A system for seasonally recovering waste heat from low-temperature flue gas and desulfurization slurry to synergistically eliminate white spots.

Abstract

This invention discloses a system for seasonally recovering waste heat from low-temperature flue gas and desulfurization slurry to synergistically eliminate white plumes. The system includes a flash tower, an indirect heat exchanger, and a type I absorption heat pump. Addressing the difficulties in recovering and utilizing heat and water resources from saturated wet flue gas and slurry after desulfurization, as well as the inability to continuously utilize system waste heat, this system utilizes a flash tower, indirect heat exchanger, and type I absorption heat pump to recover waste heat from the slurry for seasonal heating of the heat network return water and pre-drying of fuel. Heat from the saturated wet flue gas is used seasonally to preheat the heat network return water or air via the indirect heat exchanger. Water in the desulfurized slurry and flue gas is collected and treated for continued use in system makeup water, reducing system water consumption. This invention achieves seasonal and continuous utilization of waste heat from desulfurized flue gas and slurry through valve opening and closing, improving system energy efficiency while reducing the possibility of "white plume" formation, thus contributing to further energy conservation and emission reduction goals for coal-fired power plants.

Description

Technical Field

[0001] This invention belongs to the field of waste heat utilization and energy conservation and environmental protection in coal-fired power plants, and specifically relates to a system for seasonally recovering waste heat from low-temperature flue gas and desulfurization slurry to synergistically eliminate whitening. Background Technology

[0002] For a considerable period in the future, the energy structure dominated by coal will not fundamentally change. With increasingly severe environmental problems, coal-fired power plants are undertaking more energy conservation and emission reduction tasks, and flue gas emission standards are becoming more stringent. Coal-fired power plants commonly use limestone-gypsum wet desulfurization technology to remove sulfur oxides and other harmful substances from flue gas. To prevent low-temperature corrosion, the temperature of the raw flue gas entering the desulfurization tower is generally between 120℃ and 180℃. Inside the desulfurization tower, the flue gas reacts counter-currently with the desulfurization slurry from bottom to top. After the reaction, the temperature of both the flue gas and the slurry is generally 50-60℃. During this process, the slurry temperature rises, and the moisture content of the flue gas increases. If the flue gas is directly discharged through the chimney, a large amount of waste heat and water resources will not be utilized, and environmental problems such as "white plumes" may also occur. Wet desulfurization processes consume a large amount of water, and the slurry needs to be cooled during the desulfurization process, during which a considerable amount of heat contained in the slurry is wasted. After desulfurization, the flue gas and slurry temperatures are low, making it difficult to find a suitable cold source and directly utilizing them is relatively challenging, resulting in low heat exchange efficiency. In northern regions, the most common way to utilize the waste heat from flue gas and slurry is to heat the heating network water; however, the system's waste heat remains unutilized at the end of the heating season, making system modifications complex. Furthermore, combined heat and power (CHP) plants often face a mismatch between heat and power demand, making the improvement of system flexibility and the decoupling of heat and power systems extremely urgent. Summary of the Invention

[0003] To address the aforementioned problems, this invention, considering the difficulties in utilizing the waste heat of desulfurized slurry and flue gas, and the challenges in continuous utilization of this waste heat, provides a system for seasonally recovering low-temperature flue gas and desulfurized slurry waste heat to synergistically eliminate "white plumes." Based on the wet desulfurization process of coal-fired power plants, it utilizes a combination of an indirect heat exchanger, a flash tower, and a first-type absorption heat pump to achieve hydrothermal recovery of the desulfurized flue gas and slurry. Through the opening and closing of a three-way valve and various other valves, the waste heat of both the desulfurized slurry and flue gas is used to heat the heating network water during the heating season, while during the non-heating season, the flue gas waste heat is used to preheat the air, and the slurry waste heat is used for preliminary fuel preheating. Water resources from the flue gas and slurry are collected and used in the system. While fully utilizing the waste heat of the slurry and flue gas, this system reduces water consumption, eliminates "white plumes," and achieves energy and water conservation.

[0004] To achieve the above objectives, the present invention employs the following technical solution:

[0005] A system for seasonally recovering low-temperature flue gas and desulfurization slurry waste heat to synergistically eliminate white spots includes a boiler furnace, a desulfurization tower, a first slurry circulation pump, a flash evaporator, a second slurry circulation pump, a first indirect heat exchanger, a first type of absorption heat pump, a mixer, a regenerator unit, a deaerator, a second indirect heat exchanger, a condenser, a steam turbine, a generator, a three-way valve at the cold side inlet of the second indirect heat exchanger, a three-way valve at the cold side outlet of the second indirect heat exchanger, an air mixer, a three-way valve at the inlet of the first type of absorption heat pump absorber, a three-way valve at the outlet of the first type of absorption heat pump condenser, a secondary heating network water outlet valve, a fuel pre-drying system, a fuel main drying system, and a booster pump.

[0006] An economizer and a main air preheater are arranged in the boiler furnace outlet flue. A dust collector and an induced draft fan are connected in sequence in the boiler furnace outlet flue. The outlet of the induced draft fan is connected to the flue gas inlet of the desulfurization tower. The bottom slurry outlet of the desulfurization tower is connected to the inlet of the first slurry circulation pump. The outlet of the first slurry circulation pump is connected to the upper slurry inlet of the flash tower. The bottom slurry outlet of the flash tower and the slurry inlet of the desulfurization tower are connected through the second slurry circulation pump to form a slurry circulation.

[0007] The flue gas outlet of the desulfurization tower is connected to the high-temperature side of the second indirect heat exchanger, and then the flue gas is introduced into the environment through the chimney; the flue gas condensate outlet of the second indirect heat exchanger is connected to the cold-side inlet of the first indirect heat exchanger; the cold-side inlet of the second indirect heat exchanger is connected to the outlet of the three-way valve of the cold-side inlet of the second indirect heat exchanger, and the cold-side outlet of the second indirect heat exchanger is connected to the inlet of the three-way valve of the cold-side outlet of the second indirect heat exchanger; the cold water inlet pipe of the heating network is connected to the heating network water inlet of the three-way valve of the cold-side inlet of the second indirect heat exchanger; the cold air inlet is connected to the air inlet of the three-way valve of the cold-side inlet of the second indirect heat exchanger; the air outlet of the three-way valve of the cold-side outlet of the second indirect heat exchanger is connected to the second inlet of the air mixer, and the outlet of the air mixer is connected to the inlet of the main air preheater; the heating network water outlet of the three-way valve of the cold-side outlet of the second indirect heat exchanger is connected to the heating network water inlet of the inlet three-way valve of the first type of absorption heat pump absorber, and the preheating fuel inlet of the three-way valve of the first type of absorption heat pump absorber is connected to the heat source outlet of the fuel pre-drying system.

[0008] The flash steam outlet of the flash tower is connected to the high-temperature side inlet of the first indirect heat exchanger, the high-temperature side outlet of the first indirect heat exchanger is connected to the evaporator inlet of the first type of absorption heat pump, and the cold side outlet of the first indirect heat exchanger is connected to the flue gas condensate inlet of the mixer.

[0009] The turbine extraction steam outlet is connected to the generator inlet of the first type of absorption heat pump, the generator outlet of the first type of absorption heat pump is connected to the deaerator heating steam inlet, the absorber inlet of the first type of absorption heat pump is connected to the absorber inlet three-way valve outlet of the first type of absorption heat pump, and the condenser outlet of the first type of absorption heat pump is connected to the condenser outlet three-way valve inlet of the first type of absorption heat pump.

[0010] The outlet three-way valve of the first type absorption heat pump condenser connects the outlet of the heating network water to the inlet of the secondary heating network water outlet valve, and the outlet of the secondary heating network water outlet valve connects to the heat user system; the outlet three-way valve of the first type absorption heat pump condenser connects the preheating fuel outlet to the heat source inlet of the fuel pre-drying system, and the fuel outlet of the fuel pre-drying system connects to the fuel inlet of the main fuel drying system.

[0011] The steam turbine and generator are coaxially connected. The steam turbine outlet is connected to the condenser exhaust steam inlet, the condenser condensate outlet is connected to the mixer condensate inlet, the condenser is connected to the regenerator inlet via a booster pump, and the regenerator outlet is connected to the deaerator condensate inlet.

[0012] A further improvement of the present invention is that it also includes a slurry condensate collector, wherein the evaporator outlet of the first type of absorption heat pump is connected to the slurry condensate collector.

[0013] A further improvement of the present invention is that it also includes a cold air inlet valve, wherein the cold air inlet is connected to the inlet valve of the cold air inlet valve, and the outlet valve of the cold air inlet valve is connected to the air inlet of the cold side inlet three-way valve of the second indirect heat exchanger.

[0014] A further improvement of the present invention is that it also includes a primary heating network water inlet valve, wherein the heating network cold water inlet pipe is connected to the inlet of the primary heating network water inlet valve, and the outlet of the primary heating network water inlet valve is connected to the heating network water inlet of the cold side inlet three-way valve of the second indirect heat exchanger.

[0015] A further improvement of the present invention is that it also includes a cold air outlet valve, wherein the air outlet of the cold side outlet three-way valve of the second indirect heat exchanger is connected to the inlet of the cold air outlet valve, and the outlet of the cold air outlet valve is connected to the second inlet of the air mixer.

[0016] A further improvement of the present invention is that it also includes a primary heating network water outlet valve and a secondary heating network water inlet valve. The heating network water outlet of the second indirect heat exchanger cold side outlet three-way valve is connected to the inlet of the primary heating network water outlet valve. The outlet of the primary heating network water outlet valve is connected to the inlet of the secondary heating network water inlet valve. The heating network water inlet of the first type of absorption heat pump absorber inlet three-way valve is connected to the outlet of the secondary heating network water inlet valve.

[0017] A further improvement of the present invention is that it also includes a fuel pre-drying inlet valve, wherein the inlet three-way valve of the first type of absorption heat pump absorber preheats the fuel inlet and connects to the outlet of the fuel pre-drying inlet valve, and the inlet of the fuel pre-drying inlet valve is connected to the heat source outlet of the fuel pre-drying system.

[0018] A further improvement of the present invention is that it also includes a fuel pre-drying outlet valve, wherein the outlet of the first type of absorption heat pump condenser 3-way valve is connected to the inlet of the fuel pre-drying outlet valve, and the outlet of the fuel pre-drying outlet valve is connected to the heat source inlet of the fuel pre-drying system.

[0019] A further improvement of this invention is that, during the heating season, the cold air inlet valve, cold air outlet valve, fuel pre-drying inlet valve, and fuel pre-drying outlet valve are closed, while the primary heating network water inlet valve, primary heating network water outlet valve, secondary heating network water inlet valve, and secondary heating network water outlet valve are open. At this time, all the cold air enters through the first inlet of the air mixer and is heated to the corresponding temperature by the main air preheater before being sent into the furnace. All the fuel is dried by the main fuel drying system. At this time, both the flue gas and the slurry are used to heat the heating network water, which can be heated to a preset temperature.

[0020] A further improvement of this invention is that, during the non-heating season, the cold air inlet valve, cold air outlet valve, fuel pre-drying inlet valve, and fuel pre-drying outlet valve are open, while the primary heating network water inlet valve, primary heating network water outlet valve, secondary heating network water inlet valve, and secondary heating network water outlet valve are closed. At this time, part of the cold air enters from the first inlet of the air mixer, and part enters from the inlet of the cold air inlet valve. A portion of the cold air is heated by the flue gas in the second indirect heat exchanger and then mixed with the cold air entering from the first inlet of the air mixer. The mixed air then enters the main air preheater. The fuel is first pre-dried by the fuel pre-drying system through a first-type absorption heat pump, and then dried by the main fuel drying system.

[0021] The system for synergistic whitening of low-temperature flue gas and desulfurization slurry waste heat recovery in a seasonal manner provided by the present invention has the following advantages:

[0022] 1. By opening and closing valves, the hydrothermal resources in the desulfurized slurry and flue gas can be continuously utilized seasonally, thereby improving system efficiency and achieving environmental protection.

[0023] 2. By using an indirect heat exchanger, the waste heat of flue gas is used to preheat air or preheat the cooling water of the heating network. The water resources recovered from the flue gas are also exchanged with flash steam through the indirect heat exchanger. The flash steam is condensed into liquid water at a higher temperature. The heated flue gas condensate is mixed with the turbine condensate and then pressurized before entering the low-pressure heater, thus realizing flue gas water heat recovery. The condensate recovered from the flue gas is heated and used for power plant makeup water, achieving the purpose of energy and water conservation.

[0024] 3. The first type of absorption heat pump is used to recover the waste heat in the desulfurized slurry through flash tower and indirect heat exchanger. Steam extracted from the turbine, which is readily available in the power plant, is selected as the driving heat source and then fed into the deaerator to continue to participate in the system power cycle, so as to realize the recycling of slurry and the deep utilization of low temperature waste heat.

[0025] 4. Wet desulfurization consumes a large amount of water. The water obtained through flash evaporation and indirect heat exchangers is of high quality. After heat exchange in the first type of heat pump, the collected water can be used for desulfurization slurry or system makeup water, which reduces the system water consumption and realizes the efficient recycling of water resources.

[0026] 5. During the heating season, all waste heat can be used to heat the heating network water to achieve combined heat and power. By reheating the heating network water through flue gas and slurry, its temperature can be adjusted to the ideal operating conditions, eliminating the need for subsequent adjustment of the heating network water through a more complex system.

[0027] 6. During the non-heating season, the waste heat of flue gas is used to preheat the air, and the waste heat of the slurry is used for pre-drying. All of these methods improve boiler efficiency, promote stable combustion in the boiler, and make the system more energy-efficient.

[0028] 7. By reducing the slurry temperature and recovering the waste heat and water resources from the saturated wet flue gas after desulfurization, the system efficiency is improved while achieving the environmental protection effect of eliminating "white plumes".

[0029] 8. By setting up a slurry condensate collector, the wet desulfurization process consumes a huge amount of water. The water quality after flash steam condensation is relatively good. After collection and treatment, it can be used for system water supply, thus saving water resources. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a system for the synergistic elimination of whitening by seasonally recovering low-temperature flue gas and waste heat from desulfurization slurry, according to the present invention.

[0031] Figure 2 This is a schematic diagram of the heating season timekeeping system.

[0032] Figure 3 This is a schematic diagram of the system during the non-heating season.

[0033] Explanation of reference numerals in the attached figures:

[0034] 1 is the boiler furnace; 2 is the economizer; 3 is the main air preheater; 4 is the dust collector; 5 is the induced draft fan; 6 is the desulfurization tower; 7 is the first slurry circulation pump; 8 is the flash evaporator; 9 is the second slurry circulation pump; 10 is the first indirect heat exchanger; 11 is the first type of absorption heat pump; 12 is the mixer; 13 is the regenerator unit; 14 is the deaerator; 15 is the second indirect heat exchanger; 16 is the slurry condensate collector; 17 is the condenser; 18 is the steam turbine; 19 is the generator; 20 is the cold air inlet valve; 21 is the primary heating network water inlet valve; 22 is... 23 is the three-way valve at the cold side inlet of the second indirect heat exchanger; 24 is the three-way valve at the cold side outlet of the second indirect heat exchanger; 25 is the primary heating network water outlet valve; 26 is the cold air outlet valve; 27 is the three-way valve at the inlet of the first type of absorption heat pump absorber; 28 is the secondary heating network water inlet valve; 29 is the fuel pre-drying inlet valve; 30 is the three-way valve at the outlet of the first type of absorption heat pump condenser; 31 is the secondary heating network water outlet valve; 32 is the fuel pre-drying outlet valve; 33 is the fuel pre-drying system; 34 is the main fuel drying system; and 35 is the booster pump. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to the accompanying drawings:

[0036] See Figure 1 This invention provides a system for seasonally recovering low-temperature flue gas and desulfurization slurry waste heat to synergistically eliminate white spots. The system includes a boiler furnace 1, economizer 2, main air preheater 3, dust collector 4, induced draft fan 5, desulfurization tower 6, first slurry circulation pump 7, flash evaporator 8, second slurry circulation pump 9, first indirect heat exchanger 10, first type absorption heat pump 11, mixer 12, regeneration heater group 13, deaerator 14, second indirect heat exchanger 15, slurry condensate collector 16, condenser 17, steam turbine 18, generator 19, and cold air inlet valve 20. 21. Primary heating network water inlet valve; 22. Secondary indirect heat exchanger cold side inlet three-way valve; 23. Secondary indirect heat exchanger cold side outlet three-way valve; 24. Primary heating network water outlet valve; 25. Cold air outlet valve; 26. Air mixer; 27. Type I absorption heat pump absorber inlet three-way valve; 28. Secondary heating network water inlet valve; 29. ​​Fuel pre-drying inlet valve; 30. Type I absorption heat pump condenser outlet three-way valve; 31. Secondary heating network water outlet valve; 32. Fuel pre-drying outlet valve; 33. Fuel pre-drying system; 34. Fuel main drying system; and 35. Booster pump.

[0037] The system can be divided into two systems, one for heating season and one for non-heating season, by controlling the opening and closing of valves. The boiler furnace 1 outlet flue is equipped with an economizer 2, a main air preheater 3, a dust collector 4, and an induced draft fan 5. Flue gas enters the bottom flue gas inlet of the desulfurization tower 6 through the outlet of the induced draft fan 5. The bottom slurry outlet of the desulfurization tower 6 is connected to the inlet of the first slurry circulation pump 7. The outlet of the first slurry circulation pump 7 is connected to the upper slurry inlet of the flash tower 8. The bottom slurry outlet of the flash tower 8 is connected to the slurry inlet of the desulfurization tower 6 through a second slurry circulation pump 9, forming a slurry circulation system.

[0038] The flue gas outlet of desulfurization tower 6 is connected to the high-temperature side of the second indirect heat exchanger 15, and then the flue gas is introduced into the environment through the chimney; the flue gas condensate outlet of the second indirect heat exchanger 15 is connected to the cold-side inlet of the first indirect heat exchanger 10; the cold-side inlet of the second indirect heat exchanger 15 is connected to the outlet of the cold-side inlet three-way valve 22 of the second indirect heat exchanger, and the cold-side outlet of the second indirect heat exchanger 15 is connected to the inlet of the cold-side outlet three-way valve 23 of the second indirect heat exchanger; the cold water inlet pipe of the heating network is connected to the inlet of the primary heating network water inlet valve 21, and the outlet of the primary heating network water inlet valve 21 is connected to the heating network water inlet of the cold-side inlet three-way valve 22 of the second indirect heat exchanger; the cold air inlet is connected to the inlet valve of the cold air inlet valve 20, and the outlet valve of the cold air inlet valve 20 is connected to the cold-side inlet three-way valve 22 of the second indirect heat exchanger. The air inlet of valve 22 is connected to the air outlet of the three-way valve 23 at the cold side outlet of the second indirect heat exchanger, which is connected to the inlet of the cold air outlet valve 25. The outlet of the cold air outlet valve 25 is connected to the second inlet of the air mixer 26, and the outlet of the air mixer 26 is connected to the inlet of the main air preheater 3. The hot water outlet of the three-way valve 23 at the cold side outlet of the second indirect heat exchanger is connected to the inlet of the primary hot water outlet valve 24, and the outlet of the primary hot water outlet valve 24 is connected to the inlet of the secondary hot water inlet valve 28. During the heating season, the cold air inlet valve 20 and the cold air outlet valve 25 are closed, and the primary hot water inlet valve 21 and the primary hot water outlet valve 24 are open. During the non-heating season, the cold air inlet valve 20 and the cold air outlet valve 25 are open, and the primary hot water inlet valve 21 and the primary hot water outlet valve 24 are closed.

[0039] The flash steam outlet of flash tower 8 is connected to the high-temperature side inlet of the first indirect heat exchanger 10. The high-temperature side outlet of the first indirect heat exchanger 10 is connected to the evaporator inlet of the first type of absorption heat pump 11. The cold side outlet of the first indirect heat exchanger 10 is connected to the flue gas condensate inlet of mixer 12. The evaporator outlet of the first type of absorption heat pump 11 is connected to slurry condensate collector 16, where condensate is collected. The steam extraction outlet of turbine 18 is connected to the generator inlet of the first type of absorption heat pump 11. The generator outlet of the first type of absorption heat pump 11 is connected to deaerator 14 for heating steam. The steam inlet of the first-type absorption heat pump 11 is connected to the inlet of the first-type absorption heat pump absorber inlet three-way valve 27; the condenser outlet of the first-type absorption heat pump 11 is connected to the inlet of the first-type absorption heat pump condenser outlet three-way valve 30; the heat network water inlet of the first-type absorption heat pump absorber inlet three-way valve 27 is connected to the outlet of the secondary heat network water inlet valve 28; the preheating fuel inlet of the first-type absorption heat pump absorber inlet three-way valve 27 is connected to the outlet of the fuel pre-drying inlet valve 29; and the inlet of the fuel pre-drying inlet valve 29 is connected to the heat source outlet of the fuel pre-drying system 33. The outlet of the first-type absorption heat pump condenser 30 is connected to the inlet of the secondary heating network water outlet valve 31, and the outlet of the secondary heating network water outlet valve 31 is connected to the heat user system; the outlet of the first-type absorption heat pump condenser 30 is connected to the inlet of the preheating fuel outlet valve 32, and the outlet of the preheating fuel outlet valve 32 is connected to the heat source inlet of the preheating fuel system 33, and the fuel outlet of the preheating fuel system 33 is connected to the fuel inlet of the main fuel drying system 34; during the heating season, the preheating fuel inlet valve 29 and the preheating fuel outlet valve 32 are closed, and the secondary heating network water outlet valve 31 is connected to the heat user system; Secondary heating network water inlet valve 28 and secondary heating network water outlet valve 31 are open; during the non-heating season, fuel pre-drying inlet valve 29 and fuel pre-drying outlet valve 32 are open, and secondary heating network water inlet valve 28 and secondary heating network water outlet valve 31 are closed; steam turbine 18 is coaxially connected to generator 19, steam turbine 18 outlet is connected to condenser 17 exhaust steam inlet, condenser 17 condensate outlet is connected to mixer 12 condensate inlet, condenser 17 is connected to regenerator 13 inlet via booster pump 35, and regenerator 13 outlet is connected to deaerator 14 condensate inlet.

[0040] The specific working process of this invention is as follows:

[0041] See Figure 2During the heating season, flue gas flows from the boiler furnace 1 through the economizer 2, main air preheater 3, and dust collector 4, and is introduced by the induced draft fan 5 into the flue gas inlet at the bottom of the desulfurization tower 6. At the bottom of the desulfurization tower 6, the flue gas contacts, reacts with, and exchanges heat with the low-temperature desulfurization slurry from bottom to top. The cooled and humidified clean flue gas flows from the flue gas outlet at the top of the desulfurization tower 6 to the high-temperature side inlet of the second indirect heat exchanger 15. Inside the second indirect heat exchanger 15, the flue gas exchanges heat with cold water from the heating network. The flue gas condensate flows to the cold side inlet of the first indirect heat exchanger 10. The pre-heated heating network water flows into the absorber of the first absorption heat pump 11 through the three-way valve 23 at the cold side outlet of the second indirect heat exchanger, the primary heating network water outlet valve 24, the secondary heating network water inlet valve 28, and the three-way valve 27 at the inlet of the first type of absorption heat pump absorber.

[0042] The high-temperature slurry, heated by the flue gas, enters the upper part of the flash tower 8 via the first slurry circulation pump 7. Upon entering the flash tower, the pressure of the high-temperature slurry rapidly decreases, causing the water in the slurry to flash into steam, and the slurry temperature drops. Subsequently, the low-temperature slurry, after treatment, flows from the second slurry circulation pump 9 into the top slurry inlet of the desulfurization tower 6, continuing to react with the flue gas. The flash steam flows from the flash tower 8 to the high-temperature side inlet of the first indirect heat exchanger 10, where it is condensed by the flue gas condensate. The condensed flash steam then flows into the evaporator of a type-I absorption heat pump 11. After heat exchange, the flash condensate is collected by the slurry condensate collector 16.

[0043] The extraction steam outlet of turbine 18 is connected to the generator inlet of the first-type absorption heat pump 11. Driven by the extraction steam from turbine 18, the condensate from the slurry flash steam is heated by the secondary heating network water through the first-type absorption heat pump 11. The heated network water flows to the heat user through the three-way valve 30 at the condenser outlet of the first-type absorption heat pump and the secondary heating network water outlet valve 31. Turbine 18 is coaxially connected to generator 19. The exhaust steam from turbine 18 is condensed by condenser 17 and flows into mixer 12 to mix with flue gas condensate. After mixing, it flows into regenerator group 13 through booster pump 35 and is heated by regenerator group 13 before flowing into deaerator 14. The extraction steam from turbine 18 after heat exchange in the first-type absorption heat pump 11 flows from the generator outlet of the first-type absorption heat pump 11 to deaerator 14.

[0044] See Figure 3During the non-heating season, flue gas flows from the boiler furnace 1 through the economizer 2, main air preheater 3, and dust collector 4, and is introduced by the induced draft fan 5 into the flue gas inlet at the bottom of the desulfurization tower 6. At the bottom of the desulfurization tower 6, the flue gas contacts, reacts with, and exchanges heat with the low-temperature desulfurization slurry from bottom to top. The cooled and humidified clean flue gas flows from the flue gas outlet at the top of the desulfurization tower 6 to the high-temperature side inlet of the second indirect heat exchanger 15. In the second indirect heat exchanger 15, the flue gas heats the cold air. The preheated air flows into the air mixer 26, mixes with the air from the air mixer 26, and then flows to the main air preheater 3. In the main air preheater 3, it is heated by the original flue gas, and the flue gas condensate flows to the cold side inlet of the first indirect heat exchanger 10.

[0045] The high-temperature slurry, heated by the flue gas, enters the upper part of the flash tower 8 via the first slurry circulation pump 7. Upon entering the flash tower, the pressure of the high-temperature slurry rapidly decreases, causing the water in the slurry to flash into steam, and the slurry temperature drops. Subsequently, the low-temperature slurry, after treatment, flows from the second slurry circulation pump 9 into the top slurry inlet of the desulfurization tower 6, continuing to react with the flue gas. The flash steam flows from the flash tower 8 to the high-temperature side inlet of the first indirect heat exchanger 10, where it is condensed by the flue gas condensate. The condensed flash steam then flows into the evaporator of a type-I absorption heat pump 11. After heat exchange, the flash condensate is collected by the slurry condensate collector 16.

[0046] The heat source medium from the fuel pre-drying system 33 flows into the absorber of the first-type absorption heat pump 11 via the fuel pre-drying inlet valve 29 and the three-way valve 27 of the first-type absorption heat pump absorber. The steam extraction outlet of the turbine 18 is connected to the generator inlet of the first-type absorption heat pump 11. Driven by the steam extraction of the turbine 18, the condensate from the flash steam of the slurry is reheated by the first-type absorption heat pump 11. The heated heat source medium from the fuel pre-drying system 33 flows from the three-way valve 30 of the first-type absorption heat pump condenser outlet and the fuel pre-drying outlet valve 32 to the fuel pre-drying system 33. It then enters the main fuel drying system 34 for further drying after being pre-dried by the fuel pre-drying system 33. The fully dried fuel then enters the boiler furnace 1.

[0047] Steam turbine 18 is coaxially connected to generator 19. Exhaust steam from turbine 18 is condensed by condenser 17 and flows into mixer 12, where it mixes with flue gas condensate. The mixture then flows through booster pump 35 into regenerator assembly 13, where it is heated before flowing into deaerator 14. Steam extracted from turbine 18 after heat exchange in the first-type absorption heat pump 11 flows from the generator outlet of the first-type absorption heat pump 11 to deaerator 14.

[0048] The present invention provides a system for seasonal recovery of low-temperature flue gas and desulfurization slurry waste heat to jointly eliminate whitening. The steps are as follows: (1) recovering water and heat resources in saturated wet flue gas through an indirect heat exchanger for preheating air or preheating heating network water; (2) recovering waste heat of desulfurized slurry through a flash tower, an indirect heat exchanger and a first-type absorption heat pump to pre-dry fuel or further heat heating network water and collect slurry condensate; (3) using steam extraction from a steam turbine to drive the first-type absorption heat pump, and then the heat exchanged into the deaerator.

[0049] Furthermore, depending on the actual situation, a specific type of first-class absorption heat pump can be selected, such as a lithium bromide absorption heat pump.

[0050] Furthermore, different types of indirect heat exchangers can be selected based on the temperature of the original flue gas and the temperature of the flue gas after desulfurization to meet the system requirements.

[0051] Furthermore, according to the requirements of wet desulfurization process, desulfurization towers are usually equipped with demister layers, spray layers and backwash layers, etc. The slurry after flash evaporation needs to be treated before it can be used for desulfurization.

[0052] The above content is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any simple deductions or substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the concept of the present invention, should be regarded as falling within the scope of patent protection of the present invention as determined by the submitted claims.

Claims

1. A system for seasonally recovering waste heat from low-temperature flue gas and desulfurization slurry to synergistically eliminate whitening, characterized in that, It includes a boiler furnace (1), a desulfurization tower (6), a first slurry circulation pump (7), a flash tower (8), a second slurry circulation pump (9), a first indirect heat exchanger (10), a first type of absorption heat pump (11), a mixer (12), a regenerator unit (13), a deaerator (14), a second indirect heat exchanger (15), a condenser (17), a steam turbine (18), a generator (19), a three-way valve (22) at the cold side inlet of the second indirect heat exchanger, a three-way valve (23) at the cold side outlet of the second indirect heat exchanger, an air mixer (26), a three-way valve (27) at the inlet of the first type of absorption heat pump absorber, a three-way valve (30) at the outlet of the first type of absorption heat pump condenser, a secondary heating network water outlet valve (31), a fuel pre-drying system (33), a fuel main drying system (34), and a booster pump (35). An economizer (2) and a main air preheater (3) are arranged in the outlet flue of the boiler furnace (1). A dust collector (4) and an induced draft fan (5) are connected in sequence in the outlet flue of the boiler furnace (1). The outlet of the induced draft fan (5) is connected to the flue gas inlet of the desulfurization tower (6). The bottom slurry outlet of the desulfurization tower (6) is connected to the inlet of the first slurry circulation pump (7). The outlet of the first slurry circulation pump (7) is connected to the upper slurry inlet of the flash tower (8). The bottom slurry outlet of the flash tower (8) is connected to the slurry inlet of the desulfurization tower (6) through the second slurry circulation pump (9) to form a slurry circulation. The flue gas outlet of the desulfurization tower (6) is connected to the high-temperature side of the second indirect heat exchanger (15), and then the flue gas is introduced into the environment through the chimney; the flue gas condensate outlet of the second indirect heat exchanger (15) is connected to the cold-side inlet of the first indirect heat exchanger (10); the cold-side inlet of the second indirect heat exchanger (15) is connected to the outlet of the three-way valve (22) of the cold-side inlet of the second indirect heat exchanger, and the cold-side outlet of the second indirect heat exchanger (15) is connected to the inlet of the three-way valve (23) of the cold-side outlet of the second indirect heat exchanger; the cold water inlet pipe of the heating network is connected to the cold-side inlet three-way valve (22) of the second indirect heat exchanger and the heating network water inlet. The cold air inlet is connected to the air inlet of the cold side inlet three-way valve (22) of the second indirect heat exchanger; the air outlet of the cold side outlet three-way valve (23) of the second indirect heat exchanger is connected to the second inlet of the air mixer (26), and the outlet of the air mixer (26) is connected to the inlet of the main air preheater (3); the hot water outlet of the cold side outlet three-way valve (23) of the second indirect heat exchanger is connected to the hot water inlet of the first type of absorption heat pump absorber inlet three-way valve (27), and the preheating fuel inlet of the first type of absorption heat pump absorber inlet three-way valve (27) is connected to the heat source outlet of the fuel pre-drying system (33); The flash steam outlet of the flash tower (8) is connected to the high-temperature side inlet of the first indirect heat exchanger (10), the high-temperature side outlet of the first indirect heat exchanger (10) is connected to the evaporator inlet of the first type of absorption heat pump (11), and the cold side outlet of the first indirect heat exchanger (10) is connected to the flue gas condensate inlet of the mixer (12). The steam extraction outlet of the steam turbine (18) is connected to the generator inlet of the first type of absorption heat pump (11), the generator outlet of the first type of absorption heat pump (11) is connected to the heating steam inlet of the deaerator (14), the absorber inlet of the first type of absorption heat pump (11) is connected to the outlet of the three-way valve (27) of the absorber of the first type of absorption heat pump, and the condenser outlet of the first type of absorption heat pump (11) is connected to the inlet of the three-way valve (30) of the condenser outlet of the first type of absorption heat pump. The outlet three-way valve (30) of the first type of absorption heat pump condenser connects to the inlet of the secondary heating network water outlet valve (31), and the outlet of the secondary heating network water outlet valve (31) connects to the heat user system; the outlet three-way valve (30) of the first type of absorption heat pump condenser connects to the heat source inlet of the fuel pre-drying system (33), and the fuel outlet of the fuel pre-drying system (33) connects to the fuel inlet of the main fuel drying system (34). The steam turbine (18) is coaxially connected to the generator (19). The outlet of the steam turbine (18) is connected to the exhaust steam inlet of the condenser (17). The condensate outlet of the condenser (17) is connected to the condensate inlet of the mixer (12). The condenser (17) is connected to the inlet of the regenerator group (13) through the booster pump (35). The outlet of the regenerator group (13) is connected to the condensate inlet of the deaerator (14). It also includes a slurry condensate collector (16), and the evaporator outlet of the first type of absorption heat pump (11) is connected to the slurry condensate collector (16); It also includes a cold air inlet valve (20), the cold air inlet is connected to the inlet valve of the cold air inlet valve (20), and the outlet valve of the cold air inlet valve (20) is connected to the air inlet of the cold side inlet three-way valve (22) of the second indirect heat exchanger; It also includes a primary heating network water inlet valve (21), a heating network cold water inlet pipe connected to the inlet of the primary heating network water inlet valve (21), and a primary heating network water inlet valve (21) outlet connected to the second indirect heat exchanger cold side inlet three-way valve (22) heating network water inlet; During the heating season, both flue gas and slurry are used to heat the heating network water, which can be heated to the preset temperature. During the non-heating season, some cold air is heated by flue gas in the second indirect heat exchanger (15) and then enters the main air preheater (3). The fuel is first pre-dried by the fuel pre-drying system (33) through the first type of absorption heat pump (11), and then dried by the fuel main drying system (34).

2. The system for seasonally recovering low-temperature flue gas and desulfurization slurry waste heat to synergistically eliminate whitening, as described in claim 1, is characterized in that... It also includes a cold air outlet valve (25), the air outlet of the second indirect heat exchanger cold side outlet three-way valve (23) is connected to the inlet of the cold air outlet valve (25), and the outlet of the cold air outlet valve (25) is connected to the second inlet of the air mixer (26).

3. The system for seasonally recovering low-temperature flue gas and desulfurization slurry waste heat to synergistically eliminate whitening, as described in claim 2, is characterized in that... It also includes a primary heating network water outlet valve (24) and a secondary heating network water inlet valve (28). The heating network water outlet of the second indirect heat exchanger cold side outlet three-way valve (23) is connected to the inlet of the primary heating network water outlet valve (24). The outlet of the primary heating network water outlet valve (24) is connected to the inlet of the secondary heating network water inlet valve (28). The heating network water inlet of the first type of absorption heat pump absorber inlet three-way valve (27) is connected to the outlet of the secondary heating network water inlet valve (28).

4. The system for seasonally recovering low-temperature flue gas and desulfurization slurry waste heat to synergistically eliminate whitening, as described in claim 3, is characterized in that... It also includes a fuel pre-drying inlet valve (29), a first-class absorption heat pump absorber inlet three-way valve (27) for preheating fuel inlet connected to the fuel pre-drying inlet valve (29) outlet, and a fuel pre-drying inlet valve (29) inlet connected to the fuel pre-drying system (33) heat source outlet.

5. The system for seasonally recovering low-temperature flue gas and desulfurization slurry waste heat to synergistically eliminate whitening, as described in claim 4, is characterized in that... It also includes a fuel pre-drying outlet valve (32), a first-class absorption heat pump condenser outlet three-way valve (30) preheating fuel outlet connected to the inlet of the fuel pre-drying outlet valve (32), and the outlet of the fuel pre-drying outlet valve (32) connected to the heat source inlet of the fuel pre-drying system (33).

6. The system for seasonally recovering low-temperature flue gas and desulfurization slurry waste heat to synergistically eliminate whitening, as described in claim 5, is characterized in that... During the heating season, the cold air inlet valve (20), cold air outlet valve (25), fuel pre-drying inlet valve (29) and fuel pre-drying outlet valve (32) are closed, while the primary heating network water inlet valve (21), primary heating network water outlet valve (24), secondary heating network water inlet valve (28) and secondary heating network water outlet valve (31) are opened. At this time, all the cold air enters through the first inlet of the air mixer (26) and is heated to the corresponding temperature by the main air preheater (3) before being sent into the furnace (1). All the fuel is dried by the main fuel drying system (34).

7. The system for seasonally recovering low-temperature flue gas and desulfurization slurry waste heat to synergistically eliminate whitening, as described in claim 5, is characterized in that... During the non-heating season, the cold air inlet valve (20), cold air outlet valve (25), fuel pre-drying inlet valve (29) and fuel pre-drying outlet valve (32) are opened, and the primary heating network water inlet valve (21), primary heating network water outlet valve (24), secondary heating network water inlet valve (28) and secondary heating network water outlet valve (31) are closed. At this time, part of the cold air enters from the first inlet of the air mixer (26), part enters from the inlet of the cold air inlet valve (20), and part of the cold air is heated by the flue gas in the second indirect heat exchanger (15) and then mixed with the cold air entering from the first inlet of the air mixer (26). The mixed air enters the main air preheater (3).

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