Compression fire hot standby thermodynamic system coupled with solar heat storage and operation method

Abstract

The invention provides a pressing fire hot standby thermodynamic system coupled with solar heat storage and an operation method, and belongs to the field of circulating fluidized bed unit equipment. The system is provided with a solar thermal collector, a high / low-temperature fused salt tank, a fused salt-water heat exchanger and a fused salt-steam heat exchanger, wherein a fused salt outlet of the solar thermal collector, the high-temperature fused salt tank, a high-temperature fused salt pump, an eighth three-way valve, the fused salt-water heat exchanger, a seventh three-way valve, a low-temperature fused salt tank, a low-temperature fused salt pump and a fused salt inlet of the solar thermal collector are communicated in sequence; a second outlet of the eighth three-way valve communicates with a fused salt side inlet of the fused salt-steam heat exchanger, and a fused salt side outlet of the fused salt-steam heat exchanger communicates with a second inlet of the seventh three-way valve. During operation, solar energy is stored in fused salt of the high-temperature fused salt tank in a conventional state; when fire pressing hot standby is started, energy in the fused salt passes through the heat exchanger to heat feed water / steam to generate steam meeting the requirement for safe operation of the steam turbine. According to the method, the banking-up period is prolonged, and the deep peak regulation capacity is improved.

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 defects or deficiencies in the prior art, the present invention aims to provide a pressure-fire standby thermal power system coupled with solar energy storage and an operation method thereof. By coupling a circulating fluidized bed unit and a molten salt energy storage system using solar energy, solar energy is introduced into the pressure-fire standby thermal power system based on the circulating fluidized bed to achieve long-term pressure-fire operation of the circulating fluidized bed unit, effectively extending the pressure-fire standby duration and enhancing the deep peak shaving capacity of the unit.

[0006] To achieve the above object, the embodiments of the present invention adopt the following technical solutions:

[0007] In a first aspect, an embodiment of the present invention provides a pressure-fire standby thermal power system coupled with solar energy storage. The system includes: 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 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 provided between the connecting pipelines; 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 sequentially connected to the first regulating valve 11, the second three-way valve 19, and the inlet of the high-pressure cylinder 2. The second outlet of the first three-way valve 18 is sequentially connected to the seventh regulating valve 17 and the inlet of the third three-way valve 20; 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 sequentially connected. 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 sequentially connected; the steam outlet of the intermediate-pressure cylinder 3, the low-pressure cylinder 4, the condenser 5, the feed water pump 6, the sixth three-way valve 23, the fourth regulating valve 14, and the feed water inlet of the circulating fluidized bed boiler 1 are sequentially connected;

[0009] The second outlet of the sixth three-way valve 23 is sequentially connected to the eighth regulating valve 33, 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; wherein, the setting of the buffer tank can enable the feed water volume entering the molten salt-water heat exchanger 7 to be controlled by the intelligent flow controller 30 to adjust the opening degree 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 sequentially connected;

[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 acquisition port 301, an opening calculation module 302, a first control port 303, a second control port 304, and a third control port 305; among them,

[0013] The information acquisition port 301 is connected to the boiler temperature sensor, the high-pressure cylinder temperature sensor, the intermediate-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 acquiring 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 respectively according to the information collected by the information acquisition 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 required by the boiler at the current temperature according to the inlet and outlet temperatures of the flowing steam and the metal wall temperature in the heating surfaces of the water wall, superheater, and reheater in the boiler measured by the boiler temperature sensor in real time, and a preset temperature threshold, generate a control command and send it 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 configured to calculate the water flow at the current temperature required by the molten salt-water heat exchanger 7 and the steam flow at the current temperature required by the molten salt-steam heat exchanger according to the inlet and outlet steam temperatures and the cylinder metal wall temperatures of each cylinder of the steam turbine monitored in real time by the high-pressure cylinder temperature sensor, the intermediate-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 velocity sensor, and the blade pressure pulsation frequency monitored by the dynamic pressure sensor, and respectively generate control commands to be sent to the third control port 305 and the first control port 303 to adjust the opening degrees of the fifth regulating valve 15 and the third regulating valve 13.

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

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

[0019] Under normal conditions, the circulating fluidized bed unit operates at a 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 a closed state, and the remaining regulating valves are in a normal open state; at this time, the steam turbine side has a conventional steam-water circulation process; at the same time, under sunny conditions, the low-temperature molten salt pump 26 is started to pump the molten salt in the low-temperature molten salt tank 8 into the solar collector 28 to be heated to obtain high-temperature molten salt, which is stored in the high-temperature molten salt tank 9.

[0020] When hot standby during pressure reduction is required as needed, the circulating fluidized bed boiler is put on pressure reduction; when the boiler evaporation significantly decreases and the superheat degrees of the main steam and the reheated steam are reduced to 150°C, the high-temperature molten salt pump 27 is started 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] Meanwhile, open the sixth regulating valve 16 and the seventh regulating valve 17, and close the first regulating valve 11; open the third regulating valve 13, close the second regulating valve 12, open the eighth regulating valve 31 and the fifth regulating valve 15. The intelligent flow controller 30 adjusts the opening degree of the fourth regulating valve 14 to adjust the conveyance 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. Then, by adjusting the fifth regulating valve 15, part of the remaining feed water is controlled to enter the molten salt-water heat exchanger 7, where the feed water exchanges heat with the high-temperature molten salt. The feed water absorbs heat and becomes the main steam regeneration steam, which flows through the second three-way valve 19 and enters the high-pressure cylinder 2 to do work, 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 converges with the exhaust steam of the high-pressure cylinder 2 and then enters the cold reheat steam inlet of the circulating fluidized bed boiler as the 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 increases the steam parameters, and then flows through the fifth three-way valve 22 and enters the intermediate-pressure cylinder and the low-pressure cylinder in sequence to do work; the waste steam discharged from the low-pressure cylinder enters the condenser 5, and then is sent to the sixth three-way valve by the feed water pump 6 as the boiler feed water for circulation.

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

[0024] According to the inlet and outlet steam temperatures and the metal wall temperatures of the heat transfer surfaces of the water-cooled wall, superheater, and reheater in the boiler measured by the boiler temperature sensors in real time, and the preset temperature threshold, calculate the water flow required by the boiler at the current temperature, and generate a control command to adjust the opening degree of the fourth regulating valve 14.

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

[0026] According to the inlet and outlet steam temperatures and the cylinder metal wall temperatures of each cylinder of the steam turbine monitored by the high-pressure cylinder temperature sensor, intermediate-pressure cylinder temperature sensor, and low-pressure cylinder temperature sensor in real time, and at the same time, according to the shaft vibration amplitude monitored by the eddy current probe, the low-frequency vibration monitored by the velocity sensor, and the blade pressure pulsation frequency monitored by the dynamic pressure sensor, calculate the water flow required by the molten salt-water heat exchanger 7 at the current temperature, and generate a control command to adjust the opening degree 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 of each cylinder of the steam turbine and the cylinder metal wall temperature monitored in real time by the high-pressure cylinder temperature sensor, the intermediate-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 velocity sensor, and the blade pressure pulsation frequency monitored by the dynamic pressure sensor, calculate the steam flow rate at the current temperature required by the molten salt-steam heat exchanger 10, and generate a control command 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 hot standby thermal power system and operation method with coupled solar energy storage provided by the embodiment of the present invention, by coupling the circulating fluidized bed unit and the solar molten salt energy storage system, convert solar energy into heat energy and store it through the energy storage medium when there is sunlight. When the circulating fluidized bed unit needs to be put out of fire for operation, use the stored heat to heat the feed water to generate steam that meets the safe operation of the steam turbine, realizing the long-term hot standby operation of the circulating fluidized bed unit, effectively extending the hot standby duration of the circulating fluidized bed unit, and greatly improving the deep peak shaving ability of the unit; at the same time, extend the hot standby duration through the solar thermal energy storage method, and improve the peak shaving ability without significantly modifying the circulating fluidized bed unit itself.

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

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0033] Figure 1 is a schematic structural diagram of the hot standby thermal power system with coupled solar energy storage according to the embodiment of the present invention;

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

[0035] Figure 3 is in the embodiment of the present invention Figure 1Graph showing the relationship between the main steam flow rate and the output power of the shown hot standby thermal system under pressure

[0036] Figure 4 In the embodiments of the present invention Figure 1 Graph showing the relationship between the main steam flow rate of the described hot standby thermal system under pressure and the molten salt consumption

[0037] Explanation of reference numerals:

[0038] 1 - Circulating fluidized bed boiler; 2 - High - pressure cylinder; 3 - Intermediate - pressure cylinder; 4 - Low - pressure cylinder; 5 - Condenser; 6 - Feed water 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 acquisition 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 implementation manners

[0039] After the inventors of the present application discovered the above - mentioned problems, they conducted a detailed study on the hot standby peak - shaving technology of the existing circulating fluidized bed (CFB) boiler. The study found that after the circulating fluidized bed boiler enters the hot standby state, with the rapid reduction of the combustion intensity, the boiler evaporation capacity drops rapidly, the unit operation 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 degree of the main steam and reheat steam cannot be lower than 150 °C, and the temperature difference between the main and reheat steam shall not exceed 50 °C; when the steam parameters do not meet the safe operation parameters of the steam turbine, the hot standby operation has to be terminated. Therefore, as the hot standby time becomes longer, the fact that the main and reheat steam parameters do not meet the safe operation of the steam turbine is the main factor restricting the hot standby duration. Extending the hot standby time can significantly improve the deep - regulation ability of the unit, and solving the problem of the mismatch between the boiler and turbine parameters during the hot standby operation is the technical key to extending the hot standby time.

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

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Components of the embodiments of the present invention described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can also be combined with each other.

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

[0043] After the above in-depth analysis, the embodiments of the present invention provide a hot standby thermal power system with coupled solar energy heat storage and an operation method. By coupling a CFB power station with a solar energy heat storage system, the solar heat is stored in the molten salt tank during sunlight. When the CFB power station unit needs to be put into hot standby, the molten salt provides heat to heat the feed water at the outlet of the high-pressure heater and the low-parameter reheated steam at the outlet of the boiler reheater into regenerated steam that can meet the safe operation of the steam turbine in the molten salt-water / steam heat exchanger, avoiding the impact on the steam turbine due to the decrease in the parameters of the main steam and reheated steam generated by the boiler, so as to achieve the purpose of long-term hot standby.

[0044] As Figure 1 shown, the hot standby thermal power system with coupled solar energy heat storage includes: 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 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 provided between the connecting pipelines.

[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 sequentially connected to the first regulating valve 11, the second three-way valve 19, and the inlet of the high-pressure cylinder 2. The second outlet of the first three-way valve 18 is sequentially connected to the seventh regulating valve 17 and the inlet of the third three-way valve 20; 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 sequentially connected. 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 sequentially connected; the steam outlet of the intermediate-pressure cylinder 3, the low-pressure cylinder 4, the condenser 5, the feed water pump 6, the sixth three-way valve 23, the fourth regulating valve 14, and the feed water inlet of the circulating fluidized bed boiler 1 are sequentially connected;

[0046] The second outlet of the sixth three-way valve 23 is sequentially connected to the eighth regulating valve 33, 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; among them, the setting of the buffer tank can enable the water supply amount entering the molten salt-water heat exchanger 7 to be controlled by the intelligent flow controller 30 to adjust the opening degree 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 sequentially connected;

[0048] 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 sequentially connected; 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;

[0049] The high-temperature molten salt tank and / or the low-temperature molten salt tank stores a heat-carrying working medium; the heat-carrying working medium is a molten salt medium or any other form of heat-carrying medium existing in a liquid state; and the working temperature range of the heat-carrying working medium is 120°C - 550°C. Preferably, the molten salt medium is solar salt, with a composition of 60% NaNO3 - 40% KNO3 composition, and the working temperature range is 250°C - 550°C.

[0050] As Figure 2As shown in the figure, 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. Among them, the information collection port 301 is connected to the boiler temperature sensor, the high-pressure cylinder temperature sensor, the intermediate-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 opening degrees of the third regulating valve 13, the fourth regulating valve 14, and the fifth regulating valve 15 respectively 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 required by the boiler at the current temperature according to the inlet and outlet temperatures of the flowing steam and the metal wall temperature in the heating surfaces of the water-cooled wall, superheater, and reheater in the boiler measured by the boiler temperature sensor in real time, as well as the preset temperature threshold, generate a control command and send it to the second control port 304 to adjust the opening degree of the fourth regulating valve 14, ensure that the temperatures of each heating surface in the furnace are below the designed temperature, and prevent the boiler from being damaged due to overheating. The opening calculation module 302 is also used to calculate the water flow required by the molten salt-water heat exchanger 7 at the current temperature and the steam flow required by the molten salt-steam heat exchanger 10 at the current temperature according to the inlet and outlet steam temperatures and the cylinder metal wall temperatures of each cylinder of the steam turbine monitored by the high-pressure cylinder temperature sensor, the intermediate-pressure cylinder temperature sensor, and the low-pressure cylinder temperature sensor in real time, 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, and generate control commands respectively and send them to the third control port 305 and the first control port 303 to adjust the opening degrees of the fifth regulating valve 15 and the third regulating valve 13, and ensure the safe operation of the high-pressure cylinder, the intermediate-pressure cylinder, and the low-pressure cylinder.

[0052] Based on the provided thermo-pressure standby thermal system coupled with solar energy storage heat, the embodiment of the present invention also provides an operation method for this thermal system. The specific operation steps are as follows:

[0053] Under normal conditions, the circulating fluidized bed unit operates at a 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 normal open state; at this time, the steam-water circulation process on the steam turbine side is normal; at the same time, under sunny conditions, the low-temperature molten salt pump 26 is started to pump the molten salt in the low-temperature molten salt tank 8 into the solar collector 28 to be heated to obtain high-temperature molten salt, which is stored in the high-temperature molten salt tank 9.

[0054] When starting hot standby as needed, the circulating fluidized bed boiler is put on hot standby; when the boiler evaporation significantly decreases and the superheat degrees of the main steam and reheat steam drop to 150 °C, the high-temperature molten salt pump 27 is started 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 degree of the fourth regulating valve 14 to adjust the conveyance 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 part of the remaining feed water is controlled to enter the molten salt-water heat exchanger 7 through the fifth regulating valve 15. The feed water exchanges heat with the high-temperature molten salt, and the feed water absorbs heat and becomes the main steam regeneration steam, which flows through the second three-way valve 19 and enters the high-pressure cylinder 2 to do work, ensuring the safe operation of the high-pressure cylinder;

[0056] Since the parameters of the main steam generated by the circulating fluidized bed boiler 1 are insufficient, all of it 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 converges with the exhaust steam of the high-pressure cylinder 2 and then enters the cold reheat steam inlet of the circulating fluidized bed boiler as cold reheat steam; the reheat 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 reheat steam enters the molten salt-steam heat exchanger 10 to exchange heat with the high-temperature molten salt, absorbs heat and increases the steam parameters, and then flows through the fifth three-way valve 22 and enters the intermediate-pressure cylinder and the low-pressure cylinder in sequence to do work; the waste steam discharged from the low-pressure cylinder enters the condenser 5, and then is sent to the sixth three-way valve by the feed water pump 6 as the boiler feed water for circulation. The opening degree of the third regulating valve 13 is controlled by the intelligent controller 30, and the steam amount entering the molten salt-steam heat exchanger 10 is adjusted according to the real-time operating state of the intermediate-pressure cylinder and the low-pressure cylinder, so as to ensure that no abnormal states such as shaft vibration, overheating, and air blowing occur in each cylinder.

[0057] Apply the hot standby thermal power system and operation method of coupling solar energy storage and heat storage described in the embodiments of the present invention to a 300MW subcritical circulating fluidized bed unit to achieve hot standby. The model of the circulating fluidized bed boiler is DG1085.3 / 17.5-II1, which is a single-drum, natural circulation, circulating fluidized bed combustion mode, mainly composed of a membrane water-cooled furnace, three cooling type cyclone separators and a tail shaft surrounded by a steam-cooled wall. The steam turbine unit is a subcritical, once-through reheat, double-cylinder double-flow, single-shaft, direct air-cooled, heat supply condensing steam turbine unit, with the product model of CZK312 / N300-16.7 / 538 / 538, the rated back pressure is 14kPa, and the regenerative heaters adopt the form of a combination of 3 high-pressure heaters, 3 low-pressure heaters and a deaerator. Through the heat storage of molten salt by solar energy and the heat release in the hot standby state, and then through the control system including the intelligent flow controller 30, the key parameters in the operation process of the thermal power system are controlled, and the hot standby duration of not less than 6 hours is achieved. The specific key parameters are as follows:

[0058] The feed water flow rate at the outlet of the feed water pump 6 is 10 - 50t / h, and the preferred feed water flow rate is 15 - 20t / h, which can achieve near-zero output of the CFB unit; the boiler feed water is split by the sixth three-way valve 23. One way enters the boiler along the original path through the fourth regulating valve 14 with adjusted opening under the control of the intelligent flow controller 30, allowing the minimum feed water flow rate to enter the boiler to ensure that the heating surface in the furnace does not overheat; the other way passes through the eighth regulating valve 31 and the buffer tank 32, and then under the control of the intelligent flow controller 30, the opening of the fifth regulating valve 15 is adjusted and split into the molten salt-water heat exchanger 7, and the mass flow rate accounts for 40 - 90% of the total feed water volume, preferably 60 - 80%; the main steam comes out of the boiler and then passes through the first three-way valve 18, the seventh regulating valve 17, and the third three-way valve 20, converges 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, and is controlled by the intelligent flow controller 30 at the third regulating valve 13. 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 intermediate-pressure cylinder and the low-pressure cylinder.

[0059] Among them, the feed water volume entering the molten salt-water heat exchanger 7 and the steam volume entering the molten salt-steam heat exchanger 10 are automatically controlled by the intelligent flow controller 30. According to the operating status of each cylinder of the steam turbine, the opening of the fifth regulating valve 15 and the third regulating valve 13 are automatically adjusted to allow the minimum flow rate to enter the cylinder to ensure that no abnormal conditions such as shaft vibration, overheating, and air blowing occur in each cylinder. Preferably, the temperature of the regenerated steam at the outlet of the molten salt-water heat exchanger 7 is 390 - 530°C, and the pressure is 8 - 12MPa. The temperature of the regenerated steam at the outlet of the molten salt-steam heat exchanger 10 is 380 - 530°C.

[0060] Based on the above circulating fluidized bed unit and the parameters adopted, using solar salt as the molten salt working medium, the operation process of the above-mentioned hot standby thermal system during pressure relief is simulated. Based on the simulation parameters, the variation relationship between the main steam flow rate and the unit output power is calculated. As Figure 3 shown, when the main steam flow rate is 20 t / h, the unit output power is only 3.3 MW. After deducting the auxiliary power consumption, almost zero output to the outside can be basically achieved; as Figure 4 shown, when the main steam flow rate is 20 t / h, the pressure relief duration is controlled to be 6 h, and the molten salt consumption is about 900 t.

[0061] It can be seen from the above technical solutions that the hot standby thermal system and operation method for coupling solar energy storage provided by the embodiments of the present invention, by coupling a circulating fluidized bed unit and a solar molten salt energy storage system, store solar energy in the molten salt during sunlight. When the circulating fluidized bed unit enters the hot standby state during pressure relief, the stored heat is used to heat the feed water to generate high-parameter steam, which replaces the low-temperature steam generated by the boiler and enters the steam turbine. On the premise of ensuring the safe operation of the steam turbine, the pressure relief of the circulating fluidized bed unit is not restricted by the decrease in the boiler evaporation capacity, but depends on the layout of the solar mirror field and the heat storage capacity of the molten salt storage tank. The design of the mirror field and the storage tank can be adjusted according to the actual pressure relief duration requirements of the unit. It not only realizes the near-zero output of the unit during pressure relief, but also makes the pressure relief duration not less than 6 h, further creating conditions for the grid connection of new energy; during the hot standby operation, the intelligent flow controller automatically adjusts the feed water volume entering the boiler according to the temperature of the heating surface in the furnace, and automatically adjusts the feed water and steam flow rates entering the molten salt-water heat exchanger and the molten salt-steam heat exchanger according to the operation signals of each cylinder of the steam turbine, allowing the minimum feed water and steam to enter the boiler and the steam turbine, ensuring that the heating surface in the furnace does not exceed the temperature and ensuring that each cylinder of the steam turbine operates normally, effectively reducing the consumption of the heat storage in the boiler furnace and the heat storage of the molten salt, thereby extending the pressure relief duration, realizing the frequent and long-term operation of the CFB unit under the pressure relief condition, and improving the 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 the preferred embodiments of the present invention and the explanation of the applied technical principles, and is not intended to limit the scope of the present invention claimed. Instead, it only represents the preferred embodiments 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 the specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above 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 creative efforts belong to the scope of protection of the present invention.

Claims

1. A pressurized hot standby thermal system coupled with solar energy thermal storage, characterized in that, The system includes: 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 sequentially connected to the first regulating valve, the second three-way valve, and the inlet of the high-pressure cylinder. The second outlet of the first three-way valve is sequentially connected to the seventh regulating valve and the inlet of the third three-way valve. 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 sequentially connected. 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 sequentially connected. The steam outlet of the intermediate-pressure cylinder, the low-pressure cylinder, the condenser, the feed water pump, the sixth three-way valve, the fourth regulating valve, and the feed water inlet of the circulating fluidized bed boiler are sequentially connected. The second outlet of the sixth three-way valve is sequentially 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. Among them, the setting of the buffer tank can enable the water supply amount entering the molten salt-water heat exchanger to be controlled by the intelligent flow controller to adjust the opening degree of the fifth regulating valve. 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 sequentially connected. 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. 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 hot standby thermal power system with coupling solar energy storage and heat storage according to claim 1, characterized in that, The intelligent flow controller includes an information acquisition port, an opening calculation module, a first control port, a second control port, and a third control port. Among them, The information acquisition port is connected to the boiler temperature sensor, the high-pressure cylinder temperature sensor, the intermediate-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 for collecting corresponding parameters. The opening calculation module is simultaneously connected to the first control port, the second control port, and the third control port. 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 opening degrees of the third regulating valve, the fourth regulating valve, and the fifth regulating valve respectively according to the information collected by the information acquisition 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 hot standby thermal power system with coupling solar energy heat storage according to claim 2, characterized in that The opening calculation module of the intelligent flow controller is used to calculate the water flow required by the boiler at the current temperature according to the inlet and outlet temperatures of the flowing steam and the metal wall temperature in the heating surfaces of the water-cooled wall, superheater, and reheater in the boiler measured by the boiler temperature sensor in real time, as well as the preset temperature threshold, generate a control command and send it to the second control port to adjust the opening degree of the fourth regulating valve.

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

5. The hot standby thermal power system with coupled solar energy storage and heat storage according to claim 1, wherein The heat transfer working medium is stored in the high-temperature molten salt tank and / or the low-temperature molten salt tank; the heat transfer working medium is a molten salt medium or any other form of heat transfer medium existing in a liquid state; and the working temperature range of the heat transfer working medium is 120°C - 550°C.

6. The hot standby thermal power system with coupling solar energy thermal storage according to claim 5, wherein, The molten salt medium uses solar salt, with a composition of 60% NaNO3 - 40% KNO3 composition, and the working temperature range is 250°C - 550°C.

7. A method for operating a pressure hot standby thermal system according to any one of claims 1-6, characterized in that, The method includes: Under normal conditions, the circulating fluidized bed unit operates at normal load. The third regulating valve, the fifth regulating valve, the sixth regulating valve, the seventh regulating valve, and the eighth regulating valve are in the closed state, and the remaining regulating valves are in the normal open state; at this time, the steam-water circulation process on the steam turbine side is conventional; at the same time, under sunny conditions, the low-temperature molten salt pump is started to pump the molten salt in the low-temperature molten salt tank into the solar collector to be heated to obtain high-temperature molten salt, which is stored in the high-temperature molten salt tank. When hot standby is started as needed, the circulating fluidized bed boiler is put on hot standby; when the boiler evaporation significantly decreases and the superheat degrees of the main steam and the reheated steam are reduced to 150°C, the high-temperature molten salt pump is started 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 regulating valve and the seventh regulating valve are opened, and the first regulating valve is closed; the third regulating valve is opened, and the second regulating valve is closed. The eighth regulating valve and the fifth regulating valve are opened, and the intelligent flow controller adjusts the opening degree of the fourth regulating valve to adjust the conveyance of all boiler feed water to divert part of the boiler feed water into the circulating fluidized bed boiler, and the remaining feed water enters the buffer tank through the eighth regulating valve, and then part of the remaining feed water is controlled by adjusting the fifth regulating valve to enter the molten salt-water heat exchanger. The feed water exchanges heat with the high-temperature molten salt, and the feed water absorbs heat and becomes the main steam regeneration steam, which flows through the second three-way valve and enters the high-pressure cylinder to do work, ensuring the safe operation of the high-pressure cylinder. The main steam generated by the circulating fluidized bed boiler enters the first three-way valve and the seventh regulating valve, and then enters the first inlet of the third three-way valve. After converging with the exhaust steam from the high-pressure cylinder, it enters the cold reheat steam inlet of the circulating fluidized bed boiler as the cold reheat steam; the reheated steam of the circulating fluidized bed boiler flows through the second outlet of the fourth three-way valve. Under the control of 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 and enters the intermediate-pressure cylinder and the low-pressure cylinder in sequence to do work; the waste steam discharged from the low-pressure cylinder enters the condenser, and then is sent to the sixth three-way valve by the feed water pump as the boiler feed water for circulation.

8. The operating method of the hot standby thermal system under pressure according to claim 7, characterized in that, The intelligent flow controller adjusts the opening degree of the fourth regulating valve, and when the full boiler feed water conveyance is adjusted to a partial boiler feed water diversion into the circulating fluidized bed boiler: Based on the inlet and outlet steam temperatures and metal wall temperatures of the flowing steam in the heating surfaces of the water-cooled wall, superheater, and reheater in the boiler, as well as the metal wall temperature, measured in real time by the boiler temperature sensors, and the preset temperature threshold, calculate the water flow required by the boiler at the current temperature, and generate a control command to adjust the opening degree of the fourth regulating valve.

9. The operating method of the pressure hot standby thermal system according to claim 7, characterized in that The remaining feed water enters the buffer tank through the eighth regulating valve, and then when controlling a part of the remaining feed water to enter the molten salt-water heat exchanger by adjusting the fifth regulating valve: Based on the inlet and outlet steam temperatures and cylinder metal wall temperatures of each cylinder of the steam turbine, monitored in real time by the high-pressure cylinder temperature sensor, intermediate-pressure cylinder temperature sensor, and 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 velocity sensor, and the blade pressure pulsation frequency monitored by the dynamic pressure sensor, calculate the water flow required by the molten salt-water heat exchanger at the current temperature, and generate a control command to adjust the opening degree of the fifth regulating valve.

10. The operating method of the hot standby thermal power system according to claim 7, characterized in that, When 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, and a 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 cylinder of the steam turbine, monitored in real time by the high-pressure cylinder temperature sensor, intermediate-pressure cylinder temperature sensor, and 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 velocity sensor, and the blade pressure pulsation frequency monitored by the dynamic pressure sensor, calculate the steam flow required by the molten salt-steam heat exchanger at the current temperature, and generate a control command to adjust the opening degree of the third regulating valve.

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