GB2600186A

GB2600186A - Reverse-jet pulverized coal burner with preheating on annular wall

Info

Publication number: GB2600186A
Application number: GB2104857.4A
Authority: GB
Inventors: Li Shuiqing; Song Minhang; Huang Qian; Ma Peng
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2020-09-25
Filing date: 2021-04-06
Publication date: 2022-04-27
Also published as: CN112050203A; GB202104857D0; CN112050203B

Abstract

A reverse-jet pulverized coal burner 100 with preheating on an annular wall includes a pre-combustion structure 110, a reverse-jet assembly 120, and a secondary air assembly 130. The pre-combustion structure includes a preheating combustion chamber 111 and a central ejection pipe 112 that is fluid communicated with the preheating combustion chamber. The reverse-jet assembly includes an annular slot shaped flap 122 connected to an end of a primary pulverized coal pipe 121 and partly located at an outlet end of the pre-combustion structure, and the primary pulverized coal pipe is sleeved outside the pre-combustion structure to form a primary coal-air flow channel 1211 surrounding the pre-combustion structure. A reverse-jet channel 1221 is formed between the annular slot shaped flap and the pre-combustion structure, and the secondary air assembly includes a secondary air pipe 131 and at least one hollow swirl vane 132 at an outlet end of secondary air channel. The secondary air pipe is sleeved outside the primary pulverized coal pipe to form a secondary air channel 1311 surrounding the primary pulverized coal pipe. The arrangement provides a simple structure which is highly reliable in operation.

Description

Attorney Docket No.

REVERSE-JET PULVERIZED COAL BURNER WITH PREHEATING ON ANNULAR WALL

TECHNICAL FIELD

[0001] The present invention relates to the technical field of pulverized coal combustion equipment, and particularly relates to a reverse-jet pulverized coal burner with preheating on an annular wall.

BACKGROUND

[0002] Compared with laminar combustion, the suspension combustion uses air to carry pulverized coal, so that the contact and mixing between gas phase and particle phase are enhanced.

Therefore, the suspension combustion has great advantages in improving combustion efficiency and thermal efficiency of boilers. Compared with large-scale power plant boilers, industrial boilers have smaller furnaces, which greatly reduce the residence time of pulverized coal in the furnaces. In order to strengthen the ignition and prolong the residence time of pulverized coal in high-temperature zones of the furnace to achieve sufficient pulverized coal burnout, a pulverized coal burner with a pre-combustion chamber is often used in the industrial boiler.

100031 At present, an industrial pulverized coal burner is commonly designed for a specific coal type and a full-load operating condition. However, in practical boilers, there are always large variations in coal properties and boiler loads, resulting in unexpected problems such as combustion instability, high carbon content in fly ash, large NO emissions, and severe slagging. In addition, the conventional pulverized coal burners are complicated in structure and have many movable components, such as a central airflow pipe that extends into a pre-combustion chamber of the burner and an angle adjustment mechanism of a secondary air swirl vane. After a period of operation, the pulverized coal burner could more or less have a series of problems, such as thermal deformation and burning damage of components, and component jamming, which reduce reliability of the burner in operation.

SUMMARY

[0004] In view of this, in order to improve reliability of the pulverized coal burner in operation, to maintain high combustion efficiency and strong combustion stability, and to reduce NO emission, Attorney Docket No. the present invention provides a reverse-jet pulverized coal burner with preheating on an annular wall.

[0005] A reverse-jet pulverized coal burner with preheating on an annular wall includes a pre-combustion structure, a reverse-jet assembly, and a secondary air assembly. The pre-combustion structure includes a preheating combustion chamber and a central ejection pipe that is fluid communicated with the preheating combustion chamber. The reverse-jet assembly includes a primary pulverized coal pipe and an annular slot shaped flap. The primary pulverized coal pipe is sleeved outside the pre-combustion structure to form a primary coal-air flow channel surrounding the pre-combustion structure. The annular slot shaped flap is connected to an end of the primary pulverized coal pipe and partly located at an outlet end of the pre-combustion structure. A reverse-jet channel is formed between the annular slot shaped flap and the pre-combustion structure. The secondary air assembly includes a secondary air pipe and at least one hollow swirl vane. The secondary air pipe is sleeved outside the primary pulverized coal pipe to form a secondary air channel surrounding the primary pulverized coal pipe. The hollow swirl vane is disposed at an outlet end of secondary air channel.

[0006] In some embodiments, an inlet end of the pre-combustion structure has an arc wall forming a concave space. The concave space is fluid communicated with the preheating combustion chamber. The arc wall is configured to block and guide a primary coal-air flow.

[0007] In sonic embodiments, the secondary air assembly further includes a separation pipe. The separation pipe is disposed inside the secondary air channel, and is configured to divide the secondary air channel along a radial direction into a swirl-flow secondary air channel and a direct-flow secondary air channel.

[0008] In some embodiments, the hollow swirl vane is provided with an inner channel and a direct-flow outlet fluid communicated with the inner channel. The hollow swirl vane includes a first section and a second section joined to the first section. The first section is obliquely arranged, and an included angle is formed between the first section and a central axis of the preheating combustion chamber. The second section is adjacent to the direct-flow outlet. The second section is parallel to a central axis of the preheating combustion chamber, so that an air flow ejected out from the direct-flow outlet is a direct-flow secondary air.

[0009] In some embodiments, the secondary air assembly further includes at least one secondary air branched pipe. The secondary air branched pipe is fluid communicated with the direct-flow Attorney Docket No. secondary air channel and the inner channel of the hollow swirl vane.

[0010] In some embodiments, the at least one hollow swirl vane is a plurality of hollow swirl vanes. The plurality of hollow swirl vanes are evenly distributed along a circumferential direction on an outer wall of the primary pulverized coal pipe.

[0011] In some embodiments, the at least one secondary air branched pipe is a plurality of secondary air branched pipe, the number of the secondary air branched pipes is equal to the number of the hollow swirl vanes. Each of the secondary air branched pipes is fluid communicated with the inner channel of a corresponding hollow swirl vane.

[0012] In some embodiments, the central ejection pipe is disposed at an inlet end of the pre-combustion structure and located on a central axis of the pre-combustion structure.

[0013] In some embodiments, an end of the annular wall of the pre-combustion structure at the outlet end is extended into an annular slot defined by the annular slot shaped flap, so that the annular slot shaped flap and pre-combustion structure cooperatively form the reverse-jet channel.

[0014] In some embodiments, the reverse-jet channel is a U-shaped channel, an outer end of the U-shaped channel is fluid communicated with the primary coal-air flow channel, an inner end of the U-shaped channel is fluid communicated with the preheating combustion chamber [0015] In some embodiments, the reverse-jet pulverized coal burner further includes a separation annulus disposed at an outlet end of the central ejection pipe. The separation annulus is configured to delay mixing between a central ejection air ejected from the central ejection pipe and the primary coal-air flow flowing along a reverse direction.

100161 In some embodiments, an inner wall of the pre-combustion structure is made of wear-resistant and high-temperature resistant steel, ceramic, or silicon carbide.

[0017] In some embodiments, the burner further includes a cooling pipe disposed in the pre-combustion structure. The cooling pipe is configured to cool the inner wall of the pre-combustion 25 structure [0018] In some embodiments, the reverse-jet pulverized coal burner further includes a coal-air feeding pipe. The coal-air feeding pipe is connected to the primary pulverized coal pipe. A primary coal-air flow gradual expansion section is formed between the coal-air feeding pipe and the outer wall of the pre-combustion structure. The coal-air feeding pipe is fluid communicated with the central ejection pipe and the primary coal-air flow gradual expansion section.

Attorney Docket No. [0019] In some embodiments, the reverse-jet pulverized coal burner further includes a pulverized coal concentrator, and the pulverized coal concentrator is disposed in the primary pulverized coal pipe.

[0020] In some embodiments, the reverse-jet pulverized coal burner further includes a secondary air feeding pipe surrounding the coal-air feeding pipe. A direct-flow secondary air gradual expansion section and a swirl-flow secondary air gradual expansion section is formed between the secondary air feeding pipe and the coal-air feeding pipe. The swirl-flow secondary air gradual expansion section and the direct-flow secondary air gradual expansion section are sequentially sleeved outside the primary coal-air flow gradual expansion section. The swirl-flow secondary air gradual expansion section is fluid communicated with the swirl-flow secondary air channel. The direct-flow secondary air gradual expansion section is fluid communicated with the direct-flow secondary air channel.

[0021] In some embodiments, the reverse-jet pulverized coal burner further includes an air damper valve disposed in an inlet end of each of the swirl-flow secondary air gradual expansion section and the direct-flow secondary air gradual expansion section. The air damper valve is configured to adjust a flow rate ratio of a first flow in the swirl-flow secondary air channel to a second flow in the direct-flow secondary air channel.

100221 The embodiments of the present invention at least have the following technical effects.

[0023] 1) The burner structure is simple and reliable.

[0024] The overall structure of the reverse-jet pulverized coal burner of the present invention is simple, which fundamentally avoids the problems of thermal deformation, abrasion, and burning damage. The intensity of the swirl-flow secondary air at the outlet end of the burner can be adjusted by adjusting the flow rate ratio of swirl-flow secondary air to direct-flow secondary air, which solves the problems of vane jamming and vane adjustment difficulty in the conventional method that adjusts the swirling intensity of the secondary air by adjusting the vane angle. The reverse-jet pulverized coal burner is stable in operation and convenient for processing and maintenance.

[0025] 2) The rapid preheating, ignition, and stable combustion of pulverized coal with different coal types and loads are promoted.

[0026] The high-temperature inner recirculation zone inside the burner and the high-temperature outer recirculation zone at the outlet end of the burner are constructed by the primary coal-air flow reversely flowing inside the burner and the swirl-flow secondary air, which are conducive to rapid Attorney Docket No. heating, devolatilization, and ignition of pulverized coal with different coal types, especially the low-volatile coal, can improve the quantity and quality of precipitated volatiles, and stabilize the combustion of pulverized coal at different loads.

[0027] 3) The distribution of the high-temperature zone in the burner can be flexibly adjusted.

[0028] The location of the high-temperature flames inside the burner can be flexibly adjusted by adjusting the flow rate of the central ejection air or the ratio of the flow rate of the primary coal-air flow to the flow rate of the central ejection air. The flow rate of the central ejection air or the ratio of the flow rate of the primary coal-air flow to the flow rate of the central ejection air can be adjusted through an automatic control system and a thermocouple which monitors the flame temperature at a specific cross section inside the burner, thereby achieving an optimal distribution of the high-temperature zone in the burner. On the one hand, the central ejection air injected into the center of the preheating combustion chamber guides and concentrates the reversely flowing primary coal-air flow from the surrounding area. On the other hand, by adjusting the flow rate and velocity of the central ejection air, the entraining intensity applied on the primary coal-air flow by the central ejection air can be adjusted. As a result, the negative pressure of the inner recirculation zone and the recirculation volume of the high-temperature fluid can be regulated, thereby adjusting preheating degree of the coal-air flow, changing the residence time of pulverized coal, and adjusting the ignition location of pulverized coal and center position of the flames.

[0029] 4) The nitrogen oxide (NON) generation is reduced.

[0030] By constructing the high-temperature inner recirculation zone inside the burner and the high-temperature outer recirculation zone at the outlet end of the burner, strong reductive combustion atmospheres can be formed at these two locations, which is conducive to suppress NO generation during the combustion of pulverized coal. In addition, the separation annulus is located between the central ejection air and the reversely ejected primary coal-air flow, so that the central ejection air will not mix with the primary coal-air flow until flowing for a certain distance, which further prolongs the residence time of the primary coal-air flow in the strong reductive combustion atmosphere, thereby suppressing the NO generation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG 1 is a schematic structural view of a reverse-jet pulverized coal burner with Attorney Docket No. preheating on an annular wall according to an embodiment of the present invention.

[0032] FIG 2 is a side view of the reverse-jet pulverized coal burner shown in FIG 1.

[0033] FIG 3 is a schematic structural view showing direct-flow secondary air channels and hollow swirl vanes arranged inside the reverse-jet pulverized coal burner shown in FIG 1.

[0034] FIG 4 is a schematic structural view of one of the hollow swirl vanes shown in FIG 3.

[0035] FIG 5 is a schematic structural view of flow deployment of a first flow that is to be formed into swirl-flow secondary air and a second flow that is to be formed into direct-flow secondary air in the reverse-jet pulverized coal burner shown in FIG I. [0036] FIG 6 is a schematic structural view of the reverse-jet pulverized coal burner including extended air inflow channels according to an embodiment of the present invention.

[0037] FIG 7 is a schematic structural view of the reverse-jet pulverized coal burner including a pulverized coal concentrator according to an embodiment of the present invention.

[0038] FIG 8 is a schematic structural view of the reverse-jet pulverized coal burner including another pulverized coal concentrator according to another embodiment of the present invention.

[0039] FIG 9 is a cross-sectional view, along the A-A line in FIG 2, of the reverse-jet pulverized coal burner adopting an integrated annular channel for a primary coal-air flow.

100401 FIG. 10 is a cross-sectional view, along the A-A line in FIG 2, of the reverse-jet pulverized coal burner adopting multiple channels for a primary coal-air flow.

[0041] FIG 11 is a schematic structural view showing a cooling pipe arranged in the reverse-jet pulverized coal burner shown in FIG. 1.

[0042] FIG. 12 is a principle view of the reverse-jet pulverized coal burner shown in FIG 1.

[0043] FIG 13 is a schematic structural view showing main structural dimensions of the reverse-jet pulverized coal burner shown in FIG 1.

[0044] Reference numbers in the figures: 100, reverse-jet pulverized coal burner with preheating on an annular wall; 110, pre-combustion structure; 111, preheating combustion chamber; 112, central ejection pipe; 113, arc wall; 114, separation annulus; 120, reverse-jet assembly; 121, primary pulverized coal pipe; 1211, primary coal-air flow channel; 122, annular slot shaped flap; 1221, reverse-jet channel; 130, secondary air assembly; 131, secondary air pipe; 1311, secondary air channel; 132, hollow swirl vane; 1321, inner channel; 1322, direct-flow outlet; 133, separation pipe; 1331, swirl-flow secondary air channel; 1332, direct-flow secondary air channel; 134, secondary air Attorney Docket No. branched pipe; 140, coal-air feeding pipe; 141, coal-air inlet; 142, primary coal-air flow gradual expansion section; 143, air damper valve; 144, direct-flow secondary air gradual expansion section; 145, swirl-flow secondary air gradual expansion section; 151, swirl vane pulverized coal concentrator; 152, pulverized coal concentrating annulus; 160, cooling pipe.

DETAILED DESCRIPTION

[0045] The present invention will now be described in detail with reference to the accompanying drawings and embodiments in order to make the objects, technical solutions, and advantages of the present invention more clear. It should be understood that the specific embodiments described herein are only for explaining the present invention, and not intended to limit the present invention.

[0046] In the present invention, the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", -bottom", "inner", "outer", "clockwise", "counterclockwise", "axial" , "radial", "circumferential", and the like indicate the orientations or positional relationships on the basis of the drawings. These terms are only for describing the present invention and simplifying the description, rather than indicating or implying that the related devices or elements must have the specific orientations, or be constructed or operated in the specific orientations, and therefore cannot be understood as limitations of the present invention.

[0047] In addition, the terms "first" and "second" are used merely as labels to distinguish one element having a certain name from another element having the same name, and cannot be understood as indicating or implying any priority, precedence, or order of one element over another, or indicating the quantity of the element. Therefore, the element modified by "first" or "second" may be one or more. In the description of the present invention, "a plurality of' means at least two, such as two, three, etc., unless otherwise specifically defined.

[0048] In the present invention, unless otherwise clearly specified and defined, the terms -installed", "connected", "coupled", "fixed" and other terms should be interpreted broadly. For example, an element, when referred to as being "installed", "connected", "coupled", "fixed" to another element, unless otherwise specifically defined, may be fixedly connected, detachably connected, or integrated to the other element, may be mechanically connected or electrically connected to the other element, and may be directly connected to the other element or connected to Attorney Docket No. the other element via an intermediate element. For those of ordinary skill in the art, the specific meaning of the above-mentioned terms in the present invention can be understood according to specific circumstances.

[0049] In the present invention, unless otherwise specifically defined, an element, when referred to as being located "on" or "under" another element, may be in direct contact with the other element or contact the other element via an intermediate element. Moreover, the element, when referred to as being located "on", "above", "over" another element, may be located right above or obliquely above the other element, or merely located at a horizontal level higher than the other element; the element, when referred to as being located "under", "below", "beneath" another element, may be located right below or obliquely below the other element, or merely located at a horizontal level lower than the other element.

[0001] It should be noted that an element, when referred to as being "fixed" or "mounted" to another element, may be directly fixed or mounted to the other element or via an intermediate element. Such terms as "vertical", "horizontal", "left", "right" and the like used herein are for illustrative purposes only and are not meant to be the only ways for implementing the present invention [0002] Referring to FIG 1 to FIG 3 and FIG 12, the present invention provides a reverse-jet pulverized coal burner 100 with preheating on an annular wall. The reverse-jet pulverized coal burner 100 can be applied in industrial pulverized coal boilers. The reverse-jet pulverized coal burner 100 of the present invention can realize rich/lean combustion of pulverized coal, multi-stage high-temperature recirculations, and air-staged combustion. The reverse-jet pulverized coal burner has advantages in rapid heating and ignition, stable combustion, and burnout under the conditions of different coal types and different loads, and can reduce the NO generation during the combustion of pulverized coal. The overall structure of the reverse-jet pulverized coal burner 100 of the present invention is simple, which fundamentally avoids the problems of thermal deformation, abrasion, and burning damage, and is convenient for processing and maintenance. The flow rate ratio of swirl-flow secondary air to direct-flow secondary air can be directly adjusted in the reverse-jet pulverized coal burner 100, thereby adjusting the intensity of the swirl-flow secondary air, which solves the problems of vane jamming and vane adjustment difficulty in the conventional method that adjusts the swirling intensity of the secondary air by adjusting the vane angle, so that the reliability of the reverse-jet pulverized coal burner 100 in operation is ensured.

Attorney Docket No. [0003] Referring to FIG 1 to FIG 3 and FIG 12, in an embodiment, the reverse-jet pulverized coal burner 100 with preheating on an annular wall includes a pre-combustion structure 110, a reverse-jet assembly 120, and a secondary air assembly 130. The pre-combustion structure 110 includes a preheating combustion chamber 111 and a central ejection pipe 112 fluid communicated with the preheating combustion chamber 111. The reverse-jet assembly 120 includes a primary pulverized coal pipe 121 and an annular slot shaped flap 122. The primary pulverized coal pipe 121 is sleeved outside the pre-combustion structure 110. At least one primary coal-air flow channel 1211 surrounding the pre-combustion structure 110 is formed between the primary pulverized coal pipe 121 and the pre-combustion structure 110. The annular slot shaped flap 122 is connected to an end of the primary pulverized coal pipe 121 and partly located at an outlet end of the pre-combustion structure 110. A reverse-jet channel 1221 is formed between the annular slot shaped flap 122 and an end of the pre-combustion structure 110 that is surrounded by the annular slot shaped flap 122. The secondary air assembly 130 includes a secondary air pipe 131 and one or more hollow swirl vanes 132. The secondary air pipe 131 is sleeved outside the primary pulverized coal pipe 121. A secondary air channel 1311 surrounding the primary pulverized coal pipe 121 is defined between the primary pulverized coal pipe 121 and the secondary air pipe 131. The hollow swirl vanes 132 are disposed at an outlet end of secondary air channel 1311.

[0004] The pre-combustion structure 110 is the main structure of the reverse-jet pulverized coal burner 100. The pre-combustion structure 110 is configured to realize preheating, ignition, and stable combustion of pulverized coal carried by an air flow. The mixture of the air flow and the pulverized coal carried by the air flow is also called "coal-air flow" in the present invention. The pre-combustion structure 110 is a hollow structure, and its internal space is a preheating combustion chamber 111. The pre-combustion structure 110 includes an annular wall defining the preheating combustion chamber 111. The coal-air flow is preheated and combusted in the preheating combustion chamber 111. The pre-combustion structure 110 includes the central ejection pipe 112. An inlet end of the central ejection pipe 112 is located outside the pre-combustion structure 110, and an outlet end of the central ejection pipe 112 extends through the inlet end of the pre-combustion structure 110 into the preheating combustion chamber 111. In addition, the central ejection pipe 112 is located on the central axis of the pre-combustion structure 110. The central ejection pipe 112 serves as a guide for conveying central ejection air to the preheating combustion chamber 111, that is, injects the central ejection air into the Attorney Docket No. pre-combustion structure 110 along the central axis thereof. Optionally, the central ejection air can also be an amount of air, an amount of primary coal-air flow, or a fuel-lean coal-air flow.

[0005] The pre-combustion structure 110 has an inlet end and an outlet end. The central ejection pipe 112 is disposed at the inlet end of the pre-combustion structure 110. The outlet end of the pre-combustion structure 110 is opposite to and away from the central ejection pipe 112. The cross-sectional area of the preheating combustion chamber 111 gradually increases from the inlet end to the outlet end. Optionally, the central ejection pipe 112 is a tubular member with a circular cross section or a rectangular cross section.

[0006] The reverse-jet assembly 120 is sleeved outside the pre-combustion structure 110. The reverse-jet assembly 120 can convey the coal-air flow along the outer periphery of the pre-combustion structure 110, and guide the coal-air flow to enter the preheating combustion chamber 111 from the outlet end of the pre-combustion structure 110. Specifically, the reverse-jet assembly 120 includes the primary pulverized coal pipe 121 and the annular slot shaped flap 122. The primary pulverized coal pipe 121 is sleeved outside the pre-combustion structure 110. The inner wall of the primary pulverized coal pipe 121 and the outer wall of the pre-combustion structure 110 are coaxially arranged and spaced from each other, thereby defining the primary coal-air flow channel 1211 with an annular shape. The primary coal-air flow channel 1211 is configured for conveying the primary coal-air flow. Optionally, the primary coal-air flow can also be a fuel-rich coal-air flow.

[0007] The primary coal-air flow channel 1211 has an inlet end and an outlet end. The inlet end of the primary coal-air flow channel 1211 is located at the inlet end of the pre-combustion structure 110. The outlet end of the primary coal-air flow channel 1211 is adjacent to the outlet end of the pre-combustion structure 110. The primary coal-air flow is input from the inlet end of the primary coal-air flow channel 1211 and output from the outlet end of the primary coal-air flow channel 1211. The annular slot shaped flap 122 is located at the outlet end of the primary pulverized coal pipe 121, and is partially located at the outlet end of the pre-combustion structure 110. That is, the annular slot shaped flap 122 covers the outlet end of the primary coal-air flow channel 1211 and the periphery of the preheating combustion chamber 111 at the outlet end of the pre-combustion structure 110. Optionally, referring to FIG 1, FIG 9, and FIG 10, the primary coal-air flow channel 1211 can be a single annular channel (as shown in FIG 9), or can include a plurality of primary coal-air flow sub-channels evenly arranged along the circumferential direction of the pre-combustion structure 110 Attorney Docket No. (as shown in FIG 10).

[0008] Referring to FIG 1, FIG 6, FIG 7, FIG 8, and FIG 12, along the axial direction of the reverse-jet pulverized coal burner 100, the cross section of the annular slot shaped flap 122 is curved to have a slot shape; referring to FIG 9 and FIG 10, along the horizontal direction of the reverse-jet pulverized coal burner 100, the cross section of the annular slot shaped flap 122 has an annular shape; as a result, the annular slot shaped flap 122 overall defines an annular slot. The end of the annular wall of the pre-combustion structure 110 at the outlet end is extended into the annular slot, so that the annular slot shaped flap 122 and pre-combustion structure 110 cooperatively define the reverse-jet channel 1221 at the outlet end of the pre-combustion structure 110. After the primary coal-air flow enters the primary coal-air flow channel 1211 and encounters the annular slot shaped flap 122, the flowing direction of the primary coal-air flow can be reversed, so that the primary coal-air flow can be injected from the reverse-jet channel 1221 into the preheating combustion chamber 111, and can flow along the inner wall (i.e., the annular wall) defining the preheating combustion chamber 111. The annular slot shaped flap 122 guides the primary coal-air flow conveyed by the primary coal-air flow channel 1211 into the preheating combustion chamber 111. In an embodiment, the bottom of the annular slot defined by the annular slot shaped flap 122 is arc-shaped. The edge of the pre-combustion structure 110 extends into the annular slot of the annular slot shaped flap 122, thereby forming a U-shaped channel, i.e., the reverse-jet channel 1221, in the annular slot shaped flap 122. An outer end of the U-shaped channel is fluid communicated with the primary coal-air flow channel 1211. An inner end of the U-shaped channel is fluid communicated with the preheating combustion chamber 111.

[0009] After the primary coal-air flow is injected into the preheating combustion chamber 111 via the reverse-jet channel 1221, the primary coal-air flow will encounter an arc wall 113 of the pre-combustion structure 110 at the inlet end of the pre-combustion structure 110. The primary coal-air flow blocked by the arc wall 113 of the pre-combustion structure 110 can be guided reversely back and concentrated at the center of the pre-combustion structure 110, then finally ejected out from the outlet end of the preheating combustion chamber 111. In other words, the primary coal-air flow experiences two flow-direction reverses during the flowing in the reverse-jet pulverized coal burner 100. The first flow-direction reverse is due to the action of the annular slot shaped flap 122, by which the primary coal-air flow reversely flows along the reverse-jet channel 1221. The second flow-direction reverse is that, in the preheating combustion chamber 111, the primary coal-air flow Attorney Docket No. flowing along the inner wall of the pre-combustion structure 110 is blocked and guided by the arc wall 113 to reversely flow once again. In the present embodiment, the arc wall 113 has an arc shape. In other embodiments, the arc wall 113 can also include multiple arc sections or curved walls.

[0010] The secondary air assembly 130 is sleeved outside the reverse-jet assembly 120. The secondary air assembly 130 is configured to convey secondary air to the outlet end of the pre-combustion structure 110, thereby supplying air for combustion of pulverized coal and constructing a high-temperature outer recirculation zone at the outlet end of the burner 100. Specifically, the secondary air assembly 130 includes a secondary air pipe 131 and one or more hollow swirl vanes 132. The secondary air pipe 131 is sleeved outside the primary pulverized coal pipe 121. A secondary air channel 1311 surrounding the primary pulverized coal pipe 121 is formed between the primary pulverized coal pipe 121 and the secondary air pipe 131. More specifically, the inner wall of the secondary air pipe 131 and the outer wall of the primary pulverized coal pipe 121 are coaxially arranged and spaced from each other, thereby defining the secondary air channel 1311 with an annular shape. The secondary air channel 1311 is configured for conveying the secondary air.

[0011] The secondary air channel 1311 has an inlet end and an outlet end. The inlet end of the secondary air channel 1311 is located at the inlet end of the pre-combustion structure 110. The outlet end of the secondary air channel 1311 is adjacent to the outlet end of the pre-combustion structure 110. The secondary air is input from the inlet end of the secondary air channel 1311 and output from the outlet end of the secondary air channel 1311. The hollow swirl vanes 132 are disposed at the outlet end of the secondary air channel 1311. The hollow swirl vanes 132 are configured to form the secondary air into swirling air flows (i.e., swirl-flow secondary air). After passing through the hollow swirl vanes 132, the secondary air conveyed in the secondary air channel 1311 can be swirly spewed out at a high velocity, so that a low pressure zone can be formed in the central area surrounded by the high-velocity swirl-flow secondary air, which will promote the formation of the high-temperature outer recirculation zone at the outlet end of the burner 100, thereby promoting stable combustion of pulverized coal under different conditions in load and coal type, achieving air-staged combustion, and reducing NO generation. Optionally, an included angle is defined by the hollow swirl vane 132 and the central axis of the pre-combustion structure 110, which is configured to swirl the secondary air flowing along the hollow swirl vane 132 at a high velocity.

[0012] By constructing the high-temperature inner recirculation zone inside the reverse-jet Attorney Docket No. pulverized coal burner 100 and the high-temperature outer recirculation zone at the outlet end of the reverse-jet pulverized coal burner 100, strong reductive combustion atmospheres can be formed at these two locations, which is conducive to suppress the NO generation during the combustion of pulverized coal. Specifically, the reverse flowing of the primary coal-air flow in the reverse-jet pulverized coal burner 100 creates the inner recirculation zone for the high-temperature fluid inside the pre-combustion structure 110; and the swirl-flow secondary air creates the outer recirculation zone for the high-temperature fluid at the outlet end of the pre-combustion structure 110, which are conducive to rapid heating, devolatilization, and ignition of pulverized coal with different coal types, especially the low-volatile coal, can improve the quantity and quality of precipitated volatiles, and stabilize the combustion of pulverized coal at different loads.

[0013] Inside the reverse-jet pulverized coal burner 100, the high-temperature flames generated by the combustion of pulverized coal are concentrated at the center of the preheating combustion chamber 111. Simultaneously, the high-temperature flames can heat the adjacent primary coal-air flow flowing along the inner wall of the pre-combustion structure 110, so that the primary coal-air flow that has just entered the preheating combustion chamber 111 can be preheated, and a subsequent rapid ignition of the primary coal-air flow can be promoted. Meanwhile, according to the Bernoulli's principle, a low-pressure zone can be formed between the high-velocity flows at the inner wall and the center of the preheating combustion chamber 111. The low-pressure zone is conducive to entraining the surrounding high-temperature fluid, thereby forming the inner recirculation zone located inside the burner 100, promoting ignition and stable combustion of pulverized coal with different coal types and loads, and reducing NO generation. In an embodiment, the burner 100 includes a separation annulus 114 disposed at the outlet end of the central ejection pipe 112 to extend the flowing distance of the central ejection air before the central ejection air is mixed with the primary coal-air flow. More specifically, the separation annulus 114 is located between the central ejection air and the reversely ejected primary coal-air flow, so that the central ejection air will not mix with the primary coal-air flow until flowing for a certain distance in the preheating combustion chamber 111, which further prolongs the residence time of the primary coal-air flow in the strong reductive combustion atmosphere to suppress the NO generation. In an embodiment, the outlet of the central ejection pipe 112 and the end of the separation annulus 114 are located on the same plane.

[0014] During the operation of the reverse-jet pulverized coal burner 100, the central ejection Attorney Docket No. pipe 112 conveys the central ejection air into the preheating combustion chamber 111. The primary coal-air flow channel 1211 conveys the primary coal-air flow. When encountering the annular slot shaped flap 122 at the outlet end of the primary coal-air flow channel 1211, the primary coal-air flow is reversed by the annular slot shaped flap 122 and injected into the preheating combustion chamber 111 along the reverse-jet channel 1221. Then, the primary coal-air flow flows upward along the inner wall of the preheating combustion chamber 111. After encountering the arc wall 113, the primary coal-air flow is reversed by the arc wall 113 to flow downward, so that the primary coal-air flow is concentrated at the center of the preheating combustion chamber 111, and finally downward ejected out from the outlet end of the pre-combustion structure 110. At the same time, the secondary air flows along the secondary air channel 13 II, and is swirled by the hollow swirl vane 132. The swirl-flow secondary air is swirly ejected at a certain high tangential velocity from the outlet end of the secondary air channel 1311. The central area surrounded by the high-velocity swirling secondary air forms the low pressure zone, which enhances the formation of the outer high-temperature recirculation, and further promotes the ignition and stable combustion of pulverized coal under the conditions of different coal types and different loads, and reduces the NO generation.

[0015] The above-described reverse-jet pulverized coal burner 100 does not need to include other pipelines and auxiliary structures inside the preheating combustion chamber 111, which fundamentally avoids the problems of thermal deformation, abrasion, and burning damage of the components of the burner 100 Meanwhile, the intensity of the swirl-flow secondary air at the outlet end of the burner 100 can be adjusted by adjusting the flow rate ratio of the swirl-flow secondary air to the direct-flow secondary air, which solves the problems of vane jamming and vane adjustment difficulty in the conventional method that adjusts the swirling intensity of the secondary air by adjusting the angle of the secondary air vane through a connecting rod structure. The reverse-jet pulverized coal burner 100 has a simple structure and an enhanced operating reliability, and is convenient for processing and maintenance.

[0016] In an embodiment, the reverse-jet pulverized coal burner 100 further includes airflow adjusting members disposed in the central ejection pipe 112 and the primary pulverized coal pipe 121. The airflow adjusting members are configured to adjust the flow rates of the air flows in the corresponding channels. By adjusting the flow rate of the central ejection air or the ratio of the flow rate of the primary coal-air flow to the flow rate of the central ejection air, e.g., through an automatic Attorney Docket No. control system and a temperature monitor system, the location of the high-temperature flames inside the pre-combustion structure 110 can be flexibly adjusted, thereby achieving an optimal distribution of the high-temperature zone in the burner 100. The flame temperature at a specific cross section inside the burner 100 can be monitored by using a thermocouple.

[0017] On the one hand, the central ejection air injected into the center of the preheating combustion chamber 111 guides and concentrates the reversely flowing primary coal-air flow from the surrounding area. On the other hand, by adjusting the flow rate and velocity of the central ejection air, the guiding and concentrating intensity applied on the primary coal-air flow by the central ejection air can be adjusted. As a result, the negative pressure of the inner recirculation zone and the recirculation volume of the high-temperature fluid can be regulated, thereby adjusting preheating degree of the coal-air flow, changing the residence time of pulverized coal, and adjusting the ignition location of pulverized coal and center position of the flames.

[0018] Referring to FIG I and FIG 6 to FIG 8, in an embodiment, the inlet end of the pre-combustion structure 110 has the arc wall 113 forming a concave space. The concave space is fluid communicated with the preheating combustion chamber 111. The arc wall 113 is configured to block and guide the primary coal-air flow. In other words, the inner side of the pre-combustion structure 110 has an arc-shaped recess, and the inner wall defining the arc-shaped recess is the arc wall 113. The arc wall 113 is recessed toward the inlet end of the pre-combustion structure 110.

[0019] In this way, the primary coal-air flow injected from the reverse-jet channel 1221 flows along the inner wall of the preheating combustion chamber 111 before encountering the arc wall 113.

After the primary coal-air flow is blocked and guided by the arc wall 113, the primary coal-air flow is once again reversed in direction, concentrated at the center of the pre-combustion structure 110, and then ejected out from the outlet end of the preheating combustion chamber 1 II. Optionally, the arc wall 113 has an arc shape. In other embodiments, the arc wall 113 can also include multiple arc sections or curved walls.

[0020] Referring to FIG 1 and FIG 6 to FIG 8, in an embodiment, the reverse-jet pulverized coal burner 100 also includes the separation annulus 114 disposed on the inner wall of the pre-combustion structure 110 and on the outer wall of the outlet end of the central ejection pipe 112. The separation annulus 114 is configured to delay the mixing between the high-velocity central ejection air ejected from the central ejection pipe 112 and the reversely flowing primary coal-air flow in the preheating Attorney Docket No. combustion chamber III to enhance the effect of air-staged combustion.

[0021] Referring to FIG 1, FIG 3, FIG 6, FIG 7 and FIG 8, in an embodiment, the secondary air assembly 130 further includes a separation pipe 133. The separation pipe 133 is disposed inside the secondary air channel 1311, configured to divide the secondary air channel 1311 along a radial direction into a swirl-flow secondary air channel 1331 on the inner side and a direct-flow secondary air channel 1332 on the outer side. The secondary air is divided into a first flow and a second flow by the separation pipe 133. The swirl-flow secondary air channel 1331 is configured to convey the first flow that is to be formed into swirl-flow secondary air, and the direct-flow secondary air channel 1332 is configured to convey the second flow that is to be formed into direct-flow secondary air.

[0022] The first flow flows along the swirl-flow secondary air channel 1331. When the first flow encounters the outer wall of the hollow swirl vane 132, the first flow is swirled by the hollow swirl vane 132 which is arranged at an angle with the central axis of the pre-combustion structure 110, so that the first flow is formed into the swirl-flow secondary air The swirl-flow secondary air is swirly ejected from the outlet end of the secondary air channel 1311 at a certain high tangential velocity to form the low pressure zone in the central area surrounded by the high-velocity swirling secondary air, which promotes the formation of the outer recirculation zone of high-temperature fluid at the outlet end of the burner 100. The formation of the outer recirculation zone can further promote the stable combustion of pulverized coal under the conditions of different coal types and different loads, achieve air-staged combustion, and reduce NO generation. Meanwhile, the second flow flows along the direct-flow secondary air channel 1332, passing through a secondary air branched pipe 134 and an inner channel 1321 of the hollow swirl vane 132, and finally ejected out from a direct-flow outlet 1322 along a direction parallel to the central axis of the preheating combustion chamber 111. A tangential velocity of the second flow ejected out from the direct-flow outlet 1322 is close to zero, so that the second flow is formed into the direct-flow secondary air [0023] Referring to FIG 3 to FIG 5, in an embodiment, the hollow swirl vane 132 is provided with the inner channel 1321 and the direct-flow outlet 1322 that is fluid communicated with the inner channel 1321. The inner channel 1321 is also fluid communicated with the direct-flow secondary air channel 1332. The hollow swirl vane 132 includes a first section and a second section joined to the first section. The second section is adjacent to the direct-flow outlet 1322. The first section is obliquely arranged, so that an included angle is formed between the first section of the hollow swirl Attorney Docket No. vane 132 and the central axis of the preheating combustion chamber 111. The second section is parallel to the central axis of the preheating combustion chamber 111, so that the second flow flowing through the inner channel 1321 can directly encounter the second section of the hollow swirl vane 132, and ejected out from the direct-flow outlet 1322 along the direction parallel to the central axis of the preheating combustion chamber 111. By adjusting the air rate ratio of the swirl-flow secondary air to the direct-flow secondary air, the overall intensity of the swirl-flow secondary air at the outlet end of the pre-combustion structure 110 can be flexibly adjusted.

[0024] In an embodiment, the secondary air assembly 130 further includes at least one secondary air branched pipe 134. The secondary air branched pipe 134 fluid communicates with the direct-flow secondary air channel 1332 and the inner channel 1321. The secondary air branched pipe 134 is configured to transport the second flow from the direct-flow secondary air channel 1332 to the inner channel 1321. The second flow firstly flows along the direct-flow secondary air channel 1332, and then respectively flows into a plurality of secondary air branched pipes 134 that are fluid communicated with the direct-flow secondary air channels 1332, followed by entering the inner channels 1321 of the hollow swirl vanes 132. The second flow flowing along the inner channel 1321 is finally ejected out from the direct-flow outlet 1322 in the direction parallel to the central axis of the preheating combustion chamber 111, as guided by the second section of the hollow swirl vane 132 adjacent to the direct-flow outlet 1322.

[0025] In an embodiment, the reverse-jet pulverized coal burner 100 includes a plurality of hollow swirl vanes 132, and the plurality of hollow swirl vanes 132 are evenly distributed along the circumferential direction on the outer wall of the primary pulverized coal pipe 121. The number of secondary air branched pipes 134 is equal to the number of hollow swirl vanes 132. Each secondary air branched pipe 134 is fluid communicated with the inner channel 1321 of the corresponding hollow swirl vane 132 in a one to one manner. The plurality of hollow swirl vanes 132 can ensure that the multiple flows of swirl-flow secondary air and direct-flow secondary air are evenly distributed around the outlet end of the primary pulverized coal pipe 121 and flow out at a high velocity [0026] In an embodiment, the inner wall of' the pre-combustion structure 110 is made of wear-resistant and high-temperature resistant steel, ceramic, or silicon carbide. In other words, the material of the inner wall of the preheating combustion chamber 111 can be selected from wear-resistant and high-temperature resistant steel, ceramic, or silicon carbide, so that the operating Attorney Docket No. reliability of the inner wall of the preheating combustion chamber 111 can be ensured, and abrasion and overheating of the inner wall can be avoided.

[0027] Optionally, a cooling pipe 160 is disposed in the pre-combustion structure 110. The cooling pipe 160 is configured to cool the inner wall of the pre-combustion structure 110, which can enhance wall cooling. As shown in FIG 11, one or more cooling pipes 160 are annularly or spirally disposed inside the body of the pre-combustion structure 110, surrounding the preheating combustion chamber 111, so that the inner wall of the pre-combustion structure 110 is cooled by the cooling pipe 160. Optionally, the liquid conveyed in the cooling pipe 160 is cooling water, refrigerant, or other fluid that has a cooling effect [0028] Referring to FIG 1 and FIG 6, in an embodiment, the reverse-jet pulverized coal burner further includes a coal-air feeding pipe 140. The coal-air feeding pipe 140 is disposed on the inlet end of the pre-combustion structure 110. The coal-air feeding pipe 140 includes a coal-air inlet 141. A primary coal-air flow gradual expansion section 142 surrounding the inlet end of the pre-combustion structure 110 is formed between the coal-air feeding pipe 140 and the outer wall of the pre-combustion structure 110. The coal-air inlet 141 is connected to and fluid communicated with the primary coal-air flow gradual expansion section 142. The outlet end of the primary coal-air flow gradual expansion section 142 is connected to and fluid communicated with the inlet end of the primary coal-air flow channel 1211. The coal-air inlet 141 and the central ejection pipe 112 are coaxially arranged.

[0029] In an embodiment, the reverse-jet pulverized coal burner 100 further includes a secondary air feeding pipe surrounding the coal-air feeding pipe 140. A direct-flow secondary air gradual expansion section 144 and a swirl-flow secondary air gradual expansion section 145 is formed between the secondary air feeding pipe and the coal-air feeding pipe 140. The swirl-flow secondary air gradual expansion section 145 and the direct-flow secondary air gradual expansion section 144 are sequentially sleeved outside the primary coal-air flow gradual expansion section 142. The swirl-flow secondary air gradual expansion section 145 is fluid communicated with the swirl-flow secondary air channel at the upper end thereof. The direct-flow secondary air gradual expansion section 144 is fluid communicated with the direct-flow secondary air channel at the upper end thereof Each of the inlet end of the swirl-flow secondary air gradual expansion section 145 and the direct-flow secondary air gradual expansion section 144 is provided with an air damper valve 143. The air damper valves 143 Attorney Docket No. are configured to adjust the flow rate ratio of the first flow in the swirl-flow secondary air channel 1331 to the second flow in the direct-flow secondary air channel 1332.

[0030] Optionally, the air damper valves 143 are disposed in the secondary air channel 131 I, and are configured to adjust the flow rate ratio of air flows in the swirl-flow secondary air channel 1331 and the direct-flow secondary air channel 1332. By adjusting the flow rate ratio of the swirl-flow secondary air to the direct-flow secondary air, the overall intensity of the swirl-flow secondary air at the outlet end of the pre-combustion structure 110 can be adjusted, which solves the problems of vane jamming and vane adjustment difficulty in the conventional method that adjusts the swirling intensity of the secondary air by adjusting the angle of the secondary air vane through a connecting rod structure. The reverse-jet pulverized coal burner 100 has a simple structure and an enhanced operating reliability, and is convenient for processing and maintenance.

[0031] Referring to FIG 1 and FIG 6 to FIG 8, in an embodiment, the reverse-jet pulverized coal burner 100 also includes a pulverized coal concentrator. The coal-air feeding pipe 140 is connected to the primary pulverized coal pipe 121. The coal-air feeding pipe 140 is fluid communicated with the central ejection pipe 112 and the primary coal-air flow channel 1211. The pulverized coal concentrator is disposed in the primary pulverized coal pipe 121. Optionally, the pulverized coal concentrator is disposed in the central area of the coal-air inlet 141.

[0032] During the operation of the reverse-jet pulverized coal burner 100, the primary coal-air flow enters from the coal-air inlet 141 of the coal-air feeding pipe 140. When encountering the pulverized coal concentrator, the pulverized coal particles that collide with the pulverized coal concentrator are bounced toward the inner wall of' the coal-air feeding pipe 140 under the inertia, thereby forming the fuel-rich coal-air flow in the near-wall area of the coal-air inlet 141, and forming the fuel-lean coal-air flow in the central axis area of the coal-air inlet 141. The fuel-rich coal-air flow has a high concentration of pulverized coal particles. The fuel-lean coal-air flow has a low concentration of pulverized coal particles. Correspondingly, the fuel-rich coal-air flow flows into the primary coal-air flow gradual expansion section 142, and then flows into the primary coal-air flow channel 1211, while the fuel-lean coal-air flow flows into the central ejection pipe 112.

[0033] Optionally, the pulverized coal concentrator can be a pulverized coal concentrating annulus 152 separating the pulverized coal from the air by inertia, or can be a swirl vane pulverized coal concentrator 151 separating the pulverized coal from the air by centrifugal separation. The Attorney Docket No. reverse-jet pulverized coal burner 100 having the pulverized coal concentrator can further build the rich/lean combustion of pulverized coal, promote the ignition of pulverized coal, stabilize combustion and reduce NO generation. Specifically, the reverse-jet pulverized coal burner 100 also includes the coal-air feeding pipe 140 and the pulverized coal concentrating annulus 152. The coal-air feeding pipe 140 is fluid communicated with the central ejection pipe 112 and the primary coal-air flow gradual expansion section. The pulverized coal concentrating annulus 152 is disposed in the primary pulverized coal pipe 121 [0034] In an embodiment, the reverse-jet pulverized coal burner 100 further includes the coal-air feeding pipe 140 and the swirl vane pulverized coal concentrator 151. The coal-air feeding pipe 140 is fluid communicated with the central ejection pipe 112 and the primary coal-air flow gradual expansion section. The swirl vane pulverized coal concentrator 151 is disposed in the primary pulverized coal pipe 121 [0035] Illustratively, the size of an embodiment of the reverse-jet pulverized coal burner 100 with preheating on the annular wall is described. Referring to FIG 13, the inner diameter of the smaller end of the preheating combustion chamber 111 is D; the inner diameter of the central ejection pipe 112 is a; the outer diameter of the separation annulus 114 is d; the axial dimension of the preheating combustion chamber 111 is H; the maximum distance between the outlet end of the reverse-jet channel 1221 and the arc wall 113 is Ii; wherein d=0.21) to 0.5D, a=0.02D to 0.21,); 11=1.01) to 3.0D; h=0.3H to 0.9H.

[0036] Referring to FIG I and FIG 12, during the operation of the reverse-jet pulverized coal burner 100 of the present invention, the central ejection air flowing through and guided by the central ejection pipe 112 is injected into the preheating combustion chamber 111. Meanwhile, the primary coal-air flow flows into the primary coal-air flow channel 1211 from the inlet end thereof After encountering the annular slot shaped flap 122 at the outlet end of the primary coal-air flow channel 1211, the primary coal-air flow is reversed by the annular slot shaped flap 122 and injected into the preheating combustion chamber 111 along the reverse-jet channel 1221. Then, the primary coal-air flow flows upward along the inner wall of the preheating combustion chamber 111. After encountering the arc wall 113, the primary coal-air flow is reversed by the arc wall 113 to flow downward, so that the primary coal-air flow is concentrated at the center of the preheating combustion chamber 111, and finally downward ejected out from the outlet end of the pre-combustion structure Attorney Docket No. 110. During the primary coal-air flow concentrating at the central area of the pre-combustion structure and ejecting out from the pre-combustion structure 110, the central ejection air will not mix with the primary coal-air flow until flowing for a certain distance in the preheating combustion chamber 111 as the separation annulus is disposed between the primary coal-air flow and the central ejection air. The central ejection air entrains the primary coal-air flow flowing in the opposite direction and gradually mixes with the primary coal-air flow, and finally ejects from the outlet end of the burner 100.

[0037] Inside the pre-combustion structure 110, the high-temperature flames generated by the combustion of pulverized coal are concentrated at the center of the pre-combustion structure 110.

Simultaneously, the high-temperature flames can heat adjacent primary coal-air flow flowing along the inner wall of the preheating combustion chamber 111, so that the primary coal-air flow that has just entered the preheating combustion chamber 111 can be preheated, and a subsequent rapid ignition of the primary coal-air flow can be promoted. Meanwhile, according to the Bernoulli's principle, a low-pressure zone can be formed between the high-velocity flows at the inner wall and the center of the preheating combustion chamber 111. The low-pressure zone is conducive to entraining the surrounding high-temperature fluid, thereby forming the inner recirculation zone located inside the burner 100, promoting ignition and stable combustion of pulverized coal with different coal types and loads, and reducing NO generation.

[0038] Meanwhile, in the secondary air channel 1311 outer surrounding the primary coal-air flow channel 1211, the secondary air flows into the secondary air channel 1311 from the upper inlet end of the secondary air channel 131 I, and respectively flows into the swirl-flow secondary air channel 1331 and the direct-flow secondary air channel 1332, thereby forming a first flow and a second flow. The first flow flows along the swirl-flow secondary air channel 1331. When the first flow encounters the outer wall of the hollow swirl vane 132, the first flow is swirled by the hollow swirl vane 132 which is arranged at an angle with the central axis of the pre-combustion structure 110, so that the first flow is formed into the swirl-flow secondary air. The swirl-flow secondary air is swirly ejected from the outlet end of the secondary air channel 1311 at a certain high tangential velocity to form the low pressure zone in the central area of the high-velocity swirling secondary air, which promotes the formation of the outer recirculation zone of high-temperature fluid at the outlet end of the burner 100.

The formation of the outer recirculation zone can further promote the stable combustion of pulverized Attorney Docket No. coal under the conditions of different coal types and different loads.

[0039] Meanwhile, the second flow flows along the direct-flow secondary air channel 1332, passes through a secondary air branched pipe 134 and an inner channel 1321 of the hollow swirl vane 132, and finally ejects out from a direct-flow outlet 1322 along a direction parallel to the central axis of the preheating combustion chamber 111 at a high velocity A tangential velocity of the second flow ejected out from the direct-flow outlet 1322 is close to zero, and the second flow is thereby formed into the direct-flow secondary air.

[0040] By adjusting the ratio of the flow rate of the direct-flow secondary air to the flow rate of the swirl-flow secondary air, the intensity of the swirl-flow secondary air at the outlet end of the pre-combustion structure 110 can be adjusted, so as to achieve the flexible adjustment of the overall secondary air swirl intensity at the outlet end of the burner 100 by adjusting air distribution.

[0041] By constructing the high-temperature inner recirculation zone inside the reverse-jet pulverized coal burner 100 and the high-temperature outer recirculation zone at the outlet end of the reverse-jet pulverized coal burner 100, high temperature and strong reductive combustion atmospheres can be formed at these two locations, which is conducive to suppress the NO generation during the combustion of pulverized coal, and is conducive to rapid heating, devolatilization, and ignition of pulverized coal with different coal types, especially the low-volatile coal, can improve the quantity and quality of precipitated volatiles, and stabilize the combustion of pulverized coal at different loads.

[0042] The technical features of the above-mentioned embodiments can be combined arbitrarily.

In order to make the description concise, not all possible combinations of the technical features are described in the embodiments. However, as long as there is no contradiction in the combination of these technical features, the combinations should be considered as in the scope of the present application [0043] The above-described embodiments are only several implementations of the present application, and the descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present application. It should be understood by those of ordinary skill in the art, without departing from the concept of the present application, various modifications and improvements can be made and all fall within the protection scope of the present application.

Therefore, the patent protection of the present application shall be defined by the appended claims.

Claims

Attorney Docket No.CLAIMSWhat is claimed is: 1. A reverse-jet pulverized coal burner with preheating on an annular wall, characterized in that the burner comprises: a pre-combustion structure comprising a preheating combustion chamber and a central ejection pipe that is fluid communicated with the preheating combustion chamber; a reverse-jet assembly comprising a primary pulverized coal pipe and an annular slot shaped flap, wherein the primary pulverized coal pipe is sleeved outside the pre-combustion structure to form a primary coal-air flow channel surrounding the pre-combustion structure, the annular slot shaped flap is connected to an end of the primary pulverized coal pipe and partly located at an outlet end of the pre-combustion structure, a reverse-jet channel is formed between the annular slot shaped flap and the pre-combustion structure; and a secondary air assembly comprising a secondary air pipe and at least one hollow swirl vane, wherein the secondary air pipe is sleeved outside the primary pulverized coal pipe to form a secondary air channel surrounding the primary pulverized coal pipe, the hollow swirl vane is disposed at an outlet end of secondary air channel.
2. The reverse-jet pulverized coal burner according to claim 1, wherein an inlet end of the pre-combustion structure has an arc wall forming a concave space, the concave space is fluid communicated with the preheating combustion chamber, and the arc wall is configured to block and guide a primary coal-air flow.
3. The reverse-jet pulverized coal burner according to claim 1, wherein the secondary air assembly further comprises a separation pipe, the separation pipe is disposed inside the secondary air channel, and is configured to divide the secondary air channel along a radial direction into a swirl-flow secondary air channel and a direct-flow secondary air channel.
4. The reverse-jet pulverized coal burner according to claim 3, wherein the hollow swirl vane is provided with an inner channel and a direct-flow outlet fluid communicated with the inner channel, the hollow swirl vane comprises a first section and a second section joined to the first section; the first section is obliquely arranged, an included angle is formed between the first section and a central axis of the preheating combustion chamber; the second section is adjacent to the direct-flow outlet, the Attorney Docket No. second section is parallel to a central axis of the preheating combustion chamber, so that an air flow ejected out from the direct-flow outlet is a direct-flow secondary air.
5. The reverse-jet pulverized coal burner according to claim 4, wherein the secondary air assembly further comprises at least one secondary air branched pipe, and the secondary air branched pipe is fluid communicated with the direct-flow secondary air channel and the inner channel of the hollow swirl vane.
6. The reverse-jet pulverized coal burner according to claim 5, wherein the at least one hollow swirl vane is a plurality of hollow swirl vanes, and the plurality of hollow swirl vanes are evenly distributed along a circumferential direction on an outer wall of the primary pulverized coal pipe.
7. The reverse-jet pulverized coal burner according to claim 6, wherein the at least one secondary air branched pipe is a plurality of secondary air branched pipe, the number of the secondary air branched pipes is equal to the number of the hollow swirl vanes, and each of the secondary air branched pipes is fluid communicated with the inner channel of a corresponding hollow swirl vane.
8. The reverse-jet pulverized coal burner according to claim I, wherein the central ejection pipe is disposed at an inlet end of the pre-combustion structure and located on a central axis of the pre-combustion structure.
9. The reverse-jet pulverized coal burner according to claim 1, wherein an end of the annular wall of the pre-combustion structure at the outlet end is extended into an annular slot defined by the annular slot shaped flap, so that the annular slot shaped flap and pre-combustion structure cooperatively form the reverse-jet channel.
10. The reverse-jet pulverized coal burner according to claim I, wherein the reverse-jet channel is a U-shaped channel, an outer end of the U-shaped channel is fluid communicated with the primary coal-air flow channel, an inner end of the U-shaped channel is fluid communicated with the preheating combustion chamber.
11. The reverse-jet pulverized coal burner according to any one of claims 1 to 10, further comprising a separation annulus disposed at an outlet end of the central ejection pipe, the separation annulus is configured to delay mixing between a central ejection air ejected from the central ejection pipe and the primary coal-air flow flowing along a reverse direction.
12. The reverse-jet pulverized coal burner according to any one of claims 1 to 10, wherein an inner Attorney Docket No. wall of the pre-combustion structure is made of wear-resistant and high-temperature resistant steel, ceramic, or silicon carbide.
13. The reverse-jet pulverized coal burner according to any one of claims 12, further comprising a cooling pipe disposed in the pre-combustion structure, and the cooling pipe is configured to cool the inner wall of the pre-combustion structure.
14. The reverse-jet pulverized coal burner according to any one of claims 3 to 7, further comprising a coal-air feeding pipe, the coal-air feeding pipe is connected to the primary pulverized coal pipe, a primary coal-air flow gradual expansion section is formed between the coal-air feeding pipe and the outer wall of the pre-combustion structure, the coal-air feeding pipe is fluid communicated with the central ejection pipe and the primary coal-air flow gradual expansion section.
15. The reverse-jet pulverized coal burner according to claim 14, further comprising a pulverized coal concentrator, the pulverized coal concentrator is disposed in the primary pulverized coal pipe.
16. The reverse-jet pulverized coal burner according to claim 15, further comprising a secondary air feeding pipe surrounding the coal-air feeding pipe, a direct-flow secondary air gradual expansion section and a swirl-flow secondary air gradual expansion section is formed between the secondary air feeding pipe and the coal-air feeding pipe, the swirl-flow secondary air gradual expansion section and the direct-flow secondary air gradual expansion section are sequentially sleeved outside the primary coal-air flow gradual expansion section; the swirl-flow secondary air gradual expansion section is fluid communicated with the swirl-flow secondary air channel, the direct-flow secondary air gradual expansion section is fluid communicated with the direct-flow secondary air channel.
17. The reverse-jet pulverized coal burner according to claim 16, further comprising an air damper valve disposed in an inlet end of each of the swirl-flow secondary air gradual expansion section and the direct-flow secondary air gradual expansion section; the air damper valve is configured to adjust a flow rate ratio of a first flow in the swirl-flow secondary air channel to a second flow in the direct-flow secondary air channel.