CFBC BOILER

FIELD OF INVENTION: [001] The present subject matter described herein, relates to cold cyclone CFBC boilers and more particularly, relates to air nozzles for such boilers.

BACKGROUND AND PRIOR ART:

[002] The fuel and the cold fly ash recirculated to the fluidized bed is well mixed with the hot bed material resulting in a uniform temperature distribution in the bed. This is achieved by a higher turbulence caused by introducing fluidizing air in smaller bed dimensions. Unlike the Bubbling AFBC boilers the erosion prone submerged heating surfaces are dispensed with. The recirculated cold fly ash takes over the cooling of the fluidized bed. It is in the convection pass that the heat taken is transferred to the convectional heating surfaces. The boiler has a tower- type arrangement.

[003] The first boiler pass is formed by water-cooled, gas-tight membrane tube walls. They are part of the evaporator system and are designed for natural circulation. The lower section of the first boiler pass consists of the combustion chamber with the fluidized bed and the freeboard above. The upper section is made up of a convection heating surfaces namely screen, superheaters, evaporator and a part of economizer (ECO-2). This first boiler pass is top supported allowing easy expansion downwards. The second boiler pass has remaining part of the economizer (ECO-1) heating surface and the tubular air heater.

[004] The elutriated fly ash is separated from the flue gases in cyclone separators located between the boiler first and second pass, at a temperature of around 420-

450°C. It is recirculated into the combustion chamber via a siphon system which serves as a seal. The heated combustion air from air heater is passed through the air nozzles into the fluidized bed as primary air, and above the fluidized bed into the freeboard as secondary/tertiary air. Combustion takes place within an optimum temperature of 800 C to 950 C. The flue gases are conducted to the chimney via an ESP and induced draught fan.

[005] Currently almost all the primary air nozzle designs used in the CFBC boilers are facing frequent & severe issues of nozzle head erosion and bed material back shifting in the wind box / air box below it. The back shifted material in bed in turn is again re-entrained in the primary air supplied to the air box and this bed material laden air causes internal erosion of the air nozzles from inside.

OBJECTS OF THE INVENTION:

[006] The principal objective of the present invention is to provide a specially designed air nozzle to: prevent erosion of the air nozzle head; prevent back shifting of the bed material/ ash into the air box; prevent internal erosion of the air nozzle; create controlled bed turbulence & hence uniform bed heating & bed temperature across the bed; avoiding bed hot spots & clinkerization.

SUMMARY OF THE INVENTION:

[007] The present invention relates to a mushroom head primary air nozzle (100) for a CFBC Boiler wind box/air box (302), the mushroom head primary air nozzle (100) includes a mushroom head cap (102); an intermediate channeled cap (104) configured to be coupled to the mushroom head cap (102); and an air shaft nozzle (106) configured to be coupled to the mushroom head cap (102) and the intermediate channeled cap (104). [008] In order to further understand the characteristics and technical contents of the present subject matter, a description relating thereto will be made with reference to the accompanying 'drawings. However, the drawings are illustrative only but not used to limit scope of the present subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

[009] It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system or methods in accordance with embodiments of the present subj ect matter are now described, by way of example, and with reference to the accompanying figures, in which:

[0010] Figs, la, lb, and lc respectively illustrates a parametric view of components of a mushroom head primary air nozzle 100, a perspective view of components of the mushroom head primary air nozzle 100, and a sectional view of assembled mushroom head primary air nozzle 100 in accordance with an embodiment of the present disclosure;

[0011] Fig. 2 illustrates a working principle associated with a sectional view of the mushroom head primary air nozzle 100 in accordance with an embodiment of the present disclosure;

[0012] Fig. 3 illustrates a plurality of the mushroom head primary air nozzle 100 provided on a CFBC Boiler wind box/air box 302 in accordance with an embodiment of the present disclosure; and [0013] Fig. 4 illustrates a sectional view showing welding details of the mushroom head primary air nozzle 100.

[0014] The figures depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DESCRIPTION OF THE PREFERRED EMBODIMENTS:

[0015] The present disclosure presents embodiments for a mushroom head primary air nozzle (100) for a CFBC Boiler wind box/air box (302), the mushroom head primary air nozzle (100) includes a mushroom head cap (102); an intermediate channeled cap (104) configured to be coupled to the mushroom head cap (102); and an air shaft nozzle (106) configured to be coupled to the mushroom head cap (102) and the intermediate channeled cap (104).

[0016] It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should be appreciated by those skilled in the art that conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present subject matter. It should also be appreciated by those skilled in the art that by devising various arrangements that, although not explicitly described or shown herein, embody the principles of the present subject

matter and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the present subject matter and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. The novel features which are believed to be characteristic of the present subject matter, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures.

[0017] These and other advantages of the present subject matter would be described in greater detail with reference to the following figures. It should be noted that the description merely illustrates the principles of the present subject matter. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present subject matter and are included within its scope.

[0018] Figs, la, lb, and lc respectively illustrates a parametric view of components of a mushroom head primary air nozzle 100, a perspective view of components of the mushroom head primary air nozzle 100, and a sectional view of assembled mushroom head primary air nozzle 100 in accordance with an embodiment of the present disclosure. Referring to Figs, la-lc, in an embodiment the mushroom head primary air nozzle 100 includes a mushroom head cap 102, an intermediate channeled cap 104, and an air shaft nozzle 106. In an example, a material associated with construction of the mushroom head primary air nozzle 100 is SA 297 i.e., Steel Castings with Chromium-Nickel Heat Resistant Alloy having superior tensile and yield strengths, and superior temperature withstanding capabilities. Such a material helps in eliminating high temperature erosion issues. [0019] In an example, the mushroom head cap 102 includes a plurality of annular rings 103 disposed on an outer surface of the mushroom head cap 102. An internal diameter of the plurality of annular rings 103 is equal to an outer diameter of the mushroom head cap 102. Further, the intermediate channeled cap 104 includes a plurality of ribs 105 running across a depth of the intermediate channeled cap 104, such that the plurality of ribs 105 define channels 107 in between each other.

[0020] Fig. 2 illustrates a working principle associated with a sectional view of the mushroom head primary air nozzle 100 in accordance with an embodiment of the present disclosure. As mentioned earlier, the channels 107 of the intermediate cap 104 are for air entry, and ensures free choke free air inflow to a bed above it. Further, the mushroom head cap 102 placed above the intermediate channeled cap 104 doesn't allow the direct entry of the bed material / ash into the air box 302 (See Fig. 3).

[0021] Further, as mentioned earlier, the plurality of annular rings 103 are provided at two different levels, one somewhat offset from the middle and the other one at the base of the mushroom head cap 102, along its annulus. In an embodiment, the plurality of annular rings 103 rings are provided to eliminate / restrict eddies 202 formed while the air gushes through the mushroom head primary air nozzle 100. Practically, air throws away the bed material, however material recoils back and has tendency to gush back into the mushroom head primary air nozzle 100 inlet, if these curvy eddies 202 are not prevented. This causes back shifting. But as specially designed annular rings 103 are provided, they will cut off the eddies 202 and helps in preventing the bed material back shifting and even provides proper bed turbulence and hence results in uniform heating and bed temperature distribution all along the bed.

[0022] Fig. 3 illustrates a plurality of the mushroom head primary air nozzle 100 provided on a CFBC Boiler wind box / air box 302 in accordance with an embodiment of the present disclosure. As indicated in Fig. 3 of the air box 302, the top of each of the mushroom head primary air nozzle 100 are at same level, and accordingly the base stem / shaft length is varied as the air box 302 is inclined towards a side.

[0023] Fig. 4 illustrates a sectional view showing welding details of the mushroom head primary air nozzle 100. The components of the mushroom head primary air nozzle 100, as described earlier, are welded to each other as mentioned in Fig. 4. The mushroom head primary air nozzle 100 assembly is again welded to a main nozzle steam. The nozzle steam is penetrated through the air box membrane panel (water wall) flats 402 (fines) vide SS sleeves 404 as depicted in Fig. 4.

[0024] Although embodiments for the present subject matter have been described in language specific to structural features, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features and methods are disclosed as embodiments for the present subject matter. Numerous modifications and adaptations of the sy stem/ component of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the scope of the present subject matter.