CN106482097B - The partly-premixed low nitrogen burner of percussion flow - Google Patents

Abstract

The invention relates to a partly impinging flow premixed low-nitrogen gas burner, which includes a combustion head, the combustion head includes a cylindrical air flow channel; a swirler arranged inside the cylindrical air flow channel, the swirl The device includes an outer ring, an inner ring, a swirl plate arranged between the outer ring and the inner ring, and a central blunt body arranged in the center hole of the inner ring; A fuel nozzle inside the flow channel, the fuel nozzle includes a fuel pipe and a fuel nozzle arranged on the side of the fuel pipe.

Description

Impingement flow partially premixed low nitrogen gas burner

technical field

The invention relates to a low-nitrogen gas burner, in particular to a partly premixed low-nitrogen gas burner with impinging flow.

Background technique

Nitrogen oxide (NOx) is one of the main pollution sources of the atmosphere. It can not only form acid rain or acid fog, but also an important precursor of PM2.5 secondary particulate matter. As environmental pollution continues to intensify, smog and haze frequently appear in key areas of our country, which has caused great harm to people's health. With the combustion and utilization of natural gas, petroleum liquefied gas and coal synthesis gas, the pollution of gas combustion, especially the reduction of NOx emissions, is an urgent task. Therefore, it is of great significance to control the production of NOx during the combustion of natural gas.

Combustion theory divides the formation of NOx into thermal NOx, rapid NOx and fuel NOx. The nitrogen content in natural gas is low, and the sources of NOx are mainly thermal NOx and rapid NOx. Thermal NOx refers to the oxidation of _N2 in the air used for combustion to generate NOx at high temperature; in the thermal mechanism, temperature is the key variable governing the formation of NOx. When the temperature is lower than 1500°C, the amount of thermal NOx generated is very small; when the temperature is higher than 1500°C, the reaction rate will increase by 6-7 times for every 100°C increase in temperature. Rapid NOx is generally formed by the reaction of hydrocarbon radicals and nitrogen molecules to form amines or cyano compounds, which are mainly formed in the region where the equivalence ratio is greater than 1, and its reaction temperature is lower than that of thermal NOx.

Low-nitrogen combustion technologies include staged combustion, premixed combustion, flue gas recirculation, porous media combustion, flameless combustion, and chemical looping combustion.

The principle of staged combustion technology is that the combustion temperature reaches the highest when the equivalence ratio is 1, and the combustion temperature is lower than the combustion temperature when the equivalence ratio is 1 in the case of lean or rich combustion. The distribution of the temperature field avoids local high temperature and achieves the effect of reducing NOx generation.

Premixed combustion is an effective technology to reduce NOx formation. For the control of NOx generation, the advantage of this technology is that it can realize the control of combustion temperature through the complete control of equivalence ratio. The combustion temperature is lowered by lean combustion, and the equivalence ratio of the mixture is less than 1, so that the formation of thermal NOx and rapid NOx will be reduced. However, the limiting factors that premixed combustion technology is not widely used are: unstable combustion, which may lead to flashback or flameout; large excess air coefficient, which reduces the thermal efficiency of the system.

The reduction of combustion temperature can also be achieved by flue gas recirculation. By adding the combustion products of flue gas into the combustion area, the combustion temperature is reduced. At the same time, the added flue gas reduces the partial pressure of oxygen, which will weaken the oxygen and nitrogen. The process of generating thermal NOx, thereby reducing the formation of NOx. Studies have shown that external flue gas recirculation will reduce NOx formation by 70%. The main problem of flue gas recirculation is that the reduction of oxygen partial pressure and the increase of air flow rate make combustion unstable, and phenomena such as flameout and oscillation occur.

According to the development stage of low-nitrogen combustion industrial application technology, it can be roughly divided into three development stages: first, the use of staged combustion technology can control the emission concentration of NOx at 100 mg/m ³ , but this technology may cause CO The emission concentration increased obviously; secondly, the flue gas recirculation technology can control the NOx emission concentration at 60~80mg/m ³ , and the emission level varies greatly according to the flue gas circulation ratio. It is suitable for transformation and upgrading, but it has no effect on the control of fast NOx, and increases the power consumption of the fan; thirdly, the premixed combustion technology can control the emission concentration of NOx to 10~60mg/m ³ , according to the requirements of environmental protection standards. Adjustable within a certain range, this technology has a low cost and is suitable for new projects, but it has a slight impact on the overall thermal efficiency (about 1~2% in terms of low calorific value), that is, the lower the NOx emission concentration, the lower the thermal efficiency , but there are also security issues.

Contents of the invention

In view of this, it is indeed necessary to provide an impinging flow partially premixed low-nitrogen gas burner with high thermal efficiency, low NOx emission concentration and stable combustion.

An impingement flow partial premixed low-nitrogen gas burner, which includes a combustion head, the combustion head includes a cylindrical air flow channel; a swirler arranged inside the cylindrical air flow channel, the swirler includes an outer ring, an inner ring, a swirl plate arranged between the outer ring and the inner ring, and a central blunt body arranged in the center hole of the inner ring; one is arranged on the outside of the burner swirler and is located inside the cylindrical air flow channel The fuel nozzle includes a fuel pipe and a fuel nozzle arranged on the side of the fuel pipe.

Compared with the prior art, the impinging flow partial premixed low-nitrogen gas burner provided by the present invention controls the time of combustion and oxygen mixing and the spatial distribution of the mixing fraction through fuel staging and impinging flow mixing, thereby controlling the combustion rate, The temperature of the flame area and the residence time of the reactants in the high temperature area can effectively reduce the formation of thermal and rapid NOx finally, and realize the formation of NOx to be less than 50mg/Nm ³ (@3.5%O ₂ ). The invention combines impingement flow partial premixing and swirl degree control on the combustion flame, which can meet the flame stability under relatively high flue gas recirculation conditions, thereby reducing the NOx generation to less than 20mg/Nm ³ (@3.5%O ₂ ) ultra-low emission level, but also has strong fuel adaptability.

The fuel graded partial premixed swirling impingement flow gas burner provided by the present invention has reasonable structure, wide fuel adaptability, high combustion efficiency, small pollutant discharge, stable combustion, and is suitable for industrial furnaces, reformers and gas turbines. .

Description of drawings

Fig. 1 is a schematic perspective view of the impinging flow partially premixed low-nitrogen gas burner provided by the first embodiment of the present invention.

Fig. 2 is a front view of the impinging flow partially premixed low-nitrogen gas burner provided by the embodiment of the present invention.

Fig. 3 is a front view of the swirler of the impinging flow partially premixed low-nitrogen gas burner provided by the embodiment of the present invention.

Fig. 4 is a schematic diagram of the arrangement of fuel pipes of the impinging flow partially premixed low-nitrogen gas burner provided by the embodiment of the present invention.

5 to 10 are schematic views of the position, shape and arrangement of the fuel nozzles of the impinging flow partially premixed low-nitrogen gas burner provided by the embodiment of the present invention.

Fig. 11 is a schematic perspective view of the impinging flow partially premixed low-nitrogen gas burner provided by the second embodiment of the present invention.

Description of main component symbols

Impingement flow partially premixed low nitrogen gas burner 10, 40 combustion head 20 Front runner 30 cylindrical air channel twenty one Cyclone twenty two fuel nozzle twenty three secondary fuel nozzle twenty four Flame stabilization section 25 air inlet 31 air front deflector 32 air rear deflector 33 air inlet section 34 Air Neck 35 outer ring 220 swirl sheet 221 inner circle 222 central blunt body 223 fuel pipe 230 fuel nozzle 231

The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings.

Detailed ways

The impinging flow partially premixed low-nitrogen gas burner provided by the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

Please refer to FIG. 1 , an embodiment of the present invention provides a partly premixed low-nitrogen gas burner 10 with impinging flow. The partly premixed low-nitrogen gas burner 10 includes a combustion head 20 and a front flow channel 30. The combustion head 20 It is connected and communicated with the front runner 30.

The combustion head 20 includes a cylindrical air flow passage 21, a swirler 22 arranged inside the cylindrical air flow passage 21, a fuel injector arranged outside the swirler 22 and inside the cylindrical air flow passage 21. Tube 23. The front flow passage 30 includes an air inlet 31, an air front deflector 32 and an air rear deflector 33 arranged behind the air inlet, an air inlet section 34 and an air constriction section 35. The cylindrical air flow passage 21 is set on the air constriction section 35 .

Please refer to FIG. 2 and FIG. 3 together. The swirler 22 includes an outer ring 220, an inner ring 222, a swirl piece 221 arranged between the outer ring 220 and the inner ring 222, and a center hole of the inner ring. Center blunt body 223 . The main function of the swirler 22 is to provide different air volumes and gas swirl numbers. The air volume of the cyclone can be optimized by adjusting the ratio of the outer ring 220 to the inner ring 222 and the size of the outer ring 220. After optimization, the diameter ratio of the inner ring 222 and the outer ring 220 is considered to be 1:3. In this embodiment, the diameter ratio of the inner ring 222 and the outer ring 220 is 1:3. The size of the swirl number can be optimized by adjusting the number of swirl sheets 221 and the inclination angle of the swirl sheets 221 . The number of swirl sheets 221 is 10-20, and the inclination angle range of the swirl sheets 221 is 10-30°. In this embodiment, the number of the swirl fins 221 is 32, and the inclination angle range of the swirl fins 221 is 20°. The central blunt body 223 can be made into corresponding sizes and shapes according to different combustion conditions, such as circular, square, hexagonal, rectangular, cross and elliptical to control the flow field at the burner outlet. In this embodiment, the central blunt body 223 is circular. By adjusting the above parameters, a stable recirculation zone can be generated at the outlet of the burner, and the first low-nitrogen combustion principle of this embodiment can be realized.

Please also refer to FIG. 4 , the arrangement of the fuel nozzle 23 adopts the "impact flow" generated by the high-speed impact of the fuel on the surface of the swirler, so as to achieve the effect of rapid mixing. The fuel nozzle 23 includes a fuel pipe 230 and a fuel nozzle 231 , and the fuel nozzle 231 is disposed on the side of the fuel pipe 230 or on the side and the top surface of the fuel pipe 230 . The dispersed arrangement of the fuel pipes 230 enables the fuel to have a density distribution in space, the equivalence ratio near the fuel nozzle is greater than 1, and the equivalence ratio between two fuel nozzles is less than 1, resulting in the effect of staged combustion. The fuel is jetted out from the fuel nozzle 231 at a high speed and collides with the outer ring 220 to produce the effect of collision and rapid mixing.

The mixing time and mixing fraction of fuel and air are controlled by the number of fuel pipes 230, the injection speed of fuel, the shape of fuel nozzle 231, the number of fuel nozzles 231, and the distance d between fuel nozzle 231 and outer ring 220, so as to achieve Control the combustion rate, the spatial distribution of the fuel, and the effect of the premixing degree to achieve low-nitrogen combustion and stable combustion. The number of fuel pipes 230 is 5-32, and in this embodiment, the number of fuel pipes is 8. The injection velocity of the fuel is between 100-200m/s, and in this embodiment, the injection velocity of the fuel is 150m/s. There may be 1-3 fuel nozzles 231 on the side of the fuel pipe 230 , and the top surface of the fuel pipe 230 may or may not have fuel nozzles 231 . The shape of the fuel nozzle 231 is not limited, it can be square or circular. The size of each fuel nozzle 231 and the arrangement on the side of the fuel pipe 230 can also be different. For example, please refer to Fig. 5 to Fig. 10, the side of fuel pipe 230 can have a square or circular fuel nozzle 231, also can have two circular fuel nozzles 231, and these two circular fuel nozzles 231 can be up and down The arrangement can also be arranged left and right, and there can also be three fuel nozzles 231 arranged left and right, wherein the fuel nozzle 231 in the middle is slightly larger than the fuel nozzles 231 on both sides, and the side of the fuel pipe 230 can also have a circular shape. A fuel nozzle 231, and a circular fuel nozzle 231 is arranged on the top surface. The fuel nozzle 231 can be directly arranged on the side of the fuel pipe 230 , or can be arranged on a boss on the side of the fuel pipe 230 . In this embodiment, a boss is formed on the side of the fuel pipe 230, and a circular fuel nozzle 231 is disposed on the boss. The distance d between the fuel nozzle 231 and the outer ring 220 can be 1-10 times the diameter of the fuel nozzle 231. Controlling d can control the premixing effect, preferably d is 1.5-3 times the diameter of the fuel nozzle 231. In this embodiment, d It is twice the diameter of the fuel nozzle 231. By adjusting the above parameters, the required fuel mixing degree can be generated at the outlet of the burner, and the second low-nitrogen combustion principle of this embodiment can be realized.

The air enters the burner from the air inlet 31, and the uniformity of the air is guaranteed under the action of the air front deflector 32 and the air rear deflector 33, and enters the cylindrical air flow after passing through the air inlet section 34 and the necking section 35 Channel 21, at the outlet of the burner, a part of the air flow passes through the swirl plate 221 to form a swirling air flow with a large swirl number, and a part of the air flow passes through the passages around the swirler, so that the air flow at the burner outlet is improved very well organized.

The fuel passes through the eight fuel pipes 230 and is ejected from the fuel nozzle 231 at a high speed, and has a strong collision with the outer ring 220, and is mixed with the air to achieve a partial premixing effect.

Referring to Fig. 6, the second embodiment of the present invention provides a part of the impingement flow premixed low-nitrogen gas burner 40, the structure of the part of the impingement flow part premixed low-nitrogen gas burner 40 is the same as that of the impingement flow part of the first embodiment of the present invention The structure of the premixed low-nitrogen gas burner 10 is basically the same, and the same number means the same structure as the first embodiment.

One of the differences is that a secondary fuel nozzle 24 is arranged at the outlet of the burner, and the secondary fuel nozzle 24 is distributed on the ring of the outlet of the burner, and the number is 10-40, and the diameter is 2-6mm, accounting for the total fuel The ratio is 20-80%. This ratio is adjustable and plays the role of staged combustion and reduction of nitrogen oxides. In this embodiment, the number of secondary fuel nozzles 24 is 36, with a diameter of 4mm, and the proportion of the total fuel depends on the actual situation.

Another difference is that a flame-stabilizing section 25 can also be added at the outlet of the burner, and the flame-stabilizing section 25, that is, the section where the ring of the secondary fuel outlet extends away from the burner, can be a straight section, a flaring, a contracting section. Mouth, adjustable in length, made of refractory material. The flame structure (length and diameter) can be changed by adjusting the flame stabilizing section 25, so as to adapt to different furnaces.

In the embodiment of the present invention, during operation, according to the combustion conditions, including fuel change, temperature, etc., through the design of the swirler 22 and the arrangement of the fuel nozzle 23, the swirl air volume and swirl number can be adjusted, thereby controlling Combustion mode in the recirculation zone.

The impinging flow partial premixed low-nitrogen gas burner provided by the embodiment of the present invention adopts two principles of low-nitrogen combustion and stable combustion: 1. The center of the fuel nozzle is generated at the front end of the flame at the burner outlet by the action of the swirl plate The stable combustion area of flue gas recirculation, due to the internal circulation of high-temperature hot flue gas in this area, the formation of NOx will be significantly reduced; moreover, the stable recirculation area generated by the burner is equivalent to the existence of a duty flame, which is greatly conducive to the stability of the flame. 2. Through the high-speed fuel injection and the impact of the swirl plate, a strong mixing effect is generated, so that the fuel and air are quickly mixed to achieve a partially premixed state; at the same time, through the arrangement of multiple fuel nozzles, the fuel is generated spatially. The concentration distribution achieves the effect of dispersion and staged combustion. While reducing the flame combustion temperature, the temperature field at the outlet of the burner is very uniform, which greatly reduces the generation of thermal NOx and rapid NOx; the concentration of fuel produced at the outlet of the burner distribution, so that the possibility of flashback is reduced and the combustion stability is increased. Fuel staging and partial premixing can effectively improve combustion efficiency and achieve complete combustion.

The biggest feature of the embodiment of the present invention is its low-nitrogen combustion effect, including the design of the swirler and the arrangement of the combustion nozzle to control the time and mixing fraction of combustion and oxygen, thereby controlling the combustion rate and the temperature of the flame area As well as the residence time of the reactants in the high-temperature zone, the generation of thermal and rapid NOx can be effectively reduced finally, and the formation of NOx can be less than 50mg/Nm ³ (@3.5%O ₂ ). This embodiment can cooperate well with flue gas recirculation technology to achieve stable combustion under the condition of high flue gas circulation rate, thereby reducing NOx generation to an ultra-low emission of less than 20mg/Nm ³ (@3.5%O ₂ ) Level.

Another important feature of the embodiment of the present invention is that it has good combustion stability and complete combustion. Through the design of the swirler, a recirculation zone is formed at the outlet of the burner, which plays a role in stable combustion; the arrangement of the combustion nozzle can control the premixing Effect, so that the burner does not have problems such as tempering.

The impinging flow partial premixed low-nitrogen gas burner provided by the present invention combines a variety of low-nitrogen combustion mechanisms, which is different from the diffusion combustion technology commonly used at present. The diffusion combustion technology is difficult to control fast NOx, and local hot spots The thermal NOx formed is difficult to suppress; it is also different from the lean-burn premixing technology. Due to the large excess air coefficient, the lean-burn premixing causes excessive exhaust heat loss, reduces the thermal efficiency of the system, and also has the problem of unstable combustion.

The impinging flow partially premixed low-nitrogen gas burner provided by the invention can solve the problems of unstable combustion and low thermal efficiency of the premixed flame and flue gas recirculation while reducing the generation of NOx. It has low emission of combustion pollutants, for example, ultra-low NOx emission, complete combustion, good combustion stability, high combustion efficiency, and simple and reliable structure. Both civil and industrial furnaces can be used for combustion, and have a wide range of application prospects.

In addition, those skilled in the art can also make other changes within the spirit of the present invention, and these changes made according to the spirit of the present invention should be included in the scope of protection claimed by the present invention.

Claims (10)

1. a kind of partly-premixed low nitrogen burner of percussion flow comprising combustion head, the combustion head include：

One cylindrical empty flow channel；

One is arranged in the cyclone inside the cylindrical empty flow channel, the cyclone include outer ring, inner ring, setting in the outer ring and Spinning disk between inner ring and the central bluff body that inner ring centre bore is set；

One fuel nozzle that the outside of burner cyclone is set and is located inside the cylindrical empty flow channel, the fuel nozzle Including cartridge and the fuel nozzle ports of the cartridge side are set to, fuel is sprayed from the fuel nozzle ports, and air-flow is along institute Cyclone radial direction is stated, after generating shock with the cyclone outer wall face, realization is mixed with the rapid of air, and it is pre- to reach part It is mixed.

2. the partly-premixed low nitrogen burner of percussion flow as described in claim 1, which is characterized in that in the percussion flow portion The low nitrogen burner outlet of premix is divided to be further provided with secondary fuel spout, which is distributed in the shock Stream part premixes on the annulus of low nitrogen burner outlet.

3. the partly-premixed low nitrogen burner of percussion flow as claimed in claim 2, which is characterized in that in the percussion flow portion Point low nitrogen burner outlet of premix is provided with steady flame section, which is the annulus that exports of the secondary fuel to separate institute State partly-premixed low that extended section of nitrogen burner of percussion flow.

4. the partly-premixed low nitrogen burner of percussion flow as claimed in claim 3, which is characterized in that the secondary fuel spray The quantity of mouth is 10-40, diameter 2-6mm, and accounting for total fuel ratio is 20-80%.

5. the partly-premixed low nitrogen burner of percussion flow as described in claim 1, which is characterized in that of the spinning disk Number is 10-20.

6. the partly-premixed low nitrogen burner of percussion flow as described in claim 1, which is characterized in that the spinning disk inclines Rake angle range is 10-30 °.

7. the partly-premixed low nitrogen burner of percussion flow as described in claim 1, which is characterized in that the inner ring and outer rings Diameter ratio be 1:3.

8. the partly-premixed low nitrogen burner of percussion flow as described in claim 1, which is characterized in that the root of the cartridge Number is 5-32 root.

9. the partly-premixed low nitrogen burner of percussion flow as described in claim 1, which is characterized in that each cartridge Top surface be provided with fuel nozzle ports.

10. the partly-premixed low nitrogen burner of percussion flow as described in claim 1, which is characterized in that the fuel nozzle ports Distance apart from the outer ring is 1-10 times of the fuel nozzle ports diameter.