Boiler flue gas waste heat recovery system

Abstract

The utility model discloses a boiler flue gas waste heat recovery system which comprises a smoke exhaust pipeline, one end of the smoke exhaust pipeline is provided with a smoke inlet, the other end of the smoke exhaust pipeline is provided with a smoke outlet, the smoke exhaust pipeline comprises a first-stage heat exchange area and a second-stage heat exchange area, the first-stage heat exchange area is connected with the smoke outlet, and the second-stage heat exchange area is connected with the smoke inlet; the first-stage heat exchange area is provided with first-stage heat exchange circulation, the second-stage heat exchange area is provided with second-stage heat exchange circulation, and the first-stage heat exchange circulation and the second-stage heat exchange circulation are communicated through a connecting pipe. According to the flue gas waste heat recovery system, heat in flue gas can be utilized twice through cooperation of first-stage heat exchange circulation and second-stage heat exchange circulation, the flue gas waste heat recovery efficiency is improved, and waste of flue gas waste heat is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of boilers, in particular to a boiler flue gas waste heat recovery system. Background Art

[0002] Currently, the most significant loss in boiler operation is exhaust heat loss. Reducing exhaust heat loss and rationally utilizing flue gas waste heat are crucial for energy conservation and improving the economic efficiency of power plants. Boiler waste heat recovery can recover flue gas heat. This recovered heat is then used to heat water as needed for boiler feed water and domestic water, saving fuel, lowering production costs, and reducing exhaust emissions, achieving both energy conservation and environmental protection.

[0003] A Chinese utility model patent, published as CN 210197334 U, discloses a boiler flue gas waste heat recovery system, comprising a flue gas exhaust pipe, one end of which is connected to the flue gas outlet of the boiler and the other end of which is provided with a flue gas discharge port. The flue gas exhaust pipe is provided with a recycling section, both ends of which are connected to the flue gas exhaust pipe. The flue gas exhaust pipe is provided with a first valve, which is located between the flue gas inlet and the flue gas outlet of the recycling section. The recycling section is provided with a heat exchange pipe, which is arranged along the length of the recycling section. The heat exchange pipe has an inlet and an outlet at each end, respectively, and the inlet and outlet are located on the side wall of the recycling section. The utility model passes flue gas into the recycling section, transfers the heat of the flue gas to a medium in the heat exchange pipe through the heat exchange pipe in the recycling section, and outputs the medium for utilization, thereby realizing the recovery and utilization of flue gas waste heat, improving resource utilization, and protecting the environment. Regarding the above-mentioned related technologies, the inventors believe that the following defects exist: when the water temperature in the heat exchange pipe reaches a threshold, if the water in the heat exchange pipe continues to be heated, the heat exchange efficiency will be significantly reduced, and the water temperature will also increase slowly, thereby wasting a large amount of flue gas heat resources and increasing time costs. Utility Model Content

[0004] The purpose of the present invention is to provide a boiler flue gas waste heat recovery system to solve the problems raised in the above background technology.

[0005] To achieve the above-mentioned object, the present invention provides the following technical solution: a boiler flue gas waste heat recovery system, comprising a flue gas exhaust pipe, wherein one end of the flue gas exhaust pipe is provided with a flue gas inlet, and the other end of the flue gas exhaust pipe is provided with a flue gas outlet, wherein the flue gas exhaust pipe comprises a primary heat exchange zone and a secondary heat exchange zone, wherein the primary heat exchange zone is connected to the flue gas outlet, and the secondary heat exchange zone is connected to the flue gas inlet;

[0006] The primary heat exchange zone is provided with a primary heat exchange cycle, and the secondary heat exchange zone is provided with a secondary heat exchange cycle. The primary heat exchange cycle and the secondary heat exchange cycle are connected through a connecting pipe.

[0007] Preferably, the first-level heat exchange cycle includes a first-level water tank, a first-level heat exchange tube, a first-level water inlet pipe and a first-level return pipe. The two ends of the first-level heat exchange tube are respectively connected to the first-level water inlet pipe and the first-level return pipe. The first-level water inlet pipe and the first-level return pipe are both connected to the first-level water tank. The first-level heat exchange tube is located inside the first-level heat exchange area.

[0008] Preferably, the secondary heat exchange cycle includes a secondary water tank, a secondary heat exchange tube, a secondary water inlet pipe and a secondary return pipe. The two ends of the secondary heat exchange tube are respectively connected to the secondary water inlet pipe and the secondary return pipe. The secondary water inlet pipe and the secondary return pipe are both connected to the secondary water tank. The secondary heat exchange tube is located inside the secondary heat exchange area.

[0009] Preferably, a cold water inlet pipe is provided at the upper end of the first-level water tank, and the water in the first-level water tank is circulated and heat-exchanged by a first-level water pump.

[0010] Preferably, a hot water drain pipe is provided at the upper end of the secondary water tank, and the water in the secondary water tank is circulated and heat-exchanged by a secondary water pump.

[0011] Preferably, the primary water tank and the secondary water tank are connected via a connecting pipe, and a one-way valve is provided on the connecting pipe.

[0012] Preferably, a liquid level gauge and a thermometer are provided inside the primary water tank and the secondary water tank.

[0013] Compared with the prior art, the beneficial effects of the present invention are:

[0014] The utility model raises the temperature of the water in the primary water tank to a threshold value through a primary heat exchange cycle, and then the water in the primary water tank enters the secondary water tank through a connecting pipe. The secondary heat exchange cycle allows the water in the secondary water tank to continue to exchange heat with the flue gas in the secondary heat exchange area, and heats the water temperature in the secondary water tank. Since the water in the secondary water tank already has a certain temperature, the temperature of the flue gas will not drop too much after the flue gas passes through the secondary heat exchange area. After passing through the primary heat exchange area, it can continue to exchange heat with the water in the primary water tank, and can utilize the heat in the flue gas twice, thereby improving the efficiency of flue gas waste heat recovery and reducing the waste of flue gas waste heat. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the utility model.

[0016] In the figure: 1. Smoke exhaust duct; 11. Smoke inlet; 12. Smoke exhaust outlet; 13. Primary heat exchange area; 14. Secondary heat exchange area; 2. Primary heat exchange cycle; 21. Primary water tank; 22. Primary heat exchange pipe; 23. Primary water inlet pipe; 24. Primary return pipe; 25. Cold water inlet pipe; 26. Primary water pump; 3. Secondary heat exchange cycle; 31. Secondary water tank; 32. Secondary heat exchange pipe; 33. Secondary water inlet pipe; 34. Secondary return pipe; 35. Hot water drain pipe; 36. Secondary water pump; 4. Connecting pipe; 5. One-way valve. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0018] See also Figure 1 The utility model provides a technical solution: a boiler flue gas waste heat recovery system, comprising a flue gas exhaust pipe 1, wherein the flue gas exhaust pipe 1 is provided with a smoke inlet 11 at one end and a smoke exhaust port 12 at the other end, and the flue gas exhaust pipe 1 comprises a primary heat exchange area 13 and a secondary heat exchange area 14, wherein the primary heat exchange area 13 is connected to the smoke exhaust port 12, and the secondary heat exchange area 14 is connected to the smoke inlet 11;

[0019] The primary heat exchange zone 13 is provided with a primary heat exchange cycle 2 , and the secondary heat exchange zone 14 is provided with a secondary heat exchange cycle 3 . The primary heat exchange cycle 2 and the secondary heat exchange cycle 3 are connected through a connecting pipe 4 .

[0020] Among them, the high-temperature flue gas generated by the boiler enters from the smoke inlet 11 of the smoke exhaust pipe 1 after filtering, and then passes through the secondary heat exchange area 14 and the primary heat exchange area 13 and is discharged from the smoke exhaust pipe 1 from the smoke outlet 12. When the high-temperature flue gas passes through the secondary heat exchange area 14, the secondary heat exchange cycle 3 is triggered, so that part of the heat in the high-temperature flue gas is absorbed by the secondary heat exchange cycle 3, so that the temperature of the high-temperature flue gas becomes lower. After the flue gas temperature becomes lower, when it passes through the primary heat exchange area 13, the heat in the flue gas is absorbed by the primary heat exchange cycle 2 again, so that the flue gas temperature is further reduced. Through the two heat exchange cycles, the heat in the flue gas can be fully absorbed, reducing the waste of heat resources.

[0021] The primary heat exchange cycle 2 includes a primary water tank 21, a primary heat exchange tube 22, a primary water inlet pipe 23, and a primary water return pipe 24. The two ends of the primary heat exchange tube 22 are connected to the primary water inlet pipe 23 and the primary water return pipe 24 respectively. The primary water inlet pipe 23 and the primary water return pipe 24 are both connected to the primary water tank 21. The primary heat exchange tube 22 is located inside the primary heat exchange area 13.

[0022] A cold water inlet pipe 25 is provided at the upper end of the primary water tank 21 , and the water in the primary water tank 21 is circulated and heat-exchanged by a primary water pump 26 .

[0023] Among them, cold water is discharged into the first-level water tank 21 from the cold water inlet pipe 25, and the first-level water pump 26 transports the cold water in the first-level water tank 21 to the inside of the first-level heat exchange pipe 22 through the first-level water inlet pipe 23, and exchanges heat with the flue gas in the first-level heat exchange area 13 through the first-level heat exchange pipe 22, and then enters the first-level water tank 21 again through the first-level return pipe 24. After multiple cycles of heat exchange, the temperature in the first-level water tank 21 can reach a threshold. At this time, if the water in the first-level water tank 21 continues to be heat exchanged through the first-level heat exchange cycle 2, the heat exchange efficiency will be significantly reduced, and the temperature of the water will increase slowly, thereby wasting a lot of flue gas heat resources and increasing time costs. At this time, the secondary heat exchange cycle 3 can be opened to further improve the heat exchange efficiency.

[0024] The secondary heat exchange cycle 3 includes a secondary water tank 31, a secondary heat exchange pipe 32, a secondary water inlet pipe 33 and a secondary water return pipe 34. The two ends of the secondary heat exchange pipe 32 are connected to the secondary water inlet pipe 33 and the secondary water return pipe 34 respectively. The secondary water inlet pipe 33 and the secondary water return pipe 34 are both connected to the secondary water tank 31. The secondary heat exchange pipe 32 is located inside the secondary heat exchange area 14.

[0025] A hot water drain pipe 35 is provided at the upper end of the secondary water tank 31 , and the water in the secondary water tank 31 is circulated and heat-exchanged by a secondary water pump 36 .

[0026] Among them, the primary water tank 21 and the secondary water tank 31 are connected by a connecting pipe 4, and a one-way valve 5 is provided on the connecting pipe 4. When the one-way valve 5 is opened, the water in the primary water tank 21 enters the secondary water tank 31 through the connecting pipe 4. The secondary heat exchange cycle 3 has the same principle as the primary heat exchange cycle 2. At this time, the secondary heat exchange cycle 3 allows the water in the secondary water tank 31 to continue to exchange heat with the flue gas in the secondary heat exchange area 14, and the water temperature in the secondary water tank 31 is heated and increased. Since the water in the secondary water tank 31 already has a certain temperature, the temperature of the flue gas will not drop too much after the flue gas passes through the secondary heat exchange area 14. After passing through the primary heat exchange area 13, it can continue to exchange heat with the water in the primary water tank 21, and the heat in the flue gas can be utilized twice, which improves the efficiency of flue gas waste heat recovery and reduces the waste of flue gas waste heat. In addition, the hot water in the secondary water tank 31 can be discharged through the hot water drain pipe 35.

[0027] Liquid level gauges and thermometers are provided inside the primary water tank 21 and the secondary water tank 31 , and the changes in the water level and water temperature in the primary water tank 21 and the secondary water tank 31 can be accurately known through the liquid level gauges and thermometers.

[0028] The working principle and use process of the present invention are as follows: cold water is discharged from the cold water inlet pipe 25 into the primary water tank 21, and the primary water pump 26 transports the cold water in the primary water tank 21 through the primary water inlet pipe 23 to the inside of the primary heat exchange pipe 22, and exchanges heat with the flue gas in the primary heat exchange area 13 through the primary heat exchange pipe 22, and then enters the primary water tank 21 again through the primary return pipe 24. After performing multiple cycles of heat exchange, the temperature in the primary water tank 21 can reach a threshold. At this time, if the water in the primary water tank 21 continues to exchange heat through the primary heat exchange cycle 2, the heat exchange efficiency will be significantly reduced, and the temperature of the water will be increased slowly, thereby wasting a lot of flue gas heat resources and increasing time costs. At this time, open One-way valve 5, the water in the primary water tank 21 enters the secondary water tank 31 through the connecting pipe 4. The secondary heat exchange cycle 3 has the same principle as the primary heat exchange cycle 2. At this time, the water in the secondary water tank 31 continues to exchange heat with the flue gas in the secondary heat exchange area 14 through the secondary heat exchange cycle 3, and the water temperature in the secondary water tank 31 is heated and increased. Since the water in the secondary water tank 31 already has a certain temperature, the temperature of the flue gas will not drop too much after the flue gas passes through the secondary heat exchange area 14. After passing through the primary heat exchange area 13, it can continue to exchange heat with the water in the primary water tank 21, and can utilize the heat in the flue gas twice, thereby improving the efficiency of flue gas waste heat recovery and reducing the waste of flue gas waste heat.

[0029] Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A boiler flue gas waste heat recovery system, comprising a flue gas exhaust pipe (1), wherein one end of the flue gas exhaust pipe (1) is provided with a flue gas inlet (11) and the other end is provided with a flue gas exhaust port (12), characterized in that: The smoke exhaust pipe (1) comprises a primary heat exchange area (13) and a secondary heat exchange area (14), wherein the primary heat exchange area (13) is connected to the smoke exhaust port (12), and the secondary heat exchange area (14) is connected to the smoke inlet (11); The primary heat exchange zone (13) is provided with a primary heat exchange cycle (2), and the secondary heat exchange zone (14) is provided with a secondary heat exchange cycle (3). The primary heat exchange cycle (2) and the secondary heat exchange cycle (3) are connected via a connecting pipe (4).

2. The boiler flue gas waste heat recovery system according to claim 1, characterized in that: The primary heat exchange cycle (2) comprises a primary water tank (21), a primary heat exchange pipe (22), a primary water inlet pipe (23) and a primary water return pipe (24); both ends of the primary heat exchange pipe (22) are connected to the primary water inlet pipe (23) and the primary water return pipe (24); both the primary water inlet pipe (23) and the primary water return pipe (24) are connected to the primary water tank (21); and the primary heat exchange pipe (22) is located inside the primary heat exchange area (13).

3. The boiler flue gas waste heat recovery system according to claim 2, characterized in that: The secondary heat exchange cycle (3) comprises a secondary water tank (31), a secondary heat exchange pipe (32), a secondary water inlet pipe (33) and a secondary water return pipe (34); both ends of the secondary heat exchange pipe (32) are connected to the secondary water inlet pipe (33) and the secondary water return pipe (34); both the secondary water inlet pipe (33) and the secondary water return pipe (34) are connected to the secondary water tank (31); and the secondary heat exchange pipe (32) is located inside the secondary heat exchange area (14).

4. The boiler flue gas waste heat recovery system according to claim 2, characterized in that: A cold water inlet pipe (25) is provided at the upper end of the primary water tank (21), and the water in the primary water tank (21) is circulated for heat exchange via a primary water pump (26).

5. The boiler flue gas waste heat recovery system according to claim 3, characterized in that: A hot water drain pipe (35) is provided at the upper end of the secondary water tank (31), and the water in the secondary water tank (31) is circulated for heat exchange via a secondary water pump (36).

6. The boiler flue gas waste heat recovery system according to claim 3, characterized in that: The primary water tank (21) and the secondary water tank (31) are connected via a connecting pipe (4), and a one-way valve (5) is provided on the connecting pipe (4).

7. The boiler flue gas waste heat recovery system according to claim 3, characterized in that: Liquid level gauges and thermometers are provided inside the primary water tank (21) and the secondary water tank (31).

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