Boiler construction having a boiler pressure body support system

Abstract

A boiler construction includes a boiler pressure body having a bottom and a roof at a height H from the bottom and at least four planar watertube walls forming a polygonal horizontal cross section with at least four corner sections, and a rigid support steel structure, the boiler pressure body being supported to the rigid support steel structure at a height between the bottom and roof. A vertical corner column is attached exteriorly to at least four of the at least four corner sections at a height region between the bottom and roof, and the supporting of the boiler pressure body is provided by supporting each of the vertical corner columns to the rigid support steel structure at a height from 0.1 H to 0.9 H from the bottom so as to balance vertical loads of the boiler pressure body.

Claims

1. A boiler construction comprising: a boiler pressure body having a bottom and a roof at a height H from the bottom; at least four planar watertube walls forming a polygonal horizontal cross section having at least four corner sections; a rigid support steel structure, the boiler pressure body being supported to the rigid support steel structure at a height between the bottom and the roof of the boiler pressure body; and a corresponding vertical corner column attached exteriorly to at least four of the at least four corner sections at a height region between the bottom and roof of the boiler pressure body, wherein vertical loads of the boiler pressure body are balanced solely by the corresponding vertical corner columns by supporting each of the vertical corner columns to the rigid support steel structure at a height from 0.1 H to 0.9 H from the bottom of the boiler pressure body.

2. The boiler construction according to claim 1, wherein each of the vertical corner columns is supported to the rigid support steel structure at a height from 0.4 H to 0.6 H from the bottom of the boiler pressure body.

3. The boiler construction according to claim 1, wherein at least one of the vertical corner columns is a downcomer pipe of the boiler.

4. The boiler construction according to claim 1, wherein the vertical corner columns are arranged inside a common thermal insulation with the boiler pressure body.

5. The boiler construction according to claim 1, wherein the boiler pressure body is a furnace of a fluidized bed boiler.

6. The boiler construction according to claim 1, wherein the rigid support steel structure comprises multiple vertical main support columns supported to the ground and multiple horizontal main support beams attached to the vertical main support columns at a height from 0.1 H to 0.9 H from the bottom of the boiler pressure body.

7. The boiler construction according to claim 6, wherein each of the vertical corner columns is supported to at least one of the horizontal main support beams.

8. The boiler construction according to claim 6, wherein each of the vertical corner columns is supported to at least one of the horizontal main support beams by at least one hanger rod attached to the vertical corner column by a support lug.

9. The boiler construction according to claim 6, wherein each of the vertical corner columns is supported to at least one of the horizontal main support beams by a sliding connection.

10. The boiler construction according to claim 9, wherein the sliding connection comprises a base plate attached to the vertical corner column by vertically extending ribs and a sliding bearing.

11. The boiler construction according to claim 10, wherein each of the vertical corner columns is supported by a sliding connection to two adjacent horizontal main support beams.

12. The boiler construction according to claim 1, wherein each of the vertical corner columns is attached to the respective corner section in a height region having a height of at least 5% of the height H of the boiler pressure body.

13. The boiler construction according to claim 12, wherein each of the vertical corner columns is attached to the respective corner section in a height region having a height of at least 15% of the height H of the boiler pressure body.

14. The boiler construction according to claim 1, wherein each of the vertical corner columns is attached to the respective corner section by at least one continuous metal strip so as to provide a rigid joint in a vertical direction.

15. The boiler construction according to claim 14, wherein each of the vertical corner columns is attached to the respective corner section by continuous welding of each of the at least one continuous metal strip to an outermost water tube or to a corner fin between outermost water tubes of the water tube walls forming the corner section.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 schematically illustrates a side view of a boiler according to a first preferred embodiment of the present invention.

(2) FIGS. 2a and 2b schematically illustrate two embodiments of a detail of a boiler according to the present invention.

(3) FIGS. 3a and 3b schematically illustrate other details of a boiler according to an embodiment of the present invention.

(4) FIG. 4 schematically illustrates a detail of a boiler according to a further embodiment of the present invention.

(5) FIG. 5 schematically illustrates a side view of a boiler according to a preferred embodiment of the present invention.

(6) FIG. 6 schematically illustrates a detail of a boiler according to another preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(7) FIG. 1 schematically illustrates a side view of a fluidized bed boiler construction 10, representing an embodiment of the present invention. The fluidized bed boiler construction 10 comprises a furnace 12 having a bottom 14 and a roof 16 at a height H from the bottom 14, and four planar watertube walls 18, only one of which is seen in FIG. 1. The watertube walls 18 are of a conventional type, consisting of vertical water tubes connected together by fins. The watertube walls 18 form a rectangular cross section with four corner sections 20, two of which are seen in FIG. 1. The furnace 12 comprises conventional equipment, such as inlet and outlet headers 22, 24, a flue gas duct 26, and a feed for feeding fuel 28 and primary air 30 to the furnace 12. Because such equipment is not relevant for understanding the present invention, they are not described here in detail.

(8) The furnace 12 is supported to the ground 32 via a rigid support steel structure 34 arranged around the boiler construction 10. The support steel structure 34 comprises multiple vertical main support columns 36, in practice, at least four vertical main support columns 36, and multiple horizontal main support beams 38 attached between the vertical main support columns 36. As seen in FIG. 1, the horizontal main support beams 38 are at a level L that is clearly below the roof 16 of the furnace, for example, from 0.3 H to 0.7 H from the bottom 14.

(9) According to the present invention, a vertical corner column 40 is attached, advantageously, by a continuous metal strip 42, to a vertical middle portion of each of the corner sections 20. The attachment of the vertical corner columns 40 to the respective corner sections 20 has to be strong enough to enable carrying the weight of the furnace 12. The vertical corner columns 40 are thus preferably attached to the respective corners section 20 in a height region of at least 5%, even more preferably, at least 15%, of the height H of the boiler pressure body. The vertical corner columns 40 may be portions of downcomers 44, circulating boiler water from a steam drum 46 to an inlet header 22, or other columns suitable for supporting the furnace 12.

(10) According to the embodiment shown in FIG. 1, the furnace 12 is supported to the support steel structure 34 by hanger rods 48. The upper edges of the hanger rods 48 are attached to the horizontal main support beams 38, and the lower edges of the hanger rods 48 are attached to the vertical corner columns 40 by lugs 50 attached to two sides of the vertical corner columns 40. Thus, the vertical corner columns 40 are supported to the hanger rods 48, and by them to the support steel structure 34 at the level C of the lugs 50, which level C is lower than the level L of the horizontal main support beams 38.

(11) When the furnace 12 heats up from ambient temperature to the operating temperature, thermal expansion lengthens the height and width of the furnace 12. Assuming that the hanger rods 48 stay at the ambient temperature, but the vertical corner columns 40 follow the temperature of the furnace 12, the middle portion of the furnace 12, at the level C of the lugs 50, remains at its original level. The upper portion of the furnace 12, upwards from the level C, expands upwards, and the lower portion of the furnace 12, downwards from the level C, expands downwards. The hanger rods 48 may, in practice, also be partially hot, which has to be taken into account when considering exact vertical movements of the furnace 12. In addition to the vertical expansion, the furnace 12 also experiences expansion in the horizontal direction. Horizontal movement due to horizontal expansion is made possible by tilting of the lower ends of the hanger rods 48 outwards. In order to avoid too large tilting angles, the hanger rods 48 have to have a sufficient length, such as at least about three meters. Longer hanger rods 48 absorb thermal expansion by less tilting, but they have the disadvantage of possibly increasing the height of the rigid steel construction needed for supporting the boiler pressure body at a certain height.

(12) FIGS. 1-6 show views and details of different embodiments of the present invention. The same reference numbers are generally used for the same or similar elements in the different embodiments in each of FIGS. 1-6. It is also to be understood that FIGS. 1-6 show only exemplary embodiments of the present invention, and features shown in the different embodiments can be changed to corresponding features shown in other embodiments, or to those based on the general teachings of the present description, whenever it is technically possible.

(13) FIGS. 2a and 2b schematically show in more detail a horizontal cross section of two examples of attaching a vertical corner column 40, 40′ to the corner section 20 of two water tube walls 18 by a strong vertically extending metal strip 42. In FIG. 2a, the vertical corner column 40 is a thick walled boiler pipe, preferably, a downcomer pipe of the boiler, whereas, in FIG. 2b the vertical corner column 40′ is a hollow vertical beam with a square cross sectional shape. In practice, the vertical corner column 40, 40′ may also have any other suitable cross-sectional shape. The metal strip 42 is preferably attached by continuous welding 52 to the vertical corner column 40, 40′ and to a corner fin 54, 54′ between the outermost water tubes 56 of the watertube walls 18 forming the corner section 20. FIG. 2a shows, as an example, a corner-like corner fin 54, whereas, FIG. 2b shows, as another example, a beveled corner fin 54′.

(14) The temperature difference between the corner section 20 and the vertical corner column 40 has to be relatively small in any operating condition in order to avoid unnecessary thermal fatigue. Therefore, the metal strip 42 is advantageously dimensioned so as to provide, in addition to the required strength, also sufficient thermal conductivity between the corner section 20 and the respective vertical corner column 40, 40′. The vertical corner column 40, 40′ and the watertube walls 18 of the furnace are advantageously also covered by a common insulator layer 58, as schematically shown in FIG. 2b.

(15) FIGS. 3a and 3b schematically show in horizontal cross section and in a side view, respectively, an exemplary way of hanging a vertical corner column 40 from horizontal main support beams 38 of a support steel structure 34. In this embodiment, a pair of support lugs 50 is attached to each of two opposite sides of the vertical corner column 40, and a hanger rod 48 is attached by a nut 52 at the outer end of each of the pairs of support lugs 50. Upper ends of the hanger rods 48 are locked by a suitable means to the horizontal main support beams 38, as is seen in FIG. 1.

(16) In the example shown in FIG. 3a, the support lugs 50 extend horizontally far enough to enable connecting the hanger rods 48 directly to horizontal main support beams 38 above the end portions of the support lugs 50. In practice, it may be useful to fix the upper ends of the hanger rods 48 to suitable auxiliary horizontal beams, not shown in FIG. 3a, arranged, for example, above two opposite sides of the corner column 40 and supported to the horizontal main support beams 38. FIG. 3a also shows an alternative way of attaching the corner column 40 to the corner section 20. Here, the corner column 40 is attached to the corner section 20 by two metal strips 42 connected to the two outermost water tubes 56. Using two metal strips, or even more than two metal strips, naturally further strengthens the attachment, and also improves the thermal connection of the corner column 40 to the furnace 12.

(17) FIG. 4 schematically shows a detail of another exemplary embodiment of the present invention in which a vertical corner column 40 is attached to the corner section 20 of two watertube walls 18 of the furnace 12 by a vertically extending metal strip 42 that is parallel to the extension of a water tube wall 18, instead of being at a forty-five degree angle, as shown in FIGS. 2a, 2b, and 3a. The orientation of the metal strip 42, which may, as is clear to a person skilled in the art, have still other possibilities than those described above, affects the most suitable orientation of the lugs 50, and is also a most suitable way to attach the hanger rods 48 to the horizontal main support beams 38. Especially when the vertical corner column 40 is a portion of a downcomer pipe of the boiler construction 10, there may be a need to arrange the hanging of the vertical corner column 40 from the horizontal main support beams 38, for example, by using auxiliary support beams, to avoid making extra bends to the downcomer pipe in order to go round the horizontal support beams 38.

(18) FIG. 4 also shows that the vertical corner column 40 may advantageously be connected by suitable linking pieces 58 to the buckstays 60 of the furnace 12. As has been explained above, the main function of the vertical corner columns 40 is to enable simple and efficient supporting of the furnace 12 at its middle section by the corners. The additional strength provided by the vertical corner columns 40 to the furnace 12 enclosure also provides the additional advantage of reducing the number of buckstays needed to avoid the risk of bulging of the furnace enclosure.

(19) FIG. 5 schematically shows a side view of a fluidized bed boiler construction 10′, representing another embodiment of the present invention. The construction of FIG. 5 differs from that of FIG. 1 mainly in that the vertical corner columns 40 are not hanging from the horizontal main support beams 38, but the vertical corner columns 40 are supported from below by vertically extending support lugs 50′ arranged on the main support beams 38. Therefore, the vertical corner columns 40 are supported to the support steel structure 34 at the level C of the support lugs 50′, which level C is higher than the level L of the horizontal main support beams 38. In order to enable movements relating to horizontal thermal expansion of the furnace 12, each of the support lugs 50′ is attached to a base plate 62 that is able to slide on the respective horizontal main support beam 38, or on a sliding bearing 64 attached to the main support beam 38.

(20) The support lug 50′ may, in a horizontal direction, be directed to a corner of two perpendicular to each other arranged horizontal main support beams 38, whereby, the base plate 62 is advantageously supported by a sliding bearing 64 attached to the two horizontal main support beams 38. Supporting the vertical corner columns 40 from below, as shown in FIG. 5, provides the effect that there are no horizontal main support beams 38 above the vertical corner columns. In case the vertical corner column 40 is a portion of a downcomer pipe 44, the solution of FIG. 5 thus provides the advantage that the downcomer pipe 44 can be more freely extended upwards, without a need to make extra bendings around horizontal main support beams 38.

(21) According to an advantageous embodiment, schematically shown in FIG. 6, each of the support lugs 50′ comprises multiple parallel ribs 66, such as three ribs, attached side by side to the vertical corner column 40 and on the base plate 62. FIG. 6 also shows another feature according to which two lugs 50′, 50″, or two series of ribs 66, 66′, are attached at a ninety degree angle to the vertical corner column 40. The two lugs 50′, 50″ and their base plates 62, 62′ are thereby arranged on separate sliding bearings 64, 64′ arranged on two horizontal main support beams 38, 38′, parallel to the tubewalls 18, 18′ forming the respective corner section 20. The solution of FIG. 6 is especially advantageous when there is a need to extend a vertical main support column 36 in the crossing of the horizontal main support beams 38, 38′ to a higher level than that of the horizontal support beams 38, 38′.

(22) As becomes clear from the discussion above, different embodiments of a furnace of a fluidized bed boiler with a simple and reliable supporting construction are provided. It should be understood that the elements described in connection with an embodiment can also be used in other embodiments, when possible. Corresponding supporting constructions are also applicable in a number of other applications, such as a furnace of other type of a power boiler, a convection cage, an empty pass, a solids separator, or a horizontal pass in connection with a power boiler.

(23) While the invention has been described herein by way of examples in connection with what are at present considered to be the most preferred embodiments, 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 and several other applications included within the scope of the invention as defined in the appended claims.