Grate Assembly

Abstract

A grate assembly for use in a bottom section (28) of a combustion chamber (12) of a fluidized bed boiler (10) includes a grate bottom wall (32); a protective refractory material layer (36); a plurality of nozzle arrangements (38) for supplying fluidizing primary air; and at least one grate module (40) formed in the grate bottom wall (32). Each grate module (40) includes a solids removal opening (42); and a plurality of concentric lands (46) formed in the refractory material layer (36) and separated by front faces (48) between the lands. Each front face (48) surrounds one of the lands and follows the perimeter shape of a rectangle or a rectangle with at least one shaped corner. The lands (46) define a stepped structure. Each land includes a group of nozzle devices embedded in the layer of fire-resistant material (36) and adapted to inject air through one of the front faces (48) along one of the lands (46) adjacent the front face.

Description

[Technical field]

[0001] The presented solution relates to a grate assembly for use in the bottom section of a combustion chamber of a fluidized bed boiler. The grate assembly comprises one grate module or at least two adjacent grate modules constituting the bottom section. The presented solution relates to a fluidized bed boiler used for steam generation and having a combustion chamber. [Background technology]

[0002] The bottom section of the combustion chamber of the fluidized bed boiler may include a sloped bed or sloped bed section to facilitate removal of solids as air jets and gravity transport the solids to a solids removal opening, the sloped bed being formed by a protective refractory layer. The air jets are provided by a nozzle arrangement that provides air for combustion and fluidization. The nozzle arrangement extends to various heights from the protective refractory layer.

[0003] The nozzle arrangement may impede the removal of solids or the air jets may not be optimally oriented. The nozzle arrangement may be worn down by the air jets carrying the solids or fluidized bed material. The height difference of the inclined bed containing the nozzle arrangement may vary significantly depending on the dimensions of the combustion chamber. Thus, the operation of the fluidized bed in the combustion chamber may be affected. The shape and structure of the protective refractory material layer may vary from boiler to boiler. Summary of the Invention

[0004] A grate assembly according to this solution is presented in claim 1.

[0005] A fluidized bed boiler including the above-mentioned grate assembly is presented in claim 15.

[0006] In the other claims example solutions are presented in more detail.

[0007] The grate assembly according to this solution is intended for use in the bottom section of the combustion chamber of a fluidized bed boiler.

[0008] The grate assembly includes a grate bottom wall having a plurality of cooling tubes attached to the grate bottom wall; a protective refractory material layer on the grate bottom wall and covering the plurality of cooling tubes; and a plurality of nozzle devices for supplying fluidizing primary air over the grate bottom wall and the protective refractory material layer to the combustion chamber to maintain combustion of the fuel and fluidization of the fluidized bed material.

[0009] The grate assembly further includes at least one grate module formed in the grate bottom wall, each grate module including a solids removal opening in the refractory material layer through which solids on the refractory material layer are guided downwardly toward a solids removal conduit, the solids removal conduit adapted to guide the solids through the refractory material layer and the grate bottom wall.

[0010] Each grate module further includes a plurality of concentric landings, each formed in the layer of refractory material, the lands being vertically spaced apart and separated by frontal surfaces between the lands. Each frontal surface surrounds one of the lands and follows the shape of a rectangle or a rectangular perimeter having at least one shaped corner. The lands define a stepped structure that descends toward a solids removal opening located at the center of the land. Each land includes a group of nozzle devices belonging to the plurality of nozzle devices and embedded in the layer of refractory material. The group of nozzle devices is directed to inject air through one of the frontal surfaces and along one of the lands adjacent the frontal surfaces.

[0011] According to one example, the at least one shaped corner includes a chamfer, multiple chamfers, a step, multiple steps, an inwardly extending rectangular shape, and / or an outwardly extending rectangular shape.

[0012] According to one example, each land portion includes four rows of nozzle devices, each nozzle device being aligned in a row and belonging to a group of nozzle devices. According to one example, the front surface includes four corner portions, each corner portion having at least one nozzle device belonging to a group of nozzle devices and located between two rows of nozzle devices.

[0013] A fluidized bed boiler used to generate steam includes a combustion chamber with a bottom section that includes the grate assembly described above.

[0014] The presented solution is particularly advantageous and solves the problems mentioned above.

[0015] In one example, the grate module of the presented solution provides a modular and expandable system for configuring the bottom section of the combustion chamber of a fluidized bed boiler.

[0016] In one example, the use of the grate module of the presented solution provides a way to limit the height difference between the nozzle devices. The height difference and stepped structure height of the grate assembly and grate module can be selected so that the movement of the fluidized primary air above the grate assembly occurs in a desired or controlled manner.

[0017] In one example, rows of additional nozzle devices are easily integrated within or between grate modules to ease the design of the grate assembly and layout of the bottom section of the combustion chamber.

[0018] In one example, the central location of the solids removal opening in the grate module provides an efficient method of removing solids. The size and dimensions of the grate module can be selected to efficiently transport the solids to the solids removal opening.

[0019] In one example, the presented solution provides a simple structure with a grate bottom wall and multiple parallel cooling tubes running horizontally.

[0020] In one example, the presented solution provides multiple nozzle devices embedded in a layer of refractory material constituting a stepped structure, thereby facilitating unobstructed removal of solids by the surface of the stepped structure of the grate module.

[0021] In one example, nozzle devices at the corners of the grate module are oriented to efficiently remove solids from the surface of the stepped structure.

[0022] These and other non-limiting features, characteristics, and advantages of the presented solutions are more particularly disclosed below. [Brief description of the drawings]

[0023] Below is a brief description of the drawings, which are presented for the purpose of illustrating the exemplary embodiments disclosed herein and are not intended to limit the exemplary embodiments disclosed herein. [Figure 1] 1 is a side view of an example of a steam generator or fluidized bed boiler to which the solution of the present invention can be applied; [Diagram 2] FIG. 2 is a side cross-sectional view of an example of a grate assembly applied to the solution of the present invention and constituting one grate module. [Diagram 3] FIG. 3 is a top view of an example of the grate assembly of FIG. 2 applied to the solution of the present invention; [Figure 4] FIG. 2 is a top view of an example of a grate assembly applied in the solution of the present invention and including two adjacent grate modules with an additional nozzle device. [Diagram 5] FIG. 4 is a top view of an example of a shaped corner of the grate assembly of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] In the description, the following reference numbers and designations are used to refer to the drawings: 10 Fluidized bed boiler 12 Combustion chamber 14. Cyclone 16 Combustion exhaust gas channel 18 Support frame 20 Combustion exhaust gas passage 22 Posts 24 Support beam 26 Hanger 28 Bottom Section 30 Grate Assembly 32 Grate bottom wall 34 Cooling pipe 36 Refractory material layer 38 Nozzle device 381 First row of nozzle device 382 Second row of nozzle device 383 Third row of nozzle device 384 Nozzle Unit 4th Row 40 Grate Module 42 Solids removal opening 44 Solids Removal Conduit 46 Land Department 48 Front 50 Air Plenum Chamber 52 Additional Land Section 54 Additional Front 56 Additional nozzle equipment 561 Additional row of nozzle devices 58 Corner

[0025] A more complete understanding of the features disclosed herein can be obtained by reference to the accompanying drawings. These figures are merely schematic and are not intended to illustrate the relative sizes and dimensions of the devices or their components, or to define or limit the scope of the embodiments. Certain terms used in the following description are intended to refer only to selected embodiments with respect to the drawings, and are not intended to define or limit the scope of the present disclosure. In the drawings and the following description, like number designations refer to devices or components of similar functionality.

[0026] In the following, the terms "horizontal" and "vertical" refer to the intended operating positions of the device or component under discussion when installed in a given position to achieve the functionality of the solution described. The terms "horizontal" and "vertical" are used to indicate orientation relative to an absolute reference, i.e. ground level. In the figures, the vertical direction is indicated by arrow Z and two orthogonal horizontal directions are indicated by arrows X and Y. The horizontal direction is orthogonal to the vertical direction.

[0027] Additionally, the terms "upper," "lower," "on top," "lower," "upward," and "downward" refer to the intended operating positions described above. The terms "parallel" and "orthogonal" should not be construed as requiring that structures be perfectly parallel or perfectly orthogonal to one another. The term "opposite" should not be construed as requiring that opposing directions be perfectly parallel to one another.

[0028] With reference to figure 1, an embodiment of a steam generator or fluidized bed boiler 10 to which the solution of the present invention is applied is shown. The fluidized bed boiler 10 may be part of a power plant, a steam boiler plant or a hot water boiler plant adapted for the production of electrical energy, steam and / or heating energy.

[0029] The boiler 10 includes a combustion chamber 12, or furnace, for burning a fuel, and an exhaust gas channel 16 for conveying flue gases, or combustion product gases, coming from the combustion chamber 12.

[0030] The boiler 10 may include additional devices related to the design under discussion, but are not necessarily shown. The boiler 10 may further include a cyclone separator 14 connected to the combustion chamber 12 for separating solid particles from the flue gas coming from the combustion chamber 12 and directing the flue gas to the flue gas channel 16. The boiler 10 may further include a support frame 18 for supporting the combustion chamber 12 and the flue gas channel 16 relative to the ground. The support frame 18 may include, for example, columns 22, support beams 24, and / or hangers 26 for supporting the combustion chamber 12 and / or the flue gas channel 16 relative to the support frame 18.

[0031] The boiler 10 may be a fluidized bed boiler of CFB design (circulating fluidized bed) or BFB design (bubbling fluidized bed). The fuel may be gas, solid fuel or solid waste from various sources, for example municipal waste. The fluidizing air that forms the fluidized bed and is used as primary air for combustion is fed into the combustion chamber 12 through a bottom section 28 that constitutes the lower part of the combustion chamber 12.

[0032] As shown in FIGS. 2 and 3, a grate assembly for use in the bottom section 28 of the combustion chamber of the fluidized bed boiler 10 includes a grate bottom wall 32, a protective refractory material layer 36, a plurality of nozzle assemblies 38, and at least one grate module 40.

[0033] The grate bottom wall 32 includes a plurality of cooling tubes 34 attached to the grate bottom wall 32 .

[0034] According to the example of FIG. 2, the grate bottom wall 32 extends horizontally and a plurality of cooling tubes 34 are parallel, horizontally extending and attached to the grate bottom wall 32 at spaced intervals along the grate bottom wall 32 .

[0035] According to the example of FIG. 2, the grate bottom wall 32 is constituted by a number of cooling tubes 34 separated by fins attached between the cooling tubes 34 .

[0036] A protective refractory layer 36 is positioned on the grate bottom wall 32 and covers a plurality of cooling tubes 34 .

[0037] A plurality of nozzle devices 38 are for supplying fluidizing primary air into the combustion chamber 12 for maintaining fluidization of the bed material and combustion of the fuel on the grate bottom wall 32 and the protective refractory layer 36. Each nozzle device 38 is adapted to guide the primary air arriving through the grate bottom wall 32 and the refractory layer 36 and to inject the air to be used as the fluidizing primary air.

[0038] According to the example of FIG. 2, the nozzle device 38 includes a conduit section attached to and passing through the grate bottom wall 32, and a mouth section for ejecting air guided through the conduit section.

[0039] The grate assembly 30 may, for example, include one grate module 40, or between 2 and 36 adjacent grate modules 40. According to one example, the grate modules 40 are arranged in an N×M grid, where N is equal to 1, 2, or 3, and M is equal to 2, 12, or an integer between 2 and 12.

[0040] 4, all of the grate modules 40 of the grate assembly 30 are similar. Alternatively, the grate assembly 30 may include similar and / or different grate modules 40.

[0041] Each grate module 40 includes a solids removal opening 42 , a solids removal conduit 44 , and a plurality of concentric lands 46 .

[0042] Solids removal openings 42 are formed in the refractory layer 36, through which solids on the refractory layer 36 are guided downward through the refractory layer 36 and the grate bottom wall 32 by the moving air and gravity.

[0043] According to the example of FIG. 2, the solids are directed downwardly towards a solids removal conduit 44 of the fluidized bed boiler 10 or grate assembly.

[0044] Each land 46 is formed in the layer of fire-resistant material 36. The lands 46 are vertically spaced apart and separated from one another by front faces 48 located between the lands 46.

[0045] The land 46 may, for example, define a stepped structure, such as a funnel, that descends toward a solids removal opening 42 located centrally in the land 46 .

[0046] According to the example of FIG. 2, the front surface 48 extends vertically.

[0047] Each front surface 48 surrounds one of the lands 46 and follows the shape of a rectangular perimeter or a rectangular perimeter with at least one shaped corner. Alternatively, each front surface 48 surrounds one of the lands 46 and follows the shape of a square perimeter or a square perimeter with at least one shaped corner. A square representing a rectangle is a special case of a rectangle with four sides of equal length.

[0048] According to the example of FIG. 5, the at least one shaped corner includes a chamfer (FIG. 5(b)), multiple chamfers (FIG. 5(c)), a step (FIG. 5(d)(g)), multiple steps (FIG. 5(e)(f)), a feature extending inwardly of the rectangle (FIG. 5(b)(c)(d)(e)), and / or a feature extending outwardly of the rectangle (FIG. 5(f)(g)). According to one example, all four corners of the rectangle are similar. According to one example, the corners are formed from two perpendicular edges (FIG. 5(a)).

[0049] Each land 46 includes a group of nozzle devices 38 from the plurality of nozzle devices 38. The group of nozzle devices 38 is embedded in the refractory material layer 36 and configured to inject, direct, or orient air through one of the front faces 48 and along one of the lands 46 adjacent to the one of the front faces 48. In one example, a land 46 is between one of the front faces 48 and another front face 48 that is vertically downward. In one example, a land 46 is between one of the front faces 48 and the central solids removal opening 42 of the grate module 40.

[0050] According to the example of Figure 3, the solids removal opening 42 is circular. Alternatively, the solids removal opening 42 may be, for example, rectangular, for example square or polygonal in shape.

[0051] According to the example of Figure 2, the nozzle devices 38 are adapted to eject air horizontally. According to the example of Figure 3, each nozzle device 38 is adapted to eject air in a predetermined horizontal direction specific to that nozzle device 38.

[0052] 2 and 3, each front surface 48 is formed by surfaces of a group of nozzle devices 38, or by the layer of refractory material 36, or by surfaces of both the nozzle devices 38 and the layer of refractory material 38. According to one example, nozzle devices 38 and sections of the layer of refractory material 36 alternate on the front surface 48.

[0053] According to one example, the front face of the nozzle arrangement 38 forms part of the front face 48. According to one example, the front face is included in a mouth section of the nozzle arrangement 38. According to one example, air is injected through an opening in the front face.

[0054] According to one example, a group of nozzle devices 38 are embedded in the layer of refractory material 36 such that air is ejected from the nozzle devices 38 into conduits and openings formed in the layer of refractory material 36, projecting the air through the front surface 48.

[0055] 2, the groups of nozzle devices 38 are embedded in the layer of refractory material 36 such that the upper surfaces of the nozzle devices 38 form part of the land 46. According to one example, the nozzle devices 38 alternate with sections of the layer of refractory material 36 in the land 46. According to another example, the nozzle devices 38 are embedded below the surface of the land 46.

[0056] According to the example of Fig. 3, each land 46 includes a first row 381 of nozzle devices 38, a second row 382 of nozzle devices 38, a third row 383 of nozzle devices 38 and a fourth row 384 of nozzle devices 38. The nozzle devices 38 of each row are aligned in a row and belong to the group of nozzle devices 38 mentioned above. These rows are arranged horizontally, the first row 381 and the second row 382 are parallel and located on either side of the land 46, and the third row 383 and the fourth row 384 are parallel, located on either side of the land 46 and perpendicular to the first and second rows 381, 382.

[0057] According to the example of FIG. 3, two or more nozzle devices 38 belonging to a plurality of nozzle devices 38 and located on different lands 46 are aligned in a row along a direction perpendicular to one of the rows 381, 382, ​​383, 384.

[0058] According to the example of FIG. 3, each nozzle device 38 in each row 381, 382, ​​383, 384 is configured, oriented or pointed to eject air towards the opposing row along the land portion 46 in a horizontal direction perpendicular to the opposing rows described above.

[0059] According to one example, there are between 8 and 80 nozzle devices 38 in the group of nozzle devices 38 described above.

[0060] According to one example, the grate module 40 has between 3 and 7 concentric lands 46. Alternatively, there are more than 8, such as at least 10, concentric lands 46. According to one example, the lands extend horizontally.

[0061] According to the example of Fig. 3, each front surface 48 includes four corners 58 constituting a rectangular corner, each corner including at least one nozzle device 38 belonging to the group of nozzle devices 38 described above and located between two of the mutually orthogonal rows 381, 382, ​​383, 384. The at least one nozzle device 38 is configured, oriented or directed to inject air horizontally towards the solids removal opening 42 or towards one of the four diagonally located corners 58. According to the example of Fig. 3, the at least one nozzle device 38 injects air at an angle of 45 degrees, or at an angle between 35 and 55 degrees, or at an angle between 20 and 70 degrees, in relation to the two mutually orthogonal rows described above.

[0062] According to one example, there are one, two or less than three nozzle devices 38 in the aforementioned corner portion 58. Alternatively, there are more than three nozzle devices 38 in the aforementioned corner portion 58.

[0063] According to the example of Fig. 4, the grate assembly 30 further comprises an additional land 52 on at least one side of at least one grate module 40. The additional land 52 is formed in the refractory material layer 36. The additional land 52 forms an extension to the stepped structure of the grate module 40. According to the first example of Fig. 4, the additional land 52 is separated from the top land 46 of the grate module 40 by an additional front face 54 between them. According to the second example, the additional land 52 is separated from another additional land 52 by an additional front face 54 between them.

[0064] 4, the additional land 52 and / or the additional front face 54 follow a linear shape, i.e. the additional land 52 and / or the additional front face 54 extend linearly. According to one example, the additional land 52 extends horizontally. According to one example, the additional land 52 extends linearly along one side of at least two adjacent grate modules 40.

[0065] The additional lands 54 include a group of additional nozzle devices 56 embedded in the layer of fire-resistant material 36, the additional nozzle devices being configured, oriented or oriented to inject air through one of the additional front faces 54 and along said top land 46 or said other additional land 46 adjacent to the one additional front face 54. According to one example, the additional nozzle devices 56 are adapted to inject air horizontally.

[0066] According to the example of Fig. 4, the land 46 of the grate module 40 and the additional lands 52 located on one side, two adjacent sides, or opposite sides, or three adjacent sides of the grate module 40 form the grate module 40 following a rectangular shape. According to another example, the grate module 40 follows a square shape, and the grate module 40 forms a non-square rectangular structure with the additional lands 52. According to the example of Fig. 4, the additional lands 52 will be located between two adjacent grate modules 40.

[0067] According to the example of Fig. 4, the additional land 52 comprises an additional row 561 of additional nozzle devices 56. The additional nozzle devices 56 of the additional row are aligned in a row and belong to the above-mentioned group of additional nozzle devices 56. The additional rows are arranged in the horizontal direction such that the additional row 561 is parallel to the first row 381 and the second row 382, ​​or the third row 383 and the fourth row 384.

[0068] According to the example of Fig. 4, each additional nozzle device 56 of the additional row 561 is configured, oriented or oriented to inject air towards the aforementioned row in a horizontal direction perpendicular to the aforementioned row parallel to the additional row 561. Alternatively, at least one additional nozzle device 56 at one or both ends of the additional row 561 is configured, oriented or oriented to inject air horizontally towards the solids removal opening 42 or one of the four diagonally located corners 58, the at least one additional nozzle device 56 belonging to the group of the aforementioned additional nozzle devices 56. According to an example, the at least one additional nozzle device 56 injects air at an angle of 45 degrees, an angle between 35 and 55 degrees, or an angle between 20 and 70 degrees with respect to the other additional nozzle devices 56 of the additional row 561.

[0069] In some examples, the details of the structure, operation, and characteristics of the nozzle apparatus 38 described above in relation to the layer of fire-resistant material 36, the front face 48, and the land portion 46 also apply to the additional nozzle apparatus 56 associated with the layer of fire-resistant material 36, the additional front face 54, and the additional land portion 52.

[0070] According to one example, the fluidized bed boiler 10 includes a solids collection and handling system for receiving solids coming through one or more of the solids removal openings 42 and / or solids removal conduits 44 .

[0071] According to one example, the fluidized bed boiler 10 or grate assembly further includes one or more air plenum chambers 50. The air plenum chambers 50 are adapted to receive air provided as fluidizing primary air via a plurality of nozzle devices 38, 56. The air plenum chambers 50 are located below the grate bottom wall 32. According to one example, conduit sections of the nozzle devices 38, 56 communicate with the air plenum chambers 50 for conveying air.

[0072] In this description, the singular forms "a," "an," and "the" referring to a device or component do not exclude additional or multiple corresponding devices or components, unless specifically stated otherwise.

[0073] In the description, various devices and components may be described as "comprising" other components. The terms "comprise(s), comprising," "include(s)," "having, has," and variations thereof are intended to be open-ended expressions that do not exclude the possibility of additional components, unless otherwise specified.

[0074] The various aspects and embodiments of the inventive solution disclosed in this description are intended to be illustrative and not limiting, and the inventive solution is intended to be construed as including all such aspects and embodiments covered by the appended claims.

Claims

1. A grate assembly (30) for use in a bottom section (28) of a combustion chamber (12) of a fluidized bed boiler (10), the grate assembly (30) comprising: A grate bottom wall (32); means for supplying fluidizing primary air to said combustion chamber above said grate bottom wall to maintain combustion of fuel and fluidization of bed material; At least one grate module (40); Each grate module (40) a solids removal opening (42) for directing solids downwardly through said grate bottom wall (32) therethrough; a plurality of concentric lands (46) vertically spaced apart and separated by front faces (48) between said lands; Each front surface (48) surrounds one of the lands; each land includes a group of nozzle devices from a plurality of nozzle devices (40) configured to inject air through one of said front faces (48) and along one of said lands (46) adjacent said front faces; and the land (46) defines a stepped structure that descends toward the solids removal opening (42) located at the center of the land; Each front surface (48) follows a rectangular perimeter shape; The grate assembly comprises: a plurality of cooling tubes (34) of the grate bottom wall (32) attached to the grate bottom wall; a protective refractory layer (36) on said grate bottom wall (32) and covering said plurality of cooling tubes (34); the at least one grate module (40) is formed in the grate bottom wall (32), and each of the plurality of concentric lands (46) is formed in the layer of protective refractory material (36); the solids removal opening is in the protective refractory material layer (36) and directs the solids on the protective refractory material layer downward through the protective refractory material layer and the grate bottom wall; the means for supplying the fluidized primary air includes a plurality of nozzle devices (38) for supplying fluidized primary air into the combustion chamber over the grate bottom wall and the protective refractory material layer; At each land, a group of said nozzle devices are embedded in said layer of protective fire-resistant material (36). Grate assembly.

2. 2. The grate assembly of claim 1, wherein the rectangle has at least one shaped corner, the at least one shaped corner including a chamfer, multiple chamfers, a step, multiple steps, a shape extending inwardly of the rectangle, and / or a shape extending outwardly of the rectangle.

3. 2. The grate assembly of claim 1, wherein said lands (46) extend horizontally and said nozzle arrangement (38) is adapted to eject said air horizontally.

4. 2. The grate assembly of claim 1, wherein each front surface (48) is formed by a surface of a group of the nozzle devices (38), by the protective refractory material layer (36), or by both the surface and the protective refractory material layer (36).

5. 2. The grate assembly of claim 1, wherein said grate bottom wall (32) extends horizontally and said plurality of cooling tubes (34) are parallel, horizontally extending and spaced apart along and attached to said grate bottom wall.

6. 2. The grate assembly of claim 1, wherein each land portion (46) includes a first row (381), a second row (382), a third row (383) and a fourth row (384) of horizontally arranged nozzle devices aligned in a row and belonging to the group of nozzle devices, the first row (381) and the second row (382) being parallel and located on either side of the land portion, and the third row (383) and the fourth row (384) being parallel, located on either side of the land portion and perpendicular to the first row and the second row.

7. 7. The grate assembly of claim 6, wherein each nozzle device in each row is adapted to inject air along said land toward the opposing row in a horizontal direction perpendicular to the opposing row.

8. each front surface (48) includes four corners (58) constituting corners of said rectangle, each corner having at least one nozzle device (38) belonging to said group of nozzle devices and located between two of said mutually orthogonal rows (381, 382, ​​383, 384) of nozzle devices; 2. The grate assembly of claim 1, wherein the at least one nozzle device is adapted to inject air at a horizontal angle toward the solids removal opening (42) or one of the four diagonally opposite corners (58).

9. 2. The grate assembly of claim 1, further comprising at least one air plenum chamber (50) for receiving the air supplied through the plurality of nozzle devices (38) as the fluidizing primary air, the at least one air plenum chamber being located below the grate bottom wall (32).

10. The grate assembly (30) further includes an additional land (52) formed in the protective refractory material layer (36) on at least one side of at least one of the grate modules (40), the additional land forming an extension to the stepped structure of the grate module; the additional land (52) is separated from the top land of the grate module or another additional land by an additional front surface (54) between the grate modules; 2. The grate assembly of claim 1, wherein the additional lands (54) include a group of additional nozzle devices (56) embedded in the protective refractory material layer (36), the group of additional nozzle devices adapted to inject air through one of the additional front faces (54) along the top land or other additional lands (52) adjacent the additional front faces.

11. The grate assembly of claim 10, wherein the additional land portion (54) extends linearly along one side of at least two adjacent grate modules (40).

12. 11. The grate assembly of claim 10, wherein the additional lands (54) include an additional row (561) of additional nozzle devices aligned in a row, belonging to the group of additional nozzle devices, and arranged horizontally, the additional row (561) being parallel to the first row (381) and the second row (382), or the third row (383) and the fourth row (384).

13. 13. The grate assembly of claim 12, wherein the additional land portion (54) includes at least one additional nozzle device (56) at one or both ends of the additional row (561) belonging to the group of additional nozzle devices and adapted to inject air at an angle in the horizontal direction toward the solids removal opening (42).

14. 7. The grate assembly of claim 6, wherein two or more nozzle devices belonging to the plurality of nozzle devices (38) and located on different lands (46) are aligned in a row along a direction perpendicular to the first row (381) and the second row (382), or the third row (383) and the fourth row (384).

15. A fluidized bed boiler (10) used for the production of steam and having a combustion chamber (12) with a bottom section (28) including a grate assembly (30) according to any one of claims 1 to 14.

Images