A boiler deep peak shaving system based on different arrangement of burners and a control method thereof

Abstract

The application discloses a boiler deep peak regulation system based on different arrangement of burners and a control method, belongs to the technical field of pulverized coal boiler combustion, and comprises a boiler furnace, wherein water cooling walls are arranged around the boiler furnace, the front wall and the back wall of the boiler furnace are symmetrically provided with the lowermost layer of burners, the lowermost layer of burners comprises first burner assemblies and second burner assemblies, the first burner assemblies are centrally installed, the second burner assemblies are symmetrically arranged on the two sides of the first burner assemblies, the first burner assemblies are communicated with first pulverized coal branch pipes through shunt devices, the second burner assemblies are communicated with second pulverized coal branch pipes, and the first pulverized coal branch pipes and the second pulverized coal branch pipes are communicated with a main pulverized coal pipeline. The application adopts the above-mentioned boiler deep peak regulation system based on different arrangement of burners and the control method, significantly improves the low-load stable combustion capacity, improves the water cooling wall thermal load distribution, enhances the deep peak regulation flexibility, optimizes the air bellow pressure difference adaptability, and has small reconstruction engineering quantity.

Description

Technical Field

[0001] This invention relates to the field of pulverized coal boiler combustion technology, and in particular to a deep peak-shaving system and control method for boilers based on differentiated burner arrangement. Background Technology

[0002] With the increasing proportion of new energy power generation, coal-fired power generating units need to frequently participate in deep peak shaving, and boilers often operate at 30% or even 20% of their rated load for extended periods. Existing pulverized coal boilers with opposing front and rear walls suffer from problems such as poor combustion stability, flame deviation and wall-brushing, excessively high localized heat load on the water-cooled walls, and severe coking during deep peak shaving due to the high power output of individual burners and low pulverized coal concentration in the bottom burners. Simultaneously, the uneven pressure distribution caused by the wind box structure further exacerbates the output deviation between burners, restricting the unit's low-load operating capability. Summary of the Invention

[0003] The purpose of this invention is to provide a boiler deep peak shaving system and control method based on burner differential arrangement, which significantly improves the low-load stable combustion capability, improves the heat load distribution of water-cooled walls, enhances the flexibility of deep peak shaving, optimizes the adaptability of wind box pressure difference, and requires less engineering work.

[0004] To achieve the above objectives, the present invention provides a boiler deep peak-shaving system based on differentiated burner arrangement, including a boiler furnace, with water-cooled walls arranged around the boiler furnace. A bottom layer burner is symmetrically arranged on both the front and rear walls of the boiler furnace. The bottom layer burner includes a first burner assembly and a second burner assembly. The first burner assembly is centrally mounted, and the second burner assemblies are symmetrically arranged on both sides of the first burner assembly. The first burner assembly is connected to a first pulverized coal branch pipe via a diversion device, and the second burner assembly is connected to a second pulverized coal branch pipe. Both the first and second pulverized coal branch pipes are connected to a main pulverized coal pipeline, which is connected to a coal mill.

[0005] Preferably, the first burner assembly is a low-power burner, and every two low-power burners are connected to the pulverized coal pipeline through a diversion device. The low-power burners and the diversion device, as well as the diversion device and the first pulverized coal branch pipe, are connected by flanges.

[0006] Preferably, the second burner is a high-power burner, which is directly connected to the pulverized coal pipeline via a flange, and the high-power burner is connected to the second pulverized coal branch pipe via a flange.

[0007] Preferably, the diversion device is either a Y-type diversion tee with a symmetrical structure or a Venturi type distributor, and each branch pipe of the diversion device is provided with an adjustable shrinkage orifice, and the inner wall of the diversion device is lined with wear-resistant ceramic.

[0008] Preferably, both the first and second pulverized coal branch pipes are connected to the main pulverized coal pipeline via flanges, and the main pulverized coal pipeline is connected to the coal mill via flanges and flexible compensating components.

[0009] Preferably, secondary air ducts are symmetrically arranged on the front and rear walls of the boiler furnace, and secondary air dampers are provided at the connection between the boiler furnace and the secondary air ducts. The boiler furnace is connected to the air box through the secondary air ducts, and the secondary air ducts are all connected to the boiler furnace and the air box through flanges.

[0010] Preferably, the combustion power of the low-power burner is half that of the high-power burner.

[0011] This invention provides a control method for deep peak shaving of boilers based on differentiated burner arrangement. Employing the aforementioned deep peak shaving system for boilers based on differentiated burner arrangement, the method includes the following operations: By adjusting the pulverized coal feed rate of each low-power burner, the pulverized coal concentration of a single low-power burner is maintained within 80% to 110% of the design value to ensure stable ignition under low load. The high-power burners on both sides maintain an appropriate primary air volume to prevent flames from sticking to the wall. Based on the oxygen content at the boiler furnace outlet and the water-cooled wall temperature distribution, the opening of each secondary air damper is dynamically adjusted to prioritize ensuring uniform airflow for the low-power burners in the middle area and that the airflow for the high-power burners in the side wall area meets the requirements for preventing wall erosion.

[0012] Therefore, the present invention employs the above-mentioned boiler deep peak-shaving system and control method based on burner differential arrangement, which has the following beneficial effects: 1. Significantly improves low-load stable combustion capability: After splitting, the power of a single burner is halved. With the total amount of coal remaining unchanged, the coal powder concentration can be maintained or even increased (by adjusting the adjustable orifice at the inlet of the low-power burner to achieve burner cut-off and operation). The ignition distance is shortened, and multiple small flames support each other, greatly reducing the risk of flameout. 2. Improve the heat load distribution of the water-cooled wall: Distribute the heat power to avoid local high temperature zones caused by the original large burner, reduce the risk of coking and high temperature corrosion, and extend the service life of the water-cooled wall; 3. Enhanced flexibility of deep peak shaving: It can achieve a lower load limit (such as 20%~30% of rated load), avoid premature commissioning of upper burners, and is beneficial to steam temperature control; 4. Optimize the adaptability of the bellows pressure difference: The multiple small burners in the middle area are less sensitive to the distribution of the bellows pressure difference, resulting in more uniform air distribution; large burners are retained on the side walls, utilizing their momentum penetration ability to prevent wall-attached combustion; at the same time, it can reduce the ability of the airflow to diffuse to the side walls after the burners in the middle area are counteracted, which is beneficial for controlling high-temperature corrosion. 5. Minimal renovation work: Only a diversion device needs to be added at the end of the pulverized coal pipeline, without changing the main pipeline structure from the coal mill to the burner. The construction period is short and the return on investment is high.

[0013] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the connection between a high-power burner and a low-power burner and a coal mill in a boiler deep peak-shaving system based on differentiated burner arrangement according to the present invention. Figure 2 This is a schematic diagram of the connection between the secondary air duct and the air box in a boiler deep peak-shaving system based on burner differential arrangement according to the present invention. Figure 3 This is a schematic diagram of the structure of a boiler deep peak-shaving system diversion device based on burner differential arrangement according to the present invention.

[0015] Figure Labels 1. Boiler furnace; 2. High-power burner; 3. Low-power burner; 4. Diverter; 5. Adjustable orifice; 6. Main pulverized coal pipeline; 7. Flexible compensation component; 8. Coal mill; 9. Secondary air damper; 10. Secondary air duct; 11. Air box; 12. Water-cooled wall. Detailed Implementation

[0016] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0017] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0018] Example 1 like Figures 1 to 3As shown, this invention provides a boiler deep peak-shaving system based on differentiated burner arrangement, including a boiler furnace 1. Water-cooled walls 12 are arranged around the boiler furnace 1, serving as the main evaporative heating surface, which can quickly absorb radiant heat, ensuring sufficient radiant heat exchange to maintain the stability of the working fluid circulation during low loads under deep peak-shaving conditions. The bottom layer burners are symmetrically arranged on the front and rear walls of the boiler furnace 1, forming a counter-current combustion system. Secondary air ducts 10 are symmetrically arranged on the front and rear walls of the boiler furnace 1. The number of burner layers can be designed according to actual usage requirements, with at least a bottom layer burner. The number of secondary air ducts 10 depends on the burner type, boiler capacity, and design level. A secondary damper 9 is provided at the connection between the boiler furnace 1 and the secondary air ducts 10. The boiler furnace 1 is connected to the wind box 11 via the secondary air ducts 10, and all secondary air ducts 10 are connected to the boiler furnace 1 and the wind box 11 via flanges. Secondary air duct 10 supplies combustion air to the boiler furnace 1, and secondary air damper 9 independently regulates the air distribution in each zone, thereby regulating the aerodynamic field within the boiler furnace 1. During deep peak shaving, dynamic closed-loop regulation can be performed based on the oxygen content at the furnace outlet and the wall temperature distribution of the water-cooled wall 12. This refined "zone-specific air distribution" can ensure a reducing atmosphere in the central main combustion zone to stabilize the flame, while also supplementing oxidizing air to the side wall areas to prevent excessively rich reducing atmospheres in certain areas from causing slagging.

[0019] The bottom burner includes a first burner assembly and a second burner assembly. The first burner assembly is installed in the center, and the second burner assembly is symmetrically arranged on both sides of the first burner assembly. The first burner assembly is connected to the first pulverized coal branch pipe through the diversion device 4, and the second burner assembly is connected to the second pulverized coal branch pipe. Both the first and second pulverized coal branch pipes are connected to the main pulverized coal pipeline 6, and the main pulverized coal pipeline 6 is connected to the coal mill 8.

[0020] The first burner assembly consists of a low-power burner 3. Every two low-power burners 3 are connected to the pulverized coal pipeline via a diversion device 4. The low-power burners 3 and the diversion device 4, as well as the diversion device 4 and the first pulverized coal branch pipe, are connected by flanges. The low-power burners 3 require a low stable combustion heat load, making it easier to maintain pulverized coal concentration and flame temperature at low pulverized coal feed rates, forming a stable "core fire source," thereby significantly increasing the boiler's minimum non-oil-injection stable combustion load.

[0021] The second burner is a high-power burner 2, which is directly connected to the pulverized coal pipeline via a flange. The high-power burner 2 is also connected to the second pulverized coal branch pipe via a flange. Due to its larger pulverized coal and primary air volume, the high-power burner 2 has a strong jet flow. This forms a "rigid air wall," effectively resisting flue gas disturbance within the furnace and preventing pulverized coal flames from scouring or adhering to the side water-cooled wall 12, fundamentally avoiding the risk of high-temperature corrosion and slagging of the water-cooled wall 12. The combustion power of the low-power burner 3 is half that of the high-power burner 2, making the total power of the two small flames in the middle exactly equal to that of a single large burner on one side. When the total load drops to extremely low levels, the large burners on both sides can be completely shut down or retain only minimal output, while the two small burners in the middle can still operate independently at 50% of the total lower layer output, with each burner meeting the concentration standard, achieving safe and continuous operation under ultra-low load conditions. The high-power burner 2, which was originally located in the middle section, was split into low-power burners 3. This dispersed the heat power, avoided the local high-temperature zone caused by the original high-power burner, reduced the risk of coking and high-temperature corrosion, and extended the life of the water-cooled wall 12. The multiple low-power burners 3 in the middle section reduced the sensitivity of the pressure difference distribution of the air box 11, resulting in more uniform air distribution.

[0022] The flow divider 4 is either a symmetrical Y-type flow divider tee or a Venturi-type distributor. It evenly distributes the airflow from the first pulverized coal branch pipe to the two low-power burners 3. Utilizing geometric symmetry, it ensures consistent flow resistance in the gas-solid two-phase flow within the branch pipes, guaranteeing a high degree of matching between the pulverized coal and air volume received by the two low-power burners 3, preventing airflow interference or flow deviation. Each branch pipe of the flow divider 4 is equipped with an adjustable orifice 5. During operation, the orifice 5 can be fine-tuned according to actual pulverized coal concentration fluctuations, precisely correcting the branch pipe resistance and adjusting the pulverized coal distribution ratio between the two branch pipes, keeping the pulverized coal quantity deviation between the two low-power burners 3 within ±10%. The inner wall of the flow divider 4 is lined with wear-resistant ceramic. This ceramic lining prevents direct contact between pulverized coal and the flow divider 4, thus preventing corrosion and significantly extending its service life. It also reduces concentration deviations and maintenance downtime caused by wear and pulverized coal leakage.

[0023] Both the first and second pulverized coal branch pipes are connected to the main pulverized coal pipeline 6 via flanges. The main pulverized coal pipeline 6 is connected to the coal mill 8 via flanges and flexible compensating components 7. The flange connection facilitates the replacement of worn parts during maintenance. The flexible compensating component 7 is installed at the outlet of the coal mill 8, which can effectively isolate the impact of the vibration of the coal mill 8 on the rigidity of the upstream pulverized coal pipeline and the supports, prevent the weld from cracking due to fatigue stress, and ensure the long-term reliability of the system's sealing.

[0024] This invention provides a control method for deep peak shaving of boilers based on differentiated burner arrangement. Employing the aforementioned deep peak shaving system for boilers based on differentiated burner arrangement, the method includes the following operations: By adjusting the pulverized coal feed rate of each low-power burner 3, the pulverized coal concentration of a single low-power burner 3 is maintained within the range of 80% to 110% of the design value, ensuring stable ignition under low load. The high-power burners 2 on both sides maintain an appropriate primary air volume to prevent flames from sticking to the wall. Based on the oxygen content at the boiler furnace 1 outlet and the wall temperature distribution of the water-cooled wall 12, the opening of each secondary air damper 9 is dynamically adjusted to prioritize ensuring uniform air volume for the low-power burners 3 in the middle area, and to ensure that the air volume of the high-power burners 2 in the side wall area meets the requirements for preventing wall scraping.

[0025] Example 2 A 660MW pulverized coal boiler with opposing front and rear walls is equipped with 6 coal mills per boiler, one of which is on standby. The original bottom burner layer had 6 high-power burners on both the front and rear walls, each with a thermal power of approximately 22MW. To improve the deep peak-shaving capacity, the following modifications are made: The four high-power burners in the middle area of ​​the front and rear walls were split into two low-power burners, each with a thermal power of 11MW. After the splitting, there are eight low-power burners in the middle area on both the front and rear walls.

[0026] The two high-power burners on the front wall and the two high-power burners on the rear wall (a total of four) near the two side walls remain unchanged and are not disassembled. Each burner has a thermal power of 22MW.

[0027] After the modification, the bottom layer of burners consists of 10 units on the front wall (2 high-power burners + 8 low-power burners) and 10 units on the rear wall (2 high-power burners + 8 low-power burners), with the total power remaining unchanged.

[0028] The pulverized coal pipeline diversion adopts a symmetrical Y-type tee with wear-resistant ceramic lining on the inner wall. Each branch pipe is equipped with an adjustable orifice. During the commissioning phase, the orifice opening is adjusted by isokinetic sampling to ensure that the pulverized coal deviation between the two small burners is less than 8%.

[0029] During operation, when the unit load drops below 200MW, only the bottommost burner layer is activated, all low-power burners are put into operation, and the high-power burners on the side walls are activated as needed. This further reduces the minimum stable combustion load and effectively controls the temperature deviation of the water-cooled walls.

[0030] Therefore, the present invention adopts the above-mentioned boiler deep peak shaving system and control method based on burner differential arrangement, which significantly improves the low-load stable combustion capability, improves the heat load distribution of water-cooled walls, enhances the flexibility of deep peak shaving, optimizes the adaptability of wind box pressure difference, and requires less engineering work.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A boiler deep peaking system based on differentiated arrangement of burners, characterized in that: The boiler includes a furnace, which is surrounded by water-cooled walls. The front and rear walls of the furnace are symmetrically equipped with bottom-level burners. The bottom-level burners include a first burner assembly and a second burner assembly. The first burner assembly is centrally mounted, and the second burner assemblies are symmetrically arranged on both sides of the first burner assembly. The first burner assembly is connected to a first pulverized coal branch pipe through a diversion device, and the second burner assembly is connected to a second pulverized coal branch pipe. Both the first and second pulverized coal branch pipes are connected to the main pulverized coal pipeline, which is connected to the coal mill.

2. The boiler deep peak-shaving system based on burner differential arrangement according to claim 1, characterized in that: The first burner assembly is a low-power burner. Every two low-power burners are connected to the pulverized coal pipeline through a diversion device. The low-power burners and the diversion device, as well as the diversion device and the first pulverized coal branch pipe, are connected by flanges.

3. A boiler deep peak-shaving system based on differentiated burner arrangement according to claim 2, characterized in that: The second burner is a high-power burner, which is directly connected to the pulverized coal pipeline via a flange. The high-power burner is also connected to the second pulverized coal branch pipe via a flange.

4. A boiler deep peak-shaving system based on burner differential arrangement according to claim 3, characterized in that: The diversion device is either a Y-type diversion tee with a symmetrical structure or a Venturi type distributor. Each branch pipe of the diversion device is equipped with an adjustable shrinkage orifice, and the inner wall of the diversion device is lined with wear-resistant ceramic.

5. A boiler deep peak-shaving system based on differentiated burner arrangement according to claim 4, characterized in that: Both the first and second pulverized coal branch pipes are connected to the main pulverized coal pipeline via flanges, and the main pulverized coal pipeline is connected to the coal mill via flanges and flexible compensating components.

6. A boiler deep peak-shaving system based on differentiated burner arrangement according to claim 5, characterized in that: Secondary air ducts are symmetrically arranged on the front and rear walls of the boiler furnace. Secondary air dampers are installed at the connection between the boiler furnace and the secondary air ducts. The boiler furnace is connected to the air box through the secondary air ducts. All secondary air ducts are connected to the boiler furnace and the air box through flanges.

7. A boiler deep peak-shaving system based on burner differential arrangement according to claim 6, characterized in that: The combustion power of a low-power burner is half that of a high-power burner.

8. A control method for deep peak shaving of a boiler based on differentiated burner arrangement, employing the deep peak shaving system for a boiler based on differentiated burner arrangement as described in any one of claims 1-7, characterized in that: Includes the following operations: By adjusting the pulverized coal feed rate of each low-power burner, the pulverized coal concentration of a single low-power burner is maintained within 80% to 110% of the design value to ensure stable ignition under low load. The high-power burners on both sides maintain an appropriate primary air volume to prevent flames from sticking to the wall. Based on the oxygen content at the boiler furnace outlet and the water-cooled wall temperature distribution, the opening of each secondary air damper is dynamically adjusted to prioritize ensuring uniform airflow for the low-power burners in the middle area and that the airflow for the high-power burners in the side wall area meets the requirements for preventing wall erosion.

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