Steam extraction transformation and heat supply system of secondary reheat unit

Abstract

The invention relates to the field of coal electricity, in particular to a steam extraction transformation and heat supply system of a secondary reheat unit. The existing secondary reheating unit cannot meet the requirements of heat consumption and deep peak regulation of a power plant, is difficult to transform and is easy to jump. The invention provides a secondary reheat unit steam extraction transformation and heat supply system which comprises a boiler, a heat supply part, a cylinder part with an ultrahigh pressure cylinder, a high pressure cylinder, an intermediate pressure cylinder and a low pressure cylinder, a steam extraction unit composed of an ultrahigh pressure side and steam part, a high pressure side and steam part and a low pressure side and steam part, and a condensation water and water supply part with a condenser, a condensation pump, a deaerator and an electric pump. The boiler is connected with all the parts through pipelines, when a unit is started and parameters of the ultrahigh pressure cylinder, the high pressure cylinder and the intermediate pressure cylinder are unqualified, steam sent to the pressure cylinders is sent to the heat supply part through the steam extraction unit, and water of the condenser is sent to the boiler through the condensate pump, the deaerator and the electric pump. The steam supply demand change and heat supply of the unit in the deep peak regulation period can be met, stable operation is achieved, and trip is prevented.

Description

Technical Field

[0001] The present invention relates to the field of coal power, and particularly to a steam extraction retrofit and heating system for a secondary reheat unit. Background Art

[0002] In order to meet the increasing heating demand year by year and the deep peak shaving demand of power plants when the power grid load supply exceeds demand, it is necessary to retrofit the heating system of coal-fired power units. Most of the existing heating system retrofits are for small units, and there are few large units. Small heating units have low parameters and simple system processes, so the retrofit scheme is relatively simple, easy to control, and has little impact on the power grid. The heating energy utilization rate of large units during operation is low and the energy consumption is high. Among them, the secondary reheat units have high parameters such as temperature and pressure, complex system structures, and great difficulties in retrofit and operation. They are prone to tripping during operation, which affects the safety of the power grid. Currently, there are few large unit retrofit cases to achieve auxiliary power grid peak shaving and unit operation. Summary of the Invention

[0003] To solve the technical problems that the current secondary reheat units cannot meet the heating demand and the deep peak shaving demand of power plants, have great retrofit difficulty, are prone to tripping and affect the safety of the power grid, the present invention provides a steam extraction retrofit and heating system for a secondary reheat unit, which can assist the power grid in peak shaving and the unit in safe and stable operation, prevent tripping, and at the same time provide heating, further improving the energy utilization rate and reducing the energy consumption.

[0004] Technical solution adopted by the present invention to solve the technical problem: A steam extraction retrofit and heating system for a secondary reheat unit, comprising a boiler, a heating section, a cylinder section with an ultra-high pressure cylinder, a high pressure cylinder, an intermediate pressure cylinder and a low pressure cylinder, a steam extraction unit composed of an ultra-high bypass and steam section, a high bypass and steam section, and a low bypass and steam section, and a condensate and feed water section with a condenser, a condensate pump, a deaerator and an electric feed pump. The boiler is connected to each section through pipelines. The feature is that when the unit starts up and the parameters are unqualified, the steam sent to the ultra-high pressure cylinder, the high pressure cylinder and the intermediate pressure cylinder is respectively sent to the heating section through the ultra-high bypass and steam section, the high bypass and steam section, and the low bypass and steam section for heat output. The water in the condenser is sent to the deaerator through the pipeline via the condensate pump, and the water in the deaerator is sent to the boiler through the pipeline via the electric feed pump. In the secondary reheat unit of the present invention, the problem of heating is solved by transporting steam through the ultra-high bypass and steam section, the high bypass and steam section, and the low bypass and steam section. The boiler is connected to several sections of the steam extraction unit through pipelines. The steam for heating can be flexibly used from the output of the boiler or the output of several cylinders. Furthermore, the unit can shunt all or part of the steam originally to be sent to each cylinder for work as the steam source for heating according to the actual peak shaving working conditions, or use the steam output from the work of each cylinder as the steam source for heating. When using the steam output from the cylinder body for heating, the steam inside the cylinder body can be effectively adjusted to meet the working requirements of the cylinder body for the change of the grid load, helping the unit to operate stably and preventing tripping. The water in the condenser can be sent to the boiler through the pipeline and become high-temperature and high-pressure steam after heating.

[0005] As a further improvement and supplement to the above technical solution, the present invention adopts the following technical measures: The heating section includes a mixing header, a circulating pump, a water tank, and a steam-water mixing tank. The circulating pump is driven by an electric pump or a circulating pump steam turbine. The water tank is connected to the circulating pump through a circulating pump feed water pipeline. The steam-water mixing tank is respectively connected to the circulating pump and the heating header through a pipe to the steam-water mixing tank and a steam pipe to input water and steam. The steam-water mixing tank is connected to the mixing header through a pipeline. The mixing header inputs the steam sent out by the high bypass and steam section and / or the low bypass and steam section through a pipeline. The mixing header is connected to the boiler through a header-to-boiler pipeline provided with a water pump. The heating header inputs the steam sent out by the ultra-high bypass and steam section through a first heating pipe and / or inputs the steam sent out by the high bypass and steam section through a second heating pipeline. The circulating pump steam turbine is driven by the steam sent out by the high-pressure cylinder or the intermediate-pressure cylinder through a pipeline. When the unit starts up and the parameters are unqualified, the circulating pump is driven by an electric motor. When the unit load rises or falls, the circulating pump is driven by the circulating pump steam turbine. During heating, the circulating pump operates to send the water in the water tank into the steam-water mixing tank, mix it with the steam sent from the heating header, and then output it to the mixing header through a pipeline. The mixing header can also input the steam sent out by the high bypass and steam section and / or the low bypass and steam section through other pipelines. The steam and water in the mixing header can be sent into the boiler through the header-to-boiler pipeline under the action of a water pump as needed. The circulating pump steam turbine can be driven by an electric pump when the unit startup parameters are unqualified, mainly when the steam coming out of the boiler does not meet the standards, and can be driven by the steam sent out by the high-pressure cylinder / intermediate-pressure cylinder when the unit is operating normally and the load rises and falls.

[0006] The ultra-high bypass and steam section includes a primary reheating device, a main steam pipe, an ultra-high pressure exhaust pipe, a pipe to the primary reheater, and an ultra-high bypass pipe. The two ends of the main steam pipe are respectively connected to the boiler and the ultra-high pressure cylinder. The ultra-high pressure cylinder is connected to the ultra-high pressure exhaust pipe to output steam. The two ends of the pipe to the primary reheater are respectively connected to the ultra-high pressure exhaust pipe and the primary reheating device. The two ends of the ultra-high bypass pipe are respectively connected to the main steam pipe and the pipe to the primary reheater. The pipe to the primary reheater is connected to the first heating pipe to connect to the heating header. The steam required for the operation of the ultra-high pressure cylinder comes from the boiler. When the steam index sent out by the boiler does not meet the standards, the steam sent to the ultra-high pressure cylinder can be sent from the ultra-high bypass pipe connected to the main steam pipe into the pipe to the primary reheater and sent to the primary reheating device.

[0007] The condensate and feed water section includes a condenser, condensate pump, deaerator, motor-driven boiler feed pump booster pump, boiler feed pump, and boiler feed turbine. The water in the condenser is sent to the deaerator through the pipe to the deaerator by the condensate pump. A condensate bypass pipe is connected to the pipe to the deaerator and then connected to a water tank. The water in the deaerator is sent to the boiler through a pipe by the motor-driven boiler feed pump, or is sent to the boiler through the booster pump and the boiler feed pump in sequence. The boiler feed turbine is driven by the steam sent out from the high-pressure cylinder, intermediate-pressure cylinder, or auxiliary steam header through a pipe to drive the boiler feed pump. The auxiliary steam header is connected to the steam pipe through a standby steam pipe. The boiler feed pump is connected to the pipes of the first heating pipe and the second heating pipe through two paths of the first steam cooling pipe and the second steam cooling pipe respectively to cool the water flowing through the pipes leading to the heating header. During operation, the water in the condenser can be selectively sent to the deaerator through the pipe to the deaerator and / or sent to the water tank through the pipe to the deaerator and the condensate bypass pipe under the action of the condensate pump. The water in the deaerator can be sent to the boiler through the motor-driven boiler feed pump along one path, or sent to the boiler through the booster pump and the boiler feed pump along another path. The boiler feed turbine operates with the steam sent out from the high-pressure cylinder, intermediate-pressure cylinder, or auxiliary steam header as the driving force to drive the boiler feed pump. The boiler feed pump sends water into the first heating pipe and the second heating pipe through the first and second steam cooling pipes respectively to play a role in cooling the pipes.

[0008] A pipe connecting the extraction steam from the fifth stage to the feed water turbine and a pipe connecting the extraction steam from the high-pressure turbine exhaust to the circulating pump turbine are connected between the steam supply pipes of the circulating pump turbine and the boiler feed turbine. The pipe connecting the extraction steam from the fifth stage to the feed water turbine enables the circulating pump turbine and the boiler feed turbine to share the steam sent out from the low-pressure cylinder, and the pipe connecting the extraction steam from the high-pressure turbine exhaust to the circulating pump turbine enables the circulating pump turbine and the boiler feed turbine to share the steam sent out from the high-pressure cylinder. During operation, the circulating pump turbine and the boiler feed turbine can share the same steam source for driving. The pipe connecting the extraction steam from the fifth stage to the feed water turbine and the pipe connecting the extraction steam from the high-pressure turbine exhaust to the circulating pump turbine connected between the steam supply pipes of the two turbines are respectively used to realize the extraction steam from the low-pressure cylinder exhaust as the driving steam source and the extraction steam from the high-pressure cylinder exhaust as the driving steam source, so as to share the driving steam source.

[0009] The condensate and feed water section further includes a No. 1 high-pressure heater. The No. 1 high-pressure heater is connected to the boiler through the boiler system pipe. The ultra-high-pressure cylinder is connected to the No. 1 high-pressure heater through an extraction pipe No. 1 and sends steam to it. The ultra-high-pressure turbine exhaust pipe is connected to the extraction pipe for ultra-high-pressure turbine exhaust to the extraction pipe No. 1. The other end of the extraction pipe for ultra-high-pressure turbine exhaust to the extraction pipe No. 1 is connected to the extraction pipe No. 1. The extraction pipe No. 1 is connected to the first heating pipe through the extraction pipe to the heating pipe along the steam transmission path after connecting to the extraction pipe for ultra-high-pressure turbine exhaust. After the unit operates normally, the ultra-high-pressure cylinder can output steam through multiple paths of the ultra-high-pressure bypass and the steam section. The output steam can be sent into the heating header and / or sent into the boiler after being heated by the No. 1 high-pressure heater. The steam sent into the heating header can supply heat to users, and the steam heated and temperature-raised by the No. 1 high-pressure heater is sent into the boiler, which can improve the steam output efficiency and steam effect of the boiler, reduce the boiler load and improve the efficiency, and help the unit meet the operating requirements of power grid peak shaving.

[0010] The high bypass and steam section includes a primary reheater steam pipe, a high-pressure cylinder inlet steam pipe, a high bypass pipe, a high-pressure cylinder exhaust pipe, and a high-pressure exhaust to secondary reheater pipe. One end of the primary reheater steam pipe is connected to the primary reheater device, and the other end is divided into two paths, which are respectively connected to the high-pressure cylinder inlet steam pipe and the high bypass pipe. The other ends of the high-pressure cylinder inlet steam pipe and the high bypass pipe are respectively connected to the high-pressure cylinder and the high-pressure exhaust to secondary reheater pipe. The two ends of the high-pressure exhaust to secondary reheater pipe are respectively connected to the high-pressure cylinder exhaust pipe and the secondary reheater device. The high-pressure cylinder exhaust pipe is connected to the steam output from the high-pressure cylinder. The secondary reheater device and the mixing header are connected through a low bypass pipe. The steam coming out of the primary reheater device is transported to the high-pressure cylinder through the primary reheater steam pipe. This path of steam can also be split into two paths or only select one of them according to the actual working conditions through the high-pressure cylinder inlet steam pipe and the high bypass pipe. Among them, the high-pressure cylinder inlet steam pipe directly sends steam into the high-pressure cylinder, and the steam transported by the high bypass pipe can be mixed with a part of the steam output from the high-pressure cylinder and sent into the secondary reheater device through the high-pressure exhaust to secondary reheater pipe; the steam output from the high-pressure cylinder can be sent into the secondary reheater device through the high-pressure exhaust to secondary reheater pipe.

[0011] The pipe section of the high-pressure exhaust to secondary reheater pipe along the steam transmission path after connecting to the high bypass pipe is connected to the heat supply header through the second heat supply pipe. The second heat supply pipe can split the steam transported by the secondary reheater pipe, so that in addition to the path where the steam output from the high-pressure cylinder exhaust pipe passes through the secondary reheater device and is output to the mixing header, the steam can also pass through the second heat supply pipe and be sent into the heat supply header, and then be sent into the steam-water mixing tank through the pipe to be mixed with the water sent from the water tank, and then be sent into the mixing header.

[0012] The high bypass and steam section also includes a second extraction pipe, a third extraction pipe, and a high-pressure exhaust to third extraction pipe. The two ends of the second extraction pipe are respectively connected to the high-pressure cylinder and the second high-pressure heater. The second high-pressure heater is connected to the first high-pressure heater through a pipeline output. The two ends of the third extraction pipe are respectively connected to the high-pressure cylinder and the third high-pressure heater. The third high-pressure heater is connected to the second high-pressure heater through a pipeline output. The first high-pressure heater is connected to the boiler through a pipeline output. The two ends of the high-pressure exhaust to third extraction pipe are respectively connected to the third extraction pipe and the high-pressure cylinder exhaust pipe. According to the needs of the power grid load and the actual working conditions, the steam discharged from the high-pressure cylinder through the second extraction pipe and the third extraction pipe can be heated and raised in temperature through the high-pressure heater and then sent into the heat supply header. Among them, the steam transported by the second extraction pipe is sent into the boiler after being heated by the second high-pressure heater and the first high-pressure heater in sequence. The steam transported by the third extraction pipe is sent into the boiler after being heated by the third high-pressure heater, the second high-pressure heater, and the first high-pressure heater in sequence. The steam transported by the high-pressure cylinder exhaust pipe can also be mixed with the steam transported by the third extraction pipe, and then enter the third high-pressure heater for heating.

[0013] The low bypass and steam section includes a secondary reheat device, a steam inlet pipe to the intermediate pressure cylinder, a low bypass pipe, a fifth extraction pipe, and a fifth extraction to heating pipe. The two ends of the steam inlet pipe to the intermediate pressure cylinder are respectively connected to the secondary reheat device and the intermediate pressure cylinder. The two ends of the low bypass pipe are respectively connected to the secondary reheat device and the mixing header. The two ends of the fifth extraction pipe are respectively connected to the intermediate pressure cylinder and the circulating pump steam turbine. The two ends of the fifth extraction to heating pipe are respectively connected to the fifth extraction pipe and the mixing header. The steam in the intermediate pressure cylinder can be discharged through the fifth extraction pipe and then divided into one path to enter the fifth extraction to feed water steam turbine pipe to provide a driving steam source for the circulating pump steam turbine, realizing that the low bypass and steam section supplies steam to the circulating pump steam turbine. The fifth extraction pipe also branches out another path through the fifth extraction to heating pipe to enter the mixing header and can be used for heating. The secondary reheat device heats the steam sent by the high bypass and steam section and then divides it into two paths. One path is sent to the low pressure cylinder through the steam inlet pipe to the intermediate pressure cylinder, and the other path passes through the low bypass pipe to enter the mixing header.

[0014] The beneficial technical effects of the present invention: By using the pipeline connection in the extraction unit on the existing secondary reheat unit to control the steam output from each cylinder and adjust the steam inside the cylinder to adapt to the change of working conditions, the output steam is heated and pressurized by the high-pressure heater and then sent back to the boiler, reducing the boiler load and enabling it to stably output steam, meeting the change of steam supply demand brought about by sudden changes in working conditions during deep peak shaving of the unit, thereby enabling the unit to operate stably and preventing tripping. When the unit is working, it can divide part or all of the boiler steam delivered to the cylinder section as the heat source steam for heating, or divide part of the steam output from each cylinder as the heat source steam for heating, and adjust the steam inside the corresponding cylinder while heating to cope with the change demand of the cylinder due to the change of working conditions during deep peak shaving of the unit; The condensate and feed water section outputs water to the high-pressure heater for heat exchange and temperature rise, and then sends it to the boiler to be heated into high-temperature and high-pressure steam to drive the steam turbine to work; The mixing header of the heating device obtains the heat source steam by connecting to the secondary reheat device and outputs the steam required for heating for heating users; The boiler can provide the supplement of water and steam through the condenser and / or the mixing header of the heating section during operation. Brief Description of the Drawings

[0015] 1. Figure 1 is the structural schematic diagram of the present invention.

[0016] In the figure: 1. ultra-high pressure cylinder, 1-1. main steam pipe, 1-2 ultra-high bypass pipe, 1-3. ultra-high pressure exhaust pipe, 1-4. to the primary reheater pipe, 1-5. first extraction pipe, 1-6. ultra-high exhaust to the first extraction pipe, 1-7. first extraction to the heating pipe, 1-8. first heating pipe, 2. high pressure cylinder, 2-1. primary reheated steam pipe, 2-2. high pressure cylinder inlet pipe, 2-3. high bypass pipe, 2-4. second extraction pipe, 2-5. high pressure cylinder exhaust pipe, 2-6. third extraction pipe, 2-7. high exhaust to the third extraction pipe, 2-8. high exhaust to the secondary reheater pipe, 2-9. high exhaust to the feed water turbine pipe, 2-10. high exhaust to the circulating pump turbine pipe, 2-11. second heating pipe, 3. intermediate pressure cylinder, 3-1. fifth extraction to the heating pipe, 3-2. fifth extraction pipe, 4. low pressure cylinder, 5. primary reheating device, 6. No. 2 high pressure heater, 7. secondary reheating device, 7-1. intermediate pressure cylinder inlet pipe, 7-2. low bypass pipe, 8. boiler, 9. No. 3 high pressure heater, 10. No. 1 high pressure heater, 10-1. boiler pipe, 11. heating header, 11-1. steam pipe, 11-2. standby steam pipe, 12. auxiliary steam header, 13. deaerator, 13-1. pre-pump pipe, 13-2. motor-driven feed pump, 14. pre-pump, 15. feed water turbine, 16. feed pump, 16-1. to the high pressure heater pipe, 16-2. first steam cooling pipe, 16-3. second steam cooling pipe, 17. circulating pump turbine, 17-1. fifth extraction to the feed water turbine pipe, 17-2. circulating pump, 17-3. to the steam-water mixing tank pipe, 18. steam-water mixing tank, 19. water tank, 19-1. circulating pump feed water pipe, 20. mixing header, 20-1. heating user pipe, 20-2. water pump, 20-3. header to the boiler pipe, 21. low pressure heater, 22. condenser, 22-1. condensate pump, 22-2. condensate bypass pipe, 22-3. to the deaerator pipe. Specific embodiments

[0017] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0018] As Figure 1As shown in the figure, the present invention is a steam extraction transformation and heating system for a secondary reheat unit, which includes a boiler 8, a heating section, a cylinder section, a steam extraction unit, a condensate and feed water section. The cylinder section has a coaxial arrangement of an ultra-high pressure cylinder 1, a high pressure cylinder 2, an intermediate pressure cylinder 3 and a low pressure cylinder 4. The steam extraction unit includes an ultra-high bypass and steam section, a high bypass and steam section, and a low bypass and steam section. The condensate and feed water section includes a condenser 22, a condensate pump 22-1, a deaerator 13 and an electric feed pump 13-2. The boiler 8 is connected to each section through pipelines. When the unit starts up and the parameters are unqualified, the steam sent to the ultra-high pressure cylinder 1, the high pressure cylinder 2 and the intermediate pressure cylinder 3 is all sent to the heating section through the ultra-high bypass and steam section, the high bypass and steam section, and the low bypass and steam section for heat output. The water in the condenser 22 is sent to the deaerator 13 through the condensate pump 22-1 via the pipeline to the deaerator 22-3. The water in the deaerator is sent to the boiler 8 through the electric feed pump 13-2 via the pipeline.

[0019] The unit of the present invention solves the heating problem by transporting steam through the ultra-high bypass and steam section, the high bypass and steam section, and the low bypass and steam section. The boiler is connected to several sections through pipelines. The steam output by the boiler or the steam output by several cylinders can be used as the heat source steam for heating. During operation, the unit can flexibly divert and select the steam to be sent to each cylinder as the steam source for heating according to the actual working conditions and the need for deep peak shaving of the power grid, or use the steam output by the work of each cylinder as the steam source for heating. Further, the selected steam can also be all or part of the steam on the corresponding pipeline, which helps the unit meet the demand for deep peak shaving of the power grid, while ensuring the stable operation of the unit and preventing the adjustment and impact on the power grid safety. The condenser can supply water to the boiler to help the boiler produce steam for the cylinders in the cylinder section.

[0020] Further, the heat supply section includes a mixing header 20, a circulating pump 17-2, a water tank 19, and a steam-water mixing tank 18. The circulating pump 17-2 is driven by an electric pump 13-2 or a circulating pump steam turbine 17. The water tank 19 is connected to the circulating pump 17-2 through a circulating pump feed water pipe 19-1. The steam-water mixing tank 18 is respectively connected to the circulating pump 17-2 and the heat supply header 11 through a pipe to the steam-water mixing tank 17-3 and a steam pipe 11-1 to input water and steam. The steam-water mixing tank 18 is connected to the mixing header 20 through a pipeline output. The mixing header 20 inputs the steam sent by the high bypass and steam section and / or the low bypass and steam section through a pipeline. The mixing header 20 provides heat supply services to users through a heat supply user pipe 20-1. At the same time, the mixing header 20 is connected to the boiler 8 through a header to boiler pipe 20-3 with a water pump 20-2. The heat supply header 11 inputs the steam sent by the ultra-high bypass and steam section through a first heat supply pipe 1-8 and / or inputs the steam sent by the high bypass and steam section through a second heat supply pipe 2-11. The circulating pump steam turbine 17 is driven by the steam sent by the high-pressure cylinder 2 or the intermediate-pressure cylinder 3 through a pipeline. When the unit starts up and the parameters are unqualified, the circulating pump 17-2 is driven by an electric motor. When the unit load decreases, the high bypass and steam section outputs the steam of the high-pressure cylinder 2 to drive the circulating pump steam turbine 17 to work and drive the circulating pump 17-2. When the unit load rises and is relatively high, the air supply source of the circulating pump steam turbine 17 is switched from the steam output by the high-pressure cylinder 2 described above to the steam output by the intermediate-pressure cylinder 3 through the low bypass and steam section.

[0021] The ultra-high bypass and steam section includes a primary reheating device 5, a main steam pipe 1-1, an ultra-high pressure exhaust pipe 1-3, a pipe to the primary reheating pipe 1-4, and an ultra-high bypass pipe 1-2. The two ends of the main steam pipe 1-1 are respectively connected to the boiler 8 and the ultra-high pressure cylinder 1. The ultra-high pressure cylinder 1 is connected to the ultra-high pressure exhaust pipe 1-3 to output the steam in the cylinder. The two ends of the pipe to the primary reheating pipe 1-4 are respectively connected to the ultra-high pressure exhaust pipe 1-3 and the primary reheating device 5. The two ends of the ultra-high bypass pipe 1-2 are respectively connected to the main steam pipe 1-1 and the pipe to the primary reheating pipe 1-4. The pipe to the primary reheating pipe 4 is connected to the heat supply header 11 through the first heat supply pipe 1-8.

[0022] The condensate and feed water section includes a condenser 22, a condensate pump 22-1, a deaerator 13, an electric pump 13-2, a booster pump 14, a feed water pump 16, a feed water turbine 15, and a No. 1 high-pressure heater 10. The water in the condenser 22 is sent into the deaerator 13 through the condensate pump 22-1 via the pipe 22-3 to the deaerator. A low-pressure heater 21 is also installed on the pipe 22-3 to the deaerator for preheating. The condensate bypass pipe 22-2 is connected to the water tank 19 on the pipe 22-3 to the deaerator. The water in the deaerator 13 can be sent into the boiler 8 through the electric pump 13-2 via a pipe, or through the booster pump pipe 13-1 connected to the deaerator 13, passing through the booster pump 14 and the feed water pump 16 in sequence, and then sent into the No. 3 high-pressure heater 9 via the pipe 16-1 connected to the feed water pump 16, and then output from the No. 3 high-pressure heater 9 through a pipeline, passing through the No. 2 high-pressure heater 6 and the No. 1 high-pressure heater 10 and then sent into the boiler 8; the feed water turbine 15 is driven to drive the feed water pump 16 by the steam input through a pipe from the high-pressure cylinder 2 or the intermediate-pressure cylinder 3 or the auxiliary steam header 12, and the auxiliary steam header 12 is connected to the steam pipe 11-1 for outputting steam from the heat supply header 11 through the standby steam pipe 11-2; one path of the first steam cooling pipe 16-2 of the feed water pump 16 is connected to the first heat supply pipe 1-8 to cool the first heat supply pipe 1-8 input into the heat supply header 11 by water cooling, and at the same time, one path of the second steam cooling pipe 16-3 is connected to the second heat supply pipe 2-11 to cool the second heat supply pipe 2-11 input into the heat supply header 11 by water cooling. The No. 1 high-pressure heater 10 is connected to the boiler 8 through the boiler system pipe 10-1. The ultra-high-pressure cylinder 1 is connected to the No. 1 high-pressure heater 10 through the extraction pipe 1-5 to supply steam to it. The ultra-high-pressure exhaust pipe 1-3 is connected to the ultra-high-pressure exhaust to the extraction pipe 1-6. The other end of the ultra-high-pressure exhaust to the extraction pipe 1-6 is connected to the extraction pipe 1-5. Along the steam transmission path of the extraction pipe 1-5, a pipe section after connecting to the ultra-high-pressure exhaust to the extraction pipe 1-6 is connected to the first heat supply pipe 1-8 through the extraction to the heat supply pipe 1-7, so that the exhaust steam of the ultra-high-pressure cylinder 2 can also be sent into the heat supply header 11 through the extraction to the heat supply pipe 1-7 and the first heat supply pipe 1-8 in sequence.

[0023] The high bypass and steam section includes the primary reheater steam pipe 2-1, the high-pressure cylinder steam inlet pipe 2-2, the high bypass pipe 2-3, the high-pressure cylinder exhaust pipe 2-5, the high-pressure exhaust to secondary reheater pipe 2-8, the second extraction pipe 2-4, the third extraction pipe 2-6, and the high-pressure exhaust to third extraction pipe 2-7. One end of the primary reheater steam pipe 2-1 is connected to the primary reheater device 5, and the other end is divided into two paths and respectively outputs and connects to the high-pressure cylinder steam inlet pipe 2-2 and the high bypass pipe 2-3. The output ends of the two paths of the high-pressure cylinder steam inlet pipe 2-2 and the high bypass pipe 2-3 are respectively connected to the high-pressure cylinder 2 and the high-pressure exhaust to secondary reheater pipe 2-8. The pipe section of the high-pressure exhaust to secondary reheater pipe 2-8 along the steam transmission path after accessing the high bypass pipe 2-3 is connected to the heat supply header 11 through the second heat supply pipe 2-11. The input and output ends of the high-pressure exhaust to secondary reheater pipe 2-8 are respectively connected to the high-pressure cylinder exhaust pipe 2-5 and the secondary reheater device 7. The input section of the high-pressure cylinder exhaust pipe 2-5 is connected to the high-pressure cylinder 2 to transport steam, and the output end of the high-pressure cylinder exhaust pipe is connected to the high-pressure exhaust to third extraction pipe 2-7; the secondary reheater device 7 and the mixing header 20 are connected through the low bypass pipe 7-2. The input and output ends of the second extraction pipe 2-4 are respectively connected to the high-pressure cylinder 2 and the second high-pressure heater 6. The second high-pressure heater 6 outputs through a pipe and is connected to the first high-pressure heater 10. The first high-pressure heater 10 outputs through a pipe and is connected to the boiler 8; the input and output ends of the third extraction pipe 2-6 are respectively connected to the high-pressure cylinder 2 and the third high-pressure heater 9. The third high-pressure heater 9 outputs through a pipe and is connected to the second high-pressure heater 6. The input and output ends of the high-pressure exhaust to third extraction pipe 2-7 are respectively connected to the high-pressure cylinder exhaust pipe 2-5 and the third extraction pipe 2-6.

[0024] The low bypass and steam section includes the secondary reheater device 7, the steam inlet pipe to the intermediate-pressure cylinder 7-1, the low bypass pipe 7-2, the fifth extraction pipe 3-2, and the fifth extraction to heat supply pipe 3-1. The input and output ends of the steam inlet pipe to the intermediate-pressure cylinder 7-1 are respectively connected to the secondary reheater device 7 and the intermediate-pressure cylinder 3. The input and output ends of the low bypass pipe 7-2 are respectively connected to the secondary reheater device 7 and the mixing header 20. The input and output ends of the fifth extraction pipe 3-2 are respectively connected to the intermediate-pressure cylinder 3 and the circulating pump steam turbine 17. The input and output ends of the fifth extraction to heat supply pipe 3-1 are respectively connected to the fifth extraction pipe 3-2 and the mixing header 20.

[0025] In this embodiment, the feed water pump steam turbine 15 is connected to the high-pressure exhaust to feed water pump steam turbine pipe 2-9 to dock with the high-pressure exhaust to secondary reheater pipe 2-8. Since the high-pressure exhaust to secondary reheater pipe is connected to the high-pressure cylinder exhaust pipe 2-5, the steam sent out by the high-pressure cylinder 2 can sequentially enter the feed water pump steam turbine through the high-pressure cylinder exhaust pipe, the secondary reheater pipe, and the high-pressure exhaust to feed water pump steam turbine pipe to drive its operation and drive the feed water pump 16 to operate.

[0026] In order to enable the circulating pump steam turbine and the feed water pump steam turbine to share the steam output from the intermediate pressure cylinder 3 as the driving steam source, a pipe 17-1 from the fifth extraction to the feed water steam turbine and a pipe 2-10 from the high-pressure exhaust to the circulating pump steam turbine are also connected between the fifth extraction pipe 3-2 for supplying steam to the circulating pump steam turbine 17 and the pipe 2-9 from the high-pressure exhaust to the feed water pump steam turbine 15. The pipe 17-1 from the fifth extraction to the feed water steam turbine enables the circulating pump steam turbine 17 and the feed water pump steam turbine 15 to share the steam sent out by the low-pressure cylinder 3 through the fifth extraction pipe 3-2, and the pipe 2-10 from the high-pressure exhaust to the circulating pump steam turbine enables the circulating pump steam turbine 17 and the feed water pump steam turbine 15 to share the steam sent out by the high-pressure cylinder 2 through the pipe 2-9 from the high-pressure exhaust to the feed water pump steam turbine. In addition, in this embodiment, installing valves and / or check valves on the pipelines as required are all prior arts, ensuring that the pipelines can achieve the required conveying path and conveying direction, which will not be elaborated here.

[0027] The working process of the present invention is as follows: When the parameters of the unit are just started and unqualified, specifically, four indicators such as the cleanliness, dryness, purity, and pressure / temperature stability of the common steam are unqualified, the ultra-high-pressure exhaust pipe 1-3 and the high-pressure cylinder exhaust pipe 2-5 are closed, and the steam originally to be sent into the ultra-high-pressure cylinder 1, the high-pressure cylinder 2, and the intermediate pressure cylinder 3 are all led out through the ultra-high bypass pipe 1-2, the high bypass pipe 2-3, and the low bypass pipe 7-2 respectively, and are not sent into the aforementioned three cylinders; at this time, the water in the condenser 22 is sent into the deaerator 13 under the action of the condensate pump 22-1, and the water in the deaerator is transported to the boiler 8 through the pipeline under the action of the motor-driven pump 13-2; the steam in the ultra-high bypass pipe 1-2 enters the first heat supply pipe 1-8 and then is sent into the heat supply header 11, and then enters the steam-water mixing tank 18 through the steam pipe 11-1; the steam in the low bypass pipe 7-2 enters the mixing header 20 and then supplies heat to the user through the heat supply user pipe 20-1; the circulating pump 17-2 is driven by the motor to work, pumps water out of the water tank 19 through the circulating pump feed water pipe 19-1 and enters the steam-water mixing tank 18, and then enters the steam-water mixing tank 20, and supplies heat through the heat supply user pipe 20-1.

[0028] When the parameters of the unit are qualified, the ultra-high bypass pipe 1-2, the high bypass pipe 2-3, and the low bypass pipe 7-2 are closed slightly to reduce the steam entering the three pipelines. At the same time, part of the steam of the unit enters the ultra-high-pressure cylinder 1, the high-pressure cylinder 2, and the intermediate pressure cylinder 3, giving priority to ensuring the power generation of the unit and the power supply to the power grid; the ultra-high-pressure cylinder 1 discharges steam through the ultra-high-pressure exhaust pipe 1-3, and part of the steam is branched off from the pipe to the primary reheater 1-4 and converges with the steam sent by the ultra-high bypass pipe 1-2. Part of the mixed steam enters the primary reheating device 5, and part is branched off from the first heat supply pipe 1-8 and enters the heat supply header 11; the high-pressure cylinder 2 sends out high-pressure exhaust steam through the high-pressure cylinder exhaust pipe 2-5, and then enters the heat supply header 11 through the pipe from the high-pressure exhaust to the secondary reheater 2-8 and the second heat supply pipe 2-11.

[0029] When the unit is in operation and the steam volume matches the steam required by the cylinder part of the unit, close the ultra-high bypass pipe 1-2, the high bypass pipe 2-3 and the low bypass pipe 7-2. In actual use, the above-mentioned ultra-high bypass pipe 1-2, high bypass pipe 2-3 and low bypass pipe 7-2 can be closed when the matching degree reaches more than 30%.

[0030] After the unit operates normally, start the extraction steam. The first extraction pipe 1-5 extracts steam from the ultra-high pressure cylinder 1. A part of the steam enters the first high-pressure heater 10, and a part of the steam is sent to the first heating pipe 1-8 in the heating pipeline 1-7 through the first extraction to the heating pipeline, and then sent to the heating header 11; the ultra-high pressure exhaust pipe 1-3 discharges the steam of the ultra-high pressure cylinder 1, and then enters the primary reheater 1-4 and is sent to the primary reheating device 5. At this time, the ultra-high pressure exhaust to the first extraction pipe 1-6 and the ultra-high bypass pipe 1-2 are closed; the exhaust steam of the high-pressure cylinder 2 is sent to the second high-pressure heater 6 through the second extraction pipe 2-4. The steam from the second high-pressure heater enters the first high-pressure heater 10 and is sent to the boiler 8; the third extraction pipe 2-6 discharges the steam of the high-pressure cylinder 2. One part of the steam enters the third high-pressure heater 9, and the other part enters the second heating pipe 2-11 through a branch pipe separated from the third extraction pipe 2-6 and is sent to the heating header 11; the steam conveyed by the high-pressure cylinder exhaust pipe 2-5 enters the secondary reheater 7 through the high-pressure exhaust to the secondary reheater pipe 2-8, and the high bypass pipe 2-3 remains closed.

[0031] The steam output from the secondary reheating device 7 enters the intermediate pressure cylinder 3, and the low bypass pipe 7-2 is closed; the steam output from the intermediate pressure cylinder 3 is divided into two paths. One path enters the mixing header 20 through the fifth extraction pipe 3-1, and the other path enters the circulating pump steam turbine 17 to drive its operation, and at the same time enters the feed water pump steam turbine 15 through the fifth extraction to the feed water pump steam turbine pipe 17-1 to drive its operation. The steam sent to the feed water pump steam turbine needs to meet the temperature and pressure standards. The steam drives the above two steam turbines to rotate. At this time, the circulating pump 17-2 is changed from the initial motor drive to the circulating pump steam turbine 17 drive, and at the same time the electric pump 13-2 is stopped. The feed water pump 16 operates driven by the feed water pump steam turbine 15. The water in the deaerator 13 passes through the pre-pump pipe 13-1 and is sent to the feed water pump 16 through the pre-pump 14. The function of the pre-pump here is to increase the pressure at the inlet of the feed water pump to prevent cavitation. The water from the feed water pump 16 is divided into three paths after coming out. The first path passes through the high-pressure heater pipe 16-1 and successively passes through the first high-pressure heater 10, the second high-pressure heater 6 and the third high-pressure heater 9 to the boiler pipe 10-1, and finally is sent to the boiler 8; the second path and the third path respectively pass through the first steam cooling pipe 16-2 and the second steam cooling pipe 16-3 and enter the corresponding first heating pipe 1-8 and the second heating pipe 2-11 for temperature reduction and cooling. A part of the steam in the heating header 11 is sent to the auxiliary steam header 12. The steam in the auxiliary steam header can be output in two paths. One path is used as the standby steam source of the feed water pump steam turbine 15, and the other path enters the deaerator 13 as the heating source.

[0032] When the load of the unit is reduced during peak load operation, the ultra-high exhaust to the first extraction pipe 1-6 is opened, and part of the steam coming out of the ultra-high pressure exhaust pipe 1-3 enters the first extraction pipe 1-5 through the ultra-high exhaust to the first extraction pipe 1-6, so as to alleviate the instantaneous excessive amount of steam entering the ultra-high pressure cylinder, and the first extraction pipe cannot exhaust the steam in time. At this time, the ultra-high exhaust to the first extraction pipe can assist in rapid steam exhaust, and part of the steam entering the first extraction pipe 1-5 enters the heating header 11 through the first extraction to the heating pipe 1-7; in addition, the high exhaust to the third extraction pipe 2-7 is opened, and the high pressure cylinder steam output from the high pressure cylinder exhaust pipe 2-5 enters the third extraction pipe 2-6 through the high exhaust to the third extraction pipe 2-7, and then enters the second heating pipe 2-11 through the pipeline connecting the third extraction pipe 2-6 and the second heating pipe 2-11, and is finally sent to the heating header 11 At this time, the gas source of the circulating pump steam turbine 17 and the feedwater pump steam turbine 15 is switched to the high-pressure cylinder steam output by the high-pressure cylinder exhaust pipe 2-5, the five-extraction to feedwater steam turbine pipe 17-1 is closed, and the high-pressure exhaust to the circulating pump steam turbine pipe 2-10 is opened. The steam output by the high-pressure cylinder 2 is sent to the feedwater pump steam turbine 15 through the high-pressure cylinder exhaust pipe 2-5, the high-pressure exhaust to secondary reheat pipe 2-8, and the high-pressure exhaust to the feedwater pump steam turbine pipe 2-9. At the same time, part of the steam is introduced into the rear section of the five-extraction pipe 3-2 by using the high-pressure exhaust to the circulating pump steam turbine pipe 2-10 branched off from the high-pressure exhaust to the feedwater pump steam turbine pipe 2-9, and sent to the circulating pump steam turbine 17. The steam sent out by the medium-pressure cylinder 3 through the front section of the five-extraction pipe 3-2 is all sent to the mixing manifold 20 through the five-extraction to heating pipe 3-1.

[0033] When the peak load of the unit increases, the super-high exhaust steam to the first extraction pipe 1-6 and the high-pressure cylinder exhaust pipe 2-5 are gradually closed, and the circulating pump turbine 17 and the feed water pump turbine 15 still use the steam output by the high-pressure cylinder 2. If the water temperature of the deaerator is low or the water volume is insufficient during operation, the auxiliary steam header 12 is opened to provide heating for the deaerator 13, and the water pump 20-2 is started. The steam and water in the mixing header 20 are sent to the boiler 8 through the pipeline to help quickly increase the load. At this time, the super-high bypass pipe 1-2, the high bypass pipe 2-3 and the low bypass pipe 7-2 are all closed. The three bypass pipes no longer divert the steam entering each cylinder, and all the steam enters the ultra-high pressure cylinder, the high pressure cylinder, and the medium pressure cylinder for power generation. When the unit load is high and the steam output parameters of the high pressure cylinder 2 exceed the steam supply requirement of the feed water pump turbine 15, the air supply source of the circulating pump turbine 17 and the feed water pump turbine 15 is switched from the steam output of the high pressure cylinder 2 to the steam output of the medium pressure cylinder 3 through the five extraction pipes 3-2. The No. 1 high pressure heater 10, the No. 2 high pressure heater 6 and the No. 3 high pressure heater 9 all maintain the steam discharged from the working input cylinder, which is heated and sent to the boiler 8.

Claims

1. A steam extraction retrofit and heating system for a secondary reheat unit, comprising a boiler (8), a heating section, a cylinder section with an ultra-high pressure cylinder (1), a high pressure cylinder (2), an intermediate pressure cylinder (3) and a low pressure cylinder (4), a steam extraction unit composed of an ultra-high bypass and steam section, a high bypass and steam section, and a low bypass and steam section, a condensate and feed water section with a condenser (22) and a condensate pump (22-1), a deaerator (13) and an electric feed pump (13-2), wherein the boiler (8) is connected to each section through pipelines, and the characteristics are When the ultra-high pressure cylinder (1), high pressure cylinder (2) and intermediate pressure cylinder (3) are in operation during unit startup with unqualified parameters, the steam sent to the ultra-high pressure cylinder (1), high pressure cylinder (2) and intermediate pressure cylinder (3) is respectively sent to the heating section through the ultra-high bypass and steam section, high bypass and steam section, and low bypass and steam section for heat supply output. The water in the condenser (22) is sent to the deaerator (13) through the condensate pump (22-1) via the pipeline to the deaerator (22-3), and the water in the deaerator is sent to the boiler (8) through the motor-driven pump (13-2) via the pipeline.

2. The steam extraction retrofit and heating system of the secondary reheat unit according to claim 1, characterized in that The heating section includes a mixing header (20), a circulating pump (17-2), a water tank (19), and a steam-water mixing tank (18). The circulating pump (17-2) is driven by the motor-driven pump (13-2) or the circulating pump steam turbine (17). The water tank (19) is connected to the circulating pump (17-2) through the circulating pump feed pipe (19-1). The steam-water mixing tank (18) is respectively connected to the circulating pump (17-2) and the heating header (11) through the pipe to the steam-water mixing tank (17-3) and the steam pipe (11-1) to input water and steam. The steam-water mixing tank (18) is connected to the mixing header (20) through the pipeline. The mixing header (20) inputs the steam sent out by the high bypass and steam section and / or the low bypass and steam section through the pipeline. The mixing header (20) is connected to the boiler (8) through the header to boiler pipe (20-3) provided with a water pump (20-2). The heating header (11) inputs the steam sent out by the ultra-high bypass and steam section through the first heating pipe (1-8) and / or inputs the steam sent out by the high bypass and steam section through the second heating pipe (2-11). The circulating pump steam turbine (17) is driven by the steam sent out by the high pressure cylinder (2) or the intermediate pressure cylinder (3) through the pipeline. When the unit starts up with unqualified parameters, the circulating pump (17-2) is driven by the motor. When the unit load rises or falls, the circulating pump (17-2) is driven by the circulating pump steam turbine (17).

3. The steam extraction retrofit and heating system of the double reheat unit according to claim 2, characterized in that The ultra-high bypass and steam section includes a primary reheating device (5), a main steam pipe (1-1), an ultra-high pressure exhaust pipe (1-3), a pipe to the primary reheater (1-4), and an ultra-high bypass pipe (1-2). The two ends of the main steam pipe (1-1) are respectively connected to the boiler (8) and the ultra-high pressure cylinder (1). The ultra-high pressure cylinder (1) is connected to the ultra-high pressure exhaust pipe (1-3) to output steam. The two ends of the pipe to the primary reheater (1-4) are respectively connected to the ultra-high pressure exhaust pipe (1-3) and the primary reheating device (5). The two ends of the ultra-high bypass pipe (1-2) are respectively connected to the main steam pipe (1-1) and the pipe to the primary reheater (1-4). The pipe to the primary reheater (4) is connected to the heating header (11) through the first heating pipe (1-8).

4. The steam extraction retrofit and heating system of the double reheat unit according to claim 3, characterized in that The condensate and feed water unit comprises a condenser (22), a condensate pump (22-1), a deaerator (13), an electric pump (13-2), a pre-pump (14), a feed water pump (16), and a feed water pump turbine (15). The water in the condenser (22) is sent to the deaerator (13) through the condensate pump (22-1) and a deaerator pipe (22-3). The deaerator pipe (22-3) is connected to a condensate auxiliary pipe (22-2) and a water tank (19). The water in the deaerator is sent to the boiler (8) through a pipeline through the electric pump (13-2), or is successively sent to the boiler (8) through the pre-pump (14) and a feed water pump turbine (15). The feed water pump (16) is fed into the boiler (8) through a pipeline, and the feed water pump turbine (15) drives the feed water pump (16) by inputting steam from the high pressure cylinder (2) or the medium pressure cylinder (3) or the auxiliary steam header (12) through a pipeline. The auxiliary steam header (12) is connected to the steam pipe (11-1) through a spare steam pipe (11-2); the feed water pump (16) is connected to the first heat supply pipe (1-8) and the second heat supply pipe (2-11) through a first steam cooling pipe (16-2) and a second steam cooling pipe (16-3) respectively, and the pipe water is input into the heat supply header (11) for cooling.

5. The extraction steam retrofit and heating system of the double reheat unit according to claim 4, characterized in that A five-pump-to-feedwater steam turbine pipe (17-1) and a high-discharge-to-circulating pump steam turbine pipe (2-10) are connected between the steam supply pipeline of the circulating pump steam turbine (17) and the steam supply pipeline of the feedwater pump steam turbine (15). The five-pump-to-feedwater steam turbine pipe (17-1) enables the circulating pump steam turbine (17) and the feedwater pump steam turbine (15) to share the steam delivered by the low-pressure cylinder (3), and the high-discharge-to-circulating pump steam turbine pipe (2-10) enables the circulating pump steam turbine (17) and the feedwater pump steam turbine (15) to share the steam delivered by the high-pressure cylinder (2).

6. The extraction steam retrofit and heat supply system of the double reheat unit according to claim 4, characterized in that The condensate and water supply unit also includes a No. 1 high-pressure heater (10), which is connected to the boiler (8) through the boiler system pipeline (10-1) output, and the ultra-high pressure cylinder (1) is connected to the No. 1 high-pressure heater (10) through a pumping pipe (1-5) and transmits steam to it, and the ultra-high pressure exhaust pipe (1-3) is connected to the ultra-high exhaust to a pumping pipe (1-6), and the other end of the ultra-high exhaust to a pumping pipe (1-6) is connected to a pumping pipe (1-5), and the pumping pipe (1-5) is connected to the first heat supply pipe (1-8) through a pumping to heat supply pipe (1-7) on the pipe section after connecting the ultra-high exhaust to the pumping pipe (1-6) along the steam transmission path.

7. The steam extraction retrofit and heating system for a secondary reheat unit according to claim 2, characterized in that The high bypass and steam section includes a primary reheater steam pipe (2-1), a high-pressure cylinder inlet steam pipe (2-2), a high bypass pipe (2-3), a high-pressure cylinder exhaust pipe (2-5), and a high-pressure exhaust to secondary reheater pipe (2-8). One end of the primary reheater steam pipe (2-1) is connected to the primary reheater device (5), and the other end is divided into two paths and respectively connected to the high-pressure cylinder inlet steam pipe (2-2) and the high bypass pipe (2-3). The other ends of the high-pressure cylinder inlet steam pipe (2-2) and the high bypass pipe (2-3) are respectively connected to the high-pressure cylinder (2) and the high-pressure exhaust to secondary reheater pipe (2-8). The two ends of the high-pressure exhaust to secondary reheater pipe (2-8) are respectively connected to the high-pressure cylinder exhaust pipe (2-5) and the secondary reheater device (7). The high-pressure cylinder exhaust pipe (2-5) is connected to the steam output of the high-pressure cylinder (2). The secondary reheater device (7) and the mixing header (20) are connected through a low bypass pipe (7-2).

8. The steam extraction retrofit and heating system of the double reheat unit according to claim 7, characterized in that On the pipe section of the high-pressure exhaust to secondary reheater pipe (2-8) along the steam transmission path after connecting to the high bypass pipe (2-3), it is connected to the heat supply header (11) through the second heat supply pipe (2-11).

9. The extraction steam retrofit and heat supply system of the double reheat unit according to claim 7, characterized in that The high bypass and steam section also includes a second extraction pipe (2-4), a third extraction pipe (2-6), and a high-pressure exhaust to third extraction pipe (2-7). The two ends of the second extraction pipe (2-4) are respectively connected to the high-pressure cylinder (2) and the No. 2 high-pressure heater (6). The No. 2 high-pressure heater (6) is connected to the No. 1 high-pressure heater (10) through a pipeline output. The two ends of the third extraction pipe (2-6) are respectively connected to the high-pressure cylinder (2) and the No. 3 high-pressure heater (9). The No. 3 high-pressure heater (9) is connected to the No. 2 high-pressure heater (6) through a pipeline output. The No. 1 high-pressure heater (10) is connected to the boiler (8) through a pipeline output. The two ends of the high-pressure exhaust to third extraction pipe (2-7) are respectively connected to the third extraction pipe (2-6) and the high-pressure cylinder exhaust pipe (2-5).

10. The extraction steam retrofit and heating system of the double reheat unit according to any one of claims 2 to 9, characterized in that The low bypass and steam section includes a secondary reheater device (7), a medium-pressure cylinder inlet steam pipe (7-1), a low bypass pipe (7-2), a fifth extraction pipe (3-2), and a fifth extraction to heat supply pipe (3-1). The two ends of the medium-pressure cylinder inlet steam pipe (7-1) are respectively connected to the secondary reheater device (7) and the medium-pressure cylinder (3). The two ends of the low bypass pipe (7-2) are respectively connected to the secondary reheater device (7) and the mixing header (20). The two ends of the fifth extraction pipe (3-2) are respectively connected to the medium-pressure cylinder (3) and the circulating pump steam turbine (17). The two ends of the fifth extraction to heat supply pipe (3-1) are respectively connected to the fifth extraction pipe (3-2) and the mixing header (20).

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