Environment-friendly efficient exhaust gas recirculation burner for nitriding furnace

Abstract

The environment-friendly and efficient exhaust gas recirculation combustor comprises a furnace body, the furnace body is provided with a combustion port and a smoke outlet, a combustion cylinder is arranged at the combustion port and provided with a fuel gas inlet, the environment-friendly and efficient exhaust gas recirculation combustor further comprises a backflow cylinder, an outer backflow pipe is connected between the backflow cylinder and the smoke outlet, and the outer backflow pipe is provided with a gas inlet. An inner backflow pipe is connected between the backflow cylinder and the combustion cylinder, a drainage fan is arranged in the backflow cylinder and provided with a driving shaft, the driving shaft is provided with a smoke through opening, the backflow cylinder is provided with an air through opening, a drainage taper sleeve is further arranged in the backflow cylinder, and the driving shaft is fixedly connected with turbulent flow blades. Flue gas and air are preliminarily mixed through the drainage channel, three-way disturbance depth homogenization is achieved through the rotary taper sleeve, the annular groove, the flow mixing blades and the rotational flow grooves, then airflow penetrates through air holes of the baffle to form pulsating jet flow, the pulsating jet flow is corrected into axial uniform flow through the honeycomb rectification net, the axial uniform flow is pressurized through the backflow fan and sent into the inner backflow pipe, and efficient and stable combustion is ensured.

Description

Technical Field

[0001] This invention relates to the field of burner technology, specifically to an environmentally friendly and efficient waste gas recirculation burner for nitriding furnaces. Background Technology

[0002] In high-temperature heat treatment equipment such as nitriding furnaces, exhaust gas recirculation technology is often used to reduce nitrogen oxide generation in order to meet increasingly stringent environmental emission standards. However, existing burners generally suffer from uneven mixing of flue gas and combustion air, resulting in poor combustion stability, localized high temperatures, or incomplete combustion, making it difficult to achieve both low nitrogen emissions and efficient and complete combustion.

[0003] In the prior art, for example, Chinese invention patent application (publication number CN110805897A) discloses a flue gas recirculation burner, which includes a furnace body and a combustion cylinder. One end of the combustion cylinder extends into the furnace body and is provided with a combustion port at the end. The other end of the combustion cylinder is located outside the furnace body and is provided with an air inlet device and a gas valve group at the end. The combustion cylinder is provided with a plurality of gas supply pipes connected to the gas valve group and an ignition device for igniting the gas. The furnace body is provided with a flue gas pipe. The air inlet device includes a fan connected to the combustion cylinder and an air inlet hood provided at the air inlet of the fan. An air inlet is provided at the bottom of the air inlet hood. A recirculation pipe is provided on the flue gas pipe and the recirculation pipe is connected to the side wall of the air inlet hood.

[0004] The aforementioned existing technology uses the suction force of a fan to draw both air and flue gas into the fan, and the rotation of the fan blades thoroughly mixes the air and flue gas before discharging the mixed gas into the combustion chamber, thereby diluting the oxygen in the air and reducing nitrogen oxide emissions. However, the residence time of flue gas and air in the fan is extremely short, and it is difficult to achieve uniform mixing by impeller agitation alone, which can easily lead to uneven oxygen concentration distribution, causing localized high temperatures or unstable combustion.

[0005] Therefore, there is a need for an environmentally friendly and efficient exhaust gas recirculation burner for nitriding furnaces, which can achieve full and uniform mixing of air and flue gas during the flue gas recirculation process, and avoid local oxygen concentrations that are too high or too low. Summary of the Invention

[0006] To address the problems existing in the prior art, an environmentally friendly and efficient waste gas recirculation burner for nitriding furnaces is provided. The flue gas and air are initially mixed through the diversion channel, and then three-dimensional disturbance depth homogenization is achieved through the rotating cone sleeve, annular groove, mixing blades and swirling groove. Subsequently, the airflow passes through the baffle holes to form a pulsating jet, which is corrected into an axial uniform flow by the honeycomb rectifier mesh, and then pressurized by the return fan and sent into the inner return pipe to ensure efficient and stable combustion.

[0007] To address the problems of existing technologies, this invention provides an environmentally friendly and efficient waste gas recirculation burner for a nitriding furnace, comprising a furnace body with a combustion port and a flue gas outlet. A combustion cylinder is located at the combustion port, and the combustion cylinder has a gas inlet and a gas valve. The invention also includes a return cylinder connected to the combustion cylinder, with an external return pipe connecting the return cylinder to the flue gas outlet and an internal return pipe connecting the return cylinder to the combustion cylinder. An induced draft fan, coaxial with the return cylinder, is located in the upstream region of the return cylinder. The induced draft fan has a drive shaft rotatably connected to the return cylinder, and the drive shaft is a hollow structure. Furthermore, its side wall is provided with a flue gas inlet communicating with the external return pipe. The return cylinder is provided with an air inlet on the air inlet side near the induced flow fan. The return cylinder is also provided with an induced flow cone sleeve coaxial with it. The induced flow cone sleeve and the drive shaft form an induced flow channel that gradually narrows along the airflow direction. The induced flow fan is set in the induced flow channel. The air outlet side of the induced flow fan is provided with a turbulence blade that is fixedly connected to the drive shaft. During the operation of the induced flow fan, the flue gas and air are combined in the induced flow channel and are in a premixed state. The external return pipe is provided with a flue gas valve, and the internal return pipe is provided with a flow control valve.

[0008] Preferably, a rotating cone sleeve is provided inside the reflux cylinder and in the downstream region of the diversion cone sleeve, and is fixedly arranged coaxially with it. The rotating cone sleeve is fixedly connected to the drive shaft, and an annular dispersion area communicating with the diversion channel from the inside out is formed between the rotating cone sleeve and the diversion cone sleeve.

[0009] Preferably, the downstream region of the drainage cone sleeve has annular grooves that are evenly spaced along the axial direction and whose diameter gradually increases, and the annular grooves and the rotating cone sleeve form a wave-shaped annular dispersion region.

[0010] Preferably, the rotating cone sleeve has multiple mixing blades along its circumference on the side facing the drainage cone sleeve, and each mixing blade is in clearance fit with the annular groove on the drainage cone sleeve.

[0011] Preferably, the downstream region of the flow-guiding cone sleeve is provided with an annular plate surrounding its outer circumference, and the surface of the annular plate is provided with a swirling groove at the circumferential position of the airflow outlet of the annular dispersion region to guide the outflowing airflow to form a circumferential swirling flow.

[0012] Preferably, a baffle is fixedly installed inside the reflux cylinder, which is sleeved on the rotating cone sleeve and fitted with a clearance therebetween. The surface of the baffle has a number of air holes that communicate with the swirling groove area.

[0013] Preferably, a honeycomb-shaped rectifier mesh communicating with several air holes is fixedly provided on the baffle.

[0014] Preferably, a sealing ring is fixedly provided on the side of the baffle facing the rotating cone sleeve, forming a dynamic sealing fit with its outer circumferential surface.

[0015] Preferably, the downstream region inside the reflux cylinder is provided with a reflux fan that is fixedly connected to the end of the drive shaft extending inward, and the reflux fan is disposed between the honeycomb rectifier mesh and the inner reflux pipe.

[0016] Preferably, the reflux cylinder is equipped with an air filter on the side with the air vent.

[0017] The advantages of this application compared to the prior art are: 1. This invention introduces flue gas into the return cylinder through an external return pipe, and combines it with fresh air drawn in from the air inlet in the guide channel. The negative pressure generated by the guide fan and the channel contraction structure formed by the guide cone sleeve are used to enhance turbulent mixing and form a uniform premixed gas.

[0018] The gas is then further refined and homogenized by rotating baffles and their pressure relief holes, and then sent back to the combustion chamber as needed through the internal return pipe to participate in combustion. During the process, the flow rate and pressure are dynamically regulated through flue gas valves, overflow valves, and flow control valves, which effectively improves combustion efficiency and stability, reduces emissions of pollutants such as nitrogen oxides, and achieves efficient and environmentally friendly exhaust gas recirculation combustion control.

[0019] 2. The present invention provides a multi-stage dynamic dispersion structure in the downstream region of the flow guide cone sleeve, which consists of a rotating cone sleeve, an annular groove, mixing blades, and an annular plate with an arc-shaped swirling groove. This structure allows the premixed gas to undergo radial dispersion, wave-shaped periodic expansion and compression, blade shearing and sweeping, and swirling guidance processes in sequence after flowing out of the flow guide channel.

[0020] The airflow achieves deep homogenization under the three-dimensional coupled disturbance of axial, radial and circumferential directions, and forms a stable circumferential vortex, which effectively eliminates concentration and temperature stratification, prolongs the mixing time, prevents dead zones and re-stratification, and provides a highly uniform and stable premixed airflow for subsequent combustion, thereby improving combustion stability and suppressing the generation of pollutants caused by local high temperature.

[0021] 3. This invention uses baffles to create a high-frequency pulsating jet of swirling gas as it passes through the baffle holes, thereby enhancing homogeneity. The gas is then constrained and corrected into an axially stable flow by a honeycomb rectifier. A return fan then provides additional pressurization and delivery to the rectified airflow, effectively compensating for resistance losses and preventing stagnation or backflow.

[0022] The overall process balances mixing uniformity and flow stability, providing a continuous, controllable, and low-disturbance high-quality premixed airflow for the internal recirculation pipe, ensuring precise control of efficient recirculation combustion. Attached Figure Description

[0023] Figure 1 This is a three-dimensional structural schematic diagram of an environmentally friendly and efficient waste gas recirculation burner for a nitriding furnace according to the present invention.

[0024] Figure 2This is a partial three-dimensional structural cross-sectional view of an environmentally friendly and efficient waste gas recirculation burner for a nitriding furnace according to the present invention.

[0025] Figure 3 This is a plan sectional view of the reflux cylinder and combustion cylinder of an environmentally friendly and efficient waste gas recirculation burner for a nitriding furnace according to the present invention.

[0026] Figure 4 This is a three-dimensional structural cross-sectional view of the reflux cylinder and combustion cylinder of an environmentally friendly and efficient waste gas recirculation burner for a nitriding furnace according to the present invention.

[0027] Figure 5 This is a partial three-dimensional cross-sectional view of the return cylinder and its internal structure of an environmentally friendly and efficient waste gas recirculation burner for a nitriding furnace according to the present invention.

[0028] Figure 6 This is the invention Figure 5 Enlarged diagram of point A.

[0029] Figure 7 This is the invention Figure 5 Enlarged diagram of point B.

[0030] Figure 8 This is a partial three-dimensional structural diagram of the side of the reflux cylinder of an environmentally friendly and efficient waste gas recirculation burner for a nitriding furnace, according to the present invention, where an air inlet is provided.

[0031] Figure 9 This is a partial three-dimensional exploded view of the baffle orientation of an environmentally friendly and efficient waste gas recirculation burner for a nitriding furnace according to the present invention.

[0032] Figure 10 This is a partial three-dimensional exploded view of the orientation of the honeycomb rectifier mesh of an environmentally friendly and efficient waste gas recirculation burner for a nitriding furnace according to the present invention.

[0033] The following are the labels in the diagram: 1. Furnace body; 11. Combustion port; 12. Flue gas outlet; 2. Combustion cylinder; 21. Gas inlet; 3. Return cylinder; 31. External return pipe; 32. Internal return pipe; 33. Baffle; 331. Air hole; 332. Sealing ring; 333. Ball bearing; 34. Honeycomb rectifier mesh; 4. Drainage fan; 41. Drive shaft; 411. Flue gas inlet; 412. Air inlet; 42. Turbidator blade; 5. Drainage cone sleeve; 51. Annular groove; 52. Ring plate; 521. Swirl groove; 6. Rotating cone sleeve; 61. Mixing blade; 7. Return fan. Detailed Implementation

[0034] To further understand the features, technical means, and specific objectives and functions achieved by the present invention, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

[0035] See Figures 1-6 As shown, an environmentally friendly and efficient waste gas recirculation burner for a nitriding furnace includes a furnace body 1. The furnace body 1 has a combustion port 11 and a flue gas outlet 12. A combustion cylinder 2 is provided at the combustion port 11. The combustion cylinder 2 has a gas inlet 21 and is equipped with a gas valve. It also includes a return cylinder 3 connected to the combustion cylinder 2. An external return pipe 31 is connected between the return cylinder 3 and the flue gas outlet 12. An internal return pipe 32 is connected between the return cylinder 3 and the combustion cylinder 2. An induced draft fan 4 is provided coaxially with the return cylinder 3 in the upstream region. The induced draft fan 4 has a drive shaft 41 rotatably connected to the return cylinder 3. The drive shaft 41 has a hollow structure and its side... The wall is provided with a flue gas inlet 411 that communicates with the external return pipe 31. The return cylinder 3 is provided with an air inlet 412 on the air inlet side near the duct fan 4. The return cylinder 3 is also provided with a duct conical sleeve 5 coaxial with it. The duct conical sleeve 5 and the drive shaft 41 form a duct channel that gradually narrows along the airflow direction. The duct fan 4 is set in the duct channel. The air outlet side of the duct fan 4 is provided with a turbulence blade 42 that is fixedly connected to the drive shaft 41. During the operation of the duct fan 4, the flue gas and air are premixed in the duct channel. The external return pipe 31 is provided with a flue gas valve, and the internal return pipe 32 is provided with a flow control valve.

[0036] The external return pipe 31 is also provided with an overflow port and an overflow valve.

[0037] The gas valve, flue gas valve, flow control valve, and overflow valve are not shown in the figure.

[0038] The surface of the turbulence blade 42 is provided with several pressure relief holes.

[0039] In the exhaust gas recirculation combustion system of the nitriding furnace, after the flue gas is discharged from the exhaust port 12 of the furnace body 1, it first enters the external return pipe 31. The external return pipe 31 is equipped with a flue gas valve to regulate the flue gas return flow rate, and is also equipped with an overflow port with an overflow valve, which can discharge part of the flue gas from the system when the system pressure is too high or the return demand is reduced, so as to avoid abnormal pressure rise in the return cylinder 3.

[0040] The flue gas is guided to the upstream region of the return cylinder 3 through the external return pipe 31. A flue gas inlet 411 is provided on the side wall of the drive shaft 41 in this region, allowing the flue gas to enter the hollow drive shaft 41 and subsequently flow into the inner cavity of the return cylinder 3. Simultaneously, external air is drawn in through an air inlet 412 located on the air intake side of the return cylinder 3 near the intake of the induced draft fan 4. The position of this air inlet 412 ensures that fresh air and the flue gas from the external return pipe 31 can quickly come into contact and begin mixing upon entering the return cylinder 3.

[0041] The gradually narrowing flow channel formed between the guide cone sleeve 5 and the drive shaft 41 inside the return tube 3 helps to accelerate the airflow velocity and enhance the turbulent mixing effect of flue gas and air. The guide fan 4 installed inside the flow channel generates negative pressure during high-speed operation, actively drawing air into the flow channel. As the airflow advances along the gradually narrowing flow channel, the flue gas and air mix within it, forming a premixed gas. This improves the efficiency and stability of subsequent combustion while effectively reducing the generation of harmful emissions such as nitrogen oxides.

[0042] As the drive shaft 41 rotates, the turbulence vanes 42 rotate together, further dispersing and agitating the premixed gas to make it more uniform. The several pressure relief holes on the surface of the turbulence vanes 42 not only help to balance the pressure difference on both sides of the turbulence vanes 42 and prevent structural fatigue or vibration caused by local high pressure, but also refine the airflow structure to a certain extent and improve the mixing uniformity.

[0043] The premixed gas, after being processed by the turbulence blades 42, then enters the inner reflux pipe 32. The inner reflux pipe 32 connects the reflux cylinder 3 and the combustion cylinder 2. By adjusting the opening of the control valve, the reflux ratio can be dynamically adjusted according to the combustion conditions in the furnace, thereby achieving precise control over the combustion temperature, atmosphere composition, and pollutant emissions.

[0044] Finally, the premixed gas is reintroduced into the combustion chamber 2 through the inner return pipe 32, and participates in the combustion process in conjunction with the main gas flow, completing the closed-loop path of the entire exhaust gas recirculation and achieving efficient and environmentally friendly combustion control.

[0045] See Figures 3-6 As shown, a rotating cone sleeve 6 is provided inside the return cylinder 3 and in the downstream area of ​​the diversion cone sleeve 5, and is fixedly arranged coaxially with it. The rotating cone sleeve 6 is fixedly connected to the drive shaft 41, and an annular dispersion area connected to the diversion channel from the inside to the outside is formed between the rotating cone sleeve 6 and the diversion cone sleeve 5.

[0046] After the premixed gas flows out of the inlet channel, it immediately enters an annular region downstream of the inlet cone sleeve 5, defined by a rotating cone sleeve 6 that rotates synchronously with the drive shaft 41. As the drive shaft 41 continues to rotate, the rotating cone sleeve 6 drives the surrounding airflow to rotate at high speed, causing the premixed gas that has just flowed out to be subjected to a strong circumferential shear force the instant it enters the annular region. The gas is rapidly stretched and torn, and diffuses radially outward, thus the airflow that was originally concentrated near the central axis is evenly spread across the entire annular cross-section.

[0047] Under the continuous agitation of the rotating cone sleeve 6, the gas not only violently turbulently along the circumference, but is also pushed outward due to centrifugal effect. At the same time, a local low-pressure zone is formed on the inner side, prompting more airflow to continuously replenish, forming a dynamic circulating mixture. This continuous rotational disturbance breaks down any possible concentration or temperature stratification, making the mixing of flue gas and air more delicate and uniform.

[0048] Finally, the gas, after undergoing the rotary dispersion process, leaves the annular region in a highly homogeneous and uniformly distributed state and enters the downstream reflux path. This provides more stable reaction conditions for the subsequent combustion stage, effectively suppressing localized high temperatures and pollutant formation.

[0049] See Figure 6 , Figure 9 and Figure 10 As shown, the downstream region of the drainage cone sleeve 5 has annular grooves 51 that are evenly spaced along the axial direction and whose diameter gradually increases. The annular grooves 51 and the rotating cone sleeve 6 form a wave-shaped annular dispersion region.

[0050] After the premixed gas flows out of the guide channel, it enters the annular dispersion region between the downstream area of ​​the guide cone sleeve 5 and the rotating cone sleeve 6. At this point, the gas does not flow through a smooth annular gap, but rather travels through a wave-shaped channel formed by multiple annular grooves 51 arranged axially at equal intervals and gradually expanding radially. As the rotating cone sleeve 6 rotates at high speed, the airflow continuously encounters the local spatial expansion and contraction caused by the annular grooves 51 during its forward movement. Whenever it enters the expanded portion corresponding to an annular groove 51, the flow velocity temporarily decreases, allowing the gas to diffuse laterally and fill the cavity. However, when it leaves the groove and enters the narrow region corresponding to the adjacent protrusion, the flow velocity rapidly increases again, forming local acceleration.

[0051] This periodically changing flow cross-section causes the airflow to repeatedly undergo expansion, compression, and re-expansion, inducing continuous vortex shedding and shear instability, thus enhancing turbulence intensity. Simultaneously, the circumferential motion of the rotating cone sleeve 6, superimposed on this axial undulating path, causes the gas to be stretched and mixed not only radially and axially, but also continuously disturbed in the circumferential direction, achieving deep homogenization through three-dimensional coupling. The wave-like structure also extends the residence time of the gas within the dispersion region, providing a more ample reaction window for thorough mixing of flue gas and air.

[0052] See Figure 6 , Figure 9 and Figure 10 As shown, the rotating cone sleeve 6 has multiple mixing blades 61 along its circumference on the side facing the flow-guiding cone sleeve 5. Each mixing blade 61 is in clearance fit with the annular groove 51 on the flow-guiding cone sleeve 5.

[0053] When the rotating cone sleeve 6 rotates at high speed with the drive shaft 41, the multiple mixing blades 61 on the side facing the guide cone sleeve 5 rotate synchronously around the shaft. As the gas flows through the wave-shaped annular dispersion area, each time it reaches an annular groove 51, the rotating mixing blades 61 sweep across the annular groove 51, applying strong shearing and pushing action to the stagnant or slow-flowing gas.

[0054] Meanwhile, the mixing blades 61 continuously disturb the flow field throughout the annular dispersion region during rotation, causing the gas to undergo circumferential turbulence and radial exchange while advancing axially. Because each mixing blade 61 maintains a precise gap with its corresponding annular groove 51, mechanical interference is avoided, and the disturbance energy is efficiently transferred to the airflow, preventing the formation of local dead zones.

[0055] See Figure 7 As shown, the downstream region of the flow-guiding cone sleeve 5 is provided with an annular plate 52 surrounding its outer circumference. The surface of the annular plate 52 is provided with a swirling groove 521 at the circumferential position of the airflow outlet of the annular dispersion region to guide the outflowing airflow to form a circumferential swirling flow.

[0056] The annular plate 52 has an arc-shaped swirling groove 521 on its surface, directly opposite the outlet of the annular dispersion region. The swirling groove 521 is smoothly curved along the circumference of the annular plate 52, forming a continuous curved guide channel.

[0057] After the premixed gas completes deep mixing within the wavy annular dispersion region, it flows towards the outlet of that region. At this location, the annular plate 52, located on the outer periphery of the downstream region of the guide cone sleeve 5, guides and regulates the airflow. As the airflow passes through the outlet, it is guided by the inner wall of the swirling groove 521, deflecting along the curved contour of the swirling groove 521 and gradually acquiring a tangential velocity component.

[0058] As the gas continues to flow through the swirling groove 521, the various micro-flows superimpose at the outlet section, collectively constructing a unified, circumferential swirling flow with consistent rotational direction. This rotational momentum maintains the stability of the mixing state, preventing the flue gas and air from re-stratifying during transport.

[0059] See Figure 7 and Figure 9 As shown, a baffle 33 is fixedly installed inside the reflux cylinder 3, which is sleeved on the rotating cone sleeve 6 and has a clearance fit with it. The surface of the baffle 33 has a number of air holes 331 that communicate with the swirling groove 521 area.

[0060] When the swirling gas flows out of the annular dispersion area and passes through the arc-shaped swirling groove 521 on the ring plate 52, it immediately enters the downstream area inside the return cylinder 3. After leaving the swirling groove 521, the high-speed rotating premixed gas carries strong circumferential momentum and impacts the inner side of the baffle 33. Part of the airflow is blocked and slowed down by the baffle 33, but most of the gas continues to flow forward through the air hole 331.

[0061] Because the baffle 33 remains stationary, while the rotating cone sleeve 6 and the swirling flow it drives are in continuous motion, the airflow is periodically disturbed as it passes through the vents 331. Whenever a high-pressure pulsating zone in the swirling flow sweeps past the inlet of a vent 331, that vent instantly draws in a stronger airflow. Conversely, the flow rate decreases when passing through a low-pressure zone. This dynamic pressure change causes the airflow passing through each vent 331 to form a high-frequency pulsating jet, further dispersing any remaining concentration inhomogeneities or temperature gradients.

[0062] See Figure 7 and Figure 10 As shown, a honeycomb rectifier mesh 34 connected to a plurality of air holes 331 is fixedly provided on the baffle 33.

[0063] After the swirling gas passes through the vents 331 on the baffle 33, it does not directly enter the downstream channel, but first passes through the honeycomb rectifier mesh 34. This rectifier mesh is composed of a large number of fine and parallel channels, which constrain and guide the pulsating swirling flow that has just passed through. At the moment the high-speed airflow enters the honeycomb channel, its original circumferential disturbance and lateral velocity components are repeatedly rubbed and restricted by the channel wall, large-scale vortices are cut and dissipated, and the flow direction is gradually corrected to be axially dominant.

[0064] As the gas passes through the honeycomb rectifier mesh 34, not only is the turbulence intensity moderately suppressed, but the flow also becomes more orderly and parallel. The gas flow exiting the honeycomb rectifier mesh 34 exhibits uniform, stable, and low-pulsation axial jet characteristics, which retains an appropriate amount of mixing activity while avoiding excessive disturbance that could interfere with subsequent recirculation or combustion stability, thus providing ideal intake conditions for efficient and clean combustion.

[0065] See Figure 6 and Figure 7 As shown, a sealing ring 332 is fixedly provided on the side of the baffle 33 facing the rotating cone sleeve 6, which forms a dynamic sealing fit with its outer peripheral surface.

[0066] A ball bearing 333 is provided between the baffle 33 and the rotating cone sleeve 6.

[0067] When the rotating cone sleeve 6 rotates continuously at high speed driven by the drive shaft 41, although a small gap is maintained between its outer circumferential surface and the baffle 33, the sealing ring 332 is tightly attached to the outer circumferential surface of the rotating cone sleeve 6 to prevent the disorderly leakage of high-temperature flue gas or premixed gas from this gap, forming a dynamic sealing fit. As the rotating cone sleeve 6 continues to rotate, the sealing ring 332 slides and rubs against its surface, ensuring that the airflow can only enter the honeycomb rectifier mesh 34 through the air holes 331 on the baffle 33 according to the design path, maintaining stable internal pressure and controllable flow rate of the system.

[0068] Meanwhile, the ball bearings 333 installed between the baffle 33 and the rotating cone sleeve 6 transform the original sliding contact into rolling support. When the rotating cone sleeve 6 rotates, the ball bearings 333 roll accordingly, reducing frictional resistance and wear, and ensuring the long-term stable operation of the rotating cone sleeve 6.

[0069] See Figures 3-5 and Figures 8-10 As shown, the downstream region inside the reflux cylinder 3 is provided with a reflux fan 7 that is fixedly connected to the end of the drive shaft 41 extending inward. The reflux fan 7 is disposed between the honeycomb rectifier mesh 34 and the inner reflux pipe 32.

[0070] After the premixed gas passes through the honeycomb rectifier mesh 34, the flow becomes more uniform, axial, and the pulsation is reduced. At this point, the airflow enters the downstream region of the return tube 3. Before the rectified airflow enters the inner return pipe 32, the return fan 7 actively applies suction force to further increase the gas velocity and maintain a stable pressure gradient. When the airflow passes through the return fan 7, it is given appropriate kinetic energy again, which not only compensates for the flow resistance generated by passing through the honeycomb rectifier mesh 34, but also ensures that the gas can be smoothly introduced into the inner return pipe 32 with sufficient momentum.

[0071] Meanwhile, the rotation of the recirculation fan 7 relays the already rectified airflow, preventing backflow or stagnation due to velocity decay. Since the recirculation fan 7 is located after the honeycomb rectifier mesh 34, it draws in homogenized and directional airflow, resulting in smoother operation and reducing the likelihood of surge or vortex shedding instability. Finally, the premixed gas accelerated and propelled by the recirculation fan 7 enters the inner recirculation pipe 32 in a stable, continuous, and highly responsive state, providing reliable hydrodynamic support for precise control of the recirculation flow and achieving efficient recirculation combustion.

[0072] See Figure 3 , Figure 5 and Figure 8 As shown, the return cylinder 3 has an air filter on the side with the air inlet 412.

[0073] The air filter is not shown in the figure.

[0074] When outside air is drawn into the return tube 3, it first passes through an air filter located outside the air inlet 412. This filter intercepts dust, oil, and other solid particulate impurities carried in the air, preventing them from entering the return tube 3. The clean air then continues to flow inward, merging with the flue gas introduced from the outer return pipe 31 near the inlet of the flow channel. This results in a more stable composition of the premixed gas formed after the clean air and flue gas mix, preventing interference with the combustion chemical reaction due to external pollutants. This helps maintain the purity of the atmosphere inside the nitriding furnace and the environmentally friendly and efficient combustion process.

[0075] This invention initially mixes flue gas and fresh air within a flow channel, and enhances turbulence by utilizing the negative pressure of the flow fan 4 and the contraction of the flow channel to form an initial premixed gas. Subsequently, the gas enters a multi-stage dynamic dispersion zone composed of a rotating conical sleeve 6, an annular groove 51, a mixing blade 61, and an arc-shaped swirling groove 521, where it sequentially undergoes radial dispersion, periodic expansion and compression, shear sweeping, and swirling guidance. Under axial, radial, and circumferential disturbances, it achieves deep homogenization and forms a stable swirling flow.

[0076] Next, the swirling gas passes through the baffle 33 and the air holes 331 to generate a high-frequency pulsating jet for further refinement and mixing. Then, it is corrected by the honeycomb rectifier mesh 34 into a low-pulsation, axially dominant uniform flow. The return fan 7 relays the pressurization of the rectified airflow to compensate for resistance loss and ensure stable delivery to the inner return pipe 32.

[0077] Throughout the process, the flow rate and pressure are dynamically regulated through flue gas valves, overflow valves, and flow control valves, taking into account both mixing uniformity and flow stability. This effectively suppresses local high temperatures and pollutant generation, providing high-quality premixed airflow for combustion chamber 2, and achieving efficient, precise, and environmentally friendly waste gas recirculation combustion control.

[0078] The above embodiments only illustrate one or more implementations of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of protection of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. An environmentally friendly and efficient waste gas recirculation burner for a nitriding furnace, comprising a furnace body, wherein the furnace body is provided with a combustion port and a flue gas outlet, a combustion cylinder is provided at the combustion port, and the combustion cylinder is provided with a gas inlet and equipped with a gas valve; Its features are, It also includes a return tube connected to the combustion chamber, an external return pipe connected between the return tube and the exhaust port, and an internal return pipe connected between the return tube and the combustion chamber; The upstream region inside the reflux cylinder is equipped with a coaxial ducting fan. The ducting fan has a drive shaft that is rotatably connected to the reflux cylinder. The drive shaft has a hollow structure and its side wall has a flue gas inlet that communicates with the external reflux pipe. The reflux cylinder has an air inlet on the air inlet side near the ducting fan. The return cylinder is also provided with a flow-guiding cone sleeve coaxial with it, and a flow-guiding channel that gradually narrows along the airflow direction is formed between the flow-guiding cone sleeve and the drive shaft; The air intake fan is installed in the air intake channel, and the air outlet side of the air intake fan is provided with turbulence blades that are fixedly connected to the drive shaft. During the operation of the diversion fan, the flue gas and air are premixed and merged in the diversion channel; The external return pipe is equipped with a flue gas valve; The internal reflux pipe is equipped with a flow control valve.

2. The environmentally friendly and efficient waste gas recirculation burner for a nitriding furnace according to claim 1, characterized in that, Inside the reflux cylinder and in the area downstream of the diversion cone sleeve, there is a rotating cone sleeve that is fixedly mounted coaxially with it. The rotating cone sleeve is fixedly connected to the drive shaft, and an annular dispersion area that communicates with the diversion channel from the inside out is formed between the rotating cone sleeve and the diversion cone sleeve.

3. The environmentally friendly and efficient waste gas recirculation burner for a nitriding furnace according to claim 2, characterized in that, The downstream region of the drainage cone sleeve has annular grooves that are evenly spaced along the axial direction and whose diameter gradually increases. The annular grooves and the rotating cone sleeve form a wave-shaped annular dispersion region.

4. The environmentally friendly and efficient waste gas recirculation burner for a nitriding furnace according to claim 3, characterized in that, The rotating cone sleeve has multiple mixing blades along its circumference on the side facing the drainage cone sleeve, and each mixing blade is in clearance fit with the annular groove on the drainage cone sleeve.

5. The environmentally friendly and efficient waste gas recirculation burner for a nitriding furnace according to claim 4, characterized in that, The downstream region of the flow-guiding cone sleeve is provided with an annular plate surrounding its outer circumference. The surface of the annular plate is provided with a swirling groove at the circumferential position of the airflow outlet of the annular dispersion region to guide the outflowing airflow to form a circumferential swirling flow.

6. The environmentally friendly and efficient waste gas recirculation burner for a nitriding furnace according to claim 5, characterized in that, The inside of the reflux cylinder is fixedly provided with a baffle that is sleeved on the rotating cone sleeve and fitted with it with a clearance. The surface of the baffle has a number of air holes that communicate with the swirling groove area.

7. The environmentally friendly and efficient waste gas recirculation burner for a nitriding furnace according to claim 6, characterized in that, A honeycomb-shaped rectifier mesh connected to several air holes is fixedly installed on the baffle.

8. The environmentally friendly and efficient waste gas recirculation burner for a nitriding furnace according to claim 7, characterized in that, A sealing ring is fixedly provided on the side of the baffle facing the rotating cone sleeve, forming a dynamic sealing fit with its outer circumferential surface.

9. An environmentally friendly and efficient waste gas recirculation burner for a nitriding furnace according to claim 7, characterized in that, The downstream region inside the reflux cylinder is provided with a reflux fan that is fixedly connected to the end of the drive shaft extending inward. The reflux fan is located between the honeycomb rectifier mesh and the inner reflux pipe.

10. An environmentally friendly and efficient waste gas recirculation burner for a nitriding furnace according to claim 1, characterized in that, An air filter is installed on the side of the return cylinder where the air vent is located.

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