Combustor low-nitrogen center gun and low-nitrogen combustor

Abstract

The utility model discloses a combustor low-nitrogen center gun and a low-nitrogen combustor, and relates to the field of fuel gas grading low-nitrogen combustors, the low-nitrogen combustor is suitable for fuel gas grading, the low-nitrogen center gun comprises a fuel gas vertical pipe, a fuel gas transverse pipe, a plurality of fuel gas dispersing nozzles and a fuel gas fire stabilizing sheet, and the fuel gas transverse pipe is provided with a plurality of fuel gas dispersing nozzles; each fuel gas dispersing nozzle is provided with a plurality of small-angle spraying holes; the fuel gas fire stabilizing sheet is positioned at the downstream of the fuel gas spraying direction of the fuel gas dispersing nozzle; the fuel gas vertical pipe is communicated with the fuel gas transverse pipe and used for inputting fuel gas. A low-nitrogen center gun is designed in a combustion-supporting air channel of a burner block, gas of the center gun is rapidly and evenly distributed in combustion-supporting air, and a fire stabilizing sheet is designed and arranged in the combustion-supporting air channel of the burner block at the position, corresponding to the gas concentration range, of which the gas concentration is within the gas concentration range of 80%-150% of the air excess coefficient after the gas and the air are mixed. A low-speed area and a backflow area in which fuel gas and air mixed gas flow are formed, the fuel gas of the center gun is ignited and ignited at the downstream of the fire stabilizing piece, the amount of nitrogen oxide generated by the center gun of the fuel gas grading low-nitrogen burner can be reduced, and the burner can obtain lower nitrogen oxide emission.

Description

Technical Field

[0001] This invention designs a low-NOx center gun for burners, which is suitable for gas-stage low-NOx burners and can reduce NOx emissions from burners. Background Technology

[0002] As my country's environmental emission standards become increasingly stringent, from a nitrogen oxide emission limit of 200 mg / m³... 3 Gradually reduce to 100 mg / m 3 80mg / m 3 Even stricter than 50mg / m 3 Even 30mg / m 3 Many low-NOx burners are no longer sufficient to meet the requirements; now, even lower-emission low-NOx burners are needed. Low-NOx burners come in two types: air-staged and fuel-staged. Many factors influence NOx emissions, including fuel composition, hot air temperature, furnace temperature, and air oxygen content. Typically, air-staged low-NOx burners emit around 100 mg / m³. 3 Horizontal, gas-stage low-NOx burner emissions at 50mg / m³ 3 In addition to reducing emissions, nitrogen oxide emissions can usually be halved by increasing external flue gas recirculation, but this method requires sacrificing 5% to 10% of thermal efficiency. Utility Model Content

[0003] The technical problem solved by this application is to overcome the shortcomings of the prior art and provide a low-NOx center gun for a gas-stage low-NOx burner. The center gun gas is rapidly and evenly distributed into the combustion air. In the combustion air channel of the burner brick, the highest gas concentration is located in the range of gas concentration corresponding to the excess air coefficient of 80% to 150% after the gas and air are mixed (this range takes into account both good flame stability and low NOx generation). The design and arrangement of flame stabilizers form a low-speed zone and a recirculation zone for the gas-air mixture to control the ignition point of the center gun gas, thereby reducing the NOx generation of the center gun of the gas-stage low-NOx burner and achieving lower NOx emissions from the burner.

[0004] Currently, most low-NOx burners used are staged gas low-NOx burners, and this patent also focuses on optimizing the design of staged gas low-NOx burners. One type of low-NOx center gun in this patent is an optimized design for the center gun of a staged gas low-NOx burner. By changing the combustion mode of the standard staged gas low-NOx burner center gun, and utilizing the characteristics of high airflow and low fuel in the central flame area, the diffusion combustion of the central gun gas is changed to over-premixed combustion. This significantly reduces the maximum temperature of the central flame, thereby reducing the formation of NOx in the center gun and lowering NOx emissions from the burner.

[0005] Explanation 1: Define the theoretical air-fuel ratio of the fuel gas as A (i.e. A = the volume of air that just completely combusts the fuel gas / the volume of the fuel gas), when the volume of the fuel gas is 1, the volume of air is 1*(A+A*80%), at this time the concentration of the fuel gas is 1 / [1+1*(A+A*80%)], that is, the concentration of the fuel gas with an air excess coefficient of 80% is 1 / (1+A+A*80%); similarly, the concentration of the fuel gas with an air excess coefficient of 150% is 1 / (1+A+A*150%).

[0006] Explanation 2: Corresponding to common natural gas type fuel, the flame temperature with an air excess coefficient of 80% is about 1400℃, and the low-nitrogen burner design is recognized to have a low nitrogen oxide production rate below 1400℃; the flame temperature with an air excess coefficient of 150% is about 900℃, and the fuel gas can be reliably ignited at about 600℃, and the flame temperature exceeding 900℃ can maintain reliable ignition of the fuel gas.

[0007] The technical scheme provided by the application is as follows:

[0008] A low-nitrogen central gun of a burner comprises a fuel gas vertical pipe, a fuel gas horizontal pipe, a fuel gas dispersion nozzle and a fuel gas flame stabilizing sheet, the fuel gas horizontal pipe is provided with a plurality of fuel gas dispersion nozzles, each fuel gas dispersion nozzle has a plurality of jet holes; the fuel gas flame stabilizing sheet is located in the fuel gas jetting direction of the fuel gas dispersion nozzle; the fuel gas vertical pipe is in communication with the fuel gas horizontal pipe and is used for inputting fuel gas.

[0009] The included angle between the axis of each jet hole of the fuel gas dispersion nozzle and the direction of combustion air is not more than 30°; the included angle between the fuel gas and the combustion air is avoided to be too large to generate a backflow area, and the fuel gas is ignited in advance when the concentration of the fuel gas is too high, resulting in excessive production of nitrogen oxides.

[0010] The fuel gas flame stabilizing sheet is connected to the fuel gas horizontal pipe through a fuel gas flame stabilizing sheet fixing rod, the distance between the fuel gas flame stabilizing sheet and the fuel gas dispersion nozzle is obtained through numerical simulation calculation, and the highest concentration of the fuel gas after mixing with the combustion air is ensured to be within the range of the fuel gas concentration corresponding to the air excess coefficient of 80% to 150% after the fuel gas is mixed with air.

[0011] In order to ensure that the fuel gas of the central gun can be ignited near the fuel gas flame stabilizing sheet and form a stable flame in the low-speed area and the backflow area formed downstream of the fuel gas flame stabilizing sheet, a pilot light is arranged at a position substantially flush with the fuel gas flame stabilizing sheet (within the range of -20 to +20 mm) and horizontally offset from the fuel gas flame stabilizing sheet (within the range of 30 to 50 mm); the specific position of the pilot light is preferably such that the central gun is ignited, the flame of the central gun is close to the fuel gas flame stabilizing sheet and is higher than the fuel gas flame stabilizing sheet; if the position of the pilot light is too low, the fuel gas of the central gun is ignited too early, which will result in high production of nitrogen oxides, and if the position of the pilot light is too high, the flame of the central gun is far away from the low-speed area and the backflow area formed by the fuel gas flame stabilizing sheet, which will result in jumping or even extinguishing of the flame of the central gun.

[0012] The conventional gas staged low-nitrogen burner comprises a burner brick, a wind box assembly, a peripheral gun, a long-lasting lamp and a common center gun, the burner brick is embedded in a furnace bottom refractory layer, the burner brick is provided with a square hole communicating inside and outside of a furnace wall, the wind box assembly is connected to one end of the burner brick outside the furnace wall, the long-lasting lamp and the common center gun both extend into the square hole of the burner brick through the wind box assembly, and the peripheral gun extends into the furnace wall through the burner brick; the ignition end of the long-lasting lamp is located on the side of the common center gun nozzle towards the inside of the furnace wall.

[0013] The low-nitrogen burner using the low-nitrogen center gun of the patent is obtained by replacing the common center gun of the conventional gas staged low-nitrogen burner with the low-nitrogen center gun of the patent, the gas transverse pipe is close to the wind box side in the square hole of the burner brick, the gas flame stabilizing sheet is close to the hearth side in the square hole of the burner brick, and the position of the ignition end of the long-lasting lamp is adjusted to the side of the gas flame stabilizing sheet of the low-nitrogen center gun, the vertical distance between the ignition end of the long-lasting lamp outlet and the gas flame stabilizing sheet of the low-nitrogen center gun is within the range of -20mm to +20mm, and the long-lasting lamp outlet is horizontally staggered with the gas flame stabilizing sheet of the low-nitrogen center gun by 30-50mm.

[0014] The gas transverse pipe and the gas flame stabilizing sheet are both perpendicular to the air supply direction of the combustion air in the burner brick.

[0015] Along the flow direction of the combustion air in the burner brick, the gas flame stabilizing sheet is located downstream of the gas dispersion nozzle. The gas flame stabilizing sheet is located at a position where the highest gas concentration is within the gas concentration range corresponding to the air excess coefficient of 80% to 150%.

[0016] In summary, the application at least has the following beneficial technical effects:

[0017] The application has the following advantages: (1) for the gas staged low-nitrogen burner, as long as the center gun is replaced and the flame stabilizing design is added at a suitable position in the air passage of the burner brick, the purpose of reducing the nitrogen oxide emission of the whole burner can be achieved; the other components of the original burner can be reused, and the transformation cost can be greatly reduced; (2) for the bottom burner of the cracking furnace, when the original coke burning standby condition is in a low load and high oxygen condition, the peripheral gun deviates from the low-nitrogen combustion, and the center gun itself also has no nitrogen reduction effect, so that the nitrogen oxide emission exceeds 200mg / m 3 Therefore, the nitrogen oxide emission in the coke burning standby condition needs to be reduced to 100mg / m 3 If the center gun scheme of the patent is used, when the original coke burning standby condition is in a low load and high oxygen condition, the peripheral gun is cut off and only the center gun is turned on, the nitrogen oxide emission in the coke burning standby condition can be reduced to 60mg / m 3(3) Because the center gun is added with the flame stabilizing piece, the center gun flame ignition point can be accurately controlled, the flame stability can be provided, and the flame shaking caused by the insufficient furnace negative pressure during the overload operation of the low-nitrogen burner can be eliminated. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a side view of a conventional gas staged low-nitrogen burner;

[0019] Figure 2 is a top view of a conventional gas staged low-nitrogen burner;

[0020] Figure 3 is a side view of a gas staged low-nitrogen burner using a low-nitrogen center gun;

[0021] Figure 4 is a top view of a gas staged low-nitrogen burner using a low-nitrogen center gun;

[0022] Figure 5 is a low-nitrogen center gun (including a dispersion nozzle and a flame stabilizing piece).

[0023] BRIEF DESCRIPTION OF DRAWINGS: 1, burner brick; 2, air bellow assembly; 3, peripheral gun; 4, pilot light; 5, ordinary center gun; 6, low-nitrogen center gun; 11, pilot light flame; 12, peripheral gun flame; 13, ordinary center gun flame; 14, low-nitrogen center gun flame; 21, gas vertical pipe; 22, gas horizontal pipe; 23, gas dispersion nozzle; 24, gas flame stabilizing piece; 25, gas flame stabilizing piece fixing rod. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the present application more clear, the following will combine the drawings to make a further detailed description of the embodiments disclosed in the present application.

[0025] The embodiments of the present application disclose a low-nitrogen center gun of a burner, which is suitable for any gas staged low-nitrogen oxygen combustion burner, changes the center gas diffusion combustion mode to a premixing combustion mode, reduces the amount of nitrogen oxides generated by the center gas flame, and further reduces the nitrogen oxide emission of the low-nitrogen burner.

[0026] As Figure 1 , Figure 2The structure diagram (side view and top view) of the conventional gas staged combustor, the combustor is composed of burner brick 1, wind box assembly 2, peripheral gun 3, long-lasting lamp 4, common center gun 5, combustion-supporting air enters from the air port of the wind box assembly 2, and exits from the square hole of the burner brick 1, the peripheral gun 3 penetrates through the burner brick 1 to spray outside the burner brick 1 to the square hole of the burner brick 1, and the common center gun 5 is in the square hole of the burner brick 1. When the combustor works, three flames, long-lasting lamp flame 11, peripheral gun flame 12 and common center gun flame 13, are produced, and the long-lasting lamp flame 11 can simultaneously ignite the peripheral gun flame 12 and the common center gun flame 13.

[0027] As Figure 3 , Figure 4 The structure diagram (side view and top view) of the gas staged combustor using the low-nitrogen center gun of the present patent, the combustor is composed of burner brick 1, wind box assembly 2, peripheral gun 3, long-lasting lamp 4, low-nitrogen center gun 6, combustion-supporting air enters from the air port of the wind box assembly 2, and exits from the square hole of the burner brick 1, the peripheral gun 3 penetrates through the burner brick 1 to spray outside the burner brick 1 to the square hole of the burner brick 1, and the low-nitrogen center gun 6 is in the square hole of the burner brick 1. When the combustor works, three flames, long-lasting lamp flame 11, peripheral gun flame 12 and low-nitrogen center gun flame 14, are produced, and the long-lasting lamp flame 11 can simultaneously ignite the peripheral gun flame 12 and the low-nitrogen center gun flame 14.

[0028] Figure 5The low-nitrogen central gun comprises a gas vertical pipe 21, a gas horizontal pipe 22, a gas dispersion nozzle 23, a gas flame stabilizer 24 and a gas flame stabilizer fixing rod 25. The central gun gas enters from the gas vertical pipe 21, is distributed to a plurality of gas dispersion nozzles 23 in the gas horizontal pipe 22, each gas dispersion nozzle 23 sprays the gas out of a plurality of small-angle small holes, mixes with air in the combustion air passage, and is ignited when the highest gas concentration corresponds to the range of the air excess coefficient 80% to 150% after the gas mixes with air (the gas concentration is too low to be ignited, and the concentration is too high to produce more nitrogen oxides). The low-nitrogen central gun flame is a premixed combustion flame. Compared with the diffusion combustion flame of the ordinary central gun, the highest temperature of the central gun flame is significantly reduced, and the nitrogen oxide generation amount of the central gun flame is also significantly reduced. In order to ensure that the central gun gas starts to ignite at a suitable gas concentration range, the gas flame stabilizer 24 is designed at this position. The gas flame stabilizer 24 can be welded with the gas flame stabilizer fixing rod 25 or fixed with the burner brick. If the gas flame stabilizer fixing rod 25 is used, a round cross-section thin rod structure is used to avoid the low-speed area and the backflow area before the gas and the combustion air mixture reaches the gas flame stabilizer 24, so that the central gas ignites early. The gas horizontal pipe 22 of the low-nitrogen central gun is placed in the combustion air passage of the burner brick near the air inlet, a plurality of gas dispersion nozzles 23 are designed on the gas horizontal pipe 22, and the multiple nozzles and multiple holes can quickly disperse the central gun gas. At the same time, the gas dispersion nozzle 23 is designed as a plurality of small-angle small holes, and the backflow area and the low-speed area are avoided near the gas dispersion nozzle 23 in the combustion air passage, so as to prevent the central gun gas from igniting too early. The reasonable design of the flame stabilizer position is the key to realize the low emission and stable flame of the low-nitrogen central gun.

[0029] As Figure 3The structure of the gas staged burner using the low-nitrogen center gun of the patent is shown in the side view, wherein the relative position of the long-lasting lamp 4 and the low-nitrogen center gun 6 is important, that is, the ignition end position of the outlet of the long-lasting lamp 4 is substantially flush with the vertical direction of the gas flame stabilizing strip 24 of the low-nitrogen center gun 6 (in the range of -20 to +20 mm), the ignition end position of the outlet of the long-lasting lamp 4 is staggered with the gas flame stabilizing strip in the horizontal direction by 30 to 50 mm, the outlet of the long-lasting lamp is located on the side of the gas flame stabilizing strip 24 facing the furnace, and the gas of the low-nitrogen center gun 6 and the gas of the peripheral gun 3 can be ignited at the same time, so that the long-lasting lamp flame 11 can ignite the gas of the low-nitrogen center gun 6 to form a low-nitrogen center gun flame 14 above the gas flame stabilizing strip 24 and close to the gas flame stabilizing strip 24, and the gas of the low-nitrogen center gun 6 is not directly burned to the flame stabilizing strip. If the position is too low, the gas of the low-nitrogen center gun 6 is ignited too early, the local concentration of the center gas is high, which can cause a large amount of nitrogen oxides, when the low-nitrogen center flame 14 burns to the gas flame stabilizing strip 24, the service life of the gas flame stabilizing strip 24 will be affected; if the position is too high, the gas of the center gun is ignited, the root of the flame is separated from the gas flame stabilizing strip 24, and a stable low-nitrogen center flame 14 cannot be formed, which can cause the center gun to be extinguished or the flame of the whole burner to surge.

[0030] Some known technologies in the field are used in the process of the utility model, such as Figure 1 、 Figure 2 It is a standard structure of a gas staged low-nitrogen burner, and the patent is optimized and locally improved for the center gun part. Multiple gas nozzles are designed on the center gun, which is often used on the burner. The flame stabilizing strip is designed on the burner to increase the flame stability. The long-lasting lamp is also a standard design on the burner. The low-nitrogen center gun used in the patent changes the combustion mode of the ordinary center gun, changes the gas diffusion combustion mode to the premixed combustion mode, the key is to use the characteristics of the center gun position of the gas staged low-nitrogen burner, control the air excess coefficient of the mixed gas at the ignition point, and design the structure of the stable ignition point to reduce the nitrogen oxide emission of the center gun gas flame and realize the reduction of the nitrogen oxide emission of the burner.

[0031] The utility model discloses the range of scope includes the technology and obvious replacement of disclosure, such as gas dispersion shower head (23) patent drawing shows that the shower head quantity is 8, and each is the shower head spray hole for 6 holes, such as the shower head quantity is 4~16, and each is the shower head spray hole for 3~10 holes, wherein all are to disperse gas fastly;Gas flame stabilizing sheet 24 can be designed as a long strip or design as multiple short strips, also can be designed as other flame stabilizing structure, such as the gas nozzle of small flow is designed again in the vicinity of flame stabilizing sheet to improve the stability of central gas flame, its function is all in the position of air excess coefficient 80%~150% after gas and air mix to stabilize central gas flame;The function of gas flame stabilizing sheet fixing rod 25 is to fix gas flame stabilizing sheet 24, and it can also be changed into other forms of fixed gas flame stabilizing sheet 24, such as gas flame stabilizing sheet 24 and burner brick 1 or combustor wind box 2 are connected and fixed, no matter which fixed mode is adopted, it is necessary to avoid the backflow area and low speed area in the space of gas dispersion in the burner brick channel of gas dispersion shower head 23 and gas flame stabilizing sheet 24, resulting in that central gas is ignited in advance, the patent shows that it is used for square section gas grading low nitrogen combustor, and if it is changed to be used on the circular section gas grading low nitrogen combustor, also has the same effect.

[0032] The content not described in detail in the specification of the present application is the known technology of those skilled in the art.

[0033] The present application is described in detail above in combination with specific embodiments and exemplary examples, but these descriptions cannot be understood as the limitation of the present application. Those skilled in the art understand that the technical scheme of the present application and its embodiments can be replaced, modified or improved in many ways without departing from the spirit and scope of the present application, and these all fall within the scope of the present application. The protection scope of the present application is subject to the appended claims.

Claims

1. A low-NOx center gun for a burner, characterized in that: It includes a gas vertical pipe (21), a gas horizontal pipe (22), a gas dispersion nozzle (23) and a gas flame stabilizer (24). The gas horizontal pipe (22) is provided with multiple gas dispersion nozzles (23), and each gas dispersion nozzle (23) has multiple nozzle holes. The gas stabilizing plate (24) is located downstream of the gas ejection direction of the gas dispersing nozzle (23); The gas riser (21) is connected to the gas horizontal pipe (22) for inputting gas.

2. The low-NOx center gun for a burner according to claim 1, characterized in that: The angle between the axis of each nozzle of the gas dispersion nozzle (23) and the direction of the combustion air does not exceed 30°.

3. A low-NOx center gun for a burner according to claim 1, characterized in that: A gas stabilizing plate (24) is provided downstream of the gas dispersion nozzle (23).

4. A low-NOx burner, characterized in that: The device includes a burner brick (1), a bellows assembly (2), an outer gun (3), a continuous lamp (4), and a low-NOx center gun (6) as described in any one of claims 1-3. The burner brick (1) is embedded in the refractory layer at the bottom of the furnace. The burner brick (1) has a square hole that connects the inside and outside of the furnace wall. The bellows assembly (2) is connected to the outside of the furnace wall and is connected to one end of the burner brick (1). The continuous lamp (4) and the low-NOx center gun (6) both extend through the bellows assembly (2) into the square hole of the burner brick (1). The outer gun (3) extends through the burner brick (1) into the furnace wall. The ignition end of the continuous lamp (4) is located on the side of the low-NOx center gun (6) facing the inside of the furnace wall, where the gas stabilizing plate (24) faces.

5. A low-NOx burner according to claim 4, characterized in that: The height difference between the ignition end of the lamp (4) outlet and the gas stabilizing plate (24) of the low nitrogen center gun (6) is within the range of -20mm to 20mm, and the horizontal offset is 30-50mm.

6. A low-NOx burner according to claim 4, characterized in that: The gas horizontal pipe (22) and the gas stabilizing plate (24) are both perpendicular to the air supply direction of the combustion air in the burner brick (1).

7. A low-NOx burner according to claim 4, characterized in that: Along the direction of the combustion air flow inside the burner brick (1), the gas stabilizing plate (24) is located directly downstream of the gas dispersing nozzle (23).

8. A low-NOx burner according to claim 7, characterized in that: The gas stabilizing plate (24) is located in the gas concentration range corresponding to the gas concentration range of 80% to 150% excess air coefficient after the gas and air are mixed.

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