A flue gas internal circulation low nitrogen gas burner

Abstract

The present invention relates to a gas fuel burner matched with a thermal energy device, specifically a flue gas internal circulation low-nitrogen gas burner comprising: an air duct, wherein the outlet end of the air duct has a reduced diameter portion, and an air nozzle is arranged on the reduced diameter portion; a conical air duct, wherein the conical air duct is sleeved in the reduced diameter portion of the air duct and protrudes out of the air duct, and a swirl disk is arranged inside; a guide air duct, wherein the guide air duct is sleeved on the outside of the conical air cylinder; a primary gas pipe, wherein the primary gas pipe is located at the center of the air duct and vertically penetrates the swirl disk; a secondary gas pipe, wherein the secondary gas pipe is connected to the primary gas pipe, and penetrates the reduced diameter portion and the air nozzle to enter the guide air duct; a tertiary gas pipe, wherein the tertiary gas nozzle is arranged on the periphery of the air duct; the present invention fully utilizes the kinetic energy of the gas and air by arranging two-stage combustion-supporting air and three-stage gas, mixes a larger 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 gas fuel burner matched with a thermal energy device, in particular to a flue gas internal circulation low-nitrogen fuel gas burner. Background Art

[0002] Gas 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 has launched a blue sky defense war and 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 less than 30mg / Nm 3 Ultra-low nitrogen oxide emission levels. Compared with the previous national standard of 150mg / m 3 , has been greatly improved, reaching the highest standards set by some developed countries in the world. This not only puts forward high standards and strict requirements for users of burners, but also poses challenges to burner development and manufacturing technology.

[0003] At present, most low-nitrogen burner manufacturers use flue gas recirculation (FGR) as the main method to achieve low-nitrogen combustion. The basic principle is to introduce part of the low-temperature flue gas (inert gas) discharged from the smoke pipe of the boiler into the burner and mix it with the combustion air to reduce the combustion rate and absorb the combustion heat, thereby controlling the flame temperature at a lower level. The flame energy is insufficient to allow the nitrogen in the combustion air to react with oxygen to generate nitrogen oxides, thereby achieving the purpose of controlling the NOx generation concentration.

[0004] The problems with this technical solution are: first, it increases the furnace resistance, resulting in increased power consumption of the combustion-supporting fan; second, the relatively low-temperature flue gas (generally below 180°C) produced by combustion is sucked into the combustion-supporting fan through the flue outside the furnace, mixed with the air at normal temperature, and cooled by the air. The water vapor in the flue gas will condense into liquid water, which will flow out of the burner and pollute the working environment. In addition, liquid water will cause unreliable burner ignition and insulation failure of electronic components. Third, it is necessary to establish a flue gas channel between the furnace body and the burner fan inlet, which increases the workload of burner installation. Summary of the invention

[0005] In order to solve the problems in the above-mentioned background technology, the present invention provides a low-nitrogen gas burner with internal circulation of flue gas. By arranging two-stage combustion-supporting air and three-stage fuel gas, the kinetic energy of fuel gas and air is fully utilized, and a larger flow of flue gas is mixed into the air and fuel gas, thereby reducing the combustion reaction speed and the temperature of the flame, thereby controlling the generation concentration of NOx.

[0006] The present invention adopts the following technical solution: a flue gas internal circulation low nitrogen gas burner, comprising:

[0007] The air duct has a reduced diameter portion that contracts radially inward at its outlet end, and a plurality of air nozzles are circumferentially arranged on the reduced diameter portion;

[0008] A conical air duct, wherein the conical air duct is sleeved in the reduced diameter portion of the air duct and protrudes out of the air duct, and a swirl disk is arranged inside the conical air duct, and the swirl disk is arranged coaxially with the air duct;

[0009] The guide air duct is sleeved on the outside of the conical air cylinder and is longitudinally separated from the air nozzle. The outer diameter of the guide air duct is larger than the outer diameter of the air duct.

[0010] 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;

[0011] A secondary gas pipe, which is connected to the primary gas pipe and passes through the reduced diameter portion and the air nozzle to enter the guide air duct, and a second gas nozzle is circumferentially arranged at the tail end of the secondary gas pipe;

[0012] 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;

[0013] The guide air duct and the air nozzle are separated longitudinally to form a first mixed air inlet, and the third-level fuel gas nozzle forms a second mixed air inlet.

[0014] Furthermore, the secondary gas pipe has an injection portion, which is parallel to the axis of the air duct, and a second gas nozzle is circumferentially arranged at the tail end of the injection portion, and the second gas pipe is annularly arranged on the reduced diameter portion.

[0015] Furthermore, the three-stage gas pipe includes a venturi-divergent tube, a free jet gas nozzle, a gas branch pipe nozzle and a gas branch pipe. The venturi-divergent tube, the gas branch pipe nozzle and the gas branch pipe are connected in sequence to form a first-stage three-stage gas pipe. The free jet gas nozzle and the gas branch pipe are connected to form a second-stage three-stage gas pipe. The first-stage three-stage gas pipe and the second-stage three-stage gas pipe are arranged in a ring-shaped interval on the periphery of the air duct. 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.

[0016] Furthermore, a curved pipe is provided at the outlet end of the venturi convergent tube, and the curved pipe is bent inwards.

[0017] Furthermore, the air nozzle is a rectangle with a semicircular top, and a partition plate is provided between two adjacent air nozzles.

[0018] Furthermore, the conical air duct has an outer conical surface that contracts radially inwards, and the outer conical surface is located at the front end of the outlet of the air nozzle.

[0019] Furthermore, the guide air duct is coaxially arranged with the tapered air duct, an outer cone connecting pipe is arranged at the inlet end of the guide air duct, and the air nozzle is located at the inlet end of the outer cone connecting pipe.

[0020] 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.

[0021] 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.

[0022] Furthermore, the first-level gas pipe and the second-level gas pipe are supplied with gas by the first gas pipeline, the third-level gas pipe is supplied with gas by the second gas pipeline, the gas flow of the first gas pipeline is greater than the gas flow of the second gas pipeline, and the first gas pipeline and the second gas pipeline are both equipped with gas butterfly valves.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The flue gas internal circulation low-nitrogen gas burner of the present invention is provided with two-stage combustion-supporting 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.

[0025] (2) The primary gas and secondary gas jets of the flue gas internal circulation low-nitrogen gas burner of the present invention intersect vertically with the air jet to achieve rapid mixing, and the primary gas is subjected to the action of the rotating air jet of the swirl disk, so that the combustion flame is a diffuse flame, which is stable and can be used as a duty fire to ignite the other two levels of combustible gases.

[0026] (3) The three-stage fuel gas of the flue gas internal circulation low-nitrogen fuel gas burner of the present invention is arranged in an annular manner through the venturi convergent tube and the free jet fuel gas nozzle, making full use of the free jet to make up for the insufficient amount of flue gas introduced by the venturi convergent tube, and helping to reduce the concentration of fuel gas in the front of the combustion head, which can alleviate local high temperature and help control the amount of NOx generated.

[0027] (4) The flue gas internal circulation low-nitrogen gas burner of the present invention forms multiple parallel jets by setting up multiple air nozzles, which can significantly increase the surface area of ​​the air jets and the contact area between the air jets and the surrounding flue gas, so that the air can absorb and mix with more flue gas, which helps to further control the amount of NOx generated.

[0028] (5) The flue gas internal circulation low-nitrogen gas burner of the present invention is provided with a flue gas channel at the air inlet of the fan, which is used as a channel for adding a small amount of flue gas when burning high calorific value wet natural gas. The addition of flue gas can further reduce the amount of NOx generated. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] 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.

[0030] Figure 1 It is a stereoscopic diagram of the overall structure of the flue gas internal circulation low nitrogen gas burner of the present invention;

[0031] Figure 2 It is a cross-sectional structural stereogram of the flue gas internal circulation low nitrogen gas burner of the present invention;

[0032] Figure 3 It is a cross-sectional view of the flue gas internal circulation low nitrogen gas burner of the present invention;

[0033] Figure 4 For the present invention Figure 3 Middle AA section view;

[0034] Figure 5 For the present invention Figure 3 Middle BB section view;

[0035] Figure 6 It is a schematic diagram of the flow direction of internal fuel gas, flue gas and air in the flue gas internal circulation low nitrogen fuel gas burner of the present invention;

[0036] Among them, 1-air duct, 11-reduced diameter part, 12-air nozzle, 13-first mixed gas inlet, 14-partition plate, 2-conical air duct, 21-swirl disk, 22-external conical surface, 3-guide air duct, 31-external conical pipe, 4-first gas pipe, 41-first gas nozzle, 5-secondary gas pipe, 51-injection part, 52-second gas nozzle, 61-Venturi convergent tube, 610-bend pipe, 62-free jet gas nozzle, 63-gas branch nozzle, 64-gas Gas branch pipe, 65-second gas mixture inlet, 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-electrical control box. DETAILED DESCRIPTION

[0037] 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.

[0038] like Figures 1 to 6 As shown, this embodiment provides a flue gas internal circulation low nitrogen gas burner, comprising:

[0039] The air duct 1 has a reduced diameter portion 11 which contracts radially inward at its outlet end, and a plurality of air nozzles 12 are arranged circumferentially on the reduced diameter portion 11; the conical air duct 2 is sleeved in the reduced diameter portion 11 of the air duct 1 and protrudes out of the air duct 1 (i.e., one end of the conical air duct 2 is sleeved in the air duct 1, and the outer periphery of the conical air duct 2 is fixedly connected to the inner periphery of the air duct 1, and the other end of the conical air duct 2 protrudes out of the air duct 1 and extends outward), and a swirl disk 21 is provided inside the conical air duct 2, and the swirl disk 21 is perpendicular to the axis of the air duct 1 and the conical air duct 2, and at the same time, the swirl disk 2 1 is coaxially arranged with the air duct 1 and the conical air duct 2, and the outer diameter of the swirl disk 21 is slightly smaller than the inner diameter of the conical air duct 2; the guide air duct 3 is sleeved on the outside of the conical air duct 2 and is longitudinally separated from the air nozzle 12 to form a first air mixing inlet 13, and the outer diameter of the guide air duct 3 is larger than the outer diameter of the air nozzle 12; specifically, the outer wall of the reduced diameter portion 11 at the outlet end of the air duct 1 can not only guide the smoke entering through the first air mixing inlet 13, but also gather and compress the air flow through the inner wall of the reduced diameter portion 11 to increase the flow rate of the air flow. Through the above-mentioned arrangement, this embodiment divides the combustion-supporting air into two levels. The first-level air is a rotating air jet formed in the swirl disk 21 of the conical air duct 2. The purpose of using the rotating air jet is to form a low-pressure recirculation 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 second-level air is a plurality of parallel jets ejected from the air nozzle 12. The purpose is to increase the surface area of ​​the air jet and produce the effect of sucking more flue gas.

[0040] Furthermore, this embodiment divides the gas into three levels, namely:

[0041] Primary gas: The gas ejected from the primary gas pipe 4. The primary gas pipe 4 is located at the central axis of the air duct 1 and vertically penetrates the swirl disk 21. The tail end of the primary gas pipe 4 (i.e., the position passing through the swirl disk 21) is circumferentially provided with a first gas nozzle 41, and the axis of the primary gas pipe 4 coincides with the axis of the air duct 1. Specifically, the primary gas pipe 4 is cylindrical or stepped cylindrical, and a plurality of (generally 4-20) first gas nozzles 41 are arranged on the outer cylindrical surface of the tail end of the primary gas pipe 4 (i.e., the outer cylindrical surface passing through the swirl disk 21). At the same time, a baffle is provided at the end of the primary gas pipe 4, so that the gas can only be ejected from the first gas nozzle 41. After the first gas is ejected from the first gas nozzle 41, 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 21 to achieve rapid mixing. Specifically, an ignition device 7 is provided at the air inlet end of the swirl disk 21 in the air duct 1, and an ignition hole corresponding to the ignition device 7 is provided on the first-level gas pipe 4. The first gas is mixed with the rotating air jet and ignited by the ignition device 7 (the ignition device 7 also includes an ignition electrode 71) to achieve combustion. Due to the action of the rotating air jet, the flame is a diffusion flame, which is very stable and can be used as a duty fire for 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.

[0042] Secondary gas: gas ejected from the secondary gas pipe 5, which is connected to the primary gas pipe 4 and penetrates the reduced diameter portion 11 and the air nozzle 12 to enter the guide air duct 3, and a second gas nozzle 52 is circumferentially arranged at the tail end of the secondary gas pipe 5; specifically, the secondary gas pipe 5 has an injection portion 51 and a guide portion, the injection portion 51 is connected through the guide portion and is vertically arranged, the guide portion is connected through the primary gas pipe 4, the injection portion 51 is parallel to the axis of the air duct 1, the injection portion 51 extends a distance from the combustion head, and a second gas nozzle 52 is circumferentially arranged at the tail end of the injection portion 51. The nozzle 52, the second gas pipe 5 is arranged in an annular manner on the reduced diameter part 11 (generally 3-8 secondary gas pipes 5 are arranged), and the tail end of the second gas pipe 5 (i.e. the tail end of the injection part 51) is also provided with a baffle, so that the second gas can only be ejected from the second gas nozzle 52. After the second gas is ejected from the second gas nozzle 52, a free jet is formed. 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 multiple parallel jets ejected from the air nozzle 12, and is ejected to the outlet direction of the combustion head, ignited by the on-duty fire, and burned. Figure 1 It can be seen that the secondary gas pipe 5 is not a straight pipe, but has a bent portion. The inlet end of the secondary gas pipe 5 is connected to the primary gas pipe 4, and after extending a distance to the periphery of the primary gas pipe 4, it bends and connects to the injection portion 51.

[0043] 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. The gas is transported to the tertiary gas pipe through the gas header 94;

[0044] Specifically, Figure 1 As shown, the three-stage gas pipe includes a venturi convergent tube 61, a free jet gas nozzle 62, a gas branch nozzle 63 and a gas branch pipe 64. Figure 2 As can be seen from the figure, the venturi convergent tube 61 includes an expanding tube and a reducing tube, the diameter of the expanding tube is larger than the diameter of the reducing tube, and the expanding tube and the reducing tube are connected in a smooth transition, wherein the venturi convergent tube 61, the gas branch pipe nozzle 63 and the gas branch pipe 64 are sequentially connected to form a first-level three-stage gas pipe, the connection between the venturi convergent tube 61 and the gas branch pipe nozzle 63 forms a second mixed gas inlet 65, the free jet gas nozzle 62 and the gas branch pipe 64 are connected to form a second-level three-stage gas pipe, and the two three-stage gas pipes are arranged in an annular manner at intervals in the air duct 1 The other ends of the gas branch pipes 64 are connected to the gas manifold 94, and the second mixing inlet 65 is formed at the connection between the expansion pipe of the venturi convergent tube 61 and the nozzle of the gas branch pipe 63. The third gas enters the expansion pipe of the venturi convergent tube 61 through the gas branch pipe nozzle 63. The kinetic energy of the high-speed gas jet is used to guide the smoke from the surrounding environment into the venturi convergent tube 61 through the second mixing inlet 65, mix with the gas jet, and be accelerated, and then sprayed into the flame at a relatively fast speed through the front end of the venturi convergent tube 61 to be ignited and burned.

[0045] Specifically, Figure 1 , Figure 2 , Figure 3 , Figure 6 As shown in , a curved pipe 610 is provided at the outlet end of the venturi convergent tube 61. The curved pipe 610 is bent inwards, and the mixed airflow is guided to the center of the flame through the curved pipe 610 to achieve complete combustion of the fuel gas.

[0046] Preferably, Figure 4 As shown, a second-level three-level gas pipe is arranged between every two first-level three-level gas pipes. High-speed gas is ejected from the free jet gas nozzle on the second-level three-level gas pipe. The high-speed gas flow in the turbulent state has a strong suction effect on the surrounding smoke, which draws the smoke into the gas, mixes with the gas, and ejects it forward into the flame.

[0047] It can be understood that the arrangement of the three-stage gas pipe has the following effects:

[0048] 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 61 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 61 is relatively high, and the mixed gas can be sent to a position farther in front of the burner 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 61. The gas ejected from the free jet gas nozzle 62 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 burner 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 burner head, relieve local high temperature, and help control the amount of NOx generated. The first-stage three-stage gas pipe and the second-stage three-stage gas pipe 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.

[0049] 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.

[0050] 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.

[0051] Specifically, a plurality of (4-24) air nozzles 12 are arranged outside the zooming portion 11 and the swirl disk 21 of the air duct 1. The air nozzles 12 are arranged symmetrically along the circumference. Air is ejected quickly from the air nozzles 12 to form multiple parallel jets. The multiple air jets formed by multiple air nozzles 12 can significantly increase the surface area of ​​the air jets, increase the contact area between the air jets and the flue gas entering through the first mixing inlet 13, and enable the air to entrain and mix more flue gas, which helps to further control the amount of NOx generated. In particular, when the burner is running at a low load, resulting in a low air flow rate, it can ensure that the air flow can still entrain a certain amount of flue gas. Specifically, the purpose of allowing air to entrain and mix flue gas is to use flue gas to reduce the combustion speed, absorb flame heat, reduce the combustion temperature, and control the amount of NOx generated. Since the air nozzle 12 of this embodiment is arranged at the reduced diameter portion 11 of the air duct 1, the air nozzle 12 is a special-shaped air nozzle, and the air nozzle 12 is interconnected with the air duct 1. The cross section of the air nozzle 12 of this embodiment generally adopts a rectangular shape with a semicircular top. This structure has the characteristics of large flow area, long perimeter, good manufacturing process, etc. A partition plate 14 is also arranged between two adjacent air nozzles 12 to prevent the air nozzles 12 from interfering with each other.

[0052] Specifically, the tapered air duct 2 has an outer tapered surface 22 that contracts radially inward, and the outer tapered surface 22 is located at the front end of the outlet of the air nozzle 12. According to the Coanda principle, the air flow ejected from the special-shaped air nozzle 12 will flow forward quickly along the outer tapered surface 22 of the tapered air duct 2, and the outer tapered surface 22 can significantly reduce the air flow resistance, so that the air flow can draw more smoke into the burner head, and this structure increases the air jet's ability to draw and entrain smoke.

[0053] Specifically, the guide air duct 3 is coaxially arranged with the conical air duct 2, and the two form an inner and outer concentric air duct as a secondary air channel. An outer conical pipe 31 is provided at the inlet end of the guide air duct 3, and the air nozzle 12 is located at the inlet end of the outer conical pipe 31, which is used to introduce the surrounding smoke into the secondary air channel.

[0054] It should be noted that a small portion of the combustion-supporting air entering the burner quickly flows through the swirl disk 21 located in the center. The swirl disk 21 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 21, 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.

[0055] Specifically, the parts used in the burner of this embodiment are all made of heat-resistant steel.

[0056] Furthermore, 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. Thus, the main parts of the burner are connected together to form an integrated burner, wherein the fan 8 provides the combustion-supporting air required for combustion and overcomes the flue gas back pressure in the furnace during combustion. A damper 81 is provided at the air inlet of the fan 8, and the air supply volume of the air inlet 87 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 provided on the side of the air inlet of the fan 8, and a flue gas butterfly valve 82 is configured, which is controlled by a valve actuator 83 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.

[0057] Specifically, Figure 3 , Figure 5 As shown, a high-voltage electronic igniter 84 is installed on the housing of the fan 8, and is connected to the ignition device 7 located in the air duct 1 and in front of the swirl disk 21 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.

[0058] Further, such as Figure 3 As shown, 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.

[0059] The working principle of the present invention is as follows:

[0060] 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 air nozzle 12 to form an approximate free jet. The gas enters the ignition pipeline and the two gas butterfly valves respectively through two series-connected solenoid valves 91. The high-voltage electronic igniter 84 generates an electric spark between the ignition electrodes of the ignition device 7, igniting the gas ejected from the primary gas pipe 4 to form an ignition flame. The flame passes through the swirl disk 21 to ignite the primary gas and establish the duty fire. Driven by the central air rotating jet formed by the swirl disk 21, the duty fire ignites the secondary gas to burn, forming a stronger main flame, and then ignites the tertiary gas and flue gas mixture ejected into the main flame, thereby forming a stable combustion flame in the furnace.

[0061] 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.

[0062] When the fuel gas is associated with moisture in oil wells with high light hydrocarbon content and high calorific value, or other reasons lead to high flame temperature, the NOx generation concentration cannot be stably controlled at 30mg / Nm 3 When the temperature is within the range of 0.1°C, 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.

[0063] In order to further illustrate the gas and air intake capacity of the flue gas internal circulation low nitrogen gas burner of the present invention, the present invention takes a 2MW burner as an example for calculation and analysis. Here, only the rated working condition calculation is performed. Under the rated working condition, the natural gas consumption of the burner is about 200Nm 3 / h, air consumption is 2280Nm 3 / h (air coefficient is 1.2):

[0064] (I) Calculation of gas volume for smoking

[0065] There are three levels of gas distribution: the first level accounts for 10%, the second level accounts for 20%, and the third level accounts for 70%.

[0066] Here we mainly analyze the flue gas injection capacity of the three-stage gas. Eight Venturi-divergent tubes and eight free jet nozzles are used. The gas flow rates of the Venturi-divergent tubes and free jet nozzles are equal, and the flow rate is 8.75Nm 3 / h, assuming the nozzle outlet velocity is v = 65m / s, then the nozzle diameter d j =6.8mm.

[0067] Characteristic parameters of the Venturi reducer and reducer ejector: throat diameter (reduced diameter tube) dt =20mm, the outlet diameter of the expansion tube (expansion tube) d k =30mm, then dimensionless area

[0068] Characteristic equation of venturi-divergent tube ejector

[0069]

[0070] h—Ejector outlet pressure head, approximately equal to the furnace back pressure, set to 1000Pa.

[0071] μ—nozzle flow coefficient, take 0.8

[0072] K—Energy loss coefficient of ejector, After calculation, K = 1.5

[0073] u—mass ejection coefficient, according to the target value of flue gas ejected at 1.0 times the mass of the gas, take 1.0

[0074] u c —Volume ejection coefficient, take 1.1

[0075] Substituting into the characteristic equation

[0076] H=10.6h=10600Pa

[0077] That is, the gas pressure before the nozzle outlet must reach 10600Pa in order to eject flue gas equivalent to 1 times the mass of the gas, which means that a larger ejection energy (gas potential energy) is required.

[0078] Then calculate the amount of entrained gas from the free jet nozzle, and the mass flow formula of the entrained gas is

[0079]

[0080] Where m 0 is the mass flow rate of the gas involved in the injection

[0081] ρ a is the density of smoke entrained, set to 0.646 (smoke temperature is 300°C),

[0082] ρ 0 The gas density is 0.73, d = 6.8 mm,

[0083] x is the distance between the jet and the nozzle, which is 100 mm according to the design.

[0084] Calculate m en =3.4m 0That is, the free jet gas can entrain smoke 3.4 times its own mass, which is significantly higher than the Venturi ejector. The combination of the Venturi divergent tube and the free jet gas nozzle can entrain more smoke and adapt to the required combustion scheme.

[0085] (II) Analysis of air entrainment smoke capacity

[0086] After the secondary air is ejected through the air nozzle, it can be approximately regarded as a free jet, and the smoke is entrained by the free jet of air. The equivalent diameter of the air nozzle 12 is d = 30mm, the number is 16, and the air volume accounts for 70% of the total volume, that is, 1600Nm 3 / h, the air flow rate of each nozzle is 100Nm 3 / h, air density ρ a =1.2, smoke density ρ 0 =0.65, according to the need, to draw in 25% of the smoke of the air jet flow, that is, m en =0.25m 0 , then the jet length

[0087]

[0088] This length can be achieved from the perspective of structural design.

[0089] From the above calculations, it can be seen that the use of multiple air nozzles can increase the contact area between air and surrounding smoke, thereby ensuring the amount of induced smoke.

[0090] It should be noted that the above examples are only for better illustrating the gas and air introduction capabilities of the flue gas internal circulation gas burner of the present invention, and are not intended to limit the specific structural dimensions of the present invention.

[0091] 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 gas burner, It is characterized in that include: The air duct has an outlet end with a reduced diameter portion that contracts radially inward, and a plurality of air nozzles are circumferentially arranged on the reduced diameter portion; A conical air duct, wherein the conical air duct is sleeved in the reduced diameter portion of the air duct and protrudes out of the air duct, a swirl disk is provided inside the conical air duct, and the swirl disk is coaxially arranged with the air duct; the combustion-supporting air in the air duct is divided into two levels, the first level of air is a rotating air jet formed in the swirl disk of the conical air duct, and the second level of air is a plurality of parallel jets ejected from an air nozzle; A guide air duct, wherein the guide air duct is sleeved outside the conical air duct and is longitudinally separated from the air nozzle, and the outer diameter of the guide air duct is greater than the outer diameter of 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, 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 passes through the reduced diameter portion and the air nozzle to enter the guide air 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 connected to the gas header; the three-stage gas pipe includes a venturi-divergent tube, a free jet gas nozzle, a gas branch pipe nozzle and a gas branch pipe, the venturi-divergent tube, the gas branch pipe nozzle and the gas branch pipe are sequentially connected to form a first-stage three-stage gas pipe, the free jet gas nozzle and the gas branch pipe are connected to form a second-stage three-stage gas pipe, the first-stage three-stage gas pipe and the second-stage three-stage gas pipe are annularly spaced and arranged around the periphery of the air duct, the other end of the gas branch pipe is connected to the gas header, and the connection between the venturi-divergent tube and the gas branch pipe nozzle forms a second gas mixing inlet; The guide air duct is longitudinally separated from the air nozzle to form a first air 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 gas burner according to claim 1, It is characterized in that The secondary gas pipe has an injection portion, the injection portion is parallel to the axis of the air duct, the tail end of the injection portion is circumferentially provided with the second gas nozzle, and the secondary gas pipe is annularly arranged on the reduced diameter portion.

3. The flue gas internal circulation low nitrogen gas 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.

4. The flue gas internal circulation low nitrogen gas burner according to claim 1, It is characterized in that The air nozzle is a rectangle with a semicircular top, and a partition plate is provided between two adjacent air nozzles.

5. The flue gas internal circulation low nitrogen gas burner according to claim 1, It is characterized in that The conical air duct is provided with an outer conical surface which contracts radially inwards, and the outer conical surface is located at the front end of the outlet of the air nozzle.

6. The flue gas internal circulation low nitrogen gas burner according to claim 1, It is characterized in that The guide air duct is coaxially arranged with the conical air duct, an outer conical connecting pipe is arranged at the inlet end of the guide air duct, and the air nozzle is located at the inlet end of the outer conical connecting pipe.

7. The flue gas internal circulation low nitrogen gas burner according to any one of claims 1 to 6, 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.

8. The flue gas internal circulation low nitrogen gas burner according to claim 7, It is characterized in that The first-level gas pipe and the second-level gas pipe are supplied with gas by the first gas pipeline, and the third-level gas pipe is supplied with gas by the second gas pipeline. The gas flow of the first gas pipeline is greater than the gas flow of the second gas pipeline. The first gas pipeline and the second gas pipeline are both equipped with gas butterfly valves.

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