A ternary fluoride chloride molten salt phase change heat storage material and its preparation method and application

Abstract

The present invention provides a ternary fluoride chloride molten salt phase change heat storage material and a preparation method and application thereof, which relates to the technical field of heat storage materials. The ternary fluoride chloride molten salt phase change heat storage material comprises: magnesium chloride, potassium chloride and sodium fluoride; wherein the mass ratio of magnesium chloride, potassium chloride and sodium fluoride is (30-60): (30-60): (5-10). The ternary fluoride chloride molten salt phase change heat storage material prepared by the present invention has low cost and high melting enthalpy, and overcomes the problem that nitrate series molten salts are limited in use in many scenarios.

Description

Technical Field

[0001] The present invention relates to the technical field of heat storage materials, and in particular to a ternary fluoride chloride molten salt phase change heat storage material and a preparation method and application thereof. Background Art

[0002] Molten salt, as a heat storage medium, has been successfully used in solar thermal power generation. Its main advantage is that it can store heat energy at higher temperatures, thereby improving energy utilization efficiency. However, most of the current research and applications are concentrated in the higher temperature range (above 500°C), while there are relatively few studies in the medium and high temperature domain (about 300°C to 450°C). The development of heat storage technology in the medium and high temperature domain is of great significance to improving the efficiency of industrial waste heat recovery, solar power generation and other systems.

[0003] At present, the commonly used medium and high temperature heat storage molten salt phase change materials mainly include nitrates and ternary carbonates containing lithium carbonate. Although nitrates are favored because of their low melting point and low cost, as explosive chemicals, their use is limited in many scenarios. On the other hand, although ternary carbonates have higher phase change enthalpy and specific heat capacity, they are more expensive because they contain lithium carbonate. Therefore, it is particularly important to develop a molten salt phase change material that is low-cost, easy to obtain and has good thermal properties. Summary of the invention

[0004] The embodiment of the present invention provides a ternary fluoride chloride molten salt phase change heat storage material and a preparation method and application thereof. The ternary fluoride chloride molten salt phase change heat storage material has low cost and high melting enthalpy, and overcomes the problem that nitrate series molten salts are limited in use in many scenarios.

[0005] In a first aspect, the present invention provides a ternary fluoride-chloride molten salt phase change heat storage material comprising: magnesium chloride, potassium chloride and sodium fluoride; wherein the mass ratio of magnesium chloride, potassium chloride and sodium fluoride is (30-60): (30-60): (5-10).

[0006] Preferably, the mass ratio of magnesium chloride, potassium chloride and sodium fluoride is (40-55):(40-55):(5-10).

[0007] Preferably, it is composed of magnesium chloride, potassium chloride and sodium fluoride in a mass ratio of 50:45:5

[0008] In a second aspect, the present invention provides a method for preparing a ternary fluoride chloride molten salt phase change thermal storage material, the preparation method comprising:

[0009] (1) mixing magnesium chloride, potassium chloride and sodium fluoride to obtain a mixture;

[0010] (2) The mixture is dried and heated in sequence to obtain the ternary fluoride chloride molten salt phase change heat storage material.

[0011] Preferably, the magnesium chloride is anhydrous magnesium chloride.

[0012] Preferably, the purity of the magnesium chloride is ≥98%, the purity of the potassium chloride is ≥99.5%, and the purity of the sodium fluoride is ≥98%.

[0013] Preferably, in step (1):

[0014] Magnesium chloride, potassium chloride and sodium fluoride are ground and mixed to obtain the mixture.

[0015] Preferably, in step (2):

[0016] The drying temperature is 120-180°C and the holding time is 0.5-2h;

[0017] The temperature of the heating treatment is 400-500° C., and the insulation time is 2-8 hours.

[0018] Preferably, in step (2):

[0019] The heating rate of the heating treatment is 5-10°C / min.

[0020] Preferably, in step (2):

[0021] The mixture is dried and heated in sequence to obtain a product, and the product is cooled and ground in an environment of 20-30° C. and 0%-40% relative humidity to obtain the ternary fluoride chloride molten salt phase change heat storage material.

[0022] In a third aspect, the present invention provides an application of a ternary fluoride chloride molten salt phase change heat storage material, wherein the ternary fluoride chloride molten salt phase change heat storage material is used as a heat storage medium in molten salt phase change heat storage, solar thermal power generation, industrial waste heat recovery and molten salt heat storage flexibility transformation of thermal power units.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] The MgCl2-KCl-NaF molten salt phase change material provided by the present invention has a simple preparation process, is easy to operate and control, and has a short preparation cycle, and is suitable for large-scale molten salt preparation and production. At the same time, the material has low preparation cost, low melting point, and high latent heat, and has great application potential in improving industrial waste heat recovery, solar power generation, and molten salt energy storage.

[0025] The present invention utilizes chloride molten salts with abundant reserves and good thermal stability and fluoride salts with high specific heat capacity and latent heat, and by adjusting the ratio of the components of chloride salts and fluoride salts and combining the advantages of chloride salts and fluoride salts, a molten salt with the economy and thermal stability of chloride salts and the high latent heat of fluoride salts is obtained, which significantly improves the energy storage capacity of the molten salt and reduces the cost of the molten salt, overcomes the problem that nitrate series molten salts are limited in use in many scenarios, and thus expands the application scope of molten salts in the field of medium and high temperature heat storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 is the DSC change curve of the ternary fluoride chloride molten salt phase change heat storage material prepared in Example 1 of the present invention;

[0028] Figure 2 is the DSC change curve of the ternary fluoride chloride molten salt phase change heat storage material prepared in Example 2 of the present invention;

[0029] Figure 3 is the DSC change curve of the ternary fluoride chloride molten salt phase change heat storage material prepared in Example 3 of the present invention;

[0030] Figure 4 is the TG change curve of the ternary fluoride chloride molten salt phase change heat storage material prepared in Example 1 of the present invention;

[0031] Figure 5 is the TG change curve of the ternary fluoride chloride molten salt phase change heat storage material prepared in Example 2 of the present invention;

[0032] Figure 6 This is the TG change curve of the ternary fluoride chloride molten salt phase change heat storage material prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0034] The present invention provides a ternary fluoride chloride molten salt phase change heat storage material, comprising: magnesium chloride, potassium chloride and sodium fluoride; wherein the mass ratio of magnesium chloride, potassium chloride and sodium fluoride is (30-60):(30-60):(5-10) (for example, it can be 30:60:10, 35:60:5, 40:50:10, 40:55:5, 45:45:10, 45:50:5, 50:40:10, 50:45:5, 55:35:10, 55:40:5, 60:30:10 or 60:35:5).

[0035] In the present invention, it is experimentally confirmed that, under the premise that the amount of potassium chloride and sodium fluoride is unchanged, if the amount of magnesium chloride is too much, the enthalpy of the prepared ternary fluoride chloride molten salt phase change heat storage material is low, and if the amount of magnesium chloride is too little, the melting point of the prepared ternary fluoride chloride molten salt phase change heat storage material is too high. Under the premise that the amount of potassium chloride and magnesium chloride is unchanged, if the amount of sodium fluoride is too much, the melting point of the prepared ternary fluoride chloride molten salt phase change heat storage material is too high, otherwise the enthalpy of the prepared ternary fluoride chloride molten salt phase change heat storage material is low. Under the premise that the amount of magnesium chloride and sodium fluoride is unchanged, if the amount of potassium chloride is too much or too little, the melting point of the prepared ternary fluoride chloride molten salt phase change heat storage material will increase significantly. Therefore, in order to ensure that the ternary fluoride chloride molten salt phase change heat storage material has both low melting point and high melting enthalpy, the present invention limits the mass ratio of magnesium chloride, potassium chloride and sodium fluoride to (30-60): (30-60): (5-10).

[0036] According to some preferred embodiments, the mass ratio of magnesium chloride, potassium chloride and sodium fluoride is (40-55):(40-55):(5-10) (for example, it can be 40:54:6, 41:53:6, 42:52:6, 42:50:8, 46:44:10, 48:42:10, 52:43:5 or 54:41:5).

[0037] According to some preferred embodiments, the ternary fluoride chloride molten salt phase change thermal storage material is composed of magnesium chloride, potassium chloride and sodium fluoride in a mass ratio of 45:50:5.

[0038] The present invention also provides a method for preparing a ternary fluoride chloride molten salt phase change heat storage material, the preparation method comprising:

[0039] (1) mixing magnesium chloride, potassium chloride and sodium fluoride to obtain a mixture;

[0040] (2) The mixture is dried and heated in sequence to obtain a ternary fluoride chloride molten salt phase change heat storage material.

[0041] According to some preferred embodiments, the magnesium chloride is anhydrous magnesium chloride.

[0042] According to some preferred embodiments, the purity of magnesium chloride is ≥98%, the purity of potassium chloride is ≥99.5%, and the purity of sodium fluoride is ≥98%.

[0043] According to some preferred embodiments, in step (1):

[0044] Magnesium chloride, potassium chloride and sodium fluoride are ground and mixed to obtain a mixture.

[0045] In the present invention, magnesium chloride, potassium chloride and sodium fluoride are fully mixed by existing grinding and mixing methods, including but not limited to grinding, ball milling, etc., and preferably the mixture is ground until it is uniform and has no large particles.

[0046] According to some preferred embodiments, in step (2):

[0047] The drying temperature is 120-180° C. (for example, 120° C., 130° C., 140° C., 150° C., 160° C., 170° C. or 180° C.), and the holding time is 0.5-2 h (for example, 0.5 h, 1 h, 1.5 h or 2 h);

[0048] The temperature of the heating treatment is 400-500°C (for example, it can be 400°C, 405°C, 410°C, 415°C, 420°C, 425°C, 430°C, 435°C, 440°C, 445°C, 450°C, 455°C, 460°C, 465°C, 470°C, 475°C, 480°C, 485°C, 490°C, 495°C or 500°C), and the insulation time is 2-8h (for example, it can be 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h or 8h).

[0049] According to some preferred embodiments, the heating treatment is carried out in a closed environment to further reduce the entry of moisture and prevent the product from getting damp.

[0050] In the present invention, the moisture of the mixture is further removed by drying, and the mixture is fully melted by heating.

[0051] According to some preferred embodiments, in step (2):

[0052] The heating rate of the heat treatment is 5 to 10°C / min (for example, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min or 10°C / min).

[0053] According to some preferred embodiments, in step (2), the mixture is dried and heated in sequence to obtain a product, and the product is cooled and ground in an environment of 20 to 30° C. (for example, 20° C., 22° C., 25° C., 26° C., 28° C. or 30° C.) and a relative humidity of 0% to 40% (for example, 0%, 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35% or 40%) to obtain a ternary fluoride chloride molten salt phase change thermal storage material.

[0054] In the present invention, considering that it is difficult to achieve the condition of high-purity inert atmosphere in industrial production, the molten salt product obtained by full melting can be naturally cooled to room temperature in a room temperature environment with a relative humidity of 0% to 40%. This operation process is carried out in a conventional air environment without an inert environment, thereby significantly reducing the production cost. It should be noted that the contact between the molten salt and the humid environment should be minimized during the entire preparation process to prevent the product from getting damp.

[0055] The present invention also provides an application of a ternary fluoride chloride molten salt phase change heat storage material, which can be used as a heat storage medium in molten salt phase change heat storage, solar thermal power generation, industrial waste heat recovery and molten salt heat storage flexibility transformation of thermal power units.

[0056] In order to more clearly illustrate the technical solution and advantages of the present invention, a ternary fluoride chloride molten salt phase change heat storage material and its preparation method and application are described in detail through several embodiments below.

[0057] It should be noted that the following examples and comparative examples use MgCl2 with a purity of ≥98%, KCl with a purity of ≥99.5%, and NaF with a purity of ≥98% from Fuchen (Tianjin) Chemical Reagent Co., Ltd. It should be noted that in order to further reduce the influence of impurities and moisture, the alumina crucible used is placed in an ultrasonic cleaner containing deionized water for cleaning before preparation, and the cleaned crucible is placed in a muffle furnace and calcined at a temperature of ≥600°C for 1h to remove the bound water in the crucible.

[0058] Example 1

[0059] (1) Weighing 5.0 g of MgCl2, 4.5 g of KCl, and 0.5 g of NaF respectively, mixing MgCl2, KCl, and NaF, putting them into a mortar, and grinding them thoroughly with a pestle until they are uniform to obtain a mixture;

[0060] (2) placing the mixture into a pre-treated crucible, placing the crucible into a preheated muffle furnace at 150° C., and keeping the temperature for 2 h to remove moisture from the molten salt;

[0061] Then, the crucible was covered with a lid, and the crucible was heated to 450°C at a rate of 10°C / min and kept warm for 6 hours. The product was naturally cooled to room temperature in an environment (temperature 25°C, relative humidity 40%), the molten salt was crushed and ground, and put into a sealed bag to obtain a ternary fluoride chloride molten salt phase change heat storage material.

[0062] Example 2

[0063] (1) Weighing 4.5 g of MgCl2, 5.0 g of KCl, and 0.5 g of NaF respectively, mixing MgCl2, KCl, and NaF, putting them into a mortar, and grinding them thoroughly with a pestle until they are uniform to obtain a mixture;

[0064] (2) placing the mixture into a pre-treated crucible, placing the crucible into a preheated 150° C. muffle furnace, and keeping the temperature for 1 h to remove moisture from the molten salt;

[0065] Then, the crucible is covered with a lid, and the crucible is heated to 500°C at a rate of 5°C / min and kept warm for 4 hours. The product is naturally cooled to room temperature in an environment (temperature 25°C, relative humidity 40%), the molten salt is crushed and ground, and put into a sealed bag to obtain a ternary fluoride chloride molten salt phase change heat storage material.

[0066] Example 3

[0067] (1) Weighing 5.5 g of MgCl2, 4.0 g of KCl, and 0.5 g of NaF respectively, mixing MgCl2, KCl, and NaF, putting them into a mortar, and grinding them thoroughly with a pestle until they are uniform to obtain a mixture;

[0068] (2) placing the mixture into a pre-treated crucible, placing the crucible into a preheated 150° C. muffle furnace, and keeping the temperature for 1 h to remove moisture from the molten salt;

[0069] Then, the crucible is covered with a lid, and the crucible is heated to 500°C at a rate of 5°C / min and kept warm for 2 hours. The product is naturally cooled to room temperature in an environment (temperature 25°C, relative humidity 40%), the molten salt is crushed and ground, and put into a sealed bag to obtain a ternary fluoride chloride molten salt phase change heat storage material.

[0070] Example 4

[0071] Example 4 is substantially the same as Example 1, except that the mixture includes 3.0 g MgCl2, 6.0 g KCl, and 1.0 g NaF.

[0072] Example 5

[0073] Example 5 is substantially the same as Example 1, except that during the heating treatment, the crucible is heated to 400° C. at a rate of 8° C. / min and kept at this temperature for 8 h.

[0074] Comparative Example 1

[0075] (1) Weigh 5.0 g of NaNO3 and 5.0 g of Mg(NO3)2 respectively, mix the NaNO3 and Mg(NO3)2 in a mortar, and grind them thoroughly with a pestle until they are uniform to obtain a mixture;

[0076] (2) placing the mixture into a pre-treated crucible, placing the crucible into a preheated muffle furnace at 120° C., and keeping the temperature for 2 h to remove moisture from the molten salt;

[0077] Then put the lid on the crucible, continue to heat the crucible to 400°C at a rate of 10°C / min, and keep it warm for 5 hours. Then, naturally cool the product to room temperature in an environment (temperature 25°C, relative humidity 40%), crush and grind the molten salt, put it into a sealed bag, and obtain a molten salt phase change heat storage material.

[0078] Comparative Example 2

[0079] (1) Weigh 3.0 g K2CO3, 3.0 g Na2CO3, and 4.0 g Li2CO3 respectively, mix K2CO3, Na2CO3, and Li2CO3, put them into a mortar, and grind them thoroughly with a pestle until they are uniform to obtain a mixture;

[0080] (2) placing the mixture into a pre-treated crucible, placing the crucible into a preheated muffle furnace at 120° C., and keeping the temperature for 2 h to remove moisture from the molten salt;

[0081] Then put the lid on the crucible, continue to heat the crucible to 450°C at a rate of 10°C / min, and keep it warm for 5 hours. Then naturally cool the product to room temperature in an environment (temperature 25°C, relative humidity 40%), crush and grind the molten salt, put it into a sealed bag, and obtain a molten salt phase change heat storage material.

[0082] Comparative Example 3

[0083] Weigh 3.0gLiNO3, 5.5gKNO3, 0.5gNaNO2, and 1.0gNaNO3 respectively, and then put them into an oven for drying. The oven temperature is set to 120°C for 12h, and then the temperature is raised to 200°C and dried for another 12h. When the temperature cools to 80°C, take them out and put them into a glove box for use. After the single component cools to room temperature, grind them into uniform particles in the glove box to complete the preparation of the single component salt.

[0084] Preparation of mixed molten salt heat storage material: weigh and mix the single-component salts prepared above according to a certain proportion, and put the mixed molten salt into an oven at 200°C for 2 hours to make the components in the mixed molten salt mix evenly to form molten salt, then cool it to room temperature and take it out and put it into a glove box to continue grinding it into powder for later use.

[0085] Comparative Example 4

[0086] Comparative Example 4 is substantially the same as Example 1, except that 4.5 g NaCl is used to replace 4.5 g KCl, that is, the mixture includes 5.0 g MgCl2, 4.5 g NaCl, and 0.5 g NaF.

[0087] Comparative Example 5

[0088] Comparative Example 5 is substantially the same as Example 1, except that the mixture includes 2.0 g MgCl2, 4.5 g KCl, and 0.5 g NaF.

[0089] Comparative Example 6

[0090] Comparative Example 6 is substantially the same as Example 1, except that the mixture includes 6.0 g MgCl2, 4.5 g KCl, and 0.5 g NaF.

[0091] Comparative Example 7

[0092] Comparative Example 7 is substantially the same as Example 1, except that the mixture includes 5.0 g MgCl2, 5.0 g KCl, and 0.5 g NaF.

[0093] Comparative Example 8

[0094] Comparative Example 8 is substantially the same as Example 1, except that the mixture includes 5.0 g MgCl2, 2.0 g KCl, and 0.5 g NaF.

[0095] The ternary fluoride chloride molten salt phase change heat storage materials prepared in the above Examples 1 to 5 and the molten salt phase change heat storage materials prepared in Comparative Examples 1 to 8 were tested as samples using DSC and TG, and the data shown in Table 1 were obtained. Specifically, the test method is: about 15 mg of the sample is weighed using a 0.01 mg electronic balance, and the sample is placed in an alumina crucible, and the alumina crucible is placed in a synchronous thermal analyzer and heated to 600°C, with a heating rate of 20.0°C / min and an Ar flow rate of 4NL / h. The test process was repeated three times to ensure the accuracy of the results.

[0096] Table 1

[0097]

[0098] It should be noted that the materials prepared in Comparative Examples 5, 6, and 8 were not subjected to relevant tests because no eutectic occurred.

[0099] Taking the ternary fluoride chloride molten salt phase change heat storage material prepared in Examples 1 to 3 as an example, Figures 1 to 3 The DSC curves of the ternary fluoride chloride molten salt phase change heat storage materials prepared in Examples 1 to 3 after the third cycle are shown respectively; Figures 4 to 6 The TG curves of the ternary fluoride chloride molten salt phase change thermal storage materials prepared in Examples 1 to 3 after the third cycle are shown respectively.

[0100] For Example 1, Figure 1 It can be seen that there is a secondary peak between 360 and 380°C. This peak may be due to impurities in the sample, but these components melt before the main component at a lower temperature; at 450°C, the liquid phase ratio (i.e. the melted part) of the ternary fluoride chloride molten salt phase change thermal storage material reaches 98.8%. After three cycles, the DSC curve has not changed much compared to before, indicating that the molten salt phase change thermal storage material has good stability. Figure 4 It can be observed that before heating to 150°C, the weight of the sample decreases slightly, which is mainly due to the evaporation of water in the sample; during the heating process from 150°C to 500°C, the sample does not show significant mass loss; but when the temperature exceeds 500°C, the sample weight begins to decrease, and the weight is 98.5% at 600°C. This shows that the decomposition temperature of the salt material exceeds 600°C and has good thermal stability.

[0101] For Example 2, Figure 2 It can be seen that the sample has no obvious secondary peak, its melting temperature is 392.5±2.0℃, and the phase change enthalpy is 253.92±20.0J / g. Figure 5 It can be observed that when heated to about 100°C, the weight of the sample decreases, mainly due to the evaporation of water in the sample; from 100°C to 200°C, there is no significant mass loss in the sample. However, when the temperature exceeds 200°C, the weight of the sample begins to decrease until the total mass loss reaches 7% at 480°C. Between 500 and 600°C, the mass loss of the sample slows down, and the salt loses 5% of its weight at 300°C.

[0102] For Example 3, Figure 3 It can be seen that the sample has secondary peaks at around 395°C and 455°C, which indicates that the molten salt prepared with this ratio does not form a eutectic system. Figure 6It can be seen that when the sample is heated to about 100°C, the weight of the sample decreases, mainly due to the evaporation of water in the sample; from 100°C to 200°C, the sample has no significant mass loss; however, when the temperature exceeds 200°C, the weight of the sample begins to decrease, until at 480°C, the total mass loss reaches 6%, and after this temperature continues to heat, the mass loss of the sample slows down, and the salt loses 5% weight at 350°C.

[0103] Specifically, actual calculations show that the raw material cost of MgCl2, KCl, and NaF used in the present invention is approximately RMB 6,900 to 7,055 per ton, the raw material cost of Comparative Example 1 is RMB 15,650 per ton, and the raw material cost of Comparative Example 2 is RMB 53,060 per ton.

[0104] It can be seen from the data in Table 1 that the ternary fluoride chloride molten salt phase change heat storage material prepared in the embodiment of the present invention has the advantages of low cost, high enthalpy value and good thermal stability compared with the molten salt phase change heat storage material in the comparative example, and is suitable for molten salt energy storage, solar thermal power generation and waste heat recovery and other fields, and provides a candidate medium for industrial molten salt heat storage systems in medium and high temperature domains. At the same time, the ternary fluoride chloride molten salt phase change heat storage material can be directly prepared in an air atmosphere, which is simple and safe to operate, and the raw materials are cheap and easy to obtain.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An application of a ternary fluoride chloride molten salt phase change heat storage material, characterized in that: The ternary fluoride chloride molten salt phase change heat storage material is used as a heat storage medium in molten salt phase change heat storage, solar thermal power generation, industrial waste heat recovery and molten salt heat storage flexibility transformation of thermal power units; the ternary fluoride chloride molten salt phase change heat storage material is composed of magnesium chloride, potassium chloride and sodium fluoride; wherein the mass ratio of magnesium chloride, potassium chloride and sodium fluoride is (40-55): (40-55): (5-10); The preparation method of the ternary fluoride chloride molten salt phase change heat storage material comprises: (1) mixing magnesium chloride, potassium chloride and sodium fluoride to obtain a mixture; (2) The mixture is dried and heated in sequence to obtain the ternary fluoride chloride molten salt phase change thermal storage material; the drying temperature is 120-180° C., and the insulation time is 0.5-2 h; the heating temperature is 400-500° C., and the insulation time is 2-8 h.

2. The use of the ternary fluoride chloride molten salt phase change heat storage material according to claim 1, characterized in that: It is composed of magnesium chloride, potassium chloride and sodium fluoride in a mass ratio of 50:45:

5.

3. The use of the ternary fluoride chloride molten salt phase change heat storage material according to claim 1, characterized in that: The magnesium chloride is anhydrous magnesium chloride.

4. The use of the ternary fluoride chloride molten salt phase change heat storage material according to claim 1, characterized in that: The purity of the magnesium chloride is ≥98%, the purity of the potassium chloride is ≥99.5%, and the purity of the sodium fluoride is ≥98%.

5. The use of the ternary fluoride chloride molten salt phase change heat storage material according to claim 1, characterized in that: In step (1): Magnesium chloride, potassium chloride and sodium fluoride are ground and mixed to obtain the mixture.

6. The use of the ternary fluoride chloride molten salt phase change heat storage material according to any one of claims 1 to 5, characterized in that: In step (2): the heating rate of the heating treatment is 5 to 10°C / min.

7. The use of the ternary fluoride chloride molten salt phase change heat storage material according to any one of claims 1 to 5, characterized in that: In step (2): the mixture is dried and heated in sequence to obtain a product, and the product is cooled and ground in an environment of 20 to 30° C. and a relative humidity of 0% to 40% to obtain the ternary fluoride chloride molten salt phase change thermal storage material.

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