Circulating fluidized bed boiler

Abstract

The invention relates to a circulating fluidized bed boiler (10) comprising a vertically extending furnace (12), a separator unit (14), and an exhaust gas channel (18) connected to the separator unit (14) via a cross pipe (24), the exhaust gas channel comprising a first vertically extending passageway (18.1) and a horizontally extending passageway (18.2) and a second vertically extending passageway (18.3). The first vertically extending passageway (18.1) and the horizontally extending passageway (18.2) and the second vertically extending passageway (18.3) are arranged successively in the gas flow direction, such that the horizontally extending passageway (18.2) is configured to connect the first vertically extending passageway (18.1) and the second vertically extending passageway (18.3) to each other, and the horizontally extending passageway (18.2) is arranged below the separator unit (14), which is arranged between the first vertically extending passageway (18.1) and the second vertically extending passageway (18.3).

Description

Technical Field

[0001] This invention relates to a circulating fluidized bed boiler according to the present invention. Background Technology

[0002] This invention relates to a circulating fluidized bed reactor having a vertical combustion chamber and a convection section, at least partially formed by tube walls, and a vertical cyclone separator. The gas inlet passage of the vertical cyclone separator is connected to the upper part of the combustion chamber, and a return passage for the separated solids is connected to the lower part of the combustion chamber. Fluidized bed boilers, and particularly circulating fluidized bed boilers, are known to be advantageous for the combustion of a wide variety of solid fuels (such as fuels derived from various wastes) while being configured to produce steam.

[0003] Document WO2007035169A1 discloses a furnace for burning solid waste in a fluidized bed. Flue gas from the furnace passes through an extraction chute that forms the input to a return flue, and from there exits the boiler through a rear chute. The flue gas then passes through a gas cleaning device including a cyclone separator and a filter, and is then allowed to be discharged into the air through a chimney.

[0004] Document US4686939 discloses a fluidized bed boiler comprising a primary particle trap and a passageway containing a convective heat exchanger. The particle trap is located at the transition between the top of the reactor and a first vertically extending passageway. The first vertically extending passageway is empty and does not include any inserted heat exchanger. Instead, the boiler includes an upward passageway following the first vertically extending passageway in which the convective heat exchanger is located. Cyclones are present and arranged along the upward passageway.

[0005] CN203431878U discloses a circulating fluidized bed boiler system that uses municipal solid waste as a single fuel. The boiler system has a combustion chamber and a cyclone separator connected to the combustion chamber. A vertical heat exchange flue for exhaust gas connected to the cyclone separator and a horizontal heat exchange flue providing a superheater and an economizer are disclosed.

[0006] KR101354938 discloses a fluidized bed combustion boiler for RDF fuel. The boiler has a cyclone separator connected to an air passage via a flue gas passage, and a convective heat transfer passage. The heat transfer passage includes a superheater, an economizer, and an air preheater.

[0007] All the publications mentioned above disclose a linear layout of the apparatus. This results in a rather long and cumbersome arrangement because the different parts of the boiler are arranged laterally one after another in the exhaust gas flow process.

[0008] The purpose of this invention is to provide a circulating fluidized bed boiler that greatly improves the boiler's compactness compared to existing technical solutions. Summary of the Invention

[0009] The objectives of this invention can be achieved substantially as in other disclosures herein, which include further details describing different embodiments of the invention.

[0010] According to one embodiment of the present invention, a circulating fluidized bed boiler includes a vertical extension furnace, a separator unit, a cross pipe, and an exhaust gas passage connected to the separator unit via the cross pipe. The exhaust gas passage includes a first vertical extension passage, a horizontal extension passage, and a second vertical extension passage, wherein the first vertical extension passage, the horizontal extension passage, and the second vertical extension passage are arranged sequentially in the gas flow direction during use, such that the horizontal extension passage is configured to connect the first vertical extension passage and the second vertical extension passage to each other, and the horizontal extension passage is arranged below the separator unit, which is arranged between the first vertical extension passage and the second vertical extension passage.

[0011] This minimizes and / or makes very efficient use of the ground space required by circulating fluidized bed boilers, particularly.

[0012] According to one embodiment of the invention, the furnace has a rectangular cross-section, and the horizontally extending passageway extends parallel to the rear wall of the furnace.

[0013] According to one embodiment of the invention, the furnace has a rectangular cross-section, and the horizontally extending passageway extends parallel to the rear wall of the furnace, and the intersecting pipes extend parallel to the rear wall of the furnace.

[0014] The rectangular shape of the furnace's cross-section, together with the horizontally extending passageway and the intersecting pipes pointing parallel to the rear wall of the furnace, reduces the required floor space of the boiler.

[0015] According to one embodiment of the invention, the solid return system is at least partially arranged between the first vertical extension passage and the second vertical extension passage.

[0016] When the solids return system is installed between the vertically extending exhaust gas passages, the volume occupied by the circulating fluidized bed boiler is not increased by the solids return system, but is mainly defined by the boiler, cross pipes and the vertical gas passages.

[0017] According to one embodiment of the invention, the circulating fluidized bed boiler provides a fluidized bed solid material cooler in the solid return system that provides a passage for the return of separated solids, the fluidized bed solid material cooler being arranged at least partially between the first vertical extension passage and the second vertical extension passage.

[0018] Even though, apart from the solids return channel, the fluidized bed solids cooler or the solids return system is assembled between the vertically extending exhaust gas passages, the volume occupied by the circulating fluidized bed boiler is still mainly defined by the furnace, the cross pipes, and the vertical gas passages.

[0019] According to one embodiment of the invention, the furnace has a rectangular cross-section, and the horizontally extending passageway extends parallel to the rear wall of the furnace, and the intersecting pipes extend parallel to the rear wall of the furnace, and the solids return system is arranged between the first vertically extending passageway and the second vertically extending passageway.

[0020] According to one embodiment of the invention, the furnace has a rectangular cross-section, and the horizontally extending passage extends parallel to the rear wall of the furnace, and the intersecting pipes extend parallel to the rear wall of the furnace, and a solids return system is arranged between the first vertically extending passage and the second vertically extending passage, and the circulating fluidized bed boiler is provided with a fluidized bed solids cooler in the passage of the separated solids return channel, the fluidized bed solids cooler being arranged at least partially between the first vertically extending passage and the second vertically extending passage.

[0021] According to one embodiment of the present invention, the first vertical extension passage has a first end connected to the outlet of the cross pipe and a second end, and the second vertical extension passage has a first end and a second end, and the horizontal extension passage between the first vertical extension passage and the second vertical extension passage is connected to the second end of the first vertical extension passage and the first end of the second vertical extension passage.

[0022] According to one embodiment of the present invention, the first vertical extension passage has a first end connected to the outlet of the intersecting pipe and a second end, and the second vertical extension passage has a first end and a second end, and the horizontal extension passage between the first vertical extension passage and the second vertical extension passage is connected to the second end of the first vertical extension passage and the first end of the second vertical extension passage, and the first vertical extension passage and the second vertical extension passage are perpendicular to the horizontal extension passage.

[0023] According to one embodiment of the invention, the first vertically extending passageway has no heat exchanger in its interior space. This provides the effect that exhaust gases are cooled solely by heat transfer to the walls of the first vertically extending passageway, and any deposits can be easily removed from the walls by a suitable rapping system compared to the cleaning of the internal heat exchanger bundle. This embodiment, along with any other embodiments of the invention, is feasible because the first vertically extending passageway is an integral part of the invention.

[0024] According to one embodiment of the invention, a heat exchanger is provided, which is arranged to transfer heat from the exhaust gas in the exhaust gas passage, specifically as follows: the first vertical extension passage is an empty passage without a heat exchanger in its interior space, the horizontal extension passage includes at least one heat exchanger in its interior space, and the second vertical extension passage includes at least one heat exchanger in its interior space.

[0025] According to one embodiment of the present invention, a steam generation system is arranged to be connected to the circulating fluidized bed boiler. The steam generation system includes: an economizer heat exchanger, an evaporator heat exchanger, and a superheater heat exchanger, wherein the superheater heat exchanger is arranged to be connected to the fluidized bed solid material cooler and the cross pipe, the evaporator heat exchanger is arranged to be connected to the furnace, the separator unit, and the horizontal extension passage, and the economizer heat exchanger is arranged to be connected to the second vertical extension passage, wherein the first vertical extension passage has no heat exchanger in its internal space.

[0026] According to another embodiment of the present invention, a steam generation system is arranged to be connected to the circulating fluidized bed boiler, the steam generation system comprising: an economizer heat exchanger, an evaporator heat exchanger, and a superheater heat exchanger, wherein the superheater heat exchanger is arranged to be connected to the fluidized bed solid material cooler and the cross pipe, the evaporator heat exchanger is arranged to be connected to the furnace, the separator unit, the horizontal extension passage and the second vertical extension passage, and the economizer heat exchanger is arranged to be connected to the second vertical extension passage, and the first vertical extension passage has no heat exchanger in its internal space.

[0027] Generally, the advantage of this design is that the gas passage is close to the furnace and the solid material fluidized bed cooler. Thus, due to the presence of a functionally open gas passage, the overall design reduces the required boiler space and the length of the steam pipes. This layout also offers advantages in connecting the different steam generation stages of the steam system.

[0028] According to one embodiment of the present invention, the horizontally extended passageway includes independently supported modules, each of which includes an evaporative heat exchanger, which facilitates after-sales service for the heat exchangers in the horizontally extended gas passageway.

[0029] According to one embodiment of the present invention, the horizontally extended passageway includes independently supported modules, each of which includes a heat exchanger, which facilitates after-sales service for the heat exchangers in the horizontally extended gas passageway.

[0030] Exemplary embodiments of the invention presented in this patent application should not be construed as limiting the applicability of the appended claims. The verb "comprising" is used in this patent application as an openness limitation, which does not exclude the presence of features not yet described. Unless expressly stated otherwise, the features described in the dependent claims are freely combinable. Novel features considered characteristic of the invention are specifically set forth in the appended claims. Attached Figure Description

[0031] In the following description, the invention will be illustrated with reference to the accompanying exemplary schematic diagrams, wherein:

[0032] Figure 1 The illustration shows a circulating fluidized bed boiler according to an embodiment of the present invention;

[0033] Figure 2 The diagram shows... Figure 1 Sectional view II-II;

[0034] Figure 3 The diagram shows... Figure 2 Cross-sectional view III-III;

[0035] Figure 4 The illustration shows another embodiment of the invention. Figure 1 Sectional diagram II-II; and

[0036] Figure 5 The illustration shows another embodiment of the invention. Figure 1 Cross-sectional view II-II. Detailed Implementation

[0037] Figure 1A circulating fluidized bed (CFB) boiler 10 according to an embodiment of the present invention is schematically depicted. The CFB boiler 10 includes a furnace 12, a solids separator 14 (which may generally be referred to as a separator unit), and a solids return system 16, as well as a cross duct 24 connecting the separator unit to an exhaust gas passage 18. In the most typical case, the cross duct 24 and the exhaust gas passage 18 are configured to direct the exhaust gas generated by the combustion of fuel in the CFB boiler to further treatment and ultimately to the atmosphere. The CFB boiler 10 is supported by a separate support structure, which is not shown here for clarity. In practice, relatively large boilers are arranged as top-supported, i.e., they are supported such that the boiler is arranged to be suspended from a conventional rigid support steel structure extending around and above the boiler pressure body. Relatively small boilers may be arranged as bottom-supported, wherein the vertical load of the boiler is supported only by a rigid support steel structure arranged below the boiler. The main difference between top-supported and bottom-supported structures is that, as the boiler temperature increases, thermal expansion in a top-supported boiler primarily occurs downwards, while in a bottom-supported boiler, thermal expansion primarily occurs upwards. In practice, a third alternative for supporting boiler 10 is to support it to a rigid support steel structure at its intermediate section. Thus, the lower part below the intermediate section of the boiler is top-supported, while the upper part of the boiler pressure body above the intermediate section is bottom-supported. The intermediate-supported structure is advantageous because it reduces the size of the support steel structure compared to the dimensions required for a top-supported boiler. Simultaneously, such an intermediate-supported structure reduces the need for very robust boiler walls, as is the case in bottom-supported boilers.

[0038] The following reference Figures 1 to 3 The circulating fluidized bed boiler 10 is described below. Figure 1 The circulating fluidized bed boiler 10 is shown from one side of the assembled solids separator 14, which is referred to herein as the back side of the circulating fluidized bed boiler 10, and its orientation is... Figure 3 The middle is indicated by arrow I. Figure 2 It shows Figure 1 Sectional diagram II-II, and Figure 3 It shows Figure 2Cross-sectional view III-III. The furnace 12 of the CFB extends vertically and advantageously has a rectangular cross-section, with its lower section gradually narrowing. At the lower end of the furnace 12 is a bellows 20 for introducing fluidizing gas into the furnace through a grille. The furnace 12 shown in the figure has a rectangular cross-section and has a front wall 12.1, a rear wall 12.2, a left wall 12.3, and a right wall 12.4. The furnace 12 is connected in its upper region to a solids separator 14 via a flow channel 22 connected to the rear wall 12.2 of the furnace 12. The solids separator 14 advantageously consists of a cyclone separator having its central tube as a gas outlet. In some practical applications, the separator unit may provide more than one parallel cyclone separator, or other types of separators, such as impingement separators, may be provided. The separator is cooled by an evaporative heat exchanger 26 or surface integrated into its wall, as is common in the art. Advantageously, the evaporative heat exchanger is coupled to allow for natural circulation of the evaporated water-based solution. In CFB operation, the main portion of the solid material entrained by the gas flowing from the furnace to separator 14 is separated from the gas flow. At least a portion (typically the main portion) of the separated solid material (referred to herein as solids) is returned to furnace 12 via solids return system 16.

[0039] The exhaust gas passage 18 of the circulating fluidized bed boiler 10 is connected to the separator unit via a substantially horizontally extending cross pipe 24. The cross pipe 24 is arranged to connect to the solids separator 14 at its gas outlet and to connect to a first vertically extending passage 18.1 above it. The walls of the cross pipe 24 are cooled, preferably by steam. Therefore, the cross pipe 24 includes cooled walls arranged as heat exchanger surfaces, and the internal gas space of the cross pipe 24 is empty, i.e., there is no internal heat exchanger.

[0040] The exhaust gas passage 18 includes a first vertically extending passage 18.1, with intersecting pipes connected to it. The exhaust gas passage 18 further includes a horizontally extending passage 18.2 and a second vertically extending passage 18.3. One end of the horizontally extending passage 18.2 is arranged to connect with the lower portion of the first vertically extending passage 18.1. The other end of the horizontally extending passage 18.2 is arranged to connect with the lower portion of the second vertically extending passage 18.3. The general flow direction of the gas in the circulating fluidized bed boiler is depicted by arrow A in the figure, and the general flow direction of the separated solids is indicated by arrow B. The horizontally extending passage 18.2 has a length at least equal to the width of the rear wall 12.2 of the furnace 12, such that the first and second vertically extending passages leave space for the fluidized bed heat exchanger.

[0041] The first vertical extension passage 18.1 has a first end 18.1' connected to an outlet of the cross pipe 24 and a second end 18.1'' at an end portion opposite to the first end 18.1'. A gas flow opening in the first end 18.1' of the first vertical extension passage 18.1 is located at its top, the circumference of which is formed by the end of the sidewall of the first vertical extension passage 18.1. A gas flow opening in the second end 18.1'' of the first vertical extension passage 18.1 is arranged in one of its sidewalls such that the very end portion of the passage is closed by the wall. The second vertical extension passage 18.3 has a first end 18.3' and a second end 18.3''. A horizontal extension passage 18.2 between the first and second vertical extension passages connects to the second end 18.1'' of the first vertical extension passage 18.1 and the first end 18.3' of the second vertical extension passage 18.3. A gas outlet 18.4 is located at the second end of the second vertical extension passage 18.3. Advantageously, there is a rigid connection between the furnace 12, the separator unit, the solids return system 16, and the cross-pipe, with expansion joints between the cross-pipe 24 and the first vertical extension passage 18.1, and between the first vertical extension passage 18.1 and the horizontal extension passage 18.2. The first vertical extension passage 18.1 and the second vertical extension passage 18.3 are parallel to each other and perpendicular to the horizontal extension passage 18.2. Each passage in the passage forms a straight duct for the exhaust gas. The cross-pipe is supported on top of the separator unit, meaning it does not require any additional support consisting of a steel structure.

[0042] As it comes from Figures 1 to 3 It becomes clear that the exhaust gas passage 18 is configured such that the cross duct 24, the first vertical extension passage 18.1, the horizontal extension passage 18.2, and the second vertical extension passage 18.3 are arranged successively in the gas flow direction A, such that the cross duct 24 connects the separator unit to the first vertical extension passage 18.1, and the horizontal extension passage 18.2 is configured to connect the first vertical extension passage 18.1 and the second vertical extension passage 18.3 to each other. In other words, the gas is arranged to flow from the cross duct 24 to the first vertical extension passage 18.1, in which the flue gas flows substantially downward when the fluidized bed boiler is in operation. The flue gas further flows from the first vertical extension passage 18.1 to the horizontal extension passage 18.2, in which the flue gas flows substantially horizontally. The flue gas flows further from the horizontal extension duct 18.2 into the second vertical extension duct 18.3, where it flows substantially upward. The cross duct 24 is also horizontally extended, and there, the flue gas flows substantially horizontally, but in a direction substantially opposite to the gas flow in the horizontal extension duct 18.2.

[0043] The separator unit is located at least partially between the first vertical extension passage 18.1 and the second vertical extension passage 18.3 and above the horizontal extension passage 18.2. This is particularly evident from... Figure 2 The details become clear. The internal space of furnace 12 and the separator unit are arranged adjacent to each other. A line L1 runs through the cross-section of furnace 12 and the separator unit, and a line L2 runs through the cross-section of the first vertical passage 18.1 and the second vertical passage 18.2. More specifically, in Figure 2 In the figure, line L1 passes through the center of the cross-section of the furnace 12 and the separator unit, and line L2 passes through the center of the cross-section of the first vertical channel 18.1 and the second vertical channel 18.2. Moreover, as can be seen, lines L1 and L2 are at an angle to each other. In the embodiment shown in the figure, the separator unit is positioned relative to the furnace and the vertical passages such that there is a right angle between lines L1 and L2; however, if, for example, the separator unit moves from its current position toward either of the vertical passages for some practical reason, this angle will still be substantially right-angled. This also means that the horizontally extending passage 18.2 extends parallel to both the rear wall 12.2 and the front wall 12.1 of the furnace 12, since the furnace 12 has a rectangular cross-section. In practice, it is worth noting that the direction of the intersecting pipe 24 is parallel to the direction of the horizontally extending passage 18.2. Furthermore, as particularly... Figure 2 and Figure 3 As can be seen, the separator unit is not only higher than the horizontal extension passage 18.2 in the vertical direction, but also directly above the horizontal extension passage 18.2, that is, it is in the same position in the horizontal direction.

[0044] The solids return system 16 includes a return channel 30 for separated solids, and it is arranged between a first vertical extension channel 18.1 and a second vertical extension channel 18.3. A fluidized bed solids cooler 31 is located within the passage of the separated solids return channel. According to the invention, the fluidized bed solids cooler 31 is provided with one or more heat exchangers for superheated steam, and therefore it can also be referred to as a fluidized bed heat exchanger. Furthermore, the fluidized bed solids cooler 31 is arranged at least primarily between the first vertical extension channel 18.1 and the second vertical extension channel 18.3, below the separator unit. Even though not shown in the figures, the solids return system 16 is provided with a loop seal arrangement to prevent gas from flowing back from the furnace 12 to the separator unit.

[0045] The circulating fluidized bed boiler according to the invention is particularly advantageous for the combustion of solid waste-derived fuels (such as biomass, sludge, and waste-derived fuels with various compositions). The heat generated by combustion is used for steam generation. The compact design provided by the invention is particularly advantageous for CFB boilers used for waste-derived fuels. The circulating fluidized bed boiler can be part of a power generation unit that produces electrical power. Typically, the working medium is a water-based solution. The CFB boiler 10 includes a steam generation system connected to a steam cycle that applies, for example, an approximate Rankine cycle. The steam generation system is arranged to connect to the circulating fluidized bed boiler such that it includes an economizer heat exchanger 32, an evaporative heat exchanger 26, and a superheater heat exchanger 28. The superheater heat exchanger 28 of the steam generation system is located in the fluidized bed solid material cooler 31 and in the cross pipe 24, while the evaporative heat exchanger 26 is located in the furnace 12 (cooling the furnace wall), the separator unit, in the horizontal extension passage 18.2, and also partially in the second vertical extension passage 18.3. The energy-saving heat exchanger 32 is located in the second vertical extension passage 18.3. The first vertical extension passage 18.1 has no heat exchanger bundle in its internal space 17, and therefore, the first vertical extension passage 18.1 can be referred to in practice as an empty passage. The flue gas is cooled by the cooling walls of the first vertical extension passage 18.1 to avoid or at least mitigate corrosion from chlorine and heavy metals.

[0046] All major components of the CFB boiler 10 are substantially equipped with heat shields. Due to the layout of the CFB boiler 10 according to the invention, the economizer heat exchanger 32, the evaporative heat exchanger 26, and the superheater heat exchanger 28 are adjacent to each other, and the necessary tube lengths are thus minimized, which also minimizes the need for tube insulation. To further facilitate maintenance of the CFB boiler 10, the horizontal extension passage 18.2 includes independently supported, assemblable, and removable heat exchanger modules 19, each of which is provided with an evaporative heat exchanger 26. In the embodiment shown in the figures, the horizontal extension passage 18.2 consists of four heat exchanger modules 19, the number of which is selected as needed by the actual application. The modules are configured to be removable from the gas passage in the horizontal direction. A second vertical extension passage 18.3 is independently supported from the bottom. Both the vertical and horizontal extension passages are equipped with an appropriate number of ash hoppers, which can be designed as cooled or uncooled sections.

[0047] Figure 4 Cross-sectional view II-II is shown according to another embodiment of the invention, illustrating some possibilities for adjusting the boiler system according to one embodiment of the invention. A line L1 runs through the cross-section of the furnace 12 and the separator unit, and a line L2 runs through the cross-section of the first vertical extension passage 18.1 and the second vertical extension passage 18.3. In this embodiment, with Figure 2Compared to the one shown, the second vertically extending passage 18.3 has a larger cross-sectional area, causing the passage cross-section to extend from the general wall line of the horizontally extending passage 18.2 toward the furnace 12. Furthermore, the empty passage 18.1 has a larger cross-sectional area than... Figure 2 The cross-sectional area is smaller than the cross-sectional area. Furthermore, as can be seen, lines L1 and L2 are now also at an angle to each other. In the boiler 10 according to the invention, the furnace and separator units are adjacent to each other in a first direction, which is generally in the direction of line L1. The first vertical extension passage and the second vertical extension passage and the horizontal extension passage 18.2 are arranged substantially adjacent to each other in a vertical plane in a second direction, which is generally in the direction of the rear wall 12.2 of the furnace 12. The cross-sectional areas of the first vertical extension passage and the second vertical extension passages 18.1, 18.3 are appropriately designed according to the requirements of the specific practical application. It is conceivable that in some cases, the cross-sectional area of ​​the empty passage 18.1 is larger than the cross-sectional area of ​​the second vertical extension passage 18.2, but the opposite can be true if the situation requires it. This criterion can be the desired gas velocity or pressure drop.

[0048] Figure 5 An embodiment of the invention is depicted, by which the benefits of the invention in terms of space saving in at least the exhaust gas passage 18 can be obtained, while retaining some more space between the exhaust gas passage 18 and the furnace 12. Figure 5 Implementation examples and Figure 2 The embodiment differs from the one described above, such that the intersecting conduit 24 is at an angle to the longitudinal direction of the horizontally extending passageway 18.2, i.e., not parallel. Thus, compared to... Figure 1 Compared to the diagram shown, the horizontal distance between the exhaust gas passage 18 and the furnace 12 is increased. It should be noted that... Figure 2 , 4 The features shown in Figure 5 are technically compatible with each other, allowing for free combination of them. In particular... Figure 5 The features shown provide more horizontal distance between the exhaust gas passage 18 and the furnace 12, enabling the application Figure 4 The increased cross-section of the exhaust gas passage shown is possible. This is in Figure 5 Not shown in the diagram, because this feature also allows the space to be used for other purposes.

[0049] While the invention has been described herein by way of example in relation to what is now considered the most preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various combinations or modifications of its features, as well as several other applications included within the scope of the invention, as defined in the appended claims. When such combinations are technically feasible, the details mentioned in relation to any of the foregoing embodiments may be used in conjunction with another embodiment.

Claims

1. A circulating fluidized bed boiler (10), comprising: A vertical extension furnace (12), a separator unit (14), a cross pipe (24), and an exhaust gas passage (18) connected to the separator unit (14) via the cross pipe (24), wherein the exhaust gas passage includes: A first vertical extension passage (18.1), a horizontal extension passage (18.2), and a second vertical extension passage (18.3), wherein the first vertical extension passage (18.1), the horizontal extension passage (18.2), and the second vertical extension passage (18.3) are arranged sequentially in the gas flow direction, such that the horizontal extension passage (18.2) is configured to connect the first vertical extension passage (18.1) and the second vertical extension passage (18.3) to each other, characterized in that the horizontal extension passage (18.2) is arranged below the separator unit (14), the separator unit (14) being arranged between the first vertical extension passage (18.1) and the second vertical extension passage (18.3).

2. The circulating fluidized bed boiler (10) according to claim 1, characterized in that, The furnace (12) has a rectangular cross-section, and the horizontally extending passage (18.2) extends parallel to the rear wall (12.2) of the furnace (12).

3. The circulating fluidized bed boiler (10) according to claim 2, characterized in that, The cross pipe (24) extends parallel to the rear wall (12.2) of the furnace (12).

4. The circulating fluidized bed boiler (10) according to claim 1, characterized in that, The solid return system (16) is at least partially arranged between the first vertical extension passage (18.1) and the second vertical extension passage (18.3).

5. The circulating fluidized bed boiler (10) according to claim 4, characterized in that, The circulating fluidized bed boiler (10) is provided with a fluidized bed solid material cooler (31) in the solid return system (16), the fluidized bed solid material cooler (31) being arranged at least partially between the first vertical extension passage (18.1) and the second vertical extension passage (18.3).

6. The circulating fluidized bed boiler (10) according to claim 3, characterized in that, The solid return system (16) is at least partially arranged between the first vertical extension passage (18.1) and the second vertical extension passage (18.3).

7. The circulating fluidized bed boiler (10) according to any one of claims 1 to 6, characterized in that, The first vertical extension passage (18.1) has a first end (18.1') and a second end (18.1'') connected to the outlet of the cross pipe (24), and the second vertical extension passage (18.3) has another first end (18.3') and another second end (18.3''), and the horizontal extension passage (18.2) between the first vertical extension passage and the second vertical extension passage (18.3) is connected to the second end (18.1'') of the first vertical extension passage (18.1) and the other first end (18.3') of the second vertical extension passage (18.3).

8. The circulating fluidized bed boiler (10) according to claim 7, characterized in that, The first vertical extension passage (18.1) and the second vertical extension passage (18.3) are perpendicular to the horizontal extension passage (18.2).

9. The circulating fluidized bed boiler (10) according to any one of claims 1 to 6, characterized in that, The first vertically extending passageway (18.1) has no heat exchanger in its interior space (17).

10. The circulating fluidized bed boiler (10) according to claim 5, characterized in that, A steam generation system is arranged to be connected to the circulating fluidized bed boiler (10), the steam generation system comprising: an economizer heat exchanger (32), an evaporator heat exchanger (26), and a superheater heat exchanger (28), wherein the superheater heat exchanger (28) is located in the fluidized bed solid material cooler (31) and the cross pipe (24), the evaporator heat exchanger (26) is located in the furnace (12), the separator unit (14), and the horizontal extension passage (18.2), and the economizer heat exchanger (32) is located in the second vertical extension passage (18.3), and the first vertical extension passage (18.1) has no heat exchanger in its internal space.

11. The circulating fluidized bed boiler (10) according to claim 5, characterized in that, A steam generation system is arranged to be connected to the circulating fluidized bed boiler (10), the steam generation system comprising: an economizer heat exchanger (32), an evaporator heat exchanger (26), and a superheater heat exchanger (28), wherein the superheater heat exchanger (28) is located in the fluidized bed solid material cooler (31) and the cross pipe (24), the evaporator heat exchanger (26) is located in the furnace (12), the separator unit (14), the horizontal extension passage (18.2), and the second vertical extension passage (18.3), and the economizer heat exchanger (32) is located in the second vertical extension passage (18.3), and the first vertical extension passage (18.1) has no heat exchanger in its internal space.

12. The circulating fluidized bed boiler (10) according to any one of claims 1 to 6, characterized in that, The horizontally extended passageway (18.2) includes independently supported modules (19), each of which includes an evaporative heat exchanger (26).

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