U.S. patent application number 12/669971 was filed with the patent office on 2010-07-22 for premixing burner and method for operating a premixing burner.
Invention is credited to Berthold Kostlin, Martin Lenze, Bernd Prade.
Application Number | 20100183991 12/669971 |
Document ID | / |
Family ID | 38984079 |
Filed Date | 2010-07-22 |
United States Patent
Application |
20100183991 |
Kind Code |
A1 |
Kostlin; Berthold ; et
al. |
July 22, 2010 |
Premixing burner and method for operating a premixing burner
Abstract
A method for operating a premixing burner is provided. The
premixing burner includes a premixing zone. An air mass flow and
fuel may be injected into the premixing zone, and a potential hot
gas backflow area may form. A fluid containing no fuel is injected
downstream from the fuel injection into the premixing zone in order
that a hot gas backflow area does not form. A premixing burner
including a premixing zone is also provided.
Inventors: |
Kostlin; Berthold;
(Duisburg, DE) ; Lenze; Martin; (Essen, DE)
; Prade; Bernd; (Mulheim, DE) |
Correspondence
Address: |
SIEMENS CORPORATION;INTELLECTUAL PROPERTY DEPARTMENT
170 WOOD AVENUE SOUTH
ISELIN
NJ
08830
US
|
Family ID: |
38984079 |
Appl. No.: |
12/669971 |
Filed: |
July 23, 2008 |
PCT Filed: |
July 23, 2008 |
PCT NO: |
PCT/EP2008/059658 |
371 Date: |
January 21, 2010 |
Current U.S.
Class: |
431/9 ; 110/348;
431/182; 431/8 |
Current CPC
Class: |
F23L 7/00 20130101; F23D
11/383 20130101; F23R 3/14 20130101; F23D 2900/14021 20130101; F23C
7/004 20130101; F23C 2900/07001 20130101; F23L 2900/07002 20130101;
F23R 3/286 20130101; F23L 2900/07009 20130101 |
Class at
Publication: |
431/9 ; 431/8;
110/348; 431/182 |
International
Class: |
F23D 14/24 20060101
F23D014/24; F23C 7/00 20060101 F23C007/00; F23C 5/08 20060101
F23C005/08; F23L 7/00 20060101 F23L007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 27, 2007 |
EP |
07014820.0 |
Claims
1.-18. (canceled)
19. A method for operating a premixing burner including a premixing
zone, the method comprising: injecting an air mass flow and fuel
into the premixing zone wherein a hot gas flowback region may form;
and injecting a fluid containing no fuel into the premixing zone
downstream from the fuel injection.
20. The method as claimed in claim 19, wherein the fluid is
injected along a surface of the premixing zone located in the
potential hot gas flowback region, and wherein the fluid is
injected in a main direction of air mass flow into the premixing
zone.
21. The method as claimed in claim 19, wherein the fuel is injected
at right angles to the main direction of air mass flow into the
premixing zone.
22. The method as claimed in claim 19, wherein the premixing zone
comprises a cone side and a hub side, and wherein the fuel is
injected into the premixing zone on the cone side and/or on the hub
side.
23. The method as claimed in claim 19, wherein the fuel is injected
into the premixing zone via a swirler vane.
24. The method as claimed in claim 19, wherein the fuel is a
syngas.
25. The method as claimed in claim 19, wherein the fluid is
air.
26. The method as claimed in claim 25, wherein a proportion of 10
percent of an overall air supplied to the premixing zone is
injected along the surface of the premixing zone located in the hot
gas flowback region.
27. The method as claimed in claim 19, wherein the fluid is an
inert gas.
28. The method as claimed in claim 27, wherein the inert gas is a
noble gas, carbon dioxide, water vapor or nitrogen.
29. A premixing burner, comprising: a premixing zone; an air swirl
generator including an air inlet; and a fuel nozzle, wherein a fuel
may be injected through the fuel nozzle into an air mass flow
swirled by the air swirl generator in the premixing zone where a
hot gas flowback region may form, and wherein a surface of the
premixing burner in the potential hot gas flowback region includes
an opening through which a fluid may be injected into the premixing
zone.
30. The premixing burner as claimed in claim 29, wherein the
opening is connected in such a way via a fluid channel to the air
inlet leading to the air swirl generator that a portion of the air
mass flow may be injected through the opening as the fluid into the
premixing zone.
31. The premixing burner as claimed in claim 29, wherein the
premixing zone comprises a cone side and a hub side, and wherein
the premixing zone also comprises a plurality of fuel nozzles on
the cone side and/or the hub side of the premixing zone.
32. The premixing burner as claimed in claim 29, wherein the
plurality of fuel nozzles are arranged in one or more rows lying
behind one another downstream of the air swirl generator.
33. The premixing burner as claimed in claim 29, wherein the
plurality of fuel nozzles and/or a plurality of openings are
located in the air swirl generator.
34. The premixing burner as claimed in claim 33, wherein the fuel
is injected via a fluid flow channel through the plurality of
openings into the premixing zone, and wherein the plurality of
openings are located in a main direction of air mass flow
downstream from the plurality of fuel nozzles.
35. The premixing burner as claimed in claim 29, wherein the
plurality of fuel nozzles are embodied as a plurality of round
holes.
36. The premixing burner as claimed in claim 29, wherein the
plurality of fuel nozzles are designed so that the fuel may be
injected at right angles to the main direction of air mass flow
into the premixing zone.
37. The premixing burner as claimed in claim 29, wherein the fuel
is a syngas.
38. The premixing burner as claimed in claim 29, wherein the fluid
may be injected into the premixing zone through a plurality of
openings in the main direction of air mass flow, and wherein the
fluid is injected into the premixing zone along the surface of the
premixing zone.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the US National Stage of International
Application No. PCT/EP2008/059658, filed Jul. 23, 2008 and claims
the benefit thereof. The International Application claims the
benefits of European Patent Office application No. 07014820.0 EP
filed Jul. 27, 2007. All of the applications are incorporated by
reference herein in their entirety.
FIELD OF INVENTION
[0002] The present invention relates to a premixing burner,
especially a syngas premixing burner, and to a method for operating
a premixing burner.
BACKGROUND OF INVENTION
[0003] Premixing burners typically comprise a premixing zone in
which air and fuel are mixed before the mixture is directed into a
combustion chamber. The mixture burns in said chamber, with a hot
gas under increased pressure being generated. The hot gas is
transferred on to the turbine. The primary consideration when
operating premixing burners is to keep nitrous oxide emissions low
and to avoid a flame blowback.
[0004] Syngas premixing burners are characterized by syngases being
used as a fuel in them. Compared to the classical turbine fuels of
natural gas and oil which essentially consist of hydrocarbons, the
combustible elements of the syngases are essentially carbon
monoxide and hydrogen. Depending on the gasification method and the
overall plant concept, the heating value of the syngas is around 5
to 10 times smaller than that of natural gas.
[0005] As well as the stoichiometric combustion temperature of the
syngas the mixture quality between syngas and air at the flame
front is a significant influencing variable for avoiding
temperature peaks and thereby for minimizing thermal nitrous oxide
formation.
[0006] The main elements of the syngases, in addition to carbon
monoxide and hydrogen, are also inert components. The inert
components involved are nitrogen and/or water vapor and where
necessary also carbon dioxide. As a consequence of the low heating
value, high volume flows of combustion gas must accordingly be
introduced into the combustion chamber. The result of this is that
far greater injector cross-sections are required for the combustion
of low-calorific fuels such as syngases for example than with
conventional high-calorific combustion gases.
[0007] The air mass flow introduced into the combustion chamber is
typically swirled with the aid of an air swirl generator. The fuel
is injected into this swirled air mass flow via one or more rows of
circular holes arranged next to one another or behind one
another.
[0008] To guarantee an adequate mixing of air and fuel a sufficient
penetration depth of the individual jets of fuel into the air mass
flow is necessary. Compared to high-calorific burner gases such as
natural gas, correspondingly larger, free injection cross sections
are required. The result of this is that the fuel jets disturb the
sensitive air flow, which in the final analysis leads to a local
detachment of the air flow in the feedback region of the fuel jets.
The flowback regions forming within the burner are undesired and
especially to be avoided at all costs for the combustion of
highly-reactive syngas. In the extreme case these local flowback
regions lead within the mixture zone of the burner to a flame
blowback in the premix zone and thereby to damage to the
burner.
[0009] The risk of flame blowback can be largely avoided by
highly-reactive syngases being burned in diffusion mode. To realize
low nitrous oxide emissions however heavy thinning with inert
gases, preferably with steam, is necessary. In the case of a
premixing combustion the formation of trail regions or hot gas
flowback regions within the burner can be reduced by suitable
shaping of the injection holes, but not basically avoided.
[0010] In EP 1 614 963 A1, for reducing the nitrous oxide emissions
and for preventing flame blowback in the combustion of
low-calorific fuels for the operation of a gas turbine, a method is
proposed in which a low-calorific fuel is premixed with the air in
stages.
[0011] In EP 1 614 967 A1 a further method for combustion of a
low-calorific fuel for the operation of a gas turbine is proposed
in which, within the framework of a pre-mixing, the low-calorific
fuel is premixed with a low-calorific fuel-air mixture and a
conversion of the low-calorific fuel-air mixture is avoided.
[0012] Specifically for preventing flame blowbacks, a gas turbine
with an annular combustion chamber is proposed in EP 1 507 120 A1,
in which a swirl grid is arranged in a combustion air inlet area
around the entire circumference of the annular combustion chamber,
whereby a higher flow speed of the incoming combustion air is
achieved compared to individual air inlet areas each with a swirl
grid. This gives a higher security against flame blowbacks and a
lower tendency for the formation of combustion vibrations.
SUMMARY OF INVENTION
[0013] To guarantee a secure premixing operation, a flow detachment
or a flowback region within the premix zone of the burner is to be
avoided at all costs. At the least however potential flowback
regions are to be designed such that no damage is caused to the
burner. As a rule the flowback regions occur in zones close to the
wall in the trail of the fuel gas jets.
[0014] In respect of nitrous oxide minimization the addition of
inert mass flows as a thinning medium into the air mass flow or the
fuel mass flow (quenching) is usual. The use of the leaner premix
technology makes it possible to reduce the quantity of the
quenching medium employed, which enhances the economy of the plant.
However the lack of inerting then means that the fuel is highly
reactive.
[0015] The object of the present invention is to provide an
advantageous method for operating a premixing burner in which the
formation of hot gas flowback regions is avoided. A further object
of the present invention is to provide an advantageous premixing
burner.
[0016] These objects are achieved by a method for operating a
premixing burner as claimed in the claims and a premixing burner as
claimed in the claims. The dependent claims contain further
advantageous embodiments of the invention.
[0017] The inventive method relates to a premixing burner which
comprises a premixing zone. An air mass flow and fuel are injected
into the combustion chamber, in which case a potential hot gas
flowback region can form. The inventive method is characterized in
that a fluid containing no fuel is injected into the premixing zone
downstream of the fuel injection.
[0018] By the local injection of for example cold air into the
trail or flowback regions, the formation of said regions within the
premixing zone of the burner is largely prevented. And least the
fuel in these regions is quenched and cooled off to the extent that
no reaction or no ignition of the fuel-air mixture within the
premixing zone of the burner can occur. This makes a secure
premixing operation of the burner possible.
[0019] In particular the fluid can be injected along the surface
located in the potential hot gas flowback region of the premixing
zone in the main direction of flow into the premixing zone. The
injection of a fluid along the component surface in the main
direction of flow prevents the actual formation of the hot gas
flowback region and/or quenches and cools the fuel-air mixture at
this location such that no ignition conditions obtain.
[0020] The fuel can especially be injected at right angles to the
main flow direction of the air mass flow into the premixing zone,
which is advantageous in respect of the basic mixing of air and
fuel. Basically there is the option of injecting the fuel on the
cone side and/or on the hub side into the premixing zone.
Furthermore the fuel can be injected via at least one swirler vane
into the premixing zone. The fuel concerned can especially be a
syngas.
[0021] The fluid injected along the surface located in the
potential hot gas flowback region into the premixing zone can for
example be air or an inert gas. Gases with very low reaction
capabilities, which are only involved in a few chemical reactions
for example, are referred to as inert gases. In particular carbon
dioxide, water vapor, nitrogen, but also all noble gases can be
used as an inert gas. The use of an inert gas is especially
suitable if ignition conditions for easily-ignitable fuels are to
be avoided.
[0022] When air is used as a fluid injected into the premixing zone
it is advantageous to use air of the air mass flow supplied to the
premixing zone in any event. For example a proportion of 10% of the
overall air fed to the premixing zone can be split off and injected
into the latter along the surface of the premixing zone located in
the potential hot gas flowback region. The proportion of air
injected along the surface of the premixing zone located in the
potential hot gas flowback region can be selected as required. The
preferred level of the air to be used depends in such cases on the
geometry of the premixing zone, on the speed of the air mass flow
and on the speed of the injected fuel.
[0023] The inventive premixing burner has a premixing zone, an air
swirl generator with an air inlet and one or more fuel nozzles. In
such cases the fuel can be injected through the fuel nozzles into
an air mass flow swirled by the air swirl generator in the
premixing zone, in which case a potential hot gas flowback region
can form. The inventive premixing burner is characterized in that
the premixing zone surface in the potential hot gas flowback region
has at least one opening through which a fluid can be injected into
the premixing zone. In particular openings can be present that are
arranged so that fluid can be injected in the main direction of
flow of the burner along the surface of the premixing zone.
[0024] The local injection of a fluid into the potential hot gas
flowback region largely avoids the formation of the hot gas
flowback region within the premixing zone of the burner. At the
least however the hot gas in the hot gas flowback region is
quenched and cooled off such that no reaction in the form of an
ignition of the air-gas mixture within the premixing zone of the
burner can occur. This prevents flame blowbacks and reduces the
nitrous oxide formation, but also allows a secure premixing
operation of the burner.
[0025] Preferably the premixing zone surface in the hot gas
flowback region features a number of openings. The opening or the
openings can advantageously be connected via a fluid channel to the
air supply leading to the air swirl generator so that a part of the
air can be injected through the opening as a fluid into the
combustion chamber.
[0026] The injection nozzles can be located on the cone side and/or
on the hub side of the premixing zone. Advantageously the fuel
nozzles are arranged in one or more rows lying behind one another
downstream of the air swirl generator. This makes a graduated fuel
injection possible. Furthermore the fuel nozzles and/or the
openings can be located in the air swirl generator, preferably in
at least one swirler vane.
[0027] The individual fuel nozzles can be embodied as round holes
for example. A further option consists of designing the fuel
nozzles such that the fuel can be injected at right angles to the
main flow direction of the air mass flow into the combustion
chamber, which promotes the premixing. Naturally the fuel can also
be injected at any other given angle to the air mass flow. The fuel
employed can especially involve a syngas.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Further features, characteristics and advantages of the
present invention will be explained below on the basis of an
exemplary embodiment which refers to the enclosed figures.
[0029] FIG. 1 shows a schematic diagram of a section of a part of
the premixing burner.
[0030] FIG. 2 shows a schematic diagram of the flow conditions
within the premixing burner depicted in FIG. 1.
[0031] FIG. 3 shows a schematic diagram of a section through a part
of the inventive premixing burner.
[0032] FIG. 4 shows a schematic diagram of the flow conditions
within the premixing burner depicted in FIG. 3.
[0033] FIG. 5 shows a schematic diagram of a section through a
swirler vane.
DETAILED DESCRIPTION OF INVENTION
[0034] The invention will be explained below in greater detail with
reference to FIGS. 1 to 5. FIG. 1 shows a schematic diagram of a
section through a part of a conventional premixing burner 1. The
premixing burner 1 includes elements such as a housing 7, a
premixing zone 2, a swirl generator 10 and/or one or more fuel
nozzles 11. The premixing zone is arranged radial-symmetrically
around the central axis 12. The outer side of the premixing zone 2,
viewed from the central axis 12, is referred to below as the cone
side 3. The side of the premixing zone 2 facing towards a central
axis 12 will be referred to below as the hub side 4.
[0035] An air mass flow 5 arrives at the swirl generator 10 via an
air supply inlet 16. The air swirl generator 10 swirls the air mass
flow 5 and directs this into the premixing zone 2. From there the
air mass flow is forwarded in the main direction of flow 9 to the
combustion chamber (not shown).
[0036] On the hub side 4 of the premixing zone 2 are located one or
more fuel nozzles 11. Fuel 6 is directed in the present example
through the fuel nozzles 11 at right angles to the main direction
of flow 9 of the air mass flow 5 into the premixing zone 2. A hot
gas flowback area 8 is now formed downstream towards the fuel
nozzle 11 in the main direction of flow 9. Instead of a
perpendicular injection to the main direction of flow 9 of the air
mass flow 5, the fuel 6 can also be injected at any other given
angle to the main direction of flow 9.
[0037] The flow direction of the injected fuel is indicated by
arrow 6, the flow direction of the supplied air mass flow is
indicated by arrow 5. The main direction of flow inside the
premixing zone 2 is marked by arrows 9.
[0038] The flow conditions inside the premixing zone 2 are depicted
in a schematic diagram in FIG. 2. FIG. 2 shows an overhead view of
the fuel nozzles 11 from the inside of the premixing zone 2. The
main direction of flow of the air mass flow flowing past the fuel
nozzles is indicated by arrows 9. Hot gas flowback regions 8 now
form downstream from the fuel nozzles 11 in the main direction of
flow 9. The flow direction of the hot gas flowing back is indicated
by the arrows 13.
[0039] FIG. 3 shows a schematic diagram of a section through a part
of the inventive premixing burner 1. The basic structure and the
principal functioning of the premixing burner 1 depicted in FIG. 3
essentially correspond to the premixing burner shown in connection
with FIG. 1.
[0040] In addition to the premixing burner described in connection
with FIG. 1, the inventive premixing burner features one or more
fluid inlet openings 14 which are located downstream of the fuel
nozzle or nozzles 11 in the main direction of flow 9. The fluid
inlet openings 14 open out into the premixing zone 2. Through these
fluid inlet openings in the present exemplary embodiment a fluid,
for example air or an inert gas, can be injected in the main flow
direction 9 into the premixing zone 2. The flow direction of the
injected fluid is indicated by arrows 15. In this case it runs
within the premixing zone 2 essentially in parallel to the main
direction of flow 9. The injected fluid prevents the formation of a
hot gas flowback region as occurs with the premixing learner
described in conjunction with FIG. 1.
[0041] FIG. 4 depicts schematically the flow conditions inside the
premixing zone 2 shown in FIG. 3.
[0042] An overhead view of the fuel nozzles 11 and the fluid inlet
openings 14 viewed from the premixing zone 2 can be seen in FIG. 4.
The main direction of flow of the air flowing from the swirl
generator 10 in the direction of the fuel nozzles 11 and the fluid
inlet openings 14 is indicated by arrows 9. The direction of flow
of the fluid injected through the fluid openings 14 is indicated by
arrows 15. The hot gas 13 is carried along in the main direction of
flow 9 by the inflowing of fluid. A flowback of the hot gas 13
against the main direction of flow 9 is effectively prevented in
this manner.
[0043] In the current exemplary embodiment the fluid injected by
the fluid inlet openings 14 involves air which is connected via a
fluid channel with the air mass flow 5 and is split off from the
latter. It has proved useful in respect of avoiding the flowback of
hot gas to introduce around 5% to 20%, preferably 10%, of the
overall air supplied to the premixing zone 2 via the fluid inlet
openings 14 into the premixing zone 2. Instead of air an inert gas,
for example carbon dioxide, water vapor or nitrogen can be injected
into the premixing zone via the fluid inlet openings 14. The
injection of a noble gas is however basically also possible.
[0044] The fuel can optionally be injected at right angles to the
main direction of flow 9 of the air mass flow 5 into the premixing
zone 2, as described in conjunction with FIG. 1 and FIG. 3, or the
fuel can be injected at any given angle to the main direction of
flow 9 of the air mass flow into the premixing zone 2. Basically
the fuel nozzles and 11 can be located both on the cone side 3 and
also on the hub side 4 of the premixing zone 2 or in the swirler
vanes 17. In the event of the fuel nozzles 11 being located on the
cone side 3 of the premixing zone 2, it is advantageous to also
place the fluid inlet openings 14 correspondingly on the cone side
3. The fluid inlet openings 14 should then again be located in the
main direction of flow 9 downstream to the fuel nozzles and make it
possible to inject the fluid in the main direction of flow 9.
[0045] The fuel nozzles 11 can be arranged in one or more rows line
behind one another downstream of the air swirl generator 10. They
can advantageously be embodied as round holes. The fuel injected
through them can especially involve a syngas.
[0046] A further embodiment of variant of the invention is
described below in which the fuel 6 and the fluid 15 containing no
fuel is injected into the premixing zone via swirler vanes 17. FIG.
5 shows a schematic diagram of a section through a swirler vane 17.
The swirler vane 17 has a fuel flow channel 18 within it and a
fluid flow channel 19 located downstream to it in the direction of
the main flow 9.
[0047] The fuel 6 is injected via the fuel flow channel 18 through
fuel nozzles 11 from the swirler vane 17 into the premixing zone 2.
The fluid 15, which preferably involves an inert gas, is injected
via the fluid flow channel 19 through fluid inlet openings 20, 21,
22 into the premixing zone 2. In this case the fluid inlet openings
20, 21, 22 are located in the main direction of flow 9 downstream
from the fuel nozzles 11.
[0048] In the present embodiment variant a part of the fluid 15 is
injected through fluid inlet openings 20 which are arranged
downstream next to the fuel nozzles 11, essentially against the
main direction of flow 9 into the premixing zone 2. By fluid inlet
openings 21 arranged further downstream next to the fluid inlet
openings 20 a part of the fluid 15 is injected almost at right
angles to the main direction of flow 9 into the premixing zone 2.
Further fluid inlet openings 22 are arranged downstream next to the
fluid inlet openings 21, through which a part of the fluid 15 is
injected essentially in the main direction of flow 9 into the
premixing zone 2.
[0049] The described arrangement of the fluid inlet openings 20,
21, 22 avoids any hot gas flowback region arising downstream from
the fuel nozzles 11 and thus makes possible a safe premixing
operation of the burner.
* * * * *