Central fuel gas injection type low-nitrogen burner based on fuel gas classification

Abstract

A central fuel gas injection type low-nitrogen burner based on fuel gas classification relates to the technical field of combustion and comprises a central fuel gas gun, a burner block, peripheral fuel gas guns and a burner flame holder, the burner block is cylindrical, penetrates through furnace bottom castable and extends into the inner side of the furnace bottom castable, and a hearth is arranged on the inner side of the furnace bottom castable; one end of the central gas gun penetrates into the furnace bottom castable from the outside of the furnace bottom castable and penetrates into the inner side of the burner block from the outer side of the burner block; one end of the peripheral gas gun penetrates into the furnace bottom castable from the outside of the furnace bottom castable and is positioned on the outer side of the burner block; the ends, located outside the furnace bottom castable, of the center gas gun and the peripheral gas guns are used for introducing gas, the end, close to the outside of the furnace bottom castable, of the cylindrical burner block communicates with an air inlet air bellow, and the air inlet air bellow is used for introducing combustion air into the burner block. And the combustor flame holder is arranged in the combustor burner block. And through the injection type structural design, the problem that nitric oxide is generated by combustion of the central gas fuel is further controlled.

Description

Technical Field

[0001] This application belongs to the field of combustion technology, and particularly relates to a central gas ejector type low-nitrogen burner based on gas staging. Background Art

[0002] When fuel burns, nitrogen oxides are formed due to the oxidation of nitrogen-containing substances under high-temperature conditions. Nitrogen oxides are one of the main culprits of acid rain.

[0003] Typical existing technical solutions for controlling nitrogen oxide emissions include gas staging, air staging, air ejector technology based on gas staging, etc.

[0004] Gas staging technology divides gas into two or more stages. The main structural feature is that the central gas is arranged in the combustion-supporting air passage in a diffusion combustion pattern, which plays a role in stabilizing combustion and igniting the peripheral gas. The peripheral gas is arranged outside the combustion-supporting air passage, and the reaction intensity is reduced by weakening the mixing with air, and the emission is reduced by lowering the flame temperature. Chinese invention patent CN117387068A, a staged combustion gas ejector chemical low-nitrogen burner, discloses a gas staged combustion ultra-low nitrogen oxide burner. Gas staging technology can effectively reduce the emission of nitrogen oxides, but the central gas adopts a diffusion combustion method to mix with air and burn fully, and the stoichiometric combustion of the flame front will cause the nitrogen oxides generated by the central flame to be uncontrollable. And reducing the flow rate of the central gas too much will not play the role of igniting the peripheral gas and stabilizing the flame.

[0005] Air staging technology divides air into two or more channels. The main structural feature is that the gas is arranged in one of the air channels, or multiple channels form a coupling of air staging and gas staging. The excess air coefficient of this channel is less than 1, resulting in incomplete combustion, thereby reducing the flame temperature. Chinese invention patent CN108151017A discloses an air-gas staged combustion ultra-low nitrogen oxide burner, and the unburned combustible gas continues to burn fully with the air in other channels. Diffusion combustion belongs to stoichiometric combustion, that is, the gas and air at the flame front just react fully. Therefore, although the air is in excess, the flame front temperature is still relatively high. Practice shows that the air staging and air-gas staging schemes are inferior to the gas staging scheme in controlling nitrogen oxides.

[0006] The air entrainment technology based on gas staging is one of the most advanced low-nitrogen combustion technology solutions at present. Chinese invention patent CN110779014A discloses a flue gas internal circulation ultra-low nitrogen burner and boiler, which is characterized by increasing the pressure drop of the combustion-supporting air, that is, increasing the wind speed, lengthening the length of the throat channel, and opening holes on the furnace plate side near the installation of the burner to form the principle of an ejector, achieving the effect of the combustion-supporting air sucking in flue gas. The oxygen concentration of the combustion-supporting air will decrease to a certain extent, so the flame temperature of the central gas will decrease to a certain degree. In addition, because the combustion-supporting air sucks in flue gas, forming an interlayer of air and flue gas, the combustion of the peripheral gas is delayed, reducing the flame temperature. The air entrainment technology based on gas staging greatly reduces the temperature of the central gas flame. However, due to its structural principle, the throat air duct exposed in the furnace needs to be lengthened, otherwise a serious air and entrained flue gas interlayer will cause serious pressure fluctuations in the furnace. At the same time, in order to reduce the entrainment resistance, the throat air duct exposed in the furnace is made of metal material and has a large diameter, so there is a risk of burning out the throat air duct during long-term use, especially in the case of a high-temperature furnace with hydrogen fuel. Summary of the Utility Model

[0007] The technical problem solved by this application is: overcoming the deficiencies of the prior art, providing a central gas entrainment type low-nitrogen burner based on gas staging, further controlling the problem of nitrogen oxides generated by the combustion of central gaseous fuel, and at the same time solving the problem of the metal air channel exposed in the furnace being burned out.

[0008] Through the structural design of the burner head, it is ensured that the flame of the central gas gun inside the burner block is stable and the nitrogen oxide generation amount is low, and the peripheral gas gun outside the burner block is used as the main flame, realizing ultra-low nitrogen oxide emissions. This burner can be applied to various gas furnace types in the petrochemical, coal chemical, steel and heating industries, and the power range is not limited.

[0009] The technical solution provided by this application is as follows:

[0010] A central gas entrainment type low-nitrogen burner based on gas staging, including a central gas gun, a burner block, a peripheral gas gun and a burner flame stabilizer. The burner block is cylindrical. The cylindrical burner block passes through the furnace bottom castable and extends into the inner side of the furnace bottom castable. The inner side of the furnace bottom castable is the furnace chamber. One end of the central gas gun penetrates from outside the furnace bottom castable into the furnace bottom castable and then penetrates from the outside of the burner block into the inner space of the burner block. One end of the peripheral gas gun penetrates from outside the furnace bottom castable into the furnace bottom castable and is located outside the burner block. One ends of the central gas gun and the peripheral gas gun outside the furnace bottom castable are both used for introducing gas. The end of the cylindrical burner block outside the furnace bottom castable is communicated with an air inlet air box, and the air inlet air box is used for introducing combustion-supporting air into the burner block. The burner flame stabilizer is arranged inside the burner block of the burner.

[0011] Along the air inlet direction into the burner block inside the air inlet plenum, there are a first cavity and a second cavity inside the burner block in sequence. The diameter of the first cavity is smaller than that of the second cavity, and the first cavity and the second cavity form a sudden expansion structure; the central gas gun extends into the second cavity.

[0012] The central gas gun includes a central gas gun riser pipe, a central nozzle, a central flue gas ejector pipe, and a plurality of central nozzle positioning pieces. One end of the central gas gun riser pipe is located outside the furnace bottom castable, and the other end extends into the inside of the furnace bottom castable and the end is bent and connected to the central nozzle. One end of the central flue gas ejector pipe is exposed in the furnace chamber outside the burner block and is coaxial with the axis of the central nozzle, and the other end of the central flue gas ejector pipe passes through the burner block and extends into the combustion-supporting air channel and is parallel to the flow direction of the combustion-supporting air. A plurality of central nozzle positioning pieces are connected between the central nozzle and the end of the central flue gas ejector pipe exposed in the furnace chamber outside the burner block, so as to form a gap between the central nozzle and the central flue gas ejector pipe, and the flue gas is introduced into the central flue gas ejector pipe from this gap.

[0013] The included angle c between the part of the central flue gas ejector pipe located outside the burner block and the flow direction of the combustion-supporting air is 40° - 60°.

[0014] The distance from the outlet of the central flue gas ejector pipe to the end face of the burner flame stabilizer is L3. The size of L3 is related to the pneumatic parameters and physical and chemical properties of the fuel, and its range is 20 mm to 50 mm.

[0015] The distance from the outlet of the central flue gas ejector pipe to the inner end of the burner block of the burner in the furnace bottom castable is L4. The size of L4 is related to the pneumatic parameters and physical and chemical properties of the fuel, and its range is 100 mm to 200 mm.

[0016] The spray holes of the central nozzle are coaxial with the inlet end of the central flue gas ejector pipe, and the end face distance between the end face of the central nozzle and the inlet end of the central flue gas ejector pipe is -20 mm to +30 mm; where, - means the central nozzle is inserted into the central flue gas ejector pipe, and + means there is a gap between the end of the central nozzle and the central flue gas ejector pipe in the axis direction of the central nozzle.

[0017] The minimum distance between the axis of the peripheral gas gun and the inner wall of the burner block is not less than L5. The size of L5 is related to the power of the burner. In a low-power burner, the value of L5 should not be less than 30 mm, so as to ensure that there is a certain distance between the combustion-supporting air (gas) and the peripheral gas.

[0018] The peripheral gas gun includes a peripheral gas gun riser pipe, a peripheral nozzle, a peripheral flue gas entrainment pipe, and a plurality of peripheral nozzle positioning pieces. One end of the peripheral gas gun riser pipe is located outside the furnace, and the other end extends into the furnace and is connected to the peripheral nozzle. The spray holes of the peripheral nozzle are coaxial with the inlet end of the peripheral flue gas entrainment pipe. The peripheral nozzle and the peripheral flue gas entrainment pipe are connected by a plurality of peripheral nozzle positioning pieces, so that there is a gap between the peripheral nozzle and the peripheral flue gas entrainment pipe, and the flue gas in the furnace is entrained into the peripheral flue gas entrainment pipe through this gap.

[0019] The angle between the axis of the outlet of the peripheral flue gas entrainment pipe and the direction of the combustion-supporting air injection is 0, or the outlet of the peripheral flue gas entrainment pipe is bent towards the center of the burner block. At this time, the angle between the axis of the outlet of the peripheral flue gas entrainment pipe and the direction of the combustion-supporting air injection is 0-30°.

[0020] In summary, the present application at least includes the following beneficial technical effects:

[0021] As described above, a central gas ejector type low-nitrogen burner based on gas staging. According to the principle of the gas ejector, the central gas gun is designed as an ejector structure. The gas in the riser tube forms a high-speed airflow through the nozzle and is injected into the central flue gas ejector tube. Under the action of the high-speed airflow, the flue gas mainly composed of inert gas in the combustion chamber is entrained into the central flue gas ejector tube. Under the action of strong turbulence, the gas and the flue gas are fully mixed in the central flue gas ejector tube. The mixed central gas mixture is mixed and burned with the combustion-supporting air in the burner block. Each central nozzle is provided with a spray hole, which is beneficial to increasing the entrainment amount of the flue gas. If multiple spray holes are provided for each nozzle, the distance between adjacent spray holes is too close, which will cause the entrained flue gases to interfere with each other, increase the air mass friction, reduce the entrainment amount, and cannot achieve the purpose of diluting the gas. Since the mixed central gas mixture contains a certain amount of inert gas, the flame temperature can be effectively reduced. Here, compare the combustion of 100% concentration natural gas and a mixed gas of 60% concentration natural gas mixed with 40% concentration nitrogen with 25°C combustion-supporting air at the equivalent ratio. The flame temperature of the latter is 100°C lower than that of the former. According to numerical simulation and experiments, the temperature of the latter mixed gas is reduced more than that of the former. Because the mixed gas after mixing contains combustible gas and non-combustible gas, which is equivalent to the flame being fragmented, and the flame behavior shows that the flame length becomes longer and the temperature decreases, and this characteristic is easily not considered in the analytical calculation. Because another part of the central gas ejector tube passes through the burner block and extends into the combustion-supporting air channel, the mixed gas will be cooled by the combustion-supporting air. Therefore, the problem of the increase in the temperature of the mixed gas caused by the entrainment of the flue gas in the gas ejector furnace can be ignored. Thus, the nitrogen oxides generated by the flame of the central gas gun can be effectively controlled. By controlling the above-mentioned load ratio of the central gas gun and adjusting the air excess coefficient of the throat combustion-supporting air, the oxygen concentration of the combustion-supporting gas at the outlet of the burner block can be finely controlled. Generally, the oxygen concentration at the outlet of the burner block is controlled at 15%-18%. The central gas gun is made of 310S material. In the central gas riser tube and the central nozzle, because there is always a high-speed flowing combustible gas, the temperature can be effectively reduced to ensure the safety of the riser tube and the nozzle. In the central flue gas ejector tube, the entrained flue gas is the flue gas that has undergone partial heat exchange rather than the flame. Therefore, the temperature is generally lower than 1200°C. At the same time, the relatively low-temperature fuel gas is mixed in, and the overall temperature meets the use conditions of the 310S material, ensuring the use safety of the central gas gun assembly.

[0022] As described above, a central gas ejector type low-nitrogen burner based on gas staging. The burner block thereof ensures that the central flame and the peripheral flame are separated, delays the mixing of the combustion-supporting gas at the outlet of the burner block and the gas in the peripheral gas gun, forms a staged combustion structure, disperses the heat release volume and weakens the heat release intensity, and reduces the thermal type nitrogen oxide emissions. The high-temperature resistance characteristic of the burner block can ensure that the combustion-supporting air throat structure is not burned out. The burner block thereof is designed as a sudden expansion structure from the air inlet to the outlet direction below the hole or groove of the central flue gas ejector tube, which can prevent the combustion-supporting air from escaping from the burner block at the position of the hole or groove.

[0023] As described above, a central gas ejector type low-nitrogen burner based on gas staging. According to the gas ejection principle, the peripheral gas gun is designed as an ejection structure. The gas in the rising pipe of the peripheral gas gun forms a high-speed airflow through the nozzle and is injected into the peripheral flue gas ejection pipe. Under the action of the high-speed airflow, the flue gas mainly composed of inert gas in the combustion chamber is entrained into the peripheral flue gas ejection pipe. Under the action of strong turbulence, the gas and the flue gas are fully mixed in the central flue gas ejection pipe. The mixed peripheral mixed gas is mixed and burned with the low-oxygen-concentration combustion-supporting gas at the outlet of the burner brick. Each peripheral nozzle is provided with one spray hole, which is beneficial to increasing the entrainment amount of the flue gas. If multiple spray holes are provided for each nozzle, the distance between adjacent spray holes is too close, which will cause the entrained flue gases to interfere with each other, increase the air mass friction, reduce the ejection amount, and cannot achieve the dilution purpose. Since the mixed peripheral mixed gas contains a certain amount of inert gas, and the oxygen concentration of the combustion-supporting gas at the outlet of the burner brick is lower than the oxygen concentration of normal air, a stable flame is formed downstream of the peripheral gas outlet under the heat release of the central flame, and the flame temperature is relatively low, which can effectively control the generation amount of nitrogen oxides. The peripheral gas gun is made of 310S material. In the peripheral gas rising pipe and the peripheral nozzle, because there is always a high-speed flowing combustible gas, the temperature can be effectively reduced to ensure the safety of the rising pipe and the nozzle. In the peripheral flue gas ejection pipe, the entrained flue gas is the flue gas after partial heat exchange rather than the flame, so the temperature is generally lower than 1200 °C. At the same time, the relatively low-temperature fuel gas is mixed, and the overall temperature meets the use conditions of 310S material, ensuring the use safety of the peripheral gas gun assembly.

[0024] As described above, a central gas ejector type low-nitrogen burner based on gas staging, wherein the flame stabilizer of the burner has mounting holes matching the number of central gas spray guns to ensure that the central flue gas ejection pipe passes through the flame stabilizer to form a low-speed area and ensure the stability of the central flame; the flame stabilizer of the burner can adopt a flat type or a swirl type, and the setting of the swirl intensity can control the flame length; the flame stabilizer of the burner has mounting fasteners and can be installed on a cylinder such as an igniter gun to ensure stability. Description of the Drawings

[0025] Figure 1 This is the front view of a central gas ejector type low-nitrogen burner based on gas staging described in the present application.

[0026] Figure 2 This is the top view of a central gas ejector type low-nitrogen burner based on gas staging described in the present application.

[0027] Figure 3 This is the core component - the burner head of a central gas ejector type low-nitrogen burner based on gas staging described in the present application.

[0028] Description of the attached drawing reference numerals: 1. Central gas gun; 1-1. Central nozzle; 1-2. Central gas gun riser; 1-3. Central flue gas ejector; 1-4. Central nozzle positioning piece;

[0029] 2. Burner brick;

[0030] 3. Peripheral gas gun; 3-1. Peripheral nozzle; 3-2. Peripheral gas gun riser; 3-3. Peripheral flue gas ejector; 3-4. Peripheral nozzle positioning piece;

[0031] 4. Burner flame stabilizer; 4-1. Flame stabilizer body; 4-2. Flame stabilizer mounting fastener;

[0032] 5. Air inlet plenum; 5-1. Plenum body; 5-2. High-temperature heat insulation layer; 5-3. Combustion air inlet; 5-4. Mounting flange; 5-5. Plenum cylinder insulation layer;

[0033] 6. Gas collector; 6-1. Collector; 6-2. Fuel gas inlet;

[0034] 7. Ignition gun assembly; 8. Flame detector and ignition device. Detailed implementation mode

[0035] To make the objectives, technical solutions, and advantages of the present utility model clearer, the disclosed implementation modes of the present utility model will be further described in detail below with reference to the accompanying drawings.

[0036] The embodiment of the present application discloses a central gas ejector type low-nitrogen burner based on gas staging. To reduce the generation of nitrogen oxides and the structural safety of the burner, as Figure 1 shown, it includes a core structure - the burner head, including a central gas gun 1, a burner brick 2, a peripheral gas gun 3, and a burner flame stabilizer 4. And other components supporting the burner head, including an air inlet plenum 5, a gas collector 6, an ignition gun (or pilot light) assembly 7, and a flame detector and ignition device 8, where the flame detector and ignition device 8 is an optional item. The air inlet plenum 5 includes an insulation layer.

[0037] The burner block 2 is in an annular shape, and its internal space forms a combustion-supporting air passage. The burner block 2 penetrates through the bottom furnace castable and extends into the bottom furnace castable, and the inside of the bottom furnace castable is the furnace chamber. One end of the peripheral gas gun 3 extends into the bottom furnace castable and is located outside the burner block 2, and the other end is located outside the furnace chamber. One end of the central gas gun 1 extends into the bottom furnace castable and extends into the burner block 2 from the outside of the burner block 2, and the other end is located outside the furnace chamber. The gas collector 6 includes a collector 6-1 and a fuel gas inlet 6-2. The collector 6-1 is communicated with the ends of the peripheral gas gun 3 and the central gas gun 1 located outside the furnace chamber. The fuel gas inlet 6-2 is communicated with the collector 6-1 to introduce fuel gas into the peripheral gas gun 3 and the central gas gun 1. The air inlet air box 5 is arranged outside the bottom furnace castable and is communicated with the combustion-supporting air passage for introducing combustion-supporting air into the combustion-supporting air passage. The collector 6-1 is located outside the air inlet air box 5. The burner flame stabilizer 4 is arranged inside the burner block 2. One end of the ignition gun (or pilot burner) assembly 7 is located outside the air inlet air box 5, and the ignition part at the other end is connected to the burner flame stabilizer 4. The ignition part of the ignition gun (or pilot burner) assembly 7 extends out of the end face of the burner flame stabilizer 4 for igniting the central mixed gas ejected from the central gas gun 1. When the flame detector and ignition device 8 is optionally set, the flame detector and ignition device 8 is installed on the ignition gun for monitoring the ignition condition of the flame and for igniting the gas of the ignition gun (or pilot burner).

[0038] It should be noted that in this embodiment, the central gas gun 1 and the peripheral gas gun 3 are arranged outside the air inlet air box 5 and are communicated with the gas collector 6. The central gas gun 1 and the peripheral gas gun 3 can also be arranged in the air box cylinder heat insulation layer 5-5; similarly, the gas collector 6 can be arranged below the air inlet air box 5 and is directly welded or flexibly connected by a metal hose to the central gas gun 1 and the peripheral gas gun 3. The above achieve the same purpose through the change of the structural form and are regarded as equivalent to this embodiment. The specific structure of the air inlet air box 5 is not shown in this embodiment, but it does not mean that the air inlet air box 5 of this application does not have an air distribution and diversion device. The description of each component in this embodiment is only one expression method, and is regarded as equivalent under the condition of realizing the same function. For example, the "central nozzle" is only a kind of nozzle whose function is to eject fuel gas, and the ejected fuel gas enters the middle flame area to function as igniting and stabilizing the main flame.

[0039] It should be noted that the key point of this application is that the flame that plays the role of igniting the main flame and stabilizing the flame adopts the gas ejecting flue gas technology. Therefore, it is not limited to gas secondary staging or multi-stage staging, or deformations with equivalent effects.

[0040] It should be noted that this application is applicable to fuel gases with a gas pressure higher than 5 kPa and is not limited to a specific fuel gas.

[0041] Such as Figure 2and Figure 3 As shown, according to the principle of the gas ejector, the central gas gun 1 is designed as an ejector structure. In this embodiment, the central gas gun 1 is composed of a central gas gun riser 1-2 extending into the furnace, a central nozzle 1-1, a central flue gas ejector tube 1-3, and a central nozzle positioning piece 1-4. One end of the central gas gun riser 1-2 is connected to the central nozzle 1-1 and is exposed in the furnace outside the burner brick; a part of the central flue gas ejector tube 1-3 is exposed in the furnace outside the burner brick 2 and is coaxial with the axis of the central nozzle 1-1, and another part of the central flue gas ejector tube 1-3 passes through the burner brick 2 and extends into the combustion air passage; the outlet of the central flue gas ejector tube 1-3 is parallel to the outlet of the burner brick 2; among them, the central nozzle 1-1 is of a single orifice type. The end of the central gas gun riser 1-2 exposed in the furnace forms an angle c towards the axis direction of the burner brick 2, and the range of this angle is 40° to 60°, preferably 45° in this embodiment; the central gas gun riser 1-2 is coaxially welded to the central nozzle 1-1; each central nozzle 1-1 has one orifice, and the orifice of the central nozzle 1-1 is coaxial with the inlet end of the central flue gas ejector tube 1-3, and the end face distance is -20mm to 30mm (- indicates that the central nozzle 1-1 is inserted into the central flue gas ejector tube, and -20mm means that the central nozzle 1-1 is inserted 20mm into the central flue gas ejector tube 1-3); the central nozzle 1-1 and the central flue gas ejector tube 1-3 are positioned and fixed by the central nozzle positioning piece 1-4, and the fixing method is welding. Specifically, three evenly distributed central nozzle positioning pieces 1-4 are arranged along the circumference of the central nozzle 1-1. One end of the central nozzle positioning piece 1-4 is welded to the central gas gun riser 1-2, and the other end is welded to the central flue gas ejector tube 1-3. The diameter of the central flue gas ejector tube 1-3 is 1-4 times the diameter of the central gas gun riser 1-2. Through the above settings, there is a gap between the central nozzle 1-1 and the central flue gas ejector tube 1-3. When the gas is injected into the central nozzle 1-1, the flue gas is injected into the central flue gas ejector tube 1-3 through this gap. The central flue gas ejector tube 1-3 enters the combustion air passage after passing through the burner brick 2 and forms an angle parallel to the combustion air passage after passing through an angle b (the sum of the angles b and c is 180°), which is 135° in this embodiment; the material of the central gas gun 1 is selected as 310S high-temperature resistant stainless steel; the number of the central gas guns 1 is determined by the heat release load of the burner, and the range is 3-24, and 4 are preferably selected in this embodiment.

[0042] The distance from the outlet of the central flue gas ejector pipe 1-3 to the end face of the burner flame stabilizer 4 is L3. The size of L3 is related to the pneumatic parameters and physical and chemical properties of the fuel, and its range is 20 mm to 50 mm to improve the flame stabilization effect. In this embodiment, L3 is 50 mm; the distance from the outlet of the central flue gas ejector pipe 1-3 to the inner end of the burner nozzle brick 2 in the furnace bottom castable is L4. The size of L4 is related to the pneumatic parameters and physical and chemical properties of the fuel, and its range is 100 mm to 200 mm to improve the flame stabilization effect. In this embodiment, L4 is 150 mm.

[0043] The high-speed gas flow formed after the central gas passes through the central nozzle 1-1 is ejected into the central flue gas ejector pipe 1-3. Under the action of the high-speed gas flow, the high-temperature flue gas in the furnace is entrained and enters the central flue gas ejector pipe 1-3 together with the central gas for mixing and advancing to form central mixed gas. The central mixed gas starts to burn when it ejects from the outlet of the central flue gas ejector pipe 1-3.

[0044] The height of the peripheral gas gun 3 can be higher or lower than the outlet of the nozzle brick 2; when the height of the peripheral gas gun 3 is higher than the outlet of the nozzle brick 2, the part where the height of the peripheral gas gun 3 is higher than the outlet of the nozzle brick 2 ensures that the flame generated by the combustion of the central gas gun 1 will not directly burn on the body of the peripheral gas gun 3; when the height of the peripheral gas gun 3 is lower than the outlet of the nozzle brick 2, the gap should not be too large, otherwise after the mixed gas diffuses, part of the mixed gas is disturbed by the furnace flue gas flow field and deviates from the flame area, and cannot meet the combustion-supporting gas for combustion, forming unburned gas.

[0045] The nozzle brick 2 has holes or grooves matching the number of central gas spray guns to facilitate the arrangement of the central flue gas ejector pipes of the central gas spray guns; the material of the nozzle brick is LZ60 to LZ75 inorganic material, which can withstand a temperature of up to 1650 °C and be used for a long time; the nozzle brick 2 is below the hole or groove of the central flue gas ejector pipe and is designed as a sudden expansion structure from the air inlet to the outlet direction.

[0046] In this embodiment, the nozzle brick 2 adopts a multi-petal assembled structure. During installation, first insert the central flue gas ejector pipe 1-3 into the corresponding hole or groove. After positioning, the central nozzle 1-1 and the central flue gas ejector pipe 1-3 are positioned and fixed through the central nozzle positioning piece 1-4, and the fixing method is welding.

[0047] Such as Figure 2 and Figure 3As shown in the figure, in this embodiment, the peripheral gas gun 3 is composed of a peripheral gas gun riser 3-2 extending into the furnace, a peripheral nozzle 3-1, a peripheral flue gas entrainment pipe 3-3, and a peripheral nozzle positioning piece 3-4. The end of the peripheral gas gun riser 3-2 exposed in the furnace is coaxially welded to the peripheral nozzle 3-1; the peripheral flue gas entrainment pipe 3-3 is exposed in the furnace outside the burner brick 2. The peripheral flue gas entrainment pipe 3-3 can be parallel to the outlet of the burner brick or form an angle of 0-30° towards the axis of the outlet of the burner brick; among them, the peripheral nozzle is of a single orifice type. Each peripheral nozzle 3-1 has one orifice. The orifice of the peripheral nozzle 3-1 is coaxial with the inlet end of the peripheral flue gas entrainment pipe 3-3, and the end face distance is -20 mm to 30 mm (-20 mm means the peripheral nozzle 3-1 is inserted into the peripheral flue gas entrainment pipe 3-3); the peripheral nozzle 3-1 and the peripheral flue gas entrainment pipe 3-3 are positioned and fixed by the peripheral nozzle positioning piece 3-4, and the fixing method is welding. The outlet angle a of the peripheral flue gas entrainment pipe is 0 in this embodiment, that is, the outlet is parallel to the airflow at the outlet of the burner brick; the material of the peripheral gas gun 3 is 310S high-temperature resistant stainless steel; the number of the peripheral gas guns 3 is determined by the burner load, and the range is 3-24 pieces. In this embodiment, 4 pieces are preferred. And in this embodiment, the central gas gun 1 and the peripheral gas guns 3 are circumferentially staggered.

[0048] In another embodiment, the outlet of the peripheral flue gas entrainment pipe can also be bent towards the center of the burner brick 2. At this time, the angle between the axis of the outlet of the peripheral flue gas entrainment pipe and the direction of the combustion-supporting air injection is 0-30°. The peripheral gas forms a high-speed airflow and is ejected into the peripheral flue gas entrainment pipe 3-3 through the peripheral nozzle 3-1. Under the action of the high-speed airflow, the high-temperature flue gas in the furnace is entrained and enters the peripheral flue gas entrainment pipe 3-3 together with the peripheral gas for mixing and advancing to form peripheral mixed gas; since the peripheral gas gun 3 is arranged outside the burner brick 2 and the burner brick 2 has a certain thickness, the minimum distance between the axis of the peripheral gas gun 3 and the inner wall of the burner brick 2 is not less than 30 mm. In this embodiment, L5 is 60 mm. After the peripheral mixed gas is ejected, it can contact the combustion-supporting gas (low oxygen content) later. The peripheral mixed gas has a certain time to diffuse, the flame will be elongated, and the combustion reaction will be weakened. When the combustion reaction is weakened too much, bending the outlet of the peripheral flue gas entrainment pipe towards the center of the burner brick 2 is beneficial to maintaining its stable combustion.

[0049] The flame stabilizer 4 of the burner has mounting holes matching the number of the central gas guns to ensure that the central flue gas entrainment pipe passes through the flame stabilizer 4 of the burner to form a low-speed area and ensure the stability of the central flame; the flame stabilizer can be of a flat type or a swirl type.

[0050] In this embodiment, the flame stabilizer 4 of the burner consists of a flame stabilizer body 4-1 and a flame stabilizer mounting fastener 4-2. After the burner block 2 and the central flue gas ejector tube 1-3 are installed, the flame stabilizer 4 of the burner is positioned and fixed to the igniter through the flame stabilizer mounting fastener 4-2.

[0051] In this embodiment, a combustion technical solution of gas secondary staging is disclosed, in which sufficient combustion-supporting air is mixed and burned with the central mixed gas ejected from the central flue gas ejector tube 1-3 in the air duct in the burner block 2. The high-temperature burned flue gas (formed by the mixed combustion of the central mixed gas and part of the combustion-supporting air in the air duct in the burner block 2) and the unreacted combustion-supporting air are mixed to form a combustion-supporting gas (with an oxygen concentration lower than 21%), which is mixed and burned with the peripheral mixed gas ejected from the peripheral flue gas ejector tube.

[0052] In this embodiment, the combustion-supporting air enters the burner block 2 from the combustion-supporting air inlet 5-3 through the air inlet box 5, and the wind speed is reduced at the sudden expansion position of the burner block 2, and a corner vortex low-speed area is formed at the sudden expansion position. This prevents the combustion-supporting air from entering the furnace through the installation hole position of the central flue gas ejector tube 1-3 in the burner block 2.

[0053] In this embodiment, the central gas forms a high-speed air flow after passing through the central gas riser 1-2 and the central nozzle 1-1, and is ejected into the central flue gas ejector tube 1-3. Under the action of the high-speed air flow, the high-temperature flue gas in the furnace is entrained and enters the central flue gas ejector tube 1-3 together with the central gas for mixing and advancing to form the central mixed gas. The combustion-supporting air is mixed and burned with the central mixed gas ejected from the central flue gas ejector tube 1-3 after passing through the flame stabilizer body 4-1. Since the central mixed gas ejected from the central flue gas ejector tube 1-3 contains inert gas, the combustion intensity is greatly weakened, and the flame temperature is reduced to effectively control the generation of nitrogen oxides in the central flame. Under the action of the flame stabilizer body 4-1, the central flame forms a stationary flame of temperature, which ignites the main flame of the peripheral gas.

[0054] In this embodiment, the peripheral gas forms a high-speed air flow after passing through the peripheral gas riser 3-2 and the peripheral nozzle 3-1, and is ejected into the peripheral flue gas ejector tube 3-3. Under the action of the high-speed air flow, the high-temperature flue gas in the furnace is entrained and enters the peripheral flue gas ejector tube 3-3 together with the peripheral gas for mixing and advancing to form the peripheral mixed gas. Under the action of the burner block 2, the central flame and the peripheral flame are separated at the root, which helps to delay the mixing time of the peripheral flame. After the peripheral mixed gas is ejected, it has a certain time to diffuse and elongate, thereby weakening the combustion reaction. At the same time, the peripheral mixed gas diluted by the inert gas reduces the combustion reaction intensity, forming a lower temperature space to reduce the generation of nitrogen oxides in the peripheral flame.

[0055] The content not described in detail in the specification of this application belongs to the well-known technology of those skilled in the art.

[0056] The present application has been described in detail above in conjunction with specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present application. Those skilled in the art understand that, without departing from the spirit and scope of the present application, various equivalent substitutions, modifications, or improvements can be made to the technical solutions and their implementation manners of the present application, and all of these fall within the scope of the present application. The protection scope of the present application shall be subject to the appended claims.

Claims

1. A central gas ejector type low-nitrogen burner based on gas staging, characterized in that: It includes a central gas gun (1), a burner block (2), a peripheral gas gun (3) and a burner flame stabilizer (4). The burner block (2) is cylindrical. The cylindrical burner block (2) passes through the bottom furnace castable and extends into the inner side of the bottom furnace castable. The inner side of the bottom furnace castable is the furnace chamber. One end of the central gas gun (1) is located outside the bottom furnace castable, and the other end of the central gas gun (1) penetrates into the bottom furnace castable and then penetrates into the inner space of the burner block (2) from the outside of the burner block (2). One end of the peripheral gas gun (3) is located outside the bottom furnace castable, and the other end of the peripheral gas gun (3) penetrates into the bottom furnace castable and is located outside the burner block (2). One ends of the central gas gun (1) and the peripheral gas gun (3) located outside the bottom furnace castable are both used for introducing gas. The end of the cylindrical burner block (2) located outside the bottom furnace castable is communicated with an air inlet air box (5). The air inlet air box (5) is used for introducing combustion-supporting air into the burner block (2). The burner flame stabilizer (4) is arranged inside the burner block (2).

2. The central gas ejector type low-nitrogen burner based on gas staging according to claim 1, characterized in that: Along the air inlet direction of the air inlet air box (5) into the inside of the burner block (2), there are a first cavity and a second cavity in sequence inside the burner block (2). The diameter of the first cavity is smaller than that of the second cavity. The first cavity and the second cavity form a sudden-expansion structure. The central gas gun (1) extends into the second cavity.

3. A central gas ejector type low-nitrogen burner based on gas staging according to claim 1, characterized in that: The central gas gun (1) includes a central gas gun riser pipe (1-2), a central nozzle (1-1), a central flue gas ejection pipe (1-3) and a plurality of central nozzle positioning pieces (1-4). One end of the central gas gun riser pipe (1-2) is located outside the bottom furnace castable, and the other end extends into the inner side of the bottom furnace castable and the end is bent and connected to the central nozzle (1-1). One end of the central flue gas ejection pipe (1-3) is exposed in the furnace chamber outside the burner block (2) and is coaxial with the axis of the central nozzle (1-1). The other end of the central flue gas ejection pipe (1-3) penetrates through the burner block (2) and extends into the combustion-supporting air channel and is parallel to the flow direction of the combustion-supporting air. A plurality of central nozzle positioning pieces (1-4) are connected between the central nozzle (1-1) and the end of the central flue gas ejection pipe (1-3) exposed in the furnace chamber outside the burner block (2), so as to form a gap between the central nozzle (1-1) and the central flue gas ejection pipe (1-3), and flue gas is ejected into the central flue gas ejection pipe (1-3) from this gap.

4. A central gas ejector type low-nitrogen burner based on gas staging according to claim 3, characterized in that: The included angle c between the part of the central flue gas ejection pipe (1-3) located outside the burner block (2) and the flow direction of the combustion-supporting air is 40°-60°.

5. A central gas ejector type low-nitrogen burner based on gas staging according to claim 3, characterized in that: The distance from the outlet of the central flue gas ejection pipe (1-3) to the end face of the burner flame stabilizer (4) is L3, and the range of L3 is 20mm to 50mm.

6. A central gas ejector type low-nitrogen burner based on gas staging according to claim 3, characterized in that: The distance from the outlet of the central flue gas ejection pipe (1-3) to the inner end of the burner block (2) in the bottom furnace castable is L4, and the range of L4 is 100mm to 200mm.

7. The central gas ejector type low-nitrogen burner based on gas staging according to claim 3, characterized in that: The spray holes of the central nozzle (1-1) are coaxial with the inlet end of the central flue gas ejector pipe (1-3), and the end face distance between the end face of the central nozzle (1-1) and the inlet end of the central flue gas ejector pipe (1-3) is -20 mm to +30 mm; where, - indicates that the central nozzle (1-1) is inserted into the central flue gas ejector pipe (1-3), and + indicates that there is a gap between the end of the central nozzle (1-1) and the central flue gas ejector pipe (1-3) in the axial direction of the central nozzle (1-1).

8. A central gas ejector type low-nitrogen burner based on gas staging according to claim 1, characterized in that: The minimum distance between the axis of the peripheral gas gun (3) and the inner wall of the burner block (2) is not less than L5, and the value of L5 is not less than 30 mm.

9. A central gas ejector type low-nitrogen burner based on gas staging according to claim 1, characterized in that: The peripheral gas gun (3) includes a peripheral gas gun riser pipe (3-2), a peripheral nozzle (3-1), a peripheral flue gas ejector pipe (3-3) and a plurality of peripheral nozzle positioning pieces (3-4). One end of the peripheral gas gun riser pipe (3-2) is located outside the furnace, and the other end extends into the furnace and is connected to the peripheral nozzle (3-1). The spray holes of the peripheral nozzle (3-1) are coaxial with the inlet end of the peripheral flue gas ejector pipe (3-3). The peripheral nozzle (3-1) and the peripheral flue gas ejector pipe (3-3) are connected by a plurality of peripheral nozzle positioning pieces (3-4) to form a gap between the peripheral nozzle (3-1) and the peripheral flue gas ejector pipe (3-3), and the flue gas in the furnace is drawn into the peripheral flue gas ejector pipe (3-3) through this gap.

10. A central gas ejector type low-nitrogen burner based on gas staging according to claim 9, characterized in that: The angle between the axis of the outlet of the peripheral flue gas ejector pipe and the direction of the combustion-supporting air injection is 0, or the outlet of the peripheral flue gas ejector pipe is bent towards the center of the burner block (2). At this time, the angle between the axis of the outlet of the peripheral flue gas ejector pipe and the direction of the combustion-supporting air injection is 0-30°.

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