An S-CO 2 and water vapor binary working fluid power generation system and working method

Abstract

The present invention discloses an S-CO2 and water vapor dual working fluid power generation system and a working method. The present invention is based on the transformation of the current steam turbine Rankine cycle power generation system. The high-temperature and high-pressure S-CO2 and water vapor mixed steam generated by the boiler is sent into the power generation turbine, and the S-CO2 and water vapor mixed working fluid is used for power generation, which improves the cycle power generation efficiency. At the same time, a waste heat turbine is introduced to utilize the S-CO2 waste heat after being cooled by the steam-water heat exchanger for power generation, greatly improving the energy utilization efficiency. The present invention uses a mixed dual working fluid, and the system volume is larger than that using a single S-CO2 working fluid, and it will not cause excessive vibration due to too small system volume and too compact structure, improving the safety and stability of the power generation system. In this way, both the power generation cycle efficiency can be improved, and the safe and stable operation of the unit can be achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of power generation, and particularly relates to an S-CO 2 and water vapor dual working fluid power generation system and working method. Background Technique

[0002] With the rapid development of power generation technology, in order to further improve energy utilization efficiency and reduce environmental pollutant emissions at the same time, some new circulating working fluid power generation technologies have gradually become research hotspots. At the same time, aiming at the national goal of achieving carbon peak and carbon neutrality, it is crucial to build a new power system with new energy as the main body, and the new power generation system should have the characteristics of high efficiency, flexibility, low carbon, etc. In recent years, the power generation technology using supercritical carbon dioxide (S-CO 2 ) as the circulating working fluid has received extensive attention at home and abroad. This power generation technology has the advantages of high efficiency, cleanliness, and compact structure, and can be coupled with various forms of heat sources such as fossil energy, nuclear energy, and solar energy, and has broad application prospects.

[0003] At present, the power generation power cycle of coal-fired units is mostly the steam Rankine cycle, which consists of four key devices: a boiler, a steam turbine, a feed water pump, and a condenser. The circulating working fluid water absorbs heat at a constant pressure in the boiler and becomes superheated steam. The superheated steam enters the steam turbine for adiabatic expansion to do work. The exhaust steam of the steam turbine releases heat at a constant pressure in the condenser and changes from wet steam to saturated water. The water is adiabatically compressed in the feed water pump to become unsaturated water, and finally enters the boiler to complete the cycle.

[0004] CO 2 has stable chemical properties, is non-toxic, is not flammable or explosive, has low viscosity, its compressibility is close to that of an incompressible fluid, and its critical parameters are low (7.38 MPa, 31 °C). As an energy transmission and power conversion working fluid, it has significant advantages such as large power density, good heat transfer performance, and being cheap and easy to obtain. Compared with the existing steam Rankine cycle power generation technology, the supercritical carbon dioxide (S-CO 2 ) power generation technology has the following advantages: (1) relatively high cycle efficiency; (2) small system volume and compact structure; (3) wide range of applicable heat sources; (4) environmentally friendly, etc.

[0005] In the 1950s, some research scholars had already proposed the S-CO 2 cycle system. Subsequently, a large number of scholars began to conduct theoretical and experimental research on the S-CO 2 cycle. However, up to now, the S-CO 2 cycle power generation technology is still immature, and there are some design difficulties in its system construction. The volume of the S-CO 2 turbine is greatly reduced compared with the traditional steam turbine, which has the advantages of compact equipment and fast response, but at the same time poses huge challenges to the structural stress and the seal cooling system. In addition, S-CO 2There are difficulties in manufacturing the main equipment components of the circulation system, and there is a lack of experience in the operation of the circulating power generation system.

[0006] In view of the current situation that the S-CO 2 circulating power generation technology is not yet mature, and by using S-CO 2 When using a single working fluid for circulating power generation, the system volume is too small and the structure is too compact, resulting in large structural stress, which in turn leads to relatively large vibration, affecting the safe and stable operation of the unit. Combining with the traditional steam turbine Rankine cycle power generation technology, the present invention proposes an S-CO 2 and water vapor dual working fluid power generation system. Summary of the Invention

[0007] The purpose of the present invention is to overcome the above deficiencies and provide an S-CO 2 and water vapor dual working fluid power generation system and working method. On the one hand, it improves the circulating power generation efficiency and breaks through the bottleneck of the energy utilization efficiency of the existing single working fluid power generation using water vapor; on the other hand, by using a mixed dual working fluid, the system volume is larger than that of using S-CO 2 single working fluid, and it will not cause relatively large vibration due to the too small system volume and too compact structure, improving the safety and stability of the power generation system. In this way, it can not only improve the power generation cycle efficiency but also achieve the safe and stable operation of the unit.

[0008] To achieve the above purpose, an S-CO 2 and water vapor dual working fluid power generation system includes a boiler. The S-CO 2 and water vapor mixed steam outlet of the boiler is connected to a power generation turbine, the power generation turbine is connected to a generator, the mixed steam extraction port of the power generation turbine is connected to a steam-water heat exchanger, the steam-water heat exchanger is connected to a waste heat generating turbine, the waste heat generating turbine is connected to a waste heat generator, the exhaust outlets of the waste heat generating turbine and the power generation turbine are both connected to a cooler, the liquid outlet of the cooler is connected to the steam-water heat exchanger, the gas outlet of the cooler is connected to a multi-stage compression and cooling device, the outlet of the steam-water heat exchanger is connected to the boiler, and the outlet of the multi-stage compression and cooling device is connected to the boiler.

[0009] The multi-stage compression and cooling device includes a number of compression and cooling devices connected in series. The compression and cooling device includes a compressor and a heat exchanger. The compressor is arranged upstream of the heat exchanger, and the cold source side of the heat exchanger is connected to the pipeline between the cooler and the steam-water heat exchanger.

[0010] The cooler is connected to a condensate pump, and the condensate pump and the steam-water heat exchanger are connected through a condensate pipeline.

[0011] The steam-water heat exchanger is connected to a feed water pump, and the feed water pump and the boiler are connected through a feed water pipeline.

[0012] The power generation turbine and the steam-water heat exchanger are connected through an extraction pipeline.

[0013] The power generation turbine is connected to the cooler through the exhaust steam pipeline of the power generation turbine.

[0014] A method for operating an S-CO 2 and water vapor binary working fluid power generation system, comprising the following steps:

[0015] The boiler generates a mixed steam of S-CO 2 and water vapor and feeds it into the power generation turbine;

[0016] The power generation turbine converts thermal energy into mechanical energy to drive the generator, and the power generation turbine feeds the mixed steam into the steam-water heat exchanger and discharges the mixed steam into the cooler;

[0017] The steam-water heat exchanger feeds the cooled S-CO 2 into the waste heat turbine;

[0018] The waste heat turbine converts thermal energy into mechanical energy to drive the waste heat generator, and the waste heat turbine discharges the exhaust steam into the cooler;

[0019] The cooler separates the S-CO 2 and water vapor after constant pressure heat release, feeds the condensed water into the steam-water heat exchanger, and feeds the S-CO 2 into the multi-stage compression and cooling device;

[0020] The multi-stage compression and cooling device boosts the pressure and raises the temperature of the S-CO 2 and then feeds it into the boiler;

[0021] The outlet water of the steam-water heat exchanger enters the boiler.

[0022] The compressor in the multi-stage compression and cooling device boosts the pressure of the S-CO 2 and then feeds it into the heat source side of the heat exchanger. The cold source side of the heat exchanger is the condensed water sent out by the cooler through the condensate pump.

[0023] Compared with the prior art, the present invention is modified on the basis of the existing steam turbine Rankine cycle power generation system. The high-temperature and high-pressure mixed steam of S-CO 2 and water vapor generated by the boiler is fed into the power generation turbine, and the S-CO 2 and water vapor mixed working fluid is used for power generation, which improves the cycle power generation efficiency. At the same time, a waste heat turbine is introduced to utilize the waste heat of the S-CO 2 cooled by the steam-water heat exchanger for power generation, greatly improving the energy utilization efficiency; the present invention uses a mixed binary working fluid, and the system volume is larger than that using a single S-CO 2 working fluid, and will not cause excessive vibration due to too small system volume and too compact structure, improving the safety and stability of the power generation system. In this way, both the power generation cycle efficiency can be improved and the unit can operate safely and stably. Description of the Drawings

[0024] Figure 1 System structure diagram of the present invention;

[0025] Among them, 1. Boiler, 2. Power generation turbine, 3. Generator, 4. Steam-water heat exchanger, 5. Waste heat power generation turbine, 6. Waste heat generator, 7. Cooler, 8. Condensate pump, 9. Feed water pump, 10. Compressor, 11. Heat exchanger, 12. Multi-stage compression and cooling device, 13. Extraction steam pipeline, 14. Condensate pipeline, 15. Feed water pipeline, 16. Exhaust steam pipeline of the power generation turbine. Specific implementation mode

[0026] The present invention will be further described below with reference to the accompanying drawings.

[0027] See Figure 1 , a dual working fluid power generation system of S-CO 2 and water steam, including a boiler 1. The mixed steam outlet of S-CO 2 and water steam of the boiler 1 is connected to a power generation turbine 2. The power generation turbine 2 and the generator 3 are connected to the same rotating shaft. The mixed steam outlet of the power generation turbine 2 is connected to a steam-water heat exchanger 4. The steam-water heat exchanger 4 is connected to a waste heat power generation turbine 5. The waste heat power generation turbine 5 and the waste heat generator 6 are connected to the same rotating shaft. The exhaust steam outlets of the waste heat power generation turbine 5 and the power generation turbine 2 are both connected to a cooler 7. The liquid outlet of the cooler 7 is connected to the steam-water heat exchanger 4. The gas outlet of the cooler 7 is connected to a multi-stage compression and cooling device 12. The outlet of the steam-water heat exchanger 4 is connected to the boiler 1 through a feed water pump 9. The outlet of the multi-stage compression and cooling device 12 is connected to the boiler 1.

[0028] The multi-stage compression and cooling device 12 includes a plurality of serially connected compression and cooling devices. The compression and cooling device includes a compressor 10 and a heat exchanger 11. The compressor 10 is arranged upstream of the heat exchanger 11. The cold source side of the heat exchanger 11 is connected to the condensate pipeline 14 between the cooler 7 and the steam-water heat exchanger 4 to achieve that the temperature does not exceed the limit during the S-CO 2 pressure boost, meeting the requirements of pipeline materials and operation.

[0029] The cooler 7 is connected to a condensate pump 8. The condensate pump 8 and the steam-water heat exchanger 4 are connected through the condensate pipeline 14. The steam-water heat exchanger 4 is connected to a feed water pump 9. The feed water pump 9 and the boiler 1 are connected through the feed water pipeline 15. The power generation turbine 2 and the steam-water heat exchanger 4 are connected through an extraction steam pipeline 13. The power generation turbine 2 and the cooler 7 are connected through an exhaust steam pipeline 16 of the power generation turbine.

[0030] A working method of a dual working fluid power generation system of S-CO 2 and water steam includes the following steps:

[0031] The boiler 1 generates high-temperature and high-pressure S-CO 2 and water steam mixed steam and sends it into the power generation turbine 2;

[0032] The mixed steam adiabatically expands in the power generation turbine 2, converting thermal energy into mechanical energy to drive the generator 3, achieving power generation by doing external work. Part of the mixed steam at the Nth stage of the power generation turbine 2 is sent into the steam-water heat exchanger 4 through the extraction steam pipeline 13, and the exhaust steam of the mixed steam is sent into the cooler 7 through the exhaust steam pipeline 16 of the power generation turbine;

[0033] The steam-water heat exchanger 4 sends the cooled S-CO 2 into the waste heat turbine 5 for adiabatic expansion, converting thermal energy into mechanical energy and transmitting it to the waste heat generator 6 through the rotating shaft;

[0034] The waste heat turbine 5 converts thermal energy into mechanical energy to drive the waste heat generator 6, and the waste heat turbine 5 sends the exhaust steam into the cooler 7;

[0035] The cooler 7 separates the S-CO 2 and water vapor after constant-pressure heat release, sends the condensed water into the steam-water heat exchanger 4 through the condensate pipeline 14, and the cooler 7 sends the S-CO 2 into the multi-stage compression and cooling device 12;

[0036] The compressor 10 in the multi-stage compression and cooling device 12 boosts the pressure of the S-CO 2 and sends it into the heat source side of the heat exchanger 11. The cold source side of the heat exchanger 11 is the condensed water in the condensate pipeline 14. After being compressed by the multi-stage compressor 10 and cooled by the heat exchanger 11, the S-CO2 is boosted in pressure and temperature and finally enters the boiler 1.

[0037] The water vapor from the extraction steam pipeline 13 and the water from the condensate pipeline 14 enter the steam-water heat exchanger 4 for heat exchange and then all become liquid water, which are together fed into the feed water pump 9 and enter the boiler 1 after adiabatic compression.

[0038] S-CO 2 and water respectively enter the boiler 1 for constant-pressure heat absorption, generating high-temperature and high-pressure S-CO 2 and steam mixed steam to complete the thermodynamic cycle;

[0039] The heat source side of the heat exchanger 11 in the multi-stage compression and cooling device 12 is S-CO 2 , and the cold source side is the condensed water, achieving the purpose of using the condensed water to cool the S-CO 2 .

[0040] S-CO 2 and the steam mixed working fluid cycle power generation system's main thermodynamic parameters are shown in Table 1.

[0041] Table 1 Main thermodynamic parameters of the S-CO 2 and steam mixed working fluid cycle power generation system

[0042]

[0043]

Claims

1. A working method of an S-CO 2 and water vapor binary working fluid power generation system It is characterized in that The power generation system includes a boiler (1), and the S-CO of the boiler (1) 2 and the mixed steam outlet of the steam are connected to a power generation turbine (2), the power generation turbine (2) is connected to a generator (3), the mixed steam extraction port of the power generation turbine (2) is connected to a steam-water heat exchanger (4), the steam-water heat exchanger (4) is connected to a waste heat power generation turbine (5), the waste heat power generation turbine (5) is connected to a waste heat generator (6), the exhaust steam outlets of the waste heat power generation turbine (5) and the power generation turbine (2) are both connected to a cooler (7), the liquid outlet of the cooler (7) is connected to the steam-water heat exchanger (4), the gas outlet of the cooler (7) is connected to a multi-stage compression and cooling device (12), the outlet of the steam-water heat exchanger (4) is connected to the boiler (1), and the outlet of the multi-stage compression and cooling device (12) is connected to the boiler (1); The multi-stage compression and cooling device (12) includes a plurality of serially connected compression and cooling devices. The compression and cooling device includes a compressor (10) and a heat exchanger (11). The compressor (10) is arranged upstream of the heat exchanger (11). The cold source side of the heat exchanger (11) is connected to the pipeline between the cooler (7) and the steam-water heat exchanger (4). The cooler (7) is connected to a condensate pump (8). The condensate pump (8) and the steam-water heat exchanger (4) are connected through a condensate pipeline (14). The working method includes the following steps: The boiler (1) generates S-CO 2 and the mixed steam of water vapor, and sends it into the power generation turbine (2); The power generation turbine (2) converts thermal energy into mechanical energy to drive the generator (3). The power generation turbine (2) sends the extracted steam of the mixed steam into the steam-water heat exchanger (4) and sends the exhaust steam of the mixed steam into the cooler (7). The steam-water heat exchanger (4) sends the cooled S-CO 2 to the waste heat power generation turbine (5); The waste heat power generation turbine (5) converts thermal energy into mechanical energy to drive the waste heat generator (6). The waste heat power generation turbine (5) sends the exhaust steam into the cooler (7). The cooler (7) separates S-CO 2 and water vapor after releasing heat at constant pressure, sends the condensed water into the steam-water heat exchanger (4), and sends S-CO 2 into the multi-stage compression and cooling device (12); The multi-stage compression and cooling device (12) sends S-CO 2 after boosting the pressure and raising the temperature into the boiler (1); the compressor (10) in the multi-stage compression and cooling device (12) boosts the pressure of S-CO 2 and then sends it to the heat source side of the heat exchanger (11), and the cold source side of the heat exchanger (11) is the condensed water sent out by the cooler (7) through the condensate pump (8). The outlet water of the steam-water heat exchanger (4) enters the boiler (1).

2. The working method of a S-CO 2 and water vapor binary working fluid power generation system according to claim 1, It is characterized in that The steam-water heat exchanger (4) is connected to a feed water pump (9). The feed water pump (9) and the boiler (1) are connected through a feed water pipeline (15).

3. The working method of a binary working fluid power generation system using S-CO 2 and water vapor, It is characterized in that The power generation turbine (2) and the steam-water heat exchanger (4) are connected through an extraction steam pipeline (13).

4. The working method of a S-CO 2 and water vapor dual working fluid power generation system according to claim 1, It is characterized in that The power generation turbine (2) and the cooler (7) are connected through a power generation turbine exhaust steam pipeline (16).

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