CN108003847A - A kind of high heat conduction MgO doping nitric acid Molten Salt Heat Transfer heat accumulatings and its in-situ synthesized and application - Google Patents

Abstract

The invention belongs to the field of large-scale utilization of renewable energy and thermal energy storage and transmission, and discloses a high thermal conductivity MgO-doped nitric acid molten salt heat transfer heat storage material and its in-situ generation method and application. The method comprises the following steps: mixing dried potassium nitrate and sodium nitrate according to the ratio of the lowest eutectic point of the binary phase diagram to obtain the raw material mixture I of molten nitric acid salt; according to the mass ratio, it is equivalent to MgO: molten salt of nitric acid is (2.5～10.0 ): (97.5～90.0) ratio, adding magnesium chloride hexahydrate or magnesium nitrate hexahydrate into the mixture I to obtain magnesium chloride hexahydrate or magnesium nitrate hexahydrate doped with nitrate molten salt raw material mixture II; after mixing the mixture II evenly, the procedure Raise the temperature to 420-500°C and keep the temperature constant for 10-24 hours to ensure that MgO is generated and crystallized in situ to form a uniform fluid of MgO-doped nitric acid molten salt; the fluid is naturally cooled to room temperature and crushed to obtain a high thermal conductivity MgO-doped nitric acid molten salt Heat storage material.

Description

A high thermal conductivity MgO doped nitric acid molten salt heat transfer heat storage material and its in-situ generation method and application

technical field

The invention belongs to the field of large-scale utilization of renewable energy and thermal energy storage and transmission, and particularly relates to a high thermal conductivity MgO-doped nitric acid molten salt heat transfer heat storage material and its in-situ generation method and application.

Background technique

High-efficiency heat transfer and heat storage technology can effectively solve the problems of intermittent and unstable energy supply in the process of large-scale utilization of solar energy and recovery of industrial waste heat, and can effectively improve energy conversion and utilization efficiency. Among them, the development of high-efficiency heat transfer and heat storage materials is the key to the development of high-efficiency heat transfer and heat storage technologies.

Molten salt has the characteristics of high working temperature, low vapor pressure, wide working temperature range, good thermal stability, and relatively low cost. It is an important medium-high temperature heat transfer and heat storage material. Nitric acid molten salt has become the first choice for medium and high temperature heat transfer and heat storage materials due to its low melting point and large specific heat capacity. Among them, binary nitric acid molten salt (60wt.% NaNO ₃ -40wt.% KNO ₃ , melting point 220°C) has been successfully Solar thermal power plants for commercial operation. However, molten salt has the problem of low thermal conductivity of high temperature liquid. In practical applications, the thermal conductivity of molten salt high-temperature liquid determines the heat transfer efficiency of the molten salt heat transfer process, which in turn affects energy conversion and utilization efficiency. For this reason, the thermal conductivity of molten salt high-temperature liquid must be improved. Chinese invention patent applications with application numbers CN201310029569.6, CN201310053597.1, CN201310732781.9 and CN201310733405.1 add solid nanoparticles and water glass to the molten salt by mechanical stirring to improve the thermal stability of the molten salt, and claim to add nano The thermal conductivity of molten nitric acid salt after particles is high. However, in these instructions, no evidence was found to prove that the addition of nanoparticles by mechanical methods can effectively improve the thermal conductivity of molten salts, and the addition of nanoparticles by mechanical stirring cannot effectively solve the problem of agglomeration of the added particles, resulting in the possibility that the fluid may have solid/liquid Separation issues.

Contents of the invention

In order to overcome the problem of low thermal conductivity of molten salt of nitric acid in the prior art, and the shortcomings and deficiencies that the mechanical method of adding nanoparticles can effectively improve the thermal conductivity of molten salt, and at the same time, in order to overcome the existing mechanical stirring method of adding solid particles It is difficult to effectively solve the defect of phase separation between molten salt liquid and solid particles caused by agglomeration of particles. The primary purpose of the present invention is to provide an in-situ generation method of a high thermal conductivity MgO-doped nitric acid molten salt heat transfer and heat storage material.

Another object of the present invention is to provide a high thermal conductivity MgO-doped nitric acid molten salt heat transfer heat storage material obtained by the above-mentioned in-situ generation method; Evenly suspended in salt fluid without sedimentation, it has better heat transfer and heat storage performance and stability.

Another object of the present invention is to provide the application of the above-mentioned high thermal conductivity MgO doped nitrate molten salt heat transfer and heat storage material.

The object of the invention is achieved through the following technical solutions:

An in-situ generation method of a high thermal conductivity MgO doped nitric acid molten salt heat transfer heat storage material, comprising the following steps:

(1) the saltpetre after drying and sodium nitrate are mixed by the lowest eutectic point ratio of its binary phase diagram, obtain the raw material mixture I of nitric acid molten salt;

(2) Add MgCl ₂ 6H ₂ O or Mg(NO ₃ ) ₂ 6H ₂ O to the step (1 ) in the mixture I prepared by MgCl ₂ 6H ₂ O or Mg(NO ₃ ) ₂ 6H ₂ O doped nitric acid molten salt raw material mixture II;

(3) After mixing the mixture II obtained in step (2) evenly, the temperature is programmed to rise to 420° C. to 500° C., and the temperature is kept constant for 10 to 24 hours to ensure that MgO is generated and crystallized in situ, forming a uniform fluid of MgO doped nitric acid molten salt;

(4) The homogeneous fluid obtained in step (3) is naturally cooled to room temperature and pulverized to obtain a heat transfer and heat storage material of MgO doped nitric acid molten salt with high thermal conductivity.

The temperature programming described in step (3) is to heat to the constant temperature reaction temperature with a heating rate of 10° C./min.

A high thermal conductivity MgO doped nitric acid molten salt heat transfer and heat storage material obtained by the above-mentioned in-situ generation method.

The application of the above-mentioned high thermal conductivity MgO doped nitric acid molten salt heat transfer heat storage material in the field of industrial high temperature waste heat recovery and tower solar thermal power generation.

Compared with the prior art, the present invention has the following advantages and effects:

(1) The present invention provides a method for preparing high thermal conductivity MgO-doped nitric acid molten salt heat transfer and heat storage materials by an in-situ generation method, which can make the in-situ generated MgO particles uniformly and stably distributed in the molten salt fluid without agglomeration and non-agglomeration Settling can effectively solve the technical defects of particle agglomeration that cannot be overcome by mechanical stirring.

(2) prove by measuring fluid high-temperature thermal conductivity, compared with the nitric acid molten salt that does not contain MgO, the thermal conductivity of the fluid of the MgO-doped nitric acid molten salt heat transfer heat storage material prepared by the in-situ generation method provided by the present invention Significantly improved; overcame the disadvantage of low thermal conductivity of molten salt of nitric acid, which is unfavorable for heat transfer, while retaining the advantages of low melting point of molten salt of nitric acid; high thermal conductivity can effectively improve the heat transfer efficiency of molten salt; low melting point characteristics can greatly reduce storage capacity Insulation energy consumption of thermal system.

(3) Another significant advantage of the high thermal conductivity MgO-doped nitric acid molten salt heat transfer and heat storage material prepared by the in-situ generation method provided by the present invention is that there is a strong interaction between the in-situ generated MgO particles and the molten salt liquid The interaction can effectively increase the specific heat of the MgO-doped nitric acid molten salt fluid, and the high specific heat can greatly increase the heat storage/release of the molten salt fluid in a single cycle, and effectively reduce the pumping power consumption.

(4) Compared with the high thermal conductivity metal-chloride molten salt heat transfer and heat storage material provided by the existing application number CN201510134557.9 Chinese invention patent application, the high thermal conductivity MgO doped material prepared by the in-situ generation method provided by the present invention Nitric acid molten salt heat transfer and heat storage material has a lower melting point and greater specific heat; the melting point of the high thermal conductivity MgO-doped nitric acid molten salt prepared by the present invention is 220.6°C, and the application number is CN201510134557.9 provided by the Chinese invention patent application The melting point of the metal-chloride molten salt is 776.7°C. The high melting point makes it difficult to measure the thermal conductivity of the metal-chloride molten salt liquid; the high thermal conductivity MgO-doped nitric acid molten salt prepared by the in-situ generation method provided by the present invention Heat transfer and heat storage materials, the specific heat of the fluid ranges from 1.4 to 1.9 J·g ^-1 ·K ^-1 ; the ratio of the metal-chloride molten salt fluid provided by the Chinese invention patent application with the application number CN201510134557.9 The heat only fluctuates within the range of 0.92～0.93J·g ^-1 ·K ^-1 .

(5) Compared with the metal-carbonate molten salt heat transfer heat storage material provided by the existing application number CN201710362154.9 Chinese patent application, the high thermal conductivity MgO doped nitric acid molten salt heat transfer material prepared by the in-situ generation method provided by the present invention Heat storage material with lower melting point and greater thermal conductivity improvement rate; application number CN201710362154.9 Chinese patent application provides metal-carbonate molten salt heat transfer and heat storage material (melting point 397.7 ℃), the metal additives in it Only up to 3%, the maximum increase rate of thermal conductivity of carbonate molten salt is 11%; in the high thermal conductivity MgO doped nitric acid molten salt prepared by the present invention, the doping amount of MgO can be greater than 5%; when MgO doped nitric acid molten salt When the MgO doping amount in the medium is equivalent to the maximum metal addition amount of 3% in the metal-carbonate molten salt, that is, when the MgO doping amount in the MgO-doped nitric acid molten salt is only 3.5%, the increase rate of the thermal conductivity of the nitric acid molten salt is just up to 34%.

(6) Compared with the Chinese invention patent application whose application numbers are CN201310029569.6, CN201310053597.1, CN201310732781.9 and CN201310733405.1, using mechanical stirring method to add solid nanoparticles and water glass to molten salt, the present invention provides The MgO doped in the high thermal conductivity MgO-doped nitric acid molten salt prepared by the in-situ generation method is generated by the direct hydrolysis of the raw material magnesium chloride hexahydrate or magnesium nitrate hexahydrate in the molten salt, rather than adding solid nanoparticles later. The interaction between the MgO particles generated in situ and the molten salt is stronger than the interaction between the added nanoparticles and the molten salt in the later stage, so it is inferred that the specific heat increase rate of the MgO-doped nitric acid molten salt provided by the present invention is greater than that added in the later stage. The increase rate of the specific heat of the material made of particles. In addition, the Chinese invention patent applications with application numbers CN201310029569.6, CN201310053597.1, CN201310732781.9 and CN201310733405.1 described that the doping salt prepared by adding solid nanoparticles and water glass to molten salt by mechanical stirring method is claimed to be " High thermal conductivity", but there is no actual measurement data in the application documents to prove the phenomenon of "high thermal conductivity" it claims. The present invention has clear measurement data to prove that the high thermal conductivity MgO-doped nitric acid molten salt heat transfer and heat storage material prepared by the in-situ generation method provided by the present invention has larger specific heat and higher thermal conductivity.

(7) The high thermal conductivity MgO-doped nitric acid molten salt heat transfer and heat storage material prepared by the in-situ generation method provided by the present invention can be applied to the fields of high-temperature waste heat recovery and tower solar thermal power generation.

Description of drawings

Fig. 1 is a photogram of a nitric acid molten salt fluid; wherein, the left side is a binary nitric acid molten salt fluid, and the right side is the MgO-doped nitric acid molten salt fluid prepared in Example 5.

Fig. 2 is the analysis figure of the melting point measurement result of different molten salts; Wherein, a is nitric acid molten salt, b is the MgO doped nitric acid molten salt prepared in embodiment 1, c is the MgO doped nitric acid molten salt prepared in embodiment 4, d MgO doped nitric acid molten salt fluid prepared for Example 5.

Fig. 3 is the specific heat measurement result analysis figure of different molten salt fluids; Wherein, a is nitric acid molten salt, b is the MgO doped nitric acid molten salt fluid prepared in Example 1, and c is the MgO doped nitric acid molten salt fluid prepared in Example 4. Salt fluid, d is the MgO-doped nitric acid molten salt fluid prepared in Example 5.

Fig. 4 is the thermal conductivity measurement result analysis figure of different molten salts; Wherein, a is nitric acid molten salt, b is the MgO-doped nitric acid molten salt fluid prepared in Example 1, and c is the MgO-doped nitric acid molten salt prepared in Example 4 Fluid, d is the MgO doped nitric acid molten salt fluid prepared in Example 5.

Specific implementation method

The present invention will be further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

Example 1

A method for preparing a high thermal conductivity MgO-doped nitric acid molten salt heat transfer and heat storage material by an in-situ generation method, the specific implementation steps are as follows:

Dried potassium nitrate and sodium nitrate are mixed by the lowest eutectic point ratio of its binary phase diagram to obtain the raw material mixture I of nitric acid molten salt; (NO ₃ ) ₂ ·6H ₂ O was added into the mixture I to obtain the Mg(NO ₃ ) ₂ ·6H ₂ O-doped nitric acid molten salt raw material mixture II. After mixing the mixture II evenly, the temperature was raised to 420°C at a heating rate of 10°C/min until the molten salt melted, and reacted at a constant temperature for 10 hours to form a uniformly suspended MgO-doped nitric acid molten salt fluid without phase separation, and cooled naturally to room temperature. Mechanical pulverization to obtain a high thermal conductivity MgO doped nitric acid molten salt heat transfer heat storage material.

Using a differential scanning calorimeter, the standard sapphire method is used to measure the specific heat of the MgO-doped nitric acid molten salt high-temperature fluid (220 ° C ~ 400 ° C) prepared in Example 1: under the same protective air flow and heating rate, by Measure the heat flow curve of the empty crucible, the heat flow curve of the same crucible plus the sapphire standard sample, and the heat flow curve of the prepared MgO-doped nitric acid molten salt sample in the same crucible, and calculate the ratio of the prepared MgO-doped nitric acid molten salt sample by the standard comparison method. hot. From one of the three obtained heat flow curves: the heat flow curve of the MgO-doped nitric acid molten salt sample prepared by the crucible, the melting point of the molten salt was determined by standard methods. As a comparison, the same measurement of melting point and specific heat was carried out for the binary nitric acid molten salt prepared according to the ratio of the lowest eutectic point of the binary phase diagram of potassium nitrate and sodium nitrate, and the measurement results are shown in Figure 2, Figure 3 and Table 1. The thermal diffusivity and thermal conductivity of the MgO-doped nitric acid molten salt high-temperature fluid prepared in Example 1 were measured using the LFA 457 laser thermal conductivity meter produced by the German NETZSCH company, and the measurement temperature range was 220 ° C to 400 ° C; for comparison, At the same time, in the same temperature range, the thermal diffusivity and thermal conductivity of the binary nitric acid molten salt high-temperature fluid were measured, and the results are shown in Figure 4, Table 1 and Table 2.

Under the same measuring condition of the same instrument, the 2.5%MgO doped nitric acid molten salt fusing point prepared by the present embodiment 1 remains almost unchanged (as shown in Fig. 2 curve a and curve b); specific heat slightly improves (as shown in Fig. 3 Curve a and curve b and shown in Table 1); the thermal diffusivity is significantly improved, and the thermal conductivity is greatly improved, as shown in Table 1, Figure 4 curve a and curve b and Table 2. Compared with the metal-chloride molten salt with a melting point of 772.2°C prepared in the best embodiment 2 disclosed in the Chinese patent application with the application number CN201510134557.9, the melting point of the 2.5% MgO-doped nitric acid molten salt prepared in this example is 221.2°C, a substantial decrease of about 551.0°C, as shown in Table 1. The application number is CN201510134557.9 The metal-chloride molten salt thermal conductivity given in the Chinese patent application is the normal temperature thermal conductivity of the metal-chloride molten salt measured by the Hotdisk TPS2500 thermal constant analyzer in a solid state, which is the same as that prepared by the present invention The thermal conductivity of MgO-doped nitric acid molten salt high-temperature liquid is not comparable. Since the melting point of the metal-chloride molten salt provided in the CN201510134557.9 Chinese patent application is too high, it is difficult to measure the thermal conductivity of the fluid with existing measurement techniques, so the thermal conductivity of the high-temperature fluid is not given. Compared with the 11% increase rate of the maximum increase rate of the thermal conductivity of carbonate molten salt by adding 2.6% metal given in the Chinese patent application with the application number CN201710362154.9, the application of the present invention can increase the thermal conductivity of nitric acid molten salt by 31% by adding 2.5% MgO, and The melting point of the MgO-doped nitric acid molten salt prepared by the application of the present invention is only 221°C, which is 176.5°C lower than the melting point of the metal-carbonate molten salt of 397.7°C given in the Chinese patent application with application number CN201710362154.9.

Fig. 1 left side figure is binary nitric acid molten salt fluid physical photo, and the right side of Fig. 1 is the 5.0%MgO doped nitric acid molten salt fluid physical photo prepared by embodiment 4.

Example 2

A method for preparing a high thermal conductivity MgO-doped nitric acid molten salt heat transfer and heat storage material by an in-situ generation method, the specific implementation steps are as follows:

Dried potassium nitrate and sodium nitrate are mixed by the lowest eutectic point ratio of its binary phase diagram to obtain the raw material mixture I of nitric acid molten salt; ₂ ·6H ₂ O was added to the mixture I to obtain the MgCl ₂ ·6H ₂ O doped nitric acid molten salt raw material mixture II. After mixing the mixture II evenly, the temperature was raised to 450°C at a heating rate of 10°C/min until the molten salt melted, and reacted at a constant temperature for 15 hours to form a uniformly suspended MgO-doped nitric acid molten salt fluid without phase separation, and cooled naturally to room temperature. Mechanical pulverization to obtain a high thermal conductivity MgO doped nitric acid molten salt heat transfer heat storage material.

The measuring method is the same as in Example 1, and the results are shown in Table 1 and Table 2. The melting point of the 3.5% MgO-doped nitric acid molten salt prepared in the present embodiment has almost no change compared with the melting point of the binary nitric acid molten salt, and the specific heat has also been improved; The specific heat is also slightly improved, and the thermal diffusivity is significantly improved compared with the 2.5% MgO doped nitric acid molten salt and the binary nitric acid molten salt obtained in Example 1, and the thermal conductivity of the high-temperature liquid is compared with the binary nitrate and the obtained embodiment 1. The 2.5% MgO doped nitric acid molten salt also has a significant increase.

Example 3

A method for preparing a high thermal conductivity MgO-doped nitric acid molten salt heat transfer and heat storage material by an in-situ generation method, the specific implementation steps are as follows:

Dried potassium nitrate and sodium nitrate are mixed by the lowest eutectic point ratio of its binary phase diagram to obtain the raw material mixture I of nitric acid molten salt; (NO ₃ ) ₂ ·6H ₂ O was added into the mixture I to obtain the Mg(NO ₃ ) ₂ ·6H ₂ O-doped nitric acid molten salt raw material mixture II. After the mixture II was mixed evenly, the temperature was raised to 500°C at a heating rate of 10°C/min until the molten salt melted, and reacted at a constant temperature for 24 hours to form a uniformly suspended MgO-doped nitric acid molten salt fluid without phase separation, and cooled naturally to room temperature. Mechanical pulverization to obtain a high thermal conductivity MgO doped nitric acid molten salt heat transfer heat storage material.

The measuring method is the same as in Example 1, and the results are shown in Table 1 and Table 2. Compared with the melting point of binary nitric acid molten salt, the melting point of the 4.5% MgO doped nitric acid molten salt prepared in this example remains almost unchanged, and the specific heat is significantly improved, and the thermal diffusion is better than that of the 3.5% MgO doped salt prepared in Example 2. The thermal diffusion data of the nitric acid molten salt has also been significantly improved, and the thermal conductivity of the high-temperature liquid is significantly higher than that of the high-temperature liquid of the binary nitric acid molten salt. The result of this embodiment shows that the 4.5% MgO doped by the in-situ generation method can effectively improve the thermal conductivity of the molten nitric acid salt high-temperature liquid, which is beneficial to the enhancement of heat transfer.

Example 4

A method for preparing a high thermal conductivity MgO-doped nitric acid molten salt heat transfer and heat storage material by an in-situ generation method, the specific implementation steps are as follows:

Dried potassium nitrate and sodium nitrate are mixed by the lowest eutectic point ratio of its binary phase diagram to obtain the raw material mixture I of nitric acid molten salt; ₂ ·6H ₂ O was added to the mixture I to obtain the MgCl ₂ ·6H ₂ O doped nitric acid molten salt raw material mixture II. After the mixture II was mixed evenly, the temperature was raised to 480°C at a heating rate of 10°C/min until the molten salt melted, and the constant temperature was reacted for 18 hours to form a uniformly suspended MgO-doped nitric acid molten salt fluid without phase separation, and cooled naturally to room temperature. Mechanical pulverization to obtain a high thermal conductivity MgO doped nitric acid molten salt heat transfer heat storage material.

The measuring method is the same as in Example 1, and the results are shown in Figures 2 to 4 and Tables 1 to 2. Compared with the melting point of the binary nitric acid molten salt, the melting point of the 5.0% MgO-doped nitric acid molten salt prepared in this example has almost no change, and the specific heat has obviously increased. The thermal diffusion data of the 4.5% MgO doped nitric acid molten salt obtained in example 3 also has significantly improved thermal diffusion ratio; The thermal conductivity of the liquid. The result of this embodiment shows that doping 5.0% MgO by in-situ generation method can also improve the thermal conductivity of the high-temperature liquid of molten nitric acid salt, which is beneficial to enhance heat transfer.

The physical photographs of the 5.0% MgO-doped nitric acid molten salt liquid and the binary nitric acid molten salt liquid prepared in Example 4 are shown in Figure 1, the left side is the binary nitrate liquid, and the right side is the prepared 5.0% MgO-doped nitric acid molten salt liquid. Miscellaneous nitric acid molten salt liquid. It can be seen from the figure that in the prepared 5.0% MgO-doped nitric acid molten salt liquid, MgO is uniformly and stably suspended in the nitrate, without phase separation with the nitric acid molten salt.

Example 5

A method for preparing a high thermal conductivity MgO-doped nitric acid molten salt heat transfer and heat storage material by an in-situ generation method, the specific implementation steps are as follows:

Dried potassium nitrate and sodium nitrate are mixed by the lowest eutectic point ratio of its binary phase diagram to obtain the raw material mixture I of nitric acid molten salt; ₂ ·6H ₂ O was added to the mixture I to obtain the MgCl ₂ ·6H ₂ O doped nitric acid molten salt raw material mixture II. After the mixture II was mixed evenly, the temperature was raised to 500°C at a heating rate of 10°C/min until the molten salt melted, and reacted at a constant temperature for 24 hours to form a uniformly suspended MgO-doped nitric acid molten salt fluid without phase separation, and cooled naturally to room temperature. Mechanical pulverization to obtain a high thermal conductivity MgO doped nitric acid molten salt heat transfer heat storage material.

The measuring method is the same as in Example 1, and the results are shown in Figures 2 to 4 and Tables 1 to 2. Compared with the melting point of the binary nitric acid molten salt, the melting point of the 10.0% MgO-doped nitric acid molten salt prepared in this example is slightly lower, the specific heat is greatly improved, and the thermal diffusion data is also greatly improved. The thermal conductivity of the high-temperature liquid Still relatively large. The result of this embodiment shows that doping 10.0% MgO by in-situ generation method can also improve the thermal conductivity of molten nitric acid salt high-temperature liquid, which is beneficial to enhance heat transfer.

Table 1 Different molten salt heat transfer and storage materials and their corresponding melting points, specific heat, and thermal diffusivity

Table 2 Thermal conductivity of different molten salt heat transfer and storage materials and their high-temperature liquids

The purpose of the present invention can also be achieved by using the common nitric acid molten salt in the prior art as a raw material to obtain a nitric acid molten salt material with high thermal conductivity, low melting point, large specific heat capacity, and better heat transfer and heat storage performance of high-temperature liquid.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (4)

1. a kind of in-situ synthesized of high heat conduction MgO doping nitric acid Molten Salt Heat Transfer heat accumulating, it is characterised in that including following step Suddenly：

(1) dried potassium nitrate and sodium nitrate are mixed in the lowest total of the melting point ratio of its binary phase diagraml, obtains nitric acid fused salt Raw mixture I；

(2) according to mass ratio equivalent to MgO:Nitric acid fused salt is (2.5~10.0):(97.5~90.0) ratio, by MgCl₂· 6H₂O or Mg (NO₃)₂·6H₂O is added in the mixture I of step (1) preparation, obtains MgCl₂·6H₂O or Mg (NO₃)₂·6H₂O Adulterate nitric acid fused salt raw mixture II；

(3) after mixing, to 420 DEG C~500 DEG C, constant temperature 10~24 is small for temperature programming for the mixtures II for obtaining step (2) When ensure MgO in-situ preparations and crystallization, form MgO doping nitric acid fused salt homogeneous (uniform) fluids；

(4) the homogeneous (uniform) fluid cooled to room temperature that obtains step (3) simultaneously crushes, and obtains high heat conduction MgO doping nitric acid fused salts Conduct heat heat accumulating.

2. a kind of in-situ synthesized of high heat conduction MgO doping nitric acid Molten Salt Heat Transfer heat accumulating according to claim 1, its It is characterized in that：Temperature programming described in step (3) is to be heated to isothermal reaction temperature with the heating rate of 10 DEG C/min.

A kind of 3. high heat conduction MgO doping nitric acid Molten Salt Heat Transfer heat accumulatings that in-situ synthesized as described in claim 1 obtains.

4. high heat conduction MgO according to claim 3 adulterates nitric acid Molten Salt Heat Transfer heat accumulating in industrial high temperature waste heat recovery With the application in tower type solar energy thermal power generation field.