CN114440214A - Non-premixed air classification low NOx combustor - Google Patents
Non-premixed air classification low NOx combustor Download PDFInfo
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- CN114440214A CN114440214A CN202210079180.1A CN202210079180A CN114440214A CN 114440214 A CN114440214 A CN 114440214A CN 202210079180 A CN202210079180 A CN 202210079180A CN 114440214 A CN114440214 A CN 114440214A
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- 238000002485 combustion reaction Methods 0.000 claims abstract description 76
- 239000007789 gas Substances 0.000 claims description 98
- 239000002737 fuel gas Substances 0.000 claims description 8
- 230000014759 maintenance of location Effects 0.000 abstract description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 14
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 12
- 239000001301 oxygen Substances 0.000 description 12
- 229910052760 oxygen Inorganic materials 0.000 description 12
- 238000006243 chemical reaction Methods 0.000 description 11
- 229910052757 nitrogen Inorganic materials 0.000 description 7
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 4
- 239000000446 fuel Substances 0.000 description 4
- 229910017604 nitric acid Inorganic materials 0.000 description 4
- 238000003916 acid precipitation Methods 0.000 description 3
- 239000003054 catalyst Substances 0.000 description 3
- 230000003111 delayed effect Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000003344 environmental pollutant Substances 0.000 description 3
- 239000010763 heavy fuel oil Substances 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 231100000719 pollutant Toxicity 0.000 description 3
- 230000002349 favourable effect Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000003570 air Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000000567 combustion gas Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000008676 import Effects 0.000 description 1
- 239000013461 intermediate chemical Substances 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000000618 nitrogen fertilizer Substances 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000002689 soil Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
- F23D14/20—Non-premix gas burners, i.e. in which gaseous fuel is mixed with combustion air on arrival at the combustion zone
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
- F23D14/46—Details, e.g. noise reduction means
- F23D14/60—Devices for simultaneous control of gas and combustion air
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
- F23D14/46—Details, e.g. noise reduction means
- F23D14/70—Baffles or like flow-disturbing devices
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
- F23D14/46—Details, e.g. noise reduction means
- F23D14/72—Safety devices, e.g. operative in case of failure of gas supply
- F23D14/82—Preventing flashback or blowback
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
- F23L9/00—Passages or apertures for delivering secondary air for completing combustion of fuel
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
Abstract
The invention relates to a low NOx burner, in particular to a non-premixed air classification low NOx burner, which comprises a non-premixed channel arranged in the burner and a secondary air channel arranged on the side wall of the burner, wherein the non-premixed channel is arranged in the burner; the non-premixing passage comprises a gas passage and an air passage; the air channel and the non-premixing channel are coaxially arranged, and the gas channel is an annular gap between the air channel and the non-premixing channel; the secondary air channel is provided with a plurality of secondary air channels which are arranged on the side wall of the combustor at the front end of the outlet of the non-premixing channel along the circumferential direction. Compared with the prior art, the invention combines air classification and designs a fast gas flow rate structure, so that the temperature of combustion flame is effectively reduced, the gas retention time is effectively shortened, the generation of NOx is further inhibited, and the low-NOx combustion is realized.
Description
Technical Field
The invention relates to a low NOx burner, in particular to a non-premixed air classification low NOx burner.
Background
Among the atmospheric pollutants, NOx is the main cause of acid rain formation. The naturally emitted NOx mainly comes from the decomposition of organic matters in soil and ocean and belongs to the nitrogen circulation process in the nature; NOx emitted by man-made activities, mostly from the combustion process of fossil fuels, such as automobiles, airplanes, internal combustion engines and industrial kilns; also from processes for the production and use of nitric acid, such as nitrogen fertilizer plants, organic intermediate plants, nonferrous and ferrous metal smelters, etc. At high temperatureUnder combustion conditions, NOx exists primarily as NO, with about 95% NO in the initial NOx emissions. However, NO is very reactive with oxygen in the air to form NO2Therefore, NOx in the atmosphere is commonly expressed as NO2Exist in the form of (1). In the presence of high temperature or cloud2Further reacts with water molecules to form nitric acid (HNO) which is a second important acid component in acid rain3). In the presence of a catalyst, e.g. under suitable gas phase conditions, N02The conversion to nitric acid is accelerated. Especially when NO is present2With SO2And when the catalyst exists at the same time, the catalyst can mutually catalyze to form nitric acid at a higher speed. With the rapid development of the modern industry, acid rain weather is more frequent.
In recent years, with the coming of the atmospheric pollutant emission standard in China, the increasing of the environmental protection treatment force and the deepening of the policy of energy conservation and emission reduction, the requirement on the NOx emission index is gradually increased, and the emission value of the conventional common gas-fired boiler cannot meet the national emission requirement. For this reason, gas boiler manufacturers are actively exploring ways to achieve standard emissions. The NOx generated in the combustion process is mainly thermal NOx, and the generated amount of the NOx is related to various factors such as combustion temperature, oxygen concentration in a high-temperature region, stagnation time of combustion gas in the high-temperature region and the like. Therefore, the optimization of the combustion mode of the combustor and the reduction of the generation and the emission of NOx from the source are an important way for reducing the NOx.
Disclosure of Invention
The present invention is directed to solving at least one of the above problems and providing a non-premixed air staged low NOx burner, which can adjust the oxygen distribution amount by air staging technique, and can effectively lower the flame combustion temperature, thereby achieving low NOx emission during the combustion process of the burner.
The purpose of the invention is realized by the following technical scheme:
a non-premixed air classification low NOx burner comprises a non-premixed channel arranged inside the burner and a secondary air channel arranged on the side wall of the burner;
the non-premixing channel comprises a gas channel and an air channel; the air channel and the non-premixing channel are coaxially arranged, and the gas channel is an annular gap between the air channel and the non-premixing channel;
the secondary air channel is provided with a plurality of secondary air channels which are arranged on the side wall of the combustor at the front end of the outlet of the non-premixing channel along the circumferential direction.
Preferably, the amount of air entering the burner from the air channel is 80% of the theoretical amount of air for complete combustion of the gas; the amount of air taken in from the secondary air channel is such that the excess air factor inside the burner is greater than 1. The air quantity entering the burner from the air channel is 80% of the theoretical air quantity of the complete combustion of the fuel gas, so that the air excess coefficient alpha is 0.8, the optimal excess air coefficient is obtained, and the emission of NOx concentration and other pollutant concentrations can be minimized.
The primary air flowing out of the air channel is mixed with the gas for combustion, and the air is only 80% of the theoretical air quantity of complete combustion, belongs to an oxygen-poor environment, and at the moment, the air excess coefficient alpha is less than 1, so that the gas cannot be completely combusted, the temperature of flame generated by gas combustion is reduced, and the emission of thermal NOx can be reduced; and meanwhile, the combustion process can be delayed, and the reaction rate of NOx is reduced in a reducing atmosphere. Excess secondary air is then introduced through the secondary air channel such that the air excess factor α >1 promotes complete combustion of the gas.
Preferably, the air channel is in a circular truncated cone shape, and the diameter of an inlet of the air channel is larger than that of an outlet of the air channel; the diameter of the inlet of the gas channel is larger than that of the outlet. The air channel and the gas channel are designed to be large in inlet and small in outlet, so that the flow velocity of air and gas entering the air channel and the gas channel can be accelerated, the residence time of the gas at the outlet of the non-premixing channel is further reduced, and the formation of NOx is favorably inhibited.
Preferably, a plurality of swirl vanes are arranged in the gas channel to divide the gas channel into a plurality of gas sub-channels. Namely, the swirl vanes are uniformly distributed between the outer side of the air channel and the inner side of the gas channel by taking the center line of the non-premixing channel as the center of a circle.
Preferably, the swirl vanes are provided with 8 vanes which evenly divide the gas channel into 8 branch gas channels. Namely, two adjacent swirl vanes are uniformly distributed outside the air channel at an interval of 45 degrees.
Preferably, the twist angle of the swirl vanes from the inlet to the outlet of the gas channel is 45 degrees, and the difference between the outflow directions of the gas and the air at the outlet is 45 degrees. The setting of the torsion angle of whirl blade can make the gas have an angle when mixing with the air, can strengthen the degree of mixing of gas and air, is favorable to the degree of the mixture of gas and air and gas burning. At 45 degrees, namely the swirl vanes are arranged perpendicular to the air channel at the inlet of the non-premixing channel and form an angle of 45 degrees with the tangent line of the air channel at the outlet, so that the mixing of air and fuel gas is more facilitated.
Preferably, the inlet of the gas channel and the inlet of the air channel are both connected with a fan. Air and gas are respectively pressed into the air channel and the gas channel through the fan, so that backflow of the gas and the air can be prevented, and potential safety hazards can be eliminated.
Preferably, the number of the secondary air channels is 8, and the secondary air channels are uniformly arranged along the circumferential direction; the secondary air channel is arranged perpendicular to the side wall of the combustor. The excessive secondary air can be provided to the inner part of the burner from all directions through a plurality of secondary air channels, and the stable combustion of the fuel gas is assisted.
Preferably, the secondary air channel is arranged perpendicular to the burner side wall. That is, the secondary air channels can be divided into 4 pairs, and the connecting line of each pair of secondary air channels passes through the center of the burner; and is centrosymmetric as a whole, namely the interval between two adjacent secondary air channels is 45 degrees. The design can lead the excessive secondary air entering the combustor to be aligned with the flame generated by combustion, and a large amount of fresh air and the unburned residual fuel are combusted, so that the air excess coefficient alpha is more than 1 at the moment, the fuel is promoted to be fully combusted, the flame in a combustion area can be reduced, the residence time of nitrogen and oxygen in the flame is reduced, and the generation of thermal NOx can be further reduced.
Preferably, the secondary air passage is a cylindrical passage with a diameter of 1/4 which is the diameter of the outlet of the non-premixing passage. The diameter of the secondary air channel can influence the flow and the flow speed of secondary air entering the combustor, and the requirement that after the secondary air is added, the air excess coefficient alpha is more than 1 so as to realize complete combustion of fuel gas is met; and the secondary air flow rate is prevented from being too large, so that the flame size is excessively influenced, and the combustion effect of the combustor is further influenced. When the diameter is too small, the secondary air intake quantity can not meet the demand quantity of the residual fuel at a later time, namely the flow of the secondary air can not reach the requirement of an air excess coefficient alpha > 1; when the air inflow of the secondary air passage is too large, the flow rate of the secondary air is greatly reduced, and the residence time of nitrogen and oxygen at the flame is greatly prolonged. 1/4, the proportion just meets the requirement, so the low NOx burner has more excellent performance effect.
At combustion temperatures up to 1500 ℃, the concentration of thermal NOx can amount to 30% of the total nitrogen oxide concentration, with the reaction rate increasing exponentially as the reaction temperature T increases. When T <1300 ℃, the amount of NOx produced is not large, and when T >1300 ℃, the reaction rate increases by 6 to 7 times for every 100 ℃ increase in T. As a result, the combustion temperature is lowered, the gas stop time is shortened, and the generation of NOx can be effectively reduced, thereby realizing low-NOx combustion.
The working principle of the invention is as follows:
the primary air and the gas respectively enter the combustor from the air channel and the gas channel of the non-premixing channel in a non-premixing mode, and then are combusted at the outlet of the non-premixing channel, and because the entering amount of the primary air is 80% of the theoretical air amount of complete combustion, the complete combustion cannot be realized by the primary combustion, and the temperature of flame generated by the combustion is low; then, the excess secondary air is supplemented into the combustor through the secondary air channel, so that the excess air coefficient alpha inside the combustor is larger than 1, and the gas is completely combusted.
Compared with the prior art, the invention has the following beneficial effects:
1. the air mixed with the fuel gas for combustion is divided into primary air and secondary air, wherein the consumption of the primary air is only 80 percent of the theoretical air amount, so that the primary combustion is incomplete, the flame temperature is low, and the generation of NOx can be effectively reduced; then introducing excessive secondary air to realize complete combustion of the fuel gas. By the aid of the principle of air staged combustion, the combustion temperature of flame can be effectively controlled to be at a low level, generation of NOx can be effectively inhibited, and low-NOx combustion is realized.
2. The swirl vanes with a certain torsion angle are arranged in the gas channel, so that the gas can be mixed with the air in a certain direction, and the mixing degree of the gas and the air can be further improved; meanwhile, the air channel and the gas channel in the non-premixing channel are arranged in a large inlet and a small outlet, so that the flow speed of air and gas at the outlet can be increased, the residence time of mixed gas at flame can be reduced, and the formation of NOx is inhibited.
3. The side wall of the combustor at the front end of the outlet of the non-premixing channel is provided with a plurality of secondary air channels, so that an oxygen source can be provided for flame inside the combustor from multiple directions, and the full combustion of fuel gas is promoted; meanwhile, the excessive secondary air entering the combustor can also inhibit the size of flame generated by combustion, further reduce the retention time of nitrogen and oxygen in the flame, and further can continuously reduce the formation of thermal NOx.
4. Air and gas are respectively introduced into the air channel and the gas channel in a fan mode, so that gas backflow can be prevented, and the phenomenon of backfire of the combustor is avoided. The traditional non-premixed combustion can preheat gas before mixed combustion and is not limited by ignition points, so that the low-calorific-value fuel can reach higher combustion temperature; in addition, non-premixed combustion can also produce a combustion flame slowly and safely. However, in the conventional non-premixed combustion, the mixing is not uniform, which causes a part of the fuel to be fully combusted, and another part of the fuel to be incompletely combusted, thereby generating NOx. The invention combines non-premixed combustion and air classification, and has the advantages of air classification: the oxygen amount in the primary combustion area is insufficient, so that the combustion speed and the temperature level are reduced, the thermal NOx is reduced, meanwhile, nitrogen is decomposed in the combustion to generate a large amount of intermediate active products NHi (intermediate chemical bonds generated by nitrogen, oxygen in air and hydrogen in high-temperature combustion chemical reaction), HCN can reduce part of generated NO, and the generation of the NOx is further inhibited; the oxygen amount in the secondary combustion area is sufficient, and the temperature at the position is low, so that excessive NOx is not generated, higher combustion temperature can be obtained, meanwhile, the residual fuel in primary combustion can be consumed through excessive secondary oxygen, the condition of uneven mixing of non-premixed combustion is overcome, and the emission of NOx can be obviously reduced.
5. The invention combines air classification and quickens gas flow velocity, can effectively reduce the temperature of combustion flame, effectively shortens gas detention time, and can effectively inhibit the generation of NOx by combining the air classification and the gas detention time, thereby further realizing low NOx combustion.
Drawings
FIG. 1 is a schematic perspective view of a burner of the present invention;
FIG. 2 is a schematic right-view structural view of the burner of the present invention;
FIG. 3 is a schematic left side view of the burner of the present invention;
FIG. 4 is a schematic front view of the burner of the present invention;
FIG. 5 is a sectional view of the primary burnout zone and the secondary burnout zone of the burner of the present invention;
FIG. 6 is a schematic top view of a non-premixing passage in the combustor of the present invention;
FIG. 7 is a schematic view of the A-A section (section A-A in FIG. 6) of the burner of the present invention;
FIG. 8 is a schematic view of a section B-B of the burner of the present invention (section B-B in FIG. 7);
in the figure: 1-a burner; 2-non-premix channel; 3-an air channel; 4-a gas channel; 5-swirl vanes; 6-secondary air channel.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments.
Examples
A non-premixed air staged low NOx burner 1, as shown in fig. 1-8, comprising a non-premixed channel 2 arranged inside the burner 1 and a secondary air channel 6 arranged on the side wall of the burner 1; the non-premixing passage 2 comprises a gas passage 4 and an air passage 3; the air channel 3 and the non-premixing channel 2 are coaxially arranged, and the gas channel 4 is an annular gap between the air channel 3 and the non-premixing channel 2; the secondary air channels 6 are arranged on the side wall of the combustor 1 at the front end of the outlet of the non-premixing channel 2 along the circumferential direction.
More specifically, in the present embodiment:
the air quantity entering the combustor 1 from the air channel 3 is 80% of the theoretical air quantity of the complete combustion of the gas, so that the flame temperature generated by the combustion of the gas is lower, and the emission of thermal NOx can be reduced; meanwhile, the combustion process can be delayed, and the reaction rate of NOx is reduced in a reducing atmosphere; the amount of air entering from the secondary air channel 6 makes the excess air factor inside the burner 1 greater than 1, and the gas is completely combusted. As shown in fig. 1 and 4, the burner 1 is generally cylindrical, the non-premixing passage 2 extends from the left side of the burner 1 to a position about 3/5 inside the burner, the non-premixing passage 2 is circular truncated cone-shaped, the inlet has a large diameter, the outlet has a small diameter, and an included angle of 45 degrees is formed between the side wall of the non-premixing passage and the side wall of the burner 1. The non-premixing passage 2 is divided into an air passage 3 and a gas passage 4, wherein the air passage 3 is a truncated cone-shaped passage coaxial with the non-premixing passage 2 (same as the non-premixing passage 2, the inlet has a large diameter, and the outlet has a small diameter), and the gas passage 4 is an annular space formed between the air passage 3 and the non-premixing passage 2. The inclination of the side wall of the air channel 3 is slightly larger than 45 degrees, so that the gas channel 4 also has a shape of a large-diameter inlet and a small-diameter outlet. The gas and the air are pressed into the gas channel 4 and the air channel 3 through the fan to prevent gas backflow, so that a fast flow rate exists, the speed of the gas and the air can be further accelerated through the channel with the large inlet and the small outlet, the gas flow rate at the outlet is accelerated, the residence time at the flame combustion position is shortened, and further the generation of NOx can be inhibited and reduced. The gas channel 4 is divided into 8 branch gas channels by arranging 8 swirl vanes 5 in the gas channel 4, the swirl vanes 5 use the central line of the non-premixing channel 2 as the center of a circle, and the two adjacent swirl vanes 5 are uniformly distributed in the combustion channel at an interval of 45 degrees. The swirl vanes 5 have a twist angle of 45 °, that is, at the inlet of the gas channel 4, each swirl vane 5 is perpendicular to the air channel 3, when the non-premixed channel 2 extends to the outlet to the inside of the combustor 1, the swirl vane 5 and the tangent of the air channel 3 form an angle of 45 °, the twist direction of each swirl vane 5 is consistent, and the twist change rate is also consistent, so that each partial gas channel is consistent (the same condition is adopted for setting in this embodiment, if there is a special requirement for the mixture of gas and air, the setting can also be performed according to the actual requirement, for example, half of the swirl vanes 5 have a twist angle of 30 °, the other half of the swirl vanes 5 have a twist angle of 60 °, and the two kinds of swirl vanes 5 are alternately set, etc.). Through setting up the whirl blade 5 that has the torsion angle, the gas can advance along whirl blade 5's angle and direction when flowing, and then can mix with the air with 45 directions mutually in the exit, can improve the degree of mixing of gas and air, is favorable to the burning of gas.
On the side wall of the burner 1 in front of the outlet of the non-premixing channel 2, 8 secondary air channels 6 are arranged and evenly distributed along the circumferential direction, and the difference between every two adjacent secondary air channels 6 is 45 degrees. The secondary air channel 6 is arranged perpendicular to the side wall of the combustor 1, so that the entering secondary air can directly aim at the center, namely flame burning at the outlet of the non-premixed channel 2, the volume of the flame can be reduced through the impact of the air, the residence time of nitrogen and oxygen in the flame is reduced, and the generation of thermal NOx can be further reduced; meanwhile, air is supplemented to the inner part of the burner 1 from a plurality of directions, so that the flame can be uniformly burnt. The secondary air passageway 6 is a cylindrical passageway having a diameter of about 1/6 of the diameter of the outlet of the non-premixed passageway 2, and a smaller diameter also allows for a faster flow rate of secondary air to reduce the flame volume.
At combustion temperatures up to 1500 ℃, the concentration of thermal NOx can amount to 30% of the total nitrogen oxide concentration, with the reaction rate increasing exponentially as the reaction temperature T increases. When T <1300 ℃, the amount of NOx produced is not large, and when T >1300 ℃, the reaction rate increases by 6 to 7 times for every 100 ℃ increase in T. Therefore, the combustion temperature is lowered, the gas stop time is shortened, the generation of NOx can be effectively reduced, and the low-NOx combustion can be realized.
As shown in fig. 5, the entire burner 1 can be divided into a primary burnout zone in which the mixture gas flowing out from the gas passage 4 and the air passage 3 is burned, and a secondary burnout zone in which the combustion of the gas is continued after sufficient replenishment of the secondary air is performed through the secondary air passage 6. When primary air flowing out of the air channel 3 is mixed with gas for combustion, the air is only 80% of the theoretical air quantity of complete combustion and belongs to an oxygen-poor environment, at the moment, the air excess coefficient alpha is less than 1, complete combustion cannot be carried out, the temperature of flame generated by gas combustion is low, and the emission of thermal NOx can be reduced; and meanwhile, the combustion process can be delayed, and the reaction rate of NOx is reduced in a reducing atmosphere. Excess secondary air is then introduced through the secondary air channel 6, with an air excess factor α >1, promoting complete combustion of the gas. In addition, through big import, the gas passage design of little export (gas passageway 4 and air passageway 3 all adopt the design that the inlet diameter is greater than the outlet diameter, the flow of gas and air with higher speed) and the design of the torsion angle of whirl blade 5 (the tangent line of whirl blade 5 and air passageway 3 at the exit of gas passageway 4 is 45, makes gas and air mix with 45 orientation emergence), impel gas and air can take place more abundant mixture, and can make gas acceleratedly pass through flame burning department, shorten the dwell time. Through the combined use of two kinds of structures, can effectively reduce flame combustion temperature, shorten gaseous residence time, and then can reduce the production of heating power type NOx, realize low NOx burning.
The working principle of the invention is as follows:
the primary air and the gas respectively enter the combustor 1 from the air channel 3 and the gas channel 4 of the non-premixing channel 2 in a non-premixing mode, and then are combusted at the outlet of the non-premixing channel 2, and because the entering amount of the primary air is 80% of the theoretical air amount of complete combustion, the complete combustion cannot be realized in the primary combustion, and the temperature of flame generated by the combustion is low; excess secondary air is then added to the burner 1 via the secondary air channel 6, so that the excess air ratio α >1 inside the burner 1 promotes complete combustion of the gas.
The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.
Claims (10)
1. A non-premixed air staged low NOx burner is characterized by comprising a non-premixed passage (2) arranged inside a burner (1) and a secondary air passage (6) arranged on the side wall of the burner (1);
the non-premixing channel (2) comprises a gas channel (4) and an air channel (3); the air channel (3) and the non-premixing channel (2) are coaxially arranged, and the gas channel (4) is an annular gap between the air channel (3) and the non-premixing channel (2);
the secondary air channel (6) is provided with a plurality of secondary air channels which are arranged on the side wall of the combustor (1) at the front end of the outlet of the non-premixing channel (2) along the circumferential direction.
2. A non-premixed air staged low NOx burner according to claim 1, characterized in that the amount of air entering the burner (1) from the air channel (3) is 80% of the theoretical amount of air for complete combustion of the gas; the amount of air entering from the secondary air channel (6) is such that the excess air factor inside the burner (1) is greater than 1.
3. A non-premixed air staged low NOx burner according to claim 1, characterized in that said air passages (3) are frustoconical with an inlet diameter larger than an outlet diameter; the diameter of the inlet of the fuel gas channel (4) is larger than that of the outlet.
4. A non-premixed air staged low NOx burner according to any of claims 1 to 3, characterized in that a plurality of swirl vanes (5) are provided in the gas channel (4) to divide the gas channel (4) evenly into a plurality of staged gas channels (4).
5. A non-premixed air staged low NOx burner according to claim 4, wherein said swirl vanes (5) are provided with 8, dividing the gas channel (4) evenly into 8 sub-gas channels.
6. A non-premixed air staged low NOx burner according to claim 4, wherein the twist angle of the swirl vanes (5) from the inlet to the outlet of the gas channel (4) is 45 °, and the difference between the outflow directions of gas and air at the outlet is 45 °.
7. A non-premixed air staged low NOx burner according to claim 1, characterized in that the inlet of the gas channel (4) and the inlet of the air channel (3) are connected with a fan.
8. A non-premixed air staged low NOx burner according to claim 1, characterized in that said secondary air channels (6) are provided in 8, circumferentially uniform arrangement.
9. A non-premixed air staged low NOx burner according to claim 8, characterized in that said secondary air channel (6) is arranged perpendicular to the burner (1) side wall.
10. A non-premixed air staged low NOx burner according to claim 8, characterized by the fact that said secondary air channel (6) is a cylindrical channel with a diameter 1/4 of the outlet diameter of the non-premixed channel (2).
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