Dual fuel burner and boiler with staged ignition, staged air distribution and flue gas recirculation

Abstract

The present invention provides a dual-fuel burner and boiler with staged ignition, staged air distribution and flue gas recirculation, which includes an ignition gas pipe, a central air pipe, a primary air chamber, a secondary air chamber, a main combustion chamber, a pre-combustion chamber, an ignition gun and a recirculation air chamber. The central air pipe is sleeved outside the ignition gas pipe, the primary air chamber is sleeved outside the central air pipe, the secondary air chamber is sleeved outside the primary air chamber, the main combustion chamber is sleeved outside the secondary air chamber. The air outlets of the central air pipe, the primary air chamber and the secondary air chamber, as well as the gas outlets of the ignition gas pipe and the main combustion chamber are located inside the pre-combustion chamber. The ignition gun is installed on the pre-combustion chamber, and the recirculation air chamber is arranged outside the pre-combustion chamber. It solves the problems of unsatisfactory low-nitrogen combustion effect and poor operation safety of the current dual-fuel burner, and achieves the purpose of improving the combustion efficiency and reducing the NO X emission at the initial stage.

Description

Technical Field

[0001] The invention belongs to the technical field of burners, and in particular relates to a dual-fuel burner and a boiler with staged ignition, staged air distribution and flue gas recirculation. Background Art

[0002] In view of my country's existing coal-based energy structure and the continuous improvement of national energy conservation and emission reduction standards, especially in recent years as the country is committed to international energy cooperation and introduction, the supply of high-quality fuels such as natural gas has also been greatly alleviated. Therefore, new low-nitrogen and high-efficiency pulverized coal and gas combustion technologies have been vigorously promoted and applied.

[0003] Industrial boilers have always played an important role in my country's economic operation. At present, the international situation is changing day by day, the surrounding environment is not stable, and energy security issues still exist. Single fuel boilers may be unable to be put into operation due to fuel supply problems, resulting in significant economic losses. Therefore, it is very necessary to develop a new type of high-efficiency low-nitrogen burner suitable for both pulverized coal and gas. Existing burners that use pulverized coal and gas are mostly simple combinations with poor operating safety and unsatisfactory low-nitrogen combustion effects. Summary of the invention

[0004] The present invention provides a dual-fuel burner and boiler with staged ignition, staged air distribution and flue gas recirculation, which are used to solve the problems of unsatisfactory low-nitrogen combustion effect and poor operation safety of the current dual-fuel burner.

[0005] The present invention provides a dual-fuel burner and boiler with staged ignition and staged air distribution and flue gas recirculation, comprising an ignition gas pipe, a central air duct, a primary air chamber, a secondary air chamber, a main combustion chamber, a pre-combustion chamber, an ignition gun, and a circulating air chamber. The central air duct is sleeved on the outside of the ignition gas pipe, the primary air chamber is sleeved on the outside of the central air duct, the secondary air chamber is sleeved on the outside of the primary air chamber, the main combustion chamber is sleeved on the outside of the secondary air chamber, the air outlets of the central air duct, the primary air chamber, the secondary air chamber and the ignition gas pipe and the main combustion chamber are located inside the pre-combustion chamber, the ignition gun is installed on the pre-combustion chamber, and the circulating air chamber is arranged outside the pre-combustion chamber.

[0006] Preferably, the secondary air chamber is divided into two inner and outer air chambers, wherein the inner secondary air chamber is provided with inner secondary air swirl blades at the air outlet, and the outer secondary air chamber is provided with outer secondary air swirl blades at the air outlet.

[0007] Preferably, an inner secondary regulating baffle is provided at the air inlet of the inner secondary air chamber, and an outer secondary regulating baffle is provided at the air inlet of the outer secondary air chamber.

[0008] Preferably, a central wind cyclone is provided at the air outlet of the central air duct.

[0009] Preferably, the end of the ignition gas pipe has a conical end face, and two inner and outer circles of spray holes are arranged on the conical end face, and the jet angle of the two spray holes symmetrically arranged in the same circle is 90°.

[0010] Preferably, the ignition gas pipe is connected to an air intake pipeline through a hose, and the air intake pipeline is connected to a gas matching valve group, and the gas matching valve group includes a manual ball valve, a pneumatic ball valve and an electric regulating valve.

[0011] Preferably, a fixed tangential swirl blade is provided on the inner wall at the end of the circulating air chamber, and the angle between the fixed tangential swirl blade and its axis is 18°.

[0012] Preferably, the angle between the inner secondary air swirl blade and its axis is 55°, and the angle between the outer secondary air swirl blade and its axis is 25°.

[0013] Preferably, the end of the main combustion chamber has four groups of gas spray holes, and the four groups of gas spray holes are symmetrically arranged at the upper, lower, left and right positions of the circumference of the end of the main combustion chamber.

[0014] The present invention also provides a boiler, which adopts the dual-fuel burner with staged ignition, staged air distribution and flue gas recirculation described in the present invention.

[0015] Beneficial effects of the present invention:

[0016] The structures that can burn pulverized coal and gas are cleverly coupled together, and NO can be achieved when burning pulverized coal or gas alone. X The effect of low emission is achieved; when burning pulverized coal, dense phase powder transportation, secondary air classification and proportion adjustment are adopted, swirl blades are used to guide the swirl flow to enhance the swirl flow intensity and low-temperature flue gas recirculation is introduced from the pre-combustion chamber, thereby achieving low-nitrogen combustion of pulverized coal; when burning natural gas, fuel classification, swirl air distribution, FIR+FGR flue gas internal and external double circulation technology are adopted to reduce NO X Reduced to 30mg / Nm 3 the following. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic structural diagram of a dual-fuel burner with staged ignition and staged air distribution and flue gas recirculation according to the present invention;

[0018] Figure 2 A top view of the central air duct of a dual-fuel burner with staged ignition and staged air distribution and flue gas recirculation according to the present invention;

[0019] Figure 3 It is a cross-sectional view of the central air duct of the dual-fuel burner with staged ignition and staged air distribution and flue gas recirculation according to the present invention;

[0020] Figure 4It is a schematic diagram of the gas matching valve group of the dual-fuel burner with staged ignition and staged air distribution and flue gas recirculation of the present invention;

[0021] Figure 5 A top view of the air outlet of the main combustion chamber of a dual-fuel burner with staged ignition and staged air distribution using flue gas recirculation according to the present invention.

[0022] Figure annotation:

[0023] 1. Ignition gas pipe; 2. Central air duct; 3. Primary air chamber; 4. Secondary air chamber; 40. Inner secondary air chamber; 401. Inner secondary air swirl blade; 402. Inner secondary regulating baffle; 41. Outer secondary air chamber; 411. Outer secondary air swirl blade; 412. Outer secondary regulating baffle; 5. Main combustion chamber; 6. Pre-combustion chamber; 7. Ignition gun; 8. Circulating air chamber; 9. Fixed tangential swirl blade, 10. Gas spray hole 11. Spray hole; 12. Manual ball valve; 13. Pneumatic ball valve; 14. Electric regulating valve. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and cannot be understood as limiting the specific protection scope of the present invention.

[0025] Example

[0026] Reference Figure 1 The dual-fuel burner with graded ignition and graded air distribution and flue gas recirculation in this embodiment includes an ignition gas pipe 1, a central air pipe 2, a primary air chamber 3, a secondary air chamber 4, a main combustion chamber 5, a pre-combustion chamber 6, an ignition gun 7, and a circulation air chamber 8. The central air pipe 2 is sleeved on the outside of the ignition gas pipe 1, the primary air chamber 3 is sleeved on the outside of the central air pipe 2, the secondary air chamber 4 is sleeved on the outside of the primary air chamber 3, and the main combustion chamber 5 is sleeved on the outside of the secondary air chamber 4. The central air pipe 2, the primary air chamber 3, the secondary air chamber 4, the air outlets of the ignition gas pipe 1 and the main combustion chamber 5 are located inside the pre-combustion chamber 6, the ignition gun 7 is installed on the pre-combustion chamber 6, and the circulation air chamber 8 is arranged outside the pre-combustion chamber 6. The secondary air chamber 4 is divided into two inner and outer air chambers: an inner secondary air chamber 40 and an outer secondary air chamber 41. The ignition gun 7 in this embodiment is a pneumatic advance and retreat type, and exits the pre-combustion chamber 6 after ignition to prevent overheating and damage, thereby extending the service life. In this embodiment, the inner wall of the pre-combustion chamber 6 is cast with refractory material and can withstand high temperatures.

[0027] The gas is injected into the pre-combustion chamber 6 through the small air gun connected to the ignition gas pipe 1 as the ignition source. During ignition, the amount of gas and air entering the pre-combustion chamber 6 is controlled to prevent deflagration. After the flame is stable, the amount of gas and air is adjusted to reach the rated thermal power of the small air gun. The entire ignition process is safe and controllable.

[0028] The burner of this embodiment is divided into four stages of air distribution when working. In the first stage, the central air is supplied by the central air duct 2, and the central air accounts for about 15%. The primary air is provided by the Roots blower, and the primary air carries the coal powder and is sprayed into the pre-combustion chamber 6 through the primary air chamber 3. The primary air accounts for about 5%, the wind speed is about 20m / s, and the coal powder concentration is 2.5-4kg / Nm 3 The central wind drives the gas flame to fully contact and mix with the coal powder flow. Because the coal powder has a high concentration and is easy to ignite, the initial combustion component of the coal powder is mainly volatile matter. This stage is mainly supplied with oxygen by primary wind and central wind. In this embodiment, a central wind electric regulating valve is provided before the central wind enters the burner, which can adjust and control the air volume.

[0029] The second stage: the internal secondary air is introduced from the internal secondary air chamber 40 to provide oxygen for the continuous combustion of the pulverized coal. The internal secondary air accounts for about 45%, with a wind speed of 30-35m / s, which is a strong swirl flow, so that the turbulence intensity of the pulverized coal is enhanced, diffused to the surroundings, and a recirculation zone is formed in the front.

[0030] The third stage: the external secondary air is introduced from the external secondary air chamber 41, and the external secondary air accounts for about 35%, with a wind speed of 38-42m / s, which is a weak swirl. The wind speed of the external secondary air is higher than that of the internal secondary air, and it is wrapped around the outer periphery of the internal secondary air, and mixed with the coal powder later than the internal secondary air, and continues to provide oxygen for the combustion of coal powder. The external secondary air has a weak swirl, high flow rate, and is constrained by the inner wall of the pre-combustion chamber 6, which shapes and restrains the internal coal powder jet, prevents the coal powder from diffusing and attenuating too quickly, maintains the rigidity of the coal powder jet, and continues to replenish the oxygen required for coal powder combustion.

[0031] The fourth stage: circulating air is introduced from the circulating air chamber 8, with a wind speed of 38-42m / s. The circulating air is taken from the low-temperature flue gas after the dust collector, and the residual oxygen in the flue gas is used to continue to provide oxygen for the combustion of coal powder. The circulating air can be adjusted to 10-20% of the total air volume.

[0032] The burner of this embodiment uses a combination of dense phase powder delivery, 4-stage graded air distribution technology, and the introduction of low-temperature flue gas recirculation into the pre-combustion chamber 6 to adjust the oxygen supply at each stage of coal powder combustion, slow down the coal powder combustion process, and reduce the intensity of coal powder combustion. The low-temperature recirculated flue gas introduced into the outer wall of the pre-combustion chamber 6 can also reduce the temperature of the pre-combustion chamber 6 and effectively prevent the coking of coal powder. The introduction of low-temperature recirculated flue gas further reduces the combustion center temperature, reduces the generation of thermal NOx, and supplies the residual oxygen in the flue gas to achieve the burnout process of coal powder.

[0033] In order to adjust the air intake of the inner secondary air and the outer secondary air, as a preferred implementation of this embodiment, the inner secondary air chamber 40 is provided with an inner secondary air swirl blade 401 at the air outlet, and the outer secondary air chamber 41 is provided with an outer secondary air swirl blade 411 at the air outlet. The inner secondary air swirl blade 401 has an angle of 55° with its axis, and the outer secondary air swirl blade 411 has an angle of 25° with its axis.

[0034] As a preferred implementation of this embodiment, an inner secondary regulating baffle 402 is provided at the air inlet of the inner secondary air chamber 40, and an outer secondary regulating baffle 412 is provided at the air inlet of the outer secondary air chamber 41. The openings of the inner secondary regulating baffle 402 and the outer secondary regulating baffle 412 are adjusted to form a certain reducing atmosphere (excess air coefficient ≤ 1) in the high temperature area at the center of the flame while maintaining stable combustion of the torch, thereby suppressing the generation of fuel-type NOx.

[0035] As a preferred implementation of this embodiment, a central wind cyclone 21 is provided at the air outlet of the central wind duct 2. The central wind is diffused by the central wind cyclone 21 to play a "coal spreading" role. Its disturbance effect makes the coal powder fully contact with the gas flame when the coal powder is ignited, which is convenient for igniting the coal powder. Figure 2 , 3 The end of the ignition gas pipe 1 has a conical end face, on which two inner and outer circles of spray holes 11 are arranged. The jet angle a of the two spray holes 11 symmetrically arranged in the same circle is 90°. After the gas is sprayed out from the spray holes 11, it spreads outward at an angle of 90°, contacts with the outer circle center wind and is fully mixed. The combined design of the ignition gas pipe 1 and the center wind swirler 21 enables the flame formed after the burner of this embodiment is ignited to completely cover the air and powder outlet of the primary wind chamber 3, making it easy to ignite the coal powder. When the main gas is burned, the small gas gun continues to operate, and the ignition gas pipe 1 provides a "duty flame" for the main gas combustion, thereby improving the combustion stability.

[0036] Reference Figure 4As a preferred implementation of this embodiment, the ignition gas pipe 1 is connected to the air intake pipeline through a hose, and the air intake pipeline is connected to the gas matching valve group, and the gas matching valve group includes a manual ball valve 12, a pneumatic ball valve 13 and an electric regulating valve 14. The pneumatic ball valve 13 in the gas matching valve group can be opened and closed quickly, and plays a control role in the on-off of the gas. The opening of the electric regulating valve 14 is driven by an electric actuator and linked with the central wind electric regulating valve. A low-fire position verification switch is specially set and installed on the electric regulating valve 14 to ensure that the ignition program can only be started when the opening of the regulating valve is at a low-fire position (set to 20% of the total opening). During ignition, the opening of the electric regulating valve 14 is set to a low-fire position, and it is linked with the central wind electric regulating valve to ensure that a small amount of gas enters the burner at the beginning of ignition. The high-voltage electric spark generated by the ignition gun 7 directly ignites the low-fire position gas ejected from the ignition gas pipe 1, controls the amount of gas during ignition, and prevents furnace explosion. After ignition, the flame is monitored. When successful ignition is detected, the electric regulating valve 14 is linked with the central air electric regulating valve, slowly opened and adjusted to the rated value. At this time, the thermal power of the small air gun is sufficient to ignite the coal powder or the main gas.

[0037] The ignition gas pipe 1 cooperates with the central wind swirler 21 to form a conical "fire curtain" that spreads forward and outward. When burning coal powder, the primary air chamber 3 can be completely "intercepted" to successfully achieve coal powder ignition; the conical "fire curtain" continues to spread to the nozzle of the main combustion chamber 5, and the main gas can be smoothly ignited when burning gas.

[0038] The design of the nozzle 11 of the ignition gas pipe 1 interacts with the central wind cyclone 21. After ignition, a stable combustion area with gas and flue gas reflux is generated in the front area of ​​the central wind outlet. Due to the internal circulation of high-temperature flue gas in this area, NO x generate.

[0039] As a preferred implementation of this embodiment, a fixed tangential swirl blade 9 is provided on the inner wall at the end of the circulating air chamber 8, and the angle between the fixed tangential swirl blade 9 and its axis is 18°.

[0040] Reference Figure 5 As a preferred implementation of this embodiment, the end of the main combustion chamber 5 has four groups of gas spray holes 10, and the four groups of gas spray holes 10 are symmetrically arranged at the upper, lower, left and right positions of the circumference of the end of the main combustion chamber 5. The main gas is sprayed into the pre-combustion chamber 6 at high speed by the four groups of gas spray holes 10, and the main gas combustion air is swirl-fed into the secondary air chamber 4, with the "duty flame" as the center, forming four flames at the upper, lower, left and right sides. The high-speed jet gas flame produces a Venturi effect, driving the vulgar flame to form internal smoke entrainment. When the main gas is sprayed in, a thick and thin distribution of the fuel flow on the combustion cross section is formed, which slows down the combustion rate, forms an internal smoke circulation, reduces the flame temperature, and reduces thermal NO X formation.

[0041] The present invention also provides a boiler, which can be horizontal or vertical. The boiler adopts the dual-fuel burner with staged ignition, staged air distribution and flue gas recirculation described in the present invention. The burner of this embodiment can be installed on the front wall, rear wall, front and rear wall opposite each other or top-mounted.

Claims

1. A dual-fuel burner with staged ignition and staged air distribution and flue gas recirculation, characterized in that: It includes an ignition gas pipe, a central air duct, a primary air chamber, a secondary air chamber, a main combustion chamber, a pre-combustion chamber, an ignition gun, and a circulating air chamber. The central air duct is sleeved on the outside of the ignition gas pipe, the primary air chamber is sleeved on the outside of the central air duct, the secondary air chamber is sleeved on the outside of the primary air chamber, the main combustion chamber is sleeved on the outside of the secondary air chamber, the central air duct, the primary air chamber, the secondary air chamber air outlets, the ignition gas pipe, and the main combustion chamber air outlets are located inside the pre-combustion chamber, the ignition gun is installed on the pre-combustion chamber, and the circulating air chamber is arranged outside the pre-combustion chamber; The secondary air chamber is divided into two inner and outer air chambers, wherein the inner secondary air chamber is provided with inner secondary air swirl blades at the air outlet, and the outer secondary air chamber is provided with outer secondary air swirl blades at the air outlet; A central wind cyclone is provided at the air outlet of the central air duct; The end of the main combustion chamber is provided with four groups of gas spray holes, and the four groups of gas spray holes are symmetrically arranged at the upper, lower, left and right positions of the circumference of the end of the main combustion chamber.

2. The dual-fuel burner with staged ignition and staged air distribution and flue gas recirculation according to claim 1 is characterized in that: An inner secondary regulating baffle is provided at the air inlet of the inner secondary air chamber, and an outer secondary regulating baffle is provided at the air inlet of the outer secondary air chamber.

3. The dual-fuel burner with staged ignition and staged air distribution and flue gas recirculation according to claim 1 is characterized in that: The end of the ignition gas pipe has a conical end face, and two inner and outer circles of spray holes are arranged on the conical end face. The jet angle of the two spray holes symmetrically arranged in the same circle is 90°.

4. The dual-fuel burner with staged ignition and staged air distribution and flue gas recirculation according to claim 1 or 3, characterized in that: The ignition gas pipe is connected to an air intake pipeline through a hose, and the air intake pipeline is connected to a gas matching valve group, and the gas matching valve group includes a manual ball valve, a pneumatic ball valve and an electric regulating valve.

5. The dual-fuel burner with staged ignition and staged air distribution and flue gas recirculation according to claim 1 is characterized in that: A fixed tangential swirl blade is arranged on the inner wall at the end of the circulating air chamber, and the angle between the fixed tangential swirl blade and its axis is 18°.

6. The dual-fuel burner with staged ignition and staged air distribution and flue gas recirculation according to claim 1 is characterized in that: The included angle between the inner secondary air swirl blade and its axis is 55°, and the included angle between the outer secondary air swirl blade and its axis is 25°.

7. A boiler, characterized in that: A dual-fuel burner with staged ignition, staged air distribution and flue gas recirculation as claimed in any one of claims 1 to 6.

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