Water quality dynamic regulation method in ultrapure water hydrogen production process

Abstract

The present application relates to the technical field of hydrogen production by electrolysis of water, and particularly relates to a water quality dynamic regulation method in hydrogen production by ultra-pure water, comprising: symmetrically arranging voltage monitoring points on both sides of a proton exchange membrane, synchronously collecting anode voltage signals and cathode voltage signals and conductivity at key positions, respectively establishing an electrochemical mirror baseline of water quality and a water quality change mirror baseline, determining water quality abnormalities by calculating the deviation of the two mirrors, combining the deviation direction of the electrochemical mirror and the change characteristics of the deviation of the water quality change mirror, accurately distinguishing four types of abnormalities, i.e. metal ion pollution on the anode side, scale ion accumulation on the cathode side, abnormality of the proton exchange membrane and sudden pollution of the water inlet, and locating the sources, and executing single-end reinforcement, synchronous reinforcement or protection strategies accordingly. The present application realizes early identification and targeted regulation of water quality abnormalities, and can effectively reduce water treatment energy consumption and prolong the service life of electrolytic cells.

Description

Technical Field

[0001] This invention relates to the field of hydrogen production technology through water electrolysis, and more particularly to a method for dynamic water quality control during the ultrapure water hydrogen production process. Background Technology

[0002] Proton exchange membrane (PEM) electrolysis for hydrogen production has become a core technology for renewable energy consumption and large-scale green hydrogen production due to its advantages such as fast response speed, high current density, and good hydrogen purity. Water quality is a key factor determining the operating efficiency and service life of PEM electrolyzers. The system requires a continuous supply of ultrapure water. Trace metal ions, scaling ions, and membrane degradation products can all poison the catalyst layer, clog the flow channels, or accelerate the aging of the proton exchange membrane, ultimately leading to irreversible performance degradation of the electrolyzer.

[0003] Current water quality control technologies largely rely on single-point conductivity monitoring at the anode inlet, which only reflects the overall quality of the influent and cannot distinguish between endogenous pollution such as anode-side plate corrosion, cathode-side ion concentration, and proton exchange membrane degradation, and exogenous pollution in the influent. Furthermore, it is difficult to accurately pinpoint the circuit and location of anomalies. Corresponding control strategies generally employ a one-size-fits-all approach of simultaneous purification across the entire system, resulting in unnecessary waste of water treatment energy and materials, and also exhibiting a lag in anomaly response. By the time conductivity indicators show significant abnormalities, the core components of the electrolyzer have already suffered irreversible damage. Therefore, developing a method capable of accurately identifying the type and source of water quality anomalies and achieving targeted dynamic control is of great significance for improving the operational stability and economy of PEM water electrolysis hydrogen production systems. Summary of the Invention

[0004] To address this issue, the present invention provides a method for dynamic water quality control during ultrapure water hydrogen production, which overcomes the problem in the prior art where electrochemical signals and water quality parameters are combined for analysis and collaborative determination of abnormal sources, resulting in an inability to accurately distinguish pollution types and control directions.

[0005] To achieve the above objectives, this invention provides a method for dynamic water quality control in the ultrapure water hydrogen production process, applicable to a PEM electrolysis water hydrogen production device comprising a PEM electrolyzer, a DC power supply, an anode-side water supply circuit, and a cathode-side return water circuit, comprising: Voltage signals at the anode monitoring point at the anode inlet and the corresponding cathode monitoring point at the cathode outlet are collected synchronously at a preset sampling frequency. Conductivity at the anode inlet, anode outlet and cathode outlet are also collected synchronously. The voltage signals of the anode and the cathode are extracted to obtain the anode ripple energy of the anode characteristic frequency band and the cathode ripple energy of the cathode characteristic frequency band. An energy mapping function between the anode ripple energy and the cathode ripple energy is established as a water quality electrochemical mirror baseline. The conductivity differences at the anode outlet, cathode outlet, and anode inlet were calculated to obtain the conductivity changes on the anode side and the cathode side, and a conductivity mapping function was established as a mirror baseline for water quality changes. The anode ripple energy, the cathode ripple energy, the change in conductivity on the anode side, and the change in conductivity on the cathode side are continuously determined to determine the electrochemical mirror deviation and the water quality change mirror deviation in order to determine whether the water quality is abnormal. Based on the anomaly determination results, the water quality anomaly type and anomaly source direction are determined according to the change characteristics of the electrochemical mirror deviation direction and the water quality change mirror deviation. Based on the type and direction of the water quality anomaly, corresponding water quality control strategies are implemented, including single-end enhancement strategies, simultaneous enhancement strategies, and protection strategies.

[0006] As a preferred technical solution for dynamic water quality control in the ultrapure water hydrogen production process, the anode monitoring point is set on the anode side plate of the electrolysis unit where the anode inlet is located, and the cathode monitoring point is set on the cathode side plate of the electrolysis unit where the cathode outlet is located. The anode monitoring point and the cathode monitoring point are arranged opposite each other with the proton exchange membrane as the plane of symmetry.

[0007] As a preferred technical solution for dynamic water quality control in the ultrapure water hydrogen production process, the steps for establishing the water quality electrochemical mirror baseline include: The anode ripple component of the anode characteristic frequency band and the cathode ripple component of the cathode characteristic frequency band are extracted from the voltage signals of the anode monitoring point and the cathode monitoring point, respectively. Calculate the anode ripple energy based on the anode ripple component, and calculate the cathode ripple energy based on the cathode ripple component. Using the anode ripple energy as the input and the cathode ripple energy as the output, an energy mapping function is established as the water quality electrochemical mirror baseline.

[0008] As a preferred technical solution for dynamic water quality control in the ultrapure water hydrogen production process, the step of establishing the water quality change mirror baseline includes: Calculate the difference between the anode outlet conductivity and the anode inlet conductivity to obtain the change in conductivity on the anode side; calculate the difference between the cathode outlet conductivity and the anode inlet conductivity to obtain the change in conductivity on the cathode side. Using the change in conductivity on the anode side as the input and the change in conductivity on the cathode side as the output, a conductivity mapping function is established as the mirror baseline of the water quality change.

[0009] As a preferred technical solution for dynamic water quality control in the ultrapure water hydrogen production process, determining the electrochemical mirror deviation and the water quality change mirror deviation includes: Within a preset time window, the anode ripple energy, the cathode ripple energy, the change in anode-side conductivity, and the change in cathode-side conductivity are continuously acquired at several sampling times. Based on the water quality electrochemical mirror baseline, the expected cathode ripple energy at each sampling time is obtained, and based on the water quality change mirror baseline, the expected cathode ripple energy at each sampling time is obtained. The difference between the cathode ripple energy at each sampling time and the corresponding expected cathode ripple energy is calculated to obtain the electrochemical mirror residual sequence. The difference between the change in cathode-side conductivity and the corresponding expected change in cathode-side conductivity is calculated to obtain the water quality change mirror residual sequence. The electrochemical mirror deviation is determined based on the relative average deviation of the electrochemical mirror residual sequence, and the water quality change mirror deviation is determined based on the relative average deviation of the water quality change mirror residual sequence.

[0010] As a preferred technical solution for dynamic water quality control in the ultrapure water hydrogen production process, determining whether water quality is abnormal based on the electrochemical mirror deviation and the water quality change mirror deviation includes: When the electrochemical mirror deviation exceeds a preset electrochemical deviation threshold, and / or the water quality change mirror deviation exceeds a preset water quality deviation threshold, it is determined that the water quality is abnormal. When both the electrochemical mirror deviation and the water quality change mirror deviation do not exceed the corresponding threshold, it is determined that the water quality is not abnormal.

[0011] As a preferred technical solution for dynamic water quality control in ultrapure water hydrogen production, in response to the determination result of abnormal water quality, the characteristics of the change in the direction of electrochemical mirror deviation and the mirror deviation of water quality change are determined, including: Calculate the arithmetic mean of the electrochemical mirror residual sequence, and determine the direction of deviation of the electrochemical mirror based on the sign of the arithmetic mean; The slope of the water quality change mirror residual sequence within the preset time window is calculated as the change characteristic of the water quality change mirror deviation; If the slope is greater than or equal to the preset trend threshold, the change characteristic of the water quality change mirror deviation is determined to be a positive change; otherwise, it is determined to be a change without trend.

[0012] As a preferred technical solution for dynamic water quality control in ultrapure water hydrogen production, determining the type and direction of water quality anomalies includes: When the water quality change mirror deviation is a positive change, if the direction of the electrochemical mirror deviation is positive, the water quality anomaly type is determined to be metal ion pollution on the anode side, and the source of the anomaly is the anode side water supply circuit; if the direction of the electrochemical mirror deviation is negative, the water quality anomaly type is scale ion accumulation on the cathode side, and the source of the anomaly is the cathode side return water circuit. When the water quality change mirror deviation is a trendless change, if the direction of the electrochemical mirror deviation is positive, the water quality anomaly type is determined to be a proton exchange membrane anomaly; if the direction of the electrochemical mirror deviation is negative, the water quality anomaly type is determined to be a sudden pollution of the influent water quality.

[0013] As a preferred technical solution for dynamic water quality control in ultrapure water hydrogen production, a corresponding water quality control strategy is implemented based on the type and direction of the water quality anomaly, including: In response to the metal ion contamination on the anode side, a single-end enhancement strategy on the anode side is implemented to adjust the operating parameters of the water purification unit in the anode side water supply circuit. In response to the accumulation of scale ions on the cathode side, a single-end enhancement strategy is implemented on the cathode side to adjust the operating parameters of the water purification unit in the cathode side return water circuit. In response to the sudden pollution of the influent water quality, the synchronous enhancement strategy is implemented, and the operating parameters of the water purification units in the anode-side water supply circuit and the cathode-side return water circuit are adjusted simultaneously. In response to the proton exchange membrane malfunction, the protection strategy is executed to reduce the operating load of the PEM electrolyzer or to stop the electrolysis process of the PEM electrolyzer.

[0014] As a preferred technical solution for dynamic water quality control in the ultrapure water hydrogen production process, the adjustment of operating parameters includes increasing the processing flow rate of the water purification unit or switching to a standby water purification unit.

[0015] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention constructs a collaborative judgment system for water quality electrochemical mirror baseline and water quality change mirror baseline through dual-dimensional fusion analysis of electrochemical signals and water quality parameters, enabling early identification, precise source tracing, and targeted regulation of water quality anomalies. Utilizing the coupling law of anode and cathode electrochemical responses, this invention can capture minute disturbances at the electrochemical level before water quality indicators show significant anomalies, shortening the anomaly identification lag time. Through a combination of deviation direction and change characteristics, it accurately distinguishes four types of operating conditions: anode metal ion contamination, cathode scaling accumulation, membrane anomalies, and sudden influent contamination, clearly identifying the anomaly source loop. Differentiated control strategies are implemented for different anomalies, avoiding energy waste in the entire system purification and reducing consumable consumption. Simultaneously, through protection strategies under membrane anomalies, damage to core components is reduced, the service life of the electrolyzer is extended, and the operational stability of the PEM water electrolysis hydrogen production system is effectively improved. Attached Figure Description

[0016] Figure 1 This is a flowchart of the water quality dynamic control method in the ultrapure water hydrogen production process according to an embodiment of the present invention; Figure 2 This is a flowchart illustrating the determination of electrochemical mirror deviation and water quality change mirror deviation in embodiments of the present invention. Figure 3 This is a logic diagram for determining whether water quality is abnormal in an embodiment of the present invention. Detailed Implementation

[0017] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0018] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0019] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0020] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0021] Please see Figures 1-3 As shown, this invention provides a method for dynamic water quality control in the ultrapure water hydrogen production process, applied to a PEM electrolysis water hydrogen production device including a PEM electrolyzer, a DC power supply, an anode-side water supply circuit, and a cathode-side return water circuit, comprising: Step S1: At a preset sampling frequency, the voltage signals of the anode monitoring point at the anode inlet and the corresponding cathode monitoring point at the cathode outlet are collected synchronously, and the conductivity of the anode inlet, anode outlet and cathode outlet are collected synchronously. Step S2: Perform feature extraction on the voltage signal of the anode and the voltage of the cathode to obtain the anode ripple energy of the anode characteristic frequency band and the cathode ripple energy of the cathode characteristic frequency band, and establish the energy mapping function between the anode ripple energy and the cathode ripple energy as the water quality electrochemical mirror baseline. Step S3: Calculate the conductivity difference between the anode outlet, cathode outlet and anode inlet respectively to obtain the conductivity change on the anode side and the conductivity change on the cathode side, and establish a conductivity mapping function as a mirror baseline for water quality changes; Step S4: Continuously determine the anode ripple energy, the cathode ripple energy, the change in anode-side conductivity, and the change in cathode-side conductivity, and determine the electrochemical mirror deviation and the water quality change mirror deviation to determine whether the water quality is abnormal; Step S5: Based on the anomaly determination results, determine the water quality anomaly type and anomaly source direction according to the change characteristics of the electrochemical mirror deviation direction and the water quality change mirror deviation. Step S6: Based on the type of water quality anomaly and the direction of the anomaly source, execute the corresponding water quality control strategy. The water quality control strategy includes a single-end enhancement strategy, a synchronous enhancement strategy, and a protection strategy.

[0022] In this embodiment, the PEM electrolysis water production equipment includes a PEM electrolyzer, a DC power supply, an anode-side water supply circuit, and a cathode-side return water circuit. The anode-side water supply circuit is used to supply ultrapure water to the anode side of the PEM electrolyzer, and the cathode-side return water circuit is used to receive and return water discharged from the cathode side.

[0023] In order to enable the collected data to simultaneously reflect the electrochemical response and water quality changes, this embodiment sets an anode monitoring point on the anode side plate of the electrolysis unit where the anode inlet is located, and sets a cathode monitoring point on the cathode side plate of the electrolysis unit where the cathode outlet is located, and sets the anode monitoring point and cathode monitoring point opposite each other with the proton exchange membrane as the axis of symmetry.

[0024] Understandably, the two voltage monitoring points correspond to the anode and cathode regions on either side of the proton exchange membrane within the same electrolysis unit, respectively. This reduces the impact of structural, flow field, and load differences between different electrolysis units on the subsequent establishment of mirror relationships. The PEM electrolyzer is composed of multiple electrolysis units stacked in series. The water quality state within each electrolysis unit varies along the flow channel. The anode-side water quality of the electrolysis unit near the inlet is closest to the original inlet water quality, while the cathode-side water quality of the electrolysis unit near the outlet reflects the return water quality accumulated throughout the flow channel. Furthermore, since the anode-side supply circuit and the cathode-side return water circuit form a counter-flow relationship within the electrolysis unit, the data obtained with the proton exchange membrane as the plane of symmetry is the most representative of the water quality.

[0025] In implementation, the preset sampling frequency is determined based on the ripple characteristics of the voltage signal and the rate of change of water quality parameters. Since the voltage signals from the anode and cathode monitoring points are used to extract the anode ripple energy of the anode characteristic frequency band and the cathode ripple energy of the cathode characteristic frequency band, their sampling frequency should be able to cover the DC power supply output ripple and its electrochemical response frequency range formed within the PEM electrolyzer, satisfying the Nyquist sampling theorem to fully preserve the ripple characteristics. Specifically, under normal water quality and stable operating conditions, the raw voltage signals from the anode and cathode monitoring points can be collected, and spectral analysis can be performed on the raw voltage signals to determine the main ripple frequencies and their corresponding characteristic frequency bands; then, the sampling frequency of the voltage signal is determined based on the upper limit frequency of the characteristic frequency band.

[0026] When the characteristic frequency band obtained from calibration is in the range of tens to hundreds of hertz, the sampling frequency of the voltage signal can be selected as 1 kHz, 2 kHz or 5 kHz. The actual sampling frequency is determined by the DC power supply output characteristics, the impedance characteristics of the PEM electrolytic cell and the characteristic frequency band obtained from the calibration results.

[0027] The sampling frequency of conductivity is lower than that of voltage signals, but the collected data are synchronized with voltage signals using the same clock source or the same timestamp rule. Conductivity reflects the changes in water quality caused by water circulation and transmembrane migration, and its rate of change is lower than that of voltage ripple signals, so it does not need to be continuously collected using the high-frequency sampling method of voltage signals.

[0028] In practice, the voltage signal can be formed into a continuous voltage sampling sequence at a higher sampling frequency, and the conductivity can be formed into water quality sampling data according to a preset water quality sampling period. The voltage ripple energy and conductivity within the same water quality sampling period are then matched with a set of synchronous sampling data using timestamps. Generally, conductivity is collected with a sampling period of 30s to 60s. The specific sampling period is determined when a known water quality change occurs in the anode-side water supply circuit or the cathode-side return water circuit. The response time of conductivity is recorded, and a sampling period that reflects the response process is selected.

[0029] Under healthy and stable operating conditions, there is an inherent coupling relationship between changes in anode and cathode water quality at the electrical signal level. The charge transfer process of the oxygen evolution reaction at the anode is sensitive to impurities such as metal ions, mainly affecting the mid-to-high frequency range of voltage ripple. The mass transfer process of the hydrogen evolution reaction at the cathode is sensitive to substances such as organic acid radicals and scale ions, mainly affecting the low frequency range of voltage ripple. Under normal operating conditions, there is a stable correspondence between the ripple energy changes of the two.

[0030] In implementation, the anode ripple component and cathode ripple component of the anode characteristic frequency band are extracted from the voltage signals of the anode monitoring point and the cathode characteristic frequency band, respectively. The anode and cathode characteristic frequency bands can be determined through a limited number of calibration tests. Specifically, when the PEM water electrolysis hydrogen production equipment is operating under normal water quality conditions, the voltage signals of the anode and cathode monitoring points are collected, and the voltage signals are subjected to spectrum analysis. The frequency range that exists simultaneously on both the anode and cathode sides and can reflect the DC power supply ripple transmission and the electrochemical response of the electrolysis unit is selected as the characteristic frequency band.

[0031] For example, when the main ripple of a DC power supply is concentrated near a certain switching frequency and its low-order harmonics, the frequency range near the switching frequency can be used as the anode characteristic frequency band and the cathode characteristic frequency band. The upper and lower limits of the characteristic frequency band can be determined based on the distribution of the spectral peak in multiple normal operation data. Generally, a fixed bandwidth on both sides of the center frequency of the spectral peak is taken, or a frequency range that can cover the main energy distribution of the peak is taken.

[0032] After extracting the anode and cathode ripple components, the anode ripple energy and cathode ripple energy are calculated separately. During calculation, the anode ripple energy can be obtained by energy integration or sum of squares of the anode ripple component within the anode characteristic frequency band; similarly, the cathode ripple energy can be obtained. Using the anode ripple energy as the input and the cathode ripple energy as the output, an energy mapping function between the anode and cathode ripple energies is established, and this energy mapping function is used as the water quality electrochemical mirror baseline. This energy mapping function can be obtained by linear regression, piecewise linear fitting, or polynomial fitting of multiple sets of synchronously sampled data under normal water quality conditions.

[0033] Generally, when the anode ripple energy and the cathode ripple energy are approximately linearly related within the normal operating range, a linear regression can be used to establish an energy mapping function; when the relationship between the two differs under different load ranges, a segmented mapping relationship can be established according to the DC power supply output state or the electrolytic cell operating state.

[0034] During the operation of PEM electrolyzers, there are fixed patterns of water and ion migration across the membrane. There is a stable proportional relationship between the water quality changes on the anode side caused by membrane degradation and bipolar plate corrosion and the water quality changes on the cathode side caused by ion concentration and transmembrane migration.

[0035] Furthermore, the water quality change at the anode outlet is a cumulative change in the water quality at the anode inlet after passing through the anode flow channel. After entering the anode flow channel, ultrapure water flows through the proton exchange membrane, catalyst layer, anode-side electrode plate, and adjacent flow channel structures under high potential, acidic, and oxidizing conditions on the anode side. If the proton exchange membrane degrades, fluoride ions can be released into the anode-side water; if the anode-side electrode plate or related metal components corrode, titanium ions or other metal ions can be released into the anode-side water. Therefore, the anode outlet reflects the endogenous water quality changes superimposed after the ultrapure water flows through the electrochemical region on the anode side.

[0036] The water quality changes at the cathode outlet are the result of the combined effects of transmembrane migration and the accumulation of cathode-side return water. Water and some ionic components from the anode side can migrate to the cathode side under the influence of membrane interface interactions, concentration gradients, electric fields, and water migration. The ionic components migrating to the cathode side are transported along the cathode flow channel with the cathode-side return water, forming a concentrated reflection of the accumulated water quality state at the cathode outlet. For scaling-related ions such as calcium and magnesium ions, their main sources can be influent residues, precipitation from system materials, or external contaminant input; when these ions enter the cathode-side return water, the cathode outlet can reflect their accumulated state within the cathode-side flow channel.

[0037] Therefore, the anode outlet reflects the release of endogenous pollutants after the anode side flows through the electrolysis unit, while the cathode outlet reflects the cumulative water quality status after transmembrane migration and cathode side return water transport. Using the anode inlet as a common baseline, and calculating the conductivity changes of the anode and cathode outlets relative to the anode inlet separately, the water quality changes on both the anode and cathode sides are established on the same influent water quality basis, thus providing a physical basis for establishing a mirror baseline for water quality changes.

[0038] Under normal and stable operating conditions, the ripple energy of the anode and the ripple energy of the cathode, as well as the changes in conductivity on the anode and the cathode sides, will exhibit small random fluctuations around the corresponding mirror baseline, and the fluctuations of the residual sequence will remain at a low level. When the water quality changes abnormally, the coupling relationship between the parameters on both sides will be systematically broken, the dispersion of the residuals will show a continuous increasing trend, and the relative average deviation will also increase significantly.

[0039] Specifically, the anode ripple energy, cathode ripple energy, anode-side conductivity change, and cathode-side conductivity change are continuously acquired at several sampling moments according to a preset time window. The preset time window can be determined based on the voltage ripple feature extraction period and the water quality parameter response time. A limited number of stable operation tests are conducted under normal water quality conditions, recording the fluctuations in voltage ripple energy and conductivity changes within different time windows. A time window that covers the water quality parameter response process without excessively delaying anomaly identification is selected. Generally, the preset time window is 5 min to 10 min.

[0040] At each sampling moment, the current anode ripple energy is input into the energy mapping function corresponding to the water quality electrochemical mirror baseline to obtain the expected cathode ripple energy at that sampling moment. Then, the difference between the current cathode ripple energy and the expected cathode ripple energy is calculated to obtain the electrochemical mirror residual at that sampling moment. Multiple electrochemical mirror residuals are arranged according to the sampling moment order within a preset time window to obtain an electrochemical mirror residual sequence.

[0041] The current change in anode-side conductivity is input into the conductivity mapping function corresponding to the water quality change mirror baseline to obtain the expected change in cathode-side conductivity at that sampling moment. The difference between the current change in cathode-side conductivity and the expected change in cathode-side conductivity is calculated to obtain the water quality change mirror residual at that sampling moment. Multiple water quality change mirror residuals are arranged in the order of sampling moments within a preset time window to obtain a water quality change mirror residual sequence.

[0042] To quantify the overall deviation of the residual sequence, this implementation method uses the relative average deviation as a statistical indicator. The relative average deviation is calculated as the ratio of the sum of the absolute values ​​of all residuals in the residual sequence to the number of residuals, then divided by the mean of the corresponding measured values ​​of the residual sequence. The resulting relative average deviation of the electrochemical mirror residual sequence is the electrochemical mirror deviation, and the relative average deviation of the water quality change mirror residual sequence is the water quality change mirror deviation. In this invention, the electrochemical mirror deviation and water quality change mirror deviation determined by the relative average deviation can reduce the influence of single-point sampling noise, gas-liquid disturbance, instantaneous fluctuation of DC power supply and local fluctuation of water flow on the judgment of anomalies, so that the deviation can reflect the continuous deviation state of the mirror relationship over a period of time, and make the deviation comparable in different load ranges.

[0043] In this embodiment, water quality anomaly determination is based on both electrochemical mirror deviation and water quality change mirror deviation. This setup aims to avoid relying solely on voltage ripple signals or water quality parameter signals for judgment, allowing anomaly determination to simultaneously consider deviations in both electrochemical response and water quality change. When at least one of the electrochemical mirror deviation or water quality change mirror deviation exceeds its corresponding threshold, it indicates that the current operating state has deviated from the normal mirror baseline, thus determining that water quality is abnormal. When neither exceeds its corresponding threshold, it indicates that both the current electrochemical response and water quality change are within the normal mirror relationship range, thus determining that water quality is not abnormal.

[0044] Specifically, the preset electrochemical deviation threshold can be determined based on the distribution of electrochemical mirror image deviation under normal water quality conditions. Specifically, after the PEM water electrolysis hydrogen production equipment completes rinsing and circulation and is in a stable operating state, a limited number of normal water quality samples are collected. All electrochemical mirror image deviation and water quality change mirror image deviation data are collected after the system has been running continuously for 72 hours under healthy and stable operating conditions. The average value of the electrochemical mirror image deviation under normal water quality conditions plus three standard deviations is used as the preset electrochemical deviation threshold, and the average value of the water quality change mirror image deviation under normal conditions plus three standard deviations is used as the preset water quality deviation threshold. Generally, the preset electrochemical deviation threshold is 0.08–0.10, and the preset water quality deviation threshold is 0.1–0.12.

[0045] During the operation, within each preset time window, the electrochemical mirror deviation and the water quality change mirror deviation are first calculated, and then compared with preset electrochemical deviation thresholds and preset water quality deviation thresholds, respectively. When the electrochemical mirror deviation exceeds the preset electrochemical deviation threshold, it indicates that the cathode-side voltage ripple response has deviated from the water quality electrochemical mirror baseline; when the water quality change mirror deviation exceeds the preset water quality deviation threshold, it indicates that the cathode-side conductivity change has deviated from the water quality change mirror baseline. As long as either of the above deviations exceeds the corresponding threshold, the water quality is determined to be abnormal, and the abnormality determination result is provided to the subsequent cross-validation steps for the water quality abnormality type and the direction of the abnormality source.

[0046] In practice, for the deviation direction of the electrochemical mirror image, the arithmetic mean of the electrochemical mirror image residual sequence within the current preset time window is directly calculated. If the arithmetic mean is positive, it indicates that the measured value of the cathode ripple energy within this time window is generally higher than the expected value obtained from the anode ripple energy through the energy mapping function, and the deviation direction of the electrochemical mirror image is positive; if the arithmetic mean is negative, it indicates that the measured value of the cathode ripple energy is generally lower than the expected value, and the deviation direction is negative.

[0047] To determine the characteristics of water quality change mirror deviation, the slope of the water quality change mirror residual sequence within the current preset time window is calculated. The slope can be obtained by performing linear regression on the residual values ​​at each sampling time within the time window; the slope of the regression line is the change characteristic value. A preset trend threshold is used to distinguish the significance level of the slope. If the slope is greater than or equal to the preset trend threshold, it indicates that the residual shows a continuous increasing trend within the time window, and is judged as a positive change; if the slope is less than the preset trend threshold, it indicates that the residual does not show a continuous increasing trend, and is judged as a no-trend change. The preset trend threshold is determined by continuously collecting water quality change mirror residual sequences for multiple time windows under normal water quality conditions, calculating the slope of each time window, and taking the 95th percentile of the absolute value sequence of the slope under normal conditions as the reference value of the preset trend threshold. Generally, the preset trend threshold is 0.05 to 0.15.

[0048] Understandably, based on the actual operating patterns of PEM water electrolysis hydrogen production equipment, under normal abnormal operating conditions, the water quality parameters on both the anode and cathode sides almost always only increase and never continuously decrease. Metal ion contamination on the anode side originates from plate corrosion or the release of membrane degradation products, leading to an increase in anode outlet conductivity. Scale accumulation on the cathode side results from the continuous concentration of transmembrane migrating ions, also leading to an increase in cathode outlet conductivity. Membrane degradation releases components such as fluoride ions into the anode water, similarly causing an increase in water quality parameters. Sudden influent contamination occurs when additional ions are introduced from upstream into the system, also manifesting as an increase in water quality parameters. Therefore, within the preset time window, the mirror residual of water quality changes almost never shows a continuous negative change. If, in rare cases, a negative slope is observed in the residual sequence and its absolute value exceeds the preset trend threshold (i.e., a negative change occurs), it can be classified as a no-trend change and processed accordingly, or the sensor self-check process can be triggered to rule out measurement link anomalies, rather than being used as the sole basis for anomaly type determination.

[0049] The effects of water quality anomalies from different sources on the electrochemical responses of anodes and cathodes and water quality parameters vary significantly over time. These differences lead to corresponding combinations of deviation directions and change characteristics, which enable accurate differentiation of anomaly types and their sources.

[0050] Specifically, when the electrochemical mirror deviation is positive and the water quality change mirror deviation is also positive, metal ion pollution on the anode side causes an instantaneous change in the charge transfer impedance of the oxygen evolution reaction. This electrochemical disturbance is transmitted to the cathode side via the proton exchange membrane, enhancing the overpotential ripple response of the cathode hydrogen evolution reaction. Simultaneously, metal ions continuously migrate across the membrane under the influence of the electric field and concentration gradient, causing the ion load on the cathode side to continuously increase within the time window, resulting in a positive change in the water quality change mirror residual. The synergistic combination of enhanced electrochemical response and increased water quality parameters points to the release of endogenous pollution on the anode side and its continuous migration to the cathode side, indicating that the abnormal source is the anode side water supply circuit.

[0051] When the electrochemical mirror image deviation is negative and the water quality change mirror image deviation is positive, scale ions on the cathode side continuously concentrate in the return water loop. Once the concentration of calcium and magnesium ions exceeds the solubility limit, they deposit on the cathode catalyst surface, covering active sites and hindering mass transfer pathways. This suppresses charge transfer and mass transfer processes in the cathode hydrogen evolution reaction, resulting in a negative deviation of the cathode ripple energy. Simultaneously, the physical concentration of scale ions in the cathode-side return water causes a continuous increase in conductivity, leading to a positive change in the water quality change mirror image residual. This inverse combination of weakened electrochemical response and increased water quality parameters points to internal scale accumulation on the cathode side, indicating the abnormal source is the cathode-side return water loop.

[0052] When the electrochemical mirror deviation is positive and the water quality change mirror deviation shows no trend, the proton exchange membrane (PEM) degradation releases fluoride ions and organic acid anions, altering the electrochemical state and double-layer structure of the anode interface. This interfacial impedance change causes a positive deviation in the cathode ripple response through electrochemical coupling. However, the amount of released substances is limited in the early stages of membrane degradation, and the transmembrane migration rate of degradation products is lower than that of metal ions. Within the preset time window, a detectable ion concentration accumulation trend has not yet formed on the cathode side, and the water quality change mirror residual does not show a continuous increasing trend. The combination of electrochemical response preceding water quality change points to an anomaly in the membrane material inside the PEM electrolyzer, and the source of the anomaly is determined to be inside the PEM electrolyzer.

[0053] When the electrochemical mirror deviation is negative and the water quality change mirror deviation shows no trend, a sudden pollution event in the influent enters both the anode and cathode circuits simultaneously via the front end of the anode-side water supply circuit within a short period. This external pollutant rapidly interferes with the mass transfer conditions of the cathode catalyst layer, causing a negative deviation in the overpotential ripple response of the cathode hydrogen evolution reaction. However, because the pollution enters both circuits simultaneously, the conductivity difference mapping between the anode inlet and cathode outlet has not yet formed a stable deviation within the time window, and the water quality change mirror residual does not show a continuous trend. This combination of prior electrochemical response and an unbroken water quality mapping relationship points to a sudden upstream external pollution event, with the abnormal source determined to be the front end of the anode-side water supply circuit.

[0054] Water quality anomalies from different sources have different diffusion paths and impact mechanisms. Pollution generated on the anode side mainly diffuses to the cathode through transmembrane migration, while pollution generated on the cathode side mainly accumulates in the return water loop. Influent pollution can affect both loops simultaneously, and internal membrane anomalies require priority protection of core components rather than simply purifying the water.

[0055] Specifically, when the contamination is determined to be metal ion pollution on the anode side, the pollution source is located inside the anode side, and metal ions are released into the anode side water flow through electrode corrosion or catalyst layer degradation. In this case, a single-end enhancement strategy is implemented on the anode side. Only the operating parameters of the water purification unit within the anode side supply circuit are adjusted, increasing the circulation flow rate of the water purification unit in that circuit to enhance the removal capacity of metal ions. The cathode side return water circuit maintains its original operating parameters because no independent pollution accumulation has yet formed on the cathode side, requiring no additional treatment.

[0056] When scale ion accumulation is detected on the cathode side, the source of contamination is located inside the cathode side, where calcium and magnesium ions continuously concentrate and may deposit in the cathode return water circuit. In this case, a single-end enhancement strategy is implemented on the cathode side. Only the operating parameters of the water purification unit within the cathode-side return water circuit are adjusted, increasing the flow distribution ratio of the cathode-side water purification unit. This allows more return water to pass through the ion exchange unit to remove scale ions before returning to the circulation. The operating parameters of the anode-side water supply circuit remain unchanged.

[0057] When a sudden pollution event is detected in the influent, pollutants enter both the anode and cathode side circuits simultaneously from the upstream water treatment system via the anode inlet, affecting both sides. In this situation, a simultaneous enhancement strategy is implemented, adjusting the operating parameters of the water purification units in both the anode-side supply circuit and the cathode-side return circuit. This increases the treatment intensity on both sides, rapidly reducing the concentration of external pollutants in the circulating water and shortening the residence time of pollutants within the water system.

[0058] In practice, the polishing mixed bed is a water purification unit in the anode-side water supply circuit, used to remove impurities such as metal ions from the anode circulating water. The bypass fine treatment branch is a water purification unit in the cathode-side return water circuit, used to remove scale ions and other impurities from the cathode return water.

[0059] When adjusting the operating parameters of the anode-side purification unit, the adjustment range is determined based on the degree to which the change in anode-side conductivity deviates from the normal range. A greater deviation results in a larger flow rate increase. The calculation determines the extent to which the change in anode-side conductivity within the current preset time window exceeds the average change in anode-side conductivity under normal operating conditions. The average and fluctuation range under normal operating conditions are recorded when establishing the water quality change mirror baseline. The deviation equals the current value minus the normal average, and the degree of deviation is determined by the ratio of the deviation to the normal average. The average change in anode-side conductivity under normal operating conditions is determined based on the anode-side conductivity change corresponding to the expected change in cathode-side conductivity given by the water quality change mirror baseline.

[0060] When adjusting the operating parameters of the cathode-side purification unit, the increase in the shunt ratio is determined based on the deviation of the change in cathode-side conductivity. The calculation considers the change in cathode-side conductivity within the current preset time window and its excess relative to the average change in cathode-side conductivity under normal operating conditions. The method for determining the average and fluctuation range under normal operating conditions is the same as that for the anode side.

[0061] During simultaneous enhancement, the flow rate increase or split ratio increase on both sides is synchronously matched according to the slope ratio of the conductivity mapping function. This slope characterizes the proportional relationship between the change in conductivity on the anode side and the change in conductivity on the cathode side under normal operating conditions. During simultaneous enhancement, if the flow rate increase on the anode side is ΔA, then the flow rate increase on the cathode side is ΔC = ΔA × k, where k is the slope value. Under normal operating conditions, the ion loading ratio on both sides is determined by the transmembrane migration law of water, which is consistent with the conductivity mapping slope k. Therefore, using k as the matching ratio of the purification capacity increase on both sides can maintain the relative proportion of the treatment intensity increase on both sides consistent with the normal coupling law, avoiding excessive treatment on one side that disrupts the original balance.

[0062] When a proton exchange membrane (PEM) malfunction is detected, the source of contamination is the degradation or damage to the membrane material itself. This is a problem inherent to the equipment and cannot be resolved through purification methods within the water treatment system. Continuing normal electrolysis operation may accelerate membrane damage or further deteriorate the purity of the produced gas. In this case, a protection strategy should be implemented, reducing the operating load of the PEM electrolyzer and lowering the DC power output to the minimum safe limit to reduce ion migration flux and mechanical stress on the membrane. If the membrane malfunction is severe or the deviation does not return to normal after load reduction, the electrolysis process should be further stopped, and the membrane condition should be checked offline or replaced.

[0063] The processing capacity of a water purification unit is directly related to its operating parameters. Within a certain range, increasing the processing flow rate can increase the amount of impurities removed per unit time, while switching to a standby water purification unit can provide sufficient purification margin when the main unit's processing capacity is insufficient.

[0064] During operation, increasing the flow rate of the water purification unit is suitable for mild to moderate water quality anomalies, rapidly improving purification efficiency without interrupting system operation. Switching to the standby water purification unit involves switching the water flow from the operating main unit to the standby unit via a valve. This is suitable for severe water quality anomalies or when the main unit is nearing saturation, providing stronger purification capacity and longer continuous operation time. The switching trigger for the standby water purification unit is when the conductivity difference between the inlet and outlet of the main unit falls below a preset value, which is determined based on the characteristics of the purification material and the system's water quality requirements.

[0065] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for dynamic water quality control in ultrapure water hydrogen production, applied to a PEM electrolysis water production device including a PEM electrolyzer, a DC power supply, an anode-side water supply circuit, and a cathode-side return water circuit, characterized in that, include: Voltage signals at the anode monitoring point at the anode inlet and the corresponding cathode monitoring point at the cathode outlet are collected synchronously at a preset sampling frequency. Conductivity at the anode inlet, anode outlet and cathode outlet are also collected synchronously. The voltage signals of the anode and the cathode are extracted to obtain the anode ripple energy of the anode characteristic frequency band and the cathode ripple energy of the cathode characteristic frequency band. An energy mapping function between the anode ripple energy and the cathode ripple energy is established as a water quality electrochemical mirror baseline. The conductivity differences at the anode outlet, cathode outlet, and anode inlet were calculated to obtain the conductivity changes on the anode side and the cathode side, and a conductivity mapping function was established as a mirror baseline for water quality changes. The anode ripple energy, the cathode ripple energy, the change in conductivity on the anode side, and the change in conductivity on the cathode side are continuously determined to determine the electrochemical mirror deviation and the water quality change mirror deviation in order to determine whether the water quality is abnormal. Based on the anomaly determination results, the water quality anomaly type and anomaly source direction are determined according to the change characteristics of the electrochemical mirror deviation direction and the water quality change mirror deviation. Based on the type and direction of the water quality anomaly, corresponding water quality control strategies are implemented, including single-end enhancement strategies, simultaneous enhancement strategies, and protection strategies.

2. The method for dynamic water quality control in the ultrapure water hydrogen production process according to claim 1, characterized in that, The anode monitoring point is set on the anode side plate of the electrolysis unit where the anode inlet is located, and the cathode monitoring point is set on the cathode side plate of the electrolysis unit where the cathode outlet is located. The anode monitoring point and the cathode monitoring point are arranged opposite each other with the proton exchange membrane as the plane of symmetry.

3. The method for dynamic water quality control in the ultrapure water hydrogen production process according to claim 2, characterized in that, The steps for establishing the aforementioned water quality electrochemical mirror baseline include: The anode ripple component of the anode characteristic frequency band and the cathode ripple component of the cathode characteristic frequency band are extracted from the voltage signals of the anode monitoring point and the cathode monitoring point, respectively. Calculate the anode ripple energy based on the anode ripple component, and calculate the cathode ripple energy based on the cathode ripple component. Using the anode ripple energy as the input and the cathode ripple energy as the output, an energy mapping function is established as the water quality electrochemical mirror baseline.

4. The method for dynamic water quality control in the ultrapure water hydrogen production process according to claim 1, characterized in that, The steps for establishing the water quality change mirror baseline include: Calculate the difference between the anode outlet conductivity and the anode inlet conductivity to obtain the change in conductivity on the anode side; calculate the difference between the cathode outlet conductivity and the anode inlet conductivity to obtain the change in conductivity on the cathode side. Using the change in conductivity on the anode side as the input and the change in conductivity on the cathode side as the output, a conductivity mapping function is established as the mirror baseline of the water quality change.

5. The method for dynamic water quality control in the ultrapure water hydrogen production process according to claim 4, characterized in that, Determining the electrochemical mirror image deviation and the water quality change mirror image deviation includes: Within a preset time window, the anode ripple energy, the cathode ripple energy, the change in anode-side conductivity, and the change in cathode-side conductivity are continuously acquired at several sampling times. Based on the water quality electrochemical mirror baseline, the expected cathode ripple energy at each sampling time is obtained, and based on the water quality change mirror baseline, the expected cathode ripple energy at each sampling time is obtained. The difference between the cathode ripple energy at each sampling time and the corresponding expected cathode ripple energy is calculated to obtain the electrochemical mirror residual sequence. The difference between the change in cathode-side conductivity and the corresponding expected change in cathode-side conductivity is calculated to obtain the water quality change mirror residual sequence. The electrochemical mirror deviation is determined based on the relative average deviation of the electrochemical mirror residual sequence, and the water quality change mirror deviation is determined based on the relative average deviation of the water quality change mirror residual sequence.

6. The method for dynamic water quality control in the ultrapure water hydrogen production process according to claim 5, characterized in that, Determining whether water quality is abnormal based on the electrochemical mirror deviation and the water quality change mirror deviation includes: When the electrochemical mirror deviation exceeds a preset electrochemical deviation threshold, and / or the water quality change mirror deviation exceeds a preset water quality deviation threshold, it is determined that the water quality is abnormal. When both the electrochemical mirror deviation and the water quality change mirror deviation do not exceed the corresponding threshold, it is determined that the water quality is not abnormal.

7. The method for dynamic water quality control in the ultrapure water hydrogen production process according to claim 6, characterized in that, In response to the determination of the abnormal water quality, the characteristics of the change in the direction of the electrochemical mirror image deviation and the mirror image deviation of the water quality change are determined, including: Calculate the arithmetic mean of the electrochemical mirror residual sequence, and determine the direction of deviation of the electrochemical mirror based on the sign of the arithmetic mean; The slope of the water quality change mirror residual sequence within the preset time window is calculated as the change characteristic of the water quality change mirror deviation; If the slope is greater than or equal to the preset trend threshold, the change characteristic of the water quality change mirror deviation is determined to be a positive change; otherwise, it is determined to be a change without trend.

8. The method for dynamic water quality control in the ultrapure water hydrogen production process according to claim 7, characterized in that, Determining the type and direction of the water quality anomaly includes: When the water quality change mirror deviation is a positive change, if the direction of the electrochemical mirror deviation is positive, the water quality anomaly type is determined to be metal ion pollution on the anode side, and the source of the anomaly is the anode side water supply circuit; if the direction of the electrochemical mirror deviation is negative, the water quality anomaly type is scale ion accumulation on the cathode side, and the source of the anomaly is the cathode side return water circuit. When the water quality change mirror deviation is a trendless change, if the direction of the electrochemical mirror deviation is positive, the water quality anomaly type is determined to be a proton exchange membrane anomaly; if the direction of the electrochemical mirror deviation is negative, the water quality anomaly type is determined to be a sudden pollution of the influent water quality.

9. The method for dynamic water quality control in the ultrapure water hydrogen production process according to claim 8, characterized in that, Based on the type and direction of the water quality anomaly, implement corresponding water quality control strategies, including: In response to the metal ion contamination on the anode side, a single-end enhancement strategy on the anode side is implemented to adjust the operating parameters of the water purification unit in the anode side water supply circuit. In response to the accumulation of scale ions on the cathode side, a single-end enhancement strategy is implemented on the cathode side to adjust the operating parameters of the water purification unit in the cathode side return water circuit. In response to the sudden pollution of the influent water quality, the synchronous enhancement strategy is implemented, and the operating parameters of the water purification units in the anode-side water supply circuit and the cathode-side return water circuit are adjusted simultaneously. In response to the proton exchange membrane malfunction, the protection strategy is executed to reduce the operating load of the PEM electrolyzer or to stop the electrolysis process of the PEM electrolyzer.

10. The method for dynamic water quality control in the ultrapure water hydrogen production process according to claim 9, characterized in that, The adjustment of operating parameters includes increasing the processing flow rate of the water purification unit or switching to a standby water purification unit.

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