A thermal power plant flue gas waste heat utilization device, system and method

Abstract

The application discloses a thermal power plant flue gas waste heat utilization device, system and method, and belongs to the technical field of flue gas waste heat recovery. The device comprises a shell, a center cylinder arranged in the inner cavity of the shell and forming an annular air channel with the shell, upper and lower water collecting cavities fixed on the upper and lower ends of the center cylinder, the peripheral surface of the upper and lower water collecting cavities connected with U-shaped heat exchange pipes, and water passing pipes respectively communicated with the upper and lower water collecting cavities and provided with flow regulating valves. In the system, the gas inlet of a dust collector is connected with hot flue gas, the gas outlet is connected with the gas inlet pipe of the waste heat utilization device; the gas inlet of a desulfurization device is connected with the gas outlet pipe of the waste heat utilization device; and the water inlet pipe and the water outlet pipe of the waste heat utilization device are respectively connected with a warm air heater and a heat exchanger. The application recovers flue gas waste heat, uses the heated circulating heat exchange medium to supply the warm air heater to heat air, saves electric heating energy consumption, and preheats the steam turbine condensate water through the heat exchanger, reduces the fuel required for heating the condensate water by the boiler, and reduces the coal consumption of power generation in the power plant.

Description

Technical Field

[0001] This invention relates to the field of flue gas waste heat recovery technology, specifically to a device, system, and method for utilizing flue gas waste heat from a thermal power plant. Background Technology

[0002] During the operation of boilers in thermal power plants, a large amount of high-temperature flue gas is continuously generated. This flue gas contains a significant amount of recoverable waste heat. Efficiently recovering and utilizing this waste heat is crucial for reducing coal consumption in power generation, minimizing energy waste, and improving the economic efficiency of unit operation. Currently, the industry commonly uses flue gas waste heat exchange devices for waste heat recovery. However, existing waste heat utilization devices and systems still have some technical shortcomings in actual operation. For example, in traditional waste heat exchange devices, the flue gas flows in a straight line, resulting in a short residence distance within the heat exchange equipment and limited contact time with the heat exchange tubes. This leads to insufficient heat exchange between the flue gas and the heat exchange medium, resulting in a higher usage of heat exchange tubes and a lower waste heat recovery rate. Furthermore, existing waste heat utilization devices lack a flue gas temperature control mechanism. If excessive heat exchange leads to excessively low flue gas temperatures, it may cause the inlet flue gas temperature of subsequent desulfurization units to fail to meet standards, leading to abnormal operating conditions and decreased desulfurization efficiency in the desulfurization system. Summary of the Invention

[0003] To address the aforementioned technical shortcomings, this invention provides a device, system, and method for utilizing waste heat from flue gas in thermal power plants. This invention flexibly adjusts the heat exchange intensity and flue gas temperature without affecting the overall circulation of the medium, thus balancing the dual requirements of efficient waste heat recovery and stable operation of the desulfurization system.

[0004] This invention adopts the following technical solution: a waste heat recovery device for flue gas from a thermal power plant, comprising:

[0005] The enclosed outer shell has an air inlet pipe and an air outlet pipe connected to the top and bottom respectively; The central cylinder is coaxially arranged in the inner cavity of the outer shell; an annular air passage is formed between the central cylinder and the outer shell; The lower water collection chamber is fixed at the lower end of the central cylinder and has a water inlet pipe that extends out of the outer shell; The upper water collection chamber is fixed at the upper end of the central cylinder and has a water outlet pipe that extends out of the outer shell; The lower water collection chamber is connected to the upper water collection chamber via a U-shaped heat exchange tube. The heat exchange tube passes parallel through the air passage and connects the lower and upper water collection chambers. The heat exchange tubes are evenly distributed around the central cylinder. The inlet and outlet pipes allow the circulating heat exchange medium to flow in and out in a cycle. The central cylinder has a water pipe at both ends that are respectively connected to the lower water collection chamber and the upper water collection chamber. A flow regulating valve with a shut-off function is installed in the water pipe.

[0006] Preferably, the lower water collection chamber has a cylindrical water collection chamber at one end near the central cylinder, and multiple parallel and spaced flow equalization plates on the side of the water collection chamber away from the central cylinder. A conical cover plate is fixed at the lower end of the lower water collection chamber, and the water inlet pipe is arranged at the center of the cover plate.

[0007] Preferably, the flow equalization plate is an annular plate with evenly distributed small holes. The central hole of the flow equalization plate is opposite to the water pipe, and the diameter of the central hole is larger than the inner diameter of the water pipe.

[0008] Preferably, the heat exchange tube is connected to the side wall of the water collection chamber; An axial flow impeller is rotatably mounted at the end of the water pipe. A cleaning assembly is installed at the end of the axial flow impeller away from the water pipe. The cleaning assembly has cleaning brushes around its periphery for cleaning the side walls of the water collection chamber.

[0009] Preferably, the end of the water pipe has an installation cavity for installing an axial flow impeller, and the end of the water pipe is fixed with an extension sleeve for installing another axial flow impeller; the end of the extension sleeve near the water pipe has an inwardly extending positioning step, the positioning step is limited between the two axial flow impellers, and the two axial flow impellers are fixed together by tie bolts on the shaft.

[0010] Preferably, the outer shell is cylindrical, and the air inlet pipe and air outlet pipe are installed tangentially to the outer shell.

[0011] A waste heat recovery system for flue gas from a thermal power plant includes a waste heat recovery device for flue gas from a thermal power plant, and further includes: The dust collector has an inlet connected to the hot flue gas discharged from the boiler and an outlet connected to the inlet pipe of the waste heat recovery device. The desulfurization unit has its inlet connected to the outlet pipe of the waste heat recovery unit; A warm air heater is connected to the inlet and outlet pipes of the waste heat recovery device and is used to heat the air. The heat exchanger is connected to the inlet and outlet pipes of the waste heat utilization device and is used to heat the condensate of the steam turbine.

[0012] Preferably, two central cylinders are arranged coaxially, and the lower water collection cavity at the lower end of the upper central cylinder is fixedly connected to the upper water collection cavity at the upper end of the lower central cylinder; the lower water collection cavity at the lower end of the upper central cylinder is connected to an auxiliary water pipe that extends out of the outer shell for draining water. The heat exchanger is connected to the inlet pipe, outlet pipe, and auxiliary water pipe of the waste heat utilization device.

[0013] A method for utilizing waste heat from flue gas in a thermal power plant involves employing a waste heat utilization system for flue gas in a thermal power plant. The temperature of the circulating heat exchange medium flowing out of the waste heat utilization device is controlled by adjusting the flow regulating valve, and / or the water output ratio of the outlet water pipe and auxiliary water pipe is adjusted to control the temperature of the hot flue gas flowing out of the waste heat utilization device to be between 70-85℃. The circulating heat exchange medium from the waste heat recovery device is preferentially supplied to the air heater.

[0014] The beneficial effects of this invention are as follows: The flue gas temperature can be flexibly adjusted by setting up a central water pipe and flow regulating valve. Without changing the overall circulation medium flow rate of the system, a portion of the medium is directly connected to the upper and lower water collection chambers, bypassing the heat exchange tubes. This regulates the outlet water temperature and indirectly controls the flue gas outlet temperature, thus stabilizing the flue gas temperature at 70°C. 85℃; When adopting a double central cylinder structure, the exhaust temperature can also be controlled by adjusting the water ratio of the auxiliary water pipe and the outlet water pipe, and two different temperature heat exchange media can be output to prioritize the heat source supply of the heater and adapt to the needs of users with multiple heat sources. The hot flue gas forms a spiral flow inside the shell, effectively extending the flue gas flow path, increasing the contact time between the flue gas and the U-shaped heat exchange tube, and improving the waste heat exchange efficiency of the flue gas; the spiral airflow circumferentially washes the fluoroplastic U-shaped heat exchange tube, causing the heat exchange tube to oscillate slightly, which can shake off the dust accumulated on the tube wall surface, reduce dust accumulation, and reduce the frequency of dust cleaning; an axial flow impeller linkage cleaning component is set at the water pipe, which can drive the cleaning brush to clean the docking port of the heat exchange tube in a short time, inhibiting the accumulation of scale at the tube opening; The waste heat recovery system recovers waste heat from flue gas. After heating, the circulating heat exchange medium is used to supply the air heater to heat the air, saving energy consumption for electric heating. On the other hand, it is connected to the heat exchanger to preheat the steam turbine condensate, reducing the fuel required for boiler heating of condensate, thereby reducing the coal consumption of power plant generation and improving the overall energy utilization rate of the thermal power plant. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a perspective view of a waste heat recovery device for flue gas from a thermal power plant according to the present invention.

[0017] Figure 2 This is a perspective view of a waste heat recovery device for flue gas in a thermal power plant according to the present invention (the outer casing is hidden in the figure).

[0018] Figure 3 This is a cross-sectional view of a waste heat recovery device for flue gas in a thermal power plant according to the present invention.

[0019] Figure 4 for Figure 3 Enlarged view of point A in the middle.

[0020] Figure 5 This is a schematic diagram of a waste heat recovery system for flue gas from a thermal power plant according to the present invention.

[0021] Figure 6 This is a cross-sectional view of another embodiment of a waste heat recovery device for flue gas in a thermal power plant according to the present invention.

[0022] Figure 7 This is a schematic diagram of another embodiment of a waste heat recovery system for flue gas in a thermal power plant according to the present invention.

[0023] Explanation of reference numerals in the attached figures: 1. Outer shell; 101. Air passage; 11. Inlet pipe; 12. Outlet pipe; 2. Center tube; 3. Lower water collection chamber; 301. Water collection chamber; 31. Flow equalization plate; 32. Cover plate; 33. Inlet pipe; 34. Auxiliary water pipe; 4. Upper water collection chamber; 41. Water outlet pipe; 5. Heat exchanger tubes; 6. Water pipe; 61. Flow regulating valve; 62. Extension sleeve; 621. Positioning step; 7. Sweeping assembly; 71. Sweeping brush; 72. Axial flow impeller; 73. Tie bolt.

[0024] 10. Waste heat recovery device; 20. Dust collector; 30. Desulfurization device; 40. Air heater; 50. Heat exchanger. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1: like Figures 1 to 3As shown, this invention provides a waste heat recovery device 10 for flue gas from a thermal power plant, comprising a closed outer shell 1, a central cylinder 2 mounted at the axial center of the outer shell 1, and cylindrical lower water collection chamber 3 and upper water collection chamber 4 respectively connected to both ends of the central cylinder 2. The outer shell 1 is formed by connecting two symmetrical cylindrical cylinders, and the upper and lower ends of the outer shell 1 have circular holes for positioning and matching with the lower water collection chamber 3 and upper water collection chamber 4. The inner wall of the outer shell 1, together with the central cylinder 2, lower water collection chamber 3, and upper water collection chamber 4, forms an annular air passage 101; an inlet pipe 11 and an outlet pipe 12 are correspondingly connected to the circumferential surfaces of the upper and lower ends of the outer shell 1, and the inlet pipe 11 and outlet pipe 12 are respectively installed tangentially to the outer shell 1; when hot flue gas is introduced into the inlet pipe 11, the hot flue gas flows in a spiral manner, increasing the travel distance of the hot flue gas in the outer shell 1, so as to achieve more complete heat exchange with the heat exchange tube 5.

[0027] Combination Figures 1 to 4 As shown, the lower water collection cavity 3 and the upper water collection cavity 4 have symmetrical structures. This embodiment will be illustrated using the lower water collection cavity 3 as an example: The lower water collection chamber 3 has a cylindrical structure with a sealed upper end. The upper end contains a cylindrical water collection chamber 301, and the lower end contains multiple parallel, spaced flow equalization plates 31. A conical cover plate 32 is fixed to the open lower end of the lower water collection chamber 3. The center of the cover plate 32 protrudes downwards and fixes the water inlet pipe 33. The cover plate 32 and the end of the lower water collection chamber 3 are fixed together to the circular hole at the lower end of the outer shell 1. In this embodiment, the flow equalization plate 31 is connected to the cover plate 32 and can be pulled out downwards with the end cap to facilitate the assembly of the internal components of the water collection chamber 301. The flow equalization plate 31 is an annular plate with evenly distributed small holes to disperse the water flow, facilitating the inlet and outlet of water in each heat exchange tube 5 within the water collection chamber 301 and avoiding or reducing the problem of poor water flow in some heat exchange tubes 5. The axial hole of the flow equalization plate 31 is opposite to the water pipe 6, and the diameter of the axial hole is larger than the inner diameter of the water pipe 6. Under special circumstances, when the flow regulating valve 61 in the water pipe 6 is opened to the maximum, the axial hole of the flow equalization plate 31 can increase the speed at which the water flows into the water pipe 6 and increase the instantaneous flow rate of the water pipe 6.

[0028] Combination Figures 1 to 3As shown, the circumferential surfaces of the water collection chambers 301 in the lower water collection chamber 3 and the upper water collection chamber 4 are connected to U-shaped heat exchange tubes 5. Each heat exchange tube 5 passes parallel through the air passage 101 and connects the lower water collection chamber 3 and the upper water collection chamber 4. In this embodiment, each group of heat exchange tubes 5 is evenly distributed around the central cylinder 2, and each group of heat exchange tubes 5 is sequentially fitted from the inside to the outside and is located on the same plane. During operation, the circulating heat exchange medium flows into the inlet pipe 33. After the circulating heat exchange medium enters the water collection chamber 301 after the lower water collection chamber 3, it flows through the peripheral heat exchange tubes 5 to the water collection chamber 301 after the upper water collection chamber 4, and finally flows out through the outlet pipe 41, forming a closed loop. In this embodiment, the heat exchange tubes 5 are made of fluoroplastic. Since the hot flue gas in the air passage 101 flows in a spiral manner and is tangent to the U-shaped heat exchange tubes 5 in the circumferential direction, it can blow each U-shaped heat exchange tube 5 to have a certain slight oscillation in the circumferential direction, which is beneficial to shake off the dust on the tube surface and reduce dust accumulation.

[0029] In addition, a water pipe 6 is arranged along the axis of the central cylinder 2. The two ends of the water pipe 6 are connected to the lower water collection chamber 3 and the upper water collection chamber 4, respectively, so that the water collection chambers 301 in the lower water collection chamber 3 and the upper water collection chamber 4 are directly connected. A flow regulating valve 61 with a shut-off function is installed in the water pipe 6. The flow regulating valve 61 can regulate the flow rate of the circulating heat exchange medium from the lower water collection chamber 3 to the upper water collection chamber 4. The purpose of this is that, without changing the overall circulation speed of the circulating heat exchange medium, by adjusting the flow rate of the circulating heat exchange medium from the lower water collection chamber 3 to the upper water collection chamber 4, the outflow temperature of the circulating heat exchange medium can be reduced, thereby controlling the outflow temperature of the hot flue gas and ensuring that the hot flue gas will not affect the subsequent desulfurization operation due to excessively low temperature.

[0030] Combination Figure 3 , Figure 4As shown, in another embodiment, an axial flow impeller 72 is optionally rotatably mounted at the end of the water pipe 6. The axial flow impeller 72 is connected to a cleaning assembly 7 for cleaning the junction of the heat exchange tube 5 and the water collection chamber 301, preventing rapid scale buildup at the port of the heat exchange tube 5 and extending the maintenance interval of the heat exchange tube 5. Specifically, the inner diameter of the end of the water pipe 6 is enlarged to form a mounting cavity for mounting the axial flow impeller 72. An extension sleeve 62 is then connected to the end of the water pipe 6. The extension sleeve 62 has a mounting cavity inside for mounting another axial flow impeller 72. The two axial flow impellers 72 are fixed together by a tie bolt 73 with a central axis. The two ends of the tie bolt 73 are rounded semi-elliptical. The end of the extension sleeve 62 near the water pipe 6 has an inwardly extending positioning step 621, which is positioned between the two axial flow impellers 72. Since the two axial flow impellers 72 are already connected together by the tie bolt 73, the positioning step 621 can achieve the positioning of the two axial flow impellers 72. The cleaning assembly 7 is fixed to the outer end of the extension sleeve 62. Multiple evenly distributed cleaning brushes 71 are located around the cleaning assembly 7. These brushes 71 are aligned with the interfaces of each heat exchange tube 5 in the water collection chamber 301, and are used to clean the ports of the heat exchange tubes 5. During operation, the flow regulating valve 61 is fully opened for a short period at regular intervals to increase the flow rate of the circulating heat exchange medium through the water pipe 6. This drives the two axial flow impellers 72 to rotate the cleaning assembly 7, thus cleaning the ports of the heat exchange tubes 5. Then, the flow regulating valve 61 is closed to avoid excessively affecting the heat recovery of the hot flue gas.

[0031] Example 2: Based on the above embodiment one, as follows Figure 5 As shown, this embodiment provides a waste heat recovery system for flue gas from a thermal power plant. The inlet of the dust collector 20 is connected to the hot flue gas discharged from the boiler, and its outlet is connected to the inlet pipe 11 of the waste heat recovery device 10. The inlet of the desulfurization device 30 is connected to the outlet pipe 12 of the waste heat recovery device 10, and its outlet is connected to the chimney. The air heater 40 is connected to the inlet pipe 33 and outlet pipe 41 of the waste heat recovery device 10, using the heated circulating heat exchange medium to heat the air, thereby regulating the indoor temperature and saving electricity. The heat exchanger 50 is connected to the inlet pipe 33 and outlet pipe 41 of the waste heat recovery device 10, using the heated circulating heat exchange medium to preheat the condensate of the steam turbine, reducing coal consumption for power generation.

[0032] Combination Figures 1 to 3 ,as well as Figure 6As shown, in another embodiment, the waste heat utilization device 10 differs from the first embodiment in that: two central cylinders 2 are coaxially arranged in the outer shell 1, and the two lower water collection chambers 3 and the upper water collection chamber 4 in the middle are directly and fixedly connected after removing the cover plate 32. The lower water collection chambers 3 are connected to auxiliary water pipes 34, which extend out of the outer shell 1 to discharge the circulating heat exchange medium. The auxiliary water pipes 34 and the outlet pipe 41 can output circulating heat exchange media at different temperatures, and by controlling the flow rates of the auxiliary water pipes 34 and the outlet pipe 41, the overall outflow temperature of the circulating heat exchange medium can be adjusted, thereby controlling the outflow temperature of the hot flue gas. The waste heat utilization system using this waste heat utilization device 10 is as follows: Figure 7 As shown, the air heater 40 is connected to the inlet pipe 33 and outlet pipe 41 of the waste heat utilization device 10, and the heat exchanger 50 is connected to the inlet pipe 33, outlet pipe 41 and auxiliary water pipe 34 of the waste heat utilization device 10. The circulating heat exchange medium flowing out of the outlet pipe 41 is preferentially supplied to the air heater 40 to ensure the normal operation of the air heater 40.

[0033] Example 3: Based on the above-described Embodiment 2, this embodiment provides a method for utilizing waste heat from flue gas in a thermal power plant. By adjusting the flow regulating valve 61, the temperature of the circulating heat exchange medium exiting the waste heat utilization device 10 is controlled, maintaining the temperature of the hot flue gas exiting the waste heat utilization device 10 between 70-85°C. This ensures that the hot flue gas does not affect subsequent desulfurization operations due to excessively low temperatures. For example, increasing the flow rate through the flow regulating valve 61 prevents some of the circulating heat exchange medium from passing through the corresponding heat exchange tube 5, thereby increasing the temperature of the hot flue gas exiting the waste heat utilization device 10, and vice versa.

[0034] Alternatively, the temperature of the hot flue gas exiting the waste heat utilization device 10 can be controlled between 70-85℃ by adjusting the water output ratio of the outlet pipe 41 and the auxiliary water pipe 34, ensuring that the hot flue gas does not affect subsequent desulfurization operations due to excessively low temperature. For example, increasing the flow rate of the circulating heat exchange medium through the auxiliary water pipe 34 and decreasing the flow rate of the circulating heat exchange medium through the outlet pipe 41 can also reduce the amount of circulating heat exchange medium passing through the entire heat exchange pipe 5, thereby increasing the temperature of the hot flue gas exiting the waste heat utilization device 10, and vice versa.

[0035] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

Claims

1. A device for utilizing waste heat from flue gas in a thermal power plant, characterized in that, include: The enclosed outer shell has an air inlet pipe and an air outlet pipe connected to the top and bottom respectively; The central tube is coaxially arranged in the inner cavity of the outer shell; An annular air passage is formed between the central cylinder and the outer shell; The lower water collection chamber is fixed at the lower end of the central cylinder and has a water inlet pipe that extends out of the outer shell; The upper water collection chamber is fixed at the upper end of the central cylinder and has a water outlet pipe that extends out of the outer shell; The lower water collection chamber is connected to the upper water collection chamber via a U-shaped heat exchange tube. The heat exchange tube passes parallel through the air passage and connects the lower and upper water collection chambers. The heat exchange tubes are evenly distributed around the central cylinder. The inlet and outlet pipes allow the circulating heat exchange medium to flow in and out in a cycle. The central cylinder has a water pipe at both ends that are respectively connected to the lower water collection chamber and the upper water collection chamber. A flow regulating valve with a shut-off function is installed in the water pipe.

2. The waste heat recovery device for flue gas in a thermal power plant according to claim 1, characterized in that: The lower water collection chamber has a cylindrical water collection chamber at one end near the central cylinder. The side of the water collection chamber away from the central cylinder has multiple parallel and spaced flow equalization plates. A conical cover plate is fixed at the lower end of the lower water collection chamber, and the water inlet pipe is located at the center of the cover plate.

3. The waste heat recovery device for flue gas in a thermal power plant according to claim 2, characterized in that: The flow equalization plate is an annular plate with evenly distributed small holes. The central hole of the flow equalization plate is opposite to the water pipe, and the diameter of the central hole is larger than the inner diameter of the water pipe.

4. The waste heat recovery device for flue gas in a thermal power plant according to claim 2, characterized in that: The heat exchange tube is connected to the side wall of the water collection chamber; An axial flow impeller is rotatably mounted at the end of the water pipe. A cleaning assembly is installed at the end of the axial flow impeller away from the water pipe. The cleaning assembly has cleaning brushes around its periphery for cleaning the side walls of the water collection chamber.

5. The waste heat recovery device for flue gas in a thermal power plant according to claim 4, characterized in that: The end of the water pipe has a mounting cavity for installing an axial flow impeller, and an extension sleeve for installing another axial flow impeller is fixed to the end of the water pipe; the end of the extension sleeve near the water pipe has an inwardly extending positioning step, which is limited between the two axial flow impellers, and the two axial flow impellers are fixed together by tie bolts on the shaft.

6. The waste heat recovery device for flue gas in a thermal power plant according to claim 1, characterized in that: The outer shell is cylindrical, and the air inlet pipe and air outlet pipe are installed tangentially to the outer shell.

7. A waste heat recovery system for flue gas from a thermal power plant, comprising the waste heat recovery device for flue gas from a thermal power plant as described in any one of claims 1 to 6, characterized in that, Also includes: The dust collector has an inlet connected to the hot flue gas discharged from the boiler and an outlet connected to the inlet pipe of the waste heat utilization device. The desulfurization unit has its inlet connected to the outlet pipe of the waste heat recovery unit; A warm air heater is connected to the inlet and outlet pipes of the waste heat recovery device and is used to heat the air. The heat exchanger is connected to the inlet and outlet pipes of the waste heat utilization device and is used to heat the condensate of the steam turbine.

8. A waste heat recovery system for flue gas from a thermal power plant according to claim 7, characterized in that: Two central cylinders are arranged coaxially. The lower water collection chamber at the lower end of the upper central cylinder is fixedly connected to the upper water collection chamber at the upper end of the lower central cylinder. The lower water collection chamber at the lower end of the upper central cylinder is connected to an auxiliary water pipe that extends out of the outer shell for draining water. The heat exchanger is connected to the inlet pipe, outlet pipe, and auxiliary water pipe of the waste heat utilization device.

9. A method for utilizing waste heat from flue gas in a thermal power plant, employing a waste heat utilization system for flue gas in a thermal power plant as described in claim 7 or 8, characterized in that: The temperature of the circulating heat exchange medium flowing out of the waste heat utilization device is controlled by adjusting the flow regulating valve, and the temperature of the hot flue gas flowing out of the waste heat utilization device is controlled to be 70-85℃. The circulating heat exchange medium from the waste heat recovery device is preferentially supplied to the air heater.

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