A kind of direct flow burner suitable for biomass blending combustion
By designing a DC burner with secondary air for biomass co-firing, and optimizing the burner structure and parameters such as air volume and velocity, the corrosion problem of the heating surface during biomass combustion was solved. This achieved a reasonable distribution and mixing of fuel and air, improved combustion efficiency, reduced fuel costs, and contributed to carbon emission reduction.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- NORTH CHINA POWER ENG
- Filing Date
- 2025-07-24
- Publication Date
- 2026-07-14
AI Technical Summary
When biomass is burned, the heated surfaces are prone to coking and corrosion, which makes it impossible for coal-fired power plants to operate stably for a long time. Existing DC burner designs cannot effectively solve the problems of fuel and air distribution and mixing when biomass and coal are co-fired.
A DC burner with secondary air sandwiched between the burner and biomass was designed, including an inner primary air channel, an outer primary air channel, a sandwiched secondary air channel, an upper secondary air channel, a lower secondary air channel, and a tertiary air channel. By optimizing the burner structure and parameters such as air volume, air velocity, and incident angle, the reasonable distribution and mixing of fuel and air is ensured, thereby reducing fuel costs and contributing to carbon emission reduction.
It effectively solves the problem of fouling and corrosion of heating surfaces during biomass co-firing, improves combustion efficiency, reduces fuel costs, and achieves the goal of carbon emission reduction.
Smart Images
Figure CN224498494U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of burner technology, and specifically relates to a DC burner with secondary air for biomass co-firing. Background Technology
[0002] Biomass is a zero-carbon emission fuel and has abundant resources in my country. However, the heating surfaces of biomass are prone to coking and corrosion during combustion, causing most direct-fired power plants to be unable to operate stably for long periods. Blending biomass briquettes with biomass and modifying the burner design can effectively alleviate these problems.
[0003] In my country's large-scale coal-fired power plant boilers, once-through burners are the most widely used due to their good adaptability to different coal types. The once-through burner is placed at the four corners of the furnace, with the geometric axis of the outlet airflow directed towards an imaginary tangential circle at the center of the furnace. This creates a strong rotation of the airflow in the burner area. During combustion, due to the high viscosity of the flue gas inside the furnace, the airflow converges upwards to form a slightly rotating rising flame, hence the name tangential combustion. For some low-volatile coal types, a layer of high-velocity secondary air, called perimeter air, surrounds the primary air nozzle of the once-through burner. The perimeter air layer is thin, with a small volume but high velocity, which helps to entrain the surrounding high-temperature flue gas into the primary air flow, while preventing the pulverized coal flare from sticking to the wall and preventing pulverized coal from separating from the airflow. The design of arranging the secondary air in the middle of the primary air is called "sandwich air," transforming the "air-encased coal" structure into a "coal-encased air" structure, achieving a similar effect.
[0004] Table 1 shows the composition and combustion characteristics of biomass fuel and coal. Biomass has a high volatile matter content, and blending it with coal can improve the overall ignition of the fuel and the boiler thermal efficiency. Based on the above analysis, this utility model designs a burner coupling scheme, aiming to develop high-proportion biomass co-firing technology for coal-fired units and alleviate the problem of fouling and corrosion on heating surfaces.
[0005] Table 1. Performance of biomass fuels and coal in terms of composition and combustion characteristics
[0006] Utility Model Content
[0007] The technical problem to be solved by this utility model is to provide a DC burner with secondary air for biomass co-firing, which solves the problems of fouling and corrosion of the heating surface of biomass co-firing in coal-fired units, and ensures reasonable distribution and mixing of fuel and air, thereby reducing fuel costs and contributing to carbon emission reduction.
[0008] According to the technical solution of this utility model, this utility model provides a DC burner with secondary air for biomass co-firing, including an inner primary air channel for conveying pulverized coal, an outer primary air channel for conveying biomass fuel, a secondary air channel, an upper secondary air channel, a lower secondary air channel, and a tertiary air channel; the outer primary air channel is annular and located outside the inner primary air channel, the secondary air channel is located between the inner and outer primary air channels, the upper secondary air channel is located above the outer primary air channel, the lower secondary air channel is located below the outer primary air channel, and the tertiary air channel is located above the upper secondary air channel.
[0009] In some embodiments, the nozzle of the inner primary air duct is elongated with a height greater than its width, and the nozzle of the inner primary air duct is flared outward.
[0010] And / or, the outer contour of the nozzle of the outer primary air duct is elongated with a height greater than its width, and the nozzle of the outer primary air duct is concave.
[0011] In some embodiments, the width of the nozzle in the inner primary air duct is 30mm to 130mm, and the aspect ratio is less than or equal to 4.
[0012] In some embodiments, the nozzles of the secondary air duct are multiple nozzles evenly distributed around the inner primary air duct.
[0013] In some embodiments, the nozzle diameter of the secondary air duct is 15mm to 25mm, and the distance between the edge of the nozzle of the secondary air duct and the edge of the nozzle of the inner primary air duct and the outer primary air duct is 18mm to 35mm.
[0014] In some embodiments, the nozzles of the upper secondary air duct, lower secondary air duct, and / or tertiary air duct are provided with adjustable baffles that can adjust the tilt angle.
[0015] Compared with the prior art, the beneficial technical effects of this utility model are as follows:
[0016] In this utility model of a DC burner with secondary air for biomass co-firing, the secondary air acts as a perimeter air and a sandwich air for the inner primary air (pulverized coal) and outer primary air (biomass), respectively. It can cool the channel nozzles, supplement oxygen for the highly concentrated airflow, entrain high-temperature flue gas to promote ignition, and improve the rigidity of the primary air jet to reduce airflow slagging against the wall. The secondary air is one of the important means of adjusting combustion under different fuels and loads. The various channels cooperate with each other to ensure the rational distribution and mixing of fuel and air. This solution can be applied to the transformation of coal-fired power plants to co-fire biomass and the clean upgrading of industrial boilers, which can reduce fuel costs and help reduce carbon emissions. Attached Figure Description
[0017] Figure 1This is a schematic diagram of the burner structure provided by this utility model.
[0018] Figure 2 yes Figure 1 The dimensions of the structure shown are provided.
[0019] Figure 3 yes Figure 2 Enlarged view of the inner primary air duct, outer primary air duct, and secondary air duct section.
[0020] Explanation of reference numerals in the attached figures:
[0021] 1. Inner primary air duct; 2. Outer primary air duct; 3. Interlocking secondary air duct; 4. Upper secondary air duct; 5. Lower secondary air duct; 6. Tertiary air duct. Detailed Implementation
[0022] This invention provides a DC burner with secondary air for biomass co-firing, wherein the fuel is a mixture of biomass and pulverized coal. It mainly solves the problems of fouling and corrosion of the heating surface of biomass co-firing in coal-fired units by optimizing combustion efficiency and controlling pollutants through staged combustion and secondary air structure. It ensures reasonable distribution and mixing of fuel and air, which can reduce fuel costs and help reduce carbon emissions.
[0023] Please see Figure 1 This utility model discloses a secondary air-cooled direct-current burner suitable for biomass co-firing, installed in the boiler furnace. It includes an inner primary air channel 1 for conveying pulverized coal, an outer primary air channel 2 for conveying biomass fuel, a secondary air channel 3, an upper secondary air channel 4, a lower secondary air channel 5, and a tertiary air channel 6 for conveying exhaust gas. Generally, each of the above channels is equipped with a device for adjusting the air volume, air velocity, and / or incident angle. The inner primary air channel 1 is located at the innermost layer, the outer primary air channel 2 is annular and located around the inner primary air channel 1, and the secondary air channel 3 is located between the inner primary air channel 1 and the outer primary air channel 2, with a certain gap between the secondary air channel 3 and the nozzle edges of the inner and outer primary air channels. The upper secondary air channel 4 is located above the outer primary air channel 2, the lower secondary air channel 5 is located below the outer primary air channel 2, and the tertiary air channel 6 is located at the uppermost layer, above the upper secondary air channel 4. The burner of this utility model adopts a three-stage air distribution system. When the boiler changes the blending ratio or operates under different loads, the air volume, air velocity and incident angle of the primary air, secondary air, tertiary air and sandwich air are mainly adjusted.
[0024] In a preferred embodiment, the nozzle of the inner primary air channel 1 is elongated with a height greater than its width, and the nozzle of the inner primary air channel 1 is slightly flared outward. Specifically, the flared structure has an outwardly expanding flared end at the outlet of the nozzle of the inner primary air channel 1. This flared structure acts as a guide, causing the inner primary air to be ejected at a slightly outward tilt, thereby ensuring that the pulverized coal is fully mixed with the outer primary air and the secondary air during ejection. More specifically, for example, the width of the nozzle of the inner primary air channel 1 is 30mm to 130mm, and the height-to-width ratio is less than or equal to 4, to prevent an excessively large height-to-width ratio from causing poor jet rigidity, deviating from the wall, and forming slag.
[0025] The outer contour of the nozzle of the outer primary air channel 2 is elongated with a height greater than its width, and the nozzle of the outer primary air channel 2 is slightly concave. Specifically, the concave structure includes, for example, an outer contour and / or inner contour output section that curves or tilts inward (towards the center of the ring). This concave structure acts as a guide, causing the outer primary air to be ejected at a slightly inward tilt, allowing the biomass fuel to be fully mixed with the inner primary air and secondary air during ejection. More specifically, for example, the tubular component of the outer contour of the outer primary air channel 2 is located outside the inner primary air channel 1 and is spaced apart from the inner primary air channel 1, thereby forming a ring-shaped (square ring in the illustrated embodiment) nozzle structure.
[0026] The secondary air channel 3 is used to introduce a specific flow rate and velocity of air between the inner primary air (pulverized coal) and the outer primary air (biomass fuel) to form an air layer. Preferably, the nozzles of the secondary air channel 3 are multiple nozzles evenly distributed around the inner primary air channel 1, which spray air between the biomass and pulverized coal to achieve a good mixing effect. More specifically, for example, the nozzle diameter of the secondary air channel 3 is 15mm to 25mm to form an air layer with a thickness of 15mm to 25mm; the distance between the edge of the nozzle of the secondary air channel 3 and the edge of the nozzle of the inner primary air channel 1 and the outer primary air channel 2 is 18mm to 35mm, so that the distance between the secondary air and the inner and outer primary air is maintained at 18mm to 35mm.
[0027] Preferably, the nozzles of the upper secondary air duct 4, the lower secondary air duct 5, and / or the tertiary air duct 6 are equipped with adjustable baffles capable of adjusting the tilt angle, so as to adjust the corresponding airflow injection angle. Further, at least at the nozzle of the tertiary air duct 6, an adjustable baffle is provided so that the direction of the exhaust gas injected into the furnace is, for example, tilted downwards at 5° to 15°, while for fuels that are difficult to ignite, this tilt angle is smaller or not tilted downwards.
[0028] Specifically, such as Figure 2 , Figure 3In the embodiment shown, the tertiary air duct 6, the upper secondary air duct 4, the outer primary air duct 2, and the lower secondary air duct 5 are arranged sequentially from top to bottom at intervals. The total height from the upper end of the tertiary air duct 6 to the lower end of the lower secondary air duct 5 is 3600mm. The outer contour height of the outer primary air duct 2 is 600mm, and the inner contour height is 520mm. The contour height of the inner primary air duct 1 is 400mm. The nozzles of the secondary air duct 3 are distributed between the inner contour of the outer primary air duct 2 and the inner primary air duct 1, and the nozzle diameter is 20mm.
[0029] Based on the DC burner structure of this utility model, this utility model provides a working method for a DC burner with secondary air for biomass co-firing, which includes the following contents.
[0030] First, air and biomass fuel are introduced into the furnace for ignition and combustion through the outer primary air duct 2. At the same time, air is introduced into the furnace through the secondary air duct 3, the upper secondary air duct 4, and the lower secondary air duct 5, and exhaust gas is introduced into the furnace through the tertiary air duct 6. As the furnace temperature rises to the first temperature, it enters the continuous combustion stage. When the furnace temperature exceeds the second temperature, air and pulverized coal are introduced into the furnace through the inner primary air duct 1.
[0031] More specifically, the first temperature is approximately 600°C (e.g., 600°C ± 50°C), the second temperature is approximately 850°C (e.g., 850°C ± 50°C), and the final furnace temperature is maintained between 1000°C and 2000°C.
[0032] Preferably, the overall excess air coefficient of combustion is 1.2 to 1.25.
[0033] Preferably, the air volume ratio of the internal primary air in the internal primary air duct 1 is 15% to 25%, the air velocity is 20 m / s to 30 m / s, and the air temperature is 300℃ to 350℃, so as to reduce the heat (ignition heat) required to heat the pulverized coal airflow to the ignition temperature.
[0034] The primary air volume in primary air duct 2 is 15%–25%, and the air velocity is 15 m / s–25 m / s. The finer the biomass fuel particle size, the higher the volatile matter content, and the lower the moisture content, the lower the primary air velocity. The temperature of the primary air (preheated air) is generally controlled between 180℃ and 220℃ to ensure good ignition and combustion efficiency while keeping slagging and corrosion risks at acceptable levels; specifically, it depends on the type of biomass; the higher the volatile matter content of the biomass fuel, the lower the primary air temperature.
[0035] The total secondary air rate in the secondary air passage 3, upper secondary air passage 4, and lower secondary air passage 5 is 30% to 40%.
[0036] The secondary air in the secondary air duct 3 accounts for 10% to 15% of the total secondary air volume, with a wind speed of 50 m / s to 60 m / s (more specifically, 55 m / s) and a wind temperature of 320℃ to 380℃. The secondary air volume is adjusted by the opening of the damper at the inlet to adapt to different fuel characteristics and combustion conditions. When the quality of the coal deteriorates, the amount of secondary air is reduced.
[0037] In the upper secondary air duct 4, the upper secondary air volume accounts for 40%–45% of the total secondary air volume, and the air temperature is 320℃–380℃. In the lower secondary air duct 5, the lower secondary air volume accounts for 40%–45% of the total secondary air volume, and the air temperature is 320℃–380℃. In this embodiment, the upper and lower secondary air volumes have the same volume.
[0038] The upper secondary air in the upper secondary air passage 4 is inclined downward at 3° to 15° to lower the position of the flame center; the lower secondary air in the lower secondary air passage 5 provides oxygen from the lower side of the fuel flow to prevent the flame from rushing downward. It is injected into the combustion zone from multiple dimensions at an angle, which not only ensures the oxygen required for fuel combustion, but also strengthens the airflow disturbance, enhances the mixing process, and improves the burnout rate.
[0039] The ratio of the secondary air velocity to the primary air velocity is 1.1 to 2.3. The secondary air is injected into the furnace at a certain angle, and its main function is to provide sufficient oxygen for the combustion process and control the temperature and airflow field of the combustion zone.
[0040] The tertiary air (exhaust air) in the tertiary air passage 6 has a wind rate of less than 10% to 20%, a wind speed of 50 m / s to 60 m / s, and a wind temperature of less than 100℃.
[0041] In a specific embodiment, biomass pellets are first fed into the furnace by external primary air (18 m / s) for ignition and combustion. Simultaneously, secondary air at a velocity of 55 m / s, slightly higher than the primary air, is introduced, with a secondary air velocity of 25 m / s and a tertiary air velocity of 50 m / s. As the furnace temperature rises to 600°C, the boiler enters the continuous combustion stage. When the furnace temperature exceeds 850°C, internal primary air (20 m / s) is introduced to carry coal into the furnace. Ultimately, the boiler furnace temperature is maintained within the medium temperature range of 1000°C to 2000°C, with fly ash containing 2.8% carbon and NO. x Emissions 185 mg / m³ 3 We should try to increase the efficiency as much as possible while ensuring that no slag forms inside the furnace.
[0042] The design characteristics of the DC burner in the above embodiments are shown in the table below.
[0043]
[0044] For the inner primary air (pulverized coal) and the outer primary air (biomass), the secondary air acts as perimeter air and sandwich air, respectively. It can cool the channel nozzles, replenish oxygen for the highly concentrated airflow, entrain high-temperature flue gas to promote ignition, and increase the rigidity of the primary air jet to reduce airflow slagging against the wall. The secondary air is one of the important means of regulating combustion under variable fuel and variable load. The various channels cooperate with each other to ensure the rational distribution and mixing of fuel and air.
[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it; obviously, the described embodiments are some embodiments of this utility model, but not all embodiments; based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model; in the absence of conflict, the embodiments and features in the embodiments of this utility model can be combined with each other; modifications to the technical solutions described in the foregoing embodiments, or equivalent substitutions for some of the technical features, do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.
Claims
1. A secondary air-cooled direct-current burner suitable for biomass co-firing, characterized in that, It includes an inner primary air duct (1) for conveying pulverized coal, an outer primary air duct (2) for conveying biomass fuel, a secondary air duct (3), an upper secondary air duct (4), a lower secondary air duct (5), and a tertiary air duct (6); the outer primary air duct (2) is annular and located outside the inner primary air duct (1), the secondary air duct (3) is located between the inner primary air duct (1) and the outer primary air duct (2), the upper secondary air duct (4) is located above the outer primary air duct (2), the lower secondary air duct (5) is located below the outer primary air duct (2), and the tertiary air duct (6) is located above the upper secondary air duct (4).
2. The DC burner with secondary air for biomass co-firing according to claim 1, characterized in that, The nozzle of the inner primary air passage (1) is long and narrow with a height greater than its width, and the nozzle of the inner primary air passage (1) is outwardly flared. And / or, the outer contour of the nozzle of the outer primary air passage (2) is a narrow shape with a height greater than its width, and the nozzle of the outer primary air passage (2) is concave.
3. The DC burner with secondary air for biomass co-firing according to claim 2, characterized in that, The width of the nozzle of the inner primary air duct (1) is 30mm to 130mm, and the height-to-width ratio is less than or equal to 4.
4. The DC burner with secondary air for biomass co-firing according to claim 1, characterized in that, The nozzles of the secondary air passage (3) are multiple nozzles evenly distributed around the inner primary air passage (1).
5. The DC burner with secondary air for biomass co-firing according to claim 4, characterized in that, The nozzle diameter of the secondary air passage (3) is 15mm to 25mm, and the distance between the edge of the nozzle of the secondary air passage (3) and the nozzle of the inner primary air passage (1) and the nozzle of the outer primary air passage (2) is 18mm to 35mm.
6. The DC burner with secondary air for biomass co-firing according to claim 1, characterized in that, Adjustable baffles with adjustable tilt angles are provided at the nozzles of the upper secondary air duct (4), lower secondary air duct (5) and / or tertiary air duct (6).