Boiler shutdown protection agent for thermal power plants and method for preparing the same

Abstract

The application provides a boiler shutdown protective agent for thermal power plants and a preparation method thereof, relates to the technical field of corrosion prevention of thermal power plant equipment, and comprises 15-25 parts of a film forming agent, 5-13 parts of a neutralizing agent, 10-20 parts of an oxime oxygen scavenger, 20-40 parts of a gas phase corrosion inhibitor, 2-5 parts of benzotriazole, and 5-8 parts of polyethylene glycol octylphenyl ether. The preparation method comprises the following steps: adding the neutralizing agent into a reaction kettle to adjust the pH value of a mixed solution; adding the film forming agent, the oxime oxygen scavenger and the benzotriazole into the mixed solution in sequence to form a protective agent base solution; adding the remaining neutralizing agent after the pH value is adjusted, and then adding the gas phase corrosion inhibitor; and adding polyethylene glycol octylphenyl ether and the remaining imidazoline oleic acid into the intermediate solution after the intermediate solution is heated to a set temperature for dispersion treatment. The application solves the problems of easy stratification or precipitation and uneven adsorption and film formation of active ingredients on the metal surface of the boiler, and achieves the technical effects of improving stability, film forming effect and protection ability.

Description

Technical Field

[0001] This invention relates to the field of corrosion protection technology for thermal equipment in power plants, and in particular to a boiler shutdown protection agent for thermal power plants and its preparation method. Background Technology

[0002] During boiler shutdown for standby or maintenance in thermal power plants, system depressurization leads to decreased sealing performance. The metal surfaces of the steam-water system readily come into contact with oxygen in the air and residual moisture within the system, triggering rapid electrochemical corrosion at a rate far exceeding that during normal operation. Prolonged shutdown corrosion can cause thinning of the boiler's metal tube walls, pitting and microcracks, and in severe cases, rust peeling. This not only significantly shortens the boiler's lifespan and increases maintenance costs but also creates safety hazards, threatening the reliability of subsequent start-ups and shutdowns and the long-term stability of the unit.

[0003] Currently, the boiler shutdown protection agents used in existing technologies for thermal power plants mainly consist of a single amine neutralizing agent or a simple film-forming agent compounded together; a few compound products simply combine two raw materials. The corresponding preparation methods are generally quite crude, involving adding all kinds of raw materials into a reaction vessel at room temperature and mixing them.

[0004] Therefore, in practical applications, existing boiler shutdown protection agents have poor stability due to their simple formulation design. During long-term storage, the protection agents are prone to stratification, precipitation, or component failure. In addition, the preparation method of direct mixing and stirring also results in some raw materials in the protection agent not reacting fully, and the utilization rate of active ingredients is low. This leads to uneven adsorption and film formation of the active ingredients on the boiler metal surface, resulting in insufficient density of the protective film, which cannot effectively block the contact between oxygen and moisture and the metal surface, making it difficult to form a durable and effective protective layer during shutdown. Summary of the Invention

[0005] The purpose of this invention is to provide a boiler shutdown protection agent for thermal power plants and its preparation method, so as to alleviate the technical problems in the prior art that are prone to stratification or precipitation and uneven adsorption film formation of active ingredients on the boiler metal surface.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: This invention provides a boiler shutdown protection agent for thermal power plants; It consists of the following components in parts by weight: Film-forming agent 15-25 parts; neutralizing agent 5-13 parts; oxime oxygen scavenger 10-20 parts; vapor phase corrosion inhibitor 20-40 parts; benzotriazole 2-5 parts; polyethylene glycol octylphenyl ether 5-8 parts.

[0007] Furthermore, the film-forming agent includes octadecylamine and imidazoline oleate; octadecylamine is 10-15 parts and imidazoline oleate is 5-10 parts; Furthermore, the neutralizing agent includes morpholine and ammonia; morpholine is 2 to 5 parts and ammonia is 3 to 8 parts.

[0008] Furthermore, the oxime-based oxygen scavengers include acetone oxime and dimethyl ketoxime; the amount of acetone oxime is 5 to 10 parts, and the amount of dimethyl ketoxime is 5 to 10 parts.

[0009] Furthermore, the vapor phase corrosion inhibitor includes cyclohexylamine carbonate and diisopropylamine nitrite; the amount of cyclohexylamine carbonate is 15-25 parts, and the amount of diisopropylamine nitrite is 5-15 parts.

[0010] The present invention also provides a method for preparing a boiler shutdown protection agent for thermal power plants, which is used to prepare the above-mentioned boiler shutdown protection agent for thermal power plants; Includes the following steps: Step 1: First, add 2 to 4 parts of neutralizing agent to the reaction vessel, start the stirring device to mix, and monitor and adjust the pH value of the mixed solution to the preset range during the stirring process; Step 2: Add 10-15 parts of octadecylamine, 4-8 parts of imidazoline oleate, 10-20 parts of oxime oxygen scavenger and 2-5 parts of benzotriazole to the mixed solution in sequence; adjust the temperature of the reaction vessel and stir continuously to form a protective agent base solution; Step 3: Add the remaining neutralizer to the base solution of the protective agent to adjust the pH value, and then add 20-40 parts of vapor phase corrosion inhibitor to form an intermediate solution; Step 4: After heating the intermediate liquid to the set temperature, add 5-8 parts of polyethylene glycol octylphenyl ether and the remaining oleic acid imidazoline to the reaction vessel for dispersion treatment. After dispersion is completed, test and package to obtain the boiler shutdown protection agent for thermal power plants.

[0011] Furthermore, step 1 is implemented in the following specific steps: Weigh 2 to 4 parts of the neutralizing agent and add them to the reaction vessel. Stir and mix, and record the pH value every 30 seconds. Adjust the pH value of the mixed solution to 8.0 to 8.5. If the pH value is below 8.0, add ammonia; if it is above 8.5, add morpholine until the pH value stabilizes within the preset range.

[0012] Furthermore, step 2 is implemented in the following specific steps: After ensuring the pH of the mixed solution is stable at 8.0–8.5 for at least 5 minutes, add the following ingredients in the following order: octadecylamine, imidazoline oleate, acetone oxime, dimethyl ketone oxime, and benzotriazole. Heat the solution to 40–45°C and stir continuously for 30 minutes. Stop heating and continue stirring to form the protective agent base solution.

[0013] Furthermore, step 3 is implemented in the following specific steps: Add the remaining morpholine and ammonia to the base solution of the protective agent, and adjust the pH of the base solution to 9.5-10.5 while stirring. Add the cyclohexylamine carbonate and diisopropylamine nitrite in that order until completely dissolved to form an intermediate solution.

[0014] Furthermore, step 4 is implemented in the following specific steps: Step 4.1: First, heat the intermediate liquid to 75-85℃, start the circulation system and keep it warm for 15-20 minutes to form a composite intermediate liquid containing stable activated micelles; Step 4.2: Add polyethylene glycol octylphenyl ether and the remaining 1-2 parts of oleic acid imidazoline in sequence. Use a gradient stirring speed of 250 rpm for 2-5 minutes, 900 rpm for 10-12 minutes, and 450 rpm for 15-18 minutes to defoam and control the micelle particle size to be stable at 50-200 nanometers. Step 4.3: After dispersion, allow the mixture to cool naturally to room temperature. Take samples from the top, middle, and bottom of the reactor for testing. Once the samples pass the test, fill and seal the micelle dispersion to obtain the boiler shutdown protection agent for thermal power plants.

[0015] Beneficial effects: The boiler shutdown protection agent provided by this invention comprises, by weight, the following components: 15-25 parts film-forming agent; 5-13 parts neutralizing agent; 10-20 parts oxime-based oxygen scavenger; 20-40 parts vapor-phase corrosion inhibitor; 2-5 parts benzotriazole; and 5-8 parts polyethylene glycol octylphenyl ether. The stepwise addition of polyethylene glycol octylphenyl ether in combination with imidazoline oleate significantly improves system compatibility, prevents stratification and precipitation, and controls the micelle particle size to the nanoscale, greatly enhancing corrosion inhibition and film uniformity. The compound system provided by this invention solves the defects of traditional single protective agents, such as easy stratification, precipitation, and failure. It offers high corrosion inhibition efficiency and comprehensive protective coverage, reducing the risk of electrochemical corrosion during boiler shutdown.

[0016] The preparation method provided by this invention first controls the pH of the system in stages to build a stable reaction environment, and then adds materials in a specific order to ensure that each component reacts fully. Combined with heat preservation and gradient stirring, the micelle particle size is precisely controlled within 50-200 nanometers, which can break the aggregation of components, improve the uniformity and stability of the system, significantly improve the film-forming effect and protective ability of the shutdown compound protective agent on the metal surface of the boiler, reduce the risk of corrosion and scaling during shutdown, facilitate rapid use when the boiler is shut down, and reduce the complexity of operation. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 A flowchart illustrating the preparation method of a boiler shutdown protection agent for thermal power plants provided in this embodiment of the invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0020] In a first aspect, the present invention provides a boiler shutdown protection agent for thermal power plants, which, by weight, comprises the following components: 15-25 parts of film-forming agent; 5-13 parts of neutralizing agent; 10-20 parts of oxime deoxidizer; 20-40 parts of vapor phase corrosion inhibitor; 2-5 parts of benzotriazole; and 5-8 parts of polyethylene glycol octylphenyl ether.

[0021] In embodiments of the present invention, the film-forming agent may be, but is not limited to, 15 parts, 20 parts, or 25 parts by weight. According to the weight parts, the neutralizing agent can be, but is not limited to, 5 parts, 9 parts or 13 parts; Oxime-based oxygen scavengers can be, but are not limited to, 10, 15, or 20 parts by weight; According to the weight parts, the vapor phase corrosion inhibitor can be, but is not limited to, 20 parts, 30 parts or 40 parts; Benzotriazole can be available in 2, 3 or 5 parts by weight; According to the parts by weight, polyethylene glycol octylphenyl ether can be 5 parts, 6 parts or 8 parts.

[0022] In embodiments of the present invention, 15 to 25 parts of the film-forming agent comprises 10 to 15 parts of octadecylamine and 5 to 10 parts of imidazoline oleate. For example, it can be 10 parts of octadecylamine and 5 parts of imidazoline oleate.

[0023] In embodiments of the present invention, 5 to 13 parts of the neutralizing agent comprises 2 to 5 parts of morpholine and 3 to 8 parts of ammonia. For example, it can be 5 parts of morpholine and 8 parts of ammonia.

[0024] In embodiments of the present invention, 10-20 parts of the oxime-based oxygen scavenger comprises 5-10 parts of acetone oxime and 5-10 parts of dimethyl ketoxime. For example, it can be 10 parts of acetone oxime and 10 parts of dimethyl ketoxime.

[0025] In embodiments of the present invention, 20-40 parts of the vapor phase corrosion inhibitor comprises 15-25 parts of cyclohexylamine carbonate and 5-15 parts of diisopropylamine nitrite. For example, it can be 25 parts of cyclohexylamine carbonate and 15 parts of diisopropylamine nitrite.

[0026] It should be noted that the 15-25 parts of film-forming agent include octadecylamine and imidazoline oleate added in portions. It can be quickly adsorbed and spread on the metal surface of the boiler to form a continuous and dense physical protective film, which can effectively isolate oxygen in the air and residual moisture in the system from direct contact with the metal substrate, thus blocking the occurrence of electrochemical corrosion from a physical level.

[0027] It should be noted that 5-13 parts of neutralizing agent can maintain a stable alkaline environment in the protective agent system, while neutralizing the acidic corrosive media within the system. Depending on the actual pH value, adding morpholine and ammonia in batches can stabilize the system's pH, ensuring that the active components for film formation, oxygen removal, and corrosion inhibition function stably under suitable conditions. This prevents the agents from becoming ineffective due to pH imbalance, and the mild alkaline environment will not cause alkaline corrosion damage to metal equipment.

[0028] It should be noted that 10-20 parts of oxime-based oxygen scavengers can quickly remove residual dissolved oxygen in the system after boiler shutdown, blocking the reaction pathway between oxygen and metal at the source of corrosion. These oxygen scavengers have a mild reaction, produce harmless and residue-free decomposition products, and will not generate deposits or contaminants in the system. They also exhibit good compatibility with film-forming and corrosion-inhibiting components, synergistically enhancing the overall corrosion protection effect.

[0029] It should be noted that 20 to 40 parts of vapor phase corrosion inhibitor have excellent vapor phase volatility performance, and can fully volatilize and diffuse in the sealed water and steam system of the boiler, achieving corrosion inhibition protection without dead angles in the whole system.

[0030] It should be noted that 2-5 parts of benzotriazole, as a specialized metal passivating agent, can rapidly combine with metal ions such as iron and copper on the boiler metal surface to form a stable chemical passivation film, further enhancing the corrosion resistance of the metal substrate. This component can inhibit pitting and intergranular corrosion on the metal surface, reduce the formation of corrosion cracks, and complement the film-forming and corrosion-inhibiting components.

[0031] It should be noted that 5-8 parts of polyethylene glycol octylphenyl ether, as a nonionic surfactant, can effectively reduce the interfacial tension of the protective agent system, improve the compatibility between the components within the system, and prevent the protective agent from stratifying, precipitating, or agglomerating during long-term storage. Simultaneously, this component can assist the active component in uniformly dispersing on the metal surface, improving micellar stability and film uniformity, allowing the protective agent to spread rapidly and form a uniform film after addition. This ensures both the storage stability of the product and optimizes the film-forming effect and protective efficiency during field use.

[0032] Secondly, such as Figure 1 As shown, the present invention provides a method for preparing a boiler shutdown protective agent for thermal power plants, comprising the following steps: Step 1: First, add 2 to 4 parts by weight of neutralizing agent to the reaction vessel, start the stirring device to mix, and monitor and adjust the pH value of the mixed solution to the preset range during the stirring process; Specifically, based on the total amount of each raw material to be prepared according to the pre-set amount of the compound protective agent, weigh 2 to 4 parts of the neutralizing agent (weigh 1 to 2 parts of morpholine and 1 to 2 parts of ammonia water respectively), then add the weighed morpholine and ammonia water to the reaction vessel, and then start the stirring device to stir the morpholine and ammonia water to make the morpholine and ammonia water fully mixed in the reaction vessel. During the stirring, record the pH value of the mixed solution every 30 seconds to determine whether the pH value of the mixed solution reaches between 8.0 and 8.5.

[0033] Based on the real-time pH value, if the pH value is below 8.0, ammonia water is added and stirring is continued, with the pH value monitored again after 1 minute; if the pH value is above 8.5, morpholine is added and stirring is continued, with the pH value monitored again after 1 minute. The pH value of the mixed solution is repeatedly adjusted until the pH value stabilizes between 8.0 and 8.5.

[0034] Step 2: Add 10-15 parts of octadecylamine, 4-8 parts of imidazoline oleate, 10-20 parts of oxime oxygen scavenger and 2-5 parts of benzotriazole to the mixed solution in sequence; adjust the temperature of the reaction vessel and stir continuously to form the protective agent base solution; Specifically, continuously monitor the pH value of the mixed solution in the reactor to ensure that the value is stable between 8.0 and 8.5 for at least 5 minutes. Then, according to the requirements, weigh out 10-15 parts of octadecylamine, 4-8 parts of imidazoline oleate, 5-10 parts of acetone oxime, 5-10 parts of dimethyl ketoxime, and 2-5 parts of benzotriazole. Add each weighed raw material to the mixed solution one by one in the following order: octadecylamine, imidazoline oleate, acetone oxime, dimethyl ketoxime, and benzotriazole. Keep the stirring device running continuously after each raw material is added.

[0035] After all five raw materials are added, the heating device of the reactor is started to heat the solution inside the reactor. At the same time, the mixture is continuously stirred during the heating process, and the temperature change inside the reactor is monitored in real time until the temperature inside the reactor reaches 40-45°C. After the temperature inside the reactor reaches 40-45°C, the heating device is kept running stably, and the mixture is stirred continuously for 30 minutes to ensure that the five raw materials react fully. The state of the mixed solution inside the reactor is observed regularly to gradually form the base liquid of the protective agent. After stirring for 30 minutes, the heating is stopped, and the stirring is maintained.

[0036] Step 3: After adjusting the pH value by adding the remaining neutralizing agent to the base solution of the protective agent, add 20-40 parts of vapor phase corrosion inhibitor to form an intermediate solution; Specifically, add the remaining 1-3 parts of morpholine and 2-6 parts of ammonia to the reactor while stirring to ensure thorough mixing of the newly added raw materials with the liquid in the reactor. While stirring continuously, record the pH value of the base solution every 30 seconds and observe the trend. If the pH value is below 9.5, add ammonia; if the pH value is above 10.5, add morpholine until the base solution stabilizes between 9.5 and 10.5. After the pH value of the base solution is stabilized, add the two raw materials one at a time to the reactor, first 15-25 parts of cyclohexylamine carbonate, then 5-15 parts of diisopropylamine nitrite, while stirring continuously until both raw materials are completely dissolved, forming a stable intermediate solution.

[0037] Step 4: After heating the intermediate liquid to the set temperature, add 5-8 parts of polyethylene glycol octylphenyl ether and the remaining oleic acid imidazoline to the reaction vessel for dispersion treatment. After dispersion is completed, test and package to obtain the boiler shutdown protection agent for thermal power plants.

[0038] Specifically, in step 4.1, the heating device of the reactor is started to heat the intermediate liquid, and the mixture is continuously stirred during the heating process to ensure that the intermediate liquid is heated evenly. At the same time, the temperature reading of the intermediate liquid is recorded every minute. If the temperature rise rate exceeds the preset threshold, the heating power is reduced; otherwise, the heating power is increased until the temperature of the intermediate liquid reaches 75-85°C. When the temperature reaches 75-85°C, the power of the heating device is adjusted to keep the temperature stable within this range. At the same time, the circulation system of the reactor is started to circulate the intermediate liquid. The temperature is then maintained for 15-20 minutes to form a composite intermediate liquid. After the temperature is maintained for the preset time, the addition of the device and the circulation system are stopped, and the stirring is maintained. The composite intermediate liquid is observed to form a uniform activated system. When the composite intermediate liquid completes prepolymerization, stable activated micelles are obtained.

[0039] Specifically, in step 4.2, weigh out 5-8 parts of polyethylene glycol octylphenyl ether and 1-2 parts of imidazoline oleate. Then, add the two raw materials to the reaction vessel in the order of polyethylene glycol octylphenyl ether first, followed by imidazoline oleate. Maintain a basic stirring speed of 250 rpm during the feeding process to allow the two raw materials to contact the intermediate liquid and begin to disperse, forming a micellar dispersion. Observe the state of the micellar dispersion in the vessel every 1 minute during stirring, and monitor the particle size every 2 minutes to initially observe the particle size change trend of the micellar dispersion. After stirring for 2-5 minutes, reduce the stirring speed... The stirring speed was steadily increased to 900 rpm and maintained for 10-12 minutes. During this time, the fineness of the micelle dispersion was observed every 2 minutes and the particle size was monitored every 3 minutes to observe the agglomerate breaking effect and particle size change. After maintaining the 900 rpm speed, the stirring speed was steadily reduced to 450 rpm and maintained for 15-18 minutes to defoam the micelle dispersion. The particle size was monitored every 3 minutes, and the stirring speed was adjusted according to the particle size monitoring results to ensure that the particle size of the activated gel remained stable within the range of 50-200 nanometers.

[0040] Specifically, in step 4.3, after dispersion, the heating and stirring devices of the reactor are turned off, allowing the micelle dispersion in the reactor to cool naturally to room temperature. During the cooling process, the state of the micelle dispersion in the reactor is observed every 5 minutes to check for any abnormalities. After the micelle dispersion has completely cooled to room temperature, a multi-point sampling method is used to extract equal amounts of micelle dispersion from the top, middle, and bottom of the reactor. The samples from the three locations are mixed evenly, and the pH value and micelle particle size of the samples are tested sequentially according to the preset testing standards to ensure that the pH value and micelle particle size are within the preset standard range. At the same time, the content of each component in the sample is checked to see if it meets the preset formula requirements. Then, the micelle dispersion that has passed the test in the reactor is transferred to a dedicated filling device, and the filling container is immediately sealed after filling to obtain the shutdown compound protective agent.

[0041] Example 1 This embodiment 1 provides a boiler shutdown protection agent for thermal power plants, which is composed of the following components by weight: 15 parts of film-forming agent (10 parts of octadecylamine and 5 parts of imidazoline oleate); 5 parts of neutralizing agent (2 parts of morpholine and 3 parts of ammonia); 10 parts of oxime scavenger (5 parts of acetone oxime and 5 parts of dimethyl ketone oxime); 20 parts of vapor phase corrosion inhibitor (15 parts of cyclohexylamine carbonate and 5 parts of diisopropylamine nitrite); 2 parts of benzotriazole; and 5 parts of polyethylene glycol octylphenyl ether.

[0042] The preparation method in this embodiment adopts the preparation method described above.

[0043] Example 2 This embodiment 2 provides a boiler shutdown protection agent for thermal power plants, which is composed of the following components by weight: 20 parts of film-forming agent (12 parts of octadecylamine and 8 parts of imidazoline oleate); 9 parts of neutralizing agent (4 parts of morpholine and 5 parts of ammonia); 15 parts of oxime scavenger (7 parts of acetone oxime and 8 parts of dimethyl ketone oxime); 30 parts of vapor phase corrosion inhibitor (20 parts of acetone oxime and 10 parts of dimethyl ketone oxime); 3 parts of benzotriazole; and 6 parts of polyethylene glycol octylphenyl ether.

[0044] The preparation method of this Example 2 is the same as that of Example 1.

[0045] Example 3 This embodiment 3 provides a boiler shutdown protection agent for thermal power plants, which is composed of the following components by weight: 25 parts of film-forming agent (15 parts of octadecylamine and 10 parts of imidazoline oleate); 13 parts of neutralizing agent (5 parts of morpholine and 8 parts of ammonia); 20 parts of oxime scavenger (10 parts of acetone oxime and 10 parts of dimethyl ketone oxime); 40 parts of vapor phase corrosion inhibitor (25 parts of acetone oxime and 15 parts of dimethyl ketone oxime); 5 parts of benzotriazole; and 8 parts of polyethylene glycol octylphenyl ether.

[0046] The preparation method of this Example 3 is the same as that of Example 1.

[0047] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that 5 parts of polyethylene glycol octylphenyl ether were not added. The preparation method was the same as in Example 1.

[0048] Comparative Example 2 Comparative Example 1 has the same components and weight parts as Example 1. The difference is that in the preparation method, all 5 parts of oleic acid imidazoline were directly added in step 2 without subsequent addition, and the other conditions remained unchanged.

[0049] The boiler shutdown protection agents for thermal power plants generated in Example 1, Comparative Example 1, and Comparative Example 2 were allowed to stand for 72 hours. The results are shown in Table 1.

[0050]

[0051] Table 1 As shown in Table 1, the present invention is far superior to traditional formulations and conventional mixing methods. Regarding stability after 72 hours of standing, the product of Example 1 showed no stratification or precipitation, maintaining a homogeneous and stable system. Comparative Example 1, without added polyethylene glycol octylphenyl ether, exhibited significant stratification and bottom precipitation, while Comparative Example 2, with a single addition of oleic acid imidazoline, showed slight stratification and upper layer turbidity; neither could achieve long-term stable storage. In terms of micelle size control, the average particle size of Example 1 was 126 nm, stably within the ideal nanoscale range of 50-200 nm, demonstrating excellent dispersibility. Comparative Example 1 showed severe micelle agglomeration with a particle size far exceeding 500 nm, and Comparative Example 2 also had a particle size of 382 nm, both exhibiting significant particle agglomeration. Regarding corrosion inhibition performance, Example 1 achieved a corrosion inhibition rate of 92.4% for boiler steel sheets, while Comparative Example 1 only achieved 68.7% and Comparative Example 2 only 75.1%, demonstrating a significant improvement in protection efficiency. Regarding the film formation on the metal surface, the embodiments were able to form a uniform, dense, and continuous complete protective film; Comparative Example 1 showed discontinuous film formation with exposed metal, and Comparative Example 2 showed uneven film thickness, neither of which could provide comprehensive and reliable protection for the boiler metal.

[0052] Overall, the addition of polyethylene glycol octylphenyl ether component and the stepwise addition of oleic acid imidazoline in the preparation method of this invention can synergistically improve the system compatibility, break up component agglomeration, and precisely control the micelle size, ultimately achieving simultaneous improvement in product stability, corrosion inhibition rate and film quality.

[0053] Finally, it should be noted that the specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A boiler shutdown protection agent for thermal power plants, characterized in that, It consists of the following components in parts by weight: Film-forming agent 15-25 parts; neutralizing agent 5-13 parts; oxime oxygen scavenger 10-20 parts; vapor phase corrosion inhibitor 20-40 parts; benzotriazole 2-5 parts; polyethylene glycol octylphenyl ether 5-8 parts.

2. The boiler shutdown protection agent for thermal power plants according to claim 1, characterized in that, The film-forming agent includes octadecylamine and imidazoline oleate; the octadecylamine is 10-15 parts and the imidazoline oleate is 5-10 parts.

3. The boiler shutdown protection agent for thermal power plants according to claim 2, characterized in that, The neutralizing agent includes morpholine and ammonia; the morpholine is 2 to 5 parts and the ammonia is 3 to 8 parts.

4. The boiler shutdown protection agent for thermal power plants according to claim 3, characterized in that, The oxime-based oxygen scavenger includes acetone oxime and dimethyl ketoxime; the amount of acetone oxime is 5 to 10 parts, and the amount of dimethyl ketoxime is 5 to 10 parts.

5. The boiler shutdown protection agent for thermal power plants according to claim 4, characterized in that, The vapor phase corrosion inhibitor comprises cyclohexylamine carbonate and diisopropylamine nitrite; the cyclohexylamine carbonate is 15-25 parts and the diisopropylamine nitrite is 5-15 parts.

6. A method for preparing a boiler shutdown protection agent for thermal power plants, used to prepare the boiler shutdown protection agent for thermal power plants as described in any one of claims 1 to 5. Its features are, Includes the following steps: Step 1: First, add 2 to 4 parts of neutralizing agent to the reaction vessel, start the stirring device to mix, and monitor and adjust the pH value of the mixed solution to the preset range during the stirring process; Step 2: Add 10-15 parts of octadecylamine, 4-8 parts of imidazoline oleate, 10-20 parts of oxime oxygen scavenger and 2-5 parts of benzotriazole to the mixed solution in sequence; adjust the temperature of the reaction vessel and stir continuously to form a protective agent base solution; Step 3: Add the remaining neutralizing agent to the base solution of the protective agent to adjust the pH value, and then add 20-40 parts of vapor phase corrosion inhibitor to form an intermediate solution; Step 4: After heating the intermediate liquid to the set temperature, add 5-8 parts of polyethylene glycol octylphenyl ether and the remaining oleic acid imidazoline to the reaction vessel for dispersion treatment. After dispersion is completed, test and package to obtain the boiler shutdown protection agent for thermal power plants.

7. The method for preparing the boiler shutdown protection agent for thermal power plants according to claim 6, characterized in that, Step 1 is implemented in the following steps: Weigh 2 to 4 parts of the neutralizing agent and add them to the reaction vessel. Stir and mix, and record the pH value every 30 seconds. Adjust the pH value of the mixed solution to 8.0 to 8.

5. If the pH value is below 8.0, add ammonia; if it is above 8.5, add morpholine until the pH value stabilizes within the preset range.

8. The method for preparing the boiler shutdown protection agent for thermal power plants according to claim 6, characterized in that, Step 2 is implemented in the following steps: After ensuring the pH of the mixed solution is stable at 8.0–8.5 for at least 5 minutes, add the following ingredients in the following order: octadecylamine, imidazoline oleate, acetone oxime, dimethyl ketone oxime, and benzotriazole. Heat the solution to 40–45°C and stir continuously for 30 minutes. Stop heating and continue stirring to form the protective agent base solution.

9. The method for preparing the boiler shutdown protection agent for thermal power plants according to claim 6, characterized in that, Step 3 is implemented in the following steps: Add the remaining morpholine and ammonia to the base solution of the protective agent, and adjust the pH of the base solution to 9.5-10.5 while stirring. Add the cyclohexylamine carbonate and diisopropylamine nitrite in that order until completely dissolved to form an intermediate solution.

10. The method for preparing the boiler shutdown protection agent for thermal power plants according to claim 6, characterized in that, Step 4 is implemented in the following steps: Step 4.1: First, heat the intermediate liquid to 75-85°C, start the circulation system and keep it warm for 15-20 minutes to form a composite intermediate liquid containing stable activated micelles; Step 4.2: Add polyethylene glycol octylphenyl ether and the remaining 1-2 parts of oleic acid imidazoline in sequence. Use a gradient stirring speed of 250 rpm for 2-5 minutes, 900 rpm for 10-12 minutes, and 450 rpm for 15-18 minutes to defoam and control the micelle particle size to be stable at 50-200 nanometers. Step 4.3: After dispersion, allow the mixture to cool naturally to room temperature. Take samples from the top, middle, and bottom of the reactor for testing. Once the samples pass the test, fill and seal the micelle dispersion to obtain the boiler shutdown protection agent for thermal power plants.

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