Multi-channel central tube adjustable low-nitrogen swirl burner for co-firing of pulverized coal and biomass

Abstract

The present invention discloses a multi-channel adjustable central tube swirl burner for co-firing pulverized coal and biomass. The burner includes, from the inside to the outside, a central biomass air duct, a pulverized coal air duct, an outer-layer biomass air duct, a swirl air duct, and a direct-current air duct. A slideway is arranged on the outer wall surface of the central air duct and cooperates with a slider arranged on the inner wall surface of the pulverized coal air duct to enable the adjustment of the central air duct, so as to achieve the purpose of inhibiting NOx generation by changing the ignition position of the central biomass air-powder; an adjustable air guide cylinder is nested in the flare at the outer wall of the swirl air duct, and the flare length can be adjusted in real time during the combustion process to adapt to coal types with different ignition characteristics and further reduce NOx emissions; the present invention adopts a design of fuel staged combustion, and two streams of biomass powder respectively undertake the tasks of igniting the pulverized coal and reducing NOx, which not only enables the efficient combustion of the mixture of biomass powder and pulverized coal, reduces the generation of nitrogen oxides, but also can conveniently and stably adjust the operating characteristics of the burner under various operating conditions and changes in fuel types.

Description

Technical Field

[0001] The present invention relates to the technical field of combustion of biomass powder and blends of biomass powder and coal powder. More specifically, it relates to a multi-channel central tube adjustable low-nitrogen swirl burner applicable to co-combustion of coal powder and biomass. Background Art

[0002] Biomass energy is regarded as the fourth-largest energy source after coal, oil, and natural gas due to its wide sources and clean and green characteristics. The total biomass in China accounts for about one-third of the primary energy and is the fuel second only to coal. At the same time, since thermal power plants are the main power generation equipment in China, there is a great need for low-pollution and low-cost renewable fuels. Therefore, using existing coal-fired boilers for co-combustion of biomass and coal powder has broad application prospects. However, the problems that still need to be solved urgently in the co-combustion of biomass and coal powder are how to achieve efficient combustion of fuels and effective control of NOx during the combustion process. The fuel staging combustion technology is one of the effective measures among many methods for reducing NOx, and its effect of reducing NOx is far better than technologies such as air staging combustion and flue gas recirculation. However, there are few examples in China of applying the fuel staging technology to burners. Summary of the Invention

[0003] To solve the deficiencies existing in the above-mentioned prior art, the purpose of the present invention is to provide a multi-channel central tube adjustable low-nitrogen swirl burner applicable to co-combustion of coal powder and biomass, which can not only achieve fuel staging combustion, efficient combustion of blends of biomass powder and coal powder, and inhibit the generation of NOx, but also conveniently and stably adjust the operating characteristics of the burner under various operating conditions and fuel variations.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is:

[0005] A multi-channel central tube adjustable low-nitrogen swirl burner applicable to co-combustion of coal powder and biomass includes, from inside to outside, a central biomass air duct, a coal powder air duct, an outer biomass air duct, a swirl air duct, and a direct current air duct. Slideways are arranged circumferentially on the outer wall surface of the central biomass air duct, and sliders are arranged circumferentially on the inner wall surface of the coal powder air duct. The sliders and the slideways cooperate to enable the axial displacement of the central biomass air duct.

[0006] Biomass air duct connectors are arranged circumferentially in the outer biomass air duct, swirl vanes are arranged circumferentially in the swirl air duct, and direct current air duct connectors are arranged circumferentially in the direct current air duct.

[0007] An adjustable air guide cylinder is nested in the flared opening on the outer wall of the swirl air duct. The adjustable air guide cylinder is connected to a flexible rod. The flexible rod is arranged in a square channel inside the outer wall of the swirl air duct. By pushing or pulling the flexible rod, the adjustable air guide cylinder can be driven to extend or retract into the flared opening, realizing real-time adjustment of the length of the flared opening of the swirl air duct.

[0008] Compared with the prior art, the present invention has the following advantages:

[0009] 1. The present invention adopts the fuel staged combustion technology, and the biomass fuel is divided into two streams and fed in: the central biomass air-powder and the outer-layer biomass air-powder. The outer-layer biomass directly contacts the air and serves as the initial combustion ignition source of the mixed fuel; the pulverized coal is sandwiched between the central biomass air-powder and the outer-layer biomass air-powder as the main fuel. This arrangement can delay the time point of fresh air mixing into the pulverized coal, reduce the ignition heat of the pulverized coal fuel, and together with the ignition of the outer-layer biomass and the central recirculation high-temperature flue gas, raise the temperature of the pulverized coal air flow to form the central main torch; the central biomass is added to burn at the tail of the torch, reducing most of the NOx generated by the combustion of the pulverized coal into N and N2, and at the same time inhibiting the generation of new NOx; finally, the external direct current air and swirling air play the role of burnout, enabling the fuel to burn completely. The advantages of this arrangement are that in addition to the fuel staged combustion technology inhibiting the generation of NOx, another advantage is that the combustion of the outer-layer biomass consumes a part of the oxygen entering the pulverized coal flame, making the pulverized coal flame a lean-oxygen combustion in the main combustion zone of the burner layer, further reducing the generation of NOx.

[0010] 2. The present invention realizes the axial adjustability of the central biomass air duct through the cooperation of the slider and the slideway. By monitoring the nitrogen oxide content in the exhaust gas, the extending length of the central biomass air duct can be adjusted in real time to change the position where the central biomass is added to the torch, realizing real-time online combustion adjustment and reducing the NOx emission. And this design can also conveniently and stably adjust the operating characteristics of the burner under various operating conditions and fuel changes, realizing the reduction of nitrogen oxide generation on the premise of efficient combustion of the mixture of biomass powder and pulverized coal.

[0011] 3. The present invention drives the adjustable air guide cylinder to extend or retract into the flare by pushing and pulling the soft rod arranged in the square channel inside the outer wall of the swirling air duct, realizing the real-time adjustability of the flare length. When the nitrogen oxide content in the exhaust gas is too high, the flare length can be increased, making the internal recirculation zone longer and wider, increasing the recirculation flow rate, and diversifying the internal swirl, which is beneficial to the reduction of NOx by the central biomass air. For the working conditions with fuel changes, if the fuel has a high volatile content or high calorific value, the adjustable air guide cylinder is extended into the flare; if the fuel has a low volatile content or low calorific value, the adjustable air guide cylinder is retracted into the flare to enable the biomass to burn earlier and provide the ignition heat required by the pulverized coal. Description of the Drawings

[0012] Figure 1 is a schematic structural diagram of a multi-channel central adjustable low-nitrogen swirl burner applicable to the co-combustion of pulverized coal and biomass of the present invention.

[0013] Figure 2 is Figure 1 the view from direction A of

[0014] Figure 3It is a schematic diagram for realizing the axial position adjustment of the central biomass air duct.

[0015] Figure 4 It is a schematic diagram for realizing the adjustment of the flare length of the outer wall of the swirl air duct.

[0016] Figure 5 It is a schematic diagram of a flexible rod and an adjustable air guide duct. Specific embodiments

[0017] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0018] As Figure 1 and Figure 2 shown, the present invention is a multi-channel central tube adjustable low-nitrogen swirl burner applicable to the co-combustion of pulverized coal and biomass, which includes a central biomass air duct 5, a pulverized coal air duct 4, an outer-layer biomass air duct 3, a swirl air duct 2, and a direct-current air duct 1 from the inside to the outside. Biomass air duct connectors 10 are circumferentially arranged inside the outer-layer biomass air duct 3, swirl vanes 8 are circumferentially arranged inside the swirl air duct 2, and direct-current air duct connectors 11 are circumferentially arranged inside the direct-current air duct 1.

[0019] As Figure 3 shown, slideways 6 are circumferentially arranged along the outer wall surface of the central biomass air duct 5, and sliders 7 are circumferentially arranged along the inner wall surface of the pulverized coal air duct 4. The cooperation between the sliders 7 and the slideways 6 can realize the axial displacement of the central biomass air duct 5.

[0020] As Figure 4 and Figure 5 shown, an adjustable air guide cylinder 13 is nested inside the flare of the outer wall of the swirl air duct 2. The adjustable air guide cylinder 13 is connected to a flexible rod 9. The flexible rod 9 is arranged in a square channel 12 inside the outer wall of the swirl air duct 2. By pushing or pulling the flexible rod 9, the adjustable air guide cylinder 13 can be driven to extend or retract into the flare, realizing the real-time adjustability of the flare length.

[0021] The working principle of the present invention is as follows: The fuel staging combustion technology is adopted, and the biomass fuel is divided into two parts, namely the central biomass pulverized coal-air mixture and the outer biomass pulverized coal-air mixture, which are sent in separately. The outer biomass pulverized coal-air mixture is in direct contact with air, providing the initial ignition heat for the mixed fuel. The pulverized coal, as the main fuel, is sandwiched between the central biomass pulverized coal-air mixture and the outer biomass pulverized coal-air mixture, delaying the mixing of fresh air, reducing the ignition heat, and together with the ignition of the outer biomass and the high-temperature flue gas in the central recirculation zone, raising the temperature of the pulverized coal air flow to form the central main torch. The central biomass is added to burn at the tail of the torch, reducing most of the NOx generated by the combustion of pulverized coal into N and N2, and at the same time inhibiting the generation of new NOx. Finally, the external direct current air and swirling air play the role of burnout, and the complete combustion process is finally completed. By monitoring the content of nitrogen oxides in the exhaust gas, the insertion length of the central biomass air duct is adjusted in real time to change the position where the central biomass is added to the central main torch, reducing the NOx emissions. At the same time, the flare length of the outer wall of the swirling air duct can also be adjusted in real time to cooperate to further inhibit the generation of NOx: when the content of nitrogen oxides in the exhaust gas is too high (greater than 10 ppm), the flare length can be increased, making the internal recirculation zone longer, wider, with a larger recirculation flow rate and a more diversified internal swirl, which is beneficial for the central biomass air to reduce NOx.

[0022] The high content of nitrogen oxides in the exhaust gas means that the content of nitrogen oxides in the exhaust gas is greater than 10 ppm; the fuel with high volatile matter or high calorific value means that the dry ash-free basis volatile matter of the fuel is greater than 35%, and the low calorific value is higher than 20 MJ / kg; the fuel with low volatile matter or low calorific value means that the dry ash-free basis volatile matter of the fuel is less than 35%, and the low calorific value is less than 20 MJ / kg.

Claims

1. A multi-channel central tube adjustable low-nitrogen swirl burner for co-firing pulverized coal and biomass, which includes a direct current air duct (1), a swirl air duct (2), an outer layer biomass air duct (3), a pulverized coal air duct (4) and a central biomass air duct (5) from outside to inside, and is characterized in that: A slideway (6) is arranged circumferentially along the outer wall surface of the central biomass air duct (5), and a slider (7) is arranged circumferentially along the inner wall surface of the pulverized coal air duct (4). The slider (7) and the slideway (6) cooperate to realize the axial displacement of the central biomass air duct (5). The fuel staged combustion technology is adopted to divide the biomass fuel into two parts, namely, the central biomass air-powder and the outer-layer biomass air-powder, and they are sent in separately. The outer-layer biomass air-powder is directly in contact with air to provide the initial ignition heat of the mixed fuel. The pulverized coal, as the main fuel, is sandwiched between the central biomass air-powder and the outer-layer biomass air-powder, delaying the mixing of fresh air, reducing the ignition heat, and increasing the temperature of the pulverized coal air flow together with the ignition of the outer-layer biomass and the central recirculation high-temperature flue gas to form the central main torch. The central biomass is added to burn at the tail of the torch, reducing most of the NOx generated by the combustion of the pulverized coal into N and N2, and at the same time inhibiting the generation of new NOx. The external direct current air and swirl air play a role in burnout, and finally complete the complete combustion process. Monitor the content of nitrogen oxides in the exhaust gas, and adjust the insertion length of the central biomass air duct (5) in real time to change the position where the central biomass is added to the central main torch and reduce the NOx emission; An adjustable air guide cylinder (13) is nested in the outer wall flare of the swirl air duct (2). The adjustable air guide cylinder (13) is connected to a flexible rod (9). The flexible rod (9) is arranged in a square channel (12) inside the outer wall of the swirl air duct (2). By pushing and pulling the flexible rod (9), the adjustable air guide cylinder (13) is driven to extend or retract into the flare, realizing the real-time adjustability of the flare length of the swirl air duct to further inhibit the generation of NOx: when the content of nitrogen oxides in the exhaust gas is high, the flare length is increased, making the internal recirculation zone longer and wider, increasing the recirculation flow rate, and diversifying the internal swirl, which is beneficial to the reduction of NOx by the central biomass air; for the working conditions with fuel changes, if the fuel has a high volatile content or high calorific value, the adjustable air guide cylinder (13) is extended out of the flare; if the fuel has a low volatile content or low calorific value, the adjustable air guide cylinder (13) is retracted into the flare to enable the biomass to burn as early as possible and provide the ignition heat required by the pulverized coal; The high content of nitrogen oxides in the exhaust gas means that the content of nitrogen oxides in the exhaust gas is greater than 10 ppm; the fuel with a high volatile content or high calorific value means that the dry ash-free basis volatile content of the fuel is greater than 35%, and the net calorific value is higher than 20 MJ / kg; the fuel with a low volatile content or low calorific value means that the dry ash-free basis volatile content of the fuel is less than 35%, and the net calorific value is less than 20 MJ / kg.

2. The multi-channel central tube adjustable low-nitrogen swirl burner for co-firing pulverized coal and biomass according to claim 1, characterized in that: Biomass air duct connectors (10) are arranged circumferentially in the outer-layer biomass air duct (3), swirl vanes (8) are arranged circumferentially in the swirl air duct (2), and direct current air duct connectors (11) are arranged circumferentially in the direct current air duct (1).

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