A flue gas internal circulation ultra-low pollutant emission combustion device suitable for natural gas

Abstract

This invention discloses an ultra-low pollutant emission combustion device for natural gas internal flue gas circulation, relating to the field of burner technology, and solving the problem of excessive initial nitrogen oxide emissions from existing gas-fired boilers. The invention features a flue gas entrainment hole on the main flame gas nozzle; an air channel constriction at the end of the air channel; and a shift flame gas pipe extending into a gas mixing cylinder with several shift flame short pipes at the end. Gas is radially ejected from the shift flame short pipes and axially ejected from the shift flame gas pipes. Upon contact with the mixed combustion-supporting gas after passing through the swirl vanes, ignition occurs. The flame rotates along the sleeve and is ejected into the furnace, superimposing with the gas ejected from the main flame gas nozzle to stabilize combustion. This invention introduces flue gas into the furnace through the high-speed fluid ejection effect formed by the air channel constriction and the main flame ejector nozzle, increasing the inert gas concentration in the combustion zone. The flue gas absorbs heat and dilutes the oxygen concentration, reducing the combustion rate and temperature, and inhibiting NOx formation.

Description

Technical Field

[0001] This invention relates to the field of burner technology, specifically to a combustion device for ultra-low pollutant emissions through flue gas recirculation suitable for natural gas. Background Technology

[0002] Compared to coal, natural gas combustion produces lower emissions of sulfur dioxide and particulate matter, and its carbon dioxide emissions are significantly lower than those of coal and petroleum fuels. However, due to the high combustion temperature, nitrogen oxide emissions are a prominent issue during natural gas combustion. Nitrogen oxides are among the most significant atmospheric pollutants, contributing not only to photochemical smog but also being a major contributor to ozone layer depletion, posing serious threats to the ecological environment and human health. In recent years, major cities have intensified their efforts to control air pollution, particularly by strictly regulating nitrogen oxide emissions from boilers and other combustion gases. For example, the "Beijing Municipal Boiler Air Pollutant Emission Standard" has further tightened the emission standards for nitrogen oxides from industrial boilers. Since April 1, 2017, the emission standard for nitrogen oxides from newly built boilers must be below 30 mg / m³. 3 However, the concentration of sulfur dioxide in boilers must be below 80 mg / m³. 3 However, the initial nitrogen oxide emissions of the vast majority of currently used gas-fired boilers are generally between 150 and 200 mg / m³. 3 The levels of nitrogen oxides (NOx) in the initial emissions are severely exceeding standards. With the implementation of new boiler emission standards, low-NOx control has received significant attention from governments at all levels and the public. Therefore, there is a need to develop a gas burner device that can effectively control the initial NOx emissions. Summary of the Invention

[0003] To address the aforementioned problem of excessive initial nitrogen oxide emissions from existing gas-fired boilers, this invention proposes an ultra-low pollutant emission combustion device with internal flue gas recirculation suitable for natural gas. This invention utilizes a narrowed air passage and the high-speed fluid ejection effect created by the main flame ejector nozzle to introduce flue gas into the furnace through the main flue gas inlet, rear flue gas entrainment hole, and front flue gas entrainment hole. This increases the inert gas content in the combustion zone. Because the flue gas absorbs heat and dilutes the oxygen concentration, the combustion rate and temperature decrease, thereby suppressing NOx formation.

[0004] This invention proposes an ultra-low pollutant emission combustion device for natural gas flue gas internal circulation, specifically comprising a standby flame gas pipe, a burner wind box, a main gas passage, an air passage, a boiler refractory layer transition section, several main flame gas pipes, several main flame gas nozzles, a gas mixing cylinder, and a standby sleeve. The burner wind box and the air passage are connected. The main gas passage and the boiler refractory layer transition section are concentrically arranged on the outer ring of the air passage, and the main gas passage and the boiler refractory layer transition section are connected. After passing through the boiler refractory layer transition section, the air passage has an air passage constriction at its end. Several main flame gas pipes are arranged inside the boiler refractory layer transition section. One end of the main flame gas pipe is connected to the main gas passage, and the other end passes through the boiler refractory layer transition section and has a main flame ejector nozzle at its end. The main flame ejector nozzle is fitted with a main flame gas nozzle. Several flue gas entrainment holes are provided on the main flame gas nozzle. The gas mixing cylinder is fitted outside the standby flame gas pipe and inside the several main flame gas nozzles, and is located in front of the air passage constriction.

[0005] The duty flame gas pipe passes through the center of the burner air box and air passage and extends into the gas mixing cylinder; the duty sleeve is fitted onto the duty flame gas pipe; several duty flame short pipes are installed on the duty flame gas pipe, and several duty flame short pipes are installed inside the duty sleeve.

[0006] Furthermore, a radial injection port for the duty flame is provided on the side wall of the end of the duty flame short tube.

[0007] Furthermore, the plurality of flue gas entrainment holes include a plurality of rear flue gas entrainment holes and a plurality of front flue gas entrainment holes. The plurality of rear flue gas entrainment holes are disposed on the main flame gas nozzle pipe wall on the outer periphery of the main flame ejector nozzle, and the plurality of front flue gas entrainment holes are disposed on the main flame gas nozzle pipe wall in front of the main flame ejector nozzle.

[0008] Furthermore, the width of the rear smoke entrainment hole is greater than that of the front smoke entrainment hole, and the length of the rear smoke entrainment hole is less than that of the front smoke entrainment hole.

[0009] Furthermore, the gas mixing cylinder is provided with a main flue gas inlet at one end facing the narrowing of the air channel, and a flared end at the other end.

[0010] Furthermore, the constricted end of the air passage extends into the main flue gas intake port.

[0011] Furthermore, the end of the duty flame gas pipe is provided with swirl vanes.

[0012] Furthermore, the duty flame short tube passes through the swirl blades.

[0013] Furthermore, the swirl blades are provided with several axial injection ports for the standby flames.

[0014] Furthermore, a main flame support plate is provided at the end of the transition section of the boiler refractory layer, which supports the air passage and several main flame gas pipes.

[0015] The beneficial effects of the ultra-low pollutant emission combustion device with flue gas internal circulation suitable for natural gas described in this invention are as follows:

[0016] (1) The flue gas internal circulation ultra-low pollutant emission combustion device for natural gas described in this invention divides the gas into a duty flame and a main combustion flame by setting a duty flame gas pipe and a main flame gas delivery pipe, thereby completing fuel classification, avoiding flame concentration, and reducing local high temperature areas.

[0017] (2) The flue gas internal circulation ultra-low pollutant emission combustion device for natural gas described in this invention gathers the duty flame through the duty sleeve, so that it burns stably in the duty sleeve, and after leaving the duty sleeve, the flame spreads rapidly and superimposes with the main combustion flame at a certain position, thus playing a role in stabilizing combustion.

[0018] (3) The flue gas internal circulation ultra-low pollutant emission combustion device for natural gas described in this invention introduces flue gas into the combustion device through the high-speed fluid ejection effect formed by the air channel narrowing and the main flame ejector nozzle, via the main flue gas entrainment inlet, the rear flue gas entrainment hole, and the front flue gas entrainment hole, thereby increasing the inert gas content in the combustion zone. As the flue gas absorbs heat and dilutes the oxygen concentration, the combustion speed and temperature decrease, thereby inhibiting the formation of NOx. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0020] In the attached diagram:

[0021] Figure 1 This is a front view of an ultra-low pollutant emission combustion device for flue gas internal circulation suitable for natural gas, as described in this invention.

[0022] Figure 2 This is a right view of a flue gas recirculation ultra-low pollutant emission combustion device suitable for natural gas, as described in this invention.

[0023] Figure 3 This is a schematic diagram of the main flame gas nozzle of an ultra-low pollutant emission combustion device for flue gas internal circulation suitable for natural gas, as described in this invention.

[0024] Among them: 1-Stationary flame gas pipe, 2-Burner air box, 3-Main flame gas delivery pipe, 4-Main gas passage, 5-Air passage, 6-Air passage constriction, 7-Boiler refractory layer transition section, 8-Main flame support plate, 9-Main flame ejector nozzle, 10-Rear flue gas entrainment hole, 11-Front flue gas entrainment hole, 12-Main flame gas nozzle, 13-Main flue gas entrainment inlet, 14-Expansion, 15-Gas mixing cylinder, 16-Stationary sleeve, 17-Stationary flame short pipe, 18-Swirl vane, 19-Stationary flame radial injection hole, 20-Stationary flame axial injection hole, 21-Main flame gas pipe. Detailed Implementation

[0025] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings:

[0026] Specific implementation method one: See Figures 1-3 This embodiment is described in detail. The ultra-low pollutant emission combustion device for natural gas flue gas internal circulation, as described in this embodiment, specifically includes a standby flame gas pipe 1, a burner wind box 2, a main gas passage 4, an air passage 5, a boiler refractory layer transition section 7, several main flame gas pipes 21, several main flame gas nozzles 12, a gas mixing cylinder 15, and a standby sleeve 16. The burner wind box 2 and the air passage 5 are connected to provide oxygen for the combustion process. The outer ring of the air passage 5 is concentrically arranged with the main gas passage 4 and the boiler refractory layer transition section 7. One end of the main gas passage 4 is connected to the burner wind box 2, and the other end is connected to the boiler refractory layer transition section 7. A main flame support plate 8 is provided at the end of the boiler refractory layer transition section 7, which supports the air passage 5 and several main flame gas pipes 21. After passing through the boiler refractory layer transition section 7 and the main flame support plate 8, the air passage 5 has an air passage narrowing 6 at its end, allowing air to pass through. After the gas flows out of the air channel 5, the flow velocity increases, forming a high-speed fluid that generates an ejector effect, attracting flue gas. Several main flame gas pipes 21 are installed inside the boiler refractory layer transition section 7. One end of the main flame gas pipe 21 is connected to the main gas channel 4, and the other end passes through the boiler refractory layer transition section 7 and is equipped with a main flame ejector nozzle 9 at the end. Several main flame gas pipes 21 are evenly distributed on the outer ring of the air channel 5. A main flame gas nozzle 12 is sleeved on the outside of the main flame ejector nozzle 9. Several flue gas entrainment holes are provided on the main flame gas nozzle 12. The gas is injected into the main flame gas nozzle 12 through the main flame ejector nozzle 9 to increase the gas flow velocity, forming a high-speed fluid that generates an ejector effect, drawing the flue gas from the flue gas entrainment holes into the main flame gas nozzle 12. A gas mixing cylinder 15 is sleeved on the outside of the duty flame gas pipe 1 and the inside of several main flame gas nozzles 12, and is located in front of the air channel constriction 6.

[0027] The standby flame gas pipe 1 passes through the center of the burner air box 2 and the air passage 5, and extends to the inside of the gas mixing cylinder 15 to deliver the gas into the gas mixing cylinder 15; the standby sleeve 16 is fitted onto the standby flame gas pipe 1, and the standby sleeve 16 is entirely inside the gas mixing cylinder 15; a number of standby flame short pipes 17 are provided on the standby flame gas pipe 1, and the number of standby flame short pipes 17 are arranged inside the standby sleeve 16; the standby flame short pipes 17 are L-shaped pipes, the short side of the L-shape of the standby flame short pipe 17 is vertically connected to the standby flame gas pipe 1, and the long side of the L-shape of the standby flame short pipe 17 is parallel to the standby flame gas pipe 1.

[0028] The duty flame short pipe 17 is provided with a duty flame radial injection port 19 on the end side wall. The duty flame gas is injected from the duty flame radial injection port 19 into the duty sleeve 16 in the radial direction of the duty flame short pipe 17. The axial power of the duty flame axial injection hole 20 is used to make the flame rotate and burn along the inner wall of the duty sleeve 16, which plays a role in converging the flame and enhancing the mixing effect of gas, flue gas and air.

[0029] The plurality of flue gas entrainment holes include a plurality of rear flue gas entrainment holes 10 and a plurality of front flue gas entrainment holes 11. The plurality of rear flue gas entrainment holes 10 are disposed on the pipe wall of the main flame gas injection pipe 12 in the area corresponding to the main flame ejector nozzle 9, and the plurality of front flue gas entrainment holes 11 are disposed on the pipe wall of the main flame gas injection pipe 12 in front of the rear flue gas entrainment holes 10. When the main combustion stage gas is ejected from the main flame ejector nozzle 9, the flow velocity of the main combustion stage gas increases, becoming a high-speed fluid and generating an ejection effect, drawing the flue gas from the plurality of rear flue gas entrainment holes 10 and the plurality of front flue gas entrainment holes 11 into the main flame gas injection pipe 12. The width of the rear flue gas entrainment hole 10 is greater than that of the front flue gas entrainment hole 11, and the length of the rear flue gas entrainment hole 10 is less than that of the front flue gas entrainment hole 11.

[0030] The gas mixing cylinder 15 is provided with a main flue gas inlet 13 at one end facing the air channel constriction 6, and a flared end 14 at the other end. The end of the air channel constriction 6 extends into the main flue gas inlet 13, thereby ensuring that the air can be fully entered into the gas mixing cylinder 15 after being accelerated by the air channel constriction 6.

[0031] The end of the duty flame gas pipe 1 is provided with a swirl vane 18, and the edge of the swirl vane 18 leaves a certain gap with the inner wall of the duty sleeve 16. Several duty flame axial injection ports 20 are provided on the swirl vane 18. After the flue gas and air pass through the swirl vane 18, they rotate in the duty sleeve 16 and fully mix with the duty flame gas flow ejected from the duty flame radial injection port 19. This part of the mixed gas rotates forward along the inner wall of the duty sleeve 16. Another part of the duty flame gas flow is ejected from the end of the duty flame gas pipe 1 through the several duty flame axial injection ports 20 provided on the swirl vane 18, which drives the mixed gas to move forward and extend into the furnace for combustion.

[0032] The position where the duty flame short pipe 17 is connected to the duty flame gas pipe 1 is located on one side of the swirl vane 18, while the end of the duty flame short pipe 17 with the duty flame radial injection port 19 passes through the swirl vane 18, so that it is located on the other side of the swirl vane 18.

[0033] The main gas pipeline 4 is equipped with a main flame gas delivery pipe 3, which provides main combustion stage gas to the combustion device.

[0034] The specific working process of the ultra-low pollutant emission combustion device with flue gas internal circulation suitable for natural gas described in this invention is as follows:

[0035] Gas is introduced into the duty flame gas pipe 1 and the main gas pipe 4, and air is introduced into the combustion device from the burner air box 2. The air passes through the burner air box 2 and the air passage 5 to the air passage constriction 6. Under the action of the air passage constriction 6, the air velocity increases, generating an entrainment effect that drives the external flue gas through the main flue gas entrainment inlet 13 into the gas mixing cylinder 15 for mixing, realizing the primary entrainment of flue gas by air. After being evenly mixed in the gas mixing cylinder 15, a portion is directly sprayed out of the gas mixing cylinder 15. Another portion enters the duty sleeve 16 and mixes with the duty gas, and is finally injected into the furnace through the flare 14 to aid combustion. The mixing of flue gas reduces the oxygen partial pressure in the combustion-supporting gas and reduces NOx formation. At the same time, the gas entering from the main gas pipeline 4 passes through the main flame gas pipe 21 and reaches the main flame ejector nozzle 9. It is then injected from the main flame ejector nozzle 9 into the main flame gas nozzle 12. Under the action of the main flame ejector nozzle 9, the flow velocity of the main combustion stage gas increases, generating an ejection effect. The gas then passes through the main flame gas nozzle 12 and is injected into the main flame gas nozzle 12 through the flare 16. After drying, the flue gas entrainment holes 10 and several pre-flue gas entrainment holes 11 draw external flue gas into the main flame gas nozzle 12, where it mixes with the main combustion stage gas, achieving secondary entrainment of the flue gas by the gas. After uniform mixing in the main flame gas nozzle 12, the gas and flue gas are injected into the furnace for combustion. A small amount of flue gas participates in secondary combustion, reducing the flame temperature. The resulting strong internal recirculation increases the mass flow rate of the medium-temperature endothermic working fluid in the flame zone, thereby reducing the amount of nitrogen oxides produced. The standby gas in the standby flame gas pipe 1 flows continuously forward. A portion of the duty flame gas from the end of the duty flame gas pipe 1 enters the duty flame short pipe 17 and is ejected through the duty flame radial injection port 19, where it mixes with the flue gas and air that are rotated by the action of the swirl vane 18. The remaining duty flame gas is ejected directly from the duty flame axial injection port 20. The mixed gas inside the duty sleeve 16 rotates along the inner wall of the duty sleeve 16 and extends axially into the furnace for combustion. At a certain position, it overlaps with the gas ejected from the main flame gas nozzle 12 to form a flame superposition, which plays a role in stabilizing combustion.

[0036] In summary, the flue gas recirculation ultra-low pollutant emission combustion device for natural gas described in this invention divides the gas into a shift flame and a main combustion flame through a shift flame gas pipe 1 and a main flame gas delivery pipe 3, thus completing fuel grading, avoiding flame concentration, and reducing local high-temperature zones. The shift flame is gathered by a shift sleeve 16, ensuring stable combustion within the sleeve. After leaving the sleeve 16, the flame rapidly diffuses, superimposing with the main combustion flame at a certain position, thus stabilizing combustion. Furthermore, the high-speed fluid ejection effect formed by the air channel constriction 6 and the main flame ejector nozzle 9 introduces flue gas into the combustion device through the main flue gas inlet 13, the rear flue gas inlet 10, and the front flue gas inlet 11, increasing the inert gas content in the combustion zone. Because the flue gas absorbs heat and dilutes the oxygen concentration, the combustion speed and temperature decrease, thereby suppressing NOx formation.

[0037] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the invention. They can also be reasonable combinations of the features described in the above embodiments. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A flue gas internally recirculating ultra-low pollutant emission combustion device suitable for natural gas, characterized in that: The system includes a standby flame gas pipe (1), a burner air box (2), a main gas passage (4), an air passage (5), a boiler refractory layer transition section (7), several main flame gas pipes (21), several main flame gas nozzles (12), a gas mixing cylinder (15), and a standby sleeve (16). The burner air box (2) and the air passage (5) are connected. The outer ring of the air passage (5) is concentrically provided with the main gas passage (4) and the boiler refractory layer transition section (7). The main gas passage (4) and the boiler refractory layer transition section (7) are connected. After the air passage (5) passes through the boiler refractory layer transition section (7), an air outlet is provided at the end. The gas passage narrows (6); the boiler refractory layer transition section (7) is provided with several main flame gas pipes (21), one end of the main flame gas pipe (21) is connected to the main gas passage (4), and the other end passes through the boiler refractory layer transition section (7) and is provided with a main flame ejector nozzle (9) at the end; the main flame ejector nozzle (9) is fitted with a main flame gas spray pipe (12); several flue gas entrainment holes are provided on the main flame gas spray pipe (12); the gas mixing cylinder (15) is fitted outside the duty flame gas pipe (1) and inside several main flame gas spray pipes (12), and is located in front of the air passage narrows (6); The duty flame gas pipe (1) passes through the center of the burner air box (2) and the air passage (5) and extends into the gas mixing cylinder (15); the duty sleeve (16) is fitted on the duty flame gas pipe (1); a number of duty flame short pipes (17) are provided on the duty flame gas pipe (1), and the number of duty flame short pipes (17) are provided inside the duty sleeve (16); The plurality of flue gas entrainment holes include a plurality of rear flue gas entrainment holes (10) and a plurality of front flue gas entrainment holes (11). The plurality of rear flue gas entrainment holes (10) are disposed on the pipe wall of the main flame gas injection pipe (12) on the outer periphery of the main flame ejector nozzle (9), and the plurality of front flue gas entrainment holes (11) are disposed on the pipe wall of the main flame gas injection pipe (12) in front of the main flame ejector nozzle (9). The width of the rear flue gas entrainment holes (10) is greater than that of the front flue gas entrainment holes (11), and the length of the rear flue gas entrainment holes (10) is less than that of the front flue gas entrainment holes (11). The end of the duty flame gas pipe (1) is provided with a swirl vane (18); a gap is provided between the edge of the swirl vane (18) and the inner wall of the duty sleeve (16); A radial jet nozzle (19) for the duty flame is provided on the side wall of the end of the duty flame short tube (17).

2. The flue gas internally recirculating ultra-low pollutant emission combustion device suitable for natural gas as claimed in claim 1, wherein: The gas mixing cylinder (15) is provided with a main flue gas inlet (13) at one end facing the air channel constriction (6), and a flared end (14) at the other end.

3. The flue gas internally recirculating ultra-low pollutant emission combustion device for natural gas of claim 2, wherein: The end of the air passage constriction (6) extends into the main flue gas inlet (13).

4. The flue gas internally recirculating ultra-low pollutant emission combustion device for natural gas of claim 1, wherein: The duty flame short tube (17) passes through the swirl blade (18).

5. The flue gas internally recirculating ultra-low pollutant emission combustion device for natural gas of claim 2, 3 or 4, characterized in that: The swirl blade (18) is provided with several axial injection ports (20) for the standby flame.

6. The flue gas internally recirculating ultra-low pollutant emission combustion device for natural gas of claim 5, wherein: The boiler refractory transition section (7) is provided with a main flame support plate (8) at its end. The main flame support plate (8) supports the air passage (5) and several main flame gas pipes (21).

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