Fused salt heat storage and full-load denitration combined method and system

Abstract

The invention belongs to the technical field of environmental protection and energy utilization, and discloses a fused salt heat storage combined full-load denitration method and system.The water outlet of a deaerator is connected with the water inlet of a high-pressure heater, the water outlet of the high-pressure heater is connected with the cold inlet of a feed water heater, and the cold outlet of the feed water heater is connected with the inlet of a boiler; the fused salt heat storage device adopts an electric heating mode, a circulating water heat exchange device is arranged in the fused salt heat storage device, a heat inlet of the feed water heater is connected with an outlet of the circulating water heat exchange device through an inlet circulating water pipeline, and a heat outlet of the feed water heater is connected with an inlet of the circulating water heat exchange device through an outlet circulating water pipeline. A circulating pump is arranged on the inlet circulating water pipeline or the outlet circulating water pipeline, and gate valves are arranged on the inlet circulating water pipeline and the outlet circulating water pipeline. The molten salt heat storage system is used for storing heat, and meanwhile full-load denitration can be achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental protection and energy utilization, and specifically relates to a method and system for molten salt heat storage combined with full-load denitrification. Background Art

[0002] Molten salt is an excellent thermal energy storage medium that can remain liquid at high temperatures and has high specific heat capacity and thermal stability. The molten salt thermal storage system can store excess heat (such as excess heat generated by power plants during off-peak periods) and release it when needed for power generation or other purposes. This not only helps balance electricity supply and demand, but also improves the utilization rate of renewable energy.

[0003] Existing denitrification technology cannot achieve ideal nitrogen oxide removal effects under all operating conditions, especially at low load, when the flue gas temperature is low and the SCR catalyst activity is reduced, and nitrogen oxides cannot be effectively removed.

[0004] In view of the problems existing in the existing denitrification technology, how to combine the existing denitrification technology with molten salt heat storage to enable the denitrification system to continue to work efficiently without affecting the power generation efficiency is an issue that needs to be urgently resolved in this field. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a method and system for molten salt heat storage combined with full-load denitrification. The present invention can achieve full-load denitrification while utilizing the molten salt heat storage system to store heat.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A molten salt heat storage combined with full-load denitrification system comprises a deaerator, a high-pressure heater, a feed water heater, and a molten salt heat storage device, wherein the water outlet of the deaerator is connected to the water inlet of the high-pressure heater, the water outlet of the high-pressure heater is connected to the cold inlet of the feed water heater, the cold outlet of the feed water heater is connected to the water inlet of the boiler, the molten salt heat storage device is heated by electric heating, a circulating water heat exchange device is arranged in the molten salt heat storage device, the hot inlet of the feed water heater is connected to the outlet of the circulating water heat exchange device through an inlet circulating water pipeline, the hot outlet of the feed water heater is connected to the inlet of the circulating water heat exchange device through an outlet circulating water pipeline, a circulating pump is arranged on the inlet circulating water pipeline or the outlet circulating water pipeline, and gate valves are arranged on both the inlet circulating water pipeline and the outlet circulating water pipeline.

[0007] Preferably, the high-pressure heater includes a No. 3 high-pressure heater, a No. 2 high-pressure heater and a No. 1 high-pressure heater connected in series in sequence, the water outlet of the deaerator is connected to the water inlet of the No. 3 high-pressure heater, the water outlet of the No. 3 high-pressure heater is connected to the water inlet of the No. 2 high-pressure heater, the water outlet of the No. 2 high-pressure heater is connected to the inlet water of the No. 1 high-pressure heater, and the water outlet of the No. 1 high-pressure heater is connected to the cold inlet of the feedwater heater.

[0008] Preferably, the drain port of the No. 1 high-pressure heater is connected to the drain inlet of the No. 2 high-pressure heater, the drain port of the No. 2 high-pressure heater is connected to the drain inlet of the No. 3 high-pressure heater, and the drain port of the No. 3 high-pressure heater is connected to the drain inlet of the deaerator.

[0009] Preferably, the molten salt heat storage device is provided with an electric heating device for heating the molten salt.

[0010] Preferably, an inlet temperature measuring point and a first electric regulating valve are provided on the inlet circulating water pipeline upstream of the gate valve. The first electric regulating valve and the inlet temperature measuring point are both connected to the boiler DCS system. The boiler DCS system can adjust the opening of the first electric regulating valve according to the temperature detected by the inlet temperature measuring point, thereby adjusting the water flow in the inlet circulating water pipeline.

[0011] Preferably, an outlet temperature measuring point and a second electric regulating valve are provided on the outlet circulating water pipeline downstream of the gate valve. The second electric regulating valve and the outlet temperature measuring point are both connected to the boiler DCS system. The boiler DCS system can adjust the opening of the second electric regulating valve according to the temperature detected by the outlet temperature measuring point, thereby adjusting the water flow in the outlet circulating water pipeline.

[0012] Preferably, the gate valves provided on the inlet circulating water pipeline and the outlet circulating water pipeline are both electric gate valves.

[0013] Preferably, a manual gate valve is also provided on the outlet circulating water pipeline, a circulating pump is provided on the outlet circulating water pipeline, and the electric gate valve and the manual gate valve on the outlet circulating water pipeline are both located on the inlet side of the circulating pump.

[0014] The present invention further provides a method for molten salt heat storage combined with full-load denitration, which is carried out by the molten salt heat storage combined with full-load denitration system of the present invention as described above, and the method comprises: When the boiler is running at high load, close the circulating pump and the gate valves on the inlet and outlet circulating water pipelines; When the boiler is running at low load, the molten salt in the molten salt heat storage device is heated, and the heated molten salt in the molten salt heat storage device heats the circulating water through the circulating water heat exchange device, the gate valves on the inlet circulating water pipeline and the outlet circulating water pipeline are opened, and the circulating pump is started to allow the circulating water heated by the circulating water heat exchange device to enter the feed water heater, and the feed water heater uses the circulating water heated by the circulating water heat exchange device to heat the water on the cold side of the feed water heater, and the water heated by the feed water heater enters the boiler, thereby increasing the economizer inlet water temperature and reducing the temperature difference between the economizer water side and the flue gas side, thereby achieving the effect of reducing the heat exchange amount of the economizer. The reduction in heat exchange will directly lead to an increase in the flue gas temperature at the economizer outlet to meet the window temperature requirement of the denitrification catalyst and achieve full-load denitrification.

[0015] Preferably: when heating the molten salt in the molten salt heat storage device, the molten salt in the molten salt heat storage device is heated to 400° C. to 500° C.; When the molten salt heated in the molten salt heat storage device heats the circulating water through the circulating water heat exchange device, the temperature of the circulating water heated by the circulating water heat exchange device is above 300°C.

[0016] The present invention has the following beneficial effects: Compared with the existing full-load denitrification method, the method and system of molten salt heat storage combined with full-load denitrification of the present invention has the advantage of heating circulating water through molten salt heat storage, and then heating boiler feed water through circulating water. After the feed water temperature increases, the water temperature at the economizer inlet increases, reducing the temperature difference between the economizer water side and the flue gas side, thereby achieving the effect of reducing the heat exchange of the economizer. The reduction in heat exchange will directly lead to an increase in the flue gas temperature at the economizer outlet, and the boiler exhaust temperature will increase accordingly, thereby increasing the flue gas temperature at the SCR inlet. At the same time, the circulating water flow rate can be adjusted by an electric regulating valve to adjust the feed water temperature, thereby further adjusting the SCR inlet flue gas temperature, so that the low SCR inlet flue gas temperature increases, meets the window temperature requirement of the denitrification catalyst, and achieves full-load denitrification. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 This is a schematic diagram of the method and system for molten salt heat storage combined with full-load denitrification according to the present invention.

[0019] In the figure: 1-deaerator, 2-No. 3 high-pressure heater, 3-No. 2 high-pressure heater, 4-No. 1 high-pressure heater, 5-outlet electric gate valve, 6-outlet temperature measuring point, 7-second electric regulating valve, 8-manual gate valve, 9-circulating pump, 10-molten salt heat storage device, 11-electric heating device, 12-inlet temperature measuring point, 13-inlet electric gate valve, 14-feed water heater, 15-circulating water heat exchange device, 16-inlet circulating water pipeline, 17-outlet circulating water pipeline, 18-first electric regulating valve. DETAILED DESCRIPTION

[0020] According to the technical solution of the present invention, without changing the essential spirit of the present invention, a person skilled in the art can propose a variety of interchangeable structures and implementations. Therefore, the following specific implementation methods and drawings are only examples of the technical solution of the present invention and should not be regarded as the entirety of the present invention or the limitation of its technical solution.

[0021] Full-load denitrification technology is committed to increasing the inlet flue gas temperature of the denitrification system at low loads to ensure that nitrogen oxide emissions always meet environmental standards. Combining molten salt heat storage with full-load denitrification can provide a more flexible and effective pollution control solution without affecting power generation efficiency. During off-peak hours, the molten salt heat storage system is used to store heat; when it is necessary to increase power output or increase the flue gas temperature to achieve full-load denitrification, the stored energy is released. This can optimize energy management and ensure the continued efficient operation of the denitrification system.

[0022] Specifically, refer to Figure 1 The system of molten salt heat storage combined with full-load denitrification in this embodiment includes a deaerator 1, a high-pressure heater, a feed water heater 14, and a molten salt heat storage device 10. The water outlet of the deaerator 1 is connected to the water inlet of the high-pressure heater, the water outlet of the high-pressure heater is connected to the cold inlet of the feed water heater 14, the cold outlet of the feed water heater 14 is connected to the water inlet of the boiler, the molten salt heat storage device 10 is heated by electric heating, and a circulating water heat exchange device 15 is provided in the molten salt heat storage device 10. The hot inlet of the feed water heater 14 is connected to the outlet of the circulating water heat exchange device 15 through an inlet circulating water pipeline 16, and the hot outlet of the feed water heater 14 is connected to the inlet of the circulating water heat exchange device 15 through an outlet circulating water pipeline 17. A circulating pump 9 is provided on the inlet circulating water pipeline 16 or the outlet circulating water pipeline 17, and gate valves are provided on the inlet circulating water pipeline 16 and the outlet circulating water pipeline 17.

[0023] The working process of the system of the above embodiment of the present invention is as follows: When the boiler is running at high load, the circulating pump 9 and the gate valves on the inlet circulating water pipeline 16 and the outlet circulating water pipeline 17 are closed; When the boiler is running at a low load, the molten salt in the molten salt heat storage device 10 is heated, and the heated molten salt in the molten salt heat storage device 10 heats the circulating water through the circulating water heat exchange device 15. The gate valves on the inlet circulating water pipeline 16 and the outlet circulating water pipeline 17 are opened, and the circulating pump 9 is started to allow the circulating water heated by the circulating water heat exchange device 15 to enter the feed water heater 14. The feed water heater 14 uses the circulating water heated by the circulating water heat exchange device 15 to heat the cold side water of the feed water heater 14. After the feed water heated by the feed water heater 14 enters the boiler, the economizer inlet water temperature increases, reducing the temperature difference between the economizer water side and the flue gas side, thereby achieving the effect of reducing the heat exchange amount of the economizer. The reduction in heat exchange will directly lead to an increase in the economizer outlet flue gas temperature, and the boiler exhaust temperature will increase accordingly, thereby increasing the SCR inlet flue gas temperature to meet the window temperature requirement of the denitration catalyst and achieve full-load denitration.

[0024] In the scheme of the above embodiment, when the molten salt in the molten salt heat storage device 10 is heated, the molten salt in the molten salt heat storage device 10 is heated to 400°C~500°C; when the heated molten salt in the molten salt heat storage device 10 heats the circulating water through the circulating water heat exchange device 15, the temperature of the circulating water heated by the circulating water heat exchange device 15 is above 300°C.

[0025] As a preferred embodiment of the present invention, in this embodiment, the high-pressure heater includes a No. 3 high-pressure heater 2, a No. 2 high-pressure heater 3 and a No. 1 high-pressure heater 4 which are connected in series in sequence, the water outlet of the deaerator 1 is connected to the water inlet of the No. 3 high-pressure heater 2, the water outlet of the No. 3 high-pressure heater 2 is connected to the water inlet of the No. 2 high-pressure heater 3, the water outlet of the No. 2 high-pressure heater 3 is connected to the inlet water of the No. 1 high-pressure heater 4, the water outlet of the No. 1 high-pressure heater 4 is connected to the cold inlet of the feed water heater 14, the drain port of the No. 1 high-pressure heater 4 is connected to the drain inlet of the No. 2 high-pressure heater 3, the drain port of the No. 2 high-pressure heater 3 is connected to the drain inlet of the No. 3 high-pressure heater 2, and the drain port of the No. 3 high-pressure heater 2 is connected to the drain inlet of the deaerator 1. Through the above structure, in this embodiment, the drain of the high-pressure heater can be reused in sequence to the previous level, which can save water and heat energy at the same time, thereby reducing energy consumption.

[0026] As a preferred embodiment of the present invention, in this embodiment, an inlet temperature measuring point 12 and a first electric regulating valve 18 are provided on the inlet circulating water pipeline 16 upstream of the gate valve, and the first electric regulating valve 18 and the inlet temperature measuring point 12 are both connected to the boiler DCS system, and the boiler DCS system can adjust the opening of the first electric regulating valve 18 according to the temperature detected by the inlet temperature measuring point 12, thereby adjusting the water flow in the inlet circulating water pipeline 16. Through the above design, this embodiment can realize automatic control of the water flow in the inlet circulating water pipeline 16 through the boiler DCS system, thereby realizing control of the hot side water temperature in the feed water heater 14, thereby realizing control of the SCR inlet flue gas temperature.

[0027] As a preferred embodiment of the present invention, in this embodiment, an outlet temperature measuring point 6 and a second electric regulating valve 7 are provided on the outlet circulating water pipeline 17 downstream of the gate valve, and the second electric regulating valve 7 and the outlet temperature measuring point 6 are both connected to the boiler DCS system. The boiler DCS system can adjust the opening of the second electric regulating valve 7 according to the temperature detected by the outlet temperature measuring point 6, thereby adjusting the water flow in the outlet circulating water pipeline 17. Through the above design, this embodiment can realize automatic control of the water flow in the outlet circulating water pipeline 17 through the boiler DCS system, thereby realizing control of the hot side water temperature in the feed water heater 14, thereby realizing control of the SCR inlet flue gas temperature.

[0028] Example 1 Reference Figure 1The molten salt heat storage combined with full-load denitrification system of this embodiment includes a deaerator 1, a No. 3 high-pressure heater 2, a No. 2 high-pressure heater 3, a No. 1 high-pressure heater 4, an outlet electric gate valve 5, an outlet temperature measuring point 6, a second electric regulating valve 7, a manual gate valve 8, a circulating pump 9, a molten salt heat storage device 10, an electric heating device 11, an inlet temperature measuring point 12, an inlet electric gate valve 13, a feedwater heater 14, a circulating water heat exchange device 15, an inlet circulating water pipeline 16, an outlet circulating water pipeline 17 and a first electric regulating valve 18. The outlet of the deaerator 1 is connected to the inlet of the No. 3 high-pressure heater 2, the outlet of the No. 3 high-pressure heater 2 is connected to the inlet of the No. 2 high-pressure heater 3, the outlet of the No. 2 high-pressure heater 3 is connected to the inlet water of the No. 1 high-pressure heater 4, and the outlet of the No. 1 high-pressure heater 4 is connected to the cold inlet of the feedwater heater 14. The drain port of the No. 1 high-pressure heater 4 is connected to the drain inlet of the No. 2 high-pressure heater 3, the drain port of the No. 2 high-pressure heater 3 is connected to the drain inlet of the No. 3 high-pressure heater 2, and the drain port of the No. 3 high-pressure heater 2 is connected to the drain inlet of the deaerator 1. The electric heating device 11 is arranged in the molten salt heat storage device 10, and is used to heat the molten salt in the molten salt heat storage device 10. The inlet electric gate valve 13, the inlet temperature measuring point 12 and the first electric regulating valve 18 are arranged on the inlet circulating water pipeline 16 in sequence. The first electric regulating valve 18 and the inlet temperature measuring point 12 are both connected to the boiler DCS system, and the boiler DCS system can adjust the opening of the first electric regulating valve 18 according to the temperature detected by the inlet temperature measuring point 12, thereby adjusting the water flow in the inlet circulating water pipeline 16. The outlet electric gate valve 5, the outlet temperature measuring point 6, the second electric regulating valve 7, the manual gate valve 8 and the circulating pump 9 are arranged on the outlet circulating water pipeline 17 in sequence. The second electric regulating valve 7 and the outlet temperature measuring point 6 are both connected to the boiler DCS system, and the boiler DCS system can adjust the opening of the second electric regulating valve 7 according to the temperature detected by the outlet temperature measuring point 6, thereby adjusting the water flow in the outlet circulating water pipeline 17. The cold outlet of the feed water heater 14 is connected to the boiler water inlet, the hot inlet of the feed water heater 14 is connected to the outlet of the circulating water heat exchange device 15 through the inlet circulating water pipeline 16, and the hot outlet of the feed water heater 14 is connected to the inlet of the circulating water heat exchange device 15 through the outlet circulating water pipeline 17.

[0029] In this embodiment, the boiler feed water enters the deaerator 1 from the low-pressure heater, enters the No. 3 high-pressure heater 2 from the deaerator 1, enters the No. 2 high-pressure heater 3 from the No. 3 high-pressure heater 2, enters the No. 1 high-pressure heater 4 from the No. 2 high-pressure heater, and enters the cold side of the feedwater heater 14 from the No. 1 high-pressure heater 4. In the No. 3 high-pressure heater 2, the No. 2 high-pressure heater 3 and the No. 1 high-pressure heater 4, as the steam cools and condenses, drainage will be formed, and the drainage of the No. 1 high-pressure heater 2 returns to the No. 2 high-pressure heater 3, the drainage of the No. 2 high-pressure heater 3 returns to the No. 3 high-pressure heater 4, and the drainage of the No. 3 high-pressure heater 4 returns to the deaerator 1. The molten salt heat storage device 10 adopts an electric heating method. When there is excess power in the power grid, at night or during the peak period of wind power generation, the excess power is used to activate the electric heating device 11. After the electric heating device 11 is powered on, heat is generated, and the heat is transferred to the molten salt in the molten salt heat storage device 10, so that the temperature of the molten salt increases. The heat of the feedwater heater 14 comes from the circulating water, and the high-temperature molten salt heats the circulating water through the circulating water heat exchange device 15. The electric heating device 11 can increase the molten salt temperature in the molten salt heat storage device 10 to 400°C~500°C, and the circulating water temperature can be increased to above 300°C. The feed water heater 14 can increase the feed water temperature by 20°C~40°C under 75%THA~40%THA conditions (THA is the heat rate acceptance condition), thereby increasing the SCR inlet flue gas temperature by 8°C~16°C. At low load, the temperature increase effect is better.

[0030] Among them, the inlet temperature measuring point 12 can detect the temperature of the circulating water after being heated by the circulating water heat exchange device 15 in the molten salt heat storage device 10. The inlet temperature measuring point 12 and the first electric regulating valve 18 are connected to the boiler DCS system, and it is determined whether to open the inlet electric gate valve 13 to put the water heater system into operation according to the actual operating conditions.

[0031] The outlet temperature measuring point 6 can detect the circulating water temperature after passing through the feed water heater 14. The outlet temperature measuring point 6 and the second electric regulating valve 7 are connected to the boiler DCS system. The opening of the electric regulating valve 7 is adjusted according to the actual operating conditions to adjust the feed water temperature. When the electric valve 7 fails, the manual gate valve 8 can be used to cut off the system.

[0032] Specifically, the molten salt heat storage combined with full-load denitrification system of this embodiment operates as follows: When the boiler is running at high load, the flue gas temperature at the inlet of the SCR module is relatively high, which can usually meet the window temperature requirements of the denitration catalyst, and the feedwater heater does not need to be put into operation. At this time, the circulation pump 9, the inlet electric gate valve 13 and the outlet electric gate valve 5 can be closed to cut out the system without affecting the original steam-water balance system.

[0033] When the boiler is running at low load, the flue gas temperature at the inlet of the SCR module is too low to meet the window temperature requirement of the denitration catalyst, and the flue gas temperature must be raised by operating the feed water heater 14. At this time, the high-temperature molten salt of 400℃~500℃ heats the circulating water through the circulating water heat exchange device 15, and the circulating water temperature can be raised to above 300℃. The inlet temperature measuring point 12 on the circulating water pipeline can detect the circulating water temperature after heating by the circulating water heat exchange device 15. Open the inlet electric gate valve 13 and the outlet electric gate valve 5 on the circulating water pipeline, start the circulating pump 9, and then adjust the circulating water flow rate through the electric regulating valve (7, 18) to adjust the heat exchange of the feed water heater 14, thereby controlling the increase of the feed water temperature, and adjusting the inlet flue gas temperature of the SCR module to meet the window temperature requirement of the denitration catalyst, and finally achieve full-load denitration.

[0034] From the above, it can be seen that the present invention can adjust the feed water temperature by controlling the electric regulating valve to adjust the circulating water flow rate, thereby increasing the flue gas temperature at the SCR module inlet to meet the window temperature requirement of the denitration catalyst and achieve full-load denitration.

[0035] It can be seen from the above scheme that the method and system of molten salt heat storage combined with full-load denitrification of the present invention uses the electric heating device to generate heat after being powered on, and the heat is transferred to the molten salt in the molten salt heat storage device to increase the temperature of the molten salt, heat the circulating water through the molten salt heat storage, and then heat the boiler feed water through the circulating water. After the feed water temperature increases, the boiler exhaust temperature increases accordingly, thereby increasing the SCR inlet flue gas temperature. At the same time, the circulating water flow rate can be adjusted by an electric regulating valve to adjust the feed water temperature, so that the low SCR inlet flue gas temperature increases, meets the window temperature requirements of the denitrification catalyst, and achieves full-load denitrification.

[0036] The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be determined that the specific embodiments of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the present invention. The scope of patent protection shall be determined by the submitted claims.

[0037] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A molten salt heat storage combined with full-load denitrification system, characterized in that: The invention comprises a deaerator (1), a high-pressure heater, a feedwater heater (14), and a molten salt heat storage device (10). The water outlet of the deaerator (1) is connected to the water inlet of the high-pressure heater, the water outlet of the high-pressure heater is connected to the cold inlet of the feedwater heater (14), the cold outlet of the feedwater heater (14) is connected to the water inlet of the boiler, the molten salt heat storage device (10) is heated by electric heating, a circulating water heat exchange device (15) is provided in the molten salt heat storage device (10), the hot inlet of the feedwater heater (14) is connected to the outlet of the circulating water heat exchange device (15) through an inlet circulating water pipeline (16), the hot outlet of the feedwater heater (14) is connected to the inlet of the circulating water heat exchange device (15) through an outlet circulating water pipeline (17), a circulating pump (9) is provided on the inlet circulating water pipeline (16) or the outlet circulating water pipeline (17), and gate valves are provided on the inlet circulating water pipeline (16) and the outlet circulating water pipeline (17).

2. A molten salt heat storage combined with full-load denitrification system according to claim 1, characterized in that: The high-pressure heater comprises a No. 3 high-pressure heater (2), a No. 2 high-pressure heater (3) and a No. 1 high-pressure heater (4) which are connected in series in sequence; the water outlet of the deaerator (1) is connected to the water inlet of the No. 3 high-pressure heater (2); the water outlet of the No. 3 high-pressure heater (2) is connected to the water inlet of the No. 2 high-pressure heater (3); the water outlet of the No. 2 high-pressure heater (3) is connected to the water inlet of the No. 1 high-pressure heater (4); and the water outlet of the No. 1 high-pressure heater (4) is connected to the cold inlet of the feedwater heater (14).

3. The system of molten salt heat storage combined with full-load denitrification according to claim 2 is characterized in that: The drain port of the No. 1 high-pressure heater (4) is connected to the drain inlet of the No. 2 high-pressure heater (3), the drain port of the No. 2 high-pressure heater (3) is connected to the drain inlet of the No. 3 high-pressure heater (2), and the drain port of the No. 3 high-pressure heater (2) is connected to the drain inlet of the deaerator (1).

4. The system of molten salt heat storage combined with full-load denitrification according to claim 1 is characterized in that: The molten salt heat storage device (10) is provided with an electric heating device (11) for heating the molten salt.

5. The molten salt heat storage combined with full-load denitrification system according to claim 1 is characterized in that: An inlet temperature measuring point (12) and a first electric regulating valve (18) are provided on the inlet circulating water pipeline (16) upstream of the gate valve. The first electric regulating valve (18) and the inlet temperature measuring point (12) are both connected to a boiler DCS system. The boiler DCS system can adjust the opening of the first electric regulating valve (18) according to the temperature detected by the inlet temperature measuring point (12), thereby adjusting the water flow in the inlet circulating water pipeline (16).

6. The molten salt heat storage combined with full-load denitrification system according to claim 1 is characterized in that: An outlet temperature measuring point (6) and a second electric regulating valve (7) are provided on the outlet circulating water pipeline (17) downstream of the gate valve. The second electric regulating valve (7) and the outlet temperature measuring point (6) are both connected to the boiler DCS system. The boiler DCS system can adjust the opening of the second electric regulating valve (7) according to the temperature detected by the outlet temperature measuring point (6), thereby adjusting the water flow in the outlet circulating water pipeline (17).

7. The system of molten salt heat storage combined with full-load denitrification according to claim 1 is characterized in that: The gate valves provided on the inlet circulating water pipeline (16) and the outlet circulating water pipeline (17) are both electric gate valves.

8. The molten salt heat storage combined with full-load denitrification system according to claim 7 is characterized in that: A manual gate valve (8) is also provided on the outlet circulating water pipeline (17), and a circulating pump (9) is provided on the outlet circulating water pipeline (17). The electric gate valve and the manual gate valve (8) on the outlet circulating water pipeline (17) are both located on the inlet side of the circulating pump (9).

9. A method of molten salt heat storage combined with full-load denitrification, characterized in that: The method of molten salt heat storage combined with full-load denitrification is carried out by the molten salt heat storage combined with full-load denitrification system according to any one of claims 1 to 8, and the method comprises: When the boiler is running at high load, the circulating pump (9) and the gate valves on the inlet circulating water pipeline (16) and the outlet circulating water pipeline (17) are closed; When the boiler is running at a low load, the molten salt in the molten salt heat storage device (10) is heated. The heated molten salt in the molten salt heat storage device (10) heats the circulating water through the circulating water heat exchange device (15). The gate valves on the inlet circulating water pipeline (16) and the outlet circulating water pipeline (17) are opened, and the circulating pump (9) is started, so that the circulating water heated by the circulating water heat exchange device (15) enters the feed water heater (14). The feed water heater (14) uses the circulating water heated by the circulating water heat exchange device (15) to heat the water on the cold side of the feed water heater (14). The water heated by the feed water heater (14) enters the boiler, thereby increasing the inlet water temperature of the economizer and reducing the temperature difference between the water side and the flue gas side of the economizer, thereby achieving the effect of reducing the heat exchange amount of the economizer. The reduction in heat exchange amount will directly lead to an increase in the flue gas temperature at the economizer outlet, so as to meet the window temperature requirement of the denitration catalyst and achieve full-load denitration.

10. The method of molten salt heat storage combined with full-load denitrification according to claim 9, characterized in that: When heating the molten salt in the molten salt heat storage device (10), the molten salt in the molten salt heat storage device (10) is heated to 400° C. to 500° C.; When the molten salt heated in the molten salt heat storage device (10) heats circulating water through the circulating water heat exchange device (15), the temperature of the circulating water heated by the circulating water heat exchange device (15) is above 300°C.

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