Dual-delay premixed short-flame low-nitrogen submerged combustion burner

Abstract

A double delayed premixed short flame low nitrogen submerged burner is characterized in that it includes a delayed premixed burner with double air distribution and a central secondary air structure. The premixed combustible gas at the burner outlet of the delayed premixed burner presents a non-uniform concentration distribution with a center-rich and a periphery-lean under the action of the central secondary air; the center-rich means that there is more fuel gas and the local equivalence ratio is closer to 1, and the periphery-lean means that there is less fuel gas and the local equivalence ratio is further away from 1. The present invention realizes high-intensity short flame low nitrogen combustion, the power is flexibly configured through the burner combination, and the combustion state is conveniently adjustable online to achieve the required stable combustion and pollutant emission indicators. Its double delayed premixing combined with the high-intensity short flame characteristics is particularly suitable for achieving ultra-low NOx emissions under stable combustion in situations where the excess air coefficient is allowed to be higher (1.1~1.6).

Description

Technical Field

[0001] The present invention relates to the technical field of industrial burners, in particular to a submerged combustion technology and a burner, specifically to a double-delayed premixed short flame low-nitrogen submerged burner. Background Art

[0002] Submerged combustion is a new and efficient combustion heating technology. The high-temperature flue gas generated after complete combustion in the combustion chamber is sprayed into the liquid to directly heat the liquid. The use of submerged combustion technology can effectively improve energy utilization and reduce environmental pollution. Submerged combustion can be applied to heating systems, sewage treatment, mining, LNG (liquefied natural gas) gasification, etc. Among them, the submerged combustion vaporizer (SCV) is a necessary gasification device for winter peak load regulation at various LNG receiving stations. SCV is not affected by seawater and atmospheric temperature. It has the advantages of rapid start-up and load adjustment, reliable operation, and is not affected by factors such as temperature. It can be quickly ignited and started, and can be quickly adjusted within a large load range. It is suitable for emergency peak load regulation and winter supply guarantee use. It has extremely high requirements for the combustion stability, safety and pollutant emissions of the SCV submerged burner under full load. At present, areas with higher environmental protection requirements in China have set the NOx emission limit at 50mg / m 3 Even lower development puts forward new technical requirements for the high-intensity short flame of submerged burners while achieving ultra-low NOx emissions.

[0003] Under the technical background of high thermal intensity and heat density of submerged burners and high requirements for combustion pollutant emissions, how to achieve high-intensity stable combustion while achieving low NOx and CO pollution emissions is the key technology of submerged burners. Existing conventional submerged burners use air staged diffusion combustion, which is difficult to meet the requirements of high combustion intensity and low pollutant emissions at the same time. Generally, the NOx emission limit is 80mg / m 3 Among the above, there is a lean premixed combustion method with high combustion intensity, but technical problems such as flame stability and thermoacoustic resonance limit the lower limits of NOx and CO and cannot meet the requirements. Auxiliary media nitrogen reduction methods such as water spraying and steam spraying can reduce NOx, but there are still practical difficulties such as limited nitrogen reduction capacity, combustion stability and efficiency, additional operating energy consumption and maintenance investment. The present invention aims to optimize the ultra-low NOx emission capability of high-intensity lean premixed submerged combustion through the technical solution of double delayed premixing, and flexibly adjust the premixing and flame shape of each burner through the online adjustable premixing degree of multiple burners, so as to achieve a high-power stable combustion state without thermal noise. Summary of the Invention

[0004] The purpose of the present invention is to design a double-delayed premixed short flame low-nitrogen submerged burner to address the problems of existing burners such as limited nitrogen reduction capacity, poor combustion stability and efficiency, and the need for additional operating energy consumption and maintenance investment.

[0005] The technical solution of the present invention is:

[0006] A double delayed premixed short flame low nitrogen submerged burner is characterized in that it includes a delayed premixed burner with double air distribution and a central secondary air structure. The premixed combustible gas at the burner outlet of the delayed premixed burner presents a non-uniform concentration distribution with the center being rich and the periphery being lean under the action of the central secondary air; the center being rich means that there is more fuel gas and the local equivalence ratio is closer to 1, and the periphery being lean means that there is less fuel gas and the local equivalence ratio is further away from 1.

[0007] The present invention also includes a multi-burner combination structure, which adjusts the uniformity of the radial mixing of gas and air at the burner outlet and the flame shape of each sub-burner flame, thereby improving combustion stability and reducing the possibility of thermal acoustic resonance. At the same time, through the delayed premixing of the central secondary air and the primary mixed gas, the equivalence ratio at the bottom of the flame is improved, so that it deviates from the high-temperature zone where high NOx is produced, thereby suppressing NOx; the central air can be adjusted on-site when it is with a valve, and when it is not with a valve, the central air volume requirement is determined according to the central equivalence ratio of each sub-burner during design, so that the opening air volume of the central air is designed.

[0008] Each burner has a convenient function of adjusting the premixing degree, and the adjustment does not require the burner to be disassembled. When multiple burners are combined, the premixing and flame shape of each burner can be flexibly adjusted online.

[0009] The burner of the present invention includes two structural forms: a single-burner burner and a multi-burner burner. The multi-burner burner is a combination form of a single-burner burner. The single-burner burner includes a combustion air supply fan 16, a main air valve 17, and a central secondary air valve 18. The main air valve 17 is used to provide main air to the outer air duct 6, and the central secondary air valve 18 is used to provide central secondary air to the central air duct 13; the combustion air supply fan 16 is connected to the burner main air flange 5 through the main air valve 17 and sends the main air into the burner housing 4, and passes through the air rectification ring 7 and the air distribution plate 8 in the internal space of the burner top plate 21 to enter the interlayer channel between the central air duct 13 and the outer air duct 6. The main air flows through the tapered necking section 3 and then enters the main burner 2. All or part of the main burner 2 is water-cooled through the water jacket 1; the fixing rod 11 has a restraining and fixing effect on the outer air duct 6; the central secondary air enters the inlet 10 of the central air duct 13 after the flow rate is adjusted by the central secondary air valve 18, and flows through the central air duct 1 3. After the central wind cone 14, it flows out from the central air outlet 15 to the main burner 2; after flowing out of the central air outlet 15, the central secondary air begins to be secondary mixed with the fuel-air mixture in the tapered necking section 3 and the main burner 2, and flows out of the burner 2 while mixing; the fuel gas enters the movable fuel gas distributor 9 from the fuel gas inlet pipe 19 through the regulating valve 20, and the distributor 9 passes through the burner top plate 21 and extends into the interlayer channel between the central wind tube 13 and the outer wind tube 6. The fuel gas is ejected from the bottom circumferential nozzle 23 of the distributor 9, contacts and mixes with the main air flowing through this interlayer channel, and flows and ejects toward the main burner 2 while mixing. During this period, it will contact with the central secondary air in the tapered necking section 3 for secondary mixing; the bottom annular channel structure of the fuel gas distributor 9 is sleeved on the outside of the central wind tube 13, and maintains an appropriate annular gap so that the fuel gas distributor 9 can move up and down along the length direction of the central wind tube 13, and is fixed by the locking mechanism 22 after adjusting to the required height position. By adjusting the upper and lower positions of the distributor 9, the relative position of the fuel gas nozzle 23 in the main air interlayer channel can be changed. The closer the nozzle 23 is to the outlet of the main burner 2, the shorter the mixing distance of the fuel gas and the main air, and the more uneven the mixing, thereby achieving different degrees of delayed premixing. Under normal circumstances, it is only necessary to adjust the degree of delayed premixing during the initial installation and combustion commissioning of the burner. When the ignition reliability, combustion stability, combustion noise, and combustion pollutants are all up to standard, the fuel gas distributor 9 can be fixed and its position can be moved without special need. The NOx emission value can reach 30-50mg / m 3 The multi-burner burner is composed of a central burner and a plurality of single-burner burners surrounding the central burner. The center of the central burner is provided with a central diffusion burner 25 which plays a role in enhancing ignition reliability and stabilizing the flame. The central burner and the single-burner burner share the gas source and the wind source.

[0010] When the central secondary air volume does not need to be adjusted through the central secondary air valve 18, the air inlet 24 should be opened directly on the central air duct 13, so that the central secondary air and the main air are both distributed by the air entering from the main air flange 5.

[0011] The combination of multi-stage air volume adjustment and multi-burner combustion adjustment can make the burner noise less than 75 decibels, and the burner vibration value is less than 2mm / s.

[0012] The beneficial effects of the present invention are:

[0013] This invention achieves high-intensity, short-flame, low-NOx combustion. Power is flexibly configured through burner combinations, and the combustion state is easily adjustable online, achieving the desired stable combustion and pollutant emission targets. Its dual-delayed premixing combined with high-intensity, short-flame characteristics is particularly suitable for achieving ultra-low NOx emissions under stable combustion in applications where a high excess air coefficient (1.1-1.6) is permitted, such as in submerged combustion heaters.

[0014] The present invention adopts a delayed premixed combustion mode of single or multiple burners, that is, the air and fuel gas are not fully premixed before combustion at the burner, and the burner outlet presents a distribution of rich fuel gas in the center and thin fuel gas in the periphery.

[0015] Each burner of the present invention has the function of conveniently adjusting the degree of premixing, and the adjustment does not require disassembly of the burner. When multiple burners are combined, the premixing and flame shape of each burner can be flexibly adjusted online to achieve the required overall low-noise stable combustion and low pollutant emission effects (for natural gas as the fuel gas, the pollutants are mainly controlled CO and NOx).

[0016] Each delayed premixed burner of the present invention is equipped with central secondary air on the basis of the inner-rich and outer-lean distribution of fuel gas, thereby realizing double delayed premixed low-nitrogen combustion.

[0017] When the present invention is a multi-burner combination, a central diffusion flame burner can be provided to ensure ignition stability and success rate.

[0018] This invention uses a cooling water jacket to cool the main and center burner tips, ensuring combustion safety. This burner outlet concentration distribution, combined with the burner water cooling design (or other effective cooling methods), helps prevent backfire. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural diagram of a single-burner submerged burner of the present invention.

[0020] Figure 2 yes Figure 1 AA section enlarged view.

[0021] Figure 3 It is a structural diagram of the multi-burner submerged burner of the present invention.

[0022] Figure 4 It is a structural diagram of a single-burner submerged burner with fixed central air distribution according to the present invention.

[0023] Figure 5 This is a schematic diagram of the principle of the double-delayed premixed short flame low-nitrogen submerged combustion of the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further described below with reference to the accompanying drawings and examples.

[0025] Example 1.

[0026] like Figure 1-2 shown.

[0027] A double delayed premixed short flame low nitrogen submerged burner, which includes a double air distribution delayed premixed burner and a central secondary air structure design. The premixed combustible gas at the outlet of a single burner presents a non-uniform concentration distribution with a center rich and a periphery light. Figure 5 As shown; thick in the center means more fuel gas, and the local equivalence ratio is closer to 1, and thin in the periphery means less fuel gas, and the local equivalence ratio is further away from 1. By adjusting the uniformity of the radial mixing of gas and air at the burner outlet, the flame shape of the burner flame is adjusted, thereby improving combustion stability and reducing the possibility of thermoacoustic resonance. At the same time, through the delayed premixing of the central secondary air and the primary mixed gas, the equivalence ratio at the bottom of the flame is improved, deviating from the high-temperature area where high NOx is produced, thereby suppressing NOx; the central air can be adjusted on site when it is equipped with a valve. The burner has the function of conveniently adjusting the degree of premixing, and the adjustment does not require disassembling the burner. As shown Figure 1As shown, each single-burner burner includes a combustion air supply fan 16, a main air valve 17, and a central secondary air valve 18. The main air valve 17 is used to provide main air to the outer air duct 6, and the central secondary air valve 18 is used to provide central secondary air to the central air duct 13; the combustion air supply fan 16 is connected to the burner main air flange 5 through the main air valve 17 and sends the main air into the burner housing 4, and passes through the internal space of the burner top plate 21 through the air straightening ring 7 and the air distribution plate 8 into the interlayer channel between the central air duct 13 and the outer air duct 6. The main air flows through the tapered necking section 3 and enters the main burner 2. All or part of the main burner 2 is water-cooled through the water jacket 1; the fixing rod 11 is used to open the outer air duct 6 Constraint and fixation function; the central secondary air enters the inlet 10 of the central air duct 13 after the flow rate is adjusted by the central secondary air valve 18, and flows through the central air duct 13 and the central air cone 14 and then flows out from the central air outlet 15 to the main burner 2; after flowing out of the central air outlet 15, the central secondary air begins to mix with the fuel-air mixture in the tapered necking section 3 and the main burner 2 for a second time, and flows out of the burner 2 while mixing; the fuel gas enters the movable fuel gas distributor 9 through the fuel gas inlet pipe 19 through the regulating valve 20, and the distributor 9 passes through the burner top plate 21 and extends into the interlayer channel between the central air duct 13 and the outer air duct 6. The fuel gas is discharged from the circumferential spray holes 23 (such as Figure 2 The fuel gas is ejected from the fuel gas distributor 9 (as shown), where it comes into contact with and mixes with the primary air flowing through this interlayer channel, flowing toward the main burner 2 while mixing. During this period, it comes into contact with the central secondary air in the tapered necking section 3 for secondary mixing. The bottom annular channel structure of the fuel gas distributor 9 is sheathed outside the central air tube 13, maintaining an appropriate annular aperture to facilitate the upward and downward movement of the fuel gas distributor 9 along the length of the central air tube 13. After being adjusted to the desired height, it is secured by the locking mechanism 22. By adjusting the vertical position of the distributor 9, the relative position of the fuel gas nozzle 23 in the primary air interlayer channel can be changed. The closer the nozzle 23 is to the outlet of the main burner 2, the shorter the mixing distance between the fuel gas and the primary air, and the more uneven the mixing, thereby achieving different degrees of delayed premixing. Under normal circumstances, the degree of delayed premixing only needs to be adjusted during the initial installation and combustion commissioning of the burner. When the ignition reliability, combustion stability, combustion noise, and combustion pollutants meet the standards, the fuel gas distributor 9 can be fixed and its position can be moved without special need. The NOx emission value can reach 30-50mg / m 3 ;

[0028] The principles of the present invention to achieve combustion stability and low pollutant emissions are:

[0029] 1) Combustion stability: Figure 5As shown, the overall excess air coefficient of the burner is relatively high, about 1.1 - 1.6, and it is a lean premixed combustion mode, presenting the high-intensity short flame combustion characteristics of premixed combustion as a whole. The fuel gas-air mixture at the outlet of each burner shows a non-uniform concentration distribution with a thick center (more fuel gas, and the local equivalence ratio is closer to 1) and a thin periphery (less fuel gas, and the local equivalence ratio deviates more from 1). The excess air coefficient a1 < a2, and during the flame combustion process, further mixing occurs while burning, that is, in the form of delayed premixing. When setting a single-burner burner, the contact and mixing position of fuel gas and air can be conveniently and flexibly adjusted to achieve different degrees of premixing (concentration distribution), so as to obtain the required combustion stability and pollutant emission values. When setting multiple burners in combination, the contact and mixing position of fuel gas and air for each burner can be conveniently and flexibly adjusted, such as making each burner produce different flame forms, thereby improving the overall flame stability of the burner and reducing combustion thermal noise.

[0030] 2) Low pollutant emissions: As Figure 5 shown, the mixture with a relatively high concentration in the center has a higher combustion temperature at the flame root because it is closer to the equivalence ratio, forming a high NOx generation area. Based on lean burn and delayed premixing, the present invention designs a central secondary air to locally reduce nitrogen in the area with a relatively thick central fuel gas. The outlet of the central secondary air is close to the outlet of the burner, mainly for secondary delayed mixing with the relatively high concentration area in the center within the flame front envelope. In this way, the equivalence ratio of the mixture at the bottom flame deviates more from 1, the combustion temperature is reduced, and the formation of a local high NOx area is inhibited. When the central secondary air is equipped with a valve, it can be adjusted on-site. When there is no valve, the central air volume requirement is determined according to the central equivalence ratio of each sub-burner during design, so as to design the air volume at the opening of the central air well.

[0031] Embodiment 2.

[0032] As Figure 4 shown.

[0033] The difference between this embodiment and Embodiment 1 is that the central secondary air volume does not need to be adjusted through the central secondary air valve 18, but air intake holes 24 are directly opened on the central air cylinder 13, so that both the central secondary air and the main air are supplied with air entering through the main air flange 5. The rest is the same as Embodiment 1.

[0034] Embodiment 3.

[0035] As Figure 3 shown.

[0036] A dual-delayed premixed short flame low-nitrogen submerged burner, which includes a delayed premixed burner with dual air distribution and a central secondary air design. The premixed combustible gas at the outlet of a single burner shows a non-uniform concentration distribution with a thick center and a thin periphery; the thick center means more fuel gas and the local equivalence ratio is closer to 1, and the thin periphery means less fuel gas and the local equivalence ratio deviates more from 1. This embodiment adopts a multi-burner combined structure. As Figure 3 As shown, by adjusting the uniformity of radial mixing of gas and air at the burner outlet, the flame shape of each sub-burner flame is adjusted, thereby improving combustion stability and reducing the possibility of thermoacoustic resonance. At the same time, by delaying the premixing of the central secondary air and the primary mixed gas, the equivalence ratio at the bottom of the flame is improved, so that it deviates from the high-temperature area where high NOx is produced, thereby suppressing NOx. The central air can be adjusted on-site when it is with a valve. When it is not with a valve, the central air volume requirement is determined according to the central equivalence ratio of each sub-burner during design, so as to design the opening air volume of the central air. Each burner has the function of conveniently adjusting the degree of premixing, and the adjustment does not require the removal of the burner. When multiple burners are combined, the premixing and flame shape of each burner can be flexibly adjusted online. As shown Figure 3 As shown, this embodiment combines the single-burner design of Example 1. The multi-burner burner comprises a central burner surrounded by multiple single-burner burners. A central diffusion burner 25 is located at the center of the central burner, enhancing ignition reliability and stabilizing the flame. The central burner and the single-burner burners share a common air and wind source. The single-burner burner structure is similar to that shown in Example 1. The combination of multi-stage air volume control and multi-burner combustion control reduces burner noise to less than 75 decibels and reduces burner vibration to less than 2 mm / s.

[0037] The parts not involved in the present invention are the same as the existing technology or can be implemented by using the existing technology.

Claims

1. A double delayed premixed short flame low nitrogen submerged burner, characterized by It includes a delayed premix burner with double air distribution and a central secondary air structure. The premixed combustible gas at the burner outlet of the delayed premix burner presents a non-uniform concentration distribution with the center being thick and the periphery being thin under the action of the central secondary air. The center being thick means that the fuel gas is more and the local equivalent ratio is closer to 1, and the periphery being thin means that the fuel gas is less and the local equivalent ratio is further away from 1. The double delayed premixed short flame low nitrogen submerged burner includes a single burner burner and a multi-burner burner. The single burner burner includes a combustion air supply fan (16), a main air valve (17), and a central secondary air valve (18). The main air valve (17) is used to provide main air to the outer air duct (6), and the central secondary air valve (18) is used to provide central secondary air to the central air duct (13). The combustion air supply fan (16) is passed through The main air is connected to the main air flange (5) of the burner through the main air valve (17) and sent into the burner shell (4), and then enters the interlayer channel between the central air tube (13) and the outer air tube (6) through the air rectifying ring (7) and the air distribution plate (8) in the internal space of the burner top plate (21). The main air flows through the tapered necking section (3) and enters the main burner (2). All or part of the main burner (2) is water-cooled through the water jacket (1); the fixing rod (11) plays a restraining and fixing role on the outer air tube (6); the central secondary air enters the inlet (10) of the central air tube (13) after the flow rate is adjusted by the central secondary air valve (18), and flows through the central air tube (13) and the central air cone (14) and then flows out from the central air outlet (15) to the main burner (2); the central secondary air is regulated by the central secondary air valve (18) and enters the inlet (10) of the central air tube (13), and flows through the central air tube (13) and the central air cone (14) and then flows out to the main burner (2); the central secondary air is regulated by the central secondary air valve (18) and enters the inlet (10) of the central air tube (13), and flows through the central air tube (13) and the central air cone (14). After flowing out of the central air outlet (15), the secondary air begins to mix with the fuel-air mixture in the tapered necking section (3) and the main burner (2) for a second time, and flows out of the main burner (2) while mixing; the fuel gas enters the movable fuel gas distributor (9) from the fuel gas inlet pipe (19) through the regulating valve (20), and the distributor (9) passes through the burner top plate (21) and extends into the sandwich channel between the central air tube (13) and the outer air tube (6), and the fuel gas is ejected from the bottom circumferential nozzle hole (23) of the distributor (9), contacts and mixes with the main air flowing through this sandwich channel, and flows toward the main burner (2) while mixing. During this period, it contacts and mixes with the central secondary air in the tapered necking section (3); the bottom annular channel structure of the fuel gas distributor (9) is sleeved The center air duct (13) is provided with an outer end and an appropriate annular aperture so that the fuel gas distributor (9) can move up and down along the length direction of the center air duct (13) and be fixed by the locking mechanism (22) after being adjusted to the desired height position; the relative position of the fuel gas nozzle (23) in the main air interlayer channel can be changed by adjusting the upper and lower positions of the distributor (9); the closer the nozzle (23) is to the outlet of the main burner (2), the shorter the mixing stroke of the fuel gas and the main air, and the more uneven the mixing, thereby achieving different degrees of delayed premixing; the multi-burner burner is composed of a center burner and a plurality of single-burner burners surrounding the center burner, and the center of the center burner is provided with a center diffusion burner (25) which plays a role in enhancing ignition reliability and stabilizing flame;The central burner and the single-burner burner share the same gas and air sources.

2. The double delayed premixed short flame low nitrogen submerged burner according to claim 1 is characterized in that It includes a multi-burner combination type, which adjusts the uniformity of the mixing of gas and air in the radial direction of the burner outlet and adjusts the flame shape of each sub-burner flame; When the center air is equipped with a valve, it can be adjusted on site. When it is not equipped with a valve, the center air volume requirement is determined according to the center equivalent ratio of each sub-burner during design, so as to design the opening air volume of the center air.

3. The double delayed premixed short flame low nitrogen submerged burner according to claim 1 is characterized in that Each burner has a convenient function of adjusting the premixing degree, and the adjustment does not require the burner to be disassembled. When multiple burners are combined, the premixing and flame shape of each burner can be flexibly adjusted online.

4. The double delayed premixed short flame low nitrogen submerged burner according to claim 1 is characterized in that When the center secondary air volume does not need to be adjusted through the center secondary air valve (18), the air inlet hole (24) should be directly opened on the center air duct (13), so that the center secondary air and the main air are both distributed by the air entering through the main air flange (5).

5. The double delayed premixed short flame low nitrogen submerged burner according to claim 1 is characterized in that The combination of multi-stage air volume adjustment and multi-burner combustion adjustment can make the burner noise less than 75 decibels, and the burner vibration value is less than 2mm / s.

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