Supercritical-transcritical CO2 coal-fired power generation system adapted to different geographical environments, climates and loads

Abstract

The present invention discloses a supercritical-transcritical carbon dioxide coal-fired power generation system adaptable to different geographical environments, climates, and loads. The system comprises a boiler subsystem, a circulation subsystem, and a refrigeration subsystem, wherein the refrigeration subsystem utilizes a LiBr absorption refrigeration device and / or a thermoelectric refrigeration device. The present invention selects a refrigeration system based on the ambient temperature, combining the advantages of absorption refrigeration and thermoelectric refrigeration to address the seasonal changes in ambient temperature and the resulting changes in the working fluid pressurization method under different climate conditions. The system also improves the utilization rate of the boiler's low-temperature flue gas waste heat and the low-temperature CO2 waste heat from the circulation cooler, thereby increasing boiler and circulation efficiency and reducing system losses. The system proposes three different operating systems to ensure safe and efficient system operation in response to geographically and climatically diverse conditions. Furthermore, the system proposes two different boiler layout structures to address the efficiency and economic benefits arising from varying system loads.

Description

Technical Field

[0001] The present invention relates to the technical field of coal-fired power generation, in particular to a supercritical-transcritical carbon dioxide coal-fired power generation system adaptable to different geographical environments, climates and loads. Background Art

[0002] my country is a major coal consumer, with coal-fired power generation maintaining a dominant position. Currently, the steam Rankine cycle is widely used in coal-fired power generation, but efficiency has hit bottlenecks due to issues such as water properties, phase change exergy losses, and material limitations. In contrast, supercritical carbon dioxide (SCO2) coal-fired power generation has become an effective approach to breaking through the efficiency bottlenecks of traditional power generation due to its high cycle efficiency, compact system structure, water conservation, and environmental friendliness.

[0003] The critical point of carbon dioxide (CO2) is 7.38 MPa and 30.98°C, which is easily achieved in practice. Because CO2's physical properties change dramatically near the critical point, with high density, low viscosity, and a small compressibility factor, this can reduce compressor power consumption and improve cycle efficiency. However, due to the high specific heat of CO2 near the critical point, water cooling requires a large amount of cooling water to ensure a good match between hot and cold streams.

[0004] The actual cooling configuration of a power plant requires consideration of numerous factors, including local climate and locational characteristics. Due to global environmental concerns, climate change, and population growth, per capita water shortages are becoming increasingly severe, making water consumption a critical issue for power plants. This is particularly true in northwest China, which is rich in coal resources but severely lacks water. Therefore, to address this water conservation issue, SCO2 cycle coal-fired power plants can utilize air cooling, significantly conserving water resources. However, actual air cooling is significantly affected by environmental factors such as seasonal variations and the shift between day and night, making it often difficult to achieve the desired temperature. In summer, with outdoor temperatures reaching 35-40°C, air cooling may only reduce the CO2 temperature to around 50°C. Furthermore, some regions experience significant diurnal temperature fluctuations, which significantly hinders system efficiency. Generally, southern China experiences prolonged periods of high temperatures, northern China experiences prolonged periods of moderate to low temperatures, and northwestern China also experiences significant diurnal temperature fluctuations. Therefore, effective solutions to address these geographical differences are still needed.

[0005] The temperature of CO2 entering the cooler is relatively high, often exceeding 100°C. Using this heat for cooling with water or air would not only cause low-temperature pollution but also result in significant exergy losses, reducing energy conversion and utilization efficiency. Furthermore, the boiler exhaust temperature is 120-130°C, and this waste heat loss is a major factor hindering boiler efficiency. Therefore, effectively utilizing these two heat sources is a key method for improving power generation systems.

[0006] For thermodynamic cycles, the impact of cold source temperature on cycle efficiency cannot be ignored. Taking the Carnot cycle as an example, under certain heat source conditions, the lower the cold source temperature, the greater the cycle efficiency. Furthermore, within the same geographic location, the cold source temperature fluctuates with the seasons, with high temperatures in summer, low temperatures in winter, and mild temperatures in spring and autumn. High ambient temperatures in summer typically lead to supercritical CO2 cycles. When temperatures are low in winter, the cooler is sufficient to cool the working fluid to a subcritical state. Therefore, effectively utilizing the ambient cold in winter offers significant potential for improving the efficiency of the CO2 cycle. This also presents challenges in addressing the need for stable and efficient operation adjustment strategies for systems operating under different operating conditions caused by seasonal changes.

[0007] Unlike conventional steam Rankine cycles, CO2 undergoes no phase change in the boiler under the same load due to the low specific heat of SCO2 at high temperatures. While this can reduce exergy losses, unlike steam boilers, the heat transfer between the working fluid and the tube wall within the CO2 boiler furnace is also a convective process between the supercritical fluid and the tube wall. This results in an excessively low heat transfer coefficient between the working fluid and the tube wall, which can easily lead to deteriorated heat transfer and affect the safe operation of the boiler. Therefore, it is necessary to find a reasonable way to improve the surface structure of the various components and pipes to accommodate the heat transfer between CO2 and the tube wall.

[0008] The greater the system load, the greater the working fluid flow rate, and therefore the larger the area of ​​each boiler heating surface. Because the working fluid in a high-load system has a longer path through the boiler heating surface, it causes greater resistance losses along the path. Furthermore, an increase in the working fluid flow rate also increases resistance losses. For the cycle, an increase in pressure drop directly increases the power consumption of the compressor or directly reduces the turbine inlet parameters. Both changes will reduce the efficiency of the cycle. Calculations have shown that for boilers below 100 megawatts, the pressure drop has little effect on the cycle efficiency; however, for boilers with loads of hundreds of megawatts or even greater, the pressure drop significantly affects the cycle efficiency. Therefore, different strategies should be adopted to address the pressure drop problem for different load systems. Summary of the Invention

[0009] Regarding the problem raised by the above background technology: For different geographical environments, the ambient temperature varies with the seasons. If it is operated according to a single system, the efficiency and economy cannot be maximized. The solution may be to design a supercritical-transcritical carbon dioxide coal-fired power generation system and corresponding adjustment strategies that can adapt to different geographical environments, climates and loads to adapt to different geographical environments and climates.

[0010] In response to the problems raised by the above background technology: For the utilization of working fluid and flue gas waste heat, the solution to improve energy conversion and utilization efficiency can be to couple the system with different refrigeration systems respectively, cool the branch working fluid to a low temperature, and use a pump to compress it to a high-pressure state. The branch high-pressure working fluid can be combined with the injection device and the high-temperature exhaust gas to mix and reheat, which can increase the cycle work, which is equivalent to converting the low-temperature waste heat into high-quality kinetic energy.

[0011] Regarding the problem raised by the above background technology: the ratio of the above-mentioned tributary working fluid varies with the ambient temperature of different systems and seasons. If the ratio cannot be well predicted by the ambient temperature, it will be difficult to operate the system to the ideal design working condition. The solution can be to find the relationship between the seasonal ambient temperature of different systems, and propose the proportional relationship between the ambient temperature and each diversion point and the corresponding adjustment method.

[0012] The above background technology raises the following issues: When the ambient temperature is high, cooling can usually only reach a supercritical state. Furthermore, higher ambient temperatures increase the compressor inlet temperature and compressor power consumption. To reduce compressor power consumption and improve cycle efficiency, a bypass preheater can be introduced, employing a single-stage intercooling method with the refrigerant as a branch flow. This method achieves two goals at once: it not only cools the main flow, reducing the power consumption of the main compressor, but also preheats the branch flow, improving energy utilization and reducing exergy losses.

[0013] Regarding the problem raised by the above background technology: when the ambient temperature is relatively low, the cooler can cool it to a liquid state. At this time, the compressor cannot be used for boosting. However, when using a pump for boosting, the problem of phase change due to temperature rise of the pump during boosting is also faced. The occurrence of this problem will cause cavitation in the pump, seriously affecting the safe operation of the pump. The solution can be to control the flow rate of the working fluid to be cooled to control the pump outlet state, so that the pump outlet state can be slightly lower than the critical state, which can ensure the safe operation of the system and reduce the power consumption of the working fluid boosting process.

[0014] In summary, the overall objectives of the present invention are to propose a supercritical-transcritical CO2 coal-fired power generation system that is adaptable to different geographical environments, climates, and loads. This system addresses the issue of seasonal changes in ambient temperature, which in turn leads to changes in the working fluid pressurization method. Furthermore, the system improves the utilization rate of the low-temperature flue gas waste heat from the boiler and the low-temperature CO2 waste heat from the recirculating cooler, thereby increasing boiler and recirculation efficiency and reducing system exergy losses.

[0015] To solve the above technical problems, the technical means adopted by the present invention are: a supercritical-transcritical carbon dioxide coal-fired power generation system that can adapt to different geographical environments, climates and loads, including a boiler subsystem, a circulation subsystem and a refrigeration subsystem, and the refrigeration subsystem adopts a LiBr absorption refrigeration device and / or a thermoelectric refrigeration device.

[0016] The boiler subsystem includes a cooling wall, a reheat wall, a superheater, a high-temperature reheater, a low-temperature reheater, an economizer, an air preheater, a flue gas absorber and an ejector.

[0017] The circulation subsystem includes a bypass regenerator, a high-temperature regenerator, a low-temperature regenerator, a cooler, a branch working fluid pump, a main working fluid pump, a bypass preheater, a first-stage main compressor, a second-stage main compressor, a recompressor, a low-pressure turbine, a medium-pressure turbine and a high-pressure turbine.

[0018] The LiBr absorption refrigeration system includes an evaporator, an absorber, a LiBr solution throttle valve, a LiBr solution pump, a LiBr solution heat exchanger, a generator, a condenser, a water throttle valve, a cold storage tank, and a heat storage tank. The LiBr absorption refrigeration system uses LiBr solution as the working fluid, with water as the refrigerant and LiBr as the absorbent. The refrigeration system is divided into a refrigerant cycle and an absorbent solution cycle. In the generator, the LiBr solution absorbs heat from the heat tank, generating water vapor that is transported to the condenser, releasing heat with the air and condensing into water. Simultaneously, the LiBr solution concentration in the generator increases. The concentrated LiBr solution, also at a high temperature, passes through the LiBr solution heat exchanger and the LiBr solution throttle valve before entering the absorber. The condensed water, after cooling through the water throttle valve, enters the evaporator to absorb the heat released by CO2. It then returns to a gaseous state at the evaporator outlet and enters the absorber, where it is absorbed by the concentrated LiBr solution, simultaneously reducing the solubility of the LiBr solution. The dilute LiBr solution, powered by the LiBr solution pump, absorbs heat from the concentrated LiBr solution in the LiBr solution heat exchanger before returning to the generator, completing the cycle. The refrigerant absorbs cold energy in the evaporator and releases it in the cold tank; water absorbs heat in the hot tank and releases it in the generator.

[0019] The thermoelectric cooling device comprises a hot-end heat storage module, a thermoelectric module, a cold-end cold storage module, and a DC power supply. The device absorbs and releases heat through the temperature difference and thermal resistance between the hot-end heat storage module and the cold-end cold storage module. The thermoelectric module comprises m pairs of PN junctions. A DC power supply is connected to the thermoelectric module, creating a potential difference across the PN junctions and generating a stable current. The heat source is the hot-end heat storage module. The thermoelectric module absorbs heat to lower the temperature of the cold-end cold storage module, generating a certain amount of cooling capacity for cooling the CO2 working medium.

[0020] The refrigeration subsystem of this system can be equipped with a LiBr absorption refrigeration unit and / or a thermoelectric refrigeration unit, enabling the formation of three supercritical-transcritical CO2 cycle coal-fired power generation systems tailored to different geographical environments, climates, and loads. Therefore, the present invention proposes three supercritical-transcritical CO2 coal-fired power generation systems tailored to different geographical environments, climates, and loads.

[0021] (1) Supercritical-transcritical CO2 cycle coal-fired power generation system adapted to the climate in southern China

[0022] The refrigeration subsystem only uses a LiBr absorption refrigeration device, and the circulation subsystem also includes a first three-way valve, a second three-way valve, a third three-way valve, a fourth three-way valve, a fifth three-way valve, a sixth three-way valve, a seventh three-way valve, an eighth three-way valve, a ninth three-way valve, a thirteenth three-way valve, an eleventh three-way valve, a twelfth three-way valve and a thirteenth three-way valve.

[0023] The outlet of the low-pressure turbine is connected to port B of the first three-way valve. Port A of the first three-way valve is connected to the bypass regenerator and port C of the second three-way valve in sequence. Port C of the first three-way valve is connected to the high-temperature regenerator, the low-temperature regenerator and port A of the second three-way valve in sequence. Port B of the second three-way valve is connected to port A of the third three-way valve. Port C of the third three-way valve is connected to the hot tank and port C of the fourth three-way valve in sequence. Port B of the third three-way valve is connected to port C of the fifth three-way valve. Port A of the fourth three-way valve and port A of the fifth three-way valve are connected to ports A and C of the sixth three-way valve respectively. Port B of the fourth three-way valve and port B of the fifth three-way valve are connected to ports A and B of the seventh three-way valve respectively. The B port of the sixth three-way valve is connected to the recompressor and the B port of the thirteenth three-way valve in sequence, the C port of the seventh three-way valve is connected to the cooler and the A port of the eighth three-way valve in sequence, the C port of the eighth three-way valve is connected to the cold tank, the branch working medium pump and the C port of the ninth three-way valve in sequence, the B port of the eighth three-way valve is connected to the A port of the eleventh three-way valve, the A port of the ninth three-way valve is connected to the B port of the thirteenth three-way valve, the B port of the ninth three-way valve is connected to the bypass preheater and the A port of the thirteenth three-way valve in sequence, the C port of the thirteenth three-way valve is connected to the bypass regenerator, the economizer and the ejector in sequence, and the B port of the eleventh three-way valve is connected to the The first-stage main compressor, the bypass preheater, the second-stage main compressor and the A port of the twelfth three-way valve, the C port of the eleventh three-way valve are connected in sequence to the mainstream working fluid pump and the B port of the twelfth three-way valve, the C port of the twelfth three-way valve is connected in sequence to the C port of the thirteenth three-way valve, the A port of the thirteenth three-way valve is connected in sequence to the high-temperature regenerator, the cooling wall, the superheater, the high-pressure turbine, the low-temperature reheater, the reheat wall and the medium-pressure turbine, the medium-pressure turbine is respectively connected to the inlet of the ejector, the high-temperature reheater and the low-pressure turbine; wherein, the hot tank is connected to the flue gas absorber to further absorb the heat of the waste flue gas in the flue gas absorber.

[0024] Due to the southern region's hot and rainy summers and mild and dry winters, temperatures remain above 20°C for most of the year, with an ambient temperature of 20°C as the boundary. This means that the CO2 Brayton cycle in southern China can only cool the working fluid above its critical point most of the time. Furthermore, due to the high temperature of the cooling source, the temperature of the waste heat required to be cooled is also relatively high. For these climatic conditions, LiBr absorption refrigeration systems are suitable. This cooling method can absorb waste heat above 70°C, while achieving a COP of around 0.7, offering high efficiency, good energy savings, and high economic benefits. During the rare periods when the ambient temperature falls below 20°C, LiBr absorption refrigeration units can also absorb a small amount of waste heat from boiler flue gas for operation. Since the ambient temperature is low, the working fluid can be cooled to a liquid state, requiring less cooling capacity per unit of working fluid. Therefore, while the cooling capacity decreases with lower ambient temperature, a larger proportion of the working fluid in the bypass stream can be cooled by the refrigeration system.

[0025] The present invention also discloses the range of valve openings that change with ambient temperature in response to the climate in southern China, as shown in Table 1: Table 1 Typical valve openings of supercritical-transcritical carbon dioxide cycle coal-fired power generation systems in response to the climate in southern China

[0026]

[0027] The mainstream working fluid enters from port A of the eighth three-way valve, and the working fluid with different flow rates flows out of the B and C outlets; at the same time, the working fluid that has done work flows into from port B of the first three-way valve, and the working fluid with different flow rates flows out of the A and C outlets. When the ambient temperature is 10-15 ℃, the flow rate ratio of the C port of the eighth three-way valve is 0.58-1, and the flow rate ratio of the A port of the first three-way valve is 0.36-0.6; when the ambient temperature is 15-20 ℃, the flow rate ratio of the C port of the eighth three-way valve is 0.38-0.58, and the flow rate ratio of the A port of the first three-way valve is 0.24-0.36; when the ambient temperature is 20-25 ℃, the flow rate ratio of the C port of the eighth three-way valve is 0.44-0.62, and the flow rate ratio of the A port of the first three-way valve is 0.27-0.46; when the ambient temperature is 25-30 ℃, the flow rate ratio of the C port of the eighth three-way valve is 0.62-0.63, and the flow rate ratio of the A port of the first three-way valve is 0.46-0.47; when the ambient temperature is greater than 30 At ℃, the flow rate ratio of the C outlet of the eighth three-way valve is greater than 0.63, and the flow rate ratio of the A outlet of the first three-way valve is greater than 0.47.

[0028] When the ambient temperature of this system is below 20°C, the cooler can cool the working fluid to a liquid state. In this case, the booster must be replaced with a pump. However, the pump increases both pressure and temperature during operation. Therefore, the working fluid is prone to phase change during operation, transitioning to a supercritical state and causing cavitation. To address this issue, this system employs the following approach:

[0029] The circulation subsystem also includes a cooling pool, and the mainstream working fluid pump is arranged in the cooling pool. For the eleventh three-way valve, the working fluid flows in from port A, wherein port B is closed and port C is opened. At this time, the working fluid flows out from port C and is pressurized by the water-immersed mainstream working fluid pump. At this time, since the main compressor is not working, the bypass preheater is also not working, that is, port A of the thirteenth-way valve and port B of the ninth three-way valve are in a closed state. The water-immersed pump can increase pressure and reduce temperature at the same time, and the cooling efficiency of the pump can be changed by changing the flow rate of the water pool, so that the working fluid does not undergo phase change. The arrangement of the water-immersed pump can not only ensure that phase change cavitation does not occur during the pressurization process, but also the cooling of the pump by the water pool can reduce the working power consumption of the pump, so that the pump can operate safely and efficiently, thereby improving the efficiency of the system.

[0030] The opening and closing conditions of the inlets and outlets of the twelfth, third, fifth, sixth, fourth, and seventh three-way valves are as follows: When the ambient temperature is below 20°C, inlet A of the twelfth three-way valve is closed, the fluid flows in through port B, and flows out through port C; inlet A and outlet C of the third three-way valve are open, and outlet B is closed; the inlet and outlet of the fifth three-way valve are all closed; inlet A of the sixth three-way valve is closed, and inlet C and outlet B are open; all inlets and outlets of the fourth three-way valve are open; inlet A and outlet C of the seventh three-way valve are open, and inlet B is closed. At this time, the fluid flows in through port A of the third three-way valve and flows out through port C; the fluid flows in through port C of the fourth three-way valve and flows out through ports A and C (the flow rate ratio of the A and B outlets is 0.2-0.4); the fluid flows in through port C of the sixth three-way valve and flows out through port B; and the fluid flows in through port A of the seventh three-way valve and flows out through port C. When the ambient temperature is above 20°C, inlet B of the twelfth three-way valve closes, and the working fluid flows in through port A and out through port C. Inlet A and outlet B of the third three-way valve open, while outlet C closes. All inlets and outlets of the fifth three-way valve open. Inlet A and outlet B of the sixth three-way valve open, while inlet C closes. All inlets and outlets of the fourth three-way valve close. Inlet B and outlet C of the seventh three-way valve open, while inlet A closes. At this point, the working fluid flows in through port A of the third three-way valve and out through port B. The working fluid flows in through port C of the fifth three-way valve and out through ports A and B (the ratio of the working fluid flow rates at the A and B outlets is 0.2-0.4). The working fluid flows in through port A of the sixth three-way valve and out through port B. The working fluid flows in through port B of the seventh three-way valve and out through port C.

[0031] (2) Supercritical-transcritical CO2 cycle coal-fired power generation system to cope with the climate in northern China

[0032] The refrigeration subsystem only uses a thermoelectric refrigeration device, and the circulation subsystem also includes a fourteenth three-way valve, a fifteenth three-way valve, a sixteenth three-way valve, a seventeenth three-way valve, an eighteenth three-way valve, a nineteenth three-way valve, a twenty-third three-way valve, a twenty-first three-way valve and a twenty-second three-way valve;

[0033] The outlet of the low-pressure turbine is connected to the B port of the fourteenth three-way valve, the A port of the fourteenth three-way valve is connected to the bypass regenerator and the C port of the fifteenth three-way valve in sequence, the C port of the fourteenth three-way valve is connected to the high-temperature regenerator, the low-temperature regenerator and the B port of the fifteenth three-way valve in sequence, the C port of the fifteenth three-way valve is connected to the hot-end heat storage module and the C port of the sixteenth three-way valve in sequence, the B port of the sixteenth three-way valve is connected to the cooler and the A port of the seventeenth three-way valve in sequence, the A port of the sixteenth three-way valve is connected to the recompressor and the B port of the twenty-second three-way valve in sequence, the C port of the seventeenth three-way valve is connected to the cold-end cold storage module and the B port of the eighteenth three-way valve in sequence, the B port of the seventeenth three-way valve is connected to the first-stage main compressor, the bypass preheater, the second-stage main compressor and the A port of the twenty-first three-way valve in sequence, and the A port of the eighteenth three-way valve is connected to the mainstream working medium in sequence The pump and the B port of the 21st three-way valve, the C port of the 18th three-way valve are connected to the branch working fluid pump and the C port of the 19th three-way valve in sequence, the A port of the 19th three-way valve is connected to the B port of the 23rd valve, the B port of the 19th three-way valve is connected to the bypass preheater and the A port of the 23rd valve in sequence, the C port of the 23rd valve is connected to the bypass regenerator, the economizer and the ejector in sequence, the C port of the 21st three-way valve is connected to the low-temperature regenerator and the C port of the 22nd three-way valve in sequence, the A port of the 22nd three-way valve is connected to the high-temperature regenerator, the cooling wall, the superheater, the high-pressure turbine, the low-temperature reheater, the reheat wall and the medium-pressure turbine in sequence, the medium-pressure turbine is respectively connected to the inlets of the ejector, the high-temperature reheater and the low-pressure turbine; the hot end heat storage module is connected to the flue gas absorber to further absorb the heat of the waste flue gas in the flue gas absorber.

[0034] Compared to the southern climate, northern climates have longer, lower winters. This allows the system's working fluid to be cooled to very low temperatures, but the waste heat from the working fluid remains relatively low. To fully utilize this cooling capacity while ensuring sufficient cooling capacity in the refrigeration system, the present invention incorporates a coupled thermoelectric cooling device for this climate. This system's thermoelectric cooling device can simultaneously absorb waste heat from the working fluid and waste heat from boiler flue gas.

[0035] The system's 17th, 18th, and 14th three-way valves all have diversion ratio issues. The range of their openings varying with ambient temperature is shown in Table 2. Table 2 Typical valve openings for a supercritical-transcritical carbon dioxide cycle coal-fired power generation system designed for northern climates

[0036]

[0037] For the seventeenth three-way valve, the working fluid flows in from port A and out from ports B and C. When the ambient temperature is below 15°C, the flow rate ratio at port C is 1; when the ambient temperature is between 15°C and 20°C, the flow rate ratio at port C is 0.96-1; when the ambient temperature is between 20°C and 25°C, the flow rate ratio at port C is 0.56-0.96; when the ambient temperature is between 25°C and 30°C, the flow rate ratio at port C is 0.53-0.56; and when the ambient temperature is above 30°C, the flow rate ratio at port C is less than 0.53.

[0038] For the 18th three-way valve: the working fluid flows in from port B and flows out from ports A and C. When the ambient temperature is below 20°C, the flow rate ratio of port C is 0.5; when the ambient temperature is above 20°C, the flow rate ratio of port C is 1.

[0039] For the fourteenth three-way valve: the working fluid flows in from port B and out from ports A and C. When the ambient temperature is below 10°C, the flow rate ratio of outlet A is less than 0.3; when the ambient temperature is 10-15°C, the flow rate ratio of outlet A is 0.3-0.31; when the ambient temperature is 15-20°C, the flow rate ratio of outlet C is 0.31; when the ambient temperature is 20-25°C, the flow rate ratio of outlet C is 0.31-0.37; when the ambient temperature is 25-30°C, the flow rate ratio of outlet C is 0.37-0.4; when the ambient temperature is greater than 35°C, the flow rate ratio of outlet C is less than 0.4.

[0040] It can be found that the flow rate ratio of the A outlet of the fourteenth three-way valve first increases and then decreases with the increase of the ambient temperature, and the flow rate ratio of the C outlet of the seventeenth three-way valve first remains stable and then decreases with the increase of the ambient temperature; while the flow rate ratio of the C outlet of the eighteenth three-way valve has only two cases of 0.5 and 1.

[0041] The working fluid undergoes two diversion processes before being pressurized. The first occurs at the recompression diversion before entering the cooler, and the second occurs at the 17th or 18th three-way valve, dividing the flow into a main stream and a tributary. When the ambient temperature is greater than 20°C, the diversion occurs at the 23rd valve, with the flow ratio allocated according to the cooling capacity of the thermoelectric cooling unit. When the ambient temperature is less than 20°C, the diversion occurs at the 18th three-way valve, artificially dividing the flow into the main stream and the tributary. The flow ratio at the A outlet of the 14th three-way valve changes with the change in the tributary flow. When the temperature is below 20°C, although the flow ratio at the C outlet of the 18th three-way valve remains at 0.5, the actual tributary flow increases due to the slight increase in the recompression diversion ratio. This is the main reason for the increase in the flow ratio at the A outlet of the 14th three-way valve. When the temperature is higher than 20 ℃, the diversion of the mainstream and branch flows occurs at the seventeenth three-way valve. The increase rate of the cooling capacity of the refrigeration system is lower than the rate of cooling required by the unit mass of the working fluid. Therefore, the flow rate ratio of the C outlet of the seventeenth three-way valve gradually decreases.

[0042] When the system's ambient temperature is below 20°C, the main compressor is inoperative, which also causes the bypass preheater to be inoperative, so the bypass branch fluid does not undergo preheating. Specifically, when the ambient temperature is below 20°C, outlet C of the 23rd valve opens, while outlet A closes; outlet A of the 19th three-way valve opens, while outlet B closes. For the 21st three-way valve, when the ambient temperature is below 20°C, inlet A closes, allowing fluid to flow in through port B and out through port C. When the ambient temperature is above 20°C, inlet B closes, allowing fluid to flow in through port A and out through port C.

[0043] (3) Supercritical-transcritical CO2 cycle coal-fired power generation system adapted to the climate in Northwest China

[0044] The refrigeration subsystem uses both a LiBr absorption refrigeration device and a thermoelectric refrigeration device.

[0045] The circulation subsystem further includes a twenty-third three-way valve, a twenty-fourth three-way valve, a twenty-fifth three-way valve, a twenty-sixth three-way valve, a twenty-seventh three-way valve, a twenty-eighth three-way valve, a twenty-ninth three-way valve, a thirty-third three-way valve, a thirty-first three-way valve, a thirty-second three-way valve, a thirty-third three-way valve, a thirty-fourth three-way valve, a thirty-fifth three-way valve, a thirty-sixth three-way valve and a thirty-seventh three-way valve;

[0046] The outlet of the low-pressure turbine is connected to the B port of the twenty-third three-way valve, the A port of the twenty-third three-way valve is connected to the bypass regenerator and the A port of the twenty-fourth three-way valve in sequence, the C port of the twenty-third three-way valve is connected to the high-temperature regenerator, the low-temperature regenerator and the B port of the twenty-fourth three-way valve in sequence, the C port of the twenty-fourth three-way valve is connected to the B port of the twenty-fifth three-way valve, the C port of the twenty-fifth three-way valve is connected to the hot tank and the C port of the twenty-sixth three-way valve in sequence, the A port of the twenty-fifth three-way valve is connected to the hot end heat storage module and the A port of the twenty-sixth three-way valve in sequence, the B port of the twenty-sixth three-way valve is connected to the C port of the twenty-seventh three-way valve, the A port of the twenty-seventh three-way valve is connected to the B port of the recompressor and the B port of the twenty-eighth three-way valve in sequence, the B port of the twenty-seventh three-way valve is connected to the cooler and the A port of the twenty-ninth three-way valve in sequence, and the B port of the twenty-ninth three-way valve is connected to the first-stage main compressor, the bypass preheater, the second-stage main compressor, the third The A port of the 13-way valve, the C port of the 29th three-way valve is connected in sequence to the A and C ports of the 31st three-way valve, the cold tank, the A and B ports of the 32nd three-way valve, the B and C ports of the 33rd three-way valve, the tributary working fluid pump, the C and B ports of the 34th three-way valve, the bypass preheater, the A and C ports of the 35th three-way valve, the bypass regenerator, the economizer and the ejector; the B port of the 31st three-way valve is connected in sequence to the cold end cold storage module and the C port of the 32nd three-way valve, the 30th The A ports of the three three-way valves are connected in sequence to the mainstream working fluid pump and the B port of the thirty-third three-way valve; the C port of the thirty-third three-way valve is connected in sequence to the low-temperature regenerator, the recompressor and the C port of the twenty-eighth three-way valve; the A port of the twenty-eighth three-way valve is connected in sequence to the high-temperature regenerator, the cooling wall, the superheater low-pressure turbine, the low-temperature reheater, the reheat wall and the medium-pressure turbine; the medium-pressure turbine is respectively connected to the inlet of the ejector, the high-temperature reheater and the low-pressure turbine; the B ports of the thirty-sixth three-way valve and the thirty-seventh three-way valve are respectively connected to the output port and the input port of the flue gas absorber; the A and C ports of the thirty-sixth three-way valve are respectively connected to the input port of the hot-end heat storage module and the hot tank; the A and C ports of the thirty-seventh three-way valve are respectively connected to the output port of the hot-end heat storage module and the hot tank.

[0047] The temperature difference between day and night is large in Northwest my country, and there is perennial drought and water shortage, and fossil energy is extremely abundant. The cooling medium of the present invention is ambient air, and coal resources are consumed, so it is very suitable for operation in the Northwest region, and can also greatly solve the problem of power shortage in the region. However, due to the large temperature difference between day and night in the region, if the refrigeration system simply uses LiBr absorption refrigeration, the cooling capacity will be small at low temperatures at night, and the system efficiency cannot be improved; but if only thermoelectric refrigeration is used, the high-temperature working fluid waste heat cannot be fully utilized due to the low COP of thermoelectric refrigeration, and the system exergy loss is large. To solve the above problems, the present invention proposes a supercritical-transcritical carbon dioxide coal-fired power generation system that simultaneously couples a thermoelectric refrigeration device and a LiBr absorption refrigeration device, which can maintain a high power generation efficiency all year round.

[0048] The opening adjustment ratios of the outlets of the twenty-third three-way valve, the twenty-ninth three-way valve and the thirty-third three-way valve are crucial to the stable operation of the system. The present invention proposes a negative feedback regulation mechanism, in which the three valves adopt electronic valves, and the valve opening can be adjusted according to the current. The opening size of each valve varies with the change of ambient temperature. At this time, the size of the electronic valve current can be adjusted according to the real-time temperature measuring device. Through the above method, although the ambient temperature changes greatly over time, the system operation process can also be quickly adjusted, thereby ensuring the efficient, stable and safe operation of the system under the designed working conditions. The range of changes in the opening of the three valves with the ambient temperature is shown in Table 3: Table 3 Typical valve opening sizes of the supercritical-transcritical carbon dioxide cycle coal-fired power generation operation system to cope with the climate in the northwest region

[0049]

[0050] For the 29th three-way valve, the working fluid flows in from port A and out from ports B and C. When the ambient temperature is below 15°C, the flow rate ratio at port C is 1; when the ambient temperature is between 15°C and 20°C, the flow rate ratio at port C is 0.96-1; when the ambient temperature is between 20°C and 25°C, the flow rate ratio at port C is 0.60-0.96; when the ambient temperature is between 25°C and 30°C, the flow rate ratio at port C is 0.62-0.63; and when the ambient temperature is greater than 35°C, the flow rate ratio at port C is greater than 0.63.

[0051] For the 33rd three-way valve: the working fluid flows in from port B and flows out from ports A and C. When the ambient temperature is below 20°C, the flow rate ratio of port C is 0.5; when the ambient temperature is above 20°C, the flow rate ratio of port C is 1.

[0052] For the 23rd three-way valve: the working fluid flows in from port B and out from ports A and C. When the ambient temperature is below 25°C, the flow rate ratio at port A is 0.5; when the ambient temperature is between 25°C and 30°C, the flow rate ratio at port A is 0.46-0.50; when the ambient temperature is above 30°C, the flow rate ratio at port C is greater than 0.47.

[0053] It can be found that the A outlet flow ratio of the 23rd three-way valve first increases, then decreases, and finally increases with the increase of ambient temperature. The C outlet flow ratio of the 29th three-way valve first remains stable, then decreases, and finally increases with the increase of ambient temperature. The C outlet flow ratio of the 33rd three-way valve has only two cases: 0.5 and 1.

[0054] When the ambient temperature is less than 20°C, the thermoelectric refrigeration device fully utilizes the low-temperature waste heat to generate sufficient cooling capacity. At this time, the separation of the main flow and the branch flow occurs in the thirty-third three-way valve 214. When the ambient temperature is greater than 20°C, the increase rate of the cooling capacity of the LiBr absorption refrigeration device is greater than the increase rate of the cooling capacity required per unit mass of the working fluid, which causes the increase in the flow ratio of the final branch flow.

[0055] When the ambient temperature in this system is below 20°C, the main compressor does not operate, which also causes the bypass preheater to not operate, so the bypass branch fluid does not undergo preheating. Specifically, when the ambient temperature is below 20°C, outlets B and C of the 35th three-way valve are open, and outlet A is closed; outlets A and C of the 34th three-way valve are open, and outlet B is closed. For the 33rd valve, when the ambient temperature is below 20°C, inlet A is closed, allowing fluid to flow in through inlet B and out through inlet C. When the ambient temperature is above 20°C, inlet B is closed, allowing fluid to flow in through inlet A and out through inlet C.

[0056] The opening and closing conditions of the inlets and outlets of the 25th, 26th, 36th, 37th, 31st, and 32nd three-way valves are as follows: when the ambient temperature is greater than 20°C, the B inlet and C outlet of the 25th three-way valve are open, and the A outlet is closed; the C inlet and B outlet of the 26th three-way valve are open, and the A inlet is closed; the B inlet and C outlet of the 36th three-way valve are open, and the A outlet is closed; the C inlet and B outlet of the 37th three-way valve are open, and the A inlet is closed; the C outlet and A inlet of the 31st three-way valve are open, and the B outlet is closed; and the A inlet and B outlet of the 32nd three-way valve are open, and the C inlet is closed. At this time, the low-temperature waste heat of the boiler and the low-temperature waste heat of the working fluid to be cooled are both used in the LiBr absorption refrigeration unit. Simultaneously, the working fluid to be further cooled also obtains cooling capacity from the cold tank of the LiBr absorption refrigeration unit. When the ambient temperature is less than 20°C, the B inlet and A outlet of the 25th three-way valve are opened, and the C outlet is closed; the A inlet and B outlet of the 26th three-way valve are opened, and the C inlet is closed; the B inlet and A outlet of the 36th three-way valve are opened, and the C outlet is closed; the A inlet and B outlet of the 37th three-way valve are opened, and the C inlet is closed; the B outlet and A inlet of the 31st three-way valve are opened, and the C outlet is closed; the C inlet and B outlet of the 32nd three-way valve are opened, and the A inlet is closed. At this time, the low-temperature waste heat of the boiler and the low-temperature waste heat of the working fluid to be cooled are both used in the thermoelectric cooling device. At the same time, the working fluid that needs further cooling also obtains cooling energy through the cold-end cold storage module of the thermoelectric cooling device.

[0057] The beneficial effects of the present invention are as follows: By coupling an absorption refrigeration subsystem with a thermoelectric refrigeration unit, using ambient air as the cooling medium and coal as the consumption, the system is well-suited for operation in Northwest my country. By controlling the operation of the absorption refrigeration subsystem and the thermoelectric refrigeration unit through valves, three different operating system states can be established to ensure safe and efficient operation of the system in response to different geographical locations and climates. This addresses the issue of seasonal changes in ambient temperature and the resulting changes in working fluid pressurization methods in different climate environments. Furthermore, the system improves the utilization rate of the boiler's low-temperature flue gas waste heat and the low-temperature CO2 waste heat from the recirculating cooler, thereby achieving the goals of improving boiler and recirculation efficiency and reducing system exergy losses. Furthermore, the present invention proposes two different boiler layouts to address efficiency and economic issues arising from varying system loads. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is a block diagram of the system working state of the present invention in response to the climate in the southern region;

[0059] Figure 2 for Figure 1 Schematic diagram of the direction of each valve;

[0060] Figure 3 for Figure 1 Comparison chart of system operation effects;

[0061] Figure 4 This is a block diagram of the system working state of the present invention in response to the climate in northern regions;

[0062] Figure 5 for Figure 4 Schematic diagram of the direction of each valve;

[0063] Figure 6 for Figure 4 Comparison chart of system operation effects;

[0064] Figure 7 This is a block diagram of the system working state of the present invention in response to the climate in the northwest region;

[0065] Figure 8 for Figure 7 Schematic diagram of the direction of each valve;

[0066] Figure 9 for Figure 7 Comparison chart of system operation effects;

[0067] Figure 10 This is a structural diagram of a small-scale pressurized pulverized coal combustion boiler according to the present invention;

[0068] Figure 11 This is a schematic structural diagram of a large-scale atmospheric pressure pulverized coal combustion boiler according to the present invention;

[0069] Figure 12 It is a schematic structural diagram of the cooling wall and the reheating wall of the present invention;

[0070] Figure 13 It is a schematic diagram of the surface structure of the outer tube and inner wall of the cooling wall and reheating wall of the present invention. DETAILED DESCRIPTION

[0071] The present invention will be further described below with reference to the accompanying drawings.

[0072] A supercritical-transcritical CO2 coal-fired power generation system includes a boiler subsystem 1, a circulation subsystem 2, and a refrigeration subsystem. The refrigeration subsystem utilizes a LiBr absorption refrigeration unit 3 and / or a thermoelectric refrigeration unit 4. The refrigeration subsystem of this system can utilize either the LiBr absorption refrigeration unit 3 or the thermoelectric refrigeration unit 4, thereby forming three supercritical-transcritical CO2 circulation coal-fired power generation operating systems tailored to different geographical environments, climates, and loads. Therefore, the present invention proposes three supercritical-transcritical CO2 coal-fired power generation systems tailored to different geographical environments, climates, and loads.

[0073] Example 1: Example of a supercritical-transcritical carbon dioxide cycle coal-fired power generation system for the southern region's climate

[0074] like Figure 1 and Figure 2 As shown, in response to the climate in the southern region, the critical-transcritical carbon dioxide coal-fired power generation system includes a boiler subsystem 1, a circulation subsystem 2 and a LiBr absorption refrigeration device 3.

[0075] The boiler subsystem includes a cooling wall 11 , a reheat wall 12 , a superheater 13 , a high-temperature reheater 14 , a low-temperature reheater 15 , an economizer 16 , an air preheater 17 , a flue gas absorber 18 and an ejector 19 .

[0076] The circulation subsystem includes a bypass regenerator 201, a high-temperature regenerator 203, a low-temperature regenerator 205, a cooler 208, a branch working fluid pump 213, a main working fluid pump 215, a bypass preheater 216, a first-stage main compressor 217, a second-stage main compressor 218, a recompressor 219, a low-pressure turbine 220, a medium-pressure turbine 221, a high-pressure turbine 222, and a valve group. The valve group includes a first three-way valve 501 (hereinafter referred to as valve 501), a second three-way valve 502 (hereinafter referred to as valve 502), a third three-way valve 503 (hereinafter referred to as valve 503), and a fourth three-way valve 504. (hereinafter referred to as valve 504), a fifth three-way valve 505 (hereinafter referred to as valve 505), a sixth three-way valve 506 (hereinafter referred to as valve 506), a seventh three-way valve 507 (hereinafter referred to as valve 507), an eighth three-way valve 508 (hereinafter referred to as valve 508), a ninth three-way valve 509 (hereinafter referred to as valve 509), a thirteenth three-way valve 510 (hereinafter referred to as valve 510), an eleventh three-way valve 511 (hereinafter referred to as valve 511), a twelfth three-way valve 512 (hereinafter referred to as valve 512) and a thirteenth three-way valve 513 (hereinafter referred to as valve 513).

[0077] The LiBr absorption refrigeration unit 3 comprises an evaporator 301, an absorber 302, a LiBr solution throttle valve 303, a LiBr solution pump 304, a LiBr solution heat exchanger 305, a generator 306, a condenser 307, a water throttle valve 308, a cold tank 309, and a hot tank 312. The LiBr absorption refrigeration unit 3 uses LiBr solution as the working fluid, with water serving as the refrigerant and LiBr serving as the absorbent. Within the generator 306, the LiBr solution absorbs heat from the hot tank 312, generating water vapor that flows into the condenser 307, releasing heat with the air and condensing into water. Simultaneously, the LiBr solution concentration within the generator 306 increases. The concentrated LiBr solution also reaches a higher temperature, passing through the LiBr solution heat exchanger 305 and the LiBr solution throttle valve 303 before entering the absorber 302. After cooling through water throttle valve 308, the condensed water enters evaporator 301 to absorb the heat released by the CO2. It then returns to a gaseous state at the outlet of evaporator 301 and flows to absorber 302, where it is absorbed by the concentrated LiBr solution, simultaneously reducing the solubility of the LiBr solution. The dilute LiBr solution, powered by LiBr solution pump 304, absorbs heat from the concentrated LiBr solution in LiBr solution heat exchanger 305 before returning to generator 306, completing the cycle. The refrigerant absorbs cold energy in evaporator 301 and releases it in cold tank 309; the water absorbs heat in hot tank 312 and releases it in generator 306.

[0078] The working fluid at the outlet of low-pressure turbine 220 passes through valve 501 and is split into two streams. One stream passes through bypass regenerator 201 and reaches valve 502. The other stream passes through high-temperature regenerator 203 and low-temperature regenerator 205, then enters valve 502 and merges into valve 503. Typically, when the ambient temperature is above 20°C, the working fluid at valve 503 flows entirely into the refrigeration system's hot tank 312 for heat release before entering valve 504 for diversion. A portion first passes through valve 506, then enters recompressor 219 for pressure boosting, flows into valve 513, and flows to valve 507. When the ambient temperature is below 20°C, the working fluid at 503 flows entirely into valve 505 for diversion. A portion passes through valve 505, then enters recompressor 219 for pressure boosting, flows into valve 513, and flows to valve 507. The working fluid at valve 507 is cooled by cooler 208 before entering valve 508 for diversion. The main stream then enters valve 511. When the ambient temperature is greater than 20°C, the working fluid in valve 511 is first compressed by the first-stage main compressor 217, then cooled by the bypass preheater 216, and finally pressurized again by the second-stage main compressor 218 before flowing into valve 512. When the ambient temperature is below 20°C, the working fluid in valve 511 flows directly through the submerged main stream pump 215 to valve 512. The branch streams are further cooled by the cold tank 309 and pressurized by the branch stream pump 213 before reaching valve 509. When the ambient temperature is greater than 20°C, the working fluid in valve 509 enters the bypass preheater 216 for preheating before reaching valve 510. When the ambient temperature is below 20°C, the working fluid in valve 509 flows directly to valve 510. The working fluid in valve 510 is heated by the bypass regenerator 201 and the economizer 16 in boiler subsystem 1 before reaching the ejector 19. The working fluid from valve 512 is heated in the low-temperature reheater 205 and then enters valve 513 to mix with the working fluid at the outlet of the recompressor 219. The working fluid then passes through the high-temperature reheater 203, the cooling stave 11, and the superheater 13 of the boiler subsystem 1, before entering the high-pressure turbine 222 to perform work and reduce temperature and pressure. The working fluid at the outlet of the high-pressure turbine 222 then passes through the low-temperature reheater 15 and the reheat stave 12 for reheating before entering the medium-pressure turbine 221 to perform work. Finally, the working fluid at the outlet of the medium-pressure turbine 221 also enters the ejector 19 to mix with the branch working fluid and increase speed. After further heating in the high-temperature reheater 14, the working fluid completes its final work in the low-pressure turbine 220. Through the above process, the CO2 working fluid completes the entire supercritical-to-transcritical carbon dioxide cycle.

[0079] Due to the southern region's hot and rainy summers and mild and dry winters, temperatures remain above 20°C for most of the year, with an ambient temperature of 20°C as the boundary. This means that the CO2 Brayton cycle in southern China can only cool the working fluid above its critical point most of the time. Furthermore, due to the high temperature of the cooling source, the temperature of the waste heat required to be cooled is also relatively high. For these climatic conditions, LiBr absorption refrigeration systems are suitable. This cooling method can absorb waste heat above 70°C, while achieving a COP of around 0.7, offering high efficiency, good energy savings, and high economic benefits. During the rare periods when the ambient temperature falls below 20°C, LiBr absorption refrigeration units can also absorb a small amount of waste heat from boiler flue gas for operation. Since the ambient temperature is low, the working fluid can be cooled to a liquid state, requiring less cooling capacity per unit of working fluid. Therefore, while the cooling capacity decreases with lower ambient temperature, a larger proportion of the working fluid in the bypass stream can be cooled by the refrigeration system.

[0080] The opening range of each valve varies with the ambient temperature in response to the climate in the southern region, as shown in Table 1: Table 1 Typical valve opening sizes of supercritical-transcritical carbon dioxide cycle coal-fired power generation operation system in response to the climate in the southern region

[0081]

[0082] The mainstream working fluid enters from port A of valve 508, and flows out of ports B and C at different flow rates; at the same time, the working fluid that has completed work flows into from port B of valve 501, and flows out of ports A and C at different flow rates. When the ambient temperature is 10-15 ℃, the flow rate ratio of valve 508's C port is 0.58-1, and the flow rate ratio of valve 501's A port is 0.36-0.6; when the ambient temperature is 15-20 ℃, the flow rate ratio of valve 508's C port is 0.38-0.58, and the flow rate ratio of valve 501's A port is 0.24-0.36; when the ambient temperature is 20-25 ℃, the flow rate ratio of valve 508's C port is 0.44-0.62, and the flow rate ratio of valve 501's A port is 0.27-0.46; when the ambient temperature is 25-30 ℃, the flow rate ratio of valve 508's C port is 0.62-0.63, and the flow rate ratio of valve 501's A port is 0.46-0.47; when the ambient temperature is greater than 30 At ℃, the flow rate ratio of the C outlet of valve 508 is greater than 0.63, and the flow rate ratio of the A outlet of valve 501 is greater than 0.47.

[0083] It can be seen that as the ambient temperature rises, both ratios show a trend of first decreasing and then increasing, with dramatic changes occurring near the critical point. When the ambient temperature is below 20°C, the cooler can cool the working fluid below the critical point. Due to significant changes in the working fluid's physical properties near the critical point, the circulating working fluid's residual heat temperature also changes significantly (at an ambient temperature of 20°C, the working fluid's residual heat temperature is 100°C; at an ambient temperature of 18°C, it is only 67°C). Therefore, the cooling capacity increases with increasing ambient temperature. Simultaneously, the final temperature of the bypass working fluid remains around 12°C. At this low ambient temperature, the cooling capacity required per unit mass of working fluid from the refrigeration system is also lower. These two factors combined lead to the phenomenon that the ratios first decrease and then increase with increasing ambient temperature. Because the working fluid undergoes a diversion process before entering the cooler, the sum of the actual tributary flow and the main flow is less than the total circulating flow. Therefore, the proportion of working fluid flow used for heat recovery in the tributary flow is smaller than the proportion of the tributary flow.

[0084] When the ambient temperature of this system is below 20°C, the cooler can cool the working fluid to a liquid state. In this case, the boosting device needs to be replaced with a pump. However, when the pump is operating, it both increases pressure and temperature. Therefore, the working fluid pump is prone to phase change during operation, transforming into a supercritical state and causing cavitation. To address this issue, the system employs the following method: the circulation subsystem 2 also includes a cooling pool 200, and the mainstream working fluid pump 215 is disposed within the cooling pool 200. Regarding valve 511, the working fluid flows in from port A, with port B closed and port C open. The working fluid then flows out from port C and is pressurized by the water-immersed mainstream working fluid pump. At this time, since the main compressor is not operating, the bypass preheater is also not operating, meaning that port A of valve 510 and port B of the ninth three-way valve 509 are closed. The water-immersed pump can simultaneously increase pressure and reduce temperature. The cooling efficiency of the pump can be adjusted by varying the flow rate in the water pool, preventing the working fluid from undergoing phase change. The arrangement of the submerged pump can not only ensure that phase change cavitation does not occur during the pressurization process, but the cooling of the pump by the water pool can also reduce the working power consumption of the pump, so that the pump can operate safely and efficiently, thereby improving the efficiency of the system.

[0085] The opening and closing conditions for the inlets and outlets of valves 512, 503, 505, 506, 504, and 507 are as follows: When the ambient temperature is below 20°C, inlet A of valve 512 is closed, the fluid flows in through port B, and flows out through port C. Inlet A and outlet C of valve 503 are open, and outlet B is closed. All inlets and outlets of valve 505 are closed. Inlet A of valve 506 is closed, inlet C and outlet B are open. All inlets and outlets of valve 504 are open. Inlet A and outlet C of valve 507 are open, and inlet B is closed. At this point, the fluid flows in through port A of valve 503 and flows out through port C. The fluid flows in through port C of valve 504 and flows out through ports A and C (the flow rate ratio of the A and B outlets is 0.2-0.4). The fluid flows in through port C of valve 506 and flows out through port B. The fluid flows in through port A of valve 507 and flows out through port C. When the ambient temperature is above 20°C, inlet B of valve 512 closes, and the fluid flows in through port A and out through port C. Inlet A and outlet B of valve 503 open, while outlet C closes. All inlets and outlets of valve 505 open. Inlet A and outlet B of valve 506 open, while inlet C closes. All inlets and outlets of valve 504 close. Inlet B and outlet C of valve 507 open, while inlet A closes. At this point, the fluid flows in through port A of valve 503 and out through port B. The fluid flows in through port C of valve 505 and out through ports A and B (the ratio of the fluid flow rates at outlets A and B is 0.2-0.4). The fluid flows in through port A of valve 506 and out through port B. The fluid flows in through port B of valve 507 and out through port C.

[0086] The bypass preheater 216 not only cools the main working fluid, reducing the compression power consumption of the secondary main compressor 218, but also preheats the high-pressure bypass branch flow. The bypass working fluid then absorbs heat and undergoes a phase change during the process. Therefore, the arrangement of the bypass preheater 216 reduces compression power consumption by reducing the amount of heat absorbed by the branch flow in the economizer 16 and the bypass regenerator 201, thereby improving the cycle's thermal efficiency and reducing the exergy losses of the process.

[0087] Through the above description of the control of each valve of the supercritical-transcritical carbon dioxide cycle coal-fired power generation system for the southern climate, the present invention also makes a comparison of the power generation efficiency of the new system and the original system of the simple recompression and reheat cycle by simulating the system when it is stably operated under the set working conditions. Figure 3 As shown in the figure, a comparison of the operating effects of the supercritical-transcritical carbon dioxide cycle coal-fired power generation system to cope with the climate in the southern region can be found. It can be found that the improved system has great advantages over the original system, especially for the southern climate with high temperatures all year round.

[0088] Example 2: Supercritical-transcritical carbon dioxide cycle coal-fired power generation operation system for the northern climate

[0089] like Figure 4 and Figure 5 As shown, in response to the climate in northern China, the critical-transcritical carbon dioxide coal-fired power generation system includes a boiler subsystem 1, a circulation subsystem 2, and a thermoelectric refrigeration device 4. The boiler subsystem 1 is the same as that in Example 1 and will not be described in detail here.

[0090] Compared with Example 1, the circulation subsystem 2 is different in that the valve group includes a fourteenth three-way valve 601 (hereinafter referred to as valve 601), a fifteenth three-way valve 602 (hereinafter referred to as valve 602), a sixteenth three-way valve 603 (hereinafter referred to as valve 603), a seventeenth three-way valve 604 (hereinafter referred to as valve 604), an eighteenth three-way valve 605 (hereinafter referred to as valve 605), a nineteenth three-way valve 606 (hereinafter referred to as valve 606), a twenty-third three-way valve 607 (hereinafter referred to as valve 607), a twenty-first three-way valve 608 (hereinafter referred to as valve 608), and a twenty-second three-way valve 609 (hereinafter referred to as valve 609).

[0091] The thermoelectric cooling device 4 comprises a hot-end heat storage module 401, a thermoelectric module 402, a cold-end cold storage module 403, and a DC power supply 404. The thermoelectric cooling device 4 utilizes the temperature difference and thermal resistance between the hot and cold ends to generate heat absorption and heat release. The thermoelectric module 402 comprises m pairs of PN junctions. A DC power supply 404 is connected to the thermoelectric module 402, creating a potential difference across the PN junctions and generating a stable current. The heat source is the hot-end heat storage module 401. The thermoelectric module absorbs heat to lower the temperature of the cold-end cold storage module 403, generating a certain amount of cooling capacity for cooling the CO2 working medium.

[0092] The working fluid at the outlet of low-pressure turbine 220 passes through valve 601 and is split into two streams. One stream passes through bypass regenerator 201 and reaches valve 602; the other stream passes through high-temperature regenerator 203 and low-temperature regenerator 205, respectively, and also enters valve 602. The combined working fluid enters the hot-end heat storage module 401 of thermoelectric refrigeration device 4, dissipating heat before reaching valve 603. The working fluid in valve 603 is split, with one stream being pressurized by recompressor 219 and entering valve 609; the other stream is cooled by cooler 208 and reaches valve 604. Typically, when the ambient temperature is greater than 20°C, the working fluid in valve 604 is pressurized by the first-stage main compressor 217, cooled by the bypass preheater 216, and re-pressurized by the second-stage main compressor 218 before reaching valve 608. The remaining portion is first cooled by the cold-end cold storage module 403 before reaching valve 605. It is then pressurized by the branch working fluid pump 213, flows through valve 606, and reaches the bypass preheater 216 for waste heat. After preheating, the branch working fluid is heated by valve 607, the bypass regenerator 201, and the economizer 16 before reaching the ejector 19. When the ambient temperature is less than 20°C, the working fluid in valve 604 does not need to be split and flows entirely to the cold-end cold storage module 403 of the thermoelectric refrigeration device 4 for further cooling before reaching valve 605. The main stream of working fluid is pressurized by main stream pump 215 and reaches valve 608. The branch stream of working fluid is pressurized by branch stream pump 213 and heated by valves 606 and 607, as well as the bypass regenerator 201 and economizer 16, before reaching ejector 19. The main stream of working fluid from valve 608 passes through the low-temperature regenerator 205 and is mixed with the outlet working fluid of the recompressor 219 at valve 609. The mixed working fluid is first heated by the high-temperature regenerator 203 and the cooling stave 11 and superheater 13 of the boiler subsystem 1 before performing work in the high-pressure turbine 222 for the first time. It is then heated by the low-temperature reheater 15 and reheat stave 12 before performing work in the medium-pressure turbine 221 for the second time. Finally, the main stream and branch streams are mixed in ejector 19, mixed and accelerated by ejector 19, and heated by the high-temperature reheater 14 before completing the final work in the low-pressure turbine 220. After the above process, the CO2 working fluid completes the entire supercritical-transcritical carbon dioxide cycle.

[0093] Compared to southern climates, northern climates are characterized by long, low winters. This allows the system's working fluid to be cooled to very low temperatures, but the waste heat from the working fluid remains relatively low. To fully utilize this cooling capacity while ensuring sufficient cooling capacity in the refrigeration system, the present invention incorporates a coupled thermoelectric refrigeration device for this climate. This system's thermoelectric refrigeration device absorbs both the working fluid's waste heat and the waste heat from boiler flue gases. Compared to LiBr absorption refrigeration devices, the lower temperature limit for waste heat absorption by the thermoelectric device is lower, resulting in higher system energy efficiency and lower system exergy losses. Furthermore, the thermoelectric device boasts a simple structure and a compact footprint.

[0094] The valves 604, 605 and 601 of the system all have the problem of diversion ratio. The range of their opening varies with the ambient temperature as shown in Table 2: Table 2 Typical valve opening sizes of supercritical-transcritical carbon dioxide cycle coal-fired power generation system for the northern climate

[0095]

[0096] For valve 604, the working fluid flows in from port A and out from ports B and C. When the ambient temperature is below 15°C, the flow rate ratio at port C is 1; when the ambient temperature is between 15°C and 20°C, the flow rate ratio at port C is 0.96-1; when the ambient temperature is between 20°C and 25°C, the flow rate ratio at port C is 0.56-0.96; when the ambient temperature is between 25°C and 30°C, the flow rate ratio at port C is 0.53-0.56; and when the ambient temperature is above 30°C, the flow rate ratio at port C is less than 0.53.

[0097] For valve 605: the working fluid flows in from port B and flows out from ports A and C. When the ambient temperature is below 20°C, the flow rate ratio at port C is 0.5; when the ambient temperature is above 20°C, the flow rate ratio at port C is 1.

[0098] For valve 601: the working fluid flows in through port B and out through ports A and C. When the ambient temperature is below 10°C, the flow rate ratio at port A is less than 0.3; when the ambient temperature is between 10-15°C, the flow rate ratio at port A is 0.3-0.31; when the ambient temperature is between 15-20°C, the flow rate ratio at port C is 0.31; when the ambient temperature is between 20-25°C, the flow rate ratio at port C is 0.31-0.37; when the ambient temperature is between 25-30°C, the flow rate ratio at port C is 0.37-0.4; and when the ambient temperature is greater than 35°C, the flow rate ratio at port C is less than 0.4.

[0099] It can be found that the flow rate ratio of the A outlet of valve 601 first increases and then decreases with the increase of ambient temperature, and the flow rate ratio of the C outlet of valve 604 first remains stable and then decreases with the increase of ambient temperature; while the flow rate ratio of the C outlet of valve 605 has only two cases: 0.5 and 1.

[0100] Before being pressurized, the working fluid undergoes two diversion processes: the first occurs during recompression before entering the cooler, and the second occurs at valve 604 or valve 605, dividing the flow into a main stream and a branch stream. When the ambient temperature is above 20°C, the diversion occurs at valve 607, with the flow ratio distributed according to the cooling capacity of the thermoelectric cooling device. When the ambient temperature is below 20°C, the diversion occurs at valve 605, artificially dividing the flow into the main stream and branch streams. The flow ratio at outlet A of valve 601 changes with the change in branch flow. When the temperature is below 20°C, although the flow ratio at outlet C of valve 214 remains at 0.5, the actual branch flow increases due to a slight increase in the recompression diversion ratio. This is the main reason for the increase in the flow ratio at outlet A of valve 601. When the temperature is above 20°C, the diversion between the main stream and branch stream occurs at valve 604. The rate of increase in the cooling capacity of the refrigeration system is slower than the rate of cooling required per unit mass of the working fluid, resulting in a gradual decrease in the flow ratio at outlet C of valve 604.

[0101] When the ambient temperature in this system is below 20°C, the main compressor does not operate, which also causes the bypass preheater to not operate, so the bypass branch fluid does not undergo preheating. Specifically, when the ambient temperature is below 20°C, outlet C of valve 607 opens and outlet A closes; outlet A of valve 606 opens and outlet B closes. Regarding valve 608, when the ambient temperature is below 20°C, inlet A closes, allowing fluid to flow in through inlet B and out through inlet C. When the ambient temperature is above 20°C, inlet B closes, allowing fluid to flow in through inlet A and out through inlet C.

[0102] Through the above description of the control of each valve of the supercritical-transcritical carbon dioxide cycle coal-fired power generation system for the northern climate, the present invention also makes a comparison of the power generation efficiency of the new system and the original system of the simple recompression and reheat cycle by simulating the system when it is stably operated under the set working conditions. Figure 6 The following figure compares the operating performance of a supercritical-transcritical CO2 cycle coal-fired power generation system designed for northern climates. The improved system demonstrates significant performance compared to the original system. When ambient temperatures are below 20°C, power generation efficiency can be maintained at over 48.5% for extended periods. This performance increases with rising ambient temperatures, due to the increased waste heat.

[0103] Example 3: Supercritical-transcritical carbon dioxide cycle coal-fired power generation operation system for the Northwest region climate

[0104] like Figure 7 and Figure 8As shown, in response to the climate in the northwest region, a critical-transcritical carbon dioxide coal-fired power generation system includes a boiler subsystem 1, a circulation subsystem 2, a LiBr absorption refrigeration device 3, and a thermoelectric refrigeration device 4. The boiler subsystem 1 is the same as that in Examples 1 and 2, the LiBr absorption refrigeration device 3 is the same as that in Example 1, and the thermoelectric refrigeration device 4 is the same as that in Example 2, and they are not described in detail here; the circulation subsystem 2 is different from Examples 1 and 2 in that the valve group includes a twenty-third three-way valve 202 (hereinafter referred to as valve 202), a twenty-fourth three-way valve 209 (hereinafter referred to as valve 209), a twenty-fifth three-way valve 313 (hereinafter referred to as valve 313), a twenty-sixth three-way valve 314 (hereinafter referred to as valve 314), a twenty-seventh three-way valve 207 (hereinafter referred to as valve 207), and a twenty-eighth three-way valve 204 (hereinafter referred to as valve 204). The following are some of the following: a twenty-ninth three-way valve 210 (hereinafter referred to as valve 210), a thirty-third three-way valve 206 (hereinafter referred to as valve 206), a thirty-first three-way valve 311 (hereinafter referred to as valve 311), a thirty-second three-way valve 310 (hereinafter referred to as valve 310), a thirty-third three-way valve 214 (hereinafter referred to as valve 214), a thirty-fourth three-way valve 212 (hereinafter referred to as valve 212), a thirty-fifth three-way valve 211 (hereinafter referred to as valve 211), a thirty-sixth three-way valve 405 (hereinafter referred to as valve 405), and a thirty-seventh three-way valve 406 (hereinafter referred to as valve 406).

[0105] The working fluid at the outlet of low-pressure turbine 220 passes through valve 202 and is split into two streams. One stream passes through bypass regenerator 201 and reaches valve 209; the other stream passes through high-temperature regenerator 203 and low-temperature regenerator 205, also entering valve 209. The combined working fluid enters valve 313. When the ambient temperature is above 20°C, the working fluid enters the heat storage tank of absorption refrigeration unit 3 to release heat before reaching valve 314. When the ambient temperature is below 20°C, the working fluid enters the hot-end heat storage module 401 of thermoelectric refrigeration unit 4 to release heat before reaching valve 314. After reaching valve 314, the working fluid flows to valve 207 for diversion. Part of the working fluid is pressurized by recompressor 219 and enters valve 204; the other part enters cooler 208 for cooling before reaching valve 210. The flow direction of the working fluid in valve 210 will also change according to the ambient temperature. When the ambient temperature is higher than 20°C, the main working fluid is pressurized by the first-stage main compressor 217, cooled by the bypass preheater 216, and pressurized by the second-stage main compressor 218 before reaching valve 206; the branch working fluid passes through valve 311 and is further cooled by the cold tank 309 of the absorption refrigeration device 3, and then pressurized by valve 310, valve 214, and the branch working fluid pump 213. It is then preheated by valve 212 and the bypass preheater 216 in sequence before entering valve 211. Finally, the branch working fluid passes through valve 211, is heated by the bypass regenerator 201 and the economizer 16 of the boiler subsystem 1, and then enters the ejector 19. When the ambient temperature is lower than 20°C, the working fluid in valve 210 passes through valve 311 and is further cooled in the cold-end cold storage module 403 in the thermoelectric refrigeration device 4. The cooled working fluid first passes through valve 310 and is then diverted at valve 214. The mainstream working fluid is pressurized by the mainstream working fluid pump 215 and reaches valve 206; the branch working fluid is pressurized by the branch working fluid pump 213 and reaches valve 212, and then passes through valve 211, the bypass regenerator 201, and the economizer 16 of the boiler subsystem 1 for heating before being directed to the ejector 19. The main stream of fluid from valve 206 passes through the low-temperature regenerator 205 and is then mixed with the outlet fluid from the recompressor 219 at valve 204. The mixed fluid is first heated by the high-temperature regenerator 203 and the cooling stave 11 and superheater 13 in the boiler subsystem 1 before performing work for the first time in the high-pressure turbine 222. It is then heated again by the low-temperature reheater 15 and reheat stave 12 before performing work for the second time in the medium-pressure turbine 221. Finally, the main stream and branch streams are first mixed and accelerated in the ejector 19 and then heated by the high-temperature reheater 14 before performing work for the final time in the low-pressure turbine 220. The CO2 cycle completes the entire supercritical-transcritical CO2 cycle through the above processes.

[0106] Northwest my country experiences significant diurnal temperature swings, perennial drought and water shortages, and an abundance of fossil energy. The present invention uses ambient air as the cooling medium, consuming coal resources, making it ideally suited for operation in the region and significantly addressing the region's power shortages. However, due to the significant diurnal temperature swings in this region, a refrigeration system solely using LiBr absorption cooling would result in reduced cooling capacity at low night temperatures, hindering system efficiency. However, using only thermoelectric cooling, due to its low COP, would prevent full utilization of the higher-temperature waste heat from the working fluid, resulting in significant system exergy losses.

[0107] To address these issues, the present invention proposes a supercritical-transcritical CO2 coal-fired power generation system that simultaneously couples a thermoelectric refrigeration unit with a LiBr absorption refrigeration unit. This system can select the refrigeration unit based on the ambient temperature, integrating the advantages of both absorption and thermoelectric refrigeration. This system can maintain high power generation efficiency year-round.

[0108] However, the adjustment ratio of the opening of each outlet of valve 202, valve 210 and valve 214 is crucial to the stable operation of the system. The present invention proposes a negative feedback regulation mechanism, in which the three valves are electronic valves, and the valve opening can be adjusted according to the current. The opening size of each valve changes with the change of ambient temperature. At this time, the size of the electronic valve current can be adjusted according to the real-time temperature measuring device. Through the above method, although the ambient temperature changes greatly over time, the system operation process can also be quickly adjusted, thereby ensuring the efficient, stable and safe operation of the system under the designed working conditions. The range of changes in the opening of the three valves with the ambient temperature is shown in Table 3: Table 3 Typical valve opening sizes of supercritical-transcritical carbon dioxide cycle coal-fired power generation operation system to cope with the climate in the northwest region

[0109]

[0110] For valve 210, the working fluid flows in from port A and out from ports B and C. When the ambient temperature is below 15°C, the flow rate ratio at port C is 1; when the ambient temperature is between 15°C and 20°C, the flow rate ratio at port C is 0.96-1; when the ambient temperature is between 20°C and 25°C, the flow rate ratio at port C is 0.60-0.96; when the ambient temperature is between 25°C and 30°C, the flow rate ratio at port C is 0.62-0.63; and when the ambient temperature is greater than 35°C, the flow rate ratio at port C is greater than 0.63.

[0111] For valve 214: the working fluid flows in from port B and flows out from ports A and C. When the ambient temperature is below 20°C, the flow rate ratio at port C is 0.5; when the ambient temperature is above 20°C, the flow rate ratio at port C is 1.

[0112] For valve 202: the working fluid flows in from port B and out from ports A and C. When the ambient temperature is below 25°C, the flow rate ratio at port A is 0.5; when the ambient temperature is between 25°C and 30°C, the flow rate ratio at port A is 0.46-0.50; when the ambient temperature is above 30°C, the flow rate ratio at port C is greater than 0.47.

[0113] It can be found that the flow rate ratio of the A outlet of the valve 202 first increases, then decreases, and finally increases as the ambient temperature increases. The flow rate ratio of the C outlet of the valve 210 first remains stable, then decreases, and finally increases as the ambient temperature increases. However, the flow rate ratio of the C outlet of the valve 214 has only two cases: 0.5 and 1.

[0114] When the ambient temperature is less than 20°C, the thermoelectric refrigeration device fully utilizes the low-temperature waste heat to generate sufficient cooling capacity. At this time, the separation of the main flow and the branch flow occurs in valve 214. When the ambient temperature is greater than 20°C, the increase rate of the cooling capacity of the LiBr absorption refrigeration device is greater than the increase rate of the cooling capacity required per unit mass of the working fluid, which causes the final branch flow rate ratio to increase.

[0115] When the ambient temperature is below 20°C, the main compressor does not operate, which also causes the bypass preheater to not operate, so the bypass branch fluid does not undergo preheating. Specifically, when the ambient temperature is below 20°C, outlets B and C of valve 211 are open, and outlet A is closed; outlets A and C of valve 212 are open, and outlet B is closed. Regarding valve 206, when the ambient temperature is below 20°C, inlet A is closed, allowing fluid to flow in through inlet B and out through inlet C. When the ambient temperature is above 20°C, inlet B is closed, allowing fluid to flow in through inlet A and out through inlet C.

[0116] The opening and closing conditions of valves 313, 314, 405, 406, 311, and 310 are as follows: when the ambient temperature is greater than 20°C, valve 313's inlet B and outlet C are open, and outlet A is closed; valve 314's inlet C and outlet B are open, and inlet A is closed; valve 405's inlet B and outlet C are open, and outlet A is closed; valve 406's inlet C and outlet B are open, and inlet A is closed; valve 311's outlet C and inlet A are open, and outlet B is closed; and valve 310's inlet A and outlet B are open, and inlet C is closed. At this point, both the boiler's low-temperature waste heat and the low-temperature waste heat of the working fluid to be cooled are used in the LiBr absorption refrigeration unit. Simultaneously, the working fluid to be further cooled also receives cooling energy from the cold tank of the LiBr absorption refrigeration unit. When the ambient temperature is less than 20°C, valve 313's inlet B and outlet A open, and outlet C close; valve 314's inlet A and outlet B open, and inlet C close; valve 405's inlet B and outlet A open, and outlet C close; valve 406's inlet A and outlet B open, and inlet C close; valve 311's outlet B and inlet A open, and outlet C close; valve 310's inlet C and outlet B open, and inlet A close. At this point, both the boiler's low-temperature waste heat and the low-temperature waste heat of the working fluid to be cooled are used in the thermoelectric cooling device. Simultaneously, the working fluid that needs further cooling also receives cooling energy from the thermoelectric cooling device's cold-end cold storage module.

[0117] Through the above description of the control of each valve of the supercritical-transcritical carbon dioxide cycle coal-fired power generation system for the climate of the Northwest region, the present invention also makes a comparison of the power generation efficiency of the new system and the original system of the simple recompression and reheat cycle by simulating the operation of the system under the set working conditions. Figure 9 The figure below compares the operating performance of a supercritical-transcritical CO2 cycle coal-fired power generation system designed for the Northwest region's climate. The improved system maintains higher power generation efficiency than the original system regardless of diurnal temperature fluctuations. Furthermore, as ambient temperature increases, the power generation efficiency of both systems decreases significantly due to the increased heat release temperature. However, as ambient temperature increases, the amount of waste heat increases significantly, significantly reducing the heat release temperature of the new system and improving the power generation efficiency of the improved system. Therefore, the improvement is more pronounced with increasing ambient temperature.

[0118] In response to the issues raised in the background art, namely the characteristics of pressure drop in boilers with different load systems, and considering the economic factors of the boiler, the present invention proposes two boiler structures to adapt to different system loads. For small-load systems where pressure drop has little impact on efficiency, economic considerations are used, and a pressurized combustion boiler is suitable, reducing boiler volume and saving manufacturing costs. For large and medium-load systems where pressure drop has a greater impact on efficiency, a normal-pressure combustion boiler is suitable, considering thermal performance, reducing boiler flow pressure drop and improving power generation efficiency.

[0119] In order to simultaneously solve the boiler economy problem and the problem of low power generation efficiency caused by large pressure drop, the present invention proposes two different solutions for different load-type systems. The above-mentioned boiler subsystem 1 can respectively adopt a small-scale pressurized pulverized coal-fired boiler or a large-scale normal-pressure pulverized coal-fired boiler.

[0120] like Figure 10 As shown, the small-scale pressurized pulverized coal-fired boiler is primarily suitable for systems below 200 MWe. The cooling wall 11, reheat wall 12, superheater 13, high-temperature reheater 14, low-temperature reheater 15, and economizer 16 are all used to heat the circulating working fluid; the flue gas absorber 18 is used to absorb heat from water for the cooling system. Furthermore, the boiler is equipped with a tubular air preheater 17 to preheat air and improve the combustion efficiency of the burner 110. Natural air is first compressed to approximately 1 MPa by compressor 109 before being fed into the preheater shell. The flue gas flows longitudinally from top to bottom within the tubes, forming a cross-flow. The air within the tubes, after heat exchange with the flue gas, is heated to form primary air (19%) and secondary air (81%) at different temperatures. Among them, the primary air is used to transport coal powder, and it can also evaporate most of the water vapor in the coal powder, playing a preheating role. The primary air temperature is 300-310 ℃; the secondary air needs to be pressurized by the compressor first and then transported to the burner 110 through the pipeline. The secondary air temperature is 320-340 ℃.

[0121] Pressurized secondary air mixes thoroughly with the pulverized coal in the furnace, improving combustion efficiency and temperature. Furthermore, because the furnace gas is under high pressure, its heat transfer intensity is greatly increased. Therefore, when the same amount of heat needs to be absorbed, the required heat transfer area is reduced. This reduces the boiler volume by 10-15% and reduces metal consumption in the furnace by 10-15%.

[0122] At the same time, tubular air preheaters also have the advantages of simple structure and easy installation and manufacturing. In addition, due to the good sealing performance of tubular air preheaters, their air leakage is relatively small, which also reduces the pressure loss of high-pressure gas flow in the preheater, helping the preheated air to meet the design requirements.

[0123] like Figure 11 As shown, the large-scale atmospheric pressure combustion pulverized coal boiler is suitable for large and medium-sized systems above 200MWe. Its burner is atmospheric pressure combustion, the boiler size is large, and the pressure drop is small. Unlike the pressurized combustion boiler, its preheater adopts a rotary air preheater. Fresh air is sent into the primary and secondary air channels of the preheater through the blower 111. The air flows from bottom to top, and the flue gas flows from top to bottom through the flue gas channel, and the two form a countercurrent flow. The secondary air temperature is 310-320 ℃, and the secondary air temperature is 370-400 ℃. After the flue gas completes the heat exchange with the air, it also needs to exchange heat with the water in the flue gas absorber. Finally, the flue gas outlet temperature is about 90 ℃.

[0124] Because large power plants require high preheated air temperatures, using a tubular air preheater would result in large dimensions and metal usage. This would also complicate the placement of tail flue gas absorbers and other components. Therefore, this type of air preheater is only suitable for small coal-fired boilers. Rotary air preheaters, on the other hand, are compact and lightweight, making them suitable for large power station boilers. However, their complex structure, small dimensions, and footprint allow for higher heated air temperatures, poor airtightness, and high air leakage make them suitable for large atmospheric-pressure combustion boilers.

[0125] In response to the problem raised in the background technology: heat transfer is easily deteriorated in the furnace, the solution provided by the present invention is to propose a sleeve jet cooling wall and reheating wall structure, and modify the inner wall of the outer tube to give it a "lotus leaf" surface structure, which can greatly improve the heat exchange between the working fluid in the tube and the wall, timely reduce the wall temperature, avoid wall overheating, and ensure the safe operation of the boiler.

[0126] The boiler cooling wall and reheating wall are arranged in the furnace. Due to the extremely high flue gas temperature in the furnace, it is easy to cause the tube to overheat. At the same time, the heat resistance of the tube material is required to be high. The present invention proposes a sleeve injection tube structure, the specific structure is as follows Figure 12 As shown, the working fluid is sprayed from the inner tube through the opening to the inner wall of the outer tube, directly causing the impact phenomenon. At the same time, the inner wall of the outer tube adopts a surface modified pipeline, which can be manufactured by laser processing and chemical coating. Figure 13 The lotus leaf-like surface structure shown is a micro-nano structure with a certain degree of roughness. When the working fluid flows through this surface, a "lotus leaf effect" occurs, and the hydrophobic wall surface will experience velocity slippage, which increases the working fluid flow rate and reduces the pressure drop loss. At the same time, under this bionic structure, the heat exchange area between the working fluid and the surface is increased, which can enhance the heat transfer between it and the wall surface. Under the action of the sleeve structure and the "lotus leaf" surface modification, the heat transfer coefficient between the working fluid and the wall surface can be increased several times, which can effectively reduce the use of materials. At the same time, the lower the temperature of the inner tube, the lower the heat resistance of the tube can be. Therefore, the cooling wall and reheat wall structure of the present invention can ensure the safe temperature and efficient and economical operation of the boiler.

[0127] The superheater and reheater structures of the small-scale supercharged pulverized coal-fired boiler and the large-scale normal-pressure pulverized coal-fired boiler adopt a serpentine tube arrangement, which has the characteristics of many elbows and long tubes, which will cause disadvantages such as large pressure drop. At the same time, due to the physical properties of carbon dioxide, its heat transfer coefficient is relatively low and the heating area is large. Therefore, the present invention adopts a surface-modified pipe, and the inner wall of the pipe is processed by laser and chemically coated to produce a surface such as Figure 13As shown in the figure, when a working fluid flows over a surface with a certain degree of roughness, the hydrophobic wall will experience velocity slip, increasing the working fluid flow rate and reducing pressure drop losses. At the same time, under this biomimetic structure, the heat exchange area between the working fluid and the surface is increased, which can enhance heat transfer between the working fluid and the wall. This modified wall structure design can effectively reduce material usage and does not cause additional flow resistance losses.

[0128] Both boilers of the present invention are arranged in a split flow mode, which effectively reduces the pressure drop of the boiler. Since the temperature of CO2 is relatively high when it enters the boiler (about 500°C), if the water-cooled walls are arranged in the traditional steam boiler manner, the furnace will radiate too much heat and cannot be fully absorbed by the water-cooled walls, which will lead to deterioration of heat transfer of the working medium in the cooling walls, overheating of the cooling walls, and the possibility of safety accidents. This system effectively absorbs the heat radiated from the furnace in a timely manner by arranging cooling walls and reheating walls in the furnace at the same time, so that the furnace outlet temperature reaches about 1000°C. The cooling walls are used for primary heating of the SCO2 cycle, and the reheating walls are used for secondary heating of the SCO2 cycle; the reheating walls and cooling walls are arranged in an upper and lower arrangement. The superheater and high-temperature reheater are arranged in the horizontal flue, the low-temperature reheater and economizer are arranged in the vertical flue, and the air preheater and flue gas absorber are arranged outside the flue and are auxiliary structures of the boiler. The cooling walls and reheating walls in the furnace absorb heat mainly by radiation, supplemented by convection; the superheater, high-temperature reheater, low-temperature reheater and economizer in the flue absorb heat mainly by convection, supplemented by radiation.

[0129] After the flue gas in the boiler's vertical flue absorbs heat in the low-temperature reheater, its temperature remains around 500°C. To effectively and efficiently utilize the waste heat from this low- and medium-temperature flue gas, this system incorporates three methods: 1. An economizer is installed to heat the high-pressure branch fluid. This heats the high-pressure fluid to a medium-high temperature while also addressing the issue of high exhaust temperatures. 2. An air preheater is installed to absorb some of the waste heat from the flue gas, reducing the flue gas outlet temperature to 120-130°C. Primary air is used to transport pulverized coal, evaporating a small amount of moisture from the coal and preheating it to a desired temperature. Secondary air is directly used to provide oxygen to the burners in the furnace. Furthermore, its higher temperature aids combustion and helps achieve a higher combustion temperature. 3. The low-temperature flue gas is directed to a flue gas absorber to absorb excess heat for use in the cooling system, reducing its temperature to around 90°C. These three methods can increase boiler efficiency to over 95%.

[0130] The present invention not only proposes three different operating systems to cope with the safe and efficient operation of the system caused by different geographical locations and climates; it also proposes two different boiler layout structures to respectively deal with the efficiency and economy issues caused by different system loads.

[0131] The above is only a preferred embodiment of the present invention and should not be used to limit the scope of implementation of the present invention. In other words, any simple equivalent changes and modifications made according to the scope of the patent application and the content of the invention description are still within the scope of the patent of the present invention.

Claims

1. A supercritical-transcritical carbon dioxide coal-fired power generation system adapted to different geographical environments, climates and loads, characterized by: The invention comprises a boiler subsystem (1), a circulation subsystem (2) and a refrigeration subsystem, wherein the refrigeration subsystem adopts a LiBr absorption refrigeration device (3) and / or a thermoelectric refrigeration device (4), forming three operation systems for different geographical environments, climates and loads; when responding to the climate in the southern region, the refrigeration subsystem adopts a LiBr absorption refrigeration device; when responding to the climate in the northern region, the refrigeration subsystem adopts a thermoelectric refrigeration device; when responding to the climate in the northwest region, the refrigeration subsystem adopts both a LiBr absorption refrigeration device and a thermoelectric refrigeration device; The boiler subsystem includes a cooling wall (11), a reheat wall (12), a superheater (13), a high-temperature reheater (14), a low-temperature reheater (15), an economizer (16), an air preheater (17), a flue gas absorber (18) and an ejector (19); The circulation subsystem includes a bypass regenerator (201), a high-temperature regenerator (203), a low-temperature regenerator (205), a cooler (208), a branch working fluid pump (213), a main working fluid pump (215), a bypass preheater (216), a first-stage main compressor (217), a second-stage main compressor (218), a recompressor (219), a low-pressure turbine (220), a medium-pressure turbine (221), and a high-pressure turbine (222); The LiBr absorption refrigeration device (3) includes an evaporator (301), an absorber (302), a LiBr solution throttle valve (303), a LiBr solution pump (304), a LiBr solution heat exchanger (305), a generator (306), a condenser (307), a water throttle valve (308), a cold tank (309) and a hot tank (312); The thermoelectric refrigeration device (4) comprises a hot-end heat storage module (401), a thermoelectric module (402), a cold-end cold storage module (403), and a DC power supply (404).

2. The supercritical-transcritical carbon dioxide coal-fired power generation system adapted to different geographical environments, climates and loads according to claim 1 is characterized in that: When the refrigeration subsystem only uses the LiBr absorption refrigeration device (3), the circulation subsystem (2) further includes a first three-way valve (501), a second three-way valve (502), a third three-way valve (503), a fourth three-way valve (504), a fifth three-way valve (505), a sixth three-way valve (506), a seventh three-way valve (507), an eighth three-way valve (508), a ninth three-way valve (509), a thirteenth three-way valve (510), an eleventh three-way valve (511), a twelfth three-way valve (512), and a thirteenth three-way valve (513); The outlet of the low-pressure turbine (220) is connected to the B port of the first three-way valve (501), the A port of the first three-way valve (501) is connected in sequence to the bypass regenerator (201) and the C port of the second three-way valve (502), the C port of the first three-way valve (501) is connected in sequence to the high-temperature regenerator (203), the low-temperature regenerator (205) and the A port of the second three-way valve (502), the B port of the second three-way valve (502) is connected to the A port of the third three-way valve (503), and the third three-way valve (503) is connected to the B port of the second three-way valve (502). The C port of (503) is connected to the hot tank (312) and the C port of the fourth three-way valve (504) in sequence, the B port of the third three-way valve (503) is connected to the C port of the fifth three-way valve (505), the A port of the fourth three-way valve (504) and the A port of the fifth three-way valve (505) are connected to the A port and the C port of the sixth three-way valve (506) respectively, the B port of the fourth three-way valve (504) and the B port of the fifth three-way valve (505) are connected to the A port and the B port of the seventh three-way valve (507) respectively, The B port of the sixth three-way valve (506) is connected to the recompressor (219) and the B port of the thirteenth three-way valve (513) in sequence. The C port of the seventh three-way valve (507) is connected to the cooler (208) and the A port of the eighth three-way valve (508) in sequence. The C port of the eighth three-way valve (508) is connected to the cold tank (309), the branch working fluid pump (213) and the C port of the ninth three-way valve (509) in sequence. The B port of the eighth three-way valve (508) is connected to the The port is connected to the A port of the eleventh three-way valve (511), the A port of the ninth three-way valve (509) is connected to the B port of the thirteenth three-way valve (510), the B port of the ninth three-way valve (509) is connected to the bypass preheater (216) and the A port of the thirteenth three-way valve (510) in sequence, the C port of the thirteenth three-way valve (510) is connected to the bypass regenerator (201), the economizer (16) and the ejector (19) in sequence, the eleventh three-way valve (511) The B port of the valve is connected in sequence to the primary main compressor (217), the bypass preheater (216), the secondary main compressor (218) and the A port of the twelfth three-way valve (512); the C port of the eleventh three-way valve (511) is connected in sequence to the mainstream working fluid pump (215) and the B port of the twelfth three-way valve (512); the C port of the twelfth three-way valve (512) is connected in sequence to the low-temperature regenerator (205) and the C port of the thirteenth three-way valve (513); Port A of the thirteen-way valve (513) is connected in sequence to the high-temperature regenerator (203), the cooling wall (11), the superheater (13), the high-pressure turbine (222), the low-temperature reheater (15), the reheat wall (12) and the medium-pressure turbine (221). The medium-pressure turbine (221) is respectively connected to the ejector (19), the high-temperature reheater (14) and the low-pressure turbine (220). The hot tank (312) is connected to the flue gas absorber (18).

3. The supercritical-transcritical carbon dioxide coal-fired power generation system adapted to different geographical environments, climates and loads according to claim 2 is characterized in that: When the ambient temperature is 10-15 ℃, the flow rate ratio of the C port of the eighth three-way valve (508) is 0.58-1, and the flow rate ratio of the A port of the first three-way valve (501) is 0.36-0.6; when the ambient temperature is 15-20 ℃, the flow rate ratio of the C port of the eighth three-way valve (508) is 0.38-0.58, and the flow rate ratio of the A port of the first three-way valve (501) is 0.24-0.36; when the ambient temperature is 20-25 ℃, the flow rate ratio of the C port of the eighth three-way valve (508) is 0.44-0.62, and the flow rate ratio of the A port of the first three-way valve (501) is 0.27-0.46; when the ambient temperature is 25-30 When the ambient temperature is greater than 30°C, the C outlet flow rate ratio of the eighth three-way valve (508) is 0.62-0.63, and the A outlet flow rate ratio of the first three-way valve (501) is 0.46-0.47; when the ambient temperature is greater than 30°C, the C outlet flow rate ratio of the eighth three-way valve (508) is greater than 0.63, and the A outlet flow rate ratio of the first three-way valve (501) is greater than 0.

47.

4. The supercritical-transcritical carbon dioxide coal-fired power generation system adapted to different geographical environments, climates and loads according to claim 2 is characterized in that: When the ambient temperature is lower than 20° C., the circulation subsystem (2) further includes a cooling pool (200), the mainstream working fluid pump (215) is arranged in the cooling pool (200), and the B port of the eleventh three-way valve (511), the A port of the thirteenth three-way valve (510), and the B port of the ninth three-way valve (509) are all in a closed state.

5. The supercritical-transcritical carbon dioxide coal-fired power generation system adapted to different geographical environments, climates and loads according to claim 2, 3 or 4, characterized in that: When the ambient temperature is lower than 20°C, the A port of the twelfth three-way valve (512) is closed, the B port of the third three-way valve (503) is closed, the A, B and C ports of the fifth three-way valve (505) are all closed, the A port of the sixth three-way valve (506) is closed, the A, B and C ports of the fourth three-way valve (504) are all opened, and the B port of the seventh three-way valve (507) is closed; when the ambient temperature is higher than 20°C, the B inlet of the twelfth three-way valve (512) is closed, the C port of the third three-way valve (503) is closed, the A, B and C ports of the fifth three-way valve (505) are all opened; the C port of the sixth three-way valve (506) is closed, the A, B and C ports of the fourth three-way valve (504) are all closed, and the A port of the seventh three-way valve (507) is closed.

6. The supercritical-transcritical carbon dioxide coal-fired power generation system adapted to different geographical environments, climates and loads according to claim 1 is characterized in that: When the refrigeration subsystem only uses the thermoelectric refrigeration device (4), the circulation subsystem (2) further includes a fourteenth three-way valve (601), a fifteenth three-way valve (602), a sixteenth three-way valve (603), a seventeenth three-way valve (604), an eighteenth three-way valve (605), a nineteenth three-way valve (606), a twenty-third three-way valve (607), a twenty-first three-way valve (608), and a twenty-second three-way valve (609); The outlet of the low-pressure turbine (220) is connected to the B port of the fourteenth three-way valve (601), the A port of the fourteenth three-way valve (601) is connected in sequence to the bypass regenerator (201) and the C port of the fifteenth three-way valve (602), the C port of the fourteenth three-way valve (601) is connected in sequence to the high-temperature regenerator (203), the low-temperature regenerator (205) and the B port of the fifteenth three-way valve (602), the C port of the fifteenth three-way valve (602) is connected in sequence to the hot end heat storage module (401) and the C port of the sixteenth three-way valve (603), and the B port of the sixteenth three-way valve (603) is connected in sequence to the cooler ( 208) and the A port of the seventeenth three-way valve (604), the A port of the sixteenth three-way valve (603) is connected in sequence to the recompressor (219) and the B port of the twenty-second three-way valve (609), the C port of the seventeenth three-way valve (604) is connected in sequence to the cold end cold storage module (403) and the B port of the eighteenth three-way valve (605), the B port of the seventeenth three-way valve (604) is connected in sequence to the primary main compressor (217), the bypass preheater (216), the secondary main compressor (218) and the A port of the twenty-first three-way valve (608), the A port of the eighteenth three-way valve (605) is connected in sequence The main working medium pump (215) and the B port of the twenty-first three-way valve (608), the C port of the eighteenth three-way valve (605) are connected in sequence to the branch working medium pump (213) and the C port of the nineteenth three-way valve (606), the A port of the nineteenth three-way valve (606) is connected to the B port of the twenty-third valve (607), the B port of the nineteenth three-way valve (606) is connected in sequence to the bypass preheater (216) and the A port of the twenty-third valve (607), the C port of the twenty-third valve (607) is connected in sequence to the bypass regenerator (201), the economizer (16) and the ejector (19), the twenty-first The C port of the three-way valve (608) is connected in sequence to the low-temperature regenerator (205) and the C port of the twenty-second three-way valve (609); the A port of the twenty-second three-way valve (609) is connected in sequence to the high-temperature regenerator (203), the cooling wall (11), the superheater (13), the high-pressure turbine (222), the low-temperature reheater (15), the reheat wall (12) and the medium-pressure turbine (221); the medium-pressure turbine (221) is connected to the inlet of the ejector (19), the high-temperature reheater (14) and the low-pressure turbine (220); the hot end heat storage module (401) is connected to the flue gas absorber (18).

7. The supercritical-transcritical carbon dioxide coal-fired power generation system adapted to different geographical environments, climates and loads according to claim 6 is characterized in that: For the seventeenth three-way valve (604): the working medium flows in from the A port of the seventeenth three-way valve (604), and flows out from the B and C ports of the seventeenth three-way valve (604); when the ambient temperature is lower than 15°C, the C outlet flow ratio of the seventeenth three-way valve (604) is 1; when the ambient temperature is 15-20°C, the C outlet flow ratio of the seventeenth three-way valve (604) is 0.96-1; when the ambient temperature is 20-25°C, the C outlet flow ratio of the seventeenth three-way valve (604) is 0.56-0.96; when the ambient temperature is 25-30°C, the C outlet flow ratio of the seventeenth three-way valve (604) is 0.53-0.56; when the ambient temperature is greater than 30°C, the C outlet flow ratio of the seventeenth three-way valve (604) is lower than 0.53; For the eighteenth three-way valve (605): the working fluid flows in from the B port of the eighteenth three-way valve (605) and flows out from the A and C ports of the eighteenth three-way valve (605); when the ambient temperature is lower than 20°C, the flow rate ratio of the C outlet of the eighteenth three-way valve (605) is 0.5; when the ambient temperature is higher than 20°C, the flow rate ratio of the C outlet of the eighteenth three-way valve (605) is 1; For the fourteenth three-way valve (601): the working fluid flows into the B port of the fourteenth three-way valve (601) and flows out of the A and C ports of the fourteenth three-way valve (601). When the ambient temperature is lower than 10°C, the flow rate ratio of the A outlet of the fourteenth three-way valve (601) is lower than 0.3; when the ambient temperature is 10-15°C, the flow rate ratio of the A outlet of the fourteenth three-way valve (601) is 0.3-0.31; when the ambient temperature is 15-20°C, the flow rate ratio of the C outlet of the fourteenth three-way valve (601) is 0.31; when the ambient temperature is 20-25°C, the flow rate ratio of the C outlet of the fourteenth three-way valve (601) is 0.31-0.37; when the ambient temperature is 25-30°C, the flow rate ratio of the C outlet of the fourteenth three-way valve (601) is 0.37-0.4; when the ambient temperature is greater than 35 At ℃, the C outlet flow ratio of the fourteenth three-way valve (601) is lower than 0.

4.

8. The supercritical-transcritical carbon dioxide coal-fired power generation system adapted to different geographical environments, climates and loads according to claim 6 or 7, characterized in that: When the ambient temperature is lower than 20°C, the A port of the 23rd valve (607) and the A port of the 21st three-way valve (608) are closed, and the B port of the 19th three-way valve (606) is closed; when the ambient temperature is higher than 20°C, the B port of the 21st three-way valve (608) is closed.

9. The supercritical-transcritical carbon dioxide coal-fired power generation system adapted to different geographical environments, climates and loads according to claim 1 is characterized in that: When the refrigeration subsystem simultaneously adopts the LiBr absorption refrigeration device (3) and the thermoelectric refrigeration device (4), the circulation subsystem (2) further includes a twenty-third three-way valve (202), a twenty-fourth three-way valve (209), a twenty-fifth three-way valve (313), a twenty-sixth three-way valve (314), a twenty-seventh three-way valve (207), a twenty-eighth three-way valve (204), a twenty-ninth three-way valve (210), a thirty-third three-way valve (206), a thirty-first three-way valve (311), a thirty-second three-way valve (310), a thirty-third three-way valve (214), a thirty-fourth three-way valve (212), a thirty-fifth three-way valve (211), a thirty-sixth three-way valve (405), and a thirty-seventh three-way valve (406); The outlet of the low-pressure turbine (220) is connected to the B port of the twenty-third three-way valve (202), the A port of the twenty-third three-way valve (202) is connected in sequence to the bypass regenerator (201) and the A port of the twenty-fourth three-way valve (209), the C port of the twenty-third three-way valve (202) is connected in sequence to the high-temperature regenerator (203), the low-temperature regenerator (205) and the B port of the twenty-fourth three-way valve (209), the C port of the twenty-fourth three-way valve (209) is connected to the B port of the twenty-fifth three-way valve (313), the C port of the twenty-fifth three-way valve (313) is connected in sequence to the C port of the hot tank (312) and the C port of the twenty-sixth three-way valve (314), and the twenty-fifth three-way valve (314) is connected in sequence to the hot tank (312). The port A of the door (313) is connected in sequence to the hot end heat storage module (401) and the port A of the twenty-sixth three-way valve (314); the port B of the twenty-sixth three-way valve (314) is connected to the port C of the twenty-seventh three-way valve (207); the port A of the twenty-seventh three-way valve (207) is connected in sequence to the re-compressor (219) and the port B of the twenty-eighth three-way valve (204); the port B of the twenty-seventh three-way valve (207) is connected in sequence to the cooler (208) and the port A of the twenty-ninth three-way valve (210); the port B of the twenty-ninth three-way valve (210) is connected in sequence to the first-stage main compressor (217), the bypass preheater (216), the second-stage main compressor (218), the thirty-first three-way valve (219), the second-stage main compressor ... The A port of the three-way valve (206) and the C port of the twenty-ninth three-way valve (210) are sequentially connected to the A and C ports of the thirty-first three-way valve (311), the cold tank (309), the A and B ports of the thirty-second three-way valve (310), the B and C ports of the thirty-third three-way valve (214), the branch working fluid pump (213), the C and B ports of the thirty-fourth three-way valve (212), the bypass preheater (216), the A and C ports of the thirty-fifth three-way valve (211), the bypass regenerator (201), the economizer (16) and the ejector (19); the B port of the thirty-first three-way valve (311) is sequentially connected to the cold end cold storage module (403) and the C port of the thirty-second three-way valve (310), the The A port of the thirty-third three-way valve (214) is connected in sequence to the main working fluid pump (215) and the B port of the thirty-third valve (206); the C port of the thirty-third valve (206) is connected in sequence to the low-temperature regenerator (205), the recompressor (219) and the C port of the twenty-eighth three-way valve (204); the A port of the twenty-eighth three-way valve (204) is connected in sequence to the high-temperature regenerator (203), the cooling wall (11), the superheater (13), the low-pressure turbine (220), the low-temperature reheater (15), the reheat wall (12) and the medium-pressure turbine (221); the medium-pressure turbine (221) is connected to the inlets of the ejector (19), the high-temperature reheater (14) and the low-pressure turbine (220);The B ports of the thirty-sixth three-way valve (405) and the thirty-seventh three-way valve (406) are connected to the output port and the input port of the flue gas absorber (18), respectively; the A and C ports of the thirty-sixth three-way valve (405) are connected to the input port of the hot end heat storage module (401) and the hot tank (312), respectively; and the A and C ports of the thirty-seventh three-way valve (406) are connected to the output port of the hot end heat storage module (401) and the hot tank (312), respectively.

10. The supercritical-transcritical carbon dioxide coal-fired power generation system adapted to different geographical environments, climates and loads according to claim 9, characterized in that: When the ambient temperature is higher than 20°C, the B port of the thirty-third-way valve (206), the A port of the third three-way valve (503), the A port of the fourth three-way valve (504), the B port of the ninth three-way valve (509), the C port of the thirteenth-way valve (510), the A port of the fourteenth three-way valve (601), and the A port of the fifteenth three-way valve (602) are cut off; when the ambient temperature is lower than 20°C, the A port of the thirty-fifth three-way valve (211), the B port of the thirty-fourth three-way valve (212), the A port of the thirty-third-way valve (206), the C port of the third three-way valve (503), the C port of the fourth three-way valve (504), the C port of the ninth three-way valve (509), the A port of the thirteenth-way valve (510), the C port of the fourteenth three-way valve (601), and the C port of the fifteenth three-way valve (602) are cut off; For the twenty-ninth three-way valve (210): the working medium flows into the A port of the twenty-ninth three-way valve (210) and flows out of the B and C ports of the twenty-ninth three-way valve (210). When the ambient temperature is lower than 15°C, the flow rate ratio of the C port of the twenty-ninth three-way valve (210) is 1; when the ambient temperature is 15-20°C, the flow rate ratio of the C port of the twenty-ninth three-way valve (210) is 0.96-1; when the ambient temperature is 20-25°C, the flow rate ratio of the C port of the twenty-ninth three-way valve (210) is 0.60-0.96; when the ambient temperature is 25-30°C, the flow rate ratio of the C port of the twenty-ninth three-way valve (210) is 0.62-0.63; when the ambient temperature is greater than 35°C, the flow rate ratio of the C port of the twenty-ninth three-way valve (210) is greater than 0.63; For the thirty-third three-way valve (214): the working fluid flows in from the B port of the thirty-third three-way valve (214), and flows out from the A and C ports of the thirty-third three-way valve (214). When the ambient temperature is lower than 20°C, the flow rate ratio of the C port of the thirty-third three-way valve (214) is 0.5; when the ambient temperature is higher than 20°C, the flow rate ratio of the C port of the thirty-third three-way valve (214) is 1; For the twenty-third three-way valve (202): the working medium flows into the B port of the twenty-third three-way valve (202) and flows out of the A and C ports of the twenty-third three-way valve (202). When the ambient temperature is lower than 25°C, the flow rate ratio of the A port of the twenty-third three-way valve (202) is 0.5; when the ambient temperature is 25-30°C, the flow rate ratio of the A port of the twenty-third three-way valve (202) is 0.46-0.50; when the ambient temperature is greater than 30°C, the flow rate ratio of the C port of the twenty-third three-way valve (202) is greater than 0.47.

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