Molten salt heat storage system with front steam turbine and operation method of molten salt heat storage system

Abstract

The invention discloses a fused salt heat storage system with a front steam turbine and an operation method of the fused salt heat storage system, and belongs to the technical field of coal-fired power generation. The exhaust steam of the front steam turbine is heated through bypass reheat steam, so that the outlet steam temperature of the high-pressure cylinder of the steam turbine is within a reasonable range, threat to safe operation of the high-pressure cylinder is avoided, and meanwhile energy outside the system does not need to be consumed; meanwhile, bypass reheat steam after steam exhaust of the front steam turbine is heated is used for further heating the fused salt for heat storage, on the basis that the minimum heat load of a boiler of the coal-fired power generation system is maintained, the minimum electric load rate of the coal-fired power generation system is reduced, and renewable energy source power consumption of a power grid is promoted; superheated steam generated by the fused salt heat storage system is injected into the front steam turbine to do work outwards for power generation, gradient utilization of energy is achieved, the rapid load changing capacity of the coal-fired power generation system is improved, and the safe and stable operation capacity of the coal-fired power generation system is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of coal-fired power generation, and in particular to a molten salt heat storage system with a front steam turbine and an operation method thereof. Background Art

[0002] Since renewable energy sources such as wind and solar energy are intermittent and volatile, the output of wind and solar power plants has a strong time-varying characteristic. The large-scale grid connection of renewable energy power will pose a huge threat to the safe and stable operation of the power grid. Therefore, traditional coal-fired power generation systems need to utilize their own adjustable characteristics, give full play to their peak-shaving effect, and promote the consumption of renewable power in the power grid.

[0003] However, in the process of deep peak regulation of coal-fired power plants, their operating conditions often deviate from the designed conditions, resulting in reduced power generation efficiency of coal-fired power generation systems and reduced economic efficiency of coal-fired power generation systems. In addition, in order to ensure the safe and stable operation of boilers in coal-fired power generation systems, the minimum power load rate of coal-fired power generation systems is generally 20%~30%, but even so, it is difficult to meet the growing needs of renewable energy. The problem of reduced power generation efficiency of coal-fired power generation systems at low loads can be solved by configuring a pre-installed steam turbine, but the main steam works in the pre-installed steam turbine before entering the high-pressure cylinder, which will cause the outlet steam temperature of the high-pressure cylinder to decrease, threatening the safe operation of the high-pressure cylinder.

[0004] Therefore, how to maintain the outlet steam temperature of the high-pressure cylinder on the basis of reducing the minimum power load rate of the coal-fired power generation system has become a technical problem that the current technical personnel in this field need to solve urgently. Summary of the invention

[0005] The object of the present invention is to provide a molten salt heat storage system with a pre-installed steam turbine and an operation method thereof, so as to overcome the problem in the prior art that the outlet steam temperature of the high-pressure cylinder is reduced due to the pre-installed steam turbine.

[0006] The present invention solves the above technical problems through the following technical solutions: The present invention provides a molten salt heat storage system with a pre-installed steam turbine, comprising a molten salt heat storage system and a coal-fired power generation system coupled therewith, wherein the molten salt heat storage system comprises a pre-installed steam turbine, an auxiliary generator, a steam-steam heat exchanger, a reheat steam-molten salt heat exchanger, a low-temperature molten salt tank, a high-temperature molten salt tank and a feedwater-molten salt heat exchanger; The main steam outlet of the coal-fired power generation system is divided into two routes. The first main steam outlet merges with the steam outlet of the feedwater-molten salt heat exchanger and then connects to the steam inlet of the front steam turbine. The second main steam outlet is connected to the steam inlet of the high-pressure cylinder of the steam turbine of the coal-fired power generation system. The front steam turbine is connected to the auxiliary generator for external power generation. The steam outlet of the front steam turbine is divided into two routes, one of which is connected to the low-temperature side steam inlet of the steam-steam heat exchanger, and the other is connected to the steam inlet of the high-pressure cylinder of the steam turbine. The reheat steam outlet of the coal-fired power generation system is connected to the high-temperature side steam inlet of the steam-steam heat exchanger, the low-temperature side steam outlet of the steam-steam heat exchanger is connected to the steam inlet of the high-pressure cylinder of the steam turbine after merging with the second main steam outlet, and the high-temperature side steam outlet of the steam-steam heat exchanger is connected to the water working medium inlet of the coal-fired power generation system through the water working medium inlet of the reheat steam-molten salt heat exchanger and the water working medium outlet of the reheat steam-molten salt heat exchanger in sequence; the molten salt outlet of the reheat steam-molten salt heat exchanger is connected to the molten salt inlet of the reheat steam-molten salt heat exchanger through the high-temperature molten salt tank, the feed water-molten salt heat exchanger, and the low-temperature molten salt tank in sequence; The boiler feed water of the coal-fired power generation system is connected to the water working medium inlet of the feed water-molten salt heat exchanger.

[0007] A further improvement of the present invention is that it also includes a main steam diverter valve and a first control valve. The first main steam outlet is connected to the steam inlet of the front steam turbine after merging with the steam outlet of the feed water-molten salt heat exchanger through the main steam diverter valve. The low-temperature side steam outlet of the steam-steam heat exchanger is connected to the steam inlet of the turbine high-pressure cylinder after merging with the second main steam outlet through the first control valve.

[0008] A further improvement of the present invention is that it also includes a second control valve and a third control valve, and the steam outlet of the front steam turbine is divided into two paths, one of which is connected to the low-temperature side steam inlet of the steam-steam heat exchanger through the second control valve, and the other is connected to the steam inlet of the coal-fired power generation system through the third control valve.

[0009] A further improvement of the present invention is that it also includes a reheat steam diverter valve, and the reheat steam outlet of the coal-fired power generation system is connected to the high-temperature side steam inlet of the steam-steam heat exchanger through the reheat steam diverter valve.

[0010] A further improvement of the present invention is that the maximum steam diversion flow rate of the reheat steam diverter valve is 28% of the total mass flow rate of the reheat steam.

[0011] A further improvement of the present invention is that it also includes a low-temperature molten salt pump and a high-temperature molten salt pump. The molten salt outlet of the low-temperature molten salt tank is connected to the molten salt inlet of the reheat steam-molten salt heat exchanger via the low-temperature molten salt pump, and the molten salt outlet of the high-temperature molten salt tank is connected to the molten salt inlet of the feed water-molten salt heat exchanger via the high-temperature molten salt pump.

[0012] A further improvement of the present invention is that it also includes a feed water diverter valve, and the boiler feed water of the coal-fired power generation system is connected to the water working medium inlet of the feed water-molten salt heat exchanger through the feed water diverter valve.

[0013] A further improvement of the present invention is that the steam-steam heat exchanger, the reheat steam-molten salt heat exchanger and the feed water-molten salt heat exchanger are all partition-type heat exchangers.

[0014] A further improvement of the present invention is that the temperature of the steam outlet at the low temperature side of the steam-steam heat exchanger is greater than 500°C, and the temperature range of the molten salt heat storage system is between 120°C and 280°C.

[0015] The present invention also provides a method for operating a molten salt heat storage system with a pre-installed steam turbine, using the molten salt heat storage system with a pre-installed steam turbine as described above; When the coal-fired power generation system is in normal operation, the coal-fired power generation system does not provide main steam and reheat steam to the molten salt heat storage system, and the molten salt heat storage system does not operate; When the coal-fired power generation system is in a low-load operation state, the main steam outlet of the coal-fired power generation system transmits all the main steam to the forward steam turbine through the first main steam outlet, and drives the auxiliary generator to generate power externally through the forward steam turbine, thereby reducing the throttling loss of the main steam; the reheat steam outlet of the coal-fired power generation system transmits reheat steam to the steam-steam heat exchanger, and the exhaust steam of the forward steam turbine is heated by the reheat steam. The heated exhaust steam heats the low-temperature molten salt in the low-temperature molten salt tank for heat storage, and the reheated steam after heat exchange is transmitted to the high-pressure cylinder of the steam turbine, thereby maintaining the outlet steam temperature of the high-pressure cylinder of the steam turbine; When the coal-fired power generation system is in a high-load operation state, the coal-fired power generation system does not provide main steam to the molten salt heat storage system, but only transmits reheated steam to the steam-steam heat exchanger through the reheated steam outlet, releases the heat stored in the high-temperature molten salt tank, and heats the boiler feed water of the coal-fired power generation system through the feed water-molten salt heat exchanger to generate superheated steam, so that the front steam turbine drives the auxiliary generator to generate power externally, and transmits the exhaust steam of the front steam turbine to the steam inlet of the coal-fired power generation system, thereby improving the load change rate of the coal-fired power generation system.

[0016] Compared with the prior art, the positive and progressive effects of the present invention are: The molten salt heat storage system with a pre-installed steam turbine provided by the present invention utilizes bypass reheat steam to heat the exhaust steam of the pre-installed steam turbine, so that the outlet steam temperature of the high-pressure cylinder of the steam turbine is within a reasonable range, avoiding threats to the safe operation of the high-pressure cylinder, and at the same time, there is no need to consume energy outside the system; at the same time, the bypass reheat steam after heating the exhaust steam of the pre-installed steam turbine is further used to heat the molten salt for heat storage, thereby reducing the minimum electrical load rate of the coal-fired power generation system on the basis of maintaining the minimum thermal load of the boiler of the coal-fired power generation system, and promoting the renewable energy power consumption of the power grid; the superheated steam generated by the molten salt heat storage system is injected into the pre-installed steam turbine for external work and power generation, which not only realizes the cascade utilization of energy, but also improves the rapid load change capability of the coal-fired power generation system, and effectively improves the safe and stable operation capability of the coal-fired power generation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0018] Figure 1 This is a connection diagram of a molten salt heat storage system with a front steam turbine according to the present invention; Among them, boiler-1, turbine high-pressure cylinder-2, turbine intermediate-pressure cylinder-3, turbine low-pressure cylinder-4, generator-5, condenser-6, condensate pump-7, low-pressure heater-8, deaerator-9, feed water pump-10, high-pressure heater-11, main steam diverter valve-12, first control valve-13, front steam turbine-14, auxiliary generator-15, second control valve-16, third control valve-17, reheat steam diverter valve-18, steam-steam heat exchanger-19, reheat steam-molten salt heat exchanger-20, low-temperature molten salt tank-21, low-temperature molten salt pump-22, high-temperature molten salt tank-23, high-temperature molten salt pump-24, feed water-molten salt heat exchanger-25, feed water diverter valve-26. DETAILED DESCRIPTION

[0019] In order to make the purpose, 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 in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0020] 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 invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0022] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0023] In addition, it should be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments, which are intended to explain the present invention rather than to limit it.

[0025] A molten salt heat storage system with a pre-installed steam turbine, comprising a molten salt heat storage system and a coal-fired power generation system coupled thereto, wherein the molten salt heat storage system comprises a pre-installed steam turbine 14, an auxiliary generator 15, a steam-steam heat exchanger 19, a reheated steam-molten salt heat exchanger 20, a low-temperature molten salt tank 21, a high-temperature molten salt tank 23 and a feedwater-molten salt heat exchanger 25; The main steam outlet of the coal-fired power generation system is divided into two routes. The first main steam outlet merges with the steam outlet of the feedwater-molten salt heat exchanger 25 and then connects to the steam inlet of the front steam turbine 14. The second main steam outlet is connected to the steam inlet of the high-pressure cylinder 2 of the steam turbine of the coal-fired power generation system. The front steam turbine 14 is connected to the auxiliary generator 15 for external power generation. The steam outlet of the front steam turbine 14 is divided into two routes, one of which is connected to the low-temperature side steam inlet of the steam-steam heat exchanger 19, and the other is connected to the steam inlet of the high-pressure cylinder 2 of the steam turbine. The reheat steam outlet of the coal-fired power generation system is connected to the high-temperature side steam inlet of the steam-steam heat exchanger 19, and the low-temperature side steam outlet of the steam-steam heat exchanger 19 is connected to the steam inlet of the high-pressure cylinder 2 of the steam turbine after merging with the second main steam outlet. The high-temperature side steam outlet of the steam-steam heat exchanger 19 is connected to the water working medium inlet of the coal-fired power generation system through the water working medium inlet of the reheat steam-molten salt heat exchanger 20 and the water working medium outlet of the reheat steam-molten salt heat exchanger 20 in sequence; the molten salt outlet of the reheat steam-molten salt heat exchanger 20 is connected to the molten salt inlet of the reheat steam-molten salt heat exchanger 20 in sequence through the high-temperature molten salt tank 23, the feed water-molten salt heat exchanger 25, and the low-temperature molten salt tank 21; The boiler feed water of the coal-fired power generation system is connected to the water working medium inlet of the feed water-molten salt heat exchanger 25.

[0026] Specifically, it also includes a main steam diverter valve 12 and a first control valve 13. The first main steam outlet is connected to the steam inlet of the front steam turbine 14 after merging with the steam outlet of the feed water-molten salt heat exchanger 25 through the main steam diverter valve 12. The low-temperature side steam outlet of the steam-steam heat exchanger 19 is connected to the steam inlet of the turbine high-pressure cylinder 2 after merging with the second main steam outlet through the first control valve 13.

[0027] Specifically, it also includes a second control valve 16 and a third control valve 17. The steam outlet of the front steam turbine 14 is divided into two paths. One path is connected to the low-temperature side steam inlet of the steam-steam heat exchanger 19 through the second control valve 16, and the other path is connected to the steam inlet of the coal-fired power generation system through the third control valve 17.

[0028] Specifically, it also includes a reheat steam diverter valve 18 , and the reheat steam outlet of the coal-fired power generation system is connected to the high-temperature side steam inlet of the steam-steam heat exchanger 19 through the reheat steam diverter valve 18 .

[0029] Specifically, the maximum steam diversion flow rate of the reheat steam diversion valve 18 is 28% of the total mass flow rate of the reheat steam.

[0030] Specifically, it also includes a low-temperature molten salt pump 22 and a high-temperature molten salt pump 24. The molten salt outlet of the low-temperature molten salt tank 21 is connected to the molten salt inlet of the reheat steam-molten salt heat exchanger 20 via the low-temperature molten salt pump 22, and the molten salt outlet of the high-temperature molten salt tank 23 is connected to the molten salt inlet of the feed water-molten salt heat exchanger 25 via the high-temperature molten salt pump 24.

[0031] Specifically, it also includes a feed water diverter valve 26 , through which the boiler feed water of the coal-fired power generation system is connected to the water working medium inlet of the feed water-molten salt heat exchanger 25 .

[0032] Specifically, the steam-steam heat exchanger 19, the reheat steam-molten salt heat exchanger 20 and the feed water-molten salt heat exchanger 25 are all partition-type heat exchangers.

[0033] Specifically, the temperature of the steam outlet at the low temperature side of the steam-steam heat exchanger 19 is greater than 500°C, and the temperature range of the molten salt heat storage system is 120°C to 280°C.

[0034] Based on the same inventive concept, the present invention also provides an operating method of a molten salt heat storage system with a pre-installed steam turbine, using the above-mentioned molten salt heat storage system with a pre-installed steam turbine; When the coal-fired power generation system is in normal operation, the coal-fired power generation system does not provide main steam and reheat steam to the molten salt heat storage system, and the molten salt heat storage system does not operate; When the coal-fired power generation system is in a low-load operation state, the main steam outlet of the coal-fired power generation system transmits all the main steam to the forward steam turbine 14 through the first main steam outlet, and drives the auxiliary generator 15 to generate power externally through the forward steam turbine 14, thereby reducing the throttling loss of the main steam; the reheat steam outlet of the coal-fired power generation system transmits reheat steam to the steam-steam heat exchanger 19, and the exhaust steam of the forward steam turbine 14 is heated by the reheat steam. The heated exhaust steam heats the low-temperature molten salt in the low-temperature molten salt tank 21 for heat storage, and the reheated steam after heat exchange is transmitted to the high-pressure cylinder 2 of the steam turbine, thereby maintaining the outlet steam temperature of the high-pressure cylinder 2 of the steam turbine; When the coal-fired power generation system is in a high-load operation state, the coal-fired power generation system does not provide main steam to the molten salt heat storage system, but only transmits reheated steam to the steam-steam heat exchanger 19 through the reheated steam outlet, releases the heat stored in the high-temperature molten salt tank 23, and heats the boiler feed water of the coal-fired power generation system through the feed water-molten salt heat exchanger 25 to generate superheated steam, so that the front steam turbine 14 drives the auxiliary generator 15 to generate power externally, and transmits the exhaust steam of the front steam turbine 14 to the steam inlet of the coal-fired power generation system, thereby improving the load change rate of the coal-fired power generation system.

[0035] Embodiment 1 See also Figure 1A molten salt heat storage system with a pre-installed steam turbine comprises a molten salt heat storage system and a coal-fired power generation system coupled therewith, wherein the coal-fired power generation system comprises a boiler 1, a steam turbine high-pressure cylinder 2, a steam turbine intermediate-pressure cylinder 3, a steam turbine low-pressure cylinder 4, a generator 5, a condenser 6, a condensate pump 7, a low-pressure heater 8, a deaerator 9, a feedwater pump 10 and a high-pressure heater 11; the main steam outlet of the boiler 1 is divided into two paths, one leading to a main steam diverter valve 12, and the other connecting to the steam inlet of the steam turbine high-pressure cylinder 2 after merging with the low-temperature side steam outlet of the steam-steam heat exchanger 19 through a first control valve 13; the steam extraction outlet of the steam turbine high-pressure cylinder 2 is connected to the steam inlet of the high-pressure heater 11, and the steam outlet of the steam turbine high-pressure cylinder 2 is connected to the reheat steam inlet of the boiler 1; the reheat steam outlet of the boiler 1 is divided into two paths, one leading to the reheat steam diverter valve 18, and the other connecting to the steam inlet of the steam turbine intermediate-pressure cylinder 3; the steam turbine intermediate-pressure cylinder 3 The steam extraction outlet is connected to the steam inlet of the deaerator 9, and the steam outlet of the intermediate pressure cylinder 3 of the steam turbine is connected to the steam inlet of the low pressure cylinder 4 of the steam turbine; the steam extraction outlet of the low pressure cylinder 4 of the steam turbine is connected to the steam inlet of the low pressure heater 8, and the steam outlet of the low pressure cylinder 4 of the steam turbine is connected to the steam inlet of the condenser 6; the water working medium outlet of the condenser 6 is connected to the water working medium inlet of the low pressure heater 8 through the condensate pump 7; the water working medium outlet of the low pressure heater 8 is connected to the water working medium inlet of the deaerator 9; the water working medium outlet of the deaerator 9 is connected to the water working medium inlet of the feed water pump 10; the water working medium outlet of the feed water pump 10 is connected to the water working medium inlet of the high pressure heater 11; the water working medium outlet of the high pressure heater 11 is divided into two paths, one leading to the feed water diverter valve 26, and the other connected to the feed water inlet of the boiler 1; the high pressure cylinder 2 of the steam turbine, the intermediate pressure cylinder 3 of the steam turbine and the low pressure cylinder 4 of the steam turbine are connected through a rotating shaft, and jointly drive the main generator 5 to output electrical power to the outside; The molten salt heat storage system includes a main steam diverter valve 12, a first control valve 13, a pre-steam turbine 14, an auxiliary generator 15, a second control valve 16, a third control valve 17, a reheat steam diverter valve 18, a steam-steam heat exchanger 19, a reheat steam-molten salt heat exchanger 20, a low-temperature molten salt tank 21, a low-temperature molten salt pump 22, a high-temperature molten salt tank 23, a high-temperature molten salt pump 24, a feed water-molten salt heat exchanger 25 and a feed water diverter valve 26; part of the main steam diverted by the main steam diverter valve 12 merges with the steam outlet working medium from the feed water-molten salt heat exchanger 25 and enters the steam inlet of the pre-steam turbine 14 together; the pre-steam turbine 14 drives the auxiliary generator 15 to generate electricity externally; the steam outlet of the pre-steam turbine 14 is divided into two paths, one of which passes through the second control valve 16 and the low-temperature side steam inlet of the steam-steam heat exchanger 19 The first control valve 13 is connected to the steam inlet of the condenser 6, and the other is connected to the steam inlet of the condenser 6 through the third control valve 17; part of the reheated steam diverted by the reheated steam diverter valve 18 enters the high-temperature side steam inlet of the steam-steam heat exchanger 19; the low-temperature side steam outlet of the steam-steam heat exchanger 19 merges with the main steam after the first control valve 13 and enters the steam inlet of the turbine high-pressure cylinder 2 together, and the high-temperature side steam outlet of the steam-steam heat exchanger 19 is connected to the water side working medium inlet of the reheated steam-molten salt heat exchanger 20; the molten salt outlet of the low-temperature molten salt tank 21 is connected to the molten salt inlet of the reheated steam-molten salt heat exchanger 20 through the low-temperature molten salt pump 22; the molten salt outlet of the reheated steam-molten salt heat exchanger 20 is connected to the molten salt inlet of the high-temperature molten salt tank 23; the water working medium outlet of the reheated steam-molten salt heat exchanger 20 is merged into the water working medium inlet of the deaerator 9; Part of the boiler feed water diverted by the feed water diverter valve 26 is connected to the water working medium inlet of the feed water-molten salt heat exchanger 25; the water working medium outlet of the feed water-molten salt heat exchanger 25 is merged with the main steam after the main steam diverter valve 12 and then merged into the steam inlet of the front steam turbine 14; the molten salt outlet of the high-temperature molten salt tank 23 is connected to the molten salt inlet of the feed water-molten salt heat exchanger 25 through the high-temperature molten salt pump 24; the molten salt outlet of the feed water-molten salt heat exchanger 25 is connected to the molten salt inlet of the low-temperature molten salt tank 21.

[0036] Embodiment 2 An operating method of a molten salt heat storage system with a pre-mounted steam turbine, using the molten salt heat storage system with a pre-mounted steam turbine described in Example 1, is as follows: When the coal-fired power generation system is in normal operation, the main steam diverter valve 12, the second control valve 16, the third control valve 17 and the reheat steam diverter valve 18 are all in the closed state, the first control valve 13 is fully opened, and the molten salt heat storage system and the front steam turbine are not in operation; When the coal-fired power generation system is in a low-load operation state, the main steam diverter valve 12, the second control valve 16 and the reheat steam diverter valve 18 are opened, the first control valve 13 and the third control valve 17 are closed, and the low-temperature molten salt pump 22 is started. First, the pre-turbine 14 is used to work to reduce the throttling loss of the main steam, and then the pre-turbine 14 exhaust steam is heated by diverting the reheat steam to increase the inlet steam temperature of the turbine high-pressure cylinder 2, thereby reducing the adverse effect of the low exhaust temperature of the turbine high-pressure cylinder 2 on the safe and stable operation of the coal-fired power generation system. Finally, the heating The reheated steam (bypass steam) flowing through the reheated steam diverter valve 18 after the exhaust steam of the front steam turbine 14 further heats the low-temperature molten salt in the low-temperature molten salt tank 21, thereby reducing the output power load rate of the coal-fired power generation system. The operation goal of the system at this stage is: on the basis of maintaining the minimum heat load of the boiler of the coal-fired power generation system, the front steam turbine 14 is used to reduce the main steam throttling loss, and at the same time, the diverted reheated steam is used to heat the exhaust steam of the front steam turbine 14 to improve the operation safety of the coal-fired power generation system, and finally the molten salt heat storage system is used to further reduce the minimum power load rate of the coal-fired power generation system; When the coal-fired power generation system is in a high-load operation state, the feed water diverter valve 26, the first control valve 13 and the third control valve 17 are opened, the main steam diverter valve 12, the reheat steam diverter valve 18 and the second control valve 16 are closed, and the high-temperature molten salt pump 24 is started. The heat stored in the molten salt heat storage system is used to heat the bypass boiler feed water in the feed water-molten salt heat exchanger 25, and the superheated steam is injected into the front turbine 14 to generate external power, thereby improving the rapid load change capability of the coal-fired power generation system. The operating goal of the system at this stage is: on the basis of not increasing the thermal load of the coal-fired power generation system boiler, by releasing the heat stored in the molten salt heat storage system, the output power of the coal-fired power generation system is quickly changed, and the load change rate of the coal-fired power generation system is improved.

[0037] Finally, it should be noted that the above-listed embodiments exist only as one or more specific forms of expression of the technical solution of the present invention. Their purpose is to clearly explain the concept, principle and application of the present invention through specific examples, and it is by no means intended to limit the protection scope of the present invention to these specific embodiments. In fact, the real value of the present invention lies in the technical ideas and innovations it proposes, rather than its form of expression or means of implementation.

[0038] For ordinary technicians in the relevant technical field, after in-depth reading and understanding of the technical solution of the present invention, they are fully capable of making various forms of changes, modifications or equivalent substitutions to the specific implementation methods of the invention based on their own professional knowledge and skills. These changes may include but are not limited to: adjusting the value range of technical parameters, optimizing algorithm processes to improve efficiency, replacing some technical components to achieve better compatibility or reduce costs, etc. As long as these changed technical solutions still substantially maintain the technical features claimed for protection by the original invention, that is, they can still achieve the core functions and effects of the present invention, then these changes should be deemed to fall within the scope of protection of the pending claims of the present invention.

[0039] In addition, with the continuous progress and development of technology, new technical means and methods continue to emerge, which also provides broad space for further improvement and perfection of the present invention. Therefore, the protection scope of the present invention should also include those reasonably foreseeable improvements and extensions based on the existing technology. As long as these improvements and extensions do not deviate from the basic principles and core concepts of the present invention, they should be regarded as equivalents of the present invention and are also protected by patent rights.

Claims

1. A molten salt heat storage system with a front steam turbine, characterized in that: It comprises a molten salt heat storage system and a coal-fired power generation system coupled thereto, wherein the molten salt heat storage system comprises a front steam turbine (14), an auxiliary generator (15), a steam-steam heat exchanger (19), a reheat steam-molten salt heat exchanger (20), a low-temperature molten salt tank (21), a high-temperature molten salt tank (23) and a feed water-molten salt heat exchanger (25); The main steam outlet of the coal-fired power generation system is divided into two paths, the first main steam outlet merges with the steam outlet of the feed water-molten salt heat exchanger (25) and then connects to the steam inlet of the front steam turbine (14), and the second main steam outlet is connected to the steam inlet of the high-pressure cylinder (2) of the steam turbine of the coal-fired power generation system; the front steam turbine (14) is connected to the auxiliary generator (15) for external power generation; the steam outlet of the front steam turbine (14) is divided into two paths, one of which is connected to the low-temperature side steam inlet of the steam-steam heat exchanger (19), and the other is connected to the steam inlet of the high-pressure cylinder (2) of the steam turbine; The reheat steam outlet of the coal-fired power generation system is connected to the high-temperature side steam inlet of the steam-steam heat exchanger (19); the low-temperature side steam outlet of the steam-steam heat exchanger (19) is connected to the steam inlet of the high-pressure cylinder (2) of the steam turbine after merging with the second main steam outlet; the high-temperature side steam outlet of the steam-steam heat exchanger (19) is connected to the water working medium inlet of the coal-fired power generation system via the water working medium inlet of the reheat steam-molten salt heat exchanger (20) and the water working medium outlet of the reheat steam-molten salt heat exchanger (20); the molten salt outlet of the reheat steam-molten salt heat exchanger (20) is connected to the molten salt inlet of the reheat steam-molten salt heat exchanger (20) via the high-temperature molten salt tank (23), the feed water-molten salt heat exchanger (25), and the low-temperature molten salt tank (21); The boiler feed water of the coal-fired power generation system is connected to the water working medium inlet of the feed water-molten salt heat exchanger (25).

2. A molten salt heat storage system with a pre-installed steam turbine according to claim 1, characterized in that: It also includes a main steam diverter valve (12) and a first control valve (13); the first main steam outlet is connected to the steam inlet of the front steam turbine (14) after merging with the steam outlet of the feed water-molten salt heat exchanger (25) through the main steam diverter valve (12); the low-temperature side steam outlet of the steam-steam heat exchanger (19) is connected to the steam inlet of the high-pressure cylinder (2) of the steam turbine after merging with the second main steam outlet through the first control valve (13).

3. The molten salt heat storage system with a pre-installed steam turbine according to claim 1, characterized in that: It also includes a second control valve (16) and a third control valve (17), wherein the steam outlet of the front steam turbine (14) is divided into two paths, one path is connected to the low-temperature side steam inlet of the steam-steam heat exchanger (19) through the second control valve (16), and the other path is connected to the steam inlet of the coal-fired power generation system through the third control valve (17).

4. The molten salt heat storage system with a pre-installed steam turbine according to claim 1, characterized in that: It also includes a reheat steam diverter valve (18), and the reheat steam outlet of the coal-fired power generation system is connected to the high-temperature side steam inlet of the steam-steam heat exchanger (19) via the reheat steam diverter valve (18).

5. The molten salt heat storage system with a pre-installed steam turbine according to claim 4, characterized in that: The maximum steam diversion flow rate of the reheat steam diverter valve (18) is 28% of the total mass flow rate of the reheat steam.

6. The molten salt heat storage system with a pre-installed steam turbine according to claim 1, characterized in that: It also includes a low-temperature molten salt pump (22) and a high-temperature molten salt pump (24); the molten salt outlet of the low-temperature molten salt tank (21) is connected to the molten salt inlet of the reheat steam-molten salt heat exchanger (20) via the low-temperature molten salt pump (22); the molten salt outlet of the high-temperature molten salt tank (23) is connected to the molten salt inlet of the feed water-molten salt heat exchanger (25) via the high-temperature molten salt pump (24).

7. The molten salt heat storage system with a pre-installed steam turbine according to claim 1, characterized in that: It also includes a feed water diverter valve (26), through which the boiler feed water of the coal-fired power generation system is connected to the water working medium inlet of the feed water-molten salt heat exchanger (25).

8. The molten salt heat storage system with a pre-installed steam turbine according to claim 1, characterized in that: The steam-steam heat exchanger (19), the reheat steam-molten salt heat exchanger (20) and the feed water-molten salt heat exchanger (25) are all partition-type heat exchangers.

9. The molten salt heat storage system with a pre-installed steam turbine according to claim 1, characterized in that: The temperature of the steam outlet at the low temperature side of the steam-steam heat exchanger (19) is greater than 500°C, and the temperature range of the molten salt heat storage system is 120°C to 280°C.

10. A method for operating a molten salt heat storage system with a pre-installed steam turbine, characterized in that: A molten salt heat storage system with a front steam turbine as described in any one of claims 1 to 9; When the coal-fired power generation system is in normal operation, the coal-fired power generation system does not provide main steam and reheat steam to the molten salt heat storage system, and the molten salt heat storage system does not operate; When the coal-fired power generation system is in a low-load operation state, the main steam outlet of the coal-fired power generation system transmits all the main steam to the front steam turbine (14) through the first main steam outlet, and drives the auxiliary generator (15) to generate power externally through the front steam turbine (14), thereby reducing the throttling loss of the main steam; the reheat steam outlet of the coal-fired power generation system transmits reheat steam to the steam-steam heat exchanger (19), and the exhaust steam of the front steam turbine (14) is heated by the reheat steam. The heated exhaust steam heats the low-temperature molten salt in the low-temperature molten salt tank (21) for heat storage. The reheat steam after heat exchange is transmitted to the high-pressure cylinder (2) of the steam turbine, thereby maintaining the outlet steam temperature of the high-pressure cylinder (2) of the steam turbine; When the coal-fired power generation system is in a high-load operation state, the coal-fired power generation system does not provide main steam to the molten salt heat storage system, but only transmits reheated steam to the steam-steam heat exchanger (19) through the reheated steam outlet, releases the heat stored in the high-temperature molten salt tank (23), heats the boiler feed water of the coal-fired power generation system through the feed water-molten salt heat exchanger (25), generates superheated steam, enables the front steam turbine (14) to drive the auxiliary generator (15) to generate power externally, and transmits the exhaust steam of the front steam turbine (14) to the steam inlet of the coal-fired power generation system, thereby improving the load change rate of the coal-fired power generation system.

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