Information
-
Patent Grant
-
6189812
-
Patent Number
6,189,812
-
Date Filed
Wednesday, February 2, 200024 years ago
-
Date Issued
Tuesday, February 20, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Sughrue, Mion, Zinn Macpeak & Seas, PLLC
-
CPC
-
US Classifications
Field of Search
US
- 239 5876
- 239 5875
- 239 590
- 239 591
- 239 5905
- 239 423
- 239 424
- 239 4245
- 239 552
- 239 553
- 239 5535
- 239 498
- 239 518
- 239 290
- 239 299
- 110 104 B
- 110 265
- 110 263
- 110 297
- 110 347
- 431 8
- 431 10
- 431 12
- 029 890142
- 122 333
-
International Classifications
-
Abstract
A nozzle for injecting pulverized coal into the combustion chamber of a thermal power plant boiler includes a first metal housing and a second metal housing surrounding the first housing and defining with it an annular space through which passes a secondary airflow. The first housing channels a primary airflow mixed with pulverized coal. The interior of the first housing is divided by refractory steel splitter plates fixed into the lateral faces thereof by nesting them therein and immobilizing them by way of keys. The second housing is fixed to the first housing by lugs disposed around the top and bottom faces of the first housing. Each housing is made up of two half-shells made from refractory steel plate bent to shape and welded.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an aimable nozzle for injecting pulverized coal into the combustion chamber of a thermal power plant boiler, the nozzle including a first metal housing in the shape of a truncated prism having a top face, a bottom face and two lateral faces, a second metal housing in the shape of a truncated prism coaxially surrounding the first housing and defining therewith an annular space through which passes a flow of secondary air, and two pivots for rotation about an axis perpendicular to the lateral faces of the first housing, wherein the first housing channels a flow of primary air mixed with pulverized coal, the housings are fastened to each other and the interior of the first housing is divided by parallel refractory steel splitter plates perpendicular to the lateral faces of the first housing.
2. Description of the Prior Art
As is well known in the art, this type of nozzle is designed to be fitted to a pulverized coal burner mounted on the walls of a combustion chamber of a thermal power plant boiler, between an ashbox and heat exchangers.
It directs pulverized coal mixed with primary air into the combustion chamber. The nozzle is aimable so that it can be inclined in a vertical plane so that the air can be directed into an area of the combustion chamber at a greater or lesser distance from the screens, in order to adjust the heating power of the boiler.
Until now the first housing has been made in one piece by casting it in refractory steel, the second housing has been made from refractory steel plate bent to shape and welded and the splitter plates inside the first housing have been welded to its lateral faces. A nozzle of this kind is exposed to very high thermal stresses. In use, the temperature in front of the nozzle (at the face of the nozzle through which the primary and secondary airflows exit) can be as high as 900° C. to 1000° C., but the temperature is only 200° C. to 300° C. at the rear and the depth is only around 400 mm. Because of radiation phenomena inside the combustion chamber, areas in front of the nozzle can be exposed to high but different temperatures. It has been noticed that these high thermal stresses lead to deformation of the component parts of the nozzle, cracks in the cast components and ruptures of the weld between the splitter plates and the lateral faces of the first housing.
The object of the invention is to propose an aimable nozzle for injecting pulverized coal into the combustion chamber of a thermal power plant boiler which has improved resistance to these thermal stresses.
The basic idea of the invention is a nozzle consisting of welded or nested plates.
SUMMARY OF THE INVENTION
The invention provides an aimable nozzle for injecting pulverized coal into the combustion chamber of a thermal power plant boiler, the nozzle including a first metal housing in the shape of a truncated prism having a top face, a bottom face and two lateral faces, a second metal housing in the shape of a truncated prism coaxially surrounding the first housing and defining therewith an annular space through which passes a flow of secondary air, and two pivots for rotation about an axis perpendicular to the lateral faces of the first housing, wherein the first housing channels a flow of primary air mixed with pulverized coal, the housings are fastened to each other and the interior of the first housing is divided by parallel refractory steel splitter plates perpendicular to the lateral faces of the first housing, and wherein:
the splitter plates are fixed to the lateral faces of the first housing by nesting their ends in openings provided in the lateral faces and the ends of the plates pass through the openings to receive immobilizing keys disposed in the annular space, allowing each splitter plate some play in a direction perpendicular to the lateral faces of the first housing;
the second housing is fixed to the first housing by lugs disposed on the top face and the bottom face of the first housing and in the space between the housings;
the first housing is made up of two half-shells made from refractory steel plate bent to shape and welded together in a median transverse plane parallel to the lateral faces of the first housing, and the second housing is made up of two half-shells made from refractory steel plate bent to shape and welded to each other in a median transverse plane perpendicular to the lateral faces of the first housing; and
the pivots are welded to the lateral faces of the first housing and pass without contact through the second housing by means of orifices provided therein.
One embodiment of the invention is described in detail hereinafter and shown in the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a highly schematic profile view in elevation of part of a burner casing fitted to the combustion chamber of a thermal power plant boiler and including aimable nozzles for injecting pulverized coal.
FIG. 2
is a diagrammatic front view of a nozzle in accordance with the invention.
FIG. 3
is a diagrammatic top view of a nozzle in accordance with the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1
shows part of a burner casing
1
which is fixed to angle irons
2
of a combustion chamber of a thermal power plant boiler. The casing is vertical when mounted in the combustion chamber of the boiler, as shown in FIG.
1
.
The casing
1
includes a series of compartments
3
,
4
,
5
,
6
,
7
which are open toward the inside of the combustion chamber and through which air is fed into the interior of the combustion chamber, the cross section of each compartment being substantially rectangular. Two adjacent compartments are separated by a plate
8
lying in a horizontal plane. The compartments of the casing are closed on the side external to the combustion chamber by registers (not shown).
An aimable nozzle is disposed at the opening (on the combustion chamber side) of each compartment to channel and direct air toward the interior of the combustion chamber.
As shown in
FIG. 1
, the compartments are different sizes depending on whether they receive a simple secondary air nozzle like the nozzles
9
,
9
′ or a fuel oil burner nozzle like the nozzle
10
or a pulverized coal burner nozzle like the nozzles
11
,
11
′.
In the arrangement shown in
FIG. 1
, the nozzle
10
of a fuel oil burner is adjacent two simple secondary air nozzles
9
,
9
′.
Each nozzle
9
,
9
′,
10
,
11
,
11
′ can be rotated about a respective horizontal axis
9
A,
9
′A,
10
A,
11
A,
11
′A in order to incline it in a vertical plane to direct air in a particular direction toward the center of the combustion chamber, between the top and bottom of the combustion chamber.
The gap between the nozzles in the casing is imposed by the operating characteristics of the combustion chamber. It is generally small because it is always a requirement to concentrate the burners to obtain the greatest possible heating power. Also, the nozzles practically shut off the openings of the compartments to enable fine adjustment of the draft and the gap left by a nozzle in the opening of a compartment can if necessary be filled in with wedges
12
.
Note that in the burner casing arrangement shown in
FIG. 1
the nozzles
9
,
9
′ and
10
and the fuel oil burner are mounted on and demounted from the casing from inside the combustion chamber but the nozzles
11
,
11
′, each of which is fastened to a pulverized coal burner, are mounted on and demounted from the casing from outside the combustion chamber.
The mechanism for inclining the nozzles
9
,
9
′ and
10
includes a vertical link
13
parallel to the casing and common to the three adjacent nozzles. The link
13
connects the pivots
9
B,
9
′B,
10
B (which are offset from the nozzle rotation axes) of the respective nozzles
9
,
9
′,
10
so that inclining any of the three nozzles
9
,
9
′ or
10
simultaneously inclines the other two nozzles by the same amount.
FIG. 1
shows that the pivots for maneuvering the nozzles
9
,
9
′,
10
are disposed at the ends of lever arms each of which rotates at the other end about the rotation axis
9
A,
9
′A,
10
A of the corresponding nozzle
9
,
9
′,
10
and rotation of which in the upward or downward direction drives movement of the corresponding nozzle in the same direction. For example, moving the actuator link
14
articulated to the nozzle
10
substantially horizontally in translation to incline the nozzle
10
inclines all three nozzles
9
,
9
′,
10
. Each nozzle
11
and
11
′ is inclined by its own actuator link
15
,
15
′.
FIGS. 2 and 3
show the welded or nested plate design of a nozzle in accordance with the invention for injecting pulverized coal, such as the nozzles
11
,
11
′ in FIG.
1
. As mentioned above, a nozzle of this kind is articulated to the body of a pulverized coal burner so that it can be inclined toward the top or toward the bottom of the combustion chamber of the boiler. The rotation axis A is shown in
FIGS. 2 and 3
and its position is shown at
11
A,
11
′A in FIG.
1
.
The aimable nozzle in accordance with the invention includes a prism-shaped first metal housing
30
with a rectangular base, truncated parallel to its base and having a top face
30
A, a bottom face
30
B and two lateral faces
30
C,
30
D. The housing
30
channels the flow of primary air mixed with pulverized coal.
The nozzle also includes a prism-shaped second metal housing
31
with a rectangular base, truncated parallel to its base, surrounding the first housing
30
coaxially and defining therewith an annular space
32
through which a flow of secondary air passes. The second housing has a top face
31
A, a bottom face
31
B and two lateral faces
31
C,
31
D. The faces
30
C,
30
D,
31
C and
31
D are parallel to each other. The angle of the prism forming the second housing can be slightly less than the angle of the prism forming the first housing so that the annular space widens in the direction from the rear of the nozzle (indicated by AR in
FIG. 1
) toward the front of the nozzle (indicated by AV in
FIG. 1
) from which the airflows exit. Moreover, as shown in
FIG. 3
, the second housing
31
is shallower in the direction of the longitudinal axis B than the first housing
30
to encourage cooling of the front of the latter by the secondary airflow.
Each of the two housings
30
and
31
is made up of two half-shells made of refractory steel plate that has been bent to shape. The housing
30
is made up of two half-shells
30
E and
30
F each of which has a substantially U-shaped cross section on the axis B and which are assembled by two continuous penetrating welds
33
,
33
′ on the faces
30
A,
30
B of the housing
30
. These welds lie in a median plane parallel to the faces
30
C,
30
D of the housing
30
and passing through the axis B.
The housing
31
consists of two half-shells
31
E and
31
F made of refractory steel plate that has been bent to shape and which each have a substantially U-shaped cross section on the axis B and are assembled by two continuous penetrating welds
34
,
34
′ on the faces
31
C,
31
D of the housing
31
. These welds lie in a median plane perpendicular to the faces
30
C,
30
D of the housing
30
and passing through the axis A.
This design of the housing of the nozzle eliminates fillet welds which cause many problems of mechanical strength when exposed to thermal stress.
The two housings
30
and
31
are fixed together by fixing lugs
36
welded to the faces
30
A and
30
B of the housing
30
and to the faces
31
A,
31
B of the housing
31
, inside the annular space
32
. These lugs are disposed in two rows of three parallel to the axis B on the faces
30
A and
30
B of the housing
30
, as shown in FIG.
3
. It is preferable for the rows of lugs
36
to be near the median vertical axis C of the nozzle to enable relative displacement of the lateral faces
30
C,
30
D relative to the lateral faces
31
C,
31
D caused by thermal stresses.
The nozzle further includes two pivots
37
A and
37
B for rotation about the axis A perpendicular to said lateral faces of the first housing, here the axis A. The pivots
37
A and
37
B are welded to the faces
30
C and
30
D of the housing
30
to the rear of the nozzle and pass without contact through the housing
31
by means of orifices therein to enable relative movement of the lateral faces of the housings
30
and
31
caused by thermal stresses.
The interior of the housing
30
is divided by parallel refractory steel splitter plates
38
,
39
perpendicular to the faces
30
C and
30
D. These plates guide the pulverized coal into the combustion chamber when the nozzle is inclined relative to a horizontal position. According to the invention, the splitter plates
38
and
39
are fixed to the lateral faces
30
C and
30
D of the housing
30
by nesting their ends in openings provided in the lateral faces. The ends of the plates pass through said openings and receive immobilizing keys
40
. The immobilizing keys are in the form of wedges forced into holes at the end of the splitter plates, for example. They are disposed in the annular space
32
, allowing each splitter plate some play in a direction perpendicular to the lateral faces
30
C and
30
D to enable them to accommodate differential expansion of the faces of the housing
30
.
The central splitter plate
41
, which extends along the rotation axis A, is fixed to the lateral faces
30
C and
30
D of the housing
30
, by welding its ends thereto, to increase the rigidity of the nozzle without compromising its resistance to thermal stresses. However, the central splitter plate has a corrugated shape enabling it to accommodate expansion of the component parts of the nozzle without stressing the welds.
The construction of the nozzle in accordance with the invention contributes to increasing its mechanical resistance to thermal stresses by reducing the effects of deformation of its component parts. As a result the service life of a nozzle of this kind is increased compared to a refractory steel casting.
Claims
- 1. An aimable nozzle for injecting pulverized coal into the combustion chamber of a thermal power plant boiler, said nozzle including a first metal housing in the shape of a truncated prism having a top face, a bottom face and two lateral faces, a second metal housing in the shape of a truncated prism coaxially surrounding said first housing and defining therewith an annular space through which passes a flow of secondary air, and two pivots for rotation about an axis perpendicular to said lateral faces of said first housing, wherein said first housing channels a flow of primary air mixed with pulverized coal, said housings are fastened to each other and the interior of said first housing is divided by parallel refractory steel splitter plates perpendicular to said lateral faces of said first housing, and wherein:said splitter plates are fixed to said lateral faces of said first housing by nesting their ends in openings provided in said lateral faces and the ends of said plates pass through said openings to receive immobilizing keys disposed in said annular space, allowing each splitter plate some play in a direction perpendicular to said lateral faces of said first housing; said second housing is fixed to said first housing by lugs disposed on said top face and said bottom face of said first housing and in said space between said housings; said first housing is made up of two half-shells made from refractory steel plate bent to shape and welded together in a median transverse plane parallel to said lateral faces of said first housing, and said second housing is made up of two half-shells made from refractory steel plate bent to shape and welded to each other in a median transverse plane perpendicular to said lateral faces of said first housing; and said pivots are welded to said lateral faces of said first housing and pass without contact through said second housing by means of orifices provided therein.
- 2. A nozzle as claimed in claim 1 further including a central splitter plate which extends along said rotation axis, has a corrugated shape and is fixed to said lateral faces of said first housing by welding its ends thereto.
Priority Claims (1)
Number |
Date |
Country |
Kind |
99 03961 |
Mar 1999 |
FR |
|
US Referenced Citations (5)
Foreign Referenced Citations (2)
Number |
Date |
Country |
2 689 211 A1 |
Oct 1993 |
FR |
2 240 619 |
Aug 1991 |
GB |