The present invention relates generally to fluid bed boilers, particularly improved fluidizing nozzle or bubble cap assemblies for air distribution grids in fluid bed boilers.
An air distribution grid is an important feature of a fluid bed boiler. Its purpose is to achieve a uniform air distribution across the bed plan area to fluidize the bed material in the furnace and to prevent backsifting of the bed material into the windbox. The most typical air distribution grid design is an array of bubble cap assemblies attached to a water-cooled membrane panel. Designs of bubble cap assemblies vary widely; two examples are shown in
During a start-up, if the boiler uses in-duct start-up burners, the air distribution grid is subjected to hot gases with a temperature that can exceed 1600° F. The bubble cap assemblies (typically made of stainless steel) have essentially the same temperature as these gases. Membrane 4, welded to tubes 5 and protected from direct contact with the hot gases by refractory 10 in the design shown in
In order to avoid the weld cracking, the design shown in
Thus, there is a need for a system which avoids weld cracking. A system not prone to air leakage is also needed, so as to avoid the resultant lowering of pressure drop across the bubble caps, and reduce the potential for bed material backsifting as well as plugging and erosion of the bubble caps.
The present invention reduces or eliminates backsifting of bed material through the bubble caps, as well as their plugging and erosion, by creating an air-tight connection between the bubble cap and the membrane while allowing their independent thermal expansions.
Accordingly, one aspect of the present invention is drawn to a system for improved air distribution in fluid bed boilers, namely a bubble cap assembly for an air distribution grid, comprising: a stem having a top region and a bottom region; a bubble cap connected to the top region of the stem; a membrane having an opening, the bottom region of the stem communicating with the opening; a flange connected to the bottom region of the stem; at least one clamp for pressing the flange against the membrane; and a gasket squeezed between the flange and the membrane by the clamp to provide an air-tight connection between the flange and the membrane.
Another aspect of the invention is drawn to a bubble cap assembly for an air distribution grid, comprising: a bifurcated stem having two top regions and a bottom region; a plurality of bubble caps, each bubble cap connected to a top region of the stem; a membrane having an opening, the bottom region of the stem communicating with the opening; a flange connected to the bottom region of the stem; at least one clamp for pressing the flange against the membrane; and a gasket squeezed between the flange and the membrane by the clamp to provide an air-tight connection between the flange and the membrane.
In some embodiments of the invention, the flange includes a recess, adapted to prevent the gasket from protruding from under the flange. A portion adjacent the recess also prevents the gasket from protruding to an inside area and potentially blocking the opening. The gasket provides an air-tight connection between the flange and the membrane.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming part of this disclosure. For a better understanding of the present invention, and the operating advantages attained by its use, reference is made to the accompanying drawings and descriptive matter, forming a part of this disclosure, in which a preferred embodiment of the invention is illustrated.
In the accompanying drawings, forming a part of this specification, and in which like reference numbers are used to refer to the same or functionally similar elements:
With reference to
With reference to
In another embodiment, shown in
Among the many advantages provided by the present invention, it should be noted that a combination of thickness and width of membrane 4 allows maintaining its temperature during a start-up within acceptable limits without refractory protection.
While specific embodiments and/or details of the invention have been shown and described above to illustrate the application of the principles of the invention, it is understood that this invention may be embodied as more fully described in the claims, or as otherwise known by those skilled in the art, including any and all equivalents, without departing from such principles.
Number | Name | Date | Kind |
---|---|---|---|
973795 | Lummus | Oct 1910 | A |
1691609 | Oskrit | Nov 1928 | A |
2084726 | Duey | Jun 1937 | A |
2398953 | O'Brien | Apr 1946 | A |
2445083 | Reed | Jul 1948 | A |
2480862 | Johnson | Sep 1949 | A |
2510556 | Collins | Jun 1950 | A |
2540781 | Glitsch | Feb 1951 | A |
2547383 | Glitsch | Apr 1951 | A |
2580260 | Winters | Dec 1951 | A |
2602652 | Haynes | Jul 1952 | A |
2612360 | Haynes | Sep 1952 | A |
2645468 | Sullivan | Jul 1953 | A |
2710177 | Young | Jun 1955 | A |
2732194 | Jackson | Jan 1956 | A |
3896996 | Roest | Jul 1975 | A |
4146950 | Powers | Apr 1979 | A |
4305895 | Heath | Dec 1981 | A |
4346054 | Lofgren | Aug 1982 | A |
4418650 | Johnson | Dec 1983 | A |
5045247 | Treese | Sep 1991 | A |
5158714 | Shih | Oct 1992 | A |
6868795 | Maryamchik | Mar 2005 | B2 |
8114359 | Maryamchik | Feb 2012 | B2 |
Number | Date | Country |
---|---|---|
2 542 628 | Oct 1984 | FR |
2 157 588 | Oct 1985 | GB |
WO 0213959 | Feb 2002 | WO |
Number | Date | Country | |
---|---|---|---|
20150321153 A1 | Nov 2015 | US |