Supercritical intermediate reheating coal gas power generation system

Abstract

The invention relates to the technical field of thermal power generation, in particular to a supercritical intermediate reheat gas power generation system which comprises a supercritical intermediate reheat gas boiler, an extraction condensing steam turbine and a power generator. An independent mixed burner and an independent coke oven gas burner are arranged in a hearth of the supercritical intermediate reheat gas boiler, and generated superheated steam is connected with a high-pressure cylinder of the extraction condensing steam turbine through a superheated steam pipeline from a supercritical steam outlet. Reheat steam after acting sequentially passes through a boiler reheater inlet header, a boiler low-temperature reheater, a high-temperature reheater and a boiler reheater outlet header to be connected with an extraction condensing steam turbine intermediate pressure cylinder; dead steam after acting enters a condenser to be condensed, and condensed water passes through a plurality of low-pressure heaters to a deaerator and a plurality of high-pressure heaters to supplement boiler feed water. The method has the beneficial effects that the problems of coal gas diffusion and environmental pollution are solved, the comprehensive energy consumption and the production cost are reduced, and carbon dioxide emission is reduced.

Description

Technical Field

[0001] This invention relates to the field of thermal power generation technology, and in particular to a supercritical intermediate reheat gas power generation system. Background Technology

[0002] Steel production processes generate large quantities of blast furnace gas, converter gas, and coke oven gas, which are important secondary energy sources for steel enterprises. Blast furnace gas is mostly used as heating fuel for steel plants and also for power generation; coke oven gas is generally used as fuel for high-temperature industrial furnaces and as city gas; converter gas is generally used as fuel for industrial kilns or other gas-fired boilers. With the improvement of gas recovery and utilization levels in steel enterprises, the deepening of energy conservation and emission reduction efforts, and the adjustment of energy use structure, along with the elimination of outdated production capacity, there is a period of excess gas after deducting internal consumption in process production, leading to its release. This gas release causes significant economic losses and environmental pollution problems for enterprises. Furthermore, the currently used high-temperature, high-pressure gas generator sets have low steam parameters and a power generation efficiency of approximately 28%, resulting in low energy utilization efficiency.

[0003] Therefore, it is necessary to improve the unit's thermal efficiency and the utilization efficiency of by-product gas by increasing the working fluid parameters above the critical parameters and adopting an intermediate reheat cycle. This will fully utilize the steel plant's own secondary energy sources to produce electricity, increase the self-generation ratio, and alleviate the company's power supply and demand imbalance. Optimizing the allocation of the company's gas resources will reduce overall energy consumption and production costs while simultaneously reducing carbon emissions, resulting in significant economic and environmental benefits. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a supercritical intermediate reheat gas power generation system that can fully recover and utilize by-product gas from steel enterprises for efficient power generation, solving the problems of gas release and environmental pollution. This increases the self-generation ratio of steel enterprises, reduces overall energy consumption and production costs, and decreases carbon dioxide emissions, achieving the goals of energy conservation and emission reduction.

[0005] To achieve the above objectives, the present invention employs the following technical solution: A supercritical intermediate reheat gas power generation system includes a supercritical intermediate reheat gas boiler, a condensing steam turbine, and a generator. The condensing steam turbine is connected to the generator. The supercritical intermediate reheat gas boiler is equipped with separate blast furnace / converter mixed burners and coke oven gas burners in its furnace. The generated superheated steam is connected to the high-pressure cylinder of the condensing steam turbine through a supercritical steam outlet and a superheated steam pipeline. The superheated steam temperature is ≥605℃ and the pressure is ≥25.4MPa.g. The steam generated after the high-pressure cylinder has done work is connected to the low-temperature reheat steam pipeline through the high-pressure cylinder exhaust port and returned to the supercritical intermediate reheat gas boiler. It then passes through the boiler reheater inlet header, the boiler low-temperature reheater, the high-temperature reheater, and the boiler reheater outlet header in sequence. The generated high-temperature reheat steam is connected to the intermediate-pressure cylinder of the extraction condensing steam turbine through the reheat steam pipeline. The high-temperature reheat steam continues to do work through the intermediate-pressure cylinder and the low-pressure cylinder. The temperature of the high-temperature reheat steam is ≥600℃ and the pressure is ≥5.125MPa.g. The exhaust steam discharged after the intermediate-pressure cylinder and low-pressure cylinder perform their work enters the condenser for condensation. The condensate is pumped by the condensate pump into the condensate treatment system. The treated condensate passes through the shaft seal cooler and multiple low-pressure heaters to the deaerator. The deaerator-qualified condensate is pressurized by the feed water pump from the deaerator feed water tank outlet and then sent to the supercritical intermediate reheat gas boiler through multiple high-pressure heaters. The extraction condensing steam turbine is equipped with multi-stage regenerative steam extraction, which supplies gas to multiple low-pressure heaters, multiple high-pressure heaters and deaerators respectively. The voltage at the generator outlet is stepped up to 66kV and 220kV by a three-winding non-excitation voltage regulating transformer before being connected to the grid.

[0006] Furthermore, a gas mixer is provided at the front end of the blast furnace-converter mixing burner, which mixes blast furnace gas and converter gas.

[0007] Furthermore, the combustion air from the blast furnace converter mixed burner and the coke oven gas burner is pressurized by the blower and then preheated in the air preheater before being sent to the furnace for combustion. The combustion air temperature is 290℃~300℃.

[0008] Furthermore, the extraction condensing steam turbine is equipped with a high-pressure bypass system, which includes a high-pressure bypass and a low-pressure bypass. The high-pressure bypass is connected to the superheated steam pipeline, desuperheated and depressurized by the high-pressure bypass valve, and then connected to the low-temperature reheat steam pipeline. The desuperheating water for the high-pressure bypass is taken from the intermediate tap of the feedwater pump. The low-pressure bypass is connected to the reheat steam pipeline, desuperheated and depressurized by the low-pressure bypass valve, and then connected to the condenser. The desuperheating water is taken from the condensate treatment system at the outlet of the condensate pump.

[0009] Furthermore, the multi-stage regenerative steam extraction consists of: a first-stage extraction steam drawn from the high-pressure cylinder to supply the high-pressure heater; a second-stage extraction steam drawn from the low-temperature reheat steam section to supply the high-pressure heater; a third-stage extraction steam drawn from the intermediate-pressure cylinder, which first passes through a steam cooler before entering the high-pressure heater; a fourth-stage extraction steam drawn from the intermediate-pressure cylinder to supply the deaerator; and fifth, sixth, seventh, and eighth-stage extraction steam drawn from the low-pressure cylinder to supply multiple low-pressure heaters.

[0010] Furthermore, the high-temperature reheat steam section of the steam turbine is equipped with an extraction steam interface. The extracted steam is desuperheated and depressurized before being sent to the steam pipeline network, providing a steam pressure of 0.7 to 0.98 MPa, a steam temperature of 300 to 313°C, and an extraction steam rate of 150 t / h to 254 t / h.

[0011] Furthermore, the condensate treatment system is equipped with a recirculation pipeline, which is connected to the condensate pipeline and returns to the condenser via a recirculation valve.

[0012] Furthermore, chemical makeup water is directly supplied to the condenser, without the need for a separate makeup water tank and pump.

[0013] Furthermore, the deaerator is equipped with two steam sources: one source is the fourth-stage extraction steam from the intermediate-pressure cylinder of the extraction-condensing steam turbine, and the other source is auxiliary steam. The auxiliary steam source is drawn from the plant steam header, and the auxiliary steam parameters are 0.6-0.8 MPa and the temperature is 250-300℃.

[0014] Furthermore, the steam supply pipeline from the fourth-stage extraction steam to the deaerator is not equipped with a pressure regulating valve, and the operating pressure varies with the unit load; however, a pressure regulating valve is installed on the auxiliary steam supply pipeline.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1) The supercritical intermediate reheat gas boiler uses blast furnace gas, converter gas and coke oven gas to generate supercritical superheated steam, which is directly fed into the steam turbine to do work. This eliminates the need for steam-water separation in the intermediate steam drum, saving equipment costs. All the heat of the steam is used for power generation, resulting in high steam utilization, high calorific value for power generation, and increased power generation.

[0016] 2) The rational reuse of blast furnace gas, converter gas and coke oven gas has improved the comprehensive utilization rate of gas in steel plants and avoided the waste of gas resources.

[0017] 3) The condensate produced by the steam turbine is heated by a multi-stage low-pressure heater and a multi-stage high-pressure heater and then sent back to the supercritical intermediate reheat gas boiler to supplement the boiler feedwater, thereby reducing the heat required for feedwater preheating, reducing energy demand rate, improving preheating efficiency, and improving the efficiency of the supercritical intermediate reheat gas boiler.

[0018] 4) The multi-stage low-pressure heater and multi-stage high-pressure heater are supplied with steam through the multi-stage regenerative steam extraction of the turbine unit. The multi-stage steam extraction recovers steam heat step by step to heat the boiler feedwater, realizing the cascade utilization of thermal energy and maintaining a highly efficient thermodynamic cycle. The turbine steam resource reuse saves energy consumption and improves steam utilization rate.

[0019] 5) This system makes full use of by-product coal gas from steel enterprises and achieves high-efficiency power generation through supercritical intermediate reheat technology. The system consists of a supercritical intermediate reheat coal gas boiler, a condensing steam turbine, and a generator. While generating electricity, it also provides steam for heating, which significantly improves the secondary energy recovery and utilization rate of steel enterprises, reduces overall energy consumption and production costs, and reduces the unit's heat consumption value to below 7300kJ / kWh. The efficiency of the once-through boiler reaches more than 90.3%, and the unit efficiency reaches more than 43%. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a supercritical intermediate reheat gas power generation system according to the present invention.

[0021] Figure 2 This is a schematic diagram of the supercritical once-through boiler structure described in this invention.

[0022] In the diagram: 1. Steam cooler; 2. High-pressure heater No. 1; 3. High-pressure heater No. 2; 4. High-pressure heater No. 3; 5. Deaerator; 6. Feedwater pump; 7. Low-pressure heater No. 5; 8. Low-pressure heater No. 6; 9. Low-pressure heater No. 7; 10. Low-pressure heater No. 8; 11. Shaft seal cooler; 12. Condensate treatment system; 13. Condensate pump; 14. Condenser; 15. Low-pressure cylinder of turbine; 16. Intermediate-pressure cylinder of turbine; 17. Turbine. 18. High-pressure cylinder; 19. Economizer; 20. High-temperature superheater; 21. Reheater outlet header; 22. Reheater inlet header; 23. High-pressure bypass valve of turbine; 24. Low-pressure bypass valve of turbine; 25. Generator; 26. High-temperature reheater; 27. Screen-type superheater; 28. Low-temperature reheater; 29. ​​Low-temperature superheater; 30. Air preheater; 31. Gas heater; 32. Integrated desulfurization and dust removal device; 33. Water-cooled wall; 34. Steam pipeline network. Detailed Implementation

[0023] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings: Example: Figure 1-2 As shown, the supercritical intermediate reheat gas power generation system consists of a 420t / h supercritical intermediate reheat gas boiler, a 135MW extraction condensing steam turbine, a 135MW generator, and other auxiliary facilities.

[0024] Blast furnace gas and converter gas are mixed in a gas mixer, then fed into a mixed gas header. After being heated in a gas heater, the mixture enters the boiler burner for combustion. Coke oven gas enters the boiler burner through a separate coke oven gas pipeline. The furnace interior is equipped with separate low-NOx double-swirl blast furnace / converter mixed burners and double-swirl coke oven gas burners, with a pressure not less than 2.5 kPa before each type of burner. Both types of burners are arranged in a left-right opposing configuration, totaling 20 burners. Sixteen low-NOx double-swirl blast furnace / converter mixed burners are used, located on the 1st, 2nd, and 3rd floors; four coke oven gas burners are used, located on the 4th floor. Each burner is equipped with an ignition gun. The gas pipeline before the burner is sequentially equipped with a regulating valve, a pneumatic quick-cut valve, and another pneumatic quick-cut valve. The burner's output power meets the evaporation capacity of a once-through boiler of 420 t / h. Cold air, pressurized by a blower, enters the boiler tubular air preheater 29 for heat exchange. The heated air, reaching 300°C, is then piped to the air-side inlet of each burner and sent to the furnace for combustion. Boiler feedwater absorbs heat released from gas combustion within the fully welded membrane water-cooled wall 32, directly heating to a supercritical state. It then passes sequentially through a low-temperature superheater 28, a screen-type superheater 26, and a high-temperature superheater 19, ultimately forming superheated steam with a temperature ≥605°C and a pressure ≥25.4 MPa.g. The high-temperature flue gas generated in the furnace passes through the screen-type superheater 26, the high-temperature superheater 19, the high-temperature reheater 25, the low-temperature reheater 27, the low-temperature superheater 28, the economizer 18, the air preheater 29, the gas heater 30, and the integrated desulfurization and dust removal equipment 31 before entering the induced draft fan. The induced draft fan then sends the flue gas into the chimney and discharges it into the atmosphere.

[0025] A superheated steam pipe is drawn from the boiler high-temperature superheater 19 and splits into two branches before the turbine speed regulating end. These branches are connected to the high-pressure main steam valves on both sides of the turbine high-pressure cylinder 17. The superheated steam enters the turbine high-pressure cylinder 17 to do work. The rated steam pressure before the main steam valve of the turbine high-pressure cylinder 17 is 24.4 MPa, and the rated temperature is 600℃. After performing work, the steam is drawn from the two exhaust ports of the high-pressure cylinder of the turbine through the low-temperature reheat steam pipeline. It is then merged into a main pipe before the high-pressure exhaust check valve and connected to the boiler reheater inlet header 21. It is then heated in sequence through the boiler low-temperature reheater 27 and high-temperature reheater 25 to generate high-temperature reheat steam. The high-temperature reheat steam is drawn from the reheater outlet header 20. The high-temperature reheat steam temperature is ≥600℃ and the pressure is ≥5.125MPa.g. It is then transported to the turbine intermediate-pressure main steam valve through the reheat steam pipeline and enters the turbine intermediate-pressure cylinder 16 and the turbine low-pressure cylinder 15 to continue performing work. The rated pressure of the steam before the intermediate-pressure main steam valve is 4.379MPa.a and the rated temperature is 600℃.

[0026] Steam exhaust from the turbine enters condenser 14 and condenses into water. The condensate is led out from condenser 14 through the main pipe and then splits into two paths to two full-capacity condensate pumps 13. The outlet pipes of condensate pumps 13 are merged into one path, which then flows through condensate treatment system 12, steam seal cooler 11, low-pressure heater No. 8 10, low-pressure heater No. 7 9, low-pressure heater No. 6 8, and low-pressure heater No. 5 7 to deaerator 5. The condensate from low-pressure heater No. 5 7 is connected to low-pressure heater No. 6 8 via a staged gravity-flow condensate draining method. The condensate from low-pressure heater No. 6 8 flows by gravity to low-pressure heater No. 7 9. The condensate from low-pressure heater No. 7 9 is pumped to the main condensate pipe at the outlet of low-pressure heater No. 7 via two backup low-pressure heater condensate pumps. The condensate from low-pressure heater No. 8 10 flows by gravity into condenser 14. A regulating valve is installed on the low-pressure heater condensate drain pipe to control the heater water level. The condensate from the shaft seal cooler 11 is drained to the condenser 14 through a multi-stage water seal. Chemical makeup water is directly supplied to the condenser 14, without the need for a separate makeup water tank and pump. This simplifies the dedicated makeup water equipment and fully utilizes the vacuum environment and low-temperature heat source of the condenser 14, allowing the makeup water to complete the preheating, pre-deoxygenation, and mixing processes within the condenser 14.

[0027] Deaerator 5 has two steam sources, one from the fourth-stage extraction steam and the other from auxiliary steam. The fourth-stage extraction steam pipeline to deaerator 5 does not have a pressure regulating valve; its operating pressure varies with the unit load, achieving sliding pressure operation. The auxiliary steam supply pipeline has a pressure regulating valve for adjusting the operating pressure of deaerator 5 during unit startup or shutdown. Deaerated boiler feedwater is pressurized from the feedwater tank outlet of deaerator 5 by feedwater pump 6 and then delivered to the boiler economizer 18 via high-pressure heaters 2, 3, 4, and steam cooler 1. Three full-capacity, vertical high-pressure heaters with built-in condensate cooling sections and one external steam cooler 1 are installed. The condensate drains from the high-pressure heaters all employ a staged gravity-flow condensate draining method, discharging from the higher-pressure heater to the lower-pressure heater. For example, condensate from high-pressure heater 2 (No. 1) flows by gravity to high-pressure heater 3 (No. 2), then to high-pressure heater 4 (No. 3), and finally, condensate from the outlet of high-pressure heater 4 flows into deaerator 5. Each circuit is equipped with a pneumatic regulating valve to control the high-pressure heater water level. The water side of the high-pressure heaters utilizes a large bypass system. In the event of a failure in any high-pressure heater, the inlet three-way valve and outlet electric gate valve of the high-pressure heater will activate rapidly, diverting feedwater through the bypass and shutting down all high-pressure heaters.

[0028] The steam turbine has eight stages of regenerative steam extraction, supplying steam to three high-pressure heaters, one deaerator, and four low-temperature heaters. The first stage of extraction steam from the high-pressure cylinder 17 supplies high-pressure heater 2 (No. 1); the second stage from the low-temperature reheat steam section supplies high-pressure heater 3 (No. 2); and the third stage from the intermediate-pressure cylinder 16 passes through steam cooler 1 before entering high-pressure heater 4 (No. 3). The fourth stage from the intermediate-pressure cylinder 16 supplies deaerator 5, and the fifth, sixth, seventh, and eighth stages from the low-pressure cylinder 15 supply low-pressure heaters 7 (No. 5), 8 (No. 6), 9 (No. 7), and 10 (No. 8), respectively. This multi-stage extraction recovers steam heat to heat the boiler feedwater, achieving cascaded utilization of thermal energy and maintaining a highly efficient thermodynamic cycle. The eight-stage regenerative steam extraction gradient regeneration provides more even heat recovery and better regeneration efficiency.

[0029] The parameters of the eight-stage regenerative extraction steam turbine under rated operating conditions of the 135MW extraction condensing steam turbine of this invention are shown in Table 1.

[0030] Table 1 - Parameters of eight-stage regenerative steam extraction for a 135MW extraction condensing steam turbine under rated operating conditions in Embodiment 1 of the present invention: A steam pipeline 33 is installed from the extraction interface of the high-temperature reheat steam section of the steam turbine to the heating network. The steam pressure is 0.7MPa and the steam temperature is 313℃. The extraction steam rate under normal operating conditions is 150t / h, and the extraction steam rate under maximum operating conditions is 254t / h.

[0031] The turbine bypass system adopts a 30% BMCR high- and low-pressure two-stage series bypass system to ensure safe unit operation. The extraction-condensing steam turbine is equipped with a high-pressure bypass system, which includes a high-pressure bypass and a low-pressure bypass. The high-pressure bypass is connected from the superheated steam pipeline, desuperheated and depressurized by the turbine high-pressure bypass valve 22, and then connected to the low-temperature reheat steam pipeline. The desuperheating water for the high-pressure bypass is taken from the intermediate tap of the feedwater pump. The low-pressure bypass is connected from the reheat steam pipeline, desuperheated and depressurized by the turbine low-pressure bypass valve 23, and then connected to the condenser. The desuperheating water is taken from the condensate treatment system at the condensate pump outlet.

[0032] The condensate treatment system is equipped with a recirculation pipeline, which is connected to the condensate pipeline at the outlet of the shaft seal cooler 11 and returns to the condenser through the recirculation valve to prevent condensate pump cavitation and ensure that there is enough condensate flowing through the shaft seal cooler 11 during unit startup and low-load operation.

[0033] The power generated by generator 24 is stepped up to 66kV and 220kV via a three-winding off-grid voltage regulating transformer, and then connected to the 66kV busbar and 220kV busbar of the steel plant substation via one 66kV cable and one 220kV overhead line, respectively. The step-up transformer has a capacity of 190MVA, a voltage ratio of 242±2×2.5% / 66±2×2.5% / 15.75kV, and short-circuit impedances between windings of UdI-II=23%, UdI-III=14%, and UdII-III=8%, respectively. The connection group is YN,d11,d11. A circuit breaker is installed at the generator outlet, with the generator outlet circuit breaker, the 66kV side circuit breaker of the step-up transformer, and the 220kV side circuit breaker serving as grid connection switches. A plant service branch is provided between the generator and the main transformer, supplying power to the plant service system via a high-voltage plant service split-winding transformer.

[0034] Table 2 shows a comparison of the beneficial effects of the embodiments of the present invention with those of the comparative examples; the comparative example is the effect of a traditional gas-fired high-temperature and high-pressure boiler generating electricity through a steam turbine.

[0035] Table 2 - Comparison of beneficial effects of the embodiments of the present invention and comparative examples: From the above embodiments and comparative examples, it can be concluded that the heat consumption of the supercritical intermediate reheat gas power generation system of the present invention is reduced to below 7300kJ / kWh, the efficiency of the DC boiler reaches more than 90.3%, and the unit efficiency reaches more than 43%.

[0036] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A supercritical intermediate reheated gas power generation system comprising a supercritical intermediate reheated gas boiler, an extraction condensing steam turbine, and an electric generator, the extraction condensing steam turbine being connected to the electric generator, characterized in that, The supercritical intermediate reheating coal gas boiler is provided with a single blast furnace converter mixed burner and a coke oven gas burner in the furnace, and the generated superheated steam is connected to the high-pressure cylinder of the extraction condensing steam turbine through a superheated steam pipeline from the supercritical steam outlet, wherein the superheated steam temperature is greater than or equal to 605 DEG C, and the pressure is greater than or equal to 25.4 MPa.g. The steam after work of the high-pressure cylinder is connected to the low-temperature reheating steam pipeline from the high-pressure cylinder exhaust port to return to the supercritical intermediate reheating coal gas boiler, sequentially passes through a boiler reheater inlet header, a boiler low-temperature reheater, a boiler high-temperature reheater and a boiler reheater outlet header, and the generated high-temperature reheating steam is connected to the intermediate-pressure cylinder of the extraction condensing steam turbine through a reheating steam pipeline, and the high-temperature reheating steam continues to work through the intermediate-pressure cylinder and the low-pressure cylinder, wherein the high-temperature reheating steam temperature is greater than or equal to 600 DEG C, and the pressure is greater than or equal to 5.125 MPa.g. The exhaust steam discharged from the intermediate-pressure cylinder and the low-pressure cylinder is condensed into the condenser, and the condensed water is extracted into the condensed water treatment system through a condensed water pump, and the treated condensed water sequentially passes through a shaft seal cooler, multiple low-pressure heaters and a deaerator; the deaerated condensed water is extracted from the deaerator feed water tank outlet through a feed water pump, and is sent to the supercritical intermediate reheating coal gas boiler through multiple high-pressure heaters. The extraction condensing steam turbine is provided with multiple levels of backheating extraction steam for supplying multiple low-pressure heaters, multiple high-pressure heaters and a deaerator. The voltage of the generator outlet is boosted to 66 kV and 220 kV through a three-winding no-excitation voltage regulating transformer and is connected to a power grid.

2. A supercritical intermediate reheated gas power generation system according to claim 1, characterized in that, The blast furnace converter mixed burner is provided with a gas mixer at the front end, and the gas mixer mixes blast furnace gas and converter gas.

3. A supercritical intermediate reheated gas power generation system according to claim 1, wherein The combustion air of the blast furnace converter mixed burner and the coke oven gas burner is pressurized through a blower, preheated through an air preheater and then sent to the furnace combustion, and the combustion air temperature is 290 DEG C to 300 DEG C.

4. A supercritical intermediate reheated gas power generation system according to claim 1, wherein The extraction condensing steam turbine is provided with a turbine high-pressure bypass system, the turbine high-pressure bypass system includes a high-pressure bypass and a low-pressure bypass; the high-pressure bypass is connected from the superheated steam pipeline, is reduced in temperature and pressure through a turbine high-pressure bypass valve and is then connected to the low-temperature reheating steam pipeline, and the temperature-reducing water is taken from the intermediate tap of the feed water pump; the low-pressure bypass is connected from the reheating steam pipeline, is reduced in temperature and pressure through a turbine low-pressure bypass valve and is then connected to the condenser, and the temperature-reducing water is taken from the condensed water treatment system at the outlet of the condensed water pump.

5. A supercritical intermediate reheated gas power generation system as claimed in claim 1 wherein, The multiple levels of backheating extraction steam are a first extraction steam taken from the high-pressure cylinder for supplying the high-pressure heater; a second extraction steam taken from the low-temperature reheating steam section for supplying the high-pressure heater; a third extraction steam taken from the intermediate-pressure cylinder, which first passes through a steam cooler and then enters the high-pressure heater; a fourth extraction steam taken from the intermediate-pressure cylinder for supplying the deaerator; and fifth, sixth, seventh and eighth extraction steams taken from the low-pressure cylinder for respectively supplying multiple low-pressure heaters.

6. A supercritical intermediate reheated gas power generation system as claimed in claim 1 wherein, The turbine high-temperature reheating steam section is provided with an extraction interface, the extracted steam is reduced in temperature and pressure and then sent to a steam pipeline network, the steam pressure is 0.7 to 0.98 MPa, the steam temperature is 300 to 313 DEG C, and the extraction amount is 150 t / h to 254 t / h.

7. A supercritical intermediate reheated gas power generation system as claimed in claim 1 wherein, The condensed water treatment system is provided with a recirculation pipeline, the recirculation pipeline is connected to the condensed water pipeline and returns to the condenser through a recirculation valve.

8. A supercritical intermediate reheated gas power generation system as claimed in claim 1 wherein, The chemical make-up water is directly supplied into the condenser without setting make-up water tank and make-up water pump.

9. A supercritical intermediate reheated gas power generation system as claimed in claim 1 wherein, The deaerator is provided with two steam sources, one from the fourth stage extraction steam of the extraction condensing steam turbine, and the other from auxiliary steam, which is drawn from the auxiliary steam main pipe and has a parameter of 0.6-0.8 MPa and a temperature of 250-300 DEG C.

10. A supercritical intermediate reheated gas power generation system as claimed in claim 9 wherein, The fourth stage extraction steam supply pipeline to the deaerator is not provided with a pressure regulating valve, and the operation pressure changes with the change of the unit load; the auxiliary steam supply pipeline is provided with a pressure regulating valve.

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