High-capacity high-temperature water heat storage system

Abstract

The invention discloses a high-capacity high-temperature water heat storage system which comprises a cold water tank (1), a water inlet pressure reducing valve (2), a drainage pump (3), a heat release heat exchanger (4), a heat storage heat exchanger (5), a hot water spherical tank group (6) and a nitrogen generation system (7). The first path, the cold water tank, the drainage pump and the heat storage heat exchanger are sequentially connected through pipelines, and then the heat storage heat exchanger is connected to each spherical tank in the hot water spherical tank group through a pipeline; in the second path, the cold water tank, the water inlet pressure reducing valve and the heat release heat exchanger are sequentially connected through pipelines, and then the heat release heat exchanger is connected to each spherical tank in the hot water spherical tank group through a pipeline; and in the third path, the nitrogen making system is connected to each spherical tank of the hot water spherical tank group through a pipeline. According to the system, air side spaces in the cold water tank and the hot water tank are independent, the design pressure of the cold water tank is reduced, the construction cost is greatly reduced, and meanwhile the occupied area and the regulation and control complexity of the system are reduced.

Description

Technical Field

[0001] The invention relates to a large-capacity high-temperature water heat storage system, belonging to the technical field of hot water energy storage. Background Art

[0002] At present, in the field of energy storage, hot water energy storage is a low-cost, high-storage density and high-safety energy storage technology, and is widely used in compressed air energy storage, industrial waste heat utilization and power system peak regulation.

[0003] Figure 4 It is a system diagram of a high-temperature water heat storage system under the prior art, including a heat-releasing heat exchanger 4, a heat-storing heat exchanger 5, a hot water spherical tank group 6, a nitrogen-making system 7 and a cold water spherical tank group 8. In the heat storage process, cold water is transferred from the cold water spherical tank group 8 to the hot water spherical tank group 6 after heat exchange through the heat-storing heat exchanger 5. In the heat-releasing process, hot water is transferred from the hot water spherical tank group 6 to the cold water spherical tank group 8 after heat exchange through the heat-releasing heat exchanger 4. Nitrogen is filled in the spherical tank as a protective gas. The tops of the hot water spherical tank group 6 and the cold water spherical tank group 8 are connected through a nitrogen balance pipe, and a nitrogen-making system 7 is provided to supplement the nitrogen consumption. Due to the existence of a gas-side connecting pipe, the gas-side spaces of the cold tank and the hot tank are connected, so the cold tank also needs to have the same pressure-bearing capacity as the hot tank, resulting in the current system having problems such as a large number of spherical tanks, a large floor area, and a large one-time investment. At the same time, the gas in the heat storage and release processes is transferred between the two tanks through the balance pipe. Changes in gas temperature can easily cause frequent pressure fluctuations and nitrogen loss, affecting the stability and economy of the overall system operation.

[0004] Taking the thermal energy storage system used in compressed air energy storage power stations as an example, in order to improve the efficiency of the system, high-temperature hot water heat storage is often used to absorb and release heat in compressed air energy storage systems. The specific method is: during the energy storage process, cold water at about 50-70°C is used to absorb the compression heat released during the air compression process, and the cold water is heated to hot water above 160°C and stored in the hot tank; during the energy release process, the hot water releases heat to maintain the temperature required for air expansion and becomes cold water for storage. At present, in order to improve the energy storage density of hot water heat storage, the hot water storage temperature is generally higher than 160°C. In order to ensure that the hot water is still liquid at high temperature, the system pressure needs to be maintained higher than the saturation pressure of water. Therefore, the system always operates within a higher pressure range during operation, resulting in greater nitrogen consumption. At the same time, the design pressure of the cold tank and the hot tank are consistent in design. Summary of the invention

[0005] In view of the problems of the current water heat storage system, such as the large number of spherical tanks, large floor space, and large operating pressure fluctuations, the problem to be solved by the present invention is to provide a large-capacity, high-temperature water heat storage system, reduce the system investment cost, reduce the system floor space and system control complexity, reduce the system pressure fluctuations and nitrogen consumption, and reduce the operation and maintenance costs.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: A large-capacity high-temperature water heat storage system is characterized in that it includes a cold water tank 1, a water inlet pressure reducing valve 2, a drainage pump 3, a heat releasing heat exchanger 4, a heat storage heat exchanger 5, a hot water spherical tank group 6 and a nitrogen making system 7; in the first route, the cold water tank 1, the drainage pump 3, and the heat storage heat exchanger 5 are connected in sequence through pipelines, and then the heat storage heat exchanger 5 is connected to each spherical tank in the hot water spherical tank group 6 through a pipeline; in the second route, the cold water tank 1, the water inlet pressure reducing valve 2, and the heat releasing heat exchanger 4 are connected in sequence through pipelines, and then the heat releasing heat exchanger 4 is connected to each spherical tank in the hot water spherical tank group 6 through a pipeline; in the third route, the nitrogen making system 7 is connected to each spherical tank in the hot water spherical tank group 6 through a pipeline.

[0007] The vertical cylindrical cold water tank 1 is a normal pressure water storage tank. Preferably, the storage tank is in the form of a floating roof tank or a dome-type cylindrical storage tank. When the storage tank is in the form of a dome-type cylindrical storage tank, the pressure inside the tank is a slight positive pressure of about 2-5 KPa, and the air side space inside the tank is nitrogen or other protective gases.

[0008] The hot water spherical tank group 6 is a spherical water storage tank, the gas side space in the tank is nitrogen or water vapor and other protective gases, the design pressure of the spherical tank is not less than 2MPa, which is 1.2-2 times the water saturation pressure at the design temperature.

[0009] The medium for exchanging heat with water in the heat-releasing heat exchanger 4 is a gaseous or liquid heat-conducting medium with an operating temperature within 50-250° C., preferably water, air or heat-conducting oil; the heat exchanger is preferably a shell and tube heat exchanger or a hairpin heat exchanger.

[0010] In the heat storage heat exchanger 5, the heat exchange form is electric heating or high-temperature medium heat transfer; preferably, the electric heating device is an electric heater, the heat transfer device is a shell and tube heat exchanger or a hairpin heat exchanger, and the heat exchange medium is water, air or thermal oil, etc.

[0011] The water storage capacity of the cold water tank is generally multiple times that of the hot water tank, that is, one cold water tank is matched with multiple hot water tanks to form a system energy storage system; preferably, the volume of the spherical tank is 1000m 3 Above, cold water tank capacity 6000 m 3 Above, one cold water tank is equipped with more than 2 spherical tanks.

[0012] The system preferably has a cold water temperature of 30°C-60°C and a thermal storage hot water temperature of 150°C-250°C.

[0013] The nitrogen production system 7 is connected to each hot tank through a nitrogen pipeline main line and a branch line, and the gas spaces of the hot tanks are interconnected through gas pipelines. When the cold tank is a dome-shaped cylindrical storage tank, the nitrogen production system 7 is connected to the cold tank through another pipeline.

[0014] The water in the high-pressure water heat storage system is deoxygenated brine.

[0015] There are two pipeline connections between the vertical cylindrical cold water tank 1 and the spherical tanks in the hot water spherical tank group 6; one pipeline connects the vertical cylindrical cold water tank 1, the water pressure reducing valve 2, the heat release heat exchanger 4 and the hot water spherical tank group 6 in sequence, and one pipeline connects the vertical cylindrical cold water tank 1, the drainage pump 3, the heat storage heat exchanger 5 and the hot water spherical tank group 6 in sequence.

[0016] The beneficial effects of the present invention are: 1 The present invention reduces the design pressure of the cold tank by making the gas side spaces of the cold tank and the hot tank independent of each other, greatly reduces the wall thickness of the cold tank and thus reduces the cost.

[0017] 2 Under normal pressure or slightly positive pressure conditions, the cold tank is changed into a vertical cylindrical storage tank, which can be designed with a larger storage volume, reducing the floor space and the complexity of system regulation.

[0018] 3. It avoids the pressure fluctuation caused by temperature when the gas flows from one tank to another during operation, and greatly reduces the nitrogen consumption during the system operation. It improves the system operation stability and reduces the system operation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a system diagram of a large-capacity high-temperature water heat storage system of the present invention.

[0020] Figure 2 This is a system diagram of a large-capacity high-temperature water heat storage system of the present invention, in which the cold tank is a vaulted cylindrical storage tank.

[0021] Figure 3 This is a schematic diagram of a large-capacity high-temperature water heat storage system of the present invention, in which a cold tank is matched with four hot water spherical tanks.

[0022] Figure 4 It is a system diagram of a high-temperature water heat storage system under the existing technology.

[0023] Figure numerals: cold water tank 1, water inlet pressure reducing valve 2, drainage pump 3, heat release heat exchanger 4, heat storage heat exchanger 5, hot water spherical tank group 6, nitrogen production system 7 and cold water spherical tank group 8. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0025] like Figure 1 The figure shows a schematic diagram of a large-capacity high-temperature water heat storage system of the present invention. The main components of the system are a vertical cylindrical cold water tank, a water inlet pressure reducing valve, a drainage pump, a heat release heat exchanger, a heat storage heat exchanger, a hot water spherical tank group and a nitrogen production system. The heat storage process is that cold water passes through the vertical cylindrical cold water tank and is pressurized by the drainage pump and then passes into the heat storage heat exchanger. After being heated, it becomes hot water and is passed into the hot water spherical tank group for storage; the heat release process is that the high-temperature hot water in the hot water spherical tank group passes through the heat release heat exchanger and is cooled into cold water. After being reduced in pressure by the pressure reducing valve, it is passed into the vertical cylindrical cold water tank for storage. When the system is operated for the first time, nitrogen is filled through the nitrogen production system for nitrogen protection.

[0026] As a preferred embodiment of the present invention, cold water is stored in a cold tank at 30°C-60°C, and hot water is stored in a hot tank at 150°C-250°C. In order to ensure that the hot water is stored in the tank in liquid form without vaporization or boiling, the system pressure needs to be maintained above the saturation pressure. In the original heat storage system, due to the existence of the gas-side connecting pipe, the pressures of the cold and hot water tanks are consistent. Therefore, the cold tank design is also required to have the same pressure-bearing capacity as the hot tank. The present invention eliminates the gas-side connecting pipe. Therefore, the cold tank only needs to maintain normal pressure to meet the requirements of operating at normal pressure or slightly positive pressure of 1kPa-5kPa. The design pressure is greatly reduced, the design wall thickness is correspondingly thinned, and the design volume can be as high as 10,000m 3 above.

[0027] As a preferred embodiment of the present invention, the water inlet and outlet pipes and the nitrogen inlet and outlet pipes of the hot water spherical tank group 6 are connected to the main pipe through branch pipes. Therefore, when a single spherical tank fails or is under maintenance, the spherical tank branch pipe is cut off from the pipeline system, and the spherical tank is repaired and maintained without affecting the normal operation of other spherical tanks in the system.

[0028] As a preferred embodiment of the present invention, when the system stores heat, cold water flows out of the vertical cylindrical cold water tank 1, is pressurized to the system pressure by the drainage pump 3, and then enters the heat storage heat exchanger 5 to exchange heat with the external heat source. After the cold water reaches the design temperature of the hot water, it flows into the hot water tank. The water inlet method of the hot water spherical tank can be designed to be designed so that multiple hot water tanks can be filled with water at the same time or in sequence according to design requirements. The heat exchange form can be selected by electric heating or heat exchange through a heat exchanger according to different application scenarios, so that the energy storage scenarios of the system are more abundant. Whether it is used for valley electricity consumption or recycling of abandoned electricity from new energy sources, the system can meet the corresponding energy storage needs.

[0029] As a preferred embodiment of the present invention, when the system releases heat, hot water flows out of the spherical tank and enters the heat release heat exchanger 4 to exchange heat with the medium to be heated. Then the temperature drops to the design temperature of cold water, and then the pressure is reduced to a relatively low pressure through the pressure reducing valve and enters the vertical cylindrical cold water tank 1 to complete the heat release process.

[0030] As a preferred embodiment of the present invention, the water quality requirement in the system is deoxygenated and demineralized water. If the cold water tank adopts a floating roof tank, there is no need to consider nitrogen sealing, and the cold tank does not need to replenish or discharge nitrogen during operation, and nitrogen consumption is greatly reduced.

[0031] Figure 2 A schematic diagram of a large-capacity high-temperature water heat storage system of the present invention, in which the cold tank is a dome-type cylindrical storage tank, and Figure 1 Compared with the cylindrical cold water tank, the form of the cold water tank is changed from a floating roof tank to a dome roof tank, and the connecting pipes between the cold water tank and the nitrogen production system are increased.

[0032] As a preferred embodiment of the present invention, a cold water tank in the form of a dome tank needs to be isolated from the air by nitrogen sealing. During the operation of the system, the nitrogen pressure in the cold water tank using the dome tank fluctuates up and down in a slightly positive pressure state as the liquid level changes, and it is necessary to discharge and replenish the corresponding nitrogen in a timely manner. However, due to the low pressure in the cold water tank itself, the nitrogen consumption generated during the operation is much less than that of the current conventional spherical tank system. The pressure and temperature in the hot water tank itself are relatively high, and the evaporation of water vapor is large. The pressure will fluctuate during the operation of the system. Since the design pressure of the hot tank itself is 1.2-2 times the saturated pressure of water, the hot tank itself has a pressure-bearing capacity, which can meet the system pressure fluctuations between the saturated pressure of water and the maximum pressure of the system. During normal operation, no or only a small amount of nitrogen needs to be discharged, and the nitrogen consumption is small. Based on safety considerations, the spherical tank can be provided with corresponding safety valves and exhaust valves in the spherical tank to prevent accidental overpressure, and a nitrogen production system can be configured to replenish air or supplement the normal operation nitrogen consumption in an emergency. In the original heat storage system, due to the existence of the gas-side connecting pipe, the gas is transferred between the cold and hot tanks during the heat storage and release process. During operation, the low-temperature nitrogen in the cold tank will enter the hot tank, and the high-temperature gas in the hot tank will enter the cold tank. On the one hand, the temperature will change and cause pressure fluctuations. During the operation, it is necessary to discharge or replenish nitrogen in time according to the system pressure fluctuations. The system itself is under a relatively high pressure, the nitrogen density is large, and the nitrogen exhaust consumption is large; on the other hand, it will cause a temperature difference in the spherical tank body, generating temperature difference stress. However, the gas temperature in the hot tank of the present invention fluctuates little, the pressure changes more smoothly, the nitrogen consumption during operation is very small, and the operating cost is low.

[0033] like Figure 3 As shown, it is a simplified diagram of a large-capacity high-temperature water heat storage system cold tank matched with four hot water spherical tanks of the present invention.

[0034] As a preferred embodiment of the present invention, the system schematically shows Figure 3 The figure shows a combination of one cold water heat storage system and four hot water spherical tank heat storage systems. In actual projects, one cold water heat storage system and several hot water spherical tank heat storage systems can be combined according to actual project needs.

[0035] As a preferred embodiment of the present invention, Figure 3 The system shown in Figure 4 The system diagram of the high-temperature water heat storage system under the existing technology is shown in the figure for preliminary economic comparison. If the current conventional water heat storage system is used, the system needs to include 4 cold water spherical tanks and 4 hot water spherical tanks and related auxiliary equipment. Taking the parameters of the conventional hot water spherical tank of the current 300MW compressed air energy storage power station as an example for preliminary economic analysis and comparison, the relevant parameters are as follows: The volume of a single spherical tank is 3500m 3 , design temperature 200℃, heat storage temperature 190℃, heat release temperature 50℃, design pressure 2MPa, design life 30 years; vertical cold water tank design volume 15000m 3 , design temperature 70℃, heat release temperature 50℃, design pressure 2kpa, design life 30 years. If the conventional water heat storage system is adopted, the system spherical tank cost is about 8 million yuan, the initial investment is about 64 million yuan, the power consumption of the water pump and the nitrogen production cost during operation are 7.2 million and 120 million yuan respectively, and the total cost is about 190 million yuan; if the patented solution is adopted, the vertical cylindrical storage tank costs about 3 million yuan, the initial investment is about 35 million yuan, the power consumption of the water pump and the nitrogen production cost during operation are 37.5 million and 18.5 million yuan respectively, and the total cost is about 91 million yuan. From the results of the preliminary economic analysis, the patented solution has obvious advantages over the conventional solution. Although the power consumption of the pump is increased, the initial investment and nitrogen loss of the system are less. Therefore, on the whole, the overall investment and operating cost of the patented solution are still highly economical. Nitrogen itself does not participate in empowerment. It is only filled into the system as a protective gas to isolate the air in the tank and prevent air from entering the spherical tank and causing high-temperature oxygen corrosion. In actual projects, nitrogen filling protection is still the main method considering the maturity of technology and steam source.

[0036] In summary, the present invention provides a large-capacity high-temperature water heat storage system. By allowing the gas side spaces of the cold tank and the hot tank to operate independently, on the one hand, the design wall thickness and design pressure of the cold tank are reduced, and a larger design volume can be selected for the cold tank, thereby reducing the system footprint and construction costs. On the other hand, the pressure fluctuations and nitrogen consumption caused by the flow of gas between the cold and hot tanks are greatly reduced, thereby improving the system stability and reducing the system operating costs.

[0037] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and improvements can be made without departing from the principles of the present invention. These improvements and improvements are also regarded as the protection scope of the present invention. The protection scope of the present invention shall be based on the definition of the claims.

Claims

1. A large-capacity high-temperature water heat storage system, characterized in that: It comprises a cold water tank (1), a water inlet pressure reducing valve (2), a drainage pump (3), a heat release heat exchanger (4), a heat storage heat exchanger (5), a hot water ball tank group (6) and a nitrogen production system (7); In the first route, the cold water tank (1), the drainage pump (3), and the heat storage heat exchanger (5) are connected in sequence through pipelines, and then the heat storage heat exchanger (5) is connected to each spherical tank in the hot water spherical tank group (6) through pipelines; In the second route, the cold water tank (1), the water inlet pressure reducing valve (2), and the heat release heat exchanger (4) are connected in sequence through pipelines, and then the heat release heat exchanger (4) is connected to each spherical tank in the hot water spherical tank group (6) through a pipeline; Thirdly, the nitrogen production system (7) is connected to each spherical tank of the hot water spherical tank group (6) through a pipeline.

2. A large-capacity high-temperature water heat storage system according to claim 1, characterized in that: The cold water tank (1) is a vertical cylindrical tank and a normal pressure water storage tank. The storage tank is in the form of a floating roof tank or a dome-type cylindrical tank. When the storage tank is in the form of a dome-type cylindrical tank, the pressure inside the tank is maintained in a slightly positive pressure state of 1 kPa to 5 kPa, and the air side space inside the tank is nitrogen or other protective gas.

3. A large-capacity high-temperature water heat storage system according to claim 1, characterized in that: The hot water spherical tank group (6) is a spherical water storage tank, the air side space inside the tank is nitrogen or water vapor protective gas, and the design pressure of the spherical tank is not less than 2MPa, which is 1.2-2 times the water saturation pressure at the design temperature.

4. A large-capacity high-temperature water heat storage system according to claim 1, characterized in that: The medium that exchanges heat with water in the heat-releasing heat exchanger (4) is a gaseous or liquid heat-conducting medium with an operating temperature within a range of 50-250° C.; the heat exchanger is in the form of a shell and tube heat exchanger or a hairpin heat exchanger.

5. A large-capacity high-temperature water heat storage system according to claim 1, characterized in that: In the heat storage heat exchanger (5), the heat exchange device is an electric heating device or a high-temperature medium heat transfer device; the electric heating device is an electric heater, the high-temperature medium heat transfer device is a shell and tube heat exchanger or a hairpin heat exchanger, and the heat exchange medium is water, air or heat transfer oil, etc.

6. A large-capacity high-temperature water heat storage system according to claim 1, characterized in that: The water storage capacity of the cold water tank is generally multiple times that of the hot water tank, that is, one cold water tank is combined with multiple hot water tanks to form a system energy storage system; the capacity of a single hot water ball tank is 1000m 3 Above, the capacity of a single cold water tank is 6000m 3 Above, one cold water tank is equipped with more than 2 spherical tanks.

7. A large-capacity high-temperature water heat storage system according to claim 1, characterized in that: The temperature of the cold water in the cold water tank is 30°C-60°C, and the temperature of the stored hot water in the hot water ball tank group is 150°C-250°C.

8. A large-capacity high-temperature water heat storage system according to claim 1, characterized in that: The nitrogen production system (7) is connected to each hot tank through a nitrogen pipeline main line and a branch line respectively, each branch line is provided with a valve, and the gas spaces of the hot tanks are interconnected through the gas pipeline; when the cold tank is a dome-type cylindrical storage tank, the nitrogen production system (7) is connected to the cold tank through another pipeline.

9. A large-capacity high-temperature water heat storage system according to claim 1, characterized in that: The water in the large-capacity high-temperature water heat storage system is deoxygenated brine.

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