Method for preparing high-temperature corrosion protection molten salt by modifying oxide nanoparticles

Abstract

The present invention relates to the field of material corrosion protection, and aims to provide a method for preparing high-temperature corrosion protection molten salt by modifying oxide nanoparticles. The molten salt is prepared by doping oxide nanoparticles into NaCl-KCl-CaCl2 chloride molten salt, and the mass fraction of oxide nanoparticles in the final molten salt product is 0.1-2%. The present invention is simple to operate, safe and environmentally friendly, and has significant effects; it only needs to add an appropriate amount of oxide nanoparticles to conventional chloride molten salt and mix them evenly to increase the service life of the molten salt container and reduce the maintenance cost of the molten salt container. It overcomes the strong corrosive disadvantage of traditional chloride molten salts and can be further applied as a new type of heat transfer and heat storage medium, especially in high-temperature heat storage environments; the added oxide nanoparticles have a low mass proportion in the molten salt system, stable physical and chemical properties, and have little effect on the thermal properties of the original molten salt system.

Description

Technical Field

[0001] The present invention relates to the field of material corrosion protection, and in particular to a molten salt high-temperature corrosion protection method using modified oxide nanoparticles. Background Art

[0002] Molten salt refers to a liquid in a molten state formed when one or more salts reach their melting point during the heating process. It has the advantages of good thermal stability, high heat storage density, low viscosity, wide temperature range and low production cost. It is currently the most widely used heat storage material in solar thermal power generation.

[0003] Among common molten salt materials, nitrates, carbonates, and chlorides all possess excellent heat capacity and thermal conductivity. In low- to medium-temperature thermal storage environments (300°C to 600°C), nitrates are widely used in existing solar thermal systems due to their low corrosiveness and excellent overall thermal performance. However, in high-temperature thermal storage environments (>600°C), nitrates have poor thermal stability and are prone to decomposition, making them difficult to use. Carbonates have higher thermal stability than nitrates, but they have higher melting points, a narrower operating temperature range, and poorer thermal storage capacity.

[0004] Chloride salts are of various types and are inexpensive. They can be made into chloride molten salts with different melting points as needed. They have a wide operating temperature range, high latent heat of phase change, low viscosity and are not easy to clog pipes. They also have excellent thermal stability at high temperatures (>600°C). They are considered to be the most promising heat storage and thermal conductive materials in the next generation of molten salt technology and have great potential for development and utilization. However, the strong corrosiveness of chloride molten salts on the metal matrix materials of molten salt containers limits their further application in the energy field. At the same time, compared with medium and low temperature heat storage environments (300°C to 600°C), the corrosion rate of molten salts on metal matrix materials in high temperature heat storage environments (>600°C) is higher, so the requirements for molten salt corrosion protection of metal materials are also higher.

[0005] The existing methods for protecting against high-temperature corrosion in molten salts mainly include the use of corrosion-resistant alloys and spraying of corrosion-resistant coatings. Corrosion-resistant alloys include super austenitic stainless steel, iron-nickel-based corrosion-resistant alloys, nickel-based corrosion-resistant alloys, etc. Using corrosion-resistant alloys as metal matrix materials can effectively slow down the rate of molten salt corrosion, but their manufacturing process is complex, the cost is high, and they are difficult to promote. Because the cost is lower than that of corrosion-resistant alloys, the protection method of spraying corrosion-resistant coatings is widely adopted. For example, Wuhan University sprays Ni-Mo-Al2O3 metal coatings on the surface of metal substrates to prevent molten chloride corrosion, and the Northwest Institute of Nonferrous Metals uses ZrO2 as the main material mixed with Lu2O3, In2O3 and Al2O3 to prepare thermal barrier coatings, both of which have good corrosion resistance. However, this method also has problems such as complex operation and high maintenance difficulty.

[0006] In summary, developing a new method for high-temperature corrosion protection against molten salt is in line with actual needs. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a molten salt high-temperature corrosion protection method using modified oxide nanoparticles.

[0008] To solve the technical problem, the solution of the present invention is:

[0009] The invention provides a molten salt with high-temperature corrosion protection performance. Oxide nanoparticles are added to NaCl-KCl-CaCl2 chloride molten salt. The mass fraction of the oxide nanoparticles in the final molten salt product is 0.1-2%.

[0010] As a preferred solution of the present invention, in the final molten salt product, the mass ratio of NaCl:KCl:CaCl2 is 4-6:2.5-3.5:1.5-2.5.

[0011] As a preferred solution of the present invention, the particle size of the oxide nanoparticles ranges from 5 nm to 100 nm, and the oxide nanoparticles are any one of SiO2 nanoparticles, TiO2 nanoparticles, and Al2O3 nanoparticles.

[0012] The present invention further provides a method for preparing the aforementioned molten salt having high-temperature corrosion protection performance by modifying oxide nanoparticles, comprising the following steps:

[0013] (1) Preparation of chloride salt mixture

[0014] Weigh the dried powdered single-component chloride salts according to the mass ratio of NaCl:KCl:CaCl2=4-6:2.5-3.5:1.5-2.5; mix and stir the chloride salts to obtain a chloride salt mixture; or

[0015] A mixed chloride product produced by an industrial device, whose main components are NaCl, KCl and CaCl2 in a mass ratio of 4-6:2.5-3.5:1.5-2.5, is taken; and then dried to obtain a chloride mixture;

[0016] (2) Preparation of molten salt products

[0017] The chloride salt mixture is mixed with oxide nanoparticles and stirred evenly to obtain a chloride salt doped mixture; under inert atmosphere protection conditions, the chloride salt doped mixture is heated in a static state until it is melted and maintained at a constant temperature until a liquid with uniform composition is formed; then cooled to a solid, crushed and ground to obtain a molten salt product with high temperature corrosion protection performance; or,

[0018] Under inert atmosphere, the chloride salt mixture is heated in a static state until it melts and maintained at a constant temperature until a liquid with uniform composition is formed; it is then cooled to a solid, crushed, and ground into a fine powder to obtain a chloride molten salt; oxide nanoparticles are added to the chloride molten salt, and the mixture is thoroughly stirred and mixed to obtain a molten salt product with high-temperature corrosion protection properties;

[0019] In the final molten salt product, the mass fraction of the oxide nanoparticles is 0.1-2%.

[0020] As a preferred embodiment of the present invention, the inert atmosphere protection condition refers to using nitrogen or argon as a sealed protective atmosphere or continuously introducing nitrogen or argon to form a protective atmosphere when heating the chloride salt doped mixture or the chloride salt mixture.

[0021] As a preferred solution of the present invention, the purity of the oxide nanoparticles is not less than 99%.

[0022] As a preferred embodiment of the present invention, the purity of the single-component chloride salt NaCl, KCl or CaCl2 is not less than 95%;

[0023] As a preferred solution of the present invention, the drying treatment refers to placing the single-component chloride salt or mixed chloride salt product under constant temperature and ventilation conditions and drying it at a temperature of 120° C. for at least 24 hours.

[0024] As a preferred embodiment of the present invention, the chloride salt-doped mixture or the chloride salt mixture is heated until it is melted and then maintained at a constant temperature for at least 3 hours.

[0025] Furthermore,

[0026] The oxide nanoparticles of the present invention are required to have stable chemical properties and not react with chloride molten salt systems or metal structural materials under working conditions. Al2O3 nanoparticles are a more preferred solution.

[0027] Taking into account the protective effect of molten salt corrosion and the cost of additives, the mass percentage of the oxide nanoparticles is 0.3-0.5%, which is a more preferred solution.

[0028] The purity of the oxide nanoparticles is preferably 99.9%. In a molten salt working environment, solid impurities from the oxide nanoparticles may absorb oxidizing impurities such as oxygen in the molten salt, forming oxidized cores that accelerate corrosion. Therefore, the impurities in the oxide nanoparticles should be as small as possible.

[0029] The particle size of the oxide nanoparticles is preferably 30-50 nm, more preferably 10-30 nm, and most preferably 5-10 nm. The reason is that oxide nanoparticles with small particle sizes are more likely to combine with metal oxides generated by corrosion and are more effective in filling defects in the metal oxide layer.

[0030] The molten salt product of the present invention typically comes into direct contact with stainless steel equipment during storage, transportation, and use. Conventional equipment manufacturing materials in the art are preferably austenitic stainless steels, including one or more of 316 stainless steel, 316L stainless steel, 304 stainless steel, and 304L stainless steel. Alternatively, conventional corrosion-resistant alloys in the art may be selected, preferably nickel-based corrosion-resistant alloys and / or iron-nickel-based corrosion-resistant alloys.

[0031] Since inert gas does not react with any component in conventional chloride salts, chloride salt mixtures, conventional chloride molten salts, and low-corrosion high-temperature molten salt products, the entire preparation process of the present invention is carried out under an inert atmosphere, generally using nitrogen or argon.

[0032] On the basis of conforming to the common sense in this field, any combination of the above-mentioned preferred conditions can obtain the preferred embodiments of the present invention.

[0033] Description of the invention principle:

[0034] Compared to nitrates, which are currently widely used for heat storage at medium and low temperatures (300°C to 600°C) but easily decompose at high temperatures (>600°C), chloride molten salts are chemically stable at high temperatures and have a wider temperature range of application, making them excellent thermal storage and thermal conductivity materials for high-temperature heat storage environments. However, they have the disadvantage of being highly corrosive. This invention, by adding oxide nanoparticles to the chloride molten salt system, suppresses the corrosion of chloride molten salt on metal structural materials, thus overcoming the drawback of chloride molten salt's strong corrosiveness.

[0035] The specific technical principles are described as follows:

[0036] Under high-temperature operating conditions, the corrosive impurities in conventional chloride molten salts, such as water, oxygen, and hydrates, react with metallic structural materials to form metal oxides. These metal oxides, generated by initial corrosion, form a metal oxide layer on the surface of the corroded metal, isolating the metal matrix from the corrosive impurities in the molten salt and slowing the corrosion rate. However, the chloride ions in chloride molten salts have a small radius and strong penetrating power, making them easily adsorbed by metal surfaces. Therefore, they easily penetrate and even destroy the metal oxide layer, causing the corrosive impurities in the molten salt to continuously react with the metal matrix, maintaining a high corrosion rate.

[0037] In the present invention, oxide nanoparticles are added and dispersed into a conventional chloride molten salt system. When the high-temperature molten salt corrodes the metal surface, the oxide nanoparticles enter the corrosion interface between the molten salt and the metal, combining with the metal oxide to form a protective outer layer, preventing ions in the molten salt from eroding the metal surface. This reduces the critical stability boundary for corrosive impurities in the molten salt to corrode the metal substrate, further stabilizing the oxidation scale and achieving corrosion inhibition.

[0038] The present invention can choose to use commercial products (powdered single-component chloride salt products NaCl, KCl and CaCl2) as basic raw materials, and by adding oxide nanoparticles before or after melting, a molten salt product with high-temperature corrosion protection performance is prepared. The present invention can also choose to use a mixed chloride salt product (with NaCl, KCl and CaCl2 as the main components in a specified proportion) extracted from industrial fly ash water washings or other waste liquids as the basic raw material. Considering that oxide nanoparticles have the characteristic of being easily adsorbed, if the basic raw material contains moisture, the oxide nanoparticles will agglomerate on the external crystal surface, resulting in an inability to disperse evenly. Therefore, the basic raw material needs to be dried before performing the melting operation.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] (1) The molten salt high-temperature corrosion protection method of the present invention is simple to operate, safe, environmentally friendly, and effective. Simply by adding an appropriate amount of oxide nanoparticles to a conventional chloride molten salt and mixing them evenly, the service life of the molten salt container can be increased and the maintenance cost of the molten salt container can be reduced.

[0041] (2) The present invention overcomes the strong corrosiveness of traditional chloride molten salt, making it further applicable as a new heat transfer and heat storage medium, especially in high-temperature heat storage environments.

[0042] (3) The oxide nanoparticles added in the present invention have a low mass proportion in the molten salt system, stable physical and chemical properties, and have basically no effect on the thermal properties of the original molten salt system, and even have a certain improvement. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described below in conjunction with specific embodiments. Obviously, the embodiments described are only the most basic embodiments of the present invention, rather than all embodiments. Other embodiments based on the present invention are all within the scope of protection of the present invention.

[0044] In the following embodiments, the NaCl, KCl, CaCl2, and SiO2, TiO2, Al2O3 nanoparticles used are all commercially available reagent products. Among them, the purity of NaCl, KCl, and CaCl2 is 99%, and the purity of the oxide nanoparticles is 99.9%. The ternary chloride salt in each embodiment can also be replaced by a mixed chloride salt product produced by an industrial device (for example, a waste incineration plant in Zhejiang Province utilizes fly ash water to wash salt and then evaporate and crystallize to produce regenerated salt, in which the total content of NaCl, KCl, and CaCl2 is greater than 98%). In each embodiment, the timing of mixing the oxide nanoparticles is also changed to be before the high-temperature melting treatment, keeping other process parameters unchanged.

[0045] Example 1:

[0046] 1. Conventional ternary chloride salt preparation

[0047] In a dry air environment, sodium chloride, potassium chloride and calcium chloride powders were placed in an oven at 120°C and dried for 24 hours. After cooling, they were weighed according to a mass ratio of 4:3.5:2.5, fully stirred and mixed, placed in a muffle furnace and sealed with nitrogen, statically heated until melted, and kept at a constant temperature for 3 hours to form a liquid with uniform composition. After cooling, the mixture was taken out, crushed, ground and stored in a desiccator to obtain a conventional ternary chloride salt.

[0048] 2. Preparation of low-corrosion high-temperature molten salt

[0049] In a dry air environment, 99.9 g of conventional ternary chloride salt was weighed, 0.1 g of SiO2 nanoparticles with a particle size of 5 to 10 nm (mass fraction 0.1%) was added, and the mixture was mixed evenly to obtain a molten salt product.

[0050] 3. Metal Sample Preparation

[0051] Use plasma cutting to cut 304 stainless steel plates into samples of 20 mm × 20 mm × 2 mm in size, polish the samples with 80-grit sandpaper, ultrasonically clean them with deionized water, acetone, and alcohol in sequence, dry them at 105°C, and cool them to room temperature for later use.

[0052] 4. Molten salt corrosion test

[0053] Weigh the metal sample using an electronic balance and record the weight. Place the stainless steel sample in a zirconia crucible, allowing the low-corrosion, high-temperature molten salt to cover the stainless steel sample. Place the zirconia crucible in a muffle furnace, continuously flow nitrogen, and heat to 800°C, maintaining the temperature for 72 hours.

[0054] Example 2:

[0055] 1. Conventional ternary chloride salt preparation

[0056] In a dry air environment, sodium chloride, potassium chloride and calcium chloride powders were placed in an oven at 120°C and dried for 24 hours. After cooling, they were weighed in a mass ratio of 5:3:2, fully stirred and mixed, placed in a muffle furnace and continuously introduced with nitrogen, statically heated until melted, and kept at a constant temperature for 3 hours to form a liquid with uniform composition. After cooling, they were taken out, crushed, ground and stored in a desiccator to obtain conventional ternary chloride salt.

[0057] 2. Preparation of low-corrosion high-temperature molten salt

[0058] In a dry air environment, 99.0 g of conventional ternary chloride salt was weighed, 1.0 g of Al2O3 nanoparticles (mass fraction 1.0%) with a particle size of 30 to 50 nm was added, and the mixture was mixed evenly to obtain a molten salt product.

[0059] 3. Metal Sample Preparation

[0060] The nickel-based corrosion-resistant alloy was cut into samples of 20 mm × 20 mm × 2 mm using plasma cutting, polished with 80-grit sandpaper, ultrasonically cleaned with deionized water, acetone, and alcohol in sequence, dried at 105°C, and cooled to room temperature for later use.

[0061] 4. Molten salt corrosion test

[0062] Weigh the metal sample using an electronic balance and record the weight. Place the stainless steel sample in a zirconia crucible, allowing the low-corrosion, high-temperature molten salt to cover the stainless steel sample. Place the zirconia crucible in a muffle furnace, continuously flow nitrogen, and heat to 800°C, maintaining the temperature for 72 hours.

[0063] Example 3:

[0064] 1. Conventional ternary chloride salt preparation

[0065] In a dry air environment, sodium chloride, potassium chloride and calcium chloride powders were placed in an oven at 120°C and dried for 24 hours. After cooling, they were weighed according to a mass ratio of 6:2.5:1.5, fully stirred and mixed, placed in a muffle furnace and sealed with argon, statically heated to melt, and kept at a constant temperature for 3 hours to form a liquid with uniform composition. After cooling, the mixture was taken out, crushed, ground and stored in a desiccator to obtain a conventional ternary chloride salt.

[0066] 2. Preparation of low-corrosion high-temperature molten salt

[0067] In a dry air environment, 98.0 g of conventional ternary chloride salt was weighed, 2.0 g of TiO2 nanoparticles with a particle size of 50 to 100 nm (mass fraction 2.0%) was added, and the mixture was mixed evenly to obtain a molten salt product.

[0068] 3. Metal Sample Preparation

[0069] Use plasma cutting to cut 316L stainless steel plates into samples of 20 mm × 20 mm × 2 mm in size, polish the samples with 80-grit sandpaper, ultrasonically clean them with deionized water, acetone, and alcohol in sequence, dry them at 105 °C, and cool them to room temperature for later use.

[0070] 4. Molten salt corrosion test

[0071] Weigh the metal sample using an electronic balance and record the weight. Place the stainless steel sample in a zirconia crucible, allowing the low-corrosion, high-temperature molten salt to cover the stainless steel sample. Place the zirconia crucible in a muffle furnace, continuously flow nitrogen, and heat to 800°C, maintaining the temperature for 72 hours.

[0072] Example 4:

[0073] 1. Conventional ternary chloride salt preparation

[0074] In a dry air environment, sodium chloride, potassium chloride and calcium chloride powders were placed in an oven at 120°C and dried for 24 hours. After cooling, they were weighed in a mass ratio of 5:3:2, fully stirred and mixed, placed in a muffle furnace and sealed with nitrogen, statically heated until melted, and kept at a constant temperature for 3 hours to form a liquid with uniform composition. After cooling, the mixture was taken out, crushed, ground and stored in a desiccator to obtain a conventional ternary chloride salt.

[0075] 2. Preparation of low-corrosion high-temperature molten salt

[0076] In a dry air environment, 99.5 g of conventional ternary chloride salt was weighed, 0.5 g of Al2O3 nanoparticles with a particle size of 5 to 10 nm (mass fraction 0.5%) was added, and the mixture was mixed evenly to obtain a molten salt product.

[0077] 3. Metal Sample Preparation

[0078] Use plasma cutting to cut 316L stainless steel plates into samples of 20 mm × 20 mm × 2 mm in size, polish the samples with 80-grit sandpaper, ultrasonically clean them with deionized water, acetone, and alcohol in sequence, dry them at 105 °C, and cool them to room temperature for later use.

[0079] 4. Molten salt corrosion test

[0080] Weigh the metal sample using an electronic balance and record the weight. Place the stainless steel sample in a zirconia crucible, allowing the low-corrosion, high-temperature molten salt to cover the stainless steel sample. Place the zirconia crucible in a muffle furnace, continuously flow nitrogen, and heat to 800°C, maintaining the temperature for 72 hours.

[0081] Example 5:

[0082] 1. Conventional ternary chloride salt preparation

[0083] In a dry air environment, sodium chloride, potassium chloride and calcium chloride powders were placed in an oven at 120°C and dried for 24 hours. After cooling, they were weighed in a mass ratio of 5:3:2, fully stirred and mixed, placed in a muffle furnace and sealed with nitrogen, statically heated until melted, and kept at a constant temperature for 3 hours to form a liquid with uniform composition. After cooling, the mixture was taken out, crushed, ground and stored in a desiccator to obtain a conventional ternary chloride salt.

[0084] 2. Preparation of low-corrosion high-temperature molten salt

[0085] In a dry air environment, 99.0 g of conventional ternary chloride salt was weighed, 1.0 g of Al2O3 nanoparticles with a particle size of 5 to 10 nm (mass fraction 1.0%) was added, and the mixture was mixed evenly to obtain a molten salt product.

[0086] 3. Metal Sample Preparation

[0087] Use plasma cutting to cut 316L stainless steel plates into samples of 20 mm × 20 mm × 2 mm in size, polish the samples with 80-grit sandpaper, ultrasonically clean them with deionized water, acetone, and alcohol in sequence, dry them at 105 °C, and cool them to room temperature for later use.

[0088] 4. Molten salt corrosion test

[0089] Weigh the metal sample using an electronic balance and record the weight. Place the stainless steel sample in a zirconia crucible, allowing the low-corrosion, high-temperature molten salt to cover the stainless steel sample. Place the zirconia crucible in a muffle furnace, continuously flow nitrogen, and heat to 800°C, maintaining the temperature for 72 hours.

[0090] Example 6:

[0091] 1. Conventional ternary chloride salt preparation

[0092] In a dry air environment, sodium chloride, potassium chloride and calcium chloride powders were placed in an oven at 120°C and dried for 24 hours. After cooling, they were weighed in a mass ratio of 5:3:2, fully stirred and mixed, placed in a muffle furnace and sealed with nitrogen, statically heated until melted, and kept at a constant temperature for 3 hours to form a liquid with uniform composition. After cooling, the mixture was taken out, crushed, ground and stored in a desiccator to obtain a conventional ternary chloride salt.

[0093] 2. Preparation of low-corrosion high-temperature molten salt

[0094] In a dry air environment, 99.0 g of conventional ternary chloride salt was weighed, 1.0 g of TiO2 nanoparticles with a particle size of 5 to 10 nm (mass fraction 1.0%) was added, and the mixture was mixed evenly to obtain a molten salt product.

[0095] 3. Metal Sample Preparation

[0096] Use plasma cutting to cut 316L stainless steel plates into samples of 20 mm × 20 mm × 2 mm in size, polish the samples with 80-grit sandpaper, ultrasonically clean them with deionized water, acetone, and alcohol in sequence, dry them at 105 °C, and cool them to room temperature for later use.

[0097] 4. Molten salt corrosion test

[0098] Weigh the metal sample using an electronic balance and record the weight. Place the stainless steel sample in a zirconia crucible, allowing the low-corrosion, high-temperature molten salt to cover the stainless steel sample. Place the zirconia crucible in a muffle furnace, continuously flow nitrogen, and heat to 800°C, maintaining the temperature for 72 hours.

[0099] Example 7:

[0100] 1. Conventional ternary chloride salt preparation

[0101] In a dry air environment, sodium chloride, potassium chloride and calcium chloride powders were placed in an oven at 120°C and dried for 24 hours. After cooling, they were weighed in a mass ratio of 5:3:2, fully stirred and mixed, placed in a muffle furnace and sealed with nitrogen, statically heated until melted, and kept at a constant temperature for 3 hours to form a liquid with uniform composition. After cooling, the mixture was taken out, crushed, ground and stored in a desiccator to obtain a conventional ternary chloride salt.

[0102] 2. Preparation of low-corrosion high-temperature molten salt

[0103] In a dry air environment, 99.0 g of conventional ternary chloride salt was weighed, 1.0 g of TiO2 nanoparticles with a particle size of 15 to 20 nm (mass fraction 1.0%) was added, and the mixture was mixed evenly to obtain a molten salt product.

[0104] 3. Metal Sample Preparation

[0105] Use plasma cutting to cut 316L stainless steel plates into samples of 20 mm × 20 mm × 2 mm in size, polish the samples with 80-grit sandpaper, ultrasonically clean them with deionized water, acetone, and alcohol in sequence, dry them at 105 °C, and cool them to room temperature for later use.

[0106] 4. Molten salt corrosion test

[0107] Weigh the metal sample using an electronic balance and record the weight. Place the stainless steel sample in a zirconia crucible, allowing the low-corrosion, high-temperature molten salt to cover the stainless steel sample. Place the zirconia crucible in a muffle furnace, continuously flow nitrogen, and heat to 800°C, maintaining the temperature for 72 hours.

[0108] Example 8:

[0109] 1. Conventional ternary chloride salt preparation

[0110] In a dry air environment, sodium chloride, potassium chloride and calcium chloride powders were placed in an oven at 120°C and dried for 24 hours. After cooling, they were weighed in a mass ratio of 5:3:2, fully stirred and mixed, placed in a muffle furnace and sealed with nitrogen, statically heated until melted, and kept at a constant temperature for 3 hours to form a liquid with uniform composition. After cooling, the mixture was taken out, crushed, ground and stored in a desiccator to obtain a conventional ternary chloride salt.

[0111] 2. Preparation of low-corrosion high-temperature molten salt

[0112] In a dry air environment, 99.0 g of conventional ternary chloride salt was weighed, 1.0 g of SiO2 nanoparticles with a particle size of 15 to 20 nm (mass fraction 1.0%) was added, and the mixture was mixed evenly to obtain a molten salt product.

[0113] 3. Metal Sample Preparation

[0114] Use plasma cutting to cut 316L stainless steel plates into samples of 20 mm × 20 mm × 2 mm in size, polish the samples with 80-grit sandpaper, ultrasonically clean them with deionized water, acetone, and alcohol in sequence, dry them at 105 °C, and cool them to room temperature for later use.

[0115] 4. Molten salt corrosion test

[0116] Weigh the metal sample using an electronic balance and record the weight. Place the stainless steel sample in a zirconia crucible, allowing the low-corrosion, high-temperature molten salt to cover the stainless steel sample. Place the zirconia crucible in a muffle furnace, continuously flow nitrogen, and heat to 800°C, maintaining the temperature for 72 hours.

[0117] Comparative Example 1:

[0118] In this comparative example, no oxide nanoparticles were added, and the remaining conditions were the same as those in Example 4.

[0119] Effect embodiment 1:

[0120] After the molten salt corrosion test, the crucible was allowed to cool naturally to room temperature. The metal samples were removed and cleaned in an ultrasonic cleaner using deionized water and then alcohol, dried, and cooled to room temperature. An electronic balance was used to weigh Examples 4-8 and Comparative Example 1. The mass changes of the samples before and after corrosion were compared. The corrosion weight loss was calculated and the average of the replicates was taken. The results are shown in Table 1.

[0121] Considering that the test conditions of Examples 1-3 are quite different from those of the comparative example, only the molten salt corrosion test data of Examples 4 to 8 are used in Table 1 for comparison with the comparative example.

[0122] Table 1 Corrosion weight loss of 316L stainless steel in chloride molten salt at 800℃ for 72h

[0123]

[0124]

[0125] As shown in Table 1, Al2O3 / TiO2 / SiO2 nanoparticles all exhibit significant protective effects against high-temperature corrosion caused by chloride molten salts. In Examples 4-8, 5-10 nm Al2O3 nanoparticles with a mass ratio of 0.5% exhibited the best protective effect. Al2O3 nanoparticles with a particle size of 5-10 nm exhibited superior protective effects to TiO2 nanoparticles. TiO2 nanoparticles with a particle size of 15-20 nm exhibited superior protective effects to SiO2 nanoparticles.

[0126] The above are specific embodiments of the present invention. It is apparent that those skilled in the art may make various subsequent applications, supplements, modifications, and variations to the present invention without departing from the spirit and scope of the present invention. To the extent that such applications, supplements, modifications, and variations fall within the scope of the claims and their equivalents, the present invention is intended to encompass such applications, supplements, modifications, and variations.

Claims

1. A method for preparing molten salt with high-temperature corrosion protection performance by modifying oxide nanoparticles, characterized in that: The following steps are involved: (1) Preparation of chloride salt mixture According to the mass ratio of NaCl: KCl: CaCl2 = 4~6: 2.5~3.5: 1.5~2.5, weigh the dried powdered single-component chloride salts respectively; mix and stir the chloride salts to obtain a chloride salt mixture; or, A mixed chloride product produced by an industrial device, whose main components are NaCl, KCl and CaCl2 in a mass ratio of 4-6:2.5-3.5:1.5-2.5, is taken; and then dried to obtain a chloride mixture; (2) Preparation of molten salt products The chloride salt mixture is mixed with oxide nanoparticles and stirred evenly to obtain a chloride salt doped mixture; under inert atmosphere protection conditions, the chloride salt doped mixture is heated in a static state until it is melted and maintained at a constant temperature until a liquid with uniform composition is formed; then cooled to a solid, crushed and ground to obtain a molten salt product with high temperature corrosion protection performance; or, Under inert atmosphere, the chloride salt mixture is heated in a static state until it melts and maintained at a constant temperature until a liquid with uniform composition is formed; it is then cooled to a solid, crushed, and ground into a fine powder to obtain a chloride molten salt; oxide nanoparticles are added to the chloride molten salt, and the mixture is thoroughly stirred and mixed to obtain a molten salt product with high-temperature corrosion protection properties; The oxide nanoparticles have a particle size range of 5nm~100nm and are any one of SiO2 nanoparticles, TiO2 nanoparticles, and Al2O3 nanoparticles; in the final molten salt product, the mass fraction of the oxide nanoparticles is 0.1~2%; when the corrosive impurities contained in the chloride molten salt react with the surface material of the metal container to generate metal oxides, a corrosion interface is formed due to the penetration of the metal oxide layer by chloride ions; the oxide nanoparticles uniformly dispersed in the chloride molten salt will enter the corrosion interface, combine with the metal oxide to form a protective outer layer, reduce the critical stable boundary of corrosion, and play a role in stabilizing the oxidation scale and inhibiting corrosion.

2. The method according to claim 1, characterized in that The inert atmosphere protection condition refers to using nitrogen or argon as a sealed protective atmosphere or continuously introducing nitrogen or argon to form a protective atmosphere when heating the chloride salt doped mixture or the chloride salt mixture.

3. The method according to claim 1, characterized in that The purity of the oxide nanoparticles is not less than 99%.

4. The method according to claim 1, wherein The purity of the single-component chloride salt NaCl, KCl or CaCl2 is not less than 95%.

5. The method according to claim 1, wherein The drying treatment refers to placing a single-component chloride salt or a mixed chloride salt product under constant temperature and ventilation conditions and drying it at a temperature of 120° C. for at least 24 hours.

6. The method according to claim 1, characterized in that After heating the chloride salt doped mixture or the chloride salt mixture until it is melted, the temperature is maintained at a constant level for at least 3 hours.

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