A supercritical carbon dioxide cycle power generation peak-shaving system and peak-shaving method

Abstract

This invention belongs to the field of advanced power cycle power generation technology, and discloses a supercritical carbon dioxide cycle power generation peak-shaving system and method. The turbine mechanical equipment of the supercritical carbon dioxide cycle power generation peak-shaving system mainly includes a turbine, a compressor, and a heat exchanger. The main compressor or re-compressor is shaft-connected to and driven by the turbine, while the other compressors are connected to independent drive structures. This invention arranges the main compressor or re-compressor shaft-connected to the turbine, enabling the turbine to directly drive the compressor, thereby reducing the additional energy loss caused by the electric motor driving the compressor and improving efficiency. The independent shaft arrangement of the other compressors allows for flexible adjustment of their shaft speeds under peak-shaving loads, adapting flexibly to changes in peak-shaving loads. This facilitates optimizing operating parameters under peak-shaving loads, ensuring that the system's power generation efficiency does not decrease significantly during peak-shaving scenarios.

Description

Technical Field

[0001] This invention belongs to the field of advanced power cycle power generation technology, and more specifically, relates to a supercritical carbon dioxide cycle power generation peak shaving system and peak shaving method. Background Technology

[0002] Concentrated solar power (CSP) systems equipped with thermal storage devices can flexibly regulate the output power. They can not only provide stable power as baseload power plants, but also have the potential to become clean and reliable peak-shaving power plants. They can be used to absorb excess photovoltaic and wind power in future high-proportion renewable energy systems, thereby promoting the large-scale grid connection of renewable energy power.

[0003] Among the many CSP technologies, tower solar thermal power generation technology, which combines high-temperature heat absorption, heat storage devices, and a supercritical CO2 (S-CO2) Brayton cycle, has great potential to further improve power generation efficiency and reduce power generation costs, and therefore has received widespread attention in recent years. As an important heat-work conversion device in CSP systems, the operating characteristics of the S-CO2 cycle have a significant impact on the operating performance of CSP systems, making research on S-CO2 cycle design optimization and operating parameter control very important.

[0004] While existing supercritical CO2 cycle systems have great potential for improving power generation efficiency and reducing costs when used for power generation, they can only guarantee high efficiency under rated load. When used for peak shaving, their efficiency drops significantly with changes in peak load. Therefore, given the urgent peak shaving needs of future high-proportion renewable energy systems, determining the optimal design scheme for cycle equipment to ensure flexible, efficient, and safe operation under complex changing load conditions requires in-depth exploration. Summary of the Invention

[0005] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a supercritical carbon dioxide cycle power generation peak shaving system and peak shaving method, which solves the problem that the power generation efficiency of the existing supercritical CO2 cycle system will be greatly reduced with the change of peak shaving load when used in peak shaving scenarios. It can meet the requirements of flexible operation of the cycle under partial load, and also takes into account the high efficiency performance of the cycle, making it suitable for peak shaving scenarios.

[0006] To achieve the above objectives, according to one aspect of the present invention, a supercritical carbon dioxide cycle power generation and peak shaving system is provided. The turbine mechanical equipment of the supercritical carbon dioxide cycle power generation and peak shaving system includes a turbine, a pre-compressor, a main compressor, and a re-compressor, wherein the main compressor or the re-compressor is arranged with the turbine on a shaft and driven by the turbine, and the other compressors are connected to independent drive structures.

[0007] According to the supercritical carbon dioxide cycle power generation peak-shaving system provided by the present invention, when the required peak-shaving load is 30%-55% of the rated load, the main compressor is arranged with the turbine in a shaft connection, and the pre-compressor and the re-compressor are respectively connected to independent drive structures;

[0008] When the required peak load is 55%-100% of the rated load, the recompressor is arranged with the turbine on a shaft, and the precompressor and the main compressor are respectively connected to independent drive structures.

[0009] According to the supercritical carbon dioxide cycle power generation and peak shaving system provided by the present invention, the supercritical carbon dioxide cycle power generation and peak shaving system further includes: a high-temperature regenerator, a low-temperature regenerator, a precooler, a diversion valve, an intercooler, and a heater;

[0010] The turbine outlet is connected to the first inlet of the high-temperature regenerator, the first outlet of the high-temperature regenerator is connected to the first inlet of the low-temperature regenerator, the second outlet of the high-temperature regenerator is connected to the inlet of the heater, the outlet of the heater is connected to the inlet of the turbine, the first outlet of the low-temperature regenerator is connected to the inlet of the precooler, the outlet of the precooler is connected to the inlet of the precompressor, the outlet of the precompressor is connected to the inlet of the intercooler and the inlet of the recompressor respectively through the diversion valve, the outlet of the intercooler is connected to the inlet of the main compressor, the outlet of the main compressor is connected to the second inlet of the low-temperature regenerator, the second outlet of the low-temperature regenerator is connected to the second inlet of the high-temperature regenerator, and the outlet of the recompressor is connected to the second inlet of the high-temperature regenerator.

[0011] According to the supercritical carbon dioxide cycle power generation peak shaving system provided by the present invention, the heating medium in the heater is molten salt; the flow ratio of the flow divider valve is 0.5-0.6.

[0012] According to the supercritical carbon dioxide cycle power generation peak shaving system provided by the present invention, the inlet medium temperature of the turbine is greater than or equal to 600°C; the inlet medium temperatures of the pre-compressor, the main compressor and the re-compressor are each greater than 30.98°C.

[0013] According to another aspect of the present invention, a method for supercritical carbon dioxide cycle power generation and peak shaving is provided, based on the supercritical carbon dioxide cycle power generation and peak shaving system described in any one of the preceding claims, the method comprising:

[0014] The main compressor or the re-compressor is connected to the turbine and driven by the turbine, while the other compressors are connected to independent drive structures. This is used for peak shaving within the range of 30%-100% of the rated load.

[0015] According to the supercritical carbon dioxide cycle power generation peak shaving method provided by the present invention, when the required peak shaving load is 30%-55% of the rated load, the main compressor and the turbine are arranged in a shaft-connected manner, and the pre-compressor and the re-compressor are respectively connected to independent drive structures;

[0016] When the required peak load is 55%-100% of the rated load, the recompressor is arranged with the turbine on a shaft, and the precompressor and the main compressor are respectively connected to independent drive structures.

[0017] According to the supercritical carbon dioxide cycle power generation peak shaving method provided by the present invention, when the main compressor and the turbine are arranged in a shaft connection scheme, as the required peak shaving load decreases, the shaft speed of the main compressor and the re-compressor gradually decreases, and the shaft speed of the pre-compressor gradually increases.

[0018] According to the supercritical carbon dioxide cycle power generation peak shaving method provided by the present invention, when the recompressor and the turbine are arranged in a shaft connection scheme, as the required peak shaving load decreases, the shaft speed of the recompressor gradually decreases, the shaft speed of the main compressor first decreases and then increases, and the shaft speed of the precompressor gradually increases.

[0019] According to the supercritical carbon dioxide cycle power generation peak shaving method provided by the present invention, the system split ratio remains constant during the change of the required peak shaving load; wherein the split ratio is the ratio of the working fluid flow rate of the main compressor to the total working fluid flow rate of the main compressor and the re-compressor.

[0020] In summary, compared with the prior art, the supercritical carbon dioxide cycle power generation peak-shaving system and peak-shaving method provided by this invention offer the following advantages:

[0021] 1. By arranging the main compressor or recompressor on a shaft connected to the turbine, and the other compressors on independent shafts, the turbine can directly drive the compressors, thereby reducing the additional energy loss caused by the electric motor driving the compressors and thus improving efficiency. Furthermore, the independent shaft arrangement of the other compressors allows for flexible adjustment of their shaft speeds. The shaft speeds of the main compressor or recompressor can also be adjusted via the turbine. When used in peak-shaving scenarios, the three compressors can independently adjust their shaft speeds as the peak-shaving load changes, thus flexibly adapting to changes in peak-shaving load. This helps to optimize and obtain the best operating parameters under peak-shaving load conditions, thereby ensuring that the system's power generation efficiency does not decrease significantly under peak-shaving scenarios.

[0022] 2. This system not only meets the requirements for flexible operation under partial load, but also takes into account the high efficiency of the cycle, making it suitable for peak shaving scenarios;

[0023] 3. By thoroughly considering the operating characteristics of the three types of compressors under different loads, including the power consumption characteristics of the three types of compressors and the performance change characteristics with load variations, different cycle setting schemes are proposed based on different peak shaving depth requirements, which is conducive to maximizing the power generation efficiency of the cycle under peak shaving scenarios. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the supercritical carbon dioxide cycle power generation and peak shaving system provided by the present invention, with the main compressor and turbine shafts arranged together.

[0025] Figure 2 This is a schematic diagram of the supercritical carbon dioxide cycle power generation and peak shaving system provided by the present invention, with the compressor and turbine shafts arranged together.

[0026] Figure 3 These are schematic diagrams of the systems provided in Comparative Example 1 and Comparative Example 2 of this invention;

[0027] Figure 4 These are schematic diagrams of the systems provided in Comparative Examples 3 and 4 of this invention.

[0028] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0029] 1. Turbine; 2. High-temperature regenerator; 3. Low-temperature regenerator; 4. Precooler; 5. Pre-compressor; 6. Diverter valve; 7. Intercooler; 8. Main compressor; 9. Recompressor; 10. Heater. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0031] Please see Figure 1 and Figure 2 The present invention provides a supercritical carbon dioxide cycle power generation peak shaving system. The peak shaving system includes a supercritical carbon dioxide cycle system. The turbine mechanical equipment of the supercritical carbon dioxide cycle system includes a turbine 1, a pre-compressor 5, a main compressor 8, and a re-compressor 9. The main compressor 8 or the re-compressor 9 is arranged with the turbine 1 on a shaft and driven by the turbine 1. The other compressors are connected to independent drive structures.

[0032] This peak-shaving system is formed by a supercritical carbon dioxide cycle system, which can be a Brayton cycle system, a power generation system that uses supercritical carbon dioxide as the working medium. A supercritical carbon dioxide cycle system typically includes a compressor and a turbine 1, as well as other related structures for realizing the power generation cycle. The implementation of this cycle system is well known to those skilled in the art and will not be described in detail here. In this embodiment, the cycle system has three compressors: a pre-compressor 5, a main compressor 8, and a re-compressor 9.

[0033] Furthermore, this embodiment proposes to connect the main compressor 8 or the recompressor 9 to the turbine 1 via a shaft, thereby driving it through the turbine 1. Other compressors are configured as independent drives, i.e., independent split-shaft arrangements, driven by independent electric motors. This makes the cycle system suitable for peak-shaving scenarios. Specifically, firstly, this embodiment considers that, based on the thermodynamic performance analysis of the S-CO2 cycle, the total power consumption of the compressor can account for 25%-30% of the output power of the turbine 1. Therefore, the compression power consumption is enormous. By connecting the turbine 1 to the compressor via a shaft, the turbine 1 can directly drive the compressor, thereby reducing the additional energy loss caused by the electric motor driving the compressor, thus improving efficiency.

[0034] Secondly, this embodiment also considers the significant differences in operating pressure ratios and working fluid flow rates among the multiple compressors in the circulation system, as well as the different rotational speeds of the compressors. Under varying operating conditions, relatively independent control is required; that is, in variable load peak-shaving operation scenarios, each compressor needs to adjust its shaft speed to regulate its pressure ratio and flow rate. Therefore, this embodiment selects one compressor and connects it to turbine 1 on a single shaft, while the other compressors are driven independently. Each of the other compressors can be connected to a separate electric motor for driving.

[0035] Specifically, in the arrangement of turbine 1 and main compressor 8, the shaft speed of turbine 1 is consistent with that of main compressor 8, while the shaft speeds of pre-compressor 5 and re-compressor 9 can be flexibly adjusted; in the arrangement of turbine 1 and re-compressor 9, the shaft speed of turbine 1 is consistent with that of re-compressor 9, while the shaft speeds of pre-compressor 5 and main compressor 8 can be flexibly adjusted. Therefore, this embodiment not only meets the requirements for flexible cyclic operation under partial load but also ensures high-efficiency cyclic performance.

[0036] The supercritical carbon dioxide cycle power generation peak-shaving system provided by this invention proposes to arrange the main compressor 8 or re-compressor 9 on a shaft connected to the turbine 1, while other compressors are arranged independently on separate shafts. The shaft connection between turbine 1 and the compressors allows turbine 1 to directly drive the compressors, thereby reducing the additional energy loss caused by the electric motor driving the compressors and thus improving efficiency. Furthermore, the independent shaft arrangement of the other compressors allows for flexible adjustment of their shaft speeds. The shaft speeds of the main compressor or re-compressor can also be adjusted via the turbine. In peak-shaving scenarios, the three compressors can independently adjust their shaft speeds according to changes in peak-shaving load, thus flexibly adapting to changes in peak-shaving load. This facilitates optimizing operating parameters under peak-shaving load conditions, ensuring that the system's power generation efficiency does not decrease significantly during peak-shaving scenarios. This system not only meets the requirements for flexible operation under partial load but also takes into account the high efficiency of the cycle, making it suitable for peak-shaving scenarios.

[0037] Furthermore, research has shown that this supercritical carbon dioxide cycle power generation peak-shaving system, by selecting the main compressor 8 or the re-compressor 9 to be connected to the turbine 1 and arranged with other compressors driven independently, can be used for peak-shaving loads within the range of 30%-100% of the rated load. It can achieve efficient and flexible operation of tens to hundreds of MW of installed capacity under 30%-100% load demand.

[0038] The supercritical carbon dioxide cycle power generation and peak-shaving system selected in this embodiment is equipped with three compressors: a pre-compressor, a main compressor, and a re-compressor. By introducing the pre-compressor, an intermediate cooling process is introduced on the basis of the recompression cycle, thus forming a partial cooling cycle. Compared with the recompression cycle, this cycle can further reduce the compressor power consumption, thereby improving the cycle efficiency.

[0039] Furthermore, when the required peak load is 30%-55% of the rated load, the main compressor 8 is arranged with the turbine 1 on a shaft, and the pre-compressor 5 and the re-compressor 9 are each connected to an independent drive structure; when the required peak load is 55%-100% of the rated load, the re-compressor 9 is arranged with the turbine 1 on a shaft, and the pre-compressor 5 and the main compressor 8 are each connected to an independent drive structure.

[0040] This embodiment takes into account that under high load, the re-compressor has the highest power consumption among the three types of compressors. The arrangement of the re-compressor and turbine shaft can minimize the additional power consumption caused by the electric motor driving the compressor. Therefore, the thermal efficiency of this arrangement is higher under high load. As the load decreases, the performance of the main compressor degrades the most among the three types of compressors. The main compressor and turbine shaft arrangement cycle has the smallest pressure ratio change under partial load. Therefore, the main compressor cycle efficiency is higher, and the turbine work capacity decay is also the smallest. Therefore, the thermal efficiency of the main compressor and turbine shaft arrangement is higher when dealing with deep load adjustment.

[0041] Based on different peak-shaving depth requirements, there are two mechanical arrangement forms for turbine 1, which enable the supercritical carbon dioxide cycle system to exhibit higher operating efficiency in different variable load ranges. One is when the peak-shaving load is mostly 30%-55% of the cycle's rated power, the main compressor 8 is arranged with turbine 1 on a shaft. The other is when the peak-shaving load is mostly 55%-100% of the cycle's rated power, the re-compressor 9 is arranged with turbine 1 on a shaft. The mechanical work consumed by the compressor arranged with turbine 1 on a shaft is provided by turbine 1, and the other compressors are driven by independent electric motors.

[0042] Specifically, the arrangement of turbine 1 and main compressor 8, or turbine 1 and recompressor 9, can be configured according to actual peak-shaving requirements. When the actual required peak-shaving load is concentrated between 30% and 55% of the rated load, the arrangement of main compressor 8 and turbine 1 can be used; when the actual required peak-shaving load is concentrated between 55% and 100% of the rated load, the arrangement of recompressor 9 and turbine 1 can be used. The specific required peak-shaving load can be determined based on the user's actual operating load over a year. If the user's actual operating load is mostly concentrated between 30% and 55% of the rated load over a year, the arrangement of main compressor 8 and turbine 1 can be used for that user; if the user's actual operating load is mostly concentrated between 55% and 100% of the rated load over a year, the arrangement of recompressor 9 and turbine 1 can be used for that user.

[0043] Furthermore, specifically, this invention selects a supercritical CO2 partial cooling cycle as the research object. The supercritical CO2 cycle system further includes: a high-temperature regenerator 2, a low-temperature regenerator 3, a precooler 4, a flow divider valve 6, an intercooler 7, and a heater 10; that is, the main compressor 8 or re-compressor 9 in the partial cooling cycle is arranged on a shaft connected to the turbine 1, while the other compressors are arranged on independent shafts. The supercritical CO2 partial cooling cycle includes: turbine 1, high-temperature regenerator 2, low-temperature regenerator 3, precooler 4, pre-compressor 5, flow divider valve 6, intercooler 7, main compressor 8, re-compressor 9, and heater 10. The main compressor 8 or re-compressor 9 is arranged on a shaft connected to the turbine 1, and the mechanical work consumed is provided by the turbine 1, while the other compressors are driven by independent electric motors.

[0044] Specifically, the outlet of turbine 1 is connected to the first inlet of the high-temperature regenerator 2, the first outlet of the high-temperature regenerator 2 is connected to the first inlet of the low-temperature regenerator 3, the second outlet of the high-temperature regenerator 2 is connected to the inlet of the heater 10, the outlet of the heater 10 is connected to the inlet of turbine 1, the first outlet of the low-temperature regenerator 3 is connected to the inlet of the pre-compressor 5, the outlet of the pre-compressor 5 is connected to the inlet of the main compressor 8 and the inlet of the re-compressor 9 respectively through the diversion valve 6, the outlet of the main compressor 8 is connected to the second inlet of the low-temperature regenerator 3, the second outlet of the low-temperature regenerator 3 is connected to the second inlet of the high-temperature regenerator 2, the outlet of the re-compressor 9 is connected to the second inlet of the high-temperature regenerator 2, the pre-cooler 4 is provided at the inlet of the pre-compressor 5, and the intercooler 7 is provided at the inlet of the main compressor 8.

[0045] Furthermore, the heating medium in the heater 10 is molten salt; the molten salt can be formed by solar heating. The flow ratio of the diversion valve 6 is 0.5-0.6; the flow ratio of the diversion valve 6 is the ratio of the working fluid flow rate into the main compressor 8 through the diversion valve 6 to the total working fluid flow rate at the inlet of the diversion valve 6. Studies have shown that a flow ratio within this range can achieve better power generation efficiency under different peak loads.

[0046] Furthermore, the inlet medium temperature of turbine 1 is greater than or equal to 600°C; the inlet medium temperatures of the pre-compressor 5, the main compressor 8, and the re-compressor 9 are each greater than 30.98°C. When the inlet temperature of turbine 1 is higher than 600°C, the supercritical CO2 cycle has a thermal efficiency advantage over the traditional steam Rankine cycle, and this advantage becomes more pronounced as the temperature increases. The compressor inlet temperature needs to be maintained above the critical temperature of 30.98°C, and lowering the compressor inlet temperature is beneficial for improving the cycle's thermal efficiency.

[0047] Furthermore, the present invention also provides a supercritical carbon dioxide cycle power generation peak shaving method based on the supercritical carbon dioxide cycle power generation peak shaving system described in any of the above embodiments. The method includes: arranging the main compressor 8 or the re-compressor 9 with the turbine 1 and driving it by the turbine 1, while connecting the remaining compressors to independent drive structures, for peak shaving within the range of 30%-100% of the rated load.

[0048] Furthermore, when the required peak load is 30%-55% of the rated load, the main compressor 8 is arranged with the turbine 1 on a shaft, and the pre-compressor 5 and the re-compressor 9 are respectively connected to independent drive structures; when the required peak load is 55%-100% of the rated load, the re-compressor 9 is arranged with the turbine 1 on a shaft, and the pre-compressor 5 and the main compressor 8 are respectively connected to independent drive structures.

[0049] Specifically, according to the test results, when the inlet temperature of the circulating turbine 1 is raised to 750°C and the inlet temperature of the three compressors is 35°C, the operating efficiency of the partial cooling cycle of the turbine 1 and the main compressor 8 under 30%-100% load is 43.01%-49.85%, and the operating efficiency of the partial cooling cycle of the turbine 1 and the re-compressor 9 under 30%-100% load is 41.58%-50.38%.

[0050] A comparison of the operating efficiency of the two turbine-1 mechanical arrangement circulation systems under variable load conditions reveals that the circulation system with turbine 1 and main compressor 8 shafts connected together exhibits a significant efficiency advantage during deep peak load conditions (30%-55% load), while the circulation system with turbine 1 and recompressor 9 shafts connected together is even more efficient at higher loads (55%-100% load). This is mainly because, under low loads during deep peak load conditions, the output power of turbine 1 hardly decreases when absorbing a unit of heat, and the power consumption of the compressor is lower, thus resulting in higher circulation efficiency at low loads.

[0051] Furthermore, this invention provides a specific control strategy for a supercritical carbon dioxide cycle power generation peak-shaving system when used for peak shaving, which can optimize and obtain the optimal operating parameters under different loads. Specifically, when the main compressor 8 and the turbine 1 are arranged in a shaft-connected configuration, as the required peak-shaving load decreases, the shaft speeds of the main compressor 8 and the re-compressor 9 gradually decrease, while the shaft speed of the pre-compressor 5 gradually increases.

[0052] Furthermore, when the recompressor 9 and the turbine 1 are arranged in a shaft-connected configuration, as the required peak load decreases, the shaft speed of the recompressor 9 gradually decreases, the shaft speed of the main compressor 8 first decreases and then increases, and the shaft speed of the precompressor 5 gradually increases.

[0053] Furthermore, during the required peak load change, the system's flow split ratio remains constant; wherein the flow split ratio is the ratio of the working fluid flow rate of the main compressor 8 to the total working fluid flow rate of the main compressor 8 and the re-compressor 9.

[0054] Specifically, during actual operation, the circulation system is heated by a high-temperature ternary chloride salt and cooled by air. The inlet temperature of turbine 1 is 750°C, and the inlet temperature of all three compressors is 35°C. Under design conditions, i.e., rated load, the circulation system of turbine 1 and main compressor 8 is arranged in a shaft configuration. Figure 1 The power generation efficiency of the system shown is 49.85%. The circulating system consisting of turbine 1 and recompressor 9 connected in a shaft configuration is... Figure 2 The power generation efficiency of the system shown is 50.38%. Under non-design operating conditions, the maximum pressure, minimum pressure, intermediate cooling pressure, and flow ratio of the circulation system can be adjusted by flexibly controlling the shaft speed of each compressor and the flow divider valve 6, wherein the shaft speed of turbine 1 is consistent with that of the main compressor 8 or the re-compressor 9.

[0055] For a cycle in which turbine 1 and main compressor 8 are connected on a shaft, the shaft speeds of main compressor 8 and recompressor 9 decrease as the load decreases, but the shaft speed of precompressor 5 increases as the load decreases, while the opening of diverter valve 6 remains almost unchanged. For the cycle in which turbine 1 and recompressor 9 are connected on a shaft, as the load decreases, the shaft speed of recompressor 9 decreases, the shaft speed of main compressor 8 first decreases and then increases when the required peak load is below 50% of the rated load, the shaft speed of precompressor 5 increases, and the opening of diverter valve 6 remains almost unchanged.

[0056] The compressor shaft speed increases as the load decreases primarily to cope with the continuously increasing compressor specific enthalpy. Consequently, the highest, lowest, and intermediate cooling pressures of the cycle gradually decrease, while the split ratio remains almost constant at around 0.56. That is, the split ratio can be 0.56.

[0057] Furthermore, when the required peak load is 30%-55% of the rated load, turbine 1 and main compressor 8 are arranged in a shaft-connected manner. Within this load variation range, as the required peak load decreases, the shaft speed of the main compressor 8 and the re-compressor 9 gradually decreases, while the shaft speed of the pre-compressor 5 gradually increases.

[0058] Furthermore, when the required peak load is 55%-100% of the rated load, the turbine 1 and the re-compressor 9 are arranged in a shaft-connected configuration. Within this load variation range, as the required peak load decreases, the shaft speeds of the main compressor 8 and the re-compressor 9 gradually decrease, while the shaft speed of the pre-compressor 5 gradually increases.

[0059] Furthermore, the purpose of this invention is to provide a mechanical optimization layout scheme for a supercritical CO2 circulating turbine that is efficient and flexible in peak shaving scenarios. This scheme is based on research on the optimization of design parameters and the control of operating parameters of a supercritical carbon dioxide circulating system, determines the layout scheme of the circulating equipment and the control strategy of operating parameters, and optimizes to obtain the best operating parameters and operating efficiency of the circulation under partial load.

[0060] Specifically, this invention discloses a mechanical optimization arrangement scheme for a supercritical CO2 cycle turbine 1 under peak-shaving scenarios. This scheme is proposed for a partially cooled supercritical CO2 cycle, which consists of one turbine 1, three compressors, two regenerators, one heater, and two air coolers. By optimizing the arrangement of turbine 1 and the compressors, the cycle can be ensured to operate safely and efficiently under peak-shaving conditions. Specifically, when frequently handling deep peak-shaving demands (load < 55%), turbine 1 is coupled to the main compressor 8, which is driven by turbine 1. When handling relatively high variable load demands (load > 55%), turbine 1 is coupled to a re-compressor 9, which is driven by turbine 1. Meanwhile, the remaining compressors are arranged on separate shafts and driven by independent motors. Under variable load conditions, the shaft speed of turbine 1 is adjusted according to the shaft speed of the coupled compressors, while the shaft speeds of the other compressors are independently adjusted based on the actual pressure ratio and flow rate. Through optimization, the variable load operating parameters and efficiency of the cycle under peak-shaving scenarios can be obtained. This scheme takes into account the flexibility and efficiency of supercritical CO2 cycle operation under variable load conditions, which helps to improve the power supply economy and reliability of high-temperature solar thermal power generation peak-shaving power plants based on supercritical CO2 cycles.

[0061] Compared to the scheme where turbine 1 is arranged with the main compressor 8, re-compressor 9, and pre-compressor 5 all on the same shaft, this invention allows for more flexible adjustment of compressor shaft speeds in peak-shaving scenarios, achieving deep peak-shaving in the cycle. Compared to the scheme where turbine 1, main compressor 8, re-compressor 9, and pre-compressor 5 are arranged on separate shafts, the scheme proposed in this invention has higher thermal efficiency under all operating conditions, while still meeting the flexible adjustment of the shaft speeds of each turbine 1 mechanical device under varying operating conditions. To address different types of peak-shaving needs, this invention optimizes the mechanical arrangement of the circulating turbine 1. When the load demand is mostly between 30% and 55%, a cycle with turbine 1 and main compressor 8 on the same shaft is recommended; when the load demand is mostly between 55% and 100%, a cycle with turbine 1 and re-compressor 9 on the same shaft is recommended. The following specific examples and comparative proportions further illustrate this:

[0062] Specific example 1:

[0063] like Figure 1 As shown, in Example 1 of this invention, the mechanical arrangement of the supercritical CO2 cycle turbine 1 is as follows: turbine 1 and main compressor 8 are arranged on a shaft, with the main compressor 8 directly driven by turbine 1; recompressor 9 and precompressor 5 are arranged on separate shafts and driven by independent electric motors. The rated power of the cycle is 100MW. The optimized highest, lowest, and intermediate cooling pressures and split ratios obtained under 100% rated load are 25MPa, 5.75MPa, 8.38MPa, and 0.561, respectively. The shaft speeds of turbine 1 and main compressor 8 are 15500rpm, the shaft speed of recompressor 9 is 18700rpm, the shaft speed of precompressor 5 is 4100rpm, and the rated power generation efficiency of the cycle is 49.85%.

[0064] Specific example 2:

[0065] like Figure 1 As shown, Example 2 of the present invention uses the same cycle as Example 1. In peak-shaving scenarios, the cycle output power needs to be adjusted according to changing load demand. The shaft speed of turbine 1 and the shaft speed of main compressor 8 are adjusted in real time, while the shaft speeds of re-compressor 9 and pre-compressor 5 are adjusted independently. When the load demand decreases to 30% of the rated value, the cycle's highest, lowest, and intermediate cooling pressures, as well as the split ratio, are adjusted to 10.44 MPa, 4.04 MPa, 7.49 MPa, and 0.560, respectively, and the cycle's power generation efficiency decreases to 43.01%.

[0066] Specific example 3:

[0067] like Figure 2As shown, in Example 3 of this invention, the mechanical arrangement of the supercritical CO2 cycle turbine 1 is as follows: the recompressor 9 is shaft-connected to the turbine 1 and is directly driven by the turbine 1; the precompressor 5 and the main compressor 8 are shaft-connected and driven by independent electric motors. The rated power of the cycle is 100MW. The optimized highest, lowest, and intermediate cooling pressures and the split ratio obtained at 100% rated load are 25MPa, 5.56MPa, 8.40MPa, and 0.561, respectively. The shaft speeds of the turbine 1 and the recompressor 9 are 19000rpm, the shaft speed of the main compressor 8 is 15600rpm, the shaft speed of the precompressor 5 is 4400rpm, and the rated power generation efficiency of the cycle is 50.38%.

[0068] Specific example 4:

[0069] like Figure 2 As shown, Example 4 of the present invention uses the same cycle as Example 3. In the peak-shaving scenario, the shaft speed of turbine 1 and the shaft speed of re-compressor 9 are adjusted in real time, while the shaft speeds of main compressor 8 and pre-compressor 5 are adjusted independently. When the load demand decreases to 30% of the rated value, the highest, lowest, and intermediate cooling pressures and the split ratio of the cycle are adjusted to 11.03 MPa, 4.16 MPa, 7.23 MPa, and 0.557, respectively, and the power generation efficiency of the cycle decreases to 41.58%.

[0070] Comparative Example 1:

[0071] like Figure 3 As shown, Comparative Example 1 of the present invention is a scheme in which all mechanical components of the supercritical CO2 cycle turbine 1 are arranged in a split-shaft configuration. In this scheme, the turbine 1 is directly connected to a generator for power generation, and the re-compressor 9, pre-compressor 5, and main compressor 8 are each driven by an independent electric motor. The rated power of the cycle remains 100MW. The optimized highest, lowest, and intermediate cooling pressures and the split ratio of the cycle at 100% rated load are 25MPa, 5.73MPa, 8.51MPa, and 0.561, respectively, and the rated power generation efficiency of the cycle is 49.21%.

[0072] Comparative Example 2:

[0073] like Figure 3 As shown, Comparative Example 2 of the present invention uses the same cycle as Comparative Example 1. In the peak-shaving scenario, the shaft speed of each turbine 1 is independently controlled. When the load demand decreases to 30% of the rated value, the highest, lowest, and intermediate cooling pressures and the split ratio of the cycle are adjusted to 11.05 MPa, 3.81 MPa, 7.28 MPa, and 0.558, respectively, and the power generation efficiency of the cycle decreases to 40.69%.

[0074] Comparative Example 3:

[0075] like Figure 4As shown, in Comparative Example 3 of the present invention, the mechanical arrangement of the supercritical CO2 cycle turbine 1 is as follows: turbine 1 and pre-compressor 5 are arranged on a shaft, with pre-compressor 5 directly driven by turbine 1; main compressor 8 and re-compressor 9 are arranged on separate shafts and driven by independent electric motors. The rated power of the cycle remains 100MW. The optimized highest, lowest, and intermediate cooling pressures and the split ratio of the cycle at 100% rated load are 25MPa, 5.12MPa, 8.57MPa, and 0.561, respectively, and the rated power generation efficiency of the cycle is 50.10%.

[0076] Comparative Example 4:

[0077] like Figure 4 As shown, Comparative Example 4 of the present invention uses the same cycle as Comparative Example 3. In the peak-shaving scenario, the shaft speed of turbine 1 and the shaft speed of pre-compressor 5 are adjusted in real time, while the shaft speeds of main compressor 8 and re-compressor 9 are adjusted independently. When the load demand decreases to 30% of the rated value, the highest, lowest, and intermediate cooling pressures and the split ratio of the cycle are adjusted to 11.36 MPa, 4.46 MPa, 6.76 MPa, and 0.562, respectively, and the power generation efficiency of the cycle decreases to 39.63%.

[0078] Through specific examples and comparative analyses, it can be found that the two optimized mechanical arrangement schemes of the supercritical CO2 cycle turbine 1 proposed in this invention can effectively balance the flexibility and efficiency of the cycle under peak-shaving operation scenarios. Compared with schemes such as the fully split-shaft arrangement of turbine 1 and the shaft-connected arrangement of turbine 1 and pre-compressor 5, the scheme of shaft-connected arrangement of turbine 1 and recompressor 9 proposed in this invention can further improve power generation efficiency, with absolute values ​​of power generation efficiency increased by 1.17% and 0.28% respectively under rated load. When dealing with deep peak-shaving demands, the efficiency advantage of the scheme of shaft-connected arrangement of turbine 1 and main compressor 8 proposed in this invention is significant. For example, when the load is 30% of the rated value, the cycle power generation efficiency can still reach 43.01%, which is an absolute value increase of 2.32%, 3.38%, and 1.43% respectively compared with the schemes of fully split-shaft arrangement of turbine 1, shaft-connected arrangement of turbine 1 and pre-compressor 5, and shaft-connected arrangement of turbine 1 and recompressor 9.

[0079] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A supercritical carbon dioxide cycle power generation and peak-shaving system, characterized in that, The peak-shaving system is formed by a supercritical carbon dioxide cycle system, which is a Brayton cycle system and a power generation system that uses supercritical carbon dioxide as the working medium. The turbine mechanical equipment of the supercritical carbon dioxide cycle power generation peak-shaving system includes a turbine, a pre-compressor, a main compressor, and a re-compressor. The main compressor or the re-compressor is connected to the turbine and driven by the turbine, while the other compressors are connected to independent drive structures. When the required peak load is 30%-55% of the rated load, the main compressor is arranged with the turbine on a shaft, and the pre-compressor and the re-compressor are respectively connected to independent drive structures; When the required peak load is 55%-100% of the rated load, the recompressor is arranged with the turbine on a shaft, and the precompressor and the main compressor are respectively connected to independent drive structures.

2. The supercritical carbon dioxide cycle power generation and peak-shaving system as described in claim 1, characterized in that, The supercritical carbon dioxide cycle power generation and peak shaving system also includes: a high-temperature regenerator, a low-temperature regenerator, a precooler, a diversion valve, an intercooler, and a heater; The turbine outlet is connected to the first inlet of the high-temperature regenerator, the first outlet of the high-temperature regenerator is connected to the first inlet of the low-temperature regenerator, the second outlet of the high-temperature regenerator is connected to the inlet of the heater, the outlet of the heater is connected to the inlet of the turbine, the first outlet of the low-temperature regenerator is connected to the inlet of the precooler, the outlet of the precooler is connected to the inlet of the precompressor, the outlet of the precompressor is connected to the inlet of the intercooler and the inlet of the recompressor respectively through the diversion valve, the outlet of the intercooler is connected to the inlet of the main compressor, the outlet of the main compressor is connected to the second inlet of the low-temperature regenerator, the second outlet of the low-temperature regenerator is connected to the second inlet of the high-temperature regenerator, and the outlet of the recompressor is connected to the second inlet of the high-temperature regenerator.

3. The supercritical carbon dioxide cycle power generation and peak-shaving system as described in claim 2, characterized in that, The heating medium in the heater is molten salt; the flow divider valve has a flow divider ratio of 0.5-0.

6.

4. The supercritical carbon dioxide cycle power generation and peak-shaving system as described in claim 1, characterized in that, The inlet medium temperature of the turbine is greater than or equal to 600°C; the inlet medium temperatures of the pre-compressor, the main compressor, and the re-compressor are each greater than 30.98°C.

5. A method for peak shaving in supercritical carbon dioxide cycle power generation, characterized in that, Based on the supercritical carbon dioxide cycle power generation and peak-shaving system according to any one of claims 1-4, the method includes: The main compressor or the re-compressor is connected to the turbine and driven by the turbine, while the other compressors are connected to independent drive structures. This system is used for peak shaving within the range of 30%-100% of the rated load.

6. The supercritical carbon dioxide cycle power generation peak shaving method as described in claim 5, characterized in that, When the required peak load is 30%-55% of the rated load, the main compressor is arranged to be connected to the turbine, and the pre-compressor and the re-compressor are respectively connected to independent drive structures; When the required peak load is 55%-100% of the rated load, the recompressor is arranged with the turbine on a shaft, and the precompressor and the main compressor are respectively connected to independent drive structures.

7. The supercritical carbon dioxide cycle power generation peak shaving method as described in claim 5, characterized in that, When the main compressor and the turbine are arranged in a shaft-connected configuration, as the required peak load decreases, the shaft speeds of the main compressor and the re-compressor gradually decrease, while the shaft speed of the pre-compressor gradually increases.

8. The supercritical carbon dioxide cycle power generation peak shaving method as described in claim 5, characterized in that, When the recompressor and turbine are arranged in a shaft configuration, as the required peak load decreases, the shaft speed of the recompressor gradually decreases, the shaft speed of the main compressor first decreases and then increases, and the shaft speed of the precompressor gradually increases.

9. The supercritical carbon dioxide cycle power generation peak shaving method as described in claim 5, characterized in that, During the required peak load change, the system's flow split ratio remains constant; wherein the flow split ratio is the ratio of the working fluid flow rate of the main compressor to the total working fluid flow rate of the main compressor and the re-compressor.

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