Application of biological bacteria in stainless steel material resistance to chloride ion corrosion

Abstract

The application provides application of a biological bacterial agent in stainless steel material resistance to chlorine ion corrosion, the biological bacterial agent is composed of a compound bacterial agent and a compound regulator in a mass ratio of 1:(0.5-2), the compound bacterial agent is composed of 5-30 parts of nitrifying bacteria dry powder, 15-25 parts of bacillus subtilis dry powder, 15-25 parts of denitrifying bacteria dry powder, 5-20 parts of photosynthetic bacteria dry powder, 8-20 parts of sulfur filamentous bacteria dry powder, 8-20 parts of methane bacteria dry powder, 15-30 parts of monocrystalline arabinose dry powder, 3-8 parts of vitamin C and 5-15 parts of carbonic acid amide, and the compound regulator is composed of 2-6 parts of active lysozyme dry powder, 20-40 parts of monocrystalline glucose dry powder, 20-60 parts of ammonium sulfate, 10-25 parts of ammonium chloride and 2-6 parts of ammonium molybdate. The biological bacterial agent can form a microbial membrane on the surface of the stainless steel, thereby greatly improving the resistance of the stainless steel to chlorine ion corrosion, and making it possible for the water circulation system to run under an ultrahigh concentration ratio.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and more specifically, to the application of biological agents in resisting chloride ion corrosion of stainless steel materials. Background Technology

[0002] Thermal power plants consume and discharge enormous amounts of water, accounting for a high proportion of total industrial water use. Therefore, actively promoting in-depth water conservation is of paramount importance for the survival and sustainable development of enterprises.

[0003] Circulating cooling water systems use water as the cooling medium and consist of heat exchange equipment, cooling equipment, water pumps, pipelines, and other related equipment. Their operational stability is crucial for ensuring continuous production in enterprises. Traditional circulating cooling water treatment involves adding chemical agents such as scale and corrosion inhibitors, sulfuric acid, bactericides, algaecides, and slime removers, which easily causes secondary pollution and results in low concentration ratios, large volumes of makeup water, and large volumes of wastewater. To address this, Chinese Patent Application No. 201510603628.5 discloses a biochemical water treatment agent and its application method. Through the natural regulation of the ecological balance by microorganisms in the circulating water system, a high concentration ratio of 7-9 times can be achieved, resulting in excellent water-saving effects.

[0004] However, according to DL / T712-2021 "Guidelines for Material Selection of Condensers and Auxiliary Coolers Tubes in Power Plants", the maximum allowable chloride ion concentration for stainless steel materials in circulating water systems is shown in Table 1 below.

[0005]

[0006] If the concentration ratio of the circulating water system is too high, the chloride ion content in the circulating water will exceed the chloride ion content of stainless steel, causing corrosion and seriously affecting the safe, stable, and economical operation of the circulating water system. Furthermore, current cooling water circulating systems use municipal greywater and reverse osmosis concentrate as makeup water sources. The reverse osmosis concentrate has a high chloride ion content, resulting in a limited concentration ratio. Clearly, high chloride ion concentration has become a significant factor affecting further water conservation in circulating water systems.

[0007] In view of this, the present invention is hereby proposed. Summary of the Invention

[0008] The problem solved by this invention is that existing stainless steel materials have poor resistance to chloride ion corrosion, which cannot meet the requirements of high concentration ratio operation of circulating water systems.

[0009] To address the aforementioned problems, this invention provides an application of a biological agent in resisting chloride ion corrosion of stainless steel materials. The biological agent comprises a composite agent and a composite regulator in a mass ratio of 1:(0.5-2). The composite agent consists of 5-30 parts of nitrifying bacteria dry powder, 15-25 parts of Bacillus subtilis dry powder, 15-25 parts of denitrifying bacteria dry powder, 5-20 parts of photosynthetic bacteria dry powder, 8-20 parts of sulfur filament bacteria dry powder, 8-20 parts of methanogenic bacteria dry powder, 15-30 parts of monocrystalline arabinose dry powder, 3-8 parts of vitamin C, and 5-15 parts of carbonate. The composite regulator consists of 2-6 parts of active lysozyme dry powder, 20-40 parts of monocrystalline glucose dry powder, 20-60 parts of ammonium sulfate, 10-25 parts of ammonium chloride, and 2-6 parts of ammonium molybdate.

[0010] Preferably, the biological agent is composed of a compound bacterial agent and a compound regulator in a mass ratio of 1:(0.5-2). The compound bacterial agent is composed of 5-15 parts of nitrifying bacteria dry powder, 15-20 parts of Bacillus subtilis dry powder, 15-20 parts of denitrifying bacteria dry powder, 5-15 parts of photosynthetic bacteria dry powder, 8-13 parts of sulfur filament bacteria dry powder, 12-20 parts of methanogenic bacteria dry powder, 15-30 parts of monocrystalline arabinose dry powder, 3-6 parts of vitamin C, and 10-15 parts of carbonate. The compound regulator is composed of 4-6 parts of active lysozyme dry powder, 20-35 parts of monocrystalline glucose dry powder, 30-50 parts of ammonium sulfate, 15-25 parts of ammonium chloride, and 3-6 parts of ammonium molybdate.

[0011] Preferably, the compound microbial agent is composed of 12-15 parts of nitrifying bacteria dry powder, 15-18 parts of Bacillus subtilis dry powder, 15-18 parts of denitrifying bacteria dry powder, 5-8 parts of photosynthetic bacteria dry powder, 11-13 parts of sulfur filament bacteria dry powder, 16-18 parts of methanogenic bacteria dry powder, 15-18 parts of monocrystalline arabinose dry powder, 4-5 parts of vitamin C, and 12-15 parts of carbonate. The compound regulator is composed of 5-6 parts of active lysozyme dry powder, 25-35 parts of monocrystalline glucose dry powder, 35-45 parts of ammonium sulfate, 18-22 parts of ammonium chloride, and 4-6 parts of ammonium molybdate.

[0012] Preferably, the stainless steel material is at least one of 304, 316, 316L, 317, and 317L.

[0013] Preferably, the stainless steel material is used to prepare the cooling water circulation system and can directly contact the circulating water. The cooling water circulation system includes a cooling tower, a circulating water pool, a first circulating water pipe, a second circulating water pipe, a sewage pipe, a makeup water pipe, and a condenser. The circulating water output end of the circulating water pool is connected to one end of the water side of the condenser through the first circulating water pipe, and the other end of the water side of the condenser is connected to the circulating water input end of the cooling tower through the second circulating water pipe. A pH sensor, a corrosion rate meter, and a second conductivity meter are installed on the second circulating water pipe, and the pH sensor and corrosion rate meter are both close to the condenser. A first conductivity meter and a makeup water pump are sequentially installed on the makeup water pipe, and a sewage pump is installed on the sewage pipe.

[0014] Preferably, the circulating cooling water system further includes a control system, which is electrically connected to the pH sensor, the first conductivity meter, the second conductivity meter, the corrosion rate meter, the water supply pump, and the sewage pump, respectively.

[0015] Preferably, the concentration ratio N of the circulating water system is in the range of 12-20. More preferably, the concentration ratio N is in the range of 16-20 times or 16-18 times.

[0016] Compared with existing technologies, the application of the biological agent of the present invention in the resistance to chloride ion corrosion in cooling water circulation systems has the following beneficial effects: 1) The biological agent can form a microbial film on the surface of stainless steel, thereby significantly improving the stainless steel's resistance to chloride ion corrosion; 2) By adding active lysozyme to form a composite regulator, since its destructive effect on Bacillus subtilis, a Gram-positive bacterium, is stronger than that on other Gram-negative bacteria, it can regulate the microbial composition in the biological community, while also having a certain degree of irritation to microorganisms, which is conducive to the formation of a biofilm with better corrosion resistance; 3) By combining the biological agent with the corrosion prediction rate, it is possible to respond to possible corrosion in advance, thereby making it possible to further increase the concentration ratio of the circulating water treatment system, resulting in significant water-saving effects. Attached Figure Description

[0017] Figure 1 These are microscopic images of different samples after acid washing in Experimental Example 1 of this invention, magnified 220 times. Figure 2 This is a schematic diagram of the experimental apparatus used in Experiment Example 2 of the present invention; Figure 3 This is the water quality change curve during the experiment in Experiment Example 2 of this invention; Figure 4 This shows the potential changes of electrodes made of different materials in open circuit in Experiment Example 2 of this invention; Figure 5 The following is an example of the variation in linear polarization resistance of electrodes made of different materials in an open circuit in Experiment Example 2 of this invention; Figure 6 The following are the surface conditions of different corrosion test pieces in Experimental Example 2 of the present invention, where A represents after the test and B represents after pickling; Figure 7 These are SEM images of the surfaces of different observation test pieces after acid washing in Experiment Example 2 of this invention; Figure 8 SEM images of the surface deposits of the specimen in Experiment Example 2 of this invention, a-50000x, b-10000x; Figure 9 This is a schematic diagram of the overall structure of the circulating water cooling system described in Embodiment 3 of the present invention; Explanation of reference numerals in the attached figures: 1-Cooling tower, 2-Circulating water tank, 3-Sewage pipe, 31-Sewage pump, 4-Make-up water pipe, 41-First conductivity meter, 42-Make-up water pump, 5-Circulating pump, 6-pH sensor, 7-Second conductivity meter, 8-First circulating water pipe, 9-Condenser, 10-Second circulating water pipe, 11-Dosing pipe, 111-Dosing tank, 112-Dosing pump; 12-Corrosion rate meter. Detailed Implementation

[0018] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Without conflict, the technical features in the embodiments of the present invention can be combined with each other.

[0019] Currently, thermal power plants account for 20% of the total industrial water consumption, which has become a constraint on the construction and development of the power industry in northern regions. In order to save water, cooling water in thermal power plants and many other industries is continuously recycled in open-loop cooling water systems, and the concentration ratio is the most important factor in the amount of water used.

[0020] Current technologies rely on the frequent addition of chemical agents such as corrosion inhibitors, scale inhibitors, and bactericides, along with timely water replenishment and drainage, to prevent corrosion and scaling in circulating water systems. The concentration ratio is typically around 3-5 times. However, with the use of biological agents, the natural regulation by microorganisms within the circulating water system allows for stable operation at concentration ratios of 7-9 times (e.g., CN105130016A) or even 12-15 times (e.g., CN115893724A). Further increasing the concentration ratio at these levels results in high chloride ion concentrations, significantly increasing the corrosive effect on the circulating water system.

[0021] Furthermore, circulating water systems typically utilize municipal greywater and reverse osmosis concentrate as makeup water sources, with chloride ion contents of approximately 63.46 mg / ml and 255.2 mg / ml, respectively. Increasing the amount of reverse osmosis concentrate will exacerbate the chloride ion corrosion problem in circulating water systems at high concentration rates. Therefore, the applicant conducted the following experiments: Experimental Example 1: Stainless Steel Chloride Ion Resistance Test at Constant Temperature Water samples were taken from the circulating water system in operation. The system had been previously treated with biological agents. An appropriate amount of sodium chloride was added to the water samples to prepare solutions with chloride ion concentrations of 1000, 1500, 2000, 2500, and 3000 mg / L.

[0022] Condenser tubes of different materials listed in Table 2 were cut to the same length and pretreated. The treatment process followed the standard "GB / T 18175-2014 Determination of Corrosion Inhibition Performance of Water Treatment Agents - Rotary Plating Method". They were then immersed in the solution in plastic bottles and placed in a preheated 36°C constant temperature water bath shaker, which was shaken at a constant speed of 100 rpm for 30 days. The compound regulator was added daily to meet the normal growth requirements of microorganisms.

[0023] After the experiment, the samples were weighed, and the corrosion rate was calculated based on the weight change. The results are shown in Table 2. Additionally, the samples were acid-washed and then observed under a microscope; the results are shown in Table 2. Figure 1 The pickling operation is existing technology and will not be described in detail here.

[0024]

[0025] ND: Below the detection limit Depend on Figure 1 As shown in Table 2, no pinholes appeared on the surface of the pickled stainless steel test tubes, indicating that no pitting corrosion or other corrosion phenomena occurred. After adding the compound bacterial agent, the 304 passivated (Xiamen University), 316L passivated (Xiamen University), 316L (Shiyan, Hubei), 316L (Jingxi Institute), and 317L (Baoding Thermal Power) test tubes did not exhibit obvious corrosion behavior in solutions with chloride ion concentrations of 1000, 1500, 2000, 2500, and 3000 mg / L.

[0026] Experimental Example 2: Stainless Steel Chloride Ion Tolerance Dynamic Concentration Test 1. Experimental Design Adopting such Figure 2 The apparatus shown is used for experiments. The apparatus consists of a circulating water tank 2, a heater, a level gauge, a pipeline filter, a circulating water pump, a rotor flow meter, an electrochemical electrode tank, a plate holder, a cooling tower 1, a cooling tower pool, and a makeup water tank. The cooling tower pool is located at the bottom of the cooling tower 1. The cooling tower pool is sequentially connected to the circulating water tank 2, the pipeline filter, the rotor flow meter, the electrochemical electrode tank, and the plate holder. The circulating water tank 2 is equipped with a heater and a level gauge. There are multiple plate holders, which are arranged in parallel with each other.

[0027] Water samples were taken from the circulating water system, which had been pre-treated with biological agents. The experimental temperature was set at 36℃, and water was replenished daily to eliminate evaporation losses. The replenished water consisted of circulating water samples with added sodium chloride to create a gradient concentration of chloride ions. The experiment lasted for 60 days. A compound regulator was added daily to meet the normal growth requirements of the microorganisms, and pH, conductivity, and Cl- were monitored. - Indicators and results are shown below. Figure 3 .

[0028] Simultaneously, corrosion electrochemical and corrosion test piece analyses were performed. Specifically, corrosion test pieces and observation test pieces were prepared according to Table 3. Test pieces were pretreated according to the standard "GB / T 18175-2014 Determination of Corrosion Inhibition Performance of Water Treatment Agents - Rotary Hanging Method". After treatment, the test pieces were installed in the hanging device. Simultaneously, the electrochemical working electrode was prepared using the stainless steel material shown in Table 3, with an effective electrode area of ​​0.5 cm². 2 After mechanical polishing and cleaning with distilled water, it is installed into the electrochemical electrode cell.

[0029] Electrochemical measurements were performed using a conventional three-electrode electrochemical setup. The reference electrode was a saturated calomel electrode (SCE) placed within an L-shaped salt bridge containing saturated potassium chloride solution. The auxiliary electrode was a 10 mm × 10 mm platinum sheet electrode. Electrochemical measurements were conducted at regular intervals using the working electrode and the circulating water available at that time. All electrochemical measurements were performed on an electrochemical workstation. Results are shown below. Figure 4-6 .

[0030] After the experiment, the samples were weighed and the corrosion rate was calculated based on the weight change; the results are shown in Table 3. Additionally, the samples were acid-washed and then observed under a microscope; the results are shown in Table 3. Figure 7-8 .

[0031] Experimental results 2.1 Water quality analysis Depend on Figure 3 It can be seen that the solution pH value continuously decreased from 8.37 to 7.84 within 0-10 days, and then remained in the range of 7.74-7.85; while the solution conductivity and Cl... - The concentration increased linearly due to evaporation and concentration, as well as the additional addition of chloride ions. At 60 days, the solution conductivity reached 14.76 mS / cm. - The concentration reached 6097.4 mg / L.

[0032] 2.2 Corrosion Electrochemical Analysis Depend on Figure 4It can be seen that the OCP values ​​of electrodes made of all materials showed a positive shift, indicating that microorganisms gradually attached to the metal surface and a microbial film gradually formed. Specifically, the OCP values ​​of the electrodes showed a significant positive shift within 0-20 days, during which the microorganisms were in a rapid growth phase on the metal surface. After 20 days, the OCP value changed less, indicating that the microbial growth was in a stable phase and the microbial film had basically formed.

[0033] Depend on Figure 5 It can be seen that the Rp values ​​of electrodes of different materials all show a trend of first increasing and then decreasing over time. During the period of 0-16 days, microorganisms attach and grow on the surface of stainless steel electrodes, and microbial films gradually form, which inhibits corrosion, so the Rp value of the electrode gradually increases. This is the formation period of microbial films, and the chloride ion concentration is low, so chloride ions have little effect on the metal electrode and the microbial film on its surface. After the 16th day, the salt concentration in the water gradually increases, and the Rp value of the electrode gradually decreases.

[0034] The chloride ion concentration at 60 days of the experiment was 6097 mg / L, far exceeding the limit specified in the standard "DL / T 712-2010 Guidelines for Material Selection of Condenser and Auxiliary Equipment Cooler Tubes in Power Plants". Based on actual field conditions, the chloride ion concentration in the circulating water is often below 6000 mg / L, at which point the dynamic concentration test is stopped. At this chloride ion concentration, the Rp value did not show a significant decreasing trend. This is because the formed microbial film has a protective effect on the metal electrodes. As the chloride ion concentration increases, the microbial film on the electrode surface is gradually destroyed, but at this stage, it does not penetrate the microbial film to corrode the metal substrate, and no obvious corrosion behavior occurs.

[0035] 2.3 Corrosion Test Piece Analysis

[0036]

[0037] Table 3 shows that none of the stainless steel specimens exhibited corrosion weight loss after the experiment, and the corrosion rate was less than the limit of 0.005 mm / a. This indicates that the biological agent formed a dense microbial film on the surface of the stainless steel specimens, which could prevent chloride ions from corroding the stainless steel substrate. Similarly, according to... Figure 7 It can be seen that after the test, a "coating layer" appeared on the surface of all stainless steel test pieces. The coating layer has a "rod-like" biological cell structure and contains some particulate impurities. It covers the entire surface of the test piece. The surface of the stainless steel test piece after pickling is smooth and has a metallic luster, indicating that no corrosion phenomena such as pitting corrosion occurred. Example

[0038] like Figure 9As shown, a circulating cooling water system includes a cooling tower 1, a circulating water pool 2, a sewage pipe 3, a sewage pump 31, a water supply pipe 4, a first conductivity meter 41, a water supply pump 42, a circulating pump 5, a pH sensor 6, a second conductivity meter 7, a first circulating water pipe 8, a condenser 9, a second circulating water pipe 10, a chemical dosing pipe 11, a chemical dosing tank 111, a chemical dosing pump 112, and a corrosion rate meter 12. The circulating water output end of the circulating water tank 2 is connected to one end of the water side of the condenser 9 through the first circulating water pipe 8, and the other end of the water side of the condenser 9 is connected to the circulating water input end of the cooling tower 1 through the second circulating water pipe 10. The chemical dosing pipe 11 is connected to the second circulating water pipe 10.

[0039] Preferably, a 220V fixed power supply is selected near the condenser 9 and connected to the area near the upper side of the grating plate of the drainage pump pit, with one power supply for each of units 1 and 2, each with a power of 0.5kW, to serve as the power supply for the second conductivity meter 7 and pH sensor 6, respectively.

[0040] Specifically, a circulating pump 5 and a condenser 9 are sequentially installed on the first circulating water pipeline 8.

[0041] A pH sensor 6, a second conductivity meter 7, and a corrosion rate meter 12 are sequentially installed on the first circulating water pipe 8. In this application, the pH sensor 6 installed in the circulating cooling water system can monitor the pH value of the circulating cooling water, the second conductivity meter 7 can detect the water quality of the circulating water online, and the corrosion rate meter 12 can monitor the instantaneous corrosion rate of the circulating cooling water on the metal online.

[0042] As an example of the present invention, the corrosion rate meter 12 uses linear polarization (LPR) to determine the linear polarization resistance of the metal electrode. Electrochemical polarization is achieved by applying a small potential perturbation to the test system near the open-circuit potential of the metal, and the resulting direct current is measured. Since the polarization potential and current are nearly linearly related under low current density polarization, their ratio is the linear polarization resistance, which is inversely proportional to the corrosion rate. Linear polarization is a relatively small-perturbation electrochemical testing method that does not significantly affect microbial metabolic activity, enabling continuous monitoring of metal corrosion rates.

[0043] The corrosion rate meter 12 obtains a stable potential value by measuring the open circuit potential (OCP) under current water quality conditions. A linear DC potential scan is performed within a narrow range (±10mV) relative to the open circuit potential using a linear polarization method, controlling the polarization potential within the micro-polarization region of the open circuit potential. The polarization potential and polarization current of the working electrode are measured at regular intervals; the slope at zero point yields the linear polarization resistance (RP), calculated using the following formula:

[0044]

[0045]

[0046] In the formula: R P —Linear polarization resistance, kΩ / cm 2 ; E —Polarization potential, mV; i —Polarization current, μA / cm 2 ; i corr —Corrosion current density, μA / cm 2 ; β a —Anode Tafel slope, mV; β c —Cathode Tafel slope, mV; v i —Instantaneous corrosion rate, mm / a; M —Molar amount of the metal, g / mol; n —Number of electrons transferred; F —Faraday constant, 96500 C / mol; ρ —Density of the specimen material, g / cm³ 3 .

[0047] A higher linear polarization resistance indicates a lower corrosion rate of the metal and a better anti-corrosion effect of the biological agent.

[0048] Specifically, the sewage discharge pipe 3 and the water replenishment pipe 4 are respectively connected to the circulating water tank 2. The sewage discharge pipe 3 is equipped with a sewage pump 31, and the water replenishment pipe 4 is equipped with a water replenishment pump 42 and a first conductivity meter 41. In this application, the sewage discharge flow rate and the water replenishment flow rate can be controlled by adjusting the start-up of the sewage pump 31 and the water replenishment pump 32 as needed, so that the conductivity and concentration ratio of the circulating cooling water are maintained within a certain range. The first conductivity meter can detect the water quality of the circulating water online.

[0049] Specifically, the dosing pipeline 11 is equipped with a dosing tank 111 and a dosing pump 112. In this application, the water quality parameters of the circulating water can be detected by the pH sensor 6, the first conductivity meter 41, and the second conductivity meter 7, and the concentration ratio can be calculated for dosing and sewage discharge. The dosing pump 112 provides power to add the required reagents to the dosing tank 111 to meet the requirements of the circulating water quality standards.

[0050] The present invention also provides a method for controlling the operation of circulating cooling water, comprising: S1, Circulating cooling water biochemical treatment Before starting the circulating cooling water system, a bactericide is added to the circulating water tank 2 for sterilization. After a period of time, the activated microbial preparation and compound regulator are added to the dosing tank 111. The dosing pump 112 provides power to put them into the dosing pipeline 11, and then enters the circulating cooling water system, finally reaching the circulating water tank 2. The compound microbial preparation and compound regulator are used to build a micro-ecological system in the circulating cooling water system.

[0051] Preferably, the steps include: S11. Add 0.03-0.05% sodium hypochlorite or other bactericides and algaecides to the circulating cooling water to kill microorganisms in the circulating cooling water; S12, The residual chlorine content should be reduced to 0.1 mg∙L. -1 Then, compound bacterial agents and biological regulators are added in proportion through the dosing pipe 11 to construct a micro-ecological system.

[0052] As an example of the present invention, the biological agent comprises 12 parts of nitrifying bacteria dry powder, 16 parts of Bacillus subtilis dry powder, 16 parts of denitrifying bacteria dry powder, 8 parts of photosynthetic bacteria dry powder, 12 parts of sulfur filament bacteria dry powder, 16 parts of methanogenic bacteria dry powder, 16 parts of monocrystalline arabinose dry powder, 5 parts of vitamin C, and 14 parts of carbonate amide. The composite regulator comprises 6 parts of lysozyme dry powder, 40 parts of ammonium sulfate, 22 parts of ammonium chloride, and 5 parts of ammonium molybdate.

[0053] Preferably, the nitrifying bacteria powder, Bacillus subtilis powder, denitrifying bacteria powder, and active lysozyme powder are produced by Cangzhou Wangfa Biotechnology Research Institute Co., Ltd., the photosynthetic bacteria powder and sulfur filament bacteria powder are produced by Jiangsu Lvke Biotechnology Co., Ltd., and the methanogenic bacteria powder is produced by Shandong Sukehan Bioengineering Co., Ltd.

[0054] Preferably, step S12 includes: S121, The residual chlorine content should be reduced to 0.1 mg∙L. -1 Then, the compound microbial agent and the compound regulator are added in proportion through the dosing pipe 11; as an example of the present invention, the addition proportions of the compound microbial agent and the compound regulator are 0.01% and 0.03%, respectively.

[0055] S122. Measure the initial pH value -H0 and the pH value -H1 of the circulating cooling water after 48 hours of operation, and determine whether H1 < H0. If yes, proceed to step S123; otherwise, add 0.005% compound bacterial agent again. S123. Determine if H1 > 8. If yes, add 0.015% compound regulator; if no, proceed to step S2. When the pH value decreases, it indicates that the active microorganisms have adapted to the circulating cooling water quality and begun to metabolize. When H1 > 8, add compound regulator to the circulating water. When H1 < 8, it indicates that the microbial activity has met the requirements for circulating cooling water treatment.

[0056] S2. Real-time monitoring based on the first conductivity table 41 and the second conductivity table 7, and calculation of the concentration factor N;

[0057] in: κ i —Real-time conductivity of circulating cooling water, μs / cm; κ 0 — Conductivity of circulating water, μs / cm.

[0058] The concentration ratio of circulating cooling water is usually measured manually—that is, the ratio of salt content (dissolved solids) in circulating water to makeup water. However, this method has several drawbacks: 1) the waste liquid needs to be treated, wasting financial, material, and human resources; 2) the chemicals used are toxic, endangering the safety of operators; 3) silver nitrate, used for chloride ion testing, is expensive, increasing operating costs; 4) online chloride and calcium ion detectors require high investment and are inaccurate; 5) manual sampling followed by testing, especially for salt content (dissolved solids), takes a long time, and the calculation and notification to the shift operator for circulating water quality adjustment also takes a considerable amount of time, resulting in delays and potential corrosion and scaling problems in the circulating water system. The concentration ratio method of this invention overcomes these shortcomings.

[0059] S3. Automatically control the operation of circulating cooling water based on concentration ratio and pH.

[0060] The compound bacterial agent can consume the alkalinity of the circulating cooling water to control the pH < 8.2, thereby ensuring that there are no carbonate (CO3) ions participating in scaling in the circulating cooling water. 2- ) and hydroxide ions (OH) - Ions are used to prevent scaling in the circulating cooling water. Depending on the concentration factor, appropriate measures are taken. When the pH is close to the lower control limit, the instantaneous corrosion rate of the metal electrode is measured by a corrosion rate meter. The GM(1,1) model is used to predict the metal corrosion rate at future moments. Adjusting the amount of circulating cooling water to make up the water and the amount of wastewater discharged can prevent corrosion of the circulating cooling water system, thereby achieving continuous and stable operation at high concentration factors.

[0061] Step S3 includes: S31, Determine t k If the concentration factor N is greater than 5, proceed to step S32; otherwise, proceed to step S33. S32. Determine whether the pH of the circulating cooling water meets the condition of 7.5 < pH < 8.2. If yes, control the circulating water system to continue operating according to the preset conditions; if no, add compound bacterial agent or start the water replenishment pump 42. As an example of the present invention, when pH < 7.5, start the water replenishment pump 42 to replenish 2-5% of water and add 0.001% compound regulator at the same time; when pH > 8.2, add 0.005% compound bacterial agent; or start the water replenishment pump 42 to replenish 2-5% of water.

[0062] S33. Determine if the pH of the circulating cooling water is <8.2. If yes, proceed to step S34; otherwise, add 0.006% compound bacterial agent. S34. Determine if the pH of the circulating cooling water is <7.5. If yes, turn on the water replenishment pump 42 and replenish 5-10% of the water. If no, proceed to step S35. S35. Determine if the pH of the circulating cooling water is <7.7. If yes, proceed to step S36; otherwise, control the circulating water system to continue operating according to the preset conditions. S36. Calculate and determine whether t is true based on GM(1,1). k+1 Predicted instantaneous corrosion rate X at time t. k+1 ’ <A, if yes, then control the circulating water system to continue operating according to the preset conditions; if no, then start the water supply pump 42 and the sewage pump 31.

[0063] As an example of the present invention, the 3-20% circulating cooling water is replaced by turning on the water replenishment pump 42 and the sewage pump 31; preferably, the 3-5% circulating cooling water is replaced by turning on the water replenishment pump 42 and the sewage pump 31, while the concentration coefficient N=N*80%.

[0064] The time interval for measuring the instantaneous corrosion rate X can be 1 hour, 3 hours, 6 hours, 24 hours, etc. Preferably, t k+1 -t k =6h. This setting ensures accurate and reliable data for predicting the instantaneous corrosion rate X, while allowing sufficient time for adjustments, thereby achieving stable and reliable operation at high concentration ratios.

[0065] The predicted value X of the instantaneous corrosion rate k+1 ’ Prediction is performed using the grey theory GM(1,1) model: Establish a system with variable X(0) ={X (0) {(i), i=1,2,...,n} represents the non-negative monotonic raw data sequence of instantaneous metal corrosion rates collected. A grey prediction model for the time series is established. First, X... (0) One accumulation generates one accumulation sequence: X (1) ={X (1) ( k ), k =1,2,...,n} Where: X (1) ( k )= X (0) ( i )=X (1) ( k -1)+ X (0) ( k ) For X (1) ( k The following whitened differential equation can be established:

[0066] That is, the solution to the above whitening differential equation in the GM(1,1) model is:

[0067] The predicted value is:

[0068] Where: X—instantaneous corrosion rate of metal, in millimeters per year (mm / a); k — time series, in units of year (a), or month, day or hour; a—Development coefficient; u—Grey effect coefficient.

[0069] Preferably, step S36 further includes: S361, according to t K Instantaneous corrosion rate X at time point k Calculate and determine whether t is true using the GM(1,1) model. n+1 Predicted instantaneous corrosion rate X at time t. k+1 ’ <A, if yes, then control the circulating water system to continue operating according to the preset conditions; if no, proceed to step S362; According to t K-1 Instantaneous corrosion rate X at time point k-1 Calculate t k Predicted instantaneous corrosion rate X at time point k’ Determine if X k ’ / X K <1 and X k+1 ’ / X k ’ If the value is greater than 1, then start the water supply pump 42 and the sewage pump 31; otherwise, start the sewage pump 31.

[0070] This setup uses microbial metabolic activity to keep the circulating cooling water system operating at a high concentration ratio, while utilizing the microbial film formed by microbial metabolism to inhibit corrosion of stainless steel. In addition, it uses the predicted trend of metal corrosion rate to adjust dynamic responses such as water replenishment or sewage discharge in advance to prevent corrosion of metals, thereby further increasing the concentration ratio to 16-18 times and further achieving water conservation.

[0071] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. The application of biological agents in resisting chloride ion corrosion of stainless steel materials, characterized in that, The biological agent comprises a compound bacterial agent and a compound regulator. The compound bacterial agent consists of 5-30 parts of nitrifying bacteria dry powder, 15-25 parts of Bacillus subtilis dry powder, 15-25 parts of denitrifying bacteria dry powder, 5-20 parts of photosynthetic bacteria dry powder, 8-20 parts of sulfur filament bacteria dry powder, 8-20 parts of methanogenic bacteria dry powder, 15-30 parts of monocrystalline arabinose dry powder, 3-8 parts of vitamin C, and 5-15 parts of carbonate. The compound regulator consists of 2-6 parts of active lysozyme dry powder, 20-40 parts of monocrystalline glucose dry powder, 20-60 parts of ammonium sulfate, 10-25 parts of ammonium chloride, and 2-6 parts of ammonium molybdate. The stainless steel material is in direct contact with the circulating cooling water of the circulating cooling water system, and the application includes the following steps: S1. Circulating cooling water biochemical treatment, including: S11. Add 0.03-0.05% sodium hypochlorite to the circulating cooling water to kill microorganisms in the circulating cooling water; S12. Add compound bacterial agents and compound regulators through the dosing pipeline to construct a micro-ecological system, including: S121, until the residual chlorine content drops to 0.1 mg∙L -1 Then, add compound bacterial agent at 0.01% and compound regulator at 0.03% through the dosing pipeline; S122. Measure the initial pH value -H0 and the pH value -H1 of the circulating cooling water after 48 hours of operation, and determine whether H1 < H0. If yes, proceed to step S123; otherwise, add 0.005% compound bacterial agent again. S123. Determine whether H1 > 8. If yes, add 0.015% compound regulator; otherwise, proceed to step S2. S2. Monitor and calculate the concentration factor N in real time; S3. Operational control is performed based on the predicted values ​​of the concentration ratio N, pH, and instantaneous corrosion rate of the circulating cooling water, including: S31, Determine t k If the concentration factor N > 5 is satisfied at the time, proceed to step S32; otherwise, proceed to step S33. S32. Determine whether the pH of the circulating cooling water meets the condition of 7.5 < pH < 8.

2. If yes, control the circulating cooling water system to continue operating according to the preset conditions; if no, add compound bacterial agent or start the water replenishment pump. When pH < 7.5, start the water replenishment pump to replenish 2-5% of water; when pH > 8.2, add 0.005% compound bacterial agent. S33. Determine whether the pH of the circulating cooling water is <8.

2. If yes, proceed to step S34; otherwise, add 0.006% compound bacterial agent. S34. Determine if the pH of the circulating cooling water is less than 7.

5. If yes, turn on the water replenishment pump and add 5-10% water. If no, proceed to step S35. S35. Determine whether the pH of the circulating cooling water is less than 7.

7. If yes, proceed to step S36; otherwise, control the circulating cooling water system to continue operating according to the preset conditions. S36, according to t k Instantaneous corrosion rate X at time point k The grey theory GM(1,1) model is used to calculate and determine whether t is satisfied. k+1 Predicted instantaneous corrosion rate X at time point k+1 If A is true, then control the circulating cooling water system to continue operating according to the preset conditions; otherwise, proceed to step S37. S37, according to t k-1 Instantaneous corrosion rate X at time point k-1 Calculate t k Predicted instantaneous corrosion rate X at time point k Determine if X is satisfied. k ' / X k <1 and X k+1 ' / X k If the value is greater than 1, then turn on the water supply pump and the sewage pump; otherwise, turn on the sewage pump.

2. The application according to claim 1, characterized in that, The stainless steel material is at least one of 304, 316, 316L, 317, and 317L.

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