the diaphragm PTFE gasket shape is required to be consistent.

[0057] The thickness range of the diaphragm PTFE gasket is determined by the actual measurement of the diaphragm thickness d d , the step size is 0.05 mm, and the thickness is sequentially superimposed, i.e. d d , d d1 , d d2 ……d dn (where d di =d d +i*0.05, the range of n can be determined according to the actual test results subsequently). The electrode, electrode-adapted PTFE, diaphragm, and diaphragm-adapted PTFE are combined, and an empty electrolytic cell plate or a plate of the same material is used as a pressure piece each time, and the combined parts are clamped therein and the relative positions are ensured to be at the geometric center without slipping. Turn on the pressure instrument, fix the axial pressure to F axis , record the relative position when the pressure head starts to contact the plate and the final stable position, and obtain the compression amount Δd i at this time. The actual working thickness d wi at this time is d di +d c +d a -Δd i . The gasket thickness combination that meets Δd i ≤6%×(d di +d c +d a ) is selected, and the gasket combination within the range is recorded and the electrode and diaphragm are replaced to prepare for the next Ohm test.

[0058] Use the actual electrolytic cell to be tested, respectively, and install the gasket-electrode-diaphragm combination in the above thickness range in the actual tank, and connect the system liquid path. Use an electrochemical workstation to connect the electrolytic cell, and use green and white (working electrode and SENSE) to connect the positive electrode, and yellow and red (reference electrode and counter electrode) to connect the negative electrode. Use the electrochemical impedance spectroscopy function to measure the actual static EIS under open circuit conditions. Compare the EIS curves under different thickness combinations, and select the thickness result with the smallest Ohm impedance. Finally, the best gasket thickness combination is obtained.

[0059] As Figure 3The embodiment shown is a method for designing the optimal gasket thickness of an alkaline electrolyzer. Based on the experimental data of the high school new energy laboratory, the PTFE gasket thickness of an alkaline electrolyzer is optimized using the above method, which includes the following steps:

[0060] Step 1: Obtain the specific tank body fastening bolt parameters from the electrolyzer manufacturer, including the recommended fastening torque T and bolt pitch p. Use the formula to calculate the equivalent axial pressure. After calculation, the equivalent axial fastening force F is obtained axis 9300N, so the stable pressure value of the electric pressure cylinder is selected as 9300N as the axial working pressure.

[0061] Step 2: Select double-sided nickel mesh and organic diaphragm as the working combination to be tested. According to the size data provided by the distributor, the nominal thickness of the nickel mesh and the diaphragm is 0.3mm and 0.5mm respectively. Select 2*2cm nickel mesh and 3*3 diaphragm as the working size, and after net cutting, use the thickness gauge to measure and confirm that the size meets the above nominal thickness, and the total thickness is confirmed to be 1.1mm. Since it was found in the pre-experiment that the nickel mesh electrode thickness did not change during the process of directly applying axial pressure to the working combination, but the diaphragm was compressed and deformed by the electrode, therefore, in the process of selecting the gasket thickness, the thickness of the diaphragm PTFE gasket is used as the variable, thereby ensuring the uniqueness of the variable and the axial symmetry. According to the 0.5mm (diaphragm thickness) as the reference, 0.6mm, 0.5mm, 0.4mm and 0.3mm are selected as the diaphragm gasket thickness, and the two-sided nickel mesh electrode uses 0.3mm gasket. Use the electrolyzer plate combination without bolts as the pressing component, clamp the electrode and its gasket, the diaphragm and its gasket into two plates, and turn on the press to make it clamped to ensure the position of the parts is fixed. Then turn on the press to add pressure, when the measured pressure value reaches 9300N, keep it for 1min. After 1min of constant pressure, reset the press, remove the electrolyzer working parts, and note that the relative position of the electrode and diaphragm should not be changed at this time. Measure the total thickness of the electrode and diaphragm.

[0062] Step 3: According to the total thickness of the electrode and diaphragm obtained in step 2 under different diaphragm gasket thicknesses, it is found that the working thickness changes under the conditions of diaphragm thickness of 0.3mm, 0.4mm and 0.5mm can meet Δd i ≤6%×(d di +d c +d a) requirements, so these three diaphragm gasket thicknesses were screened for the next ohm test. Use the same electrode, diaphragm and its thickness as the test combination, install it into the measured electrolytic cell, and use a torque wrench to ensure that the bolt torque meets the test pressure. Connect it to the actual working alkali solution system and open the liquid circuit, connect the electrochemical workstation to the electrolytic cell tab, turn on the workstation after the liquid circuit has been running for 1 minute, select the EIS mode, set the test voltage to open circuit voltage, the frequency range is 100000Hz to 0.1Hz, and start the test. After the test is completed, intercept the intersection of the curve and the horizontal axis in the impedance diagram to obtain the ohmic value of the entire cell under this gasket thickness, and select the lowest result to obtain the optimal gasket thickness that meets the requirements.

[0063] According to the results shown in Table 1, 0.4 mm diaphragm gasket and 0.3 mm electrode gasket on both sides of the electrode were selected as the optimal tooling thickness for the electrolytic cell.

[0064] Table 1 Axial static compression and real slot ohm test results under different diaphragm gasket thicknesses

[0065]

[0066] In summary, this invention, while building upon existing methods for securing electrolytic cell fixtures, simultaneously considers the impact of interfacial conductivity and mass transfer on the electrochemical reaction near the electrode-diaphragm interface. By incorporating electrochemical impedance and the degree of contact between the reaction interfaces as analytical tools, it effectively enhances the intensity of alkaline water electrolysis reactions, unifies assembly standards, and provides technical support for the energy-saving development of alkaline water electrolysis technology, thereby increasing economic benefits.

[0067] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for optimizing the thickness of a tooling gasket for an alkaline electrolytic cell, characterized in that: The following steps are involved: S1: Obtain the single bolt torque, bolt pitch, and number of bolts of the electrolytic cell, and calculate the actual axial force of the electrolytic cell to be tested; S2: Based on the axial force results obtained in S1, a pressing device with a corresponding pressure range is selected to perform a pressing operation on gasket-containing components of different thicknesses to obtain an acceptable gasket thickness range; S3: Based on the acceptable gasket thickness range obtained in S2, the tooling is assembled in the actual electrolytic cell and the static ohmic values ​​at different thicknesses are obtained using an electrochemical workstation to obtain the optimal gasket thickness result; In S1, the actual axial force of the electrolytic cell to be tested is calculated as follows: in: : Actual axial force of the electrolytic cell to be measured, unit: N; : Single bolt torque, obtained from the electrolyzer user manual provided by the manufacturer or actual operating conditions, unit: Nm; : Bolt pitch, unit: mm; : number of bolts; In S3, the following sub-steps are included: Using the actual electrolytic cell to be tested, perform actual cell installation on the gasket-electrode-diaphragm combinations that fall within the acceptable gasket thickness range obtained in S2; Connect the electrochemical workstation to the electrolytic cell; Using the electrochemical impedance spectroscopy function of the electrochemical workstation, static EIS measurements were performed on gasket-electrode-diaphragm combinations of different thicknesses in the open circuit state; The EIS curves under different thickness combinations were compared, and the thickness result with the smallest ohmic impedance was selected and determined as the optimal gasket thickness combination.

2. The method for optimizing the thickness of a tooling gasket for an alkaline electrolytic cell according to claim 1, wherein: S2 includes the following specific steps: Measure the thickness of the electrodes and membranes to be tested; Adapt PTFE gaskets of equal thickness to the thickness of the cathode and anode; Select the thickness range of PTFE gasket for diaphragm; Combine the electrode, the electrode-adapted PTFE, the diaphragm, and the diaphragm-adapted PTFE; Based on the compression during the test, the actual working thickness is determined; Filter gasket thickness combinations to obtain information on gasket combinations that fall within the acceptable range.

3. The method for optimizing the thickness of a tooling gasket for an alkaline electrolytic cell according to claim 2, wherein: In S2, the thickness of the electrodes and membranes to be measured includes the thickness of the cathode and anode as well as the thickness of the diaphragm; In S2, in the process of adapting polytetrafluoroethylene (PTFE) gaskets of equal thickness according to the thickness of the cathode and anode: the shape of the gasket is consistent with the cross-sectional shape of the electrolytic cell and its internal flow field area can accommodate the electrodes, and the shape of the PTFE gasket for the diaphragm is required to be consistent.

4. The method for optimizing the thickness of a tooling gasket for an alkaline electrolytic cell according to claim 2, wherein: In S2, when selecting the thickness range of the PTFE gasket for the diaphragm, the measured diaphragm thickness is used as the lower reference value of the thickness, and the step size is 0.05 mm, and the setting is performed in sequence.

5. The method for optimizing the thickness of a tooling gasket for an alkaline electrolytic cell according to claim 2, wherein: In S2, during the process of assembling the electrode, the electrode-adapted PTFE, the diaphragm, and the diaphragm-adapted PTFE, an empty electrolytic cell plate is used as a pressure piece each time to clamp the assembled parts and ensure that the relative positions are in the geometric center and will not slip.

6. The method for optimizing the thickness of a tooling gasket for an alkaline electrolytic cell according to claim 2, wherein: In S2, the process of determining the actual working thickness based on the compression amount during the test includes: turning on the pressure instrument, fixing the axial pressure to the axial pressure calculated in S1, recording the relative position when the pressure head begins to contact the plate and the final stable position, obtaining the compression amount at this time, and thus determining the actual working thickness.

7. The method for optimizing the thickness of a tooling gasket for an alkaline electrolytic cell according to claim 1, wherein: In S3, during the static EIS measurement, the working electrode and the SENSE are connected to the positive electrode, and the reference electrode and the counter electrode are connected to the negative electrode.

8. The method for optimizing the thickness of a tooling gasket for an alkaline electrolytic cell according to claim 1, wherein: In S3, the specific process of determining the optimal gasket thickness combination includes: comparing the EIS curves under different thickness combinations, focusing on the part of the curve reflecting the ohmic impedance, intercepting the intersection of the curve and the horizontal axis in the impedance diagram to obtain the ohmic value of the entire electrolytic cell under the gasket thickness, and by comparing the ohmic values ​​corresponding to each thickness combination, selecting the thickness result with the smallest ohmic impedance and determining it as the optimal gasket thickness combination.

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