Ultra-low NOx burner

Abstract

The ultralow NOx burner comprises a peripheral gun, a central ring gun, an incandescent light, an air bellow, a brick supporting plate, an inner-layer brick and an outer-layer brick. A plurality of peripheral guns are evenly distributed on the inner wall of a combustor shell, an incandescent light is installed in the center of an inner cavity of the shell, a center ring gun is arranged around the incandescent light, a brick supporting plate is installed above the combustor shell, an inner-layer brick and an outer-layer brick are installed on the brick supporting plate, and a hollow cavity formed in the inner side of the inner-layer brick forms a primary air channel. A cavity between the inner-layer brick and the outer-layer brick is a secondary air channel, the upper portion of the outer-layer brick is closed up, and the air bellow is installed on the combustor shell and communicated with an inner cavity of the shell. According to the combustor, the limitation of single grading of a traditional combustor is broken through, and accurate control over the grading proportion and the combustion height of gas and air collaborative grading is achieved through the two layers of spray guns and the two layers of burner bricks.

Description

Technical Field

[0001] This invention belongs to the field of industrial combustion equipment technology, and relates to an ultra-low NOx burner, specifically an ultra-low NOx burner for a gas-air co-stage heating furnace. Background Technology

[0002] The existing low-NOx combustion technologies in heating furnace burners are mainly staged combustion of fuel gas or staged combustion of air, combined with the flue gas recirculation technology that is mostly equipped with existing burners, which can only guarantee 60 mg / Nm³. 3 Strive for 50 mg / Nm 3 For higher emission standards, it is necessary to rely on subsequent denitrification devices, which increases construction costs and catalyst investment.

[0004] The synergy between gas staging and air staging technologies presents significant challenges for burner design, especially the precise control of the staging ratio and combustion height of gas and air. The primary and secondary combustion zones must not be coupled to prevent the peak flame temperature from rising to the threshold for rapid formation of thermal NOx.

[0005] To resolve the aforementioned contradictions, there is an urgent need in this field to develop a low-NOx combustion system that allows for the coordinated staged combustion of fuel gas and air. Summary of the Invention

[0006] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose an ultra-low NOx burner.

[0007] The solution of the present invention is: An ultra-low NOx burner includes an outer ring gun, a central ring gun, a continuous lamp, a bellows, a brick support plate, an inner layer of bricks, and an outer layer of bricks; Multiple peripheral guns are evenly distributed on the inner wall of the burner shell. A continuous lamp is installed in the center of the inner cavity of the shell, and a central ring gun is arranged around the continuous lamp. The bottoms of the peripheral guns, the central ring gun, and the continuous lamp all protrude from the lower end of the burner shell. A brick support plate is installed on the top of the burner shell. Inner and outer bricks are installed on the brick support plate, and the hollow cavity formed on the inner side of the inner brick constitutes the primary air channel. The cavity between the inner and outer bricks is the secondary air channel. The upper parts of the central ring gun and the continuous lamp extend into the hollow cavity of the inner brick. Both the primary and secondary air channels are connected to the inner cavity of the burner shell. The lower part of the outer brick is columnar, and the upper part is frustum-shaped. The inner diameter of the uppermost opening of the outer brick is smaller than the inner diameter of the column. The air box is installed on the burner shell and is connected to the inner cavity of the shell. The outer ring gun is equipped with an upward main spray hole and a horizontal spray hole above it. The horizontal spray hole faces the outer layer brick, and the outer layer brick has a pre-set opening at the position corresponding to the horizontal spray hole. The central ring gun is equipped with a spray hole directly above and a spray hole diagonally above. The diagonally above spray hole faces the inner wall of the inner layer brick.

[0008] Preferably, the acute angle between the center of the upward main nozzle above the outer gun and the vertical direction is 5°-12°.

[0009] Preferably, the lower surface area of ​​the primary air duct accounts for 15%-25% of the sum of the lower surface areas of the primary air duct and the secondary air duct.

[0010] Preferably, a distance should be left between the outer side of the inner layer brick and the inner side of the outer layer brick.

[0011] Preferably, the minimum horizontal distance between the outer side of the inner layer brick and the inner side of the outer layer brick The thickness ranges from 10mm to 40mm.

[0012] Preferably, the load of the central ring gun accounts for 10-15% of the total burner load.

[0013] Preferably, the burner air-fuel ratio is achieved by controlling the ratio of fuel intake volume between the central annular cavity and the bottom of the outer gun, as well as the minimum annular gap area between the inner and outer brick layers. .

[0014] The advantages of this invention compared to the prior art are: 1. Ultra-low NOx emissions: The primary combustion zone features lean-burn, oxygen-rich combustion within the burner bricks, resulting in combustion deviating from the stoichiometric ratio and a combustion temperature ≤1500℃. The secondary combustion zone utilizes the diluted non-combustible components within the furnace, further reducing localized flame temperatures to ≤1300℃ and suppressing thermal NOx formation. In the outer nozzle ejection zone, the combustion gas ignites inert gases within the furnace, resulting in lower localized oxygen content and temperatures, thereby reducing nitrogen oxide emissions.

[0015] 2. The burner brick structure is simple and effective. Through the structural changes of the two layers of burner bricks, it can adapt to the flame height of different loads and different fuels, ensuring that the two combustion zones do not interfere with each other, thereby minimizing NOx generation in the interference zone.

[0016] 3. By synergistically controlling the oxygen concentration, temperature, and burner brick spatial configuration, NOx emission concentration can be reduced to below 30 mg / Nm³. Attached Figure Description

[0017] Figure 1 This is a cross-sectional view of an ultra-low NOx burner according to the present invention; Figure 2 This is a dynamic airflow diagram of an ultra-low NOx burner according to the present invention. Detailed Implementation

[0018] The invention will now be further described with reference to the accompanying drawings.

[0019] This invention aims to overcome the limitations of traditional single-stage low-NOx technology in furnace burners and solve the problem of low NOx deep removal efficiency. Specific objectives include: 1. Without the need for external power, the oxygen concentration in the secondary combustion zone is ≤15%, and the oxygen concentration in the secondary air zone inside the brick is ≤20%, achieved through self-ejected flue gas. 2. By synergistically controlling the oxygen concentration, temperature, and burner brick spatial configuration, a primary combustion zone with lean combustion and oxygen enrichment is formed, with a combustion temperature ≤1500℃; a secondary combustion zone with flue gas mixing and a combustion temperature ≤1300℃, and no interference between the primary and secondary combustion zones, thereby ensuring that the NOx emission concentration is reduced to below 30 mg / Nm³.

[0020] Staged combustion technology refers to the use of staged combustion gases to deviate from the stoichiometric ratio of the combustion reaction, thereby reducing the local high-temperature zone of combustion and thus reducing nitrogen oxide emissions.

[0021] like Figure 1 and Figure 2 As shown, the burner of the present invention includes an outer ring gun 1, a central ring gun 2, a continuous lamp 3, a bellows 4, a brick support plate 5, an inner layer brick 6, and an outer layer brick 7.

[0022] Multiple peripheral guns 1 are evenly distributed on the inner wall of the burner shell. A continuous lamp 3 is installed at the center of the inner cavity of the shell, and a central ring gun 2 is arranged around the continuous lamp 3. The bottoms of the peripheral guns 1, the central ring gun 2, and the continuous lamp 3 all extend through the lower end of the burner shell. A brick support plate 5 is installed above the burner shell. Inner bricks 6 and outer bricks 7 are installed on the brick support plate 5, and the hollow cavity formed on the inner side of the inner bricks 6 forms a primary air channel 101. The cavity between the inner bricks 6 and the outer bricks 7 is a secondary air channel 102. Both the primary air channel 101 and the secondary air channel 102 are connected to the inner cavity of the burner shell. The lower part of the outer brick 7 is columnar, and the upper part is frustum-shaped, and the inner diameter of the uppermost opening of the outer brick is smaller than the inner diameter of the column. The air box 4 is installed on the burner shell and is connected to the inner cavity of the shell. The bellows 4 is installed on the burner shell and communicates with the inner cavity of the shell; the outer gun 1 is provided with an upward spray hole and a horizontal spray hole, the horizontal spray hole facing the outer layer brick, and a pre-set opening on the outer layer brick corresponding to the horizontal spray hole; the central ring gun 2 is provided with a direct upward spray hole and an oblique upward spray hole, the oblique upward spray hole facing the inner wall of the inner layer brick.

[0023] This invention proposes a structure consisting of two layers of spray guns and two layers of burner bricks, as detailed below: 1. Primary combustion zone: Primary air volume accounts for 15-25% of the total air volume, and the central ring nozzle accounts for 10-15% of the total load, based on the air-fuel ratio. The lean-burn, oxygen-enriched combustion method limits the primary combustion temperature to ≤1500℃, suppressing the formation of thermal NOx. The air-fuel ratio of the burner is achieved by controlling the ratio of fuel intake from the central annular cavity to the bottom of the outer nozzle, as well as the minimum annular gap area between the inner and outer bricks. The lower surface area of ​​the primary air duct accounts for 15%-25% of the combined lower surface area of ​​the primary and secondary air ducts, thus achieving a primary air volume of 15%-25% of the total air volume.

[0024] The primary and secondary air distribution ratio of the straight-tube brick is directly proportional to the inlet area. However, due to the thermal expansion caused by combustion within the inner layer of brick, a tapering brick shape is designed at the top of the outer layer of brick to utilize the minimum annular gap area s between the inner and outer layers of brick (e.g., ...). Figure 2 (As shown) It compensates for the volume expansion caused by the temperature rise in the primary combustion zone, effectively balancing the thermal expansion of combustion and the back pressure of secondary air caused by the narrowing, so that the ratio of primary air to secondary air meets the design requirements.

[0025] The ignition method utilizes a semi-premixed continuous lamp to provide a stable ignition source. The central ring gun has multiple nozzle angles; some nozzles direct the gas flow drastically after it hits the inner layer brick, creating a short burst of combustion in conjunction with the stable ignition source from the continuous lamp. Other gas is directed towards the higher primary combustion zone. Due to the obstruction of the inner layer brick, the flame diameter in the primary combustion zone will not completely fill the outlet of the outer burner brick. To ensure that the flame does not suddenly expand and fill the outer burner brick due to the sudden expansion of the flow channel, a gap must be maintained between the outer side of the inner layer brick and the inner side of the outer layer brick. The horizontal distance is maintained. The high-speed secondary airflow isolates the outer ring combustion gases from the high-temperature central flame. Since the high-speed secondary airflow is unaffected by the central ring combustion, maintaining a lower temperature effectively prevents the outer ring combustion gases from being ignited.

[0026] 2. Kinetic Gradient Ejector: The peripheral gun's gas load accounts for 85-90% of the total load, and the gas injection velocity can instantaneously reach the local speed of sound, forming a negative pressure zone with a pressure difference ≥500 Pa, autonomously inducing the mixing of furnace flue gas and gas. The vertical inclination angle of the peripheral gun's main nozzle should be as small as possible to avoid flame interference in the primary combustion zone. At the same time, the nozzle's inclination angle should still maintain a slight angle towards the burner centerline to ensure that the secondary air and peripheral gun gas contact and ignite at a certain height. Therefore, the acute angle between the center of the upward main nozzle and the vertical direction is designed to be 5°-12°. Through the mixing of the gas-side ejected flue gas and the primary combustion products on the air side, the secondary combustion temperature is ≤1300℃, and the NOx generation approaches zero.

[0027] The gas mixture from the outer gun is injected into the pre-reserved openings in the outer brick. Since the gas concentration does not reach the lower limit of flammability, the gas, flue gas, and air at the opening will only mix and not burn, and will flow along the outer wall, reducing the oxygen content of the secondary air.

[0028] 3. Multi-dimensional gradient layer: The combustion gases from the continuous lamp and the central ring gun burn out not far from the brick opening, the volume of combustion products no longer expands, the local static pressure rises, and the secondary air near the center experiences local backflow under pressure, further preventing the combustion gases from the outer guns from being ignited. The primary combustion products and secondary air slowly mix in the multi-dimensional gradient layer, further reducing the oxygen content.

[0029] The secondary air system employs a triple design: it draws in some flue gas through openings within the brickwork; it mixes with the burnout products from the primary combustion zone; and it draws in some flue gas from the outer combustion guns. The secondary air, drawing in some flue gas through the openings, mixes with the high-temperature flue gas and primary combustion products within the furnace, exchanging heat and mixing with them. It then converges with the outer combustion guns in the secondary combustion zone. The non-combustible components dilute the gas and oxygen concentrations, preventing excessively high flame temperatures and the formation of large amounts of thermal NOx; NOx formation approaches zero.

[0030] The specific process of this invention is as follows: Combustion air enters the burner through the bellows 4, and after passing through the brick support plate 5, it is divided into two streams by the inner bricks 6. These streams enter the furnace through the primary air passage 101 and the secondary air passage 102, respectively. The primary air volume accounts for 15-25% of the total air volume. The primary air passage 101 contains a central ring lance 2 and a continuous lamp 3, with the central load accounting for 10-15% of the total load. The inner bricks 6 are 80mm-200mm higher than the central ring lance 2, and the central ring lance 2 is 30mm-80mm higher than the continuous lamp 3. The central ring lance 2 has two types of nozzle angles: the first is an upward-sloping nozzle, ensuring it faces the brick side and does not spray into the secondary air passage 102; the second is sprayed towards the higher primary combustion zone 201. The central ring lance 2 is ignited by the continuous lamp 3, forming the primary combustion zone 201 within the primary air passage 101. A gap must be maintained between the inner bricks 6 and the outer bricks 7. Horizontal distance. The thickness is 10mm-40mm. After passing through the first combustion zone 201, where the combustion products and part of the secondary air are mixed and exchanged for heat in the multi-dimensional gradient layer 202.

[0031] The gas from each outer gun 1 is divided into two streams, which are ejected from the outer gun ejection area 204. One stream is horizontally injected into the secondary air channel 102 through the outer brick opening area 205, and the other stream is injected into the secondary combustion zone 203.

[0032] This invention effectively reduces nitrogen oxide emissions while reducing costs through staged fuel combustion, staged air combustion, flue gas self-ejection circulation, and delayed combustion technologies.

[0033] This invention has the following innovations: 1. Primary Combustion Zone: By precisely controlling the gas ratio, primary air ratio, and inner burner brick size of the central ring burner, lean-burn and oxygen-rich combustion is ensured within the primary combustion zone. The central flame does not completely fill the outer burner brick outlet. High-speed airflow isolates the outer burner gas from contact with the high-temperature flame. The high-speed secondary air is unaffected by the central ring burner combustion, maintaining a lower temperature to effectively prevent the outer burner gas from being ignited. The tapered design at the top of the outer brick utilizes the minimum annular gap area between the inner and outer bricks to compensate for the volume expansion caused by the temperature rise in the primary combustion zone, thereby offsetting the secondary air back pressure caused by the tapered outer brick, ensuring the primary and secondary air ratios meet design requirements.

[0034] 2. Kinetic gradient ejection: The negative pressure zone formed by the high-speed injection of gas from the outer gun autonomously ejects the flue gas and fuel gas in the furnace. The gas from the outer gun will not be ignited in the furnace bottom or bricks because it does not meet the combustion conditions. The non-combustible components in the flue gas dilute the concentration of fuel gas and oxygen, thereby reducing the peak flame temperature.

[0035] 3. Multi-dimensional gradient layer: The combustion gases from the continuous lamp and the central ring lamp burn completely at a certain height, preventing further expansion of the combustion products. This leads to a local increase in static pressure, and the secondary air near the center experiences localized backflow under pressure, further preventing the outer lamp combustion gases from being ignited. Because the secondary air irradiates some flue gas through openings in the brick, and the outer lamp combustion gases also irradiate some flue gas, in the secondary combustion zone at the intersection of the outer lamps, non-combustible components dilute the gas and oxygen concentrations, preventing excessively high flame temperatures and the formation of thermal NOx.

[0036] This invention ensures that the two combustion zones do not interfere with each other by changing the structure of the two-layer burner bricks, breaking through the limitation of the single stage of traditional burners. Through the structure of two-layer spray guns and two-layer burner bricks, it achieves precise control of the stage ratio and combustion height of gas and air co-stage.

[0037] The parts of this invention not described in detail are common knowledge to those skilled in the art.

Claims

1. An ultra-low NOx burner, characterized in that: Includes outer ring gun (1), central ring gun (2), constant lamp (3), bellows (4), brick support plate (5), inner brick (6), outer brick (7); Multiple peripheral guns (1) are evenly distributed on the inner wall of the burner shell. A continuous lamp (3) is installed in the center of the inner cavity of the shell. A central ring gun (2) is arranged around the continuous lamp (3). The bottoms of the peripheral guns (1), the central ring guns (2), and the continuous lamp (3) all protrude from the lower end of the burner shell. A brick support plate (5) is installed on the top of the burner shell. Inner bricks (6) and outer bricks (7) are installed on the brick support plate (5), and the hollow cavity formed on the inner side of the inner bricks (6) constitutes the primary air channel (10). 1) The cavity between the inner brick (6) and the outer brick (7) is a secondary air channel (102). The upper part of the central ring gun (2) and the continuous lamp (3) extends into the hollow cavity of the inner brick. The primary air channel (101) and the secondary air channel (102) are both connected to the inner cavity of the burner shell. The lower part of the outer brick (7) is columnar and the upper part is frustum-shaped. The inner diameter of the uppermost opening of the outer brick is smaller than the inner diameter of the column. The wind box (4) is installed on the burner shell and is connected to the inner cavity of the shell. Above the outer gun are an upward main spray hole and a horizontal spray hole. The horizontal spray hole faces the outer brick, and a pre-set opening is provided on the outer brick at the position corresponding to the horizontal spray hole. The central ring gun is equipped with a spray hole directly above and a spray hole at an angle above, with the spray hole at the angle above facing the inner wall of the inner brick layer.

2. The ultra-low NOx burner according to claim 1, characterized in that: The acute angle between the center of the upward main nozzle above the outer gun and the vertical direction is 5°-12°.

3. The ultra-low NOx burner according to claim 1, characterized in that: The lower surface area of ​​the primary air duct accounts for 15%-25% of the combined lower surface area of ​​the primary and secondary air ducts.

4. The ultra-low NOx burner according to claim 1, characterized in that: A distance must be left between the outer side of the inner layer bricks and the inner side of the outer layer bricks.

5. The ultra-low NOx burner according to claim 4, characterized in that: Minimum horizontal distance between the outer side of the inner layer brick and the inner side of the outer layer brick The thickness ranges from 10mm to 40mm.

6. The ultra-low NOx burner according to claim 1, characterized in that: The load of the central ring lance accounts for 10-15% of the total burner load.

7. The ultra-low NOx burner according to claim 1, characterized in that: The air-fuel ratio of the burner is achieved by controlling the ratio of fuel intake volume between the central annular cavity and the bottom of the outer gun, as well as the minimum annular gap area between the inner and outer bricks. .

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