Method for inhibiting attenuation of pressing force of PEM screw pressing electrolytic cell pile

Abstract

The invention relates to the technical field of electrolytic hydrogen production, and discloses a method for inhibiting attenuation of a pressing force of a PEM screw pressing electrolytic cell stack. The method specifically comprises the following steps: S1, based on main factors of pressing force decline of a PEM screw pressing electrolytic cell pile, establishing a pressing force attenuation model of the PEM screw pressing electrolytic cell pile; s2, acquiring data such as pressing force, corrosion depth and dynamic modulus; s3, adjusting model parameters; s4, comparing a corrected model prediction result with new experimental data, and if an error exceeds a limit, repeating the steps 2-3; s5, constructing a digital model highly similar to the physical entity in the virtual space based on the corrected model; and S6, monitoring, analyzing and optimizing the working parameter physical entity of the PEM screw pressing system through real-time data exchange and analysis, and delaying the attenuation of the pressing force of PEM screw pressing. According to the residual life prediction of the pressing force attenuation model, the dynamic adjustment of the operation parameters is carried out, so that the self-adaptive control is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrolytic hydrogen production, and particularly relates to a method for suppressing the attenuation of the pressing force of a PEM screw-pressed electrolytic cell stack. Background Art

[0002] A PEM electrolytic cell stack is composed of electrode plates, current collector plates, end plates, seals, etc. The pressing force applied through the combination of screws and end plates is combined into a stack. The pressing force can be provided by point pressure, line pressure, and surface pressure. Therefore, many assembly methods have been derived, and the stack is assembled through different pressing methods. Currently, the more common stack pressing methods on the market are the screw pressing method and the strap pressing method.

[0003] Screw pressing is a uniform pressing method of screw + end plate. The core of the uniform pressing method is to generate as uniform a pressing force as possible on each component in the stack. That is, the point pressure generated by the screw is converted into uniform stress on the entire stack through a thick end plate. The pressing force has a significant impact on the PEM electrolytic cell stack of the screw pressing method, and the performance and stability of the stack will be affected by it. The pressing force cannot be too large or too small, and it must be within a reasonable range. From the perspective of the stack structure, the pressing force will affect each part.

[0004] The influence of the pressing force on the membrane electrode is mainly reflected in that a smaller pressing force will also lead to insufficient contact area and contact force between the bipolar plate and the membrane electrode, resulting in an increase in contact resistance and a decrease in the performance of the stack. At the same time, the pressing force will also affect the porosity of the membrane electrode, thereby affecting the water and gas permeability of the membrane electrode. A larger pressing force will cause plastic deformation of the membrane electrode and change its characteristics. High pressure also poses a greater risk to the proton exchange membrane. A higher pressure combined with the expansion and contraction process of the proton exchange membrane will make the proton exchange membrane more prone to cracks and pinholes.

[0005] The influence of the pressing force on the sealing structure is mainly reflected in that when the pressing force is too small, the sealing structure in the stack cannot play an adequate sealing role, resulting in air leakage and causing safety problems. If it is not pressed tightly enough, the friction force between the components will also decrease accordingly. When the stack encounters situations such as shaking and impact that will generate transverse stress on the stack, the friction force between the components is not sufficient to maintain the structural stability of the stack, and the misalignment between the components will cause the stack to malfunction.

[0006] The stack sealing structure is often made of fluororubber materials. Research shows that although temperature is the main factor affecting its lifespan, high stress in the stack will also accelerate this aging process to a certain extent. The main manifestation of the aging sealing material is that its thickness will decrease, and this phenomenon will in turn affect the compression force. As the material ages, a method for self-adaptive or adjustable pressing force is an urgent problem to be solved in the industry. Summary of the Invention

[0007] Aiming at the deficiencies of the prior art, the present invention provides a method for suppressing the attenuation of the pressing force of a PEM screw-pressed electrolytic cell stack. By analyzing the main factors causing the attenuation of the pressing force of the PEM screw-pressed electrolytic cell stack, a pressing force attenuation model of the PEM screw-pressed electrolytic cell stack is established. According to the prediction of the remaining life of the pressing force attenuation model, the operating parameters are dynamically adjusted, so as to achieve adaptive control.

[0008] To achieve the above purpose of adaptive control of the pressing force, the present invention provides the following technical solutions:

[0009] A method for suppressing the attenuation of the pressing force of a PEM screw-pressed electrolytic cell stack specifically includes the following steps:

[0010] S1: Based on the main factors causing the attenuation of the pressing force of the PEM screw-pressed electrolytic cell stack, establish a pressing force attenuation model of the PEM screw-pressed electrolytic cell stack;

[0011] S2: Model parameter calibration: Obtain the pressing force, corrosion depth parameters, etc. through accelerated aging experiments, vibration table tests, etc., consult relevant manual data, or assign empirical values to determine the model parameters;

[0012] S3: Model correction: Numerically solve the pressing force attenuation model of the PEM screw-pressed electrolytic cell stack, compare it with the experimental results, and adjust the model parameters;

[0013] S4: Verification and re-iteration: Compare the prediction results of the corrected model with the new experimental data. If the error exceeds the limit, repeat steps 2-3;

[0014] S5: On the basis of the pressing force attenuation model of the PEM screw-pressed electrolytic cell stack established in steps S1-S4, construct a digital model in the virtual space that is highly similar to the physical entity;

[0015] S6: Through real-time data exchange and analysis, monitor, analyze and optimize the working parameters of the physical entity of the PEM screw-pressed system, so as to delay the attenuation of the pressing force of the PEM screw-pressed.

[0016] Further, the pressing force attenuation model equation of the PEM screw-pressed electrolytic cell stack in step S1 is:

[0017] F(t) = F0 - ΔF 蠕变 (t) - ΔF 热应力 (t) - ΔF 腐蚀 (t) - ΔF 振动 (t)

[0018] Further, the ΔF 蠕变(t) The calculation can define the creep parameters as a function of the aging time, the environmental factors of temperature T and pH value based on the basic equation of creep, and introduce the acceleration factors of temperature and chemical corrosion for model construction.

[0019] Furthermore, the ΔF 蠕变 (t) The calculation control equation is:

[0020]

[0021] Furthermore, comprehensively considering the influences of chemical corrosion, electrochemical corrosion, stress-accelerated corrosion, aging time t aging and environmental factors (temperature T, pH value, humidity H, stress σ), the ΔF 腐蚀 (t) The calculation control equation is:

[0022]

[0023] Among them, the time-varying parameter equation of the chemical corrosion parameter is:

[0024]

[0025] The time-varying parameter equation of the electrochemical corrosion parameter is:

[0026]

[0027] The time-varying parameter equation of the stress-accelerated corrosion parameter is:

[0028]

[0029] Furthermore, the calculation control equation of the ΔF vibration(t) is:

[0030]

[0031] Furthermore, the ΔF 热应力 (t) The calculation control equation is:

[0032]

[0033] Compared with the prior art, the present invention provides a method for suppressing the decay of the pressing force of a PEM screw-pressed electrolytic cell stack, having the following beneficial effects:

[0034] First, through multiple experiments and model corrections, the parameters or designs are gradually optimized, the model prediction accuracy is improved or the sealing design is optimized, and the model parameters or structures are continuously adjusted to make them more consistent with the actual operation data.

[0035] Second, based on the remaining life prediction of the compression force decay model, the operating parameters are dynamically adjusted to achieve adaptive control. By real-time monitoring the sealing state and feedback-adjusting the operating parameters, the sealing life can be extended. Description of the Drawings

[0036] Figure 1 It is a flow chart of the method for suppressing the compression force decay of the PEM screw-compressed electrolytic cell stack; Specific Embodiments

[0037] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0038] A method for suppressing the compression force decay of a PEM screw-compressed electrolytic cell stack specifically includes the following steps:

[0039] S1: Based on the main factors of the compression force decay of the PEM screw-compressed electrolytic cell stack, establish a compression force decay model of the PEM screw-compressed electrolytic cell stack;

[0040] S2: Model parameter calibration: Obtain the compression force, corrosion depth parameters, etc. through accelerated aging experiments, vibration table tests, etc., consult relevant manual data, or assign empirical values to determine the model parameters;

[0041] S3: Model correction: Numerically solve the compression force decay model of the PEM screw-compressed electrolytic cell stack, compare it with the experimental results, and adjust the model parameters;

[0042] S4: Verification and re-iteration: Compare the prediction results of the corrected model with the new experimental data. If the error exceeds the limit, repeat steps 2 - 3;

[0043] S5: On the basis of the compression force decay model of the PEM screw-compressed electrolytic cell stack established in steps S1 - S4, construct a digital model in the virtual space that is highly similar to the physical entity;

[0044] S6: Through real-time data exchange and analysis, monitor, analyze, and optimize the working parameters of the physical entity of the PEM screw-compression system, and achieve delaying the compression force decay of the PEM screw-compression.

[0045] Furthermore, the main factors affecting the attenuation of the compression force of the PEM electrolytic cell stack in step S1 include material creep, which is mainly reflected in the plastic deformation of bipolar plates, sealing gaskets, etc. under long-term stress; thermal stress relaxation, which is mainly reflected in the expansion / contraction of materials caused by temperature fluctuations and the release of residual stress; chemical corrosion, which is mainly reflected in the erosion of metal or polymer materials by acidic / alkaline environments; mechanical vibration, which is mainly reflected in micro-displacement caused by external vibrations or internal fluid pressure fluctuations; and assembly error accumulation, which is mainly reflected in the misalignment or deformation of components after long-term operation. Based on the main factors of the attenuation of the compression force of the PEM electrolytic cell stack, a compression force attenuation model of the PEM screw compression electrolytic cell stack is established.

[0046] The compression force F(t) can be expressed as the superposition effect of various factors, and the compression force attenuation model equation can be expressed as:

[0047] F(t)=F0-ΔF 蠕变 (t)-ΔF 热应力 (t)-ΔF 腐蚀 (t)-ΔF 振动 (t)

[0048] As a preferred embodiment: ΔF 蠕变 (t) The calculation model can be constructed based on the basic equation of creep, which is:

[0049] ε c =A·σ n ·e -QRT

[0050] Among them, ε c : creep rate; σ: stress; A, n: material constants; Q: creep activation energy; R, T: gas constant, temperature.

[0051] Material aging may change creep parameters such as A, n, and Q. In the application of PEM gaskets, the gaskets are usually in a high temperature and acidic environment and are subjected to mechanical pressure, which may cause creep and aging of the material. Therefore, it is necessary to consider how aging affects these parameters and thus affects the creep equation. Aging is specifically manifested as the change of parameters A, n, and Q over time or environmental conditions. Modify the creep equation and express A, n, and Q as a function of aging time. In addition, the working environment of PEM gaskets is usually high temperature, humidity, and acidity (due to the presence of proton exchange membranes), so the aging model needs to consider the impact of these environmental factors on material parameters. Humidity and acidic environments may accelerate the aging of materials, so humidity, pH value, etc. need to be introduced as acceleration factors in the model to adjust the change rate of A, n, and Q.

[0052] The creep parameter is defined as the aging time t aging And the function of environmental factors (temperature T, pH value):

[0053] The time-varying models of the parameters A, n, and Q are as follows:

[0054]

[0055] n(t aging ) = n0 + k n ·ln(1 + t aging / τ n )

[0056]

[0057] k A , m A , k n , τ n , k Q : Aging kinetic parameters. For k A , m A , k n , τ n , k Q Experimental calibration

[0058] Furthermore, introduce the acceleration factors of temperature and chemical corrosion:

[0059]

[0060] Where: C H+ The proton concentration is related to the acidity of the electrolyte; α A , β A , α Q , β Q : Environmental sensitivity index. The environmental acceleration factor comprehensively characterizes the synergistic effect of temperature and chemical corrosion through T γ , pH δ

[0061] Adjust the parameters of the above series of equations, unify the parameters, and introduce each influencing factor as a product term into the expression of the creep rate. Then, solve the variation of the pressing force with time through integral or differential equations, and integrate the above equations into a single equation containing aging time, temperature, chemical corrosion, and environmental factors. The specific expression of this equation is:

[0062]

[0063] Symbol definition:

[0064] k A , kn, k Q : Aging kinetic parameters of the material (time-related);

[0065] α A , β A , α​n , β n , α Q , β Q : Environmental sensitivity index (corresponding to the powers of temperature T and pH respectively);

[0066] γ, δ: Sensitivity indices of temperature and chemical corrosion in the acceleration factor.

[0067] The above parameters are calibrated through an accelerated aging creep experiment on the data of the fluororubber gasket after aging for 1000 hours. Regularly record the change in the gasket thickness (laser displacement sensor), and obtain the creep compliance curve through DMA (dynamic mechanical analysis) to back-calculate A(t), n(t), and Q(t).

[0068] As a preferred implementation: ΔF 热应力 (t) can be modeled based on the basic equation of the thermal stress relaxation model, and the basic equation of the thermal stress relaxation model is:

[0069] where

[0070] τ: Relaxation time

[0071] η: Viscosity coefficient

[0072] E: Elastic modulus

[0073] When the material ages, its viscoelastic properties change, and the elastic modulus E and viscosity coefficient η may change with the aging time, resulting in a change in the relaxation time τ = η / E.

[0074] Furthermore, regarding E and η as functions of time or aging degree, introduce the aging time t aging , and model the time-varying nature of the elastic modulus E and viscosity coefficient η parameters:

[0075] Define E and η as functions of the aging time t aging :

[0076] The elastic modulus E decreases: The molecular chains break or the cross-linking is damaged, and the material becomes softer. Establish an exponential decay time-varying model for the elastic modulus:

[0077] (Elastic property degradation), where is the environmental acceleration degradation term, is the humidity / chemical corrosion coupling term.

[0078] The viscosity coefficient η increases: The molecular chain movement is hindered, the fluidity decreases, and establish a power-law growth time-varying model for the viscosity coefficient η:

[0079] (Viscous resistance accumulation), where is the environmental acceleration hardening term, is the humidity / chemical corrosion coupling term.

[0080] Adjust the parameters, express the time-varying models of the elastic modulus E and the viscosity coefficient η using exponential or power functions containing environmental factors, and then substitute them into the thermal stress equation. Integrate the above equations into a single equation containing aging time, temperature, chemical corrosion, and environmental factors. The specific expression of this equation is:

[0081]

[0082] Parameter description: Temperature: T, Humidity: H, The pH value accelerates the material aging through the exponential term exp(k·T α ·H β ·PH γ ), and the coupling term (H·PH) φ describes the synergistic effect of humidity and chemical corrosion.

[0083] Parameter definition:

[0084] k E , k η : Environment-sensitive aging rate constant;

[0085] Α, β, γ: Sensitivity indices of temperature, humidity, pH;

[0086] φ E , φ η : Sensitivity index of the humidity and chemical corrosion coupling term.

[0087] As a preferred implementation: ΔF 腐蚀 (t) The calculation model can be constructed based on the basic equation of corrosion. Its corrosion rate equation also needs to comprehensively consider the basic equations of chemical, electrochemical, and mechanical factor corrosion. The corrosion rate (thickness loss rate) is superimposed by three parts:

[0088] dL / dt = Chemical corrosion + Electrochemical corrosion + Stress-accelerated corrosion

[0089] Acidic environment (H+ erosion) dominates:

[0090]

[0091] Parameter meaning:

[0092] k0: Intrinsic corrosion rate of the material (fluororubber: 10-5)

[0093] Proton concentration (electrolyte acidity, pH = 2 → CH+ = 0.01mol / L)

[0094] n: Reaction order (fluororubber: 0.5–1.0)

[0095] Ea: Activation energy (fluororubber: 40–60 kJ / mol)

[0096] R = 8.314

[0097] T: Temperature (K)

[0098] (2) Electrochemical corrosion

[0099] Galvanic corrosion occurs when in contact with metal components:

[0100]

[0101] Parameter meaning:

[0102] i corr : Corrosion current density (measured by Tafel polarization, fluororubber: 0.1–1 μA / cm2)

[0103] M: Material molar mass (fluororubber: 64 g / mol)

[0104] z: Charge transfer number (usually taken as 2–3)

[0105] F = 96485 C / mol

[0106] ρ: Density (fluororubber: 1.8 g / cm 3 )

[0107] (3) Stress accelerated corrosion

[0108] Mechanical stress (compression force, vibration) induces microcracks:

[0109]

[0110] Parameter meaning:

[0111] σ: Applied stress (MPa, typical compression force 5–15 MPa)

[0112] σ y : Material yield strength (fluororubber: 5–10 MPa)

[0113] α = 0.1–0.3

[0114] m = 1.5–2.0 (experimentally calibrated)

[0115] Taking into account the effects of chemical corrosion, electrochemical corrosion, stress accelerated corrosion, aging time t aging and environmental factors (temperature T, pH value, humidity H, stress σ), the final equation for adjusting the unified parameter is:

[0116]

[0117] Time-varying parameter model in the equation:

[0118] Chemical corrosion parameter (dominated by H+ erosion):

[0119]

[0120] Electrochemical corrosion parameter (galvanic corrosion):

[0121]

[0122] Stress-accelerated corrosion parameter (microcrack propagation):

[0123]

[0124] Symbol definitions:

[0125] k F : Conversion coefficient between corrosion thickness loss and compaction force loss (determined by material mechanical properties);

[0126] k chem,0 , i corr,0 , α0: Initial corrosion parameter;

[0127] k C , k I , k α : Aging kinetic parameter;

[0128] α C , β C , γ C , φ C : Sensitivity indices of chemical corrosion to temperature, pH, humidity, and coupling terms, obtained by experimental calibration;

[0129] α I , β I , γ I , φ I : Sensitivity indices of electrochemical corrosion, obtained by experimental calibration;

[0130] α α , β α , γ α , φ α : Sensitivity indices of stress-accelerated corrosion, obtained by experimental calibration;

[0131] N, m: Reaction order and stress exponent (fluororubber: n = 0.5 - 1.0, m = 1.5 - 2.0);

[0132] σ y : Material yield strength (fluororubber: refer to relevant manuals).

[0133] Description:

[0134] Corrosion rate integration: The total corrosion rate is linearly superimposed by chemical, electrochemical, and stress-accelerated corrosion, and after integration, it is converted into the clamping force loss ΔF F (t) through k 腐蚀 (t).

[0135] Environment and aging coupling:

[0136] The time-varying parameters k chem , i corr , α are all regulated by the aging time t aging , temperature T, pH value, degree H, and the coupling term (pH·H) φ to characterize the multi-factor synergistic effect.

[0137] As a preferred implementation, vibration may cause fatigue damage to the material, which in turn affects the clamping force. Fatigue damage is usually related to the number of cycles, but here vibration may need to be regarded as a dynamic stress, related to time. In addition, the aging time t aging may accelerate the fatigue process of the material because the material properties (such as elastic modulus, strength) degrade with aging.

[0138] Taking into account the vibration stress amplitude σ v , vibration frequency f, aging time t aging , and the time-varying degradation of the material fatigue characteristics, the final equation for calculating ΔF vibration(t) is:

[0139]

[0140] Vibration fatigue damage model:

[0141] Based on the fatigue damage accumulation theory, it is assumed that the clamping force loss is related to the vibration stress amplitude

[0142] σv, vibration frequency f, time t, and aging time t aging are related.

[0143] The power-law term characterizes the non-linear effect of the stress amplitude on the damage

[0144] The exponential term exp(k N ·t aging ) describes the exponential decay of the material fatigue life with aging

[0145] Aging time coupling term: The power-law term is introduced to capture the acceleration effect of long-term aging on fatigue damage (t ref is the reference time scale)

[0146] Parameter definition kv: conversion coefficient of vibration damage and compaction force loss;

[0147] m: vibration stress sensitivity index (fluororubber: m ≈ 2 - 3);

[0148] k N : fatigue life aging attenuation rate constant;

[0149] p: long-term aging acceleration index (to be calibrated by experiment);

[0150] tref: aging time normalization constant (e.g., tref = 1000 h).

[0151] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for suppressing attenuation of the compression force of a PEM screw-compressed electrolytic cell stack, characterized in that: The specific steps include: S1: Based on the main factors of the compression force decay of the PEM screw compression electrolytic cell stack, a compression force decay model of the PEM screw compression electrolytic cell stack is established; S2: Model parameter calibration: Obtain the clamping force and corrosion depth parameters through accelerated aging experiments, vibration table tests, etc., consult relevant manual data, or assign empirical values ​​to determine the model parameters; S3: Model modification: numerically solve the PEM screw compression electrolytic cell stack compression force attenuation model, compare it with the experimental results, and adjust the model parameters; S4: Verification and re-iteration: Compare the prediction results of the revised model with the new experimental data. If the error exceeds the limit, repeat steps 2–3; S5: Based on the PEM screw compression electrolytic cell stack compression force attenuation model established in steps S1 to S4, a digital model highly similar to the physical entity is constructed in a virtual space; S6: Through real-time data exchange and analysis, the physical entity of the working parameters of the PEM screw compression system is monitored, analyzed and optimized, so as to delay the attenuation of the PEM screw compression force.

2. The method for suppressing attenuation of the compression force of a PEM screw-compressed electrolytic cell stack according to claim 1, characterized in that: The model equation for the attenuation of the compression force of the PEM screw pressing the electrolytic cell stack in step S1 is: F(t)=F0-ΔF 蠕变 (t)-ΔF 热应力 (t)-ΔF 腐蚀 (t)-ΔF 振动 (t) Among them, F0 is the initial pressing force.

3. The method for suppressing attenuation of the compression force of a PEM screw-compressed electrolytic cell stack according to claim 2, characterized in that: The ΔF 蠕变 (t) The calculation can be based on the basic creep equation to define the creep parameters as a function of the aging time and environmental factors, temperature T, and pH value. At the same time, the acceleration factors of temperature and chemical corrosion are introduced to calculate ΔF 蠕变 (t) Computational model construction.

4. The method for suppressing attenuation of the compression force of a PEM screw-compressed electrolytic cell stack according to claim 2, characterized in that: The ΔF 蠕变 (t) The calculation model equation is:

5. The method for suppressing attenuation of the compression force of a PEM screw-compressed electrolytic cell stack according to claim 2, characterized in that: Comprehensively consider chemical corrosion, electrochemical corrosion, stress accelerated corrosion, aging time t aging and environmental factors, and ΔF 腐蚀 (t) Computational model construction.

6. The method for suppressing attenuation of the compression force of a PEM screw-compressed electrolytic cell stack according to claim 2, characterized in that: The ΔF 腐蚀 (t) The calculation model equation is: Among them, the time-varying parameter equation of chemical corrosion parameters is: The time-varying parameter equation of electrochemical corrosion parameters is: The time-varying parameter equation of stress accelerated corrosion parameters is:

7. The method for suppressing attenuation of the compression force of a PEM screw-compressed electrolytic cell stack according to claim 2, characterized in that: The ΔF 振动 (t) The control equation for calculation is:

8. The method for suppressing attenuation of the compression force of a PEM screw-compressed electrolytic cell stack according to claim 2, characterized in that: The ΔF 热应力 (t) The control equation for calculation is:

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