Shutdown maintenance agent suitable for thermal boiler, and preparation method and application thereof

Abstract

The invention discloses a shutdown maintenance agent suitable for a thermal boiler and a preparation method and application thereof, through the synergistic effect of various agents, a protective film with a multi-stage composite structure and multiple functions is formed, and the protective film has excellent corrosion resistance. Wherein the base layer provides firm adhesive force, the function enhancement layer enhances wear resistance, high temperature resistance and antibacterial ability, the environment-friendly corrosion inhibitor and the metal surface form a protective complex, the bionic micro-nano functional particles remarkably reduce the surface free energy of the protective film, the super-hydrophobic effect is achieved, the contact angle between the protective film and water is larger than 155 degrees, and the protective film has good water resistance. The contact between a corrosive medium and the inner wall of the boiler is effectively isolated, and the anti-corrosion effect is further improved. A simulation experiment shows that the boiler maintained by adopting the corrosion inhibitor is good in film forming effect, the corrosion rate is greatly reduced, the corrosion process is effectively restrained, and the structural integrity of a boiler system is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of boiler maintenance for thermal power units, specifically to a chemical agent, preparation method, and application suitable for boiler shutdown maintenance. Background Technology

[0002] As an indispensable key piece of equipment in industrial production, the operating status of boiler units directly affects the efficiency and safety of the entire production process. During shutdown, the metal surfaces inside the boiler are highly susceptible to oxidation and corrosion due to contact with air and residual moisture. This corrosion not only gradually damages the boiler's physical structure and shortens its service life, but also triggers a series of malfunctions such as cracks and leaks upon restarting, seriously threatening the safety and continuity of production.

[0003] Traditional maintenance methods, such as drying and nitrogen purging, while able to slow down corrosion to some extent, also have many drawbacks. Drying requires a large amount of heat energy, resulting in high energy consumption and cumbersome operation. Furthermore, for large boilers, the drying process is lengthy and inefficient. Nitrogen purging requires a continuous supply of high-purity nitrogen, which is costly and requires extremely high sealing. If the seal is not tight, nitrogen leakage will significantly reduce the maintenance effect. In addition, these traditional methods only provide simple drying or inert gas replacement of the boiler's internal environment and cannot fundamentally prevent corrosive media from contacting the metal surface, failing to meet the modern industrial requirements for efficient, economical, and long-lasting boiler maintenance.

[0004] With the development of technology, film-forming technology has been gradually applied to boiler maintenance. However, existing film-forming technologies have significant shortcomings in terms of protective film performance. On the one hand, they lack multi-level functional synergy; existing films mostly possess only a single anti-corrosion function, unable to cope with the complex environment inside the boiler. They cannot withstand the residual high temperatures that may remain after boiler shutdown, nor can they inhibit the growth of microorganisms on the film surface. On the other hand, in terms of surface performance control, existing film-forming technologies struggle to achieve superhydrophobic effects. The contact angle of the protective film with water is generally less than 120°, failing to effectively repel water vapor and liquids containing corrosive ions. This allows water films to easily spread on the protective film surface and gradually penetrate through the film's micropores, cracks, or interface defects to the interface between the film and the metal, gradually corroding the metal surface. Simultaneously, some film-forming materials use strong adhesive components to improve adhesion, making the film difficult to remove. Complex cleaning procedures are required before the next startup, increasing operating costs and time. Conversely, easily removable films often suffer from loose structures and insufficient protective capabilities, creating a contradiction between "protective effect and operability." Furthermore, since existing technologies cannot effectively suppress the formation of corrosion products, cold flushing during the next boiler startup requires a significant amount of time to remove corrosion residues, severely impacting production efficiency.

[0005] In terms of environmental protection, existing film-forming agents mostly rely on organic solvents containing benzene, esters and other compounds. During preparation and application, they release a large amount of volatile organic compounds (VOCs), which not only pollute the environment but also pose a potential threat to the health of operators, which is contrary to the green and environmentally friendly requirements of modern industry.

[0006] In summary, there is an urgent need in the field of boiler shutdown maintenance for thermal power units for a new film-forming maintenance method that can effectively solve the above problems, in order to meet the multiple requirements of industrial production for boiler performance, lifespan, environmental protection, and intelligent maintenance. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the purpose of this invention is to provide a chemical agent, preparation method and application suitable for shutdown maintenance of thermal boilers.

[0008] To achieve the above objectives, the technical solution of the present invention provides, in one aspect, a maintenance agent suitable for shutdown of thermal boilers, comprising a base layer agent, a functional enhancement layer mixture, an environmentally friendly corrosion inhibitor, and a mixture of biomimetic micro / nano functional particles, wherein the mass ratio of the four components is 3:2:1.5:0.5; wherein,

[0009] The base layer agents include silicone-modified polyurethane emulsion, epoxy resin emulsion and polyacrylate emulsion, with a mass ratio of 5:3:2.

[0010] The functional enhancement layer mixture includes surface-modified alumina particles, nano-silver antibacterial agent, and zinc ion antibacterial agent, with a mass ratio of 6:4:1.

[0011] The environmentally friendly corrosion inhibitor includes chitosan derivatives, plant tannins, and bentonite modifiers, with a mass ratio of 4:3:3.

[0012] The biomimetic micro / nano functional particle mixture includes zinc micron particles modified with perfluorooctyl ethanol and nanodiamond particles modified with hexafluoroisopropanol, with a mass ratio of 3:1.

[0013] The agent can form a protective film with a multi-level composite structure and function on the inner wall of the boiler. The contact angle of this protective film with water is greater than 155°, and it has excellent anti-corrosion effect, high temperature resistance and antibacterial properties. It can effectively isolate the corrosive medium from the contact between the boiler inner wall, significantly extend the service life of the boiler, and is easy to remove.

[0014] Furthermore, the preparation method of the base layer agent is as follows:

[0015] (1) First, the organosilicon intermediate polysiloxane is mixed and reacted with the polyurethane prepolymer, and then emulsified to obtain organosilicon modified polyurethane emulsion.

[0016] (2) Preheat the epoxy resin emulsion and polyacrylate emulsion separately, then mix them with the silicone-modified polyurethane emulsion, stir, and finally keep warm and mature to obtain a uniform and stable base layer agent; so as to form a uniform and firm base layer on the inner wall of the boiler, providing a stable substrate for subsequent film formation.

[0017] Further, in step (1), the mass ratio of the organosilicon intermediate polysiloxane to the polyurethane prepolymer is 15-25:75-85; the reaction temperature is 60℃-70℃, and the time is 3h-5h; the emulsification method is: at 40℃-50℃, stir at 1500r / min-1800r / min for 30min-60min, and then stir at 300r / min-500r / min for 15min-20min to defoam.

[0018] Furthermore, in step (2), the preheating temperature is 40℃-50℃ and the time is 1h-2h; the stirring speed is 200r / min-300r / min and the time is 30min-45min; the maturation temperature is 60℃-70℃ and the time is 2h-3h.

[0019] Furthermore, the preparation method of the functional enhancement layer mixture is as follows:

[0020] (1) Surface modification of alumina particles to imbue their surface with active groups; the specific method is as follows:

[0021] ① Chemical oxidation: Alumina particles are placed in a mixed acid solution and stirred (300 r / min–400 r / min) for reaction; after the reaction is completed, they are rinsed until neutral and dried; through chemical oxidation, oxygen vacancies and active hydroxyl groups are introduced on the surface of alumina particles. These active groups can react with other pharmaceutical components, enhance the interaction between particles and film-forming agents, and improve the bonding strength and water resistance of the composite film;

[0022] ② The chemically oxidized alumina particles are uniformly dispersed in anhydrous ethanol, and then an appropriate amount of silane coupling agent is added for reaction. After the reaction is completed, the particles are washed to remove unreacted silane coupling agent and dried. One end of the silane coupling agent molecule can react with the hydroxyl groups on the surface of the alumina particles, and the other end contains active groups that can participate in the film-forming reaction, such as vinyl groups, which can cross-link with other organic components in the film-forming agent, thereby further enhancing the compatibility and bonding force between the alumina particles and the film-forming agent, and improving the high temperature resistance and wear resistance of the composite film.

[0023] (2) The alumina particles, nano-silver antibacterial agent and zinc ion antibacterial agent modified in step (1) are mixed and added to deionized water. The mixture is dispersed in deionized water using ultrasonic dispersion technology to obtain a uniformly dispersed functional enhancement layer mixture, so as to enhance the wear resistance, high temperature resistance and antibacterial properties of the membrane, while improving the structural strength and stability of the membrane.

[0024] Furthermore, in step (1) ①, the particle size of the alumina particles is 50nm-300nm; the mixed acid solution is a mixed solution of nitric acid and sulfuric acid with a volume ratio of 1:1; the reaction temperature is 60℃-80℃ and the time is 3h-5h; the drying temperature is 100℃-120℃ and the time is 2h-3h.

[0025] Furthermore, in step (1) ②, the mass ratio of chemically oxidized alumina particles to silane coupling agent is 1:0.1-0.3; the silane coupling agent is KH-570; the reaction temperature is 60℃-70℃, and the time is 1h-2h; the drying temperature is 80℃-100℃, and the time is 3h-4h.

[0026] Furthermore, in step (2), the amount of deionized water used is 8-12 times the total mass of the surface-modified alumina particles, nano-silver antibacterial agent, and zinc ion antibacterial agent.

[0027] Furthermore, the preparation method of the environmentally friendly corrosion inhibitor is as follows:

[0028] (1) Chitosan is mixed with a modifying agent and reacted to obtain a chitosan derivative;

[0029] (2) The bentonite is acidified to make it have a larger specific surface area and stronger adsorption capacity, thus obtaining a bentonite modified product.

[0030] (3) Chitosan derivatives, plant tannins and bentonite modifiers are mixed and stirred (400r / min-500r / min) to obtain an environmentally friendly corrosion inhibitor; it can form a dense protective complex with the metal surface, enhance the anti-corrosion effect, and at the same time has good environmental performance.

[0031] Furthermore, in step (1), the mass ratio of chitosan to the modifying agent is 1:1.2, and the modifying agent is maleic anhydride; the reaction temperature is 70℃-80℃, and the time is 6h-8h.

[0032] Further, in step (2), the acidification modification method is as follows: add bentonite to the acid solution at a solid-liquid mass ratio of 1:8-1:10, stir at a constant temperature (stirring speed of 400r / min-500r / min), filter, wash, and dry.

[0033] Furthermore, the acid solution is a hydrochloric acid solution with a concentration of 1.0 mol / L to 2.0 mol / L or a sulfuric acid solution with a concentration of 0.5 mol / L to 1.0 mol / L.

[0034] Furthermore, the constant temperature stirring temperature is 80℃-90℃, and the time is 2h-4h; the drying temperature is 105℃, and the time is 6h.

[0035] Furthermore, in step (3), the stirring temperature is 60-70℃ and the stirring time is 2h-3h.

[0036] Furthermore, the preparation method of the biomimetic micro / nano functional particle mixture is as follows:

[0037] Zinc micron particles modified with perfluorooctyl ethanol and nanodiamond particles modified with hexafluoroisopropanol were mixed and stirred (at a speed of 400 r / min-600 r / min for 30 min-45 min) to obtain a uniformly dispersed biomimetic micro-nano functional particle mixture. Its surface energy is extremely low, which can significantly reduce the surface free energy of the protective film and achieve a superhydrophobic effect with a water contact angle greater than 155°, further enhancing the protective film's ability to isolate corrosive media.

[0038] Furthermore, the preparation method of zinc micron particles modified by perfluorooctyl ethanol is as follows: zinc powder with a particle size of 1μm-5μm is ultrasonically dispersed in anhydrous ethanol for 10min, and then 1% HCl solution is added for light etching for 5min. The ratio of zinc powder to HCl solution is 1g:3-5mL. After rinsing until neutral, the zinc powder is placed in 95% ethanol solution, and 3%-5% of the zinc powder mass of perfluorooctyl ethanol is added. After reacting at 70℃ for 2h, it is taken out and dried at 80℃ for 2h.

[0039] Furthermore, the preparation method of hexafluoroisopropanol modified nanodiamond particles is as follows: 30nm-60nm nanodiamonds are dispersed in anhydrous ethanol, 5%-8% of hexafluoroisopropanol by weight of nanodiamonds is added dropwise, and 1% of triethylamine by weight of diamonds is added as a catalyst. After reacting at 60℃ for 3h, the particles are removed and dried at 80℃ for 2h.

[0040] On the other hand, the technical solution of the present invention is to provide a method for preparing the aforementioned chemical agent suitable for boiler shutdown maintenance, wherein the basic layer agent, the functional enhancement layer mixture, the environmentally friendly corrosion inhibitor and the biomimetic micro-nano functional particle mixture are weighed according to the mass ratio, mixed and stirred evenly (at a speed of 200 r / min-300 r / min).

[0041] On the other hand, the technical solution of the present invention is to provide a method for using the aforementioned chemical agent for boiler shutdown maintenance. The agent is injected into the boiler system through an injection pump to circulate the agent within the boiler, ensuring that the agent fully covers the inner surface of the boiler and is evenly adsorbed on the inner wall of the boiler to form the prototype of a multi-level composite protective film. After circulation, the remaining agent is slowly discharged from the boiler system through the drain valve at the bottom of the boiler, and the agent is solidified within the inner wall of the boiler, ultimately forming a uniform and dense multi-level composite protective film.

[0042] The agent circulates in the boiler at a rate of 0.5 m / s to 1.5 m / s for 1 to 3 hours; the curing time is 1 to 2 hours.

[0043] When the protective film needs to be removed, use water with a pressure of 0.4MPa-0.6MPa to rinse and remove the surface protective film. There will be no residual agent on the inner wall of the boiler after cleaning, which will not affect the next start-up.

[0044] Beneficial effects of the invention

[0045] This invention utilizes the synergistic effect of multiple agents to form a protective film with a multi-level composite structure and multiple functions, exhibiting excellent anti-corrosion performance. The base layer provides strong adhesion, the functional enhancement layer strengthens wear resistance, high-temperature resistance, and antibacterial capabilities, the environmentally friendly corrosion inhibitor forms a protective complex with the metal surface, and the biomimetic micro-nano functional particles significantly reduce the surface free energy of the protective film, achieving a superhydrophobic effect. This results in a water contact angle greater than 155°, effectively isolating corrosive media from contact with the boiler's inner wall and further enhancing the anti-corrosion effect. Simulation experiments show that boilers maintained using this invention exhibit a significantly reduced corrosion rate, effectively curbing the corrosion process and ensuring the structural integrity of the boiler system. Attached Figure Description

[0046] Figure 1 The results show the hydrophobicity characterization of the film formed according to the present invention (the angle between the two lines represents the contact angle of the material with water). Detailed Implementation

[0047] The specific embodiments of the present invention will be further described in detail below with reference to examples.

[0048] Example 1: A method for shutdown maintenance of thermal boilers

[0049] (1) Preparation of maintenance agents for shutdown of thermal boilers

[0050] (a) Base layer agent: First, the organosilicon intermediate polysiloxane and polyurethane prepolymer are mixed at a mass ratio of 20:80 and reacted at 65°C for 4 hours. Then, the mixture is emulsified (stirred at 1600 r / min for 50 minutes at 45°C, and then stirred at 400 r / min for 18 minutes to defoam) to obtain an organosilicon modified polyurethane emulsion. The epoxy resin emulsion and polyacrylate emulsion are preheated at 45°C for 1.5 hours and then mixed with the organosilicon modified polyurethane emulsion (the mass ratio of organosilicon modified polyurethane emulsion, epoxy resin emulsion and polyacrylate emulsion is 5:3:2). The mixture is stirred at 250 r / min for 38 minutes and then cured at 65°C for 2.5 hours to obtain a uniform and stable base layer agent.

[0051] (b) Functional Enhancement Layer Mixture: The alumina particles were surface-modified to impart active groups. First, chemical oxidation was performed. Alumina particles with a diameter of 50 nm were placed in a mixed acid solution (nitric acid: sulfuric acid, 1:1, v / v) and stirred at 70°C for 4 h (350 r / min). After the reaction, the particles were repeatedly rinsed with deionized water until neutral and then dried at 110°C for 2.5 h. The chemically oxidized alumina particles were then dispersed in anhydrous ethanol and ultrasonically dispersed for 30 min to ensure uniform dispersion. An appropriate amount of silane coupling agent was then added, with a mass ratio of chemically oxidized alumina particles to silane coupling agent of 1:0.2, and the mixture was reacted at 65°C for 1.5 h. After the reaction, the particles were centrifuged and washed four times with anhydrous ethanol to remove unreacted silane coupling agent and then dried at 90°C for 3.5 h. Finally, the modified alumina particles, nano-silver antibacterial agent, and zinc ion antibacterial agent were mixed in a mass ratio of 6:4:1 and added to deionized water. The mixture was then dispersed in deionized water using ultrasonic dispersion technology. The amount of deionized water was 10 times the total mass of the modified alumina particles, nano-silver antibacterial agent, and zinc ion antibacterial agent to obtain a uniformly dispersed functional enhancement layer mixture.

[0052] (c) Environmentally friendly corrosion inhibitor: First, chitosan and maleic anhydride are mixed at a mass ratio of 1:1.2 and reacted at 75℃ for 7 hours to obtain a chitosan derivative; then, bentonite-modified material is prepared: bentonite is acid-modified by adding it to a 1.0 mol / L hydrochloric acid solution at a solid-liquid mass ratio of 1:9, and stirred at 85℃ for 3 hours (450 r / min). The mixture is then filtered while hot, washed four times with deionized water, and dried at 105℃ for 6 hours to give it a larger specific surface area and stronger adsorption capacity; finally, chitosan derivative, plant tannins, and bentonite-modified material are mixed at a mass ratio of 4:3:3 and stirred at 65℃ for 2.5 hours (450 r / min) to obtain an environmentally friendly corrosion inhibitor.

[0053] (d) Biomimetic micro-nano functional particle mixture: zinc micron particles modified with perfluorooctyl ethanol and nanodiamond particles modified with hexafluoroisopropanol were mixed at a mass ratio of 3:1 and stirred at 500 r / min for 38 min to obtain a uniformly dispersed biomimetic micro-nano functional particle mixture.

[0054] The preparation method of zinc micron particles modified by perfluorooctyl ethanol is as follows: zinc powder with a particle size of 3 μm is ultrasonically dispersed in anhydrous ethanol for 10 min, and then lightly etched in 1% HCl solution for 5 min. The ratio of zinc powder to HCl solution is 1 g: 4 mL. After rinsing with deionized water until neutral, the zinc powder is placed in 95% (v / v) ethanol solution, and 4% of the zinc powder mass of perfluorooctyl ethanol is added. After reacting at 70℃ for 2 h, the solution is taken out and dried at 80℃ for 2 h.

[0055] The preparation method of hexafluoroisopropanol modified nanodiamond particles is as follows: 50nm nanodiamond particles are dispersed in anhydrous ethanol, 6% hexafluoroisopropanol by mass of nanodiamond particles is added dropwise, and 1% triethylamine by mass of diamond particles is added as a catalyst. After reacting at 60℃ for 3h, the particles are taken out and dried at 80℃ for 2h.

[0056] (2) Film-forming operation

[0057] (a) Mixing of reagents: The base layer reagent, the functional enhancement layer mixture, the environmentally friendly corrosion inhibitor, and the biomimetic micro / nano functional particle mixture were taken in a mass ratio of 3:2:1.5:0.5 and mixed in a dynamic mixer. First, the base layer reagent was stirred at a speed of 250 r / min. Then, the functional enhancement layer mixture, the environmentally friendly corrosion inhibitor, and the biomimetic micro / nano functional particle mixture were added slowly in sequence. After each component was added, the mixture was stirred at the same speed for 13 min to ensure that all components were fully and evenly mixed to obtain the furnace shutdown maintenance reagent.

[0058] (b) Circulation injection: The agent is injected into the boiler system through the injection pump, and the flow rate of the agent in the boiler is controlled at 1m / s. The agent is circulated for 2 hours to ensure that the agent fully covers the inner surface of the boiler and that the agent is evenly adsorbed on the inner wall of the boiler to form the prototype of a multi-level composite protective film.

[0059] (c) Excess reagent discharge: After circulation, the remaining reagent is slowly discharged from the boiler system through the drain valve at the bottom of the boiler. The reagent solidifies on the inner wall of the boiler within 1-2 hours, ultimately forming a uniform and dense multi-level composite protective film. The resulting protective film has a water contact angle greater than 155°, exhibiting excellent anti-corrosion effects. Figure 1 ).

[0060] Comparison of effects after maintenance:

[0061] A comprehensive inspection was conducted on a certain type of thermal power unit boiler before shutdown. The previous shutdown maintenance of this experimental unit was carried out by nitrogen purging. This maintenance adopted the method of the present invention. The comparison of the data with the previous cold flushing data of the experimental unit boiler is shown in Table 1.

[0062] Table 1 Comparison of Cold Rinse Time

[0063]

[0064]

[0065] Therefore, it can be seen that the maintenance method of the present invention can significantly reduce the time for cold rinsing by about 15.4%-28.3%, indicating that the shutdown maintenance method of the present invention has excellent maintenance and corrosion prevention effects.

[0066] Example 2: A method for shutdown maintenance of thermal boilers

[0067] (1) Preparation of maintenance agents for shutdown of thermal boilers

[0068] (a) Base layer agent: First, the organosilicon intermediate polysiloxane and polyurethane prepolymer are mixed at a mass ratio of 15:85 and reacted at 70°C for 3 hours. Then, the mixture is emulsified (stirred at 1800 r / min for 30 minutes at 50°C, and then stirred at 500 r / min for 15 minutes to defoam) to obtain organosilicon modified polyurethane emulsion. The epoxy resin emulsion and polyacrylate emulsion are preheated at 50°C for 1 hour and then mixed with the organosilicon modified polyurethane emulsion (the mass ratio of organosilicon modified polyurethane emulsion, epoxy resin emulsion and polyacrylate emulsion is 5:3:2). The mixture is stirred at 300 r / min for 30 minutes and then cured at 70°C for 2 hours to obtain a uniform and stable base layer agent.

[0069] (b) Functional Enhancement Layer Mixture: The alumina particles were surface-modified to impart active groups. First, chemical oxidation was performed. Alumina particles with a diameter of 200 nm were placed in a mixed acid solution (nitric acid: sulfuric acid, 1:1, v / v) and stirred at 80°C for 3 hours (400 r / min). After the reaction, the particles were repeatedly rinsed with deionized water until neutral and then dried at 120°C for 2 hours. The chemically oxidized alumina particles were then dispersed in anhydrous ethanol and ultrasonically dispersed for 30 minutes to ensure uniform dispersion. An appropriate amount of silane coupling agent was then added, with a mass ratio of chemically oxidized alumina particles to silane coupling agent of 1:0.3, and the mixture was reacted at 70°C for 1 hour. After the reaction, the particles were centrifuged and washed five times with anhydrous ethanol to remove unreacted silane coupling agent and then dried at 100°C for 3 hours. Finally, the modified alumina particles, nano-silver antibacterial agent, and zinc ion antibacterial agent were mixed in a mass ratio of 6:4:1 and added to deionized water. The mixture was then dispersed in deionized water using ultrasonic dispersion technology. The amount of deionized water was 12 times the total mass of the modified alumina particles, nano-silver antibacterial agent, and zinc ion antibacterial agent to obtain a uniformly dispersed functional enhancement layer mixture.

[0070] (c) Environmentally friendly corrosion inhibitor: First, chitosan and maleic anhydride are mixed at a mass ratio of 1:1.2 and reacted at 80℃ for 6 hours to obtain chitosan derivatives; then, bentonite modified material is prepared: bentonite is acidified and modified by adding bentonite to a 1.0 mol / L sulfuric acid solution at a solid-liquid mass ratio of 1:10, stirring at 90℃ for 2 hours (500 r / min), filtering while hot, washing with deionized water 5 times, and drying at 105℃ for 6 hours to give it a larger specific surface area and stronger adsorption; finally, chitosan derivatives, plant tannins and bentonite modified material are mixed at a mass ratio of 4:3:3 and stirred at 70℃ for 2 hours (500 r / min) to obtain environmentally friendly corrosion inhibitor.

[0071] (d) Biomimetic micro-nano functional particle mixture: zinc micron particles modified with perfluorooctyl ethanol and nanodiamond particles modified with hexafluoroisopropanol were mixed at a mass ratio of 3:1 and stirred at 600 r / min for 30 min to obtain a uniformly dispersed biomimetic micro-nano functional particle mixture.

[0072] The preparation method of zinc micron particles modified by perfluorooctyl ethanol is as follows: zinc powder with a particle size of 5 μm is ultrasonically dispersed in anhydrous ethanol for 10 min, and then 1% HCl solution is added for light etching for 5 min. The ratio of zinc powder to HCl solution is 1 g: 3 mL. After rinsing with deionized water until neutral, the zinc powder is placed in 95% (v / v) ethanol solution, and 5% of the zinc powder mass of perfluorooctyl ethanol is added. After reacting at 70℃ for 2 h, the solution is taken out and dried at 80℃ for 2 h.

[0073] The preparation method of hexafluoroisopropanol modified nanodiamond particles is as follows: 60nm nanodiamond particles are dispersed in anhydrous ethanol, 8% hexafluoroisopropanol by mass of nanodiamond particles is added dropwise, and 1% triethylamine by mass of diamond particles is added as a catalyst. After reacting at 60℃ for 3h, the particles are taken out and dried at 80℃ for 2h.

[0074] (2) Film-forming operation

[0075] (a) Mixing of reagents: The base layer reagent, the functional enhancement layer mixture, the environmentally friendly corrosion inhibitor, and the biomimetic micro / nano functional particle mixture were taken in a mass ratio of 3:2:1.5:0.5 and mixed in a dynamic mixer. First, the base layer reagent was stirred at a speed of 300 r / min. Then, the functional enhancement layer mixture, the environmentally friendly corrosion inhibitor, and the biomimetic micro / nano functional particle mixture were added slowly in sequence. After each component was added, the mixture was stirred at the same speed for 15 min to ensure that all components were fully and evenly mixed to obtain the furnace shutdown maintenance reagent.

[0076] (b) Circulation injection: The agent is injected into the boiler system through the injection pump. The flow rate of the agent in the boiler is controlled at 1.5m / s and circulated for 1 hour to ensure that the agent fully covers the inner surface of the boiler and that the agent is evenly adsorbed on the inner wall of the boiler to form the prototype of a multi-level composite protective film.

[0077] (c) Discharge of excess agent: After the circulation is completed, the remaining agent is slowly discharged from the boiler system through the drain valve at the bottom of the boiler. The agent is cured on the inner wall of the boiler within 1-2 hours, and finally forms a uniform and dense multi-level composite protective film.

[0078] Comparison of effects after maintenance:

[0079] A comprehensive inspection was conducted on another type of thermal power unit boiler before shutdown. The previous shutdown maintenance of this experimental unit was carried out by hot boiler draining. This maintenance adopted the method of the present invention. The comparison of the data with the previous cold flushing data of the experimental unit boiler is shown in Table 2.

[0080] Table 2 Comparison of Cold Rinse Time

[0081]

[0082]

[0083] Therefore, the maintenance method of this invention can significantly reduce the time required for cold rinsing, by approximately 43.4%.

[0084] -53.1% indicates that the shutdown maintenance method of the present invention has excellent maintenance and corrosion prevention effects.

[0085] Example 3: A method for shutdown maintenance of thermal boilers

[0086] (1) Preparation of maintenance agents for shutdown of thermal boilers

[0087] (a) Base layer agent: First, the organosilicon intermediate polysiloxane and polyurethane prepolymer are mixed at a mass ratio of 25:75 and reacted at 60°C for 5 hours. Then, after emulsification treatment (stirring at 1500 r / min for 60 minutes at 40°C, and then stirring at 300 r / min for 20 minutes to defoam), organosilicon modified polyurethane emulsion is obtained. The epoxy resin emulsion and polyacrylate emulsion are preheated at 40°C for 2 hours, and then mixed with the organosilicon modified polyurethane emulsion (the mass ratio of organosilicon modified polyurethane emulsion, epoxy resin emulsion and polyacrylate emulsion is 5:3:2). The mixture is stirred at 200 r / min for 45 minutes and finally cured at 60°C for 3 hours to obtain a uniform and stable base layer agent.

[0088] (b) Functional Enhancement Layer Mixture: The alumina particles were surface-modified to impart active groups. First, chemical oxidation was performed. Alumina particles with a diameter of 300 nm were placed in a mixed acid solution (nitric acid: sulfuric acid, 1:1, v / v) and stirred at 60°C for 5 h (300 r / min). After the reaction, the particles were repeatedly rinsed with deionized water until neutral and then dried at 100°C for 3 h. The chemically oxidized alumina particles were then dispersed in anhydrous ethanol and ultrasonically dispersed for 30 min to ensure uniform dispersion. An appropriate amount of silane coupling agent was then added, with a mass ratio of chemically oxidized alumina particles to silane coupling agent of 1:0.1, and the mixture was reacted at 60°C for 2 h. After the reaction, the particles were washed three times by centrifugation with anhydrous ethanol to remove unreacted silane coupling agent and dried at 80°C for 4 h. Finally, the modified alumina particles, nano-silver antibacterial agent, and zinc ion antibacterial agent were mixed in a mass ratio of 6:4:1 and added to deionized water. The mixture was then dispersed in deionized water using ultrasonic dispersion technology. The amount of deionized water was 8 times the total mass of the modified alumina particles, nano-silver antibacterial agent, and zinc ion antibacterial agent to obtain a uniformly dispersed functional enhancement layer mixture.

[0089] (c) Environmentally friendly corrosion inhibitor: First, chitosan and maleic anhydride are mixed at a mass ratio of 1:1.2 and reacted at 70℃ for 8 hours to obtain chitosan derivatives; then, bentonite modified material is prepared: bentonite is acidified and added to a 2.0 mol / L hydrochloric acid solution at a solid-liquid mass ratio of 1:8, stirred at 80℃ for 4 hours (400 r / min), filtered while hot, washed three times with deionized water, and dried at 105℃ for 6 hours to give it a larger specific surface area and stronger adsorption; finally, chitosan derivatives, plant tannins and bentonite modified material are mixed at a mass ratio of 4:3:3 and stirred at 60℃ for 3 hours (400 r / min) to obtain environmentally friendly corrosion inhibitor.

[0090] (d) Biomimetic micro-nano functional particle mixture: zinc micron particles modified with perfluorooctyl ethanol and nanodiamond particles modified with hexafluoroisopropanol were mixed at a mass ratio of 3:1 and stirred at 400 r / min for 45 min to obtain a uniformly dispersed biomimetic micro-nano functional particle mixture.

[0091] The preparation method of zinc micron particles modified by perfluorooctyl ethanol is as follows: zinc powder with a particle size of 1 μm is ultrasonically dispersed in anhydrous ethanol for 10 min, and then 1% HCl solution is added for light etching for 5 min. The ratio of zinc powder to HCl solution is 1 g: 5 mL. After rinsing with deionized water until neutral, the zinc powder is placed in 95% (v / v) ethanol solution, and 3% of the zinc powder mass of perfluorooctyl ethanol is added. After reacting at 70℃ for 2 h, the solution is taken out and dried at 80℃ for 2 h.

[0092] The preparation method of hexafluoroisopropanol modified nanodiamond particles is as follows: 30nm nanodiamond particles are dispersed in anhydrous ethanol, 5% hexafluoroisopropanol by mass of nanodiamond particles is added dropwise, and 1% triethylamine by mass of diamond particles is added as a catalyst. After reacting at 60℃ for 3h, the particles are taken out and dried at 80℃ for 2h.

[0093] (2) Film-forming operation

[0094] (a) Mixing of reagents: The base layer reagent, the functional enhancement layer mixture, the environmentally friendly corrosion inhibitor, and the biomimetic micro / nano functional particle mixture were taken in a mass ratio of 3:2:1.5:0.5 and mixed in a dynamic mixer. First, the base layer reagent was stirred at a speed of 200 r / min. Then, the functional enhancement layer mixture, the environmentally friendly corrosion inhibitor, and the biomimetic micro / nano functional particle mixture were added slowly in sequence. After each component was added, the mixture was stirred at the same speed for 13 min to ensure that all components were fully and evenly mixed to obtain the furnace shutdown maintenance reagent.

[0095] (b) Circulation injection: The agent is injected into the boiler system through the injection pump, and the flow rate of the agent in the boiler is controlled at 0.5m / s. The agent is circulated for 3 hours to ensure that the agent fully covers the inner surface of the boiler and that the agent is evenly adsorbed on the inner wall of the boiler to form the prototype of a multi-level composite protective film.

[0096] (c) Discharge of excess agent: After the circulation is completed, the remaining agent is slowly discharged from the boiler system through the drain valve at the bottom of the boiler. The agent is cured on the inner wall of the boiler within 1-2 hours, and finally forms a uniform and dense multi-level composite protective film.

[0097] Comparative Example 1

[0098] The scale inhibition and corrosion inhibition performance of the agents in Examples 1-3 above were compared with those in the invention patent "Phosphorus-free mixture for boiler shutdown protection and daily operation chemical treatment" (application number: 202311140707.8) (Example 1 as comparative example 1). The test method used in the patent (the same below) was adopted. The results are shown in Table 3.

[0099] Table 3 Comparison of Scale Inhibition and Corrosion Inhibition Performance

[0100] Pharmaceutical samples Scale inhibition rate, % Corrosion inhibition rate, % Example 1 98.7 96.5 Example 2 98.1 97.2 Example 3 98.3 96.9 Comparative Example 1 94.8 92.7

[0101] Therefore, compared with the methods in the current patents, the maintenance method of the present invention has significantly improved scale inhibition and corrosion inhibition performance, indicating that the shutdown maintenance method of the present invention has excellent maintenance, scale inhibition and corrosion inhibition effects.

[0102] Comparative Example 2

[0103] The scale inhibition and corrosion inhibition performance of Example 1 and Comparative Example 2 were compared and tested. The difference between the formulation in Comparative Example 2 and the formulation in Example 1 is that Comparative Example 2 does not contain the functional enhancement layer mixture. The comparative test results are shown in Table 4.

[0104] Table 4 Comparison of Scale Inhibition and Corrosion Inhibition Performance

[0105] Pharmaceutical samples Scale inhibition rate, % Corrosion inhibition rate, % Example 1 98.5 96.7 Comparative Example 2 71.2 66.4

[0106] As can be seen, compared with Comparative Example 2, the maintenance method of the present invention can significantly improve the scale inhibition rate and corrosion inhibition rate. This is because the functional enhancement layer mixture of the present invention can effectively enhance the wear resistance, high temperature resistance and antibacterial properties of the membrane, while improving the structural strength and stability of the membrane, thereby improving the scale inhibition and corrosion inhibition performance.

[0107] Comparative Example 3

[0108] The scale inhibition and corrosion inhibition performance of Example 1 and Comparative Example 3 were compared and tested. The difference between the formulation in Comparative Example 3 and the formulation in Example 1 is that Comparative Example 3 does not contain an environmentally friendly corrosion inhibitor. The comparative test results are shown in Table 5.

[0109] Table 5 Comparison of Scale Inhibition and Corrosion Inhibition Performance

[0110] Pharmaceutical samples Scale inhibition rate, % Corrosion inhibition rate, % Example 1 97.7 96.1 Comparative Example 3 92.4 90.5

[0111] It can be seen that, compared with Comparative Example 3, the maintenance method of the present invention has superior scale inhibition and corrosion inhibition performance, indicating that the environmentally friendly corrosion inhibitor of the present invention can form a dense protective complex with the metal surface, thereby enhancing the anti-corrosion effect.

[0112] Comparative Example 4

[0113] The scale inhibition and corrosion inhibition performance of Example 1 and Comparative Example 4 were compared and tested. The difference between the formulation in Comparative Example 4 and the formulation in Example 1 is that Comparative Example 4 does not contain the biomimetic micro-nano functional particle mixture. The comparative test results are shown in Table 6.

[0114] Table 6 Comparison of Scale Inhibition and Corrosion Inhibition Performance

[0115] Pharmaceutical samples Scale inhibition rate, % Corrosion inhibition rate, % Example 1 98.6 96.4 Comparative Example 4 78.5 73.2

[0116] As can be seen, in Comparative Example 4, without the presence of the biomimetic micro-nano functional particle mixture, the scale inhibition performance and corrosion inhibition performance are significantly reduced compared to Example 1. This indicates that the biomimetic micro-nano functional particle mixture described in this invention can significantly reduce the surface free energy of the protective film, achieve a superhydrophobic effect with a water contact angle greater than 155°, and further enhance the protective film's ability to isolate corrosive media.

[0117] Comparative Example 5

[0118] The scale inhibition and corrosion inhibition performance of Example 1 and Comparative Example 5 were compared and tested. The difference between the formulation of Comparative Example 5 and that of Example 1 is that the organosilicon-modified polyurethane adhesive in the base layer agent of Example 1 was replaced with polydimethylsiloxane adhesive. The comparative test results are shown in Table 7.

[0119] Table 7 Comparison of Scale Inhibition and Corrosion Inhibition Performance

[0120] Pharmaceutical samples Scale inhibition rate, % Corrosion inhibition rate, % Example 1 97.5 95.8 Comparative Example 5 68.3 61.2

[0121] As can be seen, in Comparative Example 5, when the organosilicon-modified polyurethane adhesive in the base layer agent of Example 1 was replaced with polydimethylsiloxane adhesive, the scale inhibition performance and corrosion inhibition performance were significantly reduced compared with Example 1, and the degree of reduction was greater than that of the other comparative examples mentioned above. This further demonstrates that the shutdown maintenance method of the present invention has excellent maintenance, scale inhibition and corrosion inhibition effects.

[0122] Comparative Example 6

[0123] The scale inhibition and corrosion inhibition performance of Example 1 and Comparative Example 6 were compared and tested. The difference between the formulation of Comparative Example 6 and that of Example 1 is that the alumina in the functional enhancement layer mixture of Comparative Example 6 is not surface modified. The comparative test results are shown in Table 8.

[0124] Table 8 Comparison of Scale Inhibition and Corrosion Inhibition Performance

[0125] Pharmaceutical samples Scale inhibition rate, % Corrosion inhibition rate, % Example 1 98.1 96.1 Comparative Example 6 90.3 89.2

[0126] It can be seen that, without surface modification, the scale inhibition and corrosion inhibition performance of the functional enhancement layer mixture in Comparative Example 6 is significantly reduced compared to Example 1. This is because the modified alumina can further enhance the compatibility and bonding force between the alumina particles and the film-forming agent, thereby improving the high temperature resistance and wear resistance of the composite film.

[0127] As can be seen from the above embodiments, the present invention is applicable to the shutdown maintenance agent of thermal boilers, which has the advantages of good film-forming effect and excellent anti-corrosion performance. It can effectively extend the service life of boilers, reduce maintenance costs, and has significant economic and social benefits.

Claims

1. A chemical agent suitable for boiler shutdown maintenance, characterized in that, It includes a base layer agent, a functional enhancement layer mixture, an environmentally friendly corrosion inhibitor, and a mixture of biomimetic micro / nano functional particles, with a mass ratio of 3:2:1.5:0.5; among which, The base layer agents include silicone-modified polyurethane emulsion, epoxy resin emulsion and polyacrylate emulsion, with a mass ratio of 5:3:

2. The functional enhancement layer mixture includes surface-modified alumina particles, nano-silver antibacterial agent, and zinc ion antibacterial agent, with a mass ratio of 6:4:

1. The environmentally friendly corrosion inhibitor includes chitosan derivatives, plant tannins, and bentonite modifiers, with a mass ratio of 4:3:

3. The biomimetic micro / nano functional particle mixture includes zinc micron particles modified with perfluorooctyl ethanol and nanodiamond particles modified with hexafluoroisopropanol, with a mass ratio of 3:

1.

2. The chemical agent for boiler shutdown maintenance according to claim 1, characterized in that, The preparation method of the base layer agent is as follows: (1) First, the organosilicon intermediate polysiloxane is mixed and reacted with the polyurethane prepolymer, and then emulsified to obtain organosilicon modified polyurethane emulsion. (2) Preheat the epoxy resin emulsion and polyacrylate emulsion separately, then mix them with the silicone-modified polyurethane emulsion, stir, and finally keep warm to mature, so as to obtain a uniform and stable base layer agent.

3. The chemical agent for boiler shutdown maintenance according to claim 2, characterized in that, In step (1), the mass ratio of organosilicon intermediate polysiloxane to polyurethane prepolymer is 15-25:75-85; the reaction temperature is 60℃-70℃, and the time is 3h-5h; the emulsification method is: stirring at 1500r / min-1800r / min for 30min-60min at 40℃-50℃, and then stirring at 300r / min-500r / min for 15min-20min to defoam. In step (2), the preheating temperature is 40℃-50℃ and the time is 1h-2h; the stirring time is 30min-45min; the maturation temperature is 60℃-70℃ and the time is 2h-3h.

4. The chemical agent for boiler shutdown maintenance according to claim 1, characterized in that, The preparation method of the functional enhancement layer mixture is as follows: (1) Surface modification of alumina particles to imbue their surface with active groups; the specific method is as follows: ① Chemical oxidation: Place alumina particles in a mixed acid solution and stir to react; after the reaction is complete, rinse until neutral and dry; ② The chemically oxidized alumina particles are uniformly dispersed in anhydrous ethanol, and then an appropriate amount of silane coupling agent is added for reaction; after the reaction is completed, the mixture is washed to remove unreacted silane coupling agent and dried. (2) The alumina particles, nano-silver antibacterial agent and zinc ion antibacterial agent modified in step (1) are mixed and added to deionized water. The mixture is dispersed in deionized water using ultrasonic dispersion technology to obtain a uniformly dispersed functional enhancement layer mixture.

5. The chemical agent for boiler shutdown maintenance according to claim 4, characterized in that, In step (1)①, the particle size of alumina particles is 50nm-300nm; the mixed acid solution is a mixed solution of nitric acid and sulfuric acid with a volume ratio of 1:1; the reaction temperature is 60℃-80℃ and the time is 3h-5h; the drying temperature is 100℃-120℃ and the time is 2h-3h. In step (1) ②, the mass ratio of chemically oxidized alumina particles to silane coupling agent is 1:0.1-0.3; the silane coupling agent is KH-570; the reaction temperature is 60℃-70℃, and the time is 1h-2h; the drying temperature is 80℃-100℃, and the time is 3h-4h. In step (2), the amount of deionized water used is 8-12 times the total mass of the surface-modified alumina particles, nano-silver antibacterial agent and zinc ion antibacterial agent.

6. The chemical agent for boiler shutdown maintenance according to claim 1, characterized in that, The preparation method of the environmentally friendly corrosion inhibitor is as follows: (1) Chitosan is mixed with a modifying agent and reacted to obtain a chitosan derivative; (2) The bentonite is acidified to make it have a larger specific surface area and stronger adsorption capacity, thus obtaining a bentonite modified product. (3) Mix chitosan derivatives, plant tannins and bentonite modifiers and stir to obtain an environmentally friendly corrosion inhibitor.

7. The chemical agent for boiler shutdown maintenance according to claim 6, characterized in that, In step (1), the mass ratio of chitosan to the modifying agent is 1:1.2, and the modifying agent is maleic anhydride; the reaction temperature is 70℃-80℃, and the reaction time is 6h-8h. In step (2), the acidification modification method is as follows: add bentonite to acid solution, stir at constant temperature, filter, wash, and dry; The acid solution is a hydrochloric acid solution with a concentration of 1.0 mol / L to 2.0 mol / L or a sulfuric acid solution with a concentration of 0.5 mol / L to 1.0 mol / L; The constant temperature stirring temperature is 80℃-90℃, and the time is 2h-4h; the drying temperature is 105℃, and the time is 6h. In step (3), the stirring temperature is 60-70℃ and the stirring time is 2h-3h.

8. The chemical agent for boiler shutdown maintenance according to claim 1, characterized in that, The preparation method of the biomimetic micro / nano functional particle mixture is as follows: Zinc microparticles modified with perfluorooctyl ethanol and nanodiamond particles modified with hexafluoroisopropanol were mixed and stirred to obtain a uniformly dispersed mixture of biomimetic micro and nano functional particles. The preparation method of zinc micron particles modified by perfluorooctyl ethanol is as follows: zinc powder with a particle size of 1μm-5μm is ultrasonically dispersed in anhydrous ethanol for 10min, and then 1% HCl solution is added for light etching for 5min. The ratio of zinc powder to HCl solution is 1g:3-5mL. After rinsing until neutral, the zinc powder is placed in 95% ethanol solution, and 3%-5% of the zinc powder mass of perfluorooctyl ethanol is added. After reacting at 70℃ for 2h, it is taken out and dried. The preparation method of hexafluoroisopropanol modified nanodiamond particles is as follows: 30nm-60nm nanodiamonds are dispersed in anhydrous ethanol, 5%-8% hexafluoroisopropanol by weight of nanodiamonds is added dropwise, and 1% triethylamine by weight of diamonds is added as a catalyst. After reacting at 60℃ for 3h, the particles are taken out and dried.

9. A method for preparing a shutdown maintenance agent for thermal boilers as described in any one of claims 1-8, characterized in that, Weigh the base layer agent, functional enhancement layer mixture, environmentally friendly corrosion inhibitor, and biomimetic micro / nano functional particle mixture according to the mass ratio, mix and stir evenly.

10. A method of using the chemical agent for boiler shutdown maintenance as described in any one of claims 1-8, characterized in that, The agent is injected into the boiler system through a liquid injection pump to circulate the agent inside the boiler, ensuring that the agent fully covers the internal surface of the boiler and is evenly adsorbed on the inner wall of the boiler, forming the prototype of a multi-level composite protective film. After the cycle is completed, the remaining agent is slowly discharged from the boiler system through the drain valve at the bottom of the boiler. The agent is solidified inside the boiler wall, eventually forming a uniform and dense multi-level composite protective film. The agent circulates in the boiler at a rate of 0.5 m / s to 1.5 m / s for 1 to 3 hours; the curing time is 1 to 2 hours.

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