Shielding gas complementary energy recovery system based on fused salt heat storage

Abstract

The invention relates to the technical field of fused salt heat storage, in particular to a protective gas complementary energy recovery system based on fused salt heat storage. The shielding gas complementary energy recovery system comprises a fused salt heat storage unit, a shielding gas supply unit and a shielding gas complementary energy recovery unit. Wherein the fused salt heat storage unit comprises a fused salt heater and a fused salt storage tank, and fused salt heated by the fused salt heater is introduced into the fused salt storage tank; the shielding gas supply unit is used for introducing shielding gas into the fused salt storage tank to isolate the fused salt from being in contact with air; the shielding gas complementary energy recovery unit is communicated with a shielding gas outlet of the molten salt storage tank and is used for receiving shielding gas discharged from the molten salt storage tank; the shielding gas complementary energy recovery unit comprises a turbine, and shielding gas entering the shielding gas complementary energy recovery unit drives the turbine to do work. According to the shielding gas complementary energy recovery system, the complementary energy in the shielding gas can be efficiently recovered, and the energy consumption required in the shielding gas conveying process is reduced to a certain extent.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of molten salt heat storage, in particular to a protection gas residual energy recovery system based on molten salt heat storage. BACKGROUND

[0002] In the field of molten salt heat storage, as a type of molten salt, ternary nitrite (such as a mixture of sodium nitrate, potassium nitrate, and sodium nitrite) is widely used in solar thermal power generation, industrial waste heat recovery, and other fields due to its low melting point (140-160 ℃), high heat storage density, and good thermal conductivity. However, this type of molten salt is prone to oxidation with oxygen in the air at high temperatures, leading to composition deterioration and equipment corrosion, so inert gas (such as nitrogen) is used as a protective gas to maintain the inert environment of the system, thereby avoiding contact between the molten salt and the air.

[0003] In the prior art, the protective gas covering the surface of the molten salt is usually directly discharged after completing the task of isolating air, resulting in the residual heat (usually 300-500 ℃) carried by the protective gas not being effectively utilized, thereby causing a certain degree of energy waste. In addition, in traditional molten salt heat storage systems, external power equipment (such as a gas pump) is usually needed to maintain the delivery and discharge of the protective gas, and the gas delivery process usually has high energy consumption, thereby increasing the overall operating cost of the system to some extent. SUMMARY

[0004] To solve the above problems, the present application provides a protection gas residual energy recovery system based on molten salt heat storage, which can efficiently recover the residual energy in the protective gas and reduce the energy consumption required in the delivery process of the protective gas to some extent.

[0005] The present application provides a protection gas residual energy recovery system based on molten salt heat storage, which comprises: a molten salt heat storage unit, comprising a molten salt heater and a molten salt storage tank, the molten salt heated by the molten salt heater being introduced into the molten salt storage tank; a protective gas supply unit, introducing protective gas into the molten salt storage tank to isolate the molten salt from air; a protective gas residual energy recovery unit, in communication with the protective gas outlet of the molten salt storage tank, receiving the protective gas discharged from the molten salt storage tank; the protective gas residual energy recovery unit comprises a turbine, and the protective gas entering the protective gas residual energy recovery unit drives the turbine to work.

[0006] Optionally, the molten salt heat storage unit further comprises: a steam generator connected to the molten salt storage tank, for heat exchange of the molten salt in the molten salt storage tank; a steam turbine, the steam generated by the heat exchange of the steam generator entering the steam turbine to work; The first power generation device is mechanically connected to the steam turbine and is driven by the steam turbine to generate power.

[0007] Optionally, the protective gas supply unit comprises: The pressure regulating valve regulates the air pressure of the protective gas released by the protective gas supply unit. The pressure sensor is arranged in connection with the molten salt storage tank. The oxygen content sensor is arranged in connection with the molten salt storage tank. The pressure regulating valve is communicatively connected to the pressure sensor and the oxygen content sensor, and adjusts the valve opening size of the pressure regulating valve according to the monitoring values of the pressure sensor and the oxygen content sensor.

[0008] Optionally, the protective gas provided in the protective gas supply unit is selected as nitrogen.

[0009] Optionally, the protective gas residual energy recovery unit further comprises: The second power generation device is mechanically connected to the turbine and is driven by the turbine to generate power. The condenser is in communication with the protective gas outlet of the turbine and is used to recover the residual heat energy of the protective gas discharged by the turbine.

[0010] Optionally, the protective gas residual energy recovery unit further comprises: The exhaust pipeline is in communication with the protective gas outlet of the condenser, and the protective gas recovered by the residual energy recovery is exhausted through the exhaust pipeline.

[0011] Optionally, the protective gas residual energy recovery unit further comprises: The vacuum pump is arranged between the condenser and the exhaust port of the exhaust pipeline.

[0012] Optionally, the molten salt heat storage unit further comprises a temperature sensor for monitoring the temperature change of the molten salt heat storage unit. The starting operation condition of the protective gas supply unit and the protective gas residual energy recovery unit is that the temperature in the molten salt heat storage unit rises to a threshold value monitored by the temperature sensor.

[0013] Optionally, the gas pressure in the turbine is higher than the gas pressure in the condenser, and the pressure difference of the protective gas in the protective gas residual energy recovery unit is used to drive the protective gas to flow into the condenser and be discharged through the exhaust pipeline.

[0014] Optionally, the steam inlet of the condenser is connected to the steam outlet of the steam turbine, and the steam is cooled by the condenser and enters the steam generator.

[0015] In the protective gas residual energy recovery system based on molten salt heat storage provided by the application, the molten salt surface is covered with protective gas by the protective gas supply unit, so that the molten salt is prevented from being oxidized and deteriorated after being heated by contacting air. At the same time, during the contact of the high-temperature molten salt with the protective gas, part of the energy is transferred to the protective gas, so that the protective gas that completes the task of isolating air from the molten salt carries residual energy such as heat energy and pressure energy. The recovery system sets the protective gas residual energy recovery unit to recover the residual energy contained in the above protective gas and convert the residual energy in the protective gas into other forms of energy that can be easily used through devices such as turbines, so as to improve the utilization efficiency of further energy. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 FIG. 1 is a structural schematic diagram of a protective gas residual energy recovery system based on molten salt heat storage provided by an embodiment of the application.

[0017] FIG. 1 is a structural schematic diagram of a protective gas residual energy recovery system based on molten salt heat storage provided by an embodiment of the application. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0019] In view of the fact that a protective gas is often used in the existing molten salt heat storage process to avoid oxidation of the molten salt, in order to recycle the residual energy carried by the protective gas at the end of use, so as to further improve the utilization efficiency of energy, the embodiment provides a protective gas residual energy recycling system 100 based on molten salt heat storage. The protective gas residual energy recycling system 100 comprises a molten salt heat storage unit, a protective gas supply unit and a protective gas residual energy recycling unit. The molten salt heat storage unit comprises a molten salt heater 1 and a molten salt storage tank, and the molten salt heated by the molten salt heater 1 is introduced into the molten salt storage tank; the protective gas supply unit introduces protective gas into the molten salt storage tank to isolate the molten salt from air; the protective gas residual energy recycling unit is in communication with the protective gas outlet of the molten salt storage tank and receives the protective gas discharged from the molten salt storage tank; the protective gas residual energy recycling unit comprises a turbine 8, and the protective gas discharged from the protective gas outlet of the high-temperature molten salt tank 3 enters the turbine 8 arranged in the protective gas residual energy recycling unit along the gas outlet pipeline 31 and drives the turbine 8 to work.

[0020] Figure 1 FIG. 1 is a structural schematic diagram of a protective gas residual energy recycling system 100 based on molten salt heat storage provided in the embodiment. Referring to FIG. 1, Figure 1 The molten salt storage tank adopts a double-tank design and specifically comprises a low-temperature molten salt tank 2 and a high-temperature molten salt tank 3. The molten salt inlet of the low-temperature molten salt tank 2 is connected with the molten salt inlet of the molten salt heater 1 by arranging an inlet pipeline 11. The molten salt inlet of the high-temperature molten salt tank 3 is connected with the molten salt outlet of the molten salt heater 1 by arranging an outlet pipeline 12, and the molten salt outlet of the high-temperature molten salt tank 3 is connected with the molten salt inlet of the low-temperature molten salt tank 2. The molten salt inlet of the low-temperature molten salt tank 2 and the molten salt outlet of the high-temperature molten salt tank 3 are connected by a material pipeline 22. In order to make the molten salt storage tank have high structural strength and thus adapt to high-temperature and high-pressure working conditions, the molten salt storage tank is designed as a spherical tank in the embodiment. In other embodiments, the shape of the molten salt storage tank can be designed in other forms according to specific use environment and heat storage indexes, which is not specifically limited herein.

[0021] In the embodiment, the energy stored by the molten salt heat storage unit is derived from solar radiation energy, and the molten salt heater 1 specifically adopts a light-heat collector which is spliced by a serpentine heat-absorbing tube screen. The inside of the heat-absorbing tube screen is filled with flowable molten salt. When the surface of the heat-absorbing tube screen receives solar radiation energy focused by a mirror field, heat conduction occurs between the inner and outer walls of the heat-absorbing tube screen, and the inner wall performs convective heat exchange with the molten salt flowing in the heat-absorbing tube screen. In other embodiments, the molten salt heater 1 can select or design other types of collectors according to the heat storage object and heat storage scene, which is not specifically limited herein.

[0022] In order to enable the molten salt heat storage medium to flow smoothly in the molten salt heat storage unit, in the embodiment, the molten salt heat storage unit further comprises a cold salt pump 23 and a hot salt pump 32. The cold salt pump 23 is connected with the low-temperature molten salt tank 2 and drives the molten salt in the low-temperature molten salt tank 2 to enter the molten salt heater 1 along the inlet pipeline 11. The hot salt pump 32 is connected with the high-temperature molten salt tank 3 and drives the molten salt in the high-temperature molten salt tank 3 to enter the low-temperature molten salt tank 2. In the embodiment, the molten salt heat storage unit further comprises a steam generator 5, a steam turbine 6 and a first power generation device 7. The steam generator 5 is arranged between the molten salt outlet of the high-temperature molten salt tank 3 and the molten salt inlet of the low-temperature molten salt tank 2 and uses cooling water to cool and exchange heat with the high-temperature molten salt discharged from the high-temperature molten salt tank 3. The steam inlet of the steam turbine 6 is connected with the steam outlet of the steam generator 5. During the heat exchange process of the steam generator 5, the steam generated after the cooling water absorbs the high-temperature molten salt enters the steam turbine 6 to do work. The first power generation device 7 is mechanically connected with the steam turbine 6 and is driven by the steam turbine 6 to generate power.

[0023] The operation process of the molten salt heat storage unit is as follows: when the molten salt heat storage unit starts to operate, the cold salt pump 23 is started to drive the low-temperature or normal-temperature molten salt in the low-temperature molten salt tank 2 to enter the molten salt heater 1 along the inlet pipeline 11 to be heated. After being heated, the high-temperature molten salt with heat continues to enter the high-temperature molten salt tank 3 along the outlet pipeline 12. Then, the high-temperature molten salt in the high-temperature molten salt tank 3 is transported to the steam generator 5 by the hot salt pump 32, so that the cooling water in the steam generator 5 exchanges heat with the high-temperature molten salt and is converted into steam. The steam generated by the heat exchange enters the steam turbine 6 to do work, and then the steam turbine 6 drives the first power generation device 7 to generate power. The steam that has completed the work in the steam turbine 6 enters the condenser 101 from the steam outlet of the steam turbine 6, is cooled by the condenser 101 and then returns to the steam generator 5 to exchange heat with the high-temperature molten salt. The molten salt that has completed the heat exchange and cooling in the steam generator 5 flows into the low-temperature molten salt tank 2 along the pipeline 22.

[0024] In the embodiment, in order to avoid the high-temperature molten salt formed after being heated by the molten salt heater 1 from being in contact with air to cause oxidation reaction, a protection gas supply unit is used to input protection gas into the low-temperature molten salt tank 2 and the high-temperature molten salt tank 3. The protection gas is inert gas and does not react with the molten salt. In the embodiment, the protection gas used is nitrogen. Since the density of nitrogen is greater than that of air, the nitrogen entering the low-temperature molten salt tank 2 and the high-temperature molten salt tank 3 will sink and cover the surface of the molten salt as a whole, so that the molten salt is isolated from air and oxidation and deterioration of the high-temperature molten salt after being in contact with air are avoided, thereby ensuring the continuous and normal operation of the molten salt heat storage unit.

[0025] Reference Figure 1The nitrogen provided by the protection gas supply unit of the embodiment is sourced from the nitrogen tank 4 contained therein, and the nitrogen is introduced into the molten salt storage tank from the nitrogen tank 4 to enable the molten salt to be isolated from air. During operation of the molten salt heat storage unit, the molten salt that has completed heat exchange in the steam generator 5 can still retain a small amount of residual heat. To avoid oxidation of the molten salt entering the low-temperature molten salt tank 2 with air and further recovery of the small amount of residual heat possessed by the molten salt at this time, in the embodiment, the nitrogen tank 4 is connected to the low-temperature molten salt tank 2 by a gas supply pipeline 42, and the low-temperature molten salt tank 2 is connected to the high-temperature molten salt tank 3 by a gas passage pipeline 21. The nitrogen provided by the nitrogen tank 4 will first enter the low-temperature molten salt tank 2 along the gas supply pipeline 42 to protect the molten salt and recover residual heat, and then enter the high-temperature molten salt tank 3 along the gas passage pipeline 21 from the protection gas outlet of the low-temperature molten salt tank 2 to be protected by nitrogen. At the same time, a pressure regulating valve 41 is provided on each of the gas supply pipeline 42 and the gas passage pipeline 21 to adjust the gas pressure of the protection gas released by the nitrogen tank 4 to the low-temperature molten salt tank 2 and the high-temperature molten salt tank 3.

[0026] In order to avoid waste of protective gas and ensure that the protective gas can be reasonably and timely introduced into the low-temperature molten salt tank 2 and the high-temperature molten salt tank 3 for air insulation, and in order to enable the protective gas residual energy recovery unit to recover the residual energy contained in the protective gas that has completed the air insulation task in time, in the present embodiment, the operating states of the protective gas supply unit and the protective gas residual energy recovery unit are related to the operating state of the molten salt heat storage unit. The specific relationship is that a temperature sensor (not shown in the figure) is arranged in the molten salt heat storage unit to monitor the temperature change of the molten salt heat storage unit. When the molten salt heat storage unit starts to operate, the molten salt heater 1 heats the molten salt, and under the action of the cold salt pump 23 and the hot salt pump 32, the molten salt circulates in the molten salt heat storage unit. When the temperature sensor detects that the molten salt in the molten salt heat storage unit starts to release heat and the temperature rises to a threshold value, the protective gas supply unit starts to operate, and through the automatic control system, the pressure regulating valve 41 is opened, so that the nitrogen in the nitrogen tank 4 rapidly enters the low-temperature molten salt tank 2 and the high-temperature molten salt tank 3 and completely covers the surface of the molten salt to insulate air. The nitrogen entering the high-temperature molten salt tank 3 is heated to become high-temperature nitrogen with high heat after being in contact with the high-temperature molten salt. Subsequently, the protective gas residual energy recovery unit starts to operate, and the high-temperature nitrogen discharged from the protective gas outlet of the high-temperature molten salt tank 3 enters the turbine 8, and the heat energy possessed by the high-temperature nitrogen is converted into mechanical energy by the turbine. In order to enable the mechanical energy converted by the turbine 8 to be better utilized, in the present embodiment, the protective gas residual energy recovery unit further comprises a second power generation device 9, which is mechanically connected with the turbine 8 and driven by the turbine 8 to generate electricity, thereby converting the mechanical energy into electrical energy for use. After the high-temperature nitrogen passes through the turbine 8, most of the residual energy contained therein has been converted into mechanical energy, but at this time there is still a small amount of heat energy in the nitrogen that has not been completely recovered, so in the present embodiment, the protective gas residual energy recovery unit is further provided with a condenser 101 and an exhaust pipeline 102. The condenser 101 is in communication with the protective gas outlet of the turbine 8 through the air pipeline 81, and is used to recover the residual heat energy of the protective gas discharged from the turbine 8. The exhaust pipeline 102 is in communication with the protective gas outlet of the condenser 101, and the protective gas that has completed the residual energy recovery is exhausted through the exhaust pipeline 102.

[0027] Reference Figure 1 The condenser 101 is also connected with the steam outlet of the steam turbine 6. The steam that has completed work in the steam turbine 6 can enter the condenser 101 from the steam outlet of the steam turbine 6, be cooled in the condenser 101, and then return to the steam generator 5 to exchange heat with the high-temperature molten salt. In order to enable the condenser 101 to complete the above-mentioned cooling water return process, the condenser 101 contained in the protective gas residual energy recovery unit provided in the present embodiment can be used in conjunction with the molten salt heat storage unit that can realize photo-thermal power generation.

[0028] In order to enable the protective gas to pass through the turbine 8 and the condenser 101 in turn and finally be smoothly discharged to the outside from the exhaust pipeline 102, in the embodiment, the low-pressure end of the protective gas residual energy recovery unit is matched with the low pressure of the condenser 101, that is, the gas pressure in the turbine 8 is higher than the gas pressure in the condenser 101, and the pressure difference of the protective gas in the protective gas residual energy recovery unit is used to drive the protective gas to pass through the condenser 101 and be discharged. In order to realize the low-pressure environment in the condenser 101 and form a pressure difference between the condenser 101 and the turbine 8, on the one hand, the condenser 101 reduces the temperature and pressure of the protective gas in the condenser 101 by recovering the residual heat energy of the protective gas; on the other hand, the protective gas residual energy recovery unit further comprises a vacuum pump 103. The vacuum pump 103 is arranged between the condenser 101 and the exhaust port of the exhaust pipeline 102, and is used to draw the protective gas which has completed the recovery of residual heat energy and cannot be condensed in the condenser 101 to the exhaust port of the exhaust pipeline 102, so that a low-pressure environment is formed in the condenser 101 compared with the turbine 8. At the same time, with the steam discharged by the steam turbine 6 into the condenser 101 being condensed into liquid water and re-entering the steam generator 5, the gas pressure in the condenser 101 is further reduced. That is, the pressure difference between the condenser 101 and the turbine 8 is further increased, which provides more powerful driving protection for the smooth flow of the protective gas in the protective gas residual energy recovery unit.

[0029] In the operation process of the protective gas residual energy recovery system 100, if the protective gas pressure in the high-temperature molten salt tank 3 and the low-temperature molten salt tank 2 is too large, it may affect the molten salt heat storage and the protective gas residual energy recovery performance of the protective gas residual energy recovery system 100, and even may cause damage to the equipment and leakage risk. Therefore, in the embodiment, the protective gas supply unit further comprises a cold tank pressure sensor 24, a hot tank pressure sensor 33 and an oxygen content sensor (not shown in the figure). The cold tank pressure sensor 24 is arranged at the top of the low-temperature molten salt tank 2 and is used to monitor the gas pressure in the low-temperature molten salt tank 2; the hot tank pressure sensor 33 is arranged at the top of the high-temperature molten salt tank 3 and is used to monitor the pressure in the high-temperature molten salt tank 3; the high-temperature molten salt tank 3 and the low-temperature molten salt tank 2 are each provided with an oxygen content sensor for monitoring the oxygen concentration in the molten salt storage tank. The pressure regulating valve 41 is in communication connection with the cold tank pressure sensor 24, the hot tank pressure sensor 33 and the oxygen content sensor, and the protective gas supply unit can adjust the opening size of the valve of the pressure regulating valve 41 according to the monitoring values of the cold tank pressure sensor 24, the hot tank pressure sensor 33 and the oxygen content sensor, so as to maintain the gas pressure in the molten salt storage tank stable and in a controllable state.

[0030] In the embodiment, the specific operation process of the protective gas excess energy recovery unit is as follows: when the molten salt heat storage unit starts to operate and the temperature in the molten salt heat storage unit rises to a threshold value monitored by the temperature sensor, the valve of the pressure regulating valve 41 in the protective gas excess energy recovery unit is opened, and the nitrogen in the nitrogen tank 4 is sequentially introduced into the low-temperature molten salt tank 2 and the high-temperature molten salt tank 3. At the same time, according to the data feedback of the monitoring results of the gas components and pressure in the low-temperature molten salt tank 2 and the high-temperature molten salt tank 3 by the cold tank pressure sensor 24, the hot tank pressure sensor 33 and the oxygen content sensor respectively, the control system in the protective gas excess energy recovery unit automatically adjusts the opening size of the valve of the pressure regulating valve 41. Then the nitrogen covering the surface of the molten salt in the molten salt storage tank absorbs part of the heat of the high-temperature molten salt while completing the air insulation task, so that the temperature of the nitrogen in the molten salt storage tank rises. Then the high-temperature nitrogen in the molten salt storage tank is introduced into the turbine 8 of the protective gas excess energy recovery unit, and the turbine 8 is used to convert the heat energy in the high-temperature nitrogen into mechanical energy. Then the second power generation device 9 connected with the turbine 8 is used to convert the above-mentioned mechanical energy into electrical energy for use by the outside world.

[0031] In the embodiment, since the nitrogen in which the conversion of heat energy into mechanical energy is completed in the turbine 8 contains certain residual heat energy, the nitrogen will continue to be transferred from the turbine 8 to the condenser 101 connected with the turbine 8 along the gas pipeline 81 to complete the full recovery of the residual heat energy. Then the nitrogen in the condenser 101 is driven by the vacuum pump 103 to the exhaust port of the exhaust pipeline 102 and finally discharged to the outside world or other equipment. Since the nitrogen in which the full recovery of heat energy is completed in the condenser 101 has a significantly lower temperature than the high-temperature nitrogen in the turbine 8, the gas pressure in the condenser 101 is significantly lower than that in the turbine 8. At the same time, the nitrogen in the condenser 101 which cannot be condensed is continuously discharged to the outside world by the vacuum pump 103, so that the gas pressure in the condenser 101 is further reduced, and the gas pressure difference between the turbine 8 and the condenser 101 is further increased. The gas pressure difference formed in the above-mentioned excess energy recovery process drives the nitrogen in the protective gas excess energy recovery unit to sequentially pass through the turbine 8 and the condenser 101, and finally smoothly discharged to the outside world from the exhaust pipeline 102. At this point, the protective gas excess energy recovery system 100 provided by the embodiment has fully recovered the excess energy contained in the protective gas which completes the air insulation task in the molten salt heat storage process, and the protective gas is driven to flow through by the gas pressure difference, which further reduces the energy consumption required when the protective gas excess energy recovery system 100 operates.

[0032] The above only describes the preferred embodiments of the present application and should not be used to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A shielding gas surplus energy recovery system based on molten salt heat storage, characterized in that: include: A molten salt heat storage unit comprises a molten salt heater and a molten salt storage tank, wherein the molten salt heated by the molten salt heater is passed into the molten salt storage tank; a shielding gas supply unit, for supplying shielding gas to the molten salt storage tank to isolate the molten salt from contact with air; a shielding gas residual energy recovery unit, connected to the shielding gas outlet of the molten salt storage tank, and receiving the shielding gas discharged from the molten salt storage tank; The shielding gas waste energy recovery unit includes a turbine, and the shielding gas entering the shielding gas waste energy recovery unit drives the turbine to perform work; The protective gas supply unit comprises: A pressure regulating valve, for regulating the pressure of the shielding gas released by the shielding gas supply unit; A pressure sensor is connected to the molten salt storage tank; an oxygen content sensor, connected to the molten salt storage tank; The pressure regulating valve is in communication with the pressure sensor and the oxygen content sensor, and adjusts the valve opening of the pressure regulating valve according to the monitoring values ​​of the pressure sensor and the oxygen content sensor.

2. The shielding gas residual energy recovery system according to claim 1, characterized in that: The molten salt heat storage unit further includes: a steam generator connected to the molten salt storage tank to perform heat exchange on the molten salt in the molten salt storage tank; A steam turbine, wherein the steam generated by heat exchange in the steam generator enters the steam turbine to perform work; The first power generation device is mechanically connected to the steam turbine, and the steam turbine drives the first power generation device to generate electricity.

3. The shielding gas residual energy recovery system according to claim 1, characterized in that: The protective gas provided by the protective gas supply unit is selected to be nitrogen.

4. The shielding gas residual energy recovery system according to claim 2, characterized in that: The shielding gas residual energy recovery unit also includes: a second power generation device, mechanically connected to the turbine, the turbine driving the second power generation device to generate electricity; The condenser is connected to the shielding gas outlet of the turbine and is used to recover the residual heat energy of the shielding gas discharged from the turbine.

5. The shielding gas residual energy recovery system according to claim 4, characterized in that: The shielding gas residual energy recovery unit also includes: The exhaust pipe is connected to the shielding gas outlet of the condenser, and the shielding gas after the residual energy recovery is exhausted through the exhaust pipe.

6. The shielding gas residual energy recovery system according to claim 5, characterized in that: The shielding gas residual energy recovery unit also includes: A vacuum pump is arranged between the condenser and the exhaust port of the exhaust pipe.

7. The shielding gas residual energy recovery system according to claim 1, characterized in that: The molten salt heat storage unit further includes a temperature sensor for monitoring temperature changes of the molten salt heat storage unit; The starting operation condition of the shielding gas supply unit and the shielding gas residual energy recovery unit is: the temperature in the molten salt heat storage unit monitored by the temperature sensor rises to a threshold value.

8. The shielding gas residual energy recovery system according to claim 5, characterized in that: The gas pressure in the turbine is higher than the gas pressure in the condenser, and the shielding gas pressure difference in the shielding gas residual energy recovery unit is used to drive the shielding gas to the condenser and be discharged through the exhaust pipe.

9. The shielding gas residual energy recovery system according to claim 4, characterized in that: The steam inlet of the condenser is connected to the steam outlet of the steam turbine, and the steam is cooled by the condenser and enters the steam generator.

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