A molten salt energy storage device

Abstract

The application provides a molten salt energy storage device, and relates to the technical field of thermal power generation, which comprises a cold tank, an outlet of the cold tank being connected with a tube pass inlet of a first heat exchanger; the first heat exchanger, a shell pass inlet of the first heat exchanger being connected with a tail gas outlet of a coal-fired boiler, a shell pass outlet of the first heat exchanger being connected with a tail gas purification device; a hot tank, an inlet of the hot tank being connected with an outlet of the cold tank, an outlet of the hot tank being connected with a tube pass inlet of a second heat exchanger, a tube pass outlet of the second heat exchanger being connected with an inlet of the cold tank; the second heat exchanger, a shell pass outlet of the second heat exchanger being connected with an inlet of an air preheater, an outlet of the air preheater being connected with an air inlet of the coal-fired boiler; a molten salt pump for connecting the outlet of the cold tank with the inlet of the hot tank; a temperature control assembly for maintaining the operating temperature of the cold tank being greater than or equal to 240 DEG C. The molten salt energy storage device can improve the boiler efficiency and reduce the power consumption rate under low load.

Description

Technical Field

[0001] This utility model relates to the field of thermal power generation technology, and in particular to a molten salt energy storage device. Background Technology

[0002] In thermal power plants, coal-fired units include boilers and steam turbines. The boiler's air inlet is connected to an air preheater for preheating the air. 30MW-class coal-fired units, as the main force for peak shaving in regional power grids, need to frequently operate at 20% to 50% of rated load (low load), which has the following drawbacks:

[0003] 1. Slow response speed: The boiler's heat storage release speed is slow (<2MW / min), resulting in a slow response speed to load change rate;

[0004] 2. Economic deterioration: Under 50% rated load conditions, boiler efficiency drops to 82% (rated operating conditions are 92%), and plant power consumption rate rises to 8.5%. Utility Model Content

[0005] In view of the above, this utility model provides a molten salt energy storage device, which aims to solve at least one of the defects pointed out in the background art.

[0006] To achieve the above objectives, this utility model provides the following technical solution:

[0007] This utility model provides a molten salt energy storage device, comprising:

[0008] A cold tank, the outlet of which is connected to the tube-side inlet of the first heat exchanger;

[0009] The first heat exchanger has its shell-side inlet connected to the exhaust gas outlet of the coal-fired boiler, and its shell-side outlet connected to the exhaust gas purification equipment.

[0010] A hot tank, the inlet of which is connected to the outlet of the cold tank, the outlet of which is connected to the tube-side inlet of a second heat exchanger, and the tube-side outlet of the second heat exchanger is connected to the inlet of the cold tank.

[0011] The second heat exchanger has its shell-side outlet connected to the inlet of the air preheater, and the outlet of the air preheater is connected to the air inlet of the coal-fired boiler. The air preheater is used to preheat the air entering the coal-fired boiler.

[0012] A molten salt pump is used to connect the outlet of the cold tank and the inlet of the hot tank;

[0013] Temperature control components are used to maintain the operating temperature of the cold tank at ≥240℃.

[0014] In some embodiments of this utility model, the volume of the cold tank is 80m³.

[0015] In some embodiments of this utility model, the cold tank is covered with an insulation layer.

[0016] In some embodiments of this utility model, the volume of the hot tank is 60m³.

[0017] In some embodiments of this utility model, the shell-side heat transfer coefficient of the second heat exchanger is ≥80W / m²K, and the tube-side design pressure is 12 MPa.

[0018] In some embodiments of this utility model, the hot tank is covered with an insulation layer.

[0019] In some embodiments of this utility model, the temperature control component includes:

[0020] A heater is installed inside the cold tank;

[0021] A temperature sensor is used to measure the temperature of the molten salt inside the cold tank;

[0022] The controller has its output terminal of the temperature sensor communicatively connected to its input terminal, and its output terminal communicatively connected to the control terminal of the heater.

[0023] In some embodiments of this invention, the temperature sensor is associated with the molten salt pump.

[0024] The embodiments of this utility model have at least the following advantages or beneficial effects:

[0025] Molten salt energy storage devices can achieve rapid energy storage and release. By configuring molten salt energy storage devices to operate in conjunction with coal-fired boilers, the rapid storage / release of thermal energy by molten salt energy storage devices can overcome the limitations of boiler heat storage rate. This can significantly improve the bidirectional peak-shaving capability and regulation speed of coal-fired units during load reduction and load increase phases, thereby improving boiler efficiency and reducing plant power consumption under low load conditions.

[0026] Other features and advantages of this invention will be set forth in the following description. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of a molten salt energy storage device.

[0029] Icons: 1-Cold tank, 2-Hot tank, 3-First heat exchanger, 4-Second heat exchanger, 5-Molten salt pump, 6-Heater, 7-Temperature sensor, 8-Controller, 9-Agitator, 10-Coal-fired boiler. Detailed Implementation

[0030] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the present invention.

[0031] In the description of the embodiments of this utility model, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the embodiments of this utility model, "multiple" means two or more, unless otherwise explicitly specified.

[0032] In this embodiment of the invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this embodiment of the invention according to the specific circumstances.

[0033] The embodiments of this utility model will be described in detail below.

[0034] Example

[0035] See Figure 1 This embodiment provides a molten salt energy storage device (energy storage density ≥120kWh / m³, heat release efficiency ≥90%), including: a cold tank 1, a hot tank 2, a first heat exchanger 3, a second heat exchanger 4, a molten salt pump 5, and a temperature control component.

[0036] Design parameters of cold tank 1: volume 80m³, operating temperature ≥220℃; outlet of cold tank 1 is connected to tube inlet of first heat exchanger 3; cold tank 1 is covered with an insulation layer (not shown in the figure).

[0037] The shell-side inlet of the first heat exchanger 3 is connected to the exhaust gas outlet of the coal-fired boiler 10, and the shell-side outlet of the first heat exchanger 3 is connected to the exhaust gas purification equipment (not shown in the figure).

[0038] Design parameters of hot tank 2: volume 60m³, operating temperature ≥560℃; the inlet of hot tank 2 is connected to the outlet of cold tank 1, the outlet of hot tank 2 is connected to the tube inlet of the second heat exchanger 4, and the tube outlet of the second heat exchanger 4 is connected to the inlet of cold tank 1; the tank body of hot tank 2 is covered with an insulation layer (not shown in the figure).

[0039] The shell-side outlet of the second heat exchanger 4 is connected to the inlet of the air preheater (not shown in the figure), and the outlet of the air preheater is connected to the air inlet of the coal-fired boiler 10. The air preheater is used to preheat the air entering the coal-fired boiler 10. The shell-side heat transfer coefficient of the second heat exchanger 4 is ≥80W / m²K, and the tube-side design pressure is 12 MPa.

[0040] The molten salt described above uses a binary nitrate formulation (by weight): 60% NaNO3 + 40% KNO3 (eutectic salt, melting point approximately 220 °C). The total heat storage capacity of the molten salt energy storage device is approximately 200 MWh (there can be multiple hot tanks 2 and cold tanks 1).

[0041] Molten salt pump 5 is used to connect the outlet of cold tank 1 and the inlet of hot tank 2. Parameters of molten salt pump 5: power 75kW (frequency converter control, speed 1450-2900rpm), rated head 320 m, efficiency 78%.

[0042] The temperature control assembly includes a heater 6, a temperature sensor 7, and a controller 8. The heater 6 is installed inside the cold tank 1. The temperature sensor 7 is installed on the cold tank 1 to measure the temperature of the molten salt inside the cold tank 1. The controller 8 is located in the field, and the output of the temperature sensor 7 is communicatively connected to the input of the controller 8. The output of the controller 8 is communicatively connected to the control terminal of the heater 6 to maintain the operating temperature of the cold tank 1 ≥ 240℃ and prevent the molten salt in the cold tank 1 from solidifying. The temperature control assembly may also include a stirrer 9, which is used to stir the molten salt in the cold tank 1 to ensure that the molten salt in the cold tank 1 is heated evenly when the heater 6 is working.

[0043] Cold tank 1 typically stores molten salt at 240°C. The molten salt in cold tank 1 flows through the cold side (tube side) of the first heat exchanger 3, while the tail flue gas from the coal-fired boiler 10 flows through the hot side (shell side) of the first heat exchanger 3. The molten salt in cold tank 1 and the tail flue gas exchange heat in the first heat exchanger 3. Hot tank 2 typically stores molten salt at 560°C. The molten salt in hot tank 2 flows through the hot side (tube side) of the second heat exchanger 4. Before entering the air preheater, the air flows through the cold side (shell side) of the second heat exchanger 4, where the molten salt in hot tank 2 and the air exchange heat in the second heat exchanger 4.

[0044] During the load reduction and peak shaving phase of the coal-fired unit: the 350-400℃ tail flue gas from the coal-fired boiler 10 is introduced into the first heat exchanger 3, and molten salt is pumped through the first heat exchanger 3 at a flow rate of 120t / h by the molten salt pump 5 to absorb the waste heat of the flue gas (energy storage rate 10MW / h); during the load increase and peak shaving phase of the coal-fired unit: 560℃ molten salt is transported to the upstream of the air preheater, and the air supply temperature of the air preheater is increased from 235℃ to 320℃ through the second heat exchanger 4 to achieve instantaneous release of 15MW-level heat energy; after the molten salt is cooled to 300℃ through heat exchange, it enters the cold tank 1; when the temperature inside the cold tank 1 is less than 240℃, the speed of the molten salt pump 5 can be increased (increasing the output power) while the heater 6 is started to maintain the operating temperature of the cold tank 1 ≥240℃ and prevent solidification.

[0045] In summary, this embodiment has at least the following beneficial effects:

[0046] I. Molten salt energy storage devices can achieve rapid energy storage and release. By configuring molten salt energy storage devices to operate in coordination with coal-fired boiler 10, the rapid storage / release of thermal energy by molten salt energy storage devices can overcome the limitation of boiler heat storage rate and significantly improve the bidirectional peak-shaving capability and regulation speed of coal-fired units during load reduction and load increase phases, thereby improving boiler efficiency and reducing plant power consumption under low load conditions.

[0047] Second, by setting the heater 6 and the controller 8, the heater 6 can be activated when the temperature inside the cold tank 1 is less than 240℃, so as to maintain the operating temperature of the cold tank 1 at ≥240℃, and prevent solidification and blockage.

[0048] Third, by associating the controller 8 with the molten salt pump 5, the speed of the molten salt pump 5 can be increased (output power increased) when the temperature inside the cold tank 1 is less than 240°C, thereby accelerating the flow of molten salt between the cold tank 1 and the hot tank 2 and enhancing the fluidity of the molten salt. This also helps to increase the temperature of the cold tank 1 and maintain the operating temperature of the cold tank 1 at ≥240°C.

[0049] Finally, it should be noted that the above are merely preferred embodiments of this application and are not intended to limit this application. For those skilled in the art, this application can have various modifications and variations. Without conflict, the embodiments and features described in the embodiments of this application can be arbitrarily combined with each other. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A molten salt energy storage device, characterized in that, include: A cold tank, the outlet of which is connected to the tube-side inlet of the first heat exchanger; The first heat exchanger has its shell-side inlet connected to the exhaust gas outlet of the coal-fired boiler, and its shell-side outlet connected to the exhaust gas purification equipment. A hot tank, the inlet of which is connected to the outlet of the cold tank, the outlet of which is connected to the tube-side inlet of a second heat exchanger, and the tube-side outlet of the second heat exchanger is connected to the inlet of the cold tank. The second heat exchanger has its shell-side outlet connected to the inlet of the air preheater, and the outlet of the air preheater is connected to the air inlet of the coal-fired boiler. The air preheater is used to preheat the air entering the coal-fired boiler. A molten salt pump is used to connect the outlet of the cold tank and the inlet of the hot tank; Temperature control components are used to maintain the operating temperature of the cold tank at ≥240℃.

2. The molten salt energy storage device according to claim 1, characterized in that, The cold tank has a volume of 80 m³.

3. The molten salt energy storage device according to claim 1, characterized in that, The cold tank is covered with an insulation layer.

4. The molten salt energy storage device according to claim 1, characterized in that, The hot tank has a volume of 60 m³.

5. The molten salt energy storage device according to claim 1, characterized in that, The shell-side heat transfer coefficient of the second heat exchanger is ≥80W / m²K, and the tube-side design pressure is 12 MPa.

6. The molten salt energy storage device according to claim 1, characterized in that, The hot tank is covered with an insulation layer.

7. The molten salt energy storage device according to any one of claims 1 to 6, characterized in that, The temperature control component includes: A heater is installed inside the cold tank; A temperature sensor is used to measure the temperature of the molten salt inside the cold tank; The controller has its output terminal of the temperature sensor communicatively connected to its input terminal, and its output terminal communicatively connected to the control terminal of the heater.

8. The molten salt energy storage device according to claim 7, characterized in that, The temperature sensor is associated with the molten salt pump.

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