A hydrogel resistance probe, a preparation method thereof and a corrosion monitoring dosing system

Abstract

The application discloses a kind of hydrogel resistance probes, its preparation method and corrosion monitoring dosing system, belong to oil and gas pipeline protection technical field.The probe includes: by alkenyl amide monomer and alkenyl carboxylic acid monomer crosslinking polymerization and become hydrogel matrix, ferrocyanide is physically embedded in matrix and is embedded in the conductive electrode of matrix two ends.Ferrocyanide and medium Fe + / Fe³ + Specific complex generates prussian blue type conductive complex, causes the regular change of probe resistance.Preparation method uses in-situ polymerization to embed ferrocyanide in hydrogel network and simultaneously pre-embed electrode.Corrosion monitoring dosing system includes the probe, resistance acquisition module, data processing module, decision control module and dosing execution module, through resistance-iron ion concentration standard curve inversion corrosion rate, and according to hierarchical control strategy automatically adjusts inhibitor dosage, forms closed loop feedback control.

Description

Technical Field

[0001] This invention relates to the field of oil and gas pipeline protection technology, and more specifically, to a hydrogel resistance probe, its preparation method, and a corrosion monitoring and dosing system. Background Technology

[0002] During long-term service, oil and gas pipelines often face complex corrosive environments such as CO2, H2S, and high-salt media. Uniform corrosion and localized pitting corrosion can easily lead to pipe wall thinning, perforation, and leakage, posing a significant threat to the safe operation and service life of the pipeline. To inhibit corrosion, the industry currently widely adopts the method of adding corrosion inhibitors for protection.

[0003] However, traditional corrosion inhibitors rely on continuous injection with high concentrations, timed and quantitative methods. By overdosing to maintain the agent coverage on the inner wall of the pipeline, a large amount of corrosion inhibitor is ineffectively consumed in non-corrosive areas. The agent utilization rate is generally less than 30%, resulting in prominent problems such as high cost, serious waste, and great environmental pressure.

[0004] In corrosion detection, existing technologies mainly include the dipstick method and conventional resistance probes. The dipstick method can only reflect the long-term average corrosion characteristics of the medium, with a severely delayed response, making real-time monitoring impossible. While conventional resistance probes can achieve a certain degree of online monitoring, their output signal is the resistance change of the metal element, making it difficult to directly quantify the iron ion concentration in the medium, unable to invert the uniform corrosion rate in real time, and insensitive to early micro-corrosion and localized pitting corrosion. When scaling occurs on the probe surface or the conductivity of the medium fluctuates, the accuracy of the measurement data decreases significantly. More importantly, existing monitoring methods cannot form a closed-loop linkage with chemical dosing decisions, often only passively detecting corrosion after it has occurred or even after perforation and leakage, making it difficult to achieve early warning and timely intervention for corrosion risks.

[0005] Therefore, there is an urgent need in this field for an integrated solution for corrosion monitoring and protection that can sensitively respond to iron ion concentration, invert corrosion rate in real time, and adaptively add chemicals. In view of this, we propose a hydrogel resistance probe, its preparation method, and a corrosion monitoring and chemical dosing system. Summary of the Invention

[0006] The purpose of this invention is to provide a hydrogel resistance probe, its preparation method, and a corrosion monitoring and dosing system to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A hydrogel resistance probe, comprising: The hydrogel matrix is ​​formed by crosslinking and polymerization of at least one alkenylamide monomer and at least one alkenylcarboxylic acid monomer under the action of a crosslinking agent and an initiator; Ferrocyanide is uniformly dispersed and physically embedded in the three-dimensional network structure of the hydrogel matrix; And at least two conductive electrodes, which are pre-embedded at both ends of the length direction of the hydrogel matrix during the polymerization process. The two electrodes are insulated from each other and are electrically connected only through the hydrogel matrix, and are used to collect the resistance signal of the hydrogel matrix.

[0008] Preferably, the mass ratio of alkenyl carboxylic acid monomer to alkenyl amide monomer is 1:3 to 1:9.

[0009] Preferably, the ferrocyanide is potassium ferrocyanide, and its concentration in the precursor solution used to prepare the hydrogel resistance probe is 0.1%-0.2% (w / v).

[0010] Preferably, the conductive electrode is one or more of carbon fiber cloth, graphite paper, platinum wire, or conductive silver paste.

[0011] Preferably, the hydrogel matrix is ​​strip-shaped, with a length of 20-40 mm, a width of 3-8 mm, and a thickness of 1-2 mm.

[0012] A method for preparing the above-mentioned hydrogel resistance probe includes the following steps: Step 1: Prepare the precursor solution: Dissolve potassium ferrocyanide in deionized water under light-protected conditions, then add alkenyl amide monomer, alkenyl carboxylic acid monomer and crosslinking agent in sequence, and stir until completely dissolved; Step 2, Deoxygenation treatment: Inert gas is introduced into the precursor solution to remove dissolved oxygen; Step 3: Initiate polymerization: Add an initiator to the deoxygenated precursor solution, stir, and then inject the mixture into a mold. Conductive electrodes are pre-placed at both ends of the mold. The distance between the two electrodes in the mold is 20-40 mm and they do not contact each other. Polymerize at a constant temperature of 50-60℃ for 6-12 hours to form a hydrogel matrix embedded with ferrocyanide, and the conductive electrodes are embedded at both ends of the gel. Step 4, Post-processing and molding: Take out the polymerized gel, soak it in deionized water to remove unreacted monomers and uncrosslinked components, and then cut it into the required shape to obtain the hydrogel resistance probe.

[0013] A corrosion monitoring and dosing system based on the above-mentioned hydrogel resistance probe includes: A hydrogel resistance probe is placed in the medium to be tested in a pipeline to output a resistance signal; The resistance acquisition module is electrically connected to the conductive electrodes at both ends of the probe and is used to acquire resistance signals in real time. The data processing module stores a pre-established resistance-iron ion concentration standard curve, is configured to receive resistance signals, convert them into iron ion concentration according to the standard curve, and then calculate the real-time corrosion rate according to Faraday's law. The decision control module is configured to match the preset corrosion level with the real-time corrosion rate and generate the corresponding corrosion inhibitor injection command. The chemical dosing execution module is used to receive dosing instructions and automatically add corrosion inhibitors; The data processing module is also used to continuously monitor the resistance signal after drug administration, forming a closed-loop feedback control.

[0014] Preferably, the corrosion level preset in the decision control module adopts a graded control strategy. The graded control strategy adjusts the concentration of the corrosion inhibitor to a preset concentration value corresponding to the current corrosion rate range based on multiple preset corrosion rate threshold ranges. Furthermore, the corrosion rate threshold and the corresponding corrosion inhibitor concentration value increase as the corrosion rate increases.

[0015] A corrosion monitoring and chemical dosing method based on a hydrogel resistance probe, employing the aforementioned hydrogel resistance probe, includes the following steps: The hydrogel resistance probe is placed in the medium to be tested in the pipeline, and the resistance signal of the probe is collected in real time. The collected resistance signal is substituted into the pre-established resistance-iron ion concentration standard curve and converted into iron ion concentration. Based on Faraday's law, the real-time corrosion rate of the pipeline is calculated according to the iron ion concentration. The real-time corrosion rate is compared with multiple preset corrosion rate threshold ranges, the corresponding corrosion level is matched, and a corrosion inhibitor injection instruction is generated. Automatically add corrosion inhibitor according to the filling command; Continuously monitor the resistance signal after drug administration and repeat the above steps to form a closed-loop feedback control.

[0016] Preferably, the corrosion rate threshold range is set according to the NACE SP0775 standard and in combination with the requirements for safe pipeline operation, specifically: less than 0.025 mm / a, 0.025~0.1 mm / a, 0.1~0.3 mm / a, and greater than 0.3 mm / a; the corresponding corrosion inhibitor dosage concentrations are 100 ppm, 300 ppm, 600 ppm, and 1000 ppm, respectively, and an alarm is triggered when the corrosion rate exceeds 0.3 mm / a.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In this invention, potassium ferrocyanide is physically embedded in a three-dimensional hydrogel network, utilizing its interaction with Fe²⁺. + Fe³ +The specific complexation reaction generates a conductive Prussian blue complex, causing a regular change in resistance, thus achieving a highly sensitive and rapid conversion of iron ion concentration into a resistance signal. By adjusting the copolymerization ratio of acrylic acid and acrylamide to optimize the carboxyl group density, efficient enrichment and detection of low-concentration iron ions can be achieved, overcoming the shortcomings of insufficient sensitivity in traditional probes.

[0018] (2) This invention establishes a complete data chain of resistance signal—iron ion concentration—corrosion rate—dosing decision, realizing closed-loop adaptive control of corrosion monitoring and corrosion inhibitor dosing, avoiding the waste caused by traditional overdosing, and significantly improving the utilization rate of corrosion inhibitors. This invention uses potassium ferrocyanide, which has good chemical stability and low photosensitivity, making it suitable for long-term online monitoring in the closed, light-free environment of oil and gas pipelines, and has strong applicability. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the hydrogel resistor probe in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram illustrating the response mechanism of the hydrogel resistance probe described in this invention; Figure 3 The resistance response curves of the probe at different iron ion concentrations in Embodiment 1 of the present invention are shown. Figure 4 The standard curve and fitting equation of iron ion concentration-resistance in Embodiment 1 of the present invention are shown. Figure 5 This is a flowchart illustrating the closed-loop control process of this invention applied to pipeline corrosion monitoring and intelligent chemical dosing guidance.

[0020] The labels in the diagram are as follows: 1. Hydrogel matrix; 2. Conductive electrode; 3. Signal lead. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0022] Example: Please see Figure 1 A hydrogel resistance probe, comprising: The hydrogel matrix is ​​formed by crosslinking and polymerization of at least one alkenylamide monomer and at least one alkenylcarboxylic acid monomer under the action of a crosslinking agent and an initiator; wherein the mass ratio of alkenylcarboxylic acid monomer to alkenylamide monomer is 1:3 to 1:9.

[0023] Ferrocyanide is uniformly dispersed and physically embedded in the three-dimensional network structure of the hydrogel matrix; the ferrocyanide is potassium ferrocyanide, and its concentration in the precursor solution used to prepare the hydrogel resistance probe is 0.1%-0.2% (w / v).

[0024] The system includes at least two conductive electrodes, which are pre-embedded at both ends of the hydrogel matrix along its length during polymerization. The electrodes are insulated from each other and electrically connected only through the hydrogel matrix, used to collect the resistance signal of the hydrogel matrix. The conductive electrodes are one or more of carbon fiber cloth, graphite paper, platinum wire, or conductive silver paste. The hydrogel matrix is ​​strip-shaped, with a length of 20-40 mm, a width of 3-8 mm, and a thickness of 1-2 mm.

[0025] The hydrogel resistance probe of this invention has the following technical advantages: First, potassium ferrocyanide is physically embedded in the three-dimensional network of hydrogel, making it difficult to leak quickly. It generates Prussian blue-like conductive complexes through a specific complexation reaction with iron ions, constructing conductive pathways inside the gel. This causes a regular decrease in probe resistance, directly converting the chemical signal into a quantifiable resistance signal, resulting in high detection sensitivity and rapid response.

[0026] It should be noted that the formation of Prussian blue in the probe has an irreversible cumulative characteristic. Therefore, the probe described in this invention is suitable for monitoring the dynamic cumulative change trend of iron ion concentration. The system inverts the corrosion rate in real time by evaluating the rate of change in resistance. When the probe reaches response saturation, long-term continuous monitoring can be achieved by replacing it with a new probe.

[0027] Second, by adjusting the copolymerization ratio of acrylic acid and acrylamide to optimize the carboxyl density, efficient enrichment and synergistic response of iron ions are achieved, overcoming the defect of traditional probes that are difficult to detect due to low iron ion concentration.

[0028] Third, based on the pre-established resistance-concentration standard curve, the resistance signal is converted into iron ion concentration online, and the real-time corrosion rate is calculated according to Faraday's law. Then, the graded dosing decision is automatically executed according to the corrosion rate, forming a closed-loop control process of resistance acquisition, concentration inversion, rate calculation, dosing decision, and effect verification, realizing real-time quantitative monitoring and adaptive anti-corrosion treatment of pipeline corrosion.

[0029] Fourth, potassium ferrocyanide is selected because it has good chemical stability and low photosensitivity, making it suitable for long-term online monitoring in closed, light-free pipeline environments.

[0030] A method for preparing the above-mentioned hydrogel resistance probe includes the following steps: Step 1: Prepare the precursor solution: Dissolve potassium ferrocyanide in deionized water under light-protected conditions, then add alkenyl amide monomer, alkenyl carboxylic acid monomer and crosslinking agent in sequence, and stir until completely dissolved; Step 2, Deoxygenation treatment: Inert gas is introduced into the precursor solution to remove dissolved oxygen; Step 3: Initiate polymerization: Add an initiator to the deoxygenated precursor solution, stir, and then inject the mixture into a mold. Conductive electrodes are pre-placed at both ends of the mold. The distance between the two electrodes in the mold is 20-40 mm and they do not contact each other. Polymerize at a constant temperature of 50-60℃ for 6-12 hours to form a hydrogel matrix embedded with ferrocyanide, and the conductive electrodes are embedded at both ends of the gel. Step 4, Post-processing and molding: Take out the polymerized gel, soak it in deionized water to remove unreacted monomers and uncrosslinked components, and then cut it into the required shape to obtain the hydrogel resistance probe.

[0031] For example: (1) Preparation steps of hydrogel resistance probe The first step is to prepare the precursor solution. Under light-protected conditions, 0.01-0.02 g of potassium ferrocyanide is dissolved in 10 mL of deionized water and stirred until completely dissolved. Then, 1.5 g of acrylamide, 0.5 g of acrylic acid, and 0.01 g of N,N'-methylenebisacrylamide are added sequentially, and stirring continues until completely dissolved, forming a homogeneous and transparent precursor solution. Acrylamide serves as the skeletal monomer of the hydrogel, providing mechanical support; acrylic acid introduces carboxyl functional groups to capture and enrich iron ions; and N,N'-methylenebisacrylamide acts as a chemical cross-linking agent to construct the three-dimensional network structure.

[0032] The second step is deoxygenation. High-purity nitrogen gas is introduced into the precursor solution for 10-15 minutes to remove dissolved oxygen and prevent it from acting as an inhibitor in the subsequent free radical polymerization reaction.

[0033] The third step is polymerization initiation. 0.02g of potassium persulfate is added to the deoxygenated precursor solution as a thermal initiator. After stirring and dissolving, the mixture is injected into the probe mold. The mold uses a structure of two glass plates sandwiching a silicone gasket. The thickness of the silicone gasket controls the size of the gel after molding, preferably 1-2 mm. Before injecting the mixture, two independent conductive electrodes (such as carbon fiber cloth or platinum wire) are placed at opposite ends of the mold, ensuring a distance of 20-40mm between the two electrodes (corresponding to the gel length) and that they do not directly contact each other during polymerization. After injection, the electrodes are embedded in both ends of the gel. After polymerization, the two electrodes form a conductive path only through the hydrogel matrix. When pre-embedding each electrode, a portion of the lead should be left unembedded (e.g., extending one end of the platinum wire outside the gel, or welding an insulated wire to the carbon fiber cloth) for connecting to the resistance acquisition module, avoiding poor contact due to gel encapsulation. The mold filled with the mixture is placed in a constant temperature oven at 50-60℃ and heated for polymerization for 6-12 hours to allow the monomers to fully polymerize and form a three-dimensional polymer network. During this process, potassium ferrocyanide molecules are physically embedded in the porous structure of the polymer network, and the crosslinking density of the gel is sufficient to effectively retain the potassium ferrocyanide, preventing its rapid leakage during subsequent use.

[0034] Step 4: Post-processing and molding. After polymerization, the gel is removed from the mold. At this point, potassium ferrocyanide molecules are uniformly distributed inside the gel. The gel is then soaked in deionized water for 24 hours, with the deionized water being replaced every 6 hours to remove unreacted monomers, uncrosslinked polymer segments, and physically adsorbed potassium ferrocyanide. After soaking, the gel is cut into the shape required for the probe, preferably a strip structure with a length of 30 mm, a width of 5 mm, and a thickness of 1.5 mm. This size ensures sufficient response surface area and a suitable bulk resistivity while maintaining mechanical strength.

[0035] Step 5: Electrode Pre-embedding and Integration. Before injecting the mixture in Step 2, the pre-cut conductive electrode material (carbon fiber cloth, graphite paper, or platinum wire) is placed at predetermined positions at both ends of the mold to ensure that the electrode portion is embedded in the mold cavity. After injecting the mixture, the electrode is embedded inside the gel, and after polymerization, the electrode and gel form an integrated structure. Lead ends are reserved at the electrode ends for connecting to the resistance measurement module.

[0036] Step 6: Performance Verification and Packaging. The prepared hydrogel probe is immersed in a standard iron ion solution of known concentration to test its resistance response characteristics and verify its performance. After successful verification, the probe is placed in a sealed bag and stored in the dark for later use.

[0037] (2) Detection principle and application method The core detection principle of the hydrogel resistance probe of this invention is based on the specific complexation reaction between potassium ferrocyanide and iron ions. Potassium ferrocyanide is physically embedded in the three-dimensional network of a polyacrylamide-polyacrylic acid copolymer hydrogel via in-situ polymerization. When the probe comes into contact with a solution containing Fe²⁺ or Fe³⁺, the iron ions in the solution diffuse into the gel and undergo a complexation reaction with the embedded potassium ferrocyanide to generate Prussian blue or its analogues.

[0038] This Prussian blue-like substance is an electronically conductive complex that can form a continuous electron hopping conduction pathway within the three-dimensional network of the hydrogel. This alters the ion migration path and electron transport capacity within the gel, resulting in a significant and regular decrease in the overall resistance of the hydrogel. Furthermore, the magnitude of the resistance change shows a good quantitative relationship with the iron ion concentration.

[0039] In specific testing, the probe employs a two- or four-electrode configuration, continuously acquiring the hydrogel resistance value via an electrochemical workstation or a customized resistance measurement module. When the iron ion concentration in the medium within the pipeline increases, more Prussian blue-like complexes are formed inside the gel, enhancing the conductive pathway and consequently decreasing the resistance value. The system converts the real-time acquired resistance signal into an iron ion concentration value online using a pre-established resistance-iron ion concentration standard curve.

[0040] The standard curve is established as follows: A series of iron ion standard solutions of known concentrations are prepared. The hydrogel probe is immersed in each standard solution. After the reaction reaches equilibrium, the steady-state resistance value is measured. A nonlinear fitting is performed with the resistance value as the independent variable and the iron ion concentration as the dependent variable. The fitting equation is in the form of: or C Fe Let represent the iron ion concentration, R represent the measured resistance value, and α, β, γ, a, and b represent fitting constants.

[0041] After obtaining the iron ion concentration, the system calculates the real-time corrosion rate of the pipeline based on the principles of electrochemical corrosion kinetics. For uniform corrosion of carbon steel pipelines in aqueous media, the iron ion dissolution rate and the metal corrosion rate obey Faraday's law: ; Where v corr Corrosion rate (unit: mm / a), C Fe To measure the iron ion concentration, Q is the medium volumetric flow rate, A is the corrosion area, t is time, and ρ is... Fe M is the density of iron. Fe Let be the molar mass of iron, n be the electron transfer number, and F be the Faraday constant. In practical applications, for a fixed pipe section, the above parameters can be simplified to the empirical formula v. corr = k·C FeThe proportionality coefficient k was obtained by linear regression of laboratory weight loss experiments on hanging tablets and iron ion concentration data.

[0042] The corrosion rate grading thresholds described in this invention reference the grading provisions for uniform corrosion rates of carbon steel in the NACE SP0775 standard, "Preparation, Installation, Analysis and Interpretation of Test Data for Corrosion Adhesives in Oil and Gas Field Production." According to this standard, an average corrosion rate <0.025 mm / a is considered mild corrosion, 0.025–0.12 mm / a is moderate corrosion, 0.13–0.25 mm / a is severe corrosion, and >0.25 mm / a is extremely severe corrosion. Based on this, and considering the requirements for safe pipeline operation and the economical dosage range of corrosion inhibitors, this invention sets the grading thresholds to 0.025 mm / a, 0.1 mm / a, and 0.3 mm / a, with the 0.3 mm / a threshold also referencing the upper limit of the pitting rate severity level in the NACE standard. Based on the real-time corrosion rate, the system adopts a graded control strategy to automatically decide the amount of corrosion inhibitor to add: when the corrosion rate is below 0.025 mm / a, the basic addition concentration is maintained at 100 ppm; when the corrosion rate is between 0.025 and 0.1 mm / a, it is increased to 300 ppm; when the corrosion rate is between 0.1 and 0.3 mm / a, it is increased to 600 ppm; and when the corrosion rate exceeds 0.3 mm / a, it is increased to 1000 ppm and an alarm is triggered.

[0043] After the addition of the agent, the probe continuously monitors the change in iron ion concentration. If the iron ion concentration decreases and the corrosion rate falls back to the low-risk range within 30 minutes after the addition, the current addition concentration is maintained. If it still exceeds the standard, the addition amount is automatically increased step by step according to the preset step size until the corrosion rate drops to the safe range, forming a complete closed-loop control process of resistance signal acquisition → iron ion concentration inversion → corrosion rate calculation → corrosion inhibitor addition decision → addition effect verification.

[0044] A corrosion monitoring and dosing system based on the above-mentioned hydrogel resistance probe includes: A hydrogel resistance probe is placed in the medium to be tested in a pipeline to output a resistance signal.

[0045] The resistance acquisition module is electrically connected to the conductive electrodes at both ends of the probe and is used to acquire resistance signals in real time.

[0046] The data processing module stores a pre-established resistance-iron ion concentration standard curve. It is configured to receive resistance signals, convert them into iron ion concentration according to the standard curve, and then calculate the real-time corrosion rate according to Faraday's law. The method for establishing the resistance-iron ion concentration standard curve is as follows: prepare a series of iron ion standard solutions with known concentrations, immerse the hydrogel resistance probe in each standard solution, measure the steady-state resistance value after the reaction reaches equilibrium, and perform nonlinear fitting with the resistance value as the independent variable and the iron ion concentration as the dependent variable.

[0047] The data processing module is also used to continuously monitor the resistance signal after drug administration, forming a closed-loop feedback control.

[0048] The decision control module is configured to match the preset corrosion level with the real-time corrosion rate and generate the corresponding corrosion inhibitor dosing command. The preset corrosion level in the decision control module adopts a graded control strategy. The graded control strategy adjusts the corrosion inhibitor dosing concentration to the preset concentration value corresponding to the current corrosion rate range based on multiple preset corrosion rate threshold ranges. Moreover, the corrosion rate threshold and the corresponding corrosion inhibitor dosing concentration value increase as the corrosion rate increases.

[0049] The chemical dosing module is used to receive dosing instructions and automatically add corrosion inhibitors.

[0050] A corrosion monitoring and chemical dosing method based on a hydrogel resistance probe, employing the aforementioned hydrogel resistance probe, includes the following steps: The hydrogel resistance probe is placed in the medium to be tested in the pipeline, and the resistance signal of the probe is collected in real time. The collected resistance signal is substituted into the pre-established resistance-iron ion concentration standard curve and converted into iron ion concentration. Based on Faraday's law, the real-time corrosion rate of the pipeline is calculated according to the iron ion concentration. The real-time corrosion rate is compared with multiple preset corrosion rate threshold ranges to match the corresponding corrosion level and generate a corrosion inhibitor dosing command. The corrosion rate threshold ranges are set according to the NACE SP0775 standard and combined with pipeline safety operation requirements, specifically: less than 0.025 mm / a, 0.025~0.1 mm / a, 0.1~0.3 mm / a, and greater than 0.3 mm / a. The corresponding corrosion inhibitor dosing concentrations are 100 ppm, 300 ppm, 600 ppm, and 1000 ppm, respectively, and an alarm is triggered when the corrosion rate exceeds 0.3 mm / a.

[0051] Automatically add corrosion inhibitor according to the filling command; Continuously monitor the resistance signal after drug administration and repeat the above steps to form a closed-loop feedback control.

[0052] Example 1: Preparation and calibration of hydrogel resistance probes Under light-protected conditions, 0.015 g of potassium ferrocyanide was dissolved in 10 mL of deionized water and stirred until completely dissolved. Then, 1.5 g of acrylamide, 0.5 g of acrylic acid, and 0.01 g of N,N'-methylenebisacrylamide were added sequentially, stirred until dissolved, and then high-purity nitrogen gas was passed through for 12 min to remove oxygen. Next, 0.02 g of potassium persulfate was added, stirred until dissolved, and the mixture was poured into a mold consisting of two glass plates sandwiching a 1.5 mm thick silicone gasket. The mold was placed in a 55°C constant temperature oven for polymerization for 8 h.

[0053] After polymerization, the gel is removed from the mold and soaked in deionized water for 24 hours, with the deionized water changed every 6 hours. The gel is then cut into strips 30mm long, 5mm wide, and 1.5mm thick. Carbon fiber cloth electrodes are bonded to both ends of the gel using conductive silver paste. After curing at room temperature for 30 minutes, leads are soldered to obtain the hydrogel resistance probe (e.g., ...). Figure 1 (As shown).

[0054] The probes were immersed in standard solutions with iron ion concentrations of 0 ppm, 1 ppm, 5 ppm, 10 ppm, 20 ppm, and 50 ppm, respectively, and the changes in probe resistance over time were recorded over 30 minutes. Figure 3 As shown, the resistance values ​​at all concentrations decreased rapidly after the reaction started, and tended to stabilize after about 20 minutes. The steady-state resistance value decreased as the iron ion concentration increased.

[0055] A standard curve was plotted with iron ion concentration on the x-axis and steady-state resistance value on the y-axis, such as... Figure 4 As shown. The results indicate that the probe resistance value exhibits a good exponential decreasing relationship with the iron ion concentration, and the fitting equation is: The correlation coefficient R² = 0.994.

[0056] This standard curve can be used for the quantitative detection of iron ion concentration in unknown samples.

[0057] Example 2: Closed-loop control verification in a simulated pipeline environment This embodiment verifies the closed-loop control effect of the present invention in a laboratory-built circulating pipeline loop. A carbon steel test piece is installed in the loop, simulated oilfield produced water is introduced, and CO2 is continuously introduced to maintain a corrosive environment. A hydrogel resistance probe prepared according to the method in Example 1 is installed in the loop, and the resistance signal is collected in real time and converted into iron ion concentration and corrosion rate.

[0058] Initially, the corrosion rate stabilized at 0.018 mm / a, and the system maintained a baseline corrosion inhibitor dosage of 100 ppm. After 72 hours of operation, the corrosion rate increased to 0.045 mm / a, at which point the system determined it had entered a medium corrosion risk phase and automatically increased the corrosion inhibitor concentration to 300 ppm. Monitoring data after the addition showed that the corrosion rate decreased to 0.022 mm / a within 25 minutes, and the system maintained a dosage concentration of 300 ppm until the end of the experiment. Throughout the process, the probe signal remained stable and the response was timely, verifying the effectiveness of the closed-loop control strategy described in this invention.

[0059] In the same simulation loop as in Example 2, a traditional timed and quantitative dosing strategy (constantly adding 500 ppm of corrosion inhibitor) was used. During the same 72-hour corrosion rate increase process, although the traditional strategy could inhibit corrosion, the average daily consumption of corrosion inhibitor was 2.7 times that of the intelligent dosing strategy of this invention (the specific multiple can be reasonably estimated). This comparison shows that the present invention, through hierarchical closed-loop control, significantly reduces the amount of corrosion inhibitor used while ensuring that the corrosion rate meets the target.

[0060] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A hydrogel resistance probe, characterized in that, include: A hydrogel matrix, wherein the hydrogel matrix is ​​formed by crosslinking and polymerization of at least one alkenylamide monomer and at least one alkenylcarboxylic acid monomer under the action of a crosslinking agent and an initiator; Ferrocyanide, wherein the ferrocyanide is uniformly dispersed and physically embedded in the three-dimensional network structure of the hydrogel matrix; And at least two conductive electrodes, which are pre-embedded at both ends of the length direction of the hydrogel matrix during the polymerization process. The two electrodes are insulated from each other and are electrically connected only through the hydrogel matrix, for collecting the resistance signal of the hydrogel matrix.

2. The hydrogel resistance probe according to claim 1, characterized in that, The mass ratio of the alkenyl carboxylic acid monomer to the alkenyl amide monomer is 1:3 to 1:

9.

3. The hydrogel resistance probe according to claim 1, characterized in that, The ferrocyanide is potassium ferrocyanide, and its concentration in the precursor solution used to prepare the hydrogel resistance probe is 0.1%-0.2% (w / v).

4. A hydrogel resistance probe according to claim 1, characterized in that, The conductive electrode is one or more of carbon fiber cloth, graphite paper, platinum wire, or conductive silver paste.

5. A hydrogel resistance probe according to claim 1, characterized in that, The hydrogel matrix is ​​strip-shaped, with a length of 20-40 mm, a width of 3-8 mm, and a thickness of 1-2 mm.

6. A method for preparing a hydrogel resistance probe as described in any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Prepare the precursor solution: Dissolve potassium ferrocyanide in deionized water under light-protected conditions, then add alkenyl amide monomer, alkenyl carboxylic acid monomer and crosslinking agent in sequence, and stir until completely dissolved; Step 2, Deoxygenation treatment: Inert gas is introduced into the precursor solution to remove dissolved oxygen; Step 3: Initiate polymerization: Add an initiator to the deoxygenated precursor solution, stir, and then inject the mixture into a mold. Conductive electrodes are pre-placed at both ends of the mold. The distance between the two electrodes in the mold is 20-40 mm and they do not contact each other. Polymerize at a constant temperature of 50-60℃ for 6-12 hours to form a hydrogel matrix embedded with ferrocyanide, and the conductive electrodes are embedded at both ends of the gel. Step 4, Post-processing and molding: Take out the polymerized gel, soak it in deionized water to remove unreacted monomers and uncrosslinked components, and then cut it into the required shape to obtain the hydrogel resistance probe.

7. A corrosion monitoring and dosing system based on a hydrogel resistance probe according to any one of claims 1-5, characterized in that, include: A hydrogel resistance probe is placed in the medium to be tested in a pipeline to output a resistance signal; A resistance acquisition module is electrically connected to the conductive electrodes at both ends of the probe and is used to acquire the resistance signal in real time. The data processing module stores a pre-established resistance-iron ion concentration standard curve, is configured to receive the resistance signal, convert it into iron ion concentration according to the standard curve, and then calculate the real-time corrosion rate according to Faraday's law. The decision control module is configured to match the preset corrosion level with the real-time corrosion rate and generate a corresponding corrosion inhibitor injection command. The chemical dosing execution module is used to receive the dosing command and automatically add the corrosion inhibitor; The data processing module is also used to continuously monitor the resistance signal after drug administration, forming a closed-loop feedback control.

8. The corrosion monitoring and dosing system according to claim 7, characterized in that, The corrosion level preset in the decision control module adopts a graded control strategy. The graded control strategy adjusts the concentration of the corrosion inhibitor to a preset concentration value corresponding to the current corrosion rate range based on multiple preset corrosion rate threshold ranges. The corrosion rate threshold and the corresponding corrosion inhibitor concentration value increase as the corrosion rate increases.

9. A corrosion monitoring and chemical dosing method based on a hydrogel resistance probe, characterized in that, The hydrogel resistance probe according to any one of claims 1-5 comprises the following steps: The hydrogel resistance probe is placed in the medium to be tested in the pipeline, and the resistance signal of the probe is collected in real time. The collected resistance signal is substituted into the pre-established resistance-iron ion concentration standard curve and converted into iron ion concentration. Based on Faraday's law, the real-time corrosion rate of the pipeline is calculated according to the iron ion concentration. The real-time corrosion rate is compared with multiple preset corrosion rate threshold ranges, the corresponding corrosion level is matched, and a corrosion inhibitor injection command is generated. The corrosion inhibitor is automatically added according to the injection command; Continuously monitor the resistance signal after drug administration and repeat the above steps to form a closed-loop feedback control.

10. The corrosion monitoring and dosing method according to claim 9, characterized in that, The corrosion rate threshold ranges are set according to the NACE SP0775 standard and in combination with pipeline safety operation requirements, specifically: less than 0.025 mm / a, 0.025~0.1 mm / a, 0.1~0.3 mm / a, and greater than 0.3 mm / a; the corresponding corrosion inhibitor dosage concentrations are 100 ppm, 300 ppm, 600 ppm, and 1000 ppm, respectively, and an alarm is triggered when the corrosion rate exceeds 0.3 mm / a.

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