Coal-fired cogeneration system based on composite heat accumulation step-by-step utilization and configuration method

Abstract

The application provides a coal-fired combined heat and power system based on composite heat accumulation step utilization and a configuration method, comprising a CFPP unit, a heat supply unit, a CAES unit and a MSHS unit, the system replaces the compression heat of the CAES unit with low quality into the medium-pressure cylinder extraction steam heat supply with medium quality, and then replaces the medium-pressure cylinder extraction steam heat with medium quality into the high-quality reheat steam heat; the high-quality heat is stored in the form of MSHS, which not only reduces the minimum output of the whole coupling system, but also supplies heat for the CAES unit in the energy release process by using the MSHS unit, greatly improves the maximum output of the whole coupling system, realizes the secondary replacement and upgrading of heat, and recovers waste heat by using the medium-temperature air at the outlet of the last-stage turbine to preheat the circulating feed water; in addition, the application provides a configuration method of the system, the energy storage capacity of the CAES unit and the MSHS unit is optimally configured, the maximum output of the system is further improved, the minimum output of the system is reduced, the performance of the whole system is effectively improved, and the energy consumption is reduced.

Description

Technical Field

[0001] This invention belongs to the field of cogeneration units, specifically relating to a coal-fired cogeneration system and configuration method based on composite thermal storage cascade utilization. Background Technology

[0002] The balance between power supply and demand is the core of the power system. Renewable energy is intermittent and unstable, and the random fluctuations of high-proportion wind and solar power generation significantly increase the difficulty of ensuring power balance, thus significantly increasing the requirements for the rate and magnitude of power supply and demand regulation. Coal-fired power, as a flexible resource on the power supply side, has the natural advantages of high existing installed capacity and large potential for flexibility tapping, but it also suffers from weak regulation capabilities, long start-up times, and limited flexibility. Energy storage is a key means of improving the flexibility of thermal power units. The coupling between coal-fired power generation units and compressed air energy storage units is mostly electrothermal coupling, that is, the heat of compression during energy storage is supplied to the unit, and during the energy release process, the unit extracts air as the heat source for expansion before the expander stage. Compared with simple electric coupling, this coupling method does not require thermal energy storage, which can reduce investment equipment costs and effectively improve unit performance while reducing minimum output. However, due to the air extraction during the energy release process, the maximum output is reduced, which will reduce the power regulation range and flexibility of the integrated system. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a coal-fired cogeneration system based on composite thermal storage and cascade utilization, which can further reduce minimum output, significantly increase maximum output, improve the system's adjustable range and flexibility, enhance operating efficiency, and reduce standard coal consumption rate.

[0004] The technical solution adopted in this invention is as follows:

[0005] A coal-fired cogeneration system based on composite thermal storage cascade utilization includes a CFPP unit, a heating unit, an MSHS unit, and a CAES unit.

[0006] The boiler outlet in the CFPP unit is connected to the inlet of the molten salt heater in the MSHS unit and is controlled by a first valve.

[0007] The outlet of the molten salt hot tank in the MSHS unit is connected in sequence to the inlet of the first reheater, the second reheater, and the third reheater in the CAES unit;

[0008] The outlet of the third turbine of the CAES is connected to the inlet of the feedwater preheater in the CFPP and is controlled by a third valve.

[0009] Furthermore, the heat source for the MSHS unit is reheat steam from the boiler outlet of the CFPP unit.

[0010] Furthermore, the first generator in the CFPP unit provides power to the motor in the CAES unit.

[0011] Furthermore, the outlet of the intermediate pressure cylinder in the CFPP unit is connected to the inlet of the heating network heater in the heating unit.

[0012] Furthermore, the outlet of the feedwater preheater in the CFPP unit is sequentially connected to the inlets of the first, second, and third intercoolers in the CAES unit, and is controlled by a second valve.

[0013] Furthermore, the outlet of the molten salt heater in the MSHS unit is connected to the outlet of the first high-pressure heater in the CFPP unit and they both flow into the inlet of the second high-pressure heater in the CFPP unit.

[0014] Furthermore, the outlet of the heating network heater of the heating unit is connected to the outlet of the first low-pressure heater in the CFPP unit and they both flow into the inlet of the second low-pressure heater in the CFPP unit.

[0015] Furthermore, the outlet of the heat network preheater in the heating unit is connected to the outlet of the fourth low-pressure heater in the CFPP unit and they both flow into the inlet of the third low-pressure heater in the CFPP unit.

[0016] Furthermore, the outlets of the first reheater, second reheater, and third reheater in the CAES unit are combined and connected to flow into the inlet of the molten salt cold tank in the MSHS unit.

[0017] The configuration method for a coal-fired cogeneration system based on composite thermal storage cascade utilization includes the following steps for capacity configuration of the CAES unit and the MSHS unit:

[0018] Step 1: Obtain environmental conditions, the structural form of the cogeneration unit, the boundary conditions for safe operation, and the heat source of the MSHS unit;

[0019] Step 2: Set the relevant parameters for operating the cogeneration unit independently;

[0020] Step 3: Set the total energy storage capacity, CAES unit energy storage capacity, and MSHS unit energy storage capacity;

[0021] Step 4: Determine whether the main steam flow rate during energy storage and release meets the boundary conditions for safe operation of the cogeneration unit. If not, further adjust the total energy storage capacity, CAES unit energy storage capacity, and MSHS unit energy storage capacity until all iterative calculations reach the optimal value. Efficiency and flexible operating range.

[0022] Step 5: Set the total energy storage capacity, CAES unit energy storage capacity, and MSHS unit energy storage capacity according to the optimized and adjusted parameters in Step 4.

[0023] Furthermore, the environmental conditions include ambient temperature; the structural form of the cogeneration unit and the boundary conditions for safe operation include the arrangement of low-pressure and high-pressure heaters and the minimum main steam flow rate and the safety boundary of the minimum main steam flow rate during energy storage and release, as well as the extraction steam location of the heating unit; the heat source of the MSHS unit includes the extraction steam location.

[0024] Furthermore, the total energy storage capacity includes a lower limit, an upper limit, and an adjustment step size; the CAES unit energy storage capacity includes a lower limit, an upper limit, and an adjustment step size; and the MSHS unit energy storage capacity includes a lower limit, an upper limit, and an adjustment step size.

[0025] The beneficial effects of this invention are:

[0026] This invention utilizes the MSHS system to achieve spatiotemporal heat transfer, particularly for coal-fired CHPP systems coupled with CAES units. Under a fixed heat supply, the compression heat of the lower-quality CAES unit is replaced with medium-quality intermediate-pressure cylinder extraction steam for heating, and then the medium-quality intermediate-pressure cylinder extraction steam heat is replaced with high-quality reheat steam heat. Simultaneously, the system can store high-quality heat in the form of MSHS, which not only reduces the minimum output of the entire coupled system but also allows the MSHS unit to heat the CAES unit during the energy release process, significantly increasing the maximum output of the entire coupled system. This achieves a two-stage heat replacement and upgrade, further improving the system's energy utilization rate. Furthermore, the medium-temperature air from the final turbine outlet is used to preheat the circulating feedwater, effectively recovering waste heat and further improving the overall energy efficiency of the coupled system and reducing the standard coal consumption rate.

[0027] By optimizing the configuration of total energy storage capacity, CAES unit energy storage capacity, and MSHS unit energy storage capacity, the maximum output of the system was effectively increased, while the minimum output of the system was reduced, thereby further improving the performance of the entire system and reducing energy consumption. Attached Figure Description

[0028] Figure 1 A schematic diagram of a coal-fired cogeneration system based on composite thermal storage cascade utilization;

[0029] Figure 2 This is a flowchart illustrating the configuration method of a coal-fired cogeneration system based on the cascade utilization of composite thermal storage.

[0030] Figure 3A performance comparison chart of conventional CHPP and the coal-fired cogeneration system based on composite thermal storage and cascade utilization proposed in this invention;

[0031] Figure 4 A comparison chart showing the operating output of a conventional CHPP and a coal-fired cogeneration system based on composite thermal storage and cascade utilization proposed in this invention;

[0032] Figure 5 A comparison chart of standard coal consumption rates for power generation during the energy storage and release periods of a coal-fired cogeneration system based on composite thermal storage cascade utilization;

[0033] Figure 6 This diagram illustrates a comparison of the operational areas of a conventional CHPP (Combined Thermal Power Plant) and a coal-fired cogeneration system based on composite thermal storage and cascade utilization proposed in this invention.

[0034] Reference numerals: 1. High-pressure cylinder; 2. Intermediate-pressure cylinder; 3. Low-pressure cylinder; 4. First generator; 5. Condenser; 6. Circulating water pump; 7. Feedwater preheater; 8. Fourth low-pressure heater; 9. Third low-pressure heater; 10. Second low-pressure heater; 11. First low-pressure heater; 12. Deaerator; 13. Feedwater pump; 14. Third high-pressure heater; 15. Second high-pressure heater; 16. First high-pressure heater; 17. Boiler; 18. Heat network heater; 19. Heat network; 20. Heat network preheater; 21. Molten salt heater 21. Tank; 22. Molten salt cold tank; 23. Molten salt heater; 24. First intercooler; 25. Second intercooler; 26. Third intercooler; 27. First compressor; 28. Second compressor; 29. ​​Third compressor; 30. Electric motor; 31. Gas storage chamber; 32. Throttling valve; 33. First reheater; 34. Second reheater; 35. Third reheater; 36. First turbine; 37. Second turbine; 38. Third turbine; 39. Second generator; 40. First valve; 41. Second valve; 42. Third valve. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, other embodiments obtained by those skilled in the art without creative effort are all within the protection scope of this invention.

[0036] This application discloses a coal-fired cogeneration system based on composite thermal storage cascade utilization. See [link to relevant documentation]. Figure 1As shown, it includes a CFPP (coal-fired power plant) unit, a heating unit, an MSHS (molten salt heat storage) unit, and a CAES (compressed air energy storage) unit.

[0037] The CFPP unit includes a high-pressure cylinder 1, an intermediate-pressure cylinder 2, a low-pressure cylinder 3, a first generator 4, a condenser 5, a circulating water pump 6, a feedwater preheater 7, a fourth low-pressure heater 8, a third low-pressure heater 9, a second low-pressure heater 10, a first low-pressure heater 11, a deaerator 12, a feedwater pump 13, a third high-pressure heater 14, a second high-pressure heater 15, a first high-pressure heater 16, and a boiler 17.The first outlet of the boiler 17 is connected to the inlet of the high-pressure cylinder 1. The first outlet of the high-pressure cylinder 1 is connected to the second inlet of the first high-pressure heater 16. The second outlet of the high-pressure cylinder 1 is connected to the second inlet of the boiler 17 and the second inlet of the second high-pressure heater 15. The second outlet of the boiler 17 is connected to the inlet of the intermediate-pressure cylinder 2. The first outlet of the intermediate-pressure cylinder 2 is connected to the second inlet of the third high-pressure heater 14. The second outlet of the intermediate-pressure cylinder 2 is connected to the second inlet of the deaerator 12. The third outlet of the intermediate-pressure cylinder 2 is connected to the inlet of the low-pressure cylinder 3, the second inlet of the first low-pressure heater 11, and the heating unit. The first outlet of the low-pressure cylinder 3 is connected to the second high-pressure heater 15. The second inlet of the low-pressure heater 10 is connected to the second outlet of the low-pressure cylinder 3, which is connected to the second inlet of the third low-pressure heater 9. The third outlet of the low-pressure cylinder 3 is connected to the second inlet of the fourth low-pressure heater 8, and the fourth outlet of the low-pressure cylinder 3 is connected to the first inlet of the condenser 5. The outlet of the condenser 5 is connected to the inlet of the circulating water pump 6, and the outlet of the circulating water pump 6 is connected to the first inlet of the feedwater preheater 7. The first outlet of the feedwater preheater 7 is connected to the first inlet of the fourth low-pressure heater 8, and the first outlet of the fourth low-pressure heater 8 is connected to the first inlet of the third low-pressure heater 9. The second outlet of the fourth low-pressure heater 8 is connected to the second inlet of the condenser 5. The inlet of the third low-pressure heater 9 is connected to the first outlet of the second low-pressure heater 10, and the second outlet of the third low-pressure heater 9 is connected to the third inlet of the fourth low-pressure heater 8. The first outlet of the second low-pressure heater 10 is connected to the first inlet of the first low-pressure heater 11, and the second outlet of the second low-pressure heater 10 is connected to the third inlet of the third low-pressure heater 9. The first outlet of the first low-pressure heater 11 is connected to the first inlet of the deaerator 12, and the second outlet of the first low-pressure heater 11 is connected to the third inlet of the second low-pressure heater 10. The outlet of the deaerator 12 is connected to the inlet of the feed water pump 13. The outlet of the water pump 13 is connected to the first inlet of the third high-pressure heater 14, the first outlet of the third high-pressure heater 14 is connected to the first inlet of the second high-pressure heater 15, the second outlet of the third high-pressure heater 14 is connected to the third inlet of the deaerator 12, the first outlet of the second high-pressure heater 15 is connected to the first inlet of the first high-pressure heater 16, the second outlet of the second high-pressure heater 15 is connected to the third inlet of the third high-pressure heater 14, the first outlet of the first high-pressure heater 16 is connected to the first inlet of the boiler 17, and the second outlet of the first high-pressure heater 16 is connected to the third inlet of the second high-pressure heater 15.

[0038] The CAES unit includes a first intercooler 24, a second intercooler 25, a third intercooler 26, a first compressor 27, a second compressor 28, a third compressor 29, a motor 30, a gas storage chamber 31, a throttle valve 32, a first reheater 33, a second reheater 34, a third reheater 35, a first turbine 36, a second turbine 37, a third turbine 38, a second generator 39, a second valve 41, and a third valve 42. The first outlet of the feedwater preheater 7 is connected to the inlet of the second valve 41, and the outlet of the second valve 41 is connected to... The second inlets of the first intercooler 24, the second intercooler 25, and the third intercooler 26 are connected. The second outlets of the first intercooler 24, the second intercooler 25, and the third intercooler 26 are connected to the heating unit. The inlet of the first compressor 27 is connected to ambient air. The outlet of the first compressor 27 is connected to the first inlet of the first intercooler 24. The first outlet of the first intercooler 24 is connected to the inlet of the second compressor 28. The outlet of the second compressor 28 is connected to the second intercooler 25. The first inlet of the third compressor 29 is connected to the first outlet of the second intercooler 25, the first outlet of the third compressor 29 is connected to the first inlet of the third intercooler 26, the first outlet of the third intercooler 26 is connected to the inlet of the gas storage chamber 31, the outlet of the gas storage chamber 31 is connected to the inlet of the throttle valve 32, the outlet of the throttle valve 32 is connected to the first inlet of the first reheater 33, the first outlet of the first reheater 33 is connected to the inlet of the first turbine 36, the outlet of the first turbine 36 is connected to the first inlet of the second reheater 34, the first outlet of the second reheater 34 is connected to the inlet of the second turbine 37, the outlet of the second turbine 37 is connected to the first inlet of the third reheater 35, the first outlet of the third reheater 35 is connected to the inlet of the third turbine 38, the outlet of the third turbine 38 is connected to the inlet of the third valve 42, the outlet of the third valve 42 is connected to the second inlet of the feedwater preheater 7, and the second outlet of the feedwater preheater 7 is discharged to the external environment.

[0039] The heating unit includes a heat network heater 18, a heat network 19, and a heat network preheater 20. The first outlet of the heat network heater 18 is connected to the inlet of the heat network 19, the outlet of the heat network 19 is connected to the first inlet of the heat network preheater 20, the first outlet of the heat network preheater 20 is connected to the first inlet of the heat network heater 18, the third outlet of the intermediate pressure cylinder 2 is connected to the second inlet of the heat network heater 18, the second outlet of the heat network heater 18 is connected to the third inlet of the second low-pressure heater 10, the second outlets of the first intercooler 24, the second intercooler 25, and the third intercooler 26 are connected to the second inlet of the heat network preheater 20, and the second outlet of the heat network preheater 20 is connected to the first inlet of the third low-pressure heater 9.

[0040] The MSHS unit includes a molten salt hot tank 21, a molten salt cold tank 22, a molten salt heater 23, and a first valve 40. The second outlet of the boiler 17 is connected to the inlet of the first valve 40, the outlet of the first valve 40 is connected to the second inlet of the molten salt heater 23, the second outlet of the molten salt heater 23 is connected to the third inlet of the second high-pressure heater 15, the second outlets of the first reheater 33, the second reheater 34, and the third reheater 35 are connected to the inlet of the molten salt cold tank 22, the outlet of the molten salt cold tank 22 is connected to the first inlet of the molten salt heater 23, the first outlet of the molten salt heater 23 is connected to the inlet of the molten salt hot tank 21, and the outlet of the molten salt hot tank 21 is connected to the second inlet of the first reheater 33, the second reheater 34, and the third reheater 35.

[0041] The outlet of boiler 17 in the CFPP unit is connected to the inlet of molten salt heater 23 in the MSHS unit and is controlled by the first valve 40.

[0042] The outlet of the molten salt hot tank 21 in the MSHS unit is connected in sequence to the inlet of the first reheater 33, the second reheater 34, and the third reheater 35 in the CAES unit.

[0043] The outlet of the third turbine 38 of the CAES is connected to the inlet of the feedwater preheater 7 in the CFPP and is controlled by the third valve 42.

[0044] During the energy release process, the MSHS unit provides a heat source for the pre-stage expansion of the CAES unit, eliminating the need for steam extraction and reheating by the CFPP unit. Furthermore, the mid-temperature exhaust gas at the outlet of the last turbine of the CAES unit is used to preheat the feedwater at the outlet of the condensate pump, and some of the waste heat is sent to the CFPP unit.

[0045] Furthermore, the heat source for the MSHS unit is the reheat steam from the outlet of boiler 17 in the CFPP unit.

[0046] Furthermore, the first generator 4 in the CFPP unit provides power to the motor 30 in the CAES unit.

[0047] Furthermore, the outlet of the intermediate pressure cylinder 2 in the CFPP unit is connected to the inlet of the heating network heater 18 in the heating unit.

[0048] Furthermore, the outlet of the water preheater 7 in the CFPP unit is sequentially connected to the inlets of the first intercooler 24, the second intercooler 25, and the third intercooler 26 in the CAES unit, and is controlled by the second valve 41.

[0049] Furthermore, the outlet of the molten salt heater 23 in the MSHS unit is connected to the outlet of the first high-pressure heater 16 in the CFPP unit and they both flow into the inlet of the second high-pressure heater 15 in the CFPP unit.

[0050] During the energy storage process, after the MSHS unit absorbs the heat of the reheat steam, the cooled and condensed steam and the outlet condensate of the first high-pressure heater 16 flow together into the second high-pressure heater 15.

[0051] Furthermore, the outlet of the heating network heater 18 of the heating unit is connected to the outlet of the first low-pressure heater 11 in the CFPP unit and they both flow into the inlet of the second low-pressure heater 10 in the CFPP unit.

[0052] After the heating unit absorbs the heat from the final stage of the high-pressure cylinder 1, the cooled and condensed steam and the condensate from the outlet of the first low-pressure heater 11 flow together into the second low-pressure heater 10.

[0053] Furthermore, the outlet of the heat network preheater 20 in the heating unit is connected to the outlet of the fourth low-pressure heater 8 in the CFPP unit and they both flow into the inlet of the third low-pressure heater 9 in the CFPP unit.

[0054] During the energy storage process, after the condensate pump outlet feedwater absorbs the heat of compression, it preheats the heating hot water in the heating network preheater 20. The cooled feedwater and the feedwater from the outlet of the fourth low-pressure heater 8 flow together into the third low-pressure heater 9.

[0055] Furthermore, the outlets of the first reheater 33, the second reheater 34, and the third reheater 35 in the CAES unit are merged and connected together to the inlet of the molten salt cold tank 22 in the MSHS unit.

[0056] The working process of this embodiment can be divided into an energy storage process and an energy release process.

[0057] In the CFPP unit of the energy storage process, the first valve 40 is open, the second valve 41 is open, and the third valve 42 is closed. The feedwater preheater 7 does not participate in the operation. The main steam from the boiler 17 outlet is sent to the molten salt heater 23 through the first valve 40, and the remaining main steam enters the high-pressure cylinder 1 to do work. During this period, part of the extracted steam is sent to the first high-pressure heater 16 to heat the feedwater. The cooled and depressurized steam from the outlet of the high-pressure cylinder 1 is sent to the second high-pressure heater 15 to heat the feedwater, and the remaining part is sent to the boiler 17 to absorb heat. The reheated steam is then sent to the intermediate-pressure cylinder 2 to do work. During this period, a second extraction is performed. The first stage extraction steam is sent to the third high-pressure heater 14 to heat the feedwater, and the second stage extraction steam is sent to the deaerator 12. The cooled and depressurized steam from the outlet of the intermediate-pressure cylinder 2 is sent to the first low-pressure heater 11 to heat the feedwater, part of it is sent to the heating network heater 18 for heating, and the remaining part is sent to the low-pressure cylinder 3 for final work. Steam is extracted three times. The first stage of extraction steam is sent to the second low-pressure heater 10 to heat the feedwater. The second stage of extraction steam is sent to the third low-pressure heater 9 to heat the feedwater. The third stage of extraction steam is sent to the fourth low-pressure heater 8 to heat the feedwater. After the work is completed, the steam at the outlet of the low-pressure cylinder 3 is sent to the condenser 5 for condensation and liquefaction. The liquefied steam is sent to the intercooler of the CAES unit through the circulating water pump 6 and the second valve 41. The remaining circulating feedwater is sent to the fourth low-pressure heater 8, the third low-pressure heater 9, the second low-pressure heater 10, and the first low-pressure heater 11 for gradual heating. The heated circulating feedwater is then sent to the deaerator 12, where it is combined with the second stage extraction steam from the intermediate-pressure cylinder 2 and the condensed steam at the outlet of the high-pressure cylinder 1. The feedwater at the outlet of the deaerator 12 is then sent to the third high-pressure heater 14, the second high-pressure heater 15, and the first high-pressure heater 16 for gradual heating through the feedwater pump 13. The heated feedwater is then sent to the boiler 17.

[0058] During the energy release process, the first valve 40 is closed, the second valve 41 is closed, the third valve 42 is opened, the feedwater preheater 7 is engaged, and all the main steam from the boiler 17 outlet is sent into the high-pressure cylinder 1 to do work. The circulating feedwater from the outlet of the circulating water pump 6 does not need to be diverted. It is first preheated in the feedwater preheater 7 and then sent into the fourth low-pressure heater 8.

[0059] In the heating unit of the energy storage process, the circulating water from the outlet of the circulating water pump 6 enters the first intercooler 24, the second intercooler 25, and the third intercooler 26 in the CAES unit to absorb heat from the high-temperature, high-pressure air. The heated circulating water then enters the heating network preheater 20 to preheat the heating hot water at the outlet of the heating network 19. The cooled circulating water is then sent to the third low-pressure heater 9. The preheated heating hot water then enters the heating network heater 18 to absorb heat from the steam extracted from the outlet of the intermediate-pressure cylinder 2. The hot water, further heated to the rated heating temperature, enters the heating network 19 to provide hot water to users. The cooled and condensed steam extracted from the outlet of the intermediate-pressure cylinder 2 is then sent to the second low-pressure heater 10. In the energy release process, the working principle of the heating unit is basically the same, but the heating network preheater 20 stops working, and there is no longer a diversion of circulating water or a preheating process for the heating hot water. Instead, the heating hot water at the outlet of the heating network 19 is directly sent to the heating network heater 18.

[0060] In the MSHS unit of the energy storage process, the first valve 40 is opened, and the reheat steam from the boiler 17 outlet passes through the first valve 40, sending a portion of the reheat steam into the molten salt heater 23. This heats the molten salt at the outlet of the molten salt cold tank 22 to a high temperature and then sends it to the molten salt hot tank 21 for storage. The condensed reheat steam is then sent to the second high-pressure heater 15. During the energy release process, the high-temperature molten salt in the molten salt hot tank 21 enters the first reheater 33, the second reheater 34, and the third reheater 35, heating the low-temperature high-pressure air to a high-temperature high-pressure state. The cooled molten salt then enters the molten salt cold tank 22 for storage.

[0061] In the CAES unit of the energy storage process, the second valve 41 is opened, and under the drive of the motor 30, ambient temperature and pressure air enters the first compressor 27, the first intercooler 24, the second compressor 28, the second intercooler 25, the third compressor 29, and the third intercooler 26 in sequence for multi-stage compression and inter-stage cooling. During this process, the heat of compression is absorbed by the circulating feedwater of the CFPP. The cooled high-pressure air then enters the gas storage chamber 31 for storage. During the energy release process, the third valve 42 is opened, and the high-pressure air at the outlet of the gas storage chamber 31 enters the throttle valve 32 for cooling and depressurization. Then, it enters the first reheater 33, the first turbine 36, the second reheater 34, the second turbine 37, the third reheater 35, and the third turbine 38 in sequence to absorb the heat of the high-temperature molten salt for pre-stage reheating and multi-stage expansion to do work, and drives the second generator 39 to generate electricity. The medium-temperature and low-pressure air at the outlet of the third turbine 38 then enters the feedwater preheater 7 to preheat the circulating feedwater, and finally is discharged into the atmosphere.

[0062] This embodiment discloses a configuration method for a coal-fired cogeneration system based on composite thermal storage cascade utilization. Applying the coal-fired cogeneration system based on composite thermal storage cascade utilization described in the above embodiment, the capacity of the CAES unit and the MSHS unit is configured. See [link to relevant documentation]. Figure 2 As shown, the specific steps include:

[0063] Step 1: Obtain environmental conditions, the structural form of the cogeneration unit, the boundary conditions for safe operation, and the heat source of the MSHS unit;

[0064] Step 2: Set the relevant parameters for operating the cogeneration unit independently;

[0065] Set the following parameters for a stand-alone cogeneration unit: main steam pressure, main steam temperature, main steam flow rate during energy storage and release, reheat steam pressure, reheat steam temperature, exhaust back pressure, turbine isentropic efficiency, turbine mechanical efficiency, generator efficiency, pressure difference between the upper and lower ends of the high-pressure heater, pressure difference between the upper and lower ends of the low-pressure heater, heating steam pressure, feedwater pressure, rated heating capacity, heating return water temperature, heating feedwater temperature, heating feedwater pressure, CAES unit compressor inlet pressure, compressor outlet pressure, compressor adiabatic efficiency, throttle valve pressure drop, expander unit outlet pressure, expander adiabatic efficiency, maximum operating pressure of the gas storage chamber, energy storage time, energy release time, MSHS unit molten salt hot tank temperature, molten salt cold tank temperature, and molten salt pressure.

[0066] Step 3: Set the total energy storage capacity, CAES unit energy storage capacity, and MSHS unit energy storage capacity;

[0067] Given the total energy storage capacity, the CAES unit energy storage capacity, and the MSHS unit energy storage capacity, based on all set conditions, the main steam flow rate, boiler heat consumption and coal consumption, turbine power generation, heating unit heat supply, CAES unit power generation, and the entire system's energy storage capacity are calculated during both the energy storage and release periods. Efficiency and flexible operating range.

[0068] Step 4: Determine whether the main steam flow rate during energy storage and release meets the boundary conditions for safe operation of the cogeneration unit. If not, further adjust the total energy storage capacity, CAES unit energy storage capacity, and MSHS unit energy storage capacity until all iterative calculations reach the optimal value. Efficiency and flexible operating range.

[0069] Determine whether the main steam flow rate during energy storage and energy release meets the boundary conditions for safe operation of the cogeneration unit. If not, adjust the total energy storage capacity by increasing the step size from the current value and continue the calculation.

[0070] If the main steam flow rate during energy storage and energy release meets the demand, then the entire system is judged... If the efficiency and flexible operating range are greater than the preset value, then all assumed thermodynamic parameters and thermodynamic calculation results are saved as the current optimal values ​​for the current calculation stage.

[0071] If the value is less than or equal to the preset value, the saving step is skipped and the CAES unit energy storage capacity is directly determined to meet the requirements. If it does not meet the requirements, the energy storage capacity of the CAES unit is adjusted. If the main steam flow rate is too low during energy storage or too high during energy release, the energy storage capacity of the CAES unit is reduced, and then the calculation is performed again according to the design method.

[0072] If the CAES unit energy storage capacity has not yet reached its maximum value, then increase the CAES unit energy storage capacity by one step and continue the calculation.

[0073] If the maximum value has been reached, determine whether the energy storage capacity of the MSHS unit has reached the maximum value. If it has not yet reached the maximum value, increase the energy storage capacity of the MSHS unit by one step and continue the calculation.

[0074] If the maximum value has been reached, the entire calculation process ends, and the final output is the best result among all iterative calculation steps. The optimal operating state of the system and the capacity of each device corresponding to efficiency and flexible operating range.

[0075] Step 5: Set the total energy storage capacity, CAES unit energy storage capacity, and MSHS unit energy storage capacity according to the optimized and adjusted parameters in Step 4.

[0076] The design work begins by inputting the environmental conditions (ambient temperature), the structural form of the CHPP (combined heat and power plant), and the boundary conditions for safe operation (arrangement of low / high pressure heaters, safety boundaries for minimum and maximum main steam flow during energy storage and release, and extraction location of the heating unit), as well as the heat source (extraction location) of the MSHS unit.

[0077] Assumptions are made regarding the operating parameters of a standalone CHPP, including main steam pressure, main steam temperature, main steam flow rate during energy storage and release, reheat steam pressure, reheat steam temperature, exhaust back pressure, turbine isentropic efficiency, turbine mechanical efficiency, generator efficiency, difference between the upper and lower ends of the high-pressure heater, and difference between the upper and lower ends of the low-pressure heater.

[0078] Assumptions are made regarding the operating parameters of the heating unit, including heating steam pressure, feed water pressure, rated heating capacity, heating return water temperature, heating feed water temperature, and heating feed water pressure.

[0079] The operating parameters of the two energy storage systems are assumed as follows: inlet pressure of the CAES unit compressor unit, outlet pressure of the compressor unit, compressor adiabatic efficiency, pressure drop of the throttle valve, outlet pressure of the expander unit, adiabatic efficiency of the expander, maximum working pressure of the gas storage chamber, energy storage time, energy release time, temperature of the molten salt hot tank of the MSHS unit, temperature of the molten salt cold tank, and molten salt pressure.

[0080] Assume the total energy storage capacity (including the upper limit, lower limit and adjustment step size), the energy storage capacity of the CAES unit (including the upper limit, lower limit and adjustment step size), and the energy storage capacity of the MSHS unit (including the upper limit, lower limit and adjustment step size).

[0081] Based on all assumptions, the main steam flow rate, boiler heat consumption and coal consumption, turbine power generation, heating unit heat supply, CAES unit power generation, and the entire system's power generation were calculated during both the energy storage and release periods. Efficiency and flexible operating range.

[0082] Determine whether the main steam flow rate during energy storage and energy release meets the boundary conditions for safe operation of CHPP. If not, adjust the total energy storage capacity by increasing the step size from the current value and continue the calculation.

[0083] If the main steam flow rate during energy storage and energy release meets the demand, then the entire system is judged... The range between efficiency and flexible operating range and preset values.

[0084] If the value is greater than the preset value, all assumed thermodynamic parameters and thermodynamic calculation results are saved as the current optimal value for the current calculation stage.

[0085] If the value is less than or equal to the preset value, the saving step is skipped and the system directly checks whether the CAES unit's energy storage capacity meets the requirements. If it does not meet the requirements, the energy storage capacity of the CAES unit is adjusted. If the main steam flow rate is too low during energy storage or too high during energy release, the energy storage capacity of the CAES unit is reduced, and then the calculation is performed again according to the design method.

[0086] Determine if the CAES unit's energy storage capacity has reached its maximum value. If it has not yet reached its maximum value, increase the CAES unit's energy storage capacity by one step and continue the calculation.

[0087] If the maximum value has been reached, determine whether the energy storage capacity of the MSHS unit has reached the maximum value. If it has not yet reached the maximum value, increase the energy storage capacity of the MSHS unit by one step and continue the calculation.

[0088] If the maximum value has been reached, the entire calculation process ends, and the final output is the best result among all iterative calculation steps. The optimal operating state of the system and the capacity of each device corresponding to efficiency and flexible operating range.

[0089] With the arrangement of three high-pressure units, four low-pressure units, and one deaerator, and the extraction steam position of the heating unit being the outlet of the intermediate-pressure cylinder, and the extraction steam position of the MSHS unit being reheat steam, the basic parameters of the CHPP, CAES, and MSHS units are shown in Tables 1 and 2.

[0090] Table 1

[0091]

[0092]

[0093] Table 2

[0094]

[0095] Performance comparison of conventional CHPP and the coal-fired cogeneration system based on composite thermal storage and cascade utilization proposed in this invention. Figure 3 As shown, coupling the CAES and MSHS units improved the energy efficiency of CHPP by 0.31%. Efficiency increased by 0.33%, and the average standard coal consumption rate for power generation decreased by 4.79 g / kWh.

[0096] The operating output of conventional CHPP, CHPP coupled with CAES units, and the coal-fired cogeneration system based on composite thermal storage cascade utilization proposed in this invention are compared. Figure 4 As shown, coupling the CAES unit can reduce the minimum output during energy storage by 15.1MW, but the maximum output during energy release is reduced by 14.6MW. Further coupling the MSHS unit, i.e., the coal-fired cogeneration system based on composite thermal storage cascade utilization designed in this invention, can further reduce the minimum output during energy storage by 12.6MW. Moreover, during energy release, its maximum output increases by 9.2MW compared to conventional CHPP. This indicates that simultaneously coupling the CAES unit and the MSHS unit can not only further reduce the minimum output but also increase the maximum output, significantly expanding the operating range.

[0097] The standard coal consumption rate for energy generation during the energy storage and release periods of conventional CHPP, CHPP coupled with CAES units, and the coal-fired cogeneration system based on composite thermal storage cascade utilization proposed in this invention are compared to, for example... Figure 5As shown, coupling the CAES unit can reduce the standard coal consumption rate for power generation by 34.29 g / kWh during the energy storage process, but it increases the standard coal consumption rate for power generation by 14.00 g / kWh during the energy release process. Further coupling the MSHS unit, i.e., the coal-fired cogeneration system based on composite thermal storage and cascade utilization proposed in this invention, although the standard coal consumption rate for power generation increases by 1.10 g / kWh during the energy storage process, it decreases by 7.05 g / kWh during the energy release process. Throughout the entire energy storage and energy release process, the average standard coal consumption rates for the three processes are 397.05 g / kWh, 395.16 g / kWh, and 392.26 g / kWh, respectively. The average standard coal consumption rate for power generation in the composite thermal storage CHPP is the lowest within one cycle.

[0098] The operable areas of a standalone CHPP and the coal-fired cogeneration system based on composite thermal storage and cascade utilization proposed in this invention are respectively as follows: Figure 6 As shown. Line AB represents the feasible operating domain for a single-machine CHPP, as shown. Figure 6 The area shown in red is as follows: Line AB represents the maximum power limit line, line BC represents the maximum heat load limit line, line CD represents the minimum condensing operating line, and the slope of line CD represents the elasticity coefficient of power and heat load. When operating on line CD, the unit can be regarded as back pressure operation. Line DE is the minimum electrical power limit line, which is limited by the minimum main steam mass flow rate.

[0099] Furthermore, the environmental conditions include ambient temperature; the structural form of the cogeneration unit and the boundary conditions for safe operation include the arrangement of low-pressure and high-pressure heaters and the minimum main steam flow rate and the safety boundary of the minimum main steam flow rate during energy storage and release, as well as the extraction steam location of the heating unit; the heat source of the MSHS unit includes the extraction steam location.

[0100] Furthermore, the total energy storage capacity includes a lower limit, an upper limit, and an adjustment step size; the CAES unit energy storage capacity includes a lower limit, an upper limit, and an adjustment step size; and the MSHS unit energy storage capacity includes a lower limit, an upper limit, and an adjustment step size.

[0101] According to embodiments of the present invention, a coal-fired cogeneration system based on composite thermal storage and cascade utilization utilizes MSHS (Medium-Steam Hydraulic Heat Storage) units to achieve spatiotemporal heat transfer, particularly for coal-fired CHPP (Combustion-Powered Polymer) coupled with CAES (Coal-fired Energy Storage) units. Under a fixed heat supply, the compression heat of the lower-quality CAES unit is replaced with medium-quality intermediate-pressure cylinder extraction steam for heating, and then the medium-quality intermediate-pressure cylinder extraction steam heat is replaced with high-quality reheat steam heat. Simultaneously, the system can store high-quality heat in the form of MSHS, which not only reduces the minimum output of the entire coupled system but also utilizes the MSHS units to heat the CAES units during the energy release process, significantly increasing the maximum output of the entire coupled system. This achieves a two-stage heat replacement and upgrade, further improving the system's energy utilization rate. Furthermore, the mid-temperature air from the final turbine outlet is used to preheat the circulating feedwater, effectively recovering waste heat and further improving the overall energy efficiency of the coupled system and reducing the standard coal consumption rate.

[0102] According to the configuration method of the coal-fired cogeneration system based on composite thermal storage cascade utilization according to the embodiments of the present invention, by optimizing the configuration of total energy storage capacity, CAES unit energy storage capacity and MSHS unit energy storage capacity, the maximum output of the system is effectively improved, while the minimum output of the system is reduced, thereby further improving the performance of the entire system and reducing energy consumption.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A coal-fired cogeneration system based on composite thermal storage cascade utilization, characterized in that, This includes CFPP units, heating units, MSHS units, and CAES units; The boiler outlet in the CFPP unit is connected to the inlet of the molten salt heater in the MSHS unit and controlled by a first valve; the feedwater preheater outlet in the CFPP unit is sequentially connected to the inlets of the first, second, and third intercoolers in the CAES unit and controlled by a second valve; the outlets of the first, second, and third intercoolers in the CAES unit are connected to the inlet of the heating network preheater in the heating unit. The outlet of the heat network preheater in the heating unit is connected to the outlet of the fourth low-pressure heater in the CFPP unit and they both flow into the inlet of the third low-pressure heater in the CFPP unit. The outlet of the molten salt hot tank in the MSHS unit is connected in sequence to the inlet of the first reheater, the second reheater, and the third reheater in the CAES unit; The outlet of the third turbine of the CAES unit is connected to the inlet of the feedwater preheater in the CFPP unit and is controlled by a third valve.

2. The coal-fired cogeneration system based on composite thermal storage and cascade utilization according to claim 1, characterized in that: The heat source for the MSHS unit is the reheat steam from the boiler outlet of the CFPP unit.

3. The coal-fired cogeneration system based on composite thermal storage and cascade utilization according to claim 1, characterized in that: The first generator in the CFPP unit provides power to the motor in the CAES unit.

4. The coal-fired cogeneration system based on composite thermal storage and cascade utilization according to claim 1, characterized in that: The outlet of the intermediate pressure cylinder in the CFPP unit is connected to the inlet of the heating network heater in the heating unit.

5. The coal-fired cogeneration system based on composite thermal storage and cascade utilization according to claim 1, characterized in that: The outlet of the molten salt heater in the MSHS unit is connected to the outlet of the first high-pressure heater in the CFPP unit, and they both flow into the inlet of the second high-pressure heater in the CFPP unit.

6. The coal-fired cogeneration system based on composite thermal storage and cascade utilization according to claim 1, characterized in that: The outlet of the heating network heater of the heating unit is connected to the outlet of the first low-pressure heater in the CFPP unit and they both flow into the inlet of the second low-pressure heater in the CFPP unit.

7. The coal-fired cogeneration system based on composite thermal storage and cascade utilization according to claim 1, characterized in that: The outlets of the first reheater, second reheater, and third reheater in the CAES unit are combined and connected, and converge into the inlet of the molten salt cold tank in the MSHS unit.

8. A configuration method for a coal-fired cogeneration system based on composite thermal storage cascade utilization, characterized in that: The capacity configuration of the CAES unit and the MSHS unit using the coal-fired cogeneration system based on composite thermal storage cascade utilization as described in any one of claims 1 to 7 specifically includes the following steps: Step 1: Obtain environmental conditions, the structural form of the cogeneration unit, the boundary conditions for safe operation, and the heat source of the MSHS unit; Step 2: Set the relevant parameters for operating the cogeneration unit independently; Step 3: Set the total energy storage capacity, CAES unit energy storage capacity, and MSHS unit energy storage capacity; Step 4: Determine whether the main steam flow rate during energy storage and energy release meets the boundary conditions for safe operation of the cogeneration unit. If not, further adjust the total energy storage capacity, CAES unit energy storage capacity, and MSHS unit energy storage capacity until all iterative calculations reach the optimal efficiency and flexible operating range. Step 5: Set the total energy storage capacity, CAES unit energy storage capacity, and MSHS unit energy storage capacity according to the optimized and adjusted parameters in Step 4.

9. The configuration method of a coal-fired cogeneration system based on composite thermal storage cascade utilization according to claim 8, characterized in that: The environmental conditions include ambient temperature; the structural form of the cogeneration unit and the boundary conditions for safe operation include the arrangement of low-pressure and high-pressure heaters, the minimum main steam flow rate and the safety boundary of the minimum main steam flow rate during energy storage and release, and the extraction steam location of the heating unit; the heat source of the MSHS unit includes the extraction steam location.

10. The configuration method of a coal-fired cogeneration system based on composite thermal storage cascade utilization according to claim 8, characterized in that: The total energy storage capacity includes a lower limit, an upper limit, and an adjustment step size; the energy storage capacity of the CAES unit includes a lower limit, an upper limit, and an adjustment step size; the energy storage capacity of the MSHS unit includes a lower limit, an upper limit, and an adjustment step size.

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