Steam turbine unit load adjusting system based on fused salt heat storage and operation method

Abstract

The invention discloses a steam turbine unit load adjusting system based on fused salt heat storage and an operation method. The steam turbine unit load adjusting system comprises a steam turbine unit, a heat regeneration system and a fused salt heat storage system. At least one heating steam inlet is formed in the fused salt heat storage system; a water outlet of a deaerator of the heat regeneration system is connected with one end of a three-way valve through a deaerator water drainage pipeline, and the other two ends of the three-way valve are connected with a water inlet of the fused salt heat storage system and a water inlet of the boiler through a first water drainage pipe branch and a second water drainage pipe branch respectively. A water outlet of the fused salt heat storage system is connected with the second water drainage branch pipe through a third water drainage branch pipe; a high-pressure regenerative heater is arranged on the second drainage pipe branch pipe; a condensate water outlet of the fused salt heat storage system is connected with a first water inlet of the deaerator through a first condensate water drainage pipeline; and a condensate water outlet of the high-pressure regenerative heater is connected with the first condensate water drainage pipeline through a condensate water branch pipe. The method has the advantages that the heat storage efficiency and reliability can be effectively improved, and the response speed and flexibility can be effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of steam turbine power generation, and specifically relates to a load regulation system and operation method for a steam turbine unit based on molten salt heat storage. Background Art

[0002] In modern power systems, steam turbine units, as one of the core devices in the power generation field, play a crucial role. They convert the thermal energy of fuel into mechanical energy, and then drive generators to generate electricity, meeting the huge power demands of social and economic development and residents' daily life. However, with the acceleration of industrialization and the improvement of people's living standards, power demands have shown an increasingly complex and changeable trend. Especially during the "valley load" and "peak load" periods when power load demands exhibit extreme fluctuations, the regulation ability of the power system faces unprecedented challenges.

[0003] The "valley load" period usually occurs at night or during periods of slow economic activity. At this time, power demand drops sharply. If the power generation capacity of power plants cannot be adjusted in time, it will lead to power surplus, not only wasting resources but also potentially threatening the stable operation of the power grid. On the contrary, the "peak load" period mostly occurs during the day's peak hours or under extreme weather conditions. When power demand surges, if the power supply cannot be increased in time, it may cause power shortages and affect the normal operation of society. Traditional power system regulation strategies, such as adjusting the output of generator sets, can, to a certain extent, cope with this demand fluctuation. However, in the long run, frequent adjustments will not only increase the power generation cost but also accelerate the aging of equipment due to frequent starts and stops, posing potential risks to the safety and stability of the power grid.

[0004] To more effectively address this challenge, in the prior art, thermal energy storage technology has become a promising solution. This technology stores thermal energy by using excess power to heat media such as molten salt to a high temperature during the low power demand period. When the power demand enters the peak period, this stored thermal energy is released to heat the working medium water between the deaerator and the boiler, improving the steam generation efficiency. Thus, without increasing additional fuel consumption, flexible regulation of power output is achieved. This "peak shaving and valley filling" strategy not only helps to balance power supply and demand but also effectively improves the stability and reliability of the power system, reduces dependence on traditional fossil energy, and promotes green and low-carbon development.

[0005] In actual use, power systems adopting the above thermal energy storage technology often have problems such as limited heat storage efficiency, inability to flexibly switch, insufficient system response speed, and inability to adapt to rapid peak shaving demands. Summary of the Invention

[0006] The object of the present invention is to provide a load regulation system and operation method for a steam turbine unit based on molten salt thermal energy storage, aiming at the deficiencies of the existing technology, which can improve the efficiency and reliability of the thermal energy storage technology, and effectively improve the response speed and flexibility during the regulation process of the power system.

[0007] The technical object of the present invention is achieved by the following technical solutions: A load regulation system for a steam turbine unit based on molten salt thermal energy storage includes a steam turbine unit, a regenerative system, and a molten salt thermal energy storage system; the molten salt thermal energy storage system includes a hot molten salt storage tank and a cold molten salt storage tank; the heating steam inlet of the molten salt thermal energy storage system is at least one, and the heating steam inlet is used to introduce the heating steam of the steam turbine unit; the drain outlet of the deaerator of the regenerative system is connected to one end of a three-way valve through a deaerator drain pipe, and the other two ends of the three-way valve are respectively connected to the water inlet of the molten salt thermal energy storage system and the water inlet of the boiler through a first drain pipe branch and a second drain pipe branch; the drain outlet of the molten salt thermal energy storage system is connected to the second drain pipe branch through a third drain pipe branch; a high-pressure regenerative heater of the regenerative system is provided on the second drain pipe branch; the condensate drain outlet of the molten salt thermal energy storage system is connected to the first water inlet of the deaerator through a first condensate drain pipe; the condensate drain outlet of the high-pressure regenerative heater is connected to the first condensate drain pipe through a condensate branch pipe.

[0008] Preferably, the steam turbine unit includes a boiler and a high-pressure cylinder, and the boiler is respectively connected to the first heating steam inlet of the molten salt thermal energy storage system and the steam inlet of the high-pressure cylinder through a first main steam pipe branch and a second main steam pipe branch connected to the main steam pipe; a first valve is provided on the first main steam pipe branch.

[0009] Preferably, the steam turbine unit further includes an intermediate-pressure cylinder, and the boiler is respectively connected to the second heating steam inlet of the molten salt thermal energy storage system and the steam inlet of the intermediate-pressure cylinder through a first reheat steam hot section pipe branch and a second reheat steam hot section pipe branch connected to the reheat steam hot section pipe; a second valve is provided on the first reheat steam hot section pipe branch.

[0010] Preferably, the first exhaust steam extraction port of the intermediate-pressure cylinder is connected to a first intermediate-pressure cylinder exhaust steam extraction pipe, and the first branch of the first intermediate-pressure cylinder exhaust steam extraction pipe is connected to the third heating steam inlet of the molten salt thermal energy storage system; a third valve is provided on the first branch; the second exhaust steam extraction port of the intermediate-pressure cylinder is connected to the steam inlet of the high-pressure regenerative heater of the regenerative system through a second intermediate-pressure cylinder exhaust steam extraction pipe.

[0011] Preferably, the medium-pressure cylinder is connected to the low-pressure cylinder through a connecting pipe; the drain port of the low-pressure cylinder is connected to the water inlet of the condenser through a low-pressure cylinder drain pipe; the drain port of the condenser is connected to one end of a condensate pipe, and the other end of the condensate pipe is connected to the second water inlet of the deaerator; a low-pressure feedwater heater is provided on the condensate pipe; the steam inlet of the low-pressure feedwater heater is connected to the low-pressure cylinder steam extraction port of the low-pressure cylinder through a low-pressure cylinder steam extraction pipe; the steam inlet of the deaerator is connected to the first medium-pressure cylinder exhaust steam extraction pipe through a second branch pipe.

[0012] Preferably, a condensate pump is provided on the condensate pipe between the low-pressure feedwater heater and the condenser.

[0013] Preferably, a feed water pump is provided on the deaerator drain pipe.

[0014] An operation method of the steam turbine unit load regulation system based on molten salt thermal energy storage as described above, the operation method is as follows: Low load valley period: Reduce the power generation load of the steam turbine unit, and extract main steam, reheated steam or medium-pressure cylinder exhaust steam extraction to heat the cold molten salt of the molten salt thermal energy storage system; The working medium water coming out of the condenser of the steam turbine enters the boiler for heating after being heated by the low-pressure feedwater heater and the high-pressure feedwater heater; The heated steam enters the high-pressure cylinder to do work, and the steam coming out of the high-pressure cylinder enters the boiler for heating again after doing work; Part of the steam after reheating enters the molten salt thermal energy storage system for heating, and part of it enters the medium-pressure cylinder and the low-pressure cylinder in sequence to do work, and the exhausted steam after doing work returns to the condenser for condensation, starting the next cycle; Peak load period: Deactivate the high-pressure feedwater heater, and stop extracting main steam, reheated steam and medium-pressure cylinder exhaust steam extraction; The working medium water coming out of the condenser of the steam turbine unit enters the boiler for heating after being heated by the low-pressure feedwater heater and the hot molten salt of the molten salt thermal energy storage system; The heated steam enters the high-pressure cylinder to do work, and the steam coming out of the high-pressure cylinder enters the boiler for heating again after doing work; part of the steam after reheating enters the molten salt thermal energy storage system for heating, and part of it enters the medium-pressure cylinder and the low-pressure cylinder in sequence to do work, and the exhausted steam after doing work returns to the condenser for condensation, starting the next cycle.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. The load regulation system of a steam turbine unit based on molten salt thermal energy storage according to the present invention includes a steam turbine unit, a regenerative system, and a molten salt thermal energy storage system; the molten salt thermal energy storage system includes a hot molten salt storage tank and a cold molten salt storage tank; the heating steam inlet of the molten salt thermal energy storage system is at least one, and the heating steam inlet is used to introduce the heating steam of the steam turbine unit; the exhaust port of the molten salt thermal energy storage system is connected to the boiler through an exhaust pipe; the drain port of the molten salt thermal energy storage system is connected to the first water inlet of the deaerator through a drain pipe; the drain port of the deaerator is connected to one end of a three-way valve through a deaerator drain pipe, and the other two ends of the three-way valve are respectively connected to the water inlet of the molten salt thermal energy storage system and the water inlet of the high-pressure regenerative heater of the regenerative system through a first drain pipe branch and a second drain pipe branch. By adopting this technical measure, the efficiency and reliability of the thermal energy storage technology can be effectively improved, and the response speed and flexibility in the regulation process of the power system can be effectively improved.

[0016] 2. The operation method of the load regulation system of a steam turbine unit based on molten salt thermal energy storage according to the present invention is as follows: during the "valley pressure" period with low electricity load demand, the steam turbine unit reduces power generation and uses the excess electricity load to heat the molten salt to achieve the purpose of storing heat. During the "peak top" period with high electricity load demand, the high-pressure regenerative heater is shut down, and instead, the heat stored in the molten salt is used to heat the working medium water between the deaerator and the boiler, so as to meet the demand of overloading power supply during the "peak top" period. By reasonably adjusting and distributing power generation, the high-efficiency regulation of the power system during the "valley pressure" and "peak top" periods is realized, and the response speed and flexibility in the regulation process of the power system are improved. At the same time, by optimizing the operation mode of the steam turbine unit during the "valley pressure" and "peak top" periods, the power generation cost is reduced, and the safety and stability of the power grid are not affected. By adopting this operation method, the response speed and flexibility in the regulation process of the power system can be effectively improved, the power generation cost is reduced, and the safety and stability of the power grid are not affected. Description of the Drawings

[0017] Figure 1 is the structural schematic diagram of the present invention; Reference Numerals: 11—Boiler; 12—High-pressure Cylinder; 13—Intermediate-pressure Cylinder; 131—First Intermediate-pressure Cylinder Exhaust Steam Extraction Pipe; 132—First Branch Pipe; 1321—Third Valve; 133—Second Branch Pipe; 134—Second Intermediate-pressure Cylinder Exhaust Steam Extraction Pipe; 14—Low-pressure Cylinder; 15—Generator; 16—Condenser; 161—Condensate Pipe; 162—Condensate Pump; 21—Deaerator; 211—Deaerator Drain Pipe; 212—Feed Water Pump; 22—High-pressure Regenerative Heater; 221—Condensate Branch Pipe; 23—Low-pressure Regenerative Heater; 3—Molten Salt Thermal Energy Storage System; 31—First Drain Pipe Branch; 32—Third Drain Branch; 33—First Condensate Drain Pipe; 4 - Main steam pipeline; 41 - First branch of the main steam pipeline; 411 - First valve; 42 - Second branch of the main steam pipeline; 5 - Reheat steam hot - section pipeline; 51 - First branch of the reheat steam hot - section pipeline; 511 - Second valve; 52 - Second branch of the reheat steam hot - section pipeline; 6 - Three - way valve; 61 - Second branch of the drain pipe. Detailed implementation manners

[0018] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0019] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0020] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. In addition, terms such as "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0021] Such as Figure 1As shown in the figure, a load regulation system for a steam turbine unit based on molten salt thermal energy storage includes a steam turbine unit, a regenerative system, and a molten salt thermal energy storage system 3; the molten salt thermal energy storage system 3 includes a hot molten salt storage tank and a cold molten salt storage tank; the heating steam inlet of the molten salt thermal energy storage system 3 is at least one, and the heating steam inlet is used to introduce the heating steam of the steam turbine unit; the drain outlet of the deaerator 21 of the regenerative system is connected to one end of a three-way valve 6 through a deaerator drain pipe 211, and the other two ends of the three-way valve 6 are respectively connected to the water inlet of the molten salt thermal energy storage system 3 and the water inlet of the boiler 11 through a first drain pipe branch 31 and a second drain pipe branch 61; the drain outlet of the molten salt thermal energy storage system 3 is connected to the second drain pipe branch 61 through a third drain branch; a high-pressure regenerative heater 22 of the regenerative system is provided on the second drain pipe branch 61; the condensate drain outlet of the molten salt thermal energy storage system 3 is connected to the first water inlet of the deaerator 21 through a first condensate drain pipe 33; the condensate drain outlet of the high-pressure regenerative heater 22 is connected to the first condensate drain pipe 33 through a condensate branch 221. By adopting this technical measure, the efficiency and reliability of the thermal energy storage technology can be effectively improved, and the response speed and flexibility in the regulation process of the power system can be effectively improved.

[0022] Specifically, the molten salt thermal energy storage system 3 adopts the existing technology. Through the cooperation of the cold / hot molten salt tank combination, the pumping system, the heat exchanger group, and the steam generator, the system can complete the "thermal energy storage - heat release" cycle. In this embodiment, by setting up the molten salt thermal energy storage system 3, molten salt is used as the thermal energy storage medium, and heat is stored and released through heating and cooling, so as to realize the storage and efficient utilization of thermal energy. During the low-load period: the cold molten salt absorbs the extraction steam heat of the steam turbine unit through the heating steam inlet, and after heating up, it is stored in the hot molten salt storage tank; during the peak-load period: the hot molten salt releases heat to heat the working medium water to increase the power generation load, realizing "peak shaving and valley filling". Temperature gradient management: The double-tank design avoids the mixing of cold and hot molten salts and maintains the molten salt thermal energy storage efficiency (the thermal energy storage temperature can reach 565 °C). The cold / hot molten salt storage tanks provide buffer capacity to adapt to the rapid fluctuations of the power grid load. By adopting this technical measure, it has the advantages of high-efficiency thermal energy storage and energy release. At the same time, it also has the advantage of high system stability.

[0023] The heating steam inlet of the molten salt thermal energy storage system 3 is at least one, and the steam at different positions of the steam turbine unit (such as main steam, reheated steam, exhaust steam from the intermediate-pressure cylinder, etc.) can be introduced. By adopting this technical measure, the flexibility can be effectively improved, multi-source collaborative optimization can be carried out, the adaptability is strong, and the transformation cost can be reduced. Specifically, the waste heat can be flexibly utilized; the main steam (high temperature and high pressure) directly heats the molten salt to improve the thermal energy storage efficiency; the exhaust steam from the intermediate-pressure cylinder (medium temperature and medium pressure) is used as a supplementary heat source to reduce energy waste. Multi-source collaborative optimization: Dynamically select the extraction steam source according to the power grid demand to balance the power generation and thermal energy storage demands. Strong adaptability: It is applicable to the transformation of steam turbine units with different parameters (temperature, pressure), and the transformation cost is reduced.

[0024] The drain outlet of the deaerator 21 is connected to the inlet of the molten salt thermal energy storage system 3 and the inlet of the boiler 11 through a three-way valve 6. A high-pressure feedwater heater 22 is provided on the second drain pipe branch 61. The working medium water between the deaerator 21 and the boiler 11 is used as the heating object: The working medium water between the deaerator 21 and the boiler 11 is an important part of the power system, and its temperature and pressure directly affect the operating efficiency and safety of the power system. In the high-pressure feedwater heater 22, part of the heat of the high-pressure steam is used to heat the low-pressure feedwater, thereby improving the thermal efficiency. In this embodiment, under the action of the high-pressure feedwater heater 22, the full utilization of thermal energy can be achieved, and the efficiency and reliability of thermal energy storage are further improved. Dynamic operation mode switching; Low valley period: The working medium water is preheated by the high-pressure feedwater heater 22 to maintain the basic thermal efficiency; Peak period: Switch the three-way valve 6, and the working medium water is heated by the molten salt thermal energy storage system 3 instead, and the high-pressure feedwater heater 22 is deactivated to reduce heat loss. Quick response to peak shaving requirements: The mode switching can be completed within 10 minutes, improving the flexibility of the power grid. Reducing equipment loss: The high-pressure feedwater heater 22 only operates during the low valley period, reducing the start-stop frequency and extending the equipment life.

[0025] The condensate drain outlet of the molten salt thermal energy storage system 3 is connected to the deaerator 21, and the condensate of the high-pressure feedwater heater 22 is incorporated into the same loop through a branch pipe. Efficient utilization of water resources: Recover the condensate of the molten salt heat exchanger and the high-pressure feedwater heater 22, reducing the supplement amount of the working medium water (the water saving rate can reach 15%); The preheated condensate enters the deaerator 21, reducing the deaeration energy consumption. Cascaded utilization of thermal energy: The condensate of the molten salt thermal energy storage system 3 (high temperature) is mixed with the condensate of the high-pressure feedwater heater 22 (medium temperature), optimizing the water temperature gradient, increasing the inlet water temperature of the boiler 11, and reducing fuel consumption. Anti-corrosion protection: The closed-loop circulation of the condensate reduces the dissolution of oxygen and reduces the risk of pipeline corrosion.

[0026] As Figure 1 shown, a feed pump 212 is provided on the deaerator drain pipe 211. By adopting this technical measure, the water supply guarantee is improved, the thermal cycle is optimized, and in cooperation with the molten salt thermal energy storage system, the preheated feedwater (for example, rising from 160°C to 250°C) further reduces the boiler fuel consumption (saving 5% - 8%). It also has excellent dynamic regulation ability; The feed pump is driven by frequency conversion and adjusts the flow rate in real time according to the boiler load (for example, suddenly increasing from 100% to 120%), and the response time is less than 1 minute, meeting the peak power supply demand of the power grid. During the molten salt energy release stage, it quickly matches the change in the heating amount of the working medium water to avoid the decrease in the efficiency of the boiler 11 caused by pressure fluctuations.

[0027] ‌As Figure 1As shown in the figure, the steam turbine unit includes a boiler 11, a high-pressure cylinder 12, an intermediate-pressure cylinder 13, a low-pressure cylinder 14, a generator 15, and a condenser 16; the rotors of the high-pressure cylinder 12, the intermediate-pressure cylinder 13, the low-pressure cylinder 14, and the generator 15 are coaxially arranged.

[0028] Specifically, the steam turbine unit includes a boiler 11 and a high-pressure cylinder 12. The boiler 11 is respectively connected to the first heating steam inlet of the molten salt thermal energy storage system 3 and the steam inlet of the high-pressure cylinder 12 through a first main steam pipe branch 41 and a second main steam pipe branch 42 connected to the main steam pipe 4; a first valve 411 is provided on the first main steam pipe branch 41. Through the main steam diversion + valve precise control, the core problems of low extraction steam temperature and slow peak shaving response of the traditional molten salt thermal energy storage system 3 are solved, realizing the efficient storage and flexible release of high-temperature thermal energy, and at the same time ensuring the operation stability of the steam turbine unit.

[0029] In specific implementation, the molten salt thermal energy storage system 3 has a temperature advantage when accessing the main steam, so as to improve the energy storage efficiency. The main steam temperature is usually as high as 540 - 600 °C, and the pressure exceeds 10 MPa. Directly used for heating molten salt can significantly increase the upper limit of the heat storage temperature (for example, from 400 °C to 565 °C), and the heat storage density is increased by 25% - 30%. The strong heat transfer ability of high-temperature steam shortens the heating time of cold molten salt by 30% - 40%, and improves the heat storage efficiency during the low valley period.

[0030] By adjusting the main steam extraction ratio through the first valve 411, while ensuring the basic power generation load of the high-pressure cylinder 12, the energy is flexibly distributed to the energy storage system to realize the coordinated operation of the "power generation - energy storage" dual mode. The valve opening can respond to the grid command in real time, and the load regulation delay is reduced to within 5 minutes. The main steam diversion does not need to modify the core structure of the boiler 11, only need to install branches and valves, and the transformation cost is reduced by 40% - 50%. The main steam diversion design retains the steam volume required for the normal operation of the high-pressure cylinder 12, avoiding power generation interruption caused by excessive extraction steam. Adopting this technical measure also has the advantages of fast peak shaving response speed, high load regulation flexibility, low transformation cost, and high reliability.

[0031] The second main steam pipe branch 42 is directly connected to the high-pressure cylinder 12 to ensure that the steam supply of the high-pressure cylinder 12 is not affected by the extraction steam of the molten salt thermal energy storage system 3. The high-pressure cylinder 12 always obtains a stable steam supply, avoiding the power generation power oscillation caused by the extraction steam fluctuation in the traditional peak shaving system (the fluctuation amplitude is reduced from ±10% to ±2%). If the molten salt thermal energy storage system 3 fails, closing the first valve 411 can isolate the system, and the high-pressure cylinder 12 can still operate independently to ensure the continuity of power supply.

[0032] A first valve 411 is provided on the branch pipe 41 of the first main steam pipe to accurately control the extraction steam flow rate. The extraction steam quantity is adjusted by the valve opening (for example, 0% - 30% of the main steam flow rate) to achieve the optimal ratio of heat storage and power generation, and the comprehensive energy efficiency is increased by 8% - 12%. The valve can be set as a check valve to prevent the steam from flowing back and impacting the boiler 11 when the molten salt heat storage system 3 is abnormal, thus enhancing the system safety. The valve is linked with the DCS system and automatically adjusted according to the grid load signal, reducing manual intervention and the operation and maintenance cost by 15% - 20%.

[0033] As Figure 1 shown, the steam turbine unit includes an intermediate pressure cylinder 13. The boiler 11 is respectively connected to the second heating steam inlet of the molten salt heat storage system 3 and the steam inlet of the intermediate pressure cylinder 13 through a first branch pipe 51 of the reheater steam hot section pipe 5 connected to the reheater steam hot section pipe and a second branch pipe 52 of the reheater steam hot section pipe; a second valve 511 is provided on the first branch pipe 51 of the reheater steam hot section pipe. Through the precise control of reheater steam diversion + valve, the technical bottleneck that the traditional molten salt heat storage system 3 relies on low-temperature extraction steam is broken through. By adopting this technical measure, the efficient storage and flexible release of high-grade thermal energy are realized, and it has the advantages of high-temperature heat storage, rapid response, and multi-source coordination, etc.

[0034] Specifically, the reheater steam temperature is usually 540 - 580 °C, and the pressure is 3 - 5 MPa. Directly used for heating molten salt can further increase the upper limit of the heat storage temperature (for example, from 565 °C to 580 °C), and the heat storage density increases by 10% - 15%. As the reheated product of the exhaust steam of the high-pressure cylinder 12, the thermal energy quality of the reheater steam is higher than that of the intermediate pressure cylinder exhaust steam. Using it for molten salt heat storage can avoid waste of high-grade thermal energy, and the comprehensive efficiency of the system is increased by 5% - 8%.

[0035] Dynamic heat source selection: Dual-path extraction of main steam and reheated steam. Flexibly select high-temperature heat sources according to grid demand (for example, give priority to using main steam during low-load periods and release the thermal energy of reheated steam during peak-load periods), and improve the peak shaving response speed to within 3 minutes. There is no need to modify the structure of the reheater. Only need to install a branch pipe and a valve on the reheated steam pipeline, and the retrofit cost is reduced by 30% - 40%. The second valve 511 can quickly isolate the molten salt thermal energy storage system 3 to ensure stable steam inlet to the intermediate pressure cylinder 13 and avoid affecting power generation safety during peak shaving operations. The branch pipe 52 of the second hot section pipeline of the reheated steam is directly connected to the intermediate pressure cylinder 13 to ensure that the steam supply to the intermediate pressure cylinder 13 is not affected by the extraction of the molten salt thermal energy storage system 3. At the same time, the combined use of main steam and reheated steam can double the thermal energy storage power under extreme peak shaving requirements (for example, from 100 MW to 200 MW). Reduce or cut off the steam inlet to the intermediate pressure cylinder 13 during valley electricity periods to avoid overheating and vibration of the last-stage blades of the intermediate pressure cylinder 13 due to the blowing effect under extremely low flow rates (the blade life is extended by more than 30%). Maintain a relatively high steam flow rate (more than 50% of the rated flow rate) in the reheater of the boiler 11 by diverting the reheated steam to prevent the risk of over-temperature bursting of the reheater tube wall. Use the high-grade thermal energy of the reheated steam for thermal energy storage. Compared with the thermal energy storage method using extraction steam from the intermediate pressure cylinder 13, the coal consumption per unit of thermal energy storage is reduced by 20% - 25%, and the annual coal savings reach the ten-thousand-ton level. This solution flexibly switches through the reheated steam path, while releasing the advantages of high energy density of molten salt thermal energy storage, solves the dual contradictions of the safety of the intermediate pressure cylinder 13 during low-load operation and the waste of reheated steam thermal energy in traditional peak shaving.

[0036] As Figure 1 shown, the first extraction steam port of the intermediate pressure cylinder 13 is connected to the first intermediate pressure cylinder extraction steam pipeline 131, and the first branch pipe 132 of the first intermediate pressure cylinder extraction steam pipeline 131 is connected to the third heating steam inlet of the molten salt thermal energy storage system 3; a third valve 1321 is provided on the first branch pipe 132; the second extraction steam port of the intermediate pressure cylinder 13 is connected to the steam inlet of the high-pressure regenerative heater 22 of the regenerative system through the second intermediate pressure cylinder extraction steam pipeline 134. Through the precise control of double extraction steam + valves of the intermediate pressure cylinder 13 and adopting this technical measure, the combination of cascaded utilization of thermal energy and system redundancy design is realized. It has the advantages of efficient thermal energy storage, flexible peak shaving and high reliability.

[0037] Among them, the intermediate-pressure cylinder 13 is provided with a first exhaust steam extraction port and a second exhaust steam extraction port, and the steam is shunted through a first branch pipe 132 (connected to the molten salt thermal energy storage system 3) and a second intermediate-pressure cylinder exhaust steam extraction pipeline 134 (connected to the high-pressure regenerative heater 22) respectively. A third valve 1321 is provided on the first branch pipe 132 to control the flow rate. By adopting this technical measure, the cascade utilization of thermal energy is realized. The high-temperature exhaust steam is used for molten salt thermal energy storage; the first exhaust steam extraction port extracts the high-temperature exhaust steam (about 300 - 350 °C) of the intermediate-pressure cylinder 13 to directly heat the molten salt, raising the thermal energy storage temperature to 550 - 580 °C, and the thermal energy storage efficiency is increased by 15% - 20%. The low-temperature exhaust steam is used for the regenerative system; the second exhaust steam extraction port extracts the low-temperature exhaust steam (about 200 - 250 °C) to preheat the working medium water in the high-pressure regenerative heater 22, maintaining the basic thermal efficiency and avoiding the waste of low-grade thermal energy. The second exhaust steam extraction port continuously supplies steam to the high-pressure regenerative heater 22 to ensure the normal operation of the regenerative system, avoiding the interruption of regeneration caused by the extraction of the molten salt thermal energy storage system 3, and reducing the power generation power fluctuation rate to ±1%.

[0038] A third valve 1321 is provided on the first branch pipe 132 to dynamically adjust the extraction amount of the intermediate-pressure cylinder exhaust steam. The extraction ratio is adjusted in real time through the valve opening (for example, 0% - 50%), achieving a dynamic balance between thermal energy storage and power generation, and expanding the peak shaving range to 15% - 130% of the rated load; supporting the rapid frequency regulation requirements of the power grid, with a frequency regulation accuracy of ±0.05 Hz. The valve integrates a check function to prevent the reverse flow of steam from impacting the intermediate-pressure cylinder 13 when the molten salt thermal energy storage system 3 malfunctions, avoiding blade damage.

[0039] The second exhaust steam extraction port is connected to the high-pressure regenerative heater 22 to maintain the basic function of the regenerative system. The coordinated operation of the regenerative system and the thermal energy storage system is realized. The high-pressure regenerative heater 22 continuously uses the low-temperature exhaust steam of the intermediate-pressure cylinder 13 to preheat the working medium water, and the inlet water temperature of the boiler 11 is stabilized at 160 - 180 °C, reducing the fuel consumption by 5% - 8%; avoiding the problem of the decline of the regenerative efficiency caused by excessive extraction in the traditional system.

[0040] The two exhaust steam extraction ports are used as spares for each other, and the molten salt thermal energy storage system 3 and the regenerative system operate independently. If the molten salt thermal energy storage system 3 fails, the third valve 1321 is closed, and the second exhaust steam extraction port can still supply steam to the regenerative system, and the system availability reaches 99.5%; if the regenerative system fails, the first exhaust steam extraction port can be switched to the maximum extraction amount to compensate for the loss of thermal efficiency through the molten salt thermal energy storage system 3.

[0041] Such as Figure 1As shown in the figure, the intermediate-pressure cylinder 13 is connected to the low-pressure cylinder 14 through a connecting pipe; the drain port of the low-pressure cylinder 14 is connected to the water inlet of the condenser 16 through a low-pressure cylinder drain pipe; the drain port of the condenser 16 is connected to one end of a condensate pipe 161, and the other end of the condensate pipe 161 is connected to the second water inlet of the deaerator 21; a low-pressure regenerative heater 23 is provided on the condensate pipe 161; the steam inlet of the low-pressure regenerative heater 23 is connected to the low-pressure cylinder extraction port of the low-pressure cylinder 14 through a low-pressure cylinder extraction pipe; the steam inlet of the deaerator 21 is connected to the first intermediate-pressure cylinder exhaust extraction pipe 131 through a second branch pipe 133. In specific implementation, the exhaust port on the intermediate-pressure cylinder 13 is connected to the steam inlet of the low-pressure cylinder 14 through a connecting pipe; a butterfly valve is provided on the connecting pipe. The drain port of the low-pressure regenerative heater 23 is connected to the water inlet of the condenser 16 through a pipe.

[0042] A condensate pump 162 is provided on the condensate pipe 161 between the low-pressure regenerative heater 23 and the condenser 16. By adopting this technical measure, the pressure of the condensate water circulation is maintained to ensure stable water flow transportation. The condensate water is timely transported to the low-pressure regenerative heater 23, and the condensate water is preheated by the extraction steam of the low-pressure cylinder of the steam turbine (for example, preheated from 30 °C to 80 °C), reducing the fuel consumption of the boiler (saving 1 - 1.5 kg of standard coal per ton of steam).

[0043] During the peak shaving period, the condensate pump 162 dynamically adjusts the flow rate through frequency conversion control to match the change of the steam turbine load (such as from 100% to 30% of the rated load), preventing the impact of water flow fluctuations on the regenerative system. Preventing the condenser from filling with water and backflowing into the steam turbine, avoiding blade water hammer damage, and extending the equipment life by 20% - 30%. Deep peak shaving operation: During the low grid valley period, the steam turbine operates at a low load, and the condensate pump 162 maintains a stable flow rate to avoid vacuum fluctuations in the condenser 16. High backpressure condition: When the cooling water temperature rises in summer, the condensate pump 162 compensates for the pressure rise in the condenser 16 to ensure system stability.

[0044] In this embodiment, during the "valley pressure" period, the heat supply of the main steam, reheated steam or intermediate extraction steam is increased as appropriate to heat the cold molten salt while reducing the electrical load. During the "peak top" period, the high-pressure regenerative heater 22 is deactivated by using a three-way valve 6, and instead, the molten salt is used to heat the working medium water between the deaerator 21 and the boiler 11 to replace the high-pressure regenerative heater 22, thereby increasing the power generation load, realizing flexible adjustment of the steam turbine load, and reducing the power generation cost.

[0045] The operation method of the above steam turbine unit load regulation system based on molten salt heat storage is as follows: Valley pressure period: Reduce the power generation load of the steam turbine unit, extract the main steam, reheated steam or extraction steam from the exhaust of the intermediate pressure cylinder to heat the cold molten salt in the molten salt thermal energy storage system 3. During specific implementation, according to the situation, control the steam flow rate of the extracted main steam, reheated steam or extraction steam from the exhaust of the intermediate pressure cylinder by adjusting the opening degrees of the first valve 411, the second valve 511 or the third valve 1321; while reducing the power generation load of the steam turbine unit, heat the cold molten salt in the molten salt thermal energy storage system 3.

[0046] The working medium water coming out of the condenser 16 of the steam turbine is heated by the low-pressure regenerative heater 23 and the high-pressure regenerative heater 22 and then enters the boiler 11 for heating. During specific implementation, close one end of the water inlet of the molten salt thermal energy storage system 3 through the three-way valve 6, so that the working medium water discharged from the deaerator 21 is heated by the high-pressure regenerative heater 22 and then enters the boiler 11 for heating.

[0047] The heated steam enters the high-pressure cylinder 12 to do work, and the steam coming out of the high-pressure cylinder 12 enters the boiler 11 for heating again after doing work; a part of the steam after being reheated enters the molten salt thermal energy storage system 3 for heating, and a part enters the intermediate pressure cylinder 13 and the low-pressure cylinder 14 in sequence to do work, and the exhausted steam after doing work returns to the condenser 16 for condensation, starting the next cycle.

[0048] Peak load period: Deactivate the high-pressure regenerative heater 22, and stop extracting the main steam, reheated steam and extraction steam from the exhaust of the intermediate pressure cylinder. During specific implementation, deactivate the high-pressure regenerative heater 22, and at the same time close the first valve 411, the second valve 511 and the third valve 1321 to stop extracting the main steam, reheated steam and extraction steam from the exhaust of the intermediate pressure cylinder.

[0049] The working medium water coming out of the condenser 16 of the steam turbine unit is heated by the low-pressure regenerative heater 23 and the hot molten salt in the molten salt thermal energy storage system 3 and then enters the boiler 11 for heating. During specific implementation, close one end of the second drain pipe branch 61 through the three-way valve 6, so that the working medium water discharged from the deaerator 21 is heated by the molten salt thermal energy storage system 3 and then enters the boiler 11 for heating.

[0050] The heated steam enters the high-pressure cylinder 12 to do work, and the steam coming out of the high-pressure cylinder 12 enters the boiler 11 for heating again after doing work; a part of the steam after being reheated enters the molten salt thermal energy storage system 3 for heating, and a part enters the intermediate pressure cylinder 13 and the low-pressure cylinder 14 in sequence to do work, and the exhausted steam after doing work returns to the condenser 16 for condensation, starting the next cycle.

[0051] Adopt the following operation method: during the "valley pressure reduction" period when the electrical load demand is low, the steam turbine unit reduces the power generation and uses the excess electrical load to heat the molten salt to achieve the purpose of storing heat. During the "peak top" period when the electrical load demand is high, the high-pressure regenerative heater 22 is deactivated, and instead, the heat stored in the molten salt is used to heat the working medium water between the deaerator 21 and the boiler 11, so as to meet the demand for overloading power supply during the "peak top" period.

[0052] By reasonably adjusting and distributing the power generation, the efficient regulation of the power system during the "valley pressure reduction" and "peak top" periods is realized, and the response speed and flexibility during the regulation process of the power system are improved. At the same time, by optimizing the operation modes of the steam turbine unit during the "valley pressure reduction" and "peak top" periods, the power generation cost is reduced, and the safety and stability of the power grid are not affected. By adopting this operation method, the response speed and flexibility during the regulation process of the power system can be effectively improved, the power generation cost is reduced, and the safety and stability of the power grid are not affected.

[0053] The technical solutions provided by the embodiments of the present invention have been introduced in detail above. Specific examples are used in this article to elaborate on the principles and implementation manners of the embodiments of the present invention. The descriptions of the above embodiments are only applicable to helping understand the principles of the embodiments of the present invention; at the same time, for those of ordinary skill in the art, according to the embodiments of the present invention, changes will occur in the specific implementation manners and application scopes.

Claims

1. A steam turbine unit load regulation system based on molten salt thermal energy storage, characterized in that, It includes a steam turbine unit, a regenerative system, and a molten salt thermal energy storage system; the molten salt thermal energy storage system includes a hot molten salt storage tank and a cold molten salt storage tank; there is at least one heating steam inlet for the molten salt thermal energy storage system, and the heating steam inlet is used to introduce the heating steam of the steam turbine unit. The drain outlet of the deaerator of the regenerative system is connected to one end of a three-way valve through a deaerator drain pipe, and the other two ends of the three-way valve are respectively connected to the water inlet of the molten salt thermal energy storage system and the water inlet of the boiler through a first drain pipe branch and a second drain pipe branch. The drain outlet of the molten salt thermal energy storage system is connected to the second drain pipe branch through a third drain branch. A high-pressure regenerative heater of the regenerative system is provided on the second drain pipe branch. The condensate drain outlet of the molten salt thermal energy storage system is connected to the first water inlet of the deaerator through a first condensate drain pipe; the condensate drain outlet of the high-pressure regenerative heater is connected to the first condensate drain pipe through a condensate branch pipe.

2. The load regulation system of a steam turbine unit based on molten salt heat storage according to claim 1, wherein The steam turbine unit includes a boiler and a high-pressure cylinder. The boiler is connected to the first heating steam inlet of the molten salt thermal energy storage system and the steam inlet of the high-pressure cylinder through a first main steam pipe branch and a second main steam pipe branch connected to the main steam pipe respectively; a first valve is provided on the first main steam pipe branch.

3. The load regulation system of a steam turbine unit based on molten salt heat storage according to claim 2, wherein, The steam turbine unit further includes an intermediate-pressure cylinder. The boiler is connected to the second heating steam inlet of the molten salt thermal energy storage system and the steam inlet of the intermediate-pressure cylinder through a first reheater hot section pipe branch and a second reheater hot section pipe branch connected to the reheater hot section pipe respectively; a second valve is provided on the first reheater hot section pipe branch.

4. The load regulation system of a steam turbine unit based on molten salt thermal energy storage according to claim 3, wherein, The first exhaust steam extraction port of the intermediate-pressure cylinder is connected to a first intermediate-pressure cylinder exhaust steam extraction pipe. The first branch of the first intermediate-pressure cylinder exhaust steam extraction pipe is connected to the third heating steam inlet of the molten salt thermal energy storage system; a third valve is provided on the first branch; the second exhaust steam extraction port of the intermediate-pressure cylinder is connected to the steam inlet of the high-pressure regenerative heater of the regenerative system through a second intermediate-pressure cylinder exhaust steam extraction pipe.

5. The load regulation system of a steam turbine unit based on molten salt thermal energy storage according to claim 3, wherein, The intermediate-pressure cylinder is connected to the low-pressure cylinder through a connecting pipe; the drain outlet of the low-pressure cylinder is connected to the water inlet of the condenser through a low-pressure cylinder drain pipe; the drain outlet of the condenser is connected to one end of a condensate pipe, and the other end of the condensate pipe is connected to the second water inlet of the deaerator; a low-pressure regenerative heater is provided on the condensate pipe; the steam inlet of the low-pressure regenerative heater is connected to the low-pressure cylinder extraction port of the low-pressure cylinder through a low-pressure cylinder extraction pipe; the steam inlet of the deaerator is connected to the first intermediate-pressure cylinder exhaust steam extraction pipe through a second branch.

6. The load regulation system of a steam turbine unit based on molten salt thermal energy storage according to claim 5, wherein A condensate pump is provided on the condensate pipe between the low-pressure regenerative heater and the condenser.

7. The load regulation system of a steam turbine unit based on molten salt thermal energy storage according to claim 1, wherein A feed water pump is provided on the deaerator drain pipe.

8. An operating method for a load regulation system of a steam turbine unit based on molten salt thermal energy storage as described in any one of claims 1-7, characterized in that, The operation method is as follows: Low load valley period: Reduce the power generation load of the steam turbine unit, and extract main steam, reheated steam or intermediate-pressure cylinder exhaust steam extraction to heat the cold molten salt of the molten salt thermal energy storage system. The working medium water coming out of the condenser of the steam turbine is heated by the low-pressure regenerative heater and the high-pressure regenerative heater and then enters the boiler for heating. The heated steam enters the high-pressure cylinder to do work, and the steam coming out of the high-pressure cylinder enters the boiler for heating again after doing work. Part of the steam after reheating enters the molten salt thermal energy storage system for heating, and part of it enters the intermediate pressure cylinder and the low pressure cylinder in sequence to do work. The exhausted steam after doing work returns to the condenser for condensation to start the next cycle; Peak period: Deactivate the high-pressure regenerative heaters and stop extracting the main steam, reheated steam and extraction steam from the exhaust of the intermediate pressure cylinder; The working medium water coming out of the condenser of the steam turbine unit is heated by the low-pressure regenerative heaters and the hot molten salt of the molten salt thermal energy storage system and then enters the boiler for heating; The heated steam enters the high-pressure cylinder to do work. After the steam coming out of the high-pressure cylinder does work, it enters the boiler for heating again. Part of the steam after reheating enters the molten salt thermal energy storage system for heating, and part of it enters the intermediate pressure cylinder and the low pressure cylinder in sequence to do work. The exhausted steam after doing work returns to the condenser for condensation to start the next cycle.

Images