A hot water energy storage system coupled with a steam compressor and its operation method

Abstract

This invention discloses a hot water energy storage system coupled with a steam compressor and its operation method, comprising a boiler, an intermediate-pressure cylinder, a water storage tank, a flash tank, and a steam compressor. The boiler, steam compressor, and water storage tank are sequentially connected by pipelines to form an energy storage path. A first heating path is formed by connecting the intermediate-pressure cylinder to the user end through pipelines, and a second heating path is formed by sequentially connecting the water storage tank, flash tank, steam compressor, and user end through pipelines. In this invention, when the thermal power plant needs to generate electricity at high load, saturated water in the water storage tank enters the flash tank and forms flash steam. The flash steam is pressurized by the steam compressor to form heating steam that meets the heating standard and is supplied to the user end, reducing the amount of steam extracted from the generator set and lowering the coal consumption for power generation. When the thermal power plant is deeply shaving peak loads, the reheat steam is pressurized by the steam compressor and stored in the water storage tank. The steam compressor can operate in the most economical range and avoids directly extracting high-parameter main steam.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of thermal power generation and heat supply technology, in particular to a hot water energy storage system coupled with a steam compressor and a running method thereof. BACKGROUND

[0002] Thermal power plants are required to undertake more peak-shaving tasks in the power system. At present, many peak-shaving units are taken flexible modification measures, including external electric boiler, low-pressure cylinder full-cut modification, coupling molten salt energy storage, etc.

[0003] At present, the hot water during peak-shaving is stored by using a heat storage tank, so that the purpose of peak-shaving is achieved, and energy can be stored to a certain extent. However, in the prior art, the feed water before entering the boiler is stored, and when it is needed, the boiler feed water and the stored water in the storage tank are mixed and sent into the boiler for heating. The water stored in the storage tank is saturated water before entering the boiler, and the design parameter is low. When the heat is released, the mixed water returns to the boiler, and the energy undergoes a closed cycle of “boiler-tank-boiler”. The energy does not deviate from the turbine regenerative system. This mode causes the low storage parameter to fluctuate, the utilization rate of the heat potential difference is insufficient, and the potential path of the high-temperature water directly supplied to the heat network first station to replace the steam extraction of the turbine unit is not considered, so that the two-way potential of the heat storage tank in heat-electricity decoupling and peak increase is not fully released. SUMMARY

[0004] The present application aims to solve the problems in the prior art, and provides a hot water energy storage system coupled with a steam compressor and a running method thereof.

[0005] The present application aims to solve the problems in the prior art, and provides a hot water energy storage system coupled with a steam compressor and a running method thereof.

[0006] Preferably, the exhaust port of the medium-pressure cylinder is connected with the user end through a first heat supply pipeline, and a first heat supply control valve is arranged on the first heat supply pipeline; the water outlet of the water storage tank is connected with the input port of the flash tank through a second heat supply pipeline, the gas phase outlet of the flash tank is connected with the inlet of the steam compressor through a third heat supply pipeline, and the outlet of the steam compressor is connected with the user end through a fourth heat supply pipeline; a second heat supply control valve is arranged on the second heat supply pipeline; a third heat supply control valve is arranged on the third heat supply pipeline; the boiler and the inlet of the steam compressor are connected through a first energy storage pipeline, and the outlet of the steam compressor and the water storage tank are connected through a second energy storage pipeline; and an energy storage control valve is arranged on the first energy storage pipeline.

[0007] As preferred, the liquid phase outlet of the flash tank is connected with the boiler water supply port through a backwater pipeline, and a backwater pump is arranged on the backwater pipeline.

[0008] As preferred, the first heat supply control valve, the second heat supply control valve, the third heat supply control valve and the energy storage control valve are electrically controlled valves.

[0009] As preferred, the water storage tank is provided with a water supply port and a liquid level meter, the water supply port is connected with a water supply tank through a water supply pipeline, and a water supply valve is arranged on the water supply pipeline.

[0010] A method for operating a hot water energy storage system coupled with a steam compressor, the method comprising the following steps:

[0011] When the thermal power plant is deeply peak-regulated, the energy storage control valve is opened, the reheated steam from the boiler is pressurized to a first pressure state by the steam compressor to form saturated water and enter the water storage tank for storage, thereby realizing the energy storage process.

[0012] When the operation load of the thermal power plant reaches a set threshold, the second heat supply control valve and the third heat supply control valve are opened, the water in the water storage tank enters the flash tank, low-pressure steam is generated in the flash tank, the low-pressure steam is pressurized by the steam compressor to form heat supply steam reaching the heat supply demand and supply heat to the user end, and the liquid water in the flash tank flows to the boiler through the backwater pipeline to supply water to the boiler.

[0013] As preferred, when the thermal power plant is deeply peak-regulated, the pressure of the reheated steam extracted from the boiler is lower than 2 MPa, the steam compressor pressurizes the reheated steam to 2.7 MPa to form saturated water with a temperature of 220-240 ℃.

[0014] When the operation load of the thermal power plant reaches a set threshold, the flash pressure of the flash tank is 0.6-0.8 MPa, and the flash pressure is pressurized by the steam compressor to obtain heat supply steam with a pressure greater than 1.2 MPa.

[0015] As preferred, the water temperature change rate in the water storage tank is ensured to be within an allowable range by controlling the steam flow, and the relationship is as follows:

[0016] ;

[0017] In the formula, is the maximum allowable value of the steam flow entering or flowing out of the water storage tank during the energy storage or energy release stage; V is the volume of the water storage tank, p is the density of water, and Cp is the specific heat of water. is the water temperature in the water storage tank, is the maximum allowable water temperature change rate in the water storage tank, is the steam enthalpy at the gas phase outlet of the flash tank.

[0018] The beneficial effects of this invention are as follows: When a thermal power plant needs to generate electricity at high load, the steam generated by the boiler prioritizes power generation, significantly reducing the steam extraction volume of the first heating path. At this time, the second heating path becomes the main heating path. Saturated water in the storage tank enters the flash tank and forms flash steam. After being pressurized by the steam compressor, the flash steam meets the heating standards and is supplied to the user end. Steam is released through the flash tank to supplement the heating demand. The steam supplied by the second heating path can directly replace the steam extraction from the intermediate-pressure cylinder in the first heating path, reducing the amount of steam extracted from the generator set. The saved turbine steam can continue to drive the generator set to generate electricity, effectively increasing power generation without increasing coal consumption and reducing coal consumption. When the thermal power plant is deeply shaving peak loads, the reheat steam is pressurized by the steam compressor and stored in the storage tank. The steam compressor can operate in the most economical range and avoids directly extracting high-parameter main steam, resulting in high system economy. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the hot water energy storage system coupled with a steam compressor according to the present invention.

[0020] In the diagram: 1. Water storage tank, 2. Boiler, 3. High-pressure cylinder, 4. Medium-pressure cylinder, 5. Low-pressure cylinder, 6. Steam compressor, 7. Flash tank, 8. User end, 9. First heating control valve, 10. Flow meter, 11. Level gauge, 12. Makeup water tank, 13. Second heating control valve, 14. Third heating control valve, 15. Energy storage control valve, 16. Makeup water valve, 17. First heating pipeline, 18. Second heating pipeline, 19. Third heating pipeline, 20. Fourth heating pipeline, 21. First energy storage pipeline, 22. Second energy storage pipeline, 23. Makeup water pipeline, 24. Return water pipeline. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0022] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0023] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0024] like Figure 1 As shown, a hot water energy storage system coupled with a steam compressor includes a boiler 2, a medium-pressure cylinder 4, a water storage tank 1, a flash tank 7, and a steam compressor. The boiler 2, the steam compressor, and the water storage tank 1 are connected in sequence by pipelines to form an energy storage path. The medium-pressure cylinder 4 is connected to the user terminal 8 by pipelines to form a first heating path. The water storage tank 1, the flash tank 7, the steam compressor, and the user terminal 8 are connected in sequence by pipelines to form a second heating path.

[0025] The intermediate-pressure cylinder 4 and boiler 2 are part of the steam turbine unit, which also includes a high-pressure cylinder 3 and a low-pressure cylinder 5. Boiler 2 supplies steam to the high-pressure cylinder 3 through the main steam pipeline, and supplies steam to the intermediate-pressure cylinder 4 through the intermediate-pressure steam pipeline. The intermediate-pressure cylinder 4 and the low-pressure cylinder 5 are connected through the intermediate exhaust pipeline, which supplies steam to the low-pressure cylinder 5.

[0026] In this system, the allowable working pressure inside the water storage tank 1 is between 2.7 and 3 MPa. The pressure of the saturated water stored in the water storage tank 1 is set at 2.7 MPa, and the temperature of the saturated water is maintained between 220 and 240°C. Through the second heating path of "water storage tank 1 - flash tank 7 - steam compressor - user end 8", qualified steam that meets the heating demand (pressure of 1.2 MPa) can be directly supplied to the user end 8, replacing the traditional mode of direct heating by extracting steam from the intermediate pressure cylinder 4. This heating path can complete the heating without relying on the extraction of steam from the intermediate pressure cylinder 4, realizing the decoupling of power generation and heating, that is, the heating is not affected when the power generation load is adjusted.

[0027] During normal operation of the thermal power plant, the steam generated by boiler 2 has a certain surplus. At this time, the first heating path is adopted as the main heating path, and the intermediate steam discharged from the intermediate pressure cylinder 4 is directly supplied to the user end 8 for heating. During this heating process, a small part of the heating can be completed by the second heating path.

[0028] When a thermal power plant needs to generate electricity at high load (the operating load of the generator set reaches or exceeds a set threshold), the steam generated by boiler 2 prioritizes power generation. The steam extraction volume of the first heating path is significantly reduced. At this time, the second heating path becomes the main heating path. Saturated water in storage tank 1 enters flash tank 7 and forms flash steam. After being pressurized by the steam compressor, the flash steam forms heating steam that meets the heating standard and is supplied to the user end 8. Steam is released through flash tank 7 to supplement the heating demand. The steam supplied by the second heating path can directly replace the steam extraction of the intermediate pressure cylinder 4 in the first heating path, reducing the amount of steam extracted from the generator set. The saved steam from the turbine can continue to drive the generator set to generate electricity, which is equivalent to increasing power generation without increasing coal consumption and reducing coal consumption for power generation.

[0029] In this system, the reheat steam (typically 1.4-2 MPa) drawn from boiler 2 is pressurized to 2.7 MPa through the coupled operation of the steam compressor and water storage tank 1. This raises the saturated water temperature to 228°C, significantly increasing the usable energy density per unit volume (effective thermal energy stored per unit volume) of water storage tank 1, allowing for the storage of more heat within the same tank volume. During the energy release phase (i.e., when the saturated water in water storage tank 1 generates steam and supplies heat), flash tank 7 depressurizes the high-temperature saturated water in water storage tank 1 from 2.7 MPa to 0.6-0.8 MPa (the working pressure inside flash tank 7) for flash evaporation. This greater pressure difference (thermal potential difference) generates more steam, which is then pressurized to 1.2 MPa by the compressor for user supply. Compared to the inefficient "low-parameter water mixing heating" mode in existing systems, this invention greatly improves the utilization rate of the thermal potential difference (existing electric heaters only achieve a steam generation efficiency of 26.9%), significantly reducing energy waste.

[0030] Furthermore, by coupling the operation of the steam compressor and the water storage tank 1, the pressure requirements at the front end are greatly reduced because the flash steam is pressurized by the steam compressor. This allows for a further reduction in the internal working pressure of the flash tank 7, which in turn significantly reduces the design wall thickness of the flash tank 7, thereby lowering its weight and manufacturing cost. The wall thickness of the flash tank 7 is reduced while the strength margin is increased. The reduction in the internal working pressure of the flash tank 7 also reduces the pressure difference between the inside and outside of the flash tank 7, causing a simultaneous decrease in circumferential and axial stresses. This slows down both intergranular corrosion and oxygen corrosion rates, allowing the flash tank 7 to enter a low-stress, long-life range. This extends the maintenance cycle and simultaneously reduces spare parts and labor costs. Meanwhile, the reduced working pressure of flash tank 7 lowers the saturation temperature, shifting the flash curve to the left. The same amount of heat can vaporize more feedwater and generate more steam, significantly increasing steam production. Under low pressure, the bubbly boiling zone is lengthened, the phase change interface is stabilized, the liquid level amplitude is suppressed, the water droplet entrainment rate decreases, and the dryness of the outlet steam is steadily improved. This ensures a continuous supply of uniform, low-humidity, and low-pulsation high-quality steam source to the downstream compressor, reducing the risk of liquid hammer and erosion.

[0031] When thermal power plants engage in deep peak shaving, thermal storage is required. During this process, the extraction steam pressure must be above 3 MPa to meet the storage requirements. However, the reheat steam pressure is too low, and only the main steam generated by boiler 2 can meet the requirements. Directly storing the main steam would result in significant energy cascade losses. In this application, a steam compressor is used to pressurize the reheat steam before storing it in water storage tank 1. The steam compressor can operate within its most economical range and avoids directly extracting high-parameter main steam, resulting in higher system economics.

[0032] The steam compressor can be adapted to both the energy storage path and the secondary heating path. It can flexibly switch between the two working modes by adjusting the parameters. There is no need to configure a second steam compressor, which can reduce equipment investment costs and reduce equipment footprint, and can adapt to the objective conditions of site constraints in old power plants.

[0033] Specifically, the exhaust port of the intermediate pressure cylinder 4 is connected to the user terminal 8 through the first heating pipeline 17, and the first heating pipeline 17 is equipped with a first heating control valve 9 and a flow meter 10; the outlet of the water storage tank 1 is connected to the inlet of the flash tank 7 through the second heating pipeline 18, the gas phase outlet of the flash tank 7 is connected to the inlet of the steam compressor through the third heating pipeline 19, and the outlet of the steam compressor is connected to the user terminal 8 through the fourth heating pipeline 20; the second heating pipeline 18 is equipped with a second heating control valve 13; the third heating pipeline 19 is equipped with a third heating control valve 14; the boiler 2 is connected to the inlet of the steam compressor through the first energy storage pipeline 21, and the outlet of the steam compressor is connected to the water storage tank 1 through the second energy storage pipeline 22, and the first energy storage pipeline 21 is equipped with an energy storage control valve 15.

[0034] In this embodiment, the first heating control valve 9, the second heating control valve 13, the third heating control valve 14, and the energy storage control valve 15 are all electrically adjustable valves. The electrically adjustable valves can precisely and flexibly adjust the valve opening, thereby regulating the flow rate of the medium in the pipeline.

[0035] The liquid outlet of flash tank 7 is connected to the water supply inlet of boiler 2 via a return water pipeline 24, which is equipped with a return water pump. The saturated water (pressure 0.6-0.8 MPa, temperature 162℃) remaining after flash evaporation in flash tank 7 is pumped into boiler 2 to replenish its water supply. Since the temperature of the saturated water remaining in flash tank 7 is much higher than the normal water supply temperature, the amount of coal required for boiler 2 to heat the feedwater is reduced, allowing for full heat recovery and utilization, avoiding heat waste, and indirectly reducing carbon emissions.

[0036] The water storage tank 1 is equipped with a water inlet and a level gauge 11. The water inlet is connected to the water supply tank 12 via a water supply pipe 23, and a water supply valve 16 is installed on the water supply pipe 23. The water level inside the water storage tank 1 can be monitored in real time via the level gauge 11. When the water level inside the water storage tank 1 is lower than the set water level, the water supply valve 16 can be opened to replenish water to the water storage tank 1 to maintain the water storage level in the water storage tank 1.

[0037] An operation method for a hot water energy storage system coupled with a steam compressor, the specific method is as follows:

[0038] When the thermal power plant is deep peak shaving, the energy storage control valve 15 is opened, and the reheat steam of the boiler 2 is pressurized to the first pressure state by the steam compressor to form saturated water and enter the water storage tank 1 for storage, thereby realizing the energy storage process.

[0039] When the operating load of the thermal power plant reaches the set threshold, the second heating control valve 13 and the third heating control valve 14 are opened, and the water in the water storage tank 1 enters the flash tank 7. Low-pressure steam is generated through the flash tank 7. After being pressurized by the steam compressor, the low-pressure steam forms heating steam that meets the heating demand and provides heating to the user end 8. The liquid water in the flash tank 7 flows to the boiler 2 through the return water pipeline 24 and replenishes the boiler 2.

[0040] In the above process, whether in the energy storage or release phase, the conversion occurs between the enthalpy of steam and the thermal energy stored in the saturated water within the storage tank. When the temperature of the water in the tank rises or falls, it indicates that steam is being stored in or released from the system. Therefore, to ensure the stability of the parameters within the storage tank, the steam flow rate entering or exiting the tank must be controlled during the energy storage or release phase. Controlling the steam flow rate ensures that the rate of change in water temperature within the tank remains within acceptable limits. The relationship is as follows:

[0041] ;

[0042] In the formula, V represents the maximum allowable steam flow rate entering or exiting the water storage tank during the energy storage or release phase; V is the volume of the water storage tank, ρ is the density of water, and Cp is the specific heat of water; for liquid water, ρ and Cp are constants, ρ = 1000 kg / m³. 3 Cp = 4.18 kJ / (kg*K). The water temperature inside the storage tank. This represents the maximum permissible rate of temperature change within the storage tank. This is the enthalpy of the vapor at the outlet of the flash tank (obtained from the vapor pressure and temperature using the vapor physical properties table).

[0043] During deep peak shaving at the thermal power plant, the pressure of the reheat steam extracted from boiler 2 is lower than 2 MPa. The steam compressor pressurizes the reheat steam to 2.7 MPa, thus forming saturated water at a temperature of 220-240℃. When the operating load of the thermal power plant reaches the set threshold, the flash pressure of flash tank 7 is 0.6-0.8 MPa. The steam compressor pressurizes the flash pressure to obtain heating steam with a pressure greater than 1.2 MPa.

[0044] This invention is not limited to the preferred embodiments described above. Anyone can derive other products in various forms under the guidance of this invention. However, regardless of any changes in shape or structure, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A hot water thermal storage system coupled to a vapor compressor, characterized by, The boiler, the medium-pressure cylinder, the water storage tank, the flash tank and the steam compressor are connected in sequence by pipelines to form an energy storage path; the medium-pressure cylinder and the user end are connected by a pipeline to form a first heat supply path, and the water storage tank, the flash tank, the steam compressor and the user end are connected in sequence by pipelines to form a second heat supply path; an exhaust port of the medium-pressure cylinder is connected to the user end by a first heat supply pipeline, and a first heat supply control valve is arranged on the first heat supply pipeline; a water outlet of the water storage tank is connected to an input port of the flash tank by a second heat supply pipeline, a gas phase outlet of the flash tank is connected to an inlet of the steam compressor by a third heat supply pipeline, and an outlet of the steam compressor is connected to the user end by a fourth heat supply pipeline; a second heat supply control valve is arranged on the second heat supply pipeline; a third heat supply control valve is arranged on the third heat supply pipeline; the boiler and the inlet of the steam compressor are connected by a first energy storage pipeline, and the outlet of the steam compressor and the water storage tank are connected by a second energy storage pipeline; and an energy storage control valve is arranged on the first energy storage pipeline.

2. A hot water storage energy system coupled to a vapor compressor according to claim 1, wherein, The liquid phase outlet of the flash tank is connected to a water replenishing port of the boiler by a backwater pipeline, and a backwater pump is arranged on the backwater pipeline.

3. A hot water storage energy system coupled to a vapor compressor according to claim 1, wherein, The first heat supply control valve, the second heat supply control valve, the third heat supply control valve and the energy storage control valve are all electrically controlled valves.

4. A hot water storage energy system coupled to a vapor compressor according to claim 1, wherein, A water replenishing port and a liquid level meter are arranged on the water storage tank, the water replenishing port is connected to a water replenishing tank by a water replenishing pipeline, and a water replenishing valve is arranged on the water replenishing pipeline.

5. A method of operating a hot water thermal energy storage system coupled to a vapor compressor, the hot water thermal energy storage system of claim 2, wherein, The specific method is as follows: When the thermal power plant is deeply peak-regulated, the energy storage control valve is opened, the reheated steam from the boiler is pressurized to a first pressure state by the steam compressor, saturated water is formed and stored in the water storage tank, so that the energy storage process is realized; When the operation load of the thermal power plant reaches a set threshold value, the second heat supply control valve and the third heat supply control valve are opened, the water in the water storage tank enters the flash tank, low-pressure steam is generated in the flash tank, the low-pressure steam is pressurized by the steam compressor to form heat supply steam reaching the heat supply requirement and supply heat to the user end, and the liquid water in the flash tank flows to the boiler through the backwater pipeline and replenishes water for the boiler.

6. A method of operating a coupled vapor-compressor hot-water thermal storage system according to claim 5, wherein, When the thermal power plant is deeply peak-regulated, the pressure of the reheated steam from the boiler is lower than 2 MPa, the steam compressor pressurizes the reheated steam to 2.7 MPa, so that saturated water with a temperature of 220-240°C is formed; When the operation load of the thermal power plant reaches a set threshold value, the flash pressure of the flash tank is 0.6-0.8 MPa, the flash pressure is pressurized by the steam compressor, so that heat supply steam with a pressure greater than 1.2 MPa is obtained.

7. A method of operating a coupled vapor-compressor hot-water thermal storage system according to claim 5, wherein, The water temperature change rate in the water storage tank is ensured to be within an allowable range by controlling the steam flow, and the relationship is as follows: ； wherein is the maximum allowed steam flow rate to or from the water storage tank during the charging or discharging phase; V is the volume of the water storage tank, p is the density of water, Cp is the specific heat of water; is the water temperature in the water storage tank, is the maximum allowed water temperature change rate in the water storage tank, is the steam enthalpy at the gas phase outlet of the flash tank.

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