Fuel fluidizing nozzle assembly

p00001Fuel fluidizing nozzle assembly.

p00002Background

p00003This description refers to a fuel fluidizing nozzle assembly for a fluidized bed reactor.

p00004The use of fluidized bed reactors for the incineration of residual fuels, such as municipal wastes and high alkali fuels, is generally known and involves the combustion of these fuels with air while they are fluidized in a fluidized bed. The upper section of the reactor is typically equipped with a residual fuel feed unit, and the residual fuel is burned while being fluidized by primary air that is blown through nozzle assemblies into a lower section of the reactor body.

p00005Fuels are generally low in calories and contain a high percentage of tramp material that does not burn. As fuels are fed to the fluidized bed, volatile organic compounds and coarse material are burned, such as tramp material, spent bed filling material and ash remain in the fluidized bed. Thus, a fluidized bed reactor for the incineration of residual fuels and high alkali fuels is typically equipped with means in the lower section of the reactor body that are designed to provide fluidized air to the fluidized bed, while allows the coarse material to be removed from the reactor.

p00006An example of a means for removing coarse material is shown in Figure 1, which is a top plan view of an open floor grill assembly 10 disposed in the lower portion of a fluidized bed reactor

p0000712. The grill assembly 10 includes a series of parallel and spaced air ducts 14 (also known as air pipes or bars, bubble tubes and hydrotubes) that extend side by side in a substantially horizontal plane. Air nozzle assemblies 16 are fixed to the air ducts 14 to supply fluidizing air from within the air ducts 14 to the fluidized fuel bed, which is located above the grill assembly. As the organic compounds are decomposed and burned into the fluidized bed, the coarse material is directed downward through the spaces 18 between the air ducts 14. The coarse material is then discharged into an external equipment and a portion of the bed filling material can be separated from the coarse material and returned to the fluidized bed. Examples of such grill assemblies are described in US Patent No. 5,966,839 and in US Patent No. 5,425,331.

p00008US Patent 6,571,746 B1 of Kinni, issued on June 3, 2003, shows a general fluidized bed boiler using similar parts.

p00009Figure 2 illustrates an elevation and cross-sectional view of a portion of an air duct 14 that includes nozzle assemblies 16. Each nozzle assembly 16 is formed by a hollow tube 30 having an end cap 33 welded thereon. and a plurality of nozzle holes 34 disposed therein near the end cap 33. The nozzle assemblies 16 are fixed through an upper wall 32 of the air duct 14, and air from the air duct 14 passes through the hollow tube 30 and out of the nozzle holes 34 entering the fluidized fuel bed. The air duct 14 may include pipes 36 through which a cooling medium, such as water, circulates.

p00010Although this arrangement works well when the nozzle assemblies 16 are of recent installation, the nozzle holes 34, which typically have a diameter of a quarter of an inch or less, will eventually become clogged due to the presence of materials alkaline More specifically, the alkaline material enters the nozzle assembly due to the recirculation of the gas into the reactor and the reflux of solids from the bed. These alkalis cause a sticky accumulation on the nozzle assemblies, particularly in the nozzle holes and the elbows of the tube, which results in a sealing of the nozzle assemblies. The rapid shut-off results in much less operating time than is desired between the reactor stops for maintenance. In addition, repair of the nozzle assemblies typically requires that the upper portion of the nozzle assembly be cut and that a new upper portion be welded in place, which is a time-consuming process that can exceed the duration of the stops of the nozzle. reactor.

p00011Toth US Patent 5,105,559 A, issued on April 21, 1992, shows and describes a fluidized bed arrangement with nozzles that blow air in a horizontal direction.

p00012EP 0 028 458 A2 from World Energy Resources Consultancy Services (PTY) Limited, published on May 13, 1991, describes a fluidized bed boiler system that has burners that are constructed of several pieces.

p00013Therefore, there is a need for a nozzle assembly for use in a grid assembly of a fluidized bed reactor that reduces the likelihood of clogging and, therefore, reduces the frequency of reactor shutdowns.

p00015In addition, there is a need for an easily replaceable nozzle assembly to help reduce the duration of such stops.

p00016Summary

p00017According to the aspects illustrated herein, a grill assembly is provided for a fluidized bed reactor. The grill assembly includes a plurality of parallel air ducts extending side by side in a substantially horizontal plane and defining between them spaces through which thick material descends from the fluidized bed. A plurality of nozzle assemblies is fixed to each air duct to supply fluidizing air from within the air duct to the fluidized bed. Each of the nozzle assemblies includes a nozzle formed by a tube having an inlet end in fluid communication with the air duct, and an outlet end in fluid communication with the inlet end. A hole is disposed at the outlet end of the nozzle, and the nozzle is curved near the outlet end to produce a primary direction of a stream of fluidizing air flowing from the hole to the outlet duct such that an angle ! between the primary direction and the substantially horizontal plane formed by the air ducts is between about 30 and about 90 degrees. The nozzle assembly may further include a connecting pipe arranged between the air duct and the nozzle, and a sleeve arranged around the nozzle and the connecting pipe to secure the nozzle to the connecting pipe. The nozzle may be welded and / or screwed to the sleeve.

p00018In one aspect, an inside diameter of an inlet end of the hole is chamfered to prevent an accumulation of alkaline material at the inlet end. In another aspect, an inner diameter of the connecting pipe is equal to an inner diameter of the nozzle to prevent the accumulation of material at an interface between the connecting pipe and the nozzle.

p00019Each air duct can also include a plurality of nozzle assemblies with a cap attached thereto to supply fluidizing air from within the air ducts to the fluidized bed. Each of the capped nozzle assemblies includes a tube that has an inlet end in fluid communication with the air duct and an outlet end in fluid communication with the inlet end. A cap is arranged at the outlet end, and a plurality of nozzle holes are arranged radially through the tube at the outlet end, through which the fluidizing air passes.

p00020In various aspects, the plurality of nozzle assemblies are organized in groups of three along the length of the air duct, each group of three including a first nozzle assembly disposed substantially in the center line of the air duct and second and third nozzle ducts flanking the first nozzle assembly. The primary directions of the streams of fluidizing air flowing from the holes of the first, second and third nozzle assemblies can be substantially parallel. Alternatively, the primary directions of the fluidizing air streams flowing from the holes of the second and third nozzle assemblies are angled away from the stream of fluidizing air flowing from the orifice of the first nozzle assembly.

p00021The characteristics described above and others are exemplified by the following figures and detailed description.

p00022Brief description of the drawings

p00023Referring now to the figures, which are examples of embodiment and in which the same elements are numbered in the same way:

p00024Figure 1 is a top plan view of a prior art grill assembly arranged in a fluidized bed reactor;

p00025Figure 2 is an elevational and cross-sectional view of a portion of an air duct of Figure 1 including nozzle assemblies of the prior art;

p00026Figure 3 is an elevation and cross-sectional view of a nozzle assembly in accordance with an embodiment of the present invention;

p00027Figure 4 is an elevation and cross-sectional view of an air duct of a grill assembly that includes a group of nozzle assemblies of Figure 3 in a first arrangement, taken along section 4-4 of the figure 5;

p00028Figure 5 is a top plan view of the group of nozzle assemblies of Figure 4;

p00029Figure 6 is an elevation and cross-sectional view of an air duct of a grill assembly that includes a group of nozzle assemblies of Figure 3 in a second arrangement, taken along section 6-6

p00031of figure 7;

p00032Figure 7 is a top plan view of the group of nozzle assemblies of Figure 6;

p00033Figure 8 is an elevational and cross-sectional view of an air duct of a grill assembly including a group of nozzle assemblies of Figure 3 in a third arrangement; and

p00034Figure 9 is an elevation and cross-sectional view of an air duct of a grill assembly including nozzle assemblies of Figure 3 and Figure 2.

p00035Detailed description

p00036Figure 3 is an elevation and cross-sectional view of a nozzle assembly 50 in accordance with an embodiment of the present invention. The nozzle assembly 50 includes a nozzle 52, a pipe extension 54, a hole 56 and a connecting sleeve 58. The nozzle assembly 50 is fixed to the top of an air duct 14 to supply fluidizing air from within the duct of air 14 to a bed of fluidized fuel. As will be discussed in more detail below, the nozzle assembly 50 may be used in place of the nozzle assembly 16 of the prior art shown in Figure 2 or as an addition thereto.

p00037The nozzle 52 is formed by a tube that has an inlet end 60 and an outlet end 62, and is curved near the outlet end 62 to obtain a J shape. The nozzle 52 directs a stream of fluidizing air, which has a primary direction of flow along a longitudinal axis 64 of the nozzle 52, towards the air duct 14 under an angle!, Which is the angle between the longitudinal axis 64 of the nozzle 52 and the substantially horizontal plane formed by the upper walls 32 of the air ducts 14. It has been determined that, for use with open floor grill assemblies, such as those shown in Figure 1, the angle! it is preferably between about 30 and about 90 degrees and more preferably between about 30 and about 50 degrees. Within this range, it has been found that the stream of fluidizing air sufficiently fluidizes the bed, while avoiding excessive movement of the bed and thick materials in a horizontal direction. This is important for an open floor grill assembly, where the coarse material moves down through the floor and additional mixing of the coarse material with the bed is undesirable.

p00038To get the angle! desired, the nozzle 52 is curved at an angle between about 120 degrees and about 180 degrees and more preferably between about 120 degrees and about 140 degrees. The nozzle 52 may be made of metal or other rigid material that is suitable for high temperature conditions within a fluidized bed reactor.

p00039The hole 56 is disposed at an outlet end 62 of the nozzle 52. In the example shown the hole 56 is welded into the inside diameter of the outlet end 62; however, it is contemplated that the hole may be arranged around the outside diameter of the nozzle 52 or be formed with the nozzle itself 52. The hole 56 preferably has a single opening 66 that is preferably of a diameter greater than or equal to 3/8 of an inch. . Advantageously, because the nozzle assembly 50 uses a single relatively larger opening 66 through which air flows, the nozzle assembly 50 seals less frequently than the prior art nozzles. An inlet end 68 of the hole 56 is chamfered (chamfered) with respect to said hole to prevent the accumulation of alkaline material and make the air flow into the hole more aerodynamic.

p00040The pipe extension 54 includes an inlet end 70, which is fixed to the upper part 32 of the air duct 14 by welding or the like, and an outlet end 72 that borders the inlet end 60 of the nozzle 52. The pipe extension 54 and the nozzle 52 have the same inner diameter to provide a smooth interface between the two components and thus prevent any accumulation of alkaline material in the interface. Although the pipe extension 54 is shown to be substantially straight, it is contemplated that the pipe extension 54 may include one or more elbows, as necessary for a particular application. However, it is noted that minimization of the number of elbows in the pipe extension 54 is believed to help reduce the accumulation of alkaline materials within the nozzle assembly 50.

p00041The sleeve 58 is disposed around the inlet end 60 of the nozzle 52 and the outlet end 72 of the pipe extension 54 to facilitate the connection of the nozzle 52 and the pipe extension 54. The sleeve 58 and the inlet end 60 of the nozzle 52 can be secured to each other using a threaded interface 74. The sleeve 58 is also secured to the nozzle 52 and the pipe extension 54 by welding 76. Preferably, spot welds are used between the sleeve 58 and the nozzle 52 so that the nozzle 52 can be quickly removed and replaced during a reactor shutdown. To remove or replace the nozzle 52, the spot welds 76 of the sleeve 58 are cut and then the nozzle 52 can be turned or twisted out of the sleeve 58. Advantageously, because the nozzle 52 can be quickly removed and replaced, the downtime for reactor maintenance can be reduced compared to that required for prior art nozzles, which require that the nozzle be cut and released.

p00042When designing an open floor grill assembly nozzle assemblies 50 are laid out according to a pattern to fluidize the

p00044bed and ensure that these do not have the air flow outlet pointed from a nozzle assembly 50 directly to another nozzle assembly 50. For example, Figure 4 is an elevation and cross-sectional view of an air duct 14 of a grill assembly 10 that includes a group of nozzle assemblies 50 (indicated as 50, 50 'and 50' 'in a first arrangement) and Figure 5 is a top plan view of the nozzle assembly group 50 of the figure 4. Each air duct 14 includes a plurality of nozzle assemblies 50 arranged in groups of three along the length of the air duct 14. Each group of three includes a first nozzle assembly 50 disposed substantially in the center line of the air duct 14 and second and third nozzles 50 'and 50' 'flanking the first nozzle 50. Although the three nozzle assemblies 50, 50 'and 50' 'are shown as aligned side by side, it is contemplated that one or more of the nozzle assemblies in the group may be offset from the other nozzle assemblies in the group. For example, the central nozzle assembly 50 may be offset with respect to flanking nozzle assemblies 50 'and 50' '.

p00045As shown in Figures 4 and 5, the longitudinal axes 64, 64 'and 64' 'of the nozzles 52, 52' and 52 '' can be parallel to each other. As a result, the primary directions of the streams of fluidizing air flowing from the holes 56, 56 'and 56' 'are substantially parallel. Alternatively, the longitudinal axes 64, 64 'and 64' 'of the nozzles 52, 52' and 52 '' can be arranged at an angle to each other, as shown in Figures 6 and 7. In the example shown the central nozzle 52 is aligned with the central line of the air duct 14, while the outer nozzles 52 'and 52' 'are directed towards the sides of the air duct 14. As a result, the primary directions of the fluidizing air streams flowing from the holes 56 'and 56' 'of the outer nozzle assemblies 50' and 50 '' are angled away from the stream of fluidizing air flowing from the hole 56 of the central nozzle assembly 50. With this arrangement, the air streams provided by the outer nozzle assemblies 50 'and 50' 'help direct the coarse material down to the spaces 18 between the air ducts 14. Advantageously, the direction of the air stream coming from a nozzle assembly 50 can simply be changed by rotation of the nozzle 52 inside the sleeve 58.

p00046As shown in Figure 8, one or more of the pipe extensions 50 may be angled to adjust the position of the air flow provided by the nozzles 52. In the example shown the pipe extensions 54 'and 54' 'of the outer nozzle assemblies 50 'and 50' 'are angled outwardly from the central nozzle assembly 50. In addition, as shown in Figure 9, one or more nozzle assemblies 50 may be used in conjunction with a nozzle assembly 16 of the prior art. As noted above, such nozzle assemblies 16 of the prior art are typically formed by a hollow tube 30 having an end cap 33 welded thereon and a plurality of nozzle holes 34 disposed therein near the end cap 33.