A supercritical carbon dioxide Brayton cycle thermal power generation system and process

Abstract

This invention discloses a supercritical carbon dioxide Brayton cycle thermal power generation system and process. The superheater is connected to a turbine. The turbine exhaust pipe is sequentially connected to the low-pressure side of a high-low temperature regenerator. The low-pressure side outlet of the low-temperature regenerator is connected to the inlet of a recompressor and a low-temperature air heater, respectively. The outlet of the low-temperature air heater is sequentially connected to a precooler and a main compressor. The main compressor outlet is connected to the high-pressure side inlet of the low-temperature regenerator. The recompressor outlet is connected to the high-pressure side outlet of the low-temperature regenerator, and then sequentially connected to the high-pressure side of a high-temperature regenerator and a high-temperature carbon dioxide heater. Medium- and low-temperature carbon dioxide heaters are connected in parallel with the high- and low-temperature regenerators, and flue gas air heaters are connected in parallel with the low-temperature carbon dioxide heaters. Air is heated by a fan from either the low- or high-temperature air heaters or the flue gas air heaters, and then divided into primary and secondary air before being sent to the boiler. This invention recovers some of the heat energy dissipated in the precooler, achieving cascade utilization of flue gas energy and overcoming the defect of different heat capacity flow rates of hot and cold fluids.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal power generation, and in particular relates to a supercritical carbon dioxide Brayton cycle thermal power generation system and process. Background Art

[0002] Thermal power generation generally uses the Rankine cycle with water vapor as the circulating working fluid. However, the thermal power generation technology based on the Rankine cycle has developed to a very mature stage. Due to the limitations of high-temperature materials and economic factors, it is very difficult to further improve the power generation efficiency. For this reason, countries around the world attach great importance to the research of new forms of power generation cycles to improve the power generation cycle efficiency. Among the many new power generation methods, the Brayton cycle with supercritical carbon dioxide as the working fluid is considered to be the most promising power cycle method. In the supercritical carbon dioxide Brayton cycle, the carbon dioxide working fluid needs to be precooled to near the critical point by a precooler before entering the main compressor. The high critical parameters of carbon dioxide make the working fluid temperature entering the precooler higher, and a considerable amount of heat energy (about 50% of the input energy) is dissipated, affecting the cycle efficiency of the carbon dioxide Brayton cycle. On the other hand, the flue gas at the tail of the boiler usually heats the air through an air preheater. The inlet air temperature of the air preheater is determined by the atmospheric environment, usually at 20-30°C; while the exhaust gas temperature is usually not too low due to the low-temperature corrosion temperature of the heat exchanger and the downstream process temperature, and is usually limited to 120-140°C. This makes it inevitable that the cold end of the air preheater will have a large heat exchange temperature and pressure of the cold and hot fluids, resulting in certain irreversible losses and limiting the improvement of the boiler's thermal efficiency. In summary, the traditional thermal power generation thermal system using supercritical carbon dioxide Brayton cycle still has the disadvantages of large heat dissipation of the radiator and large irreversible losses at the tail of the air preheater, and there is still a lot of room for efficiency improvement. Summary of the invention

[0003] The object of the present invention is to provide a supercritical carbon dioxide Brayton cycle thermal power generation system and process to solve the above technical problems.

[0004] The present invention is achieved by adopting the following technical solutions:

[0005] A supercritical carbon dioxide Brayton cycle thermal power generation system, comprising a boiler, a superheater, a high-temperature carbon dioxide heater, a medium-temperature carbon dioxide heater, a low-temperature carbon dioxide heater, a flue gas air heater, a turbine, a high-temperature regenerator, a low-temperature regenerator, a high-temperature air heater, a low-temperature air heater, a fan, a precooler, a main compressor and a recompressor; wherein:

[0006] The boiler is equipped with a superheater, which is connected to the turbine through a pipeline; the exhaust pipeline of the turbine is connected to the low-pressure side inlet of the high-temperature regenerator;

[0007] The low-pressure side outlet of the high-temperature regenerator is divided into two paths, one of which is connected to the low-pressure side inlet of the low-temperature regenerator, and the other is connected to the hot side inlet of the high-temperature air heater; the hot side outlet of the high-temperature air heater is connected to the low-pressure side outlet of the low-temperature regenerator, and then divided into two paths, one of which is connected to the recompressor inlet, and the other is connected to the hot side inlet of the low-temperature air heater, the hot side outlet of the low-temperature air heater is connected to the precooler inlet, the precooler outlet is connected to the main compressor inlet, the main compressor outlet is divided into two paths, one of which is connected to the high-pressure side inlet of the low-temperature regenerator, and the other is connected to the low-temperature carbon dioxide heater inlet; the low-temperature carbon dioxide heater outlet and the recompressor outlet are connected to the high-pressure side outlet of the low-temperature regenerator, and after mixing, they are divided into two paths again, one of which is connected to the high-pressure side inlet of the high-temperature regenerator, and the other is connected to the inlet of the medium-temperature carbon dioxide heater, the medium-temperature carbon dioxide heater outlet is connected to the high-pressure side outlet of the high-temperature regenerator, and after mixing, they are connected to the high-temperature carbon dioxide heater inlet;

[0008] The fan inlet is connected to the atmosphere, and the fan outlet is connected to the air side inlet of the low-temperature air heater. The air side outlet of the low-temperature air heater is divided into two paths, one is connected to the air side inlet of the high-temperature air heater, and the other is connected to the flue gas air heater inlet; the air side outlet of the high-temperature air heater and the flue gas air heater outlet are divided into primary air and secondary air.

[0009] A further improvement of the present invention is that by controlling the flow rate of carbon dioxide flowing through the high-temperature air heater, the heat capacity flow rate of carbon dioxide in the high-temperature air heater is made the same as the heat capacity flow rate of air, and the pinch point problem of the low-temperature regenerator is solved by adjusting the flow rate of the recompressor.

[0010] A further improvement of the present invention is that the heat capacity flow rate of the carbon dioxide in the low temperature carbon dioxide heater is made the same as the heat capacity flow rate of the flue gas by controlling the flow rate of the carbon dioxide flowing into the low temperature carbon dioxide heater.

[0011] A further improvement of the present invention is that the heat capacity flow rate of the carbon dioxide in the medium temperature carbon dioxide heater is made the same as the heat capacity flow rate of the flue gas by controlling the flow rate of the carbon dioxide flowing into the medium temperature carbon dioxide heater.

[0012] A further improvement of the present invention is that the carbon dioxide flowing into the precooler is cooled to reach the required main compressor inlet temperature.

[0013] A further improvement of the present invention is that it also includes a second precooler and a precompressor, the hot side outlet of the high-temperature air heater is connected to the low-pressure side outlet of the low-temperature regenerator, and then the second precooler and the precompressor are connected in sequence, and the precompressor outlet is divided into two paths, one is connected to the recompressor inlet, and the other is connected to the hot side inlet of the low-temperature air heater.

[0014] A supercritical carbon dioxide Brayton cycle thermal power generation process, based on the above-mentioned supercritical carbon dioxide Brayton cycle thermal power generation system, comprises the following steps:

[0015] The fan draws air from the atmosphere and then divides it into two streams. One stream is sent to the low-temperature air heater, where the air is heated by carbon dioxide from the low-temperature regenerator and the high-temperature air heater. The heated air is sent to the high-temperature air heater for further heating, and then divided into primary air and secondary air to participate in boiler combustion; the other stream is sent to the air preheater arranged in parallel with the low-temperature carbon dioxide heater for preheating, and then divided into primary air and secondary air to participate in boiler combustion; the flue gas generated by the combustion flows through the furnace and the tail flue in turn, transferring the heat energy released by the fuel combustion to the carbon dioxide working medium;

[0016] The high-temperature and high-pressure carbon dioxide fluid is sent to the turbine through the pipeline connecting the superheater and the turbine to expand and do work, and the turbine exhaust enters the low-pressure side of the high-temperature regenerator to heat the carbon dioxide on the high-pressure side;

[0017] The carbon dioxide flowing out from the low-pressure side of the high-temperature regenerator is divided into two streams, one stream flows into the high-temperature air heater to heat the air from the low-temperature air heater, and the other stream flows into the low-pressure side of the low-temperature regenerator to continue to release heat to heat the carbon dioxide on the high-pressure side of the low-temperature regenerator; the carbon dioxide flowing out from the low-pressure side of the low-temperature regenerator is mixed with the carbon dioxide flowing out from the high-temperature air heater and then divided into two streams, one stream flows into the recompressor for compression, and the other stream flows into the low-temperature air heater to heat the air sent in by the fan; the carbon dioxide flowing out of the low-temperature air heater is cooled by the precooler and then sent to the main compressor, and the carbon dioxide pressurized by the main compressor is divided into two streams, one stream flows into the high-pressure side of the low-temperature regenerator to be heated, and the other stream is heated by the low-temperature carbon dioxide heater and mixed with the carbon dioxide at the high-pressure side outlet of the low-temperature regenerator and the recompressor outlet; the mixed working fluid is divided into two streams again, one stream flows into the high-pressure side of the high-temperature regenerator to absorb heat, and the other stream is heated by the medium-temperature carbon dioxide heater and mixed with the carbon dioxide at the high-pressure side outlet of the high-temperature regenerator, and then sent together to the high-temperature heater of the boiler for heating.

[0018] A further improvement of the present invention is that the air preheating method in the process is applicable to other supercritical carbon dioxide Brayton cycle systems using a boiler as a heat source.

[0019] A further improvement of the present invention is that, if the air needs to be heated to a higher temperature, an air heater is added in parallel with the high-temperature regenerator, and the heat capacity flow rate of the fluid on both sides of the air heater is controlled to be the same.

[0020] The present invention has at least the following beneficial technical effects:

[0021] 1. A low-temperature air heater is added in front of the precooler to use the carbon dioxide before the precooler to heat the air to recover part of the heat energy dissipated in the precooler, which can solve the problem of large heat energy dissipation in the precooler in the traditional supercritical carbon dioxide Brayton cycle.

[0022] 2. By arranging low-temperature CO2 heaters and medium-temperature CO2 heaters, the temperature of CO2 and flue gas is matched, and the energy level matching between low-temperature flue gas and low-temperature regenerator, and between medium-temperature flue gas and high-temperature regenerator is achieved, thereby improving efficiency. At the same time, the diversion of low-temperature CO2 heaters and medium-temperature CO2 heaters also reduces the working fluid flow on the high-pressure side of the low-temperature regenerator and the high-temperature regenerator, which can alleviate the pinch point problem of the regenerator.

[0023] 3. By controlling the carbon dioxide flow rate, the heat capacity flow rate of air and the heat capacity flow rate of carbon dioxide, the heat capacity flow rate of flue gas and the heat capacity flow rate of carbon dioxide are equal, thus overcoming the defect of different heat capacity flow rates of cold and hot fluids, thereby avoiding the pinch point problem and reducing energy loss.

[0024] 4. The traditional air preheater at the tail of the boiler is eliminated. The air is preheated by the low-temperature air heater and heated to the required temperature by the high-temperature air heater and the flue gas air heater. That is, the heat of the low-temperature flue gas is utilized by the low-temperature carbon dioxide heater. By controlling the flow rate of the working fluid flowing into the low-temperature carbon dioxide heater, the heat capacity flow rate of the flue gas is made the same as the heat capacity flow rate of the carbon dioxide, thus avoiding the pinch point problem. By introducing carbon dioxide at a suitable temperature, the exhaust gas temperature can be further reduced without low-temperature corrosion or with slight corrosion, thus improving the boiler efficiency and eliminating the various defects of using a traditional air preheater. At the same time, when the carbon dioxide flow rate in the low-temperature carbon dioxide heater is not enough to fully cool the flue gas, a suitable amount of air can be introduced into the flue gas air heater to fully utilize the heat of the low-temperature flue gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of a supercritical carbon dioxide Brayton cycle thermal power generation system of the present invention.

[0026] Figure 2 It is a structural schematic diagram of another embodiment of a supercritical carbon dioxide Brayton cycle thermal power generation system of the present invention.

[0027] Description of reference numerals:

[0028] 1- boiler; 2- superheater; 3- high temperature carbon dioxide heater; 4- medium temperature carbon dioxide heater; 5- low temperature carbon dioxide heater; 6- flue gas air heater; 7- primary air; 8- secondary air; 9- turbine; 10- high temperature regenerator; 11- low temperature regenerator; 12- high temperature air heater; 13- low temperature air heater; 14- fan; 15- precooler; 16- main compressor; 17- recompressor; 18- second precooler; 19- precompressor. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] refer to Figure 1 A supercritical carbon dioxide Brayton cycle thermal power generation system provided by the present invention includes a boiler 1, a superheater 2, a high-temperature carbon dioxide heater 3, a medium-temperature carbon dioxide heater 4, a low-temperature carbon dioxide heater 5, a flue gas air heater 6, a turbine 9, a high-temperature regenerator 10, a low-temperature regenerator 11, a high-temperature air heater 12, a low-temperature air heater 13, a fan 14, a precooler 15, a main compressor 16 and a recompressor 17.

[0031] The boiler 1 is provided with a superheater 2, which is connected to the turbine 9 through a pipeline; the exhaust pipeline of the turbine 9 is connected to the low-pressure side inlet of the high-temperature regenerator 10; the low-pressure side outlet of the high-temperature regenerator 10 is divided into two paths, one of which is connected to the low-pressure side inlet of the low-temperature regenerator 11, and the other is connected to the hot side inlet of the high-temperature air heater 12; the hot side outlet of the high-temperature air heater 12 is connected to the low-pressure side outlet of the low-temperature regenerator 11, and then divided into two paths, one of which is connected to the inlet of the recompressor 17, and the other is connected to the hot side inlet of the low-temperature air heater 13; the hot side outlet of the low-temperature air heater 13 is connected to the inlet of the precooler 15, The outlet of the precooler 15 is connected to the inlet of the main compressor 16. The outlet of the main compressor 16 is divided into two paths, one of which is connected to the high-pressure side inlet of the low-temperature regenerator 11, and the other is connected to the inlet of the low-temperature carbon dioxide heater 5; the outlet of the low-temperature carbon dioxide heater 5 and the outlet of the recompressor 17 are connected to the high-pressure side outlet of the low-temperature regenerator 11, and after mixing, they are divided into two paths, one of which is connected to the high-pressure side inlet of the high-temperature regenerator 10, and the other is connected to the inlet of the medium-temperature carbon dioxide heater 4. The outlet of the medium-temperature carbon dioxide heater 4 is connected to the high-pressure side outlet of the high-temperature regenerator 10, and after mixing, they are connected to the inlet of the high-temperature carbon dioxide heater 3.

[0032] The inlet of the fan 14 is connected to the atmosphere, and the outlet of the fan 14 is connected to the air side inlet of the low-temperature air heater 13. The air side outlet of the low-temperature air heater 13 is divided into two paths, one path is connected to the air side inlet of the high-temperature air heater 12, and the other path is connected to the inlet of the flue gas air heater 6; the air side outlet of the high-temperature air heater 12 and the outlet of the flue gas air heater 6 are divided into primary air 7 and secondary air 8.

[0033] The traditional air preheater at the rear of the boiler 1 is eliminated. The air is preheated by the low-temperature air heater 13 and heated to the temperature required for fuel combustion by the high-temperature air heater 12 and the flue gas air heater 6. Depending on the type of fuel, the air generally needs to be heated to 320-350°C.

[0034] A low-temperature air heater 13 is added before the precooler 15 to recover part of the heat energy dissipated in the precooler 15, and the temperature difference at the cold end of the low-temperature air heater 13 is 10-20°C.

[0035] The flow rate of carbon dioxide flowing through the high temperature air heater 12 is controlled so that the heat capacity flow rate of carbon dioxide in the high temperature air heater 12 is the same as the heat capacity flow rate of air, and the pinch point problem of the low temperature regenerator 11 is solved by adjusting the flow rate of the recompressor 17. Since the change of air volume affects the combustion of the boiler 1, the air volume is not controlled to ensure that the heat capacity flow rate of the fluid on both sides of the high temperature air heater 12 is equal, but the flow rate of carbon dioxide flowing through the high temperature air heater 12 is controlled so that the heat capacity flow rate of the fluid on both sides of the heater is equal; the high temperature air heater 12 needs to heat the air to the temperature required for the combustion of the boiler 1; the pinch point temperature of the high temperature air heater 12 is 10-20°C, and the pinch point temperature of the low temperature regenerator 11 is 5-10°C.

[0036] The flow rate of carbon dioxide flowing into the low-temperature carbon dioxide heater 5 is controlled so that the heat capacity flow rate of carbon dioxide in the low-temperature carbon dioxide heater 5 is the same as the heat capacity flow rate of flue gas. The temperature of carbon dioxide flowing into the low-temperature carbon dioxide heater 5 should be as far as possible to ensure that low-temperature corrosion does not occur. This temperature should be selected according to the acid dew point, but it should not be too high, otherwise the circulation efficiency will be reduced. Generally, this temperature is 70-80°C. Although it may cause slight corrosion, the degree of low-temperature corrosion is much lower than that of normal air temperature; the pinch point temperature of the low-temperature carbon dioxide heater 5 is 15-30°C.

[0037] A flue gas air heater 6 is added in parallel with the low-temperature air heater 13 so as to flexibly adjust the heat capacity flow rates of the cold and hot fluids in the high-temperature air heater 12; when the carbon dioxide flow rate in the low-temperature carbon dioxide heater 5 is not enough to fully cool the flue gas, an appropriate amount of air can be introduced into the flue gas air heater 6 to fully utilize the heat of the low-temperature flue gas; the flue gas flow rate flowing through the flue gas air heater 6 and the low-temperature carbon dioxide heater 5 is adjusted by the flue gas baffle, and when the carbon dioxide flow rate in the low-temperature carbon dioxide heater 5 makes the heat capacity flow rate of carbon dioxide the same as the heat capacity flow rate of the flue gas and can fully cool the flue gas, the flue gas air heater 6 can be completely isolated; the pinch point temperature of the flue gas air heater 6 is 15-30°C.

[0038] The flow rate of carbon dioxide flowing into the medium temperature carbon dioxide heater 4 is controlled so that the heat capacity flow rate of carbon dioxide in the medium temperature carbon dioxide heater 4 is the same as the heat capacity flow rate of flue gas. The pinch point temperature of the medium temperature carbon dioxide heater 4 is 15-30°C.

[0039] Furthermore, the carbon dioxide flowing into the precooler 15 needs to be cooled to the required inlet temperature of the main compressor 16. The good performance of the supercritical carbon dioxide Brayton cycle benefits from the physical properties of carbon dioxide, especially the physical properties near the critical point. Near the critical point, the density of carbon dioxide is very large, and the density changes very drastically. It is this characteristic that greatly reduces the power consumption of the compressor, thereby improving the cycle efficiency. Therefore, carbon dioxide also needs to be cooled to near the critical temperature of carbon dioxide, generally 32°C, by the precooler 15.

[0040] The inlet pressure of the main compressor 16 is 7.4-7.9 MPa; the pinch point temperature of the high-temperature regenerator 10 is generally 5-10° C.; the low-temperature regenerator 11 and the high-temperature regenerator 10 use printed circuit board heat exchangers.

[0041] The present invention provides a supercritical carbon dioxide Brayton cycle thermal power generation process, comprising the following steps:

[0042] The fan 14 extracts air from the atmosphere and sends it to the low-temperature air heater 13. In the low-temperature air heater 13, the air is heated by the carbon dioxide from the low-temperature regenerator 11 and the high-temperature air heater 12, and then divided into two streams. One stream is sent to the high-temperature air heater 12 for further heating, and then divided into the primary air 7 and the secondary air 8 to participate in the combustion of the boiler 1; the other stream is sent to the flue gas air heater 6 arranged in parallel with the low-temperature carbon dioxide heater 5 for preheating, and then divided into the primary air 7 and the secondary air 8 to participate in the combustion of the boiler 1; the flue gas generated by the combustion flows through the furnace and the tail flue in sequence, and the heat energy released by the fuel combustion is transferred to the carbon dioxide working medium;

[0043] The high-temperature and high-pressure carbon dioxide fluid is sent to the turbine 9 through the pipeline connecting the superheater 2 and the turbine 9 to expand and do work, and the exhaust gas of the turbine 9 enters the low-pressure side of the high-temperature regenerator 10 to heat the carbon dioxide on the high-pressure side;

[0044] The carbon dioxide flowing out of the low-pressure side of the high-temperature regenerator 10 is divided into two streams, one stream flows into the high-temperature air heater 12 to heat the air from the low-temperature air heater 13, and the other stream flows into the low-pressure side of the low-temperature regenerator 11 to continue to release heat to heat the carbon dioxide on the high-pressure side of the low-temperature regenerator 11; the carbon dioxide flowing out of the low-pressure side of the low-temperature regenerator 11 is mixed with the carbon dioxide flowing out of the high-temperature air heater 12 and then divided into two streams, one stream flows into the recompressor 17 for compression, and the other stream flows into the low-temperature air heater 13 to heat the air sent in by the fan 14; the carbon dioxide flowing out of the low-pressure air heater 13 After being cooled by the precooler 15, it is sent to the main compressor 16. The carbon dioxide pressurized by the main compressor 16 is divided into two streams, one stream flows into the high-pressure side of the low-temperature regenerator 11 to be heated, and the other stream is heated by the low-temperature carbon dioxide heater 5 and mixed with the carbon dioxide at the high-pressure side outlet of the low-temperature regenerator 11 and the outlet of the recompressor 17; the mixed working fluid is divided into two streams, one stream enters the high-pressure side of the high-temperature regenerator 10 to absorb heat, and the other stream is heated by the medium-temperature carbon dioxide heater 4 and mixed with the carbon dioxide at the high-pressure side outlet of the high-temperature regenerator 10, and then sent to the high-temperature heater of the boiler 1 for heating.

[0045] For other supercritical carbon dioxide Brayton cycle systems using the boiler 1 as a heat source, such as a pre-compression cycle, a reheat cycle, etc., the preheating of air adopts the heating method of the present invention.

[0046] In practical applications, it may be necessary to heat the gas (including but not limited to air) to a higher temperature. A heater connected in parallel with the high-temperature regenerator 10 may be added, and the heat capacity flow rate of the fluid on both sides of the heater may be controlled to be the same.

[0047] refer to Figure 2 Another embodiment of a supercritical carbon dioxide Brayton cycle thermal power generation system of the present invention is different from the previous embodiment in that: this embodiment is used for a partially cooled Brayton cycle, and the partially cooled Brayton cycle system includes a boiler 1, a superheater 2, a high-temperature carbon dioxide heater 3, a medium-temperature carbon dioxide heater 4, a low-temperature carbon dioxide heater 5, a flue gas air heater 6, a turbine 9, a high-temperature regenerator 10, a low-temperature regenerator 11, a high-temperature air heater 12, a low-temperature air heater 13, a fan 14, a precooler 15, a main compressor 16, a recompressor 17, a second precooler 18 and a precompressor 19.

[0048] A superheater 2 is provided in the boiler 1, and the superheater 2 is connected to the turbine 9 through a pipeline; the exhaust pipeline of the turbine 9 is connected to the low-pressure side inlet of the high-temperature regenerator 10; the low-pressure side outlet of the high-temperature regenerator 10 is divided into two paths, one of which is connected to the low-pressure side inlet of the low-temperature regenerator 11, and the other is connected to the hot side inlet of the high-temperature air heater 12; the hot side outlet of the high-temperature air heater 12 is connected to the low-pressure side outlet of the low-temperature regenerator 11, and then connected to the second precooler 18 and the precompressor 19 in sequence, the outlet of the precompressor 19 is divided into two paths, one of which is connected to the inlet of the recompressor 17, and the other is connected to the hot side inlet of the low-temperature air heater 13, the low-temperature air heater 13 The hot side outlet is connected to the inlet of the precooler 15, the precooler 15 outlet is connected to the inlet of the main compressor 16, the main compressor 16 outlet is divided into two paths, one path is connected to the high-pressure side inlet of the low-temperature regenerator 11, and the other path is connected to the inlet of the low-temperature carbon dioxide heater 5; the low-temperature carbon dioxide heater 5 outlet and the recompressor 17 outlet are connected to the high-pressure side outlet of the low-temperature regenerator 11, and after mixing, they are divided into two paths again, one path is connected to the high-pressure side inlet of the high-temperature regenerator 10, and the other path is connected to the inlet of the medium-temperature carbon dioxide heater 4, the outlet of the medium-temperature carbon dioxide heater 4 is connected to the high-pressure side outlet of the high-temperature regenerator 10, and after mixing, they are connected to the inlet of the high-temperature carbon dioxide heater 3;

[0049] The inlet of the fan 14 is connected to the atmosphere, and the outlet of the fan 14 is connected to the air side inlet of the low-temperature air heater 13. The air side outlet of the low-temperature air heater 13 is divided into two paths, one path is connected to the air side inlet of the high-temperature air heater 12, and the other path is connected to the inlet of the flue gas air heater 6; the air side outlet of the high-temperature air heater 12 and the outlet of the flue gas air heater 6 are divided into primary air 7 and secondary air 8.

[0050] The working process of this embodiment is as follows: the fan 14 extracts air from the atmosphere and then divides it into two streams, one of which is sent to the low-temperature air heater 13, where the air is heated by the carbon dioxide from the low-temperature regenerator 11 and the high-temperature air heater 12, and the heated air is sent to the high-temperature air heater 12 for further heating, and then divided into the primary air 7 and the secondary air 8 to participate in the combustion of the boiler 1; the other stream is sent to the air preheater arranged in parallel with the low-temperature carbon dioxide heater 5 for preheating, and then divided into the primary air 7 and the secondary air 8 to participate in the combustion of the boiler 1; the flue gas generated by the combustion flows through the furnace and the tail flue in sequence, and the heat energy released by the fuel combustion is transferred to the carbon dioxide working medium; the high-temperature and high-pressure carbon dioxide fluid is sent to the turbine 9 through the pipeline connecting the superheater 2 and the turbine 9 to expand and do work, and the exhaust gas of the turbine 9 enters the low-pressure side of the high-temperature regenerator 10 to heat the carbon dioxide on the high-pressure side; the carbon dioxide flowing out from the low-pressure side of the high-temperature regenerator 10 is divided into two streams, one of which flows into the high-temperature air heater 12 to heat the air from the low-temperature air heater 13, and the other stream enters the low-pressure side of the low-temperature regenerator 11 to continue to release heat to heat the low-temperature regenerator The carbon dioxide flowing out of the low-pressure side of the low-temperature regenerator 11 is mixed with the carbon dioxide flowing out of the high-temperature air heater 12, and then cooled and released by the second precooler 18, and then sent to the pre-compressor 19 to be compressed to the required pressure and then divided into two streams, one stream flows into the re-compressor 17 for compression, and the other stream flows into the low-temperature air heater 13 to heat the air sent by the fan 14; the last stream flows through the flow control valve and mixes with the carbon dioxide flowing out of the low-temperature air heater 13; the carbon dioxide flowing out of the low-temperature air heater 13 is cooled by the precooler 15 and then sent to the main compressor 16. The carbon dioxide pressurized by the main compressor 16 is divided into two streams, one stream flows into the high-pressure side of the low-temperature regenerator 11 to be heated, and the other stream is heated by the low-temperature carbon dioxide heater 5 and mixed with the carbon dioxide at the high-pressure side outlet of the low-temperature regenerator 11 and the outlet of the re-compressor 17; the mixed working fluid is divided into two streams, one stream enters the high-pressure side of the high-temperature regenerator 10 to absorb heat, and the other stream is heated by the medium-temperature carbon dioxide heater 4 and mixed with the carbon dioxide at the high-pressure side outlet of the high-temperature regenerator 10, and then sent to the high-temperature heater of the boiler 1 together for heating.

[0051] The partial cooling cycle has the advantage that the exhaust pressure of the turbine 9 is independent of the inlet pressure of the main compressor 16, and also has the advantages of a recompression cycle.

Claims

1. A supercritical carbon dioxide Brayton cycle thermal power generation system, characterized in that: The invention comprises a boiler (1), a superheater (2), a high-temperature carbon dioxide heater (3), a medium-temperature carbon dioxide heater (4), a low-temperature carbon dioxide heater (5), a flue gas air heater (6), a turbine (9), a high-temperature regenerator (10), a low-temperature regenerator (11), a high-temperature air heater (12), a low-temperature air heater (13), a fan (14), a precooler (15), a main compressor (16) and a recompressor (17); wherein: A superheater (2) is provided in the boiler (1), and the superheater (2) is connected to a turbine (9) through a pipeline; an exhaust pipeline of the turbine (9) is connected to a low-pressure side inlet of a high-temperature regenerator (10); The low-pressure side outlet of the high-temperature regenerator (10) is divided into two paths, one of which is connected to the low-pressure side inlet of the low-temperature regenerator (11), and the other is connected to the hot side inlet of the high-temperature air heater (12); the hot side outlet of the high-temperature air heater (12) is connected to the low-pressure side outlet of the low-temperature regenerator (11), and then divided into two paths, one of which is connected to the inlet of the recompressor (17), and the other is connected to the hot side inlet of the low-temperature air heater (13); the hot side outlet of the low-temperature air heater (13) is connected to the inlet of the precooler (15), and the outlet of the precooler (15) is connected to the inlet of the main compressor (16). 6) The outlet is divided into two paths, one path is connected to the high-pressure side inlet of the low-temperature regenerator (11), and the other path is connected to the inlet of the low-temperature carbon dioxide heater (5); the outlet of the low-temperature carbon dioxide heater (5) and the outlet of the recompressor (17) are connected to the high-pressure side outlet of the low-temperature regenerator (11), and after mixing, they are divided into two paths again, one path is connected to the high-pressure side inlet of the high-temperature regenerator (10), and the other path is connected to the inlet of the medium-temperature carbon dioxide heater (4); the outlet of the medium-temperature carbon dioxide heater (4) is connected to the high-pressure side outlet of the high-temperature regenerator (10), and after mixing, they are connected to the inlet of the high-temperature carbon dioxide heater (3); The inlet of the fan (14) is connected to the atmosphere, and the outlet of the fan (14) is connected to the air side inlet of the low-temperature air heater (13). The air side outlet of the low-temperature air heater (13) is divided into two paths, one of which is connected to the air side inlet of the high-temperature air heater (12), and the other is connected to the inlet of the flue gas air heater (6). The air side outlet of the high-temperature air heater (12) and the outlet of the flue gas air heater (6) are divided into primary air (7) and secondary air (8); The carbon dioxide flowing into the precooler (15) is cooled to reach the required inlet temperature of the main compressor (16); It also includes a second precooler (18) and a precompressor (19). The hot side outlet of the high-temperature air heater (12) is connected to the low-pressure side outlet of the low-temperature regenerator (11), and then connected to the second precooler (18) and the precompressor (19) in sequence. The outlet of the precompressor (19) is divided into two paths, one of which is connected to the inlet of the recompressor (17) and the other is connected to the hot side inlet of the low-temperature air heater (13).

2. A supercritical carbon dioxide Brayton cycle thermal power generation system according to claim 1, characterized in that: By controlling the flow rate of carbon dioxide flowing through the high-temperature air heater (12), the heat capacity flow rate of carbon dioxide in the high-temperature air heater (12) is made the same as the heat capacity flow rate of air, and the pinch point problem of the low-temperature regenerator (11) is solved by adjusting the flow rate of the recompressor (17).

3. A supercritical carbon dioxide Brayton cycle thermal power generation system according to claim 1, characterized in that: By controlling the flow rate of carbon dioxide flowing into the low-temperature carbon dioxide heater (5), the heat capacity flow rate of carbon dioxide in the low-temperature carbon dioxide heater (5) is made the same as the heat capacity flow rate of flue gas.

4. A supercritical carbon dioxide Brayton cycle thermal power generation system according to claim 1, characterized in that: By controlling the flow rate of carbon dioxide flowing into the medium-temperature carbon dioxide heater (4), the heat capacity flow rate of carbon dioxide in the medium-temperature carbon dioxide heater (4) is made the same as the heat capacity flow rate of flue gas.

5. A supercritical carbon dioxide Brayton cycle thermal power generation process, characterized in that: The process is based on a supercritical carbon dioxide Brayton cycle thermal power generation system according to any one of claims 1 to 4, comprising the following steps: The fan (14) draws air from the atmosphere and then divides it into two streams. One stream is sent to the low-temperature air heater (13). In the low-temperature air heater (13), the air is heated by carbon dioxide from the low-temperature regenerator (11) and the high-temperature air heater (12). The heated air is sent to the high-temperature air heater (12) for further heating and then divided into primary air (7) and secondary air (8) to participate in the combustion of the boiler (1); the other stream is sent to the air preheater arranged in parallel with the low-temperature carbon dioxide heater (5) for preheating and then divided into primary air (7) and secondary air (8) to participate in the combustion of the boiler (1); the flue gas generated by the combustion flows through the furnace and the tail flue in sequence, transferring the heat energy released by the combustion of the fuel to the carbon dioxide working medium; The high-temperature and high-pressure carbon dioxide fluid is sent to the turbine (9) through a pipeline connecting the superheater (2) and the turbine (9) to expand and perform work, and the exhaust gas of the turbine (9) enters the low-pressure side of the high-temperature regenerator (10) to heat the carbon dioxide on the high-pressure side; The carbon dioxide flowing out of the low-pressure side of the high-temperature regenerator (10) is divided into two streams, one of which flows into the high-temperature air heater (12) to heat the air from the low-temperature air heater (13), and the other flows into the low-pressure side of the low-temperature regenerator (11) to continue to release heat to heat the carbon dioxide on the high-pressure side of the low-temperature regenerator (11); the carbon dioxide flowing out of the low-pressure side of the low-temperature regenerator (11) is mixed with the carbon dioxide flowing out of the high-temperature air heater (12) and then divided into two streams, one of which flows into the recompressor (17) for compression, and the other flows into the low-temperature air heater (13) to heat the air sent in by the fan (14 ...temperature air heater (13) After being cooled by the precooler (15), the carbon dioxide is sent to the main compressor (16). After being pressurized by the main compressor (16), the carbon dioxide is divided into two streams. One stream flows into the high-pressure side of the low-temperature regenerator (11) to be heated, and the other stream is heated by the low-temperature carbon dioxide heater (5) and mixed with the carbon dioxide at the high-pressure side outlet of the low-temperature regenerator (11) and the outlet of the recompressor (17). The mixed working fluid is further divided into two streams. One stream flows into the high-pressure side of the high-temperature regenerator (10) to absorb heat, and the other stream is heated by the medium-temperature carbon dioxide heater (4) and mixed with the carbon dioxide at the high-pressure side outlet of the high-temperature regenerator (10). Then, the two streams are sent to the high-temperature heater of the boiler (1) for heating.

6. A supercritical carbon dioxide Brayton cycle thermal power generation process according to claim 5, characterized in that: The air preheating method in this process is applicable to other supercritical carbon dioxide Brayton cycle systems using the boiler (1) as a heat source.

7. A supercritical carbon dioxide Brayton cycle thermal power generation process according to claim 5, characterized in that: If the air needs to be heated to a higher temperature, an air heater is added in parallel with the high-temperature regenerator (10), and the heat capacity flow rate of the fluid on both sides of the air heater is controlled to be the same.

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