Double stroke heat exchange flue gas backflow high energy efficiency w type radiant tube burner

Abstract

The application aims to provide a double-stroke heat exchange flue gas backflow high-energy-efficiency W-shaped radiant tube burner, which comprises a flue gas collecting box, a capillary heat exchanger, an air pipe, a main shell, an ejector nozzle, a connecting pipe, a burner, a finned tube heat exchanger and a W-shaped radiant tube. The application utilizes flue gas to perform heat exchange on two strokes of combustion-supporting air, reduces emission and consumption, lowers the exhaust gas temperature and NOx, and is easy to maintain and transform.

Description

Technical Field

[0001] This invention belongs to the field of radiant tube burners, specifically relating to a high-efficiency W-type radiant tube burner with dual-pass heat exchange and flue gas recirculation. Background Technology

[0002] With increasingly stringent requirements for energy conservation and emission reduction in China, traditional W-type self-preheating burners can no longer meet the requirements for NOx emissions and energy consumption. Currently, conventional flue gas recirculation technology suffers from high exhaust temperatures and relatively high energy consumption compared to conventional burners. To further reduce energy consumption per ton of steel, reducing emissions, saving energy, and improving energy efficiency have become the main approaches. W-type self-preheating burners are mainly used in annealing furnaces, horizontal galvanizing furnaces, normalizing furnaces, and heat treatment furnaces. This type of burner has a wide power range (generally 60–300 kW), but installation space is limited, making energy conservation and emission reduction improvements difficult. Summary of the Invention

[0003] The purpose of this invention is to provide a high-efficiency W-type radiant tube burner with dual-pass heat exchange and flue gas recirculation. This invention utilizes the flue gas to exchange heat with the combustion air at two points, reducing emissions and energy consumption, resulting in low exhaust temperature, low NOx, and simple maintenance and modification.

[0004] The technical solution adopted in this invention is:

[0005] A high-efficiency W-type radiant tube burner with dual-pass heat exchange and flue gas recirculation includes a burner (7) installed at one end of a W-type radiant tube (9) via a burner shell (7.4), a finned tube heat exchanger (8) located at the other end of the W-type radiant tube (9), a capillary heat exchanger (2) with four layers of cylinders, a main shell (4) with a smoke isolation chamber (4.4) and three interconnecting interfaces, a smoke collection box (1), and an air pipe (3); in the capillary heat exchanger (2), the cylinders... Cylinders 1 (2.5) to 4 (2.9) are arranged sequentially from the outside to the inside. Cylinder 1 (2.5) and Cylinder 2 (2.4) form a closed annular cavity. The side and one end of the annular cavity are connected to the air inlet pipe (2.6) and the inlet gas collection box (2.10) respectively. Capillary heat exchange tubes (2.7) are distributed between Cylinder 3 (2.8) and Cylinder 4 (2.9) and are sealed at both ends, connecting the inlet gas collection box (2.10) and the outlet gas collection box (2.3). Cylinder 4 (2.9), cylinder 3 (2.8), and cylinder 2 (2.4) form a labyrinthine flue gas passage. The flue gas passage outlet is connected to the smoke collection box (1). The smoke collection box (1) and the air inlet pipe (2.6) are used to connect to the external exhaust pipe and the combustion air pipe, respectively. In the main shell (4), interface 1 (4.5), interface 2 (4.6), and interface 3 (4.1) are respectively connected to the combustion air inlet of the burner shell (7.4) and the other end of the W-type radiant tube (9). The flue gas passage inlet of the capillary heat exchanger (2) is connected to the side of the smoke isolation chamber (4.4) and the ejector nozzle (5) is connected to the finned tube heat exchanger (8). The ejector nozzle (5) is located at interface one (4.5). One end of the air pipe (3) is sealed and inserted into the smoke isolation chamber (4.4) and then extends into the finned tube heat exchanger (8) to the bottom. The other end passes through interface three (4.1) and extends into cylinder four (2.9) to connect with the outlet gas collection box (2.3).

[0006] Furthermore, in the capillary heat exchanger (2), flanges (2.1) and (2.11) are installed at both ends of cylinder one (2.5), respectively. Flanges (2.1) and (2.11) are respectively connected to the smoke collection box (1) and interface three (4.1). Cylinder two (2.4) is installed at both ends on flange (2.1) and inlet gas collection box (2.10). One end of the annular cavity is sealed by flange (2.1), and the other end is sealed by inlet gas collection box (2.10), but a connection is left. Through holes are provided at both ends of cylinder three (2.8) and cylinder four (2.9) respectively on the inlet gas collection box (2.10) and the outlet gas collection box (2.3). The part of cylinder four (2.9) near the inlet gas collection box (2.10) has a connecting port, and the part of cylinder three (2.8) near the outlet gas collection box (2.3) has a connecting port on one side that connects to the air pipe (3), and the other side is sealed by a cover plate (2.2).

[0007] Furthermore, the capillary heat exchange tube (2.7) is flat and has expansion sections distributed along its length.

[0008] Furthermore, the main structure of the main shell (4) is a four-way shell (4.2) and a shell casting material (4.3). The three-way is respectively connected to interface one (4.5), interface two (4.6) and interface three (4.1). The remaining one-way is used to install the smoke isolation chamber (4.4). After the smoke isolation chamber (4.4) is installed, a sealing plate is installed to seal one end of the smoke isolation chamber (4.4) and the remaining one-way at the same time.

[0009] Furthermore, in the burner (7), the ignition electrode (7.3) and the gas pipe (7.6) both pass through the burner shell (7.4) and extend into the W-shaped radiant tube (9). The ignition electrode (7.3) and the gas pipe (7.6) are installed on the burner shell (7.4) through the end plate (7.5). The end plate (7.5) seals the burner shell (7.4). The outer end of the gas pipe (7.6) is connected to a gas pipeline, and the inner end is equipped with a gas nozzle (7.2). The gas nozzle (7.2) is equipped with an air distribution plate (7.1). The outer end of the ignition electrode (7.3) is connected to a high-voltage transformer, and the inner end extends into the air distribution plate (7.1) and presents a certain angle and distance with the nozzle hole of the gas nozzle (7.2).

[0010] Furthermore, in the air pipe (3), the air pipe body (3.3) is L-shaped, and the part of the air pipe body (3.3) inside the capillary heat exchanger (2) is provided with an expansion joint (3.2) and is connected to the outlet gas collection box (2.3) through a flange (3.1).

[0011] Furthermore, the finned tube heat exchanger (8) is cylindrical and includes a connecting tube (8.1), inner and outer finned tubes (8.2), and a ball head (8.3) welded in sequence.

[0012] Furthermore, in the smoke collection box (1), the main body (1.2) of the smoke collection box is a frustum shape that is wider at the front and narrower at the back. The side of the main body (1.2) of the smoke collection box is connected to a branch pipe (1.3) with a valve (1.4). The front and rear ends of the main body (1.2) of the smoke collection box are connected to the outside through flanges (1.5) and flanges (1.1), respectively.

[0013] Furthermore, the interface 1 (4.5) of the main housing (4) is connected to the combustion air inlet of the burner housing (7.4) via a connecting pipe (6) with an expansion joint.

[0014] The beneficial effects of this invention are:

[0015] During operation, the W-type radiant tube (9), burner housing (7.4), and main housing (4) are installed on the heating equipment. Before ignition, the valves on the combustion air pipeline are opened and adjusted according to the gas flow rate and ratio. When the controller receives the ignition command, it controls the high-voltage transformer to discharge and ignite the ignition electrode (7.3). At the same time, the valves on the gas pipeline are opened, and the gas is introduced into the burner (7), where it mixes and burns with the combustion air previously introduced into the burner (7), forming a stable flame of a specific shape. Air enters the annular cavity of the capillary heat exchanger (2) through the air inlet pipe (2.6), and then sequentially passes through the inlet gas collection box (2.10), the capillary heat exchange tube (2.7), and the outlet gas collection box (2.3) before entering the air pipe (3) to achieve the first heat exchange and temperature rise. Then, it enters the bottom of the finned tube heat exchanger (8) through the air pipe (3). The W-shaped radiant tube (9), the finned tube heat exchanger (8), and the air pipe (3) form a double-layer annular seam, and combustion air is sprayed from the air pipe (3) towards... The flue gas enters the flue gas chamber (4.4) through the annular gap between the finned tube heat exchanger (8) and the air pipe at the bottom of the finned tube heat exchanger (8), achieving a second heat exchange and temperature rise. Then, it is injected into the combustion air port of the burner shell (7.4) through the ejector nozzle (5). The ejector nozzle (5) generates a Venturi effect, causing some of the flue gas to be drawn back. The flue gas generated by combustion passes through the finned tube heat exchanger (8) along the W-shaped radiant tube (9). After the first heat exchange and temperature drop, it enters the flue gas chamber through interface two (4.6). The flue gas enters the main shell (4), and then a portion of the flue gas is drawn back to the W-type radiant tube (9) through the interface one (4.5) and the burner shell (7.4) under the Venturi effect. This portion of the flue gas mixes with the preheated combustion air in the burner (7) and participates in combustion. Another portion of the flue gas enters the capillary heat exchanger (2) through the interface three (4.1), completes the second heat exchange and cooling after passing through the flue gas channel of the capillary heat exchanger (2), and is discharged through the smoke collection box (1) and the exhaust pipe.

[0016] This invention utilizes the two-stage heat exchange of flue gas with the combustion air to raise its temperature. In the capillary heat exchanger (2), the labyrinthine flue gas channel allows the high-temperature flue gas to come into contact with the capillary heat exchange tube (2.7) as much as possible, forming strong convection and enhancing the heat exchange efficiency. In the finned tube heat exchanger (8), the W-type radiant tube (9), the finned tube heat exchanger (8), and the air tube (3) form a double-layer annular seam, so that the combustion air and flue gas are in full contact with the finned tube, further preheating the combustion air and playing a role in reducing emissions and energy consumption. It can increase energy consumption by 8-12% and the exhaust gas temperature is low.

[0017] The flue gas of this invention partially recirculates under the injection of combustion air, mixes with the preheated combustion air, and participates in combustion. This reduces the oxygen concentration and the local high temperature of the flame, forming a stable and uniform flame under high furnace temperature conditions. It also reduces the formation of thermal NOx, and the NOx formation meets the domestic ultra-low standard. This invention can be widely used in heating and heat treatment fields that require pulse combustion control and continuous adjustment. It is suitable for annealing furnaces, normalizing furnaces, heat treatment furnaces, quenching furnaces, and continuous annealing furnaces.

[0018] The burner has a wide power adjustment range, and different specifications of burners (7) can achieve heating capacities ranging from 40 to 300 kW.

[0019] The burner adopts a modular design, making maintenance and modification very simple. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a high-efficiency W-type radiant tube burner with dual-pass heat exchange flue gas recirculation in an embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram of a capillary heat exchanger in an embodiment of the present invention.

[0022] Figure 3 This is a schematic diagram of the smoke collection box in an embodiment of the present invention.

[0023] Figure 4 This is a schematic diagram of the air pipe in an embodiment of the present invention.

[0024] Figure 5 This is a schematic diagram of a finned tube heat exchanger in an embodiment of the present invention.

[0025] Figure 6 This is a schematic diagram of the main housing in an embodiment of the present invention.

[0026] Figure 7 This is a schematic diagram of the burner in an embodiment of the present invention.

[0027] Figure 8 This is a schematic diagram of a capillary heat exchanger in an embodiment of the present invention.

[0028] In the picture:

[0029] 1-Smoke collection box; 1.1-Flange; 1.2-Smoke collection box body; 1.3-Branch pipe; 1.4-Valve; 1.5-Flange;

[0030] 2-Capillary heat exchanger; 2.1-Flange; 2.2-Cover plate; 2.3-Outlet gas collection box; 2.4-Cylinder II; 2.5-Cylinder I; 2.6-Air inlet pipe; 2.7-Capillary heat exchange tube; 2.8-Cylinder III; 2.9-Cylinder IV; 2.10-Inlet gas collection box; 2.11-Flange;

[0031] 3-Air pipe; 3.1-Flange; 3.2-Expansion joint; 3.3-Air pipe body;

[0032] 4-Main shell; 4.1-Interface 3; 4.2-Four-way shell; 4.3-Shell castable; 4.4-Smoke baffle; 4.5-Interface 1; 4.6-Interface 2;

[0033] 5-Ejector nozzle;

[0034] 6-Connecting pipe;

[0035] 7-Burn; 7.1-Air distribution plate; 7.2-Gas nozzle; 7.3-Ignition electrode; 7.4-Burn housing; 7.5-End plate; 7.6-Gas pipe;

[0036] 8-Finned tube heat exchanger; 8.1-Connecting cylinder; 8.2-Inner and outer finned tubes; 8.3-Ball head;

[0037] 9-W type radiant tube. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0039] like Figures 1 to 8 As shown, a dual-stroke heat exchange flue gas recirculation high-efficiency W-type radiant tube burner includes a burner 7 installed at one end of a W-type radiant tube 9 via a burner shell 7.4, a finned tube heat exchanger 8 located at the other end of the W-type radiant tube 9, a capillary heat exchanger 2 with four layers of cylinders, a main shell 4 with a smoke isolation chamber 4.4 and three interconnecting interfaces, a smoke collection box 1, and an air pipe 3. In the capillary heat exchanger 2, cylinders 1 to 4 are arranged sequentially from the outside to the inside. Cylinders 1 and 2.4 form a closed annular cavity, and the side and one end of the annular cavity are connected to the air inlet pipe 2.6 and the inlet gas collection box 2.10, respectively. Capillary heat exchange tubes 2.7 are distributed between cylinders 3 and 4 and are sealed at both ends, connecting the inlet gas collection box 2.10 and the outlet gas collection box 2. .3, Cylindrical 4 2.9, Cylindrical 3 2.8 and Cylindrical 2 2.4 form a labyrinthine flue gas channel. The flue gas channel outlet is connected to the smoke collection box 1. The smoke collection box 1 and the air inlet pipe 2.6 are used to connect to the exhaust pipe and the combustion air pipe respectively. In the main shell 4, interface 1 4.5, interface 2 4.6 and interface 3 4.1 are respectively connected to the combustion air inlet of the burner shell 7.4, the other end of the W-type radiant tube 9 and the flue gas channel inlet of the capillary heat exchanger 2. The side of the smoke isolation chamber 4.4 is connected to the ejector nozzle 5 and one end is connected to the finned tube heat exchanger 8. The ejector nozzle 5 is located at interface 1 4.5. One end of the air pipe 3 is sealed and inserted into the smoke isolation chamber 4.4 and then extends into the finned tube heat exchanger 8 to the bottom. The other end passes through interface 3 4.1 and extends into cylinder 4 2.9 to connect with the outlet gas collection box 2.3.

[0040] like Figure 1 As shown, in this embodiment, the interface 4.5 of the main housing 4 is connected to the combustion air outlet of the burner housing 7.4 through a connecting pipe 6 with an expansion joint, so as to avoid cracking due to inconsistent thermal expansion.

[0041] like Figure 2 As shown, in this embodiment, in the capillary heat exchanger 2, flanges 2.1 and 2.11 are installed at both ends of cylinder 1 2.5, respectively. Flanges 2.1 and 2.11 are connected to the smoke collection box 1 and interface 3 4.1, respectively. Cylinder 2 2.4 is installed at both ends of flange 2.1 and inlet gas collection box 2.10. One end of the annular cavity is blocked by flange 2.1, and the other end is blocked by inlet gas collection box 2.10, but a connecting hole is left. Both ends of cylinder 3 2.8 and cylinder 4 2.9 are installed at both ends of inlet gas collection box 2.10 and outlet gas collection box 2.3, respectively. The part of cylinder 4 2.9 near inlet gas collection box 2.10 has a connecting port, and the part of cylinder 3 2.8 near outlet gas collection box 2.3 has a connecting port on one side to air pipe 3, and the other side is blocked by cover plate 2.2.

[0042] like Figure 3 As shown, in this embodiment, in the smoke collection box 1, the main body 1.2 of the smoke collection box is a frustoconical shape that is wider at the front and narrower at the back. The side of the main body 1.2 of the smoke collection box is connected to a branch pipe 1.3 with a valve 1.4. The front and rear ends of the main body 1.2 of the smoke collection box are connected to the outside through flanges 1.5 and 1.1, respectively.

[0043] like Figure 4 As shown, in this embodiment, the air pipe 3 has an L-shaped main body 3.3. The portion of the air pipe 3.3 inside the capillary heat exchanger 2 is provided with an expansion joint 3.2 and is connected to the outlet air collection box 2.3 via a flange 3.1. One end of the air pipe 3 is free, while the other end has an expansion joint 3.2 to avoid a short service life due to inconsistent thermal expansion.

[0044] like Figure 5 As shown, in this embodiment, the finned tube heat exchanger 8 is cylindrical and includes a connecting cylinder 8.1, inner and outer finned tubes 8.2, and a ball head 8.3 welded in sequence.

[0045] like Figure 6 As shown, in this embodiment, the main structure of the main shell 4 is a four-way shell 4.2 and a shell casting 4.3. The three-way is respectively connected to interface one 4.5, interface two 4.6 and interface three 4.1. The remaining one-way is used to install the smoke isolation chamber 4.4. After the smoke isolation chamber 4.4 is installed, a sealing plate is installed to seal one end of the smoke isolation chamber 4.4 and the remaining one-way at the same time.

[0046] like Figure 7As shown, in this embodiment, in the burner 7, the ignition electrode 7.3 and the gas pipe 7.6 both pass through the burner housing 7.4 and extend into the W-shaped radiant tube 9. The ignition electrode 7.3 and the gas pipe 7.6 are mounted on the burner housing 7.4 through the end plate 7.5, which seals the burner housing 7.4. The outer end of the gas pipe 7.6 is connected to a gas pipeline, and the inner end is equipped with a gas nozzle 7.2. An air distribution plate 7.1 is installed on the gas nozzle 7.2. The outer end of the ignition electrode 7.3 is connected to a high-voltage transformer, and the inner end extends into the air distribution plate 7.1 and forms a certain angle and distance with the nozzle orifice of the gas nozzle 7.2.

[0047] like Figure 8 As shown, in this embodiment, the capillary heat exchange tube 2.7 is flat and has expansion sections distributed along its length. The change from a circular shape to a flat shape increases the contact area of ​​the combustion air and reduces the preheating temperature gradient of the combustion air, while allowing for expansion to prevent cracking caused by temperature differences.

[0048] In this embodiment, the connecting cylinder 8.1 is made of 0Cr25Ni20, and the inner and outer finned tubes 8.2 and the ball head 8.3 are made of 0Cr28Ni48W5. It does not oxidize under normal use at 1180℃, has a continuous operating temperature of 1250℃, and a maximum temperature of 1350℃. In this embodiment, the capillary heat exchanger tube 2.7 is extruded from 0Cr25Ni20 material. In this embodiment, the air pipe 3 is located 20-40mm from the bottom of the finned tube heat exchanger 8. In this embodiment, there are 100 capillary heat exchanger tubes 2.7.

[0049] During operation, the W-type radiant tube 9, burner shell 7.4, and main shell 4 are installed on the heating equipment. Before ignition, the valves on the combustion air pipeline are opened and adjusted according to the gas flow rate and ratio. When the controller receives the ignition command, it controls the high-voltage transformer to discharge, causing the ignition electrode 7.3 to ignite. At the same time, the valves on the gas pipeline are opened, and the gas enters the burner 7, mixing and burning with the combustion air previously introduced into the burner 7 to form a stable flame of a specific shape. The combustion air enters the annular cavity of the capillary heat exchanger 2 through the air inlet pipe 2.6, and then sequentially passes through the inlet gas collection box 2.10, the capillary heat exchange tube 2.7, and the outlet gas collection box 2.3 before entering the air pipe 3, achieving the first heat exchange and temperature rise. Then, it enters the bottom of the finned tube heat exchanger 8 through the air pipe 3. The W-type radiant tube 9, the finned tube heat exchanger 8, and the air pipe 3 form a double-layer annular seam. The combustion air is sprayed from the air pipe 3 towards... The flue gas enters the bottom of the finned tube heat exchanger 8, and then enters the smoke isolation chamber 4.4 through the annular gap between the finned tube heat exchanger 8 and the air pipe, achieving a second heat exchange and temperature rise. Then, it is injected into the combustion air port of the burner shell 7.4 through the ejector nozzle 5. The ejector nozzle 5 generates a Venturi effect, causing some of the flue gas to be drawn back. The flue gas generated by combustion passes through the W-shaped radiant tube 9 and the finned tube heat exchanger 8. After the first heat exchange and temperature drop, it enters the main shell 4 through interface 2 4.6. Then, under the suction effect of the Venturi effect, part of the flue gas flows back to the W-shaped radiant tube 9 through interface 1 4.5 and the burner shell 7.4. This part of the flue gas mixes with the preheated combustion air in the burner 7 and participates in combustion. Another part of the flue gas enters the capillary heat exchanger 2 through interface 3 4.1. After passing through the flue gas passage of the capillary heat exchanger 2, it completes the second heat exchange and temperature drop, and is discharged through the smoke collection box 1 and the exhaust pipe.

[0050] This invention utilizes two stages of flue gas to exchange heat with the combustion air and raise its temperature. In the capillary heat exchanger 2, the labyrinthine flue gas channel allows the high-temperature flue gas to contact the capillary heat exchange tubes 2.7 as much as possible, forming strong convection and enhancing heat exchange efficiency. In the finned tube heat exchanger 8, the W-shaped radiant tubes 9, the finned tube heat exchanger 8, and the air tube 3 form a double-layer annular seam, allowing both the combustion air and flue gas to fully contact the finned tubes, further preheating the combustion air and playing a role in reducing emissions and energy consumption. It can improve energy consumption by 8-12% and the exhaust gas temperature is low.

[0051] The flue gas of this invention partially recirculates under the injection of combustion air, mixes with the preheated combustion air, and participates in combustion. This reduces the oxygen concentration and the local high temperature of the flame, forming a stable and uniform flame under high furnace temperature conditions. It also reduces the formation of thermal NOx, and the NOx formation meets the domestic ultra-low standard. This invention can be widely used in heating and heat treatment fields that require pulse combustion control and continuous adjustment. It is suitable for annealing furnaces, normalizing furnaces, heat treatment furnaces, quenching furnaces, and continuous annealing furnaces.

[0052] The burner adopts a modular design, making maintenance and modification very simple.

[0053] The burner has a wide power adjustment range, and different specifications of burners 7 can achieve heating capacities ranging from 40 to 300 kW.

[0054] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A high-efficiency W-type radiant tube burner with dual-pass heat exchange and flue gas recirculation, characterized in that: The system includes a burner (7) installed at one end of a W-type radiant tube (9) via a burner shell (7.4), a finned tube heat exchanger (8) located at the other end of the W-type radiant tube (9), a capillary heat exchanger (2) with four cylindrical layers, a main shell (4) with a smoke isolation chamber (4.4) and three interconnecting interfaces, a smoke collection box (1), and an air pipe (3); in the capillary heat exchanger (2), cylinders one (2.5) to four (2.9) are connected from the outside... The cylinders are arranged sequentially inside, with cylinder one (2.5) and cylinder two (2.4) forming a closed annular cavity. The side and one end of the annular cavity are connected to the air inlet pipe (2.6) and the inlet gas collection box (2.10) respectively. The capillary heat exchange tubes (2.7) are distributed between cylinder three (2.8) and cylinder four (2.9) and are sealed at both ends, connecting the inlet gas collection box (2.10) and the outlet gas collection box (2.3). Cylinder four (2.9) and cylinder three (2.8) and cylinder two (2.4) form a labyrinthine flue gas passage. The flue gas passage outlet is connected to the smoke collection box (1). The smoke collection box (1) and the air inlet pipe (2.6) are used to connect to the external exhaust pipe and the combustion air pipe, respectively. In the main shell (4), interface one (4.5), interface two (4.6) and interface three (4.1) are respectively connected to the combustion air outlet of the burner shell (7.4), the other end of the W-type radiant tube (9) and the capillary tube. The flue gas passage inlet of the heat exchanger (2) is connected to the side of the smoke isolation chamber (4.4) and the ejector nozzle (5) is connected to the side of the smoke isolation chamber (4.4). One end of the ejector nozzle (5) is connected to the finned tube heat exchanger (8). The ejector nozzle (5) is located at interface one (4.5). One end of the air pipe (3) is sealed and inserted into the smoke isolation chamber (4.4) and then extends into the finned tube heat exchanger (8) to the bottom. The other end passes through interface three (4.1) and extends into cylinder four (2.9) to connect with the outlet gas collection box (2.3). The capillary heat exchange tube (2.7) is flat and has expansion sections distributed along its length; The main structure of the main shell (4) is a four-way shell (4.2) and a shell casting material (4.3). The three-way is respectively connected to interface one (4.5), interface two (4.6) and interface three (4.1). The remaining one-way is used to install the smoke isolation chamber (4.4). After the smoke isolation chamber (4.4) is installed, a sealing plate is installed to seal one end of the smoke isolation chamber (4.4) and the remaining one-way at the same time.

2. The dual-pass heat exchange flue gas recirculation high-efficiency W-type radiant tube burner as described in claim 1, characterized in that: In the capillary heat exchanger (2), flanges (2.1) and (2.11) are installed at both ends of cylinder one (2.5), respectively. Flanges (2.1) and (2.11) are connected to the smoke collection box (1) and interface three (4.1) respectively. Cylinder two (2.4) is installed at both ends on flange (2.1) and inlet gas collection box (2.10). One end of the annular cavity is sealed by flange (2.1), and the other end is sealed by inlet gas collection box (2.10) but a connecting hole is left. Both ends of cylinder three (2.8) and cylinder four (2.9) are installed on the inlet gas collection box (2.10) and the outlet gas collection box (2.3) respectively. The part of cylinder four (2.9) near the inlet gas collection box (2.10) has a connecting port, and the part of cylinder three (2.8) near the outlet gas collection box (2.3) has a connecting port. One side of the outlet gas collection box (2.3) has a connecting port that connects to the air pipe (3), and the other side is sealed by a cover plate (2.2).

3. The dual-pass heat exchange flue gas recirculation high-efficiency W-type radiant tube burner as described in claim 1, characterized in that: In the burner (7), the ignition electrode (7.3) and the gas pipe (7.6) both pass through the burner shell (7.4) and extend into the W-shaped radiant tube (9). The ignition electrode (7.3) and the gas pipe (7.6) are installed on the burner shell (7.4) through the end plate (7.5). The end plate (7.5) seals the burner shell (7.4). The outer end of the gas pipe (7.6) is connected to the gas pipeline, and the inner end is installed with the gas nozzle (7.2). The gas nozzle (7.2) is installed with the air distribution plate (7.1). The outer end of the ignition electrode (7.3) is connected to the high-voltage pack, and the inner end extends into the air distribution plate (7.1) and presents a certain angle and distance with the nozzle hole of the gas nozzle (7.2).

4. The high-efficiency W-type radiant tube burner with dual-pass heat exchange and flue gas recirculation as described in claim 1, characterized in that: In the air pipe (3), the air pipe body (3.3) is L-shaped. The part of the air pipe body (3.3) inside the capillary heat exchanger (2) is provided with an expansion joint (3.2) and is connected to the outlet gas collection box (2.3) through a flange (3.1).

5. The high-efficiency W-type radiant tube burner with dual-pass heat exchange and flue gas recirculation as described in claim 1, characterized in that: The finned tube heat exchanger (8) is cylindrical and includes a connecting tube (8.1), inner and outer finned tubes (8.2), and a ball head (8.3) welded in sequence.

6. The dual-pass heat exchange flue gas recirculation high-efficiency W-type radiant tube burner as described in claim 1, characterized in that: In the smoke collection box (1), the main body (1.2) of the smoke collection box is a frustum shape that is wider at the front and narrower at the back. The side of the main body (1.2) of the smoke collection box is connected to a branch pipe (1.3) with a valve (1.4). The front and rear ends of the main body (1.2) of the smoke collection box are connected to the outside through flanges (1.5) and flanges (1.1), respectively.

7. The dual-pass heat exchange flue gas recirculation high-efficiency W-type radiant tube burner as described in claim 1, characterized in that: The interface 1 (4.5) of the main housing (4) is connected to the combustion air outlet of the burner housing (7.4) through the connecting pipe (6) with expansion joint.

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