A CO2 transcritical coupling circulation system and its working method

Abstract

The present invention discloses a CO2 transcritical coupling cycle system and a working method thereof, belonging to the field of power generation and power technology devices; the system comprises a CO2 system and a waste heat utilization system matched and coupled with the CO2 system, the CO2 system comprises a recompression cycle system, a low-pressure turbine is arranged at the rear end of the high-pressure turbine of the recompression cycle system, a pre-compressor is arranged at the air inlet end of the recompression cycle system, and a waste heat utilization system is arranged at the air outlet of the pre-compressor; the present invention can effectively improve the system cycle efficiency by further optimizing the design on the basis of the traditional recompression cycle system, and based on the improvement of the structure, the waste heat utilization system can be further coupled in the structural design, and even the waste heat utilization system can be a heat user, which can fully utilize the waste heat, realize the utilization rate of energy consumption, and reduce the loss, thereby further improving the utilization of resources.

Description

Technical Field

[0001] The invention relates to a CO2 transcritical coupling circulation system and a working method thereof, belonging to the field of power generation and power technology devices. Background Art

[0002] The transcritical CO2 closed cycle refers to CO2 as the circulating working fluid. The highest parameter of the cycle is above the critical point of CO2, which is a supercritical state; the lowest parameter of the cycle is below the critical point of CO2, which is a gaseous state. Since CO2 is easily compressed near the critical point, the CO2 temperature is generally lowered by a cooler and then pressurized to near the critical point by a pre-compressor; the CO2 temperature is lowered to the critical point by a pre-cooler; the CO2 temperature is compressed by the main compressor to reach the design parameters; the design temperature is reached after passing through a regenerator, a heater, etc.; the working fluid drives the turbine to do work and realizes external output. Since the outlet temperature of the pre-compressor is relatively high, the heat at the outlet of the pre-compressor can be recovered by coupling with the organic Rankine cycle and the Stirling cycle, thereby improving the power generation efficiency of the system. If heating is required, the system can be heated to the outside by recovering waste heat. Summary of the invention

[0003] The object of the present invention is to provide a CO2 transcritical coupled circulation system to address the above-mentioned problems, thereby achieving high efficiency of the circulation system by recovering the waste heat of the pre-compressor.

[0004] The technical solution adopted by the present invention is as follows:

[0005] A CO2 transcritical coupled cycle system, comprising a CO2 system and a waste heat utilization system coupled with the CO2 system;

[0006] The CO2 system includes a recompression cycle system, a low-pressure turbine is arranged at the rear end of the high-pressure turbine of the recompression cycle system, a pre-compressor is also arranged at the air inlet end of the recompression cycle system, and a waste heat utilization system is also arranged at the outlet of the pre-compressor, and the air passes through the waste heat utilization system and serves as the air inlet of the recompression cycle system.

[0007] Furthermore, the recompression cycle system includes a main compressor, a recompressor, a high-pressure turbine, a precooler, a low-temperature regenerator, a high-temperature regenerator, and a heat source.

[0008] Furthermore, the air inlet of the precooler is connected to the air outlet of the precompressor through the waste heat utilization system, and the precooler, main compressor, low-temperature regenerator, high-temperature regenerator, heat source, high-pressure turbine, and low-pressure turbine are connected in series in sequence;

[0009] The air inlet of the recompressor is connected to the air outlet of the precompressor through the waste heat utilization system, and the air outlet of the recompressor is connected to the air inlet of the high-temperature regenerator;

[0010] The low-pressure turbine is connected in series with a high-temperature regenerator, a low-temperature regenerator and a pre-compressor in sequence.

[0011] Furthermore, the waste heat utilization system is an organic Rankine cycle system or a Stirling cycle system.

[0012] Furthermore, the waste heat utilization system is an organic Rankine cycle system;

[0013] The organic Rankine cycle system includes a circulating expander, an evaporator, a working fluid pump, and a condenser connected in sequence. The air inlet of the condenser is connected to the air outlet of the circulating expander, the air outlet of the pre-compressor is connected to the air inlet of the evaporator, and the working fluid is delivered through the air outlet of the evaporator.

[0014] Furthermore, a reheater is provided between the high-pressure turbine and the low-pressure turbine.

[0015] Furthermore, the waste heat utilization system is a Stirling cycle system;

[0016] The Stirling cycle system includes a hot cylinder, a cold cylinder, a regenerator, a heat exchanger, and a cooler. The heat source of the heat exchanger comes from the outlet gas of the pre-compressor. The heated medium outflow end of the heat exchanger is connected to the hot cylinder, and the medium inflow end of the heat exchanger is connected in series with the regenerator, the cooler, and the cold cylinder.

[0017] A CO2 transcritical coupled circulation system working method, using the above-mentioned CO2 transcritical coupled circulation system, comprises the following steps:

[0018] The pre-compressor uses the waste heat of the compressed working fluid in the waste heat utilization system and then enters the recompression cycle system in two ways. One way is cooled to near the critical point by the pre-cooler and then enters the main compressor, and then passes through the low-temperature regenerator after being pressurized to the design pressure; the other way directly enters the re-compressor, and then is pressurized to the design pressure and mixed with the working fluid at the outlet of the low-temperature regenerator; the mixed working fluid enters the high-temperature regenerator and the heat source in turn, and then enters the high-pressure turbine to perform work; and then the working fluid at the outlet of the high-pressure turbine is further expanded and performed work by the low-pressure turbine;

[0019] After the working fluid expands through the low-pressure turbine, its pressure after passing through the high-temperature regenerator and the low-temperature regenerator is far lower than the critical point pressure of CO2. The working fluid is pressurized by the pre-compressor to reach near the critical point.

[0020] Furthermore, when the waste heat utilization system is an organic Rankine cycle system, the heat at the outlet of the pre-compressor is transferred to the organic working fluid through the evaporator, the working fluid outputs shaft work to the outside through the expander, the expanded working fluid enters the condenser and condenses into liquid, enters the working fluid pump to increase the pressure to the target pressure, and then enters the evaporator to be absorbed and evaporated into gas, and the next cycle begins.

[0021] Furthermore, when the waste heat utilization system is a Stirling cycle system, the heat exchanger absorbs heat from the outlet of the pre-compressor to raise the temperature of the working fluid, and the working fluid enters the hot cylinder to push the piston to do work externally. The expanded working fluid passes through the regenerator again to store the heat in the regenerator, and then enters the cold cylinder after reaching a predetermined temperature through the cooler. The working fluid is compressed by the piston, and the compressed working fluid passes through the regenerator again to raise the temperature of the working fluid through the stored heat. It continues to pass through the heater to heat up and starts the next cycle.

[0022] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0023] 1. A CO2 transcritical coupled cycle system and a working method thereof of the present invention can effectively improve the system cycle efficiency by further optimizing the design based on the traditional recompression cycle system. Based on the improvement of the structure, the structure design can further couple the waste heat utilization system, and even the waste heat utilization system can be a heat user, which can fully utilize the waste heat, realize the utilization rate of energy consumption, and reduce the loss, thereby further improving the utilization of resources;

[0024] 2. A CO2 transcritical coupled circulation system and a working method thereof of the present invention adopt a modular design for the entire system in terms of the structural design of the entire system. On the one hand, the structure of the entire system is clearer and simpler. On the other hand, when optimizing or changing some modules of the system, the switching of modules can be realized quickly and effectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0026] Figure 1 This is a simplified diagram of the CO2 transcritical cycle system coupled with the organic Rankine cycle system;

[0027] Figure 2 It is a simplified diagram of the CO2 transcritical cycle system coupled with the Stirling cycle system;

[0028] Figure 3 It is a schematic diagram of the structure of the recompression cycle;

[0029] Figure 4 This is a simplified diagram of a CO2 transcritical cycle system coupled with an organic Rankine cycle system (without reheating).

[0030] Markings in the figure: A - CO2 system, B - organic Rankine cycle system, C - Stirling cycle system, D - recompression cycle system, 1 - pre-compressor, 2 - main compressor, 3 - re-compressor, 4 - high-pressure turbine, 4' - low-pressure turbine, 5 - pre-cooler, 6 - low-temperature regenerator, 7 - high-temperature regenerator, 8 - heat source, 9 - reheater, I - circulation expander, II - working fluid pump, III - condenser, IV - evaporator, a - hot cylinder, b - cold cylinder, c - regenerator, d - heat exchanger, e - cooler. DETAILED DESCRIPTION

[0031] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0032] Any feature disclosed in this specification, unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0033] Example 1

[0034] A CO2 transcritical coupled cycle system, such as Figures 1 to 4 As shown, it includes a CO2 system A and a waste heat utilization system matched and coupled with the CO2 system A (CO2 transcritical cycle system);

[0035] The CO2 system A includes a recompression cycle system D, a low-pressure turbine 4' is arranged at the rear end of the high-pressure turbine 4 of the recompression cycle system D, a pre-compressor 1 is also arranged at the air inlet end of the recompression cycle system, and a waste heat utilization system is also provided at the outlet of the pre-compressor 1, and the air passes through the waste heat utilization system and serves as the air inlet of the recompression cycle system D.

[0036] In this embodiment, as a specific design, on the basis of the recompression cycle system, a pre-compressor 1 and a low-pressure turbine 4' are further added to the rear end, which is mainly to realize the coupling of the waste heat utilization system, and at the same time, further improve the efficiency of work and the efficiency of the cycle, thereby effectively realizing the waste heat reuse and circulation effect of the entire system. In addition, in the design of the waste heat utilization system, it is not only used for other systems that consume heat energy, but also can be used to supply heat to heat users, so as to make better use of the waste heat.

[0037] Based on the above specific design, more specific designs, such as Figure 3 As shown, the recompression cycle system includes a main compressor 2, a recompressor 3, a high-pressure turbine 4, a precooler 5, a low-temperature regenerator 6, a high-temperature regenerator 7, and a heat source 8.

[0038] On the basis of the above-mentioned specific structural design, the connection relationship of specific components is further designed. The air inlet of the precooler 5 is connected to the air outlet of the precompressor 1 through the waste heat utilization system. The precooler 5, the main compressor 2, the low-temperature regenerator 6, the high-temperature regenerator 7, the heat source 8, the high-pressure turbine 4, and the low-pressure turbine 4' are connected in series in sequence;

[0039] The air inlet of the recompressor 3 is connected to the air outlet of the precompressor 1 through the waste heat utilization system, and the air outlet of the recompressor 3 is connected to the air inlet of the high-temperature regenerator 7;

[0040] The low-pressure turbine 4 ′ is connected in series with the high-temperature regenerator 7 , the low-temperature regenerator 6 and the pre-compressor 1 in sequence.

[0041] On the basis of the design of the above specific structure, the flow direction and circulation path of the gas are further designed in terms of the connection relationship.

[0042] Based on the design of the above specific structure, the waste heat utilization system is an organic Rankine cycle system B or a Stirling cycle system C.

[0043] In this embodiment, as a specific description, Figure 4 As shown, the waste heat utilization system is an organic Rankine cycle system B; the organic Rankine cycle system B includes a circulating expander I, an evaporator IV, a working fluid pump II, and a condenser III which are connected in sequence, the air inlet of the condenser III is connected to the air outlet of the circulating expander I, the air outlet of the pre-compressor 1 is connected to the air inlet of the evaporator IV, and the working fluid is delivered through the air outlet of the evaporator IV.

[0044] Furthermore, if Figure 1 As shown, a reheater 9 is further provided between the high-pressure turbine 4 and the low-pressure turbine 4'.

[0045] Example 2

[0046] Based on the design of Example 1, the difference from Example 1 is that Figure 2 As shown, the waste heat utilization system is a Stirling cycle system C;

[0047] The Stirling cycle system C includes a hot cylinder a, a cold cylinder b, a regenerator c, a heat exchanger d, and a cooler e. The heat source 8 of the heat exchanger d is derived from the outlet gas of the pre-compressor 1. The heated medium outflow end of the heat exchanger d is connected to the hot cylinder a, and the medium inflow end of the heat exchanger d is connected in series with the regenerator, the cooler e, and the cold cylinder b.

[0048] Example 3

[0049] Based on the structural design of Example 1 and Example 2, the working principle thereof is further described. A CO2 transcritical coupled circulation system working method comprises the following steps:

[0050] The pre-compressor 1 uses the waste heat of the compressed working fluid in the waste heat utilization system and then enters the recompression cycle system D in two ways. One way is cooled to near the critical point by the pre-cooler 5 and then enters the main compressor 2. After being pressurized to the design pressure, it passes through the low-temperature regenerator 6; the other way directly enters the re-compressor 3, and after being pressurized to the design pressure, it is mixed with the working fluid at the outlet of the low-temperature regenerator 6; the mixed working fluid enters the high-temperature regenerator 7 and the heat source 8 in turn, and then enters the high-pressure turbine 4 to perform work; and then the working fluid at the outlet of the high-pressure turbine 4 is further expanded and performed work by the low-pressure turbine 4';

[0051] The pressure of the working medium expanded by the low-pressure turbine 4' is much lower than the critical pressure of CO2 after passing through the high-temperature regenerator 7 and the low-temperature regenerator 6. The working medium is pressurized by the pre-compressor 1 to reach a pressure close to the critical point.

[0052] On the basis of the above specific design, more specifically: when the waste heat utilization system is an organic Rankine cycle system B, the heat at the outlet of the pre-compressor 1 is transferred to the organic working fluid through the evaporator IV, the working fluid outputs shaft work to the outside through the expander, and the expanded working fluid enters the condenser III to condense into liquid, enters the working fluid pump II to increase the pressure to the target pressure, and then enters the evaporator IV to be absorbed and evaporated into gas, and the next cycle begins.

[0053] When the waste heat utilization system is the Stirling cycle system C, the heat exchanger d absorbs heat from the outlet of the pre-compressor 1 to raise the temperature of the working fluid, and the working fluid enters the hot cylinder a, pushing the piston to do work externally. The expanded working fluid passes through the regenerator again and stores the heat in the regenerator c. Then, it passes through the cooler e to reach a predetermined temperature and enters the cold cylinder b. The working fluid is compressed by the piston. The compressed working fluid passes through the regenerator again, and the temperature of the working fluid is raised by the stored heat. After continuing to pass through the heater to heat up, the next cycle begins.

[0054] In summary:

[0055] 1. A CO2 transcritical coupled cycle system and a working method thereof of the present invention can effectively improve the system cycle efficiency by further optimizing the design based on the traditional recompression cycle system. Based on the improvement of the structure, the structure design can further couple the waste heat utilization system, and even the waste heat utilization system can be a heat user, which can fully utilize the waste heat, realize the utilization rate of energy consumption, and reduce the loss, thereby further improving the utilization of resources;

[0056] 2. A CO2 transcritical coupled circulation system and a working method thereof of the present invention adopt a modular design for the entire system in terms of the structural design of the entire system. On the one hand, the structure of the entire system is clearer and simpler. On the other hand, when optimizing or changing some modules of the system, the switching of modules can be realized quickly and effectively.

[0057] The present invention is not limited to the above-mentioned specific embodiments, but extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims

1. A CO2 transcritical coupled circulation system, characterized in that: Including a CO2 system and a waste heat utilization system coupled with the CO2 system; The CO2 system includes a recompression cycle system, a low-pressure turbine is arranged at the rear end of the high-pressure turbine of the recompression cycle system, a pre-compressor is arranged at the air inlet end of the recompression cycle system, and a waste heat utilization system is arranged at the outlet of the pre-compressor, and the air passes through the waste heat utilization system and serves as the air inlet of the recompression cycle system; The recompression cycle system includes a main compressor, a recompressor, a high-pressure turbine, a precooler, a low-temperature regenerator, a high-temperature regenerator, and a heat source; The air inlet of the precooler is connected to the air outlet of the precompressor through the waste heat utilization system, and the precooler, main compressor, low-temperature regenerator, high-temperature regenerator, heat source, high-pressure turbine, and low-pressure turbine are connected in series in sequence; The air inlet of the recompressor is connected to the air outlet of the precompressor through the waste heat utilization system, and the air outlet of the recompressor is connected to the air inlet of the high-temperature regenerator; The low-pressure turbine is connected in series with a high-temperature regenerator, a low-temperature regenerator and a pre-compressor in sequence.

2. A CO2 transcritical coupled circulation system as claimed in claim 1, characterized in that: The waste heat utilization system is an organic Rankine cycle system or a Stirling cycle system.

3. A CO2 transcritical coupled circulation system as claimed in claim 2, characterized in that: The waste heat utilization system is an organic Rankine cycle system; The organic Rankine cycle system includes a circulating expander, an evaporator, a working fluid pump, and a condenser connected in sequence. The air inlet of the condenser is connected to the air outlet of the circulating expander, the air outlet of the pre-compressor is connected to the air inlet of the evaporator, and the working fluid is delivered through the air outlet of the evaporator.

4. A CO2 transcritical coupled circulation system as claimed in claim 3, characterized in that: A reheater is also provided between the high-pressure turbine and the low-pressure turbine.

5. A CO2 transcritical coupled circulation system as claimed in claim 2, characterized in that: The waste heat utilization system is a Stirling cycle system; The Stirling cycle system includes a hot cylinder, a cold cylinder, a regenerator, a heat exchanger, and a cooler. The heat source of the heat exchanger comes from the outlet gas of the pre-compressor. The heated medium outflow end of the heat exchanger is connected to the hot cylinder, and the medium inflow end of the heat exchanger is connected in series with the regenerator, the cooler, and the cold cylinder.

6. A CO2 transcritical coupled circulation system working method, using a CO2 transcritical coupled circulation system according to any one of claims 1 to 5, characterized in that: The following steps are involved: The pre-compressor uses the waste heat of the compressed working fluid in the waste heat utilization system and then enters the recompression cycle system in two ways. One way is cooled to near the critical point by the pre-cooler and then enters the main compressor. After being pressurized to the design pressure, it passes through the low-temperature regenerator; the other way directly enters the re-compressor, is pressurized to the design pressure, and then mixed with the working fluid at the outlet of the low-temperature regenerator; the mixed working fluid enters the high-temperature regenerator, the heat source in turn, and then enters the high-pressure turbine to perform work; The working fluid at the outlet of the high-pressure turbine is further expanded and works by the low-pressure turbine; After the working fluid expands through the low-pressure turbine, its pressure after passing through the high-temperature regenerator and the low-temperature regenerator is far lower than the critical point pressure of CO2. The working fluid is pressurized by the pre-compressor to reach near the critical point.

7. A CO2 transcritical coupled cycle system operating method as claimed in claim 6, characterized in that: When the waste heat utilization system is an organic Rankine cycle system, the heat at the outlet of the pre-compressor is transferred to the organic working fluid through the evaporator. The working fluid outputs shaft work to the outside through the expander. The expanded working fluid enters the condenser and condenses into liquid. It enters the working fluid pump to increase the pressure to the target pressure, and then enters the evaporator to be absorbed and evaporated into gas, and the next cycle begins.

8. A CO2 transcritical coupled cycle system operating method as claimed in claim 6, characterized in that: When the waste heat utilization system is a Stirling cycle system, the heat exchanger absorbs heat from the outlet of the pre-compressor to raise the temperature of the working fluid, and the working fluid enters the hot cylinder to push the piston to do work externally. The expanded working fluid passes through the regenerator again to store the heat in the regenerator, and then enters the cold cylinder after reaching a predetermined temperature through the cooler. The working fluid is compressed by the piston, and the compressed working fluid passes through the regenerator again to raise the temperature of the working fluid through the stored heat. It continues to pass through the heater to heat up and starts the next cycle.

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