CN-119823724-B - Quaternary mixed molten salt heat transfer and storage medium

Abstract

A quaternary mixed molten salt heat transfer and storage medium belongs to the technical field of physical heat transfer and energy storage in high and new technology. The high decomposition temperature mixed molten salt heat transfer and heat storage medium comprises the following components of 30-70wt% of potassium nitrate, 20-60wt% of sodium nitrate, 5-45wt% of sodium nitrite and 0.5-20wt% of sodium carbonate, wherein the decomposition temperature of the mixed molten salt is higher than 700 ℃, the melting point is lower than 150 ℃, and the mixed molten salt has a wider use temperature range.

Inventors

• WU YUTING
• MENG LINGRAN
• ZHANG CANCAN
• LU YUANWEI
• NA HEYA

Assignees

• 北京工业大学

Dates

Publication Date

20260512

Application Date

20241231

Claims (3)

1. 1. A quaternary mixed molten salt heat transfer and heat storage medium is characterized by comprising 43-48wt% of potassium nitrate, 38-39wt% of sodium nitrate, 12-18wt% of sodium nitrite and 1wt% of sodium carbonate.
2. 2. A preparation method of a quaternary mixed molten salt heat transfer and heat storage medium is characterized by comprising the steps of weighing the four components, fully mixing and grinding the components, then placing the components in a drying oven for constant-temperature drying, setting the heating temperature to be 150 ℃, heating the components for 96 hours to overflow moisture contained in the mixture, placing the dried molten salt in a muffle furnace for heating to 500 ℃, heating the dried molten salt for 12 hours to enable the mixture to be completely melted and uniformly mixed, namely a static melting method, taking out the molten salt after the mixed molten salt is cooled, and crushing the mixture by using an ultra-micro crusher until the fineness of the sample reaches 20-200 meshes.
3. 3. The application of the quaternary mixed molten salt heat transfer and storage medium in claim 1, which is used for supercritical carbon dioxide power generation and supercritical water vapor power generation.

Description

Quaternary mixed molten salt heat transfer and storage medium Technical field: The invention relates to a formula of mixed molten salt for medium-high temperature heat transfer and storage, and belongs to the technical field of physical heat transfer and energy storage in high and new technologies. The background technology is as follows: the pumped storage power station is the most main power grid energy storage technology at present, but because special topography conditions are needed, the pumped storage alone cannot meet the requirement of high-proportion renewable energy, and urgent needs develop novel long-time high-capacity low-cost energy storage technology beyond the pumped storage. The molten salt heat storage utilizes the temperature rise of liquid salt to absorb heat and the temperature reduction to release heat so as to realize heat storage and release. The fused salt used for heat storage is generally eutectic mixed salt formed by mixing more than two inorganic salts according to a certain proportion, and has the advantages of wide liquid temperature range, large temperature difference, large heat storage density and long service life. The double-tank liquid sensible heat storage scheme for fused salt heat storage generally has the advantages of constant inlet and outlet parameters of a heat storage and release heat exchanger/electric heater, close temperature of a heat taking fluid outlet to the temperature of a hot salt tank, simple control and the like, is a long-time energy storage technology with low cost, large capacity and long service life, and has wide application scenes in the fields of photo-thermal power generation, heat storage peak shaving of a thermal power plant, direct/heat pump heat storage power generation, heat storage, heat supply and steam supply, compressed air energy storage, compression heat storage and the like. At present, more than thirty integrated large-capacity heat-storage photo-thermal power stations are put into commercial operation worldwide (the capacity of a general assembly machine exceeds 300 kilowatts), and the longest fused salt heat-storage photo-thermal power station is successfully operated for 18 years. Improving the heat storage density of the fused salt is the development direction of fused salt heat storage, the fused salt heat storage belongs to sensible heat storage, therefore, the heat storage density of the fused salt can be obviously improved by improving the heat storage temperature difference of the fused salt. Increasing the temperature difference between the molten salt and the heat storage requires a wide liquid temperature range for the molten salt, that is, the melting point of the molten salt should be as low as possible and the decomposition temperature should be as high as possible. The improvement of the molten salt heat storage/release temperature is an effective technical approach for improving the electric heating molten salt heat storage peak regulation cogeneration, heat pump electricity storage, deep peak regulation of a thermal power plant and the energy conversion efficiency and economy of photo-thermal power generation, and particularly the development of supercritical carbon dioxide power generation and ultra-supercritical Rankine cycle power generation technologies, and the development of high-temperature molten salt heat storage materials, equipment and systems with the decomposition temperature reaching 700 ℃ is urgently required. Heat Storage materials and devices above 700 ℃ are also included in the heat Storage research project under the challenges of heat Storage and the important support of future in the united states under the heading "Energy Storage GRAND CHALLENGE Roadmap" issued in month 12 2020. The lowest use temperature of the molten salt is reduced, so that the heat of a heat source can be absorbed to the maximum extent, and the temperature lower limit requirement of the power cycle working medium of the molten salt heat storage coupling energy system is met. The low melting point can also reduce the freezing and blocking risks and the freezing and blocking preventing cost of the molten salt heat storage system, and improve the reliability of the molten salt heat storage system. At present, binary nitrate (solar salt) is adopted for fused salt heat storage, and the defects of high melting point up to 220 ℃, easy freezing and blockage of pipelines, high use temperature within 570 ℃, small heat storage temperature difference and low heat storage density exist. A few molten salts store heat using ternary nitrate (Hitec) salts with a melting point of 142 ℃, but suffer from low decomposition temperatures (above 450 ℃ the nitrite starts to oxidize) and low heat storage densities. In order to reduce the risk of freezing and blocking of the fused salt heat storage system, students at home and abroad in recent years are developing low-melting-point fused salt, particularly low-melting-point ternary salt and low-me