Cavity trapped vortex coal-fired boiler

Abstract

The invention discloses a concave cavity trapped vortex coal-fired boiler which comprises a hearth and a concave cavity trapped vortex boiler core body arranged in the hearth, and a secondary air conveying and reheating channel, an auxiliary combustion stage secondary air channel and a main combustion stage secondary air channel are arranged in the concave cavity trapped vortex boiler core body. A plurality of auxiliary combustion level direct-current combustors and a plurality of main combustion level direct-current combustors are arranged on the outer wall of the cavity trapped vortex boiler core body, and the main combustion level direct-current combustors are communicated with the secondary air conveying and reheating channel and the main combustion level secondary air channel. And the secondary combustion level direct-current combustor is communicated with the secondary air conveying and reheating channel and the secondary combustion level secondary air channel. The boiler can weaken the influence of coal type change on the starting performance and the load regulation performance of the coal-fired boiler.

Description

Technical Field

[0001] The invention belongs to the technical field of coal-fired boilers and relates to a concave cavity trapped vortex coal-fired boiler. Background Art

[0002] Coal-fired boilers are common main equipment in thermal power plants and are widely used in supercritical and ultra-supercritical generating units. Coal-fired boilers have good economy, stable and reliable boiler output, and high steam quality. However, the existing coal-fired boilers have the problem that the startup and load regulation processes are greatly affected by the coal type.

[0003] Publication No. CN107314366A discloses a π-type gas boiler using secondary air technology, the main body of which includes a boiler furnace and several gas burners, characterized in that the boiler furnace includes a front wall, left and right side walls, a rear wall and a furnace cavity provided with a main combustion zone, a reburning zone, a burnout zone and a secondary air action zone, the gas burners are arranged in layers on the front wall, the throat diameter of which is d, and include an uppermost burner and several lower burners, wherein: the secondary air action zone is composed of the furnace space between the front wall secondary air layout area arranged on the front wall and the side wall secondary air layout area arranged on the left and right side walls; the front wall secondary air layout area is arranged at the center elevation of the uppermost burner and at a distance from the uppermost burner. On the front wall in the area 10d above the center elevation of the burner; the side wall secondary air layout area is arranged on the left and right side walls at a distance d from the front wall and 10d below the center elevation of the uppermost burner; the front wall secondary air layout area and the side wall secondary air layout area are respectively regularly or irregularly provided with a plurality of secondary air nozzles in one or more layers, with several nozzles on each layer; the main combustion zone includes a confined space formed by the front wall and the left and right side walls within a distance d from the front wall, and the lower space of the furnace corresponding to the lower burner; the reburning zone is composed of the middle and lower part of the secondary air action zone and the intersection space adjacent to the main combustion zone; the burnout zone is composed of the space located in the secondary air action zone The upper space of the furnace between the upper part of zone 17 and the furnace outlet is composed; when working, the combustion air required by the gas boiler is divided into two stages and fed into the furnace. One is that 70%-95% of the combustion air enters the main combustion zone through the gas burner, so that the excess air coefficient in the main combustion zone is between 0.7-1, thereby making the fuel burn in an oxygen-deficient environment, resulting in a slow combustion speed and a low combustion temperature. At the same time, since the fuel burns in an oxygen-deficient reducing atmosphere, a large number of nitrogen-containing groups react with NOx, which increases the conversion rate of NOx to N2, thereby inhibiting the generation of NOx, which is beneficial to reducing the generation of NOx in the main combustion zone; the second is that the remaining 5%-30% of the combustion air is passed through the gas burners set on the front wall and left and right sides of the boiler. The secondary air nozzles on the wall send air into the furnace, forming a secondary air action zone in the furnace, so that the fuel that was not fully burned in the main combustion zone continues to burn in the reburning zone located near the middle and lower part of the secondary air action zone, and the NOx originally generated in the main combustion zone is further reduced, and then enters the burnout zone located between the upper part of the secondary air action zone and the furnace outlet area to continue burning until it is burned out; although the burnout zone is close to the furnace outlet and the internal air volume is sufficient to ensure that the fuel can be fully burned, the flame temperature is low, so the final NOx generation is not large, and since the previously unburned fuel can be fully burned, the CO generation is almost zero, which can ensure that the quality of the flue gas discharged from the furnace and the temperature rise are within the standard allowable range.

[0004] However, different types of coal contain varying proportions of volatile matter, moisture, ash, and fixed carbon. For example, in a chamber-fired furnace, changes in the type of coal supplied can significantly alter the boiler's startup and load regulation characteristics, regardless of whether the coal type is direct injection, tangential combustion, or swirl-opposed combustion. Improving the combustion organization and internal structural design of coal-fired boilers, ensuring that their startup and load regulation performance are largely unaffected by changes in coal type, has significant engineering significance for improving the economic efficiency and power response speed of thermal power plants. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a cavity trapped vortex coal-fired boiler, which can reduce the impact of coal type changes on the starting performance and load regulation performance of the coal-fired boiler.

[0006] To achieve the above-mentioned objectives, the present invention discloses a concave cavity trapped vortex coal-fired boiler, comprising a furnace and a concave cavity trapped vortex boiler core body arranged in the furnace, wherein the concave cavity trapped vortex boiler core body is provided with a secondary air delivery and reheating channel, an auxiliary combustion stage secondary air channel and a main combustion stage secondary air channel, and the outer wall of the concave cavity trapped vortex boiler core body is provided with a plurality of auxiliary combustion stage DC burners and a plurality of main combustion stage DC burners, wherein the main combustion stage DC burners are connected with the secondary air delivery and reheating channel and the main combustion stage secondary air channel, and the auxiliary combustion stage DC burners are connected with the secondary air delivery and reheating channel and the auxiliary combustion stage secondary air channel.

[0007] The further improvement of the cavity trapped vortex coal-fired boiler of the present invention is:

[0008] Furthermore, a main combustion stage angular vortex ring wall and a secondary combustion stage trapped vortex ring wall are provided on the inner wall of the furnace, and the secondary combustion stage trapped vortex ring wall is located below the main combustion stage angular vortex ring wall.

[0009] Furthermore, each main combustion stage DC burner is located above the main combustion stage angular vortex ring wall, and each auxiliary combustion stage DC burner is located between the auxiliary combustion stage trapped vortex ring wall and the main combustion stage angular vortex ring wall.

[0010] Furthermore, the direct current burners of each main combustion stage are evenly distributed along the circumferential direction.

[0011] Furthermore, the direct current burners of each auxiliary combustion stage are evenly distributed along the circumferential direction.

[0012] Furthermore, the secondary air delivery and reheating channel extends along the center of the concave cavity trapped vortex boiler core body through the outer wall of the backward concave cavity trapped vortex boiler core body to the main combustion stage direct current burner and the auxiliary combustion stage direct current burner.

[0013] Furthermore, the wall surface of the furnace is provided with a water-cooled wall.

[0014] Furthermore, water-cooled walls are arranged inside the main combustion stage corner vortex ring wall and the secondary combustion stage trapped vortex ring wall.

[0015] Furthermore, the core body of the cavity trapped vortex boiler is located at the center of the furnace.

[0016] The present invention discloses a concave cavity trapped vortex coal-fired boiler, comprising a furnace and a concave cavity trapped vortex boiler core body arranged in the furnace, wherein a secondary air conveying and reheating channel, a secondary combustion stage secondary air channel, and a main combustion stage secondary air channel are arranged in the concave cavity trapped vortex boiler core body, and a plurality of secondary combustion stage direct current burners and a plurality of main combustion stage direct current burners are arranged on the outer wall of the concave cavity trapped vortex boiler core body, wherein the main combustion stage direct current burners are connected to the secondary air conveying and reheating channel and the main combustion stage secondary air channel, and the secondary combustion stage direct current burners are connected to the secondary air conveying and reheating channel and the secondary combustion stage secondary air channel;

[0017] The inner wall of the furnace is provided with a main combustion stage angular vortex ring wall and a secondary combustion stage trapped vortex ring wall, and the secondary combustion stage trapped vortex ring wall is located below the main combustion stage angular vortex ring wall;

[0018] Each main combustion stage DC burner is located above the main combustion stage angular vortex ring wall, and each auxiliary combustion stage DC burner is located between the auxiliary combustion stage trapped vortex ring wall and the main combustion stage angular vortex ring wall;

[0019] The secondary air delivery and reheating channel extends along the center of the concave cavity trapped vortex boiler core body through the outer wall of the backward concave cavity trapped vortex boiler core body to the main combustion stage direct current burner and the auxiliary combustion stage direct current burner.

[0020] The present invention has the following beneficial effects:

[0021] During the specific operation of the cavity trapped vortex coal-fired boiler described in the present invention, the secondary air preheated once by the air preheater is reheated in the secondary air conveying and reheating channel, and the reheated secondary air is supplied to the auxiliary combustion stage DC burner and the main combustion stage DC burner for combustion, which effectively improves the boiler startup and load regulation performance, greatly reduces the impact of coal type changes on the performance of the coal-fired boiler, and enables the coal-fired boiler to be suitable for multiple categories and qualities of coal at the same time, which is beneficial to improving the overall economy of the generator set and the power response speed of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0023] Figure 1 It is a structural diagram of the present invention;

[0024] Figure 2 Position diagram of the main combustion stage corner vortex ring wall and the auxiliary combustion stage standing vortex ring wall.

[0025] Among them, 1 is the core body of the concave cavity trapped vortex boiler, 2 is the secondary air delivery and reheating channel, 21 is the secondary air channel of the auxiliary combustion stage, 22 is the secondary air channel of the main combustion stage, 3 is the auxiliary combustion stage direct current burner, 4 is the main combustion stage direct current burner, 5 is the furnace, 6 is the water-cooled wall, 7 is the main combustion stage angular vortex ring wall, 8 is the auxiliary combustion stage trapped vortex ring wall, 9 is the main combustion stage angular vortex area, and 10 is the auxiliary combustion stage concave cavity trapped vortex area. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0027] In the description of the present invention, it is to be understood that the terms “include” and “comprise” indicate the presence of the described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0028] It should also be understood that the terms used in the present specification are only for the purpose of describing particular embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0029] It should be further understood that the term "and / or" as used in the present specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects are in an "or" relationship.

[0030] It should be understood that although the terms "first," "second," and "third" may be used to describe preset ranges in embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are merely used to distinguish one preset range from another. For example, without departing from the scope of embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0031] The word "if," as used herein, may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to the determination" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)," depending on the context.

[0032] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0033] The accompanying drawings illustrate various schematic diagrams of structures according to embodiments disclosed herein. These figures are not drawn to scale; for clarity, some details are exaggerated and some details may be omitted. The shapes of the various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art may design regions / layers with different shapes, sizes, and relative positions as needed.

[0034] As is known to all, the cavity trapped vortex boiler is not a widely used general equipment type. The following is an analysis of its principles, research applications and characteristics:

[0035] Principle of trapped vortex generation: Under certain conditions, a backflow vortex will be generated when the main flow encounters an obstacle. When the fluid flows through an object of a certain shape, due to the effect of viscosity, the airflow will generate a backflow vortex after encountering the obstacle and the vortex will stay in the backflow area, which is called a trapped vortex. In a cavity trapped vortex boiler, a specific cavity structure may be designed to form a trapped vortex when the fluid flows through. Structural features: It may include a cavity structure, as well as components such as fuel supply and air introduction that cooperate with it. For example, it may be possible to draw on the structural features of the trapped vortex combustion chamber and set a blowing device on the front and rear walls of the cavity to form a specific vortex structure in the cavity, stabilize the flame and promote the mixing of fuel and air. During operation, the trapped vortex can stabilize the flame. In a cavity trapped vortex boiler, it may help to maintain stable combustion over a wide range of operating conditions and reduce the occurrence of unstable phenomena such as flameout.

[0036] Example 1

[0037] refer to Figure 1 and Figure 2 The concave cavity trapped vortex coal-fired boiler of the present invention includes a furnace 5 and a concave cavity trapped vortex boiler core body 1 arranged in the furnace 5, wherein the concave cavity trapped vortex boiler core body 1 is provided with a secondary air conveying and reheating channel 2, an auxiliary combustion stage secondary air channel 21 and a main combustion stage secondary air channel 22, and a plurality of auxiliary combustion stage direct current burners 3 and a plurality of main combustion stage direct current burners 4 are provided on the outer wall of the concave cavity trapped vortex boiler core body 1, wherein the main combustion stage direct current burner 4 is connected to the secondary air conveying and reheating channel 2 and the main combustion stage secondary air channel 22, and the auxiliary combustion stage direct current burner 3 is connected to the secondary air conveying and reheating channel The channel 2 is connected to the auxiliary combustion stage secondary air channel 21; the inner wall of the furnace 5 is provided with a main combustion stage angular vortex ring wall 7 and an auxiliary combustion stage trapped vortex ring wall 8, and the auxiliary combustion stage trapped vortex ring wall 8 is located below the main combustion stage angular vortex ring wall 7; each main combustion stage DC burner 4 is located above the main combustion stage angular vortex ring wall 7, and each auxiliary combustion stage DC burner 3 is located between the auxiliary combustion stage trapped vortex ring wall 8 and the main combustion stage angular vortex ring wall 7; the secondary air delivery and reheating channel 2 extends along the center of the concave cavity trapped vortex boiler core body 1 through the outer wall of the backward concave cavity trapped vortex boiler core body 1 to the main combustion stage DC burner 4 and the auxiliary combustion stage DC burner 3.

[0038] Example 2

[0039] To complete this application, please refer to Figure 1 and Figure 2 The concave cavity trapped vortex coal-fired boiler described in the present invention includes a furnace 5 and a concave cavity trapped vortex boiler core body 1 arranged in the furnace 5, wherein the concave cavity trapped vortex boiler core body 1 is provided with a secondary air conveying and reheating channel 2, an auxiliary combustion stage secondary air channel 21 and a main combustion stage secondary air channel 22, and the outer wall of the concave cavity trapped vortex boiler core body 1 is provided with a plurality of auxiliary combustion stage direct current burners 3 and a plurality of main combustion stage direct current burners 4, wherein the main combustion stage direct current burner 4 is connected with the secondary air conveying and reheating channel 2 and the main combustion stage secondary air channel 22, and the auxiliary combustion stage direct current burner 3 is connected with the secondary air conveying and reheating channel 2 and the auxiliary combustion stage secondary air channel 21.

[0040] In this embodiment, a main combustion stage angular vortex ring wall 7 and a secondary combustion stage trapped vortex ring wall 8 are provided on the inner wall of the furnace 5 , and the secondary combustion stage trapped vortex ring wall 8 is located below the main combustion stage angular vortex ring wall 7 .

[0041] In this embodiment, each main combustion stage DC burner 4 is located above the main combustion stage angular vortex ring wall 7, and each auxiliary combustion stage DC burner 3 is located between the auxiliary combustion stage trapped vortex ring wall 8 and the main combustion stage angular vortex ring wall 7.

[0042] In this embodiment, the main combustion stage DC burners 4 are evenly distributed along the circumferential direction; and the auxiliary combustion stage DC burners 3 are evenly distributed along the circumferential direction.

[0043] In this embodiment, the core body 1 of the cavity trapped vortex boiler is located at the center of the furnace 5 .

[0044] In this embodiment, the main combustion stage DC burner 4 and the auxiliary combustion stage DC burner 3 are both DC burners.

[0045] In this embodiment, the number of the main combustion stage DC burners 4 is 6-12; the number of the auxiliary combustion stage DC burners 3 is 6-12.

[0046] In this embodiment, the secondary air delivery and reheating channel 2 extends along the center of the concave cavity trapped vortex boiler core body 1 through the outer wall of the backward concave cavity trapped vortex boiler core body 1 to the main combustion stage direct current burner 4 and the auxiliary combustion stage direct current burner 3.

[0047] In this embodiment, a water-cooled wall 6 is provided on the wall surface of the furnace 5 .

[0048] Example 3

[0049] The present embodiment discloses a working method of a concave cavity trapped vortex coal-fired boiler, wherein the concave cavity trapped vortex coal-fired boiler includes a concave cavity trapped vortex boiler core body 1, a secondary air delivery and reheating channel 2, an auxiliary combustion stage secondary air channel 21, a main combustion stage secondary air channel 22, an auxiliary combustion stage direct current burner 3, a main combustion stage direct current burner 4, a furnace 5, a water-cooled wall 6, a main combustion stage angular vortex ring wall 7, an auxiliary combustion stage trapped vortex ring wall 8, a main combustion stage angular vortex zone 9 and an auxiliary combustion stage concave cavity trapped vortex zone 10. The specific connection relationship is shown in Example 2.

[0050] Specifically, the operating method of the cavity trapped vortex coal-fired boiler includes the following steps:

[0051] The secondary air preheated once by the air preheater is reheated in the secondary air conveying and reheating channel 2. The reheated secondary air is supplied to the auxiliary combustion stage DC burner 3 and the main combustion stage DC burner 4 for combustion, which can effectively improve the ignition and startup performance; the main combustion stage DC burner 4 is equipped with a separate main combustion stage secondary air channel 22, and the auxiliary combustion stage DC burner 3 is equipped with a separate auxiliary combustion stage secondary air channel 21.

[0052] In addition, when operating under low load conditions, only the auxiliary combustion stage DC burner 3 is enabled, and when operating under high load conditions, both the auxiliary combustion stage DC burner 3 and the main combustion stage DC burner 4 are enabled.

[0053] In this embodiment, the main combustion stage angular vortex ring wall 7, the auxiliary combustion stage trapped vortex ring wall 8 and the inner wall of the furnace 5 together constitute the auxiliary combustion stage concave cavity trapped vortex zone 10; the main combustion stage angular vortex ring wall 7 and the inner wall of the furnace 5 constitute the main combustion stage angular vortex zone 9; the auxiliary combustion stage flame forms a large-scale reflux trapped vortex structure in the auxiliary combustion stage concave cavity trapped vortex zone 10, which effectively improves the overall ignition and startup performance of the boiler; the main combustion stage flame forms a smaller-scale angular vortex reflux structure in the main combustion stage angular vortex zone 9, which can ensure the stable combustion of the main combustion stage flame.

[0054] Air from the blower is preheated in the air preheater and then divided into primary and secondary air for combustion in the burner. The secondary air is reheated on the surface of the trapped vortex boiler core 1 via the secondary air transport and reheat channel 2 before being delivered to the corresponding burner via the secondary combustion stage secondary air channel 21 and the primary combustion stage secondary air channel 22. Each burner is equipped with an independent secondary air channel, and the secondary air flow rate is controlled by the valve opening. The primary air is then delivered to the burner along with the qualified pulverized coal in the coal mill.

[0055] The main combustion stage angular vortex ring wall 7 and the auxiliary combustion stage trapped vortex ring wall 8 are inclined at an angle of 10° in the horizontal direction, which facilitates the movement of the remaining slag and ash from the auxiliary combustion stage concave cavity trapped vortex area 10 and the main combustion stage angular vortex area 9 into the ash hopper; water-cooled walls 6 are also distributed in the main combustion stage angular vortex ring wall 7 and the auxiliary combustion stage trapped vortex ring wall 8, which increases the volume of the water-cooled wall 6 in the boiler, which is beneficial to improving the boiler output and efficiency.

[0056] Those skilled in the art will readily identify other embodiments of the present invention after considering the specification and disclosure of the invention. This application is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

[0057] It should be understood that the present invention is not limited to the exact construction described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

[0058] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A cavity trapped vortex coal-fired boiler, characterized in that: The invention comprises a furnace (5) and a concave cavity trapped vortex boiler core body (1) arranged in the furnace (5), wherein a secondary air conveying and reheating channel (2), an auxiliary combustion stage secondary air channel (21) and a main combustion stage secondary air channel (22) are arranged in the concave cavity trapped vortex boiler core body (1), and a plurality of auxiliary combustion stage direct current burners (3) and a plurality of main combustion stage direct current burners (4) are arranged on the outer wall of the concave cavity trapped vortex boiler core body (1), wherein the main combustion stage direct current burners (4) are connected to the secondary air conveying and reheating channel (2) and the main combustion stage secondary air channel (22), and the auxiliary combustion stage direct current burners (3) are connected to the secondary air conveying and reheating channel (2) and the auxiliary combustion stage secondary air channel (21).

2. The cavity trapped vortex coal-fired boiler according to claim 1, characterized in that: A main combustion stage angular vortex ring wall (7) and a secondary combustion stage trapped vortex ring wall (8) are provided on the inner wall of the furnace (5), and the secondary combustion stage trapped vortex ring wall (8) is located below the main combustion stage angular vortex ring wall (7).

3. The cavity trapped vortex coal-fired boiler according to claim 2, characterized in that: Each main combustion stage DC burner (4) is located above the main combustion stage angular vortex ring wall (7), and each auxiliary combustion stage DC burner (3) is located between the auxiliary combustion stage trapped vortex ring wall (8) and the main combustion stage angular vortex ring wall (7).

4. The cavity trapped vortex coal-fired boiler according to claim 1, characterized in that: The main combustion stage direct current burners (4) are evenly distributed along the circumferential direction.

5. The cavity trapped vortex coal-fired boiler according to claim 1, characterized in that: The auxiliary combustion stage direct current burners (3) are evenly distributed along the circumferential direction.

6. The cavity trapped vortex coal-fired boiler according to claim 1, characterized in that: The secondary air conveying and reheating channel (2) extends along the center of the concave cavity trapped vortex boiler core body (1) through the outer wall of the backward concave cavity trapped vortex boiler core body (1) to the main combustion stage direct current burner (4) and the auxiliary combustion stage direct current burner (3).

7. The cavity trapped vortex coal-fired boiler according to claim 1, characterized in that: The wall surface of the furnace (5) is provided with a water-cooled wall (6).

8. The cavity trapped vortex coal-fired boiler according to claim 2, characterized in that: Water-cooled walls (6) are arranged inside the main combustion stage corner vortex ring wall (7) and the auxiliary combustion stage standing vortex ring wall (8).

9. The cavity trapped vortex coal-fired boiler according to claim 1, characterized in that: The core body (1) of the cavity trapped vortex boiler is located at the center of the furnace (5).

10. A cavity trapped vortex coal-fired boiler, characterized in that: The invention comprises a furnace (5) and a concave cavity trapped vortex boiler core body (1) arranged in the furnace (5), wherein a secondary air conveying and reheating channel (2), a secondary combustion stage secondary air channel (21) and a main combustion stage secondary air channel (22) are arranged in the concave cavity trapped vortex boiler core body (1), and a plurality of secondary combustion stage direct current burners (3) and a plurality of main combustion stage direct current burners (4) are arranged on the outer wall of the concave cavity trapped vortex boiler core body (1), wherein the main combustion stage direct current burners (4) are connected to the secondary air conveying and reheating channel (2) and the main combustion stage secondary air channel (22), and the secondary combustion stage direct current burners (3) are connected to the secondary air conveying and reheating channel (2) and the secondary combustion stage secondary air channel (21); A main combustion stage angular vortex ring wall (7) and a secondary combustion stage trapped vortex ring wall (8) are provided on the inner wall of the furnace (5), and the secondary combustion stage trapped vortex ring wall (8) is located below the main combustion stage angular vortex ring wall (7); Each main combustion stage DC burner (4) is located above the main combustion stage angular vortex ring wall (7), and each auxiliary combustion stage DC burner (3) is located between the auxiliary combustion stage trapped vortex ring wall (8) and the main combustion stage angular vortex ring wall (7); The secondary air conveying and reheating channel (2) extends along the center of the concave cavity trapped vortex boiler core body (1) through the outer wall of the backward concave cavity trapped vortex boiler core body (1) to the main combustion stage direct current burner (4) and the auxiliary combustion stage direct current burner (3).

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