System for recovering moisture in flue gas of boiler in power plant

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By introducing a flue gas water heat exchanger and duct system into the flue gas of a power plant boiler, the problem of unrecovered moisture and heat from the flue gas is solved, achieving water conservation and improved boiler thermal efficiency.

CN223939467UActive Publication Date: 2026-02-24彭可

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Patent Information

Application Number: CN202422902970.2
Authority / Receiving Office: CN · China
Patent Type: Utility models(China)
Current Assignee / Owner
Filing Date: 2024-11-27
Publication Date: 2026-02-24
Estimated Expiration: 2034-11-27

AI Technical Summary

Technical Problem

Existing power plant boilers cannot effectively recover moisture and heat from flue gas, resulting in water waste and reduced boiler thermal efficiency.

Method used

The system adopts a flue gas water heat exchanger combined with primary and secondary air ducts. A circulating water pump forms a circulation loop with the primary and secondary air heat exchangers to recover moisture and heat from the flue gas and heat the primary and secondary air to improve the combustion efficiency of pulverized coal.

Benefits of technology

It enables the recovery of moisture in flue gas, avoids water waste, improves boiler thermal efficiency, prevents pulverized coal freezing, saves energy, and reduces chimney exhaust temperature.

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Abstract

The utility model discloses a system for recovering moisture in flue gas of a power plant boiler, which relates to a technology for recovering moisture in flue gas of a boiler, aims to solve the problems that the moisture in the flue gas cannot be recycled and heat in the flue gas cannot be recovered in the conventional power plant boiler, and comprises a flue, a flue gas water taking heat exchanger, a primary air flue and / or a secondary air flue, an inlet of the flue is communicated with a smoke outlet of the boiler, a wet desulphurization system is installed on the flue, an outlet of the flue is communicated with a chimney, a smoke water taking heat exchanger is arranged in the flue, and air outlets of the primary air flue and the secondary air flue are connected to corresponding air inlets of the boiler respectively. The device further comprises a circulating water pump, a primary air heat exchanger and / or a secondary air heat exchanger, the primary air heat exchanger is arranged in the primary air duct, the secondary air heat exchanger is arranged in the secondary air duct, and the device is used for recycling moisture in flue gas of a boiler of a power plant, heating primary air and secondary air and replacing air heaters in the primary air and the secondary air.

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Description

Technical Field

[0001] This utility model relates to a technology for recovering moisture from boiler flue gas, and particularly to a moisture recovery system for boiler flue gas in power plants. Background Technology

[0002] Currently, a crucial performance indicator for power plants is desulfurization efficiency, requiring a minimum of 90%. Therefore, "wet desulfurization technology," which effectively removes sulfur, is adopted by almost all large power plants. Desulfurization consumes a significant portion of a power plant's water consumption. Currently, desulfurization water recovery is primarily achieved through internal circulation within the desulfurization tower; however, there has been no measure to recover the water vapor in the flue gas after wet desulfurization. The desulfurized flue gas carries over 30% water vapor; if it is directly released into the atmosphere without recovery, it will inevitably lead to a huge waste of water resources. Furthermore, existing power plant boilers directly discharge desulfurized flue gas without recovering the heat carried in the flue gas, resulting in reduced boiler thermal efficiency. Therefore, the resource utilization of water in the flue gas after wet desulfurization systems and the recovery of heat from the flue gas are key research and development directions for coal-fired power plants. Utility Model Content

[0003] In order to solve the problem that existing power plant boilers cannot utilize the moisture in flue gas as a resource and recover the heat from the flue gas, this utility model provides a moisture recovery system for power plant boiler flue gas to solve the problems mentioned in the background art.

[0004] The technical solution of this utility model is:

[0005] A moisture recovery system for boiler flue gas in a power plant includes a flue, a flue gas water heat exchanger, a primary air duct and / or a secondary air duct. The inlet of the flue is connected to the boiler's exhaust port. A wet desulfurization system is installed on the flue. The outlet of the flue is connected to the chimney. A flue gas water heat exchanger is installed inside the flue. The outlets of the primary and secondary air ducts are respectively connected to the corresponding air inlets of the boiler.

[0006] It also includes a circulating water pump, a primary air heat exchanger and / or a secondary air heat exchanger. A primary air heat exchanger is installed in the primary air duct, and a secondary air heat exchanger is installed in the secondary air duct. The flue gas water heat exchanger achieves water circulation with the primary air heat exchanger and / or the secondary air heat exchanger through the circulating water pump, and realizes the cold transfer from the primary air duct and / or the secondary air duct to the flue.

[0007] The working principle of this utility model is as follows:

[0008] The primary and / or secondary air heat exchangers, installed in the primary and / or secondary air ducts, form a circulating loop with the flue gas water heat exchanger installed in the flue through a circulating water pump. This enables heat transfer between the flue and the primary and secondary air ducts, recovering heat from the boiler exhaust gas and heating the primary and secondary air; it also preheats the pulverized coal, ensuring it enters the furnace at a certain temperature; recovering heat from the exhaust gas improves the boiler's thermal efficiency; and the heat carried away from the flue lowers the flue gas temperature, facilitating the condensation and precipitation of water vapor in the flue gas.

[0009] Compared with the prior art, the present invention has the following advantages:

[0010] 1. Water vapor in the flue gas is recovered after passing through the wet desulfurization system, avoiding water waste caused by its release into the air; 2. The primary and secondary air are heated, as are the pulverized coal, ensuring complete combustion and preventing the pulverized coal from freezing and causing blockages in winter due to cold air; 3. The system replaces the air heaters in the primary and secondary air systems, saving additional energy; 4. The system reduces the flue gas temperature of the chimney, improving the boiler's thermal efficiency. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the moisture recovery system in the boiler flue gas of this power plant.

[0012] Figure 2 This is a schematic diagram of the system after the flue gas heat recovery heat exchanger has been added.

[0013] Figure 3 This is a schematic diagram of the improved connection method for the flue gas heat recovery heat exchanger in this system.

[0014] Figure 4 This is a schematic diagram of the closed-loop flue gas water heat exchanger in this system.

[0015] Figure 5 This is a schematic diagram of the open flue gas intake water heat exchanger in this system.

[0016] Figure 6 This is a schematic diagram of the primary air heat exchanger and the secondary air heat exchanger connected in series in this system.

[0017] In the diagram: 1. Flue; 201. Flue gas water heat exchanger; 204. Circulating water pump; 205. Primary air duct; 206. Secondary air duct; 207. Primary air heat exchanger; 208. Secondary air heat exchanger; 3. Wet desulfurization system; 4. Chimney; 501. Flue gas heat recovery heat exchanger; 502. Valve I; 503. Valve II; 504. Valve III. Detailed Implementation

[0018] Specific implementation method 1: A moisture recovery system for boiler flue gas in a power plant includes a flue 1, a flue gas water heat exchanger 201, a primary air duct 205 and / or a secondary air duct 206. The inlet of the flue 1 is connected to the boiler's exhaust port. A wet desulfurization system 3 is installed on the flue 1. The outlet of the flue 1 is connected to the chimney 4. A flue gas water heat exchanger 201 is installed inside the flue 1. The outlets of the primary air duct 205 and the secondary air duct 206 are respectively connected to the corresponding air inlets of the boiler.

[0019] It also includes a circulating water pump 204, a primary air heat exchanger 207 and / or a secondary air heat exchanger 208. A primary air heat exchanger 207 is installed in the primary air duct 205, and a secondary air heat exchanger 208 is installed in the secondary air duct 206. The flue gas water heat exchanger 201 achieves water circulation with the primary air heat exchanger 207 and / or the secondary air heat exchanger 208 through the circulating water pump 204, and realizes the cold transfer from the primary air duct 205 and / or the secondary air duct 206 to the flue gas 1. In specific embodiments, only the primary air duct 205 and the primary air heat exchanger 207 may be used to absorb heat from the flue gas in the flue gas; only the secondary air duct 206 and the secondary air heat exchanger 208 may be used to absorb heat from the flue gas in the flue gas; or all three may be used simultaneously.

[0020] Furthermore, in the diagram, double arrows indicate the flow direction of flue gas and air ducts, while single arrows indicate the flow direction of water pipes. The flue gas water exchanger 201 is a device for recovering water from flue gas. By lowering the flue gas temperature, it causes water vapor to condense and be recovered, and also recovers fine water droplets from the flue gas, thus completing the water recovery process. The flue gas water exchanger 201 can be divided into an open-loop water circulation system and a closed-loop water circulation system. The outlet of the flue gas water exchanger 201 is connected to the inlet of the circulating water pump 204. The outlet of the circulating water pump 204 is connected to the inlets of the primary air heat exchanger 207 and the secondary air heat exchanger 208. The outlets of the primary air heat exchanger 207 and the secondary air heat exchanger 208 are connected to the inlet of the flue gas water exchanger 201, forming a water circulation loop. The flue gas water heat exchanger 201 is the cold end, and the primary air heat exchanger 207 and the secondary air heat exchanger 208 are the hot ends. The primary air heat exchanger 207 and the secondary air heat exchanger 208 are cooled by high-power fans (e.g., 5000KW fans) installed in the primary air duct 205 and the secondary air duct 206, respectively.

[0021] The flue gas discharged from the boiler undergoes desulfurization in the wet desulfurization system 3. After desulfurization, the water-laden flue gas is recovered at the flue gas-water heat exchanger 201. The heat absorbed by the flue gas-water heat exchanger 201 is used to heat the primary and secondary air through the primary air heat exchanger 207 and secondary air heat exchanger 208. This increases the temperature of the primary and secondary air, ensuring complete combustion of the pulverized coal; it also preheats the pulverized coal in the primary air, ensuring it enters the furnace at a certain temperature and preventing it from freezing and clogging due to cold winter air. This system replaces the air heaters in the primary and secondary air systems. Furthermore, it lowers the temperature of the flue gas discharged from the chimney 4, improving heat utilization and increasing the boiler's thermal efficiency.

[0022] Specific Implementation Method Two: See Figure 1 As shown, the flue gas water heat exchanger 201 of this embodiment is installed in the flue duct 1 located between the wet desulfurization system 3 and the chimney 4.

[0023] This embodiment further defines the installation position of the flue gas water heat exchanger 201, which is installed in the flue duct 1 between the wet desulfurization system 3 and the chimney 4. It is used to recover water in the flue gas after desulfurization and to recover the remaining heat in the flue gas. It is set up separately in the flue duct 1 to avoid heat transfer with other equipment, thereby making its condensation efficiency higher and reducing the water content of the flue gas discharged from the chimney 4.

[0024] Specific implementation method three: See Figure 1 As shown, multiple sets of primary air ducts 205 and secondary air ducts 206 are provided, and each primary air duct 205 and secondary air duct 206 is equipped with a primary air heat exchanger 207 and a secondary air heat exchanger 208, respectively. In boilers that require multiple sets of primary and secondary air ducts, multiple primary air ducts 205 connect to the primary air receiving area of the boiler, and multiple secondary air ducts 206 connect to the secondary air receiving area of the boiler.

[0025] Detailed Implementation Method Four: See [link] Figure 4 As shown, the flue gas water heat exchanger 201 in this embodiment adopts a closed water circulation system.

[0026] Furthermore, the main components of the closed-loop water circulation system consist of refrigeration pipes and condenser fins. The refrigeration pipes are used to lower the temperature of the condenser fins, ensuring they remain at a low temperature. As the flue gas passes through the condenser fins, its temperature decreases, causing water vapor in the flue gas to condense into tiny water droplets. These droplets then adhere to the condenser fins and flow down into the collection tank below, completing the recovery of water from the flue gas.

[0027] Specific implementation method five: See Figure 5 As shown, the flue gas water heat exchanger 201 in this embodiment adopts an open water circulation system.

[0028] Furthermore, the open water circulation system is mainly composed of a spray device and a water collection tank. The refrigerant is water. The flue gas flows through the flue gas water heat exchanger 201. The spray device atomizes the low-temperature water and sprays it onto the flue gas. The water vapor in the flue gas condenses and precipitates into fine water droplets. After the fine water droplets are cooled down, they no longer float and merge with the low-temperature cooling water, eventually flowing into the water collection tank below.

[0029] Specific implementation method six: See Figure 2 As shown, this embodiment also includes a flue gas heat recovery heat exchanger 501, which is installed in the flue duct 1 located between the boiler and the wet desulfurization system 3. The inlet of the flue gas heat recovery heat exchanger 501 is connected to the outlet of the flue gas water intake heat exchanger 201, and the outlet of the flue gas heat recovery heat exchanger 501 is connected to the inlet of the circulating water pump 204.

[0030] Furthermore, in this embodiment, a flue gas heat recovery heat exchanger 501 is installed before the wet desulfurization system 3. Because the flue gas temperature will drop to 50-60°C after desulfurization by the wet desulfurization system 3, the flue gas heat recovery heat exchanger 501 is installed before the wet desulfurization system 3 to recover part of the heat energy in the flue gas, thereby reducing the flue gas temperature to about 90°C before the desulfurization system 3, reducing the amount of water sprayed to lower the flue gas temperature; and increasing the temperature of the circulating water passing through the flue gas water intake heat exchanger 201 to heat the primary and secondary air, replacing the air heater.

[0031] Detailed implementation method seven: See Figure 3 As shown, this embodiment also includes valves I 502, II 503, and III 504. The outlet of the flue gas water heat exchanger 201 is connected to the inlets of valves I 502 and II 503. The outlet of valve I 502 is connected to the inlet of the flue gas heat recovery heat exchanger 501. The outlet of the flue gas heat recovery heat exchanger 501 is connected to the inlet of valve III 504. The outlet of valve III 504 is connected to the inlet of the circulating water pump 204. The outlet of valve II 503 is connected to the inlet of the circulating water pump 204.

[0032] Furthermore, this embodiment provides another connection method for the flue gas heat recovery heat exchanger 501. This connection method allows for both connection and isolation of the flue gas heat recovery heat exchanger 501. When valve I 502 and valve III 504 are opened and valve II 503 is closed, the flue gas heat recovery heat exchanger 501 is connected to the water circulation loop, and it participates in heat recovery. When valve I 502 and valve III 504 are closed and valve II 503 is opened, the flue gas heat recovery heat exchanger 501 is isolated from the water circulation loop, and it does not participate in heat recovery.

[0033] Detailed Implementation Method Eight: See also Figure 6As shown, in this embodiment, the inlet of the primary air heat exchanger 207 is connected to the outlet of the circulating water pump 204, the outlet of the primary air heat exchanger 207 is connected to the inlet of the secondary air heat exchanger 208, and the outlet of the secondary air heat exchanger 208 is connected to the flue gas water intake heat exchanger 201.

[0034] Furthermore, in this embodiment, the primary air heat exchanger 207 and the secondary air heat exchanger 208 are connected in series. This allows the heated circulating water to preferentially flow into the primary air heat exchanger 207 to heat the pulverized coal, thus achieving preferential heating of the primary air duct and the pulverized coal within it. The connection order of the primary air heat exchanger 207 and the secondary air heat exchanger 208 can be changed according to the priority of heat demand.

Claims

1. A water recovery system for boiler flue gas in a power plant, comprising a flue (1), a flue gas water heat exchanger (201), a primary air duct (205) and / or a secondary air duct (206), wherein the inlet of the flue (1) is connected to the exhaust port of the boiler, a wet desulfurization system (3) is installed on the flue (1), the outlet of the flue (1) is connected to the chimney (4), a flue gas water heat exchanger (201) is installed inside the flue (1), and the outlets of the primary air duct (205) and the secondary air duct (206) are respectively connected to the corresponding air inlets of the boiler; Its features are: It also includes a circulating water pump (204), a primary air heat exchanger (207) and / or a secondary air heat exchanger (208). The primary air duct (205) is equipped with a primary air heat exchanger (207), and the secondary air duct (206) is equipped with a secondary air heat exchanger (208). The flue gas water heat exchanger (201) realizes water circulation with the primary air heat exchanger (207) and / or the secondary air heat exchanger (208) through the circulating water pump (204), and realizes the cold transfer from the primary air duct (205) and / or the secondary air duct (206) to the flue (1). It also includes a flue gas heat recovery heat exchanger (501), which is installed in the flue (1) between the boiler and the wet desulfurization system (3). The inlet of the flue gas heat recovery heat exchanger (501) is connected to the outlet of the flue gas water intake heat exchanger (201), and the outlet of the flue gas heat recovery heat exchanger (501) is connected to the inlet of the circulating water pump (204). It also includes valve I (502), valve II (503) and valve III (504). The outlet of the flue gas water heat exchanger (201) is connected to the inlet of valve I (502) and valve II (503). The outlet of valve I (502) is connected to the inlet of the flue gas heat recovery heat exchanger (501). The outlet of the flue gas heat recovery heat exchanger (501) is connected to the inlet of valve III (504). The outlet of valve III (504) is connected to the inlet of the circulating water pump (204). The outlet of valve II (503) is connected to the inlet of the circulating water pump (204).

2. The moisture recovery system for power plant boiler flue gas according to claim 1, characterized in that: The flue gas water heat exchanger (201) is installed in the flue (1) located between the wet desulfurization system (3) and the chimney (4).

3. The moisture recovery system for power plant boiler flue gas according to claim 2, characterized in that: The primary air duct (205) and secondary air duct (206) are provided in multiple sets, and each primary air duct (205) and secondary air duct (206) is provided with a primary air heat exchanger (207) and a secondary air heat exchanger (208).

4. The moisture recovery system for power plant boiler flue gas according to claim 3, characterized in that: The flue gas water heat exchanger (201) adopts a closed water circulation system.

5. The power plant boiler flue gas moisture recovery system according to claim 3, characterized in that: The flue gas water heat exchanger (201) adopts an open water circulation system.

6. The power plant boiler flue gas moisture recovery system according to any one of claims 4 or 5, characterized in that: The inlet of the primary air heat exchanger (207) is connected to the outlet of the circulating water pump (204), the outlet of the primary air heat exchanger (207) is connected to the inlet of the secondary air heat exchanger (208), and the outlet of the secondary air heat exchanger (208) is connected to the flue gas water intake heat exchanger (201).