阅读说明：本技术 一种增强墙式切圆锅炉燃尽风气流刚性的系统及方法 (System and method for enhancing wall type tangential boiler burnout air flow rigidity ) 是由 李延臣 王刚 韩宗全 于海国 赵波 宋阳 吴庆龙 于 2021-10-21 设计创作，主要内容包括：本发明提供一种增强墙式切圆锅炉燃尽风气流刚性的系统及方法,在锅炉总风量保持恒定下,大幅度减少干燥煤粉的一次风量,降低一次风率,增加一次风量的风温,提高煤粉的干燥效率与干燥质量,同时增加二次风量,提高SOFA风气流刚性,消除煤粉气流残余旋转,保证SOFA风与煤粉气流混合,降低墙式切圆锅炉两侧烟气偏差。包括、辅助风燃烧器、角式SOFA风燃烧器、墙式SOFA风燃烧器、送风机和一次风机；其中在连接一次风机与一次风燃烧器的一次风管路上依次设置有空预器、一次风加热器和制粉系统,一次风加热器与锅炉的再热蒸汽出口连接；在连接送风机与辅助风燃烧器、角式SOFA风燃烧器和墙式SOFA风燃烧器的二次风管路上依次设置有空预器和二次风箱。(The invention provides a system and a method for enhancing rigidity of overfire air flow of a wall type circle-cutting boiler, which greatly reduce primary air quantity of dried coal powder, reduce primary air rate, increase air temperature of the primary air quantity, improve drying efficiency and drying quality of the coal powder, increase secondary air quantity, improve rigidity of SOFA air flow, eliminate residual rotation of coal powder air flow, ensure mixing of SOFA air and coal powder air flow and reduce flue gas deviation at two sides of the wall type circle-cutting boiler under the condition that total air quantity of the boiler is kept constant. The device comprises an auxiliary air burner, an angle type SOFA air burner, a wall type SOFA air burner, a blower and a primary fan; wherein, an air preheater, a primary air heater and a powder making system are sequentially arranged on a primary air pipeline connecting a primary fan and a primary air burner, and the primary air heater is connected with a reheat steam outlet of a boiler; an air preheater and a secondary air box are sequentially arranged on a secondary air pipeline which connects the air feeder with the auxiliary air burner, the angle type SOFA air burner and the wall type SOFA air burner.)

1. A system for enhancing the rigidity of the overfire air flow of a wall type tangential boiler is characterized by comprising,

a primary air burner (11) and an auxiliary air burner (10) arranged in a main combustion zone of the boiler (1);

wall type SOFA air burners (8) and angle type SOFA air burners (9) which are arranged in a burnout area of the boiler (1);

a blower (4) and a primary fan (3) are respectively connected with the auxiliary air burner (10), the angle type SOFA air burner (9) and the wall type SOFA air burner (8);

an air preheater (2), a primary air heater (5) and a pulverizing system (6) are sequentially arranged on a primary air pipeline connecting a primary fan (3) and a primary air burner (11), and the primary air heater (5) is connected with a reheat steam outlet of a boiler;

an air preheater (2) and a secondary air box (7) are sequentially arranged on a secondary air pipeline which connects the air feeder (4) with the auxiliary air burner (10), the angle type SOFA air burner (9) and the wall type SOFA air burner (8).

2. The system for enhancing the rigidity of the over-fired air flow of the wall-type tangential boiler as claimed in claim 1, wherein the outlet of the reheat steam is provided with a reheat steam adjusting door (14), the inlet of the pulverizing system (6) is provided with an air flow measuring point (12), the outlet of the pulverizing system (6) is provided with a temperature measuring point (13), and an air flow adjusting door (15) is arranged between the outlet of the air preheater (2) and the primary air heater (5).

3. A system for increasing the stiffness of the over-fired air flow of a wall-tangent-circle boiler as claimed in claim 1, characterized in that the primary air burners (11) are arranged adjacent to the secondary air burners (10).

4. A system for increasing the rigidity of the overfire air flow of a wall-tangential boiler as claimed in claim 1, wherein the wall SOFA air burners (8) are arranged above the angle SOFA air burners (9) or the wall SOFA air burners (8) are arranged at the same level as the angle SOFA air burners (9).

5. A system for enhancing the rigidity of the over-fired air flow of a wall tangent boiler as defined in claim 1, characterized in that the primary air burner (11), the auxiliary air burner (10) and the wall SOFA air burner (8) are arranged on the four furnace walls of the boiler (1), wherein the wall SOFA air burner (8) has a wall SOFA air tangent circle rotation direction opposite to the primary air tangent circle rotation direction of the primary air burner (11); the angle type SOFA air burners (9) are arranged at four corners of the boiler (1), and the angle type SOFA air burners (9) and the primary air burners (11) are arranged in a staggered mode in the vertical direction.

6. The system for enhancing the rigidity of the over-fire air flow of the wall-type tangential boiler as claimed in claim 1, wherein the pulverizing system comprises a coal mill, the inlet and the outlet of the coal mill are respectively provided with a pressure measuring point, and the inlet of the coal mill is connected with the outlet of the primary air fan (3).

7. A method for enhancing the rigidity of the over-fire air flow of a wall type tangential boiler, which is characterized in that based on the system of any one of claims 1 to 6, the method comprises the following steps,

the primary air fan (3) conveys preset primary air quantity to the air preheater (2) to be heated to form hot primary air, and the air feeder (4) conveys preset secondary air quantity to the air preheater (2) to be heated to form hot secondary air;

the hot primary air flows through the primary air heater (5), and the reheated steam of the boiler (1) heats the hot primary air to a preset primary air temperature to form high-temperature primary air;

high-temperature primary air enters the powder making system (6), coal dust in the powder making system (6) is dried, then the dried coal dust is carried into the primary air burner (11), and the coal dust is sent into the hearth of the boiler (1) through the primary air burner (11) to be burnt;

the hot secondary air flows through the secondary air box (7), and is sent into the hearth of the boiler (1) through the auxiliary air burner (10), the angle type SOFA air burner (9) and the wall type SOFA air burner (8) to be mixed with the pulverized coal and then combusted.

8. A method for increasing the rigidity of the over-fired air flow of a wall tangent circle boiler as defined in claim 7, characterized in that the total air flow into the boiler (1) is always constant, wherein the total air flow comprises the primary air flow and the secondary air flow.

9. The method for enhancing the rigidity of the over-fired air flow of the wall type tangential boiler as claimed in claim 7, wherein an air volume measuring point (12) is arranged at the inlet of the pulverizing system (6), the air volume measuring point (12) monitors the primary air volume entering the pulverizing system (6) in real time, and outputs an air volume signal according to the monitoring result, so as to control the opening degree of an air volume adjusting door (15) arranged at the outlet of the air preheater (2);

the outlet of the powder making system (6) is provided with a temperature measuring point (13), the outlet of the reheat steam is provided with a reheat steam adjusting door (14), the temperature measuring point (13) monitors the primary air temperature in the powder making system (6) in real time, and outputs a temperature signal according to a monitoring result to control the opening degree of the reheat steam adjusting door (14).

10. The method for enhancing the rigidity of the over-fired air flow of the wall-type tangential boiler as claimed in claim 7, wherein the preset primary air volume is calculated according to the designed primary air rate of the boiler (1) and the coal amount entering the boiler; the preset primary air temperature is set according to the volatile component content of the coal as fired.

Technical Field

The invention relates to the technical field of boilers and boiler environmental protection, in particular to a system and a method for enhancing rigidity of wall type tangential boiler burn-out air flow.

Background

The combustion mode of the tangential circles at four corners is that pulverized coal airflow at four corners interacts to form tangential circles, the pulverized coal is rotated and combusted in the boiler, the pulverized coal and air are fully mixed in the combustion mode, adjacent combustors can be matched with each other, the combustion stability is good, the coal type adaptability is strong, and the combustion mode is generally selected for use by large and medium coal-fired boilers in China. The arrangement mode of the burners of the tangential boiler with four corners is divided into four-corner arrangement and four-side furnace wall arrangement. The corner type four-corner tangential firing and the wall type four-corner tangential firing are respectively characterized in that the imaginary tangential circle of the corner type four-corner tangential firing is smaller, the center of the flame is close to the center of the hearth, the flue gas at the outlet of the hearth is uniformly distributed, the heat exchange quantity of the convection heating surface is uniform, and the air-coated powder type combustion is easily formed, thereby being beneficial to controlling nitrogen oxides and reducing the high-temperature corrosion of the water-cooled wall, but because the flame is close to the center of the hearth, the utilization rate of the hearth is low, particularly the characteristic of low utilization rate of the hearth in an angle type four-corner tangential firing mode of a large coal-fired boiler is obvious, therefore, part of large coal-fired boilers adopt a wall type four-corner tangential combustion mode, the combustion mode arranges the burners on the boiler wall, tangential combustion is organized by four walls, the imaginary tangential is larger, the flame hearth fullness is better, however, the wall type coal dust airflow with the four tangential corners has strong rotation rigidity, the residual rotation of the coal dust airflow at the outlet of the hearth is large, and the distribution of the smoke amount is not uniform.

In order to reduce the residual rotation of the pulverized coal airflow and simultaneously reduce the generation of nitrogen oxides in the combustion process, a four-corner tangential boiler generally needs to be provided with separate type over-fire air (SOFA air). For boilers burning coal with high water content, more primary air is needed to dry coal powder, so that the primary air rate is too high, or the primary air temperature is insufficient, the coal powder is not dried sufficiently, meanwhile, in order to control the excess air system at the outlet of the hearth to be unchanged, the using amount of secondary air needs to be reduced, because the SOFA air is taken from the secondary air, the SOFA air quantity is less, the SOFA air speed is low, the SOFA air airflow rigidity is weak, the residual rotation of the main coal powder airflow cannot be eliminated, and the amount of nitrogen oxides generated by coal powder combustion is increased.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a system and a method for enhancing the rigidity of the overfire air flow of a wall type tangential boiler, which greatly reduce the primary air quantity of dried coal powder, reduce the primary air rate, increase the air temperature of the primary air quantity, improve the drying efficiency and the drying quality of the coal powder, increase the secondary air quantity, improve the rigidity of SOFA air flow, eliminate the residual rotation of the coal powder air flow, ensure the mixing of the SOFA air and the coal powder air flow and reduce the flue gas deviation at two sides of the wall type tangential boiler under the condition that the total air quantity of the boiler is kept constant.

In order to achieve the purpose, the invention provides the following technical scheme:

a system for enhancing the rigidity of the overfire air flow of a wall type tangential boiler comprises,

the primary air burner and the auxiliary air burner are arranged in a main combustion area of the boiler;

wall type SOFA air burners and angle type SOFA air burners are arranged in a burnout area of the boiler;

the air feeder is respectively connected with the auxiliary air burner, the angle type SOFA air burner and the wall type SOFA air burner, and the primary air fan is connected with the primary air burner;

an air preheater, a primary air heater and a powder making system are sequentially arranged on a primary air pipeline connecting a primary fan and a primary air burner, and the primary air heater is connected with a reheat steam outlet of a boiler;

an air preheater and a secondary air box are sequentially arranged on a secondary air pipeline which connects the air feeder with the auxiliary air burner, the angle type SOFA air burner and the wall type SOFA air burner.

Preferably, the reheat steam outlet is provided with a reheat steam adjusting door, the inlet of the pulverizing system is provided with an air quantity measuring point, the outlet of the pulverizing system is provided with a temperature measuring point, and the air quantity adjusting door is arranged between the outlet of the air preheater and the primary air heater.

Preferably, the primary air burner is arranged adjacent to the secondary air burner.

Preferably, the wall type SOFA air burner is arranged above the angle type SOFA air burner or the wall type SOFA air burner and the angle type SOFA air burner are arranged at the same height.

Preferably, the primary air burner, the auxiliary air burner and the wall type SOFA air burner are arranged on four furnace walls of the boiler, wherein the wall type SOFA air burner has a wall type SOFA air tangential circle rotating direction opposite to the primary air tangential circle rotating direction of the primary air burner; the angle type SOFA air burners are arranged at four corners of the boiler, and the angle type SOFA air burners and the primary air burners are arranged in a staggered mode in the vertical direction.

Preferably, the coal pulverizing system comprises a coal mill, an inlet and an outlet of the coal mill are respectively provided with a pressure measuring point, and an inlet of the coal mill is connected with an outlet of the primary air fan.

A method for enhancing the rigidity of the over-fire air flow of a wall type tangential boiler comprises the following steps,

the primary air fan conveys preset primary air quantity to the air preheater to be heated to form hot primary air, and the air feeder conveys preset secondary air quantity to the air preheater to be heated to form hot secondary air;

the hot primary air flows through the primary air heater, and the reheated steam of the boiler heats the hot primary air to a preset primary air temperature to form high-temperature primary air;

high-temperature primary air enters a powder making system, coal powder in the powder making system is dried, the dried coal powder is carried into a primary air burner, and the coal powder is sent into a hearth of a boiler for burning through the primary air burner;

the hot secondary air flows through the secondary air box, and is fed into the hearth of the boiler through the auxiliary air burner, the angle type SOFA air burner and the wall type SOFA air burner to be mixed with the pulverized coal and then combusted.

Preferably, the total air volume introduced into the boiler is always kept fixed, wherein the total air volume comprises primary air volume and secondary air volume.

Preferably, an air quantity measuring point is arranged at an inlet of the pulverizing system, and is used for monitoring the primary air quantity entering the pulverizing system in real time, outputting an air quantity signal according to a monitoring result and controlling the opening degree of an air quantity adjusting door arranged at an outlet of the air preheater;

the temperature measuring point is arranged at the outlet of the pulverizing system, the reheat steam adjusting door is arranged at the reheat steam outlet, the temperature measuring point monitors the primary air temperature in the pulverizing system in real time, and outputs a temperature signal according to a monitoring result, so that the opening degree of the reheat steam adjusting door can be controlled.

Preferably, the preset primary air quantity is obtained by calculation according to the designed primary air rate of the boiler and the coal amount entering the boiler; the preset primary air temperature is set according to the volatile component content of the coal as fired.

Compared with the prior art, the invention has the following beneficial effects:

the invention provides a system for enhancing the rigidity of overfire air airflow of a wall type tangential boiler, which is characterized in that an air preheater and a primary air heater are arranged between a primary air fan and a powder making system to successively heat primary air before entering the powder making system, wherein the heat source of the primary air heater is from partial reheat steam of the boiler to heat the primary air, so that the energy is saved as much as possible, the energy of the system can be recycled, and the system is simplified; aiming at a wall type tangential firing pulverized coal boiler, in particular to a wall type tangential pulverized coal boiler burning high-moisture coal, when the amount of coal entering a boiler and the excess air coefficient of a hearth outlet are not changed, the total air volume of the boiler is always fixed, the total air volume of the boiler is composed of primary air and secondary air, wherein the secondary air is composed of auxiliary air and SOFA air, the temperature of the primary air entering a powder making system can be improved, the primary air consumption is reduced to a large extent, the drying quality and the drying efficiency of pulverized coal are improved, the secondary air consumption is improved, the rigidity of the overfire air flow is enhanced, the residual rotation of pulverized coal airflow is eliminated, the SOFA air and the pulverized coal airflow are mixed, and the flue gas deviation at two sides of the wall type tangential firing pulverized coal boiler is reduced.

Furthermore, a reheat steam adjusting door is arranged at a reheat steam outlet, an air quantity measuring point is arranged at an inlet of the pulverizing system, a temperature measuring point is arranged at an outlet of the pulverizing system, and an air quantity adjusting door is arranged at an outlet of an air preheater connected with a primary fan. The invention can set the needed primary air quantity and primary air temperature in advance according to the actual condition of boiler design and the moisture content of raw coal, and monitor in real time through the arranged air quantity measuring point and temperature measuring point, thereby controlling the opening degree of the air quantity regulating door at the outlet of the air preheater to control the primary air quantity to be always kept at the needed dosage without excessive dosage to influence the secondary air rate, controlling the opening degree of the reheating steam regulating door at the reheating steam outlet, controlling the primary air temperature at any time, and ensuring the drying effect of pulverized coal in a pulverizing system.

Drawings

FIG. 1 is a schematic structural diagram of a boiler system in an embodiment of the present invention;

FIG. 2 is a schematic diagram of the primary air burner, wall SOFA air burner and angle SOFA air burner arrangement in an embodiment of the present invention.

In the figure, a boiler 1, an air preheater 2, a primary fan 3, a blower 4, a primary air heater 5, a pulverizing system 6, a secondary air box 7, a wall type SOFA air burner 8, an angle type SOFA air burner 9, an auxiliary air burner 10, a primary air burner 11, an air quantity measuring point 12, a temperature measuring point 13, a reheat steam adjusting door 14 and an air quantity adjusting door 15.

Detailed Description

The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.

As shown in fig. 1, the system for enhancing the rigidity of the overfire air flow of the wall type tangential boiler of the present invention comprises,

a primary air burner 11 and an auxiliary air burner 10 arranged in a main combustion zone of the boiler 1;

wall type SOFA air burner 8 and angle type SOFA air burner 9 arranged in the burnout zone of the boiler 1;

a blower 4 and a primary fan 3 connected with the auxiliary air burner 10, the angle type SOFA air burner 9 and the wall type SOFA air burner 8 respectively;

an air preheater 2, a primary air heater 5 and a pulverizing system 6 are sequentially arranged on a primary air pipeline connecting a primary fan 3 and a primary air burner 11, and the primary air heater 5 is connected with a reheat steam outlet of a boiler;

an air preheater 2 and a secondary air box 7 are sequentially arranged on a secondary air pipeline which connects the blower 4 with an auxiliary air burner 10, an angle type SOFA air burner 9 and a wall type SOFA air burner 8.

The invention provides a system for enhancing rigidity of over-fired air flow of a wall type tangential boiler, which is characterized in that an air preheater 2 and a primary air heater 5 are arranged between a primary air fan 3 and a powder making system 6, and primary air before entering the powder making system 6 is heated in sequence, wherein a heat source of the primary air heater 5 is from partial reheat steam of the boiler 1 to heat the primary air, so that energy is saved as much as possible, the energy of the system can be recycled, and the system is simplified; aiming at a wall type tangential firing pulverized coal boiler, in particular to a wall type tangential pulverized coal boiler burning high-moisture coal, when the amount of coal entering the boiler and the excess air coefficient of a hearth outlet are not changed, the total air volume of the boiler is always fixed, the total air volume of the boiler is composed of primary air and secondary air, wherein the secondary air is composed of auxiliary air and SOFA air, the temperature of the primary air entering a powder making system 6 can be improved, the primary air consumption is reduced to a large extent, the drying quality and the drying efficiency of pulverized coal are improved, the secondary air consumption is improved, the rigidity of the overfire air flow is enhanced, the residual rotation of pulverized coal airflow is eliminated, the mixing of SOFA air and the pulverized coal airflow is ensured, and the flue gas deviation of two sides of the wall type tangential firing pulverized coal boiler is reduced.

Preferably, in the embodiment of the present invention, a reheat steam adjusting door 14 is disposed at a reheat steam outlet, an air quantity measuring point 12 is disposed at an inlet of the pulverizing system 6, a temperature measuring point 13 is disposed at an outlet of the pulverizing system 6, and an air quantity adjusting door 15 is disposed between an outlet of the air preheater 2 and the primary air heater 5. The invention can set the needed primary air quantity and primary air temperature in advance according to the actual condition of boiler design and the moisture content of raw coal, and monitor in real time through the arranged air quantity measuring point 12 and the temperature measuring point 13, thereby controlling the opening degree of the air quantity adjusting door 15 at the outlet of the air preheater to control the primary air quantity to be always kept at the needed dosage without excessive dosage and influencing the secondary air rate, controlling the opening degree of the reheating steam adjusting door 14 at the reheating steam outlet, controlling the primary air temperature at any time and ensuring the drying effect of pulverized coal in the pulverizing system 6.

In this embodiment, the primary air burner 11 is disposed adjacent to the secondary air burner 10.

In this embodiment, the wall type SOFA air burner 8 is arranged above the angle type SOFA air burner 9 or the wall type SOFA air burner 8 and the angle type SOFA air burner 9 are arranged at the same height.

The wall type SOFA air burner 8 can be arranged above the angle type SOFA air burner 9, can also be horizontally arranged at the same elevation as the angle type SOFA air burner 9, can be flexibly arranged according to the field condition, can increase the distance from a burnout area to the outlet of the boiler 1 on the premise of not reducing the number of the separate burners, improves the burnout rate of pulverized coal and inhibits the generation of nitrogen oxides.

In this embodiment, the primary air burners 11, the auxiliary air burners 10 and the wall type SOFA air burners 8 are arranged on the four furnace walls of the boiler 1, wherein the wall type SOFA air tangential circular rotation direction of the wall type SOFA air burners 8 is opposite to the primary air tangential circular rotation direction of the primary air burners 11; the angular SOFA air burners 9 are arranged at four corners of the boiler 1, and the angular SOFA air burners 9 are arranged to be staggered with the primary air burners 11 in the vertical direction.

Aiming at the wall type tangential pulverized coal boiler, the invention adopts a mode of combining angle type separated over-fire air and inverse tangential wall type separated over-fire air by more reasonably arranging over-fire air, thereby ensuring the full mixing of the over-fire air and pulverized coal airflow and also considering the racemization effect of the over-fire air on main pulverized coal airflow, thereby eliminating the residual rotation of the pulverized coal airflow, reducing the uneven distribution of flue gas at the outlet of a hearth caused by the residual rotation of the main pulverized coal airflow, improving the pulverized coal over-fire rate, eliminating the flue gas quantity deviation at the outlet of the hearth and effectively inhibiting the generation of nitrogen oxides.

In the embodiment, the coal pulverizing system 6 comprises a coal mill, pressure measuring points are respectively arranged at an inlet and an outlet of the coal mill, the inlet of the coal mill is connected with the outlet of the primary fan 3, the resistance of the coal mill is monitored by using a differential pressure measuring point of the coal mill, the blockage of the coal mill is indicated by large resistance of the coal mill, the coal powder in the coal mill can be carried out of the coal mill by increasing primary air quantity, and the resistance of the coal mill is reduced.

The invention relates to a method for enhancing the rigidity of overfire air flow of a wall type tangential boiler, which comprises the following steps,

the primary air fan 3 conveys preset primary air quantity to the air preheater 2 to be heated to form hot primary air, and the air feeder 4 conveys preset secondary air quantity to the air preheater 2 to be heated to form hot secondary air;

hot primary air flows through the primary air heater 5, the reheat steam adjusting door 14 is opened, and the reheat steam of the boiler 1 heats the hot primary air to a preset primary air temperature to form high-temperature primary air;

high-temperature primary air enters the powder making system 6, the coal powder in the powder making system 6 is dried, then the dried coal powder is carried into the primary air burner 11, and the coal powder is sent into the hearth of the boiler 1 for burning through the primary air burner 11;

the hot secondary air flows through a secondary air box 7, and is fed into a hearth of the boiler 1 through an auxiliary air burner 10, an angle type SOFA air burner 9 and a wall type SOFA air burner 8 to be mixed with pulverized coal and then combusted.

In the invention, the outlet of the primary air fan 3 is connected with the inlet of the air preheater 2, the primary air fan 3 sends air into the air preheater 2, the air preheater 2 is used for heating the air sent by the primary air fan 3, and the air flows out of the air preheater 2 to form hot primary air. The outlet of the air preheater 2 is connected with the inlet of the primary air heater 5, reheat steam is taken from the boiler 1 into the primary air heater 5 to further heat the hot primary air, and the further heated hot primary air flows out of the primary air heater 5 to form high-temperature primary air. The outlet of the primary air heater 5 is connected with the inlet of the powder making system 6, and the high-temperature primary air enters the powder making system 6 to dry the coal powder. The outlet of the pulverizing system 6 is connected with the inlet of the primary air burner 11, and the high-temperature primary air carrying the dried pulverized coal enters the boiler 1 through the primary air burner 11 for combustion. The primary air is used as a drying agent for the pulverized coal, and the primary air heater 5 improves the temperature of the primary air entering the pulverizing system 6 and can reduce the consumption of the primary air.

The outlet of the air feeder 4 is connected with the inlet of the air preheater 2, the air feeder 4 feeds air into the air preheater 2, the air is heated in the air preheater 2, the heated air flows out of the outlet of the air preheater 2 to form hot secondary air, the outlet of the air preheater 2 is connected with the inlet of the secondary air box 7, the outlet of the secondary air box 7 is respectively connected with the wall type SOFA air burner 8, the angle type SOFA air burner 9 and the auxiliary air burner 10, the air required by pulverized coal combustion in the boiler 1 is provided by primary air, auxiliary air, angle type SOFA air and wall type SOFA air together, and the total amount of the primary air, the auxiliary air, the angle type SOFA air and the wall type SOFA air is kept unchanged.

In this embodiment, the total air volume introduced into the boiler 1 is always kept fixed, wherein the total air volume includes the primary air volume and the secondary air volume.

In the embodiment, an air volume measuring point 12 at an inlet of the pulverizing system 6 monitors primary air volume entering the pulverizing system 6 in real time, and outputs an air volume signal according to a monitoring result, so as to control the opening degree of an air volume adjusting door 15 at an outlet of the air preheater 2 and adjust the primary air volume entering the pulverizing system 6;

and a temperature measuring point monitor 13 at the outlet of the pulverizing system 6 monitors the primary air temperature in the pulverizing system 6 in real time, and outputs a temperature signal according to a monitoring result, so as to control the opening degree of a reheat steam adjusting door 14 at a reheat steam outlet and adjust the primary air temperature entering the pulverizing system 6.

In the embodiment, the preset primary air quantity is obtained by calculation according to the designed primary air rate of the boiler and the coal amount entering the boiler; the preset primary air temperature is set according to the volatile component content of the coal as fired.

The primary air and the auxiliary air provide oxygen required by the primary combustion of the pulverized coal, but the oxygen is not enough to enable the pulverized coal to be completely combusted, and the combustion of the pulverized coal in an oxygen-deficient atmosphere is favorable for inhibiting the amount of nitrogen oxides generated by the combustion of the pulverized coal. The residual oxygen required by complete combustion of the pulverized coal is provided by angle type SOFA wind and wall type SOFA wind, wherein the angle type SOFA wind is well mixed with pulverized coal airflow and is beneficial to combustion of the pulverized coal, the wall type SOFA wind has a larger tangent circle and is opposite to the rotation direction of main pulverized coal airflow, residual rotation of the main pulverized coal airflow is favorably eliminated, and the deviation of the smoke amount at two sides of the boiler is reduced. Due to the adoption of the primary air heater 5, the primary air temperature is increased, the primary air consumption is reduced, the SOFA air consumption can be increased, and the pulverized coal combustion and the residual rotation of the main pulverized coal airflow are facilitated.