Boiler comprising a support assembly

Abstract

A support assembly (40) for supporting the furnace (22) of a boiler (10) to a support frame (12) of the boiler. The support assembly comprises first and second mounting pieces (56, 8). The first mounting piece (56) connects a pipe (18), e.g., a downpipe, to a support beam (32, 88). The second mounting piece (58) connects the same pipe (18) to another support beam (30, 86). The support assembly (40) can be positioned obliquely. Alternatively, the support frame further comprises an oblique connecting support beam (84) connecting the first and second mounting pieces. In this case, the first and second mounting pieces secure the pipe to the connecting support beam (84). The first and second mounting pieces define first and second load-bearing points (52, 4). The first or second mounting piece can be a suspension bar.

Description

Boiler comprising a support assembly Technical field The solution presented relates to a boiler comprising a support assembly for attaching a boiler furnace to a boiler support frame. The solution also relates to a boiler plant comprising a boiler, the boiler comprising a support assembly and a support frame. Background Electric boilers, especially CFB (circulating fluidized bed) and BFB (bubbling fluidized bed) steam boilers, can have bottom, top, or center support. In a bottom-supported boiler, the boiler furnace is considered the load supported from below by a support frame, which is a steel structure with horizontal support beams and vertical columns. In a top-supported boiler, the furnace is considered the load supported from above and suspended from the horizontal support beams of the support frame. In a center-supported boiler, the furnace is considered the load supported from the middle of the furnace by the support frame.The middle support system is less expensive than the top support system and there is less thermal expansion in the upper sections of the boiler than in a boiler with a bottom support system, where sealing can be problematic due to thermal expansion. Fixing the kiln to the support frame of the mid-support system can cause deflection of the kiln walls due to the load on the clamps and other support assemblies connecting the walls to the support frame, such as the support beams. As a remedy, reinforcing beams are needed to support the walls and reduce wall deflection. Therefore, special attention must be paid to bending moments in the support assemblies, induced by the kiln's own weight. Document GB 1213053 A shows a support assembly for a boiler furnace. Document WO 2017 / 220846 A1 shows a lower support boiler with a furnace. Document US 3811415 A shows a boiler furnace according to the preambles of claims 1 and 2. Compendium Claim 1 and claim 2 disclose the boiler comprising a support assembly for fixing a boiler furnace to a boiler support frame according to the solution. Claim 14 discloses the boiler plant comprising a boiler, wherein the boiler comprises a support assembly and a support frame, according to the solution. In the boiler comprising a support assembly according to the present solution, the furnace comprises four vertical flat water-tube walls that are joined together and that, in a horizontal plane, define a rectangular cross-section with four corner sections, two of the water-tube walls being joined at each corner section, the four corner sections including a first corner section in which a first water-tube wall and a second water-tube wall are joined and are transverse to each other. The boiler further comprises at least one vertically extending pipe for the transport of water and / or steam, located outside the furnace and near the first corner section. The support frame further comprises at least two horizontal support beams that are separate from the water-tube walls and include a first support beam and a second support beam that are transverse to each other. In the solution, the support assembly near the first corner section comprises a first mounting piece and a second mounting piece. The first mounting piece connects the pipe to the first support beam, or to a third support beam fixed to the first or second support beam, where the first mounting piece defines, on the first or third support beam, a first support point at which the loads incurred by the weight of the pipe and the furnace attached to the pipe are transmitted to the first or third support beam. The second mounting piece connects the same pipe to the second support beam, or to a fourth support beam fixed to the second support beam, where the second mounting piece defines, on the second or fourth support beam, a second support point at which the loads resulting from the weight of the pipe and the furnace attached to the pipe are transmitted to the second or fourth support beam.The support assembly is oblique with respect to the first and second support beams. Alternatively, the support frame further comprises a connecting support beam that is separate from the walls of the water pipe and comprises a first end attached to the first support beam, or to a third support beam fixed to the first or second support beam, and a second end attached to the second support beam, or to a fourth support beam fixed to the second support beam. In the alternative solution mentioned above, the first mounting piece connects the pipe to the connecting support beam. This first mounting piece defines a first support point on the connecting support beam, where the loads incurred by the weight of the pipe and the furnace attached to the pipe are transmitted. The second mounting piece connects the same pipe to the connecting support beam, where it defines a second support point on the connecting support beam, where the loads incurred by the weight of the pipe and the furnace attached to the pipe are transmitted. The connecting support beam is angled with respect to the first and second support beams. According to one example, the first and second assembly pieces each comprise a suspension device that suspends the pipe from one of the support beams, or alternatively from the connecting support beam, and provides one of the support points. According to one example, the suspension device is an adjustable suspension bar. According to another example, the first and second assembly pieces each comprise a support leg that rests on one of the support beams and provides one of the support points. The boiler plant according to the present solution comprises the boiler as explained above. The support assembly of the presented solution provides the benefit of reducing the bending moments to which a pipe is subjected and, in addition, avoiding deflections caused by the loads incurred by the weight of the pipe and the oven attached to the pipe. The aforementioned benefits are possible by having not one but two support points that provide two support forces, or two resultant support forces, which generate bending moments that cancel each other out, partially or completely, at the location of the pipe. The solution presented will be more fully appreciated with reference to the following detailed description of the illustrative embodiments according to the solution, when taken together with the accompanying illustrative drawings. Brief description of the drawings Figure 1 schematically illustrates, in a simplified manner, a side view of a boiler plant, a boiler, and a support frame in which the present solution is applied. Figure 2 schematically illustrates, in a simplified manner, a partial top view of the boiler plant, the boiler and the support frame of Figure 1. Figure 3 schematically illustrates the partial top view of Figure 2 and, in a detail view, a corner section of the boiler furnace according to one embodiment of the present solution. Figure 4 schematically illustrates, in a detail view, the corner section of Figure 3. Figure 5 schematically illustrates, in a detail view, a corner section of the boiler furnace of Figure 3 according to another embodiment of the present solution. Figure 6 schematically illustrates, in a detailed view, a corner section of the boiler furnace of Figure 3 according to yet another embodiment of the present solution. Figure 7 schematically illustrates, in a simplified manner, a side view of an example of a support assembly, especially adjustable hanging rods, applied in a boiler plant, a boiler and a support frame according to an embodiment of the present solution, for example, in the boiler plant, boiler and support frame shown in Figures 1, 2, 3, 4 and 6. Figure 8 schematically illustrates, in a detail view, the corner section of the boiler furnace of Figure 6 according to a further embodiment of the present solution. Figure 9 schematically illustrates, in a detailed view, the corner section of the boiler furnace of Figures 2 and 3 according to a further embodiment of the present solution. Figure 10 schematically illustrates, in a detailed view, the corner section of the boiler furnace of Figure 6 according to another embodiment of the present solution. Figure 11 schematically illustrates, in a detailed view, the corner section of the boiler furnace of Figures 2 and 3 according to another embodiment of the present solution. Detailed description In the figures, the vertical direction is indicated by an arrow Z and two orthogonal horizontal directions are indicated by arrows X and Y. The horizontal directions are orthogonal with respect to the vertical direction. The boiler plant of Figures 1 and 2 according to one embodiment of the solution comprises at least a boiler 10 with a furnace 22, a support frame 12 for securing the boiler 10 to the ground, and one or more support assemblies 40 for fixing the furnace 22 to the support frame 12. The support frame 12 comprises several horizontal support beams 16, 26, 28, 30, 32, 42 to which the furnace 22 is attached and / or which support the furnace 22 so that the furnace 22 rests on the ground. Some of the support beams may support each other. The support beams are supported on the ground by vertical pillars 14 of the support frame 12. Preferably, boiler 10 is a CFB (circulating fluidized bed) or BFB (bubbling fluidized bed) design steam boiler. Boiler 10 may include other devices relevant to the design in question but not shown in the figures, for example, a boiler and steam circulation system, flue gas channels, superheaters, an economizer, a return pass, and a fly ash collection system. The boiler 10 may further comprise a cyclone separator 24 connected to the furnace 22 for separating solid particles from the combustion gases from the furnace 22. The cyclone separator 24 is fixed to the support frame 12, for example, by one or more support assemblies, for example, support legs 70. The boiler 10 may be, as shown in Figure 1, supported in the middle in such a way that in the vertical direction the furnace 22 extends both further upwards and further downwards than at least some of the support beams mentioned above, for example, the support beam 16 which is attached to the vertical pillars 14 and the support beams 30, 32. Alternatively, the furnace 22 extends for the most part above the support beams mentioned above, or is in a vertical direction located entirely above the support beams, in which case the boiler 10 may be considered to be supported at the bottom, and the furnace 22 is supported from below. The advantage of having the boiler 10 with a middle support is that the cyclone separator 24 can be attached to the support frame 12 in such a way that the cyclone separator 24 extends further upwards than at least some of the support beams mentioned above, for example, support beam 16. The cyclone separator 24 can now be supported from below, for example, by support beam 16. As shown in Figures 2 and 3, the furnace 22 comprises four vertical, flat walls of water tubes 72, 74, 76, and 78, which are joined together such that, in a horizontal plane, particularly at the height of the aforementioned support beams, they define a rectangular cross-section with four corner sections. Two transverse water tube walls are joined at each corner section. One of the corner sections is called the first corner section. By way of example only, the first water tube wall 78 and the second water tube wall 76 can be joined at the first corner section shown in the detailed view of Figure 3. Each water-tube wall is made of water-tubes joined together by welded joints, for example. The water to be evaporated into steam is transported inside the water-tubes. Water-tube walls 72, 74, 76, 78 are joined together by welded joints, for example. Boiler 10 comprises a vertically extending pipe 18 located near the first corner section, at least at the height of the aforementioned support beams. Pipe 18 is located outside furnace 22. Boiler 10 may comprise additional piping, similar to piping 18, near one or more of the corner sections, preferably near each of the four corner sections. The additional piping may apply the same principles as piping 18 with respect to supporting furnace 22. Preferably, the cross-sectional area of ​​pipe 18 is greater than that of the water pipes in the water pipe walls. Preferably, pipe 18 has a cross-section that is circular in a horizontal plane. Preferably, pipe 18 is located outside at least one of the imaginary horizontal lines defined by the vertical planes of the water pipe walls 76, 78. Pipe 18 is for the transport of water and / or steam. Preferably, pipe 18 is a downpipe for transporting water downwards. According to an example and Figure 1, the boiler 10 may comprise at least one lower manifold 20 located below the water-tube walls 76, 78. The lower manifold 20 supplies water to at least one of the water-tube walls 76, 78, which circulates within the water-tube wall. According to an example and Figure 1, there are two manifolds 20 located below opposite water-tube walls 74, 78. Pipe 18 is connected to the lower manifold 20 to supply water to it. Therefore, the furnace 22 is supported by pipe 18 and at least one lower manifold 20. Preferably, pipe 18 is connected to furnace 22. As shown in the example and Figure 1, pipe 18 can be connected to the first corner section by means of a vertically extending welded joint 80, 82. Furnace 22 is then attached to pipe 18 by means of the welded joint 80, 82, for example. In this example, furnace 22 can also be secured to pipe 18 by the lower manifolds 20 described above. As shown in the examples in Figures 1 and 2, the support frame 12 comprises at least two, but preferably four, horizontal support beams 26, 28, 30, 32 which, in a horizontal plane, can define a rectangular space within which are located the furnace 22, the four water-tube walls 72, 74, 76, 78, and at least one water pipe 18. Preferably, there are four pipes 18 within the rectangular space. The support beams 26, 28, 30, 32 are separated from the water-tube walls 72, 74, 76, 78. The adjacent support beams that can define the rectangular space are transverse to each other, for example, the first and second support beams 30, 32. Preferably, the adjacent support beams are substantially perpendicular to each other. Preferably, support beams 26, 28, 30, 32 are substantially parallel to the nearest water pipe wall 72, 74, 76, 78. For example, the first support beam 32 is parallel to the first water pipe wall 78, and the second support beam 30 is parallel to the second water pipe wall 76. Alternatively, and in the example in Figure 2, support beam 16, 42 can take the place of support beam 26, 32. Alternatively, support beam 26, 32 can be joined to support beam 16, 42 and / or support beam 28, 30 can be attached to support beam 16, 42 by support beam 26, 32. In the example in Figure 2, support beam 26, 32 is attached to support beam 16, 42 by support beam 28, 30. Two or more support beams 16, 26, 28, 30, 32, 42 can be joined together so that they are located at the same height or at different heights. The furnace 22 of boiler 10 is fixed to the support frame 12 by at least one support assembly 34, 36, 38, 40 according to the solution. The support assembly is located, for example, in the first corner section, as shown in Figures 2, 3, 4, 5, and 6. Preferably, there are at least four support assemblies according to the solution, one in each corner section of the furnace 22. The other support assemblies 34, 36, 38 can apply elements and principles in the same way as the first support assembly 40 with respect to supporting the additional pipes 18. According to an example of the solution and Figure 3, the support assembly 40 comprises a first mounting piece 56 that connects the pipe 18 to the first support beam 32. Thus, the first pipe 18 is secured to the support frame 12 by means of the first mounting piece 56. In addition, the support assembly 40 comprises a second mounting piece 58 that connects the same pipe 18 to the second support beam 30. Therefore, the first pipe 18 is secured to the support frame 12 by means of the second mounting piece 58. Thus, the support assembly 40 with two mounting pieces 56, 58 provides the benefit of reducing the bending moments to which the pipe 18 is subjected and, in addition, avoids the deflections caused by the loads incurred by the weights of the pipe 18 and the oven 22 attached to the pipe 18. In the examples in Figures 1 and 2, the pipe 18 is attached to the first corner section, in which case the reduction of the wall deviation is achieved. The aforementioned benefits are possible by having not one but two support points that provide two support forces, or two resultant support forces, which generate bending moments that cancel each other out, partially or completely, at the location of pipe 18. Each mounting piece 56, 58 defines a support point 52, 54 through which the aforementioned loads are transmitted to the first support beam 32 or to the second support beam 30. According to an example and figure 2, the two support points 52, 54 are located on different support beams 30, 32 that are adjacent and transverse to each other. According to an example and Figure 6, the support frame 12 may comprise, in one or more corner sections, a connecting support beam 84 that is attached to two adjacent support beams 16, 26, 28, 30, 32, 42. The connecting support beam 84 is preferably horizontal and connects the two adjacent support beams. Therefore, in a horizontal plane, the position of the connecting support beam 84 is oblique with respect to the two support beams and the water pipe walls of the furnace 22. For example, the connecting support beam 84 is attached to the first and second support beams 30, 32. The connecting support beam 84 may comprise a first end attached to a support beam, for example, the first support beam 32, and a second end attached to an adjacent support beam, for example, the second support beam 30. In the example above, each mounting piece 56, 58 defines the support point 52, 54 such that the aforementioned loads are transmitted first to the connecting support beam 84 and then through it to the first and second support beams 30, 32. According to the example, the two support points 52, 54 are located on the connecting support beam 84. According to an example and as shown in Figures 2, 3, 4, 5, and 6, the first support point 52 is farther from the second support beam 30 than the pipe 18, when viewed in a direction parallel to the longitudinal direction 62 of the first support beam 32. Furthermore, the second support point 54 is farther from the first support beam 32 than the same pipe 18, when viewed in a direction parallel to the longitudinal direction 64 of the second support beam 30. Therefore, in a horizontal plane, the position of the support assembly 40 is oblique with respect to the support beams 30 and 32 and the water pipe walls 76 and 78. This provides the advantage of having a compact support assembly. According to an example and as shown in Figure 6, the support points 52, 54 are in a horizontal plane preferably at a distance from the support beams 30, 32. According to a first example, and as shown in Figures 2, 3, 4, 5, and 6, the first and second support points 52, 54 and the pipe 18 are positioned such that, in a horizontal plane, an imaginary straight line 60 (see Figure 4) extends through the first and second support points 52, 54 and also passes through the pipe 18. This makes it possible for the bending moments to cancel each other out. According to a second example, pipe 18 may have a circular cross-section in a horizontal plane, defining a center. A first imaginary straight line is defined extending horizontally through the center and the first support point 52. A second imaginary straight line is defined extending horizontally through the center and the second support point 54. According to this example, the angular difference between the first and second imaginary straight lines is less than 35 degrees, or preferably less than 25 degrees, or more preferably less than 15 degrees. In the examples shown in Figures 2, 3, 4, 5, and 6, the angular difference is substantially 0 degrees to improve the cancellation of bending moments. According to a third example, and as shown in Figures 2, 3, 4, 5, and 6, pipe 18 can have a cross-section that is circular in a horizontal plane and defines a center. A first distance is defined as the horizontal distance between the center and the first support point 52, and a second distance is defined as the horizontal distance between the same center and the second support point 54. According to this example, the first distance is substantially equal to the second distance. This provides the benefit of canceling bending moments, especially when applied with the first and / or second examples mentioned above. According to a fourth example, and as shown in Figures 2, 3, 4, 5 and 6, the first and second support points 52, 54 are, in a horizontal plane, located on opposite sides of the pipe 18. This makes it possible for the bending moments to cancel each other out. One or more of the four examples presented above can be applied simultaneously. According to an example and Figure 7, and as applied in Figures 2, 3, 4, and 6, the first assembly piece 56 may comprise a first suspension device 66 (see Figure 7) suspending the pipe 18 from the first support beam 32. Furthermore, the second assembly piece 58 may comprise a second suspension device 68 (see Figure 7) suspending the same pipe 18 from the second support beam 30. In the example of Figure 6, the connecting support beam 84 takes the place of the first and second support beams 30, 32. The first and second suspension devices 66, 68 provide the first and second support points 52, 54, respectively. The first mounting piece 56 or the second mounting piece 58, or both, may comprise a bracket that attaches to the pipe 18 to connect the pipe 18 to the first or second suspension device 66, 68. According to an example of the solution and as shown in Figure 7, the first suspension device 66 or the second suspension device 68, or both, is an adjustable suspension bar. In the case of the adjustable suspension bar, the first or second support point 52, 54 can coincide with an imaginary vertical line extending through the adjustable suspension bar. Preferably, the support point 52, 54 is located on the first or second support beam 30, 32. Alternatively, and in the example in Figure 6, the support point 52, 54 is located on the connecting support beam 84. Figures 8 and 10 show examples that complement the example shown in Figure 6, and Figures 9 and 11 show examples that complement the example shown in Figures 2 and 3. In these examples, the support frame 12 may comprise, in one or more corner sections, an additional support beam 86, 88 attached to another support beam 16, 26, 28, 30, 32, 42. The support beam 86, 88 is preferably horizontal, preferably separate from the water pipe walls 72, 74, 76, 78, or it may form a cantilever beam on the support beam 16, 26, 28, 30, 32, 42. The support beam 86, 88 may be positioned above, below, or at the same level as the support beam 16, 26, 28, 30, 32, 42. Preferably there are one or two, or more, additional support beams 86, 88. In the examples in Figures 10 and 11, the third additional support beam 88 is fixed to the second support beam 30. Alternatively, the third support beam 88 is fixed to the first support beam 32, as shown by a dashed line. The additional support beam 86, 88 can, for example, be joined to the respective support beam 30, 32 to provide support. In the examples in Figures 8, 9, 10 and 11, the additional fourth support beam 86 rests on the second support beam 30. With regard to the structure of the support beams, the pipe 18, the first and second suspension devices 66, 68, the support assembly 40, the connecting support beam 84, the mounting pieces 56, 58 and the support points 52, 54, the example in Figures 8, 9, 10 and 11 can apply the principles already explained in this description and in relation to the examples in Figure 6 and Figures 2 and 3. In the examples in Figures 8 and 10, the first end of the connecting support beam 84 is attached to the third support beam 88 (see Figure 10) or to the first support beam 32 (see Figure 8), with the second end being attached to an adjacent support beam, for example, the fourth support beam 86. In Figure 10, the third support beam 88, when supported by the first support beam 32 instead of the second support beam 30, is shown as an option marked with a dashed line indicating its intended location. In Figure 8, the third support beam 88 is not in use. According to one example, both the third support beam 88 and the fourth support beam 86 are in use and each end of the connecting support beam 84 is attached to either the third or the fourth support beam 86, 88 as described above in relation to Figure 10. In the preceding examples and in Figures 8 and 10, each mounting piece 56, 58 defines the support point 52, 54 such that the aforementioned loads are transmitted first to the connecting support beam 84 and then through it, and through the fourth support beam 86, and / or the third support beam 88, to the first and second support beams 30, 32. In Figure 8, the third support beam 88 is not in use and the aforementioned loads are transmitted to the first support beam 32 directly through the connecting support beam 84. According to the examples, the two support points 52, 54 are located on the connecting support beam 84, see Figures 8 and 10. In the preceding examples and in Figures 9 and 11, each mounting piece 56, 58 defines the support point 52, 54 through which the aforementioned loads are transmitted first to the fourth support beam 86, and / or the third support beam 88, and then through the fourth support beam 86, and / or the third support beam 88, to the first and second support beams 30, 32. In Figure 9, the third support beam 88 is not in use, and the aforementioned loads are transmitted to the first support beam 32 directly through the first support point 52. According to the examples, the first support point 52 is located on the first support beam 32 (see Figure 9) or on the third support beam 88 (see Figure 11), and the second support point 54 is located on the fourth support beam 86. See Figures 9 and 11. In the examples above, the use of the third and / or fourth support beam 86, 88 provides the advantage of providing more space between the oven 22 and the first and / or second support beam 30, 32. In the examples shown in Figures 8, 9, 10, and 11, the fourth support beam 86 and the second support beam 30 can be transverse to each other when the fourth support beam 86 rests on the second support beam 30. In this case, the fourth support beam 86 can be parallel to the first support beam 32. Furthermore, in the examples in Figures 10 and 11, the third support beam 88 and the second support beam 30 can be transverse to each other when the third support beam 88 rests on the second support beam 30. In this case, the third support beam 88 can be parallel to the first support beam 32. Alternatively, as shown by a dashed line in the examples in Figures 10 and 11, the third support beam 88 and the first support beam 32 can be transverse to each other when the third support beam 88 rests on the first support beam 30. support 32.Thus, in the examples in Figures 10 and 11, the third support beam 88 and the fourth support beam 86 can be transverse or parallel to each other. In the examples in Figures 8, 9, 10, and 11, the fourth support beam 86 can be at a distance from the first support beam 32 and the third support beam 88, when viewed in a direction parallel to the longitudinal direction 64 of the second support beam 30. Preferably, in Figures 10 and 11, the third support beam 88 is at a distance from the first support beam 32, when viewed in a direction parallel to the longitudinal direction 64 of the second support beam 30. Therefore, the pipe 18 can be placed between the first support beam 32 and the fourth support beam 86, or between the third and fourth support beams 86, 88 when viewed in the aforementioned direction. In the examples in Figures 8, 9, 10, and 11, the fourth support beam 86 can extend closer to the water pipe wall 76 than the second support beam 30 when viewed in a direction parallel to the longitudinal direction 62 of the first support beam 32. Preferably, in the examples in Figures 10 and 11, the third support beam 88 extends farther from the second support beam 30 than the fourth support beam 86 when viewed in a direction parallel to the longitudinal direction 62 of the first support beam 32. In the examples shown with a dashed line, the third support beam 88 can extend closer to the water pipe wall 78 than the first support beam 32 when viewed in a direction parallel to the longitudinal direction 64 of the second support beam 30. Alternatively, according to an example and as shown in Figure 5, the first mounting piece 56 or the second mounting piece 58, or both, may comprise a support leg 70 that is supported by the first or second support beam 30, 32. In the case of the support leg 70, the first or second support point 52, 54 may be located on the first or second support beam 30, 32, below the support leg 70. The first mounting piece 56 or the second mounting piece 58, or both, may comprise a clamp that is attached to the pipe 18 to join the pipe 18 to the support leg 70. The principles of the examples presented above regarding the structure, location, and position of the third and fourth support beams 86, 88, and those of the third and fourth support beams 30, 32, also apply to the example in Figure 5. Each support leg 70 is supported by the first or second support beam 30, 32 or, alternatively, by the third or fourth support beam 86, 88 shown in Figures 8, 9, 10, or 11. Therefore, the first or second support point 52, 54 can be located on the third or fourth support beam 86, 88, below the support leg 70. Preferably, the third support beam 88 is not in use, and the fourth support beam 86 is in use. The functions and elements described in relation to a previous example can also be used in the other examples presented above where appropriate. In particular, it should be noted that the previous examples can be applied to all four corner sections of furnace 22 of boiler 10. The solution presented earlier in relation to the support assembly can be applied to all four corner sections. Although the invention has been described by means of examples, it should be understood that the solution is not limited to the examples described, but is intended to cover various combinations or modifications within the scope of the appended claims.

Claims

1. A boiler comprising a support assembly for fixing a boiler furnace (22) (10) to a boiler support frame (12), wherein the furnace (22) comprises four vertical walls of flat water tubes (72, 74, 76, 78) joined together and, in a horizontal plane, defining a rectangular cross-section with four corner sections, two of the water tube walls being joined at each corner section, wherein the four corner sections include a first corner section at which a first water tube wall (78) and a second water tube wall (76) are joined, which are transverse to each other, and wherein the boiler (10) further comprises at least one vertically extending pipe (18) for conveying water and / or steam and located outside the furnace (22), the pipe being close to the first corner section.characterized in that: - the support frame (12) further comprises at least two horizontal support beams (26, 28, 30, 32) that are separate from the water pipe walls and include a first support beam (32) and a second support beam (30) that are transverse to each other, - wherein the support assembly (40) near the first corner section comprises - a first mounting piece (56) that connects the pipe (18) to the first support beam (32) or to a third support beam (88) connected to the first or second support beam (30, 32), wherein the first mounting piece defines, on the first or third support beam (32, 88), a first support point (52) at which the loads, incurred by the weight of the pipe and the furnace attached to the pipe, are transmitted to the first or third support beam (32, 88),and - a second mounting piece (58) joining the same pipe (18) to the second support beam (30) or to a fourth support beam (86) attached to the second support beam, wherein the second mounting piece defines, on the second or on the fourth support beam (30, 86), a second support point (54) where the loads, incurred by the weight of the pipe and the furnace attached to the pipe, are transmitted to the second or to the fourth support beam (30, 86).

2. A boiler comprising a support assembly for fixing a boiler furnace (22) to a boiler support frame (12), wherein the furnace (22) comprises four vertical walls of flat water tubes (72, 74, 76, 78) joined together and which, in a horizontal plane, define a rectangular cross-section with four corner sections, two of the water tube walls being joined at each corner section,the four corner sections include a first corner section in which a first water-tube wall (78) and a second water-tube wall (76) that are transverse to each other are joined, and - where the boiler (10) further comprises at least one vertically extending pipe (18) for the transport of water and / or steam and located outside the furnace (22), the pipe being close to the first corner section, characterized in that: - the support frame (12) further comprises - at least two horizontal support beams (26, 28, 30, 32) that are separate from the water-tube walls and include a first support beam (32) and a second support beam (30) that are transverse to each other, and - a connecting support beam (84) that is separate from the water-tube walls and comprises a first end attached to the first support beam (32) or to a third support beam (88) fixed to the first or second support beam (30, 32) ,and a second end attached to the second support beam (30) or to a fourth support beam (86) fixed to the second support beam, wherein the connecting support beam (84) is oblique with respect to the first and second support beams (30, 32), and wherein the support assembly (40) near the first corner section comprises a first mounting piece (56) connecting the pipe (18) to the connecting support beam (84), wherein the first mounting piece defines, on the connecting support beam, a first support point (52) at which the loads, incurred by the weight of the pipe and the furnace attached to the pipe, are transmitted to the connecting support beam (84), and a second mounting piece (58) connecting the same pipe (18) to the connecting support beam (84), wherein the second mounting piece defines, on the connecting support beam, a second support point (54) where the loads are transmitted,incurred by the weight of the pipe and the furnace attached to the pipe, to the connecting support beam (84).

3. The boiler comprising a support assembly of claim 1 or 2, wherein the first support point (52) is farther from the second support beam (30) than the pipe (18), when viewed in a direction parallel to the longitudinal direction of the first support beam (32), and wherein the second support point (54) is farther from the first support beam (32) than the pipe (18) itself, when viewed in a direction parallel to the longitudinal direction of the second support beam (30).

4. The boiler comprising a support assembly of claim 1, 2, or 3, wherein the first corner section is attached to the pipe (18) by means of a vertically extending welded joint (80, 82),or the pipe is separated from the water pipe walls.

5. The boiler comprising a support assembly of any of claims 1 to 4, wherein the pipe (18) is a downpipe for conveying water downwards.

6. The boiler comprising a support assembly of claim 1, wherein the first assembly (56) comprises a first suspension device (66) suspending the pipe (18) from the first or third support beam (32, 88) and providing the first support point (52), and wherein the second assembly (58) comprises a second suspension device (68) suspending the same pipe (18) from the second or fourth support beam (30, 86) and providing the second support point (54).

7. The boiler comprising a support assembly of claim 2,wherein the first mounting piece (56) comprises a first suspension device (66) that suspends the pipe (18) from the connecting support beam (84) and provides the first support point (52), and wherein the second mounting piece (58) comprises a second suspension device (68) that suspends the same pipe (18) from the connecting support beam (84) and provides the second support point (54).

8. The boiler comprising a support assembly of claim 6 or 7, wherein the first suspension device (66) or the second suspension device (68), or both, is an adjustable suspension bar.

9. The boiler comprising a support assembly of claim 1, wherein the first mounting piece (52) or the second mounting piece (54), or both, comprises a support leg (70) that is supported by the first, second, third, or fourth support beam (30, 32, 86,88) and provides the first or second support point (52, 54).

10. A boiler comprising a support assembly of any one of claims 1 to 9, wherein the first and second support points (52, 54) and the pipe (18) are positioned such that, in a horizontal plane, an imaginary straight line (60), extending through the first and second support points, also passes through the pipe.

11. The boiler comprising a support assembly of any one of claims 1 to 10, wherein the pipe (18) comprises a cross-section that is circular in a horizontal plane and defines a center for the pipe, and wherein a first distance is defined as the horizontal distance between the center and the first support point (52) and a second distance is defined as the horizontal distance between the center and the second support point (54).where the first distance is substantially equal to the second distance.

12. The boiler comprising a support assembly of any one of claims 1 to 10, wherein the pipe (18) comprises a cross-section that is circular in a horizontal plane and defines a center for the pipe, wherein a first imaginary straight line extending horizontally through the center and the first support point (52) is defined, and a second imaginary straight line extending horizontally through the center and the second support point (54) is defined, wherein the angular difference between the first and second imaginary straight lines is less than 35 degrees or preferably less than 25 degrees and most preferably less than 15 degrees.

13. The boiler comprising a support assembly of claim 1, wherein the support assembly (40) is oblique with respect to the first and second support beams (30,32) .

14. Boiler plant comprising a boiler (10) according to any one of claims 1 to 13.

15. The boiler plant of claim 14, - wherein the support frame (12) comprises support beams (16, 26, 28, 30, 32, 42, 86, 88) that are horizontal and supported on the ground by vertical pillars (14), and - wherein, in the vertical direction, the furnace (22) supported by the support beams (16, 26, 28, 30, 32, 42, 86, 88) extends both above and below the support beams.

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