A flue gas internal circulation low nitrogen burner

Abstract

The present invention relates to a burner matched with a thermal energy device, specifically a flue gas internal circulation low nitrogen burner, comprising: an air duct, the outlet end of the air duct has a reduced diameter pipe, and the tail end of the reduced diameter pipe is connected to an annular pipe; an annular ejector, the annular ejector comprises an inner ring and an outer ring, the annular pipe is arranged between the inner ring and the outer ring, an annular air nozzle is formed between the annular pipe and the inner ring, a swirl disk is arranged in the inner ring, and the swirl disk is arranged coaxially with the air duct; a primary gas pipe, the primary gas pipe is located at the center of the air duct and vertically penetrates the swirl disk; a secondary gas pipe, the secondary gas pipe is connected to the primary gas pipe and is arranged between the inner ring and the annular pipe; a tertiary gas pipe, the tertiary gas nozzle is evenly arranged on the periphery of the air duct. The present invention fully utilizes the kinetic energy of the gas and air by setting two-stage combustion-supporting air and three-stage gas, mixes a large flow of flue gas into the air and gas, reduces the combustion reaction speed, reduces the temperature of the flame, and thus controls the generation concentration of NOx.

Description

Technical Field

[0001] The invention relates to a burner matched with thermal energy equipment, in particular to a flue gas internal circulation low-nitrogen burner. Background Art

[0002] Burners are widely used in various fields of the national economy. With the continuous increase in the use of domestic natural gas resources, the control of harmful gas emissions has become increasingly strict. Natural gas is widely replacing coal and fuel oil and becoming the main clean energy. In addition, the country's requirement to launch a blue sky defense war has put forward strict requirements on harmful components such as nitrogen oxides in the flue gas emitted by burners. In Beijing, Tianjin and Hebei and other regions, it has been raised to an ultra-low nitrogen oxide emission level of less than 30mg / Nm3. Compared with the previous national standard of 150mg / m3, it has been greatly improved and reached the highest standard stipulated by some developed countries in the world. This not only puts high standards and strict requirements on users of burners, but also challenges the development and manufacturing technology of burners.

[0003] Therefore, it is particularly necessary to improve the existing burners, enhance the burners' ability to introduce flue gas, and further suppress the generation of NOx. Summary of the invention

[0004] In order to solve the problems in the above-mentioned background technology, the present invention provides a flue gas internal circulation low-nitrogen burner, which fully utilizes the kinetic energy of the gas and air by arranging two-stage combustion air and three-stage fuel gas, and mixes a larger flow of flue gas into the air and fuel gas, thereby reducing the combustion reaction speed and the flame temperature, thereby controlling the NOx generation concentration.

[0005] The present invention adopts the following technical solution: a flue gas internal circulation low nitrogen burner, comprising:

[0006] The outlet end of the air duct has a reducing pipe that contracts radially inwards, and the tail end of the reducing pipe is connected to an annular pipe;

[0007] The annular ejector comprises an inner ring and an outer ring which are arranged concentrically, wherein the diameter of the inner ring is smaller than the diameter of the annular tube, and the diameter of the outer ring is larger than the diameter of the annular tube, the annular tube is arranged between the inner ring and the outer ring, an annular air nozzle is formed between the annular tube and the inner ring, a swirl disk is arranged in the inner ring, and the swirl disk is arranged coaxially with the air duct and the inner ring;

[0008] A first-level gas pipe, which is located at the center of the air duct and vertically penetrates the swirl disk. A first gas nozzle is circumferentially arranged at the tail end of the first-level gas pipe;

[0009] A secondary gas pipe, which is connected to the primary gas pipe and is arranged between the inner ring and the annular pipe. A second gas nozzle is circumferentially arranged at the tail end of the secondary gas pipe;

[0010] Three-stage gas pipes and three-stage gas nozzles are evenly distributed around the periphery of the air duct and connected to the gas header;

[0011] A first mixed gas inlet is formed between the outer ring and the annular tube.

[0012] Furthermore, the inner ring includes an inner ring mixing tube and an inner ring diffuser, the outer ring includes an outer ring contraction tube, an outer ring mixing tube and an outer ring diffuser, the small diameter end of the outer ring contraction tube is connected to the outer ring mixing tube, a first gas mixing inlet is formed between the outer ring contraction tube and the annular tube, the inner ring mixing tube and the outer ring mixing tube are arranged correspondingly, the inner ring diffuser and the outer ring diffuser are arranged correspondingly, and the tail end of the annular tube is located between the inner ring mixing tube and the outer ring mixing tube.

[0013] Furthermore, the inner ring diffuser tube and the outer ring diffuser tube are both one of a conical ring and a cylindrical ring.

[0014] Furthermore, the inner ring mixing tube and the outer ring mixing tube form an annular mixing section, the cross-sectional area of ​​the annular mixing section is 2-3 times the outlet area of ​​the annular air nozzle, the length of the annular mixing section is 2-3 times the length of the annular air nozzle, the inner ring diffuser tube and the outer ring diffuser tube form an annular diffuser section, the length of the annular diffuser section tube is 2-5 times the length of the annular air nozzle.

[0015] Furthermore, the three-level gas pipe includes a first-level three-level gas pipe and a second-level three-level gas pipe. The first-level three-level gas pipe is formed by connecting a venturi-divergent tube, a gas branch pipe nozzle and a gas branch pipe in sequence, and the second-level three-level gas pipe is formed by connecting a free jet gas nozzle and a gas branch pipe. The first-level three-level gas pipe and the second-level three-level gas pipe are arranged at an annular interval on the periphery of the air duct, and the other end of the gas branch pipe is connected to the gas header. The connection between the venturi-divergent tube and the gas branch pipe nozzle forms a second gas mixing inlet.

[0016] Furthermore, the three-stage gas pipe includes a first-stage three-stage gas pipe, which is formed by connecting a venturi-divergent tube, a gas branch pipe nozzle and a gas branch pipe in sequence. The first-stage three-stage gas pipe is arranged around the periphery of the air duct, and the other end of the gas branch pipe is connected to the gas manifold. The connection between the venturi-divergent tube and the gas branch pipe nozzle forms a second gas mixing inlet.

[0017] Furthermore, the three-level gas pipe includes a second-level three-level gas pipe, which is formed by connecting a free jet gas nozzle and a gas branch pipe. The second-level three-level gas pipe is arranged around the periphery of the air duct, and the other end of the gas branch pipe is connected to the gas header.

[0018] Furthermore, a curved pipe is provided at the outlet end of the venturi convergent tube, and the curved pipe is bent inwards.

[0019] Furthermore, an ignition device is provided at the air inlet end of the swirl disk in the air duct, and an ignition hole corresponding to the ignition device is provided on the first-level gas pipe.

[0020] Furthermore, the burner also includes a fan, which is connected to the inlet end of the air duct, a damper is provided at the air inlet of the fan, a smoke channel is provided on the side of the air inlet of the fan, a smoke channel is provided with a smoke butterfly valve, a high-voltage electronic igniter is also provided on the fan casing, the high-voltage igniter is connected to the ignition device in the air duct, and a flame detector is also provided on the side of the air duct.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The flue gas internal circulation low-nitrogen burner of the present invention is provided with two-stage combustion air and three-stage fuel gas, which fully utilizes the kinetic energy of fuel gas and air, mixes a large flow of flue gas into the air and fuel gas, reduces the combustion reaction speed, reduces the flame temperature, and thus controls the NOx generation concentration.

[0023] (2) The primary gas and secondary gas jets of the flue gas internal circulation low-nitrogen burner of the present invention intersect vertically with the air jet to achieve rapid mixing, and the primary gas is acted upon by the rotating air jet of the swirl disk to make the combustion flame a diffuse flame, which is stable and can be used as a duty fire to ignite the other two levels of combustible gases.

[0024] (3) The flue gas internal circulation low-nitrogen burner of the present invention is arranged on a three-level gas pipe outside the burner. According to different working conditions and characteristics of the thermal equipment, the first-level three-level gas pipe or the second-level three-level gas pipe is arranged on the periphery of the air duct, or the first-level three-level gas pipe and the second-level three-level gas pipe are arranged at the same time to achieve the effect of sucking the flue gas.

[0025] (4) The flue gas internal circulation low nitrogen burner of the present invention is provided with an annular ejector to form an annular air nozzle. Secondary air is ejected from the annular air nozzle at a high speed, so that the inner boundary of the jet is close to the inner ring surface of the annular ejector to form an attached jet, and negative pressure is formed in the annular ejector, so that the surrounding flue gas is sucked into the annular mixing section. After the air and flue gas are mixed in the annular mixing section, they enter the annular diffuser, the flow velocity is reduced, and the static pressure is increased. After mixing with the gas ejected from the second gas nozzle, they are sprayed into the combustion zone at a lower speed.

[0026] (5) The flue gas internal circulation low-nitrogen burner of the present invention can adapt to different working conditions by means of different designs of the inner ring diffuser and the outer ring diffuser, has a wide range of applications, and has a good nitrogen reduction effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 It is a three-dimensional diagram of the overall structure of the flue gas internal circulation low nitrogen burner of the present invention;

[0029] Figure 2 It is a cross-sectional structural stereogram of the flue gas internal circulation low nitrogen burner of the present invention;

[0030] Figure 3 It is a cross-sectional plan view of the flue gas internal circulation low nitrogen burner of the present invention;

[0031] Figure 4 for Figure 3 Middle AA section view;

[0032] Figure 5 The three-stage gas pipe arrangement of the flue gas internal circulation low nitrogen burner of the present invention Figure 1 ;

[0033] Figure 6 The three-stage gas pipe arrangement of the flue gas internal circulation low nitrogen burner of the present invention Figure 2 ;

[0034] Figure 7 The three-stage gas pipe arrangement of the flue gas internal circulation low nitrogen burner of the present invention Figure 3 ;

[0035] Figure 8 The three-stage gas pipe arrangement of the flue gas internal circulation low nitrogen burner of the present invention Figure 4 ;

[0036] Fig. 9 It is a structural diagram of the inner cone ring annular ejector of the flue gas internal circulation low nitrogen burner of the present invention;

[0037] Fig.10 This is a structural diagram of the outer cone ring annular ejector of the flue gas internal circulation low nitrogen burner of the present invention;

[0038] Fig.11 It is a structural diagram of a double cone ring annular ejector of a flue gas internal circulation low nitrogen burner of the present invention;

[0039] Fig.12 It is a gas flow diagram of the fuel gas, air and flue gas of the flue gas internal circulation low nitrogen burner of the present invention;

[0040] Among them: 1-air duct, 11-reducing tube, 12-annular tube, 2-annular ejector, 21-inner ring, 210-inner ring mixing tube, 211-inner ring diffuser, 22-outer ring, 220-outer ring contraction tube, 221-outer ring mixing tube, 222-outer ring diffuser, 23-annular air nozzle, 24-first gas mixing inlet, 25-annular mixing part, 26-annular diffuser, 27-swirl disk, 3-first gas pipe, 31-first gas nozzle, 4-secondary gas pipe, 41-second gas nozzle, 5-first and third gas pipes, 51-Venturi convergence tube, 52-gas branch pipe Nozzle, 53-gas branch pipe, 54-second mixed gas inlet, 55-elbow pipe, 6-second stage three-stage gas pipe, 61-free jet gas nozzle, 7-ignition device, 71-ignition electrode, 8-fan, 81-damper, 82-smoke butterfly valve, 83-valve actuator, 84-high-voltage electronic igniter, 85-flame detector, 86-motor, 87-air inlet, 88-servo motor, 9-gas main line, 91-solenoid valve, 92-gas butterfly valve, 93-valve controller, 94-gas header, 95-first gas pipeline, 96-second gas pipeline, 10-electric control box. DETAILED DESCRIPTION

[0041] The following will be combined with the accompanying drawings in the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0042] like Figure 1-12 As shown, this embodiment provides a flue gas internal circulation low nitrogen burner, comprising:

[0043] The outlet end of the air duct 1 is provided with a reducing pipe 11 which contracts radially inwards, and the tail end of the reducing pipe 11 is connected with an annular pipe 12, the large diameter end of the reducing pipe 11 is fixedly connected to the outlet end of the air duct 1, and the small diameter end of the reducing pipe 11 is fixedly connected to one end of the annular pipe 12, and the connection between the air duct 1, the reducing pipe 11 and the annular pipe 12 is sealed, and air, gas and smoke cannot pass through the connection;

[0044] The annular ejector 2 comprises an inner ring 21 and an outer ring 22 which are arranged concentrically. The diameter of the inner ring 21 is smaller than the diameter of the annular tube 12, and the diameter of the outer ring 22 is larger than the diameter of the annular tube 12. The annular tube 12 is arranged between the inner ring 21 and the outer ring 22. An annular air nozzle 23 is formed between the annular tube 12 and the inner ring 21. A swirl disk 27 is arranged in the inner ring 21 coaxially with the air duct 1 and the inner ring 21. The outer diameter of the swirl disk 27 is slightly smaller than the inner diameter of the inner ring 21 at the position where the swirl disk 27 is located. A first air mixing inlet 24 is formed between the outer ring 22 and the annular tube 12. Specifically, the outer wall of the reducing tube 11 at the outlet end of the air duct 1 can not only guide the smoke entering through the first air mixing inlet 24, but also collect and compress the air flow through the inner wall of the reducing tube 11 to increase the flow rate of the air flow.

[0045] Through the above-mentioned arrangement, this embodiment divides the combustion-supporting air into two levels. The primary air is a rotating air jet formed in the swirl disk 27 of the inner ring 21. The purpose of using the rotating air jet is to form a low-speed reflux zone of the mixed gas near the center of the burner head, which can produce a good effect of stabilizing the central flame and help to strengthen the mixing of air, fuel gas and flue gas entering the burner head; the secondary air is an attached jet ejected by the annular air nozzle 23 on the annular ejector 2. The purpose is to increase the surface area of ​​the air jet and produce the effect of sucking more flue gas. The annular ejector 2 has a wider power adaptation range and is suitable for a full range of burners of large, medium and small powers.

[0046] Furthermore, this embodiment divides the gas into three levels, namely:

[0047] Primary gas: The gas ejected from the primary gas pipe 3. The primary gas pipe 3 is located at the central axis of the air duct 1 and vertically penetrates the swirl disk 27. The tail end of the primary gas pipe 3 (i.e., the position passing through the swirl disk) is circumferentially provided with a first gas nozzle 31, and the axis of the primary gas pipe 3 coincides with the axis of the air duct 1. Specifically, the primary gas pipe 3 is cylindrical or stepped cylindrical, and a plurality of (generally 4-20) first gas nozzles 31 are arranged on the outer cylindrical surface of the tail end of the primary gas pipe 3 (i.e., the outer cylindrical surface passing through the swirl disk 27). At the same time, a baffle is provided at the end of the primary gas pipe 3, so that the gas can only be ejected from the first gas nozzle 31. After the first gas is ejected from the first gas nozzle 31, a free jet of gas is formed. The free jet direction of the first gas is perpendicular to the axis of the air duct 1. The ejected first gas intersects with the rotating jet of air ejected axially from the swirl disk 27 to achieve rapid mixing. In this embodiment, an ignition device 7 is provided at the air inlet end of the swirl disk 27 in the air duct 1, and an ignition hole corresponding to the ignition device 7 is provided on the first-level gas pipe 3. The first gas is mixed with the rotating air jet and ignited by the ignition device 7 (the ignition device also includes an ignition electrode 71) to achieve combustion. Due to the effect of the rotating air jet, the flame is a diffusion flame, which is very stable and can be used as the duty fire of the burner to ignite the other two levels of gas. It should be noted that according to the national burner technical requirements, if the burner power is greater than 1200KW, an independent ignition fire must be provided.

[0048] Secondary gas: gas ejected from the secondary gas pipe 4, the secondary gas pipe 4 is connected with the primary gas pipe 3, and the secondary gas pipe 4 is arranged between the inner ring 21 and the annular pipe 12, and a second gas nozzle 41 is circumferentially arranged at the tail end of the secondary gas pipe 4; specifically, the secondary gas pipe 4 has a jet portion, the jet portion is parallel to the axis of the air duct 1, and the jet portion extends out of the combustion head for a certain distance, and a second gas nozzle 41 is circumferentially arranged at the tail end of the jet portion, and a baffle is also provided at the tail end of the second gas pipe 4 (i.e., the tail end of the jet portion), so that the second gas can only be ejected from the second gas nozzle 41, and the second gas forms a free jet after being ejected from the second gas nozzle 41, and the free jet direction of the second gas is perpendicular to the axis of the air duct 1, the ejected second gas intersects and mixes with the air jet ejected from the annular air nozzle 23, and is ejected to the outlet direction of the combustion head, ignited and burned by the on-duty fire, and then Figure 2 It can be seen that the secondary gas pipe 4 is not a straight pipe, but has a bent portion. The inlet end of the secondary gas pipe 4 is connected to the primary gas pipe 3, and after extending a distance to the periphery of the primary gas pipe 3, it bends and connects to the injection portion.

[0049] Tertiary gas: gas ejected from the tertiary gas pipe, which is evenly distributed around the periphery of the air duct 1 , and is connected to the gas header 94 , through which the gas is transported to the tertiary gas pipe.

[0050] See also Figure 1 , Figure 2 , Figure 3 , Figure 5 , Figure 6 The three-stage gas pipe of this embodiment includes a venturi convergent tube 51, a free jet gas nozzle 61, a gas branch pipe nozzle 52 and a gas branch pipe 53. The venturi convergent tube 51 includes an expanded diameter section and a reduced diameter section. The diameter of the expanded diameter section is larger than the diameter of the reduced diameter section, and the expanded diameter section and the reduced diameter section are smoothly connected. The venturi convergent tube 51, the gas branch pipe nozzle 52 and the gas branch pipe 53 are sequentially connected to form a first-stage three-stage gas pipe 5. The connection between the venturi convergent tube 51 and the gas branch pipe nozzle 52 forms a second mixed gas inlet 54. The free jet gas nozzle 61 and the gas branch pipe 53 are connected to form a second-stage three-stage The gas pipe 6, two types of three-stage gas pipes are arranged at intervals in a ring around the periphery of the air duct 1, wherein the other ends of the gas branch pipes 53 are connected to the gas header 94, and the second mixing inlet 54 is formed at the connection between the expanded diameter section of the venturi convergent tube 51 and the gas branch pipe nozzle 52. The third gas enters the expanded diameter section of the venturi convergent tube 51 through the gas branch pipe nozzle 52, and the kinetic energy of the high-speed gas jet is used to guide the smoke from the surrounding environment into the venturi convergent tube 51 through the second mixing inlet 54, where it is mixed with the gas jet and accelerated, and then sprayed into the flame at a relatively fast speed through the front end of the venturi convergent tube 51 to be ignited and burned. The present embodiment does not limit the spacing arrangement of the first-level three-stage gas pipe 5 and the second-level three-stage gas pipe 6. The first-level three-stage gas pipe 5 and the second-level three-stage gas pipe 6 can be arranged in sequence, and the free jet gas nozzle 61 on the second-level three-stage gas pipe 6 ejects high-speed gas. The high-speed gas flow in the turbulent state has a strong suction effect on the surrounding flue gas, and the flue gas is entrained into the gas, mixed with the gas, and ejected forward into the flame. This arrangement is suitable for burning high-calorific value gas, can more effectively reduce the flame temperature, avoid excessive nitrogen oxides, and is suitable for large and medium power burners. A second-level three-stage gas pipe 6 can also be arranged between every two first-level three-stage gas pipes 5. This arrangement is suitable for small and medium power burners and the working conditions of burning general calorific value gas.

[0051] It can be understood that the above arrangement of the three-stage gas pipe has the following effects:

[0052] Since the fully automatic burner adopts a low-pressure gas supply method (generally lower than 20KPa), the kinetic energy of the low-pressure gas jet is relatively small, and the amount of flue gas introduced through the venturi convergent tube 51 is limited, which cannot reach the flue gas mixing amount required for ultra-low nitrogen combustion. However, the speed of the mixed gas ejected from the venturi convergent tube 51 is relatively high, and the mixed gas can be sent to a position farther in front of the combustion head for combustion. This embodiment adopts a free jet to make up for the insufficient amount of flue gas introduced by the venturi convergent tube 51. The gas ejected from the free jet gas nozzle 61 can entrain more flue gas, and the jet speed decays faster. The free mixed jet can deliver the mixed gas to a position closer to the combustion head for combustion. The two types of three-stage gas pipes can form an effect of alternating distribution of the mixed gas front and back, which helps to reduce the concentration of gas in the front of the combustion head, relieve local high temperature, and help control the amount of NOx generated. The first-stage three-stage gas pipe 5 and the second-stage three-stage gas pipe 6 are arranged at intervals, which can also ensure that each free jet mixed gas is not disturbed by the surrounding jets, which is conducive to entraining more flue gas.

[0053] It can be understood that when high calorific value fuel gas is mixed with flue gas (an inert gas), it becomes low calorific value fuel gas, and its calorific value is significantly reduced. Therefore, the combustion speed and combustion temperature are also significantly reduced, which will produce a significant effect of controlling NOx generation. This is the purpose of mixing peripheral fuel gas into flue gas.

[0054] It can also be known that when the burner is burning, the flame at the front position of the burner, near the central axis of the burner head, has a high flame temperature due to poor heat dissipation conditions; the peripheral flame has good heat dissipation conditions, so the flame temperature is low. According to the distribution law of the flame, the gas volume is reasonably distributed on the front end surface of the burner head, that is, the gas volume is distributed in a way that the center gas volume is the least, the middle gas volume is the second, and the periphery gas volume is the most, so as to achieve the purpose of reducing the peak value of the flame temperature. The present invention divides the gas into three levels, which are arranged in a ring shape from the axis of the burner head to the periphery. Generally, the center gas volume is less than 10% of the total gas volume, the middle gas volume is about 20%, and the peripheral gas volume is not less than 65%, and a large-diameter burner head is used to reduce the peak value of the center flame temperature.

[0055] See also Figure 7 In other embodiments, only the first-stage three-stage gas nozzle 5 is arranged on the periphery of the air duct 1. This arrangement is suitable for the burner's gas with lower calorific value, as well as the working conditions of a large furnace, good heat dissipation and lower temperature. It can avoid incomplete combustion and excessive carbon monoxide due to the local combustion temperature being too low, and is suitable for low-power burners.

[0056] See also Figure 8 In other embodiments, only the second-stage and third-stage gas nozzles 6 are arranged on the periphery of the air duct 1. This arrangement does not require a high injection capacity, is suitable for lower gas pressures, is suitable for high-power burners, and is very suitable for burners installed vertically upward.

[0057] For details, see Figure 1 , Figure 2 , Figure 3 , Figure 5 , Figure 6 The outlet end of the venturi convergent tube 51 is provided with a curved tube 55, which is bent inwardly. The mixed airflow is guided to the center of the flame through the curved tube 55 to achieve complete combustion of the fuel gas.

[0058] Specifically, the annular ejector 2 includes an inner ring 21 and an outer ring 22, wherein the inner ring 21 includes an inner ring mixing tube 220 and an inner ring pressure diffuser 221, and the outer ring 22 includes an outer ring shrink tube 220, an outer ring mixing tube 221 and an outer ring pressure diffuser 222, the small diameter end of the outer ring shrink tube 220 is connected to the outer ring mixing tube 221, the large diameter end of the outer ring shrink tube 220 is located above the annular tube 12, and a first mixing tube is formed between the outer ring shrink tube 220 and the annular tube 12. An air inlet 24, an annular air nozzle 23 is formed between the annular tube 12 and the inner ring mixing tube 210, part of the inner ring mixing tube 210 is arranged correspondingly with the outer ring mixing tube 221 to form an annular mixing section 25; the inner ring diffuser 211 and the outer ring diffuser 222 are arranged correspondingly to form an annular diffuser 26; the tail end of the annular tube 12 is located between the inner ring mixing tube 210 and the outer ring mixing tube 221 or between the outer ring contraction tube 220 and the inner ring mixing tube 210.

[0059] Specifically, the inner ring diffuser tube 211 and the outer ring diffuser tube 222 are both conical rings and cylindrical rings, including the following configurations:

[0060] The first type is an inner cone ring ejector, which is suitable for low-power burners; see Fig. 9 The inner diffuser 210 of the annular ejector is a conical ring, the large diameter end of the conical ring is fixedly connected to the tail end of the inner ring mixing tube 211, and the small diameter end of the conical ring extends to a position away from the air duct 1; the outer ring diffuser 222 is a cylindrical ring, the outer diameter of the cylindrical ring is the same as the outer diameter of the outer ring mixing tube 221, the inner ring diameter of this type of ejector is relatively small, the first-level gas pipe 3, the swirl disk 27, and the ignition device 7 are all arranged in the inner ring, and the space is relatively narrow. The inner ring diffuser 211 is designed as a conical ring, which is conducive to increasing the inner ring diameter of the annular ejector 2, that is, increasing the diameter of the annular air nozzle 23. Under the premise of ensuring the required outlet area of ​​the annular air nozzle 23, the annular seam width of the annular air nozzle 23 is reduced. The annular seam width is closely related to other dimensions of the annular ejector, so it is conducive to reducing the overall size of the annular ejector, making the combustion head structure more compact, and reducing the flame directness, which can adapt to the working conditions of a small diameter furnace.

[0061] The second type is an outer cone ring ejector, which is suitable for high-power burners; see Fig.10, the inner ring diameter of the annular ejector is relatively large, and the inner ring diffuser 211 adopts a cylindrical ring to facilitate the arrangement and support of the cyclone disk 27 and the ignition device 7. For high-power burners, controlling the flame temperature is the main purpose. The outer ring diffuser 222 adopts a conical ring, and the small diameter end of the conical ring is fixedly connected to the tail end of the outer ring diffuser 222, and the large diameter end of the conical ring extends away from the air duct 1. The outer cone ring scheme can lead the secondary air to the surrounding space, which helps to increase the diameter of the main flame and reduce the heat intensity of the flame center, thereby reducing the center flame temperature. The flames distributed on the periphery can better exchange heat with the boiler water-cooled wall, effectively reducing the main flame temperature. It is conducive to the full mixing of the free jet gas flow and the combustion-supporting air, and can better match the second-stage and third-stage gas pipes using free jet nozzles to achieve complete combustion of the gas and reduce the generation of carbon monoxide. The use of free jet is conducive to the introduction of more flue gas to reduce the combustion temperature.

[0062] The third type is a double cone ring annular ejector, which is suitable for medium power burners. Fig.11 The double-cone ring annular ejector has the advantages of the inner cone ring annular ejector and the outer cone ring annular ejector. The double-cone ring annular ejector has a smaller resistance, which is conducive to ejecting more smoke under low wind pressure and has a certain power saving effect.

[0063] Specifically, the annular ejector 2 is designed to have an ejection capacity of 15%-20% of the total smoke volume, and the parameters of the annular ejector are determined based on this. The inner ring mixing tube 210 and the outer ring mixing tube 221 of the present invention constitute an annular mixing section 25, and the cross-sectional area of ​​the annular mixing section 25 is 2-3 times the outlet area of ​​the annular air nozzle 23, and the length of the annular mixing section 25 is 2-3 times the length of the annular air nozzle 23. The inner ring diffuser 211 and the outer ring diffuser 222 constitute an annular diffuser 26, and the length of the annular diffuser 26 is 2-5 times the length of the annular air nozzle 23, and the cone angles of the inner ring diffuser 211 and the outer ring diffuser 222 are 8-15°. The above parameters enable the annular ejector to have good smoke ejection capacity.

[0064] Specifically, the diameter of the air duct 1 is larger than the outer diameter of the annular air nozzle 23. The outer ring of the annular air nozzle 23 is connected to the air duct 1 through a reducing tube 11, thereby converting a low-speed air flow into a high-speed air flow. By using a small-angle reducing tube 1, the local resistance loss of the airflow can be controlled at a lower value.

[0065] The secondary air of the present invention is ejected at a high speed from the annular air nozzle 23, so that the inner boundary of the jet is in close contact with the inner annular surface of the annular ejector 2, forming an attached jet, forming a negative pressure in the annular ejector 2, and sucking the surrounding flue gas into the annular mixing section 25. After the air and flue gas are mixed in the annular mixing section 25, they enter the annular diffuser 26, the flow velocity is reduced, the static pressure is increased, and after mixing with the gas ejected from the second gas nozzle 41, they are ejected into the combustion zone at a lower speed.

[0066] It should be noted that a small portion of the combustion-supporting air entering the burner quickly flows through the swirl disk 27 located in the center. The swirl disk 27 is made of multiple overlapping blades that are at a certain angle to the axis of the air duct 1, and an air channel is provided between adjacent blades. When the air flows through the swirl disk 27, an air jet rotating around the central axis is formed under the guidance of the blades. The rotating jet has a good mixing effect, which can not only quickly mix with the primary fuel gas, but also quickly mix with the surrounding mixed gas jets, which is conducive to the rapid mixing of air, fuel gas, and flue gas, and the rapid combustion of the combustible mixture, reducing the problems of combustible gas staying, being heated, the combustion temperature rising, or cracking into carbon particles due to low mixing speed.

[0067] Specifically, the parts used in the burner of this embodiment are all made of heat-resistant steel.

[0068] For further information, see Figure 3 , Figure 4 The burner also includes a fan 8, which is connected to the inlet end of the air duct 1 and is controlled by an electric control box 10. At this point, the main parts of the burner are connected together to form an integrated burner, in which the fan 8 provides the required combustion-supporting air for combustion and overcomes the flue gas back pressure in the furnace during combustion. A damper 81 is set at the air inlet of the fan 8, and the air supply at the air inlet is automatically adjusted by a servo motor 88; the fan 8 is started by a motor 86, and a small-diameter flue gas channel is set on the side of the air inlet of the fan 1, and a flue gas butterfly valve 82 is configured, which is controlled by a valve actuator 82 and is used as a channel for mixing a small amount of flue gas when burning wet natural gas with a high calorific value. Mixing flue gas can further reduce the amount of NOx generated.

[0069] Specifically, a high-voltage electronic igniter 84 is installed on the housing of the fan 1, and is connected to the ignition device 7 located in the air duct 1 and in front of the swirl disk 27 through a high-voltage cable. A flame detector 85 is set on the side of the air duct 1 to detect whether the ignition is successful or not, and whether the main flame is established and maintained.

[0070] Furthermore, the three-stage gas of this embodiment is independently supplied by two groups of pipelines, the first-stage gas and the second-stage gas are supplied by the first gas pipeline 95, and the third-stage gas is supplied by the second gas pipeline 96. Gas butterfly valves 92 are provided at the inlet ends of the two groups of pipelines. Since the gas flow rate of the first gas pipeline 95 is significantly greater than the gas flow rate of the second gas pipeline 96, the gas flow rates of the first gas pipeline 95 and the second gas pipeline 96 are significantly different, and generally two gas butterfly valves 92 of different calibers are provided. The openings of the two gas butterfly valves 92 are adjusted by two valve controllers 93 respectively. The main gas pipeline 9 is connected to two solenoid valves 91 connected in series, and is connected to the two gas butterfly valves 92 through branch pipelines.

[0071] The working principle of the present invention is as follows:

[0072] Before ignition, the fan 8 is started to deliver combustion-supporting air to the air duct 1. A small part of the air is transformed into a rotating jet through the swirl disk 21, and most of the air is ejected through the annular air nozzle 23 to form an attached jet, which draws the surrounding smoke into the annular ejector 2. The gas enters the ignition pipeline and the two gas butterfly valves through two series-connected solenoid valves 91 respectively. The high-voltage electronic igniter 84 generates an electric spark between the ignition electrodes of the ignition device 7, ignites the gas ejected from the primary gas pipe 4, and forms an ignition flame. The flame passes through the swirl disk 27 to ignite the primary gas and establish the duty fire. Driven by the central air rotating jet formed by the swirl disk 27, the duty fire ignites the secondary gas to burn, forming a stronger main flame, and then ignites the tertiary gas and flue gas mixture injected into the main flame, thereby forming a stable combustion flame in the furnace.

[0073] Specifically, the flame is characterized by a small amount of gas in the center and a large amount of gas in the periphery, and the flame temperature in the center and the periphery tends to be uniform; the kinetic energy of the gas and air is fully utilized, a large flow of flue gas is mixed into the air and gas, the combustion reaction speed is reduced, the flame temperature is reduced, and the NOx generation concentration is controlled.

[0074] When the fuel gas is associated with oil well moisture with a high light hydrocarbon content and high calorific value, or other reasons cause the flame temperature to be high and the NOx generation concentration cannot be stably controlled within 30mg / Nm3, a small amount of flue gas (FGR) is introduced into the combustion air through the flue gas butterfly valve located on the air inlet of the fan to further control the flame temperature and reduce NOx.

[0075] The present invention is further described above with the aid of specific embodiments. However, it should be understood that the specific description here should not be construed as limiting the essence and scope of the present invention. Various modifications made to the above embodiments by ordinary technicians in the field after reading this specification are all within the scope of protection of the present invention.

Claims

1. A flue gas internal circulation low nitrogen burner, It is characterized in that include: An air duct, wherein the outlet end of the air duct has a reducing pipe that contracts radially inwards, and the tail end of the reducing pipe is connected to an annular pipe; An annular ejector, the annular ejector comprises an inner ring and an outer ring which are arranged concentrically, the diameter of the inner ring is smaller than the diameter of the annular tube, the diameter of the outer ring is larger than the diameter of the annular tube, the annular tube is arranged between the inner ring and the outer ring, an annular air nozzle is formed between the annular tube and the inner ring, a swirl disk is arranged in the inner ring, and the swirl disk is arranged coaxially with the air duct and the inner ring; the combustion-supporting air in the air duct is divided into two levels, the first-level air is an air rotating jet formed in the swirl disk of the inner ring, and the second-level air is an attached jet ejected from the annular air nozzle on the annular ejector; a first mixed air inlet is formed between the outer ring and the annular tube; A primary gas pipe, the primary gas pipe is located at the center of the air duct and vertically penetrates the swirl disk, and a first gas nozzle is circumferentially arranged at the tail end of the primary gas pipe; A secondary gas pipe, the secondary gas pipe is connected to the primary gas pipe and is arranged in a ring between the inner ring and the annular pipe, and a second gas nozzle is circumferentially arranged at the tail end of the secondary gas pipe; A three-stage gas pipe, the three-stage gas pipe is evenly distributed around the periphery of the air duct and is connected to the gas header; the three-stage gas pipe includes a first-stage three-stage gas pipe and a second-stage three-stage gas pipe, the first-stage three-stage gas pipe is formed by sequentially connecting a venturi convergent tube, a gas branch pipe nozzle and a gas branch pipe, the second-stage three-stage gas pipe is formed by connecting a free jet gas nozzle and a gas branch pipe, the first-stage three-stage gas pipe and the second-stage three-stage gas pipe are arranged at intervals around the air duct, the other end of the gas branch pipe is connected to the gas header, and the connection between the venturi convergent tube and the gas branch pipe nozzle forms a second gas mixing inlet; An ignition device is provided in the air duct at the air inlet end of the swirl disk, and an ignition hole corresponding to the ignition device is provided on the first-level gas pipe.

2. The flue gas internal circulation low nitrogen burner according to claim 1, It is characterized in that The inner ring includes an inner ring mixing tube and an inner ring diffuser, the outer ring includes an outer ring contraction tube, an outer ring mixing tube and an outer ring diffuser, the small diameter end of the outer ring contraction tube is connected to the outer ring mixing tube, the first gas mixing inlet is formed between the outer ring contraction tube and the annular tube, the inner ring mixing tube is arranged correspondingly to the outer ring mixing tube, the inner ring diffuser tube and the outer ring diffuser tube are arranged correspondingly, and the tail end of the annular tube is located between the inner ring mixing tube and the outer ring mixing tube.

3. The flue gas internal circulation low nitrogen burner according to claim 2, It is characterized in that The inner ring diffuser tube and the outer ring diffuser tube are both one of a conical ring and a cylindrical ring.

4. The flue gas internal circulation low nitrogen burner according to claim 3, It is characterized in that The inner ring mixing tube and the outer ring mixing tube form an annular mixing section, the cross-sectional area of ​​the annular mixing section is 2-3 times the outlet area of ​​the annular air nozzle, the length of the annular mixing section is 2-3 times the length of the annular air nozzle, the inner ring diffuser tube and the outer ring diffuser tube form an annular diffuser section, the length of the annular diffuser section is 2-5 times the length of the annular air nozzle.

5. The flue gas internal circulation low nitrogen burner according to claim 1, It is characterized in that The outlet end of the venturi convergent tube is provided with a curved tube, and the curved tube is bent inwards.

6. The flue gas internal circulation low nitrogen burner according to any one of claims 1 to 5, It is characterized in that It also includes a fan, which is connected to the inlet end of the air duct, a damper is provided at the air inlet of the fan, a smoke channel is provided on the side of the air inlet of the fan, a smoke channel is provided with a smoke butterfly valve, a high-voltage electronic igniter is also provided on the casing of the fan, the high-voltage electronic igniter is connected to the ignition device in the air duct, and a flame detector is also provided on the side of the air duct.

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