Multi-return gas boiler

Abstract

The application discloses a multi-return stroke gas boiler and relates to the technical field of gas boilers; the multi-return stroke gas boiler comprises a furnace cylinder, front and rear smoke boxes riveted to the two sides of the furnace cylinder, a furnace bellow arranged in the furnace cylinder, and a back burning chamber fixedly connected to the right side of the furnace bellow; first and second return stroke pipes are movably connected between the back burning chamber and the front smoke box and between the front and rear smoke boxes, respectively; a igniter is movably connected to the left side of the front smoke box; and the front and rear smoke boxes are internally provided with a heat uniformity assembly for assisting smoke flow and increasing the heating uniformity of the return stroke pipes; the capsule extrusion provides power for the smoke, ensures the smooth flow of the smoke in the second return stroke pipe, and drives the driving cylinder to move synchronously when the push plate reciprocates left and right, the driving cylinder drives the sliding block to slide in the sliding groove, thereby driving the first and second return stroke pipes to rotate, so that the hot area of the return stroke pipe is in contact with the cold water area of the soft water, the contact area of the return stroke pipe and the soft water is increased, and the heating efficiency of the soft water is improved.

Description

Technical Field

[0001] This invention relates to the field of gas-fired boiler technology, and more particularly to a multi-pass gas-fired boiler. Background Technology

[0002] As the name suggests, a gas-fired boiler is a boiler that uses gas as fuel. A multi-pass gas-fired boiler is a gas-fired boiler in which the flue gas passes through multiple heat exchange processes inside the boiler. Its core is to improve thermal efficiency by increasing the number of heat exchange processes.

[0003] The flue gas circulation inside a gas-fired boiler mainly relies on the principle of hot gas rising. As the number of return passes increases, the temperature of the hot gas generated by combustion gradually decreases, thereby slowing down the flow rate of hot gas inside the gas, and even causing the hot gas to fail to reach the end of the return pass. In addition, after the water inside the furnace is heated, there will be a stratification phenomenon of hot water on top and cold water on the bottom. Therefore, the water temperature in contact with the surrounding area of ​​the return pipe will be different, resulting in uneven heating of the water inside the furnace during the return pass and reducing the return pass heating efficiency. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of hot gas stagnation inside the boiler and uneven heating of water inside the boiler caused by the increase of the number of return passes in traditional boilers, and to propose a multi-pass gas-fired boiler.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A multi-pass gas-fired boiler includes a furnace drum, with a front smoke box and a rear smoke box riveted to both sides of the furnace drum. The furnace drum has a furnace chamber inside, and a combustion chamber is fixedly connected to the right side of the furnace chamber. A first return pipe and a second return pipe are movably connected between the combustion chamber and the front smoke box and between the front smoke box and the rear smoke box, respectively. An igniter is movably connected to the left side of the front smoke box. The boiler also includes a heat uniformity component that assists in flue gas flow and increases the heating uniformity of the return pipe inside the front and rear smoke boxes.

[0007] The uniform heating component includes a telescopic cylinder fixedly connected to the front smoke box and the rear smoke box on the side away from the furnace cylinder. Push plates are movably connected inside the front smoke box and the combustion chamber. The telescopic end of the telescopic cylinder passes through the front smoke box, the rear smoke box and the combustion chamber respectively and is fixedly connected to the push plate. A bladder is fixedly connected between the right side of the push plate on the left and the front smoke box, and a one-way valve is provided on the surface of the bladder.

[0008] As a further description of the above technical solution:

[0009] The left end of the first return pipe and the right end of the second return pipe extend into the interior of the front smoke box and the rear smoke box, respectively. The outer circular surface of the extension area of ​​the first return pipe and the second return pipe is provided with a sliding groove. The push plate is fixedly connected to a drive cylinder on the side near the furnace cylinder. The drive cylinder is sleeved on the outside of the first return pipe and the second return pipe, and the inner circular surface of the drive cylinder is fixedly connected to a slider that is slidably connected inside the sliding groove.

[0010] As a further description of the above technical solution:

[0011] Both the first and second return pipes are equipped with descaling components on their exteriors. The descaling components include end caps located inside the front and rear smoke boxes, and springs are fixedly connected between the end caps and the inner walls of the front and rear smoke boxes. The end caps seal the ends of both the first and second return pipes. A traction rope is fixedly connected between the end cap on the left side and the push plate.

[0012] As a further description of the above technical solution:

[0013] Both the first return pipe and the second return pipe are provided with scraper rods at their upper ends, and the scraper rods extend through the interior of the front smoke box and the rear smoke box and are fixedly connected to the end caps. The lower ends of the scraper rods are provided with scraper blades on both sides, and the lower middle part of the scraper rods is provided with a frosted part. The ends of the front smoke box and the rear smoke box that are close to each other are fixedly connected with limit blocks, and the other end of the scraper rods is slidably connected to the interior of the limit blocks.

[0014] As a further description of the above technical solution:

[0015] Both the first return pipe and the second return pipe are equipped with dust removal components. The dust removal components include cleaning arms located inside the first return pipe and the second return pipe. Both sides of the cleaning arms are fixedly connected to elastic telescopic rods, and the telescopic ends of the elastic telescopic rods are fixedly connected to scrapers.

[0016] As a further description of the above technical solution:

[0017] The end cap is fixedly connected to two connecting seats on both sides near the end of the cleaning arm. A rotating shaft is fixedly connected between the connecting seats. The cleaning arm is movably sleeved on the outside of the rotating shaft. A spring is fixedly connected to the lower end of the cleaning arm.

[0018] As a further description of the above technical solution:

[0019] A pressure gauge is fixedly connected to the upper end of the front smoke box, and an economizer is fixedly connected to the upper end of the rear smoke box.

[0020] As a further description of the above technical solution:

[0021] A safety valve and a steam pipe are fixedly connected to the upper end of the furnace cylinder, a control box and a water inlet pipe are fixedly connected to the front end of the furnace cylinder, and a level gauge is fixedly connected to the rear end of the furnace cylinder.

[0022] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0023] The pusher plate inside the front smoke box is pushed by a telescopic cylinder to move back and forth. When the pusher plate moves to the left, it causes the bladder to unfold, drawing the flue gas inside the front smoke box into the bladder through a one-way valve. When the pusher plate moves to the right, it squeezes the bladder, causing the flue gas inside the bladder to be discharged and enter the second return pipe. The squeezing of the bladder provides power for the flue gas, ensuring that the flue gas flows smoothly inside the second return pipe. When the pusher plate moves back and forth, it drives the drive cylinder to move synchronously. The drive cylinder drives the slider to slide inside the slide groove, thereby driving the first and second return pipes to rotate. This allows the hotter area of ​​the return pipe to come into contact with the cold water area of ​​the soft water, increasing the contact area between the return pipe and the soft water and improving the heating efficiency of the soft water. Attached Figure Description

[0024] Figure 1 A schematic diagram of the overall structure provided according to an embodiment of the present invention is shown;

[0025] Figure 2 A cross-sectional structural schematic diagram provided according to an embodiment of the present invention is shown;

[0026] Figure 3 A partial structural schematic diagram of a descaling assembly provided according to an embodiment of the present invention is shown;

[0027] Figure 4 A view showing the combination of a second return pipe and a chute according to an embodiment of the present invention is shown;

[0028] Figure 5 The present invention provides an embodiment of the invention. Figure 3 Enlarged view of point A in the middle;

[0029] Figure 6 A partial structural schematic diagram of a dust removal assembly provided according to an embodiment of the present invention is shown;

[0030] Figure 7 A schematic diagram of a scraper structure provided according to an embodiment of the present invention is shown.

[0031] Legend:

[0032] 10. Furnace drum; 11. Front smoke box; 12. Rear smoke box; 13. Furnace shell; 14. Combustion chamber; 15. First return pipe; 16. Second return pipe; 17. Ignition device; 18. Safety valve; 19. Steam pipe; 110. Water inlet pipe; 111. Pressure gauge; 112. Level gauge; 113. Control box; 114. Economizer;

[0033] 20. Uniformly heated component; 21. Telescopic cylinder; 22. Push plate; 23. Bag body; 24. One-way valve; 25. Drive cylinder; 26. Slide groove;

[0034] 30. Descaling assembly; 31. Scraper bar; 32. End cap; 33. Spring; 34. Limiting block; 35. Scraper blade; 36. Abrasive part; 37. Traction rope;

[0035] 40. Dust removal component; 41. Connecting seat; 42. Rotary shaft; 43. Cleaning arm; 44. Flexible telescopic rod; 45. Scraper; 46. Spring. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] like Figures 1-5 As shown, the present invention provides a multi-pass gas-fired boiler, comprising a furnace cylinder 10, with a front smoke box 11 and a rear smoke box 12 riveted to both sides of the furnace cylinder 10, a furnace chamber 13 inside the furnace cylinder 10, and a combustion chamber 14 fixedly connected to the right side of the combustion chamber 13. A first return pipe 15 and a second return pipe 16 are movably connected between the combustion chamber 14 and the front smoke box 11, and between the front smoke box 11 and the rear smoke box 12, respectively. An igniter 17 is movably connected to the left side of the front smoke box 11. A pressure gauge 111 is fixedly connected to the upper end of the front smoke box 11, and an economizer 114 is fixedly connected to the upper end of the rear smoke box 12; a safety valve 18 and a steam pipe 19 are fixedly connected to the upper end of the furnace cylinder 10, and a control box 113 and a water inlet pipe 110 are fixedly connected to the front end of the furnace cylinder 10, and a level gauge 112 is fixedly connected to the rear end of the furnace cylinder 10. It also includes a heating uniformity component 20 that assists in flue gas flow and increases the heating uniformity of the return pipe inside the front smoke box 11 and the rear smoke box 12.

[0038] The uniform heating component 20 includes a telescopic cylinder 21 fixedly connected to the front smoke box 11 and the rear smoke box 12 on the side away from the furnace cylinder 10. Push plates 22 are movably connected inside the front smoke box 11 and the combustion chamber 14. The telescopic end of the telescopic cylinder 21 passes through the front smoke box 11, the rear smoke box 12 and the combustion chamber 14 respectively and is fixedly connected to the push plate 22. A bladder 23 is fixedly connected between the right side of the left push plate 22 and the front smoke box 11, and a one-way valve 24 is provided on the surface of the bladder 23.

[0039] The left end of the first return pipe 15 and the right end of the second return pipe 16 extend into the interior of the front smoke box 11 and the rear smoke box 12, respectively. The outer circular surface of the extension area of ​​the first return pipe 15 and the second return pipe 16 is provided with a sliding groove 26. The push plate 22 is fixedly connected to the side near the furnace cylinder 10 with a drive cylinder 25. The drive cylinder 25 is sleeved on the outside of the first return pipe 15 and the second return pipe 16, and the inner circular surface of the drive cylinder 25 is fixedly connected with a slider that is slidably connected inside the sliding groove 26.

[0040] Specifically, firstly, soft water is injected into the furnace cylinder 10 through the water inlet pipe 110. During the water injection process, the water level inside the furnace cylinder 10 is observed through the level gauge 112 until the water level reaches the specified range and then the water injection is stopped. Then, gas is introduced into the furnace chamber 13 through the igniter 17 and the gas is ignited by the igniter 17. After that, the gas burns inside the furnace chamber 13 and heats the furnace chamber 13. The furnace chamber 13 then conducts the heat to the soft water inside the furnace cylinder 10, so that the soft water is heated to generate steam. Then, the steam is transmitted to various heat-using equipment through the steam pipe 19.

[0041] During the combustion of the gas, the unburned gas continues to burn inside the combustion chamber 14, and the combustion chamber 14 transfers heat to the soft water inside the furnace drum 10. The flue gas generated by the combustion then continues to heat the soft water through the first return pipe 15. The flue gas then enters the second return pipe 16 through the front smoke box 11 to continue heating the soft water inside the furnace drum 10. Finally, the flue gas enters the rear smoke box 12 and is treated by the economizer 114 before being discharged. The entire combustion process is controlled by the control box 113. During the combustion process, the internal pressure of the boiler is monitored in real time through the pressure gauge 111. At the same time, a safety valve 18 is configured. When the internal pressure of the boiler exceeds the specified value, the safety valve 18 automatically opens to release pressure from the boiler until the internal pressure of the boiler returns to a safe value and stops discharging.

[0042] When the boiler is working, the flue gas flows inside the return pipes based on the principle of hot air rising. As the number of return pipes increases, the flue gas velocity will slow down or even stop. Based on this, while the boiler is burning, the push plate 22 inside the front smoke box 11 is pushed by the telescopic cylinder 21 to move back and forth. When the push plate 22 moves to the left, it drives the bladder 23 to unfold, drawing the flue gas inside the front smoke box 11 into the bladder 23 through the one-way valve 24. When the push plate 22 moves to the right, it squeezes the bladder 23, causing the flue gas inside the bladder 23 to be discharged and enter the second return pipe 16. The squeezing of the bladder 23 provides power for the flue gas, ensuring that the flue gas flows smoothly inside the second return pipe 16. Regarding the smooth flow, it should be noted that since the flue gas temperature inside the combustion chamber 14 is relatively high, the flue gas can smoothly enter the first return pipe 15 without the need for a bladder 23 to provide power. When the flue gas passes through the first return pipe 15, it exchanges heat with the soft water inside the furnace drum 10. Therefore, the flue gas temperature entering the front smoke box 11 decreases and the flow rate slows down. Setting a bladder 23 inside the front smoke box 11 can provide power for the flue gas flow. In addition, this application only shows two sets of return pipes. As the number of return pipes increases, the flue gas temperature will also decrease. Therefore, in subsequent return areas, the power for flue gas flow can be increased by adding bladders 23.

[0043] In addition to the flue gas, the soft water inside the furnace drum 10 will also exhibit a stratification phenomenon after heating, with hot water on top and cold water on the bottom. Similarly, the flue gas inside the return pipe will also have a higher temperature on top and a lower temperature on the bottom. Therefore, the hotter upper part of the return pipe comes into contact with the hot water inside the furnace drum 10, while the lower part of the return pipe comes into contact with the cold water inside the furnace drum 10, which greatly reduces the heating efficiency of the flue gas on the soft water inside the furnace drum 10.

[0044] Based on this, when the push plate 22 reciprocates left and right, it drives the drive cylinder 25 to move synchronously. The drive cylinder 25 drives the slider to slide inside the slide groove 26, thereby driving the first return pipe 15 and the second return pipe 16 to rotate, so that the hotter area of ​​the return pipe comes into contact with the cold water area of ​​the soft water, increasing the contact area between the return pipe and the soft water and improving the heating efficiency of the soft water.

[0045] like Figures 2-7 As shown, both the first return pipe 15 and the second return pipe 16 are provided with descaling components 30. The descaling components 30 include end caps 32 located inside the front smoke box 11 and the rear smoke box 12. Springs 33 are fixedly connected between the end caps 32 and the inner walls of the front smoke box 11 and the rear smoke box 12. The end caps 32 block the ends of the first return pipe 15 and the second return pipe 16. A traction rope 37 is fixedly connected between the left end cap 32 and the push plate 22.

[0046] Both the upper ends of the first return pipe 15 and the second return pipe 16 are provided with scraper rods 31, and the scraper rods 31 extend through the interior of the front smoke box 11 and the rear smoke box 12 and are fixedly connected to the end cap 32. The lower ends of the scraper rods 31 are provided with scraper blades 35 on both sides, and the lower middle part of the scraper rods 31 is provided with a frosted part 36. The ends of the front smoke box 11 and the rear smoke box 12 that are close to each other are fixedly connected with limit blocks 34, and the other end of the scraper rods 31 is slidably connected to the interior of the limit blocks 34.

[0047] Specifically, after prolonged heating, a scale layer will form on the outer wall of the return pipe, which will affect the heat transfer efficiency of the return pipe. Therefore, the surface of the return pipe needs to be cleaned regularly.

[0048] When the uniformly heated component 20 is working, as the first return tube 15 and the second return tube 16 rotate, they will both come into contact with the scraper 35 at the lower part of the scraper 31. The scraper 35 will then scrape off the scale on the surface of the first return tube 15 and the second return tube 16. At the same time, when the bladder 23 contracts and squeezes the flue gas into the second return tube 16, the end cap 32 inside the rear smoke box 12 moves under the push of the flue gas, which drives the scraper 31 to move synchronously. The left push plate 22 pulls the end cap 32 through the traction rope 37, which in turn drives the scraper 31 to move synchronously. The abrasive part 36 at the lower end of the scraper 31 will then polish the scale on the surface of the first return tube 15 and the second return tube 16, making the scale on the surface of the first return tube 15 and the second return tube 16 loose, so that the scraper 35 can easily scrape off the scale, ensuring the heat transfer efficiency of the first return tube 15 and the second return tube 16.

[0049] like Figure 3 and Figure 6 As shown, both the first return pipe 15 and the second return pipe 16 are equipped with dust removal components 40. The dust removal components 40 include cleaning arms 43 located inside the first return pipe 15 and the second return pipe 16. Both sides of the cleaning arms 43 are fixedly connected with elastic telescopic rods 44, and the telescopic ends of the elastic telescopic rods 44 are fixedly connected with scrapers 45.

[0050] The end cap 32 is fixedly connected to both sides of the end near the cleaning arm 43 with a connecting seat 41. A rotating shaft 42 is fixedly connected between the connecting seats 41. The cleaning arm 43 is movably sleeved on the outside of the rotating shaft 42. A spring piece 46 is fixedly connected to the lower end of the cleaning arm 43.

[0051] Specifically, as the first return pipe 15 and the second return pipe 16 rotate, their inner walls also shift relative to the scraper 45. This allows the scraper 45 to remove the dust adhering to the inside of the first return pipe 15 and the second return pipe 16. The cleaning arm 43, which connects to the scraper 45, is movably connected at one end to the end cap 32 via a pivot 42. Therefore, the other end of the cleaning arm 43 naturally leans against the bottom of the first return pipe 15 and the second return pipe 16. The movement of the end cap 32 pulls the cleaning arm 43 to move synchronously. When the cleaning arm 43 moves, the spring plate 46 at its bottom is blocked by the scraped dust. The spring 46 swings as it moves, which can lift up the deposited dust, allowing the flue gas to smoothly carry the dust out when it passes through the first return pipe 15 and the second return pipe 16. This effectively cleans the inside of the first return pipe 15 and the second return pipe 16, further ensuring the heat transfer efficiency of the first return pipe 15 and the second return pipe 16. The up-and-down movement of the cleaning arm 43 will cause the scraper 45 to move in the same direction. Therefore, an elastic telescopic rod 44 is provided so that the scraper 45 can extend and retract freely and always keep in contact with the inner wall of the first return pipe 15 and the second return pipe 16, ensuring its cleaning efficiency.

[0052] Working principle: First, soft water is injected into the furnace cylinder 10 through the water inlet pipe 110. During the water injection process, the water level inside the furnace cylinder 10 is observed through the level gauge 112. Water injection is stopped when the water level reaches the specified range. Then, gas is introduced into the furnace chamber 13 through the igniter 17 and ignited by the igniter 17. The gas then burns inside the furnace chamber 13, heating the furnace chamber 13. The furnace chamber 13 then conducts the heat to the soft water inside the furnace cylinder 10, heating the soft water to generate steam. The steam is then transmitted to various heat-using equipment through the steam pipe 19.

[0053] During the combustion of the gas, the unburned gas continues to burn inside the combustion chamber 14, and the combustion chamber 14 transfers heat to the soft water inside the furnace drum 10. The flue gas generated by the combustion then continues to heat the soft water through the first return pipe 15. The flue gas then enters the second return pipe 16 through the front smoke box 11 to continue heating the soft water inside the furnace drum 10. Finally, the flue gas enters the rear smoke box 12 and is treated by the economizer 114 before being discharged. The entire combustion process is controlled by the control box 113. During the combustion process, the internal pressure of the boiler is monitored in real time through the pressure gauge 111. At the same time, a safety valve 18 is configured. When the internal pressure of the boiler exceeds the specified value, the safety valve 18 automatically opens to release pressure from the boiler until the internal pressure of the boiler returns to a safe value and stops discharging.

[0054] When the boiler is working, the flue gas flows inside the return pipes based on the principle of hot air rising. As the number of return pipes increases, the flue gas velocity will slow down or even stop. Based on this, while the boiler is burning, the push plate 22 inside the front smoke box 11 is pushed by the telescopic cylinder 21 to move back and forth. When the push plate 22 moves to the left, it drives the bladder 23 to unfold, drawing the flue gas inside the front smoke box 11 into the bladder 23 through the one-way valve 24. When the push plate 22 moves to the right, it squeezes the bladder 23, causing the flue gas inside the bladder 23 to be discharged and enter the second return pipe 16. The squeezing of the bladder 23 provides power for the flue gas, ensuring that the flue gas flows smoothly inside the second return pipe 16. Regarding the smooth flow, it should be noted that since the flue gas temperature inside the combustion chamber 14 is relatively high, the flue gas can smoothly enter the first return pipe 15 without the need for a bladder 23 to provide power. When the flue gas passes through the first return pipe 15, it exchanges heat with the soft water inside the furnace drum 10. Therefore, the flue gas temperature entering the front smoke box 11 decreases and the flow rate slows down. Setting a bladder 23 inside the front smoke box 11 can provide power for the flue gas flow. In addition, this application only shows two sets of return pipes. As the number of return pipes increases, the flue gas temperature will also decrease. Therefore, in subsequent return areas, the power for flue gas flow can be increased by adding bladders 23.

[0055] When the push plate 22 reciprocates left and right, it drives the drive cylinder 25 to move synchronously. The drive cylinder 25 drives the slider to slide inside the slide groove 26, thereby driving the first return pipe 15 and the second return pipe 16 to rotate, so that the hotter area of ​​the return pipe comes into contact with the cold water area of ​​the soft water, increasing the contact area between the return pipe and the soft water and improving the heating efficiency of the soft water.

[0056] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A multi-pass gas-fired boiler, comprising a furnace shell (10), a front smoke box (11) and a rear smoke box (12) respectively riveted to both sides of the furnace shell (10), a furnace chamber (13) provided inside the furnace shell (10), and a combustion chamber (14) fixedly connected to the right side of the combustion chamber (13), a first return pipe (15) and a second return pipe (16) respectively movably connected between the combustion chamber (14) and the front smoke box (11) and between the front smoke box (11) and the rear smoke box (12), and an igniter (17) movably connected to the left side of the front smoke box (11), characterized in that, It also includes a heat uniformity component (20) inside the front smoke box (11) and the rear smoke box (12) to assist in flue gas flow and increase the uniformity of heating of the return pipe. The uniform heating component (20) includes a telescopic cylinder (21) fixedly connected to the front smoke box (11) and the rear smoke box (12) on the side away from the furnace cylinder (10). The front smoke box (11) and the combustion chamber (14) are both movably connected to push plates (22). The telescopic end of the telescopic cylinder (21) passes through the front smoke box (11), the rear smoke box (12) and the combustion chamber (14) respectively and is fixedly connected to the push plate (22). The right side of the push plate (22) on the left side is fixedly connected to the front smoke box (11) and a bladder (23). The surface of the bladder (23) is provided with a one-way valve (24).

2. A multi-pass gas-fired boiler according to claim 1, characterized in that, The left end of the first return pipe (15) and the right end of the second return pipe (16) extend into the interior of the front smoke box (11) and the rear smoke box (12), respectively. The outer circular surface of the extension area of ​​the first return pipe (15) and the second return pipe (16) is provided with a sliding groove (26). The push plate (22) is fixedly connected to the side of the furnace cylinder (10) with a drive cylinder (25). The drive cylinder (25) is sleeved on the outside of the first return pipe (15) and the second return pipe (16), and the inner circular surface of the drive cylinder (25) is fixedly connected with a slider that is slidably connected inside the sliding groove (26).

3. A multi-pass gas-fired boiler according to claim 1, characterized in that, Both the first return pipe (15) and the second return pipe (16) are provided with descaling components (30). The descaling components (30) include end caps (32) located inside the front smoke box (11) and the rear smoke box (12). Springs (33) are fixedly connected between the end caps (32) and the inner walls of the front smoke box (11) and the rear smoke box (12). The end caps (32) form a seal on the ends of the first return pipe (15) and the second return pipe (16). A traction rope (37) is fixedly connected between the end caps (32) on the left side and the push plate (22).

4. A multi-pass gas-fired boiler according to claim 3, characterized in that, The upper ends of the first return pipe (15) and the second return pipe (16) are provided with scraper rods (31), and the scraper rods (31) extend through to the interior of the front smoke box (11) and the rear smoke box (12) and are fixedly connected to the end cap (32). The lower ends of the scraper rods (31) are provided with scraper blades (35) on both sides, and the lower end of the scraper rods (31) is provided with a frosted part (36) in the middle. The front smoke box (11) and the rear smoke box (12) are fixedly connected to a limiting block (34) at their adjacent ends, and the other end of the scraper rods (31) is slidably connected to the interior of the limiting block (34).

5. A multi-pass gas-fired boiler according to claim 4, characterized in that, The first return pipe (15) and the second return pipe (16) are both equipped with dust removal components (40). The dust removal components (40) include cleaning arms (43) located inside the first return pipe (15) and the second return pipe (16). Both sides of the cleaning arms (43) are fixedly connected with elastic telescopic rods (44), and the telescopic ends of the elastic telescopic rods (44) are fixedly connected with scrapers (45).

6. A multi-pass gas-fired boiler according to claim 5, characterized in that, The end cap (32) is fixedly connected to two connecting seats (41) on both sides near the cleaning arm (43). A rotating shaft (42) is fixedly connected between the connecting seats (41). The cleaning arm (43) is movably sleeved on the outside of the rotating shaft (42). A spring piece (46) is fixedly connected to the lower end of the cleaning arm (43).

7. A multi-pass gas-fired boiler according to claim 1, characterized in that, A pressure gauge (111) is fixedly connected to the upper end of the front smoke box (11), and an economizer (114) is fixedly connected to the upper end of the rear smoke box (12).

8. A multi-pass gas-fired boiler according to claim 1, characterized in that, The upper end of the furnace cylinder (10) is fixedly connected to a safety valve (18) and a steam pipe (19), and the front end of the furnace cylinder (10) is fixedly connected to a control box (113) and a water inlet pipe (110). The rear end of the furnace cylinder (10) is fixedly connected to a level gauge (112).

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