A gas low-nitrogen burner and combustion method for coupling barrier wind and staged combustion

Abstract

The present invention discloses a gas low-nitrogen burner and a combustion method that couples barrier wind with staged combustion. Through the three-dimensional arrangement of gas, air and barrier wind nozzles, air, gas and 20% to 25% of recycled flue gas are evenly divided into three stages as barrier wind and delivered into the furnace. The barrier wind can delay the direct contact between air and gas, so that the gas is fully mixed with the air before ignition and is evenly diluted by the barrier wind, thereby achieving uniform combustion and uniform temperature field in the space. At the same time, the barrier wind can also reduce the oxygen partial pressure, absorb the released heat, and reduce local high-temperature areas; in addition, through the three-dimensional arrangement of gas and air and the reasonable step-by-step distribution of gas and air into the furnace, the high-temperature combustion area is controlled to create a reducing atmosphere, even in the presence of NO x The present invention couples the barrier wind and staged combustion technology to reduce the NO x The emission concentration is reduced to less than 30mg / Nm 3 It is suitable for newly built or existing low-nitrogen gas boiler projects and has broad application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of low-nitrogen combustion of gas boilers, and in particular to a gas low-nitrogen burner and a combustion method for coupling barrier wind and staged combustion. Background Art

[0002] Compared with other fossil energy sources, natural gas basically does not generate sulfide and flue gas dust during combustion, but NO x In the future, as more natural gas is burned and utilized, how to effectively reduce the NO generated during the combustion process will be a challenge. x Emissions will be a significant undertaking.

[0003] In recent years, in order to further reduce the nitrogen oxide emissions of newly built and in-use gas boilers and improve air quality, all regions across the country have successively introduced more stringent local standards while meeting the national nitrogen oxide emission standards, forcing major burner manufacturers, boiler manufacturers, and user companies to make changes. At present, there are two main measures to achieve low-nitrogen combustion in gas boilers on the market: one is low-nitrogen burners, and the other is tail gas treatment. Compared with tail gas treatment, using low-nitrogen burners to achieve low-nitrogen combustion is more effective, stable and economical.

[0004] The development of existing low-nitrogen burners mainly focuses on how to reduce the combustion temperature, reduce the size of the reaction zone, reduce the residence time and reduce the thermal NO x The main technologies include staged combustion (including air staging and fuel staging), lean premixed combustion, flue gas recirculation, flameless combustion, swirl combustion, etc. Relevant studies have shown that the flue gas recirculation coupled staged combustion technology has a wide range of applications, and the nitrogen reduction effect can reach up to 90%. However, in actual applications, it was found that problems such as burner hierarchical structure design, unreasonable gas distribution, too high or too low flue gas recirculation rate, and corrosion of flue gas recirculation pipelines caused it to fail to meet the designed emission reduction requirements and low thermal efficiency, and even boiler surge and flameout. In view of this, it is necessary to invent a low-nitrogen burner and combustion method with low nitrogen compound emissions, high thermal efficiency, and stable combustion by optimizing the burner structure, the use of recycled flue gas, and the gas and air staging ratio. Summary of the invention

[0005] The purpose of the present invention is to provide a gas low-nitrogen burner and a combustion method that couples barrier wind and staged combustion. By sending the recycled flue gas into the furnace as barrier wind in stages, the direct contact and ignition of air and gas are delayed, so that the gas is fully mixed with more air before ignition and is evenly diluted by the barrier wind, so as to achieve uniform combustion and uniform temperature field in the space. The barrier wind can also reduce the oxygen partial pressure, absorb the released heat, and reduce the local high-temperature area. In addition, through the three-dimensional arrangement of gas and air and the reasonable step-by-step distribution, the high-temperature combustion area is controlled to create a reducing atmosphere. Even if there is NO x Most of the generated carbon will be reduced, while ensuring the thermal efficiency and stability of combustion.

[0006] The present invention is achieved by adopting the following technical solutions:

[0007] A gas low-nitrogen burner coupling barrier wind and staged combustion, comprising a burner housing, a secondary fuel pipe, a tertiary fuel pipe, a primary barrier wind nozzle, a secondary barrier wind nozzle and a tertiary barrier wind nozzle;

[0008] A primary air nozzle is arranged at the center of the burner shell, and a plurality of primary fuel pipes for direct air injection are arranged circumferentially around the primary air nozzle. With the primary air nozzle as the center, secondary air nozzles, tertiary air nozzles and quaternary air nozzles are distributed radially from the inside to the outside, and a plurality of secondary air nozzles, tertiary air nozzles and quaternary air nozzles are arranged circumferentially to inject air in a direct direction.

[0009] The secondary fuel pipes are alternately arranged on the same circumference of the secondary air nozzles for direct current injection of fuel gas; the tertiary fuel pipes are alternately arranged on the circumference between the tertiary air nozzles and the quaternary air nozzles, deviating outward from the central axis by 10 to 20°; a number of primary barrier air nozzles, secondary barrier air nozzles and tertiary barrier air nozzles are respectively arranged circumferentially around the secondary air nozzles, tertiary air nozzles and quaternary air nozzles for direct current injection of barrier air.

[0010] A further improvement of the present invention is that the fuel ejection end is at the front and the inlet end is at the rear, and the primary air nozzle, secondary air nozzle, tertiary air nozzle, quaternary air nozzle, primary barrier air nozzle, secondary barrier air nozzle and tertiary barrier air nozzle are all arranged at the rear.

[0011] A further improvement of the present invention is that the diameters of the primary fuel pipe, the secondary fuel pipe and the tertiary fuel pipe increase sequentially.

[0012] A method for low-nitrogen combustion of gas by coupling barrier wind and staged combustion, based on the low-nitrogen burner of gas by coupling barrier wind and staged combustion, comprises the following steps:

[0013] Air is injected into the central primary air nozzle in a jet-like high-speed manner, and a small amount of gas ejected from the first-level fuel pipe is sucked in and burned. The excess air coefficient in the central area near the burner is 10. The flue gas temperature after combustion is 500-600℃, forming a hollow flame with basically no NO x The flue gas produced by combustion contains a large amount of oxygen, which draws in the surrounding unburned components in the middle of the furnace and ignites and burns stably;

[0014] The secondary fuel pipe sprays 24-30% of the fuel, and the tertiary fuel pipe is offset 10-20° outward along the axis to spray 66-70% of the total fuel; the excess air coefficient of the secondary and tertiary gas combustion areas is less than 1, and they are always in an oxygen-poor state and full of reducing atmosphere, even if the NO generated locally during the combustion process x Most of it will also be restored;

[0015] The recirculated flue gas is injected as a barrier wind from the primary barrier wind nozzle, the secondary barrier wind nozzle and the tertiary barrier wind nozzle in the form of a jet. The air injected at high speed from the secondary air nozzle, the tertiary air nozzle and the quaternary air nozzle draws the barrier wind. On the one hand, it delays the direct contact and ignition of air and gas, so that the gas is fully mixed with more air before ignition and is evenly diluted by the barrier wind, so as to achieve uniform combustion and uniform temperature field in the space; on the other hand, it reduces the oxygen partial pressure, absorbs the released heat, reduces the local high temperature area, and weakens the generation of thermal NO by oxygen and nitrogen. x process.

[0016] A further improvement of the present invention is that the extracted flue gas within the temperature range of 120-150°C is evenly graded and injected through the primary barrier wind nozzle, the secondary barrier wind nozzle and the tertiary barrier wind nozzle, and the barrier wind is directly graded and sent into the furnace without mixing with the air outside the furnace, thus avoiding the problem of condensed water corroding the pipes and fans caused by the mixing of flue gas and cold air outside the furnace in the existing flue gas recirculation system.

[0017] A further improvement of the present invention is that the method is used in high altitude areas where the ambient temperature is below zero degrees in some seasons and the heat dissipation loss of the recirculating flue gas pipeline is large, and flue gas within the temperature range of 150 to 200°C should be selected.

[0018] A further improvement of the present invention is that the barrier air volume accounts for 20-25% of the total flue gas volume, reducing the generation of nitrogen oxides while ensuring the thermal efficiency and stability of combustion.

[0019] A further improvement of the present invention is that the central primary air volume accounts for 60%-70% of the total air volume.

[0020] The present invention has at least the following beneficial technical effects:

[0021] The present invention provides a gas low-nitrogen burner that couples barrier wind and staged combustion, wherein a primary air nozzle is arranged at the center of the burner, and a plurality of first-level fuel pipes for DC air injection are arranged circumferentially around the primary air nozzle; with the primary air nozzle as the center, secondary air nozzles, tertiary air nozzles and quaternary air nozzles are distributed radially in sequence from the inside to the outside; the second-level fuel pipes are alternately arranged on the same circumference of the secondary air nozzles, for DC injection of gas; the tertiary fuel pipes are alternately arranged on the circumference between the tertiary air nozzles and the quaternary air nozzles, deviating outward from the central axis by 10 to 20 degrees; a plurality of primary barrier air nozzles, secondary barrier air nozzles and tertiary barrier air nozzles are respectively arranged circumferentially around the secondary air nozzles, the tertiary air nozzles and the quaternary air nozzles, for DC injection of barrier wind. The above three-dimensional arrangement of gas, air and barrier wind nozzles can reasonably distribute the fuel amount, air amount and barrier wind amount, control the gas combustion rate, the high temperature area of ​​the furnace, the residence time of the reactants in the high temperature area, ensure complete and stable combustion while effectively controlling the generation of thermal nitrogen oxides, and achieve nitrogen oxide generation of less than 30mg / Nm3.

[0022] The present invention provides a method for low-nitrogen combustion of gas by coupling barrier wind and staged combustion. Based on the above-mentioned burner structure, 20% to 25% of the recycled flue gas is sent into the furnace as barrier wind in stages, delaying the direct contact and ignition of air and gas, allowing the gas to be fully mixed with more air before ignition and evenly diluted by the barrier wind, thereby achieving uniform combustion and uniform temperature field in the space, and the barrier wind can also reduce the oxygen partial pressure, absorb the released heat, and reduce the local high-temperature area; in addition, the three-dimensional arrangement of gas and air and the reasonable step-by-step distribution of gas and air into the furnace can control the high-temperature combustion area and create a reducing atmosphere, even if there is NO x Most of the generation will also be restored. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the three-dimensional structural principle of the present invention;

[0024] Figure 2 It is a front view of the present invention;

[0025] Figure 3 This is a diagram of the barrier wind structure.

[0026] Description of reference numerals:

[0027] 1 is the primary air nozzle; 2 is the secondary air nozzle; 3 is the tertiary air nozzle; 4 is the quaternary air nozzle; 5 is the primary barrier air nozzle; 6 is the secondary barrier air nozzle; 7 is the tertiary barrier air nozzle; 8 is the primary fuel pipe; 9 is the secondary fuel pipe; 10 is the tertiary fuel pipe; 11 is the burner shell. DETAILED DESCRIPTION

[0028] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to be able to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features described in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0029] like Figure 1 , Figure 2 and Figure 3 As shown, the present invention provides a gas low-nitrogen burner that couples barrier wind and staged combustion, including a burner housing 11, a primary air nozzle 1 arranged in the center, a first-level fuel pipe 8 arranged circumferentially around the primary air nozzle 1, and injecting gas in a straight line; secondary air nozzles 2, tertiary air nozzles 3 and quaternary air nozzles 4 are radially distributed from the inside to the outside, and are all arranged circumferentially in a straight line to inject air; the second-level fuel pipes 9 are alternately arranged on the same circumference of the secondary air nozzle 2, and inject gas in a straight line; the tertiary fuel pipes 10 are alternately arranged on the circumference between the tertiary air nozzles 3 and the quaternary air nozzles 4, and deviate outward from the central axis by 10 to 20 degrees. The first barrier air nozzles 5, the secondary barrier air nozzles 6 and the tertiary barrier air nozzles 7 are respectively arranged circumferentially around the secondary air nozzles 2, the tertiary air nozzles 3 and the quaternary air nozzles 4, and inject barrier air in a straight line.

[0030] With the fuel ejection end at the front and the inlet end at the rear, the central primary air nozzle 1, secondary air nozzle 2, tertiary air nozzle 3, quaternary air nozzle 4, primary barrier air nozzle 5, secondary barrier air nozzle 6 and tertiary barrier air nozzle 7 are all arranged at the rear.

[0031] The diameters of the primary fuel pipe 8, the secondary fuel pipe 9 and the tertiary fuel pipe 10 of the burner increase in sequence.

[0032] The present invention provides a method for low-nitrogen combustion of fuel gas by coupling barrier wind and staged combustion, comprising the following steps:

[0033] 60%-70% of the air is injected into the central primary air nozzle 1 in a jet-like high-speed manner, sucking in a small amount of gas ejected from the primary fuel pipe 8 to burn, making the excess air coefficient in the central area near the burner much greater than 1, the combustion temperature is low, forming a hollow flame, and basically no NO x The 500-600℃ flue gas produced by combustion contains a large amount of oxygen, which draws in the surrounding unburned components in the middle of the furnace and ignites and burns stably.

[0034] The secondary fuel pipe 9 injects 24-30% of the fuel amount, and the tertiary fuel pipe 10 injects 66-70% of the total fuel amount; the excess air coefficient of the secondary and tertiary gas combustion areas is about 0.4-0.5, which is always in an oxygen-poor state and full of reducing atmosphere, even if the NO generated locally during the combustion process x Most of it will be restored.

[0035] 20-25% of the recirculated flue gas is injected as a barrier wind from the primary barrier wind nozzle 5, the secondary barrier wind nozzle 6 and the tertiary barrier wind nozzle 7. 30%-40% of the air is injected as a jet from the secondary air nozzle 2, the tertiary air nozzle 3 and the quaternary air nozzle 4. The high-speed jet air entrains the barrier wind, which, on the one hand, delays the direct contact and ignition of air and gas, allowing the gas to be fully mixed with more air before ignition and evenly diluted by the barrier wind, thus achieving uniform combustion and uniform temperature field in the space; on the other hand, it reduces the oxygen partial pressure, absorbs the released heat, reduces the local high-temperature area, and weakens the generation of thermal NO by oxygen and nitrogen. x process.

[0036] The flue gas injected by the jets of the primary barrier air nozzle 5, the secondary barrier air nozzle 6 and the tertiary barrier air nozzle 7 is not mixed with the air outside the furnace and is directly sent to the furnace in stages, which completely avoids the problem of condensed water corroding the pipes and fans in the existing flue gas recirculation system due to the mixing of flue gas and cold air outside the furnace. If used in high-altitude areas, the ambient temperature is low (especially in winter), and the heat loss of the recirculating flue gas pipe is large, a higher flue gas temperature should be selected than in plain areas.

[0037] The biggest feature of the implementation of the present invention is that the combustion is completely stable while ensuring the effect of low-nitrogen combustion. Through the three-dimensional arrangement of the gas, air and barrier wind nozzles and the reasonable distribution of the fuel amount, air amount and barrier wind amount, the mixing time of the gas, air and barrier wind during the combustion process and the mixing fraction of each combustion area are controlled, thereby controlling the combustion rate, the high-temperature area of ​​the furnace, and the residence time of the reactants in the high-temperature area, ensuring that the combustion is completely stable while effectively controlling the generation of thermal nitrogen oxides, and achieving nitrogen oxide generation of less than 30mg / Nm 3 It can be used in new or existing low-nitrogen gas boiler projects and has strong engineering application scenarios.

[0038] It should be understood that this embodiment is only used to illustrate the present invention and is not intended to limit it. It should also be understood that those skilled in the art may make various modifications or equivalent substitutions to the present invention, which should all be considered within the scope of protection of the invention without departing from the principles of the present invention.

Claims

1. A gas low-nitrogen burner coupling barrier wind and staged combustion, characterized in that: It comprises a burner housing (11), a secondary fuel pipe (9), a tertiary fuel pipe (10), a primary barrier air nozzle (5), a secondary barrier air nozzle (6) and a tertiary barrier air nozzle (7); A primary air nozzle (1) is arranged at the center of the burner housing (11), and a plurality of first-level fuel pipes (8) for direct injection of air are arranged circumferentially around the primary air nozzle (1). A secondary air nozzle (2), a tertiary air nozzle (3) and a quaternary air nozzle (4) are arranged radially in sequence from the inside to the outside with the primary air nozzle (1) as the center, and a plurality of the secondary air nozzles (2), the tertiary air nozzles (3) and the quaternary air nozzles (4) are arranged circumferentially to direct injection of air. The secondary fuel pipes (9) are arranged alternately on the same circumference of the secondary air nozzle (2) for direct injection of fuel gas; the tertiary fuel pipes (10) are arranged alternately on the circumference between the tertiary air nozzle (3) and the quaternary air nozzle (4) and deviate outward from the central axis by 10 to 20 degrees; a plurality of primary barrier air nozzles (5), secondary barrier air nozzles (6) and tertiary barrier air nozzles (7) are arranged circumferentially around the secondary air nozzle (2), the tertiary air nozzle (3) and the quaternary air nozzle (4) respectively for direct injection of barrier air, wherein the barrier air is recirculated flue gas.

2. A gas low-nitrogen burner coupling barrier wind and staged combustion according to claim 1, characterized in that: With the fuel ejection end at the front and the inlet end at the rear, the primary air nozzle (1), the secondary air nozzle (2), the tertiary air nozzle (3), the quaternary air nozzle (4), the primary barrier air nozzle (5), the secondary barrier air nozzle (6) and the tertiary barrier air nozzle (7) are all arranged at the rear.

3. A gas low-nitrogen burner coupling barrier wind and staged combustion according to claim 1, characterized in that: The diameters of the primary fuel pipe (8), the secondary fuel pipe (9) and the tertiary fuel pipe (10) increase sequentially.

4. A method for low-nitrogen combustion of fuel gas by coupling barrier wind and staged combustion, characterized in that: The method is based on a gas low-nitrogen burner coupling barrier wind and staged combustion according to any one of claims 1 to 3, and comprises the following steps: Air is injected into the central primary air nozzle (1) at high speed in a jet-like manner, and a small amount of gas ejected from the primary fuel pipe (8) is sucked in and burned. The excess air coefficient in the central area near the burner is 10, and the flue gas temperature after combustion is 500-600°C, forming a hollow flame with almost no NO. x The flue gas produced by combustion contains a large amount of oxygen, which draws in the surrounding unburned components in the middle of the furnace and ignites and burns stably; The secondary fuel pipe (9) sprays 24-30% of the fuel amount, and the tertiary fuel pipe (10) is offset 10-20 degrees outward along the axis to spray 66-70% of the total fuel amount; the excess air coefficient of the secondary and tertiary fuel gas combustion areas is less than 1, and they are always in an oxygen-deficient state and full of reducing atmosphere, even if the NO generated locally during the combustion process x Most of it will also be restored; The recirculated flue gas is injected as a barrier wind in the form of a jet from the primary barrier wind nozzle (5), the secondary barrier wind nozzle (6) and the tertiary barrier wind nozzle (7). The air injected at high speed from the secondary air nozzle (2), the tertiary air nozzle (3) and the quaternary air nozzle (4) entrains the barrier wind. On the one hand, it delays the direct contact and ignition of air and gas, so that the gas is fully mixed with more air and evenly diluted by the barrier wind before ignition, thereby achieving uniform combustion and uniform temperature field in the space. On the other hand, it reduces the oxygen partial pressure, absorbs the released heat, reduces the local high temperature area, and weakens the generation of thermal NO by oxygen and nitrogen. x process.

5. A method for low-nitrogen combustion of fuel gas by coupling barrier wind and staged combustion according to claim 4, characterized in that: The extracted flue gas within the temperature range of 120 to 150° C. is uniformly graded and injected through the primary barrier air nozzle (5), the secondary barrier air nozzle (6) and the tertiary barrier air nozzle (7). The barrier air is not mixed with the air outside the furnace and is directly sent into the furnace in grades, thus avoiding the problem of condensed water corroding the pipes and the fan in the existing flue gas recirculation system due to the mixing of flue gas and cold air outside the furnace.

6. A method for low-nitrogen combustion of fuel gas by coupling barrier wind and staged combustion according to claim 4, characterized in that: This method is used in high-altitude areas where the ambient temperature is below zero degrees in some seasons and the heat dissipation loss of the recirculating flue gas duct is large. Flue gas within the temperature range of 150 to 200°C should be selected.

7. A method for low-nitrogen combustion of fuel gas by coupling barrier wind and staged combustion according to claim 4, characterized in that: The barrier air volume accounts for 20-25% of the total flue gas volume, reducing the generation of nitrogen oxides while ensuring the thermal efficiency and stability of combustion.

8. The method for low-nitrogen combustion of fuel gas by coupling barrier wind and staged combustion according to claim 4, characterized in that: The central primary air volume accounts for 60%-70% of the total air volume.

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