Supercritical carbon dioxide power cycle coal-fired boiler power generation system and temperature adjusting method

Abstract

The present application relates to a kind of supercritical carbon dioxide power cycle coal-fired boiler power generation system and temperature regulating method, system includes coal mill, hearth and with the flue connected to hearth upper end, there are heat absorption surface structure in flue from front to back interval arrangement, burner on hearth is connected coal mill;Including head-to-tail sequentially connected pre-cooler, main compressor, re-compressor, high-pressure turbine, low-pressure turbine, the shell side of high-temperature regenerator and the shell side of low-temperature regenerator;Low-pressure turbine and high-pressure turbine are driven connection with generator;Main compressor, the tube side of low-temperature regenerator, the tube side of high-temperature regenerator, hearth sequentially connect;Flue tail portion, induced draft fan, recirculation fan and the bottom of hearth sequentially connect;The shell side outlet of above-mentioned low-temperature regenerator is connected the import of re-compressor.Optimal advantage: can be fine adjustment for different air temperature deviation, multiple ways cooperate and carry out combined temperature regulating can better guarantee the efficient safe operation of supercritical carbon dioxide boiler.

Description

Technical Field

[0001] This invention relates to the field of power generation equipment, and in particular to a supercritical carbon dioxide power cycle coal-fired boiler power generation system and temperature regulation method. Background Technology

[0002] The development of thermal power generation technology is now nearing its bottleneck, and improving the efficiency of traditional coal-fired power generation systems remains extremely difficult. Using water as the working fluid, the efficiency of the steam Rankine cycle has reached its limit. To improve overall efficiency and reduce heat loss, the cycle parameters must be continuously increased, but this is limited by materials. Blindly pursuing high temperatures and pressures will make it difficult to find suitable materials capable of withstanding higher steam parameters, and investment costs will increase significantly. Due to these circumstances, supercritical carbon dioxide (SCO2) has attracted widespread attention as a novel working fluid for power systems. Carbon dioxide is easier to supercritical than water, has weaker high-temperature oxidizing properties than steam, and due to the unique physical properties of supercritical carbon dioxide, the Brayton cycle using it as the working fluid has many advantages. Compared to the steam Rankine cycle, at the same turbine inlet temperature, the S-CO2 Brayton cycle can improve efficiency by 3%-5%. Because the system uses smaller turbines and compressors, and employs efficient and compact printed circuit board heat exchangers, the power generation system becomes more compact and occupies less space. Furthermore, since supercritical carbon dioxide has a higher energy density than water, supercritical carbon dioxide boiler systems can achieve even higher efficiency given the current high-temperature resistance of steel.

[0003] Single-cycle reheating and recompression is one of the most actively researched system layouts in supercritical CO2 coal-fired power generation systems, offering advantages such as system simplicity, compact layout, and high efficiency. However, compared to traditional steam cycle power generation systems, the boiler inlet working fluid temperature in supercritical CO2 coal-fired power generation systems significantly increases from 200℃-300℃ to approximately 500℃. Due to the absence of a phase change process, traditional spray desuperheating techniques are difficult to apply. Furthermore, the Brayton cycle, with its inherent characteristics, results in a large working fluid flow rate within the supercritical CO2 boiler, approximately eight times that of the steam Rankine cycle. To ensure the safe and stable operation of the supercritical CO2 boiler, it must maintain its rated temperature and a certain degree of temperature regulation capability under different loads; otherwise, system efficiency will decrease and boiler safety issues will arise. Traditional power plant steam boilers primarily regulate superheated steam temperature through the "coal-to-water ratio" and spray desuperheating systems. However, in a supercritical CO2 boiler system, the working fluid is in a supercritical state throughout the entire system, and carbon dioxide remains gaseous. Injecting carbon dioxide into the area near the boiler inlet results in poor cooling effects due to the lack of latent heat of vaporization. The changes brought about by the working fluid have rendered traditional technical solutions ineffective for temperature regulation in supercritical carbon dioxide coal-fired boilers. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a supercritical carbon dioxide power cycle coal-fired boiler power generation system and temperature regulation method, which effectively overcomes the defects of the prior art.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0006] A supercritical carbon dioxide power cycle coal-fired boiler power generation system includes:

[0007] A supercritical carbon dioxide boiler system includes a coal mill, a furnace, and a flue connected to the upper end of the furnace. The flue has heat-receiving surface structures arranged at intervals from front to back. The burner on the furnace is connected to the pulverized coal outlet of the coal mill.

[0008] The power cycle power generation system includes a high-temperature regenerator, a low-temperature regenerator, a precooler, a main compressor, a re-compressor, a high-pressure turbine, a low-pressure turbine, and a generator. The inlet and outlet of the precooler, the inlet and outlet of the main compressor, the inlet and outlet of the re-compressor, the inlet and outlet of the high-pressure turbine, the inlet and outlet of the low-pressure turbine, the shell-side inlet and outlet of the high-temperature regenerator, and the shell-side inlet and outlet of the low-temperature regenerator are connected sequentially. The high-pressure turbine and the low-pressure turbine are jointly connected to the generator. The outlet of the main compressor, the tube-side inlet and outlet of the low-temperature regenerator, the tube-side inlet and outlet of the high-temperature regenerator, and the furnace are connected sequentially. The shell-side outlet of the low-temperature regenerator is connected to the inlet of the re-compressor.

[0009] The flue gas recirculation system includes an induced draft fan and a recirculation fan, which are sequentially connected to the tail end of the flue, the induced draft fan, the recirculation fan, and the bottom of the furnace.

[0010] Based on the above technical solution, the present invention can be further improved as follows.

[0011] Furthermore, the aforementioned heating surface structure includes a screen-type superheater, a high-temperature superheater, a high-temperature reheater, a low-temperature reheater, a low-temperature superheater, and a diversion economizer. The high-temperature superheater and the diversion economizer are respectively arranged at the location where the flue connects to the furnace and at the location near the tail end of the flue.

[0012] Furthermore, an air preheater is provided at the tail end of the flue. The outlet of the air preheater, the induced draft fan, the recirculation fan and the bottom of the furnace are connected in sequence. The flow rate of the flue gas introduced into the furnace through the recirculation fan accounts for 5-40% of the total flow rate of the flue gas at the tail end of the flue.

[0013] Furthermore, the outlet of the aforementioned air preheater is connected to the air inlet of the aforementioned coal mill via a primary air fan.

[0014] Furthermore, it also includes a heat exchanger, the shell-side inlet and outlet of which are respectively connected to the furnace, the outlet of the low-temperature regenerator, the tube-side inlet and outlet of the heat exchanger, and the inlet of the diverter economizer are connected in sequence, and the flow rate of the working fluid diverted from the outlet of the low-temperature regenerator to the tube-side inlet of the heat exchanger accounts for 0-25% of the total flow rate of the working fluid at the outlet of the low-temperature regenerator.

[0015] Furthermore, the outlet of the aforementioned mixer is connected to the inlet of the aforementioned high-temperature superheater and the inlet of the high-temperature reheater, and the flow rate of the working fluid diverted into the aforementioned mixer through the outlet of the aforementioned precooler accounts for 0-15% of the total flow rate of the working fluid at the outlet of the aforementioned precooler.

[0016] A temperature control method for a supercritical carbon dioxide power cycle coal-fired boiler power generation system is also provided, including the following methods:

[0017] S1. When the temperature of the main steam and reheat gas in the boiler is higher than or lower than the rated temperature, adjust the amount of pulverized coal fed into the pulverized coal feeding channel composed of the above-mentioned coal mill and primary air fan until the main steam and reheat gas reach the rated temperature range.

[0018] Or S2, when the deviation between the main steam temperature and the rated temperature in the boiler is 0 to +10℃ and the deviation between the reheat gas temperature and the rated temperature is -10 to 0℃, the flue gas recirculation method is adopted, and the recirculation fan connected to the above-mentioned induced draft fan is turned on. The flow rate of the flue gas introduced into the furnace through the above-mentioned recirculation fan accounts for 5% to 15% of the total flow rate of the flue gas at the tail of the above-mentioned flue.

[0019] Or S3, when the deviation between the main steam temperature and the rated temperature in the boiler is within the range of 10 to +20°C and the deviation between the reheat gas temperature and the rated temperature is within the range of -10 to 0°C, turn on the recirculation fan connected to the induced draft fan to increase flue gas recirculation; at the same time, open the channel connecting the outlet of the low-temperature regenerator to the economizer and the heat exchanger to the furnace interior, so that the high-temperature fluid working medium in the furnace and the fluid working medium from the low-temperature regenerator exchange heat through the heat exchanger. The working medium from the low-temperature regenerator is heated by the heat exchanger and then led to the economizer located at the tail of the flue.

[0020] Alternatively, in S4, when the main steam temperature in the boiler deviates from the rated temperature by 20 to +30°C and the reheat gas temperature deviates from the rated temperature by -10 to 0°C, first turn on the recirculation fan connected to the induced draft fan to increase flue gas recirculation; at the same time, open the channel connecting the low-temperature regenerator to the economizer and open the channel connecting the heat exchanger to the furnace interior, so that the high-temperature fluid working medium in the furnace and the fluid working medium from the low-temperature regenerator exchange heat through the heat exchanger; and open the channel between the precooler outlet and the high-temperature superheater, so that the low-temperature fluid working medium from the precooler can be directly mixed with the high-temperature fluid working medium through the mixer.

[0021] Or S5, when the main steam in the boiler deviates from the rated temperature by -10 to 0℃ and the reheat gas deviates from the rated temperature by 0 to +10℃, turn on the recirculation fan connected to the outlet of the induced draft fan, reduce the amount of flue gas recirculation on the basis of existing flue gas recirculation, and the flow rate of flue gas diverted into the furnace by the recirculation fan accounts for 5% to 15% of the total flow rate of flue gas at the tail of the flue.

[0022] Or S6, when the main steam temperature in the boiler deviates from the rated temperature by -10 to 0°C and the reheat gas temperature deviates from the rated temperature by 10 to +20°C, the recirculation fan connected to the outlet of the induced draft fan is turned on to reduce flue gas recirculation; at the same time, the channel connecting the outlet of the low-temperature regenerator to the economizer is turned on, and the channel connecting the heat exchanger to the furnace is turned on, so that the high-temperature fluid working medium in the furnace and the fluid working medium from the low-temperature regenerator can exchange heat through the heat exchanger.

[0023] Or S7, when the main steam temperature in the boiler deviates from the rated temperature by -10 to 0°C and the reheat gas temperature deviates from the rated temperature by 20 to +30°C, first turn on the recirculation fan connected to the outlet of the induced draft fan to reduce flue gas recirculation; at the same time, open the channel between the outlet of the precooler and the high-temperature superheater, and the low-temperature fluid working medium from the precooler is directly mixed with the high-temperature fluid working medium through the mixer.

[0024] Alternatively, if the temperature deviation is not within the range of S1-S7, the coal feed rate should be adjusted first using the method in S1 to adjust the temperature of the main gas or reheat gas with a smaller deviation to within 0 to ±10℃, and then the adjustment methods in S2-S7 should be used for adjustment.

[0025] The beneficial effects of this invention are:

[0026] 1) To address the lack of temperature control methods in supercritical carbon dioxide boilers, a variety of temperature control methods have been designed, which can be finely adjusted for different temperature deviations.

[0027] 2) A combined temperature control method for supercritical carbon dioxide coal-fired boilers is proposed. This method allows for single or multiple combinations of temperature control under different temperature deviation ranges. Since temperature control is difficult to achieve the desired effect through a single method, combining multiple methods can better ensure the efficient and safe operation of supercritical carbon dioxide boilers. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the supercritical carbon dioxide power cycle coal-fired boiler power generation system of the present invention;

[0029] Figure 2 for Figure 1 A schematic diagram showing the cooling of the low-temperature regenerator working fluid and the high-temperature working fluid through a heat exchanger.

[0030] Figure 3 for Figure 1 A schematic diagram showing the mixing and cooling of the low-temperature working fluid in the precooler with the high-temperature superheater and reheater inlet fluid in the boiler.

[0031] The attached diagram lists the components represented by each number as follows:

[0032] 1. Furnace; 2. Screen-type superheater; 3. High-temperature superheater; 4. High-temperature reheater; 5. Low-temperature reheater; 6. Low-temperature superheater; 7. Separate economizer; 8. Air preheater; 9. Induced draft fan; 10. Recirculating fan; 11. Raw coal bunker; 12. Coal feeder; 13. Coal mill; 14. Wind box; 15. High-temperature regenerator; 16. Low-temperature regenerator; 17. Precooler; 18. Main compressor; 19. Recompressor; 20. High-pressure turbine; 21. Low-pressure turbine; 22. Heat exchanger; 23. Generator; 24. Flue; 25. Mixer; 26. Primary air fan. Detailed Implementation

[0033] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0034] Example 1

[0035] like Figure 1 , 2 As shown in Figure 3, the supercritical carbon dioxide power cycle coal-fired boiler power generation system of this embodiment includes:

[0036] The supercritical carbon dioxide boiler system includes a coal mill 13, a furnace 1 and a flue 24 connected to the upper end of the furnace 1. The flue 24 has heat-receiving surface structures arranged at intervals from front to back. The burner on the furnace 1 is connected to the pulverized coal outlet of the coal mill 13.

[0037] The power cycle power generation system includes a high-temperature regenerator 15, a low-temperature regenerator 16, a precooler 17, a main compressor 18, a recompressor 19, a high-pressure turbine 20, a low-pressure turbine 21, and a generator 23. The inlet and outlet of the precooler 17, the inlet and outlet of the main compressor 18, the inlet and outlet of the recompressor 19, the inlet and outlet of the high-pressure turbine 20, the inlet and outlet of the low-pressure turbine 21, the shell-side inlet and outlet of the high-temperature regenerator 15, and the shell-side inlet and outlet of the low-temperature regenerator 16 are connected sequentially. The high-pressure turbine 20 and the low-pressure turbine 21 are... The high-pressure turbine 21 is connected to the generator 23 via a drive (the high-pressure turbine 20, the low-pressure turbine 21, and the generator 23 are coaxially connected to each other). The outlet of the main compressor 18, the tube-side inlet and outlet of the low-temperature regenerator 16, the tube-side inlet and outlet of the high-temperature regenerator 15, and the furnace 1 are connected in sequence. The outlet of the precooler 17 and the top of the furnace 1 are respectively connected to the inlet of the mixer 25. The outlet of the mixer 25 is connected to the inlet of the high-temperature superheater 3. The shell-side outlet of the low-temperature regenerator 16 is connected to the inlet of the re-compressor 19.

[0038] The flue gas recirculation system includes an induced draft fan 9 and a recirculation fan 10, and the tail end of the flue 24, the induced draft fan 9, the recirculation fan 10 and the bottom of the furnace 1 are connected in sequence.

[0039] The flue 24 is equipped with an air preheater 8 at its tail end. The outlet of the air preheater 8, the induced draft fan 9, the recirculation fan 10, and the bottom of the furnace 1 are sequentially connected. The outlet of the air preheater 8 is connected to the air inlet of the coal mill 13 via a primary air fan 26. A heat exchanger 22 is also provided, with its shell-side inlet and outlet connected to the furnace 1. The outlet of the low-temperature regenerator 16, the tube-side inlet and outlet of the heat exchanger 22, and the inlet of the economizer 7 are sequentially connected. Flow valves or shut-off valves can be installed on each of the above pipelines to control the flow and flow rate of the fluid, i.e., to control the opening of a certain section of the pipeline.

[0040] In this embodiment, the above-mentioned heating surface structure includes a screen-type superheater 2, a high-temperature superheater 3, a high-temperature reheater 4, a low-temperature reheater 5, a low-temperature superheater 6, and a flow-dividing economizer 7. The high-temperature superheater 3 and the flow-dividing economizer 7 are respectively arranged at the position where the flue 24 connects to the furnace 1 and at the position near the tail end of the flue 24. The screen-type superheater 2, the high-temperature superheater 3, the high-temperature reheater 4, the low-temperature reheater 5, and the flow-dividing economizer 7 are arranged sequentially and at intervals in the flue 24 according to the flow direction of the flue gas. The low-temperature superheater 6 is arranged side by side near the low-temperature reheater 5.

[0041] The temperature regulation method of the system in this embodiment includes the following approaches during use:

[0042] Method S1: When the temperature of the main steam and reheat gas in the boiler is higher or lower than the rated temperature, the method of adjusting the coal feed rate and CO2 flow rate is adopted until the main steam and reheat gas reach the rated temperature range. Specifically, the coal feed rate of the coal feeding channel composed of the above-mentioned coal mill 13 and primary air fan 26 is adjusted until the main steam and reheat gas reach the rated temperature range. The other units of the system are not changed.

[0043] In the above-mentioned S1 method, the coal mill 13 is connected to the coal feeder 12 at the coal inlet, the coal feeder 12 is connected to the raw coal bunker 11 at the feed inlet, and a wind box 14 is provided on the channel connecting the coal mill 13 and the burner.

[0044] Method S2: When the deviation between the main steam temperature and the rated temperature in the boiler is 0 to +10℃ and the deviation between the reheat gas temperature and the rated temperature is -10 to 0℃, flue gas recirculation is adopted. Specifically, the recirculation fan 10 connected to the induced draft fan 9 is turned on. Due to the increase in the amount of recirculated flue gas, the temperature level of the lower temperature flue gas at the tail of the boiler flows into the furnace 1, and the radiative heat absorption of the furnace 1 is reduced. The superheaters (low-temperature superheater 6 and high-temperature superheater 3) in the flue duct 24 mainly absorb radiative heat, and the reheaters (high-temperature reheater 4 and low-temperature reheater 5) are convective heating surfaces. After the recirculated flue gas increases, the flue gas velocity increases and the convective heat transfer increases, thereby causing the reheaters to heat up and the superheaters to cool down, reducing the deviation between the reheat gas and the main steam temperature and the rated temperature. Among them, the flow rate of the flue gas introduced into the furnace 1 through the recirculation fan 10 accounts for 5% to 15% of the total flow rate of the flue gas at the tail of the flue duct 24.

[0045] Method S3: When the deviation between the main steam temperature and the rated temperature in the boiler is within the range of 10 to +20℃ and the deviation between the reheat gas temperature and the rated temperature is within the range of -10 to 0℃, a flue gas recirculation method + low-temperature regenerator adjustment method is adopted. Specifically, the recirculation fan 10 connected to the induced draft fan 9 is turned on to increase flue gas recirculation; at the same time, the channel connecting the outlet of the low-temperature regenerator 16 to the economizer 7 is turned on, and the channel connecting the heat exchanger 22 to the inside of the furnace 1 is turned on, so that the high-temperature fluid working medium in the furnace 1 and the fluid working medium from the low-temperature regenerator 16 exchange heat through the heat exchanger 22. After the working medium from the low-temperature regenerator 16 is heated by the heat exchanger 22, it is led to the economizer 7 located at the tail of the flue 24, and the other branch channels remain unchanged.

[0046] Method S4: When the main steam temperature in the boiler deviates from the rated temperature by 20 to +30°C and the reheat gas temperature deviates from the rated temperature by -10 to 0°C, a flue gas recirculation method combined with a low-temperature regenerator adjustment method is adopted. Specifically, the recirculation fan 10 connected to the induced draft fan 9 is turned on first to increase flue gas recirculation; at the same time, the channel connecting the low-temperature regenerator 16 and the economizer 7 is turned on, and the channel connecting the heat exchanger 22 and the interior of the furnace 1 is turned on, so that the high-temperature fluid working medium in the furnace 1 and the fluid working medium from the low-temperature regenerator 16 exchange heat through the heat exchanger 22. The channel between the outlet of the precooler 17 and the high-temperature superheater 3 is turned on, and the low-temperature fluid working medium from the precooler 17 is directly mixed with the high-temperature fluid working medium through the mixer 25.

[0047] Method S5: When the main steam temperature in the boiler deviates from the rated temperature by -10 to 0℃ and the reheat gas temperature deviates from the rated temperature by 0 to +10℃, a flue gas recirculation method is adopted. Specifically, the recirculation fan 10 connected to the outlet of the induced draft fan 9 is turned on, and the amount of flue gas recirculation is reduced on the basis of the existing flue gas recirculation. The flow rate of the flue gas diverted into the furnace 1 by the recirculation fan 10 accounts for 5% to 15% of the total flow rate of the flue gas at the tail of the flue duct 24.

[0048] Method S6: When the main steam temperature in the boiler deviates from the rated temperature by -10 to 0℃ and the reheat gas temperature deviates from the rated temperature by 10 to +20℃, a flue gas recirculation method combined with a low-temperature regenerator adjustment method is adopted. Specifically, the recirculation fan 10 connected to the outlet of the induced draft fan 9 is turned on to reduce flue gas recirculation; at the same time, the channel connecting the outlet of the low-temperature regenerator 16 to the economizer 7 is turned on, and the channel connecting the heat exchanger 22 to the interior of the furnace 1 is turned on, so that the high-temperature fluid working medium in the furnace 1 and the fluid working medium from the low-temperature regenerator 16 exchange heat through the heat exchanger 22, while the other branch channels remain unchanged.

[0049] Method S7: When the main steam temperature in the boiler deviates from the rated temperature by -10 to 0°C and the reheat gas temperature deviates from the rated temperature by 20 to +30°C, a flue gas recirculation method combined with a precooler adjustment method is adopted. Specifically, the recirculation fan 10 connected to the outlet of the induced draft fan 9 is turned on first to reduce flue gas recirculation; at the same time, the channel between the outlet of the precooler 17 and the high-temperature superheater 3 is turned on, and the low-temperature fluid working medium from the precooler 17 is directly mixed with the high-temperature fluid working medium through the mixer 25.

[0050] Method S8: If the temperature deviation is not within the range of S1-S7, first use the method in S1 to adjust the coal feed rate, adjust the temperature of the main gas or reheat gas with a smaller deviation to within 0 to ±10℃, and then use the adjustment methods in S2-S7 for adjustment.

[0051] It should be noted that, regardless of which temperature control method is selected, the amount of flue gas diverted and the mass of fluid in the system should be optimized and adjusted according to the maximum temperature of furnace 1, the NOx concentration level, and the combustion efficiency.

[0052] More specifically, taking a 300MW supercritical carbon dioxide coal-fired boiler with main gas outlet parameters of 28MPa and 600℃ as an example, after the carbon dioxide working fluid flows out of the storage tank and is heated by the various heating surfaces in the supercritical carbon dioxide boiler, the main gas temperature is higher than the rated temperature, while the reheat gas temperature is lower than the rated temperature. At this time, since the reheater is arranged after the superheater, the first consideration is to use the flue gas recirculation method. The flue gas recirculation channel is opened to increase the flow rate of recirculated flue gas. The inflow of tail flue gas causes the temperature of furnace 1 to decrease. Since the superheater mainly absorbs radiant heat, while the reheater is a convective heating surface, the increase in flue gas recirculation can make the reheater heat up and the superheater cool down, thereby reducing the deviation between the two and the rated temperature to meet the requirements. If the deviation between the two temperatures and the rated temperature is too large, resulting in poor flue gas recirculation adjustment, the ratio of coal feed rate to CO2 flow rate can be adjusted. This involves changing the amount of pulverized coal fed into the pulverized coal feeding channel, which consists of the raw coal bunker 11, coal feeder 12, coal mill 13, wind box 14, and primary air fan 26. Increasing the ratio of coal feed rate to CO2 flow rate will raise the temperature inside the furnace 1. The increased heat will ensure that both the superheated and reheated temperatures reach or exceed the rated temperature by at least 600℃. When the rated temperature is exceeded, the overheated heating surface should be identified. Using a preheater regulation method, the low-temperature fluid working medium channel leading out from the air preheater (8) is opened. This channel is connected to the inlet of the superheated heating surface (where carbon dioxide is heated to about 590°C) through a mixer 25. The low-temperature fluid working medium in the channel and the high-temperature fluid working medium at the inlet of the superheated heating surface are directly mixed to reduce the temperature to 580°C. After the temperature is reduced in this way, the final stage superheater (low-temperature superheater 6) heats the mixed carbon dioxide working medium to the rated temperature of 600°C.

[0053] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0054] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0055] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0056] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0057] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0058] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A supercritical carbon dioxide power cycle coal-fired boiler power generation system, characterized by, include: The supercritical carbon dioxide boiler system includes a coal mill (13), a furnace (1) and a flue (24) connected to the upper end of the furnace (1). The flue (24) has heat-receiving surface structures arranged at intervals from front to back. The burner on the furnace (1) is connected to the pulverized coal outlet of the coal mill (13). The power cycle power generation system includes a high-temperature regenerator (15), a low-temperature regenerator (16), a precooler (17), a main compressor (18), a recompressor (19), a high-pressure turbine (20), a low-pressure turbine (21), and a generator (23). The inlet and outlet of the precooler (17), the inlet and outlet of the main compressor (18), the inlet and outlet of the recompressor (19), the inlet and outlet of the high-pressure turbine (20), the inlet and outlet of the low-pressure turbine (21), and the high-temperature regenerator (17) are connected to the generator. The shell-side inlet and outlet of the low-temperature regenerator (15) and the shell-side inlet and outlet of the low-temperature regenerator (16) are connected sequentially; the high-pressure turbine (20) and the low-pressure turbine (21) are connected to the generator (23) for transmission; the outlet of the main compressor (18), the tube-side inlet and outlet of the low-temperature regenerator (16), the tube-side inlet and outlet of the high-temperature regenerator (15), and the furnace (1) are connected sequentially; the shell-side outlet of the low-temperature regenerator (16) is connected to the inlet of the re-compressor (19); The flue gas recirculation system includes an induced draft fan (9) and a recirculation fan (10), and the tail end of the flue (24), the induced draft fan (9), the recirculation fan (10) and the bottom of the furnace (1) are connected in sequence. The heating surface structure includes a screen-type superheater (2), a high-temperature superheater (3), a high-temperature reheater (4), a low-temperature reheater (5), a low-temperature superheater (6), and a flow divider economizer (7). The high-temperature superheater (3) and the flow divider economizer (7) are respectively arranged at the position where the flue (24) connects to the furnace (1) and at the position near the tail end of the flue (24). An air preheater (8) is provided at the tail end of the flue (24). The outlet of the air preheater (8), the induced draft fan (9), the recirculation fan (10) and the bottom of the furnace (1) are connected in sequence. The flow rate of the flue gas introduced into the furnace (1) through the recirculation fan (10) accounts for 5-40% of the total flow rate of the flue gas at the tail end of the flue (24). It also includes a heat exchanger (22), the shell-side inlet and outlet of which are connected to the furnace (1), the outlet of the low-temperature regenerator (16), the tube-side inlet and outlet of the heat exchanger (22), and the inlet of the diverter economizer (7) are connected in sequence. The flow rate of the working fluid diverted from the outlet of the low-temperature regenerator (16) to the tube-side inlet of the heat exchanger (22) accounts for 0-25% of the total flow rate of the working fluid at the outlet of the low-temperature regenerator (16).

2. The supercritical carbon dioxide power cycle coal-fired boiler power generation system of claim 1, wherein: The outlet of the air preheater (8) is connected to the air inlet of the coal mill (13) via a primary air fan (26).

3. The supercritical carbon dioxide power cycle coal-fired boiler power generation system of claim 1, wherein: The outlet of the pre-cooler (17) and the top of the furnace (1) are connected to the inlet of a mixer (25), the outlet of the mixer (25) is connected to the inlet of the high-temperature superheater (3) and the inlet of the high-temperature reheater (4), and the flow of the fluid working medium entering the mixer (25) through the outlet of the pre-cooler (17) accounts for 0-15% of the total flow of the fluid working medium at the outlet of the pre-cooler (17).

4. A method of temperature adjustment of a supercritical carbon dioxide power cycle coal-fired boiler power generation system as claimed in claim 3, characterized by, The method comprises the following modes: S1, when the temperature of the main steam and the reheated steam in the boiler is higher than the rated steam temperature or lower than the rated steam temperature, the pulverized coal quantity of the powder feeding channel composed of the coal mill (13) and the primary air fan (26) is adjusted until the main steam and the reheated steam reach the rated steam temperature range; S2, when the deviation of the main steam from the rated steam temperature is in the range of 0~+10℃ and the deviation of the reheated steam from the rated steam temperature is in the range of -10~0℃, a flue gas recirculation mode is adopted, the recirculation fan (10) connected to the induced draft fan (9) is started, and the flow of the flue gas introduced into the furnace (1) through the recirculation fan (10) accounts for 5%~15% of the total flow of the flue gas at the tail of the flue (24); S3, when the deviation of the main steam from the rated steam temperature is in the range of 10~+20℃ and the deviation of the reheated steam from the rated steam temperature is in the range of -10~0℃, the recirculation fan (10) connected to the induced draft fan (9) is started, and the flue gas recirculation is increased; meanwhile, the channel between the outlet of the low-temperature regenerator (16) and the shunt economizer (7) is started, and the channel between the heat exchanger (22) and the inside of the furnace (1) is started, so that the high-temperature fluid working medium in the furnace (1) and the fluid working medium coming from the low-temperature regenerator (16) exchange heat through the heat exchanger (22), and the working medium coming from the low-temperature regenerator (16) is introduced into the shunt economizer (7) at the tail of the flue (24) after being heated by the heat exchanger (22); S4, when the deviation of the main steam from the rated steam temperature is in the range of 20~+30℃ and the deviation of the reheated steam from the rated steam temperature is in the range of -10~0℃, the recirculation fan (10) connected to the induced draft fan (9) is started first, and the flue gas recirculation is increased; meanwhile, the channel between the low-temperature regenerator (16) and the shunt economizer (7) is started, and the channel between the heat exchanger (22) and the inside of the furnace (1) is started, so that the high-temperature fluid working medium in the furnace (1) and the fluid working medium coming from the low-temperature regenerator (16) exchange heat through the heat exchanger (22), and the channel between the outlet of the pre-cooler (17) and the high-temperature superheater (3) is started, so that the low-temperature fluid working medium coming from the pre-cooler (17) is directly mixed with the high-temperature fluid working medium through the mixer (25). Or S5, when the main steam in the boiler deviates from the rated gas temperature by -10~0℃ and the reheat gas deviates from the rated gas temperature by 0~+10℃, open the recirculation fan (10) connected to the outlet of the induced draft fan (9), reduce the amount of flue gas recirculation on the basis of the existing flue gas recirculation, and introduce the flue gas flow through the recirculation fan (10) into the furnace (1) at 5%~15% of the total flue gas flow at the tail of the flue (24); Or S6, when the main steam in the boiler deviates from the rated gas temperature by -10~0℃ and the reheat gas deviates from the rated gas temperature by 10~+20℃, open the recirculation fan (10) connected to the outlet of the induced draft fan (9) to reduce flue gas recirculation; at the same time, open the channel connecting the outlet of the low-temperature regenerator (16) and the shunt economizer (7), and open the channel connecting the heat exchanger (22) and the furnace (1) inside, so that the high-temperature fluid working medium in the furnace (1) and the fluid working medium coming from the low-temperature regenerator (16) exchange heat through the heat exchanger (22); Or S7, when the main steam in the boiler deviates from the rated gas temperature by -10~0℃ and the reheat gas deviates from the rated gas temperature by 20~+30℃, first open the recirculation fan (10) connected to the outlet of the induced draft fan (9) to reduce flue gas recirculation; at the same time, open the channel between the outlet of the pre-cooler (17) and the high-temperature superheater (3), and the low-temperature fluid working medium from the pre-cooler (17) is mixed directly with the high-temperature fluid working medium through the mixer (25); Or S8, if the gas temperature deviation is not within the range described in S1-S7, first adjust the coal supply amount in S1, adjust the gas temperature with smaller deviation in the main gas or reheat gas to within 0~±10℃, and then use the adjustment method of S2-S7.

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