A system and method for optimizing the combustion of a opposed firing boiler in multiple combustion regimes

Abstract

The application discloses a kind of to realize the system and method of optimizing combustion of offset combustion boiler in multiple combustion mode, the system includes hot secondary air main pipe, medium-speed coal mill and several pulverized coal distributors, several pulverized coal distributors are connected with medium-speed coal mill, each pulverized coal distributor is connected with main burner and micro backup burner respectively;Each micro backup burner is arranged with micro secondary air nozzle above, and the micro secondary air nozzle is connected with hot secondary air main pipe.The application can improve the excess air coefficient of main burner close to side wall by setting pulverized coal distributor, reduce the concentration of generated reducing gas, and then realize the improvement of side wall water-cooled wall atmosphere, so as to solve the problem of high temperature corrosion of side wall water-cooled wall.The application can make the same amount of pulverized coal pass through more burners in horizontal direction to enter the furnace for combustion by setting micro backup burner, which is very beneficial to improve the uniformity of furnace heat load distribution, and helps to solve the problem of overheating of heating surface.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of coal-fired power generation, and particularly relates to a system and method for optimizing the combustion of a boiler with opposed firing conditions. BACKGROUND

[0002] Water wall high-temperature corrosion of coal-fired boilers has been one of the main reasons affecting the safe operation of units. In recent years, due to the coal market, some power plants have massively blended economic coal, among which high-sulfur coal is one of the main economic coal. With the blending of high-sulfur coal, the problem of water wall high-temperature corrosion has been exacerbated. In addition, due to the ultra-low emission transformation, the installation of low-temperature economizers and other technical transformations, the resistance of the boiler tail flue has significantly increased compared to the design. At the same time, due to the massive blending of low-calorific-value coal, the boiler flue gas volume is also significantly larger. These two factors lead to insufficient induced draft fan output, which restricts the oxygen content of the boiler under high load conditions. Reducing the oxygen content of the boiler will inevitably lead to a serious lack of oxygen in the main combustion area of the furnace, and the water wall will have a stronger reducing atmosphere, further exacerbating the problem of high-temperature corrosion. Therefore, under the condition that the coal quality cannot be changed, if measures can be taken to improve the reducing atmosphere of the water wall, the problem of water wall high-temperature corrosion can be greatly alleviated.

[0003] The start-up of opposed firing boilers is relatively simple, which is mainly due to its unique burner arrangement system. In a typical opposed firing boiler, burners are usually started in groups, which means that only a few burners can be started when necessary, without the requirement that all burners are started simultaneously or coordinated between each angle. In addition, opposed firing boilers do not require coordination between the front and rear walls or the upper and lower layers, and as long as the air-fuel ratio and swirl intensity of the burner are appropriate, stable combustion can be achieved. This start-up method not only simplifies the operation process, but also reduces the difficulty of start-up, improves the reliability and flexibility of the boiler.

[0004] Opposed firing boilers use opposed firing, with combustion air and fuel entering the furnace relatively opposite to each other and rapidly burning in the combustion chamber. This combustion method helps to achieve sufficient mixing and combustion of fuel and air, improving combustion efficiency and thermal efficiency. At the same time, the combustion chamber structure of the opposed firing boiler is relatively simple, which can effectively reduce the area of the high-temperature region of the furnace wall and reduce the wear and degradation rate of the furnace.

[0005] The opposed firing boiler is excellent in peak regulation. For example, the opposed firing tower boiler developed by the Dongfang Boiler has the characteristics of lower peak regulation depth, higher wide load economy, and lower wide load emission. The boiler can realize a minimum 20% THA peak regulation load, and the main steam reaches the rated steam temperature in the range of 20-100% load. These characteristics make the opposed firing boiler better adapt to the changing demand of the power system load, and improve the stability and reliability of the power system. However, due to the characteristics of the burner arrangement, the opposed firing boiler is prone to form an oxygen-deficient combustion condition near the side wall or part of the burner, so the side wall water wall high temperature corrosion problem and the convection heating surface over-temperature problem are typical common problems of the opposed firing boiler.

[0006] In the prior art, for the opposed firing boiler, a wall-attached air is usually added to increase the oxygen content to achieve the purpose of improving the wall-attached reducing atmosphere. However, these technologies are limited by the insufficient rigidity or insufficient air volume of the wall-attached air, and the improvement range is small.

[0007] Chinese patent CN202022778658.9 discloses an anti-corrosion, anti-wear and anti-sludging device for a wall type pulverized coal boiler, which comprises a dense and thin separation device arranged on a pulverized coal pipeline connected to the burners adjacent to the two side walls. The outlet of the dense and thin separation device is divided into two paths, one path is a thin phase pulverized coal pipeline, and the other path is a dense phase pulverized coal pipeline. The thin phase pulverized coal pipeline and the dense phase pulverized coal pipeline are connected to the burners adjacent to the two side walls. Although this patent can make the combustion process of the pulverized coal gas flow of the burners adjacent to the two side walls in an oxygen-rich combustion state, and alleviate the degree of high temperature corrosion and slagging in the furnace, it is only applicable to high-parameter wall type combustion boilers with a pulverized coal distributor. Moreover, due to the high pulverized coal concentration of the dense phase pulverized coal pipeline corresponding to the burners, the local oxygen deficiency is serious, which may cause combustion lag, increase the flue gas temperature at the furnace outlet, and cause over-temperature problems of the downstream convection heating surface. SUMMARY

[0008] To overcome the local over-temperature problem of the heating surface of the opposed firing boiler in the prior art, the purpose of the present application is to provide an opposed firing boiler combustion optimization system and method that can realize multi-element combustion conditions. The system can make the same amount of pulverized coal pass through more burners in the horizontal direction to enter the furnace for combustion, forming multi-element combustion of the burners in the same layer in the furnace, which is very beneficial to improving the uniformity of the furnace heat load distribution and helps to solve the over-temperature problem of the heating surface.

[0009] To achieve the above purpose, the present application adopts the following technical solutions:

[0010] The application provides a kind of to realize the counterflow combustion boiler combustion optimization system of multiple combustion mode, including hot secondary air main pipe, medium speed coal mill and several coal powder distributors, several coal powder distributors are connected with medium speed coal mill, each coal powder distributor is connected with main burner and micro backup burner respectively;Each micro backup burner is arranged with micro secondary air nozzle above, and the micro secondary air nozzle is connected with the hot secondary air main pipe.

[0011] The further improvement of the application is that the adjusting door is arranged between the coal powder distributor and the micro backup burner, and the adjusting door is arranged between the micro secondary air nozzle and the hot secondary air main pipe;The main burner is a cyclone burner, and the micro backup burner is a straight-flow burner.

[0012] The further improvement of the application is that the main burners arranged on the same layer are evenly arranged at the same height of the front and rear walls of the counterflow combustion boiler.

[0013] The further improvement of the application is that the micro backup burner is arranged between the two main burners and is horizontally spaced apart from any one of the main burners.

[0014] The further improvement of the application is that the micro backup burner is arranged obliquely above the main burner.

[0015] The application also provides a kind of to realize the counterflow combustion boiler combustion optimization method of multiple combustion mode, comprising the following steps:

[0016] The coal powder in the medium speed coal mill is transported to each coal powder distributor, and the coal powder distributor separates part of the coal powder, and the remaining coal powder is sent to the main burner for combustion;

[0017] The mass of the part of the coal powder is 0% to 30% of the total mass of the coal powder;

[0018] The mass of the remaining coal powder is 70% to 100% of the total mass of the coal powder.

[0019] The further improvement of the application is that the opening degree of the adjusting door between the coal powder distributor and the micro backup burner is adjusted to adjust the amount of coal powder entering the micro backup burner to be within the range of 0% to 30% of the total mass of the coal powder, and the opening degree of the adjusting door between the micro secondary air nozzle and the hot secondary air main pipe is adjusted to adjust the amount of hot secondary air entering the micro secondary air nozzle to change.

[0020] The further improvement of the application is that the coal powder in the micro backup burner is ignited by the high-temperature flue gas generated by the adjacent main burner.

[0021] The further improvement of the application is that the opening degree of the adjusting door between the coal powder distributor and the micro backup burner is adjusted to adjust the output of each main burner, and the hot secondary air is introduced through the micro secondary air nozzle for combustion support.

[0022] A further improvement of the present invention is that if the output of the medium-speed coal mill is less than the minimum output threshold, the micro standby burner is activated, and if the fire detection signal of the main burner flickers, the regulating door corresponding to the main burner is closed until the fire detection signal is normal.

[0023] Compared with the prior art, the present invention has the following technical effects:

[0024] The present invention provides a pulverized coal distributor to divert the pulverized coal, thereby increasing the excess air coefficient near the main burner on the side wall, achieving diversified combustion conditions in the furnace, reducing the concentration of the reducing gas generated, and further improving the atmosphere of the side wall water-cooled wall, thereby solving the problem of high-temperature corrosion of the side wall water-cooled wall. The present invention provides a micro-backup burner, which enables the same amount of pulverized coal to enter the furnace for combustion through more burners in the horizontal direction, which is very beneficial to improving the uniformity of the heat load distribution in the furnace and helps to solve the problem of overheating of the heating surface. The present invention does not change the overall excess air coefficient of the main burner area, and has a very limited impact on the amount of NOx generated in the boiler. The present invention has a reasonable solution and a simple system structure, and can give full play to the advantages of combustion system optimization in improving the atmosphere of the water-cooled wall.

[0025] Furthermore, the present invention provides an adjustment door between the pulverized coal distributor and the micro standby burner, which helps to carry out refined combustion optimization tests and solve the problem of excessive local heat load in some burner areas.

[0026] Furthermore, when burning difficult-to-ignite coal, the present invention solves the problem of burnout of the micro standby burner by adjusting the opening of the regulating door between the micro secondary air nozzle and the hot secondary air main pipe to adjust the change in the amount of hot secondary air entering the micro secondary air nozzle. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of the combustion optimization system of the hedge combustion boiler of the present invention.

[0028] Among them: 1-medium-speed coal mill, 2-first pulverized coal distributor, 3-second pulverized coal distributor, 4-third pulverized coal distributor, 5-fourth pulverized coal distributor, 6-first main burner, 7-second main burner, 8-third main burner, 9-fourth main burner, 10-first micro standby burner, 11-second micro standby burner, 12-third micro standby burner, 13-fourth micro standby burner, 14-first micro secondary air nozzle, 15-second micro secondary air nozzle, 16-third micro secondary air nozzle, 17-fourth micro secondary air nozzle. DETAILED DESCRIPTION

[0029] In the following certain exemplary embodiments are simply described. As will be realized by those skilled in the art, the described embodiments can be modified in various different ways without departing from the spirit or scope thereof. Accordingly, the drawings and descriptions are to be regarded as illustrative in nature rather than restrictive.

[0030] In the description of the present application, it is to be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like are based on the orientations or positional relationships shown in the drawings, and are merely intended to facilitate the description of the present application and simplify the description, and therefore cannot be understood as indicating or implying that the devices or elements indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0031] In addition, the terms "first", "second", "third", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second", etc. can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited.

[0032] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, can be fixedly connected, can be detachably connected, or integrated; can be mechanically connected, can be electrically connected, or can be communicated; can be directly connected, or indirectly connected through an intermediate medium; can be the communication or interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0033] In the present application, unless otherwise explicitly specified and limited, "on" or "under" of the first feature to the second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, "on", "above" and "above" of the first feature to the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. "Below", "below" and "below" of the first feature to the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0034] It should be understood that the terms "comprises" and "comprising", when used in this specification and associated claims, indicate the presence of the described features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0035] It should also be understood that the terminology used in the description of the application herein is for the purpose of describing only the particular embodiments and is not intended to be limiting of the application. As used in this description and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0036] It should also be further understood that the term "and / or" used in the context of the present application refers to a combination of one or more of the associated listed items, as well as all possible combinations, and includes these combinations.

[0037] Various structural diagrams according to the disclosed embodiments of the application are shown in the accompanying drawings. These diagrams are not drawn to scale, in which certain details are exaggerated for clarity and others omitted. The shapes and relative sizes of the various regions, layers, and elements illustrated in the drawings are exemplary only and can vary in actual implementation depending on manufacturing techniques and tolerances, and the skilled person can design regions / layers with different shapes, sizes, relative positions according to actual needs.

[0038] The embodiments of the application are described in detail below with reference to the accompanying drawings.

[0039] As shown in the drawings, the application provides a hedging combustion boiler combustion optimization system for realizing multi-element combustion conditions, which improves the water-cooled wall sticking reduction atmosphere through the optimization arrangement of the combustion system, and further realizes the problem of relieving the high temperature corrosion of the water-cooled wall. Figure 1

[0040] The hedging combustion boiler combustion optimization system for realizing multi-element combustion conditions of the application comprises a medium-speed coal mill 1, a plurality of coal powder distributors, a main burner connected with the coal powder distributors and a plurality of micro backup burners. An adjusting door is arranged between the coal powder distributor and the micro backup burner. The main burner is a cyclone burner, and the micro backup burner is a straight-flow burner.

[0041] Specifically, in the application, the number of the coal powder distributors can be set according to needs, such as 4, 5, 6, 7 or 8, and the number of the coal powder distributors is 4 in the following description, the coal powder distributors comprise a first coal powder distributor 2, a second coal powder distributor 3, a third coal powder distributor 4 and a fourth coal powder distributor 5. ​

[0042] Correspondingly, the number of the main burners in the application can be set according to the number of the coal powder distributors, and the main burners include the first main burner 6, the second main burner 7, the third main burner 8 and the fourth main burner 9.

[0043] Correspondingly, the number of the micro backup burners in the application can be set according to the number of the coal powder distributors, and the micro backup burners include the first micro backup burner 10, the second micro backup burner 11, the third micro backup burner 12 and the fourth micro backup burner 13.

[0044] Correspondingly, each micro backup burner is arranged above a micro secondary air nozzle, and the number of the micro secondary air nozzles can be set according to the number of the micro backup burners, and the micro secondary air nozzles include the first micro secondary air nozzle 14, the second micro secondary air nozzle 15, the third micro secondary air nozzle 16 and the fourth micro secondary air nozzle 17. Specifically, the first micro secondary air nozzle 14 is arranged above the first micro backup burner 10, the second micro secondary air nozzle 15 is arranged above the second micro backup burner 11, the third micro secondary air nozzle 16 is arranged above the third micro backup burner 12, and the fourth micro secondary air nozzle 17 is arranged above the fourth micro backup burner 13. All the backup burners are connected with the hot secondary air main pipe.

[0045] The first coal powder distributor 2, the second coal powder distributor 3, the third coal powder distributor 4 and the fourth coal powder distributor 5 are connected with the medium-speed coal mill 1 through coal powder pipelines.

[0046] The first coal powder distributor 2 is connected with the first main burner 6 and the first micro backup burner 10 through coal powder pipelines respectively; the second coal powder distributor 3 is connected with the second main burner 7 and the second micro backup burner 11 through coal powder pipelines respectively; the third coal powder distributor 4 is connected with the third main burner 8 and the third micro backup burner 12 through coal powder pipelines respectively; and the fourth coal powder distributor 5 is connected with the fourth main burner 9 and the fourth micro backup burner 13 through coal powder pipelines respectively.

[0047] The first micro secondary air nozzle 14, the second micro secondary air nozzle 15, the third micro secondary air nozzle 16 and the fourth micro secondary air nozzle 17 are connected with the hot secondary air main pipe.

[0048] Preferably, an adjusting door is arranged on the coal powder pipeline between each coal powder distributor and micro backup burner.

[0049] Preferably, an adjusting door is arranged on the pipeline between each micro secondary air nozzle and the hot secondary air main pipe.

[0050] Preferably, the same layer main burners are uniformly arranged at the same height of the front and back walls of the opposed firing boiler.

[0051] Preferably, the micro backup burners are arranged between the two main burners and horizontally spaced a distance from one of the main burners.

[0052] Preferably, the micro backup burners are arranged obliquely above the main burners with a height difference b.

[0053] Preferably, the micro secondary air nozzles are arranged directly above the corresponding micro backup burners with a distance c.

[0054] The distances a, height difference b and distance c can be determined by numerical simulation calculation to ensure that the micro backup burners can be ignited and stabilized.

[0055] The working process of the present application is as follows:

[0056] (1) The pulverized coal ground by the medium-speed coal mill 1 is transported to each pulverized coal distributor by the primary air through the pulverized coal pipeline. After separation of a small amount of pulverized coal (0% to 30% of the total coal mass before entering the distributor), the majority of the pulverized coal (70% to 100% of the total coal mass before entering the distributor) is sent to the main burners for combustion through the pulverized coal pipeline. The original secondary air quantity of the main burners is still determined according to the design value corresponding to the total coal quantity.

[0057] (2) In step (1), the pulverized coal quantity entering the micro backup burner is adjusted within the range of 0% to 30% of the total coal quantity (30% corresponding to 100% of the adjustment door opening) by adjusting the opening of the adjustment door arranged between the pulverized coal distributor and the micro backup burner (e.g. adjusting the opening by 10% to 20% each time). The pulverized coal of the micro backup burner is ignited by the high-temperature flue gas generated by the adjacent main burner, and when the difficult-to-ignite and burn-out coal is burned, hot secondary air is introduced through the micro secondary air nozzle for combustion.

[0058] (3) The output of each main burner can be adjusted as needed by adjusting the adjustment doors arranged on the pulverized coal pipeline (e.g. adjusting the opening by 10% to 20% each time), thereby optimizing the adjustment of the horizontal cross-sectional heat load distribution of the furnace.

[0059] (4) The hot secondary air quantity entering the micro secondary air nozzle is adjusted by adjusting the opening of the adjustment door arranged between the micro secondary air nozzle and the hot secondary air main pipe. The hot secondary air quantity at 100% opening is determined according to the most difficult-to-ignite and burn-out coal.

[0060] (5) When the mill output is close to the minimum value (such as 1.2 times the minimum output or less), the micro backup burner is put into use, and if there is a problem with the ignition of the main burner (specifically, the fire detection signal flickers, such as the fire detection signal intensity fluctuates in the range of 50% to 100%), the corresponding adjustment door of the main burner (such as the first main burner 6, the adjustment door corresponding to the first coal powder distributor 2 connected with the micro backup burner 10) should be gradually closed until the fire detection signal is normal.

[0061] Example 1

[0062] For the problem of high-temperature corrosion of the side wall water-cooled wall of the opposed firing boiler, the specific optimization method of example 1 is as follows:

[0063] (1) Use the maintenance opportunity to determine the high-temperature corrosion serious area of the opposed firing boiler (for example, the left wall), or install a wall atmosphere measuring point on the side wall water-cooled wall to measure the area with high CO concentration, thereby confirming the adjustment door corresponding to the burner that needs to be adjusted (close to the side wall main burner in the upstream along the flue gas flow direction, such as the first main burner 6 and the first micro backup burner 10 corresponding to the left wall, then the adjustment door connected therewith needs to be adjusted);

[0064] (2) Adjust the opening degree of the adjustment door in step (1) by 20% each time (100% opening degree corresponds to 30% total powder amount, the corresponding curve of adjustment door opening degree and powder amount can be determined through field test), and determine whether the adjustment door opening degree needs to be further increased by detecting the CO concentration of the side wall water-cooled wall atmosphere, and stop adjusting the adjustment door opening degree when the CO concentration reaches the target value (such as below 10000 ppm by volume);

[0065] (3) During the adjustment of the adjustment door opening degree connected with the micro backup burner, closely monitor the wall temperature change of each heating surface, and immediately restore the opening degree before adjustment when over-temperature problem occurs.

[0066] Example 2

[0067] For the problem of water-cooled wall over-temperature caused by local high heat load of the opposed firing boiler, the specific optimization method of example 2 is as follows:

[0068] (1) Determine the main burner (for example, the second main burner 7) corresponding to the water-cooled wall over-temperature measuring point (for example, water-cooled wall temperature measuring points 1-3 in the middle region of the furnace) along the flue gas flow direction upstream;

[0069] (2) According to the over-temperature amplitude (for example, exceeding the alarm value by 10°C) and the number (for example, 3) of the measuring point, confirm the adjustment amplitude (such as 20%) of the adjustment door;

[0070] (3) With the second main burner 7 adjacent to the first micro backup burner 10, the regulating door opening degree is reduced by 20% each time (100% opening degree corresponds to 30% total powder amount, the corresponding curve of the regulating door opening degree and the powder amount can be determined through field test) until the over-temperature measuring point display value is lower than the alarm value.

[0071] (4) If the over-temperature problem still exists after the regulating door opening degree connected to the micro first backup burner 10 is reduced to 0% opening degree, the regulating door opening degree connected to the second micro backup burner 11 is increased by 20% each time until the over-temperature measuring point display value is lower than the alarm value.

[0072] The basic principles and main features of the present application and the advantages of the present application are shown and described above, and it is obvious for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and the present application can be realized in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be regarded as exemplary and non-limiting, the scope of the present application is defined by the appended claims rather than the above description, and all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0073] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be properly combined to form other embodiments that those skilled in the art can understand. The above is only to illustrate the technical idea of the present application, and cannot limit the protection scope of the present application, and any modification made on the basis of the technical solutions according to the technical idea of the present application falls within the protection scope of the claims of the present application.

Claims

1. A combustion optimization system for a counter-fired boiler that realizes multiple combustion conditions, characterized in that: The invention comprises a hot secondary air main pipe, a medium-speed coal mill (1) and a plurality of pulverized coal distributors, wherein the plurality of pulverized coal distributors are connected to the medium-speed coal mill (1), and each pulverized coal distributor is connected to a main burner and a micro standby burner respectively; a micro secondary air nozzle is arranged above each micro standby burner, and the micro secondary air nozzle is connected to the hot secondary air main pipe; the micro standby burner is a direct current burner; an adjusting door is arranged between the pulverized coal distributor and the micro standby burner, and the micro standby burner is arranged obliquely above the main burner; The micro standby burner is arranged between the two main burners and is spaced apart from any one of the main burners horizontally.

2. The combustion optimization system for a counter-firing boiler realizing multiple combustion conditions according to claim 1 is characterized in that: An adjusting door is provided between the micro secondary air nozzle and the hot secondary air main pipe; and the main burner is a swirl burner.

3. The combustion optimization system for a hedge-fired boiler realizing multiple combustion conditions according to claim 1 is characterized in that: The main burners located on the same floor are evenly arranged at the same height on the front and rear walls of the counter-firing boiler.

4. The combustion optimization method for a hedge-fired boiler realizing a multi-combustion operating condition based on the system of claim 2 is characterized in that: The following steps are involved: The pulverized coal in the medium-speed coal mill (1) is transported to each pulverized coal distributor. After the pulverized coal distributor separates part of the pulverized coal, the rest of the pulverized coal is sent to the main burner for combustion; The mass of the partial pulverized coal is 0% to 30% of the total mass of the pulverized coal; The mass of the remaining pulverized coal is 70% to 100% of the total mass of the pulverized coal.

5. The combustion optimization method for a counter-firing boiler realizing a multi-combustion operating condition according to claim 4 is characterized in that: It also includes adjusting the amount of pulverized coal entering the micro standby burner within the range of 0% to 30% of the total mass of the pulverized coal by adjusting the opening of the regulating door between the pulverized coal distributor and the micro standby burner; and adjusting the change in the amount of hot secondary air entering the micro secondary air nozzle by adjusting the opening of the regulating door between the micro secondary air nozzle and the hot secondary air main pipe.

6. The combustion optimization method for a counter-firing boiler realizing a multi-combustion operating condition according to claim 4 is characterized in that: The pulverized coal in the micro standby burner is ignited by the high-temperature flue gas generated by the combustion of the adjacent main burner.

7. The combustion optimization method for a counter-firing boiler realizing a multi-combustion operating condition according to claim 6 is characterized in that: The output of each main burner is adjusted by adjusting the opening of the regulating door between the pulverized coal distributor and the micro standby burner; hot secondary air is introduced through the micro secondary air nozzle to assist combustion.

8. The combustion optimization method for a counter-firing boiler realizing a multi-combustion operating condition according to claim 4 is characterized in that: If the output of the medium-speed coal mill is less than the minimum output threshold, activate the micro standby burner. If the fire detection signal of the main burner flashes, close the regulating door corresponding to the main burner until the fire detection signal is normal.

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