A Multicomponent High-Performance Heat Transfer and Storage Hybrid Molten Salt with Wide Temperature Range and Its Preparation Method

Abstract

The present invention discloses a multi-component wide-temperature-range high-performance heat-transfer and heat-storage hybrid molten salt and its preparation method. The mass ratio of the components of the molten salt is as follows: potassium nitrate: 10-50 wt%; sodium nitrate: 10-50 wt%; calcium nitrate: 1-30 wt%; sodium chloride: 1-15 wt%; potassium chloride: 1-15 wt%. At the same time, a preparation method of the hybrid molten salt is disclosed. The hybrid molten salt of the present invention has the characteristics of simple and easy preparation process, wide temperature range, large specific heat capacity, good thermal stability, etc., and is an excellent heat-transfer and heat-storage medium, which can be widely applied to the field of solar thermal power generation technology.

Description

Technical Field

[0001] The present invention relates to the technical field of physical heat transfer energy storage, and particularly relates to a multi-component wide-temperature-range high-performance heat transfer and storage hybrid molten salt material and a preparation method thereof. Background Art

[0002] Since the 21st century, due to economic development and population growth, the demand for energy has been increasing day by day, the energy problem has become increasingly tense, and environmental pollution caused by excessive energy consumption has also become increasingly serious. Fossil fuels such as natural gas, coal, and oil, as traditional energy sources, will cause environmental pollution and ecological damage during their use. In addition, these energy sources are all non-renewable. Facing this severe situation, it has become a common understanding of mankind to significantly reduce the exploitation and use of fossil energy and develop new renewable energy sources. At present, the main technical problems in the field of large-scale solar power generation have been effectively solved, and the cost of solar power generation has been decreasing year by year. At the current level of technological development, the utilization of solar energy is not only possible but also feasible. Therefore, solar power generation is considered to be the optimal clean energy utilization method that can be utilized on a large scale in a short time.

[0003] In a solar thermal power generation system, the heat storage system is the most critical part of the entire system, and the energy storage material is the core factor affecting the heat storage system. The currently used energy storage materials mainly include air, water, heat transfer oil, liquid metal, and molten salt, etc. Compared with other energy storage materials, molten salt has the advantages of "four highs and three lows", namely high specific heat capacity, high heat transfer coefficient, high thermal stability, high temperature, low saturated vapor pressure, low viscosity, and low price, and has become the most widely used energy storage material in solar thermal power generation technology.

[0004] The commercially applied molten salt heat storage materials mainly include Solar salt (60% NaNO3 + 40% KNO3) and Hitec salt (7wt% NaNO3 - 53wt% KNO3 - 40wt% NaNO2); the melting point of Solar Salt molten salt is 220°C and the maximum operating temperature is 600°C. This molten salt system has good thermal stability and low cost, but due to its too high melting point, it is easy to solidify and block the pipeline during use, resulting in the risk of equipment operation. The melting point of the Hitec system is 142°C, and it has thermal stability below 454°C and can operate briefly up to 538°C, but nitrogen protection is required during use to prevent the slow oxidation of the nitrite component.

[0005] To sum up, the commercially available molten salts currently used by solar thermal power enterprises have the disadvantages of high melting point, poor thermal stability, narrow working temperature range for long-term use, and relatively high cost, and still cannot meet the requirements of advanced high-parameter solar thermal power generation, and there is an urgent need for technological breakthroughs. Summary of the Invention

[0006] Therefore, the technical problems to be solved by the present invention are to provide a multi-component high-performance heat transfer and storage hybrid molten salt material with a wide temperature range, and another technical problem to be solved by the present invention is to provide a preparation method of the multi-component high-performance heat transfer and storage hybrid molten salt material with a wide temperature range.

[0007] The technical solution of the present invention is a multi-component high-performance heat transfer and storage hybrid molten salt, which comprises the following components:

[0008] Potassium nitrate: 10 - 50 wt%

[0009] Sodium nitrate: 10 - 50 wt%

[0010] Calcium nitrate: 1 - 30 wt%

[0011] Sodium chloride: 1 - 15 wt%

[0012] Potassium chloride: 1 - 15 wt%.

[0013] According to the multi-component high-performance heat transfer and storage hybrid molten salt of the present invention, preferably, it further comprises the following components by mass percentage: nanoparticles: 0.01 - 5 wt%. The nanoparticles are preferably nano-SiO2, nano-Al2O3, nano-MgO, and nano-ZnO.

[0014] Furthermore, the multi-component high-performance heat transfer and storage hybrid molten salt comprises the following components:

[0015] Potassium nitrate: 15 - 50 wt%

[0016] Sodium nitrate: 15 - 50 wt%

[0017] Calcium nitrate: 3 - 30 wt%

[0018] Sodium chloride: 3 - 15 wt% [[ID=3C]]

[0019] Potassium chloride: 3 - 15 wt%

[0020] Nanoparticles: 0.01 - 4 wt%.

[0021] Furthermore, the multi-component high-performance heat transfer and storage hybrid molten salt comprises the following components:

[0022] Potassium nitrate: 18 - 48 wt%

[0023] Sodium nitrate: 18 - 48 wt%

[0024] Calcium nitrate: 5 - 30 wt%

[0025] Sodium chloride: 5 - 15 wt%

[0026] Potassium chloride: 5 - 15 wt%

[0027] Nanoparticles: 0.01 - 3 wt%.

[0028] The present invention also provides a method for preparing the above-mentioned multi-component wide-temperature-range high-performance heat-transfer and heat-storage hybrid molten salt, which mainly includes the following steps:

[0029] Step S1, put Ca(NO3)2·4H2O into a heating device and dry it at 100 - 120 °C for 6 - 10 hours, then grind it into fine particles, and then put it into the heating device and dry it at 160 - 200 °C for 10 - 14 hours, and transfer it to a drying oven for standby;

[0030] Step S2, grind potassium nitrate, sodium nitrate, sodium chloride, and potassium chloride into fine particles, then put them into a heating device and pre-dry them at 100 - 120 °C for 1 - 5 hours, then raise the temperature to 160 - 200 °C and dry them for 10 - 14 hours, and put them into a drying oven for standby;

[0031] Step S3, add each component into a mixing container according to the proportion, and pre-melt the multi-component salt in the heating device. First, heat the molten salt to make the internal temperature of the heating device reach 280 - 320 °C. After the molten salt melts, keep the hybrid molten salt in this state for 20 - 40 minutes, and then cool it down to room temperature;

[0032] Step S4, grind the sample obtained by pre-melting to obtain uniformly sized hybrid molten salt particles;

[0033] Step S5, heat the ground hybrid molten salt particles in the heating device. First, heat the molten salt to make the internal temperature of the heating device reach 100 - 250 °C. After the molten salt melts, keep the hybrid molten salt in this state for 30 - 70 minutes, and then cool it down to room temperature;

[0034] Step S6, grind the hybrid molten salt solid cooled to room temperature again to obtain hybrid molten salt particles, and then dry and seal this solid to obtain the wide-temperature-range high-performance heat-transfer and heat-storage hybrid molten salt.

[0035] According to the method for preparing the multi-component wide-temperature-range high-performance heat-transfer and heat-storage hybrid molten salt of the present invention, preferably, the drying oven in step S1 is a vacuum drying oven.

[0036] According to the method for preparing the multi-component wide-temperature-range high-performance heat-transfer and heat-storage hybrid molten salt of the present invention, preferably, the heating rate during heating in step S3 is 8 - 12 °C / min.

[0037] According to the method for preparing the multi-component wide-temperature-range high-performance heat-transfer and heat-storage hybrid molten salt of the present invention, preferably, the heating rate during heating in step S5 is 8 - 12 °C / min.

[0038] According to the preparation method of the multi-component wide-temperature-range high-performance heat-transfer and energy-storage hybrid molten salt of the present invention, preferably, the heating device in step S3 and step S5 is a muffle furnace.

[0039] Preferably, the fine particles in step S1 are 50-200 mesh; the fine particles in step S2 are 50-200 mesh; the fine particles in step S6 are 50-200 mesh. More preferably, the mesh number of the above fine particles is 50-150 mesh.

[0040] In the present invention, after mixing multiple molten salts to form a eutectic mixed molten salt, the melting point of the mixed molten salt can be significantly reduced; adding chloride salts to the nitrate molten salt system can greatly improve its thermal stability without increasing the melting point; adding nanoparticles to the molten salt, due to the interfacial thermal resistance between the molten salt molecules and the nanoparticles, it requires more heat to raise the temperature of the nanosalt per unit mass, thereby greatly increasing the specific heat capacity of the molten salt. Therefore, the molten salt of the present invention has a low melting point, good thermal stability, and high specific heat capacity.

[0041] Compared with the prior art, the present invention deeply studies the functions of each component, proposes a new formula, and simultaneously obtains beneficial effects:

[0042] (1) The mixed molten salt of the present invention has a low melting point, and its thermal decomposition temperature is also increased, expanding the working temperature range; the working temperature range is 120°C to 650°C.

[0043] (2) The mixed molten salt has high thermal stability, and less components volatilize during high-temperature operation; Thermal stability: The decomposition temperature can reach above 650°C

[0044] (3) The mixed molten salt has a large specific heat capacity and can be used as a large-scale heat-transfer and energy-storage medium;

[0045] (4) The method for preparing the molten salt is simple and easy to operate;

[0046] (5) The molten salt materials used are inexpensive and have low costs. Specific embodiments

[0047] The present invention will be further described in detail in combination with embodiments, but the embodiments of the present invention are not limited thereto.

[0048] Example 1

[0049] A multi-component nitrate molten salt material, the components and their mass percentages thereof are as follows: NaNO3, 15%; KNO3, 38%; Ca(NO3)2, 27%; NaCl, 10%; KCl, 9%; carbon nanoparticles, 1%. The preparation method is as follows:

[0050] Step 1: Put Ca(NO3)2·4H2O into a heating device and dry it at 100°C for 8 hours, then grind it into fine particles with a mesh size of 50, and then put it back into the heating device and dry it at 180°C for 12 hours, and place it in a vacuum drying oven for standby;

[0051] Step 2: Grind potassium nitrate, sodium nitrate, sodium chloride, and potassium chloride into fine particles with a mesh size of 50, then put them into a heating device and pre-dry at 100°C for 2 hours, then raise the temperature to 180°C and dry for 12 hours, and place it in a drying oven for standby;

[0052] Step 3: Weigh 1.5 g of NaNO3, 3.8 g of KNO3, 2.7 g of Ca(NO3)2, 1 g of NaCl, 0.9 g of KCl, and 0.1 g of carbon nanoparticles.

[0053] Step 4: Add each component to a crucible and pre-melt it in a muffle furnace. Heat from room temperature to 300°C at a rate of 10°C / min. After the molten salt melts, keep the mixed molten salt in this state for 30 minutes, and then cool it down to room temperature;

[0054] Step 5: Grind the sample obtained from pre-melting to obtain uniformly sized mixed molten salt particles;

[0055] Step 6: Heat the ground mixed molten salt particles in a muffle furnace. Heat from room temperature to 150°C at a rate of 10°C / min. After the molten salt melts, keep the mixed molten salt in this state for 60 minutes, and then cool it down to room temperature;

[0056] Step 7: Grind the mixed molten salt solid cooled to room temperature again to obtain mixed molten salt particles with a mesh size of 100, and then dry and seal this solid to obtain a wide-temperature-range high-performance heat transfer and energy storage mixed molten salt.

[0057] In this case, the melting point of the molten salt is 120°C, and the thermal decomposition temperature has also been increased to 650°C. The working temperature range of the molten salt is 120°C to 650°C.

[0058] Example 2

[0059] A multi-component nitrate molten salt material, which includes the following components and mass percentages of the components: NaNO3, 24%; KNO3, 46%; Ca(NO3)2, 15%; NaCl, 8%; KCl, 6%; nano-SiO2, 1%. The preparation method is as follows:

[0060] Step 1: Put Ca(NO3)2·4H2O into a heating device and dry it at 120°C for 8 hours, then grind it into fine particles with a mesh size of 100, and then put it back into the heating device and dry it at 200°C for 10 hours, and place it in a vacuum drying oven for standby;

[0061] Step 2: Grind potassium nitrate, sodium nitrate, sodium chloride, and potassium chloride into fine particles of 100 mesh, then place them in a heating device and pre-dry at 120 °C for 3 hours, then raise the temperature to 200 °C and dry for 10 hours, and place them in a drying oven for standby;

[0062] Step 3: Weigh 2.4 g of NaNO3, 4.6 g of KNO3, 1.5 g of Ca(NO3)2, 0.8 g of NaCl, 0.6 g of KCl, and 0.1 g of nano-SiO2.

[0063] Step 4: Add each component to a crucible and pre-melt it in a muffle furnace. Heat from room temperature to 310 °C at a rate of 8 °C / min. After the molten salt melts, keep the mixed molten salt in this state for 25 minutes, and then cool it down to room temperature;

[0064] Step 5: Grind the sample obtained by pre-melting to obtain mixed molten salt particles with uniform particle size;

[0065] Step 6: Heat the ground mixed molten salt particles in a muffle furnace. Heat from room temperature to 200 °C at a rate of 12 °C / min. After the molten salt melts, keep the mixed molten salt in this state for 45 minutes, and then cool it down to room temperature;

[0066] Step 7: Grind the mixed molten salt solid cooled to room temperature again to obtain mixed molten salt particles of 100 mesh, and then dry and seal this solid to obtain a wide-temperature-range high-performance heat-transfer and heat-storage molten salt.

[0067] The melting point of the molten salt in this case is 125 °C, and the thermal decomposition temperature reaches 670 °C. The working temperature range of the molten salt is 120 °C to 650 °C.

[0068] Example 3

[0069] A multi-component nitrate molten salt material, the components and their mass percentages included are as follows: NaNO3, 40%; KNO3, 20%; Ca(NO3)2, 18%; NaCl, 10%; KCl, 10%; nano-SiO2, 2%. The preparation method is as follows:

[0070] Step 1: Place Ca(NO3)2·4H2O in a heating device and dry at 110 °C for 10 hours, then grind it into fine particles of 100 mesh, and then place it in a heating device and dry at 180 °C for 12 hours, and place it in a vacuum drying oven for standby;

[0071] Step 2: Grind potassium nitrate, sodium nitrate, sodium chloride, and potassium chloride into fine particles of 150 mesh, then place them in a heating device and pre-dry at 110 °C for 5 hours, then raise the temperature to 180 °C and dry for 12 hours, and place them in a drying oven for standby;

[0072] Step 3: Weigh 4 g of NaNO3, 2 g of KNO3, 1.8 g of Ca(NO3)2, 1 g of NaCl, 1 g of KCl, and 0.2 g of nano-SiO2.

[0073] Step 4: Add each component to a crucible and pre-melt it in a muffle furnace. Heat it from room temperature to 320 °C at a rate of 8 °C / min. After the molten salt melts, keep the mixed molten salt in this state for 40 minutes, and then cool it down to room temperature.

[0074] Step 5: Grind the sample obtained from pre-melting to obtain mixed molten salt particles with uniform particle size.

[0075] Step 6: Heat the mixed molten salt particles obtained from grinding in a muffle furnace. Heat it from room temperature to 250 °C at a rate of 9 °C / min. After the molten salt melts, keep the mixed molten salt in this state for 35 minutes, and then cool it down to room temperature.

[0076] Step 7: Grind the mixed molten salt solid cooled to room temperature again to obtain mixed molten salt particles with a mesh size of 150, and then dry and seal this solid to obtain a high-performance heat storage and heat transfer mixed molten salt with a wide temperature range.

[0077] In this case, the melting point of the molten salt is 120 °C, and the thermal decomposition temperature reaches 666 °C. The working temperature range of the molten salt is 120 °C to 650 °C.

[0078] The mixed molten salt of the present invention has a low melting point, and the thermal decomposition temperature is also increased, expanding the working temperature range; the working temperature range is 120 °C to 650 °C. The mixed molten salt of the present invention has the characteristics of simple and easy preparation process, wide temperature range, large specific heat capacity, good thermal stability, etc., and is an excellent heat storage and heat transfer medium, which can be widely used in the field of solar thermal power generation technology.

Claims

1. A multi-component wide-temperature-range high-performance heat transfer and storage hybrid molten salt, characterized in that: It includes the following components: Potassium nitrate: 10 - 50 wt% Sodium nitrate: 10 - 50 wt% Calcium nitrate: 1 - 30 wt% Sodium chloride: 1 - 15 wt% Potassium chloride: 1 - 15 wt% Nanoparticles: 0.01 - 5 wt%; The working temperature range of the mixed molten salt is 120°C to 650°C; the decomposition temperature reaches above 650°C.

2. The multi-component wide-temperature-range high-performance heat transfer and storage hybrid molten salt according to claim 1, wherein: The multi-component wide-temperature-range high-performance heat-transfer and energy-storage mixed molten salt includes the following components: Potassium nitrate: 15 - 50 wt% Sodium nitrate: 15 - 50 wt% Calcium nitrate: 3 - 30 wt% Sodium chloride: 3 - 15 wt% Potassium chloride: 3 - 15 wt% Nanoparticles: 0.01 - 4 wt%.

3. The multi-component wide-temperature-range high-performance heat transfer and storage hybrid molten salt according to claim 1, wherein: The multi-component wide-temperature-range high-performance heat-transfer and energy-storage mixed molten salt includes the following components: Potassium nitrate: 18 - 48 wt% Sodium nitrate: 18 - 48 wt% Calcium nitrate: 5 - 30 wt% Sodium chloride: 5 - 15 wt% Potassium chloride: 5 - 15 wt% Nanoparticles: 0.01 - 3 wt%.

4. The preparation method of the multi-component wide-temperature-range high-performance heat transfer and storage hybrid molten salt according to claim 1, characterized in that: It mainly includes the following steps: Step S1: Put Ca(NO3)2·4H2O into a heating device and dry it at 100 - 120°C for 6 - 10 hours, then grind it into fine particles, and then put it into the heating device and dry it at 160 - 200°C for 10 - 14 hours, and transfer it to a drying oven for standby; Step S2: Grind potassium nitrate, sodium nitrate, sodium chloride, and potassium chloride into fine particles, then put them into a heating device and pre-dry them at 100 - 120°C for 1 - 5 hours, then raise the temperature to 160 - 200°C and dry them for 10 - 14 hours, and put them into a drying oven for standby; Step S3: Add each component into a mixing container in proportion, pre-melt the multi-component salt in a heating device. First, heat the molten salt to make the internal temperature of the heating device reach 280 - 320°C. After the molten salt melts, keep the mixed molten salt in this state for 20 - 40 minutes, and then cool it down to room temperature; Step S4: Grind the sample obtained from pre-melting to obtain mixed molten salt particles with uniform particle size; Step S5: Heat the mixed molten salt particles obtained by grinding in a heating device. First, heat the molten salt to make the internal temperature of the heating device reach 100 - 250°C. After the molten salt melts, keep the mixed molten salt in this state for 30 - 70 minutes, and then cool it down to room temperature; Step S6: Grind the mixed molten salt solid cooled to room temperature again to obtain mixed molten salt particles, and then dry and seal this solid to obtain the wide-temperature-range high-performance heat-transfer and energy-storage mixed molten salt.

5. The preparation method of the multi-component wide-temperature-range high-performance heat transfer and storage hybrid molten salt according to claim 4, characterized in that: The drying oven in Step S1 is a vacuum drying oven.

6. The preparation method of the multi-component wide-temperature-range high-performance heat-transfer and energy-storage hybrid molten salt according to claim 4, characterized in that: The heating rate during heating in Step S3 is 8 - 12°C / min.

7. The preparation method of the multi-component wide-temperature-range high-performance heat transfer and storage hybrid molten salt according to claim 4, characterized in that: The heating rate during heating in Step S5 is 8 - 12°C / min.

8. The preparation method of the multi-component wide-temperature-range high-performance heat transfer and storage hybrid molten salt according to claim 4, characterized in that: The heating devices in Step S3 and Step S5 are muffle furnaces.

9. The preparation method of the multi-component wide-temperature-range high-performance heat-transfer and heat-storage hybrid molten salt according to claim 4, wherein: The fine particles in Step S1 are 50 - 200 mesh; the fine particles in Step S2 are 50 - 200 mesh; the fine particles in Step S6 are 50 - 200 mesh.