U.S. patent application number 12/513901 was filed with the patent office on 2010-01-07 for burner with means for changing the direction of fuel flow.
Invention is credited to Jens Peter Hansen, Ib Ohlsen, Lars Skaarup Jensen.
Application Number | 20100003625 12/513901 |
Document ID | / |
Family ID | 39467493 |
Filed Date | 2010-01-07 |
United States Patent
Application |
20100003625 |
Kind Code |
A1 |
Ohlsen; Ib ; et al. |
January 7, 2010 |
BURNER WITH MEANS FOR CHANGING THE DIRECTION OF FUEL FLOW
Abstract
A description is given of a burner for introducing solid, liquid
or gaseous fuel to a burning zone of a kiln, such as a rotary kiln
for manufacturing cement clinker or the like, said burner
comprising a number of substantially concentric ducts (1, 2, 3),
being parallel to the main axis B3 of the burner, for conveying
fuel and primary air to nozzle openings, as well as a number of
additional ducts (4, 6, 7, 8) for conveying solid, fluid or gaseous
fuel to separate nozzle openings, said additional ducts being
located in the central part (10) of the burner. The burner is
characterized in that it comprises means (4a, 5) for changing the
flow direction of the fuel which is introduced via at least one of
the additional ducts in the central part (10) of the burner,
relative to the main axis B3 of the burner, at least in an
ascending direction. This will allow the individual fuel particles
to travel in a curved, approximately ballistic path, thereby
extending the time they can be maintained in the flame. Another
advantage of this configuration of the burner is that the large
particles will attain the highest, and hence the longest, path,
since the path of the smaller particles will to a greater extent
than is the case for the large ones be deflected by the primary air
which is injected via the outer annular primary air nozzle which is
parallel to the main axis of the burner. Hence it will be possible
to achieve a more uniform combustion of all particles, regardless
of their size. It will be possible to change the path of the
particles by altering the velocity or direction of injection.
Inventors: |
Ohlsen; Ib; (Gentofte,
DK) ; Skaarup Jensen; Lars; (Vallensbaek, DK)
; Hansen; Jens Peter; (Aalborg, DK) |
Correspondence
Address: |
Manelii Denison & Selter PLLC
2000 M Street, 7th Floor
Washington DC
DC
20036
US
|
Family ID: |
39467493 |
Appl. No.: |
12/513901 |
Filed: |
October 22, 2007 |
PCT Filed: |
October 22, 2007 |
PCT NO: |
PCT/IB2007/054281 |
371 Date: |
May 7, 2009 |
Current U.S.
Class: |
431/181 |
Current CPC
Class: |
F23D 2900/14481
20130101; F23D 14/22 20130101; F27D 99/0033 20130101; F27B 7/34
20130101; F23D 17/00 20130101 |
Class at
Publication: |
431/181 |
International
Class: |
F23D 17/00 20060101
F23D017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 29, 2006 |
DK |
PA200601564 |
Claims
1-10. (canceled)
11. A burner for introducing solid, liquid or gaseous fuel to a
burning zone of a kiln, such as a rotary kiln for manufacturing
cement clinker or the like, said burner comprising a number of
substantially concentric ducts, which are parallel to a main axis
of the burner, for conveying fuel and primary air to nozzle
openings, and a number of additional ducts for conveying solid,
fluid or gaseous fuel to separate nozzle openings, with said
additional ducts being located in the central part of the burner,
wherein the burner comprises means for changing the flow direction
of the fuel which is introduced via at least one of the additional
ducts in the central part of the burner, relative to the main axis
B.sub.a of the burner, at least partially in an ascending
direction.
12. A burner according to claim 11, wherein the means for changing
the flow direction of the fuel being introduced via at least one of
the additional ducts in the central part of the burner, comprises
an introduction duct which is located at the outlet end of the duct
in question in immediate extension hereof, with its centreline
forming an angle relative to the main axis of the burner.
13. A burner according to claim 12, wherein the introduction duct
is arranged so that it points upward relative to the main axis
B.sub.a of the burner at an angle between 1.degree. and
25.degree.
14. A burner according to claim 12, wherein the introduction duct
is arranged so that it points upward relative to the main axis
B.sub.a of the burner at an angle between 5.degree. and
15.degree..
15. A burner according to claim 12, wherein the introduction duct
is arranged so that it points upward relative to the main axis
B.sub.a of the burner at an angle between 7.degree. and
10.degree..
16. A burner according to claim 11, wherein the means for changing
the flow direction of the fuel which is introduced via at least one
of the additional ducts in the central part of the burner,
comprises an air duct the outlet of which is located immediately at
or at least partially enclosing the duct in question in such a way
that the centre of gravity of the outlet cross-section of the air
duct is displaced in relation to the centre of gravity of the
outlet cross-section of the duct in question.
17. A burner according to claim 12, wherein the means further
comprises an air duct, the outlet of which is located immediately
at or at least partially enclosing the duct in such a way that the
point of gravity of the outlet cross-section of the air duct is
displaced in relation to the centre of gravity of the outlet
cross-section of the duct.
18. A burner according to claim 11, wherein the means for changing
the flow direction of the fuel which is introduced via at least one
of the additional ducts in the central part of the burner comprises
a separate air duct, the outlet of which is immediately at or at
least partially enclosing the duct in question, and forming an
angle relative to the main axis B.sub.a of the burner.
19. A burner according to claim 18, wherein the air duct is
arranged so that it points upward relative to the main axis of the
burner at an angle between 8.degree. and 80.degree..
20. A burner according to claim 18, wherein the air duct is
arranged so that it points upward relative to the main axis of the
burner at an angle between 35.degree. and 60.degree..
21. A burner according to claim 12, wherein the means further
comprises a separate air duct, the outlet of which is immediately
at or at least partially enclosing the duct in question, and
forming an angle relative to the main axis B.sub.a of the
burner.
22. A burner according to claim 21, wherein the air duct is located
so that it points upward relative to the main axis at an angle
between 8.degree. and 80.degree..
23. A burner according to claim 21, wherein the air duct is located
so that it points upward relative to the main axis at an angle
between 35.degree. and 60.degree..
24. A burner according to claim 17, wherein the air duct, having an
outlet immediately at or at least partially enclosing the duct,
forms an angle relative to the main axis B.sub.a of the burner.
Description
[0001] The present invention relates to a burner for introducing
solid, liquid or gaseous fuel to a burning zone of a kiln, such as
a rotary kiln for manufacturing cement clinker or the like, said
burner comprising a number of substantially concentric ducts, which
are parallel to the main axis of the burner, for conveying fuel and
primary air to nozzle openings, and a number of additional ducts
for conveying solid, fluid or gaseous fuel to separate nozzle
openings, with said additional ducts being located in the central
part of the burner.
[0002] Burners of the aforementioned kind are known for example
from EP 965 019 and EP 967 434. These known burners comprise in the
central part one or several ducts for conveying fuel, said ducts
being surrounded by annular, concentric channels for introducing
primary air. These centrally located channels are often used for
introducing alternative fuels such as solid fuels comprising for
example plastics, paper, rubber and wood chips or liquid fuels such
as for example oil or mixtures of solid and/or liquid fuels.
[0003] When for example solid fuel is injected via a fuel duct into
a flame in a rotary kiln for cement manufacturing, it is essential
to ensure that the individual fuel particles are kept suspended for
as long as possible in order to achieve complete combustion of the
majority of the particles before they drop into the material
charge. However, it will rarely be possible to achieve complete
combustion of the largest fuel particles which will drop into the
material charge, with a continuation of the combustion process at
this location. In such cases, it would be advantageous for these
particles to be led so far into the kiln as is practicably possible
in order to achieve full combustion of the particles prior to the
discharge of the material from the kiln, always providing that the
material, as is the case in a typical rotary kiln for manufacturing
of cement, is transported in direction which is opposite to that in
which the fuel is injected. If this is not the case, unburned
particles may cause damage to the material charge in the rotary
kiln. Quite often, solid alternative fuels will have a highly
variable particle size and, as a rule, they will be less finely
comminuted than solid fossil fuels. Also, the comminution of
alternative fuels may be a relatively complex and expensive
process. Therefore, many burners are configured so that a small
amount of the primary air is injected through annular, concentric
ducts surrounding the individual ducts for alternative fuel. Such a
configuration will allow even relatively large particles to remain
suspended until complete combustion has been achieved. In EP 967
434, a description is given of separate annular ducts for primary
air which are concentrically positioned around the ducts for solid
fuel. Such a configuration would make it possible to increase the
time the fuel particles can be maintained in a state of suspension,
thereby leading to improved combustion efficiency. It is also
proposed in this patent application that the primary air is
injected subject to rotation causing the fuel particles to be
scattered further outwards in the cross-sectional area of the
flame, thereby improving combustion efficiency. However,
disadvantages may be associated with the injection of air subject
to rotation since it may cause large particles to be thrust outward
all the way to the point of the flame before complete combustion of
these particles has been achieved. This may entail risk of the fuel
particles dropping through, with attendant risk of the quality of
the material in the kiln being impaired. Also, it is a common
characteristic of the known burners that the fuel is introduced to
the kiln in a flow of direction which is substantially parallel to
the main axis of the burner. In this context, the expression "flow
direction" is taken to mean the direction described, on average, by
the fuel particles in a fuel stream. In cases where the fuel is
introduced subject to rotation, the flow direction of the fuel will
thus coincide approximately with the line of symmetry for the fuel
stream.
[0004] It is the objective of the present invention to provide a
burner by means of which the alternative fuel can be maintained in
the flame for a longer period of time without any of the
aforementioned disadvantages.
[0005] According to the invention this is achieved by a method of
the kind mentioned in the introduction and being characterized in
that the burner comprises means for changing the flow direction of
the fuel which is introduced via at least one of the additional
ducts in the central part of the burner, relative to the main axis
of the burner, at least partially in an ascending direction.
[0006] Hence it will be possible for the individual fuel particles
to travel in a curved, approximately ballistic path, thereby
extending the time they can be maintained in the flame. Another
advantage of this configuration of the burner is that the large
particles will attain the highest, and hence the longest, path,
since the path of the smaller particles will to a greater extent
than is the case for the large ones be deflected by the primary air
which is injected via the outer annular primary air nozzle which is
parallel to the main axis of the burner. Hence it will be possible
to achieve a more uniform combustion of all particles, regardless
of their size. It will be possible to change the path of the
particles by altering the velocity or direction of injection.
[0007] In principle, the means for changing the flow direction of
the fuel may be made up of any suitable means.
[0008] In one embodiment of the invention the means for changing
the flow direction of the fuel which is introduced via at least one
of the additional ducts in the central part of the burner comprises
an injection duct which is located at the outlet point of the duct
in question in immediate extension hereof, with its centreline
forming an angle relative to the main axis of the burner. It is
preferred that the injection duct is located so that it points
upward in relation to the main axis of the burner at an angle
between 1.degree. and 25.degree., preferentially between 5.degree.
and 15.degree. and most preferentially between 7.degree. and
10.degree.. It is further preferred that the lowest point of the
outlet of the injection duct is located at a level above the upper
part of the pipes of the duct in question. The injection duct may
in a special embodiment have an oval cross-section or may otherwise
be configured so that the height/width ratio is less than 1. If
this is the case, the injection velocity may be varied either by
changing the cross-sectional area of the injection duct or by
changing the airflow rate which is injected simultaneously with the
fuel.
[0009] In a second embodiment of the invention, the fuel is
introduced in parallel to the main axis of the burner. In this
embodiment of the invention the means for changing the flow
direction of the fuel which is introduced via at least one of the
additional ducts in the central part of the burner comprises an air
duct, the outlet of which is located immediately at or at least
partially enclosing the duct in question in such a way that the
centre of gravity of the outlet cross-section of the air duct is
displaced in relation to the centre of gravity of the outlet
cross-section of the duct in question. In this embodiment according
to the invention, the change in the flow direction of the fuel is
effected according to a method which involves that the
cross-section of the outlet, or in other words the flow-through
area of the air duct outlet is not uniformly distributed across the
outlet of the fuel duct in question, entailing also that the
quantity of air flowing through the air duct outlet is not
uniformly distributed across the circumference of the fuel duct
outlet in question. Since the greatest movement quantity of the air
will occur in the area or areas of the air duct outlet where the
highest air passage rates occur, the airflow in this area or these
areas will physically impact the fuel so that this flow direction
is changed in direction toward this area or these areas. This
second embodiment of the invention may be combined with the
aforementioned first embodiment.
[0010] In a third embodiment of the invention the fuel is also
introduced in parallel to the main axis of the burner. In this
third embodiment of the invention the means for changing the flow
direction of the fuel which is introduced via at least one of the
additional ducts in the central part of the burner comprises a
separate air duct, the outlet of which is located immediately at or
at least partially enclosing the duct in question, and forming an
angle relative to the main axis of the burner. In this embodiment
the flow direction of the fuel is changed according to a method
whereby the air being injected via the separate air duct forces the
fuel in a different direction determined as a function of the angle
formed by the air duct in relation to the main axis of the burner.
It is preferred that the air duct is fitted so that it points
upward relative to the main axis of the burner at an angle of
between 8.degree. and 80.degree., preferentially between 35.degree.
and 60.degree.. In this embodiment the direction and velocity of
injection will be changed by varying the airflow rate. This third
embodiment of the invention may be combined with one or both of the
embodiments described above.
[0011] The duct 4a, 4 may be configured with an outlet
cross-section which forms an angle which is different from
90.degree. relative to the centreline through the duct. Such a
configuration can be used to effect a change in the direction of
the fuel stream exclusively or in combination with the
above-mentioned embodiments.
[0012] The invention will now be described in further details with
reference to the drawing, being diagrammatical, and where
[0013] FIG. 1 shows a first embodiment of the burner according to
the invention,
[0014] FIG. 2 shows a second embodiment of the burner according to
the invention, and
[0015] FIG. 3 shows a third embodiment of the burner according to
the invention.
[0016] The FIGS. 1-3 show front views as well as sectional views of
three different embodiments of the burner according to the
invention, and they all comprise two substantially concentric ducts
1 and 2 for conveying primary air which are parallel to the main
axis B.sub.a, and a herewith concentric duct 3 for pneumatic
conveyance of coal dust and a central part 10 which comprises a
duct 4 for conveying solid alternative fuel, and a number of
additional ducts or pipes 6, 7 and 8 for ignition gas burner, oil
burner and gas burner, respectively. The burners shown in FIGS. 2
and 3 also comprise an air duct 5 which encloses the duct 4.
[0017] According to the first embodiment of the invention which is
shown in FIG. 1 the burner comprises an introduction duct 4a which
is fitted in extension of the duct 4 for conveying solid
alternative fuel. The introduction duct 4a is arranged so that it
points upward relative to the main axis of the burner at an angle a
of approximately 8.degree. relative to its centreline. As
previously mentioned, the injection velocity of the fuel can be
varied by changing the cross-sectional area of the introduction
duct 4a or by varying the airflow rate which is injected
simultaneously with the fuel.
[0018] According to the second embodiment of the invention which is
shown in FIG. 2, the burner comprises, as mentioned, an air duct 5,
the outlet of which is located so that it encloses the duct 4 for
conveying solid alternative fuel. In this embodiment, the air duct
5 is arranged so that the centre of gravity of the outlet
cross-section of the air duct 5 is displaced upwards relative to
the centre of gravity of the outlet cross-section of the duct 4.
Hence the largest quantity of air will flow through the upper part
of the air duct 5, thereby impacting the fuel stream in upward
direction, hence changing the flow of direction of the fuel in the
upward direction. This is due to the fact that the movement
quantity of the air in the shown embodiment will be greatest in the
upper area of the outlet of the air duct 5. As mentioned in the
introduction, this second embodiment of the invention may be
combined with the first embodiment described above, although this
is not shown in the drawing.
[0019] According to the third embodiment of the invention, which is
shown in FIG. 3, the burner comprises, as mentioned, an air duct 5
the outlet of which is located so that it encloses the duct 4 for
conveying solid alternative fuel. In the shown embodiment the air
duct 5 is arranged so that it points upwards, forming an angle
.beta. of approximately 65.degree. relative to the main axis of the
burner. This will cause the flow direction of the fuel to be
changed in the upward direction due to the fact that the airflow
being injected via the air duct 5 will force the fuel in the upward
direction. As previously mentioned, the direction and velocity of
injection can be changed by varying the airflow rate. This third
embodiment of the invention may as previously mentioned be combined
with one or both of the aforementioned embodiments.
* * * * *