Circulating Fluidized Bed Boiler

Abstract

The present 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 crossover duct (24), wherein the exhaust gas channel includes a first vertically extending pass (18.1), a horizontally extending pass (18.2), and a second vertically extending pass (18.3). The first vertically extending path (18.1), the horizontally extending path (18.2), and the second vertically extending path (18.3) are arranged consecutively in the gas flow direction, whereby the horizontally extending path (18.2) is configured to connect the first vertically extending path (18.1) and the second vertically extending path (18.3) to each other, and the horizontally extending path (18.2) is arranged below the separator unit (14) located between the first vertically extending path (18.1) and the second vertically extending path (18.3).

Description

[Technical field]

[0001] Technical Field

[0001] The invention relates to a circulating fluidized bed boiler according to the preamble of claim 1. [Background technology]

[0002] Background technology

[0002] The present 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 channel of which is connected to an upper part of the combustion chamber and a return path for separated solids is connected to a lower part of the combustion chamber. Fluidized bed boilers, in particular 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 waste materials, while being configured to generate steam.

[0003]

[0003] Document WO 2007035169 A1 discloses a furnace for burning solid waste in a fluidized bed. Flue gases enter the furnace into a draw-off chute that constitutes the input to a return flue, from where they proceed through a rear chute and exit the boiler. The flue gases then pass through a gas cleaning device including a cyclone and a filter before they are allowed to escape to the atmosphere through a chimney.

[0004]

[0004] The document US Patent No. 4,686,939 discloses a fluidized bed boiler with a primary particle collector and a pass containing a convection heat exchanger. The particle collector is located at the transition between the top of the reactor and a first vertically extending pass. The first vertically extending pass is an empty pass that does not include any inserted heat exchanger. Instead, the boiler comprises an upward pass after the first vertically extending pass in which the convection heat exchanger is located. There is a cyclone arranged to follow the upward pass.

[0005]

[0005] China Utility Model Application No. 203431878U discloses a circulating fluidized bed boiler system using municipal solid waste as the sole fuel. The boiler system includes 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 provided with a superheater and a coal economizer are disclosed.

[0006]

[0006] Korean Patent No. 101354938 discloses a fluidized bed combustion boiler for RDF fuel. The boiler has a cyclone separator connected to an empty path and a convective heat transfer path through a flue gas path. The heat transfer path includes a superheater, a coal economizer, and an air preheater.

[0007]

[0007] All of the above mentioned publications disclose a serial layout of the plants. Since the different parts of the boiler are arranged laterally one after the other in the course of the exhaust gas flow, this results in a rather long and cumbersome arrangement.

[0008]

[0008] The object of the present invention is to provide a circulating fluidized bed boiler which significantly increases the compactness of the boiler compared to prior art solutions. Summary of the Invention [Means for solving the problem]

[0009] Disclosure of the Invention

[0009] The objects of the invention may be achieved substantially as disclosed in the independent claims and in the other claims which describe further details of different embodiments of the invention.

[0010] According to one embodiment of the present invention, a circulating fluidized bed boiler includes a vertically extending furnace, a separator unit, a crossover duct, and an exhaust gas channel connected to the separator unit via the crossover duct. The exhaust gas channel includes a first vertically extending path, a horizontally extending path, and a second vertically extending path, the first vertically extending path, the horizontally extending path, and the second vertically extending path being successively arranged in a gas flow direction in use, whereby the horizontally extending path is configured to connect the first vertically extending path and the second vertically extending path to each other, and the horizontally extending path is arranged below the separator unit arranged between the first vertically extending path and the second vertically extending path.

[0011]

[0011] In this manner, in particular, the floor space requirement of the circulating fluidized bed boiler is minimized and / or utilized very efficiently.

[0012]

[0012] According to one embodiment of the present invention, the furnace has a rectangular cross-section and the horizontal extension path extends parallel to the rear wall of the furnace.

[0013]

[0013] According to one embodiment of the present invention, the furnace has a rectangular cross-section, the horizontal extension path extends parallel to the rear wall of the furnace, and the crossover duct extends parallel to the rear wall of the furnace.

[0014]

[0014] The rectangular shape of the cross section of the furnace, combined with the horizontally extending paths and crossover ducts guided parallel to the rear wall of the furnace, reduces the required installation area of ​​the boiler.

[0015]

[0015] According to one embodiment of the invention, a solids return system is at least partially disposed between the first vertically extending path and the second vertically extending path.

[0016]

[0016] When a solids return system is installed between the vertically extending exhaust gas paths, the occupied volume of the circulating fluidized bed boiler is not increased by the solids return system, but is mainly defined by the furnace, the crossover duct, and the vertical gas paths.

[0017]

[0017] According to one embodiment of the present invention, a circulating fluidized bed boiler is provided with a fluidized bed solids cooler in a solids return system providing a path for a return channel of separated solids, the fluidized bed solids cooler being at least partially disposed between a first vertically extending path and a second vertically extending path.

[0018]

[0018] Even when a fluidized bed solids cooler or solids return system is equipped between the vertically extending exhaust gas paths in addition to the solids return channel, the occupied volume of the circulating fluidized bed boiler is still primarily defined by the furnace, the crossover duct, and the vertical gas paths.

[0019]

[0019] According to one embodiment of the present invention, the furnace has a rectangular cross-section, the horizontally extending path extends parallel to the rear wall of the furnace, the crossover duct extends parallel to the rear wall of the furnace, and the solids return system is positioned between the first vertically extending path and the second vertically extending path.

[0020]

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

[0021]

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

[0022]

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

[0023]

[0023] According to one embodiment of the present invention, the first vertically extending path does not include a heat exchanger in its internal space. This has the advantage that the exhaust gas is cooled only by heat transfer to the walls of the first vertically extending path, where any deposits can be easily removed by a suitable hammering system, as compared to cleaning the tube bundle of the internal heat exchanger. Since the first vertically extending path is an integral part of the present invention, this embodiment can be implemented in conjunction with any other embodiment of the present invention.

[0024]

[0024] According to one embodiment of the present invention, there are heat exchangers arranged to transfer heat from the exhaust gas in the exhaust gas channel as follows: a first vertically extending path is an empty path that does not include a heat exchanger within its interior space, a horizontally extending path includes at least one heat exchanger within its interior space, and a second vertically extending path includes at least one heat exchanger within its interior space.

[0025]

[0025] According to one embodiment of the present invention, a steam generation system including a coal economizer heat exchanger, an evaporator heat exchanger, and a superheater heat exchanger is arranged in association with a circulating fluidized bed boiler, the superheater heat exchanger is arranged in association with a fluidized bed solids cooler and a crossover duct, the evaporator heat exchanger is arranged in association with a furnace, a separator unit, and a horizontally extending path, and the coal economizer heat exchanger is arranged in association with a second vertically extending path, and the first vertically extending path does not include a heat exchanger within its interior space.

[0026]

[0026] According to another embodiment of the present invention, a steam generation system including a coal economizer heat exchanger, an evaporator heat exchanger, and a superheater heat exchanger is arranged in association with a circulating fluidized bed boiler, the superheater heat exchanger is arranged in association with the fluidized bed solids cooler and the crossover duct, the evaporator heat exchanger is arranged in association with the furnace, the separator unit, the horizontally extending path, and the second vertically extending path, and the coal economizer heat exchanger is arranged in association with the second vertically extending path, and the first vertically extending path does not include a heat exchanger within its interior space.

[0027]

[0027] In general, the advantage of the design is that the gas path is close to the furnace and the solid material fluidized bed cooler. Thus, the overall design reduces the boiler space requirements and the length of steam piping, since a functionally empty gas path is included. The layout also provides advantages in terms of connecting the different steam generation stages in the steam system.

[0028]

[0028] According to one embodiment of the present invention, the horizontally extending path includes independently supported modules each including an evaporative heat exchanger, facilitating maintenance of the heat exchangers in the horizontally extending gas path.

[0029]

[0029] According to one embodiment of the present invention, the horizontally extending path includes independently supported modules each including a heat exchanger, which facilitates maintenance of the heat exchangers in the horizontally extending gas path.

[0030]

[0030] The exemplary embodiments of the invention presented in this patent application should not be interpreted as imposing limitations on the applicability of the appended claims. The verb "comprise" is used in this patent application as an open limitation that does not exclude the presence of unrecited features. The features recited in the dependent claims are mutually freely combinable unless expressly stated otherwise. The novel features believed to be characteristic of the present invention are specifically recited in the appended claims.

[0031] BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In the following, the invention will be described with reference to the accompanying exemplary schematic drawings. [Brief description of the drawings]

[0032] [Figure 1] FIG. 1 shows a circulating fluidized bed boiler according to one embodiment of the present invention. [Diagram 2] FIG. 2 shows a cross-sectional view taken along line II-II of FIG. [Diagram 3] FIG. 3 shows a cross-sectional view taken along line III-III of FIG. [Figure 4] FIG. 4 shows a cross-sectional view II-II of FIG. 1 according to another embodiment of the present invention. [Diagram 5] FIG. 5 shows a cross-sectional view II-II of FIG. 1 according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Detailed Description of the Drawings

[0032] Figure 1 shows a schematic diagram of a circulating fluidized bed (CFB) boiler 10 according to an embodiment of the present invention. The circulating fluidized bed boiler 10 comprises 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 crossover duct 24 connecting the separator unit 14 with an exhaust gas channel 18. The crossover duct 24 and the exhaust channel 18 are configured in the most general case to direct the exhaust gas generated by the combustion of fuel in the CFB boiler to further treatment and finally to the atmosphere. The circulating fluidized bed (CFB) boiler 10 is supported by a separate support structure, which is not shown here for clarity. In practical cases, the relatively large boiler is supported and arranged at the top, i.e. it is supported so that the boiler is arranged to hang from a conventional rigid supporting steel structure extending around and above the boiler pressure body. Relatively small boilers may be arranged in a bottom-supported manner, in which case the vertical load of the boiler is supported only by a rigid supporting steel structure arranged below the boiler. The main difference between a top-supported and bottom-supported arrangement is that when the temperature of the boiler increases, the thermal expansion of the top-supported boiler occurs mainly downwards, whereas in a bottom-supported boiler, the thermal expansion occurs mainly upwards. A third alternative for actually supporting the boiler 10 is to support it at its central section against a rigid supporting steel structure. Thereby, the lower part of the boiler below the central section is supported at the top, and the upper part of the boiler pressure body above the central section is supported at the bottom. The centrally supported arrangement is advantageous insofar as it reduces the size of the supporting steel structure from that required for a top-supported boiler. At the same time, such a centrally supported arrangement reduces the need for very high-strength walls of the boiler, as in the case of bottom-supported boilers.

[0034]

[0033] In the following, the circulating fluidized bed boiler 10 is described with reference to Figs. 1 to 3. Fig. 1 shows the circulating fluidized bed boiler 10 from the side to which the solids separator 14 is coupled, here called the rear side of the circulating fluidized bed boiler 10, the direction of which is indicated by the arrow I in Fig. 3. Fig. 2 shows the section II-II of Fig. 1, and Fig. 3 shows the section III-III of Fig. 2. The furnace 12 of the CFB 10 extends vertically and it advantageously has a rectangular cross section with its tapered lower section. At the lower end of the furnace 12 there is a wind box 20 for introducing the fluidizing gas into the furnace 12 through a grate. The cross section of the furnace 12 shown in the figures is of rectangular shape and it 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 the solids separator 14 by a flow channel 22 which is connected to the rear wall 12.2 of the furnace 12. The solids separator 14 advantageously consists of one cyclone separator with its central tube as gas outlet. Depending on the practical application, the separator unit may be provided with other types of separators, such as more than one parallel cyclone separators or impingement separators instead of one. The separator includes an evaporative heat exchanger or surface 26 integrated in its wall and is cooled, as is customary in the art. Advantageously, the evaporative heat exchanger is coupled so as to obtain a natural circulation of the evaporated aqueous solution. During operation of the CFB 10, the majority of the solid material entrained by the gas flowing from the furnace to the separator 14 is separated from the gas flow. At least a portion - typically the majority - of the separated solid material, referred to herein as solids, is returned to the furnace 12 via a solids return system 16.

[0035]

[0034] The exhaust gas channel 18 of the circulating fluidized bed boiler 10 is connected to the separator unit 14 through a substantially horizontally extending crossover duct 24. The crossover duct 24 is arranged to connect the solids separator 14 at its gas outlet and the first vertically extending path 18.1 above the above-mentioned part. The walls of the crossover duct 24 are cooled, preferably steam-cooled. The crossover duct 24 therefore comprises a cooled wall arranged as a heat exchanger surface 28, and the internal gas space of the crossover duct 24 is empty, i.e. does not comprise an internal heat exchanger.

[0036]

[0035] The exhaust gas channel 18 includes a first vertically extending path 18.1 to which a crossover duct is connected. The exhaust gas channel 18 further includes a horizontally extending path 18.2 and a second vertically extending path 18.3. One end of the horizontally extending path 18.2 is arranged to connect with the lower part of the first vertically extending path 18.1. The other end of the horizontally extending path 18.2 is arranged to connect with the lower part of the second vertically extending path 18.3. The overall flow direction of the gas in the circulating fluidized bed boiler is indicated by arrow A in the figure, and the overall flow direction of the separated solids is indicated by arrow B. The horizontally extending path 18.2 has a length at least equal to the width of the rear wall 12.2 of the furnace 12 so that the first and second vertically extending paths leave space for the fluidized bed heat exchanger 31.

[0037]

[0036] The first vertically extending path 18.1 has a first end 18.1' connected to the outlet of the crossover duct 24 and a second end 18.1'' at an opposite end portion of the first end 18.1'. The gas flow opening in the first end 18.1' of the first vertically extending path 18.1 is at its top and the periphery of the opening is formed by the ends of the side walls of the first vertically extending path 18.1. The gas flow opening in the second end 18.1'' of the first vertically extending path 18.1 is located in one of the side walls, whereby the extreme end of the path is closed by a wall. The second vertically extending path 18.3 has a first end 18.3' and a second end 18.3''. The horizontally extending path 18.2 between the first and second vertically extending paths is connected to the second end 18.1'' of the first vertically extending path 18.1 and to the first end 18.3' of the second vertically extending path 18.3. A gas outlet 18.4 is present at the second end of the second vertically extending path 18.3. Advantageously, there are rigid connections between the furnace 12, the separator unit 14, and the solids return system 16 and the crossover duct, and there are expansion joints between the crossover duct 24 and the first vertically extending path 18.1, and between the first vertically extending path 18.1 and the horizontally extending path 18.2. The first vertically extending path 18.1 and the second vertically extending path 18.3 are parallel to each other and perpendicular to the horizontally extending path 18.2. Each one of the paths forms a straight conduit for the exhaust gas. The crossover duct is supported on the roof of the separator unit, which means that it does not require any additional support from the steel structure.

[0038]

[0037] As is clear from Figures 1 to 3, the exhaust gas channel 18 is configured such that the crossover duct 24, the first vertically extending path 18.1, the horizontally extending path 18.2, and the second vertically extending path 18.3 are successively arranged in the gas flow direction A, so that the crossover duct 24 connects the separator unit 14 to the first vertically extending path 18.1, and the horizontally extending path 18.2 connects the first vertically extending path 18.1 and the second vertically extending path 18.3 to each other. In other words, the gas is configured to flow from the crossover duct 24 to the first vertically extending path 18.1, where the flue gas flows substantially downward when the fluidized bed boiler is used. The flue gases further flow from the first vertically extending path 18.1 to a horizontally extending path 18.2 in which the flue gases flow substantially horizontally. The flue gases further flow from the horizontally extending path 18.2 to a second vertically extending path 18.2 in which the flue gases flow substantially upwards. The crossover duct 24 also extends horizontally, in which the flue gases flow substantially horizontally, but in a direction substantially opposite to the gas flow direction in the horizontally extending path 18.2.

[0039]

[0038] The separator unit 14 is at least partially disposed between the first vertically extending path 18.1 and the second vertically extending path 18.3 and above the horizontally extending path 18.2. This is particularly evident from FIG. 2. The interior space of the furnace 12 and the separator unit 14 are disposed adjacent to each other. There is a line L1 extending through the cross section of the furnace 12 and the separator unit 14, as well as a line L2 extending through the cross section of the first vertical path 18.1 and the second vertical path 18.2. More specifically, in FIG. 2, the line L1 extends through the center of the cross section of the furnace 12 and the separator unit 14, and the line L2 extends through the center of the cross section of the first vertical path 18.1 and the second vertical path 18.2. Moreover, as can be seen from the figure, the lines L1 and L2 are at an angle to each other. In the illustrated embodiment, the position of the separator unit 14 relative to the furnace and the vertical paths is such that the angle between the lines L1 and L2 is at right angles, but if, for example, the separator unit 14 is to be moved from its current position towards one of the vertical paths for some practical reason, the angle will still be substantially at right angles. Since the furnace 12 has a rectangular cross section, this also means that the horizontally extending path 18.2 runs parallel to both the rear wall 12.2 and the front wall 12.1 of the furnace 12. In fact, it is worth noting that the direction of the crossover duct 24 is parallel to the direction of the horizontally extending path 18.2. Moreover, as can be seen especially in Figures 2 and 3, the separator unit 14 is not only at a higher level vertically relative to the horizontally extending path 18.2, but also directly above it, i.e. it is laterally at the same position.

[0040]

[0039] The solids return system 16 includes a return channel 30 for separated solids, which is arranged between the first vertically extending path 18.1 and the second vertically extending path 18.3. In the path of the return channel for separated solids, there is a fluidized bed solids cooler 31. The fluidized bed solids cooler 31 is provided, according to the present invention, with one or more heat exchangers for superheating steam, and therefore it can also be referred to as a fluidized bed heat exchanger. The fluidized bed solids cooler 31 is also arranged, at least mainly, below the separator unit 14, between the first vertically extending path 18.1 and the second vertically extending path 18.3. Although not shown in the figure, the solids return system 16 is provided with a loop seal mechanism for preventing a backflow of gas from the furnace 12 to the separator unit 14.

[0041]

[0040] The circulating fluidized bed boiler according to the present invention is particularly advantageous for the combustion of solid waste-derived fuels, such as biomass, sludge, and refuse-derived fuels, having various compositions. The heat generated by the combustion is utilized for steam generation. The compact design provided by the present invention is particularly advantageous for a CFB boiler for waste-derived fuels. The circulating fluidized bed boiler can be part of a power plant that produces electricity. Typically, the working medium is an aqueous solution. The CFB boiler 10 includes a steam generation system, for example, connected to a steam cycle that approximately applies the Rankine cycle. The steam generation system is arranged in connection with the circulating fluidized bed boiler, such that it includes an economizer heat exchanger 32, an evaporator heat exchanger 26, and a superheater heat exchanger 28. The superheater heat exchanger 28 of the steam generating system is arranged in the fluidized bed solids cooler 31 and in the crossover duct 24, and the evaporator heat exchanger 26 is arranged in the furnace 16 (cooled furnace wall), in the separator unit 14, in the horizontally extending path 18.2 and also partially in the second vertically extending path 18.3. The economizer heat exchanger 32 is arranged in the second vertically extending path 18.3. The first vertically extending path 18.1 does not include a heat exchanger tube bundle in its interior space 17, and therefore the first vertically extending path 18.1 can be practically called an empty path. The flue gas is cooled by the cooling wall of the first vertically extending path 18.1 to avoid or at least reduce chlorine and heavy metal corrosion.

[0042]

[0041] All of the main parts of the CFB boiler 10 are substantially provided with thermal insulating covers. Thanks to the layout of the CFB boiler 10 according to the invention, the economizer heat exchanger 32, the evaporator heat exchanger 26 and the superheater heat exchanger 28 are arranged adjacent to each other, thus minimizing the length of the required piping, which also minimizes the need for piping insulation. To further facilitate the maintenance of the CFB boiler 10, the horizontally extending path 18.2 includes independently supported, assembleable and disassembleable heat exchanger modules 19, each of which is provided with an evaporator heat exchanger 26. In the embodiment shown in the figure, the horizontally extending path 18.2 consists of four heat exchanger modules 19, the number of modules being selected as required by the practical application. The modules are configured to be horizontally removable from the gas path. The second vertically extending path 18.2 is independently supported from the lower part. Both the vertically extending path and the horizontally extending path are equipped with suitable ash hoppers which can be designed as cooled or uncooled parts.

[0043]

[0042] Figure 4 shows a cross-sectional view II-II according to another embodiment of the present invention, showing some possibilities of making adaptations to the boiler system 10 according to an embodiment of the present invention. There is a line L1 extending through the cross-sections of the furnace 12 and the separator unit 14, and a line L2 extending through the cross-sections of the first vertically extending path 18.1 and the second vertically extending path 18.3. In this embodiment, the second vertically extending path 18.3 has a larger cross-sectional area compared to that shown in Figure 2, and has a channel cross-section extended from the general wall line of the horizontally extending path 18.2 towards the furnace 12. Also, the empty path 18.1 has a smaller cross-sectional area than in Figure 2. Furthermore, as can be seen, the lines L1 and L2 are again at an angle to each other. In the boiler 10 according to the present invention, the furnace and the separator unit 14 are adjacent to each other in a first direction, which is generally in the direction of the line L1. The first and second vertically extending paths and the horizontally extending path 18.2 are disposed adjacent to each other in a substantially vertical plane in a second direction generally toward the rear wall 12.2 of the furnace 12. The cross-sectional areas of the first and second vertically extending paths 18.1, 18.3 are suitably designed according to the needs of a particular practical application. In some cases, the cross-sectional area of ​​the empty path 18.1 is larger than that of the second vertically extending path 18.2, but it is conceivable that the situation can be reversed if the situation requires. The criterion can be a desired gas velocity or pressure drop.

[0044]

[0043] Figure 5 shows an embodiment of the invention in which the advantages of the invention can be obtained at least in terms of the space saving of the exhaust gas channel 18, while some more clearance is ensured between the exhaust gas channel 18 and the furnace 12. The embodiment of Figure 5 differs from the one in Figure 2 in that the crossover duct 24 is at an angle to the longitudinal direction of the horizontally extending path 18.2, i.e. is not parallel to it. In this way, the horizontal distance between the exhaust gas channel 18 and the furnace 12 is increased compared to that shown in Figure 1. It should be noted that the features shown in Figures 2, 4 and 5 are technically compatible with each other in order to freely combine them with each other. In particular, the feature shown in Figure 5, which provides more horizontal distance between the exhaust gas channel 18 and the furnace 12, makes it possible to apply the increased cross section of the exhaust gas channel shown in Figure 4. This is not shown in Figure 5, because this feature also makes it possible to utilize the space for other purposes.

[0045]

[0044] Although the present invention has been described herein by way of example in relation to what is presently considered to be the most preferred embodiment, it will be understood that the present invention is not limited to the disclosed embodiment, but is intended to encompass various combinations or modifications of its features, as well as any other applications that fall within the scope of the present invention, as defined in the appended claims. Details mentioned in relation to any of the above embodiments may be used in relation to another embodiment, when such combination is technically feasible.

Claims

1. A circulating fluidized bed boiler (10), comprising: The present invention relates to a vertically extending furnace (12), a separator unit (14) connected to the furnace (12) for separating solids from a gas stream flowing from the furnace (12), a crossover duct (14) and an exhaust gas channel (18) connected to the separator unit (14) via the crossover duct (24), the exhaust gas channel comprising:

1. A circulating fluidized bed boiler (10) comprising a first vertically extending path (18.1), a horizontally extending path (18.2), and a second vertically extending path (18.3), the first vertically extending path (18.1), the horizontally extending path (18.2), and the second vertically extending path (18.3) being arranged successively in a gas flow direction, whereby the horizontally extending path (18.2) is configured to connect the first vertically extending path (18.1) and the second vertically extending path (18.3) to each other, characterized in that the horizontally extending path (18.2) is arranged below the separator unit (14) arranged between the first vertically extending path (18.1) and the second vertically extending path (18.3).

2. 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 path (18.2) runs parallel to a rear wall (12.2) of the furnace (12) to which the separator unit (14) is connected.

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

4. The separator unit (14) further comprises a solids return system (16) for returning separated solids to the furnace (12), 4. The circulating fluidized bed boiler (10) according to claim 1 or 3, characterized in that the solids return system (16) is at least partially arranged between the first vertically extending path (18.1) and the second vertically extending path (18.3).

5. 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 solids cooler (31) in the solids return system (16), the fluidized bed solids cooler (31) being at least partially arranged between the first vertically extending path (18.1) and the second vertically extending path (18.3).

6. 6. The circulating fluidized bed boiler (10) according to claim 1, characterized in that the first vertically extending path (18.1) has a first end (18.1') connected to an outlet of a crossover duct (24) and a second end (18.1''), the second vertically extending path (18.3) has a first end (18.3') and a second end (18.3''), and the horizontally extending path (18.2) between the first vertically extending path (18.1) and the second vertically extending path (18.3) is connected to the second end (18.1'') of the first vertically extending path (18.1) and the first end (18.3') of the second vertically extending path (18.3).

7. 7. The circulating fluidized bed boiler (10) according to claim 6, characterized in that the first vertically extending path (18.1) and the second vertically extending path (18.3) are each perpendicular to the horizontally extending path (18.2).

8. 7. The circulating fluidized bed boiler (10) according to claim 1 or 6, characterized in that the first vertically extending path (18.1) does not include a heat exchanger in its internal space (17).

9. 6. The circulating fluidized bed boiler (10) according to claim 5, characterized in that a steam generating system including an economizer heat exchanger (32), an evaporator heat exchanger (26), and a superheater heat exchanger (28) is disposed in association with the circulating fluidized bed boiler (10), the superheater heat exchanger (28) is disposed in association with the fluidized bed solid material cooler (31) and the crossover duct (24), the evaporator heat exchanger (26) is disposed in association with the furnace (12), the separator unit (14), and the horizontally extending pass (18.2), the economizer heat exchanger (32) is disposed in association with the second vertically extending pass (18.3), and the first vertically extending pass (18.1) does not include a heat exchanger within its interior space.

10. 6. The circulating fluidized bed boiler (10) according to claim 5, characterized in that a steam generating system including an economizer heat exchanger (32), an evaporator heat exchanger (26), and a superheater heat exchanger (28) is disposed in association with the circulating fluidized bed boiler (10), the superheater heat exchanger (28) is disposed in association with the fluidized bed solids cooler (31) and the crossover duct (24), the evaporator heat exchanger (26) is disposed in association with the furnace (12), the separator unit (14), the horizontally extending path (18.2), and the second vertically extending path (18.3), the economizer heat exchanger (32) is disposed in association with the second vertically extending path (18.3), and the first vertically extending path (18.1) does not include a heat exchanger within its interior space.

11. 11. The circulating fluidized bed boiler (10) according to any one of claims 1 to 10, characterized in that the horizontally extending paths (18.2) comprise independently supported modules (19) each including an evaporative heat exchanger (26).

Images