Dual fuel low-nitrogen burner

Abstract

The present application provides a kind of dual fuel low nitrogen combustor, including center ignition unit, premixing air cylinder, fuel distribution unit and combustion air distribution unit.Premixing air cylinder includes outer cylinder, center hole, n premixing cylinder.Center ignition unit is through center hole, and n premixing cylinder is distributed to the periphery of center air pipe along the circumferential array, so that the whole fire interface of premixing air cylinder is fully utilized, the uniform stability of flame is improved, and the generation of nitrogen oxide is reduced.Fuel distribution cylinder is divided into 4 cavities by axial front and back separation and radial inner and outer separation, compact structure, can evenly and stably distribute fuel to each injection pipe.The present application can use high and low calorific value two kinds of fuel, two kinds of gaseous fuel do not interfere with each other, independent operation, can be used simultaneously, can also be used alone, the selectivity of fuel is relatively extensive.The flame structure can keep the same, and the application occasion adaptability is improved.

Description

Technical Field

[0001] This invention relates to the field of low-NOx burner technology, specifically a dual-fuel low-NOx burner. Background Technology

[0002] With the transformation of national energy demand, the blending or separate use of low-calorific-value fuels and high-calorific-value fuels is becoming increasingly widespread, such as the simultaneous use of coke oven gas and natural gas, blast furnace gas and natural gas, etc.

[0003] Currently, in existing dual-fuel burners, the two fuels are generally arranged coaxially inside and outside. For example, patent document CN120385082A discloses a dual-fuel low-NOx burner, including a biomass gas combustion device and a natural gas combustion device. The biomass gas combustion device includes an air passage structure and a gas passage structure, and the natural gas combustion device includes an air passage structure and a gas passage structure. These structures are sequentially nested and coaxially arranged from the outside in. Although the above-mentioned prior art can achieve the co-firing of two fuels, the two fuels are distributed in sections in the flame cross-section, with the biomass gas flame in the middle and the natural gas flame on the periphery. This results in a significant difference in flame structure between individual combustion and co-firing, which may not be suitable for heating applications requiring specific flame structure. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the object of the present invention is to provide a dual-fuel low-NOx burner.

[0005] To achieve the above objectives, the technical solution adopted by the present invention to solve its technical problem is: a dual-fuel low-NOx burner, comprising: The central ignition unit is located at the center of the burner. The central ignition unit includes a central gas pipe and a central air pipe arranged from the inside to the outside. A central ignition gun is provided between the inner circumference of the central air pipe and the outer circumference of the central gas pipe. A central air inlet hole is provided on the pipe body of the central air pipe. A premixed air duct includes an outer cylinder, a central hole, n premixed cylinders, n first conduits, and n second conduits, where n ≥ 3. The central air duct is disposed through the central hole, and the n premixed cylinders are arranged in a circumferential array around the central air duct. One first conduit and one second conduit are disposed adjacent to each other on the side of two adjacent premixed cylinders and in the area close to the inner wall of the outer cylinder. A fuel distribution unit includes a fuel distribution cylinder and n first fuel first injection pipes, n first fuel second injection pipes, n second fuel first injection pipes, and n second fuel second injection pipes connected to the fuel distribution cylinder; each first fuel first injection pipe extends forward through a premixing cylinder to the front end of the burner; each second fuel first injection pipe coaxially surrounds a first fuel first injection pipe, with the head end of the second fuel first injection pipe located in the middle of the premixing cylinder; each first fuel second injection pipe extends forward through a first conduit of the premixing cylinder to the front end of the burner; each second fuel second injection pipe extends forward through a second conduit of the premixing cylinder to the front end of the burner; The combustion air distribution unit includes an outer shell and a combustion air inlet pipe. The outer shell surrounds the middle and rear part of the premixed air duct. The rear end face of the outer shell is sealed and connected to the front side plate of the fuel distribution duct. There is an air passage gap between the rear end face of the premixed air duct and the front side plate of the fuel distribution duct. The combustion air passes through this air passage gap and enters the premixed air duct, the first duct, the second duct and the central air duct.

[0006] In this invention, in the fuel distribution unit, a portion of the first fuel is first supplied to the inner cavity of the first fuel, and then ejected from the inlet of the premixing cylinder through the first fuel first injection pipe; another portion of the first fuel is first supplied to the outer cavity of the first fuel, and then ejected from the inlet of the first conduit between adjacent premixing cylinders through the second fuel second injection pipe. Similarly, a portion of the second fuel is first supplied to the inner cavity of the second fuel, mixed with combustion air in the middle of the premixing cylinder through the second fuel first injection pipe, and then ejected from the inlet of the premixing cylinder; another portion of the second fuel is first supplied to the outer cavity of the second fuel, and then ejected from the inlet of the second conduit between adjacent premixing cylinders through the second fuel second injection pipe. In the ignition structure, the central ignition unit is located at the center, providing an ignition source for the burner and simultaneously igniting the peripheral main flame. Multiple premixing cylinders, evenly distributed around the central duct, serve as main ignition cylinders, while secondary ignition cylinders are provided at the first and second conduits between adjacent premixing cylinders. This ensures full utilization of the entire ignition interface of the premixing duct, improving flame uniformity and stability, and reducing the generation of nitrogen oxides. Regarding fuel type, the first fuel uses a lower calorific value fuel, and the second fuel uses a higher calorific value fuel. The higher calorific value fuel is premixed with combustion air in a premixing cylinder to ensure complete combustion, improve combustion efficiency, and reduce pollutant emissions. The lower calorific value fuel flows out at the flame, effectively preventing backfire and improving combustion safety. The burner structure of this invention allows the two gaseous fuels to operate independently without interference, enabling simultaneous or individual use, thus offering a wide range of fuel options. The flame structure remains consistent, enhancing adaptability to various applications.

[0007] Furthermore, the fuel distribution cylinder is divided by a fuel chamber partition into a second fuel chamber and a first fuel chamber distributed axially front to back. The first fuel chamber is divided radially by a first inner ring into a first fuel inner chamber and a first fuel outer chamber distributed internally and externally. The second fuel chamber is divided radially by a second inner ring into a second fuel inner chamber and a second fuel outer chamber distributed internally and externally. n first fuel first injection pipes are connected to the first fuel inner chamber; n second fuel first injection pipes are connected to the second fuel inner chamber; n first fuel second injection pipes are connected to the first fuel outer chamber; and n second fuel second injection pipes are connected to the second fuel outer chamber.

[0008] Using the above-mentioned preferred scheme, the fuel distribution cylinder is divided into four chambers by axial front-to-back separation and radial internal-to-external separation. Fuel flows out evenly from multiple pipe holes in the walls of each chamber. The structure is compact and can distribute fuel evenly and stably to each injection pipe.

[0009] Furthermore, the number n of the premixing cylinder, the first fuel injection pipe, the first fuel injection pipe, the second fuel injection pipe, the first fuel injection pipe, and the second fuel injection pipe distributed in the circumferential direction are all 3, 4, 5, 6, or 8.

[0010] Furthermore, a central front plate is installed at the front end of the central air duct, and the central front plate is provided with multiple oblique holes for generating swirling air; a central nozzle is installed at the front end of the central gas pipe, and the central nozzle is provided with multiple central gas ejection holes extending radially outward, the central gas ejection holes extending beyond the front end face of the central front plate; the spark plug head of the central ignition gun is recessed into the front end face of the central front plate.

[0011] Using the above-mentioned preferred scheme, the oblique cut hole of the central front plate generates a swirling flow, which helps the central flame to expand circumferentially and can better ignite the various main flames distributed circumferentially.

[0012] Furthermore, the central gas ejection orifice includes a first central gas ejection orifice and a second central gas ejection orifice that are circumferentially spaced on the central nozzle. The first central gas ejection orifice is a straight orifice, and the second central gas ejection orifice includes a straight orifice section located on the inner side and an outwardly flared conical orifice section located on the outer side. The orifice diameter of the first central gas ejection orifice is greater than or equal to twice the orifice diameter of the straight orifice section of the second central gas ejection orifice.

[0013] Using the above-mentioned preferred scheme, the first central gas ejection hole has a large diameter and ejects a large amount of gas, which can be ejected to a relatively far place, improving the ability of the ignition flame to spread in a circumferential direction; the second central gas ejection hole has a small diameter in the straight section and ejects a shorter distance, and the outwardly expanding conical section allows the gas ejected from the second central gas ejection hole to diffuse nearby, which helps to stably and quickly ignite the ignition gun throughout the entire central ignition gun.

[0014] Furthermore, it also includes a central airflow regulating mechanism, which comprises a central pressure measuring tube, an airflow regulating ring, a connecting plate, and a pressure sensor. The central pressure measuring tube is axially slidably installed in the central air duct, with its front end located at the front of the inner cavity of the central air duct and its rear end located behind the rear end face of the central air duct. The pressure sensor is installed at the rear end of the central pressure measuring tube. The airflow regulating ring rests against the inner circumferential wall of the central air duct, and the outer circumference of the connecting plate is fixedly connected to the inner wall of the airflow regulating ring. The central pressure measuring tube passes through the connecting plate and is fixedly connected to it. The central pressure measuring tube drives the airflow regulating ring to move back and forth relative to the central air duct to control the area of ​​the central air inlet hole on the central air duct that is blocked by the airflow regulating ring, thereby achieving the regulation of the airflow in the central air duct.

[0015] Using the preferred scheme described above, the pressure of the combustion air in the central duct is detected by a pressure sensor, and the air intake of the central duct is adjusted by a central air volume regulating mechanism to ensure that the central duct provides an air volume that helps to stably establish the flame.

[0016] Furthermore, the central ignition gun includes an ignition gun outer cylinder, an ignition gun gas pipe, a spark plug, and an ionizing rod. The ignition gun gas pipe, spark plug, and ionizing rod are all located inside the outer cylinder. The outer cylinder wall has multiple through-holes for ignition gun combustion air. The front of the ignition gun gas pipe has a lateral ignition gas branch outlet and an axial ignition gas tube. An ignition premixing cylinder is located at the front end of the ignition gas branch outlet. There is an air passage gap between the ignition premixing cylinder and the inner wall of the outer cylinder. A first reduction disc and a second reduction disc are arranged sequentially from back to front inside the ignition premixing cylinder. Both the first and second reduction discs have multiple small holes, and the total area of ​​the small hole openings on the second reduction disc is larger than the total area of ​​the small hole openings on the first reduction disc. The ignition gas tube passes through the first and second reduction discs. The front outlet of the ignition gas tube and the front end of the spark plug are both located in front of the second reduction disc.

[0017] Using the preferred design described above, the central ignition gun does not require a separate combustion air duct; ignition can be achieved using the air from the central air duct. The ignition premixing cylinder and deceleration structure at the front end of the ignition gun provide secondary deceleration, which helps to stably establish the ignition flame.

[0018] Furthermore, the rear end of the central gas pipe is connected to a central gas inlet pipe for introducing ignition gas, and the rear end of the ignition gun gas pipe is also connected to the central gas inlet pipe.

[0019] Furthermore, a first fuel distribution plate is installed at the head end of the first fuel injection pipe, and the outer diameter of the first fuel distribution plate is 60%-80% of the inner diameter of the premixing cylinder; the first fuel distribution plate has an inner cavity communicating with the first fuel injection pipe, and a plurality of first fuel outflow holes are provided on the front wall of the first fuel distribution plate. The first fuel distribution plate is also provided with a plurality of through pipes penetrating its front wall and rear wall, and the inner hole of the through pipe is not communicating with the inner cavity of the first fuel distribution plate.

[0020] Using the above-mentioned preferred scheme, the first fuel enters the circular inner cavity of the first fuel distribution plate and flows out from several first fuel outflow holes. Several through pipes on the first fuel distribution plate are used for air (mixed with the second fuel) to pass through to the front side of the first fuel distribution plate and mix with the first fuel to participate in combustion. Another part of the mixture of the second fuel and air flows out from the gap between the first fuel distribution plate and the premixing cylinder to participate in combustion, thereby improving the uniformity of fuel and air mixing.

[0021] Further, the first fuel injection pipe includes a front pipe and a rear pipe; the head end of the second fuel injection pipe is equipped with a second fuel transfer device and a second fuel premix distributor. The second fuel transfer device includes an inner ring and an outer ring coaxially arranged. The inner hole of the inner ring is through-hole, the front end face of the inner ring and the outer ring are closed, and the rear end face is open. The front end of the inner hole of the inner ring is connected to the rear end of the front pipe of the first fuel injection pipe, the rear end of the inner hole of the inner ring is connected to the front end of the rear pipe of the first fuel injection pipe, and the rear end of the outer ring is connected to the head end of the second fuel injection pipe. The second fuel premix distributor is a plurality of such distributors, which are arranged in a circumferential array on the outer ring body. The second fuel premix distributors are cylindrical, with their outer end faces closed. The inner ports of the second fuel premix distributors pass through the outer ring body of the second fuel transition device. The second fuel premix distributors extend radially outward on the outer ring body. The cylindrical wall of the second fuel premix distributors is provided with rows of premixing holes. The second fuel in the second fuel cavity passes through the gap between the outer side of the first fuel injection pipe and the inner side of the second fuel injection pipe, reaches the second fuel transition device, and then flows out from the premixing holes of the second fuel premix distributors.

[0022] The above-mentioned preferred scheme facilitates the docking and installation of the first fuel injection pipe and the second fuel injection pipe with coaxial structure, and enables the second fuel in the second fuel injection pipe to be evenly distributed in the premixing cylinder, thereby improving the premixing uniformity.

[0023] Furthermore, the fuel distribution cylinder is equipped with a first fuel first inlet pipe connected to the first fuel inner cavity, a first fuel second inlet pipe connected to the first fuel outer cavity, a second fuel first inlet pipe connected to the second fuel inner cavity, and a second fuel second inlet pipe connected to the second fuel outer cavity. Each inlet pipe enters the corresponding cavity radially. The first fuel first inlet pipe and the first fuel second inlet pipe are respectively connected to the first fuel gas source via control valves and pipelines. The second fuel first inlet pipe and the second fuel second inlet pipe are respectively connected to the second fuel gas source via control valves and pipelines.

[0024] By adopting the above-mentioned preferred scheme, the flow rate of the inner and outer cavities can be controlled by the control valve, which facilitates the adjustment of flame performance.

[0025] Furthermore, the fuel distribution cylinder is provided with one first through pipe on one side and one second through pipe on the other side for each second fuel first injection pipe. The axial projections of the second fuel first injection pipe, the first through pipe, and the second through pipe in the same group are all located within the projection of the corresponding premixing cylinder. The first through pipe is used to install a flame detection device, and the second through pipe is used to install a temperature switch. The thermocouple head of the temperature switch is located near the rear of the head of the second fuel first injection pipe.

[0026] Using the above-mentioned preferred scheme, the selection of the positions of the first and second through pipes ensures that they do not interfere with other devices while allowing for good observation of the combustion flame. The structural layout is compact and reasonable, enabling monitoring of the flames at the front end of each premixing cylinder and monitoring of whether backfire has occurred within the premixing cylinder in a relatively small space. The temperature switch is used to monitor the temperature of the second fuel and air mixture. If the temperature is too high, it indicates that backfire has occurred, and for safety reasons, the second fuel valve should be immediately shut off. The flame detection device is used to monitor the ultraviolet signals generated by combustion. If the signal is lost, it indicates that the flame has extinguished, and all fuel valves should be immediately shut off.

[0027] Furthermore, the inner cavity of the outer shell of the combustion air distribution unit is annular. A baffle plate is fixed to the front and rear sides of the combustion air inlet and the front and rear sides of the opposite side of the combustion air inlet. The baffle plate has a 1 / 4 annular structure. A duct support plate that can be radially raised and lowered relative to the premixed air duct is provided between the two opposing baffle plates. A fixing plate extending vertically towards the air inlet side is provided at the lower part of each baffle plate. An adjusting bolt parallel to the baffle plate is threaded on the fixing plate. The lower end of the adjusting bolt is rotatably engaged with the clamping plate of the duct support plate. By adjusting the adjusting bolt, the two opposing duct support plates are moved closer or further apart to tighten or loosen the premixed air duct.

[0028] Using the preferred scheme described above, the combustion air enters the outer casing, first moving around the inner circumference, and then entering the rear of the premixing duct through the lateral gap between the two rear baffles, ensuring the uniformity of airflow within each premixing duct. The premixing duct can be tightened or loosened by adjusting four adjusting bolts, facilitating disassembly and installation.

[0029] Furthermore, the combustion air inlet pipe includes a section of inclined pipe, on which a first inspection port is opened on the pipe wall directly opposite the combustion air inlet on the outer casing, and a second inspection port is provided on the outer casing at a position directly opposite the combustion air inlet, and a detachable inspection cover is installed on both the first and second inspection ports.

[0030] By adopting the above-mentioned preferred solution, the adjusting bolts can be easily adjusted after the inspection cover is removed, which facilitates the disassembly and maintenance operation. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is one perspective view of one embodiment of the burner of the present invention.

[0033] Figure 2 This is a second perspective view of one embodiment of the burner of the present invention.

[0034] Figure 3 This is a front view of one embodiment of the burner of the present invention.

[0035] Figure 4 yes Figure 3 Sectional view along the AA direction.

[0036] Figure 5 yes Figure 3 Sectional view along the BB direction.

[0037] Figure 6 This is a perspective view of one embodiment of the center ignition unit.

[0038] Figure 7 This is one of the cross-sectional views of one embodiment of the center ignition unit.

[0039] Figure 8 This is a second cross-sectional view of one embodiment of the center ignition unit.

[0040] Figure 9This is a cross-sectional view of one embodiment of the central nozzle.

[0041] Figure 10 This is a cross-sectional view of one embodiment of the center ignition gun.

[0042] Figure 11 yes Figure 10 Enlarged view of a section at point C.

[0043] Figure 12 This is a perspective view of one embodiment of a premixed air duct.

[0044] Figure 13 This is a perspective view of one embodiment of the fuel distribution unit.

[0045] Figure 14 This is a 3D view of the rear end plate of the hidden fuel distribution cylinder in the fuel distribution unit.

[0046] Figure 15 This is a rear view of the rear end plate of the hidden fuel distribution cylinder in the fuel distribution unit.

[0047] Figure 16 This is a 3D view of the rear half of the hidden fuel distribution cylinder in the fuel distribution unit.

[0048] Figure 17 This is a rear view of the hidden rear half of the fuel distribution cylinder in the fuel distribution unit.

[0049] Figure 18 It is one of the three-dimensional diagrams showing the combined state of the first fuel injection pipe and the second fuel injection pipe.

[0050] Figure 19 This is the second three-dimensional view of the combined state of the first fuel injection pipe and the second fuel injection pipe.

[0051] Figure 20 It is a cross-sectional view of the first fuel injection pipe and the second fuel injection pipe in combination.

[0052] Figure 21 yes Figure 20 Enlarged view of a section at point D.

[0053] Figure 22 This is a perspective view of one embodiment of the combustion air distribution unit.

[0054] Figure 23 This is an axial cross-sectional view of one embodiment of the combustion air distribution unit.

[0055] Figure 24 This is a radial cross-sectional view of one embodiment of the combustion air distribution unit.

[0056] The numbers and letters in the diagram represent the names of the corresponding components: 10-Central ignition unit; 11-Central gas pipe; 111-Central gas inlet pipe; 12-Central nozzle; 121-First central gas injection hole; 122-Second central gas injection hole; 1221-Straight hole section; 1222-Conical hole section; 13-Central air duct; 131-Central air inlet hole; 14-Central front plate; 141-Beveled hole; 15-Central ignition gun; 151-Ignition gun outer cylinder; 152-Ignition gun gas pipe; 153-Ignition gas small pipe; 154-Ignition gas branch outlet; 155-Ignition premixing cylinder; 156-First reduction gear; 157-Second reduction gear; 21-Central pressure measuring tube; 22-Airflow regulating ring; 23-Connecting plate; 24-Pressure sensor; 30-Premixed air duct; 31-Outer duct; 32-Center hole; 33-Premixed cylinder; 34-First conduit; 35-Second conduit; 50 - Fuel distribution unit; 51 - Fuel distribution cylinder; 511 - First fuel inner cavity; 5111 - First fuel first inlet pipe; 512 - First fuel outer cavity; 5121 - First fuel second inlet pipe; 513 - Second fuel inner cavity; 5131 - Second fuel first inlet pipe; 514 - Second fuel outer cavity; 5141 - Second fuel second inlet pipe; 515 - Front side plate; 516 - Fuel cavity partition; 517 - First through pipe; 518 - Second through pipe; 5 2-First fuel first injection pipe; 521-First fuel first injection pipe front pipe; 522-First fuel first injection pipe rear pipe; 53-First fuel distribution plate; 531 First fuel outlet orifice; 532-Passing pipe; 54-First fuel second injection pipe; 55-Second fuel first injection pipe; 56-Second fuel transducer; 561-Inner ring body; 562-Outer ring body; 57-Second fuel premix distributor; 571-Premixing orifice; 58-Second fuel second injection pipe; 70-Combustion air distribution unit; 71-Outer shell; 711-Combustion air inlet; 72-Combustion air inlet pipe; 721-First inspection port; 722-Second inspection port; 73-Air passage distance; 74-Wind baffle; 741-Fixing plate; 75-Air duct support plate; 751-Clamping plate; 76-Adjusting bolt. Detailed Implementation

[0057] 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.

[0058] For ease of description of technical features, the orientation of "front" and "rear" in this invention refers to the direction in which the burner flame is ejected.

[0059] like Figure 1-24 As shown, one embodiment of the present invention is: a dual-fuel low-NOx burner, comprising: The central ignition unit 10 is located at the center of the burner. The central ignition unit 10 includes a central gas pipe 11 and a central air pipe 13 arranged from the inside to the outside. A central ignition gun 15 is provided between the inner circumference of the central air pipe 13 and the outer circumference of the central gas pipe 11. A central air inlet hole 131 is provided on the pipe body of the central air pipe 13. The premixing duct 30 includes an outer duct 31, a central hole 32, n premixing cylinders 33, n first conduits 34 and n second conduits 35. The central duct 13 is disposed through the central hole 32. The n premixing cylinders 33 are arranged in a circumferential array around the central duct 13. One first conduit 34 and one second conduit 35 are disposed adjacent to each other on the side of two adjacent premixing cylinders 33 and near the inner wall of the outer duct. The fuel distribution unit 50 includes a fuel distribution cylinder 51, n first fuel first injection pipes 52, n first fuel second injection pipes 54, n second fuel first injection pipes 55, and n second fuel second injection pipes 58. The fuel distribution cylinder 51 is divided by a fuel chamber partition 516 into a second fuel chamber and a first fuel chamber distributed axially front to back. The first fuel chamber is divided radially by a first inner ring into a first fuel inner chamber 511 and a first fuel outer chamber 512 distributed internally and externally. The second fuel chamber is divided radially by a second inner ring into a second fuel inner chamber 513 and a second fuel outer chamber 514 distributed internally and externally. The n first fuel first injection pipes 52 pass through the front side plate 515 and the fuel chamber partition 516 of the fuel distribution cylinder 51 and communicate with the first fuel inner chamber 511. Each first fuel first injection pipe 52 extends forward through one premixing cylinder of the premixing duct. 33 to the front end of the burner; n second fuel first injection pipes 55 pass through the front side plate 515 of the fuel distribution cylinder and communicate with the second fuel inner cavity 513, each second fuel first injection pipe 55 coaxially surrounds one first fuel first injection pipe 52, and the head end of the second fuel first injection pipe 55 is located in the middle of the premixing cylinder 33; n first fuel second injection pipes 54 pass through the front side plate 515 of the fuel distribution cylinder 51 and the fuel cavity partition 516 and communicate with the first fuel outer cavity 512, each first fuel second injection pipe 54 extends forward through one first conduit 34 of the premixing air duct to the front end of the burner; n second fuel second injection pipes 58 pass through the front side plate 515 of the fuel distribution cylinder and communicate with the second fuel outer cavity 514, each second fuel second injection pipe 58 extends forward through one second conduit 35 of the premixing air duct to the front end of the burner; The combustion air distribution unit 70 includes a housing 71 and a combustion air inlet pipe 72. The housing 71 surrounds the middle and rear part of the premixing duct 30. The rear end face of the housing 71 is sealed and connected to the front side plate 515 of the fuel distribution duct 51. There is an air passage gap 73 between the rear end face of the premixing duct 30 and the front side plate 515 of the fuel distribution duct 51. Figure 4 As indicated by the red arrow, the combustion air passes through the air passage 73 and enters the premix cylinder 33, the first duct 34, the second duct 35, and the central air duct 13.

[0060] The beneficial effects of adopting the above technical solution are: in the fuel distribution unit, such as Figure 4 As indicated by the green arrow, a portion of the first fuel is first supplied to the first fuel cavity 511, and then ejected from the premixing cylinder 33 through the first fuel injection pipe 52; as shown by the green arrow. Figure 5 As indicated by the green arrow, another portion of the first fuel is first supplied to the first fuel outer cavity 512, and then ejected through the first fuel second injection pipe 54 at the opening of the first conduit 34 between adjacent premixing cylinders. Figure 4 As indicated by the blue arrow, a portion of the second fuel is first supplied to the second fuel cavity 513, then mixed with combustion air in the middle of the premixing cylinder 33 via the second fuel first injection pipe 55, and finally sprayed out from the outlet of the premixing cylinder; as shown in the image. Figure 5 As indicated by the blue arrow, another portion of the second fuel is first supplied to the second fuel outer cavity 514, and then ejected through the second fuel second injection pipe 58 at the opening of the second conduit 35 between adjacent premixing cylinders. The fuel distribution cylinder is divided into four cavities by axial front-to-back separation and radial internal-to-external separation. Fuel flows out evenly from multiple pipe holes in the walls of each cavity, resulting in a compact structure that can evenly and stably distribute fuel to each injection pipe. In terms of the ignition structure, the central ignition unit is located at the center, providing an ignition source for the burner and simultaneously igniting the peripheral main flame. Multiple premixing cylinders evenly distributed around the central air duct serve as main flame tubes, while secondary flame tubes are provided at the first and second conduits between adjacent premixing cylinders. This ensures full utilization of the entire ignition interface of the premixing air duct, improving flame uniformity and stability, and reducing the generation of nitrogen oxides. Regarding fuel type, the first fuel uses a lower calorific value fuel, and the second fuel uses a higher calorific value fuel. For example, when coke oven gas and natural gas are co-fired, coke oven gas is used as the first fuel and natural gas as the second fuel; or when blast furnace gas and natural gas are co-fired, blast furnace gas is used as the first fuel and natural gas as the second fuel. The higher calorific value fuel is first pre-mixed with combustion air in a premixing cylinder to ensure complete combustion, improve combustion efficiency, and reduce pollutant emissions; the lower calorific value fuel flows out at the flame, effectively preventing backfire and improving combustion safety. The burner structure of this invention allows the two gaseous fuels to operate independently without interference, enabling simultaneous or individual use, thus providing a wide range of fuel options. The flame structure remains consistent, enhancing adaptability to various applications.

[0061] In other embodiments of the present invention, the number n of the premixing cylinder, the first fuel first injection pipe, the first fuel second injection pipe, the second fuel first injection pipe, and the second fuel second injection pipe distributed circumferentially can be 3, 4, 5, 6, or 8. In the various figures of the present invention, n=6.

[0062] like Figure 6 As shown, in some other embodiments of the present invention, a central front plate 14 is installed at the front end of the central air duct 13, and the central front plate 14 is provided with a plurality of obliquely cut holes 141 for generating swirling air. A central nozzle 12 is installed at the front end of the central gas pipe 11, and the central nozzle 12 is provided with a plurality of central gas ejection holes extending radially outward, the central gas ejection holes extending beyond the front end face of the central front plate 14; the spark plug head of the central ignition gun 15 is recessed into the front end face of the central front plate 14. The beneficial effect of adopting the above technical solution is that the obliquely cut holes of the central front plate generate swirling air, which helps the central flame to expand circumferentially and can better ignite the various main flames distributed circumferentially.

[0063] like Figure 9 As shown, in some embodiments of the present invention, the central gas ejection orifice includes a first central gas ejection orifice 121 and a second central gas ejection orifice 122 circumferentially spaced on the central nozzle. The first central gas ejection orifice 121 is a straight orifice, and the second central gas ejection orifice 122 includes an inner straight orifice section 1221 and an outer conical orifice section 1222. The diameter of the first central gas ejection orifice 121 is greater than or equal to twice the diameter of the straight orifice section 1221 of the second central gas ejection orifice. The beneficial effects of adopting the above technical solution are: the large diameter of the first central gas ejection orifice results in a large amount of ejected gas, which can be ejected to a relatively far distance, improving the ability of the ignition flame to spread circumferentially; the small diameter of the straight orifice section of the second central gas ejection orifice results in a shorter ejection distance, and the outer conical orifice section allows the gas ejected from the second central gas ejection orifice to diffuse nearby, thus helping to stably and quickly ignite the ignition of the ignition gun throughout the entire central ignition gun.

[0064] like Figure 8As shown, in some other embodiments of the present invention, a central airflow regulating mechanism is also included. The central airflow regulating mechanism includes a central pressure measuring tube 21, an airflow regulating ring 22, a connecting plate 23, and a pressure sensor 24. The central pressure measuring tube 21 is axially movably mounted on the central air duct 13. The front end of the central pressure measuring tube 21 is located at the front of the inner cavity of the central air duct 13, and the rear end of the central pressure measuring tube 21 is located behind the rear end face of the central air duct. The pressure sensor 24 is mounted on the rear end of the central pressure measuring tube 21. The airflow regulating ring 22 rests against the inner circumferential wall of the central air duct 13. The outer periphery of the connecting plate 23 is fixedly connected to the inner wall of the airflow regulating ring 22. The central pressure measuring tube 21 passes through the connecting plate 23 and is fixedly connected to it. The central pressure measuring tube 21 drives the airflow regulating ring 22 to move back and forth relative to the central air duct 13 to control the area of ​​the central air inlet hole 131 on the central air duct that is blocked by the airflow regulating ring 22, so as to realize the regulation of the airflow in the central air duct. The beneficial effects of adopting the above technical solution are as follows: A pressure sensor detects the pressure of the combustion air in the central duct, and a central airflow regulating mechanism adjusts the airflow into the central duct to ensure that the central duct provides sufficient airflow to help stabilize the flame. The central airflow regulating mechanism has a compact and reasonable structure; the position of the central pressure measuring tube can be adjusted at the rear end of the burner. Adjustment can be made by manually pulling or pushing the central pressure measuring tube. To facilitate monitoring of the area of ​​the blocked hole, a mark is set on the central gas pipe to indicate the amount of blocked area. Additionally, an indicator needle is welded to the central pressure measuring tube, and the opening degree is indicated by the mark on the central gas pipe aligned with the indicator needle. A linear drive mechanism can also be configured at the rear end of the burner to move the central pressure measuring tube back and forth. The controller collects and processes the airflow data detected by the pressure sensor and issues a command to control the linear drive mechanism to ensure that the airflow in the central duct detected by the pressure sensor is maintained within the set value range.

[0065] like Figure 10 , 11As shown, in some other embodiments of the present invention, the central ignition gun 15 includes an ignition gun outer cylinder 151, an ignition gun gas pipe 152, a spark plug, and an ionizing rod. The ignition gun gas pipe 152, the spark plug, and the ionizing rod are all located inside the outer cylinder 151. The outer cylinder 151 has multiple through-holes for ignition gun combustion air. The front of the ignition gun gas pipe 152 has an ignition gas branch outlet 154 for laterally ejecting gas and an ignition gas tube 153 for axially ejecting gas. An ignition premixing cylinder 155 is provided at the front end of the ignition gas branch outlet 154. An air passage gap exists between the ignition premixing cylinder 155 and the inner wall of the ignition gun's outer cylinder. Inside the ignition premixing cylinder 155, a first reduction disc 156 and a second reduction disc 157 are arranged sequentially from back to front. Both the first and second reduction discs 156 and 157 have multiple small holes, and the total area of ​​the openings of the small holes on the second reduction disc 157 is larger than the total area of ​​the openings of the small holes on the first reduction disc 156. An ignition gas pipe 153 passes through both the first and second reduction discs 156 and 157. The front outlet of the ignition gas pipe 153 and the front end of the spark plug are both located in front of the second reduction disc 157. The beneficial effects of this technical solution are: the central ignition gun does not require a separate combustion air duct; ignition can be achieved using the air from the central air duct. The ignition premixing cylinder and reduction structure at the front of the ignition gun achieve secondary deceleration, which helps to stably establish the ignition flame.

[0066] like Figure 7 As shown, in some other embodiments of the present invention, the rear end of the central gas pipe 11 is connected to a central gas inlet pipe 111 for introducing ignition gas, and the rear end of the ignition gun gas pipe 11 is also connected to the central gas inlet pipe 111.

[0067] like Figure 18 , 19 As shown, in some other embodiments of the present invention, a first fuel distribution plate 53 is installed at the head end of the first fuel injection pipe 52. The outer diameter of the first fuel distribution plate 53 is 60%-80% of the inner diameter of the premixing cylinder 33. The first fuel distribution plate 53 has an inner cavity communicating with the first fuel injection pipe 52. A plurality of first fuel outflow holes 531 are provided on the front wall of the first fuel distribution plate 53. A plurality of through pipes 532 penetrating its front and rear walls are also provided on the first fuel distribution plate 53. The inner hole of the through pipe 532 is not communicating with the inner cavity of the first fuel distribution plate 53. The beneficial effects of adopting the above technical solution are: the first fuel enters the circular inner cavity of the first fuel distribution plate and flows out from a plurality of first fuel outflow holes. A plurality of through pipes on the first fuel distribution plate are used for air (which also contains second fuel) to pass through to the front side of the first fuel distribution plate and mix with the first fuel to participate in combustion. In addition, a portion of the mixture of second fuel and air flows out from the gap between the first fuel distribution plate and the premixing cylinder to participate in combustion, thereby improving the uniformity of fuel and air mixing.

[0068] like Figure 20 , 21 As shown, in some other embodiments of the present invention, the first fuel injection pipe 52 includes a first fuel injection pipe front pipe 521 and a first fuel injection pipe rear pipe 522; the head end of the second fuel injection pipe 55 is equipped with a second fuel transfer device 56 and a second fuel premix distributor 57. The second fuel transfer device 56 includes an inner ring body 561 and an outer ring body 562 coaxially arranged. The inner hole of the inner ring body 561 is through, and the front end face between the inner ring body 561 and the outer ring body 562 is closed and the rear end face is open. The front end of the inner hole of the inner ring body 561 is connected to the rear end of the first fuel injection pipe front pipe 521, and the rear end of the inner hole of the inner ring body 561 is connected to the front end of the first fuel injection pipe rear pipe 522. The rear end of the outer ring body 562 is connected to the second fuel injection pipe 55. The head end of 5 is connected; there are multiple second fuel premix distributors 57, which are arranged in a circumferential array on the outer ring body 562. The second fuel premix distributors 57 are cylindrical, and their outer end faces are closed. The inner port of the second fuel premix distributor 57 passes through the outer ring body 562 of the second fuel transition device. The second fuel premix distributors 57 are arranged radially outward on the outer ring body 562. The cylindrical wall of the second fuel premix distributor 57 is provided with rows of premixing holes 571. The second fuel in the second fuel cavity passes through the gap between the outer side of the first fuel first injection pipe 522 and the inner side of the second fuel first injection pipe 55, reaches the second fuel transition device 56, and then flows out from the premixing holes 571 of the second fuel premix distributor. The beneficial effects of adopting the above technical solution are: it facilitates the docking and installation of the first fuel injection pipe and the second fuel injection pipe with coaxial structure, and enables the second fuel in the second fuel injection pipe to be evenly distributed in the premixing cylinder, thereby improving the premixing uniformity.

[0069] like Figure 14 As shown, in some other embodiments of the present invention, the fuel distribution cylinder 51 is equipped with a first fuel first inlet pipe 5111 communicating with the first fuel inner cavity 511, a first fuel second inlet pipe 5121 communicating with the first fuel outer cavity 512, a second fuel first inlet pipe 5131 communicating with the second fuel inner cavity 513, and a second fuel second inlet pipe 5141 communicating with the second fuel outer cavity 514. Each inlet pipe enters the corresponding cavity radially. The first fuel first inlet pipe 5111 and the first fuel second inlet pipe 5121 are respectively connected to a first fuel gas source via control valves and pipelines. The second fuel first inlet pipe 5131 and the second fuel second inlet pipe 5141 are respectively connected to a second fuel gas source via control valves and pipelines. The beneficial effect of adopting the above technical solution is that the flow rate of the inner and outer cavities can be controlled by the control valves, which facilitates the adjustment of flame performance.

[0070] like Figure 15As shown, in some embodiments of the present invention, a first through pipe 517 is provided on one side of each first fuel first injection pipe 52 on the fuel distribution cylinder 51, and a second through pipe 518 is provided on the other side. The axial projections of the first fuel first injection pipe 52, the first through pipe 517, and the second through pipe 518 in the same group are all located within the projection of the corresponding premixing cylinder 33. A flame detection device is installed in the first through pipe 517, and a temperature switch is installed in the second through pipe 518. The thermocouple tip of the temperature switch is located near the rear of the tip of the second fuel first injection pipe 55. The beneficial effects of adopting the above technical solution are: the selection of the positions of the first and second through pipes can not interfere with other devices, and the combustion flame can be observed relatively well. The structural layout is compact and reasonable, realizing the monitoring of the flame at the front end of each premixing cylinder and the monitoring of whether backfire occurs in the premixing cylinder in a small space. The temperature switch is used to monitor the temperature of the second fuel and air mixture. If the temperature is too high, it indicates that backfire has occurred. For safety reasons, the second fuel valve should be shut off immediately. The flame detector is used to monitor the ultraviolet signal generated by combustion. If the signal is lost, it indicates that the flame has been extinguished. All fuel valves should be shut off immediately.

[0071] like Figure 22-24 As shown, in some other embodiments of the present invention, the inner cavity of the outer shell 71 of the combustion air distribution unit is annular. A baffle plate 74 is fixed on the front and rear sides of the combustion air inlet 711 and the front and rear sides of the opposite side of the combustion air inlet. The baffle plate 74 has a 1 / 4 annular structure. A duct support plate 75 that can be radially raised and lowered relative to the premixed air duct is provided between the two opposing baffle plates 74. A fixing plate 741 extending vertically towards the air inlet side is provided at the lower part of each baffle plate 74. An adjusting bolt 76 parallel to the baffle plate 74 is threaded on the fixing plate 741. The lower end of the adjusting bolt 76 is rotatably engaged with the clamping plate 751 of the duct support plate 75. By adjusting the adjusting bolt 76, the two opposing duct support plates 75 are moved closer or further apart to achieve tightening or loosening of the premixed air duct 30. The beneficial effects of adopting the above technical solution are as follows: after the combustion air enters the shell, it first moves around the inner circumference, and then enters the rear side of the premixing duct through the lateral gap between the two rear baffles, ensuring the uniformity of air volume in each premixing duct. The premixing duct can be tightened and loosened by adjusting the four adjusting bolts, which facilitates the disassembly and installation of the premixing duct.

[0072] like Figure 23As shown, in some embodiments of the present invention, the combustion air inlet pipe 72 includes a section of inclined pipe. A first inspection port 721 is provided on the pipe wall of the inclined pipe directly opposite the combustion air inlet 711 on the outer casing. A second inspection port 722 is provided on the outer casing directly opposite the combustion air inlet. Removable inspection covers are installed on both the first inspection port 721 and the second inspection port 722. The beneficial effect of adopting the above technical solution is that after removing the inspection cover, the adjusting bolt can be easily adjusted, which facilitates disassembly and maintenance operations.

[0073] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A dual-fuel low-NOx burner, characterized in that, include: The central ignition unit is located at the center of the burner. The central ignition unit includes a central gas pipe and a central air pipe arranged from the inside to the outside. A central ignition gun is provided between the inner circumference of the central air pipe and the outer circumference of the central gas pipe. A central air inlet hole is provided on the pipe body of the central air pipe. A premixed air duct includes an outer cylinder, a central hole, n premixed cylinders, n first conduits and n second conduits, where n≥3. The central air duct is disposed through the central hole. The n premixed cylinders are arranged in a circumferential array around the central air duct. One first conduit and one second conduit are disposed adjacent to each other on the side of two adjacent premixed cylinders and in the area close to the inner wall of the outer cylinder. A fuel distribution unit includes a fuel distribution cylinder and n first fuel first injection pipes, n first fuel second injection pipes, n second fuel first injection pipes, and n second fuel second injection pipes connected to the fuel distribution cylinder; each first fuel first injection pipe extends forward through a premixing cylinder to the front end of the burner; each second fuel first injection pipe coaxially surrounds a first fuel first injection pipe, with the head end of the second fuel first injection pipe located in the middle of the premixing cylinder; each first fuel second injection pipe extends forward through a first conduit of the premixing cylinder to the front end of the burner; each second fuel second injection pipe extends forward through a second conduit of the premixing cylinder to the front end of the burner; Combustion air distribution unit includes an outer shell and a combustion air inlet pipe. The outer shell surrounds the middle and rear part of the premixed air duct. The rear end face of the outer shell is sealed and connected to the front side plate of the fuel distribution duct. There is an air passage gap between the rear end face of the premixed air duct and the front side plate of the fuel distribution duct. The combustion air passes through this air passage gap and enters the premixed air duct, the first duct, the second duct and the central air duct. The first fuel uses a lower calorific value fuel, and the second fuel uses a higher calorific value fuel.

2. The dual-fuel low-NOx burner according to claim 1, characterized in that, The fuel distribution cylinder is divided into a second fuel chamber and a first fuel chamber, which are axially distributed front and rear, by a fuel chamber partition. The first fuel chamber is divided into a first fuel inner chamber and a first fuel outer chamber, which are distributed inner and outer, by a first inner ring along the radial direction. The second fuel chamber is divided into a second fuel inner chamber and a second fuel outer chamber, which are distributed inner and outer, by a second inner ring along the radial direction. n first fuel first injection pipes are connected to the first fuel inner chamber; n second fuel first injection pipes are connected to the second fuel inner chamber; n first fuel second injection pipes are connected to the first fuel outer chamber; and n second fuel second injection pipes are connected to the second fuel outer chamber.

3. The dual-fuel low-NOx burner according to claim 1, characterized in that, A central front plate is installed at the front end of the central air duct, and the central front plate has multiple oblique holes for generating swirling air; a central nozzle is installed at the front end of the central gas pipe, and the central nozzle has multiple central gas ejection holes extending radially outward, the central gas ejection holes extending beyond the front end face of the central front plate; the spark plug head of the central ignition gun is recessed into the front end face of the central front plate.

4. The dual-fuel low-NOx burner according to claim 3, characterized in that, The central gas ejection orifice includes a first central gas ejection orifice and a second central gas ejection orifice that are circumferentially spaced on the central nozzle. The first central gas ejection orifice is a straight orifice, and the second central gas ejection orifice includes a straight orifice section located on the inner side and an outwardly flared conical orifice section located on the outer side. The orifice diameter of the first central gas ejection orifice is greater than or equal to twice the orifice diameter of the straight orifice section of the second central gas ejection orifice.

5. The dual-fuel low-NOx burner according to claim 1, characterized in that, It also includes a central airflow regulation mechanism, which comprises a central pressure measuring tube, an airflow regulation ring, a connecting plate, and a pressure sensor. The central pressure measuring tube is axially movably mounted on the central air duct, with its front end located at the front of the inner cavity of the central air duct and its rear end located behind the rear end face of the central air duct. The pressure sensor is mounted on the rear end of the central pressure measuring tube. The airflow regulation ring rests against the inner circumferential wall of the central air duct, and the outer circumference of the connecting plate is fixedly connected to the inner wall of the airflow regulation ring. The central pressure measuring tube passes through the connecting plate and is fixedly connected to it. The central pressure measuring tube drives the airflow regulation ring to move back and forth relative to the central air duct to control the area of ​​the central air inlet hole on the central air duct that is blocked by the airflow regulation ring, thereby achieving the regulation of the airflow in the central air duct.

6. The dual-fuel low-NOx burner according to claim 1, characterized in that, The first fuel injection pipe is equipped with a first fuel distribution plate at its head end. The outer diameter of the first fuel distribution plate is 60%-80% of the inner diameter of the premixing cylinder. The first fuel distribution plate has an inner cavity that communicates with the first fuel injection pipe. The front wall of the first fuel distribution plate is provided with a plurality of first fuel outflow holes. The first fuel distribution plate is also provided with a plurality of through pipes that penetrate its front wall and rear wall. The inner hole of the through pipe is not in communication with the inner cavity of the first fuel distribution plate.

7. The dual-fuel low-NOx burner according to claim 1, characterized in that, The first fuel injection pipe includes a front pipe and a rear pipe; the head end of the second fuel injection pipe is equipped with a second fuel transfer device and a second fuel premix distributor. The second fuel transfer device includes an inner ring and an outer ring coaxially arranged. The inner hole of the inner ring is through-hole, the front end face of the inner ring and the outer ring are closed, and the rear end face is open. The front end of the inner hole of the inner ring is connected to the rear end of the front pipe of the first fuel injection pipe, the rear end of the inner hole of the inner ring is connected to the front end of the rear pipe of the first fuel injection pipe, and the rear end of the outer ring is connected to the head end of the second fuel injection pipe. There are multiple second fuel premix distributors, which are arranged in a circumferential array on the outer ring body. The second fuel premix distributors are cylindrical, with their outer end faces closed. The inner ports of the second fuel premix distributors pass through the outer ring body of the second fuel transition device. The second fuel premix distributors extend radially outward on the outer ring body. The cylindrical wall of the second fuel premix distributors is provided with rows of premixing holes. The second fuel in the second fuel cavity passes through the gap between the outer side of the first fuel injection pipe and the inner side of the second fuel injection pipe, reaches the second fuel transition device, and then flows out from the premixing holes of the second fuel premix distributors.

8. The dual-fuel low-NOx burner according to claim 2, characterized in that, The fuel distribution cylinder is equipped with a first fuel inlet pipe connected to the first fuel inner cavity, a first fuel second inlet pipe connected to the first fuel outer cavity, a second fuel first inlet pipe connected to the second fuel inner cavity, and a second fuel second inlet pipe connected to the second fuel outer cavity. The first fuel first inlet pipe and the first fuel second inlet pipe are respectively connected to a first fuel gas source via control valves and pipelines. The second fuel first inlet pipe and the second fuel second inlet pipe are respectively connected to a second fuel gas source via control valves and pipelines.

9. The dual-fuel low-NOx burner according to claim 1, characterized in that, The inner cavity of the outer shell of the combustion air distribution unit is annular. A baffle plate is fixed to the front and rear sides of the combustion air inlet and the front and rear sides of the opposite side of the combustion air inlet. The baffle plate is a quarter-annular structure. A duct support plate that can be radially raised and lowered relative to the premixed air duct is provided between the two opposing baffle plates. A fixing plate extending vertically towards the air inlet side is provided at the lower part of each baffle plate. An adjusting bolt parallel to the baffle plate is threaded on the fixing plate. The lower end of the adjusting bolt is rotatably engaged with the clamping plate of the duct support plate. By adjusting the adjusting bolt, the two opposing duct support plates are moved closer or further apart to tighten or loosen the premixed air duct.

10. The dual-fuel low-NOx burner according to claim 1, characterized in that, The combustion air inlet pipe includes a section of inclined pipe. A first inspection port is opened on the pipe wall of the inclined pipe directly opposite the combustion air inlet on the outer casing. A second inspection port is provided on the outer casing directly opposite the combustion air inlet. A detachable inspection cover is installed on both the first and second inspection ports.

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