High-efficiency energy-saving bell-type furnace low-NOx combustion system

Abstract

The utility model discloses an efficient energy-saving bell-type furnace low NOx combustion system, which belongs to the technical field of heat treatment equipment, and comprises a bell-type furnace, a heat exchanger and a burner, the heat exchanger comprises the following structures: a heat exchange shell, a cold air port, a flue gas pipe and a flue gas outlet which are arranged on the surface of the heat exchange shell, a heat exchange pipe is arranged in the heat exchange shell, a hot air end is formed at the end part of the heat exchange pipe, and a hot air outlet is formed at the end part of the heat exchange pipe; one end of the flue gas pipe faces the hot air end, and the other end extends into the bell-type furnace; the burner comprises a burner shell and a hot air port, the end of the burner shell extends into the bell-type furnace and is provided with a flame outlet, a gas pipe and a mixing cup are arranged in the burner shell, an air hole with an opening facing the flame outlet is formed in one side of the mixing cup in a penetrating mode, and a gas outlet with an opening facing the inner wall of the mixing cup is formed in the end of the gas pipe. A hot air pipe extending to the hot air port is arranged at one end, close to the hot air end, of the heat exchanger; according to the utility model, the generation of thermal nitrogen oxides can be reduced, and the energy utilization efficiency is improved, so that the energy-saving and emission-reducing effects are realized.

Description

Technical Field

[0001] The utility model relates to the technical field of heat treatment equipment, in particular to a low-NOx combustion system for an energy-efficient bell-type furnace. Background Art

[0002] A bell-type furnace is an important heat treatment equipment. The bell-type furnace has the characteristics of a large loading capacity and high requirements for furnace temperature uniformity. The bell-type furnace usually uses heating devices such as burners to generate heat by combustion to make the furnace temperature reach the set temperature, so as to heat-treat workpieces. However, during the process of the furnace temperature of the bell-type furnace rising to the set temperature, the temperature of the flue gas passing through the heat exchanger will also become higher and higher, and the temperature of the combustion-supporting air after heat exchange through the heat exchanger will also become higher and higher. When the temperature of the combustion-supporting air is too high, it will cause the flame temperature of the burner to be too high and generate a large amount of nitrogen oxides (NOx). Nitrogen oxides are a kind of toxic substances and are also the main factors for the formation of acid rain, etc. The irregular emission of nitrogen oxides will cause serious environmental pollution. Therefore, at present, most bell-type furnaces only set up a simple heat exchanger to reduce the heat exchange amount between the combustion-supporting air and the flue gas, so as to avoid the temperature of the combustion-supporting air being too high during combustion, and thus reduce the generation of nitrogen oxides. However, this approach will waste a large amount of heat carried in the flue gas and affect the energy utilization efficiency. In today's context of energy shortage and increasing importance of environmental protection, this kind of heat waste is not conducive to energy conservation and emission reduction, and the heat in the flue gas fails to be fully recovered for preheating the combustion-supporting air, and more fuel may be consumed during the combustion process to obtain the required heat, thus increasing the operating cost.

[0003] Therefore, when using a bell-type furnace for heat treatment, how to increase the heat recovery rate of the flue gas and at the same time reduce the generation amount of nitrogen oxides has become a new research direction for heat treatment equipment manufacturers. Summary of the Utility Model

[0004] In view of the technical defects existing in the background art, the utility model provides a low-NOx combustion system for an energy-efficient bell-type furnace, which solves the above technical problems and meets the actual requirements. The specific technical solutions are as follows:

[0005] A low-NOx combustion system for an energy-efficient bell-type furnace includes a bell-type furnace, a heat exchanger, and a burner. The heat exchanger and the burner are arranged on one side of the bell-type furnace. The heat exchanger includes the following structure: a heat exchange housing with a hollow interior, a cold air inlet, a flue gas pipe, and a flue gas outlet are arranged on the surface of the heat exchange housing. A heat exchange pipe communicating with the cold air inlet and extending along the heat exchange housing is arranged in the heat exchange housing. The end of the heat exchange pipe where it extends forms a hot air end. One end of the flue gas pipe faces the hot air end and the other end extends into the bell-type furnace.

[0006] The burner includes the following structure: a burner housing with a hollow interior. One side of the burner housing is provided with a hot air inlet. The end of the burner housing extends into the bell-type furnace and is provided with a flame outlet. One end of the burner housing is provided with a gas pipe extending towards the flame outlet. The end of the gas pipe is provided with a mixing cup with an opening facing the flame outlet. The side of the mixing cup away from the flame outlet is provided with an air hole with an opening facing the flame outlet. The end of the gas pipe is provided with a gas outlet with an opening facing the inner wall of the mixing cup.

[0007] One end of the heat exchanger close to the hot air end is provided with a hot air pipe extending to the hot air inlet.

[0008] As a further technical solution of the present invention, a hot air collecting chamber is provided at the hot air end of the heat exchange tube. The inner diameter of the hot air collecting chamber gradually decreases from the end close to the heat exchange tube to the other end. The end of the hot air collecting chamber away from the heat exchange tube is provided with an ejector nozzle.

[0009] As a further technical solution of the present invention, an air housing is sleeved outside the heat exchange housing. One end of the air housing is provided with a cold air collecting chamber communicating with the heat exchange tube, and the other end communicates with the cold air inlet.

[0010] As a further technical solution of the present invention, the flue gas pipe and the flue gas outlet are arranged at opposite ends of the heat exchange housing.

[0011] As a further technical solution of the present invention, a plurality of heat exchange tubes are provided. A space allowing air to flow is provided between adjacent heat exchange tubes. The plurality of heat exchange tubes are selected from one or more of circular tubes, rectangular tubes, and special-shaped tubes.

[0012] As a further technical solution of the present invention, the hot air inlet and the flame outlet are arranged at opposite ends of the burner housing.

[0013] As a further technical solution of the present invention, the hot air pipe is provided with a plurality of hot air branch pipes extending outwards. The end of each hot air branch pipe is provided with a burner.

[0014] As a further technical solution of the present invention, both the heat exchanger and the burner are arranged outside the bell-type furnace.

[0015] As a further technical solution of the present invention, the heat exchanger is embedded inside the furnace wall of the bell-type furnace, and the burner is arranged outside the bell-type furnace.

[0016] As a further technical solution of the present invention, the heat exchanger, the burner, and the hot air pipe are all embedded inside the furnace wall of the bell-type furnace.

[0017] The beneficial effects of the present invention are as follows:

[0018] The utility model forms mixed air by guiding the flue gas to reflux and mix in the combustion-supporting air, mixes it with the fuel gas and participates in the combustion reaction, reduces the combustion reaction rate and the flame temperature in the burner, thereby reducing the generation amount of thermal NOx. Even if the combustion-supporting air can absorb a large amount of heat in the flue gas in the heat exchanger and cause the temperature to be too high, it will not cause the flame temperature to be too high when the burner burns, improving the energy utilization rate. Moreover, in the burner, the mixed air and the fuel gas are fully mixed through the mixing cup to ensure that the flame does not go out, and at the same time, the mixed air is burned in stages, further reducing the combustion reaction rate and the flame temperature, so that the combustion system has the effect of energy conservation and emission reduction. Description of the Drawings

[0019] Figure 1 is a schematic structural diagram of a high-efficiency energy-saving bell-type furnace low-NOx combustion system.

[0020] Figure 2 is a schematic diagram of the mechanism of the heat exchanger of a high-efficiency energy-saving bell-type furnace low-NOx combustion system.

[0021] Figure 3 is a schematic structural diagram of the burner of a high-efficiency energy-saving bell-type furnace low-NOx combustion system.

[0022] Figure 4 is a schematic structural diagram of the second embodiment of a high-efficiency energy-saving bell-type furnace low-NOx combustion system.

[0023] Figure 5 is a schematic structural diagram of the heat exchanger and the hot air pipe in the third embodiment of a high-efficiency energy-saving bell-type furnace low-NOx combustion system.

[0024] Figure 6 is a schematic structural diagram of the fourth embodiment of a high-efficiency energy-saving bell-type furnace low-NOx combustion system.

[0025] Figure 7 is a schematic diagram of the mechanism of the second embodiment of the heat exchanger of a high-efficiency energy-saving bell-type furnace low-NOx combustion system.

[0026] Figure 8 is a schematic structural diagram of the fifth embodiment of a high-efficiency energy-saving bell-type furnace low-NOx combustion system.

[0027] Among them: bell-type furnace 1, heat exchanger 2, heat exchange housing 21, cold air inlet 22, flue gas pipe 23, flue gas reflux pipe 231, flue gas recovery pipe 232, flue gas outlet 24, heat exchange pipe 25, hot gas collecting chamber 26, ejector nozzle 27, air housing 28, cold gas collecting chamber 29, burner 3, burner housing 31, hot air inlet 32, flame outlet 33, fuel gas pipe 34, mixing cup 35, air hole 36, fuel gas outlet 37, hot air pipe 4, hot air branch pipe 41. Detailed Embodiment

[0028] The embodiments of the present utility model will be described below in conjunction with the accompanying drawings and related embodiments. The embodiments of the present utility model are not limited to the following embodiments, and the present utility model relates to relevant necessary components in the technical field, which should be regarded as well-known technologies in the technical field and can be known and mastered by those skilled in the technical field.

[0029] As Figure 1-3 shown, an efficient and energy-saving bell-type furnace low-NOx combustion system includes a bell-type furnace 1, a heat exchanger 2, and a burner 3. The heat exchanger 2 and the burner 3 are arranged on one side of the bell-type furnace 1; the heat exchanger 2 includes the following structure: a heat exchange housing 21 with a hollow interior, a cold air inlet 22, a flue gas pipe 23, and a flue gas outlet 24 are arranged on the surface of the heat exchange housing 21. A heat exchange tube 25 that is communicated with the cold air inlet 22 and extends along the heat exchange housing 21 is arranged in the heat exchange housing 21. The end of the heat exchange tube 25 where it extends forms a hot air end. One end of the flue gas pipe 23 faces the hot air end and the other end extends into the bell-type furnace 1; the burner 3 includes the following structure: a burner housing 31 with a hollow interior, a hot air inlet 32 is arranged on one side of the burner housing 31. The end of the burner housing 31 extends into the bell-type furnace 1 and is provided with a flame outlet 33. One end of the burner housing 31 is provided with a gas pipe 34 that extends towards the flame outlet 33. The end of the gas pipe 34 where it extends is provided with a mixing cup 35 with an opening facing the flame outlet 33. An air hole 36 with an opening facing the flame outlet 33 is penetrated through the side of the mixing cup 35 away from the flame outlet 33. The end of the gas pipe 34 is provided with a gas outlet 37 with an opening facing the inner wall of the mixing cup 35. An ignition electrode with an ignition end extending into the mixing cup 35 is arranged on one side of the burner housing 31; one end of the heat exchanger 2 close to the hot air end is provided with a hot air pipe 4 that extends to the hot air inlet 32.

[0030] The utility model relates to a combustion system designed based on a bell-type furnace. The bell-type furnace 1 includes a hollow furnace chamber. When the combustion system operates, combustion-supporting air sequentially passes through a cold air port 22, a heat exchange tube 25, a hot air pipe 4, and a burner housing 31 and flows into a mixing cup 35, where it mixes with gas guided by a gas pipe 34 and is ignited by an ignition electrode to burn. The burner 3 burns to eject flames from a flame outlet 33 and generates heat to heat the furnace chamber, and then workpieces are placed in the furnace chamber for heat treatment. After the burner 3 burns, part of the flue gas carrying heat enters the heat exchanger 2 through a flue gas pipe 23. The flue gas flows through the space between a heat exchange housing 21 and the heat exchange tube 25 and is discharged from a flue gas outlet 24. At the same time, combustion-supporting air enters the heat exchange tube 25 through the cold air port 22. The combustion-supporting air exchanges heat with the flue gas through the heat exchange tube 25. The temperature of the combustion-supporting air increases after absorbing the heat in the flue gas. The combustion-supporting air that has completed heat exchange forms hot air and flows to the hot air end. Another part of the flue gas flows through the flue gas pipe 23 to the hot air end, where it mixes with the hot air to form mixed air. The mixed air sequentially passes through the hot air pipe 4 and the burner housing 31 and flows into the mixing cup 35 to mix with the gas for combustion. Since the oxygen concentration in the mixed air is relatively low, the combustion reaction can be slowed down and the flame temperature can be reduced, thereby reducing the generation amount of thermal-type nitrogen oxides. In addition, a valve can be provided at the intersection of the hot air end and the flue gas pipe 23 to control the amount of flue gas flowing to the hot air end, so that the ratio of flue gas to hot air can be controlled, and thus the reaction rate of the burner 3 combustion can be accurately controlled.

[0031] It should be noted that since the oxygen content in the mixed air is relatively low, in order to avoid the flame of the burner 3 from extinguishing due to insufficient flue gas content, the utility model can strengthen the mixing intensity of the mixed air and the gas through the cooperation of the internal structure of the mixing cup 35 and the gas pipe 34. The specific principle is as follows: After the mixed air enters the burner housing 31, part of the mixed air enters the mixing cup 35 through an air hole 36 and mixes with the gas ejected from a gas outlet 37. Since the opening of the air hole 36 faces the opening of the mixing cup 35, and the opening of the gas outlet 37 faces the inner wall of the mixing cup 35, the included angle between the flow directions of the mixed air and the gas is 90° or close to 90°. The airflows formed by the mixed air and the gas collide with each other to generate a turbulent flow effect, enabling the mixed air and the gas to be fully mixed in the mixing cup 35. The oxygen in the mixing cup 35 can come into full contact with the gas and participate in the combustion reaction, thereby improving the combustion stability of the burner 3 and keeping the flame from extinguishing. Another part of the mixed air in the burner housing 31 flows through the gap between the outside of the mixing cup 35 and the burner housing 31 to the opening of the mixing cup 35 and contacts the flame, so that the mixed air undergoes staged combustion, achieving the purpose of extending the combustion reaction zone, which can play the role of reducing the combustion reaction rate, thereby reducing the temperature of the combustion flame and the generation amount of thermal-type nitrogen oxides.

[0032] After adopting the above technical solution, the flue gas is split at the intersection of the end of the flue gas pipe 23 and the hot air end in the flue gas pipe 23. A part of the flue gas enters the heat exchanger 2 and exchanges heat with the combustion-supporting air through the heat exchange pipes 25, and the other part is mixed with the hot air through reflux and is used in the burner 3 to reduce the combustion reaction rate; as Figure 4 shown, as the second preferred embodiment of the present invention, the flue gas pipe 23 includes a flue gas reflux pipe 231 and a flue gas recovery pipe 232. The flue gas reflux pipe 231 is communicated with the hot air pipe 4, and the flue gas recovery pipe 232 is communicated with the heat exchange housing 21. The flue gas reflux pipe 231 is specifically used for guiding the flue gas into the hot air pipe 4 to be mixed with the hot air to form mixed air, which has the effect of reducing the combustion reaction rate and the generation amount of thermal NOx. The flue gas recovery pipe 232 is specifically used for guiding the flue gas into the heat exchanger 2 to exchange heat with the combustion-supporting air. The combustion-supporting air absorbs the heat in the flue gas to increase the temperature of the combustion-supporting air, improve the energy utilization rate and reduce the consumption of fuel gas, thereby playing the role of energy conservation and emission reduction.

[0033] In summary, the present invention guides the flue gas to reflux and mix in the combustion-supporting air to form mixed air and mix with the fuel gas to participate in the combustion reaction, reducing the combustion reaction rate and the flame temperature in the burner 3, thereby reducing the generation amount of thermal NOx. Even if the combustion-supporting air absorbs a large amount of heat in the flue gas in the heat exchanger 2 and causes the temperature to be too high, it will not cause the flame temperature to be too high when the burner burns, improving the energy utilization rate. Moreover, in the burner 3, the mixed cup 35 enables the mixed air and the fuel gas to be fully mixed to ensure that the flame does not go out, and at the same time, the mixed air undergoes staged combustion, further reducing the combustion reaction rate and the flame temperature, making the combustion system of the present invention have remarkable energy conservation and emission reduction effects.

[0034] As Figure 1 、 2 shown, as one of the preferred embodiments of the present invention, the heat exchange pipes 25 are provided with a hot air collecting chamber 26 at the hot air end. The inner diameter of the hot air collecting chamber 26 gradually decreases from the end close to the heat exchange pipes 25 to the other end. An ejector nozzle 27 is provided at the end of the hot air collecting chamber 26 away from the heat exchange pipes 25. The hot air collecting chamber 26 is used for collecting the hot air that has completed heat exchange. During the process of the hot air flowing towards the ejector nozzle 27, since the inner diameter of the hot air collecting chamber 26 gradually decreases, the flow rate of the hot air can be increased, so that the hot air is ejected from the ejector nozzle 27 at a higher rate to generate a high-speed air flow. The high-speed air flow will reduce the pressure around the hot air end and generate a suction effect on the flue gas, so that part of the flue gas flows to the hot air end to be mixed with the hot air after leaving the flue gas pipe 23. Moreover, increasing the flow rate of the hot air can prevent it from flowing back into the heat exchange housing 21, ensuring the air-fuel ratio during the combustion of the burner 3 and enabling the fuel gas to burn fully.

[0035] As Figure 1 、 2As shown, as one of the preferred embodiments of the present utility model, an air housing 28 is sleeved outside the heat exchange housing 21. One end of the air housing 28 is provided with a cold gas collecting chamber 29 communicating with the heat exchange tubes 25, and the other end is communicated with the cold air port 22; the air housing 28 completely wraps the heat exchange housing 21. After the air housing 28 is arranged outside the heat exchange housing 21, a cooling chamber is formed between the heat exchange housing 21 and the air housing 28. The combustion-supporting air first enters the cooling chamber after passing through the cold air port 22, and then flows along the cooling chamber into the cold gas collecting chamber 29. During this process, the combustion-supporting air can cool the heat exchange housing 21, and the heat in the heat exchange housing 21 is conducted by contacting with the flue gas. It is equivalent to the combustion-supporting air exchanging heat with the flue gas in the cooling chamber, improving the energy utilization rate. And by the combustion-supporting air flowing along the cooling chamber, the air housing 28 can be kept at a lower temperature, that is, the temperature of the surface of the heat exchanger 2 is reduced, and the heat dissipation from the surface of the heat exchanger 2 is reduced, so that there is no need to wrap heat insulation materials on the surface of the heat exchanger 2.

[0036] As Figure 1 , 2 shown, as one of the preferred embodiments of the present utility model, the flue gas pipe 23 and the flue gas outlet 24 are arranged at opposite ends of the heat exchange housing 21; the flue gas pipe 23 is used to guide the flue gas into the heat exchange housing 21, and the flue gas outlet 24 is used to discharge the flue gas that has completed heat exchange. In order to ensure that the flue gas is in full contact with the heat exchange tubes 25 and exchanges heat with the combustion-supporting air, adopting the above structure is beneficial to extending the flow path and time of the flue gas in the heat exchange housing 21, so that the heat exchange housing 21 is completely filled with the flue gas, so that the flue gas is in full contact with the heat exchange tubes 25 and exchanges heat with the combustion-supporting air, improving the heat recovery rate in the flue gas.

[0037] As Figure 1 , 2 shown, as one of the preferred embodiments of the present utility model, a plurality of heat exchange tubes 25 are provided, and a space allowing air to flow is provided between adjacent heat exchange tubes 25. The plurality of heat exchange tubes 25 are selected from one or more of circular tubes, rectangular tubes, and special-shaped tubes; in order to ensure the heat exchange efficiency between the flue gas and the combustion-supporting air, the heat exchange tubes 25 are made of a metal material or a composite material with good heat conduction performance. After a plurality of heat exchange tubes 25 with small diameters are provided, the overall specific surface area of the heat exchange tubes 25 can be increased, the contact area between the flue gas and the heat exchange tubes 25 can be increased, the heat exchange efficiency between the flue gas and the combustion-supporting air can be further improved, so that the combustion-supporting air can recover more heat carried in the flue gas, improving the energy utilization efficiency; in addition, the shape and distribution mode of the heat exchange tubes 25 are adaptively adjusted according to the internal shape of the heat exchange housing 21, and the distance between adjacent heat exchange tubes 25 is kept the same as much as possible, maximizing the density of the heat exchange tubes 25 and the overall specific surface area, and improving the heat exchange efficiency of the heat exchanger 2.

[0038] As Figure 1 ,3 As shown, as one of the preferred embodiments of the present utility model, the hot air port 32 and the flame outlet 33 are arranged at opposite ends of the burner housing 31; after adopting the above structure, the mixed air has sufficient flow space in the burner housing 31, which is beneficial to improving the stability of the air flow in the burner housing 31, so that the mixed air flows stably towards the mixing cup 35, avoiding the influence on the mixing of the mixed air with the gas due to the unstable flow of the mixed air, thereby improving the stability of the flame during burner combustion.

[0039] As Figure 5 shown, as the third preferred embodiment of the present utility model, the hot air pipe 4 is provided with a plurality of hot air branch pipes 41 extending outward, and a burner 3 is provided at the end of each hot air branch pipe 41 extending; the same heat exchanger 2 can centrally process the flue gas in a plurality of bell-type furnaces 1, guide the flue gas in all the bell-type furnaces 1 to the heat exchanger 2 through the flue gas pipe 23, and then divide the hot air after heat exchange into a plurality of burners 3 through the hot air branch pipes 41 to participate in combustion, so that there is no need to provide a heat exchanger 2 for each bell-type furnace 1, reducing the construction cost of the combustion system.

[0040] As Figure 1 shown, as one of the preferred embodiments of the present utility model, both the heat exchanger 2 and the burner 3 are arranged outside the bell-type furnace 1; the heat exchanger 2 usually extends in the vertical direction, while the burner 3 usually extends in the horizontal direction. Arranging the heat exchanger 2 and the burner 3 outside the bell-type furnace 1 can facilitate the maintenance and repair of the heat exchanger 2 and the burner 3, and the hot air pipe 4 will also be arranged outside the bell-type furnace 1. At this time, an air housing 28 or heat insulation material needs to be provided on the surface of the heat exchanger 2 to prevent the heat exchanger 2 from losing too much heat to the outside, and an appropriate amount of heat insulation material is correspondingly wrapped on the surface of the burner 3 and the surface of the hot air pipe 4 to prevent the mixed air from losing heat to the outside through the burner housing 31 or the hot air pipe 4, thereby improving the energy utilization efficiency of the combustion system.

[0041] As Figure 6 and 7 shown, as the fourth preferred embodiment of the present utility model, the heat exchanger 2 is embedded inside the furnace wall of the bell-type furnace 1, and the burner 3 is arranged outside the bell-type furnace 1; since the bell-type furnace 1 needs to ensure a high temperature in the furnace chamber for heat treatment of workpieces, the furnace wall is usually made of heat insulation materials. After adopting the above structure, there is no need to provide an air housing 28 and wrap heat insulation materials on the surface of the heat exchanger 2. The heat exchanger 2 after canceling the air housing 28 is the second preferred embodiment of the heat exchanger 2 of the present utility model. Through the furnace wall, the flue gas can be prevented from exchanging heat with the outside through the heat exchange housing 21. In addition, part of the hot air pipe 4 is arranged outside the bell-type furnace 1, and heat insulation materials need to be wrapped on the part of the hot air pipe 4 arranged outside the bell-type furnace 1 and the surface of the burner 3 to avoid unnecessary heat loss during the operation of the combustion system.

[0042] AsFigure 8 As shown in the figure, as the fifth preferred embodiment of the present utility model, the heat exchanger 2, the burner 3, and the hot air pipe 4 are all embedded inside the furnace wall of the bell-type furnace 1; while adopting the above structure, it is necessary to increase the thickness of the furnace wall of the bell-type furnace 1 on the side close to the heat exchanger 2, the burner 3, and the hot air pipe 4, so that the heat exchanger 2, the burner 3, and the hot air pipe 4 can be embedded inside the furnace wall of the bell-type furnace 1. At this time, the heat exchanger 2, the burner 3, and the hot air pipe 4 are all thermally insulated through the furnace wall of the bell-type furnace 1 to avoid unnecessary heat dissipation during the operation of the combustion system.

[0043] The above are only the preferred embodiments of the present utility model. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present utility model, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present utility model.

Claims

1. A high-efficiency and energy-saving bell-type furnace low NOx combustion system, comprising a bell-type furnace (1), a heat exchanger (2), and a burner (3), characterized in that: The heat exchanger (2) and the burner (3) are arranged on one side of the bell-type furnace (1); the heat exchanger (2) comprises the following structure: a heat exchange shell (21) with a hollow interior; a cold air inlet (22), a smoke pipe (23), and a smoke outlet (24) are arranged on the surface of the heat exchange shell (21); a heat exchange tube (25) is arranged in the heat exchange shell (21) and is connected to the cold air inlet (22) and extends along the heat exchange shell (21); the end of the heat exchange tube (25) forms a hot air end; one end of the smoke pipe (23) faces the hot air end and the other end extends into the bell-type furnace (1); The burner (3) comprises the following structure: a burner shell (31) with a hollow interior, a hot air port (32) being provided on one side of the burner shell (31), an end of the burner shell (31) extending into the bell-type furnace (1) and provided with a flame outlet (33), a gas pipe (34) extending towards the flame outlet (33) being provided at one end of the burner shell (31), a mixing cup (35) opening towards the flame outlet (33) being provided at the end of the extended gas pipe (34), an air hole (36) opening towards the flame outlet (33) being provided on the side of the mixing cup (35) away from the flame outlet (33), and a gas outlet (37) opening towards the inner wall of the mixing cup (35) being provided at the end of the gas pipe (34); A hot air pipe (4) extending to a hot air outlet (32) is provided at one end of the heat exchanger (2) close to the hot air end.

2. The high-efficiency and energy-saving bell-type furnace low NOx combustion system according to claim 1 is characterized in that: The heat exchange tube (25) is provided with a heat collecting chamber (26) at the hot air end, the inner diameter of the heat collecting chamber (26) gradually decreases from one end close to the heat exchange tube (25) to the other end, and the heat collecting chamber (26) is provided with an injection nozzle (27) at one end away from the heat exchange tube (25).

3. The high-efficiency and energy-saving bell-type furnace low NOx combustion system according to claim 1 is characterized in that: The heat exchange shell (21) is provided with an air shell (28) on its outer shell; one end of the air shell (28) is provided with a cold air collecting chamber (29) connected to the heat exchange tube (25), and the other end is connected to the cold air port (22).

4. The high-efficiency and energy-saving bell-type furnace low NOx combustion system according to claim 1 is characterized in that: The smoke pipe (23) and the smoke outlet (24) are arranged at two opposite ends of the heat exchange shell (21).

5. The high-efficiency and energy-saving bell-type furnace low NOx combustion system according to claim 1 is characterized in that: A plurality of the heat exchange tubes (25) are provided, and spaces allowing air flow are provided between adjacent heat exchange tubes (25). The plurality of heat exchange tubes (25) are selected from one or more of circular tubes, rectangular tubes, and special-shaped tubes.

6. The high-efficiency and energy-saving bell-type furnace low NOx combustion system according to claim 1 is characterized in that: The hot air port (32) and the flame outlet (33) are arranged at two opposite ends of the burner housing (31).

7. The high-efficiency and energy-saving bell-type furnace low NOx combustion system according to claim 1 is characterized in that: The hot air pipe (4) is provided with a plurality of hot air branch pipes (41) extending outwards, and a burner (3) is provided at the end of each of the hot air branch pipes (41) extending outwards.

8. The high-efficiency and energy-saving bell-type furnace low NOx combustion system according to claim 1 is characterized in that: The heat exchanger (2) and the burner (3) are both arranged outside the bell-type furnace (1).

9. The high-efficiency and energy-saving bell-type furnace low NOx combustion system according to claim 1 is characterized in that: The heat exchanger (2) is embedded in the furnace wall of the bell-type furnace (1), and the burner (3) is arranged outside the bell-type furnace (1).

10. The high-efficiency and energy-saving bell-type furnace low NOx combustion system according to claim 1 is characterized in that: The heat exchanger (2), the burner (3), and the hot air pipe (4) are all embedded in the furnace wall of the bell-type furnace (1).

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