Circulating fluidized bed boiler system

Abstract

The invention discloses a circulating fluidized bed boiler system which comprises a boiler and a processing assembly, the boiler is provided with a hearth, the hearth is suitable for burning coal, the processing assembly is provided with a processing cavity, a smoke outlet and a slag discharging opening, and the smoke outlet and the slag discharging opening are both communicated with the processing cavity. The treatment cavity is suitable for introducing solid waste, the treatment assembly is arranged in the hearth so that coal in the hearth can heat the solid waste in the treatment assembly to gasify the solid waste, the smoke outlet communicates with the hearth so that gas in the treatment assembly can flow into the boiler to be combusted, and the slag discharging opening is suitable for discharging slag of the treatment assembly. The circulating fluidized bed boiler system has the advantages of simple structure, long service life and the like.

Description

Technical Field

[0001] This invention belongs to the field of solid waste utilization technology, specifically relating to a circulating fluidized bed boiler system. Background Technology

[0002] The solid waste circulating fluidized bed boiler system is a high-efficiency and environmentally friendly solid waste treatment equipment. Its function is to reduce the volume of solid waste, treat it harmlessly, and utilize it as a resource through fluidized bed combustion technology.

[0003] In related technologies, potassium and sodium compounds in solid waste can lower the melting temperature of coal ash, causing the coal ash to soften and agglomerate prematurely on the bed or heating surface, forming coke lumps. These coke lumps can clog the pores of the boiler bed, affect the fluidization quality, and even force the boiler to shut down for cleaning, resulting in low boiler combustion efficiency and unstable operation. 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 a solid waste circulating fluidized bed boiler system with long service life, simple structure, and stable operation.

[0006] A circulating fluidized bed boiler system according to an embodiment of the present invention includes: a boiler having a furnace suitable for burning coal; a processing component having a processing chamber, a flue gas outlet, and a slag discharge outlet, the flue gas outlet and the slag discharge outlet being connected to the processing chamber, the processing chamber being suitable for introducing solid waste and the processing component being disposed in the furnace so that the coal in the furnace heats the solid waste in the processing component to gasify the solid waste, the flue gas outlet being connected to the furnace so that the gas in the processing component flows into the boiler for combustion, and the slag discharge outlet being suitable for discharging the slag from the processing component.

[0007] In this embodiment of the invention, the circulating fluidized bed boiler system is equipped with a processing component. Solid waste is pre-gasified in the processing component using the thermal energy of coal, which separates the solid waste from the coal. This prevents potassium and sodium compounds in the solid waste from directly contacting and reacting with the coal at high temperatures, effectively inhibiting the formation and adhesion of coking, and reducing the risk of coking and blockage in key components such as the furnace and heating surfaces.

[0008] In some embodiments, the processing assembly includes a furnace partition wall disposed within the furnace at the bottom of the furnace, the furnace partition wall defining the processing chamber, the flue gas outlet being formed at the top of the furnace partition wall, and the slag discharge outlet being formed at the bottom of the furnace partition wall.

[0009] In some embodiments, the circulating fluidized bed boiler system further includes: a separation component, one end of which is connected to the boiler for separating first particulate matter from the flue gas flowing out of the boiler, and the other end of which is connected to the boiler for the first particulate matter separated by the separation component to flow into the boiler; and a flue, including a first flue and a second flue connected to each other, the two ends of which are respectively connected to the other end of the separation component and the second flue, so that the flue gas flowing out of the separation component flows into the second flue through the first flue, thereby reducing the flow velocity of the flue gas through the first flue to settle the second particulate matter in the flue gas, wherein the particle size of the first particulate matter is larger than that of the second particulate matter.

[0010] In some embodiments, the circulating fluidized bed boiler system further includes a first feed pipe, the two ends of which are respectively connected to the other end of the separation component and the boiler, so that the first particulate matter flowing out of the separation component flows into the boiler through the first feed pipe. The first feed pipe extends downward and is inclined toward the boiler. A second feed pipe is provided on the first feed pipe, and the second feed pipe is adapted to allow the coal to flow into the boiler.

[0011] In some embodiments, the separation assembly includes a cyclone separator and a return feeder. One end of the cyclone separator is connected to the boiler so that flue gas flowing out of the boiler flows into the cyclone separator to separate first particulate matter in the flue gas. The other end of the cyclone separator is connected to the flue and the return feeder, so that the first particulate matter flowing out of the cyclone separator flows into the return feeder. The flue gas flowing out of the cyclone separator flows into the flue. The return feeder is connected to the boiler so that the first particulate matter flowing out of the return feeder flows into the boiler.

[0012] In some embodiments, the first flue includes a first section and a second section that are connected to each other, the first section being disposed above the second section, and the cross-sectional area of ​​the inner circumferential surface of the second section gradually decreasing from top to bottom.

[0013] In some embodiments, the circulating fluidized bed boiler system further includes a water-cooled auger, which is located below and communicates with the second section so that the second particulate matter flows into the water-cooled auger through the second section.

[0014] In some embodiments, the circulating fluidized bed boiler system further includes a control valve located between the second section and the water-cooled auger, the control valve being used to control the on / off connection between the second section and the water-cooled auger.

[0015] In some embodiments, the circulating fluidized bed boiler system further includes a superheater, an economizer, and an air preheater, wherein the superheater, the economizer, and the air preheater are sequentially arranged in the flue.

[0016] In some embodiments, the flue is provided with a fire-resistant coating. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a circulating fluidized bed boiler system according to an embodiment of the present invention.

[0018] 100. Circulating fluidized bed boiler system; 1. Boiler; 11. Furnace; 2. Processing components; 21. Processing chamber; 22. Smoke outlet; 23. Slag discharge outlet; 3. Separation components; 31. Air separator; 32. Return feeder; 4. Flue; 41. First flue; 411. First section; 412. Second section; 42. Second flue; 5. Water-cooled auger; 6. Control valve; 7. Superheater; 8. Economizer; 9. Air preheater; 10. First feed pipe; 101. Second feed pipe. 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] The circulating fluidized bed boiler system 100 according to an embodiment of the present invention is described below with reference to the accompanying drawings.

[0021] like Figure 1 As shown, the circulating fluidized bed boiler system 100 according to an embodiment of the present invention includes a boiler 1 and a processing component 2.

[0022] Boiler 1 has a furnace 11, which is suitable for burning coal. Specifically, as follows: Figure 1 As shown, boiler 1 is a circulating fluidized bed boiler system 100, and low-calorific-value coal can be fed into boiler 1 for combustion to achieve efficient recovery and utilization of low-calorific-value energy.

[0023] The processing component 2 has a processing chamber 21, a flue gas outlet 22, and a slag discharge outlet 23. Both the flue gas outlet 22 and the slag discharge outlet 23 are connected to the processing chamber 21. The processing chamber 21 is suitable for introducing solid waste, and the processing component 2 is located inside the furnace 11 so that the coal in the furnace 11 heats the solid waste in the processing component 2 to gasify it. The flue gas outlet 22 is connected to the furnace 11 so that the gas in the processing component 2 flows into the boiler 1 for combustion. The slag discharge outlet 23 is suitable for discharging the slag from the processing component 2. Specifically, as shown... Figure 1 As shown, the processing component 2 is installed in the bottom area of ​​the furnace 11. After the solid waste is introduced into the processing chamber 21, the heat released by the combustion of coal in the furnace 11 is transferred to the processing component 2, driving the solid waste to complete the gasification process in the processing chamber 21. The flue gas outlet 22 is opened at the top of the processing component 2. The flue gas outlet 22 establishes a communication channel between the processing chamber 21 and the furnace 11, so that the gasified gas can smoothly enter the furnace 11 to participate in secondary combustion. The slag discharge port 23 is set at the bottom of the processing component 2 to ensure that the slag after the reaction can be discharged in time through the slag discharge port 23.

[0024] In this embodiment of the invention, the circulating fluidized bed boiler system 100 is equipped with a processing component 2. Solid waste is pre-gasified in the processing component 2 using the thermal energy of coal, which separates the solid waste from the coal and prevents potassium and sodium compounds in the solid waste from directly contacting and reacting with the coal at high temperatures. This effectively inhibits the formation and adhesion of coking, reduces the risk of coking and blockage of key components such as the furnace 11 and heating surfaces. In addition, the pre-gasified solid waste flows smoothly into the furnace 11 of the boiler 1 in a gaseous or semi-gaseous state, mixes fully with the flame generated by coal combustion, and completes secondary combustion. This ensures that the combustible components in the waste are fully utilized, reduces the frequency of unplanned shutdowns, extends the continuous operation cycle of the boiler 1, improves the overall operating efficiency and stability of the equipment, and enhances the adaptability and processing capacity of the boiler 1 for various types of solid waste.

[0025] In some embodiments, the processing component 2 includes a furnace partition wall disposed within the furnace 11 at the bottom of the furnace 11, defining a processing chamber 21. A flue gas outlet 22 is formed at the top of the furnace partition wall, and a slag discharge outlet 23 is formed at the bottom of the furnace partition wall. Specifically, as... Figure 1 As shown, the furnace partition wall is located on the left side of the bottom of the furnace 11, dividing the furnace 11 into the furnace chamber 11 and the processing chamber 21. The inner circumferential surface of the furnace partition wall defines the processing chamber 21, and the outer circumferential surface of the furnace partition wall and the inner circumferential surface of the boiler 1 define the furnace 11. The flue gas outlet 22 is located above the furnace partition wall and communicates with the processing chamber 21. The slag discharge outlet 23 is located below the boiler 1 and communicates with the processing chamber 21. A slag inlet is provided above the furnace partition wall, through which solid waste flows into the furnace partition wall. This makes the setting of the processing component 2 more reasonable.

[0026] During the operation of the circulating fluidized bed boiler system 100 that burns solid waste, the combustion gases in the solid waste contain low-calorific-value solid waste containing chlorine, sodium, and potassium, which can cause corrosion and slagging on the tail-end heating surfaces of the boiler 1. These elements easily form low-melting-point compounds under high-temperature conditions, leading to corrosion, ash blockage, and slagging on the heating surfaces, seriously affecting the safe and stable operation of the boiler 1 and its equipment lifespan. Therefore, in some embodiments, the circulating fluidized bed boiler system 100 also includes a separation component 3 and a flue 4.

[0027] One end of the separation component 3 is connected to the boiler 1 so that the separation component 3 can separate the first particulate matter in the flue gas flowing out of the boiler 1, and the other end of the separation component 3 is connected to the boiler 1 so that the first particulate matter separated by the separation component 3 can flow into the boiler 1. Specifically, as shown in the figure Figure 1 As shown, the inlet of the separation component 3 is connected to the flue gas outlet 22 of the boiler 1 via a pipe. The flue gas generated by the combustion of the boiler 1 (containing a large number of incompletely burned solid particles) enters the separation component 3 under the influence of the airflow. The separation component 3 separates the larger particles in the flue gas from the main flue gas mass (the larger particles are usually larger than 10 μm of soot, which includes not only incompletely burned carbon particles, but also low-calorific-value solid waste containing chlorine, sodium, and potassium generated during solid waste combustion). The separated particles are then returned to the furnace 11 of the boiler 1 through the outlet of the separation component 3 to participate in the combustion reaction again. This significantly improves the combustion efficiency of the fuel and reduces energy waste, while also reducing the particulate load for subsequent flue gas treatment.

[0028] The flue 4 includes a first flue 41 and a second flue 424 connected to each other. Both ends of the first flue 41 are connected to the other end of the separation component 3 and the second flue 424, respectively, so that the flue gas flowing out of the separation component 3 flows into the second flue 424 through the first flue 41, thereby reducing the flow velocity of the flue gas through the first flue 41 and causing the second particulate matter in the flue gas to settle. The particle size of the first particulate matter is larger than that of the second particulate matter. Specifically, as shown... Figure 1As shown, flue 4 consists of a first flue 41 and a second flue 424 to achieve secondary purification of fine particulate matter in the flue gas. The two ends of the first flue 41 are connected to the other end of the separation component 3 and the inlet of the second flue 424, respectively. The cross-sectional area of ​​the inner circumference of the first flue 41 is larger than that of the inner circumference of the second flue 424 (for example, the cross-sectional area of ​​the first flue 41 can be 2-3 times that of the second flue 424). According to fluid mechanics principles, when the flue gas flowing out of the separation component 3 (which has removed most of the large particles and mainly contains smaller second particulate matter) flows into the first flue 41 with the larger cross-sectional area, the flow velocity of the flue gas will decrease (the decrease in velocity is positively correlated with the increase in cross-sectional area). The reduced flow rate allows sufficient settling time for the smaller particles in the flue gas (these are typically 1μm-10μm particles of soot, including low-calorific-value solid waste containing chlorine, sodium, and potassium generated during solid waste combustion). Under gravity, they gradually settle at the bottom of the first flue 41 (and can be periodically discharged via a subsequent ash removal device), achieving secondary dust suppression of fine particles. It should be noted that the particle size of the first particles is significantly larger than that of the second particles; this graded separation design ensures both the efficiency of the circulating combustion and the effectiveness of flue gas purification. In some embodiments, the separation assembly 3 includes a cyclone separator 31 and a return feeder 32. One end of the cyclone separator 31 is connected to the boiler 1 so that flue gas flowing out of the boiler 1 flows into the cyclone separator 31 to separate the first particulate matter in the flue gas. The other end of the cyclone separator 31 is connected to the flue 4 and the return feeder 32 respectively, so that the first particulate matter flowing out of the cyclone separator 31 flows into the return feeder 32, and the flue gas flowing out of the cyclone separator 31 flows into the flue 4. The return feeder 32 is connected to the boiler 1 so that the first particulate matter flowing out of the return feeder 32 flows into the boiler 1. Specifically, as shown... Figure 1 As shown, the inlet of the cyclone separator 31 is connected to the flue gas outlet 22 of the boiler 1. The dust-laden flue gas generated by the combustion of the boiler 1 flows into the cyclone separator 31 under the drive of the airflow. With the efficient separation effect of the strong centrifugal force field, the first particulate matter with a larger particle size in the flue gas is separated from the main body of the flue gas. The cyclone separator 31 adopts a diversion outlet design. Its particle outlet is connected to the inlet of the return feeder 32, and the flue gas outlet is connected to the inlet of the flue duct 4. At the same time, the outlet of the return feeder 32 forms a closed loop connection with the feed inlet of the boiler 1. This structural design allows the first particulate matter (including incompletely burned carbon particles and inert bed material particles) separated by the cyclone separator 31 to flow smoothly into the return feeder 32. Through the stable conveying action of the return feeder 32, it flows back into the furnace 11 of the boiler 1 to participate in the combustion reaction again. Meanwhile, the flue gas with the first particulate matter removed flows into the flue 4 at the same time, and enters the subsequent fine particle settling and deep purification process. This not only ensures the efficiency of particulate matter recycling and combustion, but also achieves precise separation of flue gas and particles, improving the stability and reliability of system operation.

[0029] In some embodiments, the circulating fluidized bed boiler system 100 further includes a first feed pipe 10, the two ends of which are respectively connected to the other end of the separation component 3 and the boiler 1, so that the first particulate matter flowing out of the separation component 3 flows into the boiler 1 through the first feed pipe 10. The first feed pipe 10 extends downward and is inclined toward the boiler 1. A second feed pipe 101 is provided on the first feed pipe 10, and the second feed pipe 101 is adapted to introduce coal so that coal and the first particulate matter flow into the boiler 1. Specifically, as Figure 1 As shown, the inlet of the first feed pipe 10 is connected to the outlet of the return feeder 32, and the outlet of the first feed pipe 10 is connected to the inlet of the boiler 1. The first feed pipe 10 extends from top to bottom and is inclined toward the boiler 1, so that the first particulate matter flows into the boiler 1 through the first feed pipe 10. The second feed pipe 101 is a vertical pipe and is located in the middle of the first feed pipe 10. The second feed pipe 101 is connected to the first feed pipe 10 and is suitable for introducing low-calorific-value coal, so that the low-calorific-value coal flows into the boiler 1 in sequence through the second feed pipe and the first feed pipe 10.

[0030] In some embodiments, the first flue 41 includes a first segment 411 and a second segment 412 that are connected to each other. The first segment 411 is disposed above the second segment 412, and the cross-sectional area of ​​the inner circumferential surface of the second segment 412 gradually decreases from top to bottom. Specifically, as... Figure 1 As shown, the second segment 412 is located at the lower end of the first segment 411 and is connected to the first segment 411. The cross-sectional shape of the first segment 411 can be consistent with the cross-sectional shape of the second flue 424. The second segment 412 is a funnel-shaped or conical structure with the cross-sectional area of ​​its inner circumference gradually decreasing from top to bottom. The contraction design of the second segment 412 not only ensures the connection with the first flue 41, but also guides the settling second particles to converge at the bottom of the second segment 412 through the gradual change in cross-sectional area. When the second particles settle in the first segment 411 under the action of gravity, they will fall into the lower second segment 412. The contraction inner wall design can prevent the particles from accumulating and stagnating in the second segment 412, ensuring that the second particles can smoothly gather and be discharged through the outlet at the bottom of the second segment 412. This completes the collection of fine particles and ensures the smooth flow of the first flue 41.

[0031] In some embodiments, the circulating fluidized bed boiler system 100 further includes a water-cooled auger 5, which is disposed below and communicates with the second section 412, so that the second particulate matter flows into the water-cooled auger 5 through the second section 412. Specifically, as Figure 1As shown, the water-cooled auger 5 is located at the lower end of the second section 412 and is connected to the second section 412, so that the second particulate matter collected in the second section 412 is transported to the storage location (such as ash silo or waste collection tank) through the water-cooled auger 5 for processing.

[0032] In some embodiments, the circulating fluidized bed boiler system 100 further includes a control valve 6, which is disposed between the second section 412 and the water-cooled auger 5. The control valve 6 is used to control the on / off state between the second section 412 and the water-cooled auger 5. Specifically, as Figure 1 As shown, the control valve 6 is located inside the lower end of the second section 412 and above the water-cooled auger 5. When the second particulate matter needs to be transported, the control valve 6 is opened to connect the second section 412 and the water-cooled auger 5; otherwise, the control valve 6 is closed to disconnect the second section 412 and the water-cooled auger 5.

[0033] In some embodiments, the circulating fluidized bed boiler system 100 further includes a superheater 7, an economizer 8, and an air preheater 9, which are sequentially arranged within the flue 4. Specifically, as... Figure 1 As shown, the superheater 7, economizer 8, and air preheater 9 are all installed in the second flue 424 and spaced apart along the length of the second flue 424. The superheater 7, economizer 8, and air preheater 9 realize the staged recovery of waste heat from the flue gas. The high-temperature flue gas first passes through the superheater 7 to heat the saturated steam, converting it into superheated steam with a higher enthalpy value. At the same time, the flue gas temperature drops to 200℃-300℃. The cooled flue gas then passes through the economizer 8 to preheat the feedwater of boiler 1, reducing the heating load of the steam drum and reducing fuel consumption. The flue gas temperature is further reduced to 100℃-150℃. Finally, the air preheater 9 is used to preheat the air required for combustion, improving combustion efficiency and reducing the exhaust gas temperature to below 100℃, minimizing heat loss and allowing the flue gas energy to be fully utilized from high temperature to low temperature, significantly improving the overall thermal efficiency of boiler 1.

[0034] In some embodiments, a fire-resistant coating is provided inside the flue 4. This fire-resistant coating improves the fire resistance of the flue 4 and extends its service life.

[0035] 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.

[0036] Furthermore, the terms "first" and "+" 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 with "first" or "+" 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.

[0037] 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.

[0038] In this invention, unless otherwise explicitly specified and limited, "above" or "below" a feature can mean that the first feature and the feature are in direct contact, or that the first feature and the feature are in indirect contact through an intermediate medium. Furthermore, "above," "on top of," and "over" a feature can mean that the first feature is directly above or diagonally above the feature, or simply that the first feature is at a higher horizontal level than the feature. "Below," "below," and "beneath" a feature can mean that the first feature is directly below or diagonally below the feature, or simply that the first feature is at a lower horizontal level than the feature.

[0039] 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.

[0040] 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. A circulating fluidized bed boiler system, characterized in that, include: A boiler having a furnace suitable for burning coal; The processing component has a processing chamber, a flue gas outlet, and a slag discharge outlet. The flue gas outlet and the slag discharge outlet are both connected to the processing chamber. Solid waste is introduced into the processing chamber, and the processing component is located inside the furnace so that the coal in the furnace heats the solid waste in the processing component to gasify the solid waste. The flue gas outlet is connected to the furnace so that the gas in the processing component flows into the boiler for combustion. The slag discharge outlet is adapted to discharge the slag from the processing component.

2. The circulating fluidized bed boiler system according to claim 1, characterized in that, The processing assembly includes a furnace partition wall located at the bottom of the furnace and defining the processing chamber. The flue gas outlet is formed at the top of the furnace partition wall, and the slag discharge outlet is formed at the bottom of the furnace partition wall.

3. The circulating fluidized bed boiler system according to claim 1, characterized in that, Also includes: A separation component, one end of which is connected to the boiler so that the separation component can separate first particulate matter from the flue gas flowing out of the boiler, and the other end of which is connected to the boiler so that the first particulate matter separated by the separation component can flow into the boiler; The flue includes a first flue and a second flue connected to each other. The two ends of the first flue are respectively connected to the other end of the separation component and the second flue, so that the flue gas flowing out of the separation component flows into the second flue through the first flue, so that the flow velocity of the flue gas through the first flue is reduced to reduce the dust of the second particulate matter in the flue gas. The particle size of the first particulate matter is larger than that of the second particulate matter.

4. The circulating fluidized bed boiler system according to claim 3, characterized in that, It also includes a first feed pipe, the two ends of which are respectively connected to the other end of the separation component and the boiler, so that the first particulate matter flowing out of the separation component flows into the boiler through the first feed pipe. The first feed pipe extends from top to bottom and is inclined toward the boiler. A second feed pipe is provided on the first feed pipe, and the second feed pipe is adapted to pass through the coal so that the coal and the first particulate matter flow into the boiler.

5. The circulating fluidized bed boiler system according to claim 3, characterized in that, The separation assembly includes a cyclone separator and a return feeder. One end of the cyclone separator is connected to the boiler so that the flue gas flowing out of the boiler flows into the cyclone separator to separate the first particulate matter in the flue gas. The other end of the cyclone separator is connected to the flue and the return feeder respectively so that the first particulate matter flowing out of the cyclone separator flows into the return feeder. The flue gas flowing out of the cyclone separator flows into the flue. The return feeder is connected to the boiler so that the first particulate matter flowing out of the return feeder flows into the boiler.

6. The circulating fluidized bed boiler system according to claim 3, characterized in that, The first flue includes a first section and a second section that are connected to each other. The first section is located above the second section, and the cross-sectional area of ​​the inner circumferential surface of the second section gradually decreases from top to bottom.

7. The circulating fluidized bed boiler system according to claim 6, characterized in that, It also includes a water-cooled auger, which is located below and connected to the second section, so that the second particulate matter flows into the water-cooled auger through the second section.

8. The circulating fluidized bed boiler system according to claim 7, characterized in that, It also includes a control valve, which is located between the second section and the water-cooled auger, and is used to control the on / off connection between the second section and the water-cooled auger.

9. The circulating fluidized bed boiler system according to claim 7, characterized in that, It also includes a superheater, an economizer, and an air preheater, which are arranged sequentially in the flue.

10. The circulating fluidized bed boiler system according to any one of claims 1-9, characterized in that, The flue is equipped with a fire-resistant coating.

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