A thermal power system coupled with solar thermal storage and its operation method

Abstract

The present invention provides a thermal power system and operating method for a pressure-fire hot standby system coupled with solar thermal storage, belonging to the field of circulating fluidized bed unit equipment. The system is equipped with a solar collector, high / low temperature molten salt tanks, a molten salt-water heat exchanger, and a molten salt-steam heat exchanger. The molten salt outlet of the solar collector, the high-temperature molten salt tank, the high-temperature molten salt pump, the eighth three-way valve, the molten salt-water heat exchanger, the seventh three-way valve, the low-temperature molten salt tank, the low-temperature molten salt pump, and the molten salt inlet of the solar collector are sequentially connected; the second outlet of the eighth three-way valve is connected to the molten salt side inlet of the molten salt-steam heat exchanger, and the molten salt side outlet of the molten salt-steam heat exchanger is connected to the second inlet of the seventh three-way valve. During operation, solar energy is stored in the molten salt in the high-temperature molten salt tank under normal conditions; when the pressure-fire hot standby system is activated, the energy in the molten salt is passed through the heat exchanger to heat the feedwater / steam to produce steam required for safe operation of the steam turbine. The present invention extends the pressure-fire cycle and improves the deep peak regulation capability.

Description

Technical Field

[0001] The present invention belongs to the field of circulating fluidized bed unit equipment, and in particular relates to a heat-resistance thermal system coupled with solar thermal storage and an operating method thereof. Background Art

[0002] Renewable energy sources such as wind power and photovoltaics offer advantages such as cleanliness, low carbon emissions, and renewable energy, but they also exhibit significant intermittency, randomness, and volatility. As wind and photovoltaic power account for an increasing proportion of total power generation, the large-scale integration of renewable energy into the grid poses a significant threat to the security and stability of the power grid. When wind and photovoltaic power are integrated into thermal power grids, peak-shaving operations are generally used to facilitate the absorption of renewable energy within a certain range. However, when the grid's peak-shaving capacity fails to meet real-time dispatch requirements, wind and solar power curtailment is unavoidable. To reduce wind and solar curtailment, promote the high-proportion absorption of renewable energy, and ensure the safe operation of the power grid, it is necessary to improve the overall peak-shaving capacity of thermal power units.

[0003] Circulating fluidized bed boilers in thermal power units can typically operate within a range of 20% to 100% of rated load for peak shaving. Furthermore, the CFB boiler contains a large amount of high-temperature bed material and refractory materials, resulting in high heat storage and thermal inertia. This allows it to operate in a simmering, low-load state, known as "hot standby" mode. This simmering, high-load peak shaving technology leverages the CFB boiler's high thermal inertia to achieve extreme peak shaving at near-zero unit output. The specific process is as follows: When the power grid requires a significant load reduction for the unit, coal feed to the CFB boiler is stopped. Once the bed temperature shows a downward trend, the conveyor and induced draft fans are stopped, and the boiler enters a simmering, low-load state. During this time, the heat stored in the CFB boiler's large amount of high-temperature bed material and refractory materials continues to heat feedwater and steam, maintaining the turbine generator set operating at a very low load. When the grid load needs to increase, the CFB boiler is quickly started from a hot state to rapidly increase the unit load, achieving extreme peak shaving for the CFB unit. The circulating fluidized bed boiler hot standby technology combined with the turbine low-pressure cylinder zero-output technology can achieve near-zero power supply to the outside of the unit, thereby achieving deep peak regulation of the unit within the full load range of 0 to 100%.

[0004] In the existing technology, when the circulating fluidized bed boiler is under pressure to prepare for peak load regulation, the coal and air of the boiler are stopped. Due to the limitation of the boiler's evaporation capacity, the temperature of the boiler's main and reheat steam drops significantly over time, and the time for maintaining safe and stable operation of the turbine is short, currently only about 1 to 2 hours. The short pressure reduction time cannot meet the peak load regulation demand of new energy grid connection. Summary of the Invention

[0005] In view of the above-mentioned defects or deficiencies in the prior art, the present invention aims to provide a compressed fire hot standby thermal system and an operating method coupled with solar thermal storage. By coupling a circulating fluidized bed unit and a solar thermal molten salt energy storage system, solar energy is introduced into the compressed fire hot standby thermal system based on the circulating fluidized bed, thereby realizing long-term compressed fire operation of the circulating fluidized bed unit, effectively extending the compressed fire hot standby time, and improving the deep peak-shaving capability of the unit.

[0006] In order to achieve the above objectives, the embodiments of the present invention adopt the following technical solutions:

[0007] In the first aspect, an embodiment of the present invention provides a pressure-fire thermal standby system coupled with solar thermal storage, the system comprising: a circulating fluidized bed boiler 1, a high-pressure cylinder 2, an intermediate-pressure cylinder 3, a low-pressure cylinder 4, a condenser 5, a feedwater pump 6, a molten salt-water heat exchanger 7, a low-temperature molten salt tank 8, a high-temperature molten salt tank 9, a molten salt-steam heat exchanger 10, a low-temperature molten salt pump 26, a high-temperature molten salt pump 27, a solar collector 28, a high-temperature steam check valve 29, an intelligent flow controller 30, and a plurality of regulating valves 11-17, 31 and three-way valves 18-25 arranged between the connecting pipes; wherein,

[0008] The main steam pipeline of the circulating fluidized bed boiler 1 is connected to the inlet of the first three-way valve 18, the first outlet of the first three-way valve 18 is connected to the first regulating valve 11, the second three-way valve 19, and the inlet of the high-pressure cylinder 2 in sequence, and the second outlet of the first three-way valve 18 is connected to the inlet of the seventh regulating valve 17 and the third three-way valve 20 in sequence; the steam outlet of the high-pressure cylinder 2, the high-pressure steam check valve 29, and the second inlet of the third three-way valve 20 are connected in sequence, and the outlet of the third three-way valve 20 is connected to the cold reheat steam inlet of the circulating fluidized bed boiler 1; the hot reheat steam outlet of the circulating fluidized bed boiler 1, the fourth three-way valve 21, the second regulating valve 12, the fifth three-way valve 22, and the inlet of the intermediate-pressure cylinder 3 are connected in sequence; the steam outlet of the intermediate-pressure cylinder 3, the low-pressure cylinder 4, the condenser 5, the feedwater pump 6, the sixth three-way valve 23, the fourth regulating valve 14, and the feedwater inlet of the circulating fluidized bed boiler 1 are connected in sequence;

[0009] The second outlet of the sixth three-way valve 23 is connected in sequence to the eighth regulating valve 31, the buffer tank 34, the fifth regulating valve 15, the water-side inlet and outlet of the molten salt-water heat exchanger 7, the sixth regulating valve 16, and the second inlet of the second three-way valve 19. The provision of the buffer tank enables the water flow rate entering the molten salt-water heat exchanger 7 to be controlled by the intelligent flow controller 30 through the opening of the fifth regulating valve 15.

[0010] The second outlet of the fourth three-way valve 21, the third regulating valve 13, the steam side inlet and outlet of the molten salt-steam heat exchanger 10, and the second inlet of the fifth three-way valve 22 are connected in sequence;

[0011] The molten salt outlet of the solar collector 28, the high-temperature molten salt tank 9, the high-temperature molten salt pump 27, the eighth three-way valve 25, the molten salt-water heat exchanger 7, the seventh three-way valve 24, the low-temperature molten salt tank 8, the low-temperature molten salt pump 26, and the molten salt inlet of the solar collector 28 are connected in sequence; among them, the second outlet of the eighth three-way valve 25 is connected to the molten salt side inlet of the molten salt-steam heat exchanger 10, and the molten salt side outlet of the molten salt-steam heat exchanger 10 is connected to the second inlet of the seventh three-way valve 24.

[0012] As a preferred embodiment of the present invention, the intelligent flow controller 30 includes an information collection port 301, an opening calculation module 302, a first control port 303, a second control port 304 and a third control port 305; wherein,

[0013] The information collection port 301 is connected to the boiler temperature sensor, high-pressure cylinder temperature sensor, medium-pressure cylinder temperature sensor, low-pressure cylinder temperature sensor, eddy current probe, speed sensor, and dynamic pressure sensor, and is internally connected to the opening calculation module 302 to collect corresponding parameters;

[0014] The opening calculation module 302 is simultaneously connected to the first control port 303, the second control port 304 and the third control port 305; the first control port 303 is connected to the third regulating valve 13, the second control port 304 is connected to the fourth regulating valve 14, and the third control port 305 is connected to the fifth regulating valve 15; the opening calculation module 302 is used to calculate the openings of the third regulating valve 13, the fourth regulating valve 14 and the fifth regulating valve 15 according to the information collected by the information collection port 301, and generate control commands according to the calculation results, and send them to the first control port 303, the second control port 304 and the third control port 305 respectively.

[0015] As a preferred embodiment of the present invention, the opening calculation module 302 of the intelligent flow controller 30 is used to calculate the water flow rate required by the boiler at the current temperature based on the inlet and outlet temperatures of the steam flowing through the heating surfaces of the water-cooled wall, superheater and reheater in the boiler and the metal wall temperature measured in real time by the boiler temperature sensor, as well as the preset temperature threshold, and generate a control command to be sent to the second control port 304 to adjust the opening of the fourth regulating valve 14.

[0016] As a preferred embodiment of the present invention, the opening calculation module 302 of the intelligent flow controller 30 is used to calculate the water flow rate at the current temperature required by the molten salt-water heat exchanger 7 and the steam flow rate at the current temperature required by the molten salt-steam heat exchanger based on the inlet and outlet steam temperatures and cylinder metal wall temperatures of each turbine cylinder monitored in real time by the high-pressure cylinder temperature sensor, the medium-pressure cylinder temperature sensor, and the low-pressure cylinder temperature sensor, and at the same time based on the shaft vibration amplitude monitored by the eddy current probe, the low-frequency vibration monitored by the speed sensor, and the blade pressure pulsation frequency monitored by the dynamic pressure sensor, and generate control commands respectively and send them to the third control port 305 and the first control port 303 to adjust the opening of the fifth regulating valve 15 and the third regulating valve 13.

[0017] As a preferred embodiment of the present invention, the high-temperature molten salt tank and / or the low-temperature molten salt tank stores a heat carrier; the heat carrier is a molten salt medium or any other form of heat carrier in a liquid state; and the operating temperature range of the heat carrier is 120°C-550°C.

[0018] As a preferred embodiment of the present invention, the molten salt medium is solar salt, the composition is 60% NaNO3-40% KNO3, and the operating temperature range is 250°C-550°C. In a second aspect, the embodiment of the present invention also provides an operating method based on the above-mentioned pressure-fire hot standby thermal system, the method comprising:

[0019] Under normal conditions, the circulating fluidized bed unit operates at normal load, with the third regulating valve 13, the fifth regulating valve 15, the sixth regulating valve 16, the seventh regulating valve 17, and the eighth regulating valve 31 closed, and the remaining regulating valves normally open. At this time, the steam turbine side follows a conventional steam-water circulation process. Simultaneously, under sunlight conditions, the low-temperature molten salt pump 26 is turned on to pump molten salt from the low-temperature molten salt tank 8 into the solar collector 28 for heating to obtain high-temperature molten salt, which is then stored in the high-temperature molten salt tank 9.

[0020] When the circulating fluidized bed boiler is turned on as needed for hot standby, the circulating fluidized bed boiler is turned on; when the boiler evaporation rate drops significantly and the superheat of the main steam and reheat steam drops to 150°C, the high-temperature molten salt pump 27 is turned on to pump the high-temperature molten salt in the high-temperature molten salt tank 9 into the molten salt-water heat exchanger 7 and the molten salt-steam heat exchanger 10;

[0021] At the same time, the sixth regulating valve 16 and the seventh regulating valve 17 are opened, and the first regulating valve 11 is closed; the third regulating valve 13 is opened, the second regulating valve 12 is closed, and the eighth regulating valve 31 and the fifth regulating valve 15 are opened. The intelligent flow controller 30 adjusts the opening of the fourth regulating valve 14 to adjust the delivery of all boiler feed water to divert part of the boiler feed water into the circulating fluidized bed boiler 1, and the remaining feed water enters the buffer tank 32 through the eighth regulating valve 31. The remaining feed water is then controlled by the adjustment of the fifth regulating valve 15 to enter the molten salt-water heat exchanger 7. The feed water exchanges heat with the high-temperature molten salt, and the feed water absorbs heat to become main steam regeneration steam, which flows through the second three-way valve 19 and enters the high-pressure cylinder 2 to perform work, thereby ensuring the safe operation of the high-pressure cylinder;

[0022] The main steam generated by the circulating fluidized bed boiler 1 enters the first inlet of the third three-way valve 20 through the first three-way valve 18 and the seventh regulating valve 17, and then merges with the exhaust steam of the high-pressure cylinder 2 to enter the cold reheat steam inlet of the circulating fluidized bed boiler as cold reheat steam; the reheated steam of the circulating fluidized bed boiler 1 flows through the second outlet of the fourth three-way valve 21, and is controlled by the intelligent flow controller 30 at the third regulating valve 13. Part of the reheated steam enters the molten salt-steam heat exchanger 10 to exchange heat with the high-temperature molten salt, absorbs heat and improves the steam parameters, and then flows through the fifth three-way valve 22 to enter the medium-pressure cylinder and the low-pressure cylinder in turn to perform work; the exhaust steam discharged from the low-pressure cylinder enters the condenser 5, and is then sent to the sixth three-way valve through the feed water pump 6 as circulating boiler feed water.

[0023] As a preferred embodiment of the present invention, the intelligent flow controller 30 adjusts the opening of the fourth regulating valve 14 to adjust the delivery of all boiler feed water to divert part of the boiler feed water into the circulating fluidized bed boiler 1:

[0024] Based on the real-time measurement of the steam inlet and outlet temperatures and metal wall temperatures of the water-cooled walls, superheaters and reheaters in the boiler by the boiler temperature sensor, as well as the preset temperature threshold, the water flow rate required by the boiler at the current temperature is calculated, and a control command is generated to adjust the opening of the fourth regulating valve 14.

[0025] As a preferred embodiment of the present invention, the remaining feed water enters the buffer tank 32 through the eighth regulating valve 31, and then the fifth regulating valve 15 is adjusted to control part of the remaining feed water to enter the molten salt-water heat exchanger 7:

[0026] According to the inlet and outlet steam temperatures and cylinder metal wall temperatures of each turbine cylinder monitored in real time by the high-pressure cylinder temperature sensor, the medium-pressure cylinder temperature sensor, and the low-pressure cylinder temperature sensor, and at the same time according to the shaft vibration amplitude monitored by the eddy current probe, the low-frequency vibration monitored by the speed sensor, and the blade pressure pulsation frequency monitored by the dynamic pressure sensor, the water flow rate required by the molten salt-water heat exchanger 7 at the current temperature is calculated, and a control command is generated to adjust the opening of the fifth regulating valve 15.

[0027] As a preferred embodiment of the present invention, the reheated steam of the circulating fluidized bed boiler 1 flows through the second outlet of the fourth three-way valve 21 and is controlled by the intelligent flow controller 30 at the third regulating valve 13. When part of the reheated steam enters the molten salt-steam heat exchanger 10 for heat exchange with the high-temperature molten salt:

[0028] According to the inlet and outlet steam temperatures and cylinder metal wall temperatures of each turbine cylinder monitored in real time by the high-pressure cylinder temperature sensor, the medium-pressure cylinder temperature sensor, and the low-pressure cylinder temperature sensor, and at the same time according to the shaft vibration amplitude monitored by the eddy current probe, the low-frequency vibration monitored by the speed sensor, and the blade pressure pulsation frequency monitored by the dynamic pressure sensor, the steam flow rate required by the molten salt-steam heat exchanger 10 at the current temperature is calculated, and a control command is generated to adjust the opening of the third regulating valve 13.

[0029] The technical solution provided by the embodiment of the present invention has the following beneficial effects:

[0030] The embodiments of the present invention provide a thermal power system and operation method coupled with solar thermal storage. By coupling a circulating fluidized bed unit and a solar thermal molten salt energy storage system, solar energy is converted into thermal energy when there is sunshine and stored through an energy storage medium. When the circulating fluidized bed unit needs to be operated with compressed fire, the stored heat is used to heat the feed water to generate steam that meets the requirements for safe operation of the steam turbine, thereby realizing long-term compressed fire operation of the circulating fluidized bed unit, effectively extending the compressed fire time of the circulating fluidized bed unit, and greatly improving the deep peak-shaving capability of the unit. At the same time, the compressed fire time is extended by means of solar thermal energy storage, thereby improving the peak-shaving capability without significantly modifying the circulating fluidized bed unit itself.

[0031] Of course, it is not necessary to achieve all of the advantages described above simultaneously in order to implement any product or method of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 This is a schematic diagram of the structure of a heat-resistance thermal system coupled with solar thermal storage according to an embodiment of the present invention;

[0034] Figure 2 This is a block diagram of the structure of the intelligent flow controller in the thermal power system coupled with solar thermal storage according to an embodiment of the present invention;

[0035] Figure 3 In the embodiment of the present invention Figure 1The relationship diagram between the main steam flow and output power of the pressure-fire hot standby thermal system shown in the figure;

[0036] Figure 4 In the embodiment of the present invention Figure 1 Relationship diagram between main steam flow and molten salt consumption of the compressed fire thermal standby thermal system.

[0037] Description of reference numerals:

[0038] 1-Circulating fluidized bed boiler; 2-High-pressure cylinder; 3-Medium-pressure cylinder; 4-Low-pressure cylinder; 5-Condenser; 6-Feedwater pump; 7-Molten salt-water heat exchanger; 8-Low-temperature molten salt tank; 9-High-temperature molten salt tank; 10-Molten salt-steam heat exchanger; 11-First regulating valve; 12-Second regulating valve; 13-Third regulating valve; 14-Fourth regulating valve; 15-Fifth regulating valve; 16-Sixth regulating valve; 17-Seventh regulating valve; 18-First three-way valve; 19-Second three-way valve; 20-Third three-way valve ;21-fourth three-way valve;22-fifth three-way valve;23-sixth three-way valve;24-seventh three-way valve;25-eighth three-way valve;26-low-temperature molten salt pump;27-high-temperature molten salt pump;28-solar collector;29-high-temperature steam check valve;30-intelligent flow controller;301-information collection port, 302-opening calculation module;303-first control port;304-second control port;305-third control port;31-eighth regulating valve;32-buffer tank. DETAILED DESCRIPTION

[0039] After discovering the above problems, the inventors of the present application have conducted a detailed study on the existing circulating fluidized bed (CFB) boiler's compressed fire hot standby peak-shaving technology. The study found that after the circulating fluidized bed boiler enters the compressed fire state, as the combustion intensity decreases rapidly, the boiler evaporation volume drops rapidly, the unit operating load decreases accordingly, and the parameters of the main and reheat steam drop rapidly; to ensure the safe operation of the steam turbine, the superheat of the main steam and reheat steam cannot be lower than 150°C, and the temperature difference between the main and reheat steam must not exceed 50°C; when the steam parameters do not meet the safe operation parameters of the steam turbine, the compressed fire operation has to be ended. Therefore, as the compressed fire time becomes longer, the main and reheat steam parameters cannot meet the safe operation of the steam turbine, which is the main influencing factor limiting the compressed fire time. Extending the compressed fire time can greatly improve the deep adjustment capability of the unit. Solving the problem of mismatch between the machine and boiler parameters during the compressed fire operation is the technical key to extending the compressed fire time.

[0040] It should be noted that the defects existing in the solutions in the above-mentioned prior art are the results obtained by the inventors after practice and careful research. Therefore, the discovery process of the above-mentioned problems and the solutions proposed in the embodiments of the present invention below for the above-mentioned problems should all be the contributions made by the inventors to the present invention in the process of the invention.

[0041] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations. It should be noted that the embodiments of the present invention and the features in the embodiments can also be combined with each other in the absence of conflict.

[0042] It should be noted that similar reference numerals and letters represent similar items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined or explained in subsequent figures. In the description of the present invention, the terms "first," "second," "third," "fourth," etc. are used only to distinguish the description and are not to be understood as indicating or implying relative importance.

[0043] After the above in-depth analysis, the embodiment of the present invention provides a thermal system and operation method for pressure-compression and hot standby coupled with solar heat storage. By coupling the CFB power station with the solar heat storage system, the solar heat is stored in a molten salt tank when there is light. When the CFB power station unit needs pressure-compression and hot standby, the molten salt provides heat to heat the high-pressure heater outlet feed water and the low-parameter reheat steam at the boiler reheat outlet in the molten salt-water / steam heat exchanger to regenerative steam that can meet the safe operation of the turbine, avoiding the impact of the decline in the parameters of the main steam and reheat steam generated by the boiler on the steam turbine, thereby achieving the purpose of long-term pressure-compression.

[0044] like Figure 1 As shown, the pressure-fire-heat standby thermal system coupled with solar thermal storage includes: a circulating fluidized bed boiler 1, a high-pressure cylinder 2, a medium-pressure cylinder 3, a low-pressure cylinder 4, a condenser 5, a feed water pump 6, a molten salt-water heat exchanger 7, a low-temperature molten salt tank 8, a high-temperature molten salt tank 9, a molten salt-steam heat exchanger 10, a low-temperature molten salt pump 26, a high-temperature molten salt pump 27, a solar collector 28, a high-temperature steam check valve 29, an intelligent flow controller 30, and a number of regulating valves 11-17, 31 and three-way valves 18-25 arranged between the connecting pipes.

[0045] Among them, the main steam pipeline of the circulating fluidized bed boiler 1 is connected to the inlet of the first three-way valve 18, the first outlet of the first three-way valve 18 is connected to the first regulating valve 11, the second three-way valve 19, and the inlet of the high-pressure cylinder 2 in sequence, and the second outlet of the first three-way valve 18 is connected to the inlet of the seventh regulating valve 17 and the third three-way valve 20 in sequence; the steam outlet of the high-pressure cylinder 2, the high-pressure steam check valve 29, and the second inlet of the third three-way valve 20 are connected in sequence, and the outlet of the third three-way valve 20 is connected to the cold reheat steam inlet of the circulating fluidized bed boiler 1; the hot reheat steam outlet of the circulating fluidized bed boiler 1, the fourth three-way valve 21, the second regulating valve 12, the fifth three-way valve 22, and the inlet of the intermediate-pressure cylinder 3 are connected in sequence; the steam outlet of the intermediate-pressure cylinder 3, the low-pressure cylinder 4, the condenser 5, the feedwater pump 6, the sixth three-way valve 23, the fourth regulating valve 14, and the feedwater inlet of the circulating fluidized bed boiler 1 are connected in sequence;

[0046] The second outlet of the sixth three-way valve 23 is connected in sequence to the eighth regulating valve 31, the buffer tank 34, the fifth regulating valve 15, the water-side inlet and outlet of the molten salt-water heat exchanger 7, the sixth regulating valve 16, and the second inlet of the second three-way valve 19. The provision of the buffer tank enables the water flow rate entering the molten salt-water heat exchanger 7 to be controlled by the intelligent flow controller 30 through the opening of the fifth regulating valve 15.

[0047] The second outlet of the fourth three-way valve 21, the third regulating valve 13, the steam side inlet and outlet of the molten salt-steam heat exchanger 10, and the second inlet of the fifth three-way valve 22 are connected in sequence;

[0048] The molten salt outlet of the solar thermal collector 28, the high-temperature molten salt tank 9, the high-temperature molten salt pump 27, the eighth three-way valve 25, the molten salt-water heat exchanger 7, the seventh three-way valve 24, the low-temperature molten salt tank 8, the low-temperature molten salt pump 26, and the molten salt inlet of the solar thermal collector 28 are connected in sequence; wherein, the second outlet of the eighth three-way valve 25 is connected to the molten salt side inlet of the molten salt-steam heat exchanger 10, and the molten salt side outlet of the molten salt-steam heat exchanger 10 is connected to the second inlet of the seventh three-way valve 24;

[0049] The high-temperature molten salt tank and / or the low-temperature molten salt tank store a heat carrier; the heat carrier is a molten salt medium or any other liquid heat carrier; and the operating temperature range of the heat carrier is 120°C to 550°C. Preferably, the molten salt medium is solar salt, having a composition of 60% NaNO3 and 40% KNO3, and an operating temperature range of 250°C to 550°C.

[0050] like Figure 2As shown, the intelligent flow controller 30 includes an information acquisition port 301, an opening calculation module 302, a first control port 303, a second control port 304 and a third control port 305; wherein, the information acquisition port 301 is connected to the boiler temperature sensor, the high-pressure cylinder temperature sensor, the medium-pressure cylinder temperature sensor, the low-pressure cylinder temperature sensor, the eddy current probe, the speed sensor, and the dynamic pressure sensor, and is internally connected to the opening calculation module 302, for collecting corresponding parameters; the opening calculation module 302 is simultaneously connected to the first control port 303, the second control port 304 and the third control port 305; the first control port 303 is connected to the third regulating valve 13, the second control port 304 is connected to the fourth regulating valve 14, and the third control port 305 is connected to the fifth regulating valve 15. The opening calculation module 302 is used to calculate the openings of the third regulating valve 13, the fourth regulating valve 14 and the fifth regulating valve 15 according to the information collected by the information collection port 301, and generate control commands according to the calculation results, and send them to the first control port 303, the second control port 304 and the third control port 305 respectively.

[0051] Preferably, the opening calculation module 302 of the intelligent flow controller 30 is used to calculate the water flow rate at the current temperature required by the boiler based on the inlet and outlet temperatures of the steam flowing through the heating surfaces of the water-cooled wall, superheater and reheater in the boiler and the metal wall temperature, as well as the preset temperature threshold, and generate a control command to be sent to the second control port 304 to adjust the opening of the fourth regulating valve 14 to ensure that the temperature of each heating surface in the furnace is below the design temperature to prevent the boiler from being damaged by overheating; the opening calculation module 302 is also used to calculate the water flow rate at the current temperature required by the boiler based on the real-time measurement of the boiler temperature sensor, the medium-pressure cylinder temperature sensor and the low-pressure cylinder temperature sensor. The steam inlet and outlet temperatures of each turbine cylinder and the metal wall temperature of the cylinder are monitored in real time by the speed sensor. At the same time, the water flow rate at the current temperature required by the molten salt-water heat exchanger 7 and the steam flow rate at the current temperature required by the molten salt-steam heat exchanger 10 are calculated based on the shaft vibration amplitude monitored by the eddy current probe, the low-frequency vibration monitored by the speed sensor, and the blade pressure pulsation frequency monitored by the dynamic pressure sensor. Control commands are generated and sent to the third control port 305 and the first control port 303 respectively to adjust the opening of the fifth regulating valve 15 and the third regulating valve 13 to ensure the safe operation of the high-pressure cylinder, the medium-pressure cylinder and the low-pressure cylinder.

[0052] Based on the above-mentioned thermal system with thermal backup coupled with solar thermal storage, an embodiment of the present invention further provides an operating method of the thermal system, and the specific operating steps are as follows:

[0053] Under normal conditions, the circulating fluidized bed unit operates at normal load, the third regulating valve 13, the fifth regulating valve 15, the sixth regulating valve 16, the seventh regulating valve 17 and the eighth regulating valve 31 are in the closed state, and the remaining regulating valves are in the normally open state; at this time, the turbine side is in the conventional steam-water circulation process; at the same time, under sunshine conditions, the low-temperature molten salt pump 26 is turned on to extract the molten salt in the low-temperature molten salt tank 8 into the solar collector 28 for heating to obtain high-temperature molten salt, which is stored in the high-temperature molten salt tank 9.

[0054] When the circulating fluidized bed boiler is turned on as needed for hot standby, the circulating fluidized bed boiler is turned on; when the boiler evaporation rate drops significantly and the superheat of the main steam and reheat steam drops to 150°C, the high-temperature molten salt pump 27 is turned on to pump the high-temperature molten salt in the high-temperature molten salt tank 9 into the molten salt-water heat exchanger 7 and the molten salt-steam heat exchanger 10;

[0055] At the same time, the sixth regulating valve 16 and the seventh regulating valve 17 are opened, the first regulating valve 11 is closed, the third regulating valve 13 is opened, the second regulating valve 12 is closed, the eighth regulating valve 31 and the fifth regulating valve 15 are opened, and the intelligent flow controller 30 adjusts the opening of the fourth regulating valve 14 to adjust the delivery of all boiler feed water to divert part of the boiler feed water into the circulating fluidized bed boiler 1 to prevent the heating surface in the furnace from overheating. The remaining feed water enters the buffer tank 32 through the eighth regulating valve 31, and then controls the remaining feed water to enter the molten salt-water heat exchanger 7 through the adjustment of the fifth regulating valve 15. The feed water exchanges heat with the high-temperature molten salt, absorbs heat, and becomes main steam regeneration steam, which flows through the second three-way valve 19 into the high-pressure cylinder 2 to perform work, ensuring the safe operation of the high-pressure cylinder;

[0056] Due to insufficient parameters, the main steam generated by the circulating fluidized bed boiler 1 flows entirely through the first three-way valve 18 and the seventh regulating valve 17, then into the first inlet of the third three-way valve 20. There, it merges with the exhaust steam from the high-pressure cylinder 2 and enters the cold reheat steam inlet of the circulating fluidized bed boiler as cold reheat steam. The reheated steam from the circulating fluidized bed boiler 1 flows through the second outlet of the fourth three-way valve 21. At the third regulating valve 13, controlled by an intelligent flow controller 30, some of the reheated steam enters the molten salt-steam heat exchanger 10, where it exchanges heat with the high-temperature molten salt. After absorbing heat and increasing the steam parameters, it flows through the fifth three-way valve 22, sequentially entering the intermediate-pressure and low-pressure cylinders to perform work. The exhaust steam from the low-pressure cylinder enters the condenser 5 and is then fed by the feedwater pump 6 to the sixth three-way valve, where it serves as circulating boiler feedwater. The intelligent controller 30 controls the opening of the third regulating valve 13, adjusting the amount of steam entering the molten salt-steam heat exchanger 10 based on the real-time operating status of the intermediate and low-pressure cylinders, thereby preventing abnormal conditions such as shaft vibration, overheating, and drafts in each cylinder.

[0057] The solar thermal storage-coupled, compressed-fire standby thermal system and operating method described in an embodiment of the present invention were applied to a 300MW subcritical circulating fluidized bed (CFB) unit to achieve compressed-fire standby. The CFB boiler, model DG1085.3 / 17.5-II1, features a single-drum, natural circulation, and CFB combustion system. It primarily consists of a membrane-type, water-cooled hearth, three cooling cyclone separators, and a tail shaft enclosed by a steam-cooled wall. The steam turbine unit, model CZK312 / N300-16.7 / 538 / 538, is a subcritical, single-stage, reheat, dual-cylinder, dual-exhaust, single-shaft, direct air-cooled, heat-supply condensing steam turbine. Its rated back pressure is 14kPa, and the regenerative heater utilizes a three-stage high-pressure heater, three-stage low-pressure heater, and a deaerator. By storing heat in the molten salt using solar energy and releasing heat in the hot standby state, and controlling the key parameters of the thermal system operation process through a control system including an intelligent flow controller 30, a hot standby time of no less than 6 hours is achieved. The specific key parameters are as follows:

[0058] The outlet water flow rate of the feed water pump 6 is 10-50 t / h, preferably 15-20 t / h, which can achieve near-zero output of the CFB unit; the boiler feed water is split through the sixth three-way valve 23, one way of which enters the boiler along the original route through the fourth regulating valve 14 with an adjusted opening under the control of the intelligent flow controller 30, allowing the minimum feed water flow to enter the boiler to ensure that the heating surface in the furnace does not overheat; the other way of which passes through the eighth regulating valve 31 and the buffer tank 32, and then adjusts the opening of the fifth regulating valve 15 under the control of the intelligent flow controller 30, and is split into the molten salt- Water heat exchanger 7, and the mass flow rate accounts for 40-90% of the total water feed volume, preferably 60-80%; after the main steam comes out of the boiler, it passes through the first three-way valve 18, the seventh regulating valve 17, and the third three-way valve 20, and merges with the exhaust steam of the high-pressure cylinder 2 and enters the circulating fluidized bed boiler 1 as cold reheat steam to generate reheat steam, and then flows through the second outlet of the fourth three-way valve 21. At the third regulating valve 13, it is controlled by the intelligent flow controller 30, and part of the reheat steam enters the molten salt-steam heat exchanger 10 to exchange heat with the high-temperature molten salt and then enters the medium-pressure cylinder and the low-pressure cylinder.

[0059] The feedwater flow rate entering the molten salt-water heat exchanger 7 and the steam flow rate entering the molten salt-steam heat exchanger 10 are automatically controlled by an intelligent flow controller 30. The openings of the fifth regulating valve 15 and the third regulating valve 13 are automatically adjusted according to the operating status of each turbine cylinder, allowing a minimum flow rate to enter the cylinders to ensure that each cylinder does not experience abnormal conditions such as shaft vibration, overheating, and blast. Preferably, the regeneration steam at the outlet of the molten salt-water heat exchanger 7 has a temperature of 390-530°C and a pressure of 8-12 MPa, while the regeneration steam at the outlet of the molten salt-steam heat exchanger 10 has a temperature of 380-530°C.

[0060] Based on the above-mentioned circulating fluidized bed unit and the parameters adopted, solar salt is used as the molten salt working fluid. The operation process of the above-mentioned thermal system with pressure-fire hot standby is simulated. Based on the simulation parameters, the relationship between the main steam flow rate and the unit output power is calculated, as shown in the following example: Figure 3 As shown in the figure, when the main steam flow rate is 20t / h, the unit output power is only 3.3MW, and after deducting the plant power consumption, it can basically achieve near-zero output to the outside; Figure 4 As shown, when the main steam flow rate is 20t / h, the controlled fire time is 6h and the molten salt consumption is about 900t.

[0061] It can be seen from the above technical solutions that the embodiment of the present invention provides a coupled solar thermal storage and heat standby thermal system and operation method. By coupling a circulating fluidized bed unit and a solar thermal molten salt energy storage system, solar energy is stored through molten salt when there is sunshine. When the circulating fluidized bed unit enters the heat standby state, the heat storage is used to heat the feed water to generate high-parameter steam instead of the low-temperature steam generated by the boiler to enter the steam turbine. Under the premise of ensuring the safe operation of the steam turbine, the heat of the circulating fluidized bed unit is not limited by the decline in boiler evaporation, but depends on the layout of the solar mirror field and the heat storage of the molten salt storage tank. The mirror field and the storage tank design can be adjusted according to the actual time requirement of the unit's heat storage, which not only achieves near-zero output of the unit during heat storage, but also makes the heat storage time not less than 6 hours, further providing new energy and The network creates conditions; during the hot standby operation with compressed fire, the intelligent flow controller automatically adjusts the amount of feed water entering the boiler according to the temperature of the heating surface in the furnace, and automatically adjusts the feed water and steam flow entering the molten salt-water heat exchanger and the molten salt-steam heat exchanger according to the operating signals of each cylinder of the steam turbine, allowing minimum feed water and steam to enter the boiler and steam turbine to ensure that the heating surface in the furnace does not overheat and that the steam turbine cylinders operate normally, effectively reducing the consumption of heat storage in the boiler furnace and molten salt heat storage, thereby extending the compressed fire time, and realizing the CFB unit to operate frequently and for a long time under compressed fire conditions, thereby improving coal saving and peak-shaving compensation benefits; at the same time, the thermal system does not require large-scale transformation of the circulating fluidized bed unit itself, with small investment and saving operation and maintenance costs.

[0062] The above description is only a preferred embodiment of the present invention and an explanation of the technical principles used. It is not intended to limit the scope of the invention to be protected, but merely represents a preferred embodiment of the present invention. Those skilled in the art should understand that the scope of the invention involved in the present invention is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the inventive concept. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative work shall fall within the scope of protection of the present invention.

Claims

1. A thermal power system coupled with solar thermal storage, characterized in that: The system comprises: The main steam pipeline of the circulating fluidized bed boiler is connected to the inlet of the first three-way valve, the first outlet of the first three-way valve is connected to the first regulating valve, the second three-way valve, and the inlet of the high-pressure cylinder in sequence, and the second outlet of the first three-way valve is connected to the inlet of the seventh regulating valve and the third three-way valve in sequence; the steam outlet of the high-pressure cylinder, the high-pressure steam check valve, and the second inlet of the third three-way valve are connected in sequence, and the outlet of the third three-way valve is connected to the cold reheat steam inlet of the circulating fluidized bed boiler; the hot reheat steam outlet of the circulating fluidized bed boiler, the fourth three-way valve, the second regulating valve, the fifth three-way valve, and the inlet of the intermediate-pressure cylinder are connected in sequence; the steam outlet of the intermediate-pressure cylinder, the low-pressure cylinder, the condenser, the feedwater pump, the sixth three-way valve, the fourth regulating valve, and the feedwater inlet of the circulating fluidized bed boiler are connected in sequence; The second outlet of the sixth three-way valve is connected to the eighth regulating valve, the buffer tank, the fifth regulating valve, the water-side inlet and outlet of the molten salt-water heat exchanger, the sixth regulating valve, and the second inlet of the second three-way valve in sequence; wherein, the provision of the buffer tank enables the water flow entering the molten salt-water heat exchanger to be achieved by controlling the opening of the fifth regulating valve by the intelligent flow controller; The second outlet of the fourth three-way valve, the third regulating valve, the steam side inlet and outlet of the molten salt-steam heat exchanger, and the second inlet of the fifth three-way valve are connected in sequence; The molten salt outlet of the solar thermal collector, the high-temperature molten salt tank, the high-temperature molten salt pump, the eighth three-way valve, the molten salt-water heat exchanger, the seventh three-way valve, the low-temperature molten salt tank, the low-temperature molten salt pump, and the molten salt inlet of the solar thermal collector are connected in sequence; among them, the second outlet of the eighth three-way valve is connected to the molten salt side inlet of the molten salt-steam heat exchanger, and the molten salt side outlet of the molten salt-steam heat exchanger is connected to the second inlet of the seventh three-way valve.

2. The solar thermal storage coupled pressure-fire heat standby thermal system according to claim 1 is characterized in that: The intelligent flow controller includes an information collection port, an opening calculation module, a first control port, a second control port and a third control port; wherein, The information collection port is connected to the boiler temperature sensor, high-pressure cylinder temperature sensor, medium-pressure cylinder temperature sensor, low-pressure cylinder temperature sensor, eddy current probe, speed sensor, and dynamic pressure sensor, and is internally connected to the opening calculation module to collect corresponding parameters; The opening calculation module is connected to the first control port, the second control port and the third control port at the same time; the first control port is connected to the third regulating valve, the second control port is connected to the fourth regulating valve, and the third control port is connected to the fifth regulating valve; the opening calculation module is used to calculate the openings of the third regulating valve, the fourth regulating valve and the fifth regulating valve respectively according to the information collected by the information collection port, and generate control commands according to the calculation results, and send them to the first control port, the second control port and the third control port respectively.

3. The solar thermal storage coupled pressure-fire heat standby thermal system according to claim 2, characterized in that: The opening calculation module of the intelligent flow controller is used to calculate the water flow rate required by the boiler at the current temperature based on the inlet and outlet temperatures of the steam flowing through the heating surfaces of the water-cooled wall, superheater and reheater in the boiler and the metal wall temperature measured in real time by the boiler temperature sensor, as well as the preset temperature threshold, generate a control command and send it to the second control port to adjust the opening of the fourth regulating valve.

4. The solar thermal storage coupled pressure-fire heat standby thermal system according to claim 2, characterized in that: The opening calculation module of the intelligent flow controller is used to calculate the water flow rate at the current temperature required by the molten salt-water heat exchanger and the steam flow rate at the current temperature required by the molten salt-steam heat exchanger based on the inlet and outlet steam temperatures and cylinder metal wall temperatures of each turbine cylinder monitored in real time by the high-pressure cylinder temperature sensor, the medium-pressure cylinder temperature sensor, and the low-pressure cylinder temperature sensor, and at the same time, based on the shaft vibration amplitude monitored by the eddy current probe, the low-frequency vibration monitored by the speed sensor, and the blade pressure pulsation frequency monitored by the dynamic pressure sensor, and generate control commands respectively and send them to the third control port and the first control port to adjust the opening of the fifth regulating valve and the third regulating valve.

5. The solar thermal storage coupled pressure-fire heat standby thermal system according to claim 1 is characterized in that: The high-temperature molten salt tank and / or the low-temperature molten salt tank stores a heat carrier; the heat carrier is a molten salt medium or any other form of heat carrier in a liquid state; and the operating temperature range of the heat carrier is 120°C-550°C.

6. The solar thermal storage coupled pressure-fire heat standby thermal system according to claim 5 is characterized in that: The molten salt medium is solar salt, which has a composition of 60% NaNO3-40% KNO3, and an operating temperature range of 250°C-550°C.

7. An operating method of the compressed-fire hot standby thermal system according to any one of claims 1 to 6, characterized in that: The method comprises: Under normal conditions, the circulating fluidized bed unit operates at normal load, with the third, fifth, sixth, seventh, and eighth regulating valves closed and the remaining regulating valves open. The steam turbine side then follows a conventional steam-water circulation process. Simultaneously, under sunlight conditions, the low-temperature molten salt pump is turned on to pump molten salt from the low-temperature molten salt tank into the solar collector for heating to obtain high-temperature molten salt, which is then stored in the high-temperature molten salt tank. When the circulating fluidized bed boiler is turned on as needed for hot standby, the circulating fluidized bed boiler is turned on; when the boiler evaporation rate drops significantly and the superheat of the main steam and reheat steam drops to 150°C, the high-temperature molten salt pump is turned on to pump the high-temperature molten salt in the high-temperature molten salt tank 9 into the molten salt-water heat exchanger and the molten salt-steam heat exchanger; At the same time, the sixth and seventh regulating valves are opened, and the first regulating valve is closed; the third regulating valve is opened, the second regulating valve is closed, and the eighth and fifth regulating valves are opened. The intelligent flow controller adjusts the opening of the fourth regulating valve to adjust the delivery of all boiler feed water to a diverted portion of the boiler feed water into the circulating fluidized bed boiler. The remaining feed water enters the buffer tank through the eighth regulating valve, and then enters the molten salt-water heat exchanger after adjusting the fifth regulating valve to control the remaining feed water. The feed water exchanges heat with the high-temperature molten salt, and the feed water absorbs heat to become main steam regeneration steam, which flows through the second three-way valve into the high-pressure cylinder to perform work, thereby ensuring the safe operation of the high-pressure cylinder; The main steam generated by the circulating fluidized bed boiler flows through the first three-way valve and the seventh regulating valve, enters the first inlet of the third three-way valve, and then merges with the exhaust steam of the high-pressure cylinder to enter the cold reheat steam inlet of the circulating fluidized bed boiler as cold reheat steam; the reheated steam of the circulating fluidized bed boiler flows through the second outlet of the fourth three-way valve, and is controlled by the intelligent flow controller at the third regulating valve. Part of the reheated steam enters the molten salt-steam heat exchanger to exchange heat with the high-temperature molten salt, absorbs heat and improves the steam parameters, and then flows through the fifth three-way valve to enter the medium-pressure cylinder and the low-pressure cylinder in turn to perform work; the exhaust steam discharged from the low-pressure cylinder enters the condenser, and is then sent to the sixth three-way valve through the feed water pump as circulating boiler feed water.

8. The method for operating a thermal system with compressed fire and hot standby according to claim 7, characterized in that: When the intelligent flow controller adjusts the opening of the fourth regulating valve to divert part of the boiler feed water from the entire boiler feed water to the circulating fluidized bed boiler: Based on the real-time measurement of the steam inlet and outlet temperatures and metal wall temperatures of the heating surfaces of the water-cooled walls, superheaters and reheaters in the boiler by the boiler temperature sensor, as well as the preset temperature threshold, the water flow rate required by the boiler at the current temperature is calculated, and a control command is generated to adjust the opening of the fourth regulating valve.

9. The method for operating a thermal system with compressed fire and hot standby according to claim 7, characterized in that: The remaining feed water enters the buffer tank through the eighth regulating valve, and then enters the molten salt-water heat exchanger through the adjustment of the fifth regulating valve: Based on the inlet and outlet steam temperatures and cylinder metal wall temperatures of each turbine cylinder monitored in real time by the high-pressure cylinder temperature sensor, the medium-pressure cylinder temperature sensor, and the low-pressure cylinder temperature sensor, and based on the shaft vibration amplitude monitored by the eddy current probe, the low-frequency vibration monitored by the speed sensor, and the blade pressure pulsation frequency monitored by the dynamic pressure sensor, the water flow rate required by the molten salt-water heat exchanger at the current temperature is calculated, and a control command is generated to adjust the opening of the fifth regulating valve.

10. The method for operating a thermal system with compressed fire and hot standby according to claim 7, characterized in that: The reheated steam of the circulating fluidized bed boiler flows through the second outlet of the fourth three-way valve and is controlled by the intelligent flow controller at the third regulating valve. Part of the reheated steam enters the molten salt-steam heat exchanger to exchange heat with the high-temperature molten salt: Based on the inlet and outlet steam temperatures and cylinder metal wall temperatures of each turbine cylinder monitored in real time by the high-pressure cylinder temperature sensor, the medium-pressure cylinder temperature sensor, and the low-pressure cylinder temperature sensor, and based on the shaft vibration amplitude monitored by the eddy current probe, the low-frequency vibration monitored by the speed sensor, and the blade pressure pulsation frequency monitored by the dynamic pressure sensor, the steam flow rate required by the molten salt-steam heat exchanger at the current temperature is calculated, and a control command is generated to adjust the opening of the third regulating valve.

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