A corrosion prevention method for carbon steel pipe based on amino acid carbon source

Abstract

This invention discloses a method for corrosion protection of carbon steel pipes based on amino acid carbon sources, belonging to the field of wastewater treatment technology, specifically the interdisciplinary field of wastewater treatment and chemical technology. This method is suitable for inhibiting corrosion of carbon steel pipes and water treatment structures caused by anaerobic microorganisms. By adding an appropriate mass of D-Cys to the raw water of a wastewater treatment plant, and using a static mixer to thoroughly mix the D-Cys with the wastewater, the concentration of D-Cys in the pipe is maintained between 0.8 mM and 1.2 mM. Utilizing the dual anti-corrosion effect of D-Cys on carbon steel, firstly, it inhibits anaerobic biofilms by altering the cell morphology of anaerobic microorganisms, thus disrupting the local anaerobic environment; secondly, it forms a D-Cys self-assembled film on the carbon steel surface, isolating corrosive media, thereby achieving the purpose of corrosion protection for wastewater treatment plant pipes and structures. Compared with existing technologies, this method has significant advantages such as simplicity, high efficiency, non-toxicity, good water solubility, and continuous effectiveness. It can achieve in-situ corrosion protection without engineering measures and without altering material properties.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically the intersection of wastewater treatment and chemical technology, and particularly relates to a method for corrosion protection of carbon steel pipes based on amino acid carbon sources. Background Technology

[0002] With the development of wastewater treatment in China, prefabricated and integrated structural systems are gradually replacing traditional civil engineering projects, and pipes and equipment made of materials such as carbon steel and stainless steel are increasingly used in urban wastewater treatment plants. However, the long residence time of anaerobic microorganisms in wastewater within pipes makes the area beneath the formed biofilm highly susceptible to localized anaerobic conditions, leading to corrosion. Furthermore, high Cl- content has strong penetrating power and easily causes electrochemical corrosion. Corrosion treatment plays a crucial role in the service life of wastewater treatment plant pipe networks and equipment, directly affecting the stable production and safety of the plant.

[0003] When wastewater treatment plants are initially built, carbon steel is often used for rust removal followed by painting to enhance corrosion resistance, which is not low-carbon and environmentally friendly. Furthermore, in later stages of use, there are numerous problems associated with shutting down and venting the wastewater treatment plant for pipeline and equipment maintenance or renovation, such as the loss of activated sludge and the overall collapse of packing materials, which seriously affect overall production planning. Therefore, finding an environmentally friendly and sustainable solution to the corrosion problem of carbon steel pipes and ensuring the long-term use of wastewater treatment plant pipelines and equipment is now an urgent issue that cannot be ignored.

[0004] Currently, wastewater treatment mainly faces the problem of insufficient carbon sources at the treatment plant, resulting in poor nitrogen and phosphorus removal efficiency and requiring a large amount of external carbon sources to improve biodegradability. While common carbon sources such as methanol, sodium acetate, and glucose are more easily utilized by denitrifying bacteria, their low toxicity, singular function, and high chemical consumption make finding carbon sources with higher cost-effectiveness and better overall performance an important direction for future reform in the wastewater treatment industry.

[0005] Solving the aforementioned technical problems has long been a challenge for technicians in this field. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for corrosion protection of carbon steel pipes based on amino acid carbon sources. This method has significant advantages such as simplicity, high efficiency, non-toxicity, good water solubility, and continuous effectiveness. It can achieve in-situ corrosion protection without engineering measures and without changing the material properties.

[0007] The present invention solves the above problems through the following technical means:

[0008] A method for corrosion protection of carbon steel pipes based on amino acid carbon sources, characterized by comprising the following control steps:

[0009] Step 1) Based on the scale of wastewater treatment in the plant area, D-cysteine ​​(D-Cys) is added quantitatively to the wastewater pipeline in real time. A closed-loop control scheme is adopted to control the concentration of D-cysteine ​​(D-Cys) in the pipeline from 0.8 mM to 1.2 mM.

[0010] Step 2) Use a static mixer to thoroughly mix D-cysteine ​​(D-Cys) and wastewater in the pipe, and ensure that the mixed wastewater is in full contact with the inner wall of the pipe;

[0011] Step 3) Monitor the wastewater influent quality of the system in real time. The monitoring indicators include total nitrogen, ammonia nitrogen and total phosphorus values, in order to control the amount of external carbon source added to the biological treatment tank.

[0012] Preferably, the D-cysteine ​​(D-Cys) is added continuously.

[0013] Preferably, the static mixer is an SK type mixer or an SVL-300 type static mixer.

[0014] Preferably, the amount of external carbon source added to the controlled biochemical tank is calculated using the following method:

[0015] The carbon source dosage C for nitrogen and phosphorus removal is calculated as C=C n +C p Calculate, where: C n This refers to the amount of external carbon source that must be added for denitrification, C p This refers to the amount of external carbon source that must be added for phosphorus removal;

[0016] The amount of external carbon source C required for denitrification n Press C n =5N, where: 5 is the amount of external carbon source required to denitrify 1 kg of NO3-N, N is the amount of TN that needs to be removed by the external carbon source, and the amount of nitrogen N to be removed by denitrification using external carbon source is calculated as N=N e -N s Calculate, where: N e The actual total nitrogen (TN) concentration (mg / L) in the effluent from the secondary sedimentation tank; N s The TN emission standard for secondary sedimentation tanks;

[0017] The amount of external carbon source C required for phosphorus removal p Press C p =15P-C, where: 15 is the CP ratio, P is the amount of TP that needs to be removed by an external carbon source, and C is the difference in carbon source between the influent and effluent. The amount of TP that needs to be removed by an external carbon source is calculated as P=P e -P s Calculate, where: P e The effluent TP concentration, P s The standard for TP discharge from the secondary sedimentation tank.

[0018] Preferably, the closed-loop control scheme includes an electromagnetic flowmeter (2), a dosing device (3), and a controller (6), wherein:

[0019] The electromagnetic flowmeter (2) is installed between the inlet end (1) of the pipeline and the intermediate pipeline (4), and a static mixer (5) is installed between the intermediate pipeline (4) and the outlet end (7) of the pipeline.

[0020] The dosing device (3) is arranged on the intermediate pipeline (4);

[0021] The controller (6) controls the dosing device (3) in real time based on the feedback information from the electromagnetic flowmeter (2) to ensure that the concentration of D-cysteine ​​(D-Cys) in the pipeline is 0.8 mM to 1.2 mM.

[0022] Preferably, the concentration of D-cysteine ​​(D-Cys) in the control pipe is 1 mM.

[0023] The invented method for corrosion protection of carbon steel pipes based on amino acid carbon sources has the following beneficial effects:

[0024] This invention uses D-cysteine ​​(D-Cys) to solve two problems in existing sewage treatment plants: pipeline corrosion and high cost of adding external carbon sources. The corrosion inhibition rate of carbon steel pipeline equipment can reach more than 75%. At this time, the amount of D-Cys added can reduce the amount of external carbon sources needed for nitrogen and phosphorus removal in sewage treatment plants. The corrosion inhibitor and carbon source used in this method have significant characteristics such as being non-toxic, harmless, water-soluble, and continuously effective.

[0025] New wastewater treatment plants can directly use D-Cys, a simple, efficient, environmentally friendly, and low-carbon corrosion inhibitor, to achieve the purpose of corrosion protection for pipelines and equipment.

[0026] The wastewater treatment plant that has been built and put into operation can carry out in-situ corrosion protection of carbon steel pipelines without engineering measures or interruption of production and venting, without affecting the overall production schedule of the plant, and ensuring production plans and the safety of life and property.

[0027] Based on the initial D-Cys dosage, adjust the dosage of external carbon source in the biological treatment tank to reduce the cost of adding external carbon source and ensure that the effluent quality consistently meets the standards. Attached Figure Description

[0028] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1This is a schematic diagram of the actual operation of the present invention;

[0030] Figure 2 This is a schematic diagram of the laboratory test of the present invention;

[0031] Figure 3 This is a static corrosion weight loss diagram of carbon steel after 3 days of D-Cys corrosion following the application of this invention.

[0032] Figure 4 This is an electrochemical corrosion characteristic diagram of carbon steel after 3 days of D-Cys corrosion according to the present invention;

[0033] Figure 5 This is a microscopic morphology image of the carbon steel surface after adding D-Cys for 3 days according to the present invention;

[0034] Figure 6 This is the infrared spectrum of carbon steel after 3 days of D-Cys corrosion following the application of this invention;

[0035] Figure 7 This is a schematic diagram of the molecular structure, highest occupied molecular orbital (HOMO), and lowest vacant orbital (LUMO) optimized by D-Cys according to the present invention.

[0036] Among them, 1-the inlet end of the intercepted pipeline, 2-electromagnetic flowmeter, 201-flow converter, 202-electromagnetic flowmeter (left-handed), 203-electromagnetic flowmeter (right-handed), 3-dosing device, 301-dosing cover, 302-dosing port, 4-intermediate pipeline, 5-static mixer, 501-mixing vane, 502-static mixer (left-handed), 503-static mixer (right-handed), 6-intelligent controller, 601-dosing control knob, 602-flow control knob, 7-the outlet end of the intercepted pipeline. Detailed Implementation

[0037] In the description of this invention, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0038] The present invention will now be described in detail with reference to the accompanying drawings. Example 1

[0039] The corrosion protection method for carbon steel pipes based on amino acid carbon sources includes the following control steps:

[0040] Step 1) Based on the scale of wastewater treatment in the plant area, D-cysteine ​​(D-Cys) is added quantitatively to the wastewater pipeline in real time. A closed-loop control scheme is adopted to control the concentration of D-cysteine ​​(D-Cys) in the pipeline from 0.8 mM to 1.2 mM.

[0041] Step 2) Use a static mixer to thoroughly mix D-cysteine ​​(D-Cys) and wastewater in the pipe, and ensure that the mixed wastewater is in full contact with the inner wall of the pipe;

[0042] Step 3) Monitor the wastewater influent quality of the system in real time. The monitoring indicators include total nitrogen, ammonia nitrogen and total phosphorus values, in order to control the amount of external carbon source added to the biological treatment tank.

[0043] Specifically, the D-cysteine ​​(D-Cys) is added continuously.

[0044] Specifically, the movement of wastewater in a static mixer follows the pattern of "division-displacement-overlapping". Displacement plays a major role in the mixing process. In practical applications, SK-type mixers, SVL-300-type static mixers, etc. can be used. Example 2

[0045] Specifically, the following calculation method is used to control the amount of external carbon source added to the biological treatment tank:

[0046] The carbon source dosage C for nitrogen and phosphorus removal (calculated as COD, mg / L) is the sum of the carbon source dosages for nitrogen removal and phosphorus removal, expressed as C=C0. n +C p Calculate, where:

[0047] The amount of external carbon source C required for denitrification n (As COD, mg / L) According to C n =5N, where: 5—5 kg of external carbon source (based on COD) is required to denitrify 1 kg of NO3-N; N—the amount of TN (mg / L) that needs to be removed by the external carbon source; the amount of nitrogen N (mg / L) that needs to be removed by denitrification using an external carbon source is calculated as N=N e -N s Calculate, where: N e — Actual total nitrogen (TN) concentration in the effluent from the secondary sedimentation tank (mg / L); N s —TN discharge standard for secondary sedimentation tank (mg / L).

[0048] The amount of external carbon source C required for phosphorus removal p (As COD, mg / L) According to Cp =15P-C, where: 15—CP ratio; P—the amount of TP (mg / L) requiring external carbon source removal; C—the difference in carbon source between influent and effluent (calculated as COD, mg / L); the amount of TP (mg / L) requiring external carbon source removal is calculated as P=P e -P s Calculate, where: P e —Effluent TP concentration (mg / L); P s —TP discharge standard for secondary sedimentation tank (mg / L).

[0049] For example: A certain integrated wastewater treatment equipment has been operating stably, with a treatment capacity of 300-500 m³. 3 The effluent discharge standards for the secondary sedimentation tank are 15 mg / L for total nitrogen, 5 mg / L for ammonia nitrogen, and 0.5 mg / L for total phosphorus. Operational data shows that ammonia nitrogen has met the standards, while the effluent total nitrogen is 20 mg / L and the effluent total phosphorus is 3 mg / L. To achieve a 75% pipeline corrosion protection effect, the dosage of D-Cys is 36.3-60.5 kg / day, and the daily dosage of sodium acetate, an external carbon source for nitrogen and phosphorus removal, is 27.6-46.0 kg. The specific calculation method is as above. The COD equivalents of D-Cys and sodium acetate are 0.71 kgCOD / kgD-Cys and 0.68 kgCOD / kgsodium acetate, respectively. The dosage of D-Cys sufficient to meet the external carbon source requirements of this integrated wastewater treatment equipment when achieving a 75% pipeline corrosion protection effect.

[0050] For example: A certain town's wastewater treatment plant has been built and is operating stably, with a treatment capacity of 10,000 cubic meters per second. 3 / d, the discharge standards for total nitrogen in the secondary sedimentation tank are 15 mg / L, ammonia nitrogen is 5 mg / L, and total phosphorus is 0.5 mg / L. Operational data shows that ammonia nitrogen has met the standards, while the effluent total nitrogen is 20 mg / L and the effluent total phosphorus is 3 mg / L. To achieve a 75% pipeline corrosion prevention effect, the dosage of D-Cys is 1210 kg / d, calculated as above. The daily dosage of sodium acetate, an additional carbon source for nitrogen and phosphorus removal, is 919 kg. The dosage of D-Cys to achieve a 75% pipeline corrosion prevention effect can meet the needs of this urban wastewater treatment plant for external carbon sources. Example 3

[0051] In practical applications, the following methods are adopted: Figure 1The hardware layout shown includes an electromagnetic flowmeter (2), a dosing device (3), and a controller (6). The electromagnetic flowmeter (2) is installed between the inlet end (1) of the pipeline and the intermediate pipeline (4). A static mixer (5) is installed between the intermediate pipeline (4) and the outlet end (7) of the pipeline. The dosing device (3) is arranged on the intermediate pipeline (4). The controller (6) controls the dosing device (3) in real time based on the feedback information from the electromagnetic flowmeter (2) to ensure that the concentration of D-cysteine ​​(D-Cys) in the pipeline is 0.8 mM to 1.2 mM.

[0052] It should be noted that within the range of D-cysteine ​​(D-Cys) concentration from 0.8 mM to 1.2 mM, when the concentration of D-cysteine ​​(D-Cys) in the pipeline is 1 mM, the above steps result in the best anti-corrosion effect of D-cysteine ​​(D-Cys) on carbon steel pipes.

[0053] Specifically, the actual application equipment includes the intercepted pipe inlet / outlet end (1) and pipe outlet end (7), electromagnetic flowmeter (2), dosing device (3), intermediate pipe (4), static mixer (5), and controller (6), wherein: the pipe inlet / outlet end (1) is integrally connected to one end of the electromagnetic flowmeter (2), the other end of the electromagnetic flowmeter (2) is integrally connected to one end of the static mixer (5) through the intermediate pipe (4) where the dosing device (3) is located, and the other end of the static mixer (5) is connected to the intercepted pipe outlet end (7); the dosing device (3) is located above the intermediate pipe (4) between the electromagnetic flowmeter (2) and the static mixer (5), and its bottom is connected to the dosing port (302) Wastewater flow; the controller (6) is set at the outer end of the pipe and is connected to the electromagnetic flow meter (2) and the dosing device (3) respectively by wires; the electromagnetic flow meter (2) includes a flow converter (201), a flow converter left-hand rotation (202) and a flow converter right-hand rotation (203); the dosing device (3) includes a dosing cover (301) and a dosing port (302); the static mixer (5) includes a mixing vane (501), a static mixer left-hand rotation (502) and a static mixer right-hand rotation (503); the controller (6) includes a dosing control knob (601) and a flow control knob (602), and the controller (6) may include existing controllers such as PLC, FPGA or MCU. Example 4

[0054] like Figures 2 to 7As shown, the experimental instruments included an electrochemical workstation (Shanghai Chenhua Instrument Co., Ltd.); X-ray diffraction (Bruker, Germany); Fourier transform infrared spectrometer (Bruker, Germany); and X-ray photoelectron spectroscopy (ULVAC-PHI). Experimental reagents included D-cysteine ​​(Aike Reagent); acetone (Sinopharm Chemical Reagent Co., Ltd.); and anhydrous ethanol (Sinopharm Chemical Reagent Co., Ltd.). The experimental carbon steel sample was a Q235B carbon steel sample with the following composition: carbon content not exceeding 0.20%; manganese content not exceeding 1.4%; nickel content not exceeding 0.30%; and chromium content not exceeding 0.30%.

[0055] In practice, the weight loss method was used. Before the corrosion test, the samples were pretreated and weighed using an electronic balance, accurate to 0.01 mg. The Q235B carbon steel samples were immersed in sewage for 3 days, then removed. Corrosion products were removed using a soft brush dipped in rust-removing solution. The samples were rinsed with distilled water and anhydrous ethanol, dried to constant weight, and cooled to room temperature before a second weighing to determine the corrosion rate. The test data were repeated three times, and the average value was used. Figure 3 It can be seen that after 3 days of corrosion, the carbon steel sample in the D-Cys environment suffered far less mass loss than the blank control environment, indicating that D-Cys has a strong corrosion inhibition effect on carbon steel immersed in sewage.

[0056] In practice, electrochemical methods can also be used. For example, a traditional three-electrode system can be employed, with a carbon steel electrode as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum electrode as the auxiliary electrode. A 1 M NaCl solution can be used as the electrolyte. The pretreated carbon steel working electrode and the platinum electrode are placed as close to each other as possible, with the reference electrode positioned between them. Electrochemical tests are then performed, and the data are analyzed using ZView 2 simulation software. Figure 4 The polarization curves show that the shape of the polarization curves did not change significantly before and after the addition of D-Cys, only shifting left and right, indicating that D-Cys inhibits the reactive sites on the carbon steel surface to slow down corrosion. After the addition of D-Cys, the corrosion potential... E corr The shift is less than 85 mV, indicating that D-Cys simultaneously inhibits the corrosion process at both the anode and cathode; and the corrosion current density... i corr The changes are much smaller than in an environment without D-Cys addition, and the corrosion inhibition rate can reach over 75%; the diameter of the capacitance ring in the impedance spectrum becomes larger, and the electrodes are less likely to gain or lose electrons during charge transfer in this environment, making corrosion less likely.

[0057] Samples were taken from wastewater and wastewater three days after the addition of D-Cys. They were then immersed in 5% glutaraldehyde solution for 30 min to fix the biofilm, followed by stepwise dehydration with anhydrous ethanol at different concentration gradients. The microstructure was observed using ApreoS scanning electron microscopy. Figure 5It can be seen that in the environment without D-Cys addition, the sample surface is covered with a layer of anaerobic microbial biofilm; while in the environment with D-Cys addition, due to the biofilm disintegration function of D-Cys, there is basically no anaerobic biofilm on the sample surface. D-Cys disrupts the local anaerobic environment under the biofilm and slows down the corrosion of the carbon steel surface.

[0058] The organic morphology of corrosion products on the surface of Q235B carbon steel after immersion in wastewater for 3 days was analyzed and determined using a Bruker TENSOR 27 Fourier transform infrared spectroscopy (FT-IR) spectrometer (Germany). Figure 6 It can be seen that after adding D-Cys, the position is at 3189 cm. −1 A strong and broad peak appeared at 1022 cm⁻¹, which was caused by the stretching vibration of surface hydroxyl groups (-OH), reflecting the role of -OH in the D-Cys corrosion inhibition process; −1 The tensile vibration peaks of COC at the point of origin clearly merged into a single strong peak, indicating that the COC group participated in the interaction between D-Cys and the rust layer-carbon steel, and formed a dense protective layer with metal ions such as Fe(II / III).

[0059] The results were completed using density functional theory (DFT) and its 6-31G(d) basis set and B3LYP correlation function, with the assistance of the Gaussian 09W program; the DFT results were visualized using Gauss View 6.0 software. Figure 7 It is known that the HOMO orbitals of D-Cys are mainly concentrated on the heteroatoms S and N. During adsorption, -CN and -CS are preferentially adsorbed, providing lone pairs of electrons to the empty d orbitals of Fe atoms to form coordinate bonds. D-Cys forms an amino acid film on the carbon steel surface, thereby slowing down corrosion. In addition, the LUMO orbital charge density distribution is scattered, mainly around O atoms, accepting electrons from the Fe surface to form back bonds, which enhances the adsorption of D-Cys on the carbon steel surface.

[0060] This method is applicable to inhibiting corrosion of carbon steel pipes and water treatment structures caused by anaerobic microorganisms. By adding an appropriate mass of D-Cys to the raw water of a wastewater treatment plant, and then thoroughly mixing the D-Cys with the wastewater using a static mixer, the concentration of D-Cys in the pipe is maintained at 1 mM. Utilizing the dual anti-corrosion effect of D-Cys on carbon steel, firstly, it inhibits anaerobic biofilms by altering the cell morphology of anaerobic microorganisms, thus disrupting the local anaerobic environment; secondly, through the coordination and feedback of heteroatoms such as O and S in its molecular structure with the empty d orbitals of Fe atoms, a self-assembled D-Cys film is formed on the carbon steel surface, isolating corrosive media and achieving the purpose of corrosion protection for wastewater treatment plant pipes and structures.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for corrosion protection of carbon steel pipes based on amino acid carbon sources, characterized in that, The following control steps are included: Step 1) Based on the scale of wastewater treatment in the plant area, D-cysteine ​​(D-Cys) is added quantitatively to the wastewater pipeline in real time. A closed-loop control scheme is adopted to control the concentration of D-cysteine ​​(D-Cys) in the pipeline from 0.8 mM to 1.2 mM. Step 2) Use a static mixer to thoroughly mix D-cysteine ​​(D-Cys) and wastewater in the pipe, and ensure that the mixed wastewater is in full contact with the inner wall of the pipe; Step 3) Monitor the influent water quality of the system in real time. The monitoring indicators include total nitrogen, ammonia nitrogen and total phosphorus values, in order to control the amount of external carbon source added to the biological treatment tank. The D-cysteine ​​(D-Cys) is added continuously. The static mixer is either an SK type mixer or an SVL-300 type static mixer; The amount of external carbon source added to the controlled biochemical tank is calculated using the following method: The carbon source dosage C for nitrogen and phosphorus removal is calculated as C=C n +C p Calculate, where: C n This refers to the amount of external carbon source that must be added for denitrification, C p This refers to the amount of external carbon source that must be added for phosphorus removal; The amount of external carbon source C required for denitrification n Press C n =5N, where: 5 is the amount of external carbon source required to denitrify 1 kg of NO3-N, N is the amount of TN that needs to be removed by the external carbon source, and the amount of nitrogen N to be removed by denitrification using external carbon source is calculated as N=N e -N s Calculate, where: N e The actual TN concentration (mg / L) in the effluent from the secondary sedimentation tank; N s The TN emission standard for secondary sedimentation tanks; The amount of external carbon source C required for phosphorus removal p Press C p =15P-C, where: 15 is the CP ratio, P is the amount of TP that needs to be removed by an external carbon source, and C is the difference in carbon source between the influent and effluent. The amount of TP that needs to be removed by an external carbon source is calculated as P=P e -P s Calculate, where: P e The effluent TP concentration, P s The standard for TP discharge from the secondary sedimentation tank.

2. The method for corrosion protection of carbon steel pipes based on amino acid carbon source according to claim 1, characterized in that, The closed-loop control scheme includes an electromagnetic flowmeter (2), a dosing device (3), and a controller (6), wherein: The electromagnetic flowmeter (2) is installed between the inlet end (1) of the pipeline and the intermediate pipeline (4), and a static mixer (5) is installed between the intermediate pipeline (4) and the outlet end (7) of the pipeline. The dosing device (3) is arranged on the intermediate pipeline (4); The controller (6) controls the dosing device (3) in real time based on the feedback information from the electromagnetic flowmeter (2) to ensure that the concentration of D-cysteine ​​(D-Cys) in the pipeline is 0.8 mM to 1.2 mM.

3. The method for corrosion protection of carbon steel pipes based on amino acid carbon sources according to claim 1, characterized in that, The concentration of D-cysteine ​​(D-Cys) in the control pipeline is 1 mM.

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