U.S. patent application number 13/758197 was filed with the patent office on 2013-06-13 for system and method using low emissions gas turbine cycle with partial air separation.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. The applicant listed for this patent is GENERAL ELECTRIC COMPANY. Invention is credited to Ahmed Mostafa ELKady, Narendra Digamber Joshi, Parag Prakash Kulkarni, Christian Lee Vandervort, Krishnakumar Venkatesan.
Application Number | 20130145771 13/758197 |
Document ID | / |
Family ID | 43705835 |
Filed Date | 2013-06-13 |
United States Patent
Application |
20130145771 |
Kind Code |
A1 |
ELKady; Ahmed Mostafa ; et
al. |
June 13, 2013 |
SYSTEM AND METHOD USING LOW EMISSIONS GAS TURBINE CYCLE WITH
PARTIAL AIR SEPARATION
Abstract
A system and method of reducing gas turbine nitric oxide
emissions includes a first combustion stage configured to burn air
vitiated with diluents to generate first combustion stage products.
A second combustion stage is configured to burn the first
combustion stage products in combination with enriched oxygen to
generate second combustion stage products having a lower level of
nitric oxide emissions than that achievable through combustion with
vitiated air alone or through combustion staging alone.
Inventors: |
ELKady; Ahmed Mostafa;
(Moason, OH) ; Joshi; Narendra Digamber;
(Schenectady, NY) ; Kulkarni; Parag Prakash;
(Niskayuna, NY) ; Vandervort; Christian Lee;
(Voorheesville, NY) ; Venkatesan; Krishnakumar;
(Clifton Park, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GENERAL ELECTRIC COMPANY; |
Schenectady |
NY |
US |
|
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
43705835 |
Appl. No.: |
13/758197 |
Filed: |
February 4, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12571073 |
Sep 30, 2009 |
8381525 |
|
|
13758197 |
|
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|
Current U.S.
Class: |
60/774 |
Current CPC
Class: |
F23L 7/00 20130101; F02C
3/20 20130101; Y02T 50/678 20130101; F02C 3/22 20130101; F23R
2900/00002 20130101; F23R 3/346 20130101; Y02E 20/16 20130101; Y02E
20/344 20130101; Y02E 20/34 20130101; F23L 2900/07002 20130101;
F23C 2900/99011 20130101; F23L 2900/07005 20130101 |
Class at
Publication: |
60/774 |
International
Class: |
F02C 3/20 20060101
F02C003/20 |
Claims
1. A method of reducing gas turbine nitric oxide emissions, the
method comprising: vitiating air with diluents; introducing the
vitiated air to a first combustion stage of a gas turbine and
generating first combustion stage combustion products therefrom;
enriching the products of combustion from the first stage with
oxygen in a second combustion stage; and burning the products of
combustion from the first stage in combination with enriched oxygen
gas to generate second combustion stage products having a lower
level of nitric oxide emissions than that achievable through
combustion with vitiated air alone or through combustion staging
alone.
2. The method according to claim 1, wherein vitiating air with
diluents comprises vitiating air with nitrogen.
3. The method according to claim 1, further comprising partially
separating air to generate the enriched oxygen gas.
4. The method according to claim 1, further comprising partially
separating air to generate the diluents.
5. The method according to claim 4, wherein partially separating
air to generate the diluents comprises partially separating air to
generate enriched nitrogen gas.
6. The method according to claim 1, further comprising burning a
predetermined gas turbine fuel in combination with the vitiated air
to generate the first combustion stage products.
7. The method according to claim 1, wherein introducing the
vitiated air to a first combustion stage of a gas turbine and
generating first combustion stage combustion products therefrom
comprises introducing the vitiated air to a first combustion stage
of a dry low emissions combustor.
8. The method according to claim 1, wherein introducing the
vitiated air to a first combustion stage of a gas turbine and
generating first combustion stage combustion products therefrom
comprises introducing the vitiated air to a first combustion stage
of a dry low nitric oxide combustor.
9. The method according to claim 1, wherein burning the products of
combustion from the second stage in combination with enriched
oxygen gas to generate second combustion stage products having a
lower level of nitric oxide emissions than that achievable through
combustion with vitiated air alone or through combustion staging
alone comprises burning the products of combustion from the second
stage in combination with enriched oxygen gas to generate second
combustion stage products having a nitric oxide level of less than
10 parts per million of the second combustion stage products.
10. The method according to claim 1, further comprising burning the
products of combustion from the second stage in combination with
enriched oxygen gas to generate second combustion stage products
having a lower level of nitric oxide emissions than that achievable
through combustion with vitiated air alone or through combustion
staging alone while maintaining combustion efficiency and carbon
monoxide emissions at levels achievable through combustion with
vitiated air alone or through combustion staging alone.
Description
[0001] This patent application is a Divisional Application of
application Ser. No. 12/571,073, filed on Sep. 30, 2009.
BACKGROUND
[0002] This invention relates generally to gas turbine power
plants, and more particularly, to a system and method for reducing
gas turbine nitric oxide (NOx) emissions without incurring
penalties associated with either combustion efficiency or carbon
monoxide (CO) emissions.
[0003] Pollutant emissions from gas turbine power plants have been
of great concern in the past several decades. Stringent regulations
have been established to lower these emissions, especially nitric
oxides to single digits. One of the solutions currently in use to
reduce these NOx emissions employs selective catalytic reactors
(SCR)s. Selective catalytic reactors undesirably are expensive,
have a large footprint, and present additional concerns regarding
ammonia slip.
[0004] Combustion with vitiated air is a proven technique for
reducing NOx emissions by affecting the NOx kinetic mechanisms,
changing the flame structure and lowering the peak flame
temperature. Combustion staging has also been shown to reduce NOx
emissions in applications including, for example, axial staging,
late lean and sequential combustion systems (reheat).
[0005] It would be desirable to provide a system and method that
further reduces NOx emissions below limits achievable using known
techniques, without incurring penalties in terms of combustion
efficiency or CO emissions.
BRIEF DESCRIPTION
[0006] Briefly, in accordance with one embodiment, a gas turbine
combustion system comprises:
[0007] a first combustion stage configured to burn air vitiated
with diluents to generate first combustion stage products; and
[0008] a second combustion stage configured to burn the first
combustion stage products in combination with enriched oxygen to
generate second combustion stage products having a lower level of
nitric oxide emissions than that achievable through combustion with
vitiated air alone or through combustion staging alone.
[0009] According to another embodiment, a method of reducing gas
turbine nitric oxide emissions comprises:
[0010] vitiating air with diluents;
[0011] introducing the vitiated air to a first combustion stage of
a gas turbine and generating first combustion stage combustion
products therefrom;
[0012] enriching the products of combustion from the first stage
with oxygen in a second stage; and
[0013] burning the products of combustion from the first stage in
combination with enriched oxygen gas to generate second combustion
stage products having a lower level of nitric oxide emissions than
that achievable through combustion with vitiated air alone or
through combustion staging alone.
DRAWINGS
[0014] These and other features, aspects, and advantages of the
present invention will become better understood when the following
detailed description is read with reference to the accompanying
drawings in which like characters represent like parts throughout
the drawings, wherein:
[0015] FIG. 1 is a simplified block diagram illustrating a low
emissions simple gas turbine with partial air separation according
to one embodiment;
[0016] FIG. 2 is a simplified block diagram illustrating a low
emissions simple gas turbine using an integral gasification
combined cycle according to one embodiment;
[0017] FIG. 3 is a graph illustrating NOx emissions reduction
utilizing a DLE combustor system according to one embodiment;
and
[0018] FIG. 4 is a graph illustrating NOx emissions reduction
utilizing a DLN combustor system according to one embodiment.
[0019] While the above-identified drawing figures set forth
alternative embodiments, other embodiments of the present invention
are also contemplated, as noted in the discussion. In all cases,
this disclosure presents illustrated embodiments of the present
invention by way of representation and not limitation. Numerous
other modifications and embodiments can be devised by those skilled
in the art which fall within the scope and spirit of the principles
of this invention.
DETAILED DESCRIPTION
[0020] While the methods and apparatus are herein described in the
context of a gas turbine engine used in an industrial environment,
it is contemplated that the method and apparatus described herein
may find utility in other combustion turbine systems applications
including, without limitation, turbines installed in aircraft.
Further, the principles and teachings set forth herein are
applicable to gas turbine engines using a variety of combustible
fuels such as, but not limited to, natural gas, gasoline, kerosene,
diesel fuel, and jet fuel.
[0021] FIG. 1 is a simplified block diagram illustrating a low
emissions simple gas turbine system 10 with partial air separation,
according to one embodiment. Gas turbine system 10 employs a
partial air separator 12 that operates to separate compressed air
supplied via an air compressor 18 into an oxygen enriched gas
stream 14 and a nitrogen enriched gas stream 16. Input air is
compressed via the air compressor 18; and the compressed air is
supplied to the partial air separator 12.
[0022] Nitrogen enriched gas stream 16 is compressed and then mixed
with compressed air from air compressor 18 to generate vitiated air
via an air mixer 19. The resultant air 20 vitiated with diluents is
transmitted to a first combustor stage 22 where it is burned and
produces products of first stage combustion. Oxygen enriched gas
stream 14 is compressed and mixed with the products of first stage
combustion together in a second combustor stage 24. The present
invention is not so limited however, and additional combustor
stages beyond just two combustor stages can be employed in
accordance with the principles described herein to achieve a
desired NOx emissions level or to achieve other desired
results.
[0023] Combining air vitiation and combustion staging as described
above was found by the present inventors to reduce NOx emissions to
very low limits that cannot be attained through either air
vitiation alone or combustion staging alone. More particularly,
this structure was found to provide a reliable technique for
reducing NOx emissions to very low limits without incurring
penalties in terms of combustion efficiency or CO emissions as
applied to gas turbine systems that may employ either dry low
emissions (DLN) combustors or dry low NOx combustors.
[0024] FIG. 3 is a graph illustrating NOx emissions reduction
utilizing the principles described herein utilizing DLE combustor
system concepts.
[0025] FIG. 4 is a graph illustrating NOx emissions reduction
utilizing the principles described herein utilizing DLN combustor
system concepts.
[0026] It should be noted that oxygen enriched gas has not
heretofore been injected into any stage of a conventional
combustion staging process. This can be attributed to the necessity
for careful management of combustion conditions to achieve stable
operation, acceptable NOx and CO emissions while remaining free of
pressure oscillations called dynamics usually related to the
combination of acoustics and unsteady energy release of the
combustion process.
[0027] DLN combustors particularly often require multiple
independently controlled fuel injection points or fuel nozzles in
each of one or more parallel identical combustors to allow gas
turbine operation from start-up through full load. Further, DLN
combustion systems often function well over a relatively narrow
range of fuel injector pressure ratio, wherein this pressure ratio
is a function of fuel flow rate, fuel passage flow area, and gas
turbine cycle pressures before and after the fuel nozzles. Proper
selection of fuel nozzle passage areas and regulation of the fuel
flows to the several fuel nozzle groups are required to manage
these pressure ratio limits. Correct fuel nozzle passage areas are
based on actual fuel properties which are nominally assumed to be
constant.
[0028] The present inventors alone discovered through
experimentation, the effects of burning fuel with vitiated air (air
mixed with diluents such as N.sub.2 and CO.sub.2 to reduce overall
oxygen concentration) on gas turbine combustion performance and
pollutant emissions, particularly in a gas turbine combustion
system that combines a first combustion stage that burns air
vitiated with diluents to generate first combustion stage products
and one or more additional combustion stages configured to burn the
first combustion stage products in combination with enriched oxygen
to generate second or subsequent combustion stage products having a
lower level of nitric oxide emissions than that achievable through
combustion with vitiated air alone or through combustion staging
alone.
[0029] One system and process for successfully lowering NOx
emissions resulting from this experimentation is shown in FIG. 1,
wherein an air stream enters a partial air separation unit that
produces two outlet streams including an N.sub.2 enriched stream
(air vitiated) and an oxygen enriched stream. Another system and
process, discussed in further detail below, for successfully
lowering NOx emissions resulting from this experimentation is shown
in FIG. 2. This system and process is useful in IGCC power plants
where an air separation unit is in place and N.sub.2 from an air
separation unit (ASU) is mixed with the combustion air to result in
a vitiated combustion air.
[0030] FIG. 2 is a simplified block diagram illustrating a low
emissions simple gas turbine system 30 using an integral
gasification combined cycle according to one embodiment. Air enters
a compressor 32 where the air is compressed and transmitted to an
air separation unit 34. The air separation unit 34 generates two
gas streams including an oxygen enriched gas stream 36 and a
nitrogen enriched gas stream 38. The nitrogen enriched gas stream
38 is mixed with the compressed air via an air mixer 40 to generate
a vitiated air mixture 42. Vitiated air 42 is transmitted to a
first stage 44 of a combustor 46 where it is burned in combination
with a synthetic gas fuel 54 to generate first stage combustion
products 48. These first stage combustion products 48 are
transmitted to a second combustor stage 50 where the first stage
combustion products 48 are mixed with the synthetic gas fuel 54 and
enriched oxygen 36 and burned to yield very low NOx emissions
combustion products 52. The principles and teachings set forth
herein are applicable to gas turbine engines using a variety of
combustible fuels such as, but not limited to, natural gas,
gasoline, kerosene, diesel fuel, and jet fuel.
[0031] In summary explanation, a gas turbine system includes a
first combustor stage configured to burn air vitiated with diluents
to generate first combustion stage products, and a second combustor
stage configured to burn the first stage combustion products in
combination with enriched oxygen to generate second combustion
stage products having nitric oxide emissions that are substantially
lower than that achievable using air vitiation or combustion
staging techniques alone. These reduced NOx emissions are obtained
without penalties in combustion efficiency or CO emissions.
[0032] The embodiments described herein may advantageously
eliminate the necessity for using selective catalytic reactors or
otherwise reduce the size and cost of selective catalytic reactors
due to using a combustor the produces lower NOx emissions than that
achievable with conventional combustors. Further, combustion
dynamics may be reduced via the embodiments described herein by
adding another controlling parameter such as oxygen concentration.
The embodiments described herein further provide a cost effective
technique for achieving reduced NOx emissions without requiring
add-on emissions system control equipment.
[0033] The embodiments described herein were found by the present
inventors to be more effective at reducing NOx emissions than
systems and methods that employ steam/water injection to a
combustor or that utilize a dry low NOx combustion system with high
premixedness efficiency.
[0034] While only certain features of the invention have been
illustrated and described herein, many modifications and changes
will occur to those skilled in the art. It is, therefore, to be
understood that the appended claims are intended to cover all such
modifications and changes as fall within the true spirit of the
invention.
* * * * *