Anode protection potential adaptive control method for concentrated sulfuric acid equipment

Abstract

The application discloses a kind of concentrated sulfuric acid equipment anode protection potential self-adaptive control method, obtains the reference potential of multiple reference electrodes, the output current of multiple cathode groups and acid temperature, acid concentration and acid flow;Through limited exploratory current on-line identification stable passivation potential window, and according to the passivation potential window of each protection area is predicted according to concentrated sulfuric acid working condition and flow propagation state;According to the dynamic response of multiple reference electrodes, determine the reliable protection potential, establish the potential influence relationship of cathode group and protection area by changing the output of cathode group respectively;Accordingly determine the target protection potential and protection demand of each area, adjust the output current of corresponding cathode group, and continuously update control parameters according to the response after adjustment, realize the closed-loop adaptive control of concentrated sulfuric acid equipment anode protection potential.

Description

Technical Field

[0001] This invention relates to the field of concentrated sulfuric acid equipment technology, specifically to an adaptive control method for the anode protection potential of concentrated sulfuric acid equipment. Background Technology

[0002] Equipment such as concentrated sulfuric acid coolers, concentrated sulfuric acid delivery pipelines, and acid separators typically use stainless steel as the main material in contact with concentrated sulfuric acid. Anodic protection is used to create a passivation film on the metal surface to reduce the corrosion rate in the concentrated sulfuric acid environment. During anodic protection, the potential of the protected metal needs to be brought into and maintained within the stable passivation region. When the potential deviates from the stable passivation region, it may enter an activated or over-passivated state, reducing the protective effect of the passivation film. Existing anodic protection systems typically detect the potential of the protected equipment using a reference electrode, compare the detected potential with a pre-set control potential, and then adjust the output current using a potentiostat. For example, existing concentrated sulfuric acid equipment usually presets a corresponding protection potential based on the acid concentration and uses a control reference electrode for closed-loop control.

[0003] However, during the actual operation of concentrated sulfuric acid equipment, acid temperature, acid concentration, and acid flow rate can vary. Simultaneously, flow conditions, electrochemical states, and passivation film states may differ in different parts of the equipment, causing the actual stable passivation potential range to change with operating conditions. Existing methods using fixed or preset protection potentials as control targets are insufficient to determine the currently applicable stable passivation potential range in real time. Adjustments are typically made only after changes in operating conditions have already caused significant changes in the reference potential or output current. Existing data also indicates that the anolyte protection current changes significantly when acid concentration decreases or acid temperature increases. Therefore, when operating conditions fluctuate, a mismatch between the set protection potential and the actual passivation state can easily occur.

[0004] Furthermore, the actual protection status of different areas in a concentrated sulfuric acid (SSA) equipment is typically characterized by a limited number of reference electrodes. When the measurement status of the reference electrodes becomes abnormal or the actual potential distribution in different areas within the equipment changes, simply adjusting the overall output current based on the deviation between a certain reference potential and a given value is insufficient to accurately reflect the actual protection requirements of different areas. This can lead to situations where some areas are underprotected while other areas experience excessively high protection currents. Therefore, identifying the actual stable passivation state during equipment operation and adaptively determining the protection potential and adjusting the anodic protection current accordingly, based on changes in SSA operating conditions, the reliability of the reference potential, and the actual response of different areas to the protection current, is a key technical problem that needs to be solved in the anodic protection control of concentrated sulfuric acid (SSA) equipment. Summary of the Invention

[0005] The purpose of this invention is to provide an adaptive control method for the anode protection potential of a concentrated sulfuric acid equipment, which can determine the target protection potential and protection requirements of each area, adjust the output current of the corresponding cathode group, and continuously update the control parameters according to the adjusted response, thereby realizing closed-loop adaptive control of the anode protection potential of the concentrated sulfuric acid equipment.

[0006] To achieve the above objectives, the present invention proposes the following technical solution: an adaptive control method for the anodic protection potential of a concentrated sulfuric acid equipment, comprising the following steps: S1. Acquire anode protection status data and concentrated sulfuric acid operating condition data during the operation of the concentrated sulfuric acid equipment. The anode protection status data includes at least the reference potential detected by multiple reference electrodes set at different locations in the concentrated sulfuric acid equipment and the output current corresponding to multiple independently adjustable cathode groups. The concentrated sulfuric acid operating condition data includes at least the acid temperature, acid concentration and acid flow rate. S2. While the concentrated sulfuric acid equipment is under anode protection, apply a limited-amplitude test current disturbance based on the current anode protection working state. Identify the current stable passivation state of the concentrated sulfuric acid equipment based on the reference potential response and anode current response corresponding to the test current disturbance, and determine the stable passivation potential window corresponding to the current operating condition. S3. Based on the changes in acid temperature, acid concentration, and acid flow rate, as well as the flow propagation state of concentrated sulfuric acid in the equipment, determine the predicted time for the propagation of the changes in concentrated sulfuric acid operating conditions to different protection zones, and predict the stable passivation potential window of different protection zones at the corresponding predicted time based on the current stable passivation potential window. S4. Based on the dynamic potential response generated by multiple reference electrodes under the disturbance of the test current, the detection reliability of each reference electrode is judged, and the reliable protection potential corresponding to each protection area is determined based on the reference electrode whose reliability meets the requirements. S5. Change the output current of different cathode groups respectively, and obtain the potential change of each protection area. Based on the correspondence between the output current change of each cathode group and the potential change of each protection area, establish the potential influence relationship between the cathode group and the protection area. S6. Based on the predicted stable passivation potential window, reliable protection potential, and potential influence relationship of each protection area, determine the target protection potential and protection requirements of each protection area respectively, and adjust the output current of the corresponding cathode group according to the protection requirements so that the anode potential of different protection areas is kept within their respective stable passivation potential window. S7. Based on the reference potential response and anode current response after the cathode group output adjustment, update the stable passivation potential window, the reliability of the reference electrode detection, and the potential influence relationship between the cathode group and the protection area to form a closed-loop adaptive control of the anode protection potential.

[0007] Furthermore, in this invention, in step S1, the concentrated sulfuric acid equipment is divided into multiple protection areas according to the spatial position of multiple reference electrodes in the concentrated sulfuric acid equipment or their position along the flow direction of concentrated sulfuric acid, and a positional correspondence between the reference electrodes, the protection areas, and the cathode group is established. Before starting adaptive control, the initial protection potential is determined based on the current acid concentration and acid temperature of the concentrated sulfuric acid equipment, so that the concentrated sulfuric acid equipment first enters the preset safety protection state, and the preset safety protection state is used as the initial working state for online identification of the stable passivation potential window.

[0008] Furthermore, in this invention, in step S2, the test current disturbance includes sequentially applying a forward test current and a reverse test current based on the current anode protection output current, and restoring the anode protection output state before the disturbance after each test current is completed; The anode current required to maintain anode protection, the reference potential change corresponding to the change in test current, and the potential recovery state after the test current is removed are obtained under each test working state. Based on the magnitude of the current required to maintain anode protection, the local response relationship between the current change and the potential change, and the potential recovery characteristics, it is determined whether the current test working state belongs to a stable passivation state.

[0009] Furthermore, in this invention, multiple trial working states are sequentially selected near the current protection potential according to different potential directions, and the potential range corresponding to the continuous stable passivation working state is determined according to the anode current response and reference potential response corresponding to each trial working state. The two boundaries of the potential range are respectively determined as the lower boundary and upper boundary of the stable passivation potential window. If, during the testing process, the increase in anodic current exceeds the set value, a sudden change occurs in the local electrochemical response, the potential fails to recover within a specified time after the testing current is removed, or the testing potential reaches the preset safety boundary, the testing in the current direction is stopped, and the corresponding stable passivation potential window boundary is determined based on the previously obtained stable passivation working state.

[0010] Furthermore, in this invention, in step S3, the predicted time for concentrated sulfuric acid to propagate from the operating condition detection location to different protection areas is determined based on the equivalent acid volume that can be accommodated between the concentrated sulfuric acid operating condition detection location and each protection area, as well as the real-time acid flow rate. Based on the historical correlation between changes in acid temperature, acid concentration, and acid flow rate and changes in the stable passivation potential window, the upper and lower boundaries of the current stable passivation potential window are corrected to obtain the predicted stable passivation potential window when concentrated sulfuric acid reaches the corresponding protection area. After the actual concentrated sulfuric acid reaches the corresponding protection area, the historical correspondence is updated based on the deviation between the re-identified stable passivation potential window and the predicted stable passivation potential window.

[0011] Furthermore, in this invention, in step S4, the static potential deviation, potential response direction, dynamic response amplitude, response delay, and recovery characteristics after the removal of the test current are extracted for each reference electrode under the same test current disturbance. The degree of abnormality and detection reliability of each reference electrode are determined based on the deviation between the dynamic response characteristics of each reference electrode and the dynamic response characteristics of adjacent reference electrodes. When the static potential of a single reference electrode becomes abnormal and its dynamic response characteristics deviate from those of other reference electrodes, the detection reliability of that reference electrode is reduced. When multiple spatially adjacent reference electrodes generate potential changes in the same direction and maintain a consistent dynamic response to the test current, while the anode protection current in the corresponding region changes, the change is determined as the actual passivation state change of the corresponding protection region.

[0012] Furthermore, in this invention, a corresponding confidence weight is determined according to the degree of abnormality of each reference electrode, such that the greater the degree of abnormality of the reference electrode, the smaller its confidence weight. The confidence protection potential of the protection area is determined according to the detection potential of multiple reference electrodes participating in the potential evaluation of the same protection area and their corresponding confidence weights. When the detection reliability of a certain reference electrode is lower than the set reliability threshold, that reference electrode will not be used alone as the basis for feedback control of the anode protection output current.

[0013] Furthermore, in this invention, in step S5, the multiple cathodes installed in the concentrated sulfuric acid equipment are divided into multiple cathode groups that can independently adjust the output current. When the concentrated sulfuric acid equipment is in a stable passivation state, the amplitude-limited identification current change is applied to different cathode groups in sequence, and the reference potential change corresponding to multiple protection areas is obtained simultaneously. Based on the change in the identification current of each cathode group and the change in the potential of each protection area caused by the change in the identification current, the degree of potential influence of each cathode group on each protection area is determined to form a potential influence matrix of multiple cathode groups on multiple protection areas. And after changes in acid temperature, acid concentration, acid flow rate, or cathode operating state, the potential influence matrix is ​​updated based on the actual potential response obtained by reapplying the identification current.

[0014] Furthermore, in this invention, in step S6, a safety margin is set within the upper and lower boundaries of the predicted stable passivation potential window of each protection region to form a safe passivation potential window for anode protection control. The safety margin is adjusted according to the identification error of the stable passivation potential window, the prediction error caused by acid temperature, acid concentration and acid flow rate, and the detection reliability of the reference electrode of the corresponding protection region. Within the safety passivation potential window, the target protection potential of each protection area is determined. When the concentrated sulfuric acid operating conditions change and the predicted stable passivation potential window of the corresponding protection area shifts, the target protection potential is adjusted before the changed concentrated sulfuric acid reaches the protection area, so that the target protection potential is far away from the risk boundary corresponding to the predicted stable passivation potential window.

[0015] Furthermore, in this invention, the protection requirements of each protection area are determined based on the deviation between the reliable protection potential and the target protection potential of each protection area, and the cathode group with a large potential influence on the protection area with a large protection requirement and a small potential influence on other protection areas close to the safety passivation potential window boundary is selected according to the potential influence matrix, and the output current of the selected cathode group is adjusted preferentially. The adjustment of the cathode group output current is subject to the following constraints: the predicted anode potential of each protection zone is within the corresponding safe passivation potential window, the output current of each cathode group does not exceed the allowable output range, and the change in output current between adjacent control cycles does not exceed the allowable change. When there is an insufficient number of reliable reference electrodes, the protection zone potential exceeds the preset safety boundary, the acid temperature or concentration exceeds the allowable operating conditions of anode protection, the output current exceeds the allowable range, or the test current causes abnormal and continuous potential deviation, the identification of stable passivation potential window and the update of potential influence matrix are suspended, and the protection control is performed using the most recent effective stable passivation potential window and potential influence relationship, or the system is switched to the preset safe anode protection control state.

[0016] Beneficial effects: The technical solution of this application has the following technical effects: This invention applies a restricted test current to a concentrated sulfuric acid equipment while maintaining anodic protection. Based on the reference potential response and anodic current response corresponding to the test current, the current stable passivation state of the equipment is identified online. This allows for the determination of a stable passivation potential window corresponding to the actual operating conditions, transforming the control basis of anodic protection from a pre-set fixed protection potential to a dynamic protection range obtained based on the actual electrochemical state of the equipment. Therefore, when operating conditions such as acid temperature, acid concentration, and acid flow rate change, the changes in the stable passivation potential window of different protection zones can be predicted based on the changes in operating conditions and their propagation within the equipment. The target protection potential can then be adjusted accordingly, reducing the control lag caused by passive adjustments after changes in operating conditions.

[0017] Meanwhile, this invention utilizes the dynamic potential response of multiple reference electrodes under the action of a test current to determine the reliability of the reference potential detection. Based on the reliable reference potential, it determines the actual protection status of different protection zones. Furthermore, by changing the output current of different cathode groups, it establishes the potential influence relationship between the cathode groups and each protection zone. Therefore, when there is a significant protection demand in a certain protection zone, the corresponding cathode group can be adjusted according to the actual potential influence relationship, rather than simply increasing the output current of the entire anode protection system. This allows the adjustment of the protection current to match the actual protection needs of different zones.

[0018] Furthermore, this invention continuously updates the stable passivation potential window, the reliability of the reference electrode detection, and the potential influence relationship between the cathode group and the protected area based on the adjusted reference potential response and anode current response. This creates a continuous closed loop for passivation state identification, operating condition change prediction, potential measurement judgment, and protective current adjustment. Therefore, it improves the adaptability of anode protection control to changes in the operating conditions and spatial potential distribution of concentrated sulfuric acid equipment, ensuring that the anode potential in different protected areas remains within the corresponding stable passivation potential window, reducing the risk of underprotection or over-polarization caused by a mismatch between the fixed set potential and the actual passivation state. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the method flow of the present invention.

[0020] Figure 2 This is a schematic diagram of an embodiment. Detailed Implementation

[0021] This embodiment uses a stainless steel acid cooler for concentrated sulfuric acid as the protected device to illustrate the method of the present invention. However, the present invention is not limited to acid coolers; it can also be used for concentrated sulfuric acid delivery pipelines, acid separators, and other concentrated sulfuric acid equipment that uses anodic polarization to form a passivation film for corrosion protection. The basic mechanism of existing anodic protection is to use the metal surface in contact with concentrated sulfuric acid as the anode. By applying a direct current, the metal is driven from an activated state through a passivation process into a stable passivation region, and the passivation film is maintained with a relatively small passivation current. If the potential exceeds the stable passivation region and enters the overpassivation region, the passivation film may also be damaged. Therefore, anodic protection is not simply about increasing the output current, but requires maintaining the actual anode potential within an appropriate stable passivation potential range.

[0022] In this embodiment, the acid cooler employs a heat exchange configuration where acid flows through the shell and water flows through the tubes. The shell, the outer surface of the heat exchange tubes, the baffles, and the corresponding metal connecting parts in contact with concentrated sulfuric acid are electrically connected to form the protected anode. Existing equipment already allows for the placement of a control reference electrode at the acid inlet and a monitoring reference electrode at the acid outlet, with the output current adjusted based on the detected potential using a potentiostat. Building upon this, this embodiment divides the acid cooler into a first protection zone, a second protection zone, and a third protection zone along the main flow direction of the acid, corresponding to the acid inlet zone, the intermediate heat exchange zone, and the acid outlet zone, respectively. At least one reference electrode is placed in each protection zone; to improve detection redundancy, two reference electrodes can be placed in one or more of these zones. Each reference electrode is connected to the potential acquisition terminal of the controller.

[0023] The acid cooler contains three independently adjustable cathode groups, designated as the first, second, and third cathode groups. Each cathode group is connected to the anode protection controller via an independent DC output channel. An electrochemical current loop is formed between the cathode groups and the protected anode using concentrated sulfuric acid. The three cathode groups do not need to correspond one-to-one with the three protected areas, as the electric field generated by one cathode group can simultaneously affect multiple protected areas. This embodiment determines the actual impact of different cathode groups on different areas through subsequent online identification, rather than artificially fixing a unique correspondence between cathodes and protected areas during the design phase.

[0024] An acid temperature detection unit, an acid concentration detection unit, and an acid flow rate detection unit are installed upstream of the acid cooler to acquire the temperature, concentration, and flow rate of concentrated sulfuric acid entering the cooler. Each detection unit, each reference electrode, and each DC output channel is connected to the controller. The controller can collect acid temperature, acid concentration, flow rate, each reference potential, the output current of each cathode group, and the total anode protection current, and can individually adjust the output current of the three cathode groups. An increase in acid temperature or a decrease in acid concentration will alter the electrochemical state of the protected metal in the concentrated sulfuric acid environment and may cause an increase in the anode protection current; therefore, acid temperature, acid concentration, and acid flow rate are used together as input parameters for adaptive control.

[0025] S1. Obtain the initial running status and establish a protected area.

[0026] After the acid cooler is put into anodic protection operation, the existing safety control parameters are first used to bring the equipment into the initial protection state. This embodiment takes the operation of approximately 98% concentrated sulfuric acid as an example. The initial value can be a protection potential confirmed through equipment design or operational debugging, such as a control parameter setting of approximately -200mV. This initial protection potential serves only as a safety starting point before online identification begins in this invention and is not a constant final control target during subsequent operation.

[0027] The controller continuously collects reference potentials, output currents of the three cathode groups, total anode protection current, acid temperature, acid concentration, and acid flow rate for the first, second, and third protection zones to obtain current operating status data. The collected data is saved synchronously over time, establishing a time-correlation relationship between the potential responses of different reference electrodes and the corresponding cathode current changes, thus ensuring a consistent time reference for subsequent dynamic response analysis.

[0028] The purpose of this step is to ensure that subsequent online identification is based on the equipment already under anodic protection, rather than starting from a natural corrosion state for a large-scale potential scan. This avoids the online identification process itself causing the equipment to be out of the safe protection zone for extended periods, and it also allows the current actual operating state of the equipment to be used as the initial state for the passivation window identification, thus making the identification results more consistent with the real-time operating conditions of the equipment.

[0029] S2. Identify the current stable passivation potential window online.

[0030] Once the equipment is operating stably, the controller uses the current protection status as the identification center and applies a limited-amplitude test current disturbance to the cathode output. For example, the change in test current can be limited to 0.5% to 5% of the current stable output current. The specific amplitude can be determined based on the effective protection area of ​​the equipment, the capacity of the DC output channel, the historical operating status, and the allowable potential disturbance range.

[0031] A complete test process includes a positive disturbance, recovery, a reverse disturbance, and another recovery. First, a small test current is added to the current output current and held until the reference potential produces a recognizable response. Then, the test current is removed, returning the device to the protection state before the test. Next, the test current is reduced by a small amount from the current output current, the potential response is recorded again, and finally, the device is restored to the original protection state.

[0032] At each test operating point, the controller acquires the anode current density required to maintain anode protection at that operating point, the reference potential change corresponding to the test current change, and the potential recovery state after the test current is removed. Based on these parameters, the passivation state evaluation quantity for that operating point is obtained. The passivation state evaluation quantity is determined according to the following formula: In the formula, P k This represents the passivation state evaluation quantity corresponding to the k-th trial operating point, used to comprehensively reflect the passivation stability of that trial operating point; k represents the sequence number of the trial operating point; j k j represents the anode current density corresponding to the stabilization of the k-th trial operating point; ref This represents the reference current density used for normalizing the anode current density, which can be determined based on historical data from stable equipment operation or initial commissioning data; κk κ represents the local electrochemical response parameter obtained from the change in test current and the corresponding change in reference potential at the k-th test operating point; ref Reference value representing local electrochemical response; ρ k This indicates the proportion of potential residuals that still exist after a specified recovery time following the removal of the test current; a1, a2, and a3 represent the weighting coefficients corresponding to the anode current density, local electrochemical response, and potential recovery characteristics, respectively, and each weighting coefficient can be set according to the equipment commissioning results.

[0033] This evaluation method does not rely on a single potential value to determine whether the equipment has been passivated. Instead, it comprehensively considers multiple actual electrochemical characteristics exhibited by the stable passivation state. When the protected stainless steel is in the stable passivation region, a relatively stable passivation film has formed on the metal surface. The anolyte current required to maintain the passivation state is relatively small. Simultaneously, it exhibits a relatively stable local response to limited small-amplitude probing disturbances, and can quickly return to its original protection state after the disturbance is removed. Therefore, the combination of these parameters provides a more complete characterization of the equipment's current actual passivation state.

[0034] The controller selects multiple adjacent test operating points along the two directions of change of the protection potential, centered on the current safe operating point. If multiple consecutive test operating points meet the preset stable passivation judgment conditions, the corresponding operating point is determined as the stable passivation operating point. When continuing to test in a certain direction, if the increase in anolyte current exceeds the set threshold, a significant abrupt change occurs in the local electrochemical response, the reference potential cannot recover within a specified time after the test current is removed, or the test potential is close to the preset hard safety boundary, the controller stops testing in the current direction and uses the vicinity of the last previously obtained stable passivation operating point as the stable passivation potential window boundary in that direction.

[0035] By conducting the aforementioned restricted probes in two directions, the lower and upper boundaries of the current stable passivation potential window for each protected region can be determined. Unlike obtaining a complete polarization curve under shutdown conditions, this embodiment only performs local, small-scale, and immediately interruptible online identification around the current safe operating point of the equipment. Therefore, it is possible to obtain the actual stable passivation potential range determined by the current material surface state, acid solution conditions, and passivation film state of the equipment without significantly affecting normal anodic protection.

[0036] S3, the stable passivation potential window for predicting changes in acid conditions after they propagate to different protection areas.

[0037] The controller continuously collects the acid temperature, acid concentration, and acid flow rate upstream of the acid cooler. When the operating conditions of the inlet concentrated sulfuric acid change, the change does not simultaneously affect all protected areas in the acid cooler, but rather propagates sequentially to the first, second, and third protected areas as the concentrated sulfuric acid flows. Therefore, this embodiment first determines the time required for the change in operating conditions to propagate from the upstream detection location to different protected areas.

[0038] The acid propagation time corresponding to the i-th protected area is determined by the following formula: In the formula, τ i V represents the predicted time required for a change in concentrated sulfuric acid operating conditions to propagate from the upstream detection location to the i-th protected area; i represents the sequence number of the protected area; V eff,i Q represents the equivalent acid volume from the acid temperature, acid concentration, and flow rate detection location to the i-th protection zone; Q represents the current volumetric flow rate of concentrated sulfuric acid.

[0039] The equivalent acid volume can be calculated and determined based on the structural dimensions of the acid cooler shell, the effective flow area, and the location of the protected area. Alternatively, during the initial commissioning phase of the equipment, a recognizable acid temperature or concentration change can be artificially generated, and the time when this change is detected by each protected area can be recorded. The equivalent acid volume can then be corrected accordingly.

[0040] After determining the operating condition propagation time, the controller predicts the stable passivation potential window for the i-th protection zone at future times based on the currently identified stable passivation potential window and the correspondence between changes in acid temperature, acid concentration, and flow rate during historical operation and changes in the stable passivation potential window. Specifically, this is expressed as follows: In the formula, Ê L,i( t+τ_i) represents the lower boundary of the stable passivation potential window of the i-th protection region at the prediction time; Ê U,i (t+τ_i) represents the upper boundary of the stable passivation potential window of the i-th protection region at the predicted time; E L,i (t) represents the lower boundary of the stable passivation potential window of the i-th protection region identified online at the current moment; E U,i (t) represents the upper boundary of the stable passivation potential window of the i-th protection region obtained through online identification at the current time; t represents the current control time; τ i ΔT represents the predicted time for changes in concentrated sulfuric acid operating conditions to propagate to the i-th protected zone; ΔT represents the change in acid temperature relative to the current stable operating state; ΔC represents the change in acid concentration relative to the current stable operating state; ΔQ represents the change in acid flow rate relative to the current stable operating state; Bi This represents the correction coefficient matrix between the operating condition changes and the stable passivation potential window changes of the i-th protection zone.

[0041] When the control method of this invention is first applied to the equipment, the initial value of the correction coefficient matrix can be determined based on the equipment debugging data or pre-obtained experimental data. After the equipment has been running continuously, only data from periods when the reference electrode detection is reliable and the equipment is in a stable passivation state are selected as valid update samples. When a predicted change in operating condition actually propagates to the corresponding protection area, the local stable passivation window is identified again through step S2. The actual window obtained by the re-identification is compared with the previously predicted window, and the deviation between the two is used to correct the correspondence used in subsequent predictions.

[0042] The main purpose of this step is not simply to assign a new protection potential based on temperature or concentration, but rather to first obtain the current stable passivation potential window of the equipment through step S2, and then predict the future direction and degree of change of this window based on the acid conditions that will soon enter the equipment. Therefore, the controller can adjust the control target in advance before the changes in operating conditions actually act on the corresponding protection area, reducing the response lag present in traditional simple feedback control.

[0043] S4. Perform dynamic reliability assessment on multiple reference electrodes.

[0044] During the online identification of the stable passivation potential window in step S2, each reference electrode is simultaneously subjected to electrochemical disturbances generated by a known probe current. Therefore, this embodiment further utilizes the same probe process to determine the detection status of each reference electrode without needing to separately stop the equipment to inspect the reference electrodes.

[0045] The controller extracts the static potential deviation, response direction to the test current, dynamic response amplitude, response delay, and recovery state after the test current is removed from each reference electrode, and compares the dynamic response of each reference electrode with the response of other reference electrodes in the same or adjacent regions.

[0046] The degree of abnormality of the i-th reference electrode is determined by the following formula: In the formula, r i D represents the degree of abnormality of the i-th reference electrode; E,i D represents the deviation of the static potential of the i-th reference electrode from the expected potential of its adjacent reliable reference electrodes. K,i D represents the amplitude deviation of the i-th reference electrode relative to the normal dynamic response; τ,i D represents the delay deviation of the i-th reference electrode relative to the normal response time; R,iThe value represents the recovery characteristic deviation of the i-th reference electrode after the test current is removed; b1, b2, b3 and b4 represent the weighting coefficients corresponding to the static potential deviation, dynamic response amplitude deviation, response delay deviation and recovery characteristic deviation, respectively.

[0047] If the static potential of a certain reference electrode shifts significantly, while other reference electrodes do not show a corresponding change, and the dynamic response amplitude, delay, or recovery state exhibited by the reference electrode after being subjected to the same test current also deviates significantly from other reference electrodes, then the controller determines that the reference electrode may have drift, contamination, aging, wiring abnormality, or other detection abnormalities, and reduces its detection reliability.

[0048] Conversely, if multiple reference electrodes in the same or adjacent protection areas simultaneously exhibit potential changes in the same direction, and they still have matching dynamic responses to the same test current, while the corresponding anode protection current in the corresponding area also changes accordingly, then this change should be preferentially identified as a change in the actual electrochemical state of the equipment, rather than simply treated as a reference electrode failure.

[0049] The controller determines the corresponding confidence weight based on the degree of anomaly of each reference electrode, and uses data from multiple reference electrodes to obtain the confidence protection potential of the corresponding protection area. In the formula, E v E represents the reliable protection potential for subsequent feedback control in the corresponding protection area; i This represents the potential detected by the i-th reference electrode involved in determining the potential of the protected area; w i The represents the confidence weight corresponding to the i-th reference electrode; i represents the reference electrode number participating in the fusion; n represents the total number of reference electrodes participating in the calculation of the current protection area's confidence protection potential.

[0050] The greater the degree of abnormality of the reference electrode, the lower its corresponding confidence weight. For reference electrodes with a confidence level below the preset threshold, they no longer need to be used as the sole feedback basis for anode protection output adjustment, but their detection data is still retained for fault alarms, status analysis, and subsequent manual maintenance.

[0051] This step addresses the problem of difficulty in determining the source of a fault based solely on the static potential difference between two reference electrodes. By applying a known common electrochemical perturbation to the device, it is possible not only to observe "how much each reference electrode has measured," but also to observe "how different reference electrodes respond to the same actual electrochemical change," thus providing a basis for distinguishing between reference electrode anomalies and changes in the actual passivation state of the device.

[0052] S5. Identify the potential influence relationship between the cathode group and different protection areas online.

[0053] After confirming that the reference potential used for feedback has sufficient reliability, the controller keeps the acid cooler within the established safe passivation potential range and applies small identification currents to the first cathode group, the second cathode group, and the third cathode group in sequence.

[0054] For example, when identifying the first cathode group, the second and third cathode groups are kept in their current output states, only the output current of the first cathode group is changed, and the changes in the reliable protection potential corresponding to the first, second, and third protection regions are recorded simultaneously. After the identification of the first cathode group is completed, the first cathode group is restored to its original output state, and then the second and third cathode groups are identified in the same way.

[0055] The degree of influence of the j-th cathode group on the actual potential of the i-th protection zone is determined by the following formula: In the formula, G ij This represents the degree of influence of the output current change of the j-th cathode group on the potential of the i-th protection zone; i represents the sequence number of the protection zone; j represents the sequence number of the cathode group; ΔI j ΔE represents the change in the identification current applied to the j-th cathode group. i This represents the change in the reliable protection potential of the i-th protection zone caused by the change in the identification current of the j-th cathode group.

[0056] After identifying multiple cathode groups using the above method, a cathode group-protected area potential influence matrix is ​​formed based on the degree of potential influence of different cathode groups on different protected areas. For example, the actual identification results may show that the first cathode group has a greater influence on the first protected area and a weaker influence on the second protected area; the second cathode group has a greater influence on the second protected area; and the third cathode group has a greater influence on the third protected area. The correspondence described here is for illustrative purposes only, and the actual potential influence relationship in the equipment shall be based on the online identification results.

[0057] The purpose of this step is to address the spatial coupling problem of the protective current within the concentrated sulfuric acid equipment. The protective current generated by the cathode group forms a current path through the concentrated sulfuric acid. The actual current distribution is affected not only by the geometric distance between the cathode and anode, but also by factors such as the equipment structure, the electrochemical characteristics of the concentrated sulfuric acid, the flow state, and the working state of the cathode itself. Therefore, this invention does not pre-define a one-to-one correspondence between the three cathode groups and the three protected areas, but rather uses the regional potential changes generated by actual current disturbances to determine the true control capability of each cathode group over each area.

[0058] S6. Generate adaptive target protection potentials for each protection zone and allocate cathode currents.

[0059] After obtaining the predicted stable passivation potential window and the current reliable protection potential for each protection zone, the controller first sets a safety margin within the upper and lower boundaries of the predicted stable passivation potential window to obtain a safe passivation potential window for actual control.

[0060] The safety margin can be adjusted based on the identification error of the stable passivation potential window, the prediction error corresponding to changes in acid temperature, acid concentration, and flow rate, and the reliability of the reference electrode. When the identification error is large, the operating conditions change rapidly, or the reliability of the reference electrode involved in the control is low, the safety margin should be increased to keep the actual target protection potential away from the risk boundary of the stable passivation potential window. When the equipment operates stably for a long time, the identification results match the actual feedback, and the reliability of the reference electrode is high, the safety margin can be appropriately reduced while meeting safety requirements.

[0061] Subsequently, the target protection potential for each protection zone is determined within the safety passivation potential window. When the acid temperature, acid concentration, and flow rate remain relatively stable, the position with a large double-sided safety margin can be used as the target protection potential. When a new acid condition is detected at the inlet, and step S3 predicts that the condition will cause the stable passivation potential window to shift after reaching a certain protection zone, the target protection potential of that zone is gradually adjusted before the corresponding acid actually reaches that protection zone, so that the target protection potential enters the predicted safety passivation potential window in advance.

[0062] The controller further compares the relationship between the current reliable protection potential and the corresponding target protection potential of each protection zone to determine the protection requirements of each zone. For example, if the third protection zone is close to the risk boundary of its safe passivation potential window, while the first protection zone still has a large safety margin, the controller selects the cathode group that has a greater impact on the third protection zone and a smaller impact on the first protection zone for priority adjustment based on the potential influence matrix established in step S5, rather than simply increasing the output current of all cathode groups at the same time.

[0063] During the adjustment of the cathode group output current, the control constraints are as follows: the predicted anode potential after adjustment in each protection zone is within its respective safe passivation potential window; the output current of each cathode group does not exceed the allowable range of the corresponding DC output channel; and the change in cathode output current between two adjacent control cycles does not exceed the allowable change. When multiple current distribution schemes satisfy the above constraints exist, the output combination that can meet the regional anode protection requirements and has a relatively small increase in total current is selected first.

[0064] Through the above method, this embodiment establishes a correspondence between "actual protection needs of each region - actual working capacity of each cathode group - cathode output current", thereby avoiding unnecessary over-polarization in other regions when a certain region needs enhanced protection by simply increasing the overall anode protection current.

[0065] S7. Continuously update adaptive control parameters based on actual feedback.

[0066] After completing the determination of the target protection potential and the distribution of the cathode current, the controller continues to collect the reliable protection potentials of the first protection zone, the second protection zone, and the third protection zone, as well as the actual anode protection current, and compares the actual response with the predicted response before adjustment.

[0067] When the actual potential change direction and degree match the prediction result, and all protection zones remain within the safe passivation potential window, the controller maintains the current control strategy and saves the current operation data as a valid operation sample.

[0068] Once the operating condition change detected at the inlet actually propagates to the corresponding protected area, a restricted probe is performed again to re-identify the stable passivation potential window of that area online. The difference between the re-identified actual stable passivation potential window and the predicted stable passivation potential window obtained in step S3 is used to update the correspondence between the operating condition change and the passivation window change.

[0069] Simultaneously, the cathode group-protection area potential influence matrix obtained in step S5 is updated based on the actual output current changes of each cathode group and the actual reliable protection potential changes of each protection area. In this way, when the cathodes are gradually consumed, the electrochemical characteristics of concentrated sulfuric acid change, or the internal flow conditions of the equipment change, the actual changes in the influence of the cathode groups on different protection areas can be reflected in the subsequent online identification results.

[0070] This embodiment further sets hard safety limits independent of the above adaptive calculation process. When the number of trusted reference electrodes is lower than the allowable number, the potential of any protected area exceeds the preset hard safety boundary, the acid temperature or acid concentration exceeds the device's allowable anode protection conditions, the anode protection output current exceeds the allowable range, or a continuous abnormal potential shift occurs after the application of the test current, the controller immediately terminates the current test process and suspends the updating of the stable passivation potential window and the potential influence matrix.

[0071] In the aforementioned abnormal situations, the most recently confirmed and effective stable passivation potential window and potential influence matrix can be frozen for restrictive control. When the abnormal state further develops or the reliability of the data required for adaptive control can no longer be guaranteed, the system switches to the safe constant potential control mode that has been pre-tested and confirmed by the equipment, and issues an alarm signal, awaiting inspection and handling by the operators. This ensures that the adaptive identification process always conforms to the equipment's safety protection requirements, preventing the equipment from deviating from a safe operating state in order to obtain identification data.

[0072] The steps S1 to S7 described above are technically interconnected. Step S1 provides equipment operating data and the spatial basis of the protected area; Step S2 determines the stable passivation potential range that the equipment is currently allowed to operate in; Step S3 predicts the future changes of this stable passivation range based on the upcoming concentrated sulfuric acid operating conditions; Step S4 determines whether the reference potential used for feedback control is reliable; Step S5 further determines the actual control effect of different cathode groups on different protected areas; Step S6 comprehensively predicts the stable passivation potential window, reliable protection potential, and potential influence relationship to generate the target protection potential and perform regionalized cathode current allocation; Step S7 updates the aforementioned identification results based on the actual potential and current responses after execution. Therefore, the data generated in the previous step constitutes the control basis for the next step, and the actual control results of the next step serve as the data source for subsequent updates in the previous step, thus forming a complete adaptive closed loop.

[0073] The above embodiments demonstrate that the present invention can transform the control basis for anodic protection of concentrated sulfuric acid equipment from a pre-fixed single protection potential to a stable passivation potential window obtained online based on the actual electrochemical state of the equipment. Even if traditional constant potential control can accurately follow the preset value, its protection effect still depends on whether the preset value is applicable to the current acid temperature, acid concentration, flow rate, and passivation state of the equipment surface. The present invention obtains the actual response of the equipment itself through a limited trial current, directly constraining the control target to the current passivation state. Therefore, it helps to reduce underprotection or overpolarization caused by the mismatch between the fixed set potential and the actual stable passivation state.

[0074] From the perspective of the underlying electrochemical mechanism, after stainless steel enters a stable passivation state through anodic polarization in concentrated sulfuric acid, a relatively stable passivation film forms on its surface, reducing the metal dissolution rate and consequently decreasing the current required to maintain this state. When the operating state approaches the activation-passivation transition region or the overpassivation region, the electrochemical reaction state of the metal surface changes, and the corresponding holding current, local current-potential response, and recovery behavior after disturbance removal also change. Therefore, obtaining these actual electrochemical responses using confined current perturbations can provide a physical basis for identifying stable passivation regions, rather than relying solely on an empirically assigned fixed protection potential.

[0075] This embodiment also reduces control lag caused by changes in acid operating conditions. The underlying reason is that the moment the inlet detection location obtains information about changes in acid temperature, concentration, or flow rate is earlier than the moment the batch of acid actually reaches the middle and outlet protection zones of the acid cooler. This invention utilizes the actual propagation time of the acid within the equipment to convert the operating condition change that has been detected at the inlet but has not yet reached the corresponding protection zone into a lead time, and predicts the future stable passivation potential window based on this lead time. This forms a condition-based feedforward control; after the batch of acid actually reaches the corresponding zone, feedback correction is performed using the actual detection results from the reference electrode, thus forming a control process that combines feedforward prediction and electrochemical feedback.

[0076] This embodiment also reduces the possibility of erroneous control caused by reference electrode abnormalities. Simply comparing the static potentials of different reference electrodes can only determine if there are differences in the measurement results, but cannot directly distinguish whether it is due to reference electrode drift or a real change in the local electrochemical state of the equipment. This invention utilizes the same known test current as a common excitation for multiple reference electrodes. When the actual state of the equipment changes, multiple spatially related reference electrodes will produce interrelated dynamic responses; while when a single reference electrode drifts, becomes poisoned, has abnormal wiring, or its performance deteriorates, its static potential and dynamic response may simultaneously exhibit inconsistencies relative to other electrodes. Therefore, by jointly judging through static data and dynamic response, the reliability of the feedback potential information can be improved.

[0077] Furthermore, this embodiment can improve the problem of mismatched protection current distribution between different protection zones. The protection current forms a spatial current loop through concentrated sulfuric acid, meaning a cathode group does not necessarily only affect a single nearby protection zone. By changing the output of each cathode group and measuring the actual potential response of multiple protection zones, the actual influence relationship of each cathode group on each protection zone under the current equipment state can be obtained. When a certain zone is underprotected, the controller can prioritize adjusting the cathode groups that have a stronger effect on that zone but a smaller incidental impact on other zones, reducing the situation of "over-polarizing one zone to protect another" from the underlying current distribution mechanism.

[0078] Therefore, the technical effect produced by this embodiment is not generated by a single isolated formula or control parameter, but is achieved through the coordinated efforts of online identification of stable passivation state, prediction of acid solution propagation, judgment of multi-reference electrode reliability, identification of multi-cathode influence relationships, and regionalized output control. The stable passivation window answers "in which potential range the equipment is allowed to operate in the present and future," the reference electrode reliability judgment answers "which potential data can be used as the basis for control," and the cathode influence relationship answers "which cathode can effectively regulate which area." Finally, the specific cathode output current is determined based on the regional protection requirements. The above technical relationships are interconnected, enabling the actual anode potential of different protection areas to better adapt to the constantly changing operating conditions of the concentrated sulfuric acid equipment.

[0079] The overall working principle of this embodiment is as follows: The acid cooler first enters the anode protection state under the confirmed safety protection parameters. The controller applies a limited trial current without interrupting normal protection, and determines the current stable passivation potential window through the actual potential and current response of the equipment itself. Then, the time for different operating conditions to propagate to each protection zone and the corresponding changes in the stable passivation potential window are predicted using the inlet acid temperature, acid concentration, and acid flow rate. At the same time, the dynamic response of multiple reference electrodes to the same trial disturbance is compared to screen for reliable regional protection potentials. Then, the output current of different cathode groups is changed to obtain the actual potential influence relationship of each cathode group on different protection zones. The controller comprehensively predicts the passivation window, reliable protection potential, and cathode influence relationship, adaptively determines the target protection potential of each zone, and prioritizes the allocation of protection current to the cathode group that is more effective in the target zone. Finally, the aforementioned parameters are continuously updated through the feedback of the adjusted actual potential and current. This forms a closed-loop control process of "state identification - operating condition prediction - measurement verification - action relationship identification - zone control - feedback update", realizing the adaptive control of the anode protection potential of the concentrated sulfuric acid equipment.

[0080] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A method for adaptive control of anodic protection potential in concentrated sulfuric acid equipment, characterized in that, Includes the following steps: S1. Acquire anode protection status data and concentrated sulfuric acid operating condition data during the operation of the concentrated sulfuric acid equipment. The anode protection status data includes at least the reference potential detected by multiple reference electrodes set at different locations in the concentrated sulfuric acid equipment and the output current corresponding to multiple independently adjustable cathode groups. The concentrated sulfuric acid operating condition data includes at least the acid temperature, acid concentration and acid flow rate. S2. While the concentrated sulfuric acid equipment is under anode protection, apply a limited-amplitude test current disturbance based on the current anode protection working state. Identify the current stable passivation state of the concentrated sulfuric acid equipment based on the reference potential response and anode current response corresponding to the test current disturbance, and determine the stable passivation potential window corresponding to the current operating condition. S3. Based on the changes in acid temperature, acid concentration, and acid flow rate, as well as the flow propagation state of concentrated sulfuric acid in the equipment, determine the predicted time for the propagation of the changes in concentrated sulfuric acid operating conditions to different protection zones, and predict the stable passivation potential window of different protection zones at the corresponding predicted time based on the current stable passivation potential window. S4. Based on the dynamic potential response generated by multiple reference electrodes under the disturbance of the test current, the detection reliability of each reference electrode is judged, and the reliable protection potential corresponding to each protection area is determined based on the reference electrode whose reliability meets the requirements. S5. Change the output current of different cathode groups respectively, and obtain the potential change of each protection area. Based on the correspondence between the output current change of each cathode group and the potential change of each protection area, establish the potential influence relationship between the cathode group and the protection area. S6. Based on the predicted stable passivation potential window, reliable protection potential, and potential influence relationship of each protection area, determine the target protection potential and protection requirements of each protection area respectively, and adjust the output current of the corresponding cathode group according to the protection requirements so that the anode potential of different protection areas is kept within their respective stable passivation potential window. S7. Based on the reference potential response and anode current response after the cathode group output adjustment, update the stable passivation potential window, the reliability of the reference electrode detection, and the potential influence relationship between the cathode group and the protection area to form a closed-loop adaptive control of the anode protection potential.

2. The adaptive control method for anolyte protection potential of a concentrated sulfuric acid equipment according to claim 1, characterized in that: In step S1, based on the spatial positions of multiple reference electrodes in the concentrated sulfuric acid equipment or their positions along the flow direction of concentrated sulfuric acid, the concentrated sulfuric acid equipment is divided into multiple protection zones, and the positional correspondence between the reference electrodes, protection zones, and cathode groups is established. Before starting adaptive control, the initial protection potential is determined based on the current acid concentration and acid temperature of the concentrated sulfuric acid equipment, so that the concentrated sulfuric acid equipment first enters the preset safety protection state, and the preset safety protection state is used as the initial working state for online identification of the stable passivation potential window.

3. The adaptive control method for anodic protection potential of a concentrated sulfuric acid equipment according to claim 2, characterized in that: In step S2, the test current disturbance includes sequentially applying a forward test current and a reverse test current based on the current anode protection output current, and restoring the anode protection output state to the state before the disturbance after each test current is completed; The anode current required to maintain anode protection, the reference potential change corresponding to the change in test current, and the potential recovery state after the test current is removed are obtained under each test working state. Based on the magnitude of the current required to maintain anode protection, the local response relationship between the current change and the potential change, and the potential recovery characteristics, it is determined whether the current test working state belongs to a stable passivation state.

4. The adaptive control method for anodic protection potential of a concentrated sulfuric acid equipment according to claim 3, characterized in that: Multiple test working states are selected sequentially according to different potential directions near the current protection potential, and the potential range corresponding to the continuous stable passivation working state is determined according to the anode current response and reference potential response corresponding to each test working state. The two boundaries of the potential range are respectively determined as the lower boundary and upper boundary of the stable passivation potential window. If, during the testing process, the increase in anodic current exceeds the set value, a sudden change occurs in the local electrochemical response, the potential fails to recover within a specified time after the testing current is removed, or the testing potential reaches the preset safety boundary, the testing in the current direction is stopped, and the corresponding stable passivation potential window boundary is determined based on the previously obtained stable passivation working state.

5. The adaptive control method for anolyte protection potential of a concentrated sulfuric acid equipment according to claim 1, characterized in that: In step S3, based on the equivalent acid volume that can be accommodated between the concentrated sulfuric acid operating condition detection location and each protection zone, and the real-time acid flow rate, the predicted time for concentrated sulfuric acid to propagate from the operating condition detection location to different protection zones is determined respectively. Based on the historical correlation between changes in acid temperature, acid concentration, and acid flow rate and changes in the stable passivation potential window, the upper and lower boundaries of the current stable passivation potential window are corrected to obtain the predicted stable passivation potential window when concentrated sulfuric acid reaches the corresponding protection area. After the actual concentrated sulfuric acid reaches the corresponding protection area, the historical correspondence is updated based on the deviation between the re-identified stable passivation potential window and the predicted stable passivation potential window.

6. The adaptive control method for anolyte protection potential of a concentrated sulfuric acid equipment according to claim 1, characterized in that: In step S4, the static potential deviation, potential response direction, dynamic response amplitude, response delay, and recovery characteristics after the removal of the test current are extracted for each reference electrode under the same test current disturbance. The degree of abnormality and detection reliability of each reference electrode are determined based on the deviation between the dynamic response characteristics of each reference electrode and the dynamic response characteristics of adjacent reference electrodes. When the static potential of a single reference electrode becomes abnormal and its dynamic response characteristics deviate from those of other reference electrodes, the detection reliability of that reference electrode is reduced. When multiple spatially adjacent reference electrodes generate potential changes in the same direction and maintain a consistent dynamic response to the test current, while the anode protection current in the corresponding region changes, the change is determined as the actual passivation state change of the corresponding protection region.

7. The adaptive control method for anolyte protection potential of a concentrated sulfuric acid equipment according to claim 6, characterized in that: The corresponding confidence weight is determined according to the degree of abnormality of each reference electrode, so that the greater the degree of abnormality of the reference electrode, the smaller its confidence weight. The confidence protection potential of the protection area is determined according to the detection potential of multiple reference electrodes participating in the potential evaluation of the same protection area and their corresponding confidence weights. When the detection reliability of a certain reference electrode is lower than the set reliability threshold, that reference electrode will not be used alone as the basis for feedback control of the anode protection output current.

8. The adaptive control method for anolyte protection potential of a concentrated sulfuric acid equipment according to claim 1, characterized in that: In step S5, the multiple cathodes installed in the concentrated sulfuric acid equipment are divided into multiple cathode groups that can independently adjust the output current. When the concentrated sulfuric acid equipment is in a stable passivation state, the amplitude-limited identification current change is applied to different cathode groups in sequence, and the reference potential change corresponding to multiple protection areas is acquired simultaneously. Based on the change in the identification current of each cathode group and the change in the potential of each protection area caused by the change in the identification current, the degree of potential influence of each cathode group on each protection area is determined to form a potential influence matrix of multiple cathode groups on multiple protection areas. And after changes in acid temperature, acid concentration, acid flow rate, or cathode operating state, the potential influence matrix is ​​updated based on the actual potential response obtained by reapplying the identification current.

9. The adaptive control method for anolyte protection potential of a concentrated sulfuric acid equipment according to claim 8, characterized in that: In step S6, safety margins are set within the upper and lower boundaries of the predicted stable passivation potential window for each protection region to form a safe passivation potential window for anode protection control. The safety margins are adjusted based on the identification error of the stable passivation potential window, the prediction error caused by acid temperature, acid concentration and acid flow rate, and the detection reliability of the reference electrode of the corresponding protection region. Within the safety passivation potential window, the target protection potential of each protection area is determined. When the concentrated sulfuric acid operating conditions change and the predicted stable passivation potential window of the corresponding protection area shifts, the target protection potential is adjusted before the changed concentrated sulfuric acid reaches the protection area, so that the target protection potential is far away from the risk boundary corresponding to the predicted stable passivation potential window.

10. The adaptive control method for anolyte protection potential of a concentrated sulfuric acid equipment according to claim 9, characterized in that: The protection requirements of each protection area are determined based on the deviation between the reliable protection potential and the target protection potential of each protection area. Based on the potential influence matrix, the cathode group that has a large potential influence on the protection area with a large protection requirement and a small potential influence on other protection areas that are close to the safety passivation potential window boundary is selected, and the output current of the selected cathode group is adjusted first. The adjustment of the cathode group output current is subject to the following constraints: the predicted anode potential of each protection zone is within the corresponding safe passivation potential window, the output current of each cathode group does not exceed the allowable output range, and the change in output current between adjacent control cycles does not exceed the allowable change. When there is an insufficient number of reliable reference electrodes, the protection zone potential exceeds the preset safety boundary, the acid temperature or concentration exceeds the allowable operating conditions of anode protection, the output current exceeds the allowable range, or the test current causes abnormal and continuous potential deviation, the identification of stable passivation potential window and the update of potential influence matrix are suspended, and the protection control is performed using the most recent effective stable passivation potential window and potential influence relationship, or the system is switched to the preset safe anode protection control state.

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