Stable combustion burner based on pulverized coal swirling preheating and multi-stage recirculation

Abstract

The invention relates to a stable combustion and nitrogen reduction combustor technology, in particular to a stable combustion combustor based on pulverized coal swirling preheating and multi-stage recirculation. According to the stable combustion burner based on pulverized coal swirling preheating and multi-stage recycling, a swirling preheating pipeline is arranged in the burner, the preheating time and the volatile analysis quantity of concentrated-phase pulverized coal can be increased through the swirling pipeline, and the structure of an existing burner is not considered; according to the combustor, a recirculation area which is stable in boundary and high in entrainment capacity is built in the combustor through arrangement of the triangular bluff bodies and the air preheating pipeline nozzles, the retention time of pulverized coal is greatly prolonged, the heat and mass transfer capacity of the pulverized coal is greatly improved, and an existing combustor does not have the synergistic effect form; the air nozzle extends to the ignition chamber, a formed small recirculation area can promote ignition of light-phase pulverized coal, high-temperature smoke in a combustion area is entrained, and continuous ignition of a plasma igniter is not needed.

Description

TECHNICAL FIELD

[0001] The present application relates to a stable combustion and nitrogen reduction burner technology, in particular to a stable combustion burner based on coal powder preheating and multi-stage recirculation. BACKGROUND

[0002] The proportion of clean energy grid access continues to rise, but the three-dimensional dilemma of energy has brought multiple constraint factors and time challenges to its development, making traditional coal power still occupy the dominant position of power supply.

[0003] In the process of power energy transformation, the current power grid hopes to adjust the real-time balance of clean energy power supply through coal power, and often needs the boiler unit to be able to operate stably at 20%-30% of its rated load. However, in the existing coal power system, most boiler units do not have flexible peak regulation and frequency modulation capability, and frequent load change or low load operation not only reduces the coal combustion rate, intensifies the operation fluctuation, but also causes excessive waste of coal resources and aggravation of harmful gas emissions.

[0004] The performance of the burner is the key to the flexible change of the load of the boiler, so a new stable combustion burner is needed to solve the above problems. SUMMARY

[0005] The main purpose of the present application is to design a stable combustion burner based on coal powder preheating and multi-stage recirculation, which can effectively realize self-sustaining stable combustion during operation by utilizing its own structural characteristics and fuel inlet mode.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is:

[0007] The present application provides a stable combustion burner based on coal powder preheating and multi-stage recirculation, which comprises: An outer barrel, the two sides of the outer barrel in the extension direction form a wind-powder inlet and a flame outlet respectively; A thick-thin separator is arranged in the outer barrel, and a spiral pipe is arranged between the outer wall of the thick-thin separator and the inner wall of the outer barrel; A plasma igniter, the ignition end extends into the inlet end of the thick-thin separator; A triangular bluff body is arranged around the inner wall of the outer barrel at the position of the spiral pipe nozzle; An air preheating pipe, comprising a compressed air inlet located on one side of the flame outlet, a third air nozzle extending into the thick-thin separator through the outlet end of the thick-thin separator, and a first air nozzle and a second air nozzle located at the position of the spiral pipe nozzle; The primary wind-powder enters the thick-thin separator after entering the wind-powder inlet and is separated into thick-phase coal powder and thin-phase coal powder; The dense phase coal powder enters the swirling pipeline, and after being sprayed out of the swirling pipeline nozzle, the dense phase coal powder collides with the high-temperature air sprayed out of the first air nozzle and the second air nozzle to form a first recirculation zone limited by the triangular bluff body. The dilute phase coal powder enters the inside of the dense-dilute separator from the inlet end of the dense-dilute separator and collides with the high-temperature air sprayed out of the third air nozzle to form a second recirculation zone.

[0008] Further, the flame outlet is provided with an internal gear-shaped tube coaxially arranged with the outer barrel.

[0009] Further, the triangular bluff body is provided with two triangular bluff bodies corresponding to the first air nozzle and the second air nozzle, and the two triangular bluff bodies stabilize the elliptical boundary of the first recirculation zone in cooperation with the air preheating pipeline between the first air nozzle and the second air nozzle.

[0010] Further, the air injection directions of the first air nozzle and the second air nozzle are both arranged to be tangent to the elliptical boundary of the first recirculation zone.

[0011] Further, the air injection direction of the first air nozzle is consistent with the axial direction of the air preheating pipeline, and the air injection direction of the second air nozzle forms an angle of 60° with the axial direction of the air preheating pipeline.

[0012] Further, the first air nozzle and the second air nozzle each include four small nozzles with a diameter of 2 mm.

[0013] Further, the air injection direction of the third air nozzle is consistent with the axial direction of the air preheating pipeline.

[0014] Further, the air preheating pipeline is coaxially arranged with the outer barrel.

[0015] Further, the temperature of the swirling pipeline nozzle is in the range of 573K to 673K.

[0016] Further, an initial pressure of 60Pa is applied to the compressed air inlet.

[0017] The present application is innovative compared with the existing burner in that:

[0018] The stable combustion burner based on coal powder swirling preheating and multi-stage recirculation is internally arranged with a swirling preheating pipeline, which can increase the preheating time of dense phase coal powder and the amount of volatile matter, and the existing burner does not consider the structure; the triangular bluff body and the air preheating pipeline nozzle arranged in the burner establish a recirculation zone with stable boundary and strong entrainment capacity, which greatly improves the residence time of coal powder and the heat exchange capacity, and the existing burner does not have the synergistic form; the air nozzle extends to the ignition chamber, and the small recirculation zone formed can promote the ignition of the light phase coal powder, and the high-temperature flue gas in the combustion area is entrained, without the need for a continuous ignition of the plasma igniter, and the existing burner does not consider the arrangement of the small recirculation zone in the ignition area, which is also the theoretical basis for the stable combustion and ignition of the present application.

[0019] The beneficial effects of the present application are:

[0020] The present application provides a stable combustion burner based on coal powder swirling preheating and multi-stage recirculation. The burner improves the combustion efficiency by optimizing fuel distribution and enhancing heat recovery efficiency, while maintaining the stability of the combustion system. Specifically, the core innovations include the following two aspects: first, the use of coal powder swirling preheating pipeline design can improve the preheating uniformity and heating time of the fuel; second, the introduction of a multi-stage recirculation system reduces the heat loss caused by insufficient mixing of air and fuel. At the same time, the multi-stage recirculation system optimizes the high-temperature flue gas circulation path and pressure distribution, making the combustion process more stable, thereby significantly improving the coal ignition capacity and preheating. In addition, the burner maintains stable combustion under low load conditions, effectively extends its service life under high load operation, and ensures the safety and economy of the system operation. Overall, the implementation of the present application can significantly improve the stable combustion capacity of the burner under variable or low load conditions, and effectively suppress the formation of early NOx. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A stable combustion burner based on coal powder swirling preheating and multi-stage recirculation is provided for the embodiment of the present application;

[0022] Figure 2 A stable combustion burner based on coal powder swirling preheating and multi-stage recirculation is provided for the embodiment of the present application;

[0023] Figure 3 A stable combustion burner based on coal powder swirling preheating and multi-stage recirculation is provided for the embodiment of the present application; Figure 1 A stable combustion burner based on coal powder swirling preheating and multi-stage recirculation is provided for the embodiment of the present application;

[0024] Figure 4 A stable combustion burner based on coal powder swirling preheating and multi-stage recirculation is provided for the embodiment of the present application; Figure 1 A stable combustion burner based on coal powder swirling preheating and multi-stage recirculation is provided for the embodiment of the present application;

[0025] Figure 5 for Figure 1 A schematic diagram of the winding method of the spiral pipe;

[0026] Figure 6 for Figure 1 A schematic diagram of the gear-shaped tube structure inside the flame outlet;

[0027] In the diagram: 1-Powder inlet; 2-Compressed air inlet; 3-Flame outlet; 4-Plasma igniter; 5-Ignition chamber; 6-Air preheating pipe; 7-Internal gear-shaped pipe; 8-Concentration separator; 9-Swirl pipe; 10-First air nozzle; 11-Second air nozzle; 12-Third air nozzle; 13-Triangular blunt body; 14-Swirl pipe nozzle; 15-First recirculation zone; 16-Second recirculation zone. Detailed Implementation

[0028] The specific embodiments of the present invention will be described in detail below.

[0029] Combination Figure 1 This embodiment provides a stable combustion burner based on pulverized coal swirl preheating and multi-stage recirculation, including an outer casing, a plasma igniter 4, a rich-lean separator 8, an ignition chamber, a first recirculation zone 15, a second recirculation zone 16, a swirl pipe 9, a triangular blunt body 13, an internal gear-shaped tube 7, an air preheating pipe 6, a first air nozzle 10, a second air nozzle 11, a third air nozzle 12, a coal-air inlet 1, a flame outlet 3, and a compressed air inlet 2.

[0030] The concentration separator 8 is located at the air-powder inlet 1, the plasma igniter 4 is located at the inlet of the concentration separator 8, the swirling pipe 9 is located on the outer wall of the concentration separator 8, the ignition end of the plasma igniter 4 is located inside the concentration separator 8, the recirculation area is located at the outlet of the concentration separator 8, the triangular blunt body 13 is located at the nozzle 14 of the swirling pipe, the air preheating pipe 6 is axially arranged inside the outer casing, and the internal gear-shaped pipe 7 is located at the flame outlet 3.

[0031] In this technical solution, the rich-lean separator 8 separates primary air and pulverized coal into a "rich-lean-rich" type. The lean phase pulverized coal flows into the ignition chamber and is ignited by the plasma igniter 4; the lower pulverized coal concentration reduces the energy required for ignition. The dense phase pulverized coal flows into the swirling pipe 9, is fully preheated by the outer wall of the rich-lean separator 8, precipitates volatiles, and is ejected from the tangential nozzle. Air flows into the burner through the air preheating pipe 6, is heated by the internal flame, and is ejected through three air nozzles at different axial positions, forming a recirculation flow field. The triangular blunt body 13 stabilizes the elliptical boundary of the recirculation zone, effectively improving the residence time of pulverized coal and the heat and mass exchange capacity within the recirculation zone. Simultaneously, the outlet design of the internal gear-shaped tube 7 further optimizes the combustion airflow distribution, significantly improving combustion stability.

[0032] The first air jet 10 and the second air jet 11 are arranged to facilitate the formation of a recirculation zone, each group of jets consisting of 4 small jets of 2 mm in diameter arranged in a circle to achieve sufficient jet velocity, wherein the first air jet 10 is arranged to inject air in the axial direction, and the second air jet 11 is arranged at an angle of 60° to the axial direction to form a more stable recirculation zone.

[0033] The third air jet 12 is arranged inside the dense-dilute separator 8, and the design of the jet is mainly to provide a higher air coefficient inside the dense-dilute separator, so that the dilute phase coal powder is more easily ignited. The second recirculation zone 16 formed by the heated high-temperature air can ignite part of the coal powder, without the need for frequent ignition of the plasma igniter 4.

[0034] The design structure of the dense-dilute separator 8 in this embodiment is similar to a "tweezer" shape, which not only ensures that the dilute phase coal powder is precisely ignited by the internal plasma igniter 4, but also effectively prevents the ignition of the external dense phase coal powder.

[0035] In the swirling pipe 9, the dense phase coal powder is injected after being fully preheated and releasing sufficient volatile matter, with an outlet temperature in the range of 573K to 673K.

[0036] An initial pressure of 60 Pa is applied to the compressed air inlet 2 to ensure the jet velocity of the air and prevent the mixing of coal powder into the air pipe.

[0037] The triangular bluff body 13 is arranged around the inner wall of the burner sleeve barrel, which can effectively limit the boundary of the recirculation zone and prevent the overheating of the burner wall.

[0038] The internal gear-shaped pipe 7 can form a tooth-shaped flow blocking area at the outlet of the burner, blocking the ejection of part of the high-temperature flue gas and high-temperature coal powder, providing backflow heat for the inside of the burner, and improving the combustion efficiency and combustion stability.

[0039] The specific working principle is described as follows: Figure 2 The primary air and coal powder enter the burner from the air and coal powder inlet 1, and are separated into dense phase coal powder and dilute phase coal powder by the dense-dilute separator 8. The dilute phase coal powder enters the inside of the dense-dilute separator 8, and the dense phase coal powder enters the swirling pipe 9. The swirling pipe 9 is arranged in a swirling manner on the outer wall of the dense-dilute separator 8. The dilute phase coal powder inside the dense-dilute separator is ignited by the plasma igniter 4, and the dense phase coal powder inside the swirling pipe 9 is preheated. The swirling arrangement of the swirling pipe 9 prolongs the preheating time of the dense phase coal powder, which can release more volatile matter to help the burner to stabilize the ignition. The structure of the swirling pipe 9 is shown in Figure 4 ,5

[0040] Compressed air from the compressed air inlet 2 into the burner inside, the air preheating pipeline 6 middle and end of the arrangement of three different axial distance of the nozzle: the first air jet 10, 11, the second air jet, the third air jet 12. The first air jet 10 and the second air jet 11 jet direction is arranged by cutting ellipse, due to the initial pressure and high mass flow, with high initial velocity when injected into the burner inside; at the same time, the dense phase of coal powder after preheating from the swirl pipe nozzle 14, with the first air jet 10 and the second air jet 11 jet out of the high temperature air collision to form the first recirculation zone 15, the first recirculation zone 15 is limited by the triangular blunt body 13, forming a boundary stable, negative pressure, strong entrainment heat and mass exchange area, improve the residence time of coal powder and temperature rise time. Swirl pipe 9 tangential nozzle arrangement as shown in Figure 3

[0041] The third air jet 12 is arranged in the dense and thin separator 8, and the thin phase of coal powder collides to form a smaller second recirculation zone 16. Since the third air jet 12 is arranged at the end of the air preheating pipeline 6, it has a longer heating time and a higher jet temperature. Combined with the second recirculation zone 16, it is easier to ignite the thin phase of coal powder, avoids the frequent ignition of the plasma igniter 4, and realizes the self-sustaining stable combustion of the burner under variable load.

[0042] As shown in Figure 6 The inner gear-shaped tube 7 at the outlet of the burner is shown in the schematic diagram. The gear-shaped structure can partially block the material of the burner flame outlet, and part of the high temperature flue gas and coal particles are blocked and backflow, returning to the combustion core of the burner, improving the conversion rate of coal and coke and the stable combustion ability of the burner.

[0043] The above is only the preferred embodiment of the present application, it should be noted that for those skilled in the art, without departing from the technical principles of the present application, can make a number of improvements and modifications, these improvements and modifications should be considered as the protection scope of the present application.​​

Claims

1. A coal dust spin-stabilized preheating and multi-stage recirculation based stable combustion burner, characterized by, The application relates to a coal powder combustion device, which comprises the following parts: an outer barrel, two sides of which in the extending direction form a wind powder inlet (1) and a flame spraying outlet (3) respectively; a thick-thin separator (8) arranged in the outer barrel, a spiral pipe (9) being arranged between the outer wall of the thick-thin separator (8) and the inner wall of the outer barrel; a plasma igniter (4), the ignition end of which extends into the inlet end of the thick-thin separator (8); a triangular bluff body (13) arranged around the position of the spiral pipe nozzle (14) on the inner wall of the outer barrel; an air preheating pipe (6) comprising a compressed air inlet (2) on one side of the flame spraying outlet (3), a third air nozzle (12) extending into the thick-thin separator (8) through the outlet end of the thick-thin separator (8), and a first air nozzle (10) and a second air nozzle arranged at the position of the spiral pipe nozzle (14); primary wind powder enters the thick-thin separator (8) through the wind powder inlet (1) and is separated into thick-phase coal powder and thin-phase coal powder; the thick-phase coal powder enters the spiral pipe (9), and the thick-phase coal powder is sprayed out of the spiral pipe nozzle (14) and collides with high-temperature air sprayed out of the first air nozzle (10) and the second air nozzle to form a first recirculation zone (15) limited by the triangular bluff body (13); the thin-phase coal powder enters the thick-thin separator (8) through the inlet end of the thick-thin separator (8) and collides with high-temperature air sprayed out of the third air nozzle (12) to form a second recirculation zone (16).

2. The coal dust spin-preheating and multi-stage recirculation based stable burner of claim 1, wherein, the flame spraying outlet (3) is provided with an inner gear-shaped pipe (7) coaxially arranged with the outer barrel.

3. The coal dust spin-venting preheating and multi-stage recirculation based stable burner of claim 1, wherein, the triangular bluff body (13) is provided with two corresponding to the first air nozzle (10) and the second air nozzle, and the two triangular bluff bodies (13) cooperate with the air preheating pipe (6) between the first air nozzle (10) and the second air nozzle to stabilize the elliptical boundary of the first recirculation zone (15).

4. The coal dust spin-preheating and multi-stage recirculation based stable burner of claim 3, wherein, the jet directions of the first air nozzle (10) and the second air nozzle are arranged to be tangent to the elliptical boundary of the first recirculation zone (15).

5. The coal dust spin-venting preheating and multi-stage recirculation based stable burner of claim 3, wherein, the jet direction of the first air nozzle (10) is consistent with the axial direction of the air preheating pipe (6), and the jet direction of the second air nozzle forms an angle of 60 degrees with the axial direction of the air preheating pipe (6).

6. The coal dust spin-venting preheating and multi-stage recirculation based stable burner of claim 1, wherein, the first air nozzle (10) and the second air nozzle each comprise four small nozzles with a diameter of 2 mm.

7. The coal dust spin-venting preheating and multi-stage recirculation based stable burner of claim 1, wherein, the jet direction of the third air nozzle (12) is consistent with the axial direction of the air preheating pipe (6).

8. The coal dust spin-venting preheating and multi-stage recirculation based stable burner of claim 1, wherein, the air preheating pipe (6) is coaxially arranged with the outer barrel.

9. The coal dust spin-venting preheating and multi-stage recirculation based stable burner of claim 1, wherein, the temperature of the spiral pipe nozzle (14) is in the range of 573 K to 673 K.

10. The coal dust spin-venting preheating and multi-stage recirculation based stable burner of claim 1, wherein, an initial pressure of 60 Pa is applied to the compressed air inlet (2).

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