A steam turbine-molten salt heat storage parallel connection deep peak shaving system and a peak shaving method

Abstract

The application discloses a steam turbine-molten salt heat storage parallel connection deep peak regulation system and a peak regulation method, and belongs to the deep peak regulation field. Main steam and reheated steam are extracted at the same time, only the sensible heat of which is used to heat molten salt, and the pressure is reduced to be respectively introduced into high-pressure cylinder exhaust steam and medium-pressure cylinder exhaust steam, and returned to the original thermal system. It is equivalent to that the steam-molten salt heater is respectively connected in parallel with the high-pressure cylinder and the medium-pressure cylinder of the steam turbine. Because the flow of the feed water and the low-temperature reheated steam entering the boiler remains unchanged, the steam parameters are matched, and the combustion of the boiler is not affected, the proportion of the extracted steam is not limited in principle, and the energy storage capacity can be larger. Because the pressure of the steam itself is used to overcome the resistance of the steam heater, a water pump or a booster is not additionally needed, and the station service power is not increased. The low-load high-quality industrial steam demand is met, the stability and the economy of the unit heat supply are improved, the unit is avoided from running in the load stage for a long time, the unit operation efficiency is improved, and the unit loss is reduced.

Description

Technical Field

[0001] This invention belongs to the field of deep peak shaving, and relates to a steam turbine-molten salt thermal storage parallel deep peak shaving system and peak shaving method. Background Technology

[0002] With the rapid development of installed capacity for new energy wind and solar power, and the increasing proportion of power generation, the power system urgently needs a large proportion of flexible power sources to improve the power structure, alleviate the pressure of system peak shaving, and solve the problem of new energy power consumption.

[0003] Existing thermal power unit flexibility retrofitting is mainly limited by issues such as limited boiler peak-shaving depth and insufficient unit economy and safety. Frequent and large-scale adjustments will shorten the service life of thermal power units and lead to lower returns; long-term operation at low load rates significantly reduces the safety, economy, and environmental friendliness of the units, which is inconsistent with the overall goal of energy conservation and emission reduction. Power-side energy storage technology can achieve energy integration and improve the peak-shaving capacity of the energy system. However, current thermal power unit thermal storage technologies are mostly for steam turbine-side domestic heating heat storage, such as hot water tanks and low-temperature phase change thermal storage, with limited energy storage capacity. They cannot play a peak-shaving role during non-heating seasons and cannot provide stable high-temperature industrial steam. Electrochemical energy storage has problems with safety and life cycle. Summary of the Invention

[0004] The purpose of this invention is to solve the problem that the thermal power unit thermal storage technology in the prior art is greatly affected by environmental factors and cannot play a peak-shaving role during the non-heating season, and to provide a turbine-molten salt thermal storage parallel deep peak-shaving system and peak-shaving method.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] The present invention proposes a steam turbine-molten salt thermal storage parallel deep peak-shaving system, including a boiler, a high-pressure molten salt heater, a hot tank, a cold tank, a low-pressure molten salt heat exchanger, a low-pressure cylinder, an intermediate-pressure cylinder, and a high-pressure cylinder;

[0007] The main steam in the boiler enters the high-pressure molten salt heater in one direction and the high-pressure cylinder in another direction to do work. The exhaust steam from the high-pressure molten salt heater and the high-pressure cylinder enter the boiler together to generate reheat steam. The reheat steam enters the low-pressure molten salt heater to heat the molten salt in one direction and the medium-pressure cylinder in another direction to do work. The exhaust steam from the low-pressure molten salt heater and the exhaust steam from the medium-pressure cylinder merge and enter the low-pressure cylinder to do work. After passing through the condensation structure, it is sent to the boiler.

[0008] Molten salt extracted from the cold tank is heated by a low-pressure molten salt heater and then enters a high-pressure molten salt heater for secondary heating. The molten salt after secondary heating is then transferred to a hot tank for storage, thus achieving thermal energy storage.

[0009] Preferably, a cryogenic molten salt pump is provided between the cold tank and the low-pressure molten salt heat exchanger.

[0010] Preferably, the condensation structure includes a condenser and a deaerator;

[0011] The low-temperature steam discharged from the low-pressure cylinder enters the condenser for processing, and the processed liquid water is introduced into the deaerator and then sent to the boiler to generate main steam.

[0012] Preferably, a feedwater pump is provided between the boiler and the deaerator.

[0013] Preferably, a condensate pump is provided between the condenser and the deaerator.

[0014] Preferably, the outlet of the hot water tank is connected in sequence to a high-temperature steam generator and a low-temperature steam generator;

[0015] The high-temperature molten salt in the hot tank undergoes heat exchange with a high-temperature steam generator and a low-temperature steam generator to form low-temperature molten salt, which is then introduced into a cold tank.

[0016] Preferably, a high-temperature lava pump is provided between the hot tank and the high-temperature steam generator.

[0017] Preferably, another outlet of the deaerator is connected to a low-temperature steam generator, another outlet of the low-temperature steam generator is connected to a high-temperature steam generator, and another outlet of the high-temperature steam generator is connected to an intermediate-pressure cylinder.

[0018] Preferably, a booster pump is installed between the deaerator and the cryogenic steam generator.

[0019] The present invention proposes a deep peak-shaving method for a steam turbine-molten salt thermal storage parallel system, comprising the following steps:

[0020] After the main steam enters the high-pressure molten salt heater and the high-pressure cylinder to do work, the exhaust steam from the high-pressure molten salt heater and the high-pressure cylinder is introduced into the boiler to generate reheat steam.

[0021] After the reheated steam enters the low-pressure molten salt heater and the intermediate-pressure cylinder, the exhaust steam in the low-pressure molten salt heater and the exhaust steam in the intermediate-pressure cylinder merge and enter the low-pressure cylinder. After passing through the condensation structure, the steam enters the boiler to continue generating main steam.

[0022] The molten salt in the cold tank is heated by the low-pressure molten salt heater and then enters the high-pressure molten salt heater. The high-pressure molten salt heater heats the molten salt a second time, and finally the molten salt after secondary heating is introduced into the hot tank for storage, thus realizing thermal energy storage.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This invention proposes a steam turbine-molten salt thermal storage parallel deep peak-shaving system. It simultaneously extracts main steam and reheat steam, utilizing only their sensible heat to heat the molten salt. After pressure reduction, the steam flows into the high-pressure cylinder exhaust and the intermediate-pressure cylinder exhaust, respectively, returning to the original thermal system. This is equivalent to the steam-molten salt heater operating in parallel with the high-pressure and intermediate-pressure cylinders of the steam turbine. Because the feedwater and low-temperature reheat steam flow rates entering the boiler remain constant, steam parameters are matched, and there is no impact on boiler combustion. The proportion of extracted steam is, in principle, unlimited, allowing for a larger energy storage capacity. Since the steam's own pressure overcomes the resistance of the steam heater, no additional water pumps or booster compressors are needed, thus reducing plant power consumption.

[0025] The present invention proposes a deep peak-shaving method for parallel operation of steam turbine-molten salt thermal storage. The method involves generating main steam and reheat steam through a boiler, and then introducing the main steam and reheat steam into a high-temperature molten salt heater and a low-pressure molten salt heater, respectively. Molten salt in the cold tank is sent to the low-pressure molten salt heater for processing, and then enters the high-temperature molten salt heater for secondary heating. Finally, it is stored in the hot tank to achieve thermal energy storage. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a diagram of the turbine-molten salt thermal storage parallel deep peak-shaving system of the present invention.

[0028] Wherein: 1-boiler, 2-high-pressure molten salt heat exchanger, 3-hot tank, 4-cold tank, 5-low-temperature molten salt pump, 6-low-temperature steam generator, 7-low-pressure molten salt heat exchanger, 8-high-temperature steam generator, 9-high-temperature molten salt pump, 10-low-pressure cylinder, 11-medium-pressure cylinder, 12-high-pressure cylinder, 13-condenser, 14-condensate pump, 15-deaerator, 16-feed water pump, 17-boosting pump. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0030] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0031] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0032] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present 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, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0033] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0034] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0035] The present invention will now be described in further detail with reference to the accompanying drawings:

[0036] This invention proposes a steam turbine-molten salt thermal storage parallel deep peak-shaving system, such as... Figure 1As shown, the system operates in two modes: energy storage and energy release. The main steam from boiler 1 enters the high-pressure molten salt heater 2 in one path and the high-pressure cylinder 12 in another, where it performs work. The exhaust steam from the high-pressure molten salt heater 2 and the high-pressure cylinder 12 both enter boiler 1 to generate reheat steam. The reheat steam then enters the low-pressure molten salt heater 7 to heat the molten salt in one path and the intermediate-pressure cylinder 11 in another, where it performs work. The exhaust steam from the low-pressure molten salt heater 7 and the intermediate-pressure cylinder 11 merge and enter the low-pressure cylinder 10, where it performs work before being sent back to boiler 1 through a condenser. Molten salt extracted from the cold tank 4 is heated by the low-pressure molten salt heater 7 and then enters the high-pressure molten salt heater 2 for secondary heating. The secondary-heated molten salt is then transferred to the hot tank 3 for storage, thus achieving thermal energy storage. A low-temperature molten salt pump 5 is installed between the cold tank 4 and the low-pressure molten salt heat exchanger 7.

[0037] The condensing structure includes a condenser 13 and a deaerator 15. A feedwater pump 16 is installed between the boiler 1 and the deaerator 15, and a condensate pump 14 is installed between the condenser 13 and the deaerator 15. Low-temperature steam discharged from the low-pressure cylinder 10 enters the condenser 13 for processing. The processed liquid water is then introduced into the deaerator 15 and fed into the boiler 1 to generate main steam. Another outlet of the deaerator 15 is connected to a low-temperature steam generator 6, another outlet of the low-temperature steam generator 6 is connected to a high-temperature steam generator 8, and another outlet of the high-temperature steam generator 8 is connected to an intermediate-pressure cylinder 11. A booster pump 17 is installed between the deaerator 15 and the low-temperature steam generator 6.

[0038] The outlet of the hot tank 3 is sequentially connected to a high-temperature steam generator 8 and a low-temperature steam generator 6. The high-temperature molten salt in the hot tank 3 undergoes heat exchange with the high-temperature steam generator 8 and the low-temperature steam generator 6 to form low-temperature molten salt, which is then introduced into the cold tank 4. A high-temperature lava pump 9 is installed between the hot tank 3 and the high-temperature steam generator 8.

[0039] The present invention proposes a deep peak-shaving method for a steam turbine-molten salt thermal storage parallel system, comprising the following steps:

[0040] Step 1: After the main steam enters the high-pressure molten salt heater 2 and the high-pressure cylinder 12 to do work, the exhaust steam in the high-pressure molten salt heater 2 and the high-pressure cylinder 12 is introduced into the boiler 1 to generate reheat steam.

[0041] Step 2: After the reheated steam enters the low-pressure molten salt heater 7 and the intermediate-pressure cylinder 11, the exhaust steam in the low-pressure molten salt heater 7 and the exhaust steam in the intermediate-pressure cylinder 11 merge and enter the low-pressure cylinder 10. After passing through the condensation structure, the steam enters the boiler 1 to continue generating main steam.

[0042] Step 3: The molten salt in the cold tank 4 is heated by the low-pressure molten salt heater 7 and then enters the high-pressure molten salt heater 2. The high-pressure molten salt heater 2 heats the molten salt a second time, and finally the molten salt after secondary heating is introduced into the hot tank 3 for storage, so as to realize thermal energy storage.

[0043] The power plant's thermal cycle is as follows: Liquid water is pumped from deaerator 15 into boiler 1 via feedwater pump 16, generating high-temperature, high-pressure main steam. This steam then enters the high-pressure cylinder 12 of the turbine for expansion and work, while its temperature and pressure decrease. It then re-enters boiler 1, where its temperature and pressure rise again, generating reheat steam. The reheat steam sequentially enters the intermediate-pressure cylinder 11 and low-pressure cylinder 10 for further expansion and work, finally entering the condenser 13 where it is condensed into liquid. This liquid then flows into deaerator 15 via condensate pump 14, completing one cycle.

[0044] After connecting the molten salt thermal storage in parallel with the high and intermediate pressure cylinders of the steam turbine, the system operates as follows:

[0045] In the energy storage state, a portion of the main steam is extracted and enters the high-pressure molten salt heater 2, where its temperature and pressure drop to the exhaust state of the high-pressure cylinder 12. This steam then enters the boiler 1 along with the exhaust from the high-pressure cylinder 12, generating reheat steam. The extracted main steam does not enter the high-pressure cylinder 12 to perform work but instead enters the high-pressure molten salt heater 2 to be cooled, thereby heating the molten salt from the low-pressure molten salt heater 7. A portion of the reheat steam is also extracted and enters the low-pressure molten salt heater 7 to be cooled. In the low-pressure molten salt heat exchanger 7, the reheat steam is cooled to the temperature and pressure of the exhaust from the intermediate-pressure cylinder 11. The molten salt exiting the cold tank 4 is heated, then enters the high-pressure molten salt heater 2 for further heating, and finally enters the hot tank 3 for storage. The steam exiting the low-pressure molten salt heater 7 mixes with the exhaust from the intermediate-pressure cylinder 11 and enters the low-pressure cylinder 10 to perform work. That is, after the main steam is cooled by the high-pressure molten salt heat exchanger 2, its parameters are kept the same as those of the exhaust steam from the high-pressure cylinder 12; after the reheat steam is cooled by the low-pressure molten salt heat exchanger 7, its parameters are kept the same as those of the exhaust steam from the intermediate-pressure cylinder 11. Therefore, the high-pressure molten salt heat exchanger 2 is connected in parallel with the high-pressure cylinder 12 of the steam turbine, and the low-pressure molten salt heat exchanger 7 is connected in parallel with the low-pressure cylinder 10.

[0046] In energy storage mode, a certain amount of both main steam and reheat steam is extracted to heat the molten salt, thus reducing the unit's power generation capacity. Simultaneously, the heat used for power generation is stored in the molten salt. The main steam and reheat steam are cooled in the high-pressure molten salt heater 2 and low-pressure molten salt heater 7, respectively. After the temperature and pressure drop, they flow into the high-pressure cylinder exhaust and the intermediate-pressure cylinder exhaust, returning to the original thermal system. This is equivalent to the high-pressure molten salt heater 2 operating in parallel with the high-pressure cylinder 12, and the low-pressure molten salt heater 7 operating in parallel with the low-pressure cylinder 10. Therefore, the feedwater and low-temperature reheat steam flow rates entering the boiler remain constant, steam parameters are matched, and there is no impact on boiler combustion. The extracted steam ratio is, in principle, unlimited, and the energy storage capacity can be larger. Because the steam's own pressure overcomes the resistance of the steam heater, no additional water pumps or booster compressors are needed, and no increase in plant power consumption is required.

[0047] In the energy release state, high-temperature molten salt flows from hot tank 3 through high-temperature molten salt pump 9 into high-temperature steam generator 8 and low-temperature steam generator 6, finally entering cold tank 4 to complete the heat energy release. On the other side of high-temperature steam generator 8 and low-temperature steam generator 6, liquid water from deaerator 15 flows through pressurization pump 17 into low-temperature steam generator 6 and high-temperature steam generator 8. The generated steam is kept the same as the reheat steam and enters the intermediate-pressure cylinder 11 and low-pressure cylinder 10 together, converting the heat energy stored in the molten salt into electrical energy and increasing the unit's power generation capacity. At the same time, the high-temperature molten salt stored in hot tank 3 flows through high-temperature steam generator 8 and low-temperature steam generator 6 through high-temperature molten salt pump 9, finally entering cold tank 4 for storage.

[0048] The present invention proposes a turbine-molten salt thermal energy storage parallel deep peak-shaving system, which has the following advantages: 1) It simultaneously extracts main steam and high-temperature reheat steam, using only their sensible heat to heat the molten salt. After the pressure drops, the steam flows into the exhaust steam of high-pressure cylinder 12 and intermediate-pressure cylinder 11, respectively, and returns to the original thermal system. This is equivalent to the steam-molten salt heater operating in parallel with the high-pressure cylinder 12 and intermediate-pressure cylinder 11 of the turbine. Because the feedwater and low-temperature reheat steam flow rates entering boiler 1 remain unchanged, the steam parameters are matched, and there is no impact on the boiler combustion. The proportion of extracted steam is, in principle, unlimited, and the energy storage capacity can be made larger. Since the pressure of the steam itself is used to overcome the resistance of the steam heater, there is no need to add additional water pumps or booster compressors, and no increase in plant power consumption. 2) The technology of solar thermal power generation steam generators with molten salt energy storage has been maturely applied. The steam generated by the energy storage system can be returned to the high-temperature reheat steam system in the original thermal system, increasing the power generation output of the original turbine's intermediate and low-pressure cylinders. The condensate from the low-pressure heater is drawn from the source, requiring a smaller booster pump head and a lower evaporator pressure design, thus reducing equipment investment compared to returning it to the main steam system. 3) The steam generated by the energy storage system can also provide industrial steam heating with specific parameters according to user needs. For thermal power units with industrial heating demands, it is difficult to provide stable industrial steam during low-load peak shaving. Equipped with a high-temperature molten salt energy storage system, the steam generation system can be designed according to the target steam parameters and flow rate, providing stable high-temperature industrial steam through a "thermal-electric decoupling" method, unaffected by peak load limitations. 4) It meets the demand for high-quality industrial steam at low loads, improving the stability and economy of unit heating; it avoids prolonged operation of the unit at load, improving unit operating efficiency and reducing unit losses.

[0049] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A steam turbine-molten salt thermal storage parallel deep peak-shaving system, characterized in that, It includes a boiler (1), a high-pressure molten salt heater (2), a hot tank (3), a cold tank (4), a low-pressure molten salt heat exchanger (7), a low-pressure cylinder (10), a medium-pressure cylinder (11), and a high-pressure cylinder (12); The main steam in the boiler (1) enters the high-pressure molten salt heater (2) in one direction and the high-pressure cylinder (12) in the other direction to do work. The exhaust steam in the high-pressure molten salt heater (2) and the high-pressure cylinder (12) enter the boiler (1) together to generate reheat steam. The reheat steam enters the low-pressure molten salt heat exchanger (7) to heat the molten salt in one direction and enters the medium-pressure cylinder (11) in the other direction to do work. The exhaust steam in the low-pressure molten salt heat exchanger (7) and the exhaust steam in the medium-pressure cylinder (11) merge into the low-pressure cylinder (10) to do work and then enter the boiler (1) through the condensation structure. Molten salt extracted from the cold tank (4) is heated by the low-pressure molten salt heat exchanger (7) and then enters the high-pressure molten salt heater (2) for secondary heating. The molten salt after secondary heating is introduced into the hot tank (3) for storage, thereby realizing thermal energy storage. The outlet of the hot tank (3) is connected in sequence to a high-temperature steam generator (8) and a low-temperature steam generator (6); The high-temperature molten salt in the hot tank (3) is heat-exchanged by the high-temperature steam generator (8) and the low-temperature steam generator (6) to form low-temperature molten salt, which is then introduced into the cold tank (4). The other outlet of the deaerator (15) is connected to the low-temperature steam generator (6), the other outlet of the low-temperature steam generator (6) is connected to the high-temperature steam generator (8), and the other outlet of the high-temperature steam generator (8) is connected to the intermediate pressure cylinder (11).

2. The turbine-molten salt thermal storage parallel deep peak-shaving system according to claim 1, characterized in that, A cryogenic molten salt pump (5) is provided between the cold tank (4) and the low-pressure molten salt heat exchanger (7).

3. The turbine-molten salt thermal storage parallel deep peak-shaving system according to claim 1, characterized in that, The condensation structure includes a condenser (13) and a deaerator (15); The low-temperature steam discharged from the low-pressure cylinder (10) enters the condenser (13) for processing, and the processed liquid water is introduced into the deaerator (15) and then sent to the boiler (1) to generate main steam.

4. The turbine-molten salt thermal storage parallel deep peak-shaving system according to claim 3, characterized in that, A feedwater pump (16) is provided between the boiler (1) and the deaerator (15).

5. The turbine-molten salt thermal storage parallel deep peak-shaving system according to claim 3, characterized in that, A condensate pump (14) is provided between the condenser (13) and the deaerator (15).

6. The turbine-molten salt thermal storage parallel deep peak-shaving system according to claim 1, characterized in that, A high-temperature lava pump (9) is installed between the hot tank (3) and the high-temperature steam generator (8).

7. The turbine-molten salt thermal storage parallel deep peak-shaving system according to claim 1, characterized in that, A booster pump (17) is installed between the deaerator (15) and the low-temperature steam generator (6).

8. A deep peak-shaving method for a steam turbine-molten salt thermal storage parallel system, characterized in that, The turbine-molten salt thermal storage parallel deep peak-shaving system according to any one of claims 1 to 7 includes the following steps: After the main steam enters the high-pressure molten salt heater (2) and the high-pressure cylinder (12) to do work, the exhaust steam in the high-pressure molten salt heater (2) and the high-pressure cylinder (12) is introduced into the boiler (1) to generate reheat steam. After the reheated steam enters the low-pressure molten salt heat exchanger (7) and the intermediate-pressure cylinder (11), the exhaust steam in the low-pressure molten salt heat exchanger (7) and the exhaust steam in the intermediate-pressure cylinder (11) merge and enter the low-pressure cylinder (10). After passing through the condensation structure, the steam enters the boiler (1) to continue generating main steam. The molten salt in the cold tank (4) is heated by the low-pressure molten salt heat exchanger (7) and then enters the high-pressure molten salt heater (2). The high-pressure molten salt heater (2) heats the molten salt a second time and finally introduces the heated molten salt into the hot tank (3) for storage, thus realizing thermal energy storage.

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