A condensable particulate matter removal coupled waste heat utilization system and method

Abstract

This invention relates to the field of flue gas treatment technology, and more particularly to a system and method for removing condensable particulate matter coupled with waste heat utilization. The system includes a primary removal unit, a secondary removal unit, a tertiary removal unit, and a cold source supply unit. The primary removal unit includes a flash tank connected to a desulfurization tower, where the slurry is cooled to perform primary condensation removal of the flue gas. The secondary removal unit includes a heat exchanger and a flue gas spray device; the outlet flue gas flows through the flue gas spray device, and the heat exchanger is connected to the spray device, where the spray liquid performs secondary condensation removal of the flue gas. The tertiary removal unit includes a condenser, where the outlet flue gas flows into the condenser for tertiary condensation removal. The cold source supply unit includes a cooling tower and a heat pump, which supplies cooling water to the removal units. This system solves the problem of insufficient removal capacity of existing systems for condensable particulate matter, while simultaneously realizing the recovery and utilization of low-temperature waste heat from the flue gas.

Description

Technical Field

[0001] This invention relates to the field of flue gas treatment technology, and in particular to a system and method for removing condensable particulate matter coupled with waste heat utilization. Background Technology

[0002] In the field of flue gas treatment technology, especially for flue gas emitted from stationary pollution sources such as coal-fired power plants, wet desulfurization systems are typically used to control sulfur dioxide. In the wet desulfurization process, after the flue gas comes into contact with the slurry in the desulfurization tower, acidic gases such as sulfur dioxide are absorbed, and at the same time the flue gas is humidified and cooled, and discharged in the form of saturated wet flue gas.

[0003] Currently, large thermal power units are generally equipped with environmental protection facilities such as dust removal, desulfurization, and denitrification, achieving ultra-low emissions of conventional pollutants such as dust, sulfur dioxide, and nitrogen oxides. However, existing dust removal and desulfurization equipment mainly targets the removal of solid particulate matter and acidic gases, and its removal efficiency for condensable particulate matter (CPM) existing in aerosol or gaseous form is limited. Studies have shown that the flue gas from wet desulfurization still contains a high concentration of condensable particulate matter. After these particles are released into the atmosphere, they will transform into fine particulate matter in the ambient air, which is an important precursor to PM2.5 and impacts the atmospheric environment.

[0004] Therefore, existing environmental protection systems lack specialized removal methods for condensable particulate matter. Condensable particulate matter in flue gas is directly emitted with saturated wet flue gas, making it difficult to meet increasingly stringent environmental requirements. Secondly, the outlet flue gas temperature of wet desulfurization is usually between 50-55℃, carrying a large amount of water vapor and low-temperature waste heat. This heat is not effectively utilized, resulting in energy waste. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a system and method for removing condensable particulate matter coupled with waste heat utilization, in order to solve the problem of insufficient removal capacity of existing wet desulfurization systems for condensable particulate matter, while simultaneously realizing the recovery and utilization of low-temperature waste heat from flue gas.

[0006] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions: A system for removing condensable particulate matter coupled with waste heat utilization includes a primary removal unit, a secondary removal unit, a tertiary removal unit, and a cold source supply unit. The primary removal unit includes a flash tank connected to a desulfurization tower, which cools the slurry and returns it to the desulfurization tower for primary condensation removal of condensable particulate matter in the flue gas. The secondary removal unit includes a heat exchanger and a flue gas spray device. The outlet flue gas flows through the flue gas spray device, and the heat exchanger is connected to the spray device. The cooled spray liquid performs secondary condensation removal of condensable particulate matter in the flue gas. The tertiary removal unit includes a condenser, which is connected to the outlet flue gas and performs tertiary condensation removal of condensable particulate matter in the flue gas. The cold source supply unit includes a cooling tower and a heat pump, which supplies cooling water to the removal units.

[0007] Optionally, a slurry switching valve is provided between the flash tank and the desulfurization tower. The slurry switching valve includes a first slurry switching valve, a second slurry switching valve, and a third slurry switching valve. The third slurry switching valve is located on the pipeline between the bottom and the top of the desulfurization tower. The first slurry switching valve is located between the pipeline and the slurry inlet of the flash tank and upstream of the third slurry switching valve. The second slurry switching valve is located between the slurry outlet of the flash tank and the pipeline and downstream of the third slurry switching valve.

[0008] Optionally, the primary removal unit further includes a waste steam condenser, the waste steam outlet of the flash tank is connected to the waste steam inlet of the waste steam condenser, the cold source supply unit is connected to the cooling water inlet of the waste steam condenser, and the waste steam condensate is pumped to the cold source supply unit or the power plant raw water tank by the waste steam condensate discharge pump. The waste steam condenser is also connected to a vacuum pump.

[0009] Optionally, the secondary removal unit further includes a circulating water tank, which is connected to the hot end of the heat exchanger. After heat exchange and cooling, the water is introduced into the flue spray device. The cold source supply unit is connected to the cold end of the heat exchanger, and the cooling water is returned to the cold source supply unit after heat exchange and heating.

[0010] Optionally, the secondary removal unit further includes a spray liquid collector, which is installed at the lower end of the flue spray device and connected to the circulating water tank.

[0011] Optionally, the three-stage removal unit further includes a centrifugal electric chiller connected to the condenser to cool the flue gas, and the condensate in the flue gas flows by gravity to the circulating water tank; the cold source supply unit is connected to the centrifugal electric chiller, and the cooling water returns to the cold source supply unit after being heated by heat exchange.

[0012] Optionally, the water in the circulating water tank is divided into two paths after passing through a heat exchanger. One path leads to the flue spray device, and the other path leads to the cold source supply unit through a water replenishment pipe. A spray liquid discharge valve is installed on the water replenishment pipe.

[0013] Optionally, a flue gas demister is also provided downstream of the condenser. The flue gas after three-stage de-misting is introduced into the flue gas demister and then discharged to the chimney.

[0014] Optionally, the cooling tower is a mechanically ventilated cooling tower, the heat pump is a lithium bromide heat pump, and the cold source supply unit further includes a cooling water switching valve. The cooling water switching valve includes a first cooling water switching valve, a second cooling water switching valve, a third cooling water switching valve, and a fourth cooling water switching valve. The first and third cooling water switching valves are connected to the mechanically ventilated cooling tower, and the second and fourth cooling water switching valves are connected to the lithium bromide heat pump.

[0015] This invention also provides a method for utilizing the waste heat from the removal of condensable particulate matter, comprising: The slurry from the desulfurization tower is led out to the flash tank for negative pressure flash evaporation. The cooled slurry is then returned to the desulfurization tower to spray the flue gas, thereby cooling the flue gas to the first set temperature range. The exhaust steam generated in the flash tank is passed into the exhaust steam condenser for condensation to form exhaust steam condensate. A flue spraying device is installed on the flue outlet of the desulfurization tower. Spraying circulating water is passed into the heat exchanger to exchange heat with cooling water. The cooled spraying circulating water enters the flue spraying device to spray the flue gas, so that the flue gas is cooled to the second set temperature range. The sprayed circulating water falls into the spray liquid collector and then returns to the circulating water tank. The flue gas, after being cooled by the flue spray device, is fed into the condenser. The condenser is fed with cold water produced by a centrifugal electric refrigeration unit to perform indirect heat exchange and cool the flue gas to the third set temperature range. The condensate in the flue gas flows by gravity to the circulating water tank. During the non-heating season, the heat pump is disconnected from the cooling water circulation loop, and the cooling tower is disconnected from the cooling water circulation loop. The cooling water is taken out from the bottom of the cooling tower and then fed into the exhaust steam condenser, heat exchanger and centrifugal electric chiller. The heated cooling water is then returned to the cooling tower. During the heating season, the cooling tower is disconnected from the cooling water circulation loop, and the heat pump is connected to the cooling water circulation loop. The cooling water flows sequentially through the waste steam condenser, heat exchanger, and centrifugal electric chiller before entering the evaporator of the heat pump to release heat and cool down. The cooled cooling water continues to flow through the waste steam condenser, heat exchanger, and centrifugal electric chiller. The heat pump absorbs the waste heat of the cooling water and transfers it to the heating network for heating.

[0016] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages: In this system, the primary removal unit is connected to the desulfurization tower via a flash tank. The cooled slurry is returned to the desulfurization tower and used to spray the flue gas, achieving primary condensation removal of condensable particulate matter. The primary removal directly cools the flue gas within the desulfurization tower. The low-temperature slurry after flash evaporation contacts the flue gas, reducing its temperature from 50-55℃ to 40-45℃, causing partial condensation of water vapor and capturing condensable particulate matter through condensation. The secondary removal unit uses a heat exchanger and a flue gas spray system. The heat exchanger cools the circulating spray water before sending it to the flue gas spray system for a second cooling process, further reducing the flue gas temperature to 30-35℃. During this process, water vapor continues to condense, further removing condensable particulate matter. The three-stage particulate matter removal unit uses a condenser to deeply cool the flue gas, reducing its temperature to 15-20°C. This causes a large amount of water vapor to condense, capturing any remaining condensable particulate matter. The cold source supply unit includes both a cooling tower and a heat pump, which can be switched according to the season. During the non-heating season, the cooling tower provides cooling water; during the heating season, the heat pump participates in the cooling water circulation and recovers waste heat. Through the synergistic effect of the three-stage cooling process, the flue gas temperature gradually decreases, and water vapor condenses in stages. Each condensation is accompanied by coagulation, thus progressively increasing the removal efficiency of condensable particulate matter. The switchable design of the cold source supply unit ensures stable operation of the system throughout the year, while also realizing the recovery and utilization of waste heat from the flue gas. This solves the problems of insufficient removal capacity of condensable particulate matter and ineffective utilization of low-temperature waste heat in existing wet desulfurization systems.

[0017] Advantages of additional aspects of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0018] 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. The drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In addition, the dimensions or spacing between the components are exaggerated to show the position of each component, and the schematic diagrams are for illustrative purposes only.

[0019] Figure 1 This is a schematic diagram of the system provided in an embodiment of the present invention; In the diagram: 1. Desulfurization tower; 2. Slurry circulation pump; 31. First slurry switching valve; 32. Second slurry switching valve; 33. Third slurry switching valve; 4. Flash tank; 5. Slurry return pump; 6. Exhaust steam condenser; 7. Vacuum pump; 8. Exhaust steam condensate discharge pump; 9. Circulating water tank; 10. Spray circulation pump; 11. Cooling water flow regulating valve; 12. Heat exchanger; 13. Spray liquid discharge valve; 14. Flue gas spray device; 15. Spray liquid collector; 16. Condenser; 17. Flue gas demister; 18. Centrifugal electric chiller; 19. Cold water circulation pump; 20. Cooling tower; 21. Cooling water circulation pump; 221. First cooling water switching valve; 222. Second cooling water switching valve; 223. Third cooling water switching valve; 224. Fourth cooling water switching valve; 23. Heat pump; Detailed Implementation It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0020] Example 1 like Figure 1 As shown in the figure, this embodiment proposes a system for deep removal of condensable particulate matter from wet desulfurization flue gas coupled with waste heat utilization. By synergistically removing condensable particulate matter and its precursors from flue gas, the system achieves deep emission reduction of condensable particulate matter in the flue gas of thermal power plants, further alleviating the generation of smog.

[0021] The system includes a primary removal unit, a secondary removal unit, a tertiary removal unit, and a cold source supply unit. The primary removal unit includes a flash tank 4, which is connected to the desulfurization tower 1. After cooling the slurry, the flash tank 4 returns to the desulfurization tower 1 to perform primary condensation removal of condensable particulate matter in the flue gas. The secondary removal unit includes a heat exchanger 12 and a flue gas spray device 14. The outlet flue gas flows through the flue gas spray device 14, and the heat exchanger 12 is connected to the flue gas spray device 14. The spray liquid after heat exchange performs secondary condensation removal of the flue gas. The tertiary removal unit includes a condenser 16, which is connected to the outlet flue gas for tertiary condensation removal. The cold source supply unit includes a cooling tower 20 and a heat pump 23, which supplies cooling water to the removal units.

[0022] The primary removal unit employs a structure combining a flash tank 4 and a desulfurization tower 1. After cooling in the flash tank 4, the slurry returns to the desulfurization tower 1, achieving initial condensation of the flue gas and enabling preliminary removal of condensable particulate matter. The secondary removal unit, through a heat exchanger 12 and a flue gas spray device 14, performs secondary condensation on the initially cooled flue gas, further enhancing particulate matter removal. The tertiary removal unit uses a condenser 16 for deep condensation of the flue gas, ensuring complete condensation and removal of condensable particulate matter. The cold source supply unit offers two supply methods: a cooling tower 20 and a heat pump 23, adaptable to different seasonal operating needs. This staged condensation structure solves the problem of insufficient removal of condensable particulate matter in existing equipment. The dual-mode cold source supply couples waste heat utilization with particulate matter removal, reducing system energy consumption.

[0023] A slurry switching valve is provided between the flash tank 4 and the desulfurization tower 1. The slurry switching valve includes a first slurry switching valve 31, a second slurry switching valve 32, and a third slurry switching valve 33. The third slurry switching valve 33 is installed on the pipeline between the bottom and the top of the desulfurization tower 1. The first slurry switching valve 31 is installed between the pipeline and the slurry inlet of the flash tank 4 and is located upstream of the third slurry switching valve 33. The second slurry switching valve 32 is installed between the slurry outlet of the flash tank 4 and the pipeline and is located downstream of the third slurry switching valve 33.

[0024] By employing a valve arrangement, when the flash evaporation system is operating normally, the first slurry switching valve 31 and the second slurry switching valve 32 are opened, while the third slurry switching valve 33 is closed. The desulfurization slurry is drawn from the bottom of the desulfurization tower 1 and enters the flash tank 4. After cooling, it returns to the top of the desulfurization tower 1 to continue spraying. When the flash evaporation system needs to be shut down, the first slurry switching valve 31 and the second slurry switching valve 32 are closed, and the third slurry switching valve 33 is opened. The desulfurization slurry circulates directly along the original pipeline without passing through the flash tank 4. This valve arrangement allows the flash evaporation system to be put into or taken out online without affecting the normal operation of the desulfurization tower 1, thus improving the system's reliability and operational flexibility.

[0025] The primary removal unit also includes a waste steam condenser 6. The waste steam outlet of the flash tank 4 is connected to the waste steam inlet of the waste steam condenser 6. The cold source supply unit is connected to the cooling water inlet of the waste steam condenser 6. The waste steam condensate is pumped to the cold source supply unit or the power plant raw water tank through the waste steam condensate discharge pump 8. The waste steam condenser 6 is also connected to a vacuum pump 7.

[0026] The low-temperature exhaust steam generated during flash evaporation in flash tank 4 under negative pressure is introduced into exhaust steam condenser 6 to exchange heat with cooling water, where it is condensed into condensate. The condensate is then pumped to the cold source supply unit or the power plant's raw water tank for recycling, avoiding water waste. Vacuum pump 7 uses frequency conversion control; by adjusting the frequency of vacuum pump 7, the negative pressure inside flash tank 4 is controlled, thereby controlling the outlet temperature of the slurry after flash evaporation. This design utilizes the exhaust steam generated during flash evaporation and, through negative pressure regulation, achieves precise control over the slurry cooling rate, ensuring the stability of the system operation.

[0027] The secondary removal unit also includes a circulating water tank 9, which is connected to the hot end of the heat exchanger 12. After heat exchange and cooling, the water is introduced into the flue spray device 14. The cold source supply unit is connected to the cold end of the heat exchanger 12. After heat exchange and heating, the cooling water is returned to the cold source supply unit.

[0028] The circulating water tank 9 serves as a storage and buffer device for the spray circulating water, ensuring a continuous supply of spray circulating water. The heat exchanger 12 employs a partitioned heat exchange method, allowing heat exchange between the spray circulating water and cooling water to control the spray circulating water temperature to 25-30℃. The cooled spray circulating water then enters the flue gas spraying device 14 to spray the flue gas, reducing its temperature to 30-35℃. The cooling water absorbs heat in the heat exchanger 12, heats up, and returns to the cold source supply unit for cooling, thus achieving the recycling of the cooling water.

[0029] The secondary removal unit also includes a spray liquid collector 15, which is installed at the lower end of the flue spray device 14 and connected to the circulating water tank 9.

[0030] When flue gas passes through the flue gas spray device 14, the sprayed circulating water falls into the spray liquid collector 15. The spray liquid collector 15 can reduce the entrainment of spray liquid caused by excessive flue gas velocity, and prevent the spray liquid from entering downstream equipment with the flue gas. The collected spray liquid falls into the circulating water tank 9 by gravity, without the need for additional power supply, thus reducing system energy consumption. This design achieves effective collection and reuse of spray circulating water, reducing the system's water replenishment volume.

[0031] The three-stage removal unit also includes a centrifugal electric chiller 18, which is connected to the condenser 16 to cool the flue gas. The condensate in the flue gas flows by gravity to the circulating water tank 9. The cold source supply unit is connected to the centrifugal electric chiller 18, and the cooling water returns to the cold source supply unit after being heated by heat exchange.

[0032] Centrifugal electric chiller 18 produces chilled water at 7-10℃, which is then pumped into condenser 16 by chilled water circulation pump 19. Low-temperature flue gas at 30-35℃ undergoes indirect heat exchange with the 7-10℃ chilled water, further reducing the flue gas temperature to 15-20℃. Condensate in the flue gas precipitates during the cooling process and flows by gravity to circulating water tank 9 for collection. As a deep cooling source, centrifugal electric chiller 18 can lower the flue gas temperature to near ambient temperature, causing a large amount of water vapor in the flue gas to condense, achieving deep removal of condensable particulate matter. Simultaneously, the condensate in the flue gas is collected and reused, reducing system water consumption.

[0033] The water in the circulating water tank 9 is divided into two paths after passing through the heat exchanger 12. One path leads to the flue spray device 14, and the other path leads to the cold source supply unit through the water replenishment pipe. The water replenishment pipe is equipped with a spray liquid discharge valve 13.

[0034] During the secondary and tertiary stages of flue gas removal, flue gas condensate is generated. This condensate flows by gravity to the circulating water tank 9, causing the water level in the tank 9 to gradually rise. When the water level rises, the spray liquid discharge valve 13 is opened, and the excess circulating liquid is pumped through the makeup water pipe to the cold source supply unit, such as into the cooling tower 20, as makeup water for the cooling tower 20, thus replenishing the water lost by evaporation and sewage discharge. This design recycles the flue gas condensate, achieving zero water consumption in the cooling system and avoiding resource waste caused by overflow of the circulating water tank 9.

[0035] A flue gas demister 17 is also provided downstream of the condenser 16. The flue gas after three-stage de-misting is introduced into the flue gas demister 17 and then discharged to the chimney.

[0036] After the flue gas undergoes three stages of cooling, although a large amount of condensable particulate matter is removed, some spray liquid droplets may still be entrained in the flue gas. The flue demister 17 adopts an external structure to further remove the droplets entrained in the flue gas, reduce the moisture content in the flue gas, and ensure the purity of the emitted flue gas. This design prevents droplets from carrying condensable particulate matter out of the system, thus improving the overall removal efficiency of the system.

[0037] The cooling tower 20 is a mechanically ventilated cooling tower 20, the heat pump 23 is a lithium bromide heat pump 23, and the cold source supply unit further includes a cooling water switching valve. The cooling water switching valve includes a first cooling water switching valve 221, a second cooling water switching valve 222, a third cooling water switching valve 223, and a fourth cooling water switching valve 224. The first cooling water switching valve 221 and the third cooling water switching valve 223 are connected to the mechanically ventilated cooling tower 20, and the second cooling water switching valve 222 and the fourth cooling water switching valve 224 are connected to the lithium bromide heat pump 23.

[0038] The switching between cooling tower 20 and heat pump 23 is achieved by combining the opening and closing of the switching valve group. During the non-heating season, the first cooling water switching valve 221 and the third cooling water switching valve 223 are opened, while the second cooling water switching valve 222 and the fourth cooling water switching valve 224 are closed, and cooling water is supplied by cooling tower 20. During the heating season, the first cooling water switching valve 221 and the third cooling water switching valve 223 are closed, while the second cooling water switching valve 222 and the fourth cooling water switching valve 224 are opened, and cooling water is circulated by heat pump 23. This valve arrangement enables the switching of operating conditions of the cold source supply unit. The lithium bromide heat pump 23 can effectively recover low-temperature waste heat, and the mechanically ventilated cooling tower 20 ensures the cooling effect during the non-heating season, enabling the system to operate efficiently in different seasons throughout the year.

[0039] Working principle: Power plant desulfurization tower 1 generally adopts a limestone wet desulfurization system. The desulfurization outlet flue gas is saturated wet flue gas, and the temperature of the desulfurization slurry is generally between 50-55℃.

[0040] By adding a slurry switching valve to the circulation pipeline after the slurry circulation pump 2, the slurry originally used for desulfurization is connected to the flash tank 4. The negative pressure of the flash tank 4 is controlled between 5-8 kPa. The desulfurization slurry undergoes negative pressure flash evaporation in the flash tank 4. The negative pressure of the flash tank 4 is controlled by the vacuum pump 7 set after the exhaust steam condenser 6. The vacuum pump 7 adopts frequency conversion control. By controlling the frequency of the vacuum pump 7, the negative pressure in the flash tank 4 is controlled, thereby controlling the temperature of the desulfurization slurry after flash evaporation.

[0041] The outlet temperature of the slurry after flash evaporation is controlled between 32-40℃. The cooled desulfurization slurry is pumped through slurry return pump 5 to the spray layer inside desulfurization tower 1 to desulfurize the flue gas while simultaneously condensing and cooling it. By controlling the change in the outlet temperature of the desulfurization slurry after flash evaporation, the cooling range of the flue gas can be adjusted, reducing the flue gas temperature from 50-55℃ to between 40-45℃. A slurry switching valve is installed on the desulfurization slurry pipeline. When the flash evaporation system is operating normally, the first slurry switching valve 31 and the second slurry switching valve 32 are opened, and the third slurry switching valve 33 is closed. When the flash evaporation system is shut down, the first slurry switching valve 31 and the second slurry switching valve 32 are closed, and the third slurry switching valve 33 is opened, thereby realizing the start-up and shutdown of the desulfurization system.

[0042] In addition, the low-temperature exhaust steam generated by flash evaporation at 32-40℃ enters the exhaust steam condenser 6 for condensation and becomes exhaust steam condensate. This part of the exhaust steam condensate is obtained by flash evaporation and has good water quality. The exhaust steam condensate can be directly pumped to the cooling tower 20 for water replenishment through the exhaust steam condensate discharge pump 8, or pumped to the power plant's raw water tank for recycling.

[0043] After being cooled by slurry flash evaporation, the flue gas enters the outlet flue of desulfurization tower 1. A flue gas spraying device 14 is installed in the flue. The circulating water for the spraying device comes from the circulating water tank 9. The spraying circulating water is pumped to the heat exchanger 12 by the spraying circulating pump 10. The spraying liquid exchanges heat with the cooling circulating water from the cooling water circulating pump 21 in the heat exchanger 12. A cooling water flow regulating valve 11 is installed on the inlet pipe of the cooling water entering the heat exchanger 12. The cooling water flow rate is regulated by the valve. Adjusting the opening of regulating valve 11 controls the outlet temperature of the spray circulating liquid to 25-30℃. The cooled spray circulating water enters the flue gas spray device 14 to spray the flue gas, reducing the flue gas temperature to between 30-35℃. The spray circulating water after spraying falls into the spray liquid collector 15 for collection, reducing the spray liquid entrainment caused by excessive flue gas flow rate. The collected spray liquid falls into the circulating water tank 9 by gravity flow, and the cycle repeats. This is the second flue gas cooling and condensation.

[0044] Since flue gas condensation causes flue gas condensate to fall into the circulating water tank 9, resulting in the water level in the tank rising higher and higher, a spray liquid discharge valve 13 is installed on the pipe before the spray device 14 in the flue gas duct. When the water level in the circulating water tank 9 rises, the spray liquid discharge valve 13 is opened to pump the circulating liquid into the cooling tower 20 as makeup water for the cooling tower 20, which can replenish the water carried away by the cooling tower 20.

[0045] After being cooled by the flue gas spray device 14, the flue gas enters the condenser 16 for further cooling. The cold water in the condenser 16 comes from the centrifugal electric chiller 18. The 7-10°C cold water produced by the centrifugal electric chiller 18 is pumped into the condenser 16 by the cold water circulation pump 19. The low-temperature flue gas of 30-35°C and the 7-10°C cold water undergo indirect heat exchange, further reducing the flue gas temperature to -15-20°C. The condensate in the flue gas flows by gravity to the circulating water tank 9. The cold water after heat exchange returns to the centrifugal electric chiller 18 for continued cooling, and the cycle repeats.

[0046] An external flue demister 17 is installed on the flue before the flue gas enters the chimney to further remove the spray liquid droplets entrained in the flue gas and reduce the moisture content in the flue gas.

[0047] Because the flue gas undergoes three stages of cooling, its temperature drops from 50-55℃ to 15-20℃. During this cooling process, the water vapor in the flue gas condenses in three stages. Through condensation, the water vapor removes condensable particulate matter from the flue gas. A flue gas demister 17 is installed at the very end of the flue gas system to further intercept moisture in the flue gas, reducing the water vapor content carried by the flue gas and ensuring the purity of the outlet flue gas.

[0048] In order to achieve deep removal of condensable particulate matter while recovering low-temperature waste heat from flue gas, this system is also equipped with a heat pump system 23, which can realize deep recovery and utilization of low-temperature waste heat from flue gas during the heating season.

[0049] Cooling water switching valves are installed on the cooling water pipeline. During the non-heating season, the first cooling water switching valve 221 and the third cooling water switching valve 223 are opened, and the second cooling water switching valve 222 and the fourth cooling water switching valve 224 are closed. The cooling water required by the exhaust steam condenser 6, heat exchanger 12, and centrifugal electric chiller 18 comes from the bottom of the cooling tower 20. The temperature of the cooling water fluctuates between 10-30℃ depending on the season. The cooling water circulation pump 21 draws water from the bottom of the cooling tower 20 and then sends it to the exhaust steam condenser 6, heat exchanger 12, and centrifugal electric chiller 18 respectively. The heated cooling water goes to the cooling tower 20 for cooling.

[0050] During the heating season, the first cooling water switching valve 221 and the third cooling water switching valve 223 are closed, while the second cooling water switching valve 222 and the fourth cooling water switching valve 224 are opened. The cooling water required for the waste steam condenser 6, heat exchanger 12, and centrifugal electric chiller 18 comes from the heat pump 23. After the cooling water enters the waste steam condenser 6, heat exchanger 12, and centrifugal electric chiller 18 and is heated to 30-35℃, it enters the evaporator of the heat pump 23. This heat is released in the evaporator and cooled to 20-25℃, serving as a cold source to continue entering the aforementioned equipment, in a continuous cycle. The 30-35℃ cooling water is absorbed by the heat pump 23 as waste heat. Driven by high-temperature driving steam, this low-temperature waste heat is transferred to the heating network water, thus realizing the recovery and utilization of flue gas heat during the heating season.

[0051] In summary: This system achieves deep removal of condensable particulate matter from flue gas throughout the year by cooling the flue gas in three stages. At the same time, it can also recover and utilize the low-temperature waste heat in the flue gas during the heating season, bringing benefits to enterprises while protecting the environment.

[0052] The system achieves flue gas cooling and condensation in desulfurization tower 1 through slurry flash evaporation technology. At the same time, the intensity of flash evaporation can be controlled by adjusting the frequency of vacuum pump 7. The flash evaporation amount can be matched according to the power plant's raw water replenishment amount to ensure the power plant's water balance.

[0053] The condensate from the flue gas in the second and third stages is collected in the circulating water tank 9, and then sprayed to the cooling tower 20 through the spray liquid discharge valve 13 to replenish the water loss of the cooling tower 20, thus achieving zero water consumption of the cooling system.

[0054] The system enables independent control of three-stage cooling. It can control the operation of the three systems according to the boiler load or cooling water temperature. When the boiler load is low or the cooling water temperature is low, one or two systems can be turned on while the others are kept as backups, thus reducing the operating costs of the system.

[0055] The flue is equipped with a spray liquid collector 15 and a flue demister 17, which further reduces the entrainment of spray water droplets by the flue gas, reduces the moisture content of the flue gas emission, and ensures the purity of the emitted flue gas.

[0056] Increasing the height of desulfurization tower 1 or adding a spray tower after the desulfurization tower will increase the flue gas resistance by 700-800 Pa, while flue gas spraying only requires an increase of 200-300 Pa of resistance.

[0057] The deep condenser 16 installed at the end of the flue can reduce the flue gas temperature to 15-20℃, realizing the deep removal of condensable particulate matter in the flue gas and the deep recovery of waste heat from the flue gas.

[0058] Example 2 A method for removing condensable particulate matter and utilizing coupled waste heat includes: The slurry from the desulfurization tower 1 is led out to the flash tank 4 for negative pressure flash evaporation. The cooled slurry is returned to the desulfurization tower 1 to spray the flue gas, thereby cooling the flue gas to the first set temperature range. The exhaust steam generated by flash tank 4 is condensed in exhaust steam condenser 6 to form exhaust steam condensate. A flue spraying device 14 is installed on the flue outlet of the desulfurization tower 1. Spraying circulating water is passed into the heat exchanger 12 to exchange heat with cooling water. The cooled spraying circulating water enters the flue spraying device 14 to spray the flue gas, so that the flue gas is cooled to the second set temperature range. The sprayed circulating water falls into the spray liquid collector 15 and then returns to the circulating water tank 9. The flue gas, after being cooled by the flue spray device 14, is fed into the condenser 16. The condenser 16 is fed with cold water produced by the centrifugal electric chiller 18 to perform indirect heat exchange and cool the flue gas to the third set temperature range. The condensate in the flue gas flows by gravity to the circulating water tank 9. During the non-heating season, the heat pump 23 is disconnected from the cooling water circulation loop, and the cooling tower 20 is disconnected from the cooling water circulation loop. The cooling water is taken out from the bottom of the cooling tower 20 and then fed into the exhaust steam condenser 6, heat exchanger 12 and centrifugal electric chiller 18 respectively. The heated cooling water is returned to the cooling tower 20. During the heating season, the cooling tower 20 is disconnected from the cooling water circulation loop, and the heat pump 23 is connected to the cooling water circulation loop. The cooling water flows sequentially through the waste steam condenser 6, heat exchanger 12 and centrifugal electric chiller 18 before entering the evaporator of the heat pump 23 to release heat and cool down. The cooled water continues to flow through the waste steam condenser 6, heat exchanger 12 and centrifugal electric chiller 18. The heat pump 23 absorbs the waste heat of the cooling water and transfers it to the heating network water for heating.

[0059] This method achieves the gradual removal of condensable particulate matter through three-stage cooling. Simultaneously, the cold source supply method is switched according to the season: cooling tower 20 provides cooling water during the non-heating season, while heat pump 23 recovers waste heat for heating during the heating season, thus coupling deep removal of condensable particulate matter with waste heat utilization. The independent control mode of the three-stage cooling allows the system to operate flexibly according to boiler load or cooling water temperature. When the load is low, some cooling systems can be activated, while the rest remain as backups, reducing operating energy consumption.

[0060] While the specific embodiments of the present invention have been described above, they are not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A system for removing condensable particulate matter coupled with waste heat utilization, characterized in that, It includes a primary removal unit, a secondary removal unit, a tertiary removal unit, and a cold source supply unit; The primary removal unit includes a flash tank, which is connected to the desulfurization tower. After cooling the slurry, it is returned to the desulfurization tower to perform primary condensation removal of condensable particulate matter in the flue gas. The secondary removal unit includes a heat exchanger and a flue spray device. The outlet flue flows through the flue spray device. The heat exchanger is connected to the flue spray device. The spray liquid after heat exchange performs secondary condensation removal of condensable particulate matter in the flue gas. The heat exchanger adopts a partitioned heat exchange method; The secondary removal unit also includes a circulating water tank, which is connected to the hot end of the heat exchanger. After heat exchange and cooling, the water is introduced into the flue spray device. The cold source supply unit is connected to the cold end of the heat exchanger. After heat exchange and heating, the cooling water is returned to the cold source supply unit. The three-stage removal unit includes a condenser, and the outlet flue is connected to the condenser. The condenser is used to perform three-stage condensation removal of condensable particulate matter in the flue gas. The three-stage removal unit also includes a centrifugal electric chiller, which is connected to the condenser to cool the flue gas. The condensate in the flue gas flows by gravity to the circulating water tank. The cold source supply unit is connected to the centrifugal electric chiller, and the cooling water returns to the cold source supply unit after being heated by heat exchange. The cold source supply unit includes a cooling tower and a heat pump, and the cooling tower or heat pump supplies cooling water to the removal unit. A slurry switching valve is provided between the flash tank and the desulfurization tower. The slurry switching valve includes a first slurry switching valve, a second slurry switching valve and a third slurry switching valve. The third slurry switching valve is installed on the pipeline between the bottom and the top of the desulfurization tower. The first slurry switching valve is installed between the pipeline and the slurry inlet of the flash tank and is located upstream of the third slurry switching valve. The second slurry switching valve is installed between the slurry outlet of the flash tank and the pipeline and is located downstream of the third slurry switching valve. The water in the circulating water tank is divided into two paths after passing through the heat exchanger. One path is connected to the flue spray device, and the other path is connected to the cold source supply unit through the water supply pipe. The water supply pipe is equipped with a spray liquid discharge valve. The cooling tower is a mechanically ventilated cooling tower, the heat pump is a lithium bromide heat pump, and the cold source supply unit further includes a cooling water switching valve. The cooling water switching valve includes a first cooling water switching valve, a second cooling water switching valve, a third cooling water switching valve, and a fourth cooling water switching valve. The first and third cooling water switching valves are connected to the mechanically ventilated cooling tower, and the second and fourth cooling water switching valves are connected to the lithium bromide heat pump.

2. The condensable particulate matter removal and waste heat utilization system as described in claim 1, characterized in that, The primary removal unit also includes a waste steam condenser. The waste steam outlet of the flash tank is connected to the waste steam inlet of the waste steam condenser. The cold source supply unit is connected to the cooling water inlet of the waste steam condenser. The waste steam condensate is pumped to the cold source supply unit or the power plant raw water tank by the waste steam condensate discharge pump. The waste steam condenser is also connected to a vacuum pump.

3. The condensable particulate matter removal and waste heat utilization system as described in claim 1, characterized in that, The secondary removal unit also includes a spray liquid collector, which is installed at the lower end of the flue spray device and connected to the circulating water tank.

4. The condensable particulate matter removal and waste heat utilization system as described in claim 1, characterized in that, A flue gas demister is also installed downstream of the condenser. The flue gas after three stages of de-misting is introduced into the flue gas demister and then discharged to the chimney.

5. A method for removing condensable particulate matter and utilizing coupled waste heat, characterized in that, The system for removing condensable particulate matter and utilizing waste heat as described in any one of claims 1-4 includes: The slurry from the desulfurization tower is led out to the flash tank for negative pressure flash evaporation. The cooled slurry is then returned to the desulfurization tower to spray the flue gas, thereby cooling the flue gas to the first set temperature range. The exhaust steam generated in the flash tank is passed into the exhaust steam condenser for condensation to form exhaust steam condensate. A flue spraying device is installed on the flue outlet of the desulfurization tower. Spraying circulating water is passed into the heat exchanger to exchange heat with cooling water. The cooled spraying circulating water enters the flue spraying device to spray the flue gas, so that the flue gas is cooled to the second set temperature range. The sprayed circulating water falls into the spray liquid collector and then returns to the circulating water tank. The flue gas, after being cooled by the flue spray device, is fed into the condenser. The condenser is fed with cold water produced by a centrifugal electric refrigeration unit to perform indirect heat exchange and cool the flue gas to the third set temperature range. The condensate in the flue gas flows by gravity to the circulating water tank. During the non-heating season, the heat pump is disconnected from the cooling water circulation loop, and the cooling tower is disconnected from the cooling water circulation loop. The cooling water is taken out from the bottom of the cooling tower and then fed into the exhaust steam condenser, heat exchanger and centrifugal electric chiller. The heated cooling water is then returned to the cooling tower. During the heating season, the cooling tower is disconnected from the cooling water circulation loop, and the heat pump is connected to the cooling water circulation loop. The cooling water flows sequentially through the waste steam condenser, heat exchanger, and centrifugal electric chiller before entering the evaporator of the heat pump to release heat and cool down. The cooled cooling water continues to flow through the waste steam condenser, heat exchanger, and centrifugal electric chiller. The heat pump absorbs the waste heat of the cooling water and transfers it to the heating network for heating.

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