A flue gas internal circulation low nitrogen burner

Abstract

The present invention discloses a flue gas internal circulation low nitrogen burner, comprising: a wind tube, a first fuel supply pipe, a second fuel supply pipe, an external ejector pipe, a fan and a flame stabilizing disk; the first fuel supply pipe is arranged inside the wind tube, and a plurality of internal branches are arranged at the front end for supplying fuel to the central flame; the second fuel supply pipe is arranged outside the wind tube for spraying fuel to form a split flame; a mixing cylinder is sleeved on the outside of the front end of the wind tube, and the channel between the mixing cylinder and the wind tube constitutes the first flue gas return port; the external ejector pipe is arranged in front of the nozzle and located inside the mixing cylinder, and its inlet constitutes the second flue gas return port; the first flue gas return port is located in front of the second flue gas return port, and the outlet of the external ejector pipe is located in front of the internal branch pipe. The present invention comprehensively utilizes the central flame stabilizing technology and the FIR technology to realize the low nitrogen combustion of flue gas internal circulation, which can effectively reduce the emission of nitrogen oxides and improve the thermal efficiency, safety and stability of combustion.

Description

Technical Field

[0001] The present invention relates to the technical field of gas burners, and particularly relates to a low-nitrogen burner with internal flue gas recirculation. Background Art

[0002] As national environmental protection policies become increasingly strict, the requirements for nitrogen oxide emissions from boilers are also getting higher and higher. Most of the low-nitrogen burners on the market currently adopt nitrogen reduction means including FGR (Flue Gas Recirculation) technology, premixed combustion technology, etc., which have inevitable disadvantages while achieving the nitrogen reduction effect. For example, burners using FGR technology are prone to problems such as flue gas condensate corrosion and surging; burners using premixed combustion technology are prone to problems such as low thermal efficiency caused by high oxygen content in the flue gas and the risk of flashback. Summary of the Invention

[0003] The purpose of the present invention is to overcome the defects existing in the above-mentioned prior art and provide a low-nitrogen burner with internal flue gas recirculation that has high thermal efficiency, high safety, and stable combustion.

[0004] To achieve the above-mentioned invention purpose, the technical solution adopted by the present invention is as follows.

[0005] A low-nitrogen burner with internal flue gas recirculation includes: a wind barrel, a first fuel supply pipe, a second fuel supply pipe, an external ejector pipe, a fan, and a flame stabilizer disc; the wind barrel is inserted into the installation hole of the heating device, and the front end of the wind barrel is exposed to the combustion chamber of the heating device for guiding the combustion-supporting air to the combustion chamber, and the rear end of the wind barrel is connected to the fan; the first fuel supply pipe is arranged inside the wind barrel, and a plurality of inner branch pipes are provided at the front end, and spray holes are provided at the ends of the inner branch pipes for supplying fuel to the central flame; the second fuel supply pipe is arranged outside the wind barrel, and a plurality of outer branch pipes are provided at the front end, and nozzles are provided at the ends of the outer branch pipes, and the nozzles are used for spraying fuel towards the combustion chamber to form a divided flame; a flame stabilizer disc is arranged inside the front end of the wind barrel, and the channel between the wind barrel and the voltage stabilizing disc is the central flame air distribution channel, and this central flame air distribution channel is used for supplying combustion-supporting air to the central flame; a mixing barrel is sleeved outside the front end of the wind barrel, and the channel between the mixing barrel and the wind barrel constitutes the first flue gas return port; the external ejector pipe is arranged in front of the nozzle and inside the mixing barrel, and the inlet of the external ejector pipe near the nozzle end constitutes the second flue gas return port; the first flue gas return port is in front of the second flue gas return port; the outlet of the external ejector pipe is in front of the inner branch pipe; on the barrel wall of the wind barrel, a plurality of air distribution openings are circumferentially provided behind the flame stabilizer disc, and the air distribution openings are used for supplying a part of the combustion-supporting air to the divided flame.

[0006] Further, a partition is provided outside the front end of the air duct, and the partition is located between the first flue gas return port and the second flue gas return port.

[0007] Further, the external ejector tube is a straight tube or a Laval tube.

[0008] Further, the second flue gas return port has a gradually narrowing inlet.

[0009] Further, the first fuel supply pipe includes a gas main pipe arranged coaxially with the air duct. A plurality of the inner branch pipes communicate with the downstream of the gas main pipe. A central nozzle is provided at the end of the gas main pipe. The jet direction of the spray holes at the ends of the inner branch pipes faces the inner wall of the mixing cylinder.

[0010] Further, the flame stabilizing disc is sleeved outside the central nozzle, and a plurality of the inner branch pipes are arranged around the outside of the flame stabilizing disc.

[0011] Further, the second fuel supply pipe includes a supply main pipe and a gas collecting bag connected to the supply main pipe. A plurality of the outer branch pipes are connected to the gas collecting bag and arranged outside the front end of the air duct.

[0012] Further, one external ejector tube is provided in front of each outer branch pipe, and the external ejector tube and the outer branch pipe are on the same straight line.

[0013] Further, the volume ratio of the combustion-supporting air passing through the central flame air distribution channel to all the combustion-supporting air is 80% - 95%, and the volume ratio of the gas ejected from the nozzle of the second fuel supply pipe to the total gas volume is 80% - 95%.

[0014] It can be seen from the above technical solutions that the embodiments of the present invention have the following advantages:

[0015] 1. By providing the first fuel supply pipe and cooperating with the flame stabilizing disc, a stable central flame is formed. Using the central flame stabilizing technology, the stability of combustion is ensured, and the safety of combustion is improved;

[0016] 2. By providing the second fuel supply pipe and cooperating with a plurality of external ejector tubes, a divided flame is formed. Using the divided flame technology, the flame temperature is reduced, which helps to reduce the emission of nitrogen oxides;

[0017] 3. Both the central flame and the divided flame are combustions deviating from the stoichiometric ratio, with low combustion temperature, high thermal efficiency, and less nitrogen oxide generation;

[0018] 4. By comprehensively using the flue gas internal circulation (FIR) technology, through the setting of the first flue gas return port and the second flue gas return port, the central main flame and the divided flame both have flue gas participating in combustion, which can effectively reduce the emission of nitrogen oxides. Description of the Drawings

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments and the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0020] Figure 1 is a cross-sectional view of a flue gas internal circulation low-nitrogen burner in an embodiment of the present invention;

[0021] Figure 2 is a perspective view of a flue gas internal circulation low-nitrogen burner in an embodiment of the present invention;

[0022] Figure 3 is a flow field schematic diagram of a flue gas internal circulation low-nitrogen burner in an embodiment of the present invention. Detailed implementation manners

[0023] In order to enable those skilled in the art to better understand the solutions of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0024] The terms "first", "second", "third", etc. in the specification, claims and drawings of the present invention are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally further include steps or units not listed, or may optionally further include other steps or units inherent to these processes, methods, products or devices.

[0025] The following will be described in detail through specific embodiments respectively.

[0026] Please refer to Figures 1 to 3 , an embodiment of the present invention provides a flue gas internal circulation low-nitrogen burner, which is composed of components such as a wind cylinder 110, a first fuel supply pipe 120, a second fuel supply pipe 130, an external injection pipe 140, a fan 150, and a flame stabilizing disk 160.

[0027] Among them, the air duct 110 is inserted into the heating device, such as the installation hole of the heating furnace body, and can be installed and fixed through the installation plate. The front end of the air duct 110 is exposed to the combustion chamber inside the heating device, and is used to direct the combustion-supporting air, such as air, to the combustion chamber. The rear end of the air duct 110 is located outside the heating device and is connected to the fan 150. A mixing cylinder 112 is sleeved outside the front end of the air duct 110.

[0028] The first fuel supply pipe 120 is arranged inside the air duct 110 and is used to supply fuel to the central flame. The first fuel supply pipe 120 may include a gas main pipe arranged coaxially with the air duct 110 and a plurality of inner branch pipes 121 provided at the front end thereof. A plurality of, for example, 6 inner branch pipes 121 may communicate downstream of the gas main pipe and are circumferentially distributed. A central nozzle 122 is provided at the end of the gas main pipe. Spray holes are opened at the ends of the gas branch pipes 121, and the spraying directions of the spray holes face the inner wall of the mixing cylinder 112.

[0029] The second fuel supply pipe 130 is arranged outside the air duct 110 and includes a supply main pipe and a gas collecting bag 131 connected to the supply main pipe. A plurality of inner branch pipes 133 are branched from the front end of the gas collecting bag 131. The plurality of inner branch pipes 133 are arranged around the outside of the front end of the air duct 110. Nozzles 132 are provided at the ends of the inner branch pipes 133, and the nozzles 132 spray gas towards the combustion chamber direction to form a divided flame.

[0030] The burner of the present invention adopts a central flame stabilization technology and is provided with a flame stabilization disk 160. The flame stabilization disk is arranged inside the front end of the air duct 110 and is sleeved outside the central nozzle 122. The plurality of inner branch pipes 121 may be arranged around the outside of the flame stabilization disk 160. An annular channel is formed between the air duct 110 and the flame stabilization disk 160 as the central flame air distribution channel 111, which is used to supply combustion-supporting air to the central flame.

[0031] The present invention adopts the FIR technology and is provided with two flue gas return ports. The channel between the air duct 110 and the mixing cylinder 112 sleeved outside its front end constitutes the first flue gas return port 114. An external ejector pipe 140 is arranged in front of each nozzle 132, and the external ejector pipe 140 and the outer branch pipe 133 may be located on the same straight line. The external ejector pipe 140 is located inside the mixing cylinder 112, and the inlet of the external ejector pipe 140 near the nozzle 132 end constitutes the second flue gas return port 142. Among them, in order to better realize the internal circulation of flue gas, the first flue gas return port 114 is located in front of the second flue gas return port 142, that is, the first flue gas return port 114 is deeper into the combustion chamber than the second flue gas return port 142; and the outlet of the external ejector pipe 140 is located in front of the inner branch pipe 12), that is, the outlet of the external ejector pipe 140 is deeper into the combustion chamber than the end spray holes of the inner branch pipe 121.

[0032] Further, a plurality of air distribution ports 113 may be circumferentially formed on the barrel wall of the air duct 110 behind the flame stabilizing disc 160. A part of the combustion-supporting air can flow out from the air distribution ports 113. The function of the air distribution ports 113 is to supply a part of the combustion-supporting air for the divided flame.

[0033] Further, a partition 141 may be provided between the first flue gas return port 114 and the second flue gas return port 142 on the outside of the front end of the air duct 110.

[0034] Further, the external ejector tube 140 may adopt a straight tube, or may also adopt a Laffal tube shape. At this time, the inlet of the first flue gas return port 114 is a gradually reducing inlet with a gradually reducing diameter.

[0035] Next, the flow field and NOx reduction principle of the burner of the present invention will be described.

[0036] The blower supplies combustion-supporting air into the air duct. Since there is a flame stabilizing disc downstream, most of the combustion-supporting air (80% - 95% by volume) flows through the central flame air distribution channel between the flame stabilizing disc and the air duct. Due to the reduction of the flow area, the flow velocity of the combustion-supporting air increases and the static pressure decreases, which will draw the flue gas in the combustion chamber into the mixing cylinder through the first flue gas return port. After the flue gas is mixed with the combustion-supporting air, it burns with the fuel (5% - 15% by volume) ejected from the inner branch pipe and the central nozzle at the end of the first fuel supply pipe to form a central flame (i.e., the main flame).

[0037] Due to the blockage of the flame stabilizing disc, the static pressure of the combustion-supporting air upstream of it increases, and a small part of the combustion-supporting air (5% - 20% by volume) flows out from the air distribution ports on the barrel wall of the air duct to provide combustion-supporting air for the divided flame.

[0038] High-pressure gas (80% - 95% by volume of the total fuel) is ejected from the nozzle of the second fuel supply pipe gas path. At the same time, it sucks the air flowing out from the air distribution ports of the air duct and the flue gas in the combustion chamber to follow through the second flue gas return port and enter the external ejector tube to participate in combustion to form a divided flame.

[0039] Among them, the central flame has more air and less gas, which is oxygen-rich combustion; the divided flame has less air and more gas, which is oxygen-deficient combustion; both the central flame and the divided flame are combustion deviating from the stoichiometric ratio, with a low combustion temperature and less nitrogen oxide generation. Moreover, both the central main flame and the divided flame have flue gas participating in combustion, forming a reducing atmosphere to further reduce the generation of nitrogen oxides.

[0040] Since the outlet of the ejector tube is in front of the inner branch pipe and the outlet faces the combustion chamber, the divided flame is in front of the central flame in the axial direction of the air duct of the divided flame, which helps to reduce the combustion intensity of the flame and is also beneficial to reducing the generation of nitrogen oxides.

[0041] In addition, the fuel gas ejected from the central nozzle of the first fuel supply pipe is mixed with the combustion-supporting air and rotates and burns close to the flame stabilizing disc to form a flame stabilizing zone.

[0042] As can be seen from the above technical solutions, the embodiments of the present invention have the following advantages:

[0043] 1. By providing the first fuel supply pipe and cooperating with the flame stabilizing disc, a stable central flame is formed. Using the central flame stabilizing technology, the stability of combustion is ensured and the safety of combustion is improved.

[0044] 2. By providing the second fuel supply pipe and cooperating with a plurality of external ejector pipes, a divided flame is formed. Using the divided flame technology, the flame temperature is reduced, which helps to reduce the emission of nitrogen oxides.

[0045] 3. Both the central flame and the divided flame are combustions deviating from the stoichiometric ratio, with a low combustion temperature, high thermal efficiency, and less nitrogen oxide generation.

[0046] 4. By comprehensively using the flue gas internal circulation (FIR) technology, by providing the first flue gas return port and the second flue gas return port, the central main flame and the divided flame both have flue gas participating in combustion, which can effectively reduce the emission of nitrogen oxides.

[0047] In the above embodiments, the descriptions of the respective embodiments have their own focuses. For the parts not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0048] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the above embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A flue gas internal circulation low nitrogen burner, characterized in that: It comprises: a wind tube (110), a first fuel supply pipe (120), a second fuel supply pipe (130), an external ejection pipe (140), a fan (150) and a flame stabilizing plate (160); The wind tube (110) is inserted into a mounting hole of the heating device, the front end of the wind tube (110) is exposed to the combustion chamber of the heating device and is used to guide the combustion-supporting air to the combustion chamber, and the rear end of the wind tube (110) is located outside the heating device and is connected to the fan (150); The first fuel supply pipe (120) is arranged inside the wind tube (110), and a plurality of inner branch pipes (121) are provided at the front end. The ends of the inner branch pipes (121) are provided with spray holes for supplying fuel to the central flame. The second fuel supply pipe (130) is arranged outside the wind tube (110), and a plurality of external branch pipes (133) are provided at the front end. A nozzle (132) is provided at the end of the external branch pipe (133). The nozzle (132) is used to spray fuel toward the combustion chamber to form a divided flame. A flame stabilizing disk (160) is disposed inside the front end of the wind tube (110); a passage between the wind tube (110) and the flame stabilizing disk (160) is a central flame air distribution passage (111); the central flame air distribution passage (111) is used to supply combustion-supporting air to the central flame; A mixing cylinder (112) is sleeved on the front end of the wind cylinder (110), and a channel between the mixing cylinder (112) and the wind cylinder (110) constitutes a first smoke return port (114); the external ejector tube (140) is arranged in front of the nozzle (132) and located inside the mixing cylinder (112), and an inlet of the external ejector tube (140) close to the nozzle (132) constitutes a second smoke return port (142); The first smoke return port (114) is located in front of the second smoke return port (142); the outlet of the external ejector pipe (140) is located in front of the internal branch pipe (121); and a plurality of air distribution ports (113) are circumferentially opened on the wall of the wind tube (110) and are located behind the flame stabilizing disk (160), and the air distribution ports (113) are used to supply a portion of combustion-supporting air for the split flame.

2. The flue gas internal circulation low nitrogen burner according to claim 1 is characterized in that: A partition plate (141) is provided outside the front end of the air cylinder (110), and the partition plate (141) is located between the first smoke return port (114) and the second smoke return port (142).

3. The flue gas internal circulation low nitrogen burner according to claim 1 is characterized in that: The external ejector tube (140) is a straight tube or a Rafael tube.

4. The flue gas internal circulation low nitrogen burner according to claim 1 is characterized in that: The second smoke return port (142) has an inlet with a gradually decreasing diameter.

5. The flue gas internal circulation low nitrogen burner according to claim 1 is characterized in that: The first fuel supply pipe (120) comprises a gas main pipe coaxially arranged with the wind tube (110); a plurality of inner branch pipes (121) are connected to the downstream of the gas main pipe; a central nozzle (122) is provided at the end of the gas main pipe; and a spray direction of a spray hole at the end of the inner branch pipe (121) is directed toward the inner wall of the mixing tube (112).

6. The flue gas internal circulation low nitrogen burner according to claim 5 is characterized in that: The flame stabilizing disk (160) is sleeved outside the central nozzle (122), and the plurality of inner branch pipes (121) surround the outer side of the flame stabilizing disk (160).

7. The flue gas internal circulation low nitrogen burner according to claim 1 is characterized in that: The second fuel supply pipe (130) includes a supply main pipe and an air collecting bag (131) connected to the supply main pipe. The plurality of external branch pipes (133) are connected to the air collecting bag (131) and are arranged outside the front end of the wind tube (110).

8. The flue gas internal circulation low nitrogen burner according to claim 1 is characterized in that: An external ejection tube (140) is arranged in front of each external branch tube (133), and the external ejection tube (140) and the external branch tube (133) are located on the same straight line.

9. The flue gas internal circulation low nitrogen burner according to claim 1, characterized in that: The volume ratio of the combustion-supporting air passing through the central flame air distribution channel (111) to the total combustion-supporting air is 80% to 95%, and the volume ratio of the fuel gas sprayed through the nozzle of the second fuel supply pipe to the total amount of fuel gas is 80% to 95%.

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