CN116727124A - Cyclone separator and circulating fluidized bed boiler with variable cross-section inlet flue - Google Patents

Abstract

The application discloses a cyclone separator with a variable cross-section inlet flue and a circulating fluidized bed boiler, wherein the cyclone separator with the variable cross-section inlet flue for the circulating fluidized bed boiler comprises the following components: a cylindrical barrel; the conical section is connected with the cylindrical barrel and is positioned below the cylindrical barrel; the exhaust pipe is arranged on the top wall of the cylindrical barrel; the inlet flue comprises a top wall, a bottom wall, an outer side wall and an inner side wall, wherein the outer side wall is connected with the top wall and the bottom wall respectively and is tangent to the cylindrical barrel, the horizontal section of the inner side wall meets the preset line shape, and the preset line shape is provided with a connecting point connected with the cylindrical barrel, an inlet point far away from the cylindrical barrel in the direction parallel to the outer side wall and a minimum section point with the minimum distance between the inlet point and the outer side wall in the direction perpendicular to the outer side wall. The cyclone separator for the circulating fluidized bed boiler with the variable cross-section inlet flue has the advantages of high separation efficiency and the like.

Description

Cyclone separator and circulating fluidized bed boiler with variable cross-section inlet flue

Technical field

The present invention relates to the technical field of thermal power generation, specifically, to a cyclone separator for a circulating fluidized bed boiler with an inlet flue of variable cross-section and a cyclone separator for a circulating fluidized bed boiler with the inlet flue of variable cross-section. circulating fluidized bed boiler.

Background technique

As the proportion of new energy power generation in the power system gradually increases, thermal power generation units need to play the role of "ballast stone" in the power system to ensure the consumption of new energy power generation and the safe operation of the power grid.

Among thermal power plants, circulating fluidized bed boilers have the advantages of wide fuel applicability, low pollution control costs, and stable low-load operation. In order to cope with the transformation of the power system, circulating fluidized bed boilers need to further leverage the advantages of fuel adaptability and deepen the large-scale application of low-priced fuels; further strengthen the furnace emission control of pollutants, especially nitrogen oxides and sulfur dioxide; further enhance Operational flexibility. The separation efficiency and other properties of the cyclone separator used in circulating fluidized bed boilers play a key role in the circulating fluidized bed's response to the transformation of the power system.

The cyclone separator for circulating fluidized bed boilers in the related art is intended to accelerate the gas and solid particles by gradually shrinking the cross-sectional area of the inlet section to improve the efficiency of the cyclone separator, but the improvement in separation efficiency is limited.

Contents of the invention

The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a cyclone separator for a circulating fluidized bed boiler with a variable cross-section inlet flue. The cyclone separator for a circulating fluidized bed boiler with a variable cross-section inlet flue has the advantage of high separation efficiency.

The present invention also proposes a circulating fluidized bed boiler having the cyclone separator for the circulating fluidized bed boiler with a variable cross-section inlet flue.

In order to achieve the above object, according to an embodiment of the first aspect of the present invention, a cyclone separator for a circulating fluidized bed boiler with a variable cross-section inlet flue is proposed. The circulating fluidized bed boiler with a variable cross-section inlet flue is used The cyclone separator includes: a cylindrical body; a tapered section connected to the cylindrical body and located below the cylindrical body; and an exhaust pipe, which is provided on the cylindrical body. The top wall; the inlet flue, the inlet flue includes a top wall, a bottom wall, an outer wall and an inner wall, and the top wall, the bottom wall, the outer wall and the inner wall jointly define the inside of the inlet and outlet flue the circulation area, the top wall is flush with the top wall of the cylindrical body, the bottom wall is parallel to the top wall and spaced apart in the up and down direction, and the outer side wall is respectively connected with the top wall and the The bottom wall is connected and tangent to the cylindrical body, and the horizontal section of the inner wall meets a predetermined line shape, and the predetermined line shape is a folded line or an arc so that the circulation area in the inlet flue is vertical to the smoke The cross-sectional area in the air inflow direction first gradually decreases and then gradually increases from the entrance of the inlet flue to the entrance of the cylindrical barrel. The predetermined linear shape has a connection point connected to the cylindrical barrel, and is parallel to the cylindrical barrel. The entry point away from the cylindrical body in the direction of the outer wall and the minimum cross-sectional point with the smallest distance from the outer wall in the direction perpendicular to the outer wall, the minimum cross-sectional point is perpendicular to the outer wall. The distance between the outer wall and the connection point in the direction is equal to 2%-5% of the diameter of the cylindrical body and the distance from the connection point in the horizontal direction parallel to the outer wall is the distance between the outer wall and the connection point. 5%-25% of the diameter of the cylinder.

The cyclone separator for circulating fluidized bed boiler with variable cross-section inlet flue according to the embodiment of the present invention has the advantages of high separation efficiency.

In addition, the cyclone separator for circulating fluidized bed boilers with variable cross-section inlet flues according to the above embodiments of the present invention can also have the following additional technical features:

According to an embodiment of the present invention, the distance between the connection point and the outer wall in a direction perpendicular to the outer wall is greater than the distance between the minimum cross-section point and the outer wall and less than the distance between the outer wall and the minimum cross-section point. The distance between the inlet point and the outer side wall is such that the inlet area of the flow area within the inlet flue is greater than the outlet area of the flow area within the inlet flue.

According to an embodiment of the present invention, the distance between the minimum cross-section point and the connection point in a direction perpendicular to the outer side wall is 120-250 mm.

According to an embodiment of the present invention, the distance between the minimum cross-section point and the connection point in a horizontal direction parallel to the outer side wall is 300-1500 mm.

According to an embodiment of the present invention, the distance between the minimum cross-section point and the connection point in a direction perpendicular to the outer side wall is 200 mm, and the distance between the minimum cross-section point and the connection point is parallel to the outer side wall. The horizontal distance of the walls is 700 mm.

According to an embodiment of the present invention, the predetermined line shape is a fold line and also has at least one secondary fold point, and the secondary fold point is farther from the outer side wall than the minimum cross-section point in a direction perpendicular to the outer side wall, and Farther from the connection point than the minimum cross-section point in a horizontal direction parallel to the outer side wall.

According to an embodiment of the present invention, the upper end of the exhaust pipe is higher than the top wall of the cylindrical barrel and the lower end extends into the cylindrical barrel.

According to an embodiment of the present invention, the diameter of the cylindrical body is 2-10 meters.

According to an embodiment of the second aspect of the present invention, a circulating fluidized bed boiler is proposed. The circulating fluidized bed boiler includes a circulating fluidized bed boiler with a variable cross-section inlet flue according to an embodiment of the first aspect of the present invention. Cyclone separators for bed boilers.

The circulating fluidized bed boiler according to the embodiment of the present invention has the advantage of high separation efficiency by using the cyclone separator for circulating fluidized bed boiler with variable cross-section inlet flue according to the embodiment of the first aspect of the present invention.

According to an embodiment of the present invention, the cyclone separator for the circulating fluidized bed boiler with variable cross-section inlet flue is composed of multiple

Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

Figure 1 is a schematic structural diagram of a cyclone separator for a circulating fluidized bed boiler with a variable cross-section inlet flue according to an embodiment of the present invention.

Figure 2 is a schematic structural diagram of a cyclone separator for a circulating fluidized bed boiler with a variable cross-section inlet flue according to a specific embodiment of the present invention.

Figure 3 is a schematic structural diagram of a cyclone separator for a circulating fluidized bed boiler with a variable cross-section inlet flue according to another specific embodiment of the present invention.

Figure 4 is a schematic structural diagram of a cyclone separator for a circulating fluidized bed boiler with a variable cross-section inlet flue according to another specific embodiment of the present invention.

Reference signs: Cyclone separator for circulating fluidized bed boiler with variable cross-section inlet flue 1, cylindrical body 11, tapered section 12, exhaust pipe 20, inlet flue 30, top wall 31, bottom wall 32, The outer side wall 33 , the inner side wall 34 , the connection point 41 , the entry point 42 , the minimum cross-section point 43 , and the secondary bending point 44 .

Detailed ways

This application is based on the inventor's discovery and understanding of the following facts and problems:

The cyclone separator for circulating fluidized bed boilers in the related art is intended to accelerate the gas and solid particles by gradually shrinking the cross-sectional area of the inlet section to improve the efficiency of the cyclone separator. However, the improvement in separation efficiency is limited, and the degree of shrinkage is difficult to determine. , when the shrinkage degree is not selected well, the separation efficiency will decrease.

Specifically, when the cross-sectional area of the inlet section of the circulating fluidized bed boiler cyclone separator in the related art shrinks at a fixed ratio, the separation efficiency is limited or even reduced.

The inlet section of some cyclone separators adopts a Venturi structure, so that the cross-sectional area of the inlet section first decreases and then increases in the direction of gas inflow. However, the influence of the Venturi structure itself on the air flow is relatively complex, and its design and installation are difficult. , the proportion of cross-sectional area change is more difficult to determine, resulting in a limited improvement in separation efficiency or even a reduction.

Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present invention and cannot be understood as limiting the present invention.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", " "Back", "Left", "Right", "Vertical", "Horizontal", "Top", "Bottom", "Inside", "Outside", "Clockwise", "Counterclockwise", "Axis", The orientations or positional relationships indicated by "radial direction", "circumferential direction", etc. are based on the orientations or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply the referred devices or components. Must have a specific orientation, be constructed and operate in a specific orientation and are therefore not to be construed as limitations of the invention. In addition, features defined as “first” and “second” may explicitly or implicitly include one or more of these features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

In the description of the present invention, it should be noted that, unless otherwise clearly stated and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection. Connection, or integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be an internal connection between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

The following describes a cyclone separator 1 for a circulating fluidized bed boiler with a variable cross-section inlet flue according to an embodiment of the present invention with reference to the accompanying drawings.

As shown in Figures 1 to 4, a cyclone separator 1 for a circulating fluidized bed boiler with a variable cross-section inlet flue according to an embodiment of the present invention includes a cylindrical body 11, a tapered section 12, an exhaust pipe 20 and an inlet flue. Road 30.

The tapered section 12 is connected to the cylindrical body 11 and is located below the cylindrical body 11 . The exhaust pipe 20 is provided on the top wall of the cylindrical body 11 . The entrance flue 30 includes a top wall 31, a bottom wall 32, an outer wall 33 and an inner wall 34. The top wall 31, the bottom wall 32, the outer wall 33 and the inner wall 34 jointly define a circulation area in the entrance flue. The top wall 31 and the cylinder The top wall of the cylinder 11 is flush, the bottom wall 32 is parallel to the top wall 31 and spaced apart in the up and down direction, the outer wall 33 is connected to the top wall 31 and the bottom wall 32 respectively and is tangent to the cylindrical cylinder 11, and the inner wall 34 The horizontal cross-section satisfies a predetermined line shape, and the predetermined line shape is a broken line or an arc so that the cross-sectional area of the circulation area in the inlet flue perpendicular to the direction of flue gas inflow is from the entrance of the inlet flue 30 to the cylindrical barrel 11 The direction of the inlet first gradually decreases and then gradually increases. The predetermined line shape has a connection point 41 connected to the cylindrical body 11, an inlet point 42 away from the cylindrical body 11 in a direction parallel to the outer wall 33, and an inlet point 42 perpendicular to the outer side. The distance between the minimum cross-section point 43 and the outer side wall 33 in the direction of the wall 33 is the smallest. The distance between the minimum cross-section point 43 and the outer side wall 33 in the direction perpendicular to the outer side wall 33 is equal to 2% of the diameter of the cylinder 11 - 5% and the distance from the connection point 41 in the horizontal direction parallel to the outer wall 33 is 5%-25% of the diameter of the cylindrical barrel 11 .

According to the cyclone separator 1 for circulating fluidized bed boilers with a variable cross-section inlet flue according to the embodiment of the present invention, the cross-sectional area of the circulation area in the inlet flue perpendicular to the flue gas inflow direction is first changed from the flue gas inflow direction. Gradually decrease and then gradually increase, so that the air flow can be effectively accelerated after passing through the inlet flue 30, thereby increasing the separation efficiency of the cyclone separator 1 for circulating fluidized bed boilers with variable cross-section inlet flues. Compared with related technologies, The cyclone separator in which the cross-sectional area of the circulation area in the entrance flue gradually decreases can avoid the cross-sectional area of the circulation area in the entrance flue from shrinking at a fixed ratio, can more effectively increase the airflow velocity, and can increase the particle size in the entrance flue 30 and non-uniformity of gas distribution to improve separation efficiency and control the increase in pressure drop.

Moreover, by making the horizontal section of the inner wall 34 satisfy a predetermined line shape, which is a polygonal line shape or an arc shape, the predetermined line shape has a connection point 41 connected to the cylindrical barrel 11 in a direction parallel to the outer side wall 33 The entry point 42 away from the cylindrical body 11 and the minimum cross-sectional point 43 with the smallest distance from the outer wall 33 in the direction perpendicular to the outer wall 33 , the minimum cross-section point 43 is connected to the connection point 41 in the direction perpendicular to the outer wall 33 The distance a between them is equal to 2%-5% of the diameter of the cylindrical barrel 11 and the distance b to the connection point 41 in the horizontal direction parallel to the outer wall 33 is 5%-25% of the diameter of the cylindrical barrel 11, so Not only can it be convenient to form a circulation area in the inlet flue whose cross-section first decreases and then increases, but the shape of the circulation area in the inlet flue can be ensured by limiting the position of the minimum cross-section point 43, thereby further improving the flow area in the inlet flue. The acceleration effect of the air flow further improves the uneven distribution of particles and gases in the circulation area in the inlet flue, thereby further improving the separation efficiency of the cyclone separator 1 for circulating fluidized bed boilers with variable cross-section inlet flues and controlling the pressure drop. increase.

Furthermore, by having the inlet flue 30 include a top wall 31 , a bottom wall 32 , an outer side wall 33 and an inner side wall 34 , the flow area within the inlet flue is adjusted only by adjusting the predetermined linear shape of the horizontal section of the inner side wall 34 Compared with the cyclone separator using a Venturi structure in the inlet section in the related art, the shape variables of the circulation area in the inlet flue can be made more simple, reducing the difficulty of selecting the shape of the circulation area in the inlet flue, and facilitating the adjustment of existing The cyclone separator is modified to simplify the design and installation difficulty of the inlet flue 30, making it easier to determine the shape of the predetermined linear shape to determine the shape of the circulation area in the inlet flue, thereby ensuring that the inlet flue 30 improves the separation efficiency. and control the increase in pressure drop.

Therefore, the cyclone separator 1 for a circulating fluidized bed boiler with a variable cross-section inlet flue according to the embodiment of the present invention has the advantage of high separation efficiency.

The following describes a cyclone separator 1 for a circulating fluidized bed boiler with a variable cross-section inlet flue according to a specific embodiment of the present invention with reference to the accompanying drawings.

In some specific embodiments of the present invention, as shown in Figures 1-4, a cyclone separator 1 for a circulating fluidized bed boiler with a variable cross-section inlet flue according to an embodiment of the present invention includes a barrel 10, an exhaust pipe 20 and entrance flue 30.

Specifically, as shown in FIGS. 2-4 , the distance between the connection point 41 and the outer wall 33 in the direction perpendicular to the outer wall 33 is greater than the distance between the minimum cross-section point 43 and the outer wall 33 and smaller than the entry point 42 The distance from the outer side wall 33 is such that the inlet area of the circulation area in the inlet flue is larger than the outlet area of the circulation area in the inlet flue. In this way, the cross-sectional area of the circulation area in the inlet flue can be made smaller as a whole on the basis that the cross-sectional area of the circulation area in the inlet flue first increases and then decreases along the flue gas inflow direction, thereby facilitating the acceleration of the air flow. , improve the acceleration effect of the inlet flue 30 on the air flow and control the increase of pressure drop.

Optionally, the diameter of the cylindrical barrel 11 is 2-10 meters, and here the diameter of the cylindrical barrel 11 is preferably 6 meters. This allows the cylindrical body 11 to have a reasonable size, which facilitates the manufacture of the cyclone separator 1 for circulating fluidized bed boilers with variable cross-section inlet flues while ensuring volume.

Further, the length of the outer side wall 33 in the horizontal direction is 6 meters. In this way, the inlet flue 30 can have a reasonable size, which facilitates the manufacture of the inlet flue 30 while ensuring the acceleration and guidance effect of the air flow.

Advantageously, as shown in Figures 2-4, the distance a between the minimum cross-section point 43 and the connection point 41 in the direction perpendicular to the outer side wall 33 is 120-300 mm, preferably 120-250 mm here. In this way, the position of the minimum cross-section point 43 can be further defined, thereby further facilitating the control of the shape of the inner wall 34 to limit the shape of the circulation area in the inlet flue, improving the acceleration effect and unevenness of the air flow by the inlet flue 30, and improving the efficiency The separation efficiency of the cyclone separator 1 of the circulating fluidized bed boiler with variable cross-section inlet flue is controlled and the increase of pressure drop is controlled.

More advantageously, as shown in FIGS. 2-4 , the distance b between the minimum cross-section point 43 and the connection point 41 in the horizontal direction parallel to the outer side wall 33 is 300-1500 mm. In this way, the position of the minimum cross-section point 43 can be further defined, thereby further facilitating the control of the shape of the inner wall 34 to limit the shape of the circulation area in the inlet flue, improving the acceleration effect and unevenness of the air flow by the inlet flue 30, and improving the efficiency The separation efficiency of the cyclone separator 1 of the circulating fluidized bed boiler with variable cross-section inlet flue is controlled and the increase of pressure drop is controlled.

In some specific examples, using the structure shown in Figure 2, the distance a between the minimum cross-section point 43 and the connection point 41 in the direction perpendicular to the outer wall is 200 mm, and the distance a between the minimum cross-section point 43 and the connection point 41 is parallel to The distance b in the horizontal direction of the outer side wall 33 is 700 mm. The numerical simulation method is used to verify the cyclone separator 1 for a circulating fluidized bed boiler with an inlet flue 30 with a of 200 mm and b of 700 mm and a variable cross-section inlet flue. Compared with the related technology, the inlet section cross-section is gradually With the reduced cyclone separator, the separation efficiency increased by 1.79%, while the increase in pressure drop was only 408.71Pa.

Those skilled in the art can understand that the above numerical simulation is only used to verify the above numerical values, and does not mean that the above numerical values are obtained through a limited number of experiments.

Figure 2 shows a cyclone separator 1 for a circulating fluidized bed boiler with a variable cross-section inlet flue according to some examples of the present invention. As shown in FIG. 2 , the predetermined line shape of the inner side wall 34 is a fold line with a single fold point and the minimum cross-sectional point 43 is the fold point.

Figure 3 shows a cyclone separator 1 for a circulating fluidized bed boiler with a variable cross-section inlet flue according to other examples of the present invention. As shown in FIG. 3 , the predetermined line shape is a fold line and also has at least one secondary fold point 44 . The secondary fold point 44 is farther away from the outer wall 33 than the minimum cross-sectional point 43 in a direction perpendicular to the outer wall 33 and parallel to the outer wall 33 . 33 is farther away from the connection point 41 than the minimum cross-section point 43 in the horizontal direction. In this way, the predetermined line shape can be a polyline with multiple fold points and the minimum cross-sectional point 43 can be one of the fold points, which can make the shape selection of the inner wall 34 more flexible.

Figure 4 shows a cyclone separator 1 for a circulating fluidized bed boiler with a variable cross-section inlet flue according to some further examples of the present invention. As shown in Figure 4, the predetermined line shape is an arc shape.

Specifically, as shown in FIG. 1 , the upper end of the exhaust pipe 20 is higher than the top wall of the cylindrical body 11 and the lower end extends into the cylindrical body 11 . This can facilitate the installation of the exhaust pipe 20 .

Optionally, the diameter of the cylindrical barrel 11 is 2-10 meters, and here the diameter of the cylindrical barrel 11 is preferably 6 meters. This allows the cylindrical body 11 to have a reasonable size, which facilitates the manufacture of the cyclone separator 1 for circulating fluidized bed boilers with variable cross-section inlet flues while ensuring volume.

The following describes a circulating fluidized bed boiler according to an embodiment of the present invention. The circulating fluidized bed boiler according to the embodiment of the present invention includes the cyclone separator 1 for the circulating fluidized bed boiler with a variable cross-section inlet flue according to the above embodiment of the present invention.

The circulating fluidized bed boiler according to the embodiment of the present invention has the advantage of high separation efficiency by using the cyclone separator 1 for circulating fluidized bed boiler with variable cross-section inlet flue according to the above embodiment of the present invention.

Optionally, there are one or more cyclone separators 1 for circulating fluidized bed boilers with variable cross-section inlet flues.

Other structures and operations of the circulating fluidized bed boiler according to the embodiment of the present invention are known to those of ordinary skill in the art and will not be described in detail here.

In the description of this specification, reference to the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" or the like is intended to be incorporated into the description of the implementation. An example or example describes a specific feature, structure, material, or characteristic that is included in at least one embodiment or example of the invention. In this specification, schematic representations 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 any one or more embodiments or examples.

Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art will appreciate that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and purposes of the invention. The scope of the invention is defined by the claims and their equivalents.

Claims (10)

1. A cyclone separator for circulating fluidized bed boilers with a variable cross-section inlet flue, which is characterized by including: cylindrical barrel; A tapered section connected to the cylindrical body and located below the cylindrical body; Exhaust pipe, the exhaust pipe is located on the top wall of the cylindrical barrel; Inlet flue, the inlet flue includes a top wall, a bottom wall, an outer wall and an inner wall, and the top wall, the bottom wall, the outer wall and the inner wall jointly define a circulation area in the inlet and outlet flue, The top wall is flush with the top wall of the cylindrical body, the bottom wall is parallel to the top wall and spaced apart in the up and down direction, and the outer side walls are connected to the top wall and the bottom wall respectively. And tangent to the cylindrical body, the horizontal section of the inner wall satisfies a predetermined line shape, and the predetermined line shape is a folded line or an arc shape so that the circulation area in the inlet flue is in a direction perpendicular to the inflow direction of the flue gas. The cross-sectional area first gradually decreases and then gradually increases from the entrance of the inlet flue to the entrance of the cylindrical barrel, and the predetermined linear shape has a connection point connected to the cylindrical barrel and is parallel to the outer side. The entry point of the cylindrical body in the wall direction is far away from the entrance point and the minimum cross-sectional point with the smallest distance from the outer wall in the direction perpendicular to the outer wall, and the minimum cross-sectional point is at a distance perpendicular to the outer wall. The distance from the connection point in the direction is equal to 2%-5% of the diameter of the cylindrical barrel and the distance from the connection point in the horizontal direction parallel to the outer wall is the cylindrical barrel. 5%-25% of diameter. 2. The cyclone separator for circulating fluidized bed boiler with variable cross-section inlet flue according to claim 1, characterized in that, in the direction perpendicular to the outer side wall, the connection point between the connecting point and the outer side wall is The distance between them is greater than the distance between the minimum cross-section point and the outer side wall and smaller than the distance between the inlet point and the outer side wall so that the inlet area of the circulation area in the inlet flue is larger than the inlet The outlet area of the circulation area within the flue. 3. The cyclone separator for circulating fluidized bed boiler with variable cross-section inlet flue according to claim 1, characterized in that the minimum cross-section point and the connection point are in a direction perpendicular to the outer side wall. The distance is 120-250mm. 4. The cyclone separator for circulating fluidized bed boiler with variable cross-section inlet flue according to claim 1, characterized in that the minimum cross-section point and the connection point are in a horizontal direction parallel to the outer side wall. The distance is 300-1500mm. 5. The cyclone separator for circulating fluidized bed boiler with variable cross-section inlet flue according to claim 1, characterized in that the minimum cross-section point and the connection point are in a direction perpendicular to the outer side wall. The distance is 200 mm and the distance between the minimum cross-section point and the connection point in the horizontal direction parallel to the outer side wall is 700 mm. 6. The cyclone separator for circulating fluidized bed boiler with variable cross-section inlet flue according to claim 1, characterized in that the predetermined line shape is a fold line and also has at least one secondary inflection point, and the secondary inflection point The connection point is farther away from the outer side wall than the minimum cross-section point in a direction perpendicular to the outer side wall and farther away from the minimum cross-section point than the minimum cross-section point in a horizontal direction parallel to the outer side wall. 7. The cyclone separator for circulating fluidized bed boiler with variable cross-section inlet flue according to claim 1, characterized in that the upper end of the exhaust pipe is higher than the top wall of the cylindrical barrel and the lower end extends into the cylinder. 8. The cyclone separator for circulating fluidized bed boiler with variable cross-section inlet flue according to claim 1, characterized in that the diameter of the cylindrical body is 2-10 meters. 9. A circulating fluidized bed boiler, characterized by comprising a cyclone separator for a circulating fluidized bed boiler with a variable cross-section inlet flue according to any one of claims 1 to 8. 10. The circulating fluidized bed boiler according to claim 9, characterized in that there are multiple cyclones for circulating fluidized bed boilers with variable cross-section inlet flues.