A combined heat and power system coupling a transcritical co2 power cycle with a transcritical co2 heat pump

Abstract

The application belongs to the technical field of heat source heat recovery, and particularly relates to a combined heat and power system of a transcritical CO2 power cycle coupled with a transcritical CO2 heat pump. The combined heat and power system comprises a primary power cycle, a secondary power cycle and a heat pump system with CO2 as a working medium and transcritical operation. The heat pump system comprises a condenser evaporator. The primary power cycle and the secondary power cycle have the same structure, and comprise a high / medium temperature heater, a primary / secondary turbine, a primary / secondary high temperature recuperator, a primary / secondary low temperature recuperator and a low pressure mixer. The low pressure mixer is connected to the condenser evaporator, and the condenser evaporator returns a hot side medium to the primary low temperature recuperator and the secondary low temperature recuperator through a booster pump. The application can realize the maximum efficiency of the segmented cycle and effectively improve the cycle efficiency by coupling the two-stage power cycle with the heat pump system, while realizing the gradient and deep utilization of heat in the high temperature zone, the medium temperature zone and the low temperature zone of the heat source.

Description

Technical Field

[0001] This invention belongs to the field of heat source recovery technology, specifically relating to a combined heat and power system of transcritical CO2 dynamic cycle coupled with transcritical CO2 heat pump. Background Technology

[0002] Waste heat and solar thermal utilization are important ways to promote synergistic efficiency in pollution reduction and carbon reduction. Common heat sources (such as geothermal energy, waste heat from industrial production processes such as metallurgy, and waste heat from the energy conversion process of internal combustion engines) have a wide temperature range. Faced with heat sources with a wide temperature range, in order to ensure the efficiency of waste heat utilization, the utilization methods are generally specific and cannot be flexibly switched. The cycle efficiency still needs to be further improved, and the overall efficiency of waste heat utilization systems still needs to be improved.

[0003] Compared with conventional steam power cycles, the transcritical CO2 Rankine power cycle has the following two significant advantages: (1) higher thermal conversion efficiency, reducing fuel and freshwater working fluid consumption; (2) simpler system structure, smaller overall equipment size, and significant space saving. Compared with supercritical CO2 Brayton power cycles, the transcritical CO2 Rankine power cycle has the following two significant advantages: (1) the transcritical CO2 Rankine power cycle generally has a lower usable waste heat temperature, and its applicable range can be as low as 100℃, with good waste heat source adaptability; (2) the cycle thermal efficiency and thermal efficiency can reach a higher level.

[0004] Therefore, leveraging the advantages of the transcritical CO2 Rankine power cycle, efficient utilization of waste heat can be further achieved. However, the condenser section of existing transcritical CO2 Rankine power cycles typically uses ambient air cooling or tap water / seawater cooling, making it difficult to achieve heat recovery and reuse, and also difficult to further reduce the condensation temperature. The cycle efficiency and system stability are both affected and limited by the ambient temperature. The method of utilizing the latent heat of condensation in the transcritical CO2 Rankine power cycle can still be further optimized. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a combined heat and power system for transcritical CO2 power cycle coupled with a transcritical CO2 heat pump.

[0006] The present invention adopts the following technical solution:

[0007] A combined heat and power system of transcritical CO2 power cycle coupled with transcritical CO2 heat pump includes a primary power cycle, a secondary power cycle and a heat pump system that use CO2 as working fluid and operate transcritically;

[0008] A heat pump system includes a condenser-evaporator, a compressor, a gas cooler, and an expansion valve connected in sequence.

[0009] The primary power cycle includes a high-temperature heater that recovers heat from the high-temperature section of the heat source, and a primary turbine, a primary high-temperature regenerator, a primary low-temperature regenerator, and a low-pressure mixer that are sequentially connected to the cold-side outlet of the high-temperature heater.

[0010] The secondary power cycle includes a medium-temperature heater connected to the hot-side outlet of the high-temperature heater to recover heat from the medium-temperature section of the heat source, and a secondary turbine, a secondary high-temperature regenerator, a secondary low-temperature regenerator, and a low-pressure mixer connected in sequence to the cold-side outlet of the medium-temperature heater.

[0011] The medium outlet of the low-pressure mixer is connected to the condenser-evaporator in the heat pump system. The hot-side outlet of the condenser-evaporator returns the hot-side medium to the cold-side inlet of the first-stage low-temperature regenerator and the second-stage low-temperature regenerator respectively through a booster pump.

[0012] Preferably, the cold-side outlet of the primary low-temperature regenerator is connected in sequence to the primary high-temperature regenerator and the high-temperature heater via a primary mixer to form a cycle; the cold-side outlet of the secondary low-temperature regenerator is connected in sequence to the secondary high-temperature regenerator and the medium-temperature heater via a secondary mixer to form a cycle.

[0013] Preferably, a first distributor is provided between the primary low-temperature regenerator and the low-pressure mixer, and the first distributor is also connected to the medium inlet of the primary mixer through a primary recompressor; a second distributor is provided between the secondary low-temperature regenerator and the low-pressure mixer, and the second distributor is also connected to the medium inlet of the secondary mixer through a secondary recompressor.

[0014] Preferably, in the heat pump system, the cold-side outlet of the gas cooler is connected to the low-temperature heater, and the hot-side outlet of the medium-temperature heater is also connected to the hot-side inlet of the low-temperature heater. The user-side working fluid to be heated absorbs heat in the gas cooler and then enters the low-temperature heater through the cold-side outlet for further heating.

[0015] Preferably, a third distributor is provided between the booster pump and the primary low-temperature regenerator and the secondary low-temperature regenerator.

[0016] Preferably, the first-stage turbine is connected to a first-stage power generation device, and the second-stage turbine is connected to a second-stage power generation device.

[0017] Preferably, when the heat source temperature is below 450°C or the system power generation efficiency is below 20%, only the first-stage power cycle is activated, and the second-stage power cycle is not activated.

[0018] The beneficial effects of this invention are as follows:

[0019] (1) The power cycle in this application adopts a two-stage transcritical CO2 Rankine cycle. Compared with supercritical CO2 Brayton cycle, steam Rankine cycle and organic Rankine cycle, it can achieve higher power generation efficiency at the same heat source temperature and has stronger adaptability to heat sources in different temperature ranges. By coupling the two-stage power cycle with a heat pump, this application can achieve deep utilization of heat in the high-temperature, medium-temperature and low-temperature ranges of the heat source while maximizing the segmented cycle efficiency, effectively improving the cycle efficiency.

[0020] (2) By coupling a two-stage transcritical CO2 Rankine cycle with a transcritical CO2 heat pump, a high-efficiency combined heat and power supply is achieved. Taking advantage of the characteristic that the CO2 evaporation temperature decreases significantly with decreasing pressure, the operating pressure of the heat pump side of the condenser evaporator can be adjusted to reduce the CO2 condensation temperature on the power cycle side within a certain range. This breaks the limitation of ambient temperature on CO2 condensation temperature and the resulting heat waste caused by conventional air cooling and water cooling methods. There is no external cooling water system, and almost all heat is efficiently recovered. This further improves system efficiency and operational reliability. In addition, it fully meets the heating needs of domestic use and has a wide range of applications. It can achieve efficient district heating and industrial heating, and further promote the synergistic effect of pollution reduction and carbon reduction. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the combined heat and power system of the transcritical CO2 power cycle coupled with the transcritical CO2 heat pump of this application.

[0022] Figure 2 This is a schematic diagram of the system without the secondary power cycle enabled.

[0023] The meanings of the symbols in the diagram are as follows:

[0024] 11-Condenser / Evaporator, 12-Compressor, 13-Gas Cooler, 131-Diverter Valve, 14-Expansion Valve;

[0025] 21-High temperature heater, 22-First stage turbine, 221-First stage power generation unit, 23-First stage high temperature regenerator, 24-First stage low temperature regenerator, 25-First stage mixer, 26-First stage distributor, 27-First stage recompressor;

[0026] 31-Medium temperature heater, 32-Second stage turbine, 321-Second stage power generation unit, 33-Second stage high temperature regenerator, 34-Second stage low temperature regenerator, 35-Second stage mixer, 36-Second stage splitter, 37-Second stage recompressor;

[0027] 40 - Low-pressure mixer, 50 - Booster pump, 60 - Low-temperature heater, 70 - Third distributor. Detailed Implementation

[0028] The technical solution of the present invention will be described in more detail below with reference to the embodiments and accompanying drawings.

[0029] like Figure 1 As shown, this application provides a combined heat and power system (CHP) of a transcritical CO2 power cycle coupled with a transcritical CO2 heat pump, comprising a primary power cycle, a secondary power cycle, and a heat pump system operating transcritically with CO2 as the working fluid. The heat pump system includes a condenser-evaporator 11, a compressor 12, a gas cooler 13, and an expansion valve 14 connected in sequence. The primary and secondary power cycles include a shared low-pressure mixer 40, a booster pump 50, and a third distributor 70.

[0030] The primary power cycle also includes a high-temperature heater 21 for recovering heat from the high-temperature section of the heat source, and a primary turbine 22, a primary high-temperature regenerator 23, and a primary low-temperature regenerator 24 connected in sequence to the cold-side outlet of the high-temperature heater 21. The cold-side outlet of the primary low-temperature regenerator 24 is connected in sequence to the primary high-temperature regenerator 23 and the high-temperature heater 21 via a primary mixer 25 to form a cycle.

[0031] The secondary power cycle also includes a medium-temperature heater 31 that recovers heat from the medium-temperature section of the heat source, and a secondary turbine 32, a secondary high-temperature regenerator 33, and a secondary low-temperature regenerator 34, which are sequentially connected to the cold-side outlet of the medium-temperature heater 31. The hot-side inlet of the medium-temperature heater 31 is connected to the hot-side outlet of the high-temperature heater 21. The cold-side outlet of the secondary low-temperature regenerator 34 is sequentially connected to the secondary high-temperature regenerator 33 and the medium-temperature heater 31 via a secondary mixer 35, forming a cycle.

[0032] The first-stage turbine 22 is connected to the first-stage power generation device 221, and the second-stage turbine 32 is connected to the second-stage power generation device 321 for generating electricity.

[0033] Both the primary low-temperature regenerator 24 and the secondary low-temperature regenerator 34 are connected to the low-pressure mixer 40. The medium outlet of the low-pressure mixer 40 is connected to the condenser-evaporator 11 in the heat pump system. The hot-side outlet of the condenser-evaporator 11 is further returned to the cold-side inlets of the primary low-temperature regenerator 24 and the secondary low-temperature regenerator 34 via the booster pump 50. That is, the heat pump system is coupled to the primary and secondary power cycles through the condenser-evaporator 11.

[0034] Furthermore, a first distributor 26 is provided between the primary low-temperature regenerator 24 and the low-pressure mixer 40, and the first distributor 26 is also connected to the medium inlet of the primary mixer 25 through a primary recompressor 27. A second distributor 36 is provided between the secondary low-temperature regenerator 34 and the low-pressure mixer 40, and the second distributor 36 is also connected to the medium inlet of the secondary mixer 35 through a secondary recompressor 37.

[0035] In the heat pump system, the cold side outlet of the gas cooler 13 is connected to the low-temperature heater 60, and the hot side outlet of the medium-temperature heater 31 is also connected to the hot side inlet of the low-temperature heater 60. The user-side working fluid to be heated absorbs heat in the gas cooler 13 and then enters the low-temperature heater 60 through the cold side outlet for further heating.

[0036] Furthermore, a diversion valve 131 is provided between the gas cooler 13 and the cryogenic heater 60. The diversion valve can separate the heated working fluid flowing out of the gas cooler 13 for direct use.

[0037] In this system, the hot-side outlet of the high-temperature heater 21 is connected to the hot-side inlet of the medium-temperature heater 31. The heat source of the high-temperature section is first used as the working fluid on the hot side of the high-temperature heater 21 to heat the CO2 of the first-stage power cycle. After cooling, it enters the medium-temperature heater 31 to heat the CO2 of the second-stage power cycle. After cooling again, it enters the low-temperature heater 60 for further cooling.

[0038] In the above system, the first-stage power cycle is as follows: heat from the high-temperature section of the heat source enters the high-temperature heater 21 through the hot-side inlet, heating the CO2 medium in the first-stage power cycle. After heating, the high-temperature and high-pressure supercritical CO2 flows out from the cold-side outlet of the high-temperature heater 21, flows through the first-stage turbine 22, and then, as the hot-side medium, passes through the first-stage high-temperature regenerator 23 and the first-stage low-temperature regenerator 24 in sequence. Then, it is divided into two parts by the first splitter 26. One part of CO2 first flows through the low-pressure mixer 40, the condenser-evaporator 11 and the booster pump 50 as the hot-side medium, and then flows through the first-stage low-temperature regenerator 24 as the cold-side medium. The other part of CO2 is compressed by the first-stage recompressor 27 and then merges with the first part of CO2 at the cold-side outlet of the first-stage low-temperature regenerator 24 through the first-stage mixer 25. Then, as the cold-side medium, it enters the first-stage high-temperature regenerator 23 and the high-temperature heater 21 in sequence to raise its temperature, completing one transcritical CO2 recompression Rankine cycle.

[0039] The secondary power cycle is as follows: heat from the intermediate temperature section of the heat source enters the intermediate temperature heater 31 through the hot side inlet, heating the CO2 medium in the secondary power cycle. After heating, the supercritical CO2 at intermediate temperature and high pressure flows out from the cold side outlet of the intermediate temperature heater 31, flows through the secondary turbine 32, and then, as the hot side medium, passes through the secondary high temperature regenerator 33 and the secondary low temperature regenerator 34 in sequence. Then, it is divided into two parts by the second splitter 36. One part of CO2 first flows through the low pressure mixer 40, the condenser evaporator 11 and the booster pump 50 as the hot side medium, and then flows through the secondary low temperature regenerator 34 as the cold side medium. The other part of CO2 is compressed by the secondary recompressor 37 and then merges with the first part of CO2 at the cold side outlet of the secondary low temperature regenerator 34 through the secondary mixer 35. Then, as the cold side medium, it enters the secondary high temperature regenerator 33 and the intermediate temperature heater 31 in sequence to raise the temperature, completing one transcritical CO2 recompression Rankine cycle.

[0040] In the heat pump system: CO2, as the cold-side medium, exchanges heat with the heat media from the primary and secondary power cycles in the condenser-evaporator, causing evaporation. After flowing through compressor 12, it releases heat to the user-side working fluid in gas cooler 13. After heat release, it passes through expansion valve 14 and re-enters condenser-evaporator 11, completing one transcritical CO2 reverse Carnot cycle. The user-side working fluid, after initial heating in gas cooler 13, flows partially or entirely through cryogenic heater 60 for further heating.

[0041] In this application, the flow splitting principle of the first splitter 26 and the second splitter 36 is as follows: Based on the inlet temperature and flow rate of the working fluid on the hot side of the high-temperature heater 21, the total flow rate of the CO2 working fluid in the first-stage power cycle is initially determined. The distribution ratio of the first splitter 26 is adjusted, and the corresponding theoretical power generation efficiency is obtained through thermodynamic calculations. The distribution ratio of the first splitter 26 corresponding to the highest theoretical power generation efficiency of the first-stage power cycle is selected. At the same time, the outlet temperature of the working fluid on the hot side of the high-temperature heater 21 is obtained and used as the inlet temperature of the hot side of the medium-temperature heater 31 in the second-stage power cycle. Then, to ensure that the working fluid temperature and pressure at the two inlet ends of the low-pressure mixer 40 are consistent, the total flow rate of the CO2 working fluid in the second-stage power cycle is initially determined. The distribution ratio of the second splitter 36 is adjusted to obtain the corresponding theoretical power generation efficiency of the second-stage power cycle. The distribution ratio of the second splitter 36 corresponding to the highest theoretical power generation efficiency of the second-stage power cycle is selected. The heat flow rate of the condenser-evaporator 11 is the total amount of CO2 entering the low-pressure mixer 40 through the first distributor 26 in the first stage power cycle and through the second distributor 36 in the second stage power cycle. The operating parameters of the heat pump are determined based on the inlet and outlet parameters of the condenser-evaporator 11.

[0042] When the heat source temperature is below 450℃, the primary power cycle operates normally, but the secondary power cycle has low power generation efficiency (usually the system power generation efficiency is below 20%). In order to reduce the system investment and operating costs, only the primary power cycle and heat pump system are activated, and the secondary power cycle is not activated. At this time, the heat source is recovered in the low temperature heater 60 after passing through the high temperature heater 21, which simplifies the system structure while ensuring high cycle efficiency.

[0043] It should be emphasized that, for certain special operating conditions, the calculated theoretical power generation efficiency can be used as the system power generation efficiency.

[0044] The system will be described below in conjunction with specific operating conditions.

[0045] Example 1

[0046] It operates normally when the heat source temperature is above 450℃.

[0047] In this embodiment, the heat source temperature is 820℃. Assuming the temperature difference at the high-temperature heater terminals is 20℃, the cold-side outlet temperature of the high-temperature heater, i.e., the turbine inlet temperature, is 800℃. The booster pump outlet pressure is 25MPa, and the outlet temperature is 13℃. After optimizing the parameters and allocation ratios, the system operating conditions are as follows:

[0048] First-stage power cycle: The cold-side outlet temperature of the high-temperature regenerator (i.e., the cold-side inlet temperature of the high-temperature heater) is 531.3℃, the turbine inlet temperature is 800℃, the isentropic efficiency is 85%, the outlet pressure is 5.5MPa, the outlet temperature is 605.9℃, the terminal temperature difference of the low-temperature regenerator is 5℃, the hot-side outlet temperature is 18℃, and the working fluid recompression ratio is 37.3%, meaning 62.7% of the working fluid enters the condenser-evaporator to release heat and condense to -1.78℃, and 37.3% of the working fluid enters the recompressor, where it is compressed to the same pressure as the cold-side outlet of the low-temperature regenerator. The two streams are then mixed and enter the high-temperature regenerator together, ultimately achieving a transcritical CO2 power cycle side power generation efficiency of 58.24%. Simultaneously, based on the high-temperature heater cold-side inlet temperature of 531.3℃ in the first-stage operating condition, the estimated hot-side inlet temperature of the intermediate-temperature heater is approximately 555℃. Assuming the terminal temperature difference of the intermediate-temperature heater is 30℃, the second-stage turbine inlet temperature is 525℃.

[0049] Second-stage power cycle: The cold-side outlet temperature of the high-temperature regenerator (which is also the cold-side inlet temperature of the medium-temperature heater) is 307.2℃, the turbine inlet temperature is 525℃, the isentropic efficiency is 85%, the outlet pressure is 5.5MPa, the terminal temperature difference of the low-temperature regenerator is 5℃, the hot-side outlet temperature is 18℃, and the working fluid recompression ratio is 37.8%, meaning 62.2% of the working fluid enters the condenser-evaporator to release heat and condense to -1.78℃, and 37.8% of the working fluid enters the recompressor, where it is compressed to the same pressure as the cold-side outlet of the low-temperature regenerator. The two streams are then mixed and enter the high-temperature regenerator together, ultimately achieving a transcritical CO2 power cycle side power generation efficiency of 48.28%. Simultaneously, based on the medium-temperature heater cold-side inlet temperature of 307.2℃ in the second-stage operating condition, the estimated hot-side inlet temperature of the low-temperature heater is approximately 340℃.

[0050] Heat pump system: Energy efficiency coefficient 4.3. Assuming the heat pump user-side outlet temperature is 50~110℃, it can directly supply domestic water and heat. It can also further utilize the low-temperature section of the high-temperature heat source (about 340℃) to further heat water or steam to above 150℃ in the low-temperature heater for industrial production.

[0051] Example 2

[0052] It operates normally when the heat source temperature is above 450℃.

[0053] In this embodiment, the heat source temperature is 620℃. Assuming the temperature difference at the high-temperature heater terminals is 20℃, the cold-side outlet temperature of the high-temperature heater, i.e., the inlet temperature of the first-stage turbine, is 600℃. The booster pump outlet pressure is 25MPa, and the outlet temperature is 13℃. After optimizing the parameters and allocation ratios, the system operating conditions are as follows:

[0054] The first-stage power cycle has the following parameters: High-temperature regenerator cold-side outlet temperature (i.e., high-temperature heater cold-side inlet temperature) is 365.6℃, turbine inlet temperature is 600℃, isentropic efficiency is 85%, outlet pressure is 5.5MPa, low-temperature regenerator terminal temperature difference is 5℃, hot-side outlet temperature is 18℃, and working fluid recompression ratio is 37.4%. This means 62.6% of the working fluid enters the condenser-evaporator to release heat and condense to -1.78℃, while 37.4% enters the recompressor, where it is compressed to the same pressure as the low-temperature regenerator cold-side outlet. The two streams then mix and enter the high-temperature regenerator together, ultimately achieving a transcritical CO2 power cycle side power generation efficiency of 51.43%. Based on the high-temperature heater cold-side inlet temperature of 365.6℃ in the first-stage operating condition, the estimated hot-side inlet temperature of the intermediate-temperature heater is approximately 385℃. Assuming an intermediate-temperature heater terminal temperature difference of 30℃, the second-stage turbine inlet temperature is 355℃.

[0055] Second-stage power cycle: The cold-side outlet temperature of the high-temperature regenerator (which is also the cold-side inlet temperature of the medium-temperature heater) is 181.5℃, the turbine inlet temperature is 355℃, the isentropic efficiency is 85%, the outlet pressure is 5.5MPa, the terminal temperature difference of the low-temperature regenerator is 5℃, the hot-side outlet temperature is 18℃, and the working fluid recompression ratio is 38%, meaning 62% of the working fluid enters the condenser-evaporator to release heat and condense to -1.78℃, and 38% of the working fluid enters the recompressor, where it is compressed to the same pressure as the cold-side outlet of the low-temperature regenerator. The two streams are then mixed and enter the high-temperature regenerator together, ultimately achieving a transcritical CO2 power cycle side power generation efficiency of 37.71%. Simultaneously, based on the 181.5℃ cold-side inlet temperature of the medium-temperature heater in the second-stage operating condition, the estimated hot-side inlet temperature of the low-temperature heater is approximately 210℃.

[0056] Heat pump system: Energy efficiency coefficient 4.3. Assuming the heat pump user-side outlet temperature is 50~110℃, it can directly supply domestic water and heat. It can also further utilize the low-temperature section of the high-temperature heat source (about 210℃) to further heat water or steam to above 120℃ in the low-temperature heater for industrial production.

[0057] Example 3

[0058] When the heat source temperature is below 450℃, a two-stage power cycle is not used.

[0059] In this embodiment, the heat source temperature is 430℃. Assuming the temperature difference at the high-temperature heater terminals is 30℃, the cold-side outlet temperature of the high-temperature heater, i.e., the inlet temperature of the first-stage turbine, is 400℃. The booster pump outlet pressure is 25MPa, and the outlet temperature is 13℃. After optimizing the parameters and allocation ratios, the system operating conditions are as follows:

[0060] The first-stage power cycle has a high-temperature regenerator cold-side outlet temperature (i.e., the high-temperature heater cold-side inlet temperature) of 214.9℃, a turbine inlet temperature of 400℃, an isentropic efficiency of 85%, an outlet pressure of 5.5MPa, a low-temperature regenerator terminal temperature difference of 5℃, a hot-side outlet temperature of 18℃, and a working fluid recompression ratio of 38%. This means that 62% of the working fluid enters the condenser-evaporator to release heat and condense to -1.78℃, while 38% of the working fluid enters the recompressor. After being compressed to the same pressure as the low-temperature regenerator cold-side outlet, the two streams are mixed and enter the high-temperature regenerator together. Ultimately, the transcritical CO2 power cycle can achieve a side power generation efficiency of 41.28%.

[0061] Meanwhile, based on the cold-side inlet temperature of 214.9℃ for the high-temperature heater in the first-stage operating condition, if a two-stage power cycle is used, the estimated hot-side inlet temperature of the medium-temperature heater is approximately 245℃. Assuming a terminal temperature difference of 30℃ for the medium-temperature heater, the inlet temperature of the second-stage turbine is only 215℃. If a two-stage power cycle is used, the power generation efficiency is only about 20%, but the system complexity increases significantly. Therefore, it is not advisable to use the two-stage power cycle for power generation. In this case, it is preferable to directly utilize waste heat to generate high-temperature water or steam. The system structure in this case can be referenced... Figure 2 .

[0062] Heat pump system: Energy efficiency coefficient 4.3. Assuming the heat pump user-side outlet temperature is 50~110℃, it can directly supply domestic water and heat. It can also further utilize the low-temperature section of the high-temperature heat source (about 245℃) to further heat water or steam to above 120℃ in the low-temperature heater for industrial production.

[0063] In summary, the system described in this application achieves high waste heat power generation efficiency, while the transcritical CO2 heat pump recovers the latent heat of condensation from the power cycle. Theoretically, the power cycle system has no energy loss, significantly improving the system's efficiency. Furthermore, the heat pump's coefficient of performance (COP) can reach 4.3, making it suitable for both industrial and domestic heating. This application, through deep and gradient utilization of high-temperature heat sources, effectively improves power generation efficiency and system efficiency, contributing to the synergistic effect of pollution reduction and carbon reduction.

[0064] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A combined heat and power system for transcritical CO2 power cycle coupled with a transcritical CO2 heat pump, characterized in that, This includes primary power cycles, secondary power cycles, and heat pump systems that use CO2 as the working fluid and operate transcritically; The heat pump system includes a condenser-evaporator (11), a compressor (12), a gas cooler (13), and an expansion valve (14) connected in sequence. The first-stage power cycle includes a high-temperature heater (21) that recovers heat from the high-temperature section of the heat source, and a first-stage turbine (22), a first-stage high-temperature regenerator (23), a first-stage low-temperature regenerator (24), and a low-pressure mixer (40) that are sequentially connected to the cold-side outlet of the high-temperature heater (21). The secondary power cycle includes a medium-temperature heater (31) connected to the hot-side outlet of the high-temperature heater (21) to recover heat from the medium-temperature section of the heat source, and a secondary turbine (32), a secondary high-temperature regenerator (33), a secondary low-temperature regenerator (34), and a low-pressure mixer (40) sequentially connected to the cold-side outlet of the medium-temperature heater (31). The medium outlet of the low-pressure mixer (40) is connected to the condenser-evaporator (11) in the heat pump system. The hot side outlet of the condenser-evaporator (11) returns the hot side medium to the cold side inlet of the first-stage low-temperature regenerator (24) and the second-stage low-temperature regenerator (34) respectively through the booster pump (50).

2. The combined heat and power system of a transcritical CO2 dynamic cycle coupled with a transcritical CO2 heat pump as described in claim 1, characterized in that, The cold-side outlet of the first-stage low-temperature regenerator (24) is connected to the first-stage high-temperature regenerator (23) and the high-temperature heater (21) in sequence through the first-stage mixer (25) to form a cycle; the cold-side outlet of the second-stage low-temperature regenerator (34) is connected to the second-stage high-temperature regenerator (33) and the medium-temperature heater (31) in sequence through the second-stage mixer (35) to form a cycle.

3. A combined heat and power system for transcritical CO2 power cycle coupled with a transcritical CO2 heat pump as described in claim 2, characterized in that, A first distributor (26) is provided between the first-stage low-temperature regenerator (24) and the low-pressure mixer (40), and the first distributor (26) is also connected to the medium inlet of the first-stage mixer (25) through a first-stage recompressor (27); a second distributor (36) is provided between the second-stage low-temperature regenerator (34) and the low-pressure mixer (40), and the second distributor (36) is also connected to the medium inlet of the second-stage mixer (35) through a second-stage recompressor (37).

4. A combined heat and power system for transcritical CO2 dynamic cycle coupled with a transcritical CO2 heat pump as described in claim 3, characterized in that, In the heat pump system, the cold side outlet of the gas cooler (13) is connected to the low-temperature heater (60), and the hot side outlet of the medium-temperature heater (31) is also connected to the hot side inlet of the low-temperature heater (60). The user-side working fluid to be heated absorbs heat in the gas cooler (13) and then enters the low-temperature heater (60) through the cold side outlet for further heating.

5. A combined heat and power system for transcritical CO2 power cycle coupled with a transcritical CO2 heat pump as described in claim 1, characterized in that, The first-stage turbine (22) is connected to the first-stage power generation device (221), and the second-stage turbine (32) is connected to the second-stage power generation device (321).

6. A combined heat and power system for transcritical CO2 dynamic cycle coupled with a transcritical CO2 heat pump as described in claim 1, characterized in that, A third distributor (70) is provided between the booster pump (50) and the primary low-temperature regenerator (24) and the secondary low-temperature regenerator (34).

7. A combined heat and power system for transcritical CO2 power cycle coupled with a transcritical CO2 heat pump as described in claim 4, characterized in that, When the heat source temperature is below 450℃ or the system power generation efficiency is below 20%, only the first-stage power cycle is activated, and the second-stage power cycle is not activated.

Images