Fused salt coupling heat storage and release system and method integrated on thermal power generating unit

Abstract

The invention discloses a fused salt coupling heat storage and release system and method integrated to a thermal power generating unit, the thermal power generating unit comprises a boiler and a steam turbine, and the system comprises a fused salt heat storage subsystem configured to absorb and store sensible heat of main steam and reheat steam of the boiler when the unit stores heat; the water storage tank heat storage subsystem is configured to absorb and store latent heat of reheated steam when the unit stores heat; and the heat source side of the steam generation subsystem is connected to the fused salt heat storage subsystem, and the steam generation subsystem is configured to generate steam through heat stored by fused salt and convey the steam to an inlet of the steam turbine intermediate pressure cylinder when the unit releases heat so as to improve the power of the unit. The molten salt is used for storing sensible heat of main steam and hot reheat steam, the water storage tank is used for storing latent heat of reheat steam, cascade heat storage is achieved, steam-water working media circulate in the boiler and the heat storage system in the heat storage process and are prevented from entering a steam turbine condenser, cold end loss is reduced, and heat storage efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of thermal power plant power generation technology, specifically to a molten salt coupled heat storage and release system and method integrated into a thermal power unit. Background Technology

[0002] With the continuous advancement of the national electricity spot market, more and more provinces are experiencing prolonged periods of zero or even negative electricity prices, necessitating deep adjustments by coal-fired power units to achieve zero output. Currently, the main technical approaches to achieving zero output for these units can be categorized into two types: First, electrochemical energy storage technology, where the unit maintains a minimum load, storing excess electricity generated by the generator in batteries. This technology suffers from issues such as poor battery safety, short lifespan, high cost, and low energy conversion efficiency. Second, thermal energy storage technology, which stores steam generated by the boiler by adding heat exchangers or thermal storage equipment. With the turbine shut down and the boiler operating at minimum load, the generator is disconnected from the grid after shutdown. However, this cannot respond to the grid's rapid load increase demands, requiring turbine restart and generator reconnection before resuming normal operation, significantly impacting the unit's flexibility.

[0003] Meanwhile, when renewable energy sources such as photovoltaics and wind power are insufficient, coal-fired power units play a crucial role in ensuring energy supply and need to be rapidly upgraded to high-load operation. This places higher demands on the load ramp-up rate of these units. Traditional methods of modifying the unit itself to increase the load ramp-up rate are no longer sufficient to meet these requirements. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a molten salt coupled heat storage and release system and method integrated into a thermal power unit, which aims to overcome at least one related technical problem existing in the background art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A molten salt coupled heat storage and release system integrated into a thermal power unit, the thermal power unit including a boiler and a steam turbine, the system comprising: The molten salt thermal storage subsystem is configured to absorb and store the sensible heat of the boiler main steam and reheat steam during unit thermal storage. The water storage tank thermal storage subsystem is configured to absorb and store the latent heat of reheat steam during unit thermal storage. The steam generation subsystem, whose heat source side is connected to the molten salt thermal storage subsystem, is configured to generate steam using the heat stored in the molten salt when the unit releases heat, and deliver it to the inlet of the intermediate pressure cylinder of the steam turbine to increase the unit power.

[0006] In order to achieve the ability to rapidly increase load while achieving zero unit output and improve overall energy utilization efficiency, this invention sets up a coupled system consisting of a molten salt thermal storage subsystem, a water tank thermal storage subsystem, and a steam generation subsystem.

[0007] During the heat storage phase, the molten salt heat storage subsystem is connected to the boiler's main steam and reheat steam pipelines to absorb the sensible heat of the high-grade steam; the water tank heat storage subsystem is connected to the reheat steam pipeline to absorb its latent heat. During the heat release phase, the steam generation subsystem obtains heat from the molten salt heat storage subsystem, its feedwater is taken from the unit's feedwater system, and the generated steam is finally connected to the inlet of the turbine's intermediate pressure cylinder.

[0008] This coupled design enables cascaded energy storage, including molten salt for high-temperature sensible heat and water tanks for intermediate-temperature latent heat, significantly reducing cold-end losses caused by direct steam discharge into the condenser in traditional thermal storage methods. Simultaneously, by injecting additional steam into the intermediate-pressure cylinder during load increases, the slow load-in process of the boiler is bypassed, thus achieving a rapid response from zero output to high load.

[0009] To specifically achieve the recovery of sensible heat from main steam and reheat steam using molten salt, in one optional embodiment, the molten salt thermal storage subsystem includes: a main steam thermal storage heat exchanger connected between the main steam outlet and the cold re-inlet of the boiler, used to store the sensible heat of the main steam; a reheat steam thermal storage heat exchanger connected downstream of the reheat steam outlet of the boiler, used to store the sensible heat of the reheat steam; a low-temperature molten salt storage tank, a high-temperature molten salt storage tank, and connecting pipelines for the storage and circulation of the molten salt medium. This structure clearly defines the separate recovery paths for the heat of the two types of high-grade steam, resulting in a clear system flow that facilitates control and energy management.

[0010] Under certain operating conditions, it may be considered to introduce the main steam and reheat steam into a combined heat exchanger for heat storage, but it is more beneficial to set up two separate heat exchangers to cope with different steam parameters and ensure system stability.

[0011] To address the issue that the main steam's temperature and pressure remain high after heat storage, and its direct return to the boiler's cold reheat pipeline could jeopardize the boiler's reheater safety, in one optional embodiment, a de-cooling and pressure-reducing device is installed at the hot-side outlet of the main steam heat storage exchanger. This device is directly connected to the outlet pipeline of the main steam heat storage exchanger, and it sprays water to cool the main steam after heat exchange, throttling and reducing its pressure to ensure that its parameters meet the safety requirements of the boiler's cold reheat inlet.

[0012] To specifically achieve the desuperheating and pressure reduction function, in one optional embodiment, the desuperheating and pressure reduction device includes a water spray desuperheater and a pressure regulating valve. The pressure regulating valve first throttles and reduces the pressure of the steam, and then the water spray desuperheater sprays atomized water into the steam, using the heat absorption of water vaporization to reduce the steam temperature.

[0013] To recover the latent heat of reheat steam and avoid working fluid loss, in one optional embodiment, the water storage tank heat storage subsystem includes: a steam-water heat exchanger, whose hot-side inlet is connected to the boiler reheat steam pipeline (usually after the reheat steam heat storage heat exchanger), for storing the latent heat of reheat steam; a low-temperature water storage tank, a high-temperature water storage tank, and connecting pipelines for storing and circulating the water medium. This system stores the condensation heat of steam in water while simultaneously recovering the condensate, achieving efficient dual utilization of thermal energy and working fluid.

[0014] Specifically, the hot-side inlet of the steam-water heat exchanger is connected to the boiler reheat steam pipeline (usually after the reheat steam storage heat exchanger), while the cold side is connected to the low-temperature and high-temperature water storage tanks via a water pump. Steam condenses and releases heat within the heat exchanger, heating the water from the low-temperature storage tank; the hot water is then stored in the high-temperature storage tank.

[0015] To further improve power generation efficiency during stable load operation of the unit, in one optional embodiment, the water storage tank thermal storage subsystem further includes a water-to-water heat exchanger. The hot side of the water-to-water heat exchanger is connected between the high-temperature water storage tank and the low-temperature water storage tank, and its cold side is connected to the pipeline between the unit's condensate pump and the deaerator, for heating the condensate during the stable load phase.

[0016] High-temperature water flows out of the high-temperature storage tank, heats the condensate from the condensate pump through a water-to-water heat exchanger, cools down, and returns to the low-temperature storage tank. The heated condensate is then incorporated into the deaerator inlet.

[0017] This process is equivalent to replacing part of the steam extraction from the low-pressure heater with the stored heat, allowing more steam to expand and do work in the low-pressure cylinder of the turbine, thereby increasing the unit's power generation and efficiency without changing fuel consumption.

[0018] To avoid the loss of working fluid and heat during the heat storage process, in one optional embodiment, the hot-side outlet of the steam-water heat exchanger is connected to the boiler's feedwater system, so that the condensate formed after the steam releases heat during the heat storage step is returned to the boiler for circulation.

[0019] The condensate formed after steam condenses in the steam-water heat exchanger is transported back to the boiler's feedwater system, such as the deaerator or the inlet of the boiler economizer, through pipelines to re-enter the thermal cycle.

[0020] This system achieves a closed-loop circulation of steam and water working fluid during the thermal storage process, avoiding waste of the working fluid. At the same time, it brings the low-temperature heat contained in the condensate back to the system, further reducing cold-end losses and improving thermal storage efficiency.

[0021] In order to efficiently produce compliant steam using molten salt, in one alternative embodiment, the steam generation subsystem includes a feedwater preheater, an evaporator, a steam drum, and a superheater, which are connected in sequence; a circulation loop exists between the steam drum and the evaporator.

[0022] The feedwater is first preheated by steam extracted from the turbine in the feedwater preheater, and then enters the evaporator where it is heated by high-temperature molten salt to produce a steam-water mixture. The mixture is separated into steam and water in the steam drum. The saturated water is recycled back to the evaporator, and the saturated steam enters the superheater where it is further heated by molten salt to become superheated steam.

[0023] In order to achieve zero on-grid power while maintaining rapid start-up capability, in an optional embodiment, the system is configured such that when the unit is operating at zero output, the boiler maintains the minimum stable combustion load, the high-pressure cylinder of the turbine does not receive steam, and the molten salt thermal storage subsystem and the water storage tank thermal storage subsystem are put into operation to store the heat generated by the boiler.

[0024] In this configuration, the boiler remains in a continuous operation, but the energy generated is not used for power generation and grid connection; instead, the vast majority is stored in the thermal storage system. The remaining small portion of energy is used by the turbine's intermediate and low-pressure cylinders to maintain the power required for plant maintenance, and the generator remains connected to the grid.

[0025] This is the core of achieving "zero output" rather than "shutdown". It solves the problem of not being able to respond quickly after a shutdown, enabling the unit to have the ability to quickly increase load within minutes at any time.

[0026] Embodiments of this application also provide a molten salt coupled heat storage and release method integrated into a thermal power unit, employing any of the molten salt coupled heat storage and release systems described in any one of the claims, and including the following steps: Thermal storage steps: When the electricity spot market has zero or negative electricity prices and the generating unit needs to maintain zero output to the grid, perform the following operations: a) Guide all the main steam generated by the boiler to flow through the molten salt thermal storage subsystem, and store its sensible heat in the molten salt; b) Guide part of the reheat steam generated by the boiler to flow through the molten salt thermal storage subsystem, and store its sensible heat in the molten salt; c) Guide the reheated steam after heat exchange in step b) to flow through the water storage tank heat storage subsystem, and store its latent heat in the water in the water storage tank; At the same time, steam is prevented from entering the high-pressure cylinder of the steam turbine, so that the intermediate-pressure cylinder and the low-pressure cylinder can maintain the operation of the plant power supply. Heat release procedure: When the power grid requires the unit to rapidly increase load, perform the following operations: d) Guide feedwater into the steam generation subsystem and use the heat stored in the molten salt thermal storage subsystem to heat the feedwater and generate steam; e) The steam generated in step d) is transported and fed into the inlet of the intermediate pressure cylinder of the steam turbine, where it is mixed with reheat steam to perform work together, thereby increasing the unit's power generation load.

[0027] The beneficial effects that the molten salt coupled heat storage and release system and method integrated into a thermal power unit disclosed in this application may bring include, but are not limited to: 1. It achieves cascaded energy storage and efficient utilization, and significantly improves the system's thermal storage efficiency.

[0028] Through an innovative coupling design, the sensible heat of the main steam and reheat steam is stored in a molten salt thermal storage subsystem, while the latent heat of the reheat steam is stored in a water tank thermal storage subsystem. This achieves "temperature-matched, tiered utilization" of the high-grade steam energy at the boiler outlet. More importantly, throughout the entire thermal storage process, the steam-water working fluid forms a closed-loop cycle within the boiler and thermal storage system, effectively preventing cold-end losses caused by high-grade energy entering the turbine condenser, fundamentally improving the energy efficiency of the thermal storage process.

[0029] 2. It achieves the unification of "zero-output" grid connection and "rapid response" capability of the unit, improving the flexibility of the unit.

[0030] This invention, through system configuration and operational optimization, enables the unit to operate with only auxiliary power while maintaining the boiler's minimum stable combustion load and preventing steam from entering the turbine's high-pressure cylinder. This achieves safe and stable zero-output grid connection. During this operation, the generator remains connected to the grid, and both the boiler and turbine are in hot standby mode. This solves the problems of traditional thermal energy storage technologies, which require shutdown and cannot quickly respond to loads. It allows the unit to rapidly increase load within minutes when the grid demands it, achieving a perfect combination of the two key flexibility indicators: deep peak shaving and rapid ramp-up.

[0031] 3. This invention provides a rapid load-increasing capability independent of the boiler body, significantly improving the unit's load-increasing rate. During the load-increasing phase, the invention utilizes stored high-temperature molten salt to rapidly generate superheated steam through the steam generation subsystem, which is then directly fed into the intermediate-pressure cylinder inlet of the turbine, instantly increasing the steam intake and power output of the intermediate-pressure cylinder. This method bypasses the slow, inertial processes of boiler combustion and heat transfer, providing the unit with an additional rapid "power channel."

[0032] 4. It improved the economic efficiency of the unit under stable load and achieved effective energy conversion.

[0033] When the unit is operating at a stable high load, the system can use the water-to-water heat exchanger in the thermal storage subsystem of the water storage tank to heat the condensate at the turbine outlet. The heated condensate is then fed into the deaerator inlet, thereby reducing the amount of steam extracted from the low-pressure heater group. This saved extracted steam will continue to expand and do work in the low-pressure cylinders of the turbine, increasing the unit's net output power and power generation efficiency while maintaining the same fuel consumption, thus increasing power generation and further improving the system's overall life-cycle economics.

[0034] 5. The system has a high degree of integration, is safe and reliable, and has wide applicability.

[0035] The system described in this invention is closely coupled with existing thermal power units, and most of the equipment is mainstream thermal power equipment with mature technology. By setting up desuperheating and pressure reducing devices, the safety of the main steam returning to the boiler reheat system after heat storage is ensured. This system is not only suitable for newly built units, but also for the flexible retrofitting of existing units, providing an effective technical path for the transformation of traditional thermal power units into reliable, supportive, and peak-shaving power sources. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the process of the molten salt coupled heat storage and release system described in some embodiments of the present invention under heat storage conditions. Figure 2 This is a schematic diagram of the process of the molten salt coupled heat storage and release system described in some embodiments of the present invention under the condition of increased load heat release. Figure 3 This is a schematic diagram of the molten salt coupled heat storage and release system under steady-state heat release conditions as described in some embodiments of the present invention. Figure 4 This is a schematic diagram illustrating the increase in unit load rate according to some embodiments of the present invention. Detailed Implementation

[0037] Various exemplary embodiments, features, and aspects of this application will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0038] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an indirect connection through an intermediate medium, or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0039] Figure 1 This is a schematic diagram of the process of a molten salt coupled heat storage and release system under heat storage conditions, as shown in some embodiments of the present invention. Figure 2This is a schematic diagram of the process of a molten salt coupled heat storage and release system under increased load heat release conditions, as shown in some embodiments of the present invention. Figure 3 This is a schematic diagram of the molten salt coupled heat storage and release system under steady-state heat release conditions, as shown in some embodiments of the present invention. Figure 4 This is a schematic diagram of the load increase rate of the coupling system shown in some embodiments of the present invention.

[0040] like Figures 1 to 3 As shown, the molten salt coupled heat storage and release system described in this embodiment of the invention is integrated into a thermal power unit. The thermal power unit includes a boiler 1, a steam turbine 2 (including a high-pressure cylinder 2.1, an intermediate-pressure cylinder 2.2, and a low-pressure cylinder 2.3), a condenser 3, a condensate pump 4, a low-pressure heater group 5, a deaerator 6, a feedwater pump 7, and a high-pressure heater group 8.

[0041] The molten salt coupled heat storage and release system mainly includes a molten salt heat storage subsystem, a water tank heat storage subsystem, and a steam generation subsystem.

[0042] The molten salt thermal storage subsystem includes a main steam thermal storage heat exchanger 9, a reheat steam thermal storage heat exchanger 10, a cryogenic molten salt storage tank 21, a cryogenic molten salt pump 22, a high-temperature molten salt storage tank 23, and connecting pipelines. The main steam thermal storage heat exchanger 9 is connected to the pipeline between the main steam outlet of boiler 1 and the cold reheat inlet of boiler 1. The reheat steam thermal storage heat exchanger 10 is connected to the pipeline downstream of the reheat steam outlet of boiler 1. A desuperheating and pressure reducing device (not shown separately in the figure) is installed on the hot-side outlet pipeline of the main steam thermal storage heat exchanger 9. The cryogenic molten salt storage tank 21 is connected to the cold-side inlets of the main steam thermal storage heat exchanger 9 and the reheat steam thermal storage heat exchanger 10 via the cryogenic molten salt pump 22. The cold-side outlets of the main steam thermal storage heat exchanger 9 and the reheat steam thermal storage heat exchanger 10 are connected to the high-temperature molten salt storage tank 23.

[0043] The water storage tank heat storage subsystem includes a steam-water heat exchanger 11, a water-to-water heat exchanger 12, a low-temperature water storage tank 13, a low-temperature water pump 14, a high-temperature water storage tank 15, a high-temperature water pump 16, and connecting pipelines. The hot-side inlet of the steam-water heat exchanger 11 is connected to the hot-side outlet pipe of the reheat steam heat storage heat exchanger 10. The hot-side outlet of the steam-water heat exchanger 11 is connected to the feedwater system of boiler 1. The low-temperature water storage tank 13 is connected to the cold-side inlet of the steam-water heat exchanger 11 via the low-temperature water pump 14, and the cold-side outlet of the steam-water heat exchanger 11 is connected to the high-temperature water storage tank 15. The hot-side inlet of the water-to-water heat exchanger 12 is connected to the high-temperature water storage tank 15 via the high-temperature water pump 16, and its hot-side outlet is connected to the low-temperature water storage tank 13. The cold side of the water-to-water heat exchanger 12 is connected to the condensate pipeline between the condensate pump 4 and the deaerator 6.

[0044] The steam generation subsystem includes a feedwater preheater 17, an evaporator 18, a steam drum 19, and a superheater 20. The feedwater inlet of the feedwater preheater 17 is connected to the inlet feedwater pipe of the high-pressure heater group 8, and its steam outlet merges with the reheat steam pipe at the inlet of the intermediate-pressure cylinder 2.2. The heat source side of the feedwater preheater 17 is connected to a section of extraction steam from the turbine 2. The hot-side outlet of the superheater 20 is connected to the hot-side inlet of the evaporator 18. The hot-side inlet of the superheater 20 is connected to the high-temperature molten salt storage tank 23 via a high-temperature molten salt pump 24, and the hot-side outlet of the evaporator 18 is connected to the low-temperature molten salt storage tank 21.

[0045] The specific steps for installing and running the system are as follows: Thermal storage process (corresponding to) Figure 1 ): When there is a zero or negative electricity price in the spot electricity market, and the generating unit needs to achieve zero output to the grid, thermal storage operation is performed.

[0046] First, the unit's operating status is adjusted to maintain boiler 1 at the minimum stable combustion load, and steam is prevented from entering the high-pressure cylinder 2.1 of the turbine. The exhaust steam discharged from the intermediate-pressure cylinder 2.2 and low-pressure cylinder 2.3 of the turbine enters the condenser 3 and is condensed into water, which is then pumped out by the condensate pump 4. After being heated by the low-pressure heater group 5, it enters the deaerator 6 for deoxygenation. The deaerated feedwater is pressurized by the feedwater pump 7, heated by the high-pressure heater group 8, and then returned to boiler 1.

[0047] Next, the cryogenic molten salt pump 22 is started, pumping the cryogenic molten salt from the cryogenic molten salt storage tank 21, which then flows through the main steam heat exchanger 9 and the reheat steam heat exchanger 10. All the main steam generated by boiler 1 is introduced into the main steam heat exchanger 9, where its sensible heat is transferred to the molten salt. After heat exchange, the main steam is processed by a desuperheating and pressure reducing device until it reaches safe parameters, and then sent to the cold reheat inlet pipe of boiler 1.

[0048] The reheat steam at the outlet of the boiler 1 reheater is divided into two paths: one path enters the intermediate pressure cylinder 2.2 and low pressure cylinder 2.3 of the steam turbine to do work, which just meets the power demand of the plant; the other path enters the reheat steam heat exchanger 10 to transfer its sensible heat to the molten salt.

[0049] After heat exchange in the reheat steam storage heat exchanger 10, part of the reheat steam is led to the high-pressure heater group 8 and the deaerator 6; the remainder enters the steam-water heat exchanger 11, where its latent heat is transferred to the water medium, and after condensing into water, it returns to the feedwater system of the boiler 1.

[0050] Low-temperature water is pumped out from low-temperature storage tank 13, flows through steam-water heat exchanger 11 to absorb heat and becomes high-temperature water, which is then stored in high-temperature storage tank 15. The molten salt, after absorbing heat, becomes high-temperature molten salt and is stored in high-temperature molten salt storage tank 23. This completes the system's heat storage process, enabling the unit to achieve zero-output grid connection without stopping the boiler and turbine.

[0051] Rapid load increase and heat release process (corresponding to) Figure 2 ): When the power grid requires the unit to rapidly increase the load, a rapid heat release operation is performed.

[0052] First, start the high-temperature molten salt pump 24 to pump the high-temperature molten salt out of the high-temperature molten salt storage tank 23, and let it flow through the heater 20 and the evaporator 18 in sequence.

[0053] Simultaneously, feedwater is drawn from the inlet of the high-pressure heater group 8 and first enters the feedwater preheater 17, where it is preheated using a section of extracted steam from the turbine 2. It then enters the evaporator 18 in a near-saturated state and is heated by molten salt to produce saturated steam. The steam-water mixture undergoes steam-water separation in the steam drum 19. The saturated water is returned to the evaporator 18 for circulation, while the saturated steam enters the superheater 20 and is heated by molten salt to become superheated steam.

[0054] The generated superheated steam is transported to the inlet of the intermediate-pressure cylinder 2.2 of the steam turbine, where it mixes with the reheated steam from the boiler to perform work together, instantly increasing the turbine's intake air volume and power output, thereby achieving a rapid increase in unit load. The main system's steam-water circulation (condenser 3 - condensate pump 4 - low-pressure heater group 5 - deaerator 6 - feedwater pump 7 - high-pressure heater group 8 - boiler 1) operates continuously to support the boiler's load increase. The molten salt, after releasing heat, becomes cryogenic molten salt and returns to the cryogenic molten salt storage tank 21.

[0055] The specific implementation methods for increasing the load rate are as follows: Figure 4 As shown: Figure 4 Taking the increase of unit load from 70% THA to 100% THA as an example, the effect of the present invention on the rate of load increase is intuitively demonstrated.

[0056] The horizontal axis of the graph represents time, and the vertical axis represents the percentage of unit load. Assuming the original unit's load increase rate is 3% THA / min, it will take 10 minutes to increase the load from 70% THA to 100% THA.

[0057] After applying this invention, during the initial load increase phase, the boiler body continues to increase its load at a rate of 3% THA / min, while the molten salt heat release system (steam generation subsystem) is simultaneously put into operation, instantly providing an additional load increase capacity equivalent to 3% THA / min. Therefore, the total load increase rate of the coupled system reaches 6% THA / min.

[0058] Within 5 minutes, the total load of the coupled system reached 100% THA, achieving the goal of rapid load increase. During the period from 5 to 10 minutes, the boiler continued to increase its load at a rate of 3% THA / min, while the molten salt system decreased its load at a rate of 3% THA / min, until it completely shut down at the 10-minute mark, with the boiler alone bearing 100% THA load. In this way, the time for the unit to reach the target load was reduced from 10 minutes to 5 minutes, significantly improving the unit's load increase rate and the grid's rapid response capability.

[0059] Steady-state exothermic process (corresponding to) Figure 3 ): When the unit is operating at a stable high load, steady-state heat release can be carried out to improve efficiency.

[0060] The high-temperature water pump 16 is started, pumping high-temperature water from the high-temperature storage tank 15 into the hot side of the water-to-water heat exchanger 12. Low-temperature condensate from the condensate pump 4 flows through the cold side of the water-to-water heat exchanger 12, where it is heated by the high-temperature water. The heated condensate is directly (or indirectly) incorporated into the inlet of the deaerator 6, thereby reducing the amount of steam extracted from the low-pressure heater group 5. This saved steam will continue to expand and do work in the low-pressure cylinder 2.3 of the turbine, increasing power generation. The water, after releasing heat and cooling, becomes low-temperature water and returns to the low-temperature storage tank 13, completing the cycle.

[0061] By operating the system using the above methods, the unit can achieve zero output and energy storage during periods of zero electricity price, respond quickly when load demand surges, and improve efficiency during stable operation, thus comprehensively enhancing the flexibility and economy of thermal power units.

[0062] By operating the system using the above methods, the unit can achieve zero output and energy storage during periods of zero electricity price, respond quickly when load demand surges, and improve efficiency during stable operation, thus comprehensively enhancing the flexibility and economy of thermal power units.

[0063] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A molten salt coupled heat storage and release system integrated into a thermal power unit, the thermal power unit comprising a boiler and a steam turbine, characterized in that, The system includes: The molten salt thermal storage subsystem is configured to absorb and store the sensible heat of the boiler main steam and reheat steam during unit thermal storage. The water storage tank thermal storage subsystem is configured to absorb and store the latent heat of reheat steam during unit thermal storage. The steam generation subsystem, whose heat source side is connected to the molten salt thermal storage subsystem, is configured to generate steam using the heat stored in the molten salt when the unit releases heat, and deliver it to the inlet of the intermediate pressure cylinder of the steam turbine to increase the unit power.

2. The system according to claim 1, characterized in that, The molten salt thermal storage subsystem includes: The main steam heat storage heat exchanger is connected between the main steam outlet of the boiler and the cold re-inlet of the boiler, and is used to store the sensible heat of the main steam. A reheat steam heat exchanger is connected downstream of the boiler's reheat steam outlet and is used to store the sensible heat of the reheat steam. Low-temperature molten salt storage tanks, high-temperature molten salt storage tanks and connecting pipelines are used for the storage and circulation of molten salt media.

3. The system according to claim 2, characterized in that, The hot-side outlet of the main steam storage heat exchanger is equipped with a de-temperature and pressure reducing device.

4. The system according to claim 3, characterized in that, The de-heating and pressure-reducing device includes a water spray de-heater and a pressure regulating valve.

5. The system according to claim 1, characterized in that, The water storage tank thermal storage subsystem includes: A steam-water heat exchanger, whose hot-side inlet is connected to the boiler reheat steam pipeline, is used to store the latent heat of the reheat steam. Low-temperature water storage tanks, high-temperature water storage tanks, and connecting pipelines are used for the storage and circulation of water media.

6. The system according to claim 5, characterized in that, The water storage tank heat storage subsystem also includes a water-to-water heat exchanger. The hot side of the water-to-water heat exchanger is connected between the high-temperature water storage tank and the low-temperature water storage tank, and its cold side is connected to the pipeline between the unit's condensate pump and the deaerator, which is used to heat the condensate during the stable load phase.

7. The system according to claim 5, characterized in that, The hot-side outlet of the steam-water heat exchanger is connected to the boiler's feedwater system, so that the condensate formed after the steam releases heat during the heat storage step is returned to the boiler for circulation.

8. The system according to claim 1, characterized in that, The steam generation subsystem includes a feedwater preheater, an evaporator, a steam drum, and a superheater, which are connected in sequence; there is a circulation loop between the steam drum and the evaporator.

9. The system according to claim 1, characterized in that, The system is configured such that when the unit is operating at zero output, the boiler maintains the minimum stable combustion load, the high-pressure cylinder of the steam turbine does not receive steam, and the molten salt thermal storage subsystem and the water tank thermal storage subsystem are put into operation to store the heat generated by the boiler.

10. A molten salt coupled heat storage and release method integrated into a thermal power unit, characterized in that, The molten salt coupled heat storage and release system as described in any one of claims 1-9 includes the following steps: Thermal storage steps: When the electricity spot market has zero or negative electricity prices and the generating unit needs to maintain zero output to the grid, perform the following operations: a) Guide all the main steam generated by the boiler to flow through the molten salt thermal storage subsystem, and store its sensible heat in the molten salt; b) Guide part of the reheat steam generated by the boiler to flow through the molten salt thermal storage subsystem, and store its sensible heat in the molten salt; c) Guide the reheated steam after heat exchange in step b) to flow through the water storage tank heat storage subsystem, and store its latent heat in the water in the water storage tank; At the same time, steam is prevented from entering the high-pressure cylinder of the steam turbine, so that the intermediate-pressure cylinder and the low-pressure cylinder can maintain the operation of the plant power supply. Heat release procedure: When the power grid requires the unit to rapidly increase load, perform the following operations: d) Guide feedwater into the steam generation subsystem and use the heat stored in the molten salt thermal storage subsystem to heat the feedwater and generate steam; e) The steam generated in step d) is transported and fed into the inlet of the intermediate pressure cylinder of the steam turbine, where it is mixed with reheat steam to perform work together, thereby increasing the unit's power generation load.

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