A compounded water treatment agent for an external cooling water system of a phase modifier and a use method thereof

Abstract

The application discloses a compounded water treatment agent for an external cooling circulating water system of a phase modifier and a use method thereof. The compounded water treatment agent is prepared by compounding a green and environment-friendly surfactant polyepoxysuccinic acid or a derivative thereof and quinoline quaternary amine salt or a derivative thereof through a compounding and synergistic principle, and the green and environment-friendly surfactant polyepoxysuccinic acid or the derivative thereof has the functions of corrosion inhibition, scale inhibition, corrosion inhibition and sterilization. The compounded water treatment agent can greatly reduce the corrosion rate of stainless steel of an external cooling water pipe, greatly improve the scale inhibition efficiency and sterilization performance of a cooling water system, and thus prevents the external cooling water system from being scaled, corroded and algal and bacterial breeding.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a compound water treatment agent for a condenser external cooling circulating water system and its application method. Background Technology

[0002] A synchronous condenser is a dynamic reactive power compensation device for the power grid, providing reliable support for voltage stability in DC transmission systems. During operation, a synchronous condenser generates a significant amount of heat. To ensure its normal operation, forced cooling measures must be implemented to dissipate this heat. Currently, most synchronous condensers are equipped with open-loop external cooling water systems. The tube sheet material of these systems is typically 304 stainless steel. The water source for open-loop circulating cooling water systems is generally industrial tap water. Because the makeup water contains hardness ions such as calcium and magnesium, corrosion-catalyzing ions such as chloride ions, and microorganisms, as operating time increases, the external cooling water continuously evaporates and concentrates, leading to a continuous increase in salts and other impurities, as well as an increase in ion content. This results in a growing amount of calcium and magnesium scale deposits on the heat exchange tubes. To prevent scale buildup on the water-side tube bundles and inside the pipes from affecting the safe and economical operation of the heat exchange equipment, chemical treatment is required for the open-loop circulating cooling water to prevent scaling and corrosion on the cooling tower shell and pipes. The chemical dosing system can continuously add corrosion and scale inhibitors according to the makeup water volume; it can also periodically add bactericides and algaecides based on the growth patterns of algae and bacteria. Based on the characteristics of the external cooling water quality and the water temperature of up to 70℃, screening and compounding highly efficient and environmentally friendly scale inhibitors, corrosion inhibitors and bactericides and algaecides will help prevent scale, corrosion and algae growth in the external cooling water system.

[0003] Several patents exist regarding the research on agents for circulating cooling water systems. Patent CN201210258569.9 discloses a method for recycling greywater into a circulating cooling water system. The method includes the following steps: (1) adding a zinc salt corrosion inhibitor and a first corrosion inhibitor to the greywater, wherein the first corrosion inhibitor contains hydroxycarboxylate and / or transition metal acid salt corrosion inhibitors, and the zinc salt corrosion inhibitor is different from the first corrosion inhibitor; (2) adding the greywater from step (1) to the circulating cooling water system as makeup water; (3) adding a phosphorus-free scale inhibitor and a copolymer scale dispersant to the circulating cooling water from step (2). This patented method can effectively inhibit corrosion of greywater delivery pipelines and circulating cooling water systems. When greywater is recycled into circulating cooling water, it is not necessary to add phosphorus corrosion inhibitors to the circulating cooling water. However, this patent only considers the corrosion and scaling problems of the circulating cold water system and does not consider the problem of bacterial and algal growth in the circulating water. Moreover, the temperature range of recycled water is around 20-30℃. In circulating cooling water with a temperature as high as 70℃, it is unknown how the scale inhibitor and corrosion inhibitor in this patent will perform.

[0004] Patent CN202222948067.0 discloses a water treatment device for the external cooling circulating water of converter station synchronous condensers, including a circulating water tank, an electrochemical water treatment device, a multi-media filtration device, and a nanofiltration water treatment device. A submersible pump is installed inside the circulating water tank, and an inlet is located on the outer shell of the circulating water tank. The outlet of the submersible pump is connected to the inlet of the electrochemical water treatment device via a pipe. The outlet of the electrochemical water treatment device is connected to the inlet of the multi-media filtration device via a pipe. The outlet of the multi-media filtration device is connected to the inlet of the nanofiltration water treatment device via a pipe. The outlet of the nanofiltration water treatment device is connected to the inlet via a pipe. This patent can reduce the content of scale-forming metal ions such as calcium and magnesium in the circulating water system, with a removal rate of over 80%, eliminating the scaling problem in the circulating water system. It also has oxidation and sterilization functions, reducing the risk of algae growth in the system, saving energy and reducing emissions, and reducing sewage discharge. However, this patent only considers the scaling and algae growth problems of the circulating cold water system and does not consider the corrosion problem of the circulating water.

[0005] Patent CN201010549402.9 discloses a reactive compound multifunctional water treatment agent and its preparation and application methods. This reactive compound multifunctional water treatment agent contains the following components in the following weight ratio: sodium chlorite: ferric sulfate: borax: itaconic acid = 1:0.8-1.5:0.01-0.03:0.05-0.1. When this agent is added to wastewater, a chemical reaction occurs between the components. The reaction products or intermediate products have bactericidal, flocculating, and adsorbing effects. Combined with the compounding effect of other components, this water treatment agent simultaneously possesses four functions: bactericidal, flocculating, adsorbing, and scale inhibition. However, this formula contains sodium chlorite, and itaconic acid is acidic. Adding it to a circulating cold water system will potentially corrode metal equipment, affecting equipment safety and lifespan.

[0006] To prevent or mitigate scaling, corrosion, and algae growth in the external cooling water system of a condenser, it is necessary to selectively screen and compound highly efficient, environmentally friendly scale and corrosion inhibitors and bactericides and algaecides based on the characteristics of the external cooling water quality and the water temperature of up to 70°C, thereby preventing scaling, corrosion, and algae growth in the external cooling water system. Summary of the Invention

[0007] To address the problems of scaling, corrosion, and algae growth in the external cooling circulating water system of a condenser at temperatures up to 70°C, this invention proposes a compound water treatment agent for the external cooling circulating water system of a condenser and its application method. Utilizing the principle of compound synergistic effect, this agent combines polyepoxysuccinic acid or its derivatives, a green and environmentally friendly surfactant that has both corrosion inhibition and scale inhibition and bactericidal properties, with quinoline quaternary ammonium salt or its derivatives. This compound agent can significantly reduce the corrosion rate of stainless steel external cooling water pipes and greatly improve the scale inhibition efficiency and bactericidal performance of the cooling water system, thereby achieving the purpose of preventing scaling, corrosion, and algae growth in the external cooling water system.

[0008] To achieve its objectives, the present invention employs the following technical solution:

[0009] This invention first discloses a compound water treatment agent for a condenser external cooling circulating water system, characterized in that: the compound water treatment agent is composed of polyepoxysuccinic acid or its derivatives and quinoline quaternary ammonium salt or its derivatives.

[0010] Preferably, in the compound water treatment agent, the mass percentage of polyepoxysuccinic acid or its derivatives is 5%-80%, and the mass percentage of quinoline quaternary ammonium salt or its derivatives is 95%-20%.

[0011] More preferably, in the compound water treatment agent, the mass percentage of polyepoxysuccinic acid or its derivatives is 10%-70%, and the mass percentage of quinoline quaternary ammonium salt or its derivatives is 90%-30%.

[0012] As a preferred option, the derivative of polyepoxysuccinic acid can be one of the following derivatives: (1) a PESA derivative synthesized by ternary copolymerization using L-cysteine, taurine and polyepoxysuccinic acid (PESA) as raw materials; (2) a derivative obtained by reacting polyepoxysuccinic acid with thiourea; (3) a derivative obtained by reacting polyepoxysuccinic acid with L-cysteine.

[0013] Preferably, the derivative of the quinoline quaternary ammonium salt can be one of benzyl quinoline quaternary ammonium salt derivative (BQD) and dimer indoleazine derivative.

[0014] The present invention also discloses a method for using the compound water treatment agent, specifically: the polyepoxysuccinic acid or its derivative and the quinoline quaternary ammonium salt or its derivative are stored separately, and when used, the polyepoxysuccinic acid or its derivative and the quinoline quaternary ammonium salt or its derivative are added to the external cooling circulating water of the condenser and stirred evenly.

[0015] As a preferred option, the dosage of the compound water treatment agent in the above-mentioned external cooling circulating water system of the condenser is calculated according to the ratio of compound water treatment agent to external cooling circulating water of the condenser as (5-200) mg: 1L.

[0016] The beneficial effects of this invention are reflected in:

[0017] The compound water treatment agent for the external cooling circulating water system of the present invention uses one of its raw materials: polyepoxysuccinic acid or its derivatives, which are nitrogen-free, non-phosphorus organic compounds with scale inhibition and corrosion inhibition functions, good biodegradability, and good thermal stability; and another raw material: quinoline quaternary ammonium salt or its derivatives, which have corrosion inhibition and bactericidal properties, are high-temperature resistant, and environmentally friendly. Therefore, the compound water treatment agent for the external cooling circulating water system of the present invention is a high-temperature resistant, green, and environmentally friendly corrosion inhibitor with corrosion inhibition, scale inhibition, and bactericidal properties.

[0018] Furthermore, the compound water treatment agent for the external cooling circulating water system of the present invention has a good corrosion inhibition effect on stainless steel in the external cooling circulating water of the condenser because the polyepoxysuccinic acid or its derivatives and quinoline quaternary ammonium salt or its derivatives have a good synergistic effect on corrosion inhibition. After compounding, its corrosion inhibition effect on stainless steel is significantly better than the corrosion inhibition effect of each raw material as a stainless steel corrosion inhibitor alone. Attached Figure Description

[0019] Figure 1 Electrochemical impedance spectroscopy of stainless steel electrodes in simulated external cooling circulating water containing different concentrations of corrosion inhibitors;

[0020] Figure 2 The scale inhibition rate of 10 mg / L polyepoxysuccinic acid (PESA) under different ambient temperatures;

[0021] Figure 3 The scale inhibition rate of 10 mg / L polyepoxysuccinic acid (PESA) with different concentrations of quinoline quaternary ammonium salt (HQ) was measured at an ambient temperature of 70℃.

[0022] Figure 4 The sterilization rate of different concentrations of quinoline quaternary ammonium salt (HQ) bactericide on circulating water bacteria;

[0023] Figure 5 The bactericidal rate of circulating water bacteria after compounding quinoline quaternary ammonium salt (HQ) bactericide with polyepoxysuccinic acid (PESA) is measured. Detailed Implementation

[0024] To more clearly illustrate the purpose, features, and advantages of this invention, the technical solution of this invention will be described in detail below with reference to illustrations and implementation examples. The following content is merely an example and explanation of the innovative idea of ​​this invention. Any modifications, additions, or similar alternatives made by those skilled in the art to the specific implementation methods described, as long as they do not deviate from the innovative idea or exceed the limits defined in these claims, should be considered within the scope of protection of this innovation.

[0025] This embodiment compares the corrosion inhibition effects of polyepoxysuccinic acid (PESA) and quinoline quaternary ammonium salt (HQ) alone, as well as a compound corrosion inhibitor composed of PESA and HQ, on stainless steel, including the following steps:

[0026] (1) Preparation of the external cooling circulation aqueous solution for simulating a camera condenser

[0027] Based on the quality of the external cooling water of the condenser, prepare a simulated external cooling circulating aqueous solution according to the composition in Table 1.

[0028] Table 1 Comparison of Test Results and Standard Values ​​of External Cooling Water Indicators for Synchronous Condenser

[0029]

[0030] (2) Corrosion performance of stainless steel in external cooling circulating water of a simulated synchronous condenser without corrosion inhibitor

[0031] Electrochemical impedance spectroscopy was used to study the corrosion performance of stainless steel in simulated external cooling circulating water without corrosion inhibitors.

[0032] (3) Corrosion inhibition effect of 10mg / LPESA on stainless steel when used alone

[0033] Electrochemical impedance spectroscopy was used to study the corrosion inhibition effect of 10 mg / L PESA alone on stainless steel in the external cooling circulating water of a simulated camera condenser.

[0034] (4) Corrosion inhibition effect of 10mg / LHQ on stainless steel when used alone

[0035] Electrochemical impedance spectroscopy was used to study the corrosion inhibition effect of 10 mg / L HQ alone on stainless steel in the external cooling circulating water of a simulated camera condenser.

[0036] (5) When the total concentration of corrosion inhibitor is 10 mg / L, the corrosion inhibition effect of PESA and HQ compounded at a concentration ratio of 7:3 on stainless steel.

[0037] Electrochemical impedance spectroscopy was used to study the corrosion inhibition effect of a PESA and HQ mixture with a concentration ratio of 7:3 on stainless steel in simulated external cooling circulating water of a camera condenser when the total concentration of corrosion inhibitor was 10 mg / L.

[0038] (6) The corrosion inhibition effect of PESA and HQ compounded at a total corrosion inhibitor concentration of 10 mg / L on stainless steel.

[0039] Electrochemical impedance spectroscopy was used to study the corrosion inhibition effect of a PESA and HQ mixture with a concentration ratio of 5:5 on stainless steel in simulated external cooling circulating water of a camera condenser when the total concentration of the corrosion inhibitor was 10 mg / L.

[0040] (7) The corrosion inhibition effect of PESA and HQ compounded at a total corrosion inhibitor concentration of 10 mg / L on stainless steel.

[0041] Electrochemical impedance spectroscopy was used to study the corrosion inhibition effect of a PESA and HQ compound with a concentration ratio of 3:7 on stainless steel in simulated external cooling circulating water of a camera condenser when the total concentration of corrosion inhibitor was 10 mg / L.

[0042] (8) Electrochemical impedance spectroscopy method

[0043] The experiment was conducted in a three-electrode system. The test medium consisted of simulated external cooling circulating water from a camera condenser, with and without corrosion inhibitors. The working electrode was a 304 stainless steel electrode, sealed with epoxy resin, with a working area of ​​1 cm². 2 The surface was polished with #1 to #6 metallographic sandpaper, degreased with anhydrous ethanol, and rinsed clean with deionized water. The auxiliary and reference electrodes were a platinum (Pt) electrode and a saturated calomel electrode (SCE), respectively. Electrochemical impedance spectroscopy measurements were performed using a Chenhua CHI700 electrochemical workstation, with a frequency range of 10 Hz. 5 Hz-0.05Hz, with a peak AC excitation signal of 5mV.

[0044] (9) Electrochemical impedance spectroscopy analysis

[0045] Figure 1 This shows the electrochemical impedance spectroscopy (EIS) of a stainless steel electrode in simulated external cooling circulating water containing different concentrations of corrosion inhibitors in a camera condenser. Generally, the larger the semicircle of the impedance spectrum, the higher the impedance of the electrode and the better the corrosion inhibition performance of the inhibitor. Figure 1 It can be seen that the stainless steel electrode with added HQ or PESA is much larger than the blank electrode, indicating that these two corrosion inhibitors have a good inhibitory effect on the corrosion of stainless steel electrodes in simulated external cooling circulating water. Moreover, under the same total concentration, the corrosion inhibition effect of PESA and HQ in the compound ratio of 7:3, 5:5, and 3:7 is higher than that of HQ or PESA alone, indicating that there is a good synergistic effect of corrosion inhibition between the two.

[0046] (10) PESA scale inhibition rate test

[0047] The scale inhibition rate of PESA was determined according to the national standard "Determination of scale inhibition performance of water treatment agents - calcium carbonate deposition method" (GB / T 16632-2019). Figure 2 The scale inhibition rate of 10 mg / L PESA in simulated external cooling circulating water of a synchronous condenser was compared under different ambient temperatures. The results show that ambient temperature has a significant impact on the scale inhibition rate of PESA. At room temperature, the scale inhibition rate of PESA is close to 100%. As the ambient temperature gradually increases from room temperature to 80℃, the scale inhibition rate of PESA gradually decreases. At an ambient temperature of 70℃, the scale inhibition rate is around 85%, still exhibiting good scale inhibition performance. Figure 3 The scale inhibition rate was measured at an ambient temperature of 70℃ after adding different concentrations of quinoline quaternary ammonium salt (HQ) to the simulated external cooling circulating water of a camera condenser containing 10 mg / L polyepoxysuccinic acid (PESA). The results showed that the scale inhibition rate was still around 85%, indicating that the addition of HQ had virtually no effect on the scale inhibition performance of PESA.

[0048] (11) HQ sterilization test

[0049] The external cooling circulating water solution of a converter station was used. Two experimental groups were set up: a sterilization experimental group and a control group without added chemicals. Different concentrations of HQ (10, 100, 150, and 200 mg / L) were added to the external cooling circulating water solution of the sterilization experimental group, and the bacterial survival rate in the circulating water was measured 24 hours after addition. Figure 4 The study compared the bactericidal rates of different concentrations of quinoline quaternary ammonium salt (HQ) bactericide on circulating water. The results showed that after adding 150 mg / L HQ, the bactericidal rate could reach over 90%, indicating that HQ has good bactericidal ability. Figure 5 The results showed that the bactericidal rate of the compound quinoline quaternary ammonium salt (HQ) bactericide and polyepoxysuccinic acid (PESA) on circulating water bacteria remained above 90%, and the addition of PESA had virtually no impact on the bactericidal performance of HQ.

[0050] Therefore, adding a compound water treatment agent consisting of PESA and HQ to the external cooling water system of the condenser can simultaneously achieve good corrosion inhibition, scale inhibition, and bactericidal effects.

[0051] The above description is merely an exemplary embodiment of the present invention and does not imply any limitation thereof. Without departing from the spirit and principles of the present invention, those skilled in the art can make various modifications and improvements to the present invention, and all such modifications and improvements should be included within the scope of protection of the present invention.

Claims

1. A compound water treatment agent for a synchronous condenser external cooling circulating water system, characterized in that: The compound water treatment agent is composed of polyepoxysuccinic acid or its derivatives and quinoline quaternary ammonium salt or its derivatives. In the compound water treatment agent, the mass percentage of polyepoxysuccinic acid or its derivatives is 5%-80%, and the mass percentage of quinoline quaternary ammonium salt or its derivatives is 20%-95%. The polyepoxysuccinic acid or its derivatives and the quinoline quaternary ammonium salt or its derivatives are stored separately. When using, the polyepoxysuccinic acid or its derivatives and the quinoline quaternary ammonium salt or its derivatives are added to the external cooling circulating water of the condenser and stirred evenly.

2. The compound water treatment agent for the external cooling circulating water system of the condenser according to claim 1, characterized in that: In the compound water treatment agent, the mass percentage of polyepoxysuccinic acid or its derivatives is 10%-70%, and the mass percentage of quinoline quaternary ammonium salt or its derivatives is 30%-90%.

3. The compound water treatment agent for the external cooling circulating water system of the condenser according to claim 1, characterized in that: The dosage of the compound water treatment agent in the external cooling circulating water system of the condenser is calculated according to the ratio of compound water treatment agent to external cooling circulating water of condenser: 5~200mg:1L.

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