Coal-fired boiler waste heat comprehensive utilization system and method adapting to seasonal temperature change
By designing a comprehensive waste heat utilization system for coal-fired boilers that adapt to seasonal temperature changes, the problem of peak energy saving potential in summer in flue gas waste heat utilization is not tapped and the low temperature corrosion and freezing in winter is achieved, and efficient flue gas heat utilization and system safety and economics are guaranteed.
Patent Information
- Application Number
- CN202411705014.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-26
- Publication Date
- 2025-02-28
AI Technical Summary
In the process of flue gas waste heat utilization, the risk of peak energy saving potential in summer is not deeply explored and the low-temperature corrosion and freezing of heat exchanger equipment during low-load operation in winter.
A comprehensive utilization system for waste heat of coal-fired boilers that adapt to seasonal temperature changes is designed, including steam turbines, bypass flue condensate regeneration system, summer peak condensate regeneration system, thermal medium water heater heating system and winter air heater anti-freeze system. Through the combined use of these systems, efficient recycling and utilization of waste heat of flue gas is achieved.
It effectively improves the efficiency of flue gas heat utilization, solves the problem that the waste heat of the boiler tail flue gas cannot be fully utilized during peak operation in summer, and prevents the low-temperature corrosion and freezing of the heat exchanger in the low-temperature environment in winter, ensuring the safety and economics of the system.
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Figure CN119532813A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of energy conservation and emission reduction in coal-fired power generation, and specifically relates to a system and method for comprehensive utilization of waste heat from coal-fired boilers that adapts to seasonal temperature changes. Background Art
[0002] Boiler exhaust heat loss is the main heat loss in coal-fired power plants, accounting for nearly 6% of the total fuel heat. Under the background of continuously reducing the energy consumption of thermal power units, how to efficiently, fully and safely utilize this part of waste heat has become a hot research direction.
[0003] In recent years, although the field of flue gas waste heat utilization has developed rapidly, there are still some key technical difficulties. For example, the energy-saving potential during the peak period of summer in the process of flue gas waste heat utilization has not been deeply explored, and under the current situation of normal low-load operation of thermal power units in winter, the heat exchanger equipment is at risk of low-temperature corrosion and freezing during operation.
[0004] In view of the above key difficulties, a number of key technologies have been developed with a problem-oriented approach to solve the difficulties in the utilization of flue gas waste heat. Summary of the invention
[0005] The present invention overcomes the shortcomings of the prior art and proposes a system and method for comprehensive utilization of waste heat from a coal-fired boiler that adapts to seasonal temperature changes. The present invention is achieved through the following technical solutions: A comprehensive utilization system of waste heat from a coal-fired boiler adapting to seasonal temperature changes, comprising a steam turbine and a coal-fired boiler, wherein the steam turbine is connected to a third low-pressure heater; further comprising a bypass flue condensate heat recovery system A, a summer peak condensate heat recovery system B, a heat medium water heater heating system C and a winter heater antifreeze system D; the bypass flue condensate heat recovery system A comprises a condensate heat exchanger; the summer peak condensate heat recovery system B comprises a heat medium water condensate heat exchanger; the heat medium water heater heating system C comprises a heat medium water flue gas heat exchanger and a primary and secondary air series heater; the winter heater antifreeze system D comprises a heat medium water steam heat exchanger; The flue of the coal-fired boiler is connected to the condensate heat exchanger and the heat medium water flue gas heat exchanger respectively; the water inlet side of the condensate heat exchanger is connected to the water outlet side of the third low-pressure heater and the condensate side of the inlet of the third low-pressure heater respectively, and the outlet side of the condensate heat exchanger is connected to the coal-fired boiler; the heat medium water flue gas heat exchanger is connected to the primary and secondary air series heater; the water outlet side of the primary and secondary air series heater is connected to the water inlet side of the heat medium water flue gas heat exchanger through a heat medium water circulation pump; the hot air outlet of the primary and secondary air series heater is connected to the coal-fired boiler; The hot air outlet of the primary and secondary air series heaters is connected to the heat medium water condensate water heat exchanger, and the condensate water inlet of the heat medium water condensate water heat exchanger is connected to the inlet of the third low-pressure heater; the water outlet of the heat medium water condensate water heat exchanger is connected to the outlet of the third low-pressure heater; The heat medium water vapor heat exchanger is connected to the heat medium water circulation pump; the heat medium water vapor heat exchanger is connected to other steam equipment through an auxiliary steam pipeline; other steam equipment provides auxiliary steam for the heat medium water vapor heat exchanger; the water inlet side of the heat medium water vapor heat exchanger is connected to the water outlet side of the primary and secondary air series heater.
[0006] Furthermore, the steam turbine is connected to a first low-pressure heater and a second low-pressure heater; the third low-pressure heater is connected to a shaft seal heater; the first low-pressure heater, the second low-pressure heater and the third low-pressure heater are connected in series in sequence, the first low-pressure heater is connected to a deaerator, and the deaerator is connected to a coal-fired boiler; the water outlet of the condensate heat exchanger is connected to the water outlet of the first low-pressure heater.
[0007] Furthermore, the inlet of the condensate heat exchanger is connected to the first condensate booster pump, and the water flow of the condensate heat exchanger is controlled by the frequency converter of the first condensate booster pump, so that the outlet water temperature of the condensate heat exchanger is automatically adjusted to be consistent with the outlet condensate temperature of the first low-pressure heater.
[0008] Furthermore, a cooling water regulating valve is provided at the inlet of the third low-pressure heater, and the condensate outlet of the shaft seal heater is connected to the cooling water regulating valve.
[0009] Furthermore, the heat medium water heater heating system C includes a constant pressure expansion water tank, which is connected to the heat medium water circulation pump through a pipeline.
[0010] Furthermore, a second condensate booster pump is provided at the condensate inlet of the heat medium water condensate heat exchanger; the second condensate booster pump inverter automatically controls the condensate temperature at the outlet of the heat medium water condensate heat exchanger to be consistent with the condensate temperature at the outlet of the third low-pressure heater.
[0011] Furthermore, the heat medium water vapor heat exchanger is connected to a drain regulating valve.
[0012] Furthermore, a bypass regulating valve is provided in the heat medium water flue gas heat exchanger.
[0013] A method for comprehensive utilization of waste heat from a coal-fired boiler that adapts to seasonal temperature changes, based on the system for comprehensive utilization of waste heat from a coal-fired boiler that adapts to seasonal temperature changes; The flue of the coal-fired boiler provides hot flue gas to the condensate heat exchanger and the heat medium water flue gas heat exchanger; The inlet of the condensate heat exchanger is connected to the first condensate booster pump, and the water flow of the condensate heat exchanger is controlled by the frequency converter of the first condensate booster pump, and the outlet water temperature of the condensate heat exchanger is automatically adjusted to be consistent with the outlet condensate temperature of the first low-pressure heater; the condensate heat exchanger uses the waste heat of the flue gas to heat the water extracted from the third low-pressure heater, reducing the steam extraction of the low-pressure cylinders of the steam turbine, and at the same time, the condensate discharged from the condensate heat exchanger is diverted to the main condensate flow of the first low-pressure heater and the second low-pressure heater, displacing the steam extraction of the first low-pressure heater and the second low-pressure heater, increasing the working capacity of the low-pressure cylinder of the steam turbine and reducing coal consumption; The waste heat of flue gas is recovered through the heat medium water flue gas heat exchanger, and the heat is dissipated to the primary and secondary air through the primary and secondary air series heater; the primary and secondary air are sent to the coal-fired boiler for use; the low-temperature condensed water of the primary and secondary air series heater enters the heat medium water flue gas heat exchanger for further heat exchange with the waste heat of flue gas; In summer, the unit is under high load, the ambient temperature is greater than 25℃, and the outlet air temperature of the primary and secondary air series heaters is greater than 60℃; at this time, the summer peak condensate heat recovery system B works, and the excess hot air of the primary and secondary air series heaters enters the heat medium water condensate heat exchanger, and exchanges heat with the low-temperature condensate of the third low-pressure heater extracted from the heat medium water condensate heat exchanger, and recovers the excess heat to the condensate heat exchanger; the steam extraction of the third low-pressure heater to the steam turbine is squeezed out through the heat medium water condensate heat exchanger, further increasing the work of the low-pressure cylinder of the steam turbine and reducing coal consumption; In the low temperature environment in winter, the return water temperature of the primary and secondary air series heater outlet is less than 30℃, the winter heater antifreeze system D works, the heat medium water vapor heat exchanger is connected to other steam equipment through the auxiliary steam pipeline; other steam equipment provides auxiliary steam for the heat medium water vapor heat exchanger; the heat medium water vapor heat exchanger supplements heat to the heat medium water smoke heat exchanger.
[0014] Furthermore, the desuperheating water regulating valve automatically controls the inlet of the first condensate booster pump to be constant at 70°C; the heat medium water circulation pump adjusts the flow of the heat medium water flue gas heat exchanger and automatically controls the outlet flue gas temperature of the heat medium water flue gas heat exchanger to be constant at 85°C; The heat medium water vapor heat exchanger is connected with a drain regulating valve; the heat medium water flue gas heat exchanger is provided with a bypass regulating valve; the drain regulating valve of the heat medium water vapor heat exchanger automatically controls the outlet water temperature to ≮72°C, and at the same time, the bypass regulating valve of the heat medium water flue gas heat exchanger is automatically closed, and all the water of the heat medium water flue gas heat exchanger enters the primary and secondary air series heaters to prevent the primary and secondary air series heater heat exchange modules from freezing.
[0015] The beneficial effects of the present invention compared with the prior art are as follows: The present invention fully recycles and utilizes the excess heat during the peak operation in summer, improves the utilization efficiency of flue gas heat, and solves the problem that the flue gas waste heat at the tail of the boiler cannot be fully utilized during the peak operation of the unit in summer.
[0016] Solve the problem of low-temperature corrosion and freezing of the cold end of the deep-regulation heat exchanger of the unit in winter, and ensure the safety and economy of the operation of the flue gas waste heat utilization system. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 It is a connection diagram of the bypass flue condensate heat recovery system A and the summer peak condensate heat recovery system B in the comprehensive utilization system of waste heat of a coal-fired boiler adapting to seasonal temperature changes described in the present invention; Figure 2 It is a connection diagram of the heat medium water heater heating system C and the winter heater antifreeze system D in the comprehensive utilization system of waste heat from a coal-fired boiler adapted to seasonal temperature changes according to the present invention; In the figure: 1 is a condensate heat exchanger, 2 is a first condensate booster pump, 3 is a first low-pressure heater, 4 is a second low-pressure heater, 5 is a third low-pressure heater, 6 is a heat medium water condensate heat exchanger, 7 is a deaerator, 8 is a cooling water regulating valve, 9 is a shaft seal heater, 10 is a second condensate booster pump, 11 is a heat medium water flue gas heat exchanger, 12 is a primary and secondary air series heater, 13 is a constant pressure expansion water tank, 14 is a heat medium water circulation pump, 15 is a bypass regulating valve, 16 is a heat medium water steam heat exchanger, and 17 is a drain regulating valve. DETAILED DESCRIPTION
[0018] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention is further described in detail in conjunction with the embodiments and the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. The technical solutions of the present invention are described in detail below in conjunction with the embodiments and the accompanying drawings, but the scope of protection is not limited thereto.
[0019] See also Figure 1 and Figure 2 This embodiment proposes a system and method for comprehensive utilization of waste heat from a coal-fired boiler that adapts to seasonal temperature changes. The system for comprehensive utilization of waste heat from a coal-fired boiler includes a steam turbine, a bypass flue condensate heat recovery system A, a summer peak condensate heat recovery system B, a heat medium water heater supplementary heating system C, and a winter heater antifreeze system D.
[0020] The bypass flue condensate heat recovery system A comprises a condensate heat exchanger 1 and a first condensate booster pump 2; The summer peak condensate heat recovery system B includes a heat medium water condensate heat exchanger 6 and a second condensate booster pump 10; The heat medium water heater supplementary heating system C includes a heat medium water smoke heat exchanger 11 and a primary and secondary air series heater 12; The winter heater antifreeze system D includes a heat medium water vapor heat exchanger 16 and a drain regulating valve 17 .
[0021] Specifically, the steam turbine is connected to the first low-pressure heater 3, the second low-pressure heater 4 and the third low-pressure heater 5; the third low-pressure heater 5 is connected to the shaft seal heater 9; the first low-pressure heater 3, the second low-pressure heater 4 and the third low-pressure heater 5 are connected in series in sequence, the first low-pressure heater 3 is connected to the deaerator 7, and the deaerator 7 is connected to the coal-fired boiler. The air preheater bypass flue is connected downstream to the condensate heat exchanger 1 of the bypass flue condensate heat recovery system A and the heat medium water flue gas heat exchanger 11 of the heat medium water heater supplementary heat system C, respectively, to provide hot flue gas to the condensate heat exchanger 1 and the heat medium water flue gas heat exchanger 11, respectively. Two hot flue gas recovery routes are formed under normal temperature environment.
[0022] 1. Hot flue gas recovery route under normal temperature environment The inlet of the condensate heat exchanger 1 is connected to the first condensate booster pump 2, and the outlet of the condensate heat exchanger 1 is connected to the outlet of the first low-pressure heater 3. The water flow of the condensate heat exchanger 1 is controlled by the inverter of the first condensate booster pump 2, and the outlet water temperature of the condensate heat exchanger 1 is automatically adjusted to be consistent with the outlet condensate temperature of the first low-pressure heater 3; the setting value of the inverter of the first condensate booster pump 2: the outlet condensate temperature of the first low-pressure heater 3 + the manual offset of the operator (±20℃).
[0023] The inlet water of the condensate heat exchanger 1 is a mixture of condensate from the outlet of the third low-pressure heater 5 and the inlet of the third low-pressure heater 5. The outlet of the third low-pressure heater 5 is the main water supply, and the inlet of the third low-pressure heater 5 is cooling water. A cooling water regulating valve 8 is provided at the inlet of the third low-pressure heater 5 to automatically control the inlet water temperature of the condensate heat exchanger 1 to be constant at 70°C. The condensate heat exchanger 1 takes the waste heat of the flue gas to heat the water extracted from the third low-pressure heater 5, thereby reducing the steam extraction of the low-pressure cylinders of the steam turbine. At the same time, the condensate discharged from the condensate heat exchanger 1 is diverted to the main condensate flow of the first low-pressure heater 3 and the second low-pressure heater 4, thereby displacing the steam extraction of the first low-pressure heater 3 and the second low-pressure heater 4, increasing the working capacity of the low-pressure cylinders of the steam turbine and reducing coal consumption.
[0024] The outlet water of the first low-pressure heater 3, the second low-pressure heater 4 and the condensate heat exchanger 1 enters the deaerator 7 and is then sent to the coal-fired boiler for utilization.
[0025] Control strategy of condensate heat exchanger 1 inlet condensate temperature regulating valve 8: The condensate after the shaft seal heater 9 is sent to the desuperheating water regulating valve 8 of the first condensate booster pump 2, which is used to adjust the inlet water temperature of the first condensate booster pump 2 to a constant 70°C. The mainstream condensate at the inlet of the condensate heat exchanger 1 is taken from the outlet of the third low-pressure heater 5, and the desuperheating water is the inlet condensate of the third low-pressure heater 5. The desuperheating water regulating valve 8 automatically controls the inlet of the first condensate booster pump 2 to a constant 70°C to prevent low-temperature corrosion of the cold end of the condensate heat exchanger 1. From the inlet of the third low-pressure heater 5 to the inlet main pipe of the first condensate booster pump 2, the desuperheating water regulating valve 8 is adjusted: the inlet water temperature of the first condensate booster pump 2 is set to 70°C.
[0026] 2. Hot flue gas recovery route 2 under normal temperature environment The heat medium water flue gas heat exchanger 11 of the heat medium water heater supplementary heating system C is connected to the primary and secondary air series heater 12; the flue gas waste heat is recovered through the heat medium water flue gas heat exchanger 11, and the exhaust gas of the air preheater is countercurrently exchanged with the heat, and the absorbed heat is dissipated to the primary and secondary air through the primary and secondary air series heater 12, forming a closed cycle on the water side. The primary and secondary air are sent to the coal-fired boiler for use.
[0027] Specifically, the heat medium water heater heating system C also includes two heat medium water circulation pumps 14; the water outlet side of the primary and secondary air series heaters 12 is connected to the water inlet side of the heat medium water flue gas heat exchanger 11 through the heat medium water circulation pump 14, and the low-temperature condensed water of the primary and secondary air series heaters 12 enters the heat medium water flue gas heat exchanger 11 to further exchange heat with the flue gas waste heat. The heat medium water heater heating system C is equipped with a constant pressure expansion water tank 13, which is automatically replenished with condensed water to stabilize the pressure.
[0028] The design environment temperature is 25℃, the heat medium water at the outlet of the heat medium water flue gas heat exchanger 11 is 90℃, and the high temperature heat medium water enters the primary and secondary air series heater 12, heating the primary and secondary air to 60℃, and the primary and secondary air series heater 12 outlet returns water to the inlet of the heat medium water circulation pump 14, in a closed cycle. The heat medium water flue gas heat exchanger 11 is provided with a bypass regulating valve 15, which automatically controls the inlet water temperature of the circulating water pump to 70℃. The inlet flue gas temperature of the heat medium water flue gas heat exchanger 11 is designed to be 115℃, and the outlet flue gas temperature drops to 85℃ and is discharged into the desulfurization tower.
[0029] Heat medium water circulation pump 14 inverter control strategy: The heat medium water flue gas heat exchanger 11 and the primary and secondary air series heater 12 form a heat medium water heater supplementary heating system C, which is equipped with two heat medium water circulation pumps 14 to adjust the flow of the heat medium water flue gas heat exchanger 11 and automatically control the outlet flue gas temperature of the heat medium water flue gas heat exchanger 11 to be constant at 85°C. The inverter of the heat medium water circulation pump 14 is adjusted: the outlet flue gas temperature of the heat medium water flue gas heat exchanger 11 (three selected).
[0030] Control strategy of the bypass regulating valve 15 at the outlet of the heat medium water flue gas heat exchanger 11: Automatically control the inlet water temperature of the heat medium water circulation pump 14 to 70℃ to prevent low temperature corrosion of the cold end of the smoke cooler. The outlet bypass regulating valve 15 of the heat medium water smoke heat exchanger 11 is adjusted: the inlet water temperature of the heat medium water circulation pump 14, the middle of the three. Set value: manually set 70±10℃.
[0031] Through two hot flue gas recovery routes, the waste heat of the flue gas of the coal-fired boiler can be recovered and utilized at normal ambient temperature. On the one hand, it can provide part of the hot water and hot air for the gas boiler, and on the other hand, it can reduce the extraction of the steam turbine, increase the working capacity of the low-pressure cylinder of the steam turbine and reduce coal consumption.
[0032] 3. Utilization of waste heat in high temperature environment in summer In summer, the unit is under high load, the ambient temperature is greater than 25℃, and the outlet air temperature of the primary and secondary air series heater 12 is greater than 60℃; at this time, the summer peak condensate heat recovery system B works, the primary and secondary air series heater 12 is connected to the heat medium water condensate heat exchanger 6, the condensate inlet of the heat medium water condensate heat exchanger 6 is the low-temperature condensate inlet of the third low-pressure heater 5, and the first condensate booster pump 2 variable frequency pump automatically maintains the outlet condensate temperature consistent with the outlet condensate temperature of the third low-pressure heater 5. The excess hot air of the primary and secondary air series heater 12 enters the heat medium water condensate heat exchanger 6, and exchanges heat with the low-temperature condensate of the third low-pressure heater 5 extracted from the heat medium water condensate heat exchanger 6, and the excess heat is recovered to the condensate system. The steam extraction of the third low-pressure heater 5 to the steam turbine is squeezed out by the heat medium water condensate heat exchanger 6, further increasing the work of the low-pressure cylinder of the steam turbine and reducing coal consumption.
[0033] A second condensate booster pump 10 is provided at the condensate inlet of the heat medium water condensate heat exchanger 6; the inverter control strategy of the second condensate booster pump 10 is: In summer, when the unit is under high load, condensate is taken from the inlet of the third low-pressure heater 5, and heat is absorbed by the heat medium water condensate heat exchanger 6. The heated condensate returns to the outlet of the third low-pressure heater 5. The second condensate booster pump 10 inverter automatically controls the condensate at the outlet of the heat medium water condensate heat exchanger 6 to be consistent with the condensate at the outlet of the third low-pressure heater 5. This part of condensate displaces the steam extraction of the third low-pressure heater 5 to the steam turbine, further increasing the working capacity of the low-pressure cylinder of the steam turbine and reducing coal consumption. The second condensate booster pump 10 inverter is adjusted: the condensate temperature at the outlet of the heat medium water condensate heat exchanger 6, and the set value is: the condensate temperature at the outlet of the third low-pressure heater 5.
[0034] 4. Utilization of waste heat in low temperature environment in winter In the winter low temperature environment, the winter heater antifreeze system D works, and the winter heater antifreeze system D includes a heat medium water vapor heat exchanger 16 and a drain regulating valve 17. The heat medium water vapor heat exchanger 16 is connected to the heat medium water circulation pump 14; the heat medium water vapor heat exchanger 16 is connected to the drain regulating valve 17; the heat medium water vapor heat exchanger 16 is connected to other steam equipment through an auxiliary steam pipeline; other steam equipment provides auxiliary steam for the heat medium water vapor heat exchanger 16. The water inlet side of the heat medium water vapor heat exchanger 16 is connected to the outlet side of the primary and secondary air series heater 12.
[0035] In winter, the temperature is low, and the return water temperature at the outlet of the primary and secondary air series heater 12 is less than 30°C, and the return water is put into the heat medium water vapor heat exchanger 16 at the outlet of the heater to supplement the heat of the heat medium water system. The drain regulating valve 17 of the heat medium water vapor heat exchanger 16 automatically controls the outlet water temperature to ≮72°C, and at the same time, the bypass regulating valve 15 of the heat medium water smoke gas heat exchanger 11 is automatically closed, and all the water in the heat medium water smoke gas heat exchanger 11 enters the primary and secondary air series heater 12 to prevent the heat exchange module of the primary and secondary air series heater 12 from freezing.
[0036] Control strategy of heat medium water vapor heat exchanger 16: In winter, when the temperature of return water at the outlet of secondary air heater is lower than 30℃, heat medium water vapor heat exchanger 16 is put into operation to supplement the heat medium water system. Drain regulating valve 17 automatically controls the outlet heat medium water to ≮72℃, and the bypass regulating valve 15 of heat medium water flue gas heat exchanger 11 is automatically closed to realize the maximum flow mode of heater operation and prevent the freezing of the primary and secondary air series heater 12 modules. Drain regulating valve 17 is adjusted: the inlet water temperature of heat medium water circulation pump 14, the middle of the three. Set value: manually set 72±10℃.
[0037] The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be determined that the specific embodiments of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the present invention, which should be regarded as belonging to the present invention and the scope of patent protection determined by the submitted claims.
Claims
1. A comprehensive utilization system of waste heat from a coal-fired boiler adapting to seasonal temperature changes, comprising a steam turbine and a coal-fired boiler, wherein the steam turbine is connected to a third low-pressure heater (5); characterized in that: It also includes a bypass flue condensate heat recovery system A, a summer peak condensate heat recovery system B, a heat medium water heater heating system C and a winter heater antifreeze system D; the bypass flue condensate heat recovery system A includes a condensate heat exchanger (1); the summer peak condensate heat recovery system B includes a heat medium water condensate heat exchanger (6); the heat medium water heater heating system C includes a heat medium water flue gas heat exchanger (11) and a primary and secondary air series heater (12); the winter heater antifreeze system D includes a heat medium water vapor heat exchanger (16); The flue of the coal-fired boiler is respectively connected to the condensate heat exchanger (1) and the heat medium water flue gas heat exchanger (11); the water inlet side of the condensate heat exchanger (1) is respectively connected to the water outlet side of the third low-pressure heater (5) and the condensate side of the inlet of the third low-pressure heater (5), and the outlet side of the condensate heat exchanger (1) is connected to the coal-fired boiler; the heat medium water flue gas heat exchanger (11) is connected to the primary and secondary air series heater (12); the water outlet side of the primary and secondary air series heater (12) is connected to the water inlet side of the heat medium water flue gas heat exchanger (11) through a heat medium water circulation pump (14); the hot air outlet of the primary and secondary air series heater (12) is connected to the coal-fired boiler; The hot air outlet of the primary and secondary air series heater (12) is connected to the heat medium water condensate heat exchanger (6), and the condensate inlet of the heat medium water condensate heat exchanger (6) is connected to the inlet of the third low-pressure heater (5); the water outlet of the heat medium water condensate heat exchanger (6) is connected to the outlet of the third low-pressure heater (5); The heat medium water vapor heat exchanger (16) is connected to the heat medium water circulation pump (14); the heat medium water vapor heat exchanger (16) is connected to other steam equipment via an auxiliary steam pipeline; the other steam equipment provides auxiliary steam for the heat medium water vapor heat exchanger (16); and the water inlet side of the heat medium water vapor heat exchanger (16) is connected to the water outlet side of the primary and secondary air series heater (12).
2. A comprehensive utilization system of waste heat from coal-fired boilers adapting to seasonal temperature changes according to claim 1, characterized in that: The steam turbine is connected to a first low-pressure heater (3) and a second low-pressure heater (4); the third low-pressure heater (5) is connected to a shaft seal heater (9); the first low-pressure heater (3), the second low-pressure heater (4) and the third low-pressure heater (5) are connected in series in sequence, the first low-pressure heater (3) is connected to a deaerator (7), and the deaerator (7) is connected to a coal-fired boiler; and the water outlet of the condensate heat exchanger (1) is connected to the water outlet of the first low-pressure heater (3).
3. The comprehensive utilization system of waste heat from coal-fired boilers adapting to seasonal temperature changes according to claim 2 is characterized in that: The inlet of the condensate heat exchanger (1) is connected to the first condensate booster pump (2), and the water flow of the condensate heat exchanger (1) is controlled by the frequency converter of the first condensate booster pump (2), so that the outlet water temperature of the condensate heat exchanger (1) is automatically adjusted to be consistent with the outlet condensate temperature of the first low-pressure heater (3).
4. The comprehensive utilization system of waste heat from coal-fired boilers adapting to seasonal temperature changes according to claim 3 is characterized in that: A cooling water regulating valve (8) is provided at the inlet of the third low-pressure heater (5), and the condensate outlet of the shaft seal heater (9) is connected to the cooling water regulating valve (8).
5. The comprehensive utilization system of waste heat from coal-fired boilers adapting to seasonal temperature changes according to claim 1 is characterized in that: The heat medium water heater heating system C comprises a constant pressure expansion water tank (13), and the constant pressure expansion water tank (13) is connected to a heat medium water circulation pump (14) via a pipeline.
6. The comprehensive utilization system of waste heat from coal-fired boilers adapting to seasonal temperature changes according to claim 1 is characterized in that: A second condensate booster pump (10) is provided at the condensate inlet of the heat medium water condensate heat exchanger (6); the frequency converter of the second condensate booster pump (10) automatically controls the temperature of the condensate at the outlet of the heat medium water condensate heat exchanger (6) to be consistent with the temperature of the condensate at the outlet of the third low-pressure heater (5).
7. The comprehensive utilization system of waste heat from coal-fired boilers adapting to seasonal temperature changes according to claim 1 is characterized in that: The heat medium water vapor heat exchanger (16) is connected to a drain regulating valve (17).
8. The comprehensive utilization system of waste heat from coal-fired boilers adapting to seasonal temperature changes according to claim 1 is characterized in that: The heat medium water flue gas heat exchanger (11) is provided with a bypass regulating valve (15).
9. A method for comprehensive utilization of waste heat from coal-fired boilers that adapts to seasonal temperature changes, characterized in that: Based on a comprehensive utilization system of waste heat from a coal-fired boiler adapted to seasonal temperature changes as described in claim 4; The flue of the coal-fired boiler is connected to a condensate heat exchanger (1) and a heat medium water flue gas heat exchanger (11) to provide hot flue gas; The inlet of the condensate heat exchanger (1) is connected to the first condensate booster pump (2), and the water flow of the condensate heat exchanger (1) is controlled by the frequency converter of the first condensate booster pump (2), so that the outlet water temperature of the condensate heat exchanger (1) is automatically adjusted to be consistent with the outlet condensate temperature of the first low-pressure heater (3); the condensate heat exchanger (1) uses the waste heat of the flue gas to heat the water extracted by the third low-pressure heater (5), thereby reducing the steam extraction of the low-pressure cylinders of the steam turbine; at the same time, the condensate discharged from the condensate heat exchanger (1) is diverted to the main condensate flow of the first low-pressure heater (3) and the second low-pressure heater (4), thereby displacing the steam extraction of the first low-pressure heater (3) and the second low-pressure heater (4), thereby increasing the working capacity of the low-pressure cylinders of the steam turbine and reducing coal consumption; Recovering flue gas waste heat through a heat medium water flue gas heat exchanger (11), dissipating heat to the primary and secondary air through a primary and secondary air series heater (12); the primary and secondary air are sent to a coal-fired boiler for use; low-temperature condensed water from the primary and secondary air series heater (12) enters the heat medium water flue gas heat exchanger (11) for further heat exchange with the flue gas waste heat; In summer, the unit is under high load, the ambient temperature is greater than 25°C, and the outlet air temperature of the primary and secondary air series heaters (12) is greater than 60°C; at this time, the summer peak condensate heat recovery system B works, and the excess hot air from the primary and secondary air series heaters (12) enters the heat medium water condensate heat exchanger (6), exchanges heat with the low-temperature condensate of the third low-pressure heater (5) extracted from the heat medium water condensate heat exchanger (6), and recovers the excess heat to the condensate heat exchanger (1); the steam extraction from the third low-pressure heater (5) to the steam turbine is displaced through the heat medium water condensate heat exchanger (6), thereby further increasing the work done by the low-pressure cylinder of the steam turbine and reducing coal consumption; In a low-temperature environment in winter, the return water temperature at the outlet of the primary and secondary air series heater (12) is less than 30°C, the winter heater antifreeze system D works, and the heat medium water vapor heat exchanger (16) is connected to other steam equipment through an auxiliary steam pipeline; the other steam equipment provides auxiliary steam for the heat medium water vapor heat exchanger (16); and the heat medium water vapor heat exchanger (16) supplements heat to the heat medium water smoke heat exchanger (11).
10. A method for comprehensive utilization of waste heat from a coal-fired boiler adapting to seasonal temperature changes according to claim 9, characterized in that: The desuperheating water regulating valve (8) automatically controls the inlet temperature of the first condensate booster pump (2) to be constant at 70°C; the heat medium water circulation pump (14) adjusts the flow rate of the heat medium water flue gas heat exchanger (11) and automatically controls the outlet temperature of the heat medium water flue gas heat exchanger (11) to be constant at 85°C; The heat medium water vapor heat exchanger (16) is connected to a drain regulating valve (17); the heat medium water smoke gas heat exchanger (11) is provided with a bypass regulating valve (15); the drain regulating valve (17) of the heat medium water vapor heat exchanger (16) automatically controls the outlet water temperature to be ≮72°C, and at the same time, the bypass regulating valve (15) of the heat medium water smoke gas heat exchanger (11) is automatically closed, so that all the water of the heat medium water smoke gas heat exchanger (11) enters the primary and secondary air series heater (12), thereby preventing the heat exchange module of the primary and secondary air series heater (12) from freezing.