Coal blending system and method for variable-load combustion high-alkali coal

Abstract

The invention provides a coal blending system and method of high-alkali coal for variable-load combustion, and belongs to the technical field of variable-load operation and coal blending combustion, in the method, high-quality coal and low-quality coal are mixed in front of a furnace to serve as coal blending types, and the coal feeding amount of the two types of coal is changed to adapt to variable loads of a boiler; in addition, high-alkali coal is subjected to blending combustion in the furnace, slag-bonding and ash deposition of combustion of the high-alkali coal can be effectively relieved through coal blending combustion, and ash content can be captured through blending combustion of inferior coal in a high load so as to achieve the effect of slowing down slag-bonding. And finally, an on-line monitoring system is arranged, key parameters of a hearth outlet are monitored in real time and fed back to corresponding parts, the corresponding parts adjust the coal amount of the three kinds of coal and the air supply amount of an air feeder to achieve the purposes of low-load stable combustion, high-load slowing down of high-alkali coal slagging and the like, the economic benefits of combustion of the high-alkali coal are effectively improved, and safe and stable operation of the boiler is guaranteed.

Description

[0001] This application is based on and claims priority to a Chinese patent application with the application number 202411637662.X and the filing date of November 15, 2024. The entire content of this Chinese patent application is hereby incorporated into this application by reference. Technical Field

[0002] The present invention relates to the technical fields of variable load operation and coal blending combustion, and particularly to a coal blending system and method for burning high-alkali coal under variable load. Background Art

[0003] The energy structure in China is characterized by rich coal, poor oil, and scarce gas, which determines that coal is the main energy consumption in China. High-alkali coal reserves are abundant in Xinjiang region of China. Xinjiang high-alkali coal is one of the important power coals in China. However, the content of alkali metals in its coal ash is relatively high, which easily causes serious slagging and fouling in boilers when directly burning high-alkali coal. Especially during variable load operation of the boiler, the temperature field, flow field in the boiler furnace, and the characteristics of alkali metal precipitation in coal will change violently, aggravating the degree of slagging and fouling. The slagging and ash accumulation on the heating surface and flue of the boiler will lead to an increase in heat transfer resistance and a decrease in heat transfer efficiency. In severe cases, it may also cause various safety problems such as over-temperature tube explosion and severe corrosion and wear of the superheater, affecting the efficient utilization of high-alkali coal and the safe operation of the boiler. Therefore, it is of great significance to solve the problem of slagging and ash accumulation during the combustion of high-alkali coal under variable load conditions. Summary of the Invention

[0004] The object of the present invention is to propose a coal blending system and method for burning high-alkali coal under variable load, which can solve the problem in the prior art of how to burn high-alkali coal under variable load conditions and reduce slagging and ash accumulation after combustion.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention proposes a coal blending system for burning high-alkali coal under variable load, including: an external blending and conveying system for high-quality and low-quality coals, an in-furnace blending and burning conveying system for high-alkali coal, a furnace combustion system, a air supply system, and a monitoring system;

[0007] The external blending and conveying system for high-quality and low-quality coals includes a coal conveyor belt, a coal bunker, a partition plate, an electric gate, a coal mill, a coal feeder, and a powder exhaust fan, which blend high-quality and low-quality coals in a certain coal quantity outside the furnace, grind them into pulverized coal, and then send them to the lower burner;

[0008] The in-furnace blending and burning conveying system for high-alkali coal includes a coal conveyor belt, a coal bunker, an electric gate, a coal mill, a coal feeder, and a powder exhaust fan, which grind high-alkali coal into pulverized coal and then send it to the upper burner;

[0009] The furnace combustion system includes six layers of burners A, B, C, D, E, and F, a main combustion zone, a co-firing zone, and a burnout zone, and burns the fed fuel in the furnace;

[0010] The air supply system includes a forced draft fan and an air preheater, and inputs hot air into the coal mill, burners, and burnout zone to transport pulverized coal and provide air for combustion;

[0011] The monitoring system monitors key parameters such as the furnace outlet temperature, furnace outlet heating rate, furnace load, and furnace outlet excess air coefficient, and feeds back to the corresponding components according to the operating conditions to adjust the operating state. The corresponding components include the electric gate of the high-quality coal bunker, the electric gate of the low-quality coal bunker, the electric gate of the high-alkali coal bunker, and the forced draft fan.

[0012] In a second aspect, the present invention proposes a coal blending method for variable load combustion of high-alkali coal using the above system, including the following steps:

[0013] S1. The system mixes two coal types of different qualities, good and bad, outside the furnace. The good and bad coals respectively fall from the coal conveying belt into the coal bunker, pass through the electric gate, fall into the coal feeder, and then are sent into the coal mill and the powder exhaust fan, and finally are sent into the three layers of burners A, B, and C for combustion in the main combustion zone.

[0014] S2. The high-alkali coal is co-fired in the furnace. It falls from the coal conveying belt into the coal bunker, passes through the electric gate, falls into the coal feeder, and then is sent into the coal mill and the powder exhaust fan, and finally is sent into the two layers of burners D and E for combustion in the co-firing zone.

[0015] S3. During the combustion process, the F-layer burner is in standby, and the monitoring system monitors key parameters such as the furnace outlet temperature, furnace outlet heating rate, furnace load, and furnace outlet excess air coefficient in real time.

[0016] S4. When the furnace operates at low load, the monitoring system feeds back the load condition to the coal blending coal bunker electric gate, the high-alkali coal bunker electric gate, and the forced draft fan. In terms of fuel, the opening of the electric gate of the high-quality coal bunker becomes larger, and the opening of the electric gate of the low-quality coal bunker becomes smaller, increasing the coal feeding amount of the high-quality coal and reducing the coal feeding amount of the low-quality coal to stabilize combustion; the opening of the electric gate of the high-alkali coal bunker is adjusted appropriately to ensure that both the furnace outlet temperature and the heating rate are lower than the set values. In terms of air supply, the forced draft fan increases the air supply volume to increase the furnace oxygen content and stabilize combustion; at the same time, the monitoring system monitors the furnace outlet excess air coefficient in real time to judge whether the furnace oxygen content reaches the expected value.

[0017] S5. When the furnace is operating at high load, the monitoring system feeds back the load situation to the coal distribution hopper electric gate, the high-alkali coal hopper electric gate, and the forced draft fan. In terms of fuel, the opening of the high-quality coal hopper electric gate becomes smaller, and the opening of the inferior-quality coal hopper electric gate becomes larger, reducing the intake of high-quality coal and increasing the intake of inferior-quality coal to improve the combustion economic efficiency. And since the content of alumina, silica, etc. in the inferior-quality coal is relatively high, when using more inferior-quality coal as the blending coal for high-alkali coal, it can effectively capture the alkali metal ash and slow down the slagging and fouling of the boiler. The opening of the high-alkali coal hopper electric gate is adjusted appropriately to ensure that both the furnace outlet temperature and the heating rate are lower than the set values. In terms of air supply, the forced draft fan reduces the air supply volume to reduce the oxygen content in the furnace and prevent excessive combustion and coking in the main combustion zone. At the same time, the monitoring system monitors the excess air coefficient at the furnace outlet in real time to determine whether the oxygen content in the furnace reaches the expected value.

[0018] S6. When the monitoring system detects that the furnace outlet temperature or the heating rate is relatively high, it indicates that the slagging and fouling in the furnace are relatively serious or the slagging and fouling rate is relatively fast at this time. At this time, the opening of the high-alkali coal hopper electric gate becomes smaller to reduce the intake of high-alkali coal. At the same time, the openings of the electric gates of the two blending coal hoppers for high-quality and inferior-quality coal become larger appropriately to increase the intake of blending coal and slow down the slagging and fouling situation of the boiler to ensure the safe operation of the boiler. The monitoring system monitors the parameters in real time and feeds them back to the corresponding components, and the corresponding components repeat the above adjustment operations until both the furnace outlet temperature and the heating rate are lower than the set values.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention provides a coal blending system and method for burning high-alkali coal with variable load. By combining out-of-furnace blending and in-furnace co-firing, while alleviating the slagging and fouling of high-alkali coal combustion, it can adjust the intake of high-quality and inferior-quality coal to adapt to the burning of high-alkali coal with variable load. The present invention also sets up a monitoring system that can monitor the furnace load change and the slagging and fouling situation in real time and feed them back to the corresponding components. The corresponding components can timely adjust the intake of coal and air supply in and out of the furnace, etc., realizing the automatic intelligent adjustment of fuel and air supply in the combustion process, and improving the production efficiency and the safety and stability of boiler operation.

[0021] Furthermore, the present invention uses high-alkali coal in the upper layer of the burner. By increasing the co-firing position, the emission rate of alkali metals is reduced, and at the same time, the temperature in the upper combustion area is relatively low, which can also slow down the slagging and fouling caused by the combustion of high-alkali coal;

[0022] Furthermore, the present invention uses inferior-quality coal as fuel under high load, which can improve the economic efficiency. After the inferior-quality coal burns, components such as alumina and silica in the ash can also capture the alkali metal ash generated by the combustion of high-alkali coal, further slowing down the slagging and fouling of high-alkali coal combustion;

[0023] Furthermore, the monitoring system arranged in the present invention and the corresponding components can quickly respond to the change of the unit load, and the variable load adaptation method is simple and reliable, avoiding the time lag in the process of adapting to variable load in the past and being unable to respond to the rapid change of load in time. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 is a schematic diagram of a coal blending system for burning high-alkali coal with variable load;

[0026] Figure 2 is an overall process block diagram of a coal blending method for burning high-alkali coal with variable load;

[0027] Figure 3 is a working schematic block diagram of the monitoring system in a coal blending system for burning high-alkali coal with variable load.

[0028] Wherein: 1 - high-quality coal conveyor belt; 2 - low-quality coal conveyor belt; 3 - partition plate; 4 - electric gate of high-quality coal bunker; 5 - electric gate of low-quality coal bunker; 6 - coal blending bunker; 7 - coal blending feeder; 8 - coal blending coal mill; 9 - coal blending powder exhaust fan; 10 - high-alkali coal conveyor belt; 11 - high-alkali coal bunker; 12 - electric gate of high-alkali coal bunker; 13 - high-alkali coal feeder; 14 - high-alkali coal mill; 15 - high-alkali coal powder exhaust fan; 16 - six-layer burners A, B, C, D, E, F; 17 - slag discharging device; 18 - forced draft fan. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0030] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0031] It should be noted that like reference numerals and letters refer to like items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0032] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the figures, or the orientation or positional relationship in which the product of the present invention is usually placed during use, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, terms such as "first", "second", etc. are only used for distinguishing descriptions and cannot be construed as indicating or implying relative importance. In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0033] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, if terms such as "set", "installed", "connected", "connected" are understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] The present invention will be further described in detail below with reference to the accompanying drawings:

[0035] See Figure 1, the present invention provides a coal blending system for burning high-alkali coal with variable load, comprising: an external blending and conveying system for high-quality and low-quality coals, an internal blending and burning conveying system for high-alkali coal, a furnace combustion system, a air supply system, and a monitoring system; the external blending and conveying system for high-quality and low-quality coals includes a high-quality coal conveyor belt 1, a low-quality coal conveyor belt 2, a coal blending hopper 6, a partition plate 3, an electric gate 4 of the high-quality coal hopper, an electric gate 5 of the low-quality coal hopper, a coal blending coal mill 8, a coal blending feeder 7, and a coal blending primary air fan 9, which blend the two coal types with different qualities outside the furnace according to a certain coal quantity, grind them into pulverized coal, and then send them into the A, B, and C layers of burners; the internal blending and burning conveying system for high-alkali coal includes a high-alkali coal conveyor belt 10, a high-alkali coal hopper 11, an electric gate 12 of the high-alkali coal hopper, a high-alkali coal mill 14, a high-alkali coal feeder 13, and a high-alkali coal primary air fan 15, which grind the high-alkali coal into pulverized coal and then send it into the D and E layers of burners; the furnace combustion system includes six layers of burners 16 of A, B, C, D, E, and F, a main combustion zone, a blending combustion zone, and a burnout zone, which burn the fuel fed into the furnace; the air supply system includes a forced draft fan 18 and an air preheater, which input hot air into the coal blending coal mill 8, the high-alkali coal mill 14, the A, B, C, D, and E layers of burners 16, and the burnout zone; the monitoring system monitors key parameters such as the furnace outlet temperature, the furnace outlet temperature rising rate, the furnace load, and the furnace outlet excess air coefficient, and feeds back to the corresponding components according to the operating conditions to adjust the operating state, and the corresponding components include the electric gate 4 of the high-quality coal hopper, the electric gate 5 of the low-quality coal hopper, the electric gate 12 of the high-alkali coal hopper, and the forced draft fan 18.

[0036] See Figure 2 , the present invention provides a coal blending method for burning high-alkali coal with variable load, comprising the following steps:

[0037] S1, the system blends two different-quality coal types outside the furnace. The high-quality and low-quality coals respectively fall from the conveyor belt into the hopper, pass through the electric gate, fall into the feeder, and then are sent into the coal mill and the primary air fan, and finally are sent into the A, B, and C layers of burners for combustion in the main combustion zone.

[0038] S2, the high-alkali coal is burned by internal blending. It falls from the conveyor belt into the hopper, passes through the electric gate, falls into the feeder, and then is sent into the coal mill and the primary air fan, and finally is sent into the D and E layers of burners for combustion in the blending combustion zone.

[0039] S3, during the combustion process, the F-layer burner is in standby, and the monitoring system monitors key parameters such as the furnace outlet temperature, the furnace outlet temperature rising rate, the furnace load, and the furnace outlet excess air coefficient in real time.

[0040] S4. When the furnace operates at low load, the monitoring system feeds back the load condition to the electric gate valves of the coal bunker for blended coal, the electric gate valve of the high-alkali coal bunker, and the forced draft fan. In terms of fuel, the opening degree of the electric gate valve of the high-quality coal bunker becomes larger, while that of the low-quality coal bunker becomes smaller, increasing the coal feed amount of high-quality coal and decreasing that of low-quality coal to stabilize combustion. The opening degree of the electric gate valve of the high-alkali coal bunker is adjusted appropriately to ensure that both the furnace outlet temperature and the heating rate are lower than the set values. In terms of air supply, the forced draft fan increases the air supply volume to increase the oxygen content in the furnace and stabilize combustion. At the same time, the monitoring system monitors the excess air coefficient at the furnace outlet in real time to determine whether the oxygen content in the furnace reaches the expected value.

[0041] S5. When the furnace operates at high load, the monitoring system feeds back the load condition to the electric gate valves of the coal bunker for blended coal, the electric gate valve of the high-alkali coal bunker, and the forced draft fan. In terms of fuel, the opening degree of the electric gate valve of the high-quality coal bunker becomes smaller, while that of the low-quality coal bunker becomes larger, decreasing the coal feed amount of high-quality coal and increasing that of low-quality coal to improve the combustion economic efficiency. And since the contents of alumina, silica, etc. in the low-quality coal are relatively high, when a relatively large amount of low-quality coal is burned as the blending coal for high-alkali coal, it can effectively capture the alkali metal ash and slow down the slagging and fouling of the boiler. The opening degree of the electric gate valve of the high-alkali coal bunker is adjusted appropriately to ensure that both the furnace outlet temperature and the heating rate are lower than the set values. In terms of air supply, the forced draft fan decreases the air supply volume to reduce the oxygen content in the furnace and prevent excessive combustion and coking in the main combustion zone. At the same time, the monitoring system monitors the excess air coefficient at the furnace outlet in real time to determine whether the oxygen content in the furnace reaches the expected value.

[0042] S6. When the monitoring system detects that the furnace outlet temperature or the heating rate is relatively high, it indicates that the slagging and fouling in the furnace are relatively serious or the slagging and fouling rate is relatively fast at this time. At this time, the opening degree of the electric gate valve of the high-alkali coal bunker becomes smaller to reduce the coal feed amount of high-alkali coal. At the same time, the opening degrees of the electric gate valves of the two types of blended coal bunkers (high-quality and low-quality) become larger appropriately to increase the coal feed amount of the blended coal, slow down the slagging and fouling situation of the boiler, and ensure the safe operation of the boiler. The monitoring system monitors the parameters in real time and feeds back to the corresponding components, and the corresponding components repeat the above adjustment operations until both the furnace outlet temperature and the heating rate are lower than the set values.

[0043] See Figure 3 , the key parameters such as the furnace outlet temperature, heating rate, operating load, and excess air coefficient are input into the monitoring system for real-time monitoring. When the monitoring system detects that the parameters such as the furnace outlet temperature, heating rate, and excess air coefficient do not meet the set standards, it feeds back to the forced draft fan, the electric gate valve of the high-quality coal bunker, the electric gate valve of the low-quality coal bunker, or the electric gate valve of the high-alkali coal bunker to adjust the air supply volume of the forced draft fan, the opening degree of the electric gate valve of the high-quality coal bunker, the opening degree of the electric gate valve of the low-quality coal bunker, or the opening degree of the electric gate valve of the high-alkali coal bunker until the monitored data returns to the standard range or can adapt to the current load.

[0044] The present invention adopts a coal blending system and method for variable-load combustion of high-alkali coal with the above structure to solve the serious slagging and fouling problems caused by variable-load combustion of high-alkali coal in a boiler. The design of the present invention is reasonable, and it can scientifically and intelligently adapt to the variable-load process and the coal quantity of high-alkali coal co-fired in the furnace, improving the economic efficiency, safety and stability of boiler combustion.

[0045] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A coal blending system for variable-load combustion of high-alkali coal, characterized in that, Including: A blending and conveying system for good and poor quality coals outside the furnace, an injection and combustion conveying system for high-alkali coal inside the furnace, a furnace combustion system, a blast system, and a monitoring system.

2. The coal blending system for variable-load combustion of high-alkali coal according to claim 1, characterized in that In the coal blending system, a combination of pre-mixing outside the furnace and injection combustion inside the furnace is adopted. Injection combustion inside the furnace can alleviate slagging and ash accumulation during the combustion of high-alkali coal, and pre-mixing outside the furnace can adapt to rapid load changes, enhance the economy of coal combustion, and further alleviate slagging and ash accumulation during the combustion of high-alkali coal under high loads.

3. The coal blending system for variable-load combustion of high-alkali coal according to claim 1, characterized in that, The blending and conveying system for good and poor quality coals outside the furnace includes: a good-quality coal conveying belt 1, a poor-quality coal conveying belt 2, a coal blending hopper 6, a partition plate 3, an electric gate 4 for the good-quality coal hopper, an electric gate 5 for the poor-quality coal hopper, a coal blending coal mill 8, a coal blending feeder 7, and a coal blending powder exhaust fan 9.

4. The coal blending system for variable-load combustion of high-alkali coal according to claim 3, wherein, The injection and combustion conveying system for high-alkali coal inside the furnace includes: a high-alkali coal conveying belt 10, a high-alkali coal hopper 11, an electric gate 12 for the high-alkali coal hopper, a high-alkali coal mill 14, a high-alkali coal feeder 13, and a high-alkali coal powder exhaust fan 15; the furnace combustion system includes six layers of burners 16, namely A, B, C, D, E, and F, a main combustion zone, an injection combustion zone, and a burnout zone.

5. The coal blending system for variable-load combustion of high-alkali coal according to claim 4, wherein The blast system includes a blower 18 and an air preheater; the monitoring system monitors key parameters such as the furnace outlet temperature, the furnace outlet temperature rise rate, the furnace load, and the furnace outlet excess air coefficient, and according to the operating conditions, feeds back to the corresponding components to adjust the operating state. The corresponding components include the electric gate 4 for the good-quality coal hopper, the electric gate 5 for the poor-quality coal hopper, the electric gate 12 for the high-alkali coal hopper, and the blower 18.

6. The coal blending system for variable-load combustion of high-alkali coal according to claim 5, characterized in that, In the said operating conditions, the furnace oxygen content is judged by monitoring the furnace outlet excess air coefficient.

7. The coal blending system for variable load combustion of high-alkali coal according to claim 5, characterized in that In the said operating conditions, the furnace slagging and ash accumulation situation is judged by monitoring the furnace outlet temperature and the furnace outlet temperature rise rate. When the furnace outlet temperature or the furnace outlet temperature rise rate is higher than the preset value, it indicates that the furnace slagging and ash accumulation is relatively serious.

8. A coal blending system for variable-load combustion of high-alkali coal according to claim 5, characterized in that The monitoring system monitors the state of the furnace combustion system in real time and feeds back to the corresponding components. The corresponding components adjust the opening degrees of the electric gates of the good-quality coal, poor-quality coal, and high-alkali coal hoppers, and the air volume sent by the blower to achieve rapid change of the coal blending amount and response to load changes.

9. A method for blending high-alkali coal with variable load, which adopts the blending system for burning high-alkali coal with variable load described in any one of claims 1-8, is characterized in that, Including the following steps: S1. In this system, two coal types with different qualities, good and poor, are blended outside the furnace. The good and poor coals respectively fall from the conveying belts into the hoppers, pass through the electric gates, fall into the feeders, and then are sent into the coal mills and powder exhaust fans, and finally are sent into the three layers of burners A, B, and C for combustion in the main combustion zone. S2. High-alkali coal is injected and burned inside the furnace. It falls from the conveying belt into the hopper, passes through the electric gate, falls into the feeder, and then is sent into the coal mill and powder exhaust fan, and finally is sent into the two layers of burners D and E for combustion in the injection combustion zone. S3. During the combustion process, the F-layer burner is in standby, and the monitoring system monitors key parameters such as the furnace outlet temperature, the furnace outlet temperature rise rate, the furnace load, and the furnace outlet excess air coefficient in real time.

10. The method for blending high-alkali coal with variable load in a blending coal system for burning high-alkali coal with variable load according to claim 9, characterized in that, Also including the following steps: S4. When the furnace operates at low load, the monitoring system feeds back the load condition to the electric gate valves of the coal bunker for blended coal, the electric gate valve of the high-alkali coal bunker, and the forced draft fan. In terms of fuel, the opening degree of the electric gate valve of the high-quality coal bunker becomes larger, and the opening degree of the electric gate valve of the low-quality coal bunker becomes smaller, increasing the coal feed rate of high-quality coal and decreasing the coal feed rate of low-quality coal to stabilize combustion. The opening degree of the electric gate valve of the high-alkali coal bunker is adjusted appropriately to ensure that both the furnace outlet temperature and the heating rate are lower than the set values. In terms of air supply, the forced draft fan increases the air supply volume to increase the oxygen content in the furnace and stabilize combustion. At the same time, the monitoring system continuously monitors the excess air coefficient at the furnace outlet to determine whether the oxygen content in the furnace reaches the expected value. S5. When the furnace operates at high load, the monitoring system feeds back the load condition to the electric gate valves of the coal bunker for blended coal, the electric gate valve of the high-alkali coal bunker, and the forced draft fan. In terms of fuel, the opening degree of the electric gate valve of the high-quality coal bunker becomes smaller, and the opening degree of the electric gate valve of the low-quality coal bunker becomes larger, decreasing the coal feed rate of high-quality coal and increasing the coal feed rate of low-quality coal to improve the combustion economic efficiency. Moreover, since the contents of alumina, silica, etc. in the low-quality coal are relatively high, when a larger amount of low-quality coal is burned as the blending coal for high-alkali coal, it can effectively capture the alkali metal ash and slow down the slagging and fouling of the boiler. The opening degree of the electric gate valve of the high-alkali coal bunker is adjusted appropriately to ensure that both the furnace outlet temperature and the heating rate are lower than the set values. In terms of air supply, the forced draft fan decreases the air supply volume to reduce the oxygen content in the furnace and prevent excessive intense combustion in the main combustion zone and slagging. At the same time, the monitoring system continuously monitors the excess air coefficient at the furnace outlet to determine whether the oxygen content in the furnace reaches the expected value. S6. When the monitoring system detects that the furnace outlet temperature or the heating rate is relatively high, it indicates that the slagging and fouling in the furnace are relatively serious or the slagging and fouling rate is relatively fast at this time. At this time, the opening degree of the electric gate valve of the high-alkali coal bunker becomes smaller to reduce the coal feed rate of high-alkali coal. At the same time, the opening degrees of the electric gate valves of the two types of blended coal bunkers (high-quality and low-quality) become appropriately larger to increase the coal feed rate of the blended coal, slow down the slagging and fouling situation of the boiler, and ensure the safe operation of the boiler. The monitoring system continuously monitors the parameters and feeds them back to the corresponding components, and the corresponding components repeat the above adjustment operations until both the furnace outlet temperature and the heating rate are lower than the set values.

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