阅读说明：本技术 切圆燃烧锅炉的超低nox燃烧系统及方法 (Ultra-low NO of tangential firing boilerXCombustion system and method ) 是由 张庆 高孟杰 浮杰 王文欣 侯丙军 于 2021-08-27 设计创作，主要内容包括：本发明涉及一种切圆燃烧锅炉的超低NO-(X)燃烧系统及方法,包括：炉膛；一次风燃烧器,其按照四角切圆的方式布置在所述炉膛下部的四个角处,一次风燃烧器包括：多层煤粉管道和一次风喷口,煤粉管道上均设置有煤粉浓淡分离装置、浓相煤粉管道和淡相煤粉管道,煤粉浓淡分离装置将煤粉管道内的风煤粉分离成浓相气流和淡相气流两部分；燃尽风喷口；其分别设置在炉膛的上部,燃尽风喷口包括燃尽风乏气喷口和燃尽风二次风喷口,燃尽风乏气喷口与淡相煤粉管道连接；二次风喷口,其设置在相邻的一次风喷口之间、设置在顶部的一次风喷口的上方以及设置在底部的一次风喷口的下方。本发明彻底解决了主燃烧区二次风与一次风配比失调的问题。(The invention relates to an ultra-low NO of a tangential firing boiler X A combustion system and method, comprising: a hearth; the primary air combustor is arranged at four corners of the lower part of the hearth in a mode of cutting circles at four corners, and comprises: the multi-layer pulverized coal pipeline and the primary air nozzle are provided with a pulverized coal thick-thin separation device, a thick-phase pulverized coal pipeline and a thin-phase pulverized coal pipeline, and the pulverized coal thick-thin separation device separates the air pulverized coal in the pulverized coal pipeline into a thick-phase airflow and a thin-phase airflow; an overfire air nozzle; the overfire air nozzles are respectively arranged at the upper part of the hearth and comprise an overfire air exhaust nozzle and an overfire air secondary air nozzle, and the overfire air exhaust nozzle is connected with a light-phase pulverized coal pipeline; secondary air nozzles arranged between adjacent primary air nozzles and above the primary air nozzles at the topAnd the lower part of the primary air nozzle is arranged at the bottom. The invention thoroughly solves the problem of the maladjustment of the ratio of the secondary air to the primary air in the main combustion area.)

1. Ultra-low NO of tangential firing boiler_XA combustion system, comprising:

a hearth;

the primary air burner is arranged at four corners of the lower part of the hearth in a manner of cutting circles at four corners, the primary air burner comprises a plurality of layers of pulverized coal pipelines and primary air nozzles, the plurality of layers of pulverized coal pipelines are connected with a coal mill, each pulverized coal pipeline is provided with a pulverized coal shade separation device, a dense-phase pulverized coal pipeline and a light-phase pulverized coal pipeline, the pulverized coal shade separation device separates pulverized coal in the pulverized coal pipeline into a dense-phase airflow and a light-phase airflow, the dense-phase airflow is introduced into the dense-phase pulverized coal pipeline, the light-phase airflow is introduced into the light-phase pulverized coal pipeline, the outlet of the dense-phase pulverized coal pipeline is connected with the primary air nozzles, and the primary air nozzles are arranged on the hearth from top to bottom;

the overfire air nozzles are arranged at the upper part of the hearth and correspond to the primary air burners one by one, and comprise an overfire air ventilation nozzle and an overfire air secondary air nozzle, and the overfire air ventilation nozzle is connected with the light-phase pulverized coal pipeline;

and the secondary air nozzles are arranged between the adjacent primary air nozzles, above the primary air nozzles at the top and below the primary air nozzles at the bottom.

2. Ultra-low NO for tangential firing boiler according to claim 1_XThe combustion system is characterized in that the over-fire air nozzles are arranged in multiple layers.

3. According to claim 1Ultra-low NO of said tangential firing boiler_XThe combustion system is characterized in that the over-fire air nozzle is provided with an adjusting mechanism to realize up-and-down swinging and left-and-right horizontal swinging.

4. Ultra-low NO for tangential firing boiler according to claim 1_XThe combustion system is characterized in that a horizontal shade burner is arranged on the dense-phase pulverized coal pipeline to perform shade separation on pulverized coal entering the dense-phase pulverized coal pipeline again, the separated dense-phase airflow enters a hearth through a primary air nozzle arranged on a fire facing side, and the separated light-phase airflow enters the hearth through a primary air nozzle arranged on a fired side.

5. Ultra-low NO for tangential firing boiler according to claim 1_XThe combustion system is characterized in that the primary air nozzle is provided with peripheral air for cooling the primary air nozzle and preventing the primary air nozzle from coking.

6. Ultra-low NO for tangential firing boiler according to claim 1_XThe combustion system is characterized in that the secondary air nozzle is a nozzle with wall-attached air.

7. Ultra-low NO for tangential firing boiler according to claim 1_XThe combustion system is characterized in that the overfire air secondary air nozzle is arranged above the overfire air exhaust nozzle.

8. Ultralow NO of tangential firing boiler_XA method of combustion, the steps comprising:

1) arranging primary air burners at four corners of the lower part of a hearth in a manner of cutting circles at four corners, wherein each primary air burner comprises a plurality of layers of pulverized coal pipelines and a primary air nozzle;

2) the method comprises the following steps that coal dust airflow enters a multi-layer coal dust pipeline and passes through a coal dust concentration and dilution separation device in the coal dust pipeline, the coal dust concentration and dilution separation device separates wind coal dust in the coal dust pipeline into a concentrated phase airflow and a dilute phase airflow, the concentrated phase airflow is introduced into a concentrated phase coal dust pipeline arranged on the coal dust pipeline, the dilute phase airflow is introduced into a dilute phase coal dust pipeline arranged on the coal dust pipeline, a primary air nozzle is connected to an outlet of the concentrated phase coal dust pipeline and arranged at the lower part of a hearth from top to bottom, the concentrated phase airflow is 50% of primary air and carries 85% -90% of coal dust, and the dilute phase airflow is 50% of primary air and carries 10% -15% of fine coal dust;

3) the dense-phase pulverized coal pipeline is provided with a horizontal dense-dilute burner, the pulverized coal entering the dense-phase pulverized coal pipeline is subjected to dense-dilute separation again, the concentrated-phase airflow separated out again enters the hearth through a primary air nozzle arranged on the fire facing side, and the dilute-phase airflow separated out again enters the hearth through a primary air nozzle arranged on the fired side;

4) the light-phase pulverized coal pipeline is connected with over-fired air exhaust nozzles which are arranged at the upper part of the hearth and correspond to the primary air burners one by one, and over-fired air secondary air nozzles corresponding to the over-fired air exhaust nozzles are also arranged at the upper part of the hearth;

5) and secondary air nozzles are arranged between the adjacent primary air nozzles, above the primary air nozzles at the top and below the primary air nozzles at the bottom, and supplement combustion air to be mixed with the primary air and the over-fire air.

Technical Field

The invention relates to the technical field of boiler combustion, in particular to an ultralow NO of a tangential firing boiler_XA combustion system and method.

Background

For a boiler using lignite, on one hand, because lignite has high moisture (30-40% of received base moisture) and low heat value (10-15 MJ/kg of received base low-level heating value), when lignite is ground by a medium-speed grinding direct blowing system, a high hot primary air temperature (360-390 ℃) and a high primary air rate (33-40%) are often required to meet the requirement of drying output.

On the other hand, with the increasingly strict national environmental protection requirements, the emission pressure of the thermal power plant is increased, the storage unit is modified by low-nitrogen combustion to meet the requirement of ultra-low emission of NOx, and the newly-built unit is required to adopt the advanced combustion technology to control the NOx at the inlet of the SCR (selective catalytic reduction) denitration device to 180mg/Nm³(conversion to O)₂6%) or less to reduce the operating cost of the SCR. Generally, a SOFA (separated over-fire air) nozzle is arranged to perform air classification in the height direction to reduce NOx (nitrogen oxide), for a lignite boiler, according to 36% of primary air rate and 28% of over-fire air rate, the secondary air for organizing combustion in a main combustion area is only less than 34%, the mass ratio of the secondary air to the primary air is less than 1 (34%/36% ═ 0.94), at the moment, no matter a WR (blast furnace face) wide-adjustment ratio combustion area is adopted, a PM (particulate matter) combustor is adopted, even a horizontal thick-thin or vertical thick-thin combustor is adopted, the problem of imbalance of the ratio of the secondary air to the primary air in the main combustion area cannot be solved, effective and good combustion cannot be organized, and the problems of combustor coking, burning loss, poor burning, coking of a hearth outlet, overheating and spheroidization of a heated surface pipe, high NOx emission concentration at an SCR (denitration device) inlet and the like exist.

Disclosure of Invention

The invention aims to provide ultralow NO of a tangential firing boiler_XThe combustion system and method solve the problem of imbalance of the ratio of secondary air and primary air in a main combustion area after a SOFA nozzle is arranged in a lignite tangential firing boiler, and the secondary air in the main combustion area is mixed with the primary airThe mass ratio of the primary air to the primary air is controlled within a reasonable range, so that good and efficient combustion can be organized.

In order to achieve the above objects, the present invention provides an ultra-low NO of a tangential firing boiler_XA combustion system, comprising:

a hearth;

the primary air burner is arranged at four corners of the lower part of the hearth in a manner of cutting circles at four corners, the primary air burner comprises a plurality of layers of pulverized coal pipelines and primary air nozzles, the plurality of layers of pulverized coal pipelines are connected with a coal mill, each pulverized coal pipeline is provided with a pulverized coal shade separation device, a dense-phase pulverized coal pipeline and a light-phase pulverized coal pipeline, the pulverized coal shade separation device separates pulverized coal in the pulverized coal pipeline into a dense-phase airflow and a light-phase airflow, the dense-phase airflow is introduced into the dense-phase pulverized coal pipeline, the light-phase airflow is introduced into the light-phase pulverized coal pipeline, the outlet of the dense-phase pulverized coal pipeline is connected with the primary air nozzles, and the primary air nozzles are arranged on the hearth from top to bottom;

the overfire air nozzles are arranged at the upper part of the hearth and correspond to the primary air burners one by one, and comprise an overfire air ventilation nozzle and an overfire air secondary air nozzle, and the overfire air ventilation nozzle is connected with the light-phase pulverized coal pipeline;

and the secondary air nozzles are arranged between the adjacent primary air nozzles, above the primary air nozzles at the top and below the primary air nozzles at the bottom.

The preferred scheme is as follows: the over-fire air nozzles are arranged in multiple layers.

The preferred scheme is as follows: the over-fire air nozzle is provided with an adjusting mechanism to realize up-and-down swinging and left-and-right horizontal swinging.

The preferred scheme is as follows: the dense-phase pulverized coal pipeline is provided with a horizontal dense-dilute burner, the pulverized coal entering the dense-phase pulverized coal pipeline is subjected to dense-dilute separation again, the dense-phase airflow separated out again enters the hearth through a primary air nozzle arranged on the side facing fire, and the dilute-phase airflow separated out again enters the hearth through a primary air nozzle arranged on the side being fired.

The preferred scheme is as follows: and the primary air nozzle is provided with peripheral air for cooling the primary air nozzle and preventing the primary air nozzle from coking.

The preferred scheme is as follows: the secondary air nozzle is set to be a nozzle with wall-attached air.

The preferred scheme is as follows: the overfire air secondary air nozzle is arranged above the overfire air exhaust nozzle.

Ultralow NO of tangential firing boiler_XA method of combustion, the steps comprising:

1) arranging primary air burners at four corners of the lower part of a hearth in a manner of cutting circles at four corners, wherein each primary air burner comprises a plurality of layers of pulverized coal pipelines and a primary air nozzle;

2) the method comprises the following steps that coal dust airflow enters a multi-layer coal dust pipeline and passes through a coal dust concentration and dilution separation device in the coal dust pipeline, the coal dust concentration and dilution separation device separates wind coal dust in the coal dust pipeline into a concentrated phase airflow and a dilute phase airflow, the concentrated phase airflow is introduced into a concentrated phase coal dust pipeline arranged on the coal dust pipeline, the dilute phase airflow is introduced into a dilute phase coal dust pipeline arranged on the coal dust pipeline, a primary air nozzle is connected to an outlet of the concentrated phase coal dust pipeline and arranged at the lower part of a hearth from top to bottom, the concentrated phase airflow is 50% of primary air and carries 85% -90% of coal dust, and the dilute phase airflow is 50% of primary air and carries 10% -15% of fine coal dust;

3) the dense-phase pulverized coal pipeline is provided with a horizontal dense-dilute burner, the pulverized coal entering the dense-phase pulverized coal pipeline is subjected to dense-dilute separation again, the concentrated-phase airflow separated out again enters the hearth through a primary air nozzle arranged on the fire facing side, and the dilute-phase airflow separated out again enters the hearth through a primary air nozzle arranged on the fired side;

4) the light-phase pulverized coal pipeline is connected with over-fired air exhaust nozzles which are arranged at the upper part of the hearth and correspond to the primary air burners one by one, and over-fired air secondary air nozzles corresponding to the over-fired air exhaust nozzles are also arranged at the upper part of the hearth;

5) and secondary air nozzles are arranged between the adjacent primary air nozzles, above the primary air nozzles at the top and below the primary air nozzles at the bottom, and supplement combustion air to be mixed with the primary air and the over-fire air.

The invention has the beneficial effects that:

1. the invention solves the problem of imbalance of the proportion of secondary air and primary air in a main combustion area of a lignite tangential firing boiler, and pulverized coal thick-thin separation devices, a thick-phase pulverized coal pipeline and a thin-phase pulverized coal pipeline are arranged on pulverized coal pipelines in the invention, wherein the pulverized coal thick-thin separation devices separate pulverized coal in the pulverized coal pipelines into two parts of a thick-phase airflow and a thin-phase airflow, and the thin-phase airflow is 50% of primary air and carries 10% -15% of fine pulverized coal; the dense-phase airflow is 50% of primary air and 85% -90% of pulverized coal, the dense-phase airflow enters the combustor, and the light-phase airflow is fed from the burnout zone above the main combustion zone and used as the burnout air to replace part of hot secondary air, so that the primary air rate of the main combustion zone is reduced, the secondary air rate of the main combustion zone is increased, the mass ratio of the secondary air to the primary air is improved, and the problem of mismatching of the secondary air and the primary air in the main combustion zone is thoroughly solved;

2. the invention thoroughly solves the problem of the maladjustment of the ratio of the secondary air to the primary air in the main combustion area, the boiler can organize good and efficient combustion, and can avoid the problems of coking and burning loss of a burner, poor combustion, coking at the outlet of a hearth, super-temperature spheroidization of a heated surface pipe, high NOx emission concentration at the inlet of an SCR (denitration device) and the like in the boiler, thereby ensuring the safe, stable, economic and environment-friendly combustion of the boiler;

3. the invention sets the multilayer secondary air nozzle as the nozzle with wall-attached air, and can solve the problem of high-temperature corrosion of the water-cooled wall in the combustion area.

Drawings

FIG. 1 is a schematic view of the combustion system of the present invention;

fig. 2 is a schematic tangential view of a tangential firing boiler according to the present invention.

Detailed Description

The present invention is further described in detail below with reference to the attached drawings so that those skilled in the art can implement the invention by referring to the description text.

It will be understood that terms such as "having," "including," and "comprising," as used herein, do not preclude the presence or addition of one or more other elements or groups thereof.

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

In the description of the present invention, it is to be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships illustrated in the drawings, and are used merely for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be construed as limiting the present 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 one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined 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; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood according to specific situations by a user of ordinary skill in the art.

As shown in FIGS. 1 and 2, the present invention providesUltra-low NO for tangential firing boiler_XA combustion system, comprising:

a hearth;

the primary air burner is arranged at four corners of the lower part of the hearth in a manner of cutting circles at four corners, the primary air burner comprises a multilayer pulverized coal pipeline 1 and a primary air nozzle, the multilayer pulverized coal pipeline 1 is connected with a coal mill, a pulverized coal shade separation device 2, a dense-phase pulverized coal pipeline 3 and a light-phase pulverized coal pipeline 4 are arranged on each pulverized coal pipeline 1, the pulverized coal shade separation device 2 separates pulverized coal in the pulverized coal pipeline 1 into two parts of a dense-phase airflow and a light-phase airflow, the dense-phase airflow is introduced into the dense-phase pulverized coal pipeline 3, the light-phase airflow is introduced into the light-phase pulverized coal pipeline 4, the primary air nozzle is connected with the outlet of the dense-phase pulverized coal pipeline 3, and the primary air nozzle is arranged on the hearth from top to bottom;

the overfire air nozzles are arranged at the upper part of the hearth and correspond to the primary air burners one by one, each overfire air nozzle comprises an overfire air exhaust nozzle 11 and an overfire air secondary air nozzle 12, and the overfire air exhaust nozzles 11 are connected with the light-phase pulverized coal pipeline 4;

the overgrate air spout is including pasting wall wind spout 8, end overgrate air spout 5 and top overgrate air spout 10, wherein, it is adjacent to paste wall wind spout 8 set up between the overgrate air spout, top overgrate air spout 10 sets up the top at the primary air spout at top and end overgrate air spout 5 sets up the below at the primary air spout of bottom.

The invention solves the problem of imbalance of the proportion of secondary air and primary air in a main combustion area of a lignite tangential firing boiler, and pulverized coal thick-thin separation devices, a thick-phase pulverized coal pipeline and a thin-phase pulverized coal pipeline are arranged on pulverized coal pipelines in the invention, wherein the pulverized coal thick-thin separation devices separate pulverized coal in the pulverized coal pipelines into two parts of a thick-phase airflow and a thin-phase airflow, and the thin-phase airflow is 50% of primary air and carries 10% -15% of fine pulverized coal; the dense-phase airflow is 50% of primary air and 85% -90% of pulverized coal, the dense-phase airflow enters the combustor, and the light-phase airflow is fed from the burnout zone above the main combustion zone and used as the burnout air to replace part of hot secondary air, so that the primary air rate of the main combustion zone is reduced, the secondary air rate of the main combustion zone is increased, the mass ratio of the secondary air to the primary air is improved, and the problem of mismatching of the secondary air and the primary air in the main combustion zone is thoroughly solved; the invention thoroughly solves the problem of the maladjustment of the ratio of the secondary air to the primary air in the main combustion area, the boiler can organize good and efficient combustion, and can avoid the problems of coking and burning loss of a burner, poor combustion, coking at the outlet of a hearth, overheating and spheroidizing of a heated surface pipe, high NOx emission concentration at the inlet of an SCR (denitration device) and the like of the boiler, thereby ensuring the safe, stable, economic and environment-friendly combustion of the boiler.

In another embodiment of the present invention, the overfire air outlets are arranged in multiple layers.

The over-fire air nozzle is arranged in multiple layers and is beneficial to all-around contact of air and fuel, oxygen-enriched combustion is formed, and the over-fire degree of the fuel is improved.

In another embodiment of the invention, the overfire air nozzle is provided with an adjusting mechanism to realize the up-and-down swinging and the left-and-right horizontal swinging of the air flow.

This embodiment is through setting up adjustment mechanism in the overfire air spout department, realizes the air current upper and lower swing and the horizontal hunting about of spout department, adjustment mechanism includes bearing and connecting rod actuating mechanism, overfire air spout one side is connected with actuating mechanism through the connecting rod, and long-range drive instruction of giving to actuating mechanism to drive the swing of overfire air spout, thereby adjust the direction of air current.

In another embodiment of the present invention, the dense-phase pulverized coal duct 3 is provided with a horizontal dense-dilute burner 6, the pulverized coal entering the dense-phase pulverized coal duct 3 is separated again into dense-dilute, the re-separated dense-phase airflow enters the furnace chamber through the primary air nozzle arranged on the side facing fire, and the re-separated light-phase airflow enters the furnace chamber through the primary air nozzle arranged on the side facing fire.

In the embodiment, the concentrated phase airflow separated again is positioned on the fire side, and the dilute phase airflow separated again is positioned on the fired side, so that the water-cooled wall can be prevented from coking and high-temperature corrosion.

In another embodiment of the invention, the primary air nozzle is provided with peripheral air for cooling the primary air nozzle and preventing coking of the primary air nozzle.

In another embodiment of the invention, the secondary air nozzle is arranged as a nozzle with wall-attached air.

This embodiment sets up multilayer overgrate air spout into the spout of taking the wall wind, can solve the high temperature corrosion problem of combustion area water-cooling wall.

In another embodiment of the invention, the overfire air secondary air nozzle 12 is disposed above the overfire air exhaust nozzle 11.

Ultralow NO of tangential firing boiler_XA method of combustion, the steps comprising:

1) arranging primary air burners at four corners of the lower part of a hearth in a manner of cutting circles at four corners, wherein each primary air burner comprises a plurality of layers of pulverized coal pipelines and a primary air nozzle;

2) the method comprises the following steps that coal dust airflow enters a multi-layer coal dust pipeline and passes through a coal dust concentration and dilution separation device in the coal dust pipeline, the coal dust concentration and dilution separation device separates wind coal dust in the coal dust pipeline into a concentrated phase airflow and a dilute phase airflow, the concentrated phase airflow is introduced into a concentrated phase coal dust pipeline arranged on the coal dust pipeline, the dilute phase airflow is introduced into a dilute phase coal dust pipeline arranged on the coal dust pipeline, a primary air nozzle is connected to an outlet of the concentrated phase coal dust pipeline and arranged on the lower portion of a hearth from top to bottom, the concentrated phase airflow is 50% of primary air and carries 85% -90% of coal dust, and the dilute phase airflow is 50% of primary air and carries 10% -15% of fine coal dust;

3) the dense-phase pulverized coal pipeline is provided with a horizontal dense-dilute burner, the pulverized coal entering the dense-phase pulverized coal pipeline is subjected to dense-dilute separation again, the concentrated-phase airflow separated out again enters the hearth through the primary air nozzle arranged on the side facing fire, and the dilute-phase airflow separated out again enters the hearth through the primary air nozzle arranged on the side being fired;

4) the light-phase pulverized coal pipeline is connected with over-fired air exhaust nozzles which are arranged at the upper part of the hearth and correspond to the primary air burners one by one, and over-fired air secondary air nozzles corresponding to the over-fired air exhaust nozzles are also arranged at the upper part of the hearth;

5) and secondary air nozzles are arranged between the adjacent primary air nozzles, above the primary air nozzles at the top and below the primary air nozzles at the bottom, and supplement combustion air to be mixed with the primary air and the over-fire air.

In another embodiment of the present invention, the present embodiment provides an ultra-low NO for a tangential firing boiler_XThe combustion system, the boiler is furnished with 7 medium-speed coal mills, the full load is 6 runs, 1 stands by, mill to each 4 primary air burners that layer supply powder, every stove totally 7 layers 28 primary air burners; the primary air burner is arranged at four corners of the lower part of the hearth in a mode of cutting circles at four corners, and comprises: the multi-layer pulverized coal pipeline 1 is connected with a coal mill, the pulverized coal 1 is provided with a pulverized coal shade separation device 2, a dense-phase pulverized coal pipeline 3 and a light-phase pulverized coal pipeline 4, the pulverized coal shade separation device 2 separates wind pulverized coal in the pulverized coal pipeline into a dense-phase airflow and a light-phase airflow, the dense-phase airflow is 50% of primary air and 85% -90% of pulverized coal, the light-phase airflow is 50% of primary air and carries 10% -15% of fine pulverized coal, the dense-phase airflow is introduced into the dense-phase pulverized coal pipeline 3, the light-phase airflow is introduced into the light-phase pulverized coal pipeline 4, an outlet of the dense-phase pulverized coal pipeline 3 is connected with the primary air nozzle, the dense-phase pulverized coal pipeline is provided with a horizontal light burner 6, dense-light separation is carried out on the pulverized coal entering the dense-phase pulverized coal pipeline again, and the dense-phase airflow separated out again enters a hearth through the primary air nozzle arranged on a fire facing side, the separated dilute phase airflow enters the hearth through a primary air nozzle arranged on the fired side;

an overfire air nozzle; the overfire air nozzles are respectively arranged at the upper part of the hearth and correspond to the primary air burners one by one, each overfire air nozzle comprises an overfire air exhaust nozzle 11 and an overfire air secondary air nozzle 12, and the overfire air exhaust nozzles 11 are connected with the light-phase pulverized coal pipeline 4 and used as overfire air to replace partial hot secondary air, so that the primary air rate of a main combustion area is reduced, the secondary air rate of the main combustion area is increased, and the problem of imbalance of the ratio of the secondary air and the primary air of the main combustion area is thoroughly solved;

the secondary air nozzle comprises a wall-attached air nozzle 8, a bottom secondary air nozzle 5 and a top secondary air nozzle 10, wherein the wall-attached air nozzle 8 is arranged between the adjacent primary air nozzles, the top secondary air nozzle 10 is arranged above the primary air nozzle at the top and the bottom secondary air nozzle 5 is arranged below the primary air nozzle at the bottom, so that the problem of high-temperature corrosion of a water-cooled wall of a combustion area can be solved.

Examples design data:

for a lignite boiler, according to the initial primary air rate of 36%, the overfire air rate of 28%, the secondary air rate of 34% and the primary air with the light phase airflow of 50%, 10% -15% of fine coal powder is carried; the dense phase airflow is calculated by 50 percent of primary air and 85 to 90 percent of coal powder:

1) according to 7 coal mills, 6 runs for 1 standby, and coal powder concentration and dilution separation calculation in the height direction is adopted:

a main combustion zone: the primary air rate is 36% x 0.5 ═ 18%; the secondary air rate was 34% + 36% × 0.5 ═ 52%.

A burnout zone: 36% × 0.5 (light phase) + 10% (secondary air) ═ 28%.

The mass ratio of the secondary air to the primary air in the main combustion area is 52%/18%/2.89%

2) According to 7 coal mills, 6 runs for 1 standby, 4 mills adopt the separation calculation of the coal powder concentration in the height direction:

a main combustion zone: the primary air rate is 24 percent/6 multiplied by 4 multiplied by 0.5+36 percent/6 multiplied by 2;

the secondary air rate is 34% + 36%/6 × 4 × 0.5 ═ 46%.

A burnout zone: 36%/6 × 4 × 0.5 (light phase) + 16% (secondary air) ═ 28%.

The mass ratio of the secondary air to the primary air in the main combustion area is 46%/24%/1.92

Therefore, the primary air rate is reduced, the secondary air rate is increased, the mass ratio of the secondary air to the primary air in the main combustion area is improved from insufficient 1 (34%/36% ═ 0.94) to 1.92-2.89, the secondary air and the primary air are in a reasonable proportioning range, and the problem of imbalance of the proportion of the secondary air to the primary air in the main combustion area is thoroughly solved.

While embodiments of the invention have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable in various fields of endeavor to which the invention pertains, and further modifications may readily be made by those skilled in the art, it being understood that the invention is not limited to the details shown and described herein without departing from the general concept defined by the appended claims and their equivalents.