In-furnace desulfurization system for external bed CFB (Circulating Fluidized Bed) boiler

Abstract

The invention provides an in-furnace desulfurization system for an external bed CFB boiler, the in-furnace desulfurization system for the external bed CFB boiler comprises a boiler body, an external bed, a flue and a feeding assembly, the boiler body, the external bed and the flue are connected in sequence, the boiler body is provided with a feeding port, and the feeding port is provided with a discharging port. The external bed is provided with a feeding port, the feeding port is connected with a coal feeder through a feeding pipeline, the external bed is provided with a blanking outlet, the blanking outlet is communicated with the boiler body through a blanking pipeline, the feeding assembly is provided with a feeding nozzle, the feeding nozzle is connected with at least one of the feeding pipeline and the blanking pipeline, and the feeding pipeline is communicated with the external bed. The feeding assembly is used for adding desulfurization powder into the boiler body. According to the in-furnace desulfurization system for the external bed CFB boiler, the desulfurization efficiency is improved, and emission of pollutants is reduced.

Description

Technical Field

[0001] This invention relates to the field of circulating fluidized bed technology, and more specifically, to an in-furnace desulfurization system for an external bed CFB boiler. Background Technology

[0002] Circulating fluidized bed (CFB) boilers have been widely used. Due to the limitations of combustion characteristics, sulfur dioxide removal from CFB boiler flue gas mainly relies on the dry desulfurization method of in-furnace calcium injection, thereby enabling the boiler flue gas to meet ultra-low emission standards.

[0003] In related technologies, the material circulation system in large circulating fluidized bed boilers with external beds has a large volume. Unburned parts of the circulating particles may undergo afterburning in large spaces such as cyclone separators and external bed heat exchangers, thereby generating new sulfur dioxide components. This makes it impossible for the boiler flue gas to stably meet ultra-low emission standards under the existing in-furnace dry desulfurization system layout. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the related art.

[0005] Therefore, embodiments of the present invention propose an in-furnace desulfurization system for an external bed CFB boiler, which improves desulfurization efficiency and reduces pollutant emissions.

[0006] An in-furnace desulfurization system for an external bed CFB boiler according to an embodiment of the present invention includes: The boiler body, the external bed, and the flue are connected in sequence. The boiler body has a feed inlet, which is connected to a coal feeder via a feed pipe. The external bed has a discharge outlet, which is connected to the boiler body via a discharge pipe. A feeding assembly having a feeding nozzle connected to at least one of the feed pipe and the discharge pipe, the feeding assembly being used to add desulfurization powder into the boiler body.

[0007] The in-furnace desulfurization system for an external bed CFB boiler, as described in this invention, adds desulfurization powder into the boiler body via a feeding assembly. This allows for more effective absorption of sulfur dioxide in the flue gas, reducing emissions. The addition of desulfurization powder also helps reduce afterburning in larger spaces such as cyclone separators and external bed heat exchangers, preventing the generation of new sulfur dioxide components.

[0008] In some embodiments, the boiler body further includes a secondary air inlet, and the feeding nozzle is connected to the secondary air inlet.

[0009] In some embodiments, the feed inlet and the discharge outlet are arranged radially opposite to each other along the boiler body, and the secondary air inlet is located above the feed inlet in the height direction of the boiler body.

[0010] In some embodiments, the extension direction of the secondary air inlet forms an angle with the width direction of the boiler body, and the secondary air inlet extends toward the side away from the feed inlet.

[0011] In some embodiments, there are multiple secondary air outlets, which are arranged at intervals along the height direction of the boiler body.

[0012] In some embodiments, the feeding assembly includes a feeding nozzle, the feeding port is disposed on the feeding nozzle, and there are multiple feeding nozzles, which are respectively arranged corresponding to the feed pipeline, the discharge pipeline and the secondary air outlet.

[0013] In some embodiments, the number of feeding nozzles arranged at the secondary air inlet is greater than or equal to half the sum of the number of feeding nozzles arranged in the feed pipe and the discharge pipe.

[0014] In some embodiments, the feeding nozzle is located at one end of the feed pipe adjacent to the coal feeder, and the feeding nozzle is located at one end of the discharge pipe adjacent to the external bed.

[0015] In some embodiments, an air distribution plate is further included, which is disposed within the boiler body and located below the feed inlet in the height direction of the boiler body.

[0016] In some embodiments, the feeding assembly further includes a desulfurization powder silo, a desulfurization feeder, and a desulfurization conveying pipe connected in sequence. A first end of the desulfurization conveying pipe is connected to the desulfurization feeder, and a second end of the desulfurization conveying pipe is connected to the feeding nozzle. The feeding assembly also includes a regulating valve and a monitoring device, both of which are located on the desulfurization conveying pipe. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the in-furnace desulfurization system for an external bed CFB boiler according to an embodiment of the present invention.

[0018] Figure label: 100. Coal feeder 1. Boiler body; 11. Feed pipe; 12. Discharge pipe; 13. Secondary air inlet; 14. Air distribution plate. 2. External bed, 3. Flue, 4. Feeding assembly; 41. Feeding nozzle; 42. Desulfurization powder silo; 43. Desulfurization feeder; 44. Desulfurization conveying pipe; 45. Regulating valve; 46. Monitoring components. Detailed Implementation

[0019] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0020] like Figure 1 As shown, the in-furnace desulfurization system for an external bed CFB boiler according to an embodiment of the present invention includes: boiler body 1, external bed 2, flue 3, and feeding assembly 4.

[0021] The boiler body 1, the external bed 2, and the flue 3 are connected in sequence. The boiler body 1 has a feed inlet, which is connected to the coal feeder 100 through a feed pipe 11. The external bed 2 has a discharge outlet, which is connected to the boiler body 1 through a discharge pipe 12. The feeding assembly 4 has a feeding nozzle, which is connected to at least one of the feed pipe 11 and the discharge pipe 12. The feeding assembly 4 is used to add desulfurization powder into the boiler body 1.

[0022] Specifically, such as Figure 1 As shown, the boiler body 1, external bed 2, and flue 3 are connected in series to form a flue gas flow path. The outlet of the boiler body 1 is connected to the inlet of the external bed 2, and the outlet of the external bed 2 is connected to the flue 3. The feed inlet of the boiler body 1 is connected to the coal feeder 100 through the feed pipe 11 for conveying coal. The discharge outlet of the external bed 2 is connected to the boiler body 1 through the discharge pipe 12 to realize the recycling of unburned particles.

[0023] Desulfurization powder (such as limestone powder) is injected into the feed pipe 11 simultaneously with the coal combustion to achieve preliminary desulfurization in the furnace. Desulfurization agent is added to the discharge pipe 12 during the circulating particle return stage to perform secondary desulfurization on the sulfur dioxide generated by afterburning.

[0024] Understandably, the design of the external bed 2 extends the particle residence time and improves combustion efficiency; simultaneously, the flue 3 is directly connected to the outlet of the external bed 2, ensuring that the flue gas completes the initial combustion reaction before entering the subsequent purification system. The desulfurizing agent is added stepwise at the coal inlet and particle circulation stage, which not only treats the sulfur dioxide generated during initial combustion but also effectively suppresses the secondary sulfur dioxide generated during afterburning.

[0025] Of course, the feeding location and dosage are dynamically adjusted based on flue gas emission data to ensure the stability of ultra-low emissions.

[0026] The in-furnace desulfurization system for an external bed CFB boiler in this embodiment of the invention adds desulfurization powder into the boiler body 1 via the feeding component 4, which can more effectively absorb sulfur dioxide in the flue gas and reduce emissions. The addition of desulfurization powder helps reduce afterburning in larger spaces such as the cyclone separator and the external bed 2 heat exchanger, thus preventing the generation of new sulfur dioxide components.

[0027] In some embodiments, the boiler body 1 also has a secondary air inlet 13, and the feeding nozzle is connected to the secondary air inlet 13.

[0028] Specifically, such as Figure 1 As shown, the secondary air inlet 13 is usually located in the upper part of the combustion chamber of the boiler body 1. It is used to introduce secondary air to supplement the oxygen required for combustion, promote the complete combustion of unburned particles, and optimize the fluidization state in the furnace.

[0029] Optionally, a desulfurizing agent nozzle can be added to the secondary air duct to mix the desulfurizing powder (such as limestone powder) with the secondary air and then inject it into the furnace together. Alternatively, a feeding nozzle can be independently set near the secondary air inlet 13 to allow the desulfurizing powder to be precisely added to the secondary air area.

[0030] Understandably, secondary air typically has a higher flow rate, allowing the desulfurization powder to be more evenly dispersed in the upper part of the combustion chamber, thus improving its contact efficiency with sulfur dioxide. Compared to adding desulfurizing agent only at the inlet or return inlet, the desulfurization powder injected by secondary air can more directly cover high-risk areas of afterburning (such as the dilute phase region), reducing local sulfur dioxide concentration peaks.

[0031] In other words, by adjusting the amount of desulfurizing agent injected into the secondary air inlet 13, the load change or fluctuation in the sulfur content of the coal can be dynamically addressed. For example: in high-sulfur coal conditions, the amount of desulfurizing agent injected into the secondary air can be increased to enhance the desulfurization of the flue gas in the middle and upper parts; in low-load conditions, the amount of calcium injected can be reduced to avoid excessive desulfurization and limestone waste.

[0032] Furthermore, the secondary air inlet 13 is equipped with a Galio outlet that coordinates with the feed line 11 for desulfurization. Specifically, the desulfurizer in the feed line 11 primarily treats the sulfur dioxide generated during initial combustion, while the desulfurizer in the secondary air inlet 13 targets sulfur dioxide from afterburning and the dilute phase region, forming a "staged desulfurization" system. The feeding from the secondary air inlet 13 complements the feeding from the discharge line 12; if afterburning still occurs in the external bed 2, desulfurizer can be supplemented through the discharge line 12, creating a triple protection system.

[0033] In some embodiments, the feed inlet and the discharge outlet are arranged radially opposite to each other along the boiler body 1, and the secondary air outlet 13 is located above the feed inlet in the height direction of the boiler body 1.

[0034] Specifically, such as Figure 1As shown, the feed inlet and discharge outlet are located at the same horizontal height of the boiler body 1, but are symmetrically distributed at 180° on the cross-section of the furnace (i.e., radially opposite). The secondary air inlets 13 are arranged above the feed inlet and spaced at certain distances along the height direction of the boiler body 1.

[0035] Understandably, after the coal and desulfurizing agent are injected into the feed inlet, they are mixed with the high-temperature circulating material returning from the discharge outlet within the furnace, enhancing the diffusion of fuel and desulfurizing agent, avoiding fluidization deviation caused by unilateral feeding, maintaining bed pressure balance, and reducing local dead zones. Secondary air is injected above the feed inlet, forming a staged combustion pattern of "bottom primary air, middle circulating disturbance, and upper secondary air," extending particle residence time and improving combustion efficiency.

[0036] It should be noted that the in-furnace desulfurization system for an external bed CFB boiler in this embodiment of the invention can optimize the desulfurization reaction path within the boiler multiple times. Firstly, the desulfurizing agent at the feed inlet rapidly decomposes into calcium oxide in the high-temperature zone (approximately 850–900°C) at the bottom of the furnace, capturing the sulfur dioxide generated during initial combustion. The circulating material returned from the feed outlet contains incompletely reacted calcium oxide, which synergistically works with the fresh desulfurizing agent injected at the feed inlet to enhance the continuity of desulfurization. The desulfurizing agent injected through the secondary air inlet 13 covers the dilute phase zone (upper part of the furnace), suppressing the sulfur dioxide generated during afterburning, forming a "full-height coverage" desulfurization network.

[0037] In some embodiments, the extension direction of the secondary air inlet 13 forms an angle with the width direction of the boiler body 1, and the secondary air inlet 13 extends toward the side away from the feed inlet.

[0038] Specifically, such as Figure 1 As shown, the secondary air outlet 13 extends in an obliquely upward direction, that is, the extension direction of the secondary air outlet 13 forms a certain angle with the horizontal direction. Optionally, the angle is 10°~45°.

[0039] Understandably, the secondary air is injected obliquely into the furnace, forming a vortex flow with the vertically rising primary air and material flow, prolonging the particle residence time and promoting contact between unburned carbon and oxygen. In contrast, the traditional secondary air, which is directly directed into the width direction, tends to penetrate the furnace directly, resulting in insufficient fluidization in the edge areas. Therefore, the obliquely extended tuyer can cover a larger furnace cross-section and reduce dead zones.

[0040] In addition, the coal and desulfurizing agent injected into the feed inlet are enriched in the lower part of the furnace. The secondary air inlet 13 is angled away from the feed inlet to prevent the airflow from carrying the desulfurizing agent at the bottom away from the high-temperature zone too early. The desulfurizing agent carried by the secondary air (connected through the feed nozzle) preferentially covers the dilute phase zone and the area with high afterburning incidence (such as near the return port of the external bed 2).

[0041] In some embodiments, there are multiple secondary air inlets 13, which are arranged at intervals along the height direction of the boiler body 1.

[0042] It is understandable that, such as Figure 1 As shown, the stepped airflow field formed by the multi-layer secondary air, combined with the radially opposed feed inlet or discharge outlet, allows the circulating material to undergo combustion and desulfurization reactions multiple times during its ascent, thereby improving the carbon conversion rate and sulfur dioxide removal rate.

[0043] In other words, arranging multiple layers of secondary air inlets 13 can match the reaction requirements of different furnace heights, accurately suppress the generation of sulfur dioxide, and dynamically adjust the air volume and calcium injection volume of each layer to adapt to complex operating conditions, while reducing the amount of limestone used and stably meeting the ultra-low emission requirements.

[0044] In some embodiments, the feeding assembly 4 includes a feeding nozzle 41, a feeding port is provided on the feeding nozzle 41, and there are multiple feeding nozzles 41, which are respectively arranged in relation to the feeding pipeline 11, the discharge pipeline 12 and the secondary air outlet 13.

[0045] Specifically, such as Figure 1 As shown, the feeding nozzle 41 can be installed at the outlet of the coal feeder 100 or on the feed pipe 11 to inject desulfurizing agent (limestone powder) synchronously with the coal combustion, achieving initial desulfurization. The feeding nozzle 41 is arranged on the return pipe near the discharge outlet of the external bed 2 to perform circulating desulfurization of unburned carbon and secondary sulfur dioxide in the circulating material. The feeding nozzle 41 is integrated in the secondary air ducts of each layer (or near the air outlet), and the desulfurizing agent is transported to the upper part of the furnace by air force to cover the afterburning desulfurization.

[0046] In other words, by coordinating the multi-nozzle feeding assembly 4 with the feed pipe 11, discharge pipe 12, and secondary air inlet 13, the desulfurization requirements of the entire combustion process can be met, eliminating emission blind spots. The differentiated calcium injection strategy enhances limestone activity, reduces operating costs, and provides a modular and scalable solution for ultra-low emissions from CFB boilers.

[0047] In some embodiments, the number of feeding nozzles 41 arranged in the secondary air outlet 13 is greater than or equal to half the sum of the number of feeding nozzles 41 arranged in the feed pipe 11 and the discharge pipe 12.

[0048] Understandably, increasing the proportion of nozzles at secondary air inlet 13 ensures adequate desulfurizer coverage in high-risk areas of afterburning (dilute phase zone and external bed 2 return material zone), thus suppressing secondary sulfur dioxide formation. In other words, by arranging a larger number of Galio nozzles at secondary air inlet 13, the total calcium injection volume of these nozzles can account for 0% to 70% of the total system volume, with the specific proportion adjusted based on the coal sulfur content and boiler height.

[0049] In other words, by designing a secondary air inlet with 13 nozzles accounting for ≥50% of the total number, the desulfurization capacity in the dilute phase zone can be significantly enhanced, making up for the shortcomings of traditional solutions. Through proportional constraints, basic desulfurization can be guaranteed under any operating condition, reducing ineffective calcium spraying in high-temperature zones and comprehensively reducing limestone consumption.

[0050] In some embodiments, the feeding nozzle 41 is arranged at one end of the feed pipe 11 near the coal feeder 100, and the feeding nozzle 41 is arranged at one end of the discharge pipe 12 near the external bed 2.

[0051] It is understandable that, such as Figure 1 As shown, calcium is sprayed near the outlet of the coal feeder 100 to ensure that the desulfurizing agent and the coal are fully mixed before entering the furnace, thus avoiding local imbalance of the sulfur-calcium ratio. Desulfurizing agent is sprayed near the material inlet of the external bed 2 to cover unburned carbon in the circulating material (temperature 600~800℃), preventing it from releasing sulfur dioxide during secondary combustion in the furnace.

[0052] In some embodiments, the boiler body 1 is further provided with an air distribution plate 14, which is disposed inside the boiler body 1 and is located below the feed inlet in the height direction of the boiler body 1.

[0053] It is understandable that, such as Figure 1 As shown, the air distribution plate 14 is horizontally installed at the bottom of the boiler body 1, and located below the feed inlet. The air distribution plate 14 is made of high-temperature resistant alloy plate or refractory concrete structure, with air cap holes (20~50mm in diameter) evenly distributed on the plate, and the air caps are connected to the primary air duct. The feed inlet is located above the air distribution plate 14, and the coal and desulfurizing agent fall into the area of ​​the air distribution plate 14 through the feed pipe 11, forming a fluidized bed with the primary air.

[0054] In other words, the air distribution plate 14 evenly sprays primary air into the bed material (coal, limestone, ash, etc.) through the air cap, ensuring that the material is fully fluidized and avoiding local dead zones or channeling. By adjusting the primary air volume and air temperature, the temperature of the dense phase zone is stabilized at 850~900℃ (the optimal desulfurization temperature window for limestone), avoiding excessively high temperatures that could cause calcium oxide sintering failure.

[0055] In some embodiments, the feeding assembly 4 further includes a desulfurization powder silo 42, a desulfurization feeder 43, and a desulfurization conveying pipe 44 connected in sequence. The first end of the desulfurization conveying pipe 44 is connected to the desulfurization feeder 43, and the second end of the desulfurization conveying pipe 44 is connected to the feeding nozzle 41. The feeding assembly 4 also includes a regulating valve 45 and a monitoring element 46, both of which are located on the desulfurization conveying pipe 44.

[0056] Specifically, such as Figure 1As shown, the desulfurization powder silo 42 is used to store desulfurizing agent and can be equipped with an arch-breaking device (such as a pneumatic hammer) to prevent powder caking. The desulfurization feeder 43 can be a frequency-controlled screw feeder or a rotary valve to precisely adjust the desulfurizing agent delivery rate. The desulfurization conveying pipe 44 is a wear-resistant ceramic-lined pipe that connects the feeder to each feeding nozzle 41 (feed pipe 11, discharge pipe 12, secondary air inlet 13 nozzle).

[0057] A regulating valve 45 is installed at a branch node of the delivery pipe to control the flow rate of desulfurizing agent at each nozzle (such as a pneumatic butterfly valve or an electric ball valve). The monitoring device 46 includes a flow meter (such as a Coriolis mass flow meter) and a pressure sensor to provide real-time feedback on the powder delivery status within the pipeline.

[0058] In other words, the feeder speed is dynamically adjusted based on boiler load and coal sulfur content changes to achieve total desulfurization agent control. The regulating valve 45 can be zone-controlled; that is, when the sulfur dioxide concentration monitoring shows that the dilute phase zone exceeds the standard, the opening of the regulating valve 45 corresponding to the secondary air inlet 13 nozzle is increased for targeted calcium supplementation. When the pressure sensor detects an abnormal increase in pipeline pressure, it automatically triggers compressed air purging or an alarm to prevent pipe blockage. The flow meter data is interlocked with the feeder; when the flow rate falls below the threshold, it automatically compensates or switches to a backup pipeline.

[0059] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0060] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0061] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0062] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0063] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0064] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An in-furnace desulfurization system for an external bed CFB boiler, characterized in that, include: The boiler body, the external bed, and the flue are connected in sequence. The boiler body has a feed inlet, which is connected to a coal feeder via a feed pipe. The external bed has a discharge outlet, which is connected to the boiler body via a discharge pipe. A feeding assembly having a feeding nozzle connected to at least one of the feed pipe and the discharge pipe, the feeding assembly being used to add desulfurization powder into the boiler body.

2. The in-furnace desulfurization system for an external bed CFB boiler according to claim 1, characterized in that, The boiler body also has a secondary air inlet, and the feeding nozzle is connected to the secondary air inlet.

3. The in-furnace desulfurization system for an external bed CFB boiler according to claim 2, characterized in that, The feed inlet and the discharge outlet are arranged radially opposite each other along the boiler body, and the secondary air inlet is located above the feed inlet in the height direction of the boiler body.

4. The in-furnace desulfurization system for an external bed CFB boiler according to claim 3, characterized in that, The extension direction of the secondary air outlet forms an angle with the width direction of the boiler body, and the secondary air outlet extends toward the side away from the feed inlet.

5. The in-furnace desulfurization system for an external bed CFB boiler according to claim 4, characterized in that, There are multiple secondary air outlets, which are arranged at intervals along the height direction of the boiler body.

6. The in-furnace desulfurization system for an external bed CFB boiler according to any one of claims 2-5, characterized in that, The feeding assembly includes a feeding nozzle, and the feeding nozzle is disposed on the feeding nozzle. There are multiple feeding nozzles, and the multiple feeding nozzles are respectively arranged corresponding to the feeding pipeline, the discharge pipeline and the secondary air outlet.

7. The in-furnace desulfurization system for an external bed CFB boiler according to claim 6, characterized in that, The number of feeding nozzles arranged at the secondary air inlet is greater than or equal to half the sum of the number of feeding nozzles arranged in the feed pipe and the discharge pipe.

8. The in-furnace desulfurization system for an external bed CFB boiler according to claim 6, characterized in that, The feeding nozzle is located at one end of the feed pipe near the coal feeder, and the feeding nozzle is located at one end of the discharge pipe near the external bed.

9. The in-furnace desulfurization system for an external bed CFB boiler according to claim 6, characterized in that, It also includes an air distribution plate, which is disposed inside the boiler body and located below the feed inlet in the height direction of the boiler body.

10. The in-furnace desulfurization system for an external bed CFB boiler according to claim 6, characterized in that, The feeding assembly also includes a desulfurization powder silo, a desulfurization feeder, and a desulfurization conveying pipe connected in sequence. The first end of the desulfurization conveying pipe is connected to the desulfurization feeder, and the second end of the desulfurization conveying pipe is connected to the feeding nozzle. The feeding assembly also includes a regulating valve and a monitoring device, both of which are located on the desulfurization conveying pipe.

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