Combustion – Fuel disperser installed in furnace – Plural feed means extending to common wall opening of furnace
Reexamination Certificate
2000-04-18
2002-05-14
Price, Carl D. (Department: 3743)
Combustion
Fuel disperser installed in furnace
Plural feed means extending to common wall opening of furnace
C431S009000, C431S183000, C239S405000, C239S406000, C239S402500
Reexamination Certificate
active
06386863
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to furnace burners, and in particular to a new and useful spin vane for fossil fuel-fired burners.
2. Description of the Related Art
Among the key physical features of burners used in industrial and utility boilers are the spin vanes which typically are located in at least one annular secondary air flow passage that surrounds the burner fuel nozzle. These spin vanes function to change the flow direction of incoming secondary (combustion) air and to impart a swirl velocity on the air as it exits the burner and mixes with the burning fuel. The imparted swirl velocity changes the air-fuel mixing characteristics of the burner and by so doing affects the emission production level and unburnt carbon losses of the combustion process. The spin vanes usually are fabricated from flat sheet metal, and they may be situated in the annular air flow passage(s) so that they are either stationary or movable in relation to the incoming air. Where the spin vanes are movable, they often may be adjusted from a completely closed position to a fully opened position. Movable spin vanes can be useful in instances where field tuning a burner is needed to meet certain performance requirements specified by a burner user.
Spin vanes may be used in both single and dual register burners.
FIG. 1
illustrates a known single register burner
10
of The Babcock & Wilcox Company (B&W) with spin vanes
11
located in annular secondary air flow passage
12
which surrounds burner nozzle
13
. Pulverized coal and primary air, which serves principally as a coal transport medium, are supplied to burner
10
at inlet
14
. Secondary air is delivered to annular secondary air flow passage
12
from windbox
15
which is positioned concentrically about passage
12
. Secondary air flow from windbox
15
to passage
12
can be controlled by sliding air damper
16
. Burner nozzle
13
and passage
12
respectively deliver the pulverized coal/primary air mixture and the secondary air to the interior of furnace
17
through opening
18
in furnace wall
19
. As indicated in
FIG. 1
, spin vanes
11
induce a swirled air flow pattern which is directed into a burner flame.
FIG. 2
depicts a known dual register burner
20
, also of B&W. Like the single register burner
10
, the dual register burner
20
has a burner nozzle
13
, a pulverized coal/primary air inlet
14
and a sliding damper
16
. Dual register burner
20
is distinguishable from single register burner
10
by inner secondary air zone
22
and outer secondary air zone
24
, both of which air zones encircle burner nozzle
13
and thereby serve as passages through which secondary air is delivered to the interior of furnace
17
. Secondary air zones
22
and
24
are separated from one another by air separation plate
25
which is positioned concentrically about burner nozzle
13
. Inner secondary air zone
22
and outer secondary air zone
24
have movable spin vanes
26
. Outer secondary air zone
24
also has stationary spin vanes
28
located upstream of movable vanes
26
situated in the outer air zone. As indicated in
FIG. 2
, inner and outer secondary air mixing patterns respectively exit from inner secondary air zone
22
and outer secondary air zone
24
and are directed into a burner flame.
For further clarity,
FIG. 3
shows an enlarged profile view of the known spin vanes
11
and
26
which have been pointed out respectively in FIG.
1
and
FIG. 2
, above. As shown in
FIG. 3
, the plate-like spin vane is defined by base edge
31
, leading edge
32
which intersects one end of base edge
31
at obtuse angle A, trailing edge
33
which intersects the other end of base edge
31
, also at obtuse angle A, and curved outer edge
34
which intercepts the ends of leading and trailing edges
32
and
33
, which are farthest from base edge
31
.
U.S. Pat. No. 1,620,180 discloses angled vanes with a projecting flange. The flange, however, is not placed in a flow path and is fixed to the vane for support purposes, and not for air flow direction.
U.S. Pat. No. 2,647,568 discloses vanes or ribs which are inclined relative to the burner's axis. While the vanes or ribs have flared and contoured surfaces, they do not have any extension perpendicular to part of the length.
U.S. Pat. No. 2,515,813 is a further example of angled vanes without an extension.
U.S. Pat. No. 3,049,055 discusses optimum vane angularity.
SUMMARY OF THE INVENTION
The present invention relates to various embodiments of a novel spin vane of the type used in fossil fuel-fired burners. More particularly, in a first embodiment three separate and distinct flat sheet metal elements are assembled and oriented relative to one another so as to provide a multi-piece spin vane which may be called a compound burner vane (CBV) or compound spin vane (CSV). The sheet metal elements are an outer vane element, an inner vane element and a rail element. Both outer and inner vane elements are aligned perpendicularly with respect to outer and inner faces of the rail element and are positioned so that the outer vane is attached to the outer face of the rail and the inner vane is attached to the inner face of the rail. While the outer and inner vane elements may be aligned relative to one another so that they divert the secondary air flow in the same direction both outside and inside of the rail element, the vane elements may be angled in relation to one another, preferably at an angle ranging from ten (10) to forty (40) degrees, so that they will divert the air flow in differing directions. Additionally, the profiles of either or both of the vane elements may be altered to create converging or diverging air flow patterns. A ratio of outer vane element height to inner vane element height (h
o
/h
i
) also may be established to provide an air flow pattern that is optimized for specific burner requirements. The structure of the invention has been found to change the secondary air flow characteristics of the known single register burner so
5
. as to mimic those of the known dual register burner. Previous measurements suggest that certain combustion-generated pollutants are lower for the dual register burners than for their single register counterparts. Thus, the invention, when applied to a known single register burner that has already been put into service, allows the burner to be quickly and inexpensively modified so that the level of its emissions are reduced to a point which is comparable to that of the known dual register burner and so that the flame produced by the modified single register burner is shorter than that of the known dual register burner. The invention also may be used in the known dual register burner in the event that a need should arise to achieve emission standards more stringent than those currently encountered by users of the known dual register burner.
Accordingly, one aspect of the present invention is drawn to a multi-piece spin vane which may be used in an air passage of either a single register or a dual register fossil fuel-fired burner, and this vane is comprised of:
A plate-like, rectangular-shaped rail element oriented in the air passage such that an outer face of the rail element is directed toward an outer wall of the air passage and an inner face of the rail element is directed toward an inner wall of the air passage;
A plate-like outer vane element which has a base edge, leading and trailing edges and an outer edge, and which is fastened at the base edge to the outer face of the rail element so that the outer vane element and the outer face of rail element are perpendicularly aligned; and
A plate-like inner vane element which also has a base edge, leading and trailing edges and an outer edge, and which is fastened to the inner face of the rail element so that the inner vane element and the inner face of the rail element are perpendicularly aligned.
Another aspect of the present invention is drawn to a fossil-fueled burner apparatus having means for providing a fossil fuel to an outlet
LaRose Jeffrey A.
LaRue Albert D.
Sarv Hamid
Waanders Peter W.
Baraona Robert C.
Marich Eric
Price Carl D.
The Babcock & Wilcox Company
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