Multi-gas species mixed combustion gas burner
By designing a multi-gas co-firing gas burner, and utilizing internal and external secondary air ducts, swirl blades, and flame stabilizers, the problems of uneven mixing of various gases and high NOx emissions were solved, achieving a stable and efficient combustion process with low NOx emissions.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DONGFANG BOILER GROUP OF DONGFANG ELECTRIC CORP
- Filing Date
- 2023-06-05
- Publication Date
- 2026-05-22
AI Technical Summary
Existing gas burners are difficult to effectively match various gases with large differences in calorific value and properties, resulting in uneven gas mixing, unstable combustion, low burnout rate and high NOx emissions, making them difficult to apply in high-power burner boilers.
The multi-gas co-firing gas burner, through the design of internal and external secondary air ducts, swirl blades and flame stabilizers, achieves good mixing and zoned combustion of gas and air. Combined with air and fuel staged technology, it forms annular and layered flames, suppresses the formation of high-temperature zones and reduces NOx generation.
It enables the co-firing of multiple gas types in any proportion, with a stable combustion process, high burnout rate, and low NOx emissions, making it suitable for high-power burner boilers.
Smart Images
Figure CN116857642B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a gas burner, and more particularly to a gas burner for multi-gas co-firing in boilers. Background Technology
[0002] A gas burner is a device that mixes and burns gas and air in a specific ratio. It mainly consists of components such as an ignition gun, secondary air duct, air distributor, and flame stabilizer. As is well known, nitrogen oxides (NOx) are one of the main pollutants causing air pollution, leading to environmental problems such as acid rain and photochemical smog, seriously endangering human health. Therefore, strict NOx emission standards have been introduced, generally limiting the concentration of NOx emitted after combustion to around 50 mg / m³, which poses a significant challenge to industrial production. Against this backdrop, the demand for low-NOx gas burners is showing a continuously growing trend.
[0003] In reality, the industrial sector is characterized by a wide variety of fuels with significant differences in calorific value and properties, such as natural gas, blast furnace gas, coke oven gas, and chemical tail gas. There are many types of existing gas burners, each with its own structure and technical characteristics. Commonly used low-NOx combustion technologies include fuel staging, air staging, and swirl combustion. However, each low-NOx combustion technology also has its own drawbacks. For example, staging and swirl combustion technologies can lead to unstable combustion and decreased thermal efficiency. Therefore, using a single low-NOx combustion technology often fails to meet the needs of actual production. Furthermore, integrating multiple fuels with significantly different calorific values into a single burner makes it difficult to ensure effective matching between the fuels and the combustion chamber. This results in problems such as a narrow range of fuel mixing ratios, uneven fuel mixing, difficulty in achieving stable and efficient co-combustion of multiple fuel types, low burnout rates, and high NOx emissions, making it unsuitable for application in high-power burner boilers.
[0004] Therefore, it is necessary to comprehensively consider the combustion and emission characteristics of various fuels, utilize a variety of low-NOx combustion technologies, and carry out integrated innovation on the combustion nozzles, air distribution, timely mixing, and controllable combustion of the burner. Summary of the Invention
[0005] The purpose of this invention is to address the aforementioned shortcomings of the prior art by providing a multi-gas co-firing gas burner that can achieve arbitrary proportions of multi-gas co-firing, ensuring good mixing of gas and air, realizing reasonable combustion zoning, and achieving low NOx emissions while maintaining stable combustion process and high burnout rate.
[0006] To achieve the above objectives, the present invention provides a multi-gas co-firing gas burner, comprising an ignition gun, a central tube, an inner secondary air duct, and an outer secondary air duct; characterized in that: the outer secondary air duct includes a connected outer secondary air inlet pipe and an outer volute, the outer volute being provided with tangential blades, and a converging nozzle connected to the front end of the outer volute; the inner secondary air duct includes a connected inner secondary air inlet pipe and an inner horizontal pipe; a low-calorific-value gas nozzle is provided between the outer volute and the inner horizontal pipe, the low-calorific-value gas nozzle is connected to a low-calorific-value gas inlet pipe, the low-calorific-value gas nozzle is provided with swirl blades, and the low-calorific-value gas nozzle comprises components connected sequentially from front to back. The system consists of a small-diameter pipe, a tapered pipe, and a large-diameter pipe. Swirl blades are located inside the small-diameter pipe, and a low-calorific-value gas inlet pipe is connected to the large-diameter pipe. A flame stabilizer is placed inside the front end of an inner horizontal pipe and fixedly connected to the central pipe. Several gas nozzles are arranged in two or more concentric rings in the inner horizontal pipe on the radially outer side of the flame stabilizer. Each gas nozzle has several small holes at its head. Gas nozzles on different rings are connected to their respective inlet pipes. At least several gas nozzles on the same ring are divided into two or more groups, and gas nozzles in different groups are staggered in the circumferential direction. Several gas nozzles in the same group are connected to the same inlet pipe.
[0007] In this invention, different types of fuel gases are fed into the burner through nozzles on different annular spray guns and low-calorific-value fuel nozzles. High-calorific-value fuel gases, such as natural gas and coke oven gas, are injected through the spray guns, while low-calorific-value fuel gases, such as blast furnace gas, are injected through the low-calorific-value fuel nozzles. These multiple fuel gases are introduced and burned independently. By adjusting the flow rate of each fuel gas, arbitrary proportions of mixed combustion of multiple fuel types can be achieved, flexibly adjusting the combustion mode. Multiple fuel gases and air are introduced along their respective flow channels, and the mixing and combustion of fuel gases and air are effectively enhanced by the swirl vanes and flame stabilizer. This avoids the rapid formation of large amounts of NOx due to uneven mixing in the initial stage of combustion and achieves combustion zoning. The fuel spray guns at each stage form a annular arrangement. When different fuel gases are blended, multi-layered annular flames can be formed, making the fuel gas as evenly dispersed as possible. This allows the fuel gas to mix and burn rapidly with the combustion air, forming a layered, circumferentially uniform combustion flame. This ensures complete combustion of the fuel gas and prevents heat concentration, which can lead to a combustion field with large temperature deviations. In addition, each fuel gas nozzle injects fuel gas through several small holes, mixing the fuel gas with air to form a small flame combustion mode. The small flames injected by each nozzle are evenly divided, suppressing the occurrence of temperature peaks and valleys. While forming independent flames, making the fuel gas blending mode adjustable, the overall combustion process more complete, and improving the burnout rate, this also avoids the formation of high-temperature zones and reduces the generation of thermal NOx.
[0008] By connecting several gas nozzles in the same group to the same air intake pipe, more types of gas can be mixed and burned, and independent air intake can be used to form a ring-shaped mixed combustion flame, forming a uniform combustion flame in the circumferential direction and avoiding the generation of high-temperature zones.
[0009] Large-diameter pipes can meet the needs of rear-end intake pipes while reducing the flow velocity of low-calorific-value gas to achieve lower resistance. Small-diameter pipes can ensure that the gas injection velocity and airflow, as well as higher velocity, generate higher swirl intensity as they pass through the swirl blades. Conical pipes ensure that no significant local resistance is generated when the airflow passes through them. Since low-calorific-value gas is a rotating jet, small-diameter pipes use straight-channel nozzles, which facilitates coordination with the high-calorific-value gas flame inside to ensure stable and efficient combustion of the calorific-value gas flow.
[0010] The air volume and wind speed can be adjusted by the adjustable tangential blades inside the outer volute and the constricted nozzle at the front end.
[0011] As a further improvement of the present invention, the several gas spray guns in the same group are connected to the same air inlet pipe through an annular distribution pipe; this facilitates the distribution of different types of gas and the replacement of spray guns.
[0012] As a further improvement of the present invention, the axis of the low-calorific-value gas nozzle is perpendicular to the cross-section of the outer volute; this can improve the mixing effect of air and low-calorific-value gas.
[0013] As a further improvement of the present invention, both the external secondary air inlet pipe and the internal secondary air inlet pipe are provided with adjusting baffles; the air volume of the external secondary air and the internal secondary air can be adjusted respectively, so as to accurately realize air grading and combustion grading, and further reduce NOx emissions.
[0014] As a further improvement of the present invention, the low-calorific-value gas inlet pipe is located tangentially to the large-diameter pipe; this can increase the swirl of the low-calorific-value gas flow, thereby improving flame stability and burnout rate during high-proportion combustion.
[0015] In summary, this invention can achieve arbitrary proportions of mixed combustion of multiple gas types, ensuring good mixing of gas and air, realizing reasonable combustion zoning, and achieving low NOx emissions while maintaining stable combustion process and high burnout rate. Attached Figure Description
[0016] Figure 1 This is a perspective view of an embodiment of the present invention.
[0017] Figure 2 This is a cross-sectional view of an embodiment of the present invention.
[0018] Figure 3 for Figure 1 A front view of the nozzle end face of the burner. Detailed Implementation
[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0020] like Figures 1 to 3As shown, this embodiment of a multi-gas co-firing gas burner includes an ignition gun 1, a central pipe 2, an inner secondary air duct, and an outer secondary air duct. The outer secondary air duct includes a connected outer secondary air inlet pipe 6 and an outer volute 4, and a contracting nozzle 5 connected to the front end of the outer volute 4. An adjusting baffle 7 is provided inside the outer secondary air inlet pipe 6, and an adjustable tangential blade 41 is provided inside the outer volute 4. The inner secondary air duct includes a connected inner secondary air inlet pipe 10 and an inner horizontal pipe 8. An adjusting baffle 11 is provided inside the internal secondary air inlet duct 10; a low-calorific-value gas nozzle 3 is provided between the outer volute 4 and the inner horizontal pipe 8, the axis of the low-calorific-value gas nozzle 3 is perpendicular to the cross-section of the outer volute 4, and the low-calorific-value gas nozzle 3 includes a small-diameter pipe 31, a tapered pipe 32 and a large-diameter pipe 33 connected sequentially from front to back, the small-diameter pipe 31 is provided with a swirl vane 34, and the large-diameter pipe 33 is connected to a low-calorific-value gas inlet pipe 35, which is located at... Tangentially, the small diameter pipe 31 has a cavity-type low-calorific-value gas nozzle at its front end. A flame stabilizer 12 is placed inside the front end of the inner horizontal pipe 8 and fixedly connected to the central pipe 2. Several gas nozzles 13, 14, 15, and 16 corresponding to different gases are provided in the inner horizontal pipe 8 on the radially outer side of the flame stabilizer 12. The gas nozzles 13 to 16 are arranged in two concentric rings. The gas nozzles 13, 14 or 15, 16 on the same ring are divided into two groups. The gas nozzles 13 and 14 in different groups are staggered in the ring direction. The gas nozzles 15 and 16 are also staggered in the ring direction. The gas nozzles 13 in the same group are all connected to the air inlet pipe 18 through the ring distribution pipe 17. Similarly, the gas nozzles 14, 15, or 16 in the same group are all connected to their respective air inlet pipes 19, 20, or 21 through their respective ring distribution pipes. The head of each gas nozzle 13 to 16 is provided with several small holes.
[0021] In this embodiment, the ignition gun 1 is located inside the central tube 2, which can also serve as a flame detector or observation hole channel. The flame stabilizer 12 is welded to the central tube 2 and can partially cover the internal secondary air, causing the internal secondary air to swirl. The degree of coverage is expressed by the ratio of the projected area of the flame stabilizer 12 at the internal secondary air outlet end face to the area of the circle formed by the inner wall of the internal secondary air channel. Depending on the change of the gas composition, the coverage ratio is usually 20% to 60%. The swirling internal secondary air is conducive to promoting the mixing of gas and secondary air, and is also conducive to flue gas recirculation and stabilizing the combustion flame.
[0022] In use, different types of gas are fed into the furnace through different gas nozzles 13-16 and the outer horizontal pipe 3. Low-calorific-value blast furnace gas (BFG) is injected through the low-calorific-value gas nozzle at the front end of the small-diameter pipe 31. High-calorific-value and higher-calorific-value natural gas (NG), partially oxidized gas (POX), coke oven gas (COG), and C4 gas (C4) are injected through gas nozzles 13, 14, 15, and 16, respectively. Appropriate numbers of various gas nozzles are arranged in a ring and injected into the furnace at different flow rates. The orifice size and number of different gas nozzles are also different, with the number of orifices determined based on the maximum load pressure of each gas. Multiple gases are introduced and burned independently. The flow rate of each gas can be adjusted by regulating valves on each inlet pipe, achieving arbitrary proportions of mixed combustion of multiple gas types and flexibly adjusting the combustion method. Multiple gases and air are introduced along their respective flow channels, passing through the inner horizontal pipe 8, the outer volute 4, and the contracting nozzle 5. This not only ensures uniform air injection at different circumferential positions but also... The gas enters the furnace and achieves air grading. Under the action of the swirl vanes 34 and the flame stabilizer 12, the mixing and combustion of gas and air are effectively enhanced. This not only avoids the large-scale generation of rapid NOx caused by uneven mixing in the early stage of combustion, but also achieves combustion zoning. The gas spray guns 13-16 form a ring arrangement pattern. When different gases are mixed, multi-layer ring flames can be formed, making the gas as evenly dispersed as possible. This also allows the gas to mix and burn rapidly with the secondary air that assists combustion, forming a layered, circumferentially uniform combustion flame. This ensures complete combustion of the gas and prevents the formation of a combustion field with large temperature deviations due to heat concentration. In addition, each gas spray gun head is injected with several small holes. The gas flow mixes with the air to form a small flame combustion mode. The small flames injected by each gun are evenly divided, suppressing the occurrence of temperature peaks and valleys. While forming independent flames, making the gas mixing mode adjustable, the overall combustion process more complete, and improving the burnout rate, it also avoids the generation of high-temperature zones and can reduce the generation of thermal NOx.
[0023] Blast furnace gas has a low calorific value, poor combustion characteristics, and a high gas flow rate. A cavity is used to homogenize the intake gas. The large-diameter pipe 33 meets the requirements of the tail-end intake pipe 35, while simultaneously reducing the flow velocity of the low-calorific-value gas to achieve lower resistance. The small-diameter pipe 31 uses a straight-channel nozzle, ensuring a high gas injection velocity. The airflow, with its higher velocity, generates a high swirling intensity through the swirl blades 34, enhancing the mixing of blast furnace gas and combustion air. The rotating jet from the annular nozzle facilitates stable and efficient combustion of the low-calorific-value gas flow in conjunction with the high-calorific-value gas flame inside. The tapered pipe 32 ensures that no significant local resistance is generated when the airflow passes through it.
[0024] Both the external secondary air inlet pipe 6 and the internal secondary air inlet pipe 10 are equipped with adjusting baffles 7 or 11, which can adjust the air volume of the external and internal secondary air respectively, accurately realizing air grading and combustion grading. The internal secondary air outlet adopts a straight channel structure, and the external secondary air outlet adopts a contraction nozzle 5 to meet the wind speed requirements. Through the annular distribution pipe 17, etc., it is convenient to distribute different types of gas and replace the spray gun.
[0025] This invention is applicable to various gases with large differences in calorific value. The gas nozzles (13-16) are rationally arranged and optimally matched with the secondary air supply for combustion, enabling ultra-low nitrogen emissions and high-efficiency combustion of various gases. A detailed analysis follows:
[0026] (1) Staged combustion: From the inside out, a central pipe 2, an inner horizontal pipe 8 and its flame stabilizer 12, gas nozzles 13-16 arranged in two rings, a low-calorific-value gas nozzle 3, an outer volute 4, and a contracting nozzle 5 are arranged concentrically to supply the air and gas required for combustion in stages. Specifically, by adjusting the baffles 7 and 11, the internal and external secondary air volumes can be adjusted in any ratio to achieve staged combustion of the combustion air. The gas nozzles 13-16 at each stage are arranged in a reasonable manner, with three layers arranged from the inside out at the nozzle for CO. The gas nozzles 15 and 16 for G and C4, and 13 and 14 for NG and POX, are used in the blast furnace gas nozzle. At the same time, the gas nozzles 13 and 14 are arranged alternately in the same circumference, and the gas nozzles 15 and 16 are arranged alternately to achieve staged combustion of fuel in the radial and circumferential directions at the burner nozzle. Each gas nozzle head is injected with several small holes. The gas flow mixes with air to form a small flame combustion mode. The small flames injected by each nozzle are evenly divided to form a uniform combustion flame in the circumferential direction, avoiding the generation of high temperature zones and reducing the formation of thermal NOx.
[0027] (2) Uniform combustion: Each gas nozzle forms a ring arrangement pattern, that is, an appropriate number of nozzles of appropriate size are arranged along the 360° area to organize combustion. When different gases are mixed, multi-layer ring flames can be formed. This structure can make the gas as uniform as possible and make the gas and combustion air mix and burn quickly, forming a layered circumferential uniform combustion flame, which makes the gas burn completely and prevents the heat from concentrating to form a combustion field with a large temperature deviation distribution, suppressing the occurrence of temperature peaks and temperature valleys, thereby improving the burnout rate of gas components such as CO and suppressing the formation of NOx.
[0028] (3) Flue gas recirculation: A flame stabilizer 12 is installed in the inner horizontal pipe 8. The secondary air flows through the flame stabilizer 12 and forms a flow field structure in the central recirculation zone. The recirculation zone structure can stabilize the initial flame of the gas. At the same time, the recirculation zone can retain the high-temperature, low-oxygen flue gas, forming a high-temperature, low-oxygen recirculation flue gas zone, which is conducive to preheating the combustion products and unreacted air and fuel, enhancing combustion, and stabilizing the flame. The outer secondary air is in the outermost layer. It is adjusted by the tangential blades 41 to form the flow field structure of the outer secondary air recirculation zone. This entrains the surrounding flue gas and mixes it into the combustion air. By adjusting the appropriate blade angle, a suitable swirling recirculation zone structure is formed to ensure that the oxygen concentration of the diluted air is at the optimal level and to suppress the formation of thermal NOx. Flue gas recirculation makes the temperature distribution in the furnace more uniform, reduces the maximum combustion temperature, shrinks the high-temperature zone, and suppresses the formation of instantaneous NOx and thermal NOx.
[0029] In summary, this invention comprehensively utilizes air staging technology, fuel staging technology, and swirl combustion technology, which can achieve low NOx emissions while maintaining stable combustion process, adjustable fuel co-firing mode, and high burnout rate. It can be applied to boilers using 35MWth class high-power burners.
[0030] The present invention has been described through the above embodiments, but it should be understood that the above embodiments are for illustrative purposes only and are not intended to limit the present invention to the scope of the described embodiments.
Claims
1. A multi-gas co-firing gas burner, comprising an ignition gun, a central tube, an inner secondary air duct, and an outer secondary air duct; characterized in that: The external secondary air duct includes a connected external secondary air inlet pipe and an outer volute. Tangential blades are installed inside the outer volute, and a converging nozzle is connected to the front end of the outer volute. The internal secondary air duct includes a connected internal secondary air inlet pipe and an internal horizontal pipe. A low-calorific-value gas nozzle is installed between the outer volute and the internal horizontal pipe. The low-calorific-value gas nozzle is connected to a low-calorific-value gas inlet pipe. Swirl blades are installed inside the low-calorific-value gas nozzle. The low-calorific-value gas nozzle includes a small-diameter pipe, a conical pipe, and a large-diameter pipe connected sequentially from front to back. The swirl blades are located inside the small-diameter pipe. The gas inlet pipe is connected to the large-diameter pipe; a flame stabilizer is placed inside the front end of the inner horizontal pipe and fixedly connected to the central pipe. Several gas nozzles are provided in the inner horizontal pipe on the radial outer side of the flame stabilizer. The gas nozzles are arranged in two or more concentric rings. Each gas nozzle has several small holes at its head. The gas nozzles on different rings are connected to their respective inlet pipes. At least the gas nozzles on the same ring are divided into two or more groups. The gas nozzles in different groups are staggered in the circumferential direction. The gas nozzles in the same group are connected to the same inlet pipe.
2. The multi-gas co-firing gas burner as described in claim 1, characterized in that: The several gas nozzles in the same group are connected to the same air inlet pipe through a ring-shaped distribution pipe.
3. A multi-gas co-firing gas burner as described in claim 1 or 2, characterized in that: The axis of the low-calorific-value gas nozzle is perpendicular to the cross-section of the outer volute.
4. A multi-gas co-firing gas burner as described in claim 3, characterized in that: Both the external secondary air inlet pipe and the internal secondary air inlet pipe are equipped with adjusting baffles.
5. A multi-gas co-firing gas burner as described in claim 4, characterized in that: The low-calorific-value gas inlet pipe is located tangentially to the large-diameter pipe.