Hydroxide and molten salt composite heat storage material and preparation method thereof

Abstract

The present invention provides a hydroxide and molten salt composite heat storage material and a preparation method thereof, which relates to the technical field of heat storage materials. The preparation method comprises: preparing Mg 0.5 Ni 0.5 (OH)2 powder, weigh low melting point salt and the above Mg in a mass ratio of 1:10 to 1:8 respectively 0.5 Ni 0.5 (OH)2 powder, mixed and ground for 5 to 30 minutes; the ground mixture was transferred to a beaker, added with distilled water to dissolve, and stirred at a constant temperature of 60 to 80 ° C for 1 to 3 hours; the mixture in the beaker was dried at 80 to 120 ° C to obtain Mg 0.5 Ni 0.5 (OH)2 and molten salt composite heat storage material, which is white powder with a particle size of 3 to 5 μm. The preparation method is simple and feasible. The composite heat storage material obtained is 0.5 Ni 0.5 The decomposition temperature of (OH)2 is 150-180℃, and the heat storage temperature is low. Low-melting-point salts can be in a molten state when storing heat, which can not only effectively block hydroxide particles, thereby preventing hydroxide particles from agglomerating, but also increase the heat transfer rate. The fast heat storage rate can effectively alleviate heat concentration and make heat distribution more uniform. The fast heat release rate can quickly release heat, so it is not easy to agglomerate and compact.

Description

Technical Field

[0001] The present invention relates to the technical field of heat storage materials, and in particular to a hydroxide and molten salt composite heat storage material and a preparation method thereof. Background Art

[0002] As global energy shortages become increasingly severe, the storage and reuse of thermal energy is becoming increasingly important, and thermal energy storage technology has become a hot topic in research and development. Thermal energy storage technology is crucial for improving energy efficiency and protecting the environment. It can be used to address the mismatch between thermal energy supply and demand, and has broad application prospects in areas such as peak-load shifting, solar energy utilization, and waste and residual heat recovery.

[0003] Heat storage methods mainly include sensible heat, latent heat and chemical heat storage. Among them, chemical heat storage uses chemical reaction processes to store and release heat. Although compared with sensible heat and latent heat, the heat storage density of chemical heat storage materials is relatively large, and the adjustable heat storage temperature range is also relatively large, which can effectively utilize space and save costs, however, chemical heat storage materials are mostly inorganic powders, the heat storage temperature is relatively high, the heat storage speed is relatively slow, and it is easy to agglomerate and compact. Summary of the Invention

[0004] The first object of the present invention is to provide a method for preparing a composite heat storage material of hydroxide and molten salt, so as to solve the technical problems existing in the prior art of heat storage materials, such as relatively high heat storage temperature, relatively slow heat storage speed, and easy agglomeration and hardening.

[0005] The preparation method of the hydroxide and molten salt composite heat storage material provided by the present invention comprises the steps of:

[0006] Preparation of Mg 0.5 Ni 0.5 (OH)2 powder: Using the homogeneous complexation coprecipitation method, first mix the MgSO4 solution and NiSO4 solution with the concentration of C and volume of V evenly, then slowly drop the NaOH solution or KOH solution with the concentration of 2C and volume of 2V into the above mixed solution, and during the dropwise addition process, set the stirring speed of the stirrer to 45-75r / s, and maintain the pH value of the solution at 9-11; after 7-9 hours, wash the generated green product until no SO4 is detected 2- After filtering, drying at 110-130℃ for 9-11h, and finally grinding into Mg 0.5 Ni 0.5 (OH)2 powder is ready for use;

[0007] Mixing and grinding: weigh low melting point salt and the above Mg in a mass ratio of 1:10 to 1:8 respectively. 0.5 Ni 0.5(OH)2 powder, the melting point of the low melting point salt is not higher than 200℃, mix and grind for 5 to 30 minutes;

[0008] Add distilled water and stir at constant temperature: Transfer the ground mixture to a beaker, add distilled water to dissolve, and stir at a constant temperature of 60-80°C for 1-3 hours;

[0009] Constant temperature drying: Dry the mixture in the beaker at 80-120°C to obtain Mg 0.5 Ni 0.5 (OH)2 and molten salt composite heat storage material, which is white powder with a particle size of 3 to 5 μm.

[0010] Optionally, the low melting point salt comprises:

[0011] 7wt% NaNO3, 53wt% KNO3 and 40wt% NaNO2, melting point 142°C;

[0012] Alternatively, 48 wt% Ca(NO3)2, 45 wt% KNO3 and 7 wt% NaNO3, melting point 120°C;

[0013] Alternatively, 16.67 wt% Ca(NO3)2·4H2O, 44.17 wt% KNO3, 5.83 wt% NaNO3 and 33.33 wt% NaNO2 has a melting point of 83.1°C.

[0014] Optionally, the low melting point salt and the Mg 0.5 Ni 0.5 The mass ratio of (OH)2 powder is 1:9.

[0015] Optionally, the concentrations of the MgSO 4 solution and the NiSO 4 solution are both 1 mol / L, and the concentrations of the NaOH solution and the KOH solution are 2 mol / L.

[0016] Optionally, the preparation of Mg 0.5 Ni 0.5 In the step of (OH)2, when adding NaOH solution or KOH solution, a flow pump is used to add the solution dropwise.

[0017] Optionally, the preparation of Mg 0.5 Ni 0.5 In the (OH)2 step, a pH detector is used to detect the pH value of the solution in real time and maintain the pH value of the solution at 10.

[0018] Optionally, the preparation of Mg 0.5 Ni 0.5 In the step of (OH)2, the stirrer is a magnetic stirrer, which is arranged at the bottom of the reactor.

[0019] Optionally, in the mixing and grinding step, the mixture is mechanically ground in an agate mortar.

[0020] Optionally, in the constant temperature drying step, the mixture after constant temperature stirring is subjected to ventilation drying for 10 to 14 hours.

[0021] The preparation method of the hydroxide and molten salt composite heat storage material provided by the present invention can achieve the following beneficial effects:

[0022] The preparation method of the hydroxide and molten salt composite heat storage material provided by the present invention is to prepare the composite hydroxide Mg 0.5 Ni 0.5 (OH)2, and then compound it with low melting point salt to finally obtain a composite heat storage material. The process is simple and feasible. 0.5 Ni 0.5 The decomposition temperature of (OH)2 is 150-180°C, which is much lower than the decomposition temperature of hydroxides such as Ca(OH)2 and Mg(OH)2 in the prior art. Therefore, heat can be stored at a relatively low temperature. The melting point of low-melting-point salts is also very low, below 200°C, and they can be in a molten state during heat storage. The molten salt can effectively block hydroxide particles, thereby effectively preventing hydroxide particle agglomeration. On the other hand, it can increase the heat transfer rate, thereby increasing the heat storage and heat release rates. The fast heat storage rate can effectively alleviate heat concentration and make heat distribution more uniform. The fast heat release rate can quickly release heat. Therefore, the prepared composite heat storage material is not prone to caking during the heat storage and release cycle. That is, the preparation method of the composite heat storage material provided by the present invention is simple and feasible. The prepared composite heat storage material has a low heat storage temperature, which greatly reduces the heat storage temperature of chemical materials and expands the heat storage temperature range of chemical materials. In addition, the heat storage and heat release rates are fast and are not prone to agglomeration and caking. This is of great significance for the promotion of chemical heat storage.

[0023] The first object of the present invention is to provide a composite heat storage material of hydroxide and molten salt to solve the technical problems of the heat storage material in the prior art, such as high heat storage temperature, slow heat storage speed, and easy agglomeration and hardening.

[0024] The hydroxide and molten salt composite heat storage material provided by the present invention is prepared by the above-mentioned preparation method of the hydroxide and molten salt composite heat storage material, and has all the above-mentioned advantages, so they are not described here in detail. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0026] Figure 1 This is a schematic diagram of the process flow of the method for preparing the hydroxide and molten salt composite heat storage material provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0027] In order to make the above-mentioned objects, features and advantages of the present invention more clearly understood, the following detailed description of the specific embodiments of the present invention is given in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0028] This embodiment provides a method for preparing a hydroxide and molten salt composite heat storage material, comprising the following steps:

[0029] Preparation of Mg 0.5 Ni 0.5 (OH)2 powder: Using the homogeneous complexation coprecipitation method, first mix the MgSO4 solution and NiSO4 solution with the concentration of C and volume of V evenly, then slowly drop the NaOH solution or KOH solution with the concentration of 2C and volume of 2V into the above mixed solution, and during the dropwise addition process, set the stirring speed of the stirrer to 45-75r / s, and maintain the pH value of the solution at 9-11; after 7-9 hours, wash the generated green product until no SO4 is detected 2- After filtering, drying at 110-130℃ for 9-11h, and finally grinding into Mg 0.5 Ni 0.5 (OH)2 powder is ready for use;

[0030] Mixing and grinding: weigh low melting point salt and the above Mg in a mass ratio of 1:10 to 1:8 respectively. 0.5 Ni 0.5 (OH)2 powder, the melting point of the low melting point salt is not higher than 200℃, mix and grind for 5 to 30 minutes;

[0031] Add distilled water and stir at constant temperature: Transfer the ground mixture to a beaker, add distilled water to dissolve, and stir at a constant temperature of 60-80°C for 1-3 hours;

[0032] Constant temperature drying: Dry the mixture in the beaker at 80-120°C to obtain Mg 0.5 Ni 0.5(OH)2 and molten salt composite heat storage material, which is white powder with a particle size of 3 to 5 μm.

[0033] The preparation method of the hydroxide and molten salt composite heat storage material provided in this embodiment is to prepare the composite hydroxide Mg 0.5 Ni 0.5 (OH)2, and then compound it with low melting point salt to finally obtain a composite heat storage material. The process is simple and feasible. 0.5 Ni 0.5 The decomposition temperature of (OH)2 is 150-180°C, significantly lower than the decomposition temperatures of hydroxides such as Ca(OH)2 and Mg(OH)2 found in the prior art. Therefore, heat can be stored at relatively low temperatures. Low-melting-point salts also have a low melting point, below 200°C, allowing them to remain in a molten state during heat storage. Molten salts, on the one hand, effectively block hydroxide particles, thereby effectively preventing hydroxide particle agglomeration; on the other hand, they increase heat transfer rates, thereby increasing heat storage and release rates. The rapid heat storage rate effectively alleviates heat concentration, making heat distribution more uniform, while the rapid heat release rate allows for rapid heat release. Therefore, the prepared composite heat storage material is less likely to clump during the heat storage and release cycles. In other words, the preparation method of the composite heat storage material provided in this embodiment is simple and feasible. The resulting composite heat storage material has a low heat storage temperature, significantly reducing the heat storage temperature of chemical materials and expanding the heat storage temperature range of chemical materials. Furthermore, the rapid heat storage and release rates make it less likely to agglomerate or clump, which is of great significance for promoting chemical heat storage.

[0034] Specifically, in this embodiment, the low-melting-point salt may include: 7wt% NaNO3, 53wt% KNO3 and 40wt% NaNO2, with a melting point of 142°C; or, 48wt% Ca(NO3)2, 45wt% KNO3 and 7wt% NaNO3, with a melting point of 120°C; or, 16.67wt% Ca(NO3)2·4H2O, 44.17wt% KNO3, 5.83wt% NaNO3 and 33.33wt% NaNO2, with a melting point of 83.1°C. Of course, in other embodiments of the present application, the low-melting-point salt is not limited to the above-mentioned combination form, and other combination forms can also be used. The user can use different combinations of low-melting-point salts according to the heat storage temperature. For example, when the heat storage temperature is relatively low, a low-melting-point salt with a low melting point is used, and when the heat storage temperature is slightly higher, a low-melting-point salt with a slightly higher melting point can be used.

[0035] Specifically, in this embodiment, the low melting point salt and Mg 0.5 Ni 0.5The mass ratio of (OH)2 powder can be 1:10, 1:9, 1:8, or any mass ratio between the two values. 0.5 Ni 0.5 The mass ratio of (OH)2 powder is 1:9.

[0036] Specifically, in this embodiment, the concentrations of the MgSO4 solution and the NiSO4 solution are both 1 mol / L, and the concentrations of the NaOH solution and the KOH solution are 2 mol / L. However, in other embodiments of the present application, the concentrations of the solutions are not limited to the above values. For example, the concentrations of the MgSO4 solution and the NiSO4 solution can also be both 1.2 mol / L, while the concentrations of the NaOH solution and the KOH solution can be 2.4 mol / L, respectively.

[0037] Specifically, in this embodiment, the volume of the MgSO4 solution and the NiSO4 solution can be 200 mL, and the concentration of the NaOH solution and the KOH solution can be 400 mL. However, in other embodiments of the present application, the concentrations of the solutions are not limited to the above values. For example, the concentrations of the MgSO4 solution and the NiSO4 solution can also be 1.2 mol / L, while the concentrations of the NaOH solution and the KOH solution can be 2.4 mol / L.

[0038] Specifically, in this embodiment, Mg 0.5 Ni 0.5 In the step of adding (OH)2, when adding NaOH solution or KOH solution, a flow pump is used and the solution is added dropwise. This is not only convenient to operate, but also accurate and labor-saving. Of course, in other embodiments of the present application, when adding NaOH solution or KOH solution, it can also be added manually.

[0039] Specifically, in this embodiment, Mg 0.5 Ni 0.5 (OH)2 step, use a pH detector to detect the pH value of the solution in real time, and maintain the pH value of the solution between 9 and 11; further, maintain the pH value of the solution at 9, 10, 11, or any pH value between the two values; preferably, maintain the pH value of the solution at 10.

[0040] Specifically, in this embodiment, Mg 0.5 Ni 0.5In the step of adding (OH)2, the stirrer is a magnetic stirrer and is arranged at the bottom of the reactor. Furthermore, in this embodiment, the stirring rate of the stirrer can be 50 to 70 r / s; more specifically, the stirring rate of the stirrer can be 45 r / s, 50 r / s, 55 r / s, 60 r / s, 65 r / s, 70 r / s, 75 r / s, or any rate between the two value points; preferably, the stirring rate of the stirrer is 60 r / s.

[0041] Specifically, in this embodiment, Mg 0.5 Ni 0.5 In the step of (OH)2, the stirring time can be specifically 7h, 7.5h, 8h, 8.5h, 9h, or any time between the two value points; preferably, the stirring time is 8h. After the stirring is completed, the generated green product can be washed with distilled water for several times until no SO4 is detected using BaCl2. 2- During drying, the drying temperature can be 110°C, 115°C, 120°C, 125°C, 130°C, or any temperature value between the two values; preferably, the drying temperature is 120°C. As for the drying time, it can be 9 hours, 9.5 hours, 10 hours, 10.5 hours, 11 hours, or any time between the two values; preferably, the drying time is 10 hours.

[0042] Specifically, in this embodiment, during the mixing and grinding step, the mixture is mechanically ground in an agate mortar. The agate mortar has high compressive strength and is resistant to acids and alkalis. Most importantly, it prevents the mortar's own contents from entering the ground material, thereby ensuring the purity and, consequently, the properties of the ground material. Of course, other instruments besides the agate mortar can also be used for grinding, as long as they can prevent the introduction of impurities during the grinding process.

[0043] Specifically, in this embodiment, the mixing and grinding time can be further 10 to 25 minutes. More specifically, the mixing and grinding time can be 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, or any time before the two value points; preferably, the mixing and grinding time can be 20 minutes.

[0044] Specifically, in this embodiment, in the step of dissolving the mixed and ground product and stirring at a constant temperature, the temperature can be controlled at 60°C, 65°C, 70°C, 75°C, 80°C, or any temperature value between the two values; preferably, the temperature during stirring can be controlled at 60-70°C, for example, 60°C. The stirring time can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, or any time between the two values; preferably, the drying time is 1-2 hours, for example, 1 hour.

[0045] Specifically, in this embodiment, in the constant temperature drying step, the mixture after constant temperature stirring is ventilated and dried for 10 to 14 hours. Furthermore, the drying time can be 11 to 13 hours. Specifically, the drying time can be 10 hours, 10.5 hours, 11 hours, 11.5 hours, 12 hours, 12.5 hours, 13 hours, 13.5 hours, 14 hours, or any time between two value points; preferably, the drying time is 12 hours.

[0046] The temperature during constant temperature drying can further be 80-100°C; specifically, the temperature during constant temperature drying can be 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, or any temperature value between the two value points; preferably, the temperature during constant temperature drying is 80°C.

[0047] This embodiment also provides a hydroxide and molten salt composite heat storage material, which is prepared using the above-mentioned preparation method of the hydroxide and molten salt composite heat storage material and has all the above-mentioned advantages, so it will not be described in detail here.

[0048] To further illustrate the present invention, the preparation method of the hydroxide and molten salt composite heat storage material provided by the present invention and the prepared hydroxide and molten salt composite heat storage material are described in more detail below in conjunction with the examples, but they should not be understood as limiting the scope of protection of the present invention.

[0049] Example 1

[0050] S110, firstly, Mg was prepared by homogeneous complexation coprecipitation method. 0.5 Ni 0.5 (OH)2 powder: Evenly mix 200mL of 1mol / L NiSO4 solution and 200mL of 1mol / L MgSO4 solution, then slowly drip 400mL of 2mol / L NaOH (or KOH) solution into the reactor. Place a magnetic stirrer at the bottom of the reactor with a stirring rate of 60r / s. Use a pH meter to maintain the pH value of the solution at around 10. After 8h, wash the green reaction product with distilled water several times until no SO4 can be detected with BaCl2 solution. 2- Filter, dry at 120℃ for 10h, and grind into green powder Mg 0.5 Ni 0.5 (OH)2 is for standby use.

[0051] S120, then refer to Figure 1 As shown, weigh 5.4g of the above Mg 0.5 Ni 0.5(OH)2 powder and 0.6g of low-melting-point salt, wherein the low-melting-point salt includes: 7wt% NaNO3+53wt% KNO3+40wt% NaNO2, whose melting point is 142℃, are transferred to an agate mortar and mechanically ground for 20min.

[0052] S130, transfer the ground mixture to a beaker, add distilled water to 20 mL, and stir at 60°C for 1 h.

[0053] S140, placing the mixture in the beaker under ventilation drying at 80°C for 12 hours to obtain a dried composite heat storage material, which is a white powder with a particle size of 3 to 5 μm.

[0054] As shown in Table 1, the dehydration decomposition temperature of the chemical heat storage material prepared in Example 1 is about 160°C at normal pressure, which is about 200°C lower than that of pure magnesium hydroxide, and the heat storage temperature is greatly reduced.

[0055] At 300℃, take 10g of the above-mentioned Mg 0.5 Ni 0.5 The (OH)2 material was placed in a tube furnace and an inert gas was passed through. The H2O produced by decomposition was detected at the outlet. No H2O was detected after 65 minutes, indicating that the decomposition reaction was complete. Meanwhile, when the pure Mg(OH)2 material was placed in a tube furnace and an inert gas was passed through, the H2O produced by decomposition was detected at the outlet. No H2O was detected after 120 minutes, indicating that the decomposition reaction was complete.

[0056] Table 1

[0057] Composite heat storage materials <![CDATA[Mg(OH)2]]> Dehydration decomposition temperature under normal pressure 160℃ 350℃ 300℃, 10g, decomposition time 65min 120 minutes

[0058] The above data show that the heat storage temperature of the composite heat storage material prepared in Example 1 is greatly reduced, and the heat storage speed is greatly improved, which is increased by nearly double.

[0059] Example 2

[0060] S210, firstly, Mg was prepared by homogeneous complexation coprecipitation method. 0.5 Ni 0.5 (OH)2 powder: Evenly mix 200mL of 1mol / L NiSO4 solution and 200mL of 1mol / L MgSO4 solution, then slowly drip 400mL of 2mol / L NaOH (or KOH) solution into the reactor. Place a magnetic stirrer at the bottom of the reactor with a stirring rate of 60r / s. Use a pH meter to maintain the pH value of the solution at around 10. After 8h, wash the green reaction product with distilled water several times until no SO4 can be detected with BaCl2 solution. 2- Filter, dry at 120℃ for 10h, and grind into green powder Mg0.5 Ni 0.5 (OH)2 is for standby use.

[0061] S220, weigh 5.4g of the above Mg 0.5 Ni 0.5 (OH)2 powder and 0.6g low-melting-point salt, wherein the low-melting-point salt includes: 48wt% Ca(NO3)2+45wt% KNO3+7wt% NaNO3, whose melting point is 120℃, are transferred to an agate mortar and mechanically ground for 20min.

[0062] S230, transfer the ground mixture to a beaker, add distilled water to 20 mL, and stir at 60°C for 1 h.

[0063] S240, placing the mixture in the beaker under ventilation drying at 80°C for 12 hours to obtain a dried composite heat storage material, which is a white powder with a particle size of 3 to 5 μm.

[0064] As shown in Table 2, the dehydration decomposition temperature of the chemical heat storage material prepared in Example 2 is about 180° C. at normal pressure, which is nearly half that of pure magnesium hydroxide, and the heat storage temperature is greatly reduced.

[0065] At 300℃, take 10g of the above-mentioned Mg 0.5 Ni 0.5 The (OH)2 material was placed in a tube furnace and an inert gas was passed through. The H2O produced by decomposition was detected at the outlet. No H2O was detected after 78 minutes, indicating that the decomposition reaction was complete. Meanwhile, when the pure Mg(OH)2 material was placed in a tube furnace and an inert gas was passed through, the H2O produced by decomposition was detected at the outlet. No H2O was detected after 120 minutes, indicating that the decomposition reaction was complete.

[0066] Table 2

[0067] Composite heat storage materials <![CDATA[Mg(OH)2]]> Dehydration decomposition temperature under normal pressure 180℃ 350℃ 300℃, 10g, decomposition time 78min 120 minutes

[0068] The above data show that the heat storage temperature of the composite heat storage material prepared in Example 2 is greatly reduced and the heat storage speed is significantly improved.

[0069] Example 3

[0070] S310, firstly, Mg was prepared by homogeneous complexation coprecipitation method. 0.5 Ni 0.5(OH)2 powder: Evenly mix 200mL of 1mol / L NiSO4 solution and 200mL of 1mol / L MgSO4 solution, then slowly drip 400mL of 2mol / L NaOH (or KOH) solution into the reactor. Place a magnetic stirrer at the bottom of the reactor with a stirring rate of 60r / s. Use a pH meter to maintain the pH value of the solution at around 10. After 8h, wash the green reaction product with distilled water several times until no SO4 can be detected with BaCl2 solution. 2- Filter, dry at 120℃ for 10h, and grind into green powder Mg 0.5 Ni 0.5 (OH)2 is for standby use.

[0071] S320, weigh 5.4g of the above Mg 0.5 Ni 0.5 (OH)2 powder and 0.6g low-melting-point salt, wherein the low-melting-point salt includes: 16.67wt% Ca(NO3)2·4H2O+44.17wt% KNO3+5.83wt% NaNO3+33.33wt% NaNO2, whose melting point is 83.1℃, are transferred to an agate mortar and mechanically ground for 20min.

[0072] S330, transfer the ground mixture to a beaker, add distilled water to 20 mL, and stir at 60°C for 1 h.

[0073] S340, placing the mixture in the beaker under ventilation drying at 80°C for 12 hours to obtain a dried composite heat storage material, which is a white powder with a particle size of 3 to 5 μm.

[0074] As shown in Table 3, the dehydration decomposition temperature of the chemical heat storage material prepared in Example 3 at normal pressure is about 200°C, which is about 150°C lower than that of pure magnesium hydroxide, and the heat storage temperature is greatly reduced.

[0075] At 300℃, take 10g of the above-mentioned Mg 0.5 Ni 0.5 The (OH)2 material was placed in a tube furnace and an inert gas was passed through. The H2O produced by decomposition was detected at the outlet. No H2O was detected after 92 minutes, indicating that the decomposition reaction was complete. Meanwhile, when the pure Mg(OH)2 material was placed in a tube furnace and an inert gas was passed through, the H2O produced by decomposition was detected at the outlet. No H2O was detected after 120 minutes, indicating that the decomposition reaction was complete.

[0076] Table 3

[0077] Composite heat storage materials <![CDATA[Mg(OH)2]]> Dehydration decomposition temperature under normal pressure 200℃ 350℃ 300℃, 10g, decomposition time 92min 120 minutes

[0078] The above data show that the heat storage temperature of the composite heat storage material prepared in Example 3 is greatly reduced and the heat storage speed is significantly improved.

[0079] Finally, it should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include," "comprise," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0080] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to the embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is to be construed in the widest manner consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a hydroxide and molten salt composite heat storage material, characterized in that: The following steps are involved: Preparation of Mg 0.5 Ni 0.5 (OH)2 powder: Using the homogeneous complexation coprecipitation method, first mix the MgSO4 solution and NiSO4 solution with the concentration of C and volume of V evenly, then slowly drop the NaOH solution or KOH solution with the concentration of 2C and volume of 2V into the above mixed solution, and during the dropwise addition process, set the stirring speed of the stirrer to 45-75r / s, and maintain the pH value of the solution at 9-11; after 7-9 hours, wash the generated green product until no SO4 is detected 2- After filtering, drying at 110-130℃ for 9-11h, and finally grinding into Mg 0.5 Ni 0.5 (OH)2 powder is ready for use; Mixing and grinding: weigh low melting point salt and the above Mg in a mass ratio of 1:10 to 1:8 respectively. 0.5 Ni 0.5 (OH)2 powder, the melting point of the low melting point salt is not higher than 200℃, mix and grind for 5 to 30 minutes; Add distilled water and stir at constant temperature: Transfer the ground mixture to a beaker, add distilled water to dissolve, and stir at a constant temperature of 60-80°C for 1-3 hours; Constant temperature drying: Dry the mixture in the beaker at 80-120°C to obtain Mg 0.5 Ni 0.5 (OH)2 and molten salt composite heat storage material, which is white powder with a particle size of 3 to 5 μm.

2. The method for preparing the hydroxide and molten salt composite heat storage material according to claim 1, characterized in that: The low melting point salt comprises: 7wt% NaNO3, 53wt% KNO3 and 40wt% NaNO2, melting point 142°C; Alternatively, 48 wt% Ca(NO3)2, 45 wt% KNO3 and 7 wt% NaNO3, melting point 120°C; Alternatively, 16.67 wt% Ca(NO3)2·4H2O, 44.17 wt% KNO3, 5.83 wt% NaNO3 and 33.33 wt% NaNO2 has a melting point of 83.1°C.

3. The method for preparing the hydroxide and molten salt composite heat storage material according to claim 1 or 2, characterized in that: The low melting point salt and the Mg 0.5 Ni 0.5 The mass ratio of (OH)2 powder is 1:

9.

4. The method for preparing the hydroxide and molten salt composite heat storage material according to claim 1, characterized in that: The concentrations of the MgSO4 solution and the NiSO4 solution are both 1 mol / L, and the concentrations of the NaOH solution and the KOH solution are both 2 mol / L.

5. The method for preparing the hydroxide and molten salt composite heat storage material according to claim 1, characterized in that: The preparation of Mg 0.5 Ni 0.5 In the step of (OH)2, when adding NaOH solution or KOH solution, a flow pump is used to add the solution dropwise.

6. The method for preparing the hydroxide and molten salt composite heat storage material according to claim 1, characterized in that: The preparation of Mg 0.5 Ni 0.5 In the (OH)2 step, a pH detector is used to detect the pH value of the solution in real time and maintain the pH value of the solution at 10.

7. The method for preparing a hydroxide and molten salt composite heat storage material according to claim 1, characterized in that: The preparation of Mg 0.5 Ni 0.5 In the step of (OH)2, the stirrer is a magnetic stirrer, which is arranged at the bottom of the reactor.

8. The method for preparing the hydroxide and molten salt composite heat storage material according to claim 1, characterized in that: In the mixing and grinding step, the mixture is mechanically ground in an agate mortar.

9. The method for preparing a hydroxide and molten salt composite heat storage material according to claim 1, characterized in that: In the constant temperature drying step, the mixture after constant temperature stirring is subjected to ventilation drying for 10 to 14 hours.

10. A hydroxide and molten salt composite heat storage material, characterized in that: The composite heat storage material of hydroxide and molten salt is prepared by the preparation method of any one of claims 1 to 9.

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