CN112050203A

CN112050203A - Annular wall heating type reverse pulverized coal burner

Info

Publication number: CN112050203A
Application number: CN202011026288.1A
Authority: CN
Inventors: 李水清; 宋民航; 黄骞; 马鹏
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2020-09-25
Filing date: 2020-09-25
Publication date: 2020-12-08
Anticipated expiration: 2040-09-25
Also published as: GB202104857D0; GB2600186A; CN112050203B; GB2600186B

Abstract

The invention provides a ring wall heating type reverse pulverized coal burner, comprising: the pre-combustion structure is provided with a pre-combustion chamber and a central injection air pipe communicated with the pre-combustion chamber; the back-spraying assembly comprises a main pulverized coal pipe and a groove-shaped baffle ring, the main pulverized coal pipe is sleeved on the outer side of the pre-burning structure body and is enclosed to form a main pulverized coal airflow channel, the groove-shaped baffle ring is connected to the end part of the main pulverized coal pipe and is partially positioned at the outlet end of the pre-burning structure body, and the groove-shaped baffle ring and the end part of the pre-burning structure body are enclosed to form a back-spraying channel; and the secondary air assembly comprises a secondary air pipe and a hollow turning-on blade, the secondary air pipe is sleeved on the outer side of the main pulverized coal pipe and surrounds the main pulverized coal pipe to form a secondary air channel, and the hollow turning-on blade is arranged at the outlet end of the secondary air channel. Other pipelines and auxiliary structures do not exist in the preheating combustion chamber, so that the annular wall heating type back-spraying pulverized coal burner is simple in structure and high in operation reliability.

Description

Annular wall heating type reverse pulverized coal burner

Technical Field

The invention relates to the technical field of pulverized coal combustion equipment, in particular to an annular wall heating type reverse pulverized coal injection combustor.

Background

With the continuous development of the coal powder processing and combustion utilization technology, for the suspension combustion mode of carrying coal powder by air, the mutual contact and mixing of gas and solid phases are strengthened, so that the suspension combustion mode has great advantages in the aspects of improving the combustion efficiency and the thermal efficiency of a boiler compared with a layer combustion mode. Compared with a large power station boiler, the industrial boiler has a smaller hearth size, so that the retention time of pulverized coal in the boiler is reduced to a great extent, and in order to prolong the retention time of the pulverized coal in the industrial boiler and promote timely temperature rise and ignition of the pulverized coal, a precombustion chamber pulverized coal burner is usually adopted in the industrial boiler to strengthen ignition of the pulverized coal and prolong the retention time of the pulverized coal in a high-temperature area so as to promote burnout of the pulverized coal.

At present, the design of industrial pulverized coal burners is mostly based on specific coal types and full-load operation conditions, and industrial boilers have the characteristics of large coal type difference and wide load adjustment range in the actual operation process, so that pulverized coal burnout difference, unstable combustion and Nitric Oxide (NO) are frequently generated under the operation of burning different coal types and variable loads_x) The discharge amount is high and the like. Meanwhile, for the traditional pulverized coal burner, the structure is more complex and comprises a plurality of groups of movable structural components, such as an airflow spray pipe extending into the pre-combustion chamber type burner and an angle adjusting mechanism of a secondary air swirl vane, so that after the pulverized coal burner is actually operated for a period of time, a series of problems of structural component bending, burning loss, structural clamping and the like exist to different degrees, and the reliability of the operation of the burner is reduced.

Disclosure of Invention

Based on the above, in order to improve the running reliability of the pulverized coal burner and simultaneously keep good high-efficiency combustion, strong stable combustion and low NO of the burner_xThe generating capacity provides an annular wall heating type reverse pulverized coal burner.

The above purpose is realized by the following technical scheme:

an annular wall-heating type pulverized coal burner comprising:

the pre-combustion structure is provided with a pre-combustion chamber and a central injection air pipe communicated with the pre-combustion chamber;

the back-spraying assembly comprises a main pulverized coal pipe and a groove-shaped baffle ring, the main pulverized coal pipe is sleeved on the outer side of the pre-burning structure body and is enclosed to form a main pulverized coal airflow channel, the groove-shaped baffle ring is connected to the end part of the main pulverized coal pipe and is partially positioned at the outlet end of the pre-burning structure body, and the groove-shaped baffle ring and the end part of the pre-burning structure body are enclosed to form a back-spraying channel; and

the secondary air assembly comprises a secondary air pipe and a hollow turning-on blade, the secondary air pipe is sleeved on the outer side of the main pulverized coal pipe and surrounds the main pulverized coal pipe to form a secondary air channel, and the hollow turning-on blade is arranged at the outlet end of the secondary air channel.

In one embodiment, the inlet end inside the pre-combustion structure has an arc-shaped wall surface forming an inward concave space, the inward concave space is communicated with the pre-combustion chamber, and the arc-shaped wall surface is used for blocking and guiding the main pulverized coal airflow to flow.

In one embodiment, the secondary air assembly further comprises a separation pipe, which is arranged in the secondary air passage and is used for separating the secondary air passage into a rotational flow secondary air passage and a direct flow secondary air passage along the radial direction.

In one embodiment, the hollow swing blade has a blade inner passage and a direct-current airflow outlet communicated with the blade inner passage, a plane of the direct-current airflow outlet facing the flow direction of the airflow in the hollow swing blade is arranged in parallel with the central axis of the preheating combustion chamber, and the direct-current airflow outlet is used for conveying direct-current secondary air.

In one embodiment, the secondary air assembly further comprises a secondary air branch pipe, and the secondary air branch pipe is communicated with the direct-current secondary air passage and the blade inner passage.

In one embodiment, the number of the hollow rotation starting blades is multiple, and the hollow rotation starting blades are uniformly distributed along the outer wall of the main pulverized coal pipe;

the number of the secondary air branch pipes is equal to that of the hollow rotation starting blades, and each secondary air branch pipe is communicated with the corresponding blade internal channel of the hollow rotation starting blade.

In one embodiment, the annular wall-heated type pulverized coal burner further comprises a separating ring, the separating ring is arranged on the outer wall of the outlet end of the central jet air pipe, and the separating ring is used for delaying the mixing between the central jet air and the pulverized coal airflow which is reversely jetted.

In one of the embodiments, the inner wall of the pre-combustion structure is made of wear resistant, high temperature resistant steel, ceramic or silicon carbide material;

a cooling pipe may be provided in the pre-burning structure for cooling an inner wall of the pre-burning structure.

In one embodiment, the annular wall-heated type reverse pulverized coal burner further comprises a pulverized coal gas inflow pipe and a pulverized coal concentrator, the pulverized coal gas inflow pipe is connected with the main pulverized coal pipe, the pulverized coal gas inflow pipe and the outer wall of the pre-combustion structure body are enclosed to form a main pulverized coal airflow divergent section, the pulverized coal gas inflow pipe is communicated with the central injection air pipe and the main pulverized coal airflow divergent section, and the pulverized coal concentrator is arranged in the pulverized coal airflow inflow pipe.

In one embodiment, the pulverized coal gas inflow pipe further comprises a direct secondary air divergent section and a rotational secondary air divergent section, and the direct secondary air divergent section and the rotational secondary air divergent section are sequentially sleeved outside the main pulverized coal gas flow divergent section; the upper ends of the direct-current secondary air divergent section and the rotational-flow secondary air divergent section are respectively communicated with the rotational-flow secondary air duct and the direct-current secondary air duct, and air door baffles are arranged in inlet channels of the rotational-flow secondary air duct and the direct-current secondary air duct; the air door baffle is used for adjusting the airflow volume ratio of the rotational flow secondary air channel and the direct current secondary air channel.

After the technical scheme is adopted, the invention at least has the following technical effects:

1) the burner has simple structure and strong reliability

The preheating combustion chamber has no other pipelines and auxiliary structures, so that the problems of high-temperature deformation, abrasion and burning loss of internal structural components of the combustor are fundamentally avoided. Meanwhile, the secondary air swirl strength at the outlet of the burner is adjusted by adjusting the air volume ratio between the swirl secondary air and the direct-current secondary air, and compared with the traditional mode of adjusting the secondary air swirl strength by adjusting the angle of a secondary air blade by adopting a connecting rod structure, the problems of blade blocking and difficult adjustment easily occurring in the traditional mechanism are solved. The combustor has the advantages of simple overall structure, high operational reliability and convenience in processing and maintenance.

2) Promote the coal dust under different coal types and loads to preheat, catch fire and stably burn in time

The main pulverized coal airflow reversely flows in the combustor and the rotational flow secondary air is arranged, a high-temperature smoke internal reflux area and a high-temperature smoke external reflux area are respectively constructed in the combustor and at the outlet of the combustor, so that the rapid heating, pyrolysis and ignition of different coal types are facilitated, the quantity and quality of separated volatile components are improved, particularly for low-volatile coal types, the pulverized coal airflow can be ensured to be heated and ignited in time, and the pulverized coal combustion stability under different loads is enhanced.

3) Flexibly adjusting the distribution position of the high-temperature zone in the combustor

The position of high-temperature flame in the combustor can be flexibly adjusted by adjusting the air quantity and the air speed of the central jet air or the air quantity ratio between the main pulverized coal airflow and the central jet air. Meanwhile, the thermocouple can be further utilized to monitor the flame temperature of a specific section in the combustor, and an automatic control system is combined to flexibly adjust the air quantity and the air speed of central injection air or the air quantity ratio between main pulverized coal airflow and the central injection air, so that the optimal high-temperature area distribution in the combustor is obtained. Specifically, the central jet air which is jetted into the preheating combustion chamber in the central area plays a role in jetting and gathering the peripheral reverse jet main pulverized coal airflow, and on the other hand, the jet strength of the central jet air on the peripheral reverse flow main pulverized coal airflow can be adjusted by adjusting the air quantity and the air speed of the central jet air, so that the negative pressure and the high-temperature flue gas reflux of a reflux area in the combustor are adjusted, the preheating degree of the pulverized coal airflow is adjusted, and the effects of changing the pulverized coal retention time and adjusting the ignition position and the flame center position of the pulverized coal are further achieved.

4) Low Nitrogen Oxides (NO)_x) Generating

By constructing the high-temperature internal reflux region inside the combustor and the high-temperature external reflux region at the outlet, the strong reductive combustion atmosphere inside the combustor and at the outlet can be formed, and NO in the pulverized coal combustion process can be inhibited_xAnd (4) generating. Meanwhile, because the separating ring is arranged between the main pulverized coal airflow which is reversely injected and the central injection air, the central injection air is gradually mixed with the main pulverized coal airflow which flows reversely after being sprayed out from the central injection air pipe for a certain distance, the combustion residence time of the pulverized coal airflow in a strong reducing atmosphere is further prolonged, and NO is inhibited_xAnd (4) generating.

Drawings

FIG. 1 is a schematic structural view of an annular wall-heating type pulverized coal burner of the present invention;

FIG. 2 is a side view of the annular wall-heated pulverized coal burner of FIG. 1;

FIG. 3 is a schematic structural arrangement diagram of a straight-flow secondary air duct and hollow turning vanes inside the annular wall-heating type pulverized coal burner shown in FIG. 1;

FIG. 4 is a schematic structural view of a hollow turning vane of the annular wall heating type pulverized coal burner shown in FIG. 3;

FIG. 5 is a schematic view showing the flow development of the direct secondary air and the swirling secondary air of the annular wall-heated pulverized coal burner shown in FIG. 1;

FIG. 6 is a schematic diagram of the annular wall heating type pulverized coal burner of FIG. 1 with an arrangement of an inlet airflow duct;

FIG. 7 is a schematic view of the annular wall-heated reverse injection pulverized coal burner of FIG. 1 with an embodiment of a pulverized coal concentrator added;

FIG. 8 is a schematic structural view of the annular wall-heated type reverse injection pulverized coal burner shown in FIG. 1 with the addition of another embodiment of a pulverized coal concentrator;

FIG. 9 is a sectional view A-A of the annular wall heated reverse injection pulverized coal burner of FIG. 1 after the use of an integral annular passage for the main pulverized coal stream;

FIG. 10 is a sectional view A-A of the annular wall-heated pulverized coal burner of FIG. 1 after multiple main pulverized coal gas flow subchannels are employed;

FIG. 11 is a schematic view showing the arrangement of cooling tubes in the annular wall-heating type pulverized coal burner shown in FIG. 1;

FIG. 12 is a schematic diagram of the annular wall-heated pulverized coal burner of FIG. 1;

fig. 13 shows the main structural dimension positions of the annular wall thermal type pulverized coal burner shown in fig. 1.

Wherein: 100. an annular wall-heating type reverse pulverized coal burner; 110. a pre-combustion structure; 111. preheating a combustion chamber; 112. a central injection air pipe; 113. an arc-shaped wall surface; 114. a spacer ring; 120. a reverse spraying component; 121. a main pulverized coal pipe; 1211. a primary pulverized coal airflow passage; 122. a groove-shaped baffle ring; 1221. a reverse spray channel; 130. a secondary air assembly; 131. a secondary air duct; 1311. a secondary air channel; 132. a hollow swing blade; 1321. a vane inner passage; 1322. a direct current airflow outlet; 133. a separation tube; 1331. a rotational flow secondary air duct; 1332. a direct current secondary air duct; 134. a secondary air branch pipe; 140. a pulverized coal gas inflow pipe; 141. a pulverized coal gas stream inlet; 142. a main coal dust airflow divergent section; 143. a damper; 144. a direct-current secondary air gradual expansion section; 145. a rotational flow secondary air gradual expansion section; 151. a swirl vane pulverized coal concentrator; 152. a pulverized coal concentrating ring; 160. and (7) cooling the tube.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are not to be considered limiting of the invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a unique embodiment.

Referring to fig. 1 to 3 and 12, the present invention provides an annular wall-heating type pulverized coal burner 100. The annular wall-heating type reverse pulverized coal burner 100 is applied to an industrial pulverized coal boiler. The annular wall-heating type reverse pulverized coal injection burner 100 can realize the dense-dilute staged combustion, the multi-stage high-temperature flue gas backflow and the air staged combustion of pulverized coal, is favorable for the rapid temperature rise, the stable combustion and the burnout of the pulverized coal under different coal types and different load conditions, and reduces NO in the pulverized coal combustion process_xAnd (4) generating. Meanwhile, the annular wall heating type reverse pulverized coal injection burner 100 is simple in overall structure, fundamentally avoids the problems of high-temperature deformation, abrasion and burning loss of internal structural components of the burner, and is convenient to process and maintain; the swirl strength of the secondary air can be adjusted by directly adjusting the airflow volume ratio between the swirl secondary air and the direct-current secondary air, the problems of blade locking and difficult adjustment easily caused by the traditional method for adjusting the swirl strength of the secondary air by adjusting the blade angle are solved, and the working reliability of the annular wall-heated type pulverized coal burner 100 is further ensured.

Referring to fig. 1 to 3 and 12, in an embodiment, an annular wall-heated pulverized coal burner 100 includes a pre-combustion structure 110, a reverse injection assembly 120, and a secondary air assembly 130. The precombustion structure 110 has a preheating combustion chamber 111 and a central ejector air duct 112 communicating with the preheating combustion chamber 111. The back-spray assembly 120 includes a main pulverized coal pipe 121 and a trough-shaped baffle ring 122, the main pulverized coal pipe 121 is sleeved outside the pre-combustion structure 110 and is enclosed to form a main pulverized coal airflow passage 1211, the trough-shaped baffle ring 122 is connected to the end of the main pulverized coal pipe 121 and is partially located at the outlet end of the pre-combustion structure 110, and the trough-shaped baffle ring 122 and the end of the pre-combustion structure 110 are enclosed to form a back-spray passage 1221. The secondary air assembly 130 includes a secondary air pipe 131 and a hollow turning vane 132, the secondary air pipe 131 is sleeved outside the main pulverized coal pipe 121 and encloses with the main pulverized coal pipe 121 to form a secondary air passage 1311, and the hollow turning vane 132 is disposed at an outlet end of the secondary air passage 1311.

The pre-combustion structure 110 is a main structure of the annular wall-heating type reverse pulverized coal injection burner 100, and is used for preheating, igniting and stably combusting pulverized coal airflow. The pre-combustion structure 110 is a hollow structure, the inner space thereof is a pre-combustion chamber 111, and the pulverized coal stream is preheated and combusted in the pre-combustion chamber 111. The pre-combustion structure 110 includes a central air injection pipe 112, one end of the central air injection pipe 112 is located outside the pre-combustion structure 110, and the other end of the central air injection pipe 112 passes through the pre-combustion structure 110 and extends into the preheating combustion chamber 111. And, the central air injection pipe 112 is located on the central axis of the pre-combustion structure 110, and the central air injection pipe 112 plays a guiding role, and is used for delivering the central air injection to the preheating combustion chamber 111 and injecting the central air injection into the preheating combustion chamber 111. Optionally, the central induced air may also be a small amount of air, a small amount of main pulverized coal airflow or light pulverized coal airflow, and the like.

The preheating combustion chamber 111 has an inlet end and an outlet end, the inlet end of the preheating combustion chamber 111 is the end provided with the central injection air duct 112, and the outlet end of the preheating combustion chamber 111 is the end far away from the central injection air duct 112. The cross-sectional area of the preheat combustion chamber 111 increases gradually from the inlet end to the outlet end. Optionally, the central ejector plenum 112 is a tubular structure having a circular or rectangular cross-section.

The back-spray assembly 120 is sleeved outside the pre-combustion structure 110, and the back-spray assembly 120 can convey the pulverized coal airflow along the outside of the pre-combustion structure 110 and guide the pulverized coal airflow into the preheating combustion chamber 111 at the outlet end of the pre-combustion structure 110. Specifically, the reverse injection assembly 120 includes a main pulverized coal pipe 121 and a groove-shaped baffle ring 122. The main pulverized coal pipe 121 is sleeved outside the pre-combustion structure 110, an annular main pulverized coal airflow passage 1211 is defined by the inner wall of the main pulverized coal pipe 121 and the outer wall of the pre-combustion structure 110, and the main pulverized coal airflow passage 1211 is used for conveying the main pulverized coal airflow. Alternatively, the primary coal stream may also be a rich coal stream.

The primary coal stream 1211 has an inlet end and an outlet end. The inlet end of the main pulverized coal airflow passage 1211 is located at one end of the pre-combustion structure 110 having the central injection air duct 112, and the outlet end of the main pulverized coal airflow passage 1211 is disposed at the same side as the outlet end of the pre-combustion structure 110. The main pulverized coal flow is input from the inlet end of the main pulverized coal flow passage 1211 and output from the outlet end. The groove-shaped baffle ring 122 is located at the outlet end of the main pulverized coal pipe 121, and the groove-shaped baffle ring 122 is partially located at the outlet end of the pre-combustion structure 110. That is, the groove-shaped baffle ring 122 covers the main pulverized coal flow passage 1211 and the edge position that shields the outlet end of the preheating combustion chamber 111. Alternatively, the primary pulverized coal flow passage 1211 may be an overall annular passage, or may be a plurality of primary pulverized coal flow subchannels uniformly arranged in the circumferential direction, as shown in fig. 1, 9, and 10.

Referring to fig. 1, 6, 7, 8 and 12, the trough-shaped baffle ring 122 and the edge of the pre-combustion structure 110 enclose a counter-jet passage 1221. After the primary pulverized coal stream enters the primary pulverized coal stream passage 1211 and contacts the groove-shaped baffle ring 122, the primary pulverized coal stream may be ejected along the reverse-injection passage 1221 and flow along the inner wall of the preheating combustion chamber 111 toward the inside of the preheating combustion chamber 111. Optionally, the slotted baffle ring 122 has an inner slot. The inner groove serves as a guide for guiding the main pulverized coal flow in the main pulverized coal flow passage 1211 into the preheating combustion chamber 111. Further, the bottom of the inner groove in the groove-shaped baffle ring 122 is arc-shaped. The edge of the pre-combustion structure 110 extends into the inner groove of the groove-shaped baffle ring 122, so that a U-shaped channel is formed in the groove-shaped baffle ring 122, the outer channel corresponding to the U-shaped channel is connected and communicated with the main pulverized coal gas flow channel 1211, and the inner channel corresponding to the U-shaped channel is connected and communicated with the pre-combustion chamber 111. The inner channel of the U-shaped channel is the reverse-jet channel 1221 to guide the main pulverized coal stream in the U-shaped channel to the preheating combustion chamber 111.

It can be understood that the main pulverized coal stream delivered to the preheating combustion chamber 111 through the reverse injection passage 1221 meets the inner wall of the inlet end of the pre-combustion structure 110, and then is blocked and guided by the arc-shaped wall surface 113 of the pre-combustion structure 110 to turn its direction, so that the main pulverized coal stream is converged near the central region of the pre-combustion structure 110 and is ejected from the outlet end of the preheating combustion chamber 111. That is, the main pulverized coal stream undergoes two reverse flows in the flowing process, the first reverse flow is generated in the reverse injection passage 1221 under the action of the groove-shaped baffle ring 122, and the second reverse flow is generated again under the action of the baffle and guide of the arc-shaped wall surface 113 as the main pulverized coal stream flows along the inner wall of the preheating combustion chamber 111. Alternatively, the arc-shaped wall surface 113 is arranged in a circular arc shape. Of course, in other embodiments of the present invention, the arc-shaped wall 113 may also include a plurality of arcs or be formed by a curve.

The secondary air assembly 130 is sleeved outside the reverse spraying assembly 120, and the secondary air assembly 130 is used for outputting secondary air to the outlet end of the pre-combustion structure 110, supplying air for pulverized coal combustion and constructing a high-temperature flue gas external reflux area at the outlet of the combustor. Specifically, the secondary air assembly 130 includes a secondary air pipe 131 and a hollow swing blade 132. The secondary duct 131 is disposed outside the main pulverized coal duct 121 and surrounds the main pulverized coal duct 121 to form a secondary air passage 1311. An annular secondary air channel 1311 is formed by enclosing the inner wall of the secondary air pipe 131 and the outer wall of the main pulverized coal pipe 121, and the secondary air channel 1311 is used for conveying secondary air.

The secondary air passage 1311 has an inlet end and an outlet end. The inlet end of the secondary air passage 1311 is located at one end of the pre-combustion structure 110 having the central ejector air pipe 112, and the outlet end of the secondary air passage 1311 is disposed at the same side as the outlet end of the pre-combustion structure 110. The overfire air is input from the inlet end of the overfire air duct 1311 and output from the outlet end. The hollow turning-on blade 132 is disposed at an outlet end of the secondary air passage 1311, and the hollow turning-on blade 132 has a turning-on function for guiding the secondary air to flow in a rotating manner. The secondary air in the secondary air channel 1311 can be sprayed at high speed after passing through the hollow turning vanes 132, a low-pressure area is formed in the central area of the high-speed rotating secondary air, the formation of a high-temperature flue gas external backflow area at the outlet of the combustor is promoted, the stable combustion of pulverized coal under different loads and coal types is promoted, the air staged combustion is realized, and NO is reduced_xAnd (4) generating. Optionally, the hollow turning vane 132 is angled with respect to the central axis of the pre-combustion structure 110 for rotating the secondary air flowing through the area outside the hollow turning vane 132 at a high speed.

Two high-temperature internal reflux regions and two high-temperature external reflux regions at the inner part and the outlet of the annular wall-heating type reverse pulverized coal burner 100 are constructed, so that the strong reductive combustion atmosphere at the inner part and the outlet of the annular wall-heating type reverse pulverized coal burner 100 is favorably formed, and NO in the pulverized coal combustion process is inhibited_xAnd (4) generating. Specifically, the arrangement of the reverse flow and the swirling secondary air of the main pulverized coal airflow in the annular wall heating type reverse pulverized coal burner 100 respectively constructs the high-temperature flue gas internal reflux region and the high-temperature flue gas external reflux region in the pre-combustion structure 110 and at the outlet end of the pre-combustion structure 110, which is beneficial to realizing the rapid temperature rise, pyrolysis and ignition of different coal types of airflows, improving the amount and quality of separated volatile components, particularly for low-volatile component coal types, ensuring the timely temperature rise and ignition of the pulverized coal airflow, simultaneously stabilizing the pulverized coal combustion under different loads, and promoting the timely preheating, ignition and stable combustion of different coal types.

In the annular wall-heating type back-spraying pulverized coal burner 100, the high-temperature flame generated by pulverized coal combustion is concentrated in the central area of the preheating combustion chamber 111 where the main pulverized coal airflow is reversely sprayed, and meanwhile, the high-temperature flame located in the central area simultaneously heats the main pulverized coal airflow just sprayed at the inner wall of the adjacent preheating combustion chamber 111, so that the preheating and temperature-raising effect is generated on the main pulverized coal airflow, and the subsequent timely ignition of the main pulverized coal airflow is promoted. Meanwhile, according to the Bernoulli principle, a low-pressure area is formed between high-speed air flows formed at the inner wall of the preheating combustion chamber 111 and the central area, the formed low-pressure area is favorable for entraining surrounding high-temperature flue gas, an internal reflux area positioned in the combustor is formed, ignition and stable combustion of coal dust under different coal types and loads are promoted, and NO is reduced_xAnd (4) generating. In addition, because the separating ring 114 is arranged between the main pulverized coal airflow which is reversely injected and the central injection air, the central injection air is gradually mixed with the main pulverized coal airflow which flows reversely after being sprayed out from the central injection air pipe 112 for a certain distance, the combustion retention time of the pulverized coal airflow in a strong reducing atmosphere is further prolonged, and NO is inhibited_xAnd (4) generating. Optionally, the outlet of the central ejector plenum 112 is coplanar with the end of the spacer ring 114.

The annular wall of the above embodimentWhen the thermal type reverse pulverized coal injection burner 100 works, the central injection air pipe 112 conveys central injection air to the interior of the preheating combustion chamber 111, the main pulverized coal air flow passage 1211 conveys main pulverized coal air flow, the main pulverized coal air flow meets the groove-shaped retaining ring at the outlet, is guided by the groove-shaped retaining ring 122, is sprayed out along the reverse injection passage 1221, flows upwards along the inner wall area of the preheating combustion chamber 111, meets the arc-shaped wall surface 113, is further bent to flow downwards under the guiding action of the arc-shaped wall surface 113, and is converged near the central area of the preheating combustion chamber 111 and sprayed out downwards from the outlet of the preheating structure 110. Meanwhile, the secondary air flows into the secondary air channel 1311, and under the rotation starting action of the hollow rotation starting blade 132, the rotational flow secondary air is ejected from the outlet of the secondary air channel 1311 at a certain tangential speed in a high-speed rotation mode, a low-pressure area is formed in the central area of the high-speed rotation secondary air, ignition and stable combustion of coal dust under different coal types and loads are promoted, and NO is reduced_xAnd (4) generating.

The preheating combustion chamber 111 of the annular wall heating type pulverized coal burner 100 has no other pipelines or auxiliary structures, so that the problems of high-temperature deformation, abrasion and burning loss of internal structural parts of the burner are fundamentally avoided. Meanwhile, the secondary air swirl strength at the outlet of the burner is adjusted by adjusting the air volume ratio between the swirl secondary air and the direct-current secondary air, and compared with the traditional mode of adjusting the secondary air swirl strength by adjusting the angle of a secondary air blade by adopting a connecting rod structure, the problems of blade blocking and difficult adjustment easily occurring in the traditional mechanism are solved. The combustor has the advantages of simple overall structure, high operational reliability and convenience in processing and maintenance. The operation reliability of the annular wall heating type reverse pulverized coal injection burner 100 is ensured, and the burner is simple in overall structure and convenient to process and maintain.

Optionally, the annular wall-heating type pulverized coal burner 100 further includes an airflow adjusting member disposed in the central injecting air duct 112 and the main pulverized coal duct 121 for adjusting the flow rate of the airflow in the corresponding passage. The high-temperature flame position in the pre-combustion structure 110 can be flexibly adjusted by adjusting the air volume of the central jet air or the air volume ratio between the main pulverized coal airflow and the central jet air, and meanwhile, the flame temperature of a specific section in the combustor can be further monitored by using a thermocouple and an automatic control system is combined to flexibly adjust the air volume and the air speed of the central jet air or the air volume ratio between the main pulverized coal airflow and the central jet air, so that the optimal high-temperature area distribution in the combustor is obtained.

The central jet air which is jetted into the interior of the preheating combustion chamber 111 in the central area plays a role in jetting and gathering the peripheral reversely-jetted main pulverized coal airflow on one hand, and on the other hand, the jet strength of the central jet air on the peripheral reversely-flowing main pulverized coal airflow can be adjusted by adjusting the air quantity and the air speed of the central jet air, so that the negative pressure and the high-temperature flue gas reflux of a reflux area in the combustor are adjusted, the preheating degree of the pulverized coal airflow is adjusted, and the effects of changing the retention time of the pulverized coal and adjusting the ignition position of the pulverized coal and the central position of flame are further achieved.

Referring to fig. 1, 6 to 8, in an embodiment, the inlet end inside the pre-combustion structure 110 has an arc-shaped wall 113 forming an inner concave space, the inner concave space is communicated with the pre-combustion chamber 111, and the arc-shaped wall 113 is used for blocking and guiding the main pulverized coal stream flow. That is, the inner side of the pre-combustion structure 110 has an arc-shaped recess, and the inner wall of the arc-shaped recess is the arc-shaped wall surface 113. The convex portion of the arc-shaped wall surface 113 is directed toward the inlet end of the pre-combustion structure 110, i.e., the concave portion of the arc-shaped wall surface 113 is communicated with the preheating combustion chamber 111.

Thus, after the main pulverized coal airflow injected from the reverse injection passage 1221 flows along the inner wall of the preheating combustion chamber 111, the main pulverized coal airflow meets the arc-shaped wall surface 113, and under the blocking and guiding actions of the arc-shaped wall surface 113, the main pulverized coal airflow is turned again to converge toward the middle region of the pre-combustion structure 110 and is ejected from the outlet end of the preheating combustion chamber 111. Alternatively, the arc-shaped wall surface 113 is arranged in a circular arc shape. Of course, in other embodiments of the present invention, the arc-shaped wall 113 may also include a plurality of arcs or be formed by a curve.

Referring to fig. 1, 6 to 8, in an embodiment, the annular wall-heating type pulverized coal burner 100 further includes a separating ring 114, and the separating ring 114 is disposed on an inner wall of the pre-combustion structure 110 and is located on an outer wall of an outlet end of the central injection air duct 112. The separating ring 114 is used for delaying the mixing between the high-speed central jet air ejected from the central jet air pipe 112 and the main pulverized coal airflow which flows in the preheating combustion chamber 111 and flows in the reverse direction, and deepens the air staged combustion effect.

Referring to fig. 1, 3, 6, 7 and 8, in an embodiment, the overfire air assembly 130 further includes a separation tube 133, and the separation tube 133 is disposed inside the overfire air duct 1311 for separating the overfire air duct 1311 into a swirling overfire air duct 1331 at an inner side and a straight overfire air duct 1332 at an outer side in a radial direction. The swirl secondary air duct 1331 is used for conveying swirl secondary air, and the direct-current secondary air duct 1332 is used for conveying direct-current secondary air.

The swirling secondary air flows along the swirling secondary air duct 1331, and after meeting the outer wall surface of the hollow turning vane, because the hollow turning vane 132 and the central axis of the pre-burning structure 110 are arranged at a certain included angle, under the turning action of the hollow turning vane 132, the swirling secondary air is ejected from the outlet of the secondary air duct 1311 at a certain tangential speed in a high-speed rotation manner, a low-pressure area is formed in the central area of the high-speed rotation secondary air, the formation of a high-temperature flue gas outer backflow area at the outlet of the combustor is promoted, the stable burning of pulverized coal under different loads and coal types is further promoted, the air staged combustion is realized, and the NO is reduced_xAnd (4) generating. Meanwhile, the direct-current secondary air flows in along the direct-current secondary air passage 1311, flows through the secondary air branch pipes 134 and the blade inner passages 1321, and is finally ejected out of the direct-current air flow outlets 1322 in a direction parallel to the central axis of the preheating combustion chamber 111, so that the tangential velocity of the air flow approaches zero, and the direct-current secondary air is formed.

Referring to fig. 3 to 5, in an embodiment, the hollow turning vane 132 has a vane inner passage 1321 and a dc airflow outlet 1322 communicated with the vane inner passage 1321, the vane inner passage 1321 is also communicated with a dc secondary air duct 1332, a plane at the dc airflow outlet 1322 facing the airflow direction in the hollow turning vane 132 is parallel to the central axis of the preheating combustion chamber 111, the dc airflow outlet is used for conveying dc secondary air, and the dc airflow outlet 1322 is used for conveying dc secondary air. The overall secondary air swirl strength at the outlet of the pre-combustion structure 110 can be adjusted by adjusting the air volume ratio between the swirl secondary air and the direct-current secondary air, so that the overall secondary air swirl strength at the outlet of the pre-combustion structure 110 can be flexibly adjusted by adjusting the air distribution.

In one embodiment, the overfire air assembly 130 further includes an overfire air manifold 134, the overfire air manifold 134 communicating the DC overfire air duct 1332 with the blade interior passages 1321. The overfire air branch 134 is used to convey overfire air from the overfire duct 1332 into the blade interior passages 1321. The direct-current secondary air flows along the direct-current secondary air duct 1332, and respectively flows into the secondary air branch pipes 134 communicated with the direct-current secondary air duct, then enters the blade inner passages 1321 in the hollow swing blades 132, flows along the blade inner passages 1321, and is finally ejected out of the direct-current air flow outlets 1322, so that the direct-current secondary air can be ejected out along the direction parallel to the central axis of the preheating combustion chamber 111 under the guiding action of the direct-current air flow outlets 1322.

In one embodiment, the number of the hollow turning vanes 132 is plural, and the plural hollow turning vanes 132 are uniformly distributed along the outer wall of the main pulverized coal pipe 121. The number of sub-air branch pipes 134 is equal to the number of the hollow swing blades 132, and each sub-air branch pipe 134 communicates with the blade internal passage 1321 of the corresponding hollow swing blade 132. The plurality of hollow turning-on blades 132 can ensure that the swirling secondary air and the direct-current secondary air are uniformly distributed along the outlet end of the main pulverized coal pipe 121 and flow out at a high speed.

In one embodiment, the inner wall of the pre-combustion structure 110 is made of wear resistant, high temperature resistant steel, ceramic, or silicon carbide material. That is, the wall surface of the preheating combustion chamber 111 can be processed by wear-resistant and high-temperature-resistant steel, and can also be lined with ceramic or silicon carbide material, so that the working reliability of the inner wall of the preheating combustion chamber 111 can be ensured, and the problems of abrasion and overheating of the inner wall surface can be prevented.

Optionally, a cooling tube 160 is provided in the pre-burning structure 110, the cooling tube 160 being used to cool the inner wall of the pre-burning structure 110. This may enhance wall cooling. As shown in fig. 11, the cooling pipe 160 is annularly provided in the precombustion structure 110, and the inner wall of the precombustion structure 110 is cooled by the cooling pipe 160. Alternatively, the cooling liquid in the cooling pipe 160 is cooling water, a refrigerant, or other media capable of cooling.

Referring to fig. 1 and 6, in an embodiment, the annular wall-heated type pulverized coal burner 100 further includes a pulverized coal gas inflow pipe 140, the pulverized coal gas inflow pipe 140 is located at an upper end portion of the pre-combustion structure 110, the pulverized coal gas inflow pipe 140 has a pulverized coal gas flow inlet 141, and the pulverized coal gas inflow pipe 140 and an outer wall of the pre-combustion structure 110 are enclosed to form a main pulverized coal gas flow divergent section 142. The pulverized coal gas stream inlet 141 is connected and communicated with the main pulverized coal gas stream divergent section 142. The outlet of the main pulverized coal airflow divergent section 142 is connected and communicated with the inlet of the main pulverized coal airflow channel 1211; the pulverized coal airflow inlet 141 is arranged coaxially with the central ejector air duct 112.

In an embodiment, the pulverized coal airflow inlet pipe 140 further includes a direct secondary air divergent section 144 and a rotational secondary air divergent section 145, and the direct secondary air divergent section 144 and the rotational secondary air divergent section 145 are sequentially sleeved outside the main pulverized coal airflow divergent section 142. The upper ends of the direct-current secondary air divergent section and the rotational-flow secondary air divergent section are respectively communicated with a rotational-flow secondary air duct and a direct-current secondary air duct, and air door baffles 143 are arranged in inlet channels of the rotational-flow secondary air duct and the direct-current secondary air duct; the damper baffle 143 is used to adjust the airflow rate of the swirl secondary duct 1331 to the dc secondary duct 1332.

Optionally, the damper baffle 143 is disposed in the secondary air duct 1311, and the damper baffle 143 is used to adjust an air volume ratio between the swirling secondary air duct 1331 and the direct-flow secondary air duct 1332 in the secondary air duct 1311. The effect of adjusting the overall secondary air swirl strength at the outlet end of the pre-combustion structure 110 can be achieved by adjusting the air volume ratio between the swirl secondary air and the direct-current secondary air, and the problems of blade blocking and difficult adjustment easily occurring in the conventional mechanism are solved compared with the traditional method of adjusting the secondary air swirl strength by adopting a connecting rod structure. The combustor has the advantages of simple overall structure, high operational reliability and convenience in processing and maintenance.

Referring to fig. 1, 6 to 8, in an embodiment, the annular wall-heating type reverse pulverized coal burner 100 further includes a pulverized coal concentrator, the pulverized coal gas inflow pipe 140 is connected to the main pulverized coal pipe 121, the pulverized coal gas inflow pipe 140 communicates the central injection air duct 112 and the main pulverized coal gas flow passage 1211, and the pulverized coal concentrator is disposed in the main pulverized coal pipe 121. Optionally, a pulverized coal concentrator is provided in the inlet center region of the pulverized coal airflow inlet 141.

In the operation process of the annular wall-heating type reverse pulverized coal burner 100, the main pulverized coal airflow firstly enters from the pulverized coal airflow inlet 141 at the upper end of the pulverized coal airflow inflow pipe 140 and meets the pulverized coal concentrator, and after pulverized coal particles in the airflow impact the pulverized coal concentrator, the pulverized coal particles are easily rebounded to the near-wall area of the pulverized coal airflow inlet 141 under the inertia effect, so that a concentrated pulverized coal airflow with high-concentration pulverized coal particles is formed, and a light pulverized coal airflow with low-concentration pulverized coal particles is formed in the axis area of the pulverized coal airflow inlet 141. Accordingly, the rich pulverized coal stream flows into the main pulverized coal stream divergent section 142 and the main pulverized coal stream passage 1211 in sequence, and the lean pulverized coal stream flows into the central injection duct 112.

Alternatively, the pulverized coal concentrator may be a pulverized coal concentrating ring 152 using inertial separation, or a swirl vane pulverized coal concentrator 151 using centrifugal separation. After the annular wall heating type reverse pulverized coal injection burner 100 is additionally provided with the pulverized coal concentrator, the thick-thin combustion of the pulverized coal can be further constructed, the ignition and stable combustion of the pulverized coal are promoted, and the NO is reduced_xAnd (4) generating. Specifically, the annular wall-heating type reverse pulverized coal burner 100 further includes a pulverized coal gas inflow pipe 140 and a pulverized coal concentration ring 152, the pulverized coal gas inflow pipe 140 communicates the central injection air pipe 112 and the main pulverized coal gas flow divergent section, and the pulverized coal concentration ring is disposed in the main pulverized coal pipe.

In one embodiment, the annular wall-heated type reverse-injection pulverized coal burner further comprises a pulverized coal gas inflow pipe and a swirl vane pulverized coal concentrator, the pulverized coal gas inflow pipe is communicated with the central injection air pipe and the main pulverized coal gas flow divergent section, and the swirl vane pulverized coal concentrator is arranged in the main pulverized coal pipe.

Illustratively, describing the dimensional schematic of the annular wall-heated pulverized coal burner 100 of one embodiment, as shown in fig. 13, the inner diameter of the small-sized end of the preheating combustion chamber 111 is D; the inner diameter of the central injection air pipe 112 is a; the outer diameter of spacer ring 114 is d; the axial dimension of the preheating combustion chamber 111 is H; the maximum distance between the outlet of the reverse-flow passage 1221 and the concave surface of the inner portion of the arc-shaped wall surface 113 is h. Wherein: d is 0.2D to 0.5D; a is 0.02D-0.2D; h is 1.0D-3.0D; h is 0.3H to 0.9H.

Referring to fig. 1 and 12, during the operation of the annular wall-heated pulverized coal burner 100 of the present invention, the central injection air flows in from the central injection air duct 112 and is centrally injected into the interior of the preheating combustion chamber 111 under the guidance of the central injection air duct 112. Meanwhile, the main pulverized coal stream flows in from the inlet end at the upper end of the main pulverized coal stream passage 1211, meets the groove-shaped baffle ring at the outlet of the main pulverized coal stream passage 1211, is guided by the groove-shaped baffle ring, is ejected from the reverse injection passage 1221 along the direction opposite to the initial flow, flows upwards along the inner wall area of the preheating combustion chamber 111, meets the pre-combustion structure 110, is blocked and guided by the arc-shaped wall surface 113 of the pre-combustion structure 110, and is deflected again, so that the main pulverized coal stream is converged near the central area of the pre-combustion structure 110 and is ejected downwards from the outlet of the pre-combustion structure 110. In the process from the main pulverized coal flow gathering to the central area of the pre-combustion structure 110 to the ejection of the pre-combustion structure 110, the separation ring 114 exists between the main pulverized coal flow ejected in the reverse direction and the central jet air, so that the central jet air is ejected from the central jet air pipe 112 for a certain distance and then is gradually mixed with the main pulverized coal flow flowing in the reverse direction. The central jet air jets the main pulverized coal airflow flowing reversely, the main pulverized coal airflow is gradually mixed with the main pulverized coal airflow, and finally the main pulverized coal airflow is jetted out from an outlet of the combustor.

In the pre-combustion structure 110, the high-temperature flame generated by the pulverized coal combustion is concentrated in the central area of the pre-combustion structure 110 where the main pulverized coal airflow is reversely injected, and meanwhile, the high-temperature flame located in the central area simultaneously heats the main pulverized coal airflow just injected from the side wall of the adjacent pre-combustion chamber 111, so as to generate a preheating and temperature-raising effect on the main pulverized coal airflow and promote the timely ignition of the subsequent main pulverized coal airflow. Meanwhile, according to the Bernoulli principle, a low-pressure area is formed between the high-speed air flows formed by the side wall and the central area of the pulverized coal preheating combustion chamber 111, the formed low-pressure area is favorable for entraining high-temperature smoke around, and an internal backflow area positioned in the combustor is formed to promote different combustion modesIgnition and stable combustion of pulverized coal under combustion load with reduced NO_xAnd (4) generating.

Meanwhile, in the secondary air duct 1311 sleeved outside the main pulverized coal airflow duct 1211, the secondary air firstly flows into the secondary air duct 1311 from an inlet at the upper end of the secondary air duct 1311, and respectively flows into the rotational flow secondary air duct 1331 and the direct flow secondary air duct 1332, wherein the airflow entering the rotational flow secondary air duct 1331 is rotational flow secondary air, and the airflow entering the direct flow secondary air duct 1332 is direct flow secondary air. Further, the swirling secondary air flows along the swirling secondary air duct 1331, and after meeting with the outer wall surface of the hollow turning vane 132, because the hollow turning vane 132 and the central axis of the pre-combustion structure 110 are arranged at a certain included angle, under the turning action of the hollow turning vane 132, the swirling secondary air is ejected out from the outlet of the secondary air duct 1311 at a high speed in a rotating manner at a certain tangential speed, a low-pressure area is formed in the central area of the high-speed rotating secondary air, the formation of a high-temperature flue gas outer backflow area at the outlet of the combustor is promoted, and the stable combustion of pulverized coal under different coal types and different loads is promoted.

Meanwhile, the direct-current secondary air flows along the direct-current secondary air duct 1332, and flows into the plurality of secondary air branch pipes 134 communicated therewith, respectively, and then enters the inside of the blade inner passage 1321 in the hollow swing blade 132, and flows along the blade inner passage 1321, and is finally ejected from the direct-current air outlet 1322. Because the plane of the straight-flow airflow outlet facing the airflow flowing direction in the hollow swing blade is parallel to the central axis of the preheating combustion chamber, the airflow is guided to the flowing direction which is the same as the central axis of the pre-combustion structure 110 under the guiding action of the outlet end surface of the straight-flow airflow outlet 1322 in the process of ejecting the airflow from the straight-flow airflow outlet 1322, so that the tangential velocity of the airflow is close to zero, and the direct-flow secondary air is ejected at high speed.

The effect of adjusting the overall secondary air swirl strength at the outlet end of the pre-combustion structure 110 can be achieved by adjusting the air volume ratio between the swirl secondary air and the direct-current secondary air, so that the flexible adjustment of the overall secondary air swirl strength at the outlet of the burner through air distribution adjustment is realized.

By constructing the burner interior andthe two high-temperature internal reflux regions and the external reflux region at the outlet are favorable for forming strong reductive combustion atmosphere in the combustor and at the outlet and inhibiting NO in the pulverized coal combustion process_xAnd (4) generating. Meanwhile, the device is favorable for realizing rapid heating, pyrolysis and ignition of different coal types of air flows, improves the quantity and quality of separated volatile matters, can ensure timely heating and ignition of the coal powder air flows especially for low-volatile coal types, and simultaneously stabilizes coal powder combustion under different loads.

The technical features of the embodiments described above can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. An annular wall-heating type pulverized coal burner, which is characterized by comprising:

2. The annular wall-heated type pulverized coal burner as claimed in claim 1, wherein the inlet end of the interior of the pre-combustion structure has an arc-shaped wall surface forming an inward-concave space, the inward-concave space is communicated with the pre-combustion chamber, and the arc-shaped wall surface is used for blocking and guiding the flow of the main pulverized coal flow.

3. The annular wall-heated type pulverized coal burner as claimed in claim 1, wherein the secondary air assembly further comprises a separation pipe disposed in the secondary air passage for separating the secondary air passage into a swirling secondary air passage and a straight secondary air passage in a radial direction.

4. The annular wall-heated pulverized coal burner as claimed in claim 3, wherein the hollow turning vane has a vane inner passage and a dc flow outlet communicating with the vane inner passage, a plane of the dc flow outlet facing a flow direction of the gas in the hollow turning vane being arranged in parallel with a central axis of the preheating combustion chamber, the dc flow outlet being for delivering a dc overfire air.

5. The annular wall-heated pulverized coal burner of claim 4, wherein the overfire air assembly further comprises an overfire air branch pipe, the overfire air branch pipe communicating the once-through overfire air passage with the blade internal passage.

6. The annular wall-heated type pulverized coal burner as claimed in claim 5, wherein the number of the hollow turning vanes is plural, and the plural hollow turning vanes are uniformly distributed along the outer wall of the main pulverized coal pipe;

7. The annular wall thermal type pulverized coal burner according to any one of claims 1 to 6, further comprising a separation ring disposed on an outer wall of an outlet end of the central injection air duct, wherein the separation ring is configured to delay mixing between the central injection air and the reversely injected pulverized coal airflow.

8. The annular wall-heating type reverse pulverized coal injection burner as claimed in any one of claims 1 to 6, wherein the inner wall of the pre-combustion structure is made of wear-resistant and high-temperature-resistant steel, ceramic or silicon carbide material;

9. The annular wall-heated type pulverized coal burner as claimed in any one of claims 3 to 6, further comprising a pulverized coal gas inflow pipe and a pulverized coal concentrator, wherein the pulverized coal gas inflow pipe is connected with the main pulverized coal pipe, the pulverized coal gas inflow pipe and the outer wall of the pre-combustion structure body are enclosed to form a main pulverized coal airflow divergent section, the pulverized coal gas inflow pipe is communicated with the central injection air pipe and the main pulverized coal airflow divergent section, and the pulverized coal concentrator is arranged in the pulverized coal airflow inflow pipe.

10. The annular wall-heated type reverse pulverized coal burner according to claim 9, wherein the pulverized coal gas inflow pipe further comprises a direct secondary air divergent section and a rotational secondary air divergent section, and the direct secondary air divergent section and the rotational secondary air divergent section are sequentially sleeved outside the main pulverized coal airflow divergent section; the upper ends of the direct-current secondary air divergent section and the rotational-flow secondary air divergent section are respectively communicated with the rotational-flow secondary air duct and the direct-current secondary air duct, and air door baffles are arranged in inlet channels of the rotational-flow secondary air duct and the direct-current secondary air duct; the air door baffle is used for adjusting the airflow volume ratio of the rotational flow secondary air channel and the direct current secondary air channel.