Grill 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 proposed solution relates to a grate assembly for use in the bottom section of the combustion chamber of a circulating fluidized bed boiler. The grate assembly includes one grate module or at least two adjacent grate modules that make up the bottom section. The proposed solution relates to a fluidized bed boiler having a combustion chamber and used for steam generation.

Background Art

[0002] The bottom section of the combustion chamber of a circulating fluidized bed boiler can include an inclined floor or inclined floor section to facilitate the removal of solids when transferring the solids to the solids removal opening by air jets and gravity. The inclined floor is formed by a protective refractory material layer. The air jets are provided by nozzle devices that supply air for combustion and fluidization. The nozzle devices extend to various heights from the protective refractory material layer.

[0003] The nozzle devices may interfere with the removal of solids, or the direction of the air jets may not be optimal. The nozzle devices may be worn by the air jets carrying solids or fluidized bed material. The height difference of the inclined floor including the nozzle devices can vary significantly depending on the dimensions of the combustion chamber. Thus, the operation of the fluidized bed in the combustion chamber can 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 grate assembly is presented in claim 15.

[0006] In other claims, examples of the solution are presented in more detail.

[0007] This grate assembly 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 fluidized primary air over the grate bottom wall and the protective refractory material layer to the combustion chamber in order to maintain the combustion of the fuel and the 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 having a solids removal opening in the refractory material layer through which solids on the refractory material layer are guided downward toward a solids removal conduit, the solids removal conduit being adapted to guide solids through the refractory material layer and the grate bottom wall.

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

[0011] For example, at least one molded corner portion includes a chamfer, multiple chamfers, a stepped portion, multiple stepped portions, a shape extending inward from the rectangle, and / or a shape extending outward from the rectangle.

[0012] In one example, each land section includes four rows of nozzle devices, each nozzle device being aligned in a single row and belonging to a group of nozzle devices. In another example, the front section includes four corner sections, each corner section belonging to a group of nozzle devices and having at least one nozzle device located between two rows of nozzle devices.

[0013] The fluidized bed boiler used for steam generation includes a combustion chamber with a bottom section containing the grate assembly described above.

[0014] The proposed solution is particularly advantageous and addresses the aforementioned challenges.

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

[0016] In one example, the use of grate modules in the proposed solution provides a method for limiting the height difference between nozzle devices. The height difference of the grate assembly and grate modules, as well as the height of the stepped structure, 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, additional rows of nozzle devices are easily integrated within or between grate modules to facilitate the design of the layout of the grate assembly and the bottom section of the combustion chamber.

[0018] In one example, the central position of the solids removal opening in the grate module provides an efficient method for removing solids. The size and dimensions of the grate module can be selected so that solids are efficiently transported to the solids removal opening.

[0019] In one example, the proposed solution provides a simple structure in which the grate bottom wall and multiple parallel cooling tubes extend horizontally.

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

[0021] In one example, the nozzle devices located at the corner portions of the fire 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 solution are disclosed more specifically below.

Brief Description of the Drawings

[0023] The following 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] A side view of an example of a steam generator or a fluidized bed boiler to which the solution of the present invention can be applied. [Figure 2] A side cross-sectional view of an example of a fire grate assembly that constitutes one fire grate module and is applied to the solution of the present invention. [Figure 3] A top view of an example of the fire grate assembly of FIG. 2 applied to the solution of the present invention. [Figure 4] A top view of an example of a fire grate assembly that includes two adjacent fire grate modules equipped with additional nozzle devices and is applied to the solution of the present invention. [Figure 5] A top view of an example of the formed corner portion of the fire grate assembly of FIG. 3.

Modes for Carrying Out the Invention

[0024] In the description, the following reference numerals and notations 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 Support column 24 Support beam 26 Hanger 28 Bottom section 30 Grate assembly 32 Grate bottom wall 34 Cooling pipe 36 Refractory layer 38 Nozzle device 381 First row of nozzle devices 382 Second row of nozzle devices 383 Third row of nozzle devices 384 Fourth row of nozzle devices 40 Grate module 42 Solid removal opening 44 Solid removal conduit 46 Land portion 48 Front surface 50 Air plenum chamber 52 Additional land portion 54 Additional front surface 56 Additional nozzle device 561 Additional row of nozzle devices 58 Corner portion

[0025] A more complete understanding of the features disclosed in this specification can be obtained by referring to the accompanying drawings. These drawings are merely schematic diagrams and are not intended to show the relative sizes and dimensions of the device or its components, nor to define or limit the scope of the embodiments. The specific terms used in the following description are intended to refer only to the embodiments selected 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 numerals designate like-functional devices or components.

[0026] In the following, the terms “horizontal” and “vertical” refer to the intended operating positions of the device or component being discussed when installed in place to achieve the function of the solution described. The terms “horizontal” and “vertical” are used to indicate directions relative to an absolute reference point, i.e., ground level. In the diagram, the vertical direction is indicated by arrow Z, and the two orthogonal horizontal directions are indicated by arrows X and Y. The horizontal directions are orthogonal to the vertical directions.

[0027] Furthermore, the terms “upper,” “lower,” “on top,” “lower,” “upward,” and “downward” relate to the intended operating positions described above. The terms “parallel” and “orthogonal” should not be interpreted as requiring that structures be perfectly parallel or perfectly orthogonal to each other. The term “opposite” should not be interpreted as requiring that opposing directions be perfectly parallel to each other.

[0028] Referring to Figure 1, one 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, steam boiler plant, or hot water boiler plant adapted for the generation of electrical energy, steam, and / or heating energy.

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

[0030] The boiler 10 may include further equipment relevant to the design being discussed, but is not necessarily illustrated. The boiler 10 may further include a cyclone separator 14 connected to the combustion chamber 12 to separate solid particles from the combustion exhaust gas coming from the combustion chamber 12 and guide the combustion exhaust gas into the exhaust gas channel 16. The boiler 10 may further include a support frame 18 that supports the combustion chamber 12 and the exhaust 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 exhaust gas channel 16 relative to the support frame 18.

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

[0032] As shown in Figures 2 and 3, the 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 devices 38, and at least one grate module 40.

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

[0034] In the example shown in Figure 2, the grate bottom wall 32 extends horizontally, and the multiple cooling tubes 34 extend horizontally in parallel and are attached to the grate bottom wall 32 at intervals along the grate bottom wall 32.

[0035] In the example shown in Figure 2, the grate bottom wall 32 is composed of multiple cooling tubes 34 separated by fins installed between them.

[0036] The protective fire-resistant material layer 36 is located on the bottom wall 32 of the grate and covers multiple cooling tubes 34.

[0037] Multiple nozzle devices 38 are for supplying fluidized primary air into the combustion chamber 12 to maintain the fluidization of the fluidized bed material and the combustion of the fuel on the grate bottom wall 32 and the protective refractory material layer 36. Each nozzle device 38 is adapted to guide the primary air that reaches through the grate bottom wall 32 and the refractory material layer 36 and to inject the air used as fluidized primary air.

[0038] In the example shown in Figure 2, the nozzle device 38 includes a conduit section attached to the grate bottom wall 32 and passing through the grate bottom wall 32, and a mouth section that ejects the air guided through the conduit section.

[0039] The grate assembly 30 includes, for example, one grate module 40, or 2 to 36 adjacent grate modules 40. In one example, the grate module 40 constitutes 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] As shown in the example in Figure 4, all 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 land sections 46.

[0042] The solid removal opening 42 is formed in the refractory material layer 36, and through the solid removal opening 42, solids on the refractory material layer 36 are guided downward through the refractory material layer 36 and the grate bottom wall 32 by moving air and gravity.

[0043] In the example shown in Figure 2, the solid material is guided downward toward the solid removal conduit 44 of the fluidized bed boiler 10 or grate assembly.

[0044] Each land portion 46 is formed in the fire-resistant material layer 36. The land portions 46 are spaced apart in the vertical direction and are separated from each other by front surfaces 48 located between them.

[0045] The land portion 46 forms, for example, a stepped structure, such as a funnel, and the funnel descends toward the solid object removal opening 42 located in the center of the land portion 46.

[0046] In the example shown in Figure 2, the front surface 48 extends vertically.

[0047] Each front 48 surrounds one of the land portions 46 and conforms to the shape of a rectangle's perimeter, or the shape of a rectangle's perimeter having at least one molded corner portion. Alternatively, each front 48 surrounds one of the land portions 46 and conforms to the shape of a square's perimeter, or the shape of a square's perimeter having at least one molded corner portion. A square representing a rectangle is a special case of a rectangle in which all four sides are of equal length.

[0048] In the example shown in Figure 5, at least one formed corner includes a chamfer (Figure 5(b)), multiple chamfers (Figure 5(c)), a stepped section (Figure 5(d)(g)), multiple stepped sections (Figure 5(e)(f)), a shape extending inward from the rectangle (Figure 5(b)(c)(d)(e)), and / or a shape extending outward from the rectangle (Figure 5(f)(g)). In one example, all four corners of the rectangle are similar. In one example, the corner is formed from two orthogonal edges (Figure 5(a)).

[0049] Each land section 46 includes a group of nozzle devices 38 belonging to a plurality of nozzle devices 38. The group of nozzle devices 38 is embedded in the refractory material layer 36 and is configured to inject, direct, or orient air through one of the fronts 48 and further along one of the land sections 46 adjacent to this front. For example, one land section 46 is located between one front 48 and another front 48 located below it in the vertical direction. For example, one land section 46 is located between one front 48 and the solids removal opening 42 at the center of the grate module 40.

[0050] In the example shown in Figure 3, the solid object removal opening 42 is circular. Alternatively, the solid object removal opening 42 may be rectangular, square, or polygonal in shape.

[0051] In the example shown in Figure 2, the nozzle device 38 is adapted to spray air horizontally. In the example shown in Figure 3, each nozzle device 38 is adapted to spray air in a predetermined horizontal direction specific to that nozzle device 38.

[0052] According to the examples in Figures 2 and 3, each front surface 48 is formed by the surface of a group of nozzle devices 38, by the fire-resistant material layer 36, or by the surfaces of both the nozzle devices 38 and the fire-resistant material layer 38. In one example, sections of the nozzle devices 38 and sections of the fire-resistant material layer 36 alternate at the front surface 48.

[0053] In one example, the front of the nozzle device 38 constitutes part of the front 48. In one example, the front is included in the mouth section of the nozzle device 38. In one example, air is injected through the opening in the front.

[0054] In one example, a group of nozzle devices 38 is embedded in the fire-resistant material layer 36 such that air is ejected from the nozzle devices 38 into conduits and openings formed in the fire-resistant material layer 36, and the air is sprayed through the front surface 48.

[0055] In the example shown in Figure 2, the group of nozzle devices 38 are embedded in the fire-resistant material layer 36 such that the upper surface of each nozzle device 38 forms part of the land portion 46. In one example, the nozzle devices 38 and sections of the fire-resistant material layer 36 alternate along the land portion 46. In another example, the nozzle devices 38 are embedded beneath the surface of the land portion 46.

[0056] According to the example in Figure 3, each land section 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 in each row are aligned in a single line and belong to the group of nozzle devices 38 described above. These rows are arranged horizontally, with the first row 381 and the second row 382 being parallel and located on both sides of the land section 46, and the third row 383 and the fourth row 384 being parallel and located on both sides of the land section 46 and perpendicular to the first and second rows 381 and 382.

[0057] In the example shown in Figure 3, two or more nozzle devices 38, each belonging to a group of nozzle devices 38 and located in different land portions 46, are aligned in a line along a direction perpendicular to one of the rows 381, 382, ​​383, and 384.

[0058] In the example shown in Figure 3, each nozzle device 38 in rows 381, 382, ​​383, and 384 is configured, directed, or aligned to spray air toward the opposing row along the land portion 46 in a horizontal direction perpendicular to the opposing row described above.

[0059] For example, the group of nozzle devices 38 described above may contain 8 to 80 nozzle devices 38.

[0060] In one example, the grate module 40 has 3 to 7 identical core land sections 46. Alternatively, it may have 8 or more, for example, at least 10 concentric land sections 46. In one example, the land sections extend horizontally.

[0061] According to the example in Figure 3, each front surface 48 includes four corner sections 58 that form a rectangular corner section, and each corner section belongs to the group of nozzle devices 38 described above and includes at least one nozzle device 38 located between two of the mutually orthogonal rows 381, 382, ​​383, and 384. The at least one nozzle device 38 is configured, directed, or aligned to spray air horizontally toward the solid removal opening 42 or one of the four diagonally located corner sections 58. According to the example in Figure 3, the at least one nozzle device 38 sprays air at an angle of 45 degrees, or an angle of 35 to 55 degrees, or an angle of 20 to 70 degrees in relation to the two mutually orthogonal rows described above.

[0062] For example, the corner section 58 described above may have one, two, or three or fewer nozzle devices 38. Alternatively, the corner section 58 may have three or more nozzle devices 38.

[0063] In the example shown in Figure 4, the grate assembly 30 further includes additional land portions 52 on at least one side of at least one grate module 40. The additional land portions 52 are formed in the refractory material layer 36. The additional land portions 52 form an extension of the stepped structure of the grate module 40. In the first example shown in Figure 4, the additional land portions 52 are separated from the uppermost land portion 46 of the grate module 40 by an additional front 54 between them (the grate modules 40). In the second example, the additional land portions 52 are separated from another additional land portion 52 by an additional front 54 between them (the grate modules 40).

[0064] In the example shown in Figure 4, the additional land portion 52 and / or additional front portion 54 follow a linear shape, i.e., the additional land portion 52 and / or additional front portion 54 extend in a straight line. In one example, the additional land portion 52 extends horizontally. In one example, the additional land portion 52 extends in a straight line along one side of at least two adjacent grate modules 40.

[0065] The additional land section 54 includes a group of additional nozzle devices 56 embedded in the fire-resistant material layer 36, the additional nozzle devices configured, directed, or aligned to spray air through one of the additional fronts 54 and further along the uppermost land section 46 or any other additional land section 46 adjacent to one of the additional fronts 54. In one example, the additional nozzle devices 56 are adapted to spray air horizontally.

[0066] In the example shown in Figure 4, the land portion 46 of the grate module 40 and additional land portions 52 located on one side, two adjacent sides, opposing sides, or three adjacent sides of the grate module 40 form a grate module 40 that conforms to a rectangular shape. In another example, the grate module 40 conforms to a square shape, and together with the additional land portions 52, the grate module 40 forms a non-square rectangular structure. In the example shown in Figure 4, the additional land portions 52 are located between two adjacent grate modules 40.

[0067] In the example of Figure 4, the additional land portion 52 includes an additional row 561 of additional nozzle devices 56. The additional nozzle devices 56 in the additional row are aligned in a row and belong to the group of additional nozzle devices 56 described above. The additional row is arranged horizontally 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] As shown in the example in Figure 4, each additional nozzle device 56 of the additional row 561 is configured, directed, or aligned to spray air toward the aforementioned row in a horizontal direction perpendicular to the 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, directed, or aligned to spray air horizontally toward the solid removal opening 42 or one of the four diagonally located corner sections 58, and at least one additional nozzle device 56 belongs to the group of additional nozzle devices 56 described above. For example, at least one additional nozzle device 56 sprays air toward the other additional nozzle devices 56 of the additional row 561 at an angle of 45 degrees, 35 to 55 degrees, or 20 to 70 degrees.

[0069] According to some examples, the details of the structure, operation, and characteristics of the nozzle device 38 described above in relation to the fire-resistant material layer 36, the front surface 48, and the land portion 46 also apply to an additional nozzle device 56 related to the fire-resistant material layer 36, an additional front surface 54, and an additional land portion 52.

[0070] For 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] In 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 supplied as fluidized primary air via a plurality of nozzle devices 38, 56. The air plenum chambers 50 are located below the grate bottom wall 32. In one example, to transport air, the conduit sections of the nozzle devices 38, 56 communicate with the air plenum chambers 50.

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

[0073] In descriptions, various devices and components may be described as "comprising" other components. The terms "comprise(s), comprising," "include(s)," and "having, has," and their variations, 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 solutions of the present invention disclosed in this description are illustrative and not intended to limit them. The solutions of the present invention are intended to be construed as including all such aspects and embodiments covered by the appended claims.

Claims

1. A grate assembly for use in the bottom section (28) of the combustion chamber (12) of a fluidized bed boiler (10), wherein the grate assembly (30) is The bottom wall of the grate (32), A device for supplying fluidized primary air from above the grate bottom wall to the combustion chamber in order to maintain the combustion of the fuel and the fluidization of the fluidized bed material, It includes at least one grate module (40), Each grate module (40) A solid matter removal opening (42) is provided, which guides the solid matter downward through the grate bottom wall (32) via the solid matter removal opening (42), A plurality of concentric land portions (46), which are spaced apart in the vertical direction and separated by front surfaces (48) between the land portions, Each front surface (48) surrounds one of the land portions, Each land portion includes a group of nozzle devices belonging to a plurality of nozzle devices (38), and the group of nozzle devices is configured to inject air through one of the front surfaces (48) along one of the land portions (46) adjacent to the front surface, and The land portion (46) defines a stepped structure that descends toward the solid object removal opening (42) located at the center of the land portion. Each front (48) follows the shape of the rectangle's perimeter, The grate assembly is, Multiple cooling tubes (34) attached to the bottom wall of the grate (32), The present invention further includes a protective fire-resistant material layer (36) located on the bottom wall (32) of the grate and covering the 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 land portions (46) is formed in the protective fire-resistant material layer (36), The solid material removal opening is located within the protective fire-resistant material layer (36) and guides the solid material on the protective fire-resistant material layer downward through the protective fire-resistant material layer and the bottom wall of the grate. The apparatus for supplying the fluidized primary air includes a plurality of nozzle devices (38) for supplying the fluidized primary air over the grate bottom wall and the protective refractory material layer into the combustion chamber. In each land section, the group of nozzle devices is embedded in the protective fire-resistant material layer (36). Each front surface (48) includes four corner sections (58) that constitute the rectangular corner section, and each corner section has at least one nozzle device (38) that belongs to the group of nozzle devices and is located between two of the mutually orthogonal rows of nozzle devices (381, 382, ​​383, 384). The at least one nozzle device is adapted to spray air at a certain angle in the horizontal direction toward the solid object removal opening (42) or one of the four corner sections (58) located diagonally opposite each other. Grill assembly.

2. The grate assembly according to claim 1, wherein the rectangle has at least one molded corner portion, the at least one molded corner portion includes a chamfer, a plurality of chamfers, a stepped portion, a plurality of stepped portions, a shape extending inward from the rectangle, and / or a shape extending outward from the rectangle.

3. The grate assembly according to claim 1, wherein the land portion (46) extends horizontally, and the nozzle device (38) is adapted to eject the air horizontally.

4. The grate assembly according to claim 1, wherein each front surface (48) is formed by the surface of the group of nozzle devices (38), or by the protective fire-resistant material layer (36), or by both the surface and the protective fire-resistant material layer (36).

5. The grate assembly according to claim 1, wherein the grate bottom wall (32) extends horizontally, and the plurality of cooling tubes (34) extend horizontally in parallel and are attached to the grate bottom wall at intervals along the grate bottom wall.

6. Each land portion (46) is aligned in a row and includes a first row (381), a second row (382), a third row (383), and a fourth row (384) of nozzle devices that are arranged horizontally and belong to the group of nozzle devices, wherein the first row (381) and the second row (382) are parallel and located on both sides of the land portion, and the third row (383) and the fourth row (384) are parallel and located on both sides of the land portion and are perpendicular to the first row and the second row, the grate assembly according to claim 1.

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

8. The grate assembly according to 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 fluidized primary air, wherein the at least one air plenum chamber is located below the grate bottom wall (32).

9. The grate assembly (30) further includes an additional land portion (52) formed in the protective fire-resistant material layer (36) on at least one side of at least one of the grate modules (40), the additional land portion forming an extension of the grate module relative to the stepped structure. The additional land portion (52) is separated from the uppermost land portion of the grate module or another additional land portion by an additional front (54) between the grate modules. The grate assembly according to claim 1, wherein the additional land portion (52) includes a group of additional nozzle devices (56) embedded in the protective fire-resistant material layer (36), the group of additional nozzle devices being adapted to inject air through one of the additional fronts (54) along the uppermost land portion or other additional land portions (52) adjacent to the additional front.

10. The grate assembly according to claim 9, wherein the additional land portion (52) extends linearly along one side of at least two adjacent grate modules (40).

11. The grate assembly according to claim 9, wherein the additional land portions (52) are aligned in a row and include an additional row (561) of additional nozzle devices that are aligned in a row, belong to the group of additional nozzle devices, and are 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).

12. The grate assembly according to claim 11, wherein the additional land portion (52) includes at least one additional nozzle device (56) at one or both ends of the additional row (561), which belongs to the group of additional nozzle devices and is adapted to inject air at a certain angle in the horizontal direction toward the solid removal opening (42).

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

14. A fluidized bed boiler (10) having a combustion chamber (12) used for generating steam, comprising a bottom section (28) including a grate assembly (30) according to any one of claims 1 to 13.

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