CN109899786B - Flameless low-nitrogen combustor and flameless low-nitrogen combustion method - Google Patents
Flameless low-nitrogen combustor and flameless low-nitrogen combustion method Download PDFInfo
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Abstract
The invention provides a flameless low-nitrogen combustor and a flameless low-nitrogen combustion method, wherein the combustor comprises an air pipe system and a fuel gas pipe system, the air pipe system comprises an air cylinder (1) which is enclosed into a mixing cavity and an air pipe extending into the mixing cavity, and the fuel gas pipe system comprises a fuel gas pipe extending into the mixing cavity; air is introduced into the air pipe, fuel gas is introduced into the fuel gas pipe, and the air and the fuel gas are mixed at a high speed, heated and diluted by high-temperature flue gas in the mixing cavity and then combusted. The burner and the burning method of the invention allow the slow burning reaction to be carried out in the atmosphere with low gas concentration and low oxygen concentration, ensure the stability and completeness of burning, effectively control the generation of thermal type and rapid type NOx and realize flameless low-nitrogen burning.
Description
Technical Field
The invention belongs to the field of industrial burners and boilers, and particularly relates to a flameless low-nitrogen burner and a flameless low-nitrogen combustion method, which are mainly used for the industrial burners and boilers.
Background
The industrial boiler combustor mostly adopts the traditional combustion mode of forced air supply and diffusion, and the main purpose of the industrial boiler combustor is burnout and safety, and few measures are taken for NOx emission. Today, for some regions 30mg/m3The following environmental requirements for NOx emissions, the main technical routes that have emerged and adopted include dispersion combustion, premixed combustion, flue gas recirculation, porous media catalytic combustion and flameless combustion:
(1) fuel-dispersed combustion or air-dispersed combustion
Both methods will eventually maintain the excess air factor of the entire system at a constant value. This technical system is complex and does not eliminate the high temperature zone of the flame.
(2) Lean premixed combustion technology
An advantage of this technique for controlling NOx production is that control of combustion temperature can be achieved with full control of equivalence ratio, thereby reducing the rate of thermal NOx production, and in some cases premixed combustion and partial premixing can reduce NOx production by 85% -90% over non-premixed combustion. In addition, complete premixing may also reduce the reduction in NOx generation control due to excess air ratio non-uniformity. If the lean premixed burner is added with the wire mesh burner to form surface combustion, the flame is more dispersed, and the NOx emission is further reduced.
However, the premixed combustion technology still has unsolved technical difficulties in safety control: firstly, the premixed gas may cause backfire due to its high flammability; secondly, the excessive air excess coefficient can cause the increase of the exhaust smoke loss, and the heat efficiency of the boiler is reduced; thirdly, the combustion head of the wire mesh is easily adhered by the melted fine dust, and the maintenance period is short. The power of the present lean premixed burner does not exceed 2MW
(3) External flue gas recirculation and internal flue gas recirculation techniques
The reduction of the combustion temperature can be achieved by adding flue gas in the flame zone, which absorbs heat and thereby reduces the combustion temperature. Combustion products of the flue gas are added into the combustion area, so that the combustion temperature is reduced, and the generation of NOx is reduced; meanwhile, the added flue gas reduces the partial pressure of oxygen, which weakens the process of generating thermal NOx by oxygen and nitrogen, thereby reducing the generation of NOx. According to different application principles, the flue gas recirculation has two application modes, namely external flue gas recirculation and internal flue gas recirculation.
For external flue gas recirculation techniques, flue gas is reintroduced into the furnace from the outlet of the boiler through an external duct. External flue gas recirculation can reduce NOx generation by 70%. The external circulation proportion also has a larger influence on the NOx control effect, the reduction range of NOx is more obvious along with the increase of the external circulation proportion, but the power consumption of the circulating fan is also increased.
For internal flue gas recirculation, the return of flue gas to the combustion zone is primarily through the gas dynamics of the burner. Internal flue gas recirculation is achieved by rotating the gas stream mainly through entrainment of high velocity jet flames or swirl burners. By creating an annular recirculation zone in the center of the flame, the hot gases will return to the burner throat, which ensures ignition of the cold, unburned gases, while reducing NOx production by lowering flame temperature and lowering oxygen partial pressure.
(4) Porous media catalytic combustion
Another way to reduce the flame temperature is to enhance the heat transfer from the flame to the outside as quickly and as much as possible. A porous medium (PIM) is added to the burner such that the combustion reaction occurs within the porous medium such that radiant and convective heat transfer from the burner to the surrounding environment is enhanced. Experiments show that the combustion temperature of the PIM burner is lower than 1600K, and the NOx generation amount is about 5-20 ppm.
PIM burners may also add a catalyst at the burner inlet so that the fuel molecules and oxidant molecules react at the catalyst surface with a relatively low activation energy. So that the reaction temperature is lower than in the case of combustion of the same type. Since the reaction process is only carried out on the surface of the catalyst, no NOx is generated, so that the generation of NOx in catalytic combustion can be reduced to 1 ppm.
The defects of catalytic combustion are that the active surface is not oxidized or evaporated at a relatively low temperature, the cost of the catalyst is relatively high, and the catalyst has a poisoning phenomenon in long-term application, so that the combustor is difficult to be applied in a large scale.
(5) Flameless combustion
the traditional flame combustion is divided into premixed combustion and diffusion combustion, and is mainly characterized by comprising the steps of (1) reacting fuel with oxygen at high temperature, wherein the higher the temperature is, the more the stability of the flame is facilitated, (②) viewing the flame peak surface (the flame generated by methane combustion is generally blue, and is yellow when soot is generated), and (③) finishing combustion of most of the fuel in a very thin flame layer, but finishing the combustion reaction in a downstream invisible area.
Typically, the flame after ignition generally acts as an igniter itself to ignite the incoming flow. This requires a high enough flame temperature to achieve the minimum ignition energy, but high flame temperatures can lead to increased NOx production.
The flameless combustion of the fuel is realized under the conditions that the temperature in the furnace is 1000 ℃, the air is preheated to 650 ℃ and the flow rate of the air flow is high. And a large amount of backflow high-temperature flue gas is formed by mixing with fresh air by utilizing the position relation between the main combustion nozzles uniformly arranged in an annular mode and the cylindrical backflow structure arranged in the center and the shearing effect of viscous fluid, the temperature of the air is increased, the air is diluted, the diluted high-temperature air is subjected to spontaneous combustion when meeting the fuel, a highly dispersed reaction zone is formed, and accordingly flameless combustion is achieved. For such flameless combustion, flue gas recirculation occurs before combustion, and possibly even during combustion, such recirculated flue gas heats the premixed fuel and air and lowers the combustion temperature, expanding the reaction zone. Flameless combustion flames are evenly distributed and the combustion temperature is low, which results in less NOx production. This type of flameless combustion generally requires special means or measures for preheating the air.
Disclosure of Invention
In order to solve the problem of high emission of NOx in gas combustion, the inventor of the invention makes a keen study to design a flameless low-nitrogen combustor and a flameless low-nitrogen combustion method, wherein the emission of NOx meets the low emission requirement, and the limitations of fuel dispersion combustion or air dispersion combustion, a lean premixed combustion technology, an external flue gas recirculation technology, an internal flue gas recirculation technology, porous medium catalytic combustion and flameless combustion do not exist, so that the invention is completed.
The invention aims to provide the following technical scheme:
(1) a flameless low-nitrogen burner comprises an air pipe system and a fuel gas pipe system, wherein the air pipe system comprises an air cylinder 1 and an air pipe, the air cylinder 1 and the air pipe extend into a mixing cavity, the air pipe system comprises a fuel gas pipe, the fuel gas pipe extends into the mixing cavity;
air is introduced into the air pipe, fuel gas is introduced into the fuel gas pipe, and the air and the fuel gas are mixed at a high speed, heated and diluted by high-temperature flue gas in the mixing cavity and then combusted.
(2) A flameless low-nitrogen combustion method is implemented by the flameless low-nitrogen combustor in the (1), and the method comprises the steps of enabling fuel gas to move opposite to high-temperature high-speed air, diluting the fuel gas by high-temperature flue gas, and then combusting the fuel gas.
According to the flameless low-nitrogen combustor and the flameless low-nitrogen combustion method provided by the invention, the following beneficial effects are achieved:
(1) according to the invention, the mixing cavity comprises a plurality of air pipes and gas pipes, the air pipes and the gas pipes are provided with spray holes in a distributed manner, the air pipes and the gas pipes are arranged in a staggered manner in a layered manner, and the gas and the air can be fully mixed in a very short time through a large number of spray holes and a large jet flow surface area;
(2) in the invention, the air duct is of an interlayer structure, so that the preliminary preheating of air in an interlayer can be realized by effectively utilizing the heat transfer of high-temperature flue gas in the mixing cavity, the heat loss of the flue gas is reduced, and the combustion efficiency is favorably improved;
(3) in the invention, the air pipes and the fuel gas pipes are arranged in a grading way, and the arrangement shape of each grade of fuel gas pipes and/or each grade of air pipes, the peripheral fuel gas pipes and/or the peripheral air pipes is matched with the section shape of the mixing cavity, thus being beneficial to improving the combustion uniformity and stability.
(4) According to the invention, through the arrangement of the air pipes and the gas pipes, different air supply and gas proportioning can be realized by controlling different orifice diameters of different areas, so that staged combustion is formed, and the emission of nitrogen oxides is further reduced.
(5) In the invention, a plurality of groups of air pipes and gas pipes with a plurality of jet holes improve the mixing of combustion and air, one flame is divided into a plurality of small flames, the thickness of the flame surface is reduced, the heat dissipation area is enlarged, the temperature of the flame is reduced, and meanwhile, under the condition that the combustion load is not changed, the small flame surface shortens the residence time of oxygen and nitrogen in the flame surface, namely a high-temperature area. In addition, the mode of multipoint arrangement and dispersive combustion avoids local concentration of heat intensity, disperses the flame core of a high-temperature area, ensures more uniform temperature of the flame area, and has obvious inhibiting effect on thermal NOx and fuel NOx by the above beneficial factors.
Drawings
FIG. 1 shows a schematic structural view of a flameless low-nitrogen burner according to a preferred embodiment of the present invention;
FIG. 2 illustrates a side cross-sectional view of a flameless low-nitrogen burner in accordance with a preferred embodiment of the present invention;
FIG. 3 illustrates a side cross-sectional view of a peripheral air duct in accordance with a preferred embodiment of the present invention;
FIG. 4 shows a side cross-sectional view of a primary air duct in accordance with a preferred embodiment of the present invention;
fig. 5 shows a cross-sectional view of a preferred embodiment according to the present invention.
The reference numbers illustrate:
1-an air duct;
2-side plate;
31-central gas pipe;
32-peripheral gas pipe;
41-primary air pipe;
42-peripheral air ducts;
5-gas supply branch pipe;
6-mounting hole I;
7-mounting hole II.
Detailed Description
The invention is explained in more detail below with reference to the figures and examples. The features and advantages of the present invention will become more apparent from the description.
The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.
As shown in fig. 1 and 2, the present invention provides a flameless low-nitrogen burner, which comprises an air duct system and a fuel gas duct system, wherein the air duct system comprises an air duct 1 which is enclosed to form a mixing chamber and an air duct extending into the mixing chamber, and the fuel gas duct system comprises a fuel gas duct extending into the mixing chamber;
the wall of the air pipe is provided with a plurality of air jet holes for jetting air with set pressure, the wall of the gas pipe is provided with a plurality of gas jet holes for jetting gas with set pressure, and the air and the gas are mixed at high speed, heated and diluted by high-temperature flue gas in the mixing cavity and then combusted.
In a preferred embodiment, the mixing chamber is a place surrounded by the side plate 2 and the air duct 1 and where gas-air or gas-air-flue gas mixing and gas combustion occur. The gas pipe and the air pipe penetrate through the side plate 2 to enter the mixing cavity, and the side plate 2 plays a supporting role in supporting the gas pipe and the air pipe.
In a preferred embodiment, the air duct 1 may be a cylinder, a cylinder with a regular polygonal cross section, a cylinder with an irregular polygonal cross section, etc., and may be divided into a cylinder with a symmetrical structure along the axial direction thereof or a cylinder with an asymmetrical structure along the axial direction thereof, preferably a cylinder with a symmetrical structure along the axial direction thereof, and more preferably a cylinder, the axial direction thereof being the length direction thereof.
The air duct 1 is of a sandwich structure, air is introduced into the sandwich layer, no hole is formed in the outer wall surface of the sandwich layer, the inner wall surface in the mixing cavity is provided with an annular air jet hole, and the air can be sprayed into the mixing cavity from the air jet hole in the inner wall surface of the air duct 1 to participate in combustion.
When the gas is ignited and the burner operates normally, the injected gas firstly entrains the surrounding smoke at a high speed, and the diluted gas and the high-temperature high-speed air which also entrains the smoke move oppositely and are fully mixed and combusted. The gas ejected at high speed absorbs the smoke gas, so that the concentration of the gas is diluted. The air ejected at high speed absorbs the smoke, so that the oxygen concentration is diluted and the combustion reaction is slowed down. The inner wall of the air duct 1 is heated to form a high-temperature state, and the air in the air duct 1 is preliminarily preheated. The sprayed air can be further heated and heated due to entrainment of high-temperature flue gas. The high temperature air-flue gas mixture, the high velocity air flow and the slower combustion reaction form the dispersive flameless combustion, the combustion coreless area and the high temperature area, and the thermal NOx and the rapid NOx are reduced.
In a preferred embodiment of the invention, the air pipes are multiple, the gas pipes are multiple, and the air pipes and the gas pipes are arranged in a staggered manner in a layered manner. In this way, gas and air are mixed more efficiently with a greater number of orifices and a greater jet surface area.
The gas pipe and the air pipe may be circular pipes, pipes having a regular polygonal cross section, pipes having an irregular polygonal cross section, or the like, and may be divided into pipes symmetrical in their axial directions or pipes asymmetrical in their axial directions, preferably pipes symmetrical in their axial directions, and more preferably circular pipes.
In a further preferred embodiment, the gas pipes comprise a central gas pipe 31 located in the centre of the mixing chamber, a peripheral gas pipe 32 located close to the inner wall of the chimney 1, and optionally stages of gas pipes interposed between the central gas pipe 31 and the peripheral gas pipe 32. In the direction from the central gas pipe 31 to the peripheral gas pipe 32, the gas pipes are named as a first-stage gas pipe, a second-stage gas pipe and … …, N is a positive integer, and the distances from the same stage of gas to the central gas pipe 31 are equal or very close.
The air ducts comprise a primary air duct 41 surrounding the central gas duct 31, a peripheral air duct 42 adjacent to the inner wall of the air duct 1, and optionally other air ducts of various stages between the primary air duct 41 and the peripheral air duct 42. In the direction from the central gas pipe 31 to the peripheral air pipe 42, the air pipes are named as a primary air pipe 41, a secondary air pipe and … …, N-grade air pipes are provided, N is a positive integer, and the distances between the same-grade air pipe and the central gas pipe 31 are equal or very close.
In a further preferred embodiment, the gas and/or air pipes and the peripheral gas and/or air pipes 32, 42 are arranged to match the cross-sectional shape of the mixing chamber to improve combustion uniformity and stability.
In a further preferred embodiment, as shown in fig. 1, the side plate 2 is circular, the air duct 1 is cylindrical, i.e. the cross section of the mixing chamber surrounded by the air duct is circular, and the gas pipes and the air pipes are arranged in the air duct 1 in a circular layered staggered manner. The gas pipe comprises a central gas pipe 31 and a peripheral gas pipe 32 which are positioned in the center of the mixing cavity, and the air pipe comprises a primary air pipe 41 surrounding the central gas pipe 31 and a peripheral air pipe 42 at the periphery of the peripheral gas pipe 32.
Preferably, the number of the central gas pipes 31 is one, the number of the primary air pipes 41 is six, the number of the peripheral gas pipes 32 is six, and the number of the peripheral air pipes 42 is six.
In a preferred embodiment of the invention, the diameters of the gas pipes at the same level and the distribution density and the pore size of the gas spray holes are the same. The central gas pipe 31, the peripheral gas pipes 32 and the gas spray holes on the gas pipes at all stages are annularly distributed in the axial direction.
Each gas pipe supplies gas through corresponding gas supply branch pipe 5, and gas supply branch pipe 5 pipe diameter and the distance of preferred gas pipe at the same level are equal.
In the invention, one end of each air pipe outside the mixing cavity is communicated with the air duct 1, and the air duct 1 supplies air uniformly.
In a preferred embodiment of the present invention, the diameters of the air ducts at the same level and the distribution density and the pore size of the air injection holes are the same. The primary air duct 41, the peripheral air duct 42, and the air injection holes of the air ducts of the respective stages are annularly distributed in the axial direction.
In another preferred embodiment of the present invention, as shown in fig. 3, the pipe diameters, the distribution densities and the pore sizes of the air nozzles of the same stage are the same. The peripheral air duct 42 is provided with air spray holes at one side, and the air spray holes are not formed at the side of the peripheral air duct 42 facing the central gas duct 31, i.e. facing the inner wall surface of the air duct 1. This unilateral trompil mode for the direction of air jet hole is unanimous on peripheral tuber pipe 42 and the dryer 1, avoids influencing the air input of dryer 1 because the diversified trompil of peripheral tuber pipe 42, reduces the timely mixture to peripheral gas pipe 32 spun gas.
As shown in fig. 4, the primary air duct 41 or other air ducts at different levels are full-wall openings, and the openings can move in opposite directions with the fuel gas ejected from the fuel gas pipes distributed around the primary air duct, so that the generated air flow is beneficial to quickly scattering the fuel gas, and is beneficial to forming dispersive combustion, burning a coreless area and a high-temperature area, and reducing the generation of thermal NOx and quick NOx.
In the invention, the multiple groups of gas pipes and air pipes with a plurality of spray holes can improve the mixing of gas and air, divide a flame into a plurality of small flames, reduce the thickness of the flame surface, enlarge the heat dissipation area, reduce the temperature of the flame, and shorten the retention time of oxygen and nitrogen in a high-temperature area by the short flame even without flame under the condition of unchanged combustion load. In addition, the mode of multipoint arrangement and dispersive combustion avoids local concentration of heat intensity, disperses the flame core in a high-temperature area, has more uniform temperature in the flame area, and has obvious inhibiting effect on thermal NOx and fuel NOx.
In the present invention, the fuel type NOx is formed by nitrogen element contained in the fuel at the time of fuel combustion. The temperature does not have a significant effect on the formation of fuel NOx.
The thermal NOx is generated mainly during combustion, nitrogen in combustion air is generated through oxidation under high-temperature flame, and the generation of the thermal NOx is influenced by the temperature, the excess air coefficient and the residence time of a high-temperature area. Where temperature is the most important factor in the thermal type, the actual combustion process may cause increased NOx formation due to the high temperature region caused by the uneven temperature distribution.
The nitrogen element in the rapid NOx is also from air in combustion, and the rapid generation is mainly because the hydrocarbon can decompose a large amount of groups such as CH, C and the like during combustion, so that the molecular bond of nitrogen can be broken, and further the NOx is generated. Fast NOx is mainly formed by the rapid reaction of hydrocarbons in the fuel.
The influence of the excess air factor on the generation of thermal NOx is a double-sided effect, and the actual combustion condition is more complicated. When the excess air factor becomes large, the oxygen concentration becomes large, the chemical reaction equilibrium is promoted to move, and the amount of generated NOx increases; meanwhile, as the excess air ratio becomes larger, the amount of generated flue gas becomes larger, and the combustion temperature is lowered, thereby lowering the generation rate. The influence of the excess air factor is therefore complex, either promoting or inhibiting, and is analyzed as a function of the circumstances. In general, the longer the reaction stays in the high-temperature region, the larger the amount of NOx produced.
The influence of the excess air ratio on the rapid NOx generation is that, at a constant temperature, as the excess air ratio becomes larger, the NOx generation amount becomes larger and then smaller, and a peak occurs.
The effect of the excess air factor on the formation of fuel-type NOx is that the conversion of nitrogen in the fuel to NOx increases as the excess air factor increases; when the excess air ratio a >1, the fuel NOx production amount is kept substantially constant; when the excess air ratio a <1, the conversion rate drops quickly.
The invention provides an implementation mode of graded dispersion combustion, flame segmentation, high-temperature core removal, low air excess coefficient, no flame and low nitrogen.
In a preferred embodiment of the present invention, the diameter of the gas spray holes of the central gas pipe 31 is larger than the diameter of each stage of gas pipe or the peripheral gas pipe 32, and preferably, in the direction from the central gas pipe 31 to the peripheral gas pipe 32, the diameter of the gas spray holes of the gas pipes is in a downward trend, which is beneficial to realizing different proportions of air supply and gas, thereby forming staged combustion and further reducing the emission of nitrogen oxides. Generally, the air excess coefficient around the central gas pipe 31 is less than 1, and the air excess coefficient of the peripheral gas pipe is more than 1, so that the staged combustion is realized.
In the present invention, as shown in fig. 5, the burner further includes an ignition device and an ion induction needle. An ignition device and an ion induction needle are arranged in the side plate 2, so that an ignition end of the ignition device and an induction end of the ion induction needle extend into a mounting hole I and a mounting hole II of the mixing cavity. Preferably, mounting holes I6 and II 7 are provided near central gas tube 31 for rapid ignition or detection of ion current.
In the invention, the flue gas generated after combustion in the mixing cavity has higher heat energy and kinetic energy, and along with the rise of the pressure in the mixing cavity, the flue gas can be spontaneously discharged out of the mixing cavity from the opposite side of the side plate 2 to carry out the subsequent heat exchange process. The process that the flue gas leaves the mixing chamber need not extra fan and drives, has reduced the energy consumption.
In another aspect of the present invention, there is provided a flameless low-nitrogen combustion method, which comprises moving fuel gas and high-temperature high-speed air in opposite directions, and combusting the fuel gas after dilution by high-temperature flue gas.
Preferably, the process of the invention is carried out by means of a flameless low-nitrogen burner as described above.
During combustion, air and fuel gas are sprayed at a high speed through a plurality of groups of spray holes, surrounding smoke is sucked in an entrainment mode and then participates in combustion, the concentration of oxygen in the air and the concentration of the fuel gas are reduced due to dilution, and the combustion reaction speed is slowed down. High-speed airflow and low combustion reaction speed, and forms dispersive combustion.
Examples
Example 1
As shown in figure 1, a flameless low-nitrogen combustor burns, dryer 1 and curb plate 2 enclose into cylindric mixing chamber, gas pipe and tuber pipe stretch into in the mixing chamber with the crisscross arrangement of ring form layering, the gas pipe comprises 1 central gas pipe 31 and 6 peripheral gas pipes 32 that are located the mixing chamber center, the tuber pipe comprises 6 one-level tuber pipes 41 that encircle central gas pipe 31 and 6 peripheral tuber pipes 42 that are close to dryer 1 outer wall, one-level tuber pipe 41 encircles central gas pipe 31, peripheral gas pipe 32 is between one-level tuber pipe 41 and peripheral tuber pipe 42, peripheral tuber pipe 42 is located outermost periphery. The central gas pipe 31 and the peripheral gas pipe 32 are provided with holes on the whole wall surface; air spray holes are formed in one side of the peripheral air pipe 42, the hole opening direction faces the central gas pipe 31, and the first-stage air pipe 41 or other air pipes at all stages are full-wall holes.
The diameter of air jet holes on the air duct 1 is 2mm, the distribution density of the air jet holes is 2000 per square meter, the air preheating temperature is 200 ℃, and the air flow rate is 15 meters per second;
the pipe diameter of the central gas pipe 31 is 60mm, the diameter of the gas spray holes is 1mm, the distribution density of the gas spray holes is 580 per square meter, and the gas flow velocity is 183 m/s;
the pipe diameter of the peripheral gas pipe 32 is 25mm, the diameter of the gas spray holes is 1mm, the distribution density of the gas spray holes is 780/square meter, and the gas flow velocity is 183 m/s;
the pipe diameter of the primary air pipe 41 is 60mm, the diameter of the air jet holes is 8mm, the distribution density of the air jet holes is 590/square meter, the air preheating temperature is 200 ℃, and the air flow rate is 15 m/s;
the diameter of the peripheral air duct 42 is 60mm, the diameter of the air jet holes is 8mm, the distribution density of the air jet holes is 440/square meter (the distribution density is based on the whole air duct), the air preheating temperature is 200 ℃, and the air flow rate is 15 m/s.
In embodiment 1, the fuel gas is introduced into the internal gas supply branch pipe from the external pipeline, then distributed to the central fuel gas pipe 31 and the peripheral fuel gas pipe 32 through the internal gas supply branch pipe, and then injected into the mixing chamber through the fuel gas injection holes, and the injected flue gas is mixed with the air according to the sequence of the primary air pipe 41 and the peripheral air pipe 42. Air is introduced into the air chamber through the external air channel, is preheated to 200 ℃ (the mixing chamber is cooled at the same time, the flue gas temperature in the mixing chamber is reduced to below 1800K) in the air chamber and then is sprayed out through the air nozzles, and the air is mixed with the gas sprayed out from the central gas pipe 31 and the peripheral gas pipes 32 respectively, so that subdivided flames, low-concentration fuel and air are realized, multi-stage sufficient mixing is realized, the combustion temperature is reduced and homogenized, and the diffusion flameless low-nitrogen combustion with low air excess coefficient is realized.
Example 2
The structure and the implementation steps of the low-nitrogen burner are consistent with those of the embodiment 1, and the difference is only that the diameters of the spray holes of different areas are different, specifically:
the diameter of air jet holes on the air duct 1 is 2mm, the distribution density of the air jet holes is 2000 per square meter, the air preheating temperature is 200 ℃, and the air flow rate is 15 meters per second;
the pipe diameter of the central gas pipe 31 is 60mm, the diameter of the gas spray holes is 1.2mm, the distribution density of the gas spray holes is 580 per square meter, and the gas flow velocity is 183 m/s;
the pipe diameter of the peripheral gas pipe 32 is 25mm, the diameter of the gas spray holes is 0.5, the distribution density of the gas spray holes is 780 per square meter, and the gas flow rate is 183 cubic meters per second;
the pipe diameter of the primary air pipe 41 is 60mm, the diameter of the air jet holes is 8mm, the distribution density of the air jet holes is 590/square meter, the air preheating temperature is 200 ℃, and the air flow rate is 15 m/s;
the pipe diameter of the peripheral air pipe 42 is 60mm, the diameter of the air jet holes is 8mm, the distribution density of the air jet holes is 440 per square meter, the air preheating temperature is 200 ℃, and the air flow rate is 15 m/s.
Comparative example 1
The invention relates to a combustion method for a boiler, which adopts a combustion device of a graded flameless low-nitrogen combustion head, which is applied by the applicant on 09.08.2017.
The structure of the low-nitrogen combustion head is consistent with that of the embodiment 1, and the difference is only that the gas pipe is composed of 1 central gas pipe 31 positioned in the center of the mixing cavity, and the air pipe system only comprises an air duct 1 which is enclosed into the mixing cavity;
wherein, the pipe diameter of the central gas pipe 31 is 60mm, the diameter of the gas jet holes is 1mm, the distribution density of the gas jet holes is 580 per square meter, and the gas flow velocity is 183 m/s;
the diameter of the air jet holes on the air duct 1 is 2mm, and the distribution density of the air jet holes is 2000 per square meter; the air preheating temperature is 200 ℃, and the air flow rate is 15 m/s.
Examples of the experiments
The burner and the boiler are assembled, different loads are adjusted, and CO (%), NOx (ppm) and O in the final tail gas are treated2The (%) content was monitored to determine the combustion. Wherein, the load is the percentage reaching the rated state of the combustion device; o is2(%) means O in the final exhaust gas2Percent by volume of (a); CO (%) refers to the volume percent of CO in the final tail gas.
TABLE 1
TABLE 2
TABLE 3
By analyzing the relevant inspection data of example 1, example 2 and comparative example 1, adjusting the orifice diameters of different regions is advantageous for reducing CO (%), NOx (ppm) emissions. Compared with the invention patent 'graded flameless low-nitrogen combustion head' combustion device applied by the applicant at 09.2017, 08.s, the invention adds the primary air pipe, the secondary air pipe and the peripheral gas pipes on the basis of the air spray holes on the inner walls of the central gas pipe and the mixing cavity, so that the structure of the dispersive flameless low-nitrogen combustion is more optimized, and the upper limit of the power of the combustion device with low nitrogen emission is improved from 200KW to 800-1000 KW.
The present invention has been described above in connection with preferred embodiments, but these embodiments are merely exemplary and merely illustrative. On the basis of the above, the invention can be subjected to various substitutions and modifications, and the substitutions and the modifications are all within the protection scope of the invention.
Claims (6)
1. The flameless low-nitrogen combustor is characterized by comprising an air pipe system and a fuel gas pipe system, wherein the air pipe system comprises an air cylinder (1) and an air pipe, the air cylinder (1) and the air pipe extend into a mixing cavity, the fuel gas pipe system comprises a fuel gas pipe, and the fuel gas pipe extends into the mixing cavity;
air is introduced into the air pipe, fuel gas is introduced into the fuel gas pipe, the air and the fuel gas are mixed at high speed and are combusted after being heated and diluted by high-temperature flue gas in the mixing cavity,
the air pipes and the gas pipes are arranged in a layered and staggered manner;
the gas pipe comprises a central gas pipe (31) positioned in the center of the mixing cavity, a peripheral gas pipe (32) close to the inner wall of the air duct (1), and various stages of gas pipes optionally between the central gas pipe (31) and the peripheral gas pipe (32);
the air pipes comprise primary air pipes (41) surrounding the central gas pipe (31), peripheral air pipes (42) close to the inner wall of the air duct (1), and optional air pipes of various stages between the primary air pipes (41) and the peripheral air pipes (42);
air spray holes are formed in one side of the peripheral air pipe (42), the hole opening direction faces to the central gas pipe (31), namely, the air spray holes are not formed in the side of the peripheral air pipe (42) facing to the inner wall surface of the air duct (1),
the first-stage air pipe (41) or other air pipes at all stages are provided with holes on the whole wall surface,
the diameter of the gas spray holes of the gas pipe is in a descending trend in the direction from the central gas pipe (31) to the peripheral gas pipe (32),
the air duct (1) is of a sandwich structure, air is introduced into the sandwich layer, the outer wall surface of the sandwich layer is not provided with holes, air spray holes are formed in the inner wall surface of the mixing cavity, and the air can be sprayed into the mixing cavity from the air spray holes in the inner wall surface of the air duct (1) to participate in combustion;
the wall of the air pipe is provided with a plurality of air jet holes for jetting air with set pressure, and the wall of the gas pipe is provided with a plurality of gas jet holes for jetting gas with set pressure, so that the air and the gas can be mixed at high speed.
2. Burner according to claim 1, characterized in that the arrangement of the stages of gas tubes and/or of the stages of air ducts and of the peripheral gas tubes (32) and/or of the peripheral air ducts (42) is shaped to match the cross-sectional shape of the mixing chamber.
3. The burner as claimed in claim 1, wherein the diameters of the gas pipes at the same level and the distribution density and the pore size of the gas spray holes are the same;
each gas pipe supplies gas through corresponding gas supply branch pipe (5), and gas supply branch pipe (5) pipe diameter and distance of gas pipe at the same stage are equal.
4. Burner according to claim 3, characterized in that the central gas tube (31), the peripheral gas tubes (32) and the gas jet holes of each stage of gas tubes are annularly distributed in the axial direction of the gas tubes.
5. The burner of claim 1, wherein the diameters of the equivalent air ducts and the distribution density and the pore size of the air injection holes are the same;
one end of each air pipe, which is positioned outside the mixing cavity, is communicated with the air duct (1) and is supplied with air by the air duct (1).
6. The burner of claim 1, wherein the gas pipe and the air pipe are pipes symmetrical in their axial directions or pipes asymmetrical in their axial directions.
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| CN110594739B (en) * | 2019-08-02 | 2020-10-30 | 华中科技大学 | Flameless combustor without preheating switching |
| CN110822417A (en) * | 2019-10-29 | 2020-02-21 | 陕西工业职业技术学院 | Full-premixing denitration system of gas industrial boiler and control method |
| CN114135870B (en) * | 2019-12-18 | 2024-03-19 | 史星宇 | Low-nitrogen combustion head, combustion device and premixing method thereof |
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