U.S. patent application number 11/372678 was filed with the patent office on 2007-02-22 for method and arrangement for monitoring a burner.
This patent application is currently assigned to AGA AB. Invention is credited to Tomas Ekman, Lennart Rangmark.
Application Number | 20070042302 11/372678 |
Document ID | / |
Family ID | 37757826 |
Filed Date | 2007-02-22 |
United States Patent
Application |
20070042302 |
Kind Code |
A1 |
Ekman; Tomas ; et
al. |
February 22, 2007 |
Method and arrangement for monitoring a burner
Abstract
A method and apparatus for monitoring combustion of a fuel with
an oxidant in an industrial furnace. The fuel and oxidant are
supplied to a burner head, and a burner outlet flame is monitored
by an ultraviolet light detector. At least one fuel channel and at
least two oxidant channels are provided and open at an outer
surface of the burner head that faces the interior of the furnace.
The fuel channel and a first oxidant channel are located at a
predetermined first distance from each other, and the fuel channel
and the second oxidant channel are located closer to each other at
a second distance. The detector is positioned at the fuel channel
or at the second oxidant channel. A fraction of the total amount of
oxidant supplied is supplied to the second oxidant channel, and
oxidant is supplied to the second oxidant channel during the entire
combustion process.
Inventors: |
Ekman; Tomas; (Saltsjo-Boo,
SE) ; Rangmark; Lennart; (Alvsjo, SE) |
Correspondence
Address: |
ALFRED J MANGELS
4729 CORNELL ROAD
CINCINNATI
OH
452412433
US
|
Assignee: |
AGA AB
Lidingo
SE
|
Family ID: |
37757826 |
Appl. No.: |
11/372678 |
Filed: |
March 10, 2006 |
Current U.S.
Class: |
431/75 |
Current CPC
Class: |
F23D 14/22 20130101;
F23D 14/32 20130101; F23N 2229/04 20200101; F23C 9/006
20130101 |
Class at
Publication: |
431/075 |
International
Class: |
F23N 5/00 20060101
F23N005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 19, 2005 |
SE |
0501840-3 |
Claims
1. A method for combustion of a fuel with an oxidant in an
industrial furnace, in which the fuel and the oxidant are supplied
to a burner head and where the flame is monitored by means of a
detector for ultraviolet light, said method comprising the steps
of: providing at least one fuel supply channel and at least two
oxidant supply channels that open at an outlet surface of the
burner head that faces into the furnace; positioning the fuel
supply channel relative to a first oxidant supply channel at a
first distance from each other; positioning the fuel supply channel
and the second oxidant supply channel relative to each other at a
second distance from each other that is smaller than the first
distance; arranging the detector at one of the fuel supply channel
and the second oxidant supply channel at a burner inlet region;
furnishing a fraction of a total supply of oxidant to the second
oxidant supply channel; and maintaining oxidant supply to the
second oxidant supply channel during an entire combustion
process.
2. A method in accordance with claim 1, including the step of
supplying between 4 and 40% of the total supply of oxidant to the
second oxidant supply channel.
3. A method in accordance with claim 1, including the step of
supplying between 5 and 15% of the total supply of oxidant to the
second oxidant supply channel.
4. A method in accordance with claim 1, including the step of
positioning the second oxidant supply channel coaxially with the
fuel supply channel.
5. A method in accordance with claim 1, including the step of
spacing the second oxidant supply channel and the fuel supply
channel from each other and in parallel relationship.
6. A burner for the combustion of a fuel with an oxidant in an
industrial furnace, in which the burner is arranged to supply fuel
and oxidant to the burner head of the burner, and wherein a
detector for ultraviolet light is present to monitor a flame
issuing from the burner head, said burner comprising: at least one
fuel supply channel and at least two oxidant supply channels that
open at an outlet surface of the burner head that faces into the
furnace; wherein the fuel supply channel and a first oxidant supply
channel are positioned at a first distance from each other; wherein
the fuel supply channel and a second oxidant supply channel are
positioned from each other at a second distance from each other
that is smaller than the first distance; wherein the detector is
positioned at one of the fuel supply channel and the second oxidant
channel at a burner inlet region; and wherein a fraction of a total
amount of oxidant supplied to the burner head is supplied to the
second oxidant supply channel.
7. A burner in accordance with claim 6, wherein the burner supplies
between 4 and 40% of the oxidant to the second oxidant supply
channel.
8. A burner in accordance with claim 6, wherein the burner supplies
between 5 and 15% of the oxidant to the second oxidant supply
channel.
9. A burner in accordance with claim 6, wherein the second oxidant
supply channel and the fuel supply channel are coaxial.
10. A burner in accordance with claim 6, wherein the second oxidant
supply channel and the fuel supply channel are spaced from each
other and in parallel relationship.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method and an arrangement
for monitoring a burner, principally burners used in industrial
furnaces.
[0003] 2. Description of the Related Art
[0004] One way of solving the problem of the formation of NO.sub.x
during the combustion of fossil fuels is to inject gases into the
combustion zone at a high rate of flow. Gaseous fuel and a gaseous
oxidant are injected into the combustion zone at a distance from
each other. The gases are injected into a burner head through
lances that are provided with nozzles. The injected gases will be
diluted with combustion products since the gases are injected at a
distance from each other. The dilution, together with the fact that
the diluted gases are first mixed at a certain distance away from
the burner head, means that the gases react with each other in a
combustion process that proceeds at a slower rate than that of
conventional combustion due to a lower concentration of the gases.
Such combustion ensures that the formation of NO.sub.x is
suppressed.
[0005] For reasons of safety, a burner must be monitored for the
presence of a flame during operation. Such monitoring usually takes
place through a UV sensor, which is a sensor that is sensitive to
ultraviolet radiation. The UV sensor is normally mounted in the
burner in such a way that the sensor sees a part of a flame that is
present.
[0006] The flame becomes longer and more spread out through the
method of combustion described above, and thus become less visible.
That makes the detection of a flame by means of the UV sensor
considerably more difficult. Furthermore, the method of combustion
described above requires that the furnace first be heated to the
spontaneous ignition temperature of the gases before combustion by
the method described above can be commenced. In that case the
furnace is operated at a temperature below approximately
800.degree. C. For reasons of safety, a burner of the type
identified above cannot be used during a heating phase because a
flame of the type described is difficult to detect at a temperature
below 800.degree. C., whereas at the same time safety regulations
specify that UV monitoring is to take place at temperatures below
800.degree. C.
[0007] The present invention solves that problem.
SUMMARY OF THE INVENTION
[0008] The present invention thus relates to a method for
monitoring a burner during the combustion of a fuel with an oxidant
in an industrial furnace. The fuel and the oxidant are supplied to
a burner head and the flame is monitored by means of a detector for
ultraviolet light. At least one channel for the supply of fuel and
at least two channels for the supply of oxidant are present in the
burner and extend to openings at a surface of the burner head that
faces into the furnace. The channel for fuel and a first channel
for oxidant are spaced from each other, and the channel for fuel
and a second channel for oxidant is spaced from the fuel channel at
a distance that is smaller than the spacing between the first
oxidant channel and the fuel channel. The detector is arranged
upstream of the burner outlet at the channel for fuel or at the
second channel for oxidant. A fraction of the total amount of
oxidant that is supplied to the burner is supplied to the second
oxidant channel, and the oxidant is supplied to the second oxidant
channel during the entire combustion process.
[0009] The invention also relates to a burner for carrying out the
method.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The structure, operation, and advantages of the present
invention will become further apparent upon consideration of the
following description, taken in conjunction with the accompanying
drawings in which:
[0011] FIG. 1 shows schematically a longitudinal cross section of a
burner head in accordance with the invention; and
[0012] FIGS. 2A, 2B, and 2C show alternative embodiments of a
central part of the outlet of the burner head as viewed from the
right side of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0013] FIG. 1 shows the burner head of a burner for the combustion
of a fuel with an oxidant in an industrial furnace. The burner is
arranged so that fuel and oxidant are supplied to the burner head
1. A UV detector 2 for the detection of ultraviolet light is
present outside of the burner head 1, at the upstream side and
adjacent to a channel that extends through the burner head, in
order to monitor light provided by a flame at the burner
outlet.
[0014] In accordance with the invention, at least one channel 3 is
present for the supply of fuel and at least two channels 4, 5 for
the supply of oxidant. Channel outlet openings are provided at
outlet surface 6 of the burner head that faces the furnace interior
(not shown). The fuel channel 3 and a first oxidant channel 5 are
spaced from each other at a predetermined distance, and the fuel
channel 3 and the second oxidant channel 4 are located closer to
each other than the spacing between fuel channel 3 and oxidant
channel 5. Fuel is introduced into fuel channel 3 at fuel inlet 3a,
and oxidant is introduced into oxidant channel 4 at oxidant inlet
4a.
[0015] FIG. 1 also shows a third oxidant channel 7 in burner head
1.
[0016] The UV detector 2 is positioned adjacent an upstream side of
the fuel channel 3 or adjacent an upstream side of the second
oxidant channel 4. It is appropriate that the UV detector is
arranged at the end of a channel that lies farthest away from the
furnace, and is so positioned that UV light from the flame passes
into the channel and impinges upon the detector. The detector is
connected to a detector circuit (not shown), by means of which
circuit the presence or absence of a flame can be determined. In
the case in which a flame is not detected, the supply of fuel and
oxidant is interrupted.
[0017] When fuel of a low heating value, such as blast furnace gas,
is used, it can be advantageous, when the detector 2 is arranged at
fuel channel 3, to arrange the detector at a special pipe that runs
within fuel channel 3.
[0018] Furthermore, the burner is arranged to supply to the second
oxidant channel 4 a fraction of the total amount of oxidant
supplied to support the combustion process.
[0019] Fuel channel 3 and the second oxidant channel 4, which are
located closer to each other than are fuel channel 3 and first
oxidant channel 5, are so positioned that a stable flame that
begins close to the burner head outlet can be maintained.
[0020] Fuel channel 3 and the first oxidant channel 5 are located
at such a distance from each other that the gases that are injected
are diluted with combustion gases adjacent to the burner head
outlet. That dilution, together with the fact that the diluted
gases are first mixed at a certain distance away from the burner
head outlet, means that the gases react with each other in a
combustion process in such a way that the formation of NO.sub.x is
suppressed, as has been described above.
[0021] It is most advantageous to use with the present invention
oxidants that have an O.sub.2 content that is greater than 85%. The
fuel can be natural gas, propane, butane, gasol, heating oil,
etc.
[0022] The oxidant is injected into the combustion zone through one
or several nozzles designed as straight pipes, or as Laval nozzles,
or as Venturi nozzles. A preferred pressure for the oxidant is an
excess pressure of at least 2 bar above that of the fuel pressure.
The greater that oxidant pressure, the greater will be the
suppression of the formation of NO.sub.x that is achieved. A
preferred oxidant pressure for normal applications is 4-5 bar. The
fuel is injected through normal nozzles at the pressure that is
available.
[0023] The distance between fuel channel 3 and the first oxidant
channel 5 should exceed approximately 40 mm in order to achieve the
desired effect.
[0024] When oxidant is supplied to the first oxidant channel 5, the
supply of oxidant to the second oxidant channel 4 continues. In
that way a stable combustion process also is obtained for fuel and
the oxidant that is supplied through the first oxidant channel
5.
[0025] As has been described above, the detector 2 is arranged at
the fuel channel 3 or at the second oxidant channel 4. Both of
those channels open out close to each other at the outlet side of
the burner head that faces the furnace, and for that reason
detection of a flame that arises from combustion of fuel with
oxidant from the second oxidant channel 4 will be extremely secure.
Fuel and the oxidant from the first oxidant channel 5 will be
combusted, provided that a flame is present.
[0026] Thus, an extremely secure indication of combustion is
obtained. That means that the present method and arrangement make
possible the detection of the flame by a UV detector under all
conceivable operating temperature conditions.
[0027] In accordance with one preferred design, between 4 and 40%
of the oxidant is supplied by the second oxidant channel 4. That
amount of oxidant provides a stable flame, while at the same time
the fraction of oxidant is sufficiently small not to adversely
influence the formation of NO.sub.x.
[0028] In accordance with a further preferred design, between 5 and
15% of the oxidant is supplied through the second oxidant channel
4.
[0029] FIGS. 2A, 2B, and 2C show different positions of the fuel
channel 3 and the second oxidant channel 4, as viewed from the
right in FIG. 1 at the area of the box indicated in FIG. 1.
[0030] In accordance with one preferred design shown in FIGS. 2A
and 2B, the second oxidant channel 4 and the fuel channel 3 are
coaxial.
[0031] In accordance with an alternative design shown in FIG. 2C,
the second oxidant channel 4 and the fuel channel 3 are spaced from
each other and are parallel to each other.
[0032] It is clear that the channels can be designed in another way
and that there can be other channels without deviating from the
innovative concept.
[0033] Furthermore, it is clear that one skilled in the art will
have no difficulty in determining dimensions and positions for the
channels such that the technical effects described above are
obtained.
[0034] Although particular embodiments of the present invention
have been illustrated and described, it will be apparent to those
skilled in the art that various changes and modifications can be
made without departing from the spirit of the present invention. It
is therefore intended to encompass within the appended claims all
such changes and modifications that fall within the scope of the
present invention.
* * * * *