Furnaces – Fuel feeders – Blower
Reexamination Certificate
2000-08-01
2001-03-20
Ferensic, Denise L. (Department: 3749)
Furnaces
Fuel feeders
Blower
C110S1010CD
Reexamination Certificate
active
06202572
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to solid fuel pulverizing and firing systems for fossil fuel furnaces of the type, wherein the fossil fuel furnace and a substantial portion of the solid fuel pulverizing and firing system by means of which solid fuel and air is supplied to the fossil fuel furnace, are operated at a predetermined pressure, and more specifically, to an exhauster employable in such solid fuel pulverizing and firing systems for fossil fuel furnaces having an improved fan assembly.
Three basic types of solid fuel pulverizer firing systems find common use. These are the direct-fired system, the semi-direct fired system, and the bin storage system. The simplest and most commonly used of these three systems, and the one to which the present invention is directed, is the direct-fired system win which solid fuel, e.g., coal, is fed in a suitable manner along with hot gases to a pulverizer. The solid fuel is simultaneously ground and dried within the pulverizer. The drying of the solid fuel is effected by the hot gases as the latter sweep through the pulverizer. As the hot gases sweep through the pulverizer they are cooled and humidified by means of the evaporation of the moisture contained in the solid fuel. Often, an exhauster is employed for purposes of removing the hot gases and the entrained fine solid fuel particles, i.e., the solid fuel that has been ground within the pulverizer, from the pulverizer. Moreover, this exhauster, when so employed, is located on the discharge side of the pulverizer and is operative to effect the delivery of the mixture of hot gases and entrained fine solid fuel particles to a fossil fuel furnace. The main advantages of the direct-fired system are simplicity, low cost and maximum safety. To this end, the fine solid particles, which can be subject to spontaneous combustion and thus are considered to be potentially hazardous, go directly to the fossil fuel furnace at high velocities, and thus are not given the opportunity to collect and possibly ignite spontaneously. Accordingly, the direct-fired system can be operated at the maximum temperatures that safety will permit.
One prior art form of such a direct-fired solid fuel pulverizer firing system is depicted in U.S. Pat. No. 3,205,843 entitled “Pulverized Coal Firing System” in which it is disclosed that solid fuel passes through the inlet chute
23
of the pulverizer
26
on to the rotating bowl
32
thereof. The solid fuel thus admitted to the pulverizer
26
is pulverized therewithin by means of the grinding rollers
36
of the pulverizer
26
, which are mounted within the pulverizer housing to provide a grinding action between the grinding rollers
36
and the grinding ring provided on the rotating bowl
32
of the pulverizer
26
. Air passes up through the pulverizer
26
between the housing thereof and the rim of the rotating bowl
32
and as the air passes the rotating bowl
32
, pulverized solid fuel is entrained in this air with the air-pulverized solid fuel mixture passing up into the classifier
40
of the pulverizer
26
, which is located in the upper portion of the pulverizer
26
. The classifier
40
is effective to separate the coarse solid fuel fractions and return these fractions to the rotating bowl
32
of the pulverizer for regrinding, while the fines retained in the air stream pass through the outlet
42
of the pulverizer
26
, which is located at the upper end of the classifier
40
. From this outlet
42
of the pulverizer
26
, the air-pulverized solid fuel mixture is conveyed to the inlet of the exhauster
46
via conduit
44
. The air-pulverized solid fuel mixture in turn is conveyed from the exhauster
46
to the fossil fuel furnace
10
through the ducts
48
.
Another prior art form of an exhauster for a solid fuel pulverizer firing system is depicted in U.S. Pat. No. 5,363,776 to Wark entitled “Exhauster Inlet Venturi”. The Wark '776 patent discloses a known pulverizer exhauster fan assembly
10
having a fan
18
with a plurality of radial fan blades
20
connected to a drive shaft
22
by a spider assembly
24
. The drive shaft
22
ends in a hub
23
which is capped by a “cooley cap” radial diverter cap
26
.
Although solid fuel pulverizer firing systems constructed in accordance with the teachings of the two issued U.S. patents to which reference has been made heretofore have been demonstrated to be operative for the purpose for which they have been designed, there has nevertheless been evidenced in the prior art a need for such solid fuel pulverizer firing systems to be further improved, and more specifically, a need for the exhauster employed therein to be improved. A limiting factor insofar as the operating efficiency of exhausters is concerned has heretofore been the need to facilitate maintenance particularly on the fan assembly thereof. The need for such maintenance is occasioned principally by the fact that the material which is transported through the exhauster is extremely abrasive. To this end, a need has thus been evidenced in the prior art for a new and improved solid fuel pulverizer firing system, and more specifically for a new and improved exhauster for such solid fuel pulverizer firing systems that would require relatively less maintenance than known exhausters.
Moreover, there has been evidenced in the prior art a need for such a new and improved exhauster for such solid fuel pulverizer firing systems that would further be characterized in a number of additional respects. One such additional characteristic which such a new and improved exhauster for such solid fuel pulverizer firing systems would desirably possess is the capability of achieving therewith an even greater reduction in the amount of erosion to which certain interior surfaces of the exhauster. A further additional characteristic which such a new and improved exhauster for such solid fuel pulverizer firing systems would desirably possess is that the exhauster would be capable of embodying all of the above-enumerated characteristics while yet retaining the existing casing of an exhauster.
It is, therefore, an object of the present invention to provide a new and improved exhauster for use in solid fuel pulverizer firing systems.
It is a further object of the present invention to provide such a new and improved exhauster for solid fuel pulverizer firing systems which is characterized by its reduced need for maintenance as compared to prior art forms of exhausters.
Yet another object of the present invention is to provide such a new and improved exhauster for solid fuel pulverizer firing systems which is characterized in that it is possible therewith to achieve all of the foregoing within the existing casing of an exhauster.
Yet a further object of the present invention is to provide such a new and improved exhauster for solid fuel pulverizer firing systems which is characterized in that use may be made thereof either in retrofit applications or in new applications.
Yet another further object of the present invention is to provide such a new and improved exhauster for solid fuel pulverizer firing systems which is characterized in that it is relatively simple in construction, relatively easy to operate, yet is relatively inexpensive to provide.
SUMMARY OF THE PRESENT INVENTION
In accordance with one aspect of the present invention, there is provided an exhauster for a pulverized solid fuel firing system which requires relatively less maintenance than known exhausters. The exhauster of the present invention includes an improved fan assembly for exhausting coal through an exhauster fan housing, the exhauster fan assembly being mountable within the housing on a shaft for rotation about a shaft rotational axis. The housing has an inlet generally aligned with the shaft rotational axis such that coal entering the housing through the inlet contacts the rotating exhauster fan and is redirected thereby along a radial outlet path.
The exhauster fan assembly includes a plurality of blades and a hub having an outer surface, a free end, and a bore for receiving therein t
Alstom Power N.V.
Ferensic Denise L.
Rinehart K. B.
Warnock Russell W.
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